连铸二冷模式对微合金钢板坯角部表层组织的影响

Effect of secondary cooling patterns on corner subsurface microstructure of microalloyed steel slab during continuous casting

为减少和预防攀枝花钢钒有限公司P510L微合金钢连铸坯角部裂纹的发生，进行了二冷区不同冷却模式对铸坯角部表层组织及表面横裂纹的影响研究。结果表明：传统弱冷模式下，大量膜状先共析铁素体连成网状，阻碍了奥氏体基体的连续性，降低了铸坯角部的热塑性。在优化冷却模式下，在铸坯角部表层2～3mm的组织细小、分布均匀，没有出现先共析铁素体膜，有利于控制铸坯表面横裂纹的发生。相对于传统弱冷模式，优化冷却模式可将铸坯角部表面横裂纹指数由3．2N至0．4，裂纹发生率得到了控制。

In order to decrease and prevent the occurrence of slab transverse corner crack, effect of secondary cooling pattern on slab corner subsurface microstructure and related surface corner transverse crack was investigated via casting of P510L steel using a slab arc continuous caster. It is shown that, under the mild cooling pattern, the formation of continuous matrix was separated by the film-like ferrite along the prior austenite grain boundary, which decreased the hot ductility of slab subsurface. Under the control cooling pattern, the microstructure was even and film-like ferrite was inhibited in the range of 2 - 3 mm to the slab surface, resulting in promoting the reduction of transversal cracking susceptibility. And compared to the mild cooling pattern, under the optimized cooling pattern, the crack index fell from 3. 2 down to 0.4.