Corrosion Resistant Alloys
NAS 329J3L (UNS S31803 / S32205) - Duplex Stainless Steel
An austenitic-ferritic duplex stainless steel, NAS 329J3L (SUS 329J3L, UNS S32205, S31803) provides high strength and superior corrosion resistance. This alloy has better localized corrosion resistance than either 316L or 317L, and is typically used for industrial purposes such as in chemical and desalination plants. Nippon Yakin supplies this product in plate, sheet and strip forms.
Coil
Sheet
Plate
Designation / Standard
| Nippon Yakin Grade | ASTM A240 | EN 10088-2 / 10028-7 | JIS G4304 / 4305 |
|---|---|---|---|
| NAS 329J3L | UNS S32205 / S31803 | 1.4462 | SUS 329J3L |
Chemical Composition
SUS 329J3L
| C | Si | Mn | P | S | Ni | Cr | Mo | N | |
|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 4.50 | 21.00 | 2.50 | 0.08 |
| Max | 0.030 | 1.00 | 2.00 | 0.040 | 0.030 | 6.50 | 24.00 | 3.50 | 0.20 |
UNS S32205
| C | Si | Mn | P | S | Ni | Cr | Mo | N | |
|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 4.5 | 22.0 | 3.0 | 0.14 |
| Max | 0.030 | 1.00 | 2.00 | 0.030 | 0.020 | 6.5 | 23.0 | 3.5 | 0.20 |
UNS S31803
| C | Si | Mn | P | S | Ni | Cr | Mo | N | |
|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 4.5 | 21.0 | 2.5 | 0.08 |
| Max | 0.030 | 1.00 | 2.00 | 0.030 | 0.020 | 6.5 | 23.0 | 3.5 | 0.20 |
Physical Properties
| Specific heat (J/kg･K) | 460 | |
| Specific resistivity (μΩ･cm) | 87.0 | |
| Thermal conductivity (W/m･K) | 13.9 | |
| Coefficient of thermal expansion (10-6/℃) | 20–100℃ | 12.7 |
| 20–200℃ | 13.1 | |
| 20–300℃ | 13.5 | |
| 20–400℃ | 13.8 | |
| Young's modulus (MPa) | 19.5 x 104 | |
| Ferromagnetism | Yes | |
| Melting point (℃) | 1420-1465 | |
Microstructure
The microstructure of NAS 329J3L is a austenitic-ferritic duplex structure, 40 to 50 percent of which is a gray ferritic phase, while the remainder is a white austenitic phase.
Image of a hot-rolled sheet, 16-mm thick, taken with an optical microscope
Mechanical Properties
Mechanical Properties at Room Temperature
SUS 329J3L
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness | |
|---|---|---|---|---|
| (Hv) | (HB) | |||
| ≥ 450 | ≥ 620 | ≥ 18 | ≤ 320 | ≤ 302 |
UNS S32205
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness | |
|---|---|---|---|---|
| (Hv) | (HB) | |||
| ≥ 450 | ≥ 655 | ≥ 25 | ― | ≤ 293 |
UNS S31803
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness | |
|---|---|---|---|---|
| (Hv) | (HB) | |||
| ≥ 450 | ≥ 620 | ≥ 25 | ― | ≤ 293 |
Examples
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness | ||
|---|---|---|---|---|---|
| (Hv) | (HB) | ||||
| Hot-rolled plate, 16-mm thick |
563 | 780 | 35 | ― | 222 |
| Cold-rolled sheet, 2-mm thick |
630 | 828 | 28 | 253 | ― |
Corrosion Resistance
The resistance of NAS 329J3L to local corrosion such as pitting, crevice and stress corrosion cracking is superior to general austenitic stainless steel products such as SUS 304 and 316L. This product also has a favorable corrosion resistance to weakly acidic solutions.
Pitting and Crevice Corrosion Resistance
| Designation | CPT (℃) | CCT (℃) |
|---|---|---|
| NAS 329J3L | 50 | 25 |
| SUS 316L | 10 | 0 |
Critical pitting corrosion temperature (CPT) and critical crevice corrosion temperature (CCT)
ASTM G48 method D in 6% FeCl3 + 1% HCl for 72 hr
SCC Resistance
| Designation | Test conditions | |||
|---|---|---|---|---|
| 20% 108℃ |
25% 110℃ |
30% 115℃ |
42% 142℃ |
|
| NAS 329J3L | ○ | ○ | × | × |
| SUS 304 | × | × | × | × |
| SUS 316L | ○ | × | × | × |
U-bend test piece in boiling MgCl2 aqueous solution for 300 hr
○: No cracks
×: Cracks present
Acid Resistance
| Designation | Test conditions | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Sulfuric acid, 80℃ | Hydrochloric acid, 80110℃ | |||||||||
| 5% | 10% | 20% | 40% | 60% | 80% | 0.1% | 1.0% | 2.0% | 3.0% | |
| NAS 329J3L | < 0.1 | 0.1 | 3.3 | 250.5 | 263.1 | 90.4 | < 0.1 | < 0.1 | 19.0 | 51.5 |
| SUS 316L | 1.1 | 2.9 | 20.1 | 291.3 | 72.0 | 11.1 | < 0.1 | 2.5 | 6.7 | 13.5 |
Workability
Between 950 and 1150° C, the hot working strength is comparable to SUS 430. This strength rapidly increases below 900° C, so care is required. After hot working, solution treatment is needed. Care should also be taken when cold working as NAS 329J3L has a higher yield strength and a lower elongation than SUS 304.
Weldability
Such welding techniques as TIG, MIG and shield metal arc welding can be used for NAS 329J3L as with standard austenitic stainless steels. A 329J3L welding consumables should be used, though preheating and post-heating are not required.
Heat Treatment
Rapid cooling is required after heating the solution treatment between 1020 and 1100° C. The cooling should be carried out as rapidly as possible to prevent 475℃ embrittlement and sigma-phase embrittlement.
Pickling
A mixture of nitric and fluoric acids is used in pickling. As descaling is slightly more difficult than with SUS 304, immerse in alkaline for a short time before pickling or use shot blasting if possible as effective descaling methods.
Applications
NAS 329J3L is used in a wide range of chemical equipment, tankers and other devices. Applications include desalination plants, seawater pumps and other seawater environments as well as paper mills, chemical tankers and flue gas desulfurization plants. It is also well suited for bridge construction due to its strength and corrosion resistance.
