JP6376048B2 - Press molding method and press mold - Google Patents

Description

  The present invention provides a press part having a substantially hat-shaped cross section that is continuous in the longitudinal direction, and an extended flange-formed part and a contracted flange-formed part formed at opposite positions across the top of the hat. The present invention relates to a press molding method and a press die formed by bending.

  In general, as shown in FIGS. 16 and 17, a press die 200 that is formed by bending a press part 100 having a substantially hat-shaped cross section continuous in the longitudinal direction has a molding surface formed along the substantially hat-shaped cross section. The lower mold punch 201, the pad 202 that presses the material SS in contact with the upper end portion (corresponding to the hat top 101) of the molding surface of the lower mold punch 201 from the upper side, and a substantially hat positioned outside the outline of the pad 202. And an upper die 203 having bending blades 203D formed along the left and right side wall portions of the die cross section. In the press die 200, the upper die 203 is lowered in a state where the material SS in contact with the upper end portion of the molding surface of the lower die punch 201 is pressed by the pad 202, and the bending blade 203D causes the material SS to be transferred to the lower die punch 201. Press and bend into a shape along the molding surface of the lower punch 201.

  However, in the pressed part 100, since the stretched flange molded part 102 and the contracted flange molded part 103 are formed at positions facing each other across the hat top 101 having a substantially hat-shaped cross section, the stretched flange molded part is formed after bending. The tensile stress α1 remains in the portion 102, and the compressive stress α2 remains in the contracted flange forming portion 103. Therefore, as shown in FIG. 18, in the pressed part 100 after bending, the stretch flange formed portion 102 is easily deformed inward by the residual tensile stress (in the direction of the arrow B <b> 1), and the contracted flange formed portion 103 is Due to the residual compressive stress, the side wall is likely to be deformed outward (in the direction of arrow B2), and a torsional deformation in which the substantially hat-shaped section rotates with respect to the section center 104 may occur. In particular, when the material SS is a so-called ultra-high-strength steel plate (for example, a steel plate having a tensile strength of about 1 to 1.2 GPa), the amount of twist of the pressed component 100 after bending is increased, and the size of the pressed component 100 is increased. There is a problem that it is difficult to guarantee the accuracy within a predetermined tolerance.

  In order to solve this problem, a method of forming the pressed part by drawing is also conceivable. However, when the material passes through the shoulder R portion of the upper die at the time of drawing, bending of the left and right side walls accompanying bending back is caused. Therefore, there is a problem that dimensional accuracy defects are likely to occur. Further, when a forming method by drawing is selected, there is a problem that the number of steps increases as compared with a case where a forming method by bending is selected.

  Therefore, when the material is the ultra-high strength steel plate, the workpiece (material) in a heated state is bent and cooled at the same time in order to improve the dimensional accuracy during forming without increasing the number of steps. Techniques related to hot stamping and hot pressing for quenching have been studied (see, for example, Patent Document 1).

International Publication No. 2011/055416

However, the hot press mold disclosed in Patent Document 1 includes a stroke-type temperature measuring device that expands and contracts by a pressure applied through a workpiece, and the temperature measuring device is a molding surface of the mold. It is provided in a state of projecting outward from the workpiece, and is configured to shrink and immerse into the mold when it receives pressure from the workpiece in contact with the workpiece. For this reason, there is a problem that the mold structure becomes complicated, the mold cost increases, and the temperature measuring device may be deformed or broken during processing, resulting in an increase in mold failure.
In the above hot press mold, the time for cooling the workpiece from a predetermined heating temperature to the quenching temperature needs to be held in the mold closed state, and the productivity is greatly reduced as compared with the cold press method. There was a problem.

  The present invention has been made in order to solve the above-described problem, and has a substantially hat-shaped cross section that is continuous in the longitudinal direction, and an extended flange-shaped part and a contracted flange-shaped part at positions facing each other across the top of the hat. In the case of forming a pressed part formed by cold bending the unrolled material, it is possible to improve its dimensional accuracy with a simple mold structure without reducing productivity. An object is to provide a press molding method and a press die.

In order to achieve the above object, a press molding method and a press die according to the present invention have the following configurations.
(1) A lower die punch, a pad for pressing a material against the lower die punch, and an upper die having a molding surface on the outer side of the pad, and having a substantially hat-shaped cross section continuous in the longitudinal direction, A press molding method for forming a press part in which a stretch flange molding part and a contraction flange molding part are formed at positions facing each other across the top of the hat by bending the unrolled material cold,
In a state where the pad presses the material portion at the top of the hat at a position away from the stretch flange molding part and the shrink flange molding part, the upper die is close to the lower punch and the stretch flange molding And a material portion forming the shrinkage flange forming portion is rotated with respect to the lower punch from the shrinkage flange forming side to the stretch flange forming side and then pressed against the lower die punch.

  In the present invention, in a state where the pad presses the material portion at the top of the hat at a position away from the stretch flange molding part and the shrink flange molding part, the upper die is close to the lower mold punch and the stretch flange molding part and The material part forming the shrinkage flange molding part is rotated and moved from the shrinkage flange molding side to the stretch flange molding side with respect to the lower mold punch, and then pressed against the lower mold punch. A tensile force that stretches along the outer edge of the material acts on the material part that forms the molded part, and a compressive force that shrinks along the outer edge of the material as the material supply increases on the material part that forms the stretch flange molded part Works. For this reason, as the bending process progresses, the margin of the outer edge of the material accompanying the bending process in the material part forming the shrinkage flange forming part is reduced, and the outer edge of the material accompanying the bending process in the material part forming the stretched flange forming part is reduced. The shortage is reduced. Therefore, in the pressed part after bending, the compressive stress remaining in the contracted flange formed portion is reduced, and the tensile stress remaining in the stretch flange formed portion is reduced. As a result, in the pressed part after bending, the residual compressive stress in the shrinkage flange molding part and the residual tensile stress in the stretch flange molding part are reduced, respectively, thereby reducing the amount of twist by which the substantially hat-shaped cross section rotates with respect to the center of the cross section. The dimensional accuracy can be improved. Further, this bending process is performed by a cold press method, and it is not necessary to heat and cool the material as in the case of a hot press or the like. Therefore, a simple mold structure may be used, and productivity is not reduced.

  Therefore, according to the present invention, the extending flange forming portion and the shrinking flange forming portion are formed at positions facing each other across the top of the hat having a substantially hat-shaped cross section that is continuous in the longitudinal direction. A press molding method that can improve the dimensional accuracy of a pressed part with a simple mold structure and without reducing productivity when forming the unrolled material by cold bending. Can be provided.

(2) In the press molding method described in (1),
The upper die presses the material portion forming the stretch flange molding portion, the contraction flange molding portion, and the top of the hat sandwiched between the lower die punches without passing through the pad. Features.

