With the trend towards larger blast furnaces, practical challenges such as the increasing demand for cooling system efficiency and the insufficient stability of the slag crust have become prominent, posing constraints on both safety and economic performance. In this paper, a three-dimensional model of a blast furnace with two parallel hoppers is developed based on the discrete element method. The process of burden moving from the belt to the upper part of the throat in the blast furnace and continuously falling is simulated. The relationship between burden distribution and primary slag formation behaviour in the blast furnace is examined. The results show that increasing the pellet ratios decreases the permeability of the middle part of the throat and promotes the movement of sinter and lump ore to the edge of the blast furnace, ensuring the permeability of the throat's edge. Additionally, increasing the proportion of pellets causes the primary slag formation temperature to vary non-monotonically, decreasing first and then increasing. When the basicity of the primary slag is maintained at 1.40 to 1.49, the mineral composition mainly includes merwinite, gehlenite and akermanite. The FeO content in the slag is a key factor in regulating the viscosity and ash melting temperature of the primary slag, with higher FeO content significantly reducing both. These findings provide a valuable basis for optimising blast furnace burden structure and regulating primary slag performance.
Basic oxygen furnace (BOF) is a key steelmaking process for yielding qualified liquid metal by removing the harmful elements sourced from the iron ore, and it features complex multiphase flow, especially the cavity, the key region strongly governing the smelting and refining. However, the understanding of the dynamic cavity characteristics, especially the periodic features within an industrial-scale BOF, remains limited. In this study, an industrial-scale BOF model is developed based on computational fluid dynamics (CFD), considering the system's multiphase nature and interactions, to quantify long-term cavity dynamics and the related periodic features. The results show that the mathematical model effectively captures the multiphase flow features inside and around the cavity. The cavity profiles, particularly, depth and radius grow significantly between 0.1 s and 0.4 s before reaching a less unsteady state. Subsequently, the cavity geometric features, including depth, radius, volume, and interfacial area, maintain distinct oscillatory behaviours over time. The time-averaged values for cavity volume, interfacial area, depth, radius, and sphericity are 0.31 m 3 , 1.95 m 2 , 0.78 m, 0.55 m, and 0.76, respectively. Furthermore, cavity depth exhibits more pronounced periodic features than other cavity properties, with the primary period being approximately 1 s for the studied scenario. This study may provide valuable insights into the further understanding and optimisation of multiphase flow behaviours within an industrial-scale BOF.
The selection of coking coal in integrated steel mills requires balancing multiple quality parameters against purchase costs. A quantitative cost-effectiveness evaluation model is proposed based on six key indicators, ash, sulfur, volatile matter, G -value, Y -value, and CSR/M40, each scored against plant-specific benchmarks using expert-assigned contribution coefficients. A single performance index is derived from the sum of deviations, which is then multiplied by the delivered price to obtain a comprehensive cost-effectiveness (CCE) value; lower CCE indicates better economic performance after quality adjustment. Applying the model to 21 commercial coking coals from a large integrated steel plant in northeastern China, all samples are systematically ranked, and inter-indicator correlations are analyzed. Results show that CSR/M40 exhibits the strongest negative correlation with CCE ( r = –0.71, p < 0.001), while price alone shows no significant correlation ( r = 0.07, p > 0.05). The model successfully identifies that high-priced coals do not always guarantee superior cost-effectiveness; conversely, several moderately priced domestic coals achieve excellent adjusted costs due to balanced quality profiles. The proposed method is transparent, easily implementable in plant-level spreadsheets, and provides a rational basis for procurement optimization. Limitations include the subjectivity of contribution coefficients and the need for strict quality thresholds for critical parameters such as CSR.
