MODELING MACROSEGREGATION DURING ELECTROSLAG REMELTING OF ALLOY 625

摘要

A numerical model of ESR is used to examine the effects of ingot diameter, process current levels, and initial composition on macrosegregation in alloy 625. Composition variations are made within the standard ranges for alloy 625 to evaluate their effect on buoyancy driven flows. Overall steady state macrosegregation, along with composition distributions are compared, to identify processing conditions that best ameliorate this defect. The composition distributions are analyzed to illustrate how macrosegregation affects the ability to meet the compositional specification. As expected, increasing the ingot size from the standard processing condition of 50 cm (20 inch) to 76.2 cm (30 inch) increases the segregation level overall and at the centerline. The segregation tends to decrease with decreasing mushy zone 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.