Refractories for Aluminum (eBook)

Andrey Yurkov graduated from the Department of Ceramics and Refractories at the Moscow Mendeleev University of Chemical Technology. He holds a Ph.D. in structural ceramics and the Dr. Sci. in materials science of refractory materials. Professor Yurkov has more than a 100 publications. His areas of expertise and interests include materials science and processing of non-oxygen and oxygen-containing ceramics and refractories, and their applications in the aluminium industry. Dr. Yurkov is currently a research scientist at the Russian Aluminium company (RUSAL). He has also served as  the organizer and chairperson of the seminar and conference, “Refractories and Carbon Cathode Materials for the Aluminium Industry”.

Preface-Second Edition 5
Preface-First Edition 7
Contents 10
Chapter 1: The Properties of Refractory and Heat Insulation Materials 14
1.1 Classifications and Some Words About Quality Control 14
1.2 Density, Porosity, and Related Characteristics Types of Porosity
1.3 Mechanical Characteristics 26
1.3.1 Compressive and Bending Strength 26
1.3.2 Elasticity Modulus, Hardness, and Weibull Modulus 31
Hardness 34
Weibull Modulus 35
1.3.3 Elements of Fracture Mechanics 36
1.4 Thermomechanical Properties 39
1.4.1 Refractoriness 39
1.4.2 Hot Modulus of Rupture 43
1.4.3 Reheat Change: Permanent Linear Change on Reheating 43
1.4.4 High-Temperature Deformation: Characteristic Points and Softening Point 45
1.4.5 reep 47
1.5 Thermal Conductivity, Heat Capacity, and Temperature Conductivity (Heat Diffusivity) 48
1.5.1 Elements of Theory 50
1.5.2 Measurement of Thermal Conductivity 57
1.5.3 Methods of Thermal Conductivity Measurements Based on Principle of Stationary Heat Flow 58
1.5.4 Methods of Thermal Conductivity Measurements Based on Principle of Nonstationary Heat Flow (Dynamic Methods) 59
1.6 Thermal Coefficient of Linear Expansion, Thermal Strains, and Thermal Shock Resistance 60
1.6.1 Thermal Coefficient of Linear Expansion 60
1.6.2 Thermal Expansion of Refractory and Heat Insulation Materials: Elements of Theory 61
1.6.3 Measurement of Linear Coefficients of Thermal Expansion 64
1.6.4 Thermal Strains 65
1.6.5 Thermal Shock 67
1.6.6 Thermal Shock Factors 69
1.6.7 Thermal Shock Resistance Measurements 70
1.7 Corrosion Resistance 71
1.7.1 Elements of Theory 73
Corrosion by Gases 73
Corrosion by Melts 74
1.7.2 Tests 79
References 81
Density, Porosity and Related Characteristics: The Types of Porosity 82
Mechanical Characteristics 83
Thermomechanical Properties 84
Thermal Conductivity, Heat Capacity, and Temperature Conductivity (Heat Diffusivity) 85
The Thermal Coefficient of the Linear Expansion, Thermal Strains, and Thermal Shock Resistance 85
Corrosion Resistance 86
Chapter 2: Refractories and Carbon Cathode Materials for Aluminum Reduction Cells 87
2.1 Aspects of Aluminum Reduction 87
2.2 Lining of Reduction Cells Preheating, Startup, and Operation
2.2.1 Brief Discussion on Reduction Cell Linings 97
2.2.2 Preheating and Startup of Reduction Cells 103
2.2.3 Service Life and the Main Causes for Shutdowns 106
2.2.4 Dry Autopsies 109
2.3 Carbon Cathode Bottom Blocks 112
2.3.1 Types and Properties 112
2.3.2 Elements of Technology, Raw Materials, and Processing 114
Raw Materials 118
Firing 127
Graphitization 130
Mechanical Milling (Finishing) 132
2.3.3 Defects in Carbon Cathode Blocks 132
2.3.4 Testing and Characterization 138
2.3.5 Grades of Carbon Cathode Blocks 143
2.3.6 Structure of Carbon Cathode Blocks in Connection with Grain Size Composition, Sintering, and Pore Size Structure 145
