The complex oolitic structure of high-phosphorus iron ore (HPIO) poses a major challenge to dephosphorization, restricting its high-value utilization. This study proposed a carbothermal smelting reduction process to simultaneously extract and enrich Fe and P from HPIO into a valuable Fe-P alloy. Thermodynamic calculations demonstrate that Fe and P are preferentially reduced and the increase of C/O ratio contributes to the enrichment of P, C, and Si elements in molten iron phase. Reduction experiments confirm that the oolitic structure begins to be destroyed at 1000 degrees C and a high temperature above 1400 degrees C is essential for the separation of iron and slag. After smelting reduction at 1600 degrees C and C/O = 1.0, a Fe-P alloy containing 1.33 wt% P was obtained with high recovery rate of 96.24% for Fe and 86.94% for P. Kinetic studies derived from thermogravimetric analyses reveal that the carbothermal reduction of HPIO is governed by rate-limiting steps: (1) interfacial chemical reaction dominates below 725 degrees C; (2) gas diffusion becomes limiting at 835 degrees C-890 degrees C; and (3) interfacial chemical reaction reemerges as the limiting step above 1000 degrees C. These findings provide fundamental insights into the reduction of HPIO and offer a promising route for the high value utilization of HPIO.

This study presents a systematic investigation into the evolution of non-metallic inclusions during the industrial continuous casting production of high-carbon chromium bearing steel. Conventional 2D characterization techniques and X-ray-based Micro-CT were employed to compare the number, type, size, and spatial distribution of inclusions throughout the LF-RH double-refining process. The results show that Al2O3 and MgO center dot Al2O3 are the dominant inclusion types formed during melting and refining, with MgO center dot Al2O3 exhibiting a strong thermodynamic tendency for formation. Due to differences in the resolution of the two characterization methods and variations in inclusion characteristics among the samples, inclusions with an equivalent diameter larger than 5 mu m show better consistency between the results obtained from the two techniques. This finding revises the assumption that X-ray-based CT techniques inherently yield larger equivalent inclusion diameters. The spatial distribution and morphological characteristics of inclusions are identified as key influencing factors. In ultraclean bearing steel characterized by non-uniform inclusion distribution and predominantly spherical oxide inclusions, when only inclusions larger than the critical equivalent diameter of 5 mu m are considered, the equivalent diameters obtained from 3D characterization are significantly smaller than those derived from 2D methods. This study provides vital industrial data for the future development of precise multidimensional characterization of inclusions in ultra-clean special steels. It also supports the establishment of a reliable 2D-3D conversion model that incorporates characteristic parameters.

The characteristics of alternating current (AC) arc play a crucial role in the heating efficiency of ladle furnaces that use arc as a heat source. In this paper, a model of stirring by blowing argon gas at the bottom of the ladle, a model of gas component transport in the cavity, and an AC arc model are established to study the distribution of slag eyes, cavity gas distribution, and AC arc characteristics in ladle furnaces. The influence of electrical operation on the AC arc characteristics of ladle furnaces is also analyzed. The research found that when the bottom-blowing gas flow rate of a single hole is 400 L/min, the average mass fraction of argon gas around the three-phase electrodes is 13.7 pct. Considering the fluctuation of cathode spots, the average temperature and average velocity of the arc column are identically distributed in the radial direction during the period, while the temperature and velocity distributions only change in the axial direction. The temperature is higher in the areas near the surface of the molten pool and the bottom of the electrode. At the same power and rated power, when the gear is increased from 4th gear to 8th gear, the area of the high-temperature zone in the arc continues to expand, the highest temperature occurs near the surface of the molten pool, and the average surface heat flux of the molten steel increases by 4.95 × 106 and 3.29 × 106 W/m2, respectively.

