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1.
P. Palai P. P. Sahoo Arghya Dey T. K. Roy V. V. Mahashabde 《Metallurgical and Materials Transactions B》2013,44(5):1185-1189
The alumina pickup in a range of mold fluxes used for continuous casting of aluminum (Al)-killed ultralow carbon, low carbon, and peritectic steel have been measured. The Al2O3 pickup in slag varies approximately from 7 to 12 pct and depends on the slag basicity. Significantly higher Al2O3 pickup reported in basic slags and polynomial relationship exists between them. The effect of chemical composition on microstructure evolution and Al2O3 partitioning during crystallization was identified in all three types of mold slags. The microsegregation of Al2O3 inclusions in the constituent phase of CaO-SiO2-Al2O3 based slag film is presented. Constitutional segregation of Al2O3 inclusion in slag was found to affect the Al2O3 pickup phenomena during continuous casting. Segregation of alkalis like Na and K was also observed in an Si-rich interdendritic matrix, whereas F was retained in the dendrites of all the slags studied. The Al2O3 inclusion partitioning and interdendritic segregation in the mold slag is studied with metallographic evidence. 相似文献
2.
Joo Hyun Park Dong Joon Min Hyo Seok Song 《Metallurgical and Materials Transactions B》2004,35(2):269-275
The viscosity of CaO-SiO2 (-MgO)-Al2O3 slags was measured to clarify the effects of Al2O3 and MgO on the structure and viscous flow of molten slags at high temperatures. Furthermore, the infrared spectra of the
quenched slags were analyzed to understand the structural role of Al2O3 in the polymerization or depolymerization of silicate network. The Al2O3 behaves as an amphoteric oxide with the composition of slags; that is, the alumina behaves as a network former up to about
10 mass pct Al2O3, while it acts as a network modifier, in parts, in the composition greater than 10 mass pct Al2O3. This amphoteric role of Al2O3 in the viscous flow of molten slags at the Newtonian flow region was diminished by the coexistence of MgO. The effect of
Al2O3 on the viscosity increase can be understood based on an increase in the degree of polymerization (DOP) by the incorporation
of the [AlO4]-tetrahedra into the [SiO4]-tetrahedral units, and this was confirmed by the infrared (IR) spectra of the quenched slags. The influence of alumina on
the viscosity decrease can be explained on the basis of a decrease in the DOP by the increase in the relative fraction of
the [AlO6]-octahedral units. The relative intensity of the IR bands for the [SiO4]-tetrahedra with low NBO/Si decreased, while that of the IR bands for [SiO4]-tetrahedra with high NBO/Si increased with increasing Al2O3 content greater than the critical point, i.e., about 10 mass pct in the present systems. The variations of the activity coefficient of slag components with composition
indirectly supported those of viscosity and structure of the aluminosilicate melts. 相似文献
3.
Cheng-Bin Shi Myung-Duk Seo Jung-Wook Cho Seon-Hyo Kim 《Metallurgical and Materials Transactions B》2014,45(3):1081-1097
Crystallization behaviors of the newly developed lime-alumina-based mold fluxes for high-aluminum transformation induced plasticity (TRIP) steels casting were experimentally studied, and compared with those of lime-silica-based mold fluxes. The effects of mold flux crystallization characteristics on heat transfer and lubrication performance in casting high-Al TRIP steels were also evaluated. The results show that the crystallization temperatures of lime-alumina-based mold fluxes are much lower than those of lime-silica-based mold fluxes. Increasing B2O3 addition suppresses the crystallization of lime-alumina-based mold fluxes, while Na2O exhibits an opposite effect. In continuous cooling of lime-alumina-based mold fluxes with high B2O3 contents and a CaO/Al2O3 ratio of 3.3, faceted cuspidine precipitates first, followed by needle-like CaO·B2O3 or 9CaO·3B2O3·CaF2. In lime-alumina-based mold flux with low B2O3 content (5.4 mass pct) and a CaO/Al2O3 ratio of 1.2, the formation of fine CaF2 takes place first, followed by blocky interconnected CaO·2Al2O3 as the dominant crystalline phase, and rod-like 2CaO·B2O3 precipitates at lower temperature during continuous cooling of the mold flux. In B2O3-free mold flux, blocky interconnected 3CaO·Al2O3 precipitates after CaF2 and 3CaO·2SiO2 formation, and takes up almost the whole crystalline fraction. The casting trials show that the mold heat transfer rate significantly decreases near the meniscus during the continuous casting using lime-alumina-mold fluxes with higher crystallinity, which brings a great reduction of surface depressions on cast slabs. However, excessive crystallinity of mold flux causes poor lubrication between mold and solidifying steel shell, which induces various defects such as drag marks on cast slab. Among the studied mold fluxes, lime-alumina-based mold fluxes with higher B2O3 contents and a CaO/Al2O3 ratio of 3.3 show comparatively improved performance. 相似文献
4.
