Our company's amorphous refractory materials are of many varieties and strong usability, mainly including lightweight alkali-resistant castables, high-strength refractory castables, steel fiber reinforced refractory castables, alkali-resistant refractory castables, clay and high-alumina refractory castables, alumina-magnesium spinel castables and various ramming materials and hot patching materials, which are widely used in thermal equipment such as cement kilns, glass kilns, metallurgy, and chemical industry.
Refractory granular materials that play a skeleton role in the particle size composition of refractory materials. They are granular materials with a particle size greater than 0.088mm made from various refractory raw materials through calcination, crushing or artificial synthesis. Aggregates are the main materials in amorphous refractory materials, generally accounting for 60%~75% of the total composition. Therefore, the material of amorphous refractory materials is generally named after the aggregate material used, such as refractory castables or refractory ramming materials with high-alumina bauxite clinker as aggregates, called high-alumina castables or high-alumina ramming materials.
Classification Refractory aggregates are classified into clay, high alumina, corundum, silica, magnesia, magnesia-alumina spinel refractory aggregates, etc. according to their materials. (See refractory dense aggregate, heat-insulating lightweight aggregate)
Products Description
According to porosity, they can be divided into dense aggregate (also called heavy aggregate) and lightweight aggregate (also called porous aggregate). Dense aggregate refers to aggregate with a porosity of no more than 30%. Dense aggregate can be divided into extra-dense aggregate (porosity ≤ 3%), high-dense aggregate (porosity 3%~10%) and ordinary dense aggregate (porosity 10%~30%). Lightweight aggregate refers to aggregate with a porosity greater than 45%. Lightweight aggregate can be divided into ordinary lightweight aggregate (porosity 45%~80%), ultra-lightweight aggregate (porosity>80%) and special lightweight aggregate (such as hollow alumina and zirconia balls).
In the production of unshaped refractory materials, refractory aggregates are generally divided into coarse aggregate, medium aggregate and fine aggregate. The particle size range of coarse, medium and fine aggregates is related to the critical particle size of the aggregate (i.e. the maximum particle size). For example, when the maximum particle size of the aggregate is 8mm, the particle size range of the coarse aggregate is 8~3mm, the particle size range of the medium aggregate is 3~1mm, and the particle size range of the fine aggregate is 1~0.088mm (or 0.074mm). Those smaller than 0.088mm (or 0.074mm) are not called aggregates, but powder (or matrix). For example, if the maximum particle size of the aggregate is 3.5mm, the particle size range of the coarse aggregate is 3.5~1.5mm, the particle size of the medium aggregate is 1.5~0.5mm, and the particle size of the fine aggregate is 0.5~0.074mm. The ideal aggregate particle gradation should be able to achieve the most compact stacking, that is, the gaps left after the coarse particles are stacked together are filled with medium particles, and the tiny gaps left after the medium particles are filled are filled with fine particles, thus forming a skeleton, and the remaining gaps are filled with powder. However, due to the irregular shape of refractory aggregate particles, it is difficult to obtain an ideal aggregate particle gradation in actual production. Usually, the aggregate gradation is determined by experiments. Generally, the coarse, medium and fine gradation ratios of aggregate are (35~45):(30~40):(15~25).
Shape Most refractory aggregate particles are multi-phase polycrystalline materials. Therefore, the shape of refractory aggregate particles is related to the crystal structure, crystallization habit and impurity content of each phase of the material itself, as well as the processing method of the material. For example, mullite obtained by electric melting method is mostly columnar polycrystalline aggregates because it is precipitated from the melt and is mostly eumorphic crystals. Therefore, according to the crystallization habit of mullite, it is mostly columnar polycrystalline aggregates. When it is broken, the grain boundary breaks along the length direction with poor bonding force, and the broken particles are mostly columnar polycrystalline particles. Mullite obtained by sintering method has needle-shaped, columnar, plate-shaped and granular shapes because the development and generation of crystals are restricted by the surrounding ring field, and they grow irregularly and interspersed with each other. Therefore, the broken particles have irregular shapes, such as flakes, needle-shaped columns, and angular shapes. On the other hand, the shape of the refractory aggregate particles after breaking is also related to the density of the material itself and the way of breaking. For example, for the ultra-dense and high-dense high-alumina clinker, if the impact or extrusion crushing method is used, the aggregate particles are mostly flake or angular; if the grinding crushing method is used, they are mostly irregular particles or nearly spherical. Therefore, in order to produce the aggregate particle shape that is more suitable for amorphous refractory materials, a more appropriate crushing method should be selected.
Application The particle shape of refractory aggregate has a great influence on the construction performance of amorphous refractory materials. The rheological properties of the mud prepared by irregularly shaped particles such as flakes, columns, needle columns, and angular shapes are poor, while the rheological properties of the mud prepared by nearly spherical and spherical particles are better. Therefore, irregularly shaped aggregate particles are used to prepare spray coatings and ramming materials, which are conducive to the interlacing, biting and pinning between particles and can improve the bonding strength. Nearly spherical and spherical particles can be used to prepare castables, coatings and injection materials, which are conducive to improving the rheological properties of the mud and improving the thixotropy, thereby helping to increase the volume density.
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