Vacuum Arc Remelting (VAR) process

Vacuum Arc Remelting (VAR) is designed to meet the needs of the aerospace, energy and nuclear industries for metal alloys for critical applications.
This process is based on refining liquid metal exposed to vacuum and controlling its solidification rate. It applies to reactive titanium or zirconium alloys, which it purifies under vacuum without contact with casting refractories, as well as to steels and superalloys, for which it improves inclusion cleanliness. The remelted cylindrical ingots have a mass of several tons.

The molten metal, falling from the primary load (consumable electrode), feeds the secondary ingot which solidifies in contact with the wall of a cooled ingot mould.
The heat source necessary for the melting is an electric arc maintained between the tip of the electrode and the top of the ingot which forms progressively within the Cu mould.
The arc operates with high intensity DC (5 to 40 kA) and low voltage (a few dozen volts). In some cases (systematically for Ti or Zr melting), the furnace is equipped with coils designed to create a vertical magnetic field in order to confer the arc a good stability.

This process has been studied intensively for more than 30 years by IJL researchers, who have founded and run a consortium with industrial users (Aubert&Duval, Timet, Framatome, Aperam Alloys, etc.).
This "SOLAR Club", named after the simulation model developed at IJL and validated by all partners, has been the framework for 11 completed PhDs (plus two in progress).
The numerical simulation of the process aiming to its optimization is the basis of these studies, which also combines laboratory-scale experiments using the technical elaboration platform at IJL, and measurements on industrial furnaces by developing specific on-board installations.

Reference:

Title : Procédé de refusion à l’arc sous vide (VAR)

Authors: Alain Jardy (IJL), Isabelle Crassous (Framatome), Sylvain Charmond (Aubert&Duval), Vincent Descotes (Aperam Alloys), Stéphane Hans (Auvert&Duval), Yvon Millet (Timet)

Journal: Techniques de l’Ingénieur

Date of publication (online): January 2022

Link: https://doi.org/10.51257/a-v1-m7822

Image caption: (left) Vacuum Arc Remelting process - principle ; (right) remelted Ti alloy ingots