WO2023107907A1

WO2023107907A1 - Methods for resistance spot welding, resistance spot welding systems and apparatus, and parts formed using resistance spot welding

Info

Publication number: WO2023107907A1
Application number: PCT/US2022/080952
Authority: WO
Inventors: Donald J. Spinella; Anthony J. Fedusa
Original assignee: Arconic Technologies Llc
Priority date: 2021-12-06
Filing date: 2022-12-05
Publication date: 2023-06-15

Abstract

Methods for resistance spot welding, systems and apparatus for resistance spot welding, and parts formed by processes including resistance spot welding are provided. The methods comprise contacting an assembly comprising at least two metallic parts with welding electrodes at a first location. A weld current is passed through the assembly at the first location with the welding electrodes, thereby forming a first resistance spot weld securing the assembly. The method comprises contacting the assembly with the welding electrodes at a second location. The second location is a first distance from the first location. A weld current is passed through the assembly at the second location with the welding electrodes, thereby forming a second resistance spot weld partially overlapping the first resistance spot weld.

Description

TITLE

METHODS FOR RESISTANCE SPOT WELDING, RESISTANCE SPOT WELDING SYSTEMS AND APPARATUS, AND PARTS FORMED USING RESISTANCE SPOT WELDING

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63/264,998, which was filed on December 6, 2021. The contents of which is hereby incorporated by reference into this specification.

FIELD OF USE

[0002] The present disclosure relates to methods for resistance spot welding, resistance spot welding systems and apparatus, and parts formed using resistance spot welding.

BACKGROUND

[0003] Current methods of fastening together parts, structures, or assemblies, such as fastening together sheets comprising metals or metal alloys, can include the use of, for example, spot welding or seam welding. There are challenges associated with fastening together metallic parts, structures, or assemblies using spot welding or seam welding.

SUMMARY

[0004] One non-limiting aspect according to the present disclosure is directed to a method for resistance spot welding. The method comprises contacting an assembly comprising at least two metallic parts with welding electrodes at a first location. A weld current is passed through the assembly at the first location with the welding electrodes, thereby forming a first resistance spot weld securing the assembly. The method further comprises contacting the assembly with the welding electrodes at a second location. The second location is a first distance from the first location. A weld current is passed through the assembly at the second location with the welding electrodes, thereby forming a second resistance spot weld partially overlapping the first resistance spot weld. [0005] A further non-limiting aspect according to the present disclosure is directed to a fusion zone comprising a second resistance spot weld partially overlapping a first resistance spot weld.

[0006] Yet another non-limiting aspect according to the present disclosure is directed to a semi-finished or finished part. The semi-finished or finished part comprises a first resistance spot weld and a second resistance spot weld overlapping with the first resistance spot weld.

[0007] Yet a further non-limiting aspect according to the present disclosure is directed to a semi-finished or finished part comprising at least two partially overlapping resistance spot welds that are individually classified as Grade A, Grade B, Grade C, or a combination thereof according to the Japanese Industrial Standard JIS Z 3140:2017. The at least two partially overlapping resistance spot welds together comprise a tensile strength of a Grade A weld or higher according to the Japanese Industrial Standard JIS Z 3140:2017.

[0008] A further non-limiting aspect according to the present disclosure is directed to a semifinished or finished part comprising a welding flange, wherein a width of the welding flange is no greater than 12.5 * √governing metal thickness.

[0009] Yet another non-limiting aspect according to the present disclosure is directed to a resistance spot welding system or apparatus comprising a power unit, a first electrode, a second electrode, and a controller. The power unit is configured to deliver a weld current. The first electrode is in electrical communication with the power unit. The second electrode is in electrical communication with the power unit and positioned opposed from the first electrode. The actuator is configured to move at least one of the first electrode and the second electrode relative to one another. The controller is in electrical communication with the power unit and the actuator. The controller is configured to contact an assembly comprising at least two metallic parts with the first electrode and the second electrode at a first location, wherein the assembly is positioned intermediate the first electrode and the second electrode. The controller is configured to pass a weld current between the first electrode and the second electrode through the assembly at the first location, thereby forming a first resistance spot weld securing together the at least two metallic parts. The controller is further configured to contact the assembly with the first electrode and the second electrode at a second location, wherein the second location is a first distance from the first location. The controller is further configured to pass a weld current between the first electrode and the second electrode through the assembly at the second location, thereby forming a second resistance spot weld overlapping with the first resistance spot weld.

[0010] It will be understood that the inventions disclosed and described in this specification are not limited to the aspects summarized in this Summary. The reader will appreciate the foregoing details, as well as others, upon considering the following detailed description of various non-limiting and non-exhaustive aspects according to this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The features and advantages of the examples, and the manner of attaining them, will become more apparent, and the examples will be better understood, by reference to the following description taken in conjunction with the accompanying drawings, wherein:

[0012] FIG. l is a schematic illustration showing certain elements of a non-limiting embodiment of a resistance spot welding system and an assembly, shown in a first configuration;

[0013] FIG. 2 is a schematic illustration of the resistance spot welding system and the assembly of FIG. 1, shown in a second configuration;

[0014] FIG. 3 is a schematic illustration of the resistance spot welding system and the assembly of FIG. 2, shown in a third configuration;

[0015] FIG. 4A is a schematic illustration of the resistance spot welding system and the assembly of FIG. 3, shown in a fourth configuration;

[0016] FIG. 4B is a detail view of area 4B in FIG. 4A;

[0017] FIG. 4C is a schematic partial illustration of the resistance spot welding system and the assembly of FIG. 4A, illustrating formation of a subsequent overlapping resistance spot weld;

[0018] FIG. 4D is a schematic partial illustration of the resistance spot welding system and the assembly of FIG. 3, illustrating formation of a fusion zone by intermittent resistance spot welds followed by gap filling between the resistance spot welds; [0019] FIG. 5 is a schematic illustration of the resistance spot welding system and the assembly of FIG. 4A, shown in a fifth configuration;

[0020] FIG. 6 is a schematic illustration of the resistance spot welding system and the assembly of FIG. 5, shown in a sixth configuration;

[0021] FIG. 7 is a schematic illustration of a part or assembly comprising a linear fusion zone comprising five overlapping resistance spot welds according to the present disclosure;

[0022] FIG. 8 is a schematic illustration of a part or assembly comprising a linear fusion zone comprising sixteen overlapping resistance spot welds according to the present disclosure;

[0023] FIG. 9 is a schematic illustration of a part or assembly comprising a curved fusion zone comprising six overlapping resistance spot welds according to the present disclosure;

[0024] FIG. 10 is a schematic illustration of part or assembly comprising a non-linear fusion zone comprising eight overlapping resistance spot welds according to the present disclosure;

[0025] FIG. 11 schematically illustrates forming a linear fusion zone on a curved surface of a finished or semi-finished part, wherein the linear fusion zone comprises six overlapping resistance spot welds according to the present disclosure;

[0026] FIG. 12A is a schematic illustration of a portion of a top surface of a semi-finished or finished part comprising a non-linear fusion zone on an edge region of the top portion comprising seven overlapping resistance spot welds according to the present disclosure;

[0027] FIG. 12B is a schematic side elevational sectional view of the semi-finished or finished part of FIG. 12 A;

[0028] FIG. 13 is a schematic illustration of a semi-finished or finished part comprising a curved fusion zone on an interior region of a flat surface of the part and comprising fifteen overlapping resistance spot welds according to the present disclosure;

[0029] FIG. 14A is a schematic top view of a semi-finished or finished part comprising linear fusion zones comprising multiple resistance spot welds on edge regions of a flat surface of the assembly according to the present disclosure; [0030] FIG. 14B is a schematic side elevational sectional view of the semi-finished or finished part of FIG. 14 A; and

[0031] FIG. 15 is a schematic perspective view of a semi-finished or finished part comprising multiple resistance spot welds and a reduced weld flange width according to the present disclosure;

[0032] FIG. 16 is a schematic perspective view of a semi-finished or finished part comprising multiple resistance spot welds and a reduced weld flange width according to the present disclosure; and

[0033] FIG. 17 is a schematic illustration showing certain elements of a non-limiting embodiment of an assembly comprising three metallic parts and a fusion zone.

[0034] The exemplifications set out herein illustrate certain non-limiting embodiments, in one form, and such exemplifications are not to be construed as limiting the scope of the appended claims and the invention in any manner.

DETAILED DESCRIPTION OF NON-LIMITING EMBODIMENTS

[0035] Various examples are described and illustrated herein to provide an overall understanding of the structure, function, and use of the disclosed systems, apparatus, parts, assemblies, and methods. The various examples described and illustrated herein are nonlimiting and non-exhaustive. Thus, the invention is not limited by the description of the various non-limiting and non-exhaustive examples disclosed herein. The features and characteristics illustrated and/or described in connection with various examples may be combined with the features and characteristics of other examples. Such modifications and variations are intended to be included within the scope of the present disclosure. The various non-limiting embodiments disclosed and described in the present disclosure can comprise, consist of, or consist essentially of the features and characteristics as variously described herein.

