Influence of a rotating electrode on the droplet formation and the refining effect in the electroslag-remelting process

• Applicants: Professor Dr.-Ing. Bernd Friedrich; Professor Dr.-Ing. Herbert Pfeifer
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: from 2016 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 309143753

During the electroslag remelting process (ESR) a metal ingot is used as an electrode which is gradually molten in a slag layer. After passing through the slag layer, the molten metal solidifies in a controlled structure within a water cooled copper mold. During this process the metals degree of purity is improved by chemical and physical refining mechanisms. Compared to ingot casting less macro segregation can be observed, due to the smaller volume of liquid metal and the inductive stirring. Furthermore micro segregation is reduced, as the local cooling rates are fairly low. At the interface between slag and the copper mold a 1 to 3 mm thick slag skin solidifies. This layer reduces both the heat loss at the copper mold and the solidification rate in the metal pool.The present research project is focused on understanding fundamental mechanisms of removing non­metallic inclusions, the evolution of controlled columnar solidification and the formation of the slag skin. The insights gained will then be applied to a remelting process using a rotating metal electrode, which is a promising process innovation that has barely been investigated so far. Due to the centrifugal force acting on the liquid metal due to the rotation at the electrode surface, the size of metal droplets is reduced while the droplets specific surface and the residence time in the slag are increased.By carrying out experimental and numerical investigations understanding the refining mechanisms and non-metallic inclusion distribution is the objective of this study. This is to be achieved by examining the nickel based Alloy 718 targeting an improved degree of cleanliness and controlled solidification in a reproducible manner.

• DFG Programme: Research Grants