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. Specified on flow-drilling screws it determines the corrosion behaviour (good general corrosion resistance) and the service temperature range (approx. -200 °C to +400 °C, subject to the property class and the joint); the dimensions are ours rather than a standard's, and are listed in full below.
Why Choose A2 Stainless Steel for Flow-Drilling Screws
The most common stainless group for indoor and general outdoor fasteners. For flow-drilling screws, 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 Flow-Drilling Screws 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 flow-drilling screws: (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 with an electrolyte present — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. Area ratio decides how bad it gets: a small stainless fastener in a large aluminum section is normally acceptable, a large stainless fastener in thin aluminum is not. Where the joint gets wet, isolate the metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Flow-Drilling Screws Available in A2 Stainless Steel
| Thread size | Clearance-hole diameter (mm) | Steel sheet range (mm) | Aluminum sheet range (mm) | Magnesium sheet range (mm) | Example drive / head |
|---|---|---|---|---|---|
| M3 | 3.6~4.0 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | varies by series |
| M3.5 | 4.3~4.8 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | varies by series |
| M4 | 5.1~5.7 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | M4×20 stainless; PH2/PZ2/T25 examples |
| M5 | 6.7~7.4 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | M5×20 stainless; PH2/PZ2/T25 examples |
| M6 | 8.2~9.1 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | varies by series |
Dimensions are independent of the material: every size above is available in A2 Stainless Steel.
Custom manufacturing · Made to drawing
Need this screw in a grade that is not listed?
A2 Stainless Steel is one of the grades the catalog describes. Lengths and thread lengths outside the standard table are the commonest request, followed by a drive the standard does not offer and a head marked with your own part number. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
