Effect of Molybdenum on Continuous Cooling Transformation of Ship Plate Steel with High Strength

The continuous cooling transformation (CCT) curves of the Mo-bearing and Mo-free high strength ship plate steels were measured by means of Vickers-hardness measurement and thermal dilation method on the Gleeble-3800 thermo-simulation machine.The microstructure transformation character was observed by optical microscopy,SEM and TEM.The influence of Mo on microstructure and CCT curves of the high strength structural ship plate steel was studied.The results show that the transition zone of bainite in the CCT curve was widened and the transition zones of ferrite and pearlite were moved towards the right when 0.2% Mo was added.In addition.In bainite the size of martensite/austenite island (M/A) was larger,the quantity of M/A island was more and the distribution of M/A island was more even and dispersive at the same cooling rate.