B7MStud bolt
ASTM A193 Grade B7M
B7 tempered back to 235 HBW maximum so it resists sulphide stress cracking. This is the grade sour service specifications call for, and every single stud is hardness tested — not one per batch.
- 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
-48 °C+427 °C−273+900 °C
Specified when NACE MR0175 / ISO 15156 applies. Note the lower yield strength: a joint designed for B7 cannot simply be re-bolted with B7M without checking the bolt load.
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 |
|---|---|---|---|---|
| ≤ 4 in (≤ M100) | 690 MPa (100 ksi) | 550 MPa (80 ksi) | 18 % | 50 % |
| > 4 – 7 in (M100–M180) | 690 MPa (100 ksi) | 515 MPa (75 ksi) | 18 % | 50 % |
Matching nuts
Matching washersASTM F436 washers, hardness-controlled to match
Recommended coatings
Equivalent grades
- AISI 4140 (tempered low)
- EN 42CrMo4 / 1.7225
- NACE MR0175 compliant bolting
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