Effect of TMCP on microstructure evolution and mechanical properties of low-carbon Ni-Nb steel
ZHOU Cheng, ZHAO Tan, ZHU Long-hao,JIN Yao-hui, LI Jia-an
(1. State Key Laboratory of Metal Material for Marine Equipment and Application, Anshan 114009, Liaoning, China; 2. Iron and Steel Research Institute, ANGANG Group, Anshan 114009, Liaoning, China)
Abstract:To study the effect of TMCP on microstructure evolution,grain size of low carbon Ni-Nb steel was reported. The microstructure characteristics evolution at different TMCP and its effect on mechanical properties were studied. The results show that microstructure consisting of polygonal ferrite and pearlite. In the case of undeformed rolling,the means of grain refinement as the cooling rate increases (lower than 5 ℃/s). However,the ferrite grain size in the microstructure decreased obviously with the increase of cooling rate in the case of deformed rolling,when the cooling rate increased above 5 ℃/s,there are a large amount of bainite is formed. The pilot plant experiment on this steel indicates that quasi-polygonal ferrite appears when cooling rate is 4 ℃/s,which improves the low temperature toughness. Granular bainite is formed after cooling at 6 ℃/s,which obviously decreases the low temperature toughness.