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14 pages, 5544 KiB

Open AccessArticle

The Phase Diagram of a CaO-Al₂O₃-VO_x Slag System under Argon Atmosphere at 1500 °C

by Chengjun Liu, Xiaoxiang Xie, Jiyu Qiu, Wenjie Li and Guojie Huo

Metals 2024, 14(1), 108; https://doi.org/10.3390/met14010108 - 16 Jan 2024

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The thermodynamic properties of the CaO-Al₂O₃-VO_x slag system are of great significance to the direct alloying of vanadium in the smelting process of vanadium steel. In this paper, the phase equilibrium relationship of the CaO-Al₂O₃ [...] Read more.

The thermodynamic properties of the CaO-Al₂O₃-VO_x slag system are of great significance to the direct alloying of vanadium in the smelting process of vanadium steel. In this paper, the phase equilibrium relationship of the CaO-Al₂O₃-VO_x system under argon atmosphere at 1500 °C was studied with a high-temperature phase equilibrium experiment. Combined with SEM-EDS, XRD, and XPS, the types and compositions of each phase of the equilibrium slag samples and the content of different valence states of the vanadium element were determined. The result shows that under argon atmosphere (p(O₂) = 10⁻³ atm) at 1500 °C, the CaO-Al₂O₃-VO_x slag system contains four three-phase regions, seven two-phase regions, and a single-phase region (glass phase). The phase equilibrium results were plotted in a CaO-Al₂O₃-V₂O₅-VO₂ spatial phase diagram, and the phase equilibrium results were projected on the CaO-Al₂O₃-V₂O₅ and CaO-Al₂O₃-VO₂ pseudo-ternary phase diagrams, respectively. In the end, the rationality of projecting the phase equilibrium results to the pseudo-ternary phase diagram was quantitatively evaluated. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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11 pages, 2477 KiB

Open AccessArticle

Viscosity Estimation of TiO₂-Bearing Blast Furnace Slag with High Al₂O₃ at 1500 °C

by Haiyan Zheng, Shifa Zhou, Shen Zhang, Yang Li, Baozhi Zhang, Fengman Shen, Zhonghua Wang and Tao Han

Metals 2023, 13(3), 573; https://doi.org/10.3390/met13030573 - 13 Mar 2023

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Abstract

Slag compositions are significant for the viscosity of blast furnace slag. An improved Urbain model (IUM) was proposed by introducing R₅ ((X(CaO) + X(MgO) + 2X(TiO₂))/(2X(SiO₂) + 3X(Al₂ [...] Read more.

Slag compositions are significant for the viscosity of blast furnace slag. An improved Urbain model (IUM) was proposed by introducing R₅ ((X(CaO) + X(MgO) + 2X(TiO₂))/(2X(SiO₂) + 3X(Al₂O₃))) and N (X(MgO)/3X(Al₂O₃)) as the model parameters. By comparing IUM with other models, the model parameters of R₅ and N are more reasonable and suitable for TiO₂-bearing blast furnace slag, and IUM for predicting viscosity has a higher precision, and its relative error is only 10%. The viscosity isolines of the CaO–SiO₂–15%Al₂O₃–MgO–2.5% TiO₂ system were plotted, and the results show that the viscosity center of the slag is between R_w₂ (w(CaO)/w(SiO₂)) = 0.77–1.39 and N_w (w(MgO)/w(Al₂O₃)) = 0–1.37, the value of the viscosity center is 0.3 Pa·s, the viscosity increases gradually from the center to the outside, and the viscosity of the slag gradually decreases with the increase in N_w and R_w₂. Furthermore, FTIR (Fourier Transform Infrared Spectroscopy) analysis was carried out in order to understand the mechanism between the slag structure and viscosity. With the increase in N_w and R_w₂, the peak values of the symmetrical stretching vibration of non-bridging oxygen in the Si–O tetrahedral structure of slag decrease, and the slag structures depolymerize, which leads to the decrease in the viscosity of the slag. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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14 pages, 3544 KiB

Open AccessArticle

Effect of B₂O₃ Addition and CaO/Al₂O₃ Ratios on Melt Structure and Viscosity of CaO–Al₂O₃-Based Slags

by Xiaobo Zhang, Chengjun Liu and Maofa Jiang

Metals 2022, 12(8), 1255; https://doi.org/10.3390/met12081255 - 26 Jul 2022

Cited by 1 | Viewed by 1255

Abstract

The effect of the addition of B₂O₃ and the CaO/Al₂O₃ ratios on the CaO–Al₂O₃–B₂O₃ melts’ structure was fully analyzed by molecular dynamics (MD) simulations. The results show that, with the [...] Read more.

