Q235热轧板带孔洞缺陷成因分析及控制

CONTROL AND ANALYSIS ON THE CAUSE OF CAVITY DEFECTS OF Q235 HOT ROLLING PLATE AND STRIP

国内某钢厂Q235热轧板带生产过程中出现少量孔洞缺陷,利用水模试验研究了Q235钢坯浇注过程拉速、水口插入深度及吹气量对结晶器内气泡分布的影响,采用金相检验、能谱分析方法对热轧板带孔洞缺陷显微组织及夹杂物进行了分析,同时对热轧板带孔洞缺陷生产工艺进行了调查。结果表明:连铸工艺参数控制不合理、熔炼样S含量偏高导致铸坯边部产生表层气孔、中部产生较严重的硫偏析,进而使钢板中部形成大量的条带状硫化物特别是低熔点FeS的大量生成导致了Q235热轧板带孔洞缺陷的产生。针对缺陷成因对炼钢生产工艺进行了优化改进,热轧板带孔洞缺陷基本得到了消除。

There were a small amount of cavity defects of hot- rolled plate and strip in domestic steel plant, the casting speed, the influence of casting speed, argon blowing and insertion depth of submerged nozzle on gas bubble in mould was investigated by water modeling, mierostructure and inclusions of cavity defects were analyzed by means of metallographic examination, energy spectrum analysis and so on,mean- while, the production process of hot-rolled plate and strip with cavity defect was investigated. The results show that the surface pores at edge slab and serious sulphur segregation at centre slab are caused by the abnormal continuous casting control and high S content in melting sample ,which lead to the formation of plenty of banded sulfide inclusions including low melting Fes in centre of plate and strip, and which result in the formation of cavity defects for hot-rolled plate and strip. In view of causes of cavity defects for hotroiled plate and strip, the steel-making production process is optimized, hot-rolled plate and strip with carity defects are basically eliminated.