Since the 1980s, a range of duplex stainless steels (DSSs) has been developed that have higher alloy content, and therefore greater corrosion resistance and strength. The commonly used DSSs have good corrosion resistance in a wide range of environments and excellent resistance to stress corrosion cracking (SCC). Their high strength and hardness also gives them excellent resistance to both erosion corrosion and cavitation. There are also cast versions of many of the duplex compositions and these have seen extensive use for pumps, valves, and other equipment.
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Duplex stainless steels (DSSs) were first invented in the early part of the 20th century, but it was not until the 1970s and 80s, with the introduction of argon oxygen decarburization (AOD) melting and the recognition of the benefits of nitrogen additions, that DSSs became attractive for widespread industrial use. DSSs have found applications in most industries, including oil and gas, marine, desalination, power, chemical and process, pulp and paper, and mineral processing.
DSSs have been adopted by many industries to varying degrees. They are the workhorse corrosion resistant alloy (CRA) of the oil and gas industry, and are also widely used in the chemical and process industries for their SCC and corrosion resistance. Superduplex stainless steel has become the main alloy for piping, pumps, and valves in seawater reverse osmosis (SWRO) desalination plants, because of its resistance to crevice corrosion in seawater.
In this book, Roger Francis reviews various duplex alloy compositions, mechanical properties, and design stresses for vessels and pipes to various codes. He also covers the basics of welding duplex alloys, both to themselves and to other alloys, and their corrosion resistance. Of most importance, the book looks at a variety of types of corrosion that may affect DSSs in service, presenting the available data and, in some cases, how to avoid problems.