含硼普碳钢表面纵裂纹控制

CONTROL MEASURES OF LONGITUDINAL CRACK ON THE SURFACE OF PLAIN BORON CARBON STEEL

安钢生产的含硼普碳钢宽板坯出现大量表面纵裂纹,为降低其对产品质量的影响,对其产生原因进行了理论分析和生产试验研究,结果表明,引起含硼普碳钢宽板坯纵裂纹的原因是结晶器内钢中B在树枝晶晶界偏析和钢质带来的凝固坯壳厚度差异,以及凝固坯壳收缩不均匀和拉速波动导致坯壳开裂。通过优化转炉脱氧工艺、调整硼合金加入时机和加入量、制定合理的结晶器冷却制度、改进拉速控制和液面操作等措施,降低了含硼钢铸坯的裂纹发生率,提高了产品质量和铸坯合格率。

Numerous longitudinal cracks appeared on the surfaces of the wide plain boron carbon steel slab made in Anyang Steel .To reduce their influence on products quality , we analyzed theoretically the causes and made production experiments .The results show that the causes of the cracks on steel surfaces are that there are slab solidification shell thickness differences , which are caused by boron boundary segregation in the branches of crystal grain in mold and the quality of molten steel , and also uneven contraction of slab solidification shell and casting speed fluctuation .Through such measures as optimizing converter de-oxidation process , adjusting the addition amount and time of boron alloy , working out reasonable mold cooling regulation , improving the casting speed control and mold level control etc ., the crack ratio of boron steel is reduced , and both product quality and cast slab qualification rate are enhanced .