Mold, hot press apparatus, and method for manufacturing hot press-formed products

Abstract

The present invention provides a mold, a hot press apparatus, and a manufacturing method that enable the easy removal of hot press-formed products from the mold. [Solution] A die for performing deep drawing on a heated blank by hot pressing. The die comprises a punch having a first punch having a punch vertical wall portion extending along the pressing direction, and a second punch positioned at the blank-side end of the first punch in the pressing direction and movable along the pressing direction relative to the first punch, a die positioned opposite the punch, and a cushion that presses the second punch toward the blank side.

Description

Technical Field

[0001] The present invention relates to a mold, a hot press device, and a method for manufacturing a hot press molded product.

Background Art

[0002] In hot press molding, various manufacturing methods have been proposed. For example, Patent Document 1 discloses a manufacturing method for producing a hot press molded product by performing hot press molding on a blank using a hot press mold including a punch top and two punch shoulder R parts, an inner pad that protrudes from the punch top by a predetermined amount and is accommodated in the punch top at the forming bottom dead center.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When performing drawing molding by hot press, the blank is rapidly cooled by the mold in a state where the mold reaches the bottom dead center, that is, in a state where the mold is clamped. As a result, the blank thermally shrinks and may adhere to the mold. There has been a concern that such a hot press molded product adhered to the mold may be difficult to remove from the mold.

[0005] An object of the present invention is to provide a mold, a hot press device, and a method for manufacturing a hot press molded product that can easily remove the hot press molded product from the mold.

Means for Solving the Problems

[0006] As one of the means for solving the above problems, the present application discloses the following plurality of aspects.

[0007] [Aspect 1] A die for performing deep drawing by hot pressing on a heated blank, A first punch having a punch vertical wall portion extending along the pressing direction, A second punch is positioned at the blank-side tip of the first punch in the pressing direction and is movable relative to the first punch along the pressing direction, A punch having, A die positioned opposite the punch, A cushion that applies pressure to the blank side of the aforementioned second punch, A mold equipped with the following features.

[0008] [Aspect 2] The second punch has a punch top and a punch shoulder having a cross-sectional R shape continuous with the outer edge of the punch top, The mold according to embodiment 1, wherein the punch vertical wall portion is smoothly continuous with the punch shoulder portion.

[0009] [Aspect 3] The first punch has a through hole that penetrates along the pressing direction, The mold according to embodiment 1 or 2, wherein the second punch has a shaft portion that can be inserted into the through hole.

[0010] [Aspect 4] A hot press apparatus comprising a mold described in any one of embodiments 1 to 3.

[0011] [Aspect 5] A manufacturing method for producing a hot press-formed product having a bottom and a vertical wall integrally provided with the bottom, using a mold, The first step involves closing the mold over the heated blank and performing press drawing molding, A manufacturing method comprising: a second step after the first step, opening the mold, pressing the bottom toward the blank side, and separating a portion of the vertical wall from the mold. [Effects of the Invention]

[0012] According to the present invention, it is possible to easily remove a hot press-formed product from a mold.

Brief Description of the Drawings

[0013] [Figure 1] It is a perspective view schematically showing a hot press-formed product manufactured by the mold according to the present embodiment. [Figure 2] It is a perspective view schematically showing a mold for performing hot press forming according to the present embodiment. [Figure 3] It is a cross-sectional view schematically showing a state in which a blank is drawn and formed by the mold according to the present embodiment, and is a view showing a state in which the blank is set in the mold. [Figure 4] It is a cross-sectional view schematically showing a state in which a blank is drawn and formed by the mold according to the present embodiment, and is a view showing a state in which the die is moving in the press direction. [Figure 5] It is a cross-sectional view schematically showing a state in which a blank is drawn and formed by the mold according to the present embodiment, and is a view showing a state in which the die has reached the bottom dead center. [Figure 6] It is a cross-sectional view schematically showing a state in which a blank is drawn and formed by the mold according to the present embodiment, and is a view showing a state in which the mold is opened and the vertical wall is separated from the mold. [Figure 7] It is a perspective view schematically showing a mold for performing hot press forming according to a modification of the present embodiment.

