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
Super Duplex 2507 Mechanical Properties (UNS S32750)
Super Duplex 2507 (UNS S32750, EN 1.4410) derives its mechanical performance from the balanced 50 to 50 austenite-ferrite microstructure, not from precipitation hardening. Yield strength of 550 MPa minimum is roughly double that of 304L austenitic stainless. Tensile strength sits at 800 to 1000 MPa with elongation of 25 to 35 percent on a typical mill heat. Hardness is restricted to 28 HRC maximum for compliance with NACE MR0175 / ISO 15156-3 sour-service requirements. Charpy V-notch impact at minus 46 degrees Celsius is 45 J minimum per NORSOK M-630, with typical heats running 60 to 100 J. Critical pitting temperature per ASTM G48 Method E is at least 50 degrees Celsius. Critical crevice temperature per ASTM G48 Method F is at least 35 degrees Celsius. Ferrite content is held within 35 to 55 percent in base material per NORSOK M-630.
The required minima below are extracted from ASTM A479, ASTM A182 F53, NORSOK M-630 material data sheets D55 and D57, ASTM A1082 (bolting), and EN 10088-3 (1.4410). Typical values reflect representative mill heats from Sandvik (SAF 2507), Industeel (UR 52N+), and Outokumpu (Avesta 2507).
Tensile and Yield Strength (Solution Annealed)
All values below apply to material in the solution-annealed and water-quenched condition. Super duplex 2507 has no aged or precipitation-hardened temper. Bar over 50 mm (2 inches) cross-section permits a slightly lower tensile minimum per ASTM A1082, reflecting the lower cooling rate achieved in heavy sections.
| Property | Spec Minimum | Typical | Test Standard |
|---|---|---|---|
| Yield strength, 0.2 percent offset (50 mm and below) | 550 MPa (80 ksi) | 620 to 720 MPa | ASTM A370 |
| Yield strength, 0.2 percent offset (over 50 mm) | 515 MPa (75 ksi) | 580 to 680 MPa | ASTM A370 |
| Tensile strength (50 mm and below) | 800 MPa (116 ksi) | 820 to 1000 MPa | ASTM A370 |
| Tensile strength (over 50 mm) | 760 MPa (110 ksi) | 800 to 950 MPa | ASTM A370 |
| Elongation in 50 mm | 15 percent (A1082) / 25 percent (A479) | 25 to 35 percent | ASTM A370 |
| Reduction of area | (not required) | 50 to 70 percent | ASTM A370 |
Hardness (Sour-Service Limit)
Two hardness limits apply to super duplex 2507. The general specification limit (ASTM A479, A1082) is 33 HRC maximum (310 HBW maximum). The sour-service limit (NACE MR0175 / ISO 15156-3) is the tighter of the two at 28 HRC maximum. Where the project specification is silent on sour service, the higher 33 HRC limit applies; where sour service is invoked, 28 HRC governs.
| Service | Hardness Maximum | Reference |
|---|---|---|
| General (no H2S) | 33 HRC / 310 HBW | ASTM A479, A1082 |
| NACE sour service | 28 HRC / 277 HBW | NACE MR0175, ISO 15156-3 |
| NORSOK M-630 (forgings, flanges) | 32 HRC / 302 HBW | NORSOK M-630 MDS D57 |
Charpy V-Notch Toughness
NORSOK M-630 requires Charpy V-notch impact testing at minus 46 degrees Celsius for super duplex material destined for North Sea service. Acceptance criteria are average 45 J minimum across three specimens, with no individual specimen below 35 J. ASTM A1082 supplementary requirement S1 invokes the same testing optionally. Loss of toughness is the earliest detectable indicator of sigma-phase contamination; a Charpy result below 45 J on a previously qualified heat is a strong signal that the solution-anneal quench was inadequate.
| Temperature, deg C | Spec Minimum | Typical |
|---|---|---|
| Plus 20 (room temperature) | (not required) | 150 to 250 J |
| Minus 20 | (not required) | 100 to 150 J |
| Minus 46 | 45 J avg, 35 J min individual | 60 to 100 J |
| Minus 80 | (not required) | 40 to 60 J |
Pitting and Crevice Resistance
Pitting and crevice resistance are quantified by laboratory tests defined in ASTM G48. A dedicated explainer for the test method is on the ASTM G48 Method E CPT page; the corrosion-resistance summary across multiple environments is on the corrosion-resistance page.
