Process of manufacturing the sinter has been considered. It has been shown that oxidation-reduction reactions significantly influence thermal phenomena of the process and formation of finished products. This influence has insufficiently been studied. In connection with this, mathematical model of carbon combustion and oxidation-reduction reactions has been developed taking into account results of experimental investigations. It has been shown that for calculating the heat-engineering characteristics of carbon combustion and oxidation-reduction reaction, it is necessary to correct experimental data.