Investigation Of Plate Welding Quality By Robot Welding Using Nondestructive Technique.
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
INVESTIGATION OF PLATE WELDING QUALITY BY ROBOT
WELDING USING NONDESTRUCTIVE TECHNIQUE
This report submitted in accordance with requirement of the Universiti Teknikal
Malaysia Melaka (UTeM) for Bachelor Degree of Manufacturing Engineering
(Manufacturing Process) with Honours.
by
HARYATIE BINTI SAMSURI
FACULTY OF MANUFACTURING ENGINEERING
2008
ABSTRACT
Joining between two metal plates by using the welding process is not produced a high
quality of final product but it has some discontinuities and defects that appear inside the
welds. These defects are actually caused from some factor either environment factor or
setting by operator before operator conducted the welding operation. For your
information, the defects still has either using manual welding or using robot welding.
But the percentage of defects that‟s found on welds after using robots welding are less
comparing with manual welding. So, the performance and its result done by robots
welding and manual welding can learn together. The welding quality, defects, skill of
the welder and position done by welder also can relate with this parameter of the causes
of welding defects. This is because the parameters effecting in welding quality is the
main factor of discontinuities caused by inadequate or careless application of proper
welding technologies or by poor welder training. From this major discontinuities that
affect weld quality are solved with a best method for controlling those parameters
factors. The internal defects or an external defect that can detect by human eyes was
tested by nondestructive testing method. But this projects, the testing methods used is
ultrasonic testing which is the classical test method based on measurements by using
ultrasonic oscillations for detection of flaws in different material. The ultrasonic testing
by give reproducible test results within narrow tolerances. Not all influences have to be
regarded by the operator. In many cases of the influences can be neglected without
exceeding the permitted measurement tolerances.
i
ABSTRAK
Hasil cantuman antara dua kepingan logam dengan menggunakan proses kimpalan tidak
semestinya menghasilkan proses kimpalan yang terbaik tetapi mempunyai beberapa
kecacatan akibat daripada beberapa faktor sama ada faktor persekitaran ataupun faktor
akibat daripada operator itu sendiri. Oleh hal yang demikian, kecacatan tetap ada
walaupun dikendalikan oleh robot kimpalan. Kecacatan yang terjadi dipengaruhi oleh
beberapa faktor sama ada pengelarasan pada mesin robot kimpalan yang diselaraskan
oleh operator seperti jumlah arus elektrik yang diselaraskan, frekuensi, kelajuan
menimpal, jenis elektrod, jenis kepingan logam dan sebagainya. Oleh hal yang
demikian, kecacatan yang tersembunyi yang tidak ditemui akan dikesan atau diperiksa
dengan mata kasar akan dikenalpasti melalui “ujian nondestructive”. Ujian ini terbahagi
kepada beberapa ujian kecil yang lain. Salah satu daripada ujian kecil yang telah
digunakan ialah ujian ultrasonik. Ujian ini majoriti diaplikasikan di serata industri di
negara ini. Ujian ultrasonik boleh dikendalikan dengan cara yang lebih senang iaitu
sample telah ditentukan dengan alat pengukuran yang efektif dan tepat. Sampel ujian
akan ditetapkan dengan membetulkan sistem alat pengukuran untuk mengelakkan
daripada terjadinya ralat semasa sampel diuji.
ii
DEDICATION
I dedicate this work to my special family, my special friend in gratitude and all my
loving friends because of her/ his patience and understanding support in all my
endeavors and special thanks to them for their love.
iii
ACKNOWLEDGEMENT
Alhamdullillah with God permission already able complete this PSM project. Wishes
express honestly gratitude to all the people who has given support during the period of
the project progress. First and foremost, a special thanks to University Technical
Malaysia Malacca especially for Prof. Dr. Mohd Razali bin Muhamad as Coordinator of
PSM project, and Mr. Sivarao a/l Subramonian as assistant Coordinator of PSM project
who constructs this programme for students to do the PSM project. Also thanks for Dr.
Mohd Rizal bin Salleh as PSM Supervisor for giving their full support, a lot of valuable
information, and guidance. Next, special appreciation goes to all friend that involve and
to beloved parents because give their full support and encouragement in doing this
project. May all of the person stated here and another person who is in some way
involved and has helped during my project time in campus and during my report writing,
be blessed and have a peace of mind in running their everyday life until the end of their
life.
