Technical field
[0001]
　The present invention is blank for press molding, produced from the blanks molded articles, the mold for producing the blank, and a method for producing the blank.
Background technique
[0002]
　Automobiles, in the production of household appliances, and members used in the building structure or the like, and formed into a predetermined shape blank (material) by the plastic working of the press molding. If the mass production of the blank, for example, cutting the metal plate into a predetermined shape by shearing.
[0003]
　Figure 1 shows an embodiment of a time of cutting by shearing a metal plate schematically. As shown in FIG. 1 (a), when shearing the metal plate 1 is first placed a metal plate 1 on the die 2. Thereafter, as shown in FIG. 1 (b), a punch 3 is moved in a direction substantially perpendicular (the direction indicated by arrow D) to the surface of the metal plate 1, to cut the metal plate 1.
[0004]
　Figure 2 is a schematic sectional view showing an example of a shearing surface of the metal plate which is cut by shearing. As shown in FIG. 2, shearing surface 4 of the metal plate 1 includes, for example, no one unit 4a, the shear surface 4b and fracture surface 4c. Shear plane is greatly plastically deformed by shearing. In the example shown in FIG. 2, by shearing, burr on the back surface side of the metal plate 1 (burr) 5 has occurred.
[0005]
　As described above, shearing surface has a shear surface which is significantly plastically deformed by shearing. Therefore, shearing surface, as compared to the machined surface formed by cutting and grinding, hard to stretch deformation, stretch-flange cracks (in shearing and cutting press working after processing, such as, the processed surface extends easy to cause cracking) occurs in the pressurized cumene. Hereinafter will be described with reference to the drawings stretch-flange cracks.
[0006]
　Figure 3 is a diagram for explaining the stretch flangeability, (a) is a perspective view showing a metal plate before stretch flangeability, (b) and (c) the metal plate after stretch flangeability it is a perspective view showing.
[0007]
　Figure 3 (a), the metal plate 6 is cut by shearing, shearing surface 6a is formed on the outer peripheral edge. Further, the outer peripheral edge of the metal plate 6, a recess 6b having a substantially L-shaped peripheral edge is provided in a plan view. Periphery of the recess 6b includes straight portion 6c, the curved portion 6d and the straight portion 6e. 3 (a), the respective lengths X1, the length Y1 and length Z1, shown straight portion 6c, the length of the curved portion 6d and the straight portion 6e.
[0008]
　Referring to FIGS. 3 (a) and (b), when subjected to flanging stretch as plane deformation against the peripheral portion of the concave portion 6b occurs, the length of the straight portion 6c and the linear portion 6e X1 , Z1 does not change, the length of the curved portion 6d becomes greater length Y2 than the length Y1. That is, the shearing plane 6a elongation deforms in the curved portion 6d. Thus, there is a case where stretch-flange cracks occur in the curved portion 6d.
[0009]
　Referring to FIG. 3 (a) and 3 (c), when subjected to flanging stretch as plane deformation against the peripheral portion of the concave portion 6b occurs, the length of the straight portion 6c and the linear portion 6e X1 , Z1 does not change (or, although not substantially change), the length of the curved portion 6d becomes greater length Y3 than the length Y1. That is, the shearing plane 6a elongation deforms in the curved portion 6d. Thus, there is a case where stretch-flange cracks occur in the curved portion 6d.
[0010]
　Occurrence of stretch-flange cracks as described above is particularly a problem for consumer electronics and for various components for automotive when produced by press molding. Recently, further weight reduction of the parts as described above has been demanded, are widely used thin steel sheet having a strength of at least 780MPa grade steel. Thus, in particular, to prevent the flange cracks extending in press forming high strength steel plate as described above is generated is desired. However, stretch-flange cracks is known to also occur in the steel sheet of a low intensity, it is necessary to prevent the stretch-flange cracks irrespective strength of the steel sheet. Therefore, to suppress the occurrence of stretch-flange cracking in shearing plane techniques have been proposed heretofore.
[0011]
　For example, in the punching tool disclosed in Patent Document 1, the tip portion of the cutting edge of the punch, convex bending blade is provided. When cutting a workpiece by a punch having the above configuration can provide the portion to be cut by the cutting edge, the tensile stress by the bending blade. In this case, the progress of cracks occurred on the workpiece by the cutting edge and the die shoulder can be promoted by the tensile stress. Accordingly, since it is cut by the cutting unit without the workpiece is compressed, it can improve the hole expandability of perforations. As a result, it is considered that the occurrence of stretch-flange cracking in shearing surface can be suppressed.
[0012]
　Shah shearing blade disclosed in Patent Document 2 includes a main shearing edge and a distal portion projection projecting in the traveling direction of the blade than the main shearing edge. When cutting a workpiece plate by shear shearing blades having the above configuration, the portion to be cut by the main shear blades, it is possible to apply tension by the tip portion protruding. Thus, also in the shear shearing blade of Patent Document 2, the same effect as the punch of Patent Document 1 is obtained.
CITATION
Patent Literature
[0013]
Patent Document 1: JP 2005-095980 Patent Publication
Patent Document 2: JP 2006-231425 JP
Summary of the Invention
Problems that the Invention is to Solve
[0014]
　As described above, the technology described in Patent Document 1 and 2 is effective in suppressing the stretch-flange cracks. However, as a result of various studies of the present inventors, the workpiece cut by using the technique of Patent Document 1 and 2, the fatigue fracture is liable to occur except portions stretch flangeability is performed starting from it was found to be. Specifically, in the workpiece cut by using the technique of Patent Document 1 and 2, the ratio of the fracture surface of the shearing surface is increased. Fracture surface generally has a large number of crack. Results of various studies of the present inventors, as a starting point the crack formed in the fracture surface, the fatigue fracture is found to be likely to occur. Therefore, in the workpiece cut by the technique of Patent Document 1 and 2, there is a problem that the fatigue strength is lowered.
[0015]
　The present invention is a blank which can suppress a decrease in can and fatigue strength suppress the occurrence of flange cracking elongation during press molding, a press molded product obtained by the blank by press molding, a mold for the blank production, and of the blank and to provide a manufacturing method.
Means for Solving the Problems
[0016]
(1) blank according to an embodiment of the present invention is a plate-like blank for press molding manufactured by shearing a metal plate, and has a shear surface and fracture surface in the thickness direction has a shearing surface which is formed in an annular shape in plan view, the edge of the shearing surface in a plan view has a curved portion which is curved concavely, the said fracture surface at the curved portion the thickness direction of the length of the average value is larger than the plate mean value of the thickness direction of the length of the fracture surface of the entire circumference of the shearing surface.