In an attempt to systematize the knowledge of the heat conduction of liquid silicates, the effective thermal diffusivities
of some synthetic slags containing CaO, Al2O3, and SiO2 have been measured, using the three-layer laser-flash method on a differential scheme in the temperature range of 1625 to
1825 K. The effective thermal diffusivities measured, which are a combination of the phononic and photonic heat-transfer mechanisms,
were found to increase with increasing temperature for all the presently investigated slags. The slag compositions were chosen
in such a way that the changes in the effective thermal diffusivities would reflect the changes in the structure of the slags.
It was observed that, at a CaO/Al2O3 molar ratio of 4.42, an increase of the SiO2 content had very little effect on the effective thermal diffusivity values. On the other hand, addition of SiO2 to a slag with the CaO/Al2O3 molar ratio of 2.59 resulted in a significant increase in the effective thermal diffusivity. The addition of Al2O3 to slags with a constant CaO/SiO2 molar ratio resulted in a marked increase in the effective thermal diffusivity. Both these trends indicate that there might
be an influence of the network formation in silicate melts on the effective thermal diffusivity. 相似文献
5.
Jiwon Park Seetharaman Sridhar Richard J. Fruehan 《Metallurgical and Materials Transactions B》2013,44(1):13-15
The activity coefficient of SiO2 in SiO2-Al2O3-CaO slags with limited Al2O3 content was measured by equilibrating Fe-C-Si melt and slags at 1873 K (1600 °C). When the Al2O3 content was between 48 and 54 wt pct, the results show that $ \gamma_{{{\text{SiO}}_{ 2} }} $ rapidly decreases as the amount of SiO2 in the slag decreases. The equilibrium amounts of Si and Al in a Fe melt in equilibrium with SiO2-Al2O3-CaO slags were calculated based on the result of this study. 相似文献
6.
By equilibrating the CaO-Al2O3-SiO2 slags with Fe - 0.0003~0.07% Al - 0.002~3.5% Si - 0.9~2.0% C alloys (mass contents in %) at 1873 K, the solubilities of carbon were measured as a function of Si contents in metal, using an alumina or lime crucible. The distribution ratios of carbon as a C2- -ion were found to be linearly related to Si contents with a slope of 1/2 at a given slag composition. The carbide capacity, , defined by (% C) , increased with increasing SiO2 contents at a given CaO/AlO1.5 molar ratio in the CaO-AlO1.5SiO2 system. 相似文献
7.
Qiang Wang Min Sun Shengtao Qiu Zhiling Tian Guoling Zhu Longmei Wang Pei Zhao 《Metallurgical and Materials Transactions B》2014,45(2):540-546
The slag-steel equilibrium reaction between the newly developed mold slag ND-MSL and 20Mn23AlV steel has been studied at high temperatures in the laboratory. The crystal morphology, microanalysis, and phase analysis of the original and final ND-MSL slags were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Results show that, in the final ND-MSL slag, the constitution of SiO2 decreased by 0.7 wt pct and Al2O3 increased by 6.46 wt pct, while the melting temperature, viscosity, and crystallization rate increased by 62 K, 0.66 dPa s, and 15 pct, respectively. NaAlSi3O8 and CaAl2Si2O8 were found to be precipitated in the final ND-MSL slag. Both the original and final ND-MSL slags have a small amount of LiF crystal and good glass form. The ND-MSL slag has little change in the composition and properties compared with the two currently used mold slags. 相似文献
8.
Hiroyasu Fujiwara 《国际钢铁研究》2000,71(3):53-60
The ferrous and ferric ion capacities, and , for the slag of CaO + Al2O3 + SiO2 are determined at 1873 K by means of the distribution equilibrium of iron between FexO dilute slags of the system and Pt + Fe alloys under a controlled atmosphere. Compared with the values of for CaO + Al2O3 binary slag at a constant ratio of Al2O3 to decreases with an increase in SiO2 content. Nearly linear relationships are observed between the logarithm of the ferrous and ferric ion capacities and the optical basicity. Applying these capacities, the relationship between (%FeT) and PO2 under iron saturation, as well as the iron redox equilibrium in slag in relation to the optical basicity were discussed. 相似文献
9.
