Philippines customer order 30 tons magnesia bricks.
Composition of magnesia bricks and magnesia silica bricks
Magnesia bricks use more than 87% sintered magnesite as raw material, and the main crystal phase of the product is periclase, and there are also alkaline refractory materials such as composite spinel, forsterite, forsterite and a small amount of glass phase. It has strong alkali resistance and weak acid resistance. Because its matrix-bonding component is mainly CMS-M2S system, its thermal conductivity is good but becomes worse with temperature rise, heat capacity increases with temperature rise, and high refractoriness ( Generally higher than 2000 ℃). However, its load softening temperature is only about 1550 ℃, and its thermal shock resistance is poor. Some of its important properties mainly depend on the characteristics of raw materials, the mineral composition and apparent rice structure formed in the product, and are closely related to the density of the product.
The raw material for magnesia-silicate bricks is mainly high-silicon magnesite with a Si02 content of about 5% to 11% in high-silicon magnesite.
(1) Raw materials and production process used
The magnesia raw material is crushed into granules and powders, and after being proportioned according to a certain ratio, a binder is added to mix and knead into mud, and then it is formed, dried, and fired to be fired. The firing temperature of Jingtong is generally 1500~1650°C, and the firing temperature of high-purity magnesia bricks is as high as 1700~1900°C. The production process of chemical bonding is basically the same, except that chemical bonding does not require high temperature firing, and only requires appropriate low temperature. Heat treatment can be made into unfired magnesia bricks.
(2) Properties and Precautions for Use
The hydration resistance of magnesia bricks is poor, and it is easy to hydrate when exposed to water, and cracks will occur, reducing its strength. Therefore, pay attention to moisture, rain and snow during storage and transportation.
Composition of magnesia chrome brick
Magnesia-chrome brick is an alkaline refractory product containing MgO55%-80%, Cr203 8%-20%, with periclase and composite spinel XO Y2O3 as the main crystal phase, of which XO is mainly MgO and FeO; Y203 is mainly Cr203, Al203, Fe203. The molar numbers of XO and Y2()3 are equal, and the excess Y203 is dissolved in the composite spinel. There are also small amounts of silicate phases (forsterite and forsterite).
Raw materials used and production process
Magnesia-chrome bricks use high-quality sintered magnesia and chromite (Cr203 30%-15%, CaO 1%-5%) as the main raw materials. The production process of magnesia bricks is roughly similar to that of magnesia bricks. Unburned magnesia bricks use inorganic magnesium salt solution as a binder. During the firing process, due to the loosening effect caused by the expansion of spinel when MgO reacts with CrO3, Al2O3 or iron oxides, pre-synthesized magnesia sand can be used to make bricks, which must be fired in an oxidizing atmosphere above 1600 ° C. become. If the nature of the atmosphere changes, Fe203 in chromite is affected by the redox reaction to form iron oxides of various valences. At the same time, Cr203 is also reduced to produce different valence compounds. Under repeated reactions, bricks will be damaged, so products with high MgO and low Cr2O3 should be used as much as possible.
According to the raw materials and process characteristics of the products, it can be divided into fused cast magnesia bricks, directly bonded magnesia bricks, silicate bonded magnesia bricks, rebonded magnesia bricks, semi-recombined magnesia bricks, pre-reacted magnesia bricks and non-reactive magnesia bricks. Burnt magnesia brick.