Investigation on Crystallization of CaO‐Al2O3‐B2O3‐BaO Slag Using Differential Scanning Calorimeter and In Situ High‐Temperature Raman Spectroscopy

CaO‐Al 2 O 3 ‐B 2 O 3 ‐based slag is among the most promising “nonreactive” mold fluxes for continuous casting of high‐aluminum steel. However, CaO‐Al 2 O 3 ‐B 2 O 3 ‐based slag system exhibits a stronger crystallization ability compared to traditional mold fluxes. Herein, calcium oxide in CaO‐Al 2 O 3 ‐10%B 2 O 3 slag is partially replaced by the same mass of barium oxide (5 and 10 mass%) to adjust the crystallization ability. The crystallization of glassy slags is then investigated using a differential scanning calorimeter and their crystallization kinetics are analyzed using the Matusita–Sakka model. The structural evolution of glassy slags from room temperature to 1200 °C is also investigated using in situ Raman spectroscopy. The kinetic analysis shows that the crystallization process of CaO‐Al 2 O 3 ‐B 2 O 3 ‐BaO glassy slags follows the surface crystallization mechanism. The predominant crystalline products are calcium monoaluminate (CaAl 2 O 4 ) and calcium borate (Ca 3 (BO 3 ) 2 ). The partial replacement of calcium oxide by barium oxide inhibits the growth of CaAl 2 O 4 in the slag by increasing the activation energy of crystal growth. The high‐temperature Raman spectroscopy study shows that the band between 700 and 900 cm −1 gets weaker relative to the band between 450 and 650 cm −1 at high temperatures. This indicates the strengthening of bending vibration of Al‐O‐Al, which is consistent with the precipitation of CaAl 2 O 4 with full oxygen bridging.