The erosion patterns of MgO·Al2O3 spinel as a crucible material in special steel smelting and its impact on molten steel cleanliness are investigated. MgO·Al2O3 spinel refractories used in industrial high-nitrogen stainless steel bearing steel smelting are analyzed and tested. Results indicate that during vacuum carbon deoxidation, MgO·Al2O3 spinel partially decomposes, and the released [Mg] reacts with Al2O3 inclusions in the steel to form MgO·Al2O3 inclusions, promoting inclusion flotation and improving molten steel cleanliness. Due to the unique structure of MgO·Al2O3 spinel, iron diffuses into the spinel form MgAl1.9Fe0.1O4, which prevents further erosion. The high-pressure nitrogen smelting process also causes a small amount of AlN on the surface of the MgO·Al2O3 spinel crucible, further enhancing its high-temperature performance. After smelting, a deposit layer primarily composed of MgO, Al2O3, and MgO·Al2O3 spinel forms on the inner wall of the crucible, indicating that floating inclusions adhere to the spinel surface, thereby reducing the incorporation into the steel and improving molten steel cleanliness. These findings provide a theoretical foundation for broader application of MgO·Al2O3 spinel as a crucible material in the field of high-quality steel.

Oxygen lancing is commonly used as an emergency measure for clearing clogged ladle seat bricks, but it causes severe refractory damage. To elucidate the underlying damage mechanisms, this study systematically investigates severe thermochemical erosion and non-uniform structural degradation of seat bricks. Results reveal that, high-speed oxygen airflow induces surface coarsening in the upper region, which physically captures calcium-rich slag and inclusions. These impurities react with corundum matrix to form a large amount of lowmelting-point 12CaO & sdot;7Al2O3, causing skeletal collapse and structural failure. In contrast, the lower region exhibits a remarkable self-protection mechanism. In-situ oxidation of residual steel produces FexO, which reacts with the matrix to generate a dense MgFeAlO4 composite spinel barrier. This ceramic layer effectively inhibits deep infiltration and preserves structural integrity. These findings confirm that degradation is driven by the combined action of airflow scouring and thermochemical erosion, providing a theoretical basis for strategies aimed at extending refractory life.

Er3+/Yb3+ co-doping CaTa4O11-BiTa7O19 intergrowth structure single crystal was prepared by molten salt synthesis (MSS), whose stacking sequence is P-O-P-P-O, which encompasses the P-O sequence of CaTa4O11 (CTO) and the P-P-O sequence of BiTa7O19 (BTO). Here, P layer is TaO7 layer, and O layer is Ca-TaO6 or Bi-TaO6 layer for CTO or BTO, respectively. This lattice structure is similar to Pr2Nb11O30, which is demonstrated by XRD and STEM technology. Under 980 nm laser excitation, the sample exhibited pure green upconversion luminescence (UCL). The CIE color coordinate can reach (0.225, 0.746), which exceeds NTSC standard. This indicates that this material can be used for UCL display field. This experiment predicts that hexagonal laminated tantalates containing TaO6 and TaO7 units can be synthesized into novel materials with different stacking sequences using MSS.

In this paper, HT-CSLM and multi-scale characterization methods were used to study the influence mechanism of CeO2 on the deterioration of thermal properties of rare earth-containing mold flux. The findings reveal that CeO2 drives a fundamental shift from homogeneous to heterogeneous crystallization. Unlike the baseline slag which exhibits deep supercooling, the addition of CeO2 induces significant melting hysteresis, where undissolved Ce-rich clusters act as heterogeneous cores to eliminate the incubation period and drastically raise the crystallization temperature. As a result, the crystal growth transforms from regular spherulites into rough, cluster-induced agglomerates. Microstructural analysis confirms that inhomogeneously distributed Ce-rich particles physically block the continuity of the cuspidine network. Therefore, the key to control the thermal properties of rare earth slag is to control the content and distribution of rare earth oxides in the slag and avoid their non-uniform distribution.

