Nippon Yakin Kogyo NAS625 Corrosion Resistant Alloys

Manufacturer: Nippon Yakin Kogyo Co., Ltd
Model : NAS625

NAS625 (UNS N06625)
Corrosion-Resistant and Heat-Resistant Nickel Alloy

NAS625 (NCF625, UNS N06625) is a nickel-chromium-molybdenum alloy with an addition of niobium. Matrix stiffening provided by molybdenum and niobium results in high strength. The alloy resists a wide range of severe corrosion environments. It also offers resistance to high temperatures. Uses include parts in chemical and garbage incinerator plants. Nippon Yakin supplies this product in plate, sheet, and strip forms.

Chemical Composition	62Ni 22Cr 9Mo 3.7Nb 0.71Ti 0.24Al
Product shape	Coil	Sheet	Plate
Workability	High-temperature strength is much higher than Type 304. Care needed when hot working. Cold workability is similar to standard austenitic stainless steels like Type 304, 316, 316, etc. The high strength needs to be considered in cold working.
Weldability	Shielded metal arc welding, TIG welding, plasma welding are possible. Susceptibility to solidification cracking is higher than Type 304.
Heat Treatment	Solution annealing at 871°C, followed by quenching in water or rapid cooling. For higher temperature annealing, 1030°C followed by rapid quenching.
Pickling	Nitric acid and hydrofluoric acid used in pickling. Descaling more difficult than Type 304, requires alkaline immersion before pickling, blasting also effective.
Applications	Chemical plants, Environment-related equipment, Oil and gas extraction.
Chemical Composition	62Ni 22Cr 9Mo 3.7Nb 0.71Ti 0.24Al

Grade/Standard

Nippon Yakin Grade	JIS G 4902	ASTM B443	EN
NAS625	NCF625	UNS N06625	—

Chemical Composition

	C	Si	Mn	P	S	Ni	Cr	Mo	Al	Ti	Fe	Co	Nb+Ta
Specification (NCF625)	≤0.10	≤0.50	≤0.50	≤0.015	≤0.015	≥58.00	20.00-23.00	8.00-10.00	≤0.40	≤0.40	≤5.00	—	3.15-4.15
Specification (UNS N06625)	≤0.10	≤0.50	≤0.50	≤0.015	≤0.015	≥58.00	20.00-23.00	8.00-10.00	≤0.40	≤0.40	≤5.00	≤1.0	3.15-4.15

Physical Properties

Density [g/cm³]	8.44
Specific heat [J/kg•K]	407
Electrical resistivity [μΩ•cm]	124
Thermal conductivity [W/m•K]	9.8
Average coefficient of thermal expansion [10⁻⁶/°C]	30–200°C 13.2
	30–300°C 13.5
	30–400°C 13.9
Young’s modulus [MPa]	19.7 × 10⁴
Magnetism	None
Melting range [°C]	1290–1350

Mechanical Properties

Mechanical Properties at Room Temperature

Grade 1 (annealed)

Specification	0.2% proof stress [MPa]	Tensile strength [MPa]	Elongation [%]
NCF625 (annealing) >0.5mm, ≤3.0mm	≥415	≥830	≥30
NCF625 (annealing) >3.0mm, ≤57.0mm	≥380	≥784	≥30
Specification UNS N06625 Grade 1 (annealed) Cold-rolled sheet, strip	≥414	≥827	≥30
Hot-rolled plate (≤57.0mm)	≥379	≥758	≥30
Cold-rolled sheet (0.95mm)	≥276	≥759	≥30
Example Hot-rolled plate 10mm	399	819	43
Example Cold-rolled sheet 3.0mm	450	859	49

Grade 2 (solution annealed)

Specification	0.2% proof stress [MPa]	Tensile strength [MPa]	Elongation [%]
NCF625 (solution treatment) >0.5mm, ≤70mm	≥275	≥690	≥30
Specification UNS N06625 Grade 2 (solution annealed)	≥276	≥690	≥30
Example Hot-rolled plate 10mm	323	738	71
Example Cold-rolled sheet 3.2mm	378	777	59

High Temperature Strength

Nippon Yakin Kogyo NAS625 Corrosion Resistant Alloys

Corrosion Resistance

Pitting Corrosion Resistance

Alloy	ASTM G48 Method A	ASTM G48 Method C Critical pitting corrosion temperature CPT (°C)
NAS185N	○	70
NAS825	○	30
NAS625*	○	103

Test conditions: ASTM G48 Method A (○: No pitting corrosion, X: Pitting corrosion)
– Test solution: 6% FeCl₃
– Test temperature: 22°C, 50°C (Recommended temperature in this test)
– Test time: 72h
*Grade 1

Crevice Corrosion Resistance

Alloy	ASTM G48 Method D Critical crevice corrosion temperature CCT (°C)
NAS185N	40
NAS825	45
NAS625*	45

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

Acid Resistance

Alloy	5%	10%	20%	40%	60%	80%
NAS185N	0.02	0.04	1.32	2.89	3.02	4.78
NAS825	0.01	0.03	0.32	2.21	2.24	3.73
NAS625*	<0.01	0.01	0.03	0.74	0.81	1.73

Test time: 24h

Reference

Alloy	JIS	UNS No.	Chemical composition
NAS185N	SUS312L	S31254	20Cr-18Ni-6Mo-0.8Cu-0.2N
NAS825	NCF825	N08825	40Ni-23Cr-3Mo-2Cu-0.7Ti
NAS625*	NCF625	N06625	62Ni-22Cr-9Mo-3.7Nb-0.2Ti-0.2Al

Workability

Because the high-temperature strength of NAS625 is extremely higher than that of Type 304, care is required when hot working. The cold workability of NAS625 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 cold 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. Susceptibility of NAS625 to solidification cracking is higher than that of Type 304.

Heat Treatment

Annealing of NAS625 is normally performed at 871°C and higher, followed by being quenched in water or rapidly cooled by other means.
Solution annealing of NAS625 is normally performed at 1093°C and higher, followed by being quenched in water or rapidly cooled by other means.

Pickling

A mixture of nitric acid and fluoric acid is used in pickling. However, because descaling is somewhat difficult in comparison with Type 304, alkali immersion before acid pickling, and if possible, shot blasting are extremely effective.

Applications

Chemical plants, Environment-related equipment, Oil and gas extraction.