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FAILURE ANALYSIS ON TIG WELDMENT
AHMAD MUSLIM BIN OTHMAN
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
FAILURE ANALYSIS ON TIG WELDMENT
Report submitted in accordance with the partial requirements of the
Universiti Teknikal Malaysia Melaka for the
Bachelor of Manufacturing Engineering (Manufacturing Process) with
Honours
By
AHMAD MUSLIM BIN OTHMAN
Faculty of Manufacturing Engineering
March 2008
UTeM Library (Pind.1/2007)
UNIVERSITI TEKNIKAL MALAYSIA MELAKA (UTeM)
BORANG PENGESAHAN STATUS TESIS*
JUDUL: FAILURE ANALYSIS ON TIG WELDMENT
SESI PENGAJIAN: 2007/2008
Saya AHMAD MUSLIM BIN OTHMAN mengaku membenarkan tesis (PSM/Sarjana/Doktor Falsafah) ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:
1. Tesis adalah hak milik Universiti Teknikal Malaysia Melaka. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan
untuk tujuan pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran
antara institusi pengajian tinggi. 4. **Sila tandakan (√)
SULIT
TERHAD
TIDAK TERHAD
(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia yang termaktub di dalam
AKTA RAHSIA RASMI 1972)
(Mengandungi maklumat TERHAD yang telah ditentukan
oleh organisasi/badan di mana penyelidikan dijalankan)
(TANDATANGAN PENULIS)
Alamat Tetap: 2769,B
Kg. Laut, 21080
Kuala Terengganu.
Tarikh:
Disahkan oleh:
(TANDATANGAN PENYELIA)
Cop Rasmi:
Tarikh:
* Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana secara penyelidikan, atau disertasi bagi pengajian secara kerja kursus dan penyelidikan, atau Laporan Projek Sarjana Muda (PSM). ** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD.
APPROVAL
This report submitted to the senate of UTeM and has been accepted as partial
fulfillment of the requirements for the degree of Bachelor of Manufacturing
Engineering (Manufacturing Process). The members of the supervisory committee
are as follow:
………………………………………….
Main Supervisor
(Official Stamp & Date)
……………………………………………
Co-Supervisor
(Official Stamp & Date)
DECLARATION
I hereby, declare this thesis entitled “Failure Analysis on TIG Weldment” is the
result of my own research except as cited in the reference.
Signature : ………………………………………….
Author Name : …………………………………………
Date : …………………………………………
AHMAD MUSLIM BIN OTHMAN
25TH March 2008
ABSTRAK
Projek sarjana muda ini mendedahkan dan membincangkan kajian tentang
analisa kegagalan dalam kimpalan arca gas tungsten (TIG Welding). Objektif projek
kajian menganalisa kegagalan dalam TIG welding ini adalah untuk mengenalpasti
jenis kegagalan atau kecacatan yang berlaku dalam proses lekatan atau pengabungan
produk. Parameter atau keadaan yang menyebabkan kegagalan atau kecacatan ini
akan dikaji dan dianalisa. Projek ini akan dijalankan di makmal mesin syop, di
Universiti Teknikal Malaysia, Melaka dan mesin yang akan digunakan ialah
kimpalan arca gas tungsten (TIG welding). Bahan yang sama seperti mild steel akan
digunakan untuk tujuan proses kimpalan, dan proses ini akan diulangi. Kegagalan
atau kecacatan yang berlaku pada proses kimpalan tersebut akan direkodkan.
Kegagalan atau kecacatan yang dijangka akan berlaku pada proses kimpalan tersebut
adalah seperti “root crack”, “porosity”, “slag inclusion” dan “lack of root fusion”.
Method yang digunakan dalam mengkaji dan menganalisa kecacatan yang berlaku
ialah “Fault Tree Analysis” (FTA) dan gambarajah tulang ikan atau gambarajah
Ishikawa. Method ini digunakan untuk mencari sebab dan penyebab yang
menyumbang berlakunya kegagalan atau kecacatan dalam proses kimpalan dan
penyelesaian akan diberi untuk teknik penggunaan kimpalan dengan betul dan mesin
“setting” dengan betul.
