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22 pages, 6079 KiB

Open AccessArticle

Simulation Model of a Steelmaking–Continuous Casting Process Based on Dynamic-Operation Rules

by Xin Shao, Qing Liu, Hongzhi Chen, Jiangshan Zhang, Shan Gao and Shaoshuai Li

Materials 2024, 17(17), 4352; https://doi.org/10.3390/ma17174352 - 3 Sep 2024

Viewed by 762

Abstract

The steelmaking–continuous casting process (SCCP) is a complex manufacturing process which exhibits the distinct features of process manufacturing. The SCCP involves a variety of production elements, such as multiple process routes, a wide array of smelting and auxiliary devices, and a variety of [...] Read more.

The steelmaking–continuous casting process (SCCP) is a complex manufacturing process which exhibits the distinct features of process manufacturing. The SCCP involves a variety of production elements, such as multiple process routes, a wide array of smelting and auxiliary devices, and a variety of raw and auxiliary materials. The production-simulation of SCCP holds a natural advantage in being able to accurately depict the intricate production behavior involved, and this serves as a crucial tool for optimizing the production operation of the SCCP. This paper thoroughly considers the various production elements involved in the SCCP, such as the fluctuation of the converter smelting cycle, fluctuation of heat weight, and ladle operation. Based on the Plant Simulation software platform, a dynamic simulation model of the SCCP is established and detailed descriptions are provided regarding the design of an SCCP using dynamic-operation rules. Additionally, a dynamic operational control program for the SCCP is developed using the SimTalk language, one which ensures the continuous operation of the caster in the SCCP, using the discrete simulation platform. The effectiveness of the proposed dynamic simulation model is verified by the total completion time of the production plan, the transfer time of the heat among the different processes, and the frequency of ladle turnover. The simulation’s results indicate that the dynamic simulation model has a satisfactory effect in simulating the actual production process. On this basis, the application effects of different schedules are compared and analyzed. Compared with a heuristic schedule, the optimized schedule based on the “furnace–machine coordinating” mode reduces the weighted value of total completion time by 8.7 min, reduces the weighted value of transfer waiting time by 45.5 min, and the number of rescheduling times is also reduced, demonstrating a better application effect and verifying the optimizing effect of the “furnace–machine coordinating” mode on the schedule. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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12 pages, 8625 KiB

Open AccessArticle

Analysis of the Steelmaking Process via Data Mining and Pearson Correlation

by Susana Carrasco-López, Martín Herrera-Trejo, Manuel Castro-Román, Fabián Castro-Uresti and Edgar Iván Castro-Cedeño

Materials 2024, 17(11), 2786; https://doi.org/10.3390/ma17112786 - 6 Jun 2024

Cited by 1 | Viewed by 716

Abstract

The continuous improvement of the steelmaking process is a critical issue for steelmakers. In the production of Ca-treated Al-killed steel, the Ca and S contents are controlled for successful inclusion modification treatment. In this study, a machine learning technique was used to build [...] Read more.

The continuous improvement of the steelmaking process is a critical issue for steelmakers. In the production of Ca-treated Al-killed steel, the Ca and S contents are controlled for successful inclusion modification treatment. In this study, a machine learning technique was used to build a decision tree classifier and thus identify the process variables that most influence the desired Ca and S contents at the end of ladle furnace refining. The attribute of the root node of the decision tree was correlated with process variables via the Pearson formalism. Thus, the attribute of the root node corresponded to the sulfur distribution coefficient at the end of the refining process, and its value allowed for the discrimination of satisfactory heats from unsatisfactory heats. The variables with higher correlation with the sulfur distribution coefficient were the content of sulfur in both steel and slag at the end of the refining process, as well as the Si content at that stage of the process. As secondary variables, the Si content and the basicity of the slag at the end of the refining process were correlated with the S content in the steel and slag, respectively, at that stage. The analysis showed that the conditions of steel and slag at the beginning of the refining process and the efficient S removal during the refining process are crucial for reaching desired Ca and S contents. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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21 pages, 38871 KiB

Open AccessArticle

Effect of Yttrium Additions on the High-Temperature Oxidation Behavior of GH4169 Ni-Based Superalloy

by Tiantian Wang, Wei Liu, Shufeng Yang, Jingshe Li, Peng Zhao and Hui Xue

Materials 2024, 17(11), 2733; https://doi.org/10.3390/ma17112733 - 4 Jun 2024

Viewed by 981

Abstract

The effect of the active element yttrium and its content on the oxidation behavior of GH4169 Ni-based superalloy at extreme temperature was studied by isothermal oxidation experiments. The results show that the oxide scale of GH4169 alloy presents a multi-layer structure, in which [...] Read more.

