Gm Global Technolgoy Operations, Inc.

David S Yang

Wu Tao

Blair E Carlson

David R Sigler

James Gregory Schroth

Anil Kumar Sachdev

Michael J Karagoulis

Pei-Chung Wang

Yu Pan

Li Sun

Jing Jing Zhang

Qi Lu

Yelena Myasnikova

Justin Allen Wolsker

Paolo A Novelletto

Wayne Cai

Dalong Gao

Hui-ping Wang

Xiang Zhao

Joshua L Solomon

Robert T Szymanski

Jeff Wang

Charles M Enloe

Curt D Horvath

Thomas B Stoughton

William P Payne

Shawn Deng

Xiaochuan Xiong

A method of laser welding together two or more overlapping metal workpieces (, or) included in a welding region () of a workpiece stack-up () involves advancing a beam spot () of a laser beam () relative to a top surface () of the workpiece stack-up along a first weld path () in a first direction () to form an elongated melt puddle () and, then, advancing the beam spot () of the laser beam () along a second weld path () in a second direction () that is opposite of the first direction while the elongated melt puddle is still in a molten state. The first weld path and the second weld path overlap so that the beam spot of the laser beam is conveyed through the elongated melt puddle when the beam spot is advanced along the second weld path.

Method for laser welding metal workpieces using a combination of weld paths

A method for joining together metal workpiece (or) includes forming a laser weld joint () in a workpiece stack-up () that fusion welds two or more overlapping metal workpiece (oror) together. The laser weld joint () has an initial top surface (). Once the laser weld joint () is formed, the method calls for impinging the laser weld joint () with a laser beam () and moving the laser beam () along the initial joint () including the initial top surface (). The laser beam () is eventually removed from the laser weld joint () to allow the melted upper portion () of the joint () to resolidify and provide the laser weld joint () with a modified top surface () that is smoother than the initial top surface (). By providing the laser weld joint with a smoother modified top surface, residual stress concentration points are removed and the laser weld joint is less liable to damage seal strips.

Method for smoothing the surface of a laser weld joint

A method of laser spot welding a workpiece stack-up () that includes at least two overlapping steel workpieces () is disclosed. The method includes directing a plurality of laser beams (&#x2033;) at the top surface () of the workpiece stack-up to create a molten steel weld pool () that penetrates into the stack-up. The molten steel weld pool is then grown to penetrate further into the stack-up by increasing an overall combined irradiance of the laser beams while reducing the total projected sectional area () of the laser beams at a plane of the top surface of the workpiece stack-up. Increasing the overall combined irradiance of the laser beams may be accomplished by moving the focal points (&#x2033;) of the laser beams closer to the top surface or by reducing the mean angle of incidence () of the laser beams so as to reduce the eccentricity of the individual projected sectional areas of the laser beams.

Multi-beam laser spot welding of coated steels

A resistance spot welding method may involve spot welding a workpiece stack-up that includes a steel workpiece and an aluminum alloy workpiece. A pair of opposed welding electrodes are pressed against opposite sides of the workpiece stack-up with one welding electrode contacting the aluminum alloy workpiece and the other welding electrode contacting the steel workpiece. The welding electrodes are constructed so that, when an electrical current is passed between the electrodes and through the workpiece stack-up, the electrical current has a greater current density in the steel workpiece than in the aluminum alloy workpiece to thereby concentrate heat within a smaller zone in the steel workpiece. Concentrating heat within a smaller zone in the steel workpiece is believed to modify the solidification behavior of the resultant molten aluminum alloy weld pool in a desirable way.

Aluminum alloy to steel welding process

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.

Electrode for resistance spot welding of dissimilar materials

A method of laser spot welding a workpiece stack-up that includes at least two overlapping steel workpieces, at least one of which includes a surface coating, is disclosed. The method includes directing a laser beam at the top surface of the workpiece stack-up to create a molten steel weld pool that penetrates into the stack-up. The molten steel weld pool is then grown to penetrate further into the stack-up by increasing an irradiance of the laser beam while reducing the projected sectional area of the laser beam at a plane of the top surface of the workpiece stack-up. Increasing the irradiance of the laser beam may be accomplished by moving a focal point of the laser beam closer to the top surface or by reducing an angle of incidence of the laser beam so as to reduce the eccentricity of the projected sectional area of the laser beam.

Method of laser spot welding coated steels

A method of laser welding a workpiece stack-up () of overlapping steel workpieces () involves heat-treating a region () of the stack-up () followed by forming a laser weld joint () that is located at least partially within the heat-treated region (). During heat-treating, one or more pre-welding laser beams () are sequentially directed at a top surface () of the workpiece stack-up () and advanced along a pre-welding beam travel pattern () so as to reduce an amount of vaporizable zinc within the stack-up (). Thereafter, the laser weld joint () is formed by directing a welding laser beam () at the top surface () of the workpiece stack-up () and advancing the welding laser beam () along a welding beam travel pattern () that at least partially overlaps with a coverage area of a pre-welding beam travel pattern () or a shared coverage area portion of multiple pre-welding beam travel patterns (). The method can help reduce an amount of vaporizable zinc within the stack-up ().