Myung-Duk Seo Cheng-Bin Shi Jung-Wook Cho Seon-Hyo Kim 《Metallurgical and Materials Transactions B》2014,45(5):1874-1886
The effects of basicity (CaO/SiO2), B2O3, and Li2O addition on the crystallization behaviors of lime-silica-based mold fluxes have been investigated by non-isothermal differential scanning calorimetry (DSC), field emission scanning electron microscopy, X-ray diffraction (XRD), and single hot thermocouple technique. It was found that the crystallization temperature of cuspidine increased with increasing the basicity of mold fluxes. The crystallization of wollastonite was suppressed with increasing the mold flux basicity due to the enhancement of cuspidine crystallization. The addition of B2O3 suppresses the crystallization of mold flux. The crystallization temperature of mold flux decreases with Li2O addition. The size of cuspidine increases, while the number of cuspidine decreases with increasing mold flux basicity. The morphology of cuspidine in mold fluxes with lower basicity is largely dendritic. The dendritic cuspidine in mold fluxes is composed of many fine cuspidine crystals. On the contrary, in mold fluxes with higher basicity, the cuspidine crystals are larger in size with mainly faceted morphology. The crystalline phase evolution was also calculated using a thermodynamic database, and compared with the experimental results determined by DSC and XRD. The results of thermodynamic calculation of crystalline phase formation are in accordance with the results determined by DSC and XRD. 相似文献
10.
Jeferson L. Klug René Hagemann Nestor C. Heck Antônio C. F. Vilela Hans P. Heller Piotr R. Scheller 《国际钢铁研究》2012,83(12):1186-1193
The main problem related to the development of fluorine‐free mould powders for slab casting is effectively controlling the heat transfer between the steel shell and mould. In commercial mould powders crystallization of cuspidine (Ca4Si2O7F2) from mould slag has a great effect on heat‐transfer control. In industrial process the crystallization rate for a fluorine‐free mould slag should be similar to the crystallization rate of cuspidine. To evaluate the crystallization rate for slags time‐temperature‐transformation (TTT) diagrams can be constructed using the Single Hot Thermocouple Technique by in situ observation. In the present work, fundamental information related to crystallization control in the CaO–SiO2–TiO2–Na2O–Al2O3 system was obtained. It was observed that the addition of Na2O in CaO–SiO2–TiO2 slags dramatically shortens the crystals' incubation times in TTT diagrams to the range of seconds. It is possible to control the crystallization kinetics in CaO–SiO2–TiO2 slags by changing the Na2O content. Some observations for the crystals' morphology are reported. 相似文献
11.
E. García‐Ramos A. Romero‐Serrano B. Zeifert P. Flores‐Sánchez M. Hallen‐López E.G. Palacios 《国际钢铁研究》2008,79(5):332-339
Chromium containing slags from stainless steelmaking may be leached by acidic environments, therefore they should be treated before being stockpiled or land filled. In this work, synthetic slags were prepared and the effect of CaO/SiO2, Cr2O3, MgO and Al2O3 contents on the stability of the mineralogical species formed was analysed. The morphology and composition of the slags were determined by XRD and SEM‐EDS, whilst their chemical stability was evaluated by leaching with an aqueous acetic acid solution. It was found that CaCr2O4 and CaCrO4 are present in slags prepared with neither MgO nor Al2O3. The Al2O3‐based slags mainly produced Ca2Al2SiO7 and the Cr(VI)‐containing oxide complex Ca4Al6CrO16, whilst MgO‐based slags produced Mg Cr2O4 as main mineralogical species. Additionally, Eh‐pH diagrams for the Ca‐Cr‐H2O and Mg‐Cr‐H2O systems at 25°C were constructed. The results showed that the lowest chromium concentration levels in the leaching liquors corresponded to MgO‐based slags owing to the stable binding of chromium in spinel with MgO. It was also observed in the Al2O3‐based slags that when increasing the slag basicity from 1 to 2, the leachability of the slags was notably increased. 相似文献
12.
The activity coefficients of FetO in CaO-Al2O3 and CaO-Al2O3-SiO2 slags with 0.01 to 5 mass pct FetO were determined at 1873 K from the data obtained in the present and previous slag-metal experiments, using an alumina or
lime crucible. It was found that the activity coefficients of FetO obeyed a dilute solution law and increased with increasing the content of SiO2. Based on the findings pertaining to the activity coefficient, the values for the activities of SiO2 and Al2O3 in CaO-Al2O3-SiO2 slags were assessed. 相似文献
13.