The effect of the active element yttrium and its content on the oxidation behavior of GH4169 Ni-based superalloy at extreme temperature was studied by isothermal oxidation experiments. The results show that the oxide scale of GH4169 alloy presents a multi-layer structure, in which the continuous and dense Cr₂O₃ oxide layer is located in the subouter layer (II layer) and the continuous Nb-rich layer is in the subinner layer (III layer). These layers can inhibit the diffusion of oxygen and alloying elements, preventing the further oxidation of the alloy. The appropriate addition of yttrium can promote the selective oxidation of Cr element, reduce the thickness of the oxide scale and the oxidation rate of the alloy, inhibit the formation of voids at the interface of the oxide scale/alloy matrix, improve the resistance of the alloy to spalling as well as the adhesion of the oxide scale, and improve the high-temperature oxidation resistance of the alloy. Of those tested, the alloy containing 0.04 wt.%Y has the lowest oxidation weight gain, the slowest oxidation rate, and less oxide scale spalling. Based on this, the effect of yttrium on the high-temperature oxidation behavior of GH4169 Ni-based superalloy and its mechanism were revealed. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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12 pages, 3282 KiB

Open AccessArticle

Study on the High-Temperature Interaction between Coke and Iron Ores with Different Layer Thicknesses

by Yong-Hong Wang, Ping Du, Jiang Diao, Bing Xie and Ming-Hua Zhu

Materials 2024, 17(6), 1358; https://doi.org/10.3390/ma17061358 - 15 Mar 2024

Cited by 1 | Viewed by 905

Abstract

Coke plays a key role as the skeleton of the charge column in BF. The gas path formed by the coke layer in the BF has a decisive influence on gas permeability. At high temperatures, the interface between coke and ore undergoes a [...] Read more.

Coke plays a key role as the skeleton of the charge column in BF. The gas path formed by the coke layer in the BF has a decisive influence on gas permeability. At high temperatures, the interface between coke and ore undergoes a melting reaction of coke and a reduction reaction of ore. The better the reducibility of the ore, the more conducive it is to the coupling reaction of ore and coke. The melting loss reaction of coke becomes more intense, and the corresponding strength of coke will decrease, which will affect the permeability of the blast furnace and is not conducive to the smooth operation of the blast furnace. Especially with a deterioration in iron ore quality, BF operation faces severe challenges, which makes it necessary to find an effective way to strengthen BF operation. In this study, a melting-dropping furnace was used to develop and clarify the high-temperature interaction between coke and iron ores with different layer thicknesses. The influencing factors were studied by establishing a gas permeability mathematical model and observing the metallographic microscope images of samples after the coke solution loss reaction. The relationships between coke layer thickness, distribution of gas flow, and pressure drop were obtained. The results showed that, under certain conditions, the gas permeability property of a furnace burden has been improved after the coke layer thickness increased. Upon observing the size of coke particles at the interface reaction site, the degree of melting loss reaction can be determined. A smaller particle size indicates more melting loss reaction. A dripping eigenvalue for molten metal was introduced to evaluate the dynamic changes in the comprehensive dripping properties of molten metal of furnace burden, which showed that the dripping eigenvalue for the molten metal could deteriorate because of the unruly thickness and the coke layer thickness should be limited through considering the operational indicators of the blast furnace. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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14 pages, 1825 KiB

Open AccessArticle

Modeling of Impurities Evaporation Reaction Order in Aluminum Alloys by the Parametric Fitting of the Logistic Function

by Aleksandar M. Mitrašinović, Jasmina Nešković, Svetlana Polavder, Sandra Petković, Željko Praštalo, Nebojša Labus and Milinko Radosavljević

Materials 2024, 17(3), 728; https://doi.org/10.3390/ma17030728 - 3 Feb 2024

Viewed by 990

Abstract

Advancements in computer capabilities enable predicting process outcomes that earlier could only be assessed after post-process analyses. In aerospace and automotive industries it is important to predict parts properties before their formation from liquid alloys. In this work, the logistic function was used [...] Read more.

