JPS6249137B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a mold, and more particularly to a method for manufacturing a mold made of a sintered body in which the substrate bonding surface of the mold has a smooth surface.

When manufacturing molds for shells and sand molds by sintering metal powder, the mold is filled with a mixture of iron powder and iron aggregate, a brazing material is placed on top of the mixture, and the brazing material is heated. A method of bonding by infiltration into the mixture may be preferably employed, but if the aggregate and brazing material are brought into direct contact, a large amount of the brazing material will be infiltrated at once, causing the aggregate to float and form on the surface. Unevenness occurs. Furthermore, if a weight is placed on top of the brazing material to increase the density of the aggregate, the surface accuracy will be degraded due to movement of the weight during operation. Therefore, there is a problem in that the amount of cutting allowance on the mold surface is large and it is difficult to control the amount, resulting in high processing allowance.

This invention was made in view of the above problem, and consists of placing a metal filter on a mixture of iron powder and iron aggregate filled in a mold, and placing a wax made of copper or copper alloy on top of the filter. Place the material,
A weight is placed on the brazing filler metal via a non-metallic plate, and the brazing filler metal is infiltrated into the mixture through a filter to improve the surface precision of the filler metal infiltration surface. It is an object of the present invention to provide a method for manufacturing a mold made of a sintered body, which prevents the aggregate of the mixture from lifting and increases the density by placing the mixture under weight.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Pressurizing a mixture 4 of an iron powder 2 and a steel aggregate 3 made of grit, cut wire, shot, milling powder, etc. into a mold forming hole having the required shape and dimensions of an inverted mold 1. fill without
A metal filter 5 is placed on the entire upper surface of the mixture, and a plate-shaped compacted powder body 6 of copper or copper alloy serving as a brazing material is placed on the filter 5.

The iron-based aggregate 3 is added to ensure the strength of the resulting mold and to prevent the volume of the mixture from decreasing during copper infiltration. Therefore, in the present invention, there is no need to pressurize the mixture during filling. Further, the powder 2 to be mixed into the mixture 4 is an iron-based powder, which is necessary for the surface precision of the obtained mold, but in consideration of the post-treatment of the obtained mold, such as nitriding, plating, etc. In addition, the brazing material is not limited to the green compacts of copper and copper alloys described above, and copper powder or copper plates may also be used.

The apparent weights of the iron powder 2, the iron-based aggregate 3, and the green compact 6, which is a brazing material, are measured, and their weight ratios are set at a ratio of 1:1:1, respectively. However, above 3
The ratio of the mold to be used is selected depending on the purpose, size, shape, etc. of the mold to be obtained, and is not limited to the above ratio.

The filter 5 prevents direct contact between the powder compact 6, which is a brazing material, and the mixture 4, and after the brazing material has penetrated into the mixture 4, they come together to form the mold surface. Therefore, the filter 5 needs to have good wettability with iron and copper, and the shape is a foam or a plate with holes,
Alternatively, it is essential that it has a shape with continuous pores, such as a sintered alloy, and that liquid brazing material can pass through it. Therefore, as the filter 5,
It is preferable to use a thick iron plate with holes, and the mold manufactured by the filter 5 can be strengthened.

A non-metallic and heat-resistant plate 7, preferably a ceramic plate, is placed on the green compact 6, and the shape and weight are such that a uniform load is applied to the entire green compact 6 on the plate 7. A weight 8 is placed.
The plate 7 prevents welding of the filter 5 and the weight 8, and has the function of ensuring the flatness of the filter 5.

As described above, after placing the metal filter 5, the powder compact 6, the non-metallic plate 7, and the weight 8 in order on the upper surface of the mixture 4, the temperature is lower than the melting point of iron and higher than the melting point of copper, for example, about 1100. The green compact 6 is heated in a gas furnace at a temperature of
It is infiltrated inside and fired. At the same time, by weighting the green compact 6 with a weight 8, weight is added to the mixture during infiltration of the green compact, preventing the aggregate from floating and maintaining the dense state of the aggregate. The firing time may be 40 to 60 minutes if the cube is 100W x 100L x 100H.

After firing in the gas furnace, cooled and iron powder 2
The iron-based aggregate 3 and the filter 5 are joined together with a brazing filler metal made of copper.

By the above method, a part of the mold in which the filter 5 is integrated is manufactured from a sintered body, and this is assembled with other molds to manufacture the entire mold. During this assembly, as shown in FIG. 2, the mold 9 manufactured by the above method is brought into contact with the substrate 10 with the front side on which the filter 5 is integrated,
Secure with bolts 11, etc. At this time, since the contact surface of the mold 9 is the surface of the filter 5, smoothness and flatness are ensured, and therefore cutting of this surface is unnecessary or can be reduced. Note that, if necessary, the contact surface of the mold 9 is fixed to the substrate 10 after being cut or ground to a required size. Furthermore, since the filter 5 is fixed to the surface of the mold, the mold itself and the bolt holes are strengthened.

As is clear from the above explanation, according to the mold manufacturing method according to the present invention, the accuracy of the mold surface of the brazing metal infiltration surface is improved, so the amount of cutting work is reduced or becomes unnecessary, and the machining cost is reduced. And the processing time can be shortened. Furthermore, by improving the precision of the mold surface and integrating the metal filter, the strength of the mounting surface to the substrate is improved. Furthermore, since the weight is applied uniformly by the weight, the density of the aggregate increases, which also has the advantage of improving the strength of the entire mold.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the method of the present invention, and FIG. 2 is a sectional view showing a state in which a mold manufactured by the above method is fixed to a substrate. DESCRIPTION OF SYMBOLS 1... Mold, 2... Iron powder, 3... Ferrous aggregate, 4... Mixture, 5... Filter, 6... Green compact, 7... Plate, 8... Weight, 9... Mold, 10... Substrate.

Claims (1)

[Claims] 1 A mixture of iron powder and iron-based aggregate is filled into a mold, copper or copper alloy is placed on top of the mixture with a metal filter interposed, and a non-metallic plate is placed on top of the copper material. and place the weight, then,
The method involves heating at a temperature lower than the melting point of iron and higher than the melting point of copper to infiltrate copper into the mixture through a filter, and then cooling and bonding the mixture and filter with copper to obtain a mold made of a sintered body. Characteristic mold manufacturing method.