Ore classification introduction

Acidic refractories

Dinas (dinas brick) contains 93-96% SiO ₂ ; 2-3% CaO ( softening temperature 1690-1730 ^o C). Quartz sand (93-97% SiO ₂ ) is used for welding and repairing individual parts of metallurgical furnaces.

Basic refractories

Magnesite (magnesite brick and metallurgical magnesite powder) consists of 91-94% MgO , 1-2% CaO , 2-3% Fe ₂ O ₃ , about 2% SiO ₂ , about 1% Al ₂ O ₃ . The refractoriness of magnesite is above 2000 ^o C, but under load it softens at 1500 ^o C. Magnesite is used for lining hearths and walls of main open-hearth, two-bath and electric steel-smelting furnaces, as well as non-ferrous metallurgy furnaces.
Chromomagnesite and magnesitechrome contain 30-70% MgO and 10-30% Cr ₂ O ₃ . Properties are approximately the same as magnesite.
Dolomite CaCO ₃ and MgCO ₃ . It is fired when the oven is heated. Bricks are made using 7-9% coal tar. Resin dolomite is used for lining converters. Fire resistance t = 1800-1900 ^o C.
Alumina refractories: fireclay (less than 65% SiO ₂ and 30-45% Al ₂ O ₃ ); high-alumina (more than 45% Al ₂ O ₃ ). Fireclay bricks are the most common refractories ( softening temperature 1770 ^o C), resistant to acidic and basic slags at t = 1250-1350 ^o C , they are cheap. Disadvantage - low softening t under load ( t = 1250-1400 ^o C ).
Fireclay bricks are used to line blast furnace shafts, heating furnaces, gas generators, cupola furnaces, and pouring ladles.
High-alumina refractories are more expensive than fireclay, but their fire resistance is higher (up to 2000 ^o C). They are used for laying high-temperature parts of metallurgical furnaces.
Aluminous refractories have weakly acidic and weakly basic properties (they are not classified into groups).