Pores are often observed in deep welds by pulsed laser welding process. This article develops a mathematical model to understand the physical phenomena related to pore formation and, subsequently, to seek solutions for pore prevention. Our simulation results reveal that, in keyhole laser welding, there are two competing mechanisms contributing to pore formation: one is the solidification rate of the molten metal and the other is the speed that molten metal backfills the keyhole after the termination of laser power. Our model has demonstrated that by controlling the laser beam profile (which in turn controls the solidification rate) or by applying an electromagnetic force after irradiation termination (which in turn controls the molten metal flow), pores can be reduced or even eliminated in the weld.

1.
T.
Ishide
,
S.
Tsubota
,
M.
Nayama
,
Y.
Shimokusu
,
T.
Nagashima
and
K.
Okimura
, 10 kW class YAG laser application for heavy components,
SPIE high-power lasers in manufacturing
, Vol.
3888
,
Osaka
,
1999
, pp.
543
550
.
2.
S.
Katayama
,
N.
Seto
,
J.
Kim
and
A.
Matsunawa
, Formation mechanism and reduction method of porosity in laser welding of stainless steel,
ICALEO
,
1997
, section G, pp.
83
92
.
3.
S.
Katayama
and
A.
Matsunawa
,
Formation mechanism and prevention of defects in laser welding of aluminum alloys
,
Proc. of CISFFEL 6
, Vol.
1
,
1998
, pp.
215
222
.
4.
S.
Katayama
,
N.
Seto
,
J.
Kim
and
A.
Matsunawa
, Formation mechanism and suppression procedure of porosity in high power laser welding of aluminum alloys,
ICALEO
,
1998
, Section C, pp.
24
33
.
5.
S.
Katayama
,
N.
Seto
,
M.
Mizutani
and
A.
Matsunawa
, Formation mechanism of porosity in high power YAG laser welding,
ICALEO
,
2000
, Section C, pp.
16
25
.
6.
N.
Seto
,
S.
Katayama
and
A.
Matsunawa
, A high–speed simultaneous observation of plasma and keyhole behavior during high power CO2 laser welding,
ICALEO
,
1999
, Section E, pp.
19
27
.
7.
S.
Katayama
,
S.
Kohsaka
,
M.
Mizutani
,
K.
Nishizawa
and
A.
Matsunawa
, Pulse shape optimization for defect prevention in pulsed laser welding of stainless steels,
ICALEO
,
1993
, pp.
487
497
.
8.
S.
Katayama
,
Y.
Kobayashi
,
N.
Seto
,
M.
Mizutani
and
A.
Matsunawa
, Effect of vacuum on penetration and defects in laser welding,
ICALEO
,
2000
, Section C, pp.
182
191
.
9.
S.
Tsukamoto
,
I.
Kawaguchi
and
G.
Arakane
, Suppression of welding defects in deep penetration CO2 laser welding,
ICALEO
,
2000
, Section C, pp.
7
15
.
10.
A.
Todate
,
Y.
Ueno
,
M.
Katsuki
,
S.
Katayama
and
A.
Matsunawa
, YAG laser weldability of carbon steel in CO2 shielding gas,
Proc. The national meeting of JWS
, No. 66, April
2000
; pp.
144
145
(in Japanese).
11.
W.H.
Zhang
, Modeling the Formation and Collapse of a Keyhole during Laser Welding Process, Ph.D. Thesis,
University of Missouri-Rolla
,
2002
.
12.
D.B.
Kothe
,
R.C.
Mjolsness
and
M.D.
Torrey
, Ripple: A computer program for incompressible flows with free surfaces, LA-12007-MS,
Los Alamos National Laboratory
,
1991
.
13.
K.C.
Chiang
and
H.L.
Tsai
,
Shrinkage-induced fluid flow and domain change in two-dimensional alloy solidification
,
Int. J. Heat Mass Transfer
, Vol.
35
,
1992
,
1763
1769
.
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