Nippon Yakin Kogyo Co., Ltd
Nippon Yakin Kogyo NAS185N Corrosion Resistant Alloys
Manufacturer: Nippon Yakin Kogyo Co., Ltd
Model: NAS185N
NAS185N (UNS S31254)
High Corrosion Resistant Super Stainless Steel
NAS185N (SUS312L, UNS S31254) is a high corrosion resistant austenitic stainless steel with a high nickel, high chromium, high molybdenum alloy design, and provides excellent corrosion resistance in severe corrosion environments such as seawater. Depending on the environment, this stainless steel offers high economy combined with corrosion resistance comparable to that of Nickel alloy and pure titanium. Nippon Yakin supplies this product in plate, sheet, and strip form.
| Chemical Composition | 20Cr 18Ni 6Mo 0.8Cu 0.2N | ||
| Product shape |  Coil |  Sheet |
Plate |
| Workability | Hot and cold workability similar to standard austenitic stainless steels like Type 304, 316; requires care due to high strength | ||
| Weldability | Various methods applicable; shielded metal arc welding, TIG welding, and plasma welding suitable. Alloy 276 consumables recommended. | ||
| Machinability | Machining is difficult but easier than with Ni-based alloys; use of ultra-hard tool and slow feed rate recommended | ||
| Heat Treatment | Solution annealing at 1150°C, quenching in water or rapid cooling | ||
| Pickling | Mixture of nitric acid and hydrofluoric acid; material should be immersed in alkaline solution before pickling, shot blasting effective | ||
| Applications | Chemical plants, Marine structures, Heat exchangers, Bleaching equipment | ||
| Certification | Manufacturable as UNS S31254, up to 40mm thickness, NORSOK M 650, NORSOK M 630 MDS R15 | ||
Steel Grade/Standard
| Nippon Yakin Grade | JIS G 4304/4305 | ASTM A240 | EN 10088-2/10028-7 |
|---|---|---|---|
| NAS185N | SUS312L | UNS S31254 | 1.4547 |
Chemical Composition
| Specification | C | Si | Mn | P | S | Ni | Cr | Mo | Cu | N |
|---|---|---|---|---|---|---|---|---|---|---|
| SUS312L | ≤0.020 | ≤0.80 | ≤1.00 | ≤0.030 | ≤0.015 | 17.50 – 19.50 | 19.00 – 21.00 | 6.00 – 7.00 | 0.50 – 1.00 | 0.16 – 0.25 |
| UNS S31254 | ≤0.020 | ≤0.80 | ≤1.00 | ≤0.030 | ≤0.010 | 17.50 – 18.50 | 19.50 – 20.50 | 6.00 – 7.00 | 0.50 – 1.00 | 0.18 – 0.25 |
| EN 1.4547 | ≤0.020 | ≤0.70 | ≤1.00 | ≤0.030 | ≤0.010 | 17.50 – 18.50 | 19.50 – 20.50 | 6.00 – 7.00 | 0.50 – 1.00 | 0.18 – 0.25 |
Physical Properties
| Property | Value |
|---|---|
| Density [g/cm³] | 8.02 |
| Specific heat [J/kg·K] 20°C | 464 |
| Electrical resistivity [µΩ·cm] | 89.4 |
| Thermal conductivity [W/m·K] | 12.3 |
| Average coefficient of thermal expansion [10⁻⁶/°C] | 20-100°C: 15.3 20-200°C: 15.7 20-300°C: 16.1 20-400°C: 16.4 |
| Young’s modulus [MPa] | 19.7 × 10⁴ |
| Magnetism | None |
| Melting range [°C] | 1360 – 1405 |
Mechanical Properties
Mechanical Properties at Room Temperature
| Specification | 0.2% proof stress [MPa] | Tensile strength [MPa] | Elongation [%] | Hardness [HV] | Hardness [HBW] | Hardness [HRBW] |
|---|---|---|---|---|---|---|
| SUS312L (sheet and strip) | ≥300 | ≥650 | ≥35 | ≤230 | ≤223 | ≤96 |
| SUS312L (plate) | ≥310 | ≥690 | ≥35 | ≤223 | ≤96 | |
| Example: Hot-rolled plate 8mm | 361 | 707 | 53 | 187 | — | |
| Cold-rolled sheet 1.5mm | 379 | 744 | 41 | 182 | — | |
Corrosion Resistance
NAS185N is a high Cr, high Mo stainless steel which provides excellent pitting corrosion resistance and crevice corrosion resistance in high Cl environments.As a high Ni steel, moreover, it provides exceptional resistance to stress corrosion cracking, positioning it as an optimal solution** for use in highly corrosive environments.
