Effect of Tempering Temperature on Mechanical Properties of 45CrNiMoVA Steel

The microstructure of low‐alloy ultra‐high strength steel after heat treatment plays a decisive role in mechanical properties. This paper systematically investigates the influence of tempering temperature on the microstructure evolution and mechanical properties of 45CrNiMoVA steel. Through tempering at different temperatures (300–550 °C), combined with microstructure characterization, fracture analysis, and mechanical property testing, the correlation mechanism between tempering temperature and material strength, toughness, and fracture behavior are revealed. The results show that when tempered at 300–430 °C, the decomposition of retained austenite and the dispersed precipitation of carbides lead to an increase in hardness. At 460 °C tempering, the microstructure uniformity is the best, the proportion of lath martensite is the highest, the carbide distribution is uniform, and the comprehensive mechanical properties are the best (tensile strength 1470 MPa, impact energy 47 J). Tempering at 550 °C promotes the coarsening of carbides and the formation of tempered sorbite, resulting in a significant decrease in material strength. The secondary tempering process further optimizes the microstructure uniformity and significantly increases the elongation (about 25% increase). The influence of secondary tempering on 45CrNiMoVA steel was studied for the first time. The research results provide a basis for optimizing the heat treatment process of 45CrNiMoVA steel.