The chemical composition of refining slag is of crucial importance in determining the cleanliness of all steels. The effect of the CaO to Al₂O₃ mass ratio in refining slag (C/A_slag) on the cleanliness of high-carbon chromium bearing steel was systematically investigated via steel-slag equilibrium experiments in a high-temperature Si–Mo tubular resistance furnace. The C/A_slag ratio in slag was designed at the values of 1.3 to 1.6, 2.0, and 2.3, while the CaO to SiO₂ mass ratio was maintained at 5.0. The C/A_slag ratio firstly influenced the activities of its components: as the C/A ratio increased, the activities of CaO and MgO rose while that of Al₂O₃ declined. These changes in slag component activities enhanced the slag’s capacity to absorb inclusions and altered the steel-slag reaction equilibrium, thereby modifying the steel composition, specifically increasing Ca and Mg contents and decreasing acid-soluble Al. Consequently, Al₂O₃-rich inclusions in the steel were transformed into lower-melting-point phases, which helped mitigate nozzle clogging during continuous casting. Consistent with this mechanism, experimental results showed that both total oxygen content (0.0012 wt.%, 0.0009 wt.%, 0.0007 wt.%, and 0.0006 wt.%) and inclusion number density (14.2 #/mm², 12.2 #/mm², 5.0 #/mm², and 5.2 #/mm²) decreased with increasing C/A_slag ratio. These experimental observations were also explained by systematic thermodynamic calculations. Comprehensively considering the fluidity of a refining slag and its effect on the cleanliness of molten steel, the C/A_slag ratio should be controlled at 2.0 when the CaO to SiO₂ mass ratio is at 5.0.

The microstructure and properties of gray cast iron are closely related. For gray cast iron with pearlite matrix, adjusting graphite characteristics to improve casting performance is the most effective method. It is of great significance to analyze the relationship between graphite characteristics and properties of gray cast iron for the development of gray cast iron with high tensile strength and high thermal conductivity. Regression models of graphite characteristics and properties of gray cast iron was established, including tensile strength and thermal conductivity. By calculating the coefficients of the two models, the different effects of graphite characteristics on the properties of gray cast iron were obtained. By testing the regression models, the feasibility of the regression analysis method in the performance analysis of gray iron castings was determined. According to the analysis results, some improvement schemes are put forward to improve the performance of castings.

Precipitation of copper sulfide in eutectoid steels (Fe-0.8 mass%C-0.3 mass%Cu-0.03 mass%S) was explored and investigated. The present copper concentration in the steel was set to be 0.3 mass%, which is generally considered to cause hot shortness. Steels prepared were heat-treated at a high temperature of 1873 K to be completely melted, followed by subsequent cooling under different conditions to vary cooling rate. Precipitates formed in the steel samples were analyzed using scanning electron microscope (SEM) and transmission electron microscope (TEM) for metallographical observation. The results indicated that copper sulfide precipitation occurs during the cooling process of solidification. The precipitated copper sulfides were mainly Cu₂S with face-centered cubic structures. The results of analysis by using field emission electron probe micro analyzer (FE-EPMA), all the samples after experiments exhibited dendritic structures, with copper and sulfur concentrated mainly in the inter-dendritic regions. Analysis using the Clyne-Kurz model revealed that the concentrations of copper and sulfur in the liquid phase exhibited differences in cooling rates where the solid fraction exceeded 0.95. When the solid phase fraction reached 0.99 or higher, the solubility product of copper and sulfur exceeded the solubility curve of Cu₂S in eutectoid steel, suggesting that copper sulfide precipitated during solidification. This micro-segregation due to the enrichment of copper and sulfur, along with FeS formed during solidification, was thought to result in the precipitation of copper sulfides with a core of FeS.

Hanging represents an extremely hazardous anomalous condition during blast furnace ironmaking, directly threatening the stability and safety of furnace operations. Timely and accurate prediction is a critical technological requirement for ensuring smooth blast furnace operation. Existing diagnosis methods struggle to fully uncover the data evolution patterns and feature correlations before and after hanging events due to insufficient utilization of multi-sensor information. To address these challenges, this paper proposes a method that integrates attention-optimized temporal convolutional networks (TCN) and bidirectional gated recurrent units (BiGRU), offering a novel and effective solution for predicting the occurrence of upper hanging. By integrating mechanistic knowledge to precisely select core sensitive data—such as blast furnace body static pressure and stock rod height—as modeling data, and using a combined oversampling and undersampling strategy to balance normal and abnormal samples. The model design incorporates the TCN to capture long-range temporal dependencies and the BiGRU to incorporate contextual information. Additionally, the proposed method introduces an attention mechanism that identifies critical time steps, aiming to enhance both the accuracy and interpretability of upper hanging prediction. Test results reveal an overall accuracy of 90.83% for the TCN-BiGRU-Attention, effectively capturing dependencies within time-series data to achieve outstanding prediction accuracy and stability in upper hanging. In comparison to other algorithms, the proposed hybrid model excels in upper hanging feature extraction and recognition, which significantly enhances the objectivity and timeliness of detection, providing reliable guidance for stable blast furnace operation.

