Method for producing press-molded article, and blank
By setting appropriate spacing and flow control areas between the stamping mold and the blank, the problems of flange folds and corner cracks during stamping and forming are solved, and a higher quality molded product is achieved.
Patent Information
- Application Number
- CN202280099377.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-08-23
- Publication Date
- 2025-03-28
AI Technical Summary
During the stamping process, especially when the radius of curvature of the corners is small, wrinkles in the flange portion and cracks in the corners and their vicinity are prone to occur.
By providing a larger spacing between the edges of the stamping mold and the edges of the blank, and providing an appropriate flow control area at the corner ends of the blank, the tensile deformation of the material is alleviated and the generation of wrinkles and cracks are suppressed.
It effectively suppresses the wrinkles on the flange portion of the stamped molded product and the cracks in the corner portion and its surrounding areas, and improves the quality and stability of the molded product.
Smart Images
Figure CN119730974A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for producing a press-formed product and a blank. Background Art
[0002] The popularity of electric vehicles is growing rapidly in order to reduce CO2 emissions based on CAFE (Corporate Average Fuel Efficiency) regulations. Currently, high-priced electric vehicles are the mainstream, but in order to lower the price of electric vehicles, it is necessary to develop components made of metals such as steel. As an example, the molding technology of battery boxes, front pillar lower parts, door inner parts, etc. made of steel materials is being developed.
[0003] Usually, these components (for example, brackets) are composed of a bottom plate portion, a longitudinal wall portion and a flange portion, and the longitudinal wall portion has a curved corner portion (also called a corner portion), and is manufactured by welding and assembling multiple components. However, in the previous forming technology, when the radius of curvature of the corner portion is relatively small and the depth of the stamping forming is deep, wrinkles sometimes occur on the flange near the corner portion. In detail, products with shapes such as brackets are generally manufactured by deep drawing. As a result of the deep drawing of the flange adjacent to the corner of the bracket, wrinkles sometimes occur. The forming of this flange is called shrinkage flange forming. This is because the width of the flange in the circumferential direction gradually shrinks as the forming progresses. As a result of the shrinkage of the width of the flange in the circumferential direction, wrinkles will occur. The higher the strength of the material to be processed, the more significant this tendency becomes. In addition, the higher the height of the longitudinal wall of the bracket, the greater the shrinkage of the flange, and therefore the more likely it is to produce wrinkles on the flange. Even if the material to be processed is pulled from the flange to the longitudinal wall of the bracket, the wrinkles generated in the shrinking flange will remain. That is, wrinkles are also generated in the longitudinal wall of the bracket. Even if the radius of curvature of the corner of the bracket is small, wrinkles are easily generated in the flange and the longitudinal wall. Furthermore, if the radius of curvature of the corner of the bracket is small, cracks along the ridge of the longitudinal wall extending from the corner of the bracket sometimes occur. The smaller the radius of curvature of the corner of the bracket, the easier it is for such cracks to occur. In addition, the higher the strength of the material to be processed, the easier it is for such cracks to occur.
[0004] As a method of suppressing wrinkles on the flange, for example, the technology of Patent Document 1 attempts to set ribs on the pressing surface of the mold to control the flow direction of the material during deep drawing. However, in the technology of Patent Document 1, the product after stamping is likely to have traces and flaws of the ribs, which may damage the appearance. In addition, in the technology of Patent Document 1, when stamping high-strength steel materials, etc., it is likely that the desired effect cannot be achieved, making it difficult to perform stable production.
[0005] Prior art literature
[0006] Patent Literature
[0007] Patent Document 1: Japanese Patent No. 2560416 Summary of the invention
[0008] Problems to be solved by the invention
[0009] The inventors have conducted intensive studies on the reasons for suppressing the occurrence of wrinkles and cracks.
[0010] Geometrically, the flange outside the corner of the bracket narrows in width as it is pulled toward the vertical wall, and thus shrinks. In addition, in a molded product in which the flange outside the corner of the bracket is wrinkled, wrinkles are also generated at the edge of the molded product. Therefore, it is easy to think that the flange outside the corner of the bracket is shrinking and deforming as a whole.
[0011] The flow resistance from the flange to the longitudinal wall is different in the portion where the ridgeline between the flange and the longitudinal wall of the bracket is straight and in the corner. Therefore, if the relative positions of the flange adjacent to the portion where the ridgeline is straight and the flange adjacent to the ridgeline of the corner are considered before and after forming, the flange adjacent to the ridgeline of the corner and its surroundings bulge in a manner separated from the ridgeline after forming. Therefore, the inventor considered whether the end of the flange (the edge of the processed material) is actually stretched. The results of finite element analysis and actual forming by damaging the blank confirmed that this assumption is correct.
