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Table of Contents
Super Duplex S32750 (UNS S32750 / 2507 / F53 / 1.4410) is guaranteed by ASTM specifications at a 550 MPa minimum 0.2% proof strength, a 795 MPa minimum tensile strength, 15% minimum elongation and a hardness ceiling of about 310 HBW / 32 HRC — roughly 3.2 times the yield strength of 316L and about 22% above Duplex 2205. That strength is what lets designers cut wall thickness, and it comes with good toughness down to −46 °C when the right supplementary tests are specified.
The mechanical properties of S32750 are the commercial argument for the grade. Its chemical composition buys corrosion resistance; its mechanical numbers buy structure: thinner walls, lighter assemblies, longer unsupported spans and smaller lifting equipment. But those numbers only pay off when you know which are guaranteed minimums, which are typical values, and which supplementary tests offshore and sour-service projects add on top.
This article sets out the full S32750 mechanical property table by product form, compares the grade with Duplex 2205 and 316L, explains what the strength advantage is worth in a real design, and shows you how to verify every number on the mill certificate. For the complete grade picture, start with the Super Duplex S32750 guide.
The binding numbers are the specification minimums, not datasheet typicals. ASTM A240 (plate), A790 (seamless and welded pipe), A276 (bar) and A182 (F53 forgings) all guarantee the same core values for S32750, with small differences in the supplementary rows.
Mechanical property requirements for UNS S32750 by specification and product form
Requirement | ASTM A240 plate | ASTM A790 pipe | ASTM A276 bar | ASTM A182 F53 |
|---|---|---|---|---|
0.2% proof strength, min | 550 MPa (80 ksi) | 550 MPa (80 ksi) | 550 MPa (80 ksi) | 550 MPa (80 ksi) |
Tensile strength, min | 795 MPa (116 ksi) | 795 MPa (116 ksi) | 795 MPa (116 ksi) | 795 MPa (116 ksi) |
Elongation, min | 15% | 15% | 15% | 15% |
Reduction of area, min | Not required | Not required | Not required | 45% |
Hardness, max | 310 HBW / 32 HRC | 310 HBW / 32 HRC | 310 HBW / 32 HRC | 310 HBW / 32 HRC |
Charpy V-notch | Not required by the base spec | Not required by the base spec | Not required by the base spec | Not required by the base spec |
Corrosion test | Not required by the base spec | Not required by the base spec | Not required by the base spec | Not required by the base spec |
Read the table the same way you would read the composition table in the S32750 chemical composition article: minimums are legal floors. Real mill certificates for a properly annealed heat typically show 580–680 MPa proof strength and 800–900 MPa tensile — comfortably above the floor, but not always, which is why the certificate must be checked heat by heat. Also notice how many rows read "not required by the base spec": Charpy toughness and corrosion testing are additions that offshore projects almost always mandate.
S32750 sits at the top of the common duplex ladder. Its 550 MPa minimum proof strength is about 22% above Duplex 2205 and roughly 3.2 times that of 316L — a gap that translates directly into wall thickness and weight in any pressure-containing design.
Minimum mechanical properties compared: S32750 vs Duplex 2205 vs 316L
Property (min) | Super Duplex S32750 | Duplex 2205 (S32205) | 316L |
|---|---|---|---|
0.2% proof strength | 550 MPa (80 ksi) | 450 MPa (65 ksi) | 170 MPa (25 ksi) |
Tensile strength | 795 MPa (116 ksi) | 620 MPa (90 ksi) | 485 MPa (70 ksi) |
Elongation | 15% | 25% | 40% |
Typical PREN | 42–43 | 34–38 | ~25 |
Relative wall, same hoop stress* | 0.31 | 0.38 | 1.00 |
*Simple hoop-stress comparison scaled by minimum proof strength, before code rules and minimum-wall limits — an indicator, not a design calculation.
The pattern to notice is the trade: as strength rises through the stainless family, guaranteed elongation falls. That is not a defect — 15% elongation is ample for pressure parts and most forming operations — but it is a real difference you can feel on the shop floor, and it is covered in the fabrication section below. The strength and corrosion comparison is treated in full in our duplex 2205 vs super duplex 2507 guide, and the background on each rung of the ladder is in what duplex 2205 is and what 316L stainless steel is.
Three things: thinner walls, lighter structures and cheaper logistics. In a simple hoop-stress calculation for a pipe or pressure shell, required wall thickness scales inversely with allowable stress. Moving from 316L to S32750 can, in principle, cut required thickness by two-thirds; in practice, codes, minimum-wall provisions, fabrication tolerances and handling robustness limit the gain, so real designs typically land 25–45% thinner than a 316L equivalent and a further step below a 2205 design.
