Resistance spot welding of aluminum-to-aluminum, aluminum-to-steel, and steel-to-steel in a specified sequence and using a cover

• US 10,682,724 B2
• Filed: 04/19/2017
• Issued: 06/16/2020
• Est. Priority Date: 04/19/2016
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Sigler, David R., Carlson, Blair E., Karagoulis, Michael J.
• Primary Examiner(s): Akar, Serkan
• Assistant Examiner(s): Liu, Chris Q
• Application Number:
  US15/491,566
• Publication Number:
  US 20170297138A1
• Time in Patent Office: 1,154 Days
• Field of Search: 219 912, 219119, 219118, 219 93, 2191171, 219 8622, 219 9122, 21912114, 21912164, 219136, 219137 R, 219 861, 219 8623, 219 8631, 219 87, 219 9123, 219 92, 219 94
• CPC Class Codes: B23K 11/115 by means of two electrodes placed opposite one another on both sides of the welded parts
• CPC Class Codes: B23K 11/166 of galvanized or tinned materials
• CPC Class Codes: B23K 11/185 of aluminium or aluminium alloys
• CPC Class Codes: B23K 11/20 of different metals
• CPC Class Codes: B23K 11/24 Electric supply or control circuits therefor
• CPC Class Codes: B23K 11/3009 Pressure electrodes
• CPC Class Codes: B23K 11/3063 Electrode maintenance, e.g. cleaning, grinding
• CPC Class Codes: B23K 11/315 with one electrode moving on a linear path
• CPC Class Codes: B23K 2101/006 Vehicles
• CPC Class Codes: B23K 2101/185 Tailored blanks
• CPC Class Codes: B23K 2103/04 Steel or steel alloys
• CPC Class Codes: B23K 2103/10 Aluminium or alloys thereof
• CPC Class Codes: B23K 2103/20 Ferrous alloys and aluminium or alloys thereof

Abstract

A series of many electrical resistance spot welds is to be formed in members of an assembled, but un-joined, body that presents workpiece stack-ups of various combinations of metal workpieces including all aluminum workpieces, all steel workpieces, and a combination of aluminum and steel workpieces. A pair of spot welding electrodes, each with a specified weld face that includes oxide-disrupting features, is used to form the required numbers of aluminum-to-aluminum spot welds, aluminum-to-steel spot welds, and steel-to-steel spot welds. A predetermined sequence of forming the various spot welds may be specified for extending the number of spot welds that can be made before the weld faces must be restored. And, during at least one of the aluminum-to-steel spot welds, a cover is inserted between the weld face of one of the welding electrodes and a side of a workpiece stack-up that includes the adjacent aluminum and steel workpieces.

Claims

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 having a first weld face and an opposed second welding electrode having a second weld face, each of the first weld face and the second weld face comprising oxide disrupting structural features, wherein the oxide-disrupting structural features on each of the first and second weld faces comprises a series of upstanding circular ridges or a series or recessed circular grooves;

assembling a fixtured assembly that includes aluminum workpieces and steel workpieces arranged to provide one or more workpiece stack-ups that include only overlapping aluminum workpieces, one or more workpiece stack-ups that include an aluminum workpiece and an overlapping adjacent steel workpiece, and one or more workpiece stack-ups that include only overlapping steel workpieces;

forming a set of aluminum-to-aluminum spot welds in the one or more workpiece stack ups that include only overlapping aluminum workpieces with the first and second welding electrodes, each of the aluminum-to-aluminum spot welds comprising an aluminum nugget that fusion welds the aluminum workpieces together;

