Round steel refers to solid, long bars of steel with a circular cross-section. Its specifications are indicated by the millimeter number of the diameter, such as "50" representing round steel with a diameter of 50 millimeters.

Round steel is categorized into three types: hot-rolled, forged, and cold drawn. Hot-rolled round steel is available in sizes ranging from 5.5 to 250 millimeters. Among them, small round steel with diameters of 5.5 to 25 millimeters is typically supplied in bundles as straight bars and is commonly used for reinforcing bars, bolts, and various mechanical components. Round steel with diameters greater than 25 millimeters is mainly used for manufacturing mechanical parts or as billets for seamless steel tubes. Differences between round steel and other reinforcing bars: 1. Appearance: Round steel has a smooth, unribbed surface, while other reinforcing bars have textured or ribbed surfaces. This results in less bonding strength between round steel and concrete compared to other reinforcing bars. 2. Composition: Round steel (first-grade steel) is a type of plain low-carbon steel, whereas other reinforcing bars are often made of alloy steel. 3. Strength: Round steel has lower strength compared to other steels, meaning that round steel with the same diameter can withstand less tensile force than other reinforcing bars. However, round steel has greater plasticity, meaning it can deform more before breaking compared to other reinforcing bars.