254 SMO vs 2507 Stainless Steel
Side-by-side comparison · Composition · Properties · Selection guide
254 SMO and super-duplex 2507 both exceed PREN 40 and serve severe chloride environments. 254 SMO retains an austenitic structure with excellent formability and established sheet fabrication, while 2507 offers much higher strength and strong seawater resistance with a narrower welding and temperature window.
Full datasheets:254 SMO Stainless Steel·2507 Stainless Steel
At a Glance
| 254 SMO | 2507 | |
|---|---|---|
| Type | Super-austenitic (6Mo) | Super-duplex (austenitic-ferritic) |
| UNS | S31254 | S32750 |
| Standard | ASTM A240/A240M | ASTM A240/A240M, A789/A790 |
| Density | 8 g/cm³ | 7.8 g/cm³ |
Corrosion Resistance and Service Limits
254 SMO
- General corrosion resistance comes from the chromium-rich passive film; nickel, molybdenum, nitrogen and copper change performance by grade.
- Check chlorides, temperature, crevices, deposits, process chemistry and cleaning conditions. A grade designation alone is not a service-life guarantee.
2507
- The mixed austenitic-ferritic structure provides high strength and improved resistance to chloride pitting and stress-corrosion cracking relative to 304/316-type grades.
- PREN is only a screening index. Temperature, crevices, weld phase balance, heat tint, deposits and actual solution chemistry still govern suitability.
Fabrication and Heat Treatment
| Operation | 254 SMO | 2507 |
|---|---|---|
| Welding | Generally weldable with a qualified procedure and matching or over-alloyed filler where required; remove heat tint when corrosion service demands it. | Use a qualified duplex procedure with controlled heat input, interpass temperature and filler to maintain phase balance, toughness and corrosion resistance. |
| Forming | Good ductility is typical, but rapid work hardening increases forming load and springback; bend radius and intermediate annealing depend on grade and reduction. | Higher yield strength increases forming load and springback. Severe cold work may require solution annealing under a qualified route. |
| Machining | Use rigid tooling, positive feeds and controlled heat because the material work-hardens; free-machining grades require separate corrosion and welding review. | Use rigid equipment, positive feeds and lower cutting speed than common austenitic grades because high strength and work hardening raise cutting load. |
| Heat treatment | Solution annealing and rapid cooling restore the intended condition where applicable. Austenitic grades are not hardened by conventional quench-and-temper treatment. | Solution anneal and rapid cooling are used to restore the specified duplex structure. Local stress relief can form harmful intermetallic phases and is not a generic remedy. |
Chemical Composition (wt%)
| Element | 254 SMO | 2507 |
|---|---|---|
| C | ≤0.020 | ≤0.030 |
| Mn | ≤1.00 | ≤1.20 |
| Si | ≤0.80 | ≤0.80 |
| Cr | 19.5–20.5 | 24.0–26.0 |
| Ni | 17.5–18.5 | 6.0–8.0 |
| Mo | 6.0–6.5 | 3.0–5.0 |
| N | 0.18–0.25 | 0.24–0.32 |
| Cu | 0.50–1.00 | — |
| P | ≤0.030 | ≤0.035 |
| S | ≤0.010 | ≤0.020 |
Mechanical Properties
| Property | 254 SMO | 2507 |
|---|---|---|
| Tensile strength | ≥650 MPa (94 ksi) | ≥795 MPa (116 ksi) |
| Yield strength (0.2%) | ≥300 MPa (44 ksi) | ≥550 MPa (80 ksi) |
| Elongation (50 mm) | ≥35% | ≥15% |
| Hardness | ≤223 HBW | ≤310 HBW |
| PREN | — | ≥40 |
Which One Should You Choose?
Choose 254 SMO for:
- Complex formed sheet and vessel fabrication
- Projects requiring an austenitic alloy system
- Flue-gas cleaning and aggressive chemical equipment
- Service where impact toughness and forming dominate
Choose 2507 for:
- High-pressure seawater and desalination piping
- Offshore systems where strength reduces wall thickness
- Warm chloride service with qualified duplex fabrication
- Forgings, bar and pressure components needing high yield strength
Our verdict
Use 254 SMO for severe corrosion where austenitic fabrication behavior and complex forming are valuable; use 2507 where seawater resistance and high strength create a clear design advantage. A lifecycle comparison must include welding qualification, product-form availability and code rules, not alloy price alone.
Cost and Availability
Compare the current stock position, mill route, minimum production quantity, processing yield, testing and delivered cost for 254 SMO and 2507 at quotation time. A fixed price ratio would be misleading because product form, size, condition and market timing can change the commercial result.
Do Not Substitute Without Review
Do not replace 254 SMO with 2507, or the reverse, from the grade name alone. Recheck chemistry, mechanical-property condition, product standard, dimensions, corrosion environment, welding procedure and project approval before substitution.
Frequently Asked Questions
Which has higher strength?
2507 by a wide margin. Its specified yield strength is roughly double that of annealed 254 SMO, which can reduce required section thickness after code review.
Which is easier to fabricate?
254 SMO generally forms like a highly alloyed austenitic grade. Both require skill, but 2507 has tighter heat-input and phase-balance controls during welding.
Can either grade handle seawater?
Both are candidates, but temperature, crevices, chlorination, flow and fabrication quality decide. Final selection needs project-specific corrosion review.
RFQ
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Technical content updated: 2026-07-29
Organizational author: Tsingshan (Shandong) Iron & Steel Co., Ltd..Review method, status and limitations.