I. Technical Principle: The Steelmaking Revolution Empowered by Electric Arc
Electric Arc Furnace Steelmaking (EAF for short) is a metallurgical process that uses the high-temperature electric arc generated between electrodes and furnace charge as a heat source to melt and refine raw materials such as scrap steel and Direct Reduced Iron (DRI) into steel. Its core principle is as follows: three-phase alternating current is passed into graphite electrodes, forming an electric arc between the electrodes and the furnace charge. The high temperature (up to over 3000°C) generated by the electric arc rapidly melts the furnace charge. Meanwhile, with the help of the oxidizing atmosphere in the furnace, slag formers, and alloy additives, harmful impurities such as sulfur, phosphorus, oxygen, and nitrogen in the raw materials are removed, and the chemical composition and temperature of the molten steel are adjusted. Finally, molten steel that meets the requirements is obtained.
Unlike traditional converter steelmaking, which relies on molten iron, EAF steelmaking uses scrap steel as the main raw material and does not require the blast furnace ironmaking process. It has a shorter production process and higher flexibility, making it the core technology of "short-process steelmaking" in the iron and steel industry.
II. Core Advantages: Dual Values of High Efficiency, Flexibility, and Low Carbon
Wide adaptability to raw materials: It can process various types of scrap steel (including industrial scrap steel, scrapped equipment, and recycled steel products) and can also be combined with direct reduced iron, pig iron, etc., to adjust the composition. It has relatively loose requirements on the grade of raw materials, which contributes to resource recycling.
High production flexibility: The capacity of a single furnace ranges from several tons to over 100 tons. It can quickly switch steel grades (such as carbon steel, alloy steel, and special steel) according to market demand, with flexible production batches. It has significant advantages in small-batch and multi-variety production.
Low-carbon and environmentally friendly characteristics: It does not consume coke (the main carbon emission source of converter steelmaking), and the carbon emission per ton of steel is only 1/3 to 1/2 of that of converter steelmaking. Combined with waste heat recovery and flue gas purification systems, dust and waste gas emissions can be effectively controlled, which meets the requirements of the "dual carbon" goals.
Excellent refining effect: The electric arc heating has high and uniform temperature, and the reactions in the furnace are easy to control. Through secondary refining (equipped with LF furnaces, VD furnaces, etc.), the purity of molten steel and alloy composition can be accurately controlled, making it suitable for producing high-quality special steel (such as bearing steel, die steel, and stainless steel).
III. Key Process Flow: The Refining Journey from Raw Materials to Molten Steel
The core process of EAF steelmaking can be divided into five stages: charging, melting, oxidation, reduction, and tapping. The entire process only takes 40 to 90 minutes (adjusted according to furnace capacity and steel grade):
Charging stage: Pretreated scrap steel (with oil and impurities removed) and slag formers (such as lime and fluorite) are loaded into the furnace through the top charging basket. In some processes, direct reduced iron is added to improve the quality of molten steel.
Melting stage: The graphite electrodes are lowered. After power is turned on, an electric arc is generated between the electrodes and the scrap steel, and the high temperature is used to rapidly melt the furnace charge. During the process, oxygen can be blown through an oxygen lance to assist melting and shorten the melting time.
Oxidation stage: Oxygen is blown into the molten pool to oxidize and remove impurities such as carbon, silicon, manganese, and phosphorus in the molten steel. At the same time, the generated oxide slag can adsorb harmful elements. A large amount of heat is released in this stage to maintain the high temperature in the furnace.
Reduction stage: Deoxidizers such as ferrosilicon, ferromanganese, and aluminum are added to remove residual oxygen in the molten steel. Then, according to the requirements of the target steel grade, alloy materials (such as ferrochromium, ferronickel, and ferromolybdenum) are added to adjust the chemical composition and ensure the performance of the steel grade.
Tapping stage: When the composition and temperature of the molten steel meet the standards, the furnace body is tilted, and the molten steel is poured into a ladle through the tap hole, which is then sent to a continuous caster for casting or further refining. The slag is discharged and recycled through the slag hole.
IV. Technological Development and Application Scenarios
As the iron and steel industry transforms towards "green and low-carbon", EAF steelmaking technology continues to upgrade: On the one hand, ultra-high-power electric arc furnaces (with a power per unit furnace capacity of ≥700kVA/t) have become the mainstream, increasing the melting efficiency by more than 30%. On the other hand, the application of scrap steel preheating technology (such as vertical furnaces and conductive preheating) and flue gas waste heat recovery systems further reduces energy consumption. In addition, the combined process of "electric arc furnace + direct reduced iron" enables short-process steelmaking in areas lacking scrap steel resources, expanding the application boundary of the technology.
In terms of application scenarios, EAF steelmaking is widely used in the production of:
Special steel: High-quality steel grades such as bearing steel, gear steel, die steel, and stainless steel;
Construction steel: Carbon steel such as rebar, wire rod, and section steel;
Mechanical manufacturing steel: Structural steel, alloy structural steel, etc.
At present, the output of EAF steel accounts for about 30% of the global steel output. In regions with abundant scrap steel resources such as Europe and the United States, this proportion has reached more than 50%, making EAF steelmaking one of the core processes in steel production.
V. Industry Trends: Greenization, Intellectualization, and Scaling
In the future, EAF steelmaking will develop in three major directions: First, low carbonization. The promotion of using green electricity (wind power, photovoltaic power) to replace traditional thermal power will further reduce carbon emissions. Some enterprises have already piloted "green electricity electric arc furnaces", which can reduce carbon emissions per ton of steel to less than 0.1 tons. Second, intellectualization. The use of the Internet of Things (IoT) and AI technology to realize real-time monitoring and automatic control of the temperature and composition in the furnace will improve production efficiency and product stability. Third, scaling. Large-scale electric arc furnaces (with a capacity of over 150 tons) have become a trend. Combined with the continuous casting and rolling process, they can achieve efficient and continuous production and reduce unit costs.
As a core technology for resource recycling and low-carbon production, EAF steelmaking is gradually replacing part of the traditional converter steelmaking capacity under the "dual carbon" goals, and has become an important support for the high-quality development of the modern iron and steel industry.
Zhangjiakou Xuanhua Innovake Drilling Machine Co., Ltd. is a joint-stock enterprise specializing in the research and development, production, and sales of metallurgical machinery and equipment for ironmaking and steelmaking.
