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在铸机内运行过程中,坯壳受到的应力作用是产生裂纹的外部因素。浇入结晶器的钢水因冷却而生成坯壳,铸坯逐渐收缩,其收缩过程分为过热度消失的液态收缩、凝固时的体积收缩和凝固后的线收缩及相变收缩等。结晶器凝固坯壳的收缩使坯壳与钢板形成较大的气隙,热阻相应也较大。由于传热不均匀,凝固速度不同,凝固坯壳厚度也不均匀。在结晶器内,由于铸坯横向温度不均匀,存在温度梯度,使凝固坯壳受到热应力;由于结晶器的摩擦作用,使凝固坯壳受到循环应
During the operation in the caster, the stress acting on the shell is an external factor causing the crack. The molten steel poured into the mold is cooled to form a blank shell, and the slab gradually shrinks. The shrinking process is divided into a liquid shrinkage that disappears when the degree of superheat disappears, a volume shrinkage when solidified, and a line shrinkage and a phase change shrinkage after solidification. Mold solidification shrinkage of the shell makes the shell and the steel sheet to form a larger air gap, the corresponding thermal resistance larger. Due to uneven heat transfer, different solidification rates, the thickness of the solidified shell is not uniform. In the mold, due to the uneven transverse temperature of the slab, there is a temperature gradient so that the solidified shell undergoes thermal stress; due to the friction of the mold, the solidified shell is subjected to a cyclic reaction