Method for manufacturing molded product

Abstract

A method for manufacturing a molded product from a tailored blank is provided. The method includes situating the tailored blank between a first and second metallic molds arranged apart from each other; achieving a held state where a flange corresponding portion is held between the first metallic mold and a holder; and forming the molded product including a top plate, a vertical wall, and a flange by pressing the tailored blank with the first and second metallic molds by bringing the first and second metallic molds close to each other while maintaining the held state. The holder is a member situated between the first and second metallic molds and holding the flange corresponding portion in coordination with the first metallic mold. In the held state, the first metallic mold and the holder hold the flange corresponding portion such that a welded portion is movable towards a top plate corresponding portion.

What is claimed is: 
     
         1 . A method for manufacturing a molded product in which a tailored blank is pressed to obtain the molded product, the method comprising:
 situating the tailored blank between a first metallic mold and a second metallic mold arranged apart from each other;   achieving a held state in which a flange corresponding portion is held between the first metallic mold and a holder; and   forming the molded product including a top plate, a vertical wall, and a flange by pressing the tailored blank with the first metallic mold and the second metallic mold by bringing the first metallic mold and the second metallic mold close to each other while maintaining the held state,   the tailored blank being a steel plate formed by joining a first steel plate and a second steel plate together by welding, the second steel plate having a plate thickness and/or a strength different from those of the first steel plate,   the tailored blank including at least one welded portion that is formed by welding an end surface of the first steel plate and an end surface of the second steel plate to each other,   the vertical wall being a plate-like portion that stands from an end of the top plate so as to surround the top plate,   the flange being a plate-like portion that extends from the vertical wall in a direction perpendicular to the vertical wall and being situated to surround the top plate in a plan view perpendicular to the top plate,   the tailored blank including a top plate corresponding portion representing a portion corresponding to the top plate, a vertical wall corresponding portion representing a portion corresponding to the vertical wall, and a flange corresponding portion representing a portion corresponding to the flange,   the top plate corresponding portion being situated in the first steel plate,   the at least one welded portion being situated in the flange corresponding portion,   the holder being a member that is situated between the first metallic mold and the second metallic mold and that holds the flange corresponding portion in coordination with the first metallic mold, and   in the held state, the first metallic mold and the holder holding the flange corresponding portion such that the at least one welded portion is displaceable towards the top plate corresponding portion.   
     
     
         2 . The method for manufacturing the molded product according to  claim 1 ,
 wherein a pressure applied to the tailored blank by the holder in the held state is set to satisfy the following mathematical formula (Formula 1);   
       
         
           
             
               
                 
                   
                     
                       X 
                       [ 
                       ton 
                       ] 
                     
                     < 
                     
                       
                         
                           Ts 
                           [ 
                           MPa 
                           ] 
                         
                         × 
                         0.005 
                         × 
                         
                           A 
                           [ 
                           
                             mm 
                             2 
                           
                           ] 
                         
                       
                       9.8 
                     
                   
                 
                 
                   
                     [ 
                     
                       Formula 
                       ⁢ 
                           
                       1 
                     
                     ] 
                   
                 
               
             
           
         
         wherein X is a pressure applied to the tailored blank by the holder, 
         wherein Ts is a tensile strength of the first steel plate, and 
         wherein A is a contact area of the holder and the tailored blank before the tailored blank is pressed by the first metallic mold and the second metallic mold. 
       
     
     
         3 . The method for manufacturing the molded product according to  claim 1 ,
 wherein a plate thickness of the first steel plate is less than a plate thickness of the second steel plate,   wherein an adjusting member for adjusting a distance between the tailored blank and the first metallic mold in the held state is disposed between the first metallic mold and the second metallic mold, and   wherein the distance between the tailored blank and the first metallic mold in the held state is adjusted to be greater than or equal to 5% and less than 20% of the plate thickness of the first steel plate by the adjusting member.   
     
     
         4 . The method for manufacturing a molded product according to  claim 1 ,
 wherein, in the forming, an amount of displacement of the at least one welded portion being displaced towards the top plate corresponding portion is designed in advance, and   wherein a portion of the first metallic mold and/or the holder that is configured to contact the at least one welded portion in the held state has a hardness greater than a hardness of the at least one welded portion.   
     
     
         5 . The method for manufacturing a molded product according to  claim 1 ,
 wherein, in a plan view perpendicular to a plate thickness direction of the tailored blank, the top plate corresponding portion is situated in a part of the tailored blank on a first side including an end portion on the first side, and   wherein the at least one welded portion extends from an end portion of the tailored blank on a second side, which is situated opposite from the end portion on the first side, to the first side so as to avoid the top plate corresponding portion.