Page 98 - 20250602 EEA QM Edition 6.0
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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.




            © EEA2025                                                                                                                                 page 98
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