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With the continuous development of thin slab casting and rolling (TSCR), and its products have been widely used in various fields, and is used to provide raw materials for downstream cold rolling process. TSCR product surface quality is not high, and high mechanical properties, cold-rolled raw materials on a large scale is still quite difficult. Therefore, the research to improve the surface quality and mechanical properties of TSCR product caused the attention of domestic and foreign experts. The project relying on to-pass the steel FTSR production line, in line with the development of CQ-level requirements of cold-rolled sheet hot rolled coil (P / O board), to achieve the \Issues first in the laboratory, a large number of boron microalloying technology research and development, to reveal the mechanism of the technology used to reduce the yield strength of hot rolled coil, analysis of the evolution of the continuous casting and rolling process coils organization, and in-depth study The hot rolled curling crack causes and control measures, and raised the yield strength below 270MPa hot rolled coil technology solutions suitable for the production of Tonghua Steel FTSR process and experimental production of four rounds in the Tonghua Iron and Steel to produce the hot-rolled coils to meet user requirements. The project the following conclusions: (1) After four pilot production, through steel have been able to independently mass production TG270 boron microalloyed steel yield strength after aging 48h to stabilize control in 270MPa below, rolled coils good surface quality, heat generation of cold. (2) TG270 Coil of boron microalloying technical production, aging 48h, yield strength 247.8MPa tensile strength 335.45MPa, elongation 45.85%, the surface quality of the product, the plate-shaped geometry, The mechanical properties are in line with user requirements. (3) the microalloying elements B is added, the low-carbon aluminum killed steel precipitates BN, these precipitates coarse particle size, generally in the 1-3μm; BN starts to precipitate at a higher temperature, thereby suppressing a small dispersion type AlN precipitates, the lifting of the AlN grain boundary pinning effect, to provide the conditions for the ferrite grains grow. (4) addition of micro-alloying elements B, steel MnS and BN composite precipitate the formation of coarse particles, indirect coarsening of MnS precipitates particles, reducing the content of the precipitates 50nm or less diminished fine MnS austenite grain growth and phase change after the ferrite grain growth inhibition, conducive to grain coarsening. (5) Add the micro-alloying elements B, N content of the liquid steel is basically stable at between 30-40ppm; determination of line strength and hot-rolled plates extending rate measurement: With the reduction of the N content, hot rolled sheet strength tends to decrease the elongation increases; when the N content of 50ppm or less, the yield strength and tensile strength are at a lower level, and high elongation, to be able to meet the heat generation cold deep red with a low-carbon steel band needs.
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