ASTM A320 / A320M Metric Edition
Joint inch-pound and SI specification for low-temperature bolting
ASTM A320 / A320M is a joint inch-pound and SI specification. The "M" suffix indicates the metric edition. Tensile and yield values appear in both ksi (inch-pound) and MPa (SI); impact energies in both ft-lbf and J; specimen sections in both inches and mm. Engineers working in metric jurisdictions (Europe, Middle East, India, Latin America) typically cite the A320M designation.
Inch-pound versus SI cross-references
- Tensile strength: 125 ksi = 860 MPa minimum (Grade L7)
- Yield strength: 105 ksi = 725 MPa minimum (Grade L7)
- Charpy V-notch test temperature: -150°F = -101°C
- Charpy minimum average energy: 40 ft-lbf = 54 J (full-size 10 x 10 mm specimens, Grade L7)
- Diameter ranges: 2-1/2 in = 65 mm
- Hardness: 321 HBW (same value in either unit system)
When to specify A320M
Specify A320M (the metric edition) when project drawings, datasheets, and material requisitions are expressed in SI units. Specify A320 (inch-pound) when working in customary US units. Both editions are identical in technical content; only the unit basis differs. Most TorqBolt EN 10204 3.1 / 3.2 certificates dual-report values in both unit systems.