JP2019202335A - Method of manufacturing pressed article - Google Patents

Abstract

To provide a method of manufacturing a pressed article having a desired shape while inhibiting a wrinkle and a break.SOLUTION: The method of manufacturing a pressed article comprises a disposing step, a third area constraining step, a first area pushing step, and a second area processing step. In the disposing step, a blank 10 including a first area 11, a second area 12, and a third area 13 is disposed in a press apparatus. The first area includes a portion to be an end 15 of a stretching flange portion. In the third area constraining step, a pad 4 and a punch 3 are caused to approach each other after the disposing step, thus the third area 13 is constrained by the pad 4 and the punch 3 with a gap between the blank 10 and the pad 4. In the first area pushing step, a die 2 and the punch 3 are caused to approach each other after the third area constraining step, and the die 2 and the first area 11 are brought in contact with each other, thus pushing the first area 11 toward the punch 3 by the die 2. In the second area processing step, the punch 3 and the second area 12 are brought in contact with each other, and the die 2 and the second area 12 are brought in contact with each other, thus processing the second area 12 by the punch 3 and the die 2.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a method for producing a press product. More specifically, the present invention relates to a method for producing a press product including an elongated flange portion by bending.

  A vehicle body frame is required to have high strength. For this reason, a metal such as a high-strength steel plate is often used as the material for the body frame. Parts constituting the vehicle body frame made of such a high-strength metal are formed by pressing.

  The cross-sectional shape of the parts constituting the body frame is often a U shape or a hat shape including the top plate portion and the vertical wall portion. Further, the body frame often has a curved portion. The curved portions are, for example, the upper and lower ends of a T-shaped center pillar extending in the vertical direction of a four-wheeled vehicle. When a part having a curved portion is formed by pressing, the curved portion is subjected to tensile stress as the material is deformed. A curved portion that receives this tensile stress is called an “elongated flange portion”. If molding is performed in which excessive tensile stress is applied to the stretch flange portion, the stretch flange portion is likely to break.

  A method for producing a pressed product in which breakage is suppressed is disclosed in, for example, Japanese Patent Application Laid-Open No. 2017-136624 (Patent Document 1).

  The method for producing a press product described in Patent Document 1 includes a die, a pressing member protruding from the die, a blank holder that faces the die and the pressing member, and a punch that faces the die and is disposed outside the blank holder. The blank is bent using a press machine. Specifically, the blank is sandwiched between the blank holder and the pressing member. Thereafter, the blank is bent by the pressing member and the convex portion of the die arranged outside the pressing member. Thereby, it is described in Patent Document 1 that molding defects of a pressed product are suppressed.

JP 2017-136624 A

  However, in general, if a press product including an elongated flange portion is formed by bending, wrinkles are likely to occur. In particular, wrinkles are likely to occur in the top plate portion of a pressed product such as a hat cross-sectional shape. If it is going to suppress generation | occurrence | production of such a wrinkle, it will be easy to produce a fracture | rupture in the edge part etc. of the press goods containing an extending flange part. Therefore, in the formation of a press product including an elongated flange portion, it is often difficult to avoid both the generation of wrinkles and the breakage while forming into a desired shape.

  An object of the present invention is to provide a method for producing a press product having a desired shape while suppressing generation and breakage of wrinkles.

  In the method for producing a press product according to the present embodiment, a press product including an elongated flange portion is produced by bending with a press device including a punch, a die facing the punch, and a pad facing the punch. The method for producing a press product includes an arrangement step, a third region restraining step, a first region pushing step, and a second region processing step. In the arranging step, a blank including a first region including a portion serving as an end of the stretch flange portion of the press product, a second region located inside the first region, and a third region located inside the second region. Place in the press machine. In the third region restraining step, the pad and the punch are brought close to each other after the placing step, and the third region is restrained by leaving a gap between the blank and the pad between the pad and the punch. In the first region pushing step, after the third region restraining step, the die and the punch are brought close to each other, the die and the first region are brought into contact with each other, and the first region is pushed into the punch side by the die. In the second region processing step, after the start of the first region pushing step, the punch and the second region are brought into contact with each other, the die and the second region are brought into contact, and the second region is processed with the punch and the die.

  According to the method for producing a press product according to the present invention, it is possible to produce a press product having a desired shape as a blank while suppressing generation and breakage of wrinkles.

FIG. 1 is a cross-sectional view showing bending. FIG. 2 is a cross-sectional view showing pad bending. FIG. 3 is a perspective view of a press product including an elongated flange portion. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a cross-sectional view showing the press device of the first embodiment. FIG. 6 is a plan view of the blank. FIG. 7 is a cross-sectional view showing an arrangement process of the first embodiment. FIG. 8 is a cross-sectional view showing a third region restraining step of the first embodiment. FIG. 9 is a cross-sectional view showing a first region pushing process of the first embodiment. FIG. 10 is a cross-sectional view showing the second region processing step of the first embodiment. FIG. 11 is a cross-sectional view showing the end of the second region processing step of the first embodiment. FIG. 12 is a cross-sectional view showing the pressing device according to the second embodiment. FIG. 13 is a cross-sectional view illustrating an arrangement process of the second embodiment. FIG. 14 is a cross-sectional view showing a third region restraining step of the second embodiment. FIG. 15 is a cross-sectional view illustrating a first region pushing process according to the second embodiment. FIG. 16 is a cross-sectional view showing a second region processing step of the second embodiment. FIG. 17 is a cross-sectional view showing the end of the second region processing step of the second embodiment. FIG. 18 is a cross-sectional view showing the press device of the third embodiment. FIG. 19 is a cross-sectional view showing the arrangement process of the third embodiment. FIG. 20 is a cross-sectional view showing a third region restraining step of the third embodiment. FIG. 21 is a cross-sectional view illustrating a first region pushing process according to the third embodiment. FIG. 22 is a cross-sectional view showing a second region processing step of the third embodiment. FIG. 23 is a cross-sectional view showing the end of the second region processing step of the third embodiment. FIG. 24 is a perspective view of a model of a pressed product formed in this example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Bending and pad bending]
First, general bending and general pad bending will be described.

  FIG. 1 is a cross-sectional view showing bending. Hereinafter, “cross section” means a cross section along the press direction unless otherwise specified. Referring to FIG. 1, general bending is performed by a punch 101 and a die 102. The blank 10 is placed on the punch 101 and the die 102 is lowered. The die top 103 closest to the die punch contacts one end of the blank 10. When the die top 103 comes into contact with one end of the blank 10, the other end of the blank on the punch top 104 moves away from the punch top 104. Since the other end of the blank 10 is away from the punch top 104, there is excess material between the die 102 and the punch top 104. When the die 102 is made to reach the bottom dead center from this state, the excess material becomes wrinkled. As a method for suppressing the generation of wrinkles due to bending, there is pad bending.

  FIG. 2 is a cross-sectional view showing pad bending. Referring to FIG. 2, general pad bending is performed by a punch 101, a die 102 and a pad 110. As described above, in simple bending, when the die top 103 starts to process one end of the blank 10, the other end of the blank 10 is separated from the punch top 104. Thus, in pad bending, the pad 110 presses the other end of the blank against the punch top 104. Thereafter, the die top 103 begins to machine one end of the blank. Therefore, during bending, the other end of the blank is not separated from the punch top 104, and the generation of wrinkles is suppressed.

  However, in the pad bending molding, the blank 10 is sandwiched between the punch 101 and the pad 110 during the molding. Therefore, the flow of the material is suppressed in the blank region sandwiched between the punch 101 and the pad 110 during pad bending. Therefore, when a press product including a stretch flange portion is subjected to pad bending molding, the blank stretch flange portion may break.

