4 Properties And Applications of Duplex Stainless Steels

Stainless steel is known for its versatility in the commercial market. Due to its strength, durability, and corrosion resistance, it finds use in many industries. Duplex stainless steel is a popular grade in the family of stainless steel. Duplex stainless steel is a two-phase alloy, and the microstructure consists of an equal proportion of ferritic phase and austenitic phase. It shows twice the strength of regular austenitic or ferritic stainless steel. Duplex stainless steel is not susceptible to stress corrosion cracking, and it offers better pitting resistance and weldability.

 

Duplex stainless steel witnessed its conception in the early 1930s. It was initially used for the reduction of intergranular corrosion. When you melt duplex stainless steel, it solidifies from the liquid phase to a ferritic structure. At room temperature, it cools down, and almost half of the composition of the ferritic grain transforms into austenitic grains. Hence, it has 50% austenite and 50% ferrite microstructure. 2205 is the most widely used duplex stainless steel grade. You can get 2205 duplex pipes to construct heat exchangers, pressure vessels, tanks, tubes, and lines in the chemical processing, oil and gas industry. They have lower molybdenum and nickel contents, and therefore a lower alloy surcharge.

 

304 stainless steel grade also shows high corrosion resistance properties. It is the most versatile and widely used austenitic stainless steel. 304 stainless steel tube price falls in the cost-effective range, which has increased its popularity in various industries. However, duplex stainless steel is also a dynamic variant, and this article further lists its multiple properties and applications.

 

Heat Resistance

 

Duplex stainless steel shows higher heat conductivity and lowers thermal expansion as compared to the austenitic grade. You can use it at temperatures as low as -50°C. At such low temperatures, it shows better ductility than ferritic stainless steel.

 

Fabrication

 

Duplex stainless steels generally have good weldability. It is welded with relatively high heat input and low interpass temperatures as it relies on a nearly equal balance of ferrite and Austenite. Specific welding methods, like resistance welding, laser welding, and electron beam welding, which can lead to highly rapid cooling, should be used cautiously.

 

Corrosion Resistance

 

Duplex stainless steel is highly corrosion-resistant. It stands superior to standard austenitic about stress corrosion cracking, even in chloride and sulfide environment. It has high resistance to intergranular corrosion.

 

Toughness And Ductility

 

Duplex stainless steel showed good impact strength because of its optimized microstructure. Its toughness and ductility properties are higher than ferritic grades and lower than austenitic steels.

 

Applications Of Duplex Stainless Steels

 

  • Used in applications that are exposed to high stresses in chloride-containing environments like seawater.
  • Oil and gas exploration and offshore rigs
  • Chemical processing, transport, and storage
  • Heat exchangers and hydraulic tubing systems
  • Structural and mechanical components
  • Pulp and paper manufacturing
  • Tubes for transporting oil and gas

 

To Conclude:

Duplex stainless steel possesses high chloride corrosion resistance. The various mechanical properties of this grade make it suitable for use in aggressive, acidic, and chloride-containing environments. The combination of both Austenite and ferrite makes it a precious material for use in various industries.

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