板坯非正常角部横裂纹产生原因分析

针对板坯连铸出现的非正常角部横裂纹,采用光学显微镜及扫描电镜等方法对缺陷进行分析。结果表明,角部横裂纹产生的原因是由于连铸机0~1段区域东侧外弧线偏差过大,造成铸坯角部在结晶器内轻微扭曲凹陷,进而热阻增加,冷速降低,形成粗大的奥氏体晶粒及超厚的沿晶先共析铁素体异常组织,恶化基体高温塑性,在后续受力过程中沿晶开裂,形成严重的角部横裂纹。通过调整铸机外弧线偏差,裂纹发生比例由60%降低到了5%以内。

Analysis of abnormal transverse corner crack in slab

In view of the abnormal corner transverse cracks in slab continuous casting, the defects were analyzed and verified by scanning optical metallographic and electron microscope. The results showed that the reason of corner transverse cracks was that the great deviation of outer arc in the east side of 0-1 section, resulting in slight distortion and depression of slab corner in the mold. Then the coarse austenite grains and ultra thick intergranular proeutectoid ferrite formed because of the increasing thermal resistance and decreasing cooling rate worsen the hot ductility of the slab. In the subsequent stress process, the serious intergranular corner transverse cracks were formed. By adjusting the radial deviation of the outer arc of the caster, he proportion of cracks is reduced from 60% to less than 5%.