Key Properties

Duplex stainless steel is a high-strength, highly corrosion-resistant stainless steel consisting of a dual phase structure of austenite and ferrite produced by adding a suitable quantity of nickel (Ni) to high-chrome (Cr) steel.

By adding molybdenum (Mo) and nitrogen (N), as well as Cr and Ni, it is possible to manufacture a variety of steel types—from lean duplex-class steel to super duplex-class steel—in a wide range of corrosion resistance levels and prices.

The major features of these types of steel are: (1) high strength, (2) high corrosion resistance, and (3) price stability.

A Wide Range of Variations

Typical chemical composition and PREN of Duplex
* PREN (Pitting Resistance Equivalent Number) = Cr%+3.3×Mo%+16×N%

NSSC offers a wide range of duplex stainless steel products, from lean class to super class. Duplex stainless steel is broadly divided into the following three types.

1) Lean duplex steel – 22% Cr-Low Ni-N type (PREN≤30): An inexpensive type that has low Ni content and contains almost no Mo.

2) Standard duplex steel – 22% Cr-5% Ni-3% Mo-N type (PREN≈35): Exhibits excellent resistance to seawater corrosion.

3) Super duplex steel – 25% Cr-7% Ni-4% Mo-N type (PREN≥40): Has corrosion resistance equivalent to that of super austenite steel.