Page 93 - QRedition5.0 062021

Quality Requirements Edition 5.0 European Enamel Association

8.0 EEA-specifications The silicon content plays an important role. Low silicon contents, below 2.5 %, are slowing
down the ferritisation process so that it is not finalized after the enamelling process has

8.1 Cast iron, suitable for enamelling been completed. An elevated outgassing, due to the conversion of perlite, causes pores

and pin holes during the final stage of firing.
8.1.1 Cast iron with lamellar graphite complying to DIN EN 1561 (grey cast iron)

Because of the perlite stabilizing effect, manganese contents more than 0.45 % should be
Chemical analysis avoided. They lead to an embrittlement and to a formation of strong stresses in the
composite material cast iron / enamel.
The following limiting values of the main elements should be kept:

a) Carbon, total C 3.20 - 3.40 Particularly critical for the enamelling are the trace elements Chromium, Molybdenum,
b) Carbon, combined C max. 0.20 Nickel, Titanium and Vanadium if the above mentioned maximal concentrations are
c) Silicon Si 2.50 - 3.25 exceeded. Consequently the perlite is that much stabilized, that only an incomplete
d) Manganese Mn max. 0.45 composition to ferrite takes place during enamelling. It leads to a fluctuating expansion
e) Phosphorus P 0.25 - 1.00 behaviour of the casting, depending upon its wall thickness.

f) Sulphur S max. 0.12
The Sulphur content is in particular to consider by applying the wet enamelling process for

Trace elements: cast iron. Sulphur contents up to max. 0.12 % in general do not cause defects.

g) Chromium Cr max. 0.05 Higher Sulphur contents can lead to severe difficulties in the enamelling because of the

h) Copper Cu max. 0.10 diffusion of Sulphur towards the cast iron surface. During the hot process the velocity of
i) Molybdenum Mo max. 0.05 oxidation is that much increased, that the thereby formed quantities of iron oxide cannot be
absorbed by the enamel.
j) Nickel Ni max. 0.10

k) Titanium Ti max. 0.05
The formation of stresses within the composite system cast iron / enamel is mainly, under
l) Vanadium V max. 0.05
consideration of different designs, a matter of the structure of the cast iron. After the casting
m) Tin Sn max. 0.10
process the structure must be Perlitic, not Cementitic.
n) Sum Cr + V + Ti max. 0.12

For the enamelling process the surface of the cast iron has to be clean and free of burned-
Saturation value: Sc = min. 1.04 max. 1.08 in sand. Its medium roughness should not exceed 300 microns.

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