A substantial number of copper alloy C27000 (yellow brass, 65Cu-35Zn) ferrules for electrical fuses cracked while in storage and while in service in paper mills and other chemical processing plants. The ferrules, made by three different manufacturers, were of several sizes. One commonly used ferrule was 3.5 cm long by 7.5 cm in diam and was drawn from 0.5 mm (0.020 in.) thick strip. Investigation (visual inspection, metallographic examination, and a mercurous nitrate test, which is an accelerated test used to detect residual stress in copper and copper alloys) of both ferrules from fuses in service and storage in...