What is Super Duplex 2507?

Super Duplex 2507 (UNS S32750, Werkstoff 1.4410, X2CrNiMoN25-7-4) is a nitrogen-enhanced super duplex stainless steel with a balanced 50 to 50 austenite-ferrite microstructure. Nominal composition is 25Cr-7Ni-3.5Mo-0.3N with no intentional copper and no intentional tungsten. PREN above 41 qualifies the alloy as super duplex per NORSOK M-630. The alloy is solution annealed at 1040 to 1100 degrees Celsius and water quenched, with no precipitation hardening or aging step.

What is Super Duplex 2507 equivalent to?

Super Duplex 2507 is registered as UNS S32750 in the Unified Numbering System and as Werkstoff 1.4410 / X2CrNiMoN25-7-4 in EN 10088-3. Mill trademarks for the same UNS S32750 chemistry include SAF 2507 (Sandvik), UR 52N+ (Industeel ArcelorMittal) and Avesta 2507 (Outokumpu). It is covered by ASTM A479 (bar), A789 (tube), A790 (pipe), A815 (fittings, designation WP-S32750), A276 (shapes), and A182 grade F53 (forgings, flanges, forged fittings).

Is Super Duplex 2507 the same as Zeron 100?

No. Both are super duplex stainless steels with PREN above 40, but they are different alloys. Zeron 100 (UNS S32760) contains nominal 0.7 percent each of copper and tungsten. Super Duplex 2507 (UNS S32750) contains neither. The forging spec for 2507 is ASTM A182 F53; for Zeron 100 it is ASTM A182 F55. The two are not drop-in substitutes when a project specification names one or the other by UNS number.

What is the PREN of Super Duplex 2507?

Super Duplex 2507 has a PREN of approximately 41 to 43, calculated using the formula Cr + 3.3 times Mo + 16 times N. A typical mill heat with 25 percent chromium, 3.8 percent molybdenum, and 0.28 percent nitrogen yields PREN about 42. NORSOK M-630 requires PREN of 40 or above for super duplex classification.

What is the heat treatment of Super Duplex 2507?

Solution annealing at 1040 to 1100 degrees Celsius followed by rapid water quench. There is no precipitation hardening, no aging, no temper. The water quench must drive the material rapidly through the 600 to 1000 degrees Celsius band to avoid sigma-phase formation, which would cut Charpy toughness by 80 percent or more and compromise pitting resistance.

Is Super Duplex 2507 acceptable for sour service?

Yes, Super Duplex 2507 is qualified for sour service per NACE MR0175 and ISO 15156-3 with hardness restricted to 28 HRC maximum and ferrite content within 35 to 65 percent. Specific H2S partial pressure and chloride limits depend on the application zone classification. TorqBolt supplies 2507 fasteners and forgings with NACE compliance certification on request.

Why does Super Duplex 2507 have no copper or tungsten?

The defining chemistry of UNS S32750 is 25Cr-7Ni-3.5Mo-0.3N with no intentional copper or tungsten addition. Adding either changes the alloy. Zeron 100 (S32760) adds about 0.7 percent each. Ferralium 255 (S32550) adds copper. Mixing these chemistries on a 2507 page is incorrect and creates a chimeric specification that does not exist in any mill datasheet or ASTM standard.

Which welding filler is correct for Super Duplex 2507?

ER2594 (overmatching, slightly higher PREN than the base) is the most common choice per AWS A5.9. ER2553 (matching) is also acceptable for less aggressive service. Both are nitrogen-enhanced fillers. Heat input should remain between about 0.5 and 2.5 kJ per millimetre, with interpass temperature below 150 degrees Celsius to avoid sigma-phase precipitation in the heat-affected zone.

What is Super Duplex 2507 used for?

Super Duplex 2507 is used in seawater service (velocities up to 6 metres per second), oil and gas downhole and surface (NACE MR0175 sour service), desalination plants (MSF, MED, RO), marine and subsea hardware (manifolds, christmas trees, jumpers), chemical processing (dilute HCl, H2SO4, HF), pulp and paper bleach plants (chlorine dioxide service), and flue gas desulfurization (WFGD absorber, quencher, outlet duct). Service temperature range is approximately minus 50 to 250 degrees Celsius continuous; sigma-phase risk above 300 degrees Celsius limits long-term high-temperature service.

0091-22-66157017

info@torqbolt.com

Home

Super Duplex Stainless Steel

Home

ISO 15156-3: Super Duplex 2507 in H2S Environments

Name: Super Duplex 2507 (UNS S32750 / EN 1.4410)
Brand: TorqBolt
SKU: TB-2507
Availability: InStock

ISO 15156 is the international standard governing materials for use in H2S-containing environments in oil and gas production. It is technically equivalent to NACE MR0175 and is published jointly. Super duplex 2507 (UNS S32750 / Werkstoff 1.4410) is qualified under ISO 15156-3, the part addressing cracking-resistant corrosion-resistant alloys (CRAs).

European, Middle East, Asia-Pacific and Brazilian projects typically cite ISO 15156 by ISO designation; North American projects cite NACE MR0175. The technical content is identical. TorqBolt supplies 2507 to ISO 15156-3 with hardness, ferrite, and heat-treatment evidence on the mill test certificate.

