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10 pages, 2686 KiB

Open AccessArticle

Experimental Study on Desulfurization and Removal of Alkali Behavior of BF Slag System in Low-Slag Ironmaking

by Lei Xu, Gele Qing, Xiangfeng Cheng, Meng Xu, Baojun Zhao and Jinfa Liao

Metals 2023, 13(2), 414; https://doi.org/10.3390/met13020414 - 16 Feb 2023

Cited by 3 | Viewed by 2656

Abstract

The increased utilization of pellets in blast furnaces is one of the directions for low-carbon ironmaking. As a result, the low slag rate may affect the desulfurization of the hot metal and the removal of alkali in the blast furnace. Effective desulfurization and [...] Read more.

The increased utilization of pellets in blast furnaces is one of the directions for low-carbon ironmaking. As a result, the low slag rate may affect the desulfurization of the hot metal and the removal of alkali in the blast furnace. Effective desulfurization and the removal of alkali in the low slag ironmaking process have become the focus of the steel industry. In this paper, the effects of slag quantity, temperature, reaction time and slag composition on the desulfurization and removal of alkali were studied using the slag-metal reaction method. It was found that the slag quantity had the same influence trend on the desulfurization and the removal of alkali. The greater the slag quantity, the more effective the desulfurization and the removal of alkali. The slag composition, temperature and reaction time had the opposite effect on the desulfurization and the removal of alkali. High temperature, long reaction time, high MgO concentration, high CaO/SiO₂ ratio and low Al₂O₃ concentration increased the desulfurization of hot metal but reduced the removal rate of alkali from the blast furnace. Applications of the experimental results on high-proportion pellet blast furnace operation are discussed. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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9 pages, 1279 KiB

Open AccessCommunication

Extraction of Sodium Tungstate from Tungsten Ore by Pyrometallurgical Smelting

by Liqiang Xu and Baojun Zhao

Metals 2023, 13(2), 312; https://doi.org/10.3390/met13020312 - 3 Feb 2023

Cited by 5 | Viewed by 2981

Abstract

Tungsten is one of the strategic metals produced from tungsten ores through sodium tungstate. The hydrometallurgical process is a common technology for extracting sodium tungstate from high-grade tungsten concentrates. The grade of tungsten ore is decreasing, and the mineral processing to produce a [...] Read more.

Tungsten is one of the strategic metals produced from tungsten ores through sodium tungstate. The hydrometallurgical process is a common technology for extracting sodium tungstate from high-grade tungsten concentrates. The grade of tungsten ore is decreasing, and the mineral processing to produce a high-grade concentrate suitable for the hydrometallurgical process is becoming more difficult. It is desirable to develop a new technology to effectively recover tungsten from the complex low-grade tungsten ores. A fundamental study on the pyrometallurgical processing of wolframite was carried out through thermodynamic calculations and high-temperature experiments. The wolframite was reacted with Na₂CO₃ and SiO₂ at 1050–1200 °C and then leached with water to obtain a sodium tungstate solution as a feed for the traditional process of APT (Ammonium paratungstate). The factors affecting the extraction rate of tungsten from wolframite were investigated in air and neutral atmosphere. The extraction rate of tungsten was found to increase with increasing Na₂O content and decrease with increasing SiO₂ addition and temperature. The extraction rate in argon was higher than that in air for wolframite. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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11 pages, 3417 KiB

Open AccessArticle

Recovery of Cu-Fe Alloy from Copper Smelting Slag

by Yi Qu, Keqin Tan, Baojun Zhao and Sui Xie

Metals 2023, 13(2), 271; https://doi.org/10.3390/met13020271 - 29 Jan 2023

Cited by 3 | Viewed by 3502

Abstract

Copper smelting slag usually contains 1–6 wt% copper, which can be recovered by pyrometallurgical and flotation processes. However, the tailing slags still consist of 0.3–0.7 wt% Cu and 35–45 wt% Fe equivalents to those in the copper and iron ores, respectively. Most of [...] Read more.

