Hot press device, method for manufacturing hot press formed product, and hot press formed product

Abstract

Provided is a hot-pressing device (1000) that comprises a punch (1200), a die (1300), and a die pad (1100) and is characterized in that there is a groove (1220) in a top surface (1210) of the punch (1200), the angle formed between a wall surface of the groove (1220) and the pressing direction (P) in a cross-section taken along the pressing direction (P) being 2°–8°, there is a refrigerant channel inside the punch (1200), the die (1300) and the die pad (1100) are arranged so as to face the punch (1200) in the pressing direction (P), the die pad (1100) facing the top surface (1210) of the punch (1200), and there is a protrusion (1120) on the die pad (1100) at a position that is opposite the groove (1220) in the pressing direction (P), the protrusion (1120) having the inverse shape of the groove (1220).

Description

Technical Field

[0001] The present disclosure relates to a hot press apparatus, a method for manufacturing a hot press molded product, and a hot press molded product. This application claims priority based on Japanese Patent Application No. 2022-085778 filed in Japan on May 26, 2022, the content of which is incorporated herein by reference.

Background Art

[0002] Conventionally, as a skeletal member of an automobile, a member obtained by processing a metal plate-like member into a predetermined cross-sectional shape has been used. When an impact due to a collision is applied to a product having a skeletal member, it is required that the skeletal member realizes a desired deformation mode and efficiently absorbs the impact. For example, Patent Document 1 discloses a bumper reinforcing member provided with small recesses and large recesses surrounding the small recesses for the purpose of increasing the peak load or increasing the energy absorption amount.

[0003] Such a skeletal member is required to achieve weight reduction and have sufficient load resistance. In recent years, with the tightening of collision safety standards for vehicles such as automobiles and the tightening of fuel consumption regulations, high-strength and lightweight members have been demanded. In order to meet such requirements, the development of lightweight skeletal members using so-called high-strength materials having high tensile strength has been promoted.

[0004] Patent Document 2 discloses a technique for press-forming a plate material into a hat-shaped molded product having unevenness on the top surface. However, when forming the unevenness on the top surface of the molded product and the shoulder adjacent to the top surface at the same time, these formations interfere with each other and it becomes difficult to form. In Patent Document 2, the unevenness on the top surface of the molded product is formed in advance, and after restraining the unevenness with a punch and a die pad, the shoulder of the molded product is formed with a punch and a die. Thus, the main point of Patent Document 2 is not to perform the two formations at the same time.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 Japanese Patent No. 5329188 Patent Document 2 Japanese Unexamined Patent Application Publication No. 2020-075275 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] When forming a hat-shaped molded product or a groove-shaped member having a groove portion on the top surface by hot pressing, when the method of Patent Document 2 is applied to hot pressing, two hot presses are required. When forming in one hot press, it is conceivable to form the groove portion on the heated plate material with a die pad and a punch, and then form the shoulder portion with a punch and a die. However, in such a case, there are two problems. First, when forming the groove portion via a spring as in Patent Document 2, since the force of the spring is weak, the die pad cannot reach the forming bottom dead center and the groove portion cannot be formed into a desired shape (a shape along the groove portion at the top of the punch). Second, even if the die pushes the die pad to reach the forming bottom dead center, local thickness reduction occurs in the groove portion of the molded product. Until the die reaches the forming bottom dead center, the workpiece between the groove portion at the top of the punch and the die pad does not contact the mold uniformly, resulting in temperature unevenness in the workpiece. The thickness reduction occurs because the locally softened portion due to the temperature unevenness of the workpiece is preferentially stretched when the die and the die pad reach the forming bottom dead center.

[0007] The present disclosure has been made in view of the above. An object of the present disclosure is to provide a hot press device capable of suppressing a decrease in the thickness and necking of a recess of a hot press molded product formed by a die pad, a method for manufacturing a hot press molded product using the device, and a hot press molded product in which a decrease in the thickness and necking of a recess of the press molded product are suppressed. MEANS FOR SOLVING THE PROBLEMS

[0008] (1) A hot press device according to one aspect of the invention according to the present disclosure includes a punch, a die, and a die pad, The top surface of the punch has a groove portion, In a cross-section along the pressing direction, the angle formed by the wall surface of the groove portion and the pressing direction is 2 to 8°, There is a refrigerant flow path inside the punch, The die and the die pad are arranged to face the punch in the pressing direction, The die pad is arranged to face the top surface of the punch, The die pad has a convex portion at a position facing the groove portion in the pressing direction, and the convex portion has a shape in which the groove portion is inverted. (2) In the hot press device of (1) above, The die has a stepped portion that contacts the die pad in the pressing direction, At the forming bottom dead center, the die pad may be in contact with the die in the pressing direction. (3) In the hot press device of (1) or (2) above, In the cross-section, the angle formed by the straight line connecting the R stop of the side edge portion of the wall surface of the groove portion and the R stop of the bottom edge portion of the wall surface of the groove portion and the pressing direction may be 2 to 8°. (4) A method for manufacturing a hot press molded product according to one aspect of the invention according to the present disclosure is A method for manufacturing a hot press molded product using the hot press device according to any one of (1) to (3) above, Placing a blank between the die and the punch, Clamping the blank with the punch and the die pad, Bringing the punch and the die closer to the forming bottom dead center in the pressing direction, characterized by including this. (5) A hot press molded product according to one aspect of the invention according to the present disclosure is A press molded product including a first plate portion in which a concave portion is formed and a second plate portion inclined with respect to the first plate portion, In a cross-sectional view in a plane in which the cross-sectional line length of the concave portion is the shortest among the planes passing through the point where the depth of the concave portion is the deepest, the angle formed by the side portion of the concave portion and the direction perpendicular to the plate surface of the first plate portion is 2 to 8°, The thickness of the thinnest part in the concave portion is 60% or more of the thickness of the portion of the first plate portion excluding the concave portion. (6) In the hot press-formed product of (5) above, In the cross-sectional view, the angle formed by the straight line connecting the R stop of the side edge portion on the side of the concave portion and the R stop of the bottom edge portion and the direction perpendicular to the plate surface of the first plate portion may be 2 to 8°.

Advantages of the Invention

[0009] According to the present disclosure, it is possible to provide a hot press device capable of suppressing a decrease in the plate thickness and necking of the concave portion of a hot press-formed product formed by a die pad, a method for manufacturing a hot press-formed product using the device, and a hot press-formed product in which a decrease in the plate thickness and necking of the concave portion of the press-formed product are suppressed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

[0011] Hereinafter, embodiments of the present disclosure will be described with examples, but it is obvious that the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained. Also, each component of the following embodiments can be combined with each other.

[0012] First, with reference to FIG. 1, a hot press-formed product 100 obtained by the hot press apparatus and the method for manufacturing a hot press-formed product according to the present embodiment will be described.

