The CO₂ Ultimate Reduction System for Cool Earth 50 (COURSE50) project has been implemented in Japan to develop low-carbon operations of blast furnaces using hydrogen-based reductant gases. A series of experiments were conducted on an experimental blast furnace constructed at Nippon Steel’s East Nippon Works in Kimitsu area. In these experiments, coke oven gas (COG) and H₂ gas at room temperature were injected from tuyeres. The maximum injection volume of the hydrogen-based reductants of COG at 190 Nm³/ton-hot metal (tHM) and H₂ gas at 315 Nm³/tHM resulted in carbon reduction rates of approximately 5.7% and 16%, respectively. In this study, we present summaries of the experimental trials and their numerical analysis for the above two cases using the three-dimensional mathematical blast furnace model. Furthermore, a numerical prediction was conducted to assess the impact of larger volumes of COG and H₂ injections than those of the trials that actually conducted. Accordingly, it was estimated that achieving a carbon reduction rate greater than 20% through hydrogen-based reductant gas injection at room temperature would be challenging. This finding indicates that compensation for input heat not derived from carbon combustion is essential to achieve further low-carbon blast furnace operation using hydrogen-based reductant gases.

In the pursuit of carbon-neutral steelmaking, alternative reducing agents such as hydrogen and bio-based fuels have gained prominence as substitutes for metallurgical coke in blast furnace operation. This study employs a detailed six-phase multicomponent mathematical model to evaluate the effects of combined hydrogen-rich gas and pulverized charcoal (PCH) injection on furnace behavior and decarbonization potential. The model solves the conservation equations of mass, momentum, energy, and species, incorporating complex gas–solid interactions throughout the shaft. Results reveal that a 25% reduction in coke rate can be achieved without compromising furnace thermal stability or permeability. The high reactivity of hydrogen, coupled with PCH combustion near the tuyeres, maintains raceway temperatures above 2100°C and preserves the cohesive zone structure. Gas flow remains homogeneous, and solid burden descent is unaffected, ensuring consistent process conditions. A transition from CO- to H₂-dominated reduction is observed, particularly for the FeO→Fe step, leading to more distributed reaction zones and improved thermal efficiency. These shifts reduce solution loss reactions and support a stable operation even under reduced coke conditions. Environmentally, total CO₂ emissions decrease, with fossil-derived emissions reduced by 45.9%. The findings validate the technical viability of hydrogen and biochar co-injection as an effective low-carbon strategy for existing blast furnaces, offering a promising route toward sustainable ironmaking aligned with global emissions targets.

The blast furnace ironmaking process has become a critical link for carbon emission reduction in steelmaking technology. As a novel low-carbon blast furnace process characterized by low coke rate, low carbon emissions, and high smelting efficiency, the top gas recycling blast furnace (TGR-BF) holds significant potential for carbon reduction within this process. In this study, a multi-fluid model was employed to investigate the smelting state, carbon-saving potential, and interactions between reducing gases in the TGR-BF under different bosh gas volume (BGV). When the BGV increased from 3681 Nm³/min to 4081 Nm³/min, the hot metal production rose from 5299.5 t/d to 5676.4 t/d, the reduction contribution rate of CO for FeO increased from 34.96% to 37.82% while that of H₂ for FeO decreased from 65.04% to 62.18%. The coke consumption for raceway combustion increased from 93.81 kg/tHM to 99.85 kg/tHM, coke consumption for direct reduction reactions rose from 20.8 kg/tHM to 22.8 kg/tHM, coke comsumptiom in carbon solution loss reactions decreased from 26.8 kg/tHM to 24.07 kg/tHM, the Global Warming Potential (GWP₁₀₀) increased from 2.39×10⁻¹⁰ to 2.59×10⁻⁹, and the total environmental impact increased from 6.10×10⁻¹⁰ to 1.09×10⁻⁹.

This study investigates carbon deposition behavior of porous iron whiskers in a CO–CO₂–H₂ gas atmosphere, aiming to enhance carbon recycling strategies for the Carbon Recycling Ironmaking Process using Deposited carbon iron ore composite (CRIP-D), a fossil-free alternative to traditional blast furnace ironmaking. The porous iron whisker, characterized by high porosity (~95%) and obtained from carbon-iron oxide composites, serves as a carbon deposition catalyst. Experiments revealed a two-stage carbon deposition process: the initial stage involves the formation of cementite (Fe₃C), while the later stage involves the metastable iron carbide Fe₅C₂, whose decomposition yields nano-sized iron particles that catalyze the growth of carbon filaments.