Advancements in computer capabilities enable predicting process outcomes that earlier could only be assessed after post-process analyses. In aerospace and automotive industries it is important to predict parts properties before their formation from liquid alloys. In this work, the logistic function was used to predict the evaporation rates of the most detrimental impurities, if the temperature of the liquid aluminum alloy was known. Then, parameters of the logistic function were used to determine the transition points where the reaction order was changing. Samples were heated to 610 °C, 660 °C, 710 °C, and 760 °C for one hour, after which the chemical analyses were performed and evaporation rates were calculated for Cd, Hg, Pb and Zn elements. The pressure inside the encapsulated area was maintained at 0.97 kPa. Whereas parameters that define the evaporation rate increase with the temperature increase, the maximum evaporation rates were deduced from the experimental data and fitted into the logistic function. The elemental evaporation in liquid-aluminum alloys is the best defined by the logistic function, since transitions from the first to zero-order-governed evaporation reactions have nonsymmetrical evaporation rate slopes between the lowest and the highest evaporation rate point. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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15 pages, 5175 KiB

Open AccessArticle

Dissolution Behavior of Lime with Different Properties into Converter Slag

by Mengxu Zhang, Jianli Li, Cao Jia and Yue Yu

Materials 2023, 16(19), 6487; https://doi.org/10.3390/ma16196487 - 29 Sep 2023

Cited by 2 | Viewed by 1050

Abstract

China’s 2022 crude steel production soared to an impressive 1.018 billion tons, and steel slag constituted approximately 10% to 15% of this massive output. However, a notable hindrance to the comprehensive utilization of steel slag arises from the fact that it contains 10% [...] Read more.

China’s 2022 crude steel production soared to an impressive 1.018 billion tons, and steel slag constituted approximately 10% to 15% of this massive output. However, a notable hindrance to the comprehensive utilization of steel slag arises from the fact that it contains 10% to 20% of free calcium oxide (f-CaO), resulting in volume instability. To address this challenge, our study delved into the dynamic transformation of the interface between lime and slag, as well as the fluctuations in the dissolution rate of lime. An Electron Probe Micro Analyzer, equipped with an energy-dispersive spectrometer, was employed for the analysis. Our findings revealed that the configuration of the reaction interface between quicklime and slag underwent alterations throughout various phases of converter smelting. At a temperature of 1400 °C, several significant transformations occurred, including the formation of a CaO-FeO solid solution, (Ca, Mg, Fe) olivine, and low-melting point (Ca, Mg) silicate minerals. With the gradual reduction in FeO content, a robust and high-melting 2CaO·SiO₂ layer emerged, generated through the interaction between CaO and (Ca, Mg, Fe) olivine. Furthermore, for lime with a particle size of 20 mm and a calcination rate of 0%, the thickest layer of 2CaO·SiO₂ was observed after 120 s of dissolution in slag A2 at 1400 °C. Overall, the dissolution rates of lime with different particle sizes in slag A1 to A4 showed a gradual increase. On the other hand, the dissolution rates of lime with different calcination rates in slag A1 to A4 exhibited an initial increase, followed by a decrease, and then another increase. The formation of a high-melting point and continuous dense 2CaO·SiO₂ layer during the dissolution process hindered the mass transfer between lime and slag. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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17 pages, 32694 KiB

Open AccessArticle

Numerical Modeling of Transient Flow Characteristics on the Top Surface of a Steel Slab Continuous Casting Strand Using a Large Eddy Simulation Combined with Volume of Fluid Model

by Yushi Tian, Haichen Zhou, Guobin Wang, Lijun Xu, Shengtao Qiu and Rong Zhu

Materials 2023, 16(16), 5665; https://doi.org/10.3390/ma16165665 - 17 Aug 2023

Cited by 2 | Viewed by 1014

Abstract

In the current study, the transient flow characteristics on the top surface of a steel slab continuous casting strand were numerically investigated using a large eddy simulation combined with volume of fluid (LES + VOF) model. The validation of numerical simulation was verified [...] Read more.

