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The effect of substrate surface conditions on the heat transfer and morphology of solidifying shells of a copper alloy has been characterized by a series of dip tests. Results showed that in the early stages of solidification, rough and grooved surface conditions provide a greater heat transfer than polished ones. The shells solidified on rough and grooved surfaces had significant localized variations in thickness, indicating that heat transfer at the substrate-metal interface was not uniform. The implication of these results on strip casting is discussed.

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To determine the optimal roll temperature in a twin-roll copper-strip caster, copper blocks preheated between 25 ЊC and 350 ЊC were immersed in a bath of molten copper for 0.5 seconds. A significant increase in the contact heat-transfer coefficient at the substrate-shell interface was obtained when the substrates were heated above 200 ЊC and the gain in the solidified shell thickness was 20 pct. The shell growth was also approximately 35 pct more uniform at a high substrate temperature, and micrographic examination showed the dendritic structure to be finer. The contact heat-transfer coefficient was decomposed into two constituents, one for the substrate and the other for the shell. The former was found to be the limiting factor in heat transfer.