Origin of grades of titanium and titanium alloys
The main characteristics and uses of the grades are examples of iodine method titanium TAD This is high-purity titanium obtained by the iodide method, so it is called iodine method titanium, or chemically pure titanium. However, there are still oxygen, nitrogen, carbon, such interstitial impurity elements, which have a great influence on the mechanical properties of pure titanium. As the purity of titanium increases, the strength and hardness of titanium decrease significantly. Therefore, the characteristics are: the chemical stability is very good, but the strength is very low. Due to the low strength of high-purity titanium, its application as a structural material is of little significance, so it is rarely used in industry. At present, industrial pure titanium and titanium alloys are widely used in industry.
Industrial Pure Titanium
The difference between TA1 TA2 TA3 industrial pure titanium and chemical pure titanium is that it contains more oxygen, nitrogen, carbon and various other impurity elements (such as iron, silicon, etc.), and it is essentially a low alloy content of titanium. alloy. Compared with chemically pure titanium, its strength is greatly improved due to the inclusion of more impurity elements. Its mechanical properties and chemical properties are similar to those of stainless steel (but compared with titanium alloys, its strength is still lower).
The characteristics of industrial pure titanium are: low strength, good plasticity, easy processing and forming, good stamping, welding, and cutting performance; good in atmosphere, seawater, wet chlorine and oxidizing, neutral, and weakly reducing media. The corrosion resistance and oxidation resistance are better than that of most austenitic stainless steels. The heat resistance is poor, and the service temperature is not too high.
Industrial pure titanium is divided into three grades: TA1, TA2 and TA3 according to its impurity content. The interstitial impurity elements of these three types of industrial pure titanium gradually increase, so their mechanical strength and hardness also gradually increase, but their plasticity and toughness decrease accordingly.
The pure titanium commonly used in industry is TA2, which causes moderate corrosion resistance and comprehensive mechanical properties. TA3 can be used when higher requirements on corrosion resistance and strength are required. For better formability, TA1 can be used.
(1) Mainly used for stamping parts and corrosion-resistant structural parts with a working temperature below 360 degrees and low stress but requiring high plasticity, such as: aircraft skeleton and skin, engine accessories, seawater corrosion-resistant pipes, valves, etc. for ships. Pump. Seawater desalination system parts, chemical heat exchangers, pumps, distillation towers, coolers, agitators, tee, impeller, solid parts, ion pumps, compressor valves and diesel engine pistons, connecting rods, leaf springs Wait.
(2) TA1 and TA2 have good low temperature toughness and high low temperature strength when the iron content is 0.095%, the oxygen content is 0.08%, the hydrogen content is 0.0009%, and the nitrogen content is 0.0062%, and can be used as -259℃ The following low temperature structural materials.
α Titanium Alloy
Alloys such as TA4 have an α-type single-phase state at room temperature and service temperature, and cannot be strengthened by heat treatment (chasing is the only treatment method), mainly relying on solid solution strengthening. The room temperature strength is generally lower than that of β-type and α+β-type titanium alloys (but higher than industrial pure titanium), while the strength and transformation at high temperature (500℃--600℃) are the highest among the three types of titanium alloys. , and the structure is stable, the oxidation resistance and welding performance are good, the corrosion resistance and machinability are also good, but the plasticity is low (the thermoplastic is still good) and the room temperature stamping performance is poor. Among them, the most widely used is TA7, which has moderate strength and sufficient plasticity in the annealed state, and has good welding performance. It can be used below 500°C. When the content of interstitial impurity elements (oxygen, hydrogen, nitrogen, etc.) is extremely low, it has good toughness and comprehensive mechanical properties at ultra-low temperature, and is one of the excellent ultra-low temperature alloys.
The tensile strength is slightly higher than that of industrial pure titanium, and it can be used as a structural material in the medium strength range. Welding wire is mainly used in China. TA5 TA6 is used for parts and welded parts that work in corrosive medium below 400 °C, such as aircraft skins, skeleton parts, compressor casings, blades, ship parts, etc. Structural parts and various die forgings that work for a long time below TA7500 ℃ can reach 900 ℃ in a short time. It can also be used as ultra-low temperature (-233°C) parts (such as containers for ultra-low temperature).
TA8500℃ long-term working parts can be used to manufacture engine compressor discs and blades. Nitrogen alloys have poor qualification stability. There are certain restrictions on use.
β Titanium Alloy
The main alloying elements of such alloys as TB2 are β-stabilizing elements such as molybdenum, chromium, and vanadium. It is easy to retain the high temperature β phase to room temperature during normalizing or grade fire, and obtain a meso-stable β single-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 smelting process is complicated, so it is not as widely used as α-type and α+β-type titanium alloys. Parts working below 350°C are mainly used to manufacture various integral heat treatment (solution, aging) sheet metal stamping parts and welded parts; such as compressor blades, wheel discs, shafts and other heavy-duty rotating parts, as well as the construction of aircraft Wait.
Alloys of TB2 are generally delivered in a solution-treated state, re-dissolved, and used after aging.
α+β Titanium Alloy
Alloys such as TC1 and TC2 have α+β type two-phase structure at high temperature, so they are named α+β type titanium alloys. It has good comprehensive mechanical properties, most of which can be strengthened by heat treatment (nitrogen TC1, TC2, TC7 cannot be strengthened by heat treatment). Below 150-500 degrees and have good heat resistance, some (such as TC1, TC2, TC3, TC4) and have good low temperature toughness and good seawater stress corrosion resistance. The disadvantage is that it is not stable enough.
This type of alloy is most widely used in TC4, and its dosage accounts for about the general production volume of existing titanium alloys. The alloy not only has good mechanical properties at room temperature, high temperature and low temperature, but also has excellent corrosion resistance in various media. At the same time, it can be welded, hot and cold forming and can be strengthened by heat treatment. Therefore, it is widely used in aerospace, shipbuilding, weapons and chemical industries. Departments are widely used.
Stamping parts, welded parts, die forgings and bending parts that work below 400 ℃. Both alloys can also be used as low temperature structural materials.
TC3 TC4 Long-term working parts below 400 ℃, structural forgings, various containers, pumps, low-temperature parts, ship pressure shells, tank accessories, etc., the strength is higher than TC1, TC2. TC6 can be used below 450℃, mainly used as aircraft engine structural material.
TC7 TC9 Long-term working parts below 500 ℃, mainly used in the compressor discs and blades of aircraft jet engines.
TC10 Parts that work for a long time below 450℃, such as aircraft structural parts. Landing brackets, honeycomb couplings, missile engine casings, weapon structural parts, etc.
