Super duplex stainless steel · PRE above 40
NAS 75N Forgings Forged to UNS S32760 and ASTM A182 F55. Rolled rings, flanges, bars, discs and shafts, melted and forged in one works.
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 rolls this grade as coil, sheet and plate. Forged components in the same chemistry are ordered to the forging specification ASTM A182 Grade F55, and that is what we make: seamless rolled rings, flanges, round bars, discs, tube sheets, shafts, sleeves and bushings, from steel melted in our own furnaces.
- Producer
- NAS 75N
- UNS
- S32760
- EN / DIN
- 1.4501 · X2CrNiMoCuWN25-7-4
- JIS
- None assigned
- Forgings
- ASTM A182 F55
- PRE
- Above 40
- Tensile
- 750 MPa / 109 ksi min
- Proof 0.2%
- 550 MPa / 80 ksi min
- Anneal
- 1100–1140 °C, water quench
- Max ring
- OD 6,000 mm
- Max piece
- 30,000 kg
- Min order
- 10 kg
Grade identity and equivalents
NAS 75N is a producer trade name, not a standard designation. To buy it, or to buy a forging equal to it, you need the standard grade behind the name.
| Producer designation | NAS 75N, Nippon Yakin Kogyo Co., Ltd. |
|---|---|
| UNS number | S32760 |
| DIN / EN | 1.4501, X2CrNiMoCuWN25-7-4 |
| JIS | None assigned. NAS 74N, which is UNS S32750 and EN 1.4410, is the grade that carries JIS SUS327L1. |
| Forging specification | ASTM A182 / A182M Grade F55 |
| Other names for the same chemistry | Zeron 100, Seacol 760 |
| Family | Ferritic-austenitic super duplex stainless steel, PRE above 40 |
| Product forms from Nippon Yakin | Coil, sheet, plate |
| Product forms from this works | Open-die forgings and ring-rolled forgings |
Enquiries for this grade reach us with two recurring errors copied from one supplier catalogue to the next. The first is that NAS 75N is a JIS grade. Nippon Yakin's own grade page shows the JIS field as blank, with UNS S32760 and EN 1.4501 as the equivalents.
The second is the claim that it outperforms 2507 super duplex. Nippon Yakin states that NAS 75N has superior localised corrosion resistance compared with UNS S32205, SUS329J3L and SUS329J4L, which are 22Cr and 25Cr duplex grades. It makes no such claim against 2507. 2507 is UNS S32750, which is Nippon Yakin's own NAS 74N, and it carries a PRE above 40 as well. The two sit in the same corrosion class.
Nippon Yakin calculates the pitting resistance equivalent as PRE = %Cr + 3.3 × %Mo + 16 × %N.
Chemical composition
Composition limits below are the published UNS S32760 and ASTM A182 F55 range, with the Nippon Yakin nominal analysis for NAS 75N shown for comparison. Balance iron.
| 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
Duplex and stainless grades are melted here in an electric arc furnace, refined in a ladle furnace and decarburised under vacuum, which is where the low carbon and the controlled nitrogen level in this grade come from. Maximum heat size is 60 tonnes. Protective-atmosphere electroslag remelting and vacuum arc remelting are available on site when a specification calls for remelted material. Because the steel is melted in the same works that forges it, the certificate traces a finished part back to its melt number rather than to a purchased billet of unknown origin.
Mechanical properties
Room-temperature requirements for ASTM A182 F55 forgings in the solution annealed and quenched condition.
| Ultimate tensile strength | 750 MPa (109 ksi) minimum, 895 MPa maximum |
|---|---|
| 0.2 per cent proof stress | 550 MPa (80 ksi) minimum |
| Elongation | 25 per cent minimum, gauge length A50 mm |
| Reduction of area | 45 per cent minimum |
| Charpy V-notch impact | Not a published A182 F55 base requirement. Offshore and subsea orders commonly add testing at −46 °C (−50 °F), frequently with a 45 J (33 ft·lbf) average acceptance level, through the client or project material data sheet. Name the governing document and we test to it. |
| Phase balance | Ferrite and austenite content and freedom from detrimental intermetallic phase are verified to ASTM A923 or ISO 17781 when the order requires it. The acceptance window follows your specification. |
Heat treatment
This is the step that decides whether a super duplex forging passes or fails its corrosion and toughness tests.
