Three-step hydraulic precise forming die and method for rectangular corrugated pipe

The invention discloses a three-step hydraulic precise forming die and method for a rectangular corrugated pipe. The three-step hydraulic precise forming die is characterized in that a lower core shaft and a lower end cover are placed on the surface of the center of a lower guide plate, a rectangular pipe blank sleeves an assembly body formed by the lower core shaft and the lower end cover, a lower end die sheet sleeves the outer side of the lower end of the rectangular pipe blank, and the lower end die sheet makes contact with the lower end cover; positioning shape-limiting die sheets and middle die sheets are alternately arranged above the lower end die sheet and on the outer side of the rectangular pipe blank, the positioning shape-limiting die sheets are arranged on the uppermost layer and the lowermost layer, an upper end die sheet is arranged above the positioning shape-limiting die sheet on the uppermost layer, and the upper end die sheet sleeves the outer side of the upper end of the rectangular pipe