Optimizing the foaming characteristics of tundish fluxes is crucial for effectively enhancing plasma-heating efficiency, necessitating a systematic investigation into the evolution of these fluxes under plasma-heating conditions. In this study, the foaming process of slags was observed, and the influence of plasma heating on slag structure was analyzed using DSC, high-speed camera imaging, XRD, Raman spectroscopy, and 27Al MAS-NMR. The results indicate that, during plasma heating, the gas source for slag foaming primarily originates from carrier gas entrainment and CO2 released from carbonate pyrolysis. Under a fixed addition level of 5 wt%, the foaming duration of the K2CO3, Na2CO3, Rb2CO3, Cs2CO3, and Li2CO3 systems decreased sequentially from 136 to 111 s, among which the N-K system exhibited the most stable foaming behavior. The N-K system was characterized by the highest BO/Si ratio (3.804) and an appropriate AlO4 fraction (66%), forming a moderately polymerized bridging-oxygen network. This structure reduced surface tension while maintaining suitable viscosity, thereby lowering the energy required for foam formation and extending foam lifetime. In contrast, Li+ led to an excessively dense network, whereas Cs+ resulted in an overly loose structure, both of which were unfavorable for foam stability. Further analysis revealed that the ultra-high-temperature and electric field environment under plasma heating promoted structural evolution of all slag systems toward more defined types, with silicate and aluminate units transforming into species and AlO4 units, respectively. These findings suggest that high temperature provides the energetic basis for structural reconstruction, while the electric field and the size effect of alkali metal ions synergistically govern the pathway and extent of structural evolution. Collectively, these results provide a theoretical foundation for compositional optimization of tundish fluxes under high-efficiency plasma-heating conditions and offer data support for subsequent industrial applications.

This paper proposes a feasible deoxidati on and titanium control gradient redesign strategy based on GCr15 bearing steel， with the aim of optimising the synergistic mechanism of deoxidation and titanium control in the stage of furnace refining. The pivotal mechanisms of deoxidation and titanium regulation are elucidated through industrial sampling of the entire industrial process. The interface reaction simulation and laboratory thermal experiments are meticulously designed and conducted to systematically verify the viability of the deoxidation and titanium control gradient redesign strategy in the management of ultra-low oxygen and titanium control in GCr15 bearing steel. Orthogonal experiments and FactSage phase equilibrium calculations have determined the CaO-Al₂O₃-SiO₂-MgO quaternary slag system （50.18%CaO-21.36%SiO₂-24.11%Al₂O₃-4.35%MgO） to be the optimal titanium removal slag system. Thermodynamic studies demonstrate a positive correlation between the rate of titanium removal and the oxygen activity of the molten steel. It is also evident that excessive deoxidation during the LF stage impedes titanium oxidative migration， thereby reducing the efficiency of titanium removal in the RH stage. Experimental evidence demonstrates that a stepped oxygen control strategy can overcome the antagonistic relationship between deoxidation and titanium control. Laboratory simulation of the RH condition reaction has been shown to reduce titanium content from 117×10-6 to 3.8×10-6 at an oxygen content of 35×10-6， with the titanium removal rate reaching 96.7%.The findings from both industrial data and laboratory experiments collectively demonstrate that LF weak deoxidation facilitates the slag gold reaction titanium removal process， enhancing the efficiency of titanium removal within the refining process as a whole. This， in turn， enables the synergistic control of oxygen and titanium. This study provides a theoretical basis and process optimization scheme for the industrial production of ultra-low oxygen titanium-bearing steel， and provides a direction to solve the problem of titanium inclusions restricting the fatigue life of bearings.

