Classification of steelmaking and refining equipment

Classification of steel refining:

Can be divided into furnace refining and furnace refining. Off-furnace refining refers to refining treatment of molten steel outside the steelmaking furnace, such as vacuum degassing, powder spraying, etc. Furnace refining refers to the refining process, such as oxygen blowing, in the steelmaking furnace. Add ore, etc.

Classified by processing object:

Can be divided into ordinary steel refining and high performance steel refining. Ordinary steel refining refers to the refining treatment of ordinary carbon steel, low alloy steel, etc., and high performance steel refining refers to the refining treatment of high strength steel, stainless steel, tool steel, etc.

Electric arc furnace: uses the arc heat generated between the electrode and the furnace material to melt the furnace material, mainly using scrap steel as raw material, and can also add some pig iron or directly reduced iron. Electric arc furnace steelmaking has the characteristics of high flexibility, the ability to produce multiple types of steel, and strong adaptability to raw materials, making it suitable for producing special steel and high alloy steel.

Ladle Refining Furnace (LF): Equipment that combines the heating and refining functions of a steelmaking furnace. The main functions include raising the temperature and insulation of the molten steel, providing new thermal energy to the molten steel through arc heating, facilitating the addition of alloys and adjusting the composition, adding slag materials, and achieving deep desulfurization and deoxidation of the molten steel; The argon stirring function blows argon gas into the molten steel through the permeable bricks at the bottom of the ladle, allowing the steel to be stirred and homogenized in terms of composition and temperature; Some ladle refining furnaces also have vacuum degassing function, which can remove gases such as hydrogen and nitrogen from the steel liquid, further reduce the oxygen and sulfur content, and obtain higher purity steel liquid.

Steelmaking and Refining Furnace Equipment

I. Primary Steelmaking Furnaces

1. Electric Arc Furnace (EAF)

• Core Principle: Use the high temperature generated by the arc between graphite electrodes and the charge to melt the raw materials (mainly scrap steel), and complete the steelmaking process through oxygen blowing, slagging and other operations.
• Structure Features: Composed of furnace body, electrode lifting system, furnace cover, tilting mechanism, and dust removal system. Modern electric arc furnaces are mostly ultra-high power (UHP) electric arc furnaces to improve smelting efficiency.
• Advantages: Flexible raw material adaptability (can use 100% scrap steel), short smelting cycle, low environmental pollution (equipped with efficient dust removal), and suitable for producing special steel and high-quality carbon steel.
• Key Parameters: Power level (UHP grade is usually 600 - 1200 kVA/t), smelting cycle (40 - 60 minutes per heat), tapping temperature (1600 - 1650°C).

2. Basic Oxygen Furnace (BOF)

• Core Principle: Take molten pig iron as the main raw material, blow high-purity oxygen into the molten iron from the top or bottom, oxidize carbon, silicon, manganese and other impurities in the molten iron, and release a large amount of heat to raise the temperature of molten steel.
• Structure Features: Mainly includes furnace body (steel shell + magnesia carbon brick lining), oxygen lance system, furnace mouth smoke hood, and tilting device. According to the oxygen blowing method, it is divided into top-blown converter, bottom-blown converter and combined blown converter.
• Advantages: High production efficiency (single furnace capacity can reach 300 - 400 tons), low production cost, and suitable for large-scale continuous production of ordinary carbon steel.
• Application Scenario: The core equipment of large-scale integrated steel plants, matching the blast furnace - converter continuous production process.

3. Induction Furnace

• Core Principle: Use electromagnetic induction to generate eddy current in the charge, and rely on the thermal effect of eddy current to melt the raw materials. It is divided into coreless induction furnace and channel induction furnace.
• Advantages: Fast heating speed, uniform temperature of molten steel, accurate composition control, and small floor space.
• Application Scenario: Suitable for small and medium-sized steel plants, used for smelting special steel, alloy steel, and precision casting blank production.

II. Secondary Refining Furnaces

1. Ladle Furnace (LF)

• Core Function: Vacuum degassing is not carried out, mainly for heating, deoxidation, desulfurization, and composition adjustment of molten steel. It uses graphite electrodes to generate arc in the ladle to heat molten steel, and removes inclusions by adding slagging agents (lime, fluorite).
• Key Advantages: Can accurately adjust the temperature of molten steel (temperature control accuracy ±5°C), improve the cleanliness of molten steel, and extend the pouring time of continuous casting.
• Application: Widely used in matching electric arc furnace and converter production lines, especially for the refining of special steel.

2. RH Vacuum Degassing Furnace

• Core Principle: Use the principle of vacuum suction and circulation to lift molten steel from the ladle into the vacuum chamber, remove dissolved gas (H, N) in molten steel under high vacuum conditions, and realize dehydrogenation, denitrification and degassing.
• Structure Features: Composed of vacuum chamber, lifting pipe, vacuum system, and molten steel circulation driving system.
• Advantages: High degassing efficiency (hydrogen content can be reduced to ≤2 ppm), short processing time, and suitable for large-scale production of high-quality steel (such as automotive panel steel, pipeline steel).

3. VD/VOD Vacuum Refining Furnace

• VD (Vacuum Degassing Furnace): Similar to RH in function, it is a static vacuum degassing equipment, suitable for small and medium-sized ladle refining, with low equipment investment.
• VOD (Vacuum Oxygen Decarburization Furnace): On the basis of VD, add oxygen blowing function, which can realize decarburization under vacuum conditions, and is mainly used for smelting stainless steel (reducing carbon content to below 0.03% while retaining chromium).

4. AOD Furnace (Argon Oxygen Decarburization Furnace)

• Core Principle: Blow a mixture of argon and oxygen into molten steel, reduce the partial pressure of CO by argon, realize decarburization at a lower temperature, and avoid the oxidation loss of chromium.
• Application Scenario: The key equipment for smelting stainless steel and high-chromium alloy steel, with high metal yield and stable product quality.

III. Key Supporting Systems

1. Ladle System: Responsible for transporting molten steel between the steelmaking furnace, refining furnace and continuous casting machine, and its lining material (magnesia carbon brick, aluminum magnesium carbon brick) directly affects the temperature loss and cleanliness of molten steel.
2. Slagging System: Add slagging agents (lime, fluorite, silica) to form a protective slag layer, which plays the roles of deoxidation, desulfurization, and adsorption of inclusions.
3. Automation Control System: Realize real-time monitoring and adjustment of smelting parameters (temperature, oxygen content, electrode current), and improve the stability and automation level of the smelting process.

IV. Development Trend

1. Green and Low-Carbon: Popularize energy-saving technologies such as waste heat recovery of flue gas and electrode thermal spray coating; develop electric arc furnaces using hydrogen-rich reducing gas to reduce carbon emissions.
2. Intelligentization: Apply technologies such as big data, artificial intelligence, and digital twins to realize the whole-process intelligent control of steelmaking and refining, and predict the quality of molten steel.
3. Large-Scale and High Efficiency: Develop large-capacity converters (400 - 500 tons) and ultra-high-power electric arc furnaces to improve single-furnace production efficiency and reduce unit energy consumption.