Patent Publication Number: US-11020785-B2

Title: Method and apparatus for manufacturing press component

Description:
TECHNICAL FIELD 
     The present invention relates to a method for manufacturing a press component, and an apparatus for manufacturing a press component. 
     BACKGROUND ART 
     The body shell of an automobile has a unit construction structure (monocoque structure). A unit construction structure is constituted by a number of framework members and formed panels that are joined together. 
     For example, a front pillar, a center pillar, a side sill, a roof rail and a side member are known as framework members. Further, for example, a hood ridge, a dash panel, a front floor panel, a rear floor front panel and a rear floor rear panel are known as formed members. 
     Framework members that have a closed cross-section such as a front pillar, a center pillar and a side sill are assembled by joining configuration members such as a front pillar reinforcement, a center pillar reinforcement and a side sill outer reinforcement to other configuration members such as an outer panel and an inner panel. 
       FIG. 14  is an explanatory drawing that illustrates an example of a framework member  1 . 
     As illustrated in  FIG. 14 , a framework member  1  is assembled by joining configuration members  2 ,  3 ,  4  and  5  together by spot welding. The configuration member  2  has a substantially hat-shaped cross-sectional shape. The substantially hat-shaped cross-sectional shape includes a top plate  2   a , a pair of left and right vertical walls  2   b  and  2   b , and flanges  2   c  and  2   c  that connect with the vertical walls  2   b  and  2   b . The top plate  2   a  has an inverted L-shaped external shape in plan view as viewed from a direction orthogonal to the top plate  2   a.    
     Note that, a configuration member also exists that has an L-shaped external shape that is opposite to the shape of the aforementioned configuration member  2  illustrated in  FIG. 14  in plan view. In the following description, a component having the aforementioned L-shaped or inverted L-shaped external shape in plan view is referred to generically as an “L-shaped component”. The strength and rigidity of the framework member  1  are secured by having an L-shaped component as a constituent element. 
       FIG. 15  is an explanatory drawing illustrating an example of a T-shaped component  6 . A top plate  6   a  of the T-shaped component  6  has a T-shaped external shape in plan view when viewed from a direction that is orthogonal to the top plate  6   a . For example, a center pillar reinforcement is known as the T-shaped component  6 . 
     Similarly to the L-shaped component  2 , the T-shaped component  6  has a substantially hat-shaped cross-sectional shape. The substantially hat-shaped cross-sectional shape has a top plate  6   a , a pair of left and right vertical walls  6   b  and  6   b , and a pair of left and right flanges  6   c  and  6   c . In addition, a Y-shaped component (refer to  FIG. 13  that is described later) is known as a modification of the T-shaped component  6 . A top plate  6   a  of the Y-shaped component has an external shape that is a Y-shape in the aforementioned plan view. In the following description, the L-shaped component  2 , the T-shaped component  6  and the Y-shaped component are referred to generically as “curved component”. 
     A curved component is usually manufactured by press working by draw forming in order to prevent the occurrence of wrinkling. 
       FIGS. 16( a ) and 16( b )  are explanatory drawings illustrating an outline of press working by draw forming, in which  FIG. 16( a )  illustrates a state prior to the start of forming, and  FIG. 16( b )  illustrates a state when forming is completed (bottom dead center of forming). 
     As illustrated in  FIG. 16( a )  and  FIG. 16( b ) , press working by draw forming is performed on a blank  10  using a die  7 , a punch  8  and a blank holder  9  to form an intermediate press component  12 . 
       FIG. 17  is an explanatory drawing illustrating an example of a press component  11  manufactured by press working by draw forming.  FIG. 18  is an explanatory drawing illustrating a blank  10  that is the forming starting material for the press component  11 .  FIG. 19  is an explanatory drawing illustrating a wrinkle suppression region  10   a  of the blank  10 .  FIG. 20  is an explanatory drawing illustrating an intermediate press component  12  as it is in a state in which press working has been performed thereon. 
     The press component  11  illustrated in  FIG. 17  is manufactured by press working by draw forming through, for example, the processes (i) to (iv) that are listed hereunder. 
     (i) The blank  10  illustrated in  FIG. 18  is disposed between the die  7  and the punch  8 . 
     (ii) The wrinkle suppression region  10   a  (hatched region in  FIG. 19 ) at the periphery of the blank  10  is firmly held by the die  7  and the blank holder  9  as illustrated in  FIG. 16( a )  and  FIG. 16( b ) . By this means, excessive inflow of the blank  10  into the press mold is suppressed. 
     (iii) By moving the die  7  and the punch  8  relatively to each other in a pressing direction (vertical direction) in which the die  7  and the punch  8  approach each other as illustrated in  FIG. 16( b ) , press working by draw forming is performed on the blank  10  to form the intermediate press component  12 . 
     (iv) By cutting off (trimming) the wrinkle suppression region  10   a  (a cutting-off region that is an unrequired portion) around the intermediate press component  12 , the press component  11  illustrated in  FIG. 17  is obtained. 
     As illustrated in  FIGS. 17 to 20 , in the press working by draw forming, excessive inflow of the blank  10  into the press mold is suppressed by the blank holder  9 . Therefore, the occurrence of wrinkles in the intermediate press component  12  that are caused by excessive inflow of the blank  10  is suppressed. 
     However, the occurrence of the cutting-off region that is an unrequired portion around the intermediate press component  12  is unavoidable. Consequently, the yield of the press component  11  decreases and the manufacturing cost of the press component  11  rises. 
       FIG. 21  is an explanatory drawing illustrating an example of the state of occurrence of pressing defects (wrinkling and cracking) in the intermediate press component  12 . 
     As illustrated in  FIG. 21 , in the intermediate press component  12 , wrinkling is liable to occur at a regions where the blank  10  is liable to excessively flow into the press mold during the draw forming process, and cracking is liable to occur at β regions where there is a partial reduction in sheet thickness during the draw forming process. 
     In particular, when it is attempted to manufacture a curved component by performing pressing working by draw forming on the blank  10  that is made from a high strength steel sheet with low ductility, wrinkling and cracking are liable to occur in the intermediate press component  12  due to insufficient ductility of the blank  10 . 
     To prevent the occurrence of such wrinkling and cracking in the intermediate press component  12 , conventionally a steel sheet that has excellent ductility but comparatively low strength has been used as the blank  10  for the curved component. Consequently, to secure the strength required for the curved component, it has been necessary to make the sheet thickness of the blank  10  thick, making an increase in the weight and an increase in the manufacturing cost of the curved component unavoidable. 
     The present applicants have previously disclosed, in Patent Document 1, a patented invention relating to a method that, even when using a blank made from a high tensile strength steel sheet having low ductility, enables press working of a curved component by bending forming with a good yield, and without wrinkling or cracking occurring. In the present description, the method relating to the aforementioned patented invention is also referred to as “free bending method”. 
     Hereunder, the aforementioned patented invention will be described referring to the aforementioned  FIG. 17  and  FIG. 22 .  FIG. 22  is an explanatory drawing that partially illustrates an outline of the patented invention disclosed by Patent Document 1. 
     The patented invention disclosed by Patent Document 1 manufactures a press component  11  by performing cold or warm press working by bending forming on a blank. As illustrated in  FIG. 17 , the press component  11  has a cross-sectional shape (for example, a hat-shaped cross-sectional shape) that includes a top plate  11   a , convex ridge lines  11   b ,  11   b , vertical walls  11   c ,  11   c , concave ridge lines  11   d ,  11   d , and flanges  11   e ,  11   e.    
