1. Properties of Sintered Fused Alumina
Sintered fused alumina is produced from Al₂O₃ (γ-Al₂O₃). After forming, it is fired at approximately 1,750–1,900°C to produce a high-performance refractory material. Its main properties include:
High refractoriness:
The refractoriness is ≥1,800°C, with a melting point of approximately 2,040–2,050°C, allowing sintered fused alumina to withstand extremely high temperatures.
High strength:
Well-developed α-Al₂O₃ crystals and a closed-pore structure give sintered alumina refractory excellent mechanical strength and high single-particle strength.
Excellent thermal shock resistance:
ts closed-pore structure helps absorb thermal stress, allowing the material to remain stable during rapid temperature changes.
Good corrosion resistance:
Except for hydrofluoric acid and phosphoric acid, it generally resists most alkalis and mineral acids.
Good thermal and electrical performance:
It provides good thermal conductivity and stable electrical properties at elevated temperatures.
Good volume stability:
With high purity and no additional additives, it has excellent volume stability and very low permanent linear change after reheating.
2. Types of Sintered Fused Alumina
The main types include:
Regular sintered fused alumina:
Made from calcined alumina, which is ground and formed into pellets or bodies before being sintered at high temperature.
Lightweight sintered alumina refractory:
Produced from transitional alumina using a foaming process to create a porous core-shell structure. Most pores are closed, and bulk density can be adjusted by controlling the amount of foaming agent.
Microporous sintered alumina refractory:
Contains more intragranular and intergranular pores, generally at the micron level. Its chemical composition is similar to sintered tabular alumina, while its porous structure provides lower bulk density, lower thermal conductivity, and good strength.
Dense sintered fused alumina:
A high-density grade with higher bulk density and lower apparent porosity than conventional sintered tabular alumina. It also offers improved wear and erosion resistance.
Sintered titanium alumina:
A specialized alumina material produced by introducing TiO₂ and firing at high temperature. The similar lattice constants of Al₂O₃ and TiO₂ allow limited substitution between Ti⁴⁺ and Al³⁺, activating the crystal lattice and improving sintering activity. This helps reduce the sintering temperature while providing high mechanical strength and good elastic resistance.
3. Applications of Sintered Fused Alumina in Refractory Materials
Due to its combination of strength, thermal stability, and corrosion resistance, sintered fused alumina is widely used in refractory applications.
Slide gates:
Its high strength and thermal shock resistance make it suitable for slide gate components used in steelmaking.
Steel ladle castables:
Lightweight and microporous grades can reduce thermal conductivity while improving thermal shock resistance, making them suitable for ladle castables.
Precast refractory shapes:
High refractoriness and wear resistance make sintered alumina refractory a suitable material for various precast refractory components.
Other refractory products:
Dense grades can be used in wear- and erosion-resistant products such as slide plates, purging plugs, and ladle impact-zone castables, helping improve service life and operational safety.
Overall, sintered fused alumina combines high-temperature resistance, mechanical strength, thermal shock resistance, and chemical stability, making it suitable for a wide range of steelmaking and high-temperature refractory applications.
