Quenching- Tempering Effects On Fracture Properties In Carburized Low Carbon Steel.
“I admit that had read this dissertation and in my opinion this dissertation is satisfactory in the aspect of scope and quality for the bestowal of Bachelor of
Mechanical Engineering (Structure and Material)”
Signature :
Supervisor Name : Pn Siti Hajar bt Sheikh Md Fadzullah Date :
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MOHD ADZWAN BIN ADDLY
THIS REPORT WAS SUBMITTED IN ACCORDANCE WITH THE PARTIAL REQUIREMENT FOR THE HONOR OF
DEGREE OF MECHANICAL ENGINEERING (MATERIAL AND STRUCTURE)
FACULTY OF MECHANICAL ENGINEERING UNIVERSITI TEKNIKAL MALAYSIA MELAKA
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“I verify that this report is my own word except summary and extract that every one of it I have clarify the resource”
Signature :
Writer Name : Mohd Adzwan Bin Addly Date :
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MOHD ADZWAN BIN ADDLY
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ACKNOWLEDGEMENT
I would like to thank my supervisor, Pn Siti Hajar bt Sheikh Md Fadzullah and co-supervisor, Pn Rafidah bt Hasan for their support, guidance and encouragement during completed this Projek Sarjana Muda.
Not forgetting, I also would like to thanks to all technician staff especially Mr Mahader, Mr Mazlan, Mr Rashdan, Mr Ridzuan and Mr Rizal for the help and collaboration during the specimen preparation, experimental and testing at laboratory. I really appreciate all of your assistance and help.
I would like to dedicate this project to my parents, friends and anyone that together helping me finishes my project. I hope this report can help future student as their revision or resource later.
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ABSTRACT
Quenching and tempering process are two common processes that are used in the industrial. Quenching is the process where the steel is rapidly cooled after carburizing by using quenching medium such as oil while tempering is the process where the steel is heated at certain temperature between 400oC to 600oC. In this research, 20 specimens of low carbon steel specimens with dimension of 100mm x 19mm x 10mm are used for heat treatment process such as carburizing, quenching, tempering and normalizing. Then the specimens were fracture by using fracture toughness test as per ASTM E399. The effect of this heat treatment process on the fracture properties were analyzed by doing statistical analysis which is hypothesis test. As for data comparison, 4 set of specimens were treated with different heat treatment process. The results from this research showed that the fracture toughness become higher when the specimen undergo quenching and tempering process. This is due to the change of microstructure in the material which it increases the ductility and strength of the specimen therefore making it tougher and durable. Furthermore, the carburizing process diffused more carbon on the specimens which resulted in a higher wear resistance and hardness surface. As a conclusion, this research gives important information and helps the industry to increase the production of steel with higher strength and longer life span.
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ABSTRAK
Proses pelindapkejutan dan pembajaan merupakan dua proses yang biasa digunakan di dalam industri. Proses pelindapkejutan merupakan proses menyejukkan keluli secara mengejut menggunakan medium pelindapkejutan seperti minyak selepas penyusukkarbonan manakala proses pembajaan merupakan proses memanaskan kembali keluli pada suhu tertentu diantara 400oC dan 600oC. Dalam kajian ini, 20 keluli karbon rendah yang berukuran 100mm x 19mm x 10mm telah digunakan untuk proses rawatan haba seperti penyusukkarbonan, pelindapkejutan, pembajaan dan penormalan. Selepas itu keluli dipatahkan menggunakan ujian keliatan patah seperti dalam ASTM E399. Kesan daripada proses rawatan haba ini keatas ciri-ciri patah dianalisis menggunakan statistik analisis iaitu ujian hipotesis. Sebagai perbandingan, 4 set specimen dirawat menggunakan proses rawatan haba yang berbeza. Keputusan daripada kajian ini menunjukkan peningkatan keatas keliatan patah apabila specimen menjalani proses pelindapkejutan dan pembajaan. Ini disebabkan berlakunya perubahan keatas struktur mikro dalam keluli tersebut yang meningkat kemuluran dan kekuatan yang menyebabkannya lebih liat dan tahan lama. Tambahan pula proses penyusukkarbonan menyebarkan lebih karbon untuk meningkatkan ketahanan haus dan kekuatan permukaan specimen. Sebagai kesimpulannya, kajian ini memberi lebih informasi dan membantu industri untuk meningkatkan pengeluaran keluli yang lebih tahan lama dan mempunyai jangka hayat yang panjang.