     The top plate  11   a  extends in first direction (direction indicated by an arrow in  FIG. 17 ). The convex ridge lines  11   b ,  11   b  are connected to the two ends in the width direction (direction orthogonal to the first direction) of the top plate  11   a , respectively. The vertical walls  11   c ,  11   e  are connected to the convex ridge lines  11   b ,  11   b , respectively. The concave ridge lines  11   d ,  11   d  are connected to the vertical walls  11   c ,  11   c , respectively. The flanges  11   e ,  11   e  are connected to the concave ridge lines  11   d ,  11   d , respectively. 
     The press component  11  also has a curved portion  13  that curves in a plan view that is orthogonal to the top plate  11   a , and by this means the press component  11  has an external shape that is an inverted L-shape. 
     According to the free bending method, as illustrated in  FIG. 22 , a blank  18  is disposed between a die  15  and a die pad  16 , and a punch  17  of a press-forming machine  14  that employs bending forming. 
     By (i) the die pad  16  applying a pressure that is 1.0 MPa or more and less than 32.0 MPa to a portion (vicinity of a portion at which the curved portion  13  of the press component  11  is to be formed)  18   a  of a portion at which the top plate  11   a  is to be formed in the blank  18 , or (ii) the die pad  16  being brought adjacent to or into contact with the punch  17  so that the distance of a gap between the die pad  16  and the punch  17  satisfies the condition of being within a range of {sheet thickness of blank  18 ×(1.0 to 1.1)}, the press component  11  is manufactured by performing press working as described hereunder while suppressing out-of-plane deformation at the portion  18   a  of the portion at which the top plate  11   a  is to be formed. 
     In a state in which a portion (portion corresponding to the base of the inverted L-shape) of the blank  18  to be formed into an end portion  11   f  in the extending direction of the top plate  11   a  is present on the same plane as a portion of the blank  18  to be formed into the top plate  11   a , the die  15  and the punch  17  are moved relative to each other in directions in which the die  15  and the punch  17  approach each other. 
     By this means, while causing the portion (portion corresponding to the base of the inverted L-shape) of the blank  18  to be formed into the end portion  11   f  to move in-plane (slide) over the portion of the die  15  at which top plate  11   a  will be formed, the vertical wall  11   c , concave ridge line  11   d  and flange  11   e  on the inner circumferential side of the curved portion  13  are formed. 
     In this way, when manufacturing the press component  11  having the curved portion  13  by performing press working on the blank  18 , during the press working, the inflow amount of the portion of the blank  18  to be formed into the end portion  11   f  in the extending direction of the top plate  11   a  that flows into the portion of the blank  18  to be formed into the vertical wall  11   c  increases. 
     Consequently, according to the free bending method, excessive tensile stress at the flange  11   e  (in the conventional press working by draw forming, a region where cracking is liable to occur due to a reduction in the sheet thickness) on the inner circumferential side of the curved portion  13  is reduced, and the occurrence of cracking is suppressed. 
     Further, according to the free bending method, at the top plate  11   a  (in the conventional press working by draw forming, a region where wrinkling is liable to occur due to excessive inflow of the blank  18 ) also, because the blank  18  is pulled, the occurrence of wrinkling is suppressed. 
     Further, according to the free bending method, a wrinkle suppression region (cutting-off region) that must be provided in the blank  18  when performing the conventional press working by draw forming is not required. Therefore, the yield of the press component  11  improves. 
     In addition, the free bending method employs press working by bending forming. Therefore, the ductility required for the blank  18  in the free bending method is less than the ductility required for a blank when performing press working by draw forming. Accordingly, it is possible to use a high strength steel sheet with comparatively low ductility as the blank  18 , and the sheet thickness of the blank  18  can be set to a small thickness, and thus a reduction in the weight of a vehicle can be achieved. 
     In Patent Document 2, the present applicants disclosed an invention in which an excess portion of a specific shape is provided at an edge section of a portion to be formed into the flange  11   e  on the inner circumferential side of the curved portion  13  in a developed blank that is used in the free bending method. 
     According to the invention disclosed by Patent Document 2, while further enhancing the formability of the vicinity of the curved portion  13  and preventing cracking of the flange  11   e  on the inner circumferential side of the curved portion  13  by means of the free bending method, excessive inflow of the blank  18  from a portion of the blank  18  to be formed into the top plate  11   a  to a portion of the blank  18  to be formed into the vertical wall  11   c  can also be suppressed, and cracking in the end portion of the top plate  11   a  can also be prevented. 
     LIST OF PRIOR ART DOCUMENTS 
     Patent Document 
     Patent Document 1: WO 2011/145679 
     Patent Document 2: WO 2014/185428 
     SUMMARY OF INVENTION 
     Technical Problem 
     The present inventors conducted intensive studies to further enhance the formability of the free bending method, and as a result newly found that even when press working is performed on the blank  18  by the free bending methods disclosed in Patent Documents 1 and 2, in some cases the press component  11  cannot be manufactured without defective forming occurring. 
     As such cases, for example, the following first case and second case may be mentioned. That is, the first case is a case that satisfies at least one of the following conditions: 
     (a) the blank  18  is made from an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more, 
     (b) a height (projection distance in a product height direction of the vertical wall  11   c ) of the press component  11  is a high height of 70 mm or more, 
     (c) a radius of curvature R 1  of the concave ridge line  11   d  of the press component  11  is a small value of 10 mm or less in side view, and 
     (d) a radius of curvature R 2  of the curved portion  13  of the press component  11  is a small value of 100 mm or less in plan view; 
     and the second case is a case that satisfies at least two or more of the following conditions: 
     (e) the blank  18  is made from an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more, 
     (f) the height (projection distance in the product height direction of the vertical wall  11   c ) of the press component  11  is 55 mm or more, 
     (g) the radius of curvature R 1  of the concave ridge line  11   d  of the press component  11  is 15 mm or less in side view, and 
     (h) the radius of curvature R 2  on the inner side of the curved portion  13  of the press component  11  is 140 mm or less in plan view. 
     In the first case or second case, even if the free bending method is used, cracking occurs in the flange  11   e  on the inner circumferential side of the curved portion  13 . 
     The present invention has been conceived to solve these new problems of the inventions disclosed in Patent Documents 1 and 2. An objective of the present invention is to provide a manufacturing method and a manufacturing apparatus for manufacturing a press component, which can manufacture a curved component without generating cracking in a flange on an inner circumferential side of the curved portion even when press working by the free bending method is performed on a blank in the aforementioned first case or second case. 
     Solution to Problem 
     The present inventors conducted intensive studies to solve the above described problem, and as a result obtained the findings A to D described hereunder to thereby complete the present invention. 
