Abstract: A method of resistance spot welding aluminum alloy workpieces together is disclosed that involves periodically texturing and dressing of at least one of the two electrode weld faces. The texturing and dressing steps help preserve the ability of the welding electrode to deliver electrical current through the overlapping aluminum alloy workpieces being welding despite the presence of one or more oxide layers on the surfaces of the workpieces and, as such, are effective in prolonging the useful life of the electrode(s).

Abstract: A resistive welding electrode includes at least a weld face constructed of a refractory-based material that exhibits an electrical conductivity that is less than or equal to 65% of the electrical conductivity of commercially pure annealed copper as defined by the International Annealed Copper Standard (IACS). A method of using the resistive welding electrode to resistance spot weld a workpiece stack-up that includes an aluminum alloy workpiece and steel workpiece that overlap and contact each other at a faying interface is also disclosed.

Abstract: A method of resistance spot welding aluminum alloy workpieces together includes several steps. In one step a welding electrode is provided. The welding electrode has a weld face. In another step, the weld face of the welding electrode is shaped to have a desired radius of curvature. The shaped weld face is then textured to a desired surface roughness, and resistance spot welding using the welding electrode is performed to the aluminum alloy workpieces. In yet another step, the weld face is dressed to an extent sufficient to remove contamination build-up that may have accumulated on the weld face from the aluminum alloy workpieces.

Abstract: A method is disclosed for using welding electrodes with a spherically-domed welding face having concentric contoured features formed into the face for better contact with workpiece surfaces. The concentric contoured features may be initially formed by rotating a cutting tool with a contoured cutting edge, the cutting edge being in engagement with the electrode face. A similar practice may be followed to re-create the weld face surface geometry if it becomes eroded or malformed during welding use. A suitable tool may have a blade-like geometry, with a mounting portion for supporting and positioning the tool in a rotating holder and a cutting edge. The cutting edge may have a contour complementary to that of the weld face and extend at least from the center of the weld face to at least the radial extent of the concentric contoured features.

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 welding electrode for use in resistance spot welding an assembly of overlying metal workpieces that includes an aluminum alloy workpiece is disclosed. The welding electrode includes a body, a convex weld face at one end of the body, and ringed protrusions that project outwardly from the convex weld face. The ringed protrusions are positioned to make contact with, and indent into, a surface of the aluminum alloy workpiece when the convex weld face is pressed against the aluminum alloy workpiece during a spot welding event. When brought into contact with the surface of the aluminum alloy workpiece, the ringed protrusions disrupt the oxide film present on the aluminum alloy workpiece surface, which improves the spot welding process.

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: 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: Weld faces of electrodes for resistance spot welding are formed with a suitable area of protrusions and/or intrusions. The size, shape, and elevation or depths of the protrusions or intrusions are determined for the formation of suitable spot welds in and between metal workpieces such as aluminum or steel panels for vehicle bodies. The protrusions or intrusions are also conceived and used to form an image on at least a visible surface of the welded article to produce an attractive appearance on the surface of the welded sheet.

Abstract: Resistance spot welding of a thin-gauge steel workpiece to another steel workpiece is achieved by through the combined use of specific spot welding electrodes and a pulsating welding current. Each of the spot welding electrodes has a weld face that is smaller in diameter than a typical steel spot welding electrode. And the pulsating welding current that is used in conjunction with the smaller-sized spot welding electrodes includes at least two stages of electrical current pulses.

Abstract: A cutting tool that can cut concentric ringed features (e.g. protruding ridges or intruding grooves) onto a weld face of an electrical resistance welding electrode is disclosed. The cutting tool includes a cutter blade that can be rotated about the electrode weld face. The cutter blade has at least one cutting surface configured to cut the concentric ringed features onto the weld face when the cutting surface is rotated relative to the weld face while engaged therewith.

Abstract: A programmable polarity module that permits rapid on-demand control of the polarities assigned to the welding electrodes retained on a welding gun is disclosed. The programmable polarity module is electrically connectable to the welding gun and a direct current power supply unit to provide direct current to the welding electrodes for exchange during spot welding. A first interchangeable polarity output lug and a second interchangeable polarity output lug of the programmable polarity module permit the polarities of the welding electrodes to be switched without having to electrically disconnect the module from the welding gun.

