B7Stud bolt
ASTM A193 Grade B7
The default stud bolt grade for flanged joints in refineries and process plants. Quenched-and-tempered chrome-moly steel giving 860 MPa tensile, almost always supplied with A194 2H nuts.
- 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
-48 °C+427 °C−273+900 °C
Below −48 °C use A320 L7, which is the same steel with a mandatory Charpy impact test. Above 427 °C use A193 B16.
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) | 720 MPa (105 ksi) | 16 % | 50 % |
| > 2½ – 4 in (M64–M100) | 795 MPa (115 ksi) | 655 MPa (95 ksi) | 16 % | 50 % |
| > 4 – 7 in (M100–M180) | 690 MPa (100 ksi) | 515 MPa (75 ksi) | 18 % | 50 % |
Matching nuts
Matching washersASTM F436 hardened washers where required by the flange design
Recommended coatings
Equivalent grades
- AISI 4140
- EN 42CrMo4 / 1.7225
- DIN 42CrMo4
- JIS SCM440
- BS EN 10269 42CrMo4
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