JPH084959B2 - High temperature fluid pressure compression method for materials - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for densifying mainly the inner surface quality of various materials by performing high temperature isotropic pressure treatment.

[Conventional technology]

There are many known methods for forming a powder material into a solid. The most common method is to form the material by cold pressing and then sinter at a high temperature, but the sintered mechanical parts obtained by such a method usually have a density of 100% or a value close to it. The drawback is that it is often not.

In order to improve the density to 100% or a value close to 100%, it is necessary to give a high compressibility at high temperature by forging, rolling, extruding, etc., or to apply high isotropic pressure at high temperature by HIP (hot isotropic compression). is necessary. For parts with complicated shapes, HIP using argon or nitrogen gas as a pressure medium is suitable, but it has the disadvantage of high cost due to complicated mechanism, use of expensive gas and long cycle time. However, it is currently applied only to high-grade parts.

As a method for greatly reducing the cycle time, there is known a hydraulic HIP (Japanese Patent Laid-Open No. 58-22307) that uses a liquid as a pressure medium, but the heat resistance of the material used for the press container, punching, etc. There is a problem of sealing property against high temperature liquid between the cylinder part and the cylinder part, and it seems that much improvement efforts are required for practical use.

In order to eliminate these drawbacks of HIP, a series of technologies collectively called pseudo-HIP was developed (The International JoP
urnal of Powder Metallurgy and Powder Technology J
It is explained in detail in ULY1985).

Typical examples thereof include a Ceracon method using ceramic particles as a pressure medium, an ROC method using a pressure medium such as a metal having fluidity at high temperature and ceramic particles.

The Ceracon method is one in which ceramic particles and materials heated to a required temperature are charged into a pressing container and then pressed, and has the advantage that the operation is simple and the cycle time is extremely short compared to HIP. But make the pressure distribution uniform
It is difficult to achieve isotropic pressure equivalent to HIP.

Further, in the ROC method, the material is cooled as it is together with the pressure medium, so that the work of removing the medium later is complicated and causes a cost increase.

[Problems to be solved by the invention]

The present invention contemplates the development of a new process using hydraulic pressure that is isotropic, has a short cycle time, and does not require or is a cumbersome sealing mechanism.

[Means and actions for solving problems]

The present invention, when a material that can be compressed by a press is subjected to high temperature isotropic pressure treatment with a fluid, the material to be compressed is housed in a capsule so as to be surrounded by a capsule pressure medium, and a heating device provided around the pressing container is used. Heat to a predetermined processing temperature,
The present invention is characterized in that the capsule is loaded into a press container that holds the pressure medium in the press container at a predetermined temperature lower than the processing temperature, and the pressure medium in the press container is pressed and compressed.

When the material to be compressed is ordinary metal material or fine ceramics material, the conditions of high temperature isotropic pressure treatment that are often used are temperature range 500 ℃ ~ 2000 ℃, pressure range 500 kg / cm ² ~ 5000
It is about kg / cm ² . In the case of hot isostatic pressing using liquid pressure, as the liquid, salts which become liquid at high temperature, glass, low melting point metal or ceramics may be used.
As described above, there are problems in the heat resistance of the material used in the pressing container and the sealing property between the punch and the inner surface of the cylinder.

For such a purpose, an appropriate material may be selected as the press container material. For example, Ni-based superalloys and Co-based superalloys are considered to be the best among the commonly used metallic heat-resistant materials.
Some have a creep rupture strength of around 1000 kg / cm ² at 00 ° C. Non-metallic materials include ceramics and carbon, and some have excellent heat resistance even at around 3000 ° C, but there are concerns about impact properties and thermal strain properties, and to use them as pressure vessels, for example, ceramics and carbon Special measures are needed to cover the surroundings with a thick, heat-resistant metallic material.

If the above materials are used, the problem of heat resistance can be overcome, but there is a strong possibility that it will be an uneconomical facility, and it will be limited to applications for the production of special high-grade materials. Therefore, in order to solve the problems of heat resistance and sealing properties of such a press container, various studies have been conducted to develop the present invention.