[Stretch flange part]
FIG. 3 is a perspective view of a press product including an elongated flange portion. In FIG. 3, the lower end part of the center pillar of a four-wheeled vehicle is shown as an example of a press product including an elongated flange part. 4 is a cross-sectional view taken along line IV-IV in FIG. 3 and 4, the cross section perpendicular to the extending direction of the center pillar 105, that is, the horizontal cross section has a hat shape. The center pillar 105 includes a top plate portion 107, a vertical wall portion 108, and a flange portion 109. Since the lower end portion of the center pillar 105 is connected to the side step 106, it is T-shaped. Therefore, the lower end portion of the center pillar 105 is curved at a substantially right angle. During molding of the curved portion, the material moves in the direction of the arrow in FIG. 3 in the curved vertical wall portion 108 and the curved flange portion 109. Therefore, tensile stress is generated in the curved vertical wall portion 108 and the curved flange portion 109. In this specification, the curved part which receives a tensile stress during such a shaping | molding is called an elongate flange part. If this tensile stress becomes excessively large, the blank breaks.

  The present inventor studied pad bending forming that suppresses wrinkles and suppresses breakage at the stretch flange portion. As described above, in the pad bending molding, the material hardly flows by sandwiching the blank between the pad and the punch. Therefore, during pad bending, the material does not flow into the stretch flange portion, the tensile stress increases, and breakage easily occurs.

  Therefore, the present inventor has arrived at the idea of sandwiching (restraining) the blank between the pad and the punch with a slight gap in pad bending. Thereby, since a blank is not completely pinched | interposed by a pad and a punch during pad bending shaping | molding, material becomes easy to flow compared with general pad bending shaping | molding. Therefore, it becomes easy for the material to flow into the stretch flange portion during pad bending, and the stretch flange portion can be prevented from breaking. Further, since the distance between the pad and the punch is only slightly larger than the thickness of the blank, the blank is not greatly separated from the punch during pad bending, and the generation of wrinkles can be suppressed.

  Furthermore, the inventor has come up with the idea that the region where the die is first formed by the die is further away from the position where the blank is constrained by the pad and the punch. In other words, the region (first region) from the end of the stretch flange portion of the blank to the position of the blank that first contacts the die, and the blank region (third region) constrained by the pad and the punch An area (second area) that does not contact the die for a certain period of time after the start of pad bending is provided. As a result, the second region starts to be pushed into the punch side by the die after a predetermined time has elapsed since the first region of the blank has started to be pushed into the punch side by the die. This means that the molding stroke of the part in contact with the first region of the die is larger than the molding stroke of the part in contact with the second region of the die. By increasing the molding stroke of the blank first region, the time during which the blank first region is molded becomes longer. Further, a blank area (third area) sandwiched between the pad and the punch while the blank area (first area and second area) not sandwiched between the pad and punch is being pushed to the punch side. The material flows. Therefore, the time during which the material in the third region of the blank flows is increased by the amount of time during which the first region is molded. Thereby, it becomes easy for material to flow into a stretch flange part from the 3rd field of a blank during fabrication, and fracture of a stretch flange part can be controlled.

  (1) A method for producing a press product of the present embodiment based on the above knowledge is a press product including a stretch flange portion by bending with a press device including a punch, a die facing the punch, and a pad facing the punch. To produce. The method for producing a press product includes an arrangement step, a third region restraining step, a first region pushing step, and a second region processing step. In the arranging step, a blank including a first region including a portion serving as an end of the stretch flange portion of the press product, a second region located inside the first region, and a third region located inside the second region. Place in the press machine. In the third region restraining step, the pad and the punch are brought close to each other after the placing step, and the third region is restrained by leaving a gap between the blank and the pad between the pad and the punch. In the first region pushing step, after the third region restraining step, the die and the punch are brought close to each other, the die and the first region are brought into contact with each other, and the first region is pushed into the punch side by the die. In the second region processing step, after the start of the first region pushing step, the punch and the second region are brought into contact with each other, the die and the second region are brought into contact, and the second region is processed with the punch and the die.

  In the placement step, the distance between the pad and the punch in the pressing direction is slightly larger than the blank thickness. That is, a slight gap is provided between the blank third region and the pad. Thereby, the material of the blank 3rd area | region becomes easy to flow, and the material of the blank 3rd area | region tends to flow into an elongate flange part during bending molding. Therefore, breakage at the stretch flange portion is suppressed. Further, since the gap between the third region of the blank and the pad is small, the third region of the blank does not greatly separate from the punch during bending. Therefore, the occurrence of wrinkles in the pressed product is suppressed. Further, in the first area pushing step, the first area of the blank on the end side of the extending flange portion is pushed ahead by the die toward the punch. After a certain time from the start of pushing in the first area, the second area of the blank is processed with a punch and die. That is, the molding stroke of the portion that contacts the first region of the die blank is increased as compared with the case where only the pad is used (conventional pad bending molding). As described above, the molding stroke increases, so that the material flows from the third region of the blank into the stretch flange portion during molding. For this reason, the material is easily supplied to the stretch flange portion, and breakage at the stretch flange portion is suppressed.

  (2) In the method for producing a pressed product of (1) above, in the third region restraining step, the gap is preferably 120% or less of the blank plate thickness. The gap is more preferably 110% or less of the blank thickness.

  If the gap is too large, the third region of the blank is greatly separated from the punch during bending, so the gap is preferably equal to or less than a predetermined value. The gap means the distance along the press direction between the punch area and the pad area that constrain the third area of the blank.

  (3) In the method for producing a pressed product according to (1) or (2) above, in the second region machining step, the die or punch is made to reach the bottom dead center, and the first region is simultaneously completed with the processing of the second region. It is preferable to finish the processing.

  If bending is performed using an integral punch and an integral die, the first region and the second region of the blank are simultaneously processed. If an integral punch and an integral die are used, the structure of the press device is simplified.

  (4) In the method for producing a pressed product of (3) above, the blank is preferably preheated before the start of the first region pushing step.

  Heating the blank increases the ductility of the blank and facilitates the formation of difficult-to-form press products. Further, in the method for producing a pressed product of the present embodiment, the second region does not contact the mold for a certain period of time after the first region is pushed in and before the processing of the second region is started. As a result, the contact time and contact area between the blank and the die before reaching the bottom dead center of the die can be reduced as much as possible, so that local deformation and unevenness of characteristics can be avoided, and hot or warm It is possible to improve the formability of the bending molding at.

  (5) In the method for producing the pressed product of (4) above, the blank is preferably made of steel, and the heating temperature of the blank is preferably 700 ° C. or higher.

  In many steels, the metal structure austenites when heated to 700 ° C. or higher. If a blank heated to 700 ° C. or higher is press-molded, the blank is quenched by contact between the blank and the mold. Thereby, a high-strength press product is obtained. Such a method is called hot stamping.

  (6) The method for producing the pressed product of the above (1) to (5) can be realized with the following configuration. The die includes a protrusion that protrudes toward the punch from the die top of the die. In the first region pushing step, the protrusion and the first region are brought into contact with each other, and the first region is pushed into the punch side by the protrusion.

  (7) The method for producing the pressed product of the above (1) to (6) can also be realized with the following configuration. The punch includes an inner pad that protrudes toward the die from the tip processed portion of the punch and is accommodated in the concave portion of the punch when the die or the punch reaches the bottom dead center. In the arranging step, the blank is arranged so that the third region is at a position corresponding to the inner pad. In the third region restraining step, the pad and the inner pad are brought close to each other, and a gap is formed between the pad and the inner pad to restrain the third region.