ABSTRACT
This project is discussed about failure analysis on Tungsten Inert Gas (TIG)
weldment. The objective of this failure analysis project is to determine and identify
the type of failure that most occur in TIG welding. The parameter that contribute to
this failure occur also will be study and identify. This failure analysis project will be
held in machine syop laboratory at Universiti Teknikal Malaysia, Melaka and the
machine that will be used is Tungstent Inert Gas welding. The same material such as
mild steel will be used to do the joining process, and this action will be repeated and
all the failure or defects that occur during this process will be recorded. The failure
that expected to be occurring during this joining process is root crack, porosity, slag
inclusion, and lack of root fusion. These all defects or failures will be analyzed using
Fault Tree Analysis (FTA) and fishbone or cause and effect diagram. This method is
used to determine the causes for this failure occur and recommendation for proper
welding technique and proper parameter setting for this machine can be suggested
after that.
DEDICATION
For my beloved parents, supervisor, lecturers, and friends who always support me
ACKNOWLEDGEMENTS
This Final Year Project Report (Projek Sarjana Muda) is realized by the
courtesy of Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia
Melaka (UTeM) in partial fulfillment for Bachelor of Engineering.
I would like to take this opportunity to express my sincere and gratitude to
my Final Year Project Supervisor, Mr. Khairul Anuar A. Rahman for his guidance,
contribution and opinion during this PSM report completion. He also gave me a lot
of advice, encouragement and support to ensure I can get what I need during this
project research and he always had a meeting with me to discuss about this project.
My greatest thanks to Manufacturing Faculty (FKP) especially to Professor
Dr. Mohd Razali b. Muhamad, Dean of Faculty of Manufacturing Engineering,
UTeM, Mr Mohd Hadzley b. Abu Bakar and all the lectures in the faculty because
their commitment to support and encourage the final year student.
I also would like to acknowledge to all FKP technicians for supporting and
gave me a lot of information about this project (PSM) and with this information, I
can complete and finished this PSM project as schedule.
Last but not list, to my entire friend and everyone who had gave me a lot of
support and valuable information during this project report completion.
TABLE OF CONTENTS
Abstrak………………………………………………………………………………...i
Abstract……………………………………………………………………………….ii
Dedication……………………………………………………………………………iii
Acknowledgement…………………………………………………………………...iv
Table of Contents…………………………………………………………………......v
List of Figures………………………………………………………………………..ix
List of Tables………………………………………………………………………...xi
Sign and Symbols………………………………………………………………...…xii
List of Appendices………………………………………………………………….viii
CHAPTER 1 INTRODUCTION…………………………………………...1
1.1 Background introduction…………………………………………………………1
1.1.1 TIG Welding……………………………………………………………2
1.1.2 Failure Analysis………………………………………………………...3
1.2 Problem Statements………………………………………………………………4
1.3 Objectives………………………………………………………………………...4
1.4 Scope of Research………………………………………………………………...4
CHAPTER 2 LITERATURE REVIEW…………………………………..5
2.1 Introduction……………………………………………………………………….5
2.2 Tungsten Inert Gas (TIG) Welding……………………………………………...11
2.2.1 TIG Welding Aluminum………………………………………………12
2.2.2 Aluminum Characteristic for TIG Welding…………………………...13
2.2.3 Filling the Gap………………………………………………………...14
2.2.4 Recommendation Filler Metal for Various Aluminum Alloys ……….15
