Manufacturing method of pressing member, manufacturing method of blank, and steel sheet

Abstract

Provided is a technique that is not restricted by the shape of the target pressing member and can suppress end cracking caused by delayed fracture. It includes the following secondary cutting process: In compression molding, when it is presumed that end cracking caused by delayed fracture may occur at the end of the pressed part, as a pretreatment for the compression molding where the above-mentioned end cracking may occur, a secondary cutting process is performed twice on at least the end including the part where end cracking may occur. In the secondary cutting process, at the first cutting, a cutting is performed to form a partial beam-shaped protrusion at the position including the part where end cracking may occur, and the above-mentioned protrusion is cut by the second cutting.

Description

Technical Field

[0001] The present invention relates to a technique for manufacturing a pressed part having a shape of a part that may cause delayed fracture during press forming.

[0002] The present invention is particularly suitable for a technique for manufacturing a pressed part using a metal plate formed of a high-strength steel plate having a tensile strength of 980 MPa or more. Background Art

[0003] Currently, for automobiles, there is a demand to improve fuel efficiency and collision safety by reducing weight. Also, for the purpose of achieving both weight reduction of the vehicle body and protection of occupants during a collision, there is a trend to use high-strength steel plates for automotive structural parts. In particular, in recent years, as high-strength steel plates, ultra-high-strength steel plates having a further high tensile strength of 980 MPa or more have been applied to vehicle bodies.

[0004] One of the problems when applying high-strength steel plates to vehicle bodies is delayed fracture. In particular, among high-strength steel plates, delayed fracture occurring from the end face (hereinafter referred to as the sheared end face) after shearing in high-strength steel plates having a tensile strength of 1180 MPa or more is an important problem.

[0005] Here, it is known that a large tensile stress remains on the sheared end face. Due to the remaining tensile stress, delayed fracture may occur over time at the sheared end face in the pressed product (pressed part). In order to suppress delayed fracture at the sheared end face, it is necessary to reduce the tensile residual stress at the sheared end face.

[0006] As a method for reducing the tensile residual stress at the sheared end face, for example, there are the following methods: a method of increasing the temperature of the steel plate during shearing (Non-Patent Documents 1 and 2), a method of using a shoulder punch during punching (Non-Patent Document 3), and a method using shaving (Non-Patent Documents 4 and Patent Document 1).

[0007] However, the method of increasing the temperature of the steel plate during shearing requires time to heat the steel plate. Therefore, this method is not applicable to mass production processes such as automobiles. In addition, the method of using a shoulder punch has a problem of a small improvement effect on the delayed fracture resistance characteristics. Further, the method using shaving has a problem of difficulty in managing the clearance in the shaving process.

[0008] In addition, Non-Patent Document 5 describes a chipping-off method using two-time extraction. However, the method of Non-Patent Document 5 is a technique for punching and cannot be applied to the outer peripheral portion of the product.

[0009] Prior Art Documents

[0010] Non-Patent Literature

[0011] Non-Patent Literature 1: Kenichiro Mori et al.: Plasticity and Processing, 52 - 609 (2011), 1114 - 1118; Non-Patent Literature 2: Kenichiro Mori et al.: Plasticity and Processing, 51 - 588 (2010), 55 - 5; Non-Patent Literature 3: The 326th Plastic Working Symposium "The Frontiers of Shearing Processing", 21 - 28

[0012] Non-Patent Literature 4: M. Murakawa, M. Suzuki, T. Shinome, F. Komuro, A. Harai, A. Matsumoto, N. Koga: Precision piercing and blanking of ultrahigh-strength steel sheets, Procedia Engineering, 81 (2014), pp. 1114 - 1120

[0013] Non-Patent Literature 5: Plasticity and Processing, Vol. 10 no. 104 (1969 - 9)

[0014] Patent Literature

[0015] Patent Literature 1: Japanese Patent Laid-Open No. 2004 - 174542 Summary of the Invention

[0016] Problems to be Solved by the Invention

[0017] The present invention is made in view of the above, and aims to provide a technique that suppresses restrictions on the shape of the target pressing member and can suppress delayed fracture over time.