2.3.7 Interaction of Carbon Cathode Blocks with Steel Shell and Collector Bars 147
Cracks Induced by Thermal Strains and Thermal Shock 149
2.3.8 Interaction of Carbon Cathode Blocks with Electrolyte During Startup and in Service: Wear, Infiltration 151
Transformations in Carbon Cathode Blocks During Service Life 153
Formation of Aluminum Carbide, Chemical Erosion Mechanism of Wear of Cathode Blocks, and Wear and Erosion Tests 153
Infiltration of Electrolyte in Permeable Pores of Carbon Cathode Blocks 157
2.3.9 Carbon Ramming Paste 161
Testing 161
Installation of Ramming Paste 166
2.4 Coatings of Carbon Cathode Blocks and New Cathode Materials 171
2.5 Side Lining Materials 178
2.5.1 Carbon Side Linings and the Causes of Their Decay 179
2.5.2 SiC Side Lining 182
2.5.3 Variants of SiC Materials (and Others) as a Side Lining 184
Nitride-Bonded SiC: Elements of Technology 185
Combiblocks 191
Defects in Nitride-Bonded SiC Side Lining 194
Changes in SiC Lining in Service and the Mechanisms of Decay 195
Corrosion Resistance Tests for Bath and Molten Aluminum 200
SiC-Based (and Non-SiC-Based) Side-Wall Materials and the Application Possibilities of Other Materials 203
2.5.4 SiC Mortars, Ramming Mixes, and Castables for Installation of SiC Side Lining 205
2.6 Refractory Barrier Materials of Cell Lining. Dry Barrier Mixes and Bricks. Properties and Chemical Resistance. Processes D... 209
2.6.1 Bricks and Dry Barrier Mixtures 209
Alumina Silica Refractory Barriers 211
Dry Barrier Mixtures 212
Corrosion Resistance Testing 213
Chemical Interaction of Sodium Fluoride Salts with Alumina Silica Refractories 214
Sodium Vapor Degradation 216
Influence of Porosity and Permeability on Corrosion Resistance of Refractories 218
More on Barriers for Electrolyte Penetration 221
2.7 Heat Refractory Insulation Materials for Reduction Cell Linings 221
2.7.1 Diatomaceous (Moler) Heat Insulation Materials 222
2.7.2 Perlite-Based Heat Insulation Materials 223
2.7.3 Vermiculite-Based Heat Insulation Materials 223
2.7.4 Calcium Silicate Heat Insulation Materials 225
Thermal Conductivity of Heat Insulation Refractory Materials for Reduction Cells 226
2.7.5 Thermal Aging of Heat Insulation Materials at Service and Thermal Conductivity of Infiltrated Heat Insulation Materials 228
Safe Temperature of Service for Heat Insulation Materials in Reduction Cells 228
References 231
Chapter 3: Refractories and Heat Insulation Materials for Cast Houses 240
3.1 Cast House 240
3.2 Physical and Chemical Interaction of Refractories with Aluminum and Aluminum Alloys 242
3.2.1 Chemical Interaction of Aluminum and Aluminum-Based Alloys with Components of Refractories 242
3.2.2 Antiwetting Admixtures to Alumina Silica Refractories 246
3.2.3 Wetting of Alumina Silica Refractories by Molten Aluminum and Aluminum Alloys 248
3.2.4 Some Words on Corrosion Mechanism 249
3.2.5 Tests for Corrosion Resistance 253
3.3 Refractory Materials 254
3.4 Elements of Lining Design 260
3.4.1 Some Words on Drying and Preheating of Furnaces 261
3.5 Melting and Holding Furnaces 265
3.6 Induction Furnaces, Ladles 268
3.6.1 Ladles 270
3.7 Launders (Runners), Casting Equipment: Elimination of Asbestos-Containing Materials 270
3.7.1 Casting Equipment (Tooling) 272
3.7.2 Ceramic Foam Filters 274
3.8 Considerations on Future Trends: Physical Chemistry of Technical Engineering Improvements? 274
References 275
Elements of Lining Design 277
Launders (Runners), Casting Equipment. Elimination of Asbestos-Containing Materials 277
Induction Furnaces, Ladles 277
Chapter 4: Refractories for Anode Baking Furnaces 278
4.1 Lining 278
References 282
Glossary 283