To systematically investigate the precipitation and evolution mechanisms of MnS during the solidification of medium-carbon low-alloy steel, in-situ observation experiments using high temperature confocal laser scanning microscopy (HT-CLSM) were conducted. The effect of cooling rate (i.e., 50, 150, and 300 °C/min) in the solidification region on the dynamic precipitation behavior of MnS was performed. The obtained results show that the MnS precipitates mainly exhibit three typical morphologies, i.e., angular, globular, and dendritic after solidification. With the increasing cooling rate, the precipitation starting temperature (Tp,s) of dendritic MnS decreases from 1290.5 to 1235.7 °C, while the finishing temperature (Tp,f) increases from 1053.3 to 1135.6 °C, resulting in a shorter precipitation time. Meanwhile, higher cooling rates can suppress the growth kinetics of MnS, leading to a significant reduction in the maximum inclusion size from 143.3 to 37.3 μm, thereby achieving a pronounced grain refinement. In addition, the increased cooling rate can enhance the microsegregation of Mn and S elements, intensifies the supersaturation level and nucleation driving force of MnS, and consequently promotes an increase of MnS number density during the final stage of solidification. The obtained findings reveal the precipitation kinetics and morphology evolution mechanism of MnS during the solidification range of 1550 to 1400 °C, providing an important theoretical guidance for controlling sulfide precipitates during solidification as well as contribute to the “inclusion/precipitate engineering” concept.

The corrosion behavior of copper in simulated groundwater with different oxygen conditions was investigated using different electrochemical techniques. Additionally, scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and Raman spectroscopy were used to characterize the corroded surfaces and identify the corrosion products. Under anaerobic conditions, copper exhibited predominantly uniform corrosion at a slow rate, with cuprous oxide (Cu2O) identified as the primary corrosion product. In an aerobic environment, additional corrosion products including cupric oxide (CuO) and basic copper carbonate (Cu-2(OH)(2)CO3) were observed, and the presence of oxygen significantly accelerated the corrosion process, resulting in an initially higher corrosion rate.

Ti/Al ratio plays a critical role in determining the formation, evolution and agglomeration behavior of non-metallic inclusions in low-carbon low-alloyed steel production. In this study, the agglomeration behavior of inclusions with varying Ti/Al ratios were systematically investigated by combining in-situ observation experiments and electron microscopies. The obtained results indicate that when Ti/Al < 1 (Ti = 5 ppm and Al = 150 ppm in sample S2, Ti = 5 ppm and Al = 420 ppm in sample S3), spherical Al2O3 inclusions could be predominantly observed, with no significant morphological changes. As the Ti/Al ratio increased to 1 (Ti = 5 ppm and Al = 6 ppm in sample S1, Ti = 460 ppm and Al = 420 ppm in sample S6), Al2O3 remains to be the thermodynamically stable oxide inclusion. However, a morphological transition of Al2O3 inclusions from spherical to irregular shapes was observed in Sample S6, suggesting that high Ti content can significantly influence the morphology of the stable oxide inclusions. When the Ti/Al ratio was increased to 2.8 (Ti = 420 ppm and Al = 150 ppm in sample S5), Al2TiO5 replaced Al2O3 as the stable oxide phase under the steel composition. Further increasing the Ti/Al ratio to a very large number (Ti = 460 ppm and Al = 1 ppm in sample S4), led to the formation of Ti3O5 as the stable oxide inclusion. In-situ observation experiments further revealed the distinct differences in the agglomeration behavior of Al2O3, Al2TiO5, and Ti3O5 inclusions. Ti3O5 inclusions exhibit a weak agglomeration tendency since the inclusions were moved following the motion of liquid steel. In contrast, Al2O3 inclusions demonstrate a long-range interaction, leading to the formation of loose clusters. Al2TiO5 inclusions showed a shorter interaction distance than Al2O3, with the attractive force ranging from 10−16 to 10−14 N. The attractive forces between inclusion pairs of Al2O3 and those of Al2TiO5 inclusions were found to be strongly dependent on the interaction distance and the radius of the guest inclusions with a smaller size.

To address the abnormal crystallization behavior of rare-earth-containing mold flux, this study investigates the effects of CeO2 addition (0-10 wt%) on the structural evolution and crystallization of a pre-melted industrial slag. Quantitative thermal analyses reveal a transition in the dominant mechanism at approximately 7.5 wt% CeO2. At low additions (<7.5 wt%), Ce ions act as network modifiers, promoting silicate depolymerization and lowering the initial melting temperature from 743.8 °C to 735 °C. Conversely, CeO2 contents ≥7.5 wt% trigger solid-phase precipitation. The massive formation of high-melting-point Ce2SiO5 phases abruptly increases the liquidus temperature to over 1212 °C. These precipitates act as heterogeneous nucleation sites, shifting the crystallization boundaries toward higher temperatures and shorter times. Ultimately, this widened melting interval and accelerated crystallization accelerate the depletion of the liquid slag film and deteriorate mold lubrication. These factual findings provide a quantitative basis for the compositional design and crystallization control of mold fluxes for rare-earth steels.