[0018] Means for Solving the Problems

[0019] To solve the problems, the gist of one aspect of the present invention is: in a method for manufacturing a pressing member, the pressing member is manufactured by one or more than two press moldings, and the method for manufacturing the pressing member includes the following secondary cutting process: in at least one of the one or more than two press moldings, when it is estimated that delayed fracture may occur at the end of the workpiece to be pressed, as a pretreatment of the press molding where end cracking may occur due to the above-mentioned delayed fracture, the end including at least the portion where the above-mentioned delayed fracture may occur is subjected to a two-stage cutting process. In the above-mentioned two-stage cutting process, at the first cutting, a cutting is performed to form a partial beam-shaped protrusion at a position including the portion where the above-mentioned delayed fracture may occur, and the above-mentioned protrusion is cut off by the second cutting.

[0020] In addition, the gist of other aspects of the present invention is as follows: in a method for manufacturing a blank, the blank is formed into a pressed part through one or more pressing processes, and the method for manufacturing the blank includes the following secondary cutting process: in at least one of the one or more pressing processes, when it is presumed that end cracking caused by delayed fracture may occur at the end of the pressed part, a secondary cutting process is performed on the end including at least the part where the above-mentioned delayed fracture may occur. In the above-mentioned secondary cutting process, at the first cutting, a cutting is performed to form a partial beam-shaped protrusion at a position including the part where the above-mentioned delayed fracture may occur, and the above-mentioned protrusion is cut off by the second cutting.

[0021] Effect of the Invention

[0022] According to the aspect of the present invention, restrictions on the shape of the target pressed part are suppressed, and delayed fracture after pressing can be suppressed. Description of the Drawings

[0023] Figure 1 Schematic diagram illustrating the secondary cutting process and subsequent pressing process based on an embodiment of the present invention.

[0024] Figure 2 Schematic diagram illustrating the pressing process in the case where the present invention is not applied.

[0025] Figure 3 Schematic diagram illustrating the case where the secondary cutting process based on the present invention is performed during processing.

[0026] Figure 4 Plan view illustrating the case where the secondary cutting process based on the present invention is performed on drawing processing.

[0027] Figure 5 Cross-sectional view illustrating the case where the secondary cutting process based on the present invention is performed on drawing processing.

[0028] Figure 6 Graph illustrating the relationship between the protrusion amount and delayed fracture. Detailed Description of the Invention

[0029] Next, embodiments of the present invention will be described with reference to the drawings.

[0030] The method for manufacturing a pressed part according to the present embodiment is a method for manufacturing a pressed part that manufactures a target pressed part through one or more pressing processes. For the pressing process in each pressing process, for example, bending forming or drawing forming is performed. And, the method for manufacturing a pressed part according to the present embodiment is a technique for the case where delayed fracture occurs along the plate end edge after pressing in at least one pressing process.​​​​​​

[0031] In the present embodiment, for ease of explanation, an example is given of the case of manufacturing the pressing member 10 having the shape shown in Figure 1 (d) by one-time pressing forming (one-time pressing process).

[0032] Figure 1 The component shape of the pressing member 10 illustrated in (d) has a top board portion 11, a longitudinal wall portion 12 continuous with the top board portion 11, and a flange portion 13 continuous with the longitudinal wall portion 12. In addition, Figure 1 the component shape of the pressing member 10 illustrated in (d) is bent in a shape that is convex on the right side when viewed from above along the length direction. Figure 1

[0033] In this example, in the case where the pressing forming of the present invention is not applied (in the case where the process of Figure 2 is omitted as in Figure 1 ), there may be a cracking possible portion where end cracking due to delayed fracture occurs in a part of the flange portion 13 on the convex side of the bend. It should be noted that, Figure 1 in (d), the mark 3 indicates the position of the cracking possible portion due to delayed fracture, Figure 2 in (d), the mark 3' indicates the position of the cracking possible portion corresponding to the actually occurring end cracking due to delayed fracture. Figure 1 (b), Figure 1 (c), Figure 2 the mark 3A in (c) indicates the position of the cracking possible portion 3 due to delayed fracture in the workpiece.