Method for laser welding steel workpieces

A method of laser welding a workpiece stack-up () that includes at least two overlapping metal workpieces () comprises advancing a laser beam () relative to a plane of a top surface () of the workpiece stack-up () from a start point () to an end point () along a beam travel pattern () at a high laser beam travel speed of greater than 8 meters per minute. The two or more overlapping metal workpieces () may be steel workpieces or they may be aluminum workpieces, and at least one of the metal workpieces () includes a surface coating (). Advancing the laser beam () along the beam travel pattern () forms a weld joint (), which includes resolidified composite workpiece material derived from each of the metal workpieces () penetrated by a molten weld pool (), that fusion welds the metal workpieces () together. The relatively high laser beam travel speed contributes to improve strength properties of the weld joint ().

Remote laser welding of overlapping metal workpieces at fast speeds

A method of laser welding a workpiece stack-up () that includes at least two overlapping aluminum workpieces comprises advancing a laser beam () relative to a plane of a top surface () of the workpiece stack-up () and along a beam travel pattern () that lies within an annular weld area () defined by an inner diameter boundary () and an outer diameter boundary () on the plane of the top surface (). The beam travel pattern () of the laser beam () surrounds a center area encircled by the annular weld area () on the plane of the top surface () so as to force entrained porosity inwards into a region of the weld joint () beneath the center area on the plane of the top surface () of the workpiece stack-up ().

Laser spot welding of overlapping aluminum workpieces

A welding electrode is disclosed that includes an electrode welding shell and a blind adapter that are joined together to cooperatively define an internal cavity. The electrode welding shell and the blind adapter may be integrally formed or they may be distinct components that are attached together. The presence of the internal cavity defined by the electrode welding shell and the blind adapter reduces the thermal mass of the welding electrode and slows the rate of conductive heat transfer from the weld face to a cooling fluid, which allows in the center of the weld face to retain heat for a longer duration once current flow through the welding electrode is terminated, thereby positively affecting the spot welding process for particular types of workpiece stack-ups including those that include an aluminum workpiece and an overlapping adjacent steel workpiece.

Welding electrode for use in a resistance spot welding workpiece stack-ups that include an aluminum workpiece and a steel workpiece

A method of laser welding a workpiece stack-up () that includes at least two overlapping steel workpieces () comprises directing a laser beam () at a top surface () of the workpiece stack-up to form a keyhole () surrounded by a molten steel weld pool (). The laser beam is conveyed along a predefined weld pattern that includes one or more nonlinear inner weld paths () and an enclosed outer peripheral weld path () surrounding the one or more nonlinear inner weld paths. During conveyance of the laser beam along the one or more nonlinear inner weld paths, the keyhole fully penetrates through the workpiece stack-up from the top surface of the stack-up to the bottom surface () of the stack-up. The method produces weld joints between the steel workpieces that do not have an intentionally imposed gap formed between their faying surfaces.

Laser welding overlapping metal workpieces

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.

Resistance spot welding steel and aluminum workpieces with electrode having insert

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

Method and apparatus for resistance spot welding overlapping steel workpieces

A method of laser welding a workpiece stack-up that includes two or more overlapping metal workpieces is disclosed. The disclosed method includes directing a laser beam at a top surface of the workpiece stack-up to create a molten metal weld pool and, optionally, a keyhole, and further gyrating the laser beam to move a focal point of the laser beam along a helical path having a central helix axis oriented transverse to the top and bottom surfaces of the workpiece stack-up. The gyration of the laser beam may even be practiced to move the focal point of the laser beam along a plurality of helical paths so as to alternately convey the focal point back-and-forth in a first overall axial direction and a second overall axial direction while advancing the laser beam relative to the top surface of the workpiece stack-up along a beam travel pattern.

Remote laser welding of overlapping metal workpieces using helical path(s)

An apparatus for trimming a sheet metal workpiece includes a base to support the sheet metal workpiece at a working position on the base. A shearing tool is connected to the base to trim the sheet metal workpiece by mechanically inducing a shearing stress on the sheet metal workpiece to form an edge at an edge location on the sheet metal workpiece. A heater is connected to the base to define a heated region on the sheet metal workpiece by heating at least the edge location on the sheet metal workpiece after the sheet metal workpiece is in the working position. The apparatus includes a temperature sensor to detect a surface temperature of the heated region.

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Pudong, China

David S Yang