Application of tungsten alloy

Filament industry

Tungsten was first used to make incandescent filaments. In 1909, W.D. Coolidge made tungsten wire by pressing, remelting, swaging and wire drawing of tungsten powder. Since then, the production of tungsten wire has developed rapidly. In 1913, I. Langmuir and W. Rogers discovered that tungsten-thorium wire (also known as thorium-tungsten wire) has better electron emission performance than pure tungsten wire, and began to use tungsten-thorium wire, which is still widely used today. In 1922, a tungsten wire with excellent sag resistance (called doped tungsten wire or non-sag tungsten wire) was developed, which is a major progress in the research of tungsten wire. Non-sag tungsten filament is an excellent filament and cathode material that is widely used. In the 1950s and 1960s, extensive research was carried out on tungsten-based alloys, hoping to develop tungsten alloys that can work at 1930-2760 ° C for making high-temperature parts used in the aerospace industry. Among them, there are many studies on tungsten-rhenium alloys. The smelting and forming technology of tungsten has also been studied, and tungsten ingots are obtained by consumable arc and electron beam smelting, and some products are made by extrusion and plastic processing; however, the smelted ingots have coarse grains and poor plasticity. , The processing is difficult, and the yield is low, so the melting-plastic processing process has not become the main means of production. With the exception of chemical vapor deposition (CVD) and plasma spraying, which can produce very few products, powder metallurgy is still the main means of manufacturing tungsten products.

sheet industry

China has been able to produce tungsten wire in the 1950s. In the 1960s, the smelting, powder metallurgy and processing technology of tungsten was studied, and now it can produce plates, sheets, foils, bars, pipes, wires and other special-shaped parts.

high temperature material

Tungsten material is used at high temperature, and the solid solution strengthening method alone has little effect on improving the high temperature strength of tungsten. However, on the basis of solid solution strengthening, dispersion (or precipitation) strengthening can greatly improve the high temperature strength, and the strengthening effect of ThO2 and precipitated HfC dispersed particles is particularly good. Both W-Hf-C and W-ThO2 alloys have high high temperature strength and creep strength at around 1900℃. The tungsten alloy used below the recrystallization temperature adopts the method of warm work hardening to produce strain strengthening, which is an effective strengthening method. For example, the thin tungsten wire has a high tensile strength, the total processing deformation rate is 99.999%, and the diameter of the thin tungsten wire is 0.015 mm, and the tensile strength at room temperature can reach 438 kgf/mm

Among the refractory metals, the ductile-brittle transition temperature of tungsten and tungsten alloys is very high. The plastic-brittle transition temperature of sintered and smelted polycrystalline tungsten is about 150 to 450 °C, which causes difficulties in processing and use, while single crystal tungsten is lower than room temperature. Interstitial impurities, microstructure and alloying elements in tungsten materials, as well as plastic working and surface state, have a great influence on the plastic-brittle transition temperature of tungsten materials. Except for rhenium, which can significantly reduce the plasticity-brittle transition temperature of tungsten, other alloying elements have little effect on reducing the plasticity-brittle transition temperature (see strengthening of metals).

Tungsten has poor oxidation resistance, and its oxidation characteristics are similar to those of molybdenum. Tungsten trioxide volatilizes above 1000 °C, resulting in "catastrophic" oxidation. Therefore, tungsten materials must be protected by vacuum or inert atmosphere when used at high temperature. If used in high temperature oxidizing atmosphere, protective coating must be added.

Military weapons industry

With the development and progress of science, tungsten alloy materials have become the raw materials for today's military products: such as bullets, armor and shells, shrapnel heads, grenades, shotguns, bullet warheads, bulletproof vehicles, armored tanks, military aviation, artillery parts, guns, etc. The armor-piercing projectile made of tungsten alloy can penetrate armor and composite armor with a large inclination angle, and is the main anti-tank weapon.