Vacuum Arc Remelting Furnace, this is a consumable electrode remelting process performed inside a vacuum chamber. Exposure of molten metal droplets to vacuum reduces free gas content in the steel providing a cleaner product with little segregation. Consistently higher yields and reproducible metals are assured through fully automated computer/load cell control throughout the remelt process eliminating the need for operator intervention. The end product is a dense ingot with minimum segregation and very low hydrogen and oxygen levels.
The VAR process involves the melting of an electrode by a controlled DC arc in a vacuum environment. The arc is established between the negative consumable electrode (cathode) and the crucible base (anode) and quickly forms a molten pool of metal. The gap between the melting electrode and metal pool (arc gap) is precisely maintained and a controlled melt rate is established.
An advanced computer control system maintains the melt rate and arc gap utilizing custom designed algorithms taking into account measurements from the load beam weighing system, measurements of the furnace voltage, and measurements of the number of drip (drop) shorts.
Refining of the metal occurs as the metal droplets falling through the arc gap are exposed to the vacuum environment and the extreme temperatures of the arc zone. This causes removal of dissolved gasses, vaporization of tramp elements, and improvement in oxide cleanliness.
Because of the water-cooled crucible, the molten pool of metal formed by the metal droplets is solidified in a directional fashion. When the melt rate and arc gap are correctly controlled this controlled solidification prevents macrosegregation and reduces the amount of microsegregation thereby enhancing the material properties of the solidified ingot.
Toward the end of the process the power is gradually reduced providing a controlled hot top maximizing the yield of useful product.

Induction Vacuum Arc Remelting furnace

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