Nippon Yakin Kogyo Co., Ltd
Nippon Yakin Kogyo NAS825 Corrosion Resistant Alloys
Manufacturer: Nippon Yakin Kogyo Co., Ltd
Model : NAS825
NAS825 (UNS N08825)
High Corrosion Resistant Nickel Alloy
NAS825 (NCF825, UNS N08825) is a high-Ni nickel alloy with high corrosion resistance, and possesses extremely high corrosion resistance against oxidizing and non-oxidizing acids. Nippon Yakin supplies this product in plate, sheet and strip form.
| Chemical Composition | 40Ni 23Cr 3Mo 2Cu 0.71Ti | ||
| Product shape |
|
 Sheet |
|
| Workability | Cold and hot workability approximately equal to Type 304, 316, and other standard austenitic stainless steels. | ||
| Weldability | Shielded metal arc welding, TIG welding, MIG welding are possible. Use Alloy 625, CNiCrMo-3 welding consumables. | ||
| Machinability | Machinability equivalent to standard austenitic stainless steels. Use high-speed steel tool or super-hard tool, slow feed speed, and large cut depth are advised. | ||
| Heat Treatment | Solution annealing at 930–1030°C, followed by quenching in water or rapidly cooling. | ||
| Pickling | Nitric acid and hydrofluoric acid are used. High corrosion resistance of NAS625 makes scale removal difficult. Alkaline solution immersion before pickling recommended. | ||
| Applications | Chemical plants, Oil and gas extraction, Sheathed heater, Umbilical cable. | ||
Coil
PlateSteel Grade/Standard
| Nippon Yakin Grade | JIS G 4902 | ASTM B424 | DIN 17750 |
|---|---|---|---|
| NAS825 | NCF825 | UNS N08825 | 2.4858 |
Chemical Composition
| C | Si | Mn | P | S | Ni | Cr | Fe | Mo | Cu | Al | Ti | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Specification (NCF825) | ≤0.05 | ≤0.50 | ≤1.00 | ≤0.030 | ≤0.015 | 38.00-46.00 | 19.50-23.50 | Bal. | 2.50-3.50 | 1.50-3.00 | ≤0.20 | 0.60-1.20 |
| Specification (UNS N08825) | ≤0.05 | ≤0.5 | ≤1.0 | — | ≤0.03 | 38.0-46.0 | 19.5-23.5 | ≥22.0 | 2.5-3.5 | 1.5-3.0 | ≤0.20 | 0.6-1.2 |
Physical Properties
| Density [g/cm³] | 8.14 |
|---|---|
| Specific heat [J/kg•K] (20°C) | 444 |
| Electrical resistivity [μΩ•cm] | 112 |
| Thermal conductivity [W/m•K] | 10.9 |
| Average coefficient of thermal expansion [10⁻⁶/°C] | 20–100°C 13.4 |
| 20–200°C 14.1 | |
| 20–500°C 15.1 | |
| 20–900°C 16.9 | |
| Young’s modulus [MPa] | 19.7 × 10⁴ |
| Magnetism | None |
| Melting range [°C] | 1370–1400 |
Mechanical Properties
Mechanical Properties at Room Temperature
| 0.2% proof stress (MPa) | Tensile strength (MPa) | Elongation (%) | Hardness (HRB) | |
|---|---|---|---|---|
| Specification (NCF825) | ≥235 | ≥580 | ≥30 | ≤207 |
| Specification (UNS N08825) | ≥241 | ≥586 | ≥30 | ≤207 |
| Cold-rolled sheet (1.0mm) | 263 | 612 | 47 | 144 |
| Hot-rolled plate (8.0mm) | 250 | 612 | 54 | 144 |
| Hot-rolled plate (33.6mm) | 235 | 588 | 48 | 137 |
High Temperature Strength
Corrosion Resistance
Because NAS825 has high contents of chromium, molybdenum, and copper, it provides excellent general (overall) corrosion resistance against oxidizing and non-oxidizing acids. Corrosion resistance against sulfuric acid is particularly good. Due to its high contents of chromium, molybdenum, and nickel, pitting corrosion resistance, crevice corrosion resistance, and stress corrosion cracking (SCC) resistance under chloride environments are also excellent in comparison with Type 316L. Because the carbon content of NAS825 is held to an extremely low level, sensitization during welding is minimal, and this is also an alloy with low grain boundary corrosion sensitivity.
