METAL CASTINGPrinciples and Practice

TV Ramana RaoB.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

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Copyright 0 1996, New Age International (P) Ltd., PublishersReprint 2003

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FOREWORD

A few years ago, in the process of selecting some practising Engineers for anAutomobile factory, it was observed that the candidates found dill;culty in naming even5 metallic castings as parts used in an automobile. I considered this a symptom ofweakness in our educational system which does not lay adequate stress on practicalaspects required by our industries. Later, as Chairman of the IIydcrabad chapter of theIndian Institute of Foundrymen, I always wished that there should be a book that dealsnot only with the manufacturing practices followed by the Indian Industries for varioustypes of metal castings but which also incorporates subjects of standards, types ofdefects, methods of inspection and testing and some practical tips on reducingrejections. And here I find Prof. T.V. Ramana Rao coming forward with a book !&la1Castings - .Princijdes and Practice: fulfilling the need of the hour.

His book which is divided in ten chapters deals with all aspects of foundrypractices, different manufachlring technologies and inspection and quality controlprocedures.

With incorporation of chapters on PPC, Organisation and MIS, ComputerApplications and Environmental Protection aspects, I am sure the book will be a verywelcome addition for the practising Managers as well as graduate shrdents.

K.K.SINHAChief Executive

NUCLEAR FUEL COMPLEXDepartment of Atomic Energy

Government of IndiaECIL (P.O.)

Hyderabad - 500 762.

PREFACE

This book is a compilation of different aspects of Metal Casting, covering the latestavailable information, Industry data and Foundry practices, brought together to servestudents of under-graduate and post-graduate courses studying the subject, as well aspractising foundry supervisors, engineers and managers. As such, the author does notclaim complete originahty in the information contained and takes credit only forcollecting, selecting and presenting the contributions to the field by many eminentresearch workers, academicians, practising foundrymen and authors. Detailedacknowledgement is attempted but any omission to mention a work quoted in this bookis sincerely regretted as it is only on the grounds of space constraints or ignorance butnot by intention.

Under-graduate students may omit certain practical aspects which are intendedmainly for foundry personnel.

I thank the publishers M/S New Age International Pvt. Ltd. for their help andguidance in making this book presentable. I am grateful to Shri K.K Sinha, Chairmanand Chief Executive of Nuclear Fuel Complex a highly honoured and eminentmetallurgist, known to me since long, for encouraging me by giving the Foreword.

Finally, this book is before you only because of the persistent inspiration providedby my wife Chandra and family members, for whom I have no words to thank.

Dr. T.V. Ramana F&LOAuthor

ACKNOWLEDGEMENTS

Apart from the Text Books, Technical Journals and other Documents referred to elsewherein this book, I respectfully wish to acknowledge the following persons specifically for theirinfluence on me and on this book, either directly or indirectly..

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Prof. M.R.Seshadri and Prof. K.Srinivasan, Indian Institute of Science, Bangalore, whotaught 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 learntvaluable practical aspects of methoding of castings.Mr. T.Kumar, STEELCAST, Bhavnagar, who has guided and gave me the opportunity tolearn production, cost and management aspects of alloy steel foundry.Mr. S.C.Gupta, M.D., R.G. Foundry Forge, Hyderabad, for giving valuable insight intotechnology, marketing and commercial aspects.Shri B.G.Sastry, formerly M.D., Ductron Castings, for his valuable suggestions duringconsultancy assignment.Dr. Md. Roshan and Dr. Prasannakumar, I.I.T., Madras, for their invaluable contributions inJournals on different aspects of Research and Development.Dr. S.Sunderrajan, D.R.D.L., Hyderabad, for his expert contributions on nonferroustechnology, 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 computerprograms.My colleagues in metal casting industry and other Academic Institutions, who gave valuablesuggestions.The management and staff members of M.J.C.E.T., Hyderabad, who gave me theirencouragement and appreciation.

Prof. T. V. Ramana RaoAuthor

Contents

Page No.

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, 73

2 Sand molding processes

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 Shellmolding, 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

1

1 5

69

4 Melting furnaces and techniques .

4.1 Classification of melting equipment, 83

4.2 Common melting furnaces in foundry, 83

4.3 Melting procedures , Practical 93aspects,

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 722process,

5 . 2 R u n n i n g a n d gating 7 2 6system,

5.3 Risering / Feeding 744systems,

5.4 Design of Castings, 757

Questions, 7 67

6 Finishing operations

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

Page No.

83

121

163

183

7.4 Quality control a.nd Quality assurance, 204

Questions, 209

8 Foundry mechanization

Page No.

2 1 1

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

1 0 New developements in metal casting 2 4 9

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, 279

Suggested experiments / practicals in metal casting lab 282

Computer Aided Metal Casting (LT. Tools) 2 8 3

Explanation of Terminology used in LT. Tools for Casting 2 8 5

UseN References 2 8 8

Index 2 9 3

1 INTRODUCTION

1.1 Metal casting as a manufacturing processMetal 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, pouringit into the shaped cavity of a mold and allowing it to solidify. The process of castinginvolves the basic operations of pattern making, sand preparation, molding, melting ofmetal, pouring in molds, cooling, shake-out, fettling, heat-treatment finishing andinspection. The flow process chart (Fig 1.1) illustrates these stages in sequence.

In comparison to other manufacturing processes like rolling, forging, welding, powdermetallurgy, machining, pressing etc., the casting process has the following advantages:

i. Advantages of casting process

4

b)

4

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

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

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