Pitting Corrosion Resistance
| Alloy | ASTM G48 Method A | ASTM G48 Method C | Critical pitting corrosion temperature CPT (°C) |
| 22°C | 50°C | ||
| NAS255 | ○ | × | 50 |
| NAS329J3L | ○ | × | 50 |
| NAS64 | ○ | ○ | 55 |
| NAS185N | ○ | ○ | 70 |
ASTM G48 Method A (○: No pitting corrosion, ×: 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 |
| Critical crevice corrosion temperature CCT (°C) | |
| NAS255 | 10 |
| NAS329J3L | 25 |
| NAS64 | 30 |
| NAS185N | 40 |
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 are in brackets) | |||||
|---|---|---|---|---|---|---|
| 45% (145°C) | 42% (143°C) | 40% (142°C) | 38% (138°C) | 35% (136°C) | 20% (108°C) | |
| NAS255 | × | × | × | × | ○ | ○ |
| NAS329J3L | × | × | × | × | × | ○ |
| NAS64 | ○ | ○ | ○ | ○ | ○ | ○ |
| NAS185N | ○ | ○ | ○ | ○ | ○ | ○ |
Test conditions: Immersion in boiling MgCl2 solution
Test time: 300h
U-bend test specimen is used.
○: No stress corrosion cracking
×: Stress corrosion cracking
Acid Resistance
Corrosion rate in sulfuric acid at 80°C (mm/y)
| Alloy | 5% | 10% | 20% | 40% | 60% | 80% |
|---|---|---|---|---|---|---|
| NAS255 | <0.01 | <0.01 | 0.76 | 2.95 | 4.85 | 5.01 |
| NAS329J3L | 0.01 | 0.17 | 4.65 | 36.5 | 40.6 | 60.74 |
| NAS64 | <0.01 | 0.07 | 1.07 | 191.9 | 198.5 | 206.72 |
| NAS185N | 0.02 | 0.04 | 1.32 | 2.89 | 3.4 | 4.78 |
Test time: 24h
Corrosion rate in hydrochloric acid at 80°C (mm/y)
| Alloy | 0.1% | 1% | 3% | 5% |
|---|---|---|---|---|
| NAS255 | 0.01 | 0.03 | 0.19 | 0.37 |
| NAS329J3L | 0.01 | 0.07 | 0.94 | 2.37 |
| NAS64 | 0.01 | 0.12 | 12.94 | 30.51 |
| NAS185N | 0.01 | 0.2 | 4.20 | 7.21 |
Test time: 24h
Reference
| Alloy | JIS | UNS No. | Chemical composition |
|---|---|---|---|
| NAS255 | SUS890L | N08904 | 20Cr-24Ni-4.3Mo-1.5Cu |
| NAS329J3L | SUS329J3L | S32205 | 22Cr-5.3Ni-3.0Mo-0.17N |
| NAS64 | — | N08904 | 25Cr-6.3Ni-3.6Mo-0.16N |
| NAS185N | SUS312L | S31254 | 20Cr-18Ni-6Mo-0.8Cu-0.2N |
Workability
The hot and cold workability of NAS185N is basically the same as that of standard austenitic stainless steels such as Type 304, Type 316, etc. However, the fact that this is a high strength material must be considered in both cold and hot working.
Weldability
Various welding methods are applicable in the same manner as with the standard austenitic stainless steels, including shielded metal arc welding, TIG welding, and plasma welding. Alloy 276 welding consumable should be used.
Machinability
As a feature of high Ni stainless steels, although machining is difficult in comparison with other standard austenitic stainless steels, it is easier than with Ni-based alloys. A standard tool should be used in machining if at all possible. It is also advisable to use a slower feed rate and deeper cutting depth.
Heat Treatment
Solution annealing of NAS185N should be performed at 1150°C and higher followed by being quenched in water or rapidly cooled by other means. (Conditions provided in ASTM A480/A480M)
Pickling
A mixture of nitric acid and hydrofluoric acid is used in pickling. However, due to the high corrosion resistance of NAS185N, 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, Flue gas desulfurization plants, Marine structures, Heat exchangers, Various types of bleaching equipment.
Certification
It is possible to manufacture UNS S31254 in accordance with the NORSOK standard below. The thickness is up to 40mm.
- NORSOK M-650
- NORSOK M-630 MDS R15
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