  Hereinafter, a method for producing the pressed product of this embodiment will be described in detail. The method for producing a press product includes an arranging step, a third region restraining step, a first region pushing step, and a second region processing step. The method for producing a press product according to the present embodiment is a method for producing a press product including an elongated flange portion by bending.

[First Embodiment]
[Pressing equipment]
The press apparatus of 1st Embodiment is demonstrated. The press apparatus of 1st Embodiment is an apparatus for implementing the method of producing the press goods of 1st Embodiment mentioned later.

  FIG. 5 is a cross-sectional view showing the press device of the first embodiment. Referring to FIG. 5, press apparatus 1 includes a punch 3, a die 2, a pad 4, and a distance block 5.

  The punch 3 is arranged as a lower die and faces the die 2 in the pressing direction. For example, the punch 3 is fixed to a bolster plate. The punch 3 includes a punch top portion 31, a punch shoulder portion 30, a punch vertical wall portion 32, and a punch bottom portion 33. The punch top portion 31 protrudes closer to the die 2 than the punch bottom portion 33 in the pressing direction. In other words, the punch top 31 is disposed above the punch bottom 33 in the vertical direction. The punch top portion 31 has a shape corresponding to the shape of the top plate portion of the press product. The punch shoulder portion 30 is provided between the punch top portion 31 and the punch vertical wall portion 32 and connects the two. The punch shoulder 30 has a curved shape in cross-sectional view.

  The punch bottom 33 is disposed outside the punch top 31. In other words, the punch bottom 33 is arranged around the punch top 31 in a plan view. That is, the “outside” in the present specification means the outer frame direction of the press device 1. The punch bottom 33 is disposed below the punch top 31 in the vertical direction. The punch bottom portion 33 has a shape corresponding to the shape of the flange portion of the press product.

  The punch vertical wall portion 32 is disposed between the punch top portion 31 and the punch bottom portion 33, and connects the punch top portion 31 and the punch bottom portion 33. The punch vertical wall portion 32 extends in the vertical direction. Here, the punch vertical wall portion 32 is not limited to the case of strictly extending in the vertical direction, but includes the case of extending in a direction inclined by 0 to 45 degrees from the vertical direction. The same applies to the die vertical wall portion 22 described later. The punch vertical wall portion 32 has a shape corresponding to the shape of the vertical wall portion of the press product.

  The die 2 is arranged as an upper mold. The die 2 is attached to a slide, for example. The slide is mounted in a known configuration, and the die 2 approaches and separates from the punch 3 by moving the slide toward and away from the punch 3.

  The die 2 includes a protruding portion 6, a die top portion 23, a die shoulder portion 20, a die vertical wall portion 22, and a concave portion 21. The recess 21 can accommodate the pad 4. The recess 21 faces the punch top 31.

  The die top 23 is disposed outside the recess 21. The die top portion 23 faces the punch bottom portion 33. The die top 23 protrudes closer to the punch 3 than the recess 21 in the pressing direction. That is, the die top 23 is disposed below the recess 21 in the vertical direction. The die top portion 23 has a shape corresponding to the shape of the flange portion of the press product. The die shoulder portion 20 is provided between the die top portion 23 and the die vertical wall portion 22 and connects the two. In cross-sectional view, the die shoulder 20 has a curved shape.

  The die vertical wall portion 22 is disposed between the concave portion 21 and the die top portion 23, and connects the concave portion 21 and the die top portion 23. The die vertical wall portion 22 extends in the vertical direction. The die vertical wall portion 22 has a shape corresponding to the shape of the vertical wall portion of the press product.

  The protrusion 6 is disposed outside the die top 23. The protrusion 6 includes a distal end portion 25. The tip portion 25 of the protruding portion protrudes closer to the punch 3 than the die top portion 23 in the pressing direction. That is, the tip 25 of the protrusion 6 is disposed below the die top 23 in the vertical direction. The tip 25 of the protrusion 6 protrudes toward the punch 3 most of each part of the die. The tip 25 of the protrusion 6 does not have a shape corresponding to the shape of the press product. This is because, as will be described later, when the die 2 reaches the bottom dead center, the protrusion 6 does not contact the blank.

  The pad 4 is attached to the recess 21 of the die 2 via the elastic member 7. The elastic member 7 is, for example, a spring, a die cushion, a hydraulic cylinder, or the like. The pad 4 includes a pad tip portion 41. The pad tip 41 faces the punch top 31 in the press direction. When the die 2 is at the top dead center position, the pad tip 41 protrudes more toward the punch 3 than the tip 25 of the die projection 6 in the pressing direction. Therefore, when the die 2 is lowered, the third region of the blank can be constrained by the pad tip portion 41 and the punch top portion 31 first.

  The distance block 5 is disposed on the punch top 31 of the punch. The distance block 5 is disposed at a position facing the pad 4 in the pressing direction. However, the distance block 5 is not arranged at the position where the blank is arranged. The distance block 5 maintains the distance between the pad 4 and the punch top 31 greater than the thickness of the third region of the blank. Therefore, the material of the distance block 5 is not particularly limited as long as it has this function. However, after the pad 4 comes into contact with the distance block 5 and the die 2 is further lowered, the pad 4 applies a force to the distance block 5 by the elastic function of the elastic member 7. Therefore, the distance block 5 is preferably a high-strength metal such as steel in order to maintain the distance between the pad 4 and the punch 3.

[Method of producing press products]
A method for producing a press product according to the first embodiment will be described. In the method for producing a press product according to the first embodiment, the press device according to the first embodiment described above is used. The method for producing the pressed product of the first embodiment is performed cold.

[Arrangement process]
FIG. 6 is a plan view of the blank. In FIG. 6, the blank shape | molded by the center pillar is shown as an example. The blank 10 includes a first region 11 including an end 15, a second region 12 located inside the first region 11, and a third region 13 located inside the second region 12. An end 15 of the first region 11 of the blank 10 is a portion that becomes an end of the stretch flange portion of the press product. For example, the portion indicated by reference numeral 111 in FIG. 4 corresponds to the portion that becomes the end of the stretch flange portion of the press product. The inside of the blank means a region in a direction away from the end 15 of the blank extending flange portion. The first region 11 is a region at a predetermined distance from the end 15 of the blank extending flange portion. This predetermined distance depends on the shape of the press product. That is, as will be described later, the first region 11 is a region from the end 15 of the stretch flange portion to the position of the blank that first contacts the die. As will be described later, the third region 13 is a blank region constrained by a pad and a punch. The second region 12 is a region between the first region 11 and the third region 13.

  The blank 10 is a metal plate such as a steel plate formed into a predetermined shape. Prior to the arranging step, a blank is obtained by forming a metal plate into a predetermined shape by punching or the like. The predetermined shape of the blank corresponds to the shape of the press product to be molded. In the present embodiment, description will be made on the assumption that the blank material is steel. However, the blank is not limited to this. The blank may be aluminum, aluminum alloy, copper, copper alloy, carbon fiber reinforced resin (CFRP), or the like.

  FIG. 7 is a cross-sectional view showing an arrangement process of the first embodiment. With reference to FIG. 7, in the arranging step, the blank 10 is arranged in the press device 1. More specifically, the third region 13 of the blank 10 is disposed on the punch top 31. In the arrangement step, the blank first region 11 and second region 12 are not in contact with the punch 3.

[Third region restraint step]
FIG. 8 is a cross-sectional view showing a third region restraining step of the first embodiment. Referring to FIG. 8, the third region restraining step is performed after the placement step. In the third region restraining step, the pad 4 and the punch 3 are brought close to each other. More specifically, the pad 4 is attached to the die 2 via an elastic member 7 such as a spring. Therefore, by lowering the die 2 toward the punch 3, the pad 4 also approaches the punch. In the pressing direction, the pad tip 41 protrudes further toward the punch 3 than the tip 25 of the protrusion 6. Therefore, when the die 2 is lowered, the blank can be restrained by the pad 4 and the punch 3 before the protruding portion 6 contacts the blank.

