Search Results (49)

Vacuum degassing (VD) is a critical refining step in electric arc furnace (EAF) steelmaking for producing clean steel with reduced nitrogen and hydrogen content. This study develops an Effective Equilibrium Reaction Zone (EERZ) model focused on denitrogenation (de-N) by simulating interfacial reactions at the bubble–steel interface (Z1). The model incorporates key process parameters such as argon flow rate, vacuum pressure, and initial nitrogen and sulfur concentrations. A robust empirical correlation was established between de-N efficiency and the mass of Z1, reducing prediction time from a day to under a minute. Additionally, the model was further improved by incorporating a dynamic surface exposure zone (Z_eye) to account for transient ladle eye effects on nitrogen removal under deep vacuum (<10 torr), validated using synchronized plant trials and Python-based video analysis. The integrated approach—combining thermodynamic-kinetic modeling, plant validation, and image-based diagnostics—provides a robust framework for optimizing VD control and enhancing nitrogen removal control in EAF-based steelmaking. Full article

There is a lack of an effective approach to measure vacuum conditions inside sealed vacuum electronic devices (VEDs) and other small-space vacuum instruments. In this study, the application performance of an innovative low-pressure gas sensor based on the emission enhancements of multi-walled carbon nanotube (MWCNT) field emitters was investigated, and the in situ vacuum performance of X-ray tubes was studied for the advantages of miniature dimension and having low power consumption, extremely low outgassing, and low thermal disturbance compared to conventional ionization gauges. The MWCNT emitters with high crystallinity presented good pressure sensing performance for nitrogen, hydrogen, and an air mixture in the range of 10⁻⁷ to 10⁻³ Pa. The miniature MWCNT sensor is able to work and remain stable with high-temperature baking, important for VED applications. The sensor monitored the in situ pressures of the sealed X-ray tubes successfully with high-power operations and a long-term storage of over two years. The investigation showed that the vacuum of the sealed X-ray tube is typical at a low 10⁻⁴ Pa level, and pre-sealing degassing treatments are able to make the X-ray tube work under high vacuum levels with less outgassing and keep a stable high vacuum for a long period of time. Full article

Splashed droplets in the vacuum chamber play an important role in decarburization and degassing in Ruhrstahl–Heraeus (RH), but the scholars do not pay attention to the behaviors of splashed droplets. Thus, it is necessary to propose a new method to investigate the splashed droplets. A Euler–Euler model and the inter-phase momentum transfer are applied to investigate the interaction between the molten steel and the bubbles, and the gas domain in the vacuum chamber is included in the computational domain in order to describe the movement of the splashed droplets. Numerical results show that the flow field predicted by Euler–Euler model agrees well with the experimental data. There is a higher gas volume fraction near the up-snorkel wall, the “fountain” formed by the upward flow from the up-snorkel exceeds 0.1 m above the free surface, and the center of the vortex between the upward stream and the downward stream is closer to the upward stream in the vacuum chamber. Full article

In order to reduce the content of harmful impurity sulfur elements in steel to meet the quality requirements of high value-added steel, efficient desulfurization of RH vacuum degassing is essential. Based on the simplex lattice composition design method, the effects of typical compositions on liquidus temperature, sulfur capacity, melting temperature, the effects of typical compositions on liquidus temperature, sulfur capacity, melting temperature, viscosity, and desulfurization rate of CaO-CaF₂- and CaO-Al₂O₃-SiO₂-based desulfurizers were studied by thermodynamic calculation, the melting temperature test, and the slag–steel contact experiment. The results show that in CaO-CaF₂- and CaO-Al₂O₃-SiO₂-based desulfurizers, the changes in CaF₂, MgO, and Al₂O₃ contents has little effect on the equilibrium S content of molten steel at lower SiO₂ contents, whereas, at higher SiO₂ contents, the equilibrium S content of the molten steel is greatly increased when the CaF₂, MgO, and Al₂O₃ content is greater than a certain value. Meanwhile, the increase in CaF₂ and MgO content reduces the high-temperature viscosity and breaking temperature (corresponding to the turning point on the viscosity–temperature curve) to varying degrees, which results in a better slag fluidity and is favorable to the prevention of crusting. With the increase in Al₂O₃ and SiO₂ content, the breaking temperature of the CaO-CaF₂-based desulfurizer is significantly reduced, which is beneficial to preventing crust. However, when the breaking temperature of CaO-Al₂O₃-SiO₂-based desulfurizer increases, part of the slag system has solidified at 1400 °C, which is easy to lead to slag crust when the temperature drops. Comprehensively, for the CaO-CaF₂-based desulfurizer, CaO = 60 wt%, CaF₂ = 30 wt%, SiO₂ = 0–5 wt%, and add a small amount of Al₂O₃ and MgO, its desulfurization effect is significant. For the CaO-Al₂O₃-SiO₂-based desulfurizer, CaO = 39–57 wt%, Al₂O₃ = 20–35 wt%, SiO₂ = 10–15 wt%, MgO = 4 wt%, CaF₂ = 4–8 wt%, its desulfurization effect meets the demand, and it can reduce equipment erosion and environmental pollution. Full article

