A New Approach to Ductile Iron Inoculation（球墨铸铁孕育的新方法）.pdf

A New Approach to Ductile Iron Inoculation T. Skaland Elkem ASA, Research Kristiansand, Norway Copyright2001 American Foundry Society ABSTRACT The objective of the present paper is to describe a new approach to inoculant design that has proven successful in improving casting performance and properties. The described inoculant represents a unique new generation of products developed for powerful cast iron inoculation. The ferrosilicon alloy contains levels of Calcium and Cerium that are adjusted to minimize chill formation and neutralize subversive trace elements in the iron. In addition, the inoculant contains small and controlled amounts of Sulphur and Oxygen in a form that make them available for reaction with the Calcium and Cerium during introduction into liquid iron. This special composition is designed to give highly powerful graphite nucleation conditions in ductile irons along with very effective chill and shrinkage reduction. Examples from foundry testing are reviewed, and the unique characteristics of this new inoculant concept described. The new inoculant is found to be more powerful than conventional ferrosilicon based inoculants, and give rise to very effective reduction in the shrinkage tendency of ductile irons. Special effectiveness has been observed in irons of low sulphur or irons of a “dead” nature from prolonged holding times. Also, results show improvements in both tensile properties as well as machinability for ferritic ductile irons. The new inoculant concept represents a patent protected design (Int.Pat.No.WO99/29911), and is available under a special trade name, 1 see footnote . INTR