Tungsten Copper Rod Machining
The melting point of tungsten and copper are two metals vary greatly, tungsten melting point of 3410 ℃, much higher than the boiling point of copper and tungsten copper incompatible, and therefore the preparation of tungsten-copper composite powder metallurgy method can be used. Improving the material density and other properties of view, foreign scholars tungsten-copper material preparation undertaken extensive research, the main methods of preparation include infiltration method, activated liquid phase sintering method, chemical co-precipitation method and explosive powder compaction.
Wherein the tungsten copper rod processing of our company mainly with infiltration, the main production process is: milling - mixing - pressing - sintering - infiltration.
Tungsten copper rod main production processes are as follows:
Infiltration, also called leaching method is the use of the capillary force of the low melting point metal wetting liquid filling certain density and strength of the porous matrix skeleton, the molten metal flow along the particle gap filling pores of porous W shares, thereby to obtain more dense material, using the W-Cu toughness prepared by this method can be greatly improved.
Infiltration into high-temperature sintering tungsten framework infiltration of copper and low temperature sintering mixed powder portion of copper infiltration methods. After high temperature sintering copper infiltration skeleton is sintered at high temperature hydrogen press-molded tungsten powder, copper is higher than the melting point of the molten copper infiltrated tungsten skeleton rely on capillary action. Furthermore, due to the high sintering temperature, sufficient reduction of tungsten powder, low melting point impurities and is not easy to restore the out-oxide can be decomposed and volatilized by the heat, obtained through this backbone having high strength, the arc operations to avoid the emergence of the phenomenon of burning. Currently, a number of medium-sized high-voltage vacuum circuit breakers and switches the development and application of tungsten copper-based contact has been very common, however, high temperature sintering tungsten framework law has its shortcomings, the production process is complicated, long production cycle, higher production costs limitations of its application.
After the low-temperature sintering mixed powder of copper infiltration is part of the tungsten powder mixed with a small amount of copper powder and sintering additives (usually nickel powder), at lower temperatures, pre-sintered in hydrogen, and then carry out infiltration sinter copper. This approach must ensure that the sintering process, restore full and degassing, and vacuum infiltration of copper and high vacuum degassing process, in order to obtain a low gas content of the vacuum tungsten copper material. W-Cu alloy produced by this method, the copper along the grain boundaries of tungsten, tungsten skeleton strong as high-temperature sintering method, as the circuit breaker contact materials, prone to erosion phenomenon. This method of higher raw material composition or the product will contain more impurities and gases. However, this method simple process, suitable for manufacturing large 20% of the copper content of W-Cu alloy.
Overall, there are some flaws infiltration sintering, liquid copper alone tungsten skeleton pore capillary action infiltration densification slower, less densification. Thick copper solidification phase and the distribution is not uniform, but also make high-temperature sintering tungsten particles grew up together, forming a thick uneven tissue, liquid copper excessive overflows component segregation occurred, and the high temperature dimensional distortion serious.
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