# UNS N08028 Forgings (Alloy 28 / Sanicro 28 / EN 1.4563)

**UNS N08028 is a high-alloy austenitic stainless steel of nominally 27 per cent chromium, 31 per cent nickel, 3.5 per cent molybdenum and 1 per cent copper.** The chromium and molybdenum give resistance to both oxidising and reducing acids, and the copper addition raises resistance to sulphuric acid in particular. It is specified mainly for phosphoric and sulphuric acid service, chloride-bearing process streams and sour wells.

Jiangyin Jiangnan Metal Co., Ltd. melts this grade in its own furnaces and forges it on the same site in Jiangyin, Jiangsu, China. The certificate traces a finished part back to its melt number rather than to a purchased billet.

Source page: https://www.steelforgepieces.com/Stainless-Steel/UNS-N08028.html
Revision: October 2026

## Supplier

| Field | Detail |
|---|---|
| Company | Jiangyin Jiangnan Metal Co., Ltd. |
| Business | Integrated melting works, open-die forge and ring rolling mill |
| Established | 1997 |
| Employees | 460, including 9 senior engineers, 32 intermediate engineers and 140 technicians |
| Plant | No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China |
| Telephone, WhatsApp, WeChat | +86 189 2135 9659 |
| Email | sales@steelforgepieces.com |
| Business hours | Monday to Saturday, 08:00 to 17:30 China Standard Time (UTC+8) |
| Class approvals | CCS, BV, DNV, LR, NK |
| Minimum order | 10 kg, no minimum piece count |
| Lead time | 20 to 60 days |

## Designations

| Designation system | Value |
|---|---|
| UNS | N08028 |
| EN number, Werkstoff | 1.4563 |
| EN name | X1NiCrMoCu 31-27-4 |
| DIN | X1NiCrMoCuN 31 27 4 |
| ISO | 4563-080-28-I |
| SS, Sweden | 2584 |
| AFNOR | Z1NCDU31-27-03 |
| Trade and common names | Alloy 28, Sanicro 28, Incoloy alloy 028 |

## Applicable standards

| Product form | Standards |
|---|---|
| Seamless tube and pipe | ASTM B668, EN 10216-5, SEW 400, SS 14 25 84, NF A49-217 |
| Plate, sheet, strip | ASTM B709, EN 10088-2 |
| Bar | EN 10088-3, EN 10272 |
| Fittings | ASTM A403, chemistry and mechanical properties to ASTM B668 |
| Code approvals | ASME BPVC Section III, Section I under Code Case 1325-18, Section VIII Division 1; VdTUV Werkstoffblatt 483 |
| Sour service | NACE MR0103, NACE MR0175 / ISO 15156 |

There is no dedicated ASTM forging specification for this grade. Forgings are normally ordered to ASTM B668 chemistry with dimensions, NDT class and mechanical testing agreed on the drawing.

## Chemical composition, weight per cent

| Element | ASTM B668 | Nominal aim |
|---|---|---|
| Carbon, C | 0.030 max | <= 0.020 |
| Silicon, Si | 1.00 max | <= 0.6 |
| Manganese, Mn | 2.50 max | <= 2.0 |
| Phosphorus, P | 0.030 max | <= 0.025 |
| Sulphur, S | 0.030 max | <= 0.010 |
| Chromium, Cr | 26.0 to 28.0 | 27 |
| Nickel, Ni | 30.0 to 34.0 | 31 |
| Molybdenum, Mo | 3.0 to 4.0 | 3.5 |
| Copper, Cu | 0.6 to 1.4 | 1.0 |
| Iron, Fe | Balance | Balance |

The copper minimum is 0.6 per cent. It is frequently printed as 0.06 per cent on trading sites, which is a decimal error. Copper is the element responsible for the grade's behaviour in sulphuric acid, so a heat analysing below 0.6 per cent is out of specification.

### Pitting resistance equivalent

PREN = %Cr + 3.3 x %Mo + 16 x %N

- Nominal composition, 27Cr and 3.5Mo: approximately 38.6, before any nitrogen contribution.
- ASTM B668 minimum composition, 26Cr and 3.0Mo: approximately 35.9.