The analyses of carbonization degree trends, sample morphology, and SEM/XRD indicate that Fe₅C₂ plays a crucial role in facilitating the second-stage carbon filament formation. In-situ high-temperature XRD experiment confirmed this transformation and correlated the decline in Fe₅C₂ peak intensity with carbon filament growth. The sulfur content in porous iron, higher than that in electrolytic iron, stabilized iron carbide formation and suppressed premature free carbon deposition.

These findings highlight the significance of controlling carbide phase evolution for efficient carbon deposition. Understanding this relationship supports the development of effective carbon recycling within the CRIP-D framework, reducing CO₂ emissions while enabling the use of non-fossil carbon sources in large-scale ironmaking.

Achieving carbon neutrality in steelmaking necessitates the transition to electric arc furnaces, where the efficient dissolution of carbon injection (C-inj) materials into molten steel is critical for maximizing carbon utilization efficiency. However, conventional carbon materials exhibit poor wettability with molten iron, limiting their dissolution efficiency during the extremely short residence time (1–3 seconds) in industrial C-inj processes. This study investigated the enhancement of the initial wettability between molten iron and graphite through metallic interlayers using high-speed imaging to quantify the wetting behavior at timescales shorter than 0.1 seconds. When platinum (Pt) thin films were deposited on graphite substrates, contact angles dramatically decreased from approximately 110° (untreated graphite) to 53° at 0.5 seconds, establishing a wetted state immediately after contact. This rapid enhancement occurs through nonreactive wetting that develops immediately after contact between Pt and molten iron, preceding slower carbon dissolution reactions. Scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) analysis confirmed that the Pt films retained structural continuity after exposure to 1773 K, in contrast to the titanium (Ti) films, which became discontinuous due to agglomeration. Increasing Pt film thickness from 0.5 to 2.0 µm improved high-temperature coverage (40–54%), showing a positive correlation with wettability for both carbon-saturated and carbon-unsaturated iron. Critically, substantial improvements were achieved even with partial coverage, demonstrating practical feasibility. The results establish that metallic interlayers can rapidly control wettability within subsecond timescales by optimizing the interfacial energy during the initial nonreactive phase, providing a promising interfacial design strategy for carbon-efficient steelmaking applications.

In the steelmaking industry, the utilization of CO₂ as a resource has become one of the important research projects. The decarburization and desilication mechanism were investigated to the extension range of low carbon condition and in Fe–C–Si ternary system in 1873 K. ¹³CO₂ and ¹⁸O₂ dual isotope gases were use to clarify the complicated oxidation process. The results showed that in Fe-1.0 mass%C-0.5 mass%Si molten alloy, CO₂ substitution part of O₂ within 40% slightly reduced the decarburization rates in the advantage area of decarburization, and after reaching the oxidation equilibrium curve, the decarburization rates were basically stable and low even 100% CO₂. However, with introducing CO₂ from 0 to 40%, the desilication rates were dropped a lot. CO₂ replacing part of O₂ was beneficial to reducing the loss of silicon during decarburization process at 1873 K. The critical value of carbon content was around 0.3 mass%, that the main limiting rate step was transformed to the diffusion of carbon in molten under the correspondindg condition of 1.2 to 3.2 Nm³/t·min gas supply intensity in the present experiments. When the gas supply was sufficient, CO₂ participation ratio was decreased and that of O₂ was increased with the carbon content decreasing. When the gas supply was insufficient, both CO₂ and O₂ participation ratios were relatively stable until the carbon transfer limiting the reactions.

An efficient scheme to reduce greenhouse gases (GHGs) emissions more than coal replacement with general biomass was proposed. Currently, rice straw is plowed into paddy fields and emits methane, which is one of the major causes of the greenhouse effect. In this scheme, the straw is used as biomass charcoal for steelmaking.

Focusing on rice paddies and steel mills as GHGs sources, methane from straw in paddies and CO₂ from coal at steel mills are currently emitted. The use of the straw in steelworks reduces both emissions, therefore it can be a more efficient GHGs reduction scheme than the use of biomass in general.

In order to evaluate the proposed scheme, methane emissions from rice straw were calculated using the regression formula of methane emission flux estimated by DeNitrification-DeComposition-Rice model (DNDC-Rice model). The methane emissions for the current amount of straw plowed into paddies and for the case where no straw was plowed were calculated, and the difference was evaluated as the methane reductions.

Additionally, the CO₂ emissions associated with coal use were considered and it was found that the proposed scheme could reduce GHGs equivalent to 2.6 to 3.8 tons of coal per ton of coal replaced when using Global Warming Potential over 100 years (GWP-100), or 5.7 to 9.3 tons with GWP-20.