  The approach between the pad 4 and the punch 3 stops before the pad contacts the blank 10 on the punch. That is, in the third region restraining step, the pad 3 and the punch 3 restrain the blank third region 13 with a gap SP. In other words, the pad 4 does not contact the blank 10, and there is a gap SP between the pad 4 and the blank 10. In short, in the third region restraining step, the pad tip portion 41, the punch top portion 31, and the distance along the pressing direction are larger than the plate thickness of the third region 13 of the blank. In order to prevent the pad 4 and the blank 10 from contacting each other, a distance block 5 is provided on the punch top 31. The distance block 5 has a thickness larger than the plate thickness of the third region 13 of the blank, and protrudes toward the pad 4 side from the surface on the pad 4 side of the third region 13 of the blank. Thereby, the approach of the pad 4 and the punch 3 stops. This gap is maintained until the molding of the press product is completed, that is, until the die 2 reaches the bottom dead center.

  Even if the blank is bent after the third region constraining step, the material in the third region of the blank flows more easily than when the blank is completely sandwiched between the pad and the punch by the gap SP without leaving a gap. Therefore, even when a press product including an elongated flange portion is molded, the material in the third region of the blank can easily flow into the elongated flange portion during molding, and breakage of the elongated flange portion can be suppressed. In the third region restraining step, the gap between the pad 4 and the blank third region 13 is not more than a predetermined distance and is small. Therefore, the 3rd area | region 13 of a blank does not leave | separate greatly from the punch top part 31 during bending molding. Therefore, it is possible to suppress the occurrence of wrinkles in the pressed product, particularly the top plate portion.

  Preferably, when the blank 3rd area | region 13 is restrained with the pad 4 and the punch 3, the distance between the pad front-end | tip part 41 and the punch top part 31 is 120% or less of the plate | board thickness of the 3rd area | region 13 of a blank. is there. As described above, the suppression of wrinkles in pad bending molding is realized by suppressing the blank 10 from separating from the punch top 31 during molding. If the gap between the pad 4 and the blank 10 is increased, the blank is easily separated from the pad during molding, and the possibility that wrinkles are generated increases. Therefore, it is preferable that the gap between the pad 4 and the blank 10 is small. Therefore, the upper limit of the distance between the pad tip portion 41 and the punch top portion 31 when the blank is restrained is 120% or less of the plate thickness of the third region 13 of the blank. More preferably, the upper limit of the distance between the pad 4 and the punch top 31 when the blank is restrained is 110% or less of the thickness of the third region 13 of the blank. More preferably, the upper limit of the distance between the pad 4 and the punch top 31 when the blank is restrained is 105% or less of the plate thickness of the third region 13 of the blank.

  On the other hand, when the blank 3rd area | region 13 is restrained with the pad 4 and the punch 3, the minimum of the distance between the pad front-end | tip part 41 and the punch top part 31 is not specifically limited. If there is any gap between the pad 4 and the blank 10 when restraining the blank, the material in the third region of the blank stretches easily during the bending and flows into the flange portion. Accordingly, the lower limit of the distance between the pad 4 and the punch top 31 when the blank is restrained is not particularly limited.

[First area pushing step]
FIG. 9 is a cross-sectional view showing a first region pushing process of the first embodiment. Referring to FIG. 9, the first region pushing step is performed after the third region restraining step. In the first region pushing step, the die 2 is further lowered to bring the die 2 and the punch 3 closer. At this time, since the pad 4 is attached to the die 2 via the elastic member 7, the distance between the pad 4 and the die 2 approaches as the elastic member 7 contracts. A distance block 5 is provided on the punch top 31. Therefore, only the die 2 approaches the punch 3 while the distance between the pad 4 and the punch top 31 is maintained at the distance in the third region restraining step.

  The die 2 is provided with a protrusion 6. In the pressing direction, the tip 25 of the protrusion 6 protrudes most toward the punch 3 as compared to the other parts of the die 2. Therefore, when the die 2 is lowered, the protrusion 6 first comes into contact with the blank 10. Further, the protrusion 6 is provided on the outermost side of the die 2. Therefore, the protrusion 6 comes into contact with the first region 11 at a predetermined distance from the end 15 of the blank. When the die 2 is further lowered, the first region of the blank is pushed into the punch 3 side by the protrusion 6 of the die. As a result, the first region 11 and the second region 12 of the blank are bent by the protrusion 6 of the die, starting from the boundary between the third region 13 and the second region 12 of the blank (the portion in contact with the punch shoulder 30). It is done.

  In the first area pushing step, the blank second area 12 does not contact the die 2 and the punch 3. More specifically, the protrusion 6 protrudes closer to the punch 3 than the die top 23 provided adjacent to the inside (pad 4 side) of the protrusion 6 of the die. Therefore, a space exists between the die top 23 and the punch bottom 33 inside the protrusion 6. In the first area pushing step, since the second area 12 exists in this space, the second area 12 does not contact the die 2 and the punch 3. When the first region 11 and the second region 12 of the blank begin to bend, the contact portion between the first region 11 and the protrusion 6 gradually moves toward the blank end 15 side.

  In the first area pushing step, the contact portion of the blank in the first area 11 with the protrusion 6 gradually moves toward the end 15 of the blank, so the blank before the die 2 reaches the bottom dead center. The end of the first region 11 (the end 15 of the elongated flange portion) comes out from the protrusion 6 of the die. More specifically, the end 15 of the elongated flange portion moves to the third region 13 side (pad 4 side) from the inner end 24 of the protrusion 6. Thereby, a 1st area | region pushing process is complete | finished. When the first area pushing process is finished, the die 2 has not reached the bottom dead center. That is, the first area pushing process ends before the second area machining process described later.

[Second area processing step]
FIG. 10 is a cross-sectional view showing the second region processing step of the first embodiment. Referring to FIG. 10, the second region processing step is performed after the start of the first region pushing step. That is, the second region processing step may be performed after the start of the first region pushing step and before the end of the first region pushing step (that is, before the end 15 of the extending flange portion comes off from the protruding portion 6). The second region processing step may be performed after the end of the first region pushing step. In the second region processing step, the punch 3 and the die 2 are in contact with the second region 12 of the blank.

  After the protrusion 6 of the die 2 contacts the first region 11 of the blank, when the die 2 continues to descend, the die top 23 of the die 2 contacts the second region 12 of the blank after a certain time. As the die 2 further descends, the blank second region 12 is pushed toward the punch 3 by the die top 23. As described above, before the die 2 reaches the bottom dead center, the first region 11 of the blank moves to the inside of the protrusion 6, that is, the space between the die top 23 and the punch bottom 33. Therefore, after the blank first region 11 moves to the region facing the die top 23, the blank first region 11 and the second region 12 are punched by the die top 23 until the die 2 reaches bottom dead center. Pushed into the side.

  FIG. 11 is a cross-sectional view showing the end of the second region processing step of the first embodiment. Referring to FIG. 11, when the die 2 reaches bottom dead center, the first region 11 and the second region 12 of the blank are formed on the vertical wall portion and the flange portion of the press product having a hat cross-sectional shape. Thereby, a 2nd area | region process process is complete | finished and a press product is obtained.

