Flanging methods, flanging molds, flanging equipment, and flanged products

Abstract

This invention relates to a flanging method, a flanging mold, a flanging apparatus, and a flanged product. The flanging method involves forming a flanging portion, including a raised portion and a bent portion, on a metal part having a formed bottom hole. The method is characterized by comprising: a pre-forming step, in which the bottom hole is enlarged, and the edge of the bottom hole is moved relative to a first direction in which the metal part is in a first range toward the periphery of the bottom hole, in the thickness direction of the metal part, forming the first range into a pre-formed portion that is raised from the metal part in the first direction; and a formal forming step, in which the pre-formed portion is deformed in a second direction opposite to the first direction, such that a portion of the second range formed on the outer diameter side of the pre-formed portion becomes the same height as the first range in the first direction, and a portion of a third range closer to the inner diameter side of the pre-formed portion than the second range becomes part of both the raised portion and the bent portion.

Description

Technical Field

[0001] This invention relates to a flanging method, a flanging mold, a flanging apparatus, and flanged products.

[0002] This application is based on and claims priority to Japan Patent Application No. 2021-027954 filed on February 24, 2021, the contents of which are incorporated herein by reference. Background Technology

[0003] There is a technique for flanging a generally cylindrical part by flanging a bottom hole in a metal part or sheet that is being processed. In this flanging process, a portion of the periphery of the bottom hole is extruded and formed into a cylindrical shape to form the flanging part. The cylindrical flange (standing portion) of the flanging part is connected to a portion of the metal part or sheet at its periphery via a bending portion. This flanging part is required to have good fatigue characteristics and dimensional accuracy. For example, Patent Document 1 discloses a technique in which compressive stress is applied to the end of the flanging part by an embossing process, thereby mitigating residual tensile stress and suppressing wrinkles and cracks that occur on the inner surface of the bending portion that forms the root of the flanging part due to the local concentration of compressive stress on the inner surface of the bending portion. In addition, as a flanging technique, a method of staged forming as described in Patent Document 2 has also been proposed.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-051609

[0007] Patent Document 2: Japanese Patent No. 5636846 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, flanging is also used in vehicle running gear parts. Parts such as lower arms and tow arms, in particular, require specific fatigue characteristics, but depending on the flanging method, tensile residual stress can easily be generated on the inner side of the bend in the flanging section. When fatigue loads are applied to parts under conditions of tensile residual stress on the inner side of the bend in the flanging section, deformation can sometimes occur in the flanging section. Furthermore, depending on the flanging method, it is generally known that microcracks of about tens of μm (internal bending cracks) can occur on the inner side of the bend, sometimes requiring shape changes such as increasing the radius of curvature of the bend.

[0010] The present invention was made in view of the above-mentioned problems, and its object is to provide a flanging method, a flanging mold, a flanging apparatus, and a flanged product that can suppress cracking in the bending portion of the flanging part.

[0011] (1) One aspect of the flanging method of the present invention is as follows: a flanging part including a raised portion and a bent portion is formed on a metal part having a bottom hole using a flanging die, characterized in that...

[0012] The above-mentioned dies for flanging include:

[0013] The first die has a first die hole and a first support surface perpendicular to the axis of the first die hole;

[0014] The second die has a second die hole and a second support surface perpendicular to the axis of the second die hole;

[0015] The bracket, having a third support surface facing the first and second support surfaces, clamps the metal part between the first and second dies; and

[0016] The punch has a shaft portion and is configured to move along the axis of the first die hole and the axis of the second die hole.

[0017] The first support surface, the second support surface, and the third support surface are arranged parallel to each other.

[0018] The diameter of the second die hole is smaller than the diameter of the first die hole, and the outer diameter of the second support surface is smaller than the diameter of the first die hole.

[0019] The above-mentioned flanging processing methods include:

[0020] In the preforming process, the bottom hole is enlarged, and the edge of the bottom hole is moved relative to the metal part in a first direction of the thickness direction of the metal part in a first range toward the periphery of the bottom hole, thereby forming the first range into a preformed portion that is integrally erected from the metal part in the first direction; and

[0021] In the formal molding process, the preformed portion is deformed in a second direction opposite to the first direction, so that a second range on the outer diameter side of the preformed portion becomes the same height as the first range in the first direction, and a portion of a third range on the inner diameter side of the preformed portion, which is closer to the second range than the first range, becomes part of the upright portion and the curved portion.

[0022] The outer diameter of the aforementioned curved portion is smaller than the outer diameter of the aforementioned preformed portion, and,

[0023] In a cross-section parallel to the above-described first direction and passing through the center of the above-described bottom hole, the maximum radius of curvature of the above-described bending portion is smaller than the minimum radius of curvature of the above-described preforming portion.

[0024] The above-described metal part is clamped between the above-described first support surface of the above-described first die and the above-described third support surface of the above-described bracket, and the above-described punch is moved relative to the above-described first die in the above-described first direction so that the above-described punch penetrates the above-described first die hole, thereby forming the above-described preforming portion between the above-described punch and the above-described first die.

[0025] In a state where the above-described metal part is clamped between the above-described first support surface and the above-described third support surface, the above-described second die is moved relative to the above-described bracket in the above-described second direction so that a part of the above-described second die penetrates between the above-described punch and the above-described first die, thereby forming the above-described flanging portion between the above-described second die, the above-described punch, and the above-described bracket.

[0026] When the difference between the radius of the above-described first die hole and the radius of the above-described second die hole is set as U, the diameter of the above-described shaft portion of the above-described punch is set as P, and the diameter of the above-described bottom hole of the above-described metal part is set as A, the following formula 1 is satisfied.

[0027] When the height of the edge portion of the above-described bottom hole of the above-described metal part is set as t and the height of the outer surface of the above-described bending portion in the above-described first direction is set as h, the following formula 2 is satisfied.

[0028] 0.5×(P - A) / 2 < U < 20×(P - A) / 2 …… Formula 1

[0029] 0.2 < h / t < 0.6 …… Formula 2.

[0030] (2) A flanging method according to one aspect of the present invention uses a flanging die including a set of preforming dies and a set of final forming dies to form a flanging portion including a standing portion and a bending portion on a metal part having a bottom hole, and is characterized in that

[0031] The above-described set of preforming dies includes:

[0032] A first die having a first die hole and a first support surface perpendicular to the axis of the first die hole; [[ID=Z9]]

[0033] A first bracket having a first bracket support surface opposed to the first support surface and arranged parallel to the first support surface, and clamping the metal part between the first die; and [[ID=Z2]]

[0034] A first punch having a first shaft portion and arranged to be movable along the axis of the first die hole.

[0035] The above set of formal molding dies includes:

[0036] The second die has a second die hole and a second support surface perpendicular to the axis of the second die hole;

[0037] The second bracket has a second bracket support surface that faces and is arranged parallel to the second support surface, and clamps the metal part between itself and the second die; and

[0038] The second punch has a second shaft portion and is configured to move along the axis of the second die hole.

[0039] The above-mentioned flanging processing methods include:

[0040] In the preforming process, the bottom hole is enlarged, and the edge of the bottom hole is moved relative to the metal part in a first direction of the thickness direction of the metal part in a first range toward the periphery of the bottom hole, thereby forming the first range into a preformed portion that is integrally erected from the metal part in the first direction; and

[0041] In the formal molding process, the preformed portion is deformed in a second direction opposite to the first direction, so that a second range on the outer diameter side of the preformed portion becomes the same height as the first range in the first direction, and a portion of a third range on the inner diameter side of the preformed portion, which is closer to the second range than the first range, becomes part of the upright portion and the curved portion.

[0042] The outer diameter of the aforementioned curved portion is smaller than the outer diameter of the aforementioned preformed portion, and,

[0043] In a cross-section parallel to the first direction and passing through the center of the bottom hole, the maximum radius of curvature of the curved portion is smaller than the minimum radius of curvature of the preformed portion.

[0044] The metal part is clamped between the first support surface of the first die and the first support surface of the first bracket, and the first punch is moved relative to the first die in the first direction so that the first punch passes through the first die hole, thereby forming the preform between the first punch and the first die.

[0045] The metal part with the preformed portion is separated from the preformed mold.

[0046] Next, the metal part with the preformed portion is placed on the support surface of the second bracket of the second bracket, with the metal part having the preformed portion formed thereon as the first direction side.

[0047] Insert the second punch into the bottom hole after diameter expansion in the first direction, and move the second die relative to the second bracket in the second direction so that the second punch passes through the second die hole. Thus, the flanging portion is formed between the second die, the second punch, and the second bracket.

[0048] The diameter of the second die hole is not greater than the diameter of the first die hole.

[0049] When the height of the edge portion of the bottom hole of the metal part is set as t and the height of the outer surface of the bending portion in the first direction is set as h, the following formula 2 is satisfied.

[0050] 0.2 < h / t < 0.6... formula 2.

[0051] (3) In the flanging method described in (2) above, it can also be that

[0052] When the difference between the radius of the first die hole and the radius of the second die hole is set as U, the diameter of the second shaft portion of the second punch is set as Ps, and the diameter of the bottom hole of the metal part is set as A, the following formula 5 is satisfied.

[0053] 0.5×(Ps - A) / 2 < U < 20×(Ps - A) / 2... formula 5.

[0054] (4) In the flanging method described in (i) or (ii) above, it can also be that

[0055] Insert the second punch into the bottom hole after diameter expansion in the first direction, and then move the second die relative to the second bracket in the second direction.

[0056] (5) In the flanging method described in (2) or (3) above, it can also be that

[0057] Move the second die relative to the second bracket in the second direction, and then insert the second punch into the bottom hole after diameter expansion in the first direction.

[0058] (6) In any of the flanging methods described in (2) to (5) above, it can also be that

[0059] The diameter of the first shaft portion of the first punch is smaller than the diameter of the second shaft portion of the second punch.

[0060] (7) In any of the flanging methods described in (2) to (6) above, it can also be that

[0061] The initial contact position between the preform and the second die is within 7 / 8 of the surface length of the curved portion of the second die shoulder in a cross section parallel to the first direction and passing through the center of the bottom hole, from the inner wall side of the second die hole.

[0062] (8) In any of the flanging processing methods described in (1) to (7) above, it is also possible to...

[0063] The tensile strength of the aforementioned metal parts is above 780 MPa.

[0064] (9) In any of the flanging processing methods described in (1) to (8) above, it is also possible to...

[0065] When the height of the edge portion of the bottom hole of the aforementioned metal part is set as t, and the thickness of the opening side end of the aforementioned upright portion is set as tb, the following formula 4 is satisfied.

[0066] tb / t<0.9 ……Equation 4.

[0067] (10) In any of the flanging processing methods described in (1) to (9) above, it is also possible to be,

[0068] Prior to the above preforming process, there is also a bottom hole forming process for forming the bottom hole of the metal part.

[0069] (11) A flanging die according to one aspect of the present invention, used for forming a flanging part including a raised portion and a bent portion on a metal part having a bottom hole, characterized in that it comprises:

[0070] The first die has a first die hole and a first support surface perpendicular to the axis of the first die hole;

[0071] The second die has a second die hole and a second support surface perpendicular to the axis of the second die hole;

[0072] The bracket, having a third support surface facing the first and second support surfaces, clamps a metal part between the first and second dies; and

[0073] The punch has a shaft portion and is configured to move along the axis of the first die hole and the axis of the second die hole.