     (A) As has been described referring to  FIG. 17  and  FIG. 22 , in the free bending method, a portion (portion corresponding to the base of the inverted L-shape) of the blank  18  to be formed into the end portion  11   f  in the extending direction of the top plate  11   a  flows in towards a portion of the blank  18  to be formed into the vertical wall  11   c  on the inner circumferential side of the curved portion  13 . By this means, in the blank  18 , material is supplied to a portion to be formed into the flange  11   e  on the inner circumferential side of the curved portion  13 . 
     Therefore, by increasing the amount by which the portion of the blank  18  to be formed into the end portion  11   f  in the extending direction of the top plate  11   a  flows into the portion of the blank  18  to be formed into the vertical wall  11   c  on the inner circumferential side of the curved portion  13 , the occurrence of cracking in the flange  11   e  on the inner circumferential side of the curved portion  13  can be prevented, and it is thus possible to raise the forming limit of the free bending method. 
     (B) However, when performing press working, a limit of the aforementioned inflow amount is geometrically determined according to the amount of change in a cross-section line length of the flange  11   e  between before and after forming of a cross-section in the inflow direction. Further, the limit of the inflow amount serves as the forming limit in the free bending method. 
     (C) When performing press-forming, the aforementioned inflow amount can be increased by, for example, forming, at the same time as the press-forming, a material inflow facilitating portion such as a bead in the vicinity (preferably, in the blank  18 , a region that is outside a region to be formed into the press component  11 ) of a portion of the blank  18  to be formed into the flange  11   e  on the inner circumferential side of the curved portion  13 . 
     (D) By making the shape of the material inflow facilitating portion a shape that can secure a cross-section line length difference in an inflow direction of the material (in the blank  18 , the maximum principal strain direction of a deformation of a portion to be formed into the flange  11   e  on the inner circumferential side of the curved portion  13 ), the aforementioned inflow amount can be increased, and by this means the forming limit in the free bending method can be raised. 
     The present invention is as described hereunder. 
     (1) A method for manufacturing a press component, by performing press working on a blank or a pre-formed blank disposed between a die and a die pad, and a punch that is disposed facing the die and die pad, which constitute a press-forming apparatus that employs bending forming, 
     the press component having a cross-sectional shape constituted by a top plate extending in a first direction, a convex ridge line connecting to an end portion of the top plate in a direction orthogonal to the first direction, a vertical wall connecting to the convex ridge line, a concave ridge line connecting to the vertical wall, and a flange connecting to the concave ridge line, and also having a curved portion that, with the convex ridge line, the vertical wall and the concave ridge line curving, provides an external shape of the top plate with an L-shape, a T-shape or a Y-shape in a plan view that is orthogonal to the top plate, 
     the method comprising, when manufacturing the press component: 
     weakly pressing a portion of the blank to be formed into a part of the top plate of the curved portion by the die pad, or subjecting the die pad to approach or come in contact with a portion of the blank to be formed into a part of the top plate of the curved portion while maintaining a gap between the die pad and the punch at a distance that is not less than a sheet thickness of the blank and not more than 1.1 times the sheet thickness of the blank, and 
     forming, in a state in which a portion of the blank to be formed into an end portion of the top plate in the first direction is present on a same plane as the portion of the blank to be formed into the top plate, the vertical wall, the concave ridge line and the flange on an inner circumferential side of the curved portion while causing the portion of the blank that is to be formed into the end portion of the top plate in the first direction to move in-plane over a portion of the die at which the top plate will be formed by relatively moving the die and the punch in directions in which the die and the punch approach each other, 
     wherein, 
     by the press working, in a vicinity of a portion of the blank to be formed into a flange on the inner circumferential side of the curved portion of the press component, one or more material inflow facilitating portions are provided, the material inflow facilitating portions increasing an inflow amount by which the portion of the blank to be formed into the end portion flows into the portion of the blank to be formed into the flange on the inner circumferential side of the curved portion, and 
     the material inflow facilitating portion includes, in a plan view orthogonal to the top plate, a cross-sectional shape in which a cross-section line length in a cross-section parallel to a straight line that is tangent to a middle position of an inner circumference of the curved portion increases with distance from the flange on the inner circumferential side of the curved portion. 
     (2) The method for manufacturing a press component described in item (1) above, wherein the method satisfies at least one of the following conditions: 
     the blank comprises an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more; 
     a projection distance of the vertical wall in a product height direction as a height of the press component is 70 mm or more; 
     a radius of curvature of the concave ridge line of the press component is 10 mm or less in side view; and 
     a radius of curvature on the inner circumferential side of the curved portion in the press component is 100 mm or less in the plan view. 
     (3) The method for manufacturing a press component described in item (1) above, wherein the method satisfies two or more of the following conditions: 
     the blank comprises an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more; 
     a projection distance of the vertical wall in a product height direction as a height of the press component is 55 mm or more; 
     a radius of curvature of the concave ridge line of the press component is 15 mm or less in side view, and 
     a radius of curvature on an inner side of the curved portion in the press component is 140 mm or less in the plan view. 
     (4) The method for manufacturing a press component described in any one of items (1) to (3) above, wherein: 
     in the blank, the material inflow facilitating portion is provided at a region that is outside of a region to be formed into the press component. 
     (5) The method for manufacturing a press component described in any one of items (1) to (4) above, wherein: 
     the cross-sectional shape includes a case where the cross-section line length is partially constant. 
     (6) The method for manufacturing a press component described in any one of items (1) to (5) above, wherein: 
     the material inflow facilitating portion is a convex bead that is convex toward a same side as the top plate of the press component, or is a concave bead that is convex toward an opposite side to the top plate of the press component. 
     (7) The method for manufacturing a press component described in any one of items (1) to (6) above, wherein: 
     the material inflow facilitating portion is provided at least in a region in which the blank is present. 
     (8) The method for manufacturing a press component described in any one of items (1) to (7) above, wherein: 
     the material inflow facilitating portion is provided in a stepped shape in a direction parallel to a sheet thickness direction of the blank. 
     (9) The method for manufacturing a press component described in any one of items (1) to (8) above, wherein: 
     the material inflow facilitating portion has an external shape obtained by connecting a meeting point of the concave ridge line and the flange in the curved portion that is formed, and an end portion of the blank at a time when the forming starts. 
     (10) The method for manufacturing a press component described in any one of items (1) to (9) above, wherein: 
     the cross-sectional shape is a hat-shaped cross-sectional shape constituted by:
         a top plate extending in a first direction,   two convex ridge lines connecting to both end portions of the top plate in a direction orthogonal to the first direction,   two vertical walls connecting to the two convex ridge lines, respectively,   two concave ridge lines connecting to the two vertical walls, respectively, and   two flanges connecting to the two concave ridge lines, respectively.       

