Gr 7Matching nuts
ASTM A194 Grade 7
Made from the same 4140 as the stud it goes on, so nut and bolt expand and contract together. The usual choice for A320 L7 in cryogenic service.
- Base material
- Chromium-molybdenum alloy steel (AISI 4140)
- Heat treatment condition
- Quenched and tempered
- Hardness, max
- 235–311 HBW (21–34 HRC)
Service temperature
-101 °C+538 °C−273+900 °C
When A320 governs, the nut carries the same low-temperature qualification as the stud.
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
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 | — | — | — | 235–311 HBW · 21–34 HRC |
Recommended coatings
Equivalent grades
- ASME SA194 Gr 7
- AISI 4140 nut
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