JP2018158384A - Shearing method and shearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the influence of work hardening on a member end face after fracture or to extend the life of a member by guiding a fracture surface generated in a workpiece in shearing to an appropriate position. SOLUTION: The shearing method includes a step of bringing the lower blade into contact with the lower surface of the work material, and the work material is relatively movable with respect to the lower blade in the thickness direction and is relatively movable in the thickness direction. The process of moving the upper blade facing the lower blade with a clearance in the surface direction of the work material that is vertical in the thickness direction until it abuts on the upper surface of the work material, and the distance from the upper blade in the surface direction is the clearance. The step of forming a groove on the upper surface of the work material at a position of 40% or more and 120% or less, and the upper blade in contact with the upper surface of the work material are defined by the groove on the upper surface of the work material as the start or end. It includes a step of further moving in the thickness direction until a fracture surface is generated. [Selection diagram] Fig. 1

Description

  The present invention relates to a shearing method and a shearing apparatus.

  Shearing is performed for cutting, punching, punching, shaving, trimming, and the like of metal members in the manufacture of metal parts used in, for example, automobiles, railway vehicles, building materials, ships, and home appliances. Generally, the shearing process is performed by pushing the upper blade from the upper side against the lower blade abutted on the member. At this time, the member plastically deforms between the upper blade and the lower blade, and finally breaks. In such a shearing process, it is known that a part affected by work hardening accompanying plastic deformation remains on the end face of the member after fracture. When performing flange-up as a post process, cracks may occur in the parts affected by work hardening.

  Therefore, various techniques for obtaining a sheared surface that is excellent in stretch flangeability by suppressing work hardening of a member during shearing have been proposed. For example, Patent Document 1 describes a technique for obtaining a sheared surface that has excellent stretch flange workability by appropriately setting the inclination angle of a punch blade using numerical simulation. Patent Document 2 discloses a technique for obtaining a sheared surface having excellent stretch flange workability by gradually increasing the clearance as it deviates from the dangerous portion determined based on the simulation of stretch flange cracking in a subsequent process. Have been described.

JP 2011-88152 A JP-A-2006-87642

  However, for example, even if the techniques described in Patent Documents 1 and 2 described above are adopted, a portion that is affected by work hardening accompanying plastic deformation does not remain on the end surface of the member. This is because when a fracture surface is generated along the surface connecting the upper blade and the lower blade in the shearing process, the fracture surface is generated across the work hardening region that has already occurred. In other words, if the fracture surface can be generated at a position away from the surface connecting the upper blade and the lower blade in the shearing process, the work hardening region remaining on the end face of the member after the fracture can be further reduced. There is a possibility.

  By the way, in the shearing process, when the fracture surface is generated from the upper blade, it is necessary to sharpen the corner of the upper blade in order to stably generate the fracture surface. However, when the corner of the upper blade is sharp, wear or chipping easily occurs due to contact with the workpiece, and the upper blade needs to be replaced in a relatively short period of time due to the change in the shape of the corner. Often becomes. On the other hand, if the fracture surface can be generated at a position away from the upper blade, it is not necessary to sharpen the corner of the upper blade. It is possible to use the upper blade over the entire area.

  Therefore, the present invention makes it possible to reduce the influence of work hardening on the end face of the member after breaking or to extend the life of the member by guiding the fracture surface generated in the workpiece during shearing to an appropriate position. It is an object of the present invention to provide a new and improved shearing method and shearing apparatus.

