Progress In Technology Of Titanium Alloy

                                   Progress in technology of titanium alloy

1. smelting extraction technology of titanium.
By reduction with sodium and magnesium reduction method is the main method of producing titanium sponge, another American improved Kroll, Armstrong method, Sri method, and conductive body intervention reduction, hunter, Armstrong method.

2. titanium alloy smelting technology.
The development of cooling hearth melting technology, including electron beam cold hearth and plasma cold hearth furnace technology. At present, cold hearth melting has reached the level of commercialization, but 25 ton ingot smelting. Energy production without segregation, inclusion of high quality titanium and titanium alloy ingots, meet the air rotating parts of high performance titanium demand; capable of producing flat ingot and hollow spindle, simplify the subsequent processing of plate and pipe, and can be a large number of recycling of residual titanium, but there are high cost, complex operation and so on. Electron beam and plasma cold hearth melting process in the United States, Japan and other developed countries, industry has been rapid development, the electron beam has been successfully applied to pure titanium and Ti-6Al-4V alloy smelting, the plasma beam is smelting complex components in titanium alloy is the most effective means. Russia has developed a similar to the cold hearth melting technology, namely "shell - consumable electrode melting". In addition, cold crucible melting technology, there have been great development, and the centrifugal casting process used in conjunction with titanium casting precision casting, is currently making the second generation of cold crucible melting furnace. The second generation cold crucible furnace can greatly improve the melting ability, shorten the smelting time, realize the complete suspension smelting, and eliminate the metal condensation. In our country, the research on the induction melting technology has been listed in the key research projects, and has made great progress in the smelting technology of titanium alloy. In 2008, I between the Kuomintang and the Communist Party of China in the production of titanium ingot 3.4 million tons, 2.4 million tons of titanium processing material; 44.5 tons of net exports of titanium sponge; 4083 tons of net exports of titanium processing material become a net exporter of titanium sponge and titanium materials.

3. precision casting technology. Lost wax casting method now known as precision casting, is a less cutting or no cutting of casting process, widely used for all types, all kinds of alloy casting, production of casting dimension precision and surface quality of casting method than other, complex, high temperature resistance, not easy to machining castings are available revestment precision casting. In recent years, the casting technology of titanium mainly developed cold crucible + ion casting technology, vacuum suction casting technology and vacuum die casting technology. The typical process of the precision casting of titanium alloy investment casting is graphite melting model case, metal tungsten surface layer ceramic shell, oxide ceramic shell. Titanium alloy material production cost is high, machining, forging, welding and so on more difficult, using precision casting technology, can improve the titanium alloy material utilization rate, reduce production cost. The mechanical properties of the metal castings are lower than that of the forgings, but the performance of the titanium precision castings is roughly similar to that of the titanium forgings, and precision casting is the best choice to reduce the cost and optimize the performance. The application of the furnace and the development of precision casting and metal molding, ceramic molding process for many large and complex thin-walled titanium castings to shorten the production time, reduce the cost of a certain space. At present, high performance titanium alloy large integral precision casting parts, most of them are the metal surface layer of ceramic shell or oxide surface layer ceramic shell mold. Large thin wall precision casting technology makes the performance of titanium castings close to titanium forgings, while the cost is about 50% lower than that of titanium forgings.

4. isothermal forging technology of titanium alloy.
Titanium alloy isothermal forging technology is a new technology, and thermo mechanical treatment can obtain the comprehensive mechanical properties optimization of isothermal forging of titanium alloy, but in the mold material, mold manufacturing and mold heating device, such as the cost of investment is higher than that of the conventional forging methods, mainly used in the manufacture of aircraft parts.

5. Heat treatment of titanium alloy. The solid solution quenching and aging hardening treatment of titanium alloy can obtain excellent technical performance and use performance, which can improve the product quality, prolong the service life and improve the economic benefit. At present, various countries have sought new heat treatment methods to meet the new requirements of titanium alloy engineering. A ceramic phase transition treatment technology, CCT technology, was developed by University of Birmingham, which was formed by heat treatment, and formed on the surface of the gamma TiA1 alloy to form alumina and titanium dioxide. With this technology, the production of gamma - TiA1 alloy engine valve, the shear resistance can be increased by 100 times. By using this technique, the TiO2 ceramic phase composite layer can be formed on the surface of TiNi shape memory alloy. Special heat treatment process is one of the key manufacturing technologies of national defense industry system. United States to accelerate the development of the space shuttle, by five companies composition consortium jointly developed for five new material forming and heat treatment process, high temperature Ti Al compounds, carbon / carbon and ceramic matrix composites, high creep strength of materials and high thermal conductivity materials.

6. welding technology of titanium alloy.
Most of the titanium alloy can use oxygen acetylene welding method for welding, all the titanium alloy can use solid-state welding method of welding (such as TIG, MIG, plasma arc welding, laser welding, electron beam welding and resistance welding). In recent years, domestic and foreign research on titanium and titanium alloy welding methods and welding results, TIG welding and laser welding of the best quality. Laser welding technology has the advantages of high power density, small heat affected zone, small residual stress and deformation, high welding speed, difficult to weld materials (ceramics, organic glass) and so on. The development direction of welding technology of titanium and titanium alloy is easy to operate and welding process automation and intelligence, so as to improve welding productivity, stability of welding quality and save energy, which is conducive to environmental protection and so on.

