JP5643615B2 - Method of shearing painted steel sheet - Google Patents

Description

  The present invention relates to a method for shearing a coated steel sheet, and in particular, a punch blade tip provided with a corner portion formed of an elliptical arc surface having a major axis along the radial direction of the punch and a minor axis along the axial direction of the punch. Used as a punch, the longer diameter is made larger than the amount of enlargement toward the outer diameter side of the punch of the coating film peeling part, so that the coating film peeling part is included on the chip side. The present invention relates to a novel improvement for making it possible to avoid the film peeling portion from remaining and to suppress the generation of enamel hair caused by the coating film peeling portion.

  As a shearing method for this type of coated steel sheet that has been used in the past, for example, the method disclosed in Patent Document 1 below can be cited. That is, in the conventional method, when the coated steel sheet placed on the die is pressed with a sheet presser and the punch is pushed into the coated steel sheet and shearing is performed, the punch has a thickness of 0.05 mm or more and the coated steel sheet thickness. The corner portion having a radius of 30% or less is provided on the punch blade edge. By using such a punch, it is possible to reduce the occurrence of so-called enamel hair at the shearing end by stretching the coating thinly at the shearing end and suppressing the peeling of the coating end by sliding when the punch is released. Suppressed.

JP 2010-172944 A

  When the inventors proceeded with the analysis of the mechanism of enamel hair generation at the shearing end, the enamel hair was not generated when the punch was released, but was already generated when the punch was pushed in, as previously thought. Newly found that. FIG. 5 is an explanatory view showing a generation mechanism of enamel hair generated at the shear end. As shown to (a) of FIG. 5, the coated steel plate 4 has the coating film 47 formed in the upper surface of the steel plate 45 which is a base material via the pre-processing film 46. As shown in FIG. In the drawing, the pretreatment film 46 is shown thick for easy understanding, whereas the coating film 47 is a film of about several μm, whereas the pretreatment film 46 is a very thin film of about several tens of nm. It is.

  As shown in FIG. 5A, when the punch 3 starts to be pushed into the coated steel plate 4, a compressive stress 50 indicated by an arrow in the drawing is applied to each of the steel plate 45, the pretreatment film 46, and the coating film 47. Works. At this time, since the pretreatment film 46 is made of a harder material than the steel plate 45 and the coating film 47, it cannot follow the slip deformation of the steel plate 45. For this reason, cracks and cohesive failure occur in the pretreatment film 46, and the coating film 47 rises. Hereinafter, the part where the coating film 47 is peeled from the steel plate 45 is referred to as a coating film peeling part 47a.

  As shown in FIG. 5B, the coating film 47 does not follow the deformation of the steel plate 45 from the middle stage to the latter half of the indentation, and the compressive stress 50 acting on the coating film 47 increases. On the other hand, the tensile stress 51 resulting from the pressing of the punch 3 acts on the steel plate 45. For this reason, the cohesive failure surface 46a of the pretreatment film 46 propagates to the inside, and the coating film peeling portion 47a is enlarged. When the punch 3 is further pushed in, the coating film peeling portion 47a is pulled by the punch 3 and the coating film 47 is broken, so that an enamel hair 48 shown in FIG. 5C is generated.

  In the conventional method as described above, a punch having a corner portion provided on the punch blade edge is used, but at the position corresponding to the lower base end of the corner portion where the punch first comes into contact with the coated steel plate, the pretreatment film is still applied. The compressive stress is acting and the coating film peeling part has generate | occur | produced. That is, in the conventional method, since the corner portion has a rounded corner surface having one radius, the radius of the corner portion cannot be set to a value that takes into account the enlargement of the coating film peeling portion, and shearing is performed. A coating film peeling part may remain in the coated steel sheet after processing, and enamel hair may be generated due to the coating film peeling part.

