Aluminum alloys having improved cast surface quality

Details Aluminum alloys having improved cast surface quality Aluminum alloys having improved cast surface quality

C - Chemistry, Metallurgy

22

C

C22C 1/02 (2006.01) C22C 1/03 (2006.01) C22C 21/00 (2006.01)

Patent

CA 2424595

Aluminum alloy compositions are disclosed, which include small amounts of calcium that result in improved surface properties of the cast aluminum. The calcium, and up to 0.25% grain refiners, are added along with alkaline earth metals, transition metals and/or rare earth metals to the aluminum alloy as a melt. The addition results in improved appearance, substantially reduced surface imperfections and reduced surface oxidation in cast ingot aluminum and aluminum alloys. The addition of small amounts of these additives, surprisingly were found to substantially eliminate vertical folds, pits and ingot cracking in more than one ingot casting technique. The additions also improved the appearance of the ingots, including reflectance. As a result, the ingots could be reduced or worked essentially right out of the casting without first conditioning the surface by, for example, scalping. Also disclosed is a method of improving the surface properties and preventing surface imperfections and cracking of cast aluminum alloys. The method includes the steps of adding calcium to a molten aluminum alloy that is essentially free of Be casting the aluminum alloy using any commonly used technique.

L'invention concerne des compositions d'alliage d'aluminium comprenant des petites quantités de calcium qui offrent des propriétés de surface améliorées à l'aluminium coulé. Le calcium, et jusqu'à 0,25 % de produits d'affinage du grain sont ajoutés à l'alliage d'aluminium avec des métaux terreux alcalins, des métaux de transition et/ou des métaux terreux rares à l'état de masse fondue. Cette addition offre une apparence améliorée, des imperfections de surface sensiblement réduites et une oxydation de surface réduite dans un lingot coulé en aluminium ou en alliages d'aluminium. L'addition de petites quantités de ces additifs, a curieusement permis de sensiblement éliminer des plis verticaux, des creux et des fissures dans les lingots dans plusieurs techniques de coulage de lingots. Les additions améliorent également l'apparence des lingots, ainsi que leur réflectance. Il en résulte que les lingots peuvent être réduits ou travaillés essentiellement hors du coulage sans conditionnement préalable de la surface par scalpage, par exemple. L'invention concerne également un procédé destiné à améliorer les propriétés de surface et à prévenir les imperfections et les fissures de surface des alliages en aluminium coulé. Ce procédé comprend les opérations d'ajout de calcium à un alliage d'aluminium fondu qui est essentiellement dépourvu de Be coulant l'alliage d'aluminium au moyen de n'importe quelle technique classique.

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