MAGNETICALLY IMPELLED ARC BUTT (MIAB) WELDING OF CHROMIUM- PLATED STEEL TUBULAR COMPONENTS UTILIZING ARC VOLTAGE MONITORING TECHNIQUES DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By David H. Phillips, M.S.W.E ***** The Ohio State University 2008 Dissertation Committee: Professor Charley Albright, Advisor Approved by Professor Dave Dickinson _________________________________ Professor John Lippold Advisor Welding Engineering Graduate Program ABSTRACT Magnetically Impelled Arc Butt (MIAB) welding is a forge welding technique which generates uniform heating at the joint through rapid rotation of an arc. This rotation results from forces imposed on the arc by an external magnetic field. MIAB welding is used extensively in Europe, but seldom utilized in the United States. The MIAB equipment is robust and relatively simple in design, and requires low upset pressures compared to processes like Friction welding. In the automotive industry, tubular construction offers many advantages due to the rigidity, light weight, and materials savings that tubes provide. In the case of automotive suspension components, tubes may be chromium-plated on the ID to reduce the erosive effects of a special damping fluid. Welding these tubes using the MIAB welding process offers unique technical challenges, but with potential for significant cost reduction vs. other welding options such as Friction welding. Based on published literature, this research project represented the first attempt to MIAB weld chromium-plated steel tubes, and to utilize voltage monitoring techniques to assess weld quality. ii Optical and SEM microscopy, tensile testing, and an ID bend test technique were all used to assess the integrity of the MIAB weldments. This analysis revealed the potential for chromium-enriched regions, most likely chromium oxides, to become trapped at the weld interface resulting in severe degradation of mechanical properties. Voltage plots generated during the arc monitoring were analyzed and correlated with Design of Experiment (DOE) statistical results and high speed video images. The DOE results revealed the individual and interactive importance of arc heating (referred to as level II) time, expulsion (referred to as level III) current, and arc gap on weld quality. Correlations were established between specific features of the arc voltage plots and weld quality. Based on arc physics theory, it was proposed that these three variables affected arc pressure, which contributed to improved expulsion and a reduction in chromium entrapment in the joint. As a result, feasibility for MIAB welding chrome-plated suspension components was established, and voltage monitoring methodology was identified as a potential quality control technique for producing this joint. iii Dedicated to my parents, whose guidance and unwavering support has always propelled me through the difficult times in my life, and my sister Barbara, who has been my “guiding light” throughout adulthood iv ACKNOWLEDGMENTS I would like to thank my advisor, Professor Charley Albright, for first providing me with the opportunity to pursue a PhD, and then supporting and encouraging me throughout the process, while always allowing me some measure of independence. I am grateful to my good friend, Dr. Anthony Ananthanarayanan, for all of his moral, technical, and financial support throughout most of my PhD studies, and for allowing me the flexibility to pursue this degree while simultaneously working at Delphi. I am thankful to Delphi for providing most of the financial support during my PhD. A special thank you goes out to Tom McCray and Jule Hegwood, who spent countless hours helping me with the DOE and statistical analysis aspect of this research. I would also like to thank Dr. Vladimir Kachinskiy who provided valuable technical insight. v VITA March 6, 1961 ……………..................... Born – Chillicothe, Ohio 1984 ……………………………………. B.S. Welding Engineering, The Ohio State University 1986 ……………………………………. M.S. Welding Engineering, The Ohio State University 1986 - 1987 …………………………….. Corporate Welding Engineer Motor Wheel Corporation Lansing, Michigan 1987 - 1992 ……………………………... Welding Engineer GE Aircraft Engines Cincinnati, Ohio 1992 - 2004 …………………………….. Market Leader, Aerospace Edison Welding Institute Columbus, Ohio 2004 – present …………………………... Senior Weld Research Engineer Delphi Kettering, Ohio PUBLICATIONS 1. D.H. Phillips, W.A. Baeslack III, “Selection and Weldability of Advanced Titanium-Base Alloys”, ASM Handbook Volume 6, Welding, Brazing, and Soldering, 524-528, (1993) vi 2. W.A. Baeslack III, D.H. Phillips, G.K. Scarr, “Characterization of the Weld Heat Affected Zone in an Alpha-Two Titanium Aluminide”, Materials