SWRCH22A冷镦钢成形过程开裂分析及质量控制

Cracking analysis and quality control in forming process for cold heading steel SWRCH22A

针对SWRCH22A冷镦钢盘条在使用过程中出现的冷镦开裂、拉拔断裂现象进行了分析。实验结果表明：冷镦开裂螺钉爆头部位与线材表面的线纹缺陷有明显对应关系,这是因连铸过程产生的铸坯皮下及角部裂纹,经过后续轧制在盘条表面形成约200μm深度的线纹及近表面的封闭微裂纹冷镦开裂所致;拉拔过程断口呈现笔尖状,断口心部位置存在约20～30μm的粗大珠光体团,其原因在于铸坯中心偏析。通过从冶炼、连铸和轧制等关键控制环节进行系统分析控制,结合生产工艺的优化和改进,使得后续生产的SWRCH22A冷镦钢盘条质量得到大幅提升,满足了用户使用要求。

The cold heading cracking and drawing fracture phenomena of SWRCH22A cold heading steel wire rod in the process of application were analyzed. The experiment results show that the cold heading cracking defects of screw are obviously related to the line defects on the surface of wire rod,which is caused by the subcutaneous and corner cracks of the casting blank produced by the continuous casting process to form lines of about 200 μm depth on the surface of wire rod and closed microcracks near the surface after the subsequent rolling. However,the fracture presents pen tip shape in the drawing process,and there is coarse pearlite colony of about 20-30 μm in the center of fracture due to the central segregation of the casting blank. Furthermore,the systematic analysis and control were carried out by controlling the smelting,continuous casting and rolling processes. Combining with the optimization and improvement of production technology,the quality of SWRCH22A cold heading steel wire rod is greatly improved to meet the user＇s requirements.