  As described above, in the method of producing a press product according to the first embodiment, the pad and the punch restrain the third region of the blank with a gap in the third region restraining step. Since this gap is a small gap of a predetermined distance or less, the third region of the blank is not greatly separated from the punch during bending. Thereby, it is hard to produce an excessive material between a pad and a punch, and generation | occurrence | production of a wrinkle is suppressed. In addition, the material in the third region tends to flow into the first region and the second region side (that is, the stretch flange portion side) during bending. For this reason, breakage due to insufficient flow of material at the stretch flange portion is suppressed. Furthermore, before the 2nd area | region processing process which is this process of press bending, in a 1st area | region pushing process, the 1st area | region of a blank is pushed in advance and a blank is bent. Thereby, the height of the protrusion 6 in the first region pushing step can be added as a forming stroke to the punch (or die) forming stroke in the second region machining step. If it does so, in order for the height of the projection part 6 to start bending in a 1st area | region pushing process in advance, the time for which a blank is bent during shaping | molding is long. Therefore, the flow of material from the third region of the blank in one molding stroke can be further increased. As a result, the amount of material flowing to the stretch flange portion increases, and the plate thickness reduction rate is suppressed. Therefore, breakage of the stretch flange portion is further suppressed.

  The first embodiment of the present invention has been described above. However, the embodiment of the present invention is not limited to this. Hereinafter, other embodiments of the present invention will be described.

[Second Embodiment]
[Pressing equipment]
The press apparatus of 2nd Embodiment is demonstrated. The press apparatus of 2nd Embodiment is an apparatus for enforcing the method of producing the press goods of 2nd Embodiment mentioned later. Compared with the press apparatus of 1st Embodiment, the press apparatus of 2nd Embodiment is not provided with a projection part, but an inner pad is provided in a punch. In the following description, the description overlapping the first embodiment is omitted.

  FIG. 12 is a cross-sectional view showing the pressing device according to the second embodiment. Referring to FIG. 12, press apparatus 1 includes a punch 3, a die 2, a pad 4, and a distance block 5.

  The punch 3 includes a punch top portion 31, a punch vertical wall portion 32, a punch bottom portion 33, an inner pad 34, and a recess 26. The inner pad 34 includes an inner pad tip portion 35. The inner pad tip portion 35 protrudes to the die 2 side from the punch top portion 31 in the pressing direction. That is, the inner pad tip 35 is disposed above the punch top 31 in the vertical direction. Inner pad tip 35 and punch top 31 have a shape corresponding to the shape of the top plate of the press product.

  The inner pad 34 is attached to the recess 26 via the elastic member 7. The elastic member 7 is, for example, a spring, a die cushion, a hydraulic cylinder, or the like. The inner pad tip 35 opposes the pad tip 41 of the pad 4 in the pressing direction. When the die 2 is at the top dead center position, the pad tip 41 of the pad 4 protrudes more toward the punch 3 than the die top 23 of the die. Therefore, when the die 2 is lowered, the third region of the blank can be constrained by the pad tip 41 and the inner pad tip 35 first.

  The distance block 5 is disposed on the inner pad tip portion 35 of the inner pad. The distance block 5 is disposed at a position facing the pad 4 in the pressing direction.

[Method of producing press products]
A method for producing a pressed product according to the second embodiment will be described. In the second embodiment, the blank is restrained by the inner pad on the die side from the punch. Since the blank restraining position is closer to the die side, the molding stroke of the punch (or die) contacting the first area of the blank can be increased. Therefore, similarly to the first embodiment, breakage of the stretch flange portion can be suppressed. The method for producing the pressed product of the second embodiment is performed cold.

[Arrangement process]
FIG. 13 is a cross-sectional view illustrating an arrangement process of the second embodiment. Referring to FIG. 13, in the arranging step, the third region 13 of the blank 10 is arranged on the inner pad 34 protruding from the punch top portion 31 toward the pad 4 side. The blank third region 13 is in contact with the inner pad 34.

[Third region restraint step]
FIG. 14 is a cross-sectional view showing a third region restraining step of the second embodiment. Referring to FIG. 14, in the third region restraining step, die 2 is lowered toward punch 3 to bring pad 4 and inner pad 34 of punch 3 closer to each other. The pad tip 41 protrudes further toward the punch 3 than the die top 23. Therefore, when the die 2 is lowered, the blank can be restrained by the pad 4 and the inner pad 34 before the die top 23 contacts the blank.

  A distance block 5 is provided on the inner pad 34 of the punch. Therefore, in the third region restraining step, the pad 3 and the punch inner pad 34 restrain the blank third region 13 with a gap SP. Therefore, even if a press product including an elongated flange portion is molded, the material of the blank third region 13 can easily flow into the elongated flange portion during molding, and the fracture of the elongated flange portion can be suppressed. Further, the gap SP between the pad 4 and the blank third region 13 is less than a predetermined distance and is small. Therefore, the third region 13 of the blank is not greatly separated from the inner pad tip portion 35 of the punch 3 during bending. Therefore, it is possible to suppress the occurrence of wrinkles in the pressed product, particularly the top plate portion.

[First area pushing step]
FIG. 15 is a cross-sectional view illustrating a first region pushing process according to the second embodiment. Referring to FIG. 15, in the first region pushing step, die 2 is further lowered. With the distance block 5, only the die 2 approaches the punch 3 while the distance between the pad 4 and the inner pad 34 is maintained at the distance in the third region restraining step.

  The die top 23 of the die 2 protrudes most toward the punch 3 as compared to the other portions of the die 2 in the pressing direction. The die top 23 is provided on the outermost side of the die 2. Therefore, the die top 23 comes into contact with the first region 11 at a predetermined distance from the end of the blank (end 15 of the elongated flange portion). When the die 2 is further lowered, the blank first region 11 is pushed into the punch 3 side by the die top 23.

  The inner pad tip portion 35 protrudes to the die 2 side from the punch top portion 31 in the pressing direction. Further, the punch top portion 31 is disposed outside the inner pad tip portion 35. Accordingly, the blank third region 13 contacts the inner pad tip 35, and the blank second region 12 does not contact the punch top 31 and the die 2. Further, when the first region 11 and the second region 12 of the blank begin to bend, the first region 11 of the blank comes into contact with the inner end of the die top 23, and the contact area between the first region 11 and the die top 23 Decrease. The contact portion of the first region 11 with the die top 23 gradually moves relative to the blank end 15 side.

[Second area processing step]
FIG. 16 is a cross-sectional view showing a second region processing step of the second embodiment. Referring to FIG. 16, when die 2 further descends after die top 23 comes into contact with first region 11 of blank 10, the second region of the blank is bent starting from the shoulder portion of the die after a certain period of time. Thereby, a 2nd area | region process process is started. And the die | dye vertical wall part 22 and the 2nd area | region 12 of a blank contact. The punch top 31 of the punch and the second region 12 of the blank come into contact with each other.

  FIG. 17 is a cross-sectional view showing the end of the second region processing step of the second embodiment. Referring to FIG. 17, when the die 2 reaches bottom dead center, the first region 11 and the second region 12 of the blank are formed on the vertical wall portion and the flange portion of the press product having a hat cross-sectional shape. Thereby, a 2nd area | region process process is complete | finished and a press product is obtained.

  As described above, also in the method for producing a press product of the second embodiment, the pad and the punch (inner pad) restrain the third region of the blank with a gap in the third region restraining step. Since this gap is a small gap of a predetermined distance or less, the third region of the blank is not greatly separated from the inner pad during bending. Thereby, it is hard to produce an excessive material between a pad and an inner pad, and generation | occurrence | production of wrinkles is suppressed. In addition, during the bending of the first region and the second region of the blank, the material of the third region tends to flow into the first region and the second region side (that is, the stretch flange portion side). For this reason, breakage due to insufficient flow of material at the stretch flange portion is suppressed. Furthermore, the first area of the blank is pushed into the punch side in advance by the die. A second region of the blank comes into contact with the die after a certain time from the contact between the die and the first region. Accordingly, in the present embodiment, the height of the inner pad in the first region pushing step (the distance between the inner pad tip portion 35 and the punch top portion 31) is used as the molding stroke in the punching stroke in the second region machining step. Can be added. As a result, as in the first embodiment, the amount of material flowing to the stretch flange portion increases, and the plate thickness reduction rate is suppressed. Therefore, breakage of the stretch flange portion is further suppressed.

