Method for manufacturing molds and hot press molded products

Abstract

A mold is provided capable of manufacturing a hot press molded product having excellent shock absorption capacity by hot press molding. The mold (10) according to the present disclosure comprises an upper mold (11) having a first molding surface (110) and a lower mold (12) having a second molding surface (120). The first molding surface (110) includes a first cooling area (113) having a plurality of first rib portions (111) and a plurality of first groove portions (112). The width of the first rib portion (111) is narrower than the width of the first groove portion (112). The second molding surface (120) includes a second cooling area (123) having a plurality of second rib portions (121) and a plurality of second groove portions (122). The width of the second rib portion (121) is narrower than the width of the second groove portion (122). In the case of hot press forming, when viewed from the normal direction of the first full cooling area (113) and the second full cooling area (123), the first rib portion (111) and the second rib portion (121) overlap at least partially.

Description

Technology Field

[0001] The present disclosure relates to a mold and a method for manufacturing a hot press formed article using the mold. Background Technology

[0002] In the automotive industry, lightweighting of the vehicle body is required to improve fuel efficiency. Furthermore, improved crash safety is also required to protect occupants during a collision. Thinning the structural members used in the vehicle body is an effective method for lightweighting the body. To achieve improved crash safety while thinning structural members, high strength is required for the materials applied to the structural members of the vehicle body. On the other hand, materials with high strength have low press formability. When high-strength materials are cold-press formed, cracks may occur during the press forming process, or a phenomenon called springback may occur where the material undergoes elastic deformation due to the stress generated during the press forming. Accordingly, hot press forming is proposed as a method for forming structural members using such high-strength materials.

[0003] In hot press forming, the material is heated to a temperature range where the microstructure becomes a single austenite phase. Then, the heated material is press-formed at a high temperature using a hot press device equipped with a mold. In hot press forming, the material is softened by heating. Therefore, the press formability of the material in hot press forming is high. In hot press forming, the material during hot press forming also comes into contact with approximately the entire forming surface of the mold. At this time, the material is heat-dissipated and quenched by the mold in contact with the material. Thus, in hot press forming, the material is quenched simultaneously with hot press forming. Therefore, high-strength hot press-formed products can be easily manufactured in hot press forming.

[0004] However, shock-absorbing members, which are a type of structural member of an automobile, require excellent shock absorption capabilities. Accordingly, a hot press forming die for forming a shock-absorbing member is proposed in Patent Document 1 (Japanese Patent Publication No. 2014-79790).

[0005] In the hot press forming disclosed in Patent Document 1, a heated material is hot press formed using a mold. During hot press forming, a refrigerant is also flowed into a part of the gap between the mold and the material to partially rapidly cool the material. Specifically, the mold of Patent Document 1 is provided with a supply port on the surface of the mold to supply the refrigerant inside the mold to the outside of the mold. The mold of Patent Document 1 is also provided with a convex portion that contacts the boundary region between the high-strength portion and the low-strength portion of the material. During hot press forming, the refrigerant is supplied from the supply port to the gap between the high-strength portion and the mold. On the other hand, the refrigerant is not supplied to the gap between the low-strength portion and the mold. The convex portion contacting the boundary between the high-strength portion and the low-strength portion blocks the refrigerant. Therefore, the refrigerant filled in the gap between the high-strength portion and the mold does not flow into the gap between the low-strength portion and the mold. As a result, a hot press molded product (shock absorbing member) having a low-strength part with excellent shock absorption capacity is manufactured. Prior art literature

[0006] Japanese Patent Publication No. 2014-79790 The problem to be solved

[0007] In the mold disclosed in Patent Document 1, a hot press molded article having a low-strength part with excellent shock absorption capacity can be manufactured. However, a hot press molded article having excellent shock absorption capacity may be manufactured by a different technology different from the technology described in Patent Document 1.

[0008] The object of the present disclosure is to provide a mold capable of producing a hot press molded article having excellent shock absorption capacity by hot press forming, and a method for producing a hot press molded article using the mold. means of solving the problem

[0009] The mold according to the present disclosure is a mold for performing hot press forming on a material.

[0010] The die comprises an upper die and a lower die. The upper die has a first forming surface. The lower die has a second forming surface. During hot press forming, the second forming surface is positioned opposite the first forming surface and, together with the first forming surface, hot press forms the material.

[0011] The first molding surface includes a first complete cooling region. The first complete cooling region has a plurality of first rib portions and a plurality of first groove portions. The plurality of first rib portions are arranged in the width direction of the first rib portions. The plurality of first groove portions are arranged in the width direction of the first groove portions. The first rib portions are formed between adjacent first groove portions. The width of the first rib portion is narrower than the width of the first groove portion.

[0012] The second molding surface includes a second complete cooling region. The second complete cooling region has a plurality of second rib portions and a plurality of second groove portions. The plurality of second rib portions are arranged in the width direction of the second rib portions. The plurality of second groove portions are arranged in the width direction of the second groove portions. The second rib portions are formed between adjacent second groove portions. The width of the second rib portion is narrower than the width of the second groove portion.

[0013] In hot press forming, when the first and second complete cooling regions are viewed from the normal direction of the first complete cooling region, the first rib portion and the second rib portion overlap at least partially.

[0014] A method for manufacturing a hot press formed article according to the present disclosure comprises a process of preparing a material and a prepared material Ac3 The method comprises a process of heating to a temperature above a certain point, a process of performing hot press forming on the heated material using the mold described above, and a process of releasing the hot press formed material from the mold to manufacture a hot press formed product. Effects of the invention

[0015] The mold according to the present disclosure can produce a hot press molded article having excellent shock absorption capacity by hot press molding. The method for producing a hot press molded article according to the present disclosure can produce a hot press molded article having excellent shock absorption capacity. Brief explanation of the drawing

[0016] FIG. 1 is a front view showing an example of a hot press device for hot press forming. FIG. 2 is a perspective view showing an example of a mold according to the present embodiment. FIG. 3 is a cross-sectional view showing the state of the mold and the material during hot press forming in the complete cooling region of an example of the mold according to the present embodiment. FIG. 4 is a cross-sectional view showing the state of the mold and the material during hot press forming in a rapid cooling region of an example of the mold according to the present embodiment. FIG. 5a is a schematic diagram of the area (100) of FIG. 3 enlarged. Figure 5b is a schematic diagram excluding material B of Figure 5a, which represents hot press forming. FIG. 5c is a cross-sectional view perpendicular to the extension direction of a first rib portion or a second rib portion having a shape different from FIG. 5a and FIG. 5b. FIG. 5d is a cross-sectional view perpendicular to the extension direction of a first rib portion or a second rib portion having a shape different from FIG. 5a to 5c. FIG. 6 is a schematic diagram of the region (100) of FIG. 3 viewed from the upper direction (normal direction of the first cooled region and the second cooled region). FIG. 7 is a schematic diagram of the area (200) of FIG. 4 enlarged. FIG. 8 is a diagram showing the relationship between Fn1 and the temperature fluctuation ΔT(°C) in the first and second slow cooling regions. Figure 9 is a schematic diagram of the heat conduction model used in the two-dimensional heat transfer simulation to create Figure 8. Figure 10 is a diagram showing the relationship between Fn2 and the cooling rate V (°C / sec) of material B during hot press forming. FIG. 11 is a perspective view showing a different example of a mold according to the present embodiment that is different from FIG. 2. FIG. 12 is a perspective view showing a different example of a mold according to the present embodiment that is different from FIG. 2 and FIG. 11. FIG. 13 is a perspective view showing another example of a mold according to the present embodiment that is different from FIG. 2, FIG. 11 and FIG. 12. FIG. 14 is a different example of a schematic diagram of an enlarged area (100) of FIG. 3, different from FIG. 5a. Figure 15 is a cross-sectional view of the line segment XV-XV in Figure 14. FIG. 16 is a different example of a schematic diagram of an enlarged area (100) of FIG. 3, distinct from FIG. 5a and FIG. 14. FIG. 17 is a schematic diagram showing only the rib portion when viewing the region (100) of FIG. 16 from the normal direction of the first complete cooling region. FIG. 18 is a different example of a schematic diagram of an enlarged area (100) of FIG. 3, distinct from FIG. 5a, FIG. 14, and FIG. 16. FIG. 19 is a schematic diagram showing only the rib portion when viewing the region (100) of FIG. 18 from the normal direction of the first complete cooling region. Specific details for implementing the invention

[0017] As mentioned above, among the structural members of an automobile, shock-absorbing members require an improvement in their ability to absorb impact energy during a collision, that is, their shock absorption capacity. Impact energy is absorbed as the structural member undergoes plastic deformation. Therefore, to increase shock absorption capacity, it is effective to be able to exhibit excellent plastic deformation ability even under high stress.

[0018] The inventors believed that if the cooling rate of the material during hot press forming could be reduced, the material could exhibit excellent plastic deformation ability even when subjected to high stress. Accordingly, the inventors examined the surface shape of the forming surface of the mold. As a result, the inventors believed that if a complete cooling region including a plurality of rib portions and a plurality of groove portions is formed on the forming surface, the cooling rate of the material during hot press forming can be reduced.

[0019] In the molded surface, the rib portion extends in a predetermined direction, and the cross-section perpendicular to the extension direction has a convex shape. In the molded surface, the groove portion extends along the extension direction of the rib portion, and the cross-section perpendicular to the extension direction has a concave shape. A plurality of rib portions and a plurality of groove portions are formed alternately.

[0020] In hot press forming, during the complete cooling region, the rib portions come into direct contact with the material to dissipate heat. On the other hand, the groove portions do not come into direct contact with the material. Therefore, if the forming surface includes multiple rib portions and multiple groove portions, the contact area between the mold and the material can be reduced during hot press forming. Consequently, the cooling rate of the material during quenching can be reduced.