In the current study, the transient flow characteristics on the top surface of a steel slab continuous casting strand were numerically investigated using a large eddy simulation combined with volume of fluid (LES + VOF) model. The validation of numerical simulation was verified via nail board measurement in the industrial continuous casting mold. The effects of casting speed on the top surface level profile and the instantaneous distribution of vortex were discussed. The level variation profile migrated after a period of time, moving from one side of the wide face of the mold to the other. The wave height and transient variation degree of the standing wave increased with an increase in the casting speed. The region near the SEN was more likely to promote the formation of vortices. The vortex generation became easier when the vorticity peaks were concentrated on the outer edge of the low-speed confluence area near the submerged entry nozzle. In addition, the effect of surface velocity on the instantaneous level fluctuation was analyzed. The frequency of level fluctuations was highest at 3~4 mm, and the high-frequency range of velocity fluctuation was 20~60 mm/s at 0.9 m/min casting speed for a 1500 mm × 200 mm caster section. The linear relationship between the level fluctuation and surface velocity magnitude was obtained. The present work aimed at evaluating the dynamic problem of the standing wave at the liquid powder–molten steel interface on the top surface of the mold, which is helpful in optimizing the casting parameters for regular casting practice and improving the quality of the steel slabs. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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18 pages, 6547 KiB

Open AccessArticle

Simulation of Spatial Distribution of Multi-Size Bubbles in a Slab Continuous-Casting Mold Water Model

by Yushi Tian, Lijun Xu, Shengtao Qiu and Rong Zhu

Materials 2023, 16(13), 4666; https://doi.org/10.3390/ma16134666 - 28 Jun 2023

Cited by 1 | Viewed by 1107

Abstract

In this paper, a fully coupled large eddy simulation model, including the volume of fluid model, the discrete phase model, the bubble-collision model, and the bubble-breakup model was used to simulate the spatial distribution of multi-size bubbles and its impact on the instantaneous [...] Read more.

In this paper, a fully coupled large eddy simulation model, including the volume of fluid model, the discrete phase model, the bubble-collision model, and the bubble-breakup model was used to simulate the spatial distribution of multi-size bubbles and its impact on the instantaneous two-phase flow in a slab continuous-casting mold. The influence of the bubble-interaction model on the bubbles’ three-dimensional spatial distribution and size distribution, as well as on two-phase flow was discussed. By comparison with the velocity on the meniscus and the average bubble diameter inside a continuous-casting slab water model, the appropriate numerical model was recommended to accurately simulate the two-phase flow and characteristics of discrete bubbles. The submerged entry nozzle and the area around it saw bubble coalescence and breakage more frequently than other areas. The key interaction between the bubbles was their bouncing in the deep region of the mold. In the mold, the average bubble diameter was 0.741 mm, and 44.5% of the total number of bubbles had an approximately average diameter. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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16 pages, 5102 KiB

Open AccessArticle

The Effect of Mold Structure and Cooling Parameters on Heat Transfer during Billet High-Speed Continuous Casting

by Sijie Wang, Pei Xu, Yongzhi Zhou, Huamei Duan, Dengfu Chen and Mujun Long

Materials 2023, 16(9), 3361; https://doi.org/10.3390/ma16093361 - 25 Apr 2023

Cited by 3 | Viewed by 2373

Abstract

Mold structure and cooling parameters are significant factors that affect the heat transfer capacity of high-speed continuous casting molds of billets. Therefore, a three-dimensional fluid flow and heat transfer model of a 160 mm × 160 mm billet mold was established, and its [...] Read more.

