1.4539 is a high-alloy, low-carbon austenitic stainless steel with molybdenum and copper additions. This datasheet presents the material within the European standard system.
With about 25% nickel, 20% chromium, 4.5% molybdenum and 1.5% copper, 1.4539 provides corrosion resistance well above standard CrNi grades. The high nickel and molybdenum give good resistance to chloride stress-corrosion cracking and to pitting, while the copper addition gives particularly good resistance to sulphuric and phosphoric acids. The very low carbon (<=0.02%) keeps it resistant to intergranular corrosion in both the delivery and the sensitised (welded) condition. It is approved for service down to -196 °C.
Typical applications include equipment for sulphuric and phosphoric acid, flue-gas desulphurization plant, seawater cooling and desalination, pulp-and-paper bleaching equipment, and components for the chemical, cryogenic, food and pharmaceutical industries.
Values for the solution-annealed condition, per EN reference data.
| Property | Value | Unit |
|---|---|---|
| Density | 8.0 | g/cm³ |
| Melting range | 1300-1390 | °C |
| Young's modulus (20 °C) | 195 | GPa |
| Thermal conductivity (20 °C) | 12 | W/m·K |
| Coefficient of thermal expansion (20-100 °C) | 15.3 | µm/m·°C |
| Specific heat (20 °C) | 450 | J/kg·K |
| Minimum service temperature | -196 | °C |
| Magnetic response | Non-magnetic (austenitic) | — |
Composition per EN 10088-2 (W.Nr. 1.4539, X1NiCrMoCu25-20-5).
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Iron | Fe | Balance | — | Base element |
| Nickel | Ni | 24.0 | 26.0 | Austenite stability; SCC resistance |
| Chromium | Cr | 19.0 | 21.0 | Passivity; corrosion resistance |
| Molybdenum | Mo | 4.0 | 5.0 | Pitting + crevice resistance |
| Copper | Cu | 1.2 | 2.0 | Sulphuric/phosphoric-acid resistance |
| Manganese | Mn | — | 2.0 | Deoxidiser |
| Silicon | Si | — | 0.70 | Deoxidiser |
| Nitrogen | N | — | 0.15 | Austenite stability |
| Carbon | C | — | 0.020 | Very low (intergranular resistance) |
| Phosphorus | P | — | 0.030 | Residual impurity |
| Sulphur | S | — | 0.010 | Residual impurity |
Nominal: 25Ni-20Cr-4.5Mo-1.5Cu. Note the tighter EN ranges (Ni 24-26, Cr 19-21) versus the broader EN.4539 bands.
Solution-annealed (+AT) condition, per EN 10088-2 for W.Nr. 1.4539.
| Property | Value | Unit |
|---|---|---|
| Tensile strength (Rm) | 520-720 | MPa |
| 0.2% proof strength (Rp0.2) | >=220 | MPa |
| 1.0% proof strength (Rp1.0) | >=260 | MPa |
| Elongation at fracture (A) | >=35 | % |
| Brinell hardness | <=220 | HB |
| Impact energy (KV, +20 °C, long.) | >=120 | J |
| Impact energy (KV, -196 °C) | >=60 | J |
Values per EN 10088-2 (the +A soft-annealed condition gives Rm 520-730, HB <=230). Confirm against the inspection certificate (EN 10204).
| Environment | Performance | Notes |
|---|---|---|
| Sulphuric acid | Excellent | Cu addition is key |
| Phosphoric acid | Excellent | Including wet-process acid |
| Chloride pitting | Good | PREN ~34-36 |
| Crevice corrosion | Good | Better than 1.4404 |
| Chloride SCC | Excellent | High Ni content |
| Intergranular (welded) | Resistant | Very low carbon |
Resistance is intermediate between standard CrNiMo grades and the 6Mo super-austenitics.
A solid-solution alloy; it cannot be hardened by heat treatment.
Solution Anneal approximately 1060-1140 °C, followed by rapid cooling (water or air) to dissolve secondary phases and retain optimum corrosion resistance.
Readily weldable by gas-shielded arc, arc and resistance welding. A matching or over-alloyed nickel-base filler maintains corrosion resistance in the weld.
| Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Excellent | Matching 1.4539 or Ni-base (NiCr21Mo type) |
| GMAW / MIG | Good | Matching 1.4539 or Ni-base |
| SMAW / stick | Good | Matching or Ni-base electrode |
No preheat required; control interpass temperature. Resistant to intergranular corrosion in the as-welded condition owing to the low carbon.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Machinability | Moderate; work-hardens; sharp tooling, slow-to-moderate speeds, positive feeds |
| Work hardening | Higher than carbon steel; avoid dwelling |
| Coolant | Ample flood coolant |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | Good ductility; work-hardens |
| Hot forming | ~1150-900 °C; solution anneal + quench afterward |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Chemical processing | Sulphuric/phosphoric-acid equipment | Cu-enhanced acid resistance |
| Flue-gas desulphurization | Scrubbers, ducting | Chloride + acid resistance |
| Pulp & paper | Bleaching equipment | Halide resistance |
| Seawater / desalination | Heat exchangers, condensers | Pitting + SCC resistance |
| Cryogenic | Equipment to -196 °C | Toughness at low temperature |
| Product Form | Standard | Notes |
|---|---|---|
| Plate, sheet and strip | EN 10088-2 · W.Nr. 1.4539 | X1NiCrMoCu25-20-5 |
| Bar, rod, wire and sections | EN 10088-3 · W.Nr. 1.4539 | — |
| Flat products for pressure | EN 10028-7 · W.Nr. 1.4539 | — |
| Seamless / welded tube | EN 10216-5 / EN 10217-7 · W.Nr. 1.4539 | — |
| Forgings | EN 10250-4 · W.Nr. 1.4539 | — |
| Sour service | ISO 15156-3 | Acid-gas applications |
High-alloy austenitic stainless steel. W.Nr. 1.4539 (X1NiCrMoCu25-20-5); EN 10088-2 / 10088-3.
| W.Nr. | Cr % | Mo % | Cu % | PREN | Best Used For |
|---|---|---|---|---|---|
| 1.4539 | 19-21 | 4.0-5.0 | 1.2-2.0 | ~34 | Sulphuric/phosphoric acid; general |
| 1.4404 | 16.5-18.5 | 2.0-2.5 | — | ~24 | General corrosion service |
| 1.4438 | 17.5-19.5 | 3.0-4.0 | — | ~30 | Higher pitting than 1.4404 |
| 1.4547 (1.4547-type) | 19.5-20.5 | 6.0-7.0 | 0.5-1.0 | ~43 | 6Mo seawater service |
| 1.4529 (926) | 19-21 | 6.0-7.0 | 0.5-1.5 | ~45 | 6Mo seawater service |




