Die, hot press device, and method for manufacturing hot press-molded product

Abstract

A mold that allows a hot press molded product to be easily removed from the mold, a hot press device, and a method for manufacturing a hot press molded product. [Solution] A mold 24 for performing drawing on a heated blank 26 by hot pressing, comprising: a first punch 32 having a punch vertical wall portion 36 extending along the press direction and an evacuation hole 44 formed on the surface of the punch vertical wall portion 36 and opening in a planar direction perpendicular to the press direction; a second punch 34 provided in the evacuation hole 44 and having a slider vertical wall portion 46 extending along the press direction and movable along the planar direction; a locking mechanism that releasably fixes the second punch 34 to a mold clamping position where the slider vertical wall portion 46 smoothly continues with the punch vertical wall portion 36; a mold release mechanism 58 that moves the second punch 34 from the mold clamping position to a retracted position on the inside in the planar direction; and a die 30 arranged opposite the first punch 32.

Description

[Technical Field]

[0001] The present invention relates to a mold, a hot press apparatus, and a method for manufacturing a hot press-formed product. [Background technology]

[0002] Various manufacturing methods have been proposed for hot press forming. For example, Patent Document 1 discloses a manufacturing method for producing a hot press-formed product by hot press forming a blank using a hot press die that includes a punch top and two punch shoulder rounded portions, and that includes an inner pad that is disposed so as to protrude from the punch top by a predetermined amount and is accommodated in the punch top at the bottom dead center of forming. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-89132 Summary of the Invention [Problem to be solved by the invention]

[0004] When drawing is performed by hot pressing, the blank is rapidly cooled by the die when the die reaches its bottom dead center, i.e., when the die is clamped. This causes the blank to thermally shrink, which can cause it to adhere to the die. There was a concern that a hot press-formed product that adheres to the die in this way would be difficult to remove from the die.

[0005] An object of the present invention is to provide a mold, a hot press apparatus, and a method for manufacturing a hot press-formed product, which allow a hot press-formed product to be easily removed from the mold. [Means for solving the problem]

[0006] The present application discloses the following aspects as one of means for solving the above problems.

[0007] [Aspect 1] A die for performing drawing on a heated blank by hot pressing, a first punch having a punch vertical wall portion extending along the pressing direction and a retraction hole formed on a surface of the punch vertical wall portion and opening in a plane direction perpendicular to the pressing direction; a second punch provided in the evacuation hole, having a slider vertical wall portion extending along the pressing direction, and movable along the surface direction; a locking mechanism that releasably fixes the second punch at a mold clamping position where the slider vertical wall portion is smoothly continuous with the punch vertical wall portion; a mold release mechanism that moves the second punch from the mold clamping position to a retracted position on the inside in the surface direction; a die disposed opposite the first punch; A mold comprising:

[0008] [Aspect 2] 2. The mold according to claim 1, wherein the mold release mechanism has a cushion that presses the second punch inward in a surface direction.

[0009] [Aspect 3] The locking mechanism is a slider inclined surface provided on the second punch and inclined outward in the surface direction from the non-blank side to the blank side; a driver inclined surface provided on the die and facing the slider inclined surface; 3. The mold of claim 1 or 2, having

[0010] [Aspect 4] The locking mechanism is a guide surface provided on the second punch, the guide surface being continuous with the non-blank side of the slider inclined surface and extending along the pressing direction; a driver outer surface provided on the die and continuous with the non-blank side of the driver inclined surface, the driver outer surface being capable of contacting the guide surface; 4. The mold of embodiment 3, comprising:

[0011] [Aspect 5] A hot press device comprising the mold according to aspect 1 or 2.

[0012] [Aspect 6] A manufacturing method for manufacturing a hot press-formed product having a bottom and a vertical wall integrally formed with the bottom, using the mold according to aspect 1, a first step of closing the die on the heated blank and performing press drawing; a second step of, after the first step, opening the mold, moving the second punch inward in the surface direction, and separating the slider vertical wall portion from the vertical wall. [Effects of the Invention]

[0013] According to the present invention, the hot press-formed product can be easily removed from the mold. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view schematically showing a hot press-formed product manufactured by the mold according to the present embodiment. [Figure 2] FIG. 1 is a perspective view schematically showing a mold for performing hot press forming according to the present embodiment. [Figure 3] FIG. 2 is a cross-sectional view schematically showing a state in which a blank is draw-formed by a die according to the present embodiment, and shows a state in which the blank is set in the die. [Figure 4] FIG. 1 is a cross-sectional view schematically showing a state in which a blank is being draw-formed by the die according to the present embodiment, and shows a state in which the die is moving in the pressing direction. [Figure 5] FIG. 1 is a cross-sectional view schematically showing a state in which a blank is being drawn using a die according to the present embodiment, and shows a state in which the die has reached bottom dead center. [Figure 6] FIG. 1 is a cross-sectional view schematically showing a state in which a blank is being drawn using a die according to this embodiment, and shows a state in which the die is opened and a vertical wall is separated from the die. [Figure 7]FIG. 1 is a perspective view schematically showing a mold for performing hot press forming according to Modification 1 of the present embodiment. [Figure 8] FIG. 10 is a perspective view schematically showing a punch according to a second modified example of the present embodiment. [Figure 9] FIG. 10 is a cross-sectional view schematically showing a state in which a blank is draw-formed by a die according to Modification 2 of the present embodiment, showing a state in which the blank is set in the die. [Figure 10] FIG. 10 is a cross-sectional view schematically showing a state in which a blank is being draw-formed by a die according to Modification 2 of this embodiment, showing a state in which the die has reached the bottom dead center. [Figure 11] FIG. 10 is a cross-sectional view schematically showing a state in which a blank is drawn using a die according to Modification 2 of this embodiment, showing a state in which the die is opened and the vertical wall is separated from the die. DETAILED DESCRIPTION OF THE INVENTION

