（1. Tangshan Heavy Plate Co., Ltd., Tangshan 063000, Hebei, China 2. School of Metallurgy, Northeastern University, Shengyang 110819, Liaoning, China 3. Technology and Research Institute, HBIS Group, Shijiazhuang 050023, Hebei, China）
Abstract：The implementation feasibility of the Q345B- Nb steel slab corners grains refinement by cyclic phase transformations at high temperature was studied by mathematical simulation according to the practical Nb micro- alloyed steel continuous casting in Tangshan Iron and Steel Plate. The simulation result showed that the corner temperature could be cooled below to 600 ℃ by setting six groups of the nozzles for the strong spray cooling of the slab corners under the mold narrow face foot rollers, and then the temperature may rise to 900 ℃ by reducing the water cooling consumption of cooling zone 3 and zone 4 in bending segment. Thus, the temperature of slab corners could meet the need of cyclic phase transformations. Based on this, the new process was applied to the practical continuous casting. The application results showed that the slab corners microstructure transferred from the austenite + ferrite film structure to the ferrite＋pearlite structure, and the grains were greatly refined to ≤20 μm by using the new technology in the range of 0~20 mm under the slab corner surface, and the cracking rate of the Nb micro- alloyed steel slab corner reduced from 5.89% of using traditional cooling process to ＜0.1%.
刘志远，王重君，蔡兆镇，李双江，安海瑞，陈长芳. 含铌微合金钢连铸坯角部裂纹控制二冷新工艺[J]. 中国冶金, 2018, 28(3): 22-29.
LIU Zhi- yuan,WANG Chong- jun,CAI Zhao- zhen,LI Shuang- jiang,AN Hai- rui,CHEN Chang- fang. New secondary cooling process for transverse corner crack control of Nb micro- alloyed steel slab[J]. China Metallurgy, 2018, 28(3): 22-29.
2018, Vol. 28 
