The significance of graphite particles in the heat exchange at the metal-mould interface during the composite flow along the mould channel
Zbigniew Konopka, Małgorzata Łągiewka, Andrzej Zyska, Maciej Nadolski Politechnika Częstochowska, Wydział Inżynierii Procesowej, Materiałowej i Fizyki Stosowanej, al. Armii Krajowej 19, 42-200 Częstochowa, Poland
Quarterly No. 1, 2008 pages 82-86
DOI:
keywords: heat exchange, heat transfer coefficient, thermal analysis, aluminium alloys
abstract Calculation results concerning the heat transfer coefficient at the metal-mould interface during flow of the AlMg10 alloy and AlMg10 matrix alloy composites with 10 and 20% volume fractions of solid graphite particles as reinforced in the channel-like cavity of the spiral castability test mould. The experimental cooling curve as well as changes of flow velocity have been determined on the basis of the measured metal temperature during flow. The cooling curve equation for the examined alloy, derived from the heat balance condition in a casting-mould system and taking into account experimental data concerning changes in metal temperature and its flow velocity, has enabled evaluation of the heat transfer coefficient at a given point of a metal stream along the mould channel. Graphic representations of changes of this coefficient against time and the channel length have been presented. Graphite particles in composite suspension cause decrease of heat transfer coefficient at the metal - mould interface. The value of heat transfer coefficient at the stream front decreases during metal flow and cooling due to the drop in its temperature and velocity. Solidification of metal retards this temperature and velocity decrease, which is decisive for the decrease of the heat transfer coefficient value.