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TABLE OF CONTENT
CHAPTER TOPIC PAGE
CONFESSION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
TABLE OF CONTENT vii
TABLE LIST ix
FIGURE LIST xiii
SYMBOL LIST xix
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CHAPTER TOPIC PAGE
CHAPTER I INTRODUCTION 1
1.0 General 1
1.1 Objective 2
1.3 Problem Statement 3
1.4 Scope of research 3
1.5 Plannning and execution 4
CHAPTER II LITERATURE REVIEW 6
2.0 Steel 6
2.1 Material properties 7
2.2 Low Carbon Steel 9
2.2.1 Types of low carbon steel 10
2.3 Heat Treatment 10
2.4 Carburizing Process 12
2.4.1 Carburizing Theory 12
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ix CHAPTER TOPIC PAGE
2.5 Quenching Process 15
2.6 Tempering Process 17
2.6.1 Structural changes on tempering 17 2.7 Fracture of steel 18 2.7.2 Fracture of Martensitic Steel 19 2.7.3 Fracture of Medium Strength Steel 19
2.7.4 Fracture Toughness Test 20
CHAPTER III METHODOLOGY 23
3.1 Materials and specimen preparations 23
3.1.1 Materials 23
3.1.2 Specimen Preparations 24
3.2 Experimental Condition 25
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CHAPTER TOPIC PAGE
3.4 Carburizing Process 27
3.4.1 Carburizing Container 27
3.4.2 Furnace 28
3.4.3 Carburizing Procedure 28
3.5 Quenching Process 30
3.5.1 Quenching Procedure 30
3.6 Tempering Process 31
3.7 Crack Propagation Examination 32 3.7.1 Axiovert Microscope MAT 200 32
CHAPTER IV RESULTS 34
4.1 Result from fracture toughness test 34 4.2 Surface specimen of treated and untreated 37
Specimen
4.3 Crack propagation 38
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xi CHAPTER TOPIC PAGE
CHAPTER V DISCUSSION 44
5.1 Comparison between uncarburize and 44 carburize-normalize specimen on fracture
toughness
5.2 Comparison between carburize-normalized 46 specimen and carburize-quenching-normalize
specimen
5.3 Comparison between carburized-quenching- 48 normalized specimen and carburized-quenching- tempering-normalizing specimen
5.4 Fracture behaviour 50
5.4.1 Fracture behaviour of uncarburized specimen 50 5.4.2 Fracture behaviour of carburized specimen 51 5.4.3 Fracture behaviour of carburized-quenching- 52
normalized specimen
5.4.4 Fracture behaviour of carburized-quenching- 53 tempering-normalized specimen
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CHAPTER TOPIC PAGE
CHAPTER VI CONCLUSION 54
CHAPTER VII RECOMMENDATION 55
REFERENCES 56
BIBLIOGRAPHY 59
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xiii
TABLE LIST
TABLE TITLE PAGE
1.1 Gantt chart of the research 4
2.1 Iron alloy phase and types of steel 7 (Source:Internet referance, 13/9/07)
2.2 Other iron based materials 7
(Source:Internet referance,13/9/07)
3.1 Chemical composition of low carbon steel 23 (Source: Internet referance, 22/9/07)
3.2 Mechanical properties of low carbon steel 24 (Source: Internet referance, 22/9/07)
3.3 Experimental condition for quenching-tempering 25 effects study
3.4 Technical data of Axiovert Microscope MAT 200 33 (Source: Internet referance, 27/9/07)
4.1 Result of fracture toughness test for uncarburize and 34 carburized specimens
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TABLE TITLE PAGE
4.2 Result of fracture toughness test for carburizing- 35 quenching- normalize specimens and carburizing-
quenching-tempering-normalize specimens
4.3 Mean Kq, fracture toughness test and variance, S for all 36 Specimen
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xv
FIGURE LIST
FIGURE TITLE PAGE
2.1 Iron carbon phase in necessary condition 8 (Source:William, 2004)
2.2 Phase diagram of temperature and carbon range 11 for certain types of heat treatment (Source:Smith and Hashemi,2006)
2.3 Phase diagram of gas carburizing process 13 (Source: Internet referance, 22/9/07)
2.4 TTT diagram of the temperature condition on 16 the surface and in the core of a specimen to
direct quenching
(Source: Prabhudev, 1988)
2.5 Change in hardness and structure during 17 tempering of eutectoid steels
(Source: Prabhudev, 1988)
2.6 Bend text figure design 21
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FIGURE TITLE PAGE
2.7 Types of forces versus displacement behavior that 21 occur in a fracture toughness
(Source:Adapted from ASTM E399)
2.8 Effect of thickness on fracture toughness of an alloy steel 22 heat treated to the high strength
(Sources: E.Dowling, 2007)
3.1 Specimen in 3 dimension 24
3.2 Dimension of the specimen 24 3.3 Instron 1331 Servo-Hydraulic Testing Machine 26
(Source: internet reference: 26/3/2008)
3.4 Three point bending test 26
3.5 Carburizing Container 27
3.6 Furnace in the laboratory 28 3.7 Specimen arrangement in container 29 3.8 Illustration of carburizing procedures 29 3.9 Quenching process using oil 30 3.10 Illustration of quenching process 31
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xvii
FIGURE TITLE PAGE
