Metal Casting Principles and Practice

METAL CASTING

Principles and Practice

TV Ramana Rao B.E. (Mech.) M.E. (Foundry) Ph.D. Professor, Mechanical Engineering, M.J. College of Engineering and Technology

0 ‘RI NEWAGEINTERNATIONAL(P)LiMKED,PUBLIS~ ?

New Delhi Bangalore Chennai Guwahati Hyderabad Kolkata Lucknow Mumbai ??

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Copyright 0 1996, New Age International (P) Ltd., Publishers Reprint 2003 NEWAGEINTEBNATIONAL(P) LIMlTED,PUBIX%IERS 4835/24, Ansari Road, Daryaganj, New Delhi - 110 002

Bangalore, Chenti,Guwahati, Hyde&ad, Kolkata, Lucknow and Mumbai

This book or any part thereof may not be reproduced in any form without the written permission of the publisher. This book cannot be sold outside the country to which it is consigned by the publisher without the prior permission of the publisher.

ISBN : 81-224-0843-s 2345678910 Published by K.K. Gupta for New Age International (P) Ltd., 4835/24, Ansari Road, Daryaganj, New Delhi-110 002 and printed in India at DeUnique, New Delhi-l 10 018.

FOREWORD A few years ago, in the process of selecting some practising Engineers for an Automobile factory, it was observed that the candidates found dill;culty in naming even 5 metallic castings as parts used in an automobile. I considered this a symptom of weakness in our educational system which does not lay adequate stress on practical aspects required by our industries. Later, as Chairman of the IIydcrabad chapter of the Indian Institute of Foundrymen, I always wished that there should be a book that deals not only with the manufacturing practices followed by the Indian Industries for various types of metal castings but which also incorporates subjects of standards, types of defects, methods of inspection and testing and some practical tips on reducing rejections. And here I find Prof. T.V. Ramana Rao coming forward with a book !&la1 Castings - .Princijdes and Practice: fulfilling the need of the hour. His book which is divided in ten chapters deals with all aspects of foundry practices, different manufachlring technologies and inspection and quality control procedures. With incorporation of chapters on PPC, Organisation and MIS, Computer Applications and Environmental Protection aspects, I am sure the book will be a very welcome addition for the practising Managers as well as graduate shrdents.

K.K.SINHA Chief Executive NUCLEAR FUEL COMPLEX Department of Atomic Energy Government of India ECIL (P.O.) Hyderabad - 500 762.

PREFACE This book is a compilation of different aspects of Metal Casting, covering the latest available information, Industry data and Foundry practices, brought together to serve students of under-graduate and post-graduate courses studying the subject, as well as practising foundry supervisors, engineers and managers. As such, the author does not claim complete originahty in the information contained and takes credit only for collecting, selecting and presenting the contributions to the field by many eminent research workers, academicians, practising foundrymen and authors. Detailed acknowledgement is attempted but any omission to mention a work quoted in this book is sincerely regretted as it is only on the grounds of space constraints or ignorance but not by intention. Under-graduate students may omit certain practical aspects which are intended mainly for foundry personnel. I thank the publishers M/S New Age International Pvt. Ltd. for their help and guidance in making this book presentable. I am grateful to Shri K.K Sinha, Chairman and Chief Executive of Nuclear Fuel Complex a highly honoured and eminent metallurgist, known to me since long, for encouraging me by giving the Foreword. Finally, this book is before you only because of the persistent inspiration provided by my wife Chandra and family members, for whom I have no words to thank.

Dr. T.V. Ramana F&LO Author

ACKNOWLEDGEMENTS Apart from the Text Books, Technical Journals and other Documents referred to elsewhere in this book, I respectfully wish to acknowledge the following persons specifically for their influence on me and on this book, either directly or indirectly. . Prof. M.R.Seshadri and Prof. K.Srinivasan, Indian Institute of Science, Bangalore, who taught me the concepts of Foundry Engineering. . Mr. S.K.Das, Mr. Karel Kalus and Mr. A.K.Banerjee, H.E.C., Ranchi, under whom I learnt valuable practical aspects of methoding of castings. . Mr. T.Kumar, STEELCAST, Bhavnagar, who has guided and gave me the opportunity to learn production, cost and management aspects of alloy steel foundry. . Mr. S.C.Gupta, M.D., R.G. Foundry Forge, Hyderabad, for giving valuable insight into technology, marketing and commercial aspects. . Shri B.G.Sastry, formerly M.D., Ductron Castings, for his valuable suggestions during consultancy assignment. . Dr. Md. Roshan and Dr. Prasannakumar, I.I.T., Madras, for their invaluable contributions in Journals on different aspects of Research and Development. . Dr. S.Sunderrajan, D.R.D.L., Hyderabad, for his expert contributions on nonferrous technology, R & D and personal encouragement as fellow I.I.F. member. . My former and present students at M.J.C.E.T., who contributed to develop the computer programs. . My colleagues in metal casting industry and other Academic Institutions, who gave valuable suggestions. . The management and staff members of M.J.C.E.T., Hyderabad, who gave me their encouragement and appreciation.

