Net shape processing for a watch crown by cold multistage forging and form rolling

摘要

By means of cold multistage forging followed by form-rolling processing in a ferritic stainless steel wire, a wristwatch crown, which is small and complicated with a groove, can he formed into its final shape in a fairly short time which is about 1/40 of the time required in conventional cutting processes. The position accuracy of the groove is improved by form-rolling performed while the bottom edge of the crown head is brought into contact with dies. Since annealing before form-rolling decreases the exfoliation of the groove that is caused by form-rolling, the surface roughness of the groove is improved. The Mannesmann defect is generated by form-rolling, however the load necessary to bend the stem of a form-rolled crown is greater than that of a cut crown.