A: The cold-headed product usually has a harder head and a softer shaft or pitch diameter, depending on how much reduction was experienced during the earlier draw/cutting stages. If the draw reductions were on the order of a typical bolt shape, the reductions would only be on the order of 5-8% to achieve precise diameter in the shank area before roll threading.

On the other hand, if the blank is cold drawn with reductions in excess of 9-12%,the properties will be rather attractive probably on the order of 70 ksi yield for 1022. Because the head receives still more reduction, it will be harder yet, approaching 100 Rb or higher. Heat treating can be used to develop uniform hardness. However, heat treating a bolt shape always carries a risk of quench cracking on the heads unless special heat Teating practices are followed. Cold-headed parts often need to be stress relief annealed or fully heat treated to remove the stress from the headed area. Then, based on the design/functional requirements of the parts, they can be annealed, hardened, and tempered, or carburized with practices that I sent to you.

In each issue of FORGING, H. James Henning answers forgers’ technical and operational questions. For more than 40 years he held key technical positions in the forging industry, most recently as director of technology for the Forging Industry Association. Henning is president of Henning Education Services, a Columbus, OH, firm specializing in customized education and training in forging technologies.

Send your technical or operational question to ASK JIM, c/o FORGING, 1300 E. 9th St., Cleveland, OH 44114-1503. Or e-mail: henningedu@aol.com.

Guidelines and recommendations offered in this column are based on information believed to be reliable and are supplied in good faith but without guarantee. Operational conditions that exist in individual plants and facilities vary widely. Users of this information should adapt it, and always exercise independent discretion in establishing plant or facility operating practice.