Abstract: The influence of alloying elements and cooling conditions after rolling on the microstructures and mechanical properties of a series of medium carbon Si-Mn-Mo-V high-strength precision-formed rebars were investigated.It is found that steel with combined addition of Mo and V appears to be the most promising one than those containing V and Nb or containing V alone under the same pro- cessing conditions.From CCT curve of the steel and the cooling curve of the bar determined by sim- ulating the cooling rate in mill practice,the reason why 40Si2MnMoV bar has excellent combination of strength and ductility is clarified.

Key words: high strength steel, composition design, rebar