I / We* admit that had read this dissertation and in my / our* opinion this dissertation is satisfactory in the aspect of scope and quality for the bestowal of Bachelor of
Mechanical Engineering (Structure and Material)
Signature :……… Name of 1st Supervisor :………....
Date :………
QUENCHING-TEMPERING EFFECTS ON HARDNESS AND COMPRESSION STRENGTH OF CARBURIZED LOW ALLOY STEEL
NORDIANA BT SIDI
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“I declare that this report is done by my own exclude the citation with the mentioned references for each.”
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ACKNOWLEDGEMENT
All praises be to Allah S.W.T, The Most Gracious, The Most Merciful for His Guidance and Blessing.
Firstly, I would like to take this opportunity to acknowledge my supervisor, Pn. Rafidah who is very committed to give the best cooperation and also for her guidance in completing this final year project. This appreciation also dedicated to my second supervisor, Mr Hamzah Mat Dom for his time and energy to make sure this project is successfully done.
Secondly, this appreciation goes to the technicians involved; Mr. Mahathir (Material Lab), Mr. Junaidi and Mr Mazlan (Machines Lab), Mr. Rashdan (Solid Lab) and Mr. Azhar (FKP Material Lab). Then, a lot of thanks to the Faculty of Mechanical Engineering UTeM, Faculty of Manufacturing Engineering UTeM, Faculty’s PSM Committee and also to my fellow friends for their helps and supports.
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ABSTRACT
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ABSTRAK
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CONTENTS
CHAPTER ITEM PAGE
DECLARATION ii
ACKNOWLEDGEMENT iii
ABSTRACT iv
ABSTRAK v
CONTENTS vi
LIST OF TABLES x
LIST OF FIGURES xii
LIST OF ABBREVIATIONS xvii
LIST OF APPENDICES xviii
CHAPTER 1 INTRODUCTION
1.1 Background 1
1.2 Objectives 2
1.3 Scopes 3
1.4 Problem Statement 3
CHATER 2 LITERATURE REVIEW
2.1 Alloy Steel 4
2.1.1 Low Alloy Steel 6
2.2 Surface Hardening 7
2.2.1 Carburizing 8
2.2.1.1 Pack Carburizing 9
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CHAPTER ITEM PAGE
2.3.1 Quenching 13
2.3.1.1 Quenching Media 15
2.3.2 Tempering 16
2.3.3 Normalizing 19
2.4 Mechanical Test (Destructive Test) 20
2.4.1 Hardness Test 21
2.4.1.1 Rockwell Test 23
2.4.2 Compression Test 25
CHAPTER 3 METHODOLOGY
3.1 Materials 27
3.2 Process Flow 31
3.2.1 Specimens Preparation 32
3.2.2 Carburizing Process 34
3.2.3 Heat Treatment Process 37 3.2.3.1 Phase 1: Carburizing and
Normalizing 38
3.2.3.2 Phase 2: Carburizing, Quenching and Normalizing
Process 39
3.2.3.3 Phase 3: Carburizing, Quenching, Tempering and
Normalizing Process 40
3.2.4 Rockwell Hardness Test 41
3.2.5 Compression test 43
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CHAPTER ITEM PAGE
CHAPTER 4 RESULT AND ANALYSIS
4.1 Hardness Test 47
4.1.1 Result 47
4.1.2 Statistical Analysis 49
4.1.2.1 Comparison between Group
5A and 5B 49
4.1.2.2 Comparison between Group
5C and 5D 52
4.1.2.3 Comparison between Group
5B and 5D 55
4.2 Compression Test 58
4.2.1 Result 58
4.2.2 Statistical Analysis 59
4.2.2.1 Comparison between Group
5A and 5B 59
4.2.2.2 Comparison between Group
5A and 5D 62
4.2.2.3 Comparison between Group
5B and 5D 65
4.2.2.4 Comparison between Group
5A and 5C 68
4.3 Summary of Hardness and Compressive
Strength Comparison by Statistical Analysis 71
CHAPTER 5 DISCUSSION
5.1 Effects On Hardness 72
5.1.1 Hardness comparison between Group
5A and 5B 73
5.1.2 Hardness comparison between Group
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CHAPTER ITEM PAGE
5.1.3 Hardness comparison between Group
5B and 5D 75
5.2 Effects On Compression Strength 76 5.2.1 Comparison of Compressive Strength
between Group 5A and 5B 77 5.2.2 Comparison of Compressive Strength
between Group 5A and 5D 78 5.2.3 Comparison of Compressive Strength
between Group 5B and 5D 79 5.2.4 Comparison of Compressive Strength
between Group 5A and 5C 80
CHAPTER 6 CONCLUSION 81
CHAPTER 7 RECOMMENDATION 82
REFERENCES 83
BIBLIOGRAPHY 85
APPENDIX A 86
APPENDIX B 88
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LIST OF TABLES
NO. TITLE PAGE
2.1 Colours formed on steel in the temperingprocess. 18 (Source: Rajput, R.K. 2000)
2.2 The examples of mechanical tests. 20
(Source: Rajput, R.K. 2000)