GHGs reduction for partial straw plowing was also evaluated by changing the ratio between the amount of straw plowed and used as charcoal substitute, and it was found that it remained constant regardless of the ratio.

Synthesis of CaCO₃ from steelmaking slag is possible to CO₂ fixation. This study investigated a two-step precipitation method to synthesize CaCO₃ powders of varying whiteness and particle sizes from steelmaking slag in an aqueous glycerol solution. The calcium (free-CaO) in the steelmaking slag was readily extracted upon contact with a glycerol solution. Subsequently, introducing CO₂ into the solution reduced the pH due to its high alkalinity, leading to the precipitation of CaCO₃. Additionally, precipitation of CaCO₃ was observed upon aging the filtrate solution post-CaCO₃ separation. By adjusting the solution’s pH to 6.7 and introducing CO₂, the whiteness of the precipitated CaCO₃ was 76.6%, while that of the post-precipitated CaCO₃ was 86.5%. The average particle size of the post-precipitated CaCO₃ was around 4.5 µm, which was 2.5 times larger than that of the initial-precipitate. Increasing the pH of the solution resulted in a decrease in the whiteness of the post-precipitated CaCO₃ and an increase in its particle size. Therefore, this method allows for easy control of the whiteness and particle size of CaCO₃ by adjusting the pH of the Ca²⁺-containing glycerol solution through CO₂ introduction without the necessity of high-pressure, high-temperature conditions or specialized equipment. This process enhances carbon capture and utilization for CaCO₃ production from steelmaking slag.

Siderite (FeCO₃) is a well-known iron carbonate mineral. Recently, efforts have been made to synthesize FeCO₃ using an environmentally friendly Carbon dioxide Capture and Utilization (CCU) process and apply it as a filler material. This study investigates the synthesis of FeCO₃ particles and the factors that affect their morphology. A rhombohedral FeCO₃ powder was produced by suspending Fe powder in water and blowing CO₂ gas into the suspension. The effects of Fe²⁺ and HCO₃^– supply behavior on the particle size were investigated. Increasing the Fe powder content in the suspension promoted Fe²⁺ dissolution, leading to larger FeCO₃ particles. Furthermore, reducing the particle size of the Fe powder to 3–5 µm and increasing the reaction temperature to 50°C promoted Fe²⁺ dissolution rate, resulting in FeCO₃ particles with an average size of approximately 0.5 µm. In contrast, increasing the CO₂ flow rate did not affect the particle size because the hydration reaction of CO₂ was the rate-limiting step. These findings indicate that the supply behavior of Fe²⁺ is the dominant factor that controls the particle size during FeCO₃ synthesis.

A new ammonia separation method for the Haber–Bosch process, which is absorption separation, requires ammonia absorbents that are applicable at high temperatures. This study investigated the ammonia absorption/desorption behaviors of CaCl₂-based absorbents (CaCl₂–LiCl, CaCl₂–LiBr, and CaCl₂–NaCl) at 473 K using pressure-swing absorption (0.1–0.5 MPa). CaCl₂ containing small amounts of lithium compounds (LiCl or LiBr) exhibited higher ammonia absorption and desorption rates than the CaCl₂ single salt. Particularly, the ammonia absorption and desorption rates of CC100LC1 (with a molar ratio of CaCl₂:LiCl = 100:1) were 23% and 11% higher than those of the CaCl₂ single salt, respectively. The ammonia absorption capacity of CC100LC1 was higher than those of conventional ammonia absorbents such as Na-Y zeolite and comparable to that of the CaCl₂ single salt. The CaCl₂–LiCl mixture is a promising ammonia absorbent for absorption separation because it can easily absorb/desorb ammonia at high temperatures.

Erythritol is a promising sugar alcohol-based phase change material (PCM) for medium-temperature thermal energy storage owing to its high latent heat (300–355 J/g), excellent thermal stability, and suitable melting point (~120°C). However, its practical application is limited by its large supercooling degree, which exceeds 90°C. This delays the heat release and lowers the thermal utilization efficiency.

This study investigates the feasibility of using amino acids as nucleating agents to suppress the supercooling of erythritol. Five amino acids—L-alanine, L-serine, L-phenylalanine, L-valine, and L-isoleucine—were mixed with erythritol at 5, 10, and 30 mol%, and their thermal behaviors were observed using differential scanning calorimetry.

