Microstructure and Property of 780 MPa Cold Rolling Dual-Phase Steel

780 MPa grade cold rolling dual phase steels was low carbon and low-alloy steel,whose main alloy element was Mn and proper quantities of Mo and Cr according to the requirements of different strength.The tested results show that: the better properties can be obtained when final-rolling at 690 ℃.The content of martensite and strength increases with the increasing of annealing temperature.780 MPa dual phase steels with the most excellent extensibility could be produced at 820 ℃.When annealing temperature is 820 ℃,the strength will be markedly increased from 80 to 100 s of annealing time.Moreover,the strength will not be obviously increased if annealing time exceeded 100 s.Therefore,the most excellent extensibility of 780 MPa dual phase steels can be achieved when the annealing time is 100 s.