[0074] The first support surface, the second support surface, and the third support surface are arranged parallel to each other.

[0075] The diameter of the second die hole is smaller than the diameter of the first die hole, and,

[0076] The outer diameter of the second support surface is smaller than the diameter of the first punch hole.

[0077] (12) A flanging processing apparatus according to one aspect of the present invention, characterized in that,

[0078] It has the dies for flanging described in (11) above, and has a drive mechanism that enables the first die, the second die, the bracket and the punch to move relative to each other.

[0079] (13) A flanged product according to one aspect of the present invention has a flanged processing portion including a raised portion and a curved portion, and a peripheral region including the curved portion, characterized in that...

[0080] In a cross-section including the axis of the aforementioned flanging portion and parallel to that axis, when the radius of curvature of the outer surface of the aforementioned bent portion is set as R,

[0081] The hardness of the flanged part at position a, where the R-stop end of the curved part connected to the peripheral region is separated from the peripheral region side in a direction perpendicular to the axis, and where the flange is separated by 0.2 mm from the side with the raised part in a direction parallel to the axis, is defined as Hva.

[0082] When the hardness of the flanged part at position b, which is 3 times the thickness of the flanged part separated from the peripheral region in a direction perpendicular to the axis and from the side where the raised part is formed in a direction parallel to the axis, is set to Hvb.

[0083] It satisfies the following equation 7, and,

[0084] The aforementioned peripheral area has indentations. When the height of the raised portion is set to Us, the indentations are located within a range of 0.5 × Us or more and 20 × Us or less from the R-stop end of the bent portion. When the thickness of the flanged part in the aforementioned peripheral area is set to ts, the maximum height or depth of the indentations in the direction parallel to the aforementioned axis exceeds ts / 20 and is less than ts / 3.

[0085] Hva / Hvb>1.03 ……Equation 7.

[0086] (14) Among the flanging products described in (13) above, it is also possible to be,

[0087] The aforementioned Hva is the average hardness measured within the range of the aforementioned cross-section defined by a square centered at the aforementioned position a, with one side having a length equal to 1 / 6 of the thickness of the aforementioned flanged workpiece.

[0088] The above-mentioned Hvb is the average hardness of the hardness measured within the range of the above-mentioned cross-section defined by a square with the above-mentioned position b as the center and the length of one side being 1 / 6 of the thickness of the above-mentioned flanging processed product.

[0089] (15) In the flanging processed product described in the above (13) or (14), it may also be that

[0090] When the thickness of the flanging processed product in the above-mentioned peripheral region is set as ts and the height of the outer surface of the above-mentioned bending portion in the direction parallel to the above-mentioned axis is set as h, the following formula 8 is satisfied.

[0091] 0.2 < h / ts < 0.6 …… Formula 8. <A

[0092] (16) In the flanging processed product described in any one of the above (13) to (15), it may also be that

[0093] When the thickness of the flanging processed product in the above-mentioned peripheral region is set as ts and the thickness of the opening side end portion of the above-mentioned erected portion is set as tb, the following formula 9 is satisfied.

[0094] tb / ts < 0.9 …… Formula 9.

[0095] (17) In the flanging processed product described in any one of the above (13) to (16), it may also be that

[0096] In the above-mentioned cross-section of the above-mentioned bending portion, there are no cracks with a depth of 20 μm or more from the surface.

[0097] (18) In the flanging processed product described in any one of the above (13) to (17), it may also be that

[0098] It is any one of a lower arm, a trailing arm, and an upper arm used in a vehicle.

[0099] Effects of the Invention

[0100] According to the present invention, it is possible to provide a flanging processing method, a flanging processing die, a flanging processing device, and a flanging processed product that can suppress the generation of cracks in the flanging processing portion. Description of the Drawings

[0101] Figure 1 It is a schematic cross-sectional view for showing the state of the compressive strain and the bending internal crack of the bending portion of the flanging processing portion. 3]

[0102] Figure 2 It is a schematic cross-sectional view for explaining the state of the隆起隆起 (the processed material (metal part) bulging) during the forming process of the flanging processing.

[0103] Figure 3(A) to (C) are schematic diagrams illustrating the forming process of conventional flanging.

[0104] Figure 4 (A) to (C) are respectively used to explain Figure 3 A summary cross-sectional view of the forming process of the flanging of (A) to (C).

[0105] Figure 5 This is a schematic cross-sectional view used to illustrate the flanging die of the first embodiment.

[0106] Figure 6 It is a summary cross-sectional view used to illustrate the state of a metal part being clamped by a mold used for flanging.

[0107] Figure 7 It is a schematic cross-sectional view used to illustrate the mold for flanging after preforming and the metal part with the preformed part.

[0108] Figure 8 It is a schematic cross-sectional view used to illustrate the mold used for flanging after the final molding and the flanged product.

[0109] Figure 9 (A) to (C) are schematic plan views illustrating the forming process of the flanging method of the first embodiment.

[0110] Figure 10 (A) to (C) are respectively used to explain Figure 9 A summary cross-sectional view of the forming process of flanging in states (A) to (C).

[0111] Figure 11 This is a schematic cross-sectional view of the preforming mold used to illustrate the flanging mold of the second embodiment.

[0112] Figure 12 This is a schematic cross-sectional view of the formal forming mold used to illustrate the flanging mold of the second embodiment.

[0113] Figure 13 This is a schematic cross-sectional view used to illustrate the preformed mold and the metal part with the preformed portion after preforming in the second embodiment.

[0114] Figure 14 This is a schematic cross-sectional view used to illustrate the state in which a metal part with a preformed portion is placed on the formal molding die in the second embodiment.

[0115] Figure 15 This is used to illustrate the process of forming the mold in the second embodiment from... Figure 14 A schematic cross-sectional view of the state in which the second punch is inserted into the expanded bottom hole.

[0116] Figure 16 This is used to illustrate the process of forming the mold in the second embodiment from... Figure 15 A schematic cross-sectional view of the state in which the second die moves relative to the second support to form the flanging part.

[0117] Figure 17 This is used to illustrate the process of forming the mold in the second embodiment from... Figure 14 A schematic cross-sectional view of the state after the preformed part is deformed due to the relative movement of the second die with respect to the second support.

[0118] Figure 18 This is a schematic cross-sectional view used to illustrate the flanged product of the third embodiment.

[0119] Figure 19 This is a schematic cross-sectional view used to illustrate the indentation of the flanged product of the third embodiment. Detailed Implementation

[0120] The inventors have discovered that during the forming process of flanging, unevenness is generated due to compressive strain on the inner surface of the bent portion, thereby producing the aforementioned internal bending cracks. Figure 1 This is a schematic cross-sectional view used to show the compressive strain and internal crack state of the bent portion in the flanging process. Figure 1 The image shows a cross-sectional view of the flanged workpiece 10 taken from a plane passing through and parallel to the axis cb of the flanging section 11, and only one end face of the flanging section 11 centered on the axis cb is shown. Figure 1 As shown, the flanging part 11 of the flanging product 10 has a bent part 12 and a raised part 13. On the outer surface 12a of the bent part 12, compressive strain is generated in the direction of the arrow in the figure during the forming process, and a bending internal crack CR is generated starting from the unevenness caused by the compressive strain.

[0121] The inventors have discovered that when the radius of curvature of the bent portion of the flanging process is extremely small relative to the thickness of the workpiece and the workpiece is a high-strength material, internal bending cracks sometimes occur. These internal bending cracks are caused by material bulging on the inner surface of the bent portion during the forming process.

[0122] exist Figure 2 The diagram shows a schematic cross-sectional view illustrating the raised state of the workpiece during the flanging process. Figure 2 This diagram illustrates the process of flanging, where the workpiece M is held by the die 20 and the support 30, and the punch 40 deforms the workpiece M to form the curved portion 12. (See diagram for example.) Figure 2As illustrated, when the radius of curvature of the die shoulder 21 corresponding to the radius of curvature of the bent portion of the flanging section is small, especially in the initial stage of the forming process, a bulge BP is generated on the outer surface 12a of the bent portion 12 that contacts the die shoulder 21. Since compressive strain occurs in such a bulge BP, it may become a cause of the aforementioned bending internal cracks. Therefore, the inventors have investigated a method for suppressing such material bulging that causes compressive strain.

[0123] The following description illustrates embodiments of the present invention, but it is obvious that the present invention is not limited to the examples described below. In the following description, specific values ​​and materials are sometimes illustrated, but other values ​​and materials can be applied as long as the effects of the present invention are achieved. Furthermore, the constituent elements of the following embodiments can be combined with each other.

[0124] [First Implementation]

[0125] The flanging method of this embodiment is a method of forming a flanged portion, including a raised portion and a bent portion, on a metal part with a bottom hole using a flanging die. The flanging die includes: a first die having a first die hole and a first support surface perpendicular to the axis of the first die hole; a second die having a second die hole and a second support surface perpendicular to the axis of the second die hole; a bracket having a third support surface facing the first and second support surfaces, and clamping the metal part between the first and second dies; and a punch having a shaft portion, configured to move along the axes of the first and second die holes. The first, second, and third support surfaces are arranged parallel to each other. The diameter of the 2nd die hole is smaller than the diameter of the 1st die hole, and the outer diameter of the 2nd support surface is smaller than the diameter of the 1st die hole. The flanging process includes: a pre-forming process, in which the bottom hole is enlarged and the edge of the bottom hole is moved relative to the metal part in a first direction of the thickness direction of the metal part in a first range toward the periphery of the bottom hole of the metal part, forming the first range into a pre-formed part that is erected from the metal part in the first direction; and a formal forming process, in which the pre-formed part is deformed in a second direction opposite to the first direction, and the second range formed in the first direction becomes a part of the erected part and the bent part, which is a part of the third range that is closer to the inner diameter side of the pre-formed part than the second range in the first direction and has the same height as the first range.

[0126] In the above flanging method, it is characterized in that the outer diameter of the bending portion is smaller than the outer diameter of the preformed portion, and in a cross-section parallel to the first direction and passing through the center of the bottom hole, the maximum curvature radius of the bending portion is smaller than the minimum curvature radius of the preformed portion. A metal part is clamped between the first supporting surface of the first die and the third supporting surface of the bracket, and the punch is moved relative to the first die in the first direction so that the punch passes through the first die hole, thereby forming a preformed portion between the punch and the first die. In a state where the metal part is clamped between the first supporting surface and the third supporting surface, the second die is moved relative to the bracket in the second direction so that a part of the second die passes through between the punch and the first die, thereby forming a flanging portion between the second die, the punch and the bracket. When the difference between the radius of the first die hole and the radius of the second die hole is set as U, the diameter of the shaft portion of the punch is set as P, and the diameter of the bottom hole of the metal part is set as A, the following formula 1 is satisfied. When the height of the edge portion of the bottom hole of the metal part is set as t and the height of the outer surface of the bending portion in the first direction is set as h, the following formula 2 is satisfied.

[0127] 0.5×(P - A) / 2 < U < 20×(P - A) / 2 … formula 1

[0128] 0.2 < h / t < 0.6 … formula 2.

