Duplex Stainless Steels
Duplex stainless steels have a ‘duplex’ two-phase micro-structure consisting of both austenitic and ferritic grains that gives them a combination of attractive properties. Duplex alloys were developed around a 22% Chromium addition level, which largely defines them from subsequent super duplex alloys which were developed around a 25% Chromium addition level for higher corrosion resistance still.
In general, they are twice as strong as either austenitic or ferritic stainless steels. They achieve good toughness and ductility, somewhere between the two. Their corrosion resistance is also very good, assuming comparable levels of Chromium, Molybdenum and Nitrogen in selected compositions. One important advantage over austenitic stainless steels is their resistance to stress corrosion cracking. Yet they are significantly more cost effective, and less prone to price variability, due to their lower nickel content.
|Alloy||Common Name||Related Specifications||Tensile Strength||Proof Test||Elongation|
|British||European||United States||N/mm2 (ksi)||N/mm2 (ksi)||(%)|
|Alloy 2205||UNS S32205 Duplex F60 (UNS31803 Duplex F51)||1.4462
UNS S32205 Duplex F60
UNS S31803 Duplex F51
|655 (95)||450 (65)||25|
|Sanmac 2205||Duplex 2205||318S13
|ASTM A276 S31803/S2205
ASTM A182 F51 / F60
|655 (95)||450 (65)||25|
Alloy 2205 is a 22% Cr duplex stainless steel, supplied in the solution annealed condition. As a duplex stainless steel, it combines the desirable aspect of properties of both austenitic and ferritic grades. The high chromium, molybdenum and nitrogen contents results in a Pitting Resistance Equivalent number (PREN) of 33-34, providing pitting and crevice corrosion resistance superior to Alloy 316L or Alloy 317L austenitic stainless steels in almost all corrosive media. Due to its excellent corrosion properties, Duplex 2205 is well suited to environments containing chlorides and hydrogen sulphide, for use in oil and gas extraction from sour wells, in refineries and in process solutions contaminated with chlorides.
Sanmac 2205 is a machinability-imporved version of the duplex (austenitic-ferritic) stainless steel Alloy 2205.
The good machining properties make Sanmac 2205 a superior alternative to standard 2205 grades and other duplex grades for applications subjected to all types of machining by extended tool life and possibilities to increase productivity.
Due to its excellent corrosion properties, Sanmac 2205 is a highly suitable material for service in environments containing chlorides and hydrogen sulfide. The material is suitable for use in the extraction of oil and gas from sour wells, in refineries and in process solutions contaminated with chlorides.
(Sanmac is a registered trademark of Sandvik Intellectual Property AB)