H08Mn2SiA盘条拉拔断裂原因分析

针对5.5 mm H08Mn2SiA盘条拉拔1.2 mm钢丝过程中出现脆断现象,对盘条进行化学成分、力学性能、夹杂物与显微组织等方面的检验,并利用扫描电镜对拉拔脆断断口进行分析。结果显示,盘条边缘形成贝氏体组织,在拉拔过程中产生严重加工硬化,致使其边缘产生微裂纹,裂纹进一步扩展造成盘条的拉拔脆断。提出改进措施:在H08Mn2SiA盘条控轧控冷过程中,将终轧温度设定为980℃,吐丝温度降低至880℃;STM辊道下的风机全停,保温罩全部关上;将STM辊道运行速度降低到0.05 m/s,使盘条在足够长的STM辊道上缓冷20～25 min,延迟型冷却方式消除了盘条边缘的异常贝氏体组织,满足用户拉拔生产的需要。

Reason analysis on drawing fracture of H08Mn2SiA wire rod

Focus on the fracture problem when diameter 5.5 mm H08Mn2SiA wire rods draw diameter 1.2 mm steel wire,and make detection of chemical composition,mechanical property,impurity and microstructure etc.and make analysis for drawing fracture via scanning electron microscope.The result shows the main reason of wire rod’s fracture is serious work hardening of wire rod’s edge Bainite that has intensively deformed and made microcrack on the fracture,which made the fracture step by step.Advanced measures: on the cooling and rolling control process for wire rod H08Mn2SiA,to set finnal casting temperature as 980 ℃,wire laying temperature as 880 ℃;to stop all fans under track STM,and close all protection screen;to slow STM’s speed down to 0.05 m/s,which ensure wire rod would be slow cooling 20~25 minutes with enough track STM.The way of slow cooling eliminates the abnormal Bainite structure of wire rod’s edge,which satisfy drawing production’s needs.