Fundamental mechanism of effects of MgO on sinter strength
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MgO-containing flux may have a series of effects on the quality of sinter and performances of the blast furnace. Thus, the fundamental mechanism of the effects of MgO on the sinter strength was investigated. Both the chemical reagent and industrial flux were used for preparing the specimens. The experimental results show that the sinter strength decreases with MgO addition. There are three reasons for it. The first reason is diffusion rate. Almost all of the CaO may react with Fe2O3 and generate CaO·Fe2O3, but most of MgO cannot react with Fe2O3, and it still remains in the state of original minerals. The diffusion rate of MgO in iron oxide is only 17.51 μm/min in 30 min. The second reason is the fluidity and ability to generate liquid phase. In the case of Fe2O3 mixed with CaO, there is some liquid phase formed above 1200 °C, while in the case of Fe2O3 mixed with MgO, even at 1200 and 1220 °C, there is still no liquid phase. The third reason is self-strength. In the case of industrial flux, the compression strength of the specimens made of Fe2O3 and limestone is 0.52 and 0.71 kN at 1150 and 1180 °C, respectively, while that of the specimens made of Fe2O3 and magnesite is 0.48 and 0.56 kN, respectively. Therefore, the fundamental mechanism of the effects of MgO additive on sinter strength can be better understood based on the diffusion rate of MgO in iron oxides, the fluidity of liquid phase, and the self-strength of bonding phase.
KeywordsMgO addition Sinter strength Blast furnace Mineralization rate Fluidity Self-strength
The authors wish to acknowledge the contributions of associates and colleagues at Northeastern University of China and Meishan Steel of China. Also, the financial supports of the National Natural Science Foundation of China (NSFC 51874080, 51774071, and 51604069) are appreciated very much.
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