Precise control of non-metallic inclusions is essential for achieving the desired mechanical properties of steels. Generally, fine inclusions are relatively difficult to remove completely during the refining process. They can serve as the heterogeneous nucleation sites for the formation of intragranular ferrite (IGF). This interlocked microstructure is the preferred type in the coarse-grain heat-affected zone of weldments to improve the toughness at low temperatures. In this study, two representative grades of low-alloy steels with 0.2 and 0.4 pct carbon were used to investigate the synergistic influence of the prior austenite grain size (PAGS) and cooling rate on IGF formation. In-situ observation experiments using high-temperature confocal laser scanning microscope, thermodynamic calculations and electron microscopy characterizations were used to investigate this synergistic effect in the two steel grades. It is found that the coarse grains can promote IGF nucleation and growth at an intermediate cooling rate, while smaller grain size requires a higher cooling rate as a driving force for IGF formation. This synergistic effect was verified in the steels with 0.2 and 0.4 pct carbon. The current work provides a quantitative study on the comprehensive influence of PAGS and cooling rate on IGF formation. The obtained findings are validated for general low-alloy steels with different carbon contents, contributing to the development of the ‘Oxide Metallurgy’ concept.

Using B2O3 as the solvent, A0.5Ta7O19:0.1Er3+/0.4 Yb3+ (A = Bi3+, Y3+, La3+, Gd3+) phosphors were synthesized by molten salt synthesis (MSS). Under 980 nm laser excitation, BiTa7O19(BTO):Er3+/Yb3+ exhibits the highest upconversion luminescence (UCL) intensity. When Bi2O3 was increased more than 30 mol%, BTO:Er3+/Yb3+ is almost single phase, however, the UCL intensity decreases. The optimal BTO:Er3+/Yb3+ sample was thermally treated to further enhance the UCL strength, which is 1.65 times than sample without thermal treatment. The green UCL integral intensity reaches 1.72 times that of β-NaYF4:Er3+/Yb3+ under 56.25 W/cm2. After thermal treatment, the average grain size of the sample decreased, suggesting that the decomposition and fusion of BTO:Er3+/Yb3+ had occurred, and grain boundaries were formed. The increase in UCL intensity caused by structural changes was discussed. The absolute temperature sensitivity and relative temperature sensitivity were 0.00969 K−1 and 0.803% K−1, respectively. The CIE color coordinate of the phosphor-converted 980 nm LEDs can reach (0.18, 0.77), which exceeds NTSC standard. The LED device exhibits a high color purity of 93.2%. All the results indicate that this material can be used for temperature sensing and luminescence display.

Commercial ferroalloys offer a resource-efficient alternative to high-purity elemental feedstocks for high-entropy alloy production, but impurity-derived inclusions require systematic evaluation. Two CoCrFeMnNi high-entropy alloys were produced by high-frequency induction melting using high-purity elemental metals (Cantor-P) and commercial FeMn, FeCr, and FeNi ferroalloys supplemented with Ni and Co (Cantor-F). Inclusion chemistry, formation, and evolution were investigated using equilibrium and Scheil-Gulliver solidification calculations, scanning electron microscope equipped with energy dispersive X-ray spectroscopy (SEM-EDS), automated inclusion analysis, electrolytic extraction, and high-temperature confocal laser scanning microscopy (HT-CLSM). FeMn mainly contained MnO and MnO-SiO2 inclusions, FeCr contained Cr2O3 and Cr2O3-MnO inclusions, and FeNi contained abundant MnS, providing potential precursors for complex inclusions in Cantor-F. The higher Si content in Cantor-F promoted SiO2-MnO-rich outer layers around Cr2O3-MnObased inclusions and increased the spheroidization of Cr2O3-MnO-Mn(S, Se)-SiO2 inclusions. The initial inclusion number densities were 617.1 and 673.4 mm-2, and the mean inclusion sizes were 1.73 and 1.81 μm, in Cantor-P and Cantor-F alloys, and the sizes of most inclusions in both alloys were smaller than 2 μm. During HT-CLSM, small Si-bearing inclusions in Cantor-F began to agglomerate at a separation of approximately 10 μm and exhibited a slightly higher apparent migration velocity. After remelting, the mean retained inclusion number densities were 45.3 mm-2 in Cantor-P and 32.4 mm-2 in Cantor-F. These results indicate a stronger apparent agglomeration and flotation tendency in Cantor-F, although the decrease cannot represent directly measured inclusion removal efficiencies.