iv
TABLE OF CONTENT
Abstract
i
Abstrak
ii
Dedication
iii
Acknowledgement
iv
Table of Content
v
List of Table
ix
List of Figures
xi
List of Abbreviations
xiii
1. INTRODUCTION
1.1
Welding
1
1.1.1
Development of Modern Welding Processes
1
1.2
Problem Statement
2
1.3
Objective
2
1.4
Scope of Research
3
2. LITERATURE REVIEW
2.1
Fusion Welding Processes
4
2.1.1
History and Development
4
2.1.2
Oxyfuel Gas Welding
4
2.1.3
Arc Welding Processes of Non- Consumable Electrode
5
2.1.4
Arc Welding Processes of Consumable Electrode
7
2.1.5
Gas Metal Arc Welding
7
2.1.6
Electrodes for Arc Welding
8
2.1.7
Welding Parameter
8
2.1.8
The Weld Joint
9
2.1.9
Weld Quality
10
v
2.2
Robot Welding
12
2.2.1
Definition
12
2.2.2
Synchromotion
12
2.2.3
Utilizing Features and Function
14
2.2.4
Simultaneous Control
15
2.2.5
Advantage and disadvantage of robot welding
17
2.3
Nondestructive Techniques (NDT)
18
2.3.1
Definition
18
2.3.2
Types of NDT Technique
19
2.3.3
Ultrasonic testing
20
2.3.4
Advantages and Disadvantage of Ultrasonic Testing
21
2.3.5
Reflection Characteristic of Sound Waves When
2.3.6
Striking Discontinuities
22
Improvement
23
3. METHODOLOGY
3.1
Sample Preparation and Gathering
24
3.2
Raw Material
24
3.2.1
Mild Steel
25
3.2.2
Stainless steel
26
3.2.3
Differentiation between mild steel and stainless steel
27
3.3
Filler Wire
29
3.4
Joint Type
29
3.5
Research Procedure
30
3.6
Welding Method
31
3.7
Parameter Selection
31
3.7.1
Constant Parameter
31
3.7.2
Variable parameter
32
3.8
Robot Welding
33
3.8.1
Description
33
vi
3.8.2
Standard Operation of Robot Welding (SOP)
34
3.8.3
Standard Operation ON and OFF System
36
3.8.4
Coding
36
3.9
Testing Method
37
3.9.1
Equipment
38
3.10
Testing Technique
41
3.10.1
Calibration of the Test Sample
42
3.10.2
Standardized of Test Sample
42
3.10.3
Performance of Test Sample
42
3.10.4
Interpretation of Result
42
3.11
Contact Testing
43
3.11.1
General
43
3.12.2
Why ultrasonic testing
44
3.11.3
Comparison between ultrasonic testing and radiographic testing
45
3.11.4
Basic Method
46
3.11.5
Testing system
47
3.11.6
Parameter consideration
49
3.11.7
Couplant
52
3.11.8
Evaluating the defect
53
3.11.9
Technique define crack from floating card
54
3.11.10
Procedure
55
4. RESULT
4.1
Welding Result
56
4.1.1
Mild Steel
56
4.1.2
Stainless Steel
58
4.2
Ultrasonic Testing Result
60
4.2.1
Mild Steel
60
4.2.2
Stainless Steel
63
vii
5. DISCUSSION
5.1
Mild Steel
67
5.2
Stainless Steel
72
5.3
Propose the appropriate method of controlling the
parameters for better welding quality
75
6. CONCLUSION
6.1 Conclusion
78
80
REFERENCES
APPENDICES A
Gannt Chart for Project Activities for PSM 1
83
Gannt Chart for Project Activities for PSM 2
84
APPENDICES B
Figure i
Figure ii
Figure iii
Figure iv
Figure v
Figure vi
viii
LIST OF TABLE
3.
METHODOLOGY
3.1
Chemical composition of mild steel filler wire
26
[Sources: Barry M. Patchett, 1998]
3.2
Chemical composition of stainless steel of filler wire
27
[Sources: Barry M. Patchett, 1998]
3.3
Description of robot welding
33
[Sources: Manual Lab Machine Shop]
4.
RESULT
Welding Result (Mild Steel)
56
4.1
Variable welding current according the reference value
56
4.2
Variable welding voltage according the reference value
57
4.3
Variable welding speed according the reference value
57
Welding Result (Stainless Steel)
58
4.4
Variable welding current according the reference value
58
4.5
Variable welding voltage according the reference value
58
4.6
Variable welding speed according the reference value
59
Ultrasonic Testing Result (Mild Steel)
60
4.7
Variable welding current
60
4.8
Variable welding voltage
61
4.9
Variable welding speed
62
Ultrasonic Testing Result (Stainless Steel)
63
4.10
Variable welding current
63
4.11
Variable welding voltage
64
4.12
Variable welding speed
65
5.