  In the present invention, the upper die presses the material portion forming the stretch flange forming portion, the shrink flange forming portion, and the top of the hat sandwiched between them to the lower punch without using a pad. In the middle of the mold die approaching the lower mold punch, the material part that forms the stretch flange molded part, the contracted flange molded part, and the top of the hat sandwiched between them is not subjected to pad restraint, Can be rotated more easily. As a result, the excess material margin at the outer edge of the material part that forms the shrink-flanged molded part is further reduced, and the shortage of the outer edge of the material that accompanies the bending process at the material part that forms the elongated flange-formed part is further reduced. Is done. As a result, in the pressed part after bending, the amount of twist by which the substantially hat-shaped cross section rotates with respect to the center of the cross section is based on the decrease in the residual compressive stress in the shrinkage flange forming part and the residual tensile stress in the stretch flange forming part. Can be further reduced.

(3) In the press molding method described in (1) or (2),
The material portion forming the stretch flange forming portion is provided with a surplus portion extending outward from the outer edge of the material.

  In the present invention, the material portion forming the stretch flange forming portion is provided with a surplus portion extending outward from the outer edge of the material, so that the surplus portion is moved downward while the upper die approaches the lower punch. It is pulled, and the rotational movement of the material part from the shrink flange forming side to the stretch flange forming side can be further promoted with respect to the lower punch. As a result, the excess material margin at the outer edge of the material part that forms the shrink-flanged molded part is further reduced, and the shortage of the outer edge of the material that accompanies the bending process at the material part that forms the elongated flange-formed part is further reduced. Is done. As a result, in the pressed part after bending, the amount of twist by which the substantially hat-shaped cross section rotates with respect to the center of the cross section is based on the decrease in the residual compressive stress in the shrinkage flange forming part and the residual tensile stress in the stretch flange forming part. Can be further reduced.

(4) In the press molding method described in (3),
The upper die and the lower die punch include an upper die convex portion and a lower die concave portion that are formed so as to constrain the surplus portion, and the extra die convex portion and the lower die concave portion form the extra die. After constraining the meat part, the bending of the material part forming the stretched flange molded part and the contracted flange molded part is completed.

  In the present invention, the upper die and the lower die punch are provided with an upper die convex portion and a lower die concave portion that are formed so as to restrain the surplus portion, and the upper die convex portion and the lower die concave portion make up the extra space. After constraining the part, the bending process of the material part forming the stretch flange forming part and the shrinking flange forming part is completed, so the surplus part is constrained (clinched) in advance between the upper mold convex part and the lower mold concave part. In this state, the bending process of the material portion that forms the stretch flange molding part and the contraction flange molding part can proceed. Therefore, the flow of the material at the time of bending of the material part forming the shrinkage flange forming part and the stretch flange forming part is substantially one-way (indicated by the arrow Q) from the shrinking flange forming side to the extending flange forming side with respect to the lower punch. Direction). As a result, in stamped parts after bending, the amount of surplus in the shrinkage flange forming part is reduced and the residual compressive stress is further reduced, and the material supply amount in the stretched flange forming part is increased and the residual tensile stress is further reduced. Thus, the amount of twist by which the substantially hat-shaped section rotates with respect to the center of the section can be reduced, and the dimensional accuracy of the entire pressed part can be further improved.

(5) In the press molding method described in any one of (1) to (4),
The material is made of a steel plate having a tensile strength of about 1 to 1.2 GPa.

  In the present invention, the material is made of a steel sheet having a tensile strength of about 1 to 1.2 GPa. Therefore, in a pressed part that has a very high tensile strength and is difficult to freeze in the shape of a normal cold press method, productivity such as hot pressing is achieved. The dimensional accuracy of the entire pressed part can be improved without using a low construction method. In addition, according to the present press molding method, it is possible to achieve high strength and light weight of the pressed part at low cost.

(6) A lower die punch, a pad that presses a material that comes into contact with the lower die punch, and an upper die that has a molding surface outside the pad, and has a substantially hat-shaped cross section that is continuous in the longitudinal direction. A press die that is formed by cold bending the unrolled material into a pressed part in which a stretch flange molding part and a contraction flange molding part are formed at positions facing each other across the top of the hat. ,
The pad is formed so as to be able to press the material portion forming the top of the hat to the lower punch at a position separated from the stretch flange molding part and the shrink flange molding part,
In the middle of bending, the upper die can rotate and move the material portion forming the stretch flange forming portion and the shrink flange forming portion from the shrink flange forming side to the stretch flange forming side with respect to the lower die punch. It is formed.

  In the present invention, the pad is formed so that the material portion forming the top of the hat can be pressed against the lower die punch at a position away from the stretch flange forming portion and the shrink flange forming portion, and the upper die is bent during the bending process. The material part forming the stretch flange molding part and the shrink flange molding part is formed so as to be able to rotate and move from the shrink flange molding side to the stretch flange molding side with respect to the lower mold punch. The material part forming the top of the hat is restrained by the lower mold punch at a position away from the stretch flange molding part and the shrink flange molding part, and the stretch flange molding part and the shrink flange molding are centered on the restrained material part. The material part that forms the part can be moved while shrinking from the flange forming side to the extending flange forming side with respect to the lower punch. . Therefore, during the bending process of the material, a tensile force that stretches along the outer edge of the material acts on the material part that forms the shrink flange forming part, and the material supply increases on the material part that forms the stretch flange forming part. Thus, a compressive force acting along the outer edge of the material acts. That is, as the bending process progresses, the excess margin of the material outer edge accompanying the bending process in the material part forming the shrinkage flange forming part is reduced, and the material outer edge meat accompanying the bending process in the material part forming the stretched flange forming part is reduced. The shortage is reduced. Therefore, in the pressed part after bending, the compressive stress remaining in the contracted flange formed portion is reduced, and the tensile stress remaining in the stretch flange formed portion is reduced. As a result, in the pressed part after bending, the residual compressive stress in the shrinkage flange molding part and the residual tensile stress in the stretch flange molding part are reduced, respectively, thereby reducing the amount of twist by which the substantially hat-shaped cross section rotates with respect to the center of the cross section. The dimensional accuracy can be improved. Further, this bending process is performed by a cold press method, and it is not necessary to heat and cool the material as in the case of a hot press or the like. Therefore, a simple mold structure may be used, and productivity is not reduced.

  Therefore, according to the present invention, there is provided a press part having a substantially hat-shaped cross section that is continuous in the longitudinal direction and having an extended flange formed portion and a contracted flange formed portion formed at opposite positions across the top of the hat. In the case of forming the unrolled material by cold bending, it is possible to provide a press die that can improve its dimensional accuracy with a simple mold structure without reducing productivity. .

(7) In the press die described in (6),
The upper die presses the material portion forming the stretch flange molding part, the shrink flange molding part, and the top of the hat sandwiched between them against the molding surface of the lower punch without using the pad. It is possible to form.

