Duplex & Super Duplex Plates Supplier in Oman and the GCC

Duplex and Super Duplex Plates: Twice the Yield Means Twice the Press

Specify 2205 instead of 316L and the vessel gets thinner, because minimum yield goes from 170 MPa to 450 MPa. The same figure decides whether the fabricator can actually make it. Rolling a shell or pressing a dished end takes force in proportion to yield strength, springback is greater, and a shop set up for austenitic work may find a duplex plate at the edge of its capacity. Duplex and super duplex plates go into seawater, chloride and offshore equipment across Oman and the GCC. The range is on the plates and sheets hub.

Forming Duplex Plate

Property	316L	2205	Super duplex	Consequence in the shop
Minimum yield strength	170 MPa	450 MPa	550 MPa	Forming force rises roughly in proportion
Springback	Low	Higher	Higher still	Overbend allowances have to be reworked, not carried over from austenitic practice
Work hardening	High	Moderate	Moderate	Duplex hardens less during forming, which helps
Minimum elongation	40 percent	25 percent	15 to 25 percent	Less ductility in reserve, so bend radii are larger

Four practical points:

Confirm press capacity before the plate is ordered, especially on heavy sections and dished ends.
Use larger bend radii than austenitic practice. Lower elongation means less margin.
Cold forming leaves residual stress and raises hardness. Heavily cold formed duplex components may need re-solution annealing, and in sour service the cold worked condition is assessed differently from the annealed one.
Hot forming has a window. Work it too hot and ferrite grows at the expense of austenite; too cool and intermetallic phases form. Hot formed components normally need re-solution annealing with a rapid water quench afterwards.

Chemical Composition

Element	2205 S31803 %	2205 S32205 %	2507 S32750 %	S32760 %
Carbon	0.030 max	0.030 max	0.030 max	0.030 max
Chromium	21.0 to 23.0	22.0 to 23.0	24.0 to 26.0	24.0 to 26.0
Nickel	4.5 to 6.5	4.5 to 6.5	6.0 to 8.0	6.0 to 8.0
Molybdenum	2.5 to 3.5	3.0 to 3.5	3.0 to 5.0	3.0 to 4.0
Nitrogen	0.08 to 0.20	0.14 to 0.20	0.24 to 0.32	0.20 to 0.30
Copper	Not specified	Not specified	0.50 max	0.50 to 1.00
Tungsten	Not specified	Not specified	Not specified	0.50 to 1.00
Manganese	2.00 max	2.00 max	1.20 max	1.00 max
Phosphorus	0.030 max	0.030 max	0.035 max	0.030 max
Sulphur	0.020 max	0.020 max	0.020 max	0.010 max

A specification saying only "2205" fits both S31803 and S32205. The nitrogen floor is where they differ: S31803 permits as little as 0.08 percent, and nitrogen is what drives austenite to re-form in the heat affected zone after welding. S32205 raises the floor to 0.14 percent and tightens chromium and molybdenum, which is why modern specifications call it up by number. Confirm the UNS number on the order.

PREN is calculated as percentage chromium plus 3.3 times percentage molybdenum plus 16 times percentage nitrogen. A grade qualifies as super duplex at 40 and above.

Mechanical Properties

Grade	Tensile strength, minimum	Yield strength, minimum	Elongation, minimum
S31803	620 MPa	450 MPa	25 percent
S32205	655 MPa	450 MPa	25 percent
S32750	795 MPa	550 MPa	15 percent
S32760	750 MPa	550 MPa	25 percent
316L for comparison	485 MPa	170 MPa	40 percent

All grades are supplied solution annealed and quenched. The strength column is the weight saving argument on offshore modules and the forming argument in the shop, and both have to be weighed on the same order.

Phase Balance and Testing

Duplex works because ferrite and austenite sit in roughly equal proportion. Rolling, hot forming and welding all disturb it, and so does any slow cool through the range around 600 to 950 degrees C where sigma phase precipitates. Sigma is hard and brittle and draws chromium and molybdenum from the surrounding metal, so it damages toughness and corrosion resistance together. Super duplex is more susceptible than 2205, because it carries more of both elements to begin with.

Test	What it confirms	When it is ordered
Ferrite content measurement	Phase balance within the required range	Standard on offshore specifications
ASTM G48 Method A	Pitting resistance with no harmful intermetallic phase	Seawater and chloride service, with the test temperature stated
Charpy impact	Toughness, and indirectly the absence of embrittling phase	Low temperature and offshore work
Microstructural examination	Direct evidence of intermetallic phase	Where the specification calls for it
Ultrasonic examination	Internal soundness and laminations	Pressure boundary plate

On heavy plate, state where the test coupons are taken. A coupon from a thin offcut does not represent the cooling rate the middle of a thick plate experienced.

