Views: 9 Author: Site Editor Publish Time: 2022-11-15 Origin: Site
Titanium powder refers to the titanium particle group with the size less than 1mm, which is a loose material. Its performance integrates the characteristics of titanium matrix and the commonness of powder. Like other powders, the properties of titanium powder include chemical properties, physical properties and technological properties. However, titanium powder and other powders have a common physical property of large specific surface, so titanium powder also has a large surface free energy. Therefore, titanium powder is more active than titanium metal, easier to react with other elements or compounds, easier to oxidize, flammable, explosive, belongs to a kind of dangerous goods. Its purity and various properties largely depend on the preparation method and technological conditions. Titanium powder is silver gray powder, can burn in nitrogen, high melting point. Titanium can be hydrogenated by adding hydrogen at a high temperature in a vacuum. After inhaling a lot of hydrogen, it becomes titanium hydride. Titanium hydride is easy to embrittlement and easier to be made into powder, which is a common method for mass production of titanium powder.
At present, there are many methods for preparing titanium powder at home and abroad, including mechanical alloying, hydrogenation dehydrogenation (HDH), atomization, metal thermal reduction and molten salt electrolysis.
Mechanical alloying is a powder preparation process in which metal or alloy powder is produced repeatedly by cold welding and fracture of powder particles through long-term intense impact and collision between powder particles and grinding ball in a high-energy ball mill, leading to the diffusion of powder atoms, so as to obtain powder. Mechanical alloying to prepare titanium and titanium alloy powder is to load titanium compound or mixed powder and development medium (usually need to add a small amount of process control agent) into high energy ball mill (argon gas protection) for grinding. In the grinding process, the powder particles are continuously grinding and gradually mixing through the continuous process of repeated welding - fracture - welding, so as to produce very fine powder particle size. The advantage of this process is that the grinding materials can be matched in any proportion, which can prepare alloy material or single metal powder.
Hydrogenation dehydrogenation method (HDH)
HDH is a process to prepare titanium powder by using the reversible properties of titanium and hydrogen. After hydrogen absorption, titanium will produce brittleness, which will be mechanically broken into titanium hydride powder and then dehydrogenated to produce titanium powder under vacuum condition at high temperature. The titanium powder produced by this process has a wide range of particle size, low cost and low requirement for raw materials, so it has become the main method of titanium powder production at home and abroad, but the titanium powder prepared by this method has a high content of O and N. In recent years, the research on the preparation of low cost and low oxygen content titanium powder is increasingly active at home and abroad.
Atomization method is a method of breaking liquid metal or alloy flow into tiny droplets, and then cooling and solidification in the environment to obtain metal powder. At present, titanium powder can be prepared by atomization method mainly by gas atomization method and centrifugal atomization method.
Gas atomization method
Gas atomization method is generally used to melt raw materials in a crucible, through the nozzle at the bottom of the crucible with high-speed gas to produce metal molten spray into a spray, condensed into metal powder.
Centrifugal atomization method
The centrifugal atomization method is used to make titanium powder by means of the centrifugal force generated by rotation, the metal is broken and thrown out in the form of mist droplets, and then the high purity spherical titanium powder is solidified. At present, centrifugal atomization methods mainly include rotating electrode method (REP), plasma rotating electrode method and electron beam rotating disk method (EBRD).
The titanium powder obtained by centrifugal atomization is spherical with smooth surface, relatively dense, good fluidity, narrow particle size distribution, and the particle size can be adjusted by rotating electrode speed. Compared with the powder prepared by gas atomization, the powder prepared by rotating electrode process does not have the common associated phase in atomized spherical titanium powder, and the powder particle size is more uniform. However, the titanium powder produced by this method has a high cost and is generally used in the field of aerospace.
