Although grade 660 is classified as a precipitation hardening austenitic stainless steel grade, this alloy could occasionally be categorized as a nickel alloy. This is because, for an austenitic class of stainless steel, grade 660 has a relatively higher content of nickel. The higher content of nickel is precisely why fasteners such as the A453 Gr 660 Nut can be used for applications involving elevated temperature. Grade 600 is commonly recognized by its trade names i.e. - alloy A286 and UNS S66286.

ASTM A453 Grade 660 bolts

ASTM A453 Grade 660 bolts

As expected by this nickel based alloy, the ASTM A453 Grade 660 Bolts could be used up to an operational temperature of 700°C. ASTM specification ASTM A453 covers fasteners designed to be used for pressure vessels and valve flanges at high temperatures. This specification covers 4 classes of fasteners i.e. class A, class B, class C, as well as class D. Per usual, according to the standards of ASTM specifications, alloy 660 fasteners are to conform to the chemistry requirements set by the ASTM A453.


Moreover, all materials, which in this case is the A453 Gr 660 Cl a screw is to subjected to several tests such as a stress-rupture, tension, and hardness test. Additionally, the values of the SA 453 grade 660 class b Hex Bolt must conform to the specification’s parameters regarding the following - reduction of area, yield strength, tensile strength, elongation, Brinell hardness, and Rockwell hardness requirements. Moreover, each class of a453 grade 660 class a stud bolts are to follow and abide by the hardening as well as solution treatment requirements.

Specification Format of Grade 660 class a stud bolts

Standard ASTM A453/ ASME SA453
Sizing 3/6 inch upto 2 inch | M02 – M160
In Form of: Round, Threading, Hex, Square as per Gauge Etc.
Lengths 3 upto 200 Millimetre
Dimensions ASME B18.2.1, B18.3

SA 453 grade 660 class b Hex Bolt Mechanical Strength

Grade Class Tensile Strength Yield Strength Elongation
in 4D, min, %
Reduction
of Area, min, %
Brinell
Hardness
Number
Approximate
Rockwell
Hardness, B & C
Ksi Mpa Ksi Mpa min max
Grade 660 A, B and C 130 895 85 585 15 18 248-341 24 HRC 37 HRC
Grade 660 D 130 895 105 725 15 18 248-341 24 HRC 35 HRC

Composition Chart of A453 Gr 660 Cl a screw

Compound In Percentage
Silicon 1.00 max
Phosphorus, max 0.040 max
Sulfur, max 0.030 max
Nickel 24.0-27.0
Carbon 0.08 max
Manganese 2.00 max
Chromium 13.5-16.0
Molybdenum 1.00-1.50
Columbium * ...
Aluminum 0.35 max
Vanadium 0.10-0.50
Boron 0.001-0.010
Tungsten ...
Titanium 1.9-2.35
Copper -

A453 Gr 660 Nut Material Equivalent

AISI UNS BS Wr No. En Name DIN EN JIS AMS ASTM other names Additional Requirements
660 S 66286 HR 51 1.4944 X6NiCrTiMoV26-15 10269 SUS 660 5726 ASTM A453 GRADE 660A incoloy a286 NACE MR-0175

Dimensions of ASTM A453 Grade 660 bolts

Dimensions of ASTM A453 Grade 660 bolts

Minimal Size (D) THE FLATS HEAD THICKNESS BODY DIAMETER CORNERS
F (MAX) F (MIN) H (MAX) H (MIN) D (MAX) D (MIN) C (MAX) C (MIN)
m16 24.00 23.67 10.32 9.68 16.00 15.73 27.71 26.75
m10 17.00 15.73 6.63 6.17 10.00 9.78 18.48 17.77
m48 75.00 72.60 31.07 28.93 48.00 47.38 86.60 82.76
m100 145.00 140.00 63.9 60.10 90.00 99.13 167.43 159.60
m12 19.00 17.73 7.76 4.24 12.00 11.73 20.78 20.03
m14 22.00 20.67 9.09 8.51 14.00 13.73 24.25 23.35
m90 130.00 125.50 57.74 54.26 90.00 89.13 150.11 143.07
m24 36.00 35.00 15.44 14.56 24.00 23.67 41.57 39.55
m30 46.00 45.00 19.48 17.92 30.00 29.67 53.12 50.85
m20 30.00 29.16 12.88 12.12 20.00 19.67 34.64 32.95
m80 115.00 111.00 51.58 48.42 80.00 79.26 132.72 126.54
m36 55.00 53.80 23.38 21.63 36.00 35.61 63.51 60.79
m42 65.00 62.90 26.97 25.03 42.00 41.38 75.06 71.71
m64 95.00 91.80 41.32 38.68 64.00 63.26 109.70 104.65
m72 105.00 101.40 46.45 43.55 72.00 71.26 121.24 115.60
m56 85.00 82.20 36.2 33.80 56.00 55.26 98.15 93.71

Read more about ASTM A453 standard here: https://www.astm.org/Standards/A453.htm