JPH07115230B2 - High temperature triaxial compression method of material - 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 that can greatly reduce the cycle time, hydraulic HIP using a liquid as a pressure medium (Japanese Patent Laid-Open No. 58-22307)
However, there are problems with the heat resistance of the material used for the press container and the sealing property against the high-temperature liquid between the punch and the cylinder part, so it seems that much improvement efforts are needed to put it to practical use. Be done.

In order to eliminate these drawbacks of HIP, a series of technologies collectively called pseudo-HIP was developed (The International Jour.
nal of Powder Metallurgy and Powder Technology JUL
It is explained in detail in Y1985). For example, the Ceracon method that uses ceramic particles as the pressure medium, the metal that has fluidity at high temperature, and the RO that uses the pressure medium of ceramic particles
The C law is a representative example.

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. However, the pressure distribution is made uniform and HI
It is difficult to achieve an isotropic pressure equivalent to P.

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 the cost becomes high.

[Problems to be solved by the invention]

The present invention is intended to develop a new process having a short cycle time and capable of exerting a pressure extremely close to isotropic pressure on a material to be processed.

[Means and actions for solving problems]

The present invention, when subjecting a material to high-temperature isotropic pressure treatment, covers a material to be treated heated to a processing temperature with a solid granular material heated to the processing temperature, and mechanically applies an external force to the granular material. It is characterized by exerting an isotropic pressure on the material to be treated by compressing it in the three axial directions.

Pressure media capable of exerting isotropic pressure on a material having a complicated shape include gas, liquid and solid. There are several methods of using a solid as a pressure medium, but the simplest method may be a seracon method in which a solid granular material is placed in a press container and uniaxially compressed by the press.

However, it is quite difficult to achieve isotropic pressure by this method. This is because the compression pressure in directions other than the pressing direction is smaller than the compression pressure in the pressing direction.

In order to make the difference between the compression pressure in the press direction and the compression pressure in the direction perpendicular to this pressure zero, it is necessary to reduce the friction between the particles so that the fluid behaves the same as a liquid.

For this reason, it is effective to mix a heat-resistant lubricating substance such as graphite or mica with the granular substance, but there is a limit to this as well, and it is quite difficult to reduce the compression pressure difference to zero.

Therefore, as a result of various studies on a method of exerting isotropic pressure on a material using a granular material, the following conclusion was reached.

That is, a method is effective in which the material to be treated heated to the processing temperature is covered with a solid granular material heated to the processing temperature, and external pressure is mechanically applied to the granular material in three axial directions orthogonal to each other.

There are various methods of applying the external pressure, but first, a method of using a punch will be described.

FIG. 1 shows an example thereof. In the figure, 1 is a press container, which is a rectangular tubular structure. In this example, faces B and C
A square opening hole H _B, H _C is formed, C, also open hole to surface F H _C, but H _F are formed, the surface D, there is no open pores in E. P _A , P _B , P _C and P _F are punches that slide on the inner surfaces of the open holes H _A , H _B , H _C and H _F , respectively.

Next, the operation procedure will be described.

First, the lower punch P _F is raised and the tip of P _F is stopped at an appropriate position in the open hole H _F. At the same time, the tips of P _A and P _B are also open holes.
Stop at an appropriate position in H _A and H _B.

Next, the solid granular material heated to the processing temperature as well as the material to be treated heated to the processing temperature is charged into the pressing container 1. The material to be treated is covered with a particulate substance. In this case, the upper surface of the granular material should be horizontal at an appropriate position in the open hole H _C.

With this, the space inside the press container formed by the press container 1 and the punches P _A , P _B , and P _F is filled with the particulate matter and the material to be treated. However, the open hole H _C direction still continues to the outer surface space of the pressing container. At this time, it is effective to apply ultrasonic vibration to the pressing container 1 in order to increase the packing density of the granular material.

Next, the punch P _C is lowered to an appropriate position in the open hole H _C. After that, with punch P _F stopped, punch P _C , P _A ,
When a compressive force of substantially the same magnitude is applied to P _B , an isotropic pressure is generated in the internal space of the press container 1, and the material to be processed is subjected to isotropic pressure at high temperature.

If the cold density of the material to be treated is about 70% or more,
By appropriately selecting the processing temperature and the magnitude of the isotropic pressure, the density of the material to be treated after the high temperature isotropic pressure treatment can be almost 100% in a processing time of several minutes to several tens of minutes. .

