Numerical Analysis of Solidification and Macrosegregation During the Hot Topping Process of H13 Steel Electroslag Remelted Ingot

A transient multi-physics coupling model is developed to investigate solidification behavior and macrosegregation patterns during the hot topping process of H13 steel electroslag remelted ingots. The model integrates electromagnetic effects, two-phase flow, heat transfer, and solute transport with redistribution. The model’s validity is verified through a laboratory experiment. Key findings reveal that the superheated slag experiences rapid cooling with the current reduction. This causes the top surface of the ingot crown to solidify prior to its interior, forming an isolated liquid region. With the hot topping duration extending from 0 to 16 minutes, the slag cooling rate decreases from 1.70 to 0.25 K/s, accompanied by a remarkable reduction in depth and volume of the isolated liquid region. The isolated liquid region is eliminated at the 16-minute hot topping process. However, prolonged hot topping aggravates the positive segregation at the ingot crown. The ingot utilization rate for carbon segregation index of < 6 pct declines from 89.31 to 88.00 pct, while the carbon range increases from 0.05461 to 0.07887 pct. The hot topping process effectively reduces the shrinkage risk but aggravates solute segregation. Determining the optimal hot topping duration requires careful balancing between minimizing head cropping (by eliminating shrinkage cavities) and maintaining acceptable composition uniformity in the ingot crown.