     (11) An apparatus for manufacturing a press component, that comprises a die and a die pad, and a punch that is disposed facing the die and die pad, and that: 
     by performing press working on a blank or a pre-formed blank that is disposed between the die and die pad and the punch, 
     manufactures a press component having a cross-sectional shape constituted by a top plate extending in a first direction, a convex ridge line connecting to an end portion in a direction orthogonal to the first direction of the top plate, a vertical wall connecting to the convex ridge line, a concave ridge line connecting to the vertical wall, and a flange connecting to the concave ridge line, and also having a curved portion that, with the convex ridge line, the vertical wall and the concave ridge line curving, provides an external shape of the top plate with an L-shape, T-shape or Y-shape in a plan view that is orthogonal to the top plate, 
     the apparatus manufacturing the press component by: 
     the die pad weakly pressing a portion of the blank to be formed into a part of the top plate of the curved portion, or the die pad approaching or contacting with a portion of the blank to be formed into a part of the top plate of the curved portion while maintaining a gap between the die pad and the punch at a distance that is not less than a sheet thickness of the blank and not more than 1.1 times the sheet thickness of the blank, and 
     in a state in which a portion of the blank to be formed into an end portion in the first direction of the top plate is present on a same plane as the portion of the blank to be formed into the top plate, by the die and the punch moving relatively in directions in which the die and the punch approach each other, forming the vertical wall, the concave ridge line and the flange on an inner circumferential side of the curved portion while causing the portion of the blank to be formed into the end portion to move in-plane over a portion of the die at which the top plate will be formed; 
     wherein: 
     the die and the punch comprise a material inflow facilitating portion forming mechanism that, by means of the press working, in a vicinity of a portion of the blank to be formed into a flange on an inner circumferential side of the curved portion of the press component, provides one or more material inflow facilitating portions that increase an amount by which a portion of the blank to be formed into the end portion flows into the portion of the blank to be formed into the flange on the inner circumferential side of the curved portion; and 
     the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion in a manner so that, in a plan view that is orthogonal to the top plate, a cross-section line length of the material inflow facilitating portion at a cross-section that is parallel to a straight line that is tangent to a center position of an inner circumference of the curved portion increases with distance from the flange on the inner circumferential side of the curved portion. 
     (12) The apparatus for manufacturing a press component described in item (11) above, the apparatus for manufacturing a press component according to claim  11 , wherein the apparatus satisfies at least one of the following conditions: 
     the blank comprises an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more; 
     a projection distance of the vertical wall in a product height direction as a height of the press component is 70 mm or more; 
     a radius of curvature of the concave ridge line of the press component is 10 mm or less in side view; and a radius of curvature on the inner circumferential side of the curved portion in the press component is 100 mm or less in the plan view. 
     (13) The apparatus for manufacturing a press component described in item (11) above, wherein the apparatus satisfies two or more of the following conditions: 
     the blank comprises an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more; 
     a projection distance of the vertical wall in a product height direction as a height of the press component is 55 mm or more; 
     a radius of curvature of the concave ridge line of the press component is 15 mm or less in side view, and 
     a radius of curvature on an inner side of the curved portion in the press component is 140 mm or less in the plan view. 
     (14) The apparatus for manufacturing a press component described in any one of items (11) to (13) above, wherein: 
     the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion at a region of the blank that is outside of a region to be formed into the press component. 
     (15) The apparatus for manufacturing a press component described in any one of items (11) to (14) above, wherein: 
     the cross-sectional shape includes a case where the cross-section line length is partially constant. 
     (16) The apparatus for manufacturing a press component described in any one of items (11) to (15) above, wherein: 
     the material inflow facilitating portion is a convex bead that is convex toward a same side as the top plate of the press component, or is a concave bead that is convex toward an opposite side to the top plate of the press component. 
     (17) The apparatus for manufacturing a press component described in any one of items (11) to (16) above, wherein: 
     the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion in at least a region in which the blank is present. 
     (18) The apparatus for manufacturing a press component described in any one of items (11) to (17) above, wherein: 
     the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion in a stepped shape in a direction parallel to a sheet thickness direction of the blank. 
     (19) The apparatus for manufacturing a press component described in any one of items (11) to (18) above, wherein: 
     the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion so as to have an external shape obtained by connecting a region of the blank to be formed into a meeting point between the concave ridge line and the flange of the curved portion, and an end portion of the blank prior to the forming. 
     (20) The apparatus for manufacturing a press component described in any one of items (11) to (19) above, wherein:
         the cross-sectional shape is a hat-shaped cross-sectional shape constituted by:   a top plate extending in a first direction,   two convex ridge lines connecting to both end portions of the top plate in a direction orthogonal to the first direction,   two vertical walls connecting to the two convex ridge lines, respectively,   two concave ridge lines connecting to the two vertical walls, respectively, and   two flanges connecting to the two concave ridge lines, respectively.       

