Abstract: A method of resistance spot welding a steel workpiece and an aluminum or aluminum alloy (“aluminum”) workpiece together includes several steps. One step involves providing a workpiece stack-up with a steel workpiece and an aluminum workpiece. Another step involves attaching a cover over a weld face of a welding electrode. The cover is made of a metal material with an electrical resistivity that is greater than an electrical resistivity of a material of the welding electrode. Yet another step involves performing multiple individual resistance spot welds to the workpiece stack-up. The cover abuts the aluminum workpiece while the individual resistance spot welds are performed. And another step involves removing the cover from the welding electrode after the individual spot welds are performed.

Abstract: A method of spot welding a workpiece stack-up that includes a steel workpiece and an aluminum alloy workpiece involves passing an electrical current through the workpieces and between welding electrodes that are constructed to affect the current density of the electrical current. The welding electrodes, more specifically, are constructed to render the density of the electrical current greater in the steel workpiece than in the aluminum alloy workpiece. This difference in current densities can be accomplished by passing, at least initially, the electrical current between a weld face of the welding electrode in contact with the steel workpiece and a perimeter region of a weld face of the welding electrode in contact with the aluminum alloy workpiece.

Abstract: A method of resistance spot welding a steel workpiece and an aluminum or aluminum alloy workpiece together includes several steps. In one step a workpiece stack-up is provided. The workpiece stack-up includes a steel workpiece and an aluminum or aluminum alloy workpiece. Another step involves providing a first welding electrode that confronts the aluminum workpiece, and providing a second welding electrode that confronts the steel workpiece. The first welding electrode has an electrode body and an insert that functions to limit or eliminate heat flux into the electrode body. Other steps of the method involve bringing the first and second welding electrodes into contact with opposite sides of the workpiece stack-up and resistance spot welding the stack-up.

Abstract: A workpiece stack-up that includes at least a steel workpiece and an aluminum-based workpiece can be resistance spot welded by employing a multi-stage spot welding method in which the passage of electrical current is controlled to perform multiple stages of weld joint development. The multiple stages include: (1) a molten weld pool growth stage in which a molten weld pool is initiated and grown within the aluminum-based workpiece; (2) a molten weld pool solidification stage in which the molten weld pool is allowed to cool and solidify into a weld nugget that forms all or part of a weld joint; (3) a weld nugget re-melting stage in which at least a portion of the weld nugget is re-melted; and (4) a re-melted weld nugget solidification stage in which the re-melted portion of the weld nugget is allowed to cool and solidify.

Abstract: Resistance spot welding of a steel workpiece to an aluminum or an aluminum alloy workpiece can be facilitated by replacing the refractory aluminum oxide-based layer(s) on at least the faying surface of the aluminum or aluminum alloy workpiece with a protective coating that is more conducive to the spot welding process. The protective coating may be a metallic coating or a metal oxide conversion coating. In a preferred embodiment, the protective coating is a coating of zinc, tin, or an oxide of titanium, zirconium, chromium, or silicon.

Abstract: The present disclosure relates a bonding system formed by a process that provides a first substrate and a second substrate. A flux coating is applied to the first contact surface, and a solder-adhesive mixture comprising an adhesive and a plurality of solder elements in at least a portion of the adhesive is applied to the first contact surface. The second substrate is positioned adjacent the solder-adhesive mixture much that a second contact surface of the second surface is opposite the first contact surface, and heat is applied to the solder-adhesive mixture by way of at least one of the first and second contact surfaces. The solder-adhesive mixture is heated to a temperature that is intended to at least partially melt or at least partially vaporize the flux coating upon contact to promote a bonding condition between the solder-adhesive mixture and the first substrate.

Abstract: The present disclosure relates a bonding system formed by a process that provides a first substrate and a second substrate. A flux coating is applied to the first contact surface, and a solder-adhesive mixture comprising an adhesive and a plurality of solder elements in at least a portion of the adhesive is applied to the first contact surface. The solder-adhesive mixture is heated to at least partially melt or at least partially vaporize the flux coating to promote a bonding condition between the solder-adhesive mixture and the first substrate. Finally, the second contact surface is then positioned adjacent the solder-adhesive mixture. The present technology additionally includes methods to produce a solder-reinforced adhesive bond joining a first substrate and a second substrate.

