Alternately direct resistance spot welding of Al-to-Al, al-to-steel, and steel-to-steel with welding electrode having oxide-disrupting structural features

Patent metadata

Field	Value
Publication number	US-10675704-B2
Application number	US-201715492482-A
Country	US
Kind code	B2
Filing date	Apr 20, 2017
Priority date	Apr 22, 2016
Publication date	Jun 9, 2020
Grant date	Jun 9, 2020

Abstract

A method of resistance spot welding workpiece stack-ups of different combinations of metal workpieces with a single weld gun using the same set of welding electrodes is disclosed. In this method, a set of opposed welding electrodes that include an original shape and oxide-disrupting structural features are used to resistance spot weld at least two of the following types of workpiece stack-ups in a particular sequence: (1) a workpiece stack-up of two or more aluminum workpieces; (2) a workpiece stack-up that includes an aluminum workpiece and an adjacent steel workpiece; and (3) a workpiece stack-up of two or more steel workpieces. The spot welding sequence calls for completing all of the aluminum-to-aluminum spot welds and/or all of the steel-to-steel spot welds last.

First claim

The invention claimed is:

1. A method of resistance spot welding workpiece stack-ups of different combinations of metal workpieces with a single weld gun using the same set of welding electrodes, the method comprising:
providing a weld gun that carries a first welding electrode and an opposed second welding electrode, each of the first and second welding electrodes having a weld face that comprises an original shape and oxide-disrupting structural features, wherein the oxide-disrupting structural features are in the form of a series of upstanding circular ridges, a series of recessed circular grooves, or a microtexture;
positioning multiple vehicle body members relative to each other to provide a plurality of workpiece stack-ups, each of the workpiece stack-ups comprising a workpiece from one of the vehicle body members and an adjacent overlapping workpiece from at least one other of the vehicle body members and further having a first side and a second side to support pressed contact by the first welding electrode against the first side of the workpiece stack-up and pressed contact by the second welding electrode against the second side of the workpiece stack-up, wherein the plurality of workpiece stack-ups comprises a plurality of first workpiece stack-ups that include an aluminum workpiece and an adjacent overlapping steel workpiece, and wherein the plurality of workpiece stack-ups further comprises at least one of (i) a plurality of second workpiece stack-ups that include only overlapping aluminum workpieces or (ii) a plurality of third workpiece stack-ups that include only overlapping steel workpieces;
forming a set of aluminum-to-steel spot welds by progressing the weld gun to each of the plurality of first workpiece stack-ups and, at least once at each of the first workpiece stack-ups, pressing the first welding electrode directly against the first side of the first workpiece stack-up and pressing the second welding electrode directly against the second side of the first workpiece stack-up at a weld site and then passing an electrical current between the first and second welding electrodes and through the first workpiece stack-up to form an aluminum-to-steel spot weld that comprises a weld joint contained within the aluminum workpiece that weld bonds the aluminum workpiece to the adjacent steel workpiece;
forming at least one of (1) a set of aluminum-to-aluminum spot welds before forming the set of aluminum-to-steel spot welds or (2) forming a set of steel-to-steel spot welds after forming the set of aluminum-to-steel spot welds,
wherein forming the set of aluminum-to-aluminum spot welds includes progressing the weld gun to each of the plurality of second workpiece stack-ups that includes only overlapping aluminum workpieces and, at least once at each of the second workpiece stack-ups, pressing the first welding electrode directly against the first side of the second workpiece stack-up and pressing the second welding electrode directly against the second side of the second workpiece stack-up at a weld site and then passing an electrical current between the first and second welding electrodes and through the second workpiece stack-up to form an aluminum-to-aluminum spot weld that comprises an aluminum nugget that fusion welds the aluminum workpieces together, and
wherein forming the set of steel-to-steel spot welds includes progressing the weld gun to each of the plurality of third workpiece stack-ups that includes only overlapping steel workpieces and, at least once at each of the third workpiece stack-ups, pressing the first welding electrode directly against the first side of the third workpiece stack-up and pressing the second welding electrode directly against the second side of the third workpiece stack-up at a weld site and then passing an electrical current between the first and second welding electrodes and through the third workpiece stack-up to form a steel-to-steel spot weld that comprises a steel nugget that fusion welds the steel workpieces together; and

