Liquid Metal Oscillation and Arc Behaviour during Welding

165 Pages·2009·7.37 MB·English

Liquid Metal Oscillation and
Arc Behaviour during Welding
The research described in this thesis was performed in the department of
Materials Science and Technology, Delft University of Technology,
Mekelweg 2, 2628CD Delft, The Netherlands.

Front cover: Stereogram of metal transfer during gas metal arc welding by B.Y.B.
Yudodibroto.
Liquid Metal Oscillation and
Arc Behaviour during Welding

Proefschrift

ter verkrijging van de graad van doctor
aan de Technische Universiteit Delft,
op gezag van de Rector Magnificus prof.ir. K.C.A.M. Luyben,
voorzitter van het College voor Promoties,
in het openbaar te verdedigen op 25 januari 2010 om 10.00 uur

door

Raden Bagus Yudharto Bharotokusumo YUDODIBROTO
materiaalkundig ingenieur
geboren te Yogyakarta, Indonesie
Dit proefschrift is goedgekeurd door de promotor:
Prof.dr. I.M. Richardson

Samenstelling promotiecommissie:

Rector Magnificus, voorzitter
Prof.dr. I.M. Richardson, Technische Universiteit Delft, promotor
Prof.dr. G. den Ouden, Technische Universiteit Delft
Prof. Y. Hirata, Osaka University (Japan)
Prof.Dr.-Ing. U. Reisgen, RWTH Aachen University (Germany)
Prof.ir. L. van der Sluis, Technische Universiteit Delft
Prof.dr. B.J. Thijsse, Technische Universiteit Delft
Dr.ir. M.J.M. Hermans, Technische Universiteit Delft

Dr.ir. M.J.M. Hermans heeft als promotiebegeleider in belangrijke mate aan de
totstandkoming van dit proefschrift bijgedragen.

ISBN: 978-90-6464-380-4

Copyright © 2010 by B.Y.B. Yudodibroto

All rights reserved. No part of the material protected by this copyright notice may
be reproduced or utilised in any form or by any means, electronic or mechanical,
including photocopying, recording or by any information storage and retrieval
system, without permission from the author.

Printed in the Netherlands.
Contents

Used nomenclature and symbols.............................................................................iv

Chapter 1
General introduction.................................................................................................1
1.1 Background.........................................................................................................1
1.2 Research goal......................................................................................................5
1.3 Thesis outline......................................................................................................7
References.................................................................................................................8

Chapter 2
Background.............................................................................................................11
2.1 Arc welding.......................................................................................................11
2.1.1 Gas tungsten arc welding..........................................................................11
2.1.2 Gas metal arc welding...............................................................................13
2.1.3 Welding arc...............................................................................................14
2.1.4 Forces in arc welding................................................................................17
2.2 Weld pool oscillation........................................................................................18
2.2.1 Weld pool oscillation during autogenous GTA welding..........................18
2.2.2 Numerical models of weld pool oscillation..............................................28
2.2.3 Weld pool oscillation during GTA welding with filler wire addition.......29
2.2.4 Weld pool oscillation during GMA welding............................................29
2.2.5 Penetration sensing and control based on weld pool oscillation...............30
2.3 Droplet oscillation.............................................................................................33
2.3.1 Pendant droplet oscillation........................................................................33
2.3.2 Free droplet oscillation.............................................................................34
Summary.................................................................................................................35
References...............................................................................................................37

Chapter 3
Liquid metal behaviour during cold-wire GTA welding........................................43
3.1 Introduction.......................................................................................................43
3.2 Experimental procedure....................................................................................44
3.2.1 Materials and consumables.......................................................................44
3.2.2 Welding system and welding conditions..................................................44
i
3.2.3 High-speed imaging system......................................................................47
3.2.4 Monitoring and analysis of electrical welding parameters.......................47
3.2.5 Weld geometry and macro-structures.......................................................48
3.3 Results and discussion......................................................................................49
3.3.1 Autogenous GTA welding........................................................................49
3.3.2 Cold-wire GTA welding...........................................................................56
3.3.3 Uninterrupted cold-wire GTA welding.....................................................60
3.3.4 Interrupted cold-wire GTA Welding........................................................66
3.3.5 Influence of filler wire addition on the weld pool oscillations frequency 73
3.5 Conclusions.......................................................................................................74
References...............................................................................................................75

