Viscosity of CaO–MgO–Al2O3–SiO2 melts containing SiC particles

The influence of SiC particle on viscosity of CaO–MgO–Al₂O₃–SiO₂ melts was investigated by the rotating-cylinder method. It was found that temperature dependence of viscosity could be described by the Arrhenius law for systems with or without SiC particle addition. The activation energies of liquid–solid mixtures were mainly determined by liquid phase. Temperature had little influence on the relative viscosity (defined as the viscosity ratio of solid–liquid mixture to pure liquid). Viscosity and relative viscosity increased as decreasing rotation speed and increasing volume fraction of SiC solid particle. For the same volume fraction of SiC particle, relative viscosity was affected by the liquid slag compositions. The relative viscosity was smaller when composition of liquid slag had a larger CaO/SiO₂ ratio or MgO/Al₂O₃ ratio. Meanwhile, it was found that the smaller SiC particle will lead to a larger relative viscosity.     

Kinetics of Na2O evaporation from CaO–Al2O3–SiO2–MgO–TiO2–Na2O slags

The present work is carried out to study the evaporation of Na₂O from CaO–Al₂O₃–SiO₂–TiO₂–MgO–Na₂O slags with high basicity and high alumina in the temperature range of 1500–1560°C. The ratio of evaporation was determined by monitoring the Na₂O content change of the slag melt under isothermal reduction conditions. The results show that the evaporation ratio increases with increasing the temperature. Higher basicity and increasing concentrations of Na₂O, Al₂O₃ are also found to increase the evaporation ratio of Na₂O, while MgO addition only slightly enhances the evaporation ratio. With TiO₂ content increasing, the evaporation ratio first increases and then decreases. The evaporation rate of Na₂O appears to be controlled by chemical reaction at the slag/gas interface in the beginning, followed by a mixed reaction-mass transfer regime, and finally a liquid-phase mass transport step. The apparent activation energy is 134.74?kJ?mol^?1 for the chemical reaction regime and 268.53?kJ?mol^?1 for the liquid-phase mass diffusion step.     

Electrochemical Corrosion of Composite Ceramics and Thermal Spray Coatings in the ZrB2–SiC–AlN System

Powder Metallurgy and Metal Ceramics - Polarization studies of the ZrB2–SiC–AlN compact ceramic material and thermal spray coatings of the same composition were conducted in a 3% NaCl...     

Effects of super-gravity field on precipitation and growth kinetics of perovskite crystals in CaO–TiO2–SiO2–Al2O3–MgO melt

The precipitation and growth behaviours of perovskite crystals from CaO–TiO₂–SiO₂–Al₂O₃–MgO melt in a super-gravity field with different gravity coefficients at different cooling rates were investigated in this study. In a super-gravity field, the first precipitated perovskite crystals migrated quickly along the super-gravity direction, and gradually concentrated and grown into larger crystals in the bottom area, while the new perovskite crystals keep precipitating and concentrating towards the bottom area simultaneously. Furthermore, by simplifying the layered samples obtained by super-gravity into three areas along super-gravity direction: slag-rich area, interface area and perovskite-rich area, the variations in volume fractions and equivalent diameters of perovskite crystals against gravity coefficients and cooling rates were obtained by weighting the values of the three areas. And the results indicated that increasing gravity coefficient was not only beneficial for the precipitation but also for the growth of perovskite crystals in the slag melt. Afterwards, the effects of super-gravity field on the precipitation and growth kinetics of perovskite crystals were further discussed.     

Effect of Na2O on Viscosity,Structure and Crystallization of CaF2–CaO–Al2O3–MgO–TiO2 Slag in Electroslag Remelting

Russian Journal of Non-Ferrous Metals - The effect of Na2O on the viscosity, structure, and crystallization behavior of CaF2–CaO–Al2O3–MgO–TiO2 slag was studied using the...     

