To understand the relationship between the thermal conductivity of the mold flux and its composition from the perspective of the local structure, the thermal conductivities of CaO–BO_1.5–AlO_1.5–SiO₂ melts were measured using the transient hot-wire method in the range of 1573–1773 K, and structural analyses were conducted using magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Additionally, the covalency of the bonds between each cation in this system and the oxygen atom was evaluated using first-principles calculations to consider the propagation of phonons between each bond. As a result, the degree of polymerization of the network structure, D_P, was calculated from the composition and results of the MAS-NMR analysis and confirmed to have a positive effect on thermal conductivity. Some samples exhibited low thermal conductivity despite a high D_P below 1673 K, owing to the formation of boroxol ring structures. Using first-principles calculations, the covalency of the B–O, Al–O, and Si–O bonds was evaluated quantitatively as the length between the center of the bonds and the center of the electron distribution, L. The standard deviation of covalency in the entire network of a sample, S_L, was obtained and confirmed to have a negative effect on thermal conductivity because a difference in covalency between bonds caused phonon scattering. Finally, by integrating our previous research, the ratio of D_P/S_L was confirmed to be an effective index for evaluating the thermal conductivities of the CaO–BO_1.5, BO_1.5–SiO₂, CaO–AlO_1.5–SiO₂, CaO–BO_1.5–SiO₂, CaO–BO_1.5–AlO_1.5, and CaO–BO_1.5–AlO_1.5–SiO₂ systems.

Induration is a thermal treatment process wherein the green pellet properties are enhanced for subsequent reduction processes such as blast furnace and DRI production. During induration, the pellet essentially undergoes (i) physical change, that is, particles sinter with each other imparting strength to the pellet and (ii) chemical change by which phase change occurs either due to reduction/oxidation or thermal decomposition. Both these changes are interdependent. In case of induration of magnetite pellet, the exothermic oxidation of magnetite to hematite generates heat within the pellet. However, for the induration of hematite pellets carbon in the form of coke breeze is added in the green pellet mix to aid heat generation by combustion within the pellet.

In this paper, the sintering of single hematite pellet is investigated isothermally using optical dilatometer. Sintering kinetics is deduced for the pellet and the effect of coke addition on sintering kinetic parameters has also been investigated. The shrinkage data, expressed in terms of sintering ratio, from the optical dilatometer is sufficient to capture sintering kinetic. The extent of sintering under isothermal condition as a function of time can be expressed in terms of power law relation as Ktⁿ. The constant K as function of sintering temperature, as sintering being a thermally activated process, can be described using Arrhenius equation. The kinetic triplet namely, time exponent(n), pre-exponential factor(k’) and the activation energy(Q) are determined for pellets with no coke to 2 wt% coke addition. This paper presents insight into the sintering mechanism of hematite pellet.

Green hydrogen is seen as crucial for the decarbonisation of the economy. Yet, some regions may lack local producing capability, necessitating hydrogen imports. Ammonia can be a cost-effective solution to indirectly transport hydrogen. Three concepts are presented for using ammonia as reductant in the Blast Furnace (BF) process. The first concept, called EASyMelt shaft, incorporates cracked ammonia into the furnace’s shaft. The second concept, NH₃ EASyMelt, takes the changes a step further and injects cracked ammonia in both the bosh and shaft tuyeres. The cracked ammonia, heated by plasma torches, replacing hot blast and coal in the bosh tuyeres. Finally, NH₃ EASyMelt is implemented with top gas recycling (TGR). The furnace operation under these scenarios is compared to conventional operation using a multi-phase BF process model. The CO₂ emissions are found to be reduced by 15% for EASyMelt shaft, 60% for NH₃ EASyMelt without TGR and 55% with it. The new concepts are also shown to have a significant impact on the thermal state, gas distribution, pressure drop and cohesive zone characteristics. The study sheds light on how ammonia could be integrated into the BF process, and the expected impact on the furnace thermochemical state and the CO₂ emissions.

For the differences in composition and proportions of input materials, end-point quality requirements and slagging specifications, it is difficult to construct a generalized model to guide steelmaking production. There is a complex connection among different heats in BOF, and this combination of correlations can be thought of as a hidden working pattern. A method named “attribute level division” is developed to exploit the correlations among heats to construct the graph of heats. The model based on the combination of label propagation algorithm (LPA) and back propagation neural network (BPNN), LPA-BP, is proposed for end-point carbon content prediction in BOF. LPA is used to discover the different community in the graph of heats and BPNN is trained to construct different models for end-point carbon content prediction for the heats from different community. The results of comparative experiment show that the LPA-BP model is higher than the baseline 2.5% when prediction error is within ±0.012%. The LPA-BP model also outperforms in some metrics, such as RMSE, MAE. This model provides a novel idea to improve the endpoint hit rate by distinguishing different communities to uncover the hidden working patterns among heats and constructing different models.

