Effect of Lubricant on the Density of Tungsten Copper Electrode

In general process of hot pressing, tungsten particles are present between particles and mold the inner wall of the different sizes of friction, the two friction to some extent hindered the densification process material, in order to obtain the desired the green density, is bound to adopt more pressing pressure. Thus, both from the quality of compacts or maintenance of the equipment from the point of view, we must try to avoid such friction. The reduced friction in the pressing process basically includes two methods: one is to adapt tungsten carbide mold with high fineness to replace the steel mold; the other one is use lubricant, which can effectively decrease the friction of particles and the mold, and it has an large influence on the density of tungsten copper electrode sintering.

However, there are some problems about lubricant: 1. It decreases the mobility of powder; 2. Adding lubricant will reduce the volume of the original blank, which makes reducing green density is not conducive to the production of high density products; 3. In the process of pressing, he degree of contact between the metal powder is reduced due to the lubricant barrier, thereby reducing the intensity of some of the powder metallurgy compacts; 4. Lubricant should be removed before the sintering or during the sintering so that it will has an influence on the appearance of sintered body and the exhaust gas may decrease the life of furnace.

After milling, molding and sintering conditions (temperature, heating rate, etc.) under the same conditions, after adding tungsten-copper composite powder sintering and milling lubricant is not added tungsten-copper composite powder lubricant milling and grinding sintered density of time comparing the relationship between added density of the sintered body is 1% of lubricant stearic acid as compared to a lower sintered density was not added lubricant. This is due to the stearic acid was added, equivalent to the introduction of certain impurities, thereby reducing the sintering activity of the powder particles, resulting in a sintered tungsten copper electrode material density decreases. Therefore, comprehensive view of tungsten copper alloy electrode density plays a leading role in the activity of the powder, friction is a minor factor.

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