High strength fasteners cold forged out of work hardening steel

Abstract

When designing fasteners, engineers should choose materials and processes that provide the strength required for the application. And if the materials can be turned into a fastener using less manufacturing steps than traditional processes, then a company making these fasteners can save time and money. For instance, high strength bolts and screws are typically produced from annealed wire. The wire is cold formed into the fastener shape and threaded. A quench-and-temper heat treatment gives the fasteners the required mechanical properties. Now high-strength fasteners can be made from work (strain) hardening steel, which eliminates wire annealing and heat treatment. In addition, fasteners made from work hardening steel offer several fastener performance benefits. This paper will describe several work hardening steels and illustrate that the fastener manufacturer cannot always use traditional processes and tooling to produce acceptable parts. Cold formed part and F.E.A. simulation results using traditional and modified processes will be presented.