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结合冶金热力学和凝固偏析模型分析了Ti--IF钢凝固过程中TiN的析出特点.Ti--IF钢凝固前期钢液中TiN夹杂无法生成,固相中TiN源自低温固相析出;凝固固相分数达到0.64时,Ti、N组元在凝固前沿富集程度增加,凝固前沿固相中开始有TiN析出;凝固末期,Ti和N的富集程度进一步增大,固液相中均能有TiN析出.采用扫描电镜分析了TiN在铸坯中的分布,从铸坯表层到中心TiN数量和尺寸存在显著变化:从铸坯表层向中心方向TiN尺寸不断增大,平均尺寸从1~2μm增大到5μm,在距离表层70~80 mm处尺寸达到最大;在铸坯厚度中间位置,TiN尺寸较大,平均尺寸为5μm左右;在铸坯中心TiN尺寸又有所变小,平均尺寸为3μm左右;在铸坯表层TiN密集程度较高,在铸坯中间和中心TiN数量密集程度显著降低.IF钢铸坯中TiN析出时机及其尺寸和数量与Ti、N组元偏析和凝固冷却速度关系密切.
The precipitation characteristics of TiN during the solidification of Ti - IF steel were analyzed by means of metallurgical thermodynamics and solidification segregation model. TiN inclusion in the molten steel of Ti - IF steel could not be formed in the solidification phase. When the phase fraction reaches 0.64, the enrichment of Ti and N elements increases in the front of solidification, and TiN precipitates in the solid phase before solidification. At the end of solidification, the enrichment of Ti and N further increases, both in solid and liquid phases TiN precipitated.The distribution of TiN in the cast slab was analyzed by scanning electron microscope (SEM), the number and size of TiN varied significantly from the surface to the center of the slab: the size of TiN increased from the slab surface to the center and the average size increased from 1 ~ 2μm The size of TiN reaches the maximum at 70-80 mm from the surface. In the middle of slab thickness, the TiN size is larger and the average size is about 5μm. At the center of the slab, TiN size is smaller and the average size is 3μm , The density of TiN in the slab surface is high and the concentration of TiN in the center and center of the slab is significantly reduced.The timing and size and amount of TiN precipitation in the steel slab of IF steel are related to the segregation and solidification cooling rate of Ti and N close.