According to some aspects of the invention, the following is provided.
[1] A step of bringing the lower blade into contact with the lower surface of the workpiece;
The upper blade that is movable relative to the lower blade in the thickness direction of the work material and that has a clearance in the surface direction of the work material perpendicular to the thickness direction is opposed to the lower blade. Moving in the thickness direction until it contacts the upper surface of
Forming a groove on the upper surface of the workpiece at a position where the distance from the upper blade in the surface direction is 40% or more and 120% or less of the clearance;
And further moving the upper blade in contact with the upper surface of the workpiece in the thickness direction until a fracture surface having a groove on the upper surface of the workpiece as a start or end is generated.
[2] The shearing method according to [1], wherein the groove on the upper surface of the workpiece is formed before the upper blade contacts the upper surface of the workpiece.
[3] The shearing method according to [1], wherein the groove on the upper surface of the workpiece is formed after the upper blade contacts the upper surface of the workpiece and before the fracture surface is generated.
[4] The method further includes a step of forming a groove in the lower surface of the workpiece near the lower blade,
The shearing method according to any one of [1] to [3], wherein the fracture surface is generated with one of the grooves on the upper surface and the lower surface of the workpiece as a start end and the other as a termination.
[5] The shearing method according to any one of [1] to [4], wherein the workpiece is a steel plate having a tensile strength of 780 MPa or higher.
[6] a lower blade that contacts the lower surface of the workpiece;
An upper blade that is movable relative to the lower blade in the thickness direction of the workpiece, and that faces the lower blade with a clearance in the surface direction of the workpiece perpendicular to the thickness direction;
And a groove forming means for forming a groove on the upper surface of the workpiece at a position where the distance from the upper blade is 40% or more and 120% or less of the clearance in the surface direction.
[7] The apparatus further includes a holder for sandwiching the workpiece with the lower blade,
The groove forming means includes the protruding portion formed at the end of the holder facing the upper blade in the surface direction, according to [6].
[8] The groove forming means is movable in the thickness direction together with the upper blade, and the protrusion is pushed in from the upper surface of the workpiece in the thickness direction later than the upper blade when the upper blade moves in the thickness direction. The shear processing apparatus according to [6], including a section.
[9] The shearing device according to any one of [6] to [8], further comprising additional groove forming means for forming a groove on the lower surface of the workpiece near the lower blade.

  According to the present invention, it is possible to reduce the influence of work hardening on the end face of a member after breakage or extend the life of a member by guiding a fracture surface generated in a workpiece in shearing to an appropriate position.

It is sectional drawing which shows the outline | summary of the shearing process which concerns on one Embodiment of this invention. It is a figure which shows the other example of the shape of the groove | channel in FIG. It is a figure which shows typically the behavior of the workpiece in one Embodiment of this invention. 1 is a schematic cross-sectional view showing a first example of a shearing apparatus having groove forming means according to an embodiment of the present invention. It is a schematic sectional drawing which shows the 2nd example of the shear processing apparatus which has the groove | channel formation means which concerns on one Embodiment of this invention. It is a schematic sectional drawing which shows the 3rd example of the shearing apparatus which has a groove | channel formation means which concerns on one Embodiment of this invention. It is a figure for demonstrating the modification of one Embodiment of this invention. It is a figure for demonstrating the model of the finite element analysis which concerns on 1st Example of this invention. It is a graph which shows the analysis result of 1st Example of this invention. It is a graph which shows the analysis result of 1st Example of this invention. It is a graph which shows the experimental result of 2nd Example of this invention. It is a graph which shows the experimental result of 2nd Example of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a cross-sectional view showing an outline of shearing according to an embodiment of the present invention. Referring to FIG. 1, the shearing device 1 includes a die 2, a punch 3, and a holder 4. The die 2 is formed with a lower blade 21 that contacts the lower surface of the workpiece 6. An upper blade 31 is formed on the punch 3. The punch 3 is driven by an electric motor or a hydraulic mechanism (not shown) and can move relative to the die 2 in the thickness direction of the workpiece 6. As the punch 3 moves, the upper blade 31 is brought into contact with the upper surface of the workpiece 6 from a position above the workpiece 6 and further pushed into the workpiece 6 as shown in the figure. It is. In the process in which the upper blade 31 is pushed into the workpiece 6, a fracture surface is generated in the workpiece 6, and thereby the portion of the workpiece 6 into which the punch 3 is pushed is cut off. The holder 4 is brought into contact with the upper surface of the workpiece 6 and sandwiches the workpiece 6 with the die 2.