The results demonstrated a significant reduction in supercooling degree (ΔT) with mixing amino acids. The 10 mol% L-alanine-mixed sample (Ery-Ala 10%) exhibited the best performance, reducing ΔT from 91.1 to 48.0°C while maintaining a high latent heat and a thermal utilization efficiency of 75.1%. Thermal cycling tests showed that the Ery-Ala 10% sample retained its thermal performance for up to 10 cycles.

These findings suggest that amino acids, especially L-alanine, effectively promote heat release (crystallization) through heterogeneous nucleation and intermolecular interactions. This study presents a simple, safe, and efficient strategy for improving the thermal performance of erythritol and advancing its potential as a PCM in medium-temperature thermal energy storage systems.

In this study, the enhancement of the thermal output of solid-gas chemical heat storage systems was investigated. Bridges made of high-thermal conductivity materials were formed among reactive particles by drying a slurry which contained graphite powder as a thermal additive and dispersant in a packed-bed reactor. First, the effect of the volume ratio of the dispersant on effective thermal conductivity was investigated. The optimum volume ratio of dispersant to graphite powder was determined. Furthermore, repetitive bridge formation increased the effective thermal conductivity. Based on these results, we investigated the thermal response of the energy-discharge process. Consequently, the temperature distribution in the radial direction of the reactor decreased owing to the formation of bridges. In addition, the thermal energy generated by the adsorption of water vapor onto the adsorbent was effectively transferred to the reactor wall. The thermal output was estimated based on the experimental results. The thermal output was increased by the formation of bridges.

The addition of highly reactive ferro-coke in a blast furnace (BF) can lower the temperature of the thermal reserve zone (TRZ) and increase gas permeability through the ore layer, resulting in a decrease in fossil fuel rate and improved shaft efficiency. Ferro-coke should possess high reactivity and sufficient mechanical strength for handling, transport, and BF use. A better understanding of the relationship between microstructure and strength in ferro-coke is needed to optimise the blend composition and maximise strength. This study investigates the mechanism of ferro-coke microstructure formation using 3D micro-computed tomography (Micro-CT) image analysis, scanning electron microscopy (SEM), and von Mises stress distribution simulation. The impacts of iron feed (iron ore and reduced iron) and binder type (high fluidity coal and coal tar pitch (CTP)) on ferro-coke microstructure and strength were analysed. The results show that ferro-coke strength primarily depends on the bonding quality of inert components and ferrous particles to the coke matrix. The porosity of ferro-coke, a sign of the thermal plasticity of the blend, was closely correlated with strength. The addition of iron ore inhibited blend plasticity and the formation of a porous structure, resulting in poor bonding of inert components to the coke matrix. Results indicated that the iron ore and its reduction in carbonisation led to the loss of thermoplasticity, thus hindering microstructure development. CTP showed a strong binding ability in the presence of both iron ore and iron powder, while high fluidity coal showed limited binding ability when iron ore was used in ferro-coke.

The addition of ultrafine ore to the sinter blend is known to impact green bed permeability and sinter productivity negatively. This study investigates several countermeasures for commercial ore blends containing up to an additional 20 mass% ultrafine ore. The countermeasures explored include the use of organic binders, the incorporation of pulverised ore particles as a binder, and the application of increased suction pressure. The results of this study were categorised into the addition of ultrafine ore to the blend (Blends A, B, and C) and the effect of binders (sodium polyacrylate, ammonium polyacrylate, and pulverised ore particles) on Blend C, that is Blends C(I), C(II), and C(III). It was found that the addition of sodium polyacrylate (Blend C(I)), ammonium polyacrylate (Blend C(II)) and pulverised ore particles (Blend C(III)) increased granule size, compared to Blend C. Although the granules increase in size with the addition of binders, it is noteworthy that adhering layer to nuclei mass ratio, R, remained unaffected at comparable moisture levels. The maximum green bed permeability increased with organic binders while the pulverised ore particles had no obvious effect. The binders improved sinter pot productivity from 32.7 t/m²/day for Blend C to 36.3 t/m²/day for Blend C(I), 36.2 t/m²/day for Blend C(II) and 36.6 t/m²/day for Blend C(III). This increase was due to an enhanced gas flow rate, higher flame front speed and a reduction in the degradation of the granules indicated by a lower <1 mm index.

Iron ore powder is the main source of NO_x in the sintering process. The existing end treatment technology is difficult to cure environmental hazards due to high cost and secondary pollution. Therefore, in this study, through the NO_x generation experiments and mechanism analysis of five kinds of iron ore powder, the low emission characteristic ore powder was selected for actual production. The results show that the NO_x emission concentration of different iron ore powders varies with temperature. As the temperature increases, the peak concentration of NO_x becomes larger, the peak time becomes shorter, and the harm becomes greater. Among them, the process concentration and peak concentration of Sijiaying powder are relatively low in the sintering process. The pre-exponential coefficient and activation energy of the apparent rate of NO formation interface reaction, the pre-exponential coefficient of the effective diffusion coefficient of gas diffusion in the product layer, and the activation energy of atomic movement are the lowest.

