ESR or electro slag remelting (also known as electro flux remelting) is a process used for remelting and refining of steels and special alloys which are used for critical applications in aircraft, thermal and nuclear power plants, defense hardware, etc.[1]
Electro Slag Remelting uses highly reactive slags (CaF is the main component) to reduce the amount of type A sulfide present in biometal alloys. It is a common practice in European industries. ESR reduces other types of inclusions as well, and is seen as an alternative to the vacuum arc remelting method that is prevalent in US industries.