A contact heating device for thermally induced (materially cohesive) seam bonding of weldable and/or gluable flat flexible material layers with each other, which are configured as a material web, a material band and/or a material piece and are arranged at least partially overlapping, is provided, the contact heating device comprising: a first terminal electrode and a second terminal electrode; and a heating element connected between the terminal electrodes; wherein the heating element is configured as a directly energized, flat, planar sheet steel blank. The present invention further relates to an automatic welding or joining machine, a hand-held device and a method.