[0034] In addition, the mark 1A indicates the flange corresponding portion in the workpiece 1 corresponding to the region that becomes the flange portion 13. Here, in the present embodiment, an example is given of the case where the position of the cracking possible portion 3 due to delayed fracture is on the end face where the flange portion 13 is formed, but it is not limited thereto. It is also conceivable that the position of the cracking possible portion 3 due to delayed fracture is on a shear plane other than the end face of the flange portion.

[0035] Here, it is known that a large tensile stress remains on the shear end face. Due to the remaining of this tensile stress, delayed fracture may occur over time on the shear end face of the pressed product (pressing member). In addition, tensile residual stress is generated at the end where compressive stress is input during pressing forming, and delayed fracture may occur over time in the pressed product (pressing member). Therefore, delayed fracture is particularly likely to occur on the shear end face and at the end where compressive stress is input during pressing.

[0036] For the confirmation of the presence or absence of the crack - prone part 3 caused by delayed fracture, and for the determination of the position of the crack - prone part 3, for example, it can be obtained by performing simulation analysis such as CAE analysis. In addition, it is also possible to actually perform press - forming and observe each part after press - forming to confirm the presence or absence of the crack - prone part 3 caused by delayed fracture and to determine the position of the crack - prone part 3.

[0037] As described above, in the case of simulation analysis, it is only necessary to evaluate delayed fracture by calculating the tensile residual stress after demolding. In addition, in the case of actual pressing, for the produced samples, for example, the tensile residual stress value of the shear end face is measured by X - ray to evaluate delayed fracture. Or for the produced samples, for example, they are immersed in hydrochloric acid with a pH of 3 for 96 hours, and then delayed fracture is evaluated based on whether there is end - cracking in the sample and the size of the cracking.

[0038] In the present embodiment, as a pretreatment for press - forming, it includes the following trimming process: The outer periphery of the blank 1 of the exemplified pressed part is sheared according to the contour shape of the part shape of the pressing part 10.

[0039] However, in the present embodiment, for the end part (at least for the position of the crack - prone part 3) of the flange - corresponding part of the flange part 13 where end - cracking caused by delayed fracture may occur in this trimming process, the secondary cutting process shown in (b) and (c) below is performed, and the aforementioned secondary cutting process is to perform the second - stage cutting based on the present invention. Figure 1 The end - cracking caused by delayed fracture may occur at the end part which has tensile residual stress after demolding of the press - forming.

[0040] Therefore, for example, when a target pressing part generates a tensile residual stress above a preset specified value by CAE analysis or the like, it is presumed that end - cracking caused by delayed fracture may occur at the end part, and the part that generates the tensile residual stress above the specified value is regarded as the part where delayed fracture may occur. In addition, for example, in the case of not applying the present invention, the part where delayed fracture occurs is regarded as the part where delayed fracture may occur.

[0041] In the present embodiment, as shown in (b), at the first - stage cutting, the end part of the flange - corresponding part 1A of the blank 1 (the pressed part) to be subjected to the secondary cutting process is cut in such a way that a partial - beam - shaped protruding part 2 is formed at the position including the part where end - cracking caused by delayed fracture may occur. Then, as shown in (c), the protruding part 2 is cut by the second - stage cutting to form the contour shape of the target end - edge of the blank 1.

[0042] In the present embodiment, as Figure 1 (b) shows, at the first - stage cutting, the end part of the flange - corresponding part 1A of the blank 1 (the pressed part) to be subjected to the secondary cutting process is cut in such a way that a partial - beam - shaped protruding part 2 is formed at the position including the part where end - cracking caused by delayed fracture may occur. Then, as shown in Figure 1 (c), the protruding part 2 is cut by the second - stage cutting to form the contour shape of the target end - edge of the blank 1.

