连铸保护渣中CaF_2含量对脱玻化性能的影响

通过运用SHTTⅡ型熔化结晶温度测试仪构建了TTT曲线,计算出不同CaF_2下保护渣脱玻化活化能;再通过X射线衍射仪并结合JADE软件计算出结晶率和分析结晶矿相;最后利用金相显微镜,观察多种回温处理下不同CaF_2含量的保护渣渣膜的表面形貌,探究CaF_2对保护渣脱玻化的影响。试验结果表明:随着CaF_2含量增加保护渣脱玻化的温度和活化能不断降低,渣膜表面粗糙度增大;随着玻璃体渣膜处理温度的升高,保护渣析出矿相种类单一化。     

Influence of SiO2 Addition on the Properties of Al2O3‐CaO‐CaF2 Slag

The Al₂O₃‐CaO‐CaF₂ slag system is used in making special quality steels by the electro‐slag re‐melting process (ESR). The purpose of our investigation was to analyse ESR slag that contained SiO₂. The slag samples with different SiO₂ fractions (0 ‐ 20 mass %) were examined by chemical analysis, differential thermal analysis, simultaneous thermal analysis, X‐ray diffraction, electron microscopy and wetting angle measurement. With addition of SiO₂ the polymerization of slags was increased due to the formation of new silicate complex compounds that influenced their melting points and wetting angles.     

Nitride capacities in CaO–SiO2 and CaO–SiO2–Al2O3 melts

Nitride capacities, , defined by (mass-% N) · in the CaO–SiO₂ and CaO–SiO₂–AI₂O₃ melts were measured in the temperature range of 1 723 to 1 923 K by a gas-slag equilibration technique using CaO, Al₂O₃, and Mo crucibles. Nitrogen content in slag, (mass-% N), was proportional to oxygen partial pressure, , to the power of ?3/4 at constant nitrogen partial pressure, . The values for increased linearly with increasing temperature and increased with the content of nitride formers, SiO₂ and Al₂O₃, but the effect of SiO₂ on value was found to be greater than that of Al₂O₃. The activity coefficients of Si_3/4N in the CaO–SiO₂ melts tended to increase with increasing the content of SiO₂.     

Fundamental thermodynamic aspects of the CaO–Al2O3–SiO2 system

The most important metallurgical effects of ladle treatment of aluminium-killed steels with calcium, are associated with the modification of alumina inclusion. For the development of the deoxidation-control model for inclusions, the thermodynamic slag model, based on the Gibbs energy minimization and modelling approaches postulated from J. Hastie et al., was used to calculate component oxide activities in the system CaO–Al₂O₃ and part of systems 3CaO · Al₂O₃ – SiO₂, 12 CaO · 7Al₂O₃ – SiO₂ and CaO · Al₂O₃ – SiO₂ at 1600°C.     

Contribution to the phase diagram CaF2–CaO–Al2O3

Critical review of the available data. Determination of the liquidus line of CaF₂-Al₂O₃ mixtures and of the CaO liquidus line in the CaF₂–CaO binary. Investigation of the heterogeneous equilibria in the CaF₂–CaO–Al₂O₃ ternary by using different techniques. Determination of the 1600°C liquidus isotherms of CaO, CaO · 2Al₂O₃, CaO · 6Al₂O₃, Al₂O₃ and of the miscibility gap.     

Thermophysical Properties of Continuous Casting Mold Flux for Advanced Steel Developments

The effect of Al₂O₃ on the crystallization and viscosity of calcium-silicate based fluxes with Na₂O and Li₂O additions used for continuous casting mold fluxes have been studied using the confocal laser scanning microscope and the rotating spindle rheometer. Al₂O₃ additions lowered the crystallization temperature of the flux and several crystalline phases for fluxes with high concentrations of SiO₂ forms depending on the cooling rate. High Al₂O₃ containing fluxes formed relatively few crystalline phases and were not highly dependent on the cooling rate. At slow cooling rates of 25 K/min for 10 and 20 wt% Al₂O₃ containing samples, SEM images revealed dendrites formed within the crystalline phases. At faster cooling rates the dendrite formation is inhibited and a spherical morphology could be observed. The substitution of SiO₂ with Al₂O₃ content modified the dominant silicate network into complex alumino-silicates. This increased the viscosity of the melt. FTIR and Raman analysis showed increased amounts of symmetric Al–O⁰ stretching with higher Al₂O₃. With higher CaO/(SiO₂ + Al₂O₃), the symmetric Al–O⁰ stretching and the Si–O–Al seems to decrease.     