Effect of TiO2 on the crystallisation behaviour of CaF2–CaO–Al2O3–MgO slag for electroslag remelting of Ti-containing tool steel

The crystallisation characteristics of CaF₂–CaO–Al₂O₃–MgO slags with various TiO₂ contents from 0 to 9.73 mass% were studied using a single hot thermocouple technique, SEM-EDS and X-ray diffraction. The crystallisation mechanism of TiO₂-bearing slag was identified based on kinetic analysis. It was found that increasing TiO₂ from 0 to 6.43 mass% inhibited the crystallisation ability of electroslag remelting-type CaF₂–CaO–Al₂O₃–MgO slag, whereas further increasing TiO₂ content up to 9.73 mass% enhanced the slag crystallisation signally. When increasing TiO₂ content to 6.43 mass%, the crystalline phase shift from CaO to Ca₁₂Al₁₄O₃₂F₂ and CaTiO₃ at high temperatures. At lower temperatures, the crystalline phase change from polygonal Ca₁₂Al₁₄O₃₂F₂ to need-like CaTiO₃. Further increasing TiO₂ content to 9.73 mass%, the crystalline phase are Ca₁₂Al₁₄O₃₂F₂ and CaTiO₃ in the range of 1473–1613?K. The crystallisation of crystalline phase in the isothermal crystallisation is surface nucleation and controlled by interface reaction when TiO₂ content is lower than 6.43 mass% in the slag. It is bulk nucleation and diffusion-controlled one-dimensional growth in slag with 9.73 mass% TiO₂.     

Electrical Properties of Highly Absorbing Ceramics in the AlN–SiC System

Powder Metallurgy and Metal Ceramics - The electrical properties of two highly absorbing AlN–SiC composites are compared at a frequency of 10.3 GHz. To estimate the dielectric constant and...     

Comparison study of slag corrosion resistance of MgO–MgAl2O4, MgO–CaO and MgO–C refractories under electromagnetic field

To illuminate the corrosion behavior of MgO-based refractories under electromagnetic field (EMF), herein, the slag corro-sion and penetration resistance of MgO–...     

A thermodynamic model for calculating manganese distribution ratio between CaO–SiO2–MgO–FeO–MnO–Al2O3–TiO2–CaF2 ironmaking slags and carbon saturated hot metal based on the IMCT

A thermodynamic model (IMCT-L_Mn) for calculating manganese distribution ratio between CaO–SiO₂–MgO–FeO–MnO–Al₂O₃–TiO₂–CaF₂ slags and carbon saturated liquid iron have been developed based on the ion and molecule coexistence theory. The predicted manganese distribution ratio shows a reliable agreement with the measured ones. With the aid of the IMCT-L_Mn model, the respective manganese distribution ratio of (Mn²⁺?+?O^2?), MnO·SiO₂, 2MnO·SiO₂, MnO·Al₂O₃, MnO·TiO₂, and 2MnO·TiO₂ are investigated. The results indicate that the structural units SiO₂?+?FeO play a key role in CaO–SiO₂–MgO–FeO–MnO–Al₂O₃–TiO₂–CaF₂ slags in demanganisation process in the course of hot metal treatment at 1673?K. The manganese distribution ratio at a given binary basicity range increases with CaF₂ content, while that decreases with TiO₂ content at different binary basicity scopes, which demonstrate that high Mn in the metal is favoured by TiO₂ content. In the present study, various critical experiments are carried out in an effort to clarify the effect of temperature on demanganisation ability, indicating that the lower temperature of molten metal is, the faster the rate of demanganisation reaction is and the shorter the thermodynamic equilibrium time is and the lower end-point Mn content is. It can be deduced from the obtained experimental results that the greater oxygen potential of slags or iron-based melts, lower content of basic oxides in slags, and lower temperature at reaction region is benefit for demanganisation reaction.     

