Deformation resistance welding of sheet metal, tubes, and similar shapes

Abstract

Welded structures having a first and a second member formed from sheet metal, tubes, and similar shapes, are economically fabricated through use of a method for joining a second member to a first member having a folded rim extending therefrom. The folded rim defines an air gap within the folded rim. The first and second members are joined together by forcing the folded rim against the second member under sufficient pressure to flatten the folded rim to a point that there remains substantially no air gap inside the folded rim, and resistance welding together the first and second members. The second member and the rim respectively define faying surfaces thereof. The air gap inside the folded rim extends generally parallel to the faying surfaces. The faying surfaces of the rim and second member are forced against one another by applying pressure through the folded rim in a direction generally perpendicular to the faying surfaces. While applying pressure, a first level of electrical current may be passed through the first and second members for softening the rim by electrical resistance heating and causing the softened rim to deform against the second member. Pressure is maintained, and a second level of electrical current, higher than the first level of current, is applied for a time sufficient to at least partially melt the folded rim and form a deformation resistance weld between the first and second member.

We claim:  
     
         1 . A method for joining a second member to a first member having a folded rim extending therefrom, with the folded rim defining an air gap therein, the method comprising: 
 forcing the folded rim against the second member under sufficient pressure to flatten the folded rim to a point that there remains substantially no air gap inside the folded rim; and    resistance welding together the first and second members.    
     
     
         2 . The method of  claim 1 , wherein the second member and folded rim respectively define faying surfaces thereof, the folded rim defines an air gap inside thereof extending generally parallel to the faying surfaces, and the method further comprises forcing the faying surfaces of the folded rim and second member against one another by applying pressure through the folded rim in a direction generally perpendicular to the faying surfaces.  
     
     
         3 . The method of  claim 2 , further comprising: 
 engaging the folded rim of the first member with a first electrode and applying pressure against the folded rim with the first electrode in a first direction generally perpendicular to the faying surfaces;    engaging the second member with a second electrode and applying pressure against the second member with the second electrode in a direction opposite the first direction; and    moving at least one of the first and second electrodes toward the other electrode while resistance welding together the first and second members.    
     
     
         4 . The method of  claim 2 , wherein the first and second members define a juncture thereof intersecting and extending from the faying surfaces, and the method further comprises: 
 engaging the folded rim of the first member with a first electrode having a potion thereof extending beyond the folded rim;    applying pressure against the folded rim with the first electrode in a first direction generally perpendicular to the faying surfaces;    engaging the second member with a second electrode;    applying pressure against the second member with the second electrode in a direction opposite the first direction;    applying an electrical current between the electrodes for resistance heating of the first and second members;    moving the first electrode toward the second electrode, while resistance welding together the first and second members, to a point where the portion of the first electrode extending beyond the folded rim contacts the second member; and    continuing to apply pressure and electrical current after the portion of the first electrode extending beyond the folded rim contacts the second member, to thereby continue resistance heating of the juncture and force a portion of the material from the melted folded rim to flow into the juncture between the first and second members for welding them together.    
     
     
         5 . The method of  claim 2  further comprising applying pressure and a first level of electrical current flow through the first and second members for a first period of time for softening the rim by electrical resistance heating and causing the softened rim to deform against the second member.  
     
     
         6 . The method of  claim 5  further comprising applying a second level of electrical current higher than the first level of current for second period of time sufficient to at least partially melt the folded rim and form a deformation resistance weld between the first and second member.  
     
     
         7 . The method of  claim 6  further comprising applying the second level of electrical current for a period of time sufficient to substantially completely melt the folded rim.  
     
     
         8 . The method of  claim 6 , wherein the first level of current is about one half of the second level of current.  
     
     
         9 . The method of  claim 6 , wherein the first and second periods of time are substantially equal in length.  
     
