# US 2019/0314915 A1 · Resistance Spot Welding Workpiece Stack-Ups Having Steel Workpieces With Surface Coatings > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0314915 A1 - Document ID: US20190314915A1 - Status: Published application - Kind: A1 - Application number: 15/952,813 - Filed: 2018-04-13 - Published: 2019-10-17 - Earliest claimed: 2018-04-13 - Assignees: GM Global Technology Operations LLC - Applicants: GM Global Technology Operations LLC - Inventors: Pei-chung Wang; Michael J. Karagoulis; Zhenke Teng; Spyros P. Mellas - Web page: https://patentgrep.com/patent/US20190314915A1 ## CPC - B23K 1/0004: {Resistance soldering} - B23K 11/115: {by means of two electrodes placed opposite one another on both sides of the welded parts} - B23K 11/163: {Welding of coated materials} - B23K 11/166: {of galvanized or tinned materials} - B23K 11/31: Electrode holders {and actuating devices therefor} - B23K 11/34: Preliminary treatment - B23K 2101/34: Coated articles {; Surface treated articles} - B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM ## Abstract A method of resistance spot welding a workpiece stack-up that includes a first steel workpiece and a second steel workpiece. The method includes several steps. The first steel workpiece can have a first surface coating. One step involves applying a filler metal to a surface of the first steel workpiece. Another step involves bringing a surface of the second steel workpiece to adjoin the filler metal. Yet another step involves clamping a first welding electrode and a second welding electrode on the first and second steel workpieces. And another step involves passing electrical current between the first and second welding electrodes and hence through the filler metal. And yet another step involves terminating passage of the electrical current in order to establish a weld joint between the first and second steel workpieces. ## Claims ### Claim 1 A method of resistance spot welding a workpiece stack-up that comprises a first steel workpiece and a second steel workpiece, the method comprising: providing the first steel workpiece and providing the second steel workpiece, at least the first steel workpiece having a first surface coating; applying a filler metal to a first surface of the first steel workpiece; bringing the second steel workpiece to the first steel workpiece, a second surface of the second steel workpiece adjoining the filler metal; clamping a first welding electrode and a second welding electrode on the first and second steel workpieces adjacent the filler metal; passing electrical current between the first and second welding electrodes and through the first and second steel workpieces and through the filler metal; and terminating passage of the electrical current to establish a weld joint between the first and second steel workpieces. ### Claim 2 (depends on 1) The method of claim 1, wherein the first steel workpiece is composed of an advanced high-strength steel (AHSS) material, and the second steel workpiece is composed of an advanced high-strength steel (AHSS) material. ### Claim 3 (depends on 1) The method of claim 1, wherein the first surface coating is composed of a zinc (Zn) material. ### Claim 4 (depends on 1) The method of claim 1, wherein the first surface coating resides on a first exterior surface of the first steel workpiece, the first exterior surface being situated opposite the first surface to which the filler metal is applied. ### Claim 5 (depends on 1) The method of claim 1, wherein the second steel workpiece has a second surface coating, the second surface coating resides on a second exterior surface of the second steel workpiece, the second exterior surface being situated opposite the second surface to which the filler metal is adjoined. ### Claim 6 (depends on 1) The method of claim 1, wherein the filler metal is composed of a low-carbon steel material. ### Claim 7 (depends on 1) The method of claim 1, wherein applying the filler metal involves coating the first surface of the first steel workpiece with the filler metal via thermal spraying. ### Claim 8 (depends on 1) The method of claim 1, wherein applying the filler metal involves layering the filler metal on the first surface of the first steel workpiece via additive manufacturing. ### Claim 9 (depends on 8) The method of claim 8, wherein layering the filler metal on the first surface of the first steel workpiece involves 3D printing. ### Claim 10 (depends on 1) The method of claim 1, wherein the established weld joint includes material of the first steel workpiece, includes material of the second steel workpiece, and includes material of the filler metal. ### Claim 11 (depends on 1) The method of claim 1, wherein the first welding electrode, the second welding electrode, or both of the first and second welding electrodes have a weld face with a radius of curvature that ranges between approximately 25 millimeters (mm) and that is approximately flat. ### Claim 12 (depends on 1) The method of claim 1, wherein the filler metal has a thickness dimension that ranges between approximately 0.05 millimeters (mm) and 2.0 mm. ### Claim 13 A method of resistance spot welding a workpiece stack-up that comprises a first steel workpiece and a second steel workpiece, the method comprising: providing the first steel workpiece and providing the second steel workpiece, the first steel workpiece being composed of an advanced high-strength steel (AHSS) material and the second steel workpiece being composed of an advanced high-strength steel (AHSS) material, the first steel workpiece having a first faying surface and having a first exterior surface situated opposite the first faying surface, the second steel workpiece having a second faying surface and having a second exterior surface situated opposite the second faying surface, a first surface coating residing on the first exterior surface, and a second surface coating residing on the second exterior surface; layering a filler metal on the first faying surface of the first steel workpiece via additive manufacturing; bringing the second steel workpiece to the first steel workpiece, the second faying surface of the second steel workpiece adjoining the filler metal; clamping a first welding electrode and a second welding electrode on the first and second steel workpieces adjacent the filler metal; passing electrical current between the first and second welding electrodes; and terminating passage of the electrical current to establish a weld joint between the first and second steel workpieces. ### Claim 14 (depends on 13) The method of claim 13, wherein the first surface coating is composed of a zinc (Zn) material, and the second surface coating is composed of a zinc (Zn) material. ### Claim 15 (depends on 13) The method of claim 13, wherein the filler metal is composed of a low-carbon steel material. ### Claim 16 (depends on 13) The method of claim 13, wherein the filler metal has a thickness dimension that ranges between approximately 0.05 millimeters (mm) and 2.0 mm. ### Claim 17 (depends on 13) The method of claim 13, wherein layering the filler metal on the first surface of the first steel workpiece involves 3D printing. ### Claim 18 (depends on 13) The method of claim 13, wherein the established weld joint includes material of the first steel workpiece, includes material of the second steel workpiece, and includes material of the filler metal. ### Claim 19 A method of resistance spot welding a workpiece stack-up that comprises a first steel workpiece and a second steel workpiece, the method comprising: providing the first steel workpiece and providing the second steel workpiece, the first steel workpiece being composed of an advanced high-strength steel (AHSS) material and the second steel workpiece being composed of an advanced high-strength steel (AHSS) material, the first steel workpiece having a first faying surface and having a first exterior surface situated opposite the first faying surface, the second steel workpiece having a second faying surface and having a second exterior surface situated opposite the second faying surface, a first surface coating residing on the first exterior surface, and a second surface coating residing on the second exterior surface, the first surface coating being composed of a zinc (Zn) material and the second surface coating being composed of a zinc (Zn) material; layering a filler metal on the first faying surface of the first steel workpiece via additive manufacturing, the filler metal being composed of a low-carbon steel material; bringing the second steel workpiece to the first steel workpiece, the second faying surface of the second steel workpiece adjoining the filler metal; clamping a first welding electrode and a second welding electrode on the first and second steel workpieces adjacent the filler metal; passing electrical current between the first and second welding electrodes; and terminating passage of the electrical current to establish a weld joint between the first and second steel workpieces, the weld joint including material of the first steel workpiece and including material of the second steel workpiece and including material of the filler metal. ### Claim 20 (depends on 19) The method of claim 19, wherein the filler metal has a thickness dimension that ranges between approximately 0.05 millimeters (mm) and 2.0 mm.