Molten Metal Surface Pattern and Its Generating Mechanism in Gray Cast Iron

Abstract

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