     Advantageous Effects of Invention 
     According to the present invention, even when press working by a free bending method is performed on a blank in the aforementioned first case or second case, an inflow amount of material can be increased and a forming limit can be raised in comparison to the free bending methods disclosed by Patent Documents 1 and 2, and it is thus possible to manufacture a press component without generating cracking in a flange on an inner circumferential side of a curved portion of a press component. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an explanatory drawing illustrating a configuration example of a manufacturing apparatus according to the present invention. 
         FIG. 2  is an explanatory drawing partially illustrating an example of a press component that was press-formed by the manufacturing apparatus according to the present invention. 
         FIG. 3  is an explanatory drawing illustrating the positional relationship between a material inflow facilitating portion forming mechanism and a concave ridge line forming portion of the manufacturing apparatus according to the present invention and a blank. 
         FIG. 4  is an explanatory drawing illustrating a cross-section in a conventional punch in which a material inflow facilitating portion forming mechanism is not provided, that corresponds to a cross-section A-A in  FIG. 1 . 
         FIG. 5  is an explanatory drawing illustrating the positional relationship between a material inflow facilitating portion forming mechanism and a concave ridge line forming portion of the manufacturing apparatus according to the present invention and a blank, and the locations of cross-sections B, C and D. 
         FIG. 6  is a graph illustrating cross-section line length differences with respect to a conventional punch at a flange forming portion of a punch at the cross-sections B, C and D. 
         FIG. 7  is an explanatory drawing illustrating a cross-section A-A of a punch in which a material inflow facilitating portion forming mechanism is provided. 
         FIG. 8  is an explanatory drawing illustrating the positional relationship between a material inflow facilitating portion forming mechanism and a concave ridge line forming portion of the manufacturing apparatus according to the present invention and a blank, and the locations of cross-sections B, C and D. 
         FIG. 9  is an explanatory drawing that shows the reason why cracking at a portion “a” of a blank is prevented by providing a material inflow facilitating portion forming mechanism constituted by a recess and a protrusion in a die and punch. 
         FIG. 10( a )  to  FIG. 10( f )  are explanatory drawings that partially illustrate examples of the shapes of protrusions or recesses that are constituent elements of various kinds of material inflow facilitating portion forming mechanisms that are provided in a punch. 
         FIG. 11( a )  and  FIG. 11( b )  are explanatory drawings that respectively illustrate another press component manufactured by the present invention. 
         FIG. 12  is an explanatory drawing illustrating an intermediate component (example embodiment of the present invention) for a T-shaped component. 
         FIG. 13  is an explanatory drawing illustrating an intermediate component (example embodiment of the present invention) for a Y-shaped component. 
         FIG. 14  is an explanatory drawing illustrating an example of a framework member. 
         FIG. 15  is an explanatory drawing illustrating an example of a T-shaped component. 
         FIG. 16( a )  and  FIG. 16( b )  are explanatory drawings illustrating an outline of press working by draw forming, in which  FIG. 16( a )  illustrates a state prior to the start of forming, and  FIG. 16( b )  illustrates a state when forming is completed (bottom dead center of forming). 
         FIG. 17  is an explanatory drawing illustrating an example of a press component manufactured by press working by draw forming. 
         FIG. 18  is an explanatory drawing illustrating a blank that is a forming starting material for a press component. 
         FIG. 19  is an explanatory drawing illustrating a wrinkle suppression region of a blank. 
         FIG. 20  is an explanatory drawing illustrating an intermediate press component as it is in a state in which press working has been performed thereon. 
         FIG. 21  is an explanatory drawing illustrating an example of the state of occurrence of pressing defects in an intermediate press component. 
         FIG. 22  is an explanatory drawing that partially illustrates an outline of the patented invention disclosed by Patent Document 1. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The manufacturing apparatus and manufacturing method according to the present invention are described hereunder. 
     In the following description, a case in which a press component  11  to be manufactured by the present invention is an L-shaped component in which a top plate  11   a  has an external shape that is an inverted L-shape in a plan view that is orthogonal to the top plate  11   a  is taken an example. However, objects to be manufactured by the present invention are not limited to an L-shaped component, and also include other curved components (T-shaped component and Y-shaped component). 
     Further, in the following description, a case in which the press component  11  and an intermediate component  11 - 1  have a hat-shaped cross-sectional shape constituted by the top plate  11   a , two convex ridge lines  11   b ,  11   b , two vertical walls  11   c ,  11   c , two concave ridge lines  11   d ,  11   d  and two flanges  11   e ,  11   e  is taken as an example. However, objects to be manufactured by the present invention are not limited to the press component  11  and the intermediate component  11 - 1  that have a hat-shaped cross-sectional shape, and also include intermediate components  11 - 2  and  11 - 3  for press components having the cross-sectional shapes shown in  FIG. 11  set forth below. 
     1. Manufacturing Apparatus  20  of the Present Invention 
       FIG. 1  is an explanatory drawing illustrating a configuration example of a manufacturing apparatus  20  according to the present invention.  FIG. 2  is an explanatory drawing partially illustrating an example of an intermediate component  11 - 1  of a press component  11  that was press-formed by the manufacturing apparatus  20 . 
     As illustrated in  FIG. 1 , the manufacturing apparatus  20  is a press-forming apparatus that employs bending forming and that uses the free bending method. 
     The manufacturing apparatus  20  includes a die  21 , a die pad  22  and a punch  23 . The punch  23  is disposed facing the die  21  and the die pad  22 . The die pad  22  is movable up and down together with the die  21 , and can also press a part of a blank  24 . 
     The manufacturing apparatus  20  manufactures the intermediate component  11 - 1  of the press component  11  having the external shape illustrated in  FIG. 2  by performing press working as cold or warm working on the blank (developed blank)  24  or on a blank (not illustrated in the drawings) which was subjected to preforming that is minor processing (for example, embossing) that is disposed between the die  21  and die pad  22  and the punch  23 . 
     The sheet thickness of the blank  24  is preferably 0.6 to 2.8 mm, more preferably 0.8 to 2.8 mm, and further preferably 1.0 to 2.8 mm. 
     The press component  11  or the intermediate component  11 - 1  has a hat-shaped cross-sectional shape. The hat-shaped cross-sectional shape is a shape that includes a top plate  11   a , two convex ridge lines  11   b ,  11   b , two vertical walls  11   c ,  11   c , two concave ridge lines  11   d ,  11   d , and two flanges  11   e ,  11   e.    
     The press component  11  or the intermediate component  11 - 1  thereof has a curved portion  13 . The curved portion  13  curves so that the external shape of the top plate  11   a  in a plan view orthogonal to the top plate  11   a  is an inverted L-shaped. 
     The top plate  11   a  extends in a first direction (arrow direction in  FIGS. 2 and 17 ). The two convex ridge lines  11   b ,  11   b  connect to both end portions in a direction which is orthogonal (that is, the width direction of the top plate  11   a ) to the first direction of the top plate  11   a . The two vertical walls  11   c ,  11   c  connect to the two convex ridge lines  11   b ,  11   b , respectively. The two concave ridge lines  11   d ,  11   d  connect to the two vertical walls  11   c ,  11   c , respectively. The two flanges  11   e ,  11   e  connect to the two concave ridge lines  11   d ,  11   d , respectively. 
     The manufacturing apparatus  20  is favorably used in the following first case and second case. 
     First case: A case satisfying one or more conditions among a condition that the blank  24  is made from an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more, a condition that a projection distance in a product height direction of the vertical wall  11   c  as a height of the press component  11  or the intermediate component  11 - 1  thereof is 70 mm or more, a condition that a radius of curvature R 1  of the concave ridge line  11   d  of the press component  11  or the intermediate component  11 - 1  thereof is 10 mm or less in side view, and a condition that a radius of curvature R 2  on an inner circumferential side of the curved portion  13  of the press component  11  or the intermediate component  11 - 1  thereof is 100 mm or less in plan view.
 
