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Metal Casting Principles and Techniques
BOOK DECEMBER 2013
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2 AUTHORS:
Yury . S. Lerner
Nageswara Rao Posinasetti
University of Northern Iowa
University of Northern Iowa
15 PUBLICATIONS 36 CITATIONS
178 PUBLICATIONS 200 CITATIONS
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Available from: Nageswara Rao Posinasetti
Retrieved on: 09 September 2015
TABLE OF CONTENTS
Preface......................................................................................................................................................... vii
Acknowledgments..................................................................................................................................... viii
Chapter 1. Introduction to Metalcasting..........................................................................1
1.1. Brief History of Metalcasting................................................................................................................1
1.2. Castings Advantages and Applications................................................................................................4
1.3. Foundry Process and Terminology.......................................................................................................4
1.4. Classification of Foundries....................................................................................................................6
1.5. Present and Future of the Foundry Industry......................................................................................6
Chapter 2. Casting Alloys...........................................................................................................9
2.1. Structure of Cast Alloys.........................................................................................................................9
2.1.1. Nucleation and Grain Growth....................................................................................................10
2.1.2. Equilibrium Diagrams................................................................................................................11
2.2. Properties and Testing of Cast Alloys.................................................................................................13
2.2.1. Mechanical Properties................................................................................................................13
2.2.2. Specific Properties Affecting Service Performance...................................................................17
2.3. Ferrous Alloys.......................................................................................................................................19
2.3.1. Cast Irons...................................................................................................................................19
2.3.2. Cast Steels..................................................................................................................................26
2.4. Nonferrous Alloys.................................................................................................................................28
2.4.1. Aluminum Alloys.......................................................................................................................28
2.4.2. Copper Alloys.............................................................................................................................30
2.4.3. Magnesium Alloys.....................................................................................................................30
2.5. Heat Treatment.....................................................................................................................................31
2.5.1. Heat Treatment of Ferrous Alloys..............................................................................................31
2.5.2. Case Hardening Methods...........................................................................................................35
2.5.3. Heat Treatment of Nonferrous Alloys........................................................................................36
Metalcasting Principles & Techniques
Chapter 3. Foundry Tooling....................................................................................................41
3.1. Selection of Pattern Type and Material.............................................................................................42
3.1.1. Pattern Materials........................................................................................................................42
3.1.2. Types of patterns........................................................................................................................43
3.2. Pattern Design .....................................................................................................................................46
3.2.1. Selection of Parting Line............................................................................................................46
3.2.2. Pattern Dimensioning.................................................................................................................46
3.2.3. Cores & Coreboxes....................................................................................................................50
3.2.4. Fillets & Radii............................................................................................................................54
3.2.5. Elimination of Details................................................................................................................55
3.3. Flasks & Chaplets................................................................................................................................55
3.4. Dimensional AccuracyCMM Applications....................................................................................57
Chapter 4. Gating Systems......................................................................................................59
4.1. Types of Gating Systems......................................................................................................................59
4.2. Elements of Gating Systems and Their Functions............................................................................60
4.2.1. Pouring Basin or Pouring Cup...................................................................................................60
4.2.2. Pouring Sprue.............................................................................................................................62
4.2.3. Sprue Base or Sprue Well...........................................................................................................62
4.2.4. Runner........................................................................................................................................62
4.2.5. Runner Extension.......................................................................................................................63
4.2.6. Gates or Ingates..........................................................................................................................63
4.3. Casting Yield.........................................................................................................................................64
4.4. Gating System Design..........................................................................................................................65
4.4.1. Basic Principles..........................................................................................................................65
4.4.2. Fluidity or Fluid Life of Molten Metal......................................................................................66
4.4.3. Pouring Time..............................................................................................................................67
4.4.4. Pressurized vs. Nonpressurized System.................................................................................... 69
4.4.5. Choke Area Calculation.............................................................................................................70
4.4.6. Ingate Design.............................................................................................................................71
4.5. Slag Trap Systems................................................................................................................................73
4.5.1. Runner Extension.......................................................................................................................73
