Welding and forming method

Abstract

A forming method in which members are forced together at an interface by causing parallel currents to flow in adjacent conductors, thereby forcing the conductors toward each other in a direction generally normal to the interface.

What is claimed is: 
     
       1. A forming method in which .[.members.]. .Iadd.electrical conductors .Iaddend.are forced together at an interface thereof, said method comprising the steps of: placing .Iadd.said .Iaddend.conductors in contact with each other .Iadd.to provide said interface therebetween; .Iaddend.   placing .[.a magnetic.]. .Iadd.an induction .Iaddend.coil .[.adjacent.]. .Iadd.and .Iaddend.said conductors .Iadd.adjacent each other with said coil and said interface disposed relative to each other so that a current flowing in said coil will induce generally parallel currents in each of said conductors at said interface with the current in one of said conductors flowing in the same direction as the current flowing in the other of said conductors;   heating the portions of said conductors at said interface; .Iaddend.and   passing .[.a forming current.]. through said coil .Iadd.a forming current of characteristic frequency and magnitude sufficient .Iaddend.to .[.induct.]. .Iadd.induce said generally parallel .Iaddend.currents in each of said conductors .[.flowing generally parallel to each other and to.]. .Iadd.at .Iaddend.said interface .Iadd.in a magnitude sufficient to force .Iaddend..[.said currents induced by said forming current causing.]. each of said conductors .[.to be forced towards.]. .Iadd.against .Iaddend.the other in a direction generally perpendicular to said interface .Iadd.and to cause forming of at least one thereof. .Iaddend. .[.2. The method of claim 1 including the step of electrically connecting said conductors prior to passing said forming current through said coil..]. .[.3. The method of claim 1 including the step of heating the portions of said members defining said interface prior to passing said forming current through said coil and wherein said forming current causes   
     
     
        said members to be forced together..]. 4. The method of claim .[.3.]. .Iadd.1 .Iaddend.wherein .[.said conductors define said interface and.]. said portions are inductively heated by passing .[.a.]. .Iadd.an alternating .Iaddend.heating current through said coil .Iadd.prior to 
     
     
        passing said forming current through said coil..Iaddend. 5. The method of claim 4 wherein said forming current causes said conductors to be welded 
     
     
        together at said interface. 6. The method of claim 1 wherein .[.said conductors define said interface and.]. the skin depth of said currents induced by said forming current is not less than the thickness of one of 
     
     
        said conductors. 7. The method of claim 1 wherein said conductors are cylindrical and define said interface and said coil surrounds the portions 
     
     
        of said conductors defining said interface. 8. The method of claim 7 wherein at least one of said conductors is tubular and the skin depth of said currents induced by said forming current is not less than the wall 
     
     
        thickness of said tubular conductor. 9. The method of claim 7 wherein said conductors are tubular, one of said conductors surrounds the other of said conductor thereby defining a generally cylindrical interface therebetween, and the skin depth of said currents induced by said forming current is .[.not less.]. .Iadd.greater .Iaddend.than the .[.total.]. radial thickness of said .[.conductors through said interface.]. .Iadd.one 
     
     
        conductor. .Iaddend. 10. The method of claim 9 wherein the portions of said conductors defining said interface are inductively heated by passing an .[.inductive.]. .Iadd.alternating .Iaddend.heating current through said coil prior to passing said forming current through said coil whereby said forming current causes said conductors to be welded together at said 
     
     
        interface. 11. The method of claim 7 wherein said conductors are cylindrical and are placed end-to-end to define .[.an.]. .Iadd.said .Iaddend.interface therebetween generally normal to the axes of said 
     
     
        conductors. 12. The method of claim 1 wherein the portions of said conductors defining said interface are inductively heated by passing an .[.inductive.]. .Iadd.alternating .Iaddend.heating current through said coil prior to passing said forming current through said coil whereby said forming current causes said conductors to be welded together at said 
     
     
        interface. 13. The method of claim 1 .[.including the steps of: placing a pair of cylindrical.]. .Iadd.wherein said .Iaddend.conductors .Iadd.are cylindrical and are placed in .Iaddend.end-to-end .Iadd.contact .Iaddend.to define .[.a first.]. .Iadd.said .Iaddend.interface therebetween substantially normal to the axes of said conductors .[.;.]. .Iadd.and further comprising the steps of: .Iaddend. placing a conductive sleeve in .Iadd.a .Iaddend.position surrounding the portions of said cylindrical conductors defining said .[.first.]. interface to define a second interface between said sleeve and one of said conductors and a third interface between said sleeve and the other of said conductors; .Iadd.and .Iaddend.   placing said .[.magnetic.]. .Iadd.induction .Iaddend.coil in .Iadd.a .Iaddend.position adjacent and generally surrounding said interfaces .[.;.]. whereby .[.passing.]. said forming current .Iadd.passing .Iaddend.through said coil .[.to induce.]. .Iadd.induces .Iaddend.currents in said conductors and said sleeve flowing generally parallel to each other and to said interfaces .[.;.]. and .[.said currents causing.]. .Iadd.causes .Iaddend.said conductors to be forced together in a generally axial direction and said conductors and said sleeve to be forced together   
     
     
        in generally radial directions. 14. The method of claim 13 wherein the portions of said sleeve and said conductors defining said .Iadd.second and third .Iaddend.interfaces are heated prior to passing said forming current 
     
     
        through said coil. 15. The method of claim 14 wherein said portions are heated by passing an .[.inductive.]. .Iadd.alternating .Iaddend.heating 
     
     
        current through said coil. 16. The method of claim 13 wherein the skin depth of said currents induced by said forming current is .[.not less.]. 
     
     
        .Iadd.greater .Iaddend.than the radial thickness of said sleeve. 17. The method of claim 13 wherein said conductors are tubular and the skin depth of said currents induced by said forming current is not less than the total radial thickness of one of said conductors and said sleeve through 
     
     
        the interface defined thereby. 18. The method of claim 17 wherein the portions of said conductors and said sleeve defining said .Iadd.second and third .Iaddend.interfaces are heated prior to passing said forming current 
     
     
        through said coil. 19. The method of claim 4 including the step of cooling 
     
     
        surfaces of said conductors during the inductive heating thereof. 20. The method of claim 4 including the steps of .Iadd.again .Iaddend.inductively heating said conductors and then .Iadd.again .Iaddend.forcing said conductors .[.together.]. .Iadd.against each other .Iaddend.by inducing parallel-flowing currents therein subsequent to the initial .[.inductive.]. heating and .Iadd.initial .Iaddend.forcing together of said conductors. .Iadd. 21. The method of claim 4 wherein said alternating current is a high frequency current..Iaddend.