[0129] In the flanging method formed by the above structure, it includes a preforming process of forming a preformed portion in one direction around the bottom hole, and a formal forming process of forming a standing portion and a bending portion of the flanging portion by deforming the preformed portion toward the side opposite to one direction. The outer diameter of the bending portion is smaller than the outer diameter of the preformed portion, and in a cross-section parallel to the first direction and passing through the center of the bottom hole, the maximum curvature radius of the bending portion is smaller than the minimum curvature radius of the preformed portion, thereby being able to suppress cracks from occurring in the bending portion of the flanging portion.

[0130] Here, Figure 3 (A) to (C) are schematic plan views for explaining the forming process of the conventional flanging, and are views observed from a top view in a direction intersecting with the surface of the metal part 1. Figure 3 (A) shows the metal part 1 having a bottom hole 2. Figure 3 (B) shows a state where the peripheral portion of the bottom hole 2 is deformed to expand the diameter of the bottom hole 2. Figure 3 (C) shows the flanged product 100 after the flanging process is completed. Figure 4 (A) to (C) are respectively used to explain Figure 3The schematic cross-sectional views of the flanging forming process in (A) to (C) show a cross-section of either the axis ca passing through the center of the bottom hole 2 and orthogonal to the surface of the metal part 1, or the axis cb passing through the flanging section 110 to be formed and parallel to these axes. Generally, the axis ca passing through the center of the bottom hole 2 and orthogonal to the surface of the metal part 1 coincides with the axis cb of the flanging section 110.

[0131] In previous flanging processing methods, such as Figure 3 as well as Figure 4 As shown, a flanging section 110 is formed by expanding the diameter of the bottom hole 2 provided in the metal part 1 and bending a portion of the metal part 1, including a raised portion 120 and a bent portion 130. However, depending on the flanging method, sometimes micro-cracks (inner bending cracks) are generated on the inner side of the bent portion 130, and sometimes it is necessary to change the shape by increasing the radius of curvature of the bent portion 130. In the flanging method of this embodiment, it is possible to suppress the generation of cracks in the bent portion of such a flanging section.

[0132] The flanging method of this embodiment will be described below. In this embodiment, the method using... Figure 5 The flanging process of the mold 1000 shown in the figure will be explained.

[0133] like Figure 5 As shown, the flanging die used in this embodiment includes: a first die 1100 having a first die hole 1110 and a first support surface 1120 perpendicular to the axis cd1 of the first die hole 1110; a second die 1200 having a second die hole 1210 and a second support surface 1220 perpendicular to the axis cd2 of the second die hole 1210; a bracket 1300 having a third support surface 1320 opposite to the first support surface 1120 and the second support surface 1220, and clamping the metal part 1 between the first die 1100 and the second die 1200; and a punch 1400 having a shaft portion 1410, configured to move along the axis cd1 of the first die hole 1110 and the axis cd2 of the second die hole 1210.

[0134] The inner wall surface 1111 of the first die hole 1110 of the first die 1100 is connected to the first support surface 1120 via the first die shoulder surface 1130. The inner wall surface 1211 of the second die hole 1210 of the second die 1200 is connected to the second support surface 1220 via the second die shoulder surface 1230. Furthermore, the second support surface 1220 is connected to the die hole side surface 1240. The die hole side surface 1240 is located on the outer periphery of the inner wall surface 1211 of the second die hole 1210. The outer diameter ro2 of the second support surface 1220 is the diameter of the die hole side surface 1240 in a cross-section along the axis cd1 of the first die hole 1110. Here, if the shape of the die hole side surface 1240 in a cross-section along the axis cd2 of the second die hole 1210 is circular, the diameter of the die hole side surface 1240 is the diameter of that circular shape. When the shape of the die hole side surface 1240 in the cross section along the axis cd2 of the second die hole 1210 is not circular, twice the maximum distance between the axis cd2 of the second die hole 1210 and the die hole side surface 1240 is taken as the diameter of the die hole side surface 1240. The second support surface 1220 and the die hole side surface 1240 can also be connected via a ridge portion (not shown), but the width of this ridge portion can be smaller. Figure 5 In the example of the first punch hole 1110, the axis cd1 is parallel to the Z-axis. Figure 5 The Z-axis, X-axis, and Y-axis of the model are orthogonal to each other.

[0135] The generally cylindrical punch 1400 includes a shaft portion 1410, the shaft side 1411 of which is connected to the top surface 1420 via a punch shoulder 1430.

[0136] In the flanging die 1000, the first support surface 1120, the second support surface 1220, and the third support surface 1320 are arranged parallel to each other. In addition, the top surface 1420 of the punch 1400 may also be arranged parallel to the first support surface 1120, the second support surface 1220, and the third support surface 1320.

[0137] The axis cd1 of the first die hole 1110 coincides with the axis cd2 of the second die hole 1210. Furthermore, the axis (not shown) of the support hole 1310 of the support 1300 coincides with the axis cd1 of the first die hole 1110. Here, the axis of the hole refers to a line passing through the center of the circle drawn from the edge of the hole and parallel to the depth direction of the hole. Additionally, the axis (not shown) of the punch 1400 coincides with the axis cd1 of the first die hole 1110. Here, the axis of the punch 1400 refers to the axis of the generally cylindrical portion of the punch.

[0138] In the flanging die 1000, the diameter rd2 of the second punch hole 1210 is smaller than the diameter rd1 of the first punch hole 1110, and the outer diameter ro2 of the second support surface 1220 is smaller than the diameter rd1 of the first punch hole.

[0139] In a cross-section along the axis cd1 of the first die hole 1110, the inner wall surface 1111 of the first die hole 1110, the inner wall surface 1211 of the second die hole 1210, and the side surface 1411 of the shaft portion of the punch 1400 can all be circular. In a cross-section along the axis cd1 of the first die hole 1110, the side surface 1240 of the die hole of the second die 1200 and the inner wall surface of the support hole 1310 of the support 1300 can be circular or other shapes. In a cross-section along the axis cd1 of the first die hole 1110, the diameter rd2 of the inner wall surface 1211 of the second die hole 1210 (the diameter of the second die hole 1210) is greater than the diameter of the shaft side surface 1411 of the punch 1400, and the diameter rd1 of the inner wall surface 1111 of the first die hole 1110 (the diameter of the first die hole 1110) is greater than the diameter of the inner wall surface 1211 of the second die hole 1210. Furthermore, in a cross-section along the axis cd1 of the first die hole 1110, the diameter of the inner wall surface 1111 of the first die hole 1110 is greater than the maximum value of the diameter of the die hole side surface 1240 of the second die 1200.

[0140] exist Figure 5 In this example, the support 1300 is connected to the spring 1500. For example, the spring 1500 may also be connected to the mold base on the side opposite to the side connected to the support 1300. Furthermore, the punch 1400 may be connected to the mold base on the side opposite to the top surface 1420 facing the first die 1100 and the second die 1200, and may also be configured to be movable. The first die 1100, the second die 1200, and the support 1300 may also be connected to a drive unit (not shown) and configured to move independently.

[0141] In the following, use Figures 6 to 10 The flanging method using the aforementioned flanging die 1000 will be described. First, a metal part 1, which is the workpiece, is placed on the third support surface 1320 of the support 1300. Preferably, the metal part 1 is positioned such that the center of the bottom hole 2 is located on the axis cd1 of the first punch hole 1110. Furthermore, in this embodiment, the example will... Figure 5 The positive direction of the Z-axis is defined as the vertical direction, but it is not limited to this. As long as the positional relationship between the flanging die 1000 and the metal part 1 can be maintained, the axis cd1 of the first punch hole 1110 may not be parallel to the vertical direction.

[0142] Next, as Figure 6 As shown, a metal part 1 is clamped between the first support surface 1120 of the first die 1100 and the third support surface 1320 of the bracket 1300.

[0143] (Preforming process)

[0144] Next, preforming is performed in the preforming process. In the preforming process, the bottom hole 2 is enlarged, and the edge portion 2a of the bottom hole 2 is moved relative to the metal part 1 in a first direction relative to the thickness direction of the metal part 1 within a first range 3 surrounding the bottom hole 2, thus forming the first range 3 into a preformed portion 4 that stands upright from the metal part 1 entirely in the first direction. The first range 3 is a range defined on the metal part 1, and the preformed portion 4 is formed on the metal part 1 by deforming the first range 3. In this embodiment, the first direction is... Figure 5 The negative direction of the Z-axis is equal to the negative direction of the Z-axis. The second direction, which will be described later, is the positive direction of the Z-axis.

[0145] Here, Figure 9 (A) indicates the state of the metal part 1 with the bottom hole 2 as viewed from above in a direction perpendicular to the surface of the metal part 1. The bottom hole 2 is defined by the edge portion 2a of the metal part 1, and the central axis of the bottom hole 2 is set as ch. Figure 9 (A) to (C) represent states observed from the same direction. Figure 10 (A) is a face passing through the central axis ch. Figure 9 A diagram showing the state of cross-section observation of metal part 1 (A). Figure 10 (A) to (C) represent states observed from the same direction. Figure 9 (B) indicates that makes Figure 9 The figure shows a metal part 1 with a preformed part 4 obtained by deforming the metal part 1 of (A). Figure 10 (A) is a face passing through the central axis ch. Figure 9 The diagram shows the cross-sectional view of the metal part 1 in (A). Here, the thickness direction of the metal part 1 is parallel to the central axis ch of the bottom hole 2. Furthermore, the first direction is the direction in which the edge 121 (opening side end) of the raised portion 120 of the flanging section 110 faces in the flanged product 100 after the formal forming process.

[0146] In the flanging process of this embodiment, in order to perform pre-forming, the punch 1400 is moved relative to the first die 1100 in the first direction in the flanging die 1000 so that the punch 1400 is inserted into the first die hole 1110, thereby forming the pre-formed part 4 between the punch 1400 and the first die 1100. Figure 7The image shows a pre-formed flanging die 1000 and a metal part 1. (See image for details.) Figure 7 As shown, in the pre-formed state, the punch 1400 is inserted into the bottom hole 2, thereby expanding the diameter of the bottom hole 2, and the first region 3 is formed into a pre-formed portion 4 that stands upright from the metal part in the first direction. Figure 7 In the state of being, the second die 1200 is moved toward the second direction, thereby causing the support 1300 to move toward the second direction via the first die 1100 connected to the second die 1200 via the spring 1600, and the spring 1500 to contract.

[0147] In this embodiment, the first die 1100 is moved toward the support 1300, but this is not a limitation; the support 1300 may also be moved toward the first die 1100. Furthermore, in this embodiment, an example is shown where the first die 1100 and the second die 1200 move simultaneously, but this is not a limitation; the first die 1100 and the second die 1200 may also be configured to move independently. Figure 6 In examples such as [examples omitted], the first die 1100 and the second die 1200 are connected by a spring 1600. Therefore, by moving the second die 1200 relative to the support 1300, the first die 1100 also moves relative to the support 1300 at the same time. Furthermore, in this embodiment, during preforming, it is sometimes preferable to have the edge portion 2a of the bottom hole 2 contact the shoulder surface 1230 of the second die, and sometimes it is preferable not to have the edge portion 2a of the bottom hole 2 contact the shoulder surface 1230 of the second die.