forming a set of aluminum-to-steel spot welds in the one or more workpiece stack-ups that include an aluminum workpiece and an adjacent overlapping steel workpiece with the first and second welding electrodes, each of the aluminum-to-steel spot welds comprising a weld joint contained within an aluminum workpiece that weld bonds the aluminum workpiece to an adjacent steel workpiece, and wherein forming at least one of the set of aluminum-to-steel spot welds in a workpiece stack-up that includes an aluminum workpiece and an overlapping adjacent steel workpiece, and further has an aluminum workpiece surface at a first side of the workpiece stack-up and a steel workpiece surface at a second side of the workpiece stack up, comprises pressing the first weld face of the first welding electrode against the aluminum workpiece surface at the first side of the workpiece stack-up and pressing the second weld face of the second welding electrode against a cover that is inserted between the second weld face and the steel workpiece surface at the second side of the workpiece stack-up to isolate the second weld face from the second side of the workpiece stack-up during current flow, wherein the cover is a cover plate that includes a planar base and an outwardly extending dome portion having a convex shape, the second weld face of the second welding electrode being pressed against the planar base and the outwardly extending dome portion being pressed against the steel workpiece surface at the second side of the workpiece stack-up; and

forming a set of steel-to-steel spot welds in the one or more workpiece stack-ups that include only overlapping steel workpieces with the first and second welding electrodes, each of the steel-to-steel spot welds comprising a steel nugget that fusion welds the steel workpieces together;

wherein the set of aluminum-to-aluminum spot welds is formed first, the set of aluminum to-steel spot welds is formed after the set of aluminum-to-aluminum spot welds, and the set of steel-to-steel spot welds is formed after the set of aluminum-to-steel spot welds.

2. The method set forth in claim 1, wherein the oxide disrupting structural features on the first weld face, the second weld face, or both the first and second weld faces comprises 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.

3. The method set forth in claim 1, wherein the oxide disrupting structural features on the first weld face, the second weld face, or both the first and second weld faces comprises a series of recessed circular grooves that are centered about and surround a central axis of the weld face and which intrude inwardly into a base weld face surface of the weld face, the series in recessed grooves including anywhere from two circular grooves to ten circular grooves starting from an innermost groove that immediately surrounds the central axis of the weld face and ending with an outermost groove that is farthest from the central axis of the weld face.

4. The method set forth in claim 1, wherein the cover plate is constructed from a dispersion strengthened copper alloy.

5. The method set forth in claim 1, wherein the cover plate is constructed from a tungsten-copper composite.

6. The method set forth in claim 1, wherein each of the one or more workpiece stack-ups that include an aluminum workpiece and an overlapping adjacent steel workpiece has an aluminum workpiece surface at a first side of the workpiece stack-up and a steel workpiece surface at a second side of the workpiece stack-up, and, wherein, during formation of each of the set of aluminum-to-steel spot welds, the cover is inserted between the second weld face of the second welding electrode and the steel workpiece surface at the second side of each of the one or more workpiece stack-ups that include an aluminum workpiece and an overlapping adjacent steel workpiece to isolate the second weld face from the steel workpiece surface of each of the one or more workpiece stack-ups that include an aluminum workpiece and an overlapping adjacent steel workpiece.

7. The method set forth in claim 1, wherein the outwardly extending dome portion of the cover plate has a diameter that is less than a diameter of the second weld face of the second welding electrode.

8. The method set forth in claim 7, wherein the outwardly extending dome portion is spherically shaped with a radius of curvature that ranges from 4 mm to 12 mm.

9. The method set forth in claim 1, wherein the cover is constructed from a copper material.

10. The method set forth in claim 1, wherein each of the set of aluminum-to-aluminum spot welds, the set of aluminum-to-steel spot welds, and the set of steel-to-steel spot welds is formed throughout a unitary body-in-white structure of an automotive passenger vehicle.

11. The method set forth in claim 1, further comprising periodically restoring each of the first weld face of the first welding electrode and the second weld face of the second welding electrode.

12. The method set forth in claim 1, wherein inserting the cover comprises rotating an arm that carries the cover about a pivot axis to bring the cover into an inserted position in which the cover is located between the second weld face of the second welding electrode and the second side of the workpiece stack-up.

13. The method set forth in claim 1, further comprising:

forming another set of aluminum-to-steel spot welds in the one or more workpiece stack ups that includes an aluminum workpiece and an adjacent overlapping steel workpiece with the first and second welding electrodes before forming the set of aluminum-to-aluminum spot welds.