[0012] The inventor has further repeatedly studied and believes that when a rectangular area perpendicular to the bisector of the angle of the blank is assumed in the blank, during forming, the rectangular area is deformed into a convex arch shape toward the corner of the blank as it is formed. The inventor believes that the concave side of the arch shape is compressed and deformed to produce wrinkles. The inventor believes that although the convex side of the arch shape is tensilely deformed, if the tensile deformation is alleviated, the deformation to the arch shape is alleviated, and as a result, the compression deformation of the concave side of the arch shape is also alleviated, which can suppress the generation of wrinkles. Specifically, the inventor thought that by making the distance between the edge of the corner of the die hole and the edge of the blank larger than before compared with the distance between the edge of the straight die hole and the edge of the blank, the deformation to the arch shape can be suppressed. The inventor thought that by setting the positional relationship between the edge of the die hole and the edge of the blank in this way, the generation of wrinkles can be suppressed. Furthermore, the inventors have conceived that, when the radius of curvature of the corner of the bracket is small, cracks generated at the ridgeline of the vertical wall extending from the corner of the bracket can be suppressed.
[0013] Here, the movement of points of the processing object before and after the press forming will be described.
[0014] Fig.17Aas well as Fig. 17B It is an explanatory diagram for explaining the movement of points (a, b, c, d) of a processing object before and after conventional press forming based on the results of finite element analysis. Fig.17A It is an explanatory diagram showing points of a processing object before conventional press forming based on the results of finite element analysis. Fig. 17B It is an explanatory diagram showing points of a processing object after press forming based on the finite element analysis results.
[0015] Points a and b are points located at the ends of the bends on the ridges of the die (edges of the die hole) after forming. Points c and d are points located at the ends of the stamped product on a line perpendicular to the extension direction of the ridges of the die passing through the ends of the bends of the die after forming. If the function of inversely calculating the blank shape from the product shape, such as the unfolded view, is used in finite element analysis software, then Fig. 17B The points (a, b, c, d) of the processing object become the points before forming. Fig.17A location.
[0016] Among the inflow of the workpiece accompanying molding, there is an inflow F that is sucked into the straight edge of the mold. A and the inflow F sucked into the curved part of the ridgeline of the mold B . In the inflow F A There is deformation resistance caused by bending of the edge line of the mold. B In addition to the deformation resistance of the object being bent at the edge of the mold, there is also the deformation resistance that the closer the object is to the edge of the mold, the more the object is compressed in the direction transverse to the inflow direction. B The deformation resistance is greater than the inflow F A The deformation resistance is high. Therefore, the flow into F A and inflow F B The inflow is uneven. A and inflow F B As a result of the uneven flow rate, the width of the flange of the molded product (the width from the edge of the mold to the edge of the molded product) is the same as the width of the flange of the molded product. B In addition, even if the flow F B The flow of F around the part A The part where the flow into F B The width of the flange of the molded product is also widened. From another point of view, even if the flow F B The flow of F around the part A The part where the flow into F B The part of the body is involved in the flow of F A The width of the flange of the molded product being pulled out also becomes wider.
[0017] The region H surrounded by the points a, b, c, and d is deformed into an arch shape by molding so as to convexly bend in the same direction as the direction in which the curved portion of the ridgeline of the mold convexly bends. Fig.17A The area H indicated by the oblique lines corresponds to the range of the corner flange after molding. Fig.17A The area H is deformed after forming. Fig. 17B The area H is indicated by the diagonal lines. Fig.17A as well as Fig. 17B As shown in the figure, points a, b, c, and d move as the molding progresses. For example, point a becomes Fig. 17B Inflow trajectory shown.
[0018] Since point a and point b are close to each other during molding, wrinkles are generated in the molded product. The inventors believe that if the deformation of the area H surrounded by points a, b, c, and d into an arch shape can be alleviated, the generation of wrinkles can be suppressed. It is believed that if the elongation between point c and point d can be suppressed, the deformation into an arch shape can be alleviated.
[0019] The inventors believe that if the corners of the blank are stretched outward, the elongation between the points c and d can be suppressed. Fig.18A as well as Fig.18B It is an explanatory diagram for explaining the movement of points (a, b, c, d) of a processing object before and after press forming according to the present invention based on the finite element analysis results. Fig.18A It is an explanatory diagram showing points of a processing object before press forming according to the present invention based on the results of finite element analysis.
