The Continuing Evolution of MgFeSi Treatments for Ductile and CG Irons

Abstract

Production of ductile iron has been linked to the use of Mg and Mg-alloys since its invention. In the early history of ductile iron production, pure or high Mg containing alloys were needed due to the higher S level in the base iron. With the introduction of basic slag cupolas and low S base iron, the high Mg containing alloys were replaced with materials with lower Mg-content providing a calmer reaction with less slag generation and more predictable results and tighter control of the final Mg level. MgFeSi was recognized early as an excellent material to introduce Mg into the cast iron melt. MgFeSi offered the possibility to design both chemical composition and sizing to accommodate needs such as reaction control for different treatment processes, trace element control, packing density, and boosting of Mg-level. One of the main goals with MgFeSi treatments is to minimize the overall addition of Mg to tight reproducible low levels to reduce the shrinkage tendency observed with high final Mg levels. This can be achieved through a combination of optimization of the MgFeSi composition as well as improvement of the treatment process. A well designed MgFeSi-treatment can reduce fume and flare, slag generation, and the need for subsequent inoculation. The history and evolution of MgFeSi treatment along with relevant recent case studies will be presented in this paper. Examples of how the MgFeSi material can be optimized will be presented both in terms of theory and case studies. Focus of case studies will be on the recent evolutions focusing on maximizing Mg-yield through delayed and calm reaction.