  The present invention has been made in order to solve the above-described problems, and the object of the present invention is to avoid the coating film peeling portion remaining on the coated steel sheet after the shearing process, and the enamel resulting from the coating film peeling portion. It is providing the shearing method of the coated steel plate which can suppress generation | occurrence | production of hair.

The shearing method of the coated steel sheet according to the present invention is performed along the radial direction of the punch when the coated steel sheet is pressed with a sheet press and the punch is pushed into the coated steel sheet to perform the shearing process. Using a punch with a corner that consists of an elliptical arc surface with a major axis and a minor axis along the axial direction of the punch as the punch, and coating from the position corresponding to the lower base end of the corner by pressing the punch by increasing the major axis than the larger amount toward the outer diameter side of the punch of the coating film peeling unit that occurs in the steel sheet, a shearing method painting steel sheet to include a coating film peeling unit in the chip side, corner short of The diameter is within the range of 5% or more and 30% or less of the thickness of the coated steel sheet to be sheared, and the major axis of the corner is within the range of 2 to 20 times the minor axis. is there.

  According to the method for shearing a coated steel sheet according to the present invention, the punch blade tip is provided with a corner portion formed of an elliptical arc surface having a major axis along the radial direction of the punch and a minor axis along the axial direction of the punch. As the length of the coating film peeled portion is increased from the position corresponding to the lower base end of the corner portion by pressing the punch, the larger diameter is larger than the amount of expansion toward the outer diameter side of the punch of the coated film peeling portion generated in the coated steel sheet. Since it is contained on the chip side, it can be avoided that the coating film peeling portion remains on the coated steel sheet after the shearing process, and the generation of enamel hair due to the coating film peeling portion can be suppressed.

  In addition, the minor axis of the corner is within the range of 5% to 30% of the thickness of the coated steel sheet to be sheared, and the major axis of the corner is not less than 2 times and not more than 20 times the minor axis. Because it is within the range, it is possible to more reliably include the coating film peeling part on the chip side while suppressing the deterioration of the shape of the shear end, and more reliably suppress the occurrence of enamel hair due to the coating film peeling part. it can.

It is a perspective view which shows the shear metal mold | die for enforcing the shear processing method of the coated steel plate by embodiment of this invention. It is sectional drawing of the punch blade edge | tip of the punch of FIG. It is explanatory drawing which shows the mechanism of the shearing process of the coated steel plate using the shear metal mold | die of FIG. It is explanatory drawing which shows the mechanism of the shearing process of FIG. 3 in detail. It is explanatory drawing which shows the generation | occurrence | production mechanism of the enamel hair which generate | occur | produces in a shearing edge part.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a perspective view showing a shear mold for carrying out a shearing method of a coated steel sheet according to an embodiment of the present invention. In the figure, a die 1, a plate presser 2, and a punch 3 are provided in the shear mold. The die 1 is a base fixed to a support member (not shown), and is a cylindrical member provided with a punching through hole 1a in the center. On the die 1, a coated steel plate 4 to be sheared is placed. The plate retainer 2 is a cylindrical member disposed above the die 1 and is provided so as to be lowered toward the die 1 so as to retain (restrain) the coated steel plate 4 placed on the die 1. . A guide hole 2 a is provided inside the plate presser 2, and a cylindrical punch 3 is inserted into the guide hole 2 a. The punch 3 is disposed above the punching through hole 1a, and is provided so as to be lowered along the guide hole 2a so as to be inserted into the punching through hole 1a.

  In addition, as shown in FIG. 5, the coated steel plate 4 has a coating film 47 formed on the upper surface of a steel plate 45 as a base material via a pretreatment film 46.

  As the steel plate 45, for example, a ferritic stainless steel plate, an austenitic stainless steel plate, a martensitic stainless steel plate, or a multiphase stainless steel plate thereof may be applied, but any steel plate may be used.