[0020] Fig.18B It is an explanatory diagram showing points of a processing object after press forming according to the present invention based on the results of finite element analysis.
[0021] Fig.18A The dotted line represents the shape of the previous blank. Point e is the intersection of the straight line passing through points b and c and the edge of the blank. Similarly, point f is the intersection of the straight line passing through points a and d and the edge of the blank. Fig.18A As shown, the blank (processed material) extends outward from point c and point d. Therefore, it is found that the elongation between point c and point d due to molding is alleviated. There are two main reasons for this. First, even if the processing object is pulled into the curved portion of the mold's ridgeline by the same length, the ratio of the distance between point e and point f is smaller than the ratio of the distance between point c and point d. In other words, the portion of the blank that is closer to the end than point c and point d prevents point c and point d from approaching each other. Second, the material that is flowed into F A The pulled-in portion increases the amount between point c and point e (between point d and point f), so the stress of elongation between point c and point d is relaxed. When the stress is relaxed, the elongation deformation is also relaxed.
[0022] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a press-formed product and a blank that can suppress the occurrence of wrinkles in the flange portion of the press-formed product and cracks in the corner portion and its vicinity.
[0023] Means for solving problems
[0024] (1) A method for manufacturing a stamped product according to one embodiment of the present invention comprises: clamping a blank by a supporting surface of a first stamping die and a supporting surface of a third stamping die; and pressing a second stamping die into the first stamping die to perform deep drawing on the blank, wherein the ridgeline of the edge of the stamping hole of the first stamping die has a curved area that is curved and extended, and when observed from a vertical direction of the blank, a first normal line passing through a first end of the ridgeline in the extension direction of the curved area is defined as a straight line L1, a second normal line passing through a second end of the ridgeline in the extension direction of the curved area is defined as a straight line L2, an intersection point of the straight line L1 and the end of the blank is defined as an intersection point M, and When the intersection of the straight line L2 and the end of the blank is defined as intersection N, the straight line passing through the intersection M and perpendicular to the straight line L1 is defined as straight line L4, the straight line passing through the intersection N and perpendicular to the straight line L2 is defined as straight line L3, the intersection of the straight line L3 and the straight line L4 is defined as intersection O, the line segment connecting the intersection M and the intersection O is defined as line segment MO, and the line segment connecting the intersection N and the intersection O is defined as line segment NO, the angular end between the intersection M and the intersection N of the blank includes the entirety of the line segment MO and the line segment NO, and a part of the angular end is located outside the area between the line segment MO and the line segment NO.
[0025] In the method for manufacturing a press-formed product having the above-described structure, since an appropriate flow control region can be defined for the blank, the occurrence of wrinkles in the flange portion of the press-formed product and cracks in the corner portion and its vicinity can be suppressed.
[0026] (2) A blank in one embodiment of the present invention is that, in an area adjacent to a square whose sides only pass through the edge of the blank and the corner of a first rectangle on the outside and whose length of one side is 40% of the short side of the first rectangle, the blank is tangent to both sides of two sides of a second rectangle on the inside, and in an area of a rectangle passing through two sides of the second rectangle and two tangent points of the blank and whose corner overlaps with that of the first rectangle, the blank is tangent to both sides of two sides of the first rectangle.
[0027] (3) The blank described in (2) above may be tangent to both of the two sides of the first rectangle within a range of 10% of the length of the short side of the first rectangle from the corner of the first rectangle.
[0028] In the blank having the above-mentioned structure, a flow control area is defined on the plate surface of the corner of the blank corresponding to the corner area of the die, thereby suppressing the generation of wrinkles on the flange of the stamped product and cracks on the corner and its vicinity.
[0029] Effects of the Invention
[0030] According to the method for manufacturing a press-formed product and the blank of the present invention, it is possible to suppress the occurrence of wrinkles in the flange portion of the press-formed product and cracks in the corner portion and its vicinity. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 It is a schematic perspective view showing the vicinity of a corner region of a first press die according to one embodiment of the present invention.
[0032] Figure 2 It is a diagram showing the vicinity of a corner region of a first press die according to one embodiment of the present invention, and is a schematic plan view when viewed from above in a direction perpendicular to the bottom surface.
[0033] Figure 3 So through Figure 2 A schematic cross-sectional view of the first punching die is shown in a plane cross-section taken along line AA'.
[0034] Figure 4 This is a schematic perspective view of a set of press dies for explaining one embodiment of the present invention.
