Analysis of Mechanical Properties SCR420 Low Alloy Steel According to Heat Treatment Before Cold Forging

This study developed a new heat treatment method, normalizing & stress relief (N.S.R), to increase productivity compared to spheroidizing annealing (S.A). The influence of different microstructures resulting from these heat treatments was investigated in cold-forged steel. Despite a shorter heat treatment time, the mechanical properties of the N.S.R alloy were found to be similar to those of the S.A alloy. The factors influencing the mechanical properties of the experimental alloys were analyzed using the Hall-Petch equation, and the predicted values closely matched the measured strength of hy-per-eutectoid steels. The primary factors affecting mechanical properties were micro-structure and dislocation density. In the case of the S.A alloy, the microstructure exhibited lower strength due to the spherical cementite structure. In contrast, the N.S.R alloy had lower strength because of a reduced dislocation density. This was achieved by stress-relief heat treatment below the A1 temperature after phase transformation. Based on the mechanical properties, cold forging simulations showed that the effective stress during cold forging of the N.S.R alloy was similar to that of the S.A alloy.