JPH0775838A - Extrusion punch and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Purpose] To form minute irregularities on the surface of a punch made of super steel alloy without causing residual stress. [Configuration] Co between WC grains is oxidized by oxidizing the surface of a cemented carbide punch. Further, the oxidation treatment is performed from the surface of the punch to a range exceeding the diameter of the WC particles. [Effect] When Co is oxidized and removed from the surface of the punch, WC particles are exposed, and corresponding to the outer diameter of the particles,
Fine irregularities occur on the surface. Therefore, the punch can be easily separated from the work during the extrusion process. Further, the removal of Co between the WCs reduces the residual stress between the WC particles bonded to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a punch made of a cemented carbide used in an apparatus for extruding an aluminum can.

[0002]

2. Description of the Related Art In an aluminum can manufacturing process, as shown in the figure, a punch 2 made of tool steel or the like presses a work 4 made of aluminum or the like to pass a die 6 for plastic deformation into a predetermined shape. Processing is being done. This extrusion process is performed in a state where the punch 2 is slightly elastically deformed in the radial direction and the work 4 is slightly elastically deformed by an external force. However, when the punch 2 is to be removed from the work 4 as shown by the chain line in the figure, the work 4 is difficult to pull out.

Considering such a problem, as shown in the figure,
Asperities with a surface roughness of about 10 μm called cross-hatching are formed on the surface of the punch 2. That is, by the cross-hatching, the punch 2
The contact area between the work 4 and the work 4 is reduced, and the flow of air between the work 4 and the work 4 is promoted so that the punch 2 can be easily separated from the work 4.

[0004]

In order to extend the life of the punch 2 and the die 6, cemented carbide may be used for these materials, but this cemented carbide has been conventionally used. There is a problem that machining is more difficult than the tool steel that is used and that much work is required for the cross-hatching. In addition, cutting such as cross hatching,
This is accompanied by residual stress on the punch 2 as a work, and there is a problem that this residual stress adversely affects the life of the punch 2.

The present invention has been made in view of the above circumstances, and a punch capable of easily processing the surface of a punch made of super-steel alloy to a predetermined surface roughness and having no residual stress due to the processing is obtained. That is the purpose.

[0006]

In order to achieve the above object, the present invention provides an extrusion punch for plastically deforming a work with a die to form a predetermined shape into a sintered body of WC and a bonding metal. The surface treatment is performed by oxidizing and removing the bonding metal between the WC particles in an oxidizing atmosphere.

Further, the depth of the surface treatment layer is set to be equal to or less than the diameter of WC particles constituting the sintered body, or 5 μm.
m or less.

[0008]

With the above-mentioned structure, W is formed on the surface of the punch.
The spaces between the particles of C form voids, and fine irregularities occur on the surface of the punch. Further, by oxidizing the binding metal within the range of the particle size of WC or less, surface treatment can be performed without impairing the strength of the surface.

[0009]

EXAMPLES The extrusion punch of the present invention is manufactured by the following steps. First, raw material powders are mixed in a predetermined ratio. Examples of the composition include a mixture of WC and Co, Ni, and Cr as binding metals, a mixture of WC and Ni as binding metals, and a mixture of Ni and Cr as binding metals. The average particle size is 0.2 to 5 μm.

The raw material powder having the above composition is put into a mold and press-molded at a predetermined pressure.

When the obtained compact is sintered, the WC particles are bonded to each other in the three-dimensional direction, and the binding metal such as Co is melted and filled between the WC particles.

The surface of the sintered body is processed into a punch having a predetermined shape by mechanical processing such as grinding.

When the punch obtained by grinding is placed in an oxidizing atmosphere, the binding metal on the surface is melted and voids are formed between the WC particles. By setting the depth of such surface treatment to be equal to or smaller than the average particle size of the WC particles, it is possible to prevent the influence of the decrease in bond strength due to the oxidation of the Co layer. The average particle size of WC when used for tools is
Since it is 2 to 5 μm, the absolute value of the depth of the oxide layer is also in this range. Further, since the surface roughness of a normal WC sintered body processed into a predetermined shape by grinding is about 0.2 mm, a predetermined effect can be obtained by increasing the surface roughness value even slightly less than this. You can Since the WC particles are three-dimensionally bonded to each other,
Even if the bound metal is removed near the surface to a depth approximately equal to the average particle size, the WC particles on the surface are bound to the WC particles in the layer below it, and thus the removal of the bound metal causes the WC on the surface to be removed. No particles fall out.

In addition, Co other than WC can be obtained by the above oxidation treatment.
When the binding metal such as is removed, the WC particles are free to displace, thus eliminating the residual stress caused by the previous steps. That is, in punch manufacturing, by performing the above-mentioned surface treatment in the final step after all the mechanical processing is completed, the residual stress generated by the mechanical processing up to that time can be removed.

After the surface is oxidized for a predetermined time, the punch is completed by washing to remove the oxidizing solution. Since this punch has fine irregularities formed on its surface, it can be easily separated from the work after extrusion.

[0015]

As is apparent from the above description, according to the present invention, an extrusion punch for plastically deforming a work with a die to form a predetermined shape is formed by a sintered body made of WC and a bonding metal. WC on its surface in an oxidizing atmosphere
Since the surface treatment is carried out by oxidizing and removing the binding metal between the particles, it is possible to easily form fine irregularities on the surface of the punch made of cemented carbide.
These irregularities can facilitate the separation of the punch from the work after extrusion by reducing the contact area between the punch and the work. Further, by removing the bonding metal on the surface, the movement of the WC particles becomes free, so that the residual stress generated during the punch manufacturing process can be eliminated and the life thereof can be extended.

Further, the depth of the surface treatment layer is set to be equal to or smaller than the diameter of WC particles constituting the sintered body, or 5 μm.
By setting it to be m or less, the depth of the surface treatment can be regulated to the range of one WC particle, and the punch strength can be maintained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a conventional example.

FIG. 2 is an enlarged view of a main part of the punch shown in FIG.

[Explanation of symbols]

 2 punch 4 work 6 die

Claims (6)

[Claims] 1. An extrusion punch for plastically deforming a work between a die and a predetermined shape, the punch comprising a sintered body of WC particles and a binding metal, the surface of which is WC.
A punch for extrusion processing, wherein a surface-treated layer formed by removing a binding metal between particles is formed. 2. A method for manufacturing an extrusion punch, which plastically deforms a work between a die and a predetermined shape to form a sintered body of WC and a bonding metal into a predetermined shape, and a predetermined shape. And a step of removing the bonding metal from the surface of the sintered body in an oxidizing atmosphere. 3. The punch for extrusion processing according to claim 1, wherein the depth of the surface treatment layer is set to be equal to or smaller than the diameter of WC particles forming the sintered body. 4. The method for manufacturing an extrusion punch according to claim 2, wherein the treatment for oxidizing the binding metal is performed to a depth equal to or smaller than the diameter of the WC particles. 5. The punch for extrusion processing according to claim 1, wherein the depth of the surface treatment layer is 5 μm or less. 6. The punch for extrusion processing according to claim 2, wherein the treatment for oxidizing the binding metal is performed from the surface to a depth of 5 μm or less.