Process and Tool Design for the High Integrity Die Casting of Aluminum and Magnesium Alloys THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Varun Nandakumar Graduate Program in Industrial and Systems Engineering The Ohio State University 2014 Master's Examination Committee: Dr. Jerald Brevick, Advisor Dr. Alan Luo Copyright by Varun Nandakumar 2014 Abstract The push for higher efficiency and lower emissions on present day automobiles have created a greater need for light alloys such as Aluminum and Magnesium to replace the customary steel parts in an automobile. A lot of these replaced parts are in structural load bearing components on a vehicle. This usually meant that processes such as the traditional High Pressure Die Casting would not be able to claim a stake in it due to its innate air and Hydrogen entrapment issues. But, with an overall higher maintenance of quality in the traditional process, it is possible to create higher integrity parts that are usable in structural applications. This thesis describes and tests some methods to improve the traditional High Pressure Die Casting process to enable it to produce higher integrity casts for Aluminum and Magnesium alloys. Methods to achieve a higher quality melt are researched and a rotary degasser is used for two experimental trials of similar Aluminum alloys. Similarly, methods to integrate vacuum into the existing setup are studied and the tooling part of the vacuum assist system with chill blocks is fully designed. The design of the chill blocks is carried out from the ground up using MAGMA and ANSYS simulation tools which were available at the Integrated Systems Engineering Lab. A designed experiment is completed to understand the effects of changing parameters on the design. Finally, the optimum design is completed on 3D CAD software and then manufactured in house. ii To Charuchechi iii Acknowledgments To Dr. Brevick - my advisor, the best teacher I’ve had and possibly the most patient man I will ever meet. I can’t even begin to describe how much I’ve enjoyed working under you. I have never come out of a discussion – be it in the hallway, on a drive or at your office, without learning something new. You have a knack of making any topic interesting and I’m going to miss popping into your room with the silliest question knowing that you will do your best to break it down for me. Thank you sir for everything. To Martin Doyle from Gibbs Die Casting at Henderson, KY- Thank you for helping us understand vacuum die casting, giving us a tour of your facility and graciously providing us with tool bits to make the sealant cut outs. To Charuchechi - Without your generosity I wouldn’t be here. Thank you for a second chance at life. To My Parents – It is a tremendous joy knowing that the two of you are constantly behind me. Thank you for always being there. To Deepta – Thanks for all the encouragement, the talks and help when I thought I couldn’t make it. To my Sister, friends and so many others who are in one way or the other responsible for my success, I am deeply humbled by all of your kindness. Last but by no means least, to my colleague William Tullos - I’ve had a great time working with you the past year and a half, thank you for always responding to my email within minutes of receiving them and your constant backing. iv Vita March 19, 1987 ..............................................Born – Bangalore, India 2008 ...............................................................B.E. Mechanical Engineering, Visvesvaraya Technological University Fall 2010 to present .......................................M.S. Industrial and Systems Engineering, The Ohio State University May 2013 to present ......................................Graduate Research Associate, Department of Industrial and Systems Engineering, The Ohio State University Fields of Study Major Field: Industrial and Systems Engineering v Table of Contents Abstract ............................................................................................................................... ii Acknowledgments.............................................................................................................. iv Vita ...................................................................................................................................... v Table of Contents ............................................................................................................... vi List of Tables ..................................................................................................................... xi List of Figures ................................................................................................................... xii Chapter 1: Introduction ....................................................................................................... 1 The High Pressure Die Casting Process .......................................................................... 1 Advantages and Limitations ............................................................................................ 4 Types of High Pressure Die Casting ............................................................................... 5 The Cold Chamber Process ......................................................................................... 6 The Hot Chamber Process ........................................................................................... 7 High Integrity Processes.................................................................................................. 8 Applications of High Pressure Die Casting .................................................................... 9 Automotive Applications ........................................................................................... 10 Structural Automotive Applications .......................................................................... 13 vi Light alloys used in Structural Die Casting .................................................................. 14 Aluminum alloys ....................................................................................................... 14 Magnesium alloys ...................................................................................................... 15 Process consideration for structural alloys in the automotive industry ......................... 16 Research Summary ........................................................................................................ 17 Objectives .................................................................................................................. 18 Approach ................................................................................................................... 18 Chapter 2: Dealing with porosity problems in HPDC .................................................. 20 Gas Porosity .................................................................................................................. 21 Hydrogen ................................................................................................................... 21 Air Entrapment .......................................................................................................... 21 Oil or water from Lubrication spray .......................................................................... 21 Solidification shrinkage................................................................................................. 22 Porosity reduction and obtaining a high integrity cast .................................................. 22 Melt quality Improvements ........................................................................................... 23 Degassing ...................................................................................................................... 23 Passive Degassing...................................................................................................... 24 Liquid argon shield .................................................................................................... 25 Gaseous argon shield ................................................................................................. 25 vii Chemical tablets ........................................................................................................ 26 Rotary Impeller Degassing ........................................................................................ 27 Flux Induced Rotary degassing ................................................................................. 28 Choosing a Purge Gas................................................................................................ 29 Additional and often overlooked Benefit of Degassing ............................................ 30 Reduced Pressure Test ............................................................................................... 30 Improved process control .............................................................................................. 31 Metallurgical Modification ........................................................................................... 33 Vacuum Die Casting ..................................................................................................... 34 Advantages of Vacuum Die Casting ......................................................................... 37 Vacural Process ........................................................................................................