改善55SiCr盘条组织的工艺研究

Study on process to improve microstructure of 55SiCr wire rod

针对55SiCr盘条在用户绕制悬架弹簧过程中出现断裂的问题,对其原因进行了分析,发现盘条搭接点位置存在大量异常组织。为此,对生产工艺进行了研究优化,钢坯加热制度降低了加热段和均热段的温度,以减小奥氏体原始晶粒度,有利于相变的完成;控轧工艺中开轧温度控制在950~960℃、终轧温度控制在830~850℃,为获得索氏体组织创造条件;对照55SiCr钢的CCT曲线,控冷工艺采用了3段冷却工艺制度,控制好终冷温度和冷却速率,使盘条搭接点位置索氏体组织体积分数由原来的20%~30%提高到65%~70%,且避免了马氏体等异常组织的产生。工艺优化后盘条通条组织稳定、均一,有效解决了弹簧缠绕断裂问题。

In view of the problem of fracture of 55SiCr wire rod in the process of winding suspension spring,the causes were analyzed,and a large number of abnormal mistructure were found in the location of wire rod lapping point.Therefore,the production process was studied and optimized.The billet heating system reduced the temperature of the heating section and the soaking section,so as to reduce the original grain size of austenite and facilitate the completion of phase transition.In the controlled rolling process,the starting and finishing rolling temperatures were controlled at 950~960℃and 830~850℃respectively to create conditions for obtaining sorbite microstructure.Compared with the CCT curve of 55SiCr steel,a three-stage cooling process system was adopted in the cooling control process to control the finishing cooling temperature and cooling rate well,so that the volume fraction of sorbite microstructure at the lapping point of wire rod increased from 20%~30%to 65%~70%,and the generation of abnormal microstructure such as martensite was avoided.After the process optimization,the wire rod structure is stable and uniform,which effectively solves the spring winding fracture problem.