Laser welding of overlapping metal workpieces assisted by varying laser beam parameters

A method of laser welding a workpiece stack-up that includes at least two overlapping metal workpieces, the method comprising:

• providing a workpiece stack-up that includes overlapping metal workpieces, the workpiece stack-up comprising at least a first metal workpiece and a second metal workpiece, the first metal workpiece providing a top surface of the workpiece stack-up and the second metal workpiece providing a bottom surface of the workpiece stack-up, wherein a faying interface is established between each pair of adjacent overlapping metal workpieces within the workpiece stack-up, and wherein all of the overlapping metal workpieces of the workpiece stack-up are steel workpieces, aluminum workpieces, or magnesium workpieces;
• advancing a beam spot of a laser beam relative to the top surface of the workpiece stack-up and along a beam travel pattern using a remote laser welding apparatus, such advancement of the beam spot of the laser beam translating a molten metal weld pool, which penetrates into the workpiece stack-up and intersects each faying interface established within the stack-up, along a corresponding route to form resolidified composite metal workpiece material derived from each of the metal workpieces penetrated by the molten metal weld pool;
• and
• varying repeatedly at least one of a power level of the laser beam, a travel speed of the laser beam, or a focal position of the laser beam while the beam spot is being advanced along the beam travel pattern from a first point to a second point.

A method of laser welding a workpiece stack-up that includes at least two overlapping metal workpieces, the method comprising:

• providing a workpiece stack-up that includes two or three overlapping metal workpieces, the workpiece stack-up comprising at least a first metal workpiece and a second metal workpiece, the first metal workpiece providing a top surface of the workpiece stack-up and the second metal workpiece providing a bottom surface of the workpiece stack-up, wherein a faying interface is established between each pair of adjacent overlapping metal workpieces within the workpiece stack-up, and wherein all of the overlapping metal workpieces of the workpiece stack-up are steel workpieces, aluminum workpieces, or magnesium workpieces;
• operating a scanning optic laser head to direct a laser beam at the top surface of the workpiece stack-up, the laser beam having a beam spot at the top surface of the workpiece stack-up and creating a molten metal weld pool and a keyhole surrounded by the molten metal weld pool, each of the molten metal weld pool and the keyhole penetrating into the workpiece stack-up from the top surface towards the bottom surface;
• and
• advancing the beam spot of the laser beam relative to the top surface of the workpiece stack-up and along a beam travel pattern through coordinated movement of tiltable scanning mirrors contained within the scanning optic laser head, such advancement of the beam spot of the laser beam translating the keyhole and the surrounding molten metal weld pool along a corresponding route to form a laser weld joint comprised of resolidified composite metal workpiece material derived from each of the metal workpieces penetrated by the molten metal weld pool;
• and
• varying repeatedly at least one of a power level of the laser beam, a travel speed of the laser beam, or a focal position of the laser beam while the beam spot is being advanced along the beam travel pattern from a first point to a second point, wherein repeatedly varying the power level comprises pulsing the power level of the laser beam between a minimum power level and a maximum power level, wherein repeatedly varying the travel speed comprises fluctuating the travel speed of the beam spot between a minimum travel speed and a maximum travel speed, and wherein repeatedly varying the focal position comprises oscillating a focal point of the laser beam along a longitudinal axis of the laser beam between a minimum focal position and a maximum focal position relative to the top surface of the workpiece stack-up.