JP2014111283A - Punching process for processed material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a punching method for a work material that can perform punching processing superior in barring performance in a few steps regardless of variation of yield strength of the work material.SOLUTION: The punching method for a work material, which punches a hole to form a nearly circular punched portion in a rolled work material by contacting a wedge-shaped punch to the rolled work material and using a die into which the punch is inserted, performs: a first step of specifying a first direction in which ductility becomes best in the work material; and a second step of setting an angle between the blade edge of the punch and the first direction to 10° or less in a directional vision of punching using the punch and contacting the punch with the work material.

Description

  The present invention relates to a method for punching a rolled workpiece used in automobiles, home appliances, building structures, ships, construction machines, various plants and the like.

  As a method for forming a hole in a metal plate such as an automobile, home appliance, or building structure, a hole punching method using a punch and a die is known. FIG. 9 is a schematic view of a conventional hole punching apparatus. With reference to the figure, punch 102 </ b> A moves downward toward die 103, whereby punching is performed on processed plate 101 set on die 103.

  FIG. 10 is a schematic diagram schematically showing the shape of the punched end face of the processed plate 101 that has been punched. As shown in the figure, a sag 104, a shear surface 105, a fracture surface 106, and a burr 107 are formed on the end surface of the hole. The sag 104 is formed when the punch 102A pushes the workpiece 101 as a whole. The shear surface 105 is formed by the workpiece 101 being drawn into the clearance between the punch 102A and the die 103 and locally stretched. The fracture surface 106 is formed by breaking the workpiece 101 drawn into the clearance between the punch 102A and the die 103. The burr 107 is generated on the back surface of the workpiece 101.

  The hole formed by punching the punch 102A is then subjected to burring. Cracks may occur at the hole edge during burring. Since such cracks occur on the hole punching surface, it can be prevented by devising a hole punching method. From this point of view, as a conventional technique, punching with a protrusion-provided punch (Patent Document 1) or scraping (Non-Patent Document 1), punching with a chamfered punch (Patent Document 2), or a chamfering die There has been proposed a hole punching using a metal (Patent Document 3) and the like.

JP-A-5-23755 JP-A-8-57557 JP 59-7437 A Plasticity and processing, Vol. 10 (1969), pp 665-671

  The inventions disclosed in Patent Documents 1 to 3 and Patent Document 4 described above have several difficulties. The method described in Patent Document 1 has an appropriate projection height that is effective for burring according to the strength of the workpiece, and cannot be applied to a process using a material with multiple strengths. Although the method described in Patent Document 2 is effective for a material in which a crack has already occurred on a hole-extracted surface, it is not effective for other materials. The method described in Patent Document 3 can be used only for conical burring. In the method described in Non-Patent Document 1, the number of steps increases and the cost increases.

  An object of the present invention is to provide a hole punching method for a workpiece capable of performing a hole punching process having excellent burring properties in one step regardless of a change in yield strength of the workpiece.

  In order to solve the above problems, the gist of the present invention is that (1) a wedge-shaped punch is brought into contact with a rolled workpiece and a die into which the punch is inserted is used. In a punching method for punching a work material to form a substantially circular punched portion, a first step of identifying a first direction having the best ductility in the work material, and a view of a punching direction by the punch And a second step of bringing the punch into contact with the workpiece by setting an angle formed by the cutting edge of the punch and the first direction to 10 ° or less. This is a hole punching method. According to the configuration of (1), it is possible to perform a punching process that excels in burring properties with a small number of steps regardless of a change in the yield strength of the workpiece.

  (2) In the configuration of (1), it is preferable that the punch has a pair of tapered surfaces that are close to each other in the punching direction center axis from the base end portion toward the blade edge portion.

(3) In the configuration of (1) or (2), it is preferable that the following formula (1) is satisfied, where β is an angle formed by the pair of tapered surfaces.
10 degrees ≤ β ≤ 85 degrees ... (1)
According to the configuration of (3), breakage of the punch is prevented.