In the conventional Al deoxidation process of GCr15 bearing steel, large-sized Ds type inclusions are prone to form, which will have a significant impact on its fatigue life. In order to reduce the hazards caused by such inclusions, the development of non-fully Al-deoxidation processes has become the direction for the advancement of bearing steel. This study conducted a systematic investigation on the Al-Si composite deoxidation process adopted by a certain steel plant. Through systematic sampling throughout the process and calculation using thermodynamic software, it was found that the type of inclusions changed from spinel to inclusions mainly consisting of 1–3 µm Al 2 O 3 -SiO 2 composite oxides. The research results show that in the initial stage of the RH vacuum process, the high vacuum environment promotes the decomposition of CaO-SiO 2 , resulting in a slight increase in [Ca] content. After the RH venting, under normal pressure conditions, [Ca] will preferentially react with [O], causing a temporary decrease in [Ca] content. In the tundish stage, due to the decrease in molten steel temperature and the increase in MgO content, the original liquid inclusions transform into high-melting-point solid inclusions. The transformation of liquid inclusions into solid form helps them rise and be removed from the molten steel. Therefore, the density of inclusions decreased from 13.98 N/mm −2 before RH vacuum treatment to 3.47 N/mm −2 after RH vacuum treatment. These findings indicate that the Al-Si deoxidation route is effective for controlling the number of large-sized inclusions and improving the purity of GCr15 bearing steel.
To address the challenge of in-process accurate prediction of phosphorus content in molten steel during top-bottom combined-blowing converter smelting, this article proposes a data-driven multi-region coupled kinetic model for phosphorus removal. First, based on actual industrial production data, three machine learning models, namely backpropagation neural network, random forest and extreme gradient boosting, were constructed to predict the terminal steel phosphorus content (temperature–sampling–oxygen phosphorus content [TSOP]). A weighted ensemble strategy was then employed to generate high-precision TSOP predictions. The predicted TSOP is fed as input to a kinetic model, which incorporates the multi-region mass transfer mechanisms of the converter's emulsion zone and slag–steel interface zone, leading to the establishment of a modified cross-region diffusion-aware phosphorus removal kinetic model. Using an industrial data-driven parameter inversion technique, systematic optimisation and calibration of key mass transfer and diffusion coefficients are conducted to effectively improve prediction accuracy, especially within the narrow, high-precision error bands critical for industrial quality control. Results show that during the temperature–sampling–carbon phase, the hit rate for phosphorus content with an absolute error of ±0.025% reaches 89.94%; during the temperature–sampling–oxygen phase, this rate increases to 96.18% for an absolute error of ±0.01%. This model synergistically integrates the advantages of data-driven and mechanism-based modelling, thereby enabling accurate characterisation of the dynamic evolution during converter phosphorus removal.
Accurate control of firing temperature is essential for quality, efficiency and energy consumption in iron ore pellet production. Traditional methods that rely on measured temperatures are limited by sparse measurement points, time lag and signal fluctuations. This study proposes a method based on interpretable machine learning to predict firing temperature and identify key influencing factors and further examines whether such a framework can provide useful short-term diagnosis under real industrial operating conditions. An eXtreme Gradient Boosting model was developed and optimised using historical data from a large-scale chain grate–rotary kiln production line. The model achieved a mean absolute error of 3.10°C, a root mean square error of 4.32°C and an R2 value of 0.73 within a 10-min prediction horizon. SHapley Additive exPlanations analysis indicated the influence of process parameters on firing temperature, demonstrating that kiln head temperature, coal injection rate and cooling exhaust temperature are critical factors. This approach enables intelligent monitoring and optimisation of the firing process, supports abnormality diagnosis and improves production efficiency and energy conservation. Future research will concentrate on improving long-term prediction accuracy and integrating causal analysis for further process optimisation.
This study investigated the interface characteristics and properties of hot roll bonded 2205 stainless steel/AH36 shipbuilding steel clad plate (2205/AH36 CP). The microstructure, element diffusion, and mechanical properties at the interface were characterised using SEM/EBSD, TEM, EDS analysis and in-situ nano-indentation tests. Results indicate a well-bonded interface with no microcracks or pores, confirming metallurgical bonding. The interface exhibited a transition zone with element diffusion, leading to the formation of a decarburising layer in AH36 and a carburising layer in 2205 steel. Nano-indentation tests revealed a hardness peak at the interface due to the formation of M23C6 phase. TEM observations confirmed the gradual transitional characteristic of the interface microstructure. Tensile tests in conjunction with digital image correlation (DIC) analysis demonstrated the ductility of the clad plate and the uniform distribution of strain, with no detected interface cracking.
