Finite Element Model of the Thermal Profile During Submerged Arc Welding with One and Two Electrodes by Alexandre J. L. LECOANET A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Chemical Engineering Department of Chemical and Materials Engineering University of Alberta © Alexandre J. L. LECOANET, 2016 Abstract: The submerged-arc welding (SAW) process is used extensively in the manufacturing of pipes. The heat flow introduced by the welding operation has a significant impact on the properties of both the weld metal and the heat affected zone (HAZ). The work presented in this thesis aims to develop a numerical heat flow model to predict the temperature profile in piece welded using SAW as a function of the welding parameters. Measurement were done using instrumented thermocouples during an operation of SAW with one electrode. The models were then compared to the measurements and a sensitivity analysis was carried out on the density, the specific heat, the parameter called “f ” in the double ellipsoid model, f and the Neumann boundary condition. The three models used are a point source model giving results similar to Rosenthal’s results, a model using a double ellipsoid heat source with constant thermal properties, and a model using a double ellipsoid heat source with varying thermal properties. The presence of the thermocouples linked to the data acquisition system used in the experiment disturbed the weld but workable data were still extracted. Then the comparison between the measurement and the simulations showed that the most accurate model is the one using a double ellipsoid heat source with varying thermal properties. It predicts well the heating and the cooling phases of all the temperature profiles recorded but it predicts the peak well only for the thermocouples located around 12 mm from the center of the plate closer it overestimates the peak. The sensitivity analysis showed that the most sensitive parameters are the thermal properties. It also showed that the parameter called “f ” in Goldak’s approach is sensitive. The Neumann f boundary condition is not a sensitive parameter. Also when measurements are done using thermocouples close to the knowing the exact location of the thermocouples is crucial. ii Preface: This thesis is an original work by Alexandre J. L. LECOANET. No part of this thesis has been previously published. Acknowledgments: For their guidance I would like to thank Professor Hani HENEIN and Professor Douglas IVEY. Dr. Barry WISKEL was of precious help for this work in general and the experiments especially. The members of the Advanced Materials and Processing Laboratory group also helped me throughout my work and for that I thank them. I would like to thank Joel PEPIN for his help for the development of the statistical model used in this work to determine the bead shape of the weld. Also, Stephen KENNY and Jason SZARKOWICZ helped me a lot to conduct the experiments. The pictures of the cross-sections analyzed here as well as some of the measurements done on them were done by David ROSE and I thank him for his time. I want to thank Les DEAN and Walter BODDEZ for their help in designing the instrumentation of the welds. I would like to give special thanks for their sponsorship, Evraz Inc. NA, Trans-Canada Pipelines, Enbridge, Alliance Pipelines, UT Quality, and the Natural Science and Engineering Research Council (NSERC) of Canada. iii Table of contents: Abstract: ........................................................................................................................................ ii Preface: ......................................................................................................................................... iii Acknowledgments: ....................................................................................................................... iii Acronyms and symbols: ............................................................................................................ xix Acronyms: ................................................................................................................................ xix Symbols – Latin alphabet: ........................................................................................................ xx Symbols – Greek alphabet: ...................................................................................................... xxi 1. Introduction: ............................................................................................................................. 1 2. Literature review: ..................................................................................................................... 4 2.1. Welding: ............................................................................................................................... 4 2.1.1. Definitions: ................................................................................................................... 4 2.1.2. Welding history:............................................................................................................ 4 2.1.3. Submerged arc welding: ............................................................................................... 5 2.2. Variables: ............................................................................................................................. 8 2.2.1. Overview of the variables involved: ............................................................................. 9 2.2.2. Input variables and their effect on the output ones: .................................................... 10 2.2.3. Additional considerations for tandem SAW: .............................................................. 14 2.3. Steel: .................................................................................................................................. 15 2.4. Pipelines: ............................................................................................................................ 15 2.4.1. General overview: ....................................................................................................... 15 2.4.2. The reasons behind the choice of micro-alloyed steel for pipelines: ......................... 16 2.4.3. Pipeline manufacturing: .............................................................................................. 17 2.5. Simulation: ........................................................................................................................ 20 2.5.1. Analytical solutions: ................................................................................................... 21 iv 2.5.2. Numerical methods: .................................................................................................... 24 2.6. Frame of the present work: ............................................................................................... 28 3. Simulation:............................................................................................................................... 30 3.1. Governing equations: ......................................................................................................... 30 3.2. Point source on a semi-infinite body: ................................................................................ 