Study on the Influence of Different Tempering Processes on Microstructure and Properties of 40Cr Steel

In this paper, the heat treatment of 40Cr steel is carried out to explore the difference of performance of 40Cr steel under different temperatures and different heat treatment conditions, and the optimal scheme is obtained. The results show that the workpiece is subjected to 850 °C normalizing plus 240°C low temperature tempering and 860°Cnormalizing plus 440°C medium temperature tempering and 860°Cnormalizing plus 520°Chigh temperature tempering. It is found that in the process of temperature increase, the infiltration A large amount of alloying elements such as carbon and chromium contained in the carbon body are incorporated into the austenite. Under the premise of ensuring the normalizing temperature is constant, as the tempering temperature increases, the hardness of the sample decreases, the toughness increases, and the microstructure of the metallographic microstructure is coarse. The samples were compared with 860°C oil quenching + 240°C low temperature tempering and 860°C normalizing + 240Clow temperature tempering samples. It was found that although the low temperature tempering after oil quenching had the highest strength, the plasticity index decreased significantly, the impact toughness value was the lowest, and the comprehensive performance was poor.