Second case: A case satisfying at least two conditions among a condition that the blank  24  is made from an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more, a condition that a height (projection distance in a product height direction of the vertical wall  11   c ) of the press component  11  or the intermediate component  11 - 1  thereof is 55 mm or more, a condition that a radius of curvature R 1  of the concave ridge line  11   d  of the press component  11  or the intermediate component  11 - 1  thereof is 15 mm or less in side view, and a condition that a radius of curvature R 2  on an inner side of the curved portion  13  of the press component  11  or the intermediate component  11 - 1  thereof is 140 mm or less in plan view.
 
     This is because, if press working by the conventional free bending method is performed on the blank  24  in the first case or the second case, cracks will be generated in the flange  11   e  on the inner circumferential side of the curved portion  13  of the obtained press component  11  or intermediate component  11 - 1  thereof, and therefore the significance of using the manufacturing apparatus  20  will be recognized. 
     The die pad  22  presses a portion of the blank  24  to be formed into a part of the top plate  11   a  at the curved portion  13  of the press component  11  with an applied pressure that is 1.0 MPa or more and less than 32.0 MPa, or comes adjacent to or into contact with the aforementioned portion of the blank  24  while maintaining the distance of a gap with respect to the punch  23  at a distance corresponding to 1.0 to 1.1 times the sheet thickness of the blank  24 . 
     By this means, while out-of-plane deformation at the aforementioned portion of the blank  24  is being suppressed by the die pad  22 , the intermediate component  11 - 1  of the press component  11  is manufactured by performing press working that is described hereunder. 
     That is, in the press working, in a state in which a portion of the blank  24  to be formed into the end portion  11   f  in the first direction of the top plate  11   a  is present on the same plane as a portion of the blank  24  to be formed into the top plate  11   a , the die  21  and the punch  23  are relatively moved in directions in which the die  21  and the punch  23  approach each other. 
     By this means, the vertical wall  11   c , the concave ridge line  11   d  and the flange  11   e  on the inner circumferential side of the curved portion  13  are formed while the portion of the blank  24  to be formed into the end portion  11   f  is caused to move in-plane (slide) over a portion of the die  21  at which the top plate  11   a  will be formed. 
     In this way, the intermediate component  11 - 1  of the press component  11  is manufactured. 
       FIG. 3  is an explanatory drawing illustrating the positional relationship between a material inflow facilitating portion forming mechanism  25  and a concave ridge line forming portion  23   b  of the manufacturing apparatus  20 , and the blank  24 . 
     In addition to performing press working by bending forming using the free bending method disclosed by Patent Documents 1 and 2 and the like, in the manufacturing apparatus  20 , as illustrated in  FIGS. 1 and 3 , a recess  21   a  and a protrusion  23   a  as the material inflow facilitating portion forming mechanism  25  for providing a material inflow facilitating portion  19  in the blank  24  are provided in the die  21  and the punch  23 , respectively, of the manufacturing apparatus  20 . The material inflow facilitating portion forming mechanism  25  is constituted by the recess  21   a  that is provided in the die  21  and the protrusion  23   a  that is provided in the punch  23 . 
     At the time of performing the press working, as illustrated in  FIG. 2 , the manufacturing apparatus  20  uses the material inflow facilitating portion forming mechanism  25  to provide the material inflow facilitating portion  19  in the vicinity (for example, at only the flange, or at the flange and the concave ridge line) of a portion of the blank  24  to be formed into the flange  11   e  on the inner circumferential side of the curved portion  13  of the intermediate component  11 - 1 . 
     As illustrated in  FIGS. 2 and 3 , preferably the material inflow facilitating portion forming mechanism  25  provides the material inflow facilitating portion  19  in a region that is outside a region (hatched region in  FIG. 3 ) of the blank  24  to be formed into the press component  11 . By this means, by cutting off the outer edge of the flange  11   e  of the intermediate component  11 - 1  as a trim line, it is possible not to leave a trace of the material inflow facilitating portion  19  in the press component  11 . 
     In a case where it is acceptable for a trace of the material inflow facilitating portion  19  to remain in the press component  11 , the material inflow facilitating portion  19  may be provided in a region of the blank  24  (hatched region in  FIG. 3 ) to be formed into the press component  11 . 
     Next, the material inflow facilitating portion forming mechanism  25  will be described in more detail. 
       FIG. 4  is an explanatory drawing illustrating a cross-section in a conventional punch  23 - 1  in which the material inflow facilitating portion forming mechanism  25  is not provided, that corresponds to a cross-section A-A in  FIG. 1 . 
       FIG. 5  is an explanatory drawing illustrating the positional relationship between the blank  24  and the material inflow facilitating portion forming mechanism  25  and concave ridge line forming portion  23   b  of the manufacturing apparatus  20 , and locations of cross-sections B, C and D. 
       FIG. 6  is a graph illustrating cross-section line length differences (inflow amounts) with respect to a conventional punch at a flange forming portion of the punch  23  at the cross-sections B, C and D. In the cross-sections B, C and D in the graph in  FIG. 6 , the left side illustrates a case according to the conventional method, and the right side illustrates a case according to the method of the present invention. Further, the cross-sections below the graph in  FIG. 6  illustrate the respective shapes of the blank  24  at the cross-sections B, C and D. 
       FIG. 7  is an explanatory drawing illustrating a cross-section A-A of the punch  23  in which the material inflow facilitating portion forming mechanism  25  is provided. 
     In the aforementioned first case or second case, if press working of the blank  24  is performed by the free bending method using the conventional punch  23 - 1 , cracking will occur at a portion “a” shown in  FIG. 4 . 
     As illustrated in  FIGS. 5 and 6 , according to the present invention, by providing the material inflow facilitating portion forming mechanism  25  that is constituted by the recess  21   a  and the protrusion  23   a , the material inflow facilitating portion  19  is provided in the intermediate component  11 - 1  by press working. 
     The cross-sections B, C and D in  FIGS. 5 and 6  are cross-sections in a material inflow direction that is parallel to a straight line that is tangent to a center position (portion “a”) of an inner circumference of the curved portion  13  in a plan view orthogonal to the top plate  11   a . The cross-sections B, C and D are cross-sections in a maximum principal strain direction of a deformation of a portion to be formed into the flange  11   e  on the inner circumferential side of the curved portion  13 . 
     The material inflow facilitating portion  19  is provided so that cross-section line lengths at the cross-sections B, C and D gradually increase with distance from the flange  11   e  on the inner circumferential side of the curved portion  13 . 
     The cross-sectional shape of the material inflow facilitating portion  19  is not limited to a shape which monotonously increases with distance from the flange  11   e  on the inner circumferential side of the curved portion  13  of the intermediate component  11 - 1 , and may be a shape that partially includes a portion at which the cross-section line length is constant. 
     That is, as illustrated in  FIG. 6 , in comparison to the conventional method in which the material inflow facilitating portion forming mechanism  25  is not provided, the material inflow facilitating portion forming mechanism  25  of the method of the present invention is provided so that a cross-section line length difference (inflow amount) relative to the conventional punch of the flange forming portion of the punch  23  increases at each of the cross-sections B, C and D, and so that the cross-section line length difference (inflow amount) at the cross-section C increases more than the cross-section line length difference (inflow amount) at the cross-section  13 , and the cross-section line length difference (inflow amount) at the cross-section D increases more than the cross-section line length difference (inflow amount) at the cross-section C. 
     In other words, in the present invention, the material inflow facilitating portion forming mechanism  25  having a shape that increases the cross-section line length difference (inflow amount) at each of the cross-sections B, C and D is provided in the die  21  as the recess  21   a  and is also provided in the punch  23  as the protrusion  23   a.    
     For example, as illustrated in  FIG. 7 , the material inflow facilitating portion  19  is exemplified as being provided as a protrusion having an external shape that is obtained by connecting the meeting point of the concave ridge line  11   d  and the flange  11   e  of the curved portion  13  that is formed, and an end portion  24   a  of the blank  24  at the time that forming starts. 
       FIG. 8  is an explanatory drawing illustrating the positional relationship between the blank  24  and the material inflow facilitating portion forming mechanism  25  and concave ridge line forming portion  23   b  of the manufacturing apparatus  20 , and the locations of cross-sections B, C and D. 
     As described above, a change differential in the inflow amount of the material that is caused by the material inflow facilitating portion forming mechanism  25  increases with distance from the portion “a” of the blank  24  through the cross-section B, the cross-section C and furthermore the cross-section D as indicated by a broad arrow in  FIG. 8 . 
     Note that, cracking at the portion “a” of the blank  24  shown in  FIG. 4  occurs when a tensile force in the circumferential direction that is not less than the rupture-yield strength of the blank  24  locally arises. Therefore, if a change in the cross-section line length difference is imparted to the portion “a”, cracking at the portion “a” will be more liable to occur. Accordingly, practically no change may be provided in the cross-section line length difference at the portion “a”. Further, it is sufficient to set a region that provides a change in the cross-section line length difference (inflow amount) as a region up to the position at which the blank  24  is present before forming, that is, up to the end portion  24   a  illustrated in  FIG. 7 . 
     Next, the function of the material inflow facilitating portion forming mechanism  25  will be described. 
       FIG. 9  is an explanatory drawing that shows the reason why cracking at the portion “a” of the blank  24  is prevented by providing the material inflow facilitating portion forming mechanism  25  that is constituted by the recess  21   a  and the protrusion  23   a , in the die  21  and the punch  23 . 
     Cracking at the portion “a” of the blank  24  is attributable to a high tensile force F in the circumferential direction of the concave ridge line  11   d  that is located at an upper part of the portion “a” in the blank  24 . In the present invention, by providing the material inflow facilitating portion forming mechanism  25  in the die  21  and the punch  23  and performing press working, the inflow amount of the blank  24  to an outer side relative to the portion “a” is increased. 
