Decisive Difference between as Cast and Tempered Graphite Distribution in Permanent Mold Spheroidal Graphite Iron Castings

Abstract

In previous pilot plant studies, the authors developed a method for producing permanent mold (PM) spheroidal graphite iron (SGI) castings that prevents chill formation under as-cast conditions. Despite the advancement, chill structures (ledeburitic cementite, Fe₃C) are still commonly from PM-SGI castings produced through current methods. Although heat treatment can decompose Fe₃C and induce graphitization, concerns remain that the distribution of tempered graphite may adversely impact mechanical properties.

This study examines the graphite distribution in both the developed and conventional PM-SGI castings. Additionally, it identifies factors contributing to undesirable graphite distribution following heat treatment. Results demonstrate that the newly developed PM casting method offers advantages not only in eliminating the need for heat treatment but also in enhancing mechanical design safety.