INFLUENCE OF FERROSILICON MANGANESE ON THE SULPHUR CONTENT AND MICROSTRUCTURE IN THE PRODUCTION OF AUSTEMPERED DUCTILE IRON (ADI)

Abstract

This study considers the effect of ferrosilicon manganese addition to austempered ductile iron, (ADI) in order to reduce its sulphur level for improved engineering applications of the material. The cast samples were austenitised in a mixture of potassium chloride, sodium chloride and barium chloride solutions and austempered in sodium nitrate and potassium nitrate solutions. Ferrosilicon manganese was added to ADI in various amounts ranging from between 47 to 326 g. The study revealed that the sulphur level retained in ADI decreased from 0.088 wt % for as-cast to 0.027 wt % when 93 g of ferrosilicon manganese was added. Below this amount of ferrosilicon manganese addition, there was no significant reduction in the sulphur level recorded in ADI. The microstructure of the metal revealed bigger graphite nodules scattered in ferrite solutions for the situation when the sulphur level was 0.027 wt. %. From the study, it was discovered that addition of small amount of ferrosilicon manganese was required to produce ADI of low level sulphur content to make the metal more acceptable for other engineering applications.