Viscosity of low silica CaO–5MgO–Al2O3–SiO2 slags

Abstract

The viscosity of CaO–5MgO–Al₂O₃–SiO₂ slag with low silica was measured by rotating cylinder method up to 1823 K. Slag compositions were chosen based on five different levels of SiO₂ content between 0 and 11·80%. The MgO content was 5·0%. The mass ratio of CaO/Al₂O₃ was varied from 0·66 to 1·95. It was shown that viscosity decreased with increasing temperature and decreased with increasing the mass ratio of CaO/Al₂O₃, following by an increase with further increasing the mass ratio of CaO/Al₂O₃. The viscosity decreased with the NBO/T ratio increasing, and the trend that flow activation energy changes with the NBO/T ratio of slag was the same as the trend that viscosity changes with the NBO/T ratio. Based on the experimental data as the boundary of the homogenous phase region, the mass triangle model was used to calculate the viscosity of low silica region.     

MgO、TiO2对镁质钒钛球团矿综合冶金性能的影响

 以球团厂实际配矿为基础,选取铁矿粉OA、OB、OC和OD,以膨润土作为黏结剂进行试验分析MgO和TiO2对镁质钒钛球团矿冶金性能的影响,并得出合适的TiO2质量分数和MgO质量分数,为生产镁质钒钛磁铁矿球团提供理论依据。结果表明,当[w(MgO)]从1.25%升高到2.34%,球团矿抗压强度从2 511降低到2 453 N/P,还原膨胀指数降低了13.17%;当[w(TiO2)]从3.97%升高到5.07%,球团矿抗压强度从2 511降低到2 383 N/P,还原膨胀指数略有下降,影响较小。球团矿中的[w(MgO)]从1.32%升高到2.38%,球团矿的熔融温度区间降低了40%,改善了其熔滴性能,但MgO固溶体等难还原矿物降低了球团的还原度指数。球团矿综合冶金性能最优的配比参数（质量分数）为OA矿粉50%、OB矿粉21%、OC矿粉10%、OD矿粉19%和膨润土1.8%。     

Dissolution behaviour of MgO based refractories in CaO–Al2O3–SiO2 slag

Abstract

Magnesium oxide (MgO) based refractories are widely used in secondary refining processes, and their dissolution into refining slag is the primary cause of their shortened lifespan. The dissolution rate was investigated for sintered MgO and commercial MgO–C and MgO–Cr₂O₃ refractories in a synthesised 50CaO–45Al₂O₃–5SiO₂ liquid (mass-%) slag. The change in slag composition was measured after a refractory sample was placed into the molten slag that was stirred by flowing argon gas at 1773?K. The dissolution rate of the sintered MgO was above those of the MgO–C and MgO–Cr₂O₃ refractories under the same gas flowrate, although the dissolution rate of all samples increased as the gas flowrate was increased from 25 to 75?mL·min^??1. The slag containing 5?mass-% FeO considerably promoted the dissolution of the MgO–C refractory because of the oxidation of carbon by FeO. The dissolution of all the refractories was greatly affected by penetration of the liquid slag, with the mass transfer of MgO in the penetrating slag at lower gas flowrates likely being the rate controlling step. At high gas flowrates, Ar bubbles covered the surface and blocked the contact between the liquid slag and the solid phase, reducing the dissolution rate.     

Component-Interaction Mechanism in the Quasibinary HfB2–Cr System

Powder Metallurgy and Metal Ceramics - The interaction of hafnium boride and chromium in the HfB2–Cr system is studied. Solid-phase interaction occurs at temperatures up to 1650 ±...     

