Study on the Structure and Wettability of CaO–Al2O3–MnO-Based Mold Flux for High-Manganese Steel Used in Ultra-Low Temperature
摘要
High-manganese steel for ultra-low temperature applications is widely used in fields such as cryogenic vessels due to its excellent low-temperature toughness. The wettability of mold flux during the continuous casting directly affects the surface quality and lubrication performance of the strands. To optimize the performance of mold flux used in high-manganese steel for ultra-low temperature, the effect of CaO/Al2O3 ratio on the microstructure, melting process, and wettability with high-manganese steel of CaO–Al2O3–MnO-based mold flux was investigated in this paper, and the correlation mechanism between the CaO/Al2O3 ratio, structure, and wettability was revealed. Raman spectroscopy and Fourier transform infrared spectroscopy were used to characterize the structure of mold flux. The contact angle was measured by the sessile drop method, and the surface tension and work of adhesion were calculated using the Mills model. The results show that the evolution of structure in mold flux is dominated by CaO/Al2O3 ratio through the dual effects of regulating the O2− dissociation and Ca2+ charge compensation. The melting process of mold flux undergoes solid state → expanded state → softened state → hemispherical state → fluid state. The contact angle fluctuates in the range of 16.0 to 19.3 deg, which is significantly positively correlated with the polymerization index. The surface tension fluctuates slightly in the range of 374.1 to 375.9 mN/m, and the work of adhesion remains in the range of 728.2 to 735.8 mJ/m2. The established correlation mechanism is: CaO/Al2O3 ratio changes the polymerization index and surface tension by regulating the aluminate structure; the variation trend of the contact angle is determined by the polymerization index; and the work of adhesion is regulated by surface tension and contact angle.