[0021] Based on the findings above, the inventors focused on the width of the rib portion and the width of the groove portion among the multiple rib portions and multiple groove portions within the complete cooling region of the molding surface and conducted a more detailed investigation. As a result, the inventors discovered that if the width of the rib portion is narrower than the width of the groove portion, the heat dissipation of the material during hot press forming is effectively reduced, thereby allowing the cooling rate to be reduced. If the cooling rate of the material during hot press forming can be slowed down, the increase in the strength of the material can be suppressed, and the shock absorption capacity can be increased.

[0022] If the width of the rib portion within the complete cooling region is made narrower than the width of the groove portion, a shock-absorbing region with reduced strength can be formed in at least a part of the hot-pressed product. However, when the width of the rib portion is made narrower than the width of the groove portion, wave deformation occurs on the surface of the hot-pressed product, and there were cases where the dimensional accuracy of the hot-pressed product was reduced. Accordingly, the inventors investigated the cause of this. As a result, the inventors obtained the following findings.

[0023] During hot press forming, a rib formed in the complete cooling area of ​​the molding surface of one of the pair of molds (upper and lower molds) may penetrate into a groove formed in the complete cooling area of ​​the molding surface of the other mold. In this case, the aforementioned wavy deformation occurs on the surface of the hot press formed product.

[0024] Based on the above findings, the inventors considered overlapping the rib portion formed in the complete cooling area of ​​one mold and the rib portion formed in the complete cooling area of ​​the other mold when viewed from the normal direction of the complete cooling area during hot press forming. If at least a portion of the rib portion formed in the complete cooling area of ​​one mold overlaps with the rib portion formed in the complete cooling area of ​​the other mold, the rib portion can be suppressed from digging into the groove.

[0025] In the mold according to the present embodiment, when the complete cooling region is viewed from the normal direction of the complete cooling region during hot press forming, the rib portion formed in one complete cooling region and the rib portion formed in the other complete cooling region overlap at least partially. As a result, the deformation of the aforementioned wave shape caused by the width of the rib portion being narrower than the width of the groove portion can be suppressed.

[0026] Based on the above findings, the mold according to the present embodiment and the method for manufacturing a hot press molded product using the mold according to the present embodiment have the following configurations.

[0027] [1]

[0028] It is a mold for performing hot press forming on a material, and

[0029] A mold having a first molding surface, and

[0030] In the case of hot press forming, a lower die is provided having a second forming surface that is positioned opposite to the first forming surface and hot press forms the material together with the first forming surface.

[0031] The above-mentioned first molded surface is,

[0032] It includes a first cooling region having a plurality of first rib portions and a plurality of first groove portions, and

[0033] A plurality of the first rib portions are arranged in the width direction of the first rib portions, and

[0034] A plurality of the first groove portions are arranged in the width direction of the first groove portions, and

[0035] The first rib portion is formed between adjacent first groove portions, and

[0036] The width of the first rib portion is narrower than the width of the first groove portion, and

[0037] The above second molded surface is,

[0038] It includes a second cooling region having a plurality of second rib portions and a plurality of second groove portions, and

[0039] A plurality of the above-mentioned second rib portions are arranged in the width direction of the above-mentioned second rib portions, and

[0040] A plurality of the above-mentioned second grooves are arranged in the width direction of the above-mentioned second grooves, and

[0041] The second rib portion is formed between adjacent second groove portions, and

[0042] The width of the second rib portion is narrower than the width of the second groove portion, and

[0043] In the case of hot press forming, when the first complete cooling region and the second complete cooling region are viewed from the normal direction of the first complete cooling region,

[0044] A mold in which the first rib portion and the second rib portion overlap at least partially.

[0045] The mold of [1] can produce a hot press molded product with excellent shock absorption capacity by hot press molding.

[0046] [2]

[0047] [1] is the mold described in [1],

[0048] In the case of hot press forming, when the first complete cooling region and the second complete cooling region are viewed from the normal direction of the first complete cooling region,

[0049] The first rib portion and the second rib portion are extended in the same direction, and

[0050] A mold in which the first groove and the second groove are extended in the same direction.

[0051] The mold of [2] can increase the simulation accuracy of heat transfer in the material during hot press forming.

[0052] [3]

[0053] [1] or [2] is a mold, and

[0054] The width of the first rib portion is 10 to 50% of the width of the first groove portion, and

[0055] A mold in which the width of the second rib portion is 10 to 50% of the width of the second groove portion.

[0056] [3] If the mold is of the type shown, the cooling rate can be slowed down during hot press forming. If the cooling rate can be slowed down, it becomes easier to stop cooling at the desired material temperature. For example, during hot press forming, cooling can be stopped between the Mf point and the Ms point, and then the heat holding process described later can be performed to adjust the amount of martensite and retained austenite in the microstructure of the material. In addition, for example, during hot press forming, cooling can be stopped at a temperature between the Ms point and 500°C, and then the heat holding process described later can be performed to make the microstructure of the material mainly bainite.

[0057] [4]

[0058] [1] to [3] is a mold described in any one of [1] to [3], and

[0059] In at least a portion of the first complete cooling region,

[0060] The width of the first rib portion is 1.0 to 8.0 mm, and

[0061] The height of the first rib portion is 0.2 to 5.0 mm, and

[0062] In at least a portion of the second complete cooling region above,

[0063] The width of the second rib portion is 1.0 to 8.0 mm, and

[0064] A mold having a second rib section height of 0.2 to 5.0 mm.

[0065] The mold of [4] can suppress temperature fluctuations of the material during hot press forming.

[0066] [5]

[0067] [2] is the mold described in [2],

[0068] The width of the first rib portion is 10 to 50% of the width of the first groove portion, and

[0069] The width of the second rib portion is 10 to 50% of the width of the second groove portion, and

[0070] The width of each of the first rib portion and the second rib portion is 1.0 to 8.0 mm, and

[0071] The height of each of the first rib portion and the second rib portion is 0.2 to 5.0 mm, and

[0072] A mold in which Fn1 defined by Equation (1) is 14 or less.

[0073]

[0074] Here, in Equation (1), Wr is the width (mm) of the first rib portion and the second rib portion, P0 = Wr / Ws, Ws is the width (mm) of the first groove portion and the second groove portion, and Hr is the height (mm) of the first rib portion and the second rib portion.

[0075] [5] In the mold, temperature fluctuations of the material during hot press forming can be further suppressed.

[0076] [6]

[0077] [2] or [5] is the mold described in [2] or [5],

[0078] The width of the first rib portion is 10 to 50% of the width of the first groove portion, and

[0079] The width of the second rib portion is 10 to 50% of the width of the second groove portion, and

[0080] The width of each of the first rib portion and the second rib portion is 1.0 to 8.0 mm, and

[0081] The height of each of the first rib portion and the second rib portion is 0.2 to 5.0 mm, and

[0082] A mold in which Fn2, defined by Equation (2), is 30 or greater.

[0083]

[0084] Here, in Equation (2), Ws is the width (mm) of the first groove and the second groove, Wr is the width (mm) of the first rib and the second rib, and Hr is the height (mm) of the first rib and the second rib.

[0085] [6] In the mold, the cooling rate of the material can be made slower. If the cooling rate can be made slower, it becomes easier to stop cooling at the desired material temperature. For example, during hot press forming, cooling can be stopped between the Mf point and the Ms point, and then the heat holding process described later can be performed to adjust the amount of martensite and retained austenite in the microstructure of the material. In addition, for example, during hot press forming, cooling can be stopped at a temperature between the Ms point and 500°C, and then the heat holding process described later can be performed to make the microstructure of the material mainly bainite.

[0086] [7]

[0087] [4] to [6] is a mold described in any one of the following:

[0088] In at least a portion of the first complete cooling region,

[0089] The width of the first rib portion is 1.0 to 4.0 mm, and is also 10 to 30% of the width of the first groove portion,

[0090] In at least a portion of the second complete cooling region above,

[0091] A mold in which the width of the second rib portion is 1.0 to 4.0 mm and is also 10 to 30% of the width of the second groove portion.

[0092] The mold of [7] can further suppress temperature fluctuations of the material during hot press forming.

[0093] [8] A method for manufacturing hot press molded products,

[0094] The process of preparing materials, and

[0095] The above-mentioned prepared material is A c3 A process of heating to a temperature above the point, and

[0096] A process of performing hot press forming on the heated material using a mold described in any one of [1] to [7], and

[0097] A method for manufacturing a hot press molded product, comprising a process of separating the hot press-molded material from the mold to manufacture the hot press molded product.

[0098] The method of manufacturing a hot press molded article of [8] can produce a hot press molded article with excellent shock absorption capacity.

[0099] [9]

[0100] [8] is a method for manufacturing a hot press formed product, and

[0101] A method for manufacturing a hot press molded product, further comprising a process of maintaining the hot press molded product manufactured by releasing it from the above mold at 100 to 500°C.

[0102] Hereinafter, a mold according to the present embodiment and a method for manufacturing a hot press molded product using the mold according to the present embodiment will be described with reference to the drawings. In addition, identical or equivalent components in each drawing are given the same reference numerals, and identical descriptions are not repeated.

[0103] [Composition of hot press device (1)]

[0104] FIG. 1 is a front view showing an example of a hot press device (1) for hot press forming. Referring to FIG. 1, the hot press device (1) has substantially the same configuration as a known hot press device, except for the mold (10) according to the present embodiment. The hot press device (1) has a frame (2), a slide (3), a bolster (4), and a mold (10) (an upper mold (11) and a lower mold (12)). In the following description, the vertical direction (up and down) of the hot press device (1) is also referred to as the V direction, the width direction of the hot press device (1) as the W direction, and the direction perpendicular to the V direction and the W direction as the L direction.

[0105] Referring to FIG. 1, a frame (2) is positioned on the upper part of a hot press device (1). The frame (2) supports a slide (3) positioned below the frame (2) so that it can be raised and lowered. The frame (2) is equipped with a driving device (not shown) that raises and lowers the slide (3). The driving device may be a mechanical mechanism or a hydraulic mechanism. The slide (3) is installed on the frame (2) and can be raised and lowered in the up and down direction by the driving device provided by the frame (2). An upper die (11) is installed on the lower surface of the slide (3). A bolster (4) is positioned below the slide (3). The upper surface of the bolster (4) faces the lower surface of the slide (3). A lower die (12) is installed on the upper surface of the bolster (4). At this time, the lower die (12) is positioned below the upper die (11).