[0017]
　In the above blanks, the length of the thickness direction of the fracture surface increases in the curved portion. In other words, the deformable portion extending at the time of press molding, it is possible to reduce the ratio of shear plane. Thus, the curved portion is easily deformed elongation, it is flanged elongation curved portion can be suppressed stretch-flange cracks occur in the curved portion. Further, portions other than the curved portion, it is possible to reduce the proportion of fracture surface than the curved portion. In other words, the rate of work hardening by shear surface can be increased. Thus, in the portion other than the curved portion, sufficient fatigue strength can be obtained. On the other hand, the curved portion is larger proportion of fracture surface. Therefore, fatigue strength of the curved portion is reduced in the state before press-forming. However, cause work hardening by flanging elongation during press-forming, the fatigue strength of the curved portion is increased. These results, without reducing the fatigue strength, can suppress the occurrence of stretch-flange cracks.
[0018]
(2) if the point where the curvature of the curved portion is maximum at the center point or viewed in the circumferential direction of the shearing surface of the curved portion as the reference point of the curved portion, said centering the reference point average value of the thickness direction of the length of the fracture surface at a given length range in the circumferential direction, than the plate mean value of the thickness direction of the length of the fracture surface of the entire circumference of the shearing surface it may be larger.
[0019]
　In this case, it is possible to suppress the stretch-flange cracking at the center of the curved portion (positional heart or portion where the curvature increases) occurs.
[0020]
(3) average value of the thickness direction of the length of the fracture surface in the range of the predetermined length than the average value of the thickness direction of the length of the fracture surface of the entire circumference of the shearing surface it may also be greater than 10% of the thickness.
[0021]
　In this case, it can be sufficiently suppressed that the stretch-flange cracks is generated in the center portion of the curved portion.
[0022]
(4) the shearing surface, the plate further comprises a sag portion located opposite to the fracture surface in the thickness direction in between the shear surface, the sagging portion of the range of the predetermined length average length of the plate thickness direction may be 20% or less of the plate thickness.
[0023]
　By shortening the length of the sagging portion can more reliably suppress the occurrence of stretch-flange cracks.
[0024]
(5) the predetermined length may be 50% of the length of the plate thickness of the blank.
[0025]
　In this case, it is possible to more reliably prevent the stretch-flange cracks is generated in the center portion of the curved portion.
[0026]
(6) wherein the predetermined length may be 2000% of the length of the plate thickness.
[0027]
　In this case, it is possible to suppress the stretch-flange cracking occurs at a sufficient range of the bending portion.
[0028]
(7) wherein the predetermined length range, curvature 5 m -1 may be a portion to be the least.
[0029]
　In this case, even in the curved portion flange deformation elongation during press-forming becomes large, sufficiently prevent the occurrence of stretch-flange cracks.
[0030]
(8) the metal plate has a hole formed by piercing, the shearing surface may be formed on the edge of the hole.
[0031]
　In this case, even when the flanging extends a peripheral portion of the hole formed by piercing, it can be prevented stretch-flange cracks are generated at the edge of the hole. Further, it is possible to suppress the fatigue strength is lowered in the periphery of the hole.
[0032]
(9) The metal plate has a peripheral edge formed by punching, said shearing surface may be formed on the outer peripheral edge.
[0033]
　In this case, even when the flanging extends an outer peripheral edge of the blank by stamping, it is possible to prevent the stretch-flange cracking occurs in the outer periphery. Further, it is possible to suppress the fatigue strength is lowered in the vicinity of the outer periphery.
[0034]
(10) the curved portion may be a portion that deforms the elongation at the time of press molding.
[0035]
　In this case, it is possible to prevent occurrence of stretch-flange cracks in a portion of the elongation deformation, in other parts, can be reliably prevented a decrease in fatigue strength.
[0036]
(11) molded article according to another embodiment of the present invention is a molded article was subjected to press molding to the blank.
[0037]
　The above molded article has and sufficient fatigue strength is prevented stretch-flange cracks.
[0038]
(12) a mold according to another embodiment of the present invention has a columnar punch and said insertable hollow die punch, placed on the die by moving the punch in a predetermined direction a die for shearing a metal plate, the punch has a bottom surface outer circumferential edge is the cutting blade, and an outer peripheral surface extending in a direction parallel from said outer edge to said predetermined direction, said outer peripheral edge includes a curved portion curved in convex or concave in plan view, the bottom surface includes a flat portion, and the cutout portion provided to include the curved portion in the recess and viewed in the predetermined direction from the flat portion including.
[0039]
　When the metal plate to Shearing (piercing or punching) using the above mold, for example, pushing the bottom surface of the punch against the metal sheet placed on the die. Thus, first, in contact with the outer edge and the metal plate on the surface of the flat portion, the shear surface on a metal plate at the contact portion is formed. Further, among the contact portions between the rear surface of the die and the metal plate, in the portion facing the outer edge of the flat portion, the shear surface is formed on the metal plate. At the time pushing amount is small punch portion facing the cutout portion of the surface of the metal plate is not in contact with the punch, not shear plane is formed in the partial. Further, among the contact portions between the rear surface of the die and the metal plate, the portion located below the notch because no large force is applied, are not formed shear surface in the partial.
[0040]
　By pushing further the punch, cracks in the contact portion between the outer edge of the flat portion on the surface of the metal plate occurs. The crack progress in the thickness direction, the fracture surface is formed on the surface side of the metal plate. Further, among the contact portions between the rear surface of the die and the metal plate, it is crack in the metal plate at a portion opposed to the outer edge of the flat portion occurs. The crack progress in the thickness direction, the fracture surface is formed on the back surface side of the metal plate. On the other hand, notch also in contact with the surface of the metal plate, the shear surface at the contact portion is formed. Further, even in a portion located below the cutout portion of the contact portion between the rear surface of the die and the metal plate, the shear surface is formed on the metal plate.
[0041]
　By pushing further the punch, it said crack occurring on the surface side and back surface side of the metal plate is not only the plate thickness direction, to progress even towards the portion located below the cutout portion of the metal plate . Thus, fracture surface also in a portion located below the cutout portion of the metal plate is formed. That is, before the notch is pressed greatly metal plate, so that the fracture surface is formed in a portion located below the notch. Thus, the fracture surface of the plate thickness direction of the length of the position below the cutout portion can be greater than the length of the plate thickness direction of the fracture surface of the other portions.
[0042]
　As described above, in the metal plate which is sheared by the punch according to the present invention, for the cut portions by cutout portions, it is possible to increase the length of the plate thickness direction of the fracture surface. Therefore, by cutting the notch portion of the flange deformed elongation at the time of press molding, it is possible to prevent the stretch-flange cracks. Also, the cut portions by the plane portion, it is possible to shorten the length of the thickness direction of the fracture surface, can be prevented fatigue strength decreases.
