帘线钢LX82A湿拉断丝原因分析和工艺改进

Analysis of breaking and process improvement of LX82A cord steel in wet‑drawing

电镜分析结果显示,LX82A盘条湿拉断口以杯锥断口为主,占比60.9%。对杯锥断口纵剖进行金相分析,钢丝断口中心线位置存在不变形异常组织,且存在晶界渗碳体。原材料心部偏析及晶界渗碳体是LX82A湿拉断丝的主要原因。通过增大连铸结晶器电磁搅拌电流,提高等轴晶率;同时优化轻压下工艺参数,消除铸坯中心“V”型偏析,减小缩孔,铸坯碳偏析指数由优化前的1.13降低到1.08。再进一步提高轧钢加热二段和均热段温度,提升高温扩散效果,最终盘条金相检验中心网状碳化物合格率提高,湿拉吨钢断丝率降低了38.2%,偏析造成的杯锥断口比例降低至42.6%。

By scanning electron microscopy,the fractures of LX82A wire rod in wet-drawing are mainly cup-cone fractures,accounting for 60.9%.The microscopic analysis of the cup-cone fracture longitudinally shows that there are abnormal and undeformed structures and grain boundary cementite at the center line of the wire fracture.The core segregation and grain boundary cementite of raw materi⁃als are the main causes of LX82A wet-drawn wire breakage.The equiaxed crystal rate can be improved by increasing the electromagnetic stirring current of continuous casting mold.At the same time,the process parameters of soft reduction are optimized to eliminate the center“V”segregation,decrease the porosity,and reduce the carbon segregation index of the billet from 1.13 to 1.08.Furthermore,the temperature of the second stage and the soaking stage in heating stove is further increased to improve the high temperature diffusion effect.By metallographic test,the qualified rate of carbides in the center of the wire rod is increased,the broken rate per ton steel of wet-drawn is reduced by 38.2%,and the broken ratio of cup-cone caused by segregation is reduced to 42.6%.