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Testing
Tensile and diameter per lot; relaxation data where the spring duty depends on it.
| Property | Method | Establishes | Where |
|---|---|---|---|
| Tensile | ASTM E8, per lot | The load the spring is designed from | Certificate |
| Elongation | Per lot | Whether the wire will coil without cracking | Certificate |
| Diameter | In-line laser micrometer, 0.001 mm | Coiling consistency | Recorded against the spool |
| Surface | Eddy current and visual | Defects that become fatigue initiation | Report |
| Relaxation | Stress relaxation test | Load retained at temperature and time | Report, on request |
Why relaxation is a separate test
Tensile tells you the wire’s strength at room temperature; it does not tell you how much load the finished spring keeps after a thousand hours at 600 °C. Where that number matters, say so at enquiry and the relaxation test is scheduled rather than assumed.