[0043]
(13) further mold according to another embodiment of the present invention has a columnar punch and said insertable hollow die punch, the punch is moved in a predetermined direction is placed on the die and a die for shearing a metal plate, wherein the die includes a hollow supporting surface supporting vital inner peripheral edge of the metal plate with the cutting blade, in a direction parallel to the predetermined direction from the inner peripheral edge and a peripheral surface inner extending, the inner peripheral edge comprises a curved portion that is curved in convex or concave in plan view, the support surface includes a flat portion, recessed from the flat portion in the predetermined direction and a plan view in and a cutout portion provided so as to include the curved portion.
[0044]
　The mold described above, notches are provided in the die. In this case, the same effect as the mold above the notch is provided on the punch is obtained.
[0045]
(14) wherein the notch depth in a direction parallel to the predetermined direction of the notch is more than 0.1 times the thickness of the metal plate and may be 0.7 times or less.
[0046]
　In this case, it is possible to appropriately delayed with respect to the timing at which the flat portion of the timing notch pushes the metal plate pushes the metal plate. Thus, in the cutting portion by the notch portion, the length of the plate thickness direction of the fracture surface can be sized appropriately.
[0047]
Method for producing a blank according to another embodiment (15) the invention provides a method of using a mold of the above manufacturing a blank for press molding, placing a metal plate on the mold die comprising to the steps, a step of shearing using a punch of the mold and placed on a metal plate on the die.
[0048]
　The blanks manufactured by the above manufacturing method, for the portion cut by the notch of the punch or die, it is possible to increase the length of the plate thickness direction of the fracture surface. Therefore, by cutting the notch portion of the flange deformed elongation at the time of press molding, it is possible to prevent the stretch-flange cracks. Also, the cut portions by the plane of the punch or die, it is possible to shorten the length of the thickness direction of the fracture surface, can be prevented fatigue strength decreases.
[0049]
(16) further method for producing a blank according to another embodiment of the present invention is a method for producing a blank according to an embodiment of the present invention using the mold described above, the metal on the die of the mold a step of mounting the plate, the placed metal plate on the die and a step of shearing using the mold punch, in the step of the shearing, the switching of the punch or the die by cutting a portion of said metal plate by away portion, at least a portion of the curved portion of the blank is formed.
[0050]
　According to the manufacturing method described above, the blank according to an embodiment of the present invention can be suitably prepared.
Effect of the invention
[0051]
　According to the present invention, a blank that can suppress the occurrence of flange cracking elongation during press molding without reducing the fatigue strength after press molding can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052]
FIG. 1 is a diagram for explaining the shearing.
FIG. 2 is a schematic sectional view showing an example of a shearing surface of the metal plate which is cut by shearing.
3 is a diagram for explaining the stretch flangeability.
It is a schematic perspective view of a blank according to the embodiment of FIG. 4 the present invention.
FIG. 5 is a schematic perspective view of a molded article according to an embodiment of the present invention.
It shows a blank according to the embodiment of FIG. 6 the present invention.
7 is an enlarged plan view showing a curved portion of the blank.
8 is a schematic perspective view of a mold according to an embodiment of the present invention.
9 is a schematic perspective view of a mold according to an embodiment of the present invention.
It is a schematic diagram illustrating a FIG. 10 punches.
11 is a diagram for explaining a method for manufacturing the blank.
12 is a diagram for explaining a method for manufacturing the blank.
13 is a diagram for explaining a method for manufacturing the blank.
14 is a diagram for explaining a method for manufacturing the blank.
15 is a diagram for explaining a method of manufacturing the blank.
It is a diagram showing another configuration of FIG. 16 notch.
It is a schematic perspective view of a mold according to another embodiment of FIG. 17 the present invention.
FIG. 18 is a schematic perspective view of a blank according to another embodiment of the present invention.
19 is a schematic perspective view showing an example of a die for manufacturing the blank of FIG. 18.
Is a plan view showing the FIG. 20 specimens.
It is a photograph of shearing surface in stretch flange portion of FIG. 21 Comparative Example 1.
22 is a photograph of shearing surface in stretch flange portion of Example 5.
23 is a diagram for explaining a stretch flange test.
DESCRIPTION OF THE INVENTION
[0053]
　Hereinafter, blank according to the present invention, the molded article, the manufacturing method of the die and the blank will be described with reference to the drawings. Note that blank according to the present invention is not limited to a specific material. As the material of the blank, for example, it can be a metal material such as steel. In the case of using a steel as the material of the blank, the type of steel is not particularly limited. There is no particular limitation on the thickness and strength of the blank may be a thickness and strength capable of shearing.
[0054]
(Configuration of the blank and the molded article)
　Figure 4 is a schematic perspective view of a blank 10 according to an embodiment of the present invention. Referring to FIG. 4, the plate-shaped blank 10 has a substantially rectangular shape in plan view, has a hole 10a in the center. Hole 10a is formed by shearing (e.g., piercing). Therefore, in this embodiment, the central portion of the blank 10, shearing surface having a ring shape is formed in plan view. In other words, the hole 10a by shearing surface of the annular is formed. It will be described later manufacturing process of the blank 10.
[0055]
　Blank 10, for example, is press-molded (burring or deep drawing, etc.) in order to parts such as for automobiles or home electronics. Specifically, for example, with reference to FIGS. 4 and 5, by subjecting the flanging extends blank 10 around the bore 10a, the molded article 12 having a flange portion 12a is manufactured. Hereinafter will be described more specifically blank 10.
[0056]
　6 (a) is a plan view showing a blank 10, FIG. 6 (b) is an A-A line enlarged sectional view of FIGS. 6 (a). In FIG. 6 (b), it shows a thickness direction of the blank 10 in the arrow X. In the following description, the thickness direction of the blank 10 and vertical blank 10.
[0057]
　Referring to FIG. 6, the blank 10 has a surface 10b and rear surface 10c extending perpendicular to the substantially parallel and plate thickness directions. Shearing surface 14 has in this order from the surface 10b side of the blank 10 in the thickness direction, sagging portion 14a, a shear plane 14b and the fracture surface 14c. In the present embodiment, the rear surface 10c side of the blank 10, back 16 are formed. In this embodiment, a 16 burr portions protruding from the rear surface 10c below the blank 10. Further, in the present embodiment, the portion from the peripheral edge of the surface 10b side of the hole 10a to the upper end of the back 16 and shearing surface 14. Accordingly, in the present embodiment, the thickness direction of the length of the shearing surface 14 is equal to the thickness t of the blank 10 (vertical distance between the surface 10b and the rear surface 10c).
