Thorium taken during a dense metal powder made from a metal thorium method of powder metallurgy. Including the two operations of powder forming and sintering. The product metal block has a purity of 99.7% and a Brinell hardness of 65, which can be processed into an electrode and used as a raw material for melting and casting.
The compressibility of the tantalum powder depends on the preparation method and its purity. The tantalum powder obtained by the metal thermal reduction method has a compressibility lower than that obtained by the molten salt electrolysis method (see metal tantalum production) because the former contains More oxygen and impurities such as ThO 2 . Oxygen in the billet deteriorates the compressibility, strength, and mechanical properties of the sintered part. Most of ThO 2 is concentrated in the oxide film, and the greater the thickness of the oxide film, the worse the compressibility of the powder. The particle size, shape, structure and volume characteristics of tantalum powder are also important factors influencing the plasticity of the powder.
Most of the tantalum powder or swarf is formed in a steel stamper. The stamper is mainly composed of a female mold, a press head and a base. Mostly formed by hydraulic hydraulic press. The forming method can be divided into a cold pressing method and a hot pressing method. The hot pressing method should select the appropriate molding material and carry out under protective gas. The cold pressure and the like of the tantalum powder are related to the density of the formed compact. When the isostatic pressure is 120 MPa, 228 to 304 MPa, and 608 to 684 MPa, the compact density is 7700, 9500, and 11000 kg/m 3 , respectively .
Pressing the blank in a heater made of copper with a vacuum sintering furnace l ~ 2h. The sintering temperature of the cold-pressed compact having a density of 10,000 to 11,000 kg/m 3 is 1373 to 1473 K, and the sintering temperature of the cold-pressed compact having a density of 1000 kg/m 3 or less is 1573 to 1623 K. The density of the sintered compact is slightly higher than the density of the compact, and the machinability is also improved.
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