Less material — thinner wall is less tonnes, and at super duplex prices per tonne the saving in tonnes usually more than offsets the premium per tonne.
Less welding — thinner walls mean smaller weld volumes, fewer weld passes and lower labour cost; welding is often the largest single cost in fabricated piping.
Lighter handling — lighter spools mean smaller cranes, cheaper supports and easier offshore installation.
Longer spans — higher strength plus a similar elastic modulus allows wider support spacing on pipe racks.
Two cautions keep the calculation honest. First, the elastic modulus is not higher — about 196–200 GPa, essentially the same as other stainless steels — so deflection- and buckling-governed members gain less than hoop-stress-governed ones. Second, buckling of thin high-strength walls must be checked: strength goes up, stiffness does not. For pipe dimensions and weights when you run the numbers, see our ASME B36.19 pipe dimension and weight tables, and for the fabrication-cost side of the wall-thickness decision, our prefabrication versus field welding cost comparison.
The 15% minimum elongation of S32750 is lower than 2205's 25% and 316L's 40%, but the grade still has generous reserve for pressure parts, and its toughness is where it genuinely excels. Properly solution-annealed S32750 typically delivers Charpy V-notch absorbed energies well above 100 J at room temperature — far beyond what most carbon steels offer.
Low-temperature duty is where the supplementary tests matter. Offshore specifications such as NORSOK M-630 (material data sheet D62 for 25Cr super duplex) require Charpy V-notch testing at −46 °C, typically with a minimum average around 45 J. A base-spec-compliant ASTM delivery carries no impact guarantee at all — if your project needs −46 °C toughness, that test must be written into the purchase order. Welds deserve particular attention: the heat-affected zone is where toughness drops first, so weld-procedure qualifications must include impact testing at the design temperature.
Practical rule: base ASTM properties are room-temperature guarantees. For anything colder than about −10 °C, or any offshore project, add Charpy V-notch testing at the minimum design temperature as a supplementary requirement — and require it on the weld-procedure qualification record as well as the parent material.
ASTM caps S32750 hardness at about 310 HBW (32 HRC). In the solution-annealed condition the material naturally sits around 230–290 HBW, so the limit rarely bites — until cold work or welding raises it. Hardness matters for two reasons: machinability planning (tool forces and speeds should be set for a 250–290 HBW material, not an annealed austenitic), and sour-service compliance.
NACE MR0175 / ISO 15156-3 accepts 25Cr super duplex in the solution-annealed condition for sour service with a hardness ceiling of 28 HRC — tighter than the ASTM limit — plus limits on the H2S partial pressure, chloride level, temperature and pH that must be verified against the current edition for the specific duty. Cold-worked product must be watched closely, because cold work raises hardness and can push a compliant heat out of the sour-service envelope. The full corrosion-side picture is in the S32750 guide; oil and gas duty is covered on our oil and gas page.
The mechanical numbers above are room-temperature guarantees; at temperature, the story changes. Code tables (ASME Section VIII Division 1 / B31.3, current editions) list S32750 to roughly 340 °C, but metallurgy argues for a lower practical cap.
Temperature behaviour of S32750 and what drives it
Regime | What happens | Practical guidance |
|---|---|---|
Below −46 °C | Toughness falls; duplex ferrite becomes the limiting phase | −46 °C is the normal offshore floor with qualified impact tests; below that, seek specialist guidance |
−46 to ~100 °C | Full properties; the sweet spot for chloride duty | Seawater, desalination, umbilicals — the grade's home territory |
100–250 °C | Proof strength declines gradually; allowable stresses fall | Re-rate allowable stress from code tables; usually still attractive vs 316L |
250–300 °C | 475 °C embrittlement kinetics start to matter on long exposure | Cap continuous service around 250–280 °C unless exposure is short |
400–540 °C | 475 °C embrittlement: ferrite hardens and toughens drops | Not suitable for continuous duty |
600–950 °C | Sigma and chi intermetallics precipitate; corrosion resistance collapses | Avoid; also the reason PWHT is forbidden and heat input must be controlled in welding |
The 600–950 °C band is not only a service limit — it is a fabrication limit. Slow cooling through that range during welding or hot forming precipitates sigma phase, which quietly destroys both toughness and corrosion resistance while hardness barely moves. This is why welding procedures for S32750 control heat input and interpass temperature so tightly; the welding side is a dedicated topic in the S32750 guide.
