Direct Resistance Heating of Aluminum Sheets for Rapid Superplastic Forming

Superplastic aluminum forming is a promising manufacturing process for the transportation industry because it allows for the manufacturing of complex body parts from a single sheet of aluminum, reducing the number of pieces and the weight of vehicles. However, the process is still limited, among other things, by the low heating rate of the sheets. Indeed, for the 5000 series aluminum alloy, a temperature between 450 and 550 degrees C must be reached, but the furnaces used are inefficient, leading to heating times in the order of similar to 3 to 6 min. A test bench has been developed to evaluate direct resistance heating as a solution. It allows heating 350 x 200 x 1 mm sheets. The uniformity of the sheet's temperature is an important factor in ensuring good formability and has been evaluated using an infrared camera. Tests show that the sheets can be heated within 20 s using a current of 6200 A, with a standard deviation of about 10 degrees C over the surface of the sheet.