1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China 2. Pangang Group Panzhihua Steel and Vanagium Co., Ltd., Panzhihua 617000, Sichuan, China
Effect of Slab Subsurface Microstructure Evolution on Transverse Cracking of Microalloyed Steel during Continuous Casting
1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China 2. Pangang Group Panzhihua Steel and Vanagium Co., Ltd., Panzhihua 617000, Sichuan, China
ժҪ 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 metallographic 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 controlled 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.
Abstract��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 metallographic 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 controlled 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.
��������:National Key Basic Research and Development Program of China
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E-mail: liyunfengcqu@163.com
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Yun-feng LI,Guang-hua WEN,Ping TANG,Jian-quan LI,Cheng-li XIANG. Effect of Slab Subsurface Microstructure Evolution on Transverse Cracking of Microalloyed Steel during Continuous Casting[J]. �й������ڿ���, 2014, 21(8): 737-744.
Yun-feng LI,Guang-hua WEN,Ping TANG,Jian-quan LI,Cheng-li XIANG. Effect of Slab Subsurface Microstructure Evolution on Transverse Cracking of Microalloyed Steel during Continuous Casting. Chinese Journal of Iron and Steel, 2014, 21(8): 737-744.
2014, Vol. 21 
