Blog
  2. ASTM
  3. Bolting
  4. ASTM A320/A320M Specification

ASTM A320/A320M Bolting Specification

Alloy Steel & Stainless Steel Bolting for Low Temperature Service

ASTM A320/A320M Hex Bolts, Heavy Hex Bolts, Studs, Socket Head Cap Screws, Threaded Rods

ASTM A320 / A320M specification covers alloy and ferritic and austenitic stainless steel bolting materials and bolting components for pressure vessels, valves, flanges, and fittings for low temperature service. To Meet the Impact Energy Requirements we at TorqBolt use only Ingot Cast Steel which is refined steel, duly killed and mercury free with lower Phosphorous and Sulphur contents with restricted gas elements. Bolting Materials such as Bars and wire rods shall be hot wrought and may be further processed by center less grinding or by cold drawing. Austenitic stainless steel may be carbide solution treated or carbide solution treated and strain-hardened. Bolting type such as Hex Bolts, Heavy Hex Bolts, Studs, Socket Head Cap Screws, Hex Cap Screws, Threaded Rods and Threaded Bars can be manufactured from ¼” to 4” in imperial and M6 to M100 in metric variants both fine threads and coarse threads. Bolting Components up to 6” can be provided at TorqBolt with the same certification. PED 2014/68/EC Certified ASTM/ASME A320/A320M Bolting is available exstock.

Related Specifications of ASTM A320/A320M Bolting

A193 A194 F436 F2882 ISO 898-1 ISO 898-2 3506-1

ASTM A320/A320M Chemical Requirements

Ferritic Steels

Grade Symbol Description C Mn P,max S,max Si Ni Cr Mo B
ASTM A320 L7, L7M, L70 Cr - Mo - B Range,% 0.38 - 0.48C 0.75 - 1.00 0.035 0.04 0.15 - 0.35 ... 0.80 - 1.10 0.15 - 0.25 ...
Product Variation, % Over or Under 0.02 0.04 0.005 over 0.005 over 0.02 ... 0.05 0.02 ...
ASTM A320 L7A, L71 C - Mo (AISI 4037) Range,% 0.38 - 0.48 0.70 - 0.90 0.035 0.04 0.15 - 0.35 ... ... 0.20- 0.30 ...
Product Variation, % Over or Under 0.02 0.03 0.005 over 0.005 over 0.02 ... ... 0.02 ...
ASTM A320 L7B, L72 Cr - Mo (AISI 4137) Range,% 0.35 - 0.40 0.70 - 0.90 0.035 0.04 0.15 - 0.35 ... 080 - 110 0.15 - 0.25 ...
Product Variation, % Over or Under 0.02 0.03 0.005 over 0.005 over 0.02 ... 0.05 0.02 ...
ASTM A320 L7C, L73 Ni - Cr - Mo (AISI 8740) Range,% 0.38 - 0.43 0.75 - 1.00 0.035 0.04 0.15 - 0.35 0.40 - 0.70 0.40 - 0.60 0.20- 0.30 ...
Product Variation, % Over or Under 0.02 0.04 0.005 over 0.005 over 0.02 0.03 0.03 0.02 ...
ASTM A320 L43 Ni - Cr - Mo (AISI 4340) Range,% 0.38 - 0.43 0.60 - 0.85 0.035 0.04 0.15 - 0.35 1.65 - 2.00 0.70 - 0.90 0.20- 0.30 ...
Product Variation, % Over or Under 0.02 0.03 0.005 over 0.005 over 0.02 0.05 0.03 0.02 ...
ASTM A320 L1 Low - C, B Range,% 0.17 - 0.24 0.70 - 1.40 0.035 0.05 0.15 - 0.30 ... ... ... 0.001 - 0.003
Product Variation, % Over or Under 0.01 0.04 0.005 over 0.005 over 0.02 ... ... ... ...

