These days MgO-C refractories are wide spread in steel making furnaces, because of the properties like: thermal shock resistance and corrosion resistance. Oxidation of carbon is one of the most important problems of these refractories, and this results increasing of porosity and decreasing the strength and corrosion resistance. Using reinforcement like: SiC and B 4 C as antioxidant, prevents oxidation of carbon and increase the strength at high temperatures. The aim of this research is formation of insitu SiC nano whiskers in MgO-C refractories. SiC by having unique characterization improves the properties of these refractories. It is prospected that the produced composite will have good resistant to thermal shock. The formation of these insitu whiskers, accomplish at usage temperature and is not an expensive additive. Some of these whiskers decomposes to Si and C during usage. Si acts as an antioxidant and prevents from oxidation of C. Also C has it’s good effects on MgO-C refractories. Initial materials including fused magnesia, sintered magnesia, flake graphite and calcinated alumina were mixed by binder and additives such as: Ferrosilicon, SiC and B 4 C were added to this mixture. The powder was pressed by 4 MPa pressure and the samples were tempered at different temperatures and times. Phase structure and morphology were detected by XRD and SEM . Bulk density (BD), Cold Crushing Strength (CCS), tensile strength with Brazilian test, Apparent porosity (AP%) and water absorption were investigated. Also the reaction between steel’s slag and the refractory was observed. Some of the samples were coked and heated to 1650 degree centigrade and formation of insitu nano whiskers was studied. The results show that by adding Ferrosilicon to samples at 1650 degree centigrade insitu SiC nano whiskers have been produced. Formation of whiskers improves the physical, mechanical and corrosion properties of these refractories. At 250 degree centigrade by adding 3wt% Ferrosilicon to samples, Strength 1.5 times increased and at 1650 degree centigrade by adding 5wt% Ferrosilicon to samples, strength 1.9 times increased. In samples with 3wt% SiC, at low temperature 1.5 times and at high temperature 1.8 times strength has been increased. In samples with 1wt% B 4 C at 250 degree centigrade strength has been increased 1.4 times. Keywords : MgO-C refractories, insitu SiC nano whiskers, Physical mechanical and corrosion properties.