In the production process of electrical steel, with respect to the industrial RH (Ruhrstahl–Heraeus), the steel producers must balance the high-circulation flow rate (operating efficiency) and the frequent cleaning of cold steel in the vacuum chamber due to the splashing of liquid steel (high maintenance costs). Excessive lifting gas flow can induce splashing, causing cold steel to adhere to the inner walls of the vacuum chamber. To address this issue, this study utilized an 80-ton RH vacuum refining unit from a specific plant as the research prototype and established a 1:2.6 scale water model for physical model simulation. Two innovative blowing methods were implemented by adding gas injection nozzles to the sidewalls and to the bottom of the vacuum chamber, respectively. The study investigated the effects of altering the blowing method on liquid surface fluctuations, flow patterns, the circulation flow rate, and the mixing time without changing the total gas flow rate. For the macroscopic flow in the RH unit, implementing side-blowing on the sidewalls of the vacuum chamber can accelerate the diffusion rate of the ink tracer, whereas implementing bottom-blowing in the vacuum chamber has little effect on the diffusion rate. The results show that modifying the blowing method can effectively reduce liquid surface fluctuations and suppress the splashing behavior within the vacuum chamber. Firstly, implementing side-blowing causes the ink tracer flow pattern within the vacuum chamber to become triangular, to increase the circulation flow rate, to shorten the residence time of the ink tracer within the chamber, and simultaneously to promote mixing in the ladle, which reduces the mixing time. Secondly, implementing bottom-blowing results in the formation of a gas column at the center of the vacuum chamber, which suppresses fluid flow within the chamber. Compared with side-blowing, it reduces the circulation flow rate and increases the mixing time in the ladle. Combined gas blowing through the up-snorkel and sidewalls is effective in solving splashing issues and reducing the mixing time in RH vacuum refining, and this method is a good candidate for industrial applications. Full article

Improving the competitiveness of steel companies is linked to sustainable, quality-compliant steel production. Therefore, new steel production technologies contributing to increased cleanliness of steel are continuously being developed and optimized. One way to achieve a high steel quality is to use electro slag remelting (ESR) technology. In this paper, the principle of ESR technology and the importance of fused slags for optimizing the process are outlined. The aim of this work was to analyze the main thermophysical properties of steel and fused slags used in the ESR process. Determination of the properties of steel and slags was performed using the FactSage calculation software, which involved the calculation of the liquid and solid temperature of steel and slags, the calculation and construction of quaternary diagrams, and the calculation of viscosity. The resulting quaternary diagrams revealed the substantial influence of chemical composition on melting temperatures of slags. In order to validate the acquired results, a CrNiMoV-type steel was subjected to investigation of its metallographic cleanliness and evaluation of its mechanical properties; the ESR process was shown to significantly improve the cleanliness of the steel and improve the mechanical properties of the steel compared to its cleanliness and quality when produced via vacuum degassing (VD) technology. During the ESR process, the average size of non-metallic inclusions was reduced from 20 μm to 10 μm, and the maximum size of non-metallic inclusions was reduced from 50 μm to 28 μm. The mechanical properties of the steel produced using ESR technology were impacted as follows: the ductility increased by 10%, contraction increased by 18%, notched toughness at 20 °C increased by 46%, and at −40 °C (respectively −50 °C) it increased by 30%. Full article

