Silicon modified low chromium ferritic alloy for high temperature use
AssigneeArmco Advanced Materials Corporation
InventorsJames A. Daniels, Joseph A. Douthett
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Abstract
A ferritic alloy steel having good creep strength and cyclic oxidation resistance at elevated temperatures up to 982.degree. C. (1800.degree. F.) with an optional final anneal at 1010.degree.-1150.degree. C. (1850.degree.-2100.degree. F.) consisting essentially of from about 0.01% to about 0.30% carbon, about 2% maximum manganese, greater than 2.35% to about 4% silicon, about 3% to about 7% chromium, about 1% maximum nickel, about 0.15% maximum nitrogen, less than 0.3% aluminum, about 2% maximum molybdenum, at least one element selected from the group of niobium, titanium, tantalum, vanadium and zirconium in an amount up to 1.0% and the balance essentially iron.
Claims13
A ferritic steel alloy having good oxidation resistance and creep strength at elevated temperatures, said alloy consisting essentially of, by weight percent, from about 0.01% to about 0.3% carbon, about 2% maximum manganese, greater than 2.35% to about 4% silicon, about 3% to about 7% chromium, about 1% maximum nickel, about 0.15% maximum nitrogen, less than 0.3% aluminum, at least one carbide and nitride forming element selected from the group of niobium, tantalum, vanadium, titanium and zirconium in an amount up to 1.0% sufficient to maintain a ferritic structure, provide a fine grain size and pin the grain boundaries to improve creep strength, and control the level of carbon and nitrogen in solution to prevent austenite formation and the balance essentially iron.
An article for service at temperatures up to 982.degree. C. (1800.degree. F.) having good oxidation and creep resistance, said article consisting essentially of, by weight %, from about 0.01% to about 0.3% carbon, about 2% maximum manganese, greater than 2.35% to about 4% silicon, about 3% to about 7% chromium, about 1% maximum nickel, about 0.15% maximum nitrogen, less than 0.3% aluminum, at least one carbide and nitride forming element selected from the group of niobium, tantalum, vanadium, titanium and zirconium in an amount up to 0.75% sufficient to maintain a ferritic structure, provide a fine grain size and pin the grain boundaries to improve creep strength, and control the level of carbon and nitrogen in solution to prevent austenite formation and the balance essentially iron.
Dependencies are inferred from the claim text.