Multiobjective Optimization for Forming Process Parameters of Ultrahigh Strength Steel BR1500HS

Abstract

This paper focuses on obtaining the optimum process parameters and improving the mechanical properties of ultrahigh strength steel BR1500S. Many experimental data are obtained, and then response surface methodology (RSM) is used to obtain the optimum parameters. Combining the experimental data with RSM, some conclusions are summarized. When the cooling rate reaches 30°C/s, martensite content in microstructure reaches up to 95%. The optimum regions of quenching hardness, tensile strength, and elongation are obtained when the temperature is about 900°C, and the holding time is about 0∼4 min. Results of multiobjective optimizations show that global optimal value is gained at 906.5°C, and the holding time is 0 min. Predicted optimum values of quenching hardness, tensile strength, and elongation are not less than 51.03 HRC, 1,671 MPa, and 8.75%, respectively. The application of RSM is notably successful in predicting the process parameters of hot forming.