According to the production process, there are hot rolled steel bars (H) and cold rolled steel bars (C). Hot-rolled steel bars are divided into smooth round steel bars (HPB300) and ribbed steel bars. The common brands of hot rolled ribbed steel bars are HRB400, HRBF400, HRB400E, HRBF400E, HRB500, HRBF500, HRB500E and HRB600. HPB300 (Grade I) is a common steel bar with a diameter of 6-12mm, commonly used in the production of stirrup, wall reinforcement, etc. HRB335 (Grade II) is a threaded steel with a diameter of 12-25mm, commonly used in bridges, dams, houses and other large and medium-sized concrete structures in the beam, column, shear wall. HRB400 (Grade III) is similar to HRB 335, but is stronger and more expensive. It is often used in special buildings such as villas. HRB500 (Grade IV) is widely used in large prestressed buildings, such as roofs, crane beams, etc.