The pretreatment film 46 is formed by applying a pretreatment liquid on the surface of the steel plate 45 and drying the pretreatment liquid. Examples of the coating pretreatment liquid used at this time include a chromate type treatment liquid and a chromate-free type treatment liquid. The pretreatment film 46 may be formed on either one side or both sides.
Although the coating method of the coating pretreatment liquid is not particularly limited, it may be appropriately selected from methods used for the production of precoated steel sheets. Such coating methods include roll coating, flow coating, curtain flow, spraying, and dipping.
The coating amount of the coating pretreatment liquid is not particularly limited, but is preferably an amount such that the adhesion amount after drying is in the range of 1 to 300 mg / m ² . When the adhesion amount is less than 1 mg / m ² , the coating film adhesion cannot be ensured sufficiently, and enamel hair may be generated due to interfacial peeling. On the other hand, when the adhesion amount exceeds 300 mg / m ² , it is not preferable from the viewpoint of cost.
Although the drying temperature of the coating pretreatment liquid is not particularly limited, it is, for example, about 40 to 180 degrees.

  The coating film 47 can be formed by a known method. For example, a paint containing an organic resin as a base may be baked after being applied to the surface of the steel plate 45 that has been subjected to the pretreatment. Although the coating method of a coating material is not specifically limited, What is necessary is just to select suitably from the method currently used for manufacture of a precoat steel plate. Such a coating method includes a roll coating method, a flow coating method, a curtain flow method, and a spray method. The baking condition may be, for example, baking at a final plate temperature of 150 to 270 degrees for 30 to 120 seconds.

The coating film 47 may contain a rust preventive pigment. From the viewpoint of reducing environmental burden, a rust preventive pigment not containing hexavalent chromium is preferable.
Such anti-corrosion pigments include zinc phosphate, zinc phosphite, magnesium magnesium phosphate, magnesium phosphate, magnesium phosphite, silica, calcium ion exchange silica, zirconium phosphate, aluminum dihydrogen tripolyphosphate, oxidation Zinc, zinc phosphomolybdate, and barium metaborate are included.

Further, the coating film 47 may contain a color pigment, a pearl pigment, a metallic pigment, and an extender pigment.
Such colored pigments include titanium oxide, carbon black, chromium oxide, iron oxide, bengara, titanium yellow, cobalt blue, cobalt green, aniline black, and phthalocyanine blue.
Metallic pigments include metal powders such as aluminum, stainless steel, and nickel.
The extender pigments include barium sulfate, titanium oxide, silica, and calcium carbonate.

Furthermore, from the viewpoint of improving the coating film hardness and wear resistance, or from the viewpoint of improving the appearance by imparting irregularities to the coating film surface, the scaly inorganic additive, inorganic fiber, granular or massive form is applied to the coating film 47. Organic aggregates, granular or massive inorganic aggregates, and matte materials may be blended.
Such scale-like inorganic additives include glass flakes, barium sulfate flakes, graphite flakes, synthetic mica flakes, synthetic alumina flakes, silica flakes, and micaceous iron oxide (MIO).
In addition, the inorganic fibers include potassium titanate fibers, wollastonite fibers, silicon carbide fibers, alumina fibers, alumina silicate fibers, silica fibers, rock wool, slag wool, glass fibers, and carbon fibers.
The organic aggregate includes acrylic beads and polyacrylonitrile beads.
Further, the inorganic aggregate and the matte material include glass beads and silica powder.

  In addition, when the steel plate 45 which is a base material is a stainless steel plate, the 1 coat clear coating film which utilized the texture of the base material is often employ | adopted. When a 1-coat clear coating is employed, a soft polyester-based clear coating or a hard acrylic clear coating is used.

  Next, FIG. 2 is a sectional view of the punch blade edge 30 of the punch 3 of FIG. In the drawing, a punch blade edge 30 for shearing the coated steel plate 4 is formed on the outer peripheral portion of the punch 3. The punch blade edge 30 is provided with a corner portion 31 formed of an elliptical arc surface having a major axis X along the radial direction 3 a of the punch 3 and a minor axis Y along the axial direction 3 b of the punch 3.

