Technology for Magnesium Castings: Design, Products & Applications
Principal Author: Mahi Sahoo Technical Editor: Susan P. Thomas
American Foundry Society Schaumburg, IL USA
Technical Editor: Susan P. Thomas/AFS Technical Reviewer: Ian Kay/Hot Metal Technology LLC Cover/ Layout Designer: Henry Parrilli/AFS Production Layout: Ric Suk/Express Printing Cover Art: BMW engine block produced in the high pressure die casting process with an overcasting of a specialty magnesium alloy around a hyper-eutectic aluminum alloy high pressure die casting insert. Published by the American Foundry Society, Schaumburg, IL USA www.afsinc.org © 2011 American Foundry Society Printed in the United States of America ISBN 978-0-87433-374-9 The American Foundry Society gratefully acknowledges the various companies and individuals that have contributed their time and effort into the making of this book. All rights reserved. No part of this publication may be reproduced in any form or by any means—electronic, graphic or mechanical, including photocopying, recording, information storage and retrieval systems without the prior written permission of the publisher. The American Foundry Society, as a body, is not responsible for the statements and opinions advanced in this publication. Nothing contained in any publication of the Society is to be construed as granting right, by implication or otherwise, for manufacture, sale or use in connection with any method, apparatus or product covered by letter patent, nor as insuring anyone against liability for infringement of letters patent. Disclaimer Trademarks/Company names used in this publication are for informational purposes only and do not imply that the products in question are licensed, endorsed or approved by AFS. In no event shall AFS be liable for any damage whatsoever arising out of or in connection with the use of the products recommended within this publication.
CONTENTS Preface/Acknowledgements.............................................................v 1. Introduction to the Magnesium Casting Industry...................1 2. Physical Metallurgy.....................................................................9 3. Solidification..............................................................................29 4. Material Selection: Sand and Investment Casting Alloys.....49 5. Corrosion Assessment Methods.............................................67 6. Heat Treatment..........................................................................87 7. Melt Control.............................................................................107 8. Process Control.......................................................................121 9. Gating and Risering in Gravity & Low Pressure Casting....125 10. Process Selection....................................................................131
10.1—Sand Casting..................................................................139
10.2—Permanent Mold Casting.............................................141
10.3—Lost Foam Casting........................................................161
10.4—High Pressure Die Casting...........................................183
10.5—Ablation Casting...........................................................197
10.6—Squeeze Casting............................................................203
10.7—Thixomolding®. ............................................................223
11. Design and Application of Cast Components......................237 12. Challenges Facing the Magnesium Industry........................263 Index................................................................................................291
PREFACE This publication is a result of the successful workshop, “Technology for Magnesium Castings: Design, Use and Applications,” conducted in 2006 at CANMET Materials Technology Laboratory, on behalf of the Magnesium Division of the American Foundry Society (AFS). Following the success of this well-attended workshop represented by attendees from the metalcasting industry, suppliers, academia and research laboratories, the Magnesium Division overwhelmingly supported the idea of creating a book. The publication of this book is very timely in view of the important role magnesium contributes to the transportation industry and other industrial applications using the latest casting and processing technologies. Being a structural material with low density and a very high strength to weight ratio, magnesium will reduce vehicle weight and in turn reduce greenhouse gas emissions and increase fuel economy. Valuable information is provided on melt control, process control, casting and solidification, heat treatment, materials selection and various casting processes such as sand, permanent mold, high pressure die, lost foam, ablation and