Dipl.-Ing. Volker Hofmann
Release agents are rarely the focus of optimization measures in smelters as their material costs are
relatively low. No substantial cost saving effects are to be expected for these products. However,
these auxiliary materials can considerably influence the overall cost structure, particularly those
innovative products addressing weak spots in the foundry process. A separating, protective thin
layer, which is heat-conductive, accelerates solidification and thus the attainable process speed
when producing semi-finished goods in permanent molds. This is true for all molten metals, with
this paper describing aluminum ingot casting. Thanks to improved separation features, the contamination
of the final products and thus of the electrolysis process or other subsequent processes is prevented.
Not least, the conformity of the final product depends on the effectiveness of the separating
agents – remnants of the release agent in the final product are often cause for scrap and thus very
cost-relevant. In addition, the longevity of the molds and refractory material depends to a significant
degree on the effectiveness of the separating agent. Another aspect is the material cycle. Mineral
coatings are involved in the foundry process in large quantities. In order to protect the environment,
machinery and human beings these substances have to the monitored and discharged of in a responsible
manner – without any doubt a cost-relevant aspect. A thin, but robust layer providing reliable
protection and separating function over the long-term offers potential for optimization of all these
aspects. Special coatings may provide the functions required. However, the maintaining of these
functions cannot be achieved with frequently applied single-use products. Therefore, a long service
life is the primary requirement a coating has to fulfil. Such semi-permanent functional coatings are
already available or are being developed. Requirement profiles, techniques and results are illustrated
in the paper.