[0043] That is, in the present embodiment, when the blank 1 is cut into the target contour shape by the trimming process, for the edge (end edge) of the flange corresponding portion 1A, it is temporarily cut into a shape having a protruding portion 2 with a partially cantilevered beam shape at a position including the crack - possible portion 3A. Then, the protruding portion 2 is cut by the second cut to form the target contour shape. Thus, in the present embodiment, the cutting process shown in Figure 1 of (b) and (c) is performed through two processes to perform the cutting process of (c) shown in Figure 2 . The processes of (b) and (c) shown in Figure 1 can also be performed through one process.

[0044] It should be noted that the secondary cutting process based on the present invention can also be performed independently of the trimming process. For example, multiple processes (not shown) can be provided between (c) and (d) of Figure 1 , and the secondary cutting process based on the present invention can be performed in these multiple processes.

[0045] Here, it is preferable that the width W (the length along the end edge of the material) of the protruding portion 2 is 1 / 3 or less of the length L along the end edge of the flange portion 13, or 150 times or less of the plate thickness of the blank 1.

[0046] Compared with the case where the temporary beam - shaped protruding portion 2 formed by the above - mentioned width W is not formed by the first cut (shearing) (refer to Figure 2 ), the cutting amount (punching allowance) of the second cut (shearing) can be obtained, and the strain input caused by shearing the crack - possible portion 3 can be more reliably suppressed (refer to the examples described later).

[0047] It should be noted that the lower limit value of the width W of the protruding portion 2 is not particularly limited as long as it includes the position where the crack - possible portion 3 is presumed to be generated and is a shearable width. The lower limit value of the width W is set to be, for example, above the opening amount at the end edge of the end - part cracking caused by delayed fracture. Considering the ease of cutting by shearing, etc., the width W of the protruding portion 2 is preferably 20 mm or more.

[0048] In addition, the protruding amount H (the maximum value of the protruding amount (protruding amount) from the target contour position) of the protruding portion 2 is preferably 10 times or less of the plate thickness of the blank 1 or 5.0 mm or less.

[0049] By making the second - cut portion into a cantilever - beam - shaped protruding portion 2, the cutting amount (punching allowance) of the second cut (shearing) can be obtained, and the strain input caused by shearing the crack - possible portion 3 can be more reliably suppressed.

[0050] The lower limit value of the protruding amount H of the protruding portion 2 is not particularly limited as long as it protrudes more than 0 mm and can be sheared. Considering the ease of shearing, etc., the lower limit value of the protruding amount H is preferably 1 mm or more, more preferably 3 mm or more.

[0051] Then, after the above secondary cutting process, the pressed part 10 that is the target in the press forming is manufactured.

[0052] By performing the above secondary cutting process as a pretreatment for the press forming where end cracking may occur, normal press forming can be used without imposing restrictions on the part shape, and cracking at the cracking possible part 3 caused by delayed fracture can be prevented.

[0053] Here, in the above description, the case of performing the above secondary cutting process as a pretreatment for the press forming is exemplified. Of course, it can also be as shown in Figure 1 (b)→(c′)→(d), and is configured in such a way that the second cutting (cutting of the protruding portion 2) is performed after the press forming into the target part shape ( Figure 1 (c′)). The effect is the same. Figure 1 (d)).

[0054] It should be noted that in the above description, the case where the cracking possible part 3 is one part is exemplified, but the present invention can also be applied to the case where there are two or more cracking possible parts 3 caused by delayed fracture. As long as the above secondary cutting process is performed on each cracking possible part 3 as a pretreatment for the press forming where end cracking may occur. However, in the case where adjacent cracking possible parts 3 are close, it is also possible to form one protruding portion 2 including the adjacent cracking possible parts 3 by the first cutting.

[0055] Here, the function and effect of the secondary cutting process will be described. The aforementioned secondary cutting process is to cut the partially cantilevered protruding portion formed by the first cutting by the second cutting.

[0056] Generally speaking, if shearing is performed, a large tensile stress remains at the edge of the pressed part. Therefore, as the subsequent press forming, if a press forming that generates tensile residual stress at the end portion 13a of the flange portion 13 along the edge of the flange portion 13 is performed, there is a tendency for the possibility of end cracking to increase.

