Duplex stainless steel is a type of stainless steel that is made up of two phases: austenite and ferrite. It is highly resistant to corrosion, which is why it has become so popular in the industrial and marine industries. The two phases of duplex stainless steel are what give it its superior strength and corrosion resistance.
Austenite is the dominant phase of duplex stainless steel. It is a fully austenitic phase, meaning it contains no ferrite or delta ferrite. It is composed of iron, chromium, nickel and molybdenum in various proportions. The properties of austenite include high strength and good impact resistance, with the ability to resist oxidation and stress corrosion cracking, even at elevated temperatures.
Ferrite is the second phase of duplex stainless steel. It is a martensitic phase, meaning it contains a small amount of ferrite and delta ferrite. Its properties include excellent resistance to chloride-ion stress corrosion cracking, pitting corrosion and chloride-induced cracking. It is also very resistant to general corrosion due to its high chromium content.
One of the attractive features of duplex stainless steel is its excellent strength-to-weight ratio. It has a higher yield strength than many other stainless steels, making it ideal for structural applications that require a light yet strong material. Duplex stainless steel is also very resistant to localized corrosion, making it a great choice for applications that are exposed to salt water or other corrosive conditions.
Another great property of duplex stainless steel is its weldability. It can be welded using standard welding processes with ease, though heat input must be limited to prevent microstructural changes. Duplex stainless steel can also be cold worked, but similar to welding, the heat input must be strictly controlled to avoid any weld imperfections.
In summary, duplex stainless steel is a type of stainless steel that is composed of two phases: austenite and ferrite. It is highly resistant to corrosion and has an excellent strength to weight ratio, making it great for structural applications. It is also very weldable and can be cold worked, though heat input must be strictly controlled. It is often used in a variety of industries, including the industrial, marine and chemical processing industries.