[0106] The mold (10) includes the upper mold (11) described above and the lower mold (12) described above. The upper mold (11) and the lower mold (12) are extended in the L direction of FIG. 1. Hereinafter, with respect to the hot press device (1) and the mold (10), the direction in which the upper mold (11) and the lower mold (12) are extended is also referred to as the "longer direction of the mold (10) (L direction)." With respect to the mold (10), the direction perpendicular to the L direction and the V direction of FIG. 1 is also referred to as the "width direction of the mold (10) (W direction)."

[0107] As described above, the upper die (11) is fixed to the lower surface of the slide (3), and the lower die (12) is fixed to the upper surface of the bolster (4). The lower die (12) is positioned below the upper die (11). When performing hot press forming, a heated material (blank) is initially placed on the lower die (12). After the material is placed, the upper die (11) slides in a V direction relative to the lower die (12), and while in contact with the material, an external force is applied to the material. That is, the upper die (11) and the lower die (12) hot press form the material. By doing so, the material is formed into a desired shape. Furthermore, during hot press forming, the forming surface of the upper die (11) and the forming surface of the lower die (12) come into contact with the material, and the upper die (11) and the lower die (12) quench the material by dissipating heat. Therefore, a hot press molded product having a desired shape and increased strength is manufactured.

[0108] The hot press device (1) may include a configuration not shown in FIG. 1. The hot press device (1) may, for example, be equipped with a cooling device for cooling a mold (10). In this case, for example, a passage through which a cooling medium passes is provided inside the mold (10). Additionally, a pump for supplying a cooling medium inside the mold (10) is arranged. The hot press device (1) may also be equipped with a conveying mechanism for conveying a material to the hot press device (1). The hot press device (1) may have a configuration not shown in FIG. 1 and may have a configuration provided by a known hot press device.

[0109] [Composition of mold (10)]

[0110] The configuration of the mold (10) in Fig. 1 will be explained in more detail.

[0111] FIG. 2 is a perspective view of the mold (10) of FIG. 1. Referring to FIG. 2, the upper mold (11) has a first molding surface (110). The first molding surface (110) is positioned on the lower surface of the upper mold (11). In FIG. 2, the first molding surface (110) includes a concave portion extending in the L direction at the center of the W direction.

[0112] The lower die (12) has a second molding surface (120). The second molding surface (120) is positioned on the upper surface of the lower die (12). In FIG. 2, the second molding surface (120) includes a convex portion extending in the L direction at the center in the W direction. During hot press forming, the second molding surface (120) is positioned opposite the first molding surface (110). Then, the second molding surface (120), together with the first molding surface (110), comes into contact with the material (blank) to hot press form the material.

[0113] [Composition of the first molded surface (110) and the second molded surface (120)]

[0114] The first molding surface (110) includes a first slow cooling region (113) indicated by a diagonal line. In FIG. 2, the first slow cooling region (113) is formed in a part of the first molding surface (110). In FIG. 2, the first molding surface (110) includes the first slow cooling region (113) and a first rapid cooling region (114).

[0115] Likewise, the second molding surface (120) includes a second slow cooling region (123) indicated by a diagonal section. In FIG. 2, the second slow cooling region (123) is formed in a part of the second molding surface (120). In FIG. 2, the second molding surface (120) includes the second slow cooling region (123) and a second rapid cooling region (124).

[0116] In the case of hot press forming, the first rapid cooling area (114) faces the second rapid cooling area (124). The first rapid cooling area (114) and the second rapid cooling area (124) form a high-strength area having high strength in the material (hot press formed product) after hot press forming.

[0117] In the case of hot press forming, the first cooled area (113) faces the second cooled area (123). The first cooled area (113) and the second cooled area (123) form an impact buffering area in the material (hot press formed product) after hot press forming, which has lower strength than the high-strength area and is prone to plastic deformation.

[0118] FIG. 3 is a cross-sectional view including V and W directions showing the state of the mold (10) and material (blank) B in the first full cooling region (113) and the second full cooling region (123) during hot press forming. FIG. 4 is a cross-sectional view including V and W directions showing the state of the mold (10) and material B in the first rapid cooling region (114) and the second rapid cooling region (124) during hot press forming. FIG. 3 and FIG. 4 show the state where the upper mold (11) has reached the bottom dead center and the mold (10) is closed. In other words, FIG. 3 and FIG. 4 show the state where approximately the entire first forming surface (110) of the upper mold (11) and approximately the entire second forming surface (120) of the lower mold (12) are in contact with material B and apply an external force to material B.

[0119] Referring to FIGS. 2 to 4, during hot press forming, material B is fitted into the upper die (11) and the lower die (12). At this time, the concave portion of the first molding surface (110) is fitted into the convex portion of the second molding surface (120). As a result, material B is formed into a hat-shaped hot press product.

[0120] The mold (10) of FIG. 2 also includes a slow cooling area (113 and 123) and a rapid cooling area (114 and 124). In the first molding surface (110) of the upper mold (11), the surface structure of the first slow cooling area (113), which forms the shock-absorbing area of ​​the hot-press molded product, is different from the surface structure of the first rapid cooling area (114), which forms the high-strength area of ​​the hot-press molded product. Likewise, in the second molding surface (120) of the lower mold (12), the surface structure of the second slow cooling area (123), which forms the shock-absorbing area of ​​the hot-press molded product, is different from the surface structure of the second rapid cooling area (124), which forms the high-strength area of ​​the hot-press molded product. The surface structures of the first molding surface (110) and the second molding surface (120) will be described further below.

[0121] [Composition of the first molded surface (110)]

[0122] [Configuration of the first cooling zone (113)]

[0123] FIG. 5a is an enlarged view of the region (100) within the first full cooling region (113) of the first molding surface (110) of FIG. 3. Referring to FIG. 5a, the first full cooling region (113) of the first molding surface (110) of the upper mold (11) has a plurality of first rib portions (111) and a plurality of first groove portions (112). FIG. 6 is a schematic diagram of the region (100) of FIG. 3 viewed from the upper direction (normal direction of the first full cooling region (113) and the second full cooling region (123)). Referring to FIG. 5a and FIG. 6, the plurality of first rib portions (111) are extended in a predetermined direction. In FIG. 5a and FIG. 6, as an example, the plurality of first rib portions (111) are extended in the L direction. However, the extension direction of the plurality of first rib sections (111) is not limited to the L direction.

[0124] A plurality of first rib sections (111) are arranged in the width direction of the first rib sections (111). The width direction of the first rib sections (111) is a direction perpendicular to the extension direction of the first rib sections (111). In FIG. 5a, the width direction of the first rib sections (111) is the W direction. However, the width direction of the first rib sections (111) is not limited to the W direction. In the present embodiment, each first rib section (111) extends in the L direction and is arranged in the W direction.

[0125] Referring to FIG. 5a, a plurality of first grooves (112) are arranged in the width direction of the first grooves (112), and a first rib (111) is formed between adjacent first grooves (112). In FIG. 5a, the first grooves (112) extend in the L direction and are arranged in the W direction, just like the first rib (111). Additionally, the first rib (111) is formed between two adjacent first grooves (112). In FIG. 5a, the plurality of first grooves (112) and the plurality of first ribs (111) all extend in the L direction, and the first grooves (112) and the first ribs (111) are arranged alternately in the W direction.

[0126] Referring to FIG. 5a, the width of the first rib portion (111) is narrower than the width of the first groove portion (112). As described above, the width of the first rib portion (111) refers to the width of the first rib portion (111) in a cross-section perpendicular to the extension direction of the first rib portion (111). In FIG. 5a, the width of the first rib portion (111) refers to the width of the first rib portion (111) in the W direction. Likewise, the width of the first groove portion (112) refers to the width of the first groove portion (112) in a cross-section perpendicular to the extension direction of the first groove portion (112). In FIG. 5a, the width of the first groove portion (112) refers to the width of the first groove portion (112) in the W direction. The width of the first rib portion (111) and the width of the first groove portion (112) can be easily obtained, for example, by using a caliper.

[0127] Referring to FIG. 5a, in this embodiment, the width of the first rib portion (111) is narrower than the width of the first groove portion (112). When the first cooled-down area (113) comes into contact with material B during hot press forming, the amount of heat dissipated from the first groove portion (112) is less than the amount of heat dissipated from the first rib portion (111). Since the width of the first rib portion (111) is narrower than the width of the first groove portion (112), the amount of heat dissipated from the first rib portion (111) can be suppressed to be less. Therefore, in the first cooled-down area (113), the cooling speed of material B can be slowed down compared to the first rapid cooling area (114). Therefore, when hot press forming is performed using the mold (10), the degree of quenching in the area of ​​material B that comes into contact with the first cooled-down area (113) can be reduced. As a result, an impact buffering area with reduced strength can be formed in material B (hot press formed product) after hot press forming.

[0128] [Composition of the first rapid cooling zone (114)]

[0129] FIG. 7 is an enlarged view of the area (200) within the first rapid cooling region (114) of the first molding surface (110) of FIG. 4. Referring to FIG. 7, in the first rapid cooling region (114) of the first molding surface (110) of the upper die (11), the first rib portion (111) and the first groove portion (112) are not formed. In other words, the first rapid cooling region (114) of the first molding surface (110) is a smooth surface. Therefore, during hot press forming, approximately the entire first rapid cooling region (114) comes into contact with material B. Therefore, in the first rapid cooling region (114), the cooling speed of material B can be increased compared to the first slow cooling region (113). Therefore, when hot press forming is performed using the mold (10), the degree of quenching in the area in contact with the first rapid cooling area (114) of material B can be increased. As a result, a high-strength area with higher strength than the shock-absorbing area can be formed in material B (hot press formed product) after hot press forming.

