NAS 660 (UNS S66286)
NAS Heat-Resistant Stainless SteelA precipitation hardening stainless steel, NAS 660 (SUH 660, UNS S66286) maintains superior strength at high temperatures 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 inplate, sheet, and strip forms.

Steel Grade/Standard
NAS

JIS G4312

AMS 5525

NAS 660

SUH 660

UNS S66286

Chemical Composition[wt %]

CSi

MnPS

Ni

CrMo

AlTi

BV

Co

Specification(SUH 660)

0.08

1.00

2.00

0.040

0.030

24.00~ 13.50~ 1.00~
27.00 16.00 1.50

0.35

1.90~ 0.001~ 0.10~
2.35 0.010 0.50—

Specification(UNS S66286)

0.08

1.00

2.00

0.025

0.025

24.00~ 13.50~ 1.00~
27.00 16.00 1.50

0.35

1.90~ 0.003~ 0.10~
2.35 0.010 0.50

1.00

Physical Properties
Density[g/cm3]

7.98

Specific heat

[J/kg . K]460

Electrical resistivity[μΩ . cm]

91

Thermal conductivity[W/m . K]-6

Average coefficient of thermal expansion [10 /°C]

Young’s modulus[MPa]

Magnetism
Melting range

150°C

12.2

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
20.1 × 104
None

[°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

[MPa]

[MPa]

[%]

[HRB]

Specification (SUH 660)

—

730

2591

Specification (UNS S66286)

—

724

2590

At least 1mm thick

Example Cold-rolled sheet

344

6654086

0.2% proof stress for reference
Special notes

Solution treatment

Solution treatment andaging

0.2% proof stress Tensile strength

Elongation

Hardness

[MPa]

[MPa]

[%]

[HRC]

Specification (SUH 660)

590

900

1524

Specification (UNS S66286)

655

965

1524~35

Example Cold-rolled sheet

774

1099

2532

Special notes

At least 1mm thick

The work hardening of NAS 660 is equivalent to Type 310S, and cold working isWork Hardening

possible on the same level.
600500NAS 660
Type 310S
Type 304

Hardness [Hv]400300200
10000

Age Hardening Behavior

204060Cold-reduction ratio [%]80

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

500
450

Solution-treatment
Reduction of 20%
Reduction of 40%
Reduction of 60%

Hardness [Hv]

400
350
300
250
200
150
1000as-rolled

300

400 500 600 700
Aging temperature [°C]8009001000

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

1200.2% proof stress [MPa]Tensile strength [MPa]Tensilestrength

Elongation

100800

80600

60400

40200

200

Elongation [%]0.2%
proof stress

1000

00200

400600800

1000

Temperature [°C]

Creep Properties
An example of test values for solution-treated NAS 660 that is aged for 16 hours at 720°C

Test temperature Rupture strength

100hr
Strengthproperties

1000hrStrengthproperties

Corrosion Resistance

Creep strengthElongation

[MPa]

[°C]

[MPa]

[%]

538

689

3559

634

593

562

3525

551

649

434

5365

414

704

304

12207

244

732

241

28——

816

90

55—

—

538

599

3

537

585

593

490

3

469

482

649

317

9

241

282

704

207

24

—

155

732

148

35

—

—

816

58—

—

—

0.5% total strain 1.0% total strain

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

Evaluation of Pitting Corrosion ResistanceTest condition: 5% NaCl, 30°C

NAS 660
Type 304

Solution treatment

0.37V

Age hardening

0.38V

Solution treatment

0.28V

NAS 660 (UNS S66286)

Weldability

Heat Treatment

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

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

Machinability

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

Applications

NAS 660 is an excellent choice when high-temperature strength is required such as
jet engines, gas turbines and turbo charger components.

For more information, please contact:
Nippon Yakin Kogyo Co., Ltd.
Material Solutions Sales Department
San-Ei Bldg., 5-8, 1-chome Kyobashi, Chuo-ku,
Tokyo 104-8365 Japan
TEL: +81-3-3273-4649 FAX: +81-3-3273-4642
E-Mail: inquiry@nyk.co.jp
URL: http://www.nyk.co.jp/en/

Note regarding the handling of property data:
The technical information contained in this product guide is representativevalues obtained in property tests and other items used to explain the performance of the product. With the exception of items specifically mentioned
as provisions of a “Standard,” the contents do not represent guaranteed
upper limit or lower limit values. The respective data given on this technicalinformation are typical examples and may be different in some cases fromthe data obtained from the actual product. No responsibility shall, therefore,
be assumed for damages arising from using the technical information data.
This information is also subject to change in the future without notice. Toobtain the most recent information, please contact Nippon Yakin.

2013.7.26