Construction steel can usually be divided into steel for steel structure and steel for reinforced concrete structure. The steel used for steel structure mainly includes ordinary carbon structural steel and low alloy structural steel. Steel bars for reinforced concrete structures can be divided into: hot-rolled steel bars, heat-treated steel bars, cold-drawn steel bars, cold-drawn low-carbon steel wires and steel strand tubes according to processing methods; smooth steel bars and threaded steel bars according to surface shape; according to the type of steel, it can be divided into low carbon steel, medium carbon steel, high carbon steel and alloy steel. my country's steel bars can be divided into five grades according to their strength: I, II, III, IV, and V.