The present work focuses on predicting the steel melt temperature following the vacuum treatment step in a vacuum tank degasser (VTD). The primary objective is to establish a comprehensive methodology for developing and validating machine learning (ML) models within this context. Another objective is to evaluate the model by analyzing the alignment of the SHAP values with metallurgical domain expectations, thereby validating the model’s predictions from a metallurgical perspective. The proposed methodology employs a Random Forest model, incorporating a grid search with domain-informed variables grouped into batches, and a robust model-selection criterion that ensures optimal predictive performance, while keeping the model as simple and stable as possible. Furthermore, the Shapley Additive Explanations (SHAP) algorithm is employed to interpret the model’s predictions. The selected model achieved a mean adjusted $R^2$ of 0.631 and a hit ratio of 75.3% for a prediction error within ±5 °C. Despite the moderate predictive performance, SHAP highlighted several aspects consistent with metallurgical domain expertise, emphasizing the importance of domain knowledge in interpreting ML models. Improving data quality and refining the model framework could enhance predictive performance. Full article

Silicon steel (electrical steel) has been used in electric motors that are important components in sustainable new energy Electrical Vehicles (EVs). The Ruhrstahl–Heraeus process is commonly used in the refining process of silicon steel. The refining effect inside the RH degasser is closely related to the flow and mixing of molten steel. In this study, a 260 t RH was used as the prototype, and the transport process of the passive scalar tracer (virtual tracer) and salt tracer (considering density effect) was studied using numerical simulation and water model research methods. The results indicate that the tracer transports from the up snorkel of the down snorkel to the bottom of the ladle, and then upwards from the bottom of the ladle to the top of the ladle. Density and gravity, respectively, play a promoting and hindering role in these two stages. In different areas of the ladle, density and gravity play a different degree of promotion and obstruction. Moreover, in different regions of the ladle, the different circulation strength leads to the different promotion degrees and obstruction degrees of the density. This results in the difference between the concentration growth rate of the salt tracer and the passive scalar in different regions of the ladle top. From the perspective of mixing time, density and gravity have no effect on the mixing time at the bottom of the ladle, and the difference between the passive scalar and NaCl solution tracer is within the range of 1–5%. For a larger dosage of tracer case, the difference range is reduced. However, at the top of the ladle, the average mixing time for the NaCl solution case is significantly longer than that of the passive scalar case, within the range of 3–14.7%. For a larger dosage of tracer case, the difference range is increased to 17.4–41.1%. It indicates that density and gravity delay the mixing of substances at the top area of the ladle, and this should be paid more attention when adding denser alloys in RH degasser. Full article

Vacuum degassing of seeds is a basic preliminary stage of the treatment process to improve the viability of seeds of various crops. In this work, the degassing process of corn seeds was experimentally and numerically analyzed by removing air or other gases from around the seeds, specifically from the seed coating, in a rough vacuum chamber. Two complementary variants were employed to understand and optimize this process to improve the quality and germination rate of the seeds. The average germination percentage on the first day was about 98%, and the germination speed of 5.0 days. Several experiments were conducted with well-established durations of 10 min and masses of 5 kg and masses of corn seeds at different temperatures to observe and record the behavior of the system, facilitating the modeling of the degasification process in the vacuum compartment. Modeling the degasification operation in the vacuum chamber allowed for determining the pressure profiles on the vacuum chamber and its lid. Numerical simulations were either conducted using a simulation program developed in the Visual Basic Applications (VBA) language for Microsoft Excel to model the degassing process in the vacuum chamber or with the assistance of specialized software (transient structural analysis and simulation program in the ANSYS Workbench environment). Statistical analysis of the correlation between experimental and estimated pressure values revealed that both the proposed mathematical model and the solution method are well-chosen, with differences expressed through the absolute error (EA) being very small, only 1.425 mbar. Structural dynamic analysis carried through the Finite Element Method (FEM) highlights that the chosen materials for manufacturing the vacuum chamber vessel (316 stainless steel—yield strength 225 MPa and tangent modulus 2091 MPa) or the chamber lid (transparent acrylic plastic—yield strength 62.35 MPa and shear modulus 1445.3 MPa) are durable and capable of withstanding the desired pressure and temperature demands in the seed treatment process. Additionally, through structural dynamic analysis, it was possible to study the deformation of system components, providing a detailed perspective on their structural distribution. Thus, the paper aims to improve the quality and survival/germination rate of corn seeds as an important step to improve corn yield through simulations and analyses (numerical and experimental) of the vacuum corn seed degassing system. The degassing process of the vacuum chamber was simulated with a simulation program developed for Microsoft Excel for Microsoft 365 MSO (Version 2401 Build 16.0.17231.20236) 64-bit in the VBA language and software (transient structural dynamic analysis in the ANSYS environment through FEM). Vacuum degassing of corn seeds involves the removal of air or other gases around the seeds or products, which is crucial in various fields such as the food, pharmaceutical, or space technology industries. Full article

