ASTM A320 Specifications
Technical Menu Posted on July 1st, 2015 by vaproThe ASTM A320 specification covers alloy steel and stainless steel bolting materials for low temperature service. This standard covers rolled, forged, or strain hardened bars, bolts, screws, studs, and stud bolts used for pressure vessels, valves, flanges, and fittings. Like the ASTM A193 specification, unless otherwise specified, the 8UN thread series is specified on fastener larger than 1” in diameter.
| Grades | |
|---|---|
| ASTM A320 L7 Alloy steel | AISI 4140/4142 Quenched and tempered |
| ASTM A320 L43 Alloy steel | AISI 4340 Quenched and tempered |
| ASTM A320 B8 Class 1 Stainless steel | AISI 304, carbide solution treated |
| ASTM A320 B8M Class 1 Stainless steel | AISI 316, carbide solution treated |
| ASTM A320 B8 Class 2 Stainless steel | AISI 304, carbide solution treated, strain hardened |
| ASTM A320 B8M Class 2 Stainless steel | AISI 316, carbide solution treated, strain hardened |
A320 Mechanical Properties
| Grade | Size | Tensile, ksi min | Yield, ksi, min | Charpy Impact | Elong, % min | RA, %, min |
|---|---|---|---|---|---|---|
| L7 | up to 21/2 | 125 | 105 | -150° F | 16 | 50 |
| L43 | sup a 4 | 125 | 105 | -150° F | 16 | 50 |
| B8 Class 1 | all | 75 | 30 | N/A | 30 | 50 |
| B8M Class 1 | all | 75 | 30 | N/A | 30 | 50 |
| B8 Class 2 | Up to 3/4 | 125 | 100 | N/A | 12 | 35 |
| 7/8 – 1 | 115 | 80 | N/A | 15 | 35 | |
| 11/8 – 11/4 | 105 | 65 | N/A | 20 | 35 | |
| 13/8 – 11/2 | 100 | 50 | N/A | 28 | 45 | |
| B8M Class 2 | Up to 3/4 | 110 | 95 | N/A | 15 | 45 |
| 7/8 – 1 | 100 | 80 | N/A | 20 | 45 | |
| 11/8 – 11/4 | 95 | 65 | N/A | 25 | 45 | |
| 13/8 – 11/2 | 90 | 50 | N/A |
A320 Chemical Properties
| Element | L7 (AISI 4140) | L43 (AISI 4340) | B8 (AISI 304) | B8M (AISI 316) |
|---|---|---|---|---|
| Carbon | 0.37 – 0.49% | 0.38 – 0.43% | 0.08% max | 0.08% max |
| Manganese | 0.65 – 1.10% | 0.75 – 1.00% | 2.00% max | 2.00% max |
| Phosphorus, max | 0.04% | 0.04% | 0.05% | 0.05% |
| Sulfur, max | 0.04% | 0.04% | 0.03% | 0.03% |
| Silicon | 0.15 – 0.35% | 0.15 – 0.35% | 1.00% max | 1.00% max |
| Chromium | 0.75 – 1.20% | 0.70 – 0.90% | 18.0 – 20.0% | 16.0 – 18.0% |
| Nickel | 1.65 – 2.00% | 8.0 – 11.0% | 10.0 – 14.0% | |
| Molybdenum | 0.15 – 0.25% | 0.20 – 0.30% | 2.00 – 3.00% |
Related: ASTM A320 Specifications on ASTM.org
