Scholars' Mine Masters Theses Student Theses and Dissertations Fall 2020 Inclusion control in steel castings Koushik Karthikeyan Balasubramanian Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Materials Science and Engineering Commons Department: Recommended Citation Balasubramanian, Koushik Karthikeyan, "Inclusion control in steel castings" (2020). Masters Theses. 7961. https://scholarsmine.mst.edu/masters_theses/7961 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]. INCLUSION CONTROL IN STEEL CASTINGS by KOUSHIK KARTHIKEYAN BALASUBRAMANIAN A THESIS Presented to the Graduate Faculty of the MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE in MATERIALS SCIENCE AND ENGINEERING 2020 Approved by: Dr.Laura Bartlett, Advisor Dr.Ronald O’Malley Dr.Simon Lekakh © 2020 KOUSHIK KARTHIKEYAN BALASUBRAMANIAN All Rights Reserved iii PUBLICATION THESIS OPTION This thesis consists of the following three articles, prepared for journal publication in the style used by the Missouri University of Science and Technology: Paper I, found on pages 39-68, has been published in the International Journal of Metalcasting (IJMC). Paper II, found on pages 69-107, are intended for submission to International Journal of Metalcasting (IJMC). Paper III, found on pages 108-135, are intended for submission to International Journal of Metalcasting (IJMC). iv ABSTRACT Non-metallic inclusions are mainly comprised of oxides, sulfides, and nitrides, and are formed in liquid steel during the melting and refining process, as a result of reoxidation, worn-out refractories, or entrained slag. The notch toughness of high strength steels is particularly susceptible to the type, number, size, and distribution of non-metallic inclusions. High manganese and aluminum austenitic steels, or Fe-Mn-Al steels, have gained much interest in the military and automotive sector because of their excellent combinations of high strength and toughness. However, these steels are subject to both oxide bifilms and aluminum nitride, AlN, inclusions which form during melting and casting. During the casting process, the gating system plays an important role in determining the casting quality and the overall level of inclusions and bifilm defects. Two solutions to control inclusions during mold filling include molten metal filtration and design of novel “naturally pressurized” gating systems that control metal flow into the casting cavity and reduce air entrainment. However, the use of filters and these naturally pressurized gating systems add an additional cost and generally reduce casting yield. In the current study, the effects of filtration and gating design on reduction of bifilms and inclusions in Fe-Mn-Al steel were determined using two novel mold designs. A parallel gating study involving an aluminum deoxidized, cast composition of SAE 8630 was also performed. The results of this study showed that ceramic foam filters were more effective at removing solid oxide bifilms and aluminum nitride inclusions from Fe-Mn-Al steel castings than the naturally pressurized gating systems. Future studies should be directed at developing naturally pressurized gating systems with filters. v ACKNOWLEDGMENTS First, I would like to thank God and my parents, Mr. M.S. Balasubramanian and Mrs. Uma Balu, for all their love, support, and sacrifices without which I would not have been able to make it this far in life. I would like to extend my heartfelt thanks and gratitude to my advisor, Dr. Laura Bartlett, for believing in me and providing me with an opportunity to work under her wing. Apart from being an advisor, she was also a great mentor, guide, and motivation. I would like to thank her for all her time and knowledge, and for helping me better myself at every stage of my journey, in graduate school. I would like to acknowledge the support provided by Dr. Ronald O’Malley, Dr. Simon Lekakh, and Dr. Mingzhi Xu for helping me understand and solve the challenges, faced in my research. I am grateful to Mr. Doug Imrie and Mr. Zach Henderson from SouthernCast Products for all their inputs and being the industrial sponsors. I am thankful to Mr. Miguel Gastelum and Mr. Dan Coyle from MagmaSoft for all the technical guidance. I would like to extend my gratitude to Mr. Nathan Inskip, Mr. Brian Bullock, Ms. Denise Eddings and Ms. Teneke Hill for their patience and time, experimental support and for ensuring that all the processes happened in a smooth and organized manner. I would like to thank the American Foundry Society for sponsoring this project. I would like to thank all my fellow graduate and undergraduate students for their support during experiments. I extend my special thanks to Michael Piston, Rairu Vaz Penna, and Soumava Chakraborty. Finally, I would like to thank my roommates, friends, and family without whom I would not be standing here. I would take this opportunity to specially mention Sivaramakrishnan Jayaram and Poorna Hariramakrishnan for being a constant source of emotional and moral support. vi TABLE OF CONTENTS Page PUBLICATION THESIS OPTION.......................................................................................... iii ABSTRACT..................................................................................................................................iv ACKNOWLEDGMENTS...........................................................................................................v LIST OF ILLUSTRATIONS...................................................................................................... x LIST OF TABLES....................................................................................................................xvii SECTION 1. INTRODUCTION..............................................................................................................1 1.1. PROJECT PURPOSE AND OVERVIEW...............................................................1 1.2. NON-METALLIC INCLUSIONS............................................................................ 6 1.2.1. Classification of Inclusions............................................................................ 6 1.2.2. Effect of Inclusions on Casting Quality........................................................ 13 1.3. BIFILMS.................................................................................................................... 17 1.3.1. Formation......................................................................................................... 17 1.3.2. Effect on Mechanical Properties....................................................................20 1.4. HIGH MANGANESE HIGH ALUMINUM STEELS.........................................23 1.4.1. Composition and Heat Treatment..................................................................24 1.4.2. Inclusions.........................................................................................................25 1.5. FILTRATION........................................................................................................... 26 1.5.1. Filtration Mechanism................................................................................... 26 1.5.2. Parameters Affecting Filtration 29 vii 1.6. GATING SYSTEM IN CASTINGS....................................................................30 1.6.1. Components of a Gating System....................................................................31 1.6.2. Pouring Cup......................................................................................................31 1.6.3. Downsprue.......................................................................................................31 1.6.4. Runners............................................................................................................ 34 1.6.5. Gating................................................................................................................35 1.6.6. Riser/Feeder.....................................................................................................38 PAPER I. FILTRATION EFFICIENCY OF INCLUSIONS IN LIGHTWEIGHT FeMnAl STEELS........................................................................................................... 39 ABSTRACT........................................................................................................................ 39 1. INTRODUCTION.........................................................................................................40 1.1. NON-METALLIC INCLUSIONS IN Fe-Mn-Al-C STEEL.............................40 1.2. FILTRATION.........................................................................................................41 2. METHODOLOGY........................................................................................................42 3. RESULTS....................................................................................................................... 47 3.1. CHEMISTRY ANALYSIS................................................................................... 48 3.2. BIFILM AND INCLUSION ANALYSIS........................................................... 50 4. DISCUSSION.................................................................................................................59