JPS6029674B2 - Manufacturing method of high-density sintered body - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a high-density sintered body.

In the production of sintered bodies, the hot press method is widely used because the scorched stripes can be densified by sintering while applying pressure. For example, solid solutions of lead zirconate (PbZr03) and lead titanate (PbTi03) used as strongly electrostatic ceramics, solid solutions in which part of the lead in the solid solutions is replaced with lanthanum, zinc sulfide, sintered sialon, etc. Used in body manufacturing.

The following method is known as a conventional hot press method.

[1] Method of using a mold a As shown in Fig. 1, competitively bonded raw material powder 3 is placed in a high temperature resistant, high strength mold 1 made of alumina, graphite, SIC, etc., and pressed into a mold made of the same material. Method of applying pressure from above and below with rod 2.

In this case, heating is carried out by using an external heater for the entire mold or by using an electrically conductive mold and passing an electric current or an induced current through it using high frequency. b. When the mold and the fritted raw material react, as shown in FIG. The push rod 2 is interposed with a mold release material 5 made of powder such as alumina, SIC, zirconia or foil such as platinum or tantalum.
How to pressurize.

is being carried out.

However, in these methods, since the pressure is uniaxial, the pressure distribution inside the mold tends to be uneven, making it difficult to obtain a uniform product.

2 Cracks are easily formed inside the primary molded body, resulting in easy damage and poor product yield.

3 The shape of the primary molded body is limited to a simple shape due to one-touch compression.

There are drawbacks such as.

As a way to eliminate the drawbacks of this method, [21] Place the sintering raw material powder in a capsule made of a diaphragm made of metal or glass in a pressure-resistant container, or store the sintered raw material powder in advance to a pressure-resistant capacity of 95% or more. A method (hereinafter referred to as mP method) has been developed in which heating is performed by passing an inert high-pressure gas such as He or Ar into a container.

This HIP method is advantageous in that sintering is performed under isotropic pressure, and therefore a sintered body with a relatively uniform and complex shape can be obtained, but on the other hand, it has the following drawbacks.

1. Since an inert high-pressure gas such as He or Fu is used as the pressure medium, the equipment becomes large and requires careful maintenance and operation.

2. Since it is necessary to use a capsule made of a metal or glass diaphragm between the pressure medium and the sintering raw material powder, it is necessary to separate the diaphragm after sintering, making the operation complicated.

3. To reduce the use of capsules, they must be pre-frozen until the open pores are eliminated.

The present invention was made to eliminate the drawbacks of the conventional hot press method and HIP method.The purpose of the present invention is to enable the use of hot press equipment as is, and to easily manufacture products with complex shapes without the need for capsules. The purpose of the present invention is to provide a method for producing high-density Akatsuki compacts.

As a result of research to achieve the above object, the present inventors found that a powder (referred to as a solid lubricant) in which a B203 layer is formed on the surface of hexagonal shebal nitride (hereinafter referred to as h-BN) has a small viscosity coefficient. , (less than 1 poise at a temperature of 500 pm or more) has the property of having low friction between powders, and this is used as a molded body of sintered raw material or in a mold in a hot press machine for producing a sintered body. When packed together with a pre-sintered molded body and sintered under pressure, the solid lubricant transmits pressure in the same direction, making it easy to obtain a uniform, high-density sintered body, and also to produce products with complex shapes. We have found that it can be manufactured and obtained.

The present invention was completed based on this knowledge. The method of the present invention includes:
A solid lubricant with a B203 layer formed on the surface of h-BN is used as a pressure medium, and a molded body of brazed raw material powder or a molded body obtained by pre-sintering the same is pressure bonded using a hot press device. This is the method to do so.

The solid lubricant with &03 layer formed on the surface of h-BN is
It is obtained by heat treating h-BN powder in a moist oxygen-containing atmosphere, for example in humid air, in humid oxygen at 500-100,000. The solid lubricant obtained in this way may be filled into a mold, and h-BN may be filled in the mold together with a sintered powder molded body or a molded body obtained by pre-sintering the same.
After filling the powder, 500 to 1
It may be heat treated at 000 pm.

The shape of the h-BN powder may be any shape such as a plate shape or a spherical shape. In addition, &03 on the surface of h-BN powder
A portion of a solid lubricant such as h-BN, graphite, mica, or molybdenum disulfide may be mixed with the layered solid lubricant.

Preliminary sintering of the molded body of the agglomerated raw material powder has a scale of 90% or less.

The method of the present invention will be explained with reference to the drawings.

FIG. 3 is a cross section of a hot press device showing this embodiment (however, the heating device is omitted). A molded body of sintered raw material powder or a pre-brined molded body 4 is filled into a mold 1 together with a solid lubricant 6 in which a B203 layer is formed on the surface of h-BN. In this case, the filling direction and position of the molded body may be in any state as long as it is embedded in the group lubricant 6. And mold 1
is heated and pressurized with push rod 2. Due to this pressurization, the solid lubricant 6 flows freely and applies pressure to the molded body 4 in all directions, thereby obtaining a uniform and dense sintered body. According to the method of the present invention, B03 (
Since a solid lubricant with a melting point of 577q0) layer is used, its excellent fluidity makes it possible to apply pressure in the same direction to a molded body of compacted powder or its pre-sintered body, resulting in a uniform high-grade A dense sintered body is obtained. Also, conventional HIP
Since it does not use inert high-pressure gas such as He or Ar as in the conventional method, the equipment does not need to be large, and conventional hot press equipment can be used as is, and even complex shapes can be easily sintered. Excellent effects can be achieved. Example 1 99.99% purity Zn○ powder was molded into a cylindrical shape, which was further hydrostatically pressed at 2 tons/cm, and 8 pieces were placed in an alumina mold with an inner diameter of 5 mm and an outer diameter of 8 mm. , h-BN powder (particle size of 10 microns or less).

This was treated in air containing steam at 500 oo for 1 hour, and then treated in air at 850 qC for 5 hours while pressurizing at 500 k9/m. What was obtained was a transparent, high-density (98% or more) Zn○ sintered body. Example 2 ZnS powder was used in place of the Zn0 powder in Example 1, and agglomerated in the same manner as in Example 1.

What was obtained was a ZnS high-density sintered body having translucency.

Example 3 A molded body was prepared in the same manner as in Example 1 by mixing 0.1 mol % of Lj20 powder with the Zn○ powder of Example 1.

Eight of these molded bodies and the pre-made h-
A solid lubricant having a B203 layer formed on the surface of the BN powder was filled and sintered in the same manner as in Example 1. Akatsuki crystals with good translucency were obtained.

[Brief explanation of the drawing]

Figure 1 shows the conventional general hot press method, Figure 2 shows the hot press method using Shigeru shaped material, and Figure 3 shows an embodiment of the present invention, in which a solid lubricant is used to pressurize the molded body. It is a schematic diagram of a method of bidding. 1... Mold, 2... Push rod, 3...
... Condensed raw material powder, 4 ... Molded body, 5 ...
...Scale material, 6...Solid lubricant. Younger brother's figure 2 figure 3

Claims (1)

[Claims] 1 B_2O_ on the surface of hexagonal boron nitride as a pressure medium
A method for producing a high-density sintered body, which is characterized by using a solid lubricant formed in three layers and pressurizing and sintering a molded body of sintered raw material powder or a molded body obtained by pre-sintering the same using a hot press device. .