Crystallization Behavior of the CaO-Al2O3-MgO System Studied with a Confocal Laser Scanning Microscope

Abstract

The crystallization behavior of a calcium-aluminate system with various MgO content from 2.5 to 7.5 wt pct and CaO/Al 2 O 3 ratios between 0.8 and 1.2 has been examined using a confocal laser scanning microscope (CLSM). CCT (continuous cooling transformation) and time temperature transformation (TTT) diagrams were constructed to identify the primary crystal phase of slag at different compositions and at cooling rates between 25 and 800 K/minutes. In the slag at a CaO/Al 2 O 3 ratio of 1.0, crystallization temperature increased during isothermal and continuous cooling with higher MgO content, and the shortest incubation time was observed at 5 wt pct MgO. When MgO content was fixed to be 5 wt pct, crystallization temperature increased with lower CaO/Al 2 O 3 ratio. According to the slag composition, cooling rates and temperature, the primary phase could be CA, or C 5 A 3 , or C 3 A, or C 3 MA 2 , or MgO, and the crystal morphology changes from dendrites to faceted crystals to columnar crystals in this composition range.

Review of Innovative Energy Savings Technology for the Electric Arc Furnace

“…In addition, maximizing metal recovery from the slags can increase productivity and decrease environmental treatment costs for the steel industry. From the works by Jung and Sohn, [73][74][75] instead of dumping the molten slag and allowing slow cooling, a controlled cooling pattern could concentrate the Fe cations into the spinel crystal structure (MgAlFeO 4 ) enriching local areas of the primary spinel crystals and separating the Fe from the amorphous phases of the slag, as illustrated in Fig. 13.…”

Effect of TiO₂ Addition on Crystallization Characteristics of CaO-Al₂O₃-based Mould Fluxes for High Al Steel Casting

“…Cho et al 5) found that lime-alumina based mould fluxes could suppress the occurrence of surface depressions and cracks by stabilizing the mould heat transfer at the initial stage of casting, but the slag film of lime-alumina mould fluxes were prone to crystallize easily during casting, which made the mould lubrication deteriorate rapidly. Jung and Sohn 12) founded that the crystallization temperature trend to decrease with the increasing ratio of CaO/Al 2 O 3 on CaO-Al 2 O 3 based mould flux. Other researchers have suggested some additives such as B 2 O 3 , MnO [13][14][15] to adjust the properties of mould fluxes to meet the demand for casting of high Al steel.…”

Effect of FeO Concentration on the Crystallization of High‐Temperature CaO–Al2O3–MgO–FeO Melts

“…Nakada and Nagata used a combination of differential thermal analysis (DTA) and X‐ray diffraction (XRD) analysis to determine the effect of the cooling rate on crystallization temperature and phase precipitation, but because of the relatively slow cooling rates of DTA, the applicability of the results was likely limited. Previous experiments on the CaO–Al 2 O 3 –MgO ternary system by the authors showed the effect of MgO on the crystallization behavior of the melts, such as crystallization temperature, incubation time, the crystal morphology, and the precipitated phase using CLSM, SEM–EDS, and XRD …”