[0058]
　Referring to FIG. 6 (a), in plan view, the periphery of the hole 10a (the inner edge of the shearing surface 14) has a plurality of straight portions 18 and a plurality of curved portions 20. In the present embodiment, the peripheral edge of the hole 10a (the inner edge of the shearing surface 14) has four straight portions 18 and four curved portions 20. Bend 20 in plan view, between the straight portion 18 and straight portion 18, it is concavely curved. In this embodiment, the curved portion 20 is curved so as to be recessed in an arc shape. Referring to FIGS. 5 and 6 (a), the curved portion 20 is a portion that deforms elongation during stretch flanging. Incidentally, parts or curvature sign of the curvature of the curved portion is changed as a boundary portion becomes zero, define the scope of the curved portion. That is, both ends of the curved portion is curved concavely, when asked the curvature of the inner edge of the shearing surface 14 in plan view, changes sign point curvature, or curvature is that zero.
[0059]
　Figure 7 is an enlarged plan view showing a (portion surrounded by one-dot chain line in FIG. 6 (a)) the curved portion 20 of the blank 10. Incidentally, in FIG. 7 shows the circumferential direction of the shearing surface 14 by the arrow Y.
[0060]
　Referring to FIG. 6 (b) and FIG. 7, the blank 10, the thickness direction of the average length of the fracture surface 14c of the curved portion 20, the thickness of the fracture surface 14c in the entire circumference of the shearing surface 14 greater than the average value in the direction of length.
[0061]
　The average value of the thickness direction of the length of the fracture surface 14c of the curved portion 20 is obtained as follows. First, equally divided into five regions bend 20 in the circumferential direction of the shearing surface 14. Then, at the boundary of the adjacent regions, measures the thickness direction of the length of the fracture surface 14c. That is, the curved portion 20, at circumferentially different positions four places shearing surface 14, to measure the thickness direction of the length of the fracture surface 14c. Then, by calculating the average value of the lengths of the measured four points, an average value in the thickness direction of the length of the fracture surface 14c of the curved portion 20. It can be obtained similarly for the plate thickness direction of the length of the average value of the sagging portion 14a and the shear plane 14b in the bending portion 20.
[0062]
　The average value in the thickness direction of the length of the fracture surface 14c in the entire circumference of the shearing plane 14 is obtained as follows. First, equally divided into a plurality of areas having a predetermined width shearing surface 14 in the circumferential direction. Then, at the boundary of the adjacent regions, measures the thickness direction of the length of the fracture surface 14c. In other words, at a plurality of locations circumferentially different positions of the shearing surface 14, to measure the thickness direction of the length of the fracture surface 14c. Then, by calculating the average value of the lengths of the plurality of positions measured, an average value in the thickness direction of the length of the fracture surface 14c in the entire circumference of the shearing surface 14. The predetermined width is set the bending portion 20 so that the length closest to the width in the case of equally divided into five regions in the circumferential direction. It can be determined similarly on anyone portion 14a and the thickness direction of the length of the average value of the shear plane 14b in the entire circumference of the shearing surface 14.
[0063]
　7, around the reference point 22 which is defined as follows, fracture surface 14c in the region R in the circumferential direction of the predetermined length of the shearing surface 14 (see FIG. 6 (b)) the length of the average value of the thickness direction is preferably larger than the plate thickness direction of the average length of the fracture surface 14c in the entire circumference of the shearing surface 14. Reference point 22, the curvature of the curved portion 20 is defined as a point having the maximum at the center point or plan view of the curved portion 20 in the circumferential direction of the shearing surface 14. The predetermined length in the range R, for example, thickness 50% of the length of the blank 10, 100% of the length of 1000% of the length, or the length 2000%. Further, for example, curvature in the curved portion 20 is 5 m -1 the range portion becomes more continues, may be defined as the range R of said predetermined length. The range R in this case, the curvature of the curved portion 20 can be determined by measuring at R gauge.
[0064]
　In the present embodiment, in the thickness direction of the fracture surface 14c in range R average length, rather than the average value in the thickness direction of the length of the fracture surface 14c in the entire circumference of the shearing surface 14, the blank 10 thickness of more than 10% larger. Further, in the present embodiment, the thickness direction of the length of the average value of the sagging portion 14a of the range R is 20% or less of the plate thickness of the blank 10. The average value in the thickness direction of the length of the fracture surface 14c in the region R is obtained as follows. First, equally divides the shearing surface 14 in the range R in the circumferential direction into five regions. Then, at the boundary of the adjacent regions, measures the thickness direction of the length of the fracture surface 14c. That is, in the range R, the circumferential direction position different four places shearing surface 14, to measure the thickness direction of the length of the fracture surface 14c. Then, by calculating the average value of the lengths of the measured four points, an average value in the thickness direction of the length of the fracture surface 14c in the region R. It can be determined similarly on the average value in the thickness direction of the length of the sagging portion 14a and the shear plane 14b at the range R.
[0065]
(Blank and effect of the molded article)
　in the blank 10, the length in the thickness direction of the fracture surface 14c is increased in the curved portion 20. In other words, the deformable portion extending at the time of press molding, it is possible to reduce the ratio of shear plane 14b. Thus, the curved portion 20 is easily deformed elongation, be flanged elongation curved portion 20 can be suppressed stretch-flange cracks is generated in the curved portion 20. Further, portions other than the curved portion 20, it is possible to reduce the ratio of the fracture surface 14c than the curved portion 20. In other words, the rate of work hardening by shear surface 14b can be increased. Thus, in the portion other than the curved portion 20, sufficient fatigue strength can be obtained. On the other hand, the bending portion 20, a large proportion of the fracture surface 14c. Therefore, fatigue strength of the curved portion 20 is lowered in a state before press-forming. However, work hardening by flanging elongation during press molding occurs, the fatigue strength of the curved portion 20 is increased. As a result, sufficient fatigue strength is obtained in the molded article 12 after press molding. These results, while suppressing the fatigue strength of the molded article 12 is reduced, it is possible to prevent the flange cracks extending in producing a molded article 12 from the blank 10 occurs.
[0066]
　In blank 10, for example, the thickness direction of the length of the mean value of the fracture surface 14c in the region R is, is set larger than the thickness direction of the length of the mean value of the fracture surface 14c in the entire circumference of the shearing surface 14 that. In this case, it is possible to suppress the stretch-flange cracks is generated in the center portion of the curved portion 20 (positional heart or portion where the curvature increases).
[0067]
　In blank 10, the length of the average value in the thickness direction of the fracture surface 14c in the region R is than the average value in the thickness direction of the length of the fracture surface 14c in the entire circumference of the shearing surface 14, the plate blank 10 10% of the thickness of more than large. Thus, it can be sufficiently suppressed that the stretch-flange cracks is generated in the center portion of the curved portion 20.
[0068]
　In blank 10, the average value in the thickness direction of the length of the sagging portion 14a of the range R is 20% or less of the plate thickness of the blank 10. Thus, it is possible to more reliably suppress the occurrence of stretch-flange cracks.