[0015] The embodiments of the present invention relate to the following aspects. [Hot press formed products] A hot-press-formed product 10 will be described with reference to FIG. 1. The hot-press-formed product 10 is used for, for example, a torque converter, a wheel disc, a battery box, or a subframe. The hot-press-formed product 10 shown in FIG. 1 has a circular cup shape in a plan view. The hot-press-formed product 10 has a bottom 12 and a vertical wall 14 formed 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 on the outer edge of the top 16. The top 16 is disk-shaped. The shoulder 18 has an R-shape that curves outward in a longitudinal cross 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 to surround the entire outer edge of the bottom 12. The other axial end 14F of the vertical wall 14 terminates in the axial direction and does not have a flange extending in a direction perpendicular to the axial direction. In this case, the flange does not include burrs that inevitably occur during press forming. That is, the hot press-formed product 10 may have burrs formed on the other axial end 14F of the vertical wall 14.

[0017] 1 is not particularly limited, but may be, for example, a diameter of 40 mm to 500 mm and a height of 5 mm to 80 mm. The angle θ formed between the outer surface of the vertical wall 14 and the thickness direction Z of the top 16 is preferably 0 degrees to 5 degrees from the center of the top 16 toward the outside.

[0018] [Hot press equipment] 2 and 3, a hot press mold used in the manufacturing method of the hot press-formed product 10 according to this embodiment will be described. The hot press apparatus 20 includes a press 22 and a mold 24 attached to the press 22. In this specification, the driving direction of the press, i.e., the direction in which force acts on the blank, is referred to as the press direction, the side toward the blank is referred to as the blank side, and the side away from the blank is referred to as the non-blank side. The direction perpendicular to the press direction is referred to as the face direction, and the "side" and "direction" toward the center of the mold are referred to as the face direction inward and inward, and the "side" and "direction" away from the center of the mold are referred to as the face direction outward and outward. The press direction is the same as the thickness direction Z of the top 16 of the hot press-formed product 10.

[0019] The die 24 is used to perform hot press forming on a blank 26 when producing the cup-shaped hot press-formed product 10. The die 24 shown in Fig. 2 includes a punch 28 and a die 30. Fig. 2 shows a state in which the blank 26 is placed between the punch 28 as a lower die and the die 30 as an upper die.

[0020] The punch 28 is provided with a coolant flow path (not shown). The punch 28 has a size corresponding to the size of the hot press-formed product 10. The punch 28 is disposed opposite the die 30 with the blank 26 interposed therebetween. The punch 28 has a first punch 32 and a second punch 34.

[0021] The first punch 32 has, in order from the non-blank side to the blank side, a punch vertical wall portion 36, a punch shoulder portion 40, and a punch top portion 42. The punch vertical wall portion 36 has a surface shaped like the outer surface of a cylinder with an axis along the pressing direction. An upper edge 36N of the punch vertical wall portion 36 is connected to an outer edge 40S of the punch shoulder 40. The punch vertical wall portion 36 has a retraction hole 44 formed in its surface and opening in the planar direction. The retraction hole 44 is a bottomed hole with its depth direction aligned with the planar direction. When viewed from the planar direction, the retraction hole 44 has a rectangular shape with its longitudinal direction aligned with the pressing direction and extends inward in the planar direction. The opening of the retraction hole 44 extends from the outer edge 40S of the punch shoulder 40 to the tip 32F of the first punch 32 on the non-blank side. In this embodiment, the punch vertical wall portion 36 has four retraction holes 44. The four retraction holes 44 are evenly arranged circumferentially around the punch vertical wall portion 36. The total circumferential length of each evacuation hole 44 is preferably 20% or more, 30% or more, 40% or more, 80% or less, 70% or less, or 60% or less of the overall circumferential length of the punch vertical wall portion 36. As shown in FIG. 3 , each evacuation hole 44 has an inner wall surface 45 on the inner side in the planar direction. The inner wall surface 45 extends in the pressing direction. That is, the evacuation hole 44 has a space defined from the opening by the inner wall surface 45.

[0022] In a longitudinal cross section, the punch shoulder 40 has an R-shape that slopes outward in the planar direction from the blank side to the non-blank side and is curved in a direction that convexly extends outward in the planar direction. That is, the outer edge 40S of the punch shoulder 40 ends up being R-shaped. The inner edge 40M of the punch shoulder 40 is connected to the outer edge 42S of the punch top 42. The punch top 42 is disposed on the blank side and has a disk-shaped surface that is perpendicular to the pressing direction.

[0023] The second punches 34 are provided in the respective retraction holes 44 so as to be movable along the surface direction. In this embodiment, the die 24 has four second punches 34. The second punches 34 have slider vertical wall portions 46 extending along the pressing direction. The slider vertical wall portions 46 have a rectangular shape with the pressing direction as the longitudinal direction when viewed from the surface direction, and are disposed within the retraction holes 44. The slider vertical wall portions 46 extend from the outer edge 40S of the punch shoulder portion 40 beyond the tip 32F of the first punch 32 on the non-blank side. The second punch 34 has an inner surface 35 facing an inner wall surface 45 on the inward side in the surface direction.

[0024] The second punch 34 is provided so as to be movable between a mold clamping position where the slider vertical wall portion 46 smoothly connects with the punch vertical wall portion 36 and a retracted position inward in the surface direction from the clamping position, i.e., where the slider vertical wall portion 46 is recessed inward in the surface direction relative to the punch vertical wall portion 36. Fig. 2 shows a state in which the slider vertical wall portion 46 has moved to the retracted position. In this embodiment, the second punch 34 stops when the inner surface 35 comes into contact with the inner wall surface 45 at the mold clamping position.

