Scholars' Mine Doctoral Dissertations Student Theses and Dissertations Fall 2019 Development of Stage-I tempered high strength cast steel for ground engaging tools Viraj Ashok Athavale Follow this and additional works at: https://scholarsmine.mst.edu/doctoral_dissertations Part of the Metallurgy Commons Department: Materials Science and Engineering Recommended Citation Athavale, Viraj Ashok, "Development of Stage-I tempered high strength cast steel for ground engaging tools" (2019). Doctoral Dissertations. 2826. https://scholarsmine.mst.edu/doctoral_dissertations/2826 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. DEVELOPMENT OF STAGE-I TEMPERED HIGH STRENGTH CAST STEEL FOR GROUND ENGAGING TOOLS by VIRAJ ASHOK ATHAVALE A DISSERTATION Presented to the Faculty of the Graduate School of the MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY in METALLURGICAL ENGINEERING 2019 Approved by: David C. Van Aken, Advisor Ronald J O’Malley Laura Bartlett Mingzhi Xu K. Chandrashekhara 2019 Viraj Ashok Athavale All Rights Reserved iii PUBLICATION DISSERTATION OPTION This dissertation consists of the following five articles, formatted in the style used by the Missouri University of Science and Technology: Paper I: On predicting quenched and tempered hardness of mixed microstructures using steel chemistry. Pages 24-43 were submitted to the proceedings of ASM Heat Treat Conference 2017. Paper II: Empirical Methods of Predicting Quenched and Tempered Hardness. Pages 44-59 were submitted to the proceedings of Steel Founders’ Society of America Technical and Operating Conference 2017. Paper III: Controlling Nitrogen Pick-Up during Induction Melting Low Alloy Steels. Pages 60-76 were submitted to the proceedings of the 121st Metalcasting Congress 2017. Paper IV: Effect of Deoxidation and Pouring Practice on the Mechanical Properties of Stage-I Tempered Cr-Ni-Mo Steel. Pages 77-111 were submitted to the proceedings of the 123rd Metalcasting Congress 2019. Paper V: Mechanical Properties and Impact Wear Resistance of 540 Brinell Hardness Mn-Si-Mo-V steel. Pages 112-150 were submitted to the proceedings of the 123rd Metalcasting Congress 2019. The Introduction, Conclusions and Recommendations and Appendix sections provide supplemental information to the dissertation topic. iv ABSTRACT Ground Engaging Tools (GET) are the expendable replacement parts used in heavy machinery used with mining or construction equipment. GET’s protect the expensive machine components from the wear and tear found common in high-impact or high-abrasion environments. The goal of this project is to develop advanced next- generation alloy choices that outperforms the existing GET materials. A method of predicting tempered hardness of mixed microstructures was formulated. Using this model, two alloy series viz. Cr-Ni-Mo and Mn-Si-Mo-V were proposed and experimented with the goal of obtaining a high strength and impact resistant cast steel. Cast iterations of Cr-Ni-Mo alloy series were used to develop a low nitrogen induction melting practice (N< 80 ppm) along with an effective deoxidation. Size of ground Si-Zr addition controls final ZrN particle size. Good mechanical properties can be obtained if ZrN particle size is limited to 2µm. A high oxygen melt practice gave 35% improvement in notch toughness. A Mn-Si-Mo-V steel was formulated to minimize solidification shrinkage porosity. Steels were heat treated to a lath martensitic microstructure, and a Stage-I tempered hardness of 53-55 HRC. Yield strength and ultimate tensile strength averaged 1482 MPa and 1930 MPa. Tensile ductility decreased with increasing porosity. Porosity should be limited to 0.04% to get elongation of 10% or more. Manganese and Nickel additions lowered the yield strength. Lowered yield to tensile strength ratio resulted in up to 46% improvement in impact wear simulated using a gouging abrasion test relative to steels currently employed. Recommendations for further cast alloy iterations, wear performance study and characterization are provided. v ACKNOWLEDGMENTS This work has been supported by Caterpillar, Inc. as a part of Next Generation GET Cast Steel project. I would like to gratefully acknowledge the following people who supported and contributed towards successful completion of this dissertation: Firstly, I would like to sincerely thank my advisor, Dr. David C. Van Aken, for giving me the opportunity to work on this project. It has been my greatest honor to work with Dr. Van Aken. His dedication towards research, patience in teaching and strive for excellence has been an inspiration. I am enormously grateful to him for all the invaluable life lessons. Secondly, many thanks to Dr. Mingzhi Xu for his assistance in the research foundry casting the alloys and with the numerous technical/non-technical discussions that motivated me doing better everyday. I would like to thank Dr. Ronald J. O’Malley, Dr. Laura Bartlett and Dr. K. Chandrashekhara for their excellent guidance throughout the course of this research. Special thanks to the Materials Research Center staff, Dr. Clarissa Wisner and Dr. Eric Bohannan for their technical assistance with electron microscopy and X-ray diffraction analysis. I am very appreciative to Mr. Nathan Inskip for his help in the machine shop. The Materials Science and Engineering Department staff, Teneke Hill and Denise Eddings who helped me arranging weekly teleconferences and shipping materials every now and then was greatly appreciated. In addition I am very grateful to all the undergraduate help I received. Special thanks to my fellow graduate students. Finally, I would like to thank my parents and my sister for the endless love and support, as well as their sacrifice in helping me reach my goals. vi TABLE OF CONTENTS Page PUBLICATION DISSERTATION OPTION.................................................................... iii ABSTRACT ....................................................................................................................... iv ACKNOWLEDGMENTS ...................................................................................................v LIST OF ILLUSTRATIONS ...............................................................................................x LIST OF TABLES ........................................................................................................... xvi NOMENCLATURE ...................................................................................................... xviii SECTION 1. INTRODUCTION ...................................................................................................... 1 2. BACKGROUND INFORMATION ........................................................................... 3 2.1. METHODS OF TESTING WEAR RESISTANCE ........................................... 9 2.2. EFFECT OF HARDNESS AND MICROSTRUCTURES .............................. 12 2.3. GETTING IMPROVED WEAR RESISTANCE ............................................. 15 2.4. TARGETED MECHANICAL PROPERTIES ................................................. 16 2.5. TEMPERING OF MARTENSITE ................................................................... 17 2.6. PREDICTING TEMPERED HARDNESS ...................................................... 20 3. SUMMARY AND GAPS ........................................................................................ 22 PAPER I. ON PREDICTING QUENCHED AND TEMPERED HARDNESS OF MIXED MICROSTRUCTURES USING STEEL CHEMISTRY ..............................................24 ABSTRACT ................................................................................................................. 24 1. INTRODUCTION .................................................................................................... 25 vii 2. EXPERIMENTAL PROCEDURE........................................................................... 30 3. RESULTS ................................................................................................................. 32 4. DISCUSSION .......................................................................................................... 33 ACKNOWLEDGEMENTS ......................................................................................... 42 REFERENCES ............................................................................................................. 42 II. EMPIRICAL METHODS OF PREDICTING QUENCHED AND TEMPERED HARDNESS ................................................................................................................. 44 ABSTRACT ................................................................................................................. 44 1. INTRODUCTION .................................................................................................... 45 2. EXPERIMENTAL PROCEDURE........................................................................... 49 3. RESULTS AND DISCUSSION .............................................................................. 52 ACKNOWLEDGEMENTS ......................................................................................... 59 REFERENCES ............................................................................................................. 59 III.