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technical knowledge

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Steelmaking process

Release date:2018-12-19 The author:www.xapyyj.com Click on:

1. Slag formation

    The operation of adjusting the slag composition, alkalinity and viscosity and the reaction ability of steel and iron production. The goal is to produce a metal with the desired composition and temperature by a slag-metal reaction. For example, oxygen top-blown converter slagging and oxygen blowing operations are used to generate slag with sufficient fluidity and alkalinity to reduce sulfur and phosphorus below the upper limit of the planned steel grade, and to cause splashing and scumming during oxygen blowing. The amount is reduced to a minimum.

2. Slag

    In the electric arc furnace steelmaking, the slagging or slag slag operation is carried out in the smelting process according to different smelting conditions and purposes. When smelting with the single slag method, the oxidized slag must be slag at the end of the oxidation; when the slag is reduced by the double slag method, the original oxidized slag must be completely released to prevent phosphorus from being returned.

3. Molten pool mixing

    Energy is supplied to the molten metal pool to cause movement of the molten metal and slag to improve the kinetic conditions of the metallurgical reaction. The molten pool agitation can be achieved by means of gas, mechanical, electromagnetic induction and the like.

4. Electric bottom blowing

    The gas such as N2, Ar, CO2, CO, CH4, O2, etc. is blown into the molten pool of the furnace according to the process requirements through a nozzle placed at the bottom of the furnace to accelerate the melting and promote the metallurgical reaction process. The bottom blowing process can shorten the smelting time, reduce the power consumption, improve the dephosphorization and desulfurization operations, increase the amount of residual manganese in the steel, and increase the yield of metals and alloys. It can make the molten steel composition and temperature more uniform, thus improving the quality of steel, reducing costs and increasing productivity.

5. Melting period

    The melting period of steelmaking is mainly for open hearth and electric furnace steelmaking. The electric arc furnace steelmaking is called the melting period from the start of the energization until the charge is completely melted, and the open hearth steelmaking is completed from the completion of the completion of the molten iron to the completion of the charge. The task of the melting period is to melt and heat the charge as soon as possible, and to make the slag in the melting period.

6. Oxidation period and decarbonization period

    The oxidation period of ordinary power electric arc furnace steelmaking usually refers to the process stage of melting, sampling and analysis of the furnace to the completion of oxidation. It is also thought to start with oxygen blowing or decarburization. The main task of the oxidation period is to oxidize carbon and phosphorus in the molten steel; remove gases and inclusions; and uniformly heat the molten steel. Decarburization is an important process in the oxidation phase. In order to ensure the purity of the steel, the decarburization amount is required to be greater than about 0.2%. With the development of refining technology outside the furnace, most of the oxidative refining of the electric arc furnace is moved to a ladle or a refining furnace.

7. Refinement period

The steelmaking process removes some elements and compounds that are harmful to the quality of the steel by slagging and other methods, and is chemically reacted into the gas phase or discharged into the slag to remove it from the molten steel.

8. Reduction period

    In the ordinary power arc furnace steelmaking operation, the time from the completion of the oxidization at the end of the oxidation to the tapping is usually referred to as the reduction period. Its main task is to make reducing slag for diffusion, deoxidation, desulfurization, control of chemical composition and temperature adjustment. At present, the high-power and ultra-power electric arc furnace steelmaking operations have cancelled the reduction period.

9. Furnace refining

    The steelmaking process of refining the molten steel in the steelmaking furnace (converter, electric furnace, etc.) to another vessel for refining is also called secondary metallurgy. The steelmaking process is therefore divided into two steps: primary refining and refining.

9.1 Initial refining: The charge is melted, dephosphorized, decarburized and main alloyed in an oxidizing atmosphere furnace.

9.2 Refining: Degassing, deoxidizing, desulfurizing, removing inclusions and fine-tuning the components of the molten steel in a vacuum, inert gas or reducing atmosphere.

9.3 The advantages of steelmaking in two steps are: improved steel quality, shorter smelting time, simplified process and lower production costs. There are many kinds of refining outside the furnace, which can be roughly divided into two types: refining under normal pressure and refining under vacuum. According to different treatment methods, it can be divided into ladle processing type furnace refining and ladle refining type furnace refining.

10. Steel liquid mixing

    Stirring of the molten steel during the refining process outside the furnace. It homogenizes the molten steel composition and temperature and promotes metallurgical reactions. Most metallurgical reaction processes are phase-interfacial reactions, and the rate of diffusion of reactants and products is a limiting step in these reactions. When the molten steel is at rest, the metallurgical reaction speed is very slow. For example, the desulfurization of the molten steel in the electric furnace takes 30 to 60 minutes. In the refining, it takes only 3 to 5 minutes to desulfurize by stirring the molten steel. When the molten steel is in a static state, the inclusions are floated and removed, and the removal speed is slow; when the molten steel is stirred, the removal rate of the inclusions increases exponentially, and is related to the stirring strength, the type and the characteristics and concentration of the inclusions.