[0025] In this embodiment, the press 22 has rails 23 provided on the mounting surface. The rails 23 extend radially from the center of the punch 28 in the planar direction. The second punch 34 is disposed at the center where the rails 23 intersect. The second punch 34 is provided so as to be movable on the rails 23 in the planar direction.

[0026] In this embodiment, the second punch 34 has a slider portion 48. The slider portion 48 faces the slider vertical wall portion 46 and is provided on the outer side of the slider vertical wall portion 46 in the planar direction. The slider portion 48 is a plate-shaped member extending in the pressing direction. The slider portion 48 has a slider inclined surface 50 and a guide surface 52. The slider inclined surface 50 and the guide surface 52 shown in FIG. 2 are recessed outward in the planar direction when viewed from the pressing direction.

[0027] The slider inclined surface 50 is provided at the connecting portion between the blank-side tip 48N of the slider portion 48 and the inner surface in the planar direction. The slider inclined surface 50 is inclined outward in the planar direction from the non-blank side toward the blank side. In the case of FIG. 2, the slider inclined surface 50 is inclined outward in the planar direction from the punch 28 toward the die 30. An outer edge 50S of the slider inclined surface 50 is connected to the surface of the blank-side tip 48N of the slider portion 48.

[0028] The guide surface 52 is the inner surface of the slider portion 48 in the planar direction. That is, the guide surface 52 is continuous with the non-blank side of the slider inclined surface 50 and extends along the pressing direction. The guide surface 52 faces inward in the planar direction. One end 52N of the guide surface 52 on the blank side is connected to the inner edge 50M of the slider inclined surface 50.

[0029] The second punch 34 has a connecting portion 54 that connects the slider vertical wall portion 46 and the slider portion 48 with a predetermined gap between them. The connecting portion 54 is a member extending in the planar direction, with an end portion 54M on the inner side in the planar direction connected to a tip 46F on the non-blank side of the slider vertical wall portion 46, and an end portion 54S on the outer side in the planar direction connected to a tip portion 48F on the non-blank side of the slider portion 48 (FIG. 3).

[0030] The second punch 34 has a driver accommodating portion 56 between the slider vertical wall portion 46 and the slider portion 48. The driver accommodating portion 56 is provided so that a driver portion, which will be described later, can enter and retract in the pressing direction.

[0031] 3, the die 24 is provided with a cushion 58 that presses the second punch 34 inward in the surface direction. The cushion 58 is not particularly limited as long as it can press the second punch 34 inward in the surface direction, and for example, a spring, a cam, a hydraulic cylinder, an air cylinder, or a ball screw that is directly actuated by a motor can be used. The cushion 58 is mechanically connected to the outer side of the second punch 34 in the surface direction, and presses the second punch 34 inward in the surface direction.

[0032] The die 30 is equipped with a coolant flow path (not shown). The die 30 has a size corresponding to the size of the hot press-formed product 10. The die 30 is disposed opposite the punch 28 with the blank 26 sandwiched between them. The surface of the die 30 facing the blank 26 has a die protruding surface 60 perpendicular to the pressing direction and a concave surface 62 recessed in a mortar shape toward the non-blank side.

[0033] The die 30 has a die top 64, a die shoulder 66, and a die vertical wall 68 (FIG. 3). The die top 64 is located on the non-blank side in the pressing direction and has a disk-shaped surface perpendicular to the pressing direction. In a longitudinal cross section, the die shoulder 66 slopes outward in the planar direction from the non-blank side to the blank side and has an R-shape that is curved in a concave direction outward in the planar direction. An inner edge 66M of the die shoulder 66 is connected to an outer edge 64S of the die top 64. The die vertical wall 68 has an inner surface like a cylinder having an axis along the pressing direction. An upper edge 68N of the die vertical wall 68 is connected to the outer edge 66S of the die shoulder 66. A lower edge 68F of the die vertical wall 68 is connected to the die protruding surface 60.

[0034] In this embodiment, the die 30 has a driver portion 70. The driver portion 70 has a driver inclined surface 72 that faces the slider inclined surface 50. The driver inclined surface 72 is provided at the connection between a driver outer surface 74, which is the outermost in the surface direction of the die 30, and the die protruding surface 60. The driver inclined surface 72 is inclined outward in the surface direction from the blank side to the non-blank side. In the case of FIG. 2, the driver inclined surface 72 is inclined outward in the surface direction from the punch 28 toward the die 30. The driver outer surface 74 is the outermost surface in the surface direction of the die 30. The driver outer surface 74 extends along the pressing direction. The driver outer surface 74 shown in FIG. 2 has the outer surface of a cylinder. The driver outer surface 74 faces outward in the surface direction.

[0035] In this embodiment, the mold 24 has a cushion 58 as a mold release mechanism. The cushion 58 can move the slider vertical wall portion 46 inward in the surface direction by pressing the second punch 34 inward in the surface direction.

[0036] In this embodiment, the mold 24 has a slider inclined surface 50 and a driver inclined surface 72 as a locking mechanism. That is, the locking mechanism of this embodiment not only fixes the slider vertical wall portion 46 at the mold clamping position, but also serves as a slide mechanism that, prior to that, moves the slider vertical wall portion 46 from a retracted position to the mold clamping position. The slider inclined surface 50 and the driver inclined surface 72 are inclined outward in the planar direction from the punch 28 toward the die 30. As a result, when the driver portion 70 and the slider portion 48 linearly move relative to the blank side in the pressing direction, a force acting outward in the planar direction is applied from the driver inclined surface 72 to the slider inclined surface 50. That is, when the driver inclined surface 72 comes into contact with the slider inclined surface 50, the driver portion 70 drives the slider portion 48 outward in the planar direction. The driver portion 70 can fix the slider vertical wall portion 46 in the mold clamping position by applying a force from the driver inclined surface 72 to the slider inclined surface 50 in an outward direction in the planar direction.

