At present, there are two ways to prepare tantalum and tantalum alloy bars. One is to make tantalum or tantalum alloy bars by electron beam melting and forging, extruding, peeling and pickling. One is to make tantalum or tantalum alloy ingots by powder metallurgy and vacuum vertical melting sintering.
The specific process of electron beam melting tantalum and tantalum alloy processing bar is as follows: the tantalum powder is put into the cladding, formed into melting blank by cold isostatic pressing at 250Mpa, and then melted into tantalum ingots with diameters of 200-600mm in electron beam furnace. After turning and skilling, tantalum rods with diameters of 55mm are forged in a 20-ton forging machine. After peeling, pickling and heat treatment, tantalum and tantalum alloy rods with diameters of 25_ are extruded.
Powder metallurgy method, case of tantalum and tantalum alloy processing rod for the specific process: the tantalum powder into 32 ~ 38 mm diameter in the bag, after 250 mpa of cold isostatic pressing molding into melting billet, after drying in vacuum sintered sintering furnace for sintering, the sintering of tantalum rod is about 25 mm in diameter, then the tantalum rod after sintering at the ends of the chuck to resection, Tantalum and tantalum alloy rods are obtained when the shear amount is about 6%~8%.
In the existing technology, the volume shrinkage of tantalum and tantalum alloy billet can reach 32% in the vertical melting sintering process. Due to the large shrinkage of tantalum rod, it is easy to fall off from the fixture, leading to the failure of sintering process. The pre-sintering process of the invention has reduced the shrinkage of tantalum and tantalum alloy billet to about 18%, so the shrinkage is significantly reduced in vertical melting sintering, so the probability of strip dropping is also greatly reduced. The pre-sintering stage is through induction sintering, the gas and low melting point impurities in the powder are removed, and the metal powder particles are bonded between the particles, so that the metal conductivity reaches more than 70% of its pure metal conductivity, which can ensure that the time of low temperature stage is greatly shortened and the sintering efficiency is improved in vertical melting vacuum sintering. For example, the vacuum vertical melting sintering process of the prior art requires a total of 7 hours /6kg, the vacuum sintering process of the present invention is 10 hours /300kg, and the vacuum vertical melting sintering process is 4 hours /6kg, which saves about 2.5 hours compared with the prior art, and the sintering efficiency is significantly improved and the cost is significantly lower.
