The difference between rebar and plain round steel bars is that rebar has longitudinal and transverse ribs on its surface, typically with two longitudinal ribs and transverse ribs evenly distributed along its length. Rebar is a type of small-section steel, mainly used as the skeleton of reinforced concrete building components. It requires certain mechanical strength, bending deformation performance, and weldability. The raw material for producing rebar is carbon structural steel or low-alloy structural steel that has undergone kill melting treatment. The finished bars are delivered in hot-rolled, normalized, or hot-rolled condition.

Hot-rolled ribbed steel bars are divided into three grades: HRB335 (formerly 20MnSi), HRB400 (formerly 20MnSiV, 20MnSiNb, 20Mnti), and HRB500. The American ASTM A615 standard uses Grade 60, Grade 75, etc., with the numbers corresponding to yield strength in ksi. The European standard EN 10080 uses the letter B followed by a number, such as B500B representing a characteristic yield strength of 500 MPa and medium ductility. The Japanese Industrial Standard JIS G3112 uses SD390, SD490, etc., where SD indicates the steel reinforcement and the number represents the minimum yield strength.

In engineering applications, different grades of steel reinforcement serve different structural functions. HRB335 is mostly used for secondary components or low-rise buildings, HRB400 has become the main steel reinforcement in cast-in-place concrete structures, and HRB500 is suitable for heavy-load scenarios such as the core tubes of super high-rise buildings and long-span bridges. For special environmental engineering, corrosion resistance is a key consideration; epoxy-coated steel reinforcement is marked with "Ep" after its designation, and stainless steel reinforcement uses the prefix "SUS".