  Here, a groove 7 is formed on the upper surface of the workpiece 6 before the punch 3 is brought into contact with the upper surface of the workpiece 6 or after the punch 3 is pushed into the workpiece 6. Is done. The groove 7 is formed at a position where the distance from the upper blade 31 is w in the surface direction of the workpiece 6, that is, in the direction perpendicular to the thickness direction of the workpiece 6. The upper blade 31 faces the lower blade 21 with a clearance C in the surface direction of the workpiece 6, but in this embodiment, the distance w is set to 40% or more and 120% or less of the clearance C. The cross-sectional shape of the groove 7 is illustrated as a symmetric V-shape, but is asymmetrical, for example, a V-shape in which one side is formed perpendicular to the surface of the workpiece 6. May be. Moreover, although the bottom part shape of the groove | channel 7 is illustrated in figure so that an acute angle may be made, you may have a curvature. In this case, the radius of curvature is preferably 0.1 mm or less, and more preferably 0.05 mm or less.

  FIG. 2 is a diagram showing another example of the shape of the groove in FIG. In the example shown in FIG. 2, the cross-sectional shape of the groove 7c formed on the upper surface of the workpiece 6 is a shape in which a plurality of V-shaped grooves are combined. In this case, the distance w may be defined as the distance from the upper blade 31 to the bottom of the groove 7 c closer to the punch 3. As will be described later, the groove formed on the upper surface of the workpiece in the present embodiment forms the start end or the end of the fractured surface due to the concentration of stress. Therefore, the cross-sectional shape of the groove can be arbitrarily designed as long as the stress can be concentrated, without being limited to the examples shown in FIGS.

  FIG. 3 is a diagram schematically showing the behavior of the workpiece in one embodiment of the present invention. FIG. 3 shows a state in which a fracture surface 61 is generated in the workpiece 6 by further pressing the upper blade 31 after contacting the upper surface of the workpiece 6. At this time, the fracture surface 61 is generated with the groove 7 formed on the upper surface of the workpiece 6 as the start end or the end. On the other hand, inside the workpiece 6, plastic deformation of the material due to the upper blade 31 being pushed in and work hardening associated therewith are generated. When the fracture surface 61 is generated in the workpiece 6, work hardening of the material occurs in the region R along the surface connecting the lower blade 21 and the upper blade 31.

  Here, when the groove 7 is not formed, the fracture surface occurs along a plane connecting the lower blade 21 and the upper blade 31 (shown by a chain line in FIG. 3). Since this fracture surface occurs across the region R where work hardening has occurred, a large portion affected by work hardening remains on the end surface of the workpiece 6 after the break. On the other hand, in this embodiment, the groove 7 is formed, and the fractured surface 61 is generated with the groove 7 as a starting end or a terminal end. As the groove 7 is separated from the upper blade 31 by a distance w as shown in FIG. 1, the fracture surface 61 crosses a portion closer to the edge of the region R or as shown in the region R. It will occur in the part that is off. As a result, in the present embodiment, the portion affected by the work hardening remaining on the end face of the workpiece 6 after the fracture can be made smaller or substantially eliminated.

  On the other hand, when the fracture surface 61 of the workpiece 6 is generated from the groove 7 separated from the upper blade 31 in the shearing process as in the present embodiment, it is not necessary to sharpen the corners of the upper blade 31. As described above, the member life can be extended by chamfering 31. Such an effect is obtained independently of the effects related to work hardening as described above. Of course, both effects may be obtained simultaneously.

  Hereinafter, with reference to FIGS. 4-6, the structural example of the shear processing apparatus which has the groove | channel formation means which concerns on one Embodiment of this invention is demonstrated. In the present embodiment, the groove 7 formed on the upper surface of the workpiece 6 may be formed in a pre-process of shearing using the die 2 and the punch 3, for example. In this case, the groove 7 is formed by a separate groove forming means that is not included in the shearing apparatus 1. On the other hand, in the shearing apparatuses 1a, 1b, and 1c according to the examples described below, the protrusions formed on the holder 4 (first example) or the punch 3 (second example) are grooves that form the grooves 7. It functions as a forming means. In this case, since the groove 7 is formed in the step of sandwiching the workpiece 6 with the die 2 using the holder 4 or the step of moving the punch 3 relative to the die 2, Simplification and speeding up of the process can be realized.

