JPH01136902A - Method for compacting powder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial field of application: The present invention is a method for processing material powder for powder metallurgy, etc. using cold fluid pressure press (cold ice static press, CIP).
This invention relates to an improvement in the method of molding.

Conventional technology: Conventionally, in CIP molding of powder, an elastic rubber body, especially urethane rubber with excellent viscoelasticity, wear resistance, and strength, is used as a mold for molding, and the mold deforms when filling the powder. In order to prevent this, the walls were made thick.

When molding powder by the CIP method using an elastic rubber body, the following drawbacks have been known.

In other words, if the friction between the inner surface of the mold and the surface of the molded product is large when the pressure is removed after pressure molding using a fluid, especially if the molded product has unevenness from which strain cannot escape, the molding The body was often damaged.

In Japanese Patent Application Laid-open No. 59-159901, long in one direction,
Therefore, in order to create a molded body that is easily damaged, thin-walled parts and thick-walled parts are formed in the longitudinal direction of the mold, and the thin-walled part takes advantage of the fact that the stress required to recover from strain is smaller than that in the thick-walled part. This prevents the molded product from being destroyed.

Problem to be Solved: However, when the mold surface includes an uneven surface from which the molded product cannot escape, it is impossible to remove the molded product without damaging the molded product.

However, the dimensional stability of the molded product is still poor due to the presence of thin parts.

Means for solving the problem: In the present invention, by using a plastic material instead of an elastic material or a material whose elasticity is negligible compared to the strength of the molded object as the material for the molding die, troubles caused by mold expansion during depressurization can be avoided. remove.

That is, the present invention Room temperature (including temperatures that require slight heating or cooling).

), when molding material powder with a room-temperature fluid pressure press: A plate-shaped body of thermoplastic resin is placed in the open part of a mold for producing a mold; The plate-shaped body is made plastic. Heating to a temperature indicated; the pressure outside the mold is made equal to the pressure inside the mold, and the plate-like body is brought into contact with the mold surface of the mold to form a molding mold with a partially open opening. ; Filling the material powder into the mold through the opening; After evacuating the inside of the mold, the opening is closed to complete the rough molded body; The rough molded body is heated to room temperature fluid pressure. This is a method for molding powder, which is characterized in that it is compressed using a press to form a molded product.

When the mold has a complicated shape, by making the mold separable into segments, the mold can be easily removed from the mold.

Suitable thermoplastic resins include those selected from polystyrene, polyvinyl chloride, polyethylene, polymethyl methacrylate, acetyl cellulose, polycarbonate, and the like.

Effect: When a thermoplastic resin plate is expanded in a mold at a temperature at which it exhibits plasticity and the pressure outside the mold is higher than the pressure inside the mold (on the mold side), the wall thickness As a result, the cooling rate of the parts is slow, and the cooling rate of the thinner parts is faster, so the thinner parts harden earlier, and the thicker parts, which are hotter, harden later, so the thickness becomes uniform in the end.

By segmenting the mold, molds with complex shapes can be made without damage.

The mold for molding causes creep before the pressure is removed, and there is little expansion when the pressure is removed. The mold is burned away when the molded product is baked in a subsequent process.

The size of the molding mold needs to be made larger than the sintered body, taking into account the shrinkage that occurs during molding.
This shrinkage margin may be determined as a result of preforming.

Example: In FIG. 1(a), a plastic resin plate (1) heated to a plastic temperature by a heating plate (4) is placed in a vacuum chamber with its lower surface side passed through a vacuum chamber passageway (3). (not shown), and by applying pressure to the upper surface side, plastic changes occur and the resin plate (1) comes into close contact with the mold surface (the pressure acting on the upper surface of the resin plate (1) causes the lower surface to The required condition is that the pressure is higher than the applied pressure, and the degree of vacuum has no technical meaning.) As already mentioned, the resin plate (1) has a self-control property that preferentially elongates and makes the thickness uniform since the thicker portions have a higher temperature. As a result, a mold (5) with a relatively uniform wall thickness is obtained as shown in (b). Also, in (a),
The mold (2) consists of a single block, but the mold for molding is
In the case of a complex shape including irregularities, it is desirable to divide the mold into segments and assemble them for use.

(B) shows a state in which the material powder (6) is filled into the molding die (5) (in which the resin plate (1) of (A) is molded). If necessary, 'shaking' is performed to increase the apparent specific gravity.The egg is a holder for the mold (5).

(c) shows a state in which fluid pressure compression is performed in a known cold fluid pressure press (CIP), and shows the body (7), the upper lid (
8) A molding mold (5) filled with material powder, which forms a pressure chamber with the lower lid (9) and has its opening (5a) hermetically closed under vacuum, is supplied from the pipe 00. The molded product is compressed by a pressurized fluid.

The product molded body is further fired to form a product, but at that time,
The mold disappears through sublimation, combustion, etc., and the fired product is completed. However, in some cases, it may be possible to cut out the data after compressing it with CIP.

Effects of the invention: In the present invention, a molding mold is manufactured using a plastic resin to be larger than the actual size by the shrinkage allowance, filled with material powder, deaerated, and airtightly closed, and then filled with room-temperature fluid. The molded product is compressed using a pressure press and fired to form a fired product, but unlike conventional molds using elastic bodies, the molded product is not damaged when the pressure is removed. That is, due to the creep phenomenon of the plastic resin at room temperature, almost no expansion occurs when the pressure is removed.

Therefore, according to the present invention, it is possible to easily manufacture fired products with complicated shapes, which has been difficult with conventional techniques.

[Brief explanation of the drawing]

Figure 1 is a process diagram illustrating the steps of the powder molding method of the present invention, and Figure (A) shows the process of processing a thermoplastic resin plate into a desired shape using a mold. Figure 3 shows a state in which a molding mold is filled with material powder, and Figure (c) shows a process of compressing the molding mold filled with material powder using a room temperature fluid pressure press. (1) Resin plate (2) Mold (3
)...Vacuum chamber passage (4)...Heating plate (5)
...Molding mold (6)...Material powder (7)...
・Room temperature fluid pressure press body

Claims (1)

[Claims] 1. When molding material powder using a room-temperature fluid press;
A thermoplastic resin plate is placed airtight; the plate is heated to a temperature that exhibits plasticity; the pressure outside the mold is made greater than the pressure inside the mold, and a portion is opened. forming a mold; filling the material powder into the mold through the opening; evacuating the inside of the mold, closing the opening to complete a rough molded body; The molded body is compressed using a room temperature fluid pressure press,
A method for molding powder, characterized by forming it into a molded product. 2. The powder molding method according to claim 1, wherein a separately provided mold is separable into segments. 3 The thermoplastic resin is polystyrene, polyvinyl chloride,
The method for molding powder according to claim 1 or 2, wherein the powder is selected from polyethylene, polymethyl methacrylate, acetyl cellulose, and polycarbonate.