Abstract: Based on the intermediate cracks in continuous casting Q235B steel 230 mm slab produced by LD-Ar route, a series of analyses the macroscopic and microscopic characteristics in intermediat cracks are done by optical microscope ,SEM and EDS. The results show that irregular arc of segments and low precision of roll gap as well as misalignment of the supporting rollers are the outer causes of forming and extending in intermediate cracks, and coarse grains and serious element segregations such as manganese, sulfur and complex inclusion compound accumuleted at the crack band are the inner causes of producing intermediate cracks. With the process measures including control segments arc ≤ ±0.3 mm, roll gap ≤ ±0.5 mm, secondary cooling water ratio 0.50 L/kg, [S] ≤0.030% , [Mn]/[S]≥15, it is available to decrease and avoid the occurrence of the cracks. As a result, the quality of the slab center quality is enhanced.

摘要： 针对LD-氩站流程生产Q235B钢230 mm连铸板坯出现的中间裂纹,利用光学显微镜、扫描电镜和能谱仪对中间裂纹宏观和微观特征进行了系统分析。结果表明,判断扇形段接弧不良、辊缝精度差、辊子错位等是中间裂纹形成的外因;裂纹带上有粗大的晶粒,且有明显的Mn、S等元素以及复合夹杂物形态聚集是铸坯产生中间裂纹的内因。通过控制接弧精度≤±0.3mm、辊缝精度≤±0.5 mm、二冷比水量0.50 L/kg、成品[S]≤0.030%、[Mn]/[S]≥15等工艺措施,减少甚至杜绝板坯中间裂纹的发生,提高了连铸板坯的心部质量。

关键词: Q235B钢, 连铸板坯, 中间裂纹, 外因, 内因