An appraisal of the Tekken test

235 Pages·2012·5.04 MB·English

University of Wollongong
Research Online
University of Wollongong Thesis Collection University of Wollongong Thesis Collections
1986
An appraisal of the Tekken test
Alan Lionel Wingrove
University of Wollongong
Recommended Citation
Wingrove, Alan Lionel, An appraisal of the Tekken test, Doctor of Philosophy thesis, Department of Metallurgy and Materials
Engineering, University of Wollongong, 1986. http://ro.uow.edu.au/theses/1606
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"AN APPRAISAL OF THE TEKKEN TEST"
A THESIS SUBMITTED IN FULFILMENT OF THE
REQUIREMENTS FOR THE AWARD
OF
THE DEGREE OF DOCTOR OF PHILOSOPHY
FROM
THE UNIVERSITY OF WOLLONGONG
BY
ALAN LIONEL WINGROVEA.S.TC.BSc. MAppSci
DEPARTMENT OF METALLURGY
and
MATERIALS ENGINEERING
MAY 1986
CANDITATE'S CERTIFICATE
This is to certify that the work presented in this thesis was carried out by
the candidate in the laboratories of the Depertment of Metallurgy and
Materials Engineering of the University of Wollongong and has not been
presented to any other university or institution for a higher degree.
Alan L.WingroveA.S.T.C. B.Sc. M.App.Sc.
ACKNOWLEDGEMENTS
The auther would firstly like to thank the Australian
Welding Research Association for the financial support that has been
given to this research. Throughout this work, virtually every member
of the staff of the Department of Metallurgy and Materials Engineering
has been helpful in some way and this has been greatly appreciated.
In particular thanks are due to the Head of Department,
Associate Professor N. F. Kennon for the use of the laboratory
facilaties and for his and Dr. D. P. Dunne's help and encouragement
during their supervision of the research.
Thanks are also due to Mr. F. Groves and the workshop staff
for design and construction of equipment and to Mrs. Ann Webb for
her assistance during the arduous task of preparing this thesis.
The donations of both the steel plate by B.H.P. Steel Slab and
Plate Products Division and the electrodes by Welding Industries of
Australia Pty. Ltd. are also greatfully acknowledged.
SYNOPSIS
Literature relevant to the weldability of steel by manual metal arc welding
has been reviewed. In particular, the process of manual metal arc welding has been
examined and current theoretical models that have been developed to predict the
structure of the weldment are discussed. Weld defects, particularly hydrogen
assisted cold cracking of the heat affected zone (HAZ) are discussed and a review of
weldability tests relevent to H AZ cracking has been made. The Japanese developed
Tekken Test has been examined in detail and the relevance of Cracking Index
measurements has been analysed.
The effects that variations to the extrinsic welding parameters of voltage,
current, and speed on Cracking Index as determined by the Tekken Test have been
examined. Intrinsic welding variables of microstructure and restraint stress have
been examined using optical and electron microscopy and a restraint stress
measuring technique. Cracking Index results have been related to the extrinsic
welding parameters by variations caused to the intrinsic variables of microstructure
and restraint stress.
It was found that increases in welding speed and voltage increased the
value of the Cracking Index and increases in welding current decreased the Cracking
Index value. The interaction of these effects produced a variation of results for
welding at constant heat input.
All three extrinsic parameters were found, independently and collectively
to affect the microstructures of both the H AZ and the weldmetal. It was found that
increases in welding voltage and current and decreases in welding speed increased
the volume fraction of proeutectoid ferrite in the H AZ with an associated decrease in
H AZ cracking. Cracking of the weldmetal was found to be related to the ferrite
morphology; fine lath (acicular) ferrite was found to be the microstructure least
susceptible to cracking. Formation of fine lath ferrite microstrucures was enhanced
by low welding speeds. From the various combinations of weldmetal and H AZ
microstructures that could be achieved a range of Cracking Index values could be
produced.
The influence that root gap of the test piece, the composition ( carbon
equivalent) of the steel plate, and the classification and manufacturing source of the
electrodes had on Cracking Index has also been studied. Increasing root gap and
carbon equivalent increased the value of Cracking Index although in the latter case
the relationship varied with welding conditions. Cracking Index was also found to
vary with electrodes of different classifications and from different manufacturing
sources. It is proposed that these Cracking Index variations are attributable to
strength incompatibilities and differences in electrode flux compositions
respectively.
It is concluded that because of the variation of results, often with
considerable scatter, produced by the interaction of all the variables, the Tekken
Test is not valid as a general method for determining weldability, but rather
provides a useful comparative test of the responses of different steels and electrodes
to welding under strictly specified welding conditions.
TABLE OF CONTENTS
CHAPTER 1 INTRODUCTION 1
CHAPTER 2 THE MANUAL METAL ARC
2.1 Introduction 9
2.2 Covered Electrodes 11
2.3 The Weld 15
2.3.1 The Weldmetal 18
2.3.2 The Heat Affected Zone 22
CHAPTER 3 WELD DEFECTS
3.1 Introduction 31
3.2 Solidification Cracking 32
3.3 Liquation Cracking 33
3.4 Reheat Cracking 33
3.5 Lamellar Tearing 34
3.6 Chevron Cracking 35
3.7 Hydrogen Assisted Cold Cracking 36
3.7.1 The Effect of Hydrogen 36
3.7.2 Microstructure 40
3.7.3 Stress 45
3.7.4 Predicting HAZ Cracking 51
CHAPTER 4 WELDABILITY TESTS
4.1 Introduction 60
4.2 The Implant Test 62
4.3 The Tensile Restraint Cracking Test 63
4 .4 The Rigid Restraint Cracking Test 64
4.5 The Lehigh Restraint Test 65
4.6 The Controlled Thermal Severity Test 66
4.7 The Tekken Test 68
CHAPTER 5 SCOPE OF THE PRESENT WORK 75
CHAPTER 6 EXPERIMENTAL
6.1 Introduction 80
6.2 Materials 81
6.3 Specimen Preparation 82
6.4 Welding Equipment and Procedures 85
6.5 Determination of Cracking Index 87
6.6 Metallography 90
6.6.1 Optical Metallography 90
6.6.2 Electron Metallography 91
6.7 Restraint Stress 91
CHAPTER 7 EXPERIMENTAL RESULTS
7.1 Introduction 94
7.2 The Effect of Welding Variables on Cracking
Index
7.2.1 Introduction 96
7.2.2 The Effect of Voltage 97
7.2.3 The Effect of Current 97
7.2.4 The Effect of Speed 97
7.2.5 The Effect of Constant Heat Input 98
7.2.6 Discussion of Results 99
7.3 The Inter-relationship Between Welding Variables,
Microstructure, Stress and Cracking Index
7.3.1 Introduction 101
7.3.2 The Effect of Voltage 102
7.3.3 The Effect of Current 113
7.3.4 The Effect of Speed 118
7.3.5 The Effect of Constant Heat Input 123
7.4 Other Factors Affecting Cracking Index
7.4.1 Introduction 127
7.4.2 Root Gap 127
7.4.3 Material Composition 129
7.4.4 Electrode Type and Manufacture 133