The morphology, number, and distribution characteristics of inclusions influence the application properties of sulfur-alloyed free-cutting steels. Herein, the three-dimensional morphology and distribution characteristics of MnS inclusions as cast and rolled were systemically explored by X-ray micro-CT. Firstly, based on the composition test and applying the Ohnaka model, the element segregation behaviour and its relation to the morphology of MnS inclusions in steel billets were elucidated. Secondly, the growth of MnS in the steel billet was analyzed using the second-phase precipitation theory. The calculation results show that MnS was generated when the solid phase fraction f_S=0.56, and the relationship between the content of elements and the morphology and distribution characteristic of MnS was established. Thirdly, the characteristics of MnS inclusions transform with various deformation amounts were investigated, and the relative plasticity of MnS reached the peak value when the deformation amount was 50%. Finally, the genetic characteristics of MnS inclusions as cast and rolled were analyzed. In practice, a series of measures composed of increasing the cooling intensity of continuous casting and rolling the billet in the range where MnS has relatively low plasticity was suggested to optimize the product machinability.

Converter completion time delay caused by uncertain events is one of the most frequent disturbances in the steelmaking-continuous casting process (SCCP) with a significant negative impact on the SCCP scheduling. Existing rescheduling methods fall short in providing a comprehensive analysis and evaluation for the production status and disturbance levels, resulting in the scheduling scheme with limited adaptability to on-site environments. This paper addresses this challenge by proposing a dynamic evaluation method for converter scheduling disturbance based on processing time prediction and disturbance influence process analysis. The proposed method consists of three steps that solve the disturbance evaluation problem by predicting the converter processing time, analysing the delay impact of the converter completion time, and solving the real-time procedure buffer capacity. This enables the dynamic scheduling of the SCCP to accurately judge the current operating rhythm and production status, and to achieve precise decision-making for scheduling. Computational experiments based on the actual case from the Chinese steelmaking plants demonstrate the accuracy and effectiveness of the proposed method in large-scale SCCP dynamic scheduling processes. Compared with other methods, the proposed method can effectively reduce the number of rescheduling in production and the deviation of the production process from the initial scheduling scheme by reasonably selecting the scheduling repair strategy, which improves the adaptability of the scheduling scheme to the actual production environment.

The interaction of hydrogen with lattice defects plays a crucial role in the hydrogen embrittlement mechanism, but the origin of hydrogen-related defects remains unclear. In this study we investigate the formation process of hydrogen-induced vacancies in austenitic stainless steel SUS 304 by positron annihilation lifetime spectroscopy. Positron lifetime measurements of hydrogen-charged samples subjected to tensile testing by different strains show that the formation of hydrogen-induced vacancies first appears when a strain of about 5% is applied. Electropolishing of the hydrogen-charged layer reveals the generation of vacancy-hydrogen complexes in the bulk underneath the hydrogen-charged layer, which develop into vacancy clusters by further application of stress. From the PALS results and complementary X-ray diffraction analysis, the dislocation density required for the formation of hydrogen-induced vacancies is quantitatively determined. Clarification of the conditions for the formation of hydrogen-induced vacancies provides important input and reference data for models of the hydrogen embrittlement in stainless steels.

In this study, we investigated the surface properties of iron subjected to corrosion in contact with frozen salt solutions, focusing on the effects of solution aeration and salt type on ferrous iron dissolution behavior. X-ray photoelectron spectroscopy (XPS) was used to examine the surface conditions after corrosion. Image analysis of the frozen media indicated that dissolved oxygen in freeze-concentrated solutions (FCS) plays a crucial role in the dissolution process. XPS analysis confirmed the formation of iron hydroxide and iron oxyhydroxide on the iron surface, suggesting a reaction mechanism similar to that observed under atmospheric conditions. Additionally, surface analysis revealed that specific salt ions—such as F⁻, Cl⁻, and Cs⁺—exhibit a tendency to adsorb onto the iron surface under conditions of pronounced dissolution. These hard anions form complexes with Fe (II) ions, thereby promoting their dissolution. Moreover, Cs⁺ ions readily adsorb onto FeOOH, creating a concentration gradient near and beyond the iron surface that further promotes iron dissolution.

We have developed experimental and data analysis techniques of imaging XAFS (X-ray absorption fine structure) and investigated the Fe chemical state distribution in iron ore sinters over a field of view wider than 10 mm. Detailed spectral interpretation was provided for oxides and calcium ferrites at different stages of reduction. At lower temperatures, crack-driven propagation of reduction reaction was observed to penetrate deeper than 1 mm, while fine-grain primary hematite underwent reduction without forming cracks. Once the reduction of calcium ferrites begins, the reduction reaction changes to relatively uniform propagation, independent of mineral phases, resulting in a layered distribution of Fe chemical states.

