Effects of Graphite, SiO2, and Fe2O3 on the Crushing Strength of Direct Reduced Iron from the Carbothermic Reduction of Residual Materials

The effects of various additives (Fe2O3. SiO2, graphite) on the crushing strength of direct reduced iron (DRI) were investigated. Using a mixture of various residual materials produced in a steel plant, the chemical composition was altered using various additives. The mixture was then agglomerated into a cylindrical pellet and reduced at 1250 degrees C for 15 min. The DRI was then tested for its crushing strength. It was found that adding graphite resulted in more carbon remaining in the DRI. Although the metallization degree of DRI was increased, the crushing strength of DRI decreased due to the presence of discontinuous carbon granules in DRI. Adding SiO2 caused the slag basicity (the ratio between CaO and SiO2) to decrease. The addition of Fe2O3 consumed the carbon content in the pellet, reducing the metallization degree of DRI. The softening and melting temperatures of slag were adjusted by changing the slag basicity and FeO content. A proper amount of Fe2O3 or SiO2 addition increased the crushing strength of DRI due to the softening of slag. Excessive Fe2O3 or SiO2 resulted in the melting of slag, which decreases crushing strength. [doi: 10.2320/matertrans.M2009299]