DISCUSSION
ix
Mild Steel
67
5.1
Welding current and its defect
67
5.2
Welding current and its defect
67
5.3
Welding voltage and its defect
69
5.4
Welding voltage and its defect
69
5.5
Welding speed and its defect
70
5.6
Welding speed and its defect
70
Stainless Steel
72
5.7
Welding current and its defect
72
5.8
Welding current and its defect
72
5.9
Welding voltage and its defect
73
5.10
Welding voltage and its defect
73
5.11
Welding speed and its defect
74
5.12
Welding speed and its defect
74
6.
CONCLUSION
6.1
House of quality between mild steel and stainless steel
x
78
LIST OF FIGURES
1. INTRODUCTION
2. LITERATURE REVIEW
2.1
Basic types of oxyacetylene flames
5
(Sources:Kalpakjian Schmid, 2001)
2.2
(a) Gas tungsten arc welding process formerly tungsten
6
inert gas welding (TIG welding). (b) Equipment TIG operations
(Sources:Kalpakjian Schmid, 2001)
2.3
The shielded metal arc welding process
7
(Sources:Kalpakjian Schmid, 2001)
2.4
The characteristics of a typical fusion weld zone
9
(Sources:Kalpakjian Schmid, 2001)
2.5
Various discontinuities in fusion welds
11
(Sources:Kalpakjian Schmid, 2001)
2.6
Robot welding
13
3. METHODOLOGY
3.1
Groove shape on the plate
25
3.2
Stainless steel plate 306L
25
3.3
Mild steel plate
26
3.4
Welding angle
32
3.5
Typical ultrasonic contact test displaying
39
(Source: Jimmy Gan, 2006)
3.6
Sweep delay adjustment
40
(Source: Jimmy Gan, 2006)
3.7
Sound beam reflection
43
(Source: Jimmy Gan, 2006)
xi
3.8
Typical contact test discontinuity indication
44
(Source: Jimmy Gan, 2006)
3.9
Schematic of pulse echo flaw detector
48
(Source: Galvery W, 2007)
3.10
Full set of ultrasonic tester machine
50
3.11
CTR screen
50
3.12
Calibration block
51
3.13
Highest echo signal
52
3.14
Lowest echo signal
52
3.15
First highest of echo signal
53
3.16
Second highest of echo signal
53
3.17
Weld size
54
5. DISCUSSION
5.1
Crack or flaw in and around a weld
66
(Source: Galvery W, 2007)
5.2
Slag inclusions
68
(Source: Galvery W, 2007)
5.3
Weld produces when use lowest speed; 10cm/min
71
5.4
Comparison of sizing accuracy in standard deviation
76
xii
LIST OF ABBREVIATION
A or AMP
-
Ampere
AC
-
Alternating Current
AE or AET
-
Alternate Ending
AS
-
Alternate Start
BP
-
Beam Path
C
-
Circular
DC
-
Direct Current
ECT
-
Eddy Current Testing
EXT INPUT
-
External Input
GMAW
-
Gas Metal Arc Welding
HAZ
-
Heat Affected Zone
HC
-
Harmonious circle
HL
-
Harmonious Line
HLO
-
Harmonious Line Orientation
HLX
-
Interpolation in Simultaneous Control
HO
-
Harmonious Circle Orientation
HP
-
Harmonious Position
IP
-
Initial Pulses
LX
-
Uniform Interpolation
MIG Welding
-
Gas Shielded Arc Welding
NDT
-
Nondestructive Testing
OAW
-
Oxyacetylene Gas Welding
OFW
-
Oxyfuel Gas Welding
P
-
Positioning
PZT
-
Zirconate Titanate
RT
-
Radiographic Testing
TIG Welding
-
Gas Tungsten Arc Welding
xiii
Sa
-
Sound Path
SD
-
Surface Distance
SOP
-
Standard Operation of Robot Welding
UT
-
Ultrasonic Testing
xiv
CHAPTER 1
INTRODUCTION
This chapter provides a general background of the project. It briefly describes the
general discussion of joining processes and focus on the subject being discussed easily.
It also explains the problem statements, objectives of the study, and scope of the
research.
1.1
Welding
Welding is one type joining process involve the partial melting and fusion of the joint
between two workpiece. Fusion welding is defined as melting together and coalescing
materials by means of heat [Kalpakjian et. al, 2006].
Joining process is carried out in the various ways. The mechanical joining method is
derived from metalworking processes. The solid techniques are based on the adhesion
and deformation [Gourd, 1998].
1.1.1
Development of Modern Welding Processes
The discovery of acetylene by combining with oxygen was produced a flame that used
for welding and cutting. It became known as oxyacetylene welding. The application of
heat generate from an electric arc between carbons electrodes is one basic for the
shielded arc welding process [Gourd, 1998].