[0069]
　In blank 10, the predetermined length in the range R is set to, for example, 50% of the length of the plate thickness of the blank 10. In this case, it is possible to more reliably prevent the stretch-flange cracks is generated in the center portion of the curved portion 20. Also, the range above predetermined length of R is, for example, may be set 2000% of the length the thickness of the blank 10. In this case, it is possible to suppress the stretch-flange cracking occurs at a sufficient range of the curved portion 20. Furthermore, range R, for example, curvature 5 m -1 may be a portion to be the least. In this case, even in the curved portion 20 of the flange deformation elongation during press-forming becomes large, sufficiently prevent the occurrence of stretch-flange cracks.
[0070]
　In the blank 10, a plurality of curved portions 20 are provided, in any one of the curved portion 20 may satisfy the requirements of the present invention. Therefore, either the curved portion 20 of the plurality of curved portions 20 may not meet the requirements of the present invention.
[0071]
(Mold blank preparation and method of manufacturing the blank)
　A method for manufacturing the blank 10 will be described using a die and mold for manufacturing the blank 10 described above.
[0072]
　8 and 9 are a schematic perspective view of a mold 24 according to an embodiment of the present invention. Referring to FIG. 8, the mold 24 comprises a hollow die 28 having an insertable hole 28a of the columnar punch 26 and the punch 26. As will be described in detail later with reference to FIG. 8, in manufacturing the blank 10 described above, first, placing the rectangular shape in plan view of the metal plate 30 on the die 28. Then, referring to FIGS. 8 and 9, the punch 26 is moved in the thickness direction of the metal plate 30 (the method shown by the arrow Z in FIG. 8), so that the lower end of the punch 26 is inserted into the hole 28a in, pushing the central portion of the metal plate 30 by the punch 26. Thus, the central portion of the metal plate 30 is cut (sheared), the hole 10a (see FIG. 4) is formed. That is, above the blank 10 (see FIG. 4) is manufactured. Hereinafter, the punch 26 and the die 28 will be specifically described. In the following description, the moving direction of the punch 26 at the time of shearing the metal plate 30 (the direction indicated by the arrow Z) and the vertical direction. Further, the lateral direction perpendicular to the upper and lower direction.
[0073]
　Figure 10 is a schematic view showing the punch 26, (a) is a side view of the punch 26, (b) is a bottom view of the punch 26.
[0074]
　Referring to FIG. 10, the punch 26 has a bottom surface 32, an outer peripheral surface 34 extending upwardly from the outer peripheral edge 32a of the bottom surface 32. In the punch 26, the outer peripheral edge 32a of the bottom surface 32 is a cutting blade. Therefore, the outer peripheral edge 32a, as can be formed a hole 10a (see FIG. 4), like the hole 10a having a substantially rectangular shape in plan view.
[0075]
　Figure 10 Referring to (b), the outer peripheral edge 32a of the bottom surface 32 includes a curved portion 36 a plurality of (four in this embodiment) which is curved in a convex shape in the bottom view (plan view). In this embodiment, each of the four corners of the substantially rectangular outer peripheral edge 32a, the curved portion 36 is provided.
[0076]
　FIG. 10 (a), referring to (b), the bottom surface 32 includes a flat portion 38, and a plurality of notch 40 that is recessed from the planar portion 38 upward (a direction parallel to the moving direction of the punch 26) . Figure 10 (a), the respective notch 40 has a rectangular shape as viewed from the side. More specifically, FIG. 10 (a), referring to (b), each notch 40, the side wall portion 40a extending from the flat portion 38 upward, 40b, and 40c, the side wall portions 40a, 40b, 40c and a ceiling portion 40d provided so as to connect the upper edge of. Side wall portions 40a, 40b, 40c are provided so as to form a substantially U-shaped in bottom view. In the present embodiment, provided to a side wall portion 40a and the side wall portion 40b are opposed to each other, and the side wall portion 40c is provided so as to connect the one end portion of the one end and the side wall 40b of the side wall portion 40a. Ceiling portion 40d is provided substantially parallel to the flat portion 38. Figure 10 Referring to (b), each notch 40, in the bottom view (plan view), is formed so as to include the center of the curved portion 36 (apex).
[0077]
　Figure 10 (a), the notch depth d of the notch 40, to set metal plate 30 over 0.1 times the thickness of the (see FIG. 9) and 0.7 times or less preferable. Figure 10 Referring to (b), the width w of the notch 40, the blank 10 is appropriately set depending on the size of the curved portion 20 (see FIG. 6) (see FIG. 6), the metal plate 30 preferably set to 50 to 2000% of the size of the plate thickness, it is more preferable to set the size of 100-1000%. Moreover, as the center line in the width direction of the notch 40 when cutting the metal plate 30 is positioned on the reference point 22 of the curved portion 20 of the blank 10, it is preferable to form the mold 24. The length of the notch 40 L is preferably at least the thickness of the metal plate 30.
[0078]
　Referring to FIG. 8, the die 28 has a hollow support surface 42 for supporting the metal plate 30, from the inner circumferential edge 42a of the supporting surface 42 and the inner peripheral surface 44 extending downward. In the die 28, the inner peripheral edge 42a of the supporting surface 42 is a cutting blade. Inner peripheral edge 42a of the support surface 42 has a shape which is similar to the outer peripheral edge 32a of the bottom surface 32, having a plurality of curved portions 46 corresponding to the plurality of curved portions 36 of the outer peripheral edge 32a. The bending portion 46 has a shape concavely curved so as to correspond to the shape of the curved portion 36. Clearance between the punch 26 and the die 28 (i.e., the clearance between the outer peripheral edge 32a and the inner peripheral edge 42a) is set to, for example, about 10% of the size of the plate thickness of the metal plate 30.
[0079]
　Hereinafter, a manufacturing method of the blank 10 by the die 24 described above will be specifically described with reference to the drawings. 11 to 15, in the manufacture of the blank 10, a punch 26 is a conceptual diagram illustrating a relationship between die 28 and the metal plate 30. Specifically, (a) 11 to 15 (see FIG. 8) the outer peripheral surface 34 of the curved portion 36 (see FIG. 8) near the punch 26, the bending portion 46 of the die 28 (see FIG. 8) in the vicinity of the inner peripheral surface 44 (see FIG. 8), and a curved portion 36 is a conceptual diagram showing the relationship between the metal plate 30 located between the (see FIG. 8) and the curved portion 46 (see FIG. 8). 11 in ~ 15 (b), the flat portion 38 of the punch 26, conceptual diagram showing the relationship between the metal plate 30 located between the supporting surface 42 of the die 28, and a flat portion 38 and the supporting surface 42 (FIG. 11 it is a conceptual view corresponding to a portion indicated by line b-b of (a)). 11 in ~ 15 (c), the notch 40 of the punch 26, conceptual diagram showing the relationship between the metal plate 30 located between the support surface 42 and the notch 40 of the die 28 and the support surface 42 (FIG. it is a 11 conceptual view corresponding to a portion indicated by line c-c of (a)). In (a) of 11-15, in order to clarify the positional relationship, it is hatched in the metal plate 30.
