When heating copper billets, the energy sources gas and electricity can also be combined. A gas-heated multi-billet furnace is used for the basic heating of the billet to typically 650 °C combined with a single billet furnace , which takes over the final heating to the final temperature required for the extrusion process and the precise temperature setting.
Depending on the billet dimensions, the required temperature increase and the desired throughput, one or more single-billet furnaces are installed on the outlet side of the gas furnace. The coils, which are adapted to the billet dimensions in an optimum way, and the subdivision into several zones enable precise temperature setting in narrow temperature windows. The power supply takes over a state-of-the-art design IGBT converter, which enables infinitely adjustable power adjustment for the individual zones depending on the measured temperature.
The rapid heating by means of induction in the single-billet furnace alone leads to a reduction in scale formation; a further reduction enables the use of protective gas. Another advantage is that the single-billet furnaces can act as a buffer in the event of process interruptions.
