1.4958 is an austenitic, solid-solution iron–nickel–chromium alloy — the high-temperature, high-creep-strength variant of the 800 series. This datasheet presents the material within the European (DIN / EN / Werkstoff-Nummer / VdTÜV) standard system.
It has nearly the same base composition as alloy 800 but with a controlled carbon content of 0.05–0.10% and a coarse grain structure (grain size 5 or coarser (ISO 643)), produced by a high-temperature anneal at approximately 1150 °C (2100 °F). This combination of controlled chemistry and coarse grain gives significantly higher creep and stress-rupture strength than alloy 800, particularly in the 593–980 °C (1100–1800 °F) range. The chromium provides oxidation and corrosion resistance; iron resists internal oxidation; and the high nickel content maintains a ductile, stable austenitic structure with strong resistance to chloride-ion stress-corrosion cracking.
It is widely used where long-term strength at elevated temperature is essential: petrochemical furnace cracker tubes, pigtails, headers and reformer tubing; ethylene and ethylene-dichloride process equipment; power-plant superheater and reheater tubing; gas-cooled-reactor heat exchangers; and industrial-furnace radiant tubes, muffles, retorts and heat-treating fixtures. Where even higher rupture strength is required, 1.4958 gradeT (W.Nr. 1.4959) is used.
Values per Special Metals official datasheet, solution-annealed (coarse-grain) condition.
| Property | Value | Unit |
|---|---|---|
| Density | 7.94 | g/cm³ |
| Melting range | 1357–1385 | °C |
| Young's modulus (20 °C) | 196.5 | GPa |
| Shear modulus (20 °C) | 73.4 | GPa |
| Poisson's ratio (20 °C) | 0.339 | — |
| Specific heat capacity (0–100 °C) | 460 | J/kg·K |
| Coefficient of thermal expansion (20–100 °C) | 14.4 | µm/m·°C |
| Magnetic permeability (21 °C, annealed) | 1.014 | Essentially non-magnetic |
| Curie temperature | –115 | °C |
| Maximum service temperature | ~980 | °C |
Composition per EN 10095 (W.Nr. 1.4876 / 1.4958, X10NiCrAlTi32-20 / 32-21).
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Nickel | Ni | 30.0 | 35.0 | Austenite stability; SCC resistance |
| Chromium | Cr | 19.0 | 23.0 | Oxidation resistance |
| Iron | Fe | 39.5 | balance | Base element |
| Carbon | C | 0.05 | 0.10 | Creep strength (800H/HT) |
| Aluminium | Al | 0.15 | 0.60 | Oxidation; with Ti (Al+Ti 0.30–1.20) |
| Titanium | Ti | 0.15 | 0.60 | Carbide former; with Al |
| Manganese | Mn | — | 1.0 | Deoxidiser |
| Silicon | Si | — | 1.0 | Deoxidiser |
| Copper | Cu | — | 0.75 | Residual |
| Phosphorus | P | — | 0.030 | Residual impurity |
| Sulphur | S | — | 0.015 | Residual impurity |
Nominal: Fe-32Ni-21Cr-Al-Ti. Al+Ti combined 0.30-1.20%. The high-temperature (1.4958) variant restricts carbon to 0.05-0.10% and uses a higher solution-anneal for creep strength.
Solution-annealed (+AT) condition, per EN 10095 for W.Nr. 1.4876 / 1.4958.
| Property | Value | Unit |
|---|---|---|
| Tensile strength (Rm) | 500–750 | MPa |
| 0.2% proof strength (Rp0.2) | ≥210 | MPa |
| Elongation at fracture (A) | ≥30 | % |
| Brinell hardness | ≤192 | HB |
Values per EN; confirm against the inspection certificate (EN 10204).
| Environment | Performance | Notes |
|---|---|---|
| Creep / stress-rupture (593–980 °C) | Outstanding | Coarse grain + controlled carbon; main advantage over alloy 800 |
| High-temperature oxidation | Excellent | Protective Cr₂O₃ scale |
| Carburisation | Good | Resists carburising furnace atmospheres |
| Nitridation | Good | Resists nitriding atmospheres |
| Chloride stress-corrosion cracking | Excellent | High Ni content |
| Nitric / organic acids | Very Good | Good aqueous resistance |
| Sulphuric / hydrochloric acid | Limited | Not recommended for strong reducing acids |
| Metallurgical stability | Excellent | Stable austenite over full service range |
An austenitic solid-solution alloy; not age-hardenable. The defining treatment is a high-temperature solution anneal to develop coarse grain.
