Tungsten Copper Wire

Tungsten copper alloy is a kind of psudoalloy, which consists of the hard phase W and the binder phase Cu two immiscible metals, so it only can be fabricated by PM (Powder Metallurgy). Tungsten copper material has both advantages of tungsten and copper, the high density, high melting point, excellent wear resistance and corrosion resistance of W; the excellent electrical and thermal conductivity, good plasticity of Cu; and at a temperature above the melting point of copper alloy of copper liquefied evaporated to absorb a lot of heat, reducing the surface temperature. So tungsten copper material is also known as heat sink materials.

According to the shapes and applications, tungsten copper products can be specifically divided into tungsten copper rod, tungsten copper block, tungsten copper plate, tungsten copper contact, tungsten copper tube, tungsten copper electrode, tungsten copper heat sink, tungsten copper wire and so on. In the early 1960s, tungsten copper wire and tungsten copper electrode has been used in EDM (Electrical Discharge Machining) and resistance welding because of its high density, high strength, excellent electrical and thermal conductivity and arc ablation resistance. So far, with the developments of relevant technologies and further study of researchers, tungsten copper begin to use in plasma electrode material processing, precision machining, spraying, LED and other electrode fields. But since the special PM structure of tungsten copper, it has been greatly limited used in wire. In order to improve the uniformity, mechanical properties and production cost, it needs to looking for new technologies and processes.

Used in EDM electrodes of tungsten copper wires are supposed to meet the following requirements:

1. On the basis of excellent electrical and thermal conductivity, it also has good resistance to spark erosion;

2. Good structure uniformity and density, in order to ensure the stability of the electrical processing and improve the utilization of electrode material;

3. It has lower machining consumption and dose not affects the quality and the overall efficiency;

4. Easy for molding, machining molds and products according to design requirements to provide a correspondingly shaped profile tungsten copper electrode bars or complex shapes.

The basic process of tungsten copper wires is : Mixing → molding or isostatic pressing → infiltration, sintering tungsten copper rod or tungsten copper block → machining. Except conventional infiltration process, there are some popular processes used more, such as high-temperature liquid phase sintering and activated liquid-phase sintering. The principle of infiltration is that porous tungsten skeleton wetted by copper liquid, under the capillary force the copper liquid flows along the W particle gap, filling the pores of porous tungsten skeleton. So tungsten copper materials have higher density, excellent sintering properties and electrical conductivity; High temperature liquid phase sintering since the sintering temperature is high, a long time, will make a lot of volatile copper phase, so that the sintered tungsten copper material density decrease, the performance will be subject to different degrees of impact, it is difficult to obtain a high density, high conductivity tungsten copper alloy material; activated liquid phase sintering improves the relative density, the hardness and tensile strength of tungsten copper by adding small amounts of trace elements (Ni, Fe, Pd, etc.). But on the contrary, the activated elements will dramatically decrease the electrical and thermal conductivity, which is not suitable for the occasions with high requirements of the conductivity.

The technologies to machine tungsten copper rod or block in wires include drawing processing, rolling processing, roller die drawing techniques and rotary forging technology. Drawing processing take advantage of metal plasticity, when working in the external force so that it is forced through the die, the metal cross-sectional area is compressed to obtain the desired cross-sectional shape and size of the processing method. Preparation of tungsten and copper wire by repeatedly hammering and drawing forming, drawing conducted at room temperature, metal products will produce obvious hardening.

But for tungsten copper with lower Cu content, it has poor plasticity, the drawing rate received extremely limited, which is difficult to draw molding; rolling process is to rely on the friction two rotating rollers and the rolling member rolling pulled into the roll gap, it is compressed to produce plastic deformation process. In addition, the rolling process can also refine the grain, improve the organization, can significantly improve the mechanical properties of the metal alloy, suitable for mass production; Roller die drawing process the billet is drawn in a non-grooved drive, freely rotating rollers consisting of, the sliding friction with the material of the die orifice was changed to rolling friction bearing, the stretching process is more effort not only suitable for drawing round wire, shaped wire may be stretched, but not suitable for low plastic material.

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