- Aug 31, 2017-


Special Piping Materials is renowned for the high volume of Duplex and Super Duplex

products that it stocks. It supplies these materials to countless companies around the

world who use its product’s in numerous applications in many different situations.

Special Piping Materials can supply many different products in both Super Duplex and

Duplex such as welded pipes, butt weld fitting, flanges, forged fittings, seamless pipes

and many more. They are available to buy from any of the company’s offices across the



Duplex stainless steels have a mixed microstructure of austenite and ferrite, the aim

being to produce a 50/50 mix, although in commercial alloys, the mix may be 40/60


Duplex steels have improved strength over austenitic stainless steels and also improved

resistance to localised corrosion, particularly pitting, crevice corrosion and stress

corrosion cracking. They are characterised by high chromium (19–28%) and

molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels. The

most used duplex stainless steel are the 2205 (22% Chromium, 5% Nickel) and the 2507

(25% Chromium, 7% Nickel); the 2507 is known as “super duplex” due to its higher

resistance to corrosion.

The mechanical properties of Duplex steels are approximately double those of singular

austenitic steels, and resistance to stress corrosion cracking is far superior to type 316

stainless steel in chloride solutions. Duplex material has ductile or brittle transition at

approximately -50 degrees.


Super Duplex pipe is known to have better stress corrosion, cracking resistance and

mechanical properties than any other type of steel. Super Duplex is an austenitic

ferritic iron chromium – nickel alloy with molybdenum addition. It has good resistance

to pitting and a very good tensile strength and high resistance to stress corrosion

cracking at moderate temperatures, compared to that of conventional austenitic

stainless steels.

The high corrosion resistance of Super Duplex pipeline supplies makes them ideal for

onshore and offshore environments in oil and gas applications. Please see our industry

pages for more information regarding the implications of Super Duplex piping.

All Duplex and Super Duplex materials stocked by Special Piping Materials are tested in

accordance with international standard such as Norsok M630、Shell MESC.