Research

18 pages, 13528 KiB

Open AccessArticle

Physical Experiments and Numerical Simulations of the Influence of Turbulence Inhibitors and the Position of Ladle Shroud on the Steel Flow in an Asymmetric Five-Strand Tundish

by Josef Walek, Markéta Tkadlečková, Marek Velička, Mario Machů, Jiří Cupek, Tomáš Huczala, Jiří Cibulka, Jan Růžička and Karel Michalek

Metals 2023, 13(11), 1821; https://doi.org/10.3390/met13111821 - 29 Oct 2023

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Abstract

The submitted article deals with the use of physical and numerical modelling to study the process of the steel flow in an asymmetric five-strand tundish that continuously casts steel. For the purposes of physical modelling, a 1:4-scale plexiglass model was used as the [...] Read more.

The submitted article deals with the use of physical and numerical modelling to study the process of the steel flow in an asymmetric five-strand tundish that continuously casts steel. For the purposes of physical modelling, a 1:4-scale plexiglass model was used as the operating tundish, and for numerical modelling, the geometry of the operating tundish was created on a 1:1 scale. A model liquid (water) was used in the physical modelling of the melt flow process, while liquid steel was used as the standard flowing medium in the numerical modelling. We assessed the relevant operating parameters influencing the characteristics of the flow of the bath in the tundish—the shape of the turbulence inhibitor, the position of the ladle shroud in relation to the turbulence inhibitor and the distance between the ladle shroud orifice and the bottom of the turbulence inhibitor. The preliminary results show that optimal steel flow characteristic results are achieved by using the TI3-C configuration. The results from both modelling methods achieved the same characteristics, therefore verifying the results of each other and demonstrating that when taken together, the results of physical and numerical modelling can be considered sufficiently informative. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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16 pages, 6265 KiB

Open AccessArticle

Effect of Mg-Ce Treatment on Inclusion Characteristics and Pitting Corrosion Behavior in EH420 Marine Steel

by Zhihong Guo, Erkang Liu, Qi Wang, Xiangjie Lou, Hongbo Liu, Yaxu Zheng, Bo Wang and Liguang Zhu

Metals 2023, 13(7), 1244; https://doi.org/10.3390/met13071244 - 07 Jul 2023

Viewed by 807

Abstract

Reasonable regulation of nonmetallic inclusions in steel can significantly improve its strength, toughness, and corrosion resistance. In this paper, EH420 marine steel was treated with Mg, Ce, and Mg-Ce to modify the inclusions. The effects of different treatments on the morphology, composition, size [...] Read more.

Reasonable regulation of nonmetallic inclusions in steel can significantly improve its strength, toughness, and corrosion resistance. In this paper, EH420 marine steel was treated with Mg, Ce, and Mg-Ce to modify the inclusions. The effects of different treatments on the morphology, composition, size distribution, induced intragranular ferrite (IGF) nucleation, and pitting resistance of inclusions were systematically analyzed using various methods. The results show that the Mg-Ce composite treatment can modify irregular MgAl₂O₄ inclusions into spherical Mg-Ce-O composite inclusions and MgO-dominated inclusions. The density of inclusions is increased from 74.8/mm² to 186.0/mm², and the average size of inclusions is decreased from 2.60 μm to 1.07 μm. The Mg-Ce-O composite inclusions are effective inclusions for inducing IGF. Furthermore, the pitting potential is increased from −503 mV to −487 mV, and the corrosion rate is decreased. The order of average electronic work function is ΦMgO < ΦCe₂O₃ < Φα-Fe < ΦAl₂O₃. Ce₂O₃ is hard to induce pitting corrosion due to its similar electronic work function to the steel matrix. Thus, the Mg-Ce composite treatment is better than that for Mg and Ce treatment alone, and has better application prospects. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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14 pages, 11066 KiB

Open AccessArticle

Efficiently Removing Hydrogen of H-Supersaturated Liquid Steel in the Vacuum Degasser with Various Gas Injection Modes

by Bing Dai, Mingming Li, Yu Yang, Lei Shao and Zongshu Zou

Metals 2023, 13(7), 1229; https://doi.org/10.3390/met13071229 - 03 Jul 2023

Viewed by 1232

Abstract

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 [...] Read more.

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 article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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10 pages, 13392 KiB

Open AccessCommunication

Influence of Slag and Refractory Materials on Inclusions during the Ladle Refining of Low Carbon Aluminum Killed Steel

by Fubin Gao, Fuming Wang, Min Jiang, Jianli Li and Xiang Zhang

Metals 2023, 13(5), 866; https://doi.org/10.3390/met13050866 - 29 Apr 2023

Cited by 1 | Viewed by 1156

Abstract

The evolution of inclusions in low carbon Al killed steel during ladle refining of was studied based on industrial experiments, in which high basicity slag was used. The results showed that inclusions experienced the changes from Al₂O₃ → MgO-Al₂ [...] Read more.

