More and more processors of aluminum strip prefer single-coil furnaces because they increase production flexibility. This means there are none of the usual compromises that are unavoidable with a multi-coil batch furnace. For this reason they are referred to as overhead furnaces. The furnaces installed to date are charged from underneath. For this reason they are called Batch-type furnaces. It is also possible to install these furnaces so that they can be charged with single coils at ground level.
The main criterion here is whether the material is to be annealed in air or process atmosphere. All alloys that tend to discolor due to the formation of manganese oxide (like alloy AA 3004, for example) have to be annealed in process atmosphere.
The HICON single-coil overhead furnace reduces temperature scatter to a minimum throughout the whole charge whilst keeping heating-up times as short as possible (e.g. for partial anneals: Δt less than ±3°C at the end of the soaking time). The gas-tight design enables trace oxygen contents of less than 0,05 %v/v to be achieved.