臺灣博碩士論文加值系統

Technology in welding is growing rapidly where to improve the welding results, which aims to determine the hardness of a material as a result of the welding process. The material used is carbon steel because carbon steel is widely used in the industry, especially in the shipping industry. This experiment uses the Gas Tungsten Arc Welding (GTAW) process. GTAW Welding or more popularly called Tungsten Inert Gas (TIG) is one type of electric arc welding with gas guard. To produce an electric arc, an unused electrode is made of tungsten or alloyed metal which has a very high melting point.
In this Research have purpose to know how big is the effect of variation of welding speed by using GTAW welding on carbon steel then used hardness test on specimen and calculation of welded specimen with variation of electric current 80 and 110 ampere, travel speed 15 and 17 cm/s, Wire speed 3.5, 4, 4.5 cm/s. In this research was done measurement of metallography, microstructure, SEM and XRD. For metallography testing to find out the grain size of basemetal, HAZ, weld metal and Non-destructive Testing (NDT) know the hardness of material in basemetal, HAZ, and for XRD to know the phase of the material.
From the result experiments, For measurement of metallography, it is known that the smallest grain size is in basemetal, then HAZ and grain size is the largest in weld metal. At the time of welding process takes place in the material ferrite material progress. In the HAZ and weld metal areas, as for hardness testing on microhardness, the area with the lowest strength is basemetal with an average of 170 ~ 205 HVN, then the second strongest area is HAZ with an average number of 205 ~ 235 HVN, the strongest is the Weld metal area with average number 230 ~ 280 HVN.

Technology in welding is growing rapidly where to improve the welding results, which aims to determine the hardness of a material as a result of the welding process. The material used is carbon steel because carbon steel is widely used in the industry, especially in the shipping industry. This experiment uses the Gas Tungsten Arc Welding (GTAW) process. GTAW Welding or more popularly called Tungsten Inert Gas (TIG) is one type of electric arc welding with gas guard. To produce an electric arc, an unused electrode is made of tungsten or alloyed metal which has a very high melting point.
In this Research have purpose to know how big is the effect of variation of welding speed by using GTAW welding on carbon steel then used hardness test on specimen and calculation of welded specimen with variation of electric current 80 and 110 ampere, travel speed 15 and 17 cm/s, Wire speed 3.5, 4, 4.5 cm/s. In this research was done measurement of metallography, microstructure, SEM and XRD. For metallography testing to find out the grain size of basemetal, HAZ, weld metal and Non-destructive Testing (NDT) know the hardness of material in basemetal, HAZ, and for XRD to know the phase of the material.
From the result experiments, For measurement of metallography, it is known that the smallest grain size is in basemetal, then HAZ and grain size is the largest in weld metal. At the time of welding process takes place in the material ferrite material progress. In the HAZ and weld metal areas, as for hardness testing on microhardness, the area with the lowest strength is basemetal with an average of 170 ~ 205 HVN, then the second strongest area is HAZ with an average number of 205 ~ 235 HVN, the strongest is the Weld metal area with average number 230 ~ 280 HVN.

Abstract I
ACKNOWLEDGMENTS II
Table of Contents III
List of Figures V
List of Tables VII
Chapter I Introduction 1
Chapter II Literatures Review 3
2.1 Fundamental of Metallurgy 3
2.1.1 Steel and Classification 3
2.1.2 Phase diagram of carbon steel (Fe - C) 4
2.2 GTAW Welding 5
2.2.1 Procedure of GTAW welding 5
2.2.2 GTAW Applications 7
2.2.3 GTAW Welding Equipment 8
2.3 Optical Metallography 8
2.4 Microstructures of Steel 10
2.4.1 Ferrite 10
2.4.2 Pearlite 11
2.4.3 Austenite 11
2.4.4 Widmanstatten ferrite 12
2.4.5 Cementite 14
2.4.6 Bainite 15
2.4.7 Martensite 16
2.5 Weldability of Steel 16
2.5.1 Characteristic features of welds 17
2.5.2 Metallurgical factors affecting weldability 19
2.6 Microanalysis 24
2.7 Scanning Electron Microscopy (SEM) 26
2.8 Microhardness (Vicker Hardness) 31
2.9 Heat Input 33
2.9.1 Measurement of Heat Input 34
2.9.2 Weld Size Related to Heat Input 36
2.9.3 Cooling Rate is a Function of Heat Input 37
Chapter III Experimental Procedure 39
3.1 Experimental Procedure 39
3.2 Material and Specimen Preparation 40
3.3 Welding Processes (GTAW) 41
3.3.1 Preparation of welding processing 41
3.2.2 GTAW processing welding 42
3.2.3 Heat Input 42
3.4 Microhardness 45
3.5 Analysis 47
3.5.1 Microetching 47
3.5.2 Metallography 47
3.5.3 Scanning Electron Microscopy 50
3.5.4 X-ray Diffraction Examinations 50
Chapter IV Results and Discussion 51
4.1 Appearance 51
4.2 Phases Constitutions 55
4.3 Grain Size 58
4.4 Microhardness 60
4.5 Effect of travel speed and wire speed 62
4.6 Solidification process 64
4.7 Temperature effect on phase formation and grain size 65
Chapter V Conclusions 68
Chapter VI Future Works 69
REFERENCES 70
APPENDIX A. Grain Size 72
APPENDIX B. Microhardness 84

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