Selection of Refractory Materials for EAF Roof

There exists a wide array of refractory materials suitable for the roof of electric arc furnaces (EAFs). Regardless of the chosen design, refractory bricks must exhibit exceptional thermal shock resistance, corrosion resistance to slag and high-temperature splashes, as well as structural integrity. Most importantly, they must ensure a robust structure that remains crack-free.

Refractory Materials for EAF Covers

1. Silicon Refractory Brick Furnace Covers

Silicon refractory brick furnace covers are constructed using silicon firebricks. These covers are lightweight and cost-effective, boasting good high-temperature structural strength and creep resistance. However, upon melting at high temperatures, SiO₂ undergoes a continuous droplet phenomenon, leading to a decrease in slag fluidity and impacting smelting operations. Consequently, higher-alumina bricks with superior properties were later adopted.

2. High-Alumina Brick Furnace Covers

High-alumina brick furnace covers utilize bricks with an 80% content of super-grade high-alumina material, as well as phosphate-bonded unfired high-alumina refractory bricks, fired mullite bricks, or unfired phosphate-bonded mullite bricks. These materials share good thermal shock resistance, making them suitable for EAF covers.

3. Alkaline Refractory Brick Furnace Covers

• Magnesium Brick Covers: Magnesium bricks stabilize the structure of the furnace cover, but iron sheets must be inserted during masonry to mitigate issues. However, the large linear expansion coefficient of magnesium bricks limits their usage quantity.
• Other Basic Bricks: These include magnesia-chrome, dolomite, and magnesia-alumina bricks. They exhibit excellent fire resistance and corrosion resistance to iron oxide and slag, performing better than high-alumina bricks under harsh conditions.

4. Integral Casting Furnace Covers

Integral casting of the furnace cover can significantly enhance its lifespan. After water cooling the furnace cover, additional water cooling is implemented around the electrodes. In terms of materials, high-alumina ultra-low cement castables combined with stainless steel fibers can increase the lifespan by 3-4 times.

Comparative Analysis

• Silicon Composite Firebricks: When silicon composite firebricks are used for EAF covers, the masonry is convenient and tight, ensuring relatively uniform stress distribution across the entire cover. However, forming these firebricks can be challenging.
• High-Alumina Bricks: Using high-alumina bricks in EAFs can achieve a lifespan of 150-200 furnaces.
• Magnesia Bricks: Although magnesia bricks outperform high-alumina bricks in certain aspects, their high thermal conductivity is a drawback.
• Low Cement Refractory Castables: These castables offer good integrity and demonstrate a noticeable improvement in usage effects.

In conclusion, selecting the appropriate refractory material for an EAF roof is crucial for ensuring operational efficiency and longevity. Each material has its unique advantages and limitations, necessitating a careful evaluation based on specific operational requirements and conditions. By choosing the right combination of materials and construction methods, EAF operators can optimize performance and reduce maintenance costs.

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