Patent ID: 8821653

Claim:
A heavy wall seamless steel pipe, comprising: a steel composition comprising: about 0.05 wt. % to about 0.16 wt. % carbon; about 0.20 wt. % to about 0.90 wt. % manganese; about 0.10 wt. % to about 0.50 wt. % silicon; about 1.20 wt. % to about 2.60 wt. % chromium; about 0.05 wt. % to about 0.50 wt. % nickel; about 0.80 wt. % to about 1.20 wt. % molybdenum; about 0.005 wt. % to about 0.12 wt. % vanadium; about 0.008 wt. % to about 0.04 wt. % aluminum; about 0.0030 wt. % to about 0.0120 wt. % nitrogen; and about 0.0010 wt. % to about 0.005 wt. % calcium; wherein the remainder of the composition comprises iron and impurities; wherein the wall thickness of the steel pipe is greater than or equal to 35 mm; and wherein the steel pipe is processed to have a yield strength greater than or equal to 450 MPa, wherein the microstructure of the steel pipe consists essentially of martensite and lower bainite, wherein martensite is in a volume percentage greater than or equal to 50% and lower bainite is in a volume percentage less than or equal to 50%, and wherein the steel pipe does not exhibit failure due at least in part to stress corrosion cracking after 720 hours when subjected to a stress of 90% of the yield stress and tested according to NACE TM0177.