• About Super Duplex Stainless Steel from Brown McFarlane
A Super Duplex stainless steel is a type of Duplex stainless steel with enhanced corrosion resistance which is categorised by its PREN being greater than 40. A standard Duplex like the S31803 grade stocked by Brown McFarlane has a PREN of around 35.
The Pitting Resistance Equivalent Number (PREN) is widely used as a means of comparing the relative corrosion resistance of different steel grades. The PREN is obtained by applying a mathematical formula to the chemical composition of a steel so that PREN = %Cr + (3.3 x %Mo) + (16 x %N).
How does Super Duplex Stainless Differ from Duplex Steel?
As a part of the Duplex family of stainless steels Super Duplex stainless has a microstructure which is split roughly 50:50 between austenite and ferrite. It differs from Duplex Stainless Steel in its chemical composition (with increased amounts of Molybdenum, Nickel, and Chromium) and its mechanical properties (higher proof stress and tensile strength). This highly alloyed product is especially designed for marine, chemical, and oil engineering applications requiring both high mechanical strength and resistance to corrosion in extremely aggressive environments (chloride-containing acids etc.).
Advantages of Super Duplex Stainless Steel
Super Duplex stainless steel, relative to other stainless steel products, gives:
o High corrosion resistance
o High resistance to stress corrosion cracking
o High yield strength and tensile strength
Uses of Super Duplex Stainless Steel
It is used extensively for offshore oil and gas applications and can be found in flow lines, risers, process vessels, separators, coolers, manifolds, and process piping. Onshore it can be found in heat exchangers, boilers, and pressure vessels in petrochemical and chemical processing plant.
S32750 (1,4410) and S32760 (1,4501)
Brown McFarlane holds an extensive stock of Super Duplex stainless steel plate and is one of the few companies to keep both S32750 (1.4410) and S32760 (1.4501) material grades. All stock plate is manufactured by Western European steel makers, third party inspected, and certified in accordance with EN 10204 3.2. All plates are also certified in accordance with NORSOK MDS D55 and any plates up to an including 35 mm thick will be to NORSOK MDS D55 Revision 4.
Plates are stocked as large format (up to 12,000 mm long and 2,500 mm wide) which is designed to minimise fabrication costs for our customers by reducing the amount of welding required. The large format also gives us the opportunity to make the best possible use of each plate when “nesting” the shapes required by our customers. Given the specialised nature of this type of steel it is no great surprise that the majority of our sales are made in cut and processed form.