High-density molding device and high-density molding method for mixed powder

Abstract

A first die is filled with a mixed powder that is a mixture of a basic metal powder and a low-melting-point lubricant powder. A first pressure is applied to the mixed powder to form a mixed powder intermediate compressed body having a protrusion that protrudes in the pressing direction as compared with the configuration of a mixed powder final compressed body. The mixed powder intermediate compressed body is heated to the melting point of the lubricant powder. The heated mixed powder intermediate compressed body is placed in a second die. A second pressure is applied to the mixed powder intermediate compressed body to press-mold the mixed powder intermediate compressed body while crushing the protrusion in the pressing direction to form the high-density mixed powder final compressed body having high density and the desired configuration.

Description

TECHNICAL FIELD[0001]The present invention relates to a high-density molding method and a high-density molding system that can form a green compact having high density (e.g., 7.75 g / cm3) by pressing a mixed powder twice.BACKGROUND ART[0002]Powder metallurgy is a technique that normally presses (compresses) a metal powder to form a green compact having a given shape, and heats the green compact to a temperature around the melting point of the metal powder to promote intergranular coupling (solidification) (i.e., sintering process). This makes it possible to inexpensively produce a mechanical part that has a complex shape and high dimensional accuracy.[0003]An improvement in mechanical strength of a green compact has been desired in order to deal with a demand for a further reduction in size and weight of mechanical parts. When a green compact is subjected to a high temperature, the magnetic properties of the green compact may deteriorate. Therefore, the subsequent high-temperature tr...

AI Technical Summary

Benefits of technology

[0037]The mixed powder high-density molding method as defined in (1) can reliably and stably produce a high-density green compact while significantly reducing the production cost. It is also possible to smoothly produce a high-quality green compact by promoting a smooth flow of the liquid lubricant while effectively utilizing the pressing capability.

[0038]The mixed powder high-density molding method as defined in (2) makes it possible to further improve the fluidity of the basic metal particles and the liquid lubricant from the center area toward the inner wall of the cavity. Specifically, it is possible to further promote a smooth flow of the liquid lubricant, and reduce the production time.

[0039]The mixed powder high-density molding method as defined in (3) makes it possible to ensure that the lubricant produces a sufficient lubricating effect during the first press molding step. It is also possible to suppress oxidation, and selectively use a wide variety of lubricants.

[0040]The mixed powder high-density molding method as defined in (4) makes it possible to further improve the fluidity of the melted lubricant in all directions during the second press molding step. Specifically, it is possible to significantly reduce the friction resistance between the basic metal particles and the friction resistance between the particles and the second die.

[0041]The mixed powder high-density molding method as defined in (5) makes it possible to easily implement the press molding step, facilitate handling, and indirectly reduce the green compact production cost.

[0042]The mixed powder high-density molding system as defined in (6) can reliably implement the mixed powder high-density molding method as defined in any one of (1) to (5), can be easily implemented, and facilitates handling. The mixed powder high-density molding system can further improve productivity.

Problems solved by technology

When a green compact is subjected to a high temperature, the magnetic properties of the green compact may deteriorate.

The green compact exhibits insufficient mechanical strength when the density of the green compact is 7.4 g / cm3 or less.

Since oxidation proceeds corresponding to the temperature and the time when applying the sintering process (high-temperature atmosphere), the lubricant coated with the powder particles burns, and a residue occurs, whereby the quality of the green compact obtained by press molding deteriorates.

The methods that improve the lubricant and the methods that improve the press molding / sintering process are complex, may increase cost, and have a problem in that handling of the material is difficult or troublesome (i.e., it may be impractical).

In particular, when producing a magnetic core for an electromechanical device (e.g., motor or transformer) using a green compact, a satisfactory magnetic core may not be produced when the density of the green compact is 7.3 g / cm3 or less.

Even when the density of the magnetic core is 7.5 g / cm3, for example, the magnetic properties and the mechanical strength of the magnetic core may be insufficient in practice.

If the heat treatment temperature is less than 500° C., breakage may occur during compression molding.

If the heat treatment temperature is more than 1000° C., the insulating coating may be decomposed (i.e., the insulating properties may be impaired).

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