     By this means, because the inflow amount of the blank  24  increases from around the portion “a”, the inflow amount of the blank  24  to the portion “a” increases. That is, the inflow amount of the blank  24  to the portion of the blank  24  to be formed into the curved portion  13  is increased by means of the material inflow facilitating portion forming mechanism  25 . Although the direction of principal strain of a deformation in the portion of the blank  24  to be formed into curved portion  13  does not change significantly, the amount of deformation thereof is reduced. 
     Thus, according to the present invention, as illustrated by arrows in  FIG. 9 , the inflow amount of the blank  24  to a portion of the blank  24  to be formed into the flange  11   e  on the inner circumferential side of the curved portion  13  of the press component  11  increases in comparison to the conventional method in which the material inflow facilitating portion forming mechanism  25  is not provided. 
     By this means, in the blank  24 , since the tensile force F in the circumferential direction of the concave ridge line  11   d  that is located at the upper part of the portion “a” can be reduced and the deformation load at the portion of the blank  24  to be formed into the curved portion  13  can be decreased, cracking is prevented at the portion “a” of the blank  24 . 
       FIG. 10( a )  to  FIG. 10( f )  are explanatory drawings that partially illustrate examples of the shape of the protrusion  23   a  or a recess  23   c  that are constituent elements of various kinds of the material inflow facilitating portion forming mechanism  25  that is provided in the punch  23 . 
     As illustrated in  FIG. 10( a ) , a protrusion that is convex toward the same side as the top plate  11   a  of the press component  11  that was described above referring to  FIG. 7  can be used as the protrusion  23   a  that is a constituent element of the material inflow facilitating portion forming mechanism  25  provided in the punch  23 . 
     As illustrated in  FIG. 10( b ) , the recess  23   c  that is convex toward the opposite side to the top plate  11   a  of the press component  11  may be used instead of the protrusion  23   a  illustrated in  FIG. 10( a ) . In this case, it need scarcely be said that a protrusion corresponding to the recess  23   c  is provided in the die  21 . 
     As illustrated in  FIG. 10( c ) , in a case where the blank  24  is small, the protrusion  23   a  may be provided in a region which is in contact with the blank  24 . 
     As described in the foregoing and as is also illustrated in  FIG. 10( d ) , in a case where it is acceptable for a trace of the material inflow facilitating portion  19  to remain in the press component  11 , the protrusion  23   a  as the material inflow facilitating portion  19  may be provided so as to extend over a region (hatched region in  FIG. 3 ) of the blank  24  to be formed into the press component  11 . 
     As illustrated in  FIG. 10( e ) , two or more of the protrusions  23   a  that are independent may be provided as constituent elements of the material inflow facilitating portion forming mechanism  25 . 
     In addition, as illustrated in  FIG. 10( f ) , the protrusion  23   a  may be provided in a stepped shape in a direction parallel to the sheet thickness direction of the blank  12 . 
     Thus, the material inflow facilitating portion forming mechanism  25  provides one or more of the material inflow facilitating portions  19  that increase an inflow amount by which a portion of the blank  24  to be formed into the end portion  11   f  of the intermediate component  11 - 1  flows into a portion of the blank  24  to be formed into the flange  11   e  on the inner circumferential side of the curved portion  13  of the intermediate component  11 - 1 . 
       FIG. 11( a )  and  FIG. 11( b )  are explanatory drawings that respectively illustrate intermediate components  11 - 2  and  11 - 3  of other press components to be manufactured by the present invention. 
     In the above description, a case of manufacturing the intermediate component  11 - 1  having the shape illustrated in  FIG. 2  by means of the present invention was taken as an example. However, the present invention is not limited to the case described above and is also applicable to a case of manufacturing the intermediate component  11 - 2  illustrated in  FIG. 11( a )  and a case of manufacturing the intermediate component  11 - 3  illustrated in  FIG. 11( b ) , that is, the intermediate components  11 - 2  and  11 - 3  that have one of the convex ridge line  11   b , the vertical wall  11   c , the concave ridge line  11   d  and the flange  11   e , respectively. 
     2. Manufacturing Method of the Present Invention 
     In the manufacturing method of the present invention, basically the intermediate component  11 - 1  of the press component  11  is manufactured by the free bending method using the manufacturing apparatus  20 . 
     The press component  11  that is taken as the manufacturing object of the present invention preferably satisfies the aforementioned first case or second case. This is because, in the press component  11  that satisfies the first case or second case, cracking occurs at the portion “a” of the blank  24  when manufactured by the conventional free bending method. 
     That is, a portion (hatched portion  18   a  in  FIG. 22 ) of the blank  24  to be formed into a part of the top plate  11   a  of the curved portion  13  of the press component  11  is pressed with an applied pressure that is 1.0 MPa or more and less than 32.0 MPa by the die pad  22 , or while maintaining the distance of a gap between the die pad  22  and the punch  23  at a distance corresponding to 1.0 to 1.1 times the sheet thickness of the blank  24 , the die pad  22  is brought adjacent to or into contact with the portion (hatched portion  18   a  in  FIG. 22 ) to be formed into the top plate  11   a  of the curved portion  13  of the press component  11 . 
     By this means, while suppressing out-of-plane deformation of the portion to be formed into a part of the top plate  11   a , the intermediate component  11 - 1  of the press component  11  is manufactured by performing press working that is described hereunder. 
     That is, in the press working, in a state in which a portion of the blank  24  to be formed into the end portion  11   f  in the first direction of the top plate  11   a  is present on the same plane as a portion of the blank  24  to be formed into the top plate  11   a , the die  21  and the punch  23  are relatively moved in directions in which the die  21  and the punch  23  approach each other. 
     By this means, the vertical wall  11   c , the concave ridge line  11   d  and the flange  11   e  on the inner circumferential side of the curved portion  13  are formed while the portion of the blank  24  to be formed into the end portion  11   f  is caused to move in-plane (slide) over a portion of the die  21  at which the top plate  11   a  will be formed. 
     By this press working, the material inflow facilitating portion forming mechanism  25  provided in the die  21  and the punch  23  provides at least one material inflow facilitating portion  19  in the vicinity of the portion of the blank  24  to be formed into the flange  11   e  on the inner circumferential side of the curved portion  13  of the intermediate component  11 - 1 . 
     According to the present invention, as described in the foregoing referring to  FIG. 9 , an inflow amount of the blank  24  to a portion of the blank  24  to be formed into the flange  11   e  on the inner circumferential side of the curved portion  13  of the intermediate component  11 - 1  increases. Therefore, in the blank  24 , the tensile force F in the circumferential direction of the concave ridge line  11   d  that is located at an upperpart of the portion “a” can be reduced, and by this means cracking at the portion “a” of the blank  24  is prevented. 
     In a case where there is no unwanted part in the intermediate component  11 - 1  that underwent press working according to the free bending method by means of the manufacturing apparatus  20 , the intermediate component  11 - 1  serves as it is as the press component  11  that is the end product. On the other hand, in a case where there is an unwanted part in the intermediate component  11 - 1 , the intermediate component  11 - 1  is made into the press component  11  by cutting off (trimming) the unwanted part including the material inflow facilitating portion  19  by taking the outer edge portion of the flange  11   e  as a trim line. 
     Example 1 
     With respect to each of the intermediate component  11 - 1  (example embodiment of the present invention) illustrated in  FIG. 2  manufactured using the manufacturing apparatus  20  illustrated in  FIG. 1 , and a press component (comparative example) manufactured using a manufacturing apparatus  14  illustrated in  FIG. 20 , a maximum sheet thickness reduction ratio at a meeting point “a” portion between the concave ridge line  11   d  and the flange  11   e  at a center position in the circumferential direction of the curved portion  13  was analyzed by the finite element method using a computer. 
     The specifications of the intermediate component  11 - 1  and the press component that were analyzed are as described hereunder: 
     Tensile strength and sheet thickness of blanks  24  and  18 : 1180 MPa or more, and 1.6 mm 
     Height (projection distance in product height direction of vertical wall  11   c ) of intermediate component  11 - 1  and press component: 60 mm 
     Radius of curvature R 1  of concave ridge line  11   d  of intermediate component  11 - 1  and press component: 20 mm in side view 
     Radius of curvature R 2  on inner side of curved portion  13  of intermediate component  11 - 1  and press component: 100 mm in plan view 
     According to this analysis, if the maximum sheet thickness reduction ratio calculated by the dynamic explicit method using the finite element method was 8% or less, it was determined that there was no cracking at the aforementioned meeting point, while if the maximum sheet thickness reduction ratio that was similarly calculated was more than 13% it was determined that there was cracking at the aforementioned meeting point. 
     As a result, it was found that the maximum sheet thickness reduction ratio at the aforementioned meeting point “a” portion of the intermediate component  11 - 1  (example embodiment of the present invention) was 8% and it thus was determined that there was no cracking at the meeting point “a” portion, while in contrast it was found that the maximum sheet thickness reduction ratio at the meeting point “a” portion of the press component (comparative example) was 13% and it was thus determined that there was cracking at the meeting point “a” portion. 
     According to the present invention, even when press working by the free bending method is performed on the blank  24  in the aforementioned first case or second case, the L-shaped component  11 - 1  can be manufactured without generating cracking in the flange  11   e  on the inner circumferential side of the curved portion  13 . 
     Example 2 
     With respect to intermediate components  11 - 1  (example embodiments of the present invention) illustrated in  FIG. 2  that were manufactured using the manufacturing apparatus  20  illustrated in  FIG. 1 , and press components (comparative examples) manufactured using the manufacturing apparatus  14  illustrated in  FIG. 20 , a maximum sheet thickness reduction ratio at a meeting point “a” portion between the concave ridge line  11   d  and the flange  11   e  at a center position in the circumferential direction of the curved portion  13  was analyzed by the finite element method using a computer. 
     Table 1 shows a summary of the specifications of the intermediate components  11 - 1  and the press components that were analyzed as well as the analysis results. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                   
                   
