High strength steel pipes with excellent toughness at low temperature and sulfide stress corrosion cracking resistance

摘要

Low-alloy steels and methods of manufacturing pipes having a wall thickness greater than or equal to about 8 mm and less than or equal to about 35 mm therefrom are provided. 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. A quenching sequence has been determined that yields a microstructure of greater than or equal to about 60% martensite by volume, and less than or equal to about 40% by volume lower bainite, without substantial formation of ferrite, upper bainite, or granular bainite. The yield strength of the quenched and tempered pipes may be greater than about 70 ksi, 80 ksi, or 90 ksi. The quenched and tempered pipes are suitable for 70 ksi, 80 ksi, and 90 ksi grades and resistant to sulfide stress corrosion cracking.

主权项

1. A seamless steel pipe, comprising:
a steel composition comprising:
Fe;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. % vanadiumabout 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 wall thickness of the steel pipe is greater than or equal to 8 mm and less than or equal to 35 mm; wherein the steel pipe is processed to have a yield strength greater than 550 MPa (80 ksi) and wherein the microstructure of the steel pipe comprises martensite in a volume percentage greater than or equal to 60% and lower bainite in a volume percentage less than or equal to 40%; wherein the microstructure of the steel pipe does not include upper bainite nor ferrite; wherein the steel pipe has a ductile to brittle transition temperature less than −70° C.; and wherein the steel pipe does not exhibit failure due at least in part to stress corrosion cracking after about 720 hours when subjected to a stress of about 90% of the yield stress and tested according to National Association of Corrosion Engineers standard TM0177.