Extrusion billets are usually heated to their extrusion temperature in gas furnaces. In cases when, for example the plant's performance has to be increased and/or quality is to be improved by producing a particularly precise temperature profile along the billet, an induction furnace is installed downstream from the gas furnace. In such cases the logs are sheared or sawn into billet lengths after the gas furnace and then loaded individually into the induction furnace. Then they are transferred into the extrusion press. As a feature of the process the axes of the two furnaces are as a rule laterally offset. Thus, relative to the press axis a second and even a third axis are formed, with corresponding space occupation ahead of the press. In all such cases until now the gas furnace and the induction furnace have been operated as individual aggregates, accepting the consequent substantial handling effort and complexity this entails. The notion of an in-line concept in which the gas and induction furnaces work as a unit, came at just the right time for our plant," says Marcus Molkner, plant manager at Constellium (formerly Alcan EP) in Crailsheim. That reference is to the presentation of an in-line heating concept for extrusion billets at 'ALUMINIUM 2009' in Essen.
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