A Three-Dimensional Comprehensive Model for Prediction of Macrosegregation in Electroslag Remelting Ingot

摘要

A transient three-dimensional (3D) comprehensive model is established to understand the macrosegregation in the electroslag remelting (ESR) process. The electromagnetism, two-phase flow and heat transfer are included. The volume of fluid (VOF) approach is employed to trace the metal droplet. The solidification is modeled by an enthalpy-based technique. The solute transport is analyzed by the continuum mixture model. A reasonable agreement is obtained between the experiment and simulation. The results indicate that the liquid composition in mushy zone becomes enriched in Ni. The interdendritic metal with a higher Ni is replaced by the Ni poor metal carried by the downward flow in the pool. The Ni composition accumulates at the pool bottom and the concentration increases with time. The species movement is dominated by the thermal buoyancy because of the forced cooling. A negative segregation in the lower part and a positive segregation in the upper part are formed in the ingot. Thanks to the rapid solidification, the Ni is immobilized before moving to the other place resulting in a lower segregation level. The segregation becomes severer with the increasing current. The maximal positive and negative segregation indexes increase from 0.02742 to 0.03226 and from -0.01346 to -0.01561 with the current ranging from 1000 A to 2000 A.