Page 98 - 20250602 EEA QM Edition 6.0

Quality Requirements Edition 6.0 European Enamel Association

For cleaning the cast iron prior to enamelling only angular shot blasting material on the
In cast iron with spherical graphite the element Magnesium has the function to
convert the lamellar crystallizing carbon (graphite) into the spherical state of basis of cast-steel or chilled cast iron has been proved. Both grades are having the
crystallization during casting and the following thermal treatment. essential hardness and edge-stability (Vickers - Hardness HV above 650). Fractionated
corundum is also very well suitable.
Due to the ferritic structure and the spherical form of graphite, steel-like elasticity
properties are attained.

Besides the nucleus formation and separation of spherical graphite, magnesium
binds Sulphur as Magnesium Sulphide. This Magnesium Sulphide is preferably
absorbed by the slag of which it reduces its surface tension considerably, so that
magnesium slags cannot be wetted by glasses.

Castings are contaminated and not suitable for enamelling if an inadequate slag
separation takes place during the casting process. Notice has to be taken of a good
slag separation. Particularly good enamelling results are attainable if a spherical
graphite iron can be produced with a magnesium content less than 0.05 %.

Just as negative as on lamellar cast iron are the trace elements Chromium,
Molybdenum, Nickel, Titanium and Vanadium if the max. concentrations, as
mentioned, are exceeded. Consequently, the perlite is that much stabilized, that only
an incomplete decomposition to ferrite takes place during enamelling. This is not only
leading to a fluctuating expansion behaviour depending on the wall thickness of the
casting; there are also zones having a structural transformation during enamelling by
which a degassing occurs.

As for the enamelling of lamellar cast iron, the surface of the casting has to be clean
and free of burned-in sand.

The medium roughness should not exceed 300 microns.

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