[0130] [Composition of the second molded surface (120)]

[0131] [Configuration of the second cooling zone (123)]

[0132] Referring to FIG. 5a, the second complete cooling area (123) of the second molding surface (120) of the lower mold (12) has a plurality of second rib portions (121) and a plurality of second groove portions (122). Referring to FIG. 5a and FIG. 6, the plurality of second rib portions (121) are extended in a predetermined direction. In FIG. 5a and FIG. 6, the plurality of second rib portions (121) are extended in the L direction. However, the extension direction of the plurality of second rib portions (121) is not limited to the L direction.

[0133] A plurality of second rib sections (121) are arranged in the width direction of the second rib sections (121). The width direction of the second rib sections (121) is a direction perpendicular to the extension direction of the second rib sections (121). In FIG. 5a, the width direction of the second rib sections (121) is the W direction. However, the width direction of the second rib sections (121) is not limited to the W direction. In the present embodiment, each second rib section (121) extends in the L direction and is arranged in the W direction.

[0134] Referring to FIG. 5a, a plurality of second grooves (122) are arranged in the width direction of the second grooves (122), and a second rib (121) is formed between adjacent second grooves (122). In FIG. 5a, the second grooves (122) extend in the L direction and are arranged in the W direction, just like the second rib (121). Additionally, the second rib (121) is formed between two adjacent second grooves (122). In FIG. 5a, the plurality of second grooves (122) and the plurality of second rib (121) all extend in the L direction, and the second grooves (122) and the second rib (121) are arranged alternately in the W direction.

[0135] Referring to FIG. 5a, the width of the second rib portion (121) is narrower than the width of the second groove portion (122). As described above, the width direction of the second rib portion (121) and the second groove portion (122) corresponds to the width direction (W direction) of the mold (10). Accordingly, in the cross-section shown in FIG. 5a, the width of the second rib portion (121) refers to the width of the second rib portion (121) in the W direction, and the width of the second groove portion (122) refers to the width of the second groove portion (122) in the W direction. The width of the second rib portion (121) and the width of the second groove portion (122) can be determined, for example, using a caliper.

[0136] Referring to FIG. 5a, the width of the second rib portion (121) is narrower than the width of the second groove portion (122). As described above, the width of the second rib portion (121) refers to the width of the second rib portion (121) in a cross-section perpendicular to the extension direction of the second rib portion (121). Therefore, the same effect as the relationship between the width of the first rib portion (111) and the width of the first groove portion (112) described above is obtained. Specifically, when the second complete cooling area (123) comes into contact with material B during hot press forming, the amount of heat dissipated from the second groove portion (122) is less than the amount of heat dissipated from the second rib portion (121). Since the width of the second rib portion (121) is narrower than the width of the second groove portion (122), the amount of heat dissipated from the second rib portion (121) can be suppressed to be less. Therefore, in the second slow cooling region (123), the cooling speed of material B can be slowed down compared to the second rapid cooling region (124) described later. Therefore, when hot press forming is performed using the mold (10), the degree of quenching in the area of ​​material B that is in contact with the second slow cooling region (123) can be reduced. As a result, a shock-absorbing region with reduced strength can be formed in material B (hot press formed product) after hot press forming.

[0137] [Composition of the second rapid cooling zone (124)]

[0138] Referring to FIG. 7, in the second rapid cooling region (124) of the second molding surface (120) of the lower mold (12), the second rib portion (121) and the second groove portion (122) are not formed. That is, the second rapid cooling region (124) of the second molding surface (120) is a smooth surface. Therefore, when hot press forming, approximately the entire second rapid cooling region (124) comes into contact with material B. Therefore, in the second rapid cooling region (124), the cooling speed of material B can be accelerated compared to the second slow cooling region (123). Therefore, when hot press forming is performed using the mold (10), the degree of quenching in the area of ​​material B that comes into contact with the second rapid cooling region (124) can be increased. As a result, a high-strength region with higher strength than the shock-absorbing region can be formed in material B (hot press formed product) after hot press forming.

[0139] [Relationship between the first rib section (111) and the second rib section (121)]

[0140] In addition, in the mold (10), when the first complete cooling area (113) of the first molding surface (110) and the second complete cooling area (123) of the second molding surface (120) are viewed from the normal direction of the first complete cooling area (113), the first rib portion (111) and the second rib portion (121) overlap at least partially. The term "when hot press forming" as used here means a state in which approximately the entire molding surface (110) of the upper mold (11) and approximately the entire molding surface (120) of the lower mold (12) are in contact with material B and apply an external force to material B, and means a state in which the mold (10) is closed and the upper mold (11) is maintained at the bottom dead center while material B is cooled by the mold (10).

[0141] In this case, as illustrated in FIG. 5a, during hot press forming, the first rib portion (111) does not penetrate into the second groove portion (122), and the second rib portion (121) does not penetrate into the first groove portion (112). Therefore, during hot press forming, the first rib portion (111) penetrates into the second groove portion (122), or the second rib portion (121) penetrates into the first groove portion (112), thereby suppressing the deformation of material B into a wavy shape.

[0142] [Features of the mold (10)]

[0143] As described above, in the mold (10) of the present embodiment, the width of the first rib portion (111) of the first complete cooling area (113) is narrower than the width of the first groove portion (112). Additionally, the width of the second rib portion (121) of the second complete cooling area (123) is narrower than the width of the second groove portion (122). Therefore, when hot press forming is performed using the mold (10), the cooling speed is suppressed in the area of ​​material B inserted in the first complete cooling area (113) and the second complete cooling area (123). Consequently, within the hot press formed product, it is possible to form an impact buffering area with suppressed strength and a high-strength area with higher strength than the impact buffering area. Additionally, when the first complete cooling area (113) and the second complete cooling area (123) are viewed from the normal direction of the first complete cooling area (113), at least a portion of the first rib portion (111) and the second rib portion (121) overlap. Therefore, in the shock-absorbing area, the deformation of material B into a wave shape can be suppressed.

[0144] [Regarding the preferred shape of the mold (10)]

[0145] In the first complete cooling area (113) and the second complete cooling area (123), preferably, the first rib portion (111) and the second rib portion (121) are extended in the same direction. Also, the first groove portion (112) and the second groove portion (122) are extended in the same way. In FIGS. 5a and FIGS. 6, the first rib portion (111) and the second rib portion (121) are extended in the L direction, and the first groove portion (112) and the second groove portion (122) are extended in the L direction.

[0146] As described above, when the first rib portion (111), the first groove portion (112), the second rib portion (121), and the second groove portion (122) are all extended in the same direction, it is sufficient to perform a two-dimensional simulation for the heat transfer of material B. That is, if a two-dimensional simulation is performed on a cross-section perpendicular to the extension direction of the first rib portion (111), the first groove portion (112), the second rib portion (121), and the second groove portion (122) (i.e., the cross-section shown in FIG. 5a), the result is substantially the same as the result obtained by a three-dimensional simulation. Therefore, there is no need to perform a three-dimensional simulation. Consequently, it becomes possible to perform a more easy and accurate simulation of the heat transfer of material B. In other words, the cooling rate can be controlled more easily and accurately. In this case, it becomes possible to control the desired microstructure by using simulation based on the chemical composition of material B.

[0147] For example, if material B is steel, and as a result of hot press forming material B, the hot press formed product has a microstructure containing not only a hard phase but also retained austenite, the shock absorption capacity of the hot press formed product is further enhanced. Here, the hard phase consists of martensite and / or bainite.

[0148] [Desirable relationship between the first rib portion (111) and the first groove portion (112), and desirable relationship between the second rib portion (121) and the second groove portion (122)]

[0149] Preferably, the width of the first rib portion (111) formed in the cooled-down area (113) is 10 to 50% of the width of the first groove portion (112), and the width of the second rib portion (121) formed in the cooled-down area (123) is 10 to 50% of the width of the second groove portion (122).

[0150] If the width of the first rib portion (111) is 10% or more of the width of the first groove portion (112), the first rib portion (111) properly dissipates heat from material B. In this case, the cooling rate of material B can be suppressed from becoming excessively slow. As a result, the formation of ferrite and pearlite in the microstructure of material B can be suppressed, thereby promoting the formation of a hard phase, or a hard phase and residual austenite. As a result, the shock absorption capacity of the hot press molded product is improved.

[0151] Meanwhile, if the width of the first rib portion (111) is 50% or less of the width of the first groove portion (112), the cooling rate can be slowed down during hot press forming. If the cooling rate can be slowed down, it becomes easier to stop cooling at a desired material temperature. For example, cooling can be stopped between the Mf point and the Ms point to adjust the amount of martensite and retained austenite produced. For example, cooling can be stopped at a temperature higher than the Ms point to make the microstructure of the material a bainite-based structure.

[0152] Accordingly, preferably, the width of the first rib portion (111) is 10 to 50% of the width of the first groove portion (112).

[0153] A more preferred upper limit of the ratio of the width of the first rib portion (111) to the width of the first groove portion (112) is 45%, more preferably 40%, and even more preferably 35%.

[0154] A more preferred lower limit of the ratio of the width of the first rib portion (111) to the width of the first groove portion (112) is 12%, and more preferably 14%.

[0155] FIG. 5b is a schematic diagram excluding material B of FIG. 5a, which illustrates hot press forming. Here, the width of the first rib portion (111) is defined as follows. Among the surfaces of the first rib portion (111), the surface facing the second forming surface (120) is defined as the normal surface of the first rib portion (111). That is, among the surfaces of the first rib portion (111), the surface in contact with material B during hot press forming is defined as the "normal surface." As shown in FIG. 5b, in a cross-section perpendicular to the extension direction of the first rib portion (111), the width W of the normal surface (111P) 111P is defined as the width of the first rib portion (111). The width W of the normal surface (111P). 111P That is, it corresponds to the length of the normal plane (111P) in a direction perpendicular to the extension direction of the first rib (111) and the normal direction of the normal plane (111P) (W direction in FIG. 5b).

