Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Reexamination Certificate
1999-08-17
2001-07-03
Jenkins, Daniel (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
C075S230000, C075S245000, C075S249000, C501S088000, C501S087000, C501S094000, C501S096100, C501S108000, C501S132000
Reexamination Certificate
active
06254657
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a molding method for powder particles and a molded product obtained by this method. In particular, the present invention relates to a molding method for powder particles for obtaining a molded product having a high particle filling density by chemically reacting a powdery raw material so that the particles are joined to one another, and the molded product obtained by this method.
2. Description of the Related Art
Conventionally, there have been methods for producing molded products by pressurizing and molding powdery raw materials, including, for example, a molding method based on the use of isostatic pressurization. The present inventors have been already suggested such a molding method based on the use of isostatic pressurization in Japanese Laid-Open Patent Publication No. 4-211904. In this method, a mixture obtained by adding a liquid to a powdery raw material is subjected to uniaxial molding under pressure, wherein excessive liquid is removed to mold a preliminary molded product.
However, in the case of the molding method based on the use of the isostatic pressurization as described above, the filling state of particles in the preliminary molded product should be taken into consideration. Namely, it has been confirmed that the particles are joined to one another in a manner of point-to-point contact by the aid of the intermolecular force.
SUMMARY OF THE INVENTION
A general object of the present invention is to provide a molding method for powder particles, which is excellent in molding performance and which makes it possible to obtain a preliminary molded product excellent in heat resistance and strength by enhancing mutual bonding between particles in the preliminary molded product, and a molded product obtained by this method.
A principal object of the present invention is to provide a molding method for powder particles, which makes it possible to obtain a molded product having excellent strength by performing isostatic pressurization after adding a liquid additive to a powdery raw material to cause an exothermic reaction, and reacting the powder particles with each other without increasing the amount of the liquid additive, and a molded product obtained by this method.
Another object of the present invention is to provide a molding method for powder particles, in which an exothermic reaction between the powder particles and a liquid additive is suppressed in the initial stage of the molding process, the exothermic reaction is allowed to occur at a desired timing, the heat generated by the exothermic reaction allows the raw material particles to be melted and fused with each other, and thus the particles are integrated with each other to increase the strength of a preliminary molded product, and a molded product obtained by this method.
Still another object of the present invention is to provide a molding method for powder particles, in which a mixture comprising the powder particles and a liquid additive is subjected to molding in a mold by the aid of isostatic pressurization, an excessive amount of the liquid additive is gradually discharged from the mold to allow the timing of pressurization to coincident with that of an exothermic reaction, and thus the raw material particles are appropriately dispersed by the aid of the pressurization and the exothermic action so that the filling rate is improved, and a molded product obtained by this method.
Still another object of the present invention is to provide a molding method for powder particles, in which the mixture as described above is molded in a mold, the liquid quantity is discharged by exposing the mixture to air, the raw material particles are coated with a gas of a reaction product produced as a result of the exothermic reaction while making it possible to obtain high fluidity, the mold is filled with the particles even when they are left to stand stationarily while making it possible to obtain a preliminary molded product having a desired shape, the raw material particles are melted and fused with each other after the gas disappears owing to occurrence of an additional exothermic reaction, and thus the strength of the preliminary product is increased, and a molded product obtained by this method.
Still another object of the present invention is to provide a molding method for powder particles, which makes it possible to more effectively avoid the occurrence of an active exothermic reaction before a desired timing by adding, to a mixture, a regulatory agent to suppress the exothermic reaction between the powder particles and a liquid additive up to the critical point so that a molded product excellent in quality is obtained, and a molded product obtained by this method.
Still another object of the present invention is to provide a molding method for powder particles, in which a preliminary molded product is sintered in a state in which the preliminary molded product maintains open pores by the aid of isostatic pressurization after completion of the isostatic pressurization step, so that the density of the molded product is increased, consequently making it possible to obtain the molded product excellent in strength, and a molded product obtained by this method.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.
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Birch & Stewart Kolasch & Birch, LLP
Honda Giken Kogyo Kabushiki Kaisha
Jenkins Daniel
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