Austenitic Steels

Grade Symbol UNS Designation C, max Mn, max P, max S, max Si, max Ni Cr Mo Se Ti N Nb E  + Ta
ASTM A320 B8, B8A S 30400(304) Range,% 0.08 2.00 0.045
0.030		 1.00 8.0-11.0 18.0 - 20.0 ... ... ... ... ...
Product Variation, % Over or Under 0.01 over 0.04 over 0.010 over 0.005 over 0.05 over 0.15 0.20 ... ... ... ... ...
ASTM A320 B8C, B8CA S 34700(347) Range,% 0.08 2.00 0.045
0.030		 1.00 9.0- 12.0 17.0- 19.0 ... ... ... ... 10 × C content, min -1.10 max
Product Variation, % Over or Under 0.01 over 0.04 over 0.010 over 0.005 over 0.05 over 0.15 0.20 ... ... ... ... 0.05 under
ASTM A320 B8T, B8TA S 32100(321) Range,% 0.08 2.00 0.045 0.030, max 1.00 9.0- 12.0 17.0- 19.0 ... ... 5 × (C+N) min -0.7 max 010, max ...
Product Variation, % Over or Under 0.01 over 0.04 over 0.010 over 0.005 over 0.05 over 0.15 0.20 ... ... 0.05 under 1 ...
ASTM A320 B8P, B8PA S 30500 Range,% 0.12 2.00 0.045 0.030, max 1.00 11- 13.0 17.0- 19.0 ... ... ... ... ...
Product Variation, % Over or Under 0.01 over 0.04 over 0.010 over 0.005 over 0.05 over 0.15 0.20 ... ... ... ... ...
ASTM A320 B8F, B8FA S 30300(303) Range,% 0.15 2.00 0.20 00.15, min 1.00 8.0 - 10.0 17.0- 19.0 ... ... ... ... ...
Product Variation, % Over or Under 0.01 over 0.04 over 0.010 over 0.20 0.05 over 0.10 0.20 ... ... ... ... ...
S 30323(303Se) Range,% 0.15 2.00 0.20 0.06, max 1.00 8.0 - 10.0 17.0- 19.0 ... 00.15- 035 ... ... ...
Product Variation, % Over or Under 0.01 over 0.04 over 0.010 over 0.010 over 0.05 over 0.10 0.20 ... 0.03 under ... ... ...
ASTM A320 B8F, B8FA S 30300(303) Range,% 0.01 over 0.04 over 0.010 over 0.02 0.05 over 0.1 0.2 . . . . . . . . . ... ...
Product Variation, % Over or Under 0.15 2 0.2 0.06, max 1 8.0-10.0 17.0-19.0 . . . 0.15-0.35 . . . ... ...
S 30323(303Se) Range,% 0.01 over 0.04 over 0.010 over 0.010 over 0.05 over 0.1 0.2 . . . 0.03 under . . . ... ...
Product Variation, % Over or Under 0.08 2 0.045 0.030, max 1 10.0-14.0 16.0-18.0 2.00-3.00 . . . . . . ... ...
ASTM A320 B8M, B8MA S 31600(316) Range,% 0.08 2.00 0.045 0.030, max 1.00 10.0 - 14.0 16.0 - 18.0 2.00 - 3.00 ... ... ... ...
Product Variation, % Over or Under 0.01 over 0.04 over 0.010 over 0.005 over 0.05 over 0.15 0.20 0.10 ... ... ... ...
ASTM A320 B8LN, B8LNA S 30453 Range,% 0.030 2.00 0.045 0.030 1.00 8.0-11 18.0-20.0 ... ... ... 0.10-0.16 ...
Product Variation, % Over or Under 0.005 over 0.04 over 0.010 over 0.005 over 0.05 over 0.15 0.20 ... ... ... 0.01 ...
ASTM A320 B8MLN, B8MLNA S 31653 Range,% 0.030 2.00 0.045 0.030 1.00 10.0-13.0 16.0-18.0 2.00-3.00 ... ... 0.10-0.16 ...
Product Variation, % Over or Under 0.005 over 0.04 over 0.010 over 0.005 over 0.05 over 0.15 0.20 0.10 ... ... 0.01 ...
  • (A) The intentional addition of Bi, Se, Te, and Pb is not permitted except for Grade B8F, in which selenium is specified and required.
  • (B) Typical steel compositions used for this grade include 4140, 4142, 4140.10- 4140H, 4142H, and 4145H.
  • (C) For the L7M grade, a minimum carbon content of 0.28 % is permitted provided that the required tensile properties are met in the section sizes involved; the use of AISI 4130 or 4130H is allowed.
  • (D) Class 1 are made from solution-treated material. Class 1A products (B8A, B8CA, B8MA, B8PA, B8FA, and B8TA) are solution-treated in the finished condition. Class 2 products are solution-treated and strain-hardened.
  • (E) Niobium and columbium are interchangeable names for the same element and both names are acceptable for use in A01.22 specifications.

