High-strength high-toughness precipitation-hardened steel
AssigneeGeneral Electric Company
InventorJohn William Short
Life of this patent
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Abstract
A stainless steel alloy that exhibits both high strength and toughness as a result of having particular ranges for chemistry, tempering temperatures and grain size. The alloy is a precipitation-hardened martensitic stainless steel with an ultimate tensile strength of at least 1200 MPa, a Charpy impact toughness of greater than 55 J, and a grain size of ASTM 5 or finer. The alloy consists essentially of, by weight, 14.0 to 16.0 percent chromium, 6.0 to 7.0 percent nickel, 1.25 to 1.75 percent copper, 0.5 to 1.0 percent molybdenum, 0.03 to 0.5 percent carbon, niobium in an amount by weight of ten to twenty times greater than carbon, the balance iron, minor alloying constituents and impurities.
Claims11
A precipitation-hardened stainless steel alloy consisting of, by weight:
- 14.0 to 16.0 percent chromium;
- 6.0 to 7.0 percent nickel;
- 1.25 to 1.75 percent copper;
- 0.5 to 1.0 percent molybdenum;
- 0.03 to 0.5 percent carbon;
- niobium in an amount by weight of ten to twenty times greater than carbon;
- not greater than 1.0 percent manganese;
- not greater than 1.0 percent silicon;
- not greater than 0.1 percent vanadium;
- not greater than 0.1 percent tin;
- not greater than 0.030 percent nitrogen;
- not greater than 0.020 percent phosphorus;
- not greater than 0.025 percent aluminum;
- not greater than 0.008 percent sulfur;
- not greater than 0.005 percent silver;
- not greater than 0.005 percent lead;
- and
- the balance being essentially iron;
- wherein the alloy has been tempered at a temperature of about 480° C. to about 525° C. to have an ultimate tensile strength of at least 1200 MPa and a Charpy impact toughness of at least 70 J.
A steam turbine component formed of a precipitation-hardened stainless steel alloy consisting of, by weight:
- about 14.5 percent chromium;
- about 6.5 percent nickel;
- about 1.5 percent copper,
- about 0.7 percent molybdenum;
- 0.03 to 0.4 percent carbon;
- niobium in an amount by weight of 10.0 to about 15 times greater than carbon;
- about 0.3 to about 0.8 percent manganese;
- about 0.2 to about 0.5 percent silicon;
- not greater than 0.05 percent vanadium;
- not greater than 0.01 percent tin;
- not greater than 0.030 percent nitrogen;
- not greater than 0.015 percent phosphorus;
- not greater than 0.020 percent aluminum;
- not greater than 0.0002 percent sulfur;
- not greater than 0.0001 percent silver;
- not greater than 0.0001 percent lead;
- the balance being essentially iron;
- wherein the alloy has a grain size of ASTM 7 or finer, a delta ferrite content of less than 0.5 weight percent, an ultimate tensile strength of at least 1275 MPa, a Charpy impact toughness of at least 80 J, and has been tempered at a temperature of about 480° C. to about 500° C.
Dependencies are inferred from the claim text.