11. Ladle feeding wire

    The wire is fed into the ladle by a wire-feeding deoxidizing, desulfurizing and fine-tuning powder, such as Ca-Si powder, or directly feeding aluminum wire, carbon wire, etc. for deep desulfurization, calcium treatment and fine tuning of molten steel. A method of components such as carbon and aluminum. It also has the function of cleaning molten steel and improving the morphology of non-metallic inclusions.

12. Ladle processing

    Abbreviation for ladle processing type refining outside the furnace. It is characterized by short refining time (about 10 to 30 minutes), single refining task, no heating device for compensating for the lowering of molten steel temperature, simple process operation and less equipment investment. It has equipment for degassing, desulfurization, composition control and changing the shape of inclusions. Such as vacuum cycle degassing method (RH, DH), ladle vacuum argon method (Gazid), ladle dusting treatment (IJ, TN, SL), etc. are all such.

13. Ladle refining

    Abbreviation for ladle refining furnace refining. It is characterized by a longer refining time than the ladle treatment (about 60-180 minutes), a variety of refining functions, a heating device that compensates for the reduced temperature of the molten steel, and is suitable for various types of high-alloy steels and special-performance steels (such as ultra-pure steel). Kind of refining. Vacuum oxygen decarburization (VOD), vacuum arc heating degassing (VAD), ladle refining (ASEA-SKF), closed argon component fine-tuning (CAS), etc., are all similar; There is also an argon oxygen decarburization method (AOD).

14. Inert gas treatment

    Injecting an inert gas into the molten steel, the gas itself does not participate in the metallurgical reaction, but each small bubble rising from the molten steel is equivalent to a "small vacuum chamber" (the partial pressure of H2, N2, CO in the bubble is close to Zero), with a "gas wash" effect. The principle of producing stainless steel by the refining method outside the furnace is to apply a balance between carbon chromium and temperature under different CO partial pressures. Refining and decarburization by adding oxygen to an inert gas can reduce the partial pressure of CO in the carbon-oxygen reaction. Under lower temperature conditions, the carbon content is lowered and the chromium is not oxidized.

15. Prealloying

    The process of adding one or more alloying elements to the molten steel to meet the specifications of the finished steel is called alloying. In most cases, deoxidation and alloying are carried out at the same time. Part of the deoxidizer added to the steel is consumed by deoxidation of the steel and converted into deoxidation product; the other part is absorbed by the molten steel and acts as an alloying. Before the deoxidation operation is completed, the alloying effect of the alloy added simultaneously with the deoxidizer by the absorption of molten steel is called prealloying.

16. Composition control

    Ensure that all finished steel components meet the requirements of the standard. The composition control runs through all aspects from batching to tapping, but the focus is on the control of the alloying elements during alloying. For high-quality steel, it is often required to accurately control the composition within a narrow range; generally, it is controlled by the middle and lower limits without affecting the performance of the steel.

17. Silicon enhancement

    At the end of the blowing, the silicon content in the molten steel is extremely low. In order to meet the silicon content requirements of each steel grade, a certain amount of silicon must be added in the form of an alloy material. In addition to its use as a deoxidizer, it also increases the amount of silicon in the molten steel. The amount of silicon added must be accurately calculated and should not exceed the allowable range of the blown steel.

18. End point control

    At the end of the oxygen converter steelmaking end (end of oxygen blowing), the chemical composition and temperature of the metal are simultaneously controlled to meet the steel tapping requirements of the planned steel. End point control has two methods of carbonization and carbon extraction.

19. Steel tapping

    The operation of discharging the molten steel when the temperature and composition of the molten steel reach the specified requirements of the steel to be refined. Care should be taken to prevent slag from flowing into the ladle when tapping. Additives for adjusting the temperature, composition and deoxidation of the molten steel are added to the ladle or tapping stream during the tapping process.

Xi'an Pengyuan Metallurgical Equipment Co., Ltd. was established on February 20, 2017. The company is located in Xi'an, Shaanxi, China. Its main business is the design and manufacture of metallurgical equipment (electric arc furnace, submerged arc furnace, ladle refining furnace, other refining furnaces and metallurgical auxiliary equipment). The company's vision is to become a service-oriented leading enterprise that can provide users with advanced and applicable complete smelting technology solutions. The company is determined to make “Pengyuan Metallurgy” into the electric furnace industry. Excellent brand. Pay attention to us, keep abreast of the latest developments in the industry, hotline: 13819831910.

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