  FIG. 4 is a schematic cross-sectional view showing a first example of a shearing apparatus having groove forming means according to an embodiment of the present invention. Referring to FIG. 4, in the shearing apparatus 1 a according to this example, the protrusion 41 formed on the holder 4 forms the groove 7 on the upper surface of the workpiece 6. Specifically, the protrusion 41 is formed at the end of the holder 4 facing the upper blade 31 in the surface direction of the workpiece 6. Therefore, in this example, the groove 7 is formed when the workpiece 6 is sandwiched between the holder 4 and the die 2 before the upper blade 31 contacts the upper surface of the workpiece 6 by the movement of the punch 3. Is done.

  FIG. 5 is a schematic cross-sectional view showing a second example of a shearing apparatus having groove forming means according to an embodiment of the present invention. Referring to FIG. 5, in the shearing apparatus 1 b according to this example, the protrusion 32 formed on the punch 3 forms a groove 7 on the upper surface of the workpiece 6. Specifically, the protruding portion 32 is formed so as to protrude above the upper blade 31 toward the clearance C from the upper blade 31. With such a structure, the protrusion 32 moves in the thickness direction of the workpiece 6 together with the upper blade 31, and reaches the upper surface of the workpiece 6 later than the upper blade 31. Therefore, in this example, the groove 7 is formed until the fracture surface 61 is formed in the workpiece 6 by the further movement of the punch 3 after the upper blade 31 contacts the upper surface of the workpiece 6 by the movement of the punch 3. In between, it forms by the protrusion part 32 pushed in from the upper surface of the workpiece 6 in the thickness direction of the workpiece 6 later than the upper blade 31.

  FIG. 6 is a schematic cross-sectional view showing a third example of a shearing apparatus having groove forming means according to an embodiment of the present invention. Referring to FIG. 6, in the shearing apparatus 1 c according to the present example, the protrusion 32 formed on the punch 3 forms the groove 7 on the upper surface of the workpiece 6, as in the second example. As a difference from the second example, in this example, the protruding portion 32 is attached to the punch 3 via an elastic body 33. The elastic body 33 is formed of a material having a Young's modulus smaller than that of the punch 3, that is, a high elasticity. Thus, the protrusion 32 can be formed in the same direction as the upper blade 31 or below the upper blade 31 in the thickness direction of the workpiece 6. In this case, the protrusion 32 reaches the upper surface of the workpiece 6 simultaneously with the upper blade 31 or before the upper blade 31, but is further pushed into the workpiece 6 until the elastic body 33 is compressed. The groove 7 is not formed. During this time, the upper blade 31 comes into contact with the upper surface of the workpiece 6 by the movement of the punch 3. Thereafter, as the elastic body 33 is compressed, the protrusion 32 is pushed from the upper surface of the workpiece 6 in the thickness direction of the workpiece 6 with a delay from the upper blade 31, and the workpiece is processed by the further movement of the punch 3. The groove 7 is formed until the fracture surface 61 is formed in the material 6.

  FIG. 7 is a diagram for explaining a modification of the embodiment of the present invention. Referring to FIG. 7, in the shearing device 1 d according to the modified example, the groove 7 a is formed on the upper surface of the workpiece 6, and the groove 7 b is formed on the lower surface of the workpiece 6. The groove 7a on the upper surface of the workpiece 6 is formed at a position where the distance from the upper blade 31 is w in the surface direction of the workpiece 6 as in the example described with reference to FIGS. Is done. On the other hand, the groove 7 b on the lower surface of the workpiece 6 is formed by an additional groove forming means, specifically, a protrusion 22 formed on the die 2. Here, the protrusion 22 is formed in the vicinity of the lower blade 21. The lower blade 21 and the protrusion 22 may be the same part. Accordingly, in the illustrated example, when the punch 3 is pushed into the workpiece 6, the fracture surface 61 is formed with one of the grooves 7 a and 7 b as a start end and the other as an end.