Transition towards fossil-free iron and steel production increases the role of electric arc furnaces (EAF), whereas the role of blast furnaces (BF) decreases. This has drawn an increasing attention towards the valorisation of EAF slag with the target in the high value applications such as supplementary cementitious materials (SCM). This is supported not only by the declining production of the granulated blast furnace slag (GBFS) currently widely used as a SCM, but also common targets for both cement and steel industry to reduce carbon dioxide emissions. Due to their different chemical and mineralogical composition, structure and properties in comparison to GBFS, the EAF slag cannot be used as SCMs as such. It is widely considered that usage as SCM would require treatments such as modification of the composition towards lower basicity, removal of certain components (e.g. via reduction), controlled and sufficiently fast cooling as well as a feasible way to even out the potential differences due to use of different kind of raw materials in the EAF; that is, steel scrap, DRI reduced with either hydrogen or other reductants, Fe-containing secondary materials such as briquetted dusts and so on. The purpose of this study has been to supplement the experimental studies with thermodynamic simulations in which both equilibrium and Scheil-Gulliver calculations were made for different slag systems with varying compositions. Although not being able to simulate the formation of amorphous glass phase obtained with fast cooling of low basicity slag, computational thermodynamics nevertheless offer a tool to quickly estimate the effect of different slag treatments on the stabilities, amounts, compositions and solidification orders of solid crystalline phases as well as solidus and liquidus temperatures. According to the results, the simulations can predict the amount of monoxide phase relatively well, whereas the amount of spinel is overestimated in the simulations. The most probable reason for this is the lack of time for the nucleation and growth of the spinel phase in the rapid cooling of the experimental samples. Concerning the compositions, the compositions of the spinel phases were predicted more accurately in comparison to the monoxide phase, for which the shares of MgO and FeO varied significantly between the samples.
Cooling non-uniformity in the Stelmor air-cooling line causes persistent temperature differences between the overlap-dense and loosely packed regions of wire rod coils, leading to heterogeneous phase transformation and inconsistent mechanical properties. This study investigates the effects of grate plate configuration on cooling non-uniformity and phase transformation of 82Mn wire rod coils using a three-step coupled numerical approach. The plenum-chamber airflow was first resolved to obtain nozzle-outlet velocity distributions under different fan conditions and grate plate configurations. These distributions were applied as boundary conditions to compute the coil-scale flow field and convective heat transfer coefficient distribution. The wire rod cooling curves and phase transformation evolution were then predicted by incorporating forced convection, thermal radiation and transformation latent heat release. The predicted temperature histories agree well with industrial measurements, with a maximum deviation of approximately 30 K (less than 3% of the initial wire temperature of 1193 K). The results show that although the grate plate effectively redirects cooling air towards the overlap-dense edge regions, geometric shielding by the densely stacked wire loops remains the dominant factor limiting local forced convection. Phase transformation starts first in the low-density coil-centre region and is delayed in the overlap-dense regions by about 8 to 10 s. At the cooling line exit, the temperature difference between the overlap region and coil centre reaches 74 K, 72 K and 68 K for the Type-C, Type-B and Type-A configurations, respectively. The variation of only 6 K across configurations demonstrates that adjusting the grate plate hole diameter alone has limited effectiveness in improving cooling uniformity. Further improvement requires coordinated optimisation of grate plate configuration, fan operating conditions and roller speed.
