Duplex steel sheet is a type of steel composed of two different and distinct types of cold-rolled stainless steel welded together. Due to its high chromium content, it has higher strength and superior corrosion resistance than other ferritic and austenitic stainless steels. Common composition for duplex steel sheet includes 20% chromium, 3–5% nickel, 5-6% molybdenum, 0.2–0.3% nitrogen, 1–3 % manganese, up to 2% silicon and sulfur in trace amounts.
Duplex steel is an iron-based alloy composed of Ferrite and Austenite and offers a combination of advantages not found in other alloys. It's extremely resistant to wear, corrosion and pitting due to its high chromium content. In addition, it's very strong with excellent tensile strength and offers improved weldability compared to austenitic stainless steel. As such, duplex steel sheets can be used extensively in applications requiring superior resistance properties like chemical processing tanks, food processing equipment, etc.