Content Overview1. API Casing Steel Grades 1. Common Application Casing (H40, J55, K55, M65, N80, R95) 2. Corrosion-Resistant Casing (L80，C90，T95, C110) 3. Deep Well Casing (P110, Q125) API Casing Steel Grades Most casing steel grades are largely of the same chemical composition. What gives each grade its distinct properties is the kind of heat treatment applied. Casing grades mainly differ in their yield strength, tensile strength, and hardness. Additional tests required by API 5CT for certain groups of casing make sure that each casing grade is suitable for its intended application. Common Application Casing (H40, J55, K55, M65, N80, R95) Due to their lower price compared to other steel grades, casing pipes of grades J55, K55, and N80 are a popular choice for wells without stringent anti-corrosion or strength requirements. M65, and R95 are newer grades, each with their own field of application. These casing grades mainly differ in their yield strength and tensile strength. H40 Yield strength: 276-552 MPa (40-80 ksi), Minimum tensile strength: 414 MPa (60 ksi) API color code: Either none or 1 black band J55 Yield strength: 379-552 MPa (55-80 ksi), Yield strength: 379-552 MPa (55-80 ksi). but its minimum tensile strength is about 26% higher compared to J55. M65 is the only steel grade among the general purpose casing grades with the requirement of a restricted maximum hardness. Yield strength: 552-758 MPa (55-80 ksi). 1 red band + 1 bright green band (N80-Q) . Minimum tensile strength: 586 MPa (85 ksi) API color code: 1 bright green band + 1 blue band N80 (N80-1. but N80-Q. Minimum tensile strength: 665 MPa (95 ksi) API color code: 2 bright green bands M65 Not used that often. shows a higher resistance to internal pressure and collapsing. On the other hand. N80-Q) Both N80-1 and N80-Q have the same yield strength and tensile strength. casing N80-1 is cheaper to produce and the first choice were a higher collapse resistance in not needed. Yield strength: 448-586 MPa (65-85 ksi). which is quenched and tempered. Minimum tensile strength: 689 MPa (100 ksi) API color code: 1 red (N80-1). Minimum tensile strength: 517 MPa (75 ksi) API color code: 1 bright green band K55 API grade K55 has the same yield as grade J55. Yield strength: 655-758 MPa (95-110 ksi). L80-9Cr. L80-13Cr) Yield strength: 552-665 MPa (80-95 ksi). L80 (L80-1.R95 Same yield strength range and tensile strength as grade T95. Minimum tensile strength: 727 MPa (105 ksi) API color code: 1 brown band Corrosion-Resistant Casing (L80，C90，T95. C110) Sour Service API 5CT steel grades L80-1. T95. C110) Grain size: Grain size finer than ASTM 5 (C90. and C110 show a higher resistance to sulfide stress cracking in H2S environments due to lower limits of sulfur and phosphorous as well as the addition of the following mandatory tests: Hardness: Limited maximum hardness (L80，C90，T95. T95. but without the requirement for SSC or hardness tests. C90. 1 red + 1 brown + 2 yellow (L80 9Cr). C110) Sulfide stress cracking (SSC): Passing NACE 0177 (C90. Steel grade R95 therefore is a better-priced alternative to T95 in wells without the risk of sulfide stress cracking. C110) Sweet Service Casing grades L80-9Cr and L80-13Cr are suitable for application in CO2 environments. Minimum tensile strength: 655 MPa (95 ksi) API color code (bands): 1 red + 1 brown (L80). T95. mainly because of their higher chromium content. 1 red + 1 brown + 1 yellow (L80 13Cr) . Deep Well Casing (P110.C90 (C90-1) Yield strength: 621-724 MPa (90-105) ksi. However. it is the responsibility of the buyer to determine if a given sour service casing grade is suitable for the intended application. P110 and Q125 are ideally suited for high pressure formations in deep wells. Q125) With the highest yield strengths among all API 5CT casing grades. P110 Yield strength: 758-965 MPa (110-140 ksi) . as steel becomes more susceptible to sulfide stress cracking the higher the yield strength. Minimum tensile strength: 689 MPa (100 ksi) API color code: 1 purple band T95 (T95-1) Yield strength: 655-785 MPa (95-110 ksi). both grades should not be used in H2S environments. Minimum tensile strength: 724 (105 ksi) API color code: 1 silver band C110 Yield strength: 758-828 MPa (110-120 ksi) Minimum tensile strength: 793 MPa (115 ksi) API color code: 1 white band + 2 brown bands Note that despite that additional test requirements. Minimum tensile strength: 862 MPa (125 ksi) API color code: 1 white band Q125 (Q125-1) Yield strength: 862-1.034 MPa (125-150 ksi) Minimum tensile strength: 931 MPa (135 ksi) API color code: 1 orange band .