JPS61140328A - Formation of superplastic material by using granular body as pressure-transmitting medium - Google Patents

Abstract

PURPOSE:To press-form easily a superplastic metal sheet-stock by preparing only a die used for transferring a shape of product and using granular bodies as a pressure-transmitting medium equivalent to a punch. CONSTITUTION:A superplastic metal sheet-stock 2 is put on a die 1 used for transferring a shape of product, and a cylinder 3 having optional dimensions is set on the outer circumference of stock 2. When granular bodies 4 charged into the cylinder 3 is pressed under the conditions of temperature and straining rate, capable of developing the superplasticity of stock 2, through a pressing tool 5, the shape of die 1 is transferred to the sheet-stock 2 by the granular bodies 4 playing the role of a transmitting medium or pressure. Graphite, metallic, or ceramic powder having a particle size of about several microns - several hundred microns is used for said granular body.

Description

[Detailed description of the invention] Technical field of a0 invention The present invention 1 relates to a method for forming a superplastic metal plate.

b. Prior art and problems Superplasticity is a phenomenon in which a material groans abnormally under certain conditions and its deformation resistance is significantly reduced.As a general guideline, the elongation in a tensile test is 300 % or more.When this material is applied to molding processing, it is possible to manufacture products with complex shapes that are difficult to mold using conventional molding methods due to the lack of molding ability, 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 gas pressure-based bubble forming, which is used in plastic molding, and the metal plate can be formed as if it were a plastic plate. It is.

In this way, superplastic metal plates can be molded using plastic molding techniques, which is extremely convenient, but 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 if the degree of vacuum required for forming is not achieved, forming is impossible, and a sealing device that can withstand this must be prepared. On the other hand, in the case of blow molding, a sealing device is still required to reach the air or gas pressure necessary for molding.

In the case of mass production, it would be economically possible to form a superplastic metal plate using such a sealing device, but currently, high-mix, low-volume production is often required. There is a need for a method that can be formed as simply as possible.

In addition to the above-mentioned vacuum forming and blow molding, overnight pressure forming and rubber pressure forming are also conceivable 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.

C0 Object of the Invention In view of the above points, an object of the present invention is to provide a method for easily forming a superplastic metal plate material.

d9 Construction of the Invention As shown in FIG. 1(A), 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 powder 4 is placed in the cylinder and pressed under the I degree and strain rate that exhibits superplasticity, the powder becomes a pressure transmission medium, and as shown in Figure 1 (b), the superplastic metal The shape of the mold 1 is transferred onto the plate material 2. In this case, since the granular material 4 is flexibly deformed into the shape of the mold to which it is to be transferred, the pressurizing tool 5 is
There is no need to process the mold into the shape of the metal mold, which simplifies mold processing.

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 density of the second appearance is high and the stroke during compression molding is short.

Condition (4): 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 not the so-called “single press molding method” but the “double press molding method”.
It is effective to use 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 metal foil or a thin plate between the powder and the superplastic metal plate. Condition (2): To reduce the capacity of the pressurizing device. A powder or granule that requires a small pressing force is desirable.Condition (3): If the powder or granule has a higher apparent density, the stroke during compression will be shorter, and the amount of powder or granule used will be reduced. Condition (4): Since the powder or granule is heated to the temperature at which superplasticity occurs, it must be able to withstand that temperature.Condition (5): When taken out from the mold after molding, the powder or granule It is difficult to reuse the powder or granules if they are solidified, so it is preferable that the powder or granules do not solidify.

As a result of extensive research into materials that satisfy the above conditions as much as possible, we found that graphite powder, metal powder, ceramic powder, etc. with a particle size of several μm to several hundred μm are effective.
By using these powders, a quasi-hydrostatic pressure state can be easily created, providing a simple molding method that is far more flexible than conventional molding methods that use gas or liquid. It became clear that.

f. Examples Example 1 Zn', 22A1 superplastic material was used as the superplastic metal plate.

To explain in more detail, a powder having a particle size of 25 μm or less produced by an argon spray method was heated at 380° C. for 30 minutes, then rapidly cooled in ice water, and finally dried in vacuum. Zn-22AJ thus obtained! Using 12.5 gf of superplastic powder and using a 46 mm mold,
Compression molding was performed at a molding pressure of 5 kgf/mm" to produce a disc-shaped plate material with a diameter and thickness of 46+m++" x 1.5nna, and this was used as a material for examples.

As a pressure medium, the particle size distribution is +80 mesh 20% [
F, -80 mesh aO% or more (ao mesh is 175
Graphite powder (Nippon Graphite Industries Co., Ltd. PA
G-80) was used at about 80 gf. This graphite powder is
Filled as shown in the figure. The volume of the powder when filled is approximately 100 ci. The material shown in Figure 2 is placed in an electric furnace and the superplasticity onset temperature of the Zn-22kt superplastic material is 2.
After heating to 50℃, take it out and use a hydraulic universal testing machine to apply a pressure of 10 tonf (converted to pressure: 6 kgf).
/wa') was applied. The required time under load is approximately 1 minute and 30 seconds. When the Zn-22Af superplastic material was taken out after being pressurized, it was found that the shape of the mold was transferred and molded as shown by the broken line in FIG. 2, and the graphite powder was not solidified.