The evolution of inclusions in low carbon Al killed steel during ladle refining of was studied based on industrial experiments, in which high basicity slag was used. The results showed that inclusions experienced the changes from Al₂O₃ → MgO-Al₂O₃ → CaO-MgO-Al₂O₃ → CaO-Al₂O₃. Without calcium treatment, MgO-Al₂O₃ inclusion in steel were largely transformed into CaO-MgO-Al₂O₃ or CaO-Al₂O₃. With the aim to decrease MgO-Al₂O₃ inclusions and to clarify the effects of refining slag and refractory materials on inclusions, laboratory experiments were performed with lower basicity refining slag (lower basicity slag theoretically helps reduce spinel-type inclusions) in MgO and Al₂O₃ crucibles. The results indicated that, the dissolved Al in liquid steel would react with MgO and CaO in slag or in refractory at 1600 °C. Hence, [Mg] and [Ca] would be supplied into bulk steel. Due to the large contact area between MgO-based refractory and steel, as well as the higher activity of MgO in the refractory, Mg can be more easily reduced, which accounts for the easy modification of Al₂O₃ into MgO-Al₂O₃. By contrast, because of the limited supply of [Ca] to steel, modification of MgO-Al₂O₃ into CaO-MgO-Al₂O₃ or CaO-Al₂O₃ was incomplete. With the use of Al₂O₃-based refractory and reefing slag basicity of about 2.45, MgO-Al₂O₃ inclusions were obviously decreased. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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14 pages, 2454 KiB

Open AccessArticle

Automatic Casting Control Method of Continuous Casting Based on Improved Soft Actor–Critic Algorithm

by Xiaojun Wu, Wenze Jiang, Sheng Yuan, Hongjia Kang, Qi Gao and Jinzhou Mi

Metals 2023, 13(4), 820; https://doi.org/10.3390/met13040820 - 21 Apr 2023

Cited by 1 | Viewed by 1609

Abstract

Continuous casting production is an important stage in smelting high-quality steel, and automatic casting control based on artificial intelligence is a key technology to improve the continuous casting process and the product quality. By controlling the opening degree of the stopper rod reasonably, [...] Read more.

Continuous casting production is an important stage in smelting high-quality steel, and automatic casting control based on artificial intelligence is a key technology to improve the continuous casting process and the product quality. By controlling the opening degree of the stopper rod reasonably, the mold can be filled with liquid steel stably in the specified time window, and automatic casting can be realized. In this paper, an automatic casting control method of continuous casting based on an improved Soft Actor–Critic (SAC) algorithm is proposed. Firstly, a relational model of the stopper rod opening degree and the liquid steel outflow velocity is established according to historical casting data. Then the Markov Decision Process (MDP) model of the automatic casting problem and the reinforcement learning framework based on the SAC algorithm are established. Finally, a Heterogeneous Experience Pool (HEP) is introduced to improve the SAC algorithm. According to the simulation results, the proposed algorithm can predict the stopper rod opening degree sequence under the constraint of the target liquid level curve. Under different billet specifications and interference conditions, an accuracy of 80% of liquid level in the mold and a stopper rod opening degree stability rate of 75% can be achieved, which is 4.29% and 3.17% higher than those for the baseline algorithms, respectively. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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12 pages, 9808 KiB

Open AccessFeature PaperArticle

Research and Application of the Original Position Statistical Distribution Analysis Method for Non-Metallic Inclusions in P91 Steel

by Changwang Zhu, Lixia Yang, Lei Zhao, Yue Ma, Yang Wang, Xuejing Shen and Haizhou Wang

Metals 2023, 13(4), 793; https://doi.org/10.3390/met13040793 - 17 Apr 2023

Viewed by 1060

Abstract

Heat-resistant P91 martensitic steel is used to produce high-temperature steam pipelines in (ultra) critical power plants. However, non-metallic inclusions are inevitably produced in the metallurgical process. The type, composition, morphology, quantities, size and distribution of these inclusions have significant influences on the properties [...] Read more.

Heat-resistant P91 martensitic steel is used to produce high-temperature steam pipelines in (ultra) critical power plants. However, non-metallic inclusions are inevitably produced in the metallurgical process. The type, composition, morphology, quantities, size and distribution of these inclusions have significant influences on the properties of materials. The present work developed an original position statistical distribution analysis method to characterize non-metallic inclusions in P91 steel based on scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). Two samples from P91 steel pipes fabricated by different processes were examined. The non-metallic inclusions in these samples could be divided into spherical oxides, strand-shaped oxides, spherical sulfides, spherical oxygen–sulfur compounds, strip sulfides and other inclusions. The amount, proportional area, particle sizes, original positions and statistical distribution results of non-metallic inclusions in different processed samples were assessed, and the causes and effects of these inclusions were analyzed. This novel method could provide diversified information on inclusions, which is helpful for the improvement of metallurgical processes and service performance evaluations. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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15 pages, 4549 KiB