Air jet erosion is a major degradation mechanism affecting metallic components operating under particle-laden environments. In the present study, a WC–12Co coating reinforced with 5 wt-% CrB 2 and 5 wt-% TiC was deposited on SS304 stainless steel using the high velocity oxy-fuel (HVOF) spraying process to improve erosion resistance. The developed coating exhibited a dense microstructure with an average thickness of 331 ± 3 μm, low porosity of 1.21 ± 0.09%, and uniform distribution of W, Co, Cr, Ti, and B throughout the coating. Mechanical characterization revealed a significant increase in hardness from 212 ± 7 HV for SS304 to 1232 ± 29 HV for the coated sample. Air jet erosion testing was performed according to ASTM G76 using a Central Composite Design by varying jet velocity, particle size, and impingement angle. The erosion loss of SS304 varied between 10.49 and 29.53 mg, whereas the coated samples exhibited lower erosion values ranging from 6.31 to 25.58 mg. Analysis of variance confirmed that jet velocity was the most influential parameter governing erosion behavior, followed by particle size and impingement angle. The developed quadratic models exhibited high coefficients of determination exceeding 0.99, indicating excellent predictive capability. Post-erosion examination revealed that the coating primarily experienced localized micropitting, particle detachment, and erosion crater formation, while the substrate exhibited severe surface degradation, material extrusion, and surface peeling. The results demonstrate that the incorporation of CrB 2 and TiC significantly enhances the erosion resistance of WC–12Co coatings, making them suitable for applications subjected to severe particle impingement conditions.
Molecular dynamics simulations were used to investigate the structural evolution of Ce 2 O 3 -CaF 2 -CaO-Al 2 O 3 slag with Ce 2 O 3 content ranging from 0 wt% to 16 wt% at 1873 K. The results show that increasing Ce 2 O 3 content leads to a shift in the role of F − from network former to modifier, as Ce 3+ ions replace F − with O 2− in [AlO 3 F] 4− units. Slag polymerisation increases up to 12 wt% Ce 2 O 3 , as evidenced by an increase in bridging oxygen from 30·8% to 39·2% and a rise in complex Q 3 +Q 4 units from 18·1% to 43·4%. However, at 16 wt%, excess O 2− ions disrupt the network, leading to depolymerisation. Consequently, the viscosity was calculated from diffusion coefficients derived from mean square displacement analysis. It exhibits a non-monotonic trend, increasing with Ce 2 O 3 content up to 12 wt% and decreasing at 16 wt%. This study highlights the effect of Ce 2 O 3 on slag structure and diffusion, providing insights for optimising Electroslag Remelting slag design. The simulation framework can be extended to other rare earth-modified slags and combined with experiments to further validate the polymerisation-depolymerisation mechanism.
Hydrogen-based shaft furnaces use hydrogen instead of coke and are regarded as a key route for low-carbon steel production. However, under high-temperature direct reduction conditions, sticking of direct reduced iron may occur, which deteriorates bed permeability and affects production stability. In this study, reduction-under-load tests were conducted to simulate the atmosphere of a hydrogen-based shaft furnace and to investigate the effects of total reduction time, temperature, and coating materials (CaO, MgO, TiO2) on the sticking behavior of vanadium-titanium pellets. The results show that sticking was strongly affected by reduction time at 1100 degrees C. When the total reduction time reached 2.5 h, the sticking index and sticking strength reached their maximum values of 97.11% and 16.23 N, respectively, and then decreased with further extension of time, while the metallization rate gradually declined. Increasing temperature markedly intensified sticking behavior, whereas the metallization rate changed little. Among the coating materials, TiO2 exhibited the strongest inhibitory effect by forming a dense barrier layer and Fe-Ti-O interfacial products that reduced direct particle contact and suppressed the development of sticking phases.
