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The function and principle of the four steelmaking furnaces- EAF, AOD furnace, LF and VD furnace

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Description:This article introduces the working principle and function of EAF, AOD furnace, LF furnace and VD vacuum furnace respectively.

The principle and function of electric furnace, AOD furnace, LF furnace and VD vacuum furnace

Electric furnace

The electric furnace steelmaking method mainly uses arc heat, and the temperature in the arc action area is as high as 4000 °C. The smelting process is generally divided into melting period, oxidation period and reduction period. In the furnace, not only an oxidizing atmosphere but also a reducing atmosphere can be formed, so the efficiency of dephosphorization and desulfurization is very high.

Electric furnace steelmaking using scrap steel as raw material has less capital investment than the blast furnace converter method. At the same time, due to the development of direct reduction, metallized pellets are provided for electric furnaces to replace most scrap steel, thus greatly promoting electric furnace steelmaking.

Function: It is mainly used to smelt high-quality steel, alloy steel and stainless steel molten steel. It belongs to the first production process of smelting stainless steel. Its main function is to melt molten steel, dephosphorize and desulfurize.

The principle and function of electric furnace, AOD furnace, LF furnace and VD vacuum furnace

AOD furnace

The AOD furnace method (argon oxygen decarburization) refines stainless steel using advanced technology. It offers simple equipment, convenient operation, strong adaptability, low investment, and low production cost, making it widely used.

Operators inject molten iron from the blast furnace and molten steel from the electric furnace into the AOD furnace via a ladle. During smelting, they blow a mixed gas of O2, Ar, or N2 into the molten steel to decarburize it. This process adjusts the composition and temperature of the molten steel, producing qualified stainless steel materials.


The delivery and adjustment of the mixed gas during refining form one of the main systems of the argon oxygen furnace. The oxygen production workshop produces gas, which is transported into the gas storage tank near the workshop through pipelines. After metering, decompression, adjustment, and mixing, operators send the mixed gas into the furnace through the side gun according to the flow rate and proportion required by the process.

At the start of smelting, operators blow oxygen into the molten pool from the top furnace mouth using a double-layer water-cooled oxygen pipe for decarburization. During refining, they feed mixed gas into the furnace through a side gun installed on the side wall opposite the tapping hole and close to the furnace bottom.

When charging and tapping, they tilt the furnace body forward at an angle, positioning the tuyere above the liquid steel level. During normal blowing, the tuyere sinks deep into the molten pool. The tuyere’s central tube blows in a mixture of oxygen and argon or nitrogen. By adjusting the oxygen and argon ratio, they reduce the partial pressure of carbon monoxide, achieving decarburization and chromium preservation.

The AOD furnace tuyere is unique and gas-cooled. It has a double-layer sleeve structure. The outer tube passes argon or nitrogen to cool the tuyere, while the inner tube passes a mixture of oxygen and nitrogen or argon. Operators use the air mask ring’s flow control to ensure optimal operation. They can control the flow of the air mask ring’s central tube and the air mask ring from the main control room.

Using three side gun technology. It can enhance the oxygen supply intensity and improve the yield of metal materials, and this technology can shorten the AOD smelting time. The stable and reliable control system can reduce the consumption of gas and various raw materials in smelting, and obtain stable product quality.


The main function of AOD is to remove carbon and play the role of refining.

The principle and function of electric furnace, AOD furnace, LF furnace and VD vacuum furnace

LF furnace

LF furnace (LADLE FURNACE) is the ladle refining furnace, which is the main refining equipment outside the furnace in steel production. LF furnace generally refers to the refining furnace in the steel industry. In fact, it is a special form of electric arc furnace.

The refining of the LF furnace mainly relies on the white slag in the barrel. In a low-oxygen atmosphere (5% oxygen content), argon is blown into the barrel for stirring. The molten steel from the primary furnace is heated by graphite electrodes for refining.

Argon stirring accelerates the chemical reaction between slag and steel. Arc heating for temperature compensation ensures longer refining time. This reduces the oxygen and sulfur content in the steel. Inclusions are rated as O~O. Level 1 according to ASTM.

The LF furnace can work with an electric furnace to replace its reduction period. It can also cooperate with an oxygen converter to produce high-quality alloy steel. Additionally, the LF furnace is vital for controlling composition, temperature, and preserving molten steel in continuous casting workshops, especially for alloy steel.

The emergence of the LF furnace has created a new joint production line: LD-LF-RH-CC (continuous casting) for high-quality steel. The LF furnace handles most reduction and refining in this line. It processes nearly all steel grades, from special to common steel, using different process systems based on quality control needs. Among secondary refining equipment, the LF furnace offers the highest cost performance.

LF has the following characteristics:

① Desulfurization

②Temperature adjustment

③Precise composition fine-tuning

④ Improve the purity of molten steel


It mainly has the following functions:

  1. The LF furnace connects with the electric furnace, speeding up the production cycle of the electric furnace and improving the quality of electric furnace steel.
  2. The LF furnace connects with the LD converter, reducing and refining the converter steel. This connection improves steel quality and enables the production of new steel types.

(3) The LF furnace can strictly adjust the composition and temperature of molten steel, which is beneficial to the hardenability of steel and the continuous casting of special steel.

After being refined by AOD, it is refined in LF furnace, which belongs to secondary refining, and the reduction of inclusions ensures the purity of molten steel;

The principle and function of electric furnace, AOD furnace, LF furnace and VD vacuum furnace

VD vacuum furnace

The VD refining method treats molten steel using vacuum technology. Operators place the primary molten steel from an electric furnace or converter into a closed tank for vacuuming. They blow argon at the bottom of the ladle and stir it simultaneously.

After melting and preliminary blowing in electric furnaces and converters, they transfer the steel to a vacuum tank (vacuum chamber). Through bottom blowing argon stirring and vacuum degassing, they obtain pure molten steel.

The VD furnace typically pairs with the LF furnace. The LF furnaces adjusts the composition and temperature, while the VD furnace handles degassing, stirring, and other tasks. An oxygen lance on the VD furnace’s vacuum cover allows for smelting stainless steel, transforming it into a VOD furnace.


The VD furnace functions as a widely used vacuum refining equipment. It provides excellent degassing and deoxidation effects, effectively reducing the hydrogen and nitrogen content in steel. It removes oxygen in steel through carbon and oxygen reactions.

Additionally, it enables complete desulfurization through the reaction between slag and molten steel. The VD furnace also ensures uniform composition and temperature in the steel.

LMM YOTAI established in 2007. Our production technology comes from Japanese Yotai. As an experienced and international player in the refractories industry. We have succeeded in expanding both the breadth of its product range and the depth of its services. From raw material selection, refractory portofio & optimization, installation & services & recycle of used refractories on site to further reduce client’s Opex & Capex in refractory consumption per ton steel output, meanwhile improve product quality of client.

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