The Effect of Directionally Chilled Microstructure on Hypereutectic High-Chromium White Cast Iron

Abstract

This study examined the effect of fluid convection on microstructures of directionally solidified high-chromium white cast iron (ASTM A532-87 Class III) with carbon equivalents of 4.5. The iron was first melted in a high-frequency induction furnace, and then poured into a sandwiched cylindrical Furan resin sand mold. The middle part is a chilled copper mold kept cold by circulating water, enabling simultaneous directional solidification in the upper and lower zones. The microstructure thus solidified is affected by directionally chilled between these parts. Distribution of temperature in the mold during cast solidification was measured by K-type thermocouples. The measured results show that the lower zone has stronger thermal convection and faster cooling rate than the upper zone. The lower zone has smaller liquidus and solidus gradients than the upper zone.