Method for creating a resistance weld bond between two metals

Abstract

An electrode used for resistance welding is described. In an embodiment, the electrode comprises a two-part construction having an electrode tip portion that is removably contactable to an electrode base. The electrode is constructed such that the respective base and electrode tip portions may be composed of metals having differing melting temperatures, in particular a significant difference in melting temperature of at least 100° C. or more. The electrode is preferably constructed so that the electrode tip portion can be easily removed, thereby leaving the base portion within the fixture.

What is claimed is: 
     
         1 . A method of creating a resistance weld bond between two metals, comprising the steps of:
 a) providing a first workpiece metal;   b) providing a second workpiece metal;   c) providing an electrical resistance weld instrument comprising a first resistance welding electrode and a second resistance welding electrode positioned opposed from the first resistance welding electrode and an electrical power source electrically connected to the first and second resistance welding electrodes, wherein either or both of the first and second resistance welding electrode comprises:
 i) an electrode base portion composed of a first electrically conductive material comprising an electrode base body having an electrode base proximal end with an electrode base proximal surface that extends along a longitudinal axis to an electrode base portion distal end with an electrode base distal surface; 
 ii) an electrode tip portion composed of a second electrically conductive material comprising an electrode tip body having an electrode tip proximal end with an electrode tip proximal surface that extends along the longitudinal axis to an electrode tip distal end with an electrode distal surface; and 
 iii) wherein the electrode tip portion is contactable to the electrode base portion so that electrical energy is conductible therebetween; 
   d) placing the first and second workpiece metals between the opposing first and second resistance welding electrodes; and   e) applying a current to the first and second resistance welding electrodes that causes the first workpiece metal and the second workpiece metal to join together.   
     
     
         2 . The method of  claim 1 , including applying at least about 1 kA of direct electrical current to the first and second resistance welding electrodes. 
     
     
         3 . The method of  claim 1 , including the first workpiece metal having a first melting temperature that is at least about 125° C. less than a second melting temperature of the second workpiece metal. 
     
     
         4 . The method of  claim 1 , including pulsating the electrical current at an interval duration ranging from between 10 milliseconds to about 100 milliseconds. 
     
     
         5 . The method of  claim 1 , including selecting the electrode base first material from the group consisting of copper, aluminum, stainless steel, gold, silver, palladium, alloys, and mixtures thereof. 
     
     
         6 . The method of  claim 1 , including selecting the electrode tip second material from the group consisting of molybdenum, tungsten, tantalum, cobalt, nickel, niobium, rhenium, and mixtures thereof 
     
     
         7 . The method of  claim 1 , including providing the electrode tip second material with substantially the same material composition as either the first or second workpiece materials. 
     
     
         8 . The method of  claim 1 , including providing the electrode tip portion with an electrode tip groove having a groove depth and a groove length, wherein the electrode tip groove depth extends through the electrode tip distal surface at least partially towards the electrode tip proximal end and the electrode tip groove length extending perpendicular to the longitudinal axis 
     
     
         9 . The method of  claim 8 , including providing the electrode tip groove comprising a cross section shape oriented perpendicular to the longitudinal axis, the shape selected from the group consisting of a “V”, a “U”, a rectangle, a square, a hexagon and a curved shape. 
     
     
         10 . The method of  claim 1 , including providing the electrode tip portion with an electrode tip ridge having a ridge length oriented perpendicular to the longitudinal axis that extends outwardly from the electrode tip proximal surface, the ridge configured to be mateably received within an electrode base slot having an electrode base slot depth and an electrode base slot length, wherein the electrode base slot depth extends through the electrode base distal surface at least partially towards the electrode base proximal end, the electrode base slot length extending perpendicular to the longitudinal axis.