Surface Transversal Crack on S355ML Beam Blank
-
摘要: 采用金相检测、SEM、TEM、能谱、水口流场分析等方法, 并通过对连铸坯热成像温度分析, 对S355ML异形坯表面横裂纹产生原因进行研究。结果表明:直通型水口流场分布不合理;异形坯表面存在较大的温度梯度, 特别是从翼缘顶端到腹板R角处, 异形坯在矫直段处于铸坯脆性区;并且在S355ML异形坯大量析出碳氮化物破坏钢的高温热塑性, 从而使铸坯裂纹敏感性增加。通过优化二冷制度, 窄成分控制等措施, 矫直时避开铸坯第Ⅲ脆性区, 提高铸坯表面质量。Abstract: The causes of surface transverse crack on S355 ML beam blanks had been investigated by metallographic,SEM,TEM observations and nozzle flow field analysis,in combination with thermal imaging temperature of continuous casting billet. Results show that the flow field distribution of through-type nozzle is unsuitable. The surface of beam blank exist great temperature gradient,especially from top of flange to the web R Angle,thus profiled billet fall in brittle zone during straightening. Furthermore,lots of carbonitride precipitation in S355 ML shaped blank damage high temperature ductility of steel,and thus increase the slab crack sensitivity. By optimizing secondary cooling system and controlling composition at narrow range,the billet can be avoided to fall in Ⅲ brittle zone when being straighten and then slab surface quality can be improved.
-
Key words:
- continuous casting /
- beam blank /
- surface transversal crack /
- the Ⅲ brittle zone
点击查看大图
计量
- 文章访问数: 7
- HTML全文浏览量: 2
- PDF下载量: 1
- 被引次数: 0