Improvement of the Metallurgical Quality of Ductile Iron by Conditioning

Abstract

Using thermal analysis a preliminary study of the evolution of the metallurgical quality was carried out, concluding that it was strongly deteriorated during the Mg treatment, worsened at the pouring furnace. In order to improve the metallurgical quality a new phase of conditioning before the Mg treatment has been implemented. Also a special ladle was designed and built to be able to perform this new process stage in a robust manner. In this way the main objective was reached, increasing the metallurgical quality of the melt inside the treatment ladle and also at the pouring furnace, obtaining at the same time better process stability. The metallurgical quality improvement reflects at the cooling curves (stable solidification patterns), at the microstructure (higher nodule count, better graphite distribution and more ferrite content in the matrix) and at the mechanical properties (less tensile strength, higher elongation, less hardness and higher impact toughness) of the casting parts.