Copper smelting slag usually contains 1–6 wt% copper, which can be recovered by pyrometallurgical and flotation processes. However, the tailing slags still consist of 0.3–0.7 wt% Cu and 35–45 wt% Fe equivalents to those in the copper and iron ores, respectively. Most of the research was focused on the recovery of iron from the tailing slags. Copper can increase the mechanical strength, corrosion resistance and antibacterial property of some steels. A new process to recover copper and iron directly and fully from hot copper smelting slag is proposed to produce Cu-Fe alloy for steel production. Effects of flux, temperature, reaction time, reductant type and addition on the recovery of copper and iron were investigated by high-temperature experiments and thermodynamic calculations. It was found that, with 5% CaO and 13–16% carbon additions, most of the copper and iron can be recovered from copper smelting slag at 1350–1400 °C. The copper and iron contents of the reduced slag are lower than 0.1% and 0.5%, respectively, at optimum condition. The new process has the advantages of low energy consumption, low flux addition and high recovery of copper and iron. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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26 pages, 6055 KiB

Open AccessArticle

Phase Equilibria Studies in the CaO-MgO-Al₂O₃-SiO₂ System with Al₂O₃/SiO₂ Weight Ratio of 0.4

by Jinfa Liao, Gele Qing and Baojun Zhao

Metals 2023, 13(2), 224; https://doi.org/10.3390/met13020224 - 25 Jan 2023

Cited by 8 | Viewed by 4117

Abstract

With the raw materials for ironmaking becoming increasingly complex, more accurate phase equilibrium information on the slag is needed to refine the blast furnace operation to reduce the energy cost and CO₂ emissions. CaO-SiO₂-Al₂O₃-MgO is a [...] Read more.

With the raw materials for ironmaking becoming increasingly complex, more accurate phase equilibrium information on the slag is needed to refine the blast furnace operation to reduce the energy cost and CO₂ emissions. CaO-SiO₂-Al₂O₃-MgO is a basic system of ironmaking slag in which CaO and MgO mainly come from the flux, SiO₂ and Al₂O₃ are mainly from raw materials. The effect of flux additions on the phase equilibrium of the slag can be described by a pseudo-ternary system CaO-MgO-(Al₂O₃+SiO₂) at a fixed Al₂O₃/SiO₂ ratio of 0.4. Liquidus temperatures and solid solutions in the CaO-MgO-Al₂O₃-SiO₂ system with Al₂O₃/SiO₂ weight ratio of 0.4 have been experimentally determined using high temperature equilibration and quenching techniques followed by electron probe microanalysis. Dicalcium silicate (Ca₂SiO₄), cordierite (2MgO·2Al₂O₃·5SiO₂), spinel (MgO·Al₂O₃), merwinite (3CaO·MgO·2SiO₂), anorthite (CaO·Al₂O₃·2SiO₂), mullite (Al₂O₃·SiO₂), periclase (MgO), melilite (2CaO·MgO·2SiO₂-2CaO·Al₂O₃·SiO₂) and forsterite (Mg₂SiO₄) are the major primary phases in the composition range investigated. A series of pseudo-binary phase diagrams have been constructed to demonstrate the application of the phase diagrams on blast furnace operation. Composition of the solid solutions corresponding to the liquidus have been accurately measured and will be used for the development of the thermodynamic database. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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10 pages, 1577 KiB

Open AccessArticle

Enhanced Productivity of Bottom-Blowing Copper-Smelting Process Using Plume Eye

by Jinfa Liao, Keqin Tan and Baojun Zhao

Metals 2023, 13(2), 217; https://doi.org/10.3390/met13020217 - 23 Jan 2023

Cited by 2 | Viewed by 2705

Abstract

Bottom-blowing copper smelting is a bath smelting technology recently developed in China. It has the advantages of good adaptability of raw materials, high oxygen utilization and thermal efficiency, and flexible production capacity. Plume eye is a unique phenomenon observed in the bottom-blowing copper-smelting [...] Read more.