[0057] In contrast, by performing the secondary cutting process of the present invention on the part where end cracking caused by delayed fracture may occur, the tensile residual stress at the shearing end face is reduced (refer to the examples). As a result, in the present embodiment, it is possible to prevent restrictions on the part shape and to prevent end cracking caused by delayed fracture due to tensile residual stress.

[0058] Here, an example of the conventional processing is as follows Figure 2 In the case of forming an end portion at a position that becomes a flange by cutting through a single cut, since cutting is performed at the cutting position (the right-side cutting position) indicated by the dotted line in Figure 2 (a), the cutting area formed by the width W1 of the cutting portion and the protruding amount H1 from the cutting position is large.

[0059] In contrast, as shown in Figure 1 , based on the present invention, in the case of a secondary cutting process in which a partially beam-shaped protruding portion 2 is formed by a first cut (cutting at the position of the dotted line in Figure 1 (a)) and the protruding portion 2 is cut by a second cut, the cutting area formed by the width W of the cutting portion and the protruding amount H by the second cut is small (refer to Figure 1 (b)(c)). And, as shown in Figure 1 (b), since a partially cantilever beam-shaped protruding portion 2 is formed by the first cut in the secondary cutting process based on the present invention, the width W of the cutting portion (protruding portion 2) to be cut by the second cut is significantly reduced and protrudes in a cantilever beam shape. Therefore, if the protruding portion 2 is cut by the second cut, it is presumed that the deflection of the steel plate in the advancing direction of the cutting becomes larger, and the strain in the severe deformation region during cutting can be alleviated by alleviating the strain input during cutting, thereby alleviating the tensile residual stress.

[0060] It should be noted that since materials with higher tensile strength are more likely to cause delayed fracture, the present invention preferably uses, for example, high-tensile steel plates with a tensile strength of 590 MPa or more. Of course, the raw material of the blank 1 is not limited to steel, and ferroalloys such as stainless steel can also be applied, and furthermore, non-ferrous materials and non-metallic materials can also be applied. In addition, the pressed component 10 manufactured by the present embodiment is preferably used as an automotive component, for example, but the present invention is not limited to automotive components and can also be applied to all processing for press-forming a sheet material.

[0061] In addition, in the above embodiment, the case of manufacturing the target pressed component 10 by one-stage press-forming is illustrated. Generally, the more complex the component shape of the pressed component is, the more likely it is to manufacture the target pressed component by press-forming in two or more stages (multiple pressing processes). In addition, in the case of manufacturing the target pressed component by multiple press-formings, the press-forming that causes delayed fracture is not limited to the final process. In addition, there are also cases where delayed fracture occurs individually in press-formings of two or more stages.

[0062] For example, when manufacturing a target compression-molded part through five-stage compression molding, if it is estimated by simulation analysis such as CAE that there is a tensile stress above a specified residual value in the fourth stage of compression molding and there is a possibility of delayed fracture, the above-described secondary cutting process may be performed before the compression molding in the fourth stage.

[0063] Figure 3 An example of the case of manufacturing a target compression-molded part through multi-stage compression molding is shown (refer to Figure 3 (e)). Figure 3 The example shown is the shape after separately compression-molding Figure 3 (b) and (e). In the case where there is a possible cracking part 3 due to delayed fracture in the compression-molded part formed into the shape of Figure 3 (e). In this example, as shown in Figure 3 (c), the flange portion 13 of the compression-molded part formed by the first compression molding ( Figure 3 (b)) is cut in such a way that a partial beam-shaped protruding portion 2 is formed at a position including the portion where end cracking may occur. As shown in Figure 3 (d), the protruding portion is cut by a second cutting to form the contour shape of the target end edge. Then, the second compression molding is performed (refer to Figure 3 (e)). Thereby, end cracking in the possible cracking part 3 can be suppressed.

[0064] In addition, as shown in Figure 4 and Figure 5 , the secondary cutting process of the present invention can also be applied to drawing. Figure 4 and Figure 5 In the example shown, before performing the compression molding ( Figure 4 (d), Figure 5 (d)) in which the central portion is expanded by drawing, the secondary cutting process is performed on the possible cracking part due to delayed fracture.

