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
ASTM A276: Super Duplex 2507 Bar and Shapes
ASTM A276 is the standard specification for stainless steel bars and shapes for general use. It is the alternate bar specification for super duplex 2507 (UNS S32750 / Werkstoff 1.4410), running parallel to ASTM A479. A276 is the older, broader bar standard; A479 is the newer pressure-vessel-focused bar standard. Both cover the same chemistry for UNS S32750.
TorqBolt supplies A276 UNS S32750 round, hex, square, and flat bar across diameters 6 mm to 250 mm, with mill test certificates that cross-reference A276 and A479 chemistry on the same heat.
ASTM A276 Scope
A276 covers stainless steel bars (round, hex, square, flat, and other shapes) for general use, including general-service machined parts, fabricated equipment, and components for moderate temperature and corrosive service. The standard governs chemistry, mechanical properties, heat treatment, dimensions, surface condition, and traceability for hot-finished and cold-finished bars and shapes. Within A276, the duplex / super duplex grades include UNS S32750 alongside S31803, S32550, S32760, and others.
A276 vs A479: Choose by Application
| Aspect | A276 | A479 |
|---|---|---|
| Title | Stainless bar for general use | Stainless bar for pressure vessels and general service |
| Pressure-vessel application | General service; not the primary spec for ASME pressure vessels | Approved for ASME pressure-vessel components |
| Chemistry for UNS S32750 | Same as A479 | Same as A276 |
| Mechanical requirements | Same as A479 | Same as A276 |
| Heat treatment | Same: solution annealed and water quenched | Same: solution annealed and water quenched |
| Typical use | Machined components, structural shapes, valve internals | Pressure-vessel internals, ASME-coded fabrications, flange forgings |
For super duplex 2507, A276 and A479 are technically interchangeable at the chemistry and mechanical level. Project specifications choose based on the regulatory framework: ASME pressure-vessel work cites A479; general machined components cite A276.
A276 Chemistry for UNS S32750
| Element | Min % | Max % |
|---|---|---|
| Carbon (C) | (no min) | 0.030 |
| Chromium (Cr) | 24.0 | 26.0 |
| Nickel (Ni) | 6.0 | 8.0 |
| Molybdenum (Mo) | 3.0 | 5.0 |
| Nitrogen (N) | 0.24 | 0.32 |
| Manganese (Mn) | (no min) | 1.20 |
| Silicon (Si) | (no min) | 0.80 |
| Phosphorus (P) | (no min) | 0.035 |
| Sulfur (S) | (no min) | 0.020 |
| Copper (Cu) | (no min) | 0.50 max, residual, not intentional |
A276 Mechanical Requirements
| Property | Minimum |
|---|---|
| Tensile strength | 795 MPa (116 ksi) |
| Yield strength (0.2 percent) | 550 MPa (80 ksi) |
| Elongation in 50 mm | 15 percent |
| Hardness | 32 HRC max (or 310 HBW) |
Heat Treatment
Solution annealing at 1040 to 1100 degrees Celsius followed by rapid water quench. Identical to the A479 heat treatment for the same UNS S32750 chemistry. Heavy section bars require careful quench design to drive the centre through the 600 to 1000 degrees Celsius critical band fast enough to suppress sigma-phase precipitation.
Bar Forms Supplied to A276
- Round bar 6 mm to 250 mm diameter
- Hex bar across-flats sizes for fastener manufacture
- Square bar for machined components
- Flat bar for structural and machined parts
- Bright drawn bar (cold-finished) for tighter dimensional tolerance
- Forged round bar for sections above 250 mm
Required Tests
| Test | Method |
|---|---|
| Chemistry | ASTM E1086 family |
| Tensile | ASTM A370 / E8 |
| Hardness | ASTM E10 (HBW) / E18 (HRC) |
| Ferrite (when invoked) | ASTM E562 point count |
| Intermetallic (when invoked) | ASTM A923 Method A or C |
| Pitting (when invoked) | ASTM G48 Method A |
Typical Applications under A276
- Valve trim (gates, seats, stems) for super duplex bodies
- Pump shafts and impellers in chloride and seawater service
- Machined manifold components for offshore and FPSO
- Structural shapes for marine and offshore platforms
- Fastener bar stock for hot-headed and machined bolting (typically cross-certified to A479 or A1082)
- Heat-exchanger tubesheet machined parts
Related Standards
- ASTM A479: bar spec for pressure-vessel and general service
- ASTM A182 F53: forging / flange / forged-fitting spec
- ASTM A789: tube spec
- ASTM A790: pipe spec
- ASTM A815: wrought fittings (WP-S32750)
- EN 10088-3: European bar / wire spec (Werkstoff 1.4410)
- NORSOK M-630: MDS D55
- NACE MR0175 / ISO 15156-3: sour service requirements
ASTM A276 Frequently Asked Questions
What does ASTM A276 cover for UNS S32750?
A276 specifies super duplex 2507 round, hex, square, flat bar and other shapes for general service in solution-annealed and water-quenched condition. The grade is UNS S32750 with chemistry 24-26 Cr, 6-8 Ni, 3-5 Mo, 0.24-0.32 N.
What is the difference between A276 and A479 for 2507?
Same chemistry, same mechanical, same heat treatment. A276 is the broader stainless bar spec for general service; A479 is the bar spec approved for ASME pressure vessels. Project specifications choose based on regulatory context: ASME pressure-vessel work cites A479; general machined components cite A276. Mill heats are routinely cross-certified to both.
What heat treatment is applied?
Solution annealing at 1040 to 1100 degrees Celsius followed by rapid water quench. Identical to A479. The water quench drives the bar through the 600 to 1000 degrees Celsius critical band rapidly, suppressing sigma-phase precipitation.
What yield strength does A276 require for 2507?
550 MPa (80 ksi) minimum yield, 795 MPa (116 ksi) minimum tensile, 15 percent minimum elongation. Hardness 32 HRC max, tightened to 28 HRC max for sour service per NACE MR0175.
Can A276 bar be used for machined valve trim?
Yes. A276 is a common choice for machined valve trim (gates, seats, stems) in super duplex bodies. The bar comes solution annealed; machining produces the finished trim. Hardness must remain within 28 HRC for sour service applications.
Is A276 acceptable for fastener bar stock?
Common practice is to cross-certify the heat to A479 (or A1082 for the finished fastener) when supplying fastener bar stock. A276 alone is admissible when project specifications cite A276 by name. Mill test certificates routinely list both A276 and A479 against the same UNS S32750 heat.
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