[0080]
　Referring to FIG. 8, as described above, in manufacturing the blank 10, firstly, placing a metal plate 30 on the supporting surface 42 of the die 28. Thereafter, as shown in FIGS. 11 and 12, by moving the punch 26 pushes the flat portion 38 of the punch 26 to the metal plate 30. Thus, the outer edge of the flat portion 38, shearing surface 48 on the surface side of the metal plate 30 (see FIG. 12) is formed. Further, in a portion facing the outer edge of the flat portion 38 of the contact portion between the rear surface of the die 28 and the metal plate 30, the shear surface 50 is formed by the inner peripheral edge 42a of the supporting surface 42 of the die 28. FIG. 12 (a), the as shown in (c), at the time the amount is small pushing punch 26, a ceiling portion 40d of the cutout portion 40 is not in contact with the metal plate 30. Therefore, in the metal plate 30, the shear surface in the portion facing the notch 40 is not formed. Further, among the contact portion between the die 28 and the metal plate 30, the portion located below the notch 40 since no large force is applied, it is not formed shear surface in the partial.
[0081]
　FIG. 13 (a), the (b), the by further pushing in the punch 26, the surface of the metal plate 30, is caused cracks 52 coming to the contact portion between the outer edge of the flat portion 38. Further, FIG. 13 (a), the (c), the ceiling 40d of the notch 40 is also in contact with the surface of the metal plate 30. Thus, at the contact portion between the ceiling portion 40d and the metal plate 30, metal plate 30 Nisen section 54 is formed. Furthermore, as shown in FIG. 13 (a) ~ (c), the contact portion between the inner peripheral edge 42a and the metal plate 30 of the support surface 42 of the die 28, the crack 56 come to the metal plate 30 occurs.
[0082]
　By further pushing in the punch 26, cracks 52, 56 progress in the thickness direction of the metal plate 30, as shown in FIG. 14 (a), (b), broken on the surface side and back surface side of the metal plate 30 section 58, 60 is formed. FIG. 14 (a), the as shown in (c), cracks 52 and 56 (see FIG. 13) is also toward the contact portion between the metal plate 30 not only the plate thickness direction notch 40 to progress. Thus, even under the notch 40, the fracture surface 58, 60 is formed. That is, before the notch 40 is pressed greatly to the metal plate 30, to form a sufficiently large fracture surface 14c (see FIG. 6) in a portion located below the notch 40 of the metal plate 30 can. Finally, by further pushing in the punch 26, as shown in FIG. 15, further progress fracture surfaces 58 and 60, a portion of the metal plate 30 is cut. As a result, the blank 10 is completed.
[0083]
(Effect of the manufacturing method using a die and mold)
　when producing blank 10 by the manufacturing method described above using a die 24, before the notch 40 is pressed greatly to the metal plate 30, it is possible to form the fracture surface 14c sufficiently large in a portion located below the notch 40 of the metal plate 30. Thus, the thickness direction of the length of the fracture surface 14c of the position below the notch 40, can be made larger than the plate thickness direction of the length of the fracture surface 14c of the other portions. Therefore, by cutting the notches 40 parts of the flange deformed elongation at the time of press molding, it is possible to prevent the stretch-flange cracks. Also, the cut portions by the plane portion 38, it is possible to shorten the plate thickness direction of the length of the fracture surface 14c, it is possible to prevent the fatigue strength is lowered.
[0084]
　In the mold 24, the notch depth of the notch 40 is set, for example, more than 0.1 times the thickness of the metal plate 30 and 0.7 times or less. In this case, the timing at which the notch 40 pushes the metal plate 30 is planar portion 38 can be delayed properly with respect to the timing of pushing the metal plate 30. Thus, in the cut portions by notch 40, thereby the plate thickness direction of the length of the fracture surface 14c to the appropriate size.
[0085]
　Mold 24 according to the present invention can be manufactured only by locally changing the shape of the cutting blades of a conventional punch (portion corresponding to the outer peripheral edge 32a of the bottom surface 32). Therefore, if the protruding portions are provided on the punch (for example, see Patent Document 1 described above) in comparison with, it is possible to reduce the manufacturing cost of the mold. Also in shearing tool of various shapes, since it is not necessary to consider the whole of the tool shape it can be easily applied to mass production site. Further, when the flange crack growth in press forming has occurred, the punch can be added a new notch 40 in the end mill or the like to the portion corresponding to the position where the cracking of the blank occurs. As a result, it is possible to solve the flange crack growth in the field correspondence. From this point, it can be readily applied to mass production site. The same applies to the die to be described later with another punch and notch described later.
[0086]
　Incidentally, the likely site stretch flange crack occurs in the shearing surface of the blank, previously, it is preferable to identify by performing numerical calculations or stretch flange testing. Then, to cut the notches of the identified site may constitute a mold. In this case, it is possible to reduce the processing cost of the manufacturing cost and the blank mold.
[0087]
(Another example of the mold)
　In the above embodiment, the punch 26 has been described having a side view rectangular notch 40, the shape of the notch is not limited to the above example. For example, as shown in FIG. 16 (a), it may be provided notch 62 having a side view trapezoidal shape to the punch. Incidentally, notch 62, similar to the notch 40, a side wall portion 62a, 62b, a 62c and the ceiling portion 62d. Side wall portions 62a, 62b are inclined such that progressively spacing increases toward the upper side as viewed from the side is narrowed. As a result of various studies of the present inventors, in order to advance efficiently crack the notch 62, the side wall portion 62a with respect to the vertical plane, it is preferable inclination angle of 62b is 30 ° or less.
[0088]
　Further, for example, as shown in FIG. 16 (b), may be provided notch 64 having a side view semicircular punch. Further, for example, as shown in FIG. 16 (c), it may be provided flat portion 38 and the side wall portion 66a, the boundary between the 66b R portion 66c, a notch 66 having a 66d in punch. In this case, it is possible to prevent damage to the boundary portion between the cutout portion 66 and the flat portion 38. Incidentally, R portions 66c, 66d radius of curvature is preferably from 0.01 ~ 0.1 mm. Further, for example, as shown in FIG. 16 (d), may be provided flat portion 38 and the side wall portion 68a, chamfer 68c at the boundary between the 68b, the cutout portion 68 having a 68d in punch. In this case, it is possible to prevent damage to the boundary portion between the cutout portion 68 and the flat portion 38.
[0089]
　In the above embodiment has been described punch 26 having a plurality of notch 40, instead of providing the notch in the punch may be provided with a notch in the die.
