Titanium was discovered in 1793 and put into industrial production in the early 1950s. At present, it has become the third metal material after iron and aluminum. It is widely used in various fields in industry, and its rapid development is related to the following characteristics.
(1) abundant reserves in the earth's crust, accounting for the fourth largest metal reserves, next to Al, Fe and Mg.
(2) low relative density (p=4.5g/cm3), high specific strength (b and), high plasticity, toughness and good processing performance.
(3) good performance at high or low temperature. Some titanium alloys and industrial pure titanium have good plasticity and toughness at ultra-low temperature (-253℃) while some titanium alloys maintain high thermal stability at 550℃.
(4) excellent corrosion resistance, it is wider than the stainless steel blunt state, oxidation film resistance to chlorine ion ability. Corrosion resistance in the oceanic atmosphere, seawater, wet chlorine, chloride, hypochlorous acid, sulfide, sulfate, most oxidizing acids and organic compounds.
In addition, the elastic modulus of titanium is small, only about half of that of steel, which is its disadvantage. The thermal conductivity of titanium is 1/4 of that of iron. Therefore, the titanium equipment shell running at high temperature is prone to greater thermal stress, but this defect is compensated for by its low linear expansion coefficient. The creep resistance of titanium is poor, not only at high temperature, even if the normal temperature may creep, therefore, in the design of equipment in addition to strength calculation, but also for creep accounting, which is easy to be ignored.
