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 Stainless Steel Properties (Mechanical and Corrosion)
The super duplex stainless steel properties set out below cover mechanical strength, toughness, hardness, corrosion resistance and physical properties for the four common super duplex grades: 2507 (UNS S32750), Zeron 100 (UNS S32760), Ferralium 255 (UNS S32550) and DP3W (UNS S39274). Property data is taken from ASTM A479, EN 10088-3, NORSOK M-630 and ASTM A182.
Across the family, super duplex steels deliver yield strength roughly twice that of austenitic 316L, Critical Pitting Temperature above 50 degrees Celsius in the standard ASTM G48 ferric chloride test, and acceptable Charpy V-notch toughness down to minus 46 degrees Celsius for Norwegian Continental Shelf service. The property windows below are the basis for design and inspection.
Mechanical Properties
Required minimum mechanical properties per ASTM A479 in the solution-annealed condition. There is no aging or precipitation-hardening step in the heat-treatment cycle.
| Property | 2507 (S32750) | Zeron 100 (S32760) | Ferralium 255 (S32550) | Test Standard |
|---|---|---|---|---|
| Yield strength (0.2% offset, MPa min) | 550 | 550 | 550 | ASTM A370 |
| Tensile strength (MPa min) | 795 | 750 | 760 | ASTM A370 |
| Elongation in 50 mm (%) | 15 | 25 | 15 | ASTM A370 |
| Hardness (HRC max, sour service) | 32 (28 sour) | 32 (28 sour) | 32 (28 sour) | ASTM E18, NACE MR0175 |
| Charpy V-notch at minus 46 C (J min) | 45 | 45 | 45 | NORSOK M-630, ASTM E23 |
Typical mill heats run substantially above the minima: 620 to 720 MPa yield, 800 to 1000 MPa tensile, 25 to 35 percent elongation, and 60 to 100 J Charpy at minus 46 degrees Celsius for 2507 base metal.
Elevated Temperature Properties
Super duplex stainless steel yield strength reduces moderately with temperature. Continuous service temperature is roughly minus 50 to 250 degrees Celsius. Above 300 degrees Celsius, sigma-phase precipitation kinetics become significant and limit long-term service.
| Temperature | 2507 Yield (MPa, typical) | 2507 Tensile (MPa, typical) |
|---|---|---|
| 20 degrees Celsius | 620 to 720 | 800 to 1000 |
| 100 degrees Celsius | 540 to 640 | 720 to 920 |
| 200 degrees Celsius | 480 to 580 | 670 to 870 |
| 250 degrees Celsius | 460 to 560 | 650 to 850 |
Corrosion Resistance
Critical Pitting Temperature (CPT) and Critical Crevice Temperature (CCT) per ASTM G48, measured in 6 percent ferric chloride. The CPT is the practical service-temperature ceiling in chloride-bearing media.
| Property | 2507 (S32750) | Zeron 100 (S32760) | 2205 (S32205, reference) |
|---|---|---|---|
| CPT, ASTM G48 Method E (degrees Celsius) | 50 to 70 | 55 to 75 | 30 to 40 |
| CCT, ASTM G48 Method F (degrees Celsius) | 35 to 50 | 40 to 55 | 20 to 30 |
| PREN (typical) | 41 to 43 | 41 to 44 | 34 to 38 |
The PREN reference page PREN reference sets out the calculation and the standard NORSOK M-630 PREN 40 threshold.
Phase Balance and Ferrite Content
NORSOK M-630 requires ferrite content of 35 to 55 percent in base metal and 35 to 65 percent in weld metal. Mills target 45 to 50 percent ferrite for solution-annealed bar and plate. Ferrite content is measured per ASTM E562 (point count) or by Ferritescope (calibrated magnetic induction). Ferrite outside the window indicates incorrect chemistry, incorrect solution-annealing temperature, or incorrect cooling rate.
