Wetting and corrosion behavior of MgO substrates by CaO-Al2O3-SiO2-(MgO) molten slags

The corrosion of refractory is generally related to the wetting between slag and refractory. Investigating the wetting and corrosion characteristics of refractory by molten slag has a positive significance to elucidating the corrosion mechanism and understanding the slag resistance. In this work, the apparent contact angles of the CaO-Al2O3-SiO2-(MgO) molten slags on microporous magnesia aggregate (MM) and fused magnesia (FM) substrates were respectively measured by sessile drop method under Ar atmosphere at 1550 degrees C. The dissolution of the MM substrate and the slag penetration behavior were investigated by combining the theoretical calculation of the FactSage thermodynamic software with the examination of SEM-EDS. The results show that MM substrate had a better slag resistance than FM substrate. The final apparent contact angles (theta(f)) of slags with the CaO/SiO2 values of 3, 5 and 11 on MM substrate were 15.8 degrees, 21.4 degrees, and 9.2 degrees, respectively, and that with the MgO content of 3, 6 and 9 mass% were 11.1 degrees, 14.2 degrees, and 52.5 degrees, respectively. The larger the CaO/SiO2 value of the slag, the more beneficial it was to slowing down the dissolution of MM and FM substrates; the original slag with MgO was also beneficial to lessening the dissolution of the MM substrate, which was better than that with a high CaO/SiO2 value. The formation of MA could inhibit the slag from penetrating. In addition, for slags with different CaO/SiO2 values, the effects of surface tension and viscosity on slag penetration were more significant than that of contact angle; for slags with different MgO contents, the effect of contact angle on slag penetration was more significant than those of surface tension and viscosity.

Automated summary

The wetting and corrosion characteristics of refractory by molten slag are important for understanding the corrosion mechanism and slag resistance. The study found that microporous magnesia aggregate has better slag resistance compared to fused magnesia. Slags with higher CaO/SiO2 value and MgO content have a greater ability to slow down the dissolution of refractory substrate. Surface tension and viscosity have a more significant impact on slag penetration than contact angle.