Characteristics of MgAl₂O₄-TiN Complex Inclusion Precipitation and Growth during Solidification of GCr15SiMn in ESR Process

Abstract

MgAl₂O₄-TiN complex inclusion found in GCr15SiMn ESR ingot with MgAl₂O₄ as the core and TiN as the periphery is of great harm to steel. The characteristics of this complex inclusion precipitation and growth during solidification of metal molten pool have been theoretically investigated with the help of thermodynamics and kinetics. The results demonstrate that during solidification of metal molten pool, TiN will precipitate on the existed core MgAl₂O₄ due to the microsegregation of solutes Ti and N. The effect of high cooling rate on the size of complex inclusion with the core MgAl₂O₄ from the consumable electrode is not significant, particularly for larger size of the core, while with the core MgAl₂O₄ formed during solidification, its size is greatly affected by the cooling rate, which will possibly provide a useful method of distinguishing the source of the core MgAl₂O₄ under high cooling rate. At the same cooling rate, the growing extent of periphery TiN decreases with the increasing size of the core MgAl₂O₄. Meanwhile, decreasing C content in steel within the upper and lower limit will decrease the percentage of this complex inclusion.