Method of forming a flanged tubular member in hydroforming

A method of forming a flanged tubular member, comprising the steps of:

• positioning a tubular blank between open, mating pre-form die halves, the tubular blank having an interior surface and an outer surface with a wall therebetween, the pre-form die halves defining:
• a tubular cavity portion;
• and
• an intermediate flange cavity portion;
• then
• applying at least nominal internal hydraulic pressure to the blank interior;
• closing the die halves, thereby substantially simultaneously;
• deforming the blank within the pre-form die tubular cavity portion;
• defining an intermediate flange from a portion of the blank in the pre-form die flange cavity portion;
• increasing the hydraulic pressure to expand and conform the blank to the tubular cavity portion and the intermediate flange cavity portion;
• decreasing the hydraulic pressure;
• separating the pre-form die halves;
• transferring the pre-formed blank to a final die;
• positioning the pre-formed blank between open mating final die halves, the pre-formed blank having an interior pre-formed surface and an outer pre-formed surface with a pre-formed wall therebetween, the final die halves defining:
• a final die tubular cross section cavity portion;
• a final die flange cavity portion;
• and
• a final die hem cavity portion;
• then
• applying at least nominal internal hydraulic pressure to the pre-formed blank;
• closing the final die halves, thereby substantially simultaneously:
• deforming the pre-formed blank within the final die tubular cavity portion;
• defining a flange in the final die flange cavity portion;
• defining an intermediate final hem in the hem flange cavity portion;
• increasing the hydraulic pressure to expand and conform the outer surface of the preformed blank to the final die tubular cavity portion and the final die hem cavity portion, thereby converting the pre-formed blank to a final hydroformed member having a flange and a hem with a cavity therein.