Corrosion Resistant Alloys
NAS 254N (UNS S32053) - Super Austenitic Stainless Steel
A highly corrosion-resistant austenitic stainless steel, NAS 254N (SUS 836L, UNS S32053, ASME code case 2445-1) is high in nickel, chromium and molybdenum content. NAS 254N is endowed with excellent resistance to corrosion even in such harsh environments as high temperature seawater. Among the corrosion-resistant stainless steel alloys on the market, NAS 254N is an economic choice with corrosion resistance comparable to Hastelloy® alloys and pure titanium. 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 254N | UNS S32053 | ― | SUS 836L |
Chemical Composition
SUS 836L
| C | Si | Mn | P | S | Ni | Cr | Mo | N | |
|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 24.00 | 19.00 | 5.00 | ― |
| Max | 0.030 | 1.00 | 2.00 | 0.045 | 0.030 | 26.00 | 24.00 | 7.00 | 0.25 |
UNS S32053
| C | Si | Mn | P | S | Ni | Cr | Mo | N | |
|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 24.0 | 22.0 | 5.0 | 0.17 |
| Max | 0.030 | 1.00 | 1.00 | 0.030 | 0.010 | 26.0 | 24.0 | 6.0 | 0.22 |
Physical Properties
| Specific heat (J/kg･K) | 460 | |
| Specific resistivity (μΩ･cm) | 93.1 | |
| Thermal conductivity (W/m･K) | 10.9 | |
| Coefficient of thermal expansion (10-6/℃) | 30–200℃ | 14.9 |
| 30–300℃ | 15.5 | |
| 30–400℃ | 16.0 | |
| Young's modulus (MPa) | 18.8 x 104 | |
| Ferromagnetism | None | |
| Melting point (℃) | 1330-1390 | |
Mechanical Properties
Mechanical Properties at Room Temperature
SUS 836L
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness | |
|---|---|---|---|---|
| (Hv) | (HB) | |||
| ≥ 275 | ≥ 640 | ≥ 40 | ≤ 230 | ≤ 217 |
UNS S32053
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness | |
|---|---|---|---|---|
| (Hv) | (HB) | |||
| ≥ 295 | ≥ 640 | ≥ 40 | ― | ≤ 217 |
Examples
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness | ||
|---|---|---|---|---|---|
| (Hv) | (HB) | ||||
| Cold-rolled sheet, 2-mm thick |
354 | 722 | 48 | 185 | 166 |
| Hot-rolled plate, 6-mm thick |
377 | 744 | 49 | ― | 176 |
| Hot-rolled plate, 16-mm thick |
381 | 747 | 52 | ― | 174 |
High-Temperature Strength
Corrosion Resistance
NAS 254N is high in both chromium and molybdenum, which endow this stainless steel with excellent pitting corrosion and crevice corrosion resistance in high-chlorine environments. Its high nickel content also provides exceptional stress corrosion cracking resistance.
Pitting Corrosion Resistance
Stress Corrosion Cracking (SCC) Resistance
| Conditions | Occurrence of SCC | |
|---|---|---|
| MgCl2 | 30% Boil, 300hr | NO SCC |
| 35% Boil, 300hr | NO SCC | |
| 42% Boil, 300hr | SCC | |
| 20%NaCl + 1%Na2Cr-2O7 . 2H2O, 300hr Temp.105℃ | NO SCC | |
Test conditions: U-bending test piece, 2-mm thick, #400 finish)
Weather Resistance
Atmospheric exposure test data (exposure period: 2 years)
| Alloy | PRE | Inland environment (Hirakata) | Urban residential environment (Tokyo) | Coastal clean environment (Sotobo, Chiba) | Coastal industrial environment (Kawasaki) | Marine environment (splash conditions) |
|---|---|---|---|---|---|---|
| SUS 304 | 18 | ○ | △ | × | × | × |
| SUS 316 | 24 | ○ | ○ | × | × | × |
| NAS 64 | 38 | ○ | ○ | ○ | ○ | △ |
| NAS 254N | 44 | ○ | ○ | ○ | ○ | ○ |
* Pitting resistance equivalent, %Cr + 3.3 x %Mo + 16 x %N
○: No rusting
△: Maximum pitting depth ≪ 15 µm
×: Maximum pitting depth > 15 µm
Workability
Although NAS 254N can be hot- and cold-worked much like standard austenitic stainless steels such as SUS 304 and SUS 316, the high strength of the alloy must be kept in mind when doing so.
Weldability
Our NAS 254N alloy can be shield metal arc welded, TIG welded and plasma welded much as any standard austenitic stainless steel. We recommend using Hastelloy® C-type welding consumables with this material.
Machinability
As with any stainless steel endowed with a high nickel content, machining NAS 254N is more challenging than standard austenitic stainless steels, though NAS 254N is more easily handled than other nickel-based alloys. We recommend the use of an cemented carbide tool, and suggest combining a slower feed rate with a greater cutting depth.
Heat Treatment
As NAS 254N is an austenitic stainless steel, the same sort of heat treatment may be used. Typical heat treatments include:
- Solution treatment: 1125-1175℃ Water cooling
- Stress relief: 450-550℃ Air cooling
Pickling
A mixture of nitric and hydrofluoric acids is used in pickling. To the extent that NAS 254N is more resistant to corrosion than SUS 304, descaling is more difficult. Alkaline immersion for a short time before acid pickling and shot blasting if possible are effective at descaling.
Applications
- Seawater environments: marine structures, desalination systems, seawater heat exchangers, condenser tubes
- Chemical plants: PC manufacturing plants, bisphenol A manufacturing plants, carbon black manufacturing plants
- Pulp and paper mills: bleaching devices, scrubbers
- Medical and pharmaceutical product plants: centrifugal separators, reactor tanks
- Food production plants: soy sauce fermentation tanks, salty mirin tanks, dressing production equipment
- Salt production plants: Concentrated salt storage tanks, heated cans, evaporators, salt transportation production lines
- Anti-pollution equipment: thermal generation flue gas desulfurization plants
* Hastelloy is a registered trademark of Haynes International, Inc.
