Slag Degassing for Electroslag Remelting Using Cold Start

Abstract

The effect of slag degassing prior to cold start electroslag remelting (ESR) was investigated using various heat treatments of a commercial 40CaF2 – 30CaO – 30Al2O3 slag. The slag was either degassed in a vacuum heat treatment furnace or in a box furnace in air. Vacuum heat treatment included partial pressure of Ar gas. Several temperatures, ramp rates and/or holding times were investigated for each condition and the pressure was monitored for the heat treatment in the furnace with controlled atmosphere. A research scale 200 kg capacity ESR furnace was used for the experiments along with 1018 steel and 316 stainless steel electrodes. Significant differences in ingot quality were related to the sidewall and the presence of pores which were primarily located near the bottom of the ingot. Adjustments in the heat treatment temperature for heat treatment in air eventually led to an ingot quality near that obtained using slag degassed under vacuum and/or in a controlled atmosphere.