Full Papers The 3rd Thailand Metallurgy Conference (TMETC 3) “Metallurgical Research for Thailand Development” 26 – 27 October 2009 Century Park Hotel, Bangkok, Thailand Organized by Department of Materials Engineering, Kasetsart University Iron and Steel Institute of Thailand National Metal and Materials Technology Center Sponsored by Sahaviriya Steel Industries Public Co., Ltd Thai Parkerizing Co., Ltd Boon Rawd Brewery Co., Ltd. Thai Nippon Steel Engineering & Construction Corp., Ltd. Advance Pinnacle Technologies Pte Ltd. DKSH Ltd. Council of Engineers, Thailand Wisit Locharoenrat Department of Materials Engineering.‐Ing. Weerasak Udomkichdacha National Metal and Materials Technology Center Assoc. Chatchai Somsiri Thainox Stainless Pcl. Ratchatee Techapiesancharoenkij Mr. Prof. Technical Committee Faculty of Engineering. Paritud Bhandhubanyong National Science and Technology Development Agency Assoc. Ekkarut Viyanit Dr. Aphichart Rodchanarowan Dr. Kritsada Prapakorn Dr. Prof. Julathep Kajornchaiyakul Dr. Patiphan Juijerm National Metal and Materials Technology Center Dr. Dr. Thanawat Meesak . Kasetsart University Advisory Committee Mr. Parinya Chakartnarodom Dr. Ampika Bansiddhi Dr. Wikrom Vajragupta Iron and Steel Institute of Thailand Assoc. Dr. Ruangdaj Tongsri Dr. Organizing Committees Conference Chairman Asst. Kasetsart University Asst. Dr. Wisit Locharoenrat Dr. Prof. Prof. Prof. Dr. Prof. Dr. Somrerk Chandra‐Ambhorn Asst. Dr. Prof. Chulalongkorn University Ms. Dr. Tachai Luangvaranunt Dr. Dr. Prof. Dr Bovornchok Poopat Asst. Prof. Prof. Prof. Panyawat Wangyao Dr. Chulalongkorn University Assoc. Dr. King Mongkut’s University of Technology Thonburi Asst. Charkorn Jarupisitthorn Asst. Witthaya Eidhed Dr. Suvanchai Pongsugitwat Metallurgy and Materials Science Research Institute. Paiboon Choungthong Mr. Prof. Dr. Prof. Patama Visuttipitukul Dr. Yuttanant Boonyongmaneerat Dr.Faculty of Engineering. Prof. Ekasit Nisaratanaporn Mr. Seksak Asavavisithchai Asst. Gobboon Lothongkum Assoc. Kanokwan Saengkiettiyut Dr. King Mongkut’s University of Technology Thonburi Assoc. Siriporn Rojananan Dr. Dr Sombun Charoeuvilaisiri School of Energy. Prasonk Sricharoenchai Asso. Boonrat Lohwongwatana .‐Ing. Prof. King Mongkut's University of Technology North Bangkok Asst. Nattapong Sornsuwit Dr. Prof. Dr. Nutthita Chuankrerkkul Faculty of Engineering. Environment and Materials. Preecha Termsuksawad Faculty of Engineering. Chaowalit Limmaneevichitr Assoc. Dr. Sawai Danchaivijit Asst. Pongsak Tuengsook Dr. Tippaban Palathai Dr. Noppadol Kumanuvong Dr. Jessada Wannasin Dr. Narong Akkarapattanagoon Dr. Dr. Rattana Borisuttikul Dr. Thawatchai Plookphol Asst. Prof. Institute of Engineering.School of Metallurgical Engineering. Suranaree University of Technology Dr. Prof. Sakhob Kumkoa . Dr. Usanee Kitkamthorn Faculty of Science. Prince of Songkla University Asst. Torranin Chairuangsri Faculty of Engineering. Dr. Prof. Chiangmai University Assoc. However. degenerate and may fail in service or be declared unfit for further service on the basis of inspection and remaining life assessments. Songkla. welding can change the microstructure. Thus mechanical properties were degraded in weld metal and heat affected zone (HAZ). 90112 Thailand Tel: +6674 287323 Fax: +6674 212897 Email: b_rainning@hotmail. Prince of Songkla University. This is a widely used low alloy steel that offers an advantageous due to high hardness.The 3rd Thailand Metallurgy Conference Effect of welding processes on the microstructure and hardness properties of weld metal on low alloy steel AISI 4340 S. As the machine part-members age. the microstructure and hardness properties of weld metal on low alloy steel AISI 4340 have been investigated using shielded metal arc welding. grain boundary ferrite. P. Welding. Shielded metal arc welding (SMAW). Introduction Low alloy steel AISI 4340 are used in heavy duties engineering application for a long time. Faculty of Engineering. However. The results have revealed that the hardness of the weld metal fabricated using flux cored arc welding process is greater than the weld metal fabricated using shielded metal arc welding and metal active gas welding process. polygonal ferrite and sideplate ferrite. Keywords : AISI 4340. Limna. The samples were mutipass welding. The microstructure and hardness properties in weld metal were investigated by using optical microscope and micro hardness tester. Metal Active Gas welding (MAG) and Flux cored arc welding (FCAW) process AF‐02 . the machine part-members are repaired by welding processes. Hatyai.com Abstract In this work. metal active gas welding and flux cored arc welding processes which the composition of filler wire nearly the same alloying elements. Muangjunburee Department of Mining and Materials Engineering. Acicular ferrite. Polygonal ferrite 1. Therefore. the microstructure of weld metal fabricated using flux cored arc welding process indicates higher volume fraction of acicular ferrite than metal active gas welding and shielded metal arc welding process. high strength and excellent toughness [1-3]. The microstructure of weld metal all three processes consisted of acicular ferrite. FCAW process has became more popular due to higher deposition rate and a better weld quality as compared to SMAW process [5]. This paper presents an investigation of microstructure and hardness of weld and base metal change after welding by SMAW.1. MAG and FCAW processes. MAG and FCAW are a semi or fully automatic arc welding process in which the electrode is continuously fed to the weld area. polygonal ferrite and sideplate ferrite. The weld metal microstructure was revealed by etching with a freshly prepared 2% natal solution. samples were polished to a 1 µ alumina finish. lower cost and a better control of geometry. The typical microstructures of base metal and weld metal are presented in Fig. Vicker’s microhardness testing machine was used to measure the weld metal and base metal. 3.3. Among these are increasing of productivity. The samples were ground surface until 1200 grits. SMAW is a manual process. Metal Active Gas arc welding (MAG) and Flux cored wire arc welding (FCAW). Electrodes and process parameters used to fabricate the weld are given in table 1. After that. Experimental The base metal used in this investigation was the commercial AISI 4340 steel. Results Microstructures The main aim of this investigation was to understand the microstructure of welded sample with different processes such as SMAW. On the other hand.The 3rd Thailand Metallurgy Conference are widely used in welding repair of machine part-members [4. The microstructure feature of the base metal shows tempered bainite (Fig. An optical AF‐02 . Single bevel butt joints were prepared to fabricate the weld. The microstructure analysis of the weld metals were studied using a light optical microscope. Solid wire used in MAG but FCAW used flux cord wire that has the flux material in the core of the tube [4]. However. MAG and FCAW processes. In general. Welding completion were post-weld heat treatment at 550๐C for 1 hour. Volume fraction of microstructures is presented in Fig. Cross section samples were cut from the all weld samples.5]. the microstructures of weld metal obtained from all processes consisted of acicular ferrite. Automatic welding processes are favored over manual processes for the fabrication of welded joints for number of reasons. The chemical composition of base metal and weld metal is shown in table 2. The samples were multi-pass welded by Shielded Metal arc welding (SMAW). 2.1a). 4 1.30 0.08 0.05 0.005 P 0. A V mm/min KJ/mm Table 2 Chemical composition of base metal and weld metals Type of materials Base metal SMAW MAG FCAW C 0.41 350 12 1.4 0.23 0. the hardness distribution of the weld’s cross section was clearly found to be different among process. Weld metals fabricated using SMAW. 350 350 4 145 26 160 1.2 230 25 300 1.5 0. The hardness of the base metal is approximate 290 HV.40 Ni 1.4 Cr 0. From this figure.5 1.4 0.4 2.2.39 0.72 2.50 Mo 0.0 2.The 3rd Thailand Metallurgy Conference microstructures of weld metals fabricated using SMAW.05 Mn 0.6 0.40 Si 0.15 350 12 1.50 Hardness Vicker’s hardness testing machine was used to measure the weld metal and the base metal hardness and the values are presented in Fig. 230 and 275 HV. MAG and FCAW processes present predominantly acicular ferrite.019 0.8 0. MAG and FCAW processes exhibit 250.024 0.015 S 0.19 0. AF‐02 .74 1.5 2. The hardness value of samples fabricated by FCAW revealed higher hardness in the area of weld metal than samples fabricated by MAG and FCAW processes.2 230 25 300 1. respectively. Table 1 Welding conditions Parameter Electrode Types (AWS) Unit ๐ ๐ SMAW E11018-G 4R MAG H ER110S-G FCAW E110T5-K4H4 Preheat temperature Electrode baking temperature Mixer gas flow rate Filler diameter Current Voltage Welding speed Heat input C C for 1 hr.15 l/min mm. However. the microstructure of weld metal fabricated using FCAW process indicates higher volume fraction of acicular ferrite than MAG and SMAW processes. (c) MAG. weld metal (middle) and base metal (right) of the samples were fabricated by SMAW. (d) FCAW Fig. 1. 2. Optical microstructures of base metal and weld metal: (a) Base metal.The 3rd Thailand Metallurgy Conference a b c d Fig. (b) SMAW. MAG and FCAW AF‐02 . Vicker’s hardness distribution of base metal (left). When cooled at sufficiently low rates. was fabricated by SMAW and 1. Thus if the heat input is higher the content of the acicular ferrite will be very less and vice versa. On the other hand higher heat input will enhance the formation of coarse pro-eutectoid ferrite or polygonal ferrite in the weld metal region. polygonal ferrite and sideplate ferrite. The microstructure of the weld metal region consisted of acicular ferrite. It has been accepted that polygonal ferrite is bad for weld metal toughness because it offers little resistance to cleavage crack propagation. The difference in the ferrite morphology in low alloy steel welds is due to the difference in heat input. The formation of acicular ferrite is controlled by weld heat input.15 KJ/mm. Therefore. Discussion It is a common practice to correlate the various weld metal properties with heat input. the welding process has a significant in the weld metal microstructure.3. Volume fraction of microstructures in different processes. The general effect of increasing the cooling rate is to lower transformation temperatures. Acicular ferrite is formed in the interior of the original austenite grains by direct nucleation from the inclusions resulting in a randomly oriented short ferrite needles with a basket weave features. Weld cooling rate plays the decisive role in determining weld microstructure in high strength steels. AF‐02 . was fabricated by MAG and FCAW. heat input of 1. This has a direct influence in weld metal hardness. An acicular ferrite microstructure has the potential of combining high strength and high toughness. In the present investigation. In addition. 4. grain boundary ferrite. the microstructure predominantly tends to become polygonal ferrite. the results confirm that the hardness in weld metal fabricated using FCAW process higher than weld metal fabricated using MAG and SMAW process.41 KJ/mm.The 3rd Thailand Metallurgy Conference Fig. Muangjunburee. Madhusdhan Reddy. V. [2] P. Balasubramanian and G. 7. Journal of Materials and Design. The First South-East Asia IIW Congress: 273-277. D. AF‐02 . Hat.Lant. Robsinson. 2008.Spafford and J. Journal of Materials Processing Technology 87: 198-206. polygonal ferrite and sideplate ferrite are influenced by heat input. B. Proceedings of international Conference the Frontiers of Technolog: 321-324. Thanks are also to the Department of Mining and Materials Engineering.Conclusions The microstructure and hardness properties of weld metal on low alloy steel AISI 4340 fabricated using SMAW. 2. Review of weld repair procedures for low alloy steels designed to minimize the risk of future cracking. Magudeeswaran. 2007. Thailand for providing equipment and facilities.Yai.The 3rd Thailand Metallurgy Conference 5. 3. [4] G. 2007. [3] Woei Shyan Lee and Tzay Tian Su. [5] T. Acknowledgements The author gratefully acknowledge the financial support from the electric Generating Authority of Thailand (EGAT). Effect of welding processes and consumables on high cycle fatigue life of high strength. The microstructure constituents such as acicular ferrite. 6. MAG and FCAW processes have been investigated and the conclusions are as follow: 1. Improvement of metallurgical and Mechanical properties of welding surfacing on high strength steel AISI 4340 by Post-weld heat treatment.L. International Journal of Pressure Vessels and Piping 78: 813-818.Storesund.Muangjunburee. 1999. quenched and tempered steel joints. The hardness of weld metal is significantly depending on microstructure. Mechanical properties and microstructural features of AISI 4340 high-strength alloy steel under quenched and tempered conditions. 2004. References [1] P. Prince of Songkla University. FCAW process indicates both microstructure and hardness better than SMAW and MAG processes. Improvement of Metallurgical and Mechanical Properties of Welding Surfacing on High Strength Steel AISI 4340 by Various Preheating Temperatures. The 3rd Thailand Metallurgy Conference An investigation of microstructural change of low alloy steel AISI 4150 by Seebeck coefficient T. School of Energy Environment and Materials. Nakhon Ratchasima. microstructure AF‐05 . low alloyed steel. which can be altered by electronic properties or microstructure changes. It is useful to develop a non-destructive method to characterize its properties and microstructures. have been widely used in various applications. oil and water. The Seebeck coefficient was measured relative to that of copper. Institute of Engineering. the Seebeck coefficient measurement could be possibly applied to study microstructure of low alloyed steels. The Seebeck effect is a phenomenon in which the electrical potential gradient develops due to temperature difference. Termsuksawadb* a School of Metallurgical Engineering. Keywords: Seebeck coefficient. P. Fax: 0-2427-9062 Email: preecha. respectively. XRD. The result indicated that Seebeck coefficient increases with hardness. Bangkok 10140 Thailand.th Abstract Low alloyed steel.ter@kmutt. In addition one of the samples was cooled in salt bath at 350 oC for 1 hour before water cooled. whose hardness can be increased by heat treatment. The specimens were heat-treated at 900 oC for 1 hour. After heat treatment. Samrana. The magnitude of the Seebeck effect is demonstrated by the Seebeck coefficient. which is controlled by microstructure. The materials in this study were cylindrical carbon steels AISI 4150 with diameter of 1.ac. An x-ray diffractometry (XRD) and optical microscopy (OM) were used to characterize their crystal structures and microstructures. and then cooled to room temperature in furnace and in various mediums: air. heat treatment. King Mongkut's University of Technology Thonburi. 30000 Thailand b Division of Materials Technology. In conclusion.3 cm and length of 3 cm. Suranaree University of Technology. Tel: 0-2470-8643. it is normally destructively characterized and tested by many approaches such as microstructure characterization by optical microscope and hardness testing. Effects of microstructure of carbon steel on Seebeck coefficient were studied by various research groups [4-7]. S AB = lim ΔV [1]. Phonondrag thermoelectric power is very small and can be negligible at room temperature or above. thermoelectric power increased with amounts of AlN and carbon precipitation. Effect of annealing on thermoelectric power of low carbon steel containing 460 ppm aluminium and 74 ppm nitrogen was investigates by Brami et al [4]. Seebeck coefficient or thermoelectric power is ΔT →0 ΔT contributed by two components: diffusion and phonon-drag thermoelectric power. mechanical properties of heat treated steels such as hardness and strength are examined by some destructive tests. it is useful to develop a nondestructive technique to predict these properties. chromium and molybdenum. m . Typically. Seebeck coefficient will be negative. where dk 2 2 d 2E and are Plank’s dk 2 constant. pipelines. structural steel parts. positive Seebeck coefficient is found when hole is a carrier. Both electrical conductivity and effective mass are function of microstructure and electronic structure. The magnitude of Seebeck coefficient depends on effective mass and difficulty of carrier transport. etc. In this study. and be increased with the AF‐05 . Seebeck coefficient depends on these structures as well. as a result. One of the candidates is Seebeck coefficient or thermoelectric power measurement which measure amount of induced voltage developed by temperature difference. In contrast. If a carrier is an electron.The 3rd Thailand Metallurgy Conference Introduction Low alloy steels are steels with additions of alloying elements such as nickel. Because these steels possess good mechanical properties. Seebeck coefficient was found to be decreased with increasing defect concentration or amount of dissolved element in the matrix. These alloying elements increase hardenability of the steels. After heat treatment. is calculated by m* = * 2 d 2E . as a result. they have been widely used in many applications such as automobile parts. It should be noted that sign of Seebeck coefficient depends on types of carriers [3]. respectively. Effective mass is defined as curvature of electronic structure at the Fermi level [2]. For ultra low carbon steel. mechanical properties of these steels can be improved by heat treatment. Diffusion thermoelectric power is a function of electrical conductivity and effective mass [2]. microstructure of the steels is altered and their mechanical properties such as hardness and strength were improved. Therefore. effective mass. and curvature of electronic structure at Fermi level. From this definition. 75-1. relative to Seebeck coefficient of copper. and subsequently cooled in different media: furnace cool. Seebeck coefficient of copper (μV/K). The absolute Seebeck coefficient was calculated by the equation: Sa = ΔV + S Cu ΔT (1) where S a .2 0. indicated that Seebeck coefficient can be increased with grain size of austenite due to decreasing of grain boundary concentration. In addition. 6].15-0. main alloying elements in this steel are chromium and molybdenum. ΔV and ΔT are absolute Seebeck coefficient (μV/K). it is possible to study effect of heat treatment on microstructure and mechanical properties of low alloy steel via Seebeck coefficient. whose diameter is 1. analyzed by emission spectroscopy (wt. Experimental procedure Low alloy steel grade AISI 4150. Caballero et al. From literatures. The temperature at the cold side is about 26 oC and temperature difference between hot and cold AF‐05 . The configuration of the Seebeck coefficient apparatus was demonstrated in figure 1.3 cm. studied the effect of carbide precipitation on Seebeck coefficient of heat treated stainless steel [7]. water cool and oil cooled. therefore. Table 1: composition of sample.035 0. Three observations for each treatment were conducted.53 0.489 Mn 0.The 3rd Thailand Metallurgy Conference amount of precipitation [5. From this table.021 S < 0.15-0. Seebeck coefficients.851 Mo 0.789 P < 0. of each sample were measured after heat treatment. respectively.3 0. air cool. induced voltage difference (V) and temperature difference. In addition.00 0. S Cu .