Method and apparatus for resistance spot welding overlapping steel workpieces

Patent metadata

Field	Value
Publication number	US-10675701-B2
Application number	US-201715638699-A
Country	US
Kind code	B2
Filing date	Jun 30, 2017
Priority date	Jun 30, 2017
Publication date	Jun 9, 2020
Grant date	Jun 9, 2020

Abstract

A method of resistance spot welding a workpiece stack-up comprising overlapping first and second steel workpieces is disclosed, wherein at least one of the steel workpieces comprises an advanced high-strength steel substrate. The workpiece stack-up is positioned between a pair of opposed first and second welding electrodes. A cover is disposed between at least one of the first steel workpiece and the first welding electrode or the second steel workpiece and the second welding electrode at an intended weld site. The workpiece stack-up is clamped between the first and second welding electrodes at the weld site such that at least one of the weld faces of the first and second welding electrodes presses against the cover. The first and second steel workpieces are welded together by passing an electrical current between the first and second welding electrodes at the weld site.

First claim

What is claimed is:

1. A method of resistance spot welding overlapping steel workpieces, the method comprising:
providing a workpiece stack-up comprising a first steel workpiece and a second steel workpiece that overlap each other at a weld site, the first steel workpiece having an exterior outer surface that provides a first side of the workpiece stack up and the second steel workpiece having an exterior outer surface that provides a second side of the workpiece stack-up, wherein at least one of the first and second steel workpieces comprises an advanced high-strength steel substrate having an ultimate tensile strength of greater than 550 MPa and a microstructure that includes greater than 5 vol % austenite, martensite, or bainite at ambient temperature;
positioning the workpiece stack-up between a pair of opposed first and second welding electrodes such that a weld face of the first welding electrode faces toward the first side of the workpiece stack-up and a weld face of the second welding electrode faces toward the second side of the workpiece stack-up, and wherein a cover is disposed between at least one of the first steel workpiece and the first welding electrode or the second steel workpiece and the second welding electrode at the weld site;
clamping the workpiece stack-up between the first and second welding electrodes at the weld site such that at least one of the weld faces of the first and second welding electrodes presses against the cover; and
welding the first and second steel workpieces together by passing an electrical current between the first and second welding electrodes at the weld site,
wherein the cover comprises an iron alloy having an ultimate tensile strength less than that of the advanced high-strength steel substrate.

2. The method set forth in claim 1 wherein the first steel workpiece comprises an advanced high-strength steel substrate having an ultimate tensile strength of greater than 550 MPa and a microstructure that includes greater than 5 vol % austenite, martensite, or bainite at ambient temperature, and wherein the workpiece stack-up is positioned between the opposed first and second welding electrodes such that the cover is disposed between the first steel workpiece and the first welding electrode at the weld site.

3. The method set forth in claim 1 wherein the second steel workpiece comprises an advanced high-strength steel substrate having an ultimate tensile strength of greater than 550 MPa and a microstructure that includes greater than 5 vol % austenite, martensite, or bainite at ambient temperature, and wherein the workpiece stack-up is positioned between the opposed first and second welding electrodes such that the cover is disposed between the second steel workpiece and the second welding electrode at the weld site.

4. The method set forth in claim 1 wherein both the first and second steel workpieces comprise an advanced high-strength steel substrate having an ultimate tensile strength of greater than 550 MPa and a microstructure that includes greater than 5 vol % austenite, martensite, or bainite at ambient temperature, and wherein the workpiece stack-up is positioned between the opposed first and second welding electrodes such that a first cover is disposed between the first steel workpiece and the first welding electrode and a second cover is disposed between the second steel workpiece and the second welding electrode at the weld site.

5. The method set forth in claim 1 wherein the advanced high-strength steel substrate has a surface coating that comprises a metal or metal alloy having a relatively low melting point, as compared to that of the advanced high-strength steel substrate.

6. The method set forth in claim 5 wherein the surface coating comprises zinc or a zinc-based alloy.

7. The method set forth in claim 1 wherein the advanced high-strength steel substrate comprises 3-100 vol % austenite at ambient temperature.

8. The method set forth in claim 1 wherein the advanced high-strength steel substrate has an ultimate tensile strength of greater than 780 MPa.

9. The method set forth in claim 1 wherein the advanced high-strength steel substrate comprises complex phase (CP), ferritic-bainitic (FB), martensitic (MS), hot formed (HF), press hardened (PHS), quenching and partitioning (Q&P), transformation induced plasticity (TRIP), or twinning induced plasticity (TWIP) steel.

10. The method set forth in claim 1 wherein the cover exhibits a microstructure that includes less than 5 vol % austenite at ambient temperature.

11. The method set forth in claim 1 wherein the microstructure of the cover at ambient temperature consists of ferrite or a combination of ferrite and pearlite.

12. The method set forth in claim 1 wherein the cover has a thickness less than that of the first and second steel workpieces.

13. The method set forth in claim 1 wherein the cover is disposed between at least one of the first steel workpiece and the first welding electrode or the second steel workpiece and the second welding electrode at the weld site by depositing a layer of a ferrous material on at least one of the exterior outer surface of the first steel workpiece or the exterior outer surface of the second steel workpiece.

14. The method set forth in claim 1 wherein the cover is inserted between at least one of the first steel workpiece and the first welding electrode or the second steel workpiece and the second welding electrode at the weld site prior to clamping the workpiece stack-up between the first and second welding electrodes.

15. The method set forth in claim 14 wherein, after the cover is inserted between at least one of the first steel workpiece and the first welding electrode or the second steel workpiece and the second welding electrode at the weld site, an end portion of the cover is severed from a remaining portion of the cover.

16. The method set forth in claim 15 wherein the end portion of the cover is severed from the remaining portion of the cover along a perforated seam.

17. The method set forth in claim 1 wherein a faying interface is established between each pair of adjacent overlapping steel workpieces within the workpiece stack-up at the weld site, and the overlapping steel workpieces are welded together by passing an electrical current between the first and second welding electrodes and across each faying interface at the weld site.

18. The method set forth in claim 1 wherein the first steel workpiece has a faying surface that overlaps and contacts a faying surface of the second steel workpiece to establish a single faying interface within the workpiece stack-up.

19. The method set forth in claim 1 wherein the workpiece stack-up further includes a third steel workpiece disposed between the first and second steel workpieces, the third steel workpiece having two opposed faying surfaces, wherein one faying surface of the third steel workpiece overlaps and contacts a faying surface of the first steel workpiece and the other faying surface of the third steel workpiece overlaps and contacts a faying surface of the second steel workpiece such that two faying interfaces are established within the workpiece stack-up.

20. The method set forth in claim 1 wherein the cover consists of steel having an ultimate tensile strength less than that of both the first and second steel workpieces.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Yang David
• Tao Wu
• Lu Qi
• Carlson Blair E

Classifications

• B23K11/166

  of galvanized or tinned materials · CPC title

• B23K11/364

  Clamping contacts · CPC title

• B32B15/011 Primary

  all layers being formed of iron alloys or steels · CPC title

• B23K11/115 Primary

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

• B23K2103/04

  Steel {or steel} alloys · CPC title