Because of the active reaction between tantalum and oxygen, tantalum workpieces must avoid heat treatment in an atmosphere even in the presence of a little air. Therefore, almost all annealing is carried out in a high vacuum, and the air tightness of the heating furnace must be very high. Generally, the heat treatment temperature of tantalum is generally 950 ~ 1300 ℃, and there is no phase transformation between tantalum and commonly used tantalum alloy in this temperature range. The heat treatment is only used for annealing, so the heating temperature and cooling rate are not important. In order to produce complete recrystallization, it is better to heat treat a little longer. Tantalum has high purity. The grains become very large by annealing. The size of crystal particles is determined by cold working, purity, temperature and process steps. Therefore, temperature control and process control are important means to determine the crystal size. Tantalum, unlike many other metals, must be very clean before heat treatment. If it is not cleaned very clean, surface contamination caused by hydrogen, oxygen, nitrogen and carbon will occur and become brittle (hardened) tissue. Because hydrogen, oxygen, nitrogen and carbon are very active intrusive elements within the temperature range of tantalum annealing, once contaminated by these elements, they can be removed by other means except remelting