Manufacturer: Nippon Yakin Kogyo Co., Ltd
Model : NAS64

NAS64 (UNS S32506)
High Corrosion Resistant Duplex Stainless Steel

Nippon Yakin developed NAS64 (SUS329J4L, UNS S32506), an austenitic-ferritic stainless steel that provides excellent corrosion resistance against phosphoric acid, acetic acid, and various sulfur compounds. In particular, its high chromium and molybdenum composition significantly improves its localized corrosion resistance compared to Type 316L. Nippon Yakin supplies this product in plate, sheet, and strip form.

Chemical Composition	25Cr-6.5Ni-3.3Mo-0.17N
Product Shape	Coil	Sheet	Plate
Workability	High temperature strength is similar to Type 430 in the range of 950-1150°C. However, the steel shows a rapid increase in strength below 900ÂC. Exercise care when working with this material for cold workability, as it has high proof stress and low elongation compared to Type 304.
Weldability	You can apply various welding methods, such as shielded metal arc welding, TIG welding, and plasma welding, in the same way as with standard austenitic stainless steels. Use the same duplex grade type welding consumable.
Heat Treatment	NAS454 is not hardened by heat treatment. After heating to a solution treatment temperature of 1050-1080°C, quenching is necessary. Cool the material as rapidly as possible to minimize its exposure time to the embrittlement temperature range (475°C embrittlement, phase embrittlement).
Pickling	They use a mixture of nitric acid and hydrofluoric acid for pickling.However, descaling is somewhat difficult in comparison with Type 304. Performing alkaline immersion before acid pickling and, if possible, shot blasting, is extremely effective.
Applications	Water storage tank, Chemical plants, Environment-related equipment, Geothermal power generation, Papermaking plants, Seawater pump.

Steel Grade/Standard

Nippon Yakin Grade	JIS G 4304/4305	ASTM A240	EN
NAS 64	SUS 329J4L	UNS S32506	—

Chemical Composition

	C	Si	Mn	P	S	Ni	Cr	Mo	N
Specification (SUS 329J4L)	≦0.030	≦1.50	≦2.00	≦0.040	≦0.030	7.50 ~ 8.00	25.00 ~ 26.00	3.00 ~ 3.50	0.05 ~ 0.20
Specification (UNS S32506)	≦0.030	≦1.00	≦2.00	≦0.030	≦0.015	6.90 ~ 7.20	26.00 ~ 27.00	2.00 ~ 3.00	0.05 ~ 0.20

Physical Properties

Density [g/cm³]	7.80
Specific heat [J/kg·K]	460
Electrical resistivity [μΩ·cm]	82.5
Thermal conductivity [W/m·K]	13.0
Average coefficient of thermal expansion [10⁻⁶/°C]	30 ~ 200°C: 12.0 30 ~ 300°C: 12.4 30 ~ 400°C: 12.8
Young’s modulus [MPa]	21.4 × 10⁴
Magnetism	Y (magnetizable)
Melting range [°C]	1420 ~ 1465

Mechanical Properties

Mechanical Properties at Room Temperature

Specification	0.2% proof stress [MPa]	Tensile strength [MPa]	Elongation [%]	Hardness [HB]
Specification (SUS 329J4L)	≥450	≥620	≥18	≤302
Specification (UNS S32506)	≥450	≥620	≥18	—
Example: Cold-rolled sheet 1.6mm	657	800	26	—
Example: Hot-rolled plate 16mm	—	732	853	—

NAS64 exhibits excellent localized corrosion resistance, including resistance to pitting corrosion and stress corrosion cracking, allowing its use in environments where Type 316L cannot perform. In particular, its pitting and crevice corrosion resistance is far superior.

Pitting Corrosion Resistance

Alloy	ASTM G48 Method A		ASTM G48 Method C
	22°C	50°C	Critical pitting corrosion temperature CPT (°C)
SUS 316L	×	×	15
NAS 329J3L	○	×	55

Test conditions: 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)
SUS 316L	<10
NAS 329J3L	30

 Test conditions: ASTM G48 Method D
Test solution: 6% FeCl₃ + 1% HCl
Test time: 72h

Stress Corrosion Cracking Resistance

Alloy	45% (155°C)	42% (143°C)	40% (138°C)	38% (134°C)	35% (126°C)	30% (115°C)	25% (110°C)	20% (108°C)
SUS 316L	×	×	×	×	×	×	×	○
NAS 329J3L	×	×	×	×	×	×	○	○
NAS 64	×	×	×	×	×	○	○	○

 Test conditions: Immersion in boiling MgCl₂ solution
Test time: 300h
They use a U-bend test specimen.
○: No stress corrosion cracking      ×: Stress corrosion cracking

Corrosion rate in sulfuric acid at 80°C (mm/y)

Alloy	5%	10%	20%	40%	60%	80%
SUS 316L	1.67	4.69	71.91	746.9	704.5	337.4
NAS 329J3L	0.01	0.17	4.65	365.9	1456	106.4
NAS 64	<0.01	0.02	1.07	191.9	1054	60.72

Test time: 24h

Corrosion rate in hydrochloric acid at 80°C (mm/y)

Alloy	0.1%	1%	2%	3%
SUS 316L	0.01	2.73	7.65	14.68
NAS 329J3L	0.02	0.03	31.10	60.62
NAS 64	0.01	0.02	1.41	7.21

Test time: 24h

Alloy	JIS	UNS No.	Chemical composition
SUS 316L	S31603	17Cr-12Ni-2Mo
NAS 329J3L	S32205	22Cr-5.3Ni-3.2Mo-0.16N
NAS 64	S32506	25Cr-6.5Ni-3.3Mo-0.17N

Workability

High temperature strength is similar to Type 430 in the range of 950-1150°C. However, the steel shows a rapid increase in strength below 900°C. Regarding cold workability, care is required as proof stress is high and elongation is low in comparison with Type 304.

Weldability

Various welding methods are applicable in the same manner as with standard austenitic stainless steels, including shielded metal arc welding, TIG welding, and plasma welding. Use of welding electrodes for UNS S32506 is recommended. Preheating and post-heating are not necessary. In welding, the interpass temperature should be no more than 100°C to prevent formation of intermetallic compounds.

Heat Treatment

Solution annealing of NAS64 should be performed at the temperature range from 1020 to 1120°C 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 fluoridic acid is used in pickling. However, descaling is somewhat difficult in comparison with Type 304. Alkaline immersion before acid pickling, and if possible, shot blasting are extremely effective.

Applications

Water storage tank, chemical plants, environment-related equipment, geothermal power generation, papermaking plants, seawater pump