Bottom-blowing copper smelting is a bath smelting technology recently developed in China. It has the advantages of good adaptability of raw materials, high oxygen utilization and thermal efficiency, and flexible production capacity. Plume eye is a unique phenomenon observed in the bottom-blowing copper-smelting furnace where the slag on the surface of the bath is pushed away by the high-pressure gas injected from the bottom. The existence of plume eye was first confirmed by analyzing the quenched industrial samples collected above the gas injection area and then investigated by laboratory water model experiments. Combining the plant operating data and the smelting mechanism of the copper concentrate, the role of the plume eye in bottom-blowing-enhanced smelting is analyzed. It reveals that the direct dissolution of copper concentrate as a low-grade matte into the molten matte can significantly accelerate the reactions between the concentrate and oxygen. The productivity of the bottom-blowing furnace is therefore increased as a result. The effects of the gas flow rate and thickness of the matte and of the slag layer on the diameter of the plume eye were studied using water-model experiments. It was found that increasing the gas flow and the thickness of the matte and reducing the thickness of the slag can increase the diameter of the plume eye. This work is of great significance for further understanding the copper bottom-blowing smelting technology and optimizing industrial operations. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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11 pages, 2015 KiB

Open AccessFeature PaperArticle

Control of Copper Content in Flash Smelting Slag and the Recovery of Valuable Metals from Slag—A Thermodynamic Consideration

by Sui Xie, Xinhua Yuan, Fupeng Liu and Baojun Zhao

Metals 2023, 13(1), 153; https://doi.org/10.3390/met13010153 - 11 Jan 2023

Cited by 5 | Viewed by 3947

Abstract

To determine slag properties and the factors influencing these properties for optimization of operating conditions in the copper flash smelting process, the composition and microstructures of the quenched smelting and converting slags have been analyzed. Thermodynamic software FactSage 8.2 has been used to [...] Read more.

To determine slag properties and the factors influencing these properties for optimization of operating conditions in the copper flash smelting process, the composition and microstructures of the quenched smelting and converting slags have been analyzed. Thermodynamic software FactSage 8.2 has been used to investigate the effects of matte grade, SO₂ partial pressure, and the Fe/SiO₂ ratio on the liquidus temperature and the copper content of the smelting slag. The possibility to recover valuable metals from the smelting and converting slags through pyrometallurgical reduction by carbon is also discussed. It was found that the flash smelting slag temperature is usually higher than its liquidus temperature and the copper (1.2% Cu) is mainly present in the slag as dissolved copper. In the copper flash smelting process, the copper content in the slag can be decreased by decreasing the Fe/SiO₂ ratio and temperature. In pyrometallurgical slag reduction, most Cu, Mo, and Ni can be recovered as an alloy. The conditions of recovery such as the ratio of smelting slag to converting slag, temperature, and reduction extent have been discussed. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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11 pages, 1790 KiB

Open AccessArticle

Distribution and Control of Arsenic during Copper Converting and Refining

by Feiyan Xu, Tao Weng, Keqin Tan, Jinfa Liao, Baojun Zhao and Sui Xie

Metals 2023, 13(1), 85; https://doi.org/10.3390/met13010085 - 29 Dec 2022

Cited by 5 | Viewed by 3626

Abstract

Arsenic content in copper concentrates is continuously increasing worldwide. It is desirable to remove arsenic from copper in the earlier stages of copper making due to the deposition of arsenic to cathode copper during the electrorefining process. Effects of temperature, flux, and oxygen [...] Read more.

Arsenic content in copper concentrates is continuously increasing worldwide. It is desirable to remove arsenic from copper in the earlier stages of copper making due to the deposition of arsenic to cathode copper during the electrorefining process. Effects of temperature, flux, and oxygen on the distribution of arsenic during copper converting and fire refining processes were studied using FactSage 8.2. The results showed that arsenic can be effectively removed by proper selection of converting and refining slags. The decrease in Fe/SiO₂ or Fe/CaO ratio in the converting slag is favorable for arsenic distributed to slag. CaO is more effective than SiO₂ in decreasing the liquidus temperature of the slag and arsenic content in the blister copper during the converting process. Na₂O or CaO as a flux is effective to remove arsenic in the fire refining process. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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15 pages, 2068 KiB

Open AccessArticle

A Metallurgical Dynamics-Based Method for Production State Characterization and End-Point Time Prediction of Basic Oxygen Furnace Steelmaking

by Qingting Qian, Qianqian Dong, Jinwu Xu, Wei Zhao and Min Li

Metals 2023, 13(1), 2; https://doi.org/10.3390/met13010002 - 20 Dec 2022

Cited by 6 | Viewed by 2146

Abstract

Basic Oxygen Furnace (BOF) steelmaking is an important way for steel production. Correctly recognizing different blowing periods and abnormal refining states is significant to ensure normal production process, while accurately predicting the end-point time helps to increase the first-time qualification rate of molten [...] Read more.

