CSP工艺Q235 B热轧带钢边部裂纹成因分析

为减少采用CSP工艺生产的Q235B热轧带钢边部裂纹缺陷,分别在Q235 B连铸坯和热轧带钢裂纹处进行取样,通过宏观形貌、金相组织、扫描电镜及能谱分析等方法,研究铸坯角部横裂纹与热轧带钢边部裂纹的演变规律和形态变化. 结果表明,结晶器卷渣、冷却不均匀是产生连铸坯角部裂纹的主要原因;第2道次过渡带钢的金相组织中出现混晶现象,裂纹边上存在脱碳现象;热轧带钢边部裂纹主要源自于铸坯裂纹,并在轧制过程中得到扩展. 根据连铸工艺参数,对边部裂纹缺陷率与液渣层厚度、保护渣消耗量、结晶器振动参数、中间包过热度、结晶器传热参数以及铸坯宽度的关系进行统计分析,并提出相应的边部裂纹控制工艺措施.

A causal analysis of edge cracks on Q235B hot rolling strip produced by CSP

In order to resolve cracks on the edges of Q235B hot rolling strip produced by CSP, samples were taken of Q235B continuous casting slab and hot-rolled coil on the cracking point, respectively, and macro-structural, metallographical, SEM and electron probe analyses were conducted to study the evolution of slab corner cracks and strip edge cracks. The results show that slag entrainment in the mould, which leads to uneven cooling, is the main cause of slab corner cracks. The mixed crystal and decarburized structure are discovered in F2 transition strip, and edge cracks in hot rolling strip result from cracks in the slab and extend in the rolling process. Based on the technical parameters of contin- uous casting, statistical analyses were carried out of the thickness of liquid layer, consumption of casting powder, oscillation parameters, tundish superheat degree, mould heat transfer, and slab section, and appropriate measures for crack control were proposed.