Sulfur—Its Effects, Removal, or Modification in Vacuum Melting

Abstract

Sulfur has long been recognized as one of several elements causing considerable property, difficulty in vacuum melting. Once introduced, usually via raw materials, traditional vacuum melting techniques must be modified to reduce sulfur to acceptable levels. Individual effects of sulfur on certain nickel, cobalt, and iron base alloys were discussed. Techniques for the removal of sulfur during vacuum melting were discussed including some thoughts on the kinetics of desulfurization. Among the sulfur removal techniques indicated are the following: Slag Base Metal Reactions Gaseous Purge Techniques Rare Earth Metal or Alloy Innoculation. The paper gives some new data with regard to the desulfurization of nickel base superalloys (notably Inco 901) by addition of elemental cerium in vacuum induction melting. Desulfurization levels to 0.001 wt% were achieved without any loss in property response or microstructural degradation.