[0013] [Hot Press-Formed Product] FIG. 1 is a perspective view of a hot press-formed product 100 and is a view including a cross-sectional view orthogonal to the longitudinal direction at the central position in the longitudinal direction of the long hot press-formed product 100. This cross-sectional view is also a cross-sectional view along the press direction P. As shown in FIG. 1, the hot press-formed product 100 according to the present embodiment is a long hot press-formed product 100, and includes a first plate portion 110 extending in the longitudinal direction of the hot press-formed product 100, a second plate portion 120 extending in the longitudinal direction of the hot press-formed product 100 and inclined with respect to the first plate portion 110, and a ridge line portion 130 that smoothly connects the first plate portion 110 and the second plate portion 120 and extends in the longitudinal direction of the hot press-formed product 100. The hot press-formed product 100 is a long member and has a longitudinal direction and a short direction orthogonal to the longitudinal direction. The longitudinal direction is the direction in which the long hot press-formed product 100 extends. In FIG. 1, the longitudinal direction of the hot press-formed product 100 is parallel to the Z-axis. The X-axis and Y-axis in FIG. 1 constitute a plane including the short direction of the hot press-formed product 100. The X-axis, Y-axis, and Z-axis in FIG. 1 are orthogonal to each other.

[0014] In the example of FIG. 1, the portion of the first plate portion 110 excluding the recess 140 is substantially flat and extends in the longitudinal direction of the hot press-formed product 100. The portion of the first plate portion 110 excluding the recess 140 has a first plate portion surface 110a and a first plate portion surface 110b on the side opposite to the first plate portion surface 110a. When the direction parallel to the longitudinal direction of the hot press-formed product 100 is defined as the length direction of the first plate portion 110, the first plate portion 110 extends in the length direction of the first plate portion 110.

[0015] The second plate portion 120 is a substantially flat plate-like portion that extends in the longitudinal direction of the hot press-formed product 100. The second plate portion 120 has a second plate portion plate surface 120a and a second plate portion plate surface 120b on the side opposite to the second plate portion plate surface 120a. When the direction parallel to the longitudinal direction of the hot press-formed product 100 is defined as the length direction of the second plate portion 120, the second plate portion 120 extends in the length direction of the second plate portion 120. When the direction orthogonal to the length direction and the plate thickness direction of the second plate portion 120 is defined as the width direction of the second plate portion 120, the second plate portion 120 extends in the width direction of the second plate portion 120. In the example of FIG. 1, the hot press-formed product 100 has a pair of second plate portions 120.

[0016] The ridge line portion 130 is a portion that smoothly connects the first plate portion 110 and the second plate portion 120 and extends in the longitudinal direction of the hot press-formed product 100. Since the second plate portion 120 is inclined with respect to the first plate portion 110, the ridge line portion 130 that connects them has a curved shape that curves so as to draw a curve in a cross-sectional view orthogonal to the longitudinal direction of the hot press-formed product 100. That the second plate portion 120 is inclined with respect to the first plate portion 110 means that the plate surfaces of the first plate portion 110 and the second plate portion 120 are not parallel. Also, the direction parallel to the longitudinal direction of the hot press-formed product 100 is defined as the length direction of the ridge line portion 130. The surface on the bending outer side of the ridge line portion 130 is defined as the ridge line outer surface 130a, and the surface on the bending inner side of the ridge line portion 130 is defined as the ridge line inner surface 130b. The first plate portion plate surface 110a and the second plate portion plate surface 120a are connected to the ridge line outer surface 130a, and the first plate portion plate surface 110b and the second plate portion plate surface 120b are connected to the ridge line inner surface 130b. One edge portion (first plate portion edge portion 110A) of the first plate portion 110 that extends in the longitudinal direction of the hot press-formed product 100 is connected to one edge portion (ridge line edge portion 130A) of the ridge line portion 130 that extends in the longitudinal direction of the hot press-formed product 100. One edge portion (second plate portion edge portion 120A) of the second plate portion 120 that extends in the longitudinal direction of the hot press-formed product 100 is connected to the other edge portion (ridge line edge portion 130B) of the ridge line portion 130 that extends in the longitudinal direction of the ridge line portion 130. In the example of FIG. 1, the hot press-formed product 100 has a pair of ridge line portions 130.

[0017] The first plate portion 110 is provided with a recess 140. When the direction parallel to the longitudinal direction of the hot press molded article 100 is defined as the length direction of the recess 140, the recess 140 extends in the length direction of the recess 140.

[0018] The recess 140 may pass through the central position in the longitudinal direction of the hot press molded article 100 and extend along the ridge line portion 130. The central position in the longitudinal direction of the hot press molded article 100 means a position included in the range of 20% of the longitudinal length of the hot press molded article 100 from the central position that bisects the longitudinal length of the hot press molded article 100. That the recess 140 extends along the ridge line portion 130 means that the recess 140 is arranged so as to be substantially parallel to a part of the adjacent ridge line portions 130.

[0019] In the second plate portion 120, a flange portion may be formed at the edge portion that extends in the longitudinal direction and is not connected to the ridge line portion 130. Note that the first plate portion 110, the second plate portion 120, or the flange portion may be provided with a hole portion, a notch, a welded portion, or the like. Further, the second plate portion 120 or the flange portion may be provided with a bead.

[0020] FIG. 2 shows a cut end face view of the hot press molded article 100 in a plane perpendicular to the longitudinal direction of the hot press molded article 100 shown in FIG. 1 in the longitudinal direction. The recess 140 is recessed in a direction perpendicular to the plate surface of the first plate portion 110 as described later. In the example of FIG. 2, the recess 140 is recessed toward the side where the second plate portion 120 is located with respect to the first plate portion 110 (the first plate portion plate surface 110b side).

[0021] In the example of FIG. 2, the recess 140 has a bottom portion 141, a pair of side portions 142, a bottom side ridge line portion 143, and a side side ridge line portion 144. The bottom portion 141 of the recess is connected to the respective side portions 142 via a pair of bottom side ridge line portions 143 at each end. Each side portion 142 is connected to the first plate portion 110 via a side side ridge line portion 144. The bottom portion 141, the side portions 142, the bottom side ridge line portion 143, and the side side ridge line portion 144 extend in the length direction of the recess 140.

[0022] The bottom 141 of the recess 140 has a bottom inner surface 141a located on the inner side of the recess 140 (the side of the side portion 142) and a bottom outer surface 141b on the side opposite to the bottom inner surface 141a. That is, the bottom inner surface 141a constitutes a part of the inner surface of the recess 140.

[0023] Fig. 3 shows an enlarged view of the vicinity of the recess 140 of the hot press molded product 100 in Fig. 2. In a plane orthogonal to the longitudinal direction of the hot press molded product 100, one of the boundaries between the first plate portion 110 and the recess 140 (the boundary between the first plate portion 110 and the side portion side ridge line portion 144) is defined as the boundary gb1, and the other boundary is defined as the boundary gb2. Here, as shown in Fig. 3, on the plane orthogonal to the longitudinal direction of the hot press molded product 100 in the longitudinal direction of the hot press molded product 100, the boundaries gb1 and gb2 are points on the plate surface on the bending outer side of the side portion side ridge line portion 144. In other words, these boundaries are also the R stops on the plate surface on the bending outer side of the side portion side ridge line portion 144.

