Direct-chill casting is the major production route for wrought aluminium and magnesium alloys that are later deformed (rolled, extruded, forged) to the final products. To aid in this process, this book provides comprehensive coverage on topics such as the history of process development in this field, industrial applications, including vertical and horizontal casting, melt preparation, fundamentals of solidification in DC casting, and more. The first book targeted for the industrial researcher and practitioner, it pulls together the practice and process of physics with the goal of improving process performance.
Autorentext
JOHN F. GRANDFIELD, PhD, is Director of Grandfield Technology Pty Ltd. Dr. Grandfield is a well-known specialist in casting and solidification of light metals. He is an active presenter and organizer of workshops and lectures.
DMITRY G. ESKIN, PhD, is Professor at Brunel University. His main scientific contributions are in physical metallurgy of aluminium alloys and solidification processing.
Ian F. Bainbridge, PhD, managed production operations and conducted R&D in the aluminium industry for fifty years.
Klappentext
Presents the latest science and technology to solve current problems and advance the field of direct-chill casting
Light alloys play an indispensable role in today's industrial society, with aluminium and magnesium two of the most important structural materials used around the world. Direct- chill casting is the principle technology for producing billets and ingots of light alloys.
This book thoroughly reviews the science and technology of direct-chill casting of light alloys and important ancillary processes. Emphasizing the needs of industrial research and practice, the book explains how the physico-chemical, thermo-physical, and thermo-mechanical aspects of light alloys all play major roles in the formation of the structure, defects, and properties of the casting.
Direct-Chill Casting of Light Alloys begins with an historical overview and then examines liquid metal supply, alloy preparation, and melt transport. Next, the book covers:
- Melt refining and impurity control
- Grain refinement
- Solidification phenomena and casting defects
- Direct-chill casting technology and operation
- Post-casting processing
- Modeling and simulation
The book ends with a discussion of key economic considerations in direct-chill casting. The authors of the book are international leaders in the field of solidification and casting research and technology. The material presented is based on a thorough review of the literature and current practice as well as the authors' firsthand experience in research and industry.
Direct-Chill Casting of Light Alloys enables technicians, engineers, and researchers to apply all the latest science and technology to solving the current challenges, advancing the field, and creating safe and sustainable commercial operations.
Inhalt
PREFACE AND ACKNOWLEDGEMENTS xi
1 DIRECT-CHILL CASTING: HISTORICAL AND INDUSTRIAL PERSPECTIVE 1
1.1 Industrial Perspective 1
1.2 Historical Development 2
References 27
2 LIQUID METAL SUPPLY, ALLOY PREPARATION, AND MELT TRANSPORT 30
2.1 Plant Layout, Metal Scheduling, and Liquid Supply 31
2.2 Alloying Elements and Master Alloys 33
2.3 Furnace Technology 37
2.3.1 Mixing Technology 40
2.3.2 Temperature Control 41
2.4 Melt Transport to and from the Furnace 43
2.4.1 Furnace Filling 43
2.4.2 Scrap Charging and Melting 44
2.4.3 Furnace Cleaning 46
2.4.4 Molten Metal Transportation from Furnace to Caster 46
2.5 Chemical Analysis 49
2.6 Magnesium Melt Protection and Handling 50
2.7 Safety 52
References 53
3 MELT REFINING AND IMPURITY CONTROL 56
3.1 Impurity Sources 58
3.1.1 Aluminium 58
3.1.2 Magnesium 61
3.2 Effect of Impurities 62
3.2.1 Dissolved Hydrogen 62
3.2.2 Dissolved Metallic Impurity Elements Including Alkali Metals 63
3.2.3 Inclusions 65
3.3 Impurity Removal 65
3.3.1 Dissolved Metal Impurities 67
3.3.2 Hydrogen Removal: Degassing 67
3.3.3 Inclusion Load Minimisation 73
3.3.4 Inclusion Removal 74
3.3.5 Alkali Metal Removal 81
3.3.6 Magnesium Flux Refining 83
3.3.7 Flux-Free Refi ning of Magnesium 85
3.4 Measurement of Impurities 85
3.4.1 Inclusion Measurement 85
3.4.2 Hydrogen Measurement 89
3.4.3 Alkali Content Measurement 91
3.5 Temperature Measurement 91
3.6 System Layouts, Safety, and Cost Considerations 92
References 94
4 GRAIN REFINEMENT 103
4.1 Historical Overview 103
4.2 Fundamentals of Grain Refinement 104
4.3 Mechanisms of Grain Refinement in Aluminium and Magnesium Alloys 112
4.3.1 Grain Refinement through Phases Formed by Alloying Elements during Solidification 113
4.3.2 Grain Refinement by Added Insoluble Particles 115
4.3.3 Grain Refinement by Indigenous Insoluble Particles 121
4.3.4 Grain Refinement by Multiplication of Solidification Sites 125
4.4 Technology of Grain Refinement in DC Casting 128
4.4.1 Grain Refining of Aluminium Alloys by AlTiB and AlTiC Master Alloy Rods 128
4.4.2 Grain Refinement Using Master Alloys Added in the Furnace 136
4.4.3 Addition of Grain Refiners as Salts, Fluxes, Compounds, and Gases 137
References 139
5 SOLIDIFICATION PHENOMENA AND CASTING DEFECTS 144
5.1 Effect of Cooling Rate and Melt Temperature on Solidifi cation of Aluminium Alloys 144
5.2 Microsegregation 148
5.3 Effects of Process Parameters on the Dendrite Structure 149
5.4 Effect of Process Parameters and Alloy Composition on the Occurrence of Specific Structure Defects 155
5.5 Macrosegregation 158
5.5.1 Mechanisms of Macrosegregation 158
5.5.2 Effects of Process Parameters on Macrosegregation during DC Casting 165
5.5.3 Effect of Composition on Macrosegregation: Macrosegregation in Commercial Alloys 169
5.6 Hot Tearing 173
5.6.1 Thermal Contraction during Solidification 174
5.6.2 Mechanical Properties in the Semi-Solid State 177
5.6.3 Mechanisms and Criteria of Hot Tearing 181
5.6.4 Application of Hot-Tearing Criteria to DC Casting of Light Alloys 191
5.6.5 Effects of Process Parameters on Hot Tearing and Shape Distortions during DC Casting 196
5.7 Cold Cracking 204
5.7.1 Mechanical Properties of As-Cast Alloys and Mechanisms of Cold Cracking 206
5.7.2 Cold-Cracking Criteria 210
5.7.3 Methods to Prevent Cold Cracking 218
5.8 Defects Related to the Technology of DC Casting 219
References 226
6 DC CASTING TECHNOLOGY AND OPERATION 235
6.1 Introduction 235
6.2 Mould Technology 236
6.2.1 Mould Heat Transfer 237
6.2.2 Water Cooling Heat Transfer 244
6.2.3 Mould Design: General Development 249
6.2.4 Electromagnetic DC Casting 253
6.2.5 Extrusion Billet Mould Technology Variants and Evolution 255
6.2.6 Gas-Pressurised Hot-Top Mould Operation 258
6.2.7 Mould Dimensions 259
6.2.8 Casting Parameters 266
6.2.9 Rolling Slab Moulds and Cast Start Technology 271
6.2.10 HDC Casting 273
6.2.11 Lubrication and Mould Friction 279
6.3 Other Equipment 281
6.3.1 Mould Table 281
6.3.2 Starting Head Base and Starting Heads 284
6.3.3 Molten Metal Delivery to the Moulds 289
6.3.4 Molten Metal Level Control 293
6.3.5 Casting Machine 298
6.3.6 Ancillary Equipment and Pit En…