SOME STUDIES ON MIG WELDING OF
ALUMINIUM AND ITS ALLOY 5083
A THESIS
SUBMITTED IN FULFILMENT OF THE
REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
By
SUNIL PANDEY
0EL.t
DEPARTMENT OF MECHANICAL ENGINEERING
INDIAN INSTITUTE OF TECHNOLOGY, DELHI
INDIA
APRIL 1986
CERTIFICATE
This is to certify that the Thesis entitled,"SOME STUDIES ON
MIG WELDING OF ALUMINIUM AND ITS ALLOY 5083"-being submitted by
Mr. Sunil Pandey to the Indian Institute'of Technology, Delhi,
for the award of the degree of "Doctor of Philosophy" in
Mechanical Engineering is a record of bonafide research work
carried out by him. He has worked under my guidance and
supervision and has fulfilled the requirements for the submission
of this Thesis which has reached the requisite standard.
The results contained in this Thesis have not been submitted,
in part or in full, to any other University or Institute for
the award of any degree or diploma.
April 1986-
(Dr. R.S. Parmar)c_
Department of Mechanical Engineering,
Indian Institute of Technology,Delhi,
Hauz Khas, New Delhi-110016,INDIA.
ii
ACKNOWLEDGEMENTS
The author is highly grateful and indebted to Dr. R.S. Parmar,
Assistant Professor of Mechanical Engineering Department,
Indian Institute of Technology, Delhi, for his precise guidance,
lively discussions, moral support and motivation without which
it would have not been possible to accomplish this work.
Prof. N.K. Tewari, Dr. R.N. Mittal, Dr. K. Gupta of Mechanical
Engineering Department are thanked for the valuable help extended
by them in providing material and support at various stages of
this work.
Professors B.L. Juneja, Head, and U.R.K. Rao are thanked for the
moral support and encouragement given throughout the performance
of the work.
Dr. R.K. Pandey, Assistant Professor and Dr. A.N. Kumar of
Applied Mechanics Department, I.I.T., Delhi, are thanked for the
valuable suggestions and guidance in carrying out the work on
fracture toughness studies. Thanks are also due to my colleagues
Mr. U.T.S. Pillai and Mr. V.R. Ranganath, both research scholars
in the same department for rendering all possible help in conducting the tests for fracture toughness studies.
Mr. Rajmani Rai, Deputy Director (Programmes), Delhi Doordarshan
is thanked for allowing the use of processing facility for 16 mm.
B & W cine films concerning metal transfer studies. Mr. K.A.
Subramanium, Film Processing Supervisor and Nh. George Blesson,
Film Processor of Delhi Doordarshan are thanked for carrying
out the job in the best possible manner.
iii
Mr. A.K. Aggarwal, Senior Design Engineer, I.D.D.C., is thanked
for lending equipment and providing technical support whenever
needed during the course of work. The author wishes that his
smiling and ever helping attitude should become an example for
others.
Mr. S. Santhanam, Officer Incharge, Film Processing Lab, Films
Division, Ministry of I&B is thanked for his ever helping
attitude shown during the processing of 16 mm B&W negative cine
films and in the making of rush prints in his lab.
Mr. D.0 Sharma of Textile Department is thanked for displaying
lot of patience during the scanning of fractured specimens on
SEM.
Thanks are also due to Mr. Sivakumar, Mr. Kirpal Singh, Mr. Azad
Pal Singh, and Mr. Ramchander of Welding and Production Engineering
Labs. and all the supporting staff of I.I.T., Delhi for rendering
help at different stages of investigations.
Mr. V.P. Gulati, and Mr. N.K. Chowdhry of Mechanical Engineering
Department, I.I.T. Delhi, are thanked for excellent typing and
tracings respectively.
Finally, I sincerely thank all my relatives and friends who
stood by me during the difficult time and provided lot of help
and encouragement to accomplish this work.
