company news about The important role of silicon in casting

Liquid cast iron contains silicon, which reduces the solubility of carbon. The higher the silicon content in the molten iron and the lower the carbon content, the more carbon will be squeezed out.

silicon ferro

It is not difficult to understand from the iron-carbon phase diagram: when the molten iron is a hypereutectic composition, the silicon content is high. During the solidification process, more carbon precipitates in the form of primary graphite until the remaining molten iron reaches the eutectic composition. Eutectic transformation occurs later; when the molten iron is a hypoeutectic composition, silicon is enriched in the primary austenite during the solidification process. During the eutectic transformation, silicon is enriched in the early crystallized eutectic austenite, inhibiting the synthesis of cementite from carbon and iron, enhancing the diffusion rate of carbon in austenite, and promoting the precipitation of carbon in the form of eutectic graphite; During the eutectoid transformation, the solid solution of silicon in austenite still inhibits the formation of cementite between carbon and iron, enhances the diffusion rate of carbon in austenite, and promotes the precipitation of carbon in the form of eutectoid graphite.

Ferro Alloy

In gray cast iron, ductile iron, vermicular graphite cast iron and black core malleable iron, carbon and silicon are the main elements that affect the shape and quantity of graphite. It is white heart malleable cast iron that basically does not contain graphite. During the decarburization annealing process, silicon promotes the diffusion of carbon in austenite, which also plays an important role in the decarburization of this malleable cast iron.
In addition, the oxygen and nitrogen in cast iron have the effect of stabilizing carbides. The silicon contained in cast iron can reduce the oxygen and nitrogen content in it, which indirectly enhances the effect of silicon on graphitization.