I. What are High-Alumina Refractory Materials?

Refractory materials manufactured using naturally occurring high-alumina clay and containing an Al2O3 content of 48% or more are called high-alumina refractory materials. High-alumina refractory materials are primarily classified into three grades: Grade I—Al2O3 content greater than 75%; Grade II—Al2O3 content between 65% and 75%; and Grade III—Al2O3 content between 48% and 65%.

II. What are Mullite Refractory Materials?

Mullite is the name of a mineral, named after the island of Mull off the west coast of Scotland where it was first discovered naturally. Natural mullite is rare, with some deposits found in Wu'an County, Hebei Province, and Lin County, Henan Province. To date, no industrially valuable deposits have been discovered worldwide. Mullite for industrial use is artificially synthesized through sintering or electrofusion. Its chemical formula is 3Al₂O₃·2SiO₂, and its theoretical composition is: Al₂O₃ 71.8%, SiO₂ 28.2%, with a theoretical density of 3.2 g/cm₃. Synthetic mullite is a high-quality refractory material, offering advantages such as uniform thermal expansion, excellent thermal shock resistance, high refractoriness under load, low high-temperature creep, and high hardness.

3. What are corundum refractory products?

Refractory materials with an Al₂O₃ content of over 90% are called corundum refractories or alumina refractories. Corundum refractories used in steelmaking primarily include air-permeable bricks and ladle nozzle blocks, slide plates, and ladle bricks.

4. What are spinel refractory materials?

Broadly speaking, spinel refers to a class of minerals with essentially the same structure, represented by the general chemical formula AO·R₂O₃ or AR₂O₄. Among them, A represents a divalent element ion, such as Fe2+, Mg2+, and R represents a trivalent element, including Fe3+, Al3+, Cr3+, etc. These same minerals exist in the form of the same crystal solid solution. Natural spinel is rare, and all spinels used in industrial production are artificially synthesized products. This type of refractory material belongs to medium and high-end refractory materials. Magnesium-aluminum spinel refractory materials and magnesia-chrome bricks are commonly used in steelmaking. Chrome-magnesia bricks are one of the more ideal refractory materials in the steelmaking process. According to Bartha's classification method, spinel refractory materials can be divided into the following three categories: (1) Those with a mass fraction of Al2O3 less than 30% are called periclase-spinel refractory materials. (2) Those with a mass fraction of Al2O3 between 30% and 68% are called spinel-periclite refractory materials. (3) Those with a mass fraction of Al2O3 between 68% and 73% are called spinel refractory materials. 5. What are dolomite-based refractory materials?

Dolomite is a sedimentary rock composed of calcium carbonate and magnesium carbonate. Its chemical formula is CaCO₃·MgCO₃ or CaO·MgO·2CO, and its structural formula is CaMg[CO₃]₂. Basic refractory materials produced primarily from dolomite are called dolomite-based refractory materials.