In the steelmaking process, lime is usually fed into the bath as a lump through the charging holes at the top of the furnace, the slag-making material floats on the slag surface, and the melting speed is slow, resulting in deep dephosphorization of molten steel is difficult. In order to improve the kinetic conditions of the molten pool and increase the velocity of the powder impacting the molten pool, this paper designs a cluster-type oxygen lance containing supersonic gas-solid blowing, which effectively solves the above problems. The jet law of supersonic gas-solid blowing oxygen gun is investigated by numerical simulation with the following results: i) Supersonic gas-solid injection reduces the peak velocity of the gas-phase jet but effectively mitigates the decay of the gas-phase velocity and extends the jet length; ii) The low-temperature gas in the center of the jet acquires energy from the high-temperature environment generated by the external ring-seam gas through convection, and thus expands sufficiently to provide sufficient energy for particle acceleration; iii) When the powder particles are larger than 0.3 kg/s, the gas-solid jet will flow at subsonic speed, greatly reducing the ability to accelerate particles, the design of supersonic gas-solid spray gun need to consider the appropriate powder-gas ratio. These findings will provide a certain research basis for supersonic lime powder delivery in the steelmaking process, which is of significance for efficient dephosphorization smelting with less slag in electric arc furnaces.

This study systematically investigates the reduction behavior of biochar-containing briquettes under varying heat-treatment parameters (temperature, time, and C/O ratio), with a focus on metallization rate, mechanical strength evolution, and microstructural transformations. The results indicate that with increasing heat-treatment temperature, the strength of the biochar-containing briquettes first decreases then increases. Within the 600–800°C range, the Fe₃O₄ phase remains stable, wherein carbonaceous networks derived from binder carbonization effectively preserve structural integrity. The critical 900–1100°C interval exhibits significant strength deterioration, attributed to attributed to lattice distortion induced by the Fe₃O₄→Fe_xO phase transition and proliferation of iron whiskers. Above 1100°C, the onset of metallic iron nucleation enhances strength (up to 0.68 MPa) and achieves a metallization rate of 91.97%. A 40-minute holding time at 1100°C further increases reduction efficiency from 69.36% to 87.64%, driven by the formation of a dense metallic iron network. The C/O ratio exerts a pronounced influence: high-C/O-ratio (0.8) briquettes develop porous architectures due to gas escape, yielding 40% lower strength than low-C/O-ratio (0.4) specimens. Conversely, the limited reducing agents at C/O = 0.4 restrict metallization to even 68.7% at 1150°C. These findings validate potential of biochar as a sustainable reductant substitute, establishing technical prerequisites for low-carbon ironmaking through optimized biochar-containing briquettes production.

SFCA-I, a form of silico-ferrite of calcium and aluminum (SFCA) in CaO–Fe₂O₃–Al₂O₃–SiO₂ system, is the key bonding phase for iron ore sintering and significantly influences sinter quality and carbon emissions in sintering process. The phase equilibria characteristics of SFCA-I are essential for the design and operation of iron ore sintering. However, most SFCA-I samples synthesized in laboratories currently lack SiO₂, indicating that the composition of SFCA-I lies within the CaO–Fe₂O₃–Al₂O₃ ternary system. In this study, the solid solution series, solid solution limits, and stable region of SFCA-I at 1200°C in air in CaO–Fe₂O₃–Al₂O₃ and CaO–Fe₂O₃–Al₂O₃–SiO₂ systems were revealed via phase equilibrium tests. The results indicate that the upper and lower solid solution limits of Al₂O₃ in SFCA-I are 1.31 wt% (i.e., 1.67 mol%) and 7.65 wt% (i.e., 9.10 mol%) at 1200°C in CaO–Fe₂O₃–Al₂O₃ system. With the increase of Al₂O₃ content, the upper limit of SiO₂ solid solution in SFCA-I is gradually decreased. The upper limit of SiO₂ solid solution in SFCA-I reaches a minimum value of 0.686 wt% when Al₂O₃ content is 7.62 wt% at 1200°C in CaO–Fe₂O₃–Al₂O₃–SiO₂ system. In addition, the XRD results prove that SFCA belongs to the solid solution of C(A,F)₃ series. The other phases encountered in the tests include Fe₂O₃, CF, C(A,F)₃, C(A,F)₂ and C₂(A,F). The relevant schematic and calculated phase diagrams are constructed. The position of SFCA-I in the CaO–Fe₂O₃–Al₂O₃ ternary system and the relations among SFCA, SFCA-I and the surrounding phases are presented.