  Here, the major axis X means a separation distance (radial separation distance X) along the radial direction 3a of the punch 3 between the lower base end 31a and the upper base end 31b of the corner portion 31, and the short diameter Y is It means the separation distance (axial separation distance Y) along the axial direction 3b of the punch 3 between the lower base end 31a and the upper base end 31b of the corner portion 31. The elliptical arc surface constituting the corner portion 31 may not be an arc surface that draws a quarter curve of the ellipse, and extends wider in the radial direction 3a of the punch 3 than in the axial direction 3b of the punch 3 ( It may be an arc surface that has been stretched). That is, when the cross section of the corner portion 31 is ¼ of the ellipse, the major axis X and the minor axis Y (the radial separation distance X and the axial separation distance Y) of the corner portion 31 and the corner portion 31 are configured. Although the major axis and minor axis of the ellipse coincide with each other, the cross section of the corner part 31 may be a 1/8 part of the ellipse that extends widely along the radial direction 3a of the punch 3. In such a case, the corner part It should be noted that the major axis X and minor axis Y of 31 do not coincide with the major axis and minor axis of the ellipse constituting the corner portion 31. In addition, by making the cross section of the corner portion 31 smaller than ¼ of the ellipse, the connection portion between the upper base end 31b of the corner portion 31 and the punch side surface can be sharpened, and the punch cutting edge 30 can be coated more smoothly. The steel plate 4 can be bitten.

  Next, FIG. 3 is an explanatory view showing the mechanism of the shearing process of the coated steel plate 4 using the shear mold of FIG. In the shearing process of the coated steel plate 4, the punch 3 is inserted into the punched through hole 1a in a state where the coated steel plate 4 placed on the die 1 is pressed by the plate holder 2 (see FIG. 1). It is done by being pushed into. As shown in FIG. 3 (a), at the initial pressing of the punch 3, a sag portion 40 is formed in the coated steel plate 4 by being pressed down by the punch 3.

  As shown in FIG. 3 (b), from the middle stage to the latter half of the push-in of the punch 3, the punch 3 is further pushed into the sag portion 40, and the die side shearing surface 41 is formed at the lower part of the coated steel plate 4. Is formed.

  As shown in FIG. 3C, when the punch 3 is further pushed in from the state of FIG. 3B, the coated steel plate 4 is sheared by the punch blade edge 30 of the punch 3 biting into the coated steel plate 4, A shear surface 42 is formed on the coated steel plate 4. Further, in the lower part of the coated steel plate 4, the coated steel plate 4 is shredded by the pressure of the punch 3, whereby a fracture surface 43 is formed. At this time, the sag portion 40 remains in the upper part of the coated steel plate 4. The size of the sag portion 40 changes according to the length of the period from when the punch 3 starts to be pressed until the punch blade edge 30 of the punch 3 bites into the coated steel plate 4. That is, the size of the sag portion 40 changes according to the size of the minor axis Y of the corner portion 31 shown in FIG.

  Here, in the sag portion 40, since the tensile stress is applied throughout the shearing process, the coating film 47 does not float and peeling of the coating film edge can be suppressed. Therefore, if the minor axis Y of the corner portion 31 is too small, compressive stress is applied at the sag portion 40, and suppression of coating film peeling cannot be expected. On the other hand, when the minor axis Y of the corner portion 31 is too large, the sagging portion 40 becomes too large. When the sag portion 40 is too large, the shear surface 42 becomes small, and the shape of the end surface of the coated steel plate 4 after the shearing process is deteriorated.

  As will be described in detail later, the minor axis Y of the corner portion 31 is preferably in the range of 5% or more and 30% or less of the plate thickness of the coated steel plate 4. By making the minor axis Y within this range, more reliably, in the sag portion of the shear end portion, applying a tensile stress throughout the shear process to suppress the peeling of the coating film end, Shape deterioration can be suppressed.

