Bar and Rod
Plate and Sheet
Strip
Pipe and Tube
Wire
Welding
Powder Material
Cast Products
Forged Products
Fittings
Fastening
Round Bar:
φ2–500 mm, 1–6 m length
Flat/Square Bar:
4–100 mm thickness/width
Hex Bar:
A/F 3–100 mm
Hollow Bar:
OD 20–300 mm
Sheet:
0.3–6 mm thickness
Medium Plate:
6–25 mm thickness
Heavy Plate:
25–100 mm thickness
Standard Strip:
0.05–3 mm thick,
10–600 mm wide
Precision strip:
0.01–0.5 mm thick,
tight tolerance ±0.005 mm
Foil:
0.005–0.1 mm thick
Seamless Tube:
OD 6–450 mm,
WT 1–50 mm,
1–12 m length
Welded Tube:
OD 10–600 mm,
WT 1–20 mm
Capillary Tube:
OD 1–10 mm,
WT 0.1–2 mm
Wire Form:
Cold Drawn Wire,
Bright Wire,
Spring Wire,
Fine Wire,
Ultra-fine Wire
General Diameter:
φ0.1–10 mm
Coil Weight:
50–500 kg,
customizable tolerance
Solid Wire:
φ0.8–4.0 mm
Flux-cored Wire:
φ1.2–4.0 mm
Welding Rod:
φ2.0–5.0 mm
Powder Form:
AM 3D Printing Powder,
Spherical Powder,
Gas-atomized Powder,
Water-atomized Powder
Particle Size:
10–150 μm
Sphericity:
≥90% for AM grade
Cast Ingot:
φ200–800 mm
Precision Casting:
min wall 0.5 mm
Cast Pipe:
OD 100–600 mm,
WT 10–50 mm
Forged Bar:
Φ35–500 mm
Forged Ring:
OD 200–2000 mm
Forging Weight:
1–5000 kg
Fittings Form:
Elbow, Tee, Reducer, Flange, Cap, Outlet, Lap Joint
Size range:
1/2''–24'' (DN15–DN600)
Wall thickness:
Sch10–Sch160, STD, XS, XXS
Pressure Class:
150–2500 LB
Fastening Form:
Bolt, Nut, Screw, Stud, Washer, Pin, Rivet
Metric: M3–M64
Imperial: #4–2.5''
Length: 6–500 mm
N08028 is a high-alloy, multi-purpose austenitic stainless steel (iron–nickel–chromium–molybdenum–copper) developed for service in highly corrosive conditions. This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.
It is characterised by very high corrosion resistance in strong acids, very good resistance to stress-corrosion cracking (SCC) and intergranular corrosion across a range of environments, high resistance to pitting and crevice corrosion, and good weldability. The high chromium (27%) and nickel (31%) contents give excellent SCC resistance; molybdenum and copper provide outstanding resistance to sulphuric and phosphoric acids; and the low carbon content (≤0.020%) minimises sensitisation in welded joints.
Originally developed for the manufacture of phosphoric acid — where it is today the most widely used metallic material for evaporator tubes by the "wet" method — it is also used in sulphuric-acid plant, deep sour oil and gas wells, fluoride-bearing off-gas handling, nuclear-plant heat exchangers, and seawater/chloride-bearing cooling-water systems. It should not be exposed to temperatures above ~593 °C (1100 °F) for prolonged periods, to avoid embrittlement.
Values per manufacturer (Alleima / Sandvik) data, solution-annealed condition.
| Property | Value | Unit |
|---|---|---|
| Density | 8.0 | g/cm³ |
| Young's modulus (20 °C) | 195 | GPa |
| Specific heat capacity (20 °C) | 460 | J/kg·K |
| Thermal conductivity (20 °C) | 12 | W/m·K |
| Electrical resistivity (20 °C) | 1.0 | µΩ·m |
| Coefficient of thermal expansion (20–100 °C) | 15.8 | µm/m·°C |
| Maximum service temperature (continuous) | ~593 | °C |
| Structure | Austenitic (FCC) | — |
Nominal composition per ASTM B668 (UNS N08028).
| Element | Symbol | Value | Role in Alloy |
|---|---|---|---|
| Iron | Fe | Balance | Base element; austenitic matrix |
| Chromium | Cr | 27 | Passive film; pitting/SCC/acid resistance |
| Nickel | Ni | 31 | SCC resistance; austenite stabiliser |
| Molybdenum | Mo | 3.5 | Pitting/crevice and reducing-acid resistance |
| Copper | Cu | 1.0 | Sulphuric/phosphoric-acid resistance |
| Nitrogen | N | ≤0.1 | Austenite stabiliser; strength |
| Carbon | C | ≤0.020 | Low; minimises sensitisation |
| Manganese | Mn | ≤2.0 | Deoxidiser |
| Silicon | Si | ≤0.7 | Deoxidiser |
| Phosphorus | P | ≤0.020 | Residual impurity |
| Sulphur | S | ≤0.010 | Residual impurity |
Typical values, solution-annealed and quenched condition (1 MPa = 1 N/mm²).