Fluctuations in pressure on the impingement wall of an air knife jet adversely affect the uniformity of the coating thickness. Vortices in the jet cause uneven local pressure and flow instability by enhancing the jet’s mixing and diffusion. To investigate the influence of vortex on pressure fluctuation during the production of high-aluminum Zn–Al–Mg steel strips, the unsteady flows of the air knife jet under three working conditions at H/d=9.1, 7.1, and 5.0 in production were numerically simulated by using the Large Eddy Simulation (LES) method, and then the vortical evolutions were analyzed by the Dynamic Mode Decomposition (DMD) method. The vortical evolution, variation in impingement pressure, the characteristic frequency of pressure fluctuations on the strip surface, and the spatial structure of the jet corresponding to the typical characteristic frequency under different working conditions were compared. At H/d=9.1, vortices are fully developed with intense mixing, leading to the most unstable impingement wall structure. At H/d=5.0, vortex mixing is weak on both sides of the jet centerline, and large-scale vortices directly impinge on the surface, forming stable coherent structures. In contrast, at H/d=7.1, both the degree of vortex mixing and flow stability lie between the other two cases. The difference in vortex evolution is a potential factor influencing the uniformity of liquid‑film thickness.

Grain growth kinetics in polycrystalline materials can be governed by either grain boundary mobility or triple-junction mobility. Boundary-controlled growth follows parabolic kinetics (growth exponent n = 2), while junction-controlled growth exhibits linear kinetics (n = 1). Predicting the dominant growth mode for a given material is crucial for microstructural control, yet the specific transition criteria between these regimes remain unclear, particularly for practically relevant three-dimensional systems. Using large-scale phase-field grain growth simulations with explicit triple-junction drag incorporation, we investigated this transition in both two-dimensional and three-dimensional systems containing initially 500000 grains. By systematically varying the triple-junction mobility, we analyzed grain growth exponent n as a function of the dimensionless drag parameter Λ, which represents the ratio of boundary to junction mobilities scaled by grain size. Results demonstrate that junction-controlled growth (n ≈ 1) occurs when Λ ≲ 0.1, while boundary-controlled growth (n ≈ 2) dominates when Λ ≳ 5–10. Remarkably, despite geometric differences between triple junctions in two dimensions (points) and three dimensions (lines), the variation of n with Λ follows approximately the same trend in both dimensions, suggesting dimensionally invariant transition criteria. Grain size distributions under junction drag continuously evolve without reaching steady states because the drag effect progressively weakens as grain size increases. These findings provide quantitative criteria for predicting growth modes in fine-grained materials, where the volume fraction and influence of triple junctions become significant.

Fixation of carbon dioxide as organic matter in marine sediment has attracted attention as a blue carbon. Steel slag, a by-product of the steel industry, can be used to improve the sediment environments through mechanisms, such as suppression of hydrogen sulfide generation; however, the effect of steel slag on increasing the carbon storage is not well known. This study showed that the addition of dephosphorization slag to sediment accelerated increase in the sedimentary organic matter when the hypoxic overlying water was aerated. Adding the iron (Fe) powder or ferrous oxide (FeO) to the sediment as the major components of the slag, the former accelerated increase in the sedimentary organic matter too. The relative abundances of sulfur-oxidizing bacteria, including Sulfurovum and Sulfurimonas, increased together with that of Hydrogenovibrio, Mariprofundus, Magnetovibrio, and Gallionella. The phenomena might be related to sulfur and/or Fe oxidation in the sediment, and these bacteria might cause increase in the sedimentary organic matter. Furthermore, addition of the Fe powder suppressed elution of the dissolved organic carbon, potentially resulting from inhibition of oxygen transfer from the surface to the lower layers of the sediment to suppress aerobic degradation.

Ni films electrodeposited from Watt’s solutions with and without thiourea addition were heat-treated to evaluate the diffusion behavior of hydrogen in the films. Hydrogen permeation measurements were taken using the Devanathan–Stachurski double cell technique. Regardless of whether thiourea was added or not, the crystal grain size of the deposited Ni films increased to several tens microns with heat treatment for 10 min at 800°C. Heat treatment of Ni films deposited with thiourea resulted in the segregation of sulfur at the grain boundaries. The hydrogen permeation rate through the deposited Ni films significantly decreased with increasing grain size due to heat treatment, regardless of whether thiourea was added. The segregation of sulfur at the grain boundaries further reduced the hydrogen permeation rate.