Published F55 practice is to cool the forging below 538 °C after hot working, then solution anneal at 1100 to 1140 °C and water quench. The quench has to carry the whole section through the sigma phase range without dwelling in it. Intermetallic precipitation costs both toughness and pitting resistance, and slow cooling out of the annealing temperature is the usual reason a duplex forging fails an A923 or a G48 test.
Section thickness therefore gets checked against quench capacity at the quoting stage, not after the forging is made. Fourteen heat treatment furnaces sit on site, including car-bottom furnaces up to 8,000 mm long and two pit furnaces 15,000 mm deep for vertical quenching of long shafts. No heat treatment is subcontracted.
Hot working, machining, welding
Hot working
Nippon Yakin notes that the high-temperature strength of this grade 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 and solution annealing always follows hot work. Cold working needs care, because proof stress is high and elongation low next to Type 304.
Machining
Expect high-nitrogen super duplex behaviour: high proof stress, a steep work-hardening rate, and tool life that punishes a dull edge. Cutting speed is the variable to reduce; feed should come down only slightly. Rigid set-ups, sharp coated carbide and plenty of coolant. We supply as-forged, proof-machined or finish-machined, so machinability can stay our problem rather than yours. Vertical lathes take up to 5,000 mm swing, horizontal lathes up to 14,000 mm between centres, and a CNC deep-hole drilling machine handles 1,600 mm diameter by 10,000 mm.
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 to keep intermetallic phases out of the weld and heat-affected zone. Descaling is harder than on Type 304, so alkali immersion before pickling, and shot blasting where possible, both help.
Forged shapes and size range
Every item is forged from a single piece of steel melted on site. No welding, no casting, no bought-in billet.
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 for machining.
Round bars and shafts
Pump shafts, spindles, stems and bar stock. Turned length to 14,000 mm, vertical quench in a 15 m pit furnace.
Discs and tube sheets
Solid forged discs, tube sheets and covers, proof-machined for volumetric inspection. To 5,000 mm machined diameter.
Sleeves, bushings, cylinders
Hollow forgings and heavy-wall sections bored from solid forged blanks, to 1,600 mm bore diameter.
Valve and wellhead parts
Bodies, bonnets, blocks, seat rings, stems, chokes, connectors and manifolds. API 6A and NACE MR0175 / ISO 15156 scope available.
| 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 diameter by 10,000 mm | CNC deep-hole drilling machine |
| Single-piece weight | Up to 30,000 kg | 60 t heat size, 6,300 t open-die press |
| Order size | From 10 kg, no minimum piece count | Commercial policy |
| Lead time | 20 to 60 days | Section size, heat treatment and test scope |
Where this grade is used
Nippon Yakin lists the applications for NAS 75N as seawater desalination plant, chemical plant and seawater pump service. Forged components in UNS S32760 appear across the same industries in heavier sections.
Typical forged items include 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 handling 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.
UNS S32760 and UNS S32750, which is ASTM A182 F53 and Nippon Yakin's NAS 74N, are both super duplex grades with a PRE above 40 and are often interchangeable on paper. S32760 differs in carrying deliberate copper and tungsten. Whether that difference matters to your service depends on the medium.
We are a forge, not a corrosion consultancy, so we will not tell you this grade beats every alternative. Send the medium, chloride concentration, temperature, pH and H₂S partial pressure, and we will say where S32760 is a reasonable fit, where S32750 does the same job, and where the honest answer is a 6Mo austenitic such as F44, or a nickel alloy such as 825 or 625. All of those we forge too.
Testing and certification
| Ultrasonic testing | EN 10228-3, SEP 1921 or ASTM A388, acceptance class per order |
|---|---|
| Mechanical testing | Tensile, hardness, Charpy V-notch at the specified temperature |
| Microstructure | Ferrite content by ASTM E562, intermetallic phase evaluation to ASTM A923 or ISO 17781 |
| Corrosion testing | ASTM G48 pitting and crevice testing on request |
| Other | Liquid penetrant inspection, positive material identification, dimensional report |
| Certification | EN 10204 3.1, or 3.2 countersigned by a third party such as BV, SGS, TÜV, LR or DNV |
| Works approvals | CCS, BV, DNV, LR, NK |
| Project specifications | We work to client and NORSOK-based material data sheets. Send the MDS and we confirm in writing which clauses we meet before you place the order, rather than after. |
What we need to quote
Four things turn an enquiry into a price and a delivery date, usually within one working day.
