Flanging part

Abstract

As a flanging component capable of suppressing the occurrence of fatigue cracks in the flanging portion, a structure satisfying the following relational expressions (1) to (3) is disclosed: 3 ≤ Ra ≤ 100... (1) 3.0 < h... (2) 24 + r - [TS / (40 + 0.28 × Ra)] < h... (3) where Ra is the arithmetic mean roughness of the flanging end face, with the unit of μm; h is the flanging height, with the unit of mm; r is the radius of curvature of the curved wall portion of the flanging portion, with the unit of mm; and TS is the tensile strength, with the unit of MPa.

Description

Technical Field

[0001] The present application discloses a burring processed part. Background Art

[0002] As disclosed in Patent Document 1, a technique has been developed to reduce the weight of parts by using high-strength steel as the raw material of the parts. Here, when a fatigue crack occurs in high-strength steel, the crack tends to develop easily. Therefore, parts made of high-strength steel tend to have difficulty ensuring fatigue durability to the extent expected by the increase in the strength of the raw material.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent No. 6610788 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] In order to improve the fatigue durability of parts, it can be considered that suppressing the occurrence of fatigue cracks in the parts themselves is effective. In particular, burring processed parts are often applied to parts that are subject to external forces, and it can be considered that fatigue cracks are likely to occur in the burring processed part. In this regard, a new technique for suppressing fatigue cracks in the burring processed part is required.

[0008] Means for Solving the Problems

[0009] As one of the means for solving the above problems, the present application discloses a burring processed part having a plate-like portion and a burring processed portion. The plate-like portion has a first surface on one side and a second surface on the side opposite to the first surface. The burring processed portion has a burring hole and a burring wall portion. The burring wall portion is provided around the burring hole, and the burring wall portion protrudes to one side compared to the first surface. The burring wall portion has a longitudinal wall portion and a curved wall portion. The longitudinal wall portion has a burring end surface on one side and is connected to the curved wall portion on the side opposite to one side. The curved wall portion is connected to the longitudinal wall portion on one side and is connected to the plate-like portion on the side opposite to one side. The burring processed portion has a structure that satisfies the following relational expressions (1) to (3):

[0010] 3≤Ra≤100…(1)

[0011] 3.0<h…(2)

[0012] 24+r-[TS / (40+0.28×Ra)]<h…(3)

[0013] Wherein,

[0014] The above Ra is the arithmetic mean roughness of the flanged end face, with the unit of μm;

[0015] The above h is the height from the above first face to the flanged end face, with the unit of mm;

[0016] The above r is the radius of curvature of the curved wall portion, with the unit of mm;

[0017] The above TS is the tensile strength of the plate-like portion, with the unit of MPa.

[0018] In the flanging processed part of the present disclosure, the diameter d of the above flanging hole can be 20.0 mm or more and 100.0 mm or less.

[0019] In the flanging processed part of the present disclosure, the above r can be 2.0 mm or more and 10.0 mm or less.

[0020] In the flanging processed part of the present disclosure, the above TS can be 780 MPa or more.

[0021] In the flanging processed part of the present disclosure, the above Ra can be 50 μm or less.

[0022] Advantages of the Invention

[0023] In the flanging processed part of the present disclosure, fatigue cracks are not likely to occur in the flanging processed portion. Brief Description of the Drawings

[0024] Figure 1 Schematically shows an example of the structure of the flanging processed part. Figure 1 In (A) is a plan view, Figure 1 In (B) and (C) are Figure 1 The sectional view taken along the line I-I of (A).

[0025] Figure 2 Shows the stress σ transmitted to the flanged end face when an external force σ0 is applied to the flanging processed part e and the stress concentration σ occurring at the valley portion of the flanged end face y1 ~σ y3 .

[0026] Figure 3 Shows a method for determining the radius of curvature of the curved wall portion.

[0027] Figure 4 Shows an example of the flow of the manufacturing method of the flanging processed part.

[0028] Figure 5 Shows an example of the CAE analysis conditions.

[0029] Figure 6 Schematically shows a blanking fatigue test piece.

[0030] Figure 7 Indicates the evaluation results of the example (tensile strength: 780 MPa).

[0031] Figure 8 Indicates the evaluation results of the example (tensile strength: 980 MPa).

[0032] Figure 9 Indicates the evaluation results of the example (tensile strength: 1180 MPa).

[0033] Figure 10 Indicates the evaluation results of the example (tensile strength: 1470 MPa). Detailed implementation mode

[0034] As Figure 1 shown in (A) to (C) therein, the flanging processed part 100 has a plate-like part 10 and a flanging processed part 20. The plate-like part 10 has a first surface 11 on one side and a second surface 12 on the side opposite to the first surface 11. The flanging processed part 20 has a flanging hole 21 and a flanging wall part 22. The flanging wall part 22 is provided around the flanging hole 21. The flanging wall part 22 protrudes to one side from the first surface 11. The flanging wall part 22 has a vertical wall part 22a and a curved wall part 22b. The vertical wall part 22a has a flanging end surface 22ax on one side and is connected to the curved wall part 22b on the side opposite to one side. The curved wall part 22b is connected to the vertical wall part 22a on one side and is connected to the plate-like part 10 on the side opposite to one side. The flanging processed part 20 has a structure that satisfies the following relational expressions (1) to (3).

