Austenite Continuous Cooling Transformation Curve of 27CrMo27S Steel

By dilatometric change referencing microscopic test and hardness measurement,the critical point at Ac1,Ac3 and Ms of 27CrMo27S steel was determined in Gleeble-3800 thermal mechanical simulator.By measuring the different expanding curves of CCT in different cooling rate,CCT diagram was obtained.The influence of cooling rate on steel microstructure and hardness was studied.The results show that in a very low range of cooling rate,bainite structure is obtained.The products of austenite transformation are ferrite,pearlite and bainite when the cooling rate is lower than 1℃/s;Those will be ferrite and bainite when the cooling rate is in the range of 1 to 6℃/s;those will be bainite and martensite when the cooling rate is in the range of 8 to 24℃/s and those will be totally martensite if the cooling rate is higher than 24℃/s.All those provide the references for productive practice and establishing new processes.