Formation and control of longitudinal cracks in hypoperitectic steel slabs

Hot delivery and charging techniques can significantly reduce energy consumption, carbon emissions, and the production cycle of products. The defect-free slab is the precondition of this techniques. Herein, the morphological characteristics of the longitudinal cracks were described in detail. The actual phase transition process and solidification shrinkage behavior were analyzed considering the effect of alloy elements. Due to the unreasonable submerged entry nozzle (SEN) structure, the vertical heat transfer is not optimal around the meniscus. When the gap cannot be filled with sufficient liquid slag, an air gap is easily formed between the solidified shell and the mould plates. The effect of uneven solidification and stress concentration on the crack formation will be enlarged by the air gap. A novel SEN with a reasonable structure can significantly improve the thickness of the liquid slag layer and solidification uniformity, and decrease the crack sensitivity of the steel.