2.2.5 Cleanliness of the Welding Surface…………………………………...16
2.3 The TIG Welding System……………………………………………………….18
2.3.1 Power Source………………………………………………………….18
2.3.2 TIG Torch……………………………………………………………..20
2.3.3 Inert Gas System………………………………………………………21
2.3.4 TIG Luxuries…………………………………………………………..21
2.3.5 TIG Electrodes………………………………………………………...22
2.3.6 TIG Filler Metal……………………………………………………….23
2.4 Type of Material Compatible with TIG…………………………………………23
2.4.1 Aluminum and Magnesium……………………………………………24
2.4.2 Steel……………………………………………………………………25
2.4.3 Copper Alloys…………………………………………………………25
2.4.4 Dissimilar Metals……………………………………………………...25
2.5 Process Variations………………………………………………………………26
2.6 Safe Working Procedures for Welding Workshop……………………………...27
2.6.1 Personal Protective Equipment………………………………………..29
2.6.2 Other Safety Precaution……………………………………………….29
2.6.3 Manufacturing Consideration…………………………………………30
2.6.4 Finish Consideration…………………………………………………..31
2.7 Type of Weld Joints in TIG……………………………………………………..31
2.8 TIG Welding Defects/Failure…………………………………………………...32
2.9 Failure Analysis Method………………………………………………………...36
2.9.1 Fishbone Diagram……………………………………………………..36
2.9.2 Fault Tree Analysis (FTA)…………………………………………….39
CHAPTER 3 METHODOLOGY………………………………………...43
3.1 Introduction……………………………………………………………………...43
3.1.1 Discussion and Confirmation on Project Title………………………...45
3.1.2 Literature Review about Project Title…………………………………45
3.1.3 Welding Equipment…………………………………………………...45
3.2 Identify the Failure Occur……………………………………………………….46
3.3 Analyze Using Fishbone Diagram………………………………………………47
3.4 Apply the Method of Fault Tree Analysis………………………………………49
3.5 Failure Analysis Methodology…………………………………………………..51
3.6 Discussion, Conclusion, and Recommendation…………………………………52
CHAPTER 4 RESULT…………………………………………………….53
4.1 Introduction……………………………………………………………………...53
4.2 Type of defects and discontinuities found……………………………………....53
4.2.1 Result for 60A current consumption…………………………………..54
4.2.2 Result for 80A current consumption…………………………………..55
4.2.3 Result for 100A current consumption………………………………....56
4.2.4 Result for 120A current consumption…………………………………58
4.3 Misalignment discontinuities……………………………………………………60
4.4 Failure analysis using FTA method……………………………………………..61
4.4.1 Porosity………………………………………………………………..61
4.4.2 Overlap………………………………………………………………...62
4.4.3 Incomplete fusion and penetration………………………………….…63
4.4.4 Underfill……………………………………………………………….64
4.4.5 Misalignment………………………………………………………….65
CHAPTER 5 DISCUSSION………………………………………………67
5.1 Discussion……………………………………………………………………….67
5.2 Accepted joint……………………………………………………...……………67
5.3 Further analysis for porosity…………………………………………………….68
5.4 Unrecognized Joint Defect…………………………………….………………..69
5.5 TIG polarity……………………………………………………………………..70
5.6 Different between discontinuities and welding defect………………………..…71
5.7 Causes for rejection and how to avoid welding defect………………………….71
5.8 Welding inspection……………………………………………………………...72
CHAPTER 6 CONCLUSION…………………………………………….73
6.1 Conclusion………………………………………………………………………73
6.2 Recommendation for further research…………………………………………..74
REFERENCES……………………………………………………………………..75
APPENDICES
A List of Recommended Tungsten Electrodes
B Fault Tree Analysis Example
C Suggested Setting for TIG Welding Aluminum
D Suggested Setting for TIG Welding Stainless Steel
E Suggested Setting for TIG Welding Plain Steel
F Gantt chart for PSM 1
G Gantt chart for PSM 2
LIST OF FIGURES
Figure 2.1 TIG Welding 11
Figure 2.2 Automotive Application 13
Figure 2.3 Power Source 18
Figure 2.4 TIG Torch Disassembled 20
Figure 2.5 Foot Pedal Controller 22
Figure 2.6 TIG Electrodes 22
Figure 2.7 TIG Filler Metal 23
