Manufacturer: Nippon Yakin Kogyo Co., Ltd
Model: NAS325N

NAS325N (UNS N08031)
High Corrosion Resistance Stainless Steel

The stainless steel NAS325N (UNS N08031) offers extremely superior corrosion resistance and is suitable for use in many severe corrosion environments. The stainless steel NAS325N (UNS N08031) offers extremely superior corrosion resistance and serves in many severe corrosion environments.. In addition to local corrosion resistance approaching that of nickel-base corrosion-resistant alloys, it also provides excellent acid resistance. Nippon Yakin supplies this product in plate, sheet, and strip form.

Chemical Composition	27Cr-31Ni-6.5Mo-1.2Cu-0.2N
Product Shape	Coil	Sheet	Plate
Workability	Cold and hot workability similar to standard austenitic stainless steels; care needed due to high strength in cold and hot conditions.
Weldability	TIG, MIG, and shielded metal arc welding are applicable; Alloy 276 consumable recommended.
Machinability	Machining is difficult compared to standard austenitic stainless steels but easier than Ni-based alloys; superhard tools and slow feed speed advised.
Heat Treatment	Solution annealing at 1150 to 1180°C, followed by quenching or rapid cooling in water.
Pickling	Nitric acid and hydrofluoric acid mixture used for pickling; alkaline solution immersion advised; shot blasting effective.
Applications	Chemical plants, Environment-related equipment, Oil and gas extraction, Heat exchangers.

Steel Grade/Standard

Nippon Yakin Grade	JIS	ASTM B625	EN
NAS325N	—	UNS N08031	—

Chemical Composition

Specification	C	Si	Mn	P	S	Ni	Cr	Mo	Cu	N
ASTM B625	≦0.015	≦0.3	≦2.0	≦0.020	≦0.010	30.0 – 32.0	26.0 – 28.0	6.0 – 7.0	1.0 – 1.4	0.15 – 0.25

Physical Properties

Density [g/cm³]	8.07
Specific heat [J/kg·K]	448
Electrical resistivity [µΩ·cm]	105
Thermal conductivity [W/m·K]	10.7
Average coefficient of thermal expansion [10⁻⁶/°C]	30 – 100°C: 15.0 30 – 200°C: 14.8 30 – 300°C: 15.0 30 – 400°C: 15.4
Young’s modulus [MPa]	19.2 × 10⁴
Magnetism	None
Melting range [°C]	1330 – 1397

Mechanical Properties

Mechanical Properties at Room Temperature

Specification	0.2% proof stress [MPa]	Tensile strength [MPa]	Elongation [%]	Hardness [HRBW]
Specification (ASTM B625)	≥276	≥650	≥40	—
Example: Cold-rolled sheet 2.0mm	396	785	50	182
Example: Hot-rolled plate 25mm	358	731	63	174

Corrosion Resistance

NAS325N has excellent pitting corrosion resistance due to its high contents of chromium and molybdenum. It also has excellent acid resistance to sulfuric acid, etc.

Pitting Corrosion Resistance

Alloy	ASTM G48 Method A		ASTM G48 Method C
	22°C	50°C	Critical pitting corrosion temperature CPT (°C)
NAS255	○	×	50
NAS329J3L	○	×	50
NAS64	○	○	55
NAS185N	○	○	70
NAS325N	○	○	100

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
NAS325N	50

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% (155°C)	42% (143°C)	40% (138°C)	38% (134°C)	35% (126°C)	30% (115°C)	25% (110°C)	20% (108°C)
NAS255	×	×	×	×	○	○	○	○
NAS329J3L	×	×	×	×	×	○	○	○
NAS64	×	×	○	○	○	○	○
NAS185N	×	×	○	○	○	○	○
NAS325N	×	×	×	×	○	○	○	○

Test conditions: Immersion in boiling MgCl₂ solution
They use a U-bend test specimen.
○: 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	0.78	2.95	0.48	5.01
NAS329J3L	0.01	0.17	4.65	365.9	1456	106.4
NAS64	<0.01	0.02	1.07	191.9	1054	60.72
NAS185N	0.02	0.04	1.02	2.11	2.16	7.76
NAS325N	—	<0.01	0.02	0.03	—	3.54

Test time: 24h

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

Alloy	0.1%	1%	2%	3%
NAS255	<0.01	0.01	2.70	3.72
NAS329J3L	0.02	0.03	31.10	60.62
NAS64	0.01	0.12	12.94	30.51
NAS185N	0.01	0.02	0.01	9.14
NAS325N	<0.01	<0.01	3.22	5.66

Test time: 24h

Reference

Alloy	JIS	UNS No.	Chemical composition
NAS255	SUS890L	N08904	20Cr-24Ni-4.3Mo-1.5Cu
NAS329J3L	SUS329J3L	S32205

Workability