Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Reexamination Certificate
2000-06-26
2002-05-14
Jenkins, Daniel J. (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
C075S240000, C419S002000, C419S014000, C419S015000
Reexamination Certificate
active
06387149
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to metal porous bodies comprising an alloy having high strength, excellent corrosion resistance and heat resistance, which have applications in electrode substrates, catalyst supports, filters, metallic composite materials and the like, and also relates to a method of preparing such metal porous bodies.
2. Description of the Related Art
Conventionally, metal porous bodies have been used in various applications such as filters and battery plates where heat resistance is required, and catalyst supports and metallic composite materials. Hence, techniques for the preparation of metal porous bodies have come to be known through a variety of documents. Furthermore, products in which an Ni-based metal porous body commercially available as “CELMET” (registered trade name) prepared by Sumitomo Electric Ind., Ltd. are already being widely used in industry.
As conventionally known methods for the preparation of metal porous bodies, there are the plating method which is performed after treating a foamed resin or the like to render the same to be electrically conductive as disclosed in Japanese Patent Application Laid-Open No. 57-174484, and the method in which metal powder is formed into a slurry, the slurry is applied to a foamed resin or the like, and sintered, as disclosed in Japanese Patent Publication No. S38-17554.
The plating method involves attachment of an electrically conductive material, vapor deposition of an electrically conductive material, or surface modification with a chemical agent, as a treatment for rendering the surface of a foamed resin or the like electrically conductive. A metal porous body is obtained by metal plating the foamed resin or the like which has been rendered electrically conductive, and then burning out and removing the resin part therefrom. Electro-plating and electroless plating, for example, can be used in the formation of the metal skeleton. However, since the both methods involve plating, a metal porous body thus obtained consists of a single metal in either case. Known alloying treatments include a method in which, after the plating with different types of metal, these metals are diffused in a later step, and a method in which, after the plating with a single metal, diffusion alloying treatment is performed.
In the sintering method, a slurry comprising metal powder and resin is coated or sprayed onto a foamed resin or the like, and then subjected to a sintering treatment after drying. With the method disclosed in the aforementioned Japanese Patent Publication No. 38-17554, alloying treatment can be performed if several types of metal materials are used.
However, although it is possible to obtain alloyed metal porous bodies, they are inferior in strength to the metal porous bodies obtained by a combination of plating and diffusion alloying treatments. This problem is related due to adhesion among the metal powders obtained by sintering.
As a means of improvement in this respect, Japanese Patent Publication No. 6-89376 discloses a method for improving the adhesion in which the surface of iron powder is oxidized while controlling the carbon content in the iron powder, so that the surface of iron is reduced during sintering as a result of an oxidation-reduction reaction between the carbon contained in the iron and the oxygen in the oxide formed on the iron surface. With this method, however, the metal parts within the iron particles take no part in the reaction. Therefore, although it provides an improvement at the boundary faces in the resultant skeleton structure, the inadequacy of the mechanical strength in the original metal structure still remains.
Furthermore, Japanese Patent Application Laid Open No. 9-231983 discloses fine-grained metal sintered porous bodies which are produced from iron oxide powder as a raw material. Since metal porous bodies consisting of iron alone are inadequate in terms of strength, corrosion resistance and heat resistance, these properties are improved by alloying in this disclosure. However, the alloying of the aforementioned invention is not realized simply by adding powder or an oxide of a metal other than iron.
Moreover, there is a trend that metal porous bodies are used more and more for preparing a metallic composite material. This technique is widely used as a means of reducing weight in which Al alloys are formed into casting, as referred to Al die-casting. However, in view of the properties of Al itself, the heat resistance etc. is inadequate, and attention is being focused on improvement of the properties of Al by alloying and methods of use for the preparation of metallic composite materials. Similarly, there is a possibility of use for reinforcing the mechanical strength of Mg alloys.
A technique for the preparation of metallic composite materials using metal porous bodies is disclosed in detail in Japanese Patent Application Laid Open No. 9-122887. According to the disclosure in this publication, composited light metal alloys can be used in particular in parts which are subject to use under severe conditions, such as sliding parts for example. Consequently, the metal porous bodies used for the preparation of such composite materials must have properties which satisfy the requirements in the application in which they are to be used.
The aforementioned “CELMET” is already being used as a metal porous body for the preparation of metallic composite materials, and a technique which is intended to bring about an especially advantageous effect in properties has been disclosed in Japanese Patent Application Laid Open No. 10-251710. According to the description, the metal porous body is obtained by applying a slurry which contains metal powder and ceramic powder onto a foamed material capable of burning out, then burning out the resin part in a reducing atmosphere where steam and/or carbon dioxide is contained in a reducing gas; and then firing the metal body in a reducing atmosphere. As a result, the ceramic particles are dispersed within a skeleton of the resultant metal porous body and a metal porous body with the properties of ceramic is obtained.
As described above, the techniques of filling the skeletons of metal porous bodies with molten metal for producing metallic composite materials have been progressed day by day for the improvement of the properties of the metallic composite materials.
As for the techniques of metallic composite materials, studies have been made on various techniques for the preparation of composite materials from Al or Mg metal and further for the preparation of composite materials from Al alloys and Mg alloys, and problems which are encountered when using metallic composite materials have been resolved by these studies. Metallic composite alloys are gaining attention and being used as materials for automobile engine parts, for example. However, the requirements for engine materials have become even more severe for the purpose of the improvements which are being made in view of the automobile exhaust gas regulations etc., and further improvement of their properties is now required. For the parts used in wear resistant piston rings in diesel engines in particular, much improved wear resistance is required to the composite materials to be used. There is also a means of compositing by using the metal porous bodies containing ceramic particles, as disclosed in the aforementioned publication, but, when such means is used, the pre-forming process of the ceramic containing metal porous body is difficult and this imposes a limitation on shape.
SUMMARY OF THE INVENTION
The present invention has been realized as a result of investigations based upon the demands for such technical improvements, and it provides a material having performance which meets these demands. Specifically, the present invention provides a metal porous body with a foam structure, a skeleton of which is composed of an alloy containing Fe and Cr, and in which a Cr carbide and/or FeCr carbide is uniformly dispersed. The amount of metal carbide
Harada Keizo
Watanabe Ken'ichi
Jenkins Daniel J.
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
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