Open AccessArticle

Flow Behavior of Liquid Steel in Fewer Strands Casting of Six-Strand Bloom Tundish

by Xianyang Wang, Sijie Wang, Hao Hu, Xin Xie, Chenhui Wu, Dengfu Chen and Mujun Long

Metals 2023, 13(4), 706; https://doi.org/10.3390/met13040706 - 04 Apr 2023

Viewed by 916

Abstract

In continuous casting, it is common to close single or multiple submerged nozzles of multi-strands tundish to adapt to production rhythm due to insufficient liquid steel or equipment failure. However, the closure of the nozzle will change the flow field in the tundish [...] Read more.

In continuous casting, it is common to close single or multiple submerged nozzles of multi-strands tundish to adapt to production rhythm due to insufficient liquid steel or equipment failure. However, the closure of the nozzle will change the flow field in the tundish and further affect the removal efficiency of inclusions in the tundish. For this reason, based on numerical simulation, the flow behavior of liquid steel and the removal of inclusion in tundish with different nozzle closed were studied, and the optimal nozzle closing scheme was obtained, which provided a basis for the selection of nozzle closing in tundish. At the same time, the gas curtain is set in the tundish to alleviate the negative effects such as the increase of dead zone caused by closing nozzle. The results show that the removal rate of inclusions with sizes 10, 30, 50, 70, and 90 μm change from 12.4%, 39.1%, 74.2%, 93.3%, and 95.6% to 14.7%, 36.4%, 76.4%, 85.3%, and 93.8%, respectively. The volume of the tundish dead zone is increased after closure of nozzle, the dead zone of the tundish is improved when the gas is installed, and the dead zone volume was reduced from 14.8% and 16.4% to 13.9 and 14.1%. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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11 pages, 79942 KiB

Open AccessCommunication

In-Situ Observation of Steel/Slag/Inclusion Interaction by Means of High-Temperature Confocal Scanning Laser Microscopy

by Julian Cejka and Susanne Katharina Michelic

Metals 2023, 13(4), 686; https://doi.org/10.3390/met13040686 - 30 Mar 2023

Cited by 3 | Viewed by 1160

Abstract

Non-metallic inclusions (NMIs) in steels have been the focus of various experimental studies due to their detrimental character. While isolated processes, such as agglomeration or dissolution, have been well investigated, holistic in-situ views with high-temperature confocal scanning laser microscopy (HT-CSLM) have been rare. [...] Read more.

Non-metallic inclusions (NMIs) in steels have been the focus of various experimental studies due to their detrimental character. While isolated processes, such as agglomeration or dissolution, have been well investigated, holistic in-situ views with high-temperature confocal scanning laser microscopy (HT-CSLM) have been rare. In this work a novel and suitable method is presented to simultaneously observe agglomeration, movement, detachment, and dissolution of non-metallic inclusions by combined the melting of steel and slag with a dual-crucible approach. Therefore, different steel/slag combinations were tested. It is shown that, with transparent that does not become tarnished by the ions stemming from the steel, the steel’s surface and non-metallic inclusions are observable. Furthermore, technological limitations are discussed, including restrictions regarding the melting point of steels and certain steel/slag combinations. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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13 pages, 2951 KiB

Open AccessArticle

Analysis of Uneven Wear Mechanism of Narrow-Face Copper Wall of Funnel Mold

by Zengxun Liu, Yaosen Yang, Pengcheng Xiao, Liguang Zhu and Luping Zhang

Metals 2023, 13(4), 666; https://doi.org/10.3390/met13040666 - 28 Mar 2023

Viewed by 826

Abstract

In thin-slab continuous casting, due to the influence of the special shape of the funnel mold, cracks at the corner of the slab shell are more likely to occur than those in conventional slab shells, and a serious wear phenomenon also appears on [...] Read more.

In thin-slab continuous casting, due to the influence of the special shape of the funnel mold, cracks at the corner of the slab shell are more likely to occur than those in conventional slab shells, and a serious wear phenomenon also appears on the narrow face of the copper wall of the mold. Aimed at the corner cracks of thin slabs and the wear phenomenon of the copper wall, a new 3D stress analysis model in a funnel mold has been developed to simulate the stress-–train behavior of the slab shell under high-speed continuous casting. The results show that at the position 600 mm below the meniscus, the gap begins to appear at the corner of the slab; the maximum value of the first principal stress appears at the corner. The shell is squeezed by the copper wall during the downward movement in the funnel mold, and the slab shell in the funnel area moves towards the narrow face. The displacement causes the deformation of the slab shell to extend to the corners, the deformed shell is pressed against the corner of the copper wall. A new type of copper wall was designed for production, and it was found that the cracks at the corner of the slab shell were greatly reduced. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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14 pages, 7375 KiB

Open AccessArticle

Physical Simulation Study on Flow Field Characteristics of Molten Steel in 70t Ladle Bottom Argon Blowing Process

by Zhiwei Li, Wei Ouyang, Zhongliang Wang, Ruixuan Zheng, Yanping Bao and Chao Gu

Metals 2023, 13(4), 639; https://doi.org/10.3390/met13040639 - 23 Mar 2023

Cited by 2 | Viewed by 1251

Abstract

In the LF refining process, argon blowing at the bottom of ladle can play an important role in unifying the composition and temperature of molten steel and removing inclusions. However, unreasonable bottom argon blowing process can also cause many problems. Slag entrapment and [...] Read more.

