A2 Stainless Steel (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70) is the most common stainless group for indoor and general outdoor fasteners. When retaining ring (circlip) are specified in this grade, the dimensions remain per ISO / DIN; the material determines corrosion behavior (good general corrosion resistance) and the service temperature range (approx. -200 °C to +400 °C, subject to the property class and the joint). Both are covered below with the size table.
Why Choose A2 Stainless Steel for Retaining Ring (Circlip) — ISO / DIN (Series 151)
The most common stainless group for indoor and general outdoor fasteners. For retaining ring (circlip) — iso / din (series 151), this matters when good general corrosion resistance is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Good general corrosion resistance |
Galvanic & Galling Considerations
For stainless retaining ring (circlip) — iso / din (series 151) the compatibility question is galvanic rather than galling: joined to aluminum or galvanized steel in wet service, stainless drives corrosion of the less-noble metal. Isolate with a coating, sleeve or non-conductive washer where the joint sees moisture. Note also that stainless is softer than hardened carbon steel, so where the part carries a wear or shear duty, check the load against the grade before substituting.
Comparable Grades
For Retaining Ring (Circlip) — ISO / DIN (Series 151), the alternative stainless grade is A4 (316). A2 (304) suits general indoor and outdoor service; A4 (316) adds molybdenum for marine and chloride environments. Where higher strength matters more than corrosion, switch to plated alloy-steel class 8.8 or 10.9.
Using Stainless Fasteners in Aluminum
Stainless steel is more noble than aluminum, so in the presence of an electrolyte — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. The effect is driven by the area ratio: a small stainless fastener in a large aluminum section is normally acceptable, while a large stainless fastener in thin aluminum is not. Where the joint is wet, isolate the two metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Retaining Ring (Circlip) — ISO / DIN (Series 151) Available in A2 Stainless Steel
| Nominal diameter (mm) | Ring diameter d1 (mm) | Groove diameter d2 (mm) | Thickness s (mm) | Type | Reference standard |
|---|---|---|---|---|---|
| 8 | 7.4 | 7.1 | 0.8 | External | DIN 471 / GB/T 894 |
| 10 | 9.3 | 9.0 | 1.0 | External | DIN 471 / GB/T 894 |
| 12 | 11.1 | 10.8 | 1.0 | External | DIN 471 / GB/T 894 |
| 16 | 15.0 | 14.7 | 1.0 | External | DIN 471 / GB/T 894 |
| 20 | 19.0 | 18.7 | 1.2 | External | DIN 471 / GB/T 894 |
| 25 | 23.9 | 23.6 | 1.2 | External | DIN 471 / GB/T 894 |
| 30 | 28.9 | 28.6 | 1.5 | External | DIN 471 / GB/T 894 |
| 40 | 38.5 | 38.2 | 1.75 | External | DIN 471 / GB/T 894 |
| 50 | 48.5 | 48.2 | 2.0 | External | DIN 471 / GB/T 894 |
| 60 | 58.3 | 58.0 | 2.0 | External | DIN 471 / GB/T 894 |
| 80 | 78.0 | 77.7 | 2.5 | External | DIN 471 / GB/T 894 |
| 100 | 98.0 | 97.7 | 3.0 | External | DIN 471 / GB/T 894 |
