| 摘要 |
<p>A method for forming a sheet made of an aluminium alloy into a component of complex shape, particularly a motor-vehicle component, such as the outer panel or the inner frame of a bonnet or a door of a motor- vehicle, provides for the blow-forming of the sheet, with the aid of pressurized gas, within a mould. The alloy constituting the sheet (L) does not have superplasticity features and the sheet (L) and/or the mould (M) are heated to a temperature in the order of 400° - 450° C for 5xxx series alloys and 450°-500° C and over for 6XXX and 7xxx series alloys. The maximum pressure reached by the forming gas is in the order of 20-30 bars and the time required for forming the sheet (L) is between 40 and 150 seconds and therefore is consistent with production rates in the automotive field. In a first part of the forming step, pressurized gas is fed into the mould while leaving that peripheral portions of the sheet (L) which are clamped within the mould are free to slide with respect to the mould, so as to enable a first forming of the sheet (L) with no substantial elongation thereof, and thereafter, in a second part of the forming step, this sliding movement is prevented and the pressurized gas is kept to be fed into the mould, so as to press the sheet against the wall of the mould (M), thus causing an elongation of the sheet (L) until its final shape is obtained.</p> |
