Study of New On‐Line Pre‐Hardening Technology of 3Cr2NiMo Plastic Die Steel

The thermal property parameters of 3Cr2NiMo plastic die steel were tested and the two‐dimensional finite element model was established in the paper. The temperature fields of 3Cr2NiMo plastic die steel plate with the thickness of 130 mm were calculated and analyzed under three quenching processes. The results showed that for all of the three processes the cooling rates could avoid the pearlite transformation zone when the temperature of the steel plate was more than 500°C. When the temperature was less than 500°C, the cooling rate of the third process was slower, and the temperature difference was effectively alleviated, which avoided large transformation stress appearance. For 3Cr2NiMo plastic die steel with the thickness of 130 mm, the third process was the best process. In the paper, the hardness and the microstructures were tested after the third process and tempering. After tempering process, the structures were all tempered sorbite, and the tempering hardness difference in the whole steel plate was less than 3HRC, and there were no cracks. The study provided references for on‐line pre‐hardening process formulation and optimization of large plastic die steel.