What Are Refractory Products For AOD Refining Furnace?

 

AOD Refining Furnace,AOD Furnaces

An AOD refining furnace (Argon-Oxygen Deoxidation) is a device used for refining stainless steel, utilizing argon and oxygen for decarburization. This method is simple to operate, convenient, and has low production costs, making it widely used in the smelting of low-carbon and ultra-low-carbon stainless steel.

The AOD furnaces design is similar to a converter, mounted on a tilting support ring.

The AOD melting furnace achieves decarburization while retaining chromium by controlling the argon-oxygen ratio to reduce the partial pressure of carbon monoxide.

It is an important smelting device for the final deoxidation and alloying of molten steel.


Refractory Materials for AOD Refining Furnace

Magnesium-calcium based refractories are commonly used in AOD furnaces because the calcium oxide (CaO) effectively resists high-basicity slag and reacts with SiO₂ and other phases in the slag to form high-melting-point phases, improving corrosion resistance. The following are some of the main types:

1. Magnesium-calcium bricks / Dolomite bricks

This is the most mainstream and widely used refractory material in AOD melting furnace.

Main components: MgO and CaO. Typically, MgO content ranges from 40% to 80%, and CaO content from 20% to 60%.

Working Principle:

Advantages of CaO: CaO reacts with SiO₂, Al₂O₃, FeO, etc., in the slag to form high-melting-point C₂S (dicalcium silicate) and C₃A (tricalcium aluminate), forming a high-viscosity "protective layer" on the brick surface, effectively preventing further penetration and erosion by the slag. It also has some resistance to fluorite (CaF₂).

Advantages of MgO: Provides high refractoriness and good resistance to alkaline slag erosion.

Classification:

  • Fired Magnesia-Calcium Bricks: High-temperature fired, high strength, and dimensionally stable.
  • Unfired Magnesia-Calcium Bricks/Chemically Bonded Bricks: Usually bonded with tar or resin, containing residual carbon, which improves impermeability and thermal shock resistance.
  • Application Areas: Critically vulnerable areas of furnace lining, such as the molten pool, slag line, and tuyeres.

2. Magnesia-chrome bricks

They were widely used in the past, but due to the environmental pollution problems caused by hexavalent chromium (Cr⁶⁺), their use has been largely phased out or strictly restricted.

  • Main components: MgO and Cr₂O₃.
  • Advantages: Good high-temperature strength, resistance to slag erosion, and thermal shock stability.
  • Disadvantages: Cr₂O₃ can generate toxic water-soluble Cr⁶⁺ under alkaline oxidation conditions, polluting the environment and groundwater.

3. Alternatives to directly bonded magnesia-chrome bricks – Chrome-free bricks

To meet environmental protection requirements, various chrome-free bricks have been developed.

  • High-iron magnesia bricks: By increasing the Fe₂O₃ content, a bonding phase such as magnesia-iron ore (MF) is formed at high temperatures, improving the degree of direct bonding. However, their impermeability is relatively poor.
  • Spinel magnesia bricks: Al₂O₃ is added to magnesia materials to generate or pre-synthesize magnesia-alumina spinel (MgAl₂O₄) in situ. It possesses good thermal shock resistance and some slag resistance, but its resistance to high-alkalinity slag and fluorite erosion is inferior to that of magnesia-calcium bricks. It is commonly used in non-critical areas or the upper and middle sections of AOD furnaces.


The core refractory material for AOD refining furnace is magnesia-calcium based refractories (fired magnesia-calcium bricks and unfired magnesia-calcium bricks), especially in critical areas such as tuyeres and slag lines. 

For environmental reasons, magnesia-chrome bricks have been completely phased out.

The entire furnace lining adopts a "comprehensive lining" concept, matching different refractory brick materials according to the damage mechanisms of different parts to achieve optimal economic and technical indicators.


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

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