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  5. ASTM A453/A453M Grade 668 Class A Specification

ASTM A453/A453M Grade 668 Class A Bolting Specification

High Temperature Precipitation Hardened Stainless Steel Bolting

ASTM A453/A453M Grade 668 Class A Hex Bolts, Push Bolts, Studs, Socket Head Cap Screws, Threaded Rods, Nuts & Washers

Related Specifications of ASTM A453/A453M Grade 668 Class A Bolting

A638 A1014 A1082 ISO 3506-5 F2281

ASTM A453/A453M Grade 668 Class A Bolting Types

Specification Grade UNS No. CLASS Type
ASTM A453/A453M Grade 668 S66285 Class A M1 M2 R1 R2

ASTM A453/A453M Grade 668 Class A Chemical requirements

Grade UNS Number Elements C Mn P S Si Ni Cr Mo W Ti Nb A Al V B Cu
ASTM A453 Grade 668 S66285 Content, % 0.08 max 2.00 max 0.040 max 0.030 max 1.00 max 17.5-21.5 13.5-16.0 1.50 max ... 2.2-2.8 ... 0.50 max 0.50 max 0.001-0.010 ...
Product Analysis, Variation Over or Under, % 0.01 over 0.04 0.005 over 0.005 over 0.05 0.2 0.2 0.05 ... 0.05 ... 0.05 over 0.03 0.0004 under to 0.001 over ...
  • (A) Or columbium plus tantalum.

ASTM A453/A453M Grade 668 Class A Mechanical Properties

Grade Class Tensile Strength, min Yield Strength (0.2 % Offset), min Elongation in 4× Diam, min, % Reduction of Area, min, % Brinell Hardness Number Approximate Rockwell Hardness, B and C
ksi MPa ksi MPa min max
ASTM A453/A453M Grade 668 A 130 895 85 585 15 18 248-341 24 HRC 37 HRC
  • (A) Bolting material sizes 3 in. [76 mm] and under in diameter.
  • (B) Bolting material sizes over 3 in. [76 mm] in diameter.
  • (C) Conversion numbers taken from Specification A193/A193M, Table number 2 (austenitic steels); others by interpolation.

Smooth-Notch Stress-Rupture Test Specimen

Specimen Dimensions Specimen Type Mid-length Gage Dia D and Notch-Root Dia F Gage Length, G Shoulder Diameter, H Notch-Root Radius
Inches 1 0.125 0.5 0.177 0.005
2 0.160 0.65 0.226 0.005
3 0.178 0.75 0.250 0.005
4 0.252 1.0 0.375 0.007
5 0.357 1.5 0.500 0.010
6 0.505 2.0 0.750 0.015
Tolerance ±0.001 ±0.05 ±0.003 ±0.0005
Millimetres 7 3.17 12.0 4.5 0.13
8 4.06 17.0 5.5 0.13
9 4.52 20.0 6.5 0.13
10 6.40 25.0 9.5 0.18
11 9.07 40.0 12.0 0.25
12 12.8 50.0 19.0 0.38
Tolerance ±0.025 ±1.3 ±0.1 ±0.01

ASTM A453/A453M Grade 668 Class A Heat Treatment

Annealing & Ageing Cycles

Grade Symbol Class Solution Treatment Hardening Treatment
ASTM A453/A453M Grade 668 A 1650 ± 25 °F [900 ± 14 °C], hold 2 h, min and liquid quench 1325 ± 25 °F [720 ± 14 °C], hold 16 h, air cool
  • (A) Times refer to the minimum time material is required to be at temperature.

Continuous Heat Treatment Charge Sizes

Diameter, in. [mm] Weight, lb [kg]
To 13/4 [44] 3000 [1400]
Over 13/4 [44] to 21/2 [63] 6000 [2700]
Over 21/2 [63] 12000 [5400]

Lot Sizes

Diameter, in. [mm] Maximum Lot Size, lb [kg]
11/2 [38] and under 200 [90]
Over 11/2 [38] to 13/4 [44], incl 300 [140]
Over 13/4 [44] to 21/2 [63], incl 600 [270]
Over 21/2 [63] 20 pieces

ASTM A453/A453M Grade 668 Class A Bolting Surface Treatment Specifications

ASTM A453/A453M Grade 668 Class A Bolting Components Marking

Product Shall be Marked with our manufacturing trade mark "TorqBolt" or "TB" along with the designated Grade.
Grade and manufacturer’s identification symbols shall be applied to one end of studs and to the heads of bolts and screws of all sizes. (If the available area is inadequate, the grade symbol may be marked on one end and the manufacturer’s identification symbol marked on the other end.) For bolts and screws smaller than 1⁄4 in. [6 mm] in diameter and studs smaller than 3⁄8 in. [10 mm] in diameter and for 1⁄4 in. [6 mm] in diameter studs requiring more than a total of three symbols, the marking shall be a matter of agreement between the purchaser and the manufacturer.

