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采用金相显微镜和扫描电镜对螺纹钢典型内裂纹漏钢坯壳的形貌进行了观察分析,探讨了该类型漏钢的特征及演变过程。研究认为,杂质元素特别是硫的晶间偏析对钢的高温强度及裂纹路径的形成有着重要的影响;结晶器内,坯壳生长不均匀导致铸坯表面产生凹陷,对应位置坯壳厚度较薄,并诱发内裂纹形成;出结晶器后,薄弱的内裂纹处承受应力集中,发生裂纹扩展,情况严重时导致漏钢产生。通过降低钢中的S含量、调整浇铸工艺参数后,螺纹钢小方坯内裂纹漏钢发生率由6.32%降低到1.10%。
The appearance of the typical cracked steel shell of rebar was observed and analyzed by optical microscopy and scanning electron microscopy. The characteristics and evolution of this type of steel breakout were discussed. It is concluded that the intergranular segregation of impurity elements, especially sulfur, has an important influence on the high temperature strength and the crack path formation of steel. The uneven growth of slab in the mold leads to the depression on the slab surface. , And induce the formation of internal cracks. After the mold is crystallized, the weak internal cracks are subjected to stress concentration and crack propagation occurs, leading to breakout in severe cases. By reducing the S content in the steel and adjusting the casting process parameters, the incidence of crack in the rebar billet decreased from 6.32% to 1.10%.