Keyword：steelmaking，EAF,LF
Description：This article introduces the working principle and function of electric furnace, AOD furnace, LF furnace and VD vacuum furnace respectively.
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.
AOD furnace
AOD furnace method (that is, argon oxygen decarburization method) is a more advanced technology for refining stainless steel. It has the advantages of simple equipment, convenient operation, strong adaptability, low investment, low production cost, etc., and is widely used.
The molten iron in the blast furnace and the molten steel melted on the electric furnace are injected into the AOD furnace through the ladle, and O2, Ar or N2 mixed gas is blown into the molten steel during smelting to decarburize the molten steel. The composition and temperature of molten steel can be used to smelt qualified stainless steel materials.
principle:
The delivery and adjustment of the mixed gas during refining is one of the main systems of the argon oxygen furnace. The gas produced by the oxygen production workshop is transported into the gas storage tank near the workshop through pipelines, and after metering, decompression, adjustment and mixing, finally the mixed gas according to the flow rate and proportion required by the process is sent into the furnace through the side gun.
At the beginning of smelting, oxygen is blown into the metal molten pool from the top furnace mouth through the double-layer water-cooled oxygen blowing pipe for decarburization. During refining, the mixed gas is fed into the side gun into the furnace (installed on the side wall opposite to the tapping hole and close to the bottom of the furnace). When charging and tapping, the furnace body is tilted forward at a certain angle, and the (side) tuyere is above the liquid steel level. During normal blowing, the tuyere sinks into the deep part of the molten pool. The central tube of the tuyere is blown into the mixed gas of oxygen and argon or nitrogen. By adjusting the ratio of oxygen and argon, the partial pressure of carbon monoxide can be reduced to achieve the purpose of decarburization and chromium preservation. The type of AOD furnace tuyere is unique, it is a gas-cooled consumption tuyere. The tuyere adopts a double-layer sleeve structure, the outer tube only passes through argon or nitrogen to cool the tuyere, and the inner tube passes through a mixture of oxygen and nitrogen, or argon. Through the flow control of the air mask ring to achieve the best operating effect, the flow of the air mask ring central tube and the air mask ring can be controlled in 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.
Function: The main function of AOD is to remove carbon and play the role of refining.
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 LF furnace mainly depends on the white slag in the barrel. In a low-oxygen atmosphere (oxygen content is 5%), argon is blown into the barrel for stirring, and the molten steel passing through the primary furnace is heated by graphite electrodes for refining. Since the argon stirring accelerates the chemical reaction between slag and steel, using arc heating for temperature compensation can ensure a longer refining time, thereby reducing the content of oxygen and sulfur in the steel, and the inclusions are rated as O according to ASTM. ~O. Level 1. LF furnace can cooperate with electric furnace to replace the reduction period of electric furnace, and can also cooperate with oxygen converter to produce high-quality alloy steel. In addition, LF furnace is also an indispensable equipment for controlling composition, temperature and preserving molten steel in continuous casting workshop, especially in alloy steel continuous casting production line. Therefore, the emergence of LF furnace has formed a new joint production line of LD-LF-RH-CC (continuous casting) to produce high-quality steel. The reduction and refining of steel in this joint production line is mainly done by LF furnace. The steel grades processed by the LF furnace involve almost all steel grades from special steel to common steel. Different process operation systems are adopted depending on the needs of quality control during production. Among all kinds of secondary refining equipment, LF furnace has the highest comprehensive cost performance.
LF has the following characteristics:
① Desulfurization
②Temperature adjustment
③Precise composition fine-tuning
④ Improve the purity of molten steel
⑤Slagging
It mainly has the following functions:
(1) The LF furnace is connected with the electric furnace, which speeds up the production cycle of the electric furnace and improves the quality of the electric furnace steel.
(2) The LF furnace is connected with the LD converter, which can reduce and refine the converter steel, so the steel quality can be improved and new steel types can be produced.
(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;
VD vacuum furnace
The VD refining method is a vacuum treatment method for molten steel that puts the primary molten steel in an electric furnace or a converter in a closed tank for vacuuming, and at the same time blows argon at the bottom of the ladle and stirs it. After melting and preliminary blowing in electric furnaces and converters, it is then placed in a vacuum tank (vacuum chamber) through the process of bottom blowing argon stirring and vacuum degassing to obtain pure molten steel.
The VD furnace is generally matched with the LF furnace. The LF furnace completes the adjustment of composition and temperature, and the VD furnace completes degassing, stirring and other tasks. There is also an oxygen lance installed on the vacuum cover of the VD furnace to smelt stainless steel, which is called a VOD furnace.
Function:
The function of VD furnace is a widely used vacuum refining equipment, which has good degassing and deoxidation effects, can effectively reduce the hydrogen and nitrogen content in steel, remove oxygen in steel through carbon and oxygen reaction, and The full reaction desulfurization of slag and molten steel also has the function of uniform composition and temperature.