The blast furncace (BF) with the operartion of top gas recycling had been generally recognized as an innovative ironmaking technology, with some significant advantages including the reduction of fuel ratios and CO₂ emission and the enhancement of BF smelting. In this work, a multi-fluid model and life cycle assement of top gas recycling-blast furnace (TGR-BF) was applied to systematically investigate the smelting behavior and carbon reduction potential with the varying theoretical combustion temperature (TCT). As the TCT increased from 2000°C to 2250°C, the production of TGR-BF increased from 5184.0 t/d to 5693.8 t/d, coke ratio increased from 220.2 kg/tHM to 248.3 kg/tHM, and the CO₂ emission increased from 893.75 kg/tHM to 1017.5 kg/tHM. The raceway coke combustion increased from 93.01 kg/tHM to 114.83 kg/tHM, coke consumption for direct reduction reactions rose from 21.39 kg/tHM to 26.86 kg/tHM, and the coke loss in carbon solution loss reactions decreased from 53.45 kg/tHM to 53.13 kg/tHM. And H₂ contribution to FeO→Fe decreased from 67.10% to 63.23%, while CO contribution to FeO→Fe increased from 32.90% to 36.77%. Increasing TCT enhanced the smelting efficiency of the TGR-BF. However, the resulting rise in coke rate caused by intensified direct reduction and tuyere combustion, coupled with the increased proportion of CO consumed during indirect reduction, adversely affected the emission reduction benefits of the TGR-BF. Consequently, these factors required comprehensive consideration when selecting the appropriate TCT level.

As one of the core components for maintaining the longevity of blast furnace, cast iron cooling staves are widely used due to their low cost and excellent castability, but the poor thermal shock resistance making them susceptible to thermal cracking and unstable temperature fluctuations. In the study, a plane located 120 mm from cold side was selected and the temperature field was obtained through numerical simulation, and the area percentage exceeding the average temperature 145°C was quantitatively calculated and defined as high-temperature region. The high-temperature region ratio offers an intuitive and quantitative benchmark for comparing stave performance under varying boundary conditions. The impact of cooling medium parameters, stave structural parameters, and hot-side gas temperature on the cooling capacity were analyzed. The results indicate that the ratio of the high-temperature region serves as a more valuable cooling capacity evaluation index than traditional hot-side temperature measurements, typically falling within a range of 30–60%. Furthermore, the ranking of key factors affecting stave cooling capacity is elucidated, with gas temperature emerging as the most significant, followed by inlet water temperature, cooling water velocity, the ratio of cooling water pipe spacing to stave edge width, cooling specific surface area, and finally, the number of cooling water pipes. These findings provide a vital theoretical foundation and practical guidance for the design and optimization of blast furnace staves, aiming to achieve efficient and stable stave operation through precise parameter regulation. Ultimately, this contributes to enhancing the safety and longevity of the blast furnace smelting process.

Horizontal segregation of sinter mixture caused by charging is one of the factors limiting the development of Super-high bed sintering. To improve charging process and reduce the horizontal segregation of mixture, the shuttle feeder and bin charging system of a 360 m² sintering machine was simulated using the discrete element method. The operational parameters of the shuttle feeder, including limit positions, dwell time, and conveying speed, were systematically optimized. The results show that after parameter optimization, the mixture flatness index decreased from 526.88 to 481.85, and the horizontal segregation index decreased from 4.08 to 3.69, representing reductions of 8.55% and 9.56%, respectively. However, significant horizontal segregation still remained. A subsequent theoretical analysis indicated that the effectiveness of shuttle charging in mitigating horizontal segregation is subject to an inherent limitation. In light of this limitation, a novel charging method, referred to as spreader plate charging, was proposed. According to the simulation results, the spreader plate charging achieved a mixture flatness index of 54.01 and a horizontal segregation index of 0.89, which were reduced by 88.79% and 75.9%, respectively, in comparison with the parameter-optimized shuttle charging. These results demonstrate a substantially enhanced horizontal uniformity of the sintering feed.

