Vacuum Arc Furnace

With the emergence of such precise industries as space, rocket science, nuclear energy, etc., vacuum furnaces became widespread. The furnaces are used for melting high-quality and high-alloy steels: stainless, structural, ball-bearing , refractory and heat-resistant alloys .

Vacuum arc furnaces provide such advantages as a low content of gases and nonmetallic inclusions in the alloy, high uniformity and density of the ingot due to directional crystallization of liquid metal, and significantly improve the properties of the metal.

Due to their design (use of a water-cooled case and stainless steel) in vacuum furnaces it is possible to achieve special conditions: the highest temperatures up to 2000 ° C and high pressures. Vacuum in furnaces allows for a wide range of heat treatments: drying, sintering, smelting, etc. The temperature regime can be controlled both manually and using a regulator.

At the end of the 19th century, metallurgy began to increasingly use the energy of electric current to produce the highest quality alloys. The discovery of the electric arc and the possibility of melting metals is associated with the name of the Russian physicist V.V. Petrov, in 1802 he created the largest galvanic battery of copper-zinc cells. A patent for the first electro-thermal furnace in 1853 was obtained by the French engineer Pichon.

In 1898 , the Frenchman P. Héroux received a patent for an electric furnace with electrodes located above the bathtub.

In 1909 , Russia began the industrial production of steel in electric furnaces; in the first year, 190 tons of high-quality steel were smelted in an electric arc furnace of the Eru construction located at the Obukhov plant in St. Petersburg. In 1911, 1,120 tons were smelted, and by 1913, 4 furnaces were already operating in factories in Russia, producing 3,500 tons of steel per year.

In 1915 , at the Motovilikhinsky plant in Perm, the first single-phase resistance steelmaking furnace was launched with heating the bath from the coal rods above it, created by Russian engineers S. S. Shteinberg and A. F. Gramolin. Subsequently, similar stoves successfully carried out military orders during the First World War.

The release of thermal energy in arc furnaces is due to the electric arc, which is a form of arc discharge in gases. With such a small arc volume, very high temperatures can be obtained due to the concentration of power in the volume. A high concentration of heat and power in the arc allows the metal to be heated in short periods of time. There are 2 types of furnaces, direct and indirect action. In direct-acting furnaces, an arc burns between a metal and an electrode; in indirect-effect furnaces, metal heating occurs by radiation; an arc burns between electrodes. Heat transfer conditions are much better in direct-acting furnaces, in which case the hot spot is located as close to the metal as possible. Part of the heat from the high temperature zone is absorbed by the metal, the arch of the furnace has a screening effect, this allows you to concentrate more power in the arc and successfully conduct heating to high temperatures. Direct-acting arc furnaces are not widely used for melting expensive metals with a low evaporation temperature, since it evaporates near the metal surface. But higher evaporation temperatures and lower cost of ferrous metals make the disadvantage of a direct-acting furnace not significant, considering the advantages of this type, such as: the ability to carry out high-temperature processing and greater productivity.

Arc furnaces are widespread in the iron and steel industry and ferroalloy industry. There are two types of arc vacuum furnaces, with a consumable and non-consumable electrode. In the first type, the arc burns between the consumable electrode and the metal bath, in the second between the graphite electrode and the molten metal.

Advantages: the possibility of non-oxidative heating of metals; in many cases, the use of low furnace pressure instead of protective and inert gases is more economical; high metal purity due to vacuum; an increase in the operating temperature in the furnace due to the protection of heaters from oxidation - the absence of contact of liquid metal with ceramic materials.

Disadvantages: limited metal residence time in the liquid state, which significantly reduces the refining capabilities of the vacuum.

Literature

• Kazachkov E.A., Chepurnoy A.D. Vacuum-arc remelting 1992
• Linchevsky B.V., Sobolevsky A.L., Kalmenev A.A. Metallurgy of ferrous metals 1986.