[0156] The height of the first rib portion (111) is defined as follows. In FIG. 5b, the height H from the top surface (111P) of the first rib portion (111) to the bottom of the groove (112P) of the first groove portion (112) 111P ...is defined as the height of the first rib portion (111). In other words, the length in the normal direction of the normal surface (111P) (in the V direction in FIG. 5b) from the top surface (111P) of the first rib portion (111) to the bottom of the groove (112P) of the first groove portion (112) is the height H of the first rib portion (111). 111P It is defined as follows.

[0157] The width of the first groove (112) is defined as follows. As shown in FIG. 5b, in a cross-section perpendicular to the extension direction of the first rib (111), the width W of the gap between the end point of one normal surface (111P) and the end point of the other normal surface (111P) of adjacent first ribs (111) is 112P is defined as the width of the first groove (112).

[0158] The width of the second rib portion (121) is defined as follows. Among the surfaces of the second rib portion (121), the surface facing the first molding surface (110) is defined as the normal surface of the second rib portion (121). That is, among the surfaces of the second rib portion (121), the surface that contacts material B during hot press forming is defined as the "normal surface." As shown in FIG. 5b, in a cross-section perpendicular to the extension direction of the second rib portion (121), the width W of the normal surface (121P) 121P is defined as the width of the second rib section (121). The width W of the normal surface (121P). 121P That is, it corresponds to the length of the normal plane (121P) in a direction perpendicular to the extension direction of the second rib (121) and the normal direction of the normal plane (121P) (W direction in FIG. 5b).

[0159] The height of the second rib portion (121) is defined as follows. In FIG. 5b, the height H from the top surface (121P) of the second rib portion (121) to the bottom of the groove (122P) of the second groove portion (122) 121P The height of the second rib portion (121) is defined as the length in the normal direction of the normal surface (121P) (in Fig. 5b V direction) from the normal surface (121P) of the second rib portion (121) to the bottom of the groove (122P) of the second groove portion (122) is defined as the height of the second rib portion (121).

[0160] The width of the second groove (122) is defined as follows. As shown in FIG. 5b, in a cross-section perpendicular to the extension direction of the second rib (121), the gap width W between the end point of one normal surface (121P) and the end point of the other normal surface (121P) of adjacent second ribs (121) 122P is defined as the width of the second groove (122).

[0161] Additionally, the shape of the first rib portion (111) or the second rib portion (121) in a cross-section perpendicular to the extension direction may be a rectangular shape as shown in FIG. 5a and FIG. 5b, or a trapezoidal shape that narrows toward the top surface (111P or 121P) as shown in FIG. 5c. Also, in the first rib portion (111) or the second rib portion (121), the corner of the top surface (111P or 121P) may be chamfered as shown in FIG. 5d, or the base of the first rib portion (111) or the second rib portion (121) may be chamfered. In addition, the edge of the normal surface (111P or 121P) may be rounded (i.e., filleted), or the base of the first rib portion (111) or the second rib portion (121) may be rounded (i.e., filleted).

[0162] In addition, if the normal surface (111P or 121P) is chamfered or filleted, the width of the normal surface (111P or 121P) shall be the width of the portion of the normal surface (111P and 121P) that is not chamfered or filleted.

[0163] As described above, the mold (10) of the present embodiment is a mold for hot press forming. When hot press forming, the temperature of material B is A c3It is higher than a point and higher than that of hot press forming. Therefore, material B during hot press forming has lower hardness and better processability compared to material during hot press forming. Therefore, the surface pressure applied to material B during hot press forming is lower than that during hot press forming. Therefore, even if the width of the first rib portion (111) is 50% or less of the width of the first groove portion (112), it is difficult for a defect to form on the surface of material B.

[0164] Similar to the relationship between the first rib portion (111) and the first groove portion (112), if the width of the second rib portion (121) is 10% or more of the width of the second groove portion (122), the excessive reduction of the cooling rate of material B can be suppressed. Therefore, the shock absorption capacity of the hot press molded product is improved.

[0165] Meanwhile, if the width of the second rib portion (121) is 50% or less of the width of the second groove portion (122), the cooling speed of material B can be appropriately slowed down. Therefore, during hot press forming, it becomes easier to adjust the cooling stop temperature (i.e., the temperature of material B when the mold (10) is separated from material B). For example, it becomes easier to adjust the cooling stop temperature to a temperature above the Ms point, to adjust the cooling stop temperature to a range between the Mf point and the Ms point, or to a range between the Ms point and 500°C.

[0166] Accordingly, the width of the second rib portion (121) is 10 to 50% of the width of the second groove portion (122).

[0167] The preferred upper limit of the ratio of the width of the second rib portion (121) to the width of the second groove portion (122) is 45%, more preferably 40%, and even more preferably 35%.

[0168] A more preferred lower limit of the ratio of the width of the second rib portion (121) to the width of the second groove portion (122) is 12%, and more preferably 14%.

[0169] Similar to the relationship between the width of the first rib portion (111) and the width of the first groove portion (112) described above, even if the width of the second rib portion (121) is 50% or less of the width of the second groove portion (122), it is difficult for a defect to form on the surface of material B.

[0170] [Desirable width and desirable height of the first rib section (111), desirable width and desirable height of the second rib section (121)]

[0171] Preferably, in at least a portion of the first cool-down area (113), the width of the first rib portion (111) is 1.0 to 8.0 mm and the height of the first rib portion (111) is 0.2 to 5.0 mm, and in at least a portion of the second cool-down area (123), the width of the second rib portion (121) is 1.0 to 8.0 mm and the height of the second rib portion (121) is 0.2 to 5.0 mm. The height of the first rib portion (111) corresponds to the depth of the first groove portion (112). Likewise, the height of the second rib portion (121) corresponds to the depth of the second groove portion (122).

[0172] If the width of the first rib portion (111) or the width of the second rib portion (121) is 8.0 mm or less, the temperature fluctuation in the width direction of the first rib portion (111) or the second rib portion (121) in material B can be reduced. Therefore, during hot press forming, the fluctuation in the cooling rate resulting from the temperature fluctuation of material B can be reduced.

[0173] Meanwhile, if the width of the first rib portion (111) or the second rib portion (121) is 1.0 mm or more, the first rib portion (111) or the second rib portion (121) becomes difficult to fold when hot press forming is performed, and productivity is increased. Accordingly, the preferred width of the first rib portion (111) is 1.0 to 8.0 mm. The preferred width of the second rib portion (121) is 1.0 to 8.0 mm.

[0174] A more preferred lower limit for the width of the first rib section (111) is 1.8 mm, and more preferably 2.0 mm. A more preferred lower limit for the width of the second rib section (121) is 1.8 mm, and more preferably 2.0 mm. In this case, the first rib section (111) and the second rib section (121) become more difficult to fold. In addition, since the dimensional precision of the first rib section (111) and the second rib section (121) is relaxed, it becomes easier to process.

[0175] If the height of the first rib portion (111) or the second rib portion (121) is 0.2 mm or more, the generation of heat dissipation from material B in the first groove portion (112) or the second groove portion (122) can be suppressed. On the other hand, if the height of the first rib portion (111) or the second rib portion (121) is 5.0 mm or less, the first rib portion (111) or the second rib portion (121) becomes difficult to fold when hot press forming is performed, and productivity is increased. Therefore, the preferred height of the first rib portion (111) is 0.2 to 5.0 mm. The preferred height of the second rib portion (121) is 0.2 to 5.0 mm.

[0176] In addition, in at least a portion of the first complete cooling area (113) and the second complete cooling area (123), if the width or height of the first rib portion (111) or the second rib portion (121) is adjusted as described above, the above-described desirable effect can be obtained in at least a portion of the said area. Therefore, in the present embodiment, in at least a portion of the first complete cooling area (113) and the second complete cooling area (123), the width or height of the first rib portion (111) or the second rib portion (121) can be adjusted as described above. Preferably, over the entire first cooling region (113), the width of the first rib portion (111) is 1.0 to 8.0 mm and the height is 0.2 to 5.0 mm, and over the entire second cooling region (123), the width of the second rib portion (121) is 1.0 to 8.0 mm and the height is 0.2 to 5.0 mm.

[0177] More preferably, in at least a portion of the first cooling area (113), the width of the first rib portion (111) is 1.0 to 4.0 mm and is also 10 to 30% of the width of the first groove portion (112), and in at least a portion of the second cooling area (123), the width of the second rib portion (121) is 1.0 to 4.0 mm and is also 10 to 30% of the width of the second groove portion (122). In this case, the cooling speed of material B can be further slowed down. Therefore, it is easier to adjust the cooling stop temperature to a desired temperature. In addition, the temperature fluctuation of material B during hot press forming can be reduced.

[0178] [About Fn1]

[0179] In the mold (10), the first rib portion (111) and the second rib portion (121) are extended in the same direction, and the first groove portion (112) and the second groove portion (122) are extended in the same direction, and the width of the first rib portion (111) is 10 to 50% of the width of the first groove portion (112), and the width of the second rib portion (121) is 10 to 50% of the width of the second groove portion (122), and the width of the first rib portion (111) and the second rib portion (121) is 1.0 to 8.0 mm, and the height of the first rib portion (111) and the second rib portion (121) is 0.2 to 5.0 mm.

[0180] In this case, preferably, Fn1 defined by Equation (1) is 14 or less.

[0181]

[0182] Here, Wr is the width (mm) of the first rib section (111) and the second rib section (121). P0 = Wr / Ws, where Ws is the width (mm) of the first groove section (112) and the second groove section (122). Hr is the height (mm) of the first rib section (111) and the second rib section (121). Fn1 will be described below.

[0183] FIG. 8 is a diagram showing the relationship between Fn1 and the temperature fluctuation ΔT (°C) in the first full cooling region (113) and the second full cooling region (123). FIG. 8 is the result obtained by the two-dimensional heat transfer simulation shown below. Specifically, the temperature distribution of material B during hot press forming and the change over time of said temperature distribution were simulated by a difference method assuming the heat conduction model shown in FIG. 9.

