JPS6055580B2 - Method for manufacturing sintered molded parts with few pores mainly composed of chromium and copper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a chromium-copper powder material, which is produced by compressing a mixed powder material of chromium and copper and subsequently sintering it in a vacuum, to be used, for example, as a contact piece for a voltage power switch in a vacuum. The present invention relates to a method for manufacturing sintered molded parts with few pores as a main component.

Composite materials whose main components are chromium/copper and vanadium/copper are highly reliable as contact piece materials for voltage power switches in vacuum.

This is because they exhibit high switching ability, good heat resistance, and sufficiently low breaking current, as well as high dielectric breakdown strength before and after power interruption. Traditionally, this material has been produced by impregnation methods, which are accompanied by various difficulties. Vacuum impregnation with an excess of copper yields sufficiently good quality components, but the reaction affinity of the chromium or vanadium forms an alloy with the crucible material or impregnated substrate, so that they can only be used once.

In addition, due to the unfavorable material composition, which contains a high proportion of coarse or ROM particles (more than 100 TrLμ), a large amount of costs. In order to avoid the loss of the impregnation crucible, a crucible-less impregnation method is applied, in which the sintered material is placed on a small-area support.

However, in this method, a change in the interfacial tension of the impregnated copper occurs at the point where the contact material is placed, so that copper melting and insufficient impregnation of the contact piece are unavoidable. In addition, in this method, the number of impregnated components? Corrosion zones up to a depth of 100 mm are observed, which makes it impossible to produce precisely molded electrode parts. Such corrosion zones could be avoided if the impregnated copper was doped with chromium up to a saturation concentration at a suitable impregnation temperature. However, due to the affinity of chromium for oxygen, even during the impregnation process in vacuum, enrichment of the impregnated alloy with oxygen components occurs.
This results in incomplete impregnation of the sintered blank. In particular, chromium or vanadium and copper powders can be made shape-stable and with almost no pores, since the sintering effect of the chromium or vanadium powder is significantly reduced due to the oxide coating. It was not possible to sinter the powder compacted body.
Therefore, for example, when a compacted body made of chromium and copper powder in a 1:1 ratio is sintered at a temperature of about 1300'C, there is almost no volume reduction, i.e. before and after the sintering process. The residual amount of pores in the pores remains unchanged. An object of the present invention is to provide a method that makes it possible to sinter a contact piece material formed from a mixed powder containing chromium and copper components so that the shape is stable and there are almost no pores. There is a particular thing.

According to the invention, this purpose is to add at least 3% iron, cobalt or nickel powder to the chromium and copper mixed powder to enhance the sintering action of the chromium component, and the sintering temperature is 1300°C. more achieved.

In this case, the added metals iron, cobalt, or nickel diffuse into chromium due to their solubility with the molten copper phase, forming a mixed crystal with chromium. do. This provides the following effects. That is, by means of the above-mentioned additive metals, in particular in the case of chromium, oxide layers which hinder sintering are dissolved, resulting in a favorable sintering effect that reduces residual porosity. Furthermore, it is added by increasing the sintering temperature to 1300℃.
The metal powder is transported by diffusion through the liquid copper, and a mixed crystalline form of the added metal and chromium is achieved in an economical time (approximately 1 hour). Note that the sintering temperature of 1300C is a standard value and a certain deviation is allowed, but it is important that this temperature is clearly above the melting point (1085℃) and below the melting point of the additive metal (1500C). It is. In alloy systems such as tungsten-copper and molybdenum-copper, sintering is already accelerated by the presence of only a few percent of nickel, but unlike these alloy systems, the material composition of the present invention In order to keep the residual porosity below 3%, at least 3% of the additive must be added.

This is based on the fact that the properties of the promoting effect in molybdenum and tungsten are fundamentally different from those in chromium. In tungsten and molybdenum,
The significance of the fact that the additives exhibit an effect even at very low concentrations is primarily that of increasing the sintering rate. This sintering rate has little relationship to the melting point at temperatures of about 1200 to 1400'C, which is a problem for molybdenum and tungsten. In contrast, the effect of the above-mentioned additive metals in chromium is primarily to dissolve the oxide layer that prevents sintering. Next, the functions and effects of the present invention will be explained in more detail based on Examples.

Example 1 Chromium powder with a particle size of 70 pm or less is mixed with 45% copper powder and 10% cobalt powder of similar particle size,
It was compressed with a breath pressure of 4MpIc71f.

Subsequently, the compressed object is 13 in a vacuum of 10-4T0rr or less.
It was sintered at 00°C for 1 hour. In this case, initially about 2
The porosity, which corresponds to % by volume, was reduced to 3% by volume or less. By this heat treatment method, the sintered body was molded according to the mold. Therefore, it was found that even complex structures can be compression molded. Example 2 Chromium powder with particle size below 70pm is mixed with 40% copper powder and 15% iron powder of similar particle size to produce 5Mp
Compressed with 1c1i presca.

Claims (1)

[Claims] 1. In a method for manufacturing sintered molded parts with few pores mainly composed of chromium and copper, which involves compressing a mixed powder material consisting of chromium and copper and then sintering it in a vacuum, the sintering effect of the chromium component is sintered chromium/copper-based material with few pores, characterized in that at least 3% of iron, cobalt or nickel powder is added to the mixed powder material and the sintering temperature is set at 1300°C to increase the Method of manufacturing shaped parts.