Figure 2.8 Type of Welds Joints 31
Figure 2.9 Type of Welds 32
Figure 2.9.1 Example of Fishbone Diagram 38
Figure 2.9.2 Example of FTA Diagram 40
Figure 3.1 Process Planning of the Project 44
Figure 3.2.1 Failure Occur during TIG Welding (bar graph) 46
Figure 3.2.2 Failure Occur During TIG Welding (Pareto Diagram) 47
Figure 3.3 Fishbone Diagram 48
Figure 3.5 Flow Chart of Failure Analysis Using TIG Welding 51
Figure 4.2 Type of defects and discontinuities found 54
Figure 4.2.1a Incomplete fusion occur 54
Figure 4.2.1b Incomplete fusion occur 55
Figure 4.2.1c Incomplete penetration occur 55
Figure 4.2.2a Underfill occur 55
Figure 4.2.2b Underfill occur 56
Figure 4.2.3a Incomplete fusion occur 56
Figure 4.2.3b Incomplete fusion occur 56
Figure 4.2.3c Porosity occur 57
Figure 4.2.3d Porosity occur 57
Figure 4.2.3e Porosity occur 57
Figure 4.2.4a Porosity and incomplete fusion occurs 58
Figure 4.2.4b Porosity and incomplete fusion occurs 58
Figure 4.2.4c Porosity occur 58
Figure 4.2.4d Overlap occur 59
Figure 4.2.4e Overlap occur 59
Figure 4.2.4f Overlap occur 59
Figure 4.3a Misalignment defect 60
Figure 4.3b Misalignment defect 60
Figure 4.3c Misalignment plate 60
Figure 4.4.1 FTA diagram of porosity 61
Figure 4.4.2 FTA diagram of overlap 62
Figure 4.4.3 FTA diagram of incomplete fusion and penetration 63
Figure 4.4.4 FTA diagram of underfill 64
Figure 4.4.5 FTA diagram of misalignment 65
Figure 5.2 Acceptance joint 67
Figure 5.3a Pore 68
Figure 5.3b Double pores 68
Figure 5.3c Entrapped bubble 68
Figure 5.4.1 Inclusion 69
Figure 5.7 Welder must be skilled to handle TIG welding 72
LIST OF TABLES
Table 2.1 Recommendation for Filler Metal 15
Table 2.2 General Cleaning Procedures for Aluminum 17
Table 2.3 Main Parameter in Power Source 19
LIST OF ABBREVIATIONS, SYMBOLS, SPECIALIZED
NOMENCLATURE
TIG - Tungsten Inert Gas Welding
GTAW - Gas Tungsten Arc Welding
SMAW - Shielded Metal Arc Welding
FTA - Fault Tree Analysis
FMEA - Failure Mode and Effect Analysis
AC - Alternating current
DC - Direct Current
AMC - Aluminum matrix composite
DCEP - Direct current with positive charge electrode
DCEN - Direct current with negative charge electrode
CHAPTER 1
INTRODUCTION
1.1 Background Introduction
Welding is a fabrication process that joins materials, usually metals or
thermoplastics, by causing coalescence. This is often done by melting the workpieces
and adding a filler material to form a pool of molten material (the weld puddle) that
cools to become a strong joint, with pressure sometimes used in conjunction with
heat, or by itself, to produce the weld. This is in contrast with soldering and brazing,
which involve melting a lower-melting-point material between the workpieces to
form a bond between them, without melting the workpieces.
There are about 100 different types of welding. Arc welding is the most
common type. It uses a welding power supply to create an electric arc between an
electrode and the base material to melt the metals at the welding point. They can use
either direct (DC) or alternating (AC) current, and consumable or non-consumable
electrodes. The welding region is sometimes protected by some type of inert or semi-
inert gas, known as a shielding gas, or an evaporating filler material. The process of
arc welding is widely used because of its low capital and running costs.
Welders use many types of welding equipment set up in a variety of
positions, such as flat, vertical, horizontal, and overhead. They may perform manual
welding, in which the work is entirely controlled by the welder, or semiautomatic
welding, in which the welder uses machinery, such as a wire feeder, to perform
welding tasks.