[0036] Any references herein to “various non-limiting embodiments”, “some non-limiting embodiments”, “certain non-limiting embodiments”, “one non-limiting embodiment”, “a non-limiting embodiment”, “an embodiment”, “one embodiment”, or like phrases mean that a particular feature, structure, or characteristic described in connection with the example is included in at least one embodiment. Thus, appearances of the phrases “various non-limiting embodiments”, “some non-limiting embodiments”, “certain non-limiting embodiments”, “one non-limiting embodiment”, “a non-limiting embodiment”, “an embodiment”, “one embodiment”, or like phrases in the specification do not necessarily refer to the same nonlimiting embodiment. Furthermore, the particular described features, structures, or characteristics may be combined in any suitable manner in one or more non-limiting embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one non-limiting embodiment may be combined, in whole or in part, with the features, structures, or characteristics of one or more other non-limiting embodiments without limitation. Such modifications and variations are intended to be included within the scope of the present non-limiting embodiments.

[0037] The present inventors observed that in certain conventional resistance spot welding techniques used for joining together aluminum or aluminum alloy sheets it can be difficult to transfer adequate heat into the sheets to produce acceptable melting and fusion. Additionally, the present inventors determined that weld flanges in resistance fusion welded aluminum or aluminum alloy structures typically are wider than with steel structures to accommodate the weld sizes required for desirable joining. The wider flanges on welded parts can drive up part weight and reduce welding performance. Furthermore, electrodes used in welding aluminum and aluminum alloys may need to be reconditioned and replaced more frequently than electrodes used in welding steel due to the harsher welding parameters required for welding aluminum and aluminum alloys in conventional resistance spot welding techniques. Conventional resistance spot welding of aluminum and aluminum alloy assemblies typically requires a larger electrode than used in resistance spot welding of iron alloy assemblies (e.g., 16 mm for steel and 20 mm for aluminum), resulting in a need for a larger weld flange to accommodate the welding electrode, a larger weld current due to the larger contact area between the assembly and the electrode, and a larger clamping force between the opposed electrodes. Furthermore, utilizing different electrodes for resistance spot welding steel and aluminum or aluminum alloys can require that fabricators maintain separate resistance spot welders for the different materials, reducing the efficiency of the manufacturing process.

[0038] Additionally, resistance seam welding typically involves two large wheel electrodes, which can be difficult to maneuver on the workpiece, may lack precision, and are not versatile (e.g., weld parameters are constant through the welding process). For example, wheel electrode are typically 100mm to 300mm in diameter and may not be able to maneuver onto, for example, tight flanges and comer areas. Additionally, resistance seam welding is typically performed with large stationary pedestal stations and the workpieces are brought to the pedestal station. It can be challenging to articulate large workpieces e.g, a car body) into a large stationary pedestal stations.

[0039] In view of these issues, the present inventors developed methods for resistance spot welding, resistance spot welding systems and apparatus, and parts formed by methods including resistance spot welding, as described herein. The methods for resistance spot welding and the resistance spot welding systems and apparatus described herein can achieve desirable melting and fusion; reduce weight of welded components, weld flange width, electrode wear, peak weld current, and/or clamping force; and/or increase efficiency of manufacturing processes.

[0040] Prior to the present disclosure, conventional resistance spot welds were spaced apart a defined minimum distance to avoid a shunting effect caused by a previously formed resistance spot weld when forming a subsequent resistance spot weld. However, the present inventors unexpectedly and surprisingly discovered that overlapping a newly formed resistance spot weld with a previously formed resistance spot weld can result in an enhanced weld fusion zone and provide improvements in the manufacturing process.

[0041] FIGs. 1-6 schematically depict different configurations of a non-limiting embodiment of a resistance spot welding system 102 and an assembly 108 of sheets being joined and illustrate a non-limiting embodiment of a method of resistance spot welding according to the present disclosure. Referring to FIG. 1, the resistance spot welding system 102 and the assembly 108 are shown in a first configuration. The resistance spot welding system 102 can comprise a first welding electrode 104a, a second welding electrode 104b positioned opposed to the first welding electrode 104a, a power unit 122 in electrical communication with the welding electrodes 104a and 104b, an actuator 124 mechanically connected to welding electrodes 104a and 104b, and a controller 126 in electrical communication with the actuator 124 and welding electrodes 104a and 104b. In various non-limiting embodiments, the resistance spot welding system 102 can comprise various other components, such as, for example, a robotic manipulator, a vision system, a cooling system, a frame, or a combination of two or more thereof. [0042] The welding electrodes 104a and 104b can form a longitudinal axis, Ai, and define a gap 106 intermediate the welding electrodes 104a and 104b. The actuator 124 can be configured to move at least one of the welding electrodes 104a and 104b relative to the other. For example, the actuator 124 can control a size of the gap 106 by moving the welding electrodes 104a and 104b along the longitudinal axis, Ai, between a first position (e.g., an open position) as illustrated in FIG. 1 and a second position (e.g., a closed position) as illustrated in FIG. 2, wherein the size of the gap 106 has been reduced.

[0043] The welding electrodes 104a and 104b can be configured to contact at least a portion of the assembly 108 at a desired location. For example, the actuator 124 can apply a clamping force to the assembly 108 with the electrodes 104a and 104b by moving the first welding electrode 104a generally in direction 118a along the longitudinal axis, Ai, and the second welding electrode 104b generally in direction 118b along the longitudinal axis, Ai, so as to contact the assembly 108. The contact can thereby compress the assembly 108 between the welding electrodes 104a and 104b in the second position illustrated in FIG. 2 to apply a clamping force to the assembly 108. The actuator 124 can remove the clamping force by retracting the welding electrodes 104a and 104b along the longitudinal axis, Ai, to the first position as illustrated in FIG. 1. The clamping force applied by the actuator 124 can be at least 10 Newtons, (N) such as, for example, at least 100 N, at least 200 N, at least 500 N, at least IkN, at least 2 kN, at least 3 kN, or at least 3.5 kN. For example, the clamping force applied by the actuator 124 to the assembly 108 can be in a range of 10 N to 20 kN, such as, for example, 100 N to 10 kN, 1 kN to 6 kN, 2 kN to 5 kN, or 3 kN to 6 kN.

[0044] In various non-limiting embodiments, the welding electrodes 104a and 104b may be moved about up to 6 degrees of freedom, such that the position and/or orientation of each of the welding electrodes 104a and 104b can change relative to the assembly 108 while the position of the welding electrodes 104a and 104b relative to one another may be the same or different. In certain non-limiting embodiments, both of the welding electrodes 104a and 104b are moveable. In various non-limiting embodiments, at least one of the welding electrodes 104a and 104b is moveable and one of the welding electrodes 104a and 104b is stationary.

[0045] In various non-limiting embodiments, the actuator 124 can be paired with a robotic manipulator and/or other movement apparatus to control the position and/or orientation of the electrodes with respect to the assembly 108. In certain non-limiting embodiments, the actuator 124 and the welding electrodes 104a and 104b can be components of a resistance spot welding gun (e.g., a transgun). Each welding electrode 104a and 104b can comprise an electrically conductive material, such as, for example, copper, a copper alloy, or another material suitable for resistance spot welding.

[0046] Referring to the detail view in FIG. 4B, the welding electrode 104a can comprise an external diameter, d₆, and the electrode 104b can comprise an external diameter, d?. In various non-limiting embodiments, the external diameter, de, and the external diameter, d?, individually can be in a range of 1 millimeter (mm) to30 mm, such as, for example, 2 mm to 20 mm, 5 mm to 25 mm, 5 mm to 20 mm, 10 mm to 25 mm, 10 mm to 20 mm, 12 mm to 16 mm, or 14 mm to 18 mm. In various non-limiting embodiments, one of the welding electrodes 104a and 104b can be a bar or a plate. For example, the welding electrode 104a can be moveable and the welding electrode 104b can be a bar or a plate and stationary.

[0047] In certain non-limiting embodiments, each welding electrodes 104a and 104b can comprise a radiused surface 104a' and 104b', respectively, configured to contact the assembly 108. Each radiused surface 104a' and 104b', can be substantially spherically shaped and have a radius Ri andR2, respectively. Radius Ri andR2, individually, can be in a range of 10 mm to 300 mm, such as, for example, 25 mm to 100 mm, or 25 mm to 75 mm. Any portion of the radiused surfaces 104a' and 104b' can contact the assembly 108 during a welding process. In certain non-limiting embodiments, each radiused surface 104a' and 104b' can comprise a flat portion. For example, the flat portion of the radiused surface 104a' and 104b' can be at a crown the welding electrodes 104a and 104b, such that the flat portion engages the assembly 108 during a resistance spot weld.

[0048] In various non-limiting embodiments, it may be desired to contact different portions of the radiused surfaces 104a' and 104b' during successive resistance spot welds to inhibit formation of hot spots, erosion, tip sticking, sheet cracking and/or expulsion. For example, as illustrated in FIG. 2, the longitudinal axis, Ai, of the welding electrodes 104a and 104b can be substantially perpendicular to a sheet line, S/, of the assembly 108 and, as illustrated in FIG. 11, the longitudinal axis, Ai, can be offset from perpendicular to a sheet line, S/, of the assembly 108. In various non-limiting embodiments, the longitudinal axis, Ai, can be offset from perpendicular to the sheet line, S/, of the assembly 108 by an angle, a. The angle, a, can be in a range of 0.1 degree to 10 degrees, such as, for example, 1 degree to 10 degrees. Portions of the welding electrodes 104a and 104b shown contacting the assembly 108 in FIG. 2 differ from the portions of the welding electrodes 104a and 104b shown contacting the assembly 108 in FIG. 11, resulting from differences in orientation of the welding electrodes 104a and 104b relative to the assembly 108.

