Influence of cavity pressure on hydrodynamic deep drawing of aluminum alloy rectangular box with wide flange

• The theoretical calculation method for the process window of cavity pressure was proposed.
• The wall thickness reduces with increase in pre-bulging pressure.
• The optimizing piecewise stroke equals to the sum of punch round radius, die entrance radii and blank thickness.
• The suitable maximum pressure for the box part lies between 18 MPa and 28 MPa.

The multi-stage deep drawing process had been traditionally adopted for the box part with super wide flange using multiple annealing procedures with problems of poor surface quality, long manufacturing cycle, high cost and low yield. The hydrodynamic deep drawing (HDD) method was suggested to solve these issues during the multi-stage drawing process, in which the loading path of cavity pressure was one of the key parameters immediately related to the product's quality. The effects of cavity pressure on forming quality and precision were explored according to theoretical analysis, numerical simulations and experiments, and the process window of cavity pressure was established through stress analysis of the corner and straight regions. Meanwhile, wall thickness distributions were investigated with different parameters, including pre-bulging pressure, piecewise stroke and maximum pressure. Furthermore, the reasonable loading path was validated by process experiments. The results indicate that the proper control of cavity pressure will be beneficial in improving the drawability of aluminum alloys effectively, and the conventional drawing process consisting of three drawing operations and two intermediate anneals can be replaced by the one-step HDD process.