Duplex & Super Duplex Steel: 2205/S31803 & 2507/S32750 Bars, Pipes, Fittings & Fasteners
Home > Duplex & Super Duplex Steel Products
Duplex: 2205 (S31803 / S32205, F51) · Super Duplex: 2507 (S32750 / S32760, F53 / F55) · Forms: Round Bars · Pipes & Tubes · Buttweld & Socket-Weld Fittings · Fasteners · Sheets
Aashish Metals supplies duplex and super duplex stainless steel, the high-strength chloride-resisting grades, across both tiers: 2205 for general duplex service and 2507 for the harshest seawater and chemical duty, as round bars, pipes and tubes, fittings and fasteners. The busiest lines are the duplex S31803 buttweld fittings and duplex S31803 fasteners, cut and certified with full traceability. If you already know the grade and the form, the tables below take you straight to the page.
When 304 or 316 isn’t strong enough or corrosion resistant enough, duplex is the solution, but not a nickel alloy. It lies between our Stainless Steel Products range and it offers approximately twice the strength and increased chloride pitting resistance and stress-corrosion cracking resistance. Both levels span the range and the fold at the bottom makes for a quick choice.
Why Duplex: Strength Plus Corrosion Resistance
Duplex steels get their name from a microstructure that is roughly half ferrite and half austenite, and that dual structure is the whole advantage. From the ferrite they take high strength, about twice the yield of standard austenitic 304 or 316, and strong resistance to chloride stress-corrosion cracking, the failure mode that troubles 316 in warm chloride service. From the austenite they keep good toughness and general corrosion resistance. The practical payoff is that a designer can use thinner walls and less metal for the same pressure, which often offsets the higher price per kilo, while getting corrosion performance that plain stainless cannot reach. The buyer’s shorthand for the corrosion tier is the PREN number, the pitting resistance equivalent: standard duplex 2205 sits around 35, and super duplex 2507 above 40, which is why 2507 is trusted in seawater where 2205 would be marginal.
Duplex or Super Duplex? The Grade Choice
| Duplex 2205 | Super Duplex 2507 | |
|---|---|---|
| UNS | S31803 / S32205 | S32750 / S32760 |
| Forging grade | F51 | F53 / F55 |
| PREN (pitting resistance) | About 35 | Above 40 |
| Chosen for | General duplex service, process, chloride-bearing media | Seawater, chlorinated and the harshest chloride duty |
| Relative cost | Lower, the volume grade | Higher, specified when 2205 is not enough |
Duplex Grades & Forms We Stock
| Grade | Best for | Forms |
|---|---|---|
| Duplex 2205 (S31803/S32205) | General duplex service, process piping, chloride media, high strength | Round bars, pipes & tubes, buttweld/socket-weld/threaded fittings, fasteners, sheets |
| Super Duplex 2507 (S32750/S32760) | Seawater, chlorinated cooling, aggressive chloride chemistry | Round bars, pipes & tubes, fittings, fasteners, sheets |
Duplex 2205 (S31803 / S32205)
2205, UNS S31803 or the tighter S32205, is the volume duplex grade and the one most enquiries mean. It combines high strength with chloride and pitting resistance well above 316, which makes it the standard for chemical process piping, oil and gas, and chloride-bearing service. We hold it as duplex S31803 round bars for machined parts, pipes and tubes, buttweld fittings, threaded fittings and fasteners. For the majority of duplex requirements, 2205 is the correct specification.
Super Duplex 2507 (S32750 / S32760)
2507, UNS S32750 or the closely related S32760 (Zeron 100 type), is super duplex: more chromium, molybdenum and nitrogen than 2205, pushing its PREN above 40 and its strength higher still. It is the grade for seawater systems, offshore and subsea equipment, desalination and chlorinated cooling, where it competes with and often replaces more expensive nickel alloys. We stock super duplex S32750 round bars, pipes and tubes, buttweld fittings and fasteners. For seawater specifically it is worth weighing against Copper Nickel, which trades some strength for natural biofouling resistance, so the right choice depends on whether strength or fouling dominates the design.
Quality, Certification & Testing
Duplex performance depends on a correct phase balance, so testing matters more here than on plain stainless. Every order ships with an EN 10204 3.1 mill test certificate, heat-number traceable, and ferrite content or phase-balance results are provided where the specification requires them, because an incorrect ferrite-austenite ratio undermines both the strength and the corrosion resistance the grade is bought for. Positive material identification confirms 2205 against 2507, NACE MR0175 documentation is available for sour service, and third-party witness through BV, SGS or TUV is arranged at order stage. Common bar, fittings and fasteners ship from stock; larger and super duplex items are confirmed on enquiry. Send the grade, the form and the quantity and the quote comes back with the certification built in.
Duplex & Super Duplex Steel: Frequently Asked Questions
Duplex 2205 (UNS S31803 and S32205, forging grade F51) and super duplex 2507 (UNS S32750 and S32760, forging grades F53 and F55), across round bars, pipes and tubes, buttweld, socket-weld and threaded fittings, fasteners and sheets. If a grade or form is not listed, ask, because we hold more than the site shows and can source to specification.
Duplex stainless steel has a microstructure that is roughly half ferrite and half austenite, which gives it about twice the strength of standard 304 or 316 along with better resistance to chloride pitting and stress-corrosion cracking. The strength lets designers use thinner walls and less metal, and the corrosion resistance suits chloride and marine service, which is why it is chosen where plain stainless is not enough but a nickel alloy is more than needed.
Alloy content and chloride resistance, measured by the PREN number. Duplex 2205 (S31803/S32205) sits around PREN 35 and is the economical volume grade for general duplex and chloride service. Super duplex 2507 (S32750/S32760) has more chromium, molybdenum and nitrogen, pushing PREN above 40, and is used for seawater, chlorinated cooling and the harshest chloride duty. Choose 2205 unless the service is severe enough to need 2507.
PREN is the pitting resistance equivalent number, a shorthand calculated from chromium, molybdenum and nitrogen content that ranks how well a grade resists chloride pitting. Higher is better. Standard duplex 2205 is around 35 and super duplex 2507 is above 40, which is the quick way to tell whether a grade will hold up in a given chloride or seawater service.
Yes. Every order ships with an EN 10204 3.1 mill test certificate that is heat-number traceable, with ferrite content or phase-balance results where the specification requires them, positive material identification, NACE MR0175 documentation for sour service and third-party witness inspection available at order stage. The phase balance matters because it underpins both the strength and the corrosion resistance of the grade.
For More Information About Duplex and Super Duplex Stainless Steel Products please call +91-22-66362223 / 66394926 or send an email to export@aashishmetal.com
Products
Special Products
PRODUCT RANGE
Please feel free to contact us. We will get back to you with 2 business days. Or just call us now.
