Effect of Austenitization Temperature Under Rapid Heating on Microstructure and Mechanical Properties of 55SiCr Steel

This study investigates the effects of austenitizing temperature on the microstructure and mechanical properties of 55SiCr steel under rapid heating conditions using electromagnetic induction heat treatment. The results indicate that the microstructure of 55SiCr steel tempered at 400 °C primarily consists of tempered martensite. When the austenitizing temperature rises from 850 to 950 °C, leading to partial dissolution of undissolved carbides and weakened grain boundary pinning. Consequently, the prior austenite grain size coarsens from 28.5 to 37.3 μm, consistent with grain growth kinetics, while the martensite lath width increases with grain coarsening. High‐temperature austenitization promotes the transformation of retained austenite morphology from blocky to film‐like, significantly enhancing its stability. The Q900 steel, with moderate RA stability, triggers the TRIP effect during deformation, achieving a reduction of area of 46% and elongation of 10.2%. Through strength–ductility balance analysis and theoretical calculations, the optimal austenitizing heating rate is determined to be 22.50 °C·s −1 , corresponding to an austenitizing temperature of 900 °C. Under this condition, the Q900 steel exhibits a tensile strength of 2070 MPa, with the improved strength of 55SiCr steel attributed to the synergistic effects of grain refinement, dislocation strengthening, and precipitation strengthening.