[0065] In this example, when cutting the blank 1 into the target sample shape, a beam-shaped protruding portion 2 ( Figure 4 (b), Figure 5 (b)) is formed at a position including the portion where delayed fracture may occur. Then, the beam-shaped protruding portion 2 is cut by a second cutting ( Figure 4 (c), Figure 5 (c)).

[0066] Then, drawing is performed on the central portion ( Figure 4 (d), Figure 5(d)), pull up the central part. The mark 17 is the part expanded by drawing. Here, the cold-rolled material has a tendency of anisotropy to crack easily in two directions, and the hot-rolled material has a tendency to crack easily in the C direction. It is only necessary to form the protrusion 2 at the end of the possible cracking part 3 in the above drawing process.

[0067] In the above description, the case where the above secondary cutting process is performed as a pretreatment of the drawing process is exemplified. It can also be as Figure 4 , 5 shown in (b)→(c′)→(d) of, and perform the second cutting (cutting of the protrusion 2) after the drawing process is the target part shape ( Figure 4 , 5 (c′) of) ( Figure 4 , 5 (d) of). The effect is the same.

[0068] Here, the secondary cutting process is not limited to the trimming process before the above-mentioned press forming, and the first cutting and the second cutting can be independently implemented as the secondary cutting process regardless of the trimming process. In addition, when there are multiple press forming processes between the first cutting and the second cutting in the secondary cutting process, among these press forming processes, it can also be configured to perform the secondary cutting process before at least one press forming is implemented.

[0069] In addition, there is no particular limitation on the shearing tool used in shearing, and any conventionally known equipment can be used. For example, it is preferable that the percentage of the distance d between the upper blade and the lower blade of the shearing tool to the plate thickness t of the pressed part, that is, the clearance C, is 5.0% or more and 30.0% or less.

[0070] When the clearance C is smaller than 5.0%, a secondary shear surface is generated during the shearing process, and the state of the shear end face is not ideal. Moreover, there is a possibility that the tensile residual stress becomes larger.

[0071] On the other hand, when the clearance C is larger than 30.0%, burrs more than a specified amount are generated on the shear end face, which may seriously damage the formability of the shear end face. In addition, uneven deformation stress is applied to the processed surface until the shearing process is completed, so there is a possibility that the tensile residual stress after the shearing process becomes larger.

[0072] More preferably, the clearance C is 10.0% or more and less than 20.0%.

[0073] Example 1

[0074] Next, the examples related to this embodiment will be described.

[0075] Here, two test materials A and B made of high-strength steel plates with a thickness of 1.4 mm were used as the objects. The dimensions of the test materials A and B before shearing were 100 mm × 100 mm.

[0076] First, the test materials were cut into dimensions of 100 mm × 50 mm by the first cutting. However, a protrusion 20C was formed during the first cutting ( Figure 6 (b)).

[0077] Next, after the first cutting process, a second cutting for cutting the protrusion 20C was carried out ( Figure 6 (c)). It should be noted that the gap during the cutting process in both the first and second cutting processes was 12.5%.

[0078] The protrusion amount H of the protrusion 20C was changed and the cutting process was carried out multiple times or more to produce multiple samples.

[0079] After producing the samples, the residual stress of the sheared end face after cutting was measured by X-ray for the end face part of the cut protrusion 20C. In addition, the produced samples were immersed in hydrochloric acid with a pH of 3 for 96 hours, and then, the presence or absence of cracking at the ends of the samples was confirmed to evaluate the stress corrosion cracking resistance characteristics.

[0080] The confirmation of the cracking was measured by X-ray, and the measurement range was set to a diameter of 300 μm. In addition, the stress at the central position was measured in two directions of the plate surface and the plate thickness of the sheared end face after the shearing process.

[0081] Table 1 shows the tensile strength of the test materials, the protrusion amount H of the protrusion 20C (shown as the ratio to the plate thickness t), the residual stress of the sheared end face, and the cracking determination results of the immersion test.

