A4 Stainless Steel Friction-Bearing Ball Spring Plungers are supplied to Trade series (GN 615.8). The grade provides superior, including marine and chloride environments 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 A4 Stainless Steel for Friction-Bearing Ball Spring Plungers
Specified for marine, coastal and chemical applications. For friction-bearing ball spring plungers, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Friction-Bearing Ball Spring Plungers in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
Two important notes for stainless friction-bearing ball spring plungers: (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 Friction-Bearing Ball Spring Plungers Available in A4 Stainless Steel
| Thread size | Length L (mm) | Ball diameter (mm) | Standard spring initial/end load (N) | High-load spring initial/end load (N) | Housing material |
|---|---|---|---|---|---|
| M5 | 12 | 2 | 4.8 / 6.8 | 10 / 14 | blackened steel or AISI 303 stainless |
| M6 | 14 | 2.5 | 6.3 / 10 | 11 / 16 | blackened steel or AISI 303 stainless |
| M8 | 16 | 3.5 | 16 / 24 | 23 / 40 | blackened steel or AISI 303 stainless |
| M10 | 19 | 4.5 | 18.8 / 31.7 | 28 / 54.3 | blackened steel or AISI 303 stainless |
| M12 | 22 | 6.5 | 26 / 49 | 39.5 / 77.3 | blackened steel or AISI 303 stainless |
| M16 | 24 | 8.5 | 38 / 68 | 50 / 88.7 | blackened steel or AISI 303 stainless |
