track boltStandards: JIS, ANSI, ASTM, DIN, BS, GB Specification: M20-M48 Surface finish:zinc plated, HDG, black,plain materials:40Cr,38Crmo-42Crmo etc. Hardness grade: 8.8s,10.9s ,12.9s Used for steel construction projects, such as the boiler steel construction of power stations, port machinery,...