STAINLESS STEEL FASTENERS
There are a diverse range of stainless steel fasteners offering different levels of corrosion resistance and strength. They are used for corrosive industrial and seawater environments, equipment, structural and architectural applications. These products can be used for all stainless steel designs and for joining other metals such as copper, aluminum, carbon steel, and zinc.
The specification of a specific fastener grade should be based on the required corrosion resistance, strength and materials that will be fastened. The fastener should have equivalent or higher corrosion resistance than the most corrosion resistant of the metal(s) being fastened. Application specific guidelines should be consulted to determine the most appropriate stainless steel grade. General guidance can be found in the SSINA Designer Handbook: Stainless Steel Fasteners. The Other Design & Specification Resources section provides some application specific guides.
Stainless steel fasteners can be manufactured by either machining or cold heading. Machining is the oldest method of fastener production, and it is still specified for very large diameters and small production runs.
Cold heading is the more common production method. It transforms wire into the desired shapes by applying enough pressure to cause the metal to plastically deform into the die and punch cavities without preheating the material. Larger production runs of bolts, screws, nails and rivets are made by cold heading, but special custom runs can also be made by this method. Cold heading can significantly increase the strength of 300-series types stainless steel fasteners.
The Carpenter Technologies web article How to Select the Right Stainless Steel or High Temperature Alloy for Heading may also be of interest.
The ASTM International standards for fastener materials and specific products (bolts, nuts, screws, and studs) are provided in the following table. There are standards for both general use and for specialized high temperature, high pressure, and cryogenic applications. It should be noted that there is no ASTM standard for stainless steel washers. You can obtain copies of the current versions of these standards from ASTM International by clicking here.
Fastener thread galling or cold welding can occur with stainless steel, aluminum, titanium and other alloys which self-generate a protective oxide surface film for corrosion protection. In applications where disassembly will not occur and any loosening of fasteners is structurally undesirable, it may be an advantage.
In applications like equipment, easy fastener removal for repairs is important and galling should be avoided. Several precautions can be taken to avoid this problem with stainless steel.
Other Design & Specification Resources
Practical guide to using marine fasteners, Nickel Institute publication 10045.
Successful Stainless Swimming Pool Design, IMOA web article.