In the LF refining process, argon blowing at the bottom of ladle can play an important role in unifying the composition and temperature of molten steel and removing inclusions. However, unreasonable bottom argon blowing process can also cause many problems. Slag entrapment and slag surface exposure may occur, affecting the steel quality. Since the working conditions of different enterprises are very different, corresponding optimization is required for specific parameters. There were some problems in 70t ladle of a steel plant, such as unclear control of bottom argon blowing system in different refining periods, unobvious floating removal effect of inclusions in ladle, high total oxygen content and large fluctuation, etc. In this study, a 1:3 physical model was established according to the similarity principle. Then, on this basis, the experimental schemes with different blowing hole positions and argon flow rates were designed for simulation experiments. By means of mixing time measurement, flow field display and oil film measurement, the optimal argon blowing position was double holes 6, 12 (2/3R), and the included angle between them was 135°. The optimal argon flow rate for wire feeding and soft blowing should be 7.6 L/min (corresponding to the actual production of 180 L/min) and 0.6 L/min (corresponding to the actual production of 15 L/min), respectively. According to this scheme, the industrial experiments showed that the contents of total oxygen and nitrogen in the whole process were reduced, the surface density of inclusions in billet was reduced by 11.81% on average, and calcium sulfide and various inclusions containing aluminum were reduced to varying degrees. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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12 pages, 13890 KiB

Open AccessArticle

Evaluation and Analysis of the Influence of Rare-Earth Ce on Inclusions in Heavy Rail Steel

by Guojun Bai, Jichun Yang and Wenjing Liang

Metals 2023, 13(3), 614; https://doi.org/10.3390/met13030614 - 19 Mar 2023

Cited by 3 | Viewed by 1063

Abstract

The effect of rare-earth Ce on the evolution behaviour of inclusions in heavy rail steel was studied. The addition of Ce can significantly reduce the number and size of class A, B, D, and Ds inclusions in the heavy rail steel smelting process. [...] Read more.

The effect of rare-earth Ce on the evolution behaviour of inclusions in heavy rail steel was studied. The addition of Ce can significantly reduce the number and size of class A, B, D, and Ds inclusions in the heavy rail steel smelting process. According to the statistical analysis of the size of inclusions in steel, the number and size of A and B inclusions in steel tend to decrease significantly, while D and Ds inclusions disappear. Ce splits the aluminium inclusion into several small-sized inclusions and improves the morphology of the large-size aluminium inclusion, thereby making aggregation and growth difficult while facilitating easy floating and removal. Because the addition of Ce reduces the concentration of S element in steel, MnS inclusions are difficult to grow. The decrease in the number and size of core inclusions required for MnS growth leads to a corresponding decrease in the number and size of MnS inclusions. Meanwhile, the S element also easily gathers on the surface of CaO–MgO–Al₂O₃–SiO₂–CeO inclusions, forming composite inclusions that are more easily removed, thus reducing the quantity and size of MnS inclusions. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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13 pages, 2881 KiB

Open AccessArticle

Effect of Different Power Supply Modes on Inclusion in 304L Stainless Steel Electroslag Ingot

by Xiaofang Shi, Bingjie Wang, Yu Wang and Lizhong Chang

Metals 2023, 13(3), 457; https://doi.org/10.3390/met13030457 - 22 Feb 2023

Cited by 1 | Viewed by 1115

Abstract

The use of low frequency or DC (i.e., direct current) operation in the electroslag remelting process may lead to the electrolysis of some oxides in the slag pool, which will adversely affect the cleanliness of the electroslag ingot. In order to confirm this [...] Read more.

