Tag: 17-4 fasteners for high strength

17-4PH for High Strength Applications

Q: Looking at options to increase the tensile strength for a socket head cap screw. We
are currently using grade 8. Would Waspaloy be a good option?

A: If you are looking for a fastener with higher strength than Grade 8 Alloy Steel (150 KSI Tensile, 130 KSI Yield), and are only interested in strength (not corrosion resistance or high temperature stability etc.) you should consider 17-4 PH. This is a precipitation hardened stainless steel that lets you fine tune the strength depending on the heat treatment. 17-4PH bolts can deliver strength of 160-220ksi UTS.

Beyond this you are getting into some very special alloys that do more than just offer high strength, like Inconel 718, Waspaloy and MP35N. These materials relative to alloy steel are very expensive and typically used for high strength applications that have other requirements such as corrosion resistance or high temperature usage.

Age Hardened 17-4PH and A286 Bolts: Strength & Ductility

Q:
An application with limited space using a #4-40 screw with an assumed tensile strength of 120,000 PSI. This screw continues to break. Do you offer a screw with a higher strength? Also, This screw is used to hold a plate to the end of an air cylinder.  It probably jars the fastener on every stroke and has about 6-8 strokes per minute.
A:
Regarding materials, there is a whole range of materials stronger than 120 ksi UTS however it sounds like you not only need strength but also a material that is ductile.  I would suggest looking at fasteners made from the age hardened stainless steels such as  A286 or 17-4 PH. Known for its high temperature oxidation resistance, A286 bolts also offer excellent high strength capabilities. A286 typically offers a min of 130ksi UTS and 85 yield. 17-4 PH bolting offers varies levels of strength depending on the age hardening process used ranging from 145ksi to 200ksi UTS (H1150 and H900 respectively). Given your application has a repetitive jarring motion you should look at the 17-4 H1150 or the A286 per ASTM A453, 660 A, B or C.   These heat treat conditions will give you much more strength but also leave you with a material that is ductile and not brittle which may be a big factor in your fastener application.