连铸保护渣性能研究及改进

对连铸保护渣的粘度—温度曲线及熔化温度性能等进行了试验研究，得出基本组分对保护渣性能的影响规律；对粘度—温度曲线形状的分析研究，确定了保护渣的性能改进方向，结合济钢连铸生产中存在的问题，开发出两种新的保护渣。     

连铸结晶器保护渣的熔化

１保护渣熔化过程和机理保护渣在钢水面上形成了所谓粉渣层－烧结层－液渣层的三层结构。保护渣熔化过程为：（１）试样中有机物氧化（脱水和汽化）；（２）碳质料的燃烧损失，时间较长，说明了渣粒烧结和熔化过程的延缓程度，与渣内所含碳粒类型和数量有关；（３）熔化突...     

Thermodynamics of manganese distribution between liquid iron and the CaO–Al2O3–SiO2–FeO–MnO system

The thermodynamics of distribution of constituents between liquid iron and the CaO–Al₂O₃–SiO₂–FeO–MnO system at 1600°C was studied using electrochemical indication of the equilibrium partial pressure of oxygen in both phases. The results show that oxidation potential of the Fe(l)–CaO–Al₂O₃–SiO₂–FeO–MnO system, expressed in terms of log p(O₂), is directly proportional to log (x(MnO) · x(FeO)/w| Mn |). Manganese distribution coefficient, L'_mn, in intersection CaO/Al₂O₃ = 1 decreases with increasing slag basicity expressed in terms of activity a(CaO) or 1/γ(MnO). Experimentally determined equilibrium constant K_Mn/Fe is equal to 2.7 for 1600°C. The number of exchanged electrons between Fe-O-Mn-Si electrode and the slag approaches the theoretical value.     

Thermodynamics of lead and bismuth in CaO–CaF2 melts

In order to understand a new refining process for removing tramp elements from alloy steels under strongly reducing conditions, the authors previously reported the thermodynamic behaviour of P, Sn, Sb, As and Cu in CaO–CaF₂ melts. In this investigation, the thermodynamic behaviour of Pb and Bi in CaO–CaF₂ melts under oxygen partial pressures from 10^?16 to 10^?20 atm was studied at temperatures ranging from 1360 to 1550°C, using a similar technique. It was shown that Pb and Bi exist in slag mainly as Ca₂Pb and Ca_1.5Bi, respectively, under very low oxygen partial pressure although a part of Pb is soluble in slags as metal. The obtained results were extrapolated to lower oxygen partial pressures to investigate the possibility of removing these tramp elements from molten iron, causing Bi to be removed from molten iron below an oxygen partial pressure of 10^?23 atm, whereas Pb is removed under higher oxygen partial pressures.     

Aufstickung von Schlacken des Systems CaO–SiO2–A12O3

Laboratoriumsuntersuchungen zur Aufstickgeschwindigkeit von flüssigen Schlacken des Systems CaO–SiO₂–Al₂O₃ in Abwesenheit und in Gegenwart von Kohlenstoff. Einflüsse von Schlackenzusammensetzung, Temperatur und Stickstoffdruck. Erörterung des Aufstickmechanismus. Deutung der Ergebnisse an Hand der Schlackenstrukturen.     

Cao—SiO2—CaF2三元渣系的挥发率

通过质量损失法对ＣａＯ－ＳｉＯ２－ＣａＦ２三元渣系挥发率与温度、渣组成的关系进行了研究。结果表明：在渣完全熔化之前有一临界温度，其值大小因渣而异，即酸性渣具有低温临界点；碱性渣具有高温临界点；中性渣则两个临界点均存在；当渣的碱度过高（Ｒ≥１．４）或ＣａＦ２含量减少（≤１０％）时，这两个临界点均不存在。临界温度对渣的挥发率有明显影响；在渣完全熔化之后，挥发率将随碱度的降低及ＣａＦ２含量的增加而提高。