CONTROL OF INTERMETALLIC COMPOUND GROWTH IN ALUMINUM TO STEEL RESISTANCE WELDING

• US 20170297136A1
• Filed: 04/12/2017
• Published: 10/19/2017
• Est. Priority Date: 04/14/2016
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Brown, Tyson W., Sigler, David R., Carlson, Blair E., Haselhuhn, Amberlee S.
• Granted Patent: US 10,857,619 B2
• Time in Patent Office: Days
• 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 11/163 Welding of coated 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 2101/006 Vehicles
• CPC Class Codes: B23K 2101/18 Sheet panels
• CPC Class Codes: B23K 2101/34 Coated articles , e.g. plated or painted; Surface treated articles
• CPC Class Codes: B23K 2101/35 Surface treated articles
• 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
• CPC Class Codes: B23K 35/002 at least one of the workpieces being of light metal
• CPC Class Codes: B23K 35/004 at least one of the workpieces being of a metal of the iron group
• CPC Class Codes: B23K 35/0294 Consumable guides
• CPC Class Codes: B23K 35/3053 Fe as the principal constituent
• CPC Class Codes: B23K 35/3612 with organic compounds as principal constituents
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/16 containing copper

Abstract

A method of resistance spot welding a workpiece stack-up that includes an aluminum workpiece and an overlapping adjacent steel workpiece so as to minimize the thickness of an intermetallic layer comprising Fe—Al intermetallic compounds involves providing reaction-slowing elements at the faying interface of the aluminum and steel workpieces. The reaction-slowing elements may include at least one of carbon, copper, silicon, nickel, manganese, cobalt, or chromium. Various ways are available for making the one or more reaction-slowing elements available at the faying interface of the aluminum and steel workpieces including being dissolved in a high strength steel or being present in an interlayer that may take on a variety of forms including a rigid shim, a flexible foil, a deposited layer adhered to and metallurgically bonded with a faying surface of the steel workpiece, or an interadjacent organic material layer that includes particles containing the reaction-slowing elements.

Claims

1. A method of resistance spot welding a workpiece stack-up that includes an aluminum workpiece and an adjacent overlapping steel workpiece so as to minimize the thickness of an intermetallic layer comprising Fe—

Al intermetallic compounds, the method comprising;

providing a workpiece stack-up that has an accessible first side and an opposed accessible second side, the workpiece stack-up comprising an aluminum workpiece and an overlapping adjacent steel workpiece and further comprising one or more reaction-slowing elements at a faying interface established between the aluminum and steel workpieces, the reaction-slowing elements comprising at least one of carbon, copper, silicon, nickel, manganese, cobalt, or chromium;

pressing a weld face of a first welding electrode against the first side of the workpiece stack-up and pressing a weld face of a second welding electrode against the second side of the workpiece stack-up in facial alignment with the weld face of the first welding electrode;

passing an electrical current between the weld faces of the first and second welding electrodes and through the workpiece stack-up to melt the aluminum workpiece and create a molten weld pool contained within the aluminum workpiece, the one or more reaction-slowing elements suppressing the formation and growth of Fe—

Al intermetallic compounds; and

terminating passage of the electrical current to thereby allow the molten weld pool to solidify into a weld joint that includes an aluminum weld nugget within the aluminum workpiece and one or more Fe—

Al intermetallic layers at a bonding surface of the weld joint.

2. The method set forth in claim 1, wherein the steel workpiece is a high strength steel having a minimum tensile strength of 300 MPa and the one or more reaction-slowing elements are dissolved therein as alloying elements of the high strength steel.

3. The method set forth in claim 2, wherein the high strength steel includes carbon in an amount of 0.010 wt % or greater, manganese in an amount of 0.5 wt % or greater, silicon in an amount of 0.030 wt % or greater, and/or copper in an amount of 0.35 wt % or less.

4. The method set forth in claim 1, wherein an interlayer disposed between a faying surface of the aluminum workpiece and a faying surface of the steel workpiece includes the reaction-slowing elements.

5. The method set forth in claim 4, wherein the interlayer is a rigid shim, the rigid shim being composed of high strength steel in which the one or more reaction-slowing elements are alloying elements of the high strength steel, or the rigid shim being composed of a custom ferrous-based alloy that includes the one or more reaction-slowing elements dissolved in a solid solution.

6. The method set forth in claim 5, wherein the interlayer is a rigid shim composed of a custom ferrous-based alloy that includes the one or more reaction-slowing elements dissolved in a solid solution, the custom ferrous-based alloy being an alloy of (1) iron and carbon with at least 0.010 wt % carbon, (2) iron and copper with at least 0.2 wt % copper, (3) iron and silicon with at least 0.030 wt % silicon, or (4) iron and manganese with at least 0.5 wt % manganese.

7. The method set forth in claim 4, wherein the interlayer is a flexible foil composed of a custom ferrous-based alloy that includes the one or more reaction-slowing elements dissolved in a solid solution.

8. The method set forth in claim 7, wherein the custom ferrous-based alloy is an alloy of (1) iron and carbon with at least 0.010 wt % carbon, (2) iron and copper with at least 0.2 wt % copper, (3) iron and silicon with at least 0.030 wt % silicon, or (4) iron and manganese with at least 0.5 wt % manganese.

9. The method set forth in claim 4, wherein the interlayer is a deposited layer adhered directly to and metallurgically bonded with the faying surface of the steel workpiece.

10. The method set forth in claim 4, wherein the interlayer is an interadjacent organic material layer that includes an organic material matrix and particles containing one or more of the reaction-slowing elements dispersed throughout and embedded within the organic material matrix.