  In the present invention, the upper die can press the material portion forming the stretch flange forming portion, the shrink flange forming portion, and the top of the hat sandwiched between them onto the molding surface of the lower punch without using a pad. In the middle of the upper die being close to the lower punch, the material portion forming the stretch flange forming portion, the shrinking flange forming portion and the top of the hat sandwiched between them is formed by the lower punch. The surface can be moved more easily without being restricted by the pad. As a result, the excess material margin at the outer edge of the material part that forms the shrink-flanged molded part is further reduced, and the shortage of the outer edge of the material that accompanies the bending process at the material part that forms the elongated flange-formed part is further reduced. Is done. As a result, in the pressed part after bending, the amount of twist by which the substantially hat-shaped cross section rotates about the cross-sectional axis is reduced based on the decrease in the residual compressive stress in the shrinkage flange forming part and the residual tensile stress in the stretch flange forming part. This can be further reduced.

(8) In the press die described in (6) or (7),
In the upper die and the lower die punch, a surplus portion extending outward from a material outer edge of a material portion forming the stretch flange formed portion is formed, and a material forming the stretch flange formed portion and the contracted flange formed portion is formed. An upper mold convex part and a lower mold concave part formed so as to be constrained before the start of bending of the part are provided.

  In the present invention, in the upper die and the lower die punch, a surplus portion extending outward from the material outer edge of the material portion forming the stretch flange formed portion is formed as a material forming the stretch flange formed portion and the contracted flange formed portion. Since the upper mold convex part and the lower mold concave part formed so as to be constrained before starting the bending process of the part, the surplus part is constrained in advance between the upper mold convex part and the lower mold concave part (clinch) In this state, the bending process of the material portion that forms the stretch flange molding part and the contraction flange molding part can proceed. Therefore, the flow of the material at the time of bending of the material portion forming the stretch flange molding part and the shrink flange molding part is substantially one-way (indicated by the arrow Q) from the shrink flange molding side to the stretch flange molding side with respect to the lower punch. Direction). As a result, in stamped parts after bending, the amount of surplus in the shrinkage flange forming part is reduced and the residual compressive stress is further reduced, and the material supply amount in the stretched flange forming part is increased and the residual tensile stress is further reduced. Thus, the amount of twist by which the substantially hat-shaped section rotates with respect to the center of the section can be reduced, and the dimensional accuracy of the entire pressed part can be further improved.

  According to the present invention, a press part having a substantially hat-shaped cross section continuous in the longitudinal direction and having an extended flange formed portion and a contracted flange formed portion formed at opposite positions across the top of the hat is developed. To provide a press molding method and a press die capable of improving the dimensional accuracy with a simple mold structure and without reducing the productivity in the case of forming the processed material by cold bending. it can.

It is a side view of the vehicle which uses the press component formed by the press molding method which concerns on embodiment of this invention. It is a top view of the press component shown in FIG. It is a top view of the raw material for forming the press component shown in FIG. 2 by a bending process. It is a top view of the blank type | mold (lower mold | type) which forms the raw material shown in FIG. It is sectional drawing at the time of the process start of the press type | mold which carries out the bending process of the press components (AA cross section) shown in FIG. It is sectional drawing at the time of the process start of the press type | mold which carries out the bending process of the press components (BB cross section) shown in FIG. It is sectional drawing in the middle of the process of the press type | mold which carries out the bending process of the press components (BB cross section) shown in FIG. It is sectional drawing in the middle of the process of the press type | mold which carries out the bending process of the press components (BB cross section) shown in FIG. It is sectional drawing at the time of completion | finish of a press die process which bends the press component (BB cross section) shown in FIG. It is sectional drawing after the bending process of the press components (BB cross section) shown in FIG. It is explanatory drawing explaining the condition where the raw material shown in FIG. 3 moves with progress of a bending process. (A) shows the initial stage of bending (80 mm UP), (B) shows the middle stage of bending (40 mm UP), (C) shows the late stage of bending (10 mm UP), and (D) shows the end of bending (bottom dead) Point). FIG. 2 is a stress distribution diagram (when the tensile strength of the material is 980 MPa) on the side of the stretch flange formed part after bending of the pressed part shown in FIG. 2, and (A) shows a stress distribution diagram by a conventional bending method; (B) shows a stress distribution diagram according to the present embodiment. FIG. 2 is a stress distribution diagram on the side of the flanged molded part after bending of the pressed part shown in FIG. 2 (when the tensile strength of the material is 980 MPa), (A) shows a stress distribution diagram by a conventional bending method; (B) shows a stress distribution diagram according to the present embodiment. FIG. 2 is a stress distribution diagram (when the tensile strength of the material is 1180 MPa) on the stretch flange forming part side after bending of the pressed part shown in FIG. 2, (A) shows a stress distribution diagram by a conventional bending method; (B) shows a stress distribution diagram according to the present embodiment. FIG. 2 is a stress distribution diagram on the side of the contracted flange formed part after bending of the press part shown in FIG. 2 (when the tensile strength of the material is 1180 MPa), (A) shows a stress distribution diagram by a conventional bending method, (B) shows a stress distribution diagram according to the present embodiment. FIG. 3 is a perspective view of a press part having a substantially hat-shaped cross section that is continuous in the longitudinal direction and having an extended flange formed portion and a contracted flange formed portion formed at positions facing each other across the top of the hat. . It is sectional drawing of the press die which forms the press component (CC cross section) shown in FIG. 16 with the conventional bending method. FIG. 18 is a cross-sectional view of a press part bent by the press die shown in FIG. 17.

  Next, a press molding method and a press die according to an embodiment of the present invention will be described in detail with reference to the drawings. First, the structure of the press part and the material formed by the press forming method according to the present embodiment will be described, and then the structure of the press mold and the material inflow operation by bending of the press forming method will be described. Next, a CAE analysis result of stress distribution in the pressed part after bending will be described.

<Structure of pressed parts and materials>
First, the structure of the press part formed by the press molding method according to the present embodiment and the material thereof will be described with reference to FIGS. FIG. 1 shows a side view of a vehicle using a press part formed by a press forming method according to an embodiment of the present invention. FIG. 2 is a plan view of the pressed part shown in FIG. FIG. 3 shows a plan view of a material for forming the pressed part shown in FIG. 2 by bending. FIG. 4 shows a plan view of a blank mold (lower mold) for forming the material shown in FIG.

  As shown in FIGS. 1 and 2, a press part 10 formed by the press molding method according to the present embodiment includes, for example, a front panel of a roof panel RF positioned above a side panel SD front part and a front door panel FD of a vehicle W. It is a reinforcement part in A pillar part AP which connects. The press part 10 has a substantially hat-shaped cross section that is continuous in the longitudinal direction, and the stretch flange molded part 12 and the contracted flange molded part 13 are located at positions facing each other across the hat top 11 (11B) of the substantially hat-shaped cross section. And are formed.

