Electroslag remelting with all-fluoride low conductivity slags

The electrical conductivity of liquids in the composition ranges CaF₂ + 0 to 12 wt pct AIF₃; CaF₂ + 0 to 20 wt pct LaF₃; and CaF₂ + 0 to 30 wt pct YF₃ has been determined at 1500° and 1600°C. It is deduced from the conductivities and the form of the phase diagrams of these systems that CaF₂ + 20 wt pct YF₃ is the optimum all-fluoride composition for electroslag melting or welding high melting point materials. It is demonstrated that pure iron, AISI 4340, AISI 321, and Hastelloy-X may all be electroslag melted without arcing through this slag using 60 Hz power. However, the initial postulate is confirmed in that only those materials with liquidus temperatures below that of the phase precipitated on freezing the slag can be made into ingots with good surface quality. The use of this slag in electroslag welding pure iron is investigated. It is inferred from the results that the slag composition chosen could probably be used to electroslag weld thick sections of titanium. Formerly Student in the Department of Metallurgy, University of British Columbia.