Working Principle and Characteristics of Vacuum Consumable Arc Furnace (VAR)

Working Principle and Characteristics of Vacuum Consumable Arc Furnace (VAR)

The world's first vacuum consumable arc furnace was born in the United States in 1950. A vacuum consumable arc furnace is an electric furnace that uses the energy of an electric arc to melt metal in a vacuum chamber. Vacuum consumable arc furnaces are mainly used to melt active metals and refractory metals such as titanium, zirconium, and molybdenum, and are also used to melt heat-resistant steel, stainless steel, tool steel, and bearing steel. In the early 1950s, it was used to remelt high-temperature alloys, showing excellent superiority and becoming one of the important means of remelting high-temperature alloys and special steels.

1. Working Principle of Vacuum Consumable Arc Furnace

During the formation of molten droplets at the lower end of the electrode and the process of molten droplets falling, certain physical and chemical reactions occur, which can remove part of the gas impurities. The process characteristics of the vacuum consumable arc furnace are that the smelting is carried out in a water-cooled copper crystallizer, which overcomes the disadvantage of metal contamination caused by the interaction between metal and refractory materials. At the same time, the molten steel is solidified and crystallized under a highly water-cooled state to obtain a uniform, shrinkage-free and dense ingot. The smelting process of vacuum consumable arc furnace is carried out under the action of DC low voltage and high current arc.

First, an arc is ignited between the lower end of the consumable electrode and the crystallizer, and an arc plasma zone is formed between the lower end of the consumable electrode and the molten pool. This zone has an extremely high temperature, which can make the end of the consumable electrode melt here first. As some non-metallic inclusions in the consumable electrode, such as oxides and nitrides, are dissociated or removed by carbon reduction under vacuum and high temperature conditions, the purpose of further purification is achieved. Since the vacuum consumable arc furnace process can remove gas and non-metallic inclusions, as well as some harmful impurities with low melting points, the cold and hot processing properties, plasticity and mechanical properties, and physical properties are significantly improved. In particular, the difference in longitudinal and transverse properties is improved, which is extremely important for ensuring the stability, consistency and reliability of material properties.

In summary, vacuum arc furnaces have the following characteristics:

(1) Under vacuum conditions, there is no slag or other materials between the consumable electrode and the ingot, so the smelted material is not contaminated during remelting.

(2) During vacuum arc furnace smelting, the smelted metal is directly exposed to the vacuum, so the degassing effect is very good, and gases such as hydrogen, nitrogen, and oxygen can be effectively removed.

(3) During vacuum arc furnace smelting, the non-metallic inclusions in the smelted metal have a light specific gravity and always float on the top of the molten metal, which results in a very pure internal structure of the ingot.

(4) Since the ingot is cooled in a water-cooled copper crucible, the cooling rate is very fast, which results in a uniform internal structure of the ingot without segregation.

(5) Under vacuum conditions, a large amount of alloying agents can be added, so high-grade alloy steel can be smelted.

(6) The short tapping time improves equipment productivity and reduces production costs.

Currently, the capacity range of vacuum arc furnaces is between 15-200 t. The heating, degassing, slag treatment and alloy adjustment processes are all carried out continuously under vacuum. The fully enclosed processing station combined with the steam jet vacuum pump provides a clean smelting equipment with no pollution to the surrounding environment.