Fe-based amorphous alloys generally suffer from detrimental effect of inclusions, and the unclear formation and evolution of inclusions lead to the lack of basis for alloy melt purification and performance enhancement. Referring to Ce-treatment in the field of steel metallurgy, the role of Ce in modifying inclusions, purifying alloy melt and enhancing glass formation of Fe-based amorphous alloys was studied in detail. Combined with the characterization of inclusions in Fe83Si2B12P3Cex (at%) alloys at different cooling rates and the thermodynamic calculation of inclusions formation, the evolution of inclusions in Ce-free and Ce-added alloys during non-equilibrium solidification was unveiled. For the Ce-free alloy, high melting point CaO–Al2O3 and Al2O3 oxide inclusions can be formed in the melt and (Ca,Ti,Mn)S sulfide inclusions precipitate during solidification due to the segregation and supersaturation of sulfur. Therefore, the increase of cooling rate suppresses the formation of sulfide inclusions and reduces the size and number density of inclusions. For the Ce-added alloy, the type of inclusions is invariant to cooling rate, because the inclusions are modified into larger Ce2S3, CeAlO3 and Ce2O2S inclusions in the melt due to the strong affinity of Ce with sulfur and oxygen. These large-sized Ce-containing inclusions in the melt are readily removed by flotation, resulting in a significantly reduced content of oxygen and sulfur as well as the number density of inclusions after Ce-treatment. This enables the preparation of Ce-added amorphous ribbon without dendritic α-Fe grains due to the reduced heterogeneous nucleation sites. Additionally, the alloying of large atom Ce will strongly interact with P, Si, B and create topological and chemical constraints, which will increase the crystallization activation energy and impede atomic diffusion, contributing to the amorphous formation of the Ce-added alloy. These findings are important and facilitate the industrialization of high-performance Fe-based amorphous alloys.

To address the failure problem associated with carburized sulfur-containing 20MnCrS5 gears, this study conducted an engineering analysis of the coupled control of austenite grain stability and MnS inclusions in 20MnCrS5 gear steel produced via the electric arc furnace short process. The distribution, composition, and morphology of inclusions in the industrial slab were analyzed. The results indicated that the average ECD of MnS-type inclusions at the 1/4-thickness and core of the slab reached 3.65 and 2.81 μm, respectively, which were significantly larger than the 1.18 μm at the slab edge. MnS-type inclusions in the slab core also exhibited a stronger tendency toward irregular shapes, with a notably higher 2D aspect ratio compared with the other sampling positions. Composite MnS inclusions nucleated on oxide cores exhibited clearer spheroidization and dispersion behaviors across different slab locations, and only minor morphological variations were observed despite differences in local cooling conditions. These findings indicate that oxide inclusions can act as effective nucleation sites for promoting MnS dispersion and spheroidization during continuous casting. Isothermal heat treatment experiments identified the temperature sensitivity of grain growth in 20MnCrS5 steel bars within the range of 800 °C to 1200 °C. An empirical grain growth equation was established. The results showed that 950 °C is the critical temperature for safe carburizing, above which controlling abnormal grain growth becomes necessary. In situ observation using high-temperature confocal microscopy directly revealed the strong pinning effect of MnS inclusions located at or near grain boundaries on boundary migration. This study contributes to the understanding of the coupled control of MnS inclusions and grain thermal stability in low-carbon, sulfur-containing Mn–Cr gear steels.

The converter steelmaking process represents a pivotal aspect of steel metallurgical production, with the characteristics of the flame at the furnace mouth serving as an indirect indicator of the internal smelting stage. Effectively identifying and predicting the smelting stage poses a significant challenge within industrial production. Traditional image-based methodologies, which rely on a single static flame image as input, demonstrate low recognition accuracy and inadequately extract the dynamic changes in smelting stage. To address this issue, the present study introduces an innovative recognition model that preprocesses flame video sequences from the furnace mouth and then employs a convolutional recurrent neural network (CRNN) to extract spatiotemporal features and derive recognition outputs. Additionally, we adopt feature layer visualization techniques to verify the model’s effectiveness and further enhance model performance by integrating the Bayesian optimization algorithm. The results indicate that the ResNet18 with convolutional block attention module (CBAM) in the convolutional layer demonstrates superior image feature extraction capabilities, achieving an accuracy of 90.70

