Evolution of micron Ti(Cx,N1-x) in TSCR process of ultra-high strength hot stamping steel
ZHANG Hao-hao1, WU Jia-lu1, LONG Mu-jun1, GUO Wei1, YANG Xiao-dong2, CHEN Deng-fu1
1. School of Materials Science and Engineering, Chongqing University, Chongqing 400044, China; 2. Steel Mill, Pangang Group Xichang Steel and Vanadium Co.,Ltd., Panzhihua 615000,Sichuan, China
Abstract：In the process of producing ultra-high strength hot stamping steel by thin slab continuous casting and rolling (TSCR) process, the key to ensure product quality and smooth production is to correctly control the process parameters and reduce the precipitation of coarse second phase in the slab as much as possible. Clarifying the precipitation evolution law of coarse micron Ti(Cx,N1-x) precipitates in TSCR process has important guiding significance for quality control and process parameter optimization in actual production. Through the combination of thermodynamic calculation and experimental research, the precipitation evolution behavior of micron Ti(Cx,N1-x) precipitates in the continuous process of TSCR continuous casting and soaking of ultra-high strength hot stamping steel was studied in detail. The evolution law of “precipitation-remelting-coarsening” of micron Ti(Cx,N1-x) phase in this process is clarified, and its precipitation growth rate, remelting rate and coarsening rate are quantitatively analyzed. The results show that the coarse micron Ti(Cx,N1-x) precipitates in 22MnB5 steel begin to precipitate in the liquid phase at the end of solidification, and the solid rate is 0.912. With the continuous reduction of continuous casting temperature, the x value in micron Ti(Cx,N1-x) phase increases from 0.1 to 0.7, and the precipitated phase of Ti(Cx,N1-x) gradually changes from N-rich phase to C-rich phase. Micron Ti(Cx,N1-x) phase grows continuously during continuous casting cooling, partially dissolves in the matrix during heating up, and then grows again in the holding stage. In the cooling, heating and holding stages of continuous casting and soaking process of TSCR process, the average rates of particle growth, dissolution and coarsening of micron Ti(Cx,N1-x) precipitates are respectively 0.007 2、-0.001 5、1.95×10-4 μm/s.
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2022, Vol. 41 
