Titanium is a high-quality, lightweight, corrosion-resistant structural material, new functional material and important bioengineering material that has been on the world’s industrial stage after World War II. It is known as second only to iron and aluminum. It has special features such as hydrogen storage, shape memory, and high damping performance. The function has extremely important strategic significance for national defense, national economic construction and social development. The development practice of various countries in the world shows that the advanced titanium industry is an important symbol of comprehensive national strength.
In the past 30 years, with the practical application of various heat treatment methods, there are more and more titanium alloys with different performance characteristics, and the application of titanium and titanium alloys in industry has become more and more extensive.
The high-purity titanium obtained by the iodization method is called "iodine method titanium" or "chemically pure titanium". However, it still contains interstitial impurity elements such as oxygen, nitrogen and carbon, which have a great influence on the mechanical properties of pure titanium.
High-purity titanium has low strength, so it is of little significance as a structural material, so it is rarely used in industry. At present, industrial pure titanium and titanium alloys are widely used in industry.
Industrial pure titanium
The characteristics of industrial pure titanium are: the strength is not high, but the plasticity is good, it is easy to be formed, stamped, welded, and has good machinability; it has good properties in the atmosphere, sea water, wet chlorine, and oxidizing, neutral, and weakly reducing media. The corrosion resistance and oxidation resistance are better than most austenitic stainless steels; but the heat resistance is poor, and the use temperature should not be too high.
Industrial pure titanium is divided into three grades: TA1, TA2, and TA3 according to its impurity content. The industrial pure titanium commonly used in industry is TA2, because of its moderate corrosion resistance and comprehensive mechanical properties.
Industrial pure titanium is mainly used for working temperature below 350℃, with little stress, but requires good plasticity stamping parts and corrosion-resistant structural parts, such as: aircraft skeletons, skins, engine accessories; seawater corrosion-resistant pipelines for ships, Valves, pumps and hydrofoils, components of seawater desalination systems.
α type titanium alloy
This type of alloy is in the α-type single-phase state at room temperature and service temperature, and cannot be heat-treated for strengthening (annealing is the only form of heat treatment), and mainly depends on solid solution strengthening. The room temperature strength is generally lower than β-type and α+β-type titanium alloys (but higher than industrial pure titanium), while the strength and creep strength at high temperatures (500-600℃) are the highest among the three types of titanium alloys, and The structure is stable, oxidation resistance and welding performance are good, corrosion resistance and machinability are also good, but the plasticity is low (the thermoplasticity is still good), and the room temperature stamping performance is poor. Among them, the most widely used is TA7, which has medium to high strength and sufficient plasticity in the annealed state, good weldability, and can be used below 500°C. When the content of interstitial impurity elements (oxygen, hydrogen, nitrogen, etc.) is extremely low, it also has good toughness and comprehensive mechanical properties at ultra-low temperatures, and is one of the excellent ultra-low temperature alloys.
β-type titanium alloy, grade TB2
The main alloying elements of this type of alloy are β-phase stabilizing elements such as molybdenum, chromium, and vanadium. It is easy to retain the high-temperature β-phase to room temperature during normalizing and quenching to obtain a relatively stable β-phase structure, so it is called β-type titanium alloy .
β-type titanium alloy can be strengthened by heat treatment, has high strength, good welding performance and pressure processing performance; but the performance is not stable enough, and the melting process is complicated, so it is not as widely used as α-type and α+β-type titanium alloy.
It can be used for parts working below 350°C, mainly used to manufacture various integral heat treatment (solution, aging) sheet metal stamping parts and welded parts, such as compressor blades, wheels, shafts and other heavy-duty rotating parts and aircraft components Wait.
α+β titanium rod and titanium alloy
This type of alloy presents α+β two-phase structure at room temperature, hence the name α+β titanium alloy. It has good comprehensive mechanical properties, most of which can be strengthened by heat treatment (but TC1, TC2, and TC7 cannot be strengthened by heat treatment), have good forging, stamping and welding properties, can be cut, have high room temperature strength, and have high strength below 150-500℃Some (such as TC1, TC2, TC3, TC4) also have good low temperature toughness and good resistance to seawater stress corrosion and hot salt stress corrosion resistance. The disadvantage is that the structure is not stable enough.
TC4 is the most widely used of this type of alloy, and its consumption accounts for about half of the existing titanium alloy production. The alloy not only has good room temperature, high temperature and low temperature mechanical properties, but also has excellent corrosion resistance in a variety of media, and can be welded, cold and hot formed, and can be strengthened by heat treatment.
Titanium is a metal with excellent properties and abundant reserves. It has the reputation of "modern metal". After half a century of development, titanium alloy preparation technology and application research have made great progress, and it has been widely used in various fields.
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