32 3.2.1. Single point source: ..................................................................................................... 32 3.2.2. Two point sources: ...................................................................................................... 41 3.3. Mixed boundary conditions: .............................................................................................. 45 3.3.1. Geometry: ................................................................................................................... 45 3.3.2. Boundary conditions considered: ................................................................................ 46 3.3.3. Results: ........................................................................................................................ 48 3.3.4. Conclusions: ................................................................................................................ 51 3.4. Double ellipsoid source: .................................................................................................... 51 3.4.1. Presentation of the source and geometry: ................................................................... 52 3.4.2. Boundary conditions: .................................................................................................. 56 3.4.3. Numerical transient calculations: ................................................................................ 56 3.4.4. Simulation with constant thermal properties: ............................................................. 57 3.4.5. Simulation with temperature dependent thermal properties: ...................................... 59 3.4.6. Simulation with two sources: ...................................................................................... 61 3.5. Conclusions: ....................................................................................................................... 65 4. Instrumented welds: ............................................................................................................... 66 4.1. Bead on plate weld: ............................................................................................................ 69 4.1.1. Bead shape analysis: ................................................................................................... 69 4.1.2. Welding stability: ........................................................................................................ 69 4.1.3. Conclusions: ................................................................................................................ 70 v 4.2. Weld on machined plate without thermocouples: .............................................................. 70 4.2.1. Bead shape analysis: ................................................................................................... 71 4.2.2. Welding stability: ........................................................................................................ 74 4.2.3. Conclusions: ................................................................................................................ 75 4.3. Weld with type B and type K thermocouples: ................................................................... 75 4.3.1. Bead shape analysis: ................................................................................................... 75 4.3.2. Welding stability: ........................................................................................................ 78 4.3.3. Temperature profiles: .................................................................................................. 78 4.3.4. Conclusions: ................................................................................................................ 81 4.4. Weld with only type K thermocouples: ............................................................................. 82 4.4.1. Bead shape analysis: ................................................................................................... 82 4.4.2. Welding stability: ........................................................................................................ 84 4.4.3. Temperature profiles: .................................................................................................. 85 4.4.4. Conclusions: ................................................................................................................ 88 4.5. Conclusions: ....................................................................................................................... 88 5. Comparison between simulation and experiments: ............................................................. 90 5.1. General presentation: ......................................................................................................... 90 5.2. Comparison for each thermocouple: .................................................................................. 92 5.2.1. R1KbZ1: ..................................................................................................................... 92 5.2.2. R1KbZ3: ..................................................................................................................... 93 5.2.3. R2KbZ1: ..................................................................................................................... 94 5.2.4. R2KbZ2: ..................................................................................................................... 95 5.2.5. R2KaZ1: ...................................................................................................................... 96 5.2.6. R2KaZ2: ...................................................................................................................... 98 5.2.7. Conclusions: ................................................................................................................ 99 vi 5.3. Sensitivity analysis: ......................................................................................................... 100 5.3.1. Density and specific heat: ......................................................................................... 101 5.3.2. Thermal conductivity: ............................................................................................... 102 5.3.3. Ff parameter: ............................................................................................................. 103 5.3.4. Mixed boundary condition coefficient: ..................................................................... 104 5.3.5. Effects of the uncertainties on the location of the thermocouples: ........................... 105 5.3.6. Conclusions on the sensitivity of the studied parameters: ........................................ 108 5.4. Conclusions: ..................................................................................................................... 109 6. Conclusions and future work: ............................................................................................. 111 6.1. Conclusions of this work: ................................................................................................ 111 6.2. Future developments: ....................................................................................................... 