Heavy wall steel pipes with excellent toughness at low temperature and sulfide stress corrosion cracking resistance

摘要

Embodiments of the present disclosure comprise carbon steels and methods of manufacturing thick walled pipes (wall thickness greater than or equal to about 35 mm) there from. In one embodiment, a steel composition is processed that yields an average prior austenite grain size greater than about 15 or 20 μm and smaller than about 100 μm. Using this composition, a quenching sequence is provided that yields a microstructure of greater than or equal to about 50% by volume, and less than or equal to about 50% by volume, lower bainite, without substantial ferrite, upper bainite, or granular bainite. After quenching, pipes may be tempered. The quenched and tempered pipes may exhibit yield strengths greater than about 450 MPa (65 ksi) or 485 (70 ksi). Mechanical property measurements find the quenched and tempered pipes suitable for 450 MPa grade and 485 MPa grade, and resistance to sulfide stress corrosion cracking.

主权项

1. 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; andabout 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.