1.1.1 Tungsten Inert Gas welding (TIG)
Tungsten Inert Gas (TIG) Welding is another name for Gas Tungsten Arc
Welding. In arc-welding, developed in the mid – 1800s, the heat required is obtained
from electrical energy. The process involves is either a consumable or a
nonconsumable electrode. An arc is produced between the tip of the electrode and
the workpiece to be welded, by using an AC or a DC power supply. The arc
temperature is about 30,000 degree Celsius that had much higher temperature than
those developed in oxyfuel-gas welding.
Tungsten Inert Gas (TIG) Welding uses a nonconsumable tungsten electrode
that creates an arc between the electrode and the weld pool. An inert shielding gas is
used in the process at no applied pressure. Argon is most commonly used as the
shielding gas, and the process may be employed with or without the addition of filler
metal.
The TIG welding process is used for a wide variety of metals and
applications, particularly aluminum, magnesium, titanium, and the refractory metals.
TIG welding also suitable especially for thin metals. The cost of the inert gas makes
this process more expensive than shielded metal arc welding (SMAW) but provides a
high quality welds and surface finish. It is used in a variety of critical applications
with a wide range of work piece thicknesses and shape and the equipment is portable.
Typical applications for TIG welding include pipes, pressure vessels and heat
exchangers. Since TIG welding can be used to weld thin metals and small objects,
the method is also used in the electronics industry.
1.1.2 Failure Analysis
Failure analysis can be defined as a method or a series of actions undertaken
to find the reasons a particular failure exists and correcting the causes. It is also the
process of collecting and analyzing data to determine the cause of a failure and how
to prevent it from recurring. It is an important discipline in many branches of
manufacturing industry, where it is a vital tool used in the development of new
products and for the improvement of existing products. It is vitally important to
understand that these two distinct elements are both essential if one is to embark on a
study of failure analysis.
There is no particular relevance to knowing the cause or causes of a certain
failure are if the problem cannot be resolved. In this definition, failure analysis can
obviously apply to numerous fields of study. In this project, I was studying failure
analysis as it applies to the TIG welding techniques.
The purpose of this project is to analyze, collecting and determine the cause
of a failure in Tungsten Inert Gas Welding (TIG) and how to prevent it from
occurring. The various technique of TIG welding also will be discuss to ensure the
best technique will be apply in various condition of welding. The welding technique
will be analyzed with the result that it produces.
In this failure analysis of TIG weldment, The Fault Tree Analysis (FTA), and
Fish bone method will be use to analyze the failure that occur in various condition of
TIG welding techniques.
1.2 Problem Statements
The failure analysis will be carried on at welding laboratory in Universiti
Teknikal Malaysia, Melaka (UTEM) at Ayer Keroh, Malacca. Before that, this
failure analysis on TIG welding were be study and the method to be used was
recognize to ensure all the probably or actual failure on TIG welding were identified.
The TIG welding was very hard to handle and because of that, it may produce a
various type of failure in product or component to be joint. The main problem of this
welding is it needs a proper technique that must be used according to the situation
such as a DC power and current setting must be matching and the use of filler metal
in welding.
1.3 Objective
1) To identify the type of failure that occurs in TIG welding.
2) To analyze the failures occur in TIG welding using FTA.
3) To identify parameter that contribute to failure occur in TIG welding.
1.4 Scopes of the Research
This project focuses on failures that occur during Tungsten Inert Gas (TIG)
welding. The failures than will be analyze using Failure Tree analysis (FTA) and
before that, a statistic such as histogram must be created to identify the type of
failure that occur. A proper welding technique must be applied to decrease the
probability of failure in TIG welding. In this project, the TIG welding instruments
will be used at Manufacturing Laboratory in UTem to complete the analysis of
failure that will be produced.
