Method of Laser Welding

A method of joining a first and a second object, each object having a substantially flat surface. The method includes the steps of: placing the objects with their surfaces in a contacting relationship along an interface, with their surfaces substantially parallel, the interface having a peripheral edge, irradiating a laser beam with a focal point onto the peripheral edge in the direction of the interface while the plates are in a contacting relationship, and moving the focal point of the laser beam along the interface in a direction transversely to the edge, to a position at a distance from the edge.

CROSS-REFERENCE TO RELATED APPLICATION

The disclosure claims the benefit of priority of co-pending European Patent Application No. 21176681.1, filed on May 28, 2021, and entitled “Method of Laser Welding,” the contents of which are incorporated in full by reference herein.

TECHNICAL FIELD

The disclosure relates to a method of laser welding a first and a second object, each object having a substantially flat surface, the method including the step of placing the objects with their surfaces in a contacting relationship along an interface.

BACKGROUND

It is known to join two metal trips in a contacting relationship by bringing the strips together between two pressure rollers. The strips are spaced apart before entering between the pressure rollers and a laser beam irradiates the strips at their point of contact prior to being pressed together to form a kissing weld.

The known method includes heavy rollers for compression of the plates and requires a relatively large footprint.

SUMMARY

It is an object of the disclosure to provide a method of laser welding two metal objects with their surfaces in a contacting relationship, thereby obtaining a strong bond. It is a further object of the disclosure to provide a method of laser welding two objects that requires a relatively small footprint and that can be easily integrated in a production environment.

Herein, a method according to the disclosure includes the steps of:placing the objects with their surfaces in a contacting relationship along the interface with their surfaces substantially parallel, the interface extending to a peripheral edge,irradiating a laser beam with a focal point onto the peripheral edge in the direction of the interface while the objects are in a contacting parallel relationship, andmoving the focal point of the laser beam along the interface in a direction transverse to the peripheral edge, to a position at a distance from the edge.

The laser beam was found to penetrate a relatively long distance from the peripheral edge by melting both metals on either side of the interface while forming a strong bond of the molten metals after switching off the beam.

In an embodiment of the method according to the disclosure, the first object includes aluminum, the second object includes copper. It was found that the welding method according to the disclosure achieves a strong copper to aluminum bond that is not brittle, over a large bonding area, resulting in a strong bond.

DESCRIPTION OF EMBODIMENTS

FIG.1shows an aluminum plate1and a copper plate2, each with a substantially flat contact surface3,4. The surfaces3,4are placed in a contacting relationship along the interface5.

The plates1,2may have a thickness T of for instance 1 mm-10 mm and may be of larger thickness such as up to 20 mm and more.

A laser source10generates a laser beam8that is focused through optics12in a focal point9onto a perimeter7of the plates3,4at the position of the interface5. In a test set up, a copper and aluminum plate were placed, according to the disclosure, with their flat surfaces in a contacting relationship, each plate having a thickness of 3 mm. Using a Trudisk 6001 laser welding device, marketed by the Trumpf GmbH, Germany, at a Laser power of 3000 W and a focal spot diameter of 0,17 mm, the laser was irradiated onto the perimeter7of the stacked plates, to melt the metal surfaces on each side of the interface5.

The focal point9of the laser penetrated a distance D of over 5 mm between the plates1,2, and as long as several cm, along the interface5, away from the perimeter7.

FIG.2shows an example of the weld15formed along the interface5of an aluminum plate1and copper plate15along a length D that may be up to several cm, or longer.

FIG.3shows an enlarged cross-section of the weld15, in a vertical orientation, along which a homogeneous alloy of the copper and aluminum is formed over a large surface area and a strong bond is achieved.