L7Stud bolt
ASTM A320 Grade L7
Chemically the same steel as B7, but every heat must pass a Charpy V-notch impact test at −101 °C. That test is the whole point of the grade — it is what makes it legal for LNG and cryogenic piping.
- Base material
- Chromium-molybdenum alloy steel (AISI 4140 / 4142 / 4145)
- Heat treatment condition
- Quenched and tempered at 593 °C minimum
- Hardness, max
- 321 HBW / 35 HRC maximum
Service temperature
-101 °C+427 °C−273+900 °C
L7 is limited to 2½ in diameter. Above that, A320 L43 (AISI 4340) carries the same impact requirement up to 4 in.
Chemical composition
| Element | Min (% by weight) | Max (% by weight) |
|---|---|---|
| C | 0.37 | 0.49 |
| Mn | 0.65 | 1.10 |
| P | — | 0.035 |
| S | — | 0.040 |
| Si | 0.15 | 0.35 |
| Cr | 0.75 | 1.20 |
| Mo | 0.15 | 0.25 |
Mechanical properties
| Diameter | Tensile strength, min | Yield strength, min | Elongation, min | Reduction of area, min |
|---|---|---|---|---|
| ≤ 2½ in (≤ M64) | 860 MPa (125 ksi) | 725 MPa (105 ksi) | 16 % | 50 % |
Charpy V-notch impact
Charpy V-notch at −101 °C: 27 J average of three specimens, 20 J minimum on any one specimen.
Matching nuts
Recommended coatings
Equivalent grades
- AISI 4140 impact tested
- EN 42CrMo4 + KV −100 °C
- ASTM A320 L7 / L7A / L7B
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