Physicochemical Properties Of Slag Research Articles

Structure and adaptability of FexO-SiO2-MgO-15 wt% CaO-0.026 wt% NiO slag with the Fe/SiO2 mass ratio of 1.2 in flash matte smelting

The high-magnesium gangue severely affects the melting performance and fluidity of slag in nickel matte smelting. To detect the adaptability when the CaO-modified slag for treating high-magnesia nickel sulfide concentrate in flash smelting, the synergistic effect of MgO and other oxides on the microstructure and physicochemical properties of slag were analyzed through molecular dynamics simulation associated with the experimental analysis. The results indicate that the MgO content increases from 5 wt% to 11 wt%, part of the Fe2+ ions in silicate are gradually replaced by Mg2+, and some of them are transformed into Fe3+ in the external atmosphere. Accordingly, the generated Fe3+ may destroy the bridge oxygen between Si4+-O2--Si4+ and more complex silicate ions will be dissociated into SiO44+. As a consequence, the Q0 proportion in the modified high-magnesia smelting slag improved from 24.33% to 29.69%, and the n(BO/T) decreased from 1.45 to 1.29. However, when MgO content is high enough, SiO44+ tetrahedron ions may attract Fe2+ and Mg2+ to form (Fe, Mg)2SiO4 with a more robust interaction network structure, resulting in an adverse effect on melting temperature and ions diffusion coefficient. The modified nickel slags with 5–11 wt% MgO represent hospitable melting temperature less than 1320 °C, viscosity lower than 0.091 Pa s, and surface tension between 0.4811 N/m to 0.4838 N/m. In brief, the CaO-modified slag turned out to be conducive for treating high-magnesium nickel sulfide concentrates in flash matte smelting, especially for those containing MgO less than 7 wt%.

Effect of Physicochemical Properties of Slag on the Removal Rate of Alumina Inclusions in the Ruhrstahl–Heraeus (RH) Refining Conditions

Effect of Physicochemical Properties of Slag on the Removal Rate of Alumina Inclusions in the Ruhrstahl–Heraeus (RH) Refining Conditions

Direct microalloying of structural steels by boron from oxide system CaO–SiO<sub>2</sub>–B<sub>2</sub>O<sub>3</sub>–Al<sub>2</sub>O<sub>3</sub>–MgO

The results of fundamental studies of the physicochemical properties of slags of the CaO–SiO2–B2O3–Al2O3–MgO system were used as the basis for the development of the technology for the formation of boron-containing slags in ladle-furnace units (LFU). The recommended composition of ladle slags (1–4% B2O3, 15% Al2O3 and 8% MgO) ensures the development of direct microalloying processes of steel with boron, low viscosity, not exceeding 0.32 Pa∙s, and preservation of sufficiently high refining properties. Colemanite (Turkey) was used as boron-containing raw material, having, %: 39–41 B2O3, 26–28 CaO, no more than 5% of SiO2 and 3% of MgO. The implementation of the developed technology of direct microalloying of structural steels of a wide grade composition by boron in the BOF shop of ArcelorMittal Temirtau JSC provided the boron content at the level of 0.001–0.008%, a decrease in the consumption of manganese-based ferroalloys from 0.3 kg/t of 08кп steel to 0.8 kg/t of steel 17Г1С-У, exclusion of additives into the ladle of ferroboron and fluorspar. The proposed mode of formation of slags of the recommended composition in the melt of LFU provided a sufficiently high degree of metal desulfurization in comparison with the existing production routes. For example, with pipe steel 17Г1С-У, despite a decrease in lime consumption by 500 kg per a heat and a decrease of the steel processing time at the LFU by 40 minutes, a high degree of desulfurization, reaching 66.7%, provided a sulfur content of 0.004% in the metal. Microalloying of structural steels by boron results in their high strength properties with invariance of plasticity apart from sufficiently high refining effect.