  The stretch flange forming portion 12 is formed in a range indicated by a thick solid line in FIG. 2 and is a stepped side wall flange portion formed in a curved shape along the front door panel FD, and the tensile stress α1 remains after bending. It's easy to do. Further, the shrinkage flange forming part 13 is a side wall flange part formed in a range shown by a thick broken line in FIG. 2 and formed in a curved shape along the roof panel RF, and has a compressive stress α2 after bending. Tends to remain. The hat top 11 (11B) sandwiched between the stretch flange molding part 12 and the contraction flange molding part 13 is formed in a planar shape with a substantially constant width while being curved in the longitudinal direction. The flange outer edge 121 of the stretch flange molding portion 12 is smoothly curved along the opening edge of the front door panel FD. The hat top 11 (11A) at a position spaced in the longitudinal direction from the stretch flange molding 12 and the shrink flange molding 13 is a hat top 11 sandwiched between the stretch flange molding 12 and the shrink flange molding 13. It is formed continuously with (11B). The hat top 11 (11A) is formed in a substantially planar shape within a range indicated by hatching in FIG. 2, and is formed so that the width on the vehicle front end side is enlarged.

  As shown in FIG. 3, the material SS used in the press molding method is unrolled so that the outer edge of the material coincides with the flange outer edge of the press part 10 when the material SS is bent by the press molding method. Here, in this press molding method, the material portion SS1A (double hatched portion) that forms the hat top 11A at a position spaced apart from the stretch flange molding portion 12 and the contraction flange molding portion 13 in the longitudinal direction is used as a lower punch. In the pressed state, the material part SS2 forming the stretch flange forming part 12 and the material part SS3 forming the shrinking flange forming part 13 by the lowering of the upper die are contracted with respect to the forming surface of the lower punch. Bending is performed by pressing the lower die punch after moving (moving in the direction of arrow R) while rotating from the side to the stretch flange forming side.

  Therefore, among material SS, material part SS2 which forms stretch flange molding part 12, material part SS3 which forms shrinkage flange molding part 13, and material part SS1B which forms hat top 11 (11B) between them are In the state before moving in the direction of the arrow R, the outer edge of the material is unfolded (indicated by a virtual line). In the middle of the bending process of the material SS, the material portion SS3 forming the shrink flange forming portion 13 is subjected to a tensile force f1 extending along the material outer edge SS31, and the material portion SS2 forming the stretch flange forming portion 12 is formed. , A compressive force f2 that increases the material supply and contracts along the material outer edge SS21 acts.

  On the other hand, since the material portion SS1A (double hatched portion) is bent in a state of being constrained with respect to the molding surface of the lower punch, at the position spaced apart from the stretch flange molding portion 12 and the contraction flange molding portion 13 in the longitudinal direction, The outer periphery of the material (single hatched portion) is unrolled so as to enter the constrained material portion SS1A (double hatched portion) from the width direction intersecting the longitudinal direction.

  Further, the material portion SS2 forming the stretch flange forming portion 12 is provided with a surplus portion YS extending outward from the material outer edge SS21. The surplus portion YS is formed with a substantially constant width along the material outer edge SS21.

  As shown in FIG. 4, the material SS is formed by supplying a long steel sheet S unwound from a coil to a blank mold from the direction of arrow T and cutting the outer edge of the material with a cutting blade SSD. The remaining scrap material SC obtained by cutting the material SS from the steel plate S is separated by cutting off both side ends of the steel plate S with a scrap blade SCD. Since the feed pitch P of the steel sheet S when cutting the material SS from the steel sheet S affects the yield of the material SS, it is preferable to set the shape of the surplus portion YS so as not to increase the feed pitch P.

<Pressure mold structure and material inflow operation by bending>
Next, the structure of the press mold and the material inflow operation by the bending process of the press forming method will be described with reference to FIGS. FIG. 5 shows a cross-sectional view at the start of processing of a press die for bending the pressed part (AA cross section) shown in FIG. FIG. 6 shows a cross-sectional view at the start of processing of a press die for bending the press part (BB cross section) shown in FIG. FIG. 7 shows a cross-sectional view in the middle of processing of a press die for bending the press part (BB cross section) shown in FIG. FIG. 8 is a cross-sectional view in the middle of processing of a press die for bending the press part (BB cross section) shown in FIG. FIG. 9 shows a cross-sectional view of the press die for bending the press part (BB cross section) shown in FIG. FIG. 10 shows a cross-sectional view of the pressed part (BB cross section) shown in FIG. 2 after bending. 11A and 11B are explanatory views for explaining the situation in which the material shown in FIG. 3 moves as the bending process proceeds. FIG. 11A shows the initial bending process (80 mm UP), and FIG. 11B shows the middle bending process (40 mm UP). ), (C) shows the later stage of bending (10 mm UP), and (D) shows the end of bending (bottom dead center).

  As shown in FIG. 5, the present press die 20 is a die for bending a material SS such as a high-tensile steel plate having a tensile strength of 980 MPa or more by a cold press method, and has a molding surface. A lower die 21, a pad 22 that presses a material SS in contact with a molding surface of the lower die punch 21 from above, and an upper die 23 having a molding surface outside the contour line of the pad 22 are provided. The pad 22 has a material portion SS1A (double hatched portion in FIG. 3) forming the hat top 11A at a position spaced apart from the stretch flange molding portion 12 and the contraction flange molding portion 13 in the longitudinal direction on the molding surface of the lower punch 21. It is formed so that it can be pressed. The pad 22 presses the material portion SS1A against the lower die punch 21 before the upper die 23 contacts the material SS. Therefore, even if the upper die 23 contacts the material SS, it is possible to prevent the material SS from being displaced with respect to the lower die punch 21.

  Further, as shown in FIG. 6, the upper die 23 is formed by padding material portions SS2, SS3, and SS1B that form the stretch flange formed portion 12, the contracted flange formed portion 13 and the hat top 11B sandwiched between them. It is formed so as to press directly against the lower punch 21 without going through 22. That is, in the present press die 20, the region in which the material SS is restrained by the lower punch 21 by the pad 22 and the region in which the material SS is not restrained by the lower punch 21 by the pad 22 are divided into two in the longitudinal direction of the material SS. It is divided.

  Therefore, in the present press die 20, the material portion SS 1 A (double hatched portion in FIG. 3) forming the hat top 11 A at the position spaced apart from the stretch flange forming portion 12 and the shrink flange forming portion 13 in the longitudinal direction is lowered by the pad 22. Restrained by the mold punch 21 to prevent the positional displacement of the material SS with respect to the lower mold punch 21, and at the same time, the upper die 23 is sandwiched between the stretch flange molded part 12 and the contracted flange molded part 13 while being lowered. The degree of freedom of material movement with respect to the lower punches 21 of the material portions SS2, SS3, SS1B forming the hat top 11B is increased.

  Further, as shown in FIG. 6, the upper die 23 and the lower die 21 are provided with a surplus flange portion YS extending outward from the material outer edge SS21 of the material portion SS2 forming the stretch flange molded portion 12, by stretch flange molding. Before starting the bending process of the material parts SS2 and SS3 forming the part 12 and the shrink flange forming part 13, an upper mold convex part 23K and a lower mold concave part 21K are formed so as to be bent downward. The lower end of the upper mold convex portion 23K is formed lower than the lower end of the upper die 23 that bends the material portion SS3 forming the shrinkage flange forming portion 13. The difference H between the heights of the material portions SS2 and SS3 forming the stretch flange forming portion 12 and the shrink flange forming portion 13 during the bending process is from the shrink flange forming side with respect to the forming surface of the lower punch 21. It is set so that it can move to the stretch flange molding side. In the upper mold convex portion 23K and the lower mold concave portion 21K, the molding surface for bending the surplus portion YS downward is formed to be slightly inclined with respect to the press direction. The inclination angle θ of the molding surfaces of the upper mold convex portion 23K and the lower mold concave portion 21K with respect to the horizontal direction is preferably about 75 to 85 °.