Thermal reduction of metal
The traditional metal thermal reduction methods for preparing titanium powder mainly include TiO2 calcium thermal reduction method and TiCl4 metal thermal reduction method. TiO2 calcium thermal reduction method is to prepare titanium powder by reducing TiO2 with metal calcium at high temperature. TiCl4 metal reduction methods include magnesium reduction method (Kroll method) and sodium reduction method (Hunter method). The titanium powder prepared by magnesium reduction method is mainly the isoexternal titanium powder produced in the process of preparing sponge titanium. Due to the high content of impurities, it is rarely used in the production of titanium powder. The titanium powder prepared by sodium reduction method has high purity, especially low content of oxygen, nitrogen, iron and carbon impurities, and good fluidity. It is one of the promising methods for producing titanium powder.
Molten salt electrolysis method
Similar to other active metals the preparation of titanium powder by electrolysis must be carried out in molten salt medium. The traditional method of molten salt electrolysis is to dissolve titanium salt in molten salt. Dow-Howmet and Timet of the United States built two electrolytic production lines respectively, but they were terminated because they could not control the reverse reaction of titanium and chlorine. At present, Ginatta Company in Italy has built a large test plant in Torino city to continue the research of this process, and put forward the diaphragm free electrochlorination and fluorination.
Titanium has been widely used in the aerospace field because of its high strength, high heat resistance and high specific strength. Titanium alloy can reduce the overall weight of the aircraft while improving the aircraft's bulletproof capability, reduce the distance of the aircraft takeoff/landing runway, and increase the aircraft's maneuverability, maneuverability and mounting capacity.
With the increasing of China's national strength, its ability to safeguard maritime rights and interests is also increasing, and the number of carrier-based aircraft is also increasing, so the demand for seawater corrosion-resistant titanium materials will increase year by year.
Studies show that titanium alloy is still the preferred material under high temperature and pressure, high corrosive medium and high chlorine environment. Since the corrosion resistance of titanium and titanium alloy are mainly used in the petrochemical field and the heat resistance is not high, the types of titanium materials are relatively simple compared with the titanium materials used in the aerospace field. The main titanium materials are industrial pure titanium and TA10. The prices of these two titanium materials are relatively cheap, and their melting technology, processing technology and welding technology are relatively mature in China, so they can be widely used in the domestic petrochemical field.
Field of ocean engineering
Due to its excellent corrosion resistance to seawater and ocean atmosphere, minimal dissolved ions, non-toxicity and no pollution to the environment, titanium material can well meet the application requirements of Marine engineering. Marine engineering is expected to become a new civil market for titanium. In Marine engineering, titanium is mainly used in offshore oil and gas development, seaside construction, coastal power plants, seawater desalination plants, ships, Marine fisheries, ocean energy conversion and other fields. The application of titanium in the field of ocean engineering can not only reduce the quality of related equipment, but also reduce the maintenance cost and extend the service life of related equipment. For example, if titanium is used in a ship, its equipment life can be extended to 30 to 40 years, while aluminum alloy, mild steel and other ships need maintenance in 10 years. Moreover, titanium material also has excellent low temperature performance, can maintain a certain plasticity at -253℃, and the volume change in low temperature environment is small, very suitable for the Arctic icebreaker and other uses.
Because of its light weight, low elastic modulus, non-toxicity, non-magnetism and low biological reaction, titanium has been recognized as the most ideal metal material for human implants in the field of biomedicine. Titanium and titanium alloy materials are widely used in orthopaedic surgery, cardiovascular system, neurosurgery, oral surgery and human external culture machine. In addition, titanium material is also used in biopharmaceutical fields because of its non-toxic and good bactericidal effect of TiO2 surface. In terms of human implants, titanium is used to prepare femoral head, dental implants, hip joints, knee joints, prostheses, fastening screws, etc. It can also be seen that titanium is mainly used in orthopedics, and orthopedics implant biomaterials account for about 38% of the market share, making it the largest market for implant biomaterials. Orthopedic implant products mainly include spinal products, trauma products, artificial joint products and neurosurgical products.