CPT International 01/2015

Surface quality with impregnation coating (left) and traditional production
(right) (Photo: Hüttenes-Albertus)
HÜTTENES ALBERTUS
Innovative coating to prevent
Foundries are increasingly faced with
a rising demand on the quality of
castings, the dimensional consistency,
and importantly the surface quality.
For many years foundrymen have
been struggling with the casting defect
“white film”, which appears on the
casting surfaces of thick-walled castings
made of nodular graphite cast iron.
This is a pockmark-like, rough area on
the casting surface, which is covered
with a white film.
The film is removed by sandblasting
the castings; however the irregular surface
remains and often leads to graphite
degeneration. The only corrective
measures described in literature [1] are
as follows:
» Lower the pouring temperature
» Increase the addition of new sand
» Examine the loss on ignition, electrical
conductivity, nitrogen content
and if necessary the phosphorous
content of the reclaimed
material
» Increase gas permeability
» Reduce the amount of curing agent
for furan resin bonded moulds
» Minimize the oxygen-affine elements,
examine the melt additives
Unfortunately the above measures
are either insufficient or cannot be
fully implemented by the customer.
For this reason, this casting defect
leads to higher fettling costs e.g. due
to rework, additional wall thickness,
and in some cases higher appraisal
costs.
The team from Hüttenes-Albertus,
Düsseldorf, Germany, has investigated
in great detail the cause of this problem.
Working in close collaboration
with selected partners from the foundry
industry, a group of R&D chemists
and product managers examined
through research the causes and conducted
field trials. An innovative impregnating
coating was developed by
closely analyzing the causes for the
emergence of the film and carrying out
individual process steps to overcome
the defect. This coating is applied to
the affected areas within an existing
process (binder system/reclaim/material)
by means of brushing. This leads
to a complete suppression of the white
film.
The HA team will present this and
other developments and solutions in
detail at the GIFA 2015.
Literature:
[1] 2. Edition: Guß- und Gefügefehler
– Stephan Hasse: Berlin - Schiele &
Schön, 2003
Hall 12 - Stand C 50
www.huettenes-albertus.com
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Giesserei Verlag GmbH 10, 20, 55
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GUT Gießerei Umwelt Technik GmbH 33
Hüttenes-Albertus Chemische Werke GmbH 56
Inspectomation GmbH 43
Klein Anlagenbau AG 45
Messe Düsseldorf GmbH 19
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GmbH & Co.KG 20
Heinrich Wagner Sinto Maschinenfabrik GmbH 29
Casting Plant & Technology 1/2015 51