[0035] 3 ≤ Ra ≤ 100…(1)

[0036] 3.0 < h…(2)

[0037] 24 + r - [TS / (40 + 0.28×Ra)] < h…(3)

[0038] Herein

[0039] Ra is the arithmetic mean roughness (μm) of the flanging end surface 22ax;

[0040] h is the height (mm) from the first surface 11 to the flanging end surface 22ax;

[0041] r is the radius of curvature (mm) of the curved wall part 22b;

[0042] TS is the tensile strength (MPa) of the plate-like part 10.

[0043] 1. Plate-like part

[0044] As Figure 1As shown in (A) to (C), the plate-like portion 10 has a first surface 11 on one side and a second surface 12 on the side opposite to the first surface 11.

[0045] Figure 1 As shown in (A) to (C), the plate-like portion 10 can exist around the flanging portion 20. In the flanging member 100, the plate-like portion 10 only needs to exist slightly. The shape of the outer edge of the plate-like portion 10 (as the planar shape of the entire flanging member 100) is not particularly limited and can be appropriately determined according to the use of the flanging member 100. The plate-like portion 10 does not need to be a completely flat plate shape. For example, it can also have unevenness, bending, notches, etc. in a part.

[0046] As Figure 1 As shown in (C), the plate-like portion 10 may also have a plate thickness t1. The plate thickness t1 can be appropriately determined according to the use. In addition, when the plate thickness t1 of the member is made thinner, the rigidity of the member decreases, so high strength of the member is required. However, there is a concern that the fatigue resistance decreases due to the high strength and thin wall of the member. In contrast, according to the technology of the present disclosure, excellent fatigue resistance can be ensured in the flanging member even when the plate thickness t1 is thin or the member is high strength. The plate thickness t1 can be, for example, 0.5 mm or more, 0.8 mm or more, 1.0 mm or more, 1.2 mm or more, or 2.0 mm or more, and can also be 10.0 mm or less, 5.0 mm or less, 4.0 mm or less, 3.0 mm or less, 2.7 mm or less, 2.5 mm or less, 2.3 mm or less, 2.1 mm or less, or 2.0 mm or less. The plate thickness t1 can be the same throughout the plate-like portion 10 or can be different for each part of the plate-like portion 10.

[0047] 2. Flanging portion

[0048] As Figure 1 As shown in (A) to (C), the flanging portion 20 has a flanging hole 21 and a flanging wall portion 22.

[0049] 2.1 Flanging hole

[0050] As Figure 1 As shown in (A) to (C), the flanging hole 21 is a hole that penetrates one side and the other side of the flanging portion 20. As Figure 1As shown in (A), the planar shape (opening shape) of the flanging hole 21 is circular. The "circle" does not need to be a perfect circle, but may have an error within an acceptable range in industrial production. For example, when the length of the straight line connecting a point on the outer edge of the opening shape of the flanging hole 21, passing through the center of the opening shape to another point on the outer edge is regarded as the diameter of the flanging hole 21, it can be regarded as "circular" when the ratio of the maximum diameter to the minimum diameter is 1.00 or more and 1.10 or less.

[0051] The size of the flanging hole 21 is not particularly limited and can be determined according to the use of the flanging member 100. As Figure 1 As shown in (C), the flanging hole 21 may have an opening shape formed by a circle with a diameter d. The diameter d of the flanging hole 21 can be, for example, 20.0 mm or more, 30.0 mm or more, 40.0 mm or more, 50.0 mm or more, 60.0 mm or more, 70.0 mm or more, 80.0 mm or more, or 90.0 mm or more, and can also be 100.0 mm or less, 90.0 mm or less, 80.0 mm or less, 70.0 mm or less, 60.0 mm or less, 50.0 mm or less, 40.0 mm or less, or 30.0 mm or less. When the diameter d is 20.0 mm or more and 100.0 mm or less, it is easy to further improve the fatigue durability of the flanging member 100. In addition, the diameter d of the flanging hole 21 can also be 5 times or more, or 10 times or more of the above-mentioned plate thickness t1, and can also be 100 times or less, or 50 times or less.

[0052] 2.2 Flanging wall

[0053] As Figure 1 As shown in (A) to (C), the flanging wall 22 is provided around the flanging hole 21. In other words, the opening shape of the flanging hole 21 is defined by the inner wall of the flanging wall 22. As Figure 1 As shown in (A) to (C), the flanging wall 22 may have a cylindrical portion.

[0054] As Figure 1 As shown in (B) and (C), the flanging wall 22 protrudes to one side from the first surface 11. The protruding direction of the flanging wall 22 can be a direction intersecting the surface direction of the plate-like portion 10, for example, a direction orthogonal to the surface direction of the plate-like portion 10.

