# NAS 75N Forgings: UNS S32760 Super Duplex

**NAS 75N is Nippon Yakin Kogyo's grade name for a super duplex stainless steel of nominal composition 25Cr-7Ni-3.6Mo-0.6Cu-0.6W-0.27N, with a pitting resistance equivalent number above 40. Nippon Yakin cross-references it to UNS S32760 and DIN/EN 1.4501, and assigns it no JIS number.**

Nippon Yakin supplies this grade as coil, sheet and plate. Forged components in the same chemistry are ordered to the forging specification ASTM A182 Grade F55. Jiangyin Jiangnan Metal Co., Ltd. forges that specification: seamless rolled rings, flanges, round bars, discs, tube sheets, shafts, sleeves and bushings, from steel melted in its own furnaces in Jiangyin, Jiangsu, China.

PRE is calculated by Nippon Yakin as PRE = %Cr + 3.3 x %Mo + 16 x %N.

## Grade identity

| Field | Detail |
|---|---|
| Producer designation | NAS 75N, Nippon Yakin Kogyo Co., Ltd. |
| UNS | S32760 |
| DIN / EN | 1.4501, X2CrNiMoCuWN25-7-4 |
| JIS | None assigned |
| Forging specification | ASTM A182 / A182M Grade F55 |
| Other names, same chemistry | Zeron 100, Seacol 760 |
| Family | Ferritic-austenitic super duplex stainless steel, PRE above 40 |
| Forms from Nippon Yakin | Coil, sheet, plate |
| Forms from this works | Open-die forgings and ring-rolled forgings |

## Two corrections

Two errors circulate in supplier catalogues for this grade.

NAS 75N is not a JIS grade. Nippon Yakin's grade page shows the JIS field blank. The grade carrying a JIS designation is NAS 74N, which is UNS S32750 and EN 1.4410, designated SUS327L1.

NAS 75N is not described by its producer as superior to 2507. Nippon Yakin states that it has superior localised corrosion resistance compared with UNS S32205, SUS329J3L and SUS329J4L. It makes no claim against 2507, which is UNS S32750, Nippon Yakin's own NAS 74N, and which also carries a PRE above 40.

## Chemical composition, weight per cent

Balance iron. Limits are the published UNS S32760 and ASTM A182 F55 range.

| Limit | C | Si | Mn | P | S | Cr | Ni | Mo | Cu | N | W |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Minimum | - | - | - | - | - | 24.00 | 6.00 | 3.00 | 0.50 | 0.20 | 0.50 |
| Maximum | 0.030 | 1.00 | 1.00 | 0.030 | 0.010 | 26.00 | 8.00 | 4.00 | 1.00 | 0.30 | 1.00 |
| NAS 75N nominal | low | - | - | - | - | 25 | 7 | 3.6 | 0.6 | 0.27 | 0.6 |

Melting route for this grade here: electric arc furnace, ladle furnace, vacuum oxygen decarburisation. Maximum heat 60 tonnes. Protective-atmosphere electroslag remelting and vacuum arc remelting available on site where a specification requires remelted material. Because the steel is melted in the works that forges it, the certificate traces the finished part back to its melt number.

## Mechanical properties, ASTM A182 F55

| Property | Requirement |
|---|---|
| Ultimate tensile strength | 750 MPa (109 ksi) min, 895 MPa max |
| 0.2 per cent proof stress | 550 MPa (80 ksi) min |
| Elongation | 25 per cent min, A50 mm |
| Reduction of area | 45 per cent min |
| Charpy V-notch impact | Not a published A182 F55 base requirement. Offshore orders commonly add testing at -46 C (-50 F), frequently with a 45 J (33 ft-lbf) average acceptance level, through the project material data sheet. |
| Phase balance | Ferrite content and freedom from intermetallic phase verified to ASTM A923 or ISO 17781 when the order requires it. |

## Heat treatment

Cool below 538 C after hot working, then solution anneal at 1100 to 1140 C and water quench. The quench must carry the full section through the sigma phase range without dwelling in it, because intermetallic precipitation costs both toughness and pitting resistance. Slow cooling out of the annealing temperature is the usual cause of a failed ASTM A923 or ASTM G48 test on duplex forgings.

Fourteen heat treatment furnaces on site, including car-bottom furnaces to 8,000 mm length and two pit furnaces 15,000 mm deep for vertical quenching of long shafts. No heat treatment is subcontracted.

## Hot working, machining, welding

Nippon Yakin reports that high-temperature strength is broadly similar to Type 430 between 950 and 1150 C, and that strength rises sharply below 900 C. Forging is finished above that point. Solution annealing always follows hot work. Cold working needs care because proof stress is high and elongation low next to Type 304.

Machining calls for reduced cutting speed, only slightly reduced feed, rigid set-ups, sharp coated carbide and plenty of coolant. Parts can be supplied as-forged, proof-machined or finish-machined.

For welding, Nippon Yakin reports that the usual processes apply, filler metal matching UNS S32760 is recommended, preheat and post-weld heat treatment are not required, and interpass temperature should be held below 100 C. Descaling is harder than on Type 304, so alkali immersion before pickling, and shot blasting where possible, both help.