This study investigated the effects of refractories (MgO vs. Al 2 O 3 ) on the cleanliness and inclusion evolution in Al-killed steel during refining with a CaO-Al 2 O 3 -SiO 2 slag (56.9% CaO, 35.0% Al 2 O 3 , 8.1% SiO 2 ), combining laboratory experiments with thermodynamic calculations. The results show that with MgO crucibles, total oxygen and sulphur contents in steel remained low (6–8 and 4–5 ppm), and inclusions were CaO-Al 2 O 3 -MgO and MgO·Al 2 O 3 -based; area fraction and average size decreased with refining time. With Al 2 O 3 crucibles, total oxygen and sulphur contents increased to 13–16 and 30–46 ppm, respectively, and sulphur reversion occurred. Inclusions were CaO-Al 2 O 3 -SiO 2 and Al 2 O 3 -based, reaching minimum area fractions after 60 min of refining. Thermodynamic calculations revealed that the dissolution of MgO crucibles enhanced the slag's absorption capacity for CaO·2Al 2 O 3 inclusions, while inhibiting the absorption of MgO and MgO·Al 2 O 3 inclusions. Conversely, Al 2 O 3 crucible dissolution weakened the slag's absorption capacity for calcium aluminate, MgO·Al 2 O 3 , and Al 2 O 3 inclusions.
Current research on gas-based direct reduced iron carburisation primarily focuses on simple CH 4 -H 2 or CO-H 2 systems, with limited attention given to carburisation behaviour under complex gas mixtures. This study examined the carburisation of direct reduced iron in CH 4 –H 2 –CO–CO 2 gas mixture across 550–950 °C combining thermogravimetry, carbon speciation (XPS, carbon-sulphur analyser) and strength/swelling measurements. Complementary density functional theory simulations examined CH 4 and CO adsorption on α-Fe(110). The results indicate that under identical carburisation duration, significant weight gain of direct reduced iron occurred at 550 and 950 °C, but was negligible between 750 and 850 °C. Within the temperature range where weight gain occurs, increasing H 2 ratio accelerates the carburisation process, while CO 2 exhibits a strong inhibitory effect. Elevating CH 4 ratio promotes carbon absorption above 850 °C, and higher CO enhances low-temperature uptake. The carbon exists primarily as graphite below 650 °C, while cementite becomes dominant at elevated temperatures. Fe 3 C generates above 850 °C, triggering the volumetric expansion and 50% compressive strength loss versus direct reduced iron. Carburising at 950 °C for 20–30 min ensures adequate Fe 3 C without inducing severe swelling or compressive strength degradation. Simulations reveal that CH 4 and CO adsorb on the α-Fe (110) surface via physical and chemical absorption, respectively. However, CH 4 transitions to chemical absorption after dehydrogenation. Electron depletion between C–H and C–O bonds reveal the carburisation pathways of CH 4 and CO on the Fe surface.
As core thermal energy equipment in steel, power, and petrochemical industries, industrial heating furnaces' combustion control directly impacts energy efficiency, costs, and pollutant emissions-critical for industrial decarbonization. However, combustion processes' high nonlinearity, time-variability, multi-disturbance, and multi-objective constraints make traditional manual/single strategies ineffective for complex fluctuations and optimization, failing high-efficiency, low-carbon demands. Recent intelligent control technologies, integrating data-driven and mechanism-based models, have advanced temperature field modeling, parameter prediction, multi-objective optimization, and advanced control, boosting accuracy, stability, and emission reduction. This paper reviews intelligent combustion control model progress, compares model applicability, addresses key limitations (e.g., poor generalization, weak real-time integration), and proposes future directions (cross-model integration, data-scarce modeling, online optimization), providing theoretical and technical references for heating furnaces' energy-efficient, lowcarbon, and intelligent upgrading.
The purity of clean steel directly governs its mechanical properties. As a highly efficient deoxidizer and sulfide modifier, magnesium plays a critical role in clean steel production. This paper reviews magnesium treatment technology, analyzes the thermodynamics and kinetics of reactions between magnesium and inclusions, elucidates the regulatory effects of magnesium on inclusion evolution, size and distribution, and presents the merits of magnesium-rare earth composite treatment. Finally, the development trends are prospected and novel processes proposed, providing guidance for fabricating high-quality clean steel.
