The present paper is an investigation into how the Al 2 O 3 /SiO 2 ratio in the compositions of mold slags influences the crystallization behavior of molten slags. The experimental work is based upon observing the crystallization events through a Confocal Scanning Laser Microscope equipped with a hot-stage. The study is motivated by the variation in crystallization that might occur in mold slags due to the pickup of alumina during continuous casting of high Al containing TRIP steels. The crystallization temperature was found to increase with increasing Al 2 O 3 /SiO 2 ratio, and the crystal morphology was dependent upon the chemical composition and isothermal temperature. The crystallization path was complex, with CaF 2 found to precipitate first, and followed by a second precipitation event. In this second event, the precipitated phase depended on the chemical composition of mold slag and changed from cuspidine to gehlenite as the mass ratio of Al 2 O 3 /SiO 2 was increased beyond 0.65, and finally Al 2 O 3 was observed when the alumina content was 30wt.% (corresponding to a mass ratio of m Al 2 O 3 =m SiO 2 ¼ 1.42).

The present research deals with an investigation of the effect of alloying element additions (Si, P, and Sb) and water vapor content P H 2 O =P H 2 ¼ 0:01 to 0:13 ð Þ on the oxidation and decarburization behavior of transformation-induced plasticity (TRIP) steels in a gas mixture of 95 vol pct argon and 5 vol pct hydrogen/steam, by thermogravimetry (TG). The oxidation proceeds primarily as an internal oxidation front in the TRIP steels, but a thin external scale on the order of a micrometer thickness exists and is comprised primarily of fayalite ((Mn,Fe) 2 SiO 4 ) and ((MnO) x (FeO) 1Àx . The oxidation products are distributed near the surface and along grain boundaries. A comparison between calculated and measured oxidation curves indicated that the oxidation and decarburization are independent. The results for TRIP steels, both with and without an Sb addition, indicate that increasing Si and P contents accelerate, whereas Sb addition suppresses, both decarburization and oxidation rates. Water vapor content has no obvious effect on decarburization but has a pronounced effect on oxidation, and decreasing water vapor content decreases the oxidation rates.

The present study is an investigation of the surface and subsurface oxidation of Mn solidsolution-strengthened interstitial-free (IF) steels with the objective of elucidating the surface evolution before coating. Thermogravimetric (TG) analysis was carried out under 95 vol pct Ar + 5 vol pct (H 2 + H 2 O) atmospheres with P H 2 O =P H 2 ranging from 0.01 to 0.13 and temperatures ranging from 800°C to 843°C. Post-exposure characterization was carried out through scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and glancing-angle X-ray diffraction (XRD) to study the external and internal oxide evolution. The oxidation proceeds as a combination of the internal and external formation of Mn oxides. Decreasing the P H 2 O =P H 2 ratios or temperature has the effect of decreasing the amount of oxidation, which is a combination of internal and external oxidation controlled by solid-state oxygen and manganese diffusion, respectively. External oxides are not continuous; they are instead concentrated near the intersection of alloy grain boundaries with the external surface. Internal oxides are concentrated along the grain boundaries. The effects of Sb (0.03 wt pct), B (10 ppm), P (0.04 and 0.08 wt pct), and Si (0.06 to 1.5 wt pct) on the oxidation were investigated. It is found that small amounts of Sb and B have a significant effect on decreasing both the external and internal oxidation, whereas Si and P increase the external and internal oxidation.