[0024] In the example of the present embodiment, the recess 140 is a portion recessed on the side of the first plate portion 110 where the second plate portion 120 is located (the first plate portion plate surface 110b side). The recess 140 may be a portion recessed on the side of the first plate portion 110 opposite to the side where the second plate portion 120 is located (the first plate portion plate surface 110a side). That is, the recess provided in the first plate portion 110 may be recessed on the side of the ridge line outer surface 130a (the outside of the hot press molded product 100) or on the side of the ridge line inner surface 130b (the inside of the hot press molded product 100).

[0025] The distance between the boundary gb1 of the recess and the boundary gb2 of the recess in a plane orthogonal to the longitudinal direction of the hot press molded product 100 is defined as the width w of the recess 140. The width w of the recess 140 does not have to be constant in the longitudinal direction of the hot press molded product 100. The width w of the recess 140 is preferably 10 mm to 52 mm because it can enhance the compressive axial force performance in the direction along the Z coordinate axis shown in Fig. 1 and the moment bending performance around the direction along the X coordinate axis. The width w of the recess 140 is preferably smaller than the length of the recess 140 in the extending direction. In the direction in which the hot press-formed product 100, which is a long member, extends, the direction connecting the boundary gb1 between both ends of the hot press-formed product 100 is defined as the longitudinal direction.

[0026] [Press device] Next, a press device (hot press device) used in the method for manufacturing a hot press-formed product according to the present embodiment will be described.

[0027] FIG. 4 shows an example of a press device (hot press device) used in the method for manufacturing a hot press-formed product according to the present embodiment. The press device 1000 shown in FIG. 4 includes a first mold 1100, a second mold 1200, and a third mold 1300 as press molds. The first mold 1100 and the second mold 1200 are relatively movable with respect to each other in the press direction P. A workpiece (blank) is sandwiched between the first mold 1100 and the second mold 1200. The third mold 1300 is arranged adjacent to the first mold 1100 in the direction along the X coordinate axis and is relatively movable with respect to the first mold 1100 and the second mold 1200. In the example of the present embodiment, the third mold 1300 is relatively movable with respect to the first mold 1100 and the second mold 1200 in the press direction P. Further, a refrigerant flow path (not shown) is provided inside the second mold 1200 of the press device 1000. Here, the press direction P in the press device 1000 is the negative direction of the Y coordinate axis. The X coordinate axis, Y coordinate axis, and Z coordinate axis in FIG. 4 are orthogonal to each other.

[0028] The first mold 1100, the second mold 1200, and the third mold 1300 have a longitudinal direction in the direction along the Z coordinate axis. FIG. 5 shows a schematic cut end view of the press device 1000 in a sectional view along the Z coordinate axis at the section line A-A shown in FIG. 4. Note that the end views in FIGS. 5 to 8 are views in a cross section along the press direction P.

[0029] The first mold 1100 has a press surface 1110 and a convex portion 1120 provided on the press surface 1110. In the example of FIG. 5, the convex portion 1120 has a bottom surface portion 1121 and a pair of side surface portions 1122. The bottom surface portion 1121 is connected to the respective side surface portions 1122 via a pair of bottom surface side ridge line portions 1123 at each end. In the example of FIG. 5, the convex portion 1120 protrudes in the negative direction of the Y coordinate axis. Each side surface portion 1122 is connected to a holding surface portion 1130 of the press surface 1110 excluding the convex portion 1120 via a side surface side ridge line portion 1124. The bottom surface portion 1121, the side surface portions 1122, the bottom surface side ridge line portions 1123, and the side surface side ridge line portions 1124 extend in the direction in which the convex portion 1120 extends, that is, in the direction along the Z coordinate axis in FIG. 4.

[0030] The second mold 1200 has a press surface (top surface) 1210 and a groove portion (concave surface portion) 1220 provided on the press surface 1210. That is, there is a groove portion 1220 on the top surface of the second mold 1200. In the example of FIG. 5, the groove portion 1220 has a bottom surface portion 1221, a pair of side surface portions 1222, bottom surface side ridge line portions 1223, and side surface side ridge line portions 1224. The bottom surface portion 1221 is connected to the respective side surface portions 1222 via a pair of bottom surface side ridge line portions 1223 at each end. In the example of FIG. 5, the groove portion 1220 has a concave shape facing in the negative direction of the Y coordinate axis. Each side surface portion 1222 is connected to a holding surface portion 1230 of the press surface 1210 excluding the groove portion 1220 via a side surface side ridge line portion 1224. The bottom surface portion 1221, the side surface portions 1222, the bottom surface side ridge line portions 1223, and the side surface side ridge line portions 1224 have a certain length and extend in the direction in which the groove portion 1220 extends, that is, in the direction along the Z coordinate axis in FIG. 4. The second mold 1200 further includes a side wall portion 1250 connected to the holding surface portion 1230 via a shoulder surface portion 1240. The shoulder surface portion 1240 is a portion that smoothly connects the holding surface portion 1230 and the side wall portion 1250, and the shoulder surface portion 1240 and the side wall portion 1250 extend in the direction in which the press surface 1210 extends, that is, in the direction along the Z coordinate axis in FIG. 4.

[0031] The convex portion 1120 of the first mold 1100 and the groove portion 1220 of the second mold 1200 have corresponding surface shapes. By sandwiching the workpiece between the first mold 1100 and the second mold 1200, a concave portion 140 is formed in the workpiece. In other words, the convex portion 1120 has a shape obtained by inverting the groove portion 1220. Also, the holding surface portion 1130 of the first mold 1100 and the holding surface portion 1230 of the second mold 1200 are parallel to each other. In the example of this embodiment, the holding surface portion 1130 and the holding surface portion 1230 are perpendicular to the pressing direction P. In the first mold 1100, there is a convex portion 1120 at a position facing the groove portion 1220 in the pressing direction P. In a cross-section along the pressing direction P, the wall surface of the groove portion 1220 has an angle of 2 to 8° with respect to the pressing direction P. More specifically, in a cross-section along the pressing direction P, the angle formed by the straight line connecting the R stop of the side surface side ridge line portion 1224 located on the side surface portion 1222 side and the R stop of the bottom surface side ridge line portion 1223 located on the side surface portion 1222 side, and the pressing direction P is 2 to 8°. The cross-section along the pressing direction P is a plane passing through a point on the bottom surface portion 1221 where the depth of the groove portion 1220 of the second mold 1200 is the deepest in the entire groove portion 1220, and having the shortest cross-sectional line length of the groove portion 1220. The depth of the groove portion 1220 includes the shortest straight line connecting the boundaries between the pair of side surface side ridge line portions 1224 and the holding surface portion 1230, and on a virtual plane where the cross-sectional line length of the groove portion 1220 is the shortest when viewed in cross-section, it means the distance from this straight line to the bottom surface portion 1221 in a direction perpendicular to the straight line connecting these boundaries. The cross-sectional line length of the groove portion 1220 can be measured by creating a 3D model based on the three-dimensional shape measurement of the second mold 1200 and deriving the plane with the shortest cross-sectional line length. The radius of curvature of the bottom surface side ridge line portion 1223 is 3 mm to 30 mm. The radius of curvature of the side surface side ridge line portion 1224 is 3 mm to 30 mm. The radius of curvature of the side surface portion 1222 is greater than 30 mm, or the side surface portion 1222 is a plane. Even if the side surface portion 1222 is curved within such a radius of curvature range, the wall surface of the groove portion 1220 can be approximated by a straight line in the above cross-section, and the angle formed by the straight line connecting the above R stops and the pressing direction P can be defined.

