Research On The Effect Of Magnesia-zirconia Powder And Environmental Protection Pitch On Properties Of The Low Carbon MgO-C Brick

With the developing of external refining technology,, low carbon magnesia-carbon refractories became a research hotspot of the magnesia-carbon refractories. This work overviewed the development and the drawbacks of low carbon magnesia-carbon material, it requires champion strength, antioxidation, corrodibility resistance and thermal shock resistance and so on. According to the requirements above, this paper studied the effect of MgO particle size, MgO granularity, magnesia-zirconia powder size and content, pitch content on structure and conventional properties of low carbon magnesia-carbon refractories.After sintered for different experimental intentions, the bulk density, apparent porosity, cold crushing strength and high temperature bending strength of the specimens were determined, respectively. Besides properties above, antioxidation resistance, thermal expansion, thermal shock resistance and corrodibility resistance also determined, the phase composition and microstructure were observed by X-ray diffraction instrument, scanning electronic microscope, respectively. Then, conclusions are obtained as follows:1) MgO particle size plays an important role in improving the properties of low carbon MgO-C refractories. Reducing MgO granule size, the apparent porosity, pore size of sample and thermal stress became smaller, the bulk density, compressive strength improved, and the thermal expansion of specimens reduced. Besides, the pore size diminished, the speed of O2 diffusion slowed, and that can improve the oxidation resistance.2) Reduce magnesia power content and increase magnesia particle content, it can cause the low carbon magnesia-carbon refractories to have the graphite relative centralism phenomenon, and this can release thermal stress, and is propitious to enhance the materials'oxidation resistance and corrosion resistance.3) The influence of particle size and quantity of magnesia-zirconia powder on properties of low carbon magnesia-carbon refractories has been investigated. The results indicated that, because of the nature characters of magnesia-zirconia powder, such as, big bulk density, good corrosion resistance and phase transformation toughening of zirconia, both particle and powder can improve the physical properties, oxidation resistance, corrosion resistance and thermal shock resistance of low carbon magnesia-carbon materials. Compared with blank sample, when the magnesia-zirconia powder content is 15%, the thickness of corrosion layer reduced 38%, and the thermal expansion ratio reduced 12.6%.4) Pitch additive can promote the formation of spinel in specimens when sintered, this caused by the fine liquidity of pitch at high temperature. Because of the formation of AlON and MgAl₂O₄, the density, cold crushing strength and thermal shock resistance of specimens improved, after thermal shock test, the conservation rate of bend strength of blank sample remains 67%, but when pitch added, the number raise to 78%. Moreover, mosaic structure can formed when pitch and resin charred, and this will increase the carbon residue of composite, and it benefit to enhance the corrosion resistance and thermal shock resistance of specimens.