Iron ore's assimilation characteristic reflecting the beginning formation temperature of liquid phase in sintering process plays very important role on the fluidity of liquid phase and bonding strength of sinter body. Experimental study of assimilation characteristics of 12 kinds of iron ores were conducted using micro-sinter equipment, and pure reagent simulating tests of assimilation characteristic were also carried out for the purpose of achieving the influence of chemical composition on the assimilation characteristic. In addition, effects of assimilation characteristic of iron ore on the fluidity and bonding capacity of bonding phase were also researched. This study showed that SiO2 and LOI promoted the assimilation of iron ore, low Al2O3 (<1.5 mass%) was good to the assimilation, but high Al2O3 (≥1.5 mass%) was bad, MgO was adverse to assimilation of magnetite concentrate. In addition, lower assimilation temperature of iron ore led to higher superheat degree of liquid phase at a certain sintering temperature, then higher liquid fluidity and bonding strength.

To achieve the action mechanism and optimal usage of dolomite in the sintering process, solid reaction tests, fluidity tests, bonding strength tests and sinter pot tests were conducted, then microstructure and energy spectrum were analysed further. Reaction temperature of dolomite with calcium ferrite was lower than that with limonite iron ore about 155°C. Fluidity of bonding phase and strength of sinter using dolomite were lower than that using light burned dolomite and serpentine owing to the higher MgO content in the calcium ferrite and formation of secondary bonding phase. Action mechanism of dolomite in sintering process mainly included 4 steps, thermal decomposition, solid reaction, formation of primary bonding phase and formation of secondary bonding phase. Dolomite mainly played it's role in the third step in which high viscosity CFM (calcium ferrite with MgO) and magnetite solid solution formed. Increasing the solid solubility of MgO in magnetite by mixing dolomite with magnetite concentrate before granulation, decreasing the dispersity of MgO in sinter mixture by increasing the particle size of dolomite appropriately, increasing the separation degree of MgO and CaO by light-burning the dolomite, and decreasing the reaction amount of MgO by using big particle size magnesia, all could decrease the content of MgO in calcium ferrite, thus showed good performance in sinter pot tests.

Return fines is unavoidably formed in sintering process, it recycles back into sintering and makes up 30 to 40% of the iron bearing materials. When deteriorated raw materials are applied, sintering process is balanced with higher ratio of return fines, which greatly affected sintering efficiency and fuel consumption. In order to reduce the return fines by effectively using, basic researches were conducted using modeled quasi-particles, consisting of return fines and sintering blend. Proper using ratio of two kinds of return fines were confirmed by measuring both granulating and bonding ability, then reasonable quasi-particle structure of return fines was proposed from the perspective of segregated basicity optimization. The results obtained were summarized as follows: Return fines generated from unassimilated iron ores, insufficient uniformity of melt, highly developed porous structure and lower internal force of eutectic structures. Assimilation ability and liquid fluidity of return fines were higher than sintering blend, resulting in promotion of low-temperature melt generation. The optimal addition of return fines from BF sieving was suggested not to surpass 30 mass% by melt generation balance, and the ratio for return fines from sintering sieving should be controlled at about 20 mass% with contradictory effect on bonding and granulation. Quasi-particles of returns fines were characterized by high compactness and uniformity at lower segregated basicity, weaken melt formation surrounding returns fines to strengthen that of iron ores was the effectively using way.

Gangue existing states largely affect the high-temperature characteristics of iron ores. Using a micro-sintering method and scanning electron microscopy, the effects of gangue content, gangue type, and gangue size on the assimilation characteristics and fluidity of liquid phase of five different iron ores were analyzed in this study. Next, the mechanism based on the reaction between gangues and sintering materials was unraveled. The results show that, as the SiO 2 levels increase in the iron ores, the lowest assimilation temperature (LAT) decreases, whereas the index of fluidity of liquid phase (IFL) increases. Below 1.5wt%, Al 2 O 3 benefits the assimilation reaction, but higher concentrations proved detrimental. Larger quartz particles increase the SiO 2 levels at the local reaction interface between the iron ore and CaO, thereby reducing the LAT. Quartz-gibbsite is more conductive to assimilation than kaolin. Quartz-gibbsite and kaolin gangues encourage the formation of liquid-phase low-Al 2 O 3 -SFCA with high IFL and high-Al 2 O 3 -SFCA with low IFL, respectively.

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