The oxidation loss of Al and Ti during the electroslag remelting (ESR) of GH4169 Ni-based superalloy is a critical issue affecting its compositional homogeneity. In this study, slag-alloy equilibrium experiments were carried out to reveal the phenomenon of “Al oxidation loss and Ti increase” and the significant influence of temperature on element oxidation loss. A thermodynamic model based on the Ion and Molecule Coexistence Theory (IMCT) and the Wagner equation was developed to accurately predict the equilibrium contents of Al and Ti, clarifying the controlling roles of key components (CaO, Al2O3, and TiO2) and temperature in the CaO-Al2O3-CaF2-MgO-TiO2 slag system. By further coupling the laws of energy and atomic conservation, a mathematical model was developed to predict the axial distribution of Al and Ti in the ESR ingots, achieving accurate predictions from laboratory-scale to industrial-scale ingots (Φ450 mm). Guided by the model, the slag composition was optimized and the slag amount was increased to 65 kg. The deviations in Al and Ti contents between the top and bottom of the industrial ingots were successfully controlled within 0.04 and 0.03 wt pct, respectively, significantly improving compositional homogeneity and providing an effective theoretical basis and practical guidance for precise composition control during the ESR process of superalloys.

This work is a continuation of our previous research. We successfully produce low-carbon gear steel containing trace tellurium (Te) through industrial production line (EAF-LF-VD-CC), and we investigate the effects of a trace Te addition on the precipitation of MnS inclusions in sulfur-containing gear steel billets, the machinability of rods, and the high-temperature vacuum carburizing performance of rods. This study demonstrates that the addition of trace Te in steel can be achieved in industrial production without causing disruptions in the steelmaking process. The Te addition effectively induces spheroidization and refinement of MnS inclusions in industrial cast billets, showing good consistency with laboratory Te alloying experimental results. Furthermore, the Te addition reduces the deformation rate of MnS inclusions during industrial rolling processes. Benefiting from the spheroidization of MnS inclusions, the chip-breaking performance during the machining of Te-containing rods is significantly optimized, along with substantial improvement in machined surface roughness. The industrial rods exhibit excellent grain stability during 960 °C high-temperature vacuum carburizing, with carburizing rates significantly enhanced compared to conventional gear steels. This work comprehensively demonstrates the multifaceted effects of Te treatment on gear steel properties, particularly providing valuable references for developing high-temperature carburizing gear steels.

A new three-dimensional multiphase numerical model was built. The volume of fluid and k–ε turbulence models were used to investigate the hot metal ladle pouring process. During the pouring process, issues such as iron splashing, overflow, and significant heat loss are prevalent. To realize efficient and stable pouring, the effects of ladle tilting velocity, flow rate, and converter tilting angle on the pouring process were examined. The model was verified by comparing the actual pouring time with the numerical results. It is shown that there is a nonlinear relationship between pouring velocity and hot metal flow rate at the ladle mouth. As the mass flow increased and the converter tilting angle decreased, the impact point of the hot metal into the converter pool shifted from the side wall to the bottom, and the impact force increased accordingly. The pouring velocity curve was optimized by the volume difference of the ladle at different angles, and an empirical formula was derived. After the optimization of pouring speed, the flow rate was stabilized between 4000 and 6000 kg/s, and the pouring time was reduced by approximately 30 s. After applying this model in actual production, the hot metal temperature inside the converter increased by approximately 5 °C statistically. This model is potential to enhance the production efficiency, stability, and safety of the pouring process between open containers.

This work studies the yield strength, fracture modes, and anisotropic evolution of oxide dispersion‐strengthened (ODS) FeCrAl cladding tubes when deformed along different directions. The results show that the {112} <111> slip system is activated as the primary slip system during the ODS FeCrAl cladding tube deformation. The development of textures in different directions is entirely different for cladding tube, i.e., in a 45° direction the initial {001} texture passes through the {112} <131> orientation transformation to the {111}<112> γ‐fiber texture; in transverse direction (TD) the initial {001} texture passes through the {001}<130> orientation to transform into the {001}<110> α‐fiber texture. In rolling direction (RD), medium strength γ‐fiber textures and α‐fiber textures are produced simultaneously. The banding of the {111}<110> and {112}<110> textures in the RD results in an uneven distribution of shear strain, which leads to premature brittle fracture of the specimen. In the 45° direction and TD, strain softening occurs in the shear band, resulting in ductile fracture of the cladding tube. The remarkable linear relationship between the yield strength and the Taylor factor indicates that the observed yield anisotropy depends mainly on the initial {001}<100> recrystallized cubic texture rather than the high aspect ratio flat shape grains along the RD.

