共查询到20条相似文献,搜索用时 0 毫秒
2.
AbstractDissolution of Al 2O 3 into molten CaO–Al 2O 3–CaF 2, a base system of mould flux for continuous casting of high Al steel, has been investigated by employing a rotating cylinder method. The dissolution rate of an alumina rod into molten CaO–Al 2O 3–CaF 2 flux increased with increase in rotating speed and temperature. The apparent activation energy for mass transport of flux C was calculated to be 255·6 kJ mol ?1. The rate controlling step during the dissolution process of the alumina rod into molten CaO–Al 2O 3–CaF 2 flux was found to be the diffusion of the solute in the flux boundary layer. The dissolution rate of alumina into molten CaO–Al 2O 3–CaF 2 flux increased with increasing CaO/Al 2O 3, and it may be caused by the increase in thermodynamic driving force and the decrease in the viscosity of the flux. When the Al 2O 3 rod was immersed into molten flux, an intermediate compound of CaO.2Al 2O 3 formed firstly and then dissolved into molten flux. 相似文献
3.
AbstractThe viscosity of the CaO–Al 2O 3–MgO slag system has been measured by the rotating cylinder method up to 1823 K. The MgO content was between 0·39 and 11·33 wt-%, and the mass ratio of CaO/Al 2O 3 was between 0·60 and 1·28. The results indicated that both the MgO content and the mass ratio of CaO/Al 2O 3 have an influence on the viscosity of the slag. The effect of the mass ratio of CaO/Al 2O 3 is larger than that of the MgO content. The viscosity decreased with increasing MgO content and then increased. The effect of the mass ratio of CaO/Al 2O 3 on the viscosity was similar. The main mineralogical compositions of the slag were determined by X-ray diffraction, and their effects on viscosity were investigated. The measured results were in good agreement with those given by the Iida model. 相似文献
4.
The phase equilibria on the solidus surface of the phase diagram of the HfO
2−Y 2O 3−La 2O 3 system have been investigated using DTA in helium up to 2500°C, TA with solar energy in air up to 3000°C, X-ray phase analysis,
petrography, and electron microscopy. Five solid solution fields based on hexagonal (H) and cubic (C) crystal modifications
of Y 2O 3, cubic modifications of HfO 2 with fluorite structure (F), high-temperature cubic modifications of La 2O 3 (X), and crystallization field of the ordered phase La 2Hf 2O 7 with the pyrochlorine (Py) type structure have been found on the solidus surface. The ternary system has three quaternary
novariant equilibria of the eutectic (1) and peritectic (2) type.
Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya,
Nos. 5–6(407), pp. 56–65, May–June, 1999. 相似文献
6.
The phase equilibrium of the system As 2S 3–Cu 2S–PbS and its pseudo binaries with low arsenic contents were studied using isothermal equilibrium and quenching experiments at temperatures between 773 and 1173 K. Based on the experimental results, the phase diagrams of these systems have been estimated. Both estimated pseudo binary phase diagrams indicate higher arsenic sulphide solubility into liquid than previously reported in the literature. The liquidus isotherms of the system As 2S 3–Cu 2S–PbS indicate narrow fully molten area widening with increasing temperature between diginite and galena primary phase fields. On a étudié l’équilibre de phase du système As2S3–Cu2S–PbS et ses pseudos binaires avec de faibles teneurs en arsenic en utilisant des expériences d’équilibre isotherme et de trempe à des températures entre 773 K et 1173 K. On a estimé les diagrammes de phase de ces systèmes en se basant sur les résultats expérimentaux. Les deux diagrammes de phase, pseudos binaires, estimés indiquent une solubilité plus élevée du sulfure d’arsenic dans le liquide que ce qui avait été rapporté auparavant dans la littérature. Les isothermes du liquidus du système As2S3–Cu2S–PbS indiquent une région étroite complètement fondue qui s’élargit avec une augmentation de la température entre les champs de phase primaire de la diginite et de la galène. 相似文献
8.