[0148] (Formal molding process)

[0149] Next, in the preforming process, in the formal forming process, the preforming part 4 is deformed in the second direction opposite to the first direction to form such that the second range 5 on the outer diameter side of the preforming part 4 becomes the same height as the first range 3 in the first direction, and a part of the third range 6 on the inner diameter side of the preforming part 4, which is closer to the second range 5, becomes part of the standing part 120 and the bending part 130 of the flanging processing part 110.

[0150] Figure 9 (C) shows the state of the flanged product 100 with the flanging section 110 provided, viewed from the edge 121 side of the upright portion 120 of the flanging section along the axis cb of the flanging section. The axis cb of the flanging section is aligned with the central axis ch of the bottom hole 2.

[0151] In addition, such as Figure 9As shown in (B), in a top view parallel to the central axis ch of the bottom hole 2, the preformed portion 4 is circular. The second range 5 is the range encompassed by the preformed portion 4 and is the range on the outer diameter side of the preformed portion 4. Furthermore, the third range 6 is the range encompassed by the preformed portion 4 and is the range on the inner diameter side of the preformed portion 4, which is closer to the second range 5. In a cross-sectional view through the central axis ch, one surface of the preformed portion 4 is located on the first direction side closer to the first surface of the first range 3 before preforming.

[0152] In the flanging process of this embodiment, with the metal part 1 held between the first support surface 1120 and the third support surface 1320, the second die 1200 is moved relative to the bracket 1300 in the second direction so that a part of the second die 1200 is inserted between the punch 1400 and the first die 1100, thereby forming the flanging part 110 between the second die 1200, the punch 1400 and the bracket 1300. Figure 8 The image shows the 1000 mold for flanging after final forming and the flanged product 100. Figure 8 In the state of, from Figure 7 The state causes the second die 1200 to move further in the second direction, causing the spring 1600 to contract, thereby making the second die 1200 and the support 1300 more aligned. Figure 7 The state is closer to the state. In the case where the first die 1100 and the second die 1200 are connected by the spring 1600, as in the configuration of the flanging die of this embodiment, in order to move the first die 1100 relative to the punch 1400 in the pre-forming process, and then move the second die 1200 relative to the punch 1400 in the formal forming process, the rebound force of the spring 1600 needs to be greater than the rebound force of the spring 1500. However, as described above, the first die 1100, the second die 1200, the support 1300, and the punch 1400 can also be configured to move independently.

[0153] like Figure 8 As shown, in the final formed state, by inserting the second die 1200 between the first die 1100 and the punch 1400, the pre-formed portion 4 is deformed in the second direction. Thus, a flanging portion 110 including a raised portion 120 and a bent portion 130 is formed.

[0154] Here, in the flanging method of this embodiment, the outer diameter of the pre-forming part 4 refers to the outer diameter of the pre-forming part 4, which is formed into a circular shape, when viewed from above in a direction parallel to the central axis ch of the bottom hole 2. The outer diameter of the pre-forming part 4 can also be described as... Figure 9The outer diameter of the circular shape defined by the edge portion 4a of the preformed portion 4, as shown in (B). The edge portion 4a of the preformed portion 4 can be defined as the boundary between a surface at the same height as the surface of the first range 3 before preforming and a surface located on the first direction side closer to the surface of the first range 3 before preforming. In the flanging method of this embodiment, an indentation (including bending marks) is generated in the area including the edge portion 4a and its vicinity by the preforming process.

[0155] In the above-described flanging process, the outer diameter of the curved portion 130 refers to the outer diameter of the curved portion 130, which is formed into a circular shape, when viewed from above in a direction parallel to the axis cb of the flanging portion 110. The outer diameter of the curved portion 130 can also be described as... Figure 9 The outer diameter of the circular shape defined by the edge portion 130a of the curved portion 130 as shown in (C). The edge portion 130a of the curved portion 130 can be defined as the boundary between a surface at the same height as the surface of the first range 3 before preforming and a surface located on the first direction side of the surface of the first range 3 before preforming.

[0156] In the above-described flanging method, the radius of curvature of the bent portion 130 is the radius of curvature in a cross-section parallel to the first direction and passing through the center of the bottom hole 2. Here, the first direction coincides with the axis cb of the flanging portion 110. In other words, the cross-section parallel to the first direction and passing through the center of the bottom hole 2 is a cross-section parallel to and including the axis cb of the flanging portion 110. The bent portion 130 may have a certain radius of curvature in this cross-section, or the radius of curvature may vary within the bent portion 130. The maximum radius of curvature of the bent portion 130 refers to the largest radius of curvature in the cross-section parallel to the first direction and passing through the center of the bottom hole 2. The shape of the concave surface of the bent portion 130, i.e., the surface located on the outer side of the flanging portion 110, corresponds to the shape of the second die shoulder surface 1230 of the second die 1200.

[0157] Similarly, the preformed part 4 may have a certain radius of curvature in a cross section parallel to the first direction and passing through the center of the bottom hole 2, or the radius of curvature may vary within the preformed part 4. The maximum radius of curvature of the preformed part 4 refers to the largest radius of curvature in a cross section parallel to the first direction and passing through the center of the bottom hole 2.

[0158] In the flanging method of the present embodiment, by including a preforming process and a formal forming process, the outer diameter of the bent portion is smaller than the outer diameter of the preformed portion, and in a cross section parallel to the first direction and passing through the center of the bottom hole, the maximum radius of curvature of the bent portion is smaller than the minimum radius of curvature of the preformed portion. Thereby, the compressive strain generated in the bent portion can be suppressed, and cracks generated in the bent portion of the flanging portion can be suppressed.

[0159] In addition, in the flanging method of the present embodiment, when the difference between the radius of the first die hole 1110 and the radius of the second die hole 1210 is set to U, the diameter of the shaft portion of the punch 1400 is set to P, and the diameter of the bottom hole 2 of the metal part 1 is set to A, the following formula 1 is satisfied. By satisfying formula 1, an appropriate preformed portion 4 can be formed in the preforming process, and compressive strain concentration can be suppressed in the formal forming process. Since U is less than 20×(P - A) / 2, the contact area between the second die 1200 and the metal part 1 can be ensured, and the raised portion can be suppressed to suppress the generation of internal cracks in the bend. Since U exceeds 0.5×(P - A) / 2, the distance at which the second die 1200 contacts the preformed portion 4 of the metal part 1 in the formal forming process becomes shorter, so the raised portion can be suppressed to suppress the generation of internal cracks in the bend. Here, the difference U between the radius of the first die hole 1110 and the radius of the second die hole 1210 is expressed as (rd1 - rd2) / 2 using the diameter rd1 of the first die hole 1110 and the diameter rd2 of the second die hole 1210.

[0160] 0.5×(P - A) / 2 < U < 20×(P - A) / 2 …… Formula 1 <000.org / 19950901>[[ID=B]]

[0161] Furthermore, in the flanging method of the present embodiment, when the height of the edge portion 2a of the bottom hole 2 of the metal part 1 is set to t, and the height of the outer surface of the bent portion 130 in the first direction is set to h, the following formula 2 is satisfied.

[0162] 0.2 < h / t < 0.6 …… Formula 2

[0163] The smaller h / t is, the easier it is to generate the above-mentioned internal cracks in the bend. The reason is that the smaller h / t is, the smaller the bending radius of the bent portion 130 of the flanging portion 110 relative to the plate thickness becomes, the greater the compressive strain on the inner surface layer of the bend becomes, and the more prominent the raised portion is formed. When h / t is less than 0.6, the effect of the flanging method of the present embodiment is more significantly exerted. In addition, when h / t is 0.2 or less, the compressive strain inside the bend is too large, so it may not be possible to suppress the formation of the raised portion and internal cracks in the bend may be generated, so h / t is set to exceed 0.2.

[0164] In addition, by making h / t fall within the above range, there is an advantage that the range of the erected portion 120 can be increased. Here, the height of the edge portion 2a of the bottom hole 2 of the metal part 1, in other words, the thickness (plate thickness) of the metal part 1 at the edge portion 2a of the bottom hole 2. The thickness of the metal part 1 at the edge portion 2a of the bottom hole 2 may also be the average value of values measured at multiple positions (for example, 5 positions) using measuring instruments such as micrometers and vernier calipers.

[0165] In addition, in the flanging method of the present embodiment, it may also be that when the difference between the radius of the first die hole 1110 and the radius of the second die hole 1210 is set as U, the diameter of the shaft portion of the punch 1400 is set as P, the diameter of the bottom hole 2 of the metal part 1 is set as A, and the height of the edge portion 2a of the bottom hole 2 of the metal part 1 is set as t, the following formula 3 is satisfied.

[0166] 2.0×(P - A) / 2 / t < U < 80×(P - A) / 2 / t …… Formula 3

[0167] By satisfying Formula 3, it is possible to take into account the range of the plate thickness t and the behavior of the metal part 1 in the preforming process, and further suppress the generation of bending internal cracks.

[0168] The flanging method of the present embodiment has the advantage that the flanging process can be implemented in one process without performing die replacement or the like.

[0169] In the flanging method of the present embodiment, as the metal part 1, a steel component with a tensile strength of 780 MPa or more is preferably used. As the metal part 1, a steel component with a tensile strength of 980 MPa or more and a steel component with a tensile strength of 1180 MPa or more are more preferably used. A JIS No. 5 tensile test piece described in JIS Z 2201 is collected from the metal part 1, and a tensile test is performed in accordance with JIS Z 2241:2011, thereby measuring the tensile strength of the metal part 1.

[0170] In the flanging method of the present embodiment, the thickness of the metal part is preferably 1.8 to 4.2 mm, more preferably 2.0 to 3.9 mm. The thickness of the metal part is further preferably 2.3 to 3.2 mm. By making the thickness of the metal part fall within such a range, the desired rigidity and lightness can be ensured. The thickness of the metal part may also be the average value of values measured at multiple flat positions (for example, 5 positions) of the metal part using measuring instruments such as micrometers and vernier calipers, excluding the bottom hole and non - flat portions such as those subjected to bending processing.

[0171] In the flanging method of this embodiment, when the height of the edge portion 2a of the bottom hole 2 of the metal part 1 is set to t, and the thickness of the opening side end (edge ​​portion 121) of the upright portion 120 is set to tb, the following formula 4 is satisfied. This provides the advantage of being able to increase the range of the upright portion. The thickness tb can also be the average value obtained by measuring multiple locations (e.g., 5 locations) using a measuring instrument such as a micrometer or vernier caliper.

[0172] tb / t<0.9 ……Equation 4

[0173] In the flanging process of this embodiment, a bottom hole forming process may be further included before the preforming process, which involves forming a bottom hole 2 on the metal part 1.

[0174] Furthermore, according to the present invention, a flanging die for the flanging method of the first embodiment is provided, characterized in that it comprises: a first die having a first die hole and a first support surface perpendicular to the axis of the first die hole; a second die having a second die hole and a second support surface perpendicular to the axis of the second die hole; a support having a third support surface facing the first support surface and the second support surface, and clamping a metal part between the first die and the second die; and a punch having a shaft portion configured to move along the axis of the first die hole and the axis of the second die hole, wherein the first support surface, the second support surface, and the third support surface are arranged parallel to each other, the diameter of the second die hole is smaller than the diameter of the first die hole, and the outer diameter of the second support surface is smaller than the diameter of the first die hole. Furthermore, according to the present invention, a flanging apparatus is provided, comprising a drive mechanism capable of moving the first die, the second die, the support, and the punch of the flanging die described in the first embodiment relative to each other.