Mold structure and cooling parameters are significant factors that affect the heat transfer capacity of high-speed continuous casting molds of billets. Therefore, a three-dimensional fluid flow and heat transfer model of a 160 mm × 160 mm billet mold was established, and its accuracy was verified. Thereby, the characteristics of heat transfer and influences of mold structure and cooling parameters on heat transfer in the high-speed continuous casting billet mold region were revealed. It was found that extending the effective length of a mold is the most valuable method to improve its heat transfer capability and achieve high-speed continuous casting. The total heat and the shell thickness at a mold outlet increased by 19% and 9.21% on average with every 100 mm extension. Enlarging the fillet radius could enhance the uniformity of heat transfer in the mold. Considering the loss of material, the optimal fillet radius of the mold was determined to be R = 10 mm. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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12 pages, 4448 KiB

Open AccessArticle

Crystallization of Slag Films of CaO-Al₂O₃-BaO-CaF₂-Li₂O-Based Mold Fluxes for High-Aluminum Steels’ Continuous Casting

by Xiao Long, Shaolei Long, Wenbo Luo, Xiang Li, Changping Tu, Yunhao Na and Jinxin Xu

Materials 2023, 16(5), 1903; https://doi.org/10.3390/ma16051903 - 25 Feb 2023

Viewed by 1645

Abstract

In this study, solidified films of CaO-Al₂O₃-BaO-CaF₂-Li₂O-based mold fluxes with different contents of Al₂O₃ addition were acquired by immersing an improved water-cooled copper probe in bulk molten slags. This probe can obtain [...] Read more.

In this study, solidified films of CaO-Al₂O₃-BaO-CaF₂-Li₂O-based mold fluxes with different contents of Al₂O₃ addition were acquired by immersing an improved water-cooled copper probe in bulk molten slags. This probe can obtain films with representative structures. Different slag temperatures and probe immersion times were employed to investigate the crystallization process. The crystals in the solidified films were identified using X-ray diffraction, the morphologies of the crystals were observed using optical microscopy and scanning electron microscopy, and the kinetic conditions, especially the activation energy of devitrified crystallization in glassy slags, were calculated and discussed based on the differential scanning calorimetry. The results indicated that after adding extra Al₂O₃, the growing speed and thickness of the solidified films increased, and more time was required for the film thickness to reach a steady state. In addition, fine spinel (MgAl₂O₄) precipitated in the films at the early stage of solidification after adding 10 wt% of extra Al₂O₃. Together with LiAlO₂, spinel (MgAl₂O₄) acted as nuclei for the precipitation of BaAl₂O₄. The apparent activation energy of initial devitrified crystallization decreased from 314.16 KJ/mol (original slag) to 297.32 KJ/mol (5 wt% Al₂O₃ added) and 269.46 KJ/mol (10 wt% Al₂O₃ added). The crystallization ratio of the films also increased after adding extra Al₂O₃. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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12 pages, 12930 KiB

Open AccessArticle

Fluid Flow in Continuous Casting Mold for Ultra-Wide Slab

by Gang Li, Lingfeng Tu, Qiangqiang Wang, Xubin Zhang and Shengping He

Materials 2023, 16(3), 1135; https://doi.org/10.3390/ma16031135 - 28 Jan 2023

Cited by 2 | Viewed by 1763

Abstract

Ultra-wide slabs have a good application market and prospect, but there is still a lack of research on the flow field. To explore the characteristics of its flow field, this study built a 0.5-scale physical model of mold using Perspex. The effect of [...] Read more.

Ultra-wide slabs have a good application market and prospect, but there is still a lack of research on the flow field. To explore the characteristics of its flow field, this study built a 0.5-scale physical model of mold using Perspex. The effect of casting speed on flow field and surface flow speed was investigated by using an ink tracer experiment and contact measurement. There were various flow patterns in the ultra-wide slab mold, and they continue to transform each other. The jet momentum from the nozzle ports was diffused by colliding with the wide face, which lowered its kinetic energy and affected its subsequent diffusion. Compared with the conventional mold, the upper flow intensity of the ultra-wide slab mold was weaker, which made its liquid surface inactive and caused it to produce a flux rim or slag strip. At different casting speeds, the average flow speed distribution of the ultra-wide slab was C-shaped. When it increased from 0.9 to 1.4 m/s, the corresponding maximum average flow speed increased from 0.08 to 0.2 m/s. At the same time, the proportion of the low-flow speed zone at the most active part of the surface also gradually decreased from more than 90% to about 49%. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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15 pages, 9887 KiB

Open AccessArticle

Design Improvement of Four-Strand Continuous-Casting Tundish Using Physical and Numerical Simulation

by Quanhui Li, Bangming Qin, Jiangshan Zhang, Hongbiao Dong, Ming Li, Biao Tao, Xinping Mao and Qing Liu

Materials 2023, 16(2), 849; https://doi.org/10.3390/ma16020849 - 15 Jan 2023

Cited by 5 | Viewed by 2391

Abstract

The flow pattern is vital for the metallurgical performance of continuous casting tundishes. The purpose of this study was to design and optimize the flow characteristics inside a four-strand tundish. Numerical simulations and water model experiments were validated and utilized to investigate the [...] Read more.