Understanding the viscous behavior of copper smelting slags is essential in increasing the process efficiency and obtaining
the discrete separation between the matte and the slag. The viscosity of the FeOt-SiO2-Al2O3 copper smelting slags was measured in the current study using the rotating spindle method. The viscosity at a fixed Al2O3 concentration decreased with increasing Fe/SiO2 ratio because of the depolymerization of the molten slag by the network-modifying free oxygen ions (O2−) supplied by FeO. The Fourier transform infrared (FTIR) analyses of the slag samples with increasing Fe/SiO2 ratio revealed that the amount of large silicate sheets decreased, whereas the amount of simpler silicate structures increased.
Al2O3 additions to the ternary FeOt-SiO2-Al2O3 slag system at a fixed Fe/SiO2 ratio showed a characteristic V-shaped pattern, where initial additions decreased the viscosity, reached a minimum, and increased
subsequently with higher Al2O3 content. The effect of Al2O3 was considered to be related to the amphoteric behavior of Al2O3, where Al2O3 initially behaves as a basic oxide and changes to an acidic oxide with variation in slag composition. Furthermore, Al2O3 additions also resulted in the high temperature phase change between fayalite/hercynite and the modification of the liquidus
temperature with Al2O3 additions affecting the viscosity of the copper smelting slag. 相似文献
14.
Hiroki Hasegawa Yasuhiro Hoshino Takeshi Kasamoto Yuuki Akaida Takaya Kowatari Yasuhiro Shiroki Hiroyuki Shibata Hiromichi Ohta Yoshio Waseda 《Metallurgical and Materials Transactions B》2012,43(6):1405-1412
The thermal conductivities of some synthetic slags containing Al2O3, CaO, and SiO2 have been determined in the temperature range between 1623?K (1350?°C) and 1823?K (1550?°C) by applying a front-heating front-detection laser-flash method. In this method, the temperature response curve is measured in the short initial time period immediately after irradiating a laser pulse. The resultant values obtained by this method are unaffected by the radiative heat transfer. The temperature dependence of the thermal conductivity values were found not to be significant for all slag samples currently investigated. The thermal conductivity (??) of samples is represented with standard deviation less than 2?pct of its value as a function of compositions as follows: $$ \lambda = - 0.48\left[ {{\text{Al}}_{ 2} {\text{O}}_{ 3} } \right] - 0.57\left[ {\text{CaO}} \right] - 0.55\left[ {{\text{SiO}}_{2} } \right] + 57.1{\text{ W m}}^{ - 1} {\text{ K}}^{ - 1} $$ where [Al2O3], [CaO], and [SiO2] are molar percent of Al2O3, CaO and SiO2, respectively. The equation is suggested to cover the region of the following compositions: 8.0?mol pct < Al2O3 <21.0?mol pct, 31.5?mol pct < CaO <41.5?mol pct and 43.0?mol pct < SiO2 <58.1?mol pct. The addition of Al2O3 to slags with a constant CaO/SiO2 molar ratio resulted in an increase in thermal conductivity. In contrast, the effects of addition of SiO2 and CaO are found to be insignificant. 相似文献
15.
A thermodynamic model for calculating the mass action concentrations of structural units in CaO–SiO2–MgO–FeO–MnO–Al2O3–CaF2 slags, i.e., the IMCT‐Ni model, has been developed based on the ion and molecule coexistence theory (IMCT). The calculated comprehensive mass action concentration of iron oxides $N_{{\rm Fe}_{t} {\rm O}} $ has been compared with the reported activity of iron oxide $a_{{\rm Fe}_{t} {\rm O}} $ in 14 FeO‐containing slag systems from literatures. The good agreement between the calculated $N_{{\rm Fe}_{t} {\rm O}} $ and reported $a_{{\rm Fe}_{t} {\rm O}} $ indicates that the developed IMCT‐Ni model can be successfully applied to predict the activity of iron oxide $a_{{\rm Fe}_{t} {\rm O}} $ as well as the slag oxidation ability of CaO–FeO (s1), SiO2–FeO (s2), CaO–SiO2–FeO (s3), CaO–FeO–Al2O3 (s4), SiO2–MgO–FeO (s5), SiO2–FeO–Al2O3 (s6), CaO–SiO2–FeO–Al2O3 (s7), CaO–SiO2–MgO–FeO–Al2O3 (s8), SiO2–FeO–MnO (s9), SiO2–FeO–MnO–Al2O3 (s10), FeO–MnO (s11), FeO–MnO–Al2O3 (s12), CaO–FeO–CaF2 (s13), and CaO–SiO2–FeO–CaF2 slags (s14) in a temperature range of 1473–1973 K. 相似文献
16.
Qifeng Shu 《国际钢铁研究》2009,80(2):107-113
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
17.