1
1.2
Problem statement
Today we can see the welding are generally used in manual or using the automated
robot. So, both of two categories of welding methods are totally different. For the
manual welding, these processes use a power supply created by welder to create and
maintain an electric arc between an electrode and the base material to melt metals at the
welding point. They was used either direct (DC) or alternating current (AC), and
consumable or nonconsumable electrodes. The welding region is sometimes protected
by some type of inert or semi inert gas, known as a shielding gas and filler material is
sometimes used as well. Meanwhile for robots welding, are the parameters was already
setting by operator with its controller.
Then, the welding process done by robots as the robots is the welder. But for manual
welding, the welder is human. So the final product after welding process are difference
each other because both of them have their own criteria. So from this case, we can know
mostly about the different of performance result done by robots welding and manual
welding. And at the same time the welding quality, defects, skill of the welder and
position done by welder also can relate with this case. This is because the parameters
effecting in welding quality is the main factor of discontinuities caused by inadequate or
careless application of proper welding technologies or by poor welder training. From
this major discontinuities that affect weld quality are solved with a best method for
controlling those parameters factors.
1.3
Objective
The main purpose of this project was listed below.
i.
To investigate the performance of plate welding quality and its welding defects.
ii.
To identify the parameters effecting the welding quality.
iii.
To propose the appropriate method of controlling the parameters for better
welding quality.
2
1.4
Scope of research
The scope of study was listed below.
i.
To learn how to use the robot welding practically.
ii.
To identify the parameters affected on welds.
iii.
To perform the joining works on the sample of work piece.
iv.
To carry out the testing of nondestructive techniques.
v.
To analyze the result obtained from the equipment.
vi.
To conclude the discussion discussed based on the result getting from the
experiment.
3
CHAPTER 2
LITERATURE REVIEW
This chapter describes the information from many sources that it explains to readers
what has motivated the study by giving definition, identifying the causes and effects,
listing method used, provides historical background, describing the problem faced and
stating the advantages or disadvantages.
2.1
Fusion Welding Processes
2.1.1
History and development
The welding and oxyfuel welding was developed in 1893. Acetylene was discovered in
1836 by Edmund Davy. The automatic welding was introduced in 1920 which is an
electrode wire was fed continuously [Cary et. al, 2005]. Shielded metal arc welding was
developed around 1950 by using a flux coated consumable electrode. The plasma arc
welding was developed in the same year. The electro slag welding was introduced in
1958 and it was followed by an electro gas welding in years of 1961 [Cary et. al, 2005].
2.1.2
Oxyfuel gas welding
Oxyfuel gas welding (OFW) is define as any welding process that uses a fuel gas
combined with oxygen to produce a flame. This flame is the source of the heat that is
used to melt the metals at the joint. The most common gas welding process uses
4
acetylene; this process is known as Oxyacetylene Gas Welding (OAW). Figure 2.1 is
showed the three basic types of oxyacetylene flames used in oxyfuel gas welding and
cutting operation [Kalpakjian et. al, 2006].
Figure 2.1: Basic types of oxyacetylene flames (Source: Kalpakjian Schmid, 2001)
i.
Flame type
The important factor in oxyfuel gas welding is the proportion of acetylene and
oxygen.
ii.
Filler metal
Filler metal is used to supply additional metal to the weld zone during welding. It
suited as filler rod or wire and coated with flux as to check oxidation of the
surfaces of the parts being welded by generating a gaseous shield around the
weld zone.
iii.
Pressure gas welding
The welding of two components started with the heating of the interface by
means of a torch using an oxyacetylene gas mixture. The torch was withdrawn
after the interface begins to melt.
2.1.3
Arc welding processes of non- consumable electrode
The direct current used and its polarity as the current flows is important. The selection
based on such factors as the type of electrode, metals to be welded, and depth and width
5
of the weld zone. The types of welding techniques stated and listed below [Kalpakjian
et. al, 2006].
Figure 2.2: (a) Gas tungsten arc welding process formerly tungsten inert gas welding (Source: Kalpakjian
Schmid, 2001). (b) Equipment TIG operations (Source: Kalpakjian Schmid, 2001).
i.
Gas tungsten arc welding
The filler metal is supplied from a filler wire in gas tungsten arc welding (TIG)
like Figure 2.2 above. It‟s more suitable for thin metal. The tungsten electrode is
not consumed in this operation, so that the arc gap is maintained at a constant
current level. Flux is not used but the filler wire are similar to the metal to
welded.
ii.
Plasma arc welding
A concentrated plasma arc is produced and directed towards the weld area in
plasma arc welding. Deep and narrow weld can be made by this process at high
welding speed.
iii.
Atomic hydrogen welding
An arc is generating between two tungsten electrodes in a shielding atmosphere
of hydrogen gas. The arc is maintained independently of the workpiece or part
being welded.