Welding Duplex Plate

The heat input window is narrower in both directions than austenitic practice allows. Too low and the weld metal solidifies too ferritic; too high and the heat affected zone spends too long in the precipitation range. Nitrogen in the shielding gas supports austenite re-formation in the weld, and filler with raised nickel content is standard, because an autogenous weld without filler ends up ferrite heavy.

Where an operator specification requires procedure qualification with ferrite checks and corrosion testing on the weld, it is applying to the joint the same logic the mill applied to the plate.

Where Duplex Plate Is Used

Seawater handling, firewater and cooling systems on offshore and marine installations
Desalination and water treatment vessels, brine heaters and reject streams
Produced water and separator vessels in oil and gas service
Chemical process vessels where 316L would crack from chlorides
Storage tanks for chloride bearing liquids

Equivalents and Forms

Grade	UNS	EN	Matching pipe
Duplex 2205	S31803 / S32205	1.4462	Duplex 2205 pipes
Super duplex 2507	S32750	1.4410	Super duplex 2507 pipes
Super duplex	S32760	1.4501	Super duplex S32760 pipes

Sizes are supplied to specification. Send the UNS number, thickness, width, length or cut size, testing scope and quantity.

Sour Service

NACE MR0175 / ISO 15156 Part 3 sets environmental limits for duplex stainless steels covering hydrogen sulphide partial pressure, chloride content and temperature, with a hardness limit applied, and the limits differ between standard duplex and super duplex. Cold worked material is assessed separately from annealed material, which matters on formed plate components where the forming has raised the hardness. Send the full service envelope and the forming details with the enquiry.

Duplex and Super Duplex Plates: Price Factors

Each enquiry is priced on its own, because grade, class and testing scope move the figure more than quantity does. What counts:

Grade and the alloying elements it carries
Size, pressure class, facing and bore
Schedule or wall the item is made to
Production route, forged or formed from pipe or plate
Supplementary testing and inspection scope
Order quantity and availability
Certificate level and witness requirements
Delivery terms and port of discharge

Quotations are available in USD, OMR, AED, SAR, QAR, KWD and BHD, on EXW, FOB, CFR or CIF terms.

What to send for a quotation:

item type, material grade and standard, size, pressure class, facing, schedule or wall, quantity, testing, certification, inspection, destination port and required date.

Certification, Traceability and PMI

Material comes with EN 10204 3.1 certificates as standard, and EN 10204 3.2 certificates on request. Inspection by the buyer's nominated third-party agency can be arranged; state your requirement in the RFQ. Check that the heat number on the certificate matches the marking on the item itself, and that the heat treatment condition is stated, the ferrite content and the solution annealing temperature and quench. Positive material identification confirms the grade before anything is welded in. See the MTC and EN 10204 certification guide.

Delivery and Handling

Lead time is confirmed at quotation. Fittings ship bundled or crated with bevel protection; flanges ship with face and ring groove protection, since a scored face leaks whatever the gasket. In coastal Oman, salt deposits build up on anything left in the open, so a rinse and a dry before fitting up is worth the time.

Related Plate Products

Duplex and Super Duplex Plates FAQ

Does duplex plate form like austenitic plate?

No. Forming force rises roughly with yield strength, so 2205 at 450 MPa takes far more than 316L at 170 MPa, springback is greater and bend radii have to be larger because elongation is lower.

What is the difference between S31803 and S32205?

Nitrogen mainly. S31803 permits as little as 0.08 percent while S32205 sets a floor of 0.14 percent and tightens chromium and molybdenum, giving better austenite re-formation after welding.

Does hot formed duplex need re-annealing?

Normally yes. Hot forming disturbs the phase balance, so components are re-solution annealed with a rapid water quench to restore it.

Why is ferrite content measured?

Because rolling, forming and welding can move the ferrite and austenite balance outside the required range without any change in chemistry, costing toughness or corrosion resistance.

Where should test coupons be taken on heavy plate?

From material representing the thickest section. A coupon from a thin offcut does not reflect the cooling rate the middle of a thick plate experienced.

What should I send for a quotation?

Send the UNS number, thickness, width and length or cut size, ferrite and G48 testing requirements, forming details, quantity, certification and destination port.

Request a Quote for Duplex and Super Duplex Plates

Send the UNS number rather than just 2205, with the thickness, size and testing scope. Where the plate will be rolled or pressed, say so, because the forming case and the corrosion case have to be settled on the same order.

Request a Quotation

Duplex and Super Duplex Plates: Twice the Yield Means Twice the Press