Corrosion Resistant Alloys
NAS 255 (UNS N08904) - Super Austenitic Stainless Steel
An austenitic stainless steel with corrosion resistance superior to SUS 316L and SUS 317L, NAS 255 (UNS N08904, SUS 890L) includes 1.5 percent added copper for excellent resistance against such reducing acids as sulfuric and phosphoric acid. NAS 255 is used in chemical plants as well as a wide range of other applications. Nippon Yakin supplies this product in plate, sheet and strip forms.
Coil
Sheet
Plate
Designation / Standard
| Nippon Yakin Grade | ASTM A240 | EN | JIS G4304/4305 |
|---|---|---|---|
| NAS 255 | UNS N08904 | 1.4539 | SUS 890L |
Chemical Composition
SUS 890L
| C | Si | Mn | P | S | Ni | Cr | Mo | Cu | N | |
|---|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 23.00 | 19.00 | 4.00 | 1.00 | ― |
| Max | 0.020 | 1.00 | 2.00 | 0.045 | 0.03 | 28.00 | 23.00 | 5.00 | 2.00 | ― |
UNS N08904
| C | Si | Mn | P | S | Ni | Cr | Mo | Cu | N | |
|---|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 23.0 | 19.0 | 4.0 | 1.0 | ― |
| Max | 0.020 | 1.00 | 2.00 | 0.045 | 0.035 | 28.0 | 23.0 | 5.0 | 2.0 | 0.10 |
Physical Properties
| Specific heat (J/kg･K) | 452 | |
| Specific resistivity (μΩ･cm) | 97 | |
| Thermal conductivity (W/m･K) | 12.2 | |
| Coefficient of thermal expansion (10-6/℃) | 20–200℃ | 14.9 |
| 20–300℃ | 15.3 | |
| 20–400℃ | 15.7 | |
| Young's modulus (MPa) | 19.0 x 104 | |
| Modulus of rigidity (MPa) | 71.0 x 104 | |
| Ferromagnetism | None | |
| Melting point (℃) | 1360-1397 | |
Mechanical Properties
Mechanical Properties at Room Temperature
SUS 890L
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness (HRB) |
|---|---|---|---|
| ≥ 215 | ≥ 490 | ≥ 35 | ≤ 90 |
UNS N08904
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness (HRB) |
|---|---|---|---|
| ≥ 220 | ≥ 490 | ≥ 35 | ≤ 90 |
Examples
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness (HRB) |
|
|---|---|---|---|---|
| Plate, 12-mm thick |
247 | 593 | 57.2 | 86 |
| Cold-rolled sheet, 2-mm thick |
291 | 632 | 43.0 | 79 |
| Cold-rolled sheet, 0.5-mm thick |
302 | 630 | 43.0 | 80 |
High-Temperature Strength
Corrosion Resistance
Acid Resistance
NAS 255 exhibits superior resistance to corrosion against such reducing acids as sulfuric acid and phosphoric acid.
Pitting Corrosion Resistance
Weldability
The weldability is similar to any ordinary austenitic stainless steel, and neither preheating nor post-heating are required. For consumables, we recommend a type having at least as much corrosion resistance as the environment if the conditions are severely corrosive. For less stringent environments, a consumable with a composition similar to NAS 255 may be used for metal joining.
Heat Treatment
As NAS 255 is an austenitic stainless steel, the same sort of heat treatment may be used. For solution treatment, water cooling between 1030 and 1180℃ should be used, as recommended in JIS G4305.
