Liquid Phase Formation Behavior And Mineral Phase Regulation Mechanism Of Magnesia Fluxed Pellet

With the increase of the proportion of blast furnace pellets into the furnace,the requirements pellet performance are getting higher.Acidic pellets have the following problems low basicity,low melting temperature,dripping temperature range wide and other issues.The problems seriously hinder the pellet ratio increase in charge structure.So the scholars at home and abroad have paid more attention to magnesia flux pellets.In this paper,the effects of basicity,MgO content and SiO₂ content on the performance of magnesia flux pellets were studied by using the thermal process experiment.And the effect of chemical composition on the liquid phase and crystallization behavior of magnesia-containing flux pellets was studied by using FactSage thermodynamic simulation software.By using German Leica microscope DM4500 P the effects of chemical composition on the composition and volume percentage of pellets and minerals were analyzed.The effect of basicity,MgO and SiO₂ content on the properties of magnesia flux pellets has shown that,when the basicity increased,the decrepitation temperature decreased.And the compressive strength increased first and then decreased.When the basicity was 1,the pellet would reach the highest compressive strength of 2352N/balls,and the reduction swelling index decreased.The softening start temperature and the softening range increased.With the increase of MgO content,the compressive strength of green pellets increased,but the dropping strength of green pellets decreased.The decrepitation temperature increased first and then decreased.The compressive strength of pellets decreased,and the reduction swelling index decreased.The softening start temperature increased and the softening range decreased.With the increase of SiO₂ content,the compressive strength and dropping strength of green pellets decreased,the decrepitation temperature decreased,the compressive strength of pellets increased first and then decreased,the low temperature reduction disintegration increased.The reduction swelling index decreased,the softening start temperature decreased and the softening range increased.The analysis of the effects of basicity,MgO and SiO₂ content on the liquid phase formation,crystallization and mineral composition of pellets have shown that,the increase of basicity promoted the precipitation of CaFe₂O₄ and CaFe₄O₇,increased the liquid phase of pellets and the bond rate.With the increase of MgO content,the liquid phase of pellets decreased and the bond rate decreased.The increase of SiO₂ content promoted the precipitation of CaFe₄O₇ and CaFe₂O₄,increased the liquid phase of pellets and the bond rate.When the basicity increased,the content of hematite changed a little,the content of magnetite and calcium ferrite increased,and the porosity decreased first and then increased.With the increase of MgO content,the content of hematite decreased,but the content of magnetite,calcium ferrite and porosity increased.With the increase of SiO₂ content,the content of hematite and calcium ferrite increased,the content of magnetite decreased,the porosity increased first and then decreased.In the experimental range of research,through the thermal process experiment,FactSage simulation results and mineral composition and microstructure analysis,the conclusion can be drawn that when the basicity is 1.0,MgO content is 1.8%and SiO₂ content is 5.0%,the magnesia flux pellets will show the best performance.