Skip to main content

ASTM A320 TECHNICAL DATA

 

Order A320 L7 Stud Bolts Order A320 B8 Stud Bolts Order A320 B8M Stud Bolts

 

 

Technical Data: ASTM A320 Grades and Markings ASTM A320 Mechanical Properties ASTM A320 Materials & Chemical Properties

ASTM A320 Grades and Markings

The ASTM A320 specification encompasses the standard that covers high-strength low-alloy steel shapes for bolting material used for pressure valves, flanges, vessels, and fittings for high-temperature applications.  For this specification, it covers wire, bars, bolts, studs, stud bolts, and screws. They are mainly used in chemical construction and petroleum applications. Although, this material is often utilized in national coarse thread pitches, but threads are specified 8 threads per inch (tpi) for diameters above 1 inch when being used in traditional applications.

Grades and Markings

Marking of Ferritic Steels
Grade Grade Symbol
L7 L7
L7M L7M
L70 L70
L7A L7A
L71 L71
L7B L7B
L72 L72
L7C L7C
L73 L73
L43 L43
L1 L1
Marking of Austenitic Steels
Class Grade Grade Symbol
Class 1 B8
B8C
B8M
B8F
B8P
B8T
B8LN
B8MLN 		B8
B8C
B8M
B8F
B8P
B8T
B8F or B8LN
B8G or B8MLN
Class 1A B8A
B8CA
B8MA
B8FA
B8PA
B8TA
B8LNA
B8MLNA 		B8A
B8B or B8CA
B8D or B8MA
B8FA
B8H or B8PA
B8J or B8TA
B8L or B8LNA
B8K or B8MLNA
Class 2 B8
B8C
B8M
B8F
B8P
B8T 		B8SH
B8CSH
B8MSH
B8FSH
B8PSH
B8TSH

 

ASTM A320 Mechanical Properties

ASTM A320 Specifications for Mechanical Properties governs the material specification defining mechanical properties, chemical composition, and preferential heat treatment. In addition, it governs product marking, hardness requirements, certifications, and more. ASTM A320 defines both SI (Metric) and inch-pound units.

MECHANICAL PROPERTIES

Class and Grade, Diameter, in. [mm] Heat Treatment Minimum Tempering Temperature, F°[C°] Tensile Strength,
min,
ksi [Mpa]		 Yield Strength,
min,
0.2 % offset,
ksi		 Elongation in 2 in. or 50mm,
min,
%		 Reduction of Area,
min,
%		 Hardness,
max
L7, L7A, L7B, L7C, L70, L71, L72, L73
2 1/2 [65] and underA		 Quenched and Tempered 1100 [593] 125 [860] 105 [725] 16 50 321 HBW or 35 HRC
L43
4 [100] and underA		 Quenched and Tempered 1100 [593] 125 [860] 105 [725] 16 50 321 HBW or 35 HRC
L7M
2 1/2 [65] and underA		 Quenched and Tempered 1150 [620] 100 [690] 80 [550] 18 50 235 HBW or 99 HRB
L1
1[25] and underA		 Quenched and Tempered   125 [860] 105 [725] 16 50  
Class and Grade, Diameter, in. [mm] Heat TreatmentB Tensile Strength,
min,
ksi		 Yield Strength,
min,
0.2 % offset, ksi		 Elongation in 2in or 50mm,
min,
%		 Reduction of Area,
min,
%		 Hardness, max
Class 1: B8, B8C, B8M, B8P, B8F, B8T, B8LN, B8MLN, all diameters Carbide solution treated 75 [515] 30 [205] 30 50 223 HBWB or 96 HRBC
Class 1A: B8A, B8CA, B8MA, B8PA, B8FA,
B8TA, B8LNA, B8MLNA, all diameters		 Carbide Solution Treated in the Finished Condition 75 [515] 30 [205] 30 50 192 HBW or 90 HRB
Class 2: B8, B8C, B8P, B8F, B8T: 3/4 [20] and under

over 3/4 to 1 [20 to 25], incl
over 1 to 1 1/4 [25 to 32], incl
over 1 1/4 to 1 1/2 [32 to 140], incl 		Carbide Solution Treated and Strain Hardened 125 [860]

115 [795]
105 [725]
100 [690] 		100 [690]

80 [550]
65 [450]
50 [345] 		12

15
20
28 		35

35
35
45 		321 HBW or 35 HRC

321 HBW or 35 HRC
321 HBW or 35 HRC
321 HBW or 35 HRC
Class 2: B8M: 3/4 [20] and under

over 3/4 to 1 [20 to 25], incl
over 1 to 1 1/4 [25 to 32], incl
over 1 1/4 to 1 1/2 [32 to 140], incl 		Carbide Solution Treated and Strain Hardened 110 [760]

100 [690]
95 [655]
90 [620] 		95 [655]

80 [550]
65 [450]
50 [345] 		15

20
25
30 		45

45
45
45 		321 HBW or 35 HRC

321 HBW or 35 HRC
321 HBW or 35 HRC
321 HBW or 35 HRC

AThese 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 be over 200 HBW (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 solution treated and strain hardened. Austenitic steels in the strain-hardened condition may not show uniform properties throughout the section particularly in sizes over 3⁄4 in. in diameter.
DFor sizes 3/4 in. [20 mm] in diameter and smaller, a maximum hardness of 241 HBW (100 HRB) is permitted.