Optimizing the foaming characteristics of tundish coating agent is a challenging task, which affects the heating efficiency of plasma and increases the smelting cost. In this work, the foaming behavior of CaO-Al2O3-SiO2_MgOFe2O3 slag systems modified with Li2CO3, Na2CO3, K2CO3, Rb2CO3, and Cs2CO3 was systematically investigated using the electrical current method. Additionally, the continuous cooling viscosity of the slags was monitored to evaluate their temperature-dependent rheological properties. The structural characteristics of the slags were analyzed using Raman spectroscopy and 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR). The results demonstrate that the addition of Li2CO3, Na2CO3, K2CO3, Rb2CO3, and Cs2CO3 significantly enhances slag foaming performance. The stable bubble volume fraction increases from 17.93 % to 85.92 %, while viscosity rises from 0.1174 Pa & sdot;s to 0.2054 Pa & sdot;s. The BO/Si ratio increases from 0.739 to 2.215, indicating enhanced polymerization of the [SiO4]4- tetrahedral network and a higher degree of polymerization (DOP). Concurrently, the area fraction of AlO4 decreases from 71 % to 34 %, while that of AlO5 increases from 27 % to 64 %. This shift reflects greater polymerization of the aluminosilicate network, improving thermal stability and effectively enhancing slag foaming performance. Among the studied systems, the K2CO3-modified slag exhibits optimal industrial applicability, achieving a maximum foaming efficiency of 30.33 %/min at 1600 degrees C, an average bubble volume fraction of 80.87 % during defoaming, and a viscosity of 0.1765 Pa & sdot;s. Combined with its favorable raw material costs, this system is well-suited for industrial applications. The findings of this study may provide a viable pathway to improve the efficiency of plasma heating technologies.

This study quantified the semi-solid constitutive behavior of GH4710 superalloy using a Gleeble thermo-mechanical physical simulation system. The stress–strain curves, thermal analysis curves and microstructure indicate that the GH4710 superalloy undergoes a mechanical behavioral transition from ductile to brittle to ductile during solidification. In the brittle temperature range, solid-phase creep is the only mechanism that can accommodate solidification shrinkage and thermal stresses, and the dispersion or diffusion of γ/γ′ eutectic liquid films along grain boundaries enhances the alloy’s hot tearing tendency. At this stage, the intergranular strain is transmitted through the liquid film, which converts to intergranular bridging. This process reaches a critical state as the intergranular strain reaches a critical state when the liquid film ruptures, forming a hot tearing nucleus and leading to the further development of thermal cracking. Based on the analysis of microstructural evolution and hot tearing mechanism, we introduce a new independent variable, i.e., the fraction of grain boundary area covered with liquid. The fraction of grain boundary area covered with liquid was calculated by geometrical modeling, and the value rises sharply with the increase of liquid fraction, which reflects the effective contact area of GH4710 superalloy dendrites at the end of solidification. The main novelty of the proposed constitutive model is that it is capable of continuously simulating the stress–strain evolution of GH4710 superalloy ingot throughout the cooling process from the mushy zone to room temperature, and all the necessary input data can be obtained from conventional microstructure analysis and tensile tests.