ASTM A320/A320M Mechanical Requirements

Ferritic Steels

Class and Grade, Diameter, in. [mm] Heat Treatment Minimum Tempering Temperature, °F [°C] Tensile Strength, min, ksi [MPa] Yield Strength, min, ksi [MPa] (0.2 % offset) Elongation in 2 in. or 50 mm, min, % Reduction of Area, min, % Hardness, max
ASTM A320 L7, L7A, L7B, L7C, L70, L71, L72, L73 21/2 [65] and underA quenched and tempered 1100 [593] 125[860] 105[725] 16 50 321 HBW or 35  HRC
ASTM A320 L43 4[100] and underA quenched and tempered 1100 [593] 125[860] 105[725] 16 50 321 HBW or 35  HRC
ASTM A320 L7M 21/2[65] and underA quenched and tempered 1150 [620] 100[690] 80[550] 18 50 235 HBWBor 99 HRB
ASTM A320 L1 1[25] and underA quenched and tempered . . . 125[860] 105[725] 16 50 . . .

Austenitic Steels

Grade and Class  Diameter, in. [mm] Heat Treatment Minimum Tempering Temperature, °F [°C] Tensile Strength, min, ksi [MPa] Yield Strength, min, ksi [MPa] (0.2 % offset) Elongation in 2 in. or 50 mm, min, % Reduction of Area, min, % Hardness, max
ASTM A320 B8, B8C, B8M, B8P, B8F, B8T, B8LN, B8MLN : Class 1 All diameters carbide solution treated ... 75 [515] 30 [205] 30 50 223 HBWDor  96 HRB
ASTM A320 B8A, B8CA, B8MA, B8PA, B8FA, B8TA, B8LNA, B8MLNA : Class 1A All diameters carbide solution treated in the  finished condition ... 75 [515] 30 [205] 30 50 192 HBW or 90  HRB
ASTM A320 B8, B8C, B8P, B8F, B8T : Class 2 3/4 [20] and under  carbide solution treated and strain  hardened ... 125 [860] 100 [690] 12 35 321 HBW or 35  HRC
over 3/4 to 1 [20 to 25], incl ... 115 [795] 80 [550] 15 30 321 HBW or 35  HRC
over 1 to 11/4 [25 to 32], incl ... 105 [725] 65 [450] 20 35 321 HBW or 35  HRC
over 11/4 to 11/2 [32 to 40], inclA ... 100 [690] 50 [345] 28 45 321 HBW or 35  HRC
ASTM A320 B8M : Class 2 3/4 [20] and under carbide solution treated and strain  hardened ... 110 [760] 95 [655] 15 45 321 HBW or 35  HRC
over 3/4 to 1 [20 to 25], incl ... 100 [690] 80 [550] 20 45 321 HBW or 35  HRC
over 1 to 11/4 [25 to 32], incl ... 95 [655] 65 [450] 25 45 321 HBW or 35  HRC
over 11/4 to 11/2 [32 to 40], inclA ... 90 [620] 50 [345] 30 45 321 HBW or 35  HRC
  • (A) These upper diameter limits were established on the basis that these were the largest sizes commonly available that consistently met specification property limits. They are not intended as absolute limits beyond which bolting materials could no longer be certified to the specification.
  • (B) To meet the tensile requirements, the Brinell hardness shall not be less than 200 HBW or 93 HRB.
  • (C) Class 1 products are made from solution-treated material. Class 1A products are solution treated in the finished condition for corrosion resistance; heat treatment is critical for enhancing this physical property and meeting the mechanical property requirements. Class 2 products are made from solution-treated material that has been strain hardened. Austenitic steels in the strain-hardened condition may not show uniform properties throughout the cross section, particularly in sizes over 3/4 in. [20 mm] in diameter.
  • (D) For sizes 3/4 in. [20 mm] in diameter and smaller, a maximum hardness of 241 HBW (100 HRB) is permitted.

ASTM A320/A320M Impact Test Requirements

Grade Test Temperature CVN Specimen Section Size, mm Min Average Impact Toughness of Three Test Specimens, ft-lbf [J] Min Impact Value of a Single Specimen of Set of Three, ft-lbf [J]
°F °C
ASTM A320 L7M, L70, L71, L72, L73 - 100 - 73 10 × 10 20 [27] 15 [20]
10 × 7.5 16 [22] 12 [16]
10 × 10 20 [27] 15 [20]
ASTM A320 L7, L7A, L7B, L7C, L43 - 150 - 101 10 × 7.5 16 [22] 12 [16]
10 × 10 40 [54] 30 [41]
ASTM A320 L1 - 100 - 73 10 × 7.5 32 [44] 24 [32]