[0175] [Second Implementation]

[0176] The flanging method of this embodiment is a method for forming a flanging part including an upright portion and a bent portion on a metal part with a bottom hole. It is characterized by comprising: a pre-forming process in which the bottom hole is enlarged and the edge of the bottom hole is moved relative to a first direction in which the metal part is in a first range toward the periphery of the bottom hole, forming the first range into a pre-formed portion that is upright from the metal part in the first direction; and a formal forming process in which the pre-formed portion is deformed in a second direction opposite to the first direction, forming a second range on the outer diameter side of the pre-formed portion that becomes part of a third range on the inner diameter side of the pre-formed portion, which is at the same height as the first range in the first direction and is closer to the second range than the second range. This third range becomes part of the upright portion and the bent portion, the outer diameter of the bent portion being smaller than the outer diameter of the pre-formed portion, and in a cross-section parallel to the first direction and passing through the center of the bottom hole, the maximum radius of curvature of the bent portion being smaller than the minimum radius of curvature of the pre-formed portion.

[0177] In the flanging method of this embodiment, a flanging die set including a set of pre-forming dies and a set of formal forming dies is used. The set of pre-forming dies includes: a first die having a first die hole and a first support surface perpendicular to the axis of the first die hole; a first support surface facing and parallel to the first support surface; a first support for holding a metal part between itself and the first die; and a first punch having a first shaft portion and configured to move along the axis of the first die hole. The set of formal forming dies includes: a second die having a second die hole and a second support surface perpendicular to the axis of the second die hole; a second support surface facing and parallel to the second support surface; a second support for holding a metal part between itself and the second die; and a second punch having a second shaft portion and configured to move along the axis of the second die hole, the diameter of which is less than or equal to the diameter of the first die hole.

[0178] In addition, in the flanging method of the present embodiment, by clamping a metal part between the first support surface of the first die and the first support surface of the first bracket, the first punch is moved relative to the first die in the first direction so that the first punch is inserted into the first die hole. Thus, a preformed portion is formed between the first punch and the first die. The metal part formed with the preformed portion is separated from the preforming die. Then, the metal part formed with the preformed portion is placed on the second support surface of the second bracket with the side formed with the preformed portion facing the first direction side. The second punch is inserted into the enlarged bottom hole in the first direction, and the second die is moved relative to the second bracket in the second direction so that the second punch is inserted into the second die hole. Thus, a flanging portion is formed among the second die, the second punch, and the second bracket. When the height of the edge portion of the bottom hole of the metal part is set as t and the height of the outer surface of the bent portion in the first direction is set as h, the following formula 2 is satisfied.

[0179] 0.2 < h / t < 0.6 …… formula 2

[0180] In the flanging method formed by the above configuration, it includes: a preforming process of forming a preformed portion in one direction around the bottom hole; and a formal forming process of deforming the preformed portion to the opposite side of one direction to form the standing portion and the bent portion of the flanging portion. The outer diameter of the bent portion is smaller than the outer diameter of the preformed portion. In a cross-section parallel to the first direction and passing through the center of the bottom hole, the maximum curvature radius of the bent portion is smaller than the minimum curvature radius of the preformed portion. Thus, cracks generated in the bent portion of the flanging portion can be suppressed.

[0181] Hereinafter, the flanging method of the present embodiment will be described. In addition, in the flanging method of the present embodiment, there are also similar aspects in the form of the metal part 1 during the process of forming the metal part 1 into the flanged product 100 as the workpiece. Therefore, the description will be appropriately omitted. In addition, the definitions of the first direction, the second direction, the axis, etc. are also the same as those in the first embodiment. The deformation process of the metal part 1 in the present embodiment is the same as that described in (A) to (C) of Figure 9 and (A) to (C) of Figure 10 shown.

[0182] In the flanging method of the present embodiment, in the preforming process, Figure 11The preforming mold 2000 is shown. The preforming mold 2000 includes: a first die 2100 having a first die hole 2110 and a first support surface 2120 perpendicular to the axis cd1' of the first die hole; a first bracket 2300 having a first bracket support surface 2320 disposed opposite to and parallel to the first support surface 2120, which clamps the metal part 1 between itself and the first die 2100; and a first punch 2400 having a first shaft portion 2410 configured to move along the axis cd1' of the first die hole 2110.

[0183] Furthermore, in the flanging process of this embodiment, the flanging is used in the formal forming process. Figure 12 The formal forming die 3000 is shown. The formal forming die 3000 includes: a second die 3200 having a second die hole 3210 and a second support surface 3220 perpendicular to the axis cd2' of the second die hole 3210; a second bracket 3300 having a second bracket support surface 3320 arranged opposite to and parallel to the second support surface 3220, which clamps the metal part 1 with the pre-formed portion 4 between itself and the second die 3200; and a second punch 3400 having a second shaft portion 3410, configured to move along the axis cd2' of the second die hole 3210.

[0184] Furthermore, in the pre-forming mold 2000 and the formal forming mold 3000 of this embodiment, the diameter of the second punch hole 3210 is less than or equal to the diameter of the first punch hole 2110.

[0185] In the flanging process of this embodiment, firstly, as in the first embodiment, a metal part 1 with a bottom hole is placed on a preforming mold 2000. Then, the metal part 1 is clamped between the first support surface 2120 of the first punch 2100 and the first support support surface 2320 of the first bracket 2300.

[0186] Next, in order to perform preforming, in the preforming mold 2000, the first punch 2400 is moved relative to the first die 2100 in the first direction so that the first punch 2400 is inserted into the first die hole 2110, thereby forming the preformed part 4 between the first punch 2400 and the first die 2100. Figure 13 The image shows the preformed mold 2000 and the metal part 1.

[0187] After preforming, the metal part 1 with the preformed portion 4 is separated from the preforming mold 2000. In the flanging method of this embodiment, the preforming process generates indentations (including bending marks) in the area including the edge portion 4a and its vicinity, which will be described later.

[0188] Next, as Figure 14 shown, with the metal part 1 formed with the preformed portion 4 facing the first direction side, the metal part 1 is placed on the second bracket support surface 3320 of the second bracket 3300 of the formal forming die 3000.

[0189] In the flanging method of the present embodiment, in order to perform formal forming, the second punch 3400 is inserted into the enlarged bottom hole 2 in the first direction, and the second die 3200 is relatively moved in the second direction with respect to the second bracket 3300, and the second punch 3400 is inserted through the second die hole 3210, thereby forming a flanging portion 110 between the second die 3200, the second punch 3400, and the second bracket 3300.

[0190] In the flanging method of the present embodiment, when the height of the edge portion 2a of the bottom hole 2 of the metal part 1 is set to t and the height of the outer surface of the bent portion 130 in the first direction is set to h, the following formula 2 is satisfied.

[0191] 0.2 < h / t < 0.6 …… Formula 2

[0192] The smaller h / t is, the more likely the above-mentioned bending inner crack is to occur. The reason is that the smaller h / t is, the smaller the bending radius of the bent portion 130 of the flanging portion 110 becomes with respect to the plate thickness, the greater the compressive strain of the inner surface layer of the bend becomes, and the more prominent the raised portion is formed. When h / t is less than 0.6, the effect of the flanging method of the present embodiment is more significantly exerted. In addition, when h / t is 0.2 or less, the compressive strain inside the bend becomes too large, so it may not be possible to suppress the formation of the raised portion and a bending inner crack may occur. Therefore, h / t is set to be more than 0.2.

[0193] In addition, by making h / t within the above range, there is an advantage that the range where the erected portion 120 can be increased can be achieved. Here, the height of the edge portion 2a of the bottom hole 2 of the metal part 1, in other words, is the thickness (plate thickness) of the metal part 1 at the edge portion 2a of the bottom hole 2. The thickness of the metal part 1 at the edge portion 2a of the bottom hole 2 may also be the average value of values obtained by measuring a plurality of portions (for example, 5 portions) using measuring instruments such as a micrometer and a vernier caliper.

[0194] In the flanging method of the present embodiment, it is also possible that when the difference between the radius of the first die hole 2110 and the radius of the second die hole 3210 is set as U, the diameter of the second shaft portion 3410 of the second punch 3400 is set as Ps, and the diameter of the bottom hole 2 of the metal part 1 is set as A, the following formula 5 is satisfied. By satisfying formula 5, an appropriate preformed portion 4 can be formed in the preforming process, and the concentration of compressive strain can be suppressed in the formal forming process. Since U is less than 20×(Ps - A) / 2, the contact area between the second die 3200 and the metal part 1 can be ensured, and the generation of a raised portion can be suppressed to suppress the generation of a bending internal crack. Since U exceeds 0.5×(Ps - A) / 2, the distance at which the second die 3200 contacts the preformed portion 4 of the metal part 1 in the formal forming process becomes shorter, so that the generation of a raised portion can be suppressed to suppress the generation of a bending internal crack. Here, the difference U between the radius of the first die hole 2110 and the radius of the second die hole 3210 is expressed as (rd1’ - rd2’) / 2 using the diameter rd1’ of the inner wall surface 2111 of the first die hole 2110 and the diameter rd2’ of the inner wall surface 3211 of the second die hole 3210.

[0195] 0.5×(Ps - A) / 2 < U < 20×(Ps - A) / 2 …… Formula 5

[0196] In addition, in the flanging method of the present embodiment, it is also possible that when the difference between the radius of the first die hole 2110 and the radius of the second die hole 3210 is set as U, the diameter of the second shaft portion 3410 of the second punch 3400 is set as Ps, the diameter of the bottom hole 2 of the metal part 1 is set as A, and the height of the edge portion 2a of the bottom hole 2 of the metal part 1 is set as t, the following formula 6 is satisfied.

[0197] 2.0×(Ps - A) / 2 / t < U < 80×(Ps - A) / 2 / t …… Formula 6

[0198] By satisfying formula 6, the generation of a bending internal crack can be further suppressed by taking into account the range of the plate thickness t and the behavior of the metal part 1 in the preforming process.

[0199] In the formal forming process of the flanging method of the present embodiment, the formal forming can be carried out by two methods as described below.

[0200] In the flanging method of the present embodiment, as the first method, as Figure 15 shown, first, the second punch 3400 is inserted into the expanded bottom hole 2 in the first direction. In Figure 15 the state as shown, by relatively moving the second die 3200 in the second direction with respect to the second bracket 3300, it becomes Figure 16In the state shown, a flanged product 100 with a flanged processing section 110 is obtained.

[0201] As a second method, such as Figure 17 As shown, firstly, the second die 3200 is moved relative to the second support 3300 in the second direction. The metal part 1 with the preformed portion 4 is pressed by the second support surface 3220 of the second die 3200 and the second support support surface 3320 of the second support 3300, and deformed in the second direction. In this state, as... Figure 17 As shown, a portion of the pre-formed part 4, formed through a pre-forming process, remains around the periphery of the bottom hole 2. Next, the second punch 3400 is inserted into the enlarged bottom hole 2 in the first direction, thereby forming... Figure 16 In the state shown, a flanged product 100 with a flanged processing section 110 is obtained.