113 References: ................................................................................................................................. 115 Appendices: ............................................................................................................................... 122 A. Statistical Analysis Results: ............................................................................................... 122 A.1. Wire feed speed: .......................................................................................................... 122 A.2. Reinforcement area: .................................................................................................... 123 A.3. Maximum reinforcement height: ................................................................................ 125 A.4. Bead width: ................................................................................................................. 126 A.5. Penetration area: .......................................................................................................... 128 A.6. Maximum penetration depth: ...................................................................................... 130 B. Statistical Analysis of Wire Feed Speed During Submerged Arc Welding: ...................... 134 B.1. Abstract: ...................................................................................................................... 134 B.2. Introduction: ................................................................................................................ 135 B.3. Inputs: .......................................................................................................................... 136 B.4. Methods used: ............................................................................................................. 137 vii B.5. Implementation: .......................................................................................................... 141 B.6. Results & Discussion: ................................................................................................. 143 B.7. Insignificant variables: ................................................................................................ 148 B.8. Link with properties: ................................................................................................... 148 B.9. Conclusions: ................................................................................................................ 150 B.10. Acknowledgements: .................................................................................................. 151 B.11. Symbols and Acronyms: ........................................................................................... 152 B.12. Data used for processing: .......................................................................................... 153 C. Thermo-physical properties: .............................................................................................. 155 C.1. Constant thermo-physical properties:.......................................................................... 155 C.2. Thermo-physical properties varying with the temperature: ........................................ 155 D. Additional information on the experiments: ...................................................................... 170 D.1. Temperature profiles: .................................................................................................. 170 D.2. Output of the welder: .................................................................................................. 181 E. Bead shape measurements: ................................................................................................. 196 viii Tables: Table 3.1: Input parameters used for the simulation. .................................................................... 36 Table 3.2: Parameters used to calculate the dimensions of the source presented in Figure 3.18. 56 Table 4.1: Parameters used for the experiments. .......................................................................... 66 Table 4.2: Summary of the four different welds performed and their results. .............................. 68 Table 4.3: Average values and standard deviations of the parameters given by the welder reported along with the intended values. ............................................................................................. 70 Table 4.4: Main bead shape parameters measured from the cross-sections. ................................ 74 Table 4.5: Average values and standard deviations for the parameters given by the welder along with the intended values. ....................................................................................................... 74 Table 4.6: Main bead shape parameters measured from the cross-sections. ................................ 78 Table 4.7: Average values and standard deviations of the parameters given by the welder reported along with the intended values. ............................................................................................. 78 Table 4.8: Main bead shape parameters measured from the cross-sections. ................................ 84 Table 4.9: Average values and standard deviations of the parameters given by the welder reported along with the intended values. ............................................................................................. 85 Table 5.1: Position of different thermocouples in the plane (z,y). Parameters Dz and Dy are the ones shown in Figure 5.1. ...................................................................................................... 91 Table 5.2: Strengths and weaknesses of the three models compared with measurements. .......... 99 Table A.1: Half-width of the confidence intervals for the regression of the reinforcement area. ............................................................................................................................................. 123 Table A.2: Half-width of the confidence intervals for the regression of the maximum reinforcement height. .................................................................................................................................. 125 Table A.3: Half-width of the confidence intervals for the regression of the bead width. .......... 127 Table A.4: Half-width of the confidence intervals for the regression of the penetration area. .. 129 Table A.5: Half-width of the confidence intervals for the regression of the penetration area. .. 131 Table B.1: Range in variables for analysis. ................................................................................ 137 Table B.2: Half width of the confidence intervals, for the significant variables. ....................... 143 Table B.3: List of symbols and acronyms used (Latin alphabet). .............................................. 152 Table B.4: List of symbols and acronyms used (Greek alphabet). ............................................. 152 Table B.5: Data utilized. ............................................................................................................. 153 ix Table E.1: Bead shape parameters measured on the cross-sections. .......................................... 196 x