What differences are there in the properties of cast iron and graphite cast iron?
Due to the high carbon content ALL cast irons contain graphite – either as temper carbon (malleable cast iron), flakes (lamellar and compacted graphite cast iron) or nodules (nodular or spheroidal graphite cast iron). Malleable irons are not very common these days as the heat treatment makes steel a cheaper alternative. Flake (lamellar) graphite cast irons are the least ductile – they don’t stretch much before they break (typically <1%). Hardness is around 240HB, tensile strength in the region of 250MPa (15 tsi) -These are guidelines only and there can be a large variation in properties! Compacted graphite (aka vermicular graphite) cast iron is slightly stronger and more ductile - typically 350MPa/5% with the same hardness. Nodular (spheroidal) graphite cast irons are much stronger (400-500MPa UTS) and more ductile (15%). They also show an amount of plastic deformation which is not found in the other types described above.
