Continuous Cooling Transformation Curves of 42CrMoA Steel Undercooled Austenite

The critical transition temperature Acl,Ac3 and Ms of 42CrMoA steel was determined by Gleeble-1500D thermal simulation testing machine using dilatometric method combining with metallographic-hardness method.The inflation curve and phase transition point of the steel under different cooling speed of continuous cooling was determined.The continuous cooling process and the product microstructure morphology of cold austenitic transformation was analyzed.The vickers-hardness of these products under different cooling rates were measured.The CCT diagram was obtained.The products of austenite transform were ferrite and pearlite when the cooling rate is lower than 0.1 ℃/s.Those would be ferrite,pearlite and bainite when the cooling rate is in the range of 0.2 to 0.6 ℃/s.Those would be bainite and martensite when the cooling rate is in the range of 0.7 to 17 ℃/s and those would be total martensite if the cooling rate is higher than 20 ℃/s.However,the total bainite in the sample microstructure is not obtained in the experiment.