  Next, FIG. 4 is an explanatory view showing the mechanism of the shearing process of FIG. 3 in more detail. As shown in FIG. 4A, when the punch 3 starts to be pushed into the coated steel plate 4, it corresponds to the position where the punch 3 is first brought into contact with the coated steel plate 4, that is, the lower base end 31 a of the corner portion 31. The compression deformation of the steel plate 45 occurs at the position, and the compressive stress 50 indicated by the arrow in the drawing is applied to the steel plate 45 toward the position corresponding to the lower base end 31a. At this time, since the pretreatment film (see FIG. 5) formed between the steel plate 45 and the coating film 47 cannot follow the slip deformation of the steel plate 45, cracks and cohesive failure occur in the pretreatment film. Comes up. Hereinafter, the part where the coating film 47 is peeled from the steel plate 45 is referred to as a coating film peeling part 47a.

  As shown in FIG. 4B, in the middle of pressing, the coating film 47 does not follow the deformation of the steel plate 45 and the compressive stress 50 acting on the coating film 47 increases. At this time, the tensile stress 51 resulting from the pressing of the punch 3 acts on the sagging portion 40, and in the case of a hard coating film, a coating film split portion 47b in which the coating film 47 is cracked is formed. It is in close contact. Further, the tensile stress 51 also acts on the steel plate 45, the cohesive failure surface (see FIG. 5) of the pretreatment film propagates to the inside, and the coating film peeling portion 47a is enlarged. Next, in the later pressing stage shown in FIG. 4C, the punch blade edge 30 of the punch 3 bites into the steel plate 45, and the shear surface 42 is formed on the coated steel plate 4. Thereafter, the lower region of the punch 3 is sheared as chips 4a (see FIG. 1).

  As shown in FIGS. 4A to 4C, the coating film peeling portion 47 a is enlarged from a position corresponding to the lower base end 31 a of the corner portion 31. Accordingly, the distance from the position corresponding to the lower base end 31 a of the corner portion 31 to the outer diameter position of the punch 3, that is, the major axis X (see FIG. 2) of the corner portion 31 corresponds to the lower base end 31 a of the corner portion 31. The coating film peeling part 47a can be included in the chip 4a side by making it larger than the enlarged amount 48 of the coating film peeling part 47a which goes to the outer diameter side of the punch 3 from the position. If the coating film peeling portion 47a remains on the coated steel sheet 4 after the shearing process, enamel hair is generated on the coated steel sheet 4 after the shearing process (see FIG. 5). That is, by including the coating film peeling part 47a on the chip 4a side as in the present embodiment, it is possible to avoid the coating film peeling part 47a remaining on the coated steel sheet 4 after the shearing process, and the coating film peeling part 47a. The generation of enamel hair due to the hair can be suppressed. The enlargement amount 48 of the coating film peeling portion 47a from the position corresponding to the lower base end 31a of the corner portion 31 toward the outer diameter side of the punch 3 depends on the physical properties of the pretreatment film 46 and the physical properties and thickness of the coating film 47. Can be predicted.

  As will be described in detail later, it is preferable that the major axis X of the corner portion 31 is in the range of not less than 2 times and not more than 20 times the minor axis Y of the corner portion 31. By making the major axis X within this range, the coating film peeling portion 47a can be more reliably included on the chip 4a side, and the generation of enamel hair caused by the coating film peeling portion 47a can be more reliably suppressed.

Next, specific examples will be described. The present inventors prepared the following four types of stainless steel plates as the steel plate 45. In addition, the plate | board thickness of each steel plate 45 is 0.1-0.4 mm.
(1) SUS430 (BA finish)
(2) SUS430 (No. 4 finish)
(3) SUS304 (BA finish)
(4) NSS431DP-2 (Nisshin Steel Ferrite + Martensite Duplex Stainless Steel, No. 4 Finish)

These steel plates 45 are preliminarily degreased and washed with water, and then a chromate type coating pretreatment liquid (NRC300: Nippon Parkerizing Co., Ltd.) is applied to the surface (one side) of the steel plate 45 with a bar coater and dried at 100 degrees. Thus, a pretreatment film 46 having an adhesion amount of 10 mg / m ² was formed. After the pretreatment film 46 was formed, a solvent-based acrylic paint and a polyester-type paint were applied to the upper surface of the pretreatment film 46 and baked at 230 degrees to form a film 47 having a thickness of 7 μm.