The reactivity of metallurgical coke is a key contributory factor to its integrity in the ironmaking blast furnace. Herein, the factors that influence the CO₂ gasification reactivity of individual coke inert maceral derived components (IMDC) and reactive maceral derived components (RMDC) were examined, including: Parent inertinite types, degree of microtextural anisotropy, accessibility of the IMDC; and ash chemistry.

Individual IMDC and RMDC components were formed by coking inertinite group concentrates (IC) and vitrinite group concentrates (VC), respectively. Cokes were also formed from head coals and by using different proportions of IC and VC in the coking blend. Coke lump and intrinsic gasification kinetics were compared for each case, where “intrinsic” refers to the gasification behaviour of powdered samples. The most influential factors on which the reaction rate was dependent were distinctly different between lump and powdered samples. The degree of isotropy of the carbon structure was the most important parameter controlling coke lump gasification kinetics with CO₂ at 1100°C, followed by the basicity index of head coal. Conversely, intrinsic reactivity was closely correlated with microporosity.

Importantly, the isotropy of the carbon structure was not found to be a critical parameter controlling the intrinsic gasification kinetics up to the 40% carbon conversion point. These results suggest that in the lump form where gas diffusion limits the reaction rate, carbon structure and catalytic effect of coke minerals play the dominant role in coke gasification. Such behaviour leads to a selective reaction of gas with IMDC in coke lumps due to the isotropy of carbon and greater association with minerals.

As Sweden transitions to hydrogen-based steel production, excess O₂ generated as a byproduct of H₂ production through water electrolysis is likely to be available. This presents an opportunity to use extra O₂ for reducing fuel consumption during production of iron ore pellets. Considerable heat is released as magnetite is oxidised to hematite during induration. Increased O₂ content in the process gas is expected to accelerate the exothermic oxidation reaction, allowing faster intrinsic heating of the bed. This study examines various energy scenarios utilising O₂-enriched gas (40 vol% O₂) relative to a base case that uses low-O₂ gas (13 vol% O₂). The focus is the effects of the flow rates and O₂ contents in the inflow gas on the temperature development and physicochemical properties (oxidation degree and cold compression strength) of pellets across a 100-kg pot furnace bed. Enriching the inflow gas with O₂ has advantages with regard to the aforementioned properties. Notably, utilising O₂-enriched gas at a reduced flow rate (in this case, 30% less gas volume compared with the base case) enables improved heat distribution relative to the base case with low-O₂ gas. In addition to the effects on the energy and pellet properties, the microstructures are analysed with respect to the underlying oxidation mechanisms.

The reduction disintegration index (RDI) of sintered ore, which is the main raw material of blast furnaces, greatly affects blast furnace operation. In order to improve RDI without deteriorating the reducibility index (RI), sintered ore having a CaO concentration of 20 mass%, which is higher than the conventional 10 mass% when using porous Australian iron ore, was produced, and its effects on the mineral structure, porosity, RI and RDI were evaluated.

In the sintered ore having a CaO concentration of 20 mass%, hematite decreased and calcium-ferrite (sum of other component system calcium-ferrite and binary calcium-ferrite), the SFCA-I/SFCA ratio and porosity increased in comparison with that having a CaO concentration of 10 mass%.

