The Effect Of Hot Press Forming Process Parameters On Coating Layer Behavior Of Al-Si Coated Steel

White lines on the inner surface of a corner area are sometimes observed after hot press forming of a part with Al-Si coated boron steel. Particularly in the case of thin material thickness or small radius of curvature, this phenomenon may be observed more frequently. When the cross section of these lines was investigated, concave shape due to the intrusion of coating layer into base metal was observed. When there was a severe intrusion of coating layer into base metal, locally large hardness difference of base metal around the intrusion region was measured. In addition, since the intrusion has the concave shape, there is a possibility of stress concentration when an external force acts. Thus, the study for the effect of hot press forming process parameters on the intrusion phenomenon was conducted to find a way to alleviate this phenomenon. The considered process parameters were heating temperature, heating time, and transfer time of heated blank to the die. Finally, a direction to improve this phenomenon was derived, and the effects of variations in the process parameters were explained.