Austenitic Steels At Low Temperatures

The need for alternate energy sources has led to the develop ment of prototype fusion and MHD reactors. Both possible energy systems in current designs usually require the use of magnetic fields for plasma confinement and concentration. For the creation and maintenance of large 5 to 15 tesla magnetic fields, supercon ducting magnets appear more economical. But the high magnetic fields create large forces, and the complexities of the conceptual reactors create severe space restrictions. The combination of re quirements, plus the desire to keep construction costs at a mini mum, has created a need for stronger structural alloys for service at liquid helium temperature (4 K). The complexity of the required structures requires that these alloys be weldable. Furthermore, since the plasma is influenced by magnetic fields and since magnet ic forces from the use of ferromagnetic materials in many configur ations may be additive, the best structural alloy for most applica tions should be nonmagnetic. These requirements have led to consideration of higher strength austenitic steels. Strength increases at low temperatures are achieved by the addition of nitrogen. The stability of the austenitic structure is retained by adding manganese instead of nickel, which is more expensive. Research to develop these higher strength austenitic steels is in process, primarily in Japan and the United States.

Stainless steel is still one of the fastest growing materials. Today, the austenitic stainless steel with the classic composition of 18% Cr and 8% Ni (grade 304L) is still the most widely used by far in the world. The unique characteristic of stainless steel arises from three main factors. The versatility results from high corrosion resistance, excellent low- and high-temperature properties, high toughness, formability, and weldability. The long life of stainless steels has been proven in service in a wide range of environments, together with low maintenance costs compared to other highly alloyed metallic materials. The retained value of stainless steel results from the high intrinsic value and easy recycling. Stainless steel, especially of austenitic microstructure, plays a crucial role in achieving sustainable development nowadays, so it is also important for further generations.

The book is dedicated to the behaviour of ductile materials at cryogenic temperatures, structural stability issues and reliability oriented parametric optimisation of compensation systems containing the corrugated bellows. The problems of local and global stability of systems containing bellows, coupling between the low-cycle fatigue and stability as well as evolution of plastic strain fields, micro-damage and strain induced phase transformation in the corrugated shells at cryogenic temperatures are presented. As a special feature reliability oriented optimum design of compensation systems under strength, stability, fatigue and geometrical constraints is discussed. The relevant applications in the particle accelerators and cryogenic transfer lines are shown.

Austenitic stainless steels lend themselves to a wide range of applications. However, they normally stiffer from poor wear resistance and do not respond well to traditional surface treatments. This volume. the fruit of a current status seminar, reflects the enormous strides which have been made in the last few years in the study of the expanded austenite phase (also called the S phase) and the development of new surface treatment techniques. As well as the papers presented at the seminar, the book contains selection from related papers and a comprehensive bibliography of the literature on the subject from 1979 to 2000.

Materials science is the magic that allows us to change the chemical composition and microstructure of material to regulate its corrosion-mechanical, technological, and functional properties. Five major classes of stainless steels are widely used: ferritic, austenitic, martensitic, duplex, and precipitation hardening. Austenitic stainless steels are extensively used for service down to as low as the temperature of liquid helium (-269oC). This is largely due to the lack of a clearly defined transition from ductile to brittle fracture in impact toughness testing. Steels with ferritic or martensitic structures show a sudden change from ductile (safe) to brittle (unsafe) fracture over a small temperature difference. Even the best of these steels shows this behavior at temperatures higher than -100oC and in many cases only just below zero. Various types of stainless steel are used across the whole temperature range from ambient to 1100oC. This book will be useful to scientists, engineers, masters, graduate students, and students. I hope readers will enjoy this book and that it will serve to create new materials with unique properties.

Hydrogen Gas Embrittlement: Mechanisms, Mechanics, and Design enables readers to understand complicated hydrogen-material interactions and conduct better material selection and strength design for hydrogen components. The book reviews the fundamental mechanisms of hydrogen embrittlement, the various behaviors of hydrogen in metallic materials such as diffusion, solution, and trapping, and emphasizes the necessary properties for effective strength design of various materials under the influence of hydrogen, including tensile properties, fatigue life, fatigue limit, fatigue crack-growth, and fracture toughness. Sections provide experimental data obtained in hydrogen gas at various pressures and temperatures together with the fractographic observations, including practical interpretation of hydrogen compatibility of materials based on tensile, fatigue and fracture mechanics testing results. Material testing machines and methods, the effects of hydrogen on various BCC steels, austenitic steels, and non-ferrous metals, and practical applications and methods of strength design for hydrogen vessels and components are all included as well. Enables a better understanding of hydrogen-material interactions, allowing for better material selection and strength design Provides insights on the hydrogen-induced degradation of materials strength at the atomic, macroscale and microscale Looks at a number of degradative behaviors in a variety of materials, including BCC steels, austenitic steels and non-ferrous metals Includes verification tests, case studies, applications and experimental data