April 11, 1986: (SUNIL PA DEY)
iv
ABSTRACT
With the ever increasing use of aluminiuftt and its alloys
it is but natural to find suitable means of fabricating
them into different shapes. Welding with its intrinsic
advantages naturally attracts the attention of a fabrication engineer. Welding of aluminium and its alloys unlike
welding of low carbon structural steels, however, is not a
straightforward technique. Thus inspite of the fact that
aluminium is a weldable material it is not easy to establish
proper parameters to achieve a sound weld. This is because
of the lack of data on the different aspects of aluminium
welds.
Due to the increased use' of aluminium but a lack of data
about its welding a situation is developing where basic
research in this field is urgently called for particularly
in a country like India where the said conditions are prevalent
for quite sometime . In the light of these facts it was
decided to investigate into the various aspects of welding
aluminium so as to make whatever contribution possible towards
better understanding of the vital fabrication technology.
Research work was therefore undertaken with a view to studying
different aspects of the problem viz., metal transfer, bead
geometry and shape relationships, microstructure and microhardness, weld joint design and fracture toughness of weldments.
To carryout welding by mechanised means a manipulator was
designed and developed with the help of which welding was
done with control panel quite a distance from the site of
welding so as to protect the investigator and the welder from
the ill effects of fumes and harmful .radiations.
The welding system itself was calibrated to determine accurately
the welding current. And for that purpose a large number of
experiments were carried out to develop a relationship between
welding current on one hand and wire feed rate, arc voltage
and nozzle to plate distance on the other.
Metal transfer studies were carried out with the help of high
speed cine camera in conjunction with instrumentation tape
recorder, storage oscilloscope ar►d poloroid camera. The
voltage-current transients were also recorded on the cine
film along with the photographs of the arc.
Bead geometry and shape relationships were studied in two
phases--first by varying each individual parameter of
interest and subsequently by designing the experiments using
fractional factorial technique. Mathematical models based
on regression analysis were then developed, using digital
computer, to predict the bead geometry and shape relationships
including penetration,bead width, reinforcement height, penetration shape factor, reinforcement form factor and dilution.
Microstructure of welds were studied at different magnifications by projecting them on the television screen with the
help of closed-circuit T.V.Camera Extensive microhardness
vi
surveys of welds were carried out to make the study of microstructures, of different zones of welds, more comprehensive.
Final phase of investigations included the design of various
types of butt welds which were welded by establishing suitable
parameters for different weld runs. The successfully welded
joints were then surveyed for macro-and microhardness followed
by study of their microstructures. These welds were then
evaluated for fracture toughness values using crack tip opening
displacement (CTOD) and J-integral techniques. The fractured
pieces were studied by scanning electron microscope (SEM)
for investigation into mode of failures and the types of
grains developed in different butt welds.
•▪
vi i
CONTENTS
Page
CERTIFICATE
••
ACKNOWLEDGEMENTS
• •ii
ABSTRACT
• •iv
CONTENTS
• •vii
LIST OF TABLES
• • xii
LIST OF FIGURES
• • xiv
CHAPTER-1INTRODUCTION
1.1Aluminium and Aluminium-Magnesium
Alloys
• •1-15
• •3-5
1.2Welding of Aluminium and Its Alloys• •
1.3Research Planned
5-7
..7-13
1.4Sequence of Investigations13-15
CHAPTER-2DESIGN AND FABRICATION OF WELDING
MANIPULATOR
16-24
2.1 Introduction
.. 16
2.2Design Criterion
.. 16-17
2.3Welding Specifications.. 17
2.4Manipulator Specifications.. 17-18
2.5Manipulator Table .. 18-19
2.6Drive Mechanism
.. 19
2.7Welding Gun Holder .. 19-20
2.8Control Panel
.. 20
viii
CONTENTS (Contd.)
Page
2.9
Safety
2.10
General
21
Figures
23-24
..
20-21
DESIGN OF EXPERIMENTS
..
25-40
3.1
Introduction
..
25
3.2
Theoretical Approach
..
26
3.3
Qualitative Approach
•
•
26-27
3.4
Qualitative cum Dimensional Analysis
Approach
..
