US-12617038-B2 - Laser welding method

Abstract

In a laser welding method for welding a first metal member and a second metal member, a first wobbling process is carried out in which a first laser beam is directed in a first scanning pattern along a butt-joining line and a first welded part is formed. A second wobbling process is subsequently performed in which a second laser beam is directed in a second scanning pattern along the surface of the first welded part formed through the first wobbling process and a second welded part that is wider and shallower than the first welded part is formed overlapping the first welded part. A welded part in which delayed cracking can be prevented or suppressed is thus formed.

Inventors

• Morihiko YAMAGUCHI

Assignees

• HARMONIC DRIVE SYSTEMS INC.

Dates

Publication Date

20260505

Application Date

20211028

Claims (5)

1. 1 . A laser welding method for directing a laser beam in a prescribed scanning pattern along a butt-joining line where a first metal member and a second metal member are butt-joined and welding the first and second metal members, the laser welding method comprising: performing a first wobbling process in which a first laser beam is directed in a first scanning pattern along the butt-joining line, to form a first welded part having a prescribed width and depth along the butt-joining line, and performing a second wobbling process in which a second laser beam is directed in a second scanning pattern along a surface of the first welded part formed through the first wobbling process, to form a second welded part overlapping the first welded part, the second welded part being wider and shallower than the first welded part; a scanning speed of the first laser beam in the first wobbling process is equal to a scanning speed of the second laser beam in the second wobbling process; an output of the first laser beam in the first wobbling process is greater than an output of the second laser beam in the second wobbling process; and an amplitude, in a direction orthogonal to the butt-joining line, of the first scanning pattern of the first laser beam in the first wobbling process is less than an amplitude, in the direction orthogonal to the butt-joining line, of the second scanning pattern of the second laser beam in the second wobbling process.
2. 2 . The laser welding method according to claim 1 , wherein: the first scanning pattern is such that a position to which the first laser beam is directed moves in a direction following the butt-joining line while being drawn in a circle having a first radius, a center of the circle being located at a point on the butt-joining line; and the second scanning pattern is such that a position to which the second laser beam is directed moves in a direction following the butt-joining line while being drawn in a circle having a second radius that is less than the first radius, a center of the circle having the second radius being located at a point on the butt-joining line.
3. 3 . The laser welding method according to claim 2 , wherein each of the first and second metal members to be welded is composed of carbon steel, alloy steel, or cast iron.
4. 4 . The laser welding method according to claim 3 , wherein the output of the first laser beam is set to a value equal to or less than 1,000 W, and the second radius of the second scanning pattern is set to a value equal to or less than 1.0 mm.
5. 5 . The laser welding method according to claim 2 , wherein: the first metal member is an SUJ2 material, and the second metal member is an SNCM material; the output of the first laser beam in the first wobbling process is 800 W, and the first radius of the first scanning pattern is 0.2 mm; and the output of the second laser beam in the second wobbling process is 150 W, and the second radius of the second scanning pattern is 0.8 mm.

Description

TECHNICAL FIELD The present invention relates to a laser welding method for welding a difficult-to-weld material through wobbling-assisted laser welding. BACKGROUND ART As is well known, laser welding involves directing a laser beam along a welding location using an optical system and melting a parent material in a short time, thereby making it possible to carry out welding that is not substantially affected by heat. A known laser welding method is to carry out a wobbling process, in which the laser beam is moved using a galvanometer scanner in a direction following the welding location while irradiating the welding location so as to draw a circle, in order to increase the bead width of the weld. Carrying out the wobbling process makes it possible to weld difficult-to-weld materials that are not readily welded through laser welding and to weld different types of metals. Patent Literature 1 proposes a lap fillet welding method for aluminum alloy plates that is carried out using a wobbling process. In the welding method disclosed in Patent Literature 1, periods in which laser light irradiation is enabled and disabled are repeated in an alternating manner, thereby preventing cracking in a lap-fillet-welded part. PRIOR-ART LITERATURE Patent Literature Patent Literature 1: JP 2020-078819 A DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention When difficult-to-weld materials are joined through wobbling-assisted laser welding, a problem is presented in terms of “delayed cracking,” i.e., cracking that occurs at a welding location after a prescribed number of days has elapsed. It is an object of the present invention to propose a laser welding method in which a wobbling process is used, the laser welding method making it possible to join difficult-to-weld materials or the like such that the form of weld cracking referred to as delayed cracking does not occur. Means Used to Solve the Above-Mentioned Problems In order to achieve the above object, the present invention provides a laser welding method for directing a laser beam in a prescribed scanning pattern along a line where a first metal member and a second metal member are butt-joined and welding the first and second metal members, the laser welding method being characterized in thata first wobbling process is carried out in which a first laser beam is directed in a first scanning pattern along the butt-joining line and a first welded part having a prescribed width and depth is formed along the butt-joining line, anda second wobbling process is performed in which a second laser beam is directed in a second scanning pattern along the surface of the first welded part formed through the first wobbling process and a second welded part that is wider and shallower than the first welded part is formed overlapping the first welded part. For example, by setting the output of the first laser beam high and the amplitude for the first scanning pattern low, the first welded part is formed at a butt-joining interface between the two metal members within the range of a low width and a high depth. Conversely, by setting the output of the second laser beam low and the amplitude of the second scanning pattern high, the second welded part is formed at the butt-joining interface within the range of a high width encompassing the first welded part and a depth shallower than that of the first welded part. Effects of the Invention It was confirmed that carrying out a wobbling process in two applications and forming a welded part at a butt-joining interface between two metal members as described above makes it possible to prevent or suppress delayed cracking in the welded part. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a laser welding device; and FIG. 2 is a flow chart showing a laser welding method according to the present invention. MODE FOR CARRYING OUT THE INVENTION An embodiment of a laser welding method to which the present invention is applied is described below with reference to the accompanying drawings. A laser welding device 1 used in the present invention has a typical configuration. As shown in FIG. 1, the laser welding device 1 is configured such that a laser beam L emitted from a laser beam generator 3 provided with a laser light source 2 is directed, via scanning mirrors 4a, 5a of a pair of galvanometer scanners 4, 5, along a line 13 where a first metal member 11 and a second metal member 12 to be welded are butt-joined. A wobbling process is carried out in which the scanning mirrors 4a, 5a, which turn about orthogonal axes of rotation, are caused to turn in a synchronized manner, whereby the position to which the laser beam L is directed is scanned in a prescribed scanning pattern P along the butt-joining line 13. FIG. 2 is a schematic flow chart showing a laser welding method according to the present example. In the welding method according to the present example, the first metal member 11 and the second metal member 12 are position