Effect of die properties on bending characteristics of push-through bending - bending of aluminum extrusion section III

摘要

In our previous study, we reduced the slide mark on material surfaces by optimizing the lubricant for push-through bending. In this study, we investigate contact conditions of material deformation in dies upon push-through bending. We attempt to improve slide mark by investigating the die material, surface treatment of the die and roller die set. The following was clarified. Bending deformation and flange wrinkling occur in fixed die upon push-through bending. Sliding between the material and the die begins from inside the fixed die. The cemented carbide die is excellent for obtaining ideal surface roughness of the slide mark. Hard metal dies tend to have excellent sliding characteristics. However, although cold die steel (SKD11) and high-speed steel (SKH51) are of almost equal hardness, their qualities exist harmoniously between bending member and die material without the above-mentioned relationship. When we treat the die surface, the roughness may increase. When we use the above-mentioned dies, roughness of slide mark also increases. The die surface roughnesses in Diamond Like Carbon (DLC) processing and Toyota Diffusion Coating Process (TD) are minimal, and the surfaces of their bening members are also smooth. However, their efficiency is nearly equal to that of cemented carbide die without surface treatment. The use of a roller die is effective for the improvement of the slide mark. However, roller die is in contact locally with the bending member and the contact pressure is higher than that with normal die. Thus, roller die is inferior to normal die in its curvature, deformation and flange wrinkling. The structure of the roller die is most suitable for a part to use for the appearance that is small curvature.