| Property | Spec Minimum | Typical | Test Method |
|---|---|---|---|
| PREN (Cr + 3.3 Mo + 16 N) | 40 (NORSOK M-630 super duplex threshold) | 41 to 43 | Calculation from chemistry |
| Critical pitting temperature (CPT) | 50 deg C | 55 to 70 deg C | ASTM G48 Method E (6 percent FeCl3) |
| Critical crevice temperature (CCT) | 35 deg C | 40 to 50 deg C | ASTM G48 Method F (PTFE crevice former) |
| Ferrite content, base metal | 35 to 55 percent | 45 to 50 percent | NORSOK M-630, ASTM E562 |
Elevated-Temperature Properties
Super duplex 2507 retains useful strength to about 250 degrees Celsius. Above 300 degrees Celsius, prolonged service risks progressive sigma-phase precipitation, so continuous high-temperature operation is not recommended. The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code permits design stresses for UNS S32750 up to 315 degrees Celsius (600 deg F).
| Temperature, deg C | Yield Strength (typical), MPa | Tensile Strength (typical), MPa |
|---|---|---|
| 20 (room temperature) | 620 to 720 | 820 to 1000 |
| 100 | 540 to 620 | 770 to 920 |
| 150 | 510 to 580 | 740 to 880 |
| 200 | 490 to 550 | 720 to 850 |
| 250 | 470 to 520 | 700 to 820 |
Physical Properties (Reference)
| Property | Value |
|---|---|
| Density | 7,800 kg per cubic metre |
| Modulus of elasticity (20 deg C) | 200 GPa |
| Coefficient of thermal expansion (20 to 100 deg C) | 13.0 per million per deg C |
| Thermal conductivity (20 deg C) | 15 W per metre per K |
| Specific heat capacity (20 deg C) | 500 J per kg per K |
| Electrical resistivity (20 deg C) | 0.80 micro-ohm metre |
| Magnetic permeability | Ferromagnetic (mu_r approximately 60 to 100) |
Related Super Duplex 2507 References
- UNS S32750 reference page
- Chemical composition
- Heat treatment
- Sigma-phase embrittlement
- Ferrite content (NORSOK M-630)
- Corrosion resistance
- Super duplex 2507 fasteners and pipe
Super Duplex 2507 Mechanical Properties FAQ
What is the yield strength of super duplex 2507?
Minimum yield strength is 550 MPa (80 ksi) for sections 50 mm and below per ASTM A479 and ASTM A1082. Heavier sections (above 50 mm) drop slightly to 515 MPa (75 ksi) per ASTM A1082, reflecting the slower quench rate achievable in thick cross-sections. Typical mill heats run 620 to 720 MPa.
What is the tensile strength of UNS S32750?
Minimum tensile strength is 800 MPa (116 ksi) for sections 50 mm and below. Typical heats fall in the 820 to 1000 MPa band. The combination of high tensile and high elongation (25 to 35 percent typical) is a direct consequence of the balanced austenite-ferrite microstructure.
What hardness limit applies to super duplex 2507 in sour service?
28 HRC maximum per NACE MR0175 / ISO 15156-3 for service in H2S-containing environments. The general specification limit (no sour service) is 33 HRC per ASTM A479 and A1082. Where a project invokes NACE MR0175, the 28 HRC limit governs and is verified by hardness testing on each heat-treatment lot.
What Charpy impact value is required at minus 46 degrees Celsius?
45 J average across three specimens, with no individual specimen below 35 J, per NORSOK M-630. Typical mill heats deliver 60 to 100 J. A Charpy result that drops below 45 J on a previously qualified heat is a strong signal of sigma-phase contamination from inadequate quench rate during solution annealing.
What is the critical pitting temperature of super duplex 2507?
CPT per ASTM G48 Method E (6 percent ferric chloride) is at least 50 degrees Celsius for material that meets the chemistry and heat-treatment requirements. Typical mill heats reach 55 to 70 degrees Celsius. CPT below 50 degrees Celsius generally indicates either out-of-spec chemistry (PREN below 40) or microstructural damage from improper heat treatment or welding.
Can super duplex 2507 be used above 250 degrees Celsius?
Continuous service above 300 degrees Celsius is not recommended because progressive sigma-phase precipitation reduces both toughness and corrosion resistance over time. ASME BPVC permits design stresses for UNS S32750 up to 315 degrees Celsius (600 deg F), but that is an upper bound, not a recommended operating point. For sustained higher-temperature service, an austenitic grade such as 904L or a nickel-base alloy is preferred.
What ferrite range applies to super duplex 2507?
35 to 55 percent in base material per NORSOK M-630, measured by image analysis (ASTM E562) on a polished and etched cross-section. Weld metal is permitted a wider 35 to 65 percent range to accommodate the rapid solidification cycle. Out-of-range ferrite (below 35 or above 55) signals either chemistry imbalance or solution-anneal cooling that was too slow or too fast.
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