The use of low frequency or DC (i.e., direct current) operation in the electroslag remelting process may lead to the electrolysis of some oxides in the slag pool, which will adversely affect the cleanliness of the electroslag ingot. In order to confirm this view, the effect of different power supply modes on the oxygen content and inclusions in electroslag ingot has been studied by adopting the self-designed electroslag remelting furnace as experimental equipment. The pulse heating inert gas fusion-infra-red absorption method is used for analyzing oxygen content. The analysis of non-metallic inclusion is conducted using an automatic SEM (i.e., scanning electron microscope) made by the American ASPEX Company, where the inclusion type and the inclusion size are determined. Results show that the oxygen content in the electroslag ingot increase significantly compared with that in the consumable metal electrode, whether under the frequency of 50 Hz, low-frequency, or DC. When DCSP (i.e., the consumable electrode is connected to the cathode of the DC power supply), DCRP (i.e., the consumable electrode is connected to the anode of the DC power supply), 2 Hz, 10 Hz, and 50 Hz power supply modes are adopted, the oxygen content in electroslag ingot is 155.3 ppm, 100.4 ppm, 75.8 ppm, 66.3 ppm, and 43.2 ppm respectively. With the increase in oxygen content, the number of inclusions in electroslag ingots increases significantly, and the increased inclusions are mainly Al₂O₃ inclusions. Regardless of the power supply mode, the largest diameter of inclusion is less than 20 μm. The electrolysis of Al₂O₃ is the direct reason for the increase in oxygen in the electroslag ingot when CaF₂-Al₂O₃ slag is used. With the decrease in frequency, the electrolysis trend increases, and the oxygen content and the number of inclusions also increase. However, most of the inclusions are regenerated with the decrease in metal pool temperature and solidification, so the size is fine. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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9 pages, 2452 KiB

Open AccessCommunication

Removal of Residual Element Antimony from Molten Steel by CaC₂-Containing Refining Slag

by Zihong Chen, Mengke Liu, Guojun Ma, Xiang Zhang, Tianyu Du and Zhengliang Xue

Metals 2023, 13(3), 441; https://doi.org/10.3390/met13030441 - 21 Feb 2023

Cited by 1 | Viewed by 1006

Abstract

Increasing the use of steel scrap and enhancing its recycling utilization are important strategies for fostering the low-carbon and environmental-friendly growth of the iron and steel industry in China. However, the current steelmaking processes cannot efficiently remove the residual elements in the scrap, [...] Read more.

Increasing the use of steel scrap and enhancing its recycling utilization are important strategies for fostering the low-carbon and environmental-friendly growth of the iron and steel industry in China. However, the current steelmaking processes cannot efficiently remove the residual elements in the scrap, such as Cu, Sn, As, and Sb. As a result, the above elements are recycled and accumulate in the scrap, which will eventually have a negative impact on the properties of steel. Currently, there are few studies on Sb removal from molten steel. To remove the residual element Sb in molten steel, the CaO-SiO₂-Al₂O₃ refining slag system containing CaC₂ was used, and the effect of the CaC₂ content in the molten slag, slag quantity, smelting temperature, and initial Sb and C contents in molten steel on the Sb removal ratio in the steel was investigated, and the mechanism of Sb removal by the aforementioned refining slag system was discussed in order to provide some experimental and theoretical basis for industrialization practice. When the smelting time is 5~10 min, the removal ratio of Sb from molten steel is at its peak and can reach 45.8%. The ”Sb-reversion” phenomenon will appear in the molten steel when the smelting period is progressively extended. In molten steel, CaC₂ will preferentially react with O and S, and as the smelting temperature decreases, the distribution ratio of Sb, L_Sb, improves. An increased initial Sb content in molten steel and slag quantity are beneficial to improving the removal ratio of Sb, but an increased initial C content in molten steel is detrimental to the progress of the Sb removal reaction. The removal reaction of Sb from molten steel by CaC₂ is a reversible reaction, and the diffusion of the products from the interface is the limiting factor of the overall reaction. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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12 pages, 3832 KiB

Open AccessArticle

Influence of FeS₂ and FeSi75 in Double-Chamber Sample Cup on Thermal Analysis Curve and Graphite Morphology of Molten Iron

by Ailong Jiang, Xuelei Tian, Dequan Shi, Dan Li and Guili Gao

Metals 2023, 13(2), 302; https://doi.org/10.3390/met13020302 - 01 Feb 2023

Viewed by 1059

Abstract

In the production of vermicular graphite cast iron, the allowable range of residual magnesium content in molten iron after treatment is very narrow, amounting to only 0.008%. Therefore, thermal analysis technology was used to quickly evaluate the vermiculation and inoculation level of molten [...] Read more.