Three physical properties do mechanical work in every S32750 design and are worth having to hand:
Typical physical properties of Super Duplex S32750 at room temperature
Property | Typical value | Why it matters |
|---|---|---|
Density | 7.8 g/cm³ | Same ballpark as austenitics; weight estimates carry over directly |
Elastic modulus | ~196–200 GPa | Not higher than 316L — deflection and buckling checks do not improve with the higher strength |
Thermal expansion, 20–100 °C | ~13 × 10⁻⁶ /K | Lower than austenitics; reduces thermal stress at duplex-to-carbon-steel transitions |
Magnetic response | Ferromagnetic | Normal for duplex; a magnet sticks to compliant material |
Ferrite content, annealed | ~35–55% (typically ~45%) | Phase balance governs strength, toughness and corrosion resistance together |
The ferrite number deserves a second look: in a duplex, the mechanical property table and the phase balance are the same subject. Too little ferrite and the strength floor is at risk; too much and toughness and corrosion resistance fall. Order the ferrite measurement (ASTM E562 point count or a calibrated instrument) as a supplementary requirement on any critical order — it is cheap insurance on a heat whose entire behaviour hangs on that balance.
Well — in air. S32750's high tensile strength gives it a higher fatigue strength than 2205 or 316L in clean environments, which is one reason it performs in vibrating equipment, flowlines subject to pressure cycling and rotating machinery.
The caveat is corrosion fatigue: in seawater there is no true endurance limit, and the environment takes a bigger bite out of austenitic grades than out of super duplex. S32750 retains a comparatively favourable fraction of its in-air fatigue strength in chloride media, which is part of why it is specified for subsea and marine engineering duty.
Design-side, two consequences follow. First, welds are again the weak point — fatigue cracks initiate at weld toes long before parent metal complains, so profile grinding and proper weld dressing buy more life than parent-metal selection. Second, the higher notch sensitivity of a strong duplex means details matter more: smooth transitions, avoiding undercut, and controlling weld reinforcement are worth more engineering attention than they would receive on a 316L design.
A fabricator meeting S32750 for the first time notices the strength immediately, in three practical ways:
Forming forces and springback are larger. Bending and pressing need more force and roughly double the springback allowance of austenitic stainless at comparable radii — plan the trial bend before committing the batch.
Machining is slower but predictable. The higher strength and some gumminess in the austenite phase mean reduced cutting speeds and rigid set-ups relative to carbon steel; free-machining grades are not an option in this corrosion class.
Notch sensitivity is higher. Sharp section changes and rough machined surfaces concentrate stress more aggressively than in a soft austenitic grade — significant in fatigue and in sour service, where hardness and stress concentration interact.
None of these are reasons to avoid the grade; they are simply the cost side of the strength ledger, and they are priced in by any fabricator with duplex experience. If you are weighing fabricated cost against buying standard components, our stainless steel plate buying guide covers the plate-side economics.
The certificate is where specified properties and delivered properties meet. On an EN 10204 3.1 certificate for S32750, check five things:
Certificate verification checklist for S32750 mechanical properties
Check | What to look for | Common failure |
|---|---|---|
1. Heat number match | Heat number on certificate = number stamped/tagged on the material and on your PO | Certificate belongs to a different heat |
2. Test condition | Solution annealed, typically ≥1040 °C with water quench | As-rolled or undocumented condition |
3. Tensile values | Proof ≥550 MPa and tensile ≥795 MPa, with the test piece orientation and location stated | Values copied from a datasheet instead of a real test |
4. Supplementary tests | Charpy, hardness, G48 corrosion and ferrite results if — and only if — your PO asked for them | PO omitted them, so they were never run |
5. Consistency | Values consistent with the certified chemistry and with each other | Impossible combinations (e.g. very high proof with very high elongation) suggesting a doctored document |
The chemistry side of the same certificate — heat analysis, PREN and the tungsten check that separates S32750 from S32760 — is covered in the S32750 chemical composition article. Real certificates from real heats, in our own deliveries, appear in the case studies: UNS S32750 buttwelding pipe fittings to Saudi Arabia and ASTM A815 S32750 fittings to Brazil.
Minimum purchase-order line for mechanical properties:
1. Name the grade and spec: UNS S32750 to ASTM A240 / A790 / A276, or F53 to ASTM A182 for forgings.
2. Solution-annealed condition, with the annealing temperature and quench stated on the certificate.
3. Mechanical test results per heat on an EN 10204 3.1 certificate (3.2 for safety-critical duty).
4. For cold service or offshore: Charpy V-notch at −46 °C (or the design minimum temperature) on parent metal and weld qualification.