[0037] Furthermore, in this embodiment, the mold 24 has a guide surface 52 and a driver outer surface 74 as a locking mechanism. The guide surface 52 is disposed on the inner side of the driver outer surface 74 in the planar direction, and when the guide surface 52 and the driver outer surface 74 come into contact with each other, a force acts in the planar direction between the guide surface 52 and the driver outer surface 74. In this way, when the guide surface 52 and the driver outer surface 74 come into contact with each other, the mold 24 more reliably fixes the slider vertical wall portion 46 in the mold clamping position.

[0038] The punch top 42 and the die top 64 form the top 16 of the hot press-formed product 10. The punch shoulder 40 and the die shoulder 66 form the shoulder 18 of the hot press-formed product 10. The punch vertical wall 36, the slider vertical wall 46, and the die vertical wall 68 form the vertical wall 14 of the hot press-formed product 10.

[0039] [blank] The blank 26 is, for example, a steel plate having a thickness t of 1 mm or more and 5 mm or less. The blank 26 preferably has a tensile strength of 1.0 GPa or more after quenching. The blank 26 has a circular shape when viewed in the thickness direction. The steel material used for the blank 26 has a chemical composition, for example, in mass %, of C: 0.1% to 0.8%, Si: 0.001% to 2.0%, Mn: 0.5% to 3.0%, P: 0.15% or less, and S: 0.01% or less.

[0040] The steel preferably has a chemical composition of, by mass%, sol.Al: 0.001% to 1.0%, N: 0.01% or less, B: 0.01% or less, with the balance being Fe and impurities. The chemical composition may also contain, 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.

[0041] Other additive elements such as Ti, Nb, V, Cr, Mo, Cu, and Ni may be added as necessary to improve the hardenability of the steel and ensure stable strength after hardening.

[0042] [Manufacturing method] Next, a description will be given of a method for manufacturing the hot press-formed product 10. The hot press-formed product 10 is manufactured by a heating process and a quenching process.

[0043] (Heating process) In the heating step, the blank 26 is heated to a temperature equal to or higher than the Ac3 transformation point of the blank 26 to be austenitized. The Ac3 transformation point, which indicates the austenitizing transformation temperature, is the temperature at which the blank 26 made of the above-mentioned steel material is completely austenitized, and is expressed by the following formula, for 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.

[0044] (Quenching process) The blank 26, which has been heated to the Ac3 transformation point or higher in the heating step, is hot-press-formed by closing the die 24 installed in the press of the hot press device 20. After hot-press-forming, the blank 26 is rapidly cooled by removing heat with the punch 28 and die 30 while the die is still clamped, thereby causing martensitic transformation. In other words, the quenching step includes the steps of setting, drawing, cooling, and demolding.

[0045] ·set The blank 26, which has been heated to the Ac3 transformation point or higher in the heating step, is set between the punch 28 and the die 30, as shown in Fig. 3. At this time, the blank 26 is positioned in the die 24 by, for example, a positioning pin (not shown).

[0046] ·Squeeze molding Before the start of drawing, the die 30 is at the top dead center on the non-blank side, and the second punch 34 is at the retracted position due to the pressure of the cushion 58. This state is called the starting point of the die 24. At the starting point, the die 30 is moved towards the blank, i.e., downward, toward the punch 28 . Until the die 30 reaches the bottom dead center, the central portion of the blank 26 is pressed upward by the punch top 42 and punch shoulder 40, and the outer edge portion surrounding the central portion is pressed downward by the die protruding surface 60 of the die 30 and the lower edge 68F of the die vertical wall portion 68, thereby drawing the blank 26. In this way, drawing begins on the blank 26 whose temperature is equal to or higher than the Ac3 transformation point, and the blank 26 begins to deform. Furthermore, the driver inclined surface 72 comes into contact with the slider inclined surface 50. This generates an outward force in the planar direction on the slider portion 48. When the outward force in the planar direction exceeds the pressure force of the cushion 58 that presses the second punch 34, the slider portion 48 moves outward in the planar direction. As a result, the slider vertical wall portion 46 moves outward in the planar direction together with the slider portion 48 to the mold clamping position. Furthermore, before the die 30 reaches the bottom dead center, the driver outer surface 74 comes into contact with the guide surface 52. In this way, the slider vertical wall portion 46 is fixed at the mold clamping position that is smoothly continuous with the punch vertical wall portion 36 from the retracted position. This makes it possible to form a smooth inner peripheral surface in the hot press-formed product 10. As shown in Figure 5, when the die 30 reaches the bottom dead center, the outer edge portion of the blank 26 is pulled in between the punch vertical wall portion 36, the slider vertical wall portion 46, and the die vertical wall portion 68, becoming the vertical wall 14 of the hot press-formed product 10.

[0047] ·cooling When the die 30 reaches the bottom dead center, the formed blank 26 is in close contact with the die 30 and the punch 28. This state is called die clamping. In this state, heat from the blank 26 is rapidly removed by the die 30 and the punch 28. As a result, the blank 26 undergoes martensitic transformation. In other words, the blank 26 is quenched, and becomes the hot press-formed product 10. One method of removing heat from the blank 26 is to indirectly cool it using a refrigerant that flows inside the punch 28 and the die 30. Another method of removing heat is to directly cool the blank 26 by spraying a refrigerant from the punch 28 and the die 30 onto the blank 26. The time from the heating step to the start of cooling is set to within 15 seconds. That is, the time from when the blank 26 heated in the heating step leaves the heating furnace to when the die 30 reaches the bottom dead center is set to within 15 seconds.