  (4) In the above configurations (1) to (3), the clearance between the punch and the die is preferably 0.5 to 20% of the plate thickness of the workpiece. According to the configuration of (4), punch chipping and generation of burrs can be prevented.

  (5) In the configurations of (1) to (4) above, the cutting edge portion may be a flat portion extending in a direction orthogonal to the punching direction. (6) In the configurations of (1) to (4) above, the cutting edge portion of the punch may have an R shape. According to these configurations, it is possible to suppress a decrease in tool life.

  (7) In the configurations of (1) to (6), the first direction is specified based on data on ductility obtained by performing a side bend test on the workpiece in the first step. It is preferable to do this. According to the structure of (7), the direction excellent in ductility can be pinpointed correctly.

In order to solve the above-mentioned problems, the present invention provides, as another aspect, (8) a punching method for punching the steel sheet by bringing a wedge-shaped punch into contact with the rolled steel sheet. The ductility in the direction of 45 degrees with respect to the rolling direction is 1.1 to 5.0 times the ductility in the rolling direction, and is formed between the cutting edge of the punch and the rolling direction when viewed in the punching direction with the punch. A steel plate hole punching method satisfying the following expression (2) when the angle is α.
35 degrees ≤ α ≤ 55 degrees ... (2)

  (9) In the configuration of (8), it is preferable that the punch includes a pair of tapered surfaces that are close to each other in the punching direction center axis from the base end portion toward the blade edge portion.

(10) In the configuration of (8) or (9), when the angle formed by the pair of tapered surfaces is γ, it is preferable that the following expression (3) is satisfied:
10 degrees ≤ γ ≤ 85 degrees (3)
According to the configuration of the above (10), the punch is prevented from being damaged, and the reduction in the burring property improving effect can be suppressed.

(11) In the above configurations (8) to (10), the clearance between the punch and the die into which the punch is inserted is preferably 0.5 to 20% of the plate thickness of the workpiece.
According to the configuration of (11), it is possible to prevent punch chipping and burrs.

(12) In the configurations of (8) to (11) above, the cutting edge portion may be a flat portion extending in a direction orthogonal to the punching direction.
(13) In the above configurations (8) to (11), the cutting edge portion of the punch may have an R shape. According to these configurations, it is possible to suppress a decrease in tool life.

  (14) In the above configurations (8) to (13), in the steel sheet, the ductility in the direction of 45 degrees with respect to the rolling direction is 1.1 to 5.0 times the ductility in the rolling direction. It is preferably specified by a bend test.

  According to the present invention, it is possible to perform hole punching with excellent burring properties in a small number of steps regardless of the change in yield strength of the workpiece.

It is sectional drawing of a press apparatus. It is sectional drawing which cut | disconnected the wedge type punch in the short side direction of the blade edge part along the longitudinal direction axis | shaft. It is sectional drawing which cut | disconnected the wedge type punch in the long side direction of the blade edge part along the longitudinal direction axis | shaft. It is a top view of the hole part of a workpiece, and its periphery. It is a perspective view of a side bend test device. It is a top view of a side bend test device. It is a test result of a side bend test. It is sectional drawing of another embodiment of a wedge type punch. It is sectional drawing of the press apparatus used for the conventional punching direction. The figure which shows a punching end surface.

  The applicant of the present application obtained the following knowledge when the rolled workpiece was punched with a wedge-shaped punch. FIG. 1 is a cross-sectional view of a press device for effectively carrying out the hole punching method of the workpiece according to the present embodiment. The X axis, the Y axis, and the Z axis indicate three different orthogonal axes. “Wedge” refers to an edge shape that is thicker at one end and thinner toward the other end (Kojien 4th edition, page 725). The blade shape referred to here may have a flat blade edge or an R shape.

