Refractory Materials For Steel Rolling

Refractory Materials for Steel Rolling

Reheating furnaces and soaking pits in steel rolling extensively use monolithic refractory materials as replacements for traditional brick linings. Among monolithic refractories, the proportion of castables has increased, while the use of plastics has decreased. To conserve energy, refractory fibers are widely applied in reheating furnaces and soaking pits.

1. Reheating Furnaces

Reheating furnaces are thermal equipment used to heat steel billets or small steel ingots, typically operating at temperatures of 1300–1400°C. The furnace lining is primarily constructed with fireclay bricks or third-grade high alumina bricks, which are subject to damage from high temperatures, thermal stress, gas flow erosion, and mechanical impacts. In high-temperature zones, the lower parts of the furnace walls, the furnace bottom, and the water-cooled pipe wrapping layers also suffer corrosion from molten iron oxide slag. To counter this, magnesia bricks or magnesia sand are used as protective layers.

Since the 1970s, monolithic refractory materials have been progressively applied. Gas-fired reheating furnaces use crystalline alumina fiber or aluminosilicate fiber products as the working layer, achieving significant energy-saving effects.

(1) Furnace Body

Initially constructed with fireclay bricks, the furnace body was later replaced with castables bonded with high alumina cement or phosphates. After 1980, clay-bonded or low-cement castables became widely adopted. In high-temperature zones and furnace bottoms, erosion-resistant corundum, mullite, or magnesia-chrome refractory castables are used, while wear-resistant steel-fiber-reinforced castables are applied on soaking beds.

(2) Combustion Chamber

Corundum, super-grade high alumina clinker, or magnesia-alumina spinel castables are used in combustion chambers, offering lifespans 2–3 times longer than traditional brick linings. Other areas where castables have been implemented show significantly improved performance.

2. Soaking Pits

Soaking pits are thermal equipment used in primary rolling mills to heat and homogenize steel ingots. The furnace body and roof are subject to rapid temperature fluctuations, mechanical wear, impacts, and slag corrosion. High-alumina plastics or clay-bonded high-alumina castables are employed. For the furnace mouth, corundum and mullite low-cement or cement-free castables greatly enhance service life.

The checkerwork in the regenerator uses grid bricks, with the upper part made of high-alumina bricks and the lower part using fireclay bricks. The heat exchanger, originally constructed with fireclay or fireclay-silicon carbide bricks, is now made with high-alumina silicon carbide castables, increasing service life by 50%.