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

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。     

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.     

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.     

Physicochemical Properties of the Molten Iron-Rich Slags Related to the Copper Recovery

Metallurgical and Materials Transactions B - The properties of a molten slag play an important role in the separation of the slag from the matte during copper smelting. In this study, the...     

转炉提钒渣对镁碳砖的侵蚀

在转炉提钒温度下,通过把镁碳砖试样浸入不同V2O3、FeO、TiO2、MnO、MgO含量的转炉提钒渣中,研究转炉提钒渣中氧化物含量的变化对镁碳砖侵蚀行为的影响,得出转炉提钒渣中氧化物含量与镁碳砖侵蚀速率的关系;使用SEM - EDS观察并分析侵蚀后镁碳砖的微观结构及物相组成,发现被C基质还原出来的金属铁颗粒;并基于试验...     

熔盐电脱氧法制备难熔金属及合金的研究进展

介绍了熔盐电脱氧法制备难熔金属及合金的基本原理和工艺,分析了熔盐电脱氧法的优势及目前存在的主要问题,归纳了采用熔盐电脱氧法制备难熔金属及合金的研究进展,指出了该制备工艺的发展趋势,并对其推广应用和实现大规模工业化前景等进行了讨论.