含硼钢板坯边角裂纹的成因与控制

Formation Mechanism and Control of Transverse Corner Cracking of Containing Boron Steel Slab

采用金相显微镜、扫描电镜和Gleeble-3800热模拟试验机分析了含硼微合金化钢板边角部表面裂纹的形成原因。发现二冷矫直区铸坯内弧边角部温度位于该钢种第3脆性温度区间内,拉速较低和二冷水表及喷嘴布置不合理导致了内弧两边角部温度较低。采用提高拉速、遮挡矫直区铸坯角部喷嘴和适当降低二冷水表等"热行"方法后,结合调整动态轻压下参数使得铸坯角部温度明显提高,铸坯的边角裂纹和内部质量均得到显著改善。

The optical microscope and SEM were applied to analyze the formation mechanism of transverse corner cracks of boron micro-alloyed steel slab. It is found that the cracks occur at relatively low corner temperatures of slab in straightening section that is in No. 3 brittle zone of boron steel firs. The corner temperature of slab is rela- tively low due to the relatively low casting speed, irrational distribution of secondary cooling water and sprayers. In- creasing casting speed and decreasing the cooling water flux at slab corners in the straightening section for mild cool- ing were performed first to control corner temperature above the upper limit in No. 3 brittle zone of boron steel. Combined with the adjustment of dynamic, as a result, the corner temperature of slab was increased apparently, transverse corner cracking and internal quality of slab was greatly improved