Phase equilibria of Cu–O–Al 2O 3 system were experimentally investigated in a temperature range of 1100–1400°C under 0.21?atm oxygen pressure. The experiments were conducted employing a high-temperature equilibration and quenching method. Microstructures of the quenched samples were observed with scanning electron microscope. The phase compositions in the samples were analysed with electron probe microanalysis technique. Measured solubility of Al 2O 3 into the molten oxide ranged from 0.0 to 1.8?wt-%. A small solubility of Cu 2O into Al 2O 3 was also observed ranging from 1.20 to 1.58?wt-%. 相似文献
9.
Russian Journal of Non-Ferrous Metals - The effect of K2O on phase relation and viscosity of the CaO–SiO2–25 wt % “FeO”–12 wt % ZnO–3 wt % Al2O3 slags... 相似文献
10.
The composition dependences of electrical conductivity of Fe xO–CaO–SiO 2–Al 2O 3 slags at different oxygen potentials and temperatures have been studied experimentally in the present work. From the experimental results, the total electrical conductivity and electronic conductivity for all the slags monotonously decrease as increasing CO/CO 2 ratio from about 0 to 1. With the increase of Fe xO content, the total electrical conductivity and electronic conductivity increase at a fixed CO/CO 2 ratio. It is also found that the ionic conductivity of all the studied slags increases as increasing the CO/CO 2 ratio, which is resulted from the increase of Fe 2+ ion concentration. In addition, the temperature dependences of ionic, electronic and total conductivity for different compositions obey the Arrhenius law. The electronic transference number exhibits a strong relationship with oxygen potential, but is independent of temperature. 相似文献
11.
The influence of SiC particle on viscosity of CaO–MgO–Al 2O 3–SiO 2 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/SiO 2 ratio or MgO/Al 2O 3 ratio. Meanwhile, it was found that the smaller SiC particle will lead to a larger relative viscosity. 相似文献
12.
AbstractThe viscosity of CaO–5MgO–Al 2O 3–SiO 2 slag with low silica was measured by rotating cylinder method up to 1823 K. Slag compositions were chosen based on five different levels of SiO 2 content between 0 and 11·80%. The MgO content was 5·0%. The mass ratio of CaO/Al 2O 3 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/Al 2O 3, following by an increase with further increasing the mass ratio of CaO/Al 2O 3. 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. 相似文献
13.
The new CaO–Al 2O 3–SiO 2–Li 2O–B 2O 3–Ce 2O 3 mould flux was devised to realise smooth continuous casting of Ce-bearing heat-resistant steel. The new devised mould flux was based on calcium-aluminate system, so the w(CaO)/ w(Al 2O 3) has great influence on the properties of the slag, which is similar to the basicity in the silicate system. The melting temperature, viscous properties, slag structure and crystalline phases with different w(CaO)/ w(Al 2O 3) were investigated. The melting temperature of the mould flux could remain relatively steady with w(CaO)/ w(Al 2O 3) in the range of 1.0–1.82. The main network former in the new slag was [AlO 4]-tetrahedron. The network formed by [AlO 4]-tetrahedron was destroyed by increasing w(CaO)/ w(Al 2O 3), the viscosity decreased consequently. The mould flux show weaker crystallisation tendency with increasing w(CaO)/ w(Al 2O 3). When the temperature decreased to 1100°C, the change of the fully crystallised phases with increasing w(CaO)/ w(Al 2O 3) was as follows: Li 2O·Al 2O 3?+?2CaO·Al 2O 3·SiO 2?→?Li 2O·Al 2O 3?→?Li 2O·Al 2O 3?+?3CaO·Al 2O 3?+?CaCeAlO 4. 相似文献
14.
The present work is carried out to study the evaporation of Na 2O from CaO–Al 2O 3–SiO 2–TiO 2–MgO–Na 2O slags with high basicity and high alumina in the temperature range of 1500–1560°C. The ratio of evaporation was determined by monitoring the Na 2O 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 Na 2O, Al 2O 3 are also found to increase the evaporation ratio of Na 2O, while MgO addition only slightly enhances the evaporation ratio. With TiO 2 content increasing, the evaporation ratio first increases and then decreases. The evaporation rate of Na 2O 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. 相似文献
15.
