Surface patterns such as bamboo-leaf type, pine needle type, and hexagonal type appear at around 1350°C on molten iron. These patterns are known to be used for examining the conditions of molten cast iron in cupola. In this study, the mechanism by which these surface patterns develop was examined.
The origin of the surface patterns is a surface SiO2 film formed by the oxidation of Si with CO. The difference in the radiation rate between SiO2 and molten iron makes the patterns visible. The addition of 0.02mass% S reduces the surface tension remarkably. As a result, a complex Marangoni convection occurs beneath the surface and it generates complex surface patterns. The characteristics of the molten iron improve in the order of Bamboo-leaf, Pine needle, and Hexagonal pattern. The Hexagonal pattern becomes finer with inoculation.