%) C AISI 4150 (std. The sample composition was analyzed by emission spectroscopy as shown in table 1. which increases hardenability of the steel.192 The samples were annealed at approximately 900 oC for 1 hr.25 0.48-0. This study aims to investigate this relationship in order to further develop this concept as non-destructive testing for heat treated steel. was used in this study. with the length of 3 cm.04 0.002 Cr 0.75-1.177 Si 0. The increasing of Seebeck coefficient due to amount of precipitates was also found in martensitic stainless steel when Caballero et al.) Sample 0. one of the samples was cooled in salt bath at 350 oC for 1 hr and then cooled in water. According to Vedenikov [8].The 3rd Thailand Metallurgy Conference sides in this experiment was set at 4 oC. 6]. Seebeck coefficient of pure iron at 300 K is approximately +12 μV/K. ΔS i . The contribution from solute atom to Seebeck coefficient. The crystal structures of each sample were also examined by D-8 Bruker x-ray diffractometer using Cu-Kα as x-ray source. Seebeck coefficient of steel is perturbed by element in solid solution.83 μV/K [1]. Figure 1: Diagram of Seebeck coefficient measurement apparatus Next. Among these contributions.04 s. contribution from solute atom is the greatest because solute atoms act as new diffusion centers for electron [5]. However. obeys the linear law as shown by: AF‐05 . microstructure. Seebeck coefficient of copper at 300 K is 1. hardness and microstructures of the samples were investigated by hardness test Rockwell scale C with loading of 150 kgf and optical microscope. dislocation and precipitates [5. step width of 0.02 degree and step time of 0. Results and discussion Hardness and Seebeck coefficient Harnesses and Seebeck coefficients of as-received samples and heat-treated low alloy steels after quenching with different media were shown in figure 2. Negative Seebeck coefficient pointed out that electron is carrier responsible for thermoelectric power of the samples. %). texture. grain size. therefore.The 3rd Thailand Metallurgy Conference ΔS i = ∑ K i C i (1) where Ki and Ci are the specific thermoelectric power per weight percent of solute element i (μV/(K-wt%)) and amount of solute element i (wt. It can be seen that the magnitude of specific thermoelectric power due to microstructure is less than those of solute atom in the order of magnitude. respectively. the contribution from dislocation also leads to negative Seebeck coefficient [5]. Figure 2: Hardness and Seebeck coefficients of as-received sample and heat treated low alloy steels after quenching in different media AF‐05 . The higher the carbon content. respectively. Beside contribution from solute element.087 μV/K-wt% [7]. the lower is the KC value. etc [6]. KCr and KMn were reported as -0. the negative Seebeck coefficient of steel is expected. For example the KC varies from -20 to -52 μV/K-wt% depending on carbon contents [5-7]. The value of Ki depends on various factors such as chemical composition.30 and -3 μV/Kwt%. The sign of change of Seebeck coefficient due to contribution from microstructure relies on type of phase transformation. amount of retain austenite in martensitic stainless steel leads to positive Seebeck coefficient with specific thermoelectric power constant of +0. For example. quenching in oil or water. It is well known that for fast cooling rate carbon atoms do not have enough time to diffuse out of the austenite to form equilibrium microstructure of pearlite. This phenomenon may be used to establish relationship between Seebeck coefficient and hardness. microstructure analysis is needed. However. This explanation can also be applied when the Seebeck coefficients and x-ray diffraction patterns of only oil quenched and water quenched samples are compared. AF‐05 . In addition. they are broader than those of samples quenched at low and moderate cooling rate. In addition. XRD-result Effect of cooling rate on crystal structure can be seen by x-ray diffraction pattern demonstrated in figures 3 and 4. (200) and (211). rather than chemical composition. consequently. non-equilibrium structures such as bainite or martensite will form and hardness of quenched sample increases. Figure 3 demonstrated that crystal structure of sample with low cooling rate is body center cubic with diffracted planes: (110). The distortion reduces electron movement. air quenched samples and of sample quenched in salt bath. magnitude of Seebeck coefficients of oil cooled and water cooled samples are lower than those of other samples. The reduction of the magnitude of Seebeck coefficient may be due to phase change and lattice distortion. furnace cooled. magnitude of Seebeck coefficient decreases.The 3rd Thailand Metallurgy Conference Figure 2 also demonstrates dependent of Seebeck coefficient on quenching media or cooling rate. The effect of cooling rate on Seebeck coefficient may be explained by crystal structure and microstructure as discussed later. From these figures. The shift of the peak indicates that crystal structures of the oil and water quenched sample are different from the other samples and the broader peaks indicates occurrence of lattice distortion during fast cooling.g. When cooling rate is high. crystal structures of quenched samples can be sorted into two groups: 1) samples quenched at low and moderate cooling rate and 2) samples quenched at high cooling rate. As shown in figure 2. To explain variation of Seebeck coefficients of asreceived. e. When considering at (110) peak (figure 4). Consequently. magnitude of Seebeck coefficient decreases and hardness increases. depending on cooling rate. (200) and (211) peaks tend to disappear when cooling rate is high. (110) peaks of water-quenched and oil quenched samples are shifted from those of the other samples. crystal structure is not only a factor affecting Seebeck coefficient. The 3rd Thailand Metallurgy Conference Figure 3: X-ray diffraction pattern of as received sample and quenched samples AF‐05 . The 3rd Thailand Metallurgy Conference Figure 4: [110] peak of as received sample and quenched samples Microstructure Microstructure of each sample was shown in figure 5. AF‐05 . rather than the effect of structure distortion. microstructures of oil quenched and water quench sample are martensite with some ferrite. magnitudes of Seebeck coefficients of oil quenched and water quenched samples are reduced by the existing dislocation. Therefore. it also impedes electron transport. From this figure. It is well known that dislocation density of sample quenched with high cooling rate is very high. As a result. The dislocation not only increases hardness. hardness of these samples is high. The 3rd Thailand Metallurgy Conference (a) (b) (c) (d) (e) (f) Figure 5: Microstructures of samples: a) as received. c) air. and heat-treated sample with different quenching media: b) furnace. d) saltbath. e) oil and f) water at magnification of 500x AF‐05 . Seebeck coefficient data and XRD result also point out that although crystal structures of as-received sample and of samples quenched in air and salt bath are the same. However. Unlike microstructure of furnace cooled sample. Although microstructure of furnace cooled sample is different from those of as-received and air quenched sample. The reason may be because the phases (ferrite and cementite) present in these samples are the same.The 3rd Thailand Metallurgy Conference Figure 5 also points out the presence of ferrite and pearlite in samples cooled in furnace. Consequently. The increasing of magnitude of Seebeck coefficient due to increasing grain size was also found by Caballero et al [7]. cementite in as-received. Theoretically. air cooled and salt bath cooled samples disperses all over microstructure. The higher magnitude of Seebeck coefficient may be due to larger grain size. microstructure of these samples consists of ferrite and cementite. this is not conclusive and more investigation is needed. magnitude of Seebeck coefficient of sample quenched in salt bath is higher than those of the other samples. their Seebeck coefficients are not significantly different. grain boundary behaves as an obstacle for electrical transport. For as-received sample and samples cooled in air and salt bath. the ferrite and cementite of these samples are not lies in lamellar order as illustrated in figure 6. In addition. hardness of these samples is higher than that of furnace cooled sample. AF‐05 . The nonlamellar array of ferrite and cementite is classified as bainite [9]. The 3rd Thailand Metallurgy Conference (a) (b) Figure 6: Microstructures of samples cooled in a) furnace cooled and b) salt bath at magnification of 1000x AF‐05 . Plenum Press. C. 18891897 (5) Lavaire. L..F. AISI 4150..materials.. 337 (9) Krauss G..L. 50. (7) Caballero. Acta Materialia. N. J. 1997. explanation of Seebeck coefficient by microstructure is more complicate. U. 1996. 310 (3) Kasap. R. N. New York. 1976. 1435-1439. “Study of Ageing in Strained Ultra and Extra Low Carbon Steels by Thermoelectric Power Measurement”.. C. were studied. and Merlin. J. Although Seebeck coefficient depends on crystal structure and microstructure. and Borrelly. and Sardoy. Scripta Materialia.. Schroeder P. The Theory of the Properties of Metals and Alloys. “Comparison of the Evaluation of the Carbon Content in Solid Solution in Extra-mild Steels by Thermoelectric Power and by Internal Friction”.S. V...usask.. “Thermoelectric power studies on a martensitic stainless steel”. Scripta Materialia.A. 50. and Greig D. 553-559. Mott and Jones H.. Steel: Heat Treatment and Processing Principles. Hardness of these steels can be explained directly by their microstructures.. Available : http://www. Lavaire. Foiles C. 2004.. S.78 AF‐05 .. A. 1969. 18.pdf [September 9.. Magnitude of Seebeck coefficient of quenched samples is influenced by phases present in sample and grain size. M.V. V.. Scripta Materialia. References (1) Blatt F. ASM international. (6) Massardier. Merlin.L.F. 1990. Ohio. 45..ca/samples/Thermoelectric-Seebeck..The 3rd Thailand Metallurgy Conference Conclusions Seebeck coefficients and hardness of quenched low alloy steels.G. 44. 2004. 1936.. Physics. Dover Inc. Thermoelectric Power of Metals. Soler. Thermoelectric Effects in Metals: Thermocouples [Online]. 1061-1066. Capdevila. New York (2) N. and García de Andrés. Adv. 2009] (4) Brahmi. “Study of Aluminium Nitride Precipitation in Pure Fe-Al-N Alloy by Thermoelectric Power Measurements”. 2001. Alvarez. (8) Vedernikov M. hardness of samples cannot be directly related to Seebeck coefficient. In contrast. pp. F.J. Pathumthani. and ACM sensors. To apply the ACM sensors in Thailand. BF‐04 . Chonburi. and airborne sea salt of specific location. Thailand.or. To estimate the corrosion rate.th b National Institute for Materials Science. Ibaraki. representing urban. JAPAN Tel: +81-298-59-2604 Fax: +81-298-59-2601 Abstract Atmospheric corrosion of metal depends on material compositions. With ACM sensors. we performed exposure tests of carbon steel (JIS SS400) along with ACM sensors under outdoor and sheltered conditions at three locations: (1) Rama VI Road. and marine environments. has been developed and used to sense the corrosivity in terms of galvanic current. Weather data were obtained from temperature.The 3rd Thailand Metallurgy Conference Corrosion Assessment of Carbon Steel in Thailand by Atmospheric Corrosion Monitoring (ACM) Sensors Wanida Pongsaksawada. it is possible to monitor the corrosion rate in a shorter time than the exposure test. In Japan. and urban environments. airport. Average monthly weight loss ranks from high to low as marine. Tel. The relationship between outdoor corrosion rate and ACM output is found to be linear on a log-log scale at airport and urban test stations during March 2008 – May 2009. atmospheric corrosion monitoring (ACM) sensor. Samutprakarn and (3) Royal Thai Navy Dockyard. dew. weight loss measurements were carried out on specimens exposed for 1 month period over 2 years. In this research during June 2007 – May 2009. and rain period). respectively. Sikharin Sorachota. airport.: 0-2564-6500 Fax: 0-2564-6338 Email: wanidap@mtec. Under some atmospheric conditions. temperature. weather condition (dry. made of an iron-silver galvanic couple. relative humidity. Ekkarut Viyanita. Bangkok (2) Suvarnabhumi International Airport. it is necessary to evaluate the effectiveness and correlation between the actual corrosion rate and the sensor output. and Tadashi Shinoharab a National Metal and Materials Technology Center (MTEC). these data can be converted to time of wetness and related to the corrosion rate of carbon steel. relative humidity. General testing procedure to obtain the corrosion rate is by actual exposure test of the specimen panels based on time interval plan. To accelerate the experimental study. Shitanda et al. (2009)). (2005). Linear relationship between outdoor corrosion rate and sensor galvanic current output was found at severe marine and rural/marine environments in Japan (Shinohara et al. Another electrochemical measurement by atmospheric corrosion monitoring (ACM) sensor relates galvanic current with corrosion rate. (2005)). The actual field tests usually take 10-20 years for an evaluation period. atmospheric corrosion tests had been conducted on organic-coated carbon steel by Bhamornsut et al. (2006). Tahara et al. has been developed and used to monitor the corrosivity of various atmospheric conditions in the work of Motoda et al. (2005). In Thailand. and Veleva et al. Wall et al. and temperature. The impedance and ACM sensors have been applied to monitor the corrosion in industrial plants and infrastructure. Electrochemical measurement such as AC impedance monitoring sensor has been incorporated into the atmospheric corrosion tests by Nishikata et al. Singh et al. (2005) to enhance the understanding of corrosion process and monitor quantitative parameters as a function of environmental factors. (2007). (2007). Introduction Atmospheric corrosion of metal is governed by chemical composition of thin film electrolyte on the metal surface which is dependent on air pollutants. 2. (2009). humidity. BF‐04 . (2003). The details at each site are described in Table 1. (2008). Carbon steel 1.The 3rd Thailand Metallurgy Conference Keywords Atmospheric Corrosion. (1994) and Shinohara et al. Experimental procedures Exposure test stations were selected for this field study. (2005). ACM sensor. De La Fuente et al. ACM sensor. This present research is the first to apply the ACM sensor in atmospheric corrosion study of structural steel in Thailand. (2006)). and stainless steel by Daopiset et al. simulated wet-dry cyclic tests have been performed for qualitative observation (Han et al. In Japan. zinc by Phantor et al. (2003). and the corrosion resistance of different materials (Chen et al. (2008). Weight losses and sensor outputs were evaluated. (2007) and Katayama et al. Corrosion scientists in several countries have been carried out exposure tests to investigate the effects of the environment on corrosion rates (Pourbiax (1982). made of Fe-Ag galvanic couple. The exposure tests of the test panels as well as the ACM sensors were carried out from June 2007 – May 2009 at three different environmental conditions. Sun et al. Two specimens were cleaned according to ASTM G01 to remove corrosion products. An ACM type corrosion sensor was installed on each test rack and connected to a data logger (Syrinx Inc. The tests were repeated for 24-month period. airport. during some months in rainy season. specimen panels and data were collected for analyses. Annual results were fitted to a multiple linear regression model as a function of environmental parameters. and urban atmosphere or in the increasing distance from the sea shore as expected. The sheltered environments are typically less corrosive than open air condition as seen by smaller magnitude of average corrosion losses.The 3rd Thailand Metallurgy Conference Table 1 Structural steel plates (JIS SS400) were cut into rectangular coupons with dimension of 150mm x 70mm x 6mm. and relative humidity (RH) were recorded in a memory card every 10 minutes. Figure 1 3. The initial weights of the samples were recorded. However. and mechanical polishing. Corrosivity ranks from high to low as marine. Monthly results were related to the sensor data to evaluate correlation with ACM sensor. the sheltered samples were more severely corroded than outdoor samples due to rain wash affect that removes corrosive species from the metal surface. Temperature and humidity sensors were installed under a cover at each location and connected to the data logger. relative humidity. sea salt and air pollutants. sandblasting. 1. the average monthly weight losses over two years are summarized in Table 2. The ACM sensors were replaced every month. The corroded sheltered specimens were influenced only by dew condensation. Picture of a test station is illustrated in Fig. The average weight loss was determined. whereas the specimens exposed outdoor were influenced by rain fall as well.). temperature. Table 2 BF‐04 . temperature (T). Exposure tests were carried out in open-air (outdoor) and under shelter (indoor) conditions for 1 and 12 months. (2009)). After the test. With additional data from December 2008 – May 2009. Results and discussion Short – term exposure test Monthly results from June 2007 – November 2008 were reported in the previous work (Pongsaksawad et al. Electrical current (Q). Blue oxide scales were removed by HCl acid. 028 Train [h/ y] (3) BF‐04 . two sets of one – year exposure tests were carried out at each test station during June 2007 to May 2009. Generally. For sheltered condition.850 T [°C ] + 0. the ACM sensors could be used to estimate the atmospheric corrosion rate in severe marine and rural/marine conditions. Table 3 Based on our one – year exposure test data shown in Table 3. Further study by using a long life ACM sensor is under consideration. the best correlation suggests that the outdoor corrosion rate (CR) is a function of temperature. In case of outdoor environment. one –year exposure tests are conducted and repeated to obtain reliable sampling data. where is 0. the relationship between corrosion rate and effective sensor output for urban site has a strong positive correlation (R = 0. relative humidity.7220) was observed at urban site during March 2008 – April 2009 as shown in Fig. the current during rain period (Qrain) is much higher than dew period (Qdew). The simplest model is a multiple linear function.11. 2(b). which may require another type of ACM sensor for marine environment. (2009). but not in the mild marine atmosphere.658 (1) No correlation was found at marine and airport test sites. the corrosion rates were related to the daily average electricity (Q). Figure 2 Multiple linear regression model The conventional method to predict the corrosion rate is by finding an empirical relationship with the active environmental parameters such as in the atmospheric corrosion study of Vietnam by Hong Lien et al.165 log Q [C/day] – 0.183 log Qeff [C/day] – 1. Thailand has less temperature fluctuation and longer time of wetness. In this study. (2006)).535 RH [%] + 0.The 3rd Thailand Metallurgy Conference Correlation between corrosion rate and sensor output Corrosion rates of one – month exposure test were plotted as a function of the ACM sensors output to evaluate their relationships.7113) during March 2009 – May 2009 and follows the expression: log CRairport.9 . The average corrosion rates of each phase and other environmental parameters are reported in Table 3. The best correlation (R = 0. In the atmospheric corrosion study with this Fe-Ag type ACM sensor in Japan (Shinohara et al. urban [mmpy] = 0.056 (2) No correlation is observed for marine exposure sites. As shown in Fig. and total rain time as: CR [g/ m2 / y] = 446. Thus the effective sensor output (Qeff) is defined as Qeff =Qdew + Qrain. 2(a) as: log CRurban [mmpy] = 0.2 [Shinohara 2004]. L. Higher temperature causes the water droplet on the specimen surface to evaporate.. Suphonlai. and increasing time of rain. corrosion rate can be monitored in real time without the need to conduct a long-term field test. Nakkuntod. T. The rain wash affect is not a major contribution. The calculated corrosion rates (Eq. Tanabe. (4) The outdoor corrosion losses at marine. R. 4. For marine site. 5. References Bhamornsut. 3) were plotted against the actual values as shown in Fig.ions were not taken into account since they were not monitored during the exposure period. 3 with R = 0. Atmospheric BF‐04 . Japan. C. increasing relative humidity. airport. (2) In Thailand. Conclusions (1) The atmospheric corrosion of structural steel decreases with increasing distance from the coast (marine > airport > urban). the corrosion rate is reduced. Time of rain slightly contributes to corrosion because it also washes away the corrosive residues. 6.9733. other dependent variables such as SO2 and Cl. (3) The corrosion losses can be estimated by the ACM sensor output at airport and urban test station. and H. Acknowledgement The authors gratefully acknowledge the financial support from the National Metal and Materials Technology Center (MTEC). thereby. Thailand and the technical support from the National Institute for Materials Science (NIMS). the atmospheric corrosion of structural steel under sheltered environment is generally less corrosive than that under outdoor environment. the ACM sensor is applicable for corrosion prediction at airport and urban environments. Both relative humidity and total rain time have positive affects on corrosion rate due to increasing time of wetness. However. the multi-variable model can be applied. Chotimongkol. S. and urban atmosphere increases with decreasing temperature.The 3rd Thailand Metallurgy Conference Temperature has a negative affect on corrosion rate. Figure 3 Comparing the two correlation methods discussed above. With the use of ACM sensor. Kodama. Castano.G. Wang. H. Morcillo. A305. 47.. Itomura. November 16-21.. Masuda. Tsuru.I. Chen.Y. Motoda. Itagaki. T. M. F. (1994). BF‐04 . W. Corrosion Science. A.J. Corrosion Science 47 (2005) 2599–2606. 2003. Noda. Nishikata. K. T. Proc. of Japan Society of Corrosion Engineers Conference. Lam Hong. Corrosion Science. H. Watanabe. T. September 16-19. Proc. of the 5th Thailand Materials Science and Technology Conference. L. Katayama. Wanaosod.C. Atmospheric corrosion of stainless steels 304 and 316 with different surface finishes. P. P.Izumo. Han. Corrosion Science. De La Fuente. Corrosion monitoring of nickel-containing steels in marine atmospheric environment. Characterization of initial atmospheric corrosion carbon steels by field exposure and laboratory simulation. (2007) 1420–1436.The 3rd Thailand Metallurgy Conference Degradation of organic coatings in Thailand. (2007) 2920–2935. H. Anh Truc. Kojima. Yu. of Japan Society of Corrosion Engineers Conference. Oshikawa. Wei. Xuan Hang. 49. Japan. G. Thailand. Daopiset. W.. H. M. J. 2009. J.. Suzuki. 2008. S. M. D. Wang. T.. Y. Atmospheric corrosion of carbon steel in Vietnam: The relationship between corrosion rate and environmental parameters and the classification of atmospheric corrosivity of carbon steel. Shinohara. (2005) 2578–2588. Corrosion Science.H. 49. Shih. K. Japan. Corrosion simulation of carbon steels in atmospheric environment. T. May 22-24. Zairyo-to-Kankyo. L. Thi San and H. Suzuki.C. Z. J.. and T. Y. Oung. Proc. 43. S.Fukushima and S.. Nagasawa. Y. S. Long-term atmospheric corrosion of zinc. (2005) 10011021.. S. Tzeng. Wang. 47. Tsujikawa. L. Hong Lien. T. 550. Corrosion resistance and mechanical properties of low-alloy steels under atmospheric conditions. Tahara and Y. W. and T. A. 51. Hosoya. The Linear Bilogarithmic Law for atmospheric corrosion. Applying atmospheric corrosion monitoring sensor for carbon steel under various exposure test sites in Thailand . 