Homogenous conductive heating of curved tubes

Tränkner Christine - ITG Induktionsanlagen GmbH (Germany)

Conductive heating using alternating current is a direct heating method especially suitable for long, straight metal parts as rods, pipes, strips, or wire – providing a good energy efficiency and the possibility of quickly reaching the desired temperature in the whole workpiece at the same time. However, conductive heating of curved metallic bars or tubes leads to high temperature differences between inner and outer radii due to different current densities, which affects the microstructure and thereby quality of the part. Technical solutions for homogenisation of these temperatures cannot always be adapted to industrial series production – partly because of missing process stability or flexibility – or do not provide the required quality in a short enough cycle time. But especially for temperature-sensitive applications like hardening or annealing, a good temperature homogeneity is crucial.
In this talk, we will show how the amount of heat generated in the curves can be directly influenced by specially developed water-cooled magnetic field concentrators, and how the temperature homogeneity can be significantly increased. These field concentrators have been successfully used in mass production. Application and systems engineering will be depicted.

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