[0202] In the flanging method of this embodiment, the diameter of the first shaft portion 2410 of the first punch 2400 may be smaller than the diameter of the second shaft portion 3410 of the second punch 3400. This provides the advantage of increasing the height of the erected portion. Alternatively, the diameter of the first shaft portion 2410 of the first punch 2400 and the diameter of the second shaft portion 3410 of the second punch 3400 may be the same.

[0203] In the flanging method of this embodiment, the initial contact position between the pre-forming part 4 and the second die 3200 in a cross-section parallel to the first direction and passing through the center of the bottom hole 2 is within a range of 7 / 8 of the surface length of the curved portion of the second die shoulder surface 3230 of the second die hole 3210, from the inner wall surface 3211 side of the second die hole 3210. This allows for more effective suppression of compressive strain concentration during the formal forming process.

[0204] In the flanging method of this embodiment, the first punch 2400 used in the preforming process can also be used as the second punch 3400 in the formal forming process. That is, after preforming, the metal part 1 with the preformed part 4 can be replaced with the second punch 3200 instead of separating it from the first punch 2400 and the first support 2300 for formal forming.

[0205] The flanging method of this embodiment is superior because it does not require a specially constructed mold. Furthermore, in this embodiment, the illustration of the springs connected to the first die 2100, the second die 3200, the first support 2300, or the second support 3300 is omitted, but each mold can be connected to a spring, allowing for the same configuration as in the first embodiment. The first die 2100, the second die 3200, the first support 2300, and the second support 3300 can also be connected to a drive unit (not shown), enabling independent movement. Additionally, the first punch 2400 (or the second punch 3400) can be connected to the mold base on the side opposite to the top surface 2420 (or top surface 3420) facing the first die 2100 (or the second die 3200), also enabling movement.

[0206] In the flanging method of this embodiment, a steel component with a tensile strength of 780 MPa or higher is preferably used as the metal part 1. More preferably, a steel component with a tensile strength of 980 MPa or higher, or a steel component with a tensile strength of 1180 MPa or higher, is used as the metal part 1. The tensile strength of the metal part 1 is determined by taking a JIS 5 tensile test piece as described in JIS Z 2201 and performing a tensile test according to JIS Z 2241:2011.

[0207] In the flanging method of this embodiment, the thickness of the metal part is preferably 1.8 to 4.2 mm, more preferably 2.0 to 3.9 mm. The thickness of the metal part is further preferably 2.3 to 3.2 mm. By setting the thickness of the metal part within this range, the desired rigidity and lightweight can be ensured. The thickness of the metal part can also be the average value obtained by measuring multiple planar parts (e.g., 5 parts) of the metal part using measuring instruments such as micrometers and vernier calipers, excluding non-planar parts such as bottom holes and bending operations.

[0208] In the flanging method of this embodiment, when the height of the edge portion 2a of the bottom hole 2 of the metal part 1 is set to t, and the thickness of the opening side end (edge ​​portion 121) of the upright portion 120 is set to tb, the following formula 4 is satisfied. This provides the advantage of being able to increase the range of the upright portion. The thickness tb can also be the average value obtained by measuring multiple locations (e.g., 5 locations) using a measuring instrument such as a micrometer or vernier caliper.

[0209] tb / t<0.9 ……Equation 4

[0210] In the flanging process of this embodiment, a bottom hole forming process may be further included before the preforming process, which involves forming a bottom hole 2 on the metal part 1.

[0211] Furthermore, according to the present invention, a flanging die for the flanging method of the second embodiment is provided, characterized in that it includes: a first die having a first die hole and a first support surface perpendicular to the axis of the first die hole; a second die having a second die hole and a second support surface perpendicular to the axis of the second die hole; a support having a third support surface facing the first support surface and the second support surface, and clamping a metal part between the first die and the second die; and a punch having a shaft portion configured to move along the axis of the first die hole and the axis of the second die hole, wherein the first support surface, the second support surface, and the third support surface are arranged parallel to each other, the diameter of the second die hole is smaller than the diameter of the first die hole, and the outer diameter of the second support surface is smaller than the diameter of the first die hole. Furthermore, according to the present invention, a flanging apparatus is provided, comprising a drive mechanism capable of moving the first die, the second die, the support, and the punch of the flanging die described in the second embodiment relative to each other.

[0212] [Third Implementation]

[0213] The flanging product of this embodiment is a flanging product having a flanging part including a raised portion and a curved portion, and a peripheral region surrounding the curved portion. In the flanging product of this embodiment, in a cross section including the axis of the flanging part and parallel to the axis, when the radius of curvature of the outer surface of the curved portion is set to R, the hardness of the flanging product at position a, where the curved portion connected to the peripheral region is separated by R in a direction perpendicular to the axis towards the peripheral region and separated by 0.2 mm from the side where the raised portion is formed, is set to Hva, and the hardness of the flanging product at position b, where the curved portion is separated by 3 times R in a direction perpendicular to the axis towards the peripheral region and separated by 1 / 4 of the thickness of the flanging product in the peripheral region from the side where the raised portion is formed, is set to Hvb, satisfies the following formula 7, and...

[0214] The surrounding area has indentations. When the height of the upright part is set to Us, the indentations are located in the range of 0.5×Us or more and 20×Us or less from the R-stop end of the curved part. When the thickness of the above-mentioned flanged workpiece in the surrounding area is set to ts, the maximum height or depth of the indentation in the direction parallel to the axis exceeds ts / 20 and is less than ts / 3.

[0215] Hva / Hvb>1.03 ……Equation 7

[0216] The flanged products formed by the above-described process have the advantage of high impact resistance.

[0217] Here, the hardness Hva and hardness Hvb can be determined by the method described in JIS Z 2244.

[0218] Figure 18 This is a diagram used to illustrate the flanging product 100 of this embodiment, and it is a cross-sectional view of a section passing through the axis cb of the flanging section 110 and parallel to the axis cb of the flanging section 110. Figure 18 Only one side of the flanging section 110 centered on axis cb is shown. (See image below.) Figure 18 As shown, the flanging processing section 110 of this embodiment includes a cylindrical upright section 120 and a curved section 130. The upright section 120 is connected to the curved section 130 at a connecting end 122 on the opposite side of the open end 121 of the upright section 120.

[0219] The bent portion 130 connects to the connecting end 122 of the erected portion 120 at the front end 131, and connects to the peripheral region 140 of the flanged workpiece 100 via the base end 132 on the opposite side of the front end 131. The connecting end 122 and the front end 131 may be the same location. The bent portion 130 expands in diameter from the front end 131 toward the base end 132. In a cross-section passing through and parallel to the axis cb of the flanged portion 110, the bent portion 130 is smoothly bent. The axis cb of the flanged portion 110 is an axis passing through the longitudinal axis of the cylindrical erected portion 120.

[0220] The peripheral region 140 is the area of ​​the flanged work 100 that surrounds the bent portion 130 and is connected to the base end portion 132 of the bent portion 130. Although it also depends on the shape of the flanged work 100, the peripheral region 140 is more preferably about 0.5 to 50.0 mm wide in the radial direction of the flanged portion 110 in a plane orthogonal to the axis cb of the flanged portion 110. The thickness of the flanged work in the peripheral region 140 is defined as ts. The thickness ts can also be the average value obtained by measuring multiple parts (e.g., 5 parts) of the peripheral region 140 using measuring instruments such as micrometers or vernier calipers.

[0221] In the flanged product of this embodiment, Hva can also be the average hardness measured within a range defined by a square Sa centered at position a, with one side length equal to 1 / 6 of the thickness of the flanged product, in a cross section containing the axis of the flanged part and parallel to the axis. Furthermore, Hvb can also be the average hardness measured within a range defined by a square Sb centered at position b, with one side length equal to 1 / 6 of the thickness of the flanged product, in a cross section containing the axis of the flanged part and parallel to the axis. These squares are positioned such that, in a cross section containing the axis of the flanged part and parallel to the axis, at least one side is parallel to the axis of the flanged part. That is, in each of these squares, two parallel sides are parallel to the axis of the flanged part, and two sides orthogonal to these sides are perpendicular to the axis of the flanged part. Square Sa is centered at position a. That is, the distance from position a to each vertex of square Sa is equal. The relationship between square Sb and position b is also the same.

[0222] Three to eleven samples are obtained from the area defined by these squares, and their average value is taken as the average hardness. In addition, the thickness of the flanged product can also be the average value obtained by measuring multiple parts (e.g., five parts) of the surrounding area 140 using measuring instruments such as micrometers and vernier calipers.

[0223] Next, refer to Figure 19 Explain the indentation. Figure 19 and Figure 18 The same is a partial cross-sectional view of the flanged product 100 of this embodiment, and a cross-sectional view of a section passing through the axis cb of the flanged section 110 and parallel to the axis cb of the flanged section 110. Figure 19 Only one side of the flanging section 110 centered on axis cb is shown. (See image below.) Figure 19 As shown, an indentation 150 is created in the surrounding area 140. (As indicated...) Figure 19 As illustrated, an indentation 150 may be produced on either of the two surfaces 140a or 140b in the peripheral region 140 of the flanged work 100.

[0224] During fatigue durability tests involving repeated loading on the flanged part 100, sometimes at the location of the inner bending portion of the flanged part 110 ( Figure 19Fatigue cracks occur on the outer peripheral surface 130b of the bent portion 130. This is because, due to repeated loading during fatigue durability testing, stress concentrates in the bent portion 130 of the flanging section, which becomes the starting point for deformation. Under load, fatigue cracks occur on the inner side of the bent portion 130 as the angle of the bent portion 130 decreases or increases. Conversely, in the peripheral region 140, if there is an indentation 150 within a range of 0.5 × Us to 20 × Us from the R-stop end of the bent portion, stress is also generated in this indentation 150 under repeated loading, thus reducing the stress on the inner side of the bent portion 110 (the outer peripheral surface 130b of the bent portion 130). In other words, the stress applied to the flanging portion 110 is dispersed. The reason why stress is also generated in the indentation 150 is that, since the indentation 150 produces a concave-convex shape in a direction parallel to the axis cb of the flanging section 110 (or the thickness direction of the peripheral region 140), this concave-convex shape becomes the starting point of deformation. For this reason, fatigue durability is further improved due to the presence of the indentation 150.

[0225] Indentation 150 refers to a portion of the surface of the flanged workpiece 100 that protrudes to a specified height or is recessed to a specified depth. For example... Figure 19 As illustrated, the height of the indentation 150 refers to the height of the surface of the flanged workpiece 100 protruding from the surface of the flanged workpiece 100 (in...). Figure 19 In the example, Lh is the distance from surface 140a) to the top of the protrusion in a direction parallel to the axis cb of the flanging portion 110. The top of the protrusion is the part of the protrusion that is furthest from the surface of the flanged workpiece 100 in a direction parallel to the axis cb. The depth of the indentation 150 refers to the depth from the side of the surface of the flanged workpiece 100 that is recessed from the surface of the flanged workpiece 100 (in... Figure 19 In the example, Ld is the distance from surface 140a) to the bottom of the recess in a direction parallel to the axis cb of the flanging section 110. The bottom of the recess is the part of the recess that is furthest from the surface of the flanged workpiece 100 in a direction parallel to the axis cb. The surfaces (140a, 140b) in the peripheral region 140 of the flanged workpiece 100 are generally planar portions excluding the area of ​​the indentation 150. In the flanged workpiece 100 of this embodiment, the maximum value of either the height or depth of the indentation 150 exceeds ts / 20 and is less than ts / 3.