2009. Okumura.The 3rd Thailand Metallurgy Conference Panther. Zheng. (1982). B 139. 2.. 2006. C. Singh. W. of the 3rd International Conference on Advanced Structural Steels. Yadav. Somboon. Watanabe. I. K. 107.D. 675-683. Shitanda. B. Hooper. S. J. F... Viyanit. (2009) 719–727.N. Q. Sensors and Actuators. Thailand. M. W.. Shinohara. (2008) 93–110. (2009) 292–297. Asano. Corrosion Science. 2003. A304.. Pongsaksawad. M.. Wiley. Sorachot. Atmospheric depositions and corrosion Impacts in Bangkok. A. Aug 22-24.. Itagaki. W. T. 50. A. Shinohara. I.. Proc. Japan. Datasheets of Atmospheric Corrosion behaviors of low alloyed steels with corrosivities at exposure test sites. Sun. Cole. February 12-14. Limpaseni. D. P. Proc. Troset. pp. Long-term atmospheric corrosion behaviour of aluminium alloys 2024 and 7075 in urban. Tahara. Vol. A. Influence of the alloy element on corrosion morphology of the low alloy steels BF‐04 . E. Proc. Y. New York. J. T. J. D. S. of Japan Society of Corrosion Engineers Conference. Veersai. Corrosion of low carbon steel in atmospheric environments of different chloride content. Phuket. S. M. May 22-24. coastal and industrial environments. Ayers. Pourbaix. Saha. Veersai. Korea. Screen-printed atmospheric corrosion monitoring sensor based on electrochemical impedance spectroscopy. G. Corrosion Science.of the 2nd Regional Conference on Energy Technology Towards a Clean Environment. Li. Wen. K. Shinohara. Wall. (2005) 17-32. Atmospheric corrosion of zinc induced by runoff. Characterizing corrosion behavior under atmospheric conditions using electrochemical techniques. E.. N.A. Veleva. Acosta. 51. Corrosion Science. 47. F. (2009) 2055–2062. 47. M. A. Corrosion Science. Martinez. Copeland.C.D.The 3rd Thailand Metallurgy Conference exposed to the atmospheric environments. R.. BF‐04 . Kilgo. M. Missert. Meraz.A. Corrosion Science. (2005) 2589– 2598.G. L. The 3rd Thailand Metallurgy Conference Table 1. Locations of exposure test sties Environment Location Description On the ground facing the Marine Sattahip Navy Dockyard, Chonburi Gulf of Thailand On the ground nearby the Airport Suvarnabhumi International Airport, Samutprakarn runway and industrial district On the roof top of a 7‐ story National Science and Technology Development Agency, Urban Bangkok heavy traffic building influenced by BF‐04 The 3rd Thailand Metallurgy Conference Table 2. Average monthly weight losses of outdoor and sheltered conditions Weight Loss (g/ m2) sheltered Marine June 07 – May 08 June 08 – May 09 Airport June 07 – May 08 June 08 – May 09 Urban June 07 – May 08 June 08 – May 09 46.476 44.535 39.452 37.793 28.280 30.867 outdoor 57.786 55.614 56.333 48.472 38.286 46.567 Location Phase BF‐04 The 3rd Thailand Metallurgy Conference Table 3. Corrosion rate of one- year exposure test and environmental parameters: CR [g/ m2 / y] 137.381 167.857 n/a 165.238 110.238 99.048 temperature (T), relative humidity (RH), and time of rain (Train). Site Marine Airport Urban Phase June 07 – May 08 June 08 – May 09 June 07 – May 08 June 08 – May 09 June 07 – May 08 June 08 – May 09 T [°C] 29.187 28.305 29.302 28.761 31.7668 32.490 RH [%] 66.010 55.079 58.140 48.594 55.807 40.281 Train [h/ y] 269.833 1089.667 975.833 802.167 524.167 428.667 BF‐04 The 3rd Thailand Metallurgy Conference ACM sensor Figure 1 ACM sensor and structural steel coupon on an outdoor test rack BF‐04 . The 3rd Thailand Metallurgy Conference (a) Urban sheltered environment (b) Airport and urban outdoor environment Figure 2 Linear correlations between monthly corrosion rate and effective sensor output were found at (a) urban sheltered condition (March 2008 – April 2009) and (b) airport and urban outdoor condition (March 2008 – May 2009). BF‐04 . 9474 R = 0.9733 2 200 250 Actual CR [g/ m / y] Figure 3 Calculated values compared to the actual values BF‐04 .The 3rd Thailand Metallurgy Conference 250 Calculated CR [g/ m / y] 200 150 100 50 0 0 50 100 150 2 2 R = 0. It was found that pickling efficiency in the first step directly affects the surface qualities of the final pickled sample. Homjaboka. 3191 Road. Faculty of Engineering. 324 Moo 8. The pickling mechanism of HCl and H2SO4 was discussed based on weight loss and the pickled surface qualities. Chulalongkorn University. This resulted in high remaining oxide scale and intergranular attack at the Cr-depleted layer. Bangkok 10330.L@chula. Rayong 21180. G. significantly improves the pickling efficiency of HCl.com. AISI 304 Stainless steel BF‐06 .th b Thainox Stainless Public Company Limited. Hydrochloric acid. Keywords: Pickling. which is a strong oxidizing agent. Scale. Thailand Email: whomjabok@yahoo. used to remove oxide scales. Increasing of HCl concentration and electrolytic current were not enough to improve its pickling efficiency. Nikom Pattana. S. Thailand Abstract Oxide scales are formed on AISI 304 stainless steel surface during high temperature processing as well as a Cr-depleted layer. Permpoonb. Pickling is an important process that includes mechanical and chemical operations. the multi-step pickling of AISI 304 stainless steel in HCl solution was investigated instead of H2SO4 solution for the first step of pickling. Highway no. Tambol Mabkha. Patumwan. which grows between the oxide scale and base metal. which cannot be completely removed in the second pickling step. HF+HNO3 mixed acid is traditionally used in the second step. A smooth surface without any oxide scale and free of intergranular attack can be obtained. Lothongkuma a Department of Metallurgical Engineering. In this study. The multi-step pickling is commonly used because of its higher efficiency than a single step pickling. The addition of small amount H2O2. Gobboon. HCl solution showed much lower pickling efficiency than H2SO4 solution.The 3rd Thailand Metallurgy Conference Pickling Behavior of AISI 304 Stainless Steel in Sulfuric and Hydrochloric Acid Solutions W.ac. Cr-depleted layer and to recover the surface passivity. Oxide scale and Cr-depleted layer are formed during high temperature processing. H2SO4 pickling causes black smut forming. The acid type and concentration has strong influence on surface finish quality. so that.1. In this step. Even though black smut can be removed by HNO3+HF in the next step. HNO3+HF has become widely accepted and used for removal remaining oxide scale and passivation [8]. the multi-step pickling behavior of AISI 304 austenitic stainless steel in HCl solution was experimented for replacing H2SO4 solution in the first step and the HNO3+HF mixed acid solution was used traditionally in the second step. Results were discussed based on weight loss and surface finish of the pickled samples. However. After mechanical descaling process.The 3rd Thailand Metallurgy Conference 1. The sequence at which the pickling steps are used influences the surface finish significantly. only unexposed area was painted with EPIGEN XD005 (acid-resistant at high temperature). but the surface finish has high roughness and intergranular attack. Multi-step pickling is used for pickling process because it has higher efficiency and better surface quality than single step [6-7]. test samples of 25x50x3 mm were cut. Material AISI 304 austenitic stainless steel strips were hot-rolled downs to a thickness of 3 mm. In mechanical descaling. HCl pickling has a uniform dissolution behavior with no intergranular attack [8-10]. In the second step. In this study. In the first step. Introduction Acid pickling is an important step for production of cold rolled stainless steel plate. The test samples were finally dried with air and kept in a desiccator before experiment. BF‐06 . It is aimed to remove the oxide scale as well as a Cr-depleted layer growing between the oxide scale and the base material. H2SO4 with electrolytic is general used for the first step. and clean with acetone and ethanol. Then. Experimental 2. Removing oxide scale processes consist of mechanical descaling and pickling. electrolytic was used for increase pickling efficiency [8]. H2SO4 is a cheap acid and has a good pickling efficiency. scale breaker and shot blasting were used to break up the oxide scale. This results in easily penetration of pickling solution into oxide scale and enhances the pickling efficiency [1-5]. 2. the mechanism is that the solution penetrates into metal Cr-depleted layer and the oxide scale is undercut and removed [6]. which can be improved by using with electrolytic. The chemical composition of this material is listed in Table 1. During pickling.03 1.0. Fig. Optical microscope (OM) at 200X and scanning electron microscopy (SEM) at 3000X were used for remaining oxide level analysis. BF‐06 . analyzed by OES Element C Cr Ni Mn Content 0.04 18. Characterization The surface finish was characterized with roughness profiler (Telescan 150) for surface roughness.2.0.0.029 0.0. H2SO4.0 M at 60°C or 85 °C depending on the purposed tests.3. 2. 2. HF and HNO3 electrolytes. 4.001 Balanced 2. After pickling. Fig.1Remaining oxide evaluation after the in house standard on 6 areas observation on test sample surface at 200X. 5. analytical grade was used.The 3rd Thailand Metallurgy Conference Table.1 Chemical composition (wt.076 Element Si P S Fe Content 0.0 and 6.%) of AISI 304 stainless steel used in this study. temperature was controlled constantly in a water bath with constant stirring. the samples were rinsed with tap water and brush for removal any reaction products. 3. The pickling conditions were acid concentration of 1.1 8.342 0. Pickling To prepare the HCl. Purity 50%H2O2 was used in this study.1 showed the evaluation of remaining oxide on sample surface after the in-house standard. Fig.3 Total weight loss of multi-step pickling of AISI 304 stainless steel in H2SO4 at 85°C or HCl at 85°C followed by HNO3+HF at 45°C. 3. 4a. The weight loss of H2SO4 condition was high but some oxide scale remains on pickled surface in level 2 as shown in Fig. The traditional and studied conditions for this experiment were showed in Fig.2 Multi-step pickling of AISI 304 stainless steel between the traditional and studied conditions. Fig. 2. 2) was shown in Fig. 3 and 4b. BF‐06 . HF+HNO3 mixed acid solution was still traditionally used in the second step. The total weight loss resulting from those multi-step pickling conditions (Fig.The 3rd Thailand Metallurgy Conference 3. Results and discussion HCl solution was investigated instead of H2SO4 solution for the first step of pickling. Pickling by H2SO4 solution with electrolytic followed by HNO3+HF solution increased the weight loss and allowed achieving a surface finish free of any oxide scale as shown in Fig. the step by step of BF‐06 .0 M HCl. Celis [9]. 85°C 4. which has a significant effect on the final surface finish after HNO3+HF pickling. 45 °C 4.30 μm Remaining oxide level 0 c followed by HNO3+HF.The 3rd Thailand Metallurgy Conference In case of HCl pickling instead of H2SO4 pickling.0 M H2SO4. 85°C d followed by HNO3+HF. 85°C followed by HNO3+HF. Increasing HCl concentration and HCl pickling with electrolytic did not result in increasing the pickling efficiency to be higher than H2SO4 pickling efficiency.34 μm Remaining oxide level 3 Roughness (Rq) = 3.51 μm Remaining oxide level 3 Fig. 4c).-F. 45 °C a 4. 4d. The result was not the same as report by L.-P. The surface finish of HCl pickling had rougher surface and more intergranular attack than H2SO4 pickling as shown in Fig. which said that uniform dissolution and no intergranular attack were observed by HCl pickling.0 M HCl (Electrolytic). it showed that HCl had lower pickling efficiency than H2SO4 (Fig.4 SEM surface characterization of AISI 304 stainless steel after multi-step pickling To understand mechanism of pickling by both HCl and H2SO4 in the first pickling step. 3) and much oxide scale remained (Fig. Li and J. 45 °C b Roughness (Rq) = 3.29 μm Remaining oxide level 2 Roughness (Rq) = 3.0 M H2SO4 (Electrolytic). 85°C followed by HNO3+HF. 4. 45 °C Roughness (Rq) = 3. Fig.5 Step by step weight loss of AISI 304 stainless steel after pickling in 4. After the second pickling step with HNO3+HF. HCl pickling had much lower weight loss than H2SO4 pickling and both samples surface were covered with oxide scale (Figs. HCl pickling had higher weight loss than H2SO4 pickling and the intergranular attack became more pronounced on surface finish (Fig. 5 and the surface was characterized by SEM as shown in Fig.The 3rd Thailand Metallurgy Conference weight loss was analyzed as shown in Fig. 6.0 M HCl at 85°C followed by HNO3+HF at 45°C BF‐06 . 6a and 6b). 6d).0 M H2SO4 at 85°C or 4. HCl pickling had smooth surface compared with H2SO4 pickling. 0 M HCl.6 SEM surface characterization of AISI 304 stainless steel after multi-step pickling with conditions same as in Fig. the oxide scale is removed by BF‐06 .0 M HCL. Cr-depleted layer and base metal.The 3rd Thailand Metallurgy Conference a 4.29 μm Remaining oxide level 3 Roughness (Rq) = 3. H2SO4 transports into oxide scale. 85°C Roughness (Rq) = 3.0 M H2SO4.0 M H2SO4.81 μm Remaining oxide level 3 Roughness (Rq) = 3. The original metal surface consists of oxide scale. On H2SO4 pickling in the first step. 45 °C d 4. 5 and 6) and discussion. 85°C followed by HNO3+HF. the Cr-depleted layer is attacked or dissoluted. Finally. Then. 7a and 7b. respectively.34 μm Remaining oxide level 3 Fig. 45 °C Roughness (Rq) = 3. 5 According to the previous results (Fig. 85°C followed by HNO3+HF. the evolution of surface during multi-step pickling in H2SO4 and HCl solutions followed by HNO3+HF can be described as in Fig. 85°C b 4.15 μm Remaining oxide level 3 c 4. HCl. a. 85°C Oxide scale Base Metal Base Metal Initial Surface Base Metal Base Metal First step Intergranular attack Base Metal Intergranular attack Base Metal Second step Fig. H2SO4. The final surface finish is completely free of oxide scale. The next step pickling by the selective dissolution of HNO3+HF. Most of all oxide scale and Cr-depleted layer still remain. From the result.The 3rd Thailand Metallurgy Conference undercutting. intergranular attack appears because of a selective dissolution on remaining Cr-depleted layer. Remaining oxide scale and Cr-depleted layer are almost removed. The surface is rough because H2SO4 pickling behavior is non-uniform dissolution. The same mechanism as H2SO4 is obtained. Most oxide scale but only some Cr-depleted layer is removed. 85°C Oxide scale Cr-depleted layer b. The observed surface is smooth because HCl pickling behavior is uniform dissolution. By HNO3+HF pickling in the second step. when a high enough pickling efficiency with uniform dissolution in the first step is available. However. 7b. increasing of HCl concentration and electrolytic currents were not enough to BF‐06 .7 The multi-step pickling mechanism models of intergranular attack. Multistep pickling will successively allow achieving a smooth surface finish free of any oxide scale. the most important finding is that the surface finish obtained from multi-step pickling is greatly affected by the pickling efficiency of the first step. HCl has lower pickling efficiency than H2SO4. According to the mechanism. The evolution of surface finish after pickling in HCl followed by a pickling in HNO3+HF is showed in Fig. intergranular attack appears. The temperature for this study must be fixed at 60°C because H2O2 decomposes at temperature over than 60°C. The addition of H2O2. It allowed achieving a higher pickling efficiency than H2SO4 efficiency. 9. . and no intergranular attack BF‐06 . 8. Addition of H2O2 to improve pickling efficiency of HCl in the first step resulted in increasing weight loss and having an affect on the second step pickling by HNO3+HF by decreasing weight loss. as shown in Fig.8 Step by step weight loss of AISI 304 stainless steel by pickling with HCl at 60°C or HCl+H2O2 at 60°C or H2SO4 (Electrolytic) at 85°C followed by HNO3+HF at 45°C. possibly improved the pickling efficiency of HCl. smooth surface finish free of oxide scale. Multi-step pickling was successive at 10g/L H2O2 added to HCl solution.The 3rd Thailand Metallurgy Conference improve its pickling efficiency to be more than the H2SO4 efficiency. It also reduced intergranular attack and delivered smooth surface finish as shown in Fig. Fig. which is a strong oxidizing agent. 1.0 M HCl+10g/L H2O2.9 SEM surface characterization of AISI 304 stainless steel after pickling in H2SO4. HCl solution has lower pickling efficiency than H2SO4 solution.The 3rd Thailand Metallurgy Conference a 4.92 μm Remaining oxide level 0 Roughness (Rq) = 2. BF‐06 . 60°C followed by HNO3+HF. HCl. 45 °C Roughness (Rq) = 3.24 μm Remaining oxide level 3 c 4. HCl + H2O2 solutions followed by HNO3+HF at 45°C 4. Conclusions The multi-step pickling of AISI 304 stainless steel in HCl solution as the first step followed by HNO3+HF as the second step was investigated. The mechanism models of pickling by HCl or H2SO4 in the first step were proposed. 60°C followed by HNO3+HF.0 M H2SO4 (Electrolic). The following conclusions can be drawn from this study. 60°C followed by HNO3+HF.0 M HCl.0 M HCl+10g/L H2O2. 45 °C b 4.30 μm Remaining oxide level 0 Roughness (Rq) = 3. 45 °C d 4. 45 °C Roughness (Rq) = 2. 85°C followed by HNO3+HF.95 μm Remaining oxide level 0 Fig. 2007. discussion and analysis equipment. Prentice Hall International.The 3rd Thailand Metallurgy Conference 2. ferrous and ferric ion contents on pickling behavior of AISI 304 stainless steel. P.. [6] L.1324. 2008. B. Les Editions de Physique Les Ulis. [7] L.-F. Issue 10. Beranger. Li and J. BF‐06 . 804-810. Celis. Li. Li. 1997. temperature. Corrosion Science. Internal review report Alz-Arcelor France. Chulalongkorn University. Jones. pp. Singapore. 1993. [2] Stainless Steel. Pickling of Austenitic Stainless Steels.-F.-F. 1307. 3. 2004. G. Scripta Materialia.-P. 3rd edition. pp. The thanks also go to the Thailand Research Fund (TRF) and the Office of Small and Medium Enterprises Promotion (OSMEP) for the research fund. Celis. Volume 51. C. 6. Vaes. [8] L. D. Master Thesis in Metallurgical Engineering. HCl solution can not completely remove Cr-depleted layer and oxide scale. 949-953. Daerden. pp. McGraw-Hill International Editions. Materials Science and Engineering Series. M.-F. Meers. 1st edition. References [1] Lacombe. 5. Inc. Acknowledgement The authors would like to thank the Research and Development Center of Thainox Stainless Public Company Limited for test samples. [5] Suwaree Ratanamongkolthaworn. Corrosion Science. Effects of sulfuric acid concentration. Celis. Principles and Prevention of Corrosion. H2O2 addition can improve pickling efficiency of HCl solution.-P. Li and J. Corrosion Engineering. 2002. Intergranular corrosion of 304 stainless steel pickled in acidic electrolytes. [3] Mars G. Mechanism of Single and Multiple Step Pickling of 304 Stainless Steel in Acid Electrolytes. Caenen. Volume 50. Fontana. Stainless Steel. Baroux and G. 2nd edition. Volume 47. [4] Denny A. The addition of 10g/L H2O2 is enough to deliver the smooth surface without any oxide scale and free of intergranular attack after HNO3+HF pickling. 2005. Dhondt. ASM Specialty Handbook.-P. and J. Singapore. France. 1996. 1987. Effect of hydrochloric acid on pickling of hot-rolled 304 stainless steel in iron chloride-based electrolytes. [9] L. Internal review report Alz-Arcelor France. Li. 2002.The 3rd Thailand Metallurgy Conference [10] L.-F. BF‐06 . Pickling and re-pickling of stainless steel with UGCO and UG3P+H2SO4 electrolytes. Conventional fusion welding of SSM aluminum die casting alloys is generally difficult due to the formation of blowholes in weld. In addition. Welding parameter. It was clear that the joint between cast Al alloy has increasingly expanded in the usage of casting component in automotive such as suspension. Therefore. Faculty of Engineering. Rheo casting is one of them. the joints were made by using a fixed rotating speed of 1. b Department of Mining and Materials Engineering. Prince of Songkla University. In this work. Furthermore. It involves the preparation of semi-solid metal (SSM) slurry from liquid alloys and casting the slurry into a die for component manufacturing. Hatyai. Thermo-mechanical affected zone. Two different types of tool pins. semi solid metal was obtained from a new Rheo casting technique called Gas Induced semi-solid (GISS) [1].750 rpm. Songkla. Introduction There are two types of semi-solid forming technology at the present. The Scanning electron microscope (SEM) reveals fine microstructure and uniform dispersion of Si (Silicon) particles obtained from cylindrical pin than that of square pin. cylindrical and square pin. friction stir CF‐03 . the joint made from 1. In recent year. Transverse and longitudinal tensile strengths obtained from cylindrical pin are greater than square pin. 160 mm/min with cylindrical pin shows highest strength. Key words : Semi-solid metal A356. In this work. a new welding method is required to overcome theses problems. the microstructure is also altered. Stir zone 1.co. In addition.th Abstract The effect of joining parameters and tool pin profile on microstructure and mechanical properties of semi-solid metal A356 joints produced by friction stir welding was investigated. were applied.The 3rd Thailand Metallurgy Conference The Effect of Welding Speed and Tool Pin Profile on Metallurgical and Mechanical Properties of Joining of Semi-Solid (SSM) Aluminium Alloy A356 by Friction Stir Welding Process (FSW) Thongchai Kruepue a and Prapas Muangjunbureeb a.750 rpm with varying welding speed of 80. 