A three-dimensional (3D) mathematical model was established, coupling the large eddy simulation (LES) turbulence model, heat transfer model, solidification model, discrete phase model (DPM), and dynamic mesh model. Based on the actual continuous casting (CC) end process, the numerical simulation was divided into 4 stages. A method for calculating the motion velocity of the dynamic wall and the solidified shell was proposed to achieve the coupled simulation of transient flow, heat transfer, and solidification. In stage 1, molten steel speed and jet depth decreased as casting speed reduced, while the shell thickness steadily increased. In stage 2, after the submerged entry nozzle (SEN) removal, the molten steel speed and temperature dropped rapidly, and the circulation flow dissipated. In stage 3, the remaining molten steel region gradually decreased, and complete solidification occurred at approximately 4647.5 s, with the final solidification position located about 0.28 m below the end of the last slab. Based on the actual CC end stages and the entrapped positions of inclusions, a method for calculating the actual positions of inclusions was introduced to predict the 3D spatial distribution of inclusions in a CC end slab. The normalized number (NN) of inclusions exhibited a fluctuating downward trend with the increasing distance below the end of the last slab. It was recommended to cut the last slab at 4 m to ensure cleanliness, while the 3D normalized number density (NND) of inclusions in regions beyond 7 m below the end of the last slab reached a lower stable value.

The homogeneity of composition and microstructure of high magnetic induction grain-oriented silicon steel (denoted as Hi-B steel) critically influences the magnetic properties of the final product. This study investigated the solidification structure, elemental distribution, point segregation spots, and banded carbon (C)-rich microstructures of Hi-B steel under 0 A and 400 A current intensities during continuous casting and rolling. Results indicated that electromagnetic stirring increased the equiaxed zone fraction from 13.04% to 32.6%, refining the macroscopic solidification structure of the slab. However, central solidification defects were not eliminated. In rolled materials, banded C-rich structures appeared as narrow and wide bands, which corresponded spatially and dimensionally to segregate spots, central solidification defects, and positive segregation zones beneath the white bands in slabs. Elemental distribution analysis further revealed that electromagnetic stirring extended segregation throughout the equiaxed region, intensifying segregation in both the width and thickness directions of the slab. Although current heat treatment processes reduced segregation in rolled materials, C distribution remained uneven. In pursuit of efficient quality enhancement, Hi-B steel exhibited a dense columnar dendritic structure, with solidification defects and segregation spots localized within a narrow central region. Future enhancements should prioritize optimizing the cooling rate and increasing the extent of soft reduction to further refine the solidification structure and reduce segregation.

Microsegregation in alloys has a significant effect on the steel properties. Numerical simulations using cellular automaton (CA) models are often used to predict microsegregation behavior. However, the CA model has problems quantitatively predicting the microsegregation behavior owing to the inaccuracy of the calculation of the interface curvature. In this study, we developed a two-dimensional quantitative CA model that incorporates interface curvature calculations using the height function (HF) method, correction of mass-balance errors, and solid–liquid interface movements caused by solidification and melting. In a simple calculation of the curvature of circles using the HF method, we confirmed that the HF method could calculate the curvatures of circles of various radii with an error of less than 1%. In addition, we performed simulations of the unidirectional solidification of a single dendrite of an Fe–C alloy using two CA models that implemented curvature calculation models using the conventional and HF methods, and investigated the effects of both models on dendrite morphology. The development of secondary dendrite arms was observed only in the CA model that implemented the HF method, thereby confirming the effect of the curvature calculation on dendrite morphology. Finally, we performed simulations of the multidendrite growth of an Fe–C alloy under continuous cooling at different cooling rates using the CA model that implemented the HF method. Consequently, the solute concentration in the solid exhibited an appropriate distribution following the lever rule, and the microsegregation behavior based on the cooling rate was reasonably simulated.

Addressing the propagation characteristics of radar waves in the dusty environment of blast furnaces, this paper develops an electromagnetic scattering model for the burden surface that incorporates random roughness and stockline shapes. By obtaining roughness parameters from actual samples, we establish a geometric model of the burden surface that integrates both form and texture. Utilizing the radiative transfer equation and integral equation methods, we construct a composite scattering model for the dust-burden surface interaction. The study examines the effects of surface roughness and slope on scattering characteristics and, by comparing with measured data, verifies the model’s effectiveness, providing theoretical support for the inversion of radar data.

The characterization of non-metallic inclusions is crucial for understanding their origin, behavior, and modification during steelmaking and is directly connected to process optimization and improving product quality. SEM/EDS is the state-of-the-art characterization technique, measuring microscale morphology and elemental composition of non-metallic inclusions. Automated SEM/EDS analysis evaluates thousands of microscopic particles on a sample within hours, enabling the assessment of steel cleanness. However, challenges such as artifact misinterpretation and steel matrix effects on EDS accuracy must be considered to ensure reliable results. Furthermore, the widely used standardless EDS analysis is limited to elemental compositions normalized to 100 weight-%, restricting its applicability for more detailed characterizations.

