Thermodynamic Model and Database for Sulfides Dissolved in Molten Oxide Slags

A thermodynamic model has been developed in the framework of the modified quasichemical model in the quadruplet approximation to permit the calculation of solubilities of various gaseous species (sulfide, sulfate, nitride, carbide, water, etc.) in molten slags. The model calculates the solubilities solely from knowledge of the thermodynamic activities of the component oxides and the Gibbs energies of the pure liquid components (oxides, sulfides, sulfates, etc.). In the current article, it is shown that solubilities of sulfur as sulfide in Al₂O₃-CaO-FeO-Fe₂O₃-MgO-MnO-SiO₂-TiO₂-Ti₂O₃ multicomponent slags, which are predicted from the current model with no adjustable model parameters, are in good agreement with all available experimental data. The article also provides a thorough review of experimental sulfide capacity data for this system. The model applies at all compositions from pure oxides to pure sulfides and from basic to acidic slags. By coupling this database with other evaluated databases, such as those for molten metal and gaseous phases, and with general software for Gibbs energy minimization, practically important slag/metal/gas/solid equilibria can be computed such as S-distribution ratios.     

Thermodynamic Study on BaO-CaO-CaF2 Slags for Dephosphorization of Molten Steel

Phosphorusisadetrimentalelementforsome kindsofsteel.Itiseasilysegregatedinthegrain boundaryduringthesolidificationofsteelresulting inthecold brittleness.Italsoreducesthemechani calpropertyofsteel[1].Inrecentyears,ultralow phosphorus,e.g.below0.01%or0.005%…     

Corrosion of Refractory Alloys in Molten Lithium and Lithium Chloride

Several refractory materials have been considered over the years as containment material for lithium and lithium halides. Surface modified refractory metals are being extensively investigated for containment of reactive metals, radionuclides and their compounds. An overview of experimental observations and results of liquid lithium corrosion of selected engineering refractory materials are presented. The nature of the degradation and its mechanism has been explained. The influence of temperature, microstructure, stress, impurities and service time on the corrosion behavior for various refractory alloys have been discussed. Selection rules for materials of containment for liquid lithium and lithium compounds have been suggested. Recent experimental observations on the behavior of tantalum and niobium-based refractory metal alloys in a specific molten salt environment comprising LiCl/Li₂O/Li/Li₃N at 725°C have been included in an effort to select suitable materials for molten salt equipment. It has been observed that oxygen contamination is particularly harmful for the refractory metal alloys where as nitrogen is deleterious to iron-based alloys.     

Corrosion of Refractory Alloys in Molten Lithium and Lithium Chloride

Abstract

Several refractory materials have been considered over the years as containment material for lithium and lithium halides. Surface modified refractory metals are being extensively investigated for containment of reactive metals, radionuclides and their compounds. An overview of experimental observations and results of liquid lithium corrosion of selected engineering refractory materials are presented. The nature of the degradation and its mechanism has been explained. The influence of temperature, microstructure, stress, impurities and service time on the corrosion behavior for various refractory alloys have been discussed. Selection rules for materials of containment for liquid lithium and lithium compounds have been suggested. Recent experimental observations on the behavior of tantalum and niobium-based refractory metal alloys in a specific molten salt environment comprising LiCl/Li₂O/Li/Li₃N at 725^°C have been included in an effort to select suitable materials for molten salt equipment. It has been observed that oxygen contamination is particularly harmful for the refractory metal alloys where as nitrogen is deleterious to iron-based alloys.     

氧化物熔渣的电化学还原

提出了一种从氧化物熔渣中直接提取金属的电化学方法,即采用氧离子渗透膜原电池短路法,用碳作还原剂,在CaO-SiO2-Al2O2-FeO熔渣中,利用阴极合金化原理,获得无碳铁合金。结果表明：在本实验条件下,熔渣中FeO浓度越高,外电路短路电流越大。发现熔渣的还原电流包括外电路短路电流和氧离子膜的内部短路电流,可利用外电路短路电流来监测熔渣的外电路还原率。     

Oxygen Permeation of Partly Molten Slags

The conductivities, oxygen ion transference numbers, and oxygen permeation fluxes of NiO-30, 36, 42, and 48 wt pct Bi₂O₃, In₂O₃-30, 36, 42, and 48 wt pct Bi₂O₃, ZnO-15, 20, 25, and 30 wt pct Bi₂O₃, ZrV₂O₇-16, 20, 24, and 28 wt pct V₂O₅, and BiVO₄-5, 7, 10, and 12 wt pct V₂O₅ partly molten slags have been measured by using the four-probe DC, volumetric measurements of the faradaic efficiency, and gas flow techniques, respectively, under various temperatures and oxygen partial pressure gradients. Results indicate that in the ranges of slag layer thicknesses 1 to 5 mm and temperatures 923 K to 1173 K (650 °C to 900 °C), used in the present study, the overall oxygen permeation kinetics is controlled by both chemical diffusion and surface exchange reactions. The oxygen permeation fluxes (3 × 10^?9 to 9 × 10^?8 mol/cm² s) were found to increase with volume fraction of liquid. The oxygen ion transference number was found to be in the range 0.2 to 0.8. The ambipolar conductivity, characteristic thickness, and surface exchange coefficient were estimated to be in the ranges 1.1 × 10^?3 to 2.3 × 10^?1 S/cm, 2 × 10^?2 to 7 × 10^?2 cm, and 1.3 × 10^?6 to 2.1 × 10^?6 cm/s, respectively.     

