The details of the melt flow dynamics in deep-penetration welding as well as in laser cutting are still not completely understood. In addition, control of the melt flow might help to suppress or eliminate defects such as spattering, humping or dross formation.

The present paper describes the use of a short-pulse laser to influence the behavior of the melt flow. First results show that the melt pool dynamics can be influenced very significantly with less than 1% of additional average power of pulsed laser radiation.

A 4’000 W lamp-pumped cw solid-state laser focused to a spot diameter of 450 µ m was used as heating source to generate a keyhole and the melt pool. A diode-pumped Q-switched (QS-) laser delivering 20 ns, 4 mJ pulses at 4 kHz was used to influence the melt pool. The two lasers were overlapped in the interaction region by angular multiplexing. The position of the QS-laser could be adjusted arbitrarily with respect to the cw-laser. The experiments were made on sheets of stainless steel and aluminum and analyzed by means of a high-speed camera.

Completely different effects were observed depending on the position of the QS-laser with respect to the keyhole proving that the melt pool dynamics can significantly be influenced with the additional short laser pulses. These preliminary results allow for estimations on the physical quantities such as short pulse absorption, energy transfer and melt flow speed.

1.
Lütke
,
M.
;
Himme
,
T.
;
Wetzig
,
A.
:
Recent Developments in Remote-Cutting
. Fraunhofer IRB-Verlag (
2009
) 5.
Internationaler Workshop „Faserlaser“, CD-ROM
2.
Petring
,
D.
;
Schneider
,
F.
;
Wolf
,
N.
;
Nazery
,
V.
:
How beam Quality, Power an Wavelength Influence Laser Cutting and Welding Process
. In:
Proceedings of LAMP
2009
(paper 82)
3.
Schäfer
P.
Vapour Pressure Fusion Cutting: A new Remote Cutting Method with Potential?
In:
Proc. of the 12th Intl. Workshop (Hirschegg, Austria 2010) - Process stability in laser beam welding
4.
Mann
,
K.
;
Brockmann
,
R.
;
Hangst
,
A.
:
Beam Management of High Brilliance Solid State Lasers
. Fraunhofer IRB-Verlag (
2008
) 4.
Internationaler Workshop „Faserlaser“, CD-ROM
5.
Weber
,
R.
:
Laser Induced High Pressure Cutting – An estimate
. In:
Proc. of the 11th Intl. Workshop
(
Hirschegg, Austria
2009
) - Process stability in laser beam welding
6.
Fox
,
J. A.
:
A method for improving continious wave laser penetration of metal targets
.
Journal of Applied Physics
26
(
1975
) Nr. 12, S.
682
684
.
7.
Robin
,
J.
;
Nordin
,
P.
:
Improved cw laser penetration of solids using a superimposed pulsed laser
.
Applied Physics Letters
.
29
(
1976
), Nr.1, S.
3
5
8.
Lehane
,
C.
;
Kwok
,
H. S.
:
Enhanced drilling using a dual-pulse Nd:YAG laser
.
Journal of Applied Physics
73
(
2001
) S.
45
80
9.
Berger
,
P.
;
Schuster
R.
,
Schäfer
,
P.
;
Hügel
,
H.
:
Effect of Moving Humps on Process Quality of Welding and Cutting
,
12th International Workshop: Process stability in laser beam welding II
,
10th–12th February 2010
,
Hirschegg
10.
Von Allmen
,
M.
:
Laser-Beam Interactions with Materials
.
Springer
(
Berlin
),
1987
This content is only available via PDF.
You do not currently have access to this content.