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Function and principle of each smelting furnace
Updated: 2022-04-28 Attention:
Electric furnace steelmaking mainly uses arc heat. In the arc action area, the temperature is as high as 4000 ℃. The smelting process is generally divided into melting period, oxidation period and reduction period. In the furnace, not only oxidation atmosphere but also reduction atmosphere can be caused. Therefore, the efficiency of dephosphorization and desulfurization is very high.
The electric furnace steelmaking with scrap 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 the electric furnace to replace most of the scrap, which greatly promotes the electric furnace steelmaking.
Function: at present, there are many medium frequency furnaces in China, which are mainly used to smelt high-quality steel, alloy steel and stainless steel. They belong to the first production process of smelting stainless steel, and their main functions are melting molten steel, dephosphorization and desulfurization.
AOD furnace method (i.e. argon oxygen decarburization method) is an advanced technology for refining stainless steel. It has the advantages of simple equipment, convenient operation, strong adaptability, low investment and low production cost.
The molten iron of blast furnace and molten steel melted on electric furnace are injected into AOD furnace through ladle. During smelting, O2, AR or N2 mixed gas is blown in to decarbonize the molten steel. At the same time, reducing agent, desulfurizer, ferroalloy or coolant are added into the feeding system to adjust the composition and temperature of molten steel, so as to smelt qualified stainless steel materials.
Principle: the transportation and regulation of mixed gas during refining is one of the main systems of argon oxygen furnace. The gas produced by the oxygen making workshop is respectively transported into the gas storage tank near the workshop through the pipeline, and then measured, depressurized, adjusted and mixed. Finally, the mixed gas according to the flow 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 sent into the side gun into the furnace (installed on the side wall opposite the side of the tapping port and close to the furnace bottom). When charging and tapping, the furnace body tilts forward at a certain angle, and the (side) tuyere is above the steel liquid level. During normal blowing, the tuyere sinks into the deep part of the solution tank. The mixed gas of oxygen, argon or nitrogen is blown into the central pipe of the tuyere. By adjusting the oxygen argon ratio, the partial pressure of carbon monoxide can be reduced to achieve the purpose of decarburization and chromium retention. The type of AOD furnace tuyere is unique. It is a consumable tuyere cooled by gas. The tuyere adopts double-layer casing structure, the outer pipe is only filled with argon or nitrogen to cool the tuyere, and the inner pipe is filled with mixed gas of oxygen, nitrogen or argon. The best operation effect can be achieved through the flow control of the tuyere cover ring. The flow of the central pipe of the tuyere cover ring and the tuyere cover ring can be controlled in the main control room.
Three side guns are used. It can enhance the oxygen supply intensity and improve the metal yield. 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: AOD is mainly used for decarbonization and refining.
LF furnace (ladle refining furnace) is the main refining equipment outside the furnace in iron and steel production. LF furnace generally refers to the refining furnace in the iron and steel industry. In fact, it is a special form of electric arc furnace.
LF furnace refining mainly depends on the white slag in the barrel, blowing argon into the barrel for stirring in a low oxygen atmosphere (oxygen content is 5%), and heating the molten steel passing through the primary refining furnace by graphite electrode. As argon stirring accelerates the chemical reaction between slag and steel, arc heating for temperature compensation can ensure a long refining time, so as to reduce the content of oxygen and sulfur in the steel. The inclusions are rated as O ~ o.1 according to ASTM. LF furnace can cooperate with electric furnace to replace the reduction period of electric furnace. It 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 combined production line of ld-lf-rh-cc (continuous casting) to produce high-quality steel. In this combined production line, the reduction refining of steel is mainly completed by LF furnace. The steel processed by LF furnace involves almost all steel grades from special steel to ordinary steel. Different process operation systems can be adopted according to the needs of quality control in production. Among various secondary refining equipment, LF furnace has high comprehensive cost performance.
LF has the following characteristics:
① Desulfurization
② Temperature regulation
③ Precise composition tuning
④ Improve the purity of molten steel
⑤ Slagging
It mainly has the following functions:
(1) LF furnace is connected with electric furnace, which speeds up the production cycle of electric furnace and improves the quality of electric furnace steel.
(2) LF furnace is connected with LD converter, which can reduce and refine converter steel, so it can improve steel quality and produce
Produce new steel grades.
(3) LF furnace can strictly regulate the composition and temperature of liquid steel, which is beneficial to the hardenability of steel and the continuous casting of special steel.
After AOD refining, it is refined in LF furnace, which belongs to secondary refining. The inclusion is reduced to ensure the purity of molten steel;
VD refining method is a vacuum treatment method of liquid steel, which puts the primary steelmaking liquid of electric furnace and converter into a closed tank for vacuum pumping and argon blowing and stirring at the bottom of ladle. After melting and preliminary blowing in electric furnace and converter, it is placed in vacuum tank (vacuum chamber) to obtain pure liquid steel through bottom blowing argon stirring and vacuum degassing process.
VD furnace is generally matched with LF furnace. The composition and temperature of LF furnace are adjusted respectively, and the tasks of degassing and mixing are completed by VD furnace. Oxygen lance is also installed on the vacuum cover of VD furnace to smelt stainless steel, which is called VOD furnace.
Function: VD furnace is a widely used vacuum refining equipment, which has good degassing and deoxidation effect, can effectively reduce the hydrogen and nitrogen content in steel, remove the oxygen in steel through carbon and oxygen reaction, and desulfurization through the full reaction between alkaline top slag and molten steel. In addition, it also has the function of uniform composition and temperature.
Double gold special steel - smelting process
Quality is the cornerstone of the survival and development of the enterprise. Shuangjin special steel always insists on putting product quality as the primary goal of the company, as always: gold quality, gold service, common growth and common rich enterprise values.
Good product quality must first have a good smelting process. The quality of smelting equipment directly affects the stability of subsequent product quality. For the product and customer positioning of Shuangjin special steel, the smelting method of Shuangjin special steel adheres to electric furnace + AOD refining + LF refining or electric furnace + AOD refining + LF refining + VD / VOD or + ESR electroslag to ensure the delivery of qualified and stable products.
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