[0032] The third mold 1300 has a press surface 1310. The press surface 1310 extends in the direction along the Z-axis of FIG. 4. The first mold 1100 and the third mold 1300 are arranged to face the second mold 1200 in the press direction P. The first mold 1100 is arranged to face the top surface of the second mold 1200.

[0033] Also, the third mold 1300 is connected to the slide plate 1400. Also, the first mold 1100 is connected to the slide plate 1400 via a support portion 1410 (spring or piston). As the slide plate 1400 moves, the third mold 1300 moves. As the slide plate 1400 moves, the first mold 1100 moves via the support portion 1410. The press device 1000 may be provided with drive portions (not shown) capable of independently driving the first mold 1100, the second mold 1200, and the third mold 1300, respectively. Also, any one of the first mold 1100, the second mold 1200, and the third mold 1300 may be fixed to the press device 1000.

[0034] Here, in the embodiment of the present application, the first mold 1100 is a die pad, the second mold 1200 is a punch, and the third mold 1300 is a die.

[0035] [Method for manufacturing a hot press molded product] The method for manufacturing a hot press molded product according to this embodiment is a method for manufacturing a hot press molded product in which a work material is hot pressed to form a press molded product including a first plate portion in which a recess is formed. In the method for manufacturing a hot press molded product according to this embodiment, first, as shown in FIG. 6, the work material (blank) 1 is placed between the first mold 1100 and the second mold 1200. In the example of FIG. 6, the first mold 1100 is located above the second mold 1200 in the vertical direction, and the work material 1 is placed on the holding surface portion 1230 of the second mold 1200.

[0036] In the method for manufacturing a hot press-formed product according to this embodiment, the temperature of the workpiece 1 at the start of press forming may be 600 to 800°C. Thereby, by the above-described hot press apparatus, an effect that the part can be formed while the deformation resistance is low during hot working can be obtained.

[0037] Next, the first mold 1100 and the second mold 1200 are relatively moved in the press direction P (vertically downward) and brought closer to each other. At this time, the third mold 1300 may move together with the first mold 1100, or the third mold 1300 may not move. Thereby, the portion corresponding to the first plate portion 110 in the hot press-formed product 100 of the workpiece 1 is sandwiched between the first mold 1100 and the second mold 1200.

[0038] Next, from the state where the convex portion 1120 of the first mold 1100 is in contact with the workpiece 1, the first mold 1100 is further moved in the press direction P. Thereby, as shown in FIG. 7, the workpiece 1 is sandwiched between the first mold 1100 and the second mold 1200, and a concave portion 140 is formed between the convex portion 1120 of the first mold 1100 and the groove portion 1220 of the second mold 1200.

[0039] In the method for manufacturing a hot press-formed product according to this embodiment, the pressing force when forming the concave portion 140 by the first mold 1100 and the second mold 1200 may be 0.4 to 22.0 MPa. More preferably, this pressing force may be 0.4 to 4.4 MPa. Thereby, an effect that the workpiece can be formed while the deformation resistance of the workpiece is low, and further the forming load of the first mold 1100 can be set to the minimum load force, and the mold cost can be reduced is obtained.

[0040] Thereafter, the third mold 1300 is further moved to the bottom dead center. As shown in FIG. 8, the workpiece 1 is sandwiched between the second mold 1200 and the third mold 1300, and a second plate portion 120 is formed between the second mold 1200 and the third mold 1300, and the press forming is completed. At this point, the hot press-formed product 100 is formed with a first plate portion 110, a second plate portion 120, a ridge line portion 130, and a concave portion 140. Further, a flange portion may be formed between the second mold 1200 and the third mold 1300.

[0041] From the viewpoint of formability, the first mold 1100 may reach the bottom dead center before the third mold 1300 reaches the bottom dead center, or the first mold 1100 may reach the bottom dead center simultaneously with the third mold 1300 reaching the bottom dead center.

[0042] FIG. 9 illustrates a hot press apparatus used in a method for manufacturing a hot press formed product according to another embodiment of the present disclosure. FIG. 9 is a schematic cut end face view of the press apparatus in a direction along the Z-axis in a cross-sectional line A-A as shown in FIG. 4, similar to FIG. 5. Note that the cut end face views in FIGS. 9 to 11 are views in a cross-section along the press direction P. The press apparatus 1000 shown in FIG. 9 has the same configuration as the press apparatus 1000 shown in FIG. 5 etc., except that it includes a step portion 1320, and thus the description thereof is omitted here. That is, the configuration of the press apparatus 1000 according to FIGS. 4 to 8 described above can be applied to the press apparatus 1000 shown in FIG. 9. The step portion 1320 may extend in a direction along the Z-axis. In the example of FIG. 9, two third molds 1300 are shown in the X-axis direction. These two third molds 1300 may be connected to each other in the X-axis direction.

[0043] FIG. 10 shows a state where a workpiece is sandwiched between the molds and the third mold 1300 is moved to the bottom dead center. As shown in FIG. 10, the workpiece is sandwiched between the second mold 1200 and the third mold 1300, a second plate portion 120 is formed between the second mold 1200 and the third mold 1300, and the press forming is completed. At this point, a first plate portion 110, a second plate portion 120, a ridge line portion 130, and a concave portion 140 are formed in the hot press formed product 100. Since the third mold 1300 includes the step portion 1320, at the forming bottom dead center, the first mold 1100 is in contact with the third mold 1300 in the press direction P. Thereby, even when the pressing force of the first mold 1100 is insufficient, it is possible to suppress necking. At this time, the support portion 1410 is deformed so as to contract in the press direction P.

[0044] Also, another form of the press device 1000 is shown in FIG. 11. Similar to FIG. 5 and the like, the press device 1000 in FIG. 11 is a schematic cut end face view of the press device in a sectional view along the Z-axis direction at the section line A-A as shown in FIG. 4. In the press device 1000 shown in FIG. 11, the third mold 1300 is provided only on one side. Further, the third mold 1300 is provided with a stepped portion 1320. Also, the first mold 1100 has a press surface 1140 on the side opposite to the third mold 1300 in the X-axis direction. The press surface 1140 is provided so as to be connected to the press surface 1110 of the first mold 1100. The press surface 1140 extends in the direction along the Z-axis.

[0045] The press device 1000 shown in FIG. 11 has the same configuration as the press device 1000 shown in FIG. 9 except that the third mold 1300 is provided only on one side, so the description is omitted here. That is, the configuration of the press device 1000 according to FIG. 9 can be applied to the press device 1000 shown in FIG. 11. In the press device 1000 of FIG. 11, since the area for arranging the pressurizing mechanism of the third mold 1300 on the upper side of the press device 1000 can be increased, there is an advantage that the press load design can be made more flexible.