[0049] As illustrated in FIG. 1, the assembly 108 is positioned intermediate the first welding electrode 104a and the second welding electrode 104b. The assembly 108 comprises at least two metallic parts, including a first part 108a and a second part 108b. In various non-limiting embodiments, the assembly 108 comprises three or more metallic parts (as described with respect to FIG. 17 herein). The parts within the assembly 108 can comprise, for example, a metal, a metal alloy, or a combination thereof. For example, the first part 108a can comprise a first metallic material, and the second part 108b can comprise a second metallic material. The first metallic material may be the same as or different from the second metallic material, and each part can individually comprise a metal or a metal alloy. The metal or metal alloy can comprise, for example, iron, an iron alloy, aluminum, an aluminum alloy, magnesium, a magnesium alloy, or a combination of two or more thereof. For example, at least one of the first part 108a and the second part 108b can comprise aluminum or an aluminum alloy. The aluminum alloy may comprise, for example, a 5XXX series aluminum alloy (e.g., a 5182 aluminum alloy), a 6XXX series aluminum alloy (e.g., a 6013, 6022 aluminum alloy), a 7XXX series aluminum alloy, or a combination of two or more thereof. In addition to a metal or a metal alloy, the assembly 108 can comprise various other materials such as, for example, seals and/or adhesives.

[0050] In various non-limiting embodiments, the first part 108a and the second part 108b can comprise different materials, such as, for example; one of the first part 108a and the second part 108b can comprise aluminum or an aluminum alloy and one of the first part 108a and the second part 108b can comprise an iron alloy (e.g., steel); one of the first part 108a and the second part 108b can comprise aluminum or an aluminum alloy and one of the first part 108a and the second part 108b can comprise magnesium or a magnesium alloy; one of the first part 108a and the second part 108b can comprise magnesium or a magnesium alloy and one of the first part 108a and the second part 108b can comprise an iron alloy (e.g., steel). In various non-limiting embodiments, the fusion zone 120 may not be a complete fusion of the parts 108a and 108b and may be a metallic bond where the first part 108a and the second part 108b are sufficiently mixed to secure the assembly at the location of the fusion zone. [0051] In various non-limiting embodiments, referring to FIG. 4B, each part 108a and 108b can individually comprise a thickness, t₁ and t₂, respectively, in a range of 0.1 mm to 10 mm, such as, for example, 0.1 mm to 5 mm, 0.1 mm to 6 mm, 0.2 mm to 4 mm, 0.5 mm to 6 mm, 0.8 mm to 4 mm, or 0.5 mm to 3 mm.

[0052] The power unit 122 can deliver a weld current to the electrodes 104a and 104b for a weld time. For example, the weld current can be a DC current in a range of 1 kiloamperes (kA) to 100 kA such as, for example, 5 to 50 kA, 5 to 100 kA, 10 to 50 kA, or 15 to 40 kA. The weld time, for example, can be in a range of 1 millisecond (ms) to 1 second, such as, for example, 5 ms to 500 ms, 5 ms to 100 ms, or 10 ms to 50 ms.

[0053] The controller 126 can control the weld parameters during the welding operation, such as, for example, the weld current, the weld time, the hold time, and the clamping force. For example, the controller 126 can be configured to operate the power unit 122 and thereby deliver the weld current to the welding electrodes 104a and 104b for the weld time with the power unit 122. The controller 126 can be configured to operate the actuator 124 to thereby apply a clamping force on the assembly 108 with the electrodes 104a and 104b by activating the actuator 124 to move one or both of the electrodes 104a and 104b. The controller 126 can maintain the clamping force on the assembly 108 with the electrodes 104a and 104b while the weld current is passed through the assembly 108 and then for a hold time after the weld current has been turned off. The hold time, for example, can be in a range of 1 ms to 1 second, such as, for example, 5 ms to 500 ms, 5 ms to 200 ms, or 20 ms to 200 ms. In various non-limiting embodiments, the controller 126 can control the robotic manipulator, other movement apparatus, a vision system, a cooling system, a frame, other component, or a combination of two or more thereof.

[0054] Again referring to FIGs. 1-6, a non-limiting embodiment of a method for resistance spot welding the assembly 108 with the resistance spot welding system 102 may be understood. As illustrated in FIG. 1, the assembly 108 is disposed in the gap 106 between the electrodes 104a and 104b. The assembly 108, through motion of the assembly 108 and/or the electrodes 104a and 104b, has/have been moved such that the longitudinal axis, Ai, of the electrodes 104a and 104b at least partially intersects the first location 130a on the assembly 108. [0055] Referring to FIG. 2, the first welding electrode 104a has been moved generally in direction 118a along the longitudinal axis, Ai, and the second welding electrode 104b has been moved generally in direction 118b along the longitudinal axis, Ai, such that the welding electrodes 104a and 104b contact the assembly 108 at the first location 130a and thereby apply a first clamping force to the assembly 108. The first clamping force can be at least 10 N such as, for example, at least 100 N, at least 200 N, at least 500 N, at least IkN, at least 2 kN, at least 3 kN, or at least 3.5 kN. For example, the first clamping force can be in a range of 10 N to 20 kN, such as, for example, 100 N to 10 kN, 1 kN to 6 kN, 2 kN to 5 kN, or 3 kN to 6 kN

[0056] A weld current was passed through the assembly 108 at the first location 130a with the electrodes 104a and 104b to resistively heat the first part 108a and the second part 108b so that the first part 108a and the second part 108b fused together, thereby forming a first resistance spot weld 110 securing the components of the assembly together. As used herein, a “resistance spot weld” is the region in which the component parts (e.g., sheets, layers) of the assembly between the welding electrodes have been fused together. The first resistance spot weld 110 can be referred to as the “anchor” weld because it is the first weld formed in a fusion zone 120, and the fusion zone 120 can extend along the assembly 108 from the first resistance spot weld 110.

[0057] The first resistance spot weld 110 has a diameter, di, that is measured along a direction generally parallel to the sheet line, Sz, of the assembly 108. In various non-limiting embodiments, the diameter, di, can be no greater than 6 * √ (governing metal thickness), such as, for example, no greater than 5 * √GMT . For purposes of the present disclosure, the governing metal thickness (GMT) may be determined according to American Welding Society Standard D8.2M:2017, “SPECIFICATION FOR AUTOMOTIVE WELD QUALITY-RESISTANCE SPOT WELDING OF ALUMINUM.” For example, the GMT is the metal gage (e.g., thickness of a part) in an assembly that determines the minimum acceptable weld size for the assembly. The GMT for an assembly comprising two sheets/layers, for example, is the thickness of the thinner of the two sheets/layers. Generally, the GMT for an assembly comprising three sheets/layers is the thickness of the second thinnest sheet/layer in the assembly. For example, in FIG. 4C the GMT of assembly 108 can be the lesser of ti and t2 at the first location 120a prior to formation of the first spot weld 110. In various non-limiting embodiments, the diameter, di, can be in a range of 2 * √GMT to 6 * √GMT, such as, for example, 3 * √GMT to 6 * √GMT , 3 * √GMT to 5 * √GMT , or 3 *√GMT to 4 * √GMT . Limiting the diameter, di, can reduce the weld current that must be applied by the power unit 122 to produce an acceptable fusion weld, reduce the clamping force that must be applied to the assembly 108 by the actuator 124 to produce an acceptable fusion weld, and/or reduce wear on the welding electrodes 104a and 104b resulting from the welding process.

[0058] Referring to FIG. 3, the clamping force has been at least partially removed (e.g., the welding electrodes 104a and 104b are no longer in contact with the assembly 108) or are in contact with the assembly 108 but the clamping force is less than 0.5 N, and the welding electrodes 104a and 104b can be positioned to another location on the assembly 108. As shown in FIG. 3, the welding electrodes 104a and 104b have been retracted to the first position and are no longer in contact with the assembly 108. In various non-limiting embodiments, the electrodes 104a and 104b may be at least partially in contact with the assembly 108 during movement to another location on the assembly 108. After at least partially relieving the clamping force, the assembly 108 and/or the welding electrodes 104a and 104b has/have been moved such that the longitudinal axis, Ai, of the electrodes 104a and 104b at least partially intersects the second location 130b on the assembly 108. The second location 130b can be a distance, d₃, from the first location 130a. The distance, d₃, can be a measured as the distance between center points of the respective locations 130a and 130b. In various embodiments, the distance, d₃, is such that a resistance spot weld will overlap to some extent with the resistance spot weld that is formed on the assembly next in time. In certain non-limiting embodiments, the distance, d₃, measured between locations 130a and 130b can be no greater than the diameter, di, of the first resistance spot weld 110 and so that an overlap is provided between successively-formed resistance spot welds. For example, the distance, d₃, can be no greater than 10 mm, such as, for example, no greater than 8 mm. In various non-limiting embodiments, the distance, d₃, can be in a range of 0.1 mm to 10 mm, such as, for example, 1 mm to 8 mm, 2 mm to 7 mm or 3 mm to 6 mm. The distance, d₃, can also be referred to as a weld pitch within the fusion zone 120. In various non-limiting embodiments, an overlap will be present between successively-formed resistance spot welds.