3.11 Illustration of tempering process 32 3.12 Axiovert Microscope MAT 200 33 4.1 Differentiation between untreated and treated 36
specimen in fracture toughness value
4.2 Picture of uncarburize and carburized specimen 37 4.3 Picture of carburized-quenching-normalized specimen and 38
carburized-quenching-tempering-normalize specimen
4.4 Crack propagation of uncarburized specimen 38 4.5 Crack propagation of carburized specimen 39 4.6 Crack propagation of carburized-quenching-normalize 39
Specimen
4.7 Crack propagation of carburize-quenching-tempering- 39 normalizing specimen
4.8 Graph of F-distribution 41
4.9 Graph of t-distribution 43 5.1 Comparison between the fracture toughness of carburized 44
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FIGURE TITLE PAGE
5.2 Transformation of carburized low carbon steel 45 with normalizing process
(Source: W.F. Smith, 1993)
5.3 Comparison of carburized-normalized specimen and 46 carburized-quenching-normalized specimen
5.4 Martensitic microstructure of quenched low carbon steel 47 (Source: Oppenheimer, 1995)
5.5 Comparison between carburized-quenching-normalized 48 specimen and carburized-quenching-tempering-normalized
specimen on fracture toughness
5.6 Changes during the tempering of martensite 49 (Source: Ashby, 1998)
5.7 Mechanical properties of quenched and tempered steels 49 (Source: Ashby, 1998)
5.8 Crack behaviour of uncarburized specimen 50 5.9 Crack behaviour of carburized-normalize specimen 51 5.10 Crack behaviour of carburized-quenching-normalize 52
Specimen
5.11 Crack behaviour of carburized-quenching-tempering- 53 normalize specimen
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xix
SYMBOL LIST
W = Width (cm) a = Crack length (cm) B = Thickness (cm)
S = Span (cm)
P = Force (kN)
Kq = Fracture toughness (MPa.√m) σ2
= Variance n = No of sample
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APPENDIX LIST
BIL TITLE PAGE
1 AISI 1020 Steel, cold rolled 61 2 AISI 1020 Steel , hot rolled, quenched, and tempered 63 3 Example data from fracture toughness test. 65 4 Standard Test Method for plain stress fracture 68
toughness of metallic materials (ASTM E399)
5 Table F-distribution 72
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1
CHAPTER I
INTRODUCTION
1.0 Introduction
Quenching process and tempering process are two of the most basic and
widely practiced steel heat treatment processes. Each allows the base properties and performance of the steel to be significantly enhanced, such that a relatively inexpensive and simple starting material can be used for a wide range of demanding application.
These technological developments within these two processes are often ignored in favor of high tech surface treatments. Many research studies are involved in area of surface treatments to increase the material friction and wear resistance. One of the surface treatments is quenching process which is technically developed and widely used in industry to produce extremely hard and wear resistant surface layer on metallic substrate (Selcuk et al, 1999).
Certainly the technology of quenching has changed as well as the kind of workpieces being quenched from axes and swords to gears and automotive components to the development of gas turbine blade that has been quenched in a hot isostatic pressing (HIP) quenching unit in argon under 2000 bars of pressure (Liscic et al, 1993). Even more important is the fact the simultaneously quenching has changed from an empirical skill to a scientifically founded and
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controlled process which now belongs to the area of intelligent processing of materials (Persampieri et al, 1984).
In this research, the material used in this process is low carbon steel (AISI 1020). Low carbon steel in other name called plain carbon steel is a metal alloy that has been combined by two elements iron and carbon, where other elements are present in such a small quantities to affect the properties. Steel with low carbon content has the same properties as iron and soft but it is easily to form. This is due to the carbon content rises the metal becomes harder and stronger but less ductile and more difficult to weld. The most important characteristics is the carbon content influences the yield strength of steel because they fit into the interstitial crystal lattice sites of the body-centered cubic arrangement of the iron molecules. The interstitial carbon reduces the mobility of dislocations which in turn has a hardening effect on the iron. To get dislocations to move, a high enough stress level must be applied in order to break way the dislocation (internet reference, 13/9/07). In this research, effect of quenching and tempering process on fracture properties of carburized low carbon steel was studied. This can provide reference data on fracture properties of the steel. Therefore this finding can be beneficial to expand the application of low carbon steel in industries.