[0046] In the method for manufacturing a hot press-formed product according to the present embodiment, the press forming may be performed such that the ratio of the area of the recess 140 to the area of the first plate portion 110 is 30% or more when viewed in a plan view in a direction perpendicular to the plate surface of the first plate portion 110. The direction perpendicular to the plate surface of the first plate portion 110 means a direction including the shortest straight line connecting the boundary gb1 and the boundary gb2 and perpendicular to the straight line connecting the boundary gb1 and the boundary gb2 on a virtual plane where the cross-sectional line length of the recess 140 is the shortest when viewed in a sectional view. The cross-sectional line length of the recess 140 can be measured by creating a 3D model based on the three-dimensional shape measurement of the hot press-formed product 100 and deriving the plane with the shortest cross-sectional line length. The three-dimensional shape measurement described in the present embodiment can be measured using a 3D scanner such as Atos (manufactured by GOM). The definition of the area of the first plate portion 110 and the area of the concave portion 140 will be as described later.

[0047] In the method for manufacturing a hot press-formed product according to the present embodiment, the press forming may be performed such that the maximum depth dmax of the depth d of the concave portion 140 in the press direction P is 15 mm or more. The depth d of the concave portion 140 means the depth in the press direction P. The press direction P is a direction perpendicular to the plate surface of the first plate portion 110. The maximum depth dmax means the maximum value of the depth d of the concave portion 140 over the entire concave portion 140. By the maximum depth dmax being 15 mm or more, an effect can be obtained in which the compressive axial force performance in the direction along the Z coordinate axis shown in FIG. 1 and the like and the moment bending performance around the direction along the X coordinate axis are enhanced. The depth of the concave portion 140 means the distance from the straight line in the direction perpendicular to the plate surface of the first plate portion 110 described above to the inner surface 141a of the bottom. More preferably, the maximum depth dmax is 20 mm or more for the reason of further improving the axial force and bending moment performance. More preferably, from the viewpoint of suppressing the deterioration of productivity due to an increase in the press stroke caused by an increase in the stroke of the pad, the upper limit of the maximum depth dmax is preferably 50 mm.

[0048] In the method for manufacturing a hot press-formed article according to the present embodiment, when forming the recess 140, in the plane passing through the point pd where the depth d of the recess 140 is the deepest, among the planes in which the cross-sectional line length of the recess 140 is the shortest (the cross-section cut in the press direction), the press is performed such that the angle α formed by the side portion 142 of the recess 140 and the press direction P is 2 to 8°. More specifically, among the planes passing through the point pd where the depth d of the recess 140 is the deepest, in the plane in which the cross-sectional line length of the recess 140 is the shortest, the press is performed such that the angle formed by the straight line connecting the R stop of the side portion side ridge line portion 144 located on the side portion 142 side and the R stop of the bottom side ridge line portion 143 located on the side portion 142 side and the press direction P is 2 to 8°. Note that the plane passing through the point pd where the depth d of the recess 140 is the deepest and in which the cross-sectional line length of the recess 140 is the shortest is parallel to the press direction P. The point pd where the depth d of the recess 140 is the deepest is the point where the depth d of the recess 140 is the maximum depth dmax over the entire recess 140. The radius of curvature of the bottom side ridge line portion 143 is 3 mm to 30 mm. The radius of curvature of the side portion side ridge line portion 144 is 3 mm to 30 mm. The radius of curvature of the side portion 142 is greater than 30 mm, or the side portion 142 is a flat surface. Even if the side portion 142 is curved within such a range of the radius of curvature, in the above cross-section, the side portion 142 can be approximated by a straight line, and the angle formed by the straight line connecting the R stops as described above and the press direction P can be defined.

[0049] Fig. 12 shows an end face view of a cut portion in a cross-sectional view in the plane in which the cross-sectional line length of the recess 140 is the shortest among the planes passing through the point pd where the depth d of the recess 140 is the deepest. Fig. 12 shows the hot press-formed article 100 after the hot press forming is completed and placed on the press device 1000, and is an enlarged view of the vicinity of the recess 140 of the hot press-formed article 100. As shown in Fig. 12, the cross-sectional line length of the recess 140 means the line length along the inner surface of the recess 140 from the boundary gb1 to the boundary gb2 in the plane including the shortest straight line connecting the boundary gb1 and the boundary gb2. The cross-section defining the curve C corresponding to the shape of the recess 140 is the plane in which the cross-sectional line length of the recess 140 is the shortest among the planes passing through the point pd.

[0050] The curve C corresponds to the shape of the inner surface of the recess 140 in this cross-section. The curve C has points iP1 and iP2, which are one of the end points of the side portion 142, between the boundary gb1 or the boundary gb2 and the point pd. The points iP1 and iP2 are also the R stops of the side portion side ridge line portion 144. In this cross-section, by pressing such that the angle α formed by the side portion 142 of the recess 140 and the pressing direction P is 2 to 8°, the processing of the recess 140 formed by the first die 1100 can be formed to a forming height closer to the bottom dead center, and a reduction in the plate thickness of the recess and necking can be suppressed. When the angle α is 2° or more, there is an effect that it is easy to release the mold after press forming. Also, when the angle α is 8° or less, when forming with the first die 1100, the portion of the workpiece 1 that is not in contact with the first die 1100 or the second die 1200 can be reduced, and the portion where cooling does not progress can be reduced. When there are few portions where cooling does not progress, local reduction in the plate thickness during the forming of the workpiece 1 does not lead to necking, so there is an effect that a part without excessive reduction in plate thickness or necking can be formed.

[0051] As illustrated in FIG. 12, when the side portion 142 of the recess 140 is flat, the inclination of the side portion 142 coincides with the inclination of the tangent line ti1 or the inclination of ti2. Further, the inclination of the tangent line ti1 or the inclination of ti2 coincides with the inclination of the straight line connecting the R stop of the side portion side ridge line portion 144 located on the side portion 142 side and the R stop of the bottom portion side ridge line portion 143 located on the side portion 142 side. In the example of FIG. 12 and the like, the side portions 142 are drawn to have the same inclination with respect to the pressing direction P, but the two side portions 142 may have different angles with respect to the pressing direction P as long as the angle requirements with respect to the pressing direction P are satisfied.

[0052] In the hot press-formed product 100 obtained by the manufacturing method described above, the ratio of the area of the recess 140 to the area of the first plate portion 110 may be 30% or more when viewed in a plan view in a direction perpendicular to the plate surface of the first plate portion 110. The area of the first plate portion 110 is the area of the portion including the recess 140 and excluding the second plate portion 120 and the ridge line portion 130 between the second plate portions 120.

[0053] The area of the recess 140 is the area from the boundary gb1 to the boundary gb2 when viewed in a plan view in a direction perpendicular to the plate surface of the first plate portion 110. When the area of the recess 140 with respect to the area of the first plate portion 110 is 30% or more when viewed in a plan view in a direction perpendicular to the plate surface of the first plate portion 110, an effect that the compressive axial force performance in the direction along the Z coordinate axis shown in FIG. 1 and the like and the moment bending performance around the direction along the X coordinate axis can be enhanced is obtained. More preferably, the area of the recess 140 with respect to the area of the first plate portion 110 is 50% or more because the axial force and the bending moment performance can be further improved. The area of the first plate portion 110 is the area of the range surrounded by the boundary between the ridge line portion 130 and the first plate portion 110 and the longitudinal end portion of the first plate portion 110 in a plan view in a direction perpendicular to the plate surface of the first plate portion 110. The boundary between the first plate portion 110 and the ridge line portion 130 can be specified by creating a 3D model based on the three-dimensional shape measurement of the hot press molded product 100 and detecting the boundary between the first plate portion 110 and the ridge line portion 130 from this 3D model. Similarly, the area of the recess 140 is the area of the range on the recess 140 side surrounded by the boundary between the side portion side ridge line portion 144 and the first plate portion 110. The boundary between the first plate portion 110 and the side portion side ridge line portion 144 can also be specified by creating a 3D model based on the three-dimensional shape measurement of the hot press molded product 100 and detecting the boundary between the first plate portion 110 and the side portion side ridge line portion 144 from this 3D model.