ДО ВИБОРУ РАЦІОНАЛЬНИХ СКЛАДІВ ШЛАКІВ ТА ШЛАКОУТВОРЮЮЧИХ СУМІШЕЙ ПРИ ВИРОБНИЦТВІ ЧАВУНУ ТА СТАЛІ

When solving the problem of choosing the rational chemical composition of metallurgical slags and mixtures, it is important to study their properties (viscosity, melting point, electrical conductivity, surface tension, etc.). According to scientific studies, the physicochemical properties of slag and aluminosilicate melts (including their viscosity and electrical conductivity) depend on the chemical composition of the system and temperature and reflect structural changes in the melt. The properties of slag melts are well explained by the ion theory according to which the viscosity is determined by the structure of polymer ions (SixOyz- anions), and the electrical conductivity by mobile ions by cations and/or anions (Ca2+, Mg2+, O2-, F-, and etc.). Increasing the temperature of the slag melt weakens the bonds of its structural particles (ions and/or their groups) is an important and necessary condition for improving the efficiency of heat and mass transfer processes in the system "metal-slag". The study of the relationship between viscosity and electrical conductivity and the development of criteria for assessing the structure of the slag melt, the establishment of a rational chemical composition for specific technological conditions of the smelting process of cast iron or steel is of great scientific and practical importance. The relationship between the viscosity and electrical conductivity of different oxide systems has been studied and the activation energies of viscosity (Eη) and electrical conductivity (Eχ) have been calculated. A criterion is proposed, the ratio n = Еη/Еχ, which varies in the regions: Еη>Еχ = n >1, Еη<Еχ = n <1 and Еη≈Еχ = n≈1, which indicate the presence of three structural regions: heterogeneous (Еη > Еχ = n> 1), homogeneous (Еη <Еχ = n <1) and equilibrium state of the melt (Еη≈Еχ = n≈1). The performed research has expanded the scientific ideas about the structure of slag melts, and the proposed criterion allows the choice of rational compositions of slags and mixtures in the production of iron and steel

Theoretical Basics and Technology of Smelting Steel Semiproduct in Basic Oxygen Furnaces and Electric Arc Furnaces under Magnesian Slags

The results of basic studies of the physicochemical properties of slags are used as the basis for developing the rational composition of main magnesian slags and the process techniques for their formation by the periods of blowing a basic oxygen furnace (BOF) bath and the periods of smelting in electric arc furnaces (EAFs). The record-breaking durability of furnace linings is ensured by implementing, in the furnace shop of OJSC EVRAZ NTMK, the developed set of process techniques of forming magnesian slags in the main period of blowing and a wear-resistant skull based on the final magnesian slags. These slags produce a low aggressive effect on the lining of furnaces, while maintaining high refining properties. The furnaces’ lining durability exceeds 7000 heats; that said, the high process and key performance indicators of the process are maintained. The treatment of low manganese cast irons in the 350-ton heavy furnaces of OJSC EVRAZ ZSMK under magnesian slags allows studying the features of slag formation and changes in the chemical composition of the slag by the BOF bath blowing periods. In the course of treating phosphorous cast irons in the 300-ton BOFs at JSC ArcelorMittal Temirtau, a set of process techniques is developed for forming the magnesian slags of the recommended chemical composition by the periods of phosphorus cast iron blowing and wear-resistant skulls based on moderate-basicity final magnesian slags. The implementation of the developed process techniques ensures the lining stability of BOFs for more than 5000 heatings while maintaining the high process parameters and key performance indicators of the phosphorous treatment phase. The technology of forming rationally composed magnesian slags by the periods of smelting in EAF-135 is developed in the EAF shop of PJSC Seversky Pipe Plant. The adoption of the technology ensures the record-breaking resistance of the refractory lining of the furnace for up to 1900 heats per campaign and the high process parameters and key performance indicators of the process.

Theoretical Bases and Technology of Steel Exhaustive Metal Desulfurization and Direct Microalloying with Boron Beneath Basic Boron-Containing Slags

Results of theoretical and experimental studies of the physicochemical properties of slags of the CaO–SiO2–B2O3 system containing 15% Al2O3 and 8% MgO lie at the basis for the development of technology for exhaustive desulfurization of metal beneath basic boron-containing slags formed in a steelpouring ladle in a ladle-furnace unit (LFU), and steel direct microalloying with boron. Methods of simplex lattice planning of an experiment, a software complex HSC 6.1 Chemistry (Outokumpu), and the method of electro-vibration viscosimetry are used. Results of thermodynamic modeling of the effect of slag basicity and B2O3 content on sulfur and boron equilibrium distribution coefficient between slag of the oxide system under study and low-carbon metal are presented. The quantitative effect of basicity and B2O3 content on slag viscosity containing 15% Al2O3 and 8% MgO at a temperature of 1600°C and the influence of the slag chemical composition of the oxide system under study on the degree of wear of periclase-carbon refractory material are shown. Results of studying physicochemical properties of slags of the CaO–SiO2–B2O3 system containing 15% Al2O3 and 8% MgO are a basis for developing a ladle slag composition with low viscosity and providing exhaustive metal desulfurization, and direct microalloying of boron steel with low corrosive effect on periclase-carbon refractories. Development of this technology provides, depending on the steel grade, a boron content of 0.001–0.008%, low metal sulfur concentration at 0.004–0.014%, a reduction in manganese ferroalloy consumption from 0.5 kg/ton of steel 08KP to 1.4 kg/ton of steel 09G2S, exclusion of ferroboron and fluorspar additives in the ladle, and achievement of good finished metal product mechanical properties.

