Process for welding sheet metal coated with layers

Abstract

A method for the connection of sheet metal panels coated on at least one surface with a layer by the electrical fusion of a metal, wherein the improvement comprises the steps of supplying an electric current for the fusion of metal indirectly along the sheet metal of at least one panel to the zone at which said panels are to be connected to each other, and keeping the temperature of an outer layer of at least one of said panels below the melting point of said layer.

I claim: 
     
       1. In a process of connecting, by the electrical fusion of a metal, sheet metal panels and the like articles coated on at least one surface with a layer of material differing from the sheet metal, at least one of said layers being an outer layer on superposing said sheet metal panels the improvement which consists in a. conducting the welding current from one pole of a current source directly by means of a first contact device attached to a surface area on one of said superposed metal panels, said surface area being stripped of said coating, into and through said first sheet metal panel essentially parallel to its surface to and through the predetermined welding area of said first sheet metal panel and   b. causing the welding current to pass from said welding area to and through the predetermined welding area of the second superposed sheet metal panel through said second sheet metal panel essentially parallel to its surface and through a second contact device attached to said second sheet metal panel to the other pole of the current source,   c. thereby effecting welding connection of the two sheet metal panels with each other without substantially affecting at least one of the outer layers of said coated sheet metal panels.   
     
     
       2. The process of claim 1, in which the layer of a material differing from the sheet metal is an insulating layer. 
     
     
       3. The process of claim 2, in which the insulating layer is a plastic layer. 
     
     
       4. The process of claim 2, in which the insulating layer is an oxide layer. 
     
     
       5. The proces of claim 1, in which the layer of a material differing from the sheet metal is a layer of a metal of a lower melting point than that of the sheet metal. 
     
     
       6. The proces of claim 1, in which the layer of a material differing from the sheet metal is a layer of a metal capable of alloying with the welding electrode. 
     
     
       7. The process of claim 1, in which the contact device attached to a surface area of at least one of said metal panels is an auxiliary contact electrode. 
     
     
       8. The process of claim 1, in which the contact device attached to a surface area of at least one of said metal panels is a contact tong. 
     
     
       9. The process of claim 1, in which the contact device attached to a surface area of at least one of said metal panels is a contact clamp. 
     
     
       10. The process of claim 1 additionally comprising the step of d. cooling the coating of the outer surface of at least one of said panels.   
     
     
       11. The process of claim 1, in which electrical fusion of the sheet metal is effected by electrical resistance welding.