The flow pattern is vital for the metallurgical performance of continuous casting tundishes. The purpose of this study was to design and optimize the flow characteristics inside a four-strand tundish. Numerical simulations and water model experiments were validated and utilized to investigate the flow behavior. The effect of different flow rates in the original tundish was evaluated; two modified retaining walls and a new ladle shroud were designed for optimization. The molten steel inside the original tundish tends to be more active as the flow rate increases from 3.8 L/min to 6.2 L/min, which results in a reduction in dead volume from 36.47% to 17.59% and better consistency between different outlets. The dead volume and outlet consistency inside the tundish are improved significantly when the modified walls are applied. The proper design of the diversion hole further enhances the plug volume from 6.39% to 13.44% of the tundish by forming an upstream circular flow in the casting zone. In addition, the new trumpet ladle shroud demonstrates an advantage in increasing the response time from 152.5 s to 167.5 s and alleviating the turbulence in the pouring zone, which is beneficial for clean steel production. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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18 pages, 11670 KiB

Open AccessArticle

The Thermodynamics and Kinetics of a Nitrogen Reaction in an Electric Arc Furnace Smelting Process

by Fujun Zhang, Jingshe Li, Wei Liu and Aoteng Jiao

Materials 2023, 16(1), 33; https://doi.org/10.3390/ma16010033 - 21 Dec 2022

Cited by 1 | Viewed by 2500

Abstract

The nitrogen content of electric arc furnace (EAF) steel is much higher than that of basic oxygen furnace (BOF) steel, which cannot meet the requirements of high-grade steel. Most denitrification processes only considered a single smelting condition, which leads to poor denitrification effect. [...] Read more.

The nitrogen content of electric arc furnace (EAF) steel is much higher than that of basic oxygen furnace (BOF) steel, which cannot meet the requirements of high-grade steel. Most denitrification processes only considered a single smelting condition, which leads to poor denitrification effect. In this study, a hot state experiment was conducted to simulate the melting process of EAF steelmaking and to explore the thermodynamic and kinetic constraints of the molten steel nitrogen reaction in the scrap melting, oxygen blowing decarburization, and rapid temperature rise stages. The experimental results showed that the nitrogen reaction in the molten pool during the scrap melting stage was a first-order nitrogen absorption reaction, and the reaction-limiting link was the diffusion of nitrogen atoms in the molten steel. When the carbon content increases to 4.5%, the bath temperature decreases to 1550 °C, and the nitrogen partial pressure decreases to 0.2 P^Θ, the nitrogen saturation solubility decreased to 0.0198%, 0.0318%, and 0.0178%, respectively. At the same time, the rate constants decreased to 0.132 m/min, 0.127 m/min, and 0.141 m/min, respectively. The nitrogen reaction in the oxygen blowing decarburization stage was a secondary denitrification reaction, and the reaction-limiting link was the gas–liquid interface chemical reaction. Argon had better degassing effect. When the argon flow rate increased from 100 mL/min to 300 mL/min, the reaction constant increased by about four times. When the oxygen content of molten steel was 0.0260%, the denitrification rate constant decreased by about 2.5 times. The nitrogen content of liquid steel was higher than 0.045%, and the reaction was a secondary reaction. As the nitrogen content decreased, the reaction rate decreased, and the reaction-limiting link changed from the gas–liquid interface chemical reaction to the joint control of mass transfer and chemical reaction. The oxygen content in the molten steel can not only hinder the chemical reaction of nitrogen at the gas–liquid interface, but also reduce the mass transfer rate of nitrogen atoms in the molten steel. The results provided a theoretical basis for the optimization of nitrogen removal process and further reduction of nitrogen content in liquid steel. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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19 pages, 6847 KiB

Open AccessArticle

Behavior of Mold Electromagnetic Stirring for Round Bloom Castings and Its Eccentric Stirring Problem

by Pu Wang, Hong Xiao, Zhuang Zhang, Shaoxiang Li and Jiaquan Zhang

Materials 2022, 15(24), 8814; https://doi.org/10.3390/ma15248814 - 9 Dec 2022

Cited by 6 | Viewed by 1678

Abstract

In this paper, a mold electromagnetic stirring (M-EMS) model was established to investigate the behavior of M-EMS for round bloom castings under different conditions, and an electromagnetic-flow-heat transfer-solidification coupling model was established to explore the problem of eccentric stirring for various formats of [...] Read more.