Characterization, Vol. 28, no. 1, 61-73 (1992) 3. W.A. Baeslack III, D.H. Phillips, C. English, A.P. Woodfield, “Inertia-Friction Welding of an Advanced Rapidly Solidified Titanium Alloy”, Journal of Materials Science Letters 10, 1401-1408 (1991) 4. L.C. Mallory, W.A. Baeslack III, D.H. Phillips, “Evolution of the Weld Heat- Affected Zone Microstructure in a Ti-48Al-2Cr-2Nb Gamma Titanium Aluminide”, Journal of Materials Science Letters 13, 1061-1065 (1994) 5. L.C. Mallory, W.A. Baeslack III, D.H. Phillips, T.J. Kelly, “Gas Tungsten Arc Welding of a Ti-48Al-2Cr-2Nb Gamma Titanium Aluminide”, Titanium ’92 Science and Technology, Proceedings, Symposium at 7th World Titanium Conference, San Diego, Vol.2; 29 June-2 July 1992, 1115-1122, (1993) 6. S.A. David, J.A. Horton, G.M. Goodwin, D.H. Phillips, R.W. Reed, “Weldability and Microstructure of a Titanium Aluminide”, Welding Journal, Vol. 69, no. 4, 133s- 140s, (April, 1990) 7. M.C. Juhas et. al., “Interface Characteristics of Solid Phase Welds Between Ti- 6Al-2Sn-4Zr-2Mo-0.1Si and 14Al-21Nb Titanium Aluminide” Titanium ’92 Science and Technology, Proceedings, Symposium at 7th World Titanium Conference, San Diego, Vol.2; 29 June-2 July 1992, 1453-1460, (1993) 8. K.N. Hou, et. al., “An Electron Microscopy Study of Inertia-Friction Welds in Ti- 48Al-2Cr-2Nb Gamma Titanium Aluminide”, International Trends in Welding Science and Technology, Gatlinburg, Tennessee, 1-5 June 1992, 1135-1137, (1993) FIELDS OF STUDY Major Field: Welding Engineering vii TABLE OF CONTENTS ABSTRACT.................................................................................................................................................. ii ACKNOWLEDGMENTS.............................................................................................................................v VITA..............................................................................................................................................................vi LIST OF FIGURES ......................................................................................................................................x LIST OF TABLES .....................................................................................................................................xvi CHAPTERS: 1. INTRODUCTION....................................................................................................................................1 1.1 MIAB WELD PROCESS DESCRIPTION ........................................................................................... 1 1.1.1 MIAB Welding Principles .................................................................................................... 3 1.1.2 Comparison to other Welding Processes............................................................................. 6 1.2 ARC MONITORING SYSTEMS......................................................................................................... 7 1.3 MOTIVATION FOR WELDING CHROMIUM-PLATED STEEL TUBES .................................................. 7 1.4 OBJECTIVES OF THE RESEARCH .................................................................................................... 9 2. TECHNICAL REVIEW ........................................................................................................................10 2.1 MAGNETIC FLUX AT THE MIAB WELD JOINT............................................................................. 10 2.2 ARC BEHAVIOR AT THE MIAB WELD JOINT............................................................................... 12 2.3 ARC ROTATION VELOCITY ......................................................................................................... 19 2.4 MIAB WELDING OF NON-FERROUS MATERIALS........................................................................ 23 2.5 SHIELDING GAS EFFECTS............................................................................................................ 25 2.6 HEAT FLOW IN THE MIAB WELDING PROCESSES....................................................................... 28 2.7 MIAB APPLICATIONS ................................................................................................................. 30 2.8 GENERAL WELDABILITY OF CHROMIUM-PLATED STEEL............................................................ 32 3. EXPERIMENTAL PROCEDURE .......................................................................................................36 3.1 MIAB EQUIPMENT ..................................................................................................................... 37 3.2 DESCRIPTION OF COMPONENTS AND WELD SET-UP ................................................................... 41 3.3