[0055] As Figure 1 As shown in (B), the flanging wall 22 has a vertical wall portion 22a and a curved wall portion 22b. As Figure 1 As shown in (B) and (C), the vertical wall portion 22a has a flanging end surface 22ax on one side and is connected to the curved wall portion 22b on the side opposite to the one side. The vertical wall portion 22a may have a surface along the blanking direction during flanging. Figure 1As shown in (B) and (C), in the cross-sectional shape along the central axis of the flanging hole 21, the inner wall surfaces of the opposing longitudinal wall portions 22a may be parallel to each other. In addition, as Figure 1 shown in (B) and (C), the orientation of the outer wall surface of the longitudinal wall portion 22a and the orientation of the first surface 11 of the plate-like portion 10 may also intersect each other, for example, be orthogonal to each other. In addition, as Figure 1 shown in (C), the flanging wall portion 22 may have a predetermined height h from the first surface 11 to the flanging end surface 22ax of the longitudinal wall portion 22a. Further, as Figure 1 shown in (C), the flanging end surface 22ax of the longitudinal wall portion 22a may have a predetermined arithmetic mean roughness Ra. The height h or the arithmetic mean roughness Ra will be described later.

[0056] As Figure 1 shown in (B) and (C), the curved wall portion 22b is connected to the longitudinal wall portion 22a on one side and to the plate-like portion 10 on the side opposite to the one side. The curved wall portion 22b has a radius of curvature r, and connects the plate-like portion 10 and the longitudinal wall portion 22a. For example, there is no interruption between the first surface 11 of the plate-like portion 10, the outer wall surface of the curved wall portion 22b, and the outer wall surface of the longitudinal wall portion 22a. The radius of curvature r of the curved wall portion 22b will be described later.

[0057] As Figure 1 shown in (C), the flanging wall portion 22 may have a thickness t2. The thickness t2 may be appropriately determined according to the strength for the purpose, etc. The thickness t2 may be, for example, 0.5 mm or more, 0.8 mm or more, 1.0 mm or more, 1.2 mm or more, or 1.8 mm or more, and may also be 10.0 mm or less, 5.0 mm or less, 3.0 mm or less, 2.8 mm or less, 2.6 mm or less, 2.4 mm or less, 2.2 mm or less, or 2.0 mm or less. The thickness t2 may be substantially the same throughout the flanging wall portion 22 or may vary according to each part of the flanging wall portion 22. The thickness t2 may be thicker or thinner than the plate thickness t1, but is likely to be thinner than the plate thickness t1 due to the nature of the flanging process. Specifically, the ratio t2 / t1 of the thickness t2 to the thickness t1 may be 0.5 or more, 0.6 or more, or 0.7 or more, and may also be 1.2 or less, 1.1 or less, or 1.0 or less.

[0058] 2.3 Relationship (1)

[0059] As in the above relational expression (1), in the flanging member 100, the arithmetic mean roughness Ra of the flanging end face 22ax is 3 μm or more and 100 μm or less. By making the arithmetic mean roughness Ra of the flanging end face 22ax 100 μm or less and satisfying the relational expression (3) described later, even when an external force is applied to the flanging portion 20, stress concentration on the flanging end face 22ax is less likely to occur, and fatigue cracking is less likely to occur. As a result, the fatigue durability of the flanging member 100 is improved. From the viewpoint of more effectively suppressing the occurrence of fatigue cracking, the arithmetic mean roughness Ra of the flanging end face 22ax may also be 50 μm or less. On the other hand, the closer the arithmetic mean roughness Ra of the flanging end face 22ax is to 0, the easier it is to suppress the occurrence of fatigue cracking, but it is not realistic to make the arithmetic mean roughness Ra 0. In order to reduce the arithmetic mean roughness Ra of the flanging end face 22ax, it is effective to perform a smoothing process on the flanging end face 22ax. In the flanging member 100, for example, the flanging end face 22ax can be smoothed by mechanical polishing using sandpaper or the like. In this case, the arithmetic mean roughness Ra of the flanging end face 22ax can be reduced to about 3 μm. Alternatively, the arithmetic mean roughness Ra can also be reduced to about 3 μm by performing finish machining such as reaming. In addition, in order to make the arithmetic mean roughness Ra as close as possible to 0 (for example, less than 3 μm), for example, it is effective to consider performing chemical polishing on the flanging end face 22ax. However, considering the cost, the realistic lower limit of the arithmetic mean roughness Ra of the flanging end face 22ax is about 3 μm.

[0060] As described later, after a punching hole 101a is provided in a part of the metal plate 101 as a workpiece, the peripheral portion 101b of the punching hole 101a is erected to one side, so that in the case of performing flanging, the end face defining the punching hole 101a can become the flanging end face 22ax after flanging (see Figure 4 ). The arithmetic mean roughness Ra of the flanging end face 22ax after flanging becomes larger than the arithmetic mean roughness of the end face defining the punching hole 101a before flanging. The arithmetic mean roughness of the flanging end face 22ax varies according to the degree of material removal of the flanging wall portion 22 during flanging (the degree to which the thickness t2 decreases relative to the plate thickness t1), etc. In addition, the higher the height h of the flanging portion 20, the easier it is for the arithmetic mean roughness of the flanging end face 22ax to become larger. As described later, in the flanging member 100 of the present disclosure, by performing a smoothing process such as polishing using sandpaper on the flanging end face 22ax, the arithmetic mean roughness Ra of the flanging end face 22ax can be suppressed to 100 μm or less.