90112 Thailand Tel: 074 287323 Fax: 074 212897 E-mail : Kruepue@Yahoo. 120 and 160 mm/min. driveline and engine parts. The friction stir welding (FSW) has many welding parameters.1 (Thomas : TWI). with Keller’s reagent. In this study. The shoulder of the tool was 20 mm/min. were applied. such as tool rotating speed.750 rpm of tool rotating speed and 30 of tool angle. a tool with a cylindrical pin and a tool with a square pins. Experimental The material used in this study was SSM (Semi-Solid Metal) A356 Al alloy 100 mm in length. the two different tool pin profiles as shown in Fig. only a limited number of studies have been carried out on SSM cast aluminum alloys.2 mm. welding speed and the angle of the tool. which were tightly fixed at the backing plate. Some of the necessary photographs were taken by optical microscopy (OM). scanning CF‐03 . only the welding speed was changed from 80. In this work. were traveled.1 Showing the friction stir welding 2. 120 and 160 mm/min. Fig. However. The aim of this work is to evaluate the effect of joining parameters on the microstructure and mechanical properties of the welded SSM A356 alloys in as cast condition. The welding tool was rotated in the clockwise direction and specimens. polished and etched. The length of the pin was 3. The chemical composition is listed in Table 1. The test pieces were cut in the cross-section direction. This process is effective for the welding of aluminum alloys. Other parameters were fixed at 1. ground. 2. 50 mm in width and 4 mm in thickness.The 3rd Thailand Metallurgy Conference welding (FSW) was developed as a solid state joining process in which materials are joined by the frictional heat as shown in Fig. and the diameter of the pin was 5 mm. 57 Cu 0.05 Cr 0. Cylindrical Square Fig.2 showing two different tool pin profiles Fig. The tensile test was carried out at room temperature using an Instron-type testing machine with cross-head speed of 1.01 Ti 0.3 Locations of the test specimens (A) Discard.74 Fe 0. Two kinds of tensile test specimens were prepared from the welded specimens. The Vickers hardness profile of the weld zone was measured on a cross-section and perpendicular to the welding direction using a Vickers indenter with a 100 gf load for 10 s and 0.The 3rd Thailand Metallurgy Conference electron microscope (SEM) with energy dispersive x-ray analysis (EDX) examinations. The shapes and location of the specimens for test are shown in Fig.%) Metal A356 Si 7.05 Mn 0.02 Ni 0.01 Al Bal.3.6 mm distance from welding center. (B) Microstructure. One is transverse to the weld zone and the other is longitudinal to the weld zone.32 Zn 0.06 Mg 0.67x10-2 mm s-1. (C) Tensile test and (D) Microstructure and Hardness test CF‐03 . Table 1 chemical composition of SSM A356 Al alloy (wt. However. for the cylindrical pin. zone 2 is the heat generation decreases from the stop downforce about 20 s. However. CF‐03 . 4 (a). Results and discussion 3. Therefore. that the welding temperatures during FSW decrease in the high welding speed. (a) The temperature of cylindrical pin (b) The temperature of quare pin Fig.The 3rd Thailand Metallurgy Conference 3.4 showing the temperature generation results of the friction stir welding 3. the welding flash appears at the retreating side of the weld zone where the direction of the tool rotation moves oppositely to the travel direction for every condition.5 shows the surface appearance of the friction stir welded sample obtained from cylindrical and square tool pins with various welding speeds at 1750 rpm. It demonstrate. The top surface of the joints indicate smooth surface particularly for the higher welding speeds. and zone 3 is the heat generation increases from the welding speed. the frictional area between the tool pin and the welding material is higher than that of the square pin [7]. the temperature for three welding speeds of cylindrical pin is higher than that of the square pin. On the top surface. (b).. The temperature results of FSW joints are shown in Fig.1 Effect of the temperature of friction stir welding The geometry of the tools pin affects the heat generation and the flow of the plastic material. the welding temperatures are almost the same for two tool types.2 Effect of the pin geometry on the weld surface appearance of the FSW Fig. Zone 1 is the heat generation increases from the downforce about 28 s. 6 (a)-(f). There were no voids. Free-defect joint can be obtained using two different tool pin profiles. An elliptical stir zone with an onion ring structure was generated for the cylindrical pin. cracks or other weld defects.The 3rd Thailand Metallurgy Conference 10 mm 10 mm (a) 80 mm/min (d) 80 mm/min 10 mm 10 mm (b) 120 mm/min (e) 120 mm/min 10 mm 10 mm (c) 160 mm/min (f) 160 mm/min Fig. just as shown in Fig. shaped band structure appeared to dominate the advancing side without appearing on the retreating side. However. R TMAZ SZ TMAZ A BM 1 mm R TMAZ SZ TMAZ A BM 1 mm (a) 80 mm/min (d) 80 mm/min 1 mm 1 mm (b) 120 mm/min (e) 120 mm/min 1 mm 1 mm (c) 160 mm/min (f) 160 mm/min CF‐03 . 5 showing the photos of weld surface appearance 3. There was a macroscopically visible banded structure for the square pin. 6 illustrates the macro cross-section photos of the welded joints.3 Effect of the tools pin geometry on the macro cross-section of the FSW Fig. (TMAZ) thermal-mechanical affected zone.The 3rd Thailand Metallurgy Conference Fig. (R) retreating. 6 Macro cross-section of the welded joint. (A) advancing 3. (SZ) stir zone.4 Microstructure of joint (a) Base metal of SSM A356 Al alloy (b) R-TMAZ of cylindrical pin (c) A-TMAZ of cylindrical pin CF‐03 . 7 Optical microstructure of the welded joint. (SZ) Stir zone. 7 (a) is composed of primary α phase (white region) and Al-Si eutectic structure (black region). are distributed partially in the primary α phase and CF‐03 . (R) Retreating. which are divided into the (b. The TMAZ of cylindical pin and the square pin from Fig.4. cracks or other welded defects can be observed.The 3rd Thailand Metallurgy Conference (d) R-TMAZ of square pin (e) A-TMAZ of square pin (f) SZ of cylindrical pin (g) SZ of square pin Fig.4. The slightly elongated grain structures or tention similar and a wider range of deformed structures are observed at the A-TMAZ.2 SEM microstructure of FSW The microstructure of the BM from Fig. 8 (a) is composed of primary α phase and Si particles structure (Elongated plate). d) R-TMAZ and the (c. There are no voids. 3. (A) Advancing 3. e) A-TMAZ is depending on the different microstructures at each zone. (TMAZ) Thermal-mechanical affected zone. The compression similar grain structures and a narrow range of deformed structures are observed at the R-TMAZ. 7 are formed besides the SZ. The spheroidal grain structure disappeared and finer Si particles are dispersed over the whole stir zone.1 Optical microstructure of FSW The spheroidal grain microstructure of the BM from Fig. The sharp transition between the BM and the SZ is observed in the retreating side. The microstructure of the SZ is very different from that of the BM. and goes around the pin. (a) Base metal of SSM A356 Al alloy (b) R-TMAZ of cylindrical pin (c) A-TMAZ of cylindrical pin (d) R-TMAZ of square pin (e) A-TMAZ of square pin CF‐03 . The material transports from the advanced side to the retreated side. The TMAZ of cylindical pin and the square pin from Fig. d) R-TMAZ and the (c. which are divided into the (b. e) A-TMAZ which depend on the different microstructures. 11]. the finer Si particles are homogeneously dispersed in the SZ of the cylindrica pin than the square pin and the plate-like particles disappear. This is due to the cylindrical pin generates higher friction than that of the square pin.The 3rd Thailand Metallurgy Conference formed eutectic structure. However. The smaller Si particles structures are observed for the R-TMAZ and A-TMAZ of the cylindrical pin. 8 are formed besides the SZ. back to the advanced side. The plate-like Si particles may be broken into slightly finer particles by the stirring of the welding tool [6. More heat input can improve the flow of the plastic material. The 3rd Thailand Metallurgy Conference (f) SZ of cylindrical pin (g) SZ of square pin Fig. CF‐03 . (R) Retreating. 9 Showing the tensile strength of the transverse direction with various welding speeds.22 190. (A) Advancing 3. (TMAZ) Thermal-mechanical affected zone.89 Base Base Base 143.73 173.85 193.61 Square Failuer locatio n Weld Weld Base Fig.8 shows the SEM microstructure of the welded joint.5 Effect of the pin geometry on the tensile strength Table 2 Tensile test results from transverse direction Tensile test (MPa) Welding speed (mm/min) Cylindrical Failuer locatio n 80 120 160 176.23 171. (SZ) Stir zone. the cylindrical pin indicates higher transverse tensile strength. This is because the finer Si particles are homogeneously dispersed in the SZ of the cylindrical pin than that of the square pin. However. This is because the finer Si particles are homogeneously dispersed in the SZ of the cylindrical pin than that of the square pin. 10 Showing the tensile strength of the longitudinal direction with various welding speeds. for each welding speed. the cylindrical pin indicates higher transverse tensile strength.83 193. 3. In comparison. Table 3 Tensile test results from longitudinal direction Welding speed (mm/min) 80 120 160 Tensile test (MPa) Cylindrical 172. for each welding speed. The tensile strength of the joints increases with the welding speed increases for two different tools pin.1 The transverse tensile strength of the FSW Table 2 and Fig. the longitudinal tensile strength are higher than transverse tensile strength in each parameter for both tool pins.5. However.57 190. The tensile strength of the joints increases with the welding speed increases for two different tools pin.67 Fig. 9 Show the transverse tensile strength of the friction stir welding.5. The highest tensile strength of the joints was obtained from the cylindrical pin.2 The longitudinal tensile strength of the FSW Table 3 and Fig. 10 Show the longitudinal tensile strength of the friction stir welding.67 179.23 Square 170.79 222. The highest tensile strength of the joints was obtained from the cylindrical pin.The 3rd Thailand Metallurgy Conference 3. CF‐03 . The 3rd Thailand Metallurgy Conference 4. Thailand. The temperatures for three welding speeds of cylindrical pin are higher than the square pin. cracks or other weld defects. the authors would like to thank Department of Mining and Materials Engineering. (3) The finer Si particles are homogeneously dispersed in the SZ of the cylindrical pin than that of the square pin. It demonstrates that the welding temperatures during FSW decrease in the high welding speed. Acknowledgments This work was financially supperted by TRF. Songkla. Hatyai. There were no voids. Prince of Songkla University. (2) Free-defect joint can be obtained using two different tool pin profiles. The highest tensile strength of the joints was obtained from 160 mm/min welding speed of the cylindrical pin. Conclusions (1) The geometry of the tools pin affects the heat generation. CF‐03 . (4) The transverse and longitudinal tensile strengths of the joints increase with the welding speed increases for two different tools pin. Faculty of Engineering. In addition. et al... Ma. et al. (2005) “Effect of tool shape on mechanical properties and of friction stir welded aluminum alloys” microstructure [8] Z. et al. Akhter.. PP.L. (2003) “The improvement of mechanical properties of friction-stirwelded A356 Al alloy” Material Science and Engineering A356 (2003) pp.G. vols 116-117. (2006) “Effect of Welding parameter on Microstructure in stir zone of FSW joints of Aluminum die casting alloy” Material Science and Engineering A 415 (2006) 250-254 [10] K. et al. Elangovan et al. Santella . 154159 [7] Hidetoshi Fujii et al... (2006) “Effect of pre/post T6 heat treatment on the mechanical properties of laser welded SSM cast A356 aluminium alloy”. et al. (2006) “Effect of friction stir processing on the microstructure of cast A356 aluminum” [9] Y.) 2007( “Influences of tool pin profile and welding speed on the formation of friction stir processing zone in AA2219 aluminium alloy” [11] M.176 [3] Yeong-Maw Hwang. (2005) “The influence of pin geometry on bonding and mechanical properties in friction stir weld 2014 Al alloy ” [5] K. Wannasin “Development of a Novel Semi-Solid Metal Processing Technique for Aluminium Casting Applications” [2] R.) 2005( “Effects of friction stir processing on mechanical properties of the cast aluminum alloys A319 and A356” Scripta Material 53 (2005) 201206 CF‐03 . Kumar (2007) “The role of friction stir welding tool on material flow and weld formation” A 485 (2008) 367–374 [6] W.B...Y. Lee et al. (2007) “Experimental study on temperature distributions within the workpiece during friction stir welding of aluminum alloys” [4] Yan-hua..The 3rd Thailand Metallurgy Conference References [1] J. Kim.173. including cast and wrought alloys. Burapa. the effects of rheocasting temperatures and rheocasting times on the resulting slurry temperature and microstructure of A356 aluminum alloy were investigated.The 3rd Thailand Metallurgy Conference Rheocasting of aluminum alloys by the Gas Induced Semi-Solid (GISS) process R. Songkhla. Globular structure 1. Thailand *Corresponding author. Gas Induced Semi-Solid process. Semi-solid metal. The GISS process has been successfully used in laboratory settings to process several aluminum alloys. Keywords: Aluminum alloy. Hat Yai. The consequences are oxide films and porosity defects.w@psu. Rheocasting. However. which cause several quality issues and lower the mechanical properties of the components. 90112.(1) One way to improve these problems is to apply the semisolid metal (SSM) forming technology. In this work. Janudom. it is important to determine the optimized processing conditions in order to control the resulting slurry temperature and microstructure of the alloys. Canyook. These aluminum components are mainly produced by die casting.th Abstract A new semi-solid metal processing technique has been developed to produce semi-solid slurry with more effectiveness and efficiency at lower costs for the rheocasting process. Prince of Songkla University. J. The results indicate the suitable conditions of the GISS process are longer rheocasting time and lower rheocasting temperature. Faculty of Engineering. These conditions result in the formation of fine and uniform globular structure of the primary α-Al phase.ac. SSM forming is a forming process of metal in the CF‐04 . In a conventional die casting process. This technique is called the Gas Induced Semi-Solid (GISS) process. to develop this technique for commercial applications in industrial settings. S. R. Wannasin* Department of Mining and Materials Engineering. Introduction Aluminum alloys have been widely used in many applications such as electronic and automotive components. molten metal is injected into a die cavity resulting in turbulent flow and entrapment of air inside the casting parts. e-mail: jessada. which has a wide solidification range with the solidus and liquidus temperature of 557°C and 613°C.(2) In recent years. One technique for SSM forming is to create semisolid slurry directly from the melt and then to form the slurry into parts. Materials and Experimental Procedures The aluminum alloy used in this study was a commercial cast aluminum alloy A356. Table 1. it is important to understand the effects of the key processing parameters.04 Mg 0.(3) the Advanced SemiSolid Casting Technology by Honda (Japan). the effects of the rheocasting temperatures (the liquid metal temperatures before starting the introduction of gas bubbles) and the rheocasting times (the time to introduce gas bubbles) on the resulting slurry temperature and microstructure of A356 alloy were investigated. This forming technique is called rheocasting. Inc. Inc. and the RheoDiecasting (RDC) process by Brunel University (England). Si 6. the metal is modified during solidification to have nondendritic or globular grain structure. As a result.(4) the Semi-Solid Rheocasting (SSRTM) by IdraPrince Inc.(6) the Swirl Enthalpy Equilibration Device (SEED) by Alcan (Canada)(7). In this study. (Japan).(2) The GISS process can be applied with a large number of cast and wrought alloys such as A356. ADC12. a simple and efficient rheocasting process which offers lower costs for producing semi-solid slurry is needed.42 Cu 0. 2.(9) Recently.(5) the Sub Liquidus Casting (SLCTM) by THT Presses. Chemical composition (wt%) of the aluminum A356 alloy used in this study. a new rheocasting process has been developed at the Department of Mining and Materials Engineering. Prince of Songkla University. The chemical composition of this alloy is listed in Table 1. (USA).9 Fe 0. This process is called the Gas Induced Semi-Solid (GISS). Thailand.The 3rd Thailand Metallurgy Conference semi-solid state. (USA).(8) Although several processes are successfully used in the industry. they are still quite complex and have high capital costs. 2024.10 Al Bal. respectively. CF‐04 . To utilize the process effectively and efficiently. there are various rheocasting processes that have been developed to produce semi-solid slurries.01 Ti 0. These processes include the New Rheocasting (NRCTM) process by UBE Machineries. ADC10.(9) This process uses the principle of applying a combination of localized heat extraction between a cold rod and the molten metal with vigorous convection during the initial stages of solidification to produce non-dendritic or globular grain structure. 6061 and 7075.05 Mn 0.42 Zn 0. In addition. The 3rd Thailand Metallurgy Conference The GISS process is illustrated schematically in Figure 1. Figure 2 shows the prototype of the GISS slurry maker used in this study. The machine consists of a graphite diffuser, a thermocouple, a system to control the inert gas flow rate, a system to control the air cooling and a central control unit. Thermocouple Flow meter Graphite diffuser Molten metal Inert gas bubbles Crucible Inert gas Figure 1. Schematic of the GISS process.(2) Figure 2. The prototype of the GISS slurry maker used in this study. For all the experiments, the temperature of the graphite diffuser was kept at 40°C, the diffuser surface area per the melt volume (S/V ratio) was set at 0.35, and the gas flow rate was controlled at 4 liters/minute. In the experiments, the aluminum alloy was first melted in a graphite crucible using an electric resistance furnace. The molten metal was fluxed at 710°C before the experiments. Then, about 500 grams of the melt was ladled out of the crucible using a stainless steel cup coated with a ceramic coating. Subsequently, a thermocouple was inserted near the middle of the melt to record the temperature data during the experiments. When the melt cooled down to the set rheocasting temperature, a porous graphite diffuser was immersed and fine nitrogen gas bubbles were introduced into the melt. Then, the graphite diffuser was removed from the semi-solid slurry, and the slurry was allowed to cool in air until the temperature reached 580 °C (about 45% solid CF‐04 The 3rd Thailand Metallurgy Conference fraction). The semi-solid metal was removed from the cup and quenched in water. Samples were cut from the same position from the quenched semi-solid metals. Figure 3 shows the schematic location of the samples. The samples were then prepared by a standard grinding and polishing procedure, and were then etched with the Keller’s reagent. The microstructure of the samples was observed and analyzed using an optical microscope. In this study, the experimental conditions investigated include the rheocasting temperatures and rheocasting times of 620, 635, and 650 °C, and 5, 12, 20 seconds, respectively. Middle Figure 3. Schematic of the samples and the position of the micrographs. 3. Results and Discussion Representative cooling curves and the procedure to determine the slurry temperature after the GISS process is shown in Figure 4. For example, the graphite diffuser was immersed at the rheocasting temperature of 650 °C and with the introduction of nitrogen gas bubbles for the rheocasting time of 20 s. When the bubbling was stopped and with a few seconds of delay, the slurry temperature was determined from the curve. Following this analysis, the slurry temperatures for different rheocasting temperatures and rheocasting times were acquired and summarized in Figure 5. 660 650 640 630 Temperature (C) 620 610 600 590 580 570 0 Start immersion of graphite diffuser at 650°C Check temperature of semi-solid slurry The semi-solid slurry was quenched in water at 580°C Stop immersion of graphite diffuser. Rheocasting time = 20 seconds 20 40 60 80 100 120 140 160 180 200 220 240 260 Time (s) Figure 4. Representative cooling curves of A356 alloy and the procedure to determine the semi-solid slurry temperature. CF‐04 The 3rd Thailand Metallurgy Conference 618 616 Slurry temperature (C) 614 612 610 608 606 604 602 0 Rheocasting temp. at 620 C Rheocasting temp. at 635 C Rheocasting temp. at 650 C Liquidus temperature = 613°C 5 10 15 20 25 Rheocasting time (s) Figure 5. The effects of rheocasting temperatures and rheocasting times on the slurry temperature of A356 aluminum alloy. Then, the results from the various slurry temperatures were converted to solid fraction (fs) data. The Scheil’s equation was used to estimate the solid fraction.