The present work aims to answer three essential research questions (RQs) that have previously not been explicitly dealt with in the field of applied machine learning (ML) in steel process engineering. RQ1: How many training data points are needed to create a model with near-upper-bound predictive performance on test data? RQ2: What is the near-upper-bound predictive performance on test data? RQ3: For how long can a model be used before its predictive performance starts to decrease? A methodology to answer these RQs is proposed. The methodology uses a developed sampling algorithm that samples numerous unique training and test datasets. Each sample was used to create one ML model. The predictive performance of the resulting ML models was analyzed using common statistical tools. The proposed methodology was applied to four disparate datasets from the steel industry in order to externally validate the experimental results. It was shown that the proposed methodology can be used to answer each of the three RQs. Furthermore, a few findings that contradict established ML knowledge were also found during the application of the proposed methodology. Full article

An innovative yet sustainable approach for industrial deaeration is proposed, with demonstrated results and analyses, to contribute to finding solutions to improve energy efficiency in this field. Vacuum bubbling deaeration, sharing the same working principles of solubility control and the mass diffusion through vapor (or steam) with conventional thermal deaeration processes, works, however, at lower vacuum pressures. It neither resorts to heating nor requires any third-party materials such as membranes or gases, achieving orders of magnitude of reduction in the expected energy consumption in a simple and concrete way. In this study, the mechanisms of vapor bubble generation and retention were discussed by employing a vacuum bubbling model based on the experimental apparatus at Kongju National University, which uses a venturi-nozzle bubbler. The four parameters influencing vapor bubble generation and retention were identified as vessel pressure $p_1$, nozzle depth $\Delta h$, nozzle performance $p_4-p_3$, and water temperature $T_w$. A series of deaeration experiments using the present approach for a tap water sample of 360~400 L were conducted under four different conditions to investigate the effects of the water temperature, vessel pressure, and bubbler nozzle depth. Final dissolved oxygen (DO) concentrations close to zero could be achieved with a vessel pressure of $p_1=1 \mathrm{kPa},$with different bubbling times to reach a zero mg/L reading of DO concentration (case 2 and 3), which demonstrates the vital roles of the vapor bubble generation condition of ($p_{sat}-p_3)$ and retention condition of ($p_4-p_{sat})$ in achieving the lowest DO concentration. Analysis of the test results, based on the discrete-bubble model with the measured DO concentrations and degassing rates, showed promising results in reproducing the experimental data. Though the potential of vacuum bubbling deaeration is demonstrated, for the first time, to its full extent, further research efforts are encouraged in many areas, including more case-specific validation test cases with optimum operating conditions along with the study of more detailed modeling for performance prediction, including energy analysis. Full article

Mechanical testing of glass-fibre-reinforced composite (GFRP) plates made of twill fabric and a thermoplastic recyclable infusion resin is presented. The considered thermoplastic resin, ELIUM^®, is made of poly-methylmethacrylate and can be infused with properly tuned vacuum techniques, in the same manner as all liquid resin. Tensile, flexural, and drop-dart impact tests were carried out to assess the mechanical properties of the composites considering different fabrication conditions, such as the different degassing pressure before infusion and three different infusion vacuum pressures. The work reports a methodology to infuse ELIUM resin at a relatively high vacuum pressure of 0.8 bar. X-ray microtomography analysis showed that the produced laminates are free of defects, differently from what was reported in the literature, where void problems related to a vacuum infusion pressure higher than 0.3–0.5 bar were pointed out. Vacuum pressure values influence the mechanical characteristics of the laminate: when higher vacuum pressures are adopted, the mechanical properties of the GFRP laminates are enhanced and higher values of elastic modulus and strength are obtained. On the other hand, degassing the resin before infusion does not influence the mechanical properties of the laminates. A maximum bending and tensile strength of 420 and 305 MPa were reached by using the vacuum infusion of 0.8 bar with an elastic modulus of 18.5 and 20.6 GPa, respectively. The density of the produced laminates increases at higher vacuum infusion pressure up to a maximum value of 1.81 g/cm³ with the fibre volume fraction of each laminate. Full article

