Method for preparing titanium powder
2018-11-09
The preparation method of titanium powder can be divided into two categories: mechanical method and physical chemical method. The mechanical method can be further divided into a mechanical grinding method, a gas atomizing method, and a rotating electrode method. The physical chemical method can be further divided into a reducing method and a molten salt electrolysis method. The preparation of pure titanium powder was firstly obtained by mechanically pulverizing titanium sponge. However, it is difficult to obtain a fine-grained powder by this method. Later, the method was developed. The method can produce a fine-grained titanium powder and the cost is low, but the oxygen content of the titanium powder is difficult to control.
Mechanical pulverization
The mechanical pulverization method mainly mechanically pulverizes the bulk metal into a powder by the action of crushing, crushing and grinding. Can be divided into two types of coarse and fine.
The titanium sponge obtained by the sodium reduction method is ground by a ball mill to obtain an irregular titanium powder having a chlorine content and an oxygen content of about 200 g. The titanium sponge obtained by the reduction of magnesium is mostly a large titanium crucible. It can only be coarsely crushed. It is difficult to directly grind the titanium powder by mechanical pulverization.
Hydrodehydrogenation
Since the sponge titanium with higher purity is softer and has higher toughness at normal temperature and pressure, it is more difficult to directly pulverize it to obtain finer titanium powder, and titanium will be brittle and easily broken after hydrogen absorption. Therefore, the United States, Japan, Germany, the Netherlands and other countries have developed a process for hydrogenation dehydrogenation to obtain pure titanium fine powder by utilizing the characteristics that titanium can rapidly absorb hydrogen and become brittle at a certain temperature.
During the process of preparing titanium, the hydrogenation process of titanium sponge is an exothermic reaction. When the temperature rises to about °C, the reaction is stopped when the most severe product weight gain reaches about time. The titanium sponge after hydrogen absorption becomes highly brittle titanium hydride. After cooling, it is easily broken at normal temperature. However, since the powdered titanium hydride is highly active in order to prevent contamination and ensure safe production, the crushing is carried out in a sealed apparatus under inert gas protection. Then, the hydride is heated under high vacuum to remove hydrogen to obtain titanium powder. The dehydrogenation process is an endothermic reaction. Generally, the titanium hydride is heated to above °C. Fine titanium hydride powder is easy to agglomerate during high temperature dehydrogenation. It is necessary to select an appropriate temperature according to the particle size of the dehydrogenation feedstock.
Atomization method
The atomization method is a method in which a liquid metal is directly crushed to obtain a metal powder by a certain means. There are mainly gas atomization methods and centrifugal atomization methods.
Gas atomization
The gas atomization method is to break the metal liquid flow by means of a high-speed air flow, and it is only necessary to overcome the bonding force between the liquid metal atoms to disperse it. The mechanical pulverization is a mechanical action to break the bond between the solid metal atoms. Therefore, the external force required for atomization and milling is much smaller than that of mechanical pulverization. From the point of view of energy consumption, the atomization method is an energy-saving and economical powder production method. Titanium powder production requires atomization with inert gas to prevent oxidation and contamination.