Improving mechanical performance of Al-steel weld joints by limiting steel sheet deformation

Patent metadata

Field	Value
Publication number	US-10857618-B2
Application number	US-201815907996-A
Country	US
Kind code	B2
Filing date	Feb 28, 2018
Priority date	Feb 28, 2018
Publication date	Dec 8, 2020
Grant date	Dec 8, 2020

Abstract

A method of resistance spot welding a workpiece stack-up that includes a steel workpiece and one or more aluminum workpieces involves locally stiffening the steel workpiece to resist steel workpiece deformation. The local stiffening of the steel workpiece is achieved by incorporating an electrode receiving wall into the steel workpiece along with one or more integral elevated portions of the steel workpiece that are disposed at least partially around the electrode receiving wall. The electrode receiving wall includes an electrode-contact surface and an opposed interface contact surface. During welding, a weld face of one welding electrode is pressed against the electrode-contact surface of the electrode receiving wall of the steel workpiece, and electric current is momentarily passed between that welding electrode and another welding electrode on the opposite side of the workpiece stack-up to form a weld joint that bonds to the interface contact surface of the electrode receiving wall.

First claim

What is claimed is:

1. A method of resistance spot welding a workpiece stack-up that includes a steel workpiece and at least one adjacent overlapping aluminum workpiece, the method comprising:
forming an electrode receiving wall in a steel workpiece, the electrode receiving wall having an electrode-contact surface and an opposed interface contact surface, the electrode-contact surface being at least partially defined by one or more integral elevated portions of the steel workpiece that protrude upwardly from the electrode-contact surface;
assembling the steel workpiece and one or more aluminum workpieces in overlapping fashion to form a workpiece stack-up such that the interface contact surface of the electrode receiving wall of the steel workpiece confronts and makes contact with an adjacent faying surface of the one or more aluminum workpieces to establish a faying interface;
pressing a first weld face of a first welding electrode against the electrode-contact surface of the electrode receiving wall of the steel workpiece at a first side of the workpiece stack-up;
pressing a second weld face of a second welding electrode against an exposed back surface of the one or more aluminum workpieces at a second side of the workpiece stack-up in facial alignment with the first weld face of the first welding electrode;
passing an electric current between the first weld face of the first welding electrode and the second weld face of the second welding electrode to create a molten aluminum weld pool within the one or more aluminum workpieces that wets the interface contact surface of the electrode receiving wall of the steel workpieces; and
allowing the molten aluminum weld pool to solidify into a weld joint that bonds the one or more aluminum workpieces to the steel workpiece.

2. The method set forth in claim 1 , wherein each of the one or more integral elevated portions of the steel workpiece that at least partially defines the electrode-contact surface of the electrode receiving wall is raised at least 0.5 mm above the electrode-contact surface.

3. The method set forth in claim 1 , wherein a segment of a faying surface of the steel workpiece underneath the one or more integral elevated portions of the steel workpiece confronts, but does not contact, the adjacent faying surface of the one or more aluminum workpieces, thereby defining a gap in combination with the adjacent faying surface of the one or more aluminum workpieces that at least partially surrounds the electrode receiving wall of the steel workpiece.

4. The method set forth in claim 1 , wherein the electrode-contact surface of the electrode receiving wall is fully enclosed by the one or more integrated elevated portions of the steel workpiece.

5. The method set forth in claim 1 , wherein the electrode-contact surface of the electrode receiving wall is partially enclosed by the one or more integrated elevated portions of the steel workpiece.

6. The method set forth in claim 1 , wherein the electrode receiving wall is a round castellation in which the electrode-contact surface is round or ovular in plan view and is at least partially circumscribed by an inclined wall that extends outwardly from the electrode-contact surface at an obtuse angle ranging from 95° to 150°.