This study introduces and verifies a framework for steel cleanness evaluation including automated and manual SEM/EDS analysis, data processing, and computational thermodynamics. Artifacts, with shares up to 42%, were effectively removed from automated SEM/EDS data. A matrix correction method adjusted non-metallic inclusion typification based on elemental thresholds. This significantly changed number densities of individual types, with a maximum increase of 798%, and improved the overall representation. Additionally, a novel mapping technique was developed to calculate phase equilibria based on EDS data, determining number and distribution of phases in complex non-metallic inclusions at 1600°C. Experimental cross-validation was performed using TEM. This mapping technique provides more insights into the characteristics of non-metallic inclusions compared to conventional standardless EDS analysis. The proposed framework represents a robust approach for advancing steel cleanness evaluations, enabling deeper studies on the formation and modification of non-metallic inclusions.

The combustion rate of palm kernel shell (PKS) char was measured under 3–5 vol% low oxygen concentration. The combustion rate increased with rising ash content, temperature, and oxygen concentration. Demineralizing the PKS char with hydrochloric acid resulted in a reduced combustion rate, while loading the PKS with 1.36 wt% Fe₂O₃ led to an increase. The physical properties (proximate analysis values, ultimate analysis values, and ash content) of the PKS, along with combustion conditions (combustion temperature and oxygen concentration), were used as explanatory variables, and the combustion rate, as the response variable, was predicted through machine learning across 5 model types. In the Gaussian process regression model (squared exponential kernel function), the root mean square, mean square, and mean absolute errors were closest to zero, while the coefficient of determination (R²) was closest to one. This study accurately predicted the combustion rate in the rate-determining step of a chemical reaction at low temperatures using the Gaussian process regression model (squared exponential). In addition, it was found that among the explanatory variables, the combustion temperature, volatile matter, oxygen concentration, Fe₂O₃ content, hydrogen content, and carbon content had a large effect on the combustion rate.

We investigated a novel bonding technique using Fe–Ni alloy plating as an alternative method for stainless steel bonding. This bonding process involves bonding at approximately 55°C followed by annealing at temperatures above 300°C, which is relatively low compared with conventional methods. Previous studies utilized bonding through Ni plating (NMPB; Ni Micro-Plating Bonding), which ensured a dense bond by maintaining a consistent growth rate of Ni plating crystals from opposing bonding surfaces, minimizing voids.¹⁵⁾ However, despite its effectiveness, Ni plating bonding resulted in only about one-third of the strength of the base material. In this study, we evaluated the bonding strength through shear tests by bonding stainless steel plates and wires with Fe–Ni alloys ranging from 41 to 87 wt% Ni. The shear strength of the joint as-plated, without heat treatment, was 173 MPa for Fe-87 wt% Ni alloy plating and 240 MPa for Fe-68 wt% Ni alloy plating, compared to 114 MPa for Ni plating. Thus, Fe–Ni alloy plating exhibited approximately 1.5 to 2.1 times the shear strength of Ni plating. Conversely, Fe-41 wt% Ni alloy plating showed significantly lower strength at 32 MPa. After heat treatment ranging from 300 to 800°C, the shear strength increased to 183–236 MPa for Ni plating, 182–292 MPa for Fe-87 wt% Ni alloy plating and Fe-68 wt% Ni alloy plating, while Fe-41 wt% Ni alloy plating increased to around 117 MPa.

Two orientations ({110}<001> and {110}<112>) evolve as secondary grains in heavily cold rolled reduction of 91.5% in grain-oriented silicon steel. We investigated the secondary recrystallization mechanism of these two grains by temperature gradient batch annealing method. This method induces the continuous growth of secondary grains along the temperature gradient direction. Consequently, selective growth behavior can be easily evaluated from macrostructure. Furthermore, the orientation relationships between secondary recrystallized grains and primary recrystallized grains at the interface of them can be investigated by interrupting the temperature gradient batch annealing process during the secondary recrystallization.

It was clarified that secondary grains which have higher frequency of CSL (Coincidence Site Lattice) boundaries grow more preferentially and the effective CSL boundaries tolerance angle was 10 degrees from precise CSL orientations. Both {110}<001> and {110}<112> grains statistically had a high frequency of effective CSL boundaries (more than 14.5%) and CSL boundaries corresponding to each orientation of secondary grains disappeared preferentially at growing fronts of each secondary grain.

