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1.
During the continuous casting of high‐Al steel, the dynamic reduction of silica‐based mould fluxes by the aluminium in the steel leads to changes in their composition and physical properties. The alumina‐based mould flux has been suggested as an alternative to alleviate this reduction problem. However, until now, the smooth running of high‐Al steel continuous casting has been impeded by the lack of systematic investigation of properties of this slag. In this paper, the effects of typical components on the properties of alumina‐based mould fluxes are discussed. The experimental results show that: (a) an increase in F? can reduce the viscosity while increasing the melting and break temperatures; (b) with increasing Li2O, the viscosity, melting temperature, and break temperature first decrease and then increase; (c) with the addition of BaO, the viscosity, melting temperature, and break temperature remain at a low level, while a further increase in BaO causes a decrease in viscosity, an increase in melting temperature, and the stabilization of the break temperature; (d) BaO is favorable to stabilize the properties of mould fluxes for the dissolution of additional Al2O3; (e) the crystalline phases of the mould fluxes mainly contain 12CaO · 7Al2O3 and 11CaO · 7Al2O3 · CaF2, and 12CaO · 7Al2O3 has great potential as a substitute for cuspidine.  相似文献   

2.
In Japanese steelworks, hot metal is now produced by scrap melting process. With this process removal of sulphur is very much handicapped because of very high sulphur levels (0.04 to 0.09 pct by weight) and relatively low tapping temperatures (1623 to 1723 K). In order to overcome such disadvantages, the authors explored on the phase diagrams of {CaO‐SiO2‐Al2O3‐MgO} slags, and this research revealed that those slags at 35 wt%‐Al2O3 would be good candidates as reagents for the removal of sulphur from high sulphur hot metal at relatively low temperatures. For better understanding of the thermodynamic properties of the candidate slags, in this study, activities of FexO were determined by using solid‐state electrochemical cells incorporating MgO‐stabilized zirconia and Mo + MoO2 reference electrode.  相似文献   

3.
In Japanese steelworks, hot metal is now being produced by a scrap melting process. With this process, removals of sulphur is very much handicapped because of very high sulphur levels (0.04‐ to 0.09‐ pct by weight) and relatively low tapping temperatures (1623 to 1723 K). In order to overcome such handicaps, the authors explored on the respective phase diagrams. These explorations revealed that {CaO‐SiO2‐Al2O3‐MgO} slags with Al2O3 contents of 30‐ to 35‐pct by weight would be good candidates as reagents for sulphur removal from high sulphur hot metal at relatively low temperatures. For better understanding of the thermodynamic properties of the candidate slags, in this study, sulphide capacities were determined through gas/slag equilibrium technique. The experimental results suggest that there would be, at least, a “window” to remove sulphur from high sulphur hot metal as relatively low temperatures.  相似文献   

4.
The effect of oxide component content on the low melting point zone (LMP) in the CaO‐MgO‐Al2O3‐SiO2 system has been analysed using FactSage software. The contents of dissolved elements [Si], [Mg], [O] and [Al] in liquid steel in equilibrium with the LMP inclusions in the CaO‐MgO‐Al2O3‐SiO2 system have been calculated. The results show that the CaO‐MgO‐Al2O3‐SiO2 system has the largest LMP zone (below 1400°C) when the Al2O3 content is 20% or the MgO content is 10%. The LMP zone becomes wide with the increase in CaO content (within the range of 0~30 mass%) and the decrease in SiO2 (from 25 to 5 mass%). To obtain the LMP (below 1400°C) inclusions, the [Mg], [Al] and [O] contents must be controlled within the range of 0.2~2 ppm, 1.0~2.0 ppm and 60~100 ppm, respectively.  相似文献   

5.
A study on the formation mechanism of liquid calcium aluminate inclusions from MgO‐Al2O3 spinel was carried out. It was found that spinel reacted with dissolved Ca in liquid steel forming liquid calcium aluminate phase. Stability calculations showed good agreement with the experimental result. According to the thermodynamic calculation, liquid calcium aluminate inclusions would form from spinel even at very low level of dissolved Ca content at 1873 K. At lower temperatures, the compound CaO‐2Al2O3 was found to be the stable phase at the spinelmetal interface. Potential sources of dissolved Ca during ladle processes were also discussed.  相似文献   