In the production of vermicular graphite cast iron, the allowable range of residual magnesium content in molten iron after treatment is very narrow, amounting to only 0.008%. Therefore, thermal analysis technology was used to quickly evaluate the vermiculation and inoculation level of molten iron at the furnace itself, thus allowing the molten iron to be adjusted in time. The additives in the sample cups play a crucial role in obtaining cooling curves with remarkable characteristics. In this study, either FeS₂ or FeSi75 additives were added to one chamber of a double-chamber sample cup made of resin sand, in which the cavities of the double chambers were spherical with diameters of 30 mm. The thermal analysis curves of molten iron in the double-chamber sample cup were acquired using a double channel temperature recorder, and the solidified spherical samples were analyzed quantitatively. The influence of FeS₂ or FeSi75 additives on both the cooling curves of molten iron and the graphite morphology were investigated. The experiment’s results indicated that when 0.05% FeS₂ is added to one chamber of the sample cup, the cooling curve changes to the solidification pattern of gray cast iron. The continuous increase in the FeS₂ additive has little influence on the shape of cooling curves, and the graphite changes form from vermicular to flaked. When the amount of FeS₂ is increased from 0.05% to 0.10%, the resulting graphite changes from D-type and E-type to A-type and B-type. When the amount of FeS₂ reaches 0.20%, the morphology of graphite is short and thick. With the increase in the amount of FeSi75 additive, the amount of spherical graphite in the sample cup increases gradually, and the vermicularity decreases gradually from 89% to 46%. With the increase in FeSi75 additive from 0 to 0.45%, we observed that the average diameter of graphite decreases from 23 μm to 19 μm and then increases to 22 μm. The eutectic recalescence temperature shows a decreasing trend, and the cooling curve gradually changes from a hypoeutectic to a eutectic pattern. The addition of 0.05% FeS₂ or 0.45% FeSi75 to one chamber is more appropriate for a double-chamber sample cup with two spherical cavities with diameters of 30 mm. This lays a foundation for the optimization of additives when using the double-chamber sample cup for thermal analysis of vermicular graphite cast iron. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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15 pages, 4583 KiB

Open AccessArticle

Simulation of Fluid Flow and Inclusion Removal in Five-Flow T-Type Tundishes with Porous Baffle Walls

by Shuo Zhao, Shibin Zhu, Yangyang Ge, Jianfeng Wang, Dong Xu, Zushu Li and Chao Chen

Metals 2023, 13(2), 215; https://doi.org/10.3390/met13020215 - 23 Jan 2023

Cited by 1 | Viewed by 1233

Abstract

To solve the instability of liquid steel in the continuous casting process and the inconsistent flaw detection of heavy rail steel, steel flow control was studied numerically in a tundish with a porous baffle wall by using the fluid dynamics software Fluent. The [...] Read more.

To solve the instability of liquid steel in the continuous casting process and the inconsistent flaw detection of heavy rail steel, steel flow control was studied numerically in a tundish with a porous baffle wall by using the fluid dynamics software Fluent. The opening plan of the baffle wall was improved through orthogonal optimization of the design of the holes in the porous baffle wall. The test condition was set to a left inclination angle of α₁ = 22°, a right inclination angle of α₂ = 48°, an upward elevation angle of β = 30°, and an aperture of d = 70 mm. The simulation results of the optimization scheme showed that the uniformity of the flow and temperature fields had been significantly improved, and the flow in each strand became consistent. The maximum temperature difference was 21 K in the tundish, and the maximum temperature difference of three outlets was only 1.7 K. Dead zone volume was reduced by 10.0% compared to the original tundish, and plug flow volume was increased by 14.2%. Comparing the removal efficiency of Al₂O₃ inclusions of different size, the results showed that the removal efficiency of 10 μm and 30 μm smaller inclusions was above 87%. The removal rate of ≥50 μm larger inclusions also remained about 95%. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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8 pages, 2566 KiB

Open AccessArticle

Effect of Sulfur on Antimony-Induced High-Temperature Ductility Deterioration of C-Mn Steel

by Guilin Sun, Guochun Dong, Sufen Tao, Yunjin Xia and Chao Chen

Metals 2023, 13(1), 130; https://doi.org/10.3390/met13010130 - 09 Jan 2023

Cited by 1 | Viewed by 1170

Abstract

The recycling of steel scrap is becoming more and more developed to save resources and protect the environment. However, impurities such as antimony in steel scrap cannot be economically and effectively removed, resulting in an inevitable accumulation of impurities. Once the impurity concentration [...] Read more.

The recycling of steel scrap is becoming more and more developed to save resources and protect the environment. However, impurities such as antimony in steel scrap cannot be economically and effectively removed, resulting in an inevitable accumulation of impurities. Once the impurity concentration exceeds a certain limit, they will have a great impact on the ductility deterioration and hot shortness of steel. It has been shown that sulfide can inhibit the precipitation of residual elements, such as copper at grain boundaries, in steel. The effect of sulfur on the thermoplasticity of antimony-containing C-Mn steel at 700–1100 °C was examined using a Gleeble 1500 thermodynamic simulation device (Gleeble, Poestenkill, NY, USA). Area reduction (RA%) was used to evaluate the thermal ductility. The 0.16 mass % Sb extended the range of the ductile grooves, reducing the RA% at 750–950 °C. Antimony (Sb) was found to segregate at the boundaries tested by an electron probe microanalyzer. Additionally, scanning electron microscopy was used to examine the fracture morphology, which exhibited the characteristics of intergranular failure. In contrast, the addition of sulfur to the steel compensated for the deterioration of the thermal ductility caused by the Sb. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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16 pages, 3414 KiB

