Directly spheroidizing during hot deformation in GCr15 steels

Abstract

The spheroidizing heat treatment is normally required prior to the cold forming in GCr15 steel in order to improve its machinability. In the conventional spheroidizing process, very long annealing time, generally more than 10 h, is needed to assure proper spheroidizing. It results in low productivity, high cost, and especially high energy consumption. Therefore, the possibility of directly spheroidizing during hot deformation in GCr15 steel is preliminarily explored. The effect of hot deformation parameters on the final microstructure and hardness is investigated systematically in order to develop a directly spheroidizing technology. Experimental results illustrate that low deformation temperature and slow cooling rate is the favorite in directly softening and/or spheroidizing during hot deformation, which allows the properties of as-rolled GCr15 to be applicable for post-machining without requirement of prior annealing.

Keywords

directly softening or/and spheroidizing, hot deformation, ferrite transformation, divorce eutectoid transformation (DET)