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通过对Q235B热板典型翘皮缺陷及铸坯剖面的微观组织的分析,明确了缺陷由铸坯角部微裂纹在加热炉中进一步扩展所致。同时在角部横裂纹中发现外来夹杂物,如保护渣、氧化铝,判断裂纹在结晶器中弯月面附近产生。通过合理设计钢种成分、减缓结晶器冷却、保护渣优化、合理控制锥度、设备精度保证、采用合理的加热制度等措施,使该钢种的缺陷封闭指数由4.8稳定在3.0以内。
Based on the analysis of typical warpage defects of Q235B hot plate and the microstructure of the slab section, it was clarified that the defects were caused by the further expansion of the micro-cracks in the corner of the slab in the heating furnace. In the meantime, foreign inclusions such as mold powder and alumina were found in the corner transverse crack, and the crack was determined to be generated near the meniscus in the mold. Through the reasonable design of the steel composition, slow down the mold cooling, slag optimization, reasonable control of taper, equipment accuracy assurance, the use of reasonable heating system and other measures to make the steel defect closure index 4.8 stabilized at 3.0 or less.