Influence of Different Levels of Cu Equivalent on the Hot Ductility of 20CrMnTi Steel

Abstract

AbstractThe hot ductility of 20CrMnTi steel with different levels of Cu equivalent was investigated. The results show that Sn and Cu in 20CrMnTi steel are detrimental to its hot ductility. Sn was found to segregate to the boundaries tested by EPMA, moreover, Cu was not found to segregate to boundaries, however, the fracture morphology was examined with SEM and showed many small and shallow dimples on the fracture of steels with large Cu equivalent (>0.15) and fine copper sulfide was found from carbon extraction replicas using TEM. The adverse effect of large Cu equivalent (>0.15) on the hot ductility was due to Sn segregation and fine copper sulfide in the steel as well as their retarding the occurrence of dynamic recrystallization (DRX). The proeutectoid ferrite film precipitating along the austenite grain boundary causes the ductility trough of the five examined steels. Moreover, in this case, the level of Cu equivalent should be controlled below 0.15, which would not deteriorate the hot ductility significantly.