[0226] By making the maximum height or depth of the indentation 150 exceed ts / 20, the stress dispersion effect towards the indentation 150 can be fully demonstrated. In addition, by making the maximum height or depth of the indentation 150 less than ts / 3, the fatigue crack starting from the indentation 150 can be suppressed. Further, the height Us of the erected portion 120 refers to the distance along the axis cb from the opening-side end portion 121 to the connecting end portion 122 of the erected portion 120. The R end of the bending portion 130 refers to the base end portion 132 of the bending portion 130. The range from 0.5×Us or more and 20×Us or less from the R end of the bending portion 130 means that the distance from the R end of the bending portion 130 in the direction perpendicular to the axis cb and away from the axis cb is 0.5×Us or more and the distance from the R end of the bending portion 130 is 20×Us or less, and it is a range surrounded by a concentric circle centered on the axis cb. In addition, in the direction parallel to the axis cb of the flanging portion 110, a portion where the surface of the flanged product 100 protrudes or depresses by 2% or more of the thickness ts of the flanged product in the peripheral region 140 is set as the indentation 150. A contact or non-contact shape measuring device is used to measure the height Lh or depth Ld of the indentation 150.

[0227] The indentation 150 is more preferably formed in the above range in a shape that continuously or intermittently depicts an arc centered on the axis cb when viewed from above in the direction parallel to the axis cb. In addition, the indentation 150 may be an elliptical shape in the above top view.

[0228] In the flanged product of the present embodiment, it may also be that when the thickness of the flanged product 100 in the peripheral region 140 is set as ts and the height of the outer peripheral surface 130b of the bending portion 130 in the direction parallel to the axis cb is set as h, the following formula 8 is satisfied.

[0229] 0.2 < h / ts < 0.6 …… Formula 8

[0230] Here, the height h is the distance from the contact point O between the outer peripheral surface 120a of the erected portion 120 and the outer peripheral surface 130b of the bending portion 130 to the outer peripheral surface 130b of the base end portion 132 of the bending portion 130 in a cross section passing through the axis cb of the flanging portion 110 and parallel to the axis cb of the flanging portion 110, and it is the distance in the direction parallel to the axis cb. The height h of the bending portion 130 is preferably 0.6 to 3.0 mm, and more preferably 1.3 to 2.1 mm. In addition, as the thickness ts, the plate thickness of the base end portion 132 of the bending portion 130 as shown Figure 18 <can also be adopted.

[0231] In the flanged product of this embodiment, when the thickness of the flanged product 100 in the peripheral area 140 is set as ts and the thickness of the opening side end 121 of the upright part 120 is set as tb, the following formula 9 is satisfied. The thickness tb can also be the average value obtained by measuring multiple parts (e.g., 5 parts) using measuring instruments such as micrometers and vernier calipers.

[0232] tb / ts<0.9…Equation 9

[0233] In the flanged product of this embodiment, there may be no cracks with a depth of 20 μm or more from the surface in the cross-section of the bent portion 130. This provides the advantage of improved impact resistance. Here, the surface refers to the outer peripheral surface 130b of the bent portion 130. By observing the cut cross-section using an optical microscope or the like, the presence and depth of cracks can be determined.

[0234] The flanged product of this embodiment can be preferably used as any one of the lower arm, tow arm, and upper arm used in vehicles.

[0235] The flanged product of this embodiment can also be a flanged product manufactured by the flanging method of the first or second embodiment described above.

[0236] Furthermore, one embodiment of the present invention provides a flanging method for manufacturing a flanged article of the third embodiment manufactured by the flanging method of the first embodiment. Additionally, one embodiment of the present invention provides a flanging method for manufacturing a flanged article of the third embodiment manufactured by the flanging method of the second embodiment.

[0237] Example

[0238] [Experimental Example 1]

[0239] In each experimental example, a 40mm diameter bottom hole was set on a steel component with a tensile strength of 980MPa and a plate thickness of 2.9mm. The bottom hole was then subjected to flanging processing by various methods to form a flanged part including a bent part and a raised part.

[0240] In Example 1, the flanging process was performed using the method described in the first embodiment above. The dimensions of the mold are as follows.

[0241] • Punch diameter: 50mm

[0242] • First die bore diameter: 65.2mm

[0243] • Second die bore diameter: 55.2mm

[0244] • Radius of curvature of the shoulder surface of the first die: 5mm

[0245] In Comparative Example 1, the flanging process was performed using a single mold via conventional methods. The dimensions of the mold are as follows.

[0246] • Punch diameter: 50mm

[0247] • Die bore diameter: 55.2mm

[0248] In Comparative Example 2, the flanging process was performed using the method of the first embodiment, but for Formula 1 above, U, which is the difference between the diameters of the first and second die holes, is 0.5×(PA) / 2 or less. The dimensions of the die are as follows.

[0249] • Punch diameter: 50mm

[0250] • First die bore diameter: 57.2mm

[0251] • Second die bore diameter: 55.2mm

[0252] • Radius of curvature of the shoulder surface of the first die: 5mm

[0253] In Comparative Example 3, the flanging process was performed using the method of the first embodiment, but for Formula 1 above, U is 20×(PA) / 2 or more. The dimensions of the mold are as follows.

[0254] • Punch diameter: 50mm

[0255] • First die bore diameter: 160mm

[0256] • Second die bore diameter: 55.2mm

[0257] • Radius of curvature of the shoulder surface of the first die: 5mm

[0258] Table 1 shows the results of the presence or absence of cracks larger than 20 μm relative to the h / t value. The cracks will be located inside the bent portion of the flanged part of the flanged workpiece. Figure 18 Experimental cases in which cracks larger than 20 μm were observed on the outer peripheral surface 130b of the bent portion 130 were marked as "× (bad)", and experimental cases in which no cracks larger than 20 μm were observed were marked as "○ (good)". The cross-section of the sample cut by the plane through which the axis of the flanged portion passes was ground, and observed using an optical microscope to determine whether cracks were generated. Twelve samples were collected at equal intervals around the axis cb of the flanged portion, and the determination was based on whether any sample met the above conditions. Here, h is the height of the outer surface of the bent portion of the flanged portion, and t is the height of the edge of the bottom hole of the steel component.

[0259] [Table 1]

[0260]

[0261] As shown in Table 1, it can be seen that in the flanging products produced by the flanging method of the present invention, the generation of cracks is suppressed in the range of h / t exceeding 0.2 and less than 0.6.

[0262] [Experimental Example 2]

[0263] In each experimental example, a 12mm diameter bottom hole was made on a steel component (steel plate) with a tensile strength of 980MPa, a thickness of 2.9mm, and a size of 350mm×350mm. Various methods were used to flanging this bottom hole, forming a flanged portion including a bent section and an upright section. The inner diameter of the flanged portion was 25mm. A cylindrical fixture with an outer diameter equivalent to the inner diameter of the flanged portion was inserted into the flanged portion, and the edge of the flanged portion was joined to the cylindrical fixture circumferentially by laser welding to produce a test piece. The height from the surface of the steel plate on the upright side of the flanged portion to the open end of the upright portion was set to 5.0mm, and the height of the outer surface of the bent portion of the flanged portion was set to 1.0mm. That is, the height Us of the upright portion was 4.0mm.

[0264] In Example 1, the flanging process was performed using the method described in the first embodiment above. The dimensions of the mold are as follows.

[0265] • Punch diameter: 25mm

[0266] • First die bore diameter: 40.2mm

[0267] • Second die bore diameter: 30.2mm

[0268] • Radius of curvature of the shoulder surface of the first die: 5mm

[0269] In the flanged product of Example 1, when the height of the upright portion is set to Us, the indentation around the flanged portion has a maximum height or depth exceeding ts / 20 and less than ts / 3 within a range of 0.5×Us or more and 20×Us from the R-stop end of the bent portion. That is, as shown in Table 2, the conditions for the position, height, or depth of the indentation are met, and the requirements of the present invention are satisfied.

[0270] In Comparative Example 1, the flanging process was performed using a single mold via conventional methods. The dimensions of the mold are as follows.

[0271] • Punch diameter: 25mm

[0272] • Die bore diameter: 30.2mm

[0273] • Radius of curvature of the die shoulder: 1.0mm

[0274] No indentations were observed in the flanged product of Comparative Example 1.

[0275] In Comparative Example 2, the flanging process was performed using the method described in the first embodiment. The dimensions of the mold are as follows.

[0276] • Punch diameter: 25mm

[0277] • First die bore diameter: 32.2mm

[0278] • Second die bore diameter: 30.2mm

[0279] • Radius of curvature of the shoulder surface of the first die: 15mm

[0280] In the flanged product of Comparative Example 2, although indentations were observed, the maximum height or depth of the indentation was less than ts / 20. The indentation was located within a range of 0.5 × Us or more and 20 × Us or less from the R-stop end of the bend. That is, as shown in Table 2, although the location condition of the indentation was met, the lower limit of the height or depth condition of the indentation was not met.

[0281] In Comparative Example 3, the flanging process was performed using the method described in the first embodiment. The dimensions of the mold are as follows.

[0282] • Punch diameter: 25mm

[0283] • First die bore diameter: 295mm

[0284] • Second die bore diameter: 30.2mm

[0285] • Radius of curvature of the shoulder surface of the second die: 0.5mm

[0286] In the flanged product of Comparative Example 3, although indentations were observed, the maximum height or depth of the indentation was ts / 3 or more. It can be assumed that the upper limit for the height or depth of the indentation is not met due to the small radius of curvature of the first die. Furthermore, the indentation is located on a side further away from the flanging section than a range of 0.5 × Us or more but less than 20 × Us from the R-stop end of the bend. That is, as shown in Table 2, the upper limit for the position condition of the indentation is not met, nor is the upper limit for the height or depth condition of the indentation.

[0287] In Comparative Example 4, the flanging process was performed using the method described in the first embodiment. The dimensions of the mold are as follows.

[0288] • Punch diameter: 25mm

[0289] • First die bore diameter: 295mm

[0290] • Second die bore diameter: 30.2mm

[0291] • Radius of curvature of the shoulder surface of the second die: 5mm

[0292] In the flanged product of Comparative Example 4, the maximum height or depth of the indentation exceeds ts / 20 but is less than ts / 3. However, the indentation is located on a side further away from the flanged portion than a range of 0.5×Us or more but less than 20×Us from the R-stop end of the bend. That is, as shown in Table 2, although the conditions for the height or depth of the indentation are met, the upper limit of the condition for the location of the indentation is not met.

[0293] For one end (edge) of the test piece, a displacement of +2mm to -2mm is repeatedly applied at 1Hz in a direction parallel to the axis of the flanged part, and the load is measured. This measurement is performed on the test pieces of each experimental example, and the presence of cracks is evaluated when 200,000 displacements have been applied.

