The Effect Of Carbon Black And ZrB₂Antioxidants On The Performance Of Low Carbon MgO-C Refractory

MgO-C refractory is a kind of carbon containing composite with excellentproperties of both graphite and magnesia. It has good resistance to slag erosion andthermal shock, so it has been widely used in converter, furnace, linings of refiningfurnace and slag line etc since the1970s. As the economical utilization of resource andthe development of special steel, people pay more attention to the development andapplication of low carbon MgO-C refractory.Five kinds of carbon black (semi-reinforcing carbon black, SRF; general purposefurnace black, GPF; fast extruding furnace black, FEF; spray black and high abrasionfurnace black, HAF) and fine flake graphite were used in our study. ZrB2is used asantioxidant. ZrB2can not only overcome drawbacks resulting from the consumption ofC in low carbon MgO-C refractory by reaction of Al or Si antioxidant and C, but alsosolve problem of the increasing of C resulting from reaction of B4C with O2or CO.The effect of oxidation resistance of different carbon blacks and the mechanism ofoxidation resistance of ZrB2were investigated in this paper by means of the analysis ofX-ray, SEM-EDS, TEM, TG-DSC and thermodynamics calculation of the samples.The result shows that the oxidation resistance of SRF and GFE is better (similarwith flake graphite).It is because that SRF and GEF have bigger particle size andsmaller structure than other carbon black, they can evenly distributed in MgO-Csamples. By contraries, the structure of FEF, spray black and HAF is muchcomplicated and they are easy to accumulate. It is very difficult to distribute themevenly in MgO-C samples, so they have weaker oxidation resistance relatively. The results of TG-DSC and X-ray show that ZrB2antioxidant is oxidized to ZrO2and B2O3in the process of heating, then B2O3react with MgO to form magnesiumborates which become liquid phases in high temperature. The liquid phases fill in thepores and prevent the air diffusing into the material. SEM shows ZrO2crystals aredistributed in matrix, strengthening the structure of matrix.