Abstract
Different from traditional hot stamping components with full martensite, the new tailored hot stamping (THS) components have different quenched microstructures, which results in their lower shape accuracy. To investigate the influence of different quenched phases on the springback of a component, a THS experiment of a U-shaped component was performed with segmented heating and a cooling tool. The area fractions of phases at different tool temperatures were obtained by a two-stage color tint etching procedure. Results showed that the quenched phase of the cold zone was almost full martensite. The area fraction of martensite in the hot zone was reduced to the lowest 13% at the tool temperature of 600 °C, while the bainite content reached the highest at 70%. The springback angles at different tool temperatures for quenching were measured by 3D scanning technology and the reverse modeling method. It was revealed that the springback angle increased with the increase of martensite and yet decreased with the increase of bainite. The relationship between the springback angle and the area fractions of the quenched phases was established by means of multiple linear regression analyses. The error analysis results of the predictions and measurements showed that the springback analysis model, based on the area fractions of quenched phases, could be used to predict the springback of hot stamping components with tailored properties.
Highlights
The demand for vehicle weight reduction and improved crash performance has led to the application of hot stamping of boron steel [1,2]
Quenched Phases Analysis phases of the cold zone are almost full martensite at heating tool temperatures of 25 ◦ C and 600 ◦ C, 5 displays metallography of the component quenched at different tool whichFigure indicates that the color heating tool temperature hasformed little effect on the quenched phases of the cold temperatures and micrographs, calibrated by
This may be because the cooling rate of the blank in the cold zone is greater than 100 C/s, much phasesthan of the zone are almost full martensite at heating tool temperatures of of 600 °C, higher thecold critical speed of martensite transformation
Summary
The demand for vehicle weight reduction and improved crash performance has led to the application of hot stamping of boron steel [1,2]. Some scholars have studied the influence of hot stamping process parameters on the springback of formed components [14,15,16] They concluded that the springback of the formed component gradually decreased with the increase of blank temperature and holding time. In order to understand the effect of the quenching phase content on the component springback, a THS experiment was carried out in this paper, and the quenching phase was quantitatively measured by the color metallography. The springback angles of different phase contents were obtained by non-contact 3D measurement. Effect of the quenching phase content on the component springback, a THS experiment was carried out in this paper,Study and the quenching phase was quantitatively measured by the color metallography.
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