MgO–C bricks for BOF linings

Abstract

MgO–C brick linings have become standard in basic oxygen furnaces (BOFs) all over the world. Developments in the refractory technology for BOFs over the last few years and their impact on the lifetime and performance of refractory linings are presented. These developments comprise optimised shapes for the lining of BOF and steel fibre reinforced MgO–C bricks. Optimised shapes with double wedges lead to a smooth inner surface of the refractory lining and fewer stresses and refractory consumption. Stainless steel fibre reinforced MgO–C bricks have proven to be the ultimate choice for scrap impacts or other areas with ultra high mechanical loads. They have brought down refractory wear in these particular areas significantly. Moreover, typical lining patterns of different zones in a BOF and the development of the raw material grades (MgO grades and graphite) for refractories as well as the development of lining lifetimes over the last years are discussed.     

Effects of basicity,MgO and MnO on mineralogical phases of CaO–FeOx–SiO2–P2O5 slag

The selective separation phosphorous rich phase from steel slag could be an effective way to utilise the steel slag. The mineralogical phase after cooling of steel slag is essential to selective separation of steel slag. In the present work, the mineralogical phases of CaO–FeO_x–SiO₂–P₂O₅ slag after controlled cooling were investigated by X-ray diffraction and scanning electronic microscopy and energy dispersed spectroscopy technique. It was found that the heat treatment at 1573?K would lead to the precipitation of Ca₂SiO₄–Ca₃P₂O₈ (C2S-C3P) solid solution for all samples. The heat treatment at 1273?K would lead to the precipitation of C2S-C3P, CaSiO₃ and Fe₂O₃. The increase of basicity would promote the crystallisation of CaO–FeO_x–SiO₂–P₂O₅ slag. The Effects of additions of MgO and MnO on phase formations of CaO–FeO_x–SiO₂–P₂O₅ slag were also studied. Fe₂O₃ gradually transformed into MgFe₂O₄ and MnFe₂O₄ in slag after crystallisation with addition of MgO and MnO, respectively. The sizes of MgFe₂O₄ and MnFe₂O₄ crystals increased with increases of MgO and MnO content. The increase of MgO and MnO content would promote the precipitation of MgFe₂O₄ phase and MnFe₂O_4, respectively. The precipitation of crystals from slag during cooling was interpreted by the kinetic and thermodynamic factors. It was proposed that addition of MgO and MnO in slag would be beneficial to magnetic separation of steel slag.     

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The effect of titanium on microstructure of sinter was investigated by metallographic microscope and sintering test. The results show that, with the increase of TiO2 content, the content of perovskite in binder phase has a notable increase, the content of calcium ferrite has a trend to decrease, the content of glass phase rises, the content of dicalcium silicate remains stable, the pores in sinter reduce significantly. In the structure of ore phase, most perovskite shows amorphous and allotriomorphic, which fills in the mineral powder. A little perovskite shows dendritic, which distributes intensively. Calcium ferrite shows acicular, columnar and platy structure, which distributes unequally. Dicalcium silicate distributes with willow structure. The shapes of gas hole are irregular and crack exists throughout them. Binder phase strength of sinter reduces with increase of the content of TiO2. Through the sintering cup test verifying, with the increase of TiO2 content, the tumbler decreases, which meets the influencing law of titanium on microstructure of sinter.     

Investigation of the Structure and Properties of Materials in the SiC ― TiB2 System

The structure and properties of sintered and hot-pressed materials of the SiC TiB₂ system were investigated. The optimal conditions for obtaining dense ceramics with minimum grain size of the phase components was determined. It was established that composites containing from 25 to 50 vol.@percnt; TiB₂ have a bend strength equal to 450 MPa at 20°C; this increases to 500 MPa at 1600°C for ceramics with a pseudoeutectic structure. The material is highly heat resistant in the temperature range 900-1200°C.     

Structural and Phase Transformations in Plasma-Spray ZrB2–SiC–AlN Coatings on a C/C–SiC Substrate After High-Temperature Thermal Cyclic Heating

Powder Metallurgy and Metal Ceramics - The composition and structure of a plasma-spray coating produced from a 60ZrB2 + 20SiC + 20AlN (wt.%) composite powder on a C/C–SiC substrate were...