1.1 Objectives
The objectives of this research are to study and discuss the effects of quenching-tempering processes on fracture properties of carburized low carbon steel by using statistical analysis.
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xvii
FIGURE TITLE PAGE
3.11 Illustration of tempering process 32
3.12 Axiovert Microscope MAT 200 33
4.1 Differentiation between untreated and treated 36 specimen in fracture toughness value
4.2 Picture of uncarburize and carburized specimen 37 4.3 Picture of carburized-quenching-normalized specimen and 38
carburized-quenching-tempering-normalize specimen
4.4 Crack propagation of uncarburized specimen 38 4.5 Crack propagation of carburized specimen 39 4.6 Crack propagation of carburized-quenching-normalize 39
Specimen
4.7 Crack propagation of carburize-quenching-tempering- 39 normalizing specimen
4.8 Graph of F-distribution 41
4.9 Graph of t-distribution 43
5.1 Comparison between the fracture toughness of carburized 44 and uncarburized specimen
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5.2 Transformation of carburized low carbon steel 45 with normalizing process
(Source: W.F. Smith, 1993)
5.3 Comparison of carburized-normalized specimen and 46 carburized-quenching-normalized specimen
5.4 Martensitic microstructure of quenched low carbon steel 47 (Source: Oppenheimer, 1995)
5.5 Comparison between carburized-quenching-normalized 48 specimen and carburized-quenching-tempering-normalized
specimen on fracture toughness
5.6 Changes during the tempering of martensite 49 (Source: Ashby, 1998)
5.7 Mechanical properties of quenched and tempered steels 49 (Source: Ashby, 1998)
5.8 Crack behaviour of uncarburized specimen 50 5.9 Crack behaviour of carburized-normalize specimen 51 5.10 Crack behaviour of carburized-quenching-normalize 52
Specimen
5.11 Crack behaviour of carburized-quenching-tempering- 53 normalize specimen
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xix
SYMBOL LIST
W = Width (cm)
a = Crack length (cm) B = Thickness (cm)
S = Span (cm)
P = Force (kN)
Kq = Fracture toughness (MPa.√m) σ2
= Variance n = No of sample
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APPENDIX LIST
BIL TITLE PAGE
1 AISI 1020 Steel, cold rolled 61
2 AISI 1020 Steel , hot rolled, quenched, and tempered 63 3 Example data from fracture toughness test. 65 4 Standard Test Method for plain stress fracture 68
toughness of metallic materials (ASTM E399)
5 Table F-distribution 72
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1
CHAPTER I
INTRODUCTION
1.0 Introduction
Quenching process and tempering process are two of the most basic and
widely practiced steel heat treatment processes. Each allows the base properties and performance of the steel to be significantly enhanced, such that a relatively inexpensive and simple starting material can be used for a wide range of demanding application.
These technological developments within these two processes are often ignored in favor of high tech surface treatments. Many research studies are involved in area of surface treatments to increase the material friction and wear resistance. One of the surface treatments is quenching process which is technically developed and widely used in industry to produce extremely hard and wear resistant surface layer on metallic substrate (Selcuk et al, 1999).
Certainly the technology of quenching has changed as well as the kind of workpieces being quenched from axes and swords to gears and automotive components to the development of gas turbine blade that has been quenched in a hot isostatic pressing (HIP) quenching unit in argon under 2000 bars of pressure (Liscic et al, 1993). Even more important is the fact the simultaneously quenching has changed from an empirical skill to a scientifically founded and
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In this research, the material used in this process is low carbon steel (AISI 1020). Low carbon steel in other name called plain carbon steel is a metal alloy that has been combined by two elements iron and carbon, where other elements are present in such a small quantities to affect the properties. Steel with low carbon content has the same properties as iron and soft but it is easily to form. This is due to the carbon content rises the metal becomes harder and stronger but less ductile and more difficult to weld. The most important characteristics is the carbon content influences the yield strength of steel because they fit into the interstitial crystal lattice sites of the body-centered cubic arrangement of the iron molecules. The interstitial carbon reduces the mobility of dislocations which in turn has a hardening effect on the iron. To get dislocations to move, a high enough stress level must be applied in order to break way the dislocation (internet reference, 13/9/07). In this research, effect of quenching and tempering process on fracture properties of carburized low carbon steel was studied. This can provide reference data on fracture properties of the steel. Therefore this finding can be beneficial to expand the application of low carbon steel in industries.
1.1 Objectives
The objectives of this research are to study and discuss the effects of quenching-tempering processes on fracture properties of carburized low carbon steel by using statistical analysis.