Control of Carbide Precipitation During Electroslag Remelting-Continuous Rapid Solidification of GCr15 Steel

Abstract

The effect of the electroslag remelting-continuous rapid solidification (ESR-CRS) process on element segregation and carbide precipitation in GCr15 bearing steel was investigated. The results showed that a microstructure with fewer primary carbides and less segregation can be achieved via the ESR-CRS process. In the specimen subjected to ESR, the morphology of primary carbide changed from angular to lumplike. After the ESR-CRS process, the dimension of primary carbide and the mass fraction of Cr in primary carbide decreased. With the increase of cooling intensity during the ESR-CRS process, the microstructure of ESR ingot became more refined and uniform and the size of large primary carbides in ESR ingot gradually decreased. Suppressing the formation of grain boundary cementite and primary carbide during ESR of GCr15 steel is beneficial to inhibiting the presence of large secondary carbide formation after annealing. With the increase of cooling intensity, the mass fraction of carbides in ESR ingot decreased and the mass fraction of Cr in carbides increased, whereas the types of carbides did not change; all the M3C, M3C2, and M7C3 exist before and after ESR-CRS. Al2O3 inclusions promoted the formation of Ti(N,C) by serving as preferred heterogeneous nucleation sites, whereas the formation of Ti(N,C) was suppressed through the refinement of Al2O3 inclusions by increasing the cooling intensity.