[0054] In the hot press molded product 100 according to the present embodiment, in a direction perpendicular to the plate surface of the first plate portion 110, the maximum depth dmax of the recess 140 may be 15 mm or more. When the maximum depth dmax is 15 mm or more, an effect that the compressive axial force performance in the direction along the Z coordinate axis shown in FIG. 1 and the like and the moment bending performance around the direction along the X coordinate axis can be enhanced is obtained. More preferably, the maximum depth dmax is 20 mm or more because the axial force and the bending moment performance can be further improved.

[0055] The depth d of the recess 140 means the distance from the straight line connecting the boundary gb1 and the boundary gb2 to the inner surface 141a of the bottom on a virtual plane that includes the shortest straight line connecting the boundary gb1 and the boundary gb2 and on which the sectional line length of the recess 140 is the shortest when viewed in cross section, in a direction orthogonal to the straight line connecting the boundary gb1 and the boundary gb2.

[0056] In the hot press-formed product 100 obtained by the above-described manufacturing method, in a cross-sectional view in a plane passing through the point pd where the depth d of the recess 140 is the deepest and where the sectional line length of the recess 140 is the shortest, the angle formed by the side portion 142 of the recess 140 and the direction perpendicular to the plate surface of the first plate portion 110 is 2 to 8°. Also, the plate thickness at the location where the plate thickness is the smallest in the recess 140 is 60% or more of the plate thickness at the portion of the first plate portion 110 excluding the recess 140. Here, the plate thickness of the portion excluding the recess 140 means the average value of the plate thicknesses of any three points at the portion of the first plate portion 110 excluding the recess 140. The plane passing through the point pd where the depth d of the recess 140 is the deepest and where the sectional line length of the recess 140 is the shortest is orthogonal to the plate surface of the first plate portion 110. According to the above-described manufacturing method, since a decrease in the plate thickness of the recess can be suppressed, in the hot press-formed product 100, the plate thickness at the location where the plate thickness is the smallest in the recess 140 can be made 60% or more of the plate thickness of the portion of the first plate portion 110 excluding the recess 140.

[0057] In the hot press-formed product 100 according to the present embodiment, deformation occurs in a direction orthogonal to the longitudinal direction of the hot press-formed product 100 or when a load equal to or greater than a certain level is applied in the longitudinal direction of the hot press-formed product 100. At this time, a tensile force or a compressive force is applied in a direction orthogonal to the extending direction of the recess 140. In the hot press-formed product 100 according to the present embodiment, since the plate thickness at the location where the plate thickness is the smallest in the recess 140 is 60% or more of the plate thickness of the portion of the first plate portion 110 excluding the recess 140, the axial force and bending moment performance of the member generated by the recess 140 can be enhanced.

[0058] The plate thicknesses of the first plate portion 110 and the concave portion 140 are measured by creating a 3D model based on the three-dimensional shape measurement of the hot press-formed product 100 as described above, and detecting the plate thickness from this 3D model.

[0059] In the hot press-formed product according to the present embodiment, the average plate thickness t1 of the first plate portion 110 may be 0.8 to 2.6 mm. The plate thickness of the workpiece 1 is measured at three or more locations from the 3D model, and the arithmetic mean value of the measured values of the plate thicknesses at these locations is taken as the average plate thickness t1 of the workpiece 1. The average plate thickness t1 of the first plate portion 110 is determined by the following method. At the central position in the longitudinal direction of the hot press-formed product 100, in a plane orthogonal to the longitudinal direction of the hot press-formed product 100, the plate thickness at an arbitrary position of the first plate portion 110 excluding the concave portion 140 is measured at three or more locations from the 3D model. The arithmetic mean value of the measured values of the plate thicknesses at these locations is taken as the average plate thickness t1.

[0060] In the manufacturing method of the hot press-formed product according to the present embodiment, the average plate thickness t of the workpiece 1 may be 0.8 to 2.6 mm. The plate thickness of the workpiece 1 is measured at three or more locations from the 3D model, and the arithmetic mean value of the measured values of the plate thicknesses at these locations is taken as the average plate thickness t of the workpiece 1.

[0061] The convex portion 1120 of the first mold 1100 used in the manufacturing method of the hot press-formed product according to the present embodiment may have a maximum distance in the pressing direction from the press surface 1110 to the convex portion 1120 of 15 mm or more. In the first mold 1100 used in the manufacturing method of the hot press-formed product according to the present embodiment, the pressing direction intersects the press surface 1110. Here, the maximum distance in the pressing direction from the press surface 1110 to the convex portion 1120 means the maximum distance in the pressing direction from the holding surface portion 1130 to the convex portion 1120.

[0062] Also, in a cross-sectional view in a plane passing through the point where the distance from the press surface 1110 of the first mold 1100 to the convex portion 1120 is the longest and where the cross-sectional line length of the convex portion 1120 is the shortest, on the curve corresponding to the surface shape of the convex portion 1120, the side surface portion 1222 of the groove portion 1220 of the second mold 1200 has an angle of 2 to 8° with respect to the press direction.

[0063] The press mold or press device used in the method for manufacturing a hot press-formed product according to the present disclosure is not limited to the above-described configuration, and various modifications can be applied as long as it has a configuration capable of performing the above-described press forming. For example, as one embodiment, as shown in FIG. 13, the press device 2000 may further include a fourth mold 2400. FIG. 13 is a schematic cutaway end view of the press device 2000 in a cross-sectional view in a direction along the longitudinal direction of the first mold 2100, similar to FIG. 5. The configurations of the first mold 2100, the second mold 2200, and the third mold 2300 are as described above. The fourth mold 2400 is processed while sandwiching the second plate portion 120 and the flange portion connected to the second plate portion 120 together with the third mold 2300 during press forming. By further providing the fourth mold 2400, there is an effect that the generation of wrinkles generated in the flange portion can be suppressed. Further, the third mold 2300 is connected to the slide plate 1400. Also, the first mold 2100 is connected to the slide plate 1400 via a support portion 1410 (spring or piston).

[0064] In the hot press-formed product 100 according to the present disclosure, as one embodiment, as illustrated in FIG. 14, in a longitudinal cross-sectional view of the hot press-formed product 200, a recess 250 shallower than the recess 240 may be further provided in the first plate portion 210. Thereby, there is an effect that the compressive axial force performance in the direction along the Z coordinate axis shown in FIG. 1 and the moment bending performance around the direction along the X coordinate axis can be enhanced.

[0065] In addition, in the above-described embodiment, the hot press-formed product 100 including two second plate portions 120 has been described as an example, but the hot press-formed product according to the present disclosure may include the second plate portion 120 only on one side of the first plate portion 110.

