ISSUE 3/2010

/// 03
Tomek, L.; Rusín, K.; Stachovec, I.
Influence of cement moulding sands on the structure of castings

In the interface between cement cores and iron with flake graphite were certified generation of complex allied substances – on the base Si, Fe, Al, O and Ca. These complex allied substances originate as a result of chemical reactions between molten metal and cement sand. In many cases FeS has been found. Its occurrence is evoked by CaSO4 (Bassanite) from Portland cement. Elements such as Si, Al, Ca and Fe may be released by thermal dissociation from products of cement setting. Created mathematical model proved influence of temperature and chemical composition of liquid metal on occurrence of mechanical penetration in this case. With increasing temperature and higher content of carbon in cast iron is chance of mechanical penetration higher. Average grain size of opening material is remarkable too. The higher content of sulphur is dangerous for castings of nodular iron. In additional trials the rest content of magnesium was liquidated by this element and particles of flake graphite and other forms of graphite have been found in the surface layers of nodular iron castings.




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