Combined Effects of Cooling Rate and Pre-Tempering on Microstructure and Properties of H13 Steel

The effect of quenching rate combined with pre-tempering treatments on the mechanical properties of H13 steel was systematically investigated in this study. Tensile testing, electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and X-ray diffraction analysis (XRD) were employed to study the structure–property relationships associated with different heat treatment conditions. The results showed that the specimen subjected to pre-tempering at 680 °C exhibited optimal strength performance, and fractographic analysis revealed that the specimen exhibited characteristic ductile fracture features. Further analysis revealed that increasing the quenching cooling rate effectively refined the grain size of the matrix, thereby significantly enhancing the strength of the sample. Tensile tests demonstrated optimal comprehensive mechanical performance with a yield strength of ~1050.4 MPa and elongation after fracture of ~17.1% for the oil-quenched specimen subjected to 680 °C pre-tempering treatment. The findings provide valuable experimental evidence and theoretical guidance for optimizing the heat treatment process of H13 steel and improving its failure resistance.