Solution Anneal (defining treatment) Temperature: ~1150 °C (2100 °F) Result: grain size 5 or coarser (ISO 643) — required for optimum creep and stress-rupture strength.
This higher anneal temperature (versus ~980 °C for basic alloy 800) is what distinguishes 800H. Cool rapidly through 540–760 °C where aqueous corrosion resistance is required, to limit sensitisation.
Good weldability by all common processes, similar to alloy 800. Welded fabrications for high-temperature service should use fillers matched to the application.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / GMAW | Excellent | Matching Ni-Cr-Fe filler (EN ISO 18274 S Ni 6082) |
| SAW (submerged-arc) | Good | Matching submerged-arc wire + flux |
| SMAW / stick | Good | Matching Ni-Cr-Fe electrode |
Use fillers matched to high-temperature service; for the highest-strength duty a Ni-Cr-Co-Mo filler may be specified.
Machining Guidelines
| Tooling | Cutting Speed | Feed |
|---|---|---|
| Coated carbide | 33.5–57.9 m/min | 0.20–0.89 mm/rev |
| High-speed steel | 10.7–29.0 m/min | 0.20–0.89 mm/rev |
Machining behaviour is the same as alloy 800; the alloy work-hardens during machining.
Forming Processes
| Process | Notes |
|---|---|
| Hot forming | 870–1200 °C; heavy forging 1010–1200 °C; avoid 650–870 °C (cracking risk) |
| Cold forming | Similar to 2.4816 / stainless |
| Re-anneal | ~1150 °C to restore coarse grain after heavy cold work |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Petrochemical | Furnace cracker tubes, pigtails, headers, reformer tubing | High creep-rupture strength at 593–980 °C |
| Chemical processing | Ethylene / ethylene-dichloride / acetic-anhydride / nitric-acid equipment | Strength + corrosion resistance |
| Power generation | Superheater / reheater tubing; gas-cooled-reactor heat exchangers | Long-term elevated-temperature strength |
| Industrial furnaces | Radiant tubes, muffles, retorts, heat-treating fixtures | Creep strength + oxidation resistance |
| Petroleum refining | Steam/hydrocarbon reformers, hydrodealkylation units | High-temperature stability |
| Product Form | DIN / EN Standard | VdTÜV | ISO / BS |
|---|---|---|---|
| Rod and bar | DIN 17460 | VdTÜV 412 | ISO 9723 · BS 3076NA15 |
| Forgings | DIN 17460 | — | ISO 9725 |
| Plate, sheet and strip | DIN 17460 | VdTÜV 412 | ISO 6208 · BS 3072NA15 |
| Seamless tube | DIN 17459 | VdTÜV 412 | ISO 6207 · BS 3074NA15 |
| Composition | DIN 17460 (W.Nr. 1.4958) | — | — |
| Welding consumables | Matching Ni-Cr-Fe filler (EN ISO 18274 S Ni 6082) | — | — |
VdTÜV-Werkstoffblatt 412 covers all product forms; high-temperature creep-rupture grade per EN 10095 family.
| W.Nr. | Ni % | Cr % | Other | Best Used For |
|---|---|---|---|---|
| 1.4958 | 30–35 | 19–23 | C 0.05–0.10, grain size ≥5 | High creep/rupture strength 593–980°C |
| 1.4876 | 30–35 | 19–23 | C ≤0.10, fine grain | General heat + corrosion to 816°C |
| 1.4959 | 30–35 | 19–23 | C 0.06–0.10, Al+Ti 0.85–1.20 | Highest creep-rupture strength |
| 2.4816 | ≥72 | 14–17 | Ni-base | Higher Ni; full chloride-SCC immunity |
| 1.4886 | 34–37 | 18–20 | Si 1.0–1.5 | Carburisation + thermal shock to 1148°C |




