Corrosion Resistant Alloys
NAS NW22 (UNS N06022), comparable to Hastelloy® C-22® Alloy
NAS NW22, comparable to Hastelloy® C-22® alloy, is a Ni-Cr-Mo alloy with excellent corrosion resistance in both oxidizing and reducing atmospheres. In this alloy, carbide precipitation in the heat affected zone (HAZ) is suppressed and corrosion resistance is improved by reducing the contents of C and Si. Based on these features, NAS NW22 is widely used in materials under severe environments such as chemical plants. Nippon Yakin supplies this product in plate, sheet and strip forms.
Coil
Sheet
Plate
Designation / Standard
| Nippon Yakin Grade | ASTM B575 | DIN 17744 / 17750 | JIS H4551 |
|---|---|---|---|
| NAS NW22 | UNS N06022 | 2.4602 | NW6022 |
Chemical Composition
NW6022
| C | Si | Mn | P | S | Ni | Cr | Mo | Fe | Co | W | V | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | ― | 20.0 | 12.5 | 2.0 | ― | 2.5 | ― |
| Max | 0.015 | 0.08 | 0.5 | 0.025 | 0.020 | Balance | 22.5 | 14.5 | 6.0 | 2.5 | 3.5 | 0.35 |
UNS N06022
| C | Si | Mn | P | S | Ni | Cr | Mo | Fe | Co | W | V | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | ― | 20.0 | 12.5 | 2.0 | ― | 2.5 | ― |
| Max | 0.015 | 0.08 | 0.50 | 0.02 | 0.02 | Balance | 22.5 | 14.5 | 6.0 | 2.5 | 3.5 | 0.35 |
Physical Properties
| Specific heat (J/kg･K) | 440 | |
| Specific resistivity (μΩ･cm) | 1114.0 | |
| Thermal conductivity (W/m･K) | 10.6 | |
| Thermal diffusivity (m²/s) | 2.8 x 10-6 | |
| Coefficient of thermal expansion (10-6/℃) | 20–100℃ | 12.4 |
| 20–200℃ | 12.4 | |
| 20–300℃ | 12.6 | |
| 20–400℃ | 13.1 | |
| 20–500℃ | 13.7 | |
| Young's modulus (MPa) | 20.4 x 104 | |
| Modulus of rigidity (MPa) | 78.8 x 104 | |
| Ferromagnetism | None | |
| Melting point (℃) | 1325-1372 | |
Mechanical Properties
NW 6022
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness (HRB) |
|---|---|---|---|
| ≥ 310 | ≥ 690 | ≥ 45 | ― |
UNS N06022
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness (HRB) |
|---|---|---|---|
| ≥ 310 | ≥ 690 | ≥ 45 | ≤ 100 |
Examples
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness (HRB) |
|
|---|---|---|---|---|
| Hot-rolled plate sheet, 12-mm thick |
367 | 744 | 73 | 84 |
| Cold-rolled sheet, 8-mm thick |
365 | 752 | 69 | 84 |
| Cold-rolled sheet, 3-mm thick |
383 | 782 | 57 | 86 |
Corrosion Resistance
Pitting Corrosion Resistance
| Alloy | Critical pitting corrosion temperature (CPT) | |
|---|---|---|
| 6%FeCl3 + 1%HCl solution (ASTM G48 Method C) |
Green death solution | |
| NAS NW22 | > 120℃ | > 120℃ |
| NAS NW276 | > 120℃ | > 120℃ |
| NAS 254N | 80℃ | 80℃ |
| NAS 329J3L | 50℃ | 45℃ |
| SUS 316L | 10℃ | 25℃ |
Crevice Corrosion Resistance
| Alloy | Critical pitting corrosion temperature (CCT) | |
|---|---|---|
| 6%FeCl3 + 1%HCl solution (ASTM G48 Method D) |
Green death solution | |
| NAS NW22 | > 100℃ | 110℃ |
| NAS NW276 | 100℃ | 110℃ |
| NAS 254N | 40℃ | 45℃ |
| NAS 329J3L | 25℃ | 30℃ |
| SUS 316L | < 0℃ | < 0℃ |
Test conditions:
- 1) ASTM G48 Method C: Test duration 72h
