Semi-Permanent Coatings – a Powerful Tool to Improve the Cost Effiency in Casting of Semi-Finished P

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.