[0048] Demolding After cooling, the mold 24 is opened. Specifically, the die 30 is moved toward the non-blank side, i.e., upward. When the non-driver surface 74 moves away from the guide surface 52 and the driver inclined surface 72 moves away from the slider inclined surface 50 in the pressing direction, the outward force on the slider portion 48 in the planar direction is removed, and the slider portion 48 moves inward in the planar direction due to the pressure force of the cushion 58. As a result, the slider vertical wall portion 46 moves inward in the planar direction together with the slider portion 48 to the retracted position. In this way, the slider vertical wall portion 46 separates from the vertical wall 14 of the hot press-formed product 10.

[0049] [Action and effect] In the cooling process, heat is rapidly removed from the blank 26 in the clamped state, causing the blank 26 to thermally shrink. As a result, the vertical wall 14 of the hot press-formed product 10 comes into close contact with the punch vertical wall portion 36 and the slider vertical wall portion 46.

[0050] In this embodiment, the die 24 has a cushion 58 as a die release mechanism that moves the slider vertical wall portion 46 to a retracted position. This allows the die 24 to separate the slider vertical wall portion 46 from the vertical wall 14 of the drawn hot press-formed product 10. Therefore, the hot press apparatus 20 according to this embodiment makes it possible to easily remove the hot press-formed product 10 from the die 24.

[0051] The mold 24 also has a slider inclined surface 50 and a driver inclined surface 72 that function as a locking mechanism to fix the slider vertical wall portion 46 in the mold clamping position. This allows the mold 24 to fix the second punch 34 in the mold clamping position and perform draw forming. Furthermore, the mold 24 has a driver outer surface 74 and a guide surface 52 that function as a locking mechanism, allowing the second punch 34 to be more reliably fixed in the mold clamping position.

[0052] The die 24 is provided with a slider mechanism having the slider inclined surface 50 and the driver inclined surface 72, so that during drawing, the second punch 34 can be moved from the retracted position to the die clamping position against the pressure force of the cushion 58. This allows the die 24 to perform drawing more reliably.

[0053] The second punch 34 has a driver accommodating portion 56 that receives the driver portion 70 that has moved downward, thereby enabling the die 24 to perform drawing more smoothly.

[0054] Furthermore, the mold 24 has the guide surface 52 disposed inside the driver outer surface 74 in the planar direction, and the guide surfaces 52 come into contact with each other to fix the slider portion 48 at a predetermined position in the planar direction. This allows the mold 24 to more reliably fix the slider vertical wall portion 46 at the mold clamping position.

[0055] [Variations] The present invention is not limited to the above-described embodiments and can be appropriately modified within the scope of the present invention. The examples exemplified below can be implemented alone or in combination with the above-described embodiments.

[0056] (Variation 1) Although the hot press-formed product 10 according to the above embodiment has been described as having a circular cup shape in a plan view, the present invention is not limited thereto. For example, the hot press-formed product 10 may have a rectangular container shape in a plan view.

[0057] 7 is a perspective view showing a die 24A according to a modified example for forming a hot press-formed product having a rectangular container shape in plan view. The die 24A according to this modified example differs from the die 24 of the above embodiment only in its outer shape, so like components are denoted by like reference numerals and descriptions thereof will be omitted where appropriate. The die 24A includes a punch 28A and a die 30A.

[0058] Punch 28A is disposed opposite die 30A. Punch 28A has a first punch 32A and a second punch 34A. First punch 32A has, in order from the non-blank side to the blank side, a punch vertical wall portion 36A, a punch shoulder portion 40A, and a punch top portion 42A. Punch vertical wall portion 36A has an outer surface like a rectangular pillar having an axis along the pressing direction.

[0059] The punch vertical wall portion 36A has a retraction hole 44A formed on its surface and opening in the planar direction. In this modified example, the retraction hole 44A is provided on one of the four faces of the punch vertical wall portion 36A that forms the long side when viewed from the pressing direction. The retraction hole 44A has a rectangular shape with its short side aligned with the pressing direction when viewed from the planar direction, and extends inward in the planar direction. The opening of the retraction hole 44A extends from the outer edge 40S of the punch shoulder 40A to the non-blank-side tip 32F of the first punch 32A. In this embodiment, the punch vertical wall portion 36A has two retraction holes 44A. The two retraction holes 44A are arranged opposite each other in the planar direction. The total longitudinal length of the retraction holes 44A is preferably 20% or more, 30% or more, 40% or more, 80% or less, 70% or less, or 60% or less of the outer periphery length of the punch vertical wall portion 36A when viewed from the pressing direction.

[0060] In a longitudinal cross section, the punch shoulder 40A has an R-shape that slopes outward in the planar direction from the blank side to the non-blank side and is curved in a direction that convexly curves outward in the planar direction. The punch top 42A is disposed on the blank side of the punch 28A and has a rectangular plate-like surface that is perpendicular to the pressing direction.

[0061] The second punch 34A is provided in each retraction hole 44 so as to be movable along the surface direction. That is, the die 24A has two second punches 34A. The second punch 34A has a slider vertical wall portion 46A extending along the press direction. The slider vertical wall portion 46A has a rectangular shape with its short side in the press direction when viewed from the surface direction, and is disposed within the retraction hole 44A. The slider vertical wall portion 46A extends from the outer edge 40S of the punch shoulder 40A beyond the non-blank side tip 32F of the first punch 32A. Figure 7 shows the slider vertical wall portion 46 moved to the retracted position.

