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通过对LZ50车轴钢边部增碳缺陷进行金相检验和扫描电镜检验,发现增碳处组织异常,全部为珠光体,伴随大量MnS和硅酸盐夹杂物。现场排查发现在保温帽和铸模之间有较大的缝隙,缝隙中残留有大量粉渣,而且使用的保护渣为高碳型保护渣。由此判断,浇铸过程中钢水与缝隙中的粉渣接触造成钢锭帽口线增碳,而且钢水中未被保护渣完全吸收的夹杂物也被捕捉残留在钢坯表面。
Through the metallographic examination and scanning electron microscopy examination of carbon steel defects on the edge of the LZ50 axle steel, it was found that carbon anomaly organizations, all of the pearlite, with a large number of MnS and silicate inclusions. On-site inspection revealed that there was a large gap between the insulation cap and the mold, a large amount of powder residue was left in the gap, and the mold powder used was high carbon type mold flux. From this, it is concluded that the contact between the molten steel and the slag in the gap during the casting process causes the carbonization of the ingot cap mouth, and the inclusions in the molten steel which are not completely absorbed by the mold powder are also trapped on the surface of the slab.