6
INVESTIGATION OF PLATE WELDING QUALITY BY ROBOT
WELDING USING NONDESTRUCTIVE TECHNIQUE
This report submitted in accordance with requirement of the Universiti Teknikal
Malaysia Melaka (UTeM) for Bachelor Degree of Manufacturing Engineering
(Manufacturing Process) with Honours.
by
HARYATIE BINTI SAMSURI
FACULTY OF MANUFACTURING ENGINEERING
2008
ABSTRACT
Joining between two metal plates by using the welding process is not produced a high
quality of final product but it has some discontinuities and defects that appear inside the
welds. These defects are actually caused from some factor either environment factor or
setting by operator before operator conducted the welding operation. For your
information, the defects still has either using manual welding or using robot welding.
But the percentage of defects that‟s found on welds after using robots welding are less
comparing with manual welding. So, the performance and its result done by robots
welding and manual welding can learn together. The welding quality, defects, skill of
the welder and position done by welder also can relate with this parameter of the causes
of welding defects. This is because the parameters effecting in welding quality is the
main factor of discontinuities caused by inadequate or careless application of proper
welding technologies or by poor welder training. From this major discontinuities that
affect weld quality are solved with a best method for controlling those parameters
factors. The internal defects or an external defect that can detect by human eyes was
tested by nondestructive testing method. But this projects, the testing methods used is
ultrasonic testing which is the classical test method based on measurements by using
ultrasonic oscillations for detection of flaws in different material. The ultrasonic testing
by give reproducible test results within narrow tolerances. Not all influences have to be
regarded by the operator. In many cases of the influences can be neglected without
exceeding the permitted measurement tolerances.
i
ABSTRAK
Hasil cantuman antara dua kepingan logam dengan menggunakan proses kimpalan tidak
semestinya menghasilkan proses kimpalan yang terbaik tetapi mempunyai beberapa
kecacatan akibat daripada beberapa faktor sama ada faktor persekitaran ataupun faktor
akibat daripada operator itu sendiri. Oleh hal yang demikian, kecacatan tetap ada
walaupun dikendalikan oleh robot kimpalan. Kecacatan yang terjadi dipengaruhi oleh
beberapa faktor sama ada pengelarasan pada mesin robot kimpalan yang diselaraskan
oleh operator seperti jumlah arus elektrik yang diselaraskan, frekuensi, kelajuan
menimpal, jenis elektrod, jenis kepingan logam dan sebagainya. Oleh hal yang
demikian, kecacatan yang tersembunyi yang tidak ditemui akan dikesan atau diperiksa
dengan mata kasar akan dikenalpasti melalui “ujian nondestructive”. Ujian ini terbahagi
kepada beberapa ujian kecil yang lain. Salah satu daripada ujian kecil yang telah
digunakan ialah ujian ultrasonik. Ujian ini majoriti diaplikasikan di serata industri di
negara ini. Ujian ultrasonik boleh dikendalikan dengan cara yang lebih senang iaitu
sample telah ditentukan dengan alat pengukuran yang efektif dan tepat. Sampel ujian
akan ditetapkan dengan membetulkan sistem alat pengukuran untuk mengelakkan
daripada terjadinya ralat semasa sampel diuji.
ii
DEDICATION
I dedicate this work to my special family, my special friend in gratitude and all my
loving friends because of her/ his patience and understanding support in all my
endeavors and special thanks to them for their love.
iii
ACKNOWLEDGEMENT
Alhamdullillah with God permission already able complete this PSM project. Wishes
express honestly gratitude to all the people who has given support during the period of
the project progress. First and foremost, a special thanks to University Technical
Malaysia Malacca especially for Prof. Dr. Mohd Razali bin Muhamad as Coordinator of
PSM project, and Mr. Sivarao a/l Subramonian as assistant Coordinator of PSM project
who constructs this programme for students to do the PSM project. Also thanks for Dr.
Mohd Rizal bin Salleh as PSM Supervisor for giving their full support, a lot of valuable
information, and guidance. Next, special appreciation goes to all friend that involve and
to beloved parents because give their full support and encouragement in doing this
project. May all of the person stated here and another person who is in some way
involved and has helped during my project time in campus and during my report writing,
be blessed and have a peace of mind in running their everyday life until the end of their
life.
