Effect of relaxation process on microstructure and property in low carbon bainitic steels

Continuous cooling transformation(CCT)diagram for bainitic steels was measured at different cooling rates with the dilatometer,the transformation phases were observed.The effect of different cooling rate on the transformation of bainite and the effect of the microalloy elements on mechanical properties of the experimental steels were studied.The results show that the greater bainite in the steels is observed at cooling rate of 2 ℃/s;the ferrite and the pearlite transformation can be suppressed due to the alloying V;the starting temperature for bainite transformation is enhance due to the Cr element.The results indicate that the microstructure which is based mainly on the bainite can be obtained in large range of cooling rate;the zone of bainite transformation is expanded and the grain is refined by adding the element V;the yield strength-ultimate tensile strength ratio of the experimental steels is reduced by adding the right amount of element Cr.