7. cold forming and processing technology of titanium alloy. Production technology, producing titanium sponge by Kroll Method is still the dominant process, electron beam cold hearth melting technology has on the preparation of titanium ingot reached commercial application, large forgings and precision forging technology in the continuous development and laser forming near net shape technology in constant should be used. Some conventional processing techniques such as forging and rolling have been realized. The application of artificial neural network to titanium alloy has solved some practical problems. Another way to reduce the cost of titanium alloy  manufacturing is to develop a beta titanium alloy. Titanium alloy special processing technology, laser processing technology, electron beam processing technology, ion beam and plasma processing technology, electrical processing technology, etc.. Titanium alloy solid state free forming technology includes electron beam melting, laser melting, forming technology, plasma arc forming (PTA), and laser precision metal deposition.

8. surface treatment technology of titanium alloy. From heat infiltration expansion, electroplating, vacuum coating as the representative of the traditional surface strengthening, abrasion resistance treatment technology, the development of the present stage to plasma nitriding, the application of ion beam and electron beam, laser beam is symbol of modern surface treatment technology, such as surface nitriding (gas nitriding, plasma nitriding, surface infiltration elements alloying, laser cladding and other. At present, the surface strengthening technology of titanium and titanium alloys are moving toward the application of various surface technologies and the development of the research and preparation of multilayer composite coatings.

9.  new processing technology of titanium alloy.

(1) near net forming technology.
Traditional titanium alloy material processing technology is with titanium sponge as raw material, after preparation, the preparation of the electrode - a vacuum consumable smelting - melting - open forging - Second forging, rolling or extrusion, and finally get the bar or sheet product. Near net shape forming technology of titanium and titanium alloy materials processing is to titanium sponge and titanium chip or titanium and titanium alloy powder as raw material, using PAM single ingot smelting technology of preparing casting or powder metallurgy method of preparing blank, followed by rolling or extrusion directly out of the finished product. Near net forming method includes laser forming, precision casting, precision forging, powder metallurgy, spray forming etc. various methods, forming complex shapes of titanium alloy parts, and achieve the purpose of near net shape forming. The near net shape technology of titanium alloy forging has been developed in Baosteel. The process is more and more applied to obtain the near net shape forging by placing the forging blank in the mold which is heated to the deformation temperature or close to the deformation temperature to obtain the near net shape forging. Powder injection molding (PIM) is a near net shape technology of the modern plastics injection molding technology into powder metallurgy field to form a new type of powder metallurgy, is the field of powder metallurgy developed most rapidly, the most promising a new near net shape technology. Spray forming has the advantages of rapid solidification, a new type of alloy has been developed, and the potential economic and social benefits have been shown.

(2) superplastic forming technology.
At present, titanium alloy superplastic forming technology is mainly used in the aerospace field, the development of other fields will be the inevitable trend of the development of superplastic forming technology. The latest superplastic forming processes are superplastic isothermal forging, gas pressure forming, superplastic extrusion vacuum forming, deep drawing, and non mould drawing. Titanium alloy superplastic forming technology application of superplastic isothermal forging, superplastic extrusion, superplastic gas bulging, superplastic forming and diffusion bonding with SPF / DB technology, titanium alloy superplastic forming mold material selection of etc.. Industry is gradually taking over plastic molding as an important way to solve the complex, large-scale or difficult to process materials with conventional forming methods. And the superplastic forming process of metal is called the forming technology in twenty-first Century, especially in the field of Aeronautics and Astronautics. This technology can significantly reduce the cost of components, reduce quality, save raw materials and solve the problem of processing. Superplastic forming is the forming of titanium alloy parts the best way, is very suitable for manufacturing missile parts, such as titanium alloy shell of missile, fairing, containers, Liang Hekuang and titanium ball. At present, the development of superplastic titanium alloy are: Ti-6Al-4V, Ti-6Al-5V, Ti-6Al-4V-2Ni, Ti-10V-2Fe-3Al, etc., in which the use of Ti-6Al-4V has been more widely.

(3) computer simulation technology of materials preparation and processing.
The research and development of computer simulation technology and related software of titanium and titanium alloy materials melting, casting, processing and manufacturing, heat treatment and so on have been carried out successively in the world. Through the computer simulation, the design process can avoid many disadvantages of the traditional design, save manpower and material resources, and greatly improve the accuracy of the new materials preparation and processing technology design. Titanium alloy technology development trend for the expansion and application of the further implementation of titanium and titanium were prepared and processed to be low cost, including sponge titanium production, material design and machining process of the low cost of; the development and application of high efficiency, short process flow titanium alloy processing technology, such as single cold hearth melting direct rolling technology, titanium strip continuous processing technology and; development of near net shape forming technology, including powder metallurgy, precision casting, precision forging, injection molding and other; the popularization and application of titanium, including biological titanium, car used for titanium and building with titanium.