Fiber-structure Tungsten Copper Contact

Tungsten copper is a psudoalloy, which is composed of two kinds of immiscible and has a great difference in physical and chemical properties metals. Since it has both advantages of W and Cu (high hardness, high strength, excellent corrosion resistance of W, excellent electrical and thermal conductivity of Cu) so that it has a broad application prospect in high-pressure, high-load vacuum circuit breaker and microelectronics fields. Due to the special nature of tungsten copper material itself, it is basically prepared by PM (Powder Metallurgy) process, but also for this reason that makes the structure and properties of tungsten copper alloy products subject to certain restrictions.

In order to make the organizational structure of tungsten copper contact more reasonable, the relevant researchers made many attempts in recent years, such as PIM (Powder Injection Molding), functionally graded materials, nano-structure and W-Cu tungsten fiber reinforced composite structure. Here we focused on the preparation of the fibrous structure of tungsten copper contacts and analyze the factors that affect performance and ablative infiltrated. The use of vacuum infiltration process, and select netting lamination to tungsten as weft, warp knit copper-dimensional net. Under vacuum condition, liquid copper has better liquidity and there is no air in the pores, which is more conducive to liquid copper fill-in. Tungsten braided copper mesh (copper as the infiltration time of induction of copper) and copper billets, and then the two stacked together in a vacuum sintering furnace infiltration, and sintered copper above the melting point (about 1300 ℃).

Copper in the molten state infiltrated in pores of tungsten skeleton by capillary forces, thereby connected to each other and form a dense material integrally. The advantage of using this method is that tungsten wire can distribute uniformly and copper wire can effectively induce. Since the most difficult to achieve tungsten copper contact with fiber-structure is how to make the fibers uniformly distribute in the matrix, whose distribution will affect the final properties directly. The weaving process can control tungsten wire to adjust the spacing between fibers. In addition, the distribution of copper wire at a high temperature infiltration, which presents the liquid copper supplement, under the action of surface tension, integration can reduce the surface area, prompting tungsten copper contact materials densification.

Tungsten wire diameter, infiltrated temperature and time all have an effect on the process. It uses tungsten fiber to take place of tungsten powder of conventional PM. Too large granularity of tungsten powder will have segregation and appear large area Cu-rich region, the binding force between the tungsten particles is also poor; too small granularity will prone to accumulate, leading to difficult to form a passage between the capillary and even hinder the formation of closed-cell infiltration were, so that the anti-arc erosion capacity decreases dramatically.

Fiber-structure has straight route so its density is higher after infiltration. But with the decreasing fiber diameter, it easily to form when copper was infiltrated pointed or wedge-shaped space, and solidification resistance is also large so that the defect forms. In addition, infiltration temperature has an optimum range, below the temperature which the sintered skeleton strength decreases, and the extension of sintering time, decrease the efficiency and increase energy consumption; the high temperature which the copper was in favor of lowering the viscosity of infiltration, but on the other hand the surface tension of liquid copper is reduced, and has an adverse effect on infiltration.

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