In this paper, a mold electromagnetic stirring (M-EMS) model was established to investigate the behavior of M-EMS for round bloom castings under different conditions, and an electromagnetic-flow-heat transfer-solidification coupling model was established to explore the problem of eccentric stirring for various formats of round blooms. The results show that the magnetic flux density decreased with the increase in the current frequency, but the electromagnetic torque increases first and then decreases with it, and the same structure of M-EMS for round blooms has the same optimal current frequency at any current intensity. The electromagnetic torque and electromagnetic force both increase as a quadratic function of the current intensity, and the electromagnetic torque, which drives the steel flow, can directly characterize the real M-EMS performance. The mold copper tube has a significant magnetic shielding effect on M-EMS, the stirring intensity decreases rapidly as the tube thickness increases, and the optimal stirring frequency decreases as well. In fact, the deviation between the stirrer center and the geometric center of the strand can result in the eccentric stirring phenomenon. When blooms with a section size of Φ350 mm are produced by Φ650 mm SMS-Concast casting machine, the upper region of the inner arc side and the lower region of the outer arc side are subject to a stronger washing effect, which makes the temperature of the inner and outer arcs show alternating differences. The jet flow from the five-port nozzle can suppress the difference in initial solidification symmetry between the inner and outer arcs of round blooms caused by eccentric stirring. This paper reveals the magnetic shielding effect of the mold copper tube and the magnetic field loss of the air between the stirrer and the inner and outer arcs of the copper, which lead to the stirring intensity and the eccentric stirring phenomenon. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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16 pages, 5284 KiB

Open AccessArticle

Effects of Different RH Degasser Nozzle Layouts on the Circulating Flow Rate

by Zhenming Zhang, Peng Ma, Jianhong Dong, Min Liu, Yonggang Liu and Chaobin Lai

Materials 2022, 15(23), 8476; https://doi.org/10.3390/ma15238476 - 28 Nov 2022

Cited by 2 | Viewed by 1810

Abstract

The effects of gas flow rate and 22 kinds of nozzle layouts on the circulation flow rate were researched during the RH refining process using a water model and a mathematical model. Numerical simulations agreed with the water model experiment well. The results [...] Read more.

The effects of gas flow rate and 22 kinds of nozzle layouts on the circulation flow rate were researched during the RH refining process using a water model and a mathematical model. Numerical simulations agreed with the water model experiment well. The results showed that the circulating flow rate increased with an increase of the gas flow rate. The critical value of the gas flow rate was 2.4 m³/h. Out of the 22 kinds of layouts, the 127-87 symmetrical layout was the optimal layout, for which the circulating flow rate reached 29.8 m³/h, the area of blind zone was the smallest and the mixing effect of the molten steel was the best. The working stroke and carrying capacity of the bubbles were important factors that affected the circulating flow rate. Among the four types of layouts, when the nozzles were in the one-side layout and the one-row layout, the main factor for improving the circulating flow rate was the working stroke of the bubbles. When nozzles were in the staggered layout and the symmetrical layout, the carrying capacity of the bubbles was the main factor for improving the circulating flow rate. For the same conditions, the carrying capacity of the bubbles had a greater effect on improving the circulating flow rate than the bubble stroke. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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19 pages, 11664 KiB

Open AccessArticle

Effect of Swirling Flow Nozzle on Fluid Flow and Solidification in a Round Bloom Continuous Casting Mold

by Jianli Wang, Jiayu Zhu, Yongkun Yang, Weian Wang, Guoxing Qiu and Xiaoming Li

Materials 2022, 15(23), 8474; https://doi.org/10.3390/ma15238474 - 28 Nov 2022

Cited by 4 | Viewed by 1879

Abstract

The nozzle structure has an important effect on the fluid flow in the mold, which can significantly improve the solidified shell and product quality of alloy steel round bloom. The transient fluid flow, heat transfer, and solidification behavior under different nozzle structures and [...] Read more.

