The process by which a tantalum blank is smelted in a vacuum arc furnace to form a dense metal ingot with good ductility or a special-shaped member with a special structure. This is a mature industrial method for refining tantalum, which has two functions: forming and purifying.
The principle of self - consumption electrode method and non - self - consumption electrode method. The self-consumption electrode method is the main method used in industry. Its cathode blank is made of tantalum bar by vacuum sintering method. The tantalum bar melts gradually under the action of high temperature of electric arc, and then drops into the water-cooled copper crucible for solidification and crystallization. The cathode of the non-consumptive electrode method is generally tungsten, thorium or graphite. The cathode only plays the role of maintaining the arc and does not consume itself. The tantalum blank is melted in the high temperature molten pool heated by the arc and then cooled and crystallized. The non-consumable electrode method is only used for small tantalum blank in smelting laboratory. In the process of melting, tantalum blank is purified by vacuum pump due to the escape of gas and volatile impurities, or the decomposition of unstable compounds, whether by self-consumption electrode or non-self-consumption electrode method.
The self - consumption electrode method can also be used in inert atmosphere with the help of the pressure of inert gas to cast various alloy ingot materials with easy evaporation components. The molten pool can be mixed by external magnetic field to make tantalum and tantalum alloy components uniform. Smelting tantalum blank metal is not contaminated, and can be made into a variety of shapes of castings, especially suitable for large tantalum ingots and net shaped blank such as tube blank, shaped parts. At present, the vacuum arc melting method of consumable electrode is mainly used to make large round ingots, flat ingots or special-shaped castings.
The basic structure of the consumable electrode vacuum arc melting furnace is shown in the figure, which is mainly composed of the furnace shell, electrode column, water-cooled copper crucible attached to the bottom of the furnace shell, electrode with support and transmission lifting device and vacuum system. The melting furnace is made of steel, stainless steel and water-cooled copper crucible. The electrode lifting device of the consumable electrode vacuum arc melting furnace is manual or automatic control.
