Effect of Deep Cryogenic Time on the Microstructure and Mechanical Property of Cr-Mn-Si High-Strength Alloy Steel

Cr-Mn-Si alloyed high-strength steel was subjected to deep cryogenic treatment after quenching and tempering (Q-T), the microstructure property evolution of alloy were studied. The tensile strength increased by about 30 MPa, yield decreased 10 grains refined, indicating that toughness can be relatively improved via (−120 °C × 1 h); secondary carbides precipitated inside martensitic matrix uniformly distributed; average size also significantly reduced, presenting a more uniform than Q-T samples. Furthermore, dislocation density evolved during treatment, with highest 2 h thus providing dislocation-strengthening effect. Therefore, overall properties could comprehensively Q-T.