Open AccessArticle

Effect of Ca/Mg on Distribution and Morphology of MnS Inclusions in 45MnVS Non-Quenched and Tempered Steel

by Lijuan Su, Jun Tian, Shaoyan Hu, Ming Lv, Xianglong Li, Tianpeng Qu, Deyong Wang and Tianyin Zhan

Metals 2023, 13(1), 23; https://doi.org/10.3390/met13010023 - 22 Dec 2022

Cited by 3 | Viewed by 1335

Abstract

The influence of Ca treatment, Mg treatment and Ca–Mg combined treatment on the inclusions in 45MnVS non-quenched and tempered steel were studied in the present work. After the melting experiment, a hot rolling test was carried out on the steel ingot. Additionally, the [...] Read more.

The influence of Ca treatment, Mg treatment and Ca–Mg combined treatment on the inclusions in 45MnVS non-quenched and tempered steel were studied in the present work. After the melting experiment, a hot rolling test was carried out on the steel ingot. Additionally, the composition, quantity and morphology of inclusions in the test steel samples were analyzed by automatic scanning electron microscopy (ASPEX) and an energy dispersive X-ray spectrometer connected to scanning electron microscope (SEM-EDS). The results indicated that the inclusions in 45MnVS steel mainly consisted of a large amount of sulfides and a small amount of oxides. Sulfide inclusions could be nucleated and precipitated using oxides as a core during solidification. The proportion of spindle-shaped inclusions in sulfide with smaller sizes was higher. The sizes of MnS–oxide inclusions were larger than those of MnS. After hot rolling, the proportion of spindle-shaped MnS and complex sulfides with oxide cores in the samples was increased significantly. Compared with Ca treatment and Ca–Mg treatment, more oxides were formed in the steel with Mg treatment, which can in turn become the cores for sulfide nucleation and precipitation. Thus, the proportion of MnS–oxide inclusions in steel increased. Compared with Ca treatment and Mg treatment, steel with Ca–Mg treatment was more conducive to the formation of complex sulfides, and increased the proportion of spindle-shaped sulfides in 45MnVS steel. After Ca treatment, Mg treatment and Ca–Mg combined treatment, the proportions of spindle-shaped sulfides in steel were 23.31%, 19.39% and 43.24%, respectively. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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12 pages, 6292 KiB

Open AccessEditor’s ChoiceArticle

Performance of a Nozzle to Control Bath Level Oscillations and Turbulence of the Metal-Flux Interface in Slab Molds

by María Guadalupe González-Solórzano, Rodolfo Davila Morales, Javier Guarneros, Carlos Rodrigo Muñiz-Valdés and Alfonso Nájera Bastida

Metals 2022, 12(1), 140; https://doi.org/10.3390/met12010140 - 12 Jan 2022

Cited by 3 | Viewed by 1586

Abstract

The characterization of the turbulent flow of liquid steel in a slab mold using a commercial nozzle was carried out through physical experiments and mathematical models. Six ultrasonic sensors were located at each side of the nozzle to obtain real-time plotting of the [...] Read more.

The characterization of the turbulent flow of liquid steel in a slab mold using a commercial nozzle was carried out through physical experiments and mathematical models. Six ultrasonic sensors were located at each side of the nozzle to obtain real-time plotting of the bath levels during the experimental time. An ultrasonic transducer located in the mold, 20 mm below the meniscus, determines the velocities and the turbulent variables along with the distance from the narrow face to the position of the nozzle’s outer wall. These data, together with the mathematical simulations, demonstrated a high correlation of bath level oscillations and the time-dependent behavior of the discharging jets. The flow inside the mold shows low-frequency non-symmetric patterns without a severe turbulent in the meniscus. The source of this instability is the partial opening of the slide valve gate used to control the mass flow of liquid. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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21 pages, 3272 KiB

Open AccessArticle

A Simulation-Based Digital Design Methodology for Studying Conjugate Heat Transfer in Tundish

by Dong-Yuan Sheng and Christian Windisch

Metals 2022, 12(1), 62; https://doi.org/10.3390/met12010062 - 28 Dec 2021

Cited by 6 | Viewed by 2102

Abstract

The successful design of refractory lining for a tundish is critical due to the demand of superheat control, improvement of steel cleanliness and reduction in material cost during continuous casting. A design of experiment analysis, namely, the Taguchi method, was employed to analyze [...] Read more.