[0184] FIG. 9 is a cross-sectional view in the width direction of the first rib portion (111) and the second rib portion (121) in the first cool-down area (113) and the second cool-down area (123). Material B is divided into a plurality of elements E having a unit length in the L direction, with an element width D0 = 1 mm and a thickness D1 = the plate thickness of material B (assumed to be 1.4 mm). The amount of heat Q (W / m²) per unit time (1 second) due to heat conduction and heat transfer in the i-th (i is a natural number) element E is expressed by the following formula.

[0185]

[0186] Each term of this equation was defined by the following equation.

[0187] (When element E is in contact with the first rib portion (111) and the second rib portion (121))

[0188] Q1: Heat transfer of element E to the mold per unit time due to contact heat transfer between material B and the rib section (111 or 121) (W / ㎡)

[0189]

[0190] Heat transfer coefficient h = 2000 W / m²·K

[0191] Mold temperature Tr=100℃

[0192] Tbi: Temperature of the i-th element E in material B

[0193] (When element E does not come into contact with the first rib portion (111) and the second rib portion (121))

[0194] Q1: Transfer of heat quantity of element E per unit time to the mold due to heat conduction through air in the groove (112 or 122) (W / ㎡)

[0195]

[0196] λa: Thermal conductivity of air = 0.04 W / m·K

[0197] Q2i: Transfer of heat (W / m²) per unit time from the i-1th element E to the adjacent i-th element E due to heat conduction within material B

[0198]

[0199] λb: Thermal conductivity of material B = 50 W / m·K

[0200] Tbi: Temperature of the i-th element E (material B)

[0201] Tbi-1: Temperature of the i-1th element E adjacent to the i-th element E

[0202] Δx: Distance between adjacent elements E = 1 mm

[0203] However, the temperature change ΔTb(°C) of element E per unit time accompanying the heat balance Q is expressed by the following equation.

[0204]

[0205] c: Specific heat of material B = 0.435 J / (g·K)

[0206] ρ: Density of material B = 7.8 × 10⁻⁶ 3 (g / ㎥)

[0207] In the heat conduction model described above, it was stated that the first rib portion (111) and the second rib portion (121) extend in the same direction, and the first groove portion (112) and the second groove portion (122) extend in the same direction. Additionally, it was stated that the width of the first rib portion (111) is the same as the width of the second rib portion (121), and the height of the first rib portion (111) is the same as the height of the second rib portion (121). Additionally, it was stated that the width of the first groove portion (112) is the same as the width of the second groove portion (122). Furthermore, as shown in FIG. 9, it was stated that during hot press forming, the entire top surface of the first rib portion (111) overlaps with the entire top surface of the second rib portion (121). Additionally, the cross-sectional shape perpendicular to the extension direction of the rib portions (111 and 121) was a rectangular shape.

[0208] As an initial condition, the temperature Tbi of element E at time 0 (second) was set to 622°C. Additionally, it was stated that element E is in contact with the first rib portion (111) and the second rib portion (121) in the sections of 500 to 1000 mm in the right and left directions of FIG. 9, respectively (i.e., the sections are set as the complete cooling regions (113 and 123)), and as a boundary condition, it was stated that the heat conduction within material B in element E at the point of 1000 mm in the right and left directions of FIG. 9 is insulated. Then, by performing a sequential calculation to calculate the temperature change ΔTb of element E at a time interval of 0.01 seconds, the temperature distribution of material B and its change over time were simulated.

[0209] By varying the width and height of the rib portions (111 and 121) and the width of the groove portions (112 and 122), the difference between the maximum value Tbimax and the minimum value Tbimin of Tbi in the section within 250 mm in the right and left directions of FIG. 9, respectively, was defined as the temperature fluctuation ΔT (°C) in material B. FIG. 8 was created using the calculated ΔT.

[0210] Referring to Fig. 8, when Fn1 is higher than 14, ΔT decreases rapidly along with the decrease in Fn1. Then, when Fn1 becomes 14 or lower, the degree of decrease in ΔT accompanying the decrease in Fn1 becomes gradual. When Fn1 becomes 10 or lower, the degree of decrease in ΔT accompanying the decrease in Fn1 becomes even more gradual. Therefore, in the graph of Fig. 8, inflection points exist near Fn1=14 and near Fn1=10.

[0211] Accordingly, the preferred upper limit of Fn1 is 14, and more preferably 10. If Fn1 is 14 or less, for example, the temperature fluctuation ΔT of material B becomes 110℃ or less. Also, if Fn1 is 10 or less, for example, the temperature fluctuation ΔT of material B becomes 40℃ or less.

[0212] [About Fn2]

[0213] In the mold (10), the first rib portion (111) and the second rib portion (121) are extended in the same direction, and the first groove portion (112) and the second groove portion (122) are extended in the same direction, and the width of the first rib portion (111) is 10 to 50% of the width of the first groove portion (112), and the width of the second rib portion (121) is 10 to 50% of the width of the second groove portion (122), and the width of the first rib portion (111) and the second rib portion (121) is 1.0 to 8.0 mm, and the height of the first rib portion (111) and the second rib portion (121) is 0.2 to 5.0 mm.

[0214] In this case, preferably, Fn2 defined by Equation (2) is 30 or more.

[0215]

[0216] Here, Ws is the width (mm) of the first groove (112) and the second groove (122). Wr is the width (mm) of the first rib (111) and the second rib (121). Hr is the height (mm) of the first rib (111) and the second rib (121).

[0217] Figure 10 is a diagram showing the relationship between Fn2 and the cooling rate V (°C / sec) of material B during hot press forming. Figure 10 was obtained by the aforementioned two-dimensional heat transfer simulation using the heat conduction model shown in Figure 9. In addition, in the heat transfer simulation, the cooling rate V was obtained by time averaging the temperature change of element E per unit time from time 0 to the time when the temperature of element E reaches 400°C. Here, element E used to calculate the cooling rate was defined as an element whose temperature Tbi represents Tbimax.

[0218] Referring to FIG. 10, as Fn2 increases, the cooling rate V of material B decreases rapidly, and then the degree of decrease in the cooling rate V becomes gradual. Therefore, the preferred lower limit of Fn2 is 30, more preferably 45, and even more preferably 90. If Fn2 is 30 or higher, for example, the cooling rate V of material B becomes 80°C or lower. Consequently, during hot press forming, it becomes easier to adjust the cooling stop temperature (i.e., the temperature of material B when the mold (10) is separated from material B) to a desired temperature. If Fn2 is 45 or higher, for example, the cooling rate of material B becomes 70°C / sec or lower. Consequently, it becomes even easier to adjust the cooling stop temperature to a desired temperature. If Fn2 is 90 or higher, for example, the cooling rate V of material B becomes 50°C / sec or lower. Consequently, it becomes even easier to adjust the cooling stop temperature to a desired temperature.

[0219] In the mold (10), more preferably, Fn1 is 14 or less and Fn2 is 30 or more. In this case, the temperature fluctuation ΔT of material B can be further suppressed and the cooling stop temperature can be more easily adjusted to a desired temperature.

[0220] More preferably, in the mold (10), the first rib portion (111) and the second rib portion (121) are extended in the same direction, and the first groove portion (112) and the second groove portion (122) are extended in the same direction, the width of the first rib portion (111) is 1.0 to 4.0 mm and is also 10 to 30% of the width of the first groove portion (112), and the width of the second rib portion (121) is 1.0 to 4.0 mm and is also 10 to 30% of the width of the second groove portion (122), and Fn1 is 14 or less, and / or Fn2 is 30 or more. In this case, the cooling speed of material B can be made slower. Therefore, it is easier to adjust the cooling stop temperature to a desired temperature. In addition, the temperature fluctuation of material B during hot press forming can be reduced.

[0221] [Another form of the mold (10) of this embodiment]

[0222] [Regarding the shape of the first molding surface (110) and the second molding surface (120) of the mold (10)]

[0223] The mold (10) according to the present embodiment is not limited to the above configuration. For example, the mold (10) is not limited to the shape shown in FIG. 2. The first molding surface (110) and the second molding surface (120) of the mold (10) may be curved in the longitudinal direction. Also, the cross-sectional shape perpendicular to the longitudinal direction (L direction) of the first molding surface (110) of the upper mold (11) of the mold (10) is not limited to a concave shape. The cross-sectional shape perpendicular to the longitudinal direction (L direction) of the second molding surface (120) of the lower mold (12) is not limited to a convex shape. When the first molding surface (110) of the upper mold (11) is fitted together with the second molding surface (120) of the lower mold (12), the shapes of the first molding surface (110) and the second molding surface (120) are not particularly limited.

[0224] [Regarding the arrangement of the first full cooling area (113) of the first molding surface (110) and the second full cooling area (123) of the second molding surface (120)]

[0225] Additionally, the arrangement of the first full cooling area (113) of the first molding surface (110) is not particularly limited. Likewise, the arrangement of the second full cooling area (123) of the second molding surface (120) is not particularly limited. It is sufficient that the first molding surface (110) includes the first full cooling area (113) and the second molding surface (120) includes the second full cooling area (123).

[0226] For example, the first complete cooling area (113) and the second complete cooling area (123) are not limited to the form shown in FIG. 2. FIG. 11 is a perspective view showing a different example of a mold (10) according to the present embodiment that is different from FIG. 2. As shown in FIG. 11, the first complete cooling area (113) may be disposed on the entire bottom surface of the groove of the concave portion of the first molding surface (110) of the upper mold (11) of the mold (10). The second complete cooling area (123) may be disposed on the entire top surface of the convex portion of the second molding surface (120) of the lower mold (12) of the mold (10).

[0227] FIG. 12 is a perspective view showing a different example of a mold (10) according to the present embodiment, different from FIG. 2 and FIG. 11. As shown in FIG. 12, a first cooling area (113) may be disposed on a part of the concave side of the first molding surface (110) of the upper mold (11) of the mold (10). A second cooling area (123) may be disposed on a part of the convex side of the second molding surface (120) of the lower mold (12) of the mold (10).

