Abstract: Hot stamping of ultra high-strength steels (UHSS) is a new and complex forming technology integrating metal hot forming and quenching process. In order to research the effect of austenitizing temperature and holding time on the quenching hardness, tensile strength and elongation of boron steel B1500HS, the orthogonal experiment design of two factors and five levels is carried out by using the austenitizing temperature and holding time as the design factors. Some samples of B1500HS are quenched according to the results of orthogonal experiment, the quenching hardness, tensile strength and elongation of samples are measured by using the Rockwell hardness tester and the electronic tensile testing machine. The cubic response surface models of quenching hardness, tensile strength and elongation are obtained by using the regression analysis prediction method and the results of experiment. The austenitizing temperature and holding time are optimized according to the cubic response surface model, the optimum quenching parameters are gained. The optimization results of single objective show that the predicted maximum value of quenching hardness is 52.3 HRC, the predicted maximum value of tensile strength is 1 658.94 MPa, and the predicted maximum value of elongation is about 8.80%. The optimization results of multi-objectives show that the predicted values of quenching hardness, tensile strength and elongation are not less than 50.6 HRC, 1 639.98 MPa and 8.6% respectively when the austenitizing temperature is 916.19～920.48 ℃ and the holding time is 0 min.

Key words: Hot forming, Optimization, Quenching, Response surface methodology