Macrosegregation During Electroslag Remelting of Alloy 625

A numerical model of electroslag remelting is used to examine the effects of ingot diameter, mushy zone permeability, process current levels, and initial composition on macrosegregation in alloy 625. Composition variations are made within the standard ranges for alloy 625 to alter the solutal contribution to buoyancy-driven flows and macrosegregation. Average steady-state macrosegregation and radial composition distributions are compared to identify processing conditions that best ameliorate this defect. Also, a novel approach to evaluate macrosegregation of an ingot is used, comparing the composition distribution to the alloy specification. As expected, increasing the ingot size from 51 cm (20 in.) to 76 cm (30 in.) increases the overall segregation, especially at the centerline. The segregation tends to decrease with decreasing interdendritic liquid velocity and sump depth. Processing ingots with a low current and an initial composition in the low end of the specification range is the best choice to reduce macrosegregation. (C) The Minerals, Metals & Materials Society and ASM International 2014