[0062] In the first modification, the press 22 has a rail 23A provided on the mounting surface. The rail 23A extends from the center of the surface of the punch 28A in a direction perpendicular to the surface of the slider vertical wall portion 46A. The second punch 34A is provided movably on the rail 23A along the surface direction.

[0063] In the first modification, the second punch 34A has a slider portion 48A. The slider portion 48A faces the slider vertical wall portion 46A and is provided on the outer side of the slider vertical wall portion 46A in the planar direction. The slider portion 48A has a slider inclined surface 50A and a guide surface 52A.

[0064] The slider inclined surface 50A is provided at the connection between the blank-side tip 48N of the slider portion 48A and the inner surface in the planar direction. The slider inclined surface 50A is inclined outward in the planar direction from the non-blank side to the blank side. The outer edge 50S of the slider inclined surface 50A is connected to the surface of the tip 48N of the slider portion 48A.

[0065] The guide surface 52A is the inner surface of the slider portion 48A in the planar direction. That is, the guide surface 52A is continuous with the non-blank side of the slider inclined surface 50A and extends along the pressing direction. One end 52N of the guide surface 52A on the blank side is connected to the inner edge 50M of the slider inclined surface 50A. The guide surface 52A faces inward in the planar direction.

[0066] The second punch 34A has a connecting portion 54A that connects the slider portion 48A and the slider vertical wall portion 46A with a predetermined gap provided between the slider portion 48A and the slider vertical wall portion 46A.

[0067] The second punch 34A has a driver receiving portion 56A between the slider portion 48A and the slider vertical wall portion 46A. The driver receiving portion 56A is provided so that a driver portion (described later) can enter and leave the driver receiving portion 56A along the pressing direction. The die 24A has a cushion (not shown in FIG. 7) that presses the second punch 34A inward in the surface direction.

[0068] The die 30A has a die top 64A, a die shoulder 66A, and a die vertical wall 68A. The die top 64A is located on the non-blank side and has a rectangular plate-like surface perpendicular to the pressing direction. In vertical cross section, the die shoulder 66A has an R-shape that slopes outward in the surface direction from the non-blank side to the blank side and is curved in a concave direction outward in the surface direction. The die vertical wall 68A has an inner surface like a square tube with an axis along the pressing direction.

[0069] In the first modification, the die 30A has a driver portion 70A. The driver portion 70A drives the slider portion 48A outward in the planar direction. The driver portion 70A has a driver inclined surface 72A facing the slider inclined surface 50A. The driver inclined surface 72A is provided at the connection between the die protruding surface 60A and a driver outer surface 74A, which is the outermost driver outer surface in the planar direction of the die 30A. The driver inclined surface 72A is inclined outward in the planar direction from the blank side to the non-blank side. The driver outer surface 74A extends along the pressing direction. The driver outer surface 74A shown in FIG. 7 is flat. The driver outer surface 74A faces outward in the planar direction.

[0070] In the case of the first modification, the mold 24A has a cushion as a mold release mechanism. The cushion can move the slider vertical wall portion 46A to a mold clamping position on the inner side in the planar direction by pressing the second punch 34A inward in the planar direction.

[0071] In the case of the first modification, the mold 24A has a slider inclined surface 50A and a driver inclined surface 72A as a locking mechanism. Therefore, the same effect as the above embodiment can be obtained. Furthermore, in the case of the first modification, the mold 24A has a guide surface 52A and a driver outer surface 74A as a locking mechanism, so the same effect as the above embodiment can be obtained.

[0072] (Variation 2) In the above embodiment, the slider portion 48 is provided on the outer side in the planar direction of the slider vertical wall portion 46, and is driven by the driver portion 70 provided in the die 30, but the present invention is not limited to this. A die according to Modification 2 will be described with reference to Figures 8 and 9, in which similar components to those in the above embodiment are designated by similar reference numerals. A die 24B according to Modification 2 includes a punch 28B and a die 30B.

[0073] Punch 28B has a first punch 32B and a second punch 34B (FIG. 8). First punch 32B has, in order from the non-blank side to the blank side, a punch vertical wall portion 36, a punch shoulder portion 40, and a punch top portion 42. Punch vertical wall portion 36 has a retraction hole 44 formed in its surface and opening in the planar direction.

[0074] As shown in FIG. 9, the first punch 32B has a driver portion 70B on the opposite side of the punch top 42 in the pressing direction. The driver portion 70B is a cylindrical member that protrudes from the non-blank side surface of the first punch 32B toward the non-blank side. The driver portion 70B has a driver inclined surface 72B. The driver inclined surface 72B is provided at the connection between a driver protruding surface 73B on the non-blank side of the driver portion 70B and a driver outer surface 74B in the face direction of the driver portion 70B. The driver inclined surface 72B is inclined outward in the face direction from the non-blank side toward the blank side. In the case of FIG. 9, the driver inclined surface 72B is inclined outward in the face direction from the punch 28B toward the die 30B.

[0075] The second punch 34B is provided in each retraction hole 44 so as to be movable along the surface direction. The second punch 34B has a slider vertical wall portion 46. The second punch 34B has a slider portion 48B (FIG. 9). The slider portion 48B is provided on the inner side in the surface direction relative to the slider vertical wall portion 46, i.e., on the surface opposite to the slider vertical wall portion 46. The slider portion 48B has a slider inclined surface 50B.

[0076] The slider inclined surface 50B is provided between the blank-side tip 34N of the second punch 34B and the inner surface 35 on the inner side in the planar direction. The slider inclined surface 50B is inclined outward in the planar direction from the non-blank side toward the blank side. In the case of FIG. 8, the slider inclined surface 50B is inclined outward in the planar direction from the punch 28B toward the die 30.