iv
TABLE OF CONTENT
Abstract
i
Abstrak
ii
Dedication
iii
Acknowledgement
iv
Table of Content
v
List of Table
ix
List of Figures
xi
List of Abbreviations
xiii
1. INTRODUCTION
1.1
Welding
1
1.1.1
Development of Modern Welding Processes
1
1.2
Problem Statement
2
1.3
Objective
2
1.4
Scope of Research
3
2. LITERATURE REVIEW
2.1
Fusion Welding Processes
4
2.1.1
History and Development
4
2.1.2
Oxyfuel Gas Welding
4
2.1.3
Arc Welding Processes of Non- Consumable Electrode
5
2.1.4
Arc Welding Processes of Consumable Electrode
7
2.1.5
Gas Metal Arc Welding
7
2.1.6
Electrodes for Arc Welding
8
2.1.7
Welding Parameter
8
2.1.8
The Weld Joint
9
2.1.9
Weld Quality
10
v
2.2
Robot Welding
12
2.2.1
Definition
12
2.2.2
Synchromotion
12
2.2.3
Utilizing Features and Function
14
2.2.4
Simultaneous Control
15
2.2.5
Advantage and disadvantage of robot welding
17
2.3
Nondestructive Techniques (NDT)
18
2.3.1
Definition
18
2.3.2
Types of NDT Technique
19
2.3.3
Ultrasonic testing
20
2.3.4
Advantages and Disadvantage of Ultrasonic Testing
21
2.3.5
Reflection Characteristic of Sound Waves When
2.3.6
Striking Discontinuities
22
Improvement
23
3. METHODOLOGY
3.1
Sample Preparation and Gathering
24
3.2
Raw Material
24
3.2.1
Mild Steel
25
3.2.2
Stainless steel
26
3.2.3
Differentiation between mild steel and stainless steel
27
3.3
Filler Wire
29
3.4
Joint Type
29
3.5
Research Procedure
30
3.6
Welding Method
31
3.7
Parameter Selection
31
3.7.1
Constant Parameter
31
3.7.2
Variable parameter
32
3.8
Robot Welding
33
3.8.1
Description
33
vi
3.8.2
Standard Operation of Robot Welding (SOP)
34
3.8.3
Standard Operation ON and OFF System
36
3.8.4
Coding
36
3.9
Testing Method
37
3.9.1
Equipment
38
3.10
Testing Technique
41
3.10.1
Calibration of the Test Sample
42
3.10.2
Standardized of Test Sample
42
3.10.3
Performance of Test Sample
42
3.10.4
Interpretation of Result
42
3.11
Contact Testing
43
3.11.1
General
43
3.12.2
Why ultrasonic testing
44
3.11.3
Comparison between ultrasonic testing and radiographic testing
45
3.11.4
Basic Method
46
3.11.5
Testing system
47
3.11.6
Parameter consideration
49
3.11.7
Couplant
52
3.11.8
Evaluating the defect
53
3.11.9
Technique define crack from floating card
54
3.11.10
Procedure
55
4. RESULT
4.1
Welding Result
56
4.1.1
Mild Steel
56
4.1.2
Stainless Steel
58
4.2
Ultrasonic Testing Result
60
4.2.1
Mild Steel
60
4.2.2
Stainless Steel
63
vii
5. DISCUSSION
5.1
Mild Steel
67
5.2
Stainless Steel
72
5.3
Propose the appropriate method of controlling the
parameters for better welding quality
75
6. CONCLUSION
6.1 Conclusion
78
80
REFERENCES
APPENDICES A
Gannt Chart for Project Activities for PSM 1
83
Gannt Chart for Project Activities for PSM 2
84
APPENDICES B
Figure i
Figure ii
Figure iii
Figure iv
Figure v
Figure vi
viii
LIST OF TABLE
3.
METHODOLOGY
3.1
Chemical composition of mild steel filler wire
26
[Sources: Barry M. Patchett, 1998]
3.2
Chemical composition of stainless steel of filler wire
27
[Sources: Barry M. Patchett, 1998]
3.3
Description of robot welding
33
[Sources: Manual Lab Machine Shop]
4.
RESULT
Welding Result (Mild Steel)
56
4.1
Variable welding current according the reference value
56
4.2
Variable welding voltage according the reference value
57
4.3
Variable welding speed according the reference value
57
Welding Result (Stainless Steel)
58
4.4
Variable welding current according the reference value
58
4.5
Variable welding voltage according the reference value
58
4.6
Variable welding speed according the reference value
59
Ultrasonic Testing Result (Mild Steel)
60
4.7
Variable welding current
60
4.8
Variable welding voltage
61
4.9
Variable welding speed
62
Ultrasonic Testing Result (Stainless Steel)
63
4.10
Variable welding current
63
4.11
Variable welding voltage
64
4.12
Variable welding speed
65
5.