2.3 General characteristics of hardness testing methods 22 and formulas for calculating hardness.
(Source: Kalpakjian, S. and Schmid, S. 2006)
2.4 Rockwell scales 23
(Source: Horath, L. 2001)
2.5 Equation for converting HRC and HRB to Brinell 24 Hardness.
(Source: Chapman, W.W. 2004)
3.1 Chemical composition of A-2 Low Alloy Steel 28 (Source: Farrar, J.C.M. 2004)
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NO. TITLE PAGE
3.3 Specimen distributions 32
4.1 Experimental data for Group 5A and 5B 47
4.2 Experimental data for Group 5C and 5D 48
4.3 Average hardness in Brinell for each group 49
4.4 5A vs 5B 49
4.5 5C vs 5D 52
4.6 5B vs 5D 55
4.7 Experimental data of compressive strength 58
4.8 Average compressive strength for each group 59
4.9 5A vs 5B 60
4.10 5A vs 5D 62
4.11 5B vs 5D 65
4.12 5A vs 5C 68
4.13 Conclusion of hardness compression 71
xii
LIST OF FIGURES
NO. TITLE PAGE
2.1 The effect of the percentage of alloying elements 5 on the eutectoid temperature of the transformation
of austenite to pearlite in the Fe-Fe3C phase diagram. (Source: Smith, W.F. 2004)
2.2 Hardening effects of alloying elements in solid 5 solution in fully annealed ferrite.
(Source: Internet reference 22th July 2007)
2.3 Carburizing of a low carbon steel to produce a high 8 carbon, resistant surface.
(Source: Askeland, D.R. 1994)
2.4 Carburizing powder. 10
(Source: Internet reference, 11 Sept. 2007)
2.5 Graph of quenching effects on hardness. 14 (Source: Internet reference, 17 August 2007)
2.6 Hardness variation with martensite percentage and 14 carbon content after quenching.
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NO. TITLE PAGE
2.7 Thermal cycle of quenching and tempering. 16 (Source: Rajput, R.K. 2000)
2.8 The effect of tempering temperature on the 17 mechanical properties of 1050 steel.
(Source: Askeland, D.R. 1994)
2.9 The effect of carbon and heat treatment on the 19 property of carbon steels.
(Source: Askeland, D.R, 1994)
2.10 Column action 25
(Source: Horath, L. 2001)
2.11 Compression specimen specifications 26 (Source: Horath, L. 2001)
3.1 The alloy tree 27
(Source: Farrar, J.C.M. 2004)
3.2 Evaluation of Group A of Low Alloy Steel 30 (Farrar, J.C.M 2004)
3.3 Process flow of project 31
3.4 The dimension of specimen 32
3.5 Low alloy steel specimens 32
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NO. TITLE PAGE
3.7 The wilcarbo powder was packed at the bottom of the 34 containers.
3.8 The arrangement of specimens in the container 35
3.9 The extra container 35
3.10 The container were taken out from the furnace after 36
6 hours
3.11 The specimens were taken out from the containers 36
3.12 Flow chart of heat treatment processes 37
3.13 Carburizing process 38
3.14 Normalizing process 38
3.15 The schematic diagram of the carburizing-normalizing 38 process
3.16 Carburizing process 39
3.17 Quenching process 39
3.18 Normalizing process 39
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NO. TITLE PAGE
3.20 Carburizing process 40
3.21 Quenching process 40
3.22 Tempering process 40
3.23 Normalizing process 40
3.24 The schematic diagram of the carburizing, quenching, 40 tempering and normalizing process
3.25 Hardness Test machine 41
3.26 Diamond indenter for HRC scale 41
3.27 Compression test machine 43
3.28 Difference in measurement before and after compression 45 test
3.29 Flow of hypothesis test 46
5.1 Hardness of Group 5A, 5B, 5C and 5D 72
5.2 Hardness comparison between Group 5A and 5B 73
5.3 Hardness comparison between Group 5C and 5D 75
5.4 Hardness comparison between Group 5B and 5D 76
xvi
NO. TITLE PAGE
5.6 Comparison of compressive strength between Group 77 5A and 5B
5.7 Comparison of compressive strength between Group 78 5A and 5D
5.8 Comparison of compressive strength between Group 79 5B and 5D
xvii
LIST OF ABBREVIATIONS
ASTM = American Society of Testing and Material AISI = American Iron and Steel Institute
UNS = Unified Numbering System BHN = Brinell Hardness Number HRB = Rockwell B Hardness HRC = Rockwell C Hardness
EN = Euro Norm
CO = Carbon monoxide
CO2 = Carbon dioxide
xviii
LIST OF APPENDICES
PAGE
APPENDIX A 86
Mitutoyo Conversion Table
APPENDIX B 88
Graphs of compressive strength
APPENDIX C 93
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CHAPTER 1
INTRODUCTION
1.1 Background
Low alloy steels have been developed to overcome the deficiencies of plain carbon steels that contain alloying elements to improve their properties. The principle alloying elements added to make alloy steel are manganese, nickel, chromium, molybdenum and tungsten. Alloy steels are expensive than plain carbon steel but for many applications, they are the only materials that can be used to meet engineering requirements especially in the manufacture of automobiles and trucks parts. Beside that, low alloy steels also have better combination of strength, toughness and ductility than plain carbon steel. They contain about 0.2 percent C which commonly carburized or surface heat-treated to produce a hard, wear resistance surface while maintaining a tough inner core (Smith, 2004).