After the above isotropic pressure treatment is completed, only the punch P _F is lowered to drop the particulate matter and the material to be treated. At this time,
By disposing a net through which only the particulate matter passes, the material to be treated and the particulate matter can be easily separated and collected.

Then, the punches P _A and P _B are slightly pushed to completely drop the granular substance in the pressing container. After collecting the dropped particulate matter, it is put into a heating furnace and circulated.

After that, the punch P _C is raised to set the punches P _F , P _A and P _B to appropriate positions of the open holes H _F , H _A and H _B of the press container, and the same work is repeated.

In the example of FIG. 1, the lower surface F of the pressing container is also provided with the opening hole H _F, but the lower surface F may be closed. In that case, the open holes are only H _C , H _A , and H _B , and the punches are only P _C , P _A , and P _B.

Further, the discharging of the particulate matter and the material to be compressed after completion of the isotropic pressure treatment is performed by tilting the pressing container.

Also, all sides of the press container, A in the case of FIG. 1,
Open holes may be provided in B, C, D, E and F, and 6 punches may be used, but it will generally be an excess of equipment.

The minimum number of punches is three, since at least three must be compressed in the direct direction to accurately achieve isotropic pressure. Usually, the maximum number of punches is 6, and there are 4 punch axes on one plane, but 5 or more punches on one plane are centered on the center of the material to be compressed in the plane. By installing them at equal angular intervals on the circumference,
It is possible to achieve isotropic pressure using more than one punch.

In the case of a cylindrical compressed material, 5 in the plane perpendicular to the cylinder machine.
In some cases, it may be effective to arrange more than one punch shaft, but this is also an excessive facility.

Therefore, in order to exert an isotropic pressure on the material to be processed, 3
It is sufficient to provide ~ 6 punches.

In FIG. 1, a rectangular container is used as the press container, but a cylindrical container may be used.

FIG. 2 shows the outer shape of the granular substance filled in the space inside the press container in the case of FIG. 1, FIG. 2 (a) shows the outer shape before compression by the punch, and FIG. 2 (b) shows the outer shape after compression. It is an example shown.

FIGS. 3 (a) and 3 (b) show changes in the space shape inside the pressing container before and after compression by the punch, that is, the outer shape of the granular material, when the cylindrical pressing container is used. In this case, the shape of the tip of the punch matches the shape of the inner surface of the cylinder of the pressing container.

As shown in the examples of FIGS. 2 and 3, it is preferable that the inner surface of the pressing container after completion of compression is a cube or a cylinder. This is because the pressure distribution in the granular material in this case is the most uniform.

In order to make the inner space of the pressing container smoothly approach such a cube or a cylindrical body as the compression progresses, it is necessary to pay attention to the design of the opening hole provided in the pressing container.

The open hole design of FIG. 1 will be described.

Although there are many methods of manufacturing a pressing container, an example of cutting out from a prism will be described in order to make the designing method easy to understand.

First, an open hole having a square cross section is formed so as to penetrate in the axial direction of a prism.

Next, the orthogonal open holes H _A and H _B are formed. At this time, the intersecting line L of the open holes H _A and H _B is an open hole of a size and position that matches the inner surface of the through hole. .

That is, in the case of FIG. 1, M is a side inside the through hole,
The side M and the side L are made to coincide with each other to form a straight line.

Similarly, in the case of a cylindrical pressing container, it is also preferable that the intersecting line of adjacent open holes corresponding to H _A and H _B exactly coincides with the inner surface of the cylinder.

Next, a method of compressing the capsule structure by compressing the volume of the sealed space in the sealed state will be described.

FIG. 4 shows an example thereof.

This is known as a triaxial compression test method for powder materials, etc.
It is a device devised to reduce the volume of the enclosed space (eg "Plasticity and processing" 1986-10, vol27, No.309, P112).
6 etc.).

FIG. 5 is a sectional view taken along the line AA shown in FIG.

A method of triaxially compressing a material to be treated using this apparatus will be described below.

Numbers other than the closed space 7 in the figure indicate blocks.
The arrow shown with a number is the direction in which the block corresponding to that number moves. The blocks corresponding to the numbers without arrows do not move.

In the closed space 7 surrounded by the six blocks 2, 2 ', 3, 3', 4, 4'in the figure, the material to be treated heated to the processing temperature and the granular substance heated to the processing temperature are placed. , The granular material is charged so as to surround the material to be treated.

At the time of this charging, the block 2 is raised by the illustrated plunger. After charging, the block 2 is lowered to an appropriate position to reconstruct the closed space.

