Method for splash-free welding, in particular using a solid-state laser

Patent metadata

Field	Value
Publication number	US-11786989-B2
Application number	US-202117317925-A
Country	US
Kind code	B2
Filing date	May 12, 2021
Priority date	Nov 12, 2018
Publication date	Oct 17, 2023
Grant date	Oct 17, 2023

Abstract

Laser beam welding a workpiece includes: generating first and second beam areas on the workpiece by first and second laser beams, respectively. The beam areas are guided in a feed direction relative to the workpiece. Centroids of the beam areas are not coinciding. The first beam area runs ahead of the second beam area. A length of the first beam area, measured transversely to the feed direction, is greater than or equal to that of the second. A surface area of the first beam area is greater than that of the second. A width of the first beam area, measured in the feed direction, is greater than or equal to that of the second. A laser power of the first laser beam is greater than that of the second. The second laser beam is irradiated into a weld pool generated by the first laser beam.

First claim

The invention claimed is:

1. A method for laser beam welding a workpiece, the method comprising:
generating at least a first beam area on the workpiece by a first laser beam; and
generating a second beam area on the workpiece by a second laser beam,
wherein the first beam area and the second beam area are guided in a feed direction relative to the workpiece,
wherein a centroid of the first beam area and a centroid of the second beam area are not coinciding,
wherein the first beam area runs ahead of the second beam area,
wherein a length (LE 1 ) of the first beam area, measured transversely to the feed direction, is greater than or equal to a length (LE 2 ) of the second beam area,
a surface area of the first beam area is greater than a surface area of the second beam area,
wherein a width (BE 1 ) of the first beam area, measured in the feed direction, is greater than or equal to a width (BE 2 ) of the second beam area,
wherein a laser power of the first laser beam is greater than a laser power of the second laser beam,
wherein the second laser beam is irradiated into a weld pool generated by the first laser beam, and
wherein a focus diameter (FD 2 ) of the second laser beam satisfies, at least in one direction transverse to the feed direction:

F
⁢

D
2

≥

d
Min

,

with
⁢

d
Min

=

k

d
,
Min

·
s

v

,

with k d,Min : a material-specific constant, with s: a workpiece thickness to be welded, and with v: a feed speed for the laser beam welding,
wherein the workpiece comprises stainless steel or structural steel, and wherein the material-specific constant k d,Min is between 5 and 20 mm 2 /s for stainless steel, and is between 8 and 20 mm 2 /s for structural steel.

2. The method according to claim 1 , wherein the first laser beam and the second laser beam are generated using one or more solid-state lasers.

3. The method according to claim 1 , wherein a focus diameter (FD 2 ) of the second laser beam is smaller than a focus diameter (FD 1 ) of the first laser beam, and a power density of the second laser beam is greater than a power density of the first laser beam.

4. The method according to claim 1 , wherein the length (LE 1 ) of the first beam area satisfies:
LE 1 ≥b Min , with b Min =2* d Min .

5. The method according to claim 1 , wherein a distance between the centroid of the first beam area and the centroid of the second beam area in the feed direction satisfies:
a≥a Min , with a Min =2* d Min .

6. The method according to claim 1 ,
the method comprising laser beam welding a plurality of workpieces of different workpiece thicknesses, the workpieces comprising the workpiece,
wherein a distance a between the centroid of the first beam area and the centroid of the second beam area in the feed direction is selected so as to be greater for workpieces having a greater workpiece thickness.

7. The method according to claim 1 , wherein the first beam area and the second beam area overlap.

8. The method according to claim 1 , wherein the first beam area and the second beam area are separated from one another.

9. The method according to claim 1 , wherein the first beam area comprises at least two partial beam areas lined up in a direction transverse to the feed direction and separated from one another.

10. The method according to claim 1 , wherein the first beam area comprises at least two partial beam areas lined up in the feed direction and separated from one another.

11. The method according to claim 1 , wherein the first beam area comprises at least two partial beam areas lined up in the feed direction and separated from one another, and wherein, a distance a′ between a centroid of a foremost partial beam area of the first beam area and the centroid of the second beam area in the feed direction satisfies:
a′≥a Min , with a Min =2* d Min .

12. The method according to claim 10 ,
the method comprising laser beam welding a plurality of workpieces of different workpiece thicknesses, the workpieces comprising the workpiece,
wherein a number of partial beam areas lined up in the feed direction is selected so as to be larger with a larger workpiece thickness.

13. The method according to claim 10 , wherein the partial beam areas lined up in the feed direction have a length, measured transversely to the feed direction, that decreases toward the second beam area.

14. The method according to claim 1 , wherein the laser beam welding is implemented as full penetration welding.

15. The method according to claim 9 , wherein the partial beam areas are circular.

16. The method according to claim 10 , wherein the partial beam areas are in a shape of a rectangle or a circular ring segment.

17. The method for laser beam welding a workpiece, the method comprising:
generating at least a first beam area on the workpiece by a first laser beam; and
generating a second beam area on the workpiece by a second laser beam,
wherein the first beam area and the second beam area are guided in a feed direction relative to the workpiece,
wherein a centroid of the first beam area and a centroid of the second beam area are not coinciding,
wherein the first beam area runs ahead of the second beam area,
wherein a length (LE 1 ) of the first beam area, measured transversely to the feed direction, is greater than or equal to a length (LE 2 ) of the second beam area,
a surface area of the first beam area is greater than a surface area of the second beam area,
wherein a width (BE 1 ) of the first beam area, measured in the feed direction, is greater than or equal to a width (BE 2 ) of the second beam area,
wherein a laser power of the first laser beam is greater than a laser power of the second laser beam,
wherein the second laser beam is irradiated into a weld pool generated by the first laser beam, and
wherein a distance between the centroid of the first beam area and the centroid of the second beam area in the feed direction satisfies:
a≥a Min , with a Min =2* d Min , with

d
Min

=

k

d
,
Min

·
s

v

Assignees

• Trumpf Laser & Systemtechnik Gmbh

Inventors

• Haug Patrick
• Speker Nicolai
• Opitz Marco
• Hesse Tim

Classifications

• B23K26/035 Primary

  Aligning the laser beam (automatically B23K26/042) · CPC title

• B23K26/0613

  having a common axis (B23K26/0619 takes precedence) · CPC title

• B23K26/244

  Overlap seam welding · CPC title

• B23K26/32

  taking account of the properties of the material involved · CPC title

• B23K26/24 Primary

  Seam welding · CPC title