| Property | Value | Source |
|---|---|---|
| Ultimate tensile strength | 500–750 MPa | Manufacturer / ASTM B668 |
| 0.2% proof strength (yield) | ≥220 MPa | Manufacturer / ASTM B668 |
| Elongation at break | ≥35 % | Manufacturer |
| Hardness | ~230 HB | Manufacturer |
| Impact toughness (KV, 20 °C) | >100 J | Manufacturer |
| Impact toughness (KV, –196 °C) | >60 J | Manufacturer |
Cold-worked material can be supplied with yield strength exceeding ~860 MPa (125 ksi). The alloy is not age-hardenable; higher strength is achieved by cold work. Values are typical; confirm against the mill test certificate for each delivery.
| Environment | Performance | Notes |
|---|---|---|
| Phosphoric acid (wet-process) | Outstanding | The benchmark material for evaporator tubes; far more tolerant of Cl⁻/F⁻ impurities than other high-alloy grades |
| Sulphuric acid | Outstanding | Resistant 40–70% and >85%; comparable to Alloy C in 98% H₂SO₄ |
| Hydrochloric acid | Very Good | Better than lower Cr-Mo stainless steels |
| Hydrofluoric / hydrofluosilicic acid | Very Good | Suitable where these occur as impurities |
| Nitric acid | Excellent | <0.15 mm/y in boiling 65% HNO₃ (ASTM A262 C) |
| Formic / acetic acid | Excellent | More resistant than 316L, 317L and 904L |
| Chloride stress-corrosion cracking | Outstanding | 27% Cr + 31% Ni; resists SCC where 304/316 fail |
| Pitting and crevice corrosion | High | Higher CPT than 904L and 825 |
| Sodium hydroxide (caustic) | Very Good | Superior to 304/316; alternative to pure nickel |
| Sour service (H₂S + chlorides) | Excellent | NACE MR0103 / MR0175 listed |
Austenitic; NOT age-hardenable. Heat treatment is solution annealing only; strength is increased by cold work.
Solution Anneal Temperature: ~1080–1180 °C, followed by rapid cooling (water quench) Purpose: Dissolves precipitates, restores maximum corrosion resistance, recrystallises structure.
Service limit: Avoid prolonged exposure above ~593 °C (1100 °F) to prevent embrittlement. Solution annealing may be performed after welding to relieve residual stress where required.
Good weldability. TIG/GTAW is the first choice; MMA/SMAW and gas-shielded arc welding are also suitable. As a fully austenitic steel it has low thermal conductivity and high thermal expansion, so welding sequences should be planned to minimise distortion. Recommended heat input <1.0 kJ/mm and interpass temperature <150 °C, using a string-bead technique.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Excellent (first choice) | AWS A5.9 ER383 |
| GMAW / MIG | Good | AWS A5.9 ER383 |
| SMAW / stick | Good | AWS A5.4 E383-16 |
Low carbon content makes the risk of intergranular attack after welding minimal. Solution anneal after welding if residual stress is a concern.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Work hardening | Moderately high rate; intermediate anneals may be required |
| Tooling | Rigid setup, sharp tools (austenitic-stainless practice) |
| Coolant | Flood coolant recommended |
| Preferred condition | Solution-annealed |
Forming Processes
| Process | Notes |
|---|---|
| Hot forming | Followed by solution anneal for optimal corrosion resistance |
| Cold forming | Readily cold-formed; moderately high work-hardening rate; intermediate anneals for heavy reductions |
| Annealing | Recommended after hot or cold forming to restore SCC resistance |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Phosphoric acid production | Evaporator tubes, heat exchangers, piping | Resistance to Cl⁻/F⁻-contaminated wet-process acid |
| Sulphuric acid plant | Piping, heat exchangers | 40–70% and >85% H₂SO₄ resistance |
| Oil and gas | Sour-well production tubing, casing, liners, wirelines | SCC + sour-service resistance (NACE) |
| Fertiliser / fluoride off-gas | Scrubbers, gas-recovery equipment | Fluoride-bearing off-gas resistance |
| Nuclear power | Heat exchangers | SCC, pitting, crevice resistance |
| Seawater / cooling water | Seawater piping, chloride-cooled heat exchangers | Pitting and crevice resistance |
| Product Form | ASTM Standard | ASME / Code |
|---|---|---|
| Seamless tube and pipe | ASTM B668 | ASME Code Case 1325 |
| Plate, sheet and strip | ASTM B709 | — |
| Bar | ASTM B668-related | — |
| Fittings | ASTM A403 (composition/properties per B668) | — |
| Welding consumables | AWS A5.9 ER383 · AWS A5.4 E383-16 | — |
ASME Boiler and Pressure Vessel Code approved (Section I, III, VIII Div. 1); NACE MR0103 and NACE MR0175 / ISO 15156 listed.
| UNS | Ni % | Cr % | Mo % | Other | Best Used For |
|---|---|---|---|---|---|
| N08028 | 31 | 27 | 3.5 | Cu 1.0 | Phosphoric/sulphuric acid; sour gas; SCC resistance |
| N08904 | 25 | 20 | 4.5 | Cu 1.5 | Sulphuric acid; lower-alloy economy grade |
| N08825 | 42 | 21.5 | 3 | Cu 2.3 | Phosphoric/sulphuric acid; higher Ni |
| N08020 | 34 | 20 | 2.5 | Cu 3.3 | Sulphuric acid; Nb-stabilised |
| N10276 | bal | 15.5 | 16 | W 4 | Severe reducing acids; far higher Mo |
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