EP0091526A2
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EP
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Iron-chromium-aluminium alloy and article and method therefor
Assignee: Allegheny Ludlum Corp
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Filing: 1982-11-25
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Granted: —
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Expires: 2002-11-25
Abstract
Abstract A ferritic stainless steel alloy is provided which is hot workable and is resistant to thermal cyclic oxidation and scaling at elevated temperatures. The iron-chromium-aluminium alloy contains cerium, lanthanum and other rare earths and is suitable for forming thereon an adherent textured aluminium oxide surface. The alloy comprises by weight, 8.0-25.0% chromium, 3.0-8.0% aluminium, and an addition of at least 0.002% and up to 0.05% of cerium, lanthanum, neodymium and/or praseodymium with a total of all rare earths up to 0.06%, up to 4.0% silicon, 0.06% to 1.0% manganese and normal steelmaking impurities of less than 0.050% carbon, less than 0.050% nitrogen, less than 0.020% oxygen, less than 0.040% phosphorus, less than 0.030% sulfur, less than 0.50% copper, less than 1.0% nickel, and the sum of calcium and magnesium less than 0.005%, the remainder being iron. An oxidation resistant catalytic substrate made from the alloy and a method of making the alloy are also provided.
Inventors
- 👤 George Aggen
- 👤 Paul Richard Borneman
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 11:58
CPC Classifications
C; C22; C22C; C22C38/00; C22C38/18
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
121 words
A hot workable ferritic stainless steel alloy resistant to thermal cyclic oxidation and scaling at elevated temperatures and suitable for forming thereon an adherent textured aluminium oxide surface, characterised in that the alloy consists of, by weight, 8.0-25.0% chromium, 3.0-8.0% aluminium, and an addition of at least 0.002% and up to 0.05% cerium, lanthanum, neodymium and/or praseodymium, a total of all rare earths up to 0.060%, up to 4.0% silicon, 0.06% to 1.0% manganese and normal steelmaking impurities of less than 0.050% carbon, less than 0.050% nitrogen, less than 0.020% oxygen, less than 0.040% phosphorus, less than 0.030% sulfur, less than 0.50% copper, less than 1.0% nickel, and the sum of calcium and magnesium less than 0.005%, the remainder being iron.
Claim 2
Dependent Claim
121 words
A hot workable ferritic stainless steel alloy resistant to thermal cyclic oxidation and scaling at elevated temperatures and suitable for forming thereon an adherent textured aluminium oxide surface, characterised in that the alloy consists of, by weight, 8.0-25.0% chromium, 3.0-8.0% aluminium, and an addition of at least 0.002% and up to 0.05% cerium, lanthanum, neodymium and/or praseodymium, a total of all rare earths up to 0.060%, up to 4.0% silicon, 0.06% to 1.0% manganese and normal steelmaking impurities of less than 0.050% carbon, less than 0.050% nitrogen, less than 0.020% oxygen, less than 0.040% phosphorus, less than 0.030% sulfur, less than 0.50% copper, less than 1.0% nickel, and the sum of calcium and magnesium less than 0.005%, the remainder being iron.
Claim 3
Dependent Claim
20 words
An alloy according to claim 1, characterised in that the alloy is stabilized with zirconium additions in amounts up to
Claim 4
Dependent Claim
27 words
An alloy according to claim 1 or 2, characterised in that the alloy additionally includes niobium for stabilization and elevated temperature creep strength, in amounts up to
Claim 5
Dependent Claim
21 words
An alloy according to claim 1, 2 or 3 characterized in that the rare earth addition consists of cerium and/or lanthanum.
Claim 6
Dependent Claim
36 words
An alloy according to any one of the preceding claims, characterized in that the minimum total cerium and/or lanthanum amounts in the alloy are proportional to the chromium content as expressed by % Cr 2200 .
Claim 7
Dependent Claim
30 words
An alloy according to any one of the preceding claims, characterized in that the minimum amounts of aluminium in the alloy are based on the chromium content' as expressed bv
Claim 8
Dependent Claim
16 words
An alloy according to any one of the preceding claims, characterized in-having up to 3% silicon.
Claim 9
Dependent Claim
17 words
An alloy according to any one of the preceding claims, characterized in having 0.10 to 0.50% manganese.