When Australian iron ore was used as a raw material for sintered ore, RI increased in sintered ore having a CaO concentration of 20 mass% compared with the one having a CaO concentration of 10 mass%. In addition, RDI was improved in the sintered ore having a CaO concentration of 20 mass% compared with the that having a CaO concentration of 10 mass%. This is due to the formation of binary calcium-ferrite instead of secondary hematite, which deteriorates RDI.

Utilizing the greater momentum inertia and higher specific surface area of powder lime, top-blown CaO–O₂ technology has been proposed to further improve the mixing ability of the molten bath and to increase the slagging rate in the Basic Oxygen Furnace (BOF) steelmaking process. This research presented the development of a simulation model designed for investigating the effect of centre CaO–O₂ mixed injection method on the flow field within the molten bath. The result showed that, compared to the traditional jet, the CaO–O₂ jet improved axial impaction ability of top-blown jet, while reducing its impaction ability in the radial direction. Furthermore, the CaO–O₂ jet not only improved the impaction depth, but also exhibited a smaller decrease rate in impaction depth as the lance height increased. In the conical protrusion area, a greater amount of kinetic energy from the CaO–O₂ jet was transferred into the molten bath, which enhanced the dynamic condition within the molten bath.

To address the critical problem of erosion and rupture in the tundish weir, this study employs numerical simulation to systematically explore the effects of casting speed, the distance between the weir and the long nozzle, and the distance between the weir bottom and the tundish bottom on upstream impact stress distribution. An optimization strategy to mitigate weir impact stress is proposed. The results show that the impact stress on the weir upstream surface increases with casting speed. A greater distance between the weir and the long nozzle significantly increases the average impact stress at the upstream bottom, while a larger distance between the weir bottom and the tundish bottom gradually decreases it. For the 65-ton two-strand slab tundish, under the conditions of the casting speed being 1.5 m/min, the distance between the weir and the long nozzle being 1200 mm, and the distance between the weir bottom and the tundish bottom being 300 mm, the impact stress on the upstream surface of the weir is minimized, the average residence time of molten steel in the tundish is extended, and the metallurgical performance of the tundish is significantly improved.

This paper introduces the implementation of an advanced intelligent billet distribution system at a recently built steel plant, specifically designed to address the complex challenge of synchronizing multi-strand continuous casters with three high-speed wire production lines through various integrated strategies in direct rolling scenarios. The residence-time model and C# language were used for simulation, offering real-time temperature control and dynamic adjustment capabilities that address variations in production conditions and process demands. The innovative approach of incorporating iron oxide scale trenches also significantly reduces maintenance and improves operational safety and environmental conditions. The latest statistics show that the average direct rolling rate has reached over 93%. The findings highlight the practical significance and potential of this system for wider adoption in the steel industry, providing an efficient and sustainable production solution that adapts to evolving market demands and environmental challenges.

This study presents a semi-analytical model to accurately predict roll force and setup roll gap (G_set) in the finishing stage of H-beam rolling. The model modifies Sims’ classical strip rolling formula to capture the unique geometric and deformation characteristics of H-beam sections. The cross-section is divided into web and flange regions using a rectangular approximation. A geometry-dependent correction function is then introduced to account for the effects of reduction ratio, reduction balance, and contact geometry. This function is calibrated through finite element (FE) simulations under varying rolling conditions. Parameters such as web and flange thickness reduction, junction radius, and flange inclination are systematically adjusted, and the resulting roll forces are used to optimize the function via the Nelder–Mead method.

The model is validated using two H-beam specifications from Hyundai Steel. Compared to the company’s empirical model, the proposed model reduces web and flange thickness deviations by up to 71%, demonstrating improved prediction accuracy. Statistical analysis also shows substantial reductions in standard deviation and mean error, confirming better dimensional control. This semi-analytical model provides a fast, reliable alternative to full FE simulations and manual adjustment procedures, improving both efficiency and product quality in industrial H-beam rolling.