(2) For A356 alloy, the calculation assumed a binary alloy, linear liquidus and solidus lines and the partition coefficient (k) equals 0.13. Figure 6 shows the solid fraction of A356 slurry under a combination of rheocasting temperatures and rheocasting times. 20 18 16 Solid fraction (%) Rheocasting temp. at 620 C Rheocasting temp. at 635 C Rheocasting temp. at 650 C 14 12 10 8 6 4 2 0 0 5 10 15 20 25 Rheocasting time (s) Figure 6. The effects of rheocasting temperatures and rheocasting times on the solid fraction of aluminum A356 alloy. The GISS process utilizes the cold graphite diffuser and the introduction of fine nitrogen gas bubbles to decrease the temperature of the melt below its liquidus temperature. The CF‐04 as shown in Figure 8(a). the primary α-Al phase has rosette-like morphology. When the rheocasting time increases to 20 s. most of the primary α-Al phase appears globular with some rosettelike structure. For example. respectively. 9. to achieve about 5% solid fraction in the melt. The experimental results for the case of rheocasting time of 5 seconds show that with the rheocasting temperature of 650 °C. to rosette-like. the morphology of CF‐04 . The typical microstructures of A356 alloy produced by the GISS process under the rheocasting time of 5 seconds for various rheocasting temperatures are shown in Figure 8. With the rheocasting temperatures of 635 °C and 620 °C. as shown in Figures 8(b) and 8(c). the rheocasting times should be about 7. respectively. The white phase in Figure 7 is primary α-Al phase and the dark continuous matrix is the quenched eutectic phase. The experimental results show that the primary α-Al phase varied with the solidification conditions from coarse dendritic. 635. Figure 9(a). With the rheocasting time of 12 seconds. The obtained data give the important processing information about the required rheocasting times to achieve a certain amount of solid fraction in the melt with different starting rheocasting temperatures. the rheocasting temperature is lowered and the rheocasting time is increased. the primary α-Al phase consists of mostly globular and some rosette-like grains. and to globular structure. Figure 7. and 650 °C. Microstructure of aluminum A356 alloy solidified under normal conditions showing coarse dendritic microstructure. Figure 9 shows the experimental results under different rheocasting times at the same rheocasting temperature of 620 °C. respectively. consequently. and 15 seconds for the rheocasting temperatures of 620.The 3rd Thailand Metallurgy Conference rheocasting temperature and rheocasting time affect the slurry temperature and. The microstructure of aluminum A356 alloy solidified without the application of the GISS process showing coarse dendritic structure is given in Figure 7. To create more solid phase in the melt. the solid fraction with the relationships shown in Figures 5 and 6. The 3rd Thailand Metallurgy Conference primary α-Al phase is mainly globular with a uniform distribution in the structure. which then can grow to form a non-dendritic or globular structure within a few seconds. For the GISS process. and (c) 620 °C. These results suggest that the primary α-Al phase tends to be fine globular structure with a uniform distribution in the eutectic phase when the rheocasting temperature is decreased and rheocasting time is increased. Figure 9(b). Microstructures of A356 alloy produced by the GISS process under the rheocasting time of 5 seconds for different rheocasting temperatures: (a) 650 °C. (a) (b) (c) Figure 8. With the lower CF‐04 . The results may be explained by the dendrite fragmentation mechanism. (a) (b) Figure 9. (b) 635 °C. Microstructures of A356 alloy produced by the GISS process under the rheocasting temperature of 620 °C for different rheocasting times: (a) 12 s and (b) 20 s. This process helps to generate secondary nuclei particles.(10) The non-dendritic structure is developed from a large number of initial dendrite fragments going through the ripening mechanism which results in globular grain structure. the results obtained in this study suggest that a combination of localized heat extraction with the introduction of fine nitrogen gas bubbles through the graphite diffuser to create the vigorous convection during immersion of the graphite diffuser in the molten metal causes dendrite arms to break off from the mother dendrites. . T. we would like to thank Mr.. Development of a semi-solid metal processing technique for aluminium casting applications. Masaki. In addition.. References 1. Suzuki.. Tanikawa. Aluminum. T. Songklanakarin J. Conclusions 1. 30(2): 215-220. 4.The 3rd Thailand Metallurgy Conference rheocasting temperature. de Figueredo A. Technol. This study gives important information for processing about the required rheocasting times to achieve a certain amount of solid fraction in the melt with different starting rheocasting temperatures. and Uggowitzer. 4. CF‐04 . P. K. Kuroki. H. M. 3. Thiensak Chucheep and Innovative Metal Technology (IMT) Team for helping with the experiments. 2001.. Limassol. 76(1-2): 70-75. Acknowledgements The authors would like to thank the Reverse Brain Drain Project (RBD). 3. 6.. and Yamazaki. Wabusseg. and Thanabumrungkul. Suenaga T. Sci. Cyprus. Fine and uniform globular structures for aluminum A356 alloy were obtained when the rheocasting temperature was low and the rheocasting time was long. 2004. Wannasin. Science and Technology of Semi-Solid Metal Processing. 2008. 5. the National Science and Technology Development Agency (NSTDA) for funding this research project. Ed. Metallurgical and Processing Aspects of the NRC Semi-Solid Casting Technology. The GISS process can be used to produce semi-solid slurries effectively and efficiently when the proper processing conditions are selected. 2000. 2. A. Proceedings of the 8th International Conference on Semi-Solid Processing of Alloys and Composites. H. In addition. the mother dendrites will be finer making it easier and faster for the dendrite arms to be detached. 2.A. S. H. Establishment of a Manufacturing Technology for the High Strength Aluminum Cylinder Block in Diesel Engines Applying a Rheocasting Process.. The North American Die Casting Association. Kaufmann.S. U. Umemoto.J. with longer rheocasting times. J. more dendrite arms will be detached and the longer ripening time will lead to more globular structure. A. Yurko. and Flemings. 55: 115-118. and Ji. D. Development of the Gas Induced Semi-Solid Metal Process for Aluminum Die Casting Application. Microstructure and Mechanical Properties of RheoDiecast (RDC) Aluminium Alloys. Rattanochaikul. J. 9. 141-143: 97-102. T. Fundamental Requirements for Slurry Generation in the Sub Liquidus Casting Process and the Economics of SLCTM Processing.. Grain refinement of an aluminum alloy by introducing gas bubbles during solidification.. A. 2004. and Wales. Martinez. G. U. 2006. Jorstad. 2008. A. R.C. M. R. and Kamm.The 3rd Thailand Metallurgy Conference 5. and Flemings. Solid State Phenomena Vols. M. 412(1-2): 298-306. The Use of Semi-Solid Rheocasting (SSRTM) for Automotive Casting. X. 2005.. SAE 2003 World Congress & Exhibition. Martinez. M. 43(2): 265-272. 2004. Detroit. Sci.S.C. Fang. J.A. 8. J. 7.. 6. 10. Wannasin. SEED: A New Process for Semi-Solid Forming. Fan. Scripta Materialia. Z. Proceedings of the 8th International Conference on Semi-Solid Processing of Alloys and Composites. Michigan. Cyprus. Hay. Eng. Douter. Mater.. and Flemings. S. Junudom. M.. Wannasin. Canadian Metallurgical Quarterly. S. Thieman. Limassol. J.. 2003. CF‐04 . P. which are 30% to 50% with an increment of 5%. Pracha-U-Thit Rd. 12120. As the volume fraction of PMMA increased. but it is difficult to control the process to obtain a uniform structure. Another process is the deposition method.or.*. The liquid metal is transferred using a conveyer belt to solidify. Koikula . automotive parts. Suranuntchaia a King Mongkut’s University of Technology Thonburi. 114 Thailand Science Park. This process is very effective in continuously producing large size foams. there are different manufacturing methods for metal foams. the number of pore increased but the sintered density and the mechanical properties decreased. Introduction The interest in metal foam has significantly increased due to their extended applications. A. cushions. the effects of volume fraction of spacer holder on the foam properties were studied. The 30% volume fraction of stainless steel 316L powder was mixed with varied volume fractions of binder and PMMA.The 3rd Thailand Metallurgy Conference Effects of replacing binder with powder space holder on properties of metal injection moulded foam U. for example. 2002). *E-mail: anchalm@mtec. 10140. metal injection moulding. Pathumthani. Paholyothin Rd. Spherical poly (methyl methacrylate) (PMMA) particles were used as a space holder material. There were five volume fractions of PMMA. Bangkok.. The conventional process is the gas injection method.. b National Metal and Materials Technology Center. powder space holder 1. the investment casting CF‐09 . where gas bubbles are injected into a liquid metal. In this study. filters. The results shown that the volume fraction of PMMA affected the properties. Keywords: metal foam. Manonukulb. Thungkru.th (Corresponding author) Abstract Metal foam can be produced using metal injection moulding with powder space holder. which starts from the ionic state of metal and deposits a polymeric foam preform with open cells. Currently. S. insulators and biomedical implants (Degischer and Kriszt. Similar to the deposition method. Klong Luang. 2005). PMMA was used in this work as the powder space holder. highly complex porous shape with high dimensional accuracy (Williams. which are mixing. the polymeric foam preform is dipped into graphite slurry or coated with a thin layer by metal vaporisation. Spherical and strip carbaminde particles were used as the powder space holder. 2008). This step is the debinding step and “brown” parts with the structure of foam are obtained after debinding. These two processes can produce a complex shape part. Hence. 1988). 2. It is capable of producing small parts with complex shape in a mass production scale. In addition. Metal injection moulding (MIM) is a manufacturing process combining the traditional powder metallurgy process and plastic injection moulding (German. In the first step mixing. There are four main steps. Therefore. The mixture is then granulated and injected to obtain “green” parts. The effect of powder space holder shape was also studied (Jiang et al.. MIM using powder space holder (MIM-PSH) has been developed for producing complex metal foam part (Gülsoy and German. In the investment casting method. Experiment procedures CF‐09 . metallic powder. (2008) studied the propertied of 316L foam produced by MIM with 30 and 60% volume fraction. PMMA can be easily decomposed in the debinding stage and the metal foam with uniform foam structure can be manufactured by MIM-PSH (Gülsoy and German. 2008). this work systematically investigated the effect of volume fraction of PMMA (powder space holder) on the properties of metal foam produced by MIM-PSH. Brown parts are then sintered at a high temperature to obtain a metal foam. debinding and sintering. It is noted that MIM-PSH can produce both open-cell and close-cell foams.The 3rd Thailand Metallurgy Conference method also uses a polymeric foam perform. The MIM with powder space holder for producing foam is similar to conventional MIM as shown in Fig. injection. 2007). and 10 and 40 µm average size of PMMA.. that can be fabricated by preforming the polymeric foam but both methods are expensive (Gibson and Ashby. Nishiyabu et al. MIM-PSH can be cost-effective for microsized. the polymeric foam preform is removed by thermal treatment (Ashby et al. 2000). binder and powder space holder are homogeneously blended together. 1997). Subsequently. Previous works only studied two volume fractions of powder spacer. 1. Poly (methyl methacrylate) (PMMA) is a common powder space holder. The green part is heated to remove binder and powder space holder. As a result. The 3rd Thailand Metallurgy Conference In this work. PMMA was used as the powder space holder in this work and had a particle size of 84.. Ltd. The backbone polymer provides the essential strength of the green parts. Figure 2 shows the scanning Figure 1: Schematic representation of metal injection moulding using powder space holder technique. high density polyethylene as a backbone polymer and stearic as a acid surfactant. (a) (b) Figure 2: SEM micrographs of (a) 316L powder and (b) PMMA particle. PMMA was supplied by Sunjin Chemical Co. while the PMMA particle is spherical.5 µm. Korea. The binder in this experiment comprised of three components: paraffin wax as a plasticiser. the water–atomised stainless steel 316L powder (PF-20F) provided by Atmix Co. Ltd. The surfactant strengthens the adhesion between binder and powder and weakens the agglomeration of the powder (Huang and Hsu. The powder has the average size of 10. The 316L powder is rounded. CF‐09 . electron microscopy (SEM) images of the 316L powder and PMMA particle.7 µm. The binder reduces the viscosity of the feedstock and facilitates injection moulding. 2009). Japan. was used.. The densities of the green and sintered parts were measured. Green parts were thermally debound at 450 °C for 1 hour in air and sintered at 1100 °C for 2 hours in an argon atmosphere. Volume fraction of PMMA (% vol) 30 35 40 45 50 Volume fraction of binder (% vol) 40 35 30 25 20 Volume fraction of metal powder (% vol) 30 30 30 30 30 3. This mixture was injected into tensile-test-specimen shape. The mixing and CF‐09 . Thus. The volume fraction of PMMA was increased from 30% to 50% in an increment of 5%. The solid loading of metal powder was kept constant at 30% volume fraction. grinded with silica papers and polished with diamond solution for the observation of microstructures using the optical microscopy. Figure 3 shows the variation of mixing and injection temperatures.The 3rd Thailand Metallurgy Conference Stainless steel 316L powder. mounted. PMMA and a polyacetal-based binder were mixed together in five batches with different volume fractions as shown in Table 1. Table 1. while the solid loading of metal powder was constant. Hardness in HR15W scale and tensile tests were tested and reported. the experiment was designed to replace binder with more PMMA. binder and metal powder. while the volume fraction of binder was decreased from 40% to 20% in an increment of 5%. The sample were cut. which were varied with the volume fraction of PMMA. Fraction by volume of each component: PMMA. Results and Discussion Processing parameters Most processing parameters for mixing and injection moulding were kept constant apart from the mixing and injection temperatures. The volume fraction of PMMA and binder were correspondingly varied with the constant combined volume fraction of 70%. Figure 3: Mixing and injection temperatures as a function of the volume fraction of PMMA. The sintered density decreased with increasing volume fraction of PMMA. the higher mixing and injection temperatures were required to increase flow ability (Supati et al. CF‐09 .cm-3. which is the highest sintered density. a feedstock with 50% volume fraction of PMMA contained 30% by volume of metal powder and 20% by volume of binder. 2000).The 3rd Thailand Metallurgy Conference injection temperatures increased as the volume fraction of PMMA increased and the volume fraction of binder decreased. The sample had similar green density because the volume fraction of metal powder was kept constant.cm-3. As the volume fraction of PMMA increased.49 g. This resulted in the high viscosity of feedstock and it was not possible to inject this feedstock with 50% volume fraction of PMMA regardless of the injection condition. the sintered specimen with 45% PMMA volume fraction has the lowest sintered density of 3.58 g. On the other hand. This means that during injection. The sintered density is higher than the green density for all percentages of PMMA showing consolidation during sintering. From Table 1. The average green density of all specimens was 3. As a result. Density and microstructure Figure 4 shows the green and sintered densities as a function of volume fraction of PMMA.05 g. the viscosity of feedstock was higher and it was more difficult for the feedstock to flow. The sintered density of 3. there was only 20% liquid phase during injection (binder) and 80% solid phase during injection (PMMA and metal powder). It is noted that the result for the 50% volume fraction of PMMA cannot be shown because it was not possible to inject the feedstock with 50% PMMA.cm-3 was observed in the 30% PMMA volume fraction. Therefore. The number of pores depended on the PMMA contents. The microstructure of 45% PMMA volume fraction exhibited a large number of pores distributed thoroughly inside the specimen as shown in Fig. 5. The microstructures of the sintered 316L stainless steel specimens with four different volume fractions of PMMA are shown in Fig. For all microstructures. Mechanical properties Sintered metal foam was subjected to hardness and tensile tests. The hardness of sintered parts varied with the volume fraction of PMMA as shown in Fig. All such pores retained the spherical shape of powder space holder and distributed homogeneously in the 316L stainless steel matrix. It is noticed that the 45% volume fraction of PMMA had the largest error and this volume fraction had a large number of pores. The microstructures of the specimens showed the number of pores increased with increasing volume fraction of PMMA. 5 (d). CF‐09 . The result shows that as the volume fraction of PMMA increased from 30% to 45%. The number of pores increased with the increased addition of PMMA. the hardness decreased from 32-21 HR15W. the pores were introduced by the burnout of PMMA. The error increased as the volume fraction of PMMA increased. The hardness of metal foam specimens was tested using Rockwell W (HR15W). the hardness values decreased as the number of pores in the specimens increased. 6.The 3rd Thailand Metallurgy Conference Figure 4: Green and sintered densities as a function of the volume fraction of PMMA. The error was also displayed. There were more pores distributed in the microstructure of 45% PMMA volume fraction than the other volume fractions. Figure 6: Hardness of sintered parts as a function of the volume fraction of PMMA CF‐09 .The 3rd Thailand Metallurgy Conference (a) 30% vol PMMA (b) 35% vol PMMA (c) 40% vol PMMA (d) 45% vol PMMA Figure 5: Optical microstructure of sintered parts cross section as a function of the volume fraction of PMMA. The tensile strength and elongation were dependent on the volume fraction of PMMA. The 30% volume fraction of PMMA had the highest tensile strength of 125 MPa with 14% of elongation. elongation and hardness decreased as the volume fraction of PMMA increased. which had the lowest tensile strength of 97 MPa and the elongation of 10%. both tensile strength and elongation decreased. Five different volume fractions of PMMA were varied to replace the binder and the volume fraction of metal powder was kept constant. The material used for space holding is a spherical PMMA particle. Tensile strength. CF‐09 . The lowest values were obtained for the 45% volume fraction of the PMMA. The mechanical properties decreased with increased in porosity or the volume fraction of PMMA increased.The 3rd Thailand Metallurgy Conference Figure 7 shows the tensile strength and the elongation of sintered parts as a function of the volume fraction of PMMA. The experimental results show that the sintered density was higher than the corresponding green density. Figure 7: Tensile strength and elongation of sintered parts as a function of the volume fraction of PMMA 4. As the volume fraction of PMMA increased. The sintered density decreased when the volume fraction of PMMA increased. The results are similar to the hardness results. The spherical shape pores were homogeneously dispersed in the 316L stainless steel matrix. Conclusions Stainless steel 316L foams can be produced by applying a powder space holder method to a metal injection moulding process. The number of pores increased with increasing volume fraction of PMMA. The microstructure showed that the number of pore depended on the fraction of PMMA. Huang. 1988. and Tanaka. 534-536: 981. MPIF. German R. B. F. K. H. 1: 12-19.M.A. Materials Letters.Metal Foam: A Design Guide. B. and Kriszt. Net-Shape Manufacturing of Micro Porous Metal Components by Powder Injection Molding.The 3rd Thailand Metallurgy Conference 5. N. Nishiyabu. and Bose. Hutchinson. Scripta Materialia. 2007.O. New Jersy.. Forum. Materials Science Forum. S. Fleck. 2009. S. M. 2007. Y. 58: 295-298. Injection Molding of Metals and Ceramics. R. 209: 981-984. J. K. 1997. A. L. References Ashby. 2000. J. Weinheim. C.H. Handbook of Cellular Metals. and German. R. W. B. CF‐09 .. and Ashby. A. F. M.. H. Loh N. Gülsoy. Supati. Matsuzaki. 2000. Evans. 