JPS5855861B2 - Method for manufacturing sintered composites - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a sintered composite formed by joining a high melting point metal sintered body and a general metal body.

High melting point metal sintered bodies used for electrical discharge machining electrodes and electrical contacts are mainly sintered bodies made of high melting point metals such as tungsten and molybdenum, and copper, which has higher conductivity and a relatively lower melting point than these, It is made by impregnating it with metals such as silver and silver.

This impregnated sintered body is often used as is for the electrode material, etc., but on the other hand, in order to enable magnetic chuck and work efficiently, for example, iron material is added to the tungsten-copper sintered body. A bonded sintered composite may be formed and used.

In this case, the product price can also be reduced by using an inexpensive iron material.

In order to make a sintered composite by attaching a general metal such as iron to such a high melting point metal sintered body, brazing, which is a common method, is used.

In other words, high melting point metal powder with a small amount of additives is press-molded into a predetermined shape and fired to form a sintered body, and this sintered body is layered with an infiltration material such as copper. The material is placed in a container made of graphite or the like and heated to a temperature higher than the melting point of the infiltrant in a reducing atmosphere.

Next, the excess infiltrant on the surface of the sintered body impregnated with the infiltrant is removed by machining, and the sintered body is placed facing the general metal body to be joined, and the brazing material is sandwiched between them and placed in a heating furnace, where they are brazed. to obtain a sintered composite.

Conventionally, so-called silver solder or copper solder has been used as this brazing material.

Typical silver solder and copper solder are as follows.

However, sintered composites bonded using such a brazing filler metal do not necessarily have sufficient bonding strength.

This difficulty is particularly noticeable when the joint area is large or when external force is applied to the joint.

This is thought to be due to insufficient compatibility between the brazing material and the high melting point metal sintered body, and minute voids remaining in the joint.

Therefore, when a conventional sintered composite is used as an electrode for electric discharge machining or an electric contact, local discharge or the like occurs in the minute pores, and the bonded part may peel off and fall off.

Now, attempts have been made to improve the bonding strength of such sintered composites, and the inventors have already proposed using a portion of the excess infiltrant after impregnating the high melting point metal sintered body as a brazing material. This is a suggestion.

The present invention is characterized by providing a method for producing a sintered plurality of bodies in which the bonding strength between a high-melting point metal sintered body and a general metal body is further improved. Excellent in sex.

That is, the present invention is characterized in that a material made essentially of silver and iron-based metal is used as a bonding material for bonding a high melting point metal sintered body and a general metal body.

Examples of the method of the present invention will be described below.

First, tungsten powder is pressure-molded into a predetermined shape and then fired to form a tungsten sintered body (100mm x 100m
m'X 157X7m) is obtained.

This sintered body and an infiltration material made of copper are stacked together, placed in a container made of graphite, and heated in a hydrogen atmosphere at a temperature higher than the melting point of copper (for example, about 1200° C.).

This heating causes the infiltrant to sink into the sintered body.

Excess copper on the surface of the obtained sintered body is then removed by machining to obtain a tungsten sintered body containing about 30% copper.

On the other hand, as a general metal body, hard steel (S45C) is processed into a predetermined shape (100mrrr×100mm×1511L7+1).

This sintered body and steel material are laminated with a bonding material interposed therebetween as shown in FIG.

First, as shown in Fig. 1a, a mixed powder 3 containing silver and cobalt mixed at a ratio of 60:40 is spread as a bonding material on the whole surface of a metal body 1 made of steel, and a high melting point metal sintered body is placed on top of this. Overlap 2.

The finer the powder mixture is, the better the dispersion becomes.

In this example, it was about -300 meshes.

The amount of mixed powder was approximately 0.1 to 0.2 g/cr7.

This state is shown in FIG.

This was heated to about 1300'C in a hydrogen atmosphere to join them together to obtain a sintered composite.

The bonding strength of this composite sintered body was measured by impact value and compared with the value of a conventional silver brazing material, extremely high bonding strength was obtained.

In the same manner, the impact values were measured by varying the composition and amount of the iron-based metal in the bonding material, and the results are shown in a graph in FIG.

In Figure 2, the horizontal axis shows the proportion of ferrous metals (Co, Ni, and Fe) in the bonding material, and the vertical axis shows the impact value of the sintered composite obtained by the conventional method using silver solder as the bonding material. It is the ratio of the impact value when it is set to 100.

As is clear from FIG. 2, the sintered composite produced by the method of the present invention exhibits significantly superior impact resistance compared to conventional composites.

This can be said to indicate that the bonding state between the high melting point metal sintered body and the general metal body is extremely favorable.

As the high melting point metal sintered body constituting the sintered composite, tungsten sintered body is preferable because of its excellent mechanical strength and wear resistance.Tungsten sintered body is particularly preferred when used as an electrode for electrical discharge machining or an electric contact. A material whose body is impregnated with copper or silver is preferable in terms of wear resistance and electrical properties.

Further, as the general metal body to which the sintered body is joined, iron-based metals are preferred because of their good workability, low price, and the ability to be magnetically chucked.

Further, as a bonding material, a mixture containing silver and cobalt as shown in FIG. 2 is preferable because it shows the most excellent effect and can easily be made into fine powder.

Although this bonding material was used in the form of a well-dispersed mixed powder in the above embodiments, it may also be used in the form of a paste made from a mixed powder with water, alcohol, etc. Alternatively, a mesh plate may be used.

In short, it is sufficient if they can be uniformly distributed on the joint surface.

Note that it is also conceivable to use a material made of copper and iron-based metal as the bonding material in view of its low cost.

As described above, the method of the present invention is industrially advantageous because it can easily produce a sintered composite with high bonding strength.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the method of the present invention, and FIG. 2 is a graph showing the bonding strength of a sintered composite obtained by the method of the present invention. 1... Metal body, 2... High melting point metal sintered body, 3... Mixed powder.

Claims (1)

[Scope of Claims] 1. In a method for manufacturing a sintered composite formed by joining a high melting point metal sintered body and a general metal body, the high melting point metal sintered body and the general metal body are bonded together using silver and iron-based metals. 1. A method for producing a sintered composite, which comprises laminating a high-melting point metal sintered body and a general metal body together by laminating them through a bonding material mainly composed of the following: and heat-treating the laminated bodies. 2. According to claim 1, the high melting point metal sintered body is a tungsten sintered body fermented with copper or silver, and the general metal body is an iron-based metal that can be magnetically chucked. manufacturing method. 3. The manufacturing method according to claim 1 or 2, wherein the iron-based metal of the bonding material is cobalt.