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. <00第35行

[0015] [Hot Press-Formed Product] Referring to FIG. 1, the hot press-formed product 10 will be described. The use of the hot press-formed product 10 is, for example, a torque converter, a wheel disk, a battery box, or a subframe. The hot press-formed product 10 shown in FIG. 1 has a circular cup shape in plan view. The hot press-formed product 10 has a bottom 12 and a vertical wall 14 provided integrally with the bottom 12. In this specification, the plate thickness direction Z of the top 16 may also be referred to as the axial direction.

[0016] The bottom 12 has a top 16 and a shoulder 18 provided at the outer edge of the top 16. The top 16 is disk-shaped. The shoulder 18 has an R shape curved in a direction convex outward in the longitudinal section. The inner edge 18M of the shoulder 18 is connected to the outer edge 16S of the top 16. The vertical wall 14 is cylindrical. One axial end 14N of the vertical wall 14 is connected to the outer edge 18S of the shoulder 18. That is, the hot press-formed product 10 has a bottom 12 and a vertical wall 14 provided so as to surround the entire outer circumference of the bottom 12. The other axial end 14F of the vertical wall 14 terminates axially and does not have a flange extending in a direction orthogonal to the axial direction. The flange in this case does not include burrs inevitably generated by press forming. That is, burrs may be formed at the other axial end 14F of the vertical wall 14 of the hot press-formed product 10.

[0017] The size of the hot press-formed product shown in FIG. 1 is not particularly limited, but for example, it is 40 mm or more and 500 mm or less in diameter and 5 mm or more and 80 mm or less in height. The angle θ formed between the outer surface of the vertical wall 14 and the plate thickness direction Z of the top 16 is preferably 0 degrees or more and 5 degrees or less toward the outside from the center of the top 16.

[0018] [Hot Pressing Device] Referring to Figures 2 and 3, the mold used for hot press forming in the manufacturing method of the hot press-formed product 10 according to this embodiment will be described. The hot press apparatus 20 comprises a press machine (not shown) and a mold 24 attached to the press machine. In this specification, the driving direction of the press machine, i.e., the direction in which force acts on the blank, is defined as the press direction, the side facing the blank is defined as the blank side, and the side away from the blank is defined as the non-blank side. The direction perpendicular to the press direction is defined as the surface direction, the side facing the center of the mold is defined as the inner surface direction, and the side away from the center of the mold is defined as the outer surface direction. The press direction is also the same as the thickness direction Z of the top portion 16 of the hot press-formed product 10.

[0019] The mold 24 is used to perform hot press forming on the blank 26 when manufacturing a cup-shaped hot press-formed product 10. The mold 24 shown in Figure 2 comprises a punch 28 and a die 30. Figure 2 shows the blank 26 positioned between the punch 28, which acts as the lower mold, and the die 30, which acts as the upper mold.

[0020] The punch 28 is equipped with a refrigerant flow path (not shown). The punch 28 is sized according to the size of the hot press-formed product 10. The punch 28 is positioned opposite the die 30 with the blank 26 in between. The punch 28 has a first punch 32 and a second punch 34 positioned at the blank-side tip 32N of the first punch 32 and movable along the pressing direction relative to the first punch 32.

[0021] The first punch 32 has a punch vertical wall portion 36 that extends along the pressing direction. The punch vertical wall portion 36 has a cylindrical outer surface with an axis along the pressing direction. The first punch 32 is a cylindrical member and has a through hole 38 that penetrates through the center along the pressing direction. The pair of ends 32N and 32F of the first punch 32 in the pressing direction each have a flat surface perpendicular to the pressing direction. The non-blank end 32F of the first punch 32 is fixed to the press machine. The outer edge 32S of the blank end 32N of the first punch 32 is connected to the upper end edge 36N of the punch vertical wall portion 36. The through hole 38 is located in the center of the blank end 32N of the first punch 32.

[0022] The second punch 34 has a punch top 40 and a punch shoulder 42 that is continuous with the outer edge 40S of the punch top 40. The punch top 40 is positioned on the blank side and has a disc-shaped surface perpendicular to the pressing direction. In a longitudinal cross-section, the punch shoulder 42 has an R-shape that is inclined outward in the surface direction from the blank side to the non-blank side and curved in a direction that is convex outward in the surface direction. That is, the outer edge 42S of the punch shoulder 42 is an R-shape. The inner edge 42M of the punch shoulder 42 is connected to the outer edge 40S of the punch top 40.

