Stainless steel springs

AMS5678 (17/7PH) / ASTM A313 Type 631 is by far the most commonly used material for most of the ‘new’ springs we see.

AMS5678 is a precipitation hardenable stainless steel which performs nearly as well as some high carbon steels in terms of strength and fatigue, but has the added advantage of being a stainless.

One possible area of concern with this material in the most demanding applications is its surface finish and we would recommend in some of these cases that the springs are vapour blasted or shot peened to reduce the risk of crack propagation. We always recommend that this material is Dye Penetrant Flaw Detected to a standard such as ASTM E1417 followed by a passivation such as AMS2700 Method 1 Type 2.

AMS5688 & BS 2S205 are other commonly used aerospace stainless steel grades. AMS5688 & S205 (as it is more commonly known) are both a standard 18/8 stainless (AISI302) and although not having quite the same strength or fatigue performance as a 17/7 PH Steel are cheaper to both procure and process. Where your application does not demand extreme performance these are good grades of material to specify.

There is a commercial version 18/8 stainless called X10CrNi18/8 (302S26) which is contained in EN10270-3, however this material has a lower Tensile strength than both AMS5688 & S205 giving reduced performance, we would not advise using this as an alternative without thoroughly checking the designs cycle life prior to use.

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