Hot Stamping of Ultra High-Strength Steels (eBook)

After studying in Baskent University and Virginia Commonwealth University, Eren Billur graduated and received his PhD in mechanical engineering from The Ohio State University in 2013. As a successful researcher at Center for Precision Forming, he was responsible for the coordination of sheet forming research. His focus is set on comprehensive topics like material characterization, sheet metal forming processes and finite element simulations. Dr. Billur's present positions as Technical Manager at Billur Makine and Assistant Professor of Automotive Engineering at Atilim University, both in Ankara, Turkey, are ideal endorsements that keep an overview on science and industry.

Foreword 6
Acknowledgements 8
Contents 9
Contributors 10
Acronyms 11
1 Introduction 13
1.1 Material Requirements in a Car Body 13
1.2 Steels in Automotive Industry 15
1.2.1 Mild Steels 15
1.2.2 Conventional High-Strength Steels 16
1.2.3 Advanced High-Strength Steels: The First Generation 18
1.2.4 Second-Generation AHSS 19
1.2.5 Third-Generation AHSS 21
1.3 Hot Stamping 23
References 26
2 Metallurgy of Steels 30
2.1 Phases of Steels and Their Properties 30
2.2 The Effect of Alloying Elements 32
2.3 Phase Transformations 36
References 39
3 History and Future Outlook of Hot Stamping 41
3.1 Early Developments: 1973–1990 41
3.2 Further Developments 1990s 44
3.3 Coated Blanks and Increased Usage: 2000s 44
3.4 Further Uses of Hot Stamping: 2010s 47
3.5 Summary of the 40Years 49
References 51
4 Blank Materials 55
4.1 22MnB5 55
4.2 Higher Strength Steels (> 1700MPa)
4.3 Higher Elongation/Energy Absorbing Materials 61
4.4 Other Steels for Hot Stamping 65
4.4.1 Stainless Steels 65
4.4.2 Medium-Mn Steels 65
4.4.3 Steel Composites 70
4.5 Coatings 71
4.5.1 Aluminum-Based Coatings 73
4.5.2 Zinc-Based Coatings 75
4.5.3 Varnish Coatings 80
References 81
5 A Hot Stamping Line 87
5.1 Furnaces and Heating Systems 87
5.1.1 Conventional Roller Hearth Furnaces 87
5.1.2 Roller Hearth Furnaces with Tray 90
5.1.3 Multi-chamber Furnaces 91
5.1.4 Other Heating System Designs 92
5.1.5 Heating Time Reduction 97
5.2 Material Handling Systems 98
5.3 Hot Stamping Presses 101
5.3.1 Direct Drive Hydraulic Press 101
5.3.2 Accumulator Drive Hydraulic Press 102
5.3.3 Multi-cylinder Hydraulic Press 103
5.3.4 Flywheel Hydraulic Press 103
5.3.5 Servo-Mechanical Press 106
5.4 Hot Stamping Lines by Capacity 109
References 111
6 Die Design and Manufacturing 115
6.1 Quenching Requirements 115
6.2 Designing and Manufacturing Dies with Cooling Channels 117
6.2.1 Drilled Cooling Channels 120
6.2.2 Shell and Core Design 121
6.2.3 Cast-in Cooling Channels 122
6.3 Die Materials and Treatments 123
6.3.1 Treatments/Coatings for Tool Materials 124
6.4 Novel Quenching Methods 127
6.5 Hydrogen-Induced Delayed Fracture 133
References 136
7 Post-Forming Operations 140
7.1 Typical Process Chain 140
7.2 Trimming and Piercing 142
7.2.1 Hard Cutting 142
7.2.2 Laser Cutting 145
7.2.3 Alternative Cutting Methods 147
7.3 Surface Conditioning 150
7.4 Quality Control 151
7.4.1 Blanking Quality 152
7.4.2 Preforming Quality 153
7.4.3 Hot-Forming Quality 153
7.5 Welding and Assembly 155
7.5.1 Resistance Spot Welding 155
7.5.2 Arc Welding 157
7.5.3 Other Joining Methods 158
References 160
8 Tailored Properties 165
8.1 The Need for Tailored Parts 165
8.2 Tailored Blanks 166
8.2.1 Tailor Welded Blanks 167
8.2.2 Tailor Rolled Blanks 175
8.2.3 Patchwork Blanks 178
8.3 Tailoring Final Properties 179
8.3.1 Tailored Heating (Pre Process) 180
8.3.2 Tailored Cooling (In-Die Process) 182
8.3.3 Post Process Annealing 187
8.4 Uses of Tailored Properties 187
8.4.1 Tailored Properties for Improved Energy Absorption 188
8.4.2 Reduction of Metallurgical Notch Sensitivity 189
8.4.3 Tailored Properties to Facilitate Trimming and Piercing 192
References 193
9 Hot Tube Forming 199
9.1 3DQ 200
9.2 Hot Tube Forming 203
9.3 Hot Tube Hydroforming 205
References 207
10 Computer Modeling of Hot Stamping 210
10.1 FE Modeling of Hot Stamping Process 210
10.2 Inputs to Simulation 211
10.2.1 Properties of the Blank 211
10.2.2 Properties of the Tools 214
10.2.3 Friction 214
10.2.4 Thermal Contact Conductance 215
10.3 Stages of a Simulation 216
10.3.1 Gravity 216
10.3.2 Holding 217
10.3.3 Forming 217
10.3.4 Quenching 217
10.3.5 Air Quenching 219
10.3.6 Distortion 219
10.4 Case Studies 221
10.4.1 Numisheet 2008 B-pillar 221
10.4.2 Cyclic Cooling in a Tailored Part 224
10.5 Recent Improvements in Simulation Technology 226
References 228
11 Economics of Hot Stamping 231
11.1 The Hot Stamping Industry 231
11.1.1 Steel Makers and Service Centers 232
11.1.2 Equipment Suppliers 233
11.2 Hot Stamping Lines 234
11.2.1 Tier Suppliers 235
11.2.2 Vehicle Manufacturers (OEM's) 236
11.3 Feasibility of Hot Stamping 243
11.4 Future Outlook on Hot Stamping Business 245
11.4.1 Automotive Industry 245
11.4.2 Defense Industry 245
References 247