JPH0232047B2 - - Google Patents

Description

[Detailed description of the invention] a Technical field of the invention The present invention relates to a method for forming a superplastic metal plate.

b Conventional technology and problems Superplasticity is a phenomenon in which a material elongates abnormally under certain conditions and its deformation resistance significantly decreases.As a general guideline, the elongation in a tensile test is
This refers to cases where you can get more than 300%. When this material is applied to molding processes, it has excellent moldability, so it is possible to manufacture products with complex shapes that are difficult to mold using conventional molding methods, with fewer steps.

When the superplastic metal is in the form of a plate, the working force is generally smaller than when it is in the form of a block. For this plate-shaped superplastic metal plate, it is even possible to use vacuum forming or blow molding using gas pressure, which is used in plastic forming.
Metal plates can be shaped as if they were plastic plates.

Although it is extremely convenient to be able to mold a superplastic metal plate using a plastic molding method, it is not without its problems. That is, in order to perform vacuum forming or blow molding, a sealing device is required to reach a predetermined pressure. In other words, in vacuum forming, the processing force is generated by drawing a vacuum, so forming is impossible unless the degree of vacuum required for forming is achieved, and a sealing device that can withstand this must be prepared. Must be. On the other hand, in the case of blow molding,
A sealing device is still required to reach the air or gas pressure required for molding.

In the case of mass production, it may be economically possible to form a superplastic metal plate using such a sealing device, but currently there is often a demand for high-mix, low-volume production, so it is necessary to make it as simple as possible. There is a demand for a method that can be molded.

In addition to the above-mentioned vacuum forming and blow forming, hydraulic forming and rubber pressure forming may also be considered as means for forming the superplastic metal plate material. However, in the case of hydraulic molding, there are problems similar to those of vacuum molding and blow molding in order to prevent leakage of liquid, which is a pressure medium, and it cannot be considered a simple method. In addition, in the case of rubber compression molding using rubber as a pressure medium, there are relatively few problems if it is cold processed, but superplastic materials are processed at high temperatures where they develop superplasticity, so rubber The disadvantage is that it cannot withstand the processing temperature.

Based on the above, it is hoped that a simple method for forming superplastic plates will be developed.

c. Object of the Invention In view of the above-mentioned points, an object of the present invention is to provide a method for easily forming a superplastic metal plate material.

d Structure of the Invention As shown in FIG. 1A, a superplastic metal plate 2 is placed on a mold 1 for transferring a shape, and a cylinder 3 having arbitrary dimensions is placed around its outer periphery. When the granular material 4 is placed in the cylinder and pressurized at a temperature and strain rate that exhibits superplasticity, the granular material becomes a pressure transmission medium, and as shown in FIG. This is to transfer the shape of the mold 1. in this case,
Since the granular material 4 is flexibly deformed to the shape of the mold to which it is to be transferred, there is no need to process the pressurizing tool 5 into the shape of the mold 1, which simplifies mold processing. It is possible to aim for

In this case, the properties expected of the granular material used as the pressure transmission medium are as follows.

Condition (1): The pressure state is close to hydrostatic pressure.

Condition (2): Pressure force is small.

Condition (3): The apparent density is high and the stroke during compression molding is short.

Condition (4): Must be heat resistant.

Condition (5): Do not harden when pressurized.

Conditions (1) to (5) will be explained in order. Condition (1): The closer the pressure state is to hydrostatic pressure, the better the pressure transmission efficiency and the better the formability of the superplastic metal plate material. Furthermore, if the friction between the powder and the cylinder is small, the pressure transmitted to the superplastic metal plate increases, and the pressure distribution in the direction perpendicular to the pressurizing axis becomes uniform. In order to reduce the friction between the powder and the cylinder, it is effective to use a "double-press method" rather than a so-called "single-press method." Judging from the surface quality of the formed superplastic metal plate, it is generally better for the particle size of the powder to be finer. If the particle size is too large, the powder particles will be forced into the superplastic metal plate, resulting in uneven pressure distribution acting on the plate material and poor surface quality. In order to alleviate this tendency, it is effective to place a metal foil or thin plate between the powder and the superplastic metal plate. Condition (2): In order to reduce the capacity of the pressurizing device, it is desirable to use powder and granules that require a small pressurizing force. Condition (3):
The larger the apparent density of the powder or granule, the shorter the stroke during compression, and the smaller the amount of powder or granule used. Condition (4): Since the granular material is heated to the temperature at which superplasticity occurs, it must be able to withstand that temperature. Condition (5): If the powder or granules are solidified when taken out from the mold after molding, it is difficult to reuse the powder or granules, so it is preferable that the powder or granules do not solidify.

As a result of intensive research and investigation into materials that satisfy the above conditions as much as possible, we found that graphite powder with a particle size of several micrometers to several hundred micrometers, or metal powder or ceramic powder that contains graphite as a part, is effective. Since graphite powder also functions as a powder lubricant, quasi-hydrostatic pressure can be easily created using these powders, which is much more effective than conventional molding methods using gas or liquid. It has become clear that this method provides a simple molding means with great flexibility.

f Examples Example 1 A Zn-22Al superplastic material was used as the superplastic metal plate. To explain in more detail, powder with a particle size of 25 μm or less produced by the argon atomization method was heated at 380°C for 30 minutes.
After heating for several minutes, it was rapidly cooled in ice water and finally dried in vacuum. Zn obtained in this way
Using 12.5 gf of 22Al superplastic powder, compression molding was performed using a 46 mm mold at a molding pressure of 55 Kgf/mm ² to produce a disc-shaped plate material with a diameter and thickness of 46 mm × 1.5 mm.
This was used as a material for examples.

