The CaO-SiO2-MgO-5Al2O3-30FeO five (oxide) components slag system was studied by varying the magnesium oxide (MgO) content (5.7–13.6 wt.%). The data were analyzed using the FactSage software. It was observed that the liquid network structure and precipitation of solid particles had an impact on high-temperature viscosity and foaming life. Under the same basicity (mass ratio CaO/SiO2 = 1.5) and at a temperature of 1500 °C, the MgO content was varied as 5.7 wt.%, 7.4 wt.%, 9.6 wt.%, 11.5 wt.%, and 13.6 wt.% in A0–A5. The samples at different solid concentrations, i.e., A0–A2 (0 wt.%), A3 (2.77 wt.%), A4 (6.92 wt.%), A5 (11.7 wt.%), exhibited a viscosity of 22, 47, 40, 76, 363, and 1088 mPa·s, respectively, and were simulated by FactSage software. The foaming life was 2.0 min, 7.7 min, 6.2 min, 13.4 min, 16.8 min, and 18.0 min, respectively. It was found that A5 exhibits the best effective foaming life under these environmental conditions because it can exhibit a double foaming effect formed by the precipitation of solid particles. The Si-O-Si network in liquid slag also contributed to foaming life, when there was only liquid slag bonding in the slag, whose effective foaming life was 7.7 min. In the absence of these factors, the foaming life was only 2 min.

Ladle furnace slag (LFS) is a by-product of a steel plant. As the chemical composition and free lime (f-CaO) content of each batch of slag are significantly different, it is difficult to use the same operation method to recover LFS. In this study, three types of LFS were used to partially replace lime in the dephosphorization process, and the compositions were adjusted to a fixed range by adding Al2O3. This method reduced the effect of different LFS components and significantly reduced the Ca2SiO4 amount (from 31.4% to 17.1%) in the produced modified oxidizing slag. Furthermore, after dephosphorization, the X-ray diffraction (XRD) patterns of the three LFSs indicated transformation into gehlenite and wustite. The modified oxidizing slag f-CaO content was 0.41%, which was lower than that in the electric arc furnace oxidizing slag (1.2–1.4%) and the LFS (0.9–3.4%). In addition, the expansion test results of the modified oxidizing slag showed almost no expansion, which conforms to the ASTM D2940 standards; thus, this material can be used for preparing paving materials. This study provides an approach for LFS treatment that could reduce costs within the steel industry.

The foaming process is an important part of the electric arc furnace (EAF) steelmaking process. It can promote thermal efficiency and reduce refractory consumption. FeO is a key material used during the foaming process. Unlike with other components used in forming foaming slag, the amount of FeO can be controlled by oxygen or carbon injection. Therefore, adjusting the content of FeO is the most economical foaming mode adopted for the EAFs steelmaking process. In this study, the influence of FeO content on the physical properties of slag was discussed. The melting temperature of the slag was evaluated using three methods: viscosity experiment, using Thermo-Calc simulation software, and high-temperature optical method. The experimental results revealed that the viscosity of slag increases as FeO content decreases. The results also revealed that foam height ratio exhibited a positive correlation with the viscosity of slag.

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