Wettability of Molten Fe–Al Alloys against Oxide Substrates with Various SiO₂ Activity

Abstract

The contact angle between molten Fe-Al alloy with 0.03, 0.3, and 3 mass% Al composition, and Y 2 O 3 matrix oxide substrate with 0.002, 0.32, and 1 SiO 2 activity was measured using sessile drop method in Ar atmosphere at 1 873 K, and the interfacial tension was evaluated. The contact angle and interfacial tension between the molten Fe-0.3 Al alloy and the Y 2 Si 2 O 7 + SiO 2 (a SiO2 = 1) substrate decreased over time during 60 s after the molten alloy was dropped onto the substrate. The decrease of the contact angle was 20°, and that of the interfacial tension was 628 mN•m −1 Conversely, the other contact angles and the other interfacial energies were almost stable during the same period. The decrease of the contact angles ranged between 0° and 7°, and that of the interfacial tensions ranged 4 and 195 mN•m −1 . By observing the wetting behavior for 60 min, it was recognized that the interfacial reaction between the Fe-Al alloy and the oxide substrate was the redox reaction between Al composition in the alloy and SiO 2 composition in the substrate, composed of SiO 2 decomposition reaction and Al 2 O 3 formation reaction between oxygen absorbed at the interface and Al composition in the alloy. In addition, it was indicated from the interfacial tension dependence on SiO 2 activity that the medium SiO 2 volume slag for the molten low-Al steel and the low SiO 2 volume slag for the molten high-Al steel were effective in preventing the small droplets of molten slag into the molten steel.