What are the combinations of magnesia chrome bricks?

Magnesia chrome brick combined with electrofusion

The fused recombined magnesia-chrome brick is called fused magnesia-chrome brick. The high temperature performance is between the fused cast magnesia chrome brick and the sintered magnesia chrome brick, and its load softening temperature can reach more than 1700 degrees. Generally, light-burned magnesia and chrome ore are used as raw materials, which are melted into fused magnesia-chromium sand in an electric furnace, and then crushed, ground, shaped and fired. The application field of this brick is similar to that of ordinary magnesia-chrome bricks.

Magnesium chrome bricks are directly bonded

The direct combination of magnesia-chrome bricks is developed on the basis of ordinary magnesia-chrome bricks, and its production characteristics mainly include two, one is to use pure raw materials, and the other is to use higher firing temperatures. The so-called direct combination means that there is more direct contact between the chrome ore particles in the brick and the periclase, because there is less SiO2 in the raw material (controlled at 1%-25%), and the output of silicate is less, and the silicate is fired at high temperature. Extrude into the corners of the solid phase particles. Thereby the direct binding of the solid phase is improved.

Magnesia-chrome brick co-sintering

The production process of this product is characterized by firing the mixture of magnesia and chrome ore fine powder in a certain proportion to realize the solid-phase reaction in which the secondary spinel and magnesia-chromium ore are directly combined to form a common sintered material. Fired products or chemically bonded products.

The direct bonding and microstructure uniformity of combined sintered magnesia-chrome bricks are better than those of direct-bonding bricks, and there are more periclase desolubilization phases and intergranular secondary spinels. Combined sintered magnesia-chrome bricks have a series of better properties than direct-bonded bricks, especially high temperature strength, thermal shock resistance and slag resistance.

Co-sintered bricks can also be divided into two types, one is co-sintered bricks, granules and fine powders, which are basically similar in microstructure, and the other is partially co-sintered bricks with some components, such as coarse-grained co-sintered materials and fine powders. Part of it can be mixed with fine chrome ore and magnesia paper powder in a certain proportion to make sintered and chemically bonded products different in microstructure.

Silicate combined with magnesia chrome brick

(SilicateBondedMagnesia-chromeBrick) is also known as ordinary magnesia-chrome brick. This kind of brick is made of chrome ore and magnesia, with high impurity content (mainly SiO2 and CaO), and the firing temperature is low, about 1550℃. Its microstructural feature is that the refractory grains are composed of silicates with low melting point or softening point, so they are called silicate and magnesia-chrome bricks.

The raw materials of magnesia-chrome brick production are: natural raw materials, synthetic raw materials, industrial chromium oxide and industrial alumina. Natural raw materials: such as sintered magnesia at all levels, ordinary chrome ore and low impurity chrome concentrate. Synthetic raw materials: co-sintered magnesia-chromium materials in which magnesia and chromium concentrates are finely ground, mixed, compacted, and then calcined at high temperatures; There is fused magnesia. Synthetic materials are generally low impurity raw materials.

The particles are chrome ore and the grey round particles are magnesia. Because the firing temperature of silicate and magnesia-chrome bricks is higher than 1580 °C, the magnesia particles contain a large amount of spinel desolubilization phase. The main crystalline phase in the matrix of silicate-bonded magnesia-chrome bricks is granular magnesia, and the cemented phase between magnesia and chrome ore particles or their respective particles is mostly isolated by off-white film silicate (CMS) or pores, followed by a small amount of Compound tip.

The spar (white) is filled between the periclase crystals, but the degree of direct bonding is very low. The matrix is ​​a dense network structure, the pores are mostly strips, and a few tend to be closed. Due to the different microstructural characteristics of silicate bonding.

Due to the high temperature mechanical properties and chemical attack resistance of ordinary magnesia-chromium refractory products, silicate and magnesia-chromium bricks are usually used in parts with lower performance requirements.

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