THE MACROSCALE SIMULATION OF REMELTING PROCESSES

Vacuum are remelting and electroslag remelting processes are used to p roduce large (five tonne) insets of nickel-based superalloys, titanium alloys, and other high-value-added alloys. The remelting processes pr ovide controlled solidification conditions capable of producing extrem ely uniform chemistry and microstructure; however, the con sequences o f a single defect are potentially so great, that process improvements are being vigorously pursued by the Specialty Metals Processing Consor tium. The ultimate modelling goal is the realistic description of the liquid-solid mixed-phase region of the ingot (''mushy zone''), so that solidification defects such as freckles, macrosegregation, and solidi fication white spots can be avoided. Reaching this goal requires a num erical strategy capable of yielding not only accurate temperatures at the macroscale, but also accurate temperature gradients. The numerical procedure also requires thermophysical-property data for the alloy an d some furnace data (such as contact resistance at ingot-crucible inte rfaces) as well as characterization of the heat sources.