What this is about
Buyers often see A2-70 and A4-80 on drawings and ask which stainless fastener to order. Both are austenitic stainless property classes under ISO 3506-1, but they map to different alloys and corrosion environments.
Spec comparison
| Item | A2-70 | A4-80 |
|---|---|---|
| Typical alloy | 304 / SUS304 | 316 / SUS316 |
| Property class | A2-70 (min ~700 MPa tensile for the fastener) | A4-80 (higher strength class in the A4 family) |
| Corrosion focus | General industrial, indoor, mild outdoor | Chlorides, marine splash, chemical washdown |
| Relative cost | Lower | Higher |
| Common catalog callout | Metric SHCS, hex head, machine screws | Same forms when drawings specify 316 / A4 |
When to choose A2-70 (304)
- Indoor frames, fixtures, electronics housings
- General OEM/MRO where 316 is not specified
- Cost-sensitive builds that still need stainless vs carbon steel
Shop our stocked metric lines: socket head cap screws, hex head screws, machine screws.
When to choose A4-80 (316)
- Coastal / marine-adjacent equipment
- Food / washdown areas with chlorides
- Drawings that explicitly call A4, 316, or SUS316
If your drawing says A4-80 and you only see A2-70 in a catalog, do not substitute without engineering approval. Contact sales with the drawing for 316 / A4 availability and lead time.
RFQ checklist
- Property class: A2-70 or A4-80 (do not mix on the same critical joint without review)
- Thread × length × standard (e.g. M6 × 20 · DIN 912 / ISO 4762)
- Docs: MTC, RoHS, REACH
- Ship-to country and quantity
FAQ
Q: Is A2-70 the same as 18-8?
A: Commercially related to 304 / 18-8 families; always confirm chemistry and class on the mill test certificate.
Q: Can I swap A4-80 for A2-70 to save cost?
A: Only if the drawing and corrosion environment allow it. Chloride or marine callouts usually require A4 / 316.
Q: Do you stock A2-70 on the website?
A: Yes — Pisenfasten catalogs metric 304 / A2-70 across major families. Open the catalog or a category page, then filter thread and length.
Q: How do I get A4 / 316?
A: Email sales@pisenfasten.com with SKU equivalents or the drawing; we quote production or alternate lots.