Duplex Stainless Steel Sheet: Composition and Characteristics

Duplex Stainless Steel: Composition and Characteristics

In duplex stainless steel, the ferrite and austenite phases each make up about half of the hardened structure, with the minimum phase content reaching 30%. It typically contains low carbon (C), with 18% to 28% chromium (Cr) and 3% to 10% nickel (Ni). Some grades also include alloying elements like molybdenum (Mo), copper (Cu), niobium (Nb), titanium (Ti), and nitrogen (N).

This steel combines the properties of both austenitic and ferritic stainless steel. Compared to ferritic steel, duplex stainless steel offers higher plasticity and toughness, improved resistance to intergranular corrosion, and better welding performance, while retaining the 475°C brittleness and high thermal conductivity of ferritic stainless steel. It also exhibits superplasticity. Compared to austenitic stainless steel, duplex stainless steel has higher strength and better resistance to intergranular and chloride stress corrosion. It is also known for its excellent pitting corrosion resistance and lower nickel content, making it a cost-effective option.

Product Advantages

Despite its strengths, duplex stainless steel has some limitations when compared to austenitic stainless steel:

Limited Application Range: Duplex stainless steel sheet is less versatile and must be used at temperatures below 250°C.
Lower Plasticity and Toughness: Its plasticity and toughness are lower, and it doesn’t perform as well in cold and hot working processes as austenitic stainless steel.
Brittle Zone: Duplex stainless steel has a medium temperature brittle zone, requiring strict control of heat treatment and welding processes to prevent the formation of harmful phases that could compromise its performance.

When compared to ferritic stainless steel, the main disadvantage of duplex stainless steel sheet is its higher alloy content, which increases its cost. Unlike ferritic stainless steel, it typically contains nickel, contributing to its higher price.