Technology for Magnesium Castings:Design, Products & Applications

Principal Author: Mahi SahooTechnical Editor: Susan P. Thomas

American Foundry SocietySchaumburg, IL USA

Technical Editor: Susan P. Thomas/AFS Technical Reviewer: Ian Kay/Hot Metal Technology LLCCover/ Layout Designer: Henry Parrilli/AFSProduction 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 USAwww.afsinc.org

© 2011 American Foundry SocietyPrinted 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 manu-facture, 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.

DisclaimerTrademarks/Company names used in this publication are for informational purposes only and do not imply that the products in question are licensed, endorsed or ap-proved 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). Fol-lowing the success of this well-attended workshop represented by attendees from the metalcasting industry, suppliers, academia and research laboratories, the Magnesium Division overwhelmingly sup-ported 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 tech-nologies. 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 pres-sure die, lost foam, ablation and semi-solid casting. This publication will be of great interest to many individuals involved in the metalcast-ing 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 engi-neers 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 presenta-tions. Other chapters were added to make the book invaluable for process and design engineers. Each chapter was reviewed by quali-fied metallurgists/materials engineers from the metalcasting indus-try, academia and research laboratories to ensure that only the high-est 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 cre-ation 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 Author—Gerald Cole (LightWeightStrategies LLC) Reviewer—Bob Powell (GM)

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