Method for smoothing the surface of a laser weld joint

A method comprising:

• providing a workpiece stack-up that includes two or more metal workpieces that overlap to define a welding region, the welding region of the workpiece stack-up having a top surface and a bottom surface and further establishing a faying interface between each pair of adjacent metal workpieces included in the workpiece stack-up, and wherein all of the two or more metal workpieces in the workpiece stack-up are steel workpieces, aluminum workpieces, or magnesium workpieces;
• directing a first laser beam at the top surface of the workpiece stack-up to create a molten metal weld pool that penetrates into the workpiece stack-up from the top surface of the stack-up towards the bottom surface of the stack-up and intersects the at least one faying interface established between the top and bottom surfaces of the workpiece stack-up;
• advancing a beam spot of the first laser beam relative to the top surface of the workpiece stack-up along a beam travel pattern to translate the molten metal weld pool along a corresponding route within the workpiece stack-up to form a laser weld joint comprised of resolidified composite workpiece material derived from each of the metal workpieces penetrated by the molten metal weld pool, the laser weld joint having an initial top surface adjacent to the top surface of the workpiece stack-up;
• impinging the laser weld joint with a second laser beam and moving the second laser beam along the initial top surface of the laser weld joint to melt an upper portion of the laser weld joint including the initial top surface of the laser weld joint;
• and
• removing the second laser beam from the laser weld joint to allow the upper portion of the laser weld joint to resolidify and provide the laser weld joint with a modified top surface that is smoother than the initial top surface of the laser weld joint.

A method comprising:

• providing a workpiece stack-up that includes two or three metal workpieces that overlap to define a welding region, the welding region of the workpiece stack-up having a top surface and a bottom surface and further establishing a faying interface between each pair of adjacent metal workpieces included in the workpiece stack-up, and wherein all of the two or more metal workpieces in the workpiece stack-up are steel workpieces, aluminum workpieces, or magnesium workpieces;
• operating a scanning optic laser head of a remote laser welding apparatus to direct a first laser beam at the top surface of the workpiece stack-up and, additionally, to move a beam spot of the first laser beam relative to the top surface of the workpiece stack-up within the welding region and along a beam travel pattern to translate a keyhole and a surrounding molten metal weld pool along a corresponding route within the workpiece stack-up, the translation of the keyhole and the surrounding molten metal weld pool forming a laser weld joint that extends into the workpiece stack-up and intersects each faying interface established between the top and bottom surfaces of the workpiece stack-up to fusion weld the two or three metal workpieces together, the laser weld joint having an initial top surface adjacent to the top surface of the workpiece stack-up;
• operating the scanning optic laser head of the remote laser welding apparatus to impinge the initial top surface of the laser weld joint with a second laser beam and, additionally, to move the second laser beam along the initial top surface of the laser weld joint to melt an upper portion of the laser weld joint including the initial top surface of the laser weld joint, the upper portion that is melted by the second laser beam constituting between 10 vol % and 30 vol % of the laser weld joint;
• and
• removing the second laser beam from the laser weld joint to allow the upper portion of the laser weld joint to resolidify and provide the laser weld joint with a modified top surface that is smoother than the initial top surface of the laser weld joint.