A value of 32 is the common rule-of-thumb threshold for seawater pitting resistance, so the grade sits above it across its composition range. PREN is calculated from chemistry and is not a measured property. Where pitting margin governs the design, specify a critical pitting temperature or crevice test.

## Mechanical properties, solution annealed, 20 degrees C

| Property | ASTM B668 requirement | Published bar data |
|---|---|---|
| Tensile strength, Rm | 503 MPa (73 ksi) min | 500 to 750 MPa |
| Proof strength, Rp0.2 | 214 MPa (31 ksi) min | >= 220 MPa (>= 32 ksi) |
| Elongation, A | 40 per cent min | >= 35 per cent |
| Hardness | not specified | <= 220 HB |

Bar elongation is measured on a proportional gauge length, L0 = 5.65 x square root of S0. Values from a fixed 50 mm gauge length are not directly comparable. Acceptance figures for an order are those on the agreed specification.

### Impact strength

The microstructure is fully austenitic, so impact strength stays good at room temperature and at cryogenic temperature, with published producer testing carried out down to minus 196 degrees C. In-house Charpy V-notch testing covers down to minus 60 degrees C. Testing below that is placed with an accredited third-party laboratory and reported with the mill certificate.

## Physical properties at 20 degrees C

| Property | Value |
|---|---|
| Density | 8.0 g/cm3 (0.289 lb/in3) |
| Mean thermal expansion, 20 to 100 C | 15 to 16 x 10-6 per degree C |
| Thermal conductivity | approx. 12 W/(m.K) |
| Specific heat capacity | approx. 450 J/(kg.K) |
| Electrical resistivity | approx. 1.0 micro-ohm.m |
| Magnetic response | Non-magnetic in the annealed condition |

Published thermal conductivity for this grade varies between roughly 10 and 14.5 W/(m.K) at 20 degrees C depending on the source consulted. Treat the value above as indicative.

## Heat treatment

Solution anneal at 1100 to 1160 degrees C (2010 to 2120 degrees F), hold 10 to 30 minutes, quench in water. Thin sections may be cooled rapidly in air. The alloy does not respond to precipitation hardening or to quench and temper, so strength comes from composition and cold work rather than from heat treatment.

## Corrosion behaviour

The grade is characterised by very high corrosion resistance in strong acids, very good resistance to stress corrosion cracking and intergranular corrosion, high resistance to pitting and crevice corrosion, and good weldability.

- **Phosphoric acid.** The application the alloy is best known for. Tubing in this grade has been used to replace graphite heat exchangers in wet-process phosphoric acid evaporation. High chromium with molybdenum and copper is what lets it tolerate the chloride and fluoride impurities carried over from phosphate rock.
- **Sulphuric acid.** Suited to piping and heat exchangers, with useful windows at roughly 40 to 70 per cent deaerated acid and above 85 per cent. In concentrated acid its resistance is of the same order as a nickel-chromium-molybdenum alloy of the Alloy C type.
- **Chlorides.** High chromium and molybdenum place it well against pitting and crevice corrosion in chloride-bearing media, including seawater-cooled exchangers, desalination plant and chloride-rich utility water.
- **Cracking and sour service.** High nickel gives good resistance to chloride stress corrosion cracking, and the 0.030 per cent carbon maximum limits intergranular attack after welding. Listed in NACE MR0175 / ISO 15156 and NACE MR0103. Listing is not blanket approval; acceptance depends on the environmental, hardness and condition limits those standards set.

Corrosion data is environment-specific. It is a screening tool, not a warranty of performance in a given stream.

## Welding

Weldability is good. Manual metal arc and gas-shielded arc are both suitable, with TIG the first choice.

| Parameter | Recommendation |
|---|---|
| Heat input | below 1.0 kJ/mm |
| Interpass temperature | below 150 degrees C |
| Technique | string bead, avoid wide weaving |
| TIG and MIG filler | ISO 14343 S 27 31 4 Cu L, equivalent to AWS A5.9 ER383 |
| MMA electrode | ISO 3581 E 27 31 4 Cu L R, equivalent to AWS A5.4 E383-16 |

Matching composition filler is used because an undermatched filler loses the copper and molybdenum the parent metal depends on.