6.
A model for viscosity estimation of molten slags in the Al2O2‐CaO‐MgO‐SiO2 system is presented in this work. The model is an extension to the viscosity estimation model of molten slags in the CaO‐FeO‐MgO‐MnO‐SiO2 system developed before by the present author. The present model has explicitly taken charge compensation into consideration. It is postulated that Al exists in a structural unit MAl2O4 when MO/ Al2O3 >1 for the Al2O3‐MO‐SiO2 system (MO=CaO, MgO). MAl2O4 has a similar behaviour as SiO2, i.e. it can form an Al‐O‐Al network and be depolymerised by network modifying oxides (CaO, MgO). The present model is applied in viscosity estimation of some slags within the Al2O3‐CaO‐MgO‐SiO2 system. A mean deviation of less than 25% is achieved for the present model.  相似文献   

7.
The desulfurization capacities of CaO-SiO2-Al2O3-MgO-CaF2-BaO complex flux were determined experimentally at 1873 K (1600 °C), and the effects of composition on desulfurization abilities were analyzed using the method of quadratic orthogonal regression. The results suggested that the desulfurization rate decreased with an increasing ratio of Al2O3/CaO, and the addition of BaO and MgO to the flux improved the desulfurization capability. The increase of the CaF2 content improved the desulfurization effect for high MgO contents or BaO contents bearing slags.  相似文献   

8.
A laboratory study was carried out to investigate non‐metallic inclusions in high strength alloying steel refined by high basicity slag. The results indicated that the inclusions were mainly of the CaO? MgO? Al2O3 system, Al2O3? MgO and MgO‐based inclusions. The steel/slag reaction time and Al2O3 content in slag had a great effect on inclusions characteristics. With the reaction time increasing from 30 to 180 minutes, inclusions experienced a transformation process: from mainly Al2O3? MgO system and MgO‐based inclusions to spherical CaO? MgO? Al2O3 system inclusions surrounded by a lower melting temperature surface layer of CaO? Al2O3. Formation and transformation mechanisms of the inclusions were given based on the results. It was also found that with Al2O3 content in slag reduced from 40% to 30%, [Mg] contents in steel melts were increased and MgO in slag reached saturation, which contributed to the formation of more MgO‐based inclusions and a more scattered inclusion composition distribution after 90 min reaction.  相似文献   

9.
The phase relations in the systems CaO‐FeOn‐SiO2‐Al2O3 and CaO‐FeOn‐SiO2‐MgO at 1600 °C saturated with liquid iron are described. The phase conditions in the quaternary system with aluminium oxide are so far rather unknown. An addition of aluminium oxide makes the calciumsilicates and lime saturation areas move towards the CaO corner thus enlarging the homogeneous liquidus space accordingly. Aluminium oxide can be considered as a flux in this case. The fields of different solid solutions in the system CaO‐FeOn‐SiO2‐MgO were taken into account. Some additional (2 to 4)‐phase areas occur with increasing MgO content. This causes the precipitation of magnesiowustite which dominates the system accordingly. The changed phase relations strongly influence the direction of tie‐lines and their length. Therewith, the correlation between liquid phase and solid phase, calculated via lever rule, is influenced, too.  相似文献   

10.
Viscosities of some quaternary slags in the Al2O3‐CaO‐MgO‐SiO2 system were measured using the rotating cylinder method. Eight different slag compositions were selected. These slag compositions ranging in the high basicity region were directly related to the secondary steel making operations. The measurements were carried out in the temperature range of 1720 to 1910 K. Viscosities in this system and its sub‐systems were expressed as a function of temperature and composition based on the viscosity model developed earlier at KTH. The iso‐viscosity contours in the Al2O3‐CaO‐MgO‐SiO2 system relevant to ladle slags were calculated at 1823 K and 1873 K for 5 mass% MgO and 10 mass% MgO sections. The predicted results showed good agreement with experimental values and the literature data.  相似文献   

