REDUCING DEFECTS IN REMELTING PROCESSES FOR HIGH-PERFORMANCE ALLOYS

Defect reduction is one of the most important goals in continuing rese arch to improve remelting technologies, such as vacuum arc remelting, electroslag remelting, or hearth melting (plasma or electron beam), of specialty alloys. Ingot defects may originate from several sources in these processes, such as foreign materials in the melt stock or elect rode, drop-in material from the furnace interior, and solidification d efects. Laboratory- and industrial-scale melting experiments are used by Sandia National Laboratories and the Specialty Metals Processing Co nsortium to determine relationships between melt-processing conditions and defect formation. Examples described here include freckle formati on, a solidification defect in large insets of alloy 625 (electroslag remelting), and alloy 718 (vacuum are remelting). These examples demon strate how integrated melting experiments, process modelling, and inse t analysis can guide the control of melting conditions to reduce defec ts.