Effect of Homogenisation Temperature on the Microstructure and Microhardness of As-Cast H13 Steel.

This study determined that the homogenisation temperature range of experimental as-cast H13 steel was from 1150 to 1230 °C, whilst the effect of homogenisation temperature range on the microstructural evolution and microhardness was tested. The enrichment of alloying elements in the dendrite segregation region decreased the solidus temperature of matrix, whose total content determined the maximum homogenisation temperature. The secondary dendrite branches were most dissolved at 1150 °C, and overheating appeared at 1230 °C in the segregation region. Moreover, the primary carbides underwent shrinking, passivation, fragmentation and dissolution. The secondary carbides M₂₃C₆ and M₆C were formed at the interfaces of MC/γ and M₇C₃/γ, respectively. As the homogenisation temperature increased from 1150 to 1230 °C, the value of microhardness gradually decreased from 771 to 740 HV. Nevertheless, the standard deviation value decreased first and then increased, which reached the minimum 32 HV at 1200 °C, indicating that the hardness homogeneity was the best. [ABSTRACT FROM AUTHOR]