Physical Properties
| Property | Value (2507) |
|---|---|
| Density | 7.79 g/cc |
| Modulus of elasticity (20 C) | 200 GPa |
| Thermal conductivity (20 C) | 16 W/(m K) |
| Thermal expansion (20 to 100 C) | 13.0 x 10^-6 per K |
| Specific heat (20 C) | 500 J/(kg K) |
| Electrical resistivity (20 C) | 0.80 micro-ohm m |
| Melting range | 1300 to 1390 degrees Celsius |
| Magnetic permeability | Strongly ferromagnetic (typical relative permeability 50 to 200) |
Sour Service (NACE MR0175)
Super duplex grades qualify per NACE MR0175 / ISO 15156-3 with hardness restricted to 28 HRC maximum and ferrite within 35 to 65 percent. Specific H2S partial pressure and chloride limits depend on the application zone classification under ISO 15156. The standard table for super duplex (Table A.25 in ISO 15156-3) sets envelope conditions for use as base metal and as weld metal.
Property Test Standards
| Property | Test Standard |
|---|---|
| Tensile (yield, tensile, elongation) | ASTM A370 / ASTM E8 |
| Hardness (Rockwell C) | ASTM E18 |
| Hardness (Vickers) | ASTM E92 |
| Charpy V-notch impact | ASTM E23 |
| Critical pitting temperature | ASTM G48 Method E |
| Critical crevice temperature | ASTM G48 Method F |
| Ferrite content (point count) | ASTM E562 |
| Ferrite content (magnetic induction) | ASTM A799 / Ferritescope |
| Microstructure (sigma phase) | ASTM A923 Method A / B / C |
Super Duplex Properties Frequently Asked Questions
What is the yield strength of super duplex stainless steel?
Required minimum yield strength per ASTM A479 is 550 MPa (80 ksi) for 2507, Zeron 100 and Ferralium 255 in the solution-annealed condition. Typical mill heats run at 620 to 720 MPa yield. This is roughly twice the yield strength of austenitic 316L (170 MPa min).
What is the tensile strength of super duplex stainless steel?
Required minimum tensile strength per ASTM A479 is 795 MPa (115 ksi) for 2507, 750 MPa (110 ksi) for Zeron 100, and 760 MPa for Ferralium 255 in the solution-annealed condition. Typical mill heats run at 800 to 1000 MPa tensile.
What is the hardness of super duplex stainless steel?
Required hardness per ASTM A479 is 32 HRC maximum for general service. For sour service per NACE MR0175 / ISO 15156-3, hardness is restricted to 28 HRC maximum (typical 25 to 28 HRC). Hardness above the limit signals incorrect heat treatment or excessive cold work.
What is the Critical Pitting Temperature of super duplex 2507?
CPT for 2507 in the standard ASTM G48 Method E ferric chloride test is approximately 50 to 70 degrees Celsius. CPT scales with PREN. Compared with 2205 at 30 to 40 degrees Celsius and Zeron 100 at 55 to 75 degrees Celsius, 2507 sits comfortably in the super duplex band.
What is the Charpy toughness of super duplex stainless steel?
Required Charpy V-notch toughness per NORSOK M-630 is 45 J minimum at minus 46 degrees Celsius for super duplex base metal. Typical mill heats run at 60 to 100 J. Sigma-phase precipitation collapses Charpy toughness to below 20 J, which is why ASTM A923 Methods A, B and C are used for sigma-phase screening.
What is the maximum service temperature of super duplex stainless steel?
Continuous service temperature is roughly minus 50 to 250 degrees Celsius. Above 300 degrees Celsius, sigma-phase precipitation kinetics become significant and limit long-term service. Below minus 50 degrees Celsius, ferrite-phase brittle transition reduces toughness rapidly.
Is super duplex stainless steel magnetic?
Yes. Super duplex steels contain roughly 50 percent ferrite, which is strongly ferromagnetic. Typical relative magnetic permeability is 50 to 200. This is the basis for Ferritescope measurement of phase balance per ASTM A799.
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