[0066] In addition, in the above-described embodiment, the hot press-formed article 100 including the second plate portion 120 connected to the first plate portion 110 via the ridge line portion 130 has been described. However, the hot press-formed article according to the present disclosure may not include the second plate portion or the ridge line portion. That is, even a hot press-formed article 100 composed of the first plate portion 110 provided with the concave portion 140 can obtain the effect of the present disclosure that the reduction in the plate thickness and necking of the concave portion 140 are suppressed.

[0067] The hot press-formed article 100 according to the above-described embodiment is preferably a long member. That is, when viewed in a plan view in a direction perpendicular to the plate surface of the first plate portion 110, it is preferable that the size in the longitudinal direction of the first plate portion 110 is larger than the size in the short-side direction. Further, the size in the longitudinal direction and the size in the short-side direction of the first plate portion 110 may be the same. The concave portion 140 may be provided along the longitudinal direction of the first plate portion 110, and a part of the concave portion 140 may be provided along the short-side direction of the first plate portion 110. Alternatively, a part of the concave portion 140 may extend in a direction intersecting the longitudinal direction or the short-side direction of the first plate portion 110.

[0068] The hot press-formed product 100 according to the above embodiment has a tensile strength of 1470 MPa or more. By setting the tensile strength of the hot press-formed product 100 to 1470 MPa or more, a certain yield stress can be ensured and strain can be suppressed. The tensile strength of the hot press-formed product 100 is more preferably 2000 MPa or more because it has a higher yield stress. The tensile strength of the hot press-formed product 100 is determined as follows. Specifically, a sample having a size conforming to any of the JIS No. 5 tensile test, JIS 13B tensile test, or JIS 14B tensile test is obtained from the first plate portion 110 or the second plate portion 120 of the hot press-formed product 100, and the tensile strength of this sample is measured using a universal testing machine or a hydraulic servo type strength testing machine by a method conforming to JIS Z 2241, and this tensile strength is taken as the tensile strength of the hot press-formed product 100. When a test piece specified by JIS cannot be taken, a micro tensile test piece may be used as a sample. In the micro tensile test, the width and thickness of the parallel portion are preferably 0.2 to 2.0 mm, and a test piece shape in which a uniform load is applied within the parallel portion of the tensile test is preferred. For test piece processing, wire cut electrical discharge machining is preferred. As the micro tensile test piece, for example, the test piece on pages 461 - 465 of Vol. 75 (2006), No. 6 of the Transactions of the Welding Research Institute (https: / / www.jstage.jst.go.jp / article / jjws / 75 / 6 / 75_6_461 / _pdf / -char / ja) can be adopted.

[0069] In the hot press-formed product 100 according to the above embodiment, it is more preferably that the length in the longitudinal direction is 700 to 1700 mm, and it is more preferably that the length in the width direction of the first plate portion 110 (the length from the first plate portion edge 110A to the other edge) is 30 to 200 mm. Also, in the hot press-formed product 100 according to the above embodiment, it is more preferably that the length in the width direction of the second plate portion 120 is 30 to 200 mm.

[0070] In the hot press-formed product according to the above embodiment, the concave portion may have a V-shaped cross-sectional shape including a curve in a part as shown in FIG. 15, or a cross-sectional shape composed of a curve as shown in FIG. 16.

[0071] Further, as illustrated in FIG. 15, the recess 340 of the hot press-formed product 300 may have a bottom portion 341 with a curved cross-section and a pair of side portions 342. The bottom portion 341 is connected to the side portions 342, and each side portion 342 is connected to the first plate portion 310 via a side portion side ridge line portion 344. The first plate portion 310 has a first plate portion plate surface 310a and a first plate portion plate surface 310b on the side opposite to the first plate portion plate surface 310a. The bottom portion 341 has a bottom inner surface 341a located inside the recess 340 and a bottom outer surface 341b on the side opposite to the bottom inner surface. In a plane orthogonal to the longitudinal direction of the hot press-formed product 300, one of the boundaries between the first plate portion 310 and the recess 340 (the boundary between the first plate portion 310 and the side portion side ridge line portion 344) is defined as boundary gb1, and the other boundary is defined as boundary gb2. On a plane orthogonal to the longitudinal direction of the hot press-formed product 300, the boundaries gb1 and gb2 are points on the plate surface on the outer side of the bend of the side portion side ridge line portion 344. The distance between the boundary gb1 and the boundary gb2 in a plane orthogonal to the longitudinal direction of the hot press-formed product 300 is defined as the width of the recess 340. Note that, even in the case of the shape shown in FIG. 15, the definition of the curve corresponding to the shape of the recess is the same as in the above-described embodiment.

[0072] In the example of FIG. 16, the recess 440 does not have flat side portions as illustrated in FIG. 3, and is formed of a curve corresponding to the shape of the inner surface of the recess 440. The curve is composed of a curve portion 441 and a curve portion 442, and the intersection point of the curve portion 441 and the curve portion 442 is point ip.

[0073] The shape of the first plate portion of the recess of the press-formed product according to the present disclosure is not particularly limited in plan view. FIGS. 17 to 23 illustrate modified examples of the recess provided in the first plate portion. In FIGS. 17 to 23, only the shape of the recess provided in the first plate portion is schematically shown.

[0074] The press-formed product according to the above-described embodiment is preferably used as a hot press-formed product for vehicles such as a front bumper reinforcement, a rear bumper reinforcement, a side sill outer, a side sill inner, a door impact beam, a front side member, and a rear side member.

Example

[0075] (Example 1) In Example 1, a three-point bending test was performed on a hot press-formed product having a shape with three recesses as shown in FIG. 14 in simulation. The thickness of the workpiece was 1.2 mm, and the tensile strength of the workpiece was on the order of 2000 MPa. The conditions for the simulation of the three-point bending test were three-point bending in which the center of the member was statically pressed down, and the thickness of the central recess of the member was the thickness obtained from the forming simulation. In this example, the span of the receiving jig for three-point bending was set to 1000 mm.

[0076] The area ratio of the recesses was 40%, the maximum depth was 15 mm, the width was 35 mm, and the angle formed by the side portion of the recess and the pressing direction during press forming was changed as shown in Table 1. Also, the thickness reduction rate and component performance (yield strength) in the recesses were investigated. The results are shown in Table 1. Here, based on the arithmetic mean ta of the thicknesses of any three points in the portion of the first plate part excluding the recesses and the thickness tmin of the thinnest part in the recesses, (ta - tmin) / ta is defined as the thickness reduction rate in the recesses. The thickness reduction rate in the recesses can be calculated by dividing the reduced thickness at the portion where the thickness is most reduced in the recesses by the thickness of the first plate part in simulation. The yield strength of the member for evaluating the member performance was calculated from the simulation results of the three-point bending test. Here, the yield strength is the value obtained by dividing the load received by the impactor pressing down in the three-point bending test by the weight, and this is evaluated as the component performance. Also, the load in Table 1 is the load received by the impactor from the test piece, and the weight is the weight of the hot press-formed product.

