Heat Balance of Prototype Plasma Furnace for Melting Reactive Metals

Abstract

In this paper the construction and heat balance of prototype stand for plasma melting of reactive alloys are described. The operating parameters of prototype stand during making the testing melts of titanium alloys are presented. Such parameters like arc current, mean arc voltage in plasma arc, discharge of water for plasmatron/cold crucible/working chamber cooling systems and output and input temperature of water were investigated as well. During testing melts several thermocouples were fixed in characteristic point of furnace to determine temperature distribution inside and outside the melting chamber. Automatic computer measuring stand was used for recording the changes of temperature as a function of time. The heat balance described in this paper was obtained during melting titanium alloy grade Ti-6Al-4V at decreasing pressure (10 – 13 kPa) in melting chamber with use of helium as a plasma working gas. The melting process was divided into two stages : stage I – six minutes with using second tap of transformer and stage II – three minutes with using third tap of transformer. Temperature distributions in furnace during testing melt are presented in this paper as well. Heat balance presented in this paper has shown that the thermal efficiency in stage I was 49.8 % and in stage II was 63.9 %. Thermal efficiency of the prototype plasma furnace is on the same level as in any other plasma furnaces described in technical literature.