X65管线钢连铸坯表面纵向凹陷、裂纹形成原因及对策

针对X65管线钢连铸坯表面存在的纵向凹陷及裂纹缺陷等问题,采用光学显微镜、扫描电镜及能谱仪对其进行了分析.缺陷产生的原因主要是微合金化元素Nb、Ti和V的碳氮化物在晶界偏聚所致.通过对结晶器保护渣成分、二冷曲线进行优化,控制中间包钢水过热度,规范连铸操作工艺和点检连铸设备可有效改善X65管线钢连铸坯表面的纵向凹陷和裂纹缺陷.

Causes and countermeasures of longitudinal depression and crack formation on X65 line pipe continuous casting billet surfaces

X65 line pipe continuous casting billet surfaces were analyzed by optical microscopy,scanning electron microscopy and energy dispersive spectrometry to deal with their defects of longitudinal depression and cracks.It is found that causes for these surface defects are mainly due to carbonitride segregation of micro alloying elements Nb,Ti and V at grain boundaries.These surface defects can be efficiently improved through optimizing the mold flux composition and the second cooling curve,controlling the tundish superheat,regulating the continuous casting operation process and checking the continuous casting equipment timely.