[0090]
　Figure 17 is a schematic perspective view of a mold 24a according to another embodiment of the present invention. The mold 24a is different from the mold 24 shown in FIG. 8 as shown in FIG. 17, a point having a change to die 72 points and die 28 has a punch 70 in place of the punch 26.
[0091]
　The punch 70 is different from the punch 26 is that it does not have a plurality of notch 40 (see FIG. 8). Die 72 is different from the die 28, the respective curved portions 46, is that it has a cutout portion 74 having the same shape as the notch 40. A detailed description is omitted, in the case of producing a blank 10 using a mold 24a, the same effect as in the case of producing a blank 10 using a mold 24 described above can be obtained.
[0092]
(Another example of blank)
　In the above embodiment has been described blank 10 having a hole 10a formed by piercing, the shape of the blank is not limited to the above example. The present invention can blank shearing surface to the outer peripheral edge is formed, for example, in a blank having a shearing surface formed by punching the outer periphery apply.
[0093]
　Figure 18 is a schematic perspective view of a blank according to another embodiment of the present invention. Referring to FIG. 18, plate-like and elongate blank 76 includes a central portion in the longitudinal direction has a shape that becomes narrower than both end portions in the longitudinal direction. Blank 76 is, for example, are manufactured by punching, with a shearing surface 78 having a ring shape in plan view at the outer peripheral edge. In plan view, the outer edge of the shearing surface 78 has a plurality of curved portions 80 curved in a concave shape. Although detailed description is omitted, shearing surface 78 has the same configuration as that of the shearing surface 14 of the blank 10, the curved portion 80 has the same configuration as the curved portion 20 of the blank 10. Accordingly, even in the blank 76, the same effect as the blank 10 described above is obtained.
[0094]
　Next, a description will die for manufacturing the blank 76 described above.
　Figure 19 is a schematic perspective view showing an example of a die for manufacturing the blank 76. Referring to FIG. 19, the mold 82 includes a die 86 having an insertable hole 86a of the columnar punch 84 and the punch 84.
[0095]
　Referring to FIG. 19, the punch 84 has a bottom surface 88, an outer peripheral surface 90 extending upwardly from the outer peripheral edge 88a of the bottom surface 88. In the punch 84, the outer peripheral edge 88a of the bottom surface 88 is a cutting blade. Therefore, the outer peripheral edge 88a has the same shape as the blank 76.
[0096]
　The outer peripheral edge 88a of the bottom surface 88, a plurality (two in this embodiment: Only one curved portion 92 in FIG. 19 shown.) Curved concavely in the bottom view (plan view) includes a curved portion 92 of the. Bottom 88, like the above-mentioned bottom surface 32 (see FIG. 10), a flat portion 94, a plurality of recessed from the planar portion 94 upward (a direction parallel to the direction of movement of the punch 84) (two in the present embodiment.) and a cutout portion 96 of the. Although detailed description is omitted, notch 96 has the same configuration as cutout portion 40,62,64,66 or 68 described above. Notch 96, in the bottom view (plan view), is formed to include a central (vertex) of the curved portion 92.
[0097]
　Die 86 has a hollow support surface 98 for supporting the metal plate (not shown), from the inner circumferential edge 98a of the supporting surface 98 and the inner peripheral surface 100 extending downward. In the die 86, the inner peripheral edge 98a of the supporting surface 98 is a cutting blade. Inner peripheral edge 98a of the support surface 98 has a shape which is similar to the outer peripheral edge 88a of the bottom surface 88, having a plurality of curved portions 102 corresponding to the plurality of curved portions 92 of the outer peripheral edge 88a. Curved portion 102 has a curved shape to the convex shape so as to correspond to the shape of the curved portion 92. Clearance between the punch 84 and the die 86 is set to, for example, about 10% of the size of the plate thickness of the metal plate.
[0098]
　Also in the mold 82, the punch 84 similarly to the punch 26 described above has a notch 96. Thus, even in the mold 82, the same effect as the mold 24 described above can be obtained. Similarly to the mold 24a in FIG. 17, instead of providing the notch 96 on the punch 84, it may be provided with a respective notch in the curved portion 102 of the die 86. In this case, the same effect as the mold 82 is obtained.
Example
[0099]
　The following examples illustrate the present invention in more detail, the present invention is not limited to the following examples.
[0100]
(First embodiment)
　to 780MPa grade cold rolled steel sheet having a thickness of 1.6 mm (workpiece), the same shape of the hole (30 mm × 30 mm and the hole 10a shown in FIG. 4, the curvature of the curved portion (R portion) the radius 5 mm), the shape of the punch (notch shown in FIG. 8 is a rectangular aperture width:. 0 ~ 15 mm, notch director of 0 to punch bottom throughout corners a boundary of the cutting edge and the notch portion formed by R1.0 rounded) to prepare a blank of examples 1-12. Moreover, using a punch having the same configuration as the punch of Figure 8 except that it does not have the notch to produce a blank of Comparative Example 1. Further, to produce a blank of Comparative Example 2 by a punch which is described in Patent Document 2. Clearance between the die and punch was set at 10% of the thickness of the workpiece.
[0101]
　Against a blank prepared as described above, performs burring using a burring punch of a truncated pyramid shaped ridge is curved (not shown), the flange portion as shown in FIG. 5 (burring portion) It was formed (burring test). The burring test, a burring height limit cracking occurs in the shearing surface was measured to evaluate the stretch flange formability.
[0102]
　To investigate the fatigue strength of the shearing unit was conducted plane bending fatigue test A test piece was cut out as shown in FIG. 20. Fatigue test pieces were cut out by cutting. Subjected to abrasive machining to cutting unit, increased flatness. The Shearing portion (portion corresponding to the hole formed by the punch), polishing is not performed. The maximum value of the stress applied to the test piece surface (the bending calculated from moment) as an evaluation value, and sets a stress ratio -1. Fatigue strength was the stress fracture limit at the time it reaches 10 million times life was evaluated as the fatigue limit.
[0103]
　The results of the construction and the burring test notches of the punch used for piercing shown in Table 1. Further, Table 2 shows anyone rate in shearing surface of the position not located and the corresponding equivalent elongation flange, shear plane ratio, and the fracture surface ratio. Here, stretch flange portion has a portion (four corners) corresponding to the curved portion 20 described with reference to FIG. Incidentally, it shows a photograph of the shearing surface of the stretch-flange portion of Comparative Example 1 and Example 5 in FIGS. 21 and 22 for reference.