11.
The present work was carried out with a view to re‐examine the phase diagram aspects of CaO? Al2O3? SiO2 and CaO? MgO? Al2O3? SiO2 slags with MnO additions. The aim was to confirm the homogeneous liquid range necessitated for sulfide capacities measurements of the above‐mentioned slags. The liquidus and solidus temperatures of these slags were measured by DSC and X‐ray radiograph techniques. The experimental results were compared with the liquidus and solidus temperatures obtained from literature (Slag Atlas) and commercial softwares ThermoCalc and FactSage. The results indicate that there is good agreement between the experimental values and those retrieved from literature and the commercial software in the case of the ternary system CaO? Al2O3? SiO2. For the CaO? MgO? MnO? Al2O3? SiO2 system, significant deviations were observed between the different sources. The present observations indicate that X‐ray radiography can be a very useful tool in estimating the solidus temperatures of slags while DSC would complement the information with respect to liquidus temperatures.  相似文献   

12.
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.  相似文献   

13.
In order to examine the possibility of recycling BOF slags as dephosphorization and desulphurization fluxes, experiments were performed in a system with liquid iron and artificially prepared fluxes comprising BOF slags, lime and/or sinter ore in a Al2O3 crucible at 1623 and 1673K. The phosphorus and sulphur content in liquid iron were expressed as a function of reaction time in the form of exponential decay of first order. CaF2‐free fluxes comprising BOF slags, lime and/or sinter ore showed very high capacities of dephosphorization and desulphurization, which means that BOF slags could largely be recycled in the hot metal pretreatment processes.  相似文献   

14.
The viscosities of CaO‐SiO2‐20 wt%Al2O3‐MgO slags (CaO/SiO2 = 1.0–1.2, wt%MgO = 5–13) were measured to estimate the effect of MgO on the viscous behaviour at elevated temperatures. The slag viscosity at 1773 K decreased with increasing MgO contents, which was typical of a basic oxide component at relatively low basicity (CaO/SiO2) of 1.0. The FT‐IR spectroscopic analysis of the slag structure seems to verify this behaviour. However, an unexpected contradiction with the temperature dependence was observed above 10 wt%MgO and above CaO/SiO2 of 1.2. Although the apparent activation energy was expected to decrease with additions of the basic oxide component MgO, the apparent activation energy increased. This unexpected behaviour seems to be related to the change in the primary phase field correlating to the phase diagram corresponding to the slag composition. Therefore, in order to understand the viscosity at both high Al2O3 and MgO, not only should the typical depolymerization of the slag structure with high MgO content be considered but also the primary phases of which the molten slag originates.  相似文献   

15.
The effect of oxide component content on the low melting point zone (simplified as LMP) in the CaO‐MnO‐Al2O3‐SiO2 system has been analysed by FactSage. The contents of [Si], [Mn], [O] and [Al] in liquid steel which are in equilibrium with the LMP inclusions in the CaO‐MnO‐Al2O3‐SiO2 system have been calculated. The results show that the CaO‐MnO‐Al2O3‐SiO2 system has the largest LMP zone (below 1400°C) when the Al2O3 content is 20% or the CaO content is 15%, and that the LMP zone becomes wider with increase in SiO2 and MnO contents (within the range of 0~25%). To obtain LMP inclusions (below 1400°C), [Si] and [Mn] can be controlled within a wide range, but [Al] and [O] must be controlled within the range of 0.5~5 ppm and 50~120 ppm, respectively.  相似文献   

