Welding of coated sheet or strip

Claim 1

A PROCESS FOR RESISTANCE-WELDING TOGETHER THE EDGES OF TWO COATED METAL SHEETS OR STRIPS, THE COATING HAVING ELECTRICAL INSULATING PROPERTIES AND BEING FLOWABLE UNDER RESISTANCE-WELDING HEAT AND PRESSURE, THE PROCESS COMPRISING: (A) FORMING A FLANGE AT THE EDGE OF EACH SHEET OR STRIP, (B) BRINGING THE FLANGES INTO CONTACT WITH THE INSULATING COATING SEPARATING THE METAL OF THE FLANGES, (C) PROVIDING A METALLIC CONDUCTING PATH FROM THE OUTER SIDE OF ONE OF THE CONTACTING FLANGES TO THE OUTER SIDE OF THE OTHER CONTACTING FLANGE, (D) PRESSING WELDING ELECTRODES ON SAID CONDUCTING PATH ON OPPOSITE SIDES OF SAID CONTACTING FLANGES, (E) PASSING ELECTRIC CURRENT BETWEEN THE ELECTRODES, THE CURRENT INITIALLY PASSING AROUND THE CONDUCTING PATH BY REASON OF THE INSULATING EFFECT OF THE COATING ON THE FLANGES WHILE CAUSING LOCALIZED HEATING UNDER THE ELECTRODES THEREBY MELTING THE COATING WHICH COATING FLOWS TO PROVIDE A DIRECT CURRENT PATH BETWEEN THE CAUSING WELDING OF THE FLANGES AND METALLIC CONDUCTWELDING ELECTRODES THROUGH THE FLANGES, WHICH DIRECT CURRENT PATH THE CURRENT WILL SUBSEQUENTLY FOLLOW ING PATH TOGETHER IN THE AREA OF THE PRESSING ELECTRODES, AND (F) ALLOWING THE COATING TO FLOW BACK AROUND THE WELDED AREA AND HARDEN.