NAS 660 (UNS S66286)

NAS Heat-Resistant Stainless Steel

A precipitation hardening stainless steel, NAS 660 (SUH 660, UNS S66286) maintains superior strength at high tem-
peratures up to 700°C, surpassing austenitic stainless steels. With a higher nickel content than Type 304, NAS 660
also includes such elements as titanium and aluminum for hardening. Age hardening is used to precipitate ’ phase
[Ni3 (Al, Ti)] making this an extraordinarily strong metal at high temperatures. Nippon Yakin supplies this product in
plate, sheet, and strip forms.

Steel Grade/Standard

NAS JIS G4312 AMS 5525

NAS 660 SUH 660 UNS S66286

Chemical Composition
[wt %]
C Si Mn P S Ni Cr Mo Al Ti B V Co
Specification 24.00~ 13.50~ 1.00~ 1.90~ 0.001~ 0.10~
0.08 1.00 2.00 0.040 0.030 0.35 —
(SUH 660) 27.00 16.00 1.50 2.35 0.010 0.50
Specification 24.00~ 13.50~ 1.00~ 1.90~ 0.003~ 0.10~
(UNS S66286) 0.08 1.00 2.00 0.025 0.025 0.35 1.00
27.00 16.00 1.50 2.35 0.010 0.50

Physical Properties

Density [g/cm3] 7.98

Specific heat [J/kg . K] 460
Electrical resistivity [μΩ . cm] 91
Thermal conductivity [W/m . K] 150°C 12.2
-6
Average coefficient of thermal expansion [10 /°C] 20~100°C 16.8
20~500°C 17.7
20~650°C 17.4
20~750°C 18.5
20~950°C 19.4
Young’s modulus [MPa] 20.1 × 104
Magnetism None
Melting range [°C] 1340~1400
*All of the above values were measured after aging.
 NAS 660 (UNS S66286)

Mechanical Properties

Mechanical Properties at Room Temperature

0.2% proof stress Tensile strength Elongation Hardness Special notes

Solution treatment
[MPa] [MPa] [%] [HRB]

Specification (SUH 660) — 730 25 91

Specification (UNS S66286) — 724 25 90 At least 1mm thick
Example Cold-rolled sheet 344 665 40 86 0.2% proof stress for reference

Solution treatment and 0.2% proof stress Tensile strength Elongation Hardness Special notes
aging [MPa] [MPa] [%] [HRC]

Specification (SUH 660) 590 900 15 24

Specification (UNS S66286) 655 965 15 24~35 At least 1mm thick
Example Cold-rolled sheet 774 1099 25 32

The work hardening of NAS 660 is equivalent to Type 310S, and cold working is
Work Hardening
possible on the same level.

600

500 NAS 660

Type 310S
400
Hardness [Hv]

Type 304
300

200

100

0
0 20 40 60 80
Cold-reduction ratio [%]

NAS 660 was held at various temperatures for 16 hours to investigate its age hard-
Age Hardening Behavior
ening behavior. Solution-treated NAS 660 reaches its maximum hardness at 16
hours of heat treatment around 700°C, though this temperature can be lowered if
the NAS 660 is cold rolled.

500
450
Solution-treatment
400 Reduction of 20%
Hardness [Hv]

350 Reduction of 40%

300 Reduction of 60%
250
200
150
100
0 as-rolled 300 400 500 600 700 800 900 1000
Aging temperature [°C]
 NAS 660 (UNS S66286)

High Temperatures Strength

An example of test values for Solution-treated NAS 660 that is aged for 16 hours at 720°C
Results of high-temperature tensile test
1200 120

0.2% Tensile
Elongation
1000 proof stress strength 100
0.2% proof stress [MPa]
Tensile strength [MPa]

800 80

Elongation [%]
600 60

400 40

200 20

0 0
0 200 400 600 800 1000
Temperature [°C]

Creep Properties
An example of test values for solution-treated NAS 660 that is aged for 16 hours at 720°C
Creep strength
Test temperature Rupture strength Elongation [MPa]
[°C] [MPa] [%]
0.5% total strain 1.0% total strain
538 689 3 559 634
593 562 3 525 551
100hr 649 434 5 365 414
Strength
properties 704 304 12 207 244
732 241 28 — —
816 90 55 — —
538 599 3 537 585
593 490 3 469 482
1000hr 649 317 9 241 282
Strength
properties 704 207 24 — 155
732 148 35 — —
816 58 — — —

NAS 660 provides superior corrosion resistance beyond the standard austenitic
Corrosion Resistance
stainless steel Type 304, and this does not vary even after aging.

Evaluation of Pitting Corrosion Resistance

Test condition: 5% NaCl, 30°C
Solution treatment 0.37V
NAS 660
Age hardening 0.38V
Type 304 Solution treatment 0.28V
 NAS 660 (UNS S66286)

Spot, TIG, MIG and shield metal arc welding can be used on thin NAS 660 sheets
Weldability
under similar conditions to austenitic stainless steels.

NAS 660 is a precipitation hardening alloy. Its strength is increased through aging
Heat Treatment
after solution heat treatment. Two stages of heat treatment are generally carried
out, as follows:
Solution heat treatment: 980°C; oil or water cooling
Age hardening: 720°C × 16hr; air cooling
After solution heat treatment, either oil or water cooling is required, though air cool-
ing is better for thinner metal. Note that it is important to use a suitable temperature
and holding time for aging to obtain the target strength.

Compared to standard austenitic stainless steels, NAS 660 has somewhat superior
Machinability
machining properties. Although a high-speed steel tool can be used, we recom-
mend the use of a sintered carbide tool, and suggest combining a slower feed rate
with a greater cutting depth.

NAS 660 is an excellent choice when high-temperature strength is required such as

Applications
jet engines, gas turbines and turbo charger components.

For more information, please contact: Note regarding the handling of property data:
The technical information contained in this product guide is representative
Nippon Yakin Kogyo Co., Ltd. values obtained in property tests and other items used to explain the per-
Material Solutions Sales Department formance of the product. With the exception of items specifically mentioned
as provisions of a “Standard,” the contents do not represent guaranteed
San-Ei Bldg., 5-8, 1-chome Kyobashi, Chuo-ku,
upper limit or lower limit values. The respective data given on this technical
Tokyo 104-8365 Japan information are typical examples and may be different in some cases from
the data obtained from the actual product. No responsibility shall, therefore,
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be assumed for damages arising from using the technical information data.
E-Mail: inquiry@nyk.co.jp This information is also subject to change in the future without notice. To
URL: http://www.nyk.co.jp/en/ obtain the most recent information, please contact Nippon Yakin.

2013.7.26