The effects of inoculation of yttrium rare earth containing ferrosilicon on gray cast iron

The influence of yttrium rare earth containing ferrosilicon (YRE) on the structure and properties as well as solidification behavior of gray irons was studied. It is now generally accepted that the amount of sulfur present in gray irons greatly affects the structure obtained. The yttrium rare earth elements that react strongly with sulfur influence the amount of combined and uncombined sulfur in the iron, thereby exerting a considerable effect. It can be shown from the results that the optimum YRE additions to gray cast iron have marked effects on increasing tensile strength, reducing chill, refining cell size and improving structure homogeneity. It is considered that yttrium rare earth sulfides can act as substrates for graphite nucleation, reducing undercooling and chill tendencies and increasing the number of eutectic cells. On the other hand, in excess of optimum residual yttrium rare earth content, the amount of optimum residual yttrium rare earth content, the amount of carbides in gray irons increased. The results show that YRE has both inoculating and chilling promotion duplex function which depends on the YRE content added to the irons