The nozzle structure has an important effect on the fluid flow in the mold, which can significantly improve the solidified shell and product quality of alloy steel round bloom. The transient fluid flow, heat transfer, and solidification behavior under different nozzle structures and mold electromagnetic stirring (M-EMS) are investigated using a 3D transient mathematical model. The results show that a third small recirculation zone appears near the meniscus after the application of the swirling flow nozzle (SFN). The impact depth of SFN is shallower than that of the original submerged entry nozzle (SEN) impact, and the lower circulation zone is shifted upward. The horizontal swirling flow generated by SFN can significantly weaken the washing of the initial shell by high-temperature steel and improve the uneven growth phenomenon of the inner and outer curved solidified shell caused by mold curvature. The swirling flow produced by M-EMS in the mold can also improve the washing of the initial shell by the high-temperature jet and the uneven growth of the inner and outer curved shell. M-EMS can expand the high-temperature zone in the upper part of the mold, promote the superheat dissipation of the molten steel, and promote the growth of the solidified shell. In addition, after the application of M-EMS, the tangential velocity of –15° SFN in the meniscus is smaller, and the resulting liquid level fluctuation is lower at 5.07 mm, which is less likely to produce slag entrapment and is conducive to improving the quality of round bloom. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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17 pages, 5116 KiB

Open AccessArticle

Attempt to Optimize the Corrosion Resistance of HRB400 Steel Rebar with Cr and RE

by Tao Liu, Nannan Li, Chao Liu, Jingshe Li, Tianyi Zhang, Xuequn Cheng and Shufeng Yang

Materials 2022, 15(22), 8269; https://doi.org/10.3390/ma15228269 - 21 Nov 2022

Cited by 6 | Viewed by 2243

Abstract

The corrosion resistance of the HRB400 steel rebar alloyed with Cr and rare earths (RE) was systematically studied from two aspects, including the properties of the passive film and the protectiveness of the rust layer. The results presented that Cr increased the corrosion [...] Read more.

The corrosion resistance of the HRB400 steel rebar alloyed with Cr and rare earths (RE) was systematically studied from two aspects, including the properties of the passive film and the protectiveness of the rust layer. The results presented that Cr increased the corrosion resistance of the steel rebar through stabilizing the passive film and was not involved in the formation of corrosion pits, while the pitting corrosion was initiated by the dissolution of (RE)₂O₂S inclusion, resulting in the local acidification at the bottom of the corrosion pits, which decreased the stability of the passive film. As for the long-term corrosion process, both Cr and RE decreased the corrosion rate of the steel rebar, which was related to the promotion effect on the formation of α-FeOOH in the rust layer from Cr and RE. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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Review

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18 pages, 4365 KiB

Open AccessReview

Channel-Type Induction Heating Tundish Technology for Continuous Casting: A Review

by Ziming Wang, Yue Li, Xiuzhen Wang, Xinlin Li, Qiang Yue and Hong Xiao

Materials 2023, 16(2), 493; https://doi.org/10.3390/ma16020493 - 4 Jan 2023

Cited by 7 | Viewed by 2569

Abstract

With the increasing demand for special steel, the quality of steel has become critical during the continuous casting tundish process. In recent years, tundish heating technology has played a key role in low superheat casting. Toward this, researchers have reported on the metallurgical [...] Read more.

With the increasing demand for special steel, the quality of steel has become critical during the continuous casting tundish process. In recent years, tundish heating technology has played a key role in low superheat casting. Toward this, researchers have reported on the metallurgical effects of induction heating tundish (IHT). From 1984 to date, the channel-type IHT has been investigated in the production of continuous casting of special steel. In this article, the principle of this channel-type IHT technology and equipment composition were illustrated. A brief summary and comments were undertaken on the channel-type IHT, including physical modeling and numerical modeling. The application development trend of tundish induction heating equipment is summarized combined with industrial application data, which provide a reference for a better understanding of the induction heating process of tundish. Full article

(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)

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