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treatment processes were carried out in order to compare the effect of quenching, tempering and normalizing after carburizing.
For the experimental set up, the heat treatment were divided into three phases, the first phase consists of carburizing then followed by normalizing, while for the second phase is carburizing, quenching and normalizing and the last phase consists of carburizing, quenching, tempering and normalizing. Quenching is a method of rapid cooling of a metal in a bath of liquid during heat treatment (Rajput, 2000) while the definition of tempering is a reheating of previously quenched alloy to a temperature below the critical range, holding the alloy for a specified time at that temperature, and then cooling it at a controlled rate, usually by immediate rapid quenching, to room temperature (Tomsic and Hodder, 2000). The final treatment is normalizing which it is the term applied to the process of heating the steel approximately 4°C above the critical temperature followed by cooling below this range in still air (Rajput, 2000).
After the heat treatment processes, hardness and compression strength test were carried out to study the effects of those heat treatments on low alloy steel specimens. Hardness is a material’s ability to resist surface abrasion while the compression strength is defined as malleability which it is a measure of the extent to which a material can withstand deformation in compression before failure occurs (Chapman, 2004). The data obtained from these test were compared to each other and the effects on low alloy steel were evaluated and analyzed after the three phases of heat treatments.
1.2 Objective
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1.3 Scopes
The scopes of this study are:
(a) To do literature study on carburizing process.
(b) To carry out carburizing treatment, normalizing, carburizing-quenching-normalizing, carburizing-quenching-tempering-normalizing on low alloy steel.
(c) To carry out hardness and compression test on the material, before and after treatments.
(d) To compare the data using statistical analysis in order to propose a better carburizing treatment process.
1.4 Problem Statement
In advance engineering, low alloy steels are widely used for some applications due to better combination of strength, toughness and ductility than plain carbon steel. In order to obtain the superior strength and toughness properties, there are some heat treatments that should be going through. Low alloy steels are commonly carburized to produce hard, high wear-resistant of the outer surface.
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CHAPTER 2
LITERATURE REVIEW
2.1 Alloy Steel
Smith (2004), said alloy steels have been developed to overcome the limitations of plain carbon steel which are used widely in engineering application. Some of the limitations of carbon steels are:
(a) Plain carbon steels cannot be strengthened beyond about 100,000 psi (690MPa) without a substantial loss in ductility and impact resistance.
(b) Large-section thickness of plain carbon steels can not be produced with a martensitic structure throughout. That is, they are not deep hardenable.
(c) Plain carbon steels have low corrosion and oxidation resistance.
(d) Medium-carbon plain carbon steels must be quenched rapidly to obtain a fully martensitic structure. Rapid quenching leads to possible distortion and cracking of the heat-treated part.
(e) Plain carbon steels have poor impact resistance at low temperature.
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Figure 2.1:The effect of the percentage of alloying elements on the eutectoid temperature of the transformation of austenite to pearlite in the Fe-Fe3C phase
diagram (Source: Smith, 2004).
Beside that, according to Askeland (1994), the alloying elements are added to steels to provide solution strengthening of ferrite, cause the eutectoid temperature of the Fe-Fe3C phase diagram to be raised or lowered (as shown in Figure 2.1), improve corrosion resistance and other special characteristics of the steel, and improve hardenability. Improving the hardenability is the most important in alloy and tool steels and the general effectiveness is shown in Figure 2.2:
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