  In the above modification, by forming the groove 7b on the lower surface in addition to the groove 7a on the upper surface of the workpiece 6, it is ensured that the fracture surface 61 is generated at the intended position. Moreover, the change of the end surface shape of the fracture surface 61 can be reduced by forming the groove 7b on the lower surface. In the example shown in FIG. 7, the protrusion 41 of the holder 4 forms the groove 7 a on the upper surface of the workpiece 6, but this modification is not necessarily limited to this. For example, the protruding portion 32 of the punch 3 as described with reference to FIG. 5 may form the groove 7a, or the shearing using the die 2 and the punch 3 as described with reference to FIG. The groove 7a may be formed in a pre-process.

  Next, examples of the present invention will be described. In addition, the Example of this invention demonstrated below is a finite element analysis (henceforth 1st) in order to verify about the suitable range of the distance w from the upper blade 31 of the groove | channel 7 regarding one Embodiment of this invention mentioned above. And an experiment (hereinafter, also referred to as a second embodiment) of shearing the workpiece 6 in which the grooves 7 are actually formed.

(First embodiment)
FIG. 8 is a diagram for explaining a finite element analysis model according to the first embodiment of the present invention. In the present embodiment, the workpiece 6 is a steel plate having a tensile strength of 1180 MPa class, and the plate thickness is 1.6 mm. The shearing process is punching using a punch 3 having a diameter of 10 mm. As the die 2, five types having an inner diameter of 10.16 mm, 10.32 mm, 10.48 mm, 10.64 mm, and 11.28 mm were used. In each case, the clearance C is 0.08 mm, 0.16 mm, 0.24 mm, 0.32 mm, and 0.64 mm. In the following description of the embodiments, the clearance C is described as a ratio (C / t) to the plate thickness. In each of the above cases, C / t is 5%, 10%, 15%, 20%, and 40%.

For the shearing process under the above conditions, a two-dimensional axisymmetric model with the center of the punch 3 as the symmetry axis is created as shown in FIG. 8 and static using a general finite element analysis software Abaqus as the solver. The analysis by the implicit method was performed. In the analysis, the X-axis is set in the surface direction of the workpiece 6, the Y-axis is set in the thickness direction of the workpiece 6, and the stress σ _xx applied to the target element 71 located at the bottom of the groove 7 is the tensile strength of the steel sheet. When (1180 MPa) was exceeded, the fracture surface 61 having the groove 7 as a starting end or a terminal end was generated.

Here, the analysis is performed in each of the five cases where C / t is 5%, 10%, 15%, 20%, and 40% as described above, and the distance w is 0, 0.1 mm, 0.2 mm, It implemented about the case where the groove | channel 7 was formed in the position used as 0.3 mm, 0.4 mm, and 0.6 mm. When the distance w is 0, it is difficult to distinguish between the case where the fracture surface is actually generated from the upper blade 31 and the case where the fracture surface is generated from the groove 7, but in the analysis, the stress σ of the target element 71 _{Since xx} can be calculated, the analysis was performed as an approximation when the distance w is as small as possible.

9 and 10 are graphs showing the analysis results of the first example of the present invention. In FIG. 9, the relationship between the maximum value (σ _{xx — max} ) of the stress σ _xx of the target element 71 described above and the distance w is shown. From this graph, for any C / t value, as the distance w increases, the value of σ _{xx_max} increases. When the distance w reaches a certain value, σ _{xx_max} exceeds the tensile strength (1180 MPa) of the steel sheet.

Here, in the graph of FIG. 9, the distance w at which σ _{xx_max} exceeds the tensile strength of the steel sheet varies depending on the clearance C. Therefore, as shown in FIG. 10, the maximum value (σ _{xx_max} ) of the stress σ _xx of the target element 71 and the distance The relationship (w / C) with the ratio of w to clearance C was extracted. As a result, regardless of the value of clearance C, it was found that σ _{xx_max} exceeds the tensile strength of the steel sheet in the vicinity where the ratio of distance w to clearance C exceeds 40%.

(Second embodiment)
In the second embodiment of the present invention, the workpiece 6 was actually sheared under the same conditions as in the analysis of the first embodiment. That is, the workpiece 6 is a steel plate having a tensile strength of 1180 MPa class and a plate thickness of 1.6 mm. The shearing process is punching using a punch 3 having a diameter of 10 mm. In the experiment, the distance w is 0, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm in each of the five cases where C / t is 5%, 10%, 15%, 20%, and 40%. Or the case where the groove 7 was formed at a position of 0.6 mm and the case where the groove 7 was not formed were subjected to shearing.