Pitting Corrosion Resistance
| Alloy | ASTM G48 Method A | ASTM G48 Method C Critical pitting corrosion temperature CPT (°C) |
|---|---|---|
| SUS316L | — | 15 |
| NAS329J3L | ○ | 50 |
| NAS254N | ○ | 80 |
| NAS825 | ○ | 60 |
Test conditions: ASTM G48 Method A (○: No pitting corrosion, X: Pitting corrosion)
– Test solution: 6% FeCl₃
– Test temperature: 22°C, 50°C (Recommended temperature in this test)
– Test time: 72h
Crevice Corrosion Resistance
| Alloy | ASTM G48 Method D |
|---|---|
| SUS316L | <10 |
| NAS329J3L | 25 |
| NAS254N | 45 |
| NAS825 | 10 |
Test conditions: ASTM G48 Method D
– Test solution: 6% FeCl₃ + 1% HCl
– Test time: 72h
Stress Corrosion Cracking Resistance
| Alloy | MgCl₂ concentration (boiling point °C in brackets) | 42% (153°C) | 35% (146°C) | 25% (119°C) | 20% (110°C) |
|---|---|---|---|---|---|
| SUS316L | x | x | x | x | |
| NAS329J3L | ○ | ○ | x | x | |
| NAS254N | ○ | ○ | ○ | ○ | |
| NAS825 | ○ | ○ | ○ | ○ |
Test conditions:
– Immersion in boiling MgCl₂ solution.
– Test time: 300h.
○: No stress corrosion cracking, x: Stress corrosion cracking.
Acid Resistance
Corrosion Rate in Sulfuric Acid at 80°C (mm/y)
| Alloy | 5% | 10% | 20% | 40% | 60% | 80% |
|---|---|---|---|---|---|---|
| SUS316L | 1.07 | 4.69 | 7.11 | 764.9 | 704.5 | 33.74 |
| NAS329J3L | 0.01 | 0.17 | 0.46 | 385.9 | 1456 | 108.4 |
| NAS254N | 0.02 | 0.05 | 0.08 | 2.16 | 7.73 | 2.03 |
| NAS825 | 0.03 | 0.10 | 0.22 | 0.73 | 0.23 | 0.73 |
Corrosion Rate in Hydrochloric Acid at 80°C (mm/y)
| Alloy | 0.1% | 1% | 3% | 5% |
|---|---|---|---|---|
| SUS316L | 0.06 | 0.73 | 14.88 | 31.44 |
| NAS329J3L | 0.02 | 0.27 | 3.76 | 11.86 |
| NAS254N | 0.01 | 0.01 | 0.04 | 0.11 |
| NAS825 | 0.01 | 0.22 | 2.26 | 3.14 |
Test time: 24h
Reference
| Alloy | JIS | UNS No. | Chemical Composition |
|---|---|---|---|
| SUS316L | SUS316L | S31603 | 17Cr-12Ni-2Mo |
| NAS329J3L | SUS329J3L | S32205 | 22Cr-5.3Ni-3.0Mo-0.16N |
| NAS254N | SUS329J4L | S32506 | 25Cr-6.8Ni-3.5Mo-0.17N |
| NAS825 | NCF825 | N08825 | 40Ni-23Cr-3Mo-2Cu-0.7Ti |
Workability
Cold and hot workability are approximately equal to those of standard austenitic stainless steels.
Weldability
Possible welding methods include shielded metal arc welding, TIG welding, and MIG welding, in the same manner as with standard austenitic stainless steels. As welding consumables, Alloy 625, DNiCrMo-3 should be used.
Machinability
NAS825 has machinability approximately equivalent to standard austenitic stainless steels. In machining, use of a high-speed steel tool or superhard tool and a slow feed speed and large cut depth are advised.
Heat Treatment
Solution annealing of NAS825 is normally performed at the temperature range from 930 to 1030°C followed by being quenched in water or rapidly cooled by other means.
Pickling
A mixture of nitric acid and hydrofluoric acid is used in pickling. However, due to the high corrosion resistance of NAS825, scale is somewhat difficult to remove in comparison with Type 304. Therefore, the material should be immersed in an alkaline solution before pickling, or if possible, shot blasting is extremely effective.
Applications
Chemical plants, Oil and gas extraction, Sheathed heater, Umbilical cable.
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