[0077] The die 24B includes a cushion 58 that presses the second punch 34B inward in the planar direction. The cushion 58 is mechanically connected to the inner side of the second punch 34B in the planar direction and is provided so as to apply a force inward in the planar direction to the second punch 34B. The die 24B has an interposition portion 59 between the cushions connected to the opposing second punches 34B. That is, the cushion 58 is loaded between the second punch 34B and the interposition portion 59. The die 30B differs from the above embodiment in that it does not include a driver portion.

[0078] In the case of the second modification, the mold 24B has a cushion 58 as a mold release mechanism. The cushion 58 can move the second punch 34B inward in the surface direction by pressing the second punch 34B inward in the surface direction.

[0079] In the second modification, the mold 24B has a slider inclined surface 50B and a driver inclined surface 72B as a locking mechanism. That is, the locking mechanism of the second modification not only fixes the slider vertical wall portion 46 at the mold clamping position, but also serves as a slide mechanism that moves the slider vertical wall portion 46 from the retracted position to the mold clamping position. The slider inclined surface 50B and the driver inclined surface 72B are inclined outward in the planar direction from the punch 28B to the die 30B. Because of this, a force acting outward in the planar direction acts from the driver inclined surface 72B on the slider inclined surface 50B due to linear motion in the pressing direction. As a result, the slider inclined surface 50B comes into contact with the driver inclined surface 72B, causing the driver portion 70B to drive the slider portion 48B outward in the planar direction. The force acting outward in the planar direction from the driver inclined surface 72B on the slider inclined surface 50B fixes the slider vertical wall portion 46 at the mold clamping position.

[0080] The die 24B according to the second modification can manufacture the hot press-formed product 10 through the heating step and the quenching step, similarly to the above embodiment. The steps of drawing, cooling, and demolding will be described below. ·Squeeze molding Before the start of drawing, the die 30B is at the top dead center on the non-blank side, the second punch 34B is at a retracted position due to the pressure of the cushion 58, and the first punch 32B is at a slightly upward position relative to the second punch 34B. At the starting point, the die 30B is moved downward toward the blank 28B, and drawing is initiated on the blank 26, which has a temperature equal to or higher than the Ac3 transformation point, so that the blank 26 begins to deform. When the first punch 32B is pressed downward by the die 30 via the blank 26, the first punch 32B moves downward relative to the second punch 34B, and an outward force in the planar direction is generated on the slider portion 48B. When the outward force in the planar direction exceeds the pressure force of the cushion 58 that presses the second punch 34B, the slider portion 48B moves outward in the planar direction. As a result, the slider vertical wall portion 46 moves outward in the planar direction integrally with the slider portion 48B to a position where it smoothly connects with the punch vertical wall portion 36, and stops at the mold clamping position. As shown in FIG. 9, when the die 30B reaches the bottom dead center, the outer edge portion of the blank 26 is pulled between the punch vertical wall portion 36 and the die vertical wall portion 68, forming the vertical wall 14 of the hot press-formed product 10.

[0081] ·cooling When the die 30B reaches the bottom dead center, the formed blank 26 is in close contact with the die 30 and the punch 28B. In the clamped state, heat from the blank 26 is rapidly removed by the die 30B and the punch 28B. As a result, the blank 26 undergoes martensitic transformation. In other words, the blank 26 is quenched, and becomes the hot press-formed product 10.

[0082] Demolding After cooling, the mold 24B is opened. Specifically, the die 30B is moved toward the non-blank side, i.e., upward. When the downward force on the first punch 32B is removed, the slider portion 48B moves inward in the planar direction due to the pressure of the cushion 58. As a result, the slider vertical wall portion 46 moves inward in the planar direction together with the slider portion 48B to the retracted position, as shown in FIG. 10. In this way, the vertical wall 14 of the hot press-formed product 10 is separated from the slider vertical wall portion 46. In this modification 2, the first punch 32B moves upward relative to the second punch 34B so as to be pushed out by the slider portion 48B.

[0083] In the case of Modification 2, the mold 24B has a cushion 58 as a mold release mechanism that moves the slider vertical wall portion 46 to a retracted position. Therefore, the hot press device 20 using the mold 24B according to Modification 2 can obtain the same effects as the above embodiment. Furthermore, by having a locking mechanism, the mold 24B according to Modification 2 can obtain the same effects as the above embodiment.

[0084] The die 24B according to the second modification can be made smaller by providing the slider portion 48B on the inner side in the planar direction of the slider vertical wall portion 46. In the die 24B, a driver portion 70B is provided on the first punch 32B, and the die 24B moves the first punch 32B upward relative to the second punch 34B at the starting point. This allows the die 24B to move the hot press-formed product 10 upward relative to the punch vertical wall portion 36 in the demolding process. Therefore, the hot press device 20 using the die 24B according to the second modification can more easily remove the hot press-formed product 10 from the die 24.

[0085] (Other variations) The hot press-formed product 10 according to the above embodiment has been described as having the vertical wall 14 surrounding the entire outer periphery 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 having a shape that can be formed by drawing and having vertical walls facing each other with the bottom sandwiched therebetween.

[0086] In the hot press apparatus 20 according to the above embodiment, the punch 28 is the lower die and the die 30 is the upper die, but the present invention is not limited to this, and the punch 28 may be the upper die and the die 30 may be the lower die. Also, although the pressing direction is vertical, the present invention is not limited to this, and the pressing direction may be horizontal.

[0087] Although the above embodiment has been described with respect to a case where two second punches are provided, the present invention is not limited to this, and the number of second punches may be one, two, three, or five or more.

