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Overview
Specifications
4140
The 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. Grade L7 is manufactured from AISI 4140/4142 Quenched and Tempered alloy steel.
MECHANICAL PROPERTIES
| Grade | Size | Tensile (KSI) | Yield (KSI) | Impact Temp | Elong % min | RA % min |
|---|---|---|---|---|---|---|
| L7 | up to 2-1/2″ | 125 | 105 | -150°F | 16 | 50 |
| L43 | up to 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 |
| B8 Class 2 | 7/8″ – 1″ | 115 | 80 | N/A | 15 | 35 |
| B8 Class 2 | 1-1/8″ – 1-1/4″ | 105 | 65 | N/A | 20 | 35 |
| B8 Class 2 | 1-3/8″ – 1-1/2″ | 100 | 50 | N/A | 28 | 45 |
| B8M Class 2 | Up to 3/4″ | 110 | 95 | N/A | 15 | 45 |
| B8M Class 2 | 7/8″ – 1″ | 100 | 80 | N/A | 20 | 45 |
| B8M Class 2 | 1-1/8″ – 1-1/4″ | 95 | 65 | N/A | 25 | 45 |
| B8M Class 2 | 1-3/8″ – 1-1/2″ | 90 | 50 | N/A |
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% |
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 |