Reaction mechanism between MgO crucible and AerMet100 steel during vacuum induction melting

Abstract

AerMet100 steel has strict composition and inclusion requirements. Therefore, its reaction with MgO refractory during vacuum induction melting cannot be ignored. In this study, the reaction mechanism between the MgO refractory and AerMet100 steel during the refining stage was investigated using a MgO crucible. The influence of the MgO crucible on AerMet100 steel composition and inclusions under refining vacuum pressures of 50–100 and 5–10 Pa was compared. The results indicate that SiO2, Al2O3, and MgO in the crucible decompose and are reduced by C in the liquid steel, which results in the increase of Si, dissolved Al (Als), and dissolved Mg (Mgs) content in the liquid steel. The increase of Ca content is due to the reduction of CaO in the crucible by C in the liquid steel. The reaction of Al2O3 inclusions and Mgs in the liquid steel is the primary generation method of MgO·Al2O3 spinel inclusions. As the Mgs content in the liquid steel increases, Al2O3 inclusions transform into MgO·Al2O3 spinel inclusions along the path Al2O3 + Mgs → Al2O3 with a small amount of MgO + Mgs → MgO·Al2O3 spinel. In contrast, the vacuum pressure of 50–100 Pa is more effective at controlling the composition and inclusions of AerMet100 steel and is a more appropriate choice for the refining vacuum pressure.