  Referring to FIG. 1, press apparatus 100 includes punch 2, die 3, and stopper 8. The die 3 is formed with a die hole 3a through which the punch 2 advances and retreats. The stopper 8 fixes the workpiece 1 placed on the die 3. The punch 2 moved downward toward the die hole portion 3 a comes into contact with the workpiece 1 placed on the die 3. When the punch 2 further moves down, the workpiece 1 is pressed and bent while being distorted downward by the stress. And in the state which the distortion produced, the hole is formed in the to-be-processed material 1 by the shearing effect | action of the punch 2 and die | dye 3. FIG. The workpiece 1 is formed into a plate shape by rolling.

  Next, the structure of the punch 2 will be described in detail with reference to FIGS. FIG. 2 is a cross-sectional view of the wedge-shaped punch cut along the longitudinal axis in the short side direction of the blade edge portion. FIG. 3 is a cross-sectional view of the wedge-shaped punch cut along the longitudinal axis in the long side direction of the blade edge portion. The X axis, the Y axis, and the Z axis indicate three different orthogonal axes.

  The punch 2 includes a wedge-shaped punch portion 20 at a lower end portion. The wedge-shaped punch portion 20 includes a pair of tapered surfaces 22 a and 22 b that approach the longitudinal center axis of the punch 2 from the base end portion 23 toward the blade edge portion 21. That is, the wedge-shaped punch part 20 is formed in a wedge-shaped shape in which the cross-sectional area (the cross-sectional area in the direction orthogonal to the punching direction) decreases as the distance from the base end part 23 toward the blade edge part 21 increases. Here, it is preferable that the condition of 10 degrees ≦ β ≦ 85 degrees is satisfied, where β is an angle formed by the tapered surfaces 22a and 22b. By satisfying this condition, it is possible to prevent the wedge-shaped punch portion 20 from being damaged.

  A blade edge portion 21 is formed at the tip of the wedge punch portion 20. The blade edge portion 21 is formed in a long and narrow rectangle when viewed in the X-axis direction, and extends along the YZ plane. Thus, by forming the blade edge portion 21 flat, it is possible to prevent the punch 2 from being damaged. That is, when the blade edge 21 has an acute angle, the punch 2 may be damaged, but the punch 2 can be protected by forming it flat.

  As a result of examining the characteristics of the rolled workpiece 1, the inventor has a direction in which the workpiece 1 is excellent in ductility and a direction in which the ductility is not excellent in a plane including the workpiece 1. I found Further, by performing punching in a state in which the longitudinal direction of the cutting edge portion 21 of the wedge-shaped punch portion 20 and the direction in which the work material 1 has excellent ductility are matched, cracks during burring are reduced. I discovered that I can do it.

  These technical findings will be described in detail. FIG. 4 is a plan view of the hole 1a formed in the workpiece 1 by burring after the hole punching by the wedge punch 20 and the periphery thereof. The dotted line indicates the position of the blade edge 21 at the time of punching. At the time of punching, both ends in the longitudinal direction of the cutting edge portion 21 first bite into the workpiece 1, so that plastic strain increases at this location (hereinafter referred to as a large strain portion). For this reason, in the burring process after punching, crack propagation may occur starting from the large strain portion.

  Therefore, crack propagation during burring can be effectively suppressed by reducing the plastic strain in the large strain portion. When the large strain portion of the workpiece 1 is excellent in ductility, the plastic strain can be reduced. Therefore, the present inventors have found that punching is performed in a state in which the longitudinal direction of the cutting edge portion 21 of the wedge punch portion 20 and the direction in which the work material 1 has excellent ductility are matched. According to this method, it is possible to reduce the plastic strain generated in the large strain portion when punching. As a result, the occurrence of cracks during burring can be effectively suppressed.

  That is, the plastic strain generated in the region corresponding to the long side direction of the cutting edge portion 21 is punched in a state where the direction in which the work piece 1 is excellent in ductility and the long side direction of the cutting edge portion 21 are matched. , Can be less.

  The direction in which the work material 1 is excellent in ductility can be identified by, for example, a side bend test. The side bend test will be described in detail. 5 and 6 are schematic diagrams for explaining the configuration concept and functions of the side bend test apparatus, FIG. 5 is a perspective view, and FIG. 6 is a plan view.

