November 13, 2025
The vacuum electric arc furnace represents a specialized type of industrial furnace designed to smelt metals under vacuum conditions. Operating on the principle of vacuum arc smelting, it utilizes high current and low voltage to achieve a short arc operation, which is essential for its unique smelting process.
At the heart of the vacuum arc furnace lies the phenomenon of gas arc discharge. This process is characterized by an extremely low voltage between electrodes, yet it allows a relatively large current to pass through the gas. Consequently, the temperature within the arc zone soars to approximately 5000K. The large current density observed in this setup stems from two primary sources: thermionic emission and self-emission of electrons.
Around the negative electrode, a layer of positive ions forms, creating a strong electric field. This field prompts the cathode to automatically emit electrons, which then collide with gas molecules between the two electrodes, ionizing them. This ionization process generates additional positive ions and secondary electrons. Under the influence of the electric field, these charged particles collide with the cathode and anode, respectively, producing intense heat. Notably, the cathode's temperature remains lower than that of the anode because a portion of the energy is expended in electron emission. Additionally, the recombination of some positive ions and electrons contributes to the high temperatures observed.
Vacuum arc smelting is a short arc operation that typically involves an arc voltage ranging from 22 to 65 volts, with a corresponding arc length of 20 to 50 millimeters (the latter applicable for larger ingots). This setup ensures efficient and controlled smelting within the vacuum environment.
The journey of vacuum arc furnaces began with the successful platinum wire smelting experiment in 1839. However, it took over a century for researchers to delve into the smelting of refractory metals. By 1953, vacuum electric arc furnaces had made their way into industrial production. Until 1956, the United States and several European countries continued to smelt titanium in non-expendable furnaces, while 1955 marked the beginning of steel production using expendable furnaces. Around 1960, the weight of steel ingots produced by consumable furnaces exceeded 30 tons, signaling a significant advancement. Today, the vacuum consumable furnaces manufactured by companies like Kangsai exemplify this development trend, featuring shared main power supplies, vacuum systems, and automatic control systems between two furnaces to enhance production efficiency and equipment utilization.
Heat treating workpieces or materials in a vacuum environment offers numerous advantages. It extends the service life of tools and molds by preventing oxidation and decarburization, resulting in a bright surface finish, minimal deformation, energy savings, and pollution-free operations. Moreover, vacuum heat treatment can alter the mechanical and metallurgical properties of materials, enhancing their overall performance.
Vacuum melting furnaces are primarily employed for smelting reactive and insoluble metals, hard alloys, magnetic materials, and stainless steel. Operating under low pressure (decompression) conditions, these furnaces offer several key benefits:
In summary, vacuum electric arc furnaces leverage the principles of vacuum arc discharge to offer a sophisticated and efficient means of smelting metals, with numerous advantages in terms of material quality, production efficiency, and environmental impact.
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