Energy-efficient heating of aluminium billets

The machine building company Bültmann in Neuenrade is a pioneer in the heating in static magnetic fields semi-finished aluminium products and billets for extrusion plants.

Based on the experience gained with billet heaters already in operation with superconducting coils, Bültmann jointly together with the For­schungszentrum Jülich and funded by the DBU (German Federal Environ­mental Foundation) have developed an inductive heater that generates a magnetic field without a coil.


Bültmann has already received several environmental awards for its first generation of heating furnaces using superconducting magnets. Further energy savings are possible by using permanent magnets, which in addition to the energetic advantages also promise lower investment costs.

The energy saving potential compared to the conventional induction furnaces currently in use is approx. 30 percent with this innovative technology.

The permanent magnets in a special arrangement generate a magnetic field, which is by 40% larger than in existing heaters with superconducting coil.

The billet is held in the magnetic field while the magnetic field rotates around the billet at a frequency of 20 Hz. The heating quality (temperature tolerances and temperature compensa­tion times) is 100% comparable with existing billet heaters operating with a superconducting coil.

The output of a heating unit for aluminium amounts to approx. 40 blocks per hour, heated up to 480 °C.

The energy consumption is approx. 150 kWh/t with all auxiliary units, such as hydraulics and cooling water supply.

Further advantages of this trendsetting technology are:Heater for aluminium billets

  • Rotating permanent magnets without energy supply
  • Quality of saw cut and cast quality of billets are negligible
  • No centrifugal forces affecting the billets
  • Drive acting directly onto the per­manent magnets
  • Larger magnetic field available for heating
  • Efficiency > 80%
  • Generation of a taper

The modular design makes it possible to arrange several heating units in series in order to meet the particular heating requirements.

It goes without saying that the entire concept is protected by patents.