The effect of the addition of B₂O₃ and the CaO/Al₂O₃ ratios on the CaO–Al₂O₃–B₂O₃ melts’ structure was fully analyzed by molecular dynamics (MD) simulations. The results show that, with the increase in CaO/Al₂O₃ ratios, the charge compensation for [AlO₄]⁵⁻ tetrahedron changed from the oxygen tricluster structure to the charge provided by Ca²⁺, and the structure of [AlO₄]⁵⁻ tetrahedron was stabilized. The addition of B₂O₃ reduced the degree of polymerization of the aluminate melt, which, in turn, lowered the melt viscosity; in the systems with CaO/Al₂O₃ mole ratio less than 1, the added B₂O₃ mainly existed in the form of [BO₃]³⁻, which reduced the symmetry and the strength of the melt network structures; in the higher CaO/Al₂O₃ ratio systems, the depolymerization ability of the addition of B₂O₃ on aluminate network structures was enhanced with the increase in CaO/Al₂O₃ ratios, and the overall degree of polymerization of the melt decreased. The viscosity measurement shows that B₂O₃ lowers the viscosity of CaO–Al₂O₃ melts, which was consistent with the results predicted by MD simulations. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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7 pages, 1580 KiB

Open AccessArticle

Study of the Effect of Fluxing Ability of Flux Ores on Minimizing of Copper Losses with Slags during Copper Concentrate Smelting

by Maral Dyussebekova, Bagdaulet Kenzhaliyev, Sergey Kvyatkovskiy, Sultanbek Kozhakhmetov, Anastasiya Semenova and Bulat Sukurov

Metals 2022, 12(8), 1240; https://doi.org/10.3390/met12081240 - 23 Jul 2022

Cited by 1 | Viewed by 1444

Abstract

The article describes the effect of the fluxing ability (FA) of ores used as a flux on slag formation and copper losses. In Kazakhstan, at the Balkhash copper smelting plant (BCSP), currently used fluxes have a very low SiO₂ content—about 62%—whereas the [...] Read more.

The article describes the effect of the fluxing ability (FA) of ores used as a flux on slag formation and copper losses. In Kazakhstan, at the Balkhash copper smelting plant (BCSP), currently used fluxes have a very low SiO₂ content—about 62%—whereas the Al₂O₃ content is 12%. Its fluxing ability (FA) was estimated, and it was shown that currently used silica fluxes have an exceedingly low FA. Only half of the fluxes participate in the slag formation. To obtain slags with a low magnetite concentration, a considerable surplus of flux must be added, which will result in a sharp reduction in its melt temperature, increased slag output, and therefore copper losses. The slag structure was studied by means of scanning electron microscopy and electron probe microanalysis (EPMA). To determine one of the primary causes of flux ores’ low FA, it is necessary to use the microstructural pattern of experimental samples. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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15 pages, 4091 KiB

Open AccessArticle

Effect of Slag Compositions on Change Behavior of Nitrogen in Molten Steel

by Dongping Zhan, Jiaxi Wang, Luoyi Huang and Huishu Zhang

Metals 2022, 12(5), 846; https://doi.org/10.3390/met12050846 - 16 May 2022

Cited by 1 | Viewed by 1868

Abstract

The problem of nitrogen pickup in the smelting process of the electric arc furnace (EAF) has not been solved well. Using seven slag–steel equilibrium experiments and theoretical analysis, the relation of the foaming index and optical basicity with the nitrogen capacity of slag [...] Read more.

The problem of nitrogen pickup in the smelting process of the electric arc furnace (EAF) has not been solved well. Using seven slag–steel equilibrium experiments and theoretical analysis, the relation of the foaming index and optical basicity with the nitrogen capacity of slag was clarified. Meanwhile, the effect of slag composition on the equilibrium distribution ratio of nitrogen and the mass transfer coefficient of nitrogen pickup was also studied. The results show that, with the increase in slag basicity, the nitrogen pickup amount, nitrogen pickup rate, and nitrogen equilibrium distribution ratio L_N increase. Increasing the foaming index of slag and reducing its optical basicity will increase the nitrogen capacity of slag, which is conducive to hindering the nitrogen pickup of molten steel. The relationship between slag optical basicity and nitrogen capacity can be expressed as lgC_N = −5.59lgΛ − 12.41. With the increase in the Al₂O₃ content of slag, the nitrogen pickup amount of molten steel decreases and the nitrogen pickup rate decreases. The test with MgO = 7.5% showed the highest nitrogen pickup rate and the highest nitrogen pickup mass transfer coefficient, which were 0.21 × 10⁻⁴%/min and 1.97 × 10⁻⁴ cm/s, respectively. The test with Al₂O₃ = 7.5% in slag showed the lowest nitrogen pickup rate and the lowest nitrogen pickup mass transfer coefficient, which were 0.08 × 10⁻⁴%/min and 1.35 × 10⁻⁴ cm/s, respectively. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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11 pages, 5485 KiB

