Round bar steel refers to a solid strip of steel with a circular cross section. The specifications are expressed in millimeters of diameter. For example, "50" means round steel with a diameter of 50 mm. 45# round steel is divided into hot rolling, forging and cold drawing. Hot rolled round bars are available in sizes from 5.5 to 250 mm. Among them: small round steels of 5.5-25 mm are mostly supplied in straight strips, often used as steel bars, bolts and various mechanical parts; round steels larger than 25 mm are mainly used for manufacturing mechanical parts or seamless steel tube blanks.