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Super Duplex
Super Duplex stainless steels have a ‘duplex’ two-phase microstructure consisting of both austenitic and ferritic grains that gives them a combination of attractive properties. Whilst duplex alloys were developed around a 22% Cr addition level, super duplex alloys utilise a higher 25%Cr base composition to increase the level of corrosion resistance achievable.
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. By increasing the level of chromium additions, combined with significant levels of molybdenum and nitrogen, super duplex stainless steels achieve a Pitting Resistance Equivalent number (PREN) >40, which will match or beat all but the most highly alloyed austenitic stainless steels and often provide comparable performance to some nickel alloys also. One further advantage over austenitic stainless steels is their resistance to stress corrosion cracking.
The addition of copper to these grades results in additional corrosion resistance in use not directly recognised by the formula used to calculate PREN. It has been shown that the presence of copper can inhibit the formation of pitting corrosion, and it also contributes to exceptional resistance to sulphuric acid. Resistance to sulphuric, nitric and phosphoric acid makes these products attractive for a number of applications in the chemical processing industry. Ferralium® has an appreciable higher copper content than other super duplex stainless steels, imparting superior corrosion resistance.
Super duplex stainless steels offer a cost effective option for many demanding applications – as their design foregoes high nickel additions which are expensive and subject to price volatility. If the application can utilise the high strength levels of these grades then components can be designed with smaller sections, using less material. This can benefit as a direct material cost saving, but can also contribute to overall design savings if the application involves suspended loads i.e. marine sensors, down-hole tooling.
Alloy | Common Name | Related Specifications | Tensile Strength | Proof Test | Elongation | ||
British | European | United States | N/mm2 (ksi) | N/mm2 (ksi) | (%) | ||
Ferralium 255 (Pipe & Tube) | UNS 32550 | Alloy 255 (Super Duplex 255) | 1.4507 X2CrNiMoCuN 25-6-3 Z3 CNDU 25-07 Az Norsok MDS D51 | ASTM A790 ASTM A815 | 760 (110) | 550 (80) | 15 |
Ferralium 255 – SD50 HS110 | UNS S32550 110ksi | Alloy 255 Super Duplex 255 | 1.4507 X2 CrNiMoCuN 25-6-3 Z3 CNDU 25-07 Az Norsok MDS D57 | ASTM A276/A476 F61 UNS S32550 ASME A182 F61 | 862 (125) | 758 - 965 (110 - 140) | 16 |
Ferralium 255 – 3SC for Castings | UNS S32550 | Alloy 255 CD3MCuN Grade 1C | 1.4507 Norsok MDS D56 | UNS S32550 (Super Duplex S32550) | 700 (102) | 450 (65) | 25 |
Ferralium 255 – 3SF for Forgings | UNS S32550 | Alloy 255 | 1.4507 Norsok MDS D54 | UNS S32550 (Super Duplex 32550) | 750 (109) | 550 (80) | 25 |
Ferralium 255 – FG46 Fastener Grade | UNS S32550 | Alloy 255 | 1.4507 X2CrNiMoCuN 25-6-3 Z3 CNDU 25-07 Az Norsok MDS D59 | ASTM A276/A476 UNS S32550 ASME A182 F61 | 860 (125) | 720 (104) | 16 |
Ferralium 255 – 3AF Aged Grade | UNS S32550 | Alloy 255 | 1.4507 X2CrNiMoCuN 25-6-3 Z3 CNDU 25-07 Az Norsok MDS D57 | ASTM A276 / A476 UNS S32550 ASME A182 F61 | 840 (122) | 600 (87) | 23 |
SAF2507 | Alloy 32750 | 1.4410 X2CrNiMoN 25-7-4 UNS S32750 Z3CND25.07Az Norsok MDS D57 | ASTM A182/A479 F53 CE3MN (cast grade) | 800 (116) | 550 (80) | 25 | |
Alloy 32750 | UNS S32750 | 1.4410 X2CrNiMoN 25-7-4 Z3CND25.07Az Norsok MDS D57 | ASTM A276/A476 UNS S32750 (Super Duplex 32750) ASME A182 Duplex F53 CE3MN (Cast grade) 25Cr | 800 (116) | 550 (80) | 25 | |
Alloy 32760 | UNS S32760 | 1.4501 X2CrNiMoCuWN 25-7-4 Z3CND25.06Az Norsok MDS D57 SAF32760 | ASTM A276/A476 UNS S32760 (Super Duplex 32760) ASME A182 F55 CD3MWCuN (Cast grade) 25Cr | 750 (109) | 550 (80) | 25 | |
Ferralium 255 – SD50 | UNS S32550 | Ferralium 255 – SD50 Super Duplex 255 Alloy 255 | 1.4507 X2 CrNiMoCuN 25-6-3 Z3 CNDU 25-07 Az Norsok MDS D57 Uranus 52N+ | ASTM A276/A476 UNS S32550 ASME A182 F61 UNS S32520 CD4MCuN (Cast grade) | 790 (115) | 586 (85) | 25 |
Worldwide Delivery Available
We can offer air, sea and road freight shipping options, with choice of packaging, to deliver to customers globally.
Inventory Management
Let us manage your total material requirements with call-off and consignment arrangements.
Up to 40 sizes per alloy available
More sizes equal less machining and a more cost-effective supply chain.