restoring each of the weld faces of the first and second welding electrodes to regenerate its original shape and oxide-disrupting structural features, wherein restoring each of the weld faces includes (i) inserting the weld face into a cutting socket of a cutting tool and rotating the cutting tool to shear away weld face material to reestablish the original shape of the weld face while fashioning a new series of upstanding circular ridges or a new series of recessed circular grooves or (ii) redressing the weld face by inserting the weld face into a cutting socket of a cutting tool and rotating the cutting tool to shear away weld face material to reestablish the original shape of the weld face followed by texturing the weld face with an abrasive media to establish a new microtexture of the weld face.

2. The method set forth in claim 1 , wherein forming a set of aluminum-to-aluminum spot welds is practiced before forming the set of aluminum-to-steel spot welds, and wherein restoring each of the weld faces of the first and second welding electrodes is performed after forming the set of aluminum-to-steel spot welds.

3. The method set forth in claim 1 , wherein forming a set of steel-to-steel spot welds is practiced after forming the set of aluminum-to-steel spot welds, and wherein restoring each of the weld faces of the first and second welding electrodes is performed after forming the set of steel-to-steel spot welds.

4. The method set forth in claim 1 , wherein forming a set of aluminum-to-aluminum spot welds is practiced before forming the set of aluminum-to-steel spot welds, wherein forming a set of steel-to-steel spot welds is practiced after forming the set of aluminum-to-steel spot welds, and wherein restoring each of the weld faces of the first and second welding electrodes is performed after forming the set of steel-to-steel spot welds.

5. The method set forth in claim 1 , wherein the oxide-disrupting structural features included on each weld face comprise a series of upstanding circular ridges that are centered about and surround a central axis of the weld face and which project outwardly from a base weld face surface of the weld face, the series of upstanding circular ridges including anywhere from two circular ridges to ten circular ridges starting from an innermost ridge that immediately surrounds the central axis of the weld face and ending with an outermost ridge that is farthest from the central axis of the weld face.

6. The method set forth in claim 5 , wherein restoring each of the weld faces of the first and second welding electrodes comprises:
inserting the weld face into a cutting socket of a cutting tool so that the weld face engages a cutting surface and the central axis of the weld face is aligned with an axis of rotation of the cutting tool, the cutting surface defining recessed grooves that extend from a leading edge of the cutting surface towards a trailing edge; and
rotating the cutting tool while engaged with the weld face to shear away weld face material to reestablish the original shape of the weld face while the recessed grooves fashion a new series of upstanding circular ridges that project outwardly from the base weld face surface of the weld face.

7. The method set forth in claim 6 , wherein restoring each of the weld faces of the first and second welding electrodes is performed simultaneously without removing either of the welding electrodes from the weld gun.

8. The method set forth in claim 1 , wherein the oxide-disrupting structural features included on each weld face comprise a microtexture that includes three-dimensional microscopic peaks-and-valleys covering at least 75% of a base weld face surface of the weld face to provide a surface roughness (Ra) that ranges f

Assignees

• Gm Global Tech Operations Llc

Inventors

• Sigler David R
• Carlson Blair E
• Karagoulis Michael J

Classifications

• B23K11/24

  Electric supply or control circuits therefor · CPC title

• B23K11/3063

  Electrode maintenance, e.g. cleaning, grinding · CPC title

• B23K2103/10

  Aluminium or alloys thereof · CPC title

• B23K2103/20

  Ferrous alloys and aluminium or alloys thereof · CPC title

• B23K11/115 Primary

  by means of two electrodes placed opposite one another on both sides of the welded parts · CPC title