Grade Marking
ASTM A453/A453M GRADE 668 CLASS A TB 668A M1/M2/R1/R2 NR

Threads may be formed by machining or rolling. Threads may be formed after precipitation heat treatment or after solution anneal but prior to precipitation heat treatment. Type designations are as follows:

  • Type M1 -Threads formed by machining after precipitation heat treatment.
  • Type M2 - Threads formed by machining after solution anneal but prior to precipitation heat treatment.
  • Type R1 - Threads formed by rolling after precipitation heat treatment.
  • Type R2 - Threads formed by rolling after solution anneal but prior to precipitation heat treatment.
When not specified by the purchaser, the type supplied shall be the option of the manufacturer.

ASME Dimensional Standards

B18.31.2 Imperial Continious Thread, Double End Reduced & Full Body Studsh
B18.31.1M Metric Continious Thread, Double End Reduced & Full Body Studs
B18.31.3 Threaded Rods (Inch Series)
B16.5 Imperial & Metric Full Thread Stud Bolts
B16.5 Imperial & Metric Full Thread Stud Bolts
B18.2.1 Imperial Square and Hex Bolts and Screws
B18.2.3.1M Metric Hex Cap Screws
B18.2.3.3M Metric Heavy Hex Screws
B18.2.3.5M Metric Hex Bolts
B18.3 Imperial Hexagon Socket and Spline Socket Screws
B18.3.1M Metric Socket Head Cap Screws
B18.6.7M Metric Machine Screws

B18.2.2 Imperial Square, Hex, Heavy Hex, Lock, Heavy Hex Lock Nuts
B18.2.4.1M Metric Hex Nuts
B18.2.4.6M Metric Heavy Hex Nuts
ISO 4033 Hexagon High Nuts
ISO 4032 Hexagon Nuts
ISO 4035 Hexagon Lock Nuts

ASTM A453/A453M Grade 668 Class A Bolting Certifications

  • EN 10204 3.1
  • EN 10204 3.2
  • PED 2014/68/EC
  • MERKBLATT AD 2000 W2/W7/W10
  • API 20 E BSL 1/ BSL 2
  • NACE MR 0175
  • NACE MR 0103

ASTM A453/A453M Grade 668 Class A Testing Standards

E139 Test Methods for Conducting Creep, Creep-Rupture,and Stress-Rupture Tests of Metallic Materials
E292 Test Methods for Conducting Time-for-Rupture Notch Tension Tests of Materials
A962/A962M Specification for Common Requirements for Bolting Intended for Use at Any Temperature from Cryogenic to the Creep Range

ASME Threading Specifications

ASME B1.1 Unified Inch Screw Threads (UN and UNR Thread Form)
ASME B1.3 Screw Thread Gaging System for Dimensional Acceptability - Inch Screw Threads (IN, UNR, and UNJ)
ASME B1.13M Metric Screw Threads- M Profile
ASME B1.21M Metric Screw Threads - MJ Profile
ASME B1.2 Gauges & gauging for Unified Screw Threads(Imperial)

ASTM A453/A453M Grade 668 Class A Permissible Variations in Size of Cold-Finished Bars

Specified Size, in. [mm] Permissible Variations from Specified Size, in. [mm]A
Over Under
Over 1/2 to 1 [13 to 25], excl 0.002  [0.05] 0.002  [0.05]
1 to 11/2 [25 to 38], excl 0.0025 [0.06] 0.0025 [0.06]
11/2 to 4 [38 to 100], inclB 0.003  [0.08] 0.003  [0.08]
  • (A) When it is necessary to heat treat or heat treat and pickle after cold finishing, because of special hardness or mechanical property requirements, the permissible variations are generally double those shown in the table.
  • (B) For size tolerances of sizes over 4 in. [100 mm], the manufacturer should be consulted.