                   
                   
                   
                 Maximum Sheet Thickness Reduction Ratio % 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                 With Material 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Forming Shape Conditions 
                   
                   
                 Inflow Facilitating 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Top 
                 Concave 
                 Without Material 
                   
                 Portion 
               
               
                   
                   
                   
                 Surface 
                 Ridge 
                 Inflow Facilitating 
                   
                 (Example 
               
               
                   
                 Material 
                 Formed 
                 View 
                 Line 
                 Portion 
                   
                 Embodiment of 
               
               
                   
                 Strength 
                 Height 
                 R 2   
                 R 1   
                 (Comparative 
                 Cracking 
                 the Present 
               
               
                 No 
                 MPa 
                 mm 
                 mm 
                 mm 
                 Example) 
                 Criterion 
                 Invention) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 1 
                 1180 
                 60 
                 120 
                 20 
                 13 
                 10 
                 8 
               
               
                 2 
                 980 
                 80 
                 120 
                 20 
                 16 
                 15 
                 12 
               
               
                 3 
                 980 
                 60 
                 120 
                 5 
                 18 
                 15 
                 13 
               
               
                 4 
                 980 
                 60 
                 90 
                 20 
                 17 
                 15 
                 10 
               
               
                 5 
                 1180 
                 65 
                 150 
                 20 
                 14 
                 10 
                 9 
               
               
                 6 
                 1180 
                 50 
                 150 
                 12 
                 12 
                 10 
                 8 
               
               
                 7 
                 980 
                 50 
                 130 
                 12 
                 15 
                 15 
                 12 
               
               
                 8 
                 980 
                 65 
                 130 
                 20 
                 15 
                 15 
                 11 
               
               
                 9 
                 1180 
                 50 
                 130 
                 20 
                 12 
                 10 
                 6 
               
               
                 10 
                 980 
                 65 
                 150 
                 12 
                 15 
                 15 
                 10 
               
               
                   
               
            
           
         
       
     
     According to this analysis, if the maximum sheet thickness reduction ratio of the blank  24  having a tensile strength of 980 MPa that was calculated by the dynamic explicit method using the finite element method was 15% or less it was determined that there was no cracking at the aforementioned meeting point “a” portion, and if the maximum sheet thickness reduction ratio of the blank  24  having a tensile strength of 1180 MPa that was similarly calculated was 10% or less it was determined that there was no cracking at the aforementioned meeting point. 
     As illustrated in Table 1, according to the present invention, even when press working by the free bending method is performed on the blank  24  in the aforementioned first case or second case, the L-shaped component  11 - 1  can be manufactured without generating cracking in the flange  11   e  on the inner circumferential side of the curved portion  13 . 
     Example 3 
     With respect to an intermediate component  30  (example embodiment of the present invention) of a T-shaped component that is illustrated in  FIG. 12  and an intermediate component  31  of a Y-shaped component illustrated in  FIG. 13  that were manufactured using the manufacturing apparatus  20  illustrated in  FIG. 1 , a maximum sheet thickness reduction ratio at a meeting point “a” portion between a concave ridge line and a flange at a center position in the circumferential direction of a curved portion was analyzed by the finite element method using a computer. 
     Table 2 shows a summary of the specifications of the intermediate components  30  and  31  that were analyzed as well as the analysis results for each. Note that, the term “opening angle” in Table 2 refers to an angle θ shown in  FIGS. 12 and 13 . 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                   
                   
                   
                   
                   
                   
                 Maximum Sheet Thickness Reduction Ratio % 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                 Without 
                   
                   
               
               
                   
                   
                   
                   
                   
                   
                 Material 
                   
                 With Material 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Forming Shape Conditions 
                 Inflow 
                   
                 Inflow Facilitating 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Top 
                 Concave 
                 Opening 
                 Facilitating 
                   
                 Portion (Example 
               
               
                   
                 Material 
                 Formed 
                 Surface 
                 Ridge 
                 Angle 
                 Portion 
                   
                 Embodiment of 
               
               
                   
                 Strength 
                 Height 
                 ViewR 2   
                 LineR 1   
                 Degree 
                 (Comparative 
                 Cracking 
                 the Present 
               
               
                   
                 MPa 
                 mm 
                 mm 
                 mm 
                 deg. 
                 Example) 
                 Criterion 
                 Invention) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Intermediate 
                 1180 
                 60 
                 120 
                 20 
                 90 
                 14 
                 10 
                 9 
               
               
                 component 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 30 for T- 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 shaped 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 component 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Intermediate 
                 1180 
                 60 
                 120 
                 20 
                 120 
                 11 
                 10 
                 8 
               
               
                 component 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 31 for Y- 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 shaped 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 component 
               
               
                   
               
            
           
         
       
     
     According to this analysis, if the maximum sheet thickness reduction ratio in the case of a material strength of 1180 MPa that was calculated by the dynamic explicit method using the finite element method was 10% or less it was determined that there was no cracking at the aforementioned meeting point. 
     As illustrated in Table 2, according to the present invention, even when press working by the free bending method is performed on the blank  24  in the aforementioned first case or second case, the intermediate component  30  for a T-shaped component and the intermediate component  31  for a Y-shaped component can be manufactured without generating cracking in the flange  11   e  on the inner circumferential side of the curved portion  13 .