[0059] Referring to FIG. 4 A, the first welding electrode 104a has been moved generally in direction 118a along the longitudinal axis, Ai, and the second welding electrode 104b has been moved generally in direction 118b along the longitudinal axis, Ai, such that the welding electrodes 104a and 104b contact the assembly 108 at the second location 130b. As further shown in FIG. 4 A, the welding electrodes 104a and 104b apply a second clamping force to the assembly 108. In various non-limiting embodiments in which distance, d₃, is no greater than the diameter, di, referring to FIG. 4B, the welding electrodes 104a and 104b at least partially contact an indentation 110a in a surface 108a' and/or 108a' of the assembly 108 resulting from formation of the first resistance spot weld 110. In various non-limiting embodiments, the second clamping force is the same as or different than the first clamping force. For example, the second clamping force can be different than the first clamping force, such as, for example, the second clamping force can be less than the first clamping force.

[0060] With reference to FIGs. 4A and 4B, a weld current was passed through the assembly 108 at the second location 130b with the welding electrodes 104a and 104b such that the first part 108a and the second part 108b fused together, forming a second resistance spot weld 112 overlapping the first resistance spot weld 110, securing the assembly 108. The second resistance spot weld 112 has a diameter, d₂, that is generally parallel to the sheet line of the first part 108a and the second part 108b. The diameter, d2, can be no greater than 6 * √GMT . For example, the diameter, d2, can be in a range of 2 * √GMT to 6 * √GMT , such as, for example, 3 * √GMT to 6 * √GMT , 3 * √GMT to 5 * √GMT , or 3 * √GMT to 4 * √GMT .

[0061] The first resistance spot weld 110 and the partially overlapping second resistance spot weld 112 form fusion zone 120 that is larger in area than either of the first resistance spot weld 110 and the second resistance spot weld 112 alone. The portion 114 of the fusion zone 120 is the region in which the first resistance spot weld 110 and the second resistance spot weld 112 overlap. In various non-limiting embodiments, the overlapping first resistance spot weld 110 and the second resistance spot weld 112 form an elongated fusion zone 120 securing together the component parts of the assembly 108.

[0062] Referring to FIGs. 1-6, the fusion zone 120 is illustrated as including two resistance spot welds 110 and 112 for clarity. However, each fusion zone 120 may have two or more overlapping resistance spot welds (as shown in FIGs. 1-6), such as, for example, at least three overlapping resistance spot welds, at least four overlapping resistance spot welds (e.g., fusion zone 720 comprising four overlapping resistance spot welds including anchor weld 710, as shown in FIG. 7), at least five overlapping resistance spot welds, at least six overlapping resistance spot welds (e.g., fusion zone 920 comprising six overlapping resistance spot welds with anchor weld 910, as shown in FIG. 9), at least seven overlapping resistance spot welds, at least eight resistance spot welds (e.g., fusion zone 1020 comprising eight overlapping resistance spot welds with anchor weld 1010, as shown in FIG. 10), at least sixteen overlapping resistance spot welds (e.g., fusion zone 820 comprising sixteen overlapping resistance spot welds with anchor weld 810, as shown in FIG. 8), or any other number of resistance spot weld suitable to produce a fusion zone acceptable to secure the component parts (e.g., sheets, layers) of the particular assembly that is being welded.

[0063] Referring to FIG. 4C, if desired, one or more overlapping resistance spot welds 132 can be subsequently formed, thereby extending the fusion zone 120. After at least partially removing the clamping force exerted by the welding electrodes 104a and 104b when forming the previous resistance spot weld, the location of the welding electrodes on the assembly 108 has changed, through motion of the assembly 108 and/or the welding electrodes 104a and 104b, so that the longitudinal axis, Ai, of the electrodes 104a and 104b at least partially intersects the subsequent location 130n on the assembly 108. The first welding electrode 104a has been moved generally in direction 118a along the longitudinal axis, Ai, and the second welding electrode 104b has been moved generally in direction 118b along the longitudinal axis, Ai, such that the welding electrodes 104a and 104b contact the assembly 108 at the subsequent location 130n and thereby apply a clamping force to the assembly 108 at location 13 On with welding electrodes 104a and 104b. In various non-limiting embodiments in which distance, dn, is no greater than the diameter of the previously formed resistance spot weld, the welding electrodes 104a and 104b at least partially contact an indentation 112a in the surface 108a' and/or 108a' of the assembly 108 produced during formation of the previously-formed resistance spot weld (e.g., second resistance spot weld 112). The subsequent clamping force can be the same as or different than the second clamping force.

[0064] The subsequent location 130n is a distance, dn, from the previous location (e.g., second location 130b). The distance, dn, can be a measurement between center points of the respective locations 130b and 130n (e.g., a distance between centers of the respective resistance spot welds 112 and 132). The distance, dn, can be no greater than the diameter, ds, of the previously formed resistance spot weld (e.g., second resistance spot weld 112 as shown) such that formation of another resistance spot weld will overlap with the previously formed resistance spot weld. For example, the distance, dn, can be no greater than 10 mm, such as, for example, no greater than 8 mm. In various non-limiting embodiments, the distance, dn, can be in a range of 0.1 mm to 10 mm, such as, for example, 1 mm to 8 mm, 2 mm to 7 mm, or 3 mm to 6 mm.

[0065] A weld current was passed through the assembly 108 at the subsequent location 130n with the electrodes 104a and 104b such that the first part 108a and the second part 108b of the assembly 108 fused together, thereby forming a subsequent resistance spot weld 132 partially overlapping the previous resistance spot weld (e.g., second resistance spot weld 112), securing the component parts of the assembly 108. The subsequent resistance spot weld 132 can have a diameter, ds, that is generally parallel to the sheet line, S/, of the assembly 108. The diameter, dn, can be no greater than 6 * √GMT . For example, the diameter, d2, can be in a range of 2 * √GMT to 6 * √GMT , such as, for example, 3 * √GMT to 6 * √GMT , 3 * √GMT to 5 * √GMT , or 3 * √GMT to 4 * √GMT .

[0066] The controller 126 can dynamically change the weld parameters, such as, for example, weld current, weld time, hold time, and/or a clamping force during the formation of the fusion zone 120 and/or between formations of different fusion zones. Thus, each resistance spot weld 110, 112, 116, and 132 can be formed using one or more different weld parameters. In various non-limiting embodiments, the anchor weld of a fusion zone is formed with at least one different weld parameter than a spot weld in the same fusion zone that is formed subsequent to the anchor weld. For example, the anchor weld (e.g., first resistance spot weld 110) in fusion zone 120 can be formed using a lower weld current than subsequently formed resistance spot welds (e.g., resistance spot welds 112 and 132) comprising fusion zone 120. In certain non-limiting embodiments, the anchor weld (e.g., first resistance spot weld 110) in fusion zone 120 can be formed with a weld current at least a 1 kA lower than the weld current used in forming subsequently formed resistance spot welds (e.g., resistance spot welds 112 and 132) comprising the fusion zone 120. In certain non-limiting embodiments, the subsequently formed resistance spot welds (e.g., resistance spot welds 112 and 132) can be more uniform (e.g., comprise a more uniform shape, size, and/or sheet penetration) than the anchor weld (e.g., first resistance spot weld 110) in the fusion zone 120.

[0067] Moving the assembly and/or the welding electrodes so that the welding electrodes contact a subsequent location and passing a weld current through the assembly 108 at the location can be repeated to form a fusion zone 120 of a desired size and/or shape. For example, the fusion zone 120 can be linear (as shown in, for example, FIGs. 1-8, 14A-14B, and 15), non-linear (as shown in, for example, FIGs. 10 and 12A-12B), curved (as shown in, for example, FIGs. 9, 11, and 13), or some combination of linear, non-linear, and/or curved. In one non-limiting example, FIG. 9 illustrates a circular fusion zone 920 comprising six overlapping resistance spot welds with an anchor weld 910 and wherein the subsequently formed resistance spot welds are in a counter-clockwise arrangement starting with anchor weld 910. In another non-limiting example, FIG. 10 illustrates a non-linear fusion zone 1020 comprising eight overlapping resistance spot welds with an anchor weld 1010 and wherein subsequently formed resistance spot welds were formed in a zig-zag manner starting from the anchor weld 1010. In a further non-limiting example, FIG. 11 illustrates a curved fusion zone 1120 comprising six overlapping resistance spot welds and an anchor weld 1110a. In a further non-limiting example, FIGs. 12A and 12B illustrate a non-linear fusion zone 1220 formed around a corner 1240 of the illustrated assembly and with an anchor weld 1210. In yet another non-limiting example, FIG. 13 illustrates a curved fusion zone 1320 formed around a complex curve 1340 of an assembly and with an anchor weld 1310. In yet a further non-limiting example, FIG. 14 illustrates a plurality of linear fusion zones 1420a-f that differ in the number of overlapping resistance spot welds and wherein the fusion zones 1420a-f, respectively, originate with anchor weld 1410a-f.

