Electric Arc Furnace Smelting Technology For Low Carbon Steel

 

Electric arc furnace smelting of low-carbon steel is the core and high-level embodiment of modern EAF steelmaking technology. Its no longer simply "melting scrap steel," but a precisely controlled metallurgical process. Low-carbon transformation is achieved through the adoption of new processes such as Direct Reduced Iron (DRI) + Electric Arc Furnaces.

Sanrui Electric Furnace steelmaking technology significantly shortens the smelting cycle, reduces power consumption and electrode consumption, and achieves a carbon dioxide emission reduction of over 40kg per ton of steel.

Combining green raw materials, energy conservation and consumption reduction, and intelligent process models, EAFs have achieved breakthroughs in low-carbonization and high efficiency.

Electric Arc Furnace Smelting of Low-Carbon Steel Technology

I. Goals and Challenges

Goal: 

To produce ultra-low-carbon steel with a carbon content ≤ 0.08%, or even ≤ 0.03%, while ensuring the purity of the molten steel (low phosphorus, low sulfur, low gases, and low inclusions), under the premise of high efficiency and low cost.

Challenges:

1. Deep Decarburization: Reducing carbon content from high-grade scrap steel (typically 0.3%-0.8%) to very low levels under high-temperature conditions in an electric arc furnace (EAF) requires strong oxidizing and kinetic conditions.

2. Phosphorus Control: Dephosphorization requires low-temperature, highly oxidizing, and highly basic slag, while deep decarburization requires high temperatures. These two conditions are thermodynamically contradictory, representing the biggest challenge in EAF smelting of low-carbon steel.

3. Energy Balance & Cost: Decarburization and heating require a large amount of energy (electric and chemical energy). Providing this energy efficiently and economically is crucial.

4. Refractory Material Erosion: High-temperature and highly oxidizing slag causes severe erosion of the furnace lining, especially the furnace wall and slag line.

II. Technical Measures

To address these challenges, modern electric arc furnaces have developed a series of combined technologies:

1. Enhanced Oxygen Supply Technology: 

• Oxygen lances/burners at the furnace door: Injecting oxygen and carbon powder (or fuel gas) to aid melting, decarburize, and supplement chemical energy.
• Supersonic Cluster Oxygen Lance: Inserted into the furnace wall or top, this lance provides a high-intensity, supersonic oxygen stream that strongly impacts the molten pool, significantly increasing decarburization speed and efficiency. It is a core piece of equipment for achieving highly efficient decarburization.

2. High-Efficiency Foamed Slag Technology: 

By injecting carbon powder or adding carbon inside the furnace, a large number of CO bubbles are generated in the slag, causing it to foam to a thickness of 300-500mm.

Functions: 

① Covers the electric arc, improving electrothermal efficiency (energy saving, protecting the furnace cover); 

② Expands the slag-steel reaction interface, promoting dephosphorization and decarburization; 

③ Shields the refractory materials from the radiation of the electric arc.

3. Intelligent Power Supply and Automation:

Input power is adjusted in real time according to the smelting stage (melting, oxidation, heating) to achieve optimal "electricity-oxygen" balance, resulting in energy saving and shortening the EAF smelting cycle.

4. Bulk Charge Optimization: 

Partial replacement of scrap steel with "pure scrap steel" such as direct reduced iron, hot-pressed iron, or pig iron is achieved. These raw materials have low residual element content and controllable phosphorus and sulfur content, effectively diluting harmful elements in scrap steel and providing a raw material guarantee for smelting high-purity low-carbon steel.

III. Process Flow 

Modern EAF smelting of low-carbon steel typically employs a short-process combination of "electric arc furnace + secondary refining." The electric furnace mainly undertakes melting, dephosphorization, and preliminary decarburization, while the final deep decarburization, composition fine-tuning, and precise temperature control are handled by the subsequent refining furnace.

• Flow 1: EAF → LF Furnace → RH Vacuum Degassing Unit

Electric Arc Furnace: Completes melting, slag formation, dephosphorization, and heating, reducing carbon to approximately 0.05%.

LF Furnace: Performs steel heating, precise composition adjustment, deep desulfurization, and inclusion removal.

RH: Performs deep decarburization (reducing to below 0.002%), dehydrogenation, and denitrification under vacuum circulation.

Features: This is the most classic and reliable process for producing ultra-low carbon steel (such as IF steel), offering high flexibility, but with higher investment and operating costs.

• Flow 2: Electric Arc Furnace → Ladle Refining Furnace

Integrates some refining functions (such as oxygen decarburization, alloying, and stirring) into the ladle.

Features: Shorter process, suitable for steel grades with less stringent carbon content requirements (e.g., ≥0.03%), and relatively lower cost.

• Flow 3: Electric Arc Furnace for Steelmaking → VOD Vacuum Oxygen Decarburization Unit

Particularly suitable for smelting high-alloy low-carbon/ultra-low-carbon stainless steel, and also for special high-quality low-carbon steels.

Features: Vacuum oxygen decarburization effectively inhibits chromium oxidation, achieving chromium-preserving decarburization.

In summary, modern electric arc furnaces smelting of low-carbon steel is a systematic engineering project. By strengthening core technologies such as oxygen supply, foamed slag, and intelligent control, and by efficiently cooperating with secondary refining equipment such as LF and RH as a "primary refining furnace," it successfully overcomes the contradiction between dephosphorization and decarburization, enabling the economical and efficient production of high-quality low-carbon and ultra-low-carbon steel products. It is a pillar technology of green short-process steelmaking.

Sources:

Chinese Core Journals: 《 Ironmaking 》, 《 Steelmaking 》, 《 China Metallurgy 》, 《 Special Steel 》 etc.

International Authoritative Journals: ”Ironmaking & Steelmaking“, “ Steel Research International ”, “ Metallurgical and Materials Transactions B ”, etc.

E-mail: alice@srfurnace.com  / Tel: +86 15686041999 (Alice)

E-mail: anna@srfurnace.com  / Whatsapp: +86 159 2955 5868 (Anna)

Website: www.srfurnace.com / www.srmeltingfurnace.com / 

Xi'an Sanrui Electric Furnace