[0023] The second punch 34 has a stop portion 44 on the non-blank side relative to the punch top 40 and punch shoulder 42. The stop portion 44 has a flat surface perpendicular to the pressing direction. The outer edge 44S of the stop portion 44 is connected to the outer edge 42S of the punch shoulder 42. The second punch 34 has a shaft portion 46 that extends from the stop portion 44 toward the non-blank side in the pressing direction. The shaft portion 46 is inserted into the through hole 38 of the first punch 32. The second punch 34 covers the tip 32N of the first punch 32 when the stop portion 44 is in contact with the tip 32N of the blank side of the first punch 32. That is, when viewed from the pressing direction, the first punch 32 does not protrude from the outer edge 42S of the punch shoulder 42 of the second punch 34 in a direction perpendicular to the pressing direction.

[0024] As a result, the second punch 34 is movable relative to the first punch 32 in the pressing direction by the movement of its shaft portion 46 along the through hole 38. That is, the second punch 34 is movable toward the blank side from the position where its stop portion 44 contacts the blank-side tip 32N of the first punch 32 in the pressing direction. When the stop portion 44 of the second punch 34 is in contact with the blank-side tip 32N of the first punch 32, the punch vertical wall portion 36 and the outer edge 42S of the punch shoulder portion 42 of the second punch 34 are smoothly continuous. In other words, the surface of the punch vertical wall portion 36 and the outer edge 42S of the punch shoulder portion 42 are aligned when viewed from a direction perpendicular to the pressing direction, and there is no step difference exceeding the manufacturing tolerance.

[0025] When viewed as a whole, the punch 28 has, in order from the blank side in the pressing direction, a punch top 40, a punch shoulder 42, and a punch vertical wall 36. The punch 28 can be separated at the outer edge 42S, which is the end of the rounded corner of the punch shoulder 42, into a second punch 34 including the punch top 40 and the punch shoulder 42, and a first punch 32 including the punch vertical wall 36.

[0026] As shown in Figure 3, the mold 24 includes a cushion 48 that presses the second punch 34 toward the blank side. The cushion 48 is not particularly limited as long as it can press the second punch 34 toward the blank side, and for example, a spring, a cam, a hydraulic cylinder, an air cylinder, or a ball screw driven linearly by a motor can be used. The cushion 48 is mechanically connected to the non-blank side of the shaft portion 46 and presses the second punch 34 toward the blank side through the shaft portion 46.

[0027] The die 30 is equipped with a refrigerant flow path (not shown). The die 30 is sized according to the size of the hot press-formed product 10. The die 30 is positioned opposite the punch 28 with the blank 26 in between. The surface of the die 30 facing the blank 26 has a flat surface 50 perpendicular to the pressing direction and a concave surface 52 that is recessed in a mortar shape toward the non-blank side.

[0028] The die 30 has a die top 54, a die shoulder 56, and a die vertical wall 58. The die top 54 is located on the non-blank side in the pressing direction and has a disc-shaped surface perpendicular to the pressing direction. The die shoulder 56 has an R-shape in which, in a longitudinal cross-section, it is inclined outward in the surface direction from the non-blank side toward the blank side and is curved in a direction that is concave outward in the surface direction. The inner edge 56M of the die shoulder 56 is connected to the outer edge 54S of the die top 54. The die vertical wall 58 has a cylindrical inner surface with an axis along the pressing direction. The upper edge 58N of the die vertical wall 58 is connected to the outer edge 56S of the die shoulder 56. The lower edge 58F of the die vertical wall 58 is connected to the flat surface 50.

[0029] The punch top 40 and the die top 54 form the top 16 of the hot press-formed product 10. The punch shoulder 42 and the die shoulder 56 form the shoulder 18 of the hot press-formed product 10. The punch vertical wall 36 and the die vertical wall 58 form the vertical wall 14 of the hot press-formed product 10.

