Super Duplex Zeron 100 (UNS S32760, F55)
The copper-tungsten super duplex with a guaranteed PREN of 40 — the F55 bolting grade for North Sea, Gulf of Mexico and West African offshore projects.
What Zeron 100 is.
Zeron 100 (UNS S32760) is a 25 percent chromium super duplex that adds 0.5 to 1.0 percent each of copper and tungsten. The copper improves resistance to sulfuric acid and the tungsten to crevice corrosion, and the specification guarantees a pitting resistance equivalent number of at least 40 by chemistry. It is the super duplex most often written into offshore and seawater bolting specifications as F55.
Under ASTM A1082 it is solution annealed at 2010 °F and water quenched to 109 ksi tensile and 80 ksi yield with 25 percent elongation. We machine it from certified S32760 bar with full heat traceability.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.030 |
| Manganese | Mn | — | 1.00 |
| Phosphorus | P | — | 0.030 |
| Sulfur | S | — | 0.010 |
| Silicon | Si | — | 1.00 |
| Chromium | Cr | 24.0 | 26.0 |
| Nickel | Ni | 6.0 | 8.0 |
| Molybdenum | Mo | 3.0 | 4.0 |
| Nitrogen | N | 0.20 | 0.30 |
| Copper | Cu | 0.50 | 1.00 |
| Tungsten | W | 0.50 | 1.00 |
Values per ASTM A1082/A1082M-16(2021) Tables 1 and 4 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Size | Tensile strength, min (ksi) | Yield strength, min (ksi) | Elongation, min (%) | Hardness, max |
|---|---|---|---|---|
| All sizes | 109 | 80 | 25 | 30 HRC / 290 HBW |
Values per ASTM A1082/A1082M-16(2021) Tables 1 and 4 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. PREN = %Cr + 3.3 × %Mo + 16 × %N ≥ 40.
Specifications that apply.
How Zeron 100 ships from Houston.
- Full-thread studs and stud bolts
- Hex and heavy hex bolts
- Socket head cap screws
- Hex nuts in the same alloy
- Threaded rod
- Machined components from certified bar
Zeron 100 fasteners we make.
Every item is manufactured to your drawing or standard in Zeron 100, imperial or metric, with an EN 10204 3.1 certificate.
What is Zeron 100?
Zeron 100 was developed in the UK for North Sea seawater and oil-and-gas service and is standardised as UNS S32760 and ASTM A182 F55. Its 25 percent chromium, 7 percent nickel and 3.5 percent molybdenum base matches 2507; the additions of copper and tungsten and a chemistry-guaranteed PREN of 40 set it apart. Mechanically it is a little softer than 2507 in small sizes but more ductile, with 25 percent minimum elongation.
Specifying F55 bolting
Offshore piping classes commonly call for stud bolts in S32760 to A1082 or to NORSOK MDS D57, with nuts in the same alloy and a hardness cap of 30 HRC for sour service. Because both stud and nut are duplex, thread galling is a real risk; PTFE-coated studs or an anti-seize are normal practice. Ask for Charpy impact testing at the design temperature when it is below −20 °F; A1082 S1 gives acceptance values only for the PH grades, so criteria for duplex are agreed on the order.
Testing, certification and marking
- Tensile and hardness tested per lot on the finished product
- Grade or alloy marking 32760 (A1082 Table 5) and manufacturer's identification on every piece
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
Recent Zeron 100 jobs.
Super Duplex 2507 Stainless (UNS S32750)
25 Cr super duplex with a PREN above 40 — 116 ksi tensile and 80 ksi yield for the most aggressive seawater, sour and chloride bolting.
ASTM A1082 bolting · ASTM A276 / A479 bar · ASTM A182 F51 / F60Duplex 2205 Stainless (UNS S31803 / S32205)
Twice the yield strength of 316 with far better chloride stress-corrosion resistance — the standard duplex for offshore, seawater and sour-service bolting.
ASTM B637 bar · AMS 5662 / 5663 · API 6A CRAInconel 718 (UNS N07718)
The premier high-strength nickel superalloy — 185 ksi tensile and 150 ksi yield from cryogenic temperatures to 1200 °F, with corrosion and sour-gas resistance to match.