The influence of additions of different SiC grades on the solidification of hypoeutectic and eutectic gray cast iron has been studied and compared with the additions of “FeSi 75” and pure silicon.
It is shown that additions of SiC change undercooling, microstructure as well as graphite shape and distribution in cast iron melts in a different manner than either FeSi or pure Si do. The difference is explained by the special dissolution kinetics of SiC which leads to formation of graphite and a lonqer-lastirg influence of carbon agglomerates in the melt. It is shown that SiC grades which are partially protected by SiO2 films from rapid dissolution in the iron melt show the most pronounced effect.
From the laboratory experiments it can be concluded that melt additions of special SiC grades can modify the microstructure of gray cast iron. A-graphite is more evenly distributed and formation of the Fe/Fe3C eutectic is more difficult. Similar influences are known from industrial production and can now be partially explained.