  In FIG. 5, the side bend test apparatus includes a pair of arm portions 41 (41 a, 41 b), a grip portion 42 (42 a, 42 b), and a load applying means 45. The pair of arm portions 41 (41a, 41b) are rotatably attached to two fulcrums 44 (44a, 44b) fixed at different positions, respectively. The pair of arm portions 41 (41a, 41b) includes tip portions 41at, 41bt and leg portions 41af, 41bf, respectively. The gripping portions 42 (42a, 42b) sandwich and fix both end portions of the test piece 43, which is a test piece of the workpiece, with the tip portions 41at, 41bt of the arm portions 41 (41a, 41b), respectively. The load applying means 45 applies a load for rotating the arm 41 (41a, 41b) by pressing the arm 41 (41a, 41b). The leg part 41af of one arm part 41a intersects the leg part 41bf of the other arm part 41b.

  The test piece 43 is formed with an arc-shaped punched portion at the center in the longitudinal direction, and the test piece has an arc opening (hereinafter referred to as an arc opening) side of the punched portion according to the test device. It is attached so as to be outside the tensile bend. Here, the angle α shown in FIG. 5 indicates an angle formed by the reference line extending in the direction in which the load applying means 45 moves through the planned crack portion in the arc opening and the rolling direction of the test piece 43.

  The operation of the side bend test apparatus will be described with reference to FIG. A load is applied to the rear ends 41ae and 41be of the pair of arm portions 41 (41a and 41b) by the load applying means 45 in the direction of the arrow (to the right in the drawing), that is, in the direction of the tip portion of the arm portion. As a result, the arm portions move around the pair of fulcrums 44 (44a, 44b) so that the tip portions of the pair of arm portions are separated from each other in opposite directions (the two-dot chain line in FIG. 6C). ). That is, it functions to apply a tensile force and a bending force to the test piece locked and fixed by the locking means including the arm portion and the grip portion. The interval between the fulcrums (supports) may be any as long as it can give sufficient tensile bending deformation to the test piece, and can be appropriately set in consideration of the size in the longitudinal direction of the test piece.

  Due to the tension and bending deformation caused by the load applied by the load applying means 45, the arc-shaped punched portion having the curvature radius r of the test piece 43 is deformed so that the curvature radius is increased. When the load is increased, the test piece is further deformed, and minute cracks are generated on the end face in the plate thickness direction of the test piece. As the load is increased, the minute cracks in the end face in the thickness direction penetrate in the thickness direction. When the load is further increased, the through-crack develops in the width direction of the test piece, the opening extends in the plate thickness direction, and the test piece breaks. In this side bend test apparatus, the test piece is deformed by the load applied to the test piece 43, and the ductility of the test piece 43 can be evaluated based on the deformation.

That is, in the side bend test apparatus, the deformation state of the test piece 43 changes as the load is applied. The ductility of the test piece 43 is based on the value of the strain on the plate surface when the crack penetrates the end face in the plate thickness direction of the test piece (this end face corresponds to the outside of the bend) (hereinafter abbreviated as the occurrence of the crack). Can be evaluated. Specifically, the ductility of the test piece 43 is evaluated from the aperture ratio.
Note that a strain measurement method using a grid instead of the aperture ratio may be used. Here, the opening ratio is the opening end distance D before the overload shown in FIG.
It can be calculated from (D′−D) / D × 100.

  The load applying means 45 is not particularly limited as long as it can apply a load to the rear end of the arm, such as a hydraulic or electric jack. Needless to say, the strength of the members constituting the test apparatus, such as the arms and fulcrums, may be determined in consideration of the strength of the material to be tested.

