JPS61210104A - Method for sintering metallic powder - Google Patents

Abstract

PURPOSE:To manufacture a sintered body having a fine structure by sintering metallic powder at a specified temp. under a specified pressure. CONSTITUTION:Metallic (alloy) powder is heated to a temp. >=0.4 time the m.p. of the metal (alloy) represented by absolute temp. under >=10,000atm. pressure. Since sintering proceeds at such a low temp., the coarsening and growth of grains and a precipitate are inhibited, forming a fine structure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for sintering metal powders containing alloys.

BACKGROUND OF THE INVENTION Powder metallurgy has attracted attention in recent years as a method for producing high-strength metal materials. One advantage of using powder of the metal (alloy) as a material for high-strength metal materials is that the metal (alloy) is rapidly cooled from a molten state during powder production, so that its metal structure (crystal grains and precipitation) The material becomes extremely fine, making it easier to plastically process the material, and at the same time improving its mechanical properties.

On the other hand, pores remain in powder metallurgy materials, and these residual pores significantly deteriorate the mechanical properties of the material, particularly the toughness.

To solve this problem, conventionally, the preformed powder material is heated or simultaneously heated and pressurized to eliminate residual pores.

Problems that the invention aims to solve: However, in order to eliminate residual pores by heating the powder material (so-called sintering), a temperature that melts some of the metal (alloy) or some components is required. Also, in the method of applying pressure at the same time as heating (so-called hot press sintering method, hot isostatic pressure sintering method), the melting point of the metal (alloy) expressed in absolute temperature is 0.8 times or more. Temperature is required. Under such high temperatures, metal (alloy) crystal grains and precipitates grow and become coarse, reducing the advantages of the powder metallurgy method described above.

Means and action for solving the problem Metal R (alloy) powder is heated to 0.4 of the melting point of the metal (alloy) expressed in absolute temperature under a pressure of 10,000 atmospheres or more.
By heating the metal (alloy) to a temperature that is more than double that, it is possible to sinter the metal (alloy) so that crystal grains and precipitates do not grow and become coarse.

That is, the inventors researched a method of sintering powder of the metal (alloy) at a temperature low enough to prevent the crystal grains and precipitates of gold M (alloy) from becoming coarse.
．． If the metal (alloy) is heated under a pressure of 1,000 atmospheres or more, sintering will not progress even at low temperatures, but the coarse growth of crystal grains and precipitates at high temperatures, as in conventional methods, will be suppressed. It was discovered that fine microstructures could be obtained without diminishing the advantages of powder metallurgy.

Examples Example I' An alloy powder containing 18-18% Cr and 2% No by weight, with the balance F-1
With a pressure of 0,000 atmospheres applied, it was heated to a temperature that is 0.4 times the melting point of the metal expressed in absolute temperature and held for 30 minutes. When the density of this sample was measured, the density ratio was 98.
It was more than ryu. Alloy powder of the same composition was heated at normal pressure and
A comparison with the density when sintered at ,000 atmospheres is shown in FIG.

The density ratio represents relative density, and is obtained by dividing the density of the sintered body by the theoretical density.

In Figure 1, the head is the one made by the present invention, (the one made by hot isostatic pressure sintering (2,000 atm)?) is normal pressure (1 atm).
This is due to sintering.

This means that if the metal (alloy) is heated under a pressure of 9,10,000 atmospheres or more, the density ratio will be sufficient if it is heated to a temperature that is 0.4 times or more the six melting points of the metal (alloy) expressed in absolute temperature. It turns out that it can be obtained.

Example 2 Electrolytic iron was pulverized to obtain a fine powder, and the fine powder was heated to 800° C. using a belt-type ultra-high pressure generator and heated to 800° C. for 30 minutes. When this sample was cut and the metallographic structure was examined, the results shown in Table 1 below were obtained. As a comparative example, 8006CIC at 2,000 atm.
Table 1 shows the metallographic structure of the sample heated to 800°C at 1 atm.

Table I shows that heating can significantly reduce the crystal grain size and suppress coarsening.

As described above, according to the sintering method of the present invention, a sintered body having a fine structure can be obtained without reducing the advantages of powder metallurgy.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between sintered body density, sintering pressure, and sintering pressure. Figure 1

Claims (1)

[Claims] 0.4 of the melting point of the metal (alloy) expressed in absolute temperature under a pressure of 10,000 atmospheres or more
A method for sintering metal powder, which is characterized by heating to a temperature that is twice as high or higher.