  Further, as shown in FIG. 7, when the upper die 23 is lowered from the position in contact with the material SS, the upper die convex portion 23K bends the surplus portion YS downward. At this stage, the clearance between the molding surfaces of the upper die 23 and the lower punch 21 is large, and the material portions SS2 and SS3 forming the stretch flange molding portion 12 and the shrink flange molding portion 13 have a high degree of freedom of material movement. It is in. Therefore, when the surplus portion YS is bent downward, the material portions SS2, SS3, SS1B forming the stretch flange molded portion 12, the shrink flange molded portion 13 and the hat top 11B sandwiched therebetween are While curving greatly along the molding surfaces 213 and 212 of the lower punch 21, it moves from the shrink flange molding side to the stretch flange molding side (moves in the direction of arrow R) with respect to the molding surface of the lower punch 21.

  Further, as shown in FIG. 8, when the upper die 23 is further lowered, the material portions SS2, SS3, and SS1B forming the stretch flange forming portion 12, the shrink flange forming portion 13, and the hat top 11B sandwiched therebetween. Are pressed by the shoulder R portions 231 and 232 of the upper die 23 and the shoulder R portions 214 and 215 of the lower die 21 to bend. At this stage, the surplus portion YS is sandwiched between the upper mold convex portion 23K and the lower mold concave portion 21K and is clinched (restrained), so that the material outer edge of the material portion SS2 forming the stretch flange molded portion 12 is Inflow from the SS21 side is blocked. Therefore, the material flow during bending of the material portions SS3 and SS2 forming the shrinkage flange forming portion 13 and the stretch flange forming portion 12 is changed from the shrink flange forming side to the stretch flange forming side with respect to the forming surface of the lower punch 21. There is only one-way traffic (in the direction of arrow Q).

  Therefore, as shown in FIG. 9, when the upper die 23 is lowered to the bottom dead center, the material surplus of the material outer edge SS31 accompanying the bending process in the material portion SS3 forming the shrinkage flange forming portion 13 is further reduced, The shortage of the material outer edge SS21 due to the bending process in the material portion SS2 forming the stretch flange forming portion 12 is further reduced. As a result, in the pressed part 10 after bending shown in FIG. 10, the residual compressive stress α2 of the contracted flange formed portion 13 and the residual tensile stress α1 of the stretched flange formed portion 12 are reduced. In addition, the surplus part YS is cut | disconnected along the flange outer edge 121 of the stretch flange molding part 12 in a post process.

  Next, a situation in which the material SS moves as the bending process proceeds will be described with reference to FIG. As shown in FIG. 11A, in the initial stage of bending (80 mm UP), the material SS hardly moves. The pad 22 has a material portion SS1A (double hatched portion in FIG. 3) forming the hat top 11A at a position spaced apart from the stretch flange molding portion 12 and the contraction flange molding portion 13 in the longitudinal direction on the molding surface of the lower punch 21. Pressing. Thereafter, as shown in FIG. 11 (B), in the middle stage of bending (40 mm UP), the material portion SS3 forming the shrinkage flange forming portion 13 moves in the direction of arrow R, and the material portion SS3 has an outer edge of the material. A tensile force f1 acts along SS31 and cancels the compressive force F1 accompanying the shrinkage flange molding. Further, the compression force f2 acts on the material portion SS2 forming the stretch flange molding portion 12 along the material outer edge SS21, and the tensile force F2 accompanying the stretch flange molding is canceled. In addition, as shown in FIG. 11C, also in the later stage of bending (10 mm UP), the material portion SS3 forming the shrinkage flange forming portion 13 moves in the direction of the arrow Q, and the material portion SS3 has a material outer edge. The tensile force f1 continues to act along SS31 and cancels the compressive force F1 associated with shrinkage flange molding. In addition, the compression force f2 continues to act on the material portion SS2 forming the stretch flange molding portion 12 along the material outer edge SS21, and the tensile force F2 associated with the stretch flange molding is canceled. Further, as shown in FIG. 11 (D), in the bending process completion period (bottom dead center), the shape is frozen in the state where the residual compressive stress α2 is reduced in the contracted flange forming portion 13. Further, the shape of the stretched flange molded portion 12 is frozen while the residual tensile stress α1 is reduced.

<CAE analysis results of stress distribution in press parts>
Next, the CAE analysis result of the stress distribution in the press part after bending by the present press forming method and the present press die will be described with reference to FIGS. Here, the case where the tensile strength of the material is 980 MPa and the case where the tensile strength of the material is 1180 MPa will be described by comparing the conventional bending method and the bending method of the present embodiment. In the conventional bending method, as shown in FIG. 17, the shrink flange-formed part and the stretch flange-formed part are formed with the pad pressing the top of the hat against the lower punch over the entire longitudinal direction. This is a method of bending a material part to be bent. FIG. 12 is a stress distribution diagram (when the tensile strength of the material is 980 MPa) on the stretch flange forming part side after bending of the pressed part shown in FIG. 2, and (A) is the stress distribution by the conventional bending method. The figure shows a stress distribution diagram according to the present embodiment. FIG. 13 is a stress distribution diagram (when the tensile strength of the material is 980 MPa) on the side of the contracted flange formed part after bending of the pressed part shown in FIG. 2, and (A) shows the stress distribution by the conventional bending method. The figure shows a stress distribution diagram according to the present embodiment. FIG. 14 is a stress distribution diagram (when the tensile strength of the material is 1180 MPa) on the stretch flange forming part side after bending of the pressed part shown in FIG. 2, and (A) is the stress distribution by the conventional bending method. The figure shows a stress distribution diagram according to the present embodiment. FIG. 15 is a stress distribution diagram (when the tensile strength of the material is 1180 MPa) on the side of the flange-formed part after bending of the press part shown in FIG. 2, and (A) shows the stress distribution by the conventional bending method. The figure shows a stress distribution diagram according to the present embodiment. Each stress distribution diagram is represented by contour lines for each predetermined stress range, and is displayed in seven steps (a to g) from the darker dot density to the lighter dot density. Tensile stress is generated in the areas a to c where the dot density is high. Further, compressive stress is generated in the regions eg having a low dot density. The region d is a region where the stress is substantially zero.

(When the tensile strength of the material is 980 MPa)
As shown in FIG. 12 (A), in the conventional bending method, a region a having the strongest tensile stress is continuously present in the longitudinal direction in the range of the stretch flange formed portion 12. In addition, a region b having the second highest tensile stress is widely present around the region a having the highest tensile stress. In the range of the stretch flanged portion 12, the region a having the strongest tensile stress occupies about 30% area, and the region b having the second highest tensile stress occupies the remaining 70% area.

