A2 Stainless Steel SEMS Screws with Captive Spring Washer are supplied to DIN 6900-4. The grade provides good general corrosion resistance and is largely non-magnetic; the practical service range is approx. -200 °C to +400 °C, subject to the property class and the joint. Property data, grade comparison and the full size table follow.
Why Choose A2 Stainless Steel for SEMS Screws with Captive Spring Washer
The most common stainless group for indoor and general outdoor fasteners. For sems screws with captive spring washer, 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 |
Corrosion Behavior in Service
A2 (304) gives excellent atmospheric and most-water corrosion resistance and is the most common stainless for SEMS Screws with Captive Spring Washer in indoor and general outdoor service. In chloride-bearing environments (marine air, road salt, swimming pools) consider stepping up to A4 (316).
Galvanic & Galling Considerations
Two important notes for stainless sems screws with captive spring washer: (1) stainless can gall on stainless threads under load — use a thread lubricant or anti-galling compound, especially for M6 and below; (2) when joined to aluminum or galvanized steel, stainless can drive galvanic corrosion of the less-noble metal in wet service — isolate with a coating or sleeve where appropriate.
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 SEMS Screws with Captive Spring Washer Available in A2 Stainless Steel
| Thread size | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Washer outer diameter (mm) | Cross recess | Common length range (mm) | Reference standard |
|---|---|---|---|---|---|---|---|
| M3 | 0.5 | 5.6 | 2.4 | 6.2 | PH1 / PZ1 | 5~30 | DIN 6900-4 |
| M4 | 0.7 | 8.0 | 3.1 | 8.0 | PH2 / PZ2 | 6~40 | DIN 6900-4 |
| M5 | 0.8 | 9.5 | 3.7 | 10.0 | PH2 / PZ2 | 8~50 | DIN 6900-4 |
| M6 | 1.0 | 12.0 | 4.6 | 12.2 | PH3 / PZ3 | 8~60 | DIN 6900-4 |
| M8 | 1.25 | 16.0 | 6.0 | 15.4 | PH4 / PZ4 | 10~60 | DIN 6900-4 |
| M10 | 1.5 | 20.0 | 7.5 | 18.4 | PH4 / PZ4 | 12~60 | DIN 6900-4 |
