In nature, titanium cannot appear as a pure substance, but as a stable oxide, and the metal state of titanium can be directly and violently combined with oxygen, nitrogen, hydrogen, carbon, etc., so that pure titanium is difficult to extract from oxidized ore. From the discovery of titanium to the production of pure titanium metal, it took more than a hundred years, and it was really used to show its true face in the industry after the 1950s. In modern times, because of the improvement of extraction methods, the output has increased significantly, and thus the original properties of titanium have been revealed. In theory, the method of manufacturing pure titanium is very simple, first separating iron from the impurity oxide, and treating it with chlorine to get a volatile liquid - titanium tetrachloride (TiCl4) in a closed steel reaction chamber and mixed with magnesium or sodium, because the chemical activity of magnesium or sodium is relatively large, it can reduce titanium to a metallic state. The pure titanium obtained from the reaction process is a sponge-like metal that can be cast into ingots after being melted in a vacuum. That being said, there are actually great difficulties in refining. It is difficult to control titanium when heating, because the activity of titanium is particularly large at high temperatures, it will absorb oxygen and nitrogen in the air and carbon in other substances, as long as there is 1% of these gases, it completely destroys the ductility of its forging, making titanium as fragile as pumice. Therefore, at every stage of the manufacturing process, it must be isolated from the air, either filled with blunt gas (like helium or argon), or carried out in a vacuum. In addition, when using magnesium to reduce titanium tetrachloride, there are also difficulties, if the temperature can not be adjusted at 1600℃, titanium may dissolve the iron metal in the reaction chamber.
Although steel must still be wrapped above 1300° C to isolate direct contact with nitrogen and oxygen, titanium can be processed in the same way as other metals at room temperature. The mechanical properties of titanium are far better than those of stainless steel, but the same processing device can be used for processing operations, after a long time of heating, the surface of titanium will form a layer of black extremely hard shell, which must be worn off with carbide cutting tools. However, in terms of drilling and cutting, titanium is not more difficult than stainless steel. However, titanium has not been able to completely replace iron and aluminum in the past, because its current production costs are still higher than iron or aluminum. In addition, there are many difficulties to be overcome in casting, purification, machining, etc. In the preparation of titanium alloys, the main difficulty is to avoid absorbing a large amount of oxygen and nitrogen before heating to the melting point, which seriously affects the plasticity and ductility of the alloy. Secondly, molten titanium can react chemically with any known crucible refractory.
Therefore, it is necessary to use special methods to prepare titanium alloy and products, and now it is mainly used powder metallurgy, including powder pressing method, metal powder injection molding method and lamination manufacturing method to make products.