[Third Embodiment]
[Pressing equipment]
The press apparatus of 3rd Embodiment is demonstrated. The press apparatus of 3rd Embodiment is an apparatus for enforcing the method of producing the press goods of 3rd Embodiment mentioned later. The press device of the third embodiment is provided with both the protrusions of the press device of the first embodiment and the inner pad of the punch of the second embodiment. In the following description, descriptions overlapping with the first embodiment and the second embodiment are omitted.

  FIG. 18 is a cross-sectional view showing the press device of the third embodiment. Referring to FIG. 18, press apparatus 1 includes a punch 3, a die 2, a pad 4, and a distance block 5.

  The punch 3 includes a punch top portion 31, a punch vertical wall portion 32, a punch bottom portion 33, and an inner pad 34. The distance block 5 is disposed on the inner pad tip portion 35 of the inner pad.

  The die 2 includes a protruding portion 6, a die top portion 23, a die vertical wall portion 22, and a concave portion 21. The protruding portion 6 is disposed outside the die top portion 23 and protrudes toward the punch 3 most among the portions of the die. When the die 2 is at the top dead center position, the pad tip 41 protrudes more toward the punch 3 than the protrusion 6 of the die.

[Method of producing press products]
A method for producing a pressed product according to the third embodiment will be described. In 3rd Embodiment, the press apparatus containing both the protrusion part of 1st Embodiment and the inner pad of 2nd Embodiment is used. The method for producing the pressed product of the third embodiment is performed cold.

[Arrangement process]
FIG. 19 is a cross-sectional view showing the arrangement process of the third embodiment. Referring to FIG. 19, in the arranging step, third region 13 of blank 10 is arranged on inner pad 34.

[Third region restraint step]
FIG. 20 is a cross-sectional view showing a third region restraining step of the third embodiment. Referring to FIG. 20, in the third region restraining step, die 2 is lowered toward punch 3 to bring pad 4 and inner pad 34 of punch 3 closer to each other. The pad tip 41 protrudes further toward the punch 3 than the protrusion 6. Therefore, when the die 2 is lowered, the blank can be restrained by the pad 4 and the inner pad 34 before the protrusion 6 contacts the blank 10.

  A distance block 5 is provided on the inner pad 34 of the punch. Therefore, in the third region restraining step, the pad 3 and the punch inner pad 34 restrain the blank third region 13 with a gap SP. Therefore, even if a press product including an elongated flange portion is molded, the material of the third region of the blank can easily flow into the elongated flange portion during molding, and the elongation flange portion can be prevented from breaking. Further, the gap SP between the pad 4 and the blank third region 13 is less than a predetermined distance and is small. Therefore, the third region 13 of the blank is not greatly separated from the inner pad tip portion 35 during bending. Therefore, it is possible to suppress the occurrence of wrinkles in the pressed product, particularly the top plate portion.

[First area pushing step]
FIG. 21 is a cross-sectional view illustrating a first region pushing process according to the third embodiment. Referring to FIG. 21, in the first region pushing step, die 2 is further lowered to bring die 2 and punch 3 closer to each other. With the distance block 5, only the die 2 approaches the punch 3 while the distance between the pad 4 and the inner pad 34 is maintained at the distance in the third region restraining step.

  When the die 2 is lowered, the protruding portion 6 protruding toward the punch 3 first comes into contact with the first region 11 of the blank 10. When the die 2 is further lowered, the first region 11 and the second region 12 of the blank are bent from the boundary between the second region 12 and the third region 13 by the protrusion 6 of the die.

[Second area processing step]
FIG. 22 is a cross-sectional view showing a second region processing step of the third embodiment. Referring to FIG. 22, in the second region processing step, die top 23 of the die and second region 12 of the blank come into contact with each other. In the second region processing step, the punch top 31 of the punch and the second region 12 of the blank come into contact with each other. As described above, the forming stroke of the die 2 that comes into contact with the first region 11 of the blank 10 is increased by providing the protrusion 6. In addition, since the inner pad 34 is provided, the molding stroke of the die 2 that comes into contact with the first region 11 of the blank 10 is further increased. Therefore, after the start of the first region pushing step, the fixed time during which the blank second region 12 does not contact the punch 3 and the die 2 until the processing of the blank second region 12 is started further increases. Thereby, the time for the material to flow from the third region 13 of the blank to the stretch flange portion during molding becomes longer, and the breakage at the stretch flange portion is suppressed.

  FIG. 23 is a cross-sectional view showing the end of the second region processing step of the third embodiment. Referring to FIG. 23, when die 2 reaches the bottom dead center, the second region processing step is finished, and a pressed product is obtained.

  In short, in the method for producing a pressed product according to the third embodiment, in addition to the effect of the material flowing into the stretch flange portion by the protrusion 6, the effect of the material flowing into the stretch flange portion by the inner pad 34 is also added. Therefore, as compared with the first embodiment and the second embodiment, breakage at the stretch flange portion is further suppressed.

[Fourth Embodiment]
In the fourth embodiment, a press product is formed from a heated blank. That is, the method for producing the pressed product of the fourth embodiment is performed hot or warm. For example, in a hot stamp, a press blank is formed by bending a heated blank, and when the die reaches bottom dead center, the formed press product is rapidly cooled and quenched. Thereby, a press product including a martensite structure, that is, a high-strength press product is obtained. Therefore, when a press product is formed by hot stamping and quenched, the blank needs to be made of steel.

[Pressing equipment]
A press device according to a fourth embodiment will be described. As the press device of the fourth embodiment, any of the press devices of the first to third embodiments described above can be used.

  Preferably, the protrusion 6 has a lower heat transfer coefficient than the die 2 and the punch 3. In the case of hot stamping, when the die 2 reaches the bottom dead center, the formed blank (pressed product) is quenched, so that the heat transfer coefficient of the die 2 and the punch 3 is preferably high. On the other hand, as described above, when the die 2 starts to descend after the placement process, the protrusion 6 first contacts the blank. Therefore, it is desirable that the protrusion 6 does not cool the blank from the viewpoint of ensuring the ease of flow of the blank material during bending. Further, when the die 2 reaches the bottom dead center, the protrusion 6 does not come into contact with the pressed product. Taking a hot stamp as an example, the protrusion 6 does not quench the pressed product, and thus the heat transfer coefficient may be low.

[Method of producing press products]
A method for producing a pressed product according to the fourth embodiment will be described.

  In any of the first to third embodiments described above, a heated blank such as hot, warm, or hot stamp can be used as a processing target. In the following description of the fourth embodiment, as an example, a method for producing a press product by hot stamping using the press apparatus of the first embodiment will be described. The method for producing the pressed product of the fourth embodiment includes a heating step and a cooling step in addition to the method for producing the pressed product of the first embodiment.

[Blank heating]
The blank is heated by a heating device (not shown). The heating device is not particularly limited. Examples of the heating device include a continuous heating furnace and a batch heating furnace. The heating method is not particularly limited. Examples of the heating method include gas heating and induction heating.

