ARE VOLTAGE AND HEAT EFFICIENCY DURING PLASMA ARE MELTING OF TITANIUM

The plasma are melting (PAM) process has attracted keen attention in m elting titanium, because it has many advantages such as melting under the atmospheric pressure and refining by utilizing ultra-high temperat ure and plasma gas. In particular, in melting titanium alloy, the plas ma are melting process produces less evaporation loss of alloying elem ents, enables comparatively easy composition control, and provides' le ss restrictions in material form. It is very important to raise the me lting efficiency in plasma are melting from the commercial point of vi ew. So, basic investigation was carried out on are voltage and heat ef ficiency when titanium-based materials were melted with plasma are. Th e results are summarized as follows: (1) When argon, neon, and helium are used for plasma torch gas, the plasma are voltage becomes higher i n that order, and the same tendency is found in the fraction of heat t ransferred to the molten pool. By substituting helium for argon as tor ch gas, the melting rate can become double because of the increase of are voltage and heat efficiency to the melting material. (2) When tita nium sponge is melted, are voltage increases and greatly fluctuates by the vapor of chlorides contained. Alkali atoms are detected in the pl asma are column by spectrometry analysis. The temperature of plasma ar e column is estimated. (3) Plasma are voltage is shown as a linear equ ation of the are length. The value of the intercept of the line is gre ater when helium is used as torch gas than as atmosphere gas.