Basic Oxygen Furnace (BOF) steelmaking is an important way for steel production. Correctly recognizing different blowing periods and abnormal refining states is significant to ensure normal production process, while accurately predicting the end-point time helps to increase the first-time qualification rate of molten steel. Since the decarburization products CO and CO₂ are the main compositions of off-gas, information of off-gas is explored for BOF steelmaking control. However, the problem is that most of the existing research directly gave the proportions of CO and CO₂ as model input but barely considered the variation information of off-gas to describe the production state. At the same time, the off-gas information can be expected to recognize the last blowing period and predict the end-point time earlier than the existing methods that are based on sub-lance or furnace flame image, but little literature makes an attempt. Therefore, this work proposes a new method based on functional data analysis (FDA) and phase plane (PP), defined as FDA-PP, to describe and predict the BOF steelmaking process from the metallurgical dynamics viewpoint. This method extracts the total proportion of CO and CO₂ and its first-order derivative as dynamics features of steelmaking process via FDA, which indicate the reaction velocity and acceleration of decarburization reaction, and describes the evolution of dynamics features via PP. Then, the FDA-PP method extracts the features of phase trajectories for production state recognition and end-point time prediction. Experiments on a real production dataset demonstrate that the FDA-PP method has higher production state recognition accuracy than the classical phase space, SVM, and BP methods, which is 87.78% for blowing periods of normal batches, 90.94% for splashing anomaly, and 81.29% for drying anomaly, respectively. At the same time, the FDA-PP method decreases the mean relative prediction error (MRE) of the end-point time prediction for abnormal batches by about 10% compared with the SVM and BP methods. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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12 pages, 6023 KiB

Open AccessArticle

Numerical Simulation and Application of Tundish Cover Argon Blowing for a Two-Strand Slab Continuous Casting Machine

by Yang Li, Chenhui Wu, Xin Xie, Lian Chen, Jun Chen, Xiaodong Yang and Xiaodong Ma

Metals 2022, 12(11), 1801; https://doi.org/10.3390/met12111801 - 24 Oct 2022

Cited by 2 | Viewed by 1861

Abstract

During continuous casting, argon blowing from tundish cover (ABTC) can greatly prevent the flow of the remaining air and decrease the reoxidation of molten steel in tundish. In the current study, a numerical model based on a tundish of a two-strand slab continuous [...] Read more.

During continuous casting, argon blowing from tundish cover (ABTC) can greatly prevent the flow of the remaining air and decrease the reoxidation of molten steel in tundish. In the current study, a numerical model based on a tundish of a two-strand slab continuous casting machine was established to investigate the feasibility and evaluate the protective casting effect of the ABTC process. The influence of operation parameters, including sealing schemes of tundish cover holes and the argon flow rate of the remaining oxygen content, were studied in tundish. Then, industrial trials based on the operation parameters from the numerical model were carried out to evaluate the protective effect of ABTC. The results indicate that the ABTC process has a great protective effect in avoiding increasing levels of nitrogen and losing titanium and aluminum. With the ABTC process applied, the average increment of nitrogen (△w_[N]) in steel from the end of RH to tundish decreases by 90% from 10 × 10⁻⁶ to 1 × 10⁻⁶, the average loss of titanium (△w_[Ti]) by 12.7% from 63 × 10⁻⁶ to 55 × 10⁻⁶, and the amount of aluminum (△w_[Al]) decreases by 7.1% from 70 × 10⁻⁶ to 55 × 10⁻⁶. The injecting hole and baking holes should be sealed during the period of empty tundish to efficiently discharge the air. In order to ensure that the oxygen volume fraction in tundish is less than 1%, the argon flow rate should be ≥220 Nm³/h during the period of empty tundish and ≥80 Nm³/h during the period of normal casting. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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14 pages, 3493 KiB

