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为探究涟钢连铸纵裂纹产生的原因,对钢水质量、过热度、进出水温、保护渣性能、液面波动及结晶器铜板等进行了检测、分析.认为其主要原因是:钢中部分硫含量处于较高水平,使w(Mn) /w(S)比为28.8;停产后结晶器进水温度下降幅度达到25℃,恢复生产后水温又快速上升到30～32℃；保护渣碱度波动较大,最低时达到1.1,使渣玻璃性强、导热性较好；液面波动高达6～7mm,保护渣不能均匀流入,影响结晶器的传热；另外,结晶器铜板划伤造成初生坯壳与铜板接触不良,局部温度偏高.并提出了相对应的措施,经过调整后,涟钢1号机表面纵裂纹发生率由0.50％下降到0.024％.

Cause Analysis of Longitudinal Crack on the Surface of Continuously Cast Slab

In order to explore the cause of longitudinal crack in Lianyuan Steel, measurement and analysis are carried out on the quality of liquid steel, overheating degrees, inlet and outlet temperature of water, mould powder properties, surface fluctuation, and mould copper wall. The main reason is that: the high level of the sulfur content of some steels made w(Mn)/w(S) ratio 28.8；inlet temperature of water decreases to 25℃ after stop production, and then rapidly increases to 30-32℃ when production recovers. The basicity of mould powder changes fluctuate. Minimum value reaches 1.1, which leads to vitrification of powder and high heat conductivity. Surface fluctuation can reach as high as 6-7mm, which leads to inflow inhomogeneity of mould powder and affects heat transfer. In addition, the scratch on the surface of mould copper wall results into defective contact, making the local temperature higher. The corresponding measures are put forward. The longitudinal crack rate of No.1 machine in Lianyuan Steel decreases from 0.50% to 0.024%。