On the other hand, as shown in FIG. 12B, in the bending method of this embodiment, there is no region a where the tensile stress is the strongest in the range of the stretch flange formed portion 12, and the tensile stress is 2 The second strongest region b exists continuously in the longitudinal direction. In addition, a region c having the third strongest tensile stress is widely present around the region b having the second highest tensile stress. A region d where the stress is substantially zero also exists in part. In the range of the stretch flanged portion 12, the region b where the tensile stress is the second strongest occupies an area of about 50%, the region c where the tensile stress is the third strongest occupies an area of about 40%, and the stress is substantially zero. The region d occupies an area of about 10%.
As a result, according to the present embodiment, in the stretch flange molded portion 12, the level of the tensile stress can be reduced to almost one of the three stages.

  Further, as shown in FIG. 13A, in the conventional bending method, three regions g having the strongest compressive stress exist intermittently in the longitudinal direction in the range of the contracted flange formed portion 13. In addition, around the region g where the compressive stress is the strongest, a region f where the compressive stress is the second strongest and a region e where the third is the strongest exist widely. In the range of the shrinkage flange forming portion 13, the region g having the strongest compressive stress occupies an area of about 30%, the region f having the second strongest compressive stress occupies an area of about 30%, and the compressive stress is the third. The strong region e occupies about 30% area, and the region d where the stress is substantially zero occupies about 10% area.

On the other hand, as shown in FIG. 13B, in the bending method of the present embodiment, in the range of the contracted flange formed portion 13, there is no region g where the compressive stress is the strongest, and the compressive stress is 2 The third strongest region f exists intermittently in the longitudinal direction. Further, a region e having the third strongest compressive stress is widely present around the region f having the second strongest compressive stress. There is also a region d where the stress is substantially zero. In the range of the shrinkage flange forming portion 13, the region f having the second highest compressive stress occupies an area of about 30%, the region e having the third highest compressive stress occupies an area of about 40%, and the stress is substantially zero. Region d occupies an area of about 30%.
As a result, according to the present embodiment, the level of compressive stress in the contracted flange molded portion 13 can be reduced by nearly one of the three levels.

(When the tensile strength of the material is 1180 MPa)
As shown in FIG. 14A, in the conventional bending method, the region a having the strongest tensile stress is continuously present in a very wide range in the longitudinal direction in the range of the stretch flange formed portion 12. Further, around the region a where the tensile stress is the strongest, the region b where the tensile stress is the second strongest, the region c where the tensile stress is the strongest, and the region d where the stress is substantially zero are present at a narrow interval. In the range of the stretch flanged portion 12, the region a having the strongest tensile stress occupies an area of about 90%, the region b having the second strongest stress, the region c having the third strongest stress, and the region having almost zero stress. d occupies the remaining 10% of the area.

On the other hand, as shown in FIG. 14B, in the bending method of the present embodiment, the region a having the strongest tensile stress is continuously present in the longitudinal direction in the range of the stretch flange formed portion 12. However, the range is narrow in the width direction. Further, around the region a where the tensile stress is the strongest, the region b where the tensile stress is the second strongest, the region c where the tensile stress is the strongest, and the region d where the stress is substantially zero are present at a narrow interval. In the range of the stretch flanged portion 12, the region a having the strongest tensile stress occupies an area of about 70%, the region b having the second strongest stress, the region c having the third strongest stress, and the region having almost zero stress. d occupies the remaining 30% of the area.
As a result, according to the present embodiment, the reduction level is lower than that in the case where the tensile strength is 980 MPa, but an effect of reducing the tensile stress in the stretch flange molded portion 12 is recognized.

  Further, as shown in FIG. 15A, in the conventional bending method, in the range of the contracted flange forming portion 13, a region g having the strongest compressive stress exists in a wide range in the longitudinal direction. Further, above the region g where the compressive stress is the strongest, the region f where the compressive stress is the second strongest and the region d where the stress is zero exist at a narrow interval. In the range of the contracted flange forming portion 13, the area g having the strongest compressive stress occupies an area of about 90%, and the area f having the second highest compressive stress and the area d having no stress is about 10%. Accounted for.

On the other hand, as shown in FIG. 15B, in the bending method of the present embodiment, in the range of the contracted flange formed portion 13, the region g where the compressive stress is the strongest is intermittently two in the longitudinal direction. Exists. Further, around the region g where the compressive stress is the strongest, the region f where the compressive stress is the second strongest, the region c where the compressive stress is the strongest, and the region d where the stress is substantially zero are present at a narrow interval. In the range of the shrinkage flange forming portion 13, the region g having the strongest compressive stress occupies an area of about 30%, the region f having the second strongest compressive stress occupies an area of about 40%, and the compressive stress is the third. Region e strong against stress and region d where stress is substantially zero occupy an area of about 30%.
As a result, according to the present embodiment, the reduction level is less than that in the case where the tensile strength is 980 MPa, but an effect of reducing the compressive stress in the contracted flange formed portion 13 is recognized.

<Effect>
As described above in detail, according to the press molding method of the present embodiment, the material portion SS1A that forms the hat top portion 11A at a position spaced apart from the stretch flange molding portion 12 and the contraction flange molding portion 13 in the longitudinal direction. In the state where the pad 22 is pressed against the lower punch 21, the upper die 23 is lowered to form the material portions SS 2 and SS 3 that form the stretch flange forming portion 12 and the contracted flange forming portion 13 into the lower die punch 21. The material portion SS3 that forms the shrinkage flange forming portion 13 in the course of bending of the material SS, since it is pressed against the lower punch 21 after being moved while rotating from the shrinkage flange forming side to the stretch flange forming side with respect to the surface. The tensile force f1 that extends along the outer edge SS31 of the material acts, and the material portion SS2 that forms the stretch flange formed portion 12 Compressive force f2 acts for contracting along the material outer SS21 material supply is increased. Therefore, as the bending process proceeds, the surplus of the material outer edge SS31 associated with the bending process in the material part SS3 forming the shrinkage flange forming part 13 is reduced, and the bending process in the material part SS2 forming the stretched flange forming part 12 is performed. The accompanying lack of meat at the material outer edge SS21 is reduced. Therefore, in the pressed part 10 after bending, the compressive stress α2 remaining in the contracted flange formed portion 13 is reduced, and the tensile stress α1 remaining in the stretched flange formed portion 12 is reduced. As a result, in the pressed part 10 after bending, the residual compressive stress α2 of the contracted flange molded portion 13 and the residual tensile stress α1 of the stretched flange molded portion 12 are reduced, respectively, so that the substantially hat-shaped cross section has a cross section relative to the center of the cross section. The amount of twisting to rotate can be reduced, and the dimensional accuracy can be improved. Further, this bending process is performed by a cold press method, and it is not necessary to heat and cool the material as in the case of a hot press or the like. Therefore, a simple mold structure may be used, and productivity is not reduced.

