DISTRIBUTION OF SURFACE-TEMPERATURE OF MO LTEN TITANIUM BY THERMAL PLASMA

Surface temperature of molten titanium by thermal plasma was measured by a radiation thermometer. Direct current arc plasma was generated in a transferred type plasma system, in which a tungsten rod was used as a cathode and water-cooled copper plate as an anode. Titanium in colu mn of about 3 grams in weight was melted by argon and argon -3 approxi mately 5% hydrogen plasma with the electric power of about 400 watts. The surface temperature was measured by a radiation thermometer and it was corrected by emissivity of molten titanium. The emissivity was de termined using temperatures measured by a radiation thermometer and a thermocouple. The emissivities of molten titanium were 0.33 and 0.25 i n argon plasma and argon-hydrogen plasma, respectively. The surface te mperature was the highest at the top of molten titanium and went downw ard steeply far from the top. The highest temperatures were approximat ely 2800K and 3000K in argon plasma and argon-hydrogen plasma, respect ively. High temperature area above 2200K was limited to the area where plasma flame was directly irradiated. The temperature in the other ar ea was approximately 1940K, around the melting point.