A2 / A4Stud bolt
ISO 3506-1
The metric stainless system. A2 is 304, A4 is 316 with molybdenum; the number after the dash is tensile strength ÷ 10, so A4-80 means 316 stainless at 800 MPa.
- Base material
- Austenitic stainless steel — A2 (304) and A4 (316)
- Heat treatment condition
- Cold worked to the strength grade ordered
- Hardness, max
- Not the controlling property — strength grade is verified by tensile test
Service temperature
-200 °C+400 °C−273+900 °C
Stainless threaded rod galls when tightened dry, and the risk rises with diameter. Anti-seize or a PTFE coating is not optional above M20.
Chemical composition
| Element | Min (% by weight) | Max (% by weight) | Notes |
|---|---|---|---|
| Cr | 17.0 | 19.0 | A2 |
| Ni | 8.0 | 19.0 | A2 |
| Cr | 16.0 | 18.5 | A4 |
| Ni | 10.0 | 15.0 | A4 |
| Mo | 2.0 | 3.0 | A4 |
| C | — | 0.08 | — |
Mechanical properties
| Diameter | Tensile strength, min | Yield strength, min | Elongation, min | Reduction of area, min |
|---|---|---|---|---|
| A2-70 / A4-70 (≤ M39) | 700 MPa | 450 MPa | 0.4 d | — |
| A2-80 / A4-80 (≤ M39) | 800 MPa | 600 MPa | 0.3 d | — |
| A2-50 / A4-50 (mem / soft) | 500 MPa | 210 MPa | 0.6 d | — |
Recommended coatings
Equivalent grades
- EN ISO 3506-1
- DIN 267-11
- A2 ≈ AISI 304
- A4 ≈ AISI 316
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