  Therefore, according to the present embodiment, the substantially flange-shaped cross section that is continuous in the longitudinal direction is formed, and the stretch flange molded portion and the contracted flange molded portion are formed at positions facing each other across the top of the hat of the substantially hat-shaped cross section. When forming a pressed part by bending the material with the outer edge of the material unrolled by the cold press method, the dimensional accuracy is improved without reducing productivity with a simple mold structure. It is possible to provide a press molding method that can be used.

  Further, according to the present embodiment, the upper die 23 is formed by padding the material portions SS2, SS3, and SS1B that form the stretched flange molded portion 12, the contracted flange molded portion 13, and the hat top 11B sandwiched therebetween. Since the lower die punch 21 is pressed without going through 22, the material that forms the stretch flange molding portion 12, the contraction flange molding portion 13, and the hat top portion 11 </ b> B sandwiched therebetween while the upper die 23 is lowered. The portions SS2, SS3, and SS1B are not restrained by the pad 22, and can move more easily with respect to the lower punch 21. Therefore, the material surplus of the material outer edge SS31 accompanying the bending process in the material part SS3 forming the shrinkage flange forming part 13 is further reduced, and the material outer edge SS21 accompanying the bending process in the material part SS2 forming the stretched flange forming part 12 is further reduced. Meat shortages are further reduced. As a result, in the pressed part 10 after bending, the substantially hat-shaped cross section has a cross section with respect to the center of the cross section, based on the decrease in the residual compressive stress α2 of the contracted flange formed portion 13 and the residual tensile stress α1 of the stretch flange formed portion 12 respectively. Thus, the amount of twisting to rotate can be further reduced.

  In addition, according to the present embodiment, the material portion SS2 forming the stretch flange molding portion 12 is provided with the surplus portion YS extending outward from the material outer edge SS21, so that the surplus portion of the upper die 23 is being lowered. The meat portion YS is pulled downward, and the movement of the material portions SS2, SS3, SS1B from the shrink flange forming side to the extending flange forming side can be further promoted with respect to the forming surface of the lower punch 21. Therefore, the material surplus of the material outer edge SS31 accompanying the bending process in the material part SS3 forming the shrinkage flange forming part 13 is further reduced, and the material outer edge SS21 accompanying the bending process in the material part SS2 forming the stretched flange forming part 12 is further reduced. Meat shortages are further reduced. As a result, in the pressed part 10 after bending, the substantially hat-shaped cross section has a cross section with respect to the center of the cross section, based on the decrease in the residual compressive stress α2 of the contracted flange formed portion 13 and the residual tensile stress α1 of the stretch flange formed portion 12 respectively. Thus, the amount of twisting to rotate can be further reduced.

  Further, according to the present embodiment, the upper die 23 and the lower die punch 21 are provided with an upper die convex portion 23K and a lower die concave portion 21K formed so as to bend the surplus portion YS downward. Since the surplus part YS is bent downward by the upper mold convex part 23K and the lower mold concave part 21K, the bending process of the material parts SS2 and SS3 forming the stretch flange molding part 12 and the contraction flange molding part 13 is completed. Bending of the material portions SS2 and SS3 that form the stretch flange molding portion 12 and the shrink flange molding portion 13 in a state where the surplus portion YS is previously clinched (restrained) between the upper mold convex portion 23K and the lower mold concave portion 21K. Processing can be advanced. Therefore, the material flow at the time of bending of the material portions SS3 and SS2 forming the shrinkage flange forming portion 13 and the stretch flange forming portion 12 is changed from the shrink flange forming side to the stretch flange forming side with respect to the forming surface of the lower punch 21. It can be a substantially one-way direction (in the direction of arrow Q). As a result, in the pressed part 10 after bending, the amount of surplus in the shrinkage flange forming portion 13 is reduced, the residual compressive stress α2 is further reduced, and the material supply amount in the stretched flange forming portion 12 is increased, resulting in residual tensile stress. α1 can be further reduced, the amount of twist by which the substantially hat-shaped cross section rotates with respect to the center of the cross section can be reduced, and the dimensional accuracy of the entire press part can be further improved.

  Further, according to the present embodiment, the material SS is made of a steel plate having a tensile strength of about 1 to 1.2 GPa. Therefore, in a pressed part that has a very high tensile strength and is difficult to freeze in a normal cold press method, The dimensional accuracy of the entire pressed part can be improved without using a low-productivity method such as pressing. In addition, according to the present press molding method, it is possible to achieve high strength and light weight of the pressed part at low cost.

  Further, according to the press die of the other embodiment, the pad 22 is formed by lowering the material portion SS1A forming the hat top 11A at a position spaced apart from the stretch flange molding portion 12 and the contraction flange molding portion 13 in the longitudinal direction. The upper die 23 is formed so that it can be pressed against the molding surface of the punch 21, and the upper die 23 is formed by forming the material portions SS 2 and SS 3 forming the stretch flange molding portion 12 and the contraction flange molding portion 13 during the bending process. Since it is formed so as to be able to rotate and move from the shrink flange forming side to the stretch flange forming side with respect to the surface, the pad 22 is separated from the stretch flange forming portion 12 and the shrink flange forming portion 13 during the bending process of the material SS. The material portion SS1A forming the hat top 11A is constrained to the molding surface of the lower punch 21 and the constrained material portion SS1A is the center. Thus, the material portions SS2 and SS3 forming the stretch flange molding portion 12 and the shrink flange molding portion 13 can be moved while rotating from the shrink flange molding side to the stretch flange molding side with respect to the molding surface of the lower punch 21. it can. Therefore, during the bending process of the material SS, the material portion SS3 that forms the contracted flange formed portion 13 is subjected to a tensile force f1 that extends along the material outer edge SS31, and the material portion SS2 that forms the stretched flange formed portion 12 , A compressive force f2 that increases the material supply and contracts along the material outer edge SS21 acts. That is, as the bending process proceeds, the surplus of the material outer edge SS31 accompanying the bending process in the material part SS3 that forms the contracted flange forming part 13 is reduced, and the bending process in the material part SS2 that forms the stretched flange forming part 12 is performed. The accompanying lack of meat at the material outer edge SS21 is reduced. Therefore, in the pressed part 10 after bending, the compressive stress α2 remaining in the contracted flange formed portion 13 is reduced, and the tensile stress α1 remaining in the stretched flange formed portion 12 is reduced. As a result, in the pressed part 10 after bending, the residual compressive stress α2 of the contracted flange molded portion 13 and the residual tensile stress α1 of the stretched flange molded portion 12 are reduced, respectively, so that the substantially hat-shaped cross section has a cross section with respect to the center of the cross section. The amount of twisting to rotate can be reduced, and the dimensional accuracy can be improved. Further, the main bending process is performed in a cold manner, and it is not necessary to heat and cool the material as in a hot press or the like. Therefore, a simple mold structure may be used, and productivity is not reduced.

  Therefore, according to this other embodiment, it has a substantially hat-shaped cross section that is continuous in the longitudinal direction, and the stretched flange molded part and the contracted flange molded part are located at positions facing each other across the top of the hat of the substantially hat shaped cross section. In the case of forming a stamped part by bending a material from which the outer edge of the material has been unfolded, the dimensional accuracy can be improved with a simple mold structure without reducing productivity. A press die can be provided.

