Detailed explanation of directly bonded magnesia chrome bricks

Performance index of fused cast magnesia chrome brick. The fused cast magnesia chrome brick is a refractory product made from magnesia and chrome ore by electric melting and casting. The production process of fused cast magnesia chrome bricks is shown in the figure below.

It is characterized by large and isolated pores, dense products, high strength, corrosion resistance and sensitivity to temperature changes. The chemical property of magnesia chrome brick is alkaline. Compared with magnesia brick and chrome brick, it has good thermal shock resistance, stable volume at high temperature and high load softening temperature.

Magnesia chrome brick is an alkaline refractory product containing 55% 80% MgO and 8% 20% Cr2O3, which is composed of periclase, composite spinel and a small amount of silicate phase. Composite spinels include MgAl2O4, MgFe2O4, MgCr2O4 and FeAl2O4 spinel solid solutions.

Magnesia chrome bricks have been developed rapidly since the 1960s due to the improvement of raw material purity and firing temperature. At present, according to different production methods, magnesia chrome bricks can be divided into ordinary bricks, direct bonded bricks, common fired bricks, re bonded bricks and fused cast bricks. (1) Ordinary magnesia chrome brick

This is a traditional product, with chrome ore as the coarse particle and magnesia as the fine powder. Or the two materials are composed of graded particles, and the firing temperature is generally 15501600 ℃. The microstructure of this kind of brick shows that there is little direct combination between chrome ore particles and periclase, and most of them are silicate (CMS) cementation or fissure isolation; There are few desolvated phases in periclase and few direct bonding in matrix. This kind of brick has poor mechanical properties and slag corrosion resistance.

(2) Direct bonded magnesia chrome brick

The direct bonded magnesia chrome brick is developed on the basis of ordinary magnesia chrome brick. Its production features mainly include two aspects: first, using pure raw materials, and second, using higher firing temperature. The so-called direct bonding means that there is more direct contact between chrome ore particles and periclase in the brick. Because there is less SiO2 in the raw materials (controlled below 1% 25%) and less silicate generation, the silicate is squeezed into the corner of the solid particles by means of high-temperature sintering. So as to improve the direct combination of solid phase.

The direct bonded magnesia chrome brick has high high temperature strength, slag resistance, corrosion resistance, erosion resistance, corrosion resistance, excellent thermal shock stability and volume stability at 1800 ℃ due to its high direct bonding degree.