Chapter 4
Oscillation based penetration sensing during orbital cold-wire GTA welding.......77
4.1 Introduction.......................................................................................................77
4.2 Experimental conditions...................................................................................78
4.2.1 Materials and consumables.......................................................................78
4.2.2 Welding system........................................................................................79
4.3 Results and discussion......................................................................................81
4.4 Conclusions.......................................................................................................86
References...............................................................................................................87

Chapter 5
Liquid metal and arc behaviour during pulsed-current GMA welding...................89
5.1 Introduction.......................................................................................................89
5.2 Experimental procedure....................................................................................91
5.2.1 Materials and consumables.......................................................................91
5.2.2 Welding system and parameters...............................................................91
5.2.3 High-speed imaging system and image analysis......................................93
5.2.4 Electrical signal monitoring system and data analysis.............................96
5.3 Results...............................................................................................................98
5.3.1 High-speed video observation..................................................................98
5.3.2 Voltage monitoring.................................................................................111
5.4. Discussion......................................................................................................115
5.4.1 Pendant droplet behaviour......................................................................115
5.4.2 Weld pool behaviour...............................................................................116
5.4.3 Arc behaviour.........................................................................................119
5.4.4 Influence of the weld pool, the droplet and the arc on the voltage.........120
5.5. Conclusions....................................................................................................131
References.............................................................................................................133
ii
Chapter 6
General discussion and conclusions......................................................................135
6.1 General discussion..........................................................................................135
6.2 Conclusions.....................................................................................................140

Summary...............................................................................................................143

Samenvatting........................................................................................................145

Acknowledgements...............................................................................................149

List of publications...............................................................................................151

Curriculum Vitae..................................................................................................155

iii
Used nomenclature and symbols

Symbol Description Units
A weld area mm2

A area of the pendant droplet cross-section mm2
d
A area of the wire cross-section mm2
w

D diameter mm
D equivalent diameter mm
eq
D weld pool bottom diameter mm
b
D weld pool top diameter mm
t
d/dT temperature coefficient of the surface tension N m-1 K-1
f frequency resolution Hz
x eccentricity of the arc with respect to the weld pool mm

e weld eccentricity
E electric field strength V mm-1

E electric field strength at the bright arc region V mm-1
ba
E electric field strength at the normal arc region V mm-1
na
  emission coefficient of the plasma W m-3

f oscillation frequency Hz
f pulse frequency Hz
p
f reference frequency Hz
ref
f trigger frequency Hz
t
F arc force N
arc

 surface tension N m-1

h equivalent weld pool depth mm
weld pool height mm
H weld pool depth mm

I welding current A

I welding base current A
b
I welding pulse current A
p
I welding trigger current A
t
J current density A mm-2

k wave number

l arc length mm
arc
l length of the bright arc region mm
ba
iv
Symbol Description Units
l length of the pendant droplet mm
d
l length of the normal arc region mm
na
l length of the solid wire mm
w
L weld pool bottom length mm
b
L weld pool top length mm
t
 critical wavelength mm
crit

m mass kg

n number of data
N eigenvalue for the lowest oscillation mode
0
N eigenvalue for the second lowest oscillation mode
1

P arc pressure MPa
arc
p pressure atm

R arc radius mm
 density kg m-3
 resistivity of the pendant droplet m mm
d
 resistivity of the solid wire m mm
w

S sampling rate sample s-1

t time s

t base time ms
b
t pulse time ms
p
t trigger time ms
t
t welding time s
weld

U voltage V

U voltage over the anode fall region V
an
U arc voltage V
arc
U voltage over the bright arc region V
ba
U voltage over the cathode fall region V
cat
U voltage over the arc column V
col
U voltage along the liquid droplet V
d
U voltage over the normal arc region V
na
U reference voltage V
ref
U voltage along the electrode extension V
w

v welding travel speed mm s-1
wave speed mm s-1
V volume mm3

v
Symbol Description Units
W weld pool width mm

W weld pool bottom width mm
b
WFR wire feed rate mm s-1
W weld pool top width mm
t

Constant Description Units
g acceleration due to gravity 9.8 m s-2

 magnetic permeability of free space 4π×10−7 Wb A−1 m−1


Abbreviation Meaning
GMA Gas Metal Arc
GTA Gas Tungsten Arc
P-GMA Pulsed-current Gas Metal Arc
P-GTA Pulsed-current Gas Tungsten Arc
S-GMA Short-circuiting Gas Metal Arc

vi