In the field of powder metallurgy preparation, the invention relates in particular to a manufacturing method of pure rhenium sheet which is difficult to deform. The method consists of using pre-treated high-purity ammonium rhenate, carefully selected two-stage reduction, forming and sintering high-purity rhenium powder, using an open press die, to ensure that the thin rhenium sheet billet with ratio up to 16 can be pressed. By high temperature sintering, the density can reach more than 95% of the theoretical density. Under the condition of strict control of pass deformation, the rhenium sheets with theoretical density greater than 99%, thickness up to 0.4mm and size up to 320×320mm are rolled by cold rolling and intermediate annealing. Compared with the prior art, the invention has the advantages of eliminating work hardening and producing finished rhenium products of different sizes according to demand.
Metal rhenium with high wear resistance, corrosion resistance, high conductivity, and can maintain high under the condition of high temperature and temperature shock strength and good creep resistance and good thermal performance, often used for emission cathode filament in electronic engineering, kinescope filament, special lamp filament, X - ray target material, high temperature sensor, atomic energy, and many other aspects. In particular, rhenium plays an irreplaceable role in semiconductor chip production.
However, because of the metal rhenium work hardening speed is very fast, resulting in its processing, especially deep processing ten minutes difficult. The thermal processing of rhenium using the usual refractory metal is not suitable for rhenium because the oxide is distributed along the grain boundary and forms a brittle phase, which makes thermal processing impossible. So far, the hot processing of rhenium is still in the research stage, and the use of cold processing technology has not been systematically reported.
Because of the work hardening speed of pure rhenium powder is very fast, it is not easy to be pressed into shape, and because of the wave son ratio (length width/height) of the blank is very large (greater than 16), the blank is easy to be broken due to the aftereffect of elasticity during demolding. Therefore, the invention uses adding an appropriate amount of lubricant (such as paraffin) into the powder, which can reduce the friction between the powder and the pressing die and improve the strength of the blank to achieve the purpose of forming.
Therefore, the invention adopts cold rolling process at room temperature, and strictly controls the amount of pass deformation (8 ~ 15%). Due to work hardening of rhenium speed very fast, even for a time after deformation Hardness multiply rapidly, so the calculation every time after deformation for high temperature annealing treatment in hydrogen degrees 1500 ~ 1800 ° C, the annealing time is 30 ~ 120 min), make its eliminate the phenomenon of strain hardening and controlled crystallization even close, then rolling for next time. This cycle of processing, heat treatment until to reach the required size, and finally after annealing treatment, get the finished rhenium sheet.