4.5.2. Whirl Ingate................................................................................................................................73
4.5.3. Metal Filtration in Gating Systems............................................................................................73
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Chapter 5. Risering and Feeding....................................................................................... 81
5.1. Casting Solidification and Shrinkage.................................................................................................81
5.2. Design of Risers....................................................................................................................................83
5.2.1. Riser Type and Shape.................................................................................................................83
5.2.2. Riser Dimensioning....................................................................................................................83
5.2.3. Riser Neck Dimensioning..........................................................................................................86
5.3. Feeding Distances.................................................................................................................................86
5.4. Cooling Aids..........................................................................................................................................87
5.5. Feeding Aids.........................................................................................................................................88
5.6. Grouping Castings...............................................................................................................................89
5.7. Solidification Modeling........................................................................................................................89
5.8 Case Study: Cooling Aid Selection for Aluminum Alloy Sand Mold Casting.................................92
Chapter 6. Sand Molding and Coremaking Processes.......................................99
6.1. Foundry Sands.....................................................................................................................................99
6.1.1. Types of Sands...........................................................................................................................99
6.1.2. Sand Properties.........................................................................................................................100
6.2. Green Sand System............................................................................................................................101
6.2.1. Green Sand Preparation.......................................................................................................... 102
6.2.2. Testing Green Sand Properties.................................................................................................104
6.2.3. Variables Affecting Green Sand Properties..............................................................................109
6.3. Types of Sand Molds..........................................................................................................................110
6.4. Moldmaking Processes......................................................................................................................112
6.4.1. Hand Molding..........................................................................................................................112
6.4.2. Machine Molding.....................................................................................................................113
6.4.3. Flaskless Molding....................................................................................................................115
6.5. Coremaking Processes.......................................................................................................................115
6.5.1. Hotbox (Heat-Activated) Process............................................................................................116
6.5.2. Coldbox Processes...................................................................................................................118
6.5.3. Nobake Sand Systems..............................................................................................................120
6.5.4. Corebox Design Features for Core Blowing............................................................................121
6.6. Mold and Core Venting.....................................................................................................................121
6.7. Mold and Core Coatings...................................................................................................................122
6.8. Sand Reclamation and Recycling.....................................................................................................123
6.8.1 Sand Reclamation......................................................................................................................123
6.8.2 Sand Recycling..........................................................................................................................124
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Chapter 7. Melting and Pouring Practices.................................................................127
7.1. Melting Furnaces...............................................................................................................................128
7.1.1. Refractory Lining.....................................................................................................................128
7.2. Melting of Ferrous Alloys..................................................................................................................130
7.2.1 Cupola Melting of Cast Irons....................................................................................................130
7.2.2 Induction Melting of Iron..........................................................................................................135
7.2.3. Iron Inoculation........................................................................................................................140
7.2.4. Magnesium Treatment..............................................................................................................146
7.2.5. Melting of Steel........................................................................................................................156
7.3. Melting of Nonferrous Alloys............................................................................................................158
7.3.1. Crucible Furnace......................................................................................................................158
7.3.2. Reverberatory Furnace.............................................................................................................159
7.3.3. Aluminum Alloy Melting Problems........................................................................................ 160
7.4. Pouring of Cast Alloys.......................................................................................................................161
7.4.1. Pouring Ladles.........................................................................................................................162
7.4.2. Ladleless Pouring Systems.......................................................................................................165
7.4.3. Automatic Pouring Control Systems........................................................................................166
7.5. Quality Control in Melting................................................................................................................167
7.5.1. Chemical Composition Control................................................................................................167
7.5.2. Temperature Measurement Control..........................................................................................168
7.5.3. Gas and Slag Control...............................................................................................................169
7.5.4. Chill Control in Iron Melting...................................................................................................172
Chapter 8. Special Casting Methods..............................................................................175
