Gr 4Matching nuts
ASTM A194 Grade 4
Carbon steel with 0.20–0.30 % molybdenum added so it keeps its strength at temperature. Specified with A193 B16 and A320 L7 where 2H is not accepted.
- Base material
- Carbon-molybdenum steel
- Heat treatment condition
- Quenched and tempered
- Hardness, max
- 24 HRC minimum, 38 HRC maximum
Service temperature
-101 °C+538 °C−273+900 °C
One of the two nut grades A320 permits on L7 and L43 studs.
Chemical composition
| Element | Min (% by weight) | Max (% by weight) |
|---|---|---|
| C | 0.40 | 0.50 |
| Mn | 0.70 | 0.90 |
| P | — | 0.035 |
| S | — | 0.040 |
| Si | 0.15 | 0.35 |
| Mo | 0.20 | 0.30 |
Mechanical properties
ASTM A194 does not set a separate tensile requirement for nuts. The grade is controlled by hardness and by a proof load test, which is why the strength columns below read as dashes.
| Diameter | Tensile strength, min | Yield strength, min | Elongation, min | Hardness, max |
|---|---|---|---|---|
| Tat ca / All | — | — | — | 24–38 HRC · 248–352 HBW |
Recommended coatings
Equivalent grades
- ASME SA194 Gr 4
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