Electroslag remelting of type 316 stainless steel

Comments on oxide inclusion formation/removal in the ESR process

“…Thermal models of the process generally suggest that there is minimal superheat of the liquid metal on the electrode tip, estimated at 20–30 K. If this postulate is correct, and most of the chemical reactions take place at this site we would expect the Al/O contents to reflect the lower temperature range, around 1650 K–1750 K independent of furnace size but alloy dependent. The observed Al and O contents of ingots made using slags with a high-alumina activity in small furnace practice show values equivalent to reaction at 1950–2100 K [16,25,48,50]; in large furnace practice, the same values are equivalent to 1700–1850 K [4,26,51,52]. The amount of precipitated alumina in the ingot is hence a function of the reaction temperature, which accounts for the observation that the oxygen contents of ingots made in small furnaces are generally higher than those made in industrial furnaces when processing the same alloy through the same slag.…”

“…Early reports of results on the ESR process investigations made the assumption that all electrode inclusions are dissolved by the slag [10][11][12][13], a proposition which has been the basis for several studies on small ingots [14][15][16]. The issue is clouded by the definition of inclusions, which in many cases is taken to include sulphides and nitrides in addition to oxides, although there is a substantial difference in the behaviour of oxide-based inclusions and of inclusions based on sulphur or nitrogen.…”