[0228] FIG. 13 is a perspective view showing another example of a mold (10) according to the present embodiment that is different from FIG. 2, FIG. 11, and FIG. 12. In FIG. 2, FIG. 11, and FIG. 12, the first molding surface (110) includes a first slow cooling area (113) and a first rapid cooling area (114). And, the second molding surface (120) includes a second slow cooling area (123) and a second rapid cooling area (124). In contrast, as shown in FIG. 13, the entire first molding surface (110) may be the first slow cooling area (113). Also, the entire second molding surface (120) may be the second slow cooling area (123).

[0229] As described above, if the first molding surface (110) includes a first full cooling region (113) and the second molding surface (120) includes a second full cooling region (123), the position of the first full cooling region (113) in the first molding surface (110) and the position of the second full cooling region (123) in the second molding surface (120) are not particularly limited. However, when the upper die (11) and the lower die (12) are in contact with material B and pressing material B during hot press molding, at least a portion of the first full cooling region (113) is positioned opposite to at least a portion of the second full cooling region (123).

[0230] In the present embodiment, the first complete cooling area (113) may also be defined as a part of the area where the first rib portion (111) and the first groove portion (112) are formed. Likewise, the second complete cooling area (123) may be defined as a part of the area where the second rib portion (121) and the second groove portion (122) are formed. In short, in the present embodiment, in at least a part of the first molding surface (110), the width of the first rib portion (111) is narrower than the width of the first groove portion (112), and in at least a part of the second molding surface (120), the width of the second rib portion (121) is narrower than the width of the second groove portion (122).

[0231] [Regarding the extension direction of the first rib section (111) and the second rib section (121)]

[0232] In the present embodiment, the extension direction of the first rib portion (111) and the extension direction of the second rib portion (121) are not particularly limited. For example, the first rib portion (111) and the second rib portion (121) do not have to be extended in the L direction shown in FIG. 5a and FIG. 6. FIG. 14 is another example of a schematic diagram of an enlarged area (100) of FIG. 3 that is different from FIG. 5a. FIG. 15 is a cross-sectional view along line segment XV-XV of FIG. 14. Referring to FIG. 14 and FIG. 15, in the present embodiment, the first rib portion (111), the first groove portion (112), the second rib portion (121), and the second groove portion (122) are all extended in the W direction and arranged in the L direction. In this case, the width of the first rib portion (111), the width of the first groove portion (112), the width of the second rib portion (121), and the width of the second groove portion (122) all represent the width in the L direction of the mold (10).

[0233] In hot press forming, the upper die (11) moves in the V direction together with the slide (3). As a result, material B is hot press formed by the first forming surface (110) of the upper die (11) and the second forming surface (120) of the lower die (12). When the first forming surface (110) and the second forming surface (120) have the shape shown in FIG. 2, the metal flow of material B proceeds in the W direction by hot press forming. That is, in the region (100), material B slides in the W direction with respect to the first forming surface (110) and the second forming surface (120).

[0234] As illustrated in FIGS. 14 and 15, when the first rib portion (111), the first groove portion (112), the second rib portion (121), and the second groove portion (122) all extend in the W direction, material B is less likely to receive frictional resistance from the first rib portion (111) and / or the second rib portion (121), and material B is more likely to slide relative to the first rib portion (111) and / or the second rib portion (121). Therefore, the formation of scratches on the surface of material B can be suppressed.

[0235] In this way, when the first rib portion (111), the first groove portion (112), the second rib portion (121) and the second groove portion (122) are extended in the direction of sliding movement of material B during the hot press forming process, it is possible to suppress the formation of scratches on the surface of material B during the hot press forming process.

[0236] [Regarding the arrangement relationship of the first rib section (111) and the second rib section (121)]

[0237] In the present embodiment, the arrangement of the first rib portion (111) and the second rib portion (121) does not have to completely overlap when the mold (10) is in a closed state, as shown in FIGS. 5a and FIGS. 6. FIGS. 16 is a different example of an enlarged schematic diagram of the area (100) of FIGS. 3, different from FIGS. 5a and FIGS. 14. FIGS. 17 is a schematic diagram showing only the rib portions when the area (100) of FIGS. 16 is viewed from the normal direction of the first complete cooling area (113). For example, with reference to FIGS. 16 and FIGS. 17, when the mold (10) is in a closed state, the first rib portion (111) and the second rib portion (121) may be arranged parallel to each other and overlap in an offset state. In this way, the first rib section (111) and the second rib section (121) may overlap at least partially.

[0238] In the present embodiment, the arrangement of the first rib portion (111) and the second rib portion (121) does not have to extend in the same direction as shown in FIG. 5a and FIG. 16. FIG. 18 is a different example of an enlarged schematic diagram of the region (100) of FIG. 3 that differs from FIG. 5a, FIG. 14, and FIG. 16. FIG. 19 is a schematic diagram showing only the rib portions when viewing the region (100) of FIG. 18 from the normal direction of the first complete cooling region. For example, as shown in FIG. 18 and FIG. 19, a plurality of first groove portions (112) and a plurality of first rib portions (111) may all extend in the L direction, and a plurality of second groove portions (122) and a plurality of second rib portions (121) may all extend in the W direction. In this case as well, referring to FIG. 19, when the mold (10) is in a closed state, the first rib portion (111) and the second rib portion (121) overlap at least partially.

[0239] [Regarding the first cool-down zone (113) and the second cool-down zone (123)]

[0240] In the present embodiment, it is preferable that the first complete cooling area (113) and the second complete cooling area (123) do not have a supply port for supplying a cooling medium to the surface of the first complete cooling area (113) and the second complete cooling area (123). For example, if the first complete cooling area (113) and the second complete cooling area (123) have a supply port, the material B is prone to excessive heat dissipation in the portion of the first complete cooling area (113) and the second complete cooling area (123) that has a supply port due to the air remaining in the piping inside the mold (10) (upper mold (11), lower mold (12)) passing through the supply port. Therefore, there is a possibility that temperature fluctuations of the material B may be exacerbated.

[0241] Meanwhile, the upper mold (11) and the lower mold (12) may have a cooling passage through which a cooling medium passes. In this case, the temperature of the upper mold (11) and the lower mold (12) during hot press forming can be maintained at a sufficiently low level.

[0242] [Method for manufacturing a hot press molded product using a mold (10)]

[0243] A method for manufacturing a hot press molded product by hot press molding using a mold (10) is described. The method for manufacturing a hot press molded product according to the present embodiment comprises the following steps.

[0244] · Preparation process

[0245] · Heating process

[0246] · Hot press forming process

[0247] · Type Irregular Process

[0248] The following describes each process.

[0249] [Preparation Process]

[0250] In the preparation process, material B having a desired chemical composition is prepared. In the present embodiment, material B is not particularly limited. Material B is, for example, a steel sheet. If material B is a steel sheet, the type of steel sheet is not particularly limited. Material B may be, for example, a steel sheet that has undergone surface treatment such as plating, or a steel sheet that has not undergone surface treatment such as plating (so-called raw material). When plating is performed, the plating may be hot-dip galvanizing, alloyed hot-dip galvanizing, or aluminum plating.

[0251] As described above, the chemical composition of the base steel sheet of material B is not particularly limited. The base steel sheet of material B comprises, for example, in mass%, C: 0.10 to 0.60%, Si: 0 to 5.0%, Mn: 0 to 5.0%, P: 0.100% or less, S: 0.100% or less, N: 0.100% or less, O: 0.100% or less, Al: 0 to 1.0%, Cr: 0 to 3.0%, Mo: 0 to 5.0%, V: 0 to 2.0%, Nb: 0 to 1.0%, Ti: 0 to 1.0%, B: 0 to 1.0%, Ca: 0 to 1.0%, Mg: 0 to 1.0%, Zr: 0 to 1.0%, rare earth elements: 0 to 1.0%, Co: 0 to 5.0%, W: 0 to 5.0%, It may have a chemical composition consisting of Ni: 0 to 3.0%, Cu: 0 to 3.0%, and the remainder being Fe and impurities. Here, impurities refer to elements that are incorporated from raw materials such as ore, scrap, or the manufacturing environment when steel is manufactured industrially, and are elements that are allowed within a range that does not adversely affect the hot press formed product according to the present embodiment.

[0252] The thickness of material B is not particularly limited, but is selected according to the characteristics of the hot press formed product to be obtained. For example, the thickness of material B is 0.6 to 3.2 mm. The mechanical properties of material B are also not particularly limited. Depending on the characteristics of the hot press formed product to be obtained, the mechanical properties of material B are appropriately selected. The tensile strength of material B may be, for example, 400 MPa or higher.

[0253] The method of preparing Material B is not particularly limited. For example, Material B may be prepared from molten steel having the chemical composition described above by a known manufacturing method. It may also be prepared by purchasing Material B manufactured by a third party.

[0254] [Heating Process]

[0255] In the heating process, the prepared material B is A c3 Heating is done to a temperature above the point. The heating temperature is A c3 If the temperature is below the point, material B does not become an austenite single phase. In this case, when material B is cooled during the hot press forming process, the formation of a hard phase (martensite and / or bainite) is insufficient in the region sandwiched between the first rapid cooling region (114) and the second rapid cooling region (124) of material B. Consequently, there are cases where sufficient strength is not obtained. The heating temperature is A c3 If the value is greater than that, material B prior to the hot press forming process becomes a single austenite phase. Therefore, when material B is cooled during the hot press forming process, a hard phase is sufficiently formed in the region sandwiched between the first rapid cooling region (114) and the second rapid cooling region (124) of material B. As a result, the strength of the region can be increased.

[0256] Preferably, the heating temperature is kept below 950°C. In this case, the heating time of material B can be shortened, thereby increasing productivity. Additionally, since the fuel and electricity required for heating can be reduced, manufacturing costs can be suppressed.

