Tungsten is a silver-white metal that looks like steel. Tungsten has a high melting point, low vapor pressure, and low evaporation rate. The chemical properties of tungsten are very stable, and it does not react with air and water at room temperature. There are mainly two kinds of ores to extract tungsten in our country; wolframite (tungsten iron ore) and scheelite (calcium tungstate ore). There are two types of tungsten smelting: fire method and water method. Wolframite concentrate or scheelite concentrate are used for smelting. However, due to the different smelting processes, when the deposit has both wolframite and scheelite, it is necessary to delineate Classification of ore bodies, and calculate the reserves. When the combination of wolframite and scheelite in the ore, wolframite concentrate and scheelite concentrate should be selected respectively for smelting, wolframite concentrate and scheelite concentrate. It is the main industrial raw material for tungsten extraction.
The metallurgical process of tungsten extraction mainly includes the decomposition of tungsten concentrate, the purification of tungsten solution, the preparation of pure tungsten compounds (paratungstate, tungsten trioxide), the preparation of tungsten powder, the preparation of dense tungsten and the preparation of high-purity dense tungsten. step. Dense tungsten mainly refers to tungsten bars and ingots. The former is produced by powder metallurgy, and the latter is produced by smelting. The powder metallurgy method is mainly composed of two processes of tungsten powder pressing and sintering. In industry, tungsten billets are usually prepared by two forming methods: cold pressing of steel molds and isostatic pressing at room temperature. The direct sintering method is generally used for the sintering of tungsten blanks, and the indirect sintering method is used for large-scale tungsten blanks that exceed the capacity of the sintering furnace. Pre-sintering is usually carried out in a key wire furnace, and the sintering temperature is controlled in the range of 1050-1500 ℃ depending on the properties of the billet. The main factors affecting the quality of vertical melting tungsten bars are vertical melting temperature system, raw material tungsten powder particle size, hydrogen atmosphere, forming pressure and so on. Indirect sintering mostly adopts resistance heating furnace or induction furnace. The smelting method is mainly used to produce tungsten ingots or single crystals with a purity above 99.99% (4N). Common methods include electron beam furnace smelting, vacuum arc smelting, zone smelting and plasma smelting. These are all methods of smelting tungsten ore.