## Machining

Against a machinability-improved 316 or 316L, reduce turning speed by about 50 to 55 per cent when using coated cemented carbide, with a similar reduction in other operations. Reduce feeds only slightly and with care, since a light feed lets the tool rub and work-harden the surface rather than cut it. Rigid setups, sharp positive-rake geometry and generous coolant all help. A proof-machined N08028 part carries more machining hours than the same geometry in 316.

## Production route

1. Melt. EF then LF refining, with VOD for low carbon and controlled nitrogen.
2. Remelt. Protective-atmosphere ESR where the order calls for a remelted ingot.
3. Forge. Open-die press or radial-axial ring mill.
4. Heat treat. Solution anneal and water quench.
5. Machine. Rough or finish turning, boring, CNC work.
6. Test and certify. Chemistry, mechanical, NDT, then EN 10204 3.1 or 3.2.

| Capability | Detail |
|---|---|
| Melting | EF, LF, VOD, IF, VIM, protective-atmosphere ESR, VAR. 60 t maximum heat size. |
| Presses | 6,300 t, 4,000 t and 2,000 t open-die |
| Ring mills | Radial-axial at 6 m, 3 m and 1 m |
| Heat treatment | 14 furnaces, car-bottom to 8,000 x 2,000 x 2,000 mm plus two 15 m deep pit furnaces |
| Chemical analysis | Optical emission spectrometry to ASTM E415, carbon and sulphur to ASTM E1019, handheld PMI |
| Ultrasonic testing | ASTM A388 or EN 10228-3, SEP 1921 on request |
| Surface NDT | Liquid penetrant to ASTM E165, the grade being non-magnetic |
| Mechanical testing | Tensile to ASTM A370, Charpy V-notch to minus 60 C, hardness, grain size to ASTM E112 |
| Third-party testing | ASTM A262, G28, G48, impact below minus 60 C, bench hardness |
| Certification | EN 10204 3.1, or 3.2 witnessed by BV, DNV, LR, SGS, TUV or the customer's inspector |

## Forged forms and size envelope

| Form | Typical service | Size limit |
|---|---|---|
| Seamless rolled rings | Chemical and petrochemical plant, pressure equipment, gear and slewing ring blanks | OD 50 to 6,000 mm |
| Forged rings, retaining and seat rings | Sections outside the ring mill envelope | to 30 t piece weight |
| Forged flanges and nozzles | Exchangers, pressure vessels, process piping | to 5,000 mm |
| Tube sheets, discs, covers | Exchangers and vessels, proof-machined for volumetric inspection | to 5,000 mm machined diameter |
| Forged shafts and spindles | Pumps, agitators, compressors, crystalliser and evaporator equipment | to 14,000 mm turned length |
| Bushings, sleeves, bored cylinders | Subsea and deepwater production equipment, rotating machinery | to 1,600 mm dia. x 10,000 mm |
| Round bar, blocks, bodies | Valve bodies, bonnets, stems, seat rings | by drawing |
| Wellhead and tree parts | Wellheads, Christmas trees, BOPs, risers | API 6A, NACE MR0175 |

## How to order

Send a drawing, or finished dimensions with tolerances, to sales@steelforgepieces.com. Include the quantity, the applicable standard, the NDT class, whether you need EN 10204 3.1 or 3.2, and whether the part should arrive as-forged, proof-machined or finish-machined.

Jiangyin Jiangnan Metal Co., Ltd., No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Telephone +86 189 2135 9659. Email sales@steelforgepieces.com.

## Related grades

Incoloy 825, Incoloy 926, Alloy 31, Hastelloy C-276, Hastelloy G-3, Inconel 625, Alloy 59, Nitronic 50.

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Composition and mechanical limits quoted from ASTM B668 and published producer datasheets for the grade. Figures are for guidance in material selection and are not a warranty. Acceptance criteria for any order are those stated on the agreed purchase specification.

Copyright 1997 to 2026 Jiangyin Jiangnan Metal Co., Ltd.