Modeling Viscosities of CaO-MgO-FeO-MnO-SiO2 Molten Slags

A model for estimating the viscosity of silicate melts is proposed in this article. The structural characteristics of a silicate slag can be described by the numbers of the bridging oxygen, nonbridging oxygen, and free oxygen present in the slag. A method of calculating the numbers of the different types of oxygen ions is presented in this article, which involves a simple approximation of “complete bridge breaking.” With just a few parameters, the model provides both the temperature and composition dependencies of viscosity for the pure component: SiO₂; the binary systems: MgO-SiO₂, CaO-SiO₂, FeO-SiO₂, and MnO-SiO₂; the ternary systems: CaO-MgO-SiO₂, CaO-FeO-SiO₂, MgO-FeO-SiO₂, and CaO-MnO-SiO₂; and the quaternary systems: CaO-MgO-MnO-SiO₂ and CaO-FeO-MnO-SiO₂. It was found that the ability of different basic metal oxides to decrease viscosity varies and is in the following hierarchy: FeO > MnO > CaO > MgO. Two factors influence the viscosity: The first is related to the mutual interaction among different ions, and the stronger the interaction, the higher the viscosity. The second factor is the size (radius) of basic oxide cation, with viscous flow becoming increasingly more difficult (i.e., viscosity increases) as the cation size increases. However, there is a paradox in the effect of cation radius (of the basic oxide) on the two factors. Thus, varying cation size causes competitive effects; smaller cationic radii give stronger interactions among ions but less hindrance to viscous flow (and vice versa for large cation radii).     

熔渣中氧传递机理的研究

介绍了熔渣中氧的扩散系数以及气-渣、气-渣-金及渣-金体系中氧的传递现象,分析了电子电导对熔渣中氧传递的影响,总结了熔渣中氧的传递机理,并认为改变电化学因素可以控制渣相中氧离子的迁移。     

耐火材料对钢水纯净度影响的试验研究

通过对钢包、中间包衬层内示踪剂在浇铸过程中变化的试验分析，判断衬层耐火材料在钢水中的变化情况，分析每炉钢水对耐火材料的冲刷量及耐火材料对钢水纯净度的影响程度。从而提出减少耐火材料衬层对钢水污染的措施。     

Reaction Kinetics of FeO Containing Molten Slags

The kinetic study of FeO‐containing slag is valuable if we consider slag‐gas and slag‐metal reactions in steelmaking process. In the present work, the reduction rate of Fe_tO‐SiO₂–TiO₂–MO_x (MO_x = CaO, MgO, AlO_1.5, PO_2.5) melts in equilibrium with solid iron by CO gas was measured using the thermobalance system at 1673 K. A rate equation was developed based on the results obtained. The mechanisms of the reaction and the effect of P₂0₅ as a surfactant were discussed. Solid CaO was reacted with FeO‐containing slag at 1573 to 1673 K. The CaO–slag interface was analyzed by SEM and EDX, and the reacted layers were identified. The rate of solid CaO dissolution into a stagnant FeO‐containing slag at hot‐metal temperatures was explained by the FeO diffusion in slag phase.     

钢水温度和碳对镁铝尖晶石质耐火材料侵蚀的影响

根据热力学分析和热态实验研究了钢水温度及其碳质量分数对镁铝尖晶石质耐火材料侵蚀的影响,并探讨了耐火材料的侵蚀机理。研究表明,提高温度将加剧钢水对耐火材料的侵蚀,随钢水中碳质量分数的增加,耐火材料的侵蚀指数先增加后减小。侵蚀机理包括：一是钢水中碳与耐火材料组分氧化镁反应化学侵蚀耐火材料;二是钢水向耐火材料内部的渗入以及低熔点物相在耐火材料颗粒界面的析出,降低了耐火材料颗粒间的结合力,加剧了钢水冲刷对耐火材料的损毁程度。     

钢水温度和碳对镁铝尖晶石质耐火材料侵蚀的影响

根据热力学分析和热态实验研究了钢水温度及其碳质量分数对镁铝尖晶石质耐火材料侵蚀的影响,并探讨了耐火材料的侵蚀机理。研究表明,提高温度将加剧钢水对耐火材料的侵蚀,随钢水中碳质量分数的增加,耐火材料的侵蚀指数先增加后减小。侵蚀机理包括：一是钢水中碳与耐火材料组分氧化镁反应化学侵蚀耐火材料;二是钢水向耐火材料内部的渗入以及低熔点物相在耐火材料颗粒界面的析出,降低了耐火材料颗粒间的结合力,加剧了钢水冲刷对耐火材料的损毁程度。     

