Effect of Slab Subsurface Microstructure Evolution on Transverse Cracking of Microalloyed Steel during Continuous Casting  

作　　者：Yun-feng LI Guang-hua WEN Ping TANG Jian-quan LI Cheng-li XIANG 

机构地区：[1]College of Materials Science and Engineering,Chongqing University [2]Pangang Group Panzhihua Steel and Vanagium Co.,Ltd.

出　　处：《Journal of Iron and Steel Research International》2014年第8期737-744,共8页

基　　金：Item Sponsored by National Natural Science Foundation of China(51174242)

摘　　要：As to the continuous casting process of low carbon microalloyed steel, subsurface microstructure evolution plays an important role in the slab surface cracking. In order to study the effect of the slab subsurface microstructure evolution on the transverse cracking, three different secondary cooling patterns （i. e. , mild cooling, strong cooling and controlled cooling） were performed in the corresponding slab curved continuous caster. Based on the metallo- graphic results, three transformation regions were found to be formed with the evolution of microstructures at different depths in the slab subsurface. The three regions are strong cooling transformation （SCT） region, double phase transformation （DPT） region and mild cooling transformation （MCT） region, respectively. Meanwhile, it was also found that the crack index used for evaluating slab surface cracking susceptibility was decreased when the range of the DPT region was increased. This can be explained by the fact that the double phase transformation （austenite-ferrite-austenite） occurred resulting from thermal cycling in DPT region, which resulted in promoting the refinement of prior austenite grains and inhibiting the precipitation of film-like ferrite and chain-like precipitates. Under the con- trolled cooling pattern, the widely-distributed DPT region was formed in the range of 3.5--8.0 mm to the slab surface. And compared with other cooling patterns, the cracking susceptibility is lowest with a crack index of 0.4.As to the continuous casting process of low carbon microalloyed steel, subsurface microstructure evolution plays an important role in the slab surface cracking. In order to study the effect of the slab subsurface microstructure evolution on the transverse cracking, three different secondary cooling patterns （i. e. , mild cooling, strong cooling and controlled cooling） were performed in the corresponding slab curved continuous caster. Based on the metallo- graphic results, three transformation regions were found to be formed with the evolution of microstructures at different depths in the slab subsurface. The three regions are strong cooling transformation （SCT） region, double phase transformation （DPT） region and mild cooling transformation （MCT） region, respectively. Meanwhile, it was also found that the crack index used for evaluating slab surface cracking susceptibility was decreased when the range of the DPT region was increased. This can be explained by the fact that the double phase transformation （austenite-ferrite-austenite） occurred resulting from thermal cycling in DPT region, which resulted in promoting the refinement of prior austenite grains and inhibiting the precipitation of film-like ferrite and chain-like precipitates. Under the con- trolled cooling pattern, the widely-distributed DPT region was formed in the range of 3.5--8.0 mm to the slab surface. And compared with other cooling patterns, the cracking susceptibility is lowest with a crack index of 0.4.

关 键 词：continuous casting microalloyed steel surface transversal cracking microstructure evolution cooling pattern 

分 类 号：TF777[冶金工程—钢铁冶金]