Research on continuous cooling transformation of X80 pipeline steel

The continuous cooling transformation behavior was studied after two steps deformation by Gleeble-3800 thermal mechanical simulator for X80 pipeline steel,and the continuous cooling transformation(CCT) curve was set up by thermal dilation method and metallographic method.The results show that,ferrite and bainite in the X80 steel are mainly obtained at low cooling rate,microstructure is entirely composed of bainite with different shapes when the cooling rate is higher than 1 ℃/s,as the cooling rate goes up,microstructure is refined and the hardness enhanced gradually.According to the CCT curve,when the final rolling temperature is higher than 750 ℃ and cooling rate is between 20-30 ℃/s,bainite with high-density dislocation and disperse MA constituents can be acquired in actual production,which ensures the X80 steel possess of high strength and toughness simultaneously.