Abstract: A method of laser welding a workpiece stack-up that includes two or three overlapping aluminum alloy workpieces involves constraining a free end of an overlapping portion of a first aluminum alloy workpiece against movement away from an underlying second aluminum alloy workpiece to counteract the thermally-induced forces that cause out-of-plane deformation of one or more of the aluminum alloy workpieces during laser welding. Such constraint of the free end of the first aluminum alloy workpiece may be accomplished by clamping, spot welding, or any other suitable practice. By constraining the free end of the first aluminum alloy workpiece, and thus inhibiting out-of-plane deformation of the aluminum alloy workpieces when laser welding is practiced in a nearby welding region, the occurrence of hot cracking is minimized or altogether eliminated in the final laser weld joint.

Abstract: A rotor for an electromagnetic machine and a method of assembling the rotor are provided. In one embodiment, the rotor includes a lamination stack disposed about a rotational axis a plurality of conductor bars disposed within corresponding slots formed in the lamination stack and extending beyond the longitudinal ends of the lamination stack. End rings are positioned at either end of the lamination stack and define a plurality of openings configured to receive the ends of the conductor bars. Each end ring includes separate inner and outer concentric rings. The inner and outer rings define radially outer and inner surfaces configured to abut one another and each of the concentric rings defines a portion of each conductor bar opening in the end ring.

Abstract: A spot welding electrode and a method of using the electrode to resistance spot weld a workpiece stack-up that includes an aluminum workpiece and an adjacent overlapping steel workpiece are disclosed. The spot welding electrode includes a weld face having a multistep conical geometry that includes a series of steps centered on a weld face axis. The series of steps comprises an innermost first step in the form of a central plateau and, additionally, one or more annular steps that surround the central plateau and cascade radially outwardly from the central plateau towards an outer perimeter of the weld face. The weld face has a conical cross-sectional profile in which a periphery of a top plateau surface of the central plateau and a periphery of a top annular step surface of each of the one or more annular steps are contained within a conical sectional area.

Abstract: A method for testing an electrochemical response of a sample, which is at least partially disposed within an electrolyte, includes macro scanning the sample. Macro scanning is applied across the entire sample and includes applying a first range of macro potential between the electrolyte and the sample, and measuring a first range of macro current between the electrolyte and the sample, while subject to the first range of macro potential. The macro scan is held at a first fixed macro potential within the first range of macro potential and the sample is micro scanned while held at the first fixed macro potential. Micro scanning is applied at individual points across a surface portion of the sample and includes measuring a plurality of first micro currents at each of the individual points of the surface portion of the sample. Each individual point is significantly smaller than the entire sample.

Abstract: A bobbin tool is disclosed that includes a top shoulder, a bottom shoulder, and an axial pin that extends between the top and bottom shoulders. The bottom shoulder has an annular shoulder end surface, a back surface opposite the annular shoulder end surface, and a side surface that joins the annular shoulder end surface and the back surface. One or more and radially-extending blades may be disposed on the side surface of the bottom shoulder and/or one or more axially-extending blades may be disposed on the back surface. The one or more blades provide the bobbin tool with an ability to friction stir weld a variable thickness workpiece assembly, axially plunged through the workpiece assembly along an axis of rotation of the bobbin tool, and/or be extracted through the workpiece assembly along an axis of rotation of the bobbin tool.

Abstract: A method of resistance spot welding workpiece stack-ups of different combinations of metal workpieces with a single weld gun using the same set of welding electrodes is disclosed. In this method, a set of opposed welding electrodes that include an original shape and oxide-disrupting structural features are used to resistance spot weld at least two of the following types of workpiece stack-ups in a particular sequence: (1) a workpiece stack-up of two or more aluminum workpieces; (2) a workpiece stack-up that includes an aluminum workpiece and an adjacent steel workpiece; and (3) a workpiece stack-up of two or more steel workpieces. The spot welding sequence calls for completing all of the aluminum-to-aluminum spot welds and/or all of the steel-to-steel spot welds last.

