Abstract: The delamination defects at the tail of 148 mm thickness 2.25Cr-1Mo-0.25V steel plate made of 55 t ingot is observed and analyzed by scanning electron microscope and electron probe microanalysis. The results show that the delamination defects are caused by the involvement of mold flux in the molten steel. In order to reduce the delamination defects at the tail of steel plate the smelting process is optimized,i.e. in refining process,the composite deoxidation process of carbon powder,calcium carbide and 1.2-2.0 kg/t_steel Al line is adopted. After vacuum, it is soft blown for 12-14 min. The mold casting protective slag with high viscosity,low melting point,high melting rate and large expansion coefficient is used. After optimizing the smelting process, the ratio of delamination defects at the tail of steel plate is 11.3%,9.6% and 6.9% respectively,and the scrap rate of steel plate caused by delamination defects decreases from original 8.1% to 1.7%.

Key words: 2.25Cr-1Mo-0.25V Steel, 148 mm Heavy Thickness Delamination Defect, Flux, Casting, Al₂O₃ Inclusion

摘要： 采用扫描电镜及电子探针对55t 钢锭成材148mm 厚2.25Cr-1Mo-0.25V钢板尾部分层缺陷进行观察分析，结果表明：分层缺陷是由于模铸保护渣卷入钢液造成的。为减少钢板尾部分层缺陷，对冶炼工艺进行优化，精炼过程中采用碳粉、电石及1.2～2.0kg/tAl 线复合脱氧工艺，真空后软吹12～14 min,采用高粘度、低熔点、高熔速及膨胀系数较大的模铸保护渣。优化工艺后，钢板尾部分层缺陷出现概率分别为11.3%、9.6%、6.9%,分层缺陷导致钢板废品率由原8.1%降至1.7%。

关键词: 2.25Cr-1Mo-0.25V 钢, 148 mm厚板分层缺陷, 模铸保护渣, 浇铸, Al₂O₃夹杂物