[0030] [blank] The blank 26 is, for example, a steel plate with a thickness of 1 mm to 5 mm. Preferably, the blank 26 has a tensile strength of 1.0 GPa or more after quenching. The blank 26 has a circular shape when viewed from the thickness direction. The steel material used as the blank 26 has a chemical composition of, for example, C: 0.1% to 0.8% by mass, Si: 0.001% to 2.0%, Mn: 0.5% to 3.0%, P: 0.15% or less, and S: 0.01% or less.

[0031] Furthermore, the steel material preferably contains, by mass%, sol.Al: 0.001% to 1.0%, N: 0.01% or less, and B: 0.01% or less as a chemical composition, with the remainder being Fe and impurities. Alternatively, the above chemical composition may include, in place of a portion of Fe, one or more elements selected from the group consisting of Ti, Nb, V, Cr, Mo, Cu, and Ni.

[0032] Other additive elements such as Ti, Nb, V, Cr, Mo, Cu, and Ni may be added as needed to improve the hardenability of the steel and to ensure stable strength after quenching.

[0033] [Manufacturing method] Next, a method for manufacturing the hot press-formed product 10 will be described. The hot press-formed product 10 comprises a heating step and a quenching step.

[0034] (Heating process) In the heating process, the blank 26 is heated to a temperature above its Ac3 transformation point to austenite it. The Ac3 transformation point, which indicates the austenitization transformation temperature, is the temperature at which the blank 26 made of the aforementioned steel material is completely austenitized, and is shown as follows as an example. Ac3(℃)=910-203×√C(mass%)+44.7×Si(mass%)-30×Mn(mass%)-11×Cr(mass%)+700×S(mass%)+400×Al(mass%)+50×Ti(mass%) Here, C represents carbon, Si represents silicon, Mn represents manganese, Cr represents chromium, S represents sulfur, Al represents aluminum, and Ti represents titanium.

[0035] (Heat treatment process) The blank 26, heated to above the Ac3 transformation point in the heating process, is hot-press-formed using the mold 24 installed in the press machine of the hot-pressing device 20. After hot-press forming, the blank 26 is rapidly cooled by removing heat from the punch 28 and die 30 while the mold is still clamped, thereby causing a martensitic transformation. In other words, the quenching process includes the steps of setting, deep drawing, cooling, and demolding.

[0036] ·set As shown in Figure 3, the blank 26, which has been heated to above the Ac3 transformation point in the heating process, is set between the punch 28 and the die 30. At this time, the blank 26 is positioned in the mold 24 by, for example, positioning pins (not shown).

[0037] • Deep drawing Before the deep drawing process begins, the punch 28 is in a state where the second punch 34, which is pressurized by the cushion 48, protrudes toward the blank side relative to the first punch 32. That is, a predetermined gap is provided in the pressing direction between the blank-side tip 32N of the first punch 32 and the stop portion 44 of the second punch 34. This state will be referred to as the starting point of the die 24. At the starting point, the die 30 is moved toward the blank side, i.e., downwards, toward the punch 28. As shown in Figure 4, the blank 26 is pushed downwards, and at the same time, the second punch 34 is also pushed downwards through the blank 26. When the pressing force of the die 30 exceeds the pressing force of the cushion 48 that presses the second punch 34, the second punch 34 moves downwards, and consequently, the gap between the blank-side tip 32N of the first punch 32 and the stop portion 44 of the second punch 34 gradually narrows. As the die 30 reaches its bottom dead center, the central portion of the blank 26 is pushed upward by the punch top 40 and punch shoulder 42, while the outer edge surrounding the central portion is pushed downward by the flat surface 50 of the die 30 and the lower edge 58F of the die vertical wall 58, causing the blank 26 to be drawn. In this way, when drawing is initiated on a blank 26 that is above the Ac3 transformation point, the blank 26 begins to deform. As shown in Figure 5, when the die 30 reaches its bottom dead center, the outer edge of the blank 26 is drawn between the punch vertical wall 36 and the die vertical wall 58, becoming the vertical wall 14 of the hot press-formed product 10. At this time, the stop portion 44 of the second punch 34 contacts the blank-side tip 32N of the first punch 32 and stops. This state is referred to as the end point of the mold 24. At the end point, the outer edge 42S of the punch shoulder 42 and the punch vertical wall 36 are smoothly continuous, thereby forming a smooth inner circumferential surface in the hot press-formed product 10.