The works available in the literature presenting the influence of impurities on the properties (mainly fatigue strength) of material give an answer with a high degree of probability for hard steels and large precipitations (usually above 10 µm). The impact of non-metallic impurities on the durability of high-ductility steels causes much greater problems and is much more difficult to explain. The results of the existing studies rarely take into account the diameter of the impurities in relation to the distance between the impurities. This paper presents the results of tests carried out on a low-carbon steel heated in a 100-tonne oxygen converter and deoxidized under vacuum. The fatigue strength test was carried out on cylindrical samples using rotational bending for different tempering temperatures of the steel. The quotient of the average size of the inclusions and the average distance between the inclusions were analyzed. Based on the obtained results, it was found that steel annealed in the converter and vacuum degassed has a content of both phosphorus and sulfur below 0.02% and a total volume of impurities of 0.086%. The main fraction of impurities are oxide inclusions with a diameter below 2 µm. An increase in fatigue strength was found along with an increase in the number of impurities, mainly of small diameters. Full article

Hydrogen removal of H-supersaturated liquid steel produced in a hydrogen-rich environment in an industrial vacuum degasser (VD) is simulated here using a two-phase (argon–steel) Eulerian model. The dehydrogenation efficiency is evaluated for a series of ladle plug layouts and argon-purging modes. Increasing the plug number from the prototype double-plug of the ladle to four or slightly prolonging the degassing time of a triple-plug ladle enables to obtain the specified dehydrogenation efficiency and the end-point hydrogen level. Varying the plug position of the triple-plug ladle makes no significant difference in the dehydrogenation efficiency, which, however, is improved by adjusting the plug angle. For the triple-plug ladle, the non-uniform argon-purging mode improves the melt hydrodynamic conditions, but the optimal dehydrogenation performance is achieved in the uniform mode. The plug number has the greatest impact on the dehydrogenation efficiency compared to the other ladle designs considered. The high-efficiency dehydrogenation of H-supersaturated liquid steel in the VD can be achieved through using the quadruple plugs, or by using the triple plugs positioned at 0.57R, 0.57R, and 0.41R and the angles of 108.6° and 71.4°, with the uniform argon-purging flow rate. Full article

This work investigates the effects of oxygen and humidity on black phosphorous (BP) and black arsenic phosphorous (${\mathrm{As}}_{\mathrm{x}}{\mathrm{P}}_{1-\mathrm{x}}$ ) flakes using Raman spectroscopy and in situ electric transport measurements (four-probe resistance and thermoelectric power, TEP). The results show that the incorporation of arsenic into the lattice of BP renders it more stable, with the degradation times for BP, ${\mathrm{As}}_{0.2}{\mathrm{P}}_{0.8}$, and ${\mathrm{As}}_{0.4}{\mathrm{P}}_{0.6}$ being 4, 5, and 11 days, respectively. The P-P Raman peak intensities were determined to decrease with exposure to oxygen and moisture. The TEP measurements confirmed that both BP and ${\mathrm{As}}_{\mathrm{x}}{\mathrm{P}}_{1-\mathrm{x}}$are p-type semiconductors with the TEP of ${\mathrm{As}}_{0.4}{\mathrm{P}}_{0.6}$ stabilizing more slowly than that of BP. In addition, the four-probe resistance of BP and ${\mathrm{As}}_{\mathrm{x}}{\mathrm{P}}_{1-\mathrm{x}}$ stabilized significantly faster when exposed to air after being degassed in a vacuum. This was attributed to the charge transfer between the oxygen redox potential of air and the Fermi energy (E_F) of the semiconductors. Full article