conditions may require the accomplishment of a ~- rejectable only if thev p.x~p.p.d specification require~ts mal stress relief--~ - --.~'--"--treatment. Here, the weldment is grad- in terms of type, size, distribution, or location. A rejec- /' willy heated at a prescribed rate to the stress relief range table discontinuity is referred to as a defe~. By defini- of approximately 1l00° . to 12~, (590°to 650°C) .for .~ tion, a defect is a discontinuity whose size,.shape, orien- l!10st carbol1~' After holding at this temperature tation, or location makes it detrimental to the useful for about one hour for each inch of base metal thick- service of the part in which it occurs. Discontinuities ness, the weldment is allowed to cool to about 600°F may be found in the weld metal, heat affected zone, or (315°C) at a controlled rate. The inspector may be base metal of many weldments. Four basic weld joints responsible for monitoring this operation to assure that are considered in this guide: butt, T, corner, and lap. the procedure requirements have been met. Weld and base metal discontinuities of specific types 3.4.3 Final Dimensional Examination. Another mea- are more common when certain welding processes and surement that affects the performance of a weldment is joint details are used. An example is the tungsten inclu- its dimensional accuracy. If a welded part will not fit an sion, which only occurs in welds made using gas assembly, it may be useless, even though the weld is of tungsten arc welding. Other conditions, such as !!!g!1 adequate quality. Welding heat will distort the base restraint and l~ited access to portions of a weld joint, metal. and can alter overall component dimensions. may lead to a higher than normal incidence of weld and base metal discontinuities. ~. ~ Therefore, dimensional examination after welding may be required to determine the weldment's fitness for its Each general type of discontinuity is discussed in intended use. detail in this section. Other documents may use differ- ent terminology for some of these discontinuities; 4. Weld Surface Conditions however, whenever possible, the approved AWS termi- nology, as found in ANSI/ AWS A3.0, Standard Weld- 4.1 General. This section is concerned only with dis- ing Terms and Definitions, should be used to eliminate continuities, which mayor may not be classed as defects (rejectable) depending on requirements of individual confusion. An example of additional terminology occurs specifications or codes. The intent is informational and in ANSI/ AWS D 1.1, Structural Welding Code - instructional, and meant to assist in the identification of Steel. There, "fusion-type discontinuity" is a general term which is used to describe a number of various discontinuities. Discontinuities can occur at any loca- tion in the weld. Visual inspection after the weld is discontinuities, including: slag inclusions, incomplete completed is limited to the surface condition of the fusion, incomplete joint penetration, and similar elon- weld. Discovery of subsurface defects requires that a gated discontinuities in fusion welds. Another typ..e.Qf*' visual examination be supplemented by other NDE discontinuit\: is caused by loss of shielding gas. see Fig- methods. ure 1. These disco;rtInUities are of general interest to owners, designers, and fabricators. A discontinuity is defined as an interruption of the typical structure of a weldment, such as a lack of 4.2 Porosity. Porosity is characterized by cavity typ.E homogeneity in the mechanical, metallurgical, or physi- discontinuities formed by gas en!rapment during solidi- cal characteristics of the material or weldment. A-dis.- fication. The discontinuity formed is generally spherical c£ntinuitv jSI!Q..t nece~s~Jj1y ~ d~(~ft. Qj§cQIltinuit~!Lare but may be cylindrical. Often,j!9rosity is_anindiG.atiQ.n Figure 1 - Surface Oxidation (Sugaring)in a StainlessSteel Gas TungstenArc Weld -.... that the welding pro.cess is no.t being..prot!erly co.n- lo.catio.ns. An example o.f linear Po.ro.sity,with an lliillW, o.rthat the base metal o.rfi!!ermetal is co.ntami- acco.mpanying lo.ngitudinal crack, is sho.wnin Figure 3. nat~, o.r t~ ~_!TI~tal. i~ o.f _a_.£o.Jl1R£,sitio.I} - ....- t))Y 4.2.3 Piping Porosity. Piping Po.ro.sity(also.referred inco.mpatible with.the welding [tiler metal and pro.cess. to. as wo.rmho.le o.r elo.ngated JW~o.sity)is a term fo.r ~ 4.2.1 Scattered Porosity. Scattered Po.ro.sitv is Po.rQS- elo.ngated gas disco.