This study investigates the pattern of influence of blast furnace slag tempering on the composition and structure of steel slag. The chemical composition, equilibrium phase composition, microscopic morphological characteristics and elemental composition of microscopic regions of steel slag and blast furnace slag modified by high temperature reconstruction were analyzed using X-ray diffractometer (XRD), FactSage7.1 thermodynamic analysis software, mineral phase microscopy and field emission scanning electron microscopy. The results show that blast furnace slag blending can promote the generation of a low melting point phase in the slag, as well as reducing its melting temperature and improving its high temperature kinetic conditions. On the one hand, the incorporation of blast furnace slag was found to promote the generation of C₂S in the steel slag and improve its gelling activity. Notably, at 1400 °C, the C₂S content (mass fraction) of steel slag modified with 15% high temperature reconstruction reached 39.04%, while that of unmodified steel slag at this temperature was only 16.92%, i.e., only 1/4 of the C₂S content in the modified slag. On the other hand, the incorporation of blast furnace slag inhibited the generation of a-C₂S-C₃P and calcium ferrate minerals, refined the grains of calcium–aluminum yellow feldspar, reduced the alkalinity and promoted the generation of silicate phases with high hydration activity in steel slag.

In order to transform the crystalline form of Ca₂SiO4 (C₂S) in phosphorus-containing slag from monoclinic β-polycrystalline to square γ-polycrystalline, a volume expansion of about 11% was generated, which caused the phosphorus-containing slag to undergo self-powdering. The CaO-SiO₂-Al₂O₃-MgO-MnO-P₂O₅-FeO slag system was analyzed using FactSage7.1 thermodynamic software, and the effects of different P₂O₅, FeO and basicity on the mineral phase composition of slag system were analyzed in the range of 1300~1700 °C. It was shown that P₂O₅, FeO and basicity all have an effect on the composition of the mineral phases. When the mass fraction of P₂O₅ in the slag was lower than 0.25%, it had less effect on the transformation of C₂S crystalline structure. When the P₂O₅ content was higher than 0.25%, it was favorable to the generation of low-melting-point substances, but the P₂O₅ in the slag reacted with C₂S in the silicate phase, making P⁵⁺ solidly soluble in C₂S, inhibiting the transformation of β-C₂S to γ-C₂S and hindering the self-powdering of the slag. The FeO content in the slag system ranged from 20% to 28%, and as the FeO content increased, the C₂S content in the silicate phase decreased from 33.3% to 25.9%, while the temperature at which the silicate was completely dissolved into the liquid phase decreased from 1600 °C to 1500 °C and the complete melting temperature of the slag decreased. The low FeO content facilitates the self-powdering of slag. In the high-phosphorus slag, at temperatures below 1450 °C, with the increase of basicity, the proportion of C₂S in the silicate phase first increased and then decreased. With basicity at 1.8; the highest content of silicate phase, accounting for 33.7%; and the temperature exceeding 1450 °C, the silicate phase dissolved into the liquid phase, which is conducive to the removal of phosphorus from the slag, achieving the self-powdering of high-phosphorus slag.

In order to investigate the influence of SiC on the composition and structure of mixed slag (blast-furnace slag: steel slag = 1:9), the chemical composition, equilibrium-phase composition, and microscopic morphological characteristics and elemental distribution in the microscopic region of the SiC-reagent-tempered slag samples were analyzed by X-ray diffractometer (XRD), FactSage7.1 thermodynamic analysis software, scanning electron microscope, and energy spectrum analyzer. It was found that the main physical phases of the tempered slag samples were magnesia–silica–calcite (Ca₃Mg(SiO₄)₂, C₃MS₂), calcium–aluminum yellow feldspar (Ca₂Al₂SiO₇, C₂AS), C₂S, and iron alloy. Theoretical calculations suggest that the experimental temperature should be higher than 1500 °C to facilitate the combination of P⁵⁺ with Fe and Mn in the liquid phase to form an alloy, reduce the P5+ content in the tempered slag, and create conditions for the self-powdering of the conditioned slag. The doping of the SiC reagent can increase the liquid phase line temperature and reduce the binary basicity in the liquid phase; the liquid phase line temperatures were 1150 °C, 1200 °C, and 1300 °C and the basicities in the liquid phase were 4.68, 4.13, and 3.10 for the doping amounts of 3%, 4%, and 5% of the SiC reagent, respectively. The mixed slag doped with 4% SiC reagent achieves self-powdering and reduction of ferroalloys during the air-cooling and cooling processes, realizing the purpose of “resource utilization” of blast-furnace slag and steel slag.

In order to reduce the sintering allocation scheme and lower the cost of allocation, two semi-lignite ores with similar properties and large price differences were selected for blending to achieve the purpose of complementary advantages. The sintered ore specimens were studied by using FactSage7.1, an infrared sintering furnace, and regression analysis. The results show that OA and OB iron ore powders and their mixed iron ore powders have a good linear fitting effect with an inverse relationship between bond phase strength and SiO₂ content; the bond phase strength has a positive relationship with liquid phase fluidity index; when mixing OA and OB iron ore powders in the ratio of 4:6, they have better sintering base characteristics and can be used as a new iron ore powder.