Duplex steel is a family of stainless steel which consists in equal parts austenite and ferrite. Consequently their mechanical properties are a combination of both. Its unique mechanical structure also comes from its composition. It has a two-face microstructure that reflects the face-centred cubic lattice of austenite and body-centred cubic lattice of ferrite. It is this dual faced structure that gives it the ‘duplex’ suffix.
Duplex steel casting is used in many fields today. Its high demand comes from its unique physical properties. It is stronger than most stainless steels with excellent stress corrosion cracking resistance. It is tough and highly ductile. Like all other stainless steels it also has very good resistance to corrosion.
Despite these advantages, duplex steel is one of the most affordable options. With its lower alloying composition, costs can be easily controlled. One of its traditional application is in the industrial field where it is used in many demanding conditions. But there are many other fields where it is in equally high demand.
Pulp and paper
The paper industry was the first to adopt duplex steel in the 1930s. Soon it replaced carbon steel and austenitic stainless steel. Today it is used in building the various equipments required in paper production, such as digesters, storage tanks, and bleaching equipment. The reason duplex steel was seen more and more in the industry is because it allowed for thinner plates to be used under the Sams pressure conditions. There was overall economy in the usage of duplex steels — less welding time, lower material, shipping and handling costs.
Oil and gas
Duplex steel is ideal in the very corrosive conditions of the oil and gas industry. Duplex still has a higher resistance to crevice corrosion and pitting. Its higher strength adds to its applicability. The applications of duplex steel in the oil and gas industry building piping systems, flow lines, scrubbers, pumps and separators. Duplex steel casting for the industry is often used to build super duplex steel which has better fatigue resistance and galvanic compatibility. So suitable is duplex steel in the salty sea conditions that it is also used for undersea operations. Newer versions are coming out all the time to improve the adaptability.
This is another highly corrosive environment where the duplex steel has proved to be the ideal component in building structural and transit components. The processes involved in desalination require high temperatures and high chloride conditions. Consequently most desalination equipment corrodes very quickly. The challenge is to control costs, while building materials that can withstand corrosion for long. With higher resistance to corrosion, duplex steel has been a revolutionary component. Requiring thinner plates, this steel is now used for evaporators. It also proved to be a far more cost effective option.
Food and Beverage
The F&B industry uses the duplex steel for storage and other equipment — from storing food to wines and juices.
Architecture and structural design
Perhaps the most outstanding example of duplex steel’s suitability in all kind of applications is seen in the architectural industry where many of the modern classics today utilise this steel to build stunning structure. There is now a growing interest in duplex steel because of its unique properties. It has been called an essential component in revolutionizing structural design. No wonder when many of modern structures use this steel to give life to amazing designs.
Duplex steel is used in many of the modern day classics in urban structures, including The Helix Bridge in Singapore, Stone cutter’s Bridge in Hong Kong and Lusail Pedestrian Bridge in Qatar. It is used to make a number of components, including handrails, high strength tension bars, spiders, structural supports.
Duplex steel was chosen for two main reasons — the ability to withstand corrosion and its strength to weight ratio. In location that carry high moisture, such as near seaside, duplex steel components will last long. The strength to weight ratio is another critical factor in structural design. Duplex Steel Casting is used to make thin sheets, which in turn allow us to create stunning designs. So, we have twisting and turning sheets and strands that make handrails and other support.
These are just some of the areas where duplex steel is fast replacing other types of stainless steel. But with its superior qualities and cost-effectiveness, one can expect an even wider adaption across us.