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

A method of making a heavy wall steel pipe, comprising:

• providing a steel having a carbon 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 1.2 wt. % to about 2.6 wt. % chromium;
• about 0.05 wt. % to about 0.50 wt. % nickel;
• about 0.80 wt. % to about 1.2 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;
• forming the steel into a tube having a wall thickness greater than or equal to 35 mm;
• heating the formed steel tube in a first heating operation to a temperature within the range between about 900° C. to about 1060° C.;
• quenching the formed steel tube at a rate greater than or equal to 7° C./sec, wherein the microstructure of the quenched steel 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 microstructure has an average prior austenite grain size greater than 15 μm;
• and
• tempering the quenched steel tube at a temperature within the range between about 680° C. to about 760° C.;
• wherein, after tempering, the steel tube has a yield strength greater than 450 MPa and a Charpy V-notch energy greater than or equal to 150 J/cm2.

A method of making a heavy wall steel pipe, comprising:

• providing a steel having a carbon steel composition comprising:
• 0.05 wt. % to about 0.16 wt. % carbon+/−less than 10%;
• 0.20 wt. % to about 0.90 wt. % manganese+/−less than 10%;
• 0.10 wt. % to about 0.50 wt. % silicon+/−less than 10%;
• 1.80 wt. % to about 2.60 wt. % chromium+/−less than 10%;
• 0.05 wt. % to about 0.50 wt. % nickel+/−less than 10%;
• 0.80 wt. % to about 1.20 wt. % molybdenum+/−less than 10%;
• 0.005 wt. % to about 0.12 wt. % vanadium+/−less than 10%;
• 0.008 wt. % to about 0.04 wt. % aluminum+/−less than 10%;
• 0.0030 wt. % to about 0.0120 wt. % nitrogen+/−less than 10%;
• and
• 0.0010 wt. % to about 0.005 wt. % calcium+/−less than 10%;
• wherein the remainder of the composition comprises iron and impurities;
• forming the steel into a tube having a wall thickness greater than or equal to 35 mm;
• heating the formed steel tube in a first heating operation to a temperature within the range between about 900° C. to about 1060° C.;
• quenching the formed steel tube at a rate greater than or equal to 7° C./sec, wherein the microstructure of the quenched steel is, in a volume percentage greater than or equal to 50% martensite and less than or equal to 50% lower bainite and wherein the microstructure has an average prior austenite grain size greater than 15 μm;
• and
• tempering the quenched steel tube at a temperature within the range between about 680° C. to about 760° C.;
• wherein, after tempering, the steel tube has a yield strength greater than 450 MPa and a Charpy V-notch energy greater than or equal to 150 J/cm2, 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.