[0038] ·cooling When the die 30 reaches its bottom dead center, the formed blank 26 is in close contact with the die 30 and the punch 28. This state is called mold clamping. In the clamped state, the heat of the blank 26 is rapidly removed by the die 30 and the punch 28. As a result, the blank 26 undergoes martensitic transformation. That is, the blank 26 is hardened, and thus becomes a hot-pressed product 10. One method for removing heat from the blank 26 is to cool it indirectly by using a coolant flowing inside the punch 28 and die 30. Another method for removing heat is to directly cool the blank 26 by injecting a coolant from the punch 28 and die 30. The time from the heating process to the start of cooling shall be within 15 seconds. In other words, the time from when the blank 26 heated in the heating process leaves the heating furnace until the die 30 reaches its bottom dead center shall be within 15 seconds.

[0039] • Release After cooling, the mold 24 is opened. Specifically, the die 30 is moved to the non-blank side, i.e., upward. As a result, as shown in Figure 6, the force that was pushing the second punch 34 downward is removed, and the second punch 34 moves to the blank side, i.e., upward, due to the pressure applied by the cushion 48. The gap between the stop portion 44 of the second punch 34 and the blank-side tip 32N of the first punch 32 gradually widens. The hot press-formed product 10 moves to the blank side, i.e., upward, together with the second punch 34. In this way, the vertical wall 14 of the hot press-formed product 10 separates from the punch vertical wall portion 36.

[0040] [Mechanism of Action and Effects] During the cooling process described above, the blank 26 undergoes thermal contraction as heat is rapidly removed from the blank 26 while it is clamped in place. As a result, the vertical walls 14 of the hot press-formed product 10 come into close contact with the punch vertical wall portion 36.

[0041] In this embodiment, the die 30 is moved to the non-blank side, i.e., upward, and the hot press-formed product 10 is pressed upward by the second punch 34, thereby separating the vertical wall 14 from the punch vertical wall portion 36. Therefore, the hot press apparatus 20 according to this embodiment can easily remove the hot press-formed product 10 from the mold 24.

[0042] The second punch 34 separates from the first punch 32 at the rounded end of the punch shoulder 42 (the outer edge 42S of the punch shoulder 42). Therefore, when the hot press-formed product 10 returns to the starting point after cooling, the hot press-formed product 10 is in contact with the second punch 34 at the top 16 and shoulder 18, but the contact position between the vertical wall 14 and the punch vertical wall portion 36 is shifted from the contact position at the end point. As a result, the hot press-formed product 10 can be easily removed from the mold 24. In this embodiment, the hot press apparatus 20 does not have contact with the second punch 34 when it returns to the starting point, so the hot press-formed product 10 can be removed from the second punch 34 more easily.

[0043] The second punch 34 applies pressure to the bottom 12 of the hot-pressed product 10 toward the blank side, making it difficult to deform the hot-pressed product 10. In other words, the second punch 34 has a punch top 40 and a punch shoulder 42, and applies pressure to the entire bottom 12, including the top 16 and shoulder 18 of the hot-pressed product 10, making it difficult to deform the hot-pressed product 10.

[0044] The second punch 34 has a shaft portion 46 inserted into the through hole 38 of the first punch 32, which allows it to move more reliably along the pressing direction relative to the first punch 32. At the end point, the stop portion 44 of the second punch 34 contacts the blank-side tip 32N of the first punch 32 and stops, so that a gap is less likely to form between the punch shoulder portion 42 and the punch vertical wall portion 36. Also, the punch vertical wall portion 36 is smoothly continuous with the punch shoulder portion 42. Therefore, the hot press device 20 can form a hot press molded product 10 in which the bottom 12 and the vertical wall 14 are smoothly continuous.

[0045] [Differentiation] The present invention is not limited to the embodiments described above, and can be modified as appropriate within the scope of the spirit of the invention. The examples provided below can be implemented individually or in combination with the above embodiments as appropriate.

