HRB400 high strength reinforcing steel (% ： 0. 19 ~0. 25C

0. 40 ~0. 60Si

1. 20 ~ 1.50Mn

≤0.040P

≤0. 040S) is melted by 120 t BOF-ladle argon blowing-120 mm x 120 mm billet casting process. In order to improve the comprehensive mechanical properties of Φ 12 ~22 mm ribbed bar of hot-rolled HRB4CX) steel the three kinds of microalloying process tests i. e. adding 5 kg/1 MnSiN + 0. 4 〜0. 9 kg/t FeV

10 kg/t MnSiN + 0. 25 ~ 0. 40 kg/t FeNb and only adding 0. 40 ~0. 75 kg/t VN have been carried out during steelmaking. The pitting temperature of billet is 1 150 ~ 1 250 °C

the finishing rolling temperature for reinforcing steel bar is ≥950 °C

reduction of each pass in rough rolling ≥30% and reduction of each pass in finishing rolling ≥15%

fanning cooling after rolling. Results show that the available adding amount of FeV or VN is 0. 5 kg/t and that of FeNb is 0. 3 kg/t; with microalloying by V or Nb

the grain in steel is finer obviously and each property of reinforcing steel meets the requirement of standard.