Method for manufacturing molded parts

Abstract

The present invention provides a method for manufacturing molded parts, the method being characterized by comprising: a first molding step for molding a base material to form a first molded part including a first upper flange and a pair of first web members extending in intersecting directions from the left and right ends of the first upper flange; and a second molding step for compressing the first molded part to form a second molded part including a second upper flange and a pair of second web members extending in intersecting directions from the left and right ends of the second upper flange, wherein, in a width direction cross section, the first upper flange is longer than the second upper flange and the first web members are longer than the second web members.

1 . A method for manufacturing a molded member, the method comprising:
 a first molding operation of molding a base material to mold a first molded product including a first upper flange and a pair of first web members formed to extend in an intersecting direction from both ends of the first upper flange in a left-right direction; and   a second molding operation of compressing the first molded product to mold a second molded product including a second upper flange and a pair of second web members formed to extend in an intersecting direction from both ends of the second upper flange in the left-right direction,   wherein, in a transversal cross-section, a length of the first upper flange is greater than a length of the second upper flange, and a length of the first web member is greater than a length of the second web member.   
     
     
         2 . The method of  claim 1 , wherein,
 in the transversal cross-section, the length of the first upper flange is 105% to 120% of the length of the second upper flange, and   in the transversal cross-section, the length of the first web member is 105% to 120% of the length of the second web member.   
     
     
         3 . The method of  claim 1 , wherein, in the second molding operation, molding starts in a state in which a first boundary point between the first upper flange and the first web member and a second boundary point between the second upper flange and the second web member overlap. 
     
     
         4 . The method of  claim 3 , wherein, in the second molding operation, molding proceeds while both sides of an overlapping portion of the first boundary point and the second boundary point are pressed by a mold. 
     
     
         5 . The method of  claim 1 , wherein the first molded product has a curved section around the first boundary point between the first upper flange and the first web member. 
     
     
         6 . The method of  claim 1 , wherein the first molded product has a straight section around the first boundary point between the first upper flange and the first web member. 
     
     
         7 . The method of  claim 1 , wherein, the second forming step forms a vertical bead portion, and the vertical bead portion is formed by alternating a protruding surface and a depressed surface in the front-rear direction in the second web member, and the protruding surface and the depressed surface are connected by an inclined surface. 
     
     
         8 . The method of  claim 7 , wherein the vertical bead portion is formed on the second web member and is formed in an outer protruding portion protruding in a direction in which the second web member is away from the second upper flange. 
     
     
         9 . The method of  claim 7 , wherein two to eight vertical bead portions are arranged to be spaced apart from each other in the front-rear direction of the second web member. 
     
     
         10 . The method of  claim 7 , wherein, in the vertical bead portion, a length of the depressed surface in the front-rear direction ranges from 5 times or more and 30 times or less a thickness of a base material. 
     
     
         11 . The method of  claim 7 , wherein, in the vertical bead portion, a distance between an extension line of the protruding surface and an extension line of the depressed surface is twice or more and 10 times or less the thickness of the base material. 
     
     
         12 . The method of  claim 7 , wherein, in the vertical bead portion, a length of the protruding surface in the front-rear direction is 5 times or more and 30 times or less a thickness of the base material. 
     
     
         13 . The method of  claim 7 , wherein the vertical bead portion has an arc-shaped shoulder portion formed at a boundary portion between the protruding surface and the depressed surface, and a radius of curvature of the shoulder portion is 4 times or more and 10 times or less a thickness of the base material. 
     
     
         14 . The method of  claim 1 , wherein the second molded product is formed to extend in the front-rear direction, and positions of cross-sections of the second molded product in the up-down and left-right directions vary depending on a position of the second molded product in the front-rear direction. 
     
     
         15 . The method of  claim 1 , wherein,
 in the second molded product, the second upper flange has a first position variable section ranging from 80 to 200 mm in the up-down direction, and   in the second molded product, the second upper flange has a second position variable section ranging from 40 to 120 mm in the left-right direction.   
     
     
         16 . The method of  claim 1 , wherein the base material is a steel plate having a thickness in the range of 1.2 to 1.8 mm, and the base material is steel having a tensile strength of 980 MPa or more. 
     
     
         17 . The method of  claim 1 , wherein a cold forming method is applied in the first molding operation and the second molding operation.