[0088] Although the slider vertical wall 46 has been described as extending from the outer edge 40S of the punch shoulder 40 to the non-blank-side tip 32F of the first punch 32, the present invention is not limited to this. For example, the slider vertical wall 46 may be provided as appropriate within a range from a position on the non-blank side of the punch shoulder 40 to the non-blank-side tip 32F of the first punch 32.

[0089] The mold 24 according to the above embodiment has been described as having the slider inclined surface 50, the driver inclined surface 72, the guide surface 52, and the driver outer surface 74 as a locking mechanism, but the present invention is not limited to this. As in the above-described second modification, the mold 24 may omit the guide surface 52 and the driver outer surface 74.

[0090] The mold 24 according to the above embodiment includes the slider portion 48 and the driver portion 70, and includes the slider inclined surface 50 and the driver inclined surface 72 as the locking mechanism. However, the present invention is not limited to this. That is, the mold 24 may omit the slider portion 48 and the driver portion 70. For example, the locking mechanism may include a connecting portion (not shown) such as a lock pin that releasably connects the slider vertical wall portion to the mold clamping position. The connecting portion fixes the slider vertical wall portion to the mold clamping position at the starting point. The connecting portion is released when the die 30 reaches the bottom dead center or returns to the starting point. When the mold 24 returns to the starting point, the slider vertical wall portion moves to the retracted position due to the pressure of the cushion 58. This allows the mold 24 to separate the vertical wall 14 of the hot press-formed product 10 from the slider vertical wall portion 46.

[0091] In the above embodiment, the mold release mechanism includes a cushion that presses the slider vertical wall portion 46 inward in the planar direction and moves it to a retracted position. However, the present invention is not limited to this. For example, the mold release mechanism may be a rail that slopes downward relative to the horizontal toward the inward side in the planar direction. In this case, the locking mechanism fixes the slider vertical wall portion in the mold clamping position at the starting point. The locking mechanism separates from the slider vertical wall portion 46 when the die 30 returns to the starting point after reaching the bottom dead center. As a result, the slider vertical wall portion 46 moves by its own weight along the rail that slopes downward toward the inward side in the planar direction to a retracted position on the inward side in the planar direction. In this way, the die can separate the vertical wall 14 of the hot press-formed product 10 from the slider vertical wall portion 46. [Explanation of symbols]

[0092] 10 Hot press formed products 12 bottom 14 Vertical Wall 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) 18S outer edge (shoulder) 20 Hot press equipment 22 Press machine 23, 23A rail 24, 24A, 24B molds 26 Blank 28, 28A, 28B punches 30, 30A, 30B dies 32, 32A, 32B First punch 32N Blank side tip 32F Non-blank end 34, 34A, 34B Second punch 34N Blank side tip 35 Inner surface (second punch) 36, 36A Punch vertical wall 36N Upper edge 38 through holes 40, 40A punch shoulder 40M inner edge (punch shoulder) 40S outer edge (punch shoulder) 42, 42A Punch top 42S Outer edge (top of punch) 44, 44A Retraction holes 45 Inner wall surface 46, 46A Slider vertical wall 46F Non-blank end 48, 48A, 48B Slider part 48N Blank side tip 48F Non-blank end 50, 50A, 50B Slider inclined surface (locking mechanism) 50M inner edge (slider slope) 50S outer edge (slider inclined surface) 52, 52A Guide surface (locking mechanism) 52N One end (guide surface) 54, 54A connection part 54M inner end 54S outer end 56, 56A driver housing 58 Cushion (mold release mechanism) 60, 60B die protrusion surface 62 Concave surface 64, 64A die top 64S Outer edge (top of die) 66, 66A die shoulder 66M Inner edge (die shoulder) 66S Outer edge (die shoulder) 68, 68A Die vertical wall 68N Upper edge (vertical die wall) 68F Lower edge (vertical die wall) 70, 70A, 70B driver section 72, 72A, 72B Driver inclined surface (locking mechanism) 74, 74A, 74B Driver outer surface (locking mechanism)

Claims

1. A die for performing drawing on a heated blank by hot pressing, a first punch having a punch vertical wall portion extending along the pressing direction and a retraction hole formed on a surface of the punch vertical wall portion and opening in a plane direction perpendicular to the pressing direction; a second punch provided in the evacuation hole, having a slider vertical wall portion extending along the pressing direction, and movable along the surface direction; a locking mechanism that releasably fixes the second punch at a mold clamping position where the slider vertical wall portion smoothly connects with the punch vertical wall portion; a mold release mechanism that moves the second punch from the mold clamping position to a retracted position on the inside in the surface direction; a die disposed opposite the first punch; A mold comprising:

2. The mold according to claim 1 , wherein the mold release mechanism has a cushion that presses the second punch inward in a surface direction.

3. The locking mechanism is a slider inclined surface provided on the second punch and inclined outward in the surface direction from the non-blank side to the blank side; a driver inclined surface provided on the die and facing the slider inclined surface; The mold according to claim 1 or 2, comprising:

4. The locking mechanism is a guide surface provided on the second punch, the guide surface being continuous with the non-blank side of the slider inclined surface and extending along the pressing direction; a driver outer surface provided on the die and continuous with the non-blank side of the driver inclined surface, the driver outer surface being capable of contacting the guide surface; The mold of claim 3 , comprising:

5. A hot press device comprising the mold according to claim 1 or 2.

6. A manufacturing method for manufacturing a hot press-formed product having a bottom and a vertical wall integrally formed with the bottom, using the mold according to claim 1, a first step of closing the die on the heated blank and performing press drawing; a second step of, after the first step, opening the mold, moving the second punch inward in the surface direction, and separating the slider vertical wall portion from the vertical wall.

Images