semi-solid casting. This publication will be of great interest to many individuals involved in the metalcasting industry, especially the casting designer and process engineer. It will also be an invaluable tool for students of metallurgy, materials science and metalcasting. The chapter authors are world-class scientists, professors and engineers with countless years of industrial and laboratory experience, many of them presented sessions at the workshop. The knowledge gained from their work, research and teaching has been incorporated to provide only the latest information to the reader. Their chapters offer a more in depth look at the subject matter of their presentations. Other chapters were added to make the book invaluable for process and design engineers. Each chapter was reviewed by qualified metallurgists/materials engineers from the metalcasting industry, academia and research laboratories to ensure that only the highest quality information was accepted for publication. Mahi Sahoo* President, Suraja Consulting Ottawa, Ontario, Canada *Formerly with CANMET Materials Technology Laboratory (1977-2010). Retired in 2010, currently an Emeritus Scientist at CANMET MTL
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ACKNOWLEDGEMENTS On behalf of the Magnesium Division of AFS, I would like to extend my deep gratitude and sincere thanks to the contributing authors and reviewers for their time and efforts. I must thank the members of the AFS Magnesium Division for their faith and confidence in my ability to edit and coordinate the publication of this book. The creation of this publication has been a long and exciting project and one that would not have been possible without the perseverance of many individuals. I would also like to acknowledge the assistance provided by Ms. Montserrat Tallec in the preparation of the manuscript. The moral support of the management of CANMET Materials Technology Laboratory is gratefully acknowledged. I would like to thank the following individuals and their companies for their special contributions: Chapter 1—Introduction to Magnesium Casting Industry
Author—Steve Robison (American Foundry Society) Reviewer—David Weiss (ECK Industries)
Chapter 2—Physical Metallurgy
Authors—Kumar Sadayappan (CANMET MTL) & Alan Luo (GM) Reviewer—David Schwam (Case Western Reserve University)
Chapter 3—Solidification
Authors—Alan Luo (GM) & Kumar Sadayappan (CANMET MTL) Reviewer—David Schwam (Case Western Reserve University)
Chapter 4—Material Selection: Sand and Investment Casting Alloys
Author—Ken Clark (Magnesium Elektron, USA) Reviewer—Bob Powell (GM)
Chapter 5—Corrosion Assessment Methods
Author—Wenyue Zheng (CANMET MTL) Reviewer—Gerry Wang (Research in Motion, Canada)
Chapter 6—Heat Treatment
Authors—Mahi Sahoo (CANMET MTL) & Jay Keist (WPI) Reviewer—Makhlouf Makhlouf (WPI)
Chapter 7—Melt Control
Author—Rob Bailey (B.S. Metallurgy, Inc.) Reviewer—Carl Lee (Garfield Alloys)
Chapter 8—Process Control
Author—David Weiss (ECK Industries) Reviewers—Bob Powell (GM) & Mike Marlatt (Marlatt Technologies)
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Chapter 9—Gating and Risering in Gravity & Low Pressure Casting
Author—David Weiss (ECK Industries) Reviewer—Mahi Sahoo (CANMET MTL) & Rob Bailey (B.S. Metallurgy, Inc.)
Chapter 10—Process Selection
Author—David Weiss (ECK Industries) Reviewer—Tom Prucha (American Foundry Society)
Chapter 10.1—Sand Casting
Author—David Weiss (ECK Industries) Reviewer—Bob Powell (GM)
Chapter 10.2—Permanent Mold Casting
Author—David Weiss (ECK Industries) Reviewers—Bob Powell (GM) & Mike Marlatt (Marlatt Technologies)
Chapter 10.3—Lost Foam Casting
Authors—Qingyou Han (Purdue University), Changjiang Song, (Shanghai University, China) & Mike Marlatt (Marlatt Technologies) Reviewers—Dennis Nolan (Formerly with Foseco) & David Weiss (ECK Industries)
Chapter 10.4—High Pressure Die Casting
Author—David Schwam (Case Western Reserve University) Reviewers—Mark Osborne (GM) & Steve Udvardy (NADCA)
Chapter 10.5—Ablation Casting
Authors—John Grassi (Alotech), Dave Weiss (Eck Industries) & Bruce Cox (Alotech) Reviewers—Mahi Sahoo (CANMET MTL) & Steve Robison (AFS)
Chapter 10.6—Squeeze Casting
Authors—Wojciech Kasprzak, Jason Lo (CANMET MTL) & John Jekl (Meridian) Reviewer—Mark Osborne (GM)
Chapter 10.7 – Thixomolding®
Condensed by Mahi Sahoo (CANMET MTL) from ASM Handbook, Vol. 15, Castings (2008) (Original authors—R.D. Carnahan & R.F. Decker, Thixomat, Inc.) with permis sion from ASM International.
Chapter 11—Design and Application of Cast Components
Author—Gerald Cole (LightWeightStrategies LLC) Reviewer—Mahi Sahoo (CANMET MTL)
Chapter 12—Challenges Facing the Magnesium Industry
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Author—Gerald Cole (LightWeightStrategies LLC) Reviewer—Bob Powell (GM)