DISCUSSION
ix
Mild Steel
67
5.1
Welding current and its defect
67
5.2
Welding current and its defect
67
5.3
Welding voltage and its defect
69
5.4
Welding voltage and its defect
69
5.5
Welding speed and its defect
70
5.6
Welding speed and its defect
70
Stainless Steel
72
5.7
Welding current and its defect
72
5.8
Welding current and its defect
72
5.9
Welding voltage and its defect
73
5.10
Welding voltage and its defect
73
5.11
Welding speed and its defect
74
5.12
Welding speed and its defect
74
6.
CONCLUSION
6.1
House of quality between mild steel and stainless steel
x
78
LIST OF FIGURES
1. INTRODUCTION
2. LITERATURE REVIEW
2.1
Basic types of oxyacetylene flames
5
(Sources:Kalpakjian Schmid, 2001)
2.2
(a) Gas tungsten arc welding process formerly tungsten
6
inert gas welding (TIG welding). (b) Equipment TIG operations
(Sources:Kalpakjian Schmid, 2001)
2.3
The shielded metal arc welding process
7
(Sources:Kalpakjian Schmid, 2001)
2.4
The characteristics of a typical fusion weld zone
9
(Sources:Kalpakjian Schmid, 2001)
2.5
Various discontinuities in fusion welds
11
(Sources:Kalpakjian Schmid, 2001)
2.6
Robot welding
13
3. METHODOLOGY
3.1
Groove shape on the plate
25
3.2
Stainless steel plate 306L
25
3.3
Mild steel plate
26
3.4
Welding angle
32
3.5
Typical ultrasonic contact test displaying
39
(Source: Jimmy Gan, 2006)
3.6
Sweep delay adjustment
40
(Source: Jimmy Gan, 2006)
3.7
Sound beam reflection
43
(Source: Jimmy Gan, 2006)
xi
3.8
Typical contact test discontinuity indication
44
(Source: Jimmy Gan, 2006)
3.9
Schematic of pulse echo flaw detector
48
(Source: Galvery W, 2007)
3.10
Full set of ultrasonic tester machine
50
3.11
CTR screen
50
3.12
Calibration block
51
3.13
Highest echo signal
52
3.14
Lowest echo signal
52
3.15
First highest of echo signal
53
3.16
Second highest of echo signal
53
3.17
Weld size
54
5. DISCUSSION
5.1
Crack or flaw in and around a weld
66
(Source: Galvery W, 2007)
5.2
Slag inclusions
68
(Source: Galvery W, 2007)
5.3
Weld produces when use lowest speed; 10cm/min
71
5.4
Comparison of sizing accuracy in standard deviation
76
xii
LIST OF ABBREVIATION
A or AMP
-
Ampere
AC
-
Alternating Current
AE or AET
-
Alternate Ending
AS
-
Alternate Start
BP
-
Beam Path
C
-
Circular
DC
-
Direct Current
ECT
-
Eddy Current Testing
EXT INPUT
-
External Input
GMAW
-
Gas Metal Arc Welding
HAZ
-
Heat Affected Zone
HC
-
Harmonious circle
HL
-
Harmonious Line
HLO
-
Harmonious Line Orientation
HLX
-
Interpolation in Simultaneous Control
HO
-
Harmonious Circle Orientation
HP
-
Harmonious Position
IP
-
Initial Pulses
LX
-
Uniform Interpolation
MIG Welding
-
Gas Shielded Arc Welding
NDT
-
Nondestructive Testing
OAW
-
Oxyacetylene Gas Welding
OFW
-
Oxyfuel Gas Welding
P
-
Positioning
PZT
-
Zirconate Titanate
RT
-
Radiographic Testing
TIG Welding
-
Gas Tungsten Arc Welding
xiii
Sa
-
Sound Path
SD
-
Surface Distance
SOP
-
Standard Operation of Robot Welding
UT
-
Ultrasonic Testing
xiv
CHAPTER 1
INTRODUCTION
This chapter provides a general background of the project. It briefly describes the
general discussion of joining processes and focus on the subject being discussed easily.
It also explains the problem statements, objectives of the study, and scope of the
research.
1.1
Welding
Welding is one type joining process involve the partial melting and fusion of the joint
between two workpiece. Fusion welding is defined as melting together and coalescing
materials by means of heat [Kalpakjian et. al, 2006].
Joining process is carried out in the various ways. The mechanical joining method is
derived from metalworking processes. The solid techniques are based on the adhesion
and deformation [Gourd, 1998].
1.1.1
Development of Modern Welding Processes
The discovery of acetylene by combining with oxygen was produced a flame that used
for welding and cutting. It became known as oxyacetylene welding. The application of
heat generate from an electric arc between carbons electrodes is one basic for the
shielded arc welding process [Gourd, 1998].
