Continuous cooling transformation of EQ70 steel for offshore platform

The expansion curves of EQ70 steel for offshore platform were measured by using a DIL805A dilatometer,combined with metallography and Vickers hardness measurement,the curves of continuous cooling transformation(CCT) were determined for the steel.The results show that with the cooling rate below 0.5 ℃/s,the microstructure is mainly granular bainite,with the cooling rates between 0.5 ℃/s and 2 ℃/s,the microstructure consists of granular bainite and lath bainite,and martensite forms as the cooling rate is 2 ℃/s,when cooling rate is up to 5 ℃/s,the microstructure is completely martensite.