LAUSR

The effect of the tempering temperature on mechanical properties are studied by investigating the precipitate evolution during the heat treatment of the 34CrNiMo6 steel. Five different tempering temperatures are used at the same holding time of 3 h. Then the mechanical properties of the 34CrNiMo6 steel are studied under steady-state conditions and impact conditions. The strength decreases while the elongation after breakage increases with the increasing tempering temperature. The impact-absorbing energy at 20 °C and –40 °C increases with the increasing tempering temperature. Based on the experimental results, the recommended tempering temperature is 660 °C. The differences in mechanical properties related to different tempering temperatures may be caused by the nucleation rate and growth of precipitates under different conditions. The spherification degree of cementite is more complete with the recommended tempering temperature, resulting in a decrease in mechanical properties and improvement of ductility.