7. The method set forth in claim 1 , wherein the electrode receiving wall is a linear castellation in which the electrode-contact surface is rectangular in plan view and is defined at least partially by a pair of lateral integral elevated portions of the steel workpiece, each of the lateral integral elevated portions of the steel workpiece having an inclined wall that extends outwardly from the electrode-contact surface at an obtuse angle ranging from 95° to 150°.

8. The method set forth in claim 1 , wherein the electrode receiving wall is a portion of the steel workpiece located between two spaced apart strengthening ribs, each of the strengthening ribs including an arcuate wall having an outer surface that protrudes outwardly from the electrode-contact surface and an outboard portion of a back surface of the steel workpiece outside of the electrode receiving wall.

9. The method set forth in claim 1 , wherein the steel workpiece has a thickness of 2.5 mm or less and a yield strength of 250 MPa or less, or wherein the steel workpiece has a thickness of 1.8 mm or more and a yield strength of 500 MPa or less.

10. The method set forth in claim 1 , wherein the steel workpiece has a thickness of 1.3 mm or less and a yield strength of 1000 MPa or less, or wherein the steel workpiece has a thickness of 0.6 mm or less and a yield strength of 1000 MPa or less.

11. A method of resistance spot welding a workpiece stack-up that includes a steel workpiece and at least one adjacent overlapping aluminum workpiece, the method comprising:
providing a workpiece stack-up that includes a steel workpiece which overlaps one or more aluminum workpieces at a spot weld location, the steel workpiece comprising an electrode receiving wall having an electrode-contact surface and an opposed interface contact surface, the electrode-contact surface being at least partially defined by one or more integral elevated portions of the steel workpiece that protrude outwardly from the electrode-contact surface, and the interface contact surface of the electrode receiving wall of the steel workpiece confronting and making contact with an adjacent faying surface of the one or more aluminum workpieces to establish a faying interface, wherein at least some part of the one or more integral elevated portions of the steel workpiece are located within a planar circular region that extends in a plane of the electrode-contact surface and has a radius of 5 mm to 50 mm as measured from a center of the spot weld location, and wherein anywhere from 90° to 360° of a circumference of the planar circular region is spanned by the one or more integral elevated portions of the steel workpiece;
pressing a first weld face of a first welding electrode against the electrode-contact surface of the electrode receiving wall of the steel workpiece at a first side of the workpiece stack-up;
pressing a second weld face of a second welding electrode against an exposed back surface of the one or more aluminum workpieces at a second side of the workpiece stack-up in facial alignment with the first weld face of the first welding electrode;
passing an electric current between the first weld face of the first welding electrode and the second weld face of the second welding electrode to create a molten aluminum weld pool within the one or more aluminum workpieces that wets the interface contact surface of the electrode receiving wall of the steel workpiece; and
allowing the molten aluminum weld pool to solidify into a weld joint that bonds the one or more aluminum workpieces to the steel workpiece, the weld joint extending into the one or more aluminum workpieces included in the workpiece stack-up and establishing a bonding interface with the interface contact surface of the electrode receiving wall of the steel workpiece, the weld joint including an aluminum weld nugget and a Fe—Al intermetallic layer between the aluminum weld nugget and the interface contact surface of the electrode receiving wall of the steel workpiece.

12. The method set forth in claim 11 , wherein providing the workpiece stack-up comprises:
forming the electrode receiving wall and the one or more integral elevated portions that are disposed at least partially around the electrode receiving wall in the steel workpiece; and
assembling the steel workpiece and the one or more aluminum workpieces in overlapping fashion to form the workpiece stack-up such that the interface cont

Assignees

• Gm Global Tech Operations Llc

Inventors

• Sigler David R
• Haselhuhn Amberlee S
• Carlson Blair E

Classifications

• B23K11/20

  of different metals · CPC title

• B23K11/115 Primary

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

• B23K2103/20

  Ferrous alloys and aluminium or alloys thereof · CPC title

• B23K11/36

  Auxiliary equipment (B23K11/31 takes precedence) · CPC title

• B23K11/11

  Spot welding · CPC title