45钢热轧圆钢第一阶梯面的发纹及其预防

Hair Crack on First Step Surface of Hot-rolled 45 Steel Rod and Its Prevention

对65 mm的热轧45钢圆钢进行塔形切削检验时发现,其第一阶梯面上有发纹。为了弄清发纹的形成原因,对出现发纹的圆钢进行了金相检验和化学成分分析。结果表明,第一阶梯面出现的发纹来源于连铸方坯近角部的皮下裂纹,而钢中的磷、硫元素含量较高,结晶器内冷却不均匀及足辊冷却效果不良是造成方坯近角部产生皮下裂纹的主要原因。通过控制钢中磷、硫等有害元素的含量、优化结晶器铜管圆角半径及改进足辊的冷却等措施,圆钢第一阶梯面出现发纹的问题得到了解决。

From the step-down test it was discovered that hair cracks were present on the first step surface of hot-rolled 45 rod 65 mm in diameter.The rod that showed the hair crack was subjected to metallographic examination and to chemical composition analysis in the purpose of identifying the reason why the hair crack formed.The results showed that the hair crack derived from a subsurface crack nearby the corner of the continuously cast billet,whereas the subsurface crack was mainly caused by higher phosphorus and sulfur contents,uneven cooling in the mould,and poor cooling of the foot roller.The hair crack on first step surface of hot-rolled 45 rod has been prevented by decrease in contents of objectionable elements such as phosphorus and sulfur in the steel,optimization of radius of the copper mould tube corner,and improvment in cooling of the foot roller.