~tinuities. Pil'ing Po.ro.sityin fillet ity widely distributed in a single weld bead o.rin several welds extends fro.mthe weld ro.o.tto.ward the weld face. beads o.fa multiple pass weld. Po.ro.sitywill be present When a few Po.res are seen in the weld face, careful in a weld if the welding technique, o.r materials used o.r excavatio.n will o.ften sho.Wthat there are many sub- the co.nditio.nso.fthe ~eld jo.int preparatio.n, lead to.gas surface Po.resthat do.no.textend all the way to.the weld fo.rmatio.nand entrapment. If V{eldsCo.o.I slo.wlveno.ugh face. Figure 4 is an illustratio.n o.f so.me surface Po.res - to.allo.wgas to.pass to.the surface befo.reweld so.lidifica- tio.n, there will generally be no. Po.rosity in the weld. Figure 2 illustrates the presence o.fscattered Po.ro.sity. which, when excavated, were determined to. be piping Po.ro.sity. y 4.2.2 Cluster and Linear Porosity. Cluster Po.ro.sit¥ 4.3 Incomplete Fusion. Inco.mpletefusio.nis termed as is a Io.calized gro.up o.f Po.res. It o.ften results fro.m ~ which do.es no.t o.ccur o.verthe entire base metal impro.per starting o.r sto.Pping o.f the welding pass. surfaces intended fo.rwelding and between all adjo.ining Co.Q.ditio.nscausing arc blo.Wcan also. result in cluster weld beads. Figure 5 depicts inco.mplete fusio.n which Po.roSity.Linear Po.ro.sitvis a number o.fPo.reswhich are has o.ccurred at vario.us Io.catio.nsin the weld. Figure 6 aligru:d. It o.ften o.ccurs alo.ng the weld interface, the sho.WSinco.mplete fusio.n picto.rially that Wo.uldno.t be weld ro.o.t,o.ran inter-bead bo.undary, and develo.Psby apparent during visual inspectio.n,but Wo.uldbe detected co.ntaminatio.n that causes gas to. be liberated at tho.se - - by radio.graphyo.rultraso.nicexaminatio.n. -... Figure 2 - Scattered Porosity Figure 3 - Linear Porosity with Crack Figure 4 - Surface Appearance of Piping Porosity Figure 5 - Various Locations of Incomplete Fusion Figure 6 - Incomplete Fusion Incomplete fusion can result from insufficient heat Figure 7 shows an example of incomplete fusion i~ or the improper manipulation of the weldin~~iec:- occurring at the groove face of a flux cored arc weld in t~. While it is a discontinuity more commonly asso- steel. Fjgures 8 and 9 show the presence of incomplete ciated with ~e, jt could also be caused by fusion (cold lap) between individual weld beads and the presence of contaminaD.!§ on the surface being between the weld and base metals. These conditions welded. were found in gas metal arc welds in aluminum. Figure 7 - Incomplete Fusion at the Groove Face Figure 8 - Incomplete Fusion Between Weld Beads Figure 9 - Incomplete Fusion Between the Weld and Base Metal 4.4 Incomplete Joint Penetration. Incompletejoint pen- etration is defined as penetration by weld metal that does not extend for the full thickness of the base metal in a joint with a groove weld. Figure 10 depicts some conditions which are classified as incomplete joint pene- tration. The condition shown for the single V-groove weld will only be evident using visual examination if there is access to the weld roqt side. The condition shown on the double bevel T-joint will not be evident on the completed weld, ex,cept at the starts and stops. Incomplete joint penetration mav resultfrQm insuffi- ~~_eldi~.~h~at, improDer lateral control oJ the weld- in~ arc, or improper joint confi~ration. Some welding processes have greater penetrating ability than others and would therefore be less susceptible to this problem. Many designs call for back gouging the weld root with subsequent welding on that same side to ensure that there are no areas of incomplete joint penetration or incomplete fusion. Pipe welds are especially vulnerable to these discontinuities, since the joint is usually inaccessible for welding from the root side. Often a backing ring or consumable insert is employed to aid welders in such cases (see Figure 11). Figure 12 is a Figure 10 - Incomplete Joint Penetration photograph depicting incomplete joint penetration at the weld root. Figure 11 - Incomplete Fusion with Consumable Insert Figure 12 - Incomplete Joint Penetration 4.5 Undercut. Undercut creates a transition which from the failure of a welder or welding operator to should be evaluated for a reduction in cross section, and completely fill the weld jo~nt~he!! called"for in the job for stress concentrati0l!