Strength-ductility trade-off is a common issue in oxide dispersion strengthened (ODS) steels. Here, by designing oxide nanoparticles, a dual-heterostructure ODS-FeCrAl alloy has been developed to realize the combination of high strength and high ductility. The first level is heterogeneous oxide nanoparticles with different strengthening mechanisms, and the second level is heterogeneous zones with different grain sizes. The designed 0.5Y(2)O(3) alloy achieves a perfect combination of ductility and strength at both room and high temperatures (650 degrees C) compared to a typical low Y2O3 ODS alloy (0.25Y(2)O(3)): nearly 20 % higher ductility at room temperature without any reduction in strength, and nearly 20 % higher ductility at high temperature with nearly 70 % higher strength. The optimal bimodal degree of the 0.5Y(2)O(3) alloy and the coexistence of penetrable and impenetrable oxide nanoparticles play a dominant role in the strengthening-toughening effect. As the Y2O3 content increases, the fine Y2Zr2O7 and Y2Ti2O7 particles in ODS-FeCrAl alloys gradually transform into coarse, impenetrable YAl composite oxide particles. The beneficial effect of the bimodal structure on ductility is suppressed when the Y2O3 content exceeds 0.5 wt%, which is attributed to the premature failure of the ODS-FeCrAl alloy due to debonding of the unusually coarse YAl composite oxide nanoparticles during the deformation process. The effect of oxide nanoparticle properties on the thermal stability of ODS-FeCrAl alloys was also evaluated, and it was shown that the presence of a small fraction (similar to 26 %) of YAl composite oxide particles does not reduce the thermal stability of ODS-FeCrAl alloys.

To enhance the quality of the microtitanium alloy steel, this study is the first to utilize the addition of trace amounts of magnesium in 20CrMnTi gear steel to improve the TiN inclusions and microstructure within this type of steel. Herein, the effect of different magnesium contents (0-50 ppm) on nonmetallic inclusions in steel is taken as a starting point. Simultaneously, the pinning effect of the modified inclusions on the microstructure is also explored. The results indicate that after adding magnesium, the average size of the inclusions decreases from 2.8 to 2.3 mu m, and the grain boundary mobility M decreases from 16 to 1.27 x 10-11 m4 kJ-1 s-1. Mg can reduce Ca and Ti in oxide inclusions, forming finer MgAl2O4 particles, thereby refining their size. The formed MgO and MgAl2O4 act as inhomogeneous nucleation sites for nitrides, resulting in smaller size, more uniform distribution, and less harmful TiN. Notably, TiN can provide nucleation sites for MnS. The size and distribution of sulfides are also improved during the modulation of TiN. It is found that the modulated TiN-MgO-MnS microinclusions can be used as austenitic pinning particles. These particles increase the pinning resistance and improve the grain boundary mobility, thus contributing to grain refinement. To enhance the quality of the microtitanium alloy steel, this study is the first to utilize the addition of trace amounts of magnesium in 20CrMnTi to improve the TiN inclusions and microstructure within this type of steel. It offers a new strategy for component design in the industrial production of related products.image (c) 2024 WILEY-VCH GmbH

Impurity and non-metallic inclusions control are imperative for the metallurgical quality of superalloys. In this paper, the effect of revert addition on the nitrogen removal and inclusion characteristics of GH4738 superalloy has been investigated. And a multiscale transient model for describing and predicting nitrogen removal from liquid superalloy during the refining process is developed by coupling macroscopic phenomena (including electromagnetic, fluid flow, heat, and mass transfer). A series of experimental data validate the reliability of the model. Results demonstrated that revert addition significantly suppressed the nitrogen removal efficiency and led to more nitrogen residue in the liquid superalloy, contributing to more nitrides or carbonitrides precipitation. The transient model shows that the residual nitrogen in the molten bath is spatially inhomogeneous distributed, in which the mass transfer of nitrogen between the gas–liquid interface is synergistically controlled by chamber pressure, bath temperature, and melt flow pattern. Increasing the refining power enhances the stirring intensity, which accelerates solute transport and facilitates nitrogen removal, but it also leads to a higher refining temperature that thermodynamically inhibits the denitrification reaction. Simulation results show that vacuum refining of revert superalloys by reducing the chamber pressure and increasing the metal bath stirring intensity is beneficial to obtain alloys with low nitrogen content. Considering the inhibitory effect of high temperature and revert addition, adjusting the refining power is recommended to promote nitrogen removal when the proportion of revert is more than 40 pct.