  In addition, according to the other embodiment, the upper die 23 includes the material portions SS2, SS3, and SS1B that form the stretch flange formed portion 12, the contracted flange formed portion 13, and the hat top 11B sandwiched therebetween. Since it is formed so as to be able to be pressed against the molding surface of the lower die punch 21 without using the pad 22, it is sandwiched between the stretch flange molding portion 12 and the contraction flange molding portion 13 while the upper die 23 is being lowered. The material portions SS2, SS3, SS1B forming the hat top 11B can be moved more easily without being restricted by the pad 22 with respect to the molding surface of the lower punch 21. Therefore, the material surplus of the material outer edge SS31 accompanying the bending process in the material part SS3 forming the shrinkage flange forming part 13 is further reduced, and the material outer edge SS21 accompanying the bending process in the material part SS2 forming the stretched flange forming part 12 is further reduced. Meat shortages are further reduced. As a result, in the pressed part 10 after bending, the substantially hat-shaped cross section is centered on the cross-sectional axis based on the decrease in the residual compressive stress α2 of the shrinkage flange forming portion 13 and the residual tensile stress α1 of the stretch flange forming portion 12 respectively. The amount of twisting to rotate can be further reduced.

  Further, according to the other embodiment, the upper die 23 and the lower die punch 21 extend the surplus portion YS extending outward from the material outer edge SS21 of the material portion SS2 forming the stretch flange forming portion 12. Since the material portions SS2 and SS3 forming the flange forming portion 12 and the contracted flange forming portion 13 are provided with an upper mold convex portion 23K and a lower mold concave portion 21K which are formed to be bent downward before starting the bending process. Bending of the material portions SS2 and SS3 forming the stretch flange forming portion 12 and the shrinking flange forming portion 13 in a state where the surplus portion YS is previously clinched (restrained) between the upper die 23 and the lower die 21 Can be advanced. Therefore, the material flow during bending of the material portions SS2 and SS3 forming the stretch flange molding portion 12 and the shrink flange molding portion 13 is changed from the shrink flange molding side to the stretch flange molding side with respect to the molding surface of the lower punch 21. It can be a substantially one-way direction (in the direction of arrow Q). As a result, in the pressed part 10 after bending, the amount of surplus in the shrinkage flange forming portion 13 is reduced, the residual compressive stress α2 is further reduced, and the material supply amount in the stretched flange forming portion 12 is increased, resulting in residual tensile stress. α1 can be further reduced, the amount of twist by which the substantially hat-shaped cross section rotates with respect to the center of the cross section can be reduced, and the dimensional accuracy of the entire press part can be further improved.

<Modification>
The embodiment described above can be changed as appropriate without departing from the scope of the present invention.
For example, according to the present embodiment, the upper die 23 and the lower die punch 21 are provided with an upper die convex portion 23K and a lower die concave portion 21K formed so as to bend the surplus portion YS downward. The surplus part YS is bent downward by the upper mold convex part 23K and the lower mold concave part 21K to clinch the surplus part YS. The method is not limited to the method of bending the portion YS downward. For example, the upper mold convex part 23K and the lower mold concave part 21K may be provided with a clamping mechanism that can move up and down while clamping the surplus part YS.
For example, according to the present embodiment, the material is a high-tensile steel plate having a tensile strength of 980 MPa or more. However, the present invention is not limited to this, and it is needless to say that the material can also be applied when the tensile strength is 980 MPa or less.
For example, according to the present embodiment, when press molding, the lower die 21 is fixed and the upper die 23 is moved up and down, but the upper die 23 may be fixed and the lower die 21 may be moved up and down. Absent.

  The present invention provides a press part having a substantially hat-shaped cross section that is continuous in the longitudinal direction, and an extended flange-formed part and a contracted flange-formed part formed at opposite positions across the top of the hat. It can be used as a press molding method and a press die formed by bending.

10 Press parts 11, 11A, 11B Hat top 12 Stretch flange molding 13 Shrink flange molding 20 Press die 21 Lower die punch 21K Lower die recess 22 Pad 23 Upper die 23K Upper die convex portion SS Material YS Extra portion SS1A , SS1B material part SS2, SS3 material part SS21, SS31 material outer edge

Claims (8)

A lower die punch, a pad that presses a material against the lower die punch, and an upper die having a molding surface outside the pad, and has a substantially hat-shaped cross section that is continuous in the longitudinal direction, and the top of the hat A press molding method in which a stretched flange molded part and a shrunken flange molded part are formed at opposite positions across the press part, and the unrolled material is bent and processed cold,
In a state where the pad presses the material portion at the top of the hat at a position away from the stretch flange molding part and the shrink flange molding part, the upper die is close to the lower punch and the stretch flange molding And a material portion forming the shrinkage flange molding portion is rotated with respect to the lower mold punch from the shrinkage flange molding side to the stretch flange molding side and then pressed to the lower mold punch. Molding method. In the press molding method according to claim 1,
The upper die presses the material portion forming the stretch flange molding portion, the contraction flange molding portion, and the top of the hat sandwiched between the lower die punches without passing through the pad. A press forming method characterized. In the press molding method according to claim 1 or 2,
A press molding method characterized in that a surplus portion extending outward from an outer edge of the material is provided on a material portion forming the stretch flange formed portion. In the press molding method according to claim 3,
The upper die and the lower die punch include an upper die convex portion and a lower die concave portion that are formed so as to constrain the surplus portion, and the extra die convex portion and the lower die concave portion form the extra die. After constraining a meat part, the press molding method characterized by completing the bending process of the raw material part which forms the said stretch flange molding part and the said shrink flange molding part. In the press molding method according to any one of claims 1 to 4,
The press forming method, wherein the material is a steel plate having a tensile strength of about 1 to 1.2 GPa. The hat comprises a lower die punch, a pad that presses a material abutting against the lower die punch, and an upper die having a molding surface outside the pad, and has a substantially hat-shaped cross section continuous in the longitudinal direction. A press mold in which a stretched part and a contracted flange part are formed at opposite positions across the top part, and the unrolled material is bent and processed cold,
The pad is formed so as to be able to press the material portion forming the top of the hat to the lower punch at a position separated from the stretch flange molding part and the shrink flange molding part,
In the middle of bending, the upper die can rotate and move the material portion forming the stretch flange forming portion and the shrink flange forming portion from the shrink flange forming side to the stretch flange forming side with respect to the lower die punch. A press die characterized by being formed. The press die according to claim 6, wherein
The upper die is formed so that a material portion that forms the stretch flange forming portion, the shrink flange forming portion, and the top of the hat sandwiched therebetween can be pressed against the lower punch without using the pad. A press die characterized by being made. In the press die according to claim 6 or 7,
In the upper die and the lower die punch, a surplus portion extending outward from a material outer edge of a material portion forming the stretch flange formed portion is formed, and a material forming the stretch flange formed portion and the contracted flange formed portion is formed. A press die comprising an upper mold convex part and a lower mold concave part formed so as to restrain before starting the bending process of the part.

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