As a pressure medium, the particle size distribution is +80 mesh 20
% or less, -80 mesh 80% or more (80 mesh is
Graphite powder (compatible with 175μm) (Nippon Graphite Industries Co., Ltd.)
Approximately 80gf of PAG-80) was used. This graphite powder was filled as shown in FIG. The volume of the powder when filled is approximately 100 cm ³ . The material shown in Figure 2 was placed in an electric furnace and heated to 250℃, which is the superplasticity development temperature of Zn-22Al superplastic material. 6 Kgf/mm ² ) was applied. The time required under load is approximately 1 minute and 30 seconds. When the Zn-22Al superplastic material is taken out after pressure is applied, the shape of the mold is transferred and the second
It is shaped as shown by the broken line in the figure, and
The graphite powder was not solidified.

Example 2 As shown in Figure 3, graphite powder with a finer particle size than in Example 1 (+150 mesh 1% or less, -250 mesh 75 to 90%; Nippon Graphite Industries Co., Ltd. )CB-150) from 4 to 5 gf (approximately 10 gf by volume)
cm ³ ), and the graphite powder of Example 1 was added to the upper layer.
I filled it with about 70 gf of PAG-80. Here, the reason why the entire pressure medium was not made of graphite powder with a fine particle size is because although finer particle sizes give better surface properties to molded products, smaller particle sizes generally result in lower apparent density when filled. This is to eliminate these disadvantages since the length of the cylinder is required to compensate for this and the stroke during compression becomes longer.

Pressure force is 4tonf (converted to pressure: 2.4Kgf/mm ² )
It is. The shape of the mold is as shown in FIG. 3, and the superplastic metal plate, heating temperature, pressing speed, etc. used are the same as in Example 1. As a result of forming, although the graphite powder CB-150 in contact with the superplastic plate hardened slightly, the graphite powder PAG-80 in the upper layer did not harden and could be formed as shown by the broken line in Figure 3. did it.

Example 3 As in Example 2, two types of graphite powders with different particle sizes were filled in layers. In other words, Zn―
Approximately 4 pieces of graphite powder with a smaller particle size (average particle size 10 μm; Nippon Graphite Industries Co., Ltd. ACP) is placed on the 22Al superplastic plate.
g (approximately 10 cm ³ in volume), and the graphite powder (PAG
-80) was filled. Pressure force is 10tonf (pressure 6Kg)
f/ ^mm2 . The shape of the mold is as shown in FIG. The conditions such as the superplastic metal plate used, the heating temperature, and the pressurizing speed were the same as in Examples 1 and 2. As a result, as shown by the broken line in FIG. 4, the shape of the mold could be transferred and molded with high precision.

Example 4 As shown in Figure 5, crushed iron powder (particle size distribution 177-149 μm, 5% or less, 149-
74μm50~60%, 74~44μm20~30%, -44μm15%
Approximately 300 gf of mixed powder of Nippon Magnetic Sensing Co., Ltd. ES-50) and graphite powder (ACP) was filled. In this case, the graphite powder was used as a powder lubricant, and the blending ratio was approximately 290gf of iron powder and graphite powder.
It is 10gf. This is approximately 80 in terms of volume percentage.
^cm3 : equivalent to ^30cm3 . Pressure force is 20tonf (12Kgf/
^mm2 ). The shape of the mold is as shown in FIG.
The superplastic metal plate, heating temperature, pressing speed, etc. used were the same as in Examples 1 to 3. As a result of the forming, a superplastic metal could be formed as shown by the broken line in FIG.

Example 5 In the case of Example 4, only the shape of the mold and the pressing force were changed, and the other conditions were exactly the same as in Example 4. In this case, the mold shown in FIG. 3 was used, and the pressing force was 10 tonf (6 kgf/mm ² ). As a result of molding, it was possible to mold as shown by the broken line in FIG.

[Brief explanation of drawings]

A and B in FIG. 1 are explanatory diagrams of the molding method according to the present invention, where A shows a cross section before molding, and B shows a cross section after molding. Figure 2 is a sectional view of the device and molded plate material used in Example 1;
The figure is a sectional view of the apparatus and molded plate material used in Examples 2 and 5, FIG. 4 is a sectional view of the apparatus and molded plate material used in Example 3, and FIG. 5 is a sectional view of the molded plate material used in Example 3. FIG. 4 is a cross-sectional view of the device used in Example 4 and the molded plate material. 1... Mold for transferring the shape, 2... Superplastic metal plate, 3... Cylinder, 4... Powder, 5...
...Pressure tool.

Claims (1)

[Scope of Claims] 1. When forming a superplastic metal plate material at a temperature and strain rate at which it develops superplasticity, the plate material made of the superplastic metal is placed on a die to which the shape of the product is to be transferred, and then A granular material as a pressure transmission medium consisting entirely or partially of graphite powder is placed on the
A method for forming a superplastic material using powder or granules as a pressure medium, characterized in that the superplastic metal plate material is pressure-formed using a tool through this powder or granules. 2. A method for molding a superplastic material according to claim 1, characterized in that a metallic foil or thin plate is interposed between the powder and the superplastic metal plate material.