[0068] In various non-limiting embodiments, adjusting a size of the fusion zone can enable adjustment of a strength of the weld along the assembly. For example, the governing metal thickness of an assembly and desired weld strength can be determined. Thereafter, the distance between resistance spot welds within a fusion zone (e.g., weld pitch), individual resistance spot weld size, fusion zone size and/or shape, number of resistance spot welds within a fusion zone can be dynamically determined based on the governing metal thickness and the desired weld strength.

[0069] The fusion zone 120 can be created by a continuously overlapping sequence of resistance spot welds or intermittent resistance spot welds followed by gap filling between the resistance spot welds. For example, in various non-limiting embodiments, referring to FIG. 4D, the resistance spot welds 410, 412, and 432 within a fusion zone 420 do not have to be sequentially formed. For example, first resistance spot weld 410 can be formed first and then second resistance spot weld 412 can be formed. The second resistance spot weld 412 does not overlap with the first resistance spot weld 410. Then a third resistance spot weld 432 can be formed, which overlaps with the first resistance spot weld 410 and the second resistance spot weld 412. Each resistance spot weld 410, 412, and 432 within the fusion zone 20 may not be overlapping with a previous resistance spot weld when each resistance spot weld 410, 412, and 432 is initially formed. Upon completion of the fusion area 420 the resistance spot weld 410, 412, and 432 can form a continuous fusion zone 420.

[0070] The fusion zone 120 can be formed with at least two metallic parts. For example, as shown in FIG. 6, the fusion zone 120 is formed with two metallic parts 108a and 108b. Referring to FIG. 17, the fusion zone 1720 comprising resistance spot welds including first resistance spot weld 1710, second resistance spot 1712, and third resistance spot 1732 can be formed with three metallic parts including first part 108a, the second part 108b, and a third part 1708c.

[0071] Referring back to FIG. 4A, the size and/or shape of the fusion zone 120 and, therefore, the resulting strength of the fusion zone 120 joining together the component parts of the assembly may be tailored to the desired application while minimizing typical issues encountered with larger welds (e.g., welds having a diameter > 5 * √GMT ,) such as, for example, hot spots, erosion, tip sticking, sheet cracking and/or expulsion. Wear on the welding electrodes 104a and 104b may be reduced relative to a resistance spot welding method that does not provide partially overlapping resistance spot welds. For example, wear on the welding electrodes 104a and 104b could be reduced by utilizing a lower welding current and/or a reduced clamping force relative to a resistance spot welding method that does not include partially overlapping resistance spot welds. In certain non-limiting embodiments, joining component parts of an assembly by creating a fusion zone 120 including at least two overlapping resistance spot welds can reduce the required peak weld current by, for example, at least 10% or at least 20%, and/or can reduce weld times by, for example, at least 25% or at least 30%, relative to joining component parts of the assembly with a conventional single resistance spot weld with a similar tensile yield strength.

Tailoring the shape and/or size of a fusion zone 120 including overlapping resistance spot welds produced according to non-limiting embodiments of a method of the present disclosure can allow for assembly 108 geometries that would not be acceptable or desirable if forming conventional resistance spot welds to secure the assembly’s component parts. In various non- limiting embodiments in which fusion zone 120 formed according to the present disclosure is linear or includes a linear portion, a width of the fusion zone 120 can be in a range of 3√GMT to 4 GMT and a length of the fusion zone 120 can be in a range of 6√ GMT to 12√ GMT to achieve at least the weld strength of a single conventional resistance spot weld having a diameter in a range of 5 GMT to 6√GMT . In certain non-limiting embodiments, referring to FIG. 7, the fusion zone 720 (e.g., peeled weld area) can comprise an aspect ratio (length, li, to width, wi) of at least 1.5, such as, for example, at least 2. For example, the peeled weld area can be measured according to AWS-C1.1 :2012.

[0072] Referring to FIG. 4B, indentations 110a and indentations 112a were formed in each part 108a and 108b by the welding electrodes 104a and 104b when forming the respective resistance spot welds 110 and 112. As shown, the indentation 112a created when forming the second resistance spot weld 112 overlaps with the indentation 110a created when forming the first resistance spot weld 110. In various non-limiting embodiments, the indentation 112a may have a depth the same as or less than a depth of the indentation 110a. For example, the indentation 112a may have a depth less than a depth of the indentation 110a

[0073] Surface oxides can impact the weldability of the assembly 108. For example, aluminum oxide can form on metallic parts comprising aluminum or an aluminum alloy, magnesium oxide can form on metallic parts comprising magnesium or a magnesium alloy, and coatings (e.g., galvanized coatings) can be formed on metallic parts comprising an iron alloy (e.g., steel). Forming the anchor weld (e.g., the first resistance spot weld created when forming a fusion zone, such as first resistance spot weld 110) can at least partially disrupt oxides on a surface 108a' and/or surface 108b' of the assembly 108 at the location of the anchor weld (e.g., first location 130a). The oxides can be less electrically conductive than metal or metal alloy itself. Disrupting the oxides on the surface 108a' and/or surface 108b' can enhance conduction of current between the welding electrodes 104a and 104b, and the assembly 108. In various non-limiting embodiments, at least partially disrupting oxides on the surface 108a' and/or surface 108b' of the assembly 108 at the first location 130a can improve uniformity of the magnitude of weld currents required to form the first resistance spot weld 110 and the second resistance spot weld 112 relative to the magnitude of the weld currents required to form the resistance spot welds 110 and 112 if oxides on the surfaces 108a’ and/or 108b’ are not at least partially removed.

[0074] The fusion zone 120 can be formed on a flat surface of the assembly 108, as shown, for example, in FIGs. 1-10 and 12-15, can be formed on a curved surface of the assembly 108, as shown, for example, in FIG. 11, or can be formed on a complex surface including one or more flat surfaces and/or curved surfaces. Transitioning between a flat surface and a curved surface on an assembly can be difficult in conventional resistance seam welding applications as the wheel electrodes on the seam welder can be fixed relative to one another, limited to the particular surface they were designed to weld. In various non-limiting embodiments, because the resistance spot welding process described herein is versatile, the resistance spot welding system 102 can transition from forming the fusion zone 120 on a flat surface to forming the fusion zone 120 a curved surface (or vice versa) dynamically during the resistance spot welding process. In certain non-limiting embodiments, the versatility of the formation of the fusion zone 120 enables the fusion zone 120 to be on an edge region of the assembly 108, as shown for example, in FIGs. 1-12 and 14A-15, and/or on an interior region of the assembly 108, as shown, for example, in FIG. 13.

[0075] Referring to FIG. 5, after the fusion zone 120 has been formed, the clamping force has been released or at least partially removed (e.g., reduced to less than 0.5 N such that the welding electrodes 104a and 104b can be disposed at another location on the assembly 108. As shown, the welding electrodes 104a and 104b have been retracted to the first position and are no longer in contact with the assembly 108. After at least partially removing the clamping force, the location of the welding electrodes 104a and 104b has changed on the assembly 108, through motion of the assembly 108 and/or the welding electrodes 104a and 104b, so that the longitudinal axis, Ai, of the electrodes 104a and 104b at least partially intersects the third location 130c on the assembly 108. The third location 130c is a distance, d₉ from the previously formed resistance spot weld e.g., second location 130b). The distance, d₉ can be measured as between center points of the respective locations 130b and 130c. The distance, d₉ can be greater than the diameter, d2, of the second resistance spot weld 112, such as, for example at least two times greater, at least 2.5 times greater, or at least 3 times greater. The distance, d₉ can be in a direction away from the fusion zone 120 such that formation of another resistance spot weld will not overlap with the fusion zone 120. For example, the distance, d₉ can be at least 10 mm, such as, for example, at least 15 mm, at least 20 mm, at least 25 mm, at least 30 mm, or at least 40 mm. The distance, d₉ can also be referred to as a pitch between fusion zones.

[0076] Referring to FIG. 6, the first welding electrode 104a has been moved generally in direction 118a along the longitudinal axis, Ai, and the second welding electrode 104b has been moved generally in direction 118b along the longitudinal axis, Ai, such that the welding electrodes 104a and 104b contact the assembly 108 at the third location 130c and apply a third clamping force to the assembly 108 at the third location 130c with the electrodes 104a and 104b. In various non-limiting embodiments in which distance, d₉ is greater than the diameter, d2, the welding electrodes 104a and 104b do not contact the fusion zone 120. In various non-limiting embodiments, the third clamping force is substantially the same as the first clamping force.

[0077] A weld current was passed through the assembly 108 at the third location 130c with the welding electrodes 104a and 104b such that the first part 108a and the second part 108b fused together, thereby forming a third resistance spot weld 116 that does not overlap the fusion zone 120 and which secures the assembly 108 at its location. The third resistance spot weld 112 has a diameter, d4, that is generally parallel to the sheet line, Sz, of the assembly 108. The diameter, d4, can be no greater than 6 * √GMT . For example, the diameter, d4, can be in a range of 2 * √GMT to 6 * √GMT , such as, for example, 3 * √GMT to 6 * √GMT , 3 * √GMT to 5 * GMT , or 3 * √GMT to 4 * √GMT . The third resistance spot weld 116 can be referred to as an anchor weld since it is the first resistance spot weld of fusion zone 134, and the fusion zone 134 can begin at and extend from the third resistance spot weld 116. In various non-limiting embodiments, the fusion zone 134 only includes third resistance spot weld 116 or may comprise two or more overlapping resistance spot welds.

