Abstract
As a forming method for improving the limit of deep drawing, a warm deep drawing process with hydraulic counter pressure, which is the combination of warm deep drawing process and hydraulic counter pressure deep drawing process, is proposed. As for this forming method, the improvement of limiting drawing ratio can be expected through the control of work hardening by heating flange part and the prevention of fracture by pressing the formed side wall to a punch with hydraulic pressure. According to the experiment up to the forming temperature of 200°C, by controlling the highest hydraulic pressure so that the fracture due to excessive bulging deformation does not arise, and by forming at the forming speed of 3 mm/s or less, it is successful to improve the limiting drawing ratio of A1050–O material up to D0 max/dp=3.40 in cylindrical cups and D0 max/lp=3.59 in square cups. However, at the forming temperature of 200°C, the flange part of H24 material was softened, and the improvement of its limiting drawing ratio has not been attained. Moreover, it is elucidated also that when the warm forming of H24 material is carried out, strain figures and flow marks arise, and the surface properties of the formed products are deteriorated.
