Difference between Induction Furnace and Electric Arc Furnace

I. Overview of Electric Furnace

To analyze the difference between induction furnace and electric arc furnace, we must first introduce the concept of electric furnaces. The electric furnace is a general term for furnaces that use electric energy as the heat source for steelmaking. According to the difference in the way electric energy is converted into heat energy, electric furnaces can be divided into electro-slag remelting furnaces, induction melting furnaces, electron beam furnaces, plasma furnaces, and electric arc furnaces. More than 95% of the output of electric furnace steel in the world is produced by electric arc furnaces, so electric furnace steelmaking mainly refers to electric arc furnaces. Electroslag remelting furnaces, electron beam furnaces, and plasma furnaces are mainly used for the production of special steel, not suitable for the production of carbon steel and alloy structural steel. Induction melting furnace (medium frequency induction melting furnace is used for steelmaking) and electric arc furnace are suitable for producing carbon steel and alloy structural steel.

II. Comparative Analysis of Induction Furnace and Electric Arc Furnace

1. Comparison of Production Processes

(1) The production of an electric arc furnace can be conducted with the oxygen-blowing operation. Iron and steel materials with a high carbon (C), such as pig iron and iron castings, can be added when batching. The CO bubbles generated in the process of oxygen-blowing decarburization are vacuum chambers relative to [H] and [N] in the steel, which is conducive to the diffusion and discharge of [H] and [N] in the steel to the CO bubbles, with decarburization [C] and degassing functions;

(2) Oxygen blowing and lime slagging can be used for dephosphorization [P], which has the function of dephosphorization [P];

(3) [Si], [Mn], and [Cr] in oxygen-blowing oxidized steel can avoid chemical waste caused by these elements exceeding the standard;

(4) Argon blowing and stirring in an LF furnace can remove non-metallic inclusions in molten steel, with an inclusion removal function;

(5) During the operation of the LF furnace, alloy, and strong deoxidizing materials are added to the steel, which has the functions of deoxidizing [O] and composition adjustment;

(6) LF adds lime, with desulfurization [S] function;

(7) LF power transmission and temperature rise, with temperature adjustment function;

(8) The intermediate frequency furnace does not have the conditions for oxygen blowing [C], slag forming [P], and excessive [Si], [Mn], [Cr] elements in the oxidized steel, so it cannot control [C], [P], [Si], [Mn], [Cr] and other easily oxidized elements in the primary molten steel;

To sum up, the production process of electric arc furnace+LF furnace has the functions of de [C], de [P], de [O], de [S], temperature and composition adjustment, degassing, and inclusion removal, while the intermediate frequency furnace+LF only has the functions of increasing composition, de [S], de [O], degassing (the effect of argon blowing and degassing in LF furnace is poor), de inclusion and temperature adjustment. The intermediate frequency furnace can only be regarded as a steelmaking furnace. 

2. Comparison of Production Scale

The average smelting time of the ultra-high power energy-saving electric arc furnace with the rated capacity of 60MVA and 70t eccentric bottom tapping can be shortened to 40 minutes, and the annual steel output can reach 800000 tons, while the smelting time of the medium frequency furnace with the same capacity is 60 minutes, and the annual steel output is 530000 tons. The output of the medium frequency furnace is only 67% of that of the electric furnace.

3. Quality and Variety Comparison

(1) As the production process of electric furnace+LF furnace is different from that of medium frequency furnace+LF furnace, the quality is superior to that of medium frequency furnace, which can produce special steel such as bearing steel, oil well pipe, high-quality spring steel, while the medium frequency furnace can only produce common carbon structural steel with low-quality requirements;

(2) The composition of the electric furnace+LF furnace is easy to control, and the variety hit rate can reach above 99.5%, while the medium frequency furnace [C], [P] and alloy element ingredients cannot be adjusted when they are high, and the variety hit rate is low.

(3) Matching with continuous casting

The electric furnace+LF furnace can be one-to-one matched with the continuous casting, and the production rhythm is easy to control. The induction furnace is difficult to match with the continuous casting due to the long smelting time.

4. Production Cost Comparison

(1) The medium frequency furnace has high requirements for the steel materials used, mainly the medium and heavy returned qualified scrap, and the price is high; The electric furnace has strong adaptability to iron and steel materials, such as pig iron, solid steel, slag steel, light and thin materials, sponge iron, etc. The content of easily oxidized elements [C], [P], [Si], [Mn], and [Cr] in scrap iron can be appropriately relaxed and can be purchased according to the market price. The price difference can be controlled at more than 300 yuan/t. The consumption of scrap steel with poor quality has increased, but the total cost of steel has decreased. The cost difference is 61.2 yuan;

(2) The power consumption of the intermediate frequency furnace is higher than that of the electric furnace. Because the electric furnace can use cheap oxygen energy and high-temperature flue gas to preheat the scrap steel, the heat loss of flue gas is reduced. The power consumption of the ultra-high power energy-saving continuous charging electric furnace is about 360 KWh, while the power consumption of the intermediate frequency furnace is about 660 KWh, a difference of 300 KWh, and the cost difference is 210 yuan/t;

(3) The life of the medium frequency furnace is short, only 50~80 times/session. The life of the electric furnace lining can reach more than 1000 times/session. The cost per ton of steel is about 10 yuan. The cost of the electric furnace steelmaking refractory is 20 yuan lower than that of the medium frequency furnace;

(4) The oxygen blowing of the electric furnace increases the consumption of oxygen and alloy, the power transmission of the electric furnace increases the consumption of electrodes, and the slagging of the electric furnace increases the consumption of lime;

Based on the above four cost comparisons, the production cost of an electric furnace is not higher than that of an induction furnace. As long as procurement and production are strictly controlled, the cost of electric furnace steel is lower than that of induction furnaces.

5. Investment Comparison Difference between Induction Furnace and Electric Arc Furnace

(1) The investment in electric furnace steelmaking is higher than that of medium frequency furnaces due to the supporting air separation oxygen generation equipment and SVC reactive compensation.

(2) Impact on the Power Grid

The production of ordinary electric arc furnaces has a certain impact on the power grid. The impact on the power grid can be reduced after SVC reactive power compensation device is equipped. The scrap preheating ultra-high power arc furnace is equipped with SVC reactive power compensation device. During continuous production, the whole process of foam slag submerged arc operation has no impact on the power grid.

6. The Conclusion of the Difference between Induction Furnace and Electric Arc Furnace

According to the comparison in the above aspects, in addition to the slightly higher investment in electric arc furnace steelmaking, electric arc furnace steelmaking has obvious advantages over medium-frequency furnaces in other aspects, especially in terms of quality, variety, and adaptability to waste steel raw materials, which lays a foundation for the transformation of carbon structural steel into alloy structural steel and special steel after steelmaking, and has a strong ability to adapt to the market. At the same time, it will leave room for enterprises to build sponge iron production lines in the future. Therefore, from a long-term perspective, the development prospect of electric arc furnace steelmaking is broader, and the new electric arc furnace steelmaking production line has more advantages than the medium frequency furnace production line.

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