The Thermodynamics of Some Transition Metals in Molten Slags

In the present paper, the thermodynamic behaviour of transition metals, such as Cr, Ti, Nb and V in molten slags is systematically analysed based on a literature survey. These metals exist in molten slags with multi valences. Oxygen partial pressure, slag basicity, total content of each transition metal, content of each component in slag, and temperature are the influential factors on their thermodynamic properties in molten slags. Higher basicity and strong oxidative atmosphere are generally favourable for the stable existence of transition‐metal ions with higher oxidation states. Temperature is a factor that is less influential than the above‐mentioned ones. For a transition metal in molten slag, the concentration ratio of ions of different valences depends on the activity coefficient ratio of their oxides. The present paper summarizes the activity studies regarding the transition metal oxides in various molten slags. For chromium and titanium oxides, information on CaO? SiO₂ based systems is involved. For titanium oxides, its thermodynamic behaviour in MnO? SiO₂ based slags is introduced. For niobium and vanadium, the information in Na₂O? SiO₂, CaO? CaF₂? SiO₂ systems is provided. Thermodynamic studies are described for Nb₂O₅? MnO? SiO₂ molten slag equilibrated with liquid iron at 1828 K.     

熔渣二次正规溶液模型

介绍了熔渣结构相关模型及构造模型；阐述了熔渣正规溶液模型及其成立的前提、表达式和相互作用能αｉｊ；讨论了正规溶液模型中活度标准态的变换及标准生成自由能的转换。认为扩展后的正规溶液模型可广泛用于多元渣系中较宽的组成范围，以确定渣组成活度。     

Corrosion Mechanisms of Steel and Cast Iron by Molten Aluminum

The corrosion mechanisms by liquid aluminum of three industrial materials have been studied: unalloyed steel (UAS), and ferritic and modified pearlitic cast irons (FCI and PCI, respectively). The behavior of these materials when in contact with liquid aluminum is different. Aluminum diffuses deep into the UAS and forms intermetallic compounds with iron at the surface and in the steel matrix. At the surface, only Fe₂Al₅ and FeAl₃ are found. In the matrix, FeAl₂ also is formed in agreement with the equilibrium Fe-Al diagram. From the matrix to FeAl₂, the Al content in the ferrite increases progressively until Al saturation is reached. At this step, black elongated precipitates (Al₄C₃ and/or graphite) appear. Graphite lamellas present in both FCI and PCI constitute an efficient barrier to the Al diffusion. The high silicon content of the FCI leads to the formation of a phase free from Al and saturated in Si. For the PCI, a thin layer rich in Al and Si, which is formed between the matrix and Fe₂Al₅, limits the diffusion of atoms. The effects of Cr and P added in the PCI also are discussed.     

Interfacial Reaction between Refractory Materials and Metallurgical Slags containing Fluoride

Interfacial reaction between refractory materials such as zirconia, magnesia and doloma brick, and the metallurgical slags of the CaO‐SiO₂‐MgO‐CaF₂ system with varying CaF₂ content were investigated at high temperatures using various methodologies with static and dynamic modes. To figure out the corrosion mechanism due to interfacial reaction with the slag, the slag characteristics were examined in terms of flow temperature and viscosity and the corroded interface of zirconia, magnesia and doloma refractories were analyzed by SEM‐EDS and EPMA. With an addition of CaF₂, three different layers were formed at the interface between slag and zirconia refractory. Furthermore, the corrosion of zirconia refractory was found to be accelerated with an increase of CaF₂ which facilitated the dissolution of intermediate compounds. The penetration of slag through the grain boundaries of MgO refractory is enhanced by increasing the content of CaF₂ due to an increase in the fluidity of slag in the dynamic mode. On the other hand, in the static condition, a dense Ca₂SiO₄ layer is formed at the hot face of magnesia‐doloma refractory due to a reaction between silica in slag and lime in doloma, resulting in the protection of direct corrosion of refractory brick. However, the thickness of C₂S layer decreases with increasing content of CaF₂ due to an increase in fluidity of slag.     

FeO-MnO-MgO-SiO2渣系和铁液间锰的平衡

利用炉渣结构的共存理论处理FeO-MnO-MgO-SiO₂熔渣和铁液间锰的平衡问题后,证明$K{'_{{\\rm{Mn}}}} = \\frac{{{N_{{\\rm{MnO}}}}}}{{{N_{{\\rm{FeO}}}}[\\% Mn]}}$不因炉渣碱度而改变,是相当守常的。从该规律出发计算得出的[%Mn]_计与实测的[%Mn]_实是符合的,从而证明所推导的计算模型可以反映上述四元渣系的实际情况。     

Reduction of Molten Copper Slags with Mixed CO-CH4-Ar Gas

The reduction of magnetite from slags plays an important role in many metallurgical operations. It has been found that the losses of copper metals generally increase with the increasing magnetite content in the slag. The main objective of the current article was to study the reduction process of iron oxides by mixed CO-CH₄-Ar gas from commercial copper slags. The magnetite content decreased gradually, while fayalite phase increased during the reduction process. The reduction rates of the oxides were found to be of the first-order kinetics. The rate-limiting step was the interfacial mass transfer between the gas and liquid phase which fitted the penetration model. The effects of reduction temperature and injection gas flow on the deoxidation rate are also mentioned in the study.