[0035] Figure 5A This is a schematic plan view for explaining a method for producing a press-formed product according to an embodiment of the present invention.
[0036] Figure 5B Yes means Figure 5A A top view of the vicinity of a portion of the corner ends shown.
[0037] Figure 5C It is a schematic plan view for explaining a method for producing a press-formed product according to a comparative example.
[0038] Figure 6 This is a schematic plan view for explaining a modified example of the method for producing a press-formed product according to one embodiment of the present invention.
[0039] Figure 7 This is a schematic plan view for explaining a modified example of the blank according to one embodiment of the present invention.
[0040] Figure 8 This is a schematic perspective view of a corner region for explaining one embodiment of the present invention.
[0041] Fig.9A This is a diagram showing an example of a product to which the present invention can be preferably used.
[0042] Fig. 9B This is a diagram showing an example of a product to which the present invention can be preferably used.
[0043] Fig.10 This is a diagram showing an example of a product to which the present invention can be preferably used.
[0044] Fig.11 This is a diagram showing an example of a product to which the present invention can be preferably used.
[0045] Fig.12 This is a diagram showing an example of a product to which the present invention can be preferably used.
[0046] Fig.13A This is a schematic plan view of the blank of Experimental Example 1.
[0047] Fig. 13B This is a diagram showing the distribution of maximum principal strains obtained by finite element analysis when the blank of Experimental Example 1 is press-formed.
[0048] Fig.14 This is a schematic plan view of the blank of Experimental Example 2.
[0049] Fig.15 This is a schematic plan view of the blank of Experimental Example 3.
[0050] Fig.16 This is a schematic plan view of the blank of Experimental Example 4.
[0051] Fig.17A It is an explanatory diagram showing points of a processing object before conventional press forming based on the results of finite element analysis.
[0052] Fig. 17B It is an explanatory diagram showing points of a processing object after conventional press forming based on finite element analysis results.
[0053] Fig.18A It is an explanatory diagram showing points of a processing object before press forming according to the present invention based on the results of finite element analysis.
[0054] Fig.18B It is an explanatory diagram showing points of a processing object after press forming according to the present invention based on the results of finite element analysis. DETAILED DESCRIPTION
[0055] The inventors studied the shape of the blank to be stamped in order to suppress the wrinkles generated on the flange of the stamped product. As a result, it was found that by setting a surplus portion on the shape of the previous blank, the flow direction of the material during stamping can be controlled, thereby suppressing the wrinkles on the flange and the cracks in the corner and its vicinity. However, on the other hand, the inventors also found that such wrinkles cannot be effectively suppressed by simply setting the surplus portion. Then, as a result of in-depth research, it was found that by setting an appropriate area corresponding to the shape of the blank and the shape of the mold, the wrinkles on the flange of the stamped product can be effectively suppressed.
[0056] Hereinafter, the embodiments of the present invention are described by way of example, but the present invention is certainly not limited to the examples described below. In the following description, specific numerical values and materials are sometimes illustrated, but as long as the effect of the present invention can be obtained, other numerical values and materials can also be applied. In addition, each constituent element of the following embodiments can be combined with each other.
[0057] (Manufacturing method of stamped product)
[0058] The manufacturing method of the stamped product of this embodiment includes: clamping the blank by the supporting surface of the first stamping die and the supporting surface of the third stamping die (blank clamping process); and pressing the second stamping die into the above-mentioned first stamping die to deep draw the blank (blank drawing process).
[0059] First, an example of a press die capable of performing a blank clamping step and a blank drawing step will be described.
[0060] (Stamping Die)
[0061] exist Figure 1 An example of a stamping die (first stamping die 100) that can be used in the method for manufacturing a stamped product of this embodiment is shown in FIG. Figure 2 1 is a schematic diagram showing the vicinity of the corner region 121 of the side surface 120 of the first stamping die 100, and shows a top view when viewed from a direction perpendicular to the bottom surface 110. Figure 1 as well as Figure 2 In the example, the X-axis is parallel to the direction in which the planar area on one side of the side 120 (planar area 122a) extends, the Y-axis is parallel to the direction in which the planar area on the other side of the side 120 (planar area 122b) extends, and the Z-axis is parallel to the perpendicular line of the bottom surface 110.
[0062] Figure 1 It is a schematic perspective view showing the vicinity of a corner region 121 of a side surface 120 of the first press die 100 . Figure 1The first stamping die 100 shown includes a bottom surface 110 , a side surface 120 rising from the bottom surface 110 and having a corner region 121 curved in a plan view in a direction perpendicular to the bottom surface 110 , and a support surface 140 connected to the side surface 120 via a ridgeline 130 .