ASTM A320 Materials & Chemical Properties

Material and Chemical Property Requirements for the ASTM A320 governs minimum and maximum carbon, phosphorus, manganese, sulfur, silicon, chromium, nickel, and molybdenum percent content of steel fasteners within the ASTM A320 specification. The properties also include the minimum tempering temperature requirements. 

MATERIALS & CHEMICAL PROPERTIES

Ferritic Steels
Grade Description and UNS Designation Carbon Manganese Phosphorous, max Sulfur, max Silicon Nickel Chromium Molybdenum Boron
L7, L7M, L70 Chromium-MolybdenumB 0.38-0.48C 0.75-1.00 0.035 0.040 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 ...
L7A, L71 Carbon-Molybdenum (AISI 4037) 0.35-0.40 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 ...
L7B, L72 Chromium- Molybdenum (AISI 4137)C   0.35-0.40 0.70-0.90
 0.035 0.040 0.15-0.35
 0.80-1.10 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
L7C, L73 Nickel-Chromium-Molybdenum (AISI 8740) 0.38-0.43 0.75-1.00 0.035 0.040 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 ...
L43 Nickel-Chromium-Molybdenum (AISI 4340) 0.38-0.43 0.60-0.85 0.035 0.040 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 ...
L1 Low-Carbon Boron 0.17-0.24 0.70-1.40 0.035 0.050 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 Description and UNS Designation Class Carbon Manganese Phosphorous Sulfur Silicon Nickel Chromium NiobiumE + Tantalum Molybdenum Selenium Titanium Nitrogen
B8, B8A 304, S30400 1, 1A, 2D 0.08 2.00 0.045 0.030 1.00 8.00-11.00 18.0-20.0 ... ... ... ... ...
Product Variation, %
Over or Under		 0.01 0.04 0.010 0.005 0.05 0.15 0.20 ... ... ... ... ...
B8C, B8CA 347, S31600 1, 1A, 2D 0.08 2.00 0.045 0.030 1.00 9.00-12.00 17.0-19.0 10 x carbon content, min. -1.10 max ... ... ... ...
Product Variation, %
Over or Under		 0.01 0.04 0.010 0.005 0.05 0.2 0.05 under ... ... ... ... ...
B8T, B8TA 321, S32100 1, 1A, 2D 0.08 2.00 0.045 0.030 max 1.00 9.0-12.0 17.0-19.0 ... ... ... 5 x (C+N) min - 0.7 max 0.10 max
Product Variation, %
Over or Under		 0.01 0.04 0.010 0.005 0.05 0.15 0.20 ... ... ... 0.05 under 0.01
B8P, B8PA S30500 1, 1A, 2D 0.12 2.00 0.045 0.030, max 1.00 11.0-13.0 17.0-19.0 ... ... ... ... ...
Product Variation, %
Over or Under		 0.01 0.04 0.010 0.005 0.05 0.15 0.20 ... ... ... ... ...
B8F, B8FA 303, S30300 1A, 1B, 2D 0.15 2.00 0.20 0.15, min. 1.00 8.0-10.0 17.0-19.0 ... ... 0.15-0.35 (303Se only) ... ...
Product Variation, %
Over or Under		 0.01 0.04 0.010 0.020 0.05 0.10 0.20 ... ... 0.03 under (303Se only) ... ...
B8M, B8MA 316, S31600 1A, 1B, 2D 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 0.04 0.010 0.005 0.05 0.15 0.20 ... 0.10 ... ... ...
B8LN, B8LNA S30453 1, 1A 0.03 2.00 0.045 0.030 1.00 8.0-11.0 18.0-20.0 ... ... ... ... 0.10-0.16
Product Variation, %
Over or Under		 0.005 0.04 0.010 0.005 0.05 0.15 0.20 ... ... ... ... 0.01
B8MLN, B8MLNA 31653 1, 1A 0.03 2.00 0.045 0.030 1.00 10.0-13.0 16.0-18.0 ... 2.0-3.0 ... ... 0.10-0.16
Product Variation, %
Over or Under		 0.005 0.04 0.010 0.005 0.05 0.15 0.20 ... 0.10 ... ... 0.01

AThese 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 be over 200 HBW (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 solution treated and strain hardened. Austenitic steels in the strain-hardened condition may not show uniform properties throughout the section particularly in sizes over 3⁄4 in. in diameter.
DFor sizes 3/4 in. [20 mm] in diameter and smaller, a maximum hardness of 241 HBW (100 HRB) is permitted.