The successful design of refractory lining for a tundish is critical due to the demand of superheat control, improvement of steel cleanliness and reduction in material cost during continuous casting. A design of experiment analysis, namely, the Taguchi method, was employed to analyze two-dimensional heat transfer through refractory linings of a single-strand tundish, with the consideration of the thickness and the thermal conductivity of lining materials. In addition, a three-dimensional conjugate heat transfer model was applied in the tundish, taking in account the molten steel flow and heat conduction in the linings. A special focus of this study was to demonstrate the analysis methodology of combining Taguchi and CFD modelling to explore lining design in terms of thickness and thermal conductivity for the given process conditions during tundish operations. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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23 pages, 6244 KiB

Open AccessFeature PaperArticle

Analysis of Non-Symmetrical Heat Transfers during the Casting of Steel Billets and Slabs

by Adán Ramírez-López, Omar Dávila-Maldonado, Alfonso Nájera-Bastida, Rodolfo D. Morales, Jafeth Rodríguez-Ávila and Carlos Rodrigo Muñiz-Valdés

Metals 2021, 11(9), 1380; https://doi.org/10.3390/met11091380 - 31 Aug 2021

Cited by 4 | Viewed by 2236

Abstract

The current automation of steelmaking processes is capable of complete control through programmed hardware. However, many metallurgical and operating factors, such as heat transfer control, require further studies under industrial conditions. In this context, computer simulation has become a powerful tool for reproducing [...] Read more.

The current automation of steelmaking processes is capable of complete control through programmed hardware. However, many metallurgical and operating factors, such as heat transfer control, require further studies under industrial conditions. In this context, computer simulation has become a powerful tool for reproducing the effects of industrial constraints on heat transfer. This work reports a computational model to simulate heat removal from billets’ strands in the continuous casting process. This model deals with the non-symmetric cooling conditions of a billet caster. These cooling conditions frequently occur due to plugged nozzles in the secondary cooling system (SCS). The model developed simulates the steel thermal behavior for casters with a non-symmetric distribution of the sprays in the SCS using different boundary conditions to show possible heat transfer variations. Finally, the results are compared with actual temperatures from different casters to demonstrate the predictive capacity of this algorithm’s approach. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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23 pages, 12050 KiB

Open AccessArticle

Improved Metallurgical Effect of Tundish through a Novel Induction Heating Channel for Multistrand Casting

by Haiyan Tang, Kaimin Wang, Xiaosong Li, Jinwen Liu and Jiaquan Zhang

Metals 2021, 11(7), 1075; https://doi.org/10.3390/met11071075 - 05 Jul 2021

Cited by 14 | Viewed by 2652

Abstract

Tundish with channel-type induction heating is one of new technologies adopted widely in China by the steel industry in the recent years, which can supply a constant liquid steel temperature control for the sequenced continuous casting process. For a five-strand tundish with induction [...] Read more.

Tundish with channel-type induction heating is one of new technologies adopted widely in China by the steel industry in the recent years, which can supply a constant liquid steel temperature control for the sequenced continuous casting process. For a five-strand tundish with induction heating in service, a kind of novel bifurcated split channel has been designed to solve the poor consistency of temperature and fluid flow for each strand that occurs with the conventional straight channel-type. The temperature distribution and fluid flow behaviors under the two structure modes were compared numerically by an electromagnetic-heat-flow multi-physics field coupling model. The results show that the maximum temperature difference between each strand outlet of the tundish can drop to less than 4 °C upon using the bifurcated channel, as compared to 10 °C under the original straight channel mode. According to the simulated results, case FK-A0 has been chosen as the optimized structure for industrial application. It has been verified through temperature measurements during the casting operation that the novel bifurcated split channel can improve the consistency of steel temperature for every strand of the tundish. The average temperature difference between the edge strand and the middle strand is 4.25 °C lower than the original straight channel, resulting in an upgraded metallurgical effect for the induction heated tundish. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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19 pages, 5947 KiB

Open AccessArticle

Comparison of Fluid Flow and Temperature Distribution in a Single-Strand Tundish with Different Flow Control Devices

by Dong-Yuan Sheng and Dengfu Chen

Metals 2021, 11(5), 796; https://doi.org/10.3390/met11050796 - 14 May 2021

Cited by 12 | Viewed by 2696

Abstract

The effects of flow control devices (FCD) in a single-strand tundish, including weir, dam, turbulence inhibitor and gas curtain, have been investigated using water model experiments and CFD simulations. A scaled-down water model was built up to visualize flow pattern and measure the [...] Read more.

The effects of flow control devices (FCD) in a single-strand tundish, including weir, dam, turbulence inhibitor and gas curtain, have been investigated using water model experiments and CFD simulations. A scaled-down water model was built up to visualize flow pattern and measure the residence-time distribution (RTD) of different tundish configurations. A CFD model was applied to calculate the fluid flow, heat transfer and RTD curves in the prototype tundish under the nonisothermal conditions. The Eulerian–Lagrangian approach was applied to investigate the bubble flow in the system. The results show that each FCD has its own unique function to control the flow. It is important to evaluate the combined effects of FCD based on their installations. The molten steel flow in the tundish could be improved if these flow control devices were arranged properly. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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