This study systematically investigates the effect of trace hafnium (Hf) addition (0.069 wt%) on the microstructure evolution and inclusion characteristics in V-alloyed Co-based dual-phase high-entropy alloys. The trace amount of Hf addition was found to mainly form HfOx inclusion in the matrix. This phase replaces the conventional oxide formation and could stabilize the V element in the matrix and against its oxidation. Compare with the Hf-rich HEAs, where Hf segregates at grain boundaries within an FCC-dominant matrix and forms lamellar HCP precipitates. However, Co46Cr30Mn7.5Fe7.5Ni7.5V1.5 with a trace amount of Hf enhances the blocky HCP phase formation and increases the HCP fraction from 15 % to 26 %. Non-metallic inclusion analysis here reveals that V-HEA contains HfOx alongside MnS and HfOx-MnS. In situ observations by high-temperature confocal laser scanning microscopy demonstrate that inclusion motion in the liquid matrix is governed by liquid surface flow and fluctuations. When inter-inclusion distances approach a critical value, attractive capillary force triggers the increase in velocity and acceleration and leads to a rapid collision of inclusions. Smaller inclusions exhibit a weaker attraction and are obviously influenced by the surface flow of liquid. While the larger inclusions are more prone to coarsening through agglomeration. This work provides theoretical and experimental insights into tailoring inclusion characteristics and microstructure evolution in HEAs through trace amounts of critical element addition.

CaTa4O11(CTO):Er3+/Yb3+ single crystal was prepared with employing CTO:Er3+/Yb3+ powders as precursors by molten salt synthesis (MSS) with K2Mo3O10 and B2O3 as flux in a platinum crucible. The single crystal size is the millimeter level. Under 980 nm laser excitation, it exhibits pure green upconversion luminescence (UCL). Utilizing scanning transmission electron microscopy (STEM) images recorded with a high-angle annular dark field (HAADF) detector and an annular bright field (ABF) detector, Er3+/Yb3+ substitution for sites in the Ca-Ta layer have been confirmed. Layer stacking faults were observed, which are caused by doping of ions in different valent states. The evolution process of layer stacking faults has been revealed. Compared with the precursors, the green–red ratio of single crystal has been improved, which is due to the reduction of Er3+/Yb3+ concentration, the Mo doping and the stacking multiple Ta layers, which hinders the energy transfer between layers. The absolute and relative temperature sensitivities reached 0.01005 K−1 and 0.90% K−1, respectively. In phosphor-converted 980 nm LEDs fabricated based on the samples, the CIE color coordinate can reach (0.21, 0.75), which exceeds the NTSC standard. This indicates that this crystal can be used for temperature sensing and UCL display. This experimental result provides a new idea for obtaining different periodic arrangement structures by adjusting the components in layered tantalates.

As a key structural ceramic in the continuous casting process, the structural evolution of the stopper rod during service and its inherited influence on the stability of the continuous casting process are often overlooked. Therefore, the present study systematically investigated its mechanism and influence in high-efficiency continuous casting. The results showed that the stopper rod experienced severe scouring, decarburization, clogging, and spalling during service, along with chemical reactions with molten steel. The stability and structural integrity of the stopper rod directly affected the entire continuous casting process. Specifically, changes in the stopper-rod structure first altered the molten-steel flow inside the nozzle, where the maximum inlet velocity increased eightfold. The unstable molten steel subsequently propagated into the mold, disturbing the internal flow field and intensifying mold-level fluctuations. The solidification of molten steel became non-uniform, increasing the likelihood of billet defects. In the billet, 41.89% of inclusions were concentrated near the one-quarter thickness region. Therefore, a synergistic strategy involving refining optimization, high-temperature structural ceramic materials improvement, argon-injection strengthening, and external field control was proposed to achieve high-performance stopper-rod service and stable, efficient continuous casting. The present research may provide strong support for the stable and efficient service of high-temperature structural ceramic materials and the advancement of high-efficiency continuous casting technology.

