DUPLEX AND SUPERDUPLEX MATERIAL STUDY

Duplex and superduplex steels are advanced materials that offer superior mechanical, corrosion, and erosion resistance properties over conventional stainless steels. These alloys have a two-phase microstructure consisting of austenite and ferrite phases, resulting in improved strength, toughness, and resistance to stress corrosion cracking. These properties make duplex and super duplex stainless steels ideal for applications in aggressive environments such as the oil and gas, chemical, and marine industries.

Development of Duplex and Superduplex Stainless Steels

Duplex and super duplex stainless steels were developed in the 1930s and 1940s as a result of research into the corrosion resistance of stainless steels in acidic and chloride-containing environments. Early duplex stainless steels were low in nickel and high in chromium and molybdenum to improve their corrosion resistance. However, these alloys had limited toughness and ductility, which made them difficult to fabricate and prone to cracking during welding.

In the 1960s, the development of more advanced duplex stainless steels began, incorporating additional elements such as nitrogen, copper, and tungsten to improve their mechanical properties and welding characteristics. The addition of nitrogen, in particular, increased the strength, ductility, and corrosion resistance of duplex stainless steels, leading to the development of super duplex stainless steels.

Grades of Duplex and Superduplex Stainless Steels

1. Duplex Stainless Steels (UNS S31803, S32205): These grades contain around 22% chromium, 5-6% nickel, and 3% molybdenum. They also have a small amount of nitrogen (0.1-0.2%) to improve their mechanical properties. Duplex stainless steels offer a good combination of strength, toughness, and corrosion resistance, making them suitable for a range of applications in the chemical, petrochemical, and pulp and paper industries.
2. Super Duplex Stainless Steels (UNS S32750, S32760): Super duplex stainless steels contain around 25% chromium, 7% nickel, and 3.5% molybdenum, as well as 0.3% nitrogen. These alloys have higher strength and corrosion resistance than duplex stainless steels, making them suitable for use in more demanding applications such as offshore oil and gas production, desalination plants, and chemical processing.
3. Lean Duplex Stainless Steels (UNS S32304): Lean duplex stainless steels contain around 21% chromium, 4.5% nickel, and 0.3% nitrogen. They offer good corrosion resistance and lower cost than other duplex stainless steels, making them suitable for applications in the food processing, wastewater treatment, and architectural industries.
4. Hyper Duplex Stainless Steels: Hyper duplex stainless steels are a new generation of duplex stainless steels that offer even higher strength and corrosion resistance than super duplex stainless steels. They contain around 27% chromium, 7% nickel, 4% molybdenum, and 0.8% nitrogen. Hyper duplex stainless steels are currently being developed for use in highly corrosive environments such as offshore oil and gas production and chemical processing.

Trademarked Grades

There are several trademarked duplex and superduplex stainless steel grades that have been developed to meet specific application requirements. Some of the most common ones include:

1. SAF 2205: This is one of the most widely used duplex stainless steel grades. It contains 22% chromium, 5% nickel, and 3% molybdenum, along with other alloying elements such as nitrogen and manganese. SAF 2205 offers excellent corrosion resistance, high strength, and good weldability, making it ideal for use in a range of applications, including oil and gas, chemical processing, and marine environments.
2. SAF 2507: This is a super duplex stainless steel grade that contains 25% chromium, 7% nickel, and 4% molybdenum, along with other alloying elements such as nitrogen and copper. SAF 2507 offers even higher corrosion resistance and strength than SAF 2205, making it ideal for use in highly corrosive environments such as desalination plants and offshore structures.
3. Zeron 100: This is another super duplex stainless steel grade that contains 25% chromium, 7% nickel, and 3.5% molybdenum, along with other alloying elements such as nitrogen and tungsten. Zeron 100 offers excellent corrosion resistance, high strength, and good weldability, making it ideal for use in a range of applications, including oil and gas, chemical processing, and marine environments.
4. Ferralium 255: This is a super duplex stainless steel grade that contains 25% chromium, 7% nickel, and 3.5% molybdenum, along with other alloying elements such as nitrogen and copper. Ferralium 255 offers even higher corrosion resistance and strength than SAF 2507, making it ideal for use in highly corrosive environments such as desalination plants and offshore structures.
5. LDX 2101: This is a lean duplex stainless steel grade that contains 21% chromium, 1.5% nickel, and 0.3% molybdenum, along with other alloying elements such as nitrogen and manganese. LDX 2101 offers good corrosion resistance and high strength, making it ideal for use in a range of applications, including chemical processing and marine environments.