CHAPTER 2
LITERATURE REVIEW
2.1 IINTRODUCTION (JURNAL)
Pantazopoulos, G. and Sampani, A. (2006) doing a case study on weld failure
of a rolled Zn- alloy strip that mainly used in construction industry. They found that
significant welding defects, such as linear discontinuities, edge micro cracks and
fusion zone gas porosity are detected during the investigation procedure. The size
and distribution of pores in the fusion zone affect directly the mechanical behaviors
and the workability of the welded tube. They also found that Welding defects due to
the application of improper welding procedure is a significant contributor of limited
weld workability and premature failure. [1]
Jha, A. K. et al. (2003) doing a Metallurgical analysis of cracking in
weldment of propellant tank for satellite launch vehicles that use a Medium strength
Al–Zn–Mg aluminum alloy. They found that various type of crack occur in TIG
welding area at propellant tank and cracking initiated from the root of pit, followed
the path of solute enriched dendrite caused intergranular mode of fracture. This
confirmed the cracking was due to stress corrosion. The stress introduced during
welding as contractional strain in accommodating the nozzle facilitated the cracking
phenomena. [2]
Meola, C. et al. (2004) have conduct a testing and analysis of stainless steel
welded joints between destructive and non-destructive techniques. They have found
three techniques for weld joints analysis that use micrographs, Vickers micro-
hardness measurements, and Lockin thermography. These three techniques are
synergic and helpful for a complete characterization welded joints and for
improvement of the welding method. [3]
Tarng, Y. S., Tsai, H.L. and Yeh, S.S. (1999) have done an experiment in
Modeling, optimization and classification of weld quality in tungsten inert gas
welding. In the project, they describe an intelligent modeling, optimization and
classification of weld quality in TIG welding process. A back-propagation network is
used to construct the relationships between the process parameters and the features
on the weld pool geometry. A gobal optimization algorithm called simulated
annealing is then applied to the network for solving the process parameters with
optimal weld pool geometry based on an objective function. Furthermore, the fuzzy
c-means algorithm is adopted here to classify and verify the weld quality using the
features on the weld pool geometry. Through this study, highly non-linear, strongly
coupled, multivariable TIG welding processes can be further understood, analyzed
and controlled. [4]
Liming, L. and Shengxi, W. (2006) have doing a study on the dissimilar
magnesium alloy and copper lap joint by TIG welding. During his study, they have
found that in the TIG welding of dissimilar magnesium alloy and copper,
intermetallic compounds were produced in the interfacial region. Intermetallic
compounds were the main cause of embrittleness of the joints.By using iron plate as
interlayer between magnesium alloy and copper, the embrittleness of joint was
obviously decreased and the tensile strength of the joint is higher compared with that,
without iron plate. They also noticed that Metallic oxides in the interfacial region
between iron plate and magnesium alloy were the main reasons influenced the
strength. [5]
UrenÄ, A. et al. (2000) has describes about the influence of interface
reactions on fracture mechanisms in TIG arc-welded aluminum matrix composites.
They conclude that: [6]
• TIG arc welding of aluminum matrix composites (AMC) reinforced with SiC
particles produced severe degradation of the materials because of the
formation of Al4C3 in the matrix/reinforcement interface.
• The failure mechanisms in the studied AMCs were mainly: particle fracture
for particles larger than 10 mm; and ductile matrix failure in the proximity of
the SiC/Al interface for particles smaller than 10 mm.
• Fracture of the welded composites was mainly controlled by interface
debonding through the continuous interface reaction layer, although the
formation of discontinuous tabular Al4C3 aggregates with preferential
dissolution of some SiC planes also favoured damage to particles smaller then
10 mm.
• Interfacial reactions between SiC particles and molten aluminium during
welding also produced degradation of fracture behavior of the aluminum
matrix which was associated with the Si enrichment.
• Arc welding of the studied composites presented an additional problem of
porosity in the weld, which was enhanced by the increase of the
reinforcement grade and welding power. It has been mainly characterised as
interdendritic porosity associated to the low wettability of the SiC particles by
molten aluminum.