5. For sour service: hardness ≤28 HRC per NACE MR0175 / ISO 15156-3, verified per lot.
6. Ferrite content by ASTM E562 within roughly 35–55% for critical orders.
Everything in that box closes a gap that the base ASTM specification leaves open — the same philosophy as the composition article's PREN clause: the grade name gets you the floor; the supplementary requirements get you the material you actually designed. More background on the family and its naming is in our article on the duplex numbering system, and quick answers on the F53 designation are in our duplex F53 quick questions.
What is the yield strength of S32750?
The ASTM-guaranteed minimum 0.2% proof strength is 550 MPa (80 ksi) across plate (A240), pipe (A790), bar (A276) and forgings (A182 F53). Typical mill certificates show 580–680 MPa. That is about 22% above Duplex 2205 and roughly 3.2 times the 170 MPa minimum of 316L.
What is the tensile strength of S32750?
The specification minimum is 795 MPa (116 ksi), with typical delivered values of 800–900 MPa for a properly solution-annealed heat. Compare 620 MPa minimum for Duplex 2205 and 485 MPa for 316L.
What is the elongation of S32750, and is 15% enough?
ASTM requires a minimum of 15% elongation (against 25% for 2205 and 40% for 316L). For pressure parts, flanges and standard forming operations that reserve is ample; it simply means forming needs more force and larger bend radii than an austenitic grade would. The strength-for-ductility trade is inherent to the duplex family.
What is the maximum hardness of S32750?
About 310 HBW (32 HRC) by ASTM limits. Solution-annealed material normally sits around 230–290 HBW. Sour service under NACE MR0175 / ISO 15156-3 imposes a tighter ceiling of 28 HRC, which cold work or poor welding practice can violate — so hardness verification is per-lot, not per grade.
Is S32750 suitable for low temperatures?
Yes, down to −46 °C with qualified Charpy V-notch testing, which is exactly what offshore specifications such as NORSOK M-630 D62 mandate (minimum average around 45 J at −46 °C). The base ASTM specifications carry no impact guarantee at all, so the test must be written into the purchase order, including on weld qualifications.
What is the maximum service temperature of S32750?
Code tables list S32750 to roughly 340 °C, but continuous service is normally capped at about 250–280 °C. Above roughly 400 °C the ferrite phase undergoes 475 °C embrittlement on long exposure, and between 600 and 950 °C sigma phase forms and destroys both toughness and corrosion resistance. The practical limit is set by metallurgy, not by the code table.
Is S32750 stronger than Duplex 2205?
Yes: 550 MPa versus 450 MPa minimum yield (about 22% higher) and 795 versus 620 MPa minimum tensile. The same chemistry that raises corrosion resistance — more chromium, molybdenum and nitrogen — also raises strength. The full trade-off, including cost and weldability, is in our 2205 vs 2507 guide.
Does the higher strength let me halve the wall thickness?
Not quite. In a simple hoop-stress calculation the required thickness for S32750 is about 31% of a 316L design (38% for 2205), but code allowable stresses, minimum-wall provisions, buckling of thin walls and handling robustness claw some of that back. Real designs typically land 25–45% thinner than the 316L equivalent — still a decisive saving in weight, welding and support cost.
How does S32750 behave under fatigue loading?
Its fatigue strength in air is higher than 2205 or 316L thanks to the high tensile strength, and it retains a comparatively favourable share of that strength in chlorinated seawater, where true endurance limits disappear. Weld toes remain the critical initiation sites, so weld profile control matters more than parent-metal choice in fatigue-governed designs.
What mechanical tests should appear on the S32750 mill certificate?
At minimum, per heat: tensile test (proof strength, tensile strength, elongation) on an EN 10204 3.1 certificate, tied to the heat number stamped on the material, with the solution-anneal condition stated. Add Charpy V-notch at the design minimum temperature, hardness, ferrite count and ASTM G48 corrosion testing when the duty or the project specification calls for them — the base ASTM specs require none of these additions.
We supply Super Duplex S32750 (UNS S32750 / F53 / 1.4410) plate, pipe, bar, flanges and fittings with EN 10204 3.1 certificates reporting actual tensile, hardness and — where specified — Charpy and ferrite results for every heat. Send us your design conditions and we will confirm the specification package.
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