[0061] Using a stylus probe, the arithmetic mean roughness Ra of the flanging end face 22ax is measured by moving the stylus in the thickness direction of the flanging end face. Specifically, in Figure 1 in (B) and Figure 4 in, the stylus is moved laterally on the flanging end face 22ax. The measurement uses a stylus with a tip radius of 2 μm made of diamond, the measurement force is 0.75 mN, and the measurement speed is set to 0.15 mm / s. Five arithmetic mean roughness values are arbitrarily measured along the circumference of the flanging hole, and their average value is taken as the arithmetic mean roughness of the flanging end face.

[0062] 2.4 Relationship (2)

[0063] As in the above relationship (2), in the flanging part 100, the height h from the first surface 11 to the flanging end face 22ax is greater than 3.0 mm. Thus, by making the height h of the flanging wall part 22 a height greater than 3.0 mm and satisfying the following relationship (3), even when stress σ0 occurs in the plate part 10 due to torsion or the like, the stress σ e from the plate part 10 via the flanging wall part 22 to the flanging end face 22ax also becomes smaller. As a result, stress concentration at the flanging end face 22ax is not likely to occur, and fatigue cracks are not likely to occur. The upper limit of the height h is not particularly limited. The height h can be, for example, 1000.0 mm or less, 500.0 mm or less, or 100.0 mm or less. Alternatively, the height h can also be, for example, 1000 times or less, 500 times or less, or 100 times or less of the plate thickness t1.

[0064] 2.5 Relationship (3)

[0065] In the flanging part 100 of the present disclosure, in addition to the above relationships (1) and (2), it is also important that the flanging part 20 has a structure that satisfies the above relationship (3). That is, even if, as in the above relationships (1) and (2), the arithmetic mean roughness Ra of the flanging end face 22ax is 100 μm or less and the height h of the flanging part 20 is greater than 3.0 mm, in the case where relationship (3) is not satisfied, there is a tendency that it is difficult to improve the fatigue durability of the flanging part 20.

[0066] As Figure 2 shown, when stress σ0 generated due to torsion or the like is applied to the plate part 10 of the flanging part 100, stress σ e is transmitted from the plate part 10 to the flanging end face 22ax, and stress concentration σ y1 ~σ y3If the stress concentration at the flanging end face 22ax is large, fatigue cracking is likely to occur. To suppress the stress concentration at the flanging end face 22ax, it is effective to increase the height h of the flanging portion 20. In addition, the stress concentration at the flanging end face 22ax also varies depending on factors other than the height h. According to the understanding of the inventors of the present invention, in order to reduce the stress concentration at the flanging end face 22ax and suppress the occurrence of fatigue cracking, and improve the fatigue durability of the flanging portion 20, the following means are effective:

[0067] (I) The larger the radius of curvature r of the curved wall portion 22b, the larger the height h is made;

[0068] (II) The smaller the tensile strength TS of the plate-like portion 10, the larger the height h is made;

[0069] (III) The larger the arithmetic mean roughness Ra of the flanging end face 22ax, the larger the height h is made. The inventors of the present invention conducted special research and found that the relationships regarding (I) to (III) can be organized by the above-mentioned relational expression (3).

[0070] In the above relational expression (3), the arithmetic mean roughness Ra of the flanging end face 22ax is as described above.

[0071] In the above relational expression (3), the value of the radius of curvature r of the curved wall portion 22b is not particularly limited. The radius of curvature r can be, for example, 2.0 mm or more and 10.0 mm or less. As long as the radius of curvature r of the curved wall portion 22b is 2.0 mm or more, it is difficult for wrinkles, breakage, or buckling deformation to occur in the curved wall portion 22b. When the radius of curvature r of the curved wall portion 22b is 10.0 mm or less, it is more difficult for the stress of the plate-like portion 10 to be transmitted to the longitudinal wall portion 22a and the flanging end face 22ax.

[0072] As Figure 3 shown, the radius of curvature r of the curved wall portion 22b can be determined based on the cross-sectional shape of the flanging processing member 100 and the cross-sectional shape along the central axis of the flanging hole 21. That is, as Figure 3 shown, in this cross-sectional shape, a straight line A is drawn along the first surface 11 of the plate-like portion 10 (the portion that can be regarded as flat near the curved wall portion 22b in the first surface 11), and a straight line B is drawn along the outer wall surface of the longitudinal wall portion 22a (the surface along the protruding direction during flanging processing in the outer wall surface). The intersection point O of the straight line A and the straight line B is determined. Three straight lines C, D, and E that divide the angle AOB into four equal parts are drawn from this intersection point O. The intersection points P1 of the straight line C and the outer wall surface of the curved wall portion 22b, the intersection point P2 of the straight line D and the outer wall surface of the curved wall portion 22b, and the intersection point P3 of the straight line E and the outer wall surface of the curved wall portion 22b are determined. A circle passing through these three intersection points P1, P2, and P3 is determined, and the radius of this circle is set as the radius of curvature r of the curved wall portion 22b.