Claim 10
Dependent Claim
117 words
A hot workable ferritic stainless steel alloy resistant to thermal cyclic oxidation and scaling at elevated temperatures and suitable for forming thereon an adherent textured aluminium oxide surface, characterized in that the allov consists of. bv weiaht. 12.0-23.0% chromium, from up to 8.0% aluminium, at least [%Cr/2200]% of an addition of cerium and/or lanthanum, a total of all rare earths up to 0.050%, up to 3.0% silicon, 0.10 to 0.50% manganese, and normal steelmaking impurities of less than 0.030% carbon, less than 0.030% nitrogen,less than 0.010% oxygen, less than 0.030% phosphorus, less than 0.020% sulfur, less than 0.4% copper, less than 0.4% nickel, the sum of calcium and magnesium being less than 0.003%, the remainder being iron.
Claim 11
Dependent Claim
117 words
A hot workable ferritic stainless steel alloy resistant to thermal cyclic oxidation and scaling at elevated temperatures and suitable for forming thereon an adherent textured aluminium oxide surface, characterized in that the allov consists of. bv weiaht. 12.0-23.0% chromium, from up to 8.0% aluminium, at least [%Cr/2200]% of an addition of cerium and/or lanthanum, a total of all rare earths up to 0.050%, up to 3.0% silicon, 0.10 to 0.50% manganese, and normal steelmaking impurities of less than 0.030% carbon, less than 0.030% nitrogen,less than 0.010% oxygen, less than 0.030% phosphorus, less than 0.020% sulfur, less than 0.4% copper, less than 0.4% nickel, the sum of calcium and magnesium being less than 0.003%, the remainder being iron.
Claim 12
Dependent Claim
20 words
An alloy according to claim 9, characterized in that the alloy is stabilized with zirconium additions in amounts up to
Claim 15
Dependent Claim
27 words
An alloy according to claim 9 or 10, characterized in that the alloy additionally includes niobium for stabilization and elevated temperature creep strength, in amounts up to
Claim 16
Dependent Claim
129 words
An oxidation resistant catalytic substrate comprising a hot workable ferritic stainless steel alloy having an adherent textured aluminium oxide surface thereon, said alloy being resistant to thermal cyclic oxidation and scaling at elevated temperatures, characterized in that said alloy consists of, by weight, 8.0-25.0% chromium, 3.0-8.0% aluminium, and an addition of at least 0.002% and up to 0.050% cerium, lanthanum, neodymium and/or praseodymium, a total of all rare earths up to 0.060%, up to 4.0% silicon, 0.06 to 1.0% manganese and normal steelmaking impurities of less than 0.050% carbon, less than 0.050% nitrogen, less than 0.020% oxygen, less than 0. 0 40% phosphorus, less than 0.030% sulfur, less than 0.50% copper, less than 1.0% nickel, and the sum of calcium and magnesium less than 0.005%, the remainder being iron.
Claim 17
Dependent Claim
129 words
An oxidation resistant catalytic substrate comprising a hot workable ferritic stainless steel alloy having an adherent textured aluminium oxide surface thereon, said alloy being resistant to thermal cyclic oxidation and scaling at elevated temperatures, characterized in that said alloy consists of, by weight, 8.0-25.0% chromium, 3.0-8.0% aluminium, and an addition of at least 0.002% and up to 0.050% cerium, lanthanum, neodymium and/or praseodymium, a total of all rare earths up to 0.060%, up to 4.0% silicon, 0.06 to 1.0% manganese and normal steelmaking impurities of less than 0.050% carbon, less than 0.050% nitrogen, less than 0.020% oxygen, less than 0. 0 40% phosphorus, less than 0.030% sulfur, less than 0.50% copper, less than 1.0% nickel, and the sum of calcium and magnesium less than 0.005%, the remainder being iron.
Claim 18
Dependent Claim
18 words
A substrate according to claim 12, characterised in that the steel is stabilized with zirconium additions up to
Claim 19
Dependent Claim
29 words
A substrate according to claim 12 or 13, characterised in that the steel includes niobium additions in the melt composition up to for stabilization and elevated temperature creep strength.
Claim 20
Dependent Claim
21 words
A substrate according to claim 12, 13 or 14, characterised in that the rare earth addition consists of cerium and/or lanthanum.
Claim 21
Dependent Claim
36 words
A substrate according to any one of claims 12 to 15, characterised in that the minimum total amounts of cerium and/or lanthanum in the steel are proportional to the chromium content as expressed by %Cr 2200.
Claim 22
Dependent Claim
31 words
A substrate according to any one of claims 12 to 16, characterised in that the minimum amounts of aluminium in the steel are based on the chromium content as expressed by
Claim 25
Dependent Claim
21 words
A substrate according to any one of claims 12 to 17, characterised in that the steel has up to 3% silicon.