  For example, in the case of a hot stamp, the heating step can heat the blank above the A1 transformation point of the material. In this case, the heating temperature is, for example, 700 ° C to 900 ° C. By heating a blank made of steel to the A1 transformation point or higher, the structure of the pressed product becomes martensite after the blank (pressed product) is quenched. Therefore, the strength of the press product is increased. Note that the heating temperature is not particularly limited when hot stamping (that is, quenching) is not performed. In this case, the heating temperature of the blank may be appropriately set in consideration of the blank material, the strength of the blank, the shape of the press product to be molded, and the like. After the heating of the blank, the heated blank is placed on the press device using a conveyance path, a robot arm, or the like, that is, an placing step is performed. The description of the arrangement process is omitted.

  4th Embodiment has demonstrated the case where a blank is heated before an arrangement | positioning process. However, the heating of the blank is not limited to this case. For example, the heating of the blank may be performed after the placement step and before the third region restraining step, or at the same time as or after the start of the third region restraining step and before the end of the third region restraining step. Alternatively, it may be performed simultaneously with or after the end of the third region restraining step. In short, it is only necessary that the heating step be performed before the blank is deformed by the mold. When heating a blank after an arrangement | positioning process, what is necessary is just to heat a blank using an induction heating apparatus etc.

  The heating temperature may be a temperature higher than room temperature, for example, 200 ° C. or higher when the die 2 starts to descend. The heating temperature of such a blank is measured with a radiation thermometer.

[Third region restraint step]
Referring to FIG. 8, in the third region restraining step, a gap SP exists between the blank third region 13 and the pad tip 41 due to the distance block 5. The effect of this third area restraining step in hot stamping will be described.

  As described at the beginning, when a press product including an elongated flange portion is drawn, the vertical wall portion and the flange portion of the elongated flange portion are likely to break. On the other hand, when a press product including an elongated flange portion is formed by general bending to suppress breakage, wrinkles are likely to occur in the top plate portion. As a method for forming such a difficult-to-form press product, hot or warm press forming is known. However, if the shape of the pressed product is more complex, even in hot or warm press molding, the stretch flange portion may break or the top plate portion may be wrinkled.

  In the third region restraining step of the fourth embodiment, the pad 3 and the punch 3 restrain the blank third region 13 with a gap. Therefore, the material of the third region of the blank is more likely to flow than when the pad 4 and the punch 3 completely sandwich the blank without leaving a gap. This effect is also obtained in hot or warm press molding as in the above-described cold (first to third embodiments). In the third region restraining step, the gap between the pad 4 and the blank third region 13 is not more than a predetermined distance and is small. Therefore, even in hot or warm press molding, the occurrence of wrinkles on the top plate portion of the pressed product can be suppressed.

  The third area 13 of the heated blank is in contact with the punch top 31. Since the third region 13 of the blank is removed by contact with the punch top portion 31, the third region 13 of the blank can be cooled (quenched in the case of a hot stamp).

[First area pushing step]
Referring to FIG. 9, when the bending by the die 2 is started after the third region restraining step, the first region 11 and the second region 12 of the blank start from the boundary between the second region 12 and the third region 13. Bend. At this time, since the third region of the blank is not completely sandwiched between the pad 4 and the punch 3, the third region 13 of the blank may be slightly separated from the punch top portion 31 and contact the pad tip portion 41. This contact is resistant to the flow of the blank material. However, since the ductility of the heated blank is high, even if the first region 11 and the second region 12 of the blank are bent, the third region 13 of the blank is not easily separated from the punch top 31. Contact between the third region 13 of the heated blank and the punch top 31 is suppressed. Therefore, even when a difficult-to-form press product including the stretch flange portion is molded, the material in the third region of the blank easily flows into the stretch flange portion during molding, and the break of the stretch flange portion can be suppressed.

  Further, as described above, in the first area pushing step, the die 2 (projection 6) pushes the blank first area 11 toward the punch 3 side, so that the blank second area 12 is the die 2, the pad 4, and the punch 3. Do not contact with. Therefore, the second region 12 is not easily cooled in the first region pushing step. For this reason, in the subsequent second region processing step, the material of the blank second region 12 becomes easier to flow, and the breakage of the stretch flange portion can be suppressed.

  Furthermore, as will be described later, the mold may be cooled in order to cool the pressed product, but the protrusion 6 that contacts the first region 11 of the blank is not cooled even in this case. That is, even if the protrusion 6 contacts the first region 11 of the blank, the first region 11 of the blank is not easily cooled. This is because, as described above, when the die 2 reaches the bottom dead center, the protrusion 6 does not contact the blank. Since the protrusion hardly cools the blank, in the first region pushing step, the temperature drop in the first region of the blank is small. Therefore, the local deformation | transformation of the high temperature area | region of a blank by the heat extraction of the 1st area | region of a blank is suppressed. That is, breakage of the blank is suppressed.

[Second area processing step]
Referring to FIG. 9, as in the first embodiment described above, after the protrusion 6 of the die 2 comes into contact with the first region 11 of the blank and the die 2 continues to descend, after a predetermined time, The die top 23 contacts the blank second region 12. In this way, by delaying the timing at which the second region 12 of the blank comes into contact with the mold, the difference in cooling time between the second region 12 and the first region 11 of the blank is reduced, and cooling unevenness (quenching with hot stamping) Unevenness) can be reduced. As the die 2 further descends, the blank second region 12 is pushed toward the punch 3 by the die top 23. Thereafter, the die 2 reaches the bottom dead center.

  Since the punch 3 and the die 2 are at a lower temperature than the blank 10 in the first region pushing step and the second region processing step, the blank 10 is cooled if the punch 3 and / or the die 2 come into contact with the blank 10. The punch 3 and / or the die 2 (that is, the mold) may be cooled in order to actively cool the press product. For example, a cooling path for flowing a cooling medium through the mold may be provided, or the blank may be directly water-cooled. In the case of a hot stamp, when quenching is completed, a high-strength press product is obtained. In addition, the cooling rate of a press product is suitably set according to material.

  The effect of the method for producing the pressed product of this embodiment was examined by numerical calculation. As an example of the present invention, three patterns of the present invention example 1 to the present invention example 3 were calculated. As a comparative example, five patterns of Comparative Examples 1 to 5 were calculated.

  In Example 1 of the present invention, a press product was formed assuming the press device of the first embodiment. In Example 2 of the present invention, a press product was formed assuming the press device of the second embodiment. In Invention Example 3, a press product was formed assuming the press device of the third embodiment. All of Invention Examples 1 to 3 assumed a hot press.

  In Comparative Example 1, a press product was formed on the assumption that the press apparatus except the distance block in Inventive Example 1 was used. In Comparative Example 2, a press product was formed on the assumption that the press apparatus in which the distance block was removed in Inventive Example 2 was used. In Comparative Example 3, a general pad bending molding press was assumed (see FIG. 2), and a press product was molded. All of Comparative Examples 1 to 3 assumed a hot press.

[Calculation condition]
Calculation conditions common to Invention Example 1 to Invention Example 3 and Comparative Examples 1 to 3 will be described. The numerical calculation was performed using Software LS-DYNA manufactured by Livermore Software Technology Corporation. A finite element method (FEM) was used as a calculation method. The blank was a steel plate having a plate thickness of 1.6 mm and a tensile strength at normal temperature of 600 MPa. The heating temperature of the blank was 900 ° C. The punch was fixed as a lower die, and the lowering speed of the die was 4000 mm / sec. The load applied from the elastic member to the pad when the die reached the bottom dead center was 49000N.

  FIG. 24 is a perspective view of a model of a pressed product formed in this example. Referring to FIG. 24, in this example, it was assumed that a press product that was bent 90 degrees into an L shape including the top plate portion 16, the vertical wall portion 17, and the flange portion 18 was assumed. The L-shaped region of the pressed product, that is, the stretch flange portion 14 was a quarter circle with a radius of 30 mm.

  Calculation conditions that differ between Invention Example 1 to Invention Example 3 and Comparative Examples 1 to 3 will be described.