Trinath Talapaneni Natraj Yedla Snehanshu Pal Smarajit Sarkar 《Metallurgical and Materials Transactions B》2017,48(3):1450-1462
Blast furnaces are encountering high Alumina (Al2O3 > 25 pct) in the final slag due to the charging of low-grade ores. To study the viscosity behavior of such high alumina slags, synthetic slags are prepared in the laboratory scale by maintaining a chemical composition of Al2O3 (25 to 30 wt pct) CaO/SiO2 ratio (0.8 to 1.6) and MgO (8 to 16 wt pct). A chemical thermodynamic software FactSage 7.0 is used to predict liquidus temperature and viscosity of the above slags. Experimental viscosity measurements are performed above the liquidus temperature in the range of 1748 K to 1848 K (1475 °C to 1575 °C). The viscosity values obtained from FactSage closely fit with the experimental values. The viscosity and the slag structure properties are intent by Fourier Transform Infrared (FTIR) and Raman spectroscopy. It is observed that increase in CaO/SiO2 ratio and MgO content in the slag depolymerizes the silicate structure. This leads to decrease in viscosity and activation energy (167 to 149 kJ/mol) of the slag. Also, an addition of Al2O3 content increases the viscosity of slag by polymerization of alumino-silicate structure and activation energy from 154 to 161 kJ/mol. It is witnessed that the activation energy values obtained from experiment closely fit with the Shankar model based on Arrhenius equation. 相似文献
18.
In CaO–Al2O3- and CaF2–CaO–Al2O3-slags the soluted water vapour was quantitatively determined with Fourier-Transform-lnfrared-(FT-IR-)spectroscopy. The slags were equilibrated at 1500 and 1600 °C with definite H2O- and H2O/HF-partial pressures, respectively. The liquid slags were quenched in liquid D2O. They solidified glassily. Water vapour exists in the slags soluted as OH?-ion. For all slags investigated a linear dependence of the integral extinction upon the square root of the H2O-partial pressure, respectively upon HF-partial pressure, was determined. The values of the integral extinction (CaF2–CaO–Al2O3-slags) are calibrated by a H2O-doping-technique. The solution enthalpy of H2O in CaO–Al2O3-slags was estimated: endothermal reactions. Interpretation of the vibrational range yielded in a mainly tetrahedral coordination of Al3+ with O2?- and F? -ions in the glassy state. By heating the glassily solidified CaO–Al2O3-slags were transformed into their crystalline products: shifting of IR-peaks. The CaO–Al2O3- and CaF2–CaO-slags were compared with a CaO–SiO2–Al2O3-slag. The FT-IR-method is quick. The water content can be estimated with an uncertainty of less than ± 5% and is, therefore, suitable for process control of metallurgical procedures. 相似文献
19.
The activities of SiO2 and Al2O3 in CaO-SiO2-Al2O3-MgO slags were determined at 1873 K along the liquidus lines saturated with 2CaO · SiO2, 2(Mg,Ca)O · SiO2, MgO, and MgO · Al2O3 phases using a slag-metal equilibration technique. Based on these and previous results obtained in ternary and quaternary
slags, the isoactivity lines of SiO2 and Al2O3 over the liquid region on the 0, 10, 20, 30, and 40 mass pct Al2O3 planes and those on the 10 and 20 mass pct MgO planes were determined. The activity coefficients of Fe
t
O and MnO, the phase boundary, and the solubility of MgO were also determined. 相似文献
20.
The MgO solubility in CaO–SiO2–FeO–Al2O3–MgO quinary slag system at 1823 K was measured to evaluate the effect of FeO and Al2O3 on the MgO solubility. It was found that the MgO solubility was decreased with higher optical basicity, FeO concentration, and increased with higher Al2O3 concentration. The MgO solubility was affected by activity coefficient of Mg2+ ($\gamma _{{\rm Mg}_{{\rm 2 + }} } $ ). Increase of the activity coefficient of Mg2+ ($\gamma _{{\rm Mg}_{{\rm 2 + }} } $ ) with higher FeO or lower Al2O3 decreased the MgO solubility. The increment in MgO solubility is remarkably reduced beyond a critical $X_{{\rm Al}_{2} {\rm O}_{{\rm 3}} } /(X_{{\rm Al}_{2} {\rm O}_{{\rm 3}} } + X_{{\rm FeO}} )$ ratio. The significant decrease of the increment of MgO solubility is caused by the change of the molten slag structure. The excess stability function of Al2O3 and the Fourier transform infrared (FT‐IR) analysis were applied to indirectly verify the existence of the spinel structure in the CaO–SiO2–FeO–Al2O3–MgO slag system. 相似文献