Aiming at the problem of poor low-temperature impact toughness of titanium microalloyed high-strength steel CGLC700， by thermodynamic calculations and high-temperature in-situ observations， as well as the use of electron backscattering diffraction， transmission electron microscopy， scanning electron microscopy， and optical microscopy have been used to investigate inclusions， second-phase particles， fracture morphology， and low-temperature impact toughness of the Ti-bearing high-strength steel. The results show that the reasons for the poor low-temperature impact toughness of Ti-bearing high-strength steel are related to the large-size brittle inclusions and the precipitation phase of Ti（C，N） and TiN in the steel. When the nitrogen content in steel is reduced from 0.004 9% to ≤0.003 5%， the number and size of brittle inclusions in steel can be effectively reduced， and the impact toughness of steel can be improved. Reducing the final rolling temperature from 885-895 ℃ to 875-885 °C can promote the precipitation of nanoscale TiC second phase particles and the formation of large-angle grain boundaries， and reduce the effective grain size， thereby significantly improving the low-temperature impact toughness of steel. Compared with experimental steel 1#， when the nitrogen content was reduced to ≤0.003 5% and the final rolling temperature was 875-885 °C， the average grain size in titanium microalloyed high-strength steel decreased from 3.1 μm to 2.7 μm， the proportion of small-size effective grains was higher， the large-size inclusions and number density decreased， the proportion in the large-angle grain boundary increased by 16.6%， and the low-temperature impact energy of steel could be increased from 14.75 J to 37.35 J.

In this study, the dissolution, collision, aggregation, and separation behaviors of nitride inclusions at the melt interface of GH4169 nickel-based superalloy were investigated via thermodynamic calculations combined with in situ observation via high-temperature confocal laser scanning microscope (CLSM). The results showed that the nitride inclusions were able to dissolve completely during the alloy melting process, and boundary layer diffusion was the limiting factor for dissolution. Nitride inclusions from the remelting process were reprecipitated during solidification. As the melt temperature increased, the degree of dissolution of the inclusions increased, and the dissolution rate of the inclusions increased. Second, the results of in situ observation by CLSM showed that nitride inclusions were more likely to aggregate with oxide inclusions, that separation may still occur between nitride inclusions after aggregation. The attraction of nitride–oxide inclusions was greater than that of nitride–nitride inclusions. The ability of the inclusions in the collision zone to aggregate together in contact depends on the interaction forces between the inclusions. The calculation results showed that the cavity bridge force was much greater than the capillary force and van der Waals force, which were the main forces leading to aggregation between the inclusions. Once a stable cavity bridge was formed between the inclusions, the aggregated inclusions no longer separated. In contrast, if cavity bridges formed between inclusions were substable, then fluctuations in the alloy melt would cause the substable structure to rupture, leading to the separation of inclusions.

This study provided comprehensive insights into designing and optimizing tundishes. A tundish is a fundamental reactor contributing to the metallurgical process. This reactor acts as a critical stabilizer of the molten steel flow field, and it facilitates the removal of inclusions by floatation. Numerical simulations, physical experiments, and industrial trials were systematically performed to validate a two-step optimization approach based on the tundish impact zone volume. The two-step approach was shown to facilitate the rapid preliminary optimization of the tundish. The excellent impact zone volume ratio of 19.3 pct was verified. After optimization, there was a decrease in the stagnant zone in the tundish from 22.92 to 16.27 pct relative to the primary design. Furthermore, there was a noteworthy reduction in the total mass of inclusions (TMIs) during different casting periods, as demonstrated by billet sample findings from electrolytic weighing. There was a notable reduction in the TMIs for strand 1 and strand 3 from 2.46 and 2.52 mg/10 kg to 1.06 and 1.68 mg/10 kg, respectively, at the intermediate heat, indicating an improvement in inclusion removal efficiency. The causes of cracking in the retaining walls were investigated, including the variation in cracking risk for multiposition retaining walls.