Claim 26
Dependent Claim
22 words
A substrate according to any one of claims 12 to 18, characterised in that the steel has from 0.10 to 0.50% manganese.
Claim 27
Dependent Claim
123 words
An oxidation resistant catalytic substrate comprising a hot workable ferritic stainless steel alloy having an adherent textured aluminium oxide surface thereon, said alloy being resistant to thermal cyclic oxidation and scaling at elevated temperatures, characterised in that said alloy consists of, by weight, 12.0-23.0% chromium, up to 8% aluminium, at least % of an addition of cerium and/or lanthanum, a total of all rare earths up to 0.050%, up to 3.0% silicon, 0.10 to 0.50% manganese and normal steelmaking impurities of less than 0.030% carbon, less than 0.030% nitrogen, less than 0.010% oxygen, less than 0.030% phosphorus, less than 0.020% sulfur, less than 0.40% copper, less than 0.40% nickel, and the sum of calcium and magnesium less than 0.003%, the remainder being iron.
Claim 28
Dependent Claim
123 words
An oxidation resistant catalytic substrate comprising a hot workable ferritic stainless steel alloy having an adherent textured aluminium oxide surface thereon, said alloy being resistant to thermal cyclic oxidation and scaling at elevated temperatures, characterised in that said alloy consists of, by weight, 12.0-23.0% chromium, up to 8% aluminium, at least % of an addition of cerium and/or lanthanum, a total of all rare earths up to 0.050%, up to 3.0% silicon, 0.10 to 0.50% manganese and normal steelmaking impurities of less than 0.030% carbon, less than 0.030% nitrogen, less than 0.010% oxygen, less than 0.030% phosphorus, less than 0.020% sulfur, less than 0.40% copper, less than 0.40% nickel, and the sum of calcium and magnesium less than 0.003%, the remainder being iron.
Claim 29
Dependent Claim
21 words
A substrate according to claim 20, character- ised in that said alloy is stabilised with zirconium additions in amounts up to
Claim 30
Dependent Claim
27 words
A substrate according to claim 20 or 21, characterised in that said alloy inlcudes niobium additions for stabilization and elevated temperature creep strength in amounts uo to
Claim 31
Dependent Claim
20 words
A catalytic system characterized in comprising an oxidation resistant catalytic substrate according to any one of claims 12 to 20.
Claim 32
Independent Claim
151 words
A method of making a hot workable ferritic stainless steel resistant to thermal cyclic oxidation and having a textured aluminium oxide surface resistant to scaling at elevated temperatures, characterized in that the method comprises the steps of preparing a melt consisting of, by weight, 8.0-25.0% chromium, 3.0-8.0% aluminium, an addition of at least 0.002% and up to 0.05% of cerium, lanthanum, neodymium and/or praseodymium, a total of all rare earths up to 0.060%, up to 4.0% silicon, 0.06 to 1.0% manganese and normal steelmaking impurities of less than 0.050% carbon, less than 0.050% nitrogen less than 0.020% oxygen, less than 0.040% phosphorus, less than 0.030% sulfur, less than 0.50% copper, less than 1.0% nickel, and the sum of calcium and magnesium less than 0.005%, the remainder being iron; producing a ferritic stainless steel article from the melt; and treating the steel article to form an adherent textured aluminium oxide surface thereon.
Claim 33
Independent Claim
151 words
A method of making a hot workable ferritic stainless steel resistant to thermal cyclic oxidation and having a textured aluminium oxide surface resistant to scaling at elevated temperatures, characterized in that the method comprises the steps of preparing a melt consisting of, by weight, 8.0-25.0% chromium, 3.0-8.0% aluminium, an addition of at least 0.002% and up to 0.05% of cerium, lanthanum, neodymium and/or praseodymium, a total of all rare earths up to 0.060%, up to 4.0% silicon, 0.06 to 1.0% manganese and normal steelmaking impurities of less than 0.050% carbon, less than 0.050% nitrogen less than 0.020% oxygen, less than 0.040% phosphorus, less than 0.030% sulfur, less than 0.50% copper, less than 1.0% nickel, and the sum of calcium and magnesium less than 0.005%, the remainder being iron; producing a ferritic stainless steel article from the melt; and treating the steel article to form an adherent textured aluminium oxide surface thereon.
Claim 34
Dependent Claim
24 words
A method according to claim 24, characterized in that the steel is stabilized by zirconium additions in the melt composition in amounts up to
Claim 35
Dependent Claim
24 words
A method according to claim 24 or 25, characterized in that the steel includes niobium additions in the melt composition in amounts up to
References Cited (Backward Citations)
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