§ or notch effect when fatigue is specifications, and is rarelv accepta1;>le.Figure 15 illus- a consideration. Undercut, controlled within the limits trates the configurations of underfill. A nonstandard of the specification, is not usually considered a weld term for underfill :It the root sll~ace o(a pipe weld is defect. Undercut is generally associated with improper "internal conc~." Figure 16 shows the presence of welding techniques or weld parameters, excessive weld- unae;:TIUin a flux cored arc weld in steel. i~ currents ()r_yoltages, or both. Figure 13 shows the 4.7 Overlap. Overlap is the protrusion of weld metal common configurations of undercut. Figure 14is a pho- tograph of undercut at the toe of a fillet weld in steel. beyond the weld toe, or weld root. It can occur as a result of poor control of the welding process, improper 4.6 Underfill. Underfill is a depression on the ~eld f~e selection of the welding materials, or improper prepara- or root surf~c.eextending below the adjacent surface !2f tion of materials prior to welding. If there are tightly the base metal. Underfill is usually defined as a condi- adhering oxides on the base metal that interfere with tion where the total thickness throu~h a weld is less fuslOil,overlap will often result. Figure 17depicts over- than the thickness of the adjacent base metal. It results lap conditions. Figure 13 - Examplesof Undercut --------- Figure 14 - Undercut at Fillet WeldToe Figure 15 - Underfill Figure 16 - Underfill Using Flux Cored Arc Welding in Steel Figure 17 - Overlap Overlap is a surface discontinuity that forms a mechan- and pressures of the rolling operation. Tight lamina- tions ~-'-- will sometimes - -- conduct sound across the interface ical notch, and is nearly always c~sidered reie~.~~ An illustration of overlap lSshown in Figure 18............. a~ay not be fully evaluated by ultra~c 4.8 Laminations. Laminations are flat, generally eJ2D- ~. ~ated\ ~~e ~!al <!iscontinuties.found in th~c.:~!!}ll 4.9 Seams and Laps. Seams and I!!psare longitudinal thicknes~~rea of wrought products. An example is base metal discontinuit~metimes found in forged (le"picted in Figure19. - .- and rolled products, or both. They differ from lamina- .-( Laminations may be £.ompletely internal, and are tions in that they propagate to the rolled surface even ~U then Ql)lyci~te.ctednondestructively by .!!!t~as<>..!!ic~ th~ey may run in a lamellar (llrectlOn(paraneno .ill& They may also extend to an edge or end where they the rolled surfaces) for some portion of their length. ar~e surface and may be detected by visual, When one of these discontinuities lies-parallel totlle pen~, or magnetic particle testing. They may also princioal stress. it is not generdly considered to be a be revealed when 'exposed by cutting or machining critical flaw. HoweveC;-whenseams and laps arep_er- operations. pendicular to the applied or residual stresses, they will Laminations are formed when gas voids, shrinkage often propagate as cracks. Seams and lapsareS\iTface- cavities, or nonmetallic inclusions in the original ingot cQImecteddiscontinuities. Ifuwever, their presence may are rolled flat. They generally run parallel to the surface be masked by manufacturing processes that have sub- of roIIc::d..m-Q.d.!,!c!.s and are most commonly found jn sequently modified the surface of the mill product. ~rs and plates. Some laminations are partially forge ~r seams and laps can cause cracking and welded along their interface by the high temperatures should be avoided. . Figure 18 - Overlap . I . I. . .I Figure 19 Laminations in the heat affectedyone and noUn the...wcld.,Longitu- a photograph of a longitudinal crack which has propa- dinal cracks lI!..1Yelds.made bv machine welding, are gated along the ~eld between pores of linear porosi~y. commoriIyaSso~ted with high weldingspeeos and are Figure 23 shows two transverse weld metal cracks som~11~s related to porosity that does not show at the occurring in a multipass gas metill arc weld in a high weld face. Welds having hi h'd idth ratios ay strength steel weldment. afs015e susceptib e to longitudinal cracking dueJQ.Jhe 4.10.2 Throat Cracks. Throat ~sk~!!!:e 10ngiJudi- resulting solidification pattern~. Longitudinal cracks in nal cracks in \h,~}V~!Qja£e!1.!J!t,edirection of the wel~L small welds between heavy sections are oft~ axi~They are generally, but not always, hot cracks. An of nlplO-cooling rates and hiJ!;hrestraint. Cold trans- example of a throat crack in a fillet weld is shown in ~eIsecrackS are generally the result of 10~2! Figure 24. shrinkage stresses acting on hard weld metal of low ductility. Figure 21 shows, schematically, the appearance 4.10.3 Root Cracks. Root cracks are longitudinal of both longitudinal and transverse cracks. Figure 22 is cracks in the weld root. They are generally hot cracks. LONGITUDINAL TRANSVERSE CRACK CRACK Figure 21 - Longitudinalversus TransverseCracks Figure 22 - Longitudinal Crack and Linear Poros!!I Figure 23 - Transverse Cracks Figure 24 - Throat Crack 4.10.4 Crater Cracks. Crater craili OCCIIT lLthe weld reinforcement can amplify stresses, making tne weld crater and are fprmed bYimproper termination of weld toe a more likely area for cracking to occur. Figure the we~ A nonstandard term for crater cracks is 27 shows the appearance of toe cracks in a T-joint, and s't;i crack th~ugh TIleymay have other shapes. Crater Figure 28 shows a photograph of a toe crack. cra~ are shallow hot cracks usually torniliiii a:multl~ Toe cracks initiate approximately normal to the base poi~ star-lik~clllster. Figure 25 shows a crater crack metal surface. ~e cr~.