Induction heating of thin steel strips for further stripprocessing operations below 700°C is usually performed with longitudinal flux heating. Using this method, inductors surrounding the stripgenerate a magnetic field in the lengthwise direction of the strip. The stripis thus heated by induction.
The induced current flows parallel to the surface of the strip. The frequency must be chosen so that the electromagnetic penetration depth does not exceed half the strip thickness. A depth of 30 to 40% of the thickness is preferable to obtain good efficacy. High frequencies are required with thin strips, and Elotherm uses frequencies up to 500 kHz here.
With non-magnetic strips or with strips of aluminium or other non-ferrous materials, compliance with the penetration depth condition, for example at temperatures above the Curie point (approximately 760°C), is also only possible with high frequencies.
For this reason, transverse flux heating is also used in induction heatingmethods for metallurgical processes above 700°C or with non-ferrous metal strips. SMS Elotherm advises customers on the right and future-proof choice of the appropriate method. Induction machines from SMS Elotherm generally offer more precise heating over the entire material cross-section than other methods.
Thanks to their modular structure, EloStrip induction heatingmachines for strip heating can be adapted to the desired product parameters by adjusting the number of heating coils. Typical module power capacities are 2000 to 3000 kW per inductor.
The result is high-quality stripproducts with the desired material properties. To produce temperatures above 700°C, induction heating is used for metallurgical treatments, patenting and hot rolling applications.
The process is clean, flexibly adaptable to various stripgeometries, and enables high stripspeeds. Induction heatingtasks for strip heating in the temperature range up to 700°C include:
- Paint drying
- Blue annealing