Vacuummelted

Vacuummelted refers to metal that has been melted under vacuum conditions to prevent oxidation and contamination, yielding high-purity ingots and more controlled microstructures. The term is not standard in metallurgical literature; more common descriptors are vacuum melted or specific processes such as vacuum induction melting (VIM) and vacuum arc remelting (VAR).

In vacuum melting, the material is melted in a high- or ultra-high vacuum furnace using consumable electrodes or crucibles, with refining and solidification occurring under reduced pressure. Some variants employ partial vacuum with controlled degassing steps to remove dissolved gases. The goal is to minimize interactions with atmospheric gases and to improve chemical cleanliness of the final product.

The primary benefits include reduced uptake of oxygen, hydrogen, and nitrogen, lower inclusion content, improved chemical homogeneity, refined microstructure, and reduced porosity. These advantages contribute to enhanced high-temperature properties and reliability in critical applications, especially where impurity control is essential.

Common applications and materials studied or produced by vacuummelting include nickel-based superalloys, titanium and its alloys, aerospace-grade steels, and certain refractory metals. These materials benefit from the improved purity and microstructural control when performance and integrity are paramount.

Relation to other methods: vacuum melting provides the foundational environment for processes like VIM and VAR. Differences among these methods lie in heat sources, furnace design, and specific impurity profiles achieved, though all aim to reduce contamination by performing melting under vacuum.

Limitations and considerations include high capital and operating costs, energy intensity, and the need for stringent equipment and process controls. The technique is not universally required for all metals and is chosen when impurity reduction and microstructural refinement justify the investment.