Effect Of Carbon Contents And Types On Elastic Modulus And Thermal Shock Resistance Of MgO-C Refractories

MgO-C refractory has good corrosion resistance and thermal shock resistance. Withthe progress in iron and steel making technology, low-carbon magnesia carbon brick isthe main development direction of MgO-C refractory. Due to the lower carbon content,the elastic modulus of low-carbon magnesia carbon brick will increase and the thermalconductivity of it will decrease, causing the thermal shock stability of the materialsworse. In order to solve these disadvantages of the low-carbon magnesia carbon brick,researchers at home and abroad do a lot of works for improving the carbon structure,optimizing the structure of matrix of magnesia carbon material, adopting effectiveantioxidants, etc. And there are few research on the change of elastic modulus underdifferent temperature and the relation between the elastic modulus and the thermalshock resistance..The modulus of elasticity of MgO-C with graphite, general furnace black, Alpowder and ZrB2as starting raw materials was measured by impulse excitation ofvibration (IDT) method. The phase composition and microstructure characteristics ofsamples added general furnace black under high temperature were investigated bymeans of XRD, SEM and EDX analysis. Factors affecting elastic modulus and theinteractions between thermal shock resistance and the elastic modulus were alsodiscussed.Experimental results indicated that the elastic modulus of samples heated under thecondition of reduction atmosphere in240~1000℃which decrease is due to the increaseof apparent porosity by the volatilization of the phenolic resin and part of graphiteoxidation carbide; the elastic modulus heated in1000~1400℃increased is due to the generated magnesium aluminium spinel, making some pores filled in a sample andreducing the porosity of the sample; the elastic modulus of sample containing generalfurnace black sample at1400℃has increased dramatically, which may be due to afibre formation in samples. The elastic modulus of sample containing ZrB2heated at1400℃had obvious increase which may be due to the oxidation of ZrB2, as a result,the ZrO2is generated after the oxidation of ZrB2. The ZrO2in the cooling process willtransform from tetragonal phase to the monoclinic phase, which have a certain degree ofvolume expansion and result in a decrease of internal pore size; and B2O3in the coolingprocess from high temperature to low temperature also can clog pores and make thestructure more density, which let to the elastic modulus increased.The samples added general furnace black have good thermal shock resistance. Thesamples added ZrB2have bad thermal shock resistance. The results by measuring thebending strength and the elastic modulus can be used to predict the thermal shockresistance of the sample by calculating R ’’’.