[0257] In the heating process, the method of heating material B is not particularly limited. For example, material B may be heated using a heating furnace such as an electric furnace, a gas furnace, a far-infrared furnace, or a near-infrared furnace. Additionally, material B may be heated using an electric heating device or a high-frequency induction heating device. In the heating process, the method of heating material B is not limited, and a known heating method may be appropriately selected.

[0258] [Hot Press Forming Process]

[0259] In the hot press forming process, A c3Material B, heated above a certain point, is hot-press formed using the mold (10) described above. In the hot-press forming process, material B, heated in the heating process, is loaded onto the second forming surface (120) of the lower mold (12). Then, as shown in FIG. 3, the upper mold (11) is brought relatively close to the lower mold (12), and the mold (10) is closed. At this time, material B comes into contact with the first forming surface (110) of the upper mold (11) and the second forming surface (120) of the lower mold (12). In other words, material B is sandwiched between the first forming surface (110) of the upper mold (11) and the second forming surface (120) of the lower mold (12). Hot-press forming is performed on material B using the upper mold (11) and the lower mold (12).

[0260] In addition, in the hot press forming process according to the present embodiment, material B is not cooled using a cooling medium during hot press forming. Instead, heat is dissipated from material B by the mold (10) that contacts material B during hot press forming. When the mold (10) is closed, in the first full cooling area (113), material B comes into contact with the first rib portion (111) of the first forming surface (110) of the upper mold (11). In addition, in the second full cooling area (123), material B comes into contact with the second rib portion (121) of the second forming surface (120) of the lower mold (12). At this time, the upper mold (11) and the lower mold (12) are sufficiently lower in temperature than material B. Therefore, material B is heat dissipated by the first rib portion (111) and the second rib portion (121). The temperature of the upper mold (11) and lower mold (12) is, for example, room temperature (20±15℃) to 200℃.

[0261] [Irregular Process]

[0262] In the release process, hot-press formed material B is released from the mold (10) to produce a hot-press formed product. Here, in the release process, the temperature of material B (hot-press formed product) when released from the mold (10) is defined as the cooling stop temperature. For example, if the cooling stop temperature is between the Mf point and the Ms point of the hot-press formed product, or between the Ms point and 500°C, a microstructure consisting of a hard phase, or a microstructure consisting of a hard phase and retained austenite, is obtained as the microstructure of the hot-press formed product. In this case, the obtained hot-press formed product has excellent shock absorption capacity. Accordingly, in the release process according to the present embodiment, preferably, when the temperature of the region sandwiched between the first full cooling region (113) and the second full cooling region (123) of material B is between the Mf point and the Ms point required from the chemical composition of material B, or between the Ms point and 500°C, material B is released from the mold (10).

[0263] In addition, the Ms point and Mf point of material B vary depending on the chemical composition of material B. Therefore, when obtaining a structure consisting of a hard phase or a structure consisting of a hard phase and retained austenite in material B, the preferred cooling stop temperature varies depending on the chemical composition of material B. However, according to the method of manufacturing a hot press molded product using a mold (10), the width and height of the first rib portion (111), the first groove portion (112), the second rib portion (121), and the second groove portion (122) formed in the first full cooling region (113) and the second full cooling region (123), and the chemical composition of material B, can be obtained by heat transfer simulation of the cooling rate, the change in temperature over time, and the temperature distribution after a predetermined time has elapsed after hot press molding in the region sandwiched between the first full cooling region (113) and the second full cooling region (123) in material B. Therefore, by these heat transfer simulations, a desired cooling stop temperature or the time from the start of hot press forming until demolding can be determined. Accordingly, according to the mold (10) of the present embodiment, a hot press formed article having a structure consisting of a hard phase or a structure consisting of a hard phase and retained austenite can be manufactured by hot press forming.

[0264] [Other processes]

[0265] The method for manufacturing a hot press molded article according to the present embodiment may also include other manufacturing processes other than those mentioned above. For example, the method for manufacturing a hot press molded article according to the present embodiment may perform a heating and holding process in a temperature range of 500°C or lower after the demolding process.

[0266] In the heat holding process, the hot press molded product after the demolding process is heated and held in a temperature range of 500°C or lower. Specifically, the hot press molded product manufactured by demolding from the mold (10) is held at a heating temperature of 100 to 500°C. In this case, the heat holding process allows carbon to be distributed from the hard phase in the microstructure of the hot press molded product to the residual austenite. Since carbon is concentrated in the residual austenite, the formation of residual austenite is promoted. As a result, the proportion of residual austenite in the hot press molded product increases. In this case, the residual austenite transforms into martensite during impact deformation, thereby improving the ductility of the hot press molded product (so-called TRIP (Transformation Induced Plasticity) effect). As a result, the shock absorption capacity of the hot press molded product is further increased.

[0267] The preferred upper limit for the heating holding temperature is 400°C. Additionally, it is preferable to maintain the heating holding temperature at Ms point - 209°C or higher. In this case, the shock absorption capacity of the hot press molded product becomes more stable and higher. Therefore, if Ms point - 209°C exceeds 100°C, the preferred lower limit for the heating holding temperature is Ms point - 209°C. The heating holding time is not particularly limited. The holding time at the heating holding temperature is preferably, for example, 5 seconds to 30 minutes (1800 seconds).

[0268] The embodiments of the present disclosure have been described above. However, the embodiments described above are merely examples for carrying out the present disclosure. Accordingly, the present disclosure is not limited to the embodiments described above, and may be carried out by appropriately modifying the embodiments described above within the scope without departing from the spirit thereof. Explanation of the symbols

[0269] 1: Hot press device 10: Mold 11: Hieroglyphs 110: First molded surface 111: The 1st Libe 112: 1st Home Department 113: First complete cooling zone 12: Ha-hyung 120: Second molded surface 121: The 2nd Libe 122: 2nd Home 123: Second complete cooling zone

Claims

Claim 1 A mold for performing hot press forming on a material, comprising an upper mold having a first forming surface and a lower mold having a second forming surface that is positioned opposite to the first forming surface and, together with the first forming surface, hot press forms the material during hot press forming, wherein the first forming surface includes a first cooling region having a plurality of first rib portions and a plurality of first groove portions, wherein the plurality of first rib portions are arranged in the width direction of the first rib portions and the plurality of first groove portions are arranged in the width direction of the first groove portions, wherein the first rib portions are formed between adjacent first groove portions and the width of the first rib portions is narrower than the width of the first groove portions, and the second forming surface includes a second cooling region having a plurality of second rib portions and a plurality of second groove portions, wherein the plurality of second rib portions are arranged in the width direction of the second rib portions and the plurality of second groove portions are arranged in the width direction of the second groove portions, and wherein the second rib portions A mold formed between adjacent second groove portions, wherein the width of the second rib portion is narrower than the width of the second groove portion, and during hot press forming, at least a portion of the first cooled-down area is positioned opposite to at least a portion of the second cooled-down area, and when the first cooled-down area and the second cooled-down area are viewed from the normal direction of the first cooled-down area, the first rib portion and the second rib portion overlap at least a portion. Claim 2 A mold according to claim 1, wherein, during hot press forming, at least a portion of the first cooled-down region is positioned opposite to at least a portion of the second cooled-down region, and when the first cooled-down region and the second cooled-down region are viewed from the normal direction of the first cooled-down region, the first rib portion and the second rib portion extend in the same direction, and the first groove portion and the second groove portion extend in the same direction. Claim 3 A mold according to claim 1 or 2, wherein the width of the first rib portion is 10 to 50% of the width of the first groove portion, and the width of the second rib portion is 10 to 50% of the width of the second groove portion. Claim 4 A mold according to claim 1, wherein in at least a portion of the first complete cooling region, the width of the first rib portion is 1.0 to 8.0 mm and the height of the first rib portion is 0.2 to 5.0 mm, and in at least a portion of the second complete cooling region, the width of the second rib portion is 1.0 to 8.0 mm and the height of the second rib portion is 0.2 to 5.0 mm. Claim 5 A mold according to claim 2, wherein the width of the first rib portion is 10 to 50% of the width of the first groove portion, the width of the second rib portion is 10 to 50% of the width of the second groove portion, the width of each of the first rib portion and the second rib portion is 1.0 to 8.0 mm, the height of each of the first rib portion and the second rib portion is 0.2 to 5.0 mm, and Fn1 defined by Equation (1) is 14 or less. Here, in Equation (1), Wr is the width (mm) of the first rib portion and the second rib portion, P0 = Wr / Ws, Ws is the width (mm) of the first groove portion and the second groove portion, and Hr is the height (mm) of the first rib portion and the second rib portion. Claim 6 A mold according to claim 2 or 5, wherein the width of the first rib portion is 10 to 50% of the width of the first groove portion, the width of the second rib portion is 10 to 50% of the width of the second groove portion, the width of each of the first rib portion and the second rib portion is 1.0 to 8.0 mm, the height of each of the first rib portion and the second rib portion is 0.2 to 5.0 mm, and Fn2 defined by Equation (2) is 30 or more. Here, in Equation (2), Ws is the width (mm) of the first groove and the second groove, Wr is the width (mm) of the first rib and the second rib, and Hr is the height (mm) of the first rib and the second rib. Claim 7 A mold according to claim 4 or 5, wherein in at least a portion of the first complete cooling region, the width of the first rib portion is 1.0 to 4.0 mm and is also 10 to 30% of the width of the first groove portion, and in at least a portion of the second complete cooling region, the width of the second rib portion is 1.0 to 4.0 mm and is also 10 to 30% of the width of the second groove portion. Claim 8 A method for manufacturing a hot press formed product, comprising a process for preparing a material, and the prepared material A c3 A method for manufacturing a hot press molded product, comprising: a process of heating to a temperature above a certain point; a process of performing hot press molding on the heated material using a mold described in claim 1; and a process of releasing the hot press molded material from the mold to manufacture a hot press molded product. Claim 9 A method for manufacturing a hot press molded product according to claim 8, further comprising a process of maintaining the hot press molded product manufactured by releasing it from the mold at 100 to 500°C.

Images