L7MStud bolt
ASTM A320 Grade L7M
The grade that satisfies both problems at once: cold enough for cryogenic service and soft enough for sour service. Hardness capped at 235 HBW with a Charpy test at −101 °C, and every stud hardness tested.
- Base material
- Chromium-molybdenum alloy steel (AISI 4140 / 4142 / 4145)
- Heat treatment condition
- Quenched and tempered at 620 °C minimum, hardness-controlled
- Hardness, max
- 235 HBW / 99 HRB maximum — every stud tested individually
Service temperature
-101 °C+427 °C−273+900 °C
Pair only with A194 grade 7M nuts. Mixing a 7M stud with a grade 7 nut defeats the hardness control that the sour service specification is asking for.
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) | 690 MPa (100 ksi) | 550 MPa (80 ksi) | 18 % | 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 low tempered + impact tested
- NACE MR0175 low temperature bolting
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