The problems of heat resistance and sealability of the press container are solved by making the temperature of the pressure medium as low as possible below the processing temperature. That is, it becomes possible to replace the material of the press container with a cheaper material by lowering the temperature of the pressure medium in the press container from the processing temperature, and,
This has the advantage of simplifying the material and mechanism of the seal portion between the punch and the cylinder portion.

However, if the temperature of the pressure medium is too low, boiling of the pressure medium may occur, or the internal quality of the material to be compressed may be transformed, which may cause an undesirable change in structure. There is a need.

However, if it is set too low, when the material to be compressed, which is to be densified by heating the internal temperature to the processing temperature, is charged into the pressure medium, the temperature of the surface of this material drops sharply, which adversely affects the material. . So to solve this,
It is necessary to cover the surface of this material with another material.

For other materials, the temperature drop of the material to be compressed whose internal quality is to be densified must be kept during the processing time, which is usually on the order of 10 minutes. Must be told.

For that purpose, it is preferable to enclose the material whose internal quality is to be densified in the capsule, but in order to prevent the temperature drop, the capsule must be a considerably thick material.
For example, the processing temperature is 1200 ℃ and the pressure medium temperature is 700 ℃.
In this case, in order to maintain the temperature difference of the material to be densified with a length of 10 mm φ × 10 mm for about 10 minutes without damaging the quality of the material, the thickness of the iron-based encapsulation material is about 10 mm. is necessary.

This thickness is an unrealistic value for comparatively small parts of 1 kg or less, especially in the case of parts with complex shapes, if the material is a thin encapsulation material, put the material in a capsule of an appropriate shape and However, it is necessary to make the inner surface of the capsule according to the shape of the material, which is extremely uneconomical. Further, when such a thick capsule material is used, the cost for removing the capsule after the high temperature isotropic pressure treatment becomes extremely high. Therefore, in the present invention, the capsule is made thin and a pressure medium is used in the capsule.

In order to satisfy both of thinning the capsule material and transmitting the isotropic pressure of the pressure medium to the material inside the capsule as faithfully as possible, a liquid between the capsule and the material inside the capsule at the processing temperature or It is effective to fill with solid particulate matter. As the liquid, a substance similar to that of the pressure medium may be used, and as the solid granular substance, refractory metal particles, refractory ceramic particles, or the like may be used.

In this case, when the solid granular substance alone has a low fluidity, graphite known as a lubricating material or a substance which is a liquid at the same processing temperature as the pressure medium may be mixed therein.

An example of a pressing method for realizing the above method is shown in FIG.

Reference numeral 1-1 in the figure is the lining of a pressing container, and heat-resistant alloy, superalloy, carbon, ceramic, etc. are used. 1
Reference numeral -2 is a strength member for suppressing the internal pressure applied to the press container, and high-strength steel, heat-resistant alloy, superalloy, etc. are used. 1
-3 is a heating device, and 1-4 is a resistance heating element for heating.

The pressure medium 3 is heated in a heating furnace including 1-1 to 1-4 as main constituent members. The heating temperature of this pressure medium is 200 ℃ ~ 150
It is about 0 ° C. An example of the pressure medium for each temperature range is as follows.

At around 200 ° C to 800 ° C, plastic, salt, etc.
At 0 ° C to 1000 ° C, salts, low melting point glass, low melting point metal, etc., and at 900 ° C to 1500 ° C, glass, low melting point metal, low melting point ceramic, etc.

6 is a material to be compressed whose internal quality is to be densified, 4 is a capsule, and 5 is a pressure medium in the capsule. Compressed material 6 is aluminum, copper, iron, stainless steel, magnetic material, titanium alloy,
Various materials such as aluminum alloys, superalloys, intermetallic compounds, and ceramics are targeted. The capsule 4 is made by selecting a material having good formability from the same materials as the material to be compressed, forming a thin plate, molding this, and welding.

