Due to their lower price compared to other steel grades, casing pipes of grades J55, K55 are a popular choice for wells without stringent anti-corrosion or strength requirements.In this article we will introduce the difference between K55 and J55.
●Chemical composition and physical properties
API grade K55 has the same Chemical composition as grade J55 ,they both has the same yield , but its minimum tensile strength is about 26% higher compared to J55.
Yield strength: 379-552 MPa (55-80 ksi),
Minimum tensile strength: 517 MPa (75 ksi)
Minimum tensile strength: 665 MPa (95 ksi)
●Heat treatment (PSL2 and PSL1 are different)
API 5CT J55 PSL1 and API 5CT K55 PSL2 is the same (Rolling delivery);
PSL2 :J55 and K55 should be normalized or normalized and tempered. If thickened, normalizing or normalizing and tempering should be added after thickening.
●Impact test (PSL2 and PSL1 are different)
Tubing: PSL1, J55 and K55 have no requirement; PSL2 J55 and K55 require minimum impact work 20J of full size specimen, and minimum impact work 27J of full size specimen.
Coupling: J55 and K55 impact tests are necessary. The minimum impact energy of the specimen is 20J, and the minimum impact energy of the full size specimen is 27J.
●API color code (ribbon difference)
J55:bright green band.The band is bright green with a white band
K55:2 bright green bands with no additional band
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