Method and device for resistance welding steel sandwich sheets

A method of resistance welding a component to a sandwich sheet that comprises a thermoplastic layer disposed between two metallic outer layers, the method comprising:

• heating a region of the sandwich sheet to be welded such that the thermoplastic layer softens;
• displacing the thermoplastic layer in the region to be welded by pressing the two metallic outer layers together;
• and
• welding the two metallic outer layers to the component by an electrical current flowing for welding in a first circuit via a first welding electrode disposed at a side of the sandwich sheet and a second welding electrode disposed at a side of the component, wherein the first circuit comprises a first power source,
• wherein the region of the sandwich sheet to be welded is heated by an electrical current flowing for preheating in a second circuit, wherein the second circuit comprises a second power source and an electrical conductor that is disposed between the first welding electrode and the sandwich sheet.

An apparatus for resistance welding a component to a sandwich sheet comprising a thermoplastic layer disposed between metallic outer layers, the apparatus comprising:

• a first welding electrode that is positionable on a side of the sandwich sheet;
• a second welding electrode that is positionable on a side of the component;
• a first circuit through which an electrical current for welding can flow, at least through the first and second welding electrodes, wherein the first circuit comprises a first power source;
• means for displacing the thermoplastic layer from a region of the sandwich sheet to be welded;
• and
• a second circuit comprising a second power source and an electrical conductor that is positionable between the first welding electrode and the sandwich sheet.