| Specification | NAS 75N on its own is not orderable for forgings. We quote to UNS S32760 and ASTM A182 F55 unless you nominate another document. |
|---|---|
| Geometry | A drawing in STEP, DWG or PDF. Failing that, OD by ID by height for rings, or diameter by length for bars and shafts. |
| Quantity and condition | Piece count, and whether you want as-forged, proof-machined or finish-machined. Solution annealed and quenched is standard. |
| Test and certificate scope | Impact test temperature, A923 or G48, ultrasonic class, EN 10204 3.1 or 3.2. |
Request a quotation
Jiangyin Jiangnan Metal Co., Ltd. is a melting works and open-die forge, so an enquiry goes to the people who run the furnace and the press rather than to a trading desk. Established 1997. 460 staff, including 9 senior engineers, 32 intermediate engineers and 140 technicians.
Questions we are asked
Is NAS 75N a JIS grade?
No. Nippon Yakin Kogyo's grade page for NAS 75N shows the JIS field blank and lists UNS S32760 and DIN/EN 1.4501 as the equivalents. The grade with a JIS designation is NAS 74N, which is UNS S32750 and EN 1.4410, designated SUS327L1.
If a supplier offers NAS 75N material certified to a JIS standard, ask which JIS number, because there is not one.
Which specification do I put on the purchase order?
For forgings, ASTM A182 Grade F55, or EN 1.4501 if you work to European standards. Both cover the UNS S32760 chemistry. Adding "NAS 75N equivalent" as a note is useful if your drawing inherited the Nippon Yakin name, but the orderable specification is the ASTM or EN one.
What is the difference between NAS 75N and NAS 74N?
Both are super duplex grades with a PRE number above 40. NAS 74N is UNS S32750 and EN 1.4410, nominally 25Cr-7Ni-3.8Mo-0.27N, the grade generally sold as 2507 and forged as ASTM A182 F53. NAS 75N is UNS S32760 and EN 1.4501, nominally 25Cr-7Ni-3.6Mo-0.6Cu-0.6W-0.27N, forged as ASTM A182 F55, with copper and tungsten added on purpose.
Neither is simply better than the other. The choice is driven by the service environment and by which one your project specification names.
Can you supply plate or sheet in this grade?
No. Plate, sheet and coil are the forms Nippon Yakin supplies under the NAS 75N name. We are a forge, so our scope is forged and ring-rolled shapes in the equivalent UNS S32760 chemistry. If you need plate we will say so rather than take the order and look for a way round it.
How large a forging can you make?
Up to 6,000 mm outside diameter on the ring mill and up to 30,000 kg as a single piece, limited by the 60 tonne heat size and the 6,300 tonne press. Rings below the ring mill range are made by the upset-and-punch route from about OD 50 mm.
Super duplex has a narrow hot-working window and a demanding quench, so for this grade we confirm section thickness against our quench capability before accepting the order.
What documents come with the forgings?
As a minimum, an EN 10204 3.1 certificate carrying the heat chemistry, the heat treatment record, mechanical results and NDT results, traceable to the melt number from our own furnace. EN 10204 3.2 with third-party countersignature, A923 or ISO 17781 microstructure reports, ASTM G48 corrosion test reports and PMI records are available on request.
What is the minimum order and the lead time?
Minimum order is 10 kg with no minimum piece count, so a single prototype forging is acceptable. Lead time runs 20 to 60 days depending on section size, heat treatment and the test scope on the order.
References
- Nippon Yakin Kogyo Co., Ltd. NAS75N grade page: designations, nominal composition, PRE formula, workability, weldability, heat treatment, descaling and applications. nyk.co.jp/en/products/75n.html
- Nippon Yakin Kogyo Co., Ltd. NAS74N grade page, used for the S32750 comparison. nyk.co.jp/en/products/74n.html
- Published ASTM A182 Grade F55 and UNS S32760 data for composition limits, 750 to 895 MPa tensile, 550 MPa proof stress, 25 per cent elongation, 45 per cent reduction of area, cooling below 538 °C after hot working and solution treatment at 1100 to 1140 °C.
- International Molybdenum Association, Practical Guidelines for the Fabrication of Duplex Stainless Steels, on quenching rate and intermetallic phase control.
- Works capability figures are our own: melting and forging equipment lists, furnace sizes and machining envelope as published on this site.