£ksare ge_neI~llythe re!ill!LQ.f occurring in an aluminum gas tungsten arc tack weld. thermal shrinkage stres~es acting on a weld heat In Figure 26 another aluminum gas tungsten arc weld is affected zone. Some toe cracks occur because the trans- pictured, where the exiting crater crack propagated into verse tensile properties of the heat affected zone cannot aJongit].ldipijlthrQM9!ack around the circumference of accommodate the shrinkage stresses that are imposed the circular fillet weld. by welding. 4.10.5 Toe Cracks. Toe cracks are generally cold cracks. They initiate and~propagate from the weld toe 4.10.6 Underbead and Heat Affected Zone Cracks. wnererestraint stresi~~. J:tigh~. Abrupt profile UI?-Mea~d heat affected zone cr.acks are.generally changes at the toe caused by excessive convexity or cold cracks that torm in the heat affected zone of the -.._-- Figure 25 - Crater Crack Figure 26 - Longitudinal Cracks Propagating from Crater Crack Figure 27 - Toe Cracks Figure 28 - Toe Cracks - base metal. Underbead - and heat affected zone cracks can be either lon~itudmal or 1faIlsvt:rse:-'fhev~ at regular interval& under the weld and also outline 4.12 Weld Reinforcement. Weld reinforcement is weld metal in excess of the quantity required to fill a groove weld. It is that amount of weld metal in a groove weld bou~anes ot the weld where residual stresses are hi~- that is above the base metal surface, as shown in Fig- ~ Underbead cracks can become a serious problem ure 31. when the following three elements are present simul- All weld reinforcement produces a notch effect at the taneously: weld toe. Weld reinforcement, when excessive, QQes.,not (l) Hydrogen a5!9.to the strength of t~~ss (2) Cr~ck-susceptible microstmcture raiser to amplify the applied stress. Great~r reinforce- (3) Stress ments are associated 3!!.h re.5iucedreent@!!t angles, Figure 29 depicts the occurrence of under bead crack- which result in greater notch effects. Reinforcements ing, w,hich..£annot be det~~~by visual examinatio!!,z which are excessive tend to produce significant notch /except -- if the material is sectioned.-- effects at the toe of the weld, which act as stress raisers and can produce cracking in service. 4.11 Slag Inclusion. Slag inclusions are nonmetal~ solic!.Q1aterialentrapped in weld metal or between weld 4.13 Convexity and Concavity. Convexity is the maxi- metal and base metal. Slag inclusions are regions within mum distance from the face of a convex fillet weld the weld cross section or at the weld surface where the perpendicular to a linejoining the weld toes. Convexity, once-molten flux used to protect the molten metal is as shown in Figure 32, is a term applied to a fillet weld. mechanically trapped within the solidified metal. This Like weld reinforcement, ~ thf'~mountofJhis COJ1- solidified slag represents a portion of the weld's cross vexity is exces~e, t~ notch c.reated at the weld toe section where the metal is not fused' to itself. This can could result in toe cracking. During welding, excessive result in a weakened condition which could impair the convexity can occurin the intermediate beads of multi- serviceability of the component. Although normally pass welds which may inhibit the cleaning process and thought of as being subsurface discontinuities, inclu- may lead to slag inclusions or inco!.llplet~usion. Figure sions may also appear at the weld surface, as seen in 33 depicts the presence of convexity. Figure 30. Like incomplete fusion, slag inclusions can Concavity is the maximum distance from the face of occur between the weld and base metal or between indI: a concave fillet weld perpendicular to a line joining the ~idualweldpasses.In fact:-~hlginclus1~s;; ~t~n weld toes. Concavity is only considered detrimental associated' with incomplete fusion. when it results in an undersized weld. See Figure 34. Figure 29 - Underbead Cracks Figure 30 - Slag Inclusion FACE REINFORCEMENT WELD TOE Figure 31 - Weld Reinforcement 4.14 Arc Strikes. An arc strike is a discontinuity con- 4.15 Spatter. Spatter consis~ of I1letal..partic~sexpelled sisting of any localized remelted metal. heat affected duri_l!8.fusion ~Jding that do not form a part ofihe metal, or change in the surface