1
1.2
Problem statement
Today we can see the welding are generally used in manual or using the automated
robot. So, both of two categories of welding methods are totally different. For the
manual welding, these processes use a power supply created by welder to create and
maintain an electric arc between an electrode and the base material to melt metals at the
welding point. They was used either direct (DC) or alternating current (AC), and
consumable or nonconsumable electrodes. The welding region is sometimes protected
by some type of inert or semi inert gas, known as a shielding gas and filler material is
sometimes used as well. Meanwhile for robots welding, are the parameters was already
setting by operator with its controller.
Then, the welding process done by robots as the robots is the welder. But for manual
welding, the welder is human. So the final product after welding process are difference
each other because both of them have their own criteria. So from this case, we can know
mostly about the different of performance result done by robots welding and manual
welding. And at the same time the welding quality, defects, skill of the welder and
position done by welder also can relate with this case. This is because the parameters
effecting in welding quality is the main factor of discontinuities caused by inadequate or
careless application of proper welding technologies or by poor welder training. From
this major discontinuities that affect weld quality are solved with a best method for
controlling those parameters factors.
1.3
Objective
The main purpose of this project was listed below.
i.
To investigate the performance of plate welding quality and its welding defects.
ii.
To identify the parameters effecting the welding quality.
iii.
To propose the appropriate method of controlling the parameters for better
welding quality.
2
1.4
Scope of research
The scope of study was listed below.
i.
To learn how to use the robot welding practically.
ii.
To identify the parameters affected on welds.
iii.
To perform the joining works on the sample of work piece.
iv.
To carry out the testing of nondestructive techniques.
v.
To analyze the result obtained from the equipment.
vi.
To conclude the discussion discussed based on the result getting from the
experiment.
3
CHAPTER 2
LITERATURE REVIEW
This chapter describes the information from many sources that it explains to readers
what has motivated the study by giving definition, identifying the causes and effects,
listing method used, provides historical background, describing the problem faced and
stating the advantages or disadvantages.
2.1
Fusion Welding Processes
2.1.1
History and development
The welding and oxyfuel welding was developed in 1893. Acetylene was discovered in
1836 by Edmund Davy. The automatic welding was introduced in 1920 which is an
electrode wire was fed continuously [Cary et. al, 2005]. Shielded metal arc welding was
developed around 1950 by using a flux coated consumable electrode. The plasma arc
welding was developed in the same year. The electro slag welding was introduced in
1958 and it was followed by an electro gas welding in years of 1961 [Cary et. al, 2005].
2.1.2
Oxyfuel gas welding
Oxyfuel gas welding (OFW) is define as any welding process that uses a fuel gas
combined with oxygen to produce a flame. This flame is the source of the heat that is
used to melt the metals at the joint. The most common gas welding process uses
4
acetylene; this process is known as Oxyacetylene Gas Welding (OAW). Figure 2.1 is
showed the three basic types of oxyacetylene flames used in oxyfuel gas welding and
cutting operation [Kalpakjian et. al, 2006].
Figure 2.1: Basic types of oxyacetylene flames (Source: Kalpakjian Schmid, 2001)
i.
Flame type
The important factor in oxyfuel gas welding is the proportion of acetylene and
oxygen.
ii.
Filler metal
Filler metal is used to supply additional metal to the weld zone during welding. It
suited as filler rod or wire and coated with flux as to check oxidation of the
surfaces of the parts being welded by generating a gaseous shield around the
weld zone.
iii.
Pressure gas welding
The welding of two components started with the heating of the interface by
means of a torch using an oxyacetylene gas mixture. The torch was withdrawn
after the interface begins to melt.
2.1.3
Arc welding processes of non- consumable electrode
The direct current used and its polarity as the current flows is important. The selection
based on such factors as the type of electrode, metals to be welded, and depth and width
5
of the weld zone. The types of welding techniques stated and listed below [Kalpakjian
et. al, 2006].
Figure 2.2: (a) Gas tungsten arc welding process formerly tungsten inert gas welding (Source: Kalpakjian
Schmid, 2001). (b) Equipment TIG operations (Source: Kalpakjian Schmid, 2001).
i.
Gas tungsten arc welding
The filler metal is supplied from a filler wire in gas tungsten arc welding (TIG)
like Figure 2.2 above. It‟s more suitable for thin metal. The tungsten electrode is
not consumed in this operation, so that the arc gap is maintained at a constant
current level. Flux is not used but the filler wire are similar to the metal to
welded.
ii.
Plasma arc welding
A concentrated plasma arc is produced and directed towards the weld area in
plasma arc welding. Deep and narrow weld can be made by this process at high
welding speed.
iii.
Atomic hydrogen welding
An arc is generating between two tungsten electrodes in a shielding atmosphere
of hydrogen gas. The arc is maintained independently of the workpiece or part
being welded.
6