Stamping die and forming method of U-shaped beam

The invention discloses a stamping die and a U-shaped beam forming method.The stamping die comprises an upper die assembly and a lower die, the upper die assembly comprises a female die insert arranged in the longitudinal direction, the cross section of the female die insert is in a concave shape, and the lower die assembly comprises a male die insert; the projection of the male die insert on the horizontal plane and the projection of the female die insert on the horizontal plane are staggered in the longitudinal direction. The male die insert is arranged close to the end face of one end of the female die insert, and the distance between the male die insert and the end face is T. The male die insert comprises a base part and a forming part connected to the upper portion of the base part, and the transverse distance between the two side edges of the cross section of the forming part and the vertical center line of the forming part is gradually reduced from bottom to top, so that the cross section of the formin