迁钢板坯内弧单边角横裂纹成因与对策分析

Study on Formation Mechanism and Countermeasures of Single-Sided Transverse Corner Cracks of Slab in Qiangang

针对迁钢板坯内弧单边角横裂纹成因进行了微观组织分析,对浇注过程板坯两侧角部温度进行测量,并对比了不同厂家二冷喷嘴在相同条件下的通水量。研究结果表明:安装在同一管路上的不同厂家的二冷喷嘴通水量差别较大,这些喷嘴在扇形段的混合使用是引起板坯两侧角部温度不同的主要原因。板坯温度高的一侧进入第三脆性区,导致了内弧角横裂纹发生。将二冷喷嘴全部更换为同一厂家的产品后,板坯单边角横裂纹得到解决。

To clarify formation mechanism of single-sided corner cracks in slab of Qiangang, as cast microstructure was analyzed.Corner temperature at two sides of the slab was measured during continuous casting. Water flow rate of nozzles from two suppliers was compared in laboratory. Results show that such corner cracks propagate along the original austenite grain boundaries. In laboratory test, water flow rates of cooling nozzles from the two suppliers are different when they were connected to the same air pipe and the same water pipe. Uneven water distribution along slab’s transverse direction is the main cause of corner temperature difference. The higher temperature side moved into brittle zone of the steel. Then it leads to single-sided corner cracks. Finally, this is solved by replacing cooling nozzles of one strand with nozzles from one supplier.