Duplex Stainless Steels

Duplex Stainless Steels (DSSs) are chromium-nickel-molybdenum-iron alloys that are usually in proportions optimized for equalizing the volume fractions of austenite and ferrite. Due to their ferritic-austenitic microstructure, they possess a higher mechanical strength and a better corrosion resistance than standard austenitic steels. This type of steel is now increasing its application and market field due to its very good properties and relatively low cost. This book is a review of the most recent progress achieved in the last 10 years on microstructure, corrosion resistance and mechanical strength properties, as well as applications, due to the development of new grades. Special attention will be given to fatigue and fracture behavior and to proposed models to account for mechanical behavior. Each subject will be developed in chapters written by experts recognized around the international industrial and scientific communities. The use of duplex stainless steels has grown rapidly in the last 10 years, particularly in the oil and gas industry, chemical tankers, pulp and paper as well as the chemical industry. In all these examples, topics like welding, corrosion resistance and mechanical strength properties (mainly in the fatigue domain) are crucial. Therefore, the update of welding and corrosion properties and the introduction of topics like texture effects, fatigue and fracture strength properties, and mechanical behavior modeling give this book specific focus and character.

Table of Contents:
Preface xiii Chapter 1. Process: Hot Workability 1 Isabel GUTIERREZ and Amaia IZA-MENDIA 1.1. Introduction 1 1.2. As-cast microstructure 1 1.3. Microstructural evolution during hot working 4 1.4. Mechanical behavior under hot working 16 1.5. Static softening 28 1.6. Hot workability 31 1.7. Conclusions 39 1.8. Acknowledgments 39 1.9. References 39 Chapter 2. Corrosion Resistance Properties 47 Jacques CHARLES 2.1. Introduction 47 2.2. The duplex grades and pitting resistance equivalent numbers 48 2.3. Some fundamentals concerning stainless steel corrosion resistance 50 2.4. The different forms of corrosion 60 2.5. Some complex corrosion behaviors encountered in industrial applications 100 2.6. Conclusions 111 2.7. References 111 Chapter 3. Phase Transformation and Microstructure 115 Angelo Fernando PADILHA and Ronald Lesley PLAUT 3.1. Introduction 115 3.2. Phase diagrams and typical phases 117 3.3. Solidification 120 3.4. Austenite precipitation 121 3.5. Phase changes occurring below 1,000°C 123 3.6. Cold working and annealing 132 3.7. Final remarks 134 3.8. References 135 Chapter 4. Welding Processes, Microstructural Evolution and Final Properties of Duplex and Superduplex Stainless Steels 141 Franco BONOLLO, Alberto TIZIANI and Paolo FERRO 4.1. Introduction 141 4.2. ƒÏ-ferrite ƒÏƒnaustenite transformation 142 4.3. Secondary and intermetallic phases precipitation during welding processes 145 4.4. Welding processes for DSS and SDSS 147 4.5. Final remarks 155 4.6. References 155 Chapter 5. Thermal Embrittlement of Cast Duplex Stainless Steels: Observations and Modeling 161 Andre PINEAU and Jacques BESSON 5.1. Introduction 161 5.2. Composition, elaboration, microstructure, and mechanical properties 163 5.3. Thermal embrittlement of the ferrite phase in DSS 170 5.4. Materials investigated and embrittlement heat treatments 181 5.5. Damage and rupture 186 5.6. Scale effect and scatter 189 5.7. Modeling of rupture 192 5.8. Conclusion 201 5.9. References 201 Chapter 6. Low-Cycle Fatigue at Room Temperature 209 Iris ALVAREZ-ARMAS 6.1. Introduction 209 6.2. Cyclic hardening/softening process 210 6.3. Uniaxial cyclic plasticity in DSSs 219 6.4. Final remarks 236 6.5. Acknowledgments 237 6.6. References 237 Chapter 7. Multiaxial Low-Cycle Fatigue Behavior at Room Temperature 241 Suzanne DEGALLAIX-MOREUIL 7.1. Introduction 241 7.2. Multiaxial LCF – introduction 242 7.3. Biaxial LCF of a DSS type 25-07 248 7.4. Conclusions 270 7.5. Acknowledgments 270 7.6. References 270 Chapter 8. Partition of Cyclic Plasticity in the 25Cr-7Ni-0.25N Duplex Stainless Steel Investigated by Atomic Force Microscopy 275 Jean-Bernard VOGT, Daniel SALAZAR and Ingrid PRORIOL SERRE 8.1. Introduction 275 8.2. Material 277 8.3. Experimental procedure 278 8.4. Cyclic behavior at a low strain range 280 8.5. Cyclic behavior at a high strain range 289 8.6. Conclusions 300 8.7. References 300 Chapter 9. Macro- and Micromodeling of the Monotonic and Cyclic Mechanical Behavior of a Forged DSS 303 Veronique AUBIN and Pierre EVRARD 9.1. Introduction 303 9.2. Macroscopic modeling of the mechanical behavior 304 9.3. Micromechanical modeling 318 9.4. General conclusion 332 9.5. References 334 Chapter 10. Low-Cycle Fatigue at Intermediate Temperatures 339 Alberto F. ARMAS 10.1. Introduction 339 10.2. Materials studied 342 10.3. UNS S32900 DSS 345 10.4. UNS S32750 SDSS 352 10.5. Temperature influence on the fatigue life 361 10.6. Final remarks 363 10.7. Acknowledgments 364 10.8. References 364 Chapter 11. Industrial Processing and Fatigue Response of DSSs 367 Nuri AKDUT 11.1. Introduction 367 11.2. Morphological aspects 369 11.3. The role of morphological texture on the fatigue response 372 11.4. The role of nitrogen-content on the fatigue response of DSSs 375 11.5. Cyclic plasticity and fatigue of nitrogen-alloyed DSSs – effects of cyclic softening 383 11.6. Summary and conclusions 395 11.7. References 396 Chapter 12. Applications 403 Mats LILJAS and Fredrik SJOHOLM 12.1. Introduction 403 12.2. Historical review 404 12.3. Current (modern) DSS grades 408 12.4. Modern applications 409 12.5. Conclusions 422 12.6. References 422 Appendix 425 List of Authors 429 Index 433

About the Author :
Suzanne Degallaix is Professor at the Laboratoire de Mécanique de Lille, Ecole Centrale de Lille, FRANCE. Iris Alvarez-Armas is Director of Research at the Instituto de Física Rosario, Universidad Nacional de Rosario, ARGENTINA.