Semi-recrystallized magnesia-chrome brick is a refractory product fired from partial fused magnesia-chrome sand. The main mineral compositions of semi-reclaimed magnesia-chrome bricks are periclase, spinel and a small amount of silicate. The granules are opaque, the spinel in periclase is well developed, and the matrix part is metasomatic turbidity structure. The crystals are directly bound by periclase or periclase-spinel, and the silicate phase exists in an isolated state among the grains. The thermal shock resistance of semi-reclaimed magnesia-chromium brick is better than that of directly bonded magnesia-chromium brick. The physical and chemical properties of semi-reclaimed magnesia-chromium brick are shown in table.
1. Manufacturing Technology
Using fused magnesia-chromium material as granule, adding part of chromium ore and magnesia or sintering synthesized magnesia-chromium material as fine powder, brick is made by conventional process. The fused magnesia-chromium material should be smelted in a weak oxidizing atmosphere, and there should be no more reducing phases in the material, let alone metal iron and chromium; the magnesia and chromite used as fine powder must be co-grinded, and the fineness should be guaranteed to be less than 0.088mm, accounting for more than 95%; the density of the brick is more than 3.2g/cm3 when the high tonnage press is used to form the brick. After drying, the moisture content in the kiln is less than 1.0%. The products are fired in tunnel kiln, the firing temperature is above 1750 C, and the weak oxidation atmosphere is maintained in the kiln.
2. Characteristic and Application
Semi-reclaimed magnesia-chromium bricks are compact, low porosity, high temperature strength, better thermal shock resistance than reclaimed magnesia-chromium bricks, and have strong slag corrosion resistance. It can be used in vulnerable parts of steelmaking electric furnaces, RH and DH vacuum degassing devices, VOD, LF, ASEA-SKF, AOD secondary refining slag line and other parts with serious erosion, copper converter tuyere area, cement rotary kiln firing zone and regenerator of glass furnace.
Semi-recrystallized magnesia-chromium brick has lower cost and better thermal shock resistance than recrystallized magnesia-chromium brick, which can replace recrystallized magnesia-chromium brick in a certain range.
3. Characteristics of semi-reclaimed magnesia-chrome bricks
Semi-reclaimed magnesia-chrome brick is made of high quality magnesia and fused magnesia-chrome sand. The product has good thermal shock stability and slag erosion resistance. It is suitable for VOD, AOD, LF and RH refining furnaces.