  The present inventors conducted the following enamel hair generation evaluation experiment after producing such a coated steel sheet 4. That is, a test piece was cut out from the coated steel plate 4 as described above and sheared. A cellophane tape was affixed to the shearing edge and immediately forcedly peeled off, and then the state of generation of enamel hair (coating peeling) was confirmed. For the test piece using a hard acrylic paint as the paint of the coating film 47, the surface was observed (500 times) by SEM (scanning electron microscope). On the other hand, for a test piece using a soft polyester-based paint as the paint of the coating film 47, an optical microscope observation (500 times) was performed from the cross section. The shearing is performed using a shearing die in a 15-ton press, and the processing conditions are that the processing speed is 100 spm, the punch diameter φ is 20 mm, and the die diameter has a clearance with respect to the plate thickness of 10%. Adjusted. In general, the die diameter is adjusted so that the clearance relative to the plate thickness does not exceed 15%.

Table 1 shows the results of such enamel hair generation evaluation and sagging shape evaluation.
In the enamel hair generation evaluation in the table, “◎” indicates a case where coating film peeling or coating film lifting did not occur on the coated steel sheet 4 after the shearing process. In addition, “◯” indicates a case where coating film peeling or coating film lifting occurred, but these coating film peeling or coating film lifting were discontinuous with a minute width within 30 μm from the end face. Furthermore, "x" has shown the case where the enamel hair-like coating-film peeling or coating-film lift of the width | variety exceeding 30 micrometers from the end surface generate | occur | produced.
In the sagging shape evaluation in the table, “◯” indicates a case where a normal sagging shape is exhibited. Further, “x” indicates a case where the height of the sag part greatly exceeds a half plate thickness and the shear shape is poor.

  In Examples 1 to 12 in Table 1, the minor axis Y is within the range of 5% or more and 30% or less of the plate thickness, and the major axis X of the corner part 31 is twice or more the minor axis Y of the corner part 31. And, it is within the range of 20 times or less. In contrast, Comparative Examples 1 to 3 have the major axis X outside the above range, and Comparative Examples 4 and 5 have the major axis X and the minor axis Y outside the above range. In Examples 6 and 7, the minor axis Y is outside the above range. As shown in Table 1, the results of Examples 1 to 12 could be evaluated as “◎” or “◯” in both enamel hair generation evaluation and sagging shape evaluation.

  However, the results of Comparative Examples 1 to 5 had to be evaluated with “×” as the enamel hair generation evaluation. This is because if the major axis X is less than twice the minor axis Y, the film lift due to the compressive stress occurs in the sag portion immediately below the punch blade tip 30 in the shearing process, and the film float (coating peeling) part is completely Since it cannot be contained on the chip 4a side, it is considered that enamel hair (coating film peeling) or film floating occurred. Further, when the major axis X is made larger than 20 times the minor axis Y, the effect of the step due to the arc is reduced, compressive stress is applied directly under the punch blade tip 30, and after the shearing, the coating film floating (coating film peeling) portion is cut into the chip 4a. Since it cannot be contained in the side, it is considered that enamel hair (coating peeling) or coating floating occurred.

  Moreover, the result of Comparative Examples 4-7 had to evaluate enamel hair generation | occurrence | production evaluation or sagging shape evaluation as "x". This is because when the minor axis Y is less than 5% of the plate thickness, a compressive force is applied at the initial stage of shearing and a tensile stress is applied after the middle stage of shearing at the sag portion of the shear end. It is thought that film peeling) or paint film floating occurred. Further, when the minor axis Y was more than 30% of the plate thickness, the sheared shape of the sag portion was poor regardless of whether enamel hair was generated or not, so that the product was not a product.

