L7 and L7M: low-temperature bolting
Quenched and tempered alloy steels for bolts and studs. L7M has different hardness and strength requirements from L7: M does not mean “metric”. Specify minimum design temperature and required impact testing.
What to check for low-temperature service
| Field | Check |
|---|---|
| Temperature | Minimum design temperature, test temperature and applicable code criteria |
| Charpy impact | Required energy, specimen and lot results |
| Nuts | Compatible grade and testing; for L7M assess A194 7M with applicable requirements |
| Marking and documents | Grade, lot and test traceability |
Charpy test temperature is not automatically a universal minimum service temperature. Do not transfer A193 thermal values to A320.
L7 and L7M: separate enquiries
State the exact grade and project temperature conditions. The M suffix is not interpreted as a simple indication of metric thread.
Testing requirements
Include the tests and acceptance criteria required by the project. Documentation is reviewed against the configuration and supply lot.