Rim zone metallurgy: a coating system to improve the mkcrostructure in the surface-affected zone of permanent mold cast spheroidal ductile iron

摘要

This paper introduces a rim zone metallurgy to imporve the microstructure of spheroidal ductiole iron casts into permanent mold is presented. Decisive process parameters are identified, and a coating system based on an insulating and a metallurgical coating is developed. The necessary binder disintegration is worked out so that inoculants as a part of the metallurgical coating are released into the melt and the nucleation rate in the surface affected zone of cone specimens is promoted. The influence of the metallurgical coating on the solidification shows evidence of nucleation efficiency. Additionally, a method to examine the microstructure quantitatively is introduced. Finally, typical rsults of speciment solidification are presented and the metallurgical potential of producing, for example,gradient microstructures are being shown.