This study systematically investigates the dual effects of Sb on the oxidation behavior of 65Mn steel, combining laboratory experiments with industrial-scale validation. Key findings demonstrate that Sb additions significantly suppress both continuous and isothermal oxidation, with 0.03 wt% Sb reducing mass gain by 15.9% (continuous oxidation) and achieving maximal suppression of 85.2% at 800°C (isothermal oxidation), while increasing the oxidation activation energy from 184.0 kJ·mol⁻¹ (Sb-free) to 200.7 kJ·mol⁻¹. Notably, Sb nearly eliminates IGO at the “nose temperature” of 777.6°C, where IGO depth peaks at 18.5 µm in Sb-free specimens. However, excessive Sb (0.21 wt%) induces hot shortness due to grain boundary segregation of low-melting-point Sb-rich phases (Fe-ε(FeSb) eutectic phase), causing edge cracking during hot rolling, where industrial trials reveal local Sb enrichment exceeding 26–29 wt% at crack sites (>120× bulk content). Incomplete descaling coverage at edge regions (“descaling shadow zones”) combined with localized undercooling (ΔT ≈ 120°C) promotes Sb enrichment beyond its solid solubility limit, which elucidates why Sb-induced cracking occurs exclusively at strip edges. Mechanistically, Sb enrichment at oxide/substrate interfaces blocks Fe²⁻/O²⁻ diffusion, while its volatility prevents stable oxide formation, creating a kinetic barrier. The study identifies an optimal Sb content of 0.03 wt% that balances oxidation inhibition (IGO suppression >90%) with hot shortness.

The effect of B on the surface oxidation behavior and phosphatability of cold-rolled steel sheets was investigated using 0.001 wt% B-added and B-free steels containing 0.6 wt% Si and 2.0 wt% Mn. The specimens were annealed at 800°C in a 5 vol% H₂–N₂ atmosphere with a dew point of −50°C. The surface oxides of the annealed samples were analyzed by GD-OES, FT-IR, SEM-EDX and TEM. The annealed steel sheets were then subjected to zinc phosphate treatment, and the effect of the surface oxides on phosphatability was evaluated by SEM-EDX. In the initial stage of annealing, fine granular Mn₂SiO₄ mainly formed and film-like SiO₂ partly formed on both steels. As the soaking time at 800°C increased, the granular Mn₂SiO₄ increased in the B-free steel. In contrast, in the B-added steel, the granular Mn₂SiO₄ coarsened, MnSiO₃, MnO and B₂O₃ formed, and the film-like SiO₂ formation area expanded. Addition of B reduced the melting point, causing coarsening of Mn₂SiO₄, exposing the base steel. This results in a difference in the oxygen potential between the exposed area of the steel and the oxide covered area. This local inhomogeneity of the oxygen potential changes the surface oxide species of the B-added steel. To elucidate the reason for the poor phosphatability of the B-added steel, a SEM-EDS analysis of the steel surface in the initial stage of zinc phosphate treatment was conducted, revealing that the coarse Si–Mn complex oxides and large film-like SiO₂ inhibited the zinc phosphate reaction.

A deep understanding of the chemical structure evolution during coal pyrolysis and coking is crucial for expanding coking coal resources and developing more rational coal blending schemes. Two samples of fat coal at different pyrolysis stages were prepared by using a thermogravimetry-plastometer-swelling pressure apparatus and a muffle furnace. The samples were characterized by FTIR, ¹³C NMR, XRD and Raman spectroscopy to systematically investigate the evolution of the carbon structure during pyrolysis. The results indicate that the Feibei sample, which contains a higher content and longer length of aliphatic side chains, exhibits a slower formation rate of aromatic ring systems with ≥6 rings in the later stages of pyrolysis. During the pyrolytic coking process of both coal samples, the content of aliphatic structure groups initially increased and subsequently decreased. Meanwhile, the aromatic ring systems underwent three distinct stages: initial longitudinal stacking dominated by 3–5 rings, followed by lateral expansion into larger systems comprising ≥6 rings, and subsequent vertical growth centered on ≥6 ring architectures, accompanied by a continuous reduction in the d₀₀₂ of the carbon microcrystals. This study elucidates the evolution pathway of aromatic carbon structures during the pyrolytic coking of the tested coal samples.

