JPS59170203A - Manufacture of powder molding die - Google Patents

Abstract

PURPOSE:To manufacture a molding die which is extremely easily usable for a sintered body having a hole part by using paper-like graphite as a winding tube in a core part for forming the hole part in the powder molding die. CONSTITUTION:Paper-like graphite 2 formed in the form of a winding tube by tapering the center of a graphite die 1 is fitted in the groove provided in the internal bottom part of the die 1. Cr powder is packed in the graphite die having the die 2 and a Cr sintered body is manufactured in the case of infiltrating and sintering, for example, a Cr-Cu contact point and the deviation in the position of the winding tube 2 in the stage of packing the Cr powder is prevented by providing a groove 3. The resulting Cr sintered body 4 is then placed on a Cu material 6 for infiltration placed in a graphite crucible 5. The entire part of the crucible 5 in this state is heated to the m.p. of Cu or above in a vacuum atmosphere to infiltrate the molten Cu in the hole of the body 4, thereby forming the Cr-Cu infiltrated body. Said infiltrated body is machined to a required thickness and the desired Cr-Cu contact point is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a mold for obtaining a sintered body having holes.

Generally, in order to manufacture alloy parts with a specific shape, the metal components that make up the alloy are blended, melted and
Casting is commonly used, but when the shape of the part is small, relatively simple, and in large numbers, the component metal powders are mixed together, pressed and heated, and then cast.
It is also effective to adopt a powder metallurgy method to form a sintered body.

In the powder metallurgy method, the metal powders that are the components of the alloy are usually mixed in a predetermined ratio, mixed thoroughly using a mixer, etc., and then filled into a mold and formed into the desired shape.
A sintered body is obtained by heating this powder compact to an alloy solid phase or liquid phase state. However, when the component metals of the alloy have significantly different specific gravity or are made of metals that are difficult to melt together, a sintered body is made from powder of high melting point metal components.
Since this sintered body is originally porous, an infiltration/sintering method is often used in which a low melting point metal component is infiltrated into the voids of the sintered body in a molten state.

For example, when making a contact alloy made of Cr(l!:Cu), a metal that is difficult to melt together, the sinter infiltration method is preferable to molding and sintering mixed powders of Cr and Cu. In this case, for example, a disc-shaped Cr-Cu
Usually, it is made into an alloy, but first, a cylindrical sintered Cr body of an appropriate size is made using only Cr powder, placed on top of a Cu block, and surrounded by a graphite crucible. When heated on a Cu melting point plate, Cu melts and becomes Cr.
The sintered body sinks into the Cu, and molten Cu permeates into the voids from above and below the Cr sintered body, creating a Cr-Cu infiltrated body. By machining this cylindrical Cr-Cu infiltrated body and cutting it into rings with a predetermined thickness, the desired Cr-Cu
The contact is completed. Of course, machining can be omitted by making a Cr sintered body of a predetermined thickness from the beginning and infiltrating it with Cu so that contacts can be obtained one by one, but which method you choose depends on the manufacturing equipment and You can choose the preferred one by considering the quantity and other factors.

In this way, for example, when making a disk-shaped Cr-Cu contact, the sintering/infiltration method is suitable;
Since the sintered body is a solid body, when infiltrated with Cu, C
The gas contained in the pores of the Cr sintered body cannot be discharged to the outside as dead metal, and there are places where it is trapped inside the Cr sintered body.
Therefore, molten Cu may not spread throughout the pores and may remain as uninfiltrated portions.

On the other hand, it is known that Cr-Cu contacts do not necessarily have a disk shape, but can also be made into a ring shape with a hole in the center to satisfy the contact performance. If infiltrated, the gas contained in the Cr sintered body during infiltration will also escape laterally through the cylindrical hole, so it will not be trapped and there is no need to worry about creating an uninfiltrated part of Cu. The present inventors have confirmed with actual scissors that a defect-free infiltrated body can be obtained, and that material yield can be improved by machining this infiltrated body to form a ring-shaped Cr-Cu contact. There is.

In order to obtain this ring-shaped Cr--Cu contact, a cylindrical Cr sintered body must first be produced, and a graphite mold as shown in cross section in FIG. 1 is usually used for molding it. 1st
As shown in the figure, the portion forming the central hole is tapered as shown in Figure 1 so that the sintered body can be easily removed from the graphite mold.

However, manufacturing such a graphite mold requires complicated and complicated processing, and requires a lot of man-hours and time. Furthermore, when cylindrical sintered bodies with different pore diameters are required, graphite molds must be made each time, and the management complexity of having to prepare several types of molds as needed is unavoidable. There is a drawback.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a mold for a sintered body having holes, which is extremely easy to use, and which eliminates the above-mentioned drawbacks.

The present invention is achieved by using paper graphite for forming the holes in the sintered body. The present invention will be explained below based on examples.

FIG. 2 is a cross-sectional view of a graphite-type structure for obtaining a cylindrical sintered body according to the invention. In FIG. 2, paper graphite 2, which is tapered at the center of the graphite mold and formed into a tube, is fitted into a groove 3 provided at the inner bottom of the graphite mold 1. For example, the above-mentioned Cr −
When infiltrating and sintering Cu contacts, a graphite mold having this paper graphite tube 2 is filled to create a Cr sintered body.
The groove 3 was provided in order to prevent the position of the paper graphite cylinder 2 from shifting excessively when chromium powder is heated.
The groove 3 is not necessarily necessary if care is taken to hold the top end of the paper graphite cylinder so that it does not move when filling with powder. The thus obtained Cr sintered body 4 is made of graphite as shown in FIG.
After placing the Cr sintered body 4 on top of this, when the entire graphite crucible 5 is heated in a vacuum atmosphere to a temperature higher than the melting point of Cu, the molten Cu infiltrates into the pores of the Cr sintered body 4, resulting in Cr-Cu infiltration. Physical strength S is formed. This infiltrated body can be machined to the desired thickness to obtain the desired Cr--Cu contact.

Furthermore, although the above-mentioned sintered body has a concentric cylindrical shape with a hole in the center, the hole is It may be a non-concentric sintered body or a sintered body having a plurality of holes, and can be manufactured at any time as long as it has a box-shaped outer mold.

As explained above, instead of manufacturing the part that plays the role of a core in which holes are to be formed in a powder mold by processing it integrally with the mold, paper graphite can be used as a winding tube. Because it achieves its purpose extremely easily and can be provided in any size and in any number as needed, it is extremely effective when producing prototypes of sintered bodies. It is something.

Furthermore, in the embodiments of the present invention, the case was described in which the alloy was manufactured using the sintering/infiltration method, but the ordinary sintering method in which metal powders, which are the constituent components of the alloy, are mixed and shaped and sintered is also applicable. Of course, it is possible to achieve the same effect by applying it.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional mold, Fig. 2 is a sectional view of a forming mold using a paper graphite cylinder according to the present invention, and Fig. 3 is a sectional view of the arrangement of each member showing the infiltration method. be. 1. Graphite mold, 2. Paper graphite tube, 3. Groove, 4.. Cr sintered body, 5.. graphite crucible, 6. Cu for infiltration. Figure 81 Figure 3 Figure 6

Claims (1)

[Scope of Claims] 1) A powder molding mold characterized in that a tapered paper graphite cylinder is used at a portion of the mold for molding a sintered alloy having a hole where the hole is to be molded. Production method. 2. In the method according to claim 1, sintering and
A method for manufacturing a powder molding die, characterized in that it is used for sintering high melting point component metal powder of an alloy formed by infiltration.