Metallurgy of the Electroslag Remelting Process

Whereas VAR needs vacuum for refining, in ESR the consumable electrode is dipped into a pool of slag in a water-cooled mold. An electric current (usually AC) passes through the slag, between the electrode and the ingot being formed and superheats the slag so that drops of metal are melted from the electrode. They travel through the slag to the bottom of the water-cooled mold where they solidify. The slag pool is carried upwards as the ingot forms. The new ingot of refined material builds up slowly from the bottom of the mold. It is homogeneous, directionally solidified and free from the central unsoundness that can occur in conventionally cast ingots as they solidify from the outside inwards. 

Generally the ESR process offers very high, consistent, and predictable product quality. Finely controlled solidification improves soundness and structural integrity. Ingot surface quality is improved by the formation of a solidified thin slag skin between ingot and mold wall during the remelting operation. This is why ESR is recognized as the preferred production method for high-performance superalloys that are used today in industries such as aerospace and nuclear engineering as well as for heavy forgings. Ingots are obtained with purity levels that were unheard of some years ago. Other branches of engineering are following the examples of the “high-tech” pacesetters and insist on new, high purity levels that can be obtained from ESR with the latest, most sophisticated equipment.