  Table 1 below shows whether or not the fracture surface 61 having the groove 7 as a start end or a terminal end is generated when the groove 7 is formed in the experiment according to the second embodiment as described above. In Table 1, ◎ indicates that the fracture surface 61 is generated from the groove 7 and the end face is vertical, and ○ indicates that the fracture surface 61 is generated from the groove 7 but the end face perpendicularity is not good. , X indicates a case where a fracture surface did not occur from the groove 7 (occurred from the upper blade 31). For example, when C = 0.32 mm (× when w = 0.1 mm, ◎ when w = 0.2 mm), and when C = 0.64 mm (× when w = 0.2 mm, w = 0.3 mm) The results of () indicate that the distance w is preferably set to 40% or more of the clearance C as described in the embodiment of the present invention. On the other hand, from the distribution of ◎ and ◯ in the case of C = 0.08 mm to 0.32 mm, it can be seen that when the distance w exceeds 120% of the clearance C, the perpendicularity of the end face of the workpiece after fracture is lowered. From the above, it can be said that the distance w is preferably set to 40% or more and 120% or less of the clearance C. In the experiment, it was observed that when the distance w was 200% or more of the clearance C, the fracture surface generated from the bottom of the groove 7 did not extend to the lower surface of the workpiece 6. From this result, it can be said that the distance w is preferably set to 200% or less of the clearance C.

In the following description of the second embodiment, when the groove 7 is formed, a fracture surface is generated from the groove 7 and the perpendicularity of the end face is good, the embodiment of the present invention, the groove 7 is not formed. The case where the groove 7 is formed is treated as a second comparative example.

FIG. 11 is a graph showing the hardness of the end face of the workpiece after fracture in the experiment according to the second embodiment of the present invention. In each example, the hardness is a Vickers hardness measured at 14 measurement points arranged in the thickness direction of the workpiece at a portion close to the end surface by cutting the workpiece after fracture in a direction intersecting the end surface. It was measured by performing a thickness test (JIS Z 2244). The graph of FIG. 11 shows the average value ( _{Hv_ave} ) at all measurement points of the measurement values of the Vickers hardness test in each example (Example, first comparative example, and second comparative example). .

Referring to the graph, regardless of the value of C / t, the value of _{Hv_ave in} the example is lower than that in the first comparative example and the second comparative example, and in the example, the work hardening at the end face of the workpiece after fracture is performed. It can be seen that the influence of is reduced. On the other hand, when the first comparative example and the second comparative example were compared, the groove 7 was formed, but the _{Hv_ave} value of the second comparative example in which no fracture surface was generated from the groove 7 did not form the groove 7. It was almost the same as the first comparative example.

  FIG. 12 is a graph showing the hole expandability of a workpiece after fracture in an experiment according to the second embodiment of the present invention. In each example, the hole expansion property was measured by performing a hole expansion test (JIS Z 2256) on a workpiece punched using the punch 3 having a diameter of 10 mm as described above. . The graph of FIG. 12 shows the hole expansion ratio (λ) measured by the hole expansion test in each example (Example, first comparative example, and second comparative example).

  Referring to the graph, regardless of the value of C / t, the value of λ in the example exceeds the first comparative example and the second comparative example, and the hole expandability of the workpiece after fracture is improved in the example. You can see that On the other hand, when the first comparative example and the second comparative example are compared, the value of λ in the second comparative example in which the groove 7 is formed but no fracture surface is generated from the groove 7 is the same as that in which the groove 7 is not formed. It was almost the same as 1 comparative example.

  By the embodiments as described above, the present invention is effective for reducing the effect of work hardening on the end face of the workpiece after fracture and improving workability such as hole expansion in post-processing. Indicated.