[0046] Although the hot-press-formed product 10 according to the above embodiment has been described as having a circular cup shape in plan view, the present invention is not limited to this. For example, the hot-press-formed product 10 may have a rectangular container shape in plan view.

[0047] Figure 7 is a schematic perspective view showing a modified mold 24A for forming a hot press-formed product having a rectangular container shape in plan view. Since the mold 24A in this modified example differs from the mold 24 of the above embodiment only in its external shape, the same reference numerals are used for similar components, and their descriptions are omitted as appropriate. The mold 24A comprises a punch 28A and a die 30A. The punch 28A has a first punch 32A and a second punch 34A positioned at the blank-side tip 32AN of the first punch 32A and movable along the pressing direction relative to the first punch 32A.

[0048] The first punch 32A has a punch vertical wall portion 36A that extends along the pressing direction. The punch vertical wall portion 36A has a prism-like outer surface with an axis along the pressing direction. The first punch 32A has a through hole 38A that penetrates through the center along the pressing direction.

[0049] The second punch 34A has a punch top 40A and a punch shoulder 42A that is continuous with the outer edge 40AS of the punch top 40A. The punch top 40A is located on the blank side and has a rectangular plate-like surface perpendicular to the press direction. The punch shoulder 42A has an R-shape in which, in a longitudinal cross-section, it is inclined outward in the surface direction from the blank side toward the non-blank side and is curved in a direction that is convex outward in the surface direction. The second punch 34A has a stop portion 44A on the non-blank side relative to the punch top 40A. The second punch 34A has a shaft portion 46A that extends from the stop portion 44A toward the non-blank side in the press direction. The shaft portion 46A is inserted into the through hole 38A of the first punch 32A. The die 24A, although not shown in Figure 7, includes a cushion 48 that presses the second punch 34A toward the blank side.

[0050] The die 30A has a die top 54A, a die shoulder 56A, and a die vertical wall 58A. The die top 54A is located on the non-blank side and has a rectangular plate-like surface perpendicular to the pressing direction. The die shoulder 56A has an R-shape in its longitudinal cross-section, which is inclined outward in the surface direction from the non-blank side toward the blank side and curved in a concave direction toward the surface direction. The die vertical wall 58A has an inner surface like the inside of a rectangular tube with an axis along the pressing direction.

[0051] The mold 24A according to this modified example has a second punch 34A that is pressed toward the blank side, and by pressing the hot press molded product toward the blank side with the second punch 34A, the vertical wall can be separated from the punch vertical wall portion 36A. Therefore, the mold 24A according to this modified example can obtain the same effects as the above embodiment.

[0052] The hot press-formed product 10 according to the above embodiment was described in which a vertical wall 14 is provided so as to surround the entire outer edge of the bottom 12, but the present invention is not limited to this. For example, the present invention can be applied to a hot press-formed product that has a shape that can be formed by deep drawing and has opposing vertical walls on either side of the bottom.

[0053] Although the hot press apparatus 20 according to the above embodiment was described as having a lower punch 28 and an upper die 30, the present invention is not limited to this case, and the punch 28 may be the upper die and the die 30 the lower die. Furthermore, although the case where the pressing direction is vertical was described, the present invention is not limited to this case, and the pressing direction may be horizontal.

[0054] The second punch 34 according to the above embodiment may be divided into multiple sections when viewed from the pressing direction, as long as it can evenly apply pressure to the hot-pressed product 10 toward the blank side. For example, the second punch 34 may be divided into four equal parts radially when viewed from the pressing direction, with a pair of opposing quarter punches movable relative to the first punch 32 to apply pressure to the hot-pressed product 10 toward the blank side, and the remaining pair of quarter punches fixed to the first punch 32.

[0055] In the demolding process, it is not limited to the case where the entire vertical wall 14 of the hot press-formed product 10 separates from the punch vertical wall portion 36. For example, if a part of the vertical wall 14 separates from the punch vertical wall portion 36, the hot press-formed product 10 can be easily removed from the mold 24, so a part of the vertical wall 14 may be in contact with the punch vertical wall portion 36. Furthermore, for example, the position where the vertical wall 14 and the punch vertical wall portion 36 are in contact at the end point may simply shift in the pressing direction when returning to the starting point. That is, although the vertical wall 14 adheres tightly to the punch vertical wall portion 36 due to thermal shrinkage, the position where the vertical wall 14 is in contact with the punch vertical wall portion 36 shifts as the hot press-formed product 10 is pushed out by the second punch 34, so it can be easily removed from the mold 24 compared to when it is in tight contact with the mold 24 at the end point.

