Preparation of Copper-Tungsten Composite Electrode Material with High Toughness

As resistance welding, the electrode is a very critical material, which must withstand ablation during the welding process and avoid welding with the welding material. Therefore, the requirements for the electrode material are also very high. To withstand high temperature ablation, a high melting point is first required. In the metal material, the melting point of tungsten is the highest (up to 3400 °C), and its electrical properties are also very good. Therefore, tungsten is often chosen as the electrode material.

During the welding process, the electrode is pressed against the welding material and has a certain pressure, so the electrode material must have a certain degree of toughness. However, tungsten has a large disadvantage, that is, brittleness at room temperature, which causes it to break frequently during actual use, which affects normal production.

In order to change the brittleness of tungsten at ordinary temperature, it is common to use an alloying element capable of forming a solid solution with tungsten. Recently, researchers have chosen to add copper to improve the toughness of tungsten.

Although copper and tungsten do not form a solid solution, only so-called pseudoalloys can be formed between them, but considering that they can be very wet with tungsten in a certain atmosphere, copper liquid can even be tiled in hydrogen. On the surface of tungsten, this excellent wettability enables copper and tungsten to produce an effective composite effect, which is complementary to plastic and hard, thereby improving the toughness of the electrode material, and the addition of copper does not impair the electrical properties because copper has Good electrical conductivity.

The specific process of the copper-tungsten composite electrode material is as follows: the tungsten powder with a particle size of 1-10 μm is mixed into a molding agent, pressed and formed, pre-knotted in hydrogen at 1000-1200 °C, and then sintered in a vertical melting furnace or an induction furnace at 1500 °C - 3000 °C tungsten preform containing continuous pores. The copper is placed on the tungsten billet and heated to 1100-1600 °C. At this time, the liquid copper will spread throughout the tungsten billet under the action of capillary force, and the amount of copper added is controlled between 5-15% (wt). The experiment proves that the copper infiltration atmosphere is critical, because in the vacuum atmosphere, the wettability of copper and tungsten is not very good, the wetting angle is large, so that copper and tungsten can not be well combined, and sometimes can not penetrate into the tungsten billet. However, in hydrogen, nitrogen or a mixed gas thereof, copper and tungsten are very wet, so that copper is required to be carried out in hydrogen, nitrogen or a mixed gas thereof.

The electrode material made of copper and tungsten is greatly improved in strength and toughness. The impact test at room temperature proves that the material can produce certain plastic deformation, and when it is struck at a sharp corner, it can produce mushroom-like plastic deformation. It is distinctly different from the brittle cracking of pure tungsten materials during impact.

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