The JIS G3539 PDF can be obtained from the Japanese Standards Association (JSA) or other authorized distributors. The standard is available in both Japanese and English languages.
Low carbon content (below 0.15%) provides the high ductility required for severe cold heading. Higher carbon would cause cracking during the forming of screw heads or threads.
Specifies carbon steel wires used for cold heading and forging of screws (bolts, nuts, rivets, machine screws, tapping screws) and various industrial parts.