ISO 15156 Structure

Part	Coverage
ISO 15156-1	General principles for selection of cracking-resistant materials
ISO 15156-2	Cracking-resistant carbon and low-alloy steels and use of cast irons
ISO 15156-3	Cracking-resistant CRAs and other alloys (covers super duplex 2507)

ISO 15156-3 Scope for Super Duplex 2507

Section 7 of ISO 15156-3 covers duplex and super duplex stainless steels. Annex A publishes the qualified environmental envelopes for each alloy as a function of H2S partial pressure, chloride concentration, pH, and temperature. UNS S32750 (super duplex 2507) is qualified across an envelope typically reaching 100 kPa H2S partial pressure, 120,000 ppm chloride, and 232 degrees Celsius temperature, with sub-envelopes for other combinations.

Hardness Limit

ISO 15156-3 sets the hardness limit for sour service super duplex at 28 HRC maximum. The limit applies to bulk material, weld metal, and HAZ. Mill heats of solution-annealed and water-quenched 2507 typically test at 22 to 26 HRC, comfortably within the limit. Cold-worked product is excluded unless re-annealed.

Ferrite Window

Ferrite content must fall within 35 to 65 percent, measured per ASTM E562 (point count) on a metallographic section. The window covers parent metal and weld metal. Production heats outside this window are not admissible for sour service.

Environmental Envelope

Parameter	Typical 2507 Limit
H2S partial pressure	Up to 100 kPa (about 14.5 psi) in the qualified envelope
Chloride concentration	Up to 120,000 ppm
Temperature	Up to 232 degrees Celsius
pH	Project-specific; lower pH narrows the envelope
Free sulphur	Excludes some envelopes

The qualified envelope is read from Annex A tables on a project-specific basis. A material selection diagram (MSD) is the typical tool used by metallurgy engineers to confirm the alloy fits the production fluid composition.

Required Testing

Test	Method	Acceptance
Hardness	ASTM E18 / ISO 6508	28 HRC max in bulk, weld, HAZ
Ferrite content	ASTM E562 point count	35 to 65 percent
Heat treatment	Per material spec	Solution annealed 1040 to 1100 degrees Celsius, water quench
Intermetallic phases	ASTM A923 Method A	No sigma, no chi, no nitride
SSC test (if invoked)	NACE TM0177	Per project specification

Welding under ISO 15156-3

Welds in sour service 2507 must use a qualified WPS that delivers ferrite within 35 to 65 percent across weld metal and HAZ. ER 2594 is the typical filler. Heat input is controlled to suppress sigma-phase precipitation. Post-weld solution annealing is invoked when as-welded WPS qualification cannot demonstrate compliance.

ISO 15156 vs NACE MR0175

The two standards are jointly developed and technically equivalent. ISO 15156-3 is the international designation preferred by ISO-aligned operators; NACE MR0175 is the North American designation. Compliance to one demonstrates compliance to the other; mill test certificates routinely cite both.

NACE MR0175: NACE equivalent designation
NACE TM0177: SSC laboratory test methods
ISO 11960: petroleum and natural gas industries casing and tubing
NORSOK M-630: Norwegian MDS (D55, D57)
API 6A: wellhead and Christmas tree
API 17D: subsea wellhead and tree

ISO 15156-3 Frequently Asked Questions

What part of ISO 15156 applies to super duplex 2507?

Part 3, which covers cracking-resistant corrosion-resistant alloys. Section 7 within Part 3 addresses duplex and super duplex stainless steels. Annex A publishes the qualified environmental envelopes for each alloy.

What hardness limit applies?

28 HRC maximum across bulk material, weld metal, and HAZ. Solution-annealed water-quenched 2507 typically tests at 22 to 26 HRC.

Is ISO 15156 the same as NACE MR0175?

Yes. The two standards are jointly developed and technically equivalent. ISO designation is preferred internationally; NACE designation is preferred in North America. Compliance to one demonstrates compliance to the other.

What environmental envelope qualifies super duplex 2507?

Typically up to 100 kPa H2S partial pressure, 120,000 ppm chloride, 232 degrees Celsius. The exact envelope is read from Annex A tables and depends on the combination of H2S, chloride, pH, and temperature.

What ferrite range is required?

35 to 65 percent measured per ASTM E562 point count. Window covers parent and weld metal. Heats outside this window are not admissible.

Can welds in 2507 meet ISO 15156-3 as-welded?

Yes, when a qualified WPS demonstrates ferrite within 35 to 65 percent and hardness 28 HRC max across weld metal and HAZ in the qualification coupon. ER 2594 super duplex filler with controlled heat input is the typical route. Post-weld solution annealing is invoked when as-welded qualification fails.

Standards

Surface Treatments

Certifications

ISO 9001 - 2015 Certified
PED 2014/68/EC
NACE MR0175 / ISO 15156-2
NORSOK M-650 Qualified
API 6A Certified
DFAR
MERKBLATT AD 2000 W2/W7/W10

About Us

Questions? Contact us.

Showcase of our Microsites.