The influence of the volatiles on the slag composition for the heating process

The physicochemical properties of slag are of great importance in pyrometallurgy. If there is a volatile component in the slag, evaporation will inevitably occur. As a result, the slag composition will change, and the measured results will be inconsistent with the original slag composition. Therefore, the traditional methods can be applied to determine the properties of slag, however, the change in slag composition will lead to the inaccuracy of the results. Two typical kinds of slag ESR slag with higher CaF2 and Pb smelting reduction slag with higher PbO were chosen, and melting point measurements were taken as an example to demonstrate the new method in practice. Weight loss measurements and evaporation test with thermogravimetric (TG) analysis, as well as high-temperature mass spectrometer (MS) tests were carried out to identify the volatiles. It was found that CaF2 and MgF2 is the main volatiles with a small amount of AlF3 to ESR slag and PbO is the main volatile with a small amount of ZnO. Based on these points and the weight loss, the slag melting points measured with traditional method and the slag chemical composition were modified to fit the melting point value. This way is proved to be feasible in theory and practice. Some suggestion for further research are proposed. The work will be of significance for both slag and molten salt with volatiles.

Investigation of the Physicochemical Properties of Slag Splashed on the Lining of an Oxygen Converter1

The lining of oxygen converters is a structural component, which requires permanent attention and significant investments in all metallurgical plants. These investments are connected with the necessity of application of high-cost refractory materials and with the expenses spent for the repairs of lining and relining, which strongly affects the cost of melting of steel. In this connection, in recent years, the metallurgical works all over the world try to find new efficient constructive solutions and improve the already existing technologies. One of these solutions is called the residual slag splashing technology.

Physicochemical properties of slags produced at various amounts of iron addition in lead smelting

In the process of lead production from lead-bearing materials generated in copper metallurgy, a large amount of hazardous waste in the form of slag is produced. To assess the effect of the slag on the environment, its physicochemical properties were determined. In this study, the following methods were used: wavelength dispersive X-ray fluorescence (WD XRF), X-ray diffraction (XRD), and Bunte-Baum-Reerink method to determine softening and melting points, as well as viscosity examination and leaching tests. The measurements were performed on the slag produced with two different amounts of iron addition to the lead smelting process. The resulting slags, an oxide rich phase slag and a sulfide rich phase slag have different compositions and physicochemical properties. It was found that the increase in iron addition causes an increase in the softening melting point of the oxide rich phase slag by about 100 °C, and a twofold increase in the viscosity of both slag phases. The increase in iron addition also results in the decrease in As leachability and increase in Zn, Fe, and Cu leachability from the slags. Slag produced with increased iron addition has a greater impact on the environment.

Assessing the viscosity of industrial slags

Predicting the physicochemical properties of slag is important in order to develop metallurgical technolo� gies. A significant property of slag is its viscosity, since many metallurgical processes depend on heat and mass transfer in slag. In practice, slag is heteroge� neous, as a rule, and therefore the required viscosity is obtained by regulating its composition. For this pur� pose, specialists rely on empirical formulas that only qualitative reflect the process. Difficulties in describ� ing the properties of heterogeneous slag hinder the development and use of reliable quantitative formulas. Obviously, this limits the controllability and efficiency of the technology. The mean chemical composition of heterogeneous slag does not fully characterize its properties. The development of adequate models calls for a method of calculating the phase distribution of the components and the number of phases in the slag. In that case, the effective viscosity could be estimated from the mean chemical composition and temperature on the basis of formulas for the viscosity of suspensions [1]. The possibility of applying a version of the Einstein formula to slag was discussed in [2–4] (1)

The Influence of Structure on the Physico-chemical Properties of Slags.

The current knowledge of the structures of silicate slags is summarised and the relationships between measures of the depolymerisation of the melt and various physical properties are examined. It is shown that the optical basicity when corrected for the cations required to charge-balance any AlO45- tetrahedra present, provides a reasonable measure of the depolymerisation of the melt and has the advantage over the (NBO/T) ratio that it compensates for cation effects. It is shown that the depolymerisation of the melt is the primary factor affecting most physical properties, the cations having only a secondary effect. The relationships between structure and the viscosity, electrical and thermal conductivity, diffusion coefficient, density, thermal expansion coefficient, thermodynamic and optical properties of melts are discussed.