Dr. Dmitri Kopeliovich
Electroslag Remelting (ESR) is a process of remelting a consumable electrode utilizing the heat generated by an electric current passing through a molten slag between the electrode and the solidifying ingot.
The consumable electrods are as cast or forged cylindrical parts made of an alloy to be remelt.
An electroslag remelting process (ESR) starts when the lower tip of a consumable electrode is immersed into a pool of molten slag.
The premelted slag possessing electrical conductivity is located on the water-cooled mold base connected to a power supply.
The electric current (commonly AC) passing through the the slag keeps it at high temperature, which is about 360ºF (200ºC) higher than the melting point of the remelted metal.
The electrode tip is heated by the hot slag and starts to melt forming droplets of liquid metal, which disconnect from the electrode and sink through the slag layer.
The slag composition is based on calcium fluoride (CaF2), lime (CaO) and alumina (Al2O3).
The slag composition provides the following properties:
The molten steel in form of both liquid film on the electrode tip and descending droplets contacts with the slag and get refined due to desulfurization and removal of non-metallic inclusions (sulfides and oxides).
The droplets enters the molten steel pool, bottom of which is progressively solidifying. The water-cooled copper mold provides relatively high gradient of temperature resulting in high solidification rate. Solidification front is moving upwards (unidirectional solidification) forming sound homogeneous metal structure.
The ingot has a good surface quality due to a thin slag film covering it.