[0073] In the above relation (3), the value of the tensile strength TS of the plate-like portion 10 is not particularly limited. As described above, the problem of the fatigue durability of the flanging portion 20 is particularly likely to occur in high-strength steel sheets. In this regard, the tensile strength TS of the plate-like portion 10 can be 780 MPa or more, 800 MPa or more, 850 MPa or more, 900 MPa or more, 950 MPa or more, 980 MPa or more, 1000 MPa or more, 1050 MPa or more, 1100 MPa or more, 1150 MPa or more, 1180 MPa or more, 1200 MPa or more, 1250 MPa or more, 1300 MPa or more, 1350 MPa or more, 1400 MPa or more, 1450 MPa or more, or 1470 MPa or more. The upper limit of the tensile strength of the plate-like portion 10 is not particularly limited, and can be, for example, 2500 MPa or less, 2200 MPa or less, or 2000 MPa or less. In addition, the "tensile strength" of the plate-like portion described in the present application follows ISO6892—1:2009.

[0074] According to the understanding of the inventors of the present invention, as the material becomes higher in strength, there is a tendency for the shape of the blanking end face to deteriorate and the surface roughness to increase. That is, the greater the tensile strength TS of the plate-like portion 10, the more likely the arithmetic mean roughness Ra of the flanging end face 22ax is to increase. When the tensile strength TS of the plate-like portion 10 is 780 MPa or more, in order to make the arithmetic mean roughness Ra of the flanging end face 22ax 100 μm or less, preferably 50 μm or less, for example, it is preferable to perform a smoothing treatment on the flanging end face 22ax.

[0075] 3. Material

[0076] It is obvious that the flanging part 100 is made of metal. The flanging part 100 can be composed of steel, for example. In this case, the chemical composition and metal structure of the steel are not particularly limited and can be appropriately determined according to the use of the flanging part 100. In the flanging part 100 of the present disclosure, although the required height h of the flanging part 20 varies according to the tensile strength of the plate-like part 10, it does not substantially vary according to the chemical composition and metal structure of the flanging part 100. That is, according to the technology of the present disclosure, the occurrence of fatigue cracks in the flanging part 20 can be suppressed in the flanging parts 100 having various chemical compositions and metal structures. As an example of the chemical composition, the flanging part 100 can have a chemical composition consisting of, by mass%, C: 0.01% to 1.0%, Si: 0.01% to 3.50%, Mn: 0.10% to 5.00%, P: 0.100% or less, S: 0.0300% or less, N: 0.0100% or less, O: 0% to 0.020%, Al: 0% to 1.000% or less, Cr: 0% to 2.00%, Cu: 0% to 2.00%, Ni: 0% to 2.00%, Mo: 0% to 3.00%, Co: 0% to 3.00%, Nb: 0% to 0.150%, V: 0% to 1.00%, Ti: 0% to 1.00%, W: 0% to 1.00%, Sn: 0% to 1.00%, Sb: 0% to 0.50%, Ta: 0% to 0.10%, As: 0% to 0.050%, B: 0% to 0.0100%, Ca: 0% to 0.100%, Mg: 0% to 0.100%, Zr: 0% to 0.100%, Hf: 0% to 0.100%, REM: 0% to 0.0050%, and the balance: Fe and impurities. In addition, in the above chemical composition, the lower limit of the content of any additive element can be 0.0001% or 0.001%.

[0077] 4. Number and position of flanging parts

[0078] In the flanging part 100, the number of the flanging parts 20 is not limited to one. The flanging part 100 can have a plurality of flanging parts 20. In addition, in addition to the flanging parts 20, the flanging part 100 can also have other flanging parts protruding to one side from the first surface 11, and can also have other flanging parts protruding to the other side from the second surface 12. The position of the flanging part 20 of the flanging part 100 is not particularly limited and can be appropriately determined according to the use of the flanging part 100.

[0079] 5. Use of flanging part

[0080] As described above, the flanging processing component 100 of the present disclosure is not easily subject to fatigue cracking of the flanging processing portion 20 even when an external force such as torsion is applied, and has excellent fatigue durability. In this regard, the flanging processing component 100 of the present disclosure can also be applied to a harsh environment where a large external force is applied. For example, the flanging processing component 100 of the present disclosure can also be used as a chassis part of an automobile. Specific examples of the chassis part of an automobile include a lower arm, an upper arm, and a longitudinal thrust rod.

[0081] 6. Manufacturing method of flanging processing component

[0082] The flanging processing component 100 of the present disclosure can be manufactured by performing flanging processing on a part of a metal plate as a workpiece. For example, as Figure 4 shown, the manufacturing method of the flanging processing component 100 can include the following S1 and S2, and include at least one of the following S2I and S2II.