[0082] In Table 1, the samples with "-" in the column of the protrusion amount H of the protrusion 20C are examples where the protrusion 20C was not provided and thus the second cutting was not performed.

[0083] [Table 1]

[0084]

[0085] As can be seen from Table 1, by providing the protrusion 20C in the first step and cutting the protrusion 20C in the second cutting process, the tensile residual stress of the sheared end face was reduced, and in addition, the cracking determination results of the immersion test also corresponded to it.

[0086] However, when the cutting allowance (Japanese: 切り代) of the second cutting process is set to 20 times the plate thickness, the tensile residual stress reduction effect is small. As shown in Table 1, by setting the protrusion amount H of the protrusion 20C to 1.2 times or more and less than 20 times the plate thickness of the metal plate 10, the delayed fracture resistance is greatly improved.

[0087] Furthermore, it is understood that according to the present invention, it is possible to easily suppress end cracking due to delayed fracture.

[0088] The entire contents of Japanese patent application 2020-063178 (filed on March 31, 2020) to which this application claims priority are incorporated herein by reference. Although the invention is described with reference to a limited number of embodiments, the scope of protection is not limited thereto, and changes based on the embodiments disclosed above are obvious to those skilled in the art.

[0089] Description of Reference Numerals

[0090] 1. Blank (pressed part)

[0091] 1A Flange matching part

[0092] 2. 20C protrusion

[0093] 3.3A possible cracking

[0094] 10 Pressed parts

[0095] 13 Flange

[0096] H Protrusion

[0097] W Width

Claims

1. A method for manufacturing a pressing member, wherein, The pressing component is manufactured by one or more than two times of pressing forming. The manufacturing method of the pressing component is characterized by including the following secondary cutting process: in at least one of the one or more than two times of pressing forming, when it is presumed that end cracking caused by delayed fracture may occur at the end of the workpiece to be pressed, as a pretreatment for the pressing forming where the delayed fracture may occur, the end including at least the part where the delayed fracture may occur is subjected to a two-time cutting process. In the secondary cutting process, at the first cutting, a cutting is performed to form a partial beam-shaped protrusion at a position including the part where the delayed fracture may occur, and the protrusion is cut off by the second cutting.

2. The manufacturing method of the pressing component according to claim 1, characterized in that, The width of the protrusion is set to be 1 / 3 or less of the length of the edge of the flange part where the end cracking may occur.

3. The manufacturing method of the pressing member according to claim 1, characterized in that, The width of the protrusion is set to be 150 times or less of the plate thickness of the workpiece to be pressed.

4. The manufacturing method of the pressing member according to any one of claims 1 to 3, characterized in that The protruding amount of the protrusion is set to be 10 times or less of the plate thickness of the workpiece to be pressed.

5. The manufacturing method of the pressing member according to any one of claims 1 to 3, characterized in that, The protruding amount of the protrusion is set to be 5.0 mm or less.

6. The manufacturing method of the pressing member according to any one of claims 1 to 5, characterized in that, The pressing forming is bending forming or drawing forming.

7. The manufacturing method of the pressing member according to any one of claims 1 to 3, characterized in that, After the first cutting process, the pressing forming is performed, and after the pressing forming, the second cutting process is performed.

8. A manufacturing method of a blank, which is a manufacturing method of a blank that becomes a pressing component through one or more than two times of pressing forming, and is characterized in that the manufacturing method of the blank includes the following secondary cutting process: in at least one of the one or more than two times of pressing forming, when it is presumed that end cracking caused by delayed fracture may occur at the end of the workpiece to be pressed, the end including at least the part where the delayed fracture may occur is subjected to a two-time cutting process. In the secondary cutting process, at the first cutting, a cutting is performed to form a partial beam-shaped protrusion at a position including the part where the delayed fracture may occur, and the protrusion is cut off by the second cutting.

9. A steel plate with a tensile strength of 980 MPa or more for the manufacturing method of the blank according to claim 8, and the steel plate is used as the workpiece to be pressed in the manufacturing method of the blank according to claim 8.

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