[0063] The bottom surface 110 may also be a substantially planar surface. The bottom surface 110 is connected to the side surface 120 at its outer edge 111. The entire outer edge 111 of the bottom surface 110 may be connected to the side surface 120, or a portion of the outer edge 111 may be connected to the side surface 120. A portion of the outer edge 111 has a corner portion 111a corresponding to the corner region 121 of the side surface 120. The bottom surface 110 and the side surface 120 may also be connected via a bottom side ridgeline 112 provided along the outer edge 111. In a cross-section perpendicular to the extending direction of the bottom side ridgeline 112 at each point of the bottom side ridgeline 112, the bottom surface 110 and the side surface 120 are smoothly connected via the bottom side ridgeline 112. The portion of the bottom side ridgeline 112 connected to the corner region 121 of the side surface 120 is referred to as a corner portion 112a. The bottom surface 110 may have a concave portion or a convex portion facing the out-of-plane direction of the bottom surface 110 for providing a concave-convex portion on the press-molded product.
[0064] The side surface 120 is connected to the bottom surface 110 and rises outward from the bottom surface 110. A part or all of the side surface 120 may be parallel to the vertical line of the bottom surface 110, or may be inclined relative to the vertical line of the bottom surface 110. Figure 1 or Figure 2 As shown, the side surface 120 has a corner region 121 that is curved when viewed from above in a direction perpendicular to the bottom surface 110. The corner region 121 is connected to the plane region 122 (plane region 122a and plane region 122b) of the side surface 120 at the end portion 121a and the end portion 121b. The corner region 121 may also be connected to other corner regions having different curvature radii when viewed from above in a direction perpendicular to the bottom surface 110 or to regions of the side surface 120 that are gently curved. Alternatively, the end portion of the corner region 121 may also be the end portion of the side surface 120. Figure 1 as well as Figure 2 In the example, the plane area 122a is orthogonal to the plane area 122b when viewed from above in the direction perpendicular to the bottom surface 110, but the angle between the plane area 122a and the plane area 122b when viewed from above in the direction perpendicular to the bottom surface 110 is not limited to this.
[0065] The side surface 120 is connected to the support surface 140 via the ridge 130 at the end opposite to the end connected to the bottom surface 110. In the cross-section perpendicular to the extending direction of the ridge 130 at each point of the ridge 130, the support surface 140 is provided on the side opposite to the bottom surface 110 with respect to the side surface 120. The portion of the ridge 130 connected to the corner region 121 of the side surface 120 is referred to as the curved region 131. The curved region 131 of the ridge 130 is connected to the straight region 132 (straight region 132a and straight region 132b) of the ridge 130 at the terminal portion 131a and the terminal portion 131b. The curved region 131 may be connected to other curved regions having different curvature radii in a plan view perpendicular to the bottom surface 110 or to a region of the ridge 130 that curves gently. Alternatively, the terminal portion of the curved region 131 may be the end of the ridge 130. The end portions (the end portion 131 a and the end portion 131 b ) of the curved region 131 include an end point (first end portion) P1 and an end point (second end portion) P2 , which will be described later.
[0066] exist Figure 3 The Figure 2 The plane section at the position of AA' is a schematic cross-sectional view of the first stamping die 100. Figure 3 As shown, the corner area 121 of the bottom surface 110 and the side surface 120 is smoothly connected via the corner portion 112a of the bottom surface side edge line 112, and the corner area 121 of the side surface 120 and the support surface 140 are smoothly connected via the curved area 131 of the edge line 130. Figure 3 In the example, the corner area 121 of the side surface 120 is inclined relative to the perpendicular line of the bottom surface 110. However, the corner area 121 may be perpendicular to the bottom surface 110 in each cross section perpendicular to the bottom surface 110. The first stamping die 100 has a punching hole 123. The second stamping die 200 is pressed into the punching hole 123 by relatively moving the first stamping die 100 and the second stamping die 200 described later in the approaching direction. The ridge 130 of the edge of the punching hole 123 (the edge on the second stamping die 200 side) has a curved area 131 that is curved and extended.
[0067] The first stamping die 100 may also include one or more corner regions 121. The bottom surface 110 of the first stamping die 100 corresponds to the bottom plate of the stamped product, the side surface 120 corresponds to the vertical wall of the stamped product, and the support surface 140 corresponds to the flange of the stamped product.