  Referring to FIG. 5, in the present invention example 1 and comparative example 1, when the die 2 is at the top dead center position, the pad tip 41 of the pad 4 in the pressing direction is a protrusion positioned on the pad 4 side in the pressing direction. It was closer to the 66 mm punch 3 than the tip 25 of the part. In Invention Example 1 and Comparative Example 1, when the die 2 was at the top dead center position, the tip 25 of the protrusion in the press direction was closer to the 25 mm punch 3 than the die top 23.

  Referring to FIG. 12, in Example 2 and Comparative Example 2, when the die 2 is at the top dead center position, the pad tip 41 of the pad 4 is closer to the 66 mm punch 3 than the die top 23 in the press direction. It was. When the die 2 was at the top dead center position, the inner pad tip portion 35 of the inner pad 34 was closer to the 10 mm die 2 than the punch top portion 31 in the pressing direction. The load applied from the elastic member to the inner pad when the die reached the bottom dead center was 98000N.

  Referring to FIG. 18, in Example 3 of the present invention, when the die 2 was at the top dead center position, the pad tip 41 of the pad 4 was closer to the 66 mm punch 3 than the tip 25 of the protrusion in the press direction. . In Example 3 of the present invention, when the die 2 was at the top dead center position, the tip portion 25 of the protruding portion was closer to the 25 mm punch 3 than the die top portion 23 in the pressing direction. In Invention Example 3, when the die 2 was at the top dead center position, the inner pad tip portion 35 of the inner pad 34 was closer to the 10 mm die 2 than the punch top portion 31 in the press direction. The load applied from the elastic member to the inner pad when the die reached the bottom dead center was 98000N.

  In Comparative Example 3, when the die 2 was at the top dead center position, the pad tip 41 of the pad 4 was closer to the 66 mm punch 3 than the die top 23 of the die 2 in the press direction.

  In Invention Example 1 to Invention Example 3, the length of the distance block in the pressing direction was 1.8 mm. That is, a 0.2 mm gap was provided between the blank and the pad tip.

[Calculation result]
Referring to FIG. 24, in Example 1 to Example 3 and Example 1 to Example 3 of the present invention, the plate thickness reduction rate in the stretch flange portion 14 was calculated. A larger value of the plate thickness reduction rate means that the plate thickness is reduced and breakage tends to occur. In addition, the plate | board thickness reduction | decrease rate was computed by the following formula | equation.
(Thickness reduction rate [%]) = (plate thickness before molding−plate thickness after molding) × 100 / (plate thickness before molding)

  As the evaluation of breakage, the thickness reduction rate at the boundary between the vertical wall portion 17 and the flange portion 18 at the center of the bending of the stretch flange portion 14 where breakage is most likely to occur was calculated. In addition, as an evaluation of the difficulty of breaking, the area of the vertical wall portion 17 and the flange portion 18 of the elongated flange portion 14 where the plate thickness reduction rate was 17% or more was calculated. Based on the calculated values, the ratio of Invention Example 1 to Invention Example 3 and Comparative Example 1 to Comparative Example 3 was calculated with the value of Comparative Example 1 as 100.

  The calculation results are shown in Table 1.

  In Invention Example 1 to Invention Example 3, the plate thickness reduction rate at the center of curvature of the stretch flange portion 14 was less than the value in the comparative example. That is, in Invention Example 1 to Invention Example 3, breakage of the stretch flange portion was suppressed as compared with the comparative example. Moreover, in the invention example 1-this invention example 3, the area of the area | region where plate | board thickness reduction | decrease rate is 17% or more was smaller than the comparative example. That is, in the present invention example 1 to the present invention example 3, a range in which the vertical wall portion and the flange portion are likely to be broken is suppressed as compared with the comparative example. In Examples 1 to 3 of the present invention, the thickness reduction rate of the top plate portion 16 was not large to the extent that wrinkles could occur.

  The embodiment of the present invention has been described above. However, the above-described embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately changing the above-described embodiment without departing from the spirit thereof.

  In the above-described embodiment, the case where the die is arranged as the upper die and the punch as the lower die has been described. However, the punch may be an upper die and the die may be a lower die. In short, the upper and lower sides of the press device of the above-described embodiment may be reversed.

  In the above-described embodiment, the press product may not be a product. That is, the press product obtained by the method for producing the press product of the present embodiment may be further subjected to bending, drawing, cutting, or the like.

  In the above-described embodiment, the case where one side of a press product having a hat cross-sectional shape is formed in a cross-sectional view has been described. However, it goes without saying that, in the method for producing a pressed product of the present embodiment, both sides of a pressed product having a hat cross-sectional shape may be formed in a sectional view. Moreover, the press product does not need to extend on both sides in a cross-sectional view and include flange portions. That is, the press product may extend only on one side in a sectional view and include a flange portion.

  The method for producing a pressed product of this embodiment is used for producing a pressed product including an elongated flange portion. The press product including the stretch flange portion is a part constituting a vehicle body such as a front pillar, a center pillar, a rear pillar, a front bumper, a rear bumper, and a lower arm of a four-wheeled vehicle.

1: Press device 2: Die 3: Punch 4: Pad 5: Distance block 6: Protrusion 7: Elastic member 10: Blank 11: First region 12: Second region 13: Third region 14: Stretch flange portion 15: End of stretch flange portion 21: Recess 22: Die vertical wall portion 23: Die top portion 24: Inner end of projection portion 25: Tip end portion of projection portion 31: Punch top portion 32: Punch vertical wall portion 33: Punch bottom portion 34: Inner pad 35: Inner pad tip 41: Pad tip

Claims (7)

A method of producing a press product including a stretch flange portion by bending with a punch, a press device including a die facing the punch and a pad facing the punch,
A blank including a first region including an end portion of the stretch flange portion of the press product, a second region positioned on the inner side of the first region, and a third region positioned on the inner side of the second region. An arrangement step of arranging in the press device;
A third region restraining step of bringing the pad and the punch close to each other after the placing step, and restraining the third region with a gap between the blank and the pad between the pad and the punch;
After the third region restraining step, the die and the punch are brought close to each other, the die and the first region are brought into contact with each other, and the first region pushing step of pushing the first region to the punch side by the die;
After the start of the first area pushing step, the punch and the second area are brought into contact with each other, the die and the second area are brought into contact with each other, and the second area is processed by the punch and the die. A method for producing a press product comprising an area processing step. A method for producing the press product according to claim 1,
In the third region restraining step, the gap is 120% or less of the thickness of the blank. A method for producing a press product according to claim 1 or 2,
In the second area processing step, the die or the punch is made to reach a bottom dead center, and the processing of the first area is ended simultaneously with the end of the processing of the second area. A method for producing a press product according to claim 3,
The method for producing a pressed product, wherein the blank is preheated before the start of the first region pushing step. A method for producing a press product according to claim 4,
The blank is made of steel,
The method for producing a pressed product, wherein the heating temperature of the blank is 700 ° C. or higher. A method for producing a press product according to any one of claims 1 to 5,
The die includes a protrusion protruding toward the punch from the die top of the die,
In the first region pushing step, the protruding portion and the first region are brought into contact with each other, and the first region is pushed toward the punch by the protruding portion. A method for producing the press product according to any one of claims 1 to 6,
The punch includes an inner pad that protrudes toward the die from a tip processed portion of the punch, and is accommodated in a concave portion of the punch when the die or the punch reaches a bottom dead center.
In the arranging step, the blank is arranged so that the third region is at a position corresponding to the inner pad,
In the third region restraining step, the pad and the inner pad are brought close to each other, and a gap is formed between the pad and the inner pad to restrain the third region, thereby producing a press product.

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