[0104]
[Table 1]

[0105]
[Table 2]

[0106]
　Burring test results, in the blank of Examples 2 to 12 notch depth ratio of the cut-out portion with respect to the plate thickness of the blank (%) is within the range of 10% to 70%, compared to the blank of Comparative Example 1 , burring height is increased. Moreover, in the blank of improved so the Comparative Example 2 the fracture surface rate in the whole circumference of the shearing surface, the crack in the shearing surface of the stretch flangeability outer occurs, the fatigue strength is lowered. On the other hand, in the blank of Examples 1-12, does not occur even crack the other stretch flangeability portion, the fatigue strength did not decrease.
[0107]
　In, was used 780MPa grade cold rolled steel sheet having a thickness of 1.6 mm, be employed steel other plate thickness and strength, that the same effect can be obtained, the present inventors present embodiment, It was confirmed experimentally.
[0108]
(Second embodiment)
　the 590MPa class cold-rolled steel sheet having a thickness of 1.6 mm (workpiece), and shearing with a punch 84 shown in FIG. 19 has the same shape as the blank 76 shown in FIG. 18 to prepare a blank of examples 1-12. Moreover, using a punch having the same configuration as punch 84 of FIG. 19 except that it does not have the notch to produce a blank of Comparative Example 1. Clearance between the die and punch was set at 10% of the thickness of the workpiece.
[0109]
　Shows an embodiment of a flange test stretch in FIG. 23 (a), shows the shape of the flange workpiece extends in FIG. 23 (b). As shown in FIG. 23 (a), the stretch flange test, placing the blank 108 into a die 106 supported to the pad 104. Then, by pressing the blank 108 by the punch 110, performs flanging to prepare a stretch flanging article 112 shown in FIG. 23 (b).
[0110]
　Stretch flange study, various conditions stretch flange height h1 is different (5 mm, 10 mm, 15 mm, 20 mm and 25 mm), i.e., was carried out in five conditions that plastic deformation is different in the shearing plane with the stretch flange test.
[0111]
　The results of the construction and stretch flange testing notches of the punch used in the shearing shown in Table 3. Table 4 shows anyone rate in shearing surface of the position not located and the corresponding equivalent elongation flange, shear plane ratio, and the fracture surface ratio.
[0112]
[table 3]

[0113]
[Table 4]

[0114]
　Results of stretch flange test, the blank of Examples 1-12, the stretch-flange cracking did not occur in the shearing surface. On the other hand, in the blank of Comparative Example 1, the stretch-flange cracking occurs.
Industrial Applicability
[0115]
　According to the present invention, the tool manufacturing cost is low, can be easily applied to mass production site, it is possible to provide a shearing method capable of suppressing the stretch flange crack at shearing surface. Accordingly, the present invention has high applicability in the steel processing industry.

claims
[Claim 1]
　A plate-like blank for press molding manufactured by shearing a metal plate,
　has a shearing surface formed annularly in a and viewed shear surface and fracture surface in the thickness direction ,
　the edge of the shearing surface in a plan view has a curved portion which is curved concavely,
　the average length of the value of the fracture surface of the plate thickness direction in the curved portion, broken the completely around the shearing surface greater than the average value of the thickness direction of the length of the section, the blank.
[Claim 2]
　When the point at which the curvature of the curved portion is maximum at the center point or viewed in the circumferential direction of the shearing surface of the curved portion as the reference point of the curved portion, the circumferential direction of the center of the reference point the plate mean value of the thickness direction of the length of the fracture surface at the range of the predetermined length is greater than the plate mean value of the thickness direction of the length of the fracture surface of the entire circumference of the shearing surface, wherein blank according to claim 1.
[Claim 3]
　The plate mean value of the thickness direction of the length of the fracture surface in the range of the predetermined length than said average value of the thickness direction of the length of the fracture surface of the entire circumference of the shearing surface, wherein thickness of more than 10% greater, blank according to claim 2.
[Claim 4]
　The shearing surface, the plate further comprises a sag portion located opposite to the fracture surface in between the shear plane in the thickness direction,
　the thickness of the sagging part of the range of the predetermined length the average value of the direction of the length is 20% or less of the plate thickness, the blank according to claim 2 or 3.
[Claim 5]
　Said predetermined length is 50% of the length of the plate thickness of the blank, the blank according to any of claims 2 4.
[Claim 6]
　Said predetermined length, said plate is 2000% of the length of the thickness, the blank according to any of claims 2 4.
[Claim 7]
　It said predetermined length range, curvature 5 m -1 is a portion serving as the above blank according to any one of claims 2 to 4 in.
[8.]
　The metal plate has a hole formed by piercing,
　the shearing surface is formed on the edge of the hole, blank according to any one of claims 1 to 7.
[Claim 9]
　The metal plate has an outer edge formed by stamping,
　the shearing surface is formed on the outer periphery, blank according to any one of claims 1 to 7.
[Claim 10]
　The curved portion is a portion that deforms the elongation at the time of press molding, the blank according to any one of claims 1 to 9.
[Claim 11]
　Blank according to any one of claims 1 to 10 were subjected to press molding, the molded product.
[Claim 12]
　Has a columnar punch and the punch insertable hollow die, a metal plate is moved is placed on a die of the punch in a predetermined direction a die for shearing,
　the punch, has a bottom surface outer circumferential edge is the cutting blade, and an outer peripheral surface extending in a direction parallel from the outer peripheral edge in the predetermined direction,
　wherein the outer peripheral edge includes a curved portion that is curved in convex or concave in plan view,
　the bottom surface includes a flat portion and a notch portion provided so as to include the curved portion in the recess and viewed in the predetermined direction from the flat portion, the mold.
[Claim 13]
　Has a columnar punch and the punch insertable hollow die, a metal plate is moved is placed on a die of the punch in a predetermined direction a die for shearing,
　the die, a hollow supporting surface supporting vital inner peripheral edge of the metal plate with the cutting blade, and a inner peripheral surface extending in a direction parallel from the inner peripheral edge in the predetermined direction,
　the inner peripheral edge in a plan view includes a curved portion curved in convex or concave,
　the support surface includes a flat portion and a notch portion provided so as to include the curved portion in the recess and viewed in the predetermined direction from the flat portion, Mold.
[Claim 14]
　Wherein the notch depth in a direction parallel to the predetermined direction of the notch is less plate 0.1 times and 0.7 times the thickness of the metal plate, a mold according to claim 12 or 13 .
[Claim 15]
　A method of manufacturing a blank for a press molding using a mold according to any of claims 12 to 14,
　the step of placing a metal plate on the die on the die,
　the placing on the die and a step of shearing using the die punch location metal plate, blank manufacturing method of.
[Claim 16]
　A method of manufacturing a blank according to any one of claims 1 to 10 using a mold according to any of claims 12 to 14,
　the step of placing a metal plate on the mold die When,
　the placed metal plate on the die and a step of shearing using the mold punch,
　in the step of the shearing, the metal plate by the notch of the punch or the die by cutting a portion of at least a portion of the curved portion of the blank is formed, the blank manufacturing method of.