  FIG. 7 shows the test results of the side bend test, and shows the aperture ratio when α is changed between 0 degree, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 55 degrees, and 90 degrees. A steel plate was used for the test piece 43. When α is set to 0 degrees, the aperture ratio is 75%, when α is set to 35 degrees, the aperture ratio is 81%, and when α is set to 40 degrees, the aperture ratio is 85%. When α is set to 45 degrees, the aperture ratio is 90%, when α is set to 50 degrees, the aperture ratio is 89%, and when α is set to 55 degrees, The aperture ratio was 80%, and when α was set to 90 degrees, the aperture ratio was 71%. From these test results, it was found that the ductility was most excellent in the direction (first direction) where α = 45 °, that is, the angle with respect to the rolling direction was 45 °. Furthermore, it has been found that the aperture ratio decreases as the angle increases from the first direction. Therefore, by performing hole punching in a state where the blade edge portion 21 is positioned in the direction of 35 ° ≦ α ≦ 55 °, it is possible to suppress the occurrence of cracks penetrating the plate thickness at the time of hole expansion. In other words, by setting the angle formed between the cutting edge portion 21 of the punch and the first direction to 10 degrees or less, a plate thickness penetration crack at the time of hole expansion (in other words, a large penetration through the plate in the thickness direction). (Crack) can be reduced.

  Here, when the workpiece 1 is a steel plate, when the ductility in the rolling direction is 1, the ductility in the direction of 45 ° with respect to the rolling direction must be 1.1 to 5.0. By using the workpiece 1 having such ductility characteristics, it is possible to effectively reduce the plastic strain generated at the time of punching.

Here, referring to FIG. 1, the clearance C between the punch 2 and the die 3 into which the punch 2 is inserted is preferably limited to 0.5 to 20% of the plate thickness t of the workpiece 1. When the clearance C is smaller than 0.5%, chipping occurs at the cutting edge portion 21, and when the clearance C is larger than 20%, the workpiece 1 is curved to generate burrs.
(Other embodiments)

  The workpiece 1 may be made of aluminum, magnesium, or titanium other than steel. In this case, the first direction having the most excellent ductility in the workpiece 1 is specified, and the angle formed by the cutting edge portion 21 of the punch 2 and the first direction is 10 ° or less when viewed in the punching direction by the punch 2. Then, the punch 2 is brought into contact with the workpiece 1. Thereby, the effect similar to the said embodiment can be acquired. Even for a workpiece other than a steel plate, the ductility in the direction of 45 degrees with respect to the rolling direction is preferably 1.1 to 5.0 times the ductility in the rolling direction.

  FIG. 8 is a cross-sectional view showing another embodiment of the wedge punch 20. As shown in the figure, the cutting edge portion 21 of the wedge punch 20 may have an R shape. By forming the cutting edge portion 21 in an R shape, the punch 2 can be prevented from being damaged.

DESCRIPTION OF SYMBOLS 1 Work material 2 Punch 3 Dice 20 Wedge type punch part 21 Cutting edge part 22a 22b Tapered surface 23 Base end part

Claims (6)

In the hole punching method of punching the workpiece to form a substantially circular punched portion by bringing a wedge-shaped punch into contact with the rolled workpiece and using a die into which the punch is inserted,
A first step of identifying a first direction having the best ductility in the workpiece;
A second step of bringing the punch into contact with the workpiece by setting an angle formed by a cutting edge portion of the punch and the first direction to 10 ° or less in the hole punching direction view of the punch;
A hole drilling method for a workpiece, comprising:   2. The hole punching method for a workpiece according to claim 1, wherein the punch includes a pair of tapered surfaces approaching each other from a base end portion toward a cutting edge portion toward a center axis in a punching direction of the punch. . The hole drilling method for a workpiece according to claim 1 or 2, wherein the following equation (1) is satisfied when an angle formed by the pair of tapered surfaces is β.
10 degrees ≤ β ≤ 85 degrees ... (1)   4. The hole in the workpiece according to claim 1, wherein a clearance between the punch and the die is 0.5 to 20% of a plate thickness of the workpiece. Unplugging method.   5. The hole punching method for a workpiece according to claim 1, wherein the blade edge portion is a flat portion extending in a direction orthogonal to the hole punching direction.   The method for punching a workpiece according to any one of claims 1 to 4, wherein the cutting edge portion of the punch has an R shape.

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