profile of any part of a ~eld. Those particles that are actually I!ttached to the weld or base metal resulting from an arc. Arc strikes base mej!l1agt~nt !Qthe weld are the most disconcert- result when the arc is initiated on the base metal surface ing form of spatter. Particles which are thrown away away from th~ weIQ.l9jut..either intentionally or acci- ~ the weld and basemetaI are, bv definition, sP1!tter. dentally. When this occurs, there is a localized area of In total, spatter is particles of metal which comprise the the base metal surface which is melted and then rapidly difference between the amount of filler metal melted cooled due to the massive heat sink created by the sur- and the amount of filler metal actually deposited in the rounding base metal. Arc strikes ~re 1!.0td~siQl~d weld joint. Qften not acceptable, as they could lead to cracking Normally, spatter is not considered to be a serious during the cooling process or under fatigue conditions. flaw unless its presence interferes with subsequent oper- ACTUAL THROAT EFFECTIVE THROAT r THEORETICAL THROAT Figure 32 - Convex Fillet Weld Figure 33 - Convexity Figure 35 - Spatter An effective calibration system should assure the 5.4 Surface Contact Thermometers. The surface ther- recall and calibration of all precision measuring devices mometer provides a direct indication of the surface under its control on a pre-established periodic schedule. temperature of pipe or other joint members. The Prior to using a controlled measuring device, the thermometer's permanent magnet will attach it to fer- inspector should assure that there is a calibration certi- rous base metal, but the thermometer should be other- fication label and that the calibration due date has not wise attached to nonferrous base metal. Temperature passed. Any gage which has passed its expiration date readings should be taken very close to the weld area, should be calibrated and certified prior to use. preferably within three inches of the weld on either side, In addition to calibration labels, all controlled mea- as shown in Figure 38. suring devices should have its own unique serial number. The pyrometer is an electrical instD:!!!Wlt which The serial number allows for calibration traceability in offers direct indication of temperature. -Pyrometers are . case a calibration tag inadvertently falls off. A serial often used when the temperature .!lliC.a£Predmigh! number is imperative for small gages and devices that ~seed the limits of me!:£l1xL!he.D!l.91D.Cl~rL o.f other are unable to bear a calibration tag or label. !Y£e thermQ.!!!eter~The point of the probe is placed on the work and temperature is read from the scale or digital scale. Some devices have a button that can be 5.2 Ammeters. An ammeter of the tong test type is a unique, portable instrument that will measure cur~ depressed to hold the reading, if desired. These types of instruments give a more accurate indication than either ~i~ in a circuit without making an electrical con- the surface thermometer, or the crayon discussed pre- nection to it. This is an efficient way to verify the viously. Figure 39 illustrates the use of a pyrometer. amperage that is being used during welding (check welding procedure). By placing the jaws of the tong 5.5 Weld Gages tester around a conductor carrying current, a reading in 5.5.1 Fillet Weld Gage. The fillet weld gage offers a amperes can be obtained, as shown in Figure 36. quick means of measuring most fillet welds, of V&Jn. (3.2 mm) through I in. (25. mm) in size. It measures 5.3 Temperature Sensitive Crayons. Temperature sen- both convex and concave fillet. weJds. To measure a sitive crayons are frequently used to give an approxi- convex fillet weld, the blade representing the speci- mate temperature indication. A crayon mark is made fied fillet weld siz~ with the concave curve should across the metal in the area to be checked; for example, be selected. As seen in Figure 40, the lower edge of the when_using a ~OOdegree cray£!!"the temperature of the blade is placed on the base plate with the tip of the piece will be at least 500 degrees when the crayon mark blade moved to the upright member. melts. This measurement usually should be ~de within To measure a concave fillet weld, the blade represent- one inch (25 mm) of the weld on the base metal. Crayon ing the specified fillet weld size with the double concave marks should--never be made directly onthe weld curve should be selected, as shown in Figure 41. After because of possible contamination. This is illustrated in placing the lower edge of the blade on the base plate Figure 37. with the tip touching the upright member, the projec-