It can be deduced that CSL boundaries dominate the selective growth behavior of {110}<001> and {110}<112> grains, which have two or more neighboring CSL boundaries to the matrix and thus successively grow as secondary grains. CSL boundaries are supposed to have lower grain boundary energy and higher mobility. Therefore, CSL boundaries suffer lower pinning forces from inhibitors and start to migrate from higher inhibition level (lower temperature). From these results, CSL boundaries play a dominant role in the secondary recrystallization of heavily cold rolled grain-oriented silicon steel.

The effect of the manganese content of 7% nickel-added steel on cryogenic toughness was investigated. Charpy impact tests on steels with manganese contents ranging from 0.05% to 2.16% revealed that the absorbed energy at −196°C increased with decreasing manganese content. Two steels with manganese contents of 0.2% and 0.8% were selected for a more detailed investigation of the dependence of toughness at −196°C on the intermediate heat treatment temperature, fracture behavior and retained austenite. Although the 0.2% manganese steel stably exhibited a high absorbed energy at −196°C at all intermediate heat treatment temperatures examined in this work, it was necessary to select an appropriate intermediate heat treatment temperature for the 0.8% manganese steel in order to achieve high absorbed energy at −196°C. The volume fraction, size, and nickel content of retained austenite were quantified using XRD and SEM/EDS, and the characteristics of the retained austenite in the steels with low manganese alloy designs were investigated. The cleavage-type brittle fracture that appeared in some specimens was discussed from the viewpoint of the stability of retained austenite.

We attempted to improve the strength–ductility balance in tempered martensite steel using multi-objective Bayesian optimization. The martensite steels were tempered at two stages, and fine and coarse cementite particles were mixed. Water-quenching rather than furnace-cooling between the first and second temper stages provided a better balance of strength and ductility. Moreover, the strength–ductility balance was also improved by tempering at a low temperature in the first stage and a high temperature in the second stage, rather than tempering at a high temperature in the first stage and a low temperature in the second stage. Based on these experimental results, multi-objective Bayesian optimization was used to further improve both tensile strength and total elongation. The strength–ductility balance that is better than the experimental results was achieved with a minimal number of optimization times. Additionally, machine learning suggested that it is crucial to control the average aspect ratio of cementite particles to less than 1.8 and the size of coarse cementite particles to less than 2.0 µm in order to improve the strength–ductility balance.

In this study, the chemical equilibrium experiments were systematically conducted at 1673 K under an oxygen partial pressure of 10⁻¹³ atm to investigate the precipitation of MnAl₂O₄ spinel in the CaO–SiO₂–MgO–FeO–MnO–Al₂O₃ slags. The results showed that with increasing Al₂O₃ content, Mn gradually transferred from the silicate liquid phase into the spinel phase. At 33.64 mol% Al₂O₃, the precipitation ratio of MnAl₂O₄ was approximately 80.32%, at which point the slag reached its solubility limit with respect to Al₂O₃. Therefore, 80.32% represented the maximum precipitation ratio attainable through Al₂O₃ control under the present experimental conditions. At this composition, comparison between water-quenching and slow cooling at 4 K/min revealed negligible differences in the crystal structure and composition of the spinel phase, indicating that MnAl₂O₄ precipitation predominately occurred during the high-temperature equilibration stage and remained stable upon cooling. In addition, with increasing Al₂O₃ content, the activity of MnO decreased, indicating its progressive consumption from the silicate melt and incorporation into the spinel phase.

Accurate prediction of activity in multi-component slag systems is of great significance for optimizing metallurgical processes. Existing models, which include both thermodynamic calculations and neural networks, often rely on simplifying assumptions or require extensive hyperparameter tuning. In addition, the experimental acquisition of slag activity data is difficult due to high-temperature conditions and complex procedures, resulting in limited and scarce data. To address these limitations, a novel model was proposed integrating TabPFN and SHAP analysis for activity prediction on small data. Model performance was benchmarked against existing models, and the results show that TabPFN not only surpasses other models in terms of predictive accuracy but also enables enhanced explainability by SHAP analysis. The TabPFN model achieved an R² of 0.9816, an RMSE of 0.0451, an MAE of 0.0243, and a model response time of 0.21 s. Moreover, a SiO₂ activity prediction tool was developed, featuring user-friendly operation, fast computation, and automatic model updating without the need for extensive hyperparameter tuning when new data are introduced, offering practical value for industrial deployment. This work provides a data-driven and interpretable approach for the real-time and accurate prediction of slag activity under complex process conditions.