ASTM A320/A320M Bolting Surface Treatment Specifications

A153/A153M Specification for Hot Dip Galvanising (Zinc Coating) on Iron and Steel Hardware
B633 Specification for Electrodeposited Coatings of Zinc on Iron and Steel
B695 Specification for Coatings of Zinc Mechanically Deposited on Iron and Steel
B696 Specification for Coatings of Cadmium Mechanically Deposited
B766 Specification for Electrodeposited Coatings of Cadmium
F1941/F1941M Specification for Electrodeposited Coatings on Mechanical Fasteners, Inch and Metric
F2329/F2329M Specification for Zinc Coating, Hot-Dip, Requirements for Application to Carbon and Alloy Steel Bolts, Screws, Washers, Nuts, and Special Threaded Fasteners

ASTM A320/A320M 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.

Austenitic Steels

Grade Class Grade Symbol
ASTM A320 Grade B8 Class 1 TB B8
ASTM A320 Grade B8C TB B8C
ASTM A320 Grade B8M TB B8M
ASTM A320 Grade B8F TB B8F
ASTM A320 Grade B8P TB B8P
ASTM A320 Grade B8T TB B8T
ASTM A320 Grade B8LN TB B8F or TB B8LN
ASTM A320 Grade B8MLN TB B8G or TB B8MLN
ASTM A320 Grade B8A Class 1A TB B8A
ASTM A320 Grade B8CA TB B8TB B or TB B8CA
ASTM A320 Grade B8MA TB B8D or TB B8MA
ASTM A320 Grade B8FA TB B8FA
ASTM A320 Grade B8PA TB B8H or TB B8PA
ASTM A320 Grade B8TA TB B8J or TB B8TA
ASTM A320 Grade B8LNA TB B8L or TB B8LNA
ASTM A320 Grade B8MLNA TB B8K or TB B8MLNA
ASTM A320 Grade B8 Class 2 TB B8SH
ASTM A320 Grade B8C TB B8CSH
ASTM A320 Grade B8M TB B8MSH
ASTM A320 Grade B8F TB B8FSH
ASTM A320 Grade B8P TB B8PSH
ASTM A320 Grade B8T TB B8TSH

Ferritic Steels

Grade Grade Symbol
ASTM A320 L1 TB L1
ASTM A320 L7 TB L7
ASTM A320 L7A TB L7A
ASTM A320 L7B TB L7B
ASTM A320 L7M TB L7M
ASTM A320 L7C TB L7C
ASTM A320 L43 TB L43
ASTM A320 L70 TB L70
ASTM A320 L71 TB L71
ASTM A320 L72 TB L72
ASTM A320 L73 TB L73

ASME Dimensional Standards

B18.31.2 Imperial Continious Thread, Double End Reduced & Full Body Studs
B18.31.1M Metric Continious Thread, Double End Reduced & Full Body Studs
B16.5 Imperial Full Thread Stud Bolts
B16.5 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

ASTM A320/A320M 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 A320/A320M Testing Standards

E18 Test Methods for Rockwell Hardness of Metallic Materials
E21 Test Methods for Elevated Temperature Tension Tests of Metallic Materials
E112 Test Methods for Determining Average Grain Size
E139 Test Methods for Conducting Creep, Creep-Rupture,and Stress-Rupture Tests of Metallic Materials
E150 Recommended Practice for Conducting Creep and Creep-Rupture Tension Tests of Metallic Materials Under Conditions of Rapid Heating and Short Times
E151 Recommended Practice for Tension Tests of Metallic Materials at Elevated Temperatures with Rapid Heating and Conventional or Rapid Strain Rates
E292 Test Methods for Conducting Time-for-Rupture Notch Tension Tests of Materials
E328 Test Methods for Stress Relaxation for Materials and Structures
E566 Practice for Electromagnetic (Eddy Current) Sorting of Ferrous Metals
E709 Guide for Magnetic Particle Testing
F606/F606M Test Methods for Determining the Mechanical Properties of Externally and Internally Threaded Fasteners, Washers, Direct Tension Indicators, and Rivets
F1940 Test Method for Process Control Verification to Prevent Hydrogen Embrittlement in Plated or Coated Fasteners
A962/A962M Specification for Common Requirements for Bolting Intended for Use at Any Temperature from Cryogenic to the Creep Range
A788/A788M for Steel Forgings, General Requirements

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 A320/A320M Supplementary Requirements

S1 Impact Properties
S2 Lateral Expansion
S3 Hardness Testing of Class 2 Bolting Components for ASME Applications
S4 Restriction to Use Only Ingot Cast Steel