Analysis of compressive strength and microstructure during mineralization process of flux based pellets
The compressive strength of the pellets is one of the main indicators to measure whether the pellets can en-ter the blast furnace smelting,and the compressive strength of the pellets is determined by the mineral composition and microstructure of the pellet.Zhongguan iron ore is used as the basic pelletizing raw material,and low-silica flux pellets are prepared by calcium and magnesium additives.By systematically studying the microstructure and mineral distribution morphology of pellets under different MgO content,alkalinity and SiO2 content,the change law of com-pressive strength of low silicon flux pellets was revealed.The results show that increasing the roasting temperature and alkalinity can effectively improve the compressive strength of pellets.When the SiO2 content was low,the pel-lets are mainly consolidated by hematite crystals,and the strength change is not obvious.When the mass percent of SiO2 increased to 3.5％and 4.0％,respectively,the hematite crystals were gradually interconnected into pieces,and the crystals gradually became coarse and compact,the structural strength was strong,and the compressive strength of the pellets increased.With the increase of alkalinity,hematite recrystallization is better,there are few granular alone and the crystals are interconnected into blocks,magnetite is reduced,the liquid phase of low silicon flux pellets increases during the roasting process,and the liquid phase of calcium ferrite system appears to increase the strength of the pellets.With the increase of MgO percentage,more Mg2+entered the magnetite phase,which made up for the lattice defect,and the magnesium ferrite content increased and appeared needle-like or flake distribu-tion in hematite,which inhibited the formation of liquid phase during the roasting process,and made the pores inside the pellet smaller during the cooling process,thereby improving the density of the pellet and enhancing the strength of the pellet.The content of MgO continued to increase,the content of magnetite and glass phase increased,and the content of hematite and calcium ferrite decreased relatively.And because the increase of Fe3O4 will reduce the con-junctive performance of Fe2O3,and eventually lead to the decrease of the compressive strength of the pellets.The a-bove studies provide theoretical guidance and reference for the exploration of low silica magnesium flux pellets.
flux based pelletslow silicon refined powdercompressive strengthmineral compositionmicrostruc-ture
NETL
NSTL
万方数据
