Iron-based material having excellent oxidation resistance at elevated temperatures and process for the production thereof

• US 5,612,090 A
• Filed: 06/06/1995
• Issued: 03/18/1997
• Est. Priority Date: 11/20/1992
• Status: Expired due to Fees

• Current Assignee: Nisshin Steel Company Limited (Nippon Steel Corporation)
• Original Assignee: Nisshin Steel Company Limited (Nippon Steel Corporation)
• Inventors: Morita, Yoshikazu, Saito, Minoru, Ando, Atsushi, Matsuno, Masanori, Souda, Masahiko, Miyake, Hideo, Fukui, Yasushi
• Primary Examiner(s): Beck, Shrive
• Assistant Examiner(s): MEEKS, TIMOTHY HOWARD
• Application Number:
  US08/467,637
• Time in Patent Office: 651 Days
• Field of Search: 427/248.1, 427/255.3, 427/126.4, 427/295, 427/377, 427/566, 427/585, 427/596, 427/597, 502/439
• US Class Current: 148/277
• CPC Class Codes: C23C 14/081 of aluminium, magnesium or beryllium
• CPC Class Codes: Y10T 428/12535 with additional, spatially distinct nonmetal component
• CPC Class Codes: Y10T 428/12549 Adjacent to each other
• CPC Class Codes: Y10T 428/1259 Oxide
• CPC Class Codes: Y10T 428/12611 Oxide-containing component
• CPC Class Codes: Y10T 428/12667 Oxide of transition metal or Al
• CPC Class Codes: Y10T 428/12736 Al-base component
• CPC Class Codes: Y10T 428/12757 Fe
• CPC Class Codes: Y10T 428/12764 Next to Al-base component
• CPC Class Codes: Y10T 428/252 Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/257 Iron oxide or aluminum oxide

Abstract

An iron-based heat-generating material excellent in oxidation resistance at an elevated temperature which comprises an iron-based alloy capable of generating heat by passing electricity therethrough and a coating of aluminum and oxygen formed on the surface of the alloy, the amount of the oxygen in the coating is less than the stoichiometric amount of oxygen in Al₂ O₃. The material can be prepared by vacuum evaporation of Al onto the surface of the iron-based alloy wherein an oxygen partial pressure in a vacuum gaseous atmosphere for the vacuum evaporation is adjusted so that there is formed on the surface of the alloy a coating consisting of aluminum and oxygen, the amount of the oxygen in the coating being less than the stoichiometric amount of oxygen in Al₂ O₃. When the material is heated in ambient or oxidizing atmosphere, an outermost layer of the coating is rapidly converted to Al₂ O₃.

Claims

1. A process for production of an oxidation resistant iron-based heat-generating material which comprises vacuum evaporating aluminum onto a surface of an iron-based alloy capable of generating heat by passing electricity therethrough wherein an oxygen partial pressure in a vacuum gaseous atmosphere for the vacuum evaporation is adjusted so that there is formed directly on the surface of the iron-based alloy a coating consisting of aluminum and oxygen, the amount of the oxygen in said coating being less than the stoichiometric amount of oxygen in Al₂ O₃.

2. The process of claim 1, wherein said iron based alloy comprises, by mass % an amount of C up to 0.2, an amount of Si up to 6, an amount of Mn up to 5, an amount of Al 0.4 to 8, an amount of Cr up to 35, an amount of N up to 0.3, a balance Fe and impurities.

3. The process of claim 2 wherein said iron-based alloy comprises up to 3% Mo, up to 3% Cu, one or more of Ti, Nb, Zr, V up to 1.5% in total, and one or more of rare earth metals (REM) and Y up to 0.2% in total.

4. The process of claim 1 wherein said coating consisting of aluminum and oxygen consists of 50-99 mol % of aluminum and 1-50 mol % of oxygen.

5. The process of claim 1 wherein said iron-based alloy having said coating on said surface thereof is heated to convert a portion of said coating consisting of aluminum and oxygen to an Al₂ O₃ coating thereby leaving a remaining portion of said coating consisting of aluminum and oxygen.

6. The process of claim 5 wherein said iron-based alloy having said remaining portion of said coating thereon and further having said Al₂ O₃ coating on said remaining portion of said coating is further heated to convert said remaining portion of said coating to an Al₂ O₃ coating so that said iron-based alloy is coated with Al₂ O₃ only.

7. The process of claim 1 wherein said iron-based alloy with said coating thereon is heated to convert said coating to an Al₂ O₃ coating so that said iron-based alloy is coated with said Al₂ O₃ coating.

8. The process of claim 1 wherein the aluminum is evaporated using an electron beam.

9. The process of claim 1 wherein the vacuum gaseous atmosphere contains a mixed gas of oxygen and argon.