Plasma arc melting of alloy containing active refractory metal by long ingot manufacturing method

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PROBLEM TO BE SOLVED : To prevent, without fail, the occurrence of component segregation and the occurrence of shrinkage cavity and void defects in the central part when manufacturing, by plasma arc melting, a long-size ingot of an alloy which contains, as alloy components, active refractory metal elements such as Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Y or rare earths. ŽSOLUTION : The method for manufacturing the long-size ingot of the alloy containing active refractory metals by plasma arc melting is characterized in that, in the method for applying plasma arc melting to the alloy containing active refractory metals under an argon atmosphere, a previously prepared raw-material rod of prescribed alloy composition is melted by plasma arc under the state where an argon-helium atmosphere of 30 to 200 Torr is maintained, and, while holding the resultant molten metal pool in a water-cooled copper crucible and cooling and solidifying it, a movable bottom plate of the copper crucible is drawn downward at a rate of 2 to 59 mm/min. ŽCOPYRIGHT : (C)2007, JPO&INPIT Ž