Abstract
In this study, the simulation and optimization of the partition cooling in the hot stamping process was carried out for an automotive B-pillar through minimizing the maximum thickening rate and the maximum thinning rate located in the rapid and slow cooling zones. The optimization was implemented by investigating the process parameters such as friction coefficient, sheet austenitizing temperature, holding time, heating zone temperature, the upper binder force and the lower binder force. The optimal Latin hypercube design (OLHD), the response surface methodology (RSM) and the non-dominated sorting genetic algorithm (NSGA-II) were combined to establish the relationship between process parameters and form quality objectives. After multi-objective optimization, the maximum thickening rate and the maximum thinning rate of the slow cooling zone and rapid cooling zone were 11.1% and 12.4%, 4.7% and 7.1%, respectively. Afterwards, the simulation was performed according to the optimized parameter combinations to analyze the temperature field, microstructure, tensile strength, hardness, thickening rate and thinning rate, and forming quality. Moreover, the hot stamping test and experimental results showed that the microstructure of the ferrite and pearlite structure was uniformly distributed in the slow cooling zone, and its tensile strength reached 680 MPa, the elongation was 11.4% and the hardness was 230.56 HV, while the lath martensite structure was obtained in the rapid cooling zone, with tensile strength of up to 1390 MPa, elongation of about 7.0% and hardness reaching 478.78 HV. The results of thickness, microstructure, tensile strength and the hardness test correspond well with the simulation results.
Highlights
Studies have shown that the energy consumption of the automotive body is reduced by 6–8% for every 10% reduction in vehicle body quality [1,2,3]
The parts maximum raterole in the slowmicrostructure, cooling zone, Theas temperature change in the forming plays thickening an important in the the maximum thinning rate in the slow cooling zone, the maximum thickening rate in the rapid cooling mechanical properties and forming quality
The simulation is performed according to the zone and the maximum thinning rate in the rapid cooling zone are and parameter combination in non-dominated sorting genetic algorithm (NSGA)-II multi-objective optimization to analyze the temperature 7.1%, field, respectively
Summary
Studies have shown that the energy consumption of the automotive body is reduced by 6–8% for every 10% reduction in vehicle body quality [1,2,3]. Ultra-high strength steel met the requirements of automobile safety performance and lightweight development in recent years, which has been widely used in automobile parts manufacturing [4,5]. Metals 2020, 10, 1264 protect the safety of the occupants when the car is in a side collision, high shaping and toughness are required in the lower side [8]. This means the automotive industry urgently needs to design parts with performance gradients to meet the requirements of lightweight and partition performance at the same time [9,10]
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