An equilibration quenching technique was used in this work to study experimentally the phase relations in the Cu 2S–PbS–ZnS system at the temperature range 873–1273 K. The phase diagrams and optimised thermodynamic data set have been created for the systems PbS–ZnS and Cu 2S–PbS–ZnS with the experimental results of this work and selected data reported in the literature by the CALPHAD (CALculation of PHAse Diagrams) method over the temperature range of 773–1473 K. The obtained thermodynamic dataset allows calculation of the thermodynamic properties and phase equilibria in the PbS–ZnS and Cu 2S–PbS–ZnS systems and shows good agreement with experimental results. Dans ce travail, on a utilisé une technique de trempe d’équilibration pour étudier expérimentalement les relations de phases du système Cu2S–PbS–ZnS dans la gamme de température de 873 à 1273 K. Utilisant la méthode CALPHAD (CALculation of PHAse Diagrams), on a créé les diagrammes de phases et l’ensemble de données thermodynamiques optimisées des systèmes PbS–ZnS et Cu2S–PbS–ZnS, dans la gamme de température de 773 à 1473 K, au moyen des résultats expérimentaux de ce travail et de données choisies rapportées dans la littérature. L’ensemble de données thermodynamiques obtenues permet le calcul des propriétés thermodynamiques et des équilibres de phases des systèmes PbS–ZnS et Cu2S–PbS–ZnS, qui sont en bon accord avec les données expérimentales. 相似文献
16.
AbstractMagnesium 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–Cr 2O 3 refractories in a synthesised 50CaO–45Al 2O 3–5SiO 2 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–Cr 2O 3 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. 相似文献
17.
Precise numerical simulations of blast furnace (BF) rely on accurate and convenient thermophysical property models of BF slags. Liquidus temperature ( Tliq) is one of the most fundamental properties of BF slag, however, the conventional phase equilibrium diagram method for Tliq calculation can be hardly used in numerical simulations. In this work, an accurate and simple empirical formulation suitable for Tliq calculation of BF slags in numerical simulations is established. The model was calibrated by 707 measurement representing 11 primary phase fields in SiO 2–Al 2O 3–CaO–MgO system. The calculated Tliq in present work agrees very well with the measured values, with an average error of only 17.1°C, which is much more accurate than CalPhad method. Present work also suggests that the liquidus region of BF slag at 1500°C should be slightly extended based on the classic phase equilibrium diagram. 相似文献
18.
In order to develop low fluoride or fluoride free CaO–Al 2O 3 based mould flux for casting high aluminium steel, an investigation was carried out to study the effect of substituting CaF 2 with B 2O 3 on heat transfer and crystallisation behaviour of CaO–Al 2O 3 based mould flux by employing a heat transfer simulator of mould flux and a single hot thermocouple technique. The results showed that addition of CaF 2 promoted heat transfer of CaO–Al 2O 3 based mould flux, which was opposite to the effect of CaF 2 on heat transfer in conventional CaO–SiO 2 based mould flux. Addition of CaF 2 inhibited crystallisation of CaO–Al 2O 3 based mould flux by lowering the start crystallisation temperature and prolonging the incubation time of crystallisation. B 2O 3 showed similar effects to CaF 2 on heat transfer and crystallisation of CaO–Al 2O 3 based mould flux, but its ability to promote heat transfer and suppress crystallisation was stronger than CaF 2. Ca 3B 2O 6 (melting temperature 1480°C) was found as the primary crystalline phase in fluoride free CaO–Al 2O 3 based mould flux compared with the primary crystalline phase Ca 2Al 3O 6F (melting temperature 1507°C) in fluoride bearing (20% CaF 2) CaO–Al 2O 3 based mould flux. 相似文献
20.
The projection of the solidus surface in the phase diagram for the Al 2O 3 ZrO 2 La 2O 3 system on the plane of a concentration triangle has been constructed, which consists of seven isothermal three-phase fields corresponding to three nonvariant equilibria of eutectic type and four nonvariant equilibria of peritectic type, as well as four lineated surfaces for the end of crystallization in the binary eutectics. The highest temperature on the solidus surface is 2710°C, and the lowest is 1665°C. No ternary phases and appreciable areas of solid solution are observed. Data on the bounding binary systems, liquidus and solidus surfaces have been used to construct the phase-equilibrium diagram together with a scheme for the reactions in equilibrium crystallization in the Al 2O 3 ZrO 2 La 2O 3 system. 相似文献
|