Novel Method to Improve the Microstructure and Mechanical Properties of 45 Steel

Aiming at the problems of poor hardenability and low mechanical strength of 45 steel after quenching and tempering at normal pressure, 45 steel was quenched and tempered under high pressure. The microstructure of 45 steel after high pressure quenching and tempering was analyzed by optical microscope, scanning electron microscope and transmission electron microscope, its hardness and compressive strength were tested by hardness tester and electronic universal testing machine, and compared with samples treated by the same process under atmospheric pressure. The results show that uniform and compact tempered sorbite can be obtained after high pressure quenching and tempering of 45 steel, and the precipitated granular carbides are finely dispersed, thus improving the mechanical properties of 45 steel. Under a pressure of 3 GPa, quenching at 900 °C for 15 min and 550 °C for 60 min tempering, the hardness and compressive yield strength of 45 steel were 36.3 HRC and 971 MPa, respectively, which were respectively 25.17% and 20.77% higher than the corresponding values obtained with the same process under atmospheric pressure quenching and tempering. This work provides a new method to effectively improve the mechanical properties of 45 steel.