1. New processes, technologies and new uses of titanium
1.1 Titanium preparation methods
Although titanium is relatively abundant in nature, it is a rare metal because it is dispersed and difficult to extract. At present, the preparation of titanium is divided into two categories: thermal reduction method and molten salt electrolysis method.
(1) Preparation of titanium by thermal reduction method The thermal reduction method is to reduce titanium from titanium compounds such as TiCl 4, TiO 2, K 2 TiF 6, etc. at a certain temperature using strong reducing agents such as Li, Na, Mg, Ca and their hydrides. Depending on the titanium compound, the thermal reduction method for preparing titanium can be divided into three categories:
① Redox method of titanium chloride, such as Kroll method, Hunter method, Armstrong method and EMR method;
② Redox method of titanium oxide, such as OS method, PRP process, MHR method;
③ Redox method of titanate.
Currently, only Kroll method and Hunter method can be successfully applied in industrial production. The Kroll method uses magnesium to replace titanium in chloride, while the Hunter method uses sodium to replace titanium in chloride. In addition, the Armstrong method developed by Chicago International Titanium Powder Company in the United States is similar to the Hunter method in that it also uses sodium as a reducing agent to purify titanium. The United States has begun to use this method for pre-production in factories.
(2) Preparation of titanium by molten salt electrolysis In 1959, Kroll predicted that molten salt electrolysis would replace the Kroll method and become the mainstream method for producing titanium in the next 5-10 years. Over the years, scientific research institutions and laboratories at home and abroad have developed a total of more than a dozen new technologies for preparing titanium by molten salt electrolysis.
They can be divided into the following three categories according to the raw materials:
① Electrolysis of titanates;
② Electrolysis of titanium chlorides;
③ Electrolysis of titanium oxides, including FFC Cambridge method, MER process, USTB process, QIT process, SOM method and ionic liquid electrolysis method.
1.2 New Uses of Titanium
Since the 1940s, the use of titanium has developed rapidly and has been widely used in aircraft, rockets, missiles, artificial satellites, spacecraft, ships, military industry, medical treatment, petrochemical industry and other fields. The latest research has found that the human body contains a certain amount of titanium, which can stimulate phagocytes and enhance immunity. Therefore, many laboratories are committed to the development and application of biological titanium.
2.New processes, technologies and new uses of titanium alloys
2.1 Preparation methods of titanium alloys
The traditional processing of titanium alloys generally adopts melting and casting technology. The latest processing technologies are divided into the following categories: (1) Near-net forming technology; (2) Wire friction welding technology; (3) Superplastic forming technology; (4) Computer simulation technology of material preparation and processing process.
Near-net forming technology includes laser forming, precision casting, precision die forging, powder metallurgy, injection molding and other methods. Powder metallurgy is a new process that uses titanium powder or titanium alloy powder as raw material, through forming and sintering, to manufacture titanium parts.
1. To produce powder, mechanical alloying method is generally used, using a ball mill to strongly impact, grind and stir the raw materials.
2. The alloy that has been formed into powder is pressed and formed. There are two pressing methods, namely pressure forming and pressureless forming. The purpose of this step is to obtain a certain shape and size of the pressed embryo, and to make it have a certain density and strength.
3. After the blank is subjected to discharge plasma sintering, the upper and lower dies and the energized electrodes are used to apply a specific sintering power supply and pressing pressure to the sintered powder, and high-performance titanium materials are obtained through discharge activation, thermoplastic deformation and cooling.
4. The titanium alloy after plasma sintering is subsequently processed, generally heat treatment or plastic processing.
2.2 Uses of titanium alloys
Titanium alloys were widely used in the aerospace field in the early days, mainly used to make aircraft engines or pneumatic components. At present, titanium alloys have been used in civil, factory or household devices. The new development of titanium alloys is mainly concentrated in the following five aspects.
(1) Medical titanium alloys Titanium alloys have low density and good biocompatibility, making them ideal medical materials that can be implanted in the human body.
(2) Flame-retardant titanium alloys Titanium-based alloys that can resist combustion under certain pressure, temperature and air flow rate are flame-retardant titanium alloys. The United States, Russia and China have successively developed new flame-retardant titanium alloys. Among them, the United States uses these flame-retardant titanium alloys in engines. Because these titanium alloys are not sensitive to combustion, they can greatly improve the stability of the engine.
(3) High-strength and high-toughness β-type β-type titanium alloy has the characteristics of high strength, good weldability, and excellent hot and cold processing performance. And its mechanical properties are greatly improved after solution aging treatment.
(4) Titanium aluminum compound Titanium aluminum compound has good high temperature performance, good oxidation resistance and creep resistance compared to general titanium alloys, and its density is lower than that of general titanium alloys.
(5) High-temperature titanium alloy combines rapid solidification method with powder metallurgy method, and uses fiber or particle reinforced composite materials to prepare titanium alloys with excellent high temperature mechanical characteristics. The service temperature limit of high-temperature titanium alloy is much higher than that of ordinary titanium alloy.
(6) Titanium nickel alloy The alloy composed of titanium and nickel is called "memory alloy". This alloy is made into a predetermined shape and then after shaping treatment. If it is deformed by external force, it can be restored to its original appearance by slightly heating. This alloy can be used in various fields such as instrumentation, electronic devices, etc.
