November 23, 2025
Electric Arc Furnace: Characteristics of Refractory Materials for Key Components
1. Roof Refractories
The electric arc furnace roof is typically constructed using high‑alumina bricks (Al₂O₃ content 75‑85%). Compared to silica bricks, high‑alumina bricks offer higher refractoriness, better thermal shock resistance, and greater compressive strength. Due to abundant domestic bauxite resources, high‑alumina bricks have become the dominant roof material, providing a service life approximately 2‑3 times longer than silica brick roofs.
With the rise of large‑scale, ultra‑high‑power furnaces, the durability of high‑alumina bricks has declined, leading to increased adoption of basic refractories such as fired or unfired magnesia bricks and magnesia‑chrome bricks. Pre‑cast commercial refractory shapes are also used, offering advantages over conventional masonry, including easier installation, better structural integrity, improved resistance to arc radiation, and enhanced thermal cycling performance.
2. Furnace Wall Refractories
The furnace wall is divided into general areas, the slag‑line zone, and “hot spots” near the arc. General walls are commonly built with magnesia, dolomite, or periclase bricks; some designs use unburned alkaline bricks or asphalt‑bonded magnesia‑dolomite ramming mixes. For ultra‑high‑power or specialty‑steel furnaces, magnesia‑chrome or high‑purity magnesia bricks are preferred.
The slag‑line and hot‑spot zones are the most vulnerable sections. Early designs used magnesia‑chrome bricks, achieving 100‑250 heats. Today, magnesia‑carbon bricks are widely applied due to their excellent high‑temperature stability and slag resistance, extending service life to over 300 heats.
To balance wear and prolong lining life, water‑cooled panels or jackets are often installed. A sprayed refractory coating on the inner surface helps form a protective slag layer, reducing specific refractory consumption—though at the cost of higher energy usage.
3. Furnace Bottom Refractories
The furnace bottom and banks form the hearth, which holds the charge and molten metal. The bottom lining must resist chemical attack from slag and iron oxide, prevent loosening or “floating” during reduction periods, and withstand steel penetration.
Therefore, the masonry or monolithic lining in this area should exhibit uniform properties, tight construction, high‑temperature strength, corrosion/erosion resistance, thermal shock stability, and volume stability. High‑quality magnesia or fused magnesia is used for rammed linings, with careful attention to layer thickness, density, and joint integrity.
The working lining is typically tar‑bonded magnesia brick, while the permanent lining beneath often consists of magnesia brick. The slag‑line area on the upper banks, subject to severe slag erosion, employs bricks similar to those used in wall hot spots, such as magnesia‑chrome or, preferably, magnesia‑carbon bricks.
4. Taphole Refractories
Modern eccentric bottom tapping (EBT) systems replace the tapping spout with a fixed taphole at an offset bottom position. This design eliminates tilting mechanisms, expands water‑cooled panel coverage, reduces lining wear, allows lower tap temperatures, shortens tapping time, and lowers operating costs.
EBT refractories include:
- Taphole bricks: pitch‑impregnated, fired magnesia bricks
- Pipe bricks: resin‑bonded magnesia‑carbon bricks with ~15% carbon
- End blocks: resin‑bonded magnesia‑carbon bricks with 10‑15% carbon, or Al₂O₃‑C‑SiC bricks
For smooth tapping, olivine‑based coarse sand is often used as a draining agent.
By selecting and applying appropriate refractories for each zone, furnace operators can optimize lining life, maintenance cycles, and overall process efficiency.
We are a professional electric furnace manufacturer. For further inquiries, or if you require submerged arc furnaces, electric arc furnaces, ladle refining furnaces, or other melting equipment, please do not hesitate to contact us at susan@aeaxa.com