46: 109-114. A. Khor. J. N. Cellular Solids Structure & Properties. Williams.. Butterworth-Heinemann. Gibson. PERGAMON PRESS.984. and Wadley. Sci. 2002. Degischer. Oxford.. L. Powder Injection Moulding International. Powder injection moulding in the medical and dental sectors.. and Hsu. Boston. and Tor. Mixing and Characterization of Feedstock for Powder Injection Molding. Production of micro-porous austenitic stainless steel by powder injection molding. M. Wiley. G. S.M. Effect of backbone on properties of 316L stainless steel MIM compact. H. H. P.. Gibson. 2008. hot forging (HF) at 648 MPa. respectively. On the other hand. T. Ti5Si3 was observed as main compound from both 60:40 and 70:30 mixtures. The powders were mixed by ball milling and pressed by different methods: by using uniaxial pressing at 64 MPa.com Abstract Titanium silicide compound was synthesized from the mixture of titanium and silicon powder with atomic ratios of 60:40 and 70:30. However the microstructure of samples formed by CIP and HF showed some big pore inside the sample body while sample formed at lower pressure by uniaxial press showed a more uniform pore size. It was found that the sample prepared from the 70:30 mixture has higher density than that sample of 60:40 mixture for all applied pressures. Thapnuya. The density of samples prepared from the mixture of 70:30 and 60:40 sintered at 1300oC are in the range of 53-60% and 42-55%. Keywords: Titanium silicide. J.The 3rd Thailand Metallurgy Conference Effect of temperature and pressure on the densification of titanium silicide compound P. Bangkok Tel: 02-5779274 Fax: 02 -5774160-1 E-mail: choopacha@hotmail. It was found that densities of all samples sintered at 1300 oC were not much different when applied higher forming pressure by using CIP and HF. Luangvaranuntb. Larpkiattaworna. this can produce high density sample of 99% with a few amount of small closed pore. and hot pressing (HP) at 24 MPa. S. Cold Isostatic Press. soaking time in argon atmosphere. Ikeuchia a Thailand Institute of Scienctific and Technological Research 35 Moo3 Technothani klong5 klongluang pathumthani b Chulalongkorn University Rama4 Road Pathumwan. Hot Press CF‐10 . cold isostatic pressing (CIP) at 200 MPa. Hot Forge. By increasing the sintering temperature to 1600 o C. The samples were then sintered at 1300 oC or 1600 oC for 2 h. Archimedes’ method and scanning electron microscope (SEM) was used to measured density and investigate microstructure of sintered samples. by applying a lower pressure during sintering the sample at 1600 oC by hot pressing. the density of uniaxial pressed sample was increased to 85% and pore size get smaller than the one sintered at 1300 oC. The sintered samples were characterized for phases constitution using X-ray diffraction (XRD). This means that pores are created during sintering. The sinter specimens were measured for density by Archemidis method. 200 MPa (cold isostatic pressing).32 g/cm3).1 and 2 respectively. However. Ni. average particle size < 45μm) and Si powder (99.The 3rd Thailand Metallurgy Conference 1. Results and Discussion The sintered Ti: Si specimens of 60:40 and 70:30 were characterized for phase constitution by XRD as patterns shown in Figure. Titanium silicide can be prepared by a variety of powder techniques such as hot pressing. The heating rate and soaking time were 15 °C/min and 2 hr. respectively. The mixed powder was compacted into specimens with 2 cm diameter and 0. hot isostatic pressing. and thermal or plasma spraying [3-6]. 7]. the variety of pressure and temperature were applied to prepare Ti5Si3. or Nb [4. average particle size < 45μm) were mixed in atomic ratio of 60:40 and 70:30 for 20 hr in Ar gas atmosphere. 648 MPa (hot forging) and 24 MPa (hot pressing). mechanical alloying. X-ray diffractometer (XRD) and Scanning electron microscope (SEM) were used to determine the phase constitution and microstructure of the sintered specimens respectively. TiSi. Due to the limited fracture toughness of Ti5Si3 at room temperature.7% purity. high temperature oxidation resistance. On the CF‐10 . Introduction Titanium silicide compound such as TiSi3. moderate density (4. TiC was observed together with Ti5Si3 phase. 6. Among these silicide compounds. 2. 3. most researchers have paid attention to produce multiphase in Ti5Si3 compound by addition of Al. Experiment procedures Ti powder (99. The results show that single phase of Ti5Si3 was formed in the 60:40 specimens sintered at temperature 1100-1500 °C and at high temperature of 1600 °C. and then their density and microstructure were observed.5 cm thickness using different pressure of 64 MPa (uniaxial pressing).7% purity. high hardness (11. While other specimens were sinter at 1300 and 1600 °C in argon atmostphere.3 GPa) and high young modulus (225 GPa) [1-2]. Ti5Si4 and Ti5Si3 can be prepared from various ratio of titanium and silicon metal. TiSi2. C. Ti5Si3 is known as an intermetallic compound which suitable for high temperature applications due to the properties of a high melting point (2130° C). The uniaxial pressed specimens were sintered at temperature varied from 1100 to 1600°C. Research works on densification of Ti5Si3 dependence on pressure and temperature are limited. In this paper. reactive sintering. Higher content of Ti in the specimen causes easier forming of TiC at low temperature and TiC will react with some Ti5Si3 to form Ti3SiC2 at high temperature.The 3rd Thailand Metallurgy Conference other hand. TiC can be formed together with Ti5Si3 in 70:30 specimens sintered at temperature range of 1100-1500 °C and then this TiC phase will transform to Ti3SiC2 at 1600 °C. The TiC and Ti3SiC2 phases in specimens could be from the diffusion of carbon inside the furnace into specimens during sintering process. Ti5Si3 TiC 1600 C 0 1500 C 0 Intensity 1300 C 1200 C 0 0 1100 C 0 25 30 35 40 45 50 55 60 65 70 75 80 Diffraction angle ( 2θ ) Figure 1: XRD patterns of the Ti:Si mixture of 60:40 sintering at different temperatures Ti5Si3 Ti3SiC2 TiC 16000C 15000C Intensity 13000C 12000C 11000C 25 30 35 40 45 50 55 60 65 70 75 80 Diffraction angle ( 2θ ) Figure 2: XRD patterns of the Ti:Si mixture of 70:30 sintering at different temperatures CF‐10 . 33 2. These phenomena can be explained that the Si vapor is trapped inside specimens which have been compacted at high pressure prior to sintering. and that results in smaller pores.40 41.36 4.24 70:30 57.79 2.38 2.22 53.63 4.69 MPa) CIP ( 200 MPa ) HF ( 648MPa ) 1.44 59. Si vapor generated from specimens with lower forming pressure can easily move out during sintering before densification.77 Table2 Density of TiSi mixture of 70:30 sintered at 1600°C Apparent density (Bulkdensity/ Apparent density) x100 85.70 4.34 4.35 60:40 43.84 %Porosity by Archimedis method 14. It was found that increasing the forming pressure could slightly increase the density of specimen after sintering.69 MPa) Hot press (24. On the other hand.24 MPa ) 3.63 1. 37 CF‐10 .37 70:30 4.89 70:30 2.27 4.31 4. The specimen with high Ti content yield higher density than that of lower Ti content which agree with the SEM micrographs in Figure 3 Moreover.24 1.The 3rd Thailand Metallurgy Conference Table 1 shows density of specimens formed at different pressures after sintering at 1300°C.16 Ti:Si Bulk density Uniaxial press (63. (Bulk Ti:Si Bulk density Apparent density density/Apparent density) x100 60:40 Uniaxial press (63.49 60:40 4. Table1 Density of Ti:Si mixture of 70:30 and 60:40 formed at various pressure and sintering at 1300°C.92 55.40 98. Figure 3 shows that the specimens formed at higher pressure have bigger pore size than those formed at lower pressure.31 4. by simultaneously applying low pressure (24 MPa) and heating (1600 °C) the density of specimens can be raise up to 99% which is shown in Figure 4. when the sintering temperature is raised up from 1300 °C to 1600 °C. CF‐10 . (e) 60:40 (HF 648 MPa). (c) 60:40 (CIP 200 MPa). (d) 70:30 (CIP 200 MPa). (f) 70:30 (HF 648 MPa) (a) (b) Figure 4: SEM micrographs of TiSi mixture of 70:30 sintered at 1600°C formed by (a) uniaxial press at 64 MPa and (b) hot press at 24 MPa According to Table 1 and Table 2.The 3rd Thailand Metallurgy Conference (a) (b) (c) V (d) (e) (f) Figure. the density of specimen formed at 64 MPa increases significantly from 57% to 86%. Furthermore.3 SEM micrographs of TiSi mixture of 60:40 and 70:30 formed at pressure (a) 60:40 (uniaxial Press 64 MPa). (b) 70:30 (uniaxial Press 64 MPa). 90-95 [7] L. During sintering Si vapor can generated and form the pores inside specimen.Meter. 734-737 [5] R.P Radlinski. however applying pressure during sintering is the most effective to get high densification. Acknowledgements The authors would like to thank Thailand Reasearch Fund (TRF).2nd ed. A. Hsu.The 3rd Thailand Metallurgy Conference This means that temperature is more effective on increase in density than pressure. Intermetallics 14 (2006) 33-38 [2] Massalski TB . Formation of titamium silicides Ti5Si3 and TiSi2 by self-propagating combustion synthesis.Wu.Zhang and J. Conclusions Ti5Si3 can be synthesized from Ti and Si powders (70:30 and 60:40) sintered at 1100-1600 °C. R.:1990 [3] N.Formation of titanium silicides by mechanical alloying . Chen.Mitra. 5. E. Stoloff. In-situ neutron diffraction of titanium silicide. Nanoshield Ltd.Materials Park. Oliver. Calka. Ti5Si3 and Ti5Si3–base alloys: Alloying behavior. Increasing forming pressure is insignificant in densification during sintering. Met.C. References [1] D.H. Ti5Si3. 3535-3546 CF‐10 . Kisi. during self-propagating high-temperature synthesis (SHS).al. OH: ASM Int. and A. 432 (2007).P. 1629-1641.H. Pogany. On the other hand.et.A.L.S. applying lower pressure during sintering can remarkably enhance the densification of Ti5Si3 specimens. [6] C.Trans.P.A 29A(1998).10 (1991).Microstructure and mecchanical behavior of reaction hot – pressed titanium silicide and titanium silicide based alloys and composites. Acta matter 46(10) (1998).P.Yeh. Riley. and Japan International Cooperation Agency (JICA) for the support of this work 6. and CC. Materials Science and Engineering: A 261 (1999). 4. Binary alloy phase diagrams. and retards the densification.Shanks. microstructure and mechanical property evaluation. 169-180 [4] A. W. Phase identification and microstructure were analyzed by X-Ray Diffractometer and optical microscope respectively. Faculty of Engineering. increased the hardness of all specimens.. by isothermal annealing at 750oC for 1 h and quenching in water. followed by isothermal annealing at 750oC and quenching in water. However. Powder metallurgy 1. which has high strength. Cu-10wt%Sn. 60 and 90 min. 5wt%Al and 10wt%Al. 30. Nevertheless sintered metal powders has the best performance as starting materials. dating back to the mid-1920. filters and self-lubricating bearing. It was found that the larger the addition of aluminium.Chobaomsup. sintering temperature was 830°C and 900°C and ratio of adding aluminium was 0wt%Al (no adding). The best processing condition to obtain high hardness was sintering at 900oC for 30 to 60 min. 089-128-1572 Fax: +66 2218 6942 Email:eng_mate@hotmail. high corrosion resistance. Glass. percentage of porosity and hardness were tested to clarify the effect of processing parameters.com ABSTRACT Self-Lubricating bearings are one of the oldest industrial applications of porous powder metallurgy part. They remain the highest part produced by the P/M industry. the greater was the reduction in density and hardness in all sintering conditions. Phyathai Rd. Thailand 10330 Tel: +66 2218 6947. T. durability and ease to control porosity and permeability.The 3rd Thailand Metallurgy Conference Effect of aluminium on sintered properties of Cu-10wt%Sn bearing V. They remain the highest part CF‐12 . The objective of this research was to study effect of sintering time. high thermal resistance. Self-lubricating bearings are one of the oldest industrial applications of porous P/M part. Chulalongkorn University. dating back to the mid-1920. ceramics and metallic materials can be used as the starting materials [1].Luangvaranunt Department of Metallurgical Engineering. sintering temperature and ratio of adding aluminium on sintered properties of Cu-10wt%Sn bearing that produced from powder metallurgy processing. Sintering time in the experiment was 5. Keywords: Self-Lubricating Bearing. 45. Various physical and mechanical properties such as density. Introduction Porous parts are divided into two groups. additional heat treatment after sintering. Bangkok. Weight. size were measured.The 3rd Thailand Metallurgy Conference produced by the P/M industry. stainless steel.9% pure aluminium powder were mixed and blended together in various ratio of added aluminium: 0wt%Al (no adding). 60 and 90 min under argon atmosphere. Density and porosity are measure by Archimedes’ method. 45. Fig. After sintering samples weight. (a) – (c) at center of the sample (d) – (f) at edge of the sample. titanium and aluminium. Microstructure was investigated by using optical microscope and scanning electron microscope. Pores at the center of the sample are quite round but pores at the edge of the sample are irregular. 3. 30. 5wt% and 10wt%Al sample sintered at 900 °C for 30 min. The most commonly used powders include bronze. Consequently.1 mm. height) under a pressure of 2000 kg. 3. while operating selflubricating bearing. Experimental procedures Premixed 90-10wt% of copper-tin powder and 99.1 shows microstructure of 0wt%Al.1 Sintering temperature at 900 °C It was found that microstructure of different sintering time sample look similar. 5wt% and 10wt%Al. The samples were phase identified by using X-ray Diffractometer. Results and discussion Results will be discussed in two parts: result from sample sintered at 900 °C and after heat treatment. size of the sample was measure to calculate density before sintering. Sintering is in a batch type alumina tube furnace maintained at 830 °C and 900 °C for 5. it receives acting force all the times even through it is lubricated. 2. CF‐12 . As mentioned above.3 mm. diameter and 1-1. The mixture was compacted into cylindrical shape (1. and with added aluminium the pores become more irregular. improvement self-lubricating bearing in reducing wear and has less friction coefficient by dispersion hardening make bearing has longevity. Metal powders used for porous parts are selected according to the application. nickel and nickel-base alloys. 1 microstructure of 0wt%Al. 5wt%Al and 10wt%Al samples sintered at 900°C. 5wt% and 10wt%Al sample sintered at 900°C for 30 min (a) – (c) at the center of the sample (d) – (f) at the edge of the sample Fig. 0% Al 5% Al 10% Al 9 8 Bulk Density (g/cm ) 7 6 5 4 3 2 1 0 0 20 40 60 80 100 Sintering Time (min) 3 CF‐12 .The 3rd Thailand Metallurgy Conference (a) (b) (c) (d) (e) (f) Fig.2 and 3 demonstrate the density and hardness of 0wt%Al (no adding). The same correlation as found in samples sintered at 830 °C. Therefore porosity increases and hardness reduces when adding larger amount of aluminium in all sintering time. However the hardness was maximum at 51. the greater is the reduction in density in all sintering time.63 and 5. When the samples have less density and more porosity.44 g⋅cm-3 respectively. Density of 5wt%Al and 10wt%Al adding samples sintered at 900°C for 30 min was greatest.53% and 27.3 Effect of sintering time and amount of aluminium on the hardness of Cu-10wt%Sn samples sintered at 900 °C. 2 Effect of sintering time and amount of aluminium on the density of Cu-10wt%Sn samples sintered at 900 °C. The porosity was 15.96% respectively. It is lower than the reference samples from the K.30 and 37.Powder factory. Effect of aluminium on the density of the samples is as following: the lager addition of aluminium. this can cause stress concentration at the edge of the pores. Samples without addition of aluminium have higher hardness than the ones with aluminium for all sintering time. with minimum porosity of 9. 0% Al 5% Al 10% Al STD 70 60 Hardness (HV 1kg) 50 40 30 20 10 0 0 20 40 60 80 100 Sintering Time (min) Fig.81 g⋅cm-3.The 3rd Thailand Metallurgy Conference Fig. which were 6.4 HV. Vaporization of aluminium occurs because aluminium CF‐12 .90 HV when sintered at 900°C for 5 min.53% and the maximum hardness was 54. Density of no adding aluminium samples sintered at 900°C for 30 min was the greatest which was 7. Stress concentration is one of the causes that make the sample have lower hardness. Two possible causes of pore occurrence are vaporization of aluminium and Kirkendall void. 030 0.030 0. Vapor pressure of pure aluminium obeys equation 1. This causes void in the samples.050 10 wt%Al (g) 0. 5wt%Al and 10wt%Al samples are 0.025 0. 0. [2] log (P ) = 10.055 0.375 g and 0.035 Table 1 Weight loss after sintering at 900°C for different sintering time Lubricant weight plus aluminium weight for 0wt%Al.The 3rd Thailand Metallurgy Conference has higher vapor pressure at high temperature. It can be seen that weight loss of all samples is less than lubricant weight plus aluminium weight. Sintering time (min) 5 30 45 60 90 0 wt%Al (g) 0.035 0.715 g respectively. Vapor pressure at 900 °C is 0.065 0. Long sintering time gives tin and aluminium more time to diffuse into copper and larger amount of pores were created. 60 and 90 min. Weight loss after sintering of samples sintered at 900°C for different sintering time is shown in Table 1.040 0. Therefore the main cause of pore occurrence in samples is from Kirkendall effect which is diffusion phenomenon of two species with different diffusion coefficient.045 g.015 0.17 × 10-3 Pa.040 0. CF‐12 . Fig 4 – 6 show XRD patterns of samples sintered at 900°C for 30.035 0. Atmospheric pressure is much larger than vapor pressure of pure aluminium at 900°C therefore vapor pressure effect can be neglected. In this case void caused from tin and aluminium diffusing into copper faster than the reverse.025 5 wt%Al (g) 0.035 0.917 − 16211 T Eq.1 P is a vapor pressure in Pascal and T is an absolute temperature.045 0. The 3rd Thailand Metallurgy Conference AlCu4 α 10wt% Al α α β β α Intensity (a.u.4 XRD Pattern of samples sintered at 900°C for 30 min α 60 70 80 AlCu4 α 10wt% Al α β α β α Intensity (a.u.) α 5wt% Al α α α 0wt% Al 20 30 40 50 2 Theta (Deg) Fig.5 XRD Pattern of samples sintered at 900°C for 60 min CF‐12 .) α α 5wt% Al α α α 0wt% Al 20 30 40 2 Theta (Deg) 50 60 70 80 Fig. JCPDS #44-1477) which can be found in all samples. 3. Therefore density and porosity trend are as aforementioned.) α β α α α 5wt% Al Cu 5. Relative amount of phases is as following: the amount of α phase in 10wt%Al samples sintered at 900°C increases with sintering time and amount of β phase in 10wt%Al samples sintered at 900°C decreases with increasing sintering time.6Sn α α Cu 5.6 XRD Pattern of samples sintered at 900°C for 90 min XRD pattern show that the main phase found in samples is solid solution of 10wt% tin in copper (α phase. Splitted peak also occur in the samples sintered at 900°C for 90 min. (a) – (c) at the center of the sample.2 Results from heat treatment Fig 7 shows the microstructure of samples sintered at 900°C for 30 min and heat treated at 750°C for 60 min of 0wt%Al. β phase (JCPDS #06-0621) which is solid solution of high tin content in copper (25 – 26.6Sn 0wt% Al 20 30 α α 40 50 60 70 80 2 Theta (Deg) Fig.u. While amount of α phase increase with sintering time.The 3rd Thailand Metallurgy Conference α AlCu4 AlCu4 10wt% Al Intensity (a. 5wt% and 10wt%Al sample. CF‐12 .5 wt % tin) and intermetallic compound AlCu4 (JCPDS #28-0006) still present in 10wt%Al samples. so are the vacancies occurring from diffusion of tin into copper.6Sn Cu 5. Furthermore. this splitted peak is matched with Cu-5. (d) – (f) at the edge of the sample.6Sn JCPDS files (JCPDS #31-0487). 5wt% and 10wt%Al sample (a) – (c) at the center of the sample (d) – (f) at the edge of the sample. 5wt%Al and 10wt%Al samples sintered at 900°C and heat treatment at 750°C.26 % Porosity 15. porosity and hardness of 0wt%Al (no adding). Al amount (wt%) 0 5 10 Bulk Density (g/cm3) 7.60 Table 2 Density. Hardness after heat treatment of 0wt%Al is slightly lower than before heat treatment.The 3rd Thailand Metallurgy Conference (a) (b) (c) (d) (e) (f) Fig 7 Microstructure of samples sintered at 900°C for 30 min and heat treated at 750°C for 60 min of 0wt%Al.20 39. it was found that density after heat treatment slightly lower than before heat treatment so porosity after heat treatment is slightly higher than before heat treatment.70 19.97 Hardness (HV 1kg) 51. However.43 5. Comparing density and porosity before and after heat treatment.38 6.00 69. 5wt%Al and 10wt%Al samples sintered at 900°C and heat treatment at 750°C.66 29. From the microstructures it was found that pores at center and edge of the sample slightly increase when compare to the ones before heat treatment. Table 2 show the density. porosity and hardness of 0wt%Al (no adding). the sample with added CF‐12 . Ten weight percent aluminum sample has no new phase after heat treatment. it was found that the main phase existing in samples is solid solution of tin in copper (α phase). as a new phase which was not found in the sample before heat treatment. and α phase can be found in all samples.The 3rd Thailand Metallurgy Conference aluminium. Fig. Ten weight percent samples contain α. Five weight percent samples contain both α phase and slight amount of β phase and AlCu4. 