The present application provides a low
thinning rate bending forming method, comprising the following steps: a hydraulic local expansion step, placing a straight
pipe in a hydraulic thickening die and controlling the hydraulic thickening die to operate to form an expansion deformation of a target area of the straight
pipe and ensure that the minimum wall thickness t1 after the expansion deformation is not less than the initial
pipe wall thickness t0 of the straight pipe, the target area being a corresponding area of an outer wall of the straight pipe to be bent and formed; and a bending forming step, placing the expansion-deformed straight pipe in a
numerical control bending die and controlling the
numerical control bending die to operate to bend and thin the target area until the straight pipe is bent to a target bending
radius. The present application only needs to perform expansion deformation on the target area of the straight pipe, the pipe quality is small, the material cost is low, and the working condition demand of small bending
radius and low
thinning rate is met, and the product quality and service performance are improved.