[0083] S1: A punching hole 101a is provided on a part of the metal plate 101. Here, the metal plate 101 has a first surface 11 on one side and a second surface 12 on the side opposite to the first surface 11, and a plate-like portion 10 exists around the punching hole 101a;

[0084] S2: The peripheral portion 101b of the punching hole 101a is erected to one side compared with the first surface 11 to provide a flanging processing portion 20. Here, the flanging processing portion 20 has a flanging hole 21 and a flanging wall portion 22. The flanging wall portion 22 is provided around the flanging hole 21. The flanging wall portion 22 protrudes to one side compared with the first surface 11. The flanging wall portion 22 has a vertical wall portion 22a and a curved wall portion 22b. The vertical wall portion 22a has a flanging end face 22ax on one side and is connected to the curved wall portion 22b on the side opposite to one side. The curved wall portion 22b is connected to the vertical wall portion 22a on one side and is connected to the plate-like portion 10 on the side opposite to one side;

[0085] S2I: Before the above S2, considering the curvature radius r of the curved wall portion 22b of the flanging wall portion 22, the tensile strength TS of the plate-like portion 10, and the arithmetic mean roughness Ra of the flanging end face 22ax after flanging processing, the height h of the flanging processing portion 20 provided in the above S2 is determined so that the flanging processing portion 20 has a structure that satisfies the above relational expressions (1) to (3);

[0086] S2II: After the above S2, the flanging end face 22ax is smoothed so that the flanging processing portion 20 has a structure that satisfies the above relational expressions (1) to (3).

[0087] S1 and S2 can be implemented simply by using a punch and a die. Additionally, the arithmetic mean roughness Ra of the flanging end face 22ax may vary depending on the conditions during flanging (such as the sheet pushing pressure and the degree of material reduction of the flanging wall). Therefore, it is difficult to estimate the arithmetic mean roughness Ra of the flanged end face 22ax after flanging based solely on the arithmetic mean roughness of the end face defining the punching hole 101a, and it is difficult to estimate the required height h. For example, even if a reamer process is performed on the end face defining the punching hole 101a before flanging to reduce the arithmetic mean roughness of the end face of the punching hole 101a, unevenness may occur on this end face due to flanging, and the arithmetic mean roughness Ra of the flanged end face 22a after flanging may increase significantly. Therefore, it is not certain that the desired arithmetic mean roughness Ra can be achieved on the flanged end face 22ax. In S2I, for example, the height h can be determined based on past actual situations, or can be determined through preliminary experiments, or can be determined through simulations, etc. The method of smoothing in S2II is not particularly limited. For example, the flanged end face 22ax can be smoothed by grinding. The grinding can be performed using a known method. For example, mechanical grinding using sandpaper can be cited. Or, a finishing process such as a reamer process can also be performed on the flanged end face.

[0088] Embodiment

[0089] Hereinafter, while showing embodiments, the technical effects and the like of the present disclosure will be described in more detail, but the technology of the present disclosure is not limited to the following embodiments.

[0090] 1. Evaluation Conditions and Evaluation Criteria

[0091] (1) As Figure 5 shown, through CAE analysis, the maximum value σmax of the corresponding stress generated on the flanging end face when a torsional displacement is applied to the flanged component is calculated. The analysis is performed by changing conditions such as the height h of the flanging part. Here, LS - DYNA ver971 rev9.3.0 is used as the CAE analysis software, and the analysis conditions are set so that the torsional displacement of the steel sheet end is 10°.

[0092] (2) For the punching hole defined by an end face having a specified arithmetic mean roughness Ra1, the time strength σf1 at 2 million cycles is measured through a punching fatigue test. Here, the punching fatigue test is as Figure 6As shown, a blanking fatigue test piece is taken so that the blanking hole becomes the center part of the test piece, and the test is carried out in accordance with the symmetric alternating plane bending fatigue test method described in JIS Z2275 - 1978. For various plates with different Ra1 values, blanking fatigue tests are carried out separately. In addition, Ra1 varies according to the material, reamer machining, and blanking clearance. For the σf1 values corresponding to various Ra1 values, extrapolation is performed using a regression line to obtain the 2 - million - cycle time strength corresponding value σf2 when the flanging end face has an arithmetic mean roughness Ra2.

[0093] (3) The case where the above - mentioned σmax is smaller than σf2 is set as qualified (○), and the case where σmax is equal to or greater than σf2 is set as unqualified (×).

[0094] 2. Evaluation results

[0095] The evaluation conditions and evaluation results of the examples and comparative examples are shown in Tables 1 and 2 below. In addition, Figure 7 shows the evaluation results when steel with a tensile strength TS of 780 MPa is used as the raw material, and Figure 8 shows the evaluation results when steel with a tensile strength TS of 980 MPa is used as the raw material, and Figure 9 shows the evaluation results when steel with a tensile strength TS of 1180 MPa is used as the raw material, and Figure 10 shows the evaluation results when steel with a tensile strength TS of 1470 MPa is used as the raw material. Figures 7 to 10 is plotted based on the results shown in Table 1.