Next, the block 2 is lowered by a punch (not shown). At this time, the block 2 is moved to the blocks 3, 4, 4 '.
Push down. The back surfaces of the blocks 3 and 4 are sloped, and the closed spaces are compressed in the X and Y directions by sliding on the slopes of the blocks 5 and 6 having slopes of the same angle.

Further, the enclosed space is naturally compressed in the Z direction when the block 2 is lowered by the punch. At this time, block 3
It is pushed by the block 4 and also moves in the Y direction. Block 4 '
Is pushed by the block 3 and moves in the X direction. The block 2'is pushed by the blocks 3 and 4 and moves in the X and Y directions.

If φ = 45 °, the enclosed space is compressed by the same amount in the three axial directions, so that the intended purpose is achieved.

In addition, it is desirable to apply a liquid or solid lubricant to a portion where the block contacts the capsule structure and a portion where the blocks slide. However, in this method, a large number of blocks move relative to each other, so it may be difficult for the compressive force from the punch to be transmitted to all blocks due to lack of lubricant, etc., and extra energy for compression is consumed. Need to be done.

In order to prevent this, an auxiliary cylinder for smoothing the block movement is provided, and blocks 2 ', 4', etc. can be moved in the directions of the dotted arrows shown in FIGS. 4 and 5. This is the preferred method.

Further, a method of arranging a spring or the like between the blocks which are related to each other so as to mutually assist the relative motions of the blocks is also effective. For example, in the spring 10 shown by the dotted concentric circles in FIG. 5, the downward movement of 3 assists the lateral movement of 2 '.

The material to be treated in the present invention covers a wide range such as copper, iron, stainless steel, Ti alloy, Al alloy, superalloy, magnetic material, ceramics and intermetallic compound.

The processing temperature of these materials is usually about 700 ° C to 2300 ° C.

The shape is a bulk material or a powder material. Further, in the case of a powder material or a bulk material, it may be wrapped in a capsule to be a material to be treated. The same material as the material to be processed is used as the capsule material.

As the granular material which is the pressure medium, ceramics such as Al ₂ O ₃ , BN, pyrophyllite and talc or inorganic particles, refractory metal particles, intermetallic compounds such as Ni ₃ Al and AlTi may be used.

〔Example〕

SUS304 stainless steel powder with a particle size of -100 mesh was compressed to a density of 90% with a cold press. The size of this compression molded product is 10
It is mmφ x 10 mm high.

This was subjected to high temperature isotropic pressure treatment using both the 4-axis press shown in FIG. 1 and the 1-axis press shown in FIG.

In case of 4-axis press, the internal volume after compression is 40mm × 40mm × 40mm
It has a cubic shape. The compression force is 50 ton per punch.

Same internal volume after compression in case of uniaxial press 40mm × 40mm × 40
mm. Compressive force was applied to block 2 by 150 tons.

Both the material to be treated and the granular substance were heated at 1200 ° C. for 1 hour and then pressed. Press time is 10 minutes.

When the density of the obtained stainless molded product was measured, it was about 10
It was 0%. This is comparable in quality to the ones that are normally processed with HIP for several hours.

〔The invention's effect〕

As described above, it was proved that a molded product having the same quality as that obtained by the conventional HIP can be obtained on the order of 10 minutes per cycle.

According to the method of the present invention, a high-density molded product using a powder material or the like can be easily manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory view of an apparatus of an example of a triaxial compression press system of the present invention, and FIGS. 2 (a) and 2 (b) are for press before and after press compression when a rectangular tube-shaped press container is used. 3A and 3B are explanatory views of the inner surface shape of the container, and FIGS. 3A and 3B are explanatory views of the inner surface shape of the pressing container before and after press compression when a cylindrical pressing container is used, and FIG. FIG. 5 is an explanatory view of an isotropic compression method using six blocks, and FIG. 5 is a sectional view taken along line AA of FIG. 1: Press container, H: Open hole P: Punch

Claims (2)

[Claims] 1. When subjecting a material to high-temperature isotropic pressure treatment, a material to be treated, which is stored in a container for press and heated to a processing temperature, is covered with a solid granular material heated to the processing temperature, A high temperature triaxial compression method for a material, characterized in that a compressive force is applied by a mechanical means in a triaxial direction orthogonal to the above to exert an isotropic pressure on the material to be treated. 2. A material to be treated and a granular substance are housed in a press container, and a punch is slid into one or two pre-formed open holes in each axial direction of three axes orthogonal to the container. The high temperature triaxial compression method for a material according to claim 1, wherein the granular material is subjected to mechanical pressure.