Effect of Quenching Temperature on the Microstructure and Mechanical Properties of 37CrMnMo Steel

In this study, the influence of quenching temperature on the microstructure and mechanical properties of 37CrMnMo medium‐carbon steel, which consists of tempered martensite, bainite, and carbides, was investigated using a simplified heat treatment process designed for industrial feasibility. Increasing the quenching temperature from 850 to 910 °C enlarged the prior austenite grain size, reducing the resistance to martensitic transformation and raising the martensite volume fraction from 41.3% to 51.1%, while also refining carbides from elongated to short rod‐shaped and decreasing their length from 982 to 173 nm. These changes, together with higher dislocation density, drove the yield strength to a peak of 840 MPa at 880 °C, and 831 MPa at 910 °C because of martensite lath coarsening from 194 to 222 nm at 910 °C. The higher quenching temperature also increased the high‐angle grain boundary density and refined carbides, suppressing crack initiation and propagation, thereby raising the impact energy at −20 °C from 55 to 117 J. Through this simplified heat treatment process, a favorable balance of strength and toughness was achieved via synergistic control of phase fraction, carbide morphology, dislocation density, and grain boundary characteristics.