There are many forms of refractory clay products whose basic quality requirements are alumina above 38% (usually 42-47%) and low iron low alkali metal content. These products may be uncalcined or calcined and include high performance calcined products such as mullite.
Refractory clays are used in the production of shaped and amorphous (monolithic) refractories. Brick products include fire clay bricks such as blast furnace checker bricks and high alumina bricks, such as support bricks for horizontal induction furnaces and vertical induction furnace linings. In the amorphous material sector, there are a variety of product consumption, such as refractory clay, plastic materials for overload, high alumina plastics, refractory clay and high alumina castables.
1. Refractory clay terms and definitions
The refractory clay is mainly composed of hydrated aluminum silicate, and its molecular formula is Al2O3·2SiO2·2H2O (ie, 39.5% alumina, 46.5% silica, and 14% water). Among this group of minerals, kaolin is the most abundant.
There are several terms that are currently described for refractory clay: refractory clay, flint clay (or hard clay), ball clay (or clay clay), and kaolins. However, its general feature is that these minerals contain kaolinite, and its composition is 20-45% Al2O3, <3% Fe2O3 and <3% Na2+K2O.
When the kaolinite is calcined under the condition of increasing temperature, the mineral phase changes continuously, and metakaolin (Al2Si2O7) is formed at about 550 °C, and spinel ((Al2O3) is formed at about 1000 °C. 2(SiO2)3+SiO2), which produces pseudo-mullite ([Al2O3.SiO2]2) at about 1100 °C. Another "refractory clay" product is mullite (3Al2O3·2SiO2) which can be obtained by calcining high alumina kaolin and bauxitic kaolin at 1200-1500 °C. At these temperatures, the main mineral phases of the clay are converted to mullite, cristobalite and a glassy phase.
Refractory clay
This is a siliceous clay rich in hydrated aluminum silicate, which has the ability of no deformation, cracking, softening and no paste at high temperatures. Low iron, calcium and alkali metals, close to kaolin in composition, with a good grade of at least 35% Al2O3 after calcination (Mining Terminology Dictionary, edited by the American Geological Society).
2. Vermiculite clay
A smooth, vermiculite-like refractory clay rock consisting mainly of kaolin, cleavage into a shell-like section, resistant to ripening in water. Long-term milling in water produces plasticity (Mining Terminology Dictionary, American Geological Association).
3. Cooked refractory soil
It is part of a mixture for the production of refractory bricks. It is made up of calcined clay or reground bricks. It is also called (clay) clinker. The English name is chamotte. ", American Geological Association).
4. Brahedite clay
This is a material mainly composed of (hard) boehmite (or diaspore <diaspore), which is bonded by refractory clay. The purest of the boehmite clay often contains 70-80% of Al2O3 after calcination.
5. Chinese clay
Soft clay (including ball clay), refractory clay and kaolin: <45% Al2O3
Vermiculite clay (commonly known as "Gemstone"), kaolin and high alumina ore: >45% Al2O3
High alumina clay clinker (also known as "cooked bauxite"): 75-90% Al2O3
6. Refractory mud / refractory clay mortar
Raw fire clay with calcined refractory clay or broken refractory clay bricks, or both, is milled to the appropriate fineness (Mining Terminology Dictionary, American Geological Society).
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