Abstract: A series of many electrical resistance spot welds is to be formed in members of an assembled, but un-joined, body that presents workpiece stack-ups of various combinations of metal workpieces including all aluminum workpieces, all steel workpieces, and a combination of aluminum and steel workpieces. A pair of spot welding electrodes, each with a specified weld face that includes oxide-disrupting features, is used to form the required numbers of aluminum-to-aluminum spot welds, aluminum-to-steel spot welds, and steel-to-steel spot welds. A predetermined sequence of forming the various spot welds may be specified for extending the number of spot welds that can be made before the weld faces must be restored. And, during at least one of the aluminum-to-steel spot welds, a cover is inserted between the weld face of one of the welding electrodes and a side of a workpiece stack-up that includes the adjacent aluminum and steel workpieces.

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

Abstract: A method of resistance spot welding a steel workpiece and an aluminum or aluminum alloy workpiece, and a welding electrode used therein. In one step of the method a workpiece stack-up is provided. The workpiece stack-up includes a steel workpiece and an aluminum or aluminum alloy workpiece. Another step of the method involves contacting the aluminum or aluminum alloy workpiece with a weld face of the welding electrode. The welding electrode has a body and an insert. The insert is composed of a material having an electrical resistivity that is greater than an electrical resistivity of the material of the body. The weld face has a first section defined by a surface of the insert and has a second section defined by a surface of the body. Both the first and second sections make surface-to-surface contact with the aluminum or aluminum alloy workpiece amid resistance spot welding.

Abstract: A radially slotted welding electrode is disclosed that may be used in conjunction with a companion second welding electrode to conduct resistance spot welding on a workpiece stack-up assembly that includes a steel workpiece and an overlapping adjacent aluminum workpiece, especially when an intermediate organic material layer is disposed between the workpiece faying surfaces of the steel and aluminum workpieces. The radially slotted welding electrode includes a weld face that has a central upstanding plateau and a convex dome portion that surrounds the central upstanding plateau and which includes a plurality of circumferentially spaced trapezoidal weld face sections that include transverse upstanding arcuate ridges. Together, the central upstanding plateau and the trapezoidal weld face sections of the convex dome portion define an annular channel that surrounds the central plateau and a plurality of radial slots that communicate with and extend outwards from the central channel.

Abstract: A spot weld may be formed between an aluminum workpiece and an adjacent overlapping steel workpiece with the use of opposed spot welding electrodes that have mating weld faces designed for engagement with the outer surfaces of the workpiece stack-up assembly. The electrode that engages the stack-up assembly proximate the aluminum workpiece includes a central ascending convex surface and the electrode that engages the stack-up assembly proximate the steel workpiece has an annular surface. The mating weld faces of the first and second spot welding electrodes distribute the passing electrical current along a radially outwardly expanding flow path to provide a more uniform temperature distribution over the intended spot weld interface and may also produce a deformed bonding interface within the formed weld joint. Each of these events can beneficially affect the strength of the weld joint.

Abstract: A method of adhesive weld bonding a light metal workpiece and a steel workpiece is disclosed that includes applying a plurality of discrete adhesive ribbons to a faying surface of the light metal workpiece, the faying surface of the steel workpiece, or both faying surfaces, and then assembling the workpieces together to establish one or more adhesive zones between the faying surfaces of the light metal and steel workpieces and a plurality of adhesive free zones amongst the adhesive zone(s). The method further includes forming a resistance spot weld that bonds the the light metal workpiece and the steel workpiece together at a spot weld location within one of the adhesive free zones. The formed spot weld includes a weld joint contained within the light metal workpiece that bonds to the faying interface of the steel workpiece.

Abstract: A cutting tool that can simultaneously cut and restore asymmetric weld face geometries of two welding electrodes that are subject to different degradation mechanisms is disclosed along with a method of using such a cutting tool during resistance spot welding of workpiece stack-ups that include dissimilar metal workpieces. The cutting tool includes a first cutting socket and a second cutting socket. The first cutting socket is defined by one or more first shearing surfaces and the second cutting is defined by one or more second shearing surfaces. The first shearing surface(s) and the second shearing surface(s) are profiled to cut and restore a first weld face geometry and a second weld face geometry, respectively, that are different from each other upon receipt of electrode weld faces within the cutting sockets and rotation of the cutting tool.