[0096] [Table 1]

[0097] Table 1

[0098] [Table 2]

[0099] Table 2

[0100] As shown in Tables 1, 2, and Figures 7 to 10 , it can be seen that regardless of the magnitude of the tensile strength TS, when the flanging part of the flanging - processed component has a structure that satisfies the following relational expressions (1) - (3), σmax is smaller than σf2 (the evaluation result is ○).

[0101] 3 ≤ Ra ≤ 100 …(1)

[0102] 3 < h …(2)

[0103] 24 + r-[TS / (40 + 0.28×Ra)] < h …(3)

[0104] Here, Ra is the arithmetic mean roughness (μm) of the flanging end face;

[0105] h is the height of the flanging portion (the height from the first surface of the plate-like portion to the flanging end face) (mm);

[0106] r is the radius of curvature (mm) of the curved wall portion;

[0107] TS is the tensile strength (MPa) of the plate-like portion.

[0108] In addition, in the above evaluation, regarding the radius of curvature r of the curved wall portion of the flanging portion, it is exemplified that for a steel material with a tensile strength of 780 Mpa, r = 3.0 mm, for steel materials with tensile strengths of 980 Mpa and 1180 MPa, r = 6.0 mm, and for a steel material with a tensile strength of 1470 MPa, r = 8.0 mm. However, in the technology of the present disclosure, the value of the radius of curvature r of the curved wall portion is not limited to these. According to the understanding of the inventors of the present invention, by changing the lower limit of the height h by considering the size of r as in the above formula (3), a flanging workpiece in which fatigue cracks in the flanging portion are not likely to occur can be obtained.

[0109] 3. An example of a flanging component

[0110] In order to confirm that the results of the above analysis are appropriate, a flanging workpiece was actually manufactured and a durability test was conducted.

[0111] 3.1 Comparative Example 1

[0112] A steel plate with a tensile strength TS of 780 MPa grade and a plate thickness t1 of 2.7 mm was blanked into a square with a side length of 200 mm. The center portion was blanked with a punch, and a circular punch hole with a diameter of φ20 mm was provided. The arithmetic mean roughness of the end face of the punch hole was 12 μm. By blanking the portion where the punch hole was provided with a punch and erecting the peripheral portion of the punch hole toward one side of the plate, a flanging portion having a flanging hole and a flanging wall portion was provided. The diameter d of the flanging hole was 25.0 mm, the thickness t2 of the flanging wall portion was 2.3 mm, the height h from the first surface on one side of the steel plate to the flanging end face was 12.0 mm, and the radius of curvature r of the curved wall portion was 3.0 mm. For such a flanging component, the arithmetic mean roughness Ra of the flanging end face was measured to be 105 μm. Since Ra in Comparative Example 1 exceeded 100 μm, the above relationship (1) was not satisfied, and furthermore, the above relationship (3) was not satisfied either.

[0113] 3.2 Comparative Example 2

[0114] Similar to Comparative Example 1, after obtaining the flanging processed part, the flanging end face was pressed against the die, and bending processing (coining) of the flanging curved wall part was performed. Specifically, compressive stress corresponding to the degree of change in the radius r of the flanging curved wall part was applied to the flanging end face. For such a flanging processed part, the arithmetic mean roughness Ra of the flanging end face was measured, and it did not substantially change from 105 μm. That is, in Comparative Example 2, Ra exceeded 100 μm, so at least the above relationship (1) was not satisfied.

[0115] 3.3 Comparative Example 3

[0116] A steel plate with a tensile strength TS of 780 MPa grade and a plate thickness t1 of 2.5 mm was blanked into a square with a side length of 200 mm. The center part was blanked with a punch, and a circular punching hole with a diameter of φ20 mm was set. The arithmetic mean roughness of the end face of the punching hole was 36 μm. By blanking the part with the punching hole with a punch and raising the peripheral part of the punching hole to one side of the plate, a flanging processed part with a flanging hole and a flanging wall part was set. The diameter d of the flanging hole was 25.0 mm, the thickness t2 of the flanging wall part was 2.1 mm, the height h from the first surface on one side of the steel plate to the flanging end face was 19.0 mm, and the radius of curvature r of the curved wall part was 3.0 mm. For such a flanging processed part, the arithmetic mean roughness Ra of the flanging end face was measured to be 105 μm. Since Ra exceeded 100 μm, the above relationship (1) was not satisfied. On the other hand, the left side of the above relationship (3) was 18.8 mm, and the above relationship (3) was satisfied.

[0117] 3.4 Comparative Example 4

[0118] A steel plate with a tensile strength TS of 780 MPa grade and a plate thickness t1 of 2.7 mm was blanked into a square with a side length of 200 mm. The center part was blanked with a punch, and a circular punching hole with a diameter of φ20 mm was set. Then, the end face of the punching hole was reamed to reduce the surface roughness of the end face. The arithmetic mean roughness of the end face of the punching hole with the reduced surface roughness was 5 μm. By blanking the part with the punching hole with a punch and raising the peripheral part of the punching hole to one side of the plate, a flanging processed part with a flanging hole and a flanging wall part was set. The diameter d of the flanging hole was 25.0 mm, the thickness t2 of the flanging wall part was 2.3 mm, the height h from the first surface on one side of the steel plate to the flanging end face was 18.0 mm, and the radius of curvature r of the curved wall part was 3.0 mm. For such a flanging processed part, the arithmetic mean roughness Ra of the flanging end face was measured to be 106 μm. In Comparative Example 4, Ra exceeded 100 μm, so the above relationship (1) was not satisfied, and furthermore, the above relationship (3) was not satisfied either.

