Influence of Process Parameters on the Formability of Zn-Coated Hot Stamping Steel

Herein, the effect of process parameters on the formability of Zn-coated stamping steel is analyzed, including heating temperature, soaking time, forming temperature, deformation level, and strain rate. The studied heating temperature ranges from 850 to 930 degrees C; the soaking time ranges from 3 to 7 min; the deformation level ranges from 10% to the break; and the strain rate ranges from 0.1 to 10 s(-1). The thermal mechanical property is analyzed and fitted using the power model of allometric equation. The length of microcrack is measured using scanning electron microscope (SEM). It can be concluded that the true stress decreases with the increase of the heating temperature and soaking time. The decrease of the forming temperature and the increase of the strain rate lead to the increase of the true stress. The critical strain in the thermal tension process is about 0.35. The length of microcrack is below 10 mu m for most of the cases. The optimal process parameters are proposed. The heat temperature should be at the range of 850-900 degrees C. The soaking time should not be larger than 5 min. The fracture is typical ductile fracture with dimples, resulting from the growth and emerging of microvoids.