[0056] The die 24 according to the above embodiment was described in a state where, at the starting point, the second punch 34, which is pressurized by the cushion 48, protrudes toward the blank side relative to the first punch 32. However, the present invention is not limited to this. For example, the die 24 may have a connecting part (not shown), such as a locking pin, that releasably connects the second punch 34 to the first punch 32. The connecting part fixes the second punch 34 to the first punch 32 with a stop part 44 in contact with the blank-side tip 32N of the first punch 32 at the starting point. The connecting part is released when the die 30 reaches the bottom dead center. As the die 24 returns to the starting point, the second punch 34 moves toward the blank side, i.e., upward, due to the pressure applied by the cushion 48. As a result, the vertical wall 14 of the hot press-formed product 10 separates from the punch vertical wall portion 36.

[0057] The mold 24 according to the above embodiment was described in a case where the first punch 32 and the second punch 34 are separated at the R-end of the punch shoulder 42 (outer edge 42S of the punch shoulder 42), but the present invention is not limited to this. For example, the first punch 32 may extend beyond the R-end of the punch shoulder 42 (outer edge 42S of the punch shoulder 42) and include a part of the punch vertical wall. [Explanation of Symbols]

[0058] 10 Hot press-formed products 12 bottom 14 Vertical walls 14N One end (vertical wall) 14F Other end (vertical wall) 16 Top 16M Inner edge (top) 16S outer edge (top) 18 Shoulder 18M inner edge (shoulder area) 18S Outer edge (shoulder area) 20 Hot press machine 24 molds 26 Blank 28 Punch 30 Dies 32 First punch 32N Blank tip 32F Non-blank tip 32S outer edge 34 Second punch 36 Punch vertical wall section 36N Upper edge 38 through holes 40 Punch top 40S Outer edge (punch top) 42 Punching shoulder 42M inner edge (punch shoulder area) 42S Outer edge (punch shoulder area) 44 Stop part 44S outer edge 46 Shaft section 48 cushions 50 flat surface 52 Concave surface 54 Top of the die 54S Outer edge (top of die) 56. Die shoulder section 56M Inner edge (die shoulder) 56S Outer edge (die shoulder) 58. Vertical wall section of the die 58N Upper edge (vertical wall portion of the die) 58F Lower edge (vertical wall section of the die) θ angle

Claims

1. A die for performing deep drawing by hot pressing on a heated blank, A first punch having a punch vertical wall portion extending along the pressing direction, A second punch is positioned at the blank-side tip of the first punch in the pressing direction and is movable relative to the first punch along the pressing direction, A punch having, A die positioned opposite the punch, A cushion that applies pressure to the blank side of the second punch, A mold equipped with the following features.

2. The second punch has a punch top and a punch shoulder having a cross-sectional radius shape that is continuous with the outer edge of the punch top. The mold according to claim 1, wherein the punch vertical wall portion is smoothly continuous with the punch shoulder portion.

3. The first punch has a through hole that penetrates along the pressing direction, The mold according to claim 1 or 2, wherein the second punch has a shaft portion that can be inserted into the through hole.

4. The mold according to claim 1 or 2, wherein the second punch has a stop portion that contacts the tip on the non-blank side in the pressing direction.

5. The mold according to claim 2, wherein the first punch does not protrude from the outer edge of the punch shoulder in a direction perpendicular to the pressing direction.

6. A hot press apparatus comprising the mold described in claim 1 or 2.

7. A method for manufacturing a hot press-formed product having a bottom and a vertical wall integrally provided with the bottom, using the mold described in Claim 1 or 2, The first step involves closing the mold over the heated blank and performing press drawing molding, A manufacturing method comprising: a second step after the first step, opening the mold, pressing the bottom toward the blank side, and separating a portion of the vertical wall from the mold.

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