Understanding the motion behaviors of non-metallic inclusions in the liquid metal is important for clean steel production. High-temperature confocal laser scanning microscopy is applied to investigate the effect of different Ti and Al contents on the agglomeration behavior of non-metallic inclusions in low carbon steels. Furthermore, the agglomeration mechanism of inclusions was investigated through quantitative analysis of in-situ observation experiments and a modified Kralchevsky-Paunov model. The obtained results indicate that Al2O3 is the main type inclusion in the low-alloys steels with both Al and Ti addition. This type of inclusion is more likely to absorb surrounding small-size inclusion particles, leading to a further growth for the cluster formation and contributing to a serious engineering problem, nozzle clogging. Besides, TiOx is the main type inclusion in the molten steel with only Ti addition, and this type of inclusion is less likely to agglomerate and the individual inclusion particles show a ‘free’ motion with the fluid of molten steel. The difference between these two types of inclusions is due to the difference in attractive force and action distance at the meniscus created by the inclusion/steel/Ar multiple interfaces and influenced by the physical parameters, e.g., contact angle and interface energy between inclusion and steel, and surface tension of the melt.

Fluorine-free mold flux is receiving increasing attention due to the environmental and health problems associated with using fluorinated flux in casting. However, the erosion problem in the submerged entry nozzle is still exists and not solved. Therefore, in this study, the electric field is used to improve the erosion resistance capability of the nozzle. The results show that a thick protective adhesion layer is formed on the surface of the slag-line material under the action of a negative electric field due to an electrochemical reaction. This protective layer further reacts with the CaO/SiO2 content of the fluorine-free slag-line material to generate an interfacial reaction layer composed mainly of Ca2SiO4 and CaZrO3. Due to the presence of Ca2SiO4 in the interfacial reaction layer, a small amount of crystalline transformation occurs during the cooling process. Thus, under the protection of the double protective layer generated by the action of the negative electric field, the slag-line material is not subject to the erosion of the fluorine-free mold flux, and the erosion rate is only 0.37%.

The electromagnetic swirling flow in nozzle (EMSFN) technique is designed to mitigate the adverse effects of unstable and uneven flow within the submerged entry nozzle in continuous casting. Utilizing electromagnetic forces, EMSFN stabilizes the flow within the nozzle, leading to a more controlled flow in the mold. Numerical simulations were used to quantitatively analyze the magnetic and flow fields in a slab continuous casting system under EMSFN. Results indicate that EMSFN significantly stabilizes the outflow from the nozzle, with stability increasing with higher current intensity. At 10,000 Ampere-turns (At) of the coil, meniscus fluctuations were unstable. They stabilized at 13,000 At, with minimal changes observed beyond this point. The optimal current intensity for stable mold flow, at a casting speed of 1.56 m/min, is 13,000 At. These findings confirm the effectiveness of EMSFN in stabilizing the internal flow field of the slab mold and determining optimal operational current intensity.

To achieve stable production of high-quality steel, the properties of carbon-containing refractories for ladles need further optimization. In this study, MgAl2O4-La-C refractories were successfully designed and prepared with La metal incorporated as an antioxidant. The results show that the refractory specimens containing La metal exhibit superior overall properties than those without the additive. When 2 wt% of La metal was added, significant improvements were observed in oxidation resistance, and the mechanical properties after oxidation. For specimens cured at 200 degrees C, the oxidation resistance increased by 9.99 %, and the cold compressive strength improved by 14.99 % after oxidation. Additionally, refractory specimens heat treated at 1400 degrees C demonstrated excellent thermal shock resistance with a residual strength ratio of 65.57 % after thermal shock. These enhancements are attributed to the protection of carbon by La metal and the combined effect of volume expansion and solid-phase sintering, resulting from the formation of LaAlO3 and LaMgAl11O9 phases. Therefore, this work proposes an executable method for preparing MgAl2O4-La-C refractories using La metal as an antioxidant, offering potential applications in the smelting ladles of high-quality steel production.

To extend the antierosion properties of submerged entry nozzle and enhance the fluidity of fluorine‐free slag, the present study examines the effects of an applied electric field on the wetting behavior between fluorine‐free slag and slag‐line refractories, as well as on the erosion of slag‐line refractories by fluorine‐free slag. The results indicate that the applied electric field alters wettability by influencing the dissolution and the interfacial reaction between the slag‐line refractories surface and the fluorine‐free slag. Under a positive electric field, the dissolution and interfacial reaction between the slag‐line refractories surface and the fluorine‐free slag is enhanced, reducing the apparent contact angle to ≈40° at 20 V. Conversely, under a negative electric field, the dissolution and interfacial reaction are inhibited, resulting in an apparent contact angle of about 54° at 20 V, which is roughly 14° higher than under the positive electric field. Applying an electric field not only protects the slag‐line refractories from erosion (with an erosion rate of just 0.09% under a negative electric field) but also improves the fluidity of the fluorine‐free slag. This improvement is due to the bond‐breaking of the SiOSi structure and the pulsed oscillation effect in the fluorine‐free slag.