[0077] [Table 1]

[0078] In addition, Fig. 24 shows the results of this simulation. According to Fig. 24, it was confirmed that the reduction rate of the plate thickness can be suppressed by setting the angle of the side portion of the concave portion to 8° or less with respect to the pressing direction. Also, it was found that a high component performance of 7.96 kN / kg or more, which is the target component performance, can be achieved when the angle of the side portion of the concave portion is in the range of 2° to 8° with respect to the pressing direction. Further, it was also found that when the angle of the side portion of the concave portion is 2° or more with respect to the pressing direction, it is easier to release the press-formed product from the mold. From these results, those with good comprehensive component performance judgment were rated as B (Good), and the others were rated as C (Bad). In the press-formed products according to Examples 1 to 3, the angle formed by the side portion of the concave portion and the direction perpendicular to the plate surface of the first plate portion was the same value as the angle formed by the side portion of the concave portion and the pressing direction. In Examples 1 to 3, the definition of the angle of the side portion of the concave portion with respect to the pressing direction shall be as described in the above embodiment.

[0079] (Example 2) In Example 2, a three-point bending test was conducted on a hot press-formed product having a shape with one concave portion as shown in Fig. 1 etc. in simulation. The plate thickness of the workpiece was 2.01 mm, and the tensile strength of the workpiece was on the order of 2000 MPa. The conditions for the simulation of the three-point bending test were three-point bending with static pressing at the center of the member, and the plate thickness at the central concave portion of the member was the plate thickness obtained from the forming simulation. In this example, the span of the receiving jig for the three-point bending was set to 1000 mm.

[0080] The area ratio of the concave portion was 35%, the maximum depth was 20 mm, and the width was 35 mm. The angle formed by the side portion of the concave portion and the pressing direction during press forming was changed as shown in Table 2, and the reduction rate of the plate thickness and the component performance (yield strength) in the concave portion were examined. The results are shown in Table 2. Here, the definition and calculation method of the reduction rate of the plate thickness and the component performance in the concave portion are the same as those in Example 1. Also, the definition of the load etc. in Table 2 is the same as that in Table 1.

[0081]

Table 2

[0082] Also, Fig. 25 shows the results of this simulation. According to Fig. 25, it was confirmed that the reduction rate of the plate thickness can be suppressed by setting the angle of the side part of the concave part to 8° or less with respect to the pressing direction. Also, it was found that a high component performance of 7.50 kN / kg or more, which is the target component performance, can be exhibited when the angle of the side part of the concave part is in the range of 2° to 8° with respect to the pressing direction. Further, it was also found that the press-formed product can be easily released from the mold when the angle of the side part of the concave part is 2° or more with respect to the pressing direction. From these results, those with good comprehensive component performance judgment were rated as B (Good), and the others were rated as C (Bad).

[0083] (Example 3) As shown in Table 3, the thickness of the workpiece, the number of concave parts, the tensile strength of the workpiece, and the pad pressure (pressing force of the first mold) during forming were changed, and a three-point bending test of the specimen was performed on the simulation, and a comprehensive evaluation was made from the member endurance performance and the mold cost. The cross-sectional dimensions were set such that the height of the second plate part was 65 mm and the width of the first plate part was 100 mm, the width of the concave part was 40 mm, and the depth was 23 mm. The angle of the side part of the concave part was set to 5° with respect to the pressing direction. When the number of concave parts in the first plate part was one, it was arranged at the center in the width direction, and when there were two, a shallow groove with a depth of 8 mm was provided between the central concave part in the width direction and the second plate part. The results are shown in Table 3. In this example, the span of the three-point bending receiving jig was set to 1300 mm.

[0084]

Table 3

[0085] In Table 3, in the evaluation criteria for die costs, the condition where the pad pressure is 10.0 MPa or less was set as A (Very Good), and the condition where the pad pressure exceeds 10.0 MPa and is 50.0 MPa or less was set as B (Good). Also, in the comprehensive evaluation, for those where the member strength performance evaluation result is 6.6 kN / kg or more and the die cost meets the B condition, or even if the member strength performance evaluation result is less than 6.6 kN / kg but the die cost meets the A condition, it was set as A (Very Good), and for those where the member strength performance evaluation result is less than 6.6 kN / kg and the die cost meets the B condition, it was set as B (Good).

Industrial Applicability

[0086] According to the present disclosure, it is possible to provide a hot press device capable of suppressing a decrease in the plate thickness and necking of the concave portion of a hot press-formed product formed by a die pad, a method for manufacturing a hot press-formed product using the device, and a hot press-formed product in which a decrease in the plate thickness and necking of the concave portion of the press-formed product are suppressed. Therefore, it is extremely useful industrially.

Explanation of Reference Numerals

[0087] 100 Hot press-formed product 110 First plate portion 120 Second plate portion 130 Ridge line portion 140 Concave portion 141 Bottom portion 142 Side portion 143 Bottom-side ridge line portion 144 Side-side ridge line portion 1000 Press device 1100 First die (die pad) 1200 Second die (punch) 1300 Third die (die)

Claims

1. A hot forging press apparatus comprising a punch, a die, and a die pad, wherein a groove portion is formed on the top surface of the punch, in a cross section along the pressing direction, the angle formed between the wall surface of the groove portion and the pressing direction is 2 to 8°, a refrigerant flow path is provided inside the punch, the die and the die pad are arranged to face the punch in the pressing direction, the die pad is arranged to face the top surface of the punch, a convex portion is provided on the die pad at a position facing the groove portion in the pressing direction, and the convex portion has a shape that is the reverse of the groove portion. The hot forging press apparatus is characterized by the above.

2. The die has a stepped portion that contacts the die pad in the pressing direction, at the forming bottom dead center, the die pad is in contact with the die in the pressing direction. The hot forging press apparatus according to claim 1, characterized by the above.

3. In the cross section, the angle formed between the straight line connecting the R stop of the side surface side ridge line portion and the R stop of the bottom surface side ridge line portion of the wall surface of the groove portion and the pressing direction is 2 to 8°. The hot forging press apparatus according to claim 1, characterized by the above.

4. A method for manufacturing a hot forging formed product using the hot forging press apparatus according to any one of claims 1 to 3, comprising arranging a blank between the die and the punch, clamping the blank with the punch and the die pad, and bringing the punch and the die closer to each other in the pressing direction to the forming bottom dead center. The method for manufacturing a hot forging formed product is characterized by the above.

5. A press formed product comprising a first plate portion with a recess formed therein and a second plate portion inclined with respect to the first plate portion, in a cross-sectional view in a plane where the cross-sectional line length of the recess is the shortest among the planes passing through the point where the depth of the recess is the deepest, the angle formed between the side portion of the recess and the direction perpendicular to the plate surface of the first plate portion is 2 to 8°, the plate thickness at the location where the plate thickness is the smallest in the recess is 60% or more of the plate thickness of the portion of the first plate portion excluding the recess. The hot forging formed product is characterized by the above.

6. In the cross-sectional view, the angle formed between the straight line connecting the R stop of the side surface side ridge line portion and the R stop of the bottom surface side ridge line portion of the side portion of the recess and the direction perpendicular to the plate surface of the first plate portion is 2 to 8°. The hot forging formed product according to claim 5, characterized by the above.

Images