Laser power is absorbed in laser keyhole welding by several mechanisms. In CW CO2 welding absorption into the partially ionised vapour in the keyhole by the processes of inverse bremsstrahlung and thermal conduction can be important. The energy is then transferred to the work piece by thermal conduction through the vapour. This process has recently been partially modelled mathematically. Experimental observations give a wide range of values for the possible vapour temperatures and as a result, widely varying estimates for the power absorbed can be obtained. The recent theoretical models have tended to give too high a value when compared to expectations. Most models ignore convection in the vapour, but a recent example [1] presents a theoretical form that allows for the effect in a simple manner. However, it does not attempt to find any solutions and goes no further than showing by order of magnitude arguments, that the convection effect is likely to matter. It probably has the consequence that temperature estimates obtained theoretically which ignore convection, almost certainly give values that are a good deal too high. In this paper, the model derived there is solved and the consequences studied, confirming this expectation.

1.
Dowden
,
J.M.
(
2005
)
Analytical Modelling Of Energy Transfer Through The Vapour In Laser Keyhole Welding
.
Proc. 10th NOLAMP Conference
.
Luleå University of Technology
;
127
138
.
2.
Gillies
,
B.
(
2000
)
The Double Free Boundary Value Problem of Laser Welding of Thin Sheets at Medium Speeds
. Ph.D. Thesis,
Heriot-Watt Univ.
,
Edinburgh
.
3.
Dowden
,
J.M.
(
2001
)
The Mathematics of Thermal Modeling
,
Chapman & Hall
,
225
240
.
4.
Dowden
,
J.M.
,
Kapadia
,
P.
&
Postacio lu
,
N.
(
1989
)
An analysis of the laser-plasma interaction in laser keyhole welding
.
J. Phys. D: Appl. Phys.
22
,
741
749
.
5.
Kosuge
,
S.
et al. (
1986
)
Discussion on CO2 laser induced plasmas
.
Reprints of the National Meeting of the Japan Welding Society
39
,
68
.
6.
Rockstroh
,
T.J.
&
Mazumder
,
J.
(
1985
)
Infrared thermographic temperature measurement during laser heat treatment
.
Applied Optics
24
(
9
),
1343
1345
.
7.
Sokolowski
,
W.
,
Herziger
,
G.
&
Beyer
,
E.
(
1989
)
Spectroscopic study of laser-induced plasma in the welding process of steel and aluminium
.
SPIE: High Power Lasers and Laser Machining Technology
1132
,
288
295
.
8.
Bermejo
,
D.
,
Fabbro
,
R.
,
Sabatier
,
L.
,
Leprince
,
L.
&
Orza
,
J.M.
(
1990
)
Spectroscopic studies of iron plasmas induced by a continuous high power CO2 laser
.
SPIE: The Int. Soc. for Optical Engineering
,
1279
,
118
126
.
9.
Hughes
,
T.P.
(
1975
)
Plasmas and Laser Light
.
Adam Hilger
,
London
.
10.
Vicenti
,
W.G.
&
Kruger
,
C.H.
(
1965
)
Introduction to Physical Gas Dynamics
.
Wiley
,
New York
.
11.
Eliezer
,
S.
,
Ghatak
,
A.
&
Hora
,
H.
(
1986
)
Theory and Applications: Equations of State
.
Cambridge
.
12.
Spitzer
,
L.
(
1962
)
Physics of Fully Ionized Gases
.
Interscience
,
New York
.
13.
Dowden
,
J.M.
(
2006
)
The effect of convection on the temperature in the keyhole in laser keyhole welding
.
Proceedings of M4PL 19
.
IFLT – TU Wien
.
14.
Emsley
,
J.
(
1998
)
The Elements
.
Clarendon Press
.
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