[0078] Due to the versatility of the formation of the fusion zone 120 according to various non-limiting embodiments described herein, the same welding electrodes 104a and 104b could be used to secure various materials, whereas in if using convention resistance spot welding techniques it may be necessary to utilize different electrodes to weld aluminum/aluminum alloys and to weld iron alloys (e.g., steel). For example, in various nonlimiting embodiments, the assembly 108 can comprise a first material, and a second assembly (not shown) can comprise a second material different than the first material, and the resistance spot welding system 102 according to the present disclosure including electrodes 104a and 104b can be used form resistance spot welds on both assemblies dynamically, without requiring an electrode change. In certain non-limiting embodiments, the first material comprises aluminum or an aluminum alloy and the second material comprises an iron alloy (e.g., steel). In various non-limiting embodiments, the second material comprises aluminum or an aluminum alloy and the first material comprises an iron alloy(e.g., steel).

[0079] FIGs. 11-15 are examples of semi-finished or finished parts, 1100, 1200, 1300, 1400, and 1500 produced by certain non-limiting embodiments of resistance spot welding methods and systems according to the present disclosure. In various non-limiting embodiments, each of the semi-finished or finished parts, 1100, 1200, 1300, 1400, and 1500, can be individually configured as an aerospace component or structure, an automotive component or structure, a transportation component or structure, a building and construction component or structure, or another component or structure. For example, the semi-finished or finished parts 1100, 1200, 1300, 1400, and 1500 can each be configured as an automotive component or structure.

[0080] Referring to the example shown in FIGs. 12A-12B, the semi-finished or finished part 1200 can comprise a fusion zone 1220 including an anchor weld 1210. Referring to FIG. 13, the semi-finished or finished part 1300 can comprise a fusion zone 1320 having an anchor weld 1310. Referring to the example shown in FIGs. 14A-14B, the semi-finished or finished part 1400 can comprise fusion zones 1420a, 1420b, 1420c, 1420d, 1420e, and 1420f, which comprise, respectively, anchor welds 1410a, 1410b, 1410c, 1410d, 1410e, and 1410f.

[0081] Referring to the example shown in FIG. 15, the semi-finished or finished part 1500 can comprise at least two fusion zones 1520a and 1520b including, respectively, anchor welds 1510a and 1510b. The fusion zone 1520a and/or 1520b can comprise at least two partially overlapping resistance spot welds that are individually classified as Grade A, Grade B, Grade C, or a combination thereof according to Japanese Industrial Standard JIS Z 3140:2017, and wherein the at least two partially overlapping resistance spot welds exhibit a tensile strength of a Grade A weld or higher according to Japanese Industrial Standard JIS Z 3140:2017. The semi-finished or finished part 1500 can comprise a welding flange 1536.

[0082] Referring to the example shown in FIG. 16, the semi-finished or finished part 1600 can comprise at least two fusion zones 1620a and 1620b including, respectively, anchor welds 1610a and 1610b. The fusion zone 1620a and/or 1620b can comprise at least two partially overlapping resistance spot welds that are individually classified as Grade A, Grade B, Grade C, or a combination thereof according to Japanese Industrial Standard JIS Z 3140:2017, and wherein the at least two partially overlapping resistance spot welds exhibit a tensile strength of a Grade A weld or higher according to Japanese Industrial Standard JIS Z 3140:2017. The semi-finished or finished part 1600 can comprise a welding flange 1636.

[0083] As used herein, a “welding flange” refers to an overlap between metallic parts in the assembly 108. In various non-limiting embodiments, the semi-finished or finished part 1500 and/or the semi-finished or finished part 1600 can comprise an adhesive bond between the parts 108a and 108b. In various non-limiting embodiments, the welding flanges 1536 and 1636, individually can comprise a width, w, no greater than 12.5 * √GMT , such as, for example, no greater than 11 * √GMT . In certain non-limiting embodiments, the width, w, can be in a range of 7.5 * √GMT to 12.5 * √GMT , such as, for example, 10 * √GMT to 12.5 * √GMT . The semi-finished or finished part 1500 and/or the semi-finished or finished part 1600, individually, can comprise a metal or metal alloy, such as, for example, aluminum or an aluminum alloy. In conventional semi-finished or finished parts weld flange width was typically at least 15 * √GMT due to sizing requirements for electrode access and weld diameter requirements according to ISO 18595:2007, “Resistance spot welding - Spot welding of aluminum and aluminum alloys - Weldability, welding and testing”.

[0084] EXAMPLES

[0085] The present disclosure will be more fully understood by reference to the following examples, which provide illustrative non-limiting aspects of the invention. It is understood that the invention described in this specification is not necessarily limited to the examples described in this section.

[0086] The tensile strength of various assemblies was tested. Two welding methods were used. The first welding method utilized six overlapping resistance spot welds having a 3mm pitch between resistance spot welds resulting in a fusion zone having a width of 4-5 mm (e.g., 3 * GMT) to 4 * GMT) wide by 18-20 mm (e.g., 14 * √GMT to 18 * √GMT ) long. The second welding method utilized a single spot weld having a tensile strength of a Grade A weld according to Japanese Industrial Standard JIS Z 3140:2017. Each welding method was performed on a first assembly comprising two 1.0 mm thick 6XXX series aluminum alloy sheets, a second assembly comprising two 1.6 mm 6XXX series aluminum alloy sheets, and a third assembly comprising two 1.5 mm 5XXX series aluminum alloy sheets. The tensile strength of each weld was measured according to Japanese Industrial Standard JIS Z 3140:2017 and the results of the testing are shown in Table 1 below: [0087] Table 1

[0088] Since a single resistance spot weld is generally limited to having a diameter of no greater than of 6 * √GMT or 5 * √GMT , the strength of a single resistance spot weld may be limited. A significant increase in the tensile strength of the weld was observed when creating multiple overlapping resistance spot welds.

[0089] Various aspects of non-limiting embodiments of an invention according to the present disclosure include, but are not limited to, the aspects listed in the following numbered clauses.

[0090] Clause 1. A method for resistance spot welding comprising: contacting an assembly comprising at least two metallic parts with welding electrodes at a first location; passing a weld current through the assembly at the first location with the welding electrodes, thereby forming a first resistance spot weld securing the assembly; contacting the assembly with the opposing welding electrodes at a second location, wherein the second location is a first distance from the first location; and passing a weld current through the assembly at the second location with the welding electrodes, thereby forming a second resistance spot weld partially overlapping the first resistance spot weld.

[0091] Clause 2. The method of clause 1, further comprising: contacting the assembly with the opposed welding electrodes at a third location, wherein the third location is a second distance from the second location, wherein the second distance is at least two times a diameter of the second resistance spot weld; and passing a weld current through the assembly at the third location with the welding electrodes, thereby forming a third resistance spot weld that does not overlap the first resistance spot weld or the second resistance spot weld. [0092] Clause 3. The method of clause 2, wherein the second distance is at least 10 mm.

[0093] Clause 4. The method of any one of clauses 1-3, wherein: contacting the assembly comprising the at least two metallic parts with the opposed welding electrodes at the first location comprises applying a first clamping force to the assembly; prior to contacting the assembly with the opposing welding electrodes at the second location, at least partially removing the first clamping force; and contacting the assembly with the opposing welding electrodes at the second location comprises applying a second clamping force to the assembly with the opposed welding electrodes.

[0094] Clause 5. The method of clause 4, wherein at least one of the first clamping force and the second clamping force is in a range of 10 N to 20 kN.

[0095] Clause 6. The method of any one of clauses 4-5, wherein the second clamping force is different from the first clamping force.

[0096] Clause 7. The method of any one of clauses 1-6, wherein forming the first resistance spot weld forms a first indentation in a surface of the assembly, and forming the second resistance spot weld forms a second indentation in the surface of the assembly that at least partially overlaps with the first indentation.

[0097] Clause 8. The method of clause 7, wherein the first indentation has a first depth, and the second indentation has a second depth that is the same as or less than the first depth.

[0098] Clause 9. The method of any one of clauses 1-8, wherein the first distance is no greater than 10 mm.

[0099] Clause 10. The method of any one of clauses 1-9, wherein a diameter of the first resistance spot weld is no greater than 6 * √ (governing metal thickness), wherein the governing metal thickness is determined according to American Welding Society Standard D8.2M:2017.

[0100] Clause 11. The method of any one of clauses 1-10, wherein a diameter of the second resistance spot weld is in a range of 3 * (governing metal thickness) to 6 * √ (governing metal thickness), wherein the governing metal thickness is determined according to American Welding Society Standard D8.2M:2017. [0101] Clause 12. The method of any one of clauses 1-11, wherein the first resistance spot weld and the second resistance spot weld partially overlap to form an elongated fusion zone.

