Press-forming method

Abstract

Provided is a press-forming method including three steps for preventing spring-back in a hat-shaped cross section shape of a final formed article. In the first step, from a blank, a preformed article in a first form is obtained, the preformed article including a top surface, left and right vertical walls, and left and right tapered portions extending outward from lower ends of the left and right vertical walls, respectively, of a final formed article having a hat-shaped cross section. In the second step, the compression can be applied to the entirety of the top surface, the left and right vertical walls, and the left and right flanges of the final formed article having the hat-shaped cross section, whereby the spring-back can be sufficiently prevented. In the third step, obtain the final formed article having the hat-shaped cross section.

What is claimed is: 
     
         1 . A method of press-forming, from a blank, a final formed article having a hat-shaped cross section and including a top surface, left and right vertical walls continuing to left and right ends of the top surface, left and right flanges extending from lower ends of the left and right vertical walls, respectively, and left and right bent portions interposed respectively between the left vertical wall and the left flange and between the right vertical wall and the right flange, the press-forming method comprising:
 a first step of obtaining, from the blank, a preformed article in a first form including the top surface, the left and right vertical walls, and left and right tapered portions extending outward from the lower ends of the left and right vertical walls, respectively;   a second step of forming the left and right bent portions by, in a state where the top surface of the preformed article in the first form is held by an upper die and a punch of a lower die, pushing the left and right tapered portions into recesses for curling forming provided in the lower die and forming the left and right flanges by lowering of the upper die to obtain a preformed article in a second form; and   a third step of obtaining the final formed article having the hat-shaped cross section by reforming the left and right bent portions and the left and right flanges of the preformed article in the second form.