导轨用55钢冷拉拔断裂原因分析及工艺改进

Reason Analysis and Technology Improvement on the Cold Drawing Fracture of 55 Round Bar

通过导轨低倍检验、HRB硬度分析、金相分析、断口电镜分析、拉拔强度计算等方法,分析了55钢导轨冷拔断裂的原因,分析表明是材料心部存在裂纹,而裂纹的存在是铸坯中心部位存在缩孔,轧制过程没有轧合,最终导致导轨在冷拉拔过程断裂。针对55钢中心缩孔问题,对55钢连铸过程实施了了轻压下。改进工艺实施轻压下后的铸坯轧制成Φ70 mm规格圆钢后,产品内部质量满足超声探伤A级要求,完全满足了客户使用要求。

Through the macroscopic examination,HRB hardness analysis,metallographic analysis,electron microscope analysis of fracture,drawing strength calculation etc.of the guide rail,the reason of the cold drawing fracture of 55 Steel was analyzed.The analysis showed the core crack emerged caused the drawing fracture in the steel due to the shrinkage cavity in the billet which was not rolled down completely.Against the problem of the shrinkage cavity,the continuous casting light pressure was used in the billet production.When the billet of the technology improved was rolled to Φ70 mm size round bar,the inernal quality of the products fully met level A requirement of UT and customer use showed the products also met the use requirements of the customer which achieved the good economic and social benefits.xperience of rapid recovery of furnace condition,and describes in detail the measures to prevent nodulation in blast furnace.