[0102] Clause 13. The method of any one of clauses 1-12, further comprising: contacting the assembly with the opposed welding electrodes at a subsequent location, wherein the subsequent location is a distance from a previously formed resistance spot weld that is no greater than a diameter of the previously formed resistance spot weld; passing a weld current through the assembly at the subsequent location with the welding electrodes, thereby forming a subsequent resistance spot weld partially overlapping a previously formed resistance spot weld; and repeating the contacting at a subsequent location and the passing the weld current at the subsequent location to form a fusion zone of a desired shape and/or size.

[0103] Clause 14. The method of clause 13, wherein the fusion zone is linear, non-linear, curved, or a combination thereof.

[0104] Clause 15. The method of clause 13, wherein the fusion zone is curved.

[0105] Clause 16. The method of any of clauses 13-15, wherein the second resistance spot weld and the subsequent resistance spot weld comprise a more uniform weld than the first resistance spot weld.

[0106] Clause 17. The method of any one of clauses 1-16, wherein the assembly comprises three or more metallic parts.

[0107] Clause 18. The method of any one of clauses 1-17, wherein the first location is on at least one of a flat surface of the assembly and a curved surface of the assembly.

[0108] Clause 19. The method of any one of clauses 1-18, wherein the first location is on a curved surface of the assembly.

[0109] Clause 20. The method of any one of clauses 1-19, wherein the first location is on at least one of an edge region of the assembly and an interior region of the assembly.

[0110] Clause 21. The method of any one of clauses 1-20, wherein the assembly comprises at least one of a metal and a metal alloy. [0111] Clause 22. The method of any one of clauses 1-21, wherein the assembly comprises at least one of iron, an iron alloy, aluminum, an aluminum alloy, magnesium, and a magnesium alloy.

[0112] Clause 23. The method of any one of clauses 1-22, wherein forming a first resistance spot weld securing the assembly at least partially disrupts oxides on a surface of the assembly at the first location.

[0113] Clause 24. The method of clause 23, wherein at least partially disrupting oxides from a surface of the assembly at the first location increases a uniformity of a weld current used to form the second resistance spot weld relative to a magnitude of the weld current that would be required to form the second resistance spot weld if the oxides are not at least partially removed from the surface.

[0114] Clause 25. The method of any one of clauses 1-24, wherein wear on the welding electrodes produced during the method is reduced relative to wear on the welding electrodes that would be produced during resistance spot welding method that does not provide partially overlapping resistance spot welds.

[0115] Clause 26. The method of clause 25, wherein the wear on the welding electrodes is reduced by utilizing a lower welding current, reduced clamping pressure, or a combination thereof relative to a resistance spot welding method that does not provide partially overlapping resistance spot welds.

[0116] Clause 27. The method of any one of clauses 1-26, wherein the welding electrodes define a longitudinal axis and the longitudinal axis is not substantially perpendicular to the assembly.

[0117] Clause 28. The method of any one of clauses 1-27, wherein the welding electrodes define a longitudinal axis and the longitudinal axis is substantially perpendicular to the assembly.

[0118] Clause 29. The method of any one of clauses 1-28, wherein the assembly is a first assembly, the metallic parts comprising the first assembly comprise a first material, and wherein the method further comprises: contacting a second assembly comprising at least two metallic parts with the welding electrodes at a third location, wherein the metallic parts comprising the second assembly comprise a second material different from the first material; and passing a weld current through the second assembly at the third location with the welding electrodes, thereby forming a third resistance spot weld.

[0119] Clause 30. The method of clause 29, wherein the first material comprises an iron alloy and the second material comprises aluminum or an aluminum alloy.

[0120] Clause 31. The method of any one of clauses 1-30, wherein the first distance is no greater than a first diameter of the first resistance spot weld.

[0121] Clause 32. The method of any of clauses 1-32, wherein a peak of the weld currents is at least 10% lower than a peak weld current for a single resistance spot weld with a similar tensile strength.

[0122] Clause 33. The method of any of clauses 1-33, wherein the peak weld current is at least 30% lower than a peak weld current for a single resistance spot weld with a similar tensile strength.

[0123] Clause 34. A fusion zone comprising a first resistance spot weld partially overlapping a second resistance spot weld and formed by the method of any one of clauses 1-33.

[0124] Clause 35. The fusion zone of clause 34, wherein the fusion zone comprises an aspect ratio of at least 1.5.

[0125] Clause 36. A semi-finished or finished part produced by the method of any one of clauses 1-33.

[0126] Clause 37. The semi-finished or finished part of clause 36, wherein the semi-finished or finished part comprises at least one of an aerospace part or component, an automotive part or component, a transportation part or component, and a building and construction part or component.

[0127] Clause 38. A semi-finished or finished part comprising a first resistance spot weld and a second resistance spot weld overlapping with the first resistance spot weld.

[0128] Clause 39. The semi-finished or finished part of clause 38, wherein the first resistance spot weld and the second resistance spot weld are on a flat surface of the semi-finished or finished part. [0129] Clause 40. The semi-finished or finished part of clause 38, wherein the first resistance spot weld and the second resistance spot weld are on a curved surface of the assembly.

[0130] Clause 41. The semi-finished or finished part of any one of clauses 38-40, wherein the first resistance spot weld and the second resistance spot weld are on at least one of an edge region of the semi-finished or finished part and an interior region of the semi-finished or finished part.

[0131] Clause 42. The semi-finished or finished part of any one of clauses 38-40, wherein the first resistance spot weld and the second resistance spot weld are on an edge region of the semi-finished or finished part.

[0132] Clause 43. A semi-finished or finished part comprising at least two partially overlapping resistance spot welds, wherein the at least two partially overlapping resistance spot welds, if individually classified, would be classified as Grade A, Grade B, Grade C, or a combination thereof according to Japanese Industrial Standard JIS Z 3140:2017, and wherein the at least two partially overlapping resistance spot welds together exhibit a tensile strength of a Grade A weld or higher according to Japanese Industrial Standard JIS Z 3140:2017.

[0133] Clause 44. A semi-finished or finished part comprising a welding flange, wherein a width of the welding flange is no greater than 12.5 * √governing metal thickness.

[0134] Clause 45. The semi-finished or finished part of clause 44, wherein the width of the welding flange is in a range of 7.5 * √governing metal thickness to 12.5 * √governing metal thickness.

[0135] Clause 46. The semi-finished or finished part of any one of clauses 43-45, wherein the semi-finished or finished part comprises aluminum or an aluminum alloy.

[0136] Clause 47. A resistance spot welding system or apparatus comprising: a power unit configured to deliver a weld current; a first electrode in electrical communication with the power unit; a second electrode in electrical communication with the power unit and positioned opposed from the first electrode; an actuator configured to move at least one of the first electrode and the second electrode relative to one another; and a controller in electrical communication with the power unit and the actuator; wherein the resistance spot welding system or apparatus is configured to perform the method of any one of clause 1-33.

[0137] Clause 48. A resistance spot welding system or apparatus comprising: a power unit configured to deliver a weld current; a first electrode in electrical communication with the power unit; a second electrode in electrical communication with the power unit and positioned opposed from the first electrode; an actuator configured to move at least one of the first electrode and the second electrode relative to one another; and a controller in electrical communication with the power unit and the actuator; wherein the resistance spot welding system or apparatus is configured to contact an assembly comprising at least two metallic parts with the first electrode and the second electrode at a first location, wherein the assembly is positioned intermediate the first electrode and the second electrode; pass a weld current between the first electrode and the second electrode through the assembly at the first location, thereby forming a first resistance spot weld securing the at least two metallic parts together; contact the assembly with the first electrode and the second electrode at a second location; and pass a weld current between the first electrode and the second electrode through the assembly at the second location, thereby forming a second resistance spot weld overlapping with the first resistance spot weld.

[0138] In the present disclosure, unless otherwise indicated, all numerical parameters are to be understood as being prefaced and modified in all instances by the term “about,” in which the numerical parameters possess the inherent variability characteristic of the underlying measurement techniques used to determine the numerical value of the parameter. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter described herein should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0139] Also, any numerical range recited herein includes all sub-ranges subsumed within the recited range. For example, a range of “1 to 10” includes all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10. Any maximum numerical limitation recited in this specification is intended to include all lower numerical limitations subsumed therein, and any minimum numerical limitation recited in the present disclosure is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend the present disclosure, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited. All such ranges are inherently described in the present disclosure.

[0140] The grammatical articles “a,” “an,” and “the,” as used herein, are intended to include “at least one” or “one or more,” unless otherwise indicated, even if “at least one” or “one or more” is expressly used in certain instances. Thus, the foregoing grammatical articles are used herein to refer to one or more than one (i.e., to “at least one”) of the particular identified elements. Further, the use of a singular noun includes the plural, and the use of a plural noun includes the singular, unless the context of the usage requires otherwise.

[0141] One skilled in the art will recognize that the herein described apparatus, systems, structures, methods, operations/actions, and objects, and the discussion accompanying them, are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific examples/embodiments set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class and the non-inclusion of specific components, devices, apparatus, operations/actions, and objects should not be taken as limiting. While the present disclosure provides descriptions of various specific aspects for the purpose of illustrating various aspects of the present disclosure and/or its potential applications, it is understood that variations and modifications will occur to those skilled in the art.

Accordingly, the invention or inventions described herein should be understood to be at least as broad as they are claimed and not as more narrowly defined by particular illustrative aspects provided herein.

