Method for producing platinum group alloy

Abstract

Provided is a method for producing a platinum group-based alloy capable of producing a sound molten ingot of a platinum group-based alloy in a large amount. The method for producing a platinum group-based alloy includes a molten ingot production step of a continuous casting system using a plasma arc melting furnace configured to form a plasma arc column between an electrode torch which is arranged in an upper part of a vacuum chamber and a water cooled copper crucible which is arranged in a lower part of the chamber and has a cavity having a sectional area S, the molten ingot production step including: inserting and melting an end part of a raw material bar including a platinum group-based alloy in the plasma arc column to cause the raw material bar to fall in drops on a base material in the water cooled copper crucible, to thereby form a molten pool; and solidifying a bottom part of the molten pool while maintaining a constant liquid level height of the molten pool by pulling down the base material, the molten ingot having a horizontal sectional area S (mm) and a length L (mm) satisfying the following relationship: S≧S>500, L>4√(S/π), an internal pressure of the chamber during melting being 0.8 atm or more, a pulling down speed of the base material being 10 mm/min or less.