Resmelting

Resmelting, also called remelting, is the process of melting a metal that has already solidified, typically to refine its composition, homogenize its microstructure, or recover material from scrap. It is used in secondary metallurgy and in closed-loop recycling to produce consistent ingots, billets, or slabs.

Common methods include vacuum arc remelting (VAR), electroslag remelting (ESR), and vacuum-induction melting (VIM). In VAR, a consumable electrode is melted in a water-cooled copper crucible under a vacuum to produce a purified ingot. ESR uses a molten slag to remelt the electrode or bore, yielding an ingot with controlled cleanliness and grain structure. VIM involves melting in a high-purity furnace to achieve chemical homogenization and precise alloying. All methods may employ protective atmospheres and degassing to reduce oxygen, hydrogen, and nitrogen pickup and to remove inclusions.

The main goals of resmelting are to improve chemical homogeneity, reduce impurities and segregations, refine grain structure, and tailor alloy composition. It is widely applied to steel and specialty alloys (including stainless steels and superalloys), aluminum and copper alloys, and precious metals. It also enables reclaiming and upgrading recycling streams, producing high-purity ingots for subsequent processing.

Challenges include energy intensity, potential oxide or inclusion formation, economic cost, and scale limitations. Process control is essential to prevent contamination and to achieve desired microstructures. Environmental considerations focus on emissions and slag management, particularly in large-scale operations.

See also: remelting, secondary metallurgy, recycling metallurgy.