Tetsuya Watanabe

Experiment on Degassing Effect in a Laboratory-Scale Furnace

Experiment on Degassing Effect in a Laboratory-Scale Furnace. ( Study on the refining process of vacuum arc melting-I) Tetsuya WATANABE Synopsis: The purpose of this study was to evaluate the refining procedure during consumable arc remelting in a 2000-A laboratory-scale furnace. Electrodes used forremelting were airmelted and cast ingots of Fe-Cr alloys and commercial steels AISI-304. The resultes obtained were as follows: ( 1) The carbon in alloys acted as a powerful deoxidizer in molten pool by C-0 reaction under the reduced pressure. It was presumed that the flotation of inclusions contributed to the deoxidation. ( 2) The residual nitrogen content in a vacuum-arc-melted ingot was proportional to the initial nitrogen content in electrodes used. ( 3) The removal of high vapor pressure impurities such as Pb, Sn, Cu by vaporization in vacuum arc melting were not done so successfully as in vacuum-induction-melting process. ( 4) Arc melting in Ar and N2 atmospheres was also carried out with N-155 electrodes, that contained 0.20% nitrogen as an alloying elements, could be remelted successfully without any trouble in a 1/4 to 1 atm Ar-gas chamber. On the other hand, inarc melting of AISI-304 in N2 gas atmosphere, an extremely high-arc voltage was observed and there was a remarkable nitrogen absorption up to 025%. ( 5) Melting current extremely influenced the macrostructure. Highercurrent was apt to cause a coarse dendritic structure. Lower current, however, caused a worse ingot surface.