- Chemical and mechanical property: API grade K55 has the same Chemical composition as grade J55, they both have the same yield strength, but the minimum tensile strength of K55(655 MPa or 95 KSI) is higher compared to J55(517 MPa or 75 KSI).
- API color code (bands): J55tubing end is a bright green band. The band is bright green with a white band. K55 is colored with two bright green bands with no additional band.
- Delivery: API 5CT J55 PSL2and K55 PSL2 should be normalized or normalized and tempered. If thickened, normalizing or normalizing and tempering should be added after thickening. API 5CT K55 PSL2 is the same rolling delivery with API 5CT J55 PSL1;
- Impact test: For PSL1, J55 and K55 have no requirement while for PSL2, J55 and K55 require minimum impact work 20J of the full-size specimen.
API 5CT K55/J55 Chemical Composition
| Grade | C≤ | Si≤ | Mn≤ | P≤ | S≤ | Cr≤ | Ni≤ | Cu≤ | Mo≤ | V≤ |
| API 5CT K55/J55 | 0.34-0.39 | 0.20-0.35 | 1.25-1.50 | 0.020 | 0.015 | 0.15 | 0.20 | 0.20 | / | / |
API 5CT K55/J55 Mechanical Property
| Steel Grade | Yield Strength (Mpa) | Tensile Strength (Mpa) | Total Elongation under load % |
| API 5CT K55 | 379-552 | ≥655 | 0.5 |
| API 5CT J55 | 379-552 | ≥517 | 0.5 |
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.
Post time: Oct-19-2021