Each of these duplex and super duplex stainless steel grades has been developed to meet specific application requirements. For example, SAF 2205 and Zeron 100 offer good weldability, while SAF 2507 and Ferralium 255 offer even higher corrosion resistance and strength for use in highly corrosive environments. LDX 2101, on the other hand, offers a more cost-effective solution for applications where high strength and good corrosion resistance are required but at a lower cost than super duplex stainless steels.

Super Duplex Zeron 100 Fastener Grades

Zeron 100 is further developed in higher strengths graded FG and FLT versions. Hague Fasteners have extensive experience working with these alloys.

Zeron 100 is a duplex stainless steel that is widely used in a variety of industrial applications. It is an alloy that contains a high percentage of chromium, molybdenum, and nitrogen, which provide it with exceptional corrosion resistance properties. It also has high strength and toughness, making it ideal for use in applications where mechanical stresses are present.

The higher strength graded FG and FLT versions of Zeron 100 are modifications of the standard alloy that have been designed to provide even greater strength and durability. These alloys have higher levels of nickel, nitrogen, and molybdenum, which provide them with even greater corrosion resistance and strength. They also have improved toughness, which is essential in applications where high mechanical stresses are present.

The FG version of Zeron 100 is specifically designed for use in fastener applications. It has been optimized to provide the high strength and corrosion resistance required in these applications. The FLT Grade of Zeron 100, on the other hand, is suitable for use in floating production systems, such as oil and gas platforms. It has been designed to withstand the harsh and corrosive environments found in these applications.

The applications of Zeron 100 and its higher strength grades FG and FLT are extensive. The standard alloy is commonly used in the chemical and petrochemical industries, where it is used in equipment such as pumps, valves, and heat exchangers. Its excellent corrosion resistance properties also make it ideal for use in marine applications, such as seawater desalination plants and offshore structures.

Zeron 100FG is commonly used in fastener applications, such as bolts and screws, where high strength and corrosion resistance are essential. It is also used in oil and gas production equipment, such as valves, pumps, and manifolds.

Zeron 100FLT is commonly used in floating production systems, such as offshore platforms. It is used in a variety of equipment, including risers, connectors, and subsea production systems. Its exceptional corrosion resistance and high strength make it an ideal material for these applications.

Zeron 100 and its modified FG and FLT grades are exceptional alloys that provide excellent corrosion resistance, strength, and toughness. They are widely used in a variety of industrial applications and are particularly useful in aggressive and corrosive environments. We work extensively with these alloys, and we are confident that they will continue to play a vital role in the industrial landscape for many years to come.

Environment and Applications

Duplex and superduplex stainless steels are ideal for use in aggressive environments where conventional stainless steels would fail. These alloys offer excellent resistance to pitting, crevice, and general corrosion, as well as erosion and stress corrosion cracking. Some common applications of duplex and super duplex stainless steels include:

1. Oil and Gas: Duplex and super duplex stainless steels are widely used in offshore oil and gas production, where they are exposed to highly corrosive environments containing chloride, hydrogen sulfide, and carbon dioxide. These alloys offer excellent resistance to corrosion and erosion, making them ideal for use in subsea pipelines, offshore platforms, and other critical components.

2. Chemical Processing: Duplex and super duplex stainless steels are used in chemical processing plants where they are exposed to highly acidic or alkaline environments, as well as high temperatures and pressures. These alloys offer excellent resistance to corrosion and erosion, making them ideal for use in heat exchangers, reactors, and other critical components.
3. Desalination: Super duplex stainless steels are commonly used in desalination plants, where they are exposed to highly saline environments containing chloride and other aggressive ions. These alloys offer excellent resistance to corrosion and erosion, making them ideal for use in seawater intake systems, brine concentrators, and other critical components.
4. Marine: Duplex and super duplex stainless steels are widely used in marine applications, where they are exposed to seawater and other corrosive environments. These alloys offer excellent resistance to corrosion and erosion, making them ideal for use in offshore structures, shipbuilding, and other critical components.

Duplex and super duplex stainless steels are advanced materials that offer superior mechanical, corrosion, and erosion resistance properties over conventional stainless steels. These alloys have a two-phase microstructure consisting of austenite and ferrite phases, resulting in improved strength, toughness, and resistance to stress corrosion cracking. There are several grades of duplex and super duplex stainless steels available, each with different compositions and properties, making them suitable for a range of applications in the oil and gas, chemical, desalination, marine, and other industries. The development of hyper duplex stainless steels represents a new generation of these alloys, offering even higher strength and corrosion resistance properties for use in highly corrosive environments.

For more information on DUPLEX AND SUPERDUPLEX MATERIAL STUDY talk to Hague Special Fasteners Limited