研究了钢水成分、结晶器保护渣、结晶器振动、浸入式水口、二次冷却制度等连铸工艺技术对400mm特厚板坯表面横裂纹的影响。试验结果表明,对于400mm特厚板坯,钢的化学成分及第Ⅲ脆性区的高温延塑性,是形成表面横裂纹的内因;二冷区强冷及矫直力是形成表面横裂纹的外因。在此基础上,提出了改善400mm特厚板坯表面横裂纹的有效措施：浸入式水口采用凹底结构、液渣层厚度控制在8～13mm、二次冷却制度采用弱冷方式、垂直段板坯表面温度控制在1 100℃以上、矫直段表面温度控制在940℃以上。研究结果经实际应用后,特厚板坯表面横裂纹的发生率降低到4.88%,铸坯表面质量得到很好的改善。
Factors influencing transverse cracks such as compositions of liquid steel,casting powder,mold oscillation,SEN,secondary cooling,and so on,were investigated.The results show that the compositions of liquid steel and the mechanical properties in the low ductility region Ⅲ are the internal reasons which effect transverse cracks;Strong cooling in secondary cooling area and the straightening force are the external cause.Based on these reasons mentioned above,some effective countermeasures were proposed in 400 mm ultra-thick slabs： the SEN with concave bottom,the thickness of liquid slag film keeps 8-13 mm,soft cooling in secondary cooling area,the surface temperature of slabs in vertical segment keeps above 1 100 ℃,the surface temperature in straighten segment keeps above 940 ℃.With all these countermeasures,the transverse cracks incidence of the ultra-thick slabs has been reduced to 4.88%,and the surface quality of slabs has been effectively improved.
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