Effects of Fine MgO-Bearing Flux on the Strength of Sinter before and after Low-Temperature Reduction

Decreasing the MgO content can improve most of the metallurgical properties of sinter, but the low-temperature reduction disintegration index (RDI) property will be worse. In order to improve the RDI property of sinter under certain MgO contents, the effects of fine MgO-bearing flux on the strength of sintered samples before and after reduction in three systems (Fe₂O₃-MgO, Fe₂O₃-MgO-CaO, and Fe₂O₃-MgO-CaO-SiO₂) were investigated in the present work. The experimental results show that (1) in the three systems, the percentage of fine light calcined magnesite (LCM) increases from 0 to 100%, and the compression strength of the samples before reduction increases from 0.140 to 0.187 MPa, from 0.115 to 0.175 MPa, and from 0.121 to 0.164 MPa, respectively. The compression strength of the samples after reduction increases from 0.062 to 0.151 MPa, from 0.100 to 0.156 MPa, and from 0.099 to 0.151 MPa, respectively. (2) The fundamental reason is that the fine powders can increase the specific surface area and the surface energy of the interface. It is beneficial to promoting the mineralization of MgO-bearing flux. More formation of MgO·Fe₂O₃ may increase the strength of samples before reduction. Less transformation from Fe₂O₃ to Fe₃O₄ may increase the strength of samples after reduction. The microstructures of samples are more compact and uniform. Therefore, fine LCM can improve the strength of sinter before and after reduction. The outcomes of the present work can improve the sintering quality by using the fine MgO-bearing flux in the sintering process.