Open AccessArticle

Effects of CaO, Al₂O₃ and MgO on Kinetics of Lead-Rich Slag Reduction

by Sui Xie, Chunfa Liao and Baojun Zhao

Metals 2022, 12(8), 1235; https://doi.org/10.3390/met12081235 - 22 Jul 2022

Cited by 1 | Viewed by 1549

Abstract

Lead-rich slag as a green feedstock can be used in a blast furnace or smelting reduction furnace to produce lead metal. It is desirable to understand the reduction mechanisms of lead-rich slag to optimize the reduction operations. The volume of CO/CO₂ gases [...] Read more.

Lead-rich slag as a green feedstock can be used in a blast furnace or smelting reduction furnace to produce lead metal. It is desirable to understand the reduction mechanisms of lead-rich slag to optimize the reduction operations. The volume of CO/CO₂ gases was continuously measured in the experiments to determine the reduction degree of lead-rich slag by carbon. The effects of CaO, Al₂O₃ and MgO on reaction kinetics of lead-rich slag with carbon were investigated in the temperature range 1073 to 1473 K. The activation energies of the reduction were determined experimentally in the chemically controlled and diffusion-controlled stages, and the reduction mechanism is analyzed using experimental results and thermodynamic calculations. It was found that the activation energies at the chemically controlled and diffusion-controlled stages decrease with increasing optical basicity. CaO and MgO have a similar behavior to accelerate the reduction of the lead-rich slag by carbon. In contrast, Al₂O₃ can increase the activation energies at both chemically controlled and diffusion-controlled stages resulting in a slow reaction. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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11 pages, 3143 KiB

Open AccessArticle

Liquid Formation in Sinters and Its Correlation with Softening Behaviour

by Vaishak Kamireddy, Dongqing Wang, Wen Pan, Shaoguo Chen, Tim Evans, Fengqiu Tang, Baojun Zhao and Xiaodong Ma

Metals 2022, 12(5), 885; https://doi.org/10.3390/met12050885 - 23 May 2022

Cited by 3 | Viewed by 2279

Abstract

Modern blast furnaces with extensive operational volume demand better-quality iron agglomerates as feed for stable operation. Sinter is the principal feed used in blast furnaces across Asia. Liquid generated during the sintering process plays an essential role in the coalescence of the sinter [...] Read more.

Modern blast furnaces with extensive operational volume demand better-quality iron agglomerates as feed for stable operation. Sinter is the principal feed used in blast furnaces across Asia. Liquid generated during the sintering process plays an essential role in the coalescence of the sinter blend and in sinter quality. Therefore, an estimation of liquid properties at peak bed conditions during sintering helps manage sintering liquid behaviour, leading to better control of final sinter properties. In this study, three different iron sinters were reheated to sinter bed conditions, followed by quenching. Electron probe X-ray microanalysis (EPMA) was used to identify the resultant phases and quantify their chemical compositions. The impact of sinter bulk compositions was analysed, especially on sintering liquid properties. Furthermore, experiments were conducted to study the softening and melting behaviour of the sinters, and the cohesive range of the sinters was identified. Finally, the effect of the sinter bulk compositions on sintering liquid properties and softening behaviour is detailed. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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18 pages, 8281 KiB

Open AccessArticle

Comparative Analysis on the Corrosion Resistance to Molten Iron of Four Kinds of Carbon Bricks Used in Blast Furnace Hearth

by Cui Wang, Jianliang Zhang, Wen Chen, Xiaolei Li, Kexin Jiao, Zhenping Pang, Zhongyi Wang, Tongsheng Wang and Zhengjian Liu

Metals 2022, 12(5), 871; https://doi.org/10.3390/met12050871 - 20 May 2022

Cited by 5 | Viewed by 2312

Abstract

The corrosion resistance to molten iron of four kinds of carbon bricks used in blast furnace hearth were investigated to elaborate the corrosion mechanism through the macroscopic and microscopic analysis of carbon bricks before and after reaction and thermodynamic analysis. The macroscopic analysis [...] Read more.