Flotation dryer systems are widely used to dry liquid layers on substrates such as films, paper and steel strips, and many reports discussing design optimization for better heat transfer characteristics and strip stability are available.

As an advantage of this type of system, surface defects caused by contact between a support roll and the strip are prevented by floating the strip with a jet flow. However, since the friction force between the jet flow and the strip is smaller than that between a support roll and strip, flotation systems are prone to strip walking.

This tendency is noticeable in case of bad shape strip. Thus, it is important to improve the strip centering force. To our knowledge, no systematic in-depth study on prediction of the strip centering force with flotation dryers exists in the literature, and in particular, literature which compares experimental and analytical results is very rare.

In the present study, the centering force acting on a steel strip in a flotation dryer was investigated by experiments and simplified two-dimensional fluid analyses in order to evaluate the influence of the side plate geometry and the off-center value from the center of the floatation dryer on the centering force.

The centering force in the experiment and analysis showed a good correlation. Therefore, it is thought that the centering performance of actual floatation dryers can be estimated by simplified experiments and analyses.

A novel solid-state joining method called Cold Spot Joining (CSJ) has been successfully developed. In this joining concept, the material near the joining interface is plastically deformed under high pressure to form a joining interface, resulting in the fragmentation of oxide films at the joining interface and the formation of strong interface. Medium carbon steel sheets were CS-joined under various process conditions. The joining temperature can be varied by the applied pressure during CSJ. Microstructural observations and hardness distribution indicated that the appropriate pressurization resulted in joining temperatures below the A₁ point and suppressed the formation of the brittle martensitic structure. By providing appropriate applied pressure, sound S45C spot-welded joints were successfully produced, showing plug failure of the base metal in both tensile shear and cross-tension tests. Further investigation into the mechanism of interface formation reveals that the oxide film at the interface is fragmented and expelled. At the same time, dynamic recrystallization occurs at the interface and extremely fine new grains with dispersed fine cementite are formed at the interface to achieve the sound joining with sufficient strength.

The friction-type joints using high-strength bolts are frequently employed for the assembly of structural steel components. The drawback of the combination of the friction-type joints and hot-dip galvanized steel plates for highly corrosive environments is the low slip coefficient at the friction interface in the as-coated condition. To increase the slip coefficient, labor-intensive blast processing or phosphate treatment is applied to the surface of the galvanized steel plates before assembly. In this study, we investigated the slip mechanism at the friction interface between as-galvanized steel plates through slip resistance tests on high-strength bolted friction joints, in hope of determining effective methods for overcoming the low slip coefficient in the as-coated condition. In the as-galvanized material, both the outermost Zn- and ζ(FeZn₁₃)-phase layers exhibit c-axis texture. Since the easiest basal (dislocation) slip plane for the Zn phase with the hexagonal close-packed structure is parallel to the friction interface, the Zn phase is geometrically prone to plastic deformation due to the shear stress applied on the friction interface. The evidence that the coarse-grained Zn phase was refined to small crystal grains upon macroscopic slippage at the friction interface indicated that the low slip coefficient was attributed to the readily deformable nature of the outmost Zn phase. Potential strategies for increasing the slip coefficient without pre-surface treatment include strengthening the soft Zn phase through grain refinement or texture modification, or complete removal of the Zn phase during galvanizing.

The solid–liquid interface energy anisotropy of Zn alloys remains poorly understood. Recently, characteristic 14-arm dendritic growth has been observed using time-resolved X-ray computed tomography at SPring-8 during the solidification of a Zn-4mass%Al alloy. This study investigates the dependence of the dendrite morphologies of Zn alloys on solid–liquid interface energy anisotropy through systematic phase-field simulations of the growth of an isolated equiaxed dendrite. We also develop a data assimilation system to estimate the anisotropy parameters of solid–liquid interface energy and crystal orientation in Zn alloys and validate the system through twin experiments. This study provides insights into the solidification of Zn alloys and a powerful tool for their investigation.

The Hall–Petch coefficient, which is the slope of the Hall–Petch relationship, was investigated as a means of increasing the yield strength of ferritic steels through highly efficient grain refinement strengthening. Because the Hall–Petch coefficient increases with the grain boundary segregation of solute elements such as carbon, the equilibrium grain boundary segregation behavior was theoretically calculated using the Hillert–Ohtani model, and the para-equilibrium grain boundary segregation, in which only carbon undergoes equilibrium segregation without diffusion of substitutional solute elements, was also discussed. The calculated results were correlated with the experimentally obtained Hall–Petch coefficients. To control the grain boundary segregation behavior, the solubility of carbon in ferrite was changed by altering the solution-treatment temperature, and the co-segregation of carbon steel with the addition of a third element, Mn or Si, was investigated in this study. As a result, good correspondence between the theoretically calculated values of grain boundary segregation and the experimental values of the Hall–Petch coefficient was confirmed for Fe–C and Fe–Mn–C alloys.