Direct-Bonded Magnesia Chrome Brick

Direct-bonded magnesia chrome brick

Direct bonded magnesia chrome bricks usually refers to magnesite chromite bricks made from low impurity chromite and high purity calcined magnesite, the sintering temperature is above 1700℃. The main bonding type of direct bonded magnesia chrome brick is direct contact, magnesia and chromite are closely contacted with each other, silicate is expelled to corners. Therefore,  this phenomenon is called periclase-periclase and periclase-chromite direct bonding. Comparing with ordinary magnesia chrome bricks, direct bonding magnesia chrome bricks have lower impurity ratio and higher sintering temperature. 

Magnesite chromite bricks are basic refractory product which’s main crystalline phase is periclase and magnesia chrome spinel. In direct bonded magnesia chrome brick, MgO content range is between 55%~80%. In chrome magnesia brick, MgO content is between 25%~55%. Except for direct bonded magnesia chrome brick, ordinary magnesia chrome bricks, Rebonded  magnesia chrome bricks, semi-rebonded periclase chrome bricks and unburned MgO-Cr2O3 bricks are also widely used for different applications.
 
Direct Bonded Magnesia Chrome Bricks Physiochemical Index
 

 
Direct Bonded Magnesia Chrome Bricks Characteristics

Direct bonded magnesia chrome bricks have low impurity content and high direct bonding ratio, so slag resistance and high temperature performance is better. Thermal shock resistance is excellent, under 1100℃ water cooling conditions, can reach to 4~10 times.

In direct bonded magnesia chrome brick, SiO2 content is lower than 2% or even 1%, refractoriness under load temperature is higher than 1650℃, or higher than 1700℃.

For direct bonded magnesia chrome brick production, MgO content is higher than 95%, it is better to be higher than 97%, bulk density is about 3.25g/cm3.

Direct Bonded Magnesia Chrome Bricks Application

Direct bonded magnesia chrome bricks are mainly used in rotary cement kiln, steel making electric furnace lining, refinery furnace (RH upper groove and lower groove permanent lining, VOD furnace wall), nonferrous metals smelting furnace, glass kiln regenerative chambers, lime kilns, iron mixing furnace and so on.

According to different applications, one or two types of magnesia and chrome can be used as batch material. For the production of cement kiln direct bonded magnesia chrome brick, calcined magnesite is added as the form of powder and grains, chromite is added as grains, Cr2O3 content is about 3%~14%. For the production of metallurgical furnace lining direct bonded magnesia chrome brick, Cr2O3 content should  be higher. When pure magnesia and chrome powders are used as matrix, the sintered bricks usually have expansion crack, so chrome content in matrix should be controlled in allowed range.