Open AccessArticle

Phase Equilibria of CaO-SiO₂-La₂O₃-Nb₂O₅ System in Reducing Atmosphere

by Lifeng Sun, Zhengyue Liu and Maofa Jiang

Metals 2022, 12(5), 768; https://doi.org/10.3390/met12050768 - 29 Apr 2022

Cited by 1 | Viewed by 1170

Abstract

In the current work, the phase equilibria of CaO-SiO₂-La₂O₃-Nb₂O₅ system at 1200 °C in reducing atmosphere (PO₂ = 10⁻¹⁵ atm) was investigated according to the melting separation process for extracting [...] Read more.

In the current work, the phase equilibria of CaO-SiO₂-La₂O₃-Nb₂O₅ system at 1200 °C in reducing atmosphere (PO₂ = 10⁻¹⁵ atm) was investigated according to the melting separation process for extracting lanthanum and niobium resources from Bayan Obo tailing. High temperature equilibrium experiment, scanning electron microscope, and energy dispersive spectrometer (SEM-EDS) were used to determine the compositions of equilibrium phases. According to the experiment results, the phase equilibria of the CaO-SiO₂-La₂O₃-Nb₂O₅ system in reducing atmosphere were ascertained and the 1200 °C isothermal phase diagram of CaO-SiO₂-La₂O₃-Nb₂O₅ system in reducing atmosphere was constructed. The research results not only play an important role in guiding the development of the lanthanum and niobium extraction process, but also enrich the thermodynamic data of relevant silicate slag systems. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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14 pages, 4506 KiB

Open AccessArticle

Study on Reductive Smelting of High-Iron Red Mud for Iron Recovery

by Xuewei Yang, Xin Chen, Tingan Zhang, Jiayuan Ye, Guozhi Lv and Jinshan Zhang

Metals 2022, 12(4), 639; https://doi.org/10.3390/met12040639 - 08 Apr 2022

Cited by 5 | Viewed by 1770

Abstract

In this paper, the characteristics and current problems associated with red mud and the progress of research on iron extraction from high-iron red mud are briefly described. By adding conditioning materials to red mud and quenching and tempering, the iron tailings extracted from [...] Read more.

In this paper, the characteristics and current problems associated with red mud and the progress of research on iron extraction from high-iron red mud are briefly described. By adding conditioning materials to red mud and quenching and tempering, the iron tailings extracted from red mud were reconstructed by heating to form molten tailings in the laboratory. A thermodynamic analysis of the iron reduction reaction during tailings reconstruction was performed, and the best conditions for iron extraction by calcified slag reduction were verified. The contents of CaO, Al₂O₃ and Na₂O in the reduced tailings were 37.07, 37.67 and 0.48%, respectively. According to X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, the main crystalline phases in the calcified extracted iron tailings were C₂AS and CT, which aggregated and met the expected composition standard for calcified extracted iron tailings. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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9 pages, 3105 KiB

Open AccessArticle

The Microstructure Formation in Slag Solidification at Continuous Casting Mold

by Ashutosh G. Bhagurkar and Rongshan Qin

Metals 2022, 12(4), 617; https://doi.org/10.3390/met12040617 - 02 Apr 2022

Cited by 4 | Viewed by 2074

Abstract

The microstructure of slag film solidified on the inner wall of mold in continuous casting of low carbon steel has been examined experimentally and analyzed theoretically. A puzzle for the crystallization sequence has been solved by this work, which is useful to guide [...] Read more.