[0294] Table 2 shows the results regarding the presence or absence of cracks relative to the indentation conditions. The results are shown at the moment when 200,000 displacements were applied, on the inside of the curved portion of the flanged part of the flanged workpiece. Figure 18 Experimental cases in which cracks larger than 100 μm were observed on the outer peripheral surface 130b of the curved portion 130 were marked as "× (bad)", and experimental cases in which no cracks larger than 100 μm were observed were marked as "○ (good)". The cross-section of the sample cut by a plane passing through the axis of the flanged part was ground and observed by an optical microscope to determine whether cracks were generated. Twelve samples were collected at equal intervals relative to the axis cb, and the presence or absence of cracks was determined by visual inspection.

[0295] [Table 2]

[0296] Indentation location Indentation height or depth The presence or absence of cracks Example 1 satisfy satisfy ○ Comparative Example 1 － － × Comparative Example 2 satisfy The lower limit value is not met. × Comparative Example 3 The upper limit value is not met. The upper limit value is not met. × Comparative Example 4 The upper limit value is not met. satisfy ×

[0297] As shown in Table 2, it can be seen that the flanged products of the present invention that meet the conditions of the position and height of the indentation have excellent fatigue durability.

[0298] Industrial availability

[0299] In this invention, a flanging method, a flanging mold, a flanging apparatus, and a flanged product are provided that can suppress cracks in the flanging section, thus having high industrial applicability.

[0300] Explanation of symbols

[0301] 1: Metal part; 2: Bottom hole; 3: First area; 4: Preformed part; 5: Second area; 6: Third area; 100: Flanged part; 110: Flanged part; 120: Erected part; 130: Bending part; 140: Peripheral area; 150: Indentation; 1000: Flanging die; 1100: First punch; 1111, 2111: Inner wall surface of the first punch hole; 1130, 2130: Shoulder surface of the first punch; 1200: The... 2. Die; 1211, 3211: Inner wall surface of the second die hole; 1230, 3230: Shoulder surface of the second die; 1300: Support; 1310, 2310, 3310: Support hole; 1400: Punch; 2000: Pre-forming die; 3000: Final forming die; cd: Axis of the die hole; rd1, rd1': Diameter of the first die hole; rd2, rd2': Diameter of the second die hole; ro2: Outer diameter of the second support surface.

Claims

1. A flanging process method, comprising forming a flanging portion including a raised portion and a bent portion on a metal part having a bottom hole using a flanging die, characterized in that, The above-mentioned dies for flanging include: The first die has a first die hole and a first support surface perpendicular to the axis of the first die hole; The second die has a second die hole and a second support surface perpendicular to the axis of the second die hole; The bracket, having a third support surface facing the first and second support surfaces, clamps the metal part between the first and second dies; and The punch has a shaft portion and is configured to move along the axis of the first die hole and the axis of the second die hole. The first support surface, the second support surface, and the third support surface are arranged parallel to each other. The diameter of the second die hole is smaller than the diameter of the first die hole, and the outer diameter of the second support surface is smaller than the diameter of the first die hole. The above-mentioned flanging processing methods include: In the preforming process, the bottom hole is enlarged, and the edge of the bottom hole is moved relative to the metal part in a first direction of the thickness direction of the metal part in a first range toward the periphery of the bottom hole, thereby forming the first range into a preformed portion that is integrally erected from the metal part in the first direction; and In the formal molding process, the preformed portion is deformed in a second direction opposite to the first direction, so that the height of the second range on the outer diameter side of the preformed portion in the first direction is the same as the height of the first range, and a portion of the third range on the inner diameter side of the preformed portion, which is closer to the second range than the second range, becomes part of the upright portion and the curved portion. The outer diameter of the aforementioned curved portion is smaller than the outer diameter of the aforementioned preformed portion, and, In a cross-section parallel to the first direction and passing through the center of the bottom hole, the maximum radius of curvature of the curved portion is smaller than the minimum radius of curvature of the preformed portion. The metal part is clamped between the first support surface of the first die and the third support surface of the bracket, and the punch is moved relative to the first die in the first direction so that the punch passes through the hole of the first die, thereby forming the preform between the punch and the first die. With the metal part held between the first support surface and the third support surface, the second die is moved relative to the bracket in the second direction, causing a portion of the second die to pass between the punch and the first die, thereby forming the flanged portion between the second die, the punch, and the bracket. When the difference between the radius of the first die hole and the radius of the second die hole is set as U, the diameter of the shaft portion of the punch is set as P, and the diameter of the bottom hole of the metal part is set as A, the following formula 1 is satisfied. When the height of the edge portion of the bottom hole of the above metal part is set as t, and the height of the outer surface of the bending portion in the above first direction is set as h, the following formula 2 is satisfied. 0.5×(P - A) / 2 < U < 20×(P - A) / 2 …… Formula 1 0.2 < h / t < 0.6 …… Formula 2.

2. The flanging method according to claim 1, wherein the tensile strength of the above metal part is 780 MPa or more.

3. The flanging method according to claim 1, wherein when the height of the edge portion of the bottom hole of the above metal part is set as t, and the thickness of the opening side end portion of the erected portion is set as tb, the following formula 4 is satisfied. tb / t < 0.9…… Formula 4.

4. The flanging method according to claim 1, wherein before the above preforming process, a bottom hole forming process for forming the bottom hole of the above metal part is further included.

5. A flanging method, using a flanging die including a set of preforming dies and a set of final forming dies, to form a flanging portion including an erected portion and a bending portion on a metal part formed with a bottom hole, wherein the above set of preforming dies includes: a first punching die, having a first punching die hole and a first supporting surface perpendicular to the axis of the first punching die hole; a first bracket, having a first bracket supporting surface opposed to the first supporting surface and arranged parallel to the first supporting surface, clamping the above metal part between the first punching dies; and a first punch, having a first shaft portion, arranged to be able to move along the axis of the first punching die hole, the above set of final forming dies includes: a second punching die, having a second punching die hole and a second supporting surface perpendicular to the axis of the second punching die hole; a second bracket, having a second bracket supporting surface opposed to the second supporting surface and arranged parallel to the second supporting surface, clamping the above metal part between the second punching dies; and a second punch, having a second shaft portion, arranged to be able to move along the axis of the second punching die hole, the above flanging method includes: a preforming process, expanding the above bottom hole, and relatively moving the edge portion of the above bottom hole in the first direction in the thickness direction of the metal part in the first range around the bottom hole of the metal part with respect to the metal part, forming the first range into a preformed portion that stands up from the metal part as a whole in the first direction; and a final forming process, deforming the above preformed portion in the second direction opposite to the first direction, forming the height of the second range on the outer diameter side of the preformed portion in the first direction to be the same as the height of the first range, and a part of the third range closer to the inner diameter side of the preformed portion than the second range to be a part of the erected portion and the bending portion, the outer diameter of the above bending portion is smaller than the outer diameter of the preformed portion, and in a cross-section parallel to the first direction and passing through the center of the bottom hole, the maximum curvature radius of the above bending portion is smaller than the minimum curvature radius of the preformed portion. The metal part is clamped between the first support surface of the first die and the first support surface of the first bracket, and the first punch is moved relative to the first die in the first direction so that the first punch penetrates through the first die hole, thereby forming the preformed portion between the first punch and the first die. Separate the metal part formed with the preformed portion from the preforming die. Next, with the metal part formed with the preformed portion facing the first direction side, place the metal part formed with the preformed portion on the second support surface of the second bracket. Insert the second punch into the enlarged bottom hole in the first direction, move the second die relative to the second bracket in the second direction, and make the second punch penetrate through the second die hole, thereby forming the flanging portion between the second die, the second punch, and the second bracket. The diameter of the second die hole is less than or equal to the diameter of the first die hole. When the height of the edge portion of the bottom hole of the metal part is set as t and the height of the outer surface of the bending portion in the first direction is set as h, the following formula 2 is satisfied. 0.2 < h / t < 0.6... Formula 2.

6. The flanging method according to claim 5, wherein: When the difference between the radius of the first die hole and the radius of the second die hole is set as U, the diameter of the second shaft portion of the second punch is set as Ps, and the diameter of the bottom hole of the metal part is set as A, the following formula 5 is satisfied. 0.5×(Ps - A) / 2 < U < 20×(Ps - A) / 2... Formula 5.

7. The flanging method according to claim 5, wherein: Move the second die relative to the second bracket in the second direction, and then insert the second punch into the enlarged bottom hole in the first direction.

8. The flanging method according to claim 5, wherein: The diameter of the first shaft portion of the first punch is smaller than the diameter of the second shaft portion of the second punch.

9. The flanging method according to claim 5, wherein: The initial contact position of the preformed portion and the second die is within the range from the inner wall side of the second die hole to 7 / 8 of the surface length of the curved portion of the second die shoulder of the second die hole in a cross-section parallel to the first direction and passing through the center of the bottom hole.

10. The flanging method according to any one of claims 5 to 9, wherein: Before the preforming process, a bottom hole forming process for forming the bottom hole of the metal part is further included.

11. A flanged product having a flanging portion including a standing portion and a bending portion and a peripheral region including the bending portion, wherein: In a cross-section including the axis of the flanging portion and parallel to the axis, when the radius of curvature of the outer surface of the bending portion is set as R. When the hardness of the flanging product at position a, which is separated by R in the direction perpendicular to the axis from the R end of the bent portion where the bent portion is connected to the peripheral region and separated by 0.2 mm in the direction parallel to the axis from the side where the erected portion is formed, is set as Hva, When the hardness of the flanging product at position b, which is separated by 3R in the direction perpendicular to the axis from the R end of the bent portion toward the peripheral region side and separated by 1 / 4 of the thickness of the flanging product in the peripheral region in the direction parallel to the axis from the side where the erected portion is formed, is set as Hvb, the following formula 7 is satisfied, and there is an indentation in the peripheral region. When the height of the erected portion is set as Us, the indentation is within the range of 0.5×Us or more and 20×Us or less from the R end of the bent portion. When the thickness of the flanging product in the peripheral region is set as ts, the maximum height or depth of the indentation in the direction parallel to the axis exceeds ts / 20 and is less than ts / 3. Hva / Hvb > 1.03... Formula 7.

12. The flanging product according to claim 11, wherein the above-mentioned Hva is the average hardness of the hardness measured within the range of the cross-section defined by a square with a side length of 1 / 6 of the thickness of the flanging product centered on the above-mentioned position a, and the above-mentioned Hvb is the average hardness of the hardness measured within the range of the cross-section defined by a square with a side length of 1 / 6 of the thickness of the flanging product centered on the above-mentioned position b.

13. The flanging product according to claim 11, wherein when the thickness of the flanging product in the peripheral region is set as ts and the height of the outer surface of the bent portion in the direction parallel to the axis is set as h, the following formula 8 is satisfied, 0.2 < h / ts < 0.6... Formula 8.

14. The flanging product according to claim 11, wherein when the thickness of the flanging product in the peripheral region is set as ts and the thickness of the opening-side end portion of the erected portion is set as tb, the following formula 9 is satisfied, tb / ts < 0.9... Formula 9.

15. The flanging product according to claim 11, wherein there are no cracks with a depth of 20 μm or more from the surface in the cross-section of the bent portion.

16. The flanging product according to any one of claims 11 to 15, wherein it is any one of a lower arm, a trailing arm, and an upper arm used in a vehicle.

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