Prof. T. V. Ramana Rao Author

Contents Page No. 1

1

Introduction 1.1 Metal casting as a manufacturing process, 7 1.2 Classification of foundries, 3 1.3 Foundry industry in India, 4 1.4 Challenges for Indian foundry industry, 5 1.5 Important Industiral Sectors using castingskxamples,

G

Questions, 7 3

2 Sand molding processes

15

2.1 Function of molding sand, 7 7 2.2 Classification of molding sands, 79 2.3 Ingredients, 22 2.4 Core sands, 26 2.5 Testing of molding sands and control, 28 2.6 Pattern equipment: Functions, types, materials design and construction, 3F 2.7 Green sand, Dry sand, CO, sand, Resin sand Shell molding, Investment casting, Loam sand, 53 2.8 Practical aspects, mold coatings, 57 2.9 Casting defects due to sand, molding and pattern, M Quzstions, 66

3

Molding processes using metal molds 3.1 Die casting - Gravity and Pressure, 6.9 3.2 Centrifugal casting, 75 3.3 Continuous casting, 76 3.4 Comparison of diffcrent molding p r o c e s s e s , 711 3.5 Selection of proper molding process, BO Questions, 02

69

Page No.

4 Melting furnaces and techniques

.

83

4.1 Classification of melting equipment, 83 4.2 Common melting furnaces in foundry, 83 4 . 3 Melting procedures , Practical aspects, 93 4.4 Refractories, pouring ladles, 7 72 4.5 Selection of suitable melting furnace - criteria, 7 73 4.6 Casting defects due to improper melting, 7 7 7 Questions, 7 78

5 Solidification, gating, risering and casting design 5.1

Solidification process, 722

5 . 2 Running and 5.3

121

Risering

/

gating 7 2 6 system, Feeding systems, 744

5.4 Design of Castings, 757 Questions, 7 67

6 Finishing operations

163

6.1 Fettling, cleaning, finishing, 763 6.2 Heat-treatment of castings, 766 6.3 Salvaging of defective castings, 7 78 Questions, 787

7 Inspection and quality control 7.1 Specification of castings, 783 7.2 Inspection of castings, 785 7.3 Analysis of casting defects, 795 7.4 Quality control a.nd Quality assurance, 204 Questions, 209

183

Page No.

211

8 Foundry mechanization 8.1 Mechanical equipments in foundry, 2 7 :I 8.2 Plant site location, Layout, 22 7 8.3 Plant Engineering / Maintena.nce / Services, 225 8.4 Practical aspects, 230 Questions, 232

9

Planning and management foundry

233

9.1 Planning a new foundry Project, 234 9.2 Organisation, Management Information System, 236 9.3 Production Planning and Control, 246 9.4 Practical aspects / Case studies, 247

10

New developements

in metal casting

249

10.1 New materials , processes and inspection methods, 249 10.2 Computer and IT.

applications, 258

10.3 Energy conservation, 276 10.4 Environmental pollution c.ontrol,

Suggested experiments / practicals Computer Aided Metal Casting (LT.

279

in metal casting lab Tools)

282 283

Explanation of Terminology used in LT. Tools for Casting

285

UseN

288

Index

References

293

1

INTRODUCTION

1.1 Metal casting as a manufacturing process Metal casting is one of the most ancient techniques used for manufacturing metal parts, Metal casting is the process of forming metallic objects by melting metal, pouring it into the shaped cavity of a mold and allowing it to solidify. The process of casting involves the basic operations of pattern making, sand preparation, molding, melting of metal, pouring in molds, cooling, shake-out, fettling, heat-treatment finishing and inspection. The flow process chart (Fig 1.1) illustrates these stages in sequence. In comparison to other manufacturing processes like rolling, forging, welding, powder metallurgy, machining, pressing etc., the casting process has the following advantages:

i. Advantagesof casting process 4

There is no restriction on the type of metal or alloy for casting operation. In other processes like forging only a few ductile materials can be formed whereas a brittle metal like cast iron cannot be manufactured. Eg : High alloy steels of high-melting temperature to low-melting aluminium alloys.

b)

There is no restriction on the size of the component for casting. Items from a few grams to ma.ny tons weight are produced by casting process. There are severe problems in manufacturing larger parts by processes like powder-metallurgy, forging etc. Eg : Watch cases of few grams to rolling mill-housings, kiln-tyres of 50 tons each

4

The most intricate external and internal shapes can be formed by casting process, by suitable molding and core-making techniques. No such possibility exists in the other forming methods as rolling. Eg : Automobile cylinder blocks, carburettors!, valve bodies