Resistance spot welding steel and aluminum workpieces using electrode weld face cover

Patent metadata

Field	Value
Publication number	US-10052710-B2
Application number	US-201414462655-A
Country	US
Kind code	B2
Filing date	Aug 19, 2014
Priority date	Aug 23, 2013
Publication date	Aug 21, 2018
Grant date	Aug 21, 2018

Abstract

A method of resistance spot welding a steel workpiece and an aluminum or aluminum alloy (“aluminum”) workpiece together includes several steps. One step involves providing a workpiece stack-up with a steel workpiece and an aluminum workpiece. Another step involves attaching a cover over a weld face of a welding electrode. The cover is made of a metal material with an electrical resistivity that is greater than an electrical resistivity of a material of the welding electrode. Yet another step involves performing multiple individual resistance spot welds to the workpiece stack-up. The cover abuts the aluminum workpiece while the individual resistance spot welds are performed. And another step involves removing the cover from the welding electrode after the individual spot welds are performed.

First claim

The invention claimed is:

1. A method of resistance spot welding, the method comprising:
providing a workpiece stack-up that includes a steel workpiece and an aluminum or aluminum alloy workpiece;
providing a first welding electrode positioned to contact the steel workpiece and a second welding electrode positioned to contact the aluminum or aluminum alloy workpiece, each of the first welding electrode and the second welding electrode being composed of a copper alloy;
attaching a cover at least over a weld face of the second welding electrode, the cover having a weld face and being made of a metal material with an electrical resistivity that is greater than an electrical resistivity of the copper alloy of the second welding electrode, the cover being removably attached to the second welding electrode;
performing a plurality of individual resistance spot welds to the workpiece stack-up, the cover abutting the aluminum or aluminum alloy workpiece while the individual resistance spot welds are performed; and
removing the cover from the welding electrode after the individual resistance spot welds are performed.

2. The method as set forth in claim 1 , wherein the cover is attached to the welding electrode via a crimping process, a stamping process, a screwing process, or a combination of two or more of these processes.

3. The method as set forth in claim 1 , wherein the cover is made of steel, stainless steel, molybdenum, tungsten, or niobium.

4. The method as set forth in claim 1 , wherein the cover generates heat at the aluminum or aluminum alloy workpiece upon its abutment and upon performance of an individual resistance spot weld, and the generated heat alters solidification behavior of a molten weld pool created in the aluminum or aluminum alloy workpiece via the individual resistance spot weld.

5. The method as set forth in claim 1 , further comprising:
providing a second workpiece stack-up that includes a steel workpiece and an aluminum or aluminum alloy workpiece;
attaching a second cover at least over the weld face of the second welding electrode, the second cover having a weld face and being made of a metal material with an electrical resistivity that is greater than the electrical resistivity of the copper alloy of the second welding electrode, the second cover being removably attached to the second welding electrode; and
performing a plurality of second individual resistance spot welds to the second workpiece stack-up, the second cover abutting the aluminum or aluminum alloy workpiece of the second workpiece stack-up while the second individual resistance spot welds are performed.

6. The method as set forth in claim 1 , further comprising:
performing a plurality of second individual resistance spot welds to a second workpiece stack-up that includes a first steel workpiece and a second steel workpiece, or that includes a first aluminum or aluminum alloy workpiece and a second aluminum or aluminum alloy workpiece, without the cover.

7. The method as set forth in claim 6 , further comprising dressing the weld face of the second welding electrode after the second individual resistance spot welds are performed.

8. The method as set forth in claim 7 , further comprising:
providing a third workpiece stack-up that includes a steel workpiece and an aluminum or aluminum alloy workpiece;
attaching a second cover at least over the weld face of the second welding electrode after the weld face is dressed, the second cover having a weld face and being made of a metal material with an electrical resistivity that is greater than the electrical resistivity of the copper alloy of the second welding electrode, the second cover being removably attached to the second welding electrode; and
performing a plurality of third individual resistance spot welds to the third workpiece stack-up, the second cover abutting the aluminum or aluminum alloy workpiece of the third workpiece stack-up while the third individual resistance spot welds are performed.

9. The method as set forth in claim 1 , wherein the material of the cover has an electrical resistivity that is greater than an electrical resistivity of the aluminum or aluminum alloy workpiece.

10. A welding electrode assembly comprising:
a workpiece stack-up that includes a steel workpiece and an aluminum or aluminum alloy workpiece;
a first welding electrode in contact with the steel workpiece;
a second welding electrode made of a first metal material, the second welding electrode including a weld face; and
a cover removably attached to the second welding electrode and covering at least the weld face of the second welding electrode, the cover further abutting the aluminum or aluminum alloy workpiece when resistance spot welding the steel workpiece and the aluminum or aluminum alloy workpiece together, the cover being made of a second metal material with an electrical resistivity that is greater than an electrical resistivity of the first metal material, and wherein the first welding electrode lacks a cover removably attached thereto.

11. The welding electrode assembly of claim 10 , wherein the cover is removably attached to the first welding electrode via a crimping process, a stamping process, a screwing process, or a combination of two or more of these processes.

12. The welding electrode assembly of claim 10 , wherein the second metal material of the cover is steel, stainless steel, molybdenum, tungsten, or niobium.

13. The welding electrode assembly of claim 10 , wherein the second metal material of the cover has an electrical resistivity that is greater than an electrical resistivity of the aluminum or aluminum alloy workpiece.

14. A method of resistance spot welding, the method comprising:
providing a workpiece stack-up that includes a steel workpiece and an aluminum or aluminum alloy workpiece;
providing a first welding electrode positioned to contact the steel workpiece and a second welding electrode positioned to contact the aluminum or aluminum alloy workpiece, each of the first welding electrode and the second welding electrode being composed of a copper alloy;
attaching a cover at least over a weld face of the second welding electrode, the cover having a weld face and being made of a metal material with an electrical resistivity that is greater than an electrical resistivity of the copper alloy of the second welding electrode and that is greater than an electrical resistivity of the aluminum or aluminum alloy workpiece, the cover being removably attached to the second welding electrode;
performing a plurality of individual resistance spot welds to the workpiece stack-up using the first and second welding electrodes, the cover abutting the aluminum or aluminum alloy workpiece while the individual resistance spot welds are performed;
removing the cover from the second welding electrode after the individual resistance spot welds are performed;
providing a second workpiece stack-up that includes a first steel workpiece and a second steel workpiece, or that includes a first aluminum or aluminum alloy workpiece and a second aluminum or aluminum alloy workpiece;
performing a plurality of second individual resistance spot welds to the second workpiece stack-up using the first and second welding electrodes after the cover is removed from the second welding electrode;
providing a third workpiece stack-up that includes a steel workpiece and an aluminum or aluminum alloy workpiece;
attaching the cover or a second cover at least over the weld face of the second welding electrode, the second cover, if used, being made of a metal material with an electrical resistivity that is greater tha

Assignees

• Gm Global Tech Operations Llc

Inventors

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

Classifications

• B23K2203/20

  Operations & Transport · mapped topic

• B23K11/115 Primary

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

• B23K35/0205

  Non-consumable electrodes; C-electrodes · CPC title

• B23K11/3063

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

• B23K11/20 Primary

  of different metals · CPC title