  From this result, the minor axis Y is within the range of 5% or more and 30% or less of the plate thickness, and the major axis X of the corner part 31 is in the range of not less than 2 times and not more than 20 times the minor axis Y of the corner part 31. By making it inside, it is possible to more reliably include the coating film peeling part 47a on the chip 4a side while suppressing the deterioration of the shape of the shearing end part, and the generation of enamel hair caused by the coating film peeling part 47a is more It can be seen that it can be reliably suppressed.

  In such a shearing method for a coated steel plate, when the coated steel plate 4 placed on the die 1 is pressed by the plate holder 2 and the punch 3 is pushed into the coated steel plate 4 to perform shearing, the punch 3 is used. The punch 3 has a corner 31 formed of an elliptical arc surface having a major axis X along the radial direction 3 a and a minor axis Y along the axial direction 3 b of the punch 3. The major axis X is made larger than the amount of expansion toward the outer diameter side of the punch 3 of the coating film peeling part 47a generated in the coated steel sheet 4 from the position corresponding to the lower base end 31a of the corner part 31 by pushing, and the coating film peeling part Since 47a is included on the chip 4a side, it is possible to avoid the coating film peeling portion 47a from remaining on the coated steel sheet 4 after the shearing process, and to suppress the occurrence of enamel hair due to the coating film peeling portion 47a. Since such a shearing method can more reliably suppress enamel hair, it is particularly useful in a field where a precoated stainless steel sheet having a shearing surface is used, such as home appliances.

  Further, the minor axis Y of the corner portion 31 is set within a range of 5% or more and 30% or less of the plate thickness of the coated steel plate 4 to be sheared, and the major axis X of the corner portion 31 is twice the minor axis Y. Since it is within the range of 20 times or less, it is possible to more reliably include the coating film peeling portion 47a on the chip 4a side while suppressing the deterioration of the shape of the shearing end portion, resulting from the coating film peeling portion 47a. Generation of enamel hair can be more reliably suppressed. More specifically, by setting the minor axis Y within the above-described range, the shear end portion is prevented from peeling off by simply applying a tensile stress throughout the shearing process in the sag portion of the shear end portion. It is possible to suppress the deterioration of the shape. Moreover, by making the major axis X within the above-mentioned range, the coating film peeling portion 47a can be more reliably included on the chip 4a side, and the generation of enamel hair caused by the coating film peeling portion 47a is more reliably suppressed. it can.

DESCRIPTION OF SYMBOLS 1 Die 2 Plate pressing 3 Punch 3a Radial direction 3b Axial direction 4 Painted steel plate 4a Chip 30 Punch cutting edge 31 Corner part 31a Lower base end

Claims (1)

When the coated steel plate (4) placed on the die (1) is pressed by the plate presser (2) and the punch (3) is pushed into the coated steel plate (4) for shearing, the punch ( 3) A corner portion (31) made of an elliptical arc surface having a major axis (X) along the radial direction (3a) and a minor axis (Y) along the axial direction (3b) of the punch (3) is punched. What is provided on the cutting edge (30) is used as the punch (3), and the coated steel plate (4) is moved from the position corresponding to the lower base end (31a) of the corner portion (31) by pushing the punch (3). The major axis (X) is made larger than the expansion amount of the generated coating film peeling part (47a) toward the outer diameter side of the punch (3), and the coating film peeling part (47a) is moved to the chip (4a) side. a shearing method painting steel sheet was Ru contained,
The short diameter (Y) of the corner portion (31) is within the range of 5% to 30% of the plate thickness of the coated steel plate (4) to be sheared, and the corner portion (31) The major axis (X) is in the range of 2 to 20 times the minor axis (Y).
A method of shearing a coated steel sheet, characterized in that.

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