Resistive welding electrode and method for spot welding steel and aluminum alloy workpieces with the resistive welding electrode

Patent metadata

Field	Value
Publication number	US-2016279732-A1
Application number	US-201615074690-A
Country	US
Kind code	A1
Filing date	Mar 18, 2016
Priority date	Mar 27, 2015
Publication date	Sep 29, 2016
Grant date	—

Abstract

A resistive welding electrode includes at least a weld face constructed of a refractory-based material that exhibits an electrical conductivity that is less than or equal to 65% of the electrical conductivity of commercially pure annealed copper as defined by the International Annealed Copper Standard (IACS). A method of using the resistive welding electrode to resistance spot weld a workpiece stack-up that includes an aluminum alloy workpiece and steel workpiece that overlap and contact each other at a faying interface is also disclosed.

First claim

1 . A resistive welding electrode comprising:
an electrode body; and a weld face disposed on a front end of the electrode body, and wherein at least the weld face is composed of a refractory-based material that includes at least 35 wt % of a refractory metal and has an electrical conductivity that is less than or equal to 3.8×10 7 S/m.

2 . The resistive welding electrode set forth in claim 1 , wherein the refractory-based material is elemental molybdenum or elemental tungsten.

3 . The resistive welding electrode set forth in claim 1 , wherein the refractory-based material is a metal composite that includes 35 wt % or greater of molybdenum or tungsten.

4 . The resistive welding electrode set forth in claim 3 , wherein the refractory-based material is a tungsten-copper metal composite that comprise 50 wt % to 90 wt % of a tungsten particulate phase dispersed in a copper matrix.

5 . The resistive welding electrode set forth in claim 1 , wherein the weld face has a base weld face surface having a diameter that ranges from 6 mm to 20 mm and a spherical radius of curvature ranging from 15 mm to 300 mm.

6 . The resistive welding electrode set forth in claim 5 , wherein the weld face includes a plurality of upstanding, radially-spaced circular ridges that surround a center of the weld face and project outwardly from the base weld face surface.

7 . The resistive welding electrode set forth in claim 1 , wherein the electrode body and the weld face are an integrally formed and both portions are composed of the same refractory-based material.

8 . The resistive welding electrode set forth in claim 1 , wherein the electrode comprises two component pieces that are fixedly secured together, the two component pieces comprising a first component piece that includes at least the weld face of the resistive welding electrode and a second component piece that comprises at least the electrode body of the resistive welding electrode.

9 . The resistive welding electrode set forth in claim 8 , wherein the first component piece is interference fit within an interior bore defined by the second component piece in order to fixedly secure the two component pieces together into the resistive welding electrode.

10 . A method of resistance spot welding a workpiece stack-up that includes an aluminum alloy workpiece and an adjacent steel workpiece, the method comprising:
providing a workpiece stack-up that includes an aluminum alloy workpiece and a steel workpiece that overlap and contact to establish a faying interface, the workpiece stack-up having a first side proximate the aluminum alloy workpiece and a second side proximate the steel workpiece; contacting the first side of the workpiece stack-up with a weld face of a resistive welding electrode, and wherein at least the weld face of the resistive welding electrode is composed of a refractory-based material that includes at least 35 wt % of a refractory metal and has an electrical conductivity that is less than or equal to 3.8×10 7 S/m; contacting the second side of the workpiece stack-up with a weld face of a second welding electrode; and passing an electrical current between the weld face of the resistive welding electrode and the weld face of the second welding electrode, and through the workpiece stack-up, to create a molten aluminum alloy weld pool within the aluminum alloy workpiece that lies adjacent to the steel workpiece; and ceasing passage of the electrical current to allow the molten aluminum alloy weld pool to solidify into a weld joint that bonds the adjacent aluminum alloy and steel workpieces together at their faying interface.

11 . The resistive welding electrode set forth in claim 10 , wherein the refractory-based material is elemental molybdenum or elemental tungsten.

12 . The resistive welding electrode set forth in claim 10 , wherein the refractory-based material is a metal composite that includes 35 wt % or greater of molybdenum or tungsten.

13 . The resistive welding electrode set forth in claim 12 , wherein the refractory-based material is a tungsten-copper metal composite that comprise 50 wt % to 90 wt % of a tungsten particulate phase dispersed in a copper matrix.

14 . The method set forth in claim 10 , wherein the weld face of the resistive welding electrode has a base weld face surface having a diameter that ranges from 6 mm to 20 mm and a spherical radius of curvature ranging from 15 mm to 300 mm.

15 . The method set forth in claim 14 , wherein the weld face of the resistive welding electrode includes a plurality of upstanding, radially-spaced circular ridges that surround a center of the weld face and project outwardly from the base weld face surface.

16 . The method set forth in claim 10 , wherein the resistive welding electrode further includes an electrode body that is integrally formed with the weld face, and wherein the entire resistive welding electrode is formed of the refractory-based material.

17 . The method set forth in claim 10 , wherein resistive electrode is formed of a first component piece, which includes at least the weld face, and a second component piece, which includes an electrode body that supports the weld face, and wherein the first component piece is interference fit within an interior bore defined by the second component piece in order to fixedly secure the two component pieces together.

18 . The method set forth in claim 10 , wherein the workpiece stack-up includes only the aluminum alloy workpiece and a steel workpiece that overlap and contact one another to establish the faying interface such that an exterior surface of the aluminum workpiece provides the first side of the workpiece stack-up and an exterior surface of the steel workpiece provides the second side of the workpiece stack-up.

19 . The method set forth in claim 10 , wherein the workpiece stack-up includes the aluminum alloy workpiece and a steel workpiece that overlap and contact one another to establish the faying interface, plus an additional aluminum alloy workpiece, such that an exterior surface of the additional aluminum alloy workpiece provides the first side of the workpiece stack-up and an exterior surface of the steel workpiece provides the second side of the workpiece stack-up.

20 . The method set forth in claim 10 , wherein the workpiece stack-up includes the aluminum alloy workpiece and a steel workpiece that overlap and contact one another to establish the faying interface, plus an additional steel workpiece, such that an exterior surface of the aluminum alloy workpiece provides the first side of the workpiece stack-up and an exterior surface of the additional steel workpiece provides the second side of the workpiece stack-up.

Assignees

• Gm Global Tech Operations Llc

Inventors

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

Classifications

• B23K35/32

  with the principal constituent melting at more than 1550°C · CPC title

• B23K35/0261

  Rods, electrodes or wires · CPC title

• B23K35/0205

  Non-consumable electrodes; C-electrodes · CPC title

• B23K11/3018 Primary

  Cooled pressure electrodes · CPC title

• B23K11/20

  of different metals · CPC title