Xinyu Huayuan Wollastonite Co., Ltd.
Wollastonite is a metasilicate mineral of calcium, and it is an emerging industrial mineral raw material. At present, it is mainly used in the ceramic industry, followed by metallurgical protective slag and coatings, as well as electrode coatings, asbestos substitutes, abrasive binders, glass ingredients, and fillers for the production of rubber, plastics, insulation materials, and paper. Some wollastonite can be used as a building facing material or as an ingredient in the production of white cement.
1. Characteristics of ore and mineral raw materials:
The chemical formula of wollastonite is CaSiO3, the theoretical chemical composition: CaO48.25%, SiO251.75%. Pure wollastonite is rare in nature. During its formation, Ca is sometimes partially replaced by ions such as Fe, Mn, Ti, and Sr to form a quasi-homoid, mixed with a small amount of Al and trace amounts of K and Na.
Due to different conditions such as temperature and pressure during the formation of wollastonite, three kinds of homogeneous polyhedrons may appear: 1. Tc type wollastonite with triclinic chain structure, commonly known as low temperature triclinic wollastonite; 2. monoclinic ZM type para-wollastonite with chain structure is commonly known as para-wollastonite; 3. Pseudo wollastonite with ternary ternary ring structure is commonly known as pseudo wollastonite. At present, the low temperature triclinic wollastonite is mainly used as the raw material of industrial minerals. Low-temperature triclinic wollastonite is a triclinic crystal system, mostly needle-like, fibrous or flake-shaped, often clustered in a fan-shaped, radial aggregate, and some in fine particles. White with gray, red, glass luster, cleavage surface is pearly luster, cleavage parallel to medium, can be converted into pseudo wollastonite at about 1125 degrees, then the thermal expansion coefficient increases, and due to the release of impurities such as Fe, Sr , So the color changes from white to cream, red, or brown.
The natural types of wollastonite ores are generally skarn-type ores and wollastonite-quartz-calcite-type ores. The former is mainly produced in skarn deposits, with complex mineral composition, often associated with quartz, calcite and diopside, garnet and other skarn minerals; the latter is mainly produced in contact metamorphic and regional metamorphic deposits, mineral groups It is simple and can be divided into three subcategories: wollastonite-quartz, wollastonite-calcite and wollastonite-quartz-calcite. There are usually two kinds of structural structures of wollastonite ore: dense lump ore with fine-grained granite or fibrous crystal structure. Dense massive structure. Wollastonite is in the form of fine-grained, columnar or fibrous aggregates, with individual poles Fine-grained and dense ones are in the shape of jade; coarse-grained wollastonite ore has a fibrous crystalline structure, massive, breccia-like, giant plaque-like or band-like structure. (Chrysanthemum-shaped).
Second, the use and technical indicators of wollastonite
The quality requirements of wollastonite ore for industrial applications are as follows:
(1) Wollastonite for building ceramics
Because wollastonite has a low coefficient of thermal expansion, it is easy to co-melt with silicon oxide and alumina under low temperature conditions, does not contain chemically bound water or carbonate, and has needle-like crystal forms. (Mainly glazed bricks) raw materials, which can realize rapid firing at low temperature, reduce the shrinkage rate of the product and reduce the occurrence of warping and cracking, and can improve the strength of the green body and the quality of the molding, improve the mechanical properties of the product, and thus save energy consumption. The purpose of increasing productivity and reducing costs.
Wollastonite for building ceramics generally requires wollastonite content greater than or equal to 60% (such as containing diopside is also considered a useful component, its content can be offset with wollastonite content), quartz content is less than or equal to 20%, calcite The content is less than or equal to 13%, and Fe2O3 is less than or equal to 1.7%. According to the requirements of ore chemical composition, SiO238% -58%, CaO36% -55%, CO2 less than or equal to 6%, Fe2O3 less than or equal to 7%.
(2) Wollastonite for metallurgical protective slag
It is mainly used as the base material for the production of particle slab continuous casting, die casting protective slag and carbon-free protective slag. Because the composition of wollastonite is stable, the slab is free of defects and the surface is smooth; because CaO and SiO2 in wollastonite exist in a combined state, the ratio is just in the range of alkalinity required for continuous casting, which can reduce the base of the slag The type of material, simplify the process, and make the protective slag have good thermal stability; because the wollastonite contains Al2O3 is very low, it can enhance the performance of the protective slag to absorb Al2O3. The quality requirements of metallurgical protective slag on wollastonite concentrate: wollastonite is greater than or equal to 50%, calcite is less than or equal to 50%, quartz is less than or equal to 5%, S is less than or equal to 0.01%, and P is less than or equal to 0.01%.
(3) Wollastonite for paint
Because wollastonite has bright white, needle-like particle morphology and low oil absorption, it can produce high-quality white and soft light-tone paint, improve the toughness and durability of the paint, keep the paint surface smooth and good gloss, and resist scrubbing. And anti-weathering performance, can also reduce the oil absorption of the coating and keep it alkaline, with anti-corrosion ability.
The general requirements for wollastonite mines for paints and coatings: SiO2 greater than or equal to 49%, CaO greater than or equal to 45%, Fe2O3 less than or equal to 0.2%, 325 mesh ore powder oil absorption 20 ~ 25g / 100g, water solubles less than or equal to 0.5 %, The pH value of water extraction is 7-9, and the whiteness of 325 mesh ore powder is greater than or equal to 90%.
(4) Wollastonite for welding electrodes
Wollastonite is used as a coating material for welding electrode, which can act as a fluxing and slagging additive, suppress discharge during welding, reduce spatter, improve the fluidity of slag, make the weld seam neat and beautiful, and enhance mechanical strength. The general requirements of the welding electrode on the quality of wollastonite concentrate: SiO245% -55%, CaO35% -45%, MgO less than or equal to 0.8%, S less than or equal to 0.03%, P less than 0.03%.
According to the building material industry standard "Wollastonite" (JC / T535-94) of the People's Republic of China, natural wollastonite products are divided into five categories according to particle size: block, ordinary powder, fine powder, ultra-fine powder, and needle-shaped powder. The products are classified into excellent products, first-class products, second-class products and qualified products according to quality.