Investigation of Slag Compositions and Pressure Ranges Suitable for Electroslag Remelting under Vacuum Conditions

Abstract

It is well known that high contents of oxygen and hydrogen in creep resistant structural steels like 21CrMoV5-7 have negative influence on a variety of material properties. To investigate the refining ability of various slag compositions under reduced pressure multiple experiments were performed in a 40 kW vacuum-induction furnace with the aim to ensure minimal oxygen and hydrogen contents. With regard to slag evaporation, different mixtures of fluorides and oxides as well as pure oxide systems were utilized. The pressure was varied in the range of 5 and 700 mbar. The behavior of different slags under vacuum conditions as well as the results of various chemical analysis were used to evaluate the application of the investigated slag systems for ESR under vacuum conditions. Special attention was given to easily oxidizable alloy elements as aluminum and silicon, the amount of oxygen and hydrogen as well as on formation of non-metallic inclusions.