Claims

CLAIMS What is claimed is:

1. A method for resistance spot welding comprising: contacting an assembly comprising at least two metallic parts with welding electrodes at a first location; passing a weld current through the assembly at the first location with the welding electrodes, thereby forming a first resistance spot weld securing the assembly; contacting the assembly with the welding electrodes at a second location, wherein the second location is a first distance from the first location; and passing a weld current through the assembly at the second location with the welding electrodes, thereby forming a second resistance spot weld partially overlapping the first resistance spot weld.

2. The method of claim 1, further comprising: contacting the assembly with the opposed welding electrodes at a third location, wherein the third location is a second distance from the second location, wherein the second distance is at least two times a diameter of the second resistance spot weld; and passing a weld current through the assembly at the third location with the welding electrodes, thereby forming a third resistance spot weld that does not overlap the first resistance spot weld or the second resistance spot weld.

3. The method of claim 2, wherein the second distance is at least 10 mm.

4. The method of claim 1, wherein contacting the assembly comprising the at least two metallic parts with the opposed welding electrodes at the first location comprises applying a first clamping force to the assembly; prior to contacting the assembly with the opposing welding electrodes at the second location, at least partially removing the first clamping force; and contacting the assembly with the opposing welding electrodes at the second location comprises applying a second clamping force to the assembly the opposed welding electrodes.

5. The method of claim 4, wherein at least one of the first clamping force and the second clamping force is in a range of 10 N to 20 kN.

6. The method of claim 4, wherein the second clamping force is different from the first clamping force.

7. The method of claim 1, wherein forming the first resistance spot weld forms a first indentation in a surface of the assembly and forming the second resistance spot weld forms a second indentation in the surface of the assembly that at least partially overlaps with the first indentation.

8. The method of claim 7, wherein the first indention has a first depth and the second indentation has a second depth that is the same as or less than the first depth.

9. The method of claim 1, wherein the first distance is no greater than 10 mm.

10. The method of claim 1, wherein a diameter of the first resistance spot weld is no greater than 6 * √ (governing metal thickness), wherein the governing metal thickness is determined according to American Welding Society Standard D8.2M:2017.

11. The method of claim 1, wherein a diameter of the second resistance spot weld is in a range of 3 * √ (governing metal thickness) to 6 * √ (governing metal thickness), wherein the governing metal thickness is determined according to American Welding Society Standard D8.2M:2017.

12. The method of claim 1, wherein the first resistance spot weld and the second resistance spot weld partially overlap to form an elongated fusion zone.

13. The method of claim 1, further comprising: contacting the assembly with the opposed welding electrodes at a subsequent location, wherein the subsequent location is a distance from a previously formed resistance spot weld that is no greater than a diameter of the previously formed resistance spot weld; passing a weld current through the assembly at the subsequent location with the welding electrodes, thereby forming a subsequent resistance spot weld partially overlapping the previously formed resistance spot weld; and repeating the contacting at a subsequent location and the passing the weld current at the subsequent location to form a fusion zone of a desired shape and/or size.

14. The method of claim 13, wherein the fusion zone is linear, non-linear, curved, or a combination thereof.

15. The method of claim 13, wherein the fusion zone is curved.

16. The method of claim 13, wherein the second resistance spot weld and the subsequent resistance spot weld comprise a more uniform weld than the first resistance spot weld.

17. The method of claim 1, wherein the assembly comprises three or more metallic parts.

18. The method of claim 1, wherein the first location is on at least one of a flat surface of the assembly and a curved surface of the assembly.

19. The method of claim 1, wherein the first location is on a curved surface of the assembly.

20. The method of claim 1, wherein the first location is on at least one of an edge region of the assembly and an interior region of the assembly.

21. The method of claim 1, wherein the assembly comprises at least one of a metal and a metal alloy.

22. The method of claim 1, wherein the assembly comprises at least one of iron, an iron alloy, aluminum, an aluminum alloy, magnesium, and a magnesium alloy.

23. The method of claim 1, wherein forming a first resistance spot weld securing the assembly at least partially disrupts oxides on a surface of the assembly at the first location.

24. The method of claim 23, wherein at least partially disrupting oxides from a surface of the assembly at the first location increases a uniformity of a weld current used to form the second resistance spot weld relative to a magnitude of the weld current that would be required to form the second resistance spot weld if the oxides are not at least partially removed from the surface.

25. The method of claim 1, wherein wear on the welding electrodes produced during the method is reduced relative to wear on the welding electrodes that would be produced during resistance spot welding method that does not provide partially overlapping resistance spot welds.

26. The method of claim 25, wherein the wear on the welding electrodes is reduced by utilizing a lower welding current, reduced clamping pressure, or a combination thereof relative to a resistance spot welding method that does not provide partially overlapping resistance spot welds.

27. The method of claim 1, wherein the welding electrodes define a longitudinal axis and the longitudinal axis is not substantially perpendicular to the assembly.

28. The method of claim 1, wherein the welding electrodes define a longitudinal axis and the longitudinal axis is substantially perpendicular to the assembly.

29. The method of claim 1, wherein the assembly is a first assembly, the metallic parts comprising the first assembly comprise a first material, and wherein the method further comprises: contacting a second assembly comprising at least two metallic parts with the welding electrodes at a third location, wherein the metallic parts comprising the second assembly comprise a second material different from the first material; and passing a weld current through the second assembly at the third location with the welding electrodes thereby forming a third resistance spot weld.

30. The method of claim 29, wherein the first material comprises an iron alloy and the second material comprises aluminum or an aluminum alloy.

31. The method of claim 1, wherein the first distance is no greater than a first diameter of the first resistance spot weld.

32. The method of claim 1, wherein a peak of the weld currents is at least 10% lower than a peak weld current for a single resistance spot weld with a similar tensile strength.

33. The method of claim 32, wherein the peak weld current is at least 30% lower than a peak weld current for a single resistance spot weld with a similar tensile strength.

34. A fusion zone comprising a first resistance spot weld partially overlapping a second resistance spot weld and formed by the method of claim 1.

35. The fusion zone of claim 34, wherein the fusion zone comprises an aspect ratio of at least 1.5.

36. A semi-finished or finished part produced by the method of claim 1.

37. The semi-finished or finished part of claim 36, wherein the semi-finished or finished part comprises at least one of an aerospace part or component, an automotive part or component, a transportation part or component, and a building and construction part or component.

38. A semi-finished or finished part comprising a first resistance spot weld and a second resistance spot weld overlapping with the first resistance spot weld.

39. The semi-finished or finished part of claim 38, wherein the first resistance spot weld and the second resistance spot weld are on a flat surface of the semi-finished or finished part.

40. The semi-finished or finished part of claim 38, wherein the first resistance spot weld and the second resistance spot weld are on a curved surface of the assembly.

41. The semi-finished or finished part of claim 38, wherein the first resistance spot weld and the second resistance spot weld are on at least one of an edge region of the semi-finished or finished part and an interior region of the semi-finished or finished part.

42. The semi-finished or finished part of claim 38, wherein the first resistance spot weld and the second resistance spot weld are on an edge region of the semi-finished or finished part.

43. A semi-finished or finished part comprising at least two partially overlapping resistance spot welds, wherein the at least two partially overlapping resistance spot welds, if individually classified, would be classified as Grade A, Grade B, Grade C, or a combination thereof according to Japanese Industrial Standard JIS Z 3140:2017, and wherein the at least two partially overlapping resistance spot welds together exhibit a tensile strength of a Grade A or higher weld according to Japanese Industrial Standard JIS Z 3140:2017.

44. A semi-finished or finished part comprising a welding flange, wherein a width of the welding flange is no greater than 12.5 * √governing metal thickness.

45. The semi-finished or finished part of claim 44, wherein the width of the welding flange is in a range of 7.5 * √governing metal thickness to 12.5 * √governing metal thickness.

46. The semi-finished or finished part of claim 44, wherein the semi-finished or finished part comprises aluminum or an aluminum alloy.

47. A resistance spot welding system or apparatus comprising: a power unit configured to deliver a weld current; a first electrode in electrical communication with the power unit; a second electrode in electrical communication with the power unit and positioned opposed from the first electrode; an actuator configured to move at least one of the first electrode and the second electrode relative to one another; and a controller in electrical communication with the power unit and the actuator, wherein the resistance spot welding system or apparatus is configured to perform the method of claim 1.

48. A resistance spot welding system or apparatus comprising: a power unit configured to deliver a weld current; a first electrode in electrical communication with the power unit; a second electrode in electrical communication with the power unit and positioned opposed from the first electrode; an actuator configured to move at least one of the first electrode and the second electrode relative to one another; and a controller in electrical communication with the power unit and the actuator, wherein the resistance spot welding system or apparatus is configured to: contact an assembly comprising at least two metallic parts with the first electrode and the second electrode at a first location, wherein the assembly is positioned intermediate the first electrode and the second electrode; pass a weld current between the first electrode and the second electrode through the assembly at the first location, thereby forming a first resistance spot weld securing the at least two metallic parts together; contact the assembly with the first electrode and the second electrode at a second location; and pass a weld current between the first electrode and the second electrode through the assembly at the second location, thereby forming a second resistance spot weld overlapping with the first resistance spot weld.