Abstract: A method of resistance spot welding aluminum alloy workpieces together includes several steps. In one step a welding electrode is provided. The welding electrode has a weld face. In another step, the weld face of the welding electrode is shaped to have a desired radius of curvature. The shaped weld face is then textured to a desired surface roughness, and resistance spot welding using the welding electrode is performed to the aluminum alloy workpieces. In yet another step, the weld face is dressed to an extent sufficient to remove contamination build-up that may have accumulated on the weld face from the aluminum alloy workpieces.

Abstract: Spot welding electrodes with generally dome shaped welding faces are provided with surface features for welding both aluminum alloy sheet assemblies and steel sheet assemblies. A raised circular plateau is formed on the central axis of the dome and, in one embodiment, a suitable number of round bumps are formed in concentric spacing from adjacent the circumference of the plateau toward the circular edge of the welding face. For welding steel workpieces the plateau mainly serves as the engaging feature of the electrode. Both the plateau and concentric bumps are used in penetrating light metal surfaces for suitable current passage. In another embodiment, the domed surface is shaped with concentric terraces for engagement with the workpieces.

Abstract: Spot welding electrodes with generally dome shaped welding faces are provided with surface features for welding both aluminum alloy sheet assemblies and steel sheet assemblies. A raised circular plateau is formed on the central axis of the dome and, in one embodiment, a suitable number of round bumps are formed in concentric spacing from adjacent the circumference of the plateau toward the circular edge of the welding face. For welding steel workpieces the plateau mainly serves as the engaging feature of the electrode. Both the plateau and concentric bumps are used in penetrating light metal surfaces for suitable current passage. In another embodiment, the domed surface is shaped with concentric terraces for engagement with the workpieces.

Abstract: Welding electrodes with a welding face for contact with a metal surface for electrical resistance welding are provided with concentric contoured rings formed into the face. The rings may, for example, be ridges upstanding in the face or grooves depressed into the face. The contoured rings may be radially spaced with relatively flat (depending on the curvature of the face) intervening rings. When the electrode is pressed into contact with the surface of the workpiece for delivery of a welding current, the features of the concentric rings penetrate surface oxides or other conductivity barriers. When ongoing welding operations have eroded the contoured rings they may be rapidly reformed in the weld face in a surface re-dressing operation.

Abstract: A method of monitoring and maintaining a weld cap which is executing successive resistance welds on a plurality of workpieces includes measuring a first weld indentation formed during a first resistance weld and measuring a second weld indentation formed during a second resistance weld. The measured first and second weld indentations are compared with a severe threshold. If either of the measured first or second weld indentations is greater than the severe threshold, an abnormal condition is signaled. The method may include tip dressing the weld cap based upon the signaled abnormal condition. The method may further include determining a degradation rate between the first resistance weld and the second resistance weld. The degradation rate is the time differential between the measured first and second weld indentations, and either a first or a second tip dressing schedule is chosen based upon the determined degradation rate.

Abstract: Aluminum-base alloy workpieces have surfaces with films of aluminum oxide which inhibit good contact with weld faces of resistance spot weld electrodes and the faying surfaces of, for example, sheet workpieces stacked for welding. Sometimes, the surfaces of the sheets also are coated with an adhesive or a sealer which further complicates welding. But in accordance with this invention, weld faces of opposing, round, copper welding electrodes are pressed against opposite outside surfaces of the sheets at a spot weld site and weld current is applied to the electrodes in accordance with a three-stage weld schedule to better form each weld. The weld schedule comprises a Conditioning stage (stage 1), a weld nugget Shaping stage (stage 2), and a weld nugget Sizing stage (stage 3).

Abstract: A method for welding a plurality of aluminum to aluminum welds and a plurality of steel to steel welds using the same welder includes providing a resistance spot welder with a pair of weld electrodes having an electrode face radius of curvature in the range between 20 mm and 40 mm. The series of aluminum to aluminum welds is first made, and then, after completing the aluminum to aluminum welds, the series of steel to steel welds are made. After completing the steel to steel welds the weld electrodes are cleaned by an abrasive to remove any buildup or contamination of aluminum on the electrodes. In the event the electrodes have mushroomed, then dressing of the electrodes is provided and then the abrasive cleaning is performed to restore the surface texture.

Abstract: A cutting tool that can cut concentric ringed features (e.g. protruding ridges or intruding grooves) onto a weld face of an electrical resistance welding electrode is disclosed. The cutting tool includes a cutter blade that can be rotated about the electrode weld face. The cutter blade has at least one cutting surface configured to cut the concentric ringed features onto the weld face when the cutting surface is rotated relative to the weld face while engaged therewith.