The role of the pre-heat furnace is to homogenise the metal and hold it at a temperature suitable for rolling. In order to achieve satisfactory final properties, the temperature distribution in the ingot following the pre-heat must be uniform. For this reason, pre-heat cycles are sometimes excessive in length to ensure that uniformity has been achieved, usually because the only information available to the operator is one or more surface temperatures.
If the temperature distribution in the ingot throughout the pre-heat is known, the duration of heating cycles can be optimised. Shortening cycle time is one of the best ways of saving energy per kilogram rolled, as heat is lost from the furnace even when the ingot is simply being held at temperature.
Using a process model can help to shorten ingot pre-heat times by enabling more aggressive heat-up schemes without the danger of over-heating the ingot. It also indicates ways of significantly reducing the energy losses of the process. Models are being used more and more as part of the process control and it is possible to envisage that in the near future furnace models will be running on-line, calculating the best future settings for the furnace and providing warnings of furnace malfunction much earlier than would otherwise be recognised.
The aluminium ingot preheating model is a physics-based model which predicts the internal temperatures at any location inside any aluminium ingot during the preheating operation. It achieves this from information about the flow of heated gas over the surfaces of each ingot.