The thermophysical properties of four TWIP steels with varying Cu, Al, and Si contents were measured and compared with those of austenitic stainless steel and plain carbon steel over a temperature range of 25 to 1000°C. The thermal expansion coefficient (β) of the TWIP steels was unaffected by alloying additions, averaging 22.87×10⁻⁶ °C⁻¹, which is slightly higher than that of austenitic stainless steel (19.74×10⁻⁶ °C⁻¹) and notably higher than that of plain carbon steel (12.61×10⁻⁶ °C⁻¹). Density (ρ) decreased linearly with temperature across all compositions and was further reduced by higher Cu, Al, and Si contents due to the lower atomic mass of these elements compared with Fe, with Al showing the most pronounced effect in TWIP steels. Due to the high β of TWIP steel, the ρ reduction with increasing temperature was more pronounced in TWIP steel compared to that of conventional carbon steels and stainless steels. The specific heat capacity (C_p) of TWIP steels increased with temperature, showing a trend similar to that of austenitic stainless steel. Thermal diffusivity (α) and thermal conductivity (k) also increased with temperature but decreased with alloying additions, attributed to increased thermal resistivity by solute atoms. Among the alloying elements, Al had the strongest influence on reducing α and k, followed by Si, with Cu having minimal effect. Compared to other steels, TWIP steels exhibited significantly lower k and higher β, characteristics that may induce thermal stress and increase the risk of thermal cracking during rapid thermal processes such as welding, heat treatment, machining, casting, and hot forming.

The rotary hearth furnace (RHF) process is widely employed for the efficient recycling of iron- and zinc-bearing dusts. However, the formation and deposition of secondary dust in the flue gas system significantly impair its operational availability. In this study, a laboratory-scale simulation of the RHF reduction process was conducted to collect and characterize the secondary dust formed under different temperature conditions. The distribution patterns and deposition behavior of secondary dust were systematically investigated. Results indicate that dust deposition predominantly occurs in the medium-temperature zone (873–1073 K), where ZnO and alkali metal chlorides are the dominant components, accounting for up to 76.1% of the total deposited mass. The particle size of the secondary dust first decreases and then increases with decreasing flue gas temperature. The elemental composition of the secondary dust includes Zn, Pb, K, Na, Sn, In, O, and Cl. Specifically, the Zn content decreases from 73 mass% to 44 mass%, while Cl increases sharply from 0.2 mass% to 41 mass% as the temperature drops. Minor increases in K and Pb concentrations and a slight decrease in Na are also observed. Thermodynamic modeling was applied to interpret the phase transformations and deposition mechanisms at various temperature intervals. This study provides fundamental insights into the generation and deposition behavior of secondary dust in RHF systems, offering theoretical guidance for the mitigation of dust-related issues and improvement of process reliability in industrial applications.

This report describes improved X-ray fluorescence analysis to quantify chromium as a major constituent of stainless steel and cobalt–chromium alloy samples. Stainless steel can be digested rapidly using hydrochloric and nitric acids, including aqua regia, for wet chemical analyses using atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, and inductively coupled plasma mass spectrometry. Nevertheless, because of chromium volatilization as chromyl chloride in fusion processes during glass bead preparation, this acid digestion is inapplicable for glass bead specimens of chromium-containing materials intended for use in X-ray fluorescence spectrometry. For the work described herein, microwave digestion using nitric and hydrofluoric acids was used to prepare appropriate glass bead specimens. The X-ray absorption and enhancement were negligible for the present glass bead specimens. An extremely high 2000-times dilution of 4000 mg lithium tetraborate and 2 mg sample was used. Reliable analytical values of chromium were obtainable using the suggested X-ray fluorescence analysis without matrix correction calculation.