[0119] 3.5 Comparative Example 5

[0120] A steel plate with a tensile strength TS of 980 MPa and a plate thickness t1 of 2.5 mm is blanked into a square with a side length of 200 mm. The center part is blanked with a punch, and a circular punching hole with a diameter of φ20 mm is set. By raising the peripheral part of the punching hole to one side of the plate, a flanging processing part with a flanged hole and a flanged wall part is set. The diameter d of the flanged hole is 25.0 mm, the thickness t2 of the flanged wall part is 2.2 mm, the height h from the first surface on one side of the steel plate to the flanged end surface is 10.0 mm, and the curvature radius r of the curved wall part is 6.0 mm. For such a flanging processing part, the arithmetic mean roughness Ra of the flanged end surface is measured to be 77 μm. Comparative Example 5 satisfies the above-mentioned relational expressions (1) and (2). However, on the other hand, since the value on the left side of the above-mentioned relational expression (3) is 14.1 mm, which is larger than the height h, it does not satisfy the above-mentioned relational expression (3).

[0121] 3.6 Examples

[0122] After obtaining the flanging processing part in the same manner as in Comparative Example 1, the flanged end surface is polished using sandpaper. As a result, the flanged end surface is smoothed, and the arithmetic mean roughness Ra of the flanged end surface becomes smaller to 18 μm. As a result, a flanging processing part that satisfies all of the above-mentioned relational expressions (1) to (3) can be obtained.

[0123] 3.7 Evaluation Results

[0124] A durability test is performed on each of the flanging processing parts of Comparative Examples 1 to 5 and the Examples, that is, a stress is repeatedly applied 2 million times until the maximum torsional displacement at the end of the steel plate becomes 10°. In the flanging processing parts of Comparative Examples 1 to 5, cracks occur on the flanged end surface. In contrast, no cracks occur in the flanging processing parts of the Examples.

[0125] Reference Numeral Explanation

[0126] 10 Plate-like part; 11 First surface; 12 Second surface; 20 Flanging processing part; 21 Flanged hole; 22 Flanged wall part; 22a Vertical wall part; 22ax Flanged end surface; 22b Curved wall part; 100 Flanging processing component; 101a Punching hole; 101b Peripheral part of the punching hole.

Claims

1. A flanging processing component, characterized in that, It has a plate-shaped portion and a flanging portion, The above-mentioned plate-shaped portion has a first surface on one side and a second surface on the side opposite to the above-mentioned first surface, The above-mentioned flanging portion has a flanging hole and a flanging wall portion, The above-mentioned flanging wall portion is provided around the above-mentioned flanging hole, The above-mentioned flanging wall portion protrudes to one side compared with the above-mentioned first surface, The above-mentioned flanging wall portion has a longitudinal wall portion and a curved wall portion, The above-mentioned longitudinal wall portion has a flanging end face on one side and is connected to the above-mentioned curved wall portion on the side opposite to one side, The above-mentioned curved wall portion is connected to the above-mentioned longitudinal wall portion on one side and is connected to the above-mentioned plate-shaped portion on the side opposite to one side, The above-mentioned flanging portion has a structure that satisfies the following relational expressions (1) to (3): 3≤Ra≤100…(1) 3.0<h…(2) 24+r-[TS / (40 + 0.28×Ra)] < h…(3) Wherein, The above-mentioned Ra is the arithmetic mean roughness of the above-mentioned flanging end face, and the unit is μm, The above-mentioned h is the height from the above-mentioned first surface to the above-mentioned flanging end face, and the unit is mm, The above-mentioned r is the radius of curvature of the above-mentioned curved wall portion, and the unit is mm, The above-mentioned TS is the tensile strength of the above-mentioned plate-shaped portion, and the unit is MPa.

2. The flanging processing component according to claim 1, characterized in that, The diameter d of the above-mentioned flanging hole is 20.0 mm or more and 100.0 mm or less.

3. The flanging processing component according to claim 1, characterized in that, The above-mentioned r is 2.0 mm or more and 10.0 mm or less.

4. The flanging processing component according to claim 2, characterized in that, The above-mentioned r is 2.0 mm or more and 10.0 mm or less.

5. The flanging processing component according to any one of claims 1 to 4, characterized in that, The above-mentioned TS is 780 MPa or more.

6. The flanging processing component according to any one of claims 1 to 4, characterized in that, The above-mentioned Ra is 50 μm or less.

7. The flanging processing component according to claim 5, characterized in that, The above-mentioned Ra is 50 μm or less.

Images