Titanium and titanium alloys have the advantages of low density, high specific strength, strong corrosion resistance, good creep resistance under high temperature, excellent welding performance, excellent biocompatibility and so on. They are widely used in aerospace, navigation, metallurgy, petroleum, chemical industry, power generation, automobile, medicine, electronics, sports and leisure fields. However, due to the difficulty of extracting, smelting and processing titanium, the production cost is very high. The production cost of titanium ingots is about 30 times that of steel ingots of the same quality and 6 times that of aluminum ingots, while the production cost of titanium alloy parts for aerospace is even greater because of the high processing cost.
Powder metallurgy technology is a process of directly forming powder and producing parts. Technically, parts with non segregation, stable and excellent performance and uniform structure can be obtained by this method; Economically, this method is a process with little or no chips, and the material utilization rate can reach almost 100%, saving processing costs and improving productivity
Pure titanium powder
At present, the manufacturing methods of pure titanium powder for injection molding include hydrogenation and dehydrogenation and gas atomization. Hydrogenation dehydrogenation powder is characterized by irregular fine powder, large specific surface area and high oxygen content. The shape of gas atomized powder is spherical. Compared with irregular hydrogenated dehydrogenation powder, it has good fluidity and filling, small surface area, less pollution in the preparation process, and low oxygen content. If a certain amount of hydrogenated dehydrogenation powder is added, the formability can be further improved. It is the main raw material powder for titanium injection molding.
Titanium alloy powder
The preparation methods of titanium alloy powder for injection molding mainly include: element powder mixing method and pre alloying method. The element powder mixing method is to mix the element powder according to the composition ratio of the alloy to produce the alloy powder. In order to improve the formability of the alloy powder, a certain proportion of gas atomized powder can be mixed into pure titanium powder for hydrogenation and dehydrogenation. The price of alloy powder prepared by this method is relatively low. Among the preparation methods of pre alloyed powder, gas atomization method is a cheap method that can be mass produced. Compared with pre alloyed powder, alloy powder produced by element powder mixing method is cheap, easy to form, and the process is mature. Therefore, it has a broader market prospect.
Selection of binder
Choosing the appropriate binder is the key link of injection molding. It directly affects the mixing, injection molding, degreasing and other processes, and has a great impact on the quality, degreasing and dimensional accuracy of injection molded blanks.
Binders for titanium and titanium alloy powder injection molding can be dissolved in water or organic solvents. Some binders also add catalysts to accelerate the decomposition of binders. The amount of binder has a great influence on the forming quality. Insufficient binder leads to difficult forming; Excessive binder will reduce the viscosity of the feed. The binder generally accounts for 40% - 50% of the total feed (mass fraction), and is finally removed by pyrolysis.
