Patent ID: 8381560

Claim:
A method of hydroforming a metal pipe to form a final product, in which a metal pipe is loaded into a divided mold, the mold is clamped, and then an internal pressure is applied in the metal pipe, and a pushing force is applied in an axial direction of the metal pipe, the metal pipe having an X axis along the axial direction of the metal pipe, and Y and Z axis in the metal pipe cross-section, the method comprising: in a first hydroforming step, expanding the metal pipe in an expanded direction in the Y axis only of the cross-section of the metal pipe to obtain an intermediate product, having an expanded part in the expanded direction, wherein the expanded part has a circumferential length of 90% to 100% of the circumferential length of the shape of the final product in all of the expanded part in the metal pipe axial direction, and a height greater than the height of the final product in the expanded direction and at least part of the pipe axial direction, then, in a second hydroforming step, reducing the height in the expanded direction of the intermediate product and expanding at least in the Z axis direction in all or part of the pipe axial direction while shaping the product to the final product shape.