学术论文

      Ti--IF钢凝固过程中TiN的析出机理和规律

      Precipitation mechanism and behavior of TiN during Ti-IF steel solidification

      摘要:
      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.
      Abstract:
      Characterization of TiN precipitation during Ti-IF steel solidification was analyzed by thermodynamics and the solidifica-tion segregation model. It is found that TiN inclusions cannot precipitate in liquid steel before solidification. In the earlier stage of so-lidification, TiN precipitates at low temperature in solidified steel. When the solid fraction reaches to 0.64, TiN can precipitate in solid steel around the solidification front at higher temperatures, due to the increased enrichment of Ti and N. However, at the end stage of solidification, TiN can not only precipitate in solidified steel, but also in molten steel, for the segregation of Ti and N is getting seri-ous. TiN distribution in the Ti-IF slab was observed by scanning electron microscopy ( SEM) . The results show that the number and size of TiN precipitates vary a lot from the slab surface to the center. The TiN size is increasing from the slab surface to the center, from 1-2μm to 5μm, and it is maximum in the area of 70 to 80 mm from the slab surface. In the middle of the slab in thickness, the TiN size is large, with an average size of 5μm;while in the center of the slab, the TiN size is getting smaller again, with an average size of 3μm. The TiN denseness is high in the surface layer of the slab, but decreases significantly in the center and middle. The pre-cipitation moment, the size and number of TiN precipitates are closely related with the segregation of Ti and N and the solidification rate.
      作者: 王金永 [1] 刘建华 [1] 刘建飞 [1] 冯美兰 [1] 周明伟 [2] 廖志 [2] 贾友生 [2]
      Author: WANG Jin-yong [1] LIU Jian-hua [1] LIU Jian-fei [1] FENG Mei-lan [1] ZHOU Ming-wei [2] LIAO Zhi [2] JIA You-sheng [2]
      作者单位: 北京科技大学冶金工程研究院,北京,100083 涟源钢铁集团有限公司,涟源,417009
      刊 名: 北京科技大学学报 ISTICEIPKU
      年,卷(期): 2014, (8)
      分类号: TG142.1
      机标分类号: TG1 X13
      在线出版日期: 2014年9月11日