Contributions to the Study of the Solidification Mechanism and of the Influence of Structure on the Properties of Compacted/Vermicular Graphite Cast Iron

Abstract

ABSTRACTIn the paper we have analysed some aspects of the structural,mechanical, technological and casting properties of compacted/vermicular graphite(C/VG)cast iron,with reference to our works published in the past 10 years.As regards the primary structure(eutectic solidification)we were interested in the composition and growth conditions of eutectic cells, of C/VG formation,on the basis of Mg and Si distribution,of intergranular phases,in different cooling conditions.We have also analysed the carbide formation and the inverse chill tendency. C/VG is characterised by form factors(compactness)on whose basis we propose some new typical graphite forms. The tendency to ferritic shells formation in the case of C/VG is compared with that recorded for NG,coral graphite,and FG type A,B,D. We note the possibility of favouring pearlite Dy thermal treatment,alloying and the use of a treatment-alloy with Al,Ti and other elements with a pearlitic action.We have also analysed the influence of wall thickness,cross-section geometry,holding time,anti- spheroidizing elements,nature of casting mould upon structure.Finally,we present a synthesis of the applicational properties,based on our data.