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A method and apparatus for hydroforming a metallic tube including 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; and compressing the preliminarily

A method and apparatus for hydroforming a metallic tube including 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; 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. According to the method and apparatus of the invention, frictional resistance between the metallic tube and processing tools can be reduced, and moreover, the internal pressure within the metallic tube can be reduced during expansion processing. Furthermore, the cost for the manufacture of metallic die is reduced, and in addition, yield is improved

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[ What is claimed is:] [1.] 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 ex

[ What is claimed is:] [1.] 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.