Method and apparatus for hydroforming metallic tube

A method for hydroforming a metallic tube in which part of the metallic tube is expanded through combined use of an internal pressure imposed by a fluid contained in the metallic tube and an axial compression of the metallic tube, comprising the steps of:

• preliminarily expanding the metallic tube over an axial section longer than the length of the expanded portion of a final product as measured in the axial direction of the metallic tube by a fluid pressure applied to the interior of the metallic tube, and a compressive force applied in the axial direction of the tube, thereby causing the tube material in the portion other than the portion to be preliminarily expanded to flow into the preliminary expanded portion;
• and compressing the preliminarily expanded portion in the axial direction of the metallic tube so as to form the shape of the expanded portion of the final product.