中碳结构钢表面纵裂纹产生原因分析与改善措施

介绍了本钢特钢采用235mm×265mm连铸坯生产的40Cr、40CrMn等钢种，生产(100～130)mm过程出现批量纵裂纹缺陷；研究了钢材、连铸坯裂纹形成机制，明确了钢材纵裂纹是由于连铸过程二冷水冷却不均匀，连铸坯产生皮下裂纹，加热后皮下裂纹扩展到表面所致；得出了通过改善水质，防止喷嘴堵塞，加强连铸坯缓冷，降低加热炉预热段温度等技术措施，可有效控制铸坯裂纹，解决了钢材纵裂纹缺陷。

Forming Cause and Improvement Measures of the Longitudinal Cracks in Medium Carbon Structural Steels

There were some batches of longitudinal cracks defects, during rolling into the products for 40Cr and 40CrMn steels, etc. The 235 minx 265 mm continual casting billets were rolled at Special Steel Plant of Benxi Steel. The mechanisms of the occurrence of cracks for the steel products and continual casting billets were investigated. It is clearly shown that the longitudinal cracks of steel products were resulted because the second cooling water homogeneously cooled the billets during the continual casting process, and therefore, the subsurface cracks of continual casting billets came in being, and evolved into surface cracks during subsequent heating. The subsurface cracks of continual casting billets were effectively prevented and the longitu- dinal cracks of steel products were eliminated through improving water quality, preventing the jamming nozzle, conducting slow cooling of continual casting billets and reducing preheating temperature, etc.