Example 2 As shown in Fig. 3, Zn-22Aj! 4 to 5 gf of graphite powder (+15G mesh 1% or less, -250 mesh 5 to 90%; Nippon Graphite Industries Co., Ltd. CB-150) with a finer particle size than Example 1 was placed on the superplastic metal plate. The upper layer was filled with about 70 gf of graphite powder PAG-80 of Example 1. Here, the reason why we did not use graphite powder with a fine particle size as the entire pressure medium is that although the finer the particle size, the more layered the surface texture of the molded product, if the particle size is small, the apparent density at the time of filling is generally lower. This is to eliminate these disadvantages, since the cylinder is small and the length of the cylinder is required to be extra, and the stroke during compression becomes longer.

Pressure force: 4 tonf (converted to pressure: 2.4 kgf)
/ ff1m"). The shape of the mold is as shown in Figure 3, and the superplastic metal plate used, heating temperature, pressing speed, etc. 3 are the same as in Example 1. As a result of molding, the superplastic Although the graphite powder CB-150 in contact with the plate hardened slightly, the graphite powder PAG-80 in the upper layer did not harden and could be molded as shown by the broken line in FIG.

Example 3 As in Example 2, two types of graphite powders with different particle sizes were filled in a layered manner. In other words, Zn-22A1 super! !
Graphite powder with smaller particle size (average particle size 10
About 4 g (about 10 d in volume) of Nippon Graphite Industries Co., Ltd. ACP) was filled, and the graphite powder (PAG-80) used in Examples 1 and 2 was filled in the upper layer. The pressing force was 10 tonf (pressure 6 kgf/mm"). The shape of the mold was as shown in Fig. 4. Conditions such as the superplastic metal plate used, heating temperature, and pressing speed were those of Example 1. This is the same as in Example 2. As a result, the shape of the mold was transferred and molding could be carried out with high precision, as shown by the broken line in FIG.

Example 4 ' As shown in Figure 5, crushed iron powder (particle size distribution 177-149 μm, 5% or less, 14
9~74μff150~60%, 74~44μm20~
30%, -44μm 15% or more; Japan Magnetic Separation Co., Ltd.
Approximately 300 gf of a mixed powder of E'S-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 10 gf of graphite powder to 290 gf of iron powder.
gf. This is approximately 80 arl in terms of volume ratio.
s 3Gco (corresponds to.The pressurizing force is 2Qtonf (
12kgf/III+12). The shape of the mold is the fifth
As shown in the figure. 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, the 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 completely the same as in Example 4. In this case, the mold shown in Figure 3 is used, and the pressing force is 10t.
onf (6 kgf/ma'). As a result of molding, it was possible to mold as shown by the broken line in FIG.

Example 6 770 gf of lead particles with a diameter of 0.5 M were used as the pressure medium. The shape of the mold is shown in FIG. Other conditions, such as the superplastic metal plate used, heating temperature, and pressing speed, were the same as in Example 1. As a result of molding,
Although some of the lead grains tended to harden a little, it was possible to mold them as shown by the broken lines in FIG.

Example 7 About 95 gf of A 120° powder with an average particle size of about 85 μm was used as the pressure medium. In this case, the mold shown in Fig. 2 is used, and the pressing force is 10 tonf (6 kgf/ll
lm2).

The other molding conditions (superplastic metal plate, heating temperature, pressing speed, etc.) are the same as those detailed in Example 1. As a result of the forming, it was possible to form the superplastic metal plate as shown by the broken line in FIG.

Example 8 About 20 gf of boron nitride powder (-325 mesh 98%), which is used as a high-temperature lubricant, was used as the pressure medium. The volume of the powder when filled is approximately 100cj.

The shape of the mold is as shown in Figure 6, and the pressing force is 10 tons.
f (6 kgf/mm2). The other molding conditions were the same as before. When the superplastic metal plate was taken out after the molding process, although the boron nitride powder had solidified, it was molded as shown by the broken line in Figure 6. The surface quality of the molded product was extremely excellent.

[Brief explanation of drawings]

(A) and (B) of FIG. 1 are explanatory diagrams of the molding method according to the present invention, in which (A) shows a cross section before molding, and (B) shows a cross section after molding. Figure 2 is a cross-sectional view of the apparatus and molded plate material used in Examples 1 and 7;
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. 4
FIG. 6 is a sectional view of the apparatus used in Example 6 and the plate material formed. FIG. 6 is a sectional view of the apparatus and the plate material formed in Example 8. 1. Mold for transferring the shape, 2. Superplastic metal plate, 3. Cylinder, 4. Powder, 5. Pressure tool. Figure 1 (a) Figure 1 (b) Figure 2 Figure 3 Figure 4 Figure 6 Figure 5

Claims (1)

[Claims] 1. When forming a superplastic metal plate material at a temperature and strain rate that cause superplasticity, only a die to which the shape of the product is to be transferred is prepared and used as a pressure transmission medium equivalent to a punch. A method for forming a superplastic material, characterized by pressure forming a superplastic metal plate using 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.