8.1. Permanent Mold Casting................................................................................................................. 176
8.2. Diecasting............................................................................................................................................186
8.3. Low-Pressure Diecasting...................................................................................................................190
8.4. Centrifugal Casting............................................................................................................................191
8.5. Investment Casting............................................................................................................................194
8.6. Ceramic Mold Casting.......................................................................................................................195
8.7. Lost Foam Casting.............................................................................................................................197
8.8. Continuous Casting............................................................................................................................198
8.9. Countergravity Casting.....................................................................................................................200
8.10. Semisolid Casting.............................................................................................................................201
8.11. Vacuum Molding or V-Process Casting..........................................................................................203
8.12. Case Study: External Chill Selection for Al Alloy PMC..............................................................204
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Metalcasting Principles & Techniques
Chapter 9. Shakeout, Cleaning and Quality Testing .........................................213
9.1. Shakeout ............................................................................................................................................213
9.2. Cleaning and Finishing......................................................................................................................215
9.2.1. Core Removal (Decoring)........................................................................................................215
9.2.2. Ingate/Riser Removal (Degating)............................................................................................215
9.2.3. Fins and Excess Metal Removal..............................................................................................216
9.2.4. Robotic Cleaning Operations...................................................................................................217
9.3. Quality Testing...................................................................................................................................218
Chapter 10. Casting Defects and Prevention...........................................................223
10.1. Shrinkage-Related Defects..............................................................................................................223
10.2. Gas-Related Defects.........................................................................................................................224
10.3. Mold-Related defects.......................................................................................................................225
10.4. Pouring-Related Defects..................................................................................................................226
10.5. Hot Tears and Broken or Cracked Castings..................................................................................227
Chapter 11. Design Optimization for Sand Molding...........................................229
11.1. Designing for Economical Molding................................................................................................229
11.1.1. Parting Line Determination....................................................................................................229
11.1.2. Core Positioning.....................................................................................................................230
11.1.3. Boss Positioning.....................................................................................................................231
11.1.4. Simple Economics................................................................................................................. 231
11.2. Designing for Casting Defect Prevention.......................................................................................232
11.2.1. Shrinkage................................................................................................................................232
11.2.2. Distortion................................................................................................................................233
11.2.3. Hot Tearing.............................................................................................................................234
11.2.4. Gas (Blowholes and Pinholes)...............................................................................................235
11.3. Designing to Aid Handling............................................................................................................. 236
11.4. Designing with Finite Element Analysis (FEA).............................................................................236
Chapter 12. Rapid Prototyping and
Rapid Manufacturing in Metalcasting..........................................................................
239
12.1. Rapid Prototyping (RP)...................................................................................................................239
12.2. Rapid Prototyping Technologies.....................................................................................................241
12.2.1. Stereolithography (SLA)........................................................................................................242
12.2.2. Laminated Object Manufacturing (LOM)..............................................................................242
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12.2.3. Fused Deposition Modeling (FDM).......................................................................................244
12.2.4. Selective Laser Sintering (SLS).............................................................................................245
12.2.5. 3-D Printing............................................................................................................................245
12.2.6. Laser Engineering Net Shaping (LENS)................................................................................246
12.2.7. Direct Metal Deposition (DMD)............................................................................................247
12.3. Rapid Tooling in Metalcasting........................................................................................................247
12.3.1. Sand Casting Tooling.............................................................................................................248
12.3.2. Investment Casting Tooling...................................................................................................249
12.3.3. Permanent Mold (PM) Casting Tooling.................................................................................251
12.3.4. Pressure Diecasting Tooling...................................................................................................251
12.4. RP System Selection for Metalcasting............................................................................................253
12.5. Rapid Manufacturing (RM) Concept.............................................................................................254
12.5.1. Rapid Manufacturing in Metalcasting....................................................................................254
12.6. Case Studies......................................................................................................................................254
12.6.1. Industrial Applications...........................................................................................................254
12.6.2 Art Casting Applications........................................................................................................255
Index...........................................................................................................................................................259
Metalcasting Principles & Techniques
