The inaugural vacuum consumable arc furnace emerged in the United States in 1950. This type of electric furnace harnesses the energy of an electric arc to melt metals within a vacuum chamber. Its primary applications lie in melting reactive and refractory metals like titanium, zirconium, and molybdenum, as well as heat-resistant, stainless, tool, and bearing steels. In the early 1950s, it was employed for remelting high-temperature alloys, demonstrating remarkable superiority and establishing itself as a pivotal method for refining high-temperature alloys and specialty steels.
During the formation and descent of molten droplets from the electrode's lower end, specific physical and chemical reactions transpire, enabling the elimination of some gaseous impurities. The vacuum consumable arc furnace is characterized by its smelting process conducted within a water-cooled copper crystallizer, circumventing the issue of metal contamination stemming from interactions with refractory materials. Concurrently, the molten steel solidifies and crystallizes under intense water cooling, yielding a uniform, shrinkage-free, and dense ingot. The smelting process is driven by a DC low-voltage, high-current arc.
Initially, an arc is struck between the lower end of the consumable electrode and the crystallizer, creating an arc plasma zone with exceptionally high temperatures. This zone facilitates the melting of the electrode's end. Under vacuum and high-temperature conditions, non-metallic inclusions within the electrode, such as oxides and nitrides, undergo dissociation or carbon reduction, achieving further purification. The vacuum consumable arc furnace process effectively removes gases, non-metallic inclusions, and certain low-melting-point harmful impurities, significantly enhancing the material's cold and hot processing properties, plasticity, mechanical attributes, and physical characteristics. Notably, it improves the disparity between longitudinal and transverse properties, crucial for ensuring material stability, consistency, and reliability.
In essence, vacuum arc furnaces boast the following features:
Uncontaminated Remelting: Under vacuum conditions, the absence of slag or other materials between the consumable electrode and the ingot ensures that the remelted material remains uncontaminated.
Effective Degassing: During vacuum arc furnace smelting, the metal is directly exposed to the vacuum, resulting in excellent degassing effects, efficiently removing gases like hydrogen, nitrogen, and oxygen.
Pure Internal Structure: Non-metallic inclusions in the smelted metal, being lighter, float atop the molten metal, leading to an exceptionally pure internal ingot structure.
Uniform Ingot Structure: The rapid cooling rate within the water-cooled copper crucible prevents segregation, resulting in a uniform ingot structure.
High-Grade Alloy Steel Smelting: The vacuum environment allows for the addition of substantial amounts of alloying agents, enabling the smelting of high-grade alloy steels.
Enhanced Productivity and Cost Efficiency: The short tapping time boosts equipment productivity and reduces production costs.
Currently, vacuum arc furnaces are available in capacities ranging from 15 to 200 tons. The heating, degassing, slag treatment, and alloy adjustment processes are all performed continuously under vacuum. The fully enclosed processing station, coupled with a steam jet vacuum pump, provides a clean smelting environment with no pollution to the surroundings.
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