5wt%Al contains β phase. it was found that for no adding aluminium sample contains only α phase.8 show XRD pattern of sample sintering at 900°C for 30 min and heat treated at 750°C for 60 min AlCu α 10wt% Al β α β α AlCu AlCu Intensity 5wt% Al α α β α α α 0wt% Al 20 30 40 50 60 70 80 2 Theta (Deg) Fig. increase 37% and 25% respectively. Therefore the cause of reduction of hardness of no adding aluminum sample (0wt%Al) is pores formation and coalescence.8 XRD Pattern of samples sintered at 900°C for 30 min and heat treated at 750°C for 60 min According to XRD pattern of heat treated samples. Although density of 5wt%Al sample is slightly reduced. For added aluminum sample. same as in samples before heat treatment. 5wt%Al and 10wt%Al. but the hard new phase AlCu4 existing in the sample increases its hardness. CF‐12 . β phase and AlCu4. When consider relative amount of phases in heat treated samples. POWDER METAL CO. CRC Handbook of Chemistry and Physics.The 3rd Thailand Metallurgy Conference 4. 4. CRC Press. The main cause of pore occurrence in samples is from Kirkendall effect. the greater reduction in density and hardness in all sintering conditions and they are lower than the reference samples from the factory. 6. Florida. Properties of the Elements and Inorganic Compounds. 5. Conclusions 1. Fifth Printing. 2003.Villars. The authors would like to thank K.Boca Raton. 2. References [1] ASM Powder Metallurgy Committee.Okamoto. 84th Edition. Acknowledgement This project is financially supported by the Graduated School of Chulalongkorn University. Additional heat treatment at 750°C for 60 min can increase hardness of 5wt%Al and 10wt%Al samples by 37% and 25% respectively. Porosity increases and hardness is reduced when adding larger amount of aluminium in all sintering time. A. Lide (ed).Prince & H. ASM Handbook Volume 7 Powder Metallurgy. ASM Handbook of Ternary Alloy Phases Diagrams Volume 4. 3.. 1993. The larger addition of aluminium. CF‐12 . United State of America [2] David R. LTD for providing premixed Cu-10wt%Sn powder. Vapor Pressure of the Metallic Elements [3] P. Section 4. A new package of aluminum crucible furnace and burner was designed and built. Saritporn Vittayapadung3. This paper indicates the possibility of using lard oil in combination with liquefied petroleum gas instead of diesel oil in aluminum melting process. Thailand Tel: +6653 942005 Fax: +6653 942062 Email: Svmpvn@gmail. Keywords: Lard Oil. Five kilograms of aluminum was melted in 34. Thailand Tel: +6686 6570937 Fax: +6653 942062 Email: Supakiat_31@hotmail. Lin780530@hotmail. Chiang Mai.com. Jiangsu University. combined with fuel consumption of liquefied petroleum gas at 0. LPG.64% with 33.5 baht/kg.1 baht/kg. Finally.R. Mechanical Engineering Department. Faculty of Engineering.com 3 School of Food & Biological Engineering.0027 kg/s aluminum melting cost was to 37. Faculty of Engineering. Chiang Mai.com 2 PARA Laboratory.22 minutes of melting time.0015 kg/s. with fuel consumption of lard oil at 0.47%.The 3rd Thailand Metallurgy Conference Feasibility Study of Lard Oil and LPG as Fuels for Aluminum Crucible Furnace Supakiat Supasin1. The used of diesel oil obtained fuel consumption of 0. Chiang Mai University. Chiang Mai University. Aluminum Crucible Furnace. Mechanical Engineering Department. Overall Thermal Efficiency DF‐03 . While. P.02 minutes. Generally. the overall thermal efficiency of crucible furnace using diesel oil was equal to 6. diesel oil would be used for metals melting processes. China Email: S_Vittayapadung@hotmail. Lin Lin3 1 Graduate Student. It could be concluded that lard oil has all benefit and appropriated to be used as a main fuel in melting process over the conventional use of diesel oil. Zhenjiang. Sumpun Chaitep2. The experiment results found that overall thermal efficiency of the system was equal to 6.0013 kg/s and total fuel cost for aluminum melting was 25.com Abstract This research was to study the used of alternative fuel from animal easily found in Thailand. lard oil was selected to be used in this research. a comparison of aluminum melting cost under different fuel was described using lard oil in aluminum melting process. Melting is performed in a furnace. such as. Metal casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods. Also.The 3rd Thailand Metallurgy Conference 1. Chemical reaction of animal fat is shown in Figure 1 [14]. The demand of high energy consumption was caused of high investment cost [11]. and then allowed to solidify [6]. It is generally known that the prices of diesel oil and gas fuel are daily increased. cast steel and nonferrous metal. Thailand can produce animal fat. It consists predominantly of glyceride esters of fatty acids and contains no additions of free fatty acids. The solidified part is also known as a casting. DF‐03 . external scrap. and the design can be optimized based on multiple factors. gas and drying fuel are normally used in melting process [3-5]. Virgin material. Aluminum Crucible in foundry industry is using much of energy. Figure 2 show animal slaughtered (swine. the foundry process is widely used in modern industries. Metal casting is a manufacturing process by which a liquid material is usually poured into a mold. Furnaces are refractory lined vessels that contain the material to be melted and provide the energy to melt it. swine fat or lard oil which is enough to expect used instead of diesel oil in this research. Due to. Thailand is agricultural country. which contains a hollow cavity of the desired shape. brass and aluminum would be used in metal casting process [9]. Introduction At present. Generally. if this process could be decreased the energy consumption. copper. the animal source is not specified or required to give the origin of slaughtered animals. Virgin material refers to commercially pure forms of the primary metal used to form a particular alloy. internal scrap. Furnace design is a complex process. which is ejected or broken out of the mold to complete the process. fossil oil. Diesel oil was usually used in aluminum melting process. Therefore. Electricity. Animal fat is obtained from the tissues of mammals in the commercial processes of rendering or extracting. However. it was interesting. Casting materials are usually metals or various cold setting materials that cure after mixing two or more components together [7-8]. plenty of animal husbandry is popularly practiced [13]. especially in its production process [10]. In the foundry process of some materials was also use a lot of energy consumption [12]. furnaces must be designed around the fuel being used to produce the desired temperature. In actuality. [1-2] Furnaces in foundries can be any size and they are designed according to the type of metals that are to be melted. Several specialized furnaces are used to melt the metal. especially. and alloying elements are used to charge the furnace. cattle and buffalo) for consumption in Thailand (year 2008) [15]. 000.R [Fat & Oil] [Water] Figure 1. Lard Oil as Fuel The pig abdominal fat is one of low cost product and it can be produced as the lard oil fuel with quantity ratio of 90% by mass [16]. Faculty of Engineering.O .000 1.000.000.C . it was found that animal fat.O . Animal slaughtered in Thailand 2008.OH + 3R . This would be the alternative way for energy saving and decreased the investment cost in foundry industry.R + 3H O 2 O CH2 . The main objective of this research was to design and build the burner for aluminum crucible furnace using Liquefied Petroleum Gas (LPG) combine with lard oil as fuels in aluminum melting process.000. cutting oil or illuminant. Chemical reaction of animal fat 8.OH [Glycerol] [Fatty Acid] CH2 .OH CH2 .000 2. Its specification could say that similar to diesel oil.R O CH . Lard oil is consisted chiefly of olein that is expressed from lard and used especially as a lubricant. Consequently.OH O CH2 . especially. Thailand [18].The 3rd Thailand Metallurgy Conference O CH .O .000.000 4. Chiang Mai.000 3.000 6.000 Cattle Buffalo Swine Figure 2.000 Slaughter livestock Expected Slaughter livestock N um ber 5. Table 1 show the comparative properties results between lard oil and diesel oil which was experimented in PARA laboratory. Chiang Mai University.C .000. lard oil might be used instead of fossil fuel such as diesel oil. Table 1 Property of Lard Oil and Diesel DF‐03 .000.000 7. lard oil was used as main fuel in this research [17].C . From overall review. 2.C .000. Q f • • = Fuel heat quantity. kg/s = Fuel low heating value.077 11.The 3rd Thailand Metallurgy Conference Properties of Fuels Heating Value (kJ/kg) Viscosity (cSt) (40oC) (90 C) Specific Gravity @ 25oC o Lard Oil* 41.1 Heat quantity of fuel. Air sensible heat could be calculated follow in equation (2) Q air = mair × C pair × (Ta − Tamb ) • • (2) Where.3 - 44. Q air The temperature of fuel fed in the combustion process was equal to outside temperature.2 Air sensible heat.688 Diesel Oil 42.2 – 5. in case of no fuel preheating. • 3. • Q air = Air Sensible heat.491 0. kW DF‐03 . Qf The heat quantity of fuel is calculated from the fuel combustion process which was determined from equation (1). • • Q f = m f × LHV (1) Where. kJ/kg • mf LHV 3. kW = Fuel mass flow rate. 3. Theory Crucible Furnace system used some thermal theories to calculation as follows [19-21].85 * Lard oil measured from the experiment.500 2. out In(r2 / r1 ) In(r3 / r1 + 2π kb L 2π ks L • Q wall = • (3) Where.in = Heat loss through the furnace wall. oC C pair Ta Tamb 3. The heat loss of exhaust gas at the top of furnace that was released to the outside from a stack to environment could be calculated as follow in equation (4) Q flue = m f × C p .in − Tw. mm = Radius from center of furnace to outside steel sheet. mm = = = Thermal Conductivity of refractory brick.out r1 r2 r3 kb ks L 3. oC = Radius from center of furnace to inside refractory brick. Q flue While. • Q wall Tw. Q wall The calculation of heat loss through the furnace wall consisting of refractory brick and steel sheet material was shown in equation (3). Tw. mm = Radius from center of furnace to inside steel sheet. oC = Outside temperature of furnace wall.3 Heat loss through the furnace wall. aluminum was melted by heat quantity of fuel. kW = Inside temperature of furnace wall. oC Ambient Temperature. kg/s = = = Specific heat capacity (Air). W/m-K Thermal Conductivity of steel sheet. flue × G × (T flue − Tamb ) • • (4) Where. DF‐03 . mm • Tw.4 Exhaust gas heat loss. W/m-K Height of furnace. crucible furnace was operated.The 3rd Thailand Metallurgy Conference • mair = Air mass flow rate. kJ/kgoC Air Temperature in Burner. The 3rd Thailand Metallurgy Conference • Q flue • = = = = = = Heat loss in exhaust gas; kW Fuel mass flow rate; kg/s Specific heat capacity; kJ/kgoC Temperature of exhaust gas; oC Ambient Temperature; oC An exhaust gas quantity; • mf C p , flue T flue Tamb G 3.5 Heat transfer to aluminum material, Q m The heat quantity would be transferred to aluminum material in the crucible inside the furnace. This calculation could be determined by equation (5) • ⎤ ⎡ m C (T − T ) ⎤ ⎡ mA × LH Q m = ⎢ A p , A melt start ⎥ + ⎢ ⎥ tmelt × 60 ⎣ ⎦ ⎢ (tmelt ,end − tmelt ) × 60 ⎥ ⎣ ⎦ (5) Where; • Qm mA = = Heat transfer to aluminum; kW Mass of aluminum in one batch; kg C p, A = Specific heat capacity of aluminum; kJ/kgoC = = = = = Melting point of aluminum; oC Initial temperature of aluminum; oC Latent heat; J/kg Initial melting time; min End of melting time; min Tmelt Tstart LH tmelt tmelt ,end 3.6 Thermal efficiency of crucible furnace, η furnace Thermal efficiency is a measure of the efficiency of converting a fuel to energy and useful work. It used for evaluated the performance of aluminum crucible furnace. Thermal efficiency of aluminum crucible furnace could be followed by equation (6) • η furnace = Qm • × 100 (6) Q input DF‐03 The 3rd Thailand Metallurgy Conference Where; η furnace = • Thermal efficiency; % Quantity heat product; kW Quantity heat inlet; kW Qm • = = Qinput 4. Materials & Methods 4.1 Design and Construction This research was to design and construct crucible furnace system for aluminum melting process. The crucible furnace used materials which easily found in Thailand, it consisted of Refractory brick No.SK36, Steel sheet St.37, Refractory mortar No.70AM. In case of burner (See Figure 3), its components included of stainless steel (SUS-304) pipe 4 inch, Lard oil pipe used SUS-304 size 3/8 inch diameter, Venturi size 4 inch diameter and Heat buffer was modified from refractory brick No.C2. Figure 3 shows the components of burner which constructed in our laboratory. From figure 3, air inlet at position 1 to 3, in the other hand, LPG was also supplied from position 2 to 3. Position 3 was the combustion and burner to burn LPG and air inlet. Heat transferred from position 3 (660oC) to the venturi in position 4 and heat buffer transferred heat to lard oil which moved inside the SUS-304 stainless pipe. N o. 1 2 3 4 5 6 7 D e s c rip tio n s A ir in le t L P G in le t L P G b u rn er V e n tu ri a n d la rd o il o u tle t H eat b u ffer H eat exchanger E x h a u s t o u tle t Figure 3. Components of burner Lard oil viscosity was decreased and heated up while being moved to position 4. It was then forced feed and entrained with moving air to position 5. Finally, the droplet touched high temperature heat buffer. The flame oxidation was visible through out behind position 7. DF‐03 The 3rd Thailand Metallurgy Conference The crucible furnace with burner was constructed in this research as shown in figure 4. Figure 4. Aluminum crucible furnace using liquefied petroleum gas and lard oil as fuel 4.2 Experimental Methodology The experiment of aluminum crucible furnace using petroleum gas and lard oil as fuel system for melting 5 kg/batch of aluminum was tested in PARA Laboratory, Faculty of Engineering, Chiang Mai University, Chiang Mai, Thailand. 5. Results & Discussions 5.1 Principle Burner Testing After finished burner construction, it was tested to determine the properties. Burner testing results were shown in Table 2. Table 2 Burner tested properties Mass flow rate (kg/s) No Air 1 2 3 4 5 Lard LPG Output Temp. (oC) Combustion Efficiency (%) 96.76 74.10 72.36 88.80 97.32 0.042 0.0010 0.0001 1,027.0 0.050 0.0013 0.0001 1,076.0 0.055 0.0014 0.0001 1,051.0 0.061 0.0014 0.0001 0.061 0.0012 0.0001 965.3 853.4 The testing results of burner were found that the capacity of combustion burner which was designed and constructed could be used in aluminum crucible for melting process. Because burner provided the maximum temperature (1,076oC), was higher than melting point of DF‐03 2 Aluminum melting process using lard oil and LPG as fuel The results of aluminum melting process using lard oil and LPG as fuel exhibited the temperature inside furnace. DF‐03 .0015 kg/s and 0. It was found that air flow rate representing 0. The result was shown in figure 6.030 kg/s. lard oil fuel flow rate and LPG fuel flow rate were 0.3 Aluminum melting process using diesel oil as fuel The results of aluminum melting process using diesel oil as fuel exhibited the temperature inside furnace.0302 kg/s. it obtained the highest temperature of aluminum melting was 962. Figure 5.38oC and took 34. crucible temperature and temperature of aluminum were related in this experiment. While. diesel oil fuel flow rate was 0. molten aluminum was ready to be poured into the molds. It was found that air flow rate representing 0. Graph in figure 6 indicated that the trends of temperature lines were continuously increase. Figure 5 was the burner testing.0026 kg/s.02 minutes melting time. The result was shown in figure 7. Burner testing in PARA Laboratory 5.0013 kg/s. crucible temperature and temperature of aluminum were related in this experiment. while. Aluminum temperatures in crucible furnace using LPG and lard oil as fuel 5. approximately. while.The 3rd Thailand Metallurgy Conference aluminum (660oC). air released temperature. all aluminum in crucible was melted. Finally. The experiment was done till aluminum (solid) become aluminum (liquid). 1200 1000 T em pera ture ( o C ) 800 600 400 200 0 0 5 10 15 20 Temperature in Furnace Temperature Outlet Temperature Crucible Temperature Aluminum 25 30 35 Melting Time (Minute) Figure 6. air released temperature. it was proved that lard oil with LPG as fuel in aluminum melting process could be used instead of diesel oil. all aluminum in crucible was melted.24 minute melting time consumption. 5. molten aluminum was ready poured into the molds.000oC and took 33. high heating value of diesel oil was higher than lard oil. it obtained the highest temperature of aluminum melting was 1. However.3. Graph in figure 8 showed the aluminum temperature using different fuels. While.4 The comparison of aluminum temperatures between lard oil and Diesel oil in melting system. This would be one of new choice to select and use alternative DF‐03 . The result shown in figure 8 was found that aluminum temperature using diesel oil was higher than lard oil in melting process. Burning temperature of lard oil as fuel was also enough to melt the aluminum. From item 4.The 3rd Thailand Metallurgy Conference 1200 1000 T emperature ( C ) o 800 600 400 200 0 0 5 10 15 20 25 30 35 Temperature in Furnace Temperature Outlet Temperature Crucible Temperature Aluminum Melting Time (Minute) Figure 7. The aluminum temperature comparison using different fuels Therefore.2 and 4. the aluminum temperatures caparisoned between lard oil and diesel oil in melting of 4 kg aluminum. 1200 1000 Temperature (o C) 800 600 400 200 Furnace Diesel 0 0 5 10 15 20 25 Furnace Lard Oil 30 35 Melting Time (Minute) Figure 8. the results of these 2 fuels used did not much different. Aluminum temperatures in crucible furnace using Diesel as fuel Graph in figure 7 indicated that the trends of temperature lines were continuously increase. due to. Finally. The used of diesel oil obtained fuel consumption of 0. T. References [1] B. pp 17801787. Martins and N. N. 2008. Vol. Khoei. [2] H.1 baht/kg.T. 6. 7. “Diagnostic system for boilers and furnaces using CFD and neural networks”. Afgan. The new package of aluminum crucible furnace and burner were designed and built. PARA (Propulsion & Aerodynamics Research & Application) and FAME (Food & Agricultural Machinery Engineering) Laboratories and the department of Mechanical Engineering Faculty of Engineering Chiang Mai University. “Regulation of the crystallization in a crucible Furnace”. 8.22 minutes of melting time process.0013 kg/s and aluminum melting cost was to 25. Pavlovic and A. diesel oil would be used for metals melting processes. Gethin. I. Five kilograms of aluminum was melted in 34. It could be concluded that lard oil has all benefit and appropriated to use as main fuel in melting process over the conventional use of diesel oil. Masters and D. Janicijevic.47%. remunerated the fossil fuel. Vol.0015 kg/s. Thailand. Expert Systems with Application. [3] A. Conclusions This research was to study the used of alternative fuel from animal easily found in Thailand. Journal of Crystal Growth. lard oil was selected to use in this research.R.64% with 33. a comparison of aluminum melting cost under different fuel was described using lard oil in aluminum melting process. with fuel consumption of lard oil at 0. 20. Institute for Science and Technology Research and Development. 35. “Design optimization of aluminum recycling DF‐03 . Small Gas Turbine Development Research. Calisto.5 baht/kg. This paper indicates the possibility of using lard oil in combination with liquefied petroleum gas instead of diesel oil in aluminum melting process. combined with fuel consumption of liquefied petroleum gas at 0.The 3rd Thailand Metallurgy Conference energy which easily found in Thailand. pp 339-340.0027 kg/s aluminum melting cost was to 37. Cabric. And special thanks to the School of Food & Biological Engineering for this cooperative work. Acknowledgements The authors gratefully thank the financial supports from postgraduate thesis fund. 1998. Generally. the overall thermal efficiency of crucible furnace using diesel oil was equal to 6. The experiment results were found that overall thermal efficiency of the system was equal to 6. Finally. While.02 minutes. doe. [11] G. 2008. 96-106. 2008. [7] O. Vol.dld.R. J. Russia. 1999.J. Carvalho. Mrkov. Energy. pp. Hees. [8] P. Supasin and S.V. Control Engineering Practice. P. Yang. “The effect of casting temperature on the properties of squeeze cast aluminum and zinc alloys”. Auchet. 1980.L Borman and K.R.M. Moscow. P. Masters and D. 116. pp. Zhang. Meadowcroft.go. pp. Ministry of Agriculture and Cooperative of Thailand. Werner. Iung.asp. [Online] Available: http://www. Pantoya and W. U. 2004. pp. [17] S. [6] L. [5] Y. 58-70. Gethin. Odian Store. Mir Publishers. Chaitep. Bangkok. 975-987.L. [Online] Available: http:// tonto.go.W. 487 pp. [13] Department of Livestock Development. 21. “Numerical modeling of the rotary furnace in aluminum recycling processes”.A. [4] V. Journal of Materials Processing Technology.gov/oog/diesel.The 3rd Thailand Metallurgy Conference process using Taguchi technique”. Filho. 2000.M. 2008. Vol. Khoei. 391-396. 153 pp.. BAU-Biogas advisory unit. Metallurgical Furnaces.th/i /index. Gill. 613 pp. Animal Statistics Ministry of Agriculture and Cooperative of Thailand. [Online] Available: http://www. 14431456. 153. “Lard as an Alternative Fuel Replacing Diesel Oil in Crucible Furnace”. Jackson. 1st edition. Int. Silveira and P. Rattanapanont. Biogas plants in animal husbandry. Krivandin and B. “Analysis of aluminum plates under heating in electrical and natural gas furnaces”. Malasse and C. 139. Combustion Engineering. M.dld.html [14] N. 140. 2003. pp. The 2nd Symposium on Engineering and Architecture for the Sustainable DF‐03 . Food Chemistry. Stohr and N. Minerals Engineering. Livestock Infrastructure Information. [9] A. “Characterization of a gas burner to simulate a propellant flame and evaluate aluminum particle combustion”. Sobrinho. pp.S.eia. 2002. pp 178-189. 567-572.J. [12] Energy Information Administration (EIA). Journal of Materials Processing Technology. Journal of Materials Processing Technology. J. Official Energy Statistics from the U.T.html [16] U. 2007. 2001. O. Government. 1998. 509 pp. “Continuous Scrap Melting In a Short Rotary Furnace”. Riedinger. WCB McGraw-Hill.th/jxbvict/stat_web /index _stat. Ragland. Barr and T. 127.L. I. 25. Combustion and Flame. 2008. [10] M. 2003. “First-principles simplified modeling of glass furnaces combustion chambers”. [15] Department of Livestock Development. Technical Guide to Thermal Processes. 1st edition.V. Zhenjiang. 1986. pp 194-197. 133 pp. 227 pp. [18] S. The 15th TriUniversity International Joint Seminar and Symposium. Economic. 2008. P. Engines for Biogas Theory. China. Gosse. [20] K. 1988. Modification. pp 91-94. Cambridge University: England. 2008. Chaitep and N. Vorayos. Technology Promotion Association (Thailand-Japan). S.R. 467pp. DF‐03 . Federal Republic of Germany. [21] S. Mitzlaff. 2002. Laos.The 3rd Thailand Metallurgy Conference Development in the Greater Mekong Sub-Region. Luang Prabang. Sarannit. Operation. Supasin. Heat Transfer. [19] J. “Design of Burner for Aluminum Crucible Furnace using Liquefied Petroleum Gas (LPG) and Land Oil as Fuels”. N. solid and hollow sections. Sonkhla 90112. The semi-solid metal process used in this study is the Gas Induced Semi-Solid (GISS) technique. Microstructure. this process has a high production cost due to the high investment cost of high-pressure machinery. The products from this extrusion process are near net shape and long. Aluminum extrusion. such as bars.The 3rd Thailand Metallurgy Conference Development of an aluminum semi-solid extrusion process T. In the process. Janudoma. The results show that the plunger speed and solid fraction of the semi-solid metal need to be carefully controlled to produced complete extruded parts. Gas Induced Semi-Solid (GISS) 1. Thailand. Memongkolb . the extrusion process DF‐05