27-28
3.5
Specific Quantitative Approach
..
28-29
3.6
General Quantitative Approach
..
29
3.7
Design of Experitents
..
30-37
Tables
..
38-40
CALIBRATION OF THE WELDING SYSTEM
..
41-59
4.1
Introduction
..
41-42
4.2
Steps of Investigations
..
42-50
4.3
Computer Programme
..
50
Tables
..
51-54
Figures
..
55-59
METAL TRANSFER
..
60-97
5.1
Introduction
..
60-61
5.2
Metal Transfer in MIG Welding of
Aluminium and its Alloys
..
61-68
CHAPTER-3
CHAPTER-4
CHAPTER-5
5.3
Plan of Investigations
69-70
CONTENTS (Contd.)
Page
5.4
Experimental Set-up
5.5
Experimental Procedure
71-72
5.6
Results
73-74
5.7
Analysis of Results; Slow Speed
Recording
5.8
5.9
CHAPTER-6
..
c.
70-71
74-79
Analysis of Results; High Speed
Cinematography
77-81
Analysis of Results; Effect of Metal
Transfer on Bead Geometry and
Appearance
81-82
Enures
83-97
WELD BEAD GEOMETRY AND SHAPE
RELATIONSHIPS (PART-I)
..
98-118
6.1
Introduction
.
98-101
6.2
Experimental Procedure
6.3
Results
..
103
6.4
Analysis of Results
..
103-111
Figures
..
112-118
BEAD GEOMETRY AND SHAPE RELATIONSHIPS
(PART-II)
..
119-175
7.1
Introduction
..
119-120
7.2
Plan of Investigations
..
120-121
7.3
Selection of Mathematical Models
121-123
7.4
Experimental Procedure
123-124
7.5
Estimation of the Coefficients of
the Models
..
124
7.6
Checking the Adequacy of the Models
..
124-125
7.7
Testing the Significance of the
Coefficients
CHAPTER-7
101-103
125-126
x
CONTENTS (Contd.)
Page
7.8
Results
:.9
Analysis of Results
7.10
Computer Program
•
•
134
Tables
•
•
135-150
•
•
127-134
Figures
CHAPTER-8.
126-127
151-175
METALLURGICAL TRANSFORMATIONS
..
176-212
8.1
Introduction
..
176-179
8.2
Experimental Investigations
..
179-180
8.3
Experimental. Procedure
•
.
180-182
8.4
Results
8.5
Analysis of Results
.. ' 184-198
Figures
..
199-212
WELD JOINT DESIGN AND FRACTURE
TOUGHNESS
..
213-263
9.1
Introduction
..
213-214
9.2
Types of Fractures
..
214-216
9.3
Factors Affecting Mode of Fracture
..
216-219
9.4
Methods of Determining Fracture
Toughness
..
219-227
9.5
Plan of Investigations
..
227
9.6
Experimental Procedure
..
227-231
9.7
Results
..
231-232
9.8
Analysis of Results
..
232-241
Table
..
242
Figures
..
243-263
CHAPTER-9
183-184
xi
CONTENTS (Contd.)
Page
CHAP2ER-10CONCLUSIONS
10.1Metal Transfer (Chapter-5.)
•
•
264-275
•
•
264-265
10.2Weld Bead Geometry and Shape
Relationships (Chapters 6 & 7)
265-269
10.3Microhardness and Microstructures
of Aluminium and Alloy 5083 Welds
(Chapter-8)
269-273
10.4Weld Design and Fracture Toughness
(Chapter-9)
273-275
REFERENCES
276-286
APPENDICES
287-297
Appendix I•Properties of 2K Factorial
Designs
•
•
Appendix II :Analysis of Variance Technique
(ANOVA) and Significance of
the Coefficients
Appendix III:Welding Current Programme
Appendix IV :Bead Geometry Programme (25-1
Design)
Appendixv :Bead Geometry Programme (26-2
Design)
287
288-289
•
•
290-291
292-294
295-297