The corrosion resistance to molten iron of four kinds of carbon bricks used in blast furnace hearth were investigated to elaborate the corrosion mechanism through the macroscopic and microscopic analysis of carbon bricks before and after reaction and thermodynamic analysis. The macroscopic analysis showed that brick A had the lowest degree of corrosion and highest uniformity at different heights, attributing to its moderate carbon content of 76.15%, main phases of C, Al₂O₃, SiC, and Al₆Si₂O₁₃ (mullite), and lower resistance to molten iron infiltration, etc. The microscopic analysis showed that all the carbon bricks had more and larger pores than the original carbon bricks. The phenomena of the iron beads adhering to carbon brick and iron infiltration were observed between the interface of carbon brick and molten iron. In addition, the obvious corrosion process was presented that the carbon matrix was broken and peeled off during the iron infiltration process. For the carbon brick being corroded, the dissolution of carbon was the predominant reaction. The higher the carbon solubility of the molten iron, the easier the corrosion on the carbon brick. Al₂O₃ and SiC enhanced the corrosion resistance to molten iron of carbon bricks, and SiO₂ could react with carbon to form pores as channels for the penetration of molten iron and increase the corrosion on carbon bricks. A higher graphitization degree of carbon bricks was beneficial to lessen their corrosion degree. The corrosion on carbon bricks by molten iron could be attributed to three aspects: carburization, infiltration, and scouring of molten iron. The carburization process of molten iron was the main reaction process. The molten iron infiltration into the carbon bricks facilitated the dissolution of carbon and destroyed the structure and accelerated the corrosion of the carbon bricks. The scouring of molten iron subjected the iron–carbon interface to interaction forces, promoting the separation of the exfoliated fragmented carbon brick from the iron–carbon interface to facilitate a new round of corrosion process. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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14 pages, 7062 KiB

Open AccessArticle

Predictive Modeling of Blast Furnace Gas Utilization Rate Using Different Data Pre-Processing Methods

by Dewen Jiang, Zhenyang Wang, Kejiang Li, Jianliang Zhang, Le Ju and Liangyuan Hao

Metals 2022, 12(4), 535; https://doi.org/10.3390/met12040535 - 22 Mar 2022

Cited by 11 | Viewed by 3277

Abstract

The gas utilization rate (GUR) is an important indicator parameter for reflecting the energy consumption and smooth operation of a blast furnace (BF). In this study, the original data of a BF are pre-processed by two methods, i.e., box plot and 3σ criterion, [...] Read more.

The gas utilization rate (GUR) is an important indicator parameter for reflecting the energy consumption and smooth operation of a blast furnace (BF). In this study, the original data of a BF are pre-processed by two methods, i.e., box plot and 3σ criterion, and two data sets are obtained. Then, support vector regression (SVR) is used to construct a prediction model based on the two data sets, respectively. The state parameters of a BF are selected as input parameters of the model. Gas utilization after one hour (GUR-1h), two hours (GUR-2h), and three hours (GUR-3h) are selected as output parameters, respectively. The simulation result demonstrates that using the 3σ criterion to pre-process the raw data leads to better prediction of the model compared to using the box plot. Moreover, the model has the best predictive effect when the output parameter is selected as GUR-1h. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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20 pages, 28971 KiB

Open AccessArticle

The Formation Mechanisms and Evolution of Multi-Phase Inclusions in Ti-Ca Deoxidized Offshore Structural Steel

by Zhe Rong, Hongbo Liu, Peng Zhang, Feng Wang, Geoff Wang, Baojun Zhao, Fengqiu Tang and Xiaodong Ma

Metals 2022, 12(3), 511; https://doi.org/10.3390/met12030511 - 17 Mar 2022

Cited by 4 | Viewed by 2162

Abstract

To understand and clarify the formation mechanisms and evolution of complex inclusions in Ti-Ca deoxidized offshore structural steel, inclusions in industrial steel were systematically investigated. The number density of total inclusions generally decreased from Ladle Furnace (LF), Vacuum Degassing (VD), Tundish to the [...] Read more.

