Study On Galling Position For Non-flange Square Cup Drawing With High Strength Steel

With the development of automobile industry, People request more and more on auto safety performance, energy conservation and environmental protection, which makes an inevitable trend that the use of high strength steel plate instead of ordinary steel plate. However, the formability of high strength steel is limited due to high strength, especially in the deep drawing process. Defects like adhesion and abrasion between die surface and workpiece, which are called galling in the deep drawing process, severely reduce the life of die and the surface quality of workpiece. Combining with The National Natural Science Fund Project (51175445), initial galling position is studied for non-flange square cup drawing of high strength steel, makes every effort to provide the scientific basis for reducing or eliminating the galling in the high strength steel automobile deep drawing.At first, this paper analyzes the characteristics of non-flange square cup drawing. Then relative workpiece wear and relative die galling as evaluating indicators are used to predict initial galling position in the square cup deep-drawing process. A galling position prediction model is established with the consideration of contact pressure, sliding distance, equivalent surface hardness and surface roughness change.Using DEFORM3D software, a finite element simulation of non-flange square cup drawing of high strength steel DP780is made to obtain the contact pressure and sliding distance with contact pressure. The results of simulation are applied to the galling position prediction model, so the initial galling positions of the non-flange square cup drawing are predicted. The results show that the galling on the die surface occurs easily at the bottom point of the die instead of connecting the die corner with the straight wall, and concentrated on the bottom of the straight edge junction area. On these basis, effect of process parameters such as different blank shape, different punch and die clearance, different die height and different die fillet radius on galling position and amout of galling are analyzed during non-flange square cup drawing of high strength steel, and shallow suggestions for reducing and preventing galling are put forward.Finally, the corresponding non-flange square cup drawing die structures are designed to study on the influence of die clearance on galling position. The experimental results show that the galling on the die surface occurs easily at the bottom point of the straight boundary. The predicting galling positions are consistent with the experimental results in the non-flange square cup drawing of high strength steel. With the increase of drawing number, the galling is more obvious and gradually expands to the upper die. Die clearance has no effect on the initial galling positions, only change the severity of the galling. The smaller the gap, the more obvious the galling. Therefore, the method’s feasibility and model’s credibility are verified.