1. Feeding
The operation of adding 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 steel and iron production. 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 the amount of splashing and slag spilling during oxygen blowing should be minimized.
3. Slag discharge
It refers to the slagging operation taken during the smelting process in the electric arc furnace steelmaking according to different smelting conditions and purposes. For example, when single slag method is used for smelting, oxidation slag must be removed at the end of oxidation; when double slag method is used to make reduction slag, the original oxidation slag must be completely released to prevent phosphorus from returning.
4. Molten pool mixing
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
It’s the chemical reaction to reduce the phosphorus content in molten steel. Phosphorus is one of the harmful impurities in steel. Steel with too much 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 high-quality steel requires less phosphorus.
6. Electric furnace bottom blowing electric furnace bottom blowing
Blow N2, Ar, CO2, CO, CH4, O2 and other gases into the molten pool in the furnace through the nozzle placed at the bottom of the furnace to accelerate the melting and promote 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
The melting period of steelmaking is mainly for open hearth and electric furnace steelmaking. The melting period of electric arc furnace steelmaking starts from the time of electrifying to the time when all the accompanying materials are melted, and for open hearth steelmaking, it is called melting period from the end of hot metal mixing to the end of furnace burden melting. 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 decarbonization period
The oxidation period of ordinary power electric arc furnace steelmaking usually refers to the process stage from 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
The steelmaking process uses slagging and other methods to select some elements and compounds that are harmful to the quality of steel into the gas phase or discharge or float into the slag through chemical reactions, so that they are excluded from the molten steel. The continuous casting machine 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, control of chemical composition and temperature adjustment. High-power and ultra-power electric arc furnace steelmaking operations have canceled the reduction period.
11. Refining outside the furnace
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 in a container of vacuum, inert gas or reducing atmosphere. 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. Molten steel stirring
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 molten steel in an electric furnace; while it takes only 3 to 5 minutes to stir the molten steel in 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. Feeding wire in ladle
Feed the steel ladle with deoxidation, desulfurization and fine-tuning 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 The method of carbon and aluminum components. It also has the function of cleaning molten steel and improving the shape of non-metallic inclusions.
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