What is duplex 2507 chemical composition？

"When selecting stainless steel for seawater, offshore, or chloride-rich chemical environments, buyers need to evaluate more than the grade name. The chromium, molybdenum, and nitrogen content of Super Duplex 2507 directly influence its resistance to pitting and crevice corrosion, while the product standard, heat treatment, and mill test certificate help determine whether the material meets project requirements."

 

Super duplex 2507 (also known as UNS S32750 or EN 1.4410) is a highly alloyed duplex stainless steel designed for demanding, corrosive environments. Its typical chemical composition includes approximately 25% chromium, 7% nickel, 4% molybdenum, and 0.24%–0.32% nitrogen. It is available in a variety of practical product forms, including plates, coils, pipes, bars, and wire.

 

The exact product standard depends on the form being purchased. For example, ASTM A240 is commonly specified for plate, sheet, and strip; ASTM A790 for duplex stainless steel pipe; ASTM A789 for tubing; and ASTM A182 Grade F53 for forged components.

Item	Description
Common name	Super Duplex 2507
UNS designation	S32750
EN material number	1.4410
EN material name	X2CrNiMoN25-7-4
Common alloy description	25Cr–7Ni–4Mo–N
Material family	Super duplex stainless steel
Typical PREN	Approximately 41–43, depending on actual chemistry and calculation
Common product applications	Seawater systems, offshore equipment, chemical process equipment, pressure systems

 

The chemical composition of UNS S32750 is controlled by the applicable material specification. The following table summarizes the commonly specified limits for ASTM A240 Type 2507 plate, sheet, and strip, expressed as weight percentages. Confirm the edition and product standard stated in the purchase order before procurement.

 

Chemical element	Symbol	Minimum (%)	Maximum (%)
Carbon	C	-	0.030
Chromium	Cr	24.00	26.00
Nickel	Ni	6.00	8.00
Molybdenum	Mo	3.00	5.00
Nitrogen	N	0.24	0.32
Manganese	Mn	-	1.20
Silicon	Si	-	0.80
Phosphorus	P	-	0.035
Sulfur	S	-	0.020
Copper	Cu	-	0.50
Iron	Fe	Balance	Balance

Note: "-" means no minimum limit is specified in this summary. The table is not a substitute for the complete standard or the heat-specific mill test certificate (MTC).

 

 

How is the Pitting Resistance Equivalent Number (PREN) of 2507 stainless steel calculated?

A useful screening indicator is the Pitting Resistance Equivalent Number (PREN), commonly calculated for 2507 as follows:

PREN =%Cr +3.3(%Mo) +16(%N)

Using representative values of 25% Cr, 4% Mo, and 0.28% N gives a PREN of approximately 42.7. Commercial 2507 is commonly described as having a PREN above 40, although the actual result depends on the measured chemistry and the formula specified.

Grade	Cr	Mo	N	PREN
316L	17	2.5	0.02	~24
2205	22.5	3.2	0.17	~35
2507	25	4.0	0.28	~42
255 (Zeron 100)	23	5.5	0.28	~48

 

 

Property	316L stainless steel	Duplex 2205	Super Duplex 2507
Material family	Austenitic	Duplex	Super duplex
Chromium, typical (%)	16–18	22–23	24–26
Molybdenum, typical (%)	2–3	3–3.5	3–5
Nitrogen, specified range (%)	Usually lower	0.14–0.20 for S32205	0.24–0.32
Typical PREN range	About 23–26	About 34–38	About 41–43
Relative strength	Lower	Higher than 316L	High
Typical selection	General corrosion service	Moderate-to-aggressive corrosion	More demanding chloride service

Purchasing takeaway: 2507 may be worth evaluating when 316L lacks sufficient chloride-corrosion resistance or when 2205 does not provide enough performance margin. However, the higher alloy cost and more demanding fabrication controls mean it should be selected against actual design conditions, not simply because it is a higher grade.

 

 

What are the differences between 2507 and 2205?

Compared to 2205, 2507 has a chromium (Cr) content that is approximately 2% higher (24–26% vs. 22–23%), a molybdenum (Mo) content about 1% higher (3–5% vs. 3–3.5%), and a nitrogen (N) content that is twice as high (0.24–0.32% vs. 0.14–0.20%). Additionally, 2507 has a slightly higher nickel (Ni) content (6–8% vs. 4.5–6.5%). These compositional differences result in a PREN value of ≥40 for 2507 (compared to approximately 34 for 2205), providing a 20% improvement in pitting corrosion resistance.

