The workpieces are thermally treated in an induction coil. The induction coil is normally cast with refractory concrete to provide mechanical and thermal protection for the coil. The direct installation of the water-cooled copper winding in the refractory concrete creates highly effective cooling for the lining. However, the relatively low lining temperature also causes a large temperature difference between the hot workpiece and the cooled coil, resulting in high thermal losses. In addition, ageing and infiltration as well as scale, reduces the mechanical protection effect.
With the new insulation development at hand, the challenge was to keep the temperature difference between the workpiece and the lining as low as possible, so that the heat flow and the associated heat loss to the water-cooled induction coil could be minimised. Furthermore, the wall thickness of the lining and thereby the distance between the induction coil and the workpiece had to be minimised in order to improve the electromagnetic efficiency of the inductive heat transfer.
These requirements were fulfilled with a multiple-layered coaxial structure and a combination of two materials for the insulation. This achieves a wear-resistant property on the internal side facing the workpiece, while good thermal insulation is achieved for the cold copper coil.
With the optimised insulation, energy savings of up to 8% are achieved, which also significantly increases the attractiveness of hybrid plants or systems. Thermal losses are reduced by up to 75%.
Unlike that utilised in conventional induction coils, the new thermal insulation is made of porous material and no longer from refractory concrete. This means that the time-consuming break-out work during maintenance on the coil is eliminated and possible damage to the induction coil during maintenance is also excluded. As a result, repair time can be reduced by up to 80%, enabling rapid availability of your inductor again and increased production reliability.