What Is The Appropriate Annealing Process To Obtain Fine-Grained Tantalum Sheets?

Tantalum sheets have excellent properties such as high melting point, good processing performance, corrosion resistance, low vapor pressure, and small expansion coefficient, and have important applications in the fields of electronics, chemical industry, aerospace, and atomic energy industries. In particular, tantalum capacitors in the electronics industry have the advantages of small size, light weight, high reliability, wide operating temperature range, shock resistance and long service life.

The liquid electrolyte all-tantalum capacitor shell needs to be deep drawn with tantalum sheets. In the past, the quality of deep-drawn tantalum capacitor casings in my country has not been able to meet the requirements. Among them, the coarse grain of tantalum sheets is one of the main reasons. The control of grain size mainly depends on the processing and heat treatment process.

There are two ingot production methods in the production process of tantalum sheet, powder metallurgy and vacuum melting. Ingots produced by these two methods have different impurity contents. Ingots prepared by powder metallurgy have higher impurity contents, and ingots smelted by electron beam have less impurities. According to the law of the influence of impurity content on the recrystallization temperature of pure metal, the recrystallization temperature of the two is obviously different, so the recrystallization annealing process should also be different.

It is very important to obtain fine-grained tantalum sheets, and the appropriate annealing process should be:

1) The initial recrystallization temperature of pure tantalum prepared by powder metallurgy process is about 1150°C, and the correct annealing process is 1200°C

2) Pure tantalum smelted by electron beam, the final cold deformation is 90%, annealed at 850 °C for 60 min, or annealed at 900 °C for 10 min, it is possible to obtain a pure tantalum plate with an average grain size of less than 100 μm, pure tantalum produced by powder metallurgy method. Tantalum, final cold deformation of 90%, annealed at 1 200 °C for 60 min, and its average grain size is less than 30 μm.

3) Using pure tantalum sheet with grain size less than 100μm for deep drawing, the surface quality of deep drawing parts is good.