Effect of cooling rate and austenitizing temperature on the spheroidizing annealing of 40Cr steel

To study the impact of austenitizing temperature and cooling rate on the spheroidizing annealing process of 40Cr steel, the spheroidizing annealing behavior and the mechanical properties of 40Cr steel were investigated by conventional intercritical annea-ling. It is found that with the austenitizing temperature between 760℃ and 800℃, the hardness varies as a "V" shape but the ce-mentite spheroidization rate changes as an inverted "V" shape with increasing cooling rate from 10℃·h^-1 to 30℃·h^-1. Higher sphe-roidization level and finer carbides, which are obtained at an austenitizing temperature of 760℃ and a cooling rate of 20℃·h^-1, make the steel having a better cold formability. A divorced eutectoid transformation (DET) reaction mechanism of the spheroidizing annea-ling process was proposed, and the occurrence of the divorced eutectoid transformation reaction depends strongly on austenitizing tem-perature, cooling rate and holding time.