To understand and clarify the formation mechanisms and evolution of complex inclusions in Ti-Ca deoxidized offshore structural steel, inclusions in industrial steel were systematically investigated. The number density of total inclusions generally decreased from Ladle Furnace (LF), Vacuum Degassing (VD), Tundish to the final product except for Ti and Ca addition. The major inclusions during the refining process were CaO-Al₂O₃-SiO₂-(MgO)-TiO_x and CaO-Al₂O₃-SiO₂. CaO-Al₂O₃-SiO₂-(MgO)-TiO_x inclusion initially originated from the combination of CaO-SiO₂-(MgO) in refining slag or refractory and deoxidization product Al₂O₃ and TiO₂. With the refining process proceeding and Ca addition, the Al₂O₃ concentration in the CaO-Al₂O₃-SiO₂-(MgO)-TiO_x inclusions gradually dropped while the CaO and TiO₂ concentrations gradually increased. The CaO-Al₂O₃-SiO₂ inclusions originally came from refining slag, existing as 2CaO∙ Al₂O₃∙ SiO₂, and maintained a liquid state during the early stage of LF. After Ca treatment, it was gradually transferred to 2CaO∙ SiO₂ due to Al₂O₃ continuously being reduced by Ca. The liquidus of 2CaO∙ SiO₂ inclusion was higher than that of molten steel, so they presented as a solid-state during the refining process. After welding thermal simulation, CaO-Al₂O₃-SiO₂-(MgO)-TiO_x inclusions were proven effective for inducing intragranular acicular ferrite (IAF) while CaO-Al₂O₃-SiO₂ was inert for IAF promotion. Additionally, Al₂O₃-MgO spinel in multiphase CaO-Al₂O₃-SiO₂-(MgO)-TiO_x inclusion has different formation mechanisms: (1) initial formation as individual Al₂O₃-MgO spinel as a solid-state in molten steel; (2) and it presented as a part of liquid inclusion CaO-Al₂O₃-SiO₂-(MgO)-TiO_x and firstly precipitated due to its low solubility. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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13 pages, 3466 KiB

Open AccessArticle

Formation of Complex Inclusions in Gear Steels for Modification of Manganese Sulphide

by Haseeb Ahmad, Baojun Zhao, Sha Lyu, Zongze Huang, Yingtie Xu, Sixin Zhao and Xiaodong Ma

Metals 2021, 11(12), 2051; https://doi.org/10.3390/met11122051 - 18 Dec 2021

Cited by 8 | Viewed by 4298

Abstract

Suitable MnS inclusions in gear steel can significantly improve the steel machinability and reduce the manufacturing costs. Two gear steel samples with different sulphur contents were prepared via aluminium deoxidation followed by calcium treatment. The shape, size, composition and percentage distribution of the [...] Read more.

Suitable MnS inclusions in gear steel can significantly improve the steel machinability and reduce the manufacturing costs. Two gear steel samples with different sulphur contents were prepared via aluminium deoxidation followed by calcium treatment. The shape, size, composition and percentage distribution of the inclusions present in the steel samples were analyzed using an electron probe micro-analysis (EPMA) technique. The average diameter of MnS precipitated on an oxide inclusion is less than 5 µm. It was found that the steel with high sulphur content contains a greater number of elongated MnS precipitates than low sulphur steel. Moreover, there are more oxide inclusions such as calcium-aluminates and spinels with a small amount of solid solution of (Ca,Mn)S in low content sulphur steel after calcium treatment, which indicates the modification of solid alumina inclusions into liquid aluminates. The typical inclusions generated in high sulphur steel are sulphide encapsulating oxide inclusions and some core oxides were observed as spinel. The formation mechanisms of complex inclusions with different sulphur and calcium contents are discussed. The results are in good agreement with thermodynamic calculations. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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10 pages, 2440 KiB

Open AccessArticle

The Role of Silica in the Chlorination–Volatilization of Cobalt Oxide by Using Calcium Chloride

by Peiwei Han, Zhengchen Li, Xiang Liu, Jingmin Yan and Shufeng Ye

Metals 2021, 11(12), 2036; https://doi.org/10.3390/met11122036 - 15 Dec 2021

Cited by 1 | Viewed by 2150

Abstract

The role of silica in the chlorination–volatilization of cobalt oxide, using calcium chloride, is investigated in this paper. It is found that the Co volatilization percentage of the CoO–Fe₂O₃–CaCl₂ system is not larger than 12.1%. Silica plays an [...] Read more.