 

What is the difference between S32750 and S32760?

S32750 (ASTM/US standard) and S32760 (EN/European standard) refer to the same material and have identical chemical compositions. S32760 is the designation under the EN standard (corresponding to 1.4410 / X2CrNiMoN25-7-4). In most applications, the two are interchangeable.

 

What is the maximum service temperature for 2507?

For continuous service, the maximum temperature is 300 °C (572 °F). Prolonged exposure to temperatures above this limit may lead to the precipitation of the sigma (σ) phase-a phenomenon often associated with "475 °C embrittlement"-which reduces the material's toughness and corrosion resistance. For intermittent service at temperatures up to 350 °C, please consult your supplier regarding potential derating of performance specifications.

 

Is 2507 magnetic?

Yes. 2507 is a ferritic-austenitic (duplex) steel containing 40%–60% ferrite, which renders it magnetic. This is normal and does not affect its corrosion resistance. If your application requires a non-magnetic material, 2507 is not suitable.

 

Which filler metal (welding consumable) should be used for welding 2507?

It is recommended to use ER2594 filler wire (or E2594 electrode) in accordance with the AWS A5.9 standard. For dissimilar metal welding-such as joining 2507 to other steel grades like 316L-ER309L should be used. Preheating is not required for material thicknesses under 25 mm. During welding, the interpass temperature must be kept below 150 °C. Post-weld heat treatment is not recommended, as it carries the risk of "475 °C embrittlement."

 

Super Duplex Steel 2507 Suppliers and Manufacturers

 

2507 stainless steel can be processed into thick plates, sheets, coils, strips, round bars, hexagonal bars, flat bars, seamless pipes, welded pipes, forgings, flanges, pipe fittings, wire, and various profiles. Gnee can supply products in all these forms and provide a full set of certification documents.

 

Super Duplex Steel 2507 Specification

Product Form	Standard	Typical Size Range	Surface Finish	Applications
Plate / Sheet (Hot Rolled)	ASTM A240 / SA-240	3–100 mm × 1,000–2,500 mm	No.1, Black	Heat exchanger shells, reactor linings, structural
Sheet (Cold Rolled)	ASTM A240	0.25–8 mm × 600–2,000 mm	2B, 2D, BA, Polished	Hygienic, decorative, thin-wall pressure parts
Coil / Strip	ASTM A240 / A480	0.3–6 mm × 600–2,000 mm	No.1, 2B, 2D	Stamping, forming, gaskets, spiral wound
Round Bar / Rod	ASTM A276 / A479	Ø3–500 mm	Bright, Peeled, Ground, Black	Shafts, pins, fasteners, spools
Hex Bar	ASTM A276	5–100 mm A/F	Bright	Bolts, studs, fittings
Flat / Square Bar	ASTM A276	5–150 mm	Hot Rolled, Ground	Structural, brackets, clamps
Seamless Pipe / Tube	ASTM A790 / A928	½"–10", Sch 10S–160S	Pickled, Bright	HPHT wellheads, subsea, process lines
Welded Pipe / Tube	ASTM A999	½"–24", Sch 5S–40S	ERW, Pickled	Piping, structural, low-pressure
Forgings	ASTM A182 F53	Custom (flanges, blocks, rings)	Forged + Annealed	Flanges, valve bodies, spools
Fittings & Flanges	ASTM A182 / A350	DN15–DN1200	Machined, Annealed	Piping systems, manifolds

- Technical Documentation: A Mill Test Certificate (MTC) for the specific heat/lot number is required, detailing the actual chemical composition and the results of mechanical property tests in compliance with the relevant standards.
- Quality Verification: Clearly specify all requirements in the inquiry, including dimensional inspection, surface examination, Positive Material Identification (PMI), and any other applicable non-destructive testing (NDT).
- Order-Specific Requirements: Confirm the solution-annealed condition, surface finish, tolerances, cut dimensions, marking, traceability, and export packaging requirements.

 

What is the minimum order quantity (MOQ) for 2507-grade products?

For standard, in-stock specifications, the minimum order quantity is 500 kg. For custom specifications or materials requiring compliance with NACE standards, the minimum order quantity is 1 metric ton. For thin-gauge (0.5–3 mm) cold-rolled sheets, the minimum order quantity can be as low as 200 kg.

 

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