Since there are many varieties of magnesia-chromium refractory bricks, some literatures have classified and summarized them:

(1) Silicate-bonded magnesia-chromium refractory bricks (ordinary fired magnesia-chromium bricks). This kind of brick is made of common chrome ore with high content of impurities (SiO2 and CaO) and brick-making magnesia, and the firing temperature is about 1550 ℃. The structural characteristics are: the refractory grains are combined by silicate, the apparent porosity is high, the resistance to slag erosion is poor, and the high temperature volume stability is poor.

(2) Pre-reacted magnesia-chromium refractory bricks. The magnesia (light-burned magnesia powder) and the chrome ore are co-milled and fired in a kiln, and the synthetic magnesia-chrome sand is used as the raw material to make bricks to form "pre-reacted magnesia-chrome bricks". Pre-reacted magnesia-chrome bricks are an improved type of silicate-bonded magnesia-chrome bricks.

(3) Directly combine magnesia-chromium refractory bricks. The direct-bonded magnesia-chromium refractory is made of chromium concentrate with low impurity content and relatively pure magnesia, and the firing temperature is above 1700 ℃. Its structural characteristics are: the refractory grains are mostly in direct contact, and the direct bonding degree of periclase (solid solution)-periclase (solid solution) and periclase (solid solution) spinel (solid solution) in the brick is high, so Its high temperature performance, good slag corrosion resistance, and high temperature volume stability are better than ordinary magnesia-chrome bricks.

(4) The molten grains are combined with magnesia-chromium refractory bricks (electro-dissolved and then combined with magnesia-chromium). The magnesia and chrome ore (light burnt magnesia powder or magnesite and chrome ore) are fully and uniformly reacted by the electrofusion method to synthesize periclase solid solution and spinel solid solution magnesia-chromium raw materials with more ideal structure, and then combine magnesia-chromium The brick is made of this raw material, which is called molten grain recombined magnesia-chrome brick. Since the raw materials for making refractory bricks are relatively pure, they all need to be fired at a high temperature or ultra-high temperature above 1750 °C. Its microstructure is characterized by uniform distribution of spinel and other components, low porosity, direct contact between refractory grains, high compressive strength, good corrosion resistance, and high temperature strength, but the disadvantage is thermal shock stability. poor.