The microstructure of slag film solidified on the inner wall of mold in continuous casting of low carbon steel has been examined experimentally and analyzed theoretically. A puzzle for the crystallization sequence has been solved by this work, which is useful to guide the modification of slag microstructure in efficient casting of advanced steels. The experiments observed three crystalline bands, each containing an initial block-shaped crystal sub-band and late-developed dendrite sub-band. The grain size and morphology change monotonically across the crystalline layers to form a gradient structure. The reason for this is that the solute segregation causes considerable surging of viscosity and constitutional undercooling in the liquid phase. This is rarely seen in the casting of alloys and have not been pointed out previously in the casting of oxide mixtures. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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11 pages, 4046 KiB

Open AccessArticle

Improving Effect of Graphene on Electrochemical Properties of Fe₂O₃ Anode Materials

by Guanglin Zhu, Bo Gao, Ganfeng Tu, Haifeng Liu and Ming Wang

Metals 2022, 12(4), 593; https://doi.org/10.3390/met12040593 - 30 Mar 2022

Cited by 2 | Viewed by 1447

Abstract

Transition metal oxides have a high initial charge-discharge capacity of 800–1000 mAh/g, the electrochemical performance, cyclic performance and rate performance of the composite of transition metal oxide and graphene have been improved due to the unique two-dimensional structure and excellent electrical conductivity of [...] Read more.

Transition metal oxides have a high initial charge-discharge capacity of 800–1000 mAh/g, the electrochemical performance, cyclic performance and rate performance of the composite of transition metal oxide and graphene have been improved due to the unique two-dimensional structure and excellent electrical conductivity of graphene. In this paper, iron oxides materials with different morphs were prepared by different hydrothermal reaction temperatures, and rGO/Fe₂O₃-175 °C composites with different graphene ratios were synthesized and used in the anode of lithium ion batteries. The results show that nanorod-shaped Fe₂O₃ had better electrochemical performance than spherical Fe₂O₃. 0.2rGO/Fe₂O₃-175 °C had the best cyclic performance, the first cyclic discharge capacity reaches 1372 mAh/g under the current density of 100 mA/g, and the cyclic reversible capacity remained at about 435 mAh/g after 50 cycles, illustrating that nanorods Fe₂O₃ and graphene composites can greatly buffer the volume expansion of Fe₂O₃. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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12 pages, 6482 KiB

Open AccessArticle

Effect of Fe₂O₃ on the Crystallization Behavior of Glass-Ceramics Produced from Secondary Nickel Slag

by Xiaoming Li, Xuyuan Zang, Xiangdong Xing, Jinke Li, Yuwei Ma and Tao Li

Metals 2022, 12(1), 164; https://doi.org/10.3390/met12010164 - 17 Jan 2022

Cited by 7 | Viewed by 1783

Abstract

In this paper, glass-ceramics were prepared from secondary nickel slag by the melting method. The effects of Fe₂O₃ on the crystallization behavior of glass-ceramics were investigated by differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The properties of glass-ceramics [...] Read more.

In this paper, glass-ceramics were prepared from secondary nickel slag by the melting method. The effects of Fe₂O₃ on the crystallization behavior of glass-ceramics were investigated by differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The properties of glass-ceramics such as Vickers hardness, bending strength, and acid and alkali resistance were systematically discussed. The results indicate that the crystallization temperature (Tc) and transition temperature (Tg) of the glass show a trend of decreasing and then increasing with the increase in Fe₂O₃ content. The precipitation and refinement of the crystalline phase were promoted significantly when the Fe₂O₃ content was lower (≤9.32 wt%), while the crystallinity decreased slightly when the Fe₂O₃ content increased to 12.42 wt%. The promotion of crystal precipitation led to the depolymerization of the glass network. When the Fe₂O₃ content was 9.32 wt%, the sample exhibited the best crystallization ability, consisting of uniformly distributed anorthite, ferrobustamite and glass phases, while the Vickers hardness and bending strength were 11.42 GPa and 121 MPa, respectively. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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16 pages, 3612 KiB

Open AccessArticle

Fundamental Research on Fluorine-Free Ladle Furnace Slag for Axle Steel of Electric Multiple Unit Vehicles

by Qing Zhao, Xiaohui Mei, Lei Gao, Jinwen Zhang, Zhixiang Wang, Lifeng Sun, Ron Zevenhoven and Henrik Saxén

Metals 2021, 11(12), 1973; https://doi.org/10.3390/met11121973 - 08 Dec 2021

Cited by 2 | Viewed by 2618

Abstract

Fluorine-bearing refining slag (FBS) is used to produce axle steel for electric multiple unit vehicles. To avoid environmental pollution caused by fluorine, a fluorine-free ladle furnace slag (FFS) was designed based on an industrial FBS. The effects of main components on the physical [...] Read more.

