High temperature reactions in mold flux slags: Kinetic versus composition control

Dapiaggi, Monica; Artioli, Gilberto; Carli, R.

doi:10.1016/j.jnoncrysol.2007.05.019

Cited by 18 publications

(14 citation statements)

References 8 publications

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“…[34][35][36][37] Therefore, it would be assumed that the energy generated by the rotating rod would be in the order of 10 -4 J/mol, which is extremely small and therefore not sufficient to overcome the activation energy of crystallization that in on the order of several tens to hundreds of kJ/ mol. [4][5][6]8,9) Additionally, the dependences of the crystallization temperatures on shear rate were found to be dissimilar, as shown in Fig. 9.…”

Section: Microstructural Characterizationmentioning

confidence: 99%

“…Therefore, numerous researchers have adopted various methods, including hot-thermocouple, [1][2][3][4] differential thermal analysis, [5][6][7][8][9][10] heat-treatment using a crucible and furnace, 11,12) among others, [13][14][15] to study the crystallization behavior of super-cooled slags and fluxes. However, most of these studies concerned the crystallization behavior of oxides at rest in crucibles or other containers, despite the fact that slags and fluxes are generally handled not only in the liquid-solid coexistence region, but also under a significant shear stress field created by agitation, stirring, or sliding in converters and continuous casting molds.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Agitation on Crystallization Behavior of CaO^|^ndash;SiO2^|^ndash;R2O (R = Li, Na, or K) System Characterized by Electrical Capacitance Measurement

et al. 2012

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The effect of agitation on the crystallization behavior of molten 50CaO-50SiO2 and 45CaO-45SiO2-10R2O (R = Li, Na, or K, mol%) fluxes were systematically investigated by the measurement of their electrical capacitance over a wide temperature range from liquid region to well below the liquidus temperature. It is well known that the electrical capacitance of liquids is generally much higher than that of solids owing to the differences in their respective polarization mechanisms. These differences were exploited as a sensitive indicator of the crystallization of molten calcium silicates in an experimental furnace equipped with an electrical capacitance measuring system. The system comprised a Pt-based alloy crucible and a rotating rod that allowed evaluation of the effect of agitation generated by the rod, connected to a capacitance meter (LCR meter).As expected, at a particular temperature, the electrical capacitance of the molten calcium silicates underwent a precipitous decrease by roughly three orders of magnitude, which was dependent on the chemical composition. This indicated the presence of crystallization and this was confirmed by corresponding microstructural characterization. It was also found that, for the measurements acquired with rotating rod agitation, the temperatures at which the capacitance underwent the sharp decrease were higher than that identified without the agitation. This suggests that the agitation effect induced by the rotating rod accelerates the crystallization of molten calcium silicates.

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Section: Microstructural Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Agitation on Crystallization Behavior of CaO^|^ndash;SiO2^|^ndash;R2O (R = Li, Na, or K) System Characterized by Electrical Capacitance Measurement

et al. 2012

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“…[45,47] However, in this work the E K values found for the most prominent heating, P h,1 , and cooling, P c,1 , peaks were larger for slag B than for slag A, despite that the first crystallizes faster, as seen in Section IV-C. This was also the case of the modified activation energies corresponding to the induction periods of peaks P h,1 and P c,1 , as seen in Table IV.…”

Section: Crystallization Periodmentioning

confidence: 99%

“…Thus, several researchers have processed non-isothermal DTA results that offer useful insights into the crystallization behavior of mold slags. [23,24,[43][44][45][46][47] Using the maximum peak temperature of the dominant exotherm from DTA curves obtained with different heating rates, the activation energy, E, for devitrification has been evaluated as 100 to 450 kJ/mol and it has been claimed that increases with increasing viscosity and decreasing basicity. [43] Comparative DTA measurements during cooling at À0.25 K/s (À15°C/min) showed that increased addition of MnO to a slag caused a considerable decrease in crystallization temperature, and also the authors reported a decrease in viscosity.…”

mentioning

confidence: 99%

Estimation of Time–Temperature-Transformation Diagrams of Mold Powder Slags from Thermo-analysis of Non-isothermal Crystallization

Maldonado

et al. 2014

Metall Mater Trans B

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The temperature range across the mold powder slag in the interfacial gap between the continuous casting mold and strand leads through different transformation behavior into crystalline phases. The transformation rates play a key role in determining the proportion of glassy and crystalline phases present, and thus greatly influence mold heat transfer and lubrication. Although thermal analysis has held great promise to quantify the crystallization of mold slags, so far the information it has provided is scarce. This work shows how differential scanning calorimetry, DSC, data allow evaluation of Time-Temperature-Transformation, TTT, diagrams of mold powder slags, when analyzed with the induction period and the Kissinger methods. The data required for estimating this important tool for the analysis and design of mold powders are onset temperature, T i , peak maximum temperature, T m , shape index, S, and conversion at peak maximum, x m , of the crystallization peaks appearing on thermograms obtained at various heating and cooling rates, / or À/, respectively. Industrial mold powders for casting low-and medium-carbon steels were analyzed to obtain TTT diagrams which correctly portray their different crystallization behavior. The diagrams reveal the start and end curves of the crystalline phases forming at each DSC crystallization peak. The estimated TTT curves present a correct picture of the degree of transformation observed in glass disks (~3 mm thick) treated isothermally for specified time intervals, quenched and examined with a scanning electron microscope. Additionally, the procedure developed for DSC-based TTT diagram calculation is supported by the good agreement between expected transformations and qualitative or quantitative X-ray diffraction results obtained from mold glass-powdered samples treated isothermally in a muffle furnace.

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“…Differential thermal analysis have been carried out in order to determine the changes in thermal properties of mold flux [11,12]. Recently, Dapiaggi et al [13] developed a kinetic analysis on the cuspidine crystallization with differential thermal analysis of mold flux slag. In this work, the Fourier transform infrared spectroscopy (FTIR) is proposed as a useful and complementary technique, to X-ray diffraction, to study the structure of commercial fluxes for thin slab casting.…”

Section: Introductionmentioning

confidence: 99%

An application of infrared analysis to determine the mineralogical phases formation in fluxes for thin slab casting of steel

Cruz-Ramírez

Romo-Castañeda

Hernández-Pérez

et al. 2011

Journal of Fluorine Chemistry

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High temperature reactions in mold flux slags: Kinetic versus composition control

Cited by 18 publications

References 8 publications

Effect of Agitation on Crystallization Behavior of CaO^|^ndash;SiO2^|^ndash;R2O (R = Li, Na, or K) System Characterized by Electrical Capacitance Measurement

Effect of Agitation on Crystallization Behavior of CaO^|^ndash;SiO2^|^ndash;R2O (R = Li, Na, or K) System Characterized by Electrical Capacitance Measurement

Estimation of Time–Temperature-Transformation Diagrams of Mold Powder Slags from Thermo-analysis of Non-isothermal Crystallization

An application of infrared analysis to determine the mineralogical phases formation in fluxes for thin slab casting of steel

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