## Forged shapes

- **Seamless rolled rings.** Ring-rolled from a punched preform on radial-axial mills of 1 m, 3 m and 6 m. Rectangular or contoured section.
- **Forged flanges.** Weld neck, blind, slip-on, long weld neck, orifice and special flanges, plus flange blanks.
- **Round bars and shafts.** Pump shafts, spindles, valve stems and bar stock for machining.
- **Discs and tube sheets.** Solid forged discs, tube sheets and covers, proof-machined for volumetric inspection.
- **Sleeves, bushings, cylinders.** Hollow forgings and heavy-wall sections bored from solid forged blanks.
- **Valve and wellhead parts.** Bodies, bonnets, blocks, seat rings, stems, chokes, connectors, manifolds. API 6A and NACE MR0175 / ISO 15156 scope available.

## Working envelope

| Item | Limit | Set by |
|---|---|---|
| Seamless rolled rings | OD 50 mm to OD 6,000 mm | 6 m radial-axial ring mill; upset-and-punch route below mill range |
| Forged shafts | up to 14,000 mm turned length | C61160 horizontal lathe; 15 m pit furnace for vertical quench |
| Discs, tube sheets, blocks | up to 5,000 mm machined diameter | 5,000 mm vertical turning lathe |
| Bored cylinders and hollow shafts | 1,600 mm dia x 10,000 mm | CNC deep-hole drilling machine |
| Single-piece weight | up to 30,000 kg | 60 t heat size, 6,300 t press |
| Order size | from 10 kg, no minimum piece count | Commercial policy |
| Lead time | 20 to 60 days | Section size, heat treatment, test scope |

## Applications

Nippon Yakin lists seawater desalination plant, chemical plant and seawater pump service for NAS 75N. In forged form, UNS S32760 is used for subsea and topside manifold blocks, connectors, chokes and valve bodies; flanges and spools in seawater and firewater pipework; pressure vessel and heat exchanger parts including tube sheets and covers; pumps and pump shafts in chloride-bearing media; high-pressure reverse osmosis hardware in desalination plant; absorber and pump components in flue gas desulphurisation systems; digester and liquor tank hardware in pulp and paper; and process equipment in mining and metallurgical plant.

## Grade selection

UNS S32760 and UNS S32750 (ASTM A182 F53, Nippon Yakin NAS 74N) are both super duplex grades with a PRE above 40 and are frequently interchangeable on paper. S32760 differs in carrying deliberate copper and tungsten additions. Whether that matters depends on the service environment.

We do not claim this grade outperforms every alternative. Given the medium, chloride concentration, temperature, pH and H2S partial pressure, we will say where S32760 fits, where S32750 does the same job, and where a 6Mo austenitic such as A182 F44 or a nickel alloy such as Incoloy 825 or Inconel 625 is the better answer. All of these are forged here.

## Testing and certification

| Scope | Standard |
|---|---|
| Ultrasonic testing | EN 10228-3, SEP 1921, ASTM A388 |
| Mechanical testing | Tensile, hardness, Charpy V-notch at specified temperature |
| Microstructure | ASTM E562 ferrite content; ASTM A923 or ISO 17781 intermetallic phase |
| Corrosion testing | ASTM G48 pitting and crevice testing on request |
| Other | Liquid penetrant inspection, PMI, dimensional report |
| Certification | EN 10204 3.1, or 3.2 countersigned by BV, SGS, TUV, LR or DNV |
| Works approvals | CCS, BV, DNV, LR, NK |

We work to client and NORSOK-based material data sheets. Send the MDS and we confirm in writing which clauses we meet before the order is placed.

## What we need to quote

1. **Specification.** NAS 75N alone is not orderable for forgings. We quote to UNS S32760 and ASTM A182 F55 unless another document is nominated.
2. **Geometry.** A drawing in STEP, DWG or PDF, or OD x ID x height for rings, diameter x length for bars and shafts.
3. **Quantity and condition.** Piece count, and as-forged, proof-machined or finish-machined. Solution annealed and quenched is standard.
4. **Test and certificate scope.** Impact test temperature, A923 or G48, ultrasonic class, EN 10204 3.1 or 3.2.

Prices are quoted per drawing. This grade is made to order and is not sold from stock at a list price.

## Contact

| Field | Detail |
|---|---|
| Company | Jiangyin Jiangnan Metal Co., Ltd. |
| Business | Integrated melting works, open-die forge and ring rolling mill, established 1997 |
| Staff | 460, including 9 senior engineers, 32 intermediate engineers and 140 technicians |
| Plant | No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China |
| Telephone | +86 189 2135 9659 |
| Email | sales@steelforgepieces.com |
| Page | https://www.steelforgepieces.com/Stainless-Steel/NAS-75N.html |

## References

1. Nippon Yakin Kogyo Co., Ltd., NAS75N grade page: https://www.nyk.co.jp/en/products/75n.html
2. Nippon Yakin Kogyo Co., Ltd., NAS74N grade page: https://www.nyk.co.jp/en/products/74n.html
3. Published ASTM A182 Grade F55 and UNS S32760 data for composition limits, mechanical requirements and solution treatment practice.
4. International Molybdenum Association, Practical Guidelines for the Fabrication of Duplex Stainless Steels.

Data on this page is collated for engineering guidance and does not form a warranty. Acceptance criteria are those in the purchase order and the governing material specification. Trade names are the property of their owners and are quoted for identification only. Jiangyin Jiangnan Metal Co., Ltd. is not affiliated with Nippon Yakin Kogyo Co., Ltd. Published 2 October 2026, last reviewed 3 October 2026.