As the pressure medium 5, the same material as that of the pressure medium 3 may be used as a liquid or a solid granular material, and in addition, high melting point metal particles, Pyroyphyllite particles, talc particles and high melting point ceramic particles may be used. Further, as the lubricant used by being mixed with the solid granular substance, there are graphite, mica, etc. in addition to the same material as the pressure medium 3.

The structure of the capsule 4, the pressure medium 5 and the material to be compressed 6 is heated to a suitable heating temperature, usually between 500 ° C and 2500 ° C. The heating temperature of the structure is set higher than the temperature of the pressure medium 3.
As described above, it is desirable to make this temperature difference as large as possible due to the heat resistance and sealing properties of the pressing container.

Separately, after heating the structure in the installed heating furnace, the structure is immersed in the pressure medium 3, and immediately the punch 2 is lowered to apply an isotropic pressure to the structure. The application of isotropic pressure must be completed before the temperature of the material 6 drops to a temperature unfavorable for forming the material 6. In actual work, the material and amount of the pressure medium 5 in the structure and the heating temperature of the structure are often set in consideration of the temperature decrease of the material 6.

(Example) A SUS304 stainless steel powder having a grain size of -100 mesh was compressed to a density of 90% by cold pressing. The dimensions of this compression molded product are
It is 10mmφ x 10mm high.

This was pressed by the method shown in FIG. Punch diameter
It is 60 mmφ. The following materials were used as materials for the pressing device.

Inner lining of press container 1-1 graphite, press container member 1-21N100 (Ni-based heat-resistant alloy), press punch
21N100 (Ni-based heat-resistant alloy), pressure medium 3 lead soda glass,
Capsule 4 Mild steel (1 mm thick), pressure medium 5 Al ₂ O ₃ grains (average particle size 100 μm) + graphite powder were used to obtain a compression molded product 6 of stainless steel powder.

The heat retention temperature of the pressure medium 3 is 700 ° C., the heating temperature of the capsule 4, the pressure medium 5, and the material to be compressed 6 is 1200 ° C. × 1 hour. The size of the encapsulant is 40mmφ x 60mm high.

Under these conditions, a punch compression force of 10 t was used for compression for 5 minutes to obtain a molded product having a density of almost 100%. In addition, the internal quality such as crystal grains was almost uniform.

 This is comparable to the molded product obtained by normal HIP.

〔The invention's effect〕

As described above, according to the present invention, it was demonstrated that a molded product having the same quality as that of the conventional HIP can be obtained in the order of one cycle. This is a remarkable effect as compared with the conventional HIP in which one cycle takes one hour or more.

[Brief description of drawings]

FIG. 1 is an explanatory view of an example of a pressing method for carrying out the present invention. 1-1: Lining of press container 1-2: Press container member 1-3: Heating device 1-4: Heating resistor 2: Press punch 3: Pressure medium 4: Capsule 5: Capsule pressure medium 6: Material to be compressed

Claims (3)

[Claims] 1. A heating device provided around a press container, when a material compressible by a press is subjected to high temperature isotropic pressure treatment with a fluid, the material to be compressed is enclosed in a capsule so as to be surrounded by a capsule pressure medium. To a predetermined processing temperature,
A high-temperature fluid pressure compression method for materials, characterized in that a pressure medium in a press container is held at a predetermined temperature lower than a processing temperature, a capsule is loaded into the press container, and the pressure medium in the press container is press-compressed. . 2. The temperature of the pressure medium in the press container is 200 ° C. to 150 ° C.
A method for compressing a material according to claim 1 at a temperature of 0 ° C. under high temperature fluid pressure. 3. The pressure medium filled in the capsule is a liquid, a solid granular material, or a composite material obtained by mixing a solid granular material with a liquid or solid lubricating material at the processing temperature. A method for compressing a material under high temperature fluid pressure according to claim 1.