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Introduction to the electric arc furnace steelmaking process and the art process

Views: 56     Author: Site Editor     Publish Time: 2021-03-10      Origin: Site

Introduction to the electric arc furnace steelmaking process and the art process


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 1. Adding materials


The operation of adding raw materials such as molten iron or scrap steel to the electric furnace is the first step of the electric furnace steelmaking operation.


2. Slagging


The operation of adjusting the slag composition, alkalinity, viscosity and reaction ability in the production of steel and iron. For example, the oxygen blowing operation is to generate slag with sufficient fluidity and alkalinity, which can transfer enough oxygen to the metal surface, so as to reduce the sulfur and phosphorus below the upper limit of the planned steel grade, and make the oxygen spray splash The amount of slag and spillage is minimized.


3.Slag


In the electric arc furnace steelmaking, the slagging or slagging operation is adopted in the smelting process according to different smelting conditions and purposes. For example, when smelting with single slag method, oxidation slag must be stripped off at the end of oxidation; when using double slag method to make reduction slag, the original oxidation slag must be completely released to prevent phosphorus from returning.


4. Molten pool stirring


Supply energy to the molten metal pool to make the molten metal and slag move to improve the kinetic conditions of the metallurgical reaction. The stirring of the molten pool can be achieved by means of gas, mechanical, electromagnetic induction and other methods.


5. Dephosphorization


The chemical reaction to reduce the phosphorus content in molten steel. Phosphorus is one of the harmful impurities in steel. Steel with a lot of phosphorus, when used at room temperature or lower, is prone to brittleness, which is called "cold brittleness". The higher the carbon content in steel, the more serious the embrittlement caused by phosphorus. Generally, it is stipulated that the phosphorus content of ordinary steel does not exceed 0.045%, and the high-quality steel requires less phosphorus.


6. Electric furnace bottom blowing electric furnace bottom blowing


Through the nozzle placed at the bottom of the furnace, N2, Ar, CO2, CO, CH4, O2 and other gases are blown into the molten pool in the furnace according to the process requirements to achieve the purpose of accelerating the melting and promoting the metallurgical reaction process. The use of bottom blowing technology can shorten smelting time, reduce power consumption, improve dephosphorization and desulfurization operations, increase the amount of residual manganese in steel, and increase the yield of metals and alloys. And can make the molten steel composition and temperature more uniform, thereby improving steel quality, reducing costs, and increasing productivity.


7. Melting period


Through the nozzle placed at the bottom of the furnace, N2, Ar, CO2, CO, CH4, O2 and other gases are blown into the molten pool in the furnace according to the process requirements to achieve the purpose of accelerating the melting and promoting the metallurgical reaction process. The use of bottom blowing technology can shorten smelting time, reduce power consumption, improve dephosphorization and desulfurization operations, increase the amount of residual manganese in steel, and increase the yield of metals and alloys. And can make the molten steel composition and temperature more uniform, thereby improving steel quality, reducing costs, and increasing productivity.


The melting period of steelmaking is mainly for open hearth and electric furnace steelmaking. The melting period of electric arc furnace steelmaking is called the melting period from the start of electrification to the complete melting of the furnace steel spikes, and the open-hearth steelmaking from the completion of the molten iron to the completion of the charge. The task of the melting period is to melt and heat up the charge as soon as possible, and make the slag in the melting period.


8. Oxidation period and decarburization period


The oxidation period of ordinary power electric arc furnace steelmaking usually refers to the process stage from the dissolution of the charge, sampling and analysis to the completion of the oxidation slag. Some think it started from blowing oxygen or adding ore to decarbonize. The main task of the oxidation period is to oxidize the carbon and phosphorus in the molten steel; remove the gas and inclusions; make the molten steel uniformly heated. Decarburization is an important process in the oxidation period. In order to ensure the purity of steel, the amount of decarburization is required to be greater than about 0.2%. With the development of refining technology outside the furnace, most of the oxidation refining of the electric arc furnace is moved to the ladle or refining furnace.


9. Refining period


In the steelmaking process, some elements and compounds harmful to the quality of steel are selected into the gas phase or discharged or floated into the slag through chemical reactions through slagging and other methods to remove them from the molten steel during the process operation period. The continuous caster discharges the billet. The continuous caster discharges the billet.


10. Restoration period


In ordinary power electric arc furnace steelmaking operations, the period from the completion of slagging at the end of oxidation to tapping is usually called the reduction period. Its main task is to create reduced slag for diffusion, deoxidation, desulfurization, chemical composition control and temperature adjustment. High-power and ultra-power electric arc furnace steelmaking operations have cancelled the reduction period.


11. Out-of-furnace refining


The steelmaking process in which the molten steel initially made in a steelmaking furnace (converter, electric furnace, etc.) is transferred to another vessel for refining is also called secondary metallurgy. Therefore, the steelmaking process is divided into two steps: primary smelting and refining. Primary refining: The charge is melted, dephosphorized, decarburized and main alloyed in a furnace with an oxidizing atmosphere. Refining: Degas, deoxidize, desulfurize, remove inclusions and fine-tune the composition of the molten steel in a vacuum, inert gas or reducing atmosphere container. The advantages of dividing steelmaking into two steps are: it can improve the quality of steel, the steelmaking workshop can shorten the smelting time, simplify the process and reduce the production cost. There are many types of out-of-furnace refining, which can be roughly divided into two types: out-of-furnace refining under atmospheric pressure and out-of-furnace refining under vacuum. According to different treatment methods, it can be divided into ladle processing type furnace refining and ladle refining type furnace refining.


12. Mixing of molten steel


The stirring of molten steel during the refining process outside the furnace. It homogenizes the composition and temperature of molten steel, and can promote metallurgical reactions. Most metallurgical reaction processes are phase interface reactions, and the diffusion rate of reactants and products is the limiting link of these reactions. When molten steel is in a static state, its metallurgical reaction speed is very slow. For example, it takes 30 to 60 minutes to desulfurize the molten steel in an electric furnace; while it takes only 3 to 5 minutes to stir the molten steel in the furnace refining. When molten steel is in a static state, the inclusions are removed by floating upwards, and the removal speed is slow; when the molten steel is stirred, the removal speed of the inclusions increases exponentially, and is related to the stirring strength, type, and characteristics and concentration of the inclusions.


13. Ladle wire feeding


Feed the steel ladle with deoxidation, desulfurization and fine-tuned powders, such as Ca-Si powder, or directly fed into aluminum wire, carbon wire, etc., to deep desulfurize, calcium and fine-tune the molten steel into the steel ladle through the wire feeder The method of carbon and aluminum and other ingredients. It also has the function of cleaning molten steel and improving the morphology of non-metallic inclusions.


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