  In the above-described embodiment, the shearing process was performed using a steel sheet having a tensile strength of 1180 MPa as a workpiece. However, a workpiece that can implement the present invention more effectively is, for example, a tensile strength of 780 MPa or more, more preferably It is a steel plate having a tensile strength of 980 MPa or higher and a relatively high strength. The reason for this is that the behavior of the workpiece as described above as one embodiment of the present invention is based on the premise that the steel sheet has a high sensitivity to the surface notch. This is because, since the sensitivity to notches is low, there is a high possibility that even if a groove is formed, a fracture surface does not occur from the groove (occurs from the upper blade). When the present inventors conducted an experiment similar to that of the second embodiment described above with respect to steel sheets having other tensile strengths, no fracture surface was generated from the grooves in the steel sheets having a tensile strength of less than 780 MPa.

  In the above embodiment, the shearing process is performed using a steel plate having a thickness of 1.6 mm as a workpiece, but the present invention is not limited to this example and can be effectively implemented. For example, when the bottom shape of the groove has a curvature, the larger the plate thickness of the workpiece, the smaller the relative curvature with respect to the plate thickness even with the same curvature, so the effect of generating a fracture surface from the groove increases. . Therefore, the present invention can be effectively implemented even for a workpiece having a larger plate thickness. On the other hand, when the plate thickness of the workpiece is small, the fracture surface is likely to occur from the upper blade because the workpiece is easily sheared, but by adjusting the groove formation position as in the above embodiment The fracture surface can be generated from the groove, and the portion affected by the work hardening remaining on the end face of the workpiece after the fracture can be made smaller.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 1,1a, 1b, 1c, 1d ... Shear processing apparatus, 2 ... Die, 21 ... Lower blade, 22 ... Projection part, 3 ... Punch, 31 ... Upper blade, 32 ... Projection part, 4 ... Holder, 41 ... Projection part 6 ... Work material, 61 ... Broken surface, 7, 7a, 7b, 7c ... Groove, 71 ... Target element.

Claims (9)

Contacting the lower blade with the lower surface of the workpiece;
An upper blade that is movable relative to the lower blade in the thickness direction of the workpiece and has a clearance in the surface direction of the workpiece perpendicular to the thickness direction. Moving in the thickness direction until it abuts on the upper surface of the workpiece,
Forming a groove on the upper surface of the workpiece at a position where the distance from the upper blade in the surface direction is 40% or more and 120% or less of the clearance;
And further moving the upper blade in contact with the upper surface of the workpiece in the thickness direction until a fracture surface having a groove on the upper surface of the workpiece as a starting end or a terminal end is generated. Method.   2. The shearing method according to claim 1, wherein the groove on the upper surface of the workpiece is formed before the upper blade contacts the upper surface of the workpiece.   2. The shearing method according to claim 1, wherein the groove on the upper surface of the workpiece is formed after the upper blade contacts the upper surface of the workpiece and before the fracture surface is generated. Further comprising forming a groove in the lower surface of the workpiece in the vicinity of the lower blade,
The shearing method according to any one of claims 1 to 3, wherein the fracture surface is generated with one of a groove on an upper surface and a lower surface of the workpiece as a starting end and the other as an end.   The shearing method according to any one of claims 1 to 4, wherein the workpiece is a steel plate having a tensile strength of 780 MPa or higher. A lower blade that contacts the lower surface of the workpiece;
An upper blade that is movable relative to the lower blade in the thickness direction of the workpiece and has a clearance in the surface direction of the workpiece perpendicular to the thickness direction. When,
And a groove forming means for forming a groove on the upper surface of the workpiece at a position where the distance from the upper blade is 40% or more and 120% or less of the clearance in the surface direction. A holder for clamping the workpiece between the lower blade and the lower blade;
The shearing device according to claim 6, wherein the groove forming means includes a protruding portion formed at an end portion of the holder that faces the upper blade in the surface direction.   The groove forming means is movable in the thickness direction together with the upper blade, and when the upper blade moves in the thickness direction, the thickness is increased from the upper surface of the workpiece after the upper blade. The shear processing apparatus according to claim 6, comprising a protrusion that is pushed in a direction.   The shearing device according to any one of claims 6 to 8, further comprising additional groove forming means for forming a groove on a lower surface of the workpiece in the vicinity of the lower blade.

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