The role of silica in the chlorination–volatilization of cobalt oxide, using calcium chloride, is investigated in this paper. It is found that the Co volatilization percentage of the CoO–Fe₂O₃–CaCl₂ system is not larger than 12.1%. Silica plays an important role in the chlorination–volatilization of cobalt oxide by using calcium chloride. In the CoO–SiO₂–Fe₂O₃–CaCl₂ system, the Co volatilization percentage is initially positively related to the molar ratio of SiO₂ to CaCl₂, and remains almost constant when the molar ratio of SiO₂ to CaCl₂ rises from zero to eight. The critical molar ratios of SiO₂ to CaCl₂ are 1 and 2 when the molar ratios of CaCl₂ to CoO are 8.3 and 16.6, respectively. The Co volatilization percentage remains almost constant with the increase in CaO concentration, and decreases when Al₂O₃ and MgO are added. Ca₂SiO₃Cl₂ is determined after roasting at 1073 K and 1173 K, and disappears at temperatures in excess of 1273 K in the calcines from the CoO–SiO₂–CaCl₂ system. CaSiO₃ always exists in the calcines at temperatures in excess of 973 K. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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10 pages, 2024 KiB

Open AccessArticle

Experimental Determination of Phase Equilibria in the Na₂O-SiO₂-WO₃ System

by Baojun Zhao, Kun Su and Xiaodong Ma

Metals 2021, 11(12), 2014; https://doi.org/10.3390/met11122014 - 13 Dec 2021

Cited by 3 | Viewed by 3483

Abstract

The present study investigated phase equilibria in the Na₂O-SiO₂-WO₃ system experimentally using high-temperature equilibration, quenching, and electron probe X-ray microanalysis (EPMA). New thermodynamic information on the Na₂O-SiO₂-WO₃ system was derived based on the [...] Read more.

The present study investigated phase equilibria in the Na₂O-SiO₂-WO₃ system experimentally using high-temperature equilibration, quenching, and electron probe X-ray microanalysis (EPMA). New thermodynamic information on the Na₂O-SiO₂-WO₃ system was derived based on the newly obtained experimental results and data from the literature. The primary phase fields of sodium metasilicate, sodium disilicate, and tridymite were determined along with the isotherms at 1073, 1173, and 1273 K. The solubilities of WO₃ in SiO₂, Na₂Si₂O₅, and Na₂SiO₃, and the solubility of SiO₂ in Na₂WO₄ were accurately measured using EPMA. Comparisons between the existing and newly constructed phase diagram were carried out and the differences are discussed. The phase equilibrium data will be beneficial to the future development of sustainable tungsten industries and thermodynamic modelling in WO₃ related systems. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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Review

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17 pages, 4935 KiB

Open AccessReview

Development of Bottom-Blowing Copper Smelting Technology: A Review

by Baojun Zhao and Jinfa Liao

Metals 2022, 12(2), 190; https://doi.org/10.3390/met12020190 - 20 Jan 2022

Cited by 26 | Viewed by 7472

Abstract

Bottom-blowing copper smelting technology was initiated and developed in China in the 1990s. Injection of oxygen-enriched high-pressure gas strongly stirs the molten bath consisting of matte and slag. Rapid reaction at relatively lower temperatures and good adaptability of the feed materials are the [...] Read more.

Bottom-blowing copper smelting technology was initiated and developed in China in the 1990s. Injection of oxygen-enriched high-pressure gas strongly stirs the molten bath consisting of matte and slag. Rapid reaction at relatively lower temperatures and good adaptability of the feed materials are the main advantages of this technology. Development and optimisation of bottom-blowing copper smelting technology were supported by extensive studies on the thermodynamics of the slag and the fluid dynamic of the molten bath. The history of technological development and fundamental studies related to this technology are reviewed in this paper. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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