Abstract

MENDEZ, Laura; DELVASTO, Pedro  and  QUINTERO SAYAGO, Omar. Diseño y fabricación de moldes para solidificación direccional en aleaciones de aluminio. Rev. LatinAm. Met. Mat. [online]. 2007, vol.27, n.2, pp.73-82. ISSN 0255-6952.

This work explains the design process of isolating ceramic moulds to be used in experimental set-ups for directional solidification of aluminium alloys. Six mixtures composed of silica sand, bentonite, kaolin and feldspar, in different proportions, were studied. These components were chosen due to their dimensional stability at high temperatures and also because these ceramic materials do not react with molten aluminium alloys. For the manufacturing of the moulds, a mixture composed by 60% silica, 16% bentonite, 16% kaolin and 8% feldspar (dry weight) was chosen, because it exhibited a better handling resistance (in green and also at high temperatures). This mixture also showed a good collapsibility, an important property to grant the recovery of the ingot produced during the solidification tests and the recovery of the thermocouples used. A 2 cm moulds wall thickness was determined, considering non-stationary, unidirectional, conductive heat transfer and the ease for hand-based shaping of the moulds. Drying and partial sintering of the green moulds was performed through a stepwise heat treatment that lasted 37 h (25, 70, 100, 200, 300 y 1000ºC for different times, each step). Finally, the moulds were tested by pouring a molten aluminium alloy (Al-8.86% Si-0.21% Fe), and they were found feasible for the directional solidification tests proposed.

Keywords : Insulating moulds; Moulds design; Alloys solidification.