- 2) ASTM G48 Method D: Test duration 72h, crevice formation using a multi crevice
- 3) Immersion in green death solution: Test duration 24 h, test solution 7% H2SO4 + 3% HCl + 1% FeCl3 + 1% CuCl2; a multi crevice was used for the crevice corrosion test
Intergranular Corrosion Resistance
Test conditions:
ASTM G28 Method A
Test duration: 24h in a boiling solution of 50% H2SO4 - Fe2 (SO4)3 solution
Acid Resistance
| Test solution | Temperature (℃) |
Concentration (%) |
Corrosion rate (g/m²･hr) | ||||
|---|---|---|---|---|---|---|---|
| NAS NW22 | NAS NW276 | NAS 254N* | NAS 329J3L* | SUS 316L | |||
| H2SO4 | 80 | 5 | 0.01 | 0.02 | 0.02 | 0.00 | 1.10 |
| 10 | 0.02 | 0.03 | 0.02 | 0.14 | 2.92 | ||
| 20 | 0.02 | 0.04 | 1.16 | 3.33 | 20.1 | ||
| 40 | 0.04 | 0.06 | 1.78 | 250.5 | 291.3 | ||
| 60 | 0.47 | 0.08 | 1.86 | 263.1 | 72.0 | ||
| 80 | 0.34 | 0.03 | 2.82 | 90.4 | 11.1 | ||
| Boiling | 5 | 0.14 | 0.10 | 1.43 | 0.61 | 5.45 | |
| 10 | 0.25 | 0.16 | 2.49 | 3.30 | 18.0 | ||
| 20 | 0.72 | 0.33 | 6.18 | 76.2 | 108.7 | ||
| 40 | 3.24 | 1.44 | 21.0 | 271.7 | 297.8 | ||
| HCl | 80 | 0.1 | 0.00 | 0.00 | 0.00 | 0.00 | 0.01 |
| 1.0 | 0.00 | 0.02 | 0.00 | 0.01 | 2.45 | ||
| 2.0 | 0.01 | 0.03 | 3.15 | 19.0 | 6.66 | ||
| 3.0 | 0.03 | 0.33 | 12.8 | 51.5 | 13.6 | ||
| Boiling | 0.1 | 0.00 | 0.00 | 0.00 | 0.00 | 0.01 | |
| 1.0 | 0.13 | 0.23 | 0.13 | 4.82 | 6.32 | ||
| 2.0 | 1.32 | 0.91 | 27.8 | 56.7 | 33.6 | ||
| 3.0 | 3.63 | 1.64 | 54.2 | 145.2 | 69.1 | ||
Test condition: Test duration 24h
Converted to mm/y from unit corrosion rate, g/m²･h
mm/y = g/m²･h x 8.76/d (d: density)
[d] NAS NW22: 8.70g/cm³, NAS NW276: 8.90g/cm³, NAS 254N: 8.06 g/cm³, NAS 329J3L: 7.80 g/cm³, SUS 316L: 7.98 g/cm³
* NAS 254N: 23Cr-25Ni-5.5Mo-0.2N (austenitic super stainless steel)
* NAS 329J3L: 22.5Cr-5.3Ni-3.2Mo-0.16N (duplex stainless steel)
Stress Corrosion Cracking Resistance
| Alloy | MgCl2 concentration [boiling points (℃) shown in parentheses] | |||||
|---|---|---|---|---|---|---|
| 20% (108) | 25% (110) | 30% (115) | 35% (126) | 38% (134) | 42% (142) | |
| NAS NW22 | ○ | ○ | ○ | ○ | ○ | ○ |
| NAS NW276 | ○ | ○ | ○ | ○ | ○ | ○ |
| NAS 254N | ○ | ○ | ○ | ○ | ○ | ○ |
| NAS 329J3L | ○ | ○ | × | × | × | × |
| SUS 316L | ○ | × | × | × | × | × |
For these test conditions the alloy was immersed in a boiling solution of MgCl2 for 300 h. A U-bend test piece was used
○: No stress corrosion cracks
×: Stress corrosion cracking occurred
Weldability
NAS NW22 can be welded much the same as stainless steel. We suggest that matching composition welding consumables be used. A post-weld heat treatment is not required.
Heat Treatment
The solution treatment temperature of NAS NW22 ranges from 1150 to 1170℃. Rapid cooling of the alloy is necessary after heating.
Applications
NAS NW22 is used for pharmaceutical plants, semiconductor manufacturing equipment, various types of chemical plants and flue gas desulfurization system.
* Hastelloy and C-22 are registered trademarks of Haynes International, Inc.
