Effect of soft reduction process on segregation of a 400 mm thick high-alloy steel slab

During the solidification of high-alloy steel (0.4C-1.5Mn-2Cr-0.35Mo-1.5Ni), the high temperature gradient of solidified shell as well as the columnar crystal development would contribute to the centre segregation and cracking due to the high carbon and alloy contents. The effect of soft reduction process on the segregation of a 400 mm thick high-alloy steel slab was analysed. Industrial trials in a steel mill were performed combining with segregation analysis. The inner quality of the high-alloy steel slab produced through the optimised soft reduction procedures and had a significant improvement in centre segregation. The reduction amount is increased from 20% of solid phase fraction, to avoid the segregation due to the long liquid core, and the reduction rate is deceased from 1.35 to 0.88 mm/m as well. This operation would contribute to the symmetrical distribution of solute element and decrease the segregation to avoid the cracking. An obvious improvement in centre segregation to mainly 1.0 class of high-alloy slab after procedure optimization was achieved. The quality improvement of slab would ensure the quality of downstream forging.