Influence of ingate design on macrosegregation severity in a large-size steel ingot

A 128 MT high-strength steel ingot was modelled using the finite element method. The thermal and thermomechanical behavior of the metal during solidification is considered in the simulations. The accuracy of the model was validated with experimental results of macrosegregation. Cases with a U-shape, V-shape, and H-shape ingate were investigated. The results for each case are analyzed to assess the influence of fluid flow and solute transport, during mold filling and solidification, on the macrosegregation profiles. The results of this study are used to determine an effective ingate design to improve the quality of the cast ingots. The analysis reveals and quantifies the impact of liquid metal flow field on macrosegregation. The influence of the opening angle of the ingate in limiting the well-known hump effect is demonstrated and the optimum angle determined. The longer solidification time, resulting from change in geometry, improved feeding and reduced both shrinkage and the risk of centerline porosity. The high velocity generated in the hot top region by the V-shape geometry promoted stronger residual flow and extended the isotherms further into the body of the ingot. Both the V-shape and H-shape designs demonstrated reduced macrosegregation in the upper section of the ingot.