     
         10 . The method of  claim 7  wherein the first and second members define a juncture thereof intersecting and extending from the faying surfaces, and the pressure and electrical current at the second level are maintained for a period of time sufficient for a portion of the material from the melted folded rim to flow into the juncture and weld together the first and second members.  
     
     
         11 . The method of  claim 10  wherein the juncture of the first and second members defines a gap therebetween for receipt of a portion of the material from the melted folded rim.  
     
     
         12 . The method of  claim 10 , wherein the folded rim and second member define corresponding faying surfaces thereof, and the method further comprises: 
 engaging the folded rim of the first member with a first electrode having a potion thereof extending beyond the folded rim;    applying pressure against the folded rim with the first electrode in a first direction generally perpendicular to the faying surfaces;    engaging the second member with a second electrode;    applying pressure against the second member with the second electrode in a direction opposite the first direction;    applying an electrical current between the electrodes for resistance heating of the first and second members;    moving the first electrode toward the second electrode, while resistance welding together the first and second members, to a point where the portion of the first electrode extending beyond the folded rim contacts the second member; and    continuing to apply pressure and electrical current after the portion of the first electrode extending beyond the folded rim contacts the second member, to thereby continue resistance heating of the juncture and force a portion of the material from the melted folded rim to flow into the juncture between the first and second members for welding them together.    
     
     
         13 . The method of  claim 1  wherein at least one of the first and second members has a tubular cross-section.  
     
     
         14 . The method of  claim 1  wherein neither of the first and second members has a tubular cross-section.  
     
     
         15 . The method of  claim 1  wherein the second member includes a wall thereof defining an opening therein for receipt of a portion of the first member, and the first member includes a portion thereof extending from the folded rim for insertion into the opening in the second member.  
     
     
         16 . The method of  claim 15  wherein the opening in the wall of the second member is a through hole having a longitudinal axis extending generally perpendicular to a plane defined by the folded rim, with the through hole further having a first and a second longitudinal end, the first longitudinal end being located adjacent the folded rim of the first member.  
     
     
         17 . A method for joining a second member to a first member by deformation resistance heating, the method comprising: 
 forming a folded rim on the first member having a faying surface thereof generally contoured to mate with a corresponding faying surface of the second member, with the folded rim also defining an air gap inside thereof extending generally parallel to the faying surfaces;    forcing the folded the faying surfaces of the rim and second member against one another by applying sufficient pressure through the folded rim in a direction generally perpendicular to the faying surfaces rim against the second member to flatten the folded rim to a point that there remains substantially no air gap inside the folded rim; and    applying an electrical current for resistance heating the first and second members.    
     
     
         18 . The apparatus of  claim 17  further comprising applying a filler metal to a portion of at least one of the first and second members that melts at a melting temperature lower than the melting temperature of the first and second members.  
     
     
         19 . The method of  claim 17  further comprising applying electrical current at a level and for a period of time sufficient to at least partially melt the folded rim and form a deformation resistance weld between the first and second member.  
     
     
         20 . The method of  claim 18  wherein the first and second members define a juncture thereof intersecting and extending from the faying surfaces, and the pressure and electrical current are maintained for a period of time sufficient for a portion of the material from the melted folded rim to flow into the juncture and weld together the first and second members.  
     
     
         21 . A method for deformation resistance welding together a first and a second member, the method comprising: 
 forming a folded rim on the first member, the folded rim having a faying surface thereof generally contoured to mate with a corresponding faying surface of the second member, the folded rim also defining an air gap inside thereof extending generally parallel to the faying surfaces;    forcing the faying surfaces of the rim and second member against one another by applying pressure to the folded rim in a direction generally perpendicular to the faying surfaces against the second member;    applying a first level of electrical current through the first and second members for a first period of time sufficient for softening the rim by electrical resistance heating and causing the softened rim to deform and flatten against the second member to a point that there remains substantially no air gap inside the folded rim; and    applying a second level of electrical current higher than the first level of current for second period of time sufficient to at least partially melt the folded rim and form a deformation resistance weld between the first and second member.