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Two very successful conferences - in Glasgow and Beaune - were held on duplex stainless steels during the first half of the '90s. This book takes keynote papers from each, and develops and expands them to bring the topics right up to date. There is new material to cover grades, specifications and standards, and the book is fully cross-references and indexed. The first reference book to be published on the increasingly popular duplex stainless steels, it will be widely welcomed by metallurgists, design and materials engineers, oil and gas engineers and anyone involved in materials development and properties. The first reference book on this relatively new engineering material Based on keynote papers from major international contributors Covers grades, standards and specifications
Nitrogen concentrations far in excess of Sieverts' Law calculations and as high as 0.2 wt.% have been obtained in steel welds during arc welding. Such high concentrations of nitrogen in the weld metal can originate from a variety of sources, depending on the welding operation in question. One such mechanism involves the interaction between the surrounding atmosphere, which is about 80% nitrogen, and the plasma phase above the weld pool. Impingement of the surrounding atmosphere into the arc column, which is primarily composed of an inert shielding gas, can be due, in part, to insufficient shielding of the weld metal. In other cases, nitrogen can be purposefully added to the shielding gas to enhance the microstructural evolution of the weld metal. The mechanisms responsible for enhanced nitrogen concentrations are of significant interest. In both arc melting and welding operations, a plasma phase exists above the liquid metal. This plasma phase, which is composed of a number of different species not normally observed in gas-metal systems, significantly alters the nitrogen absorption reaction in liquid iron and steel. Monatomic nitrogen (N) is considered to be the species responsible for the observed enhancements in the nitrogen concentration. This role for monatomic nitrogen is based on its significantly higher solubility in iron with partial pressures many orders of magnitude less than that for diatomic nitrogen. It has also been proposed that the total amount of nitrogen present in the liquid metal is the balance of two independent processes. Monatomic nitrogen is absorbed through the interface between the arc and the liquid metal. Once a saturation level is reached at any location on the metal surface, nitrogen is then expelled from the surface of the liquid metal. This expulsion of nitrogen from the weld pool surface occurs via a desorption reaction, in which bubbles form at the surface and other heterogeneous nucleation sites in the liquid melt. These bubbles are filled with nitrogen gas, which has been rejected from the liquid iron. Outside the arc column, the nitrogen in solution in the iron is in equilibrium with diatomic nitrogen rather than monatomic nitrogen, which dominates the arc column. Models based on the role of the plasma phase in producing these enhanced nitrogen concentrations have also been developed. For example, Gedeon and Eaga have proposed that the diatomic gas introduced into the plasma phase in the arc column partially dissociates at a temperature higher than that at the sample surface. The monatomic species is then transported to the liquid metal surface, where it is absorbed at the temperature on the liquid metal surface. Mundra and DebRoy have used this same methodology to develop a semi-quantitative model to describe the temperature at which the diatomic gas dissociates in the plasma phase. In the two-temperature model, a hypothetical temperature, T{sub d}, equal to the temperature at which the equilibrium thermal dissociation of diatomic nitrogen produces the partial pressure of monatomic nitrogen in the plasma, is defined. This dissociation temperature is in a range of 100 to 300 K higher than the temperature at the metal surface, T{sub s}, and is a measure of the partial pressure of the atomic nitrogen in the plasma. This methodology provides an order-of-magnitude agreement between the calculated and experimental nitrogen concentrations but does not strictly provide a capability for predicting the nitrogen concentration. No quantitative means for predicting the nitrogen concentration in the weld metal currently exists. In developing a quantitative model, it must be recognized that nitrogen dissolution into the weld pool is intimately tied to several simultaneously occurring physical processes. These processes include the formation of various nitrogen species in the plasma phase above the weld pool, reactions at the interface between the plasma phase and the weld pool surface, and the transport of nitrogen within the weldment by convection and diffusion. A mathematical model, which combines calculations describing each of these processes into a single model, has been developed here. The validity of this model has also been tested by comparing the modeling results with those from a series of GTA welding experiments with pure iron.
Corrosion failures of industrial components are commonly associated with welding. The reasons are many and varied. For example, welding may reduce the resistance to corrosion and environmentally assisted cracking by altering composition and microstructure, modifying mechanical properties, introducing residual stress, and creating physical defects. This book details the many forms of weld corrosion and the methods used to minimize weld corrosion. Chapters on specific alloys groups--carbon and alloy steels, stainless steels, high-nickel alloys, and nonferrous alloys--describe both general welding characteristics and the metallurgical factors that influence corrosion behavior. Corrosion problems associated with dissimilar metal weldments are also examined. Case histories document corrosion problems unique to specific industries including oil and gas, chemical processing, pulp and paper, and electric power. Special challenges caused by high-temperature environments are discussed. Commonly used methods to monitor weld corrosion and test methods for evaluation of intergranular, pitting, crevice, stress-corrosion cracking, and other forms of corrosion are also reviewed.
The most up-to-date coverage of welding metallurgy aspects and weldability issues associated with Ni-base alloys Welding Metallurgy and Weldability of Nickel-Base Alloys describes the fundamental metallurgical principles that control the microstructure and properties of welded Ni-base alloys. It serves as a practical how-to guide that enables engineers to select the proper alloys, filler metals, heat treatments, and welding conditions to ensure that failures are avoided during fabrication and service. Chapter coverage includes: Alloying additions, phase diagrams, and phase stability Solid-solution strengthened Ni-base alloys Precipitation strengthened Ni-base alloys Oxide dispersion strengthened alloys and nickel aluminides Repair welding of Ni-base alloys Dissimilar welding Weldability testing High-chromium alloys used in nuclear power applications With its excellent balance between the fundamentals and practical problem solving, the book serves as an ideal reference for scientists, engineers, and technicians, as well as a textbook for undergraduate and graduate courses in welding metallurgy.