Fluorine-bearing refining slag (FBS) is used to produce axle steel for electric multiple unit vehicles. To avoid environmental pollution caused by fluorine, a fluorine-free ladle furnace slag (FFS) was designed based on an industrial FBS. The effects of main components on the physical and metallurgical properties of slag were investigated via theoretical analysis and laboratory tests. The composition range of components of the designed FFS are w(CaO) = 40–55 wt.%, w(SiO₂) = 2–6 wt.%, w(Al₂O₃) = 30–40 wt.%, w(MgO) = 6–8 wt.%, and w(CaO)/w(Al₂O₃) = 1.25–1.50. Industrial-scale test results indicate that the FFS has similar deoxidation and desulfurization capabilities to industrial FBS. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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15 pages, 6242 KiB

Open AccessArticle

Phase Equilibria in the System CaO-SiO₂-La₂O₃-Nb₂O₅ at 1400 °C

by Chengjun Liu, Jiyu Qiu and Zhengyue Liu

Metals 2021, 11(12), 1892; https://doi.org/10.3390/met11121892 - 24 Nov 2021

Cited by 2 | Viewed by 1779

Abstract

CaO-SiO₂-La₂O₃-Nb₂O₅ system is of great significance for the pyrometallurgical utilization of Bayan Obo tailing resources. In the present work, the phase equilibrium of this quaternary system at 1400 °C was determined by a thermodynamic [...] Read more.

CaO-SiO₂-La₂O₃-Nb₂O₅ system is of great significance for the pyrometallurgical utilization of Bayan Obo tailing resources. In the present work, the phase equilibrium of this quaternary system at 1400 °C was determined by a thermodynamic equilibrium experiment. On the basis of the recently determined CaO-La₂O₃-Nb₂O₅ phase diagram, some boundary surfaces of primary phase fields of CaO-SiO₂-La₂O₃-Nb₂O₅ phase diagram were modified; then, the 1400 °C isothermal surface in the primary phase fields of SiO₂, CaNb₂O₆, Ca₂Nb₂O₇, and LaNbO₄ was constructed, respectively. On this basis, CaO-SiO₂-Nb₂O₅ pseudo-ternary phase diagrams with w(La₂O₃) = 5%, 10%, 15%, and 20% were determined, respectively. Considering the importance of equilibrium crystallization reaction type, we proposed a new rule named Tangent Line Rule to judge the univariant reaction type in the quaternary phase diagram. By applying Tangent Line Rule and Tangent Plane Rule previously proposed, some univariant and bivariant crystallization reaction types in the CaO-SiO₂-La₂O₃- Nb₂O₅ phase diagram were determined, respectively. The current work can provide original data for the establishment of a thermodynamic database of Nb-bearing and REE-bearing slag system; the proposed Tangent Line Rule will promote the application of a spatial quaternary phase diagram. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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15 pages, 608 KiB

Open AccessFeature PaperArticle

Investigation on Vanadium Chemistry in Basic-Oxygen-Furnace (BOF) Slags—A First Approach

by Sophie Wunderlich, Thomas Schirmer and Ursula E. A. Fittschen

Metals 2021, 11(11), 1869; https://doi.org/10.3390/met11111869 - 20 Nov 2021

Cited by 4 | Viewed by 1688

Abstract

Basic oxygen furnace (BOF) slag accounts for the majority of all residual materials produced during steelmaking and may typically contain certain transition metals. Vanadium, in particular, came into focus in recent years because of its potential environmental toxicity as well as its economic [...] Read more.

Basic oxygen furnace (BOF) slag accounts for the majority of all residual materials produced during steelmaking and may typically contain certain transition metals. Vanadium, in particular, came into focus in recent years because of its potential environmental toxicity as well as its economic value. This study addresses the vanadium chemistry in BOF slags to better understand its recovery and save handling of the waste stream. The experimental results from the electron probe microanalysis (EPMA) study show that vanadium is preferably incorporated in calcium orthosilicate-like compounds (COS), with two variations occurring, a low vanadium COS (COS-Si) (approx. 1 wt.%), and a high vanadium COS (COS-V) (up to 18 wt.%). Additionally, vanadium is incorporated in dicalcium ferrite-like compounds (DFS) with an average amount of 3 wt.%. Using powder x-ray diffraction analysis (PXRD), EPMA, and virtual component models, stoichiometric formulas of the main vanadium-bearing phases were postulated. The stoichiometries give an estimate of the oxidation states of vanadium in the respective hosts. According to these results, trivalent vanadium is incorporated on the Fe-position in dicalcium ferrite solid solution (DFS), and V⁴⁺ and V⁵⁺ are incorporated on the Si-position of the COS. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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