steel research international最新文献

The microstructure and composition of the scales formed are examined after being exposed to atmosphere containing 2.0% SO₂ + 5.0% O₂ for 60 min in the temperature range of 900–1200 °C. The composition of the scale post-oxidation primarily varies with temperature rather than silicon content. FeS exhibits a melting temperature of 950 °C, whereas FeSi₂O₄ melts at 1150 °C. Two mechanisms for FeS formation are proposed. Eutectoid transformation of molten FeS occurs during subsequent cooling, resulting in lamellar FeS + Fe–S–O compounds. Above 1150 °C, the melt of Fe₂SiO₄ further increases the Fe diffusion rate. This dual-liquefaction mechanism involving FeS and Fe₂SiO₄ accounts for the anomalous oxidative mass gain observed in Fe–Si alloys exposed to a sulfur-containing atmosphere.

This work presents the development and validation of a static thermochemical model for predicting process parameters in the MIDREX shaft furnace, a method used for producing direct reduced iron from lump ore and pellets. Industrial plant data is used to validate the model. Furthermore, the model is utilized to analyze the process based on different parameters. Genetic algorithm (GA) is used to estimate the critical parameters of the process (like reaction factors and extent of reactions) and validate the model with industrial data. Further investigations are conducted to assess the possibility of replacing the reformer gas (bustle gas) with hydrogen and coke oven gas (COG) to make the process greener and almost free from carbon emissions, using a systematic approach of overall heat balance, using already developed coupled thermodynamics and kinetics-based model, and further using those data to estimate the reaction factors and extent of reactions using GA to be used in the static model. The results demonstrate the feasibility of replacing hydrogen and COG without much adverse effect on the process outcomes; however, this results in better metallization and reduced carbon footprint of the process effectively.

The electric arc furnace (EAF) is a promising approach to decarbonize the iron and steel industry. In EAF steelmaking, injecting carbon into the molten slag remains crucial for creating a foamy slag, which enhances the energy efficiency of the process and protects the furnace. Biochar (BC) has emerged as a potential alternative to traditional fossil carbon for slag foaming. However, fully replacing fossil carbon with BC poses technical challenges. In this study, the partial replacement of fossil carbon with BC is considered, in the form of a petroleum coke (petcoke) and BC blend. Interestingly, a blend of petcoke and BC matches or possibly outperforms either carbon type individually, due to a synergistic effect. Using an induction furnace to simulate EAF conditions, a synthetic slag is melted, and injection carbon is added into the slag layer. The slag foaming effectiveness of petcoke, BC, and three blend cases are studied. Thermogravimetric analysis reveals that the BC is more reactive with slag compared to petcoke, which leads to an initial high intensity of CO generation. However, the CO generation was not continuous or consistent. All experimental results are combined to propose a mechanistic description of the slag foaming behavior of BC blends.

Water-based nanolubricants are playing increasingly important roles in hot steel rolling over the past decade regarding environmental protection, energy saving, and product quality improvement. The contact friction between the work roll and the workpiece under water-based nanolubrication, however, has been scarcely investigated. In this study, water-based lubricants containing 0–4.0 wt% TiO₂ nanoparticles are employed in hot rolling of a mild steel under different rolling conditions. The Taguchi method is used for the orthogonal design of the hot-rolling tests to sequence the key factors that affect the rolling force in terms of importance. The as-synthesized water-based nanolubricants indicate excellent dispersion stability after standing for 24 h, which can be readily restored to the original state via manual shaking. The coefficient of friction (COF) during the steady-state hot steel rolling is inversely calculated using a flow stress model developed from hot compression testing. A novel COF model for hot rolling of the steel is thus proposed through multiple linear regression. It is found that the result of linear regression agreed well with that of inverse calculation, indicating that the proposed COF model is applicable. Finally, the lubrication mechanism is examined through a boundary lubrication regime determined from a modified lubricant film thickness model.

The effects of rare-earth treatment on cleanliness, corrosion resistance, microstructure, and mechanical properties of 75Cr1 steel are investigated by industrial trial. In the results, it is shown that the appropriate La–Ce addition can effectively remove oxygen and sulfur elements in steel, and total oxygen (T.O) and S contents decrease by 45% and 33%, respectively. After La–Ce treatment, the typical inclusions in steel are transformed from (Mg–Al–O)–CaS composite inclusions to RE_xS_y–CaS inclusion with a small amount of Al₂O₃. The number and average size of inclusions in steel are significantly reduced, and the morphology of inclusions changes from irregular shape to spherical shape, which contributes to the improvement of the corrosion resistance of 75Cr1 steel. Furthermore, the pearlite spacing and the grain size are refined, the tensile and yield strengths are significantly enhanced in the test of La–Ce-treated steel. The 75Cr1 steels are fabricated in small batches, which avoids the nozzle clogging resulted by rare-earth treatment during continuous casting. It implies that rare-earth treatment to improve the quality of 75Cr1 steel shows the strong industrial applicability.

In this study, the prospective application of lime as a desulfurization agent for the cast-iron industry is technically examined. This investigation encompasses a series of laboratory experiments conducted under atmospheric conditions, mirroring industrial settings by exploring two distinct methods for introducing lime powder onto and into molten cast iron using surface addition and gas injection techniques. Deoxidation agents (FeSi, SiC, and Al) are also incorporated to enhance the lime-based desulfurization results. Based on the findings of this study, it is indicated that lime can be a reliable cast-iron desulfurization agent by reaching an end-sulfur concentration of <0.015 wt%, thus providing an opportunity for a sustainable alternative for the foundry industry. In this study, it is also revealed that adding a small quantity of Al is more effective at enhancing desulfurization results than Si due to its role in increasing the proportion of liquid slag during desulfurization. However, caution is advised regarding the limit of aluminum concentration in cast iron (0.1 wt%), and treatment temperatures should be kept above 1400 °C to prevent counterproductive effects and undesirable defects in the product.

Among the steelmaking slag, secondary metallurgy slag (SMS) is the most problematic to be recycled. Several attempts to recover such slag as lime replacement, slag flux, pozzolanic materials have been made for long time with pros and cons. However, the amount of recyclable slag is limited and often their employment requires higher energy demand than traditional materials. Nevertheless, the use of SMS in agriculture is poorly or never considered. In this article, the legal and technical evaluation of SMS as raw material for fertilizers production is investigated. Compliance of technical specification, toxic metals concentration, and leaching behavior allows to confirm the technical feasibility of SMS use as a raw material for fertilizers manufacture. Both from the literature data and the experimental results on 16 industrial SMS samples, the requirements for calcium-magnesium-sulfur-based fertilizers, soil correctives and for sanitizing agricultural sewage sludge, appear fully satisfied. The CaO concentration in SMS (35–60 wt%) is abundantly higher than the requirements (≥15 wt%) and CaO is present in most part as water-soluble complexes such as calcium aluminates (70 wt%), silicates (10 wt%), and sulfide (4 wt%). The pH of the SMS samples leachate is comparable to that of fresh lime (12.35 vs 12.46), highlighting a better behavior for sewage sludge sanitation with respect to limestone (9.98). The measured toxic metals and leachate elements concentration over the corresponding admittable threshold are always lower than 0.5 and 1.0 (mg kg⁻¹/mg kg⁻¹) for liming materials. Finally, these results lead to officially approve the use of SMS as soil corrective according to the Italian Fertilizer Regulation.