[email protected]. beams and rods for various applications. Prince of Songkla University. The objective of this work is to develop a new extrusion process using a semi-solid metal forming technology. a laboratory extrusion system was used to fabricate aluminum rods with the diameter of 12 mm. S. Wannasina* a Department of Mining and Materials Engineering. Thailand. *Corresponding Author: jessada. b Department of Industrial Engineering. Sonkhla 90112. Hat Yai. However. In this study.th Abstract An aluminum extrusion process is mainly used to fabricate long tubes. straight metal products with constant cross section. Introduction Extrusion is one of various forming processes that is used to produce long. Faculty of Engineering.ac. a billet is heated and forced through a die orifice. Hat Yai. Faculty of Engineering. Prince of Songkla University. Rattanochaikula. Extrusion process. However. tubes and wires [1]. To study the feasibility of the GISS extrusion process. the effects of extrusion parameters such as plunger speed and solid fraction on the extrudability and microstructure of extruded samples were investigated. Semi-Solid Metal. Key words: Aluminum alloys. the effects of the plunger speeds and solid fractions on the extrudability of an aluminum A356 alloy were investigated. Chemical composition of aluminum A356 alloy Element Si Fe 0. The chemical composition of the alloy is shown in Table 1. Several previous studies have been reported regarding the behaviors of the rheoextrusion process. In a rheo-extrusion process. To apply the rheo-extrusion process in the production of commercial parts.04 Mg 0. The slurry is forced through a die orifice to form a desired part.01 Ti 0. the metal alloy is melted in a furnace and then extruded at a temperature between the solidus and liquidus temperature of the metal alloy.The 3rd Thailand Metallurgy Conference requires a high-pressure machine to force the metal in the solid state. However.42 Zn 0. When the temperature of the molten aluminum was about 620°C. a graphite diffuser was immersed to induce nitrogen gas for 5 seconds. defects such as surface defect and piping can be present in the products of an extrusion process [1]. no complete research in the rheo-extrusion process has been published [3-5]. high fluidity of materials. A schematic drawing of the GISS technique and the GISS machine is shown in Figure 1. Table1. A semi-solid slurry with the solid fraction of about 10% was then obtained.05 Mn 0. In addition.9 Preparation of semi-solid slurry: The aluminum A356 alloy was melted in an electric furnace at the temperature of about 650°C. This research paper reports a preliminary research and development work of a new rheo-extrusion process using the Gas Induced Semi-Solid (GISS) technique. Approximately 300 grams of the molten aluminum was taken from the crucible by a ladle. and low friction force between the die and the materials [2]. 2. Semi-solid rheo-extrusion is a new extrusion process that has several advantages such as low extrusion force. Weight% 6. it is important to conduct further studies. In this study.42 Cu 0. Materials and Experimental Procedure The raw material used in this work is aluminum A356 alloy. DF‐05 .10 Al Bal. Figure 2: The schematic drawing of this extrusion process. and 6 cm/s through a die. The schematic drawing of this rheo-extrusion process is shown in Figure 2.The 3rd Thailand Metallurgy Conference (a) (b) Figure 1: (a) Schematic drawing of the GISS technique [6] and (b) the GISS machine to prepare semi-solid slurry Rheo-extrusion test: The semi-solid slurry from the GISS machine was then poured into a shot sleeve with the inner diameter of 40 mm. The holding time of the slurry in the shot sleeve. the slurry was forced by a plunger at various speeds of 2. Next. 4. was also studied in this work. This machine has a 20-ton capacity with a hydraulic system. Figure 3 shows the extrusion die and the laboratory-scale extrusion machine. a graphite support and a water-cooled tube. Figure 3: The extrusion die and laboratory-scale machine used in this study. 0 second and 5 seconds at each plunger speed. The inner diameter of the die was 12 mm. The shot sleeve was preheated to about 350°C-400°C. DF‐05 . The samples were cut and obtained from two positions as shown in Figure 4. The samples were then prepared for metallographic analysis using the standard grinding. The results show that faster plunger speed and lower holding time yield longer samples. In this work. Samples with smooth surfaces in all the area would pass the requirement. 1 inch 1 inch Sample Figure 4: The sampling position.The 3rd Thailand Metallurgy Conference Results analysis methods The extruded samples were analyzed by three criteria to determine the extrudability. Microstructure uniformity: the microstructure of samples was observed using an optical microscope. (see Table 2. The methods are briefly described as follow: Length of the samples:. Only the sample with a low plunger speed of 2 cm/s and a longer holding time of 5 s did not pass the length criteria. the length of the samples was measured after the extrusion test. DF‐05 . Results and Discussion The representative extruded samples from the experiments are given in Figure 5. Surface quality: The surface of the samples was also examined.) The results suggest that conducting the rheo-extrusion process with a high speed and with the low-solid-fraction slurry (no holding time) gives the longest length as expected since the slurry can flow easier and faster. 3. Good extruded parts should have uniform microstructure throughout the length. polishing and etching procedure. the criterion for the required length was 15 cm. shorter samples then the criterions were rejected. DF‐05 . The semi-solid extrudability of A356 Al-alloy 0s 5s length Surface length Surface 2 cm/s 4 cm/s 6 cm/s x x x x x 24cm 6cm/s 23cm 4cm/s 14cm 2cm/s (a) 35cm 6cm/s 30cm 4cm/s 27cm 2cm/s (b) Figure 5: The samples from GISS extrusion at (a) each plunger speed and 5 seconds of holding time and (b) each plunger speed and 5 seconds of holding time.The 3rd Thailand Metallurgy Conference Table 2. (a) (b) Figure 6: The surface finished of samples of (a) 4cm/s of plunger speed and holding time is 5 seconds and (b) 4cm/s of plunger speed and no holding time. when the surfaces of the samples were examined. Only the samples produced by lower speed (2-4 cm/s) and at a higher solid fraction pass the surface quality requirement.The 3rd Thailand Metallurgy Conference However. (a) Middle (b) Edge Figure 7: The representative microstructures of the cross section of the samples For all the samples. Figure 7 shows representative microstructures at the edge and the middle of the samples. only samples produced by the conditions of 4 cm/s plunger speed and holding time of 5 seconds pass the requirements of length and surface quality. the samples produced by fast speed and at a low solid fraction have surface defect as shown in Figure 6(b). The micrographs show that the solid particles are concentrated near the center of the channel DF‐05 . The fast flow speed of the slurry may cause turbulent flow causing the surface defect. the slurry will have laminar flow at the same flow speed. the microstructures at the edge and the middle are similar. By increasing the viscosity of the slurry through increasing the solid fraction. From these results. The 3rd Thailand Metallurgy Conference during the flow. At tip of samples At base of samples Plunger speed is 2 cm/s and no holding time Plunger speed is 4 cm/s and no holding time Plunger speed is 6 cm/s and no holding time Figure 8: The microstructure of each sample that no holding time. Representative microstructures of the samples at the tip and the base of the rods at various plunger speeds and holding times are given in Figure 8-9. DF‐05 . Coarse Eutectic Fine Eutectic (a) Tip (b) Base Fig 10: The different eutectic structure at each position. DF‐05 . as shown in Figure 10. Fine eutectic structure is observed at the base of the rod. The eutectic phase at the tip has coarse structure. The results show that the metals near the tip have longer solidification time so that the eutectic structure can grow larger.The 3rd Thailand Metallurgy Conference At tip of samples At base of samples Plunger speed is 2 cm/s and 5 seconds of holding time Plunger speed is 4 cm/s and 5 seconds of holding time Plunger speed is 6 cm/s and 5 seconds of holding time Figure 9: The microstructure of each sample that have 5 seconds of holding time. To improve this. In general. the amount and distribution of the primary α phase in all the samples are quite uniform. the eutectic structures in the samples at the tip and the base of the rods are different. a better cooling system should be applied in the rheo-extrusion system. However. London : CHAPMAN & HALL LTD. Zhang. This preliminary study gives important information for the development at the rhoextrusion machine using the GISS technique in the future. 2. 2. the following conclusions can be drawn: 1.S. M. WILEY-VCH Verlag GmbH & Co.D. 2005.. 5.. Conclusions From this study. Faculty of Engineering. M. Thixoforming. Pearson. The extrusion of metal.Q. 1960. and Parkins. Materials Science and Engineering A402 (2005) 170-176 4. Journal of Materials Processing Technology Vols. and Wang S. 2003. The extrusion behavior of an aluminum A356 alloy using the GISS technique is influenced by the plunger speed and the solid fraction of the slurry in the shot sleeve. DF‐05 . Zhu. D. 4. Acknowledgements The authors gratefully thank the Department of Mining and Materials Engineering. 3. The non-uniformity of the eutectic microstructure is caused by inefficient cooling of the extruded samples. KGaA. The higher solid fraction of the slurry helps reduce the surface defects of extruded parts. R. S. H.The 3rd Thailand Metallurgy Conference 4.N. References 1.H. N. Kim. Extrusion behavior of Al-Cu alloys in the semisolid state. Joo. K. B.. The extrusion behaviour of Zn-20% Al alloy in the semi-solid state. This problem can be improved by adding a better cooling system along the die. Wang. 2004. 6. Price of Songkla University for financial support and facilities. 3.H.. and Reiner. Lee.F. C. 44: 91-98. Gerhard. Wang. We also thank Miss Rungsinee Canyook for the metallographic preparations and the Innovative Metal Technology (IMT) team for all the kind supports.. L. Wannasin.The 3rd Thailand Metallurgy Conference 5. Development of a semi-solid metal processing technique for aluminum casting Technol. Wannasin. DF‐05 . S. 2008. 141-143:97-102. Development of the Gas Induce Semi-Solid Metal Process for Aluminum Die Casting Applications. S. Solid State Phenomena Vols. Byung-Min Kim and Jae-Chan Choi. 7. Sci. Jae-Ho Hwang. Rattanochaikul. Gyu-Sik Min.. 10: 1311-1328. 6. Dae-Cheol Ko. Junudom. J. and Flemings. Finite element simulation and experiment for extrusion of semi-solid Al 2024... T. J. 30(2): 215-220. MC. and Thanabumrungul. applications. Songklanakarin J. International Journal of Machine Tools and Manufacture Vols. 2080. 2920 Fax +662-8894585 ext. by using the rice husk of 65 g.th Abstract: This study aims at the preparation of silicon nitride powder from rice husk silica by chemical and thermal degradation. high-temperature separation membranes.ac. Salaya. was reacted by 3 M of hydrochloric acid concentres and then filtered the sample by plastics grate. damage tolerance and thermal shock resistance.The 3rd Thailand Metallurgy Conference The Preparation of Silicon Nitride by Silicon Source from Rice Husk Ash S. Traditionally. 5 and 6 hours.min-1. Hat yai. Rattanaveeranon1*and D. 73170. Faculty of Science. The scanning electron micrograph shows the surface morphology of silicon nitride phase consisting of fibers and/or whiskers. as a strategy to reduce dielectric constant and loss. The Si3N4 ceramics with a tailored microstructure are promising high performance materials because of such unique properties as light weight.r@rmutr. respectively. Bhongsuwan2 Department of General Education (Physics). Thailand. The composition of silica powders were mixed with carbon powders by ratio 20 : 12 wt% and calcined at temperature 1400°C at the rate of 5 °Cmin-1 under N2 atmosphere of 1 dm3. good strain tolerance.2920 2 Materials Science Program. Introduction Silicon nitride (Si3N4) has been widely used to fabricate cutting tools and high-temperature structural applications due to its excellent mechanical. Rajamangala University of Technology Rattanakosin. physical and chemical properties. then washed the sample with pure PF‐21 . Tel: +662-8894585-7 ext.The soaking temperature was maintained for a period of 4. the Si3N4 ceramics have been used as hot gas filters. Recently porous Si3N4 ceramic is also attractive in electromagnetic wave penetrating materials. Thailand. Materials and Methods Starting material. Prince of Songkla University. The XRD analysis shows the presence of cristobalite at firing temperature 1400°C and soaking time of 4 hours. The appropriate temperature for silicon nitride formation is at 1400°C with the soaking time of 6 hours. Songkhla 90110. Tel: +6674-288396 Fax: +66-74218701 * 1 Corresponding Author E-Mail : santi. Phuttamontol. and catalyst supports. X-ray diffractometry (XRD) analysis was conducted to examine the phases in the obtained silicon nitride ceramics and X-ray fluorescence(XRF) was analyzed the chemical compounds of rice husk ash. The dried powders were then sieved to 60mesh.35 0.23 0.65. Shows the distribution of particle size of silica powder. Results Table1.%) Furthermore. It was obtained the pure silica powder (SiO2) (pure silica over than 95 wt.The resultant slurry was dried to obtain an agglomerate-free powder mixture to dry box at 100 °C for at least 3 hours to ensure that the powders were completely free of alcohol. finally washed the sample with distilled water. Compounds Silica (SiO2) Alumina (Al2O3) Calcium Oxide (CaO) Others Concentrate (%) 99.The samples were prepared to mix by ration 20 : 12 wt.52 μm). dried the sample at 100 ° C with the soaking for 2 hours and then brunt the sample at 850 °C with the soaking for 3 hours (increasing temperature rate = 20 °C⋅min-1).%. Absolute ethanol was used as the milling media. 0. The laser particle sizing analyzer (LPSA) was measured an average particle.99 wt. there is a trace element such as alumina and calcium oxide of only 0.%.The 3rd Thailand Metallurgy Conference water several times.% (SiO2 : C).(more than 99 wt. shows the analysis by using XRF technique using for analyzing chemical compounds of rice husk ash (RHA).The mixtures were ball-milled for 24 h using ceramic balls. respectively. 5 and 6 hours.The sample was calcined at 1400 °C with varying the period of calcined time for 4.).41 0. The hydrochloric concentrate of 3 M is enough to remove all of the impurity in rice husk ash.01 Fig1. Table 1: Show that the chemical compounds of rice husk ash which calcined at 850°C for 3 hours. PF‐21 .The main chemical compounds of this product is silica and there is amorphous structure. The morphologies of combustion products were studied by using scanning electron microscopy (SEM). The sample was prepared by abovementione to mix with activated carbon (pure 99. 2(b).2(a). Fig. There is no silicon nitride in the sample but there is only cristobalite-silica structure Fig. the particle size is less than 10 % which is 1. respectively. Second. The sample was calcined for 6 hours. there was only the silicon nitride Fig.1 The particle size of silicon oxide was milled for 12 hours. First. α-silicon nitride and β-silicon nitride mixing in the sample. it began to have silicon nitride and silicon oxide nitride Fig. When the sample was calcined for 5 hours . Third.The 3rd Thailand Metallurgy Conference The distribution of particle size of silica powder consists of 3 types. Furthermore.2 shows the XRD pattern of silicon nitride calcined at temperature 1400 °C at the rate of 5 °C/min in nitrogen atmosphere of 1 dm3⋅min-1 soaked for 4 hours.2(c) and there were two forms . the particle size is more than 90 % which is 326. PF‐21 .(the samples were ball milled for 12 hours) 50 % 5 4 Volume (%) 3 2 1 10 % 0 10 -2 10-1 10 0 10 1 10 2 100 % 10 3 10 4 Particle size (μm) Fig. the mean particle size of silica powder is 83.66 μm.04 μm. there is unreated silica which betides the silica-cristobalite only.08 μm. Cristobalite low (a) 1 3 1 1 1-Si3N4 3-Si2N2O2 (b) 1 1 1 1 1 1-Si3N4 (c) Fig.9% with the soaking time for 4 hours PF‐21 .9% with the soaking time for 4 hours (a).3 The SEM morphology of SiO2+C compound was calcined in pure nitrogen gas 99.The 3rd Thailand Metallurgy Conference 1 2 2 2.2 The XRD pattern of SiO2+C was calcined in pure nitrogen gas 99. 5 hours (b) and 6 hours(c) Fig. it shows if the silica rice husk ash mixed with carbon at the ratio of 20 : 12 wt. the pure silica rice husk was obtained.% which is calcined at 1400 °C for 4 hours. These impurities were easily leaching by concentrate acid and then washed the sample with distilled water several times.4 The SEM morphology of SiO2+C compoundswas calcined in pure nitrogen gas 99. PF‐21 .9% withthe soaking time for 6 hours. But there is a form of silicon nitride and silicon oxide nitride impure agglutinated in the sample. there is only the silicon nitride with two forms. α-silicon nitride and β-silicon nitride mixing in the sample. Discussion The hydrochloric concentrate of 3 M is enough to remove all the impurity in rice husk ash. If the sample is calcined for 6 hours.The 3rd Thailand Metallurgy Conference Fig. silicon nitride is not obtained. From the XRD pattern. The calcined time of 6 hours was the optimal condition for preparing the silicon nitride. After that the rice husk was calcined at 850 °C (carbon was thermal decomposed at 550 °C) Finally. Fig.5 The SEM morphology of SiO2+C compoundswas calcined in pure nitrogen gas 99.9% withthe soaking time for 5 hours. it shows that the surfaces of calcined sample of 4 hours became porous which is weaving into a network across the sample but in some parts there were small sphere affiliated within a long stripe.(2004) “Effect of raw-Si particle size on the properties of sintered reaction-bonded silicon nitride” Cera Inter.. S. 140-127 [3] Lee J.C. D.. When increasing the calcined time upto 5 hours..(2004) : ‘Silicon-Nitride-Based Nanoceramic Materials’. H. 363–364 [2] Grechikhin L.Kimb H.. the there was less porous in the material of the surface then it was conglomerated into a clump and there was a little bit fiber.The 3rd Thailand Metallurgy Conference The SEM morphology Fig.. The porosity of samples were decrease when the calcined temperature was increase. But if we increased the calcined time up to 6 hours there was the least porous in the material and there was the whisker which was orthogonal with the surface of sample Conclusions The hydrochloric concentrate of 3M can well remove the impurities in rice husk and results in the purity of product more than 99 %. Hanrui Z. I. Cera Inter 29 pp.3-5 at 5.S. The silicon nitride was formed when calcined at temperature of 1400 °C more than 6 hours continuously which results in αsilicon nitride and β-silicon nitride mixing in the sample.. Inor.. Baolin Z. 30 pp. and Golubtsova E. Muna J. Hanb B.. and Wenlan L.000 magnifications.and Kim S. (2003) “Combustion synthesis of network silicon nitride porous ceramics”. pp. 965–976 PF‐21 .. Shin B. 41. References [1] Dianying C. D. Mater.