16.
The solubility of water vapour in the CaO‐SiO2‐Al2O3‐MgO quaternary slag system was measured using an inert gas fusion technique with thermal conductivity detection. The slags were equilibrated with argon‐water vapour mixture corresponding to 0.157 bar of water vapour pressure at 1873 K. The slag solubility of water vapour is proportional to the square root of vapour pressure. Since the hydroxyl capacity of slag, COH shows an independence on the relative amount of CaO or MgO in slag, the contributions of CaO and MgO on the hydroxyl capacity are equivalent on a molar basis. Whereas, Al2O3 shows a better effect on the hydroxyl capacity than SiO2. A linear relationship between hydroxyl capacity and slag basicity in logarithmic scale was obtained with the slope of 1/2, confirming the water vapour dissolution reaction into a basic slag as (O2‐) + H2O(g) = 2(OH?). The correlation between hydroxyl capacity and slag components was derived in terms of their contributing weight factors. The measured values of C'OH agree well with the calculated ones using the interaction energies of αH‐Al = ?38300 and αH‐Mg = ?22700 J determined with the aid of the regular solution model. In addition, the correlation between hydroxyl capacity and sulphide capacity was empirically derived as a formula of logCOH = 1/2logCS + (4.38 ± 0.25) through the thermodynamic expression of both capacities by virtue of the common oxygen ion activity.  相似文献   

17.
Experimental study on the LF refining of aluminum killed cold heading steel shows that calcium content in the molten steel increased to about 0.0010% at the end of refining, and the aluminum deoxized products were transformed from Al2O3 to the complex inclusions CaO–MgO–Al2O3 with lower melting point by the high basicity, high Al2O3, and strong deoxidizing slag. The inclusions are in liquid state and can be easily floated up during LF refining and continuous casting. The total oxygen content of the steel falls to about 0.0020%. The experimental technology uses only 50 m calcium wire to the 80‐t heat or even without calcium treatment. As compared to the traditional technology with higher amount of calcium for treatment, which forms CaS and CaO–MgO–Al2O3 inclusions with high melting point, the experimental technology improves the castability and reduces the manufacturing cost.  相似文献   

18.
The solubility of chlorine in CaO‐SiO2‐Al2O3‐MgO(‐CaF2) slag was measured at 1673 ‐1823 K. By estimating the chloride capacity of slags, thermodynamic behaviour of chlorine in the molten slag was investigated. Chloride capacity increased with increasing CaO / SiO2 ratio (C/S). An increase in MgO content decreased chloride capacity at C/S≥1.0 because it lowered the activity of Ca2+ which seemed to have strong affinity with Cl? in molten slag. Also, the chloride capacity decreased with increasing Al2O3 content. The affinity between the Ca2+ and Cl? ions was confirmed by measuring the infrared spectra of slags. The dissolution reaction of chlorine into slag was exothermic and its molar enthalpy was evaluated from the experimental results at 1673 ‐ 1823 K. Based on the result obtained in the present study, the quantitative prediction of chlorine distribution during the blast furnace process was performed. It was estimated that almost all chlorine in the blast furnace would be absorbed into molten slag even if the PCI ratio was increased or low quality coal with chlorine content less than 1.0 mass% was injected.  相似文献   

19.
This paper provides an informative basis on MgO saturation in secondary metallurgical slags by conducting thermo‐chemical calculations in the ternary base system Al2O3‐CaO‐SiO2 at 1600 °C, 1650 °C and 1700 °C using FactSageTM6.0. The results for lime‐aluminate and lime‐silicate slag are displayed in a straightforward and illustrative manner. In addition, approximate equations describe the temperature dependencies: a temperature rise of 50 °C increases the MgO saturation limit by about 1 wt. %.  相似文献   

20.
钢液深脱硫精炼工艺的研究   总被引:9,自引:0,他引:9  
成国光  宋波  陆钢  王新华  赵沛 《钢铁》2001,36(3):21-22,25
通过以高温钼丝炉上测定硫在钢液与BaO-CaO-MgO-Al2O3-SiO2渣系之间的平衡分配,结果表明:在常用脱硫精炼渣系CaO-MgO-Al2O3-SiO2中加入BaO能显著提高渣的硫容量。并进一步在感应炉上进行了钢液深脱硫精炼工艺的实验,得出:含BaO脱硫粉剂比传统的CaO-CaF2脱硫剂具有更强的脱硫能力。  相似文献   

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