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采用金相显微镜、扫描电镜分析了镀锌钢板180°冷弯时出现开裂的原因。发现裂纹附近的显微组织除发生轻微变形外,未见明显夹杂物和组织偏析;开裂属于韧性断裂,断裂方式与受力方向相同;开裂处有大量硅酸盐、硫化物和结晶器保护渣的复合夹杂物。认为镀锌钢板中大量的硫化物和硅酸盐夹杂物是造成钢板冷弯开裂的主要原因,对炼钢工序提出了相应的改进措施,实施后,未出现过180°冷弯开裂现象。
Using a metallographic microscope and scanning electron microscopy, the reason of cracking occurred in 180 ° cold bending galvanized steel was analyzed. No obvious inclusions and tissue segregation were found in the microstructure near the crack except slight deformation; the cracking belongs to the ductile fracture, the fracture mode is the same with the stress direction; a large amount of silicate, sulfide and mold powder Compound inclusions. It is considered that the large amount of sulfide and silicate inclusions in galvanized steel is the main reason for the cold cracking of the steel sheet. Corresponding improvement measures are proposed for the steelmaking process. After the implementation, there is no phenomenon of 180 ° cold cracking.