Lime is one of the primary slag-forming materials in steelmaking, and its rapid, complete dissolution is critical for accelerating metallurgical reactions and reducing the content of free CaO in the slag. In industrial practice, the presence of trace amounts of Al 2 O 3 in the slag may influence the dissolution behaviour of lime. In this work, a static lime dissolution experiment was employed, coupled with scanning electron microscopy– energy-dispersive spectroscopy, X-ray diffraction, and FactSage thermodynamic calculations, to investigate the effects of Al 2 O 3 on lime dissolution in a CaO–SiO 2 –FeO–P 2 O 5 slag system containing 3 mass% MgO with varying Al 2 O 3 concentrations. The results show that lime dissolution in this slag system leads to four distinct structural zones progressing outward from the lime surface: (1) a reacted lime core, (2) a CaO–FeO(MgO)-enriched layer containing Ca, Fe, Mg, and trace Al, (3) a solid-phase layer comprising dicalcium silicate (Ca 2 SiO 4 ) and Ca 2 SiO 4 –Ca 3 P 2 O 8 solid solutions, and (4) the original slag matrix. The formation of solid compounds and solid solution layers was found to impede further lime dissolution. As the Al 2 O 3 content increased from 0% to 5%, the average lime dissolution rate increased by approximately 40%. However, a further increase to 7% resulted in a negligible additional improvement of <5%. Mechanistic analysis indicated that Al 2 O 3 reacts with CaO and MgO to form MgAl 2 O 4 spinel and Ca 3 Al 2 O 6 phases, which subsequently modulate the dissolution behaviour through phase evolution effects. This study provided a systematic investigation into the non-monotonic effect and underlying mechanism of Al 2 O 3 on lime dissolution in a basic oxygen furnace-type slag containing 5% P 2 O 5 and 3% MgO.
This study investigates the influence of boron on phase transformations during continuous cooling of unalloyed cast steels. To achieve the research objective, cast steels with an appropriate chemical composition were designed and produced. One cast steel contained a micro-addition of 0.002% boron, while the other, with a similar chemical composition but without boron, served as the reference cast steel. The materials were subsequently subjected to dilatometric testing, on the basis of which Continuous Cooling Transformation (CCT) diagrams were developed. Microstructural analysis included examinations using light microscopy, as well as scanning and transmission electron microscopy. A Jominy end-quench test was also performed to assess hardenability. The test results were supplemented with discussion and conclusions. Based on the conducted studies, it can be concluded that, in the absence of alloying elements that enhance the effect of boron, the full potential of boron in improving hardenability is not realised. The benefits of its application are manifested mainly in the reduction of the critical cooling rate from over 300 to 262 °C/s, which occurs simultaneously with a decrease in the hardness of the resulting microstructures by approximately 70 HV5.
In this article, silica bricks were prepared using calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) as the mineralizer. Its reaction mechanism during the sintering of silica bricks was systematically elucidated via characterization techniques such as XRD, SEM, and X-ray CT. The results show that calcium nitrate tetrahydrate, with a low melting point (approximately 56°C ), can uniformly coat silica particles in liquid form during the mixing stage, and is successively converted into calcium nitrate and highly active CaO during the drying and sintering of the green body. The volume shrinkage associated with this transformation can precisely compensate for the expansion stress induced by the phase transformation of quartz to metastable cristobalite, thereby endowing the sintered bricks with a dense structure free of obvious cracks, together with fine and uniform intergranular pores. As a calcium-containing mineralizer, it reacts with SiO2 raw materials to form a calcium-silicate liquid phase at 1436°C , which effectively promotes the conversion of metastable cristobalite to tridymite. Compared with the traditional CaO-FeOx composite mineralizer, this mineralizer can significantly reduce the content of amorphous phases in the sintered bricks. Composition regulation and microstructure optimization directly enhance the high-temperature performance of silica bricks. The bricks doped with 5 wt% calcium nitrate tetrahydrate not only exhibit excellent high-temperature volume stability, but also achieve a thermal conductivity of 2.366 W/(m·K) while maintaining an apparent porosity of 21.4%.
