Phase Equilibrium between CaO·Al₂O₃ Saturated Molten CaO–Al₂O₃–MnO and (Ca, Mn)S Solid Solution

Abstract

Refinement of austenite grains by generating intra granular ferrite (IGF) in austenite grains is one of the most effective methods for improving the toughness of the heat-affected zone (HAZ). It is known that MnS precipitated on fine oxides enhance formation of IGF in austenite grains. Flux composed of CaO–Al₂O₃ is often used in secondary refining and Ca–Mn–Al complex oxide may form, and it is important to clarify the mechanism of MnS precipitation on oxide inclusions. Therefore, molten CaO–MnO–Al₂O₃ oxide was equilibrated with (Ca, Mn)S solid solution in Al₂O₃ crucible in an electric resistance furnace at 1648, 1698 and 1748 K in the present work. Phase relation between CaO·Al₂O₃ saturated molten CaO–MnO–Al₂O₃ oxide and (Ca, Mn)S solid solution was clarified.