Searching For a Unified Explanation of the Solidification of Cast Irons

G.L. RIVERA, R.E. BOERI, J.A. SIKORA

Beijing, China

Simposio; Eight International Symposium on the Science and Processing of Cast Iron; 2006

Tsinhua University

The present work focuses on the study of the solidification mechanism of flake, spheroidal and vermicular graphite cast irons. In particular, the morphology of the solid phases during solidification of free graphite cast irons, and its influence on the microstructure and macrostructure, are carefully revised. The experimental methods involve the use of special metallographic techniques developed earlier by the authors, and the analysis of interrupted solidification samples. The results show that, for hypo, eutectic and hypereutectic grades of any graphite morphology, austenite of free graphite cast irons always grows dendritically, resulting in a grained macrostructure similar to that observed on most metallic alloys. A substructure is found within each grain, where the usually called "eutectic cells" are located. The use of the terms "solidification unit", "eutectic grain", "eutectic colony" and "eutectic cell" to describe the different features of the solidification is discussed.