Tantalum processing

Blanking

Tantalum cannot be processed by the ordinary method of processing general metals. Generally, the initial process is a forging process heat treatment.

A slab blank or a circular medium-sized blank is produced by hammering and punching. Unlike ordinary metals, tantalum cannot be hot processed. The recrystallization temperature of rhodium exceeds 1000 ° C. If heated, excessive oxidation occurs even if a general protective layer is applied. What is more serious is that if exposed to such high temperatures, not only excessive oxidation occurs on the surface of the crucible, but oxygen can also invade between the atoms inside the matrix, making the crucible brittle. Not only oxygen, but even nitrogen, carbon and hydrogen can make cockroaches brittle. For the above reasons, the enamel is generally not subjected to hot working. When it is necessary to carry out thermal processing, a protective covering layer is to be carried out or in an inert gas atmosphere.

Heat treatment

Since the reaction of  tantalum and oxygen is active, it is necessary to avoid the atmosphere in the presence of even a little air.

Heat treatment. Therefore, almost all of the annealing is carried out in a high vacuum, and the airtightness of the heating furnace must also be high. Generally, the heat treatment temperature of ruthenium is generally between 950 and 1300 ° C. The ruthenium alloy generally does not undergo a phase change in this temperature range, and the heat treatment is only used for annealing, so the heating temperature and the cooling rate are not important. In order to produce complete recrystallization, the heat treatment time is slightly longer.

Commercially produced crucibles are of high purity. The grain size becomes very large by annealing. The size of the 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.

Unlike many other metals,  tantalum must be very clean before heat treatment. If it is not cleaned very cleanly, surface contamination caused by hydrogen, oxygen, nitrogen and carbon will occur, becoming an embrittled (hardened) structure. Because hydrogen, oxygen, nitrogen, and carbon are very active intrusive elements in the temperature range of helium annealing, once they are contaminated by these elements, they are removed except for remelting.