[0068] The stamping is performed by a set of stamping dies 1000 including the first stamping die 100, the second stamping die 200 and the third stamping die 300. Figure 4An example of a set of stamping dies 1000 including a first stamping die 100, a second stamping die 200, and a third stamping die 300 is shown in FIG. Figure 4 2 shows an example of a stamping die 1000 including a first stamping die 100 having four corner regions 121 , but the stamping die is not limited to this shape, and the number of corner regions 121 and the shape of the bottom surface 110 are not particularly limited.
[0069] The second stamping die 200 has a bottom surface 210 corresponding to the bottom surface 110 of the first stamping die 100, a side surface 220 corresponding to the side surface 120 of the first stamping die 100, and a corner area 221 corresponding to the corner area 121 of the first stamping die 100. The outer surface shapes of the bottom surface 210 and the side surface 220 of the second stamping die 200 become shapes corresponding to the outer surface shapes of the bottom surface 110 and the side surface 120 of the first stamping die 100. In a state where the blank as the workpiece is arranged between the first stamping die 100 and the second stamping die 200, the first stamping die 100 and the second stamping die 200 are relatively moved in a direction (stamping direction) in which the bottom surface 110 of the first stamping die 100 and the bottom surface 210 of the second stamping die 200 approach each other, thereby plastically deforming the blank between the first stamping die 100 and the second stamping die 200. The first stamping die 100 is also called a die, and the second stamping die 200 is also called a punch.
[0070] The third stamping die 300 has a support surface 340 corresponding to the support surface 140 of the first stamping die 100. The support surface 140 of the first stamping die 100 and the support surface 340 of the third stamping die 300 are arranged opposite to each other, and the blank as the workpiece can be clamped by the support surface 140 of the first stamping die 100 and the support surface 340 of the third stamping die 300. The blank is clamped by the support surface 140 of the first stamping die 100 and the support surface 340 of the third stamping die 300 so as to move in the in-plane direction without moving in the out-of-plane direction. When the first stamping die 100 and the second stamping die 200 are moved relatively in a state where the blank is clamped by the first stamping die 100 and the third stamping die 300, the second stamping die 200 moves relative to the third stamping die 300. The third stamping die 300 is also called a retainer.
[0071] The first stamping die 100, the second stamping die 200, and the third stamping die 300 may be constituted by a single member, or may be constituted by divided dies. In addition, the stamping die 1000 may include dies other than these dies.
[0072] The corner end portion 11 of the blank 10 will be described. Figure 5AIt is a schematic plan view for explaining the method for producing a press-formed product according to the present embodiment of the present invention. Figure 5A It is a top view in a direction perpendicular to the plate surface of the plate-shaped blank 10. Figure 5B It is shown in Figure 5A The illustrated portion of the corner end 11 of the blank 10 is in the vicinity of the corner end 11 . Figure 5B The ridgeline 130 of the die hole (punching hole 123 ) and the position of the edge of the blank 10 when the blank 10 is placed on the die (first punching die 100 ) and clamped by the blank holder (third punching die 300 ) are shown.
[0073] When the blank 10 is viewed from the vertical direction, a first normal line passing through a first end P1 in the extending direction of the ridge 130 of the bending region 131 is defined as a straight line L1, a second normal line passing through a second end P2 in the extending direction of the ridge 130 of the bending region 131 is defined as a straight line L2, an intersection point between L1 and the end of the blank 10 is defined as an intersection point M, an intersection point between the straight line L2 and the end of the blank 10 is defined as an intersection point N, a straight line passing through the intersection point M and perpendicular to the straight line L1 is defined as a straight line L4, a straight line passing through the intersection point N and perpendicular to the straight line L2 is defined as a straight line L3, an intersection point between the straight line L3 and the straight line L4 is defined as an intersection point O, a line segment connecting the intersection point M and the intersection point O is defined as a line segment MO, and a line segment connecting the intersection point N and the intersection point O is defined as a line segment NO. The end between the intersection point M and the intersection point N of the blank 10 is defined as a corner end 11. The corner end 11 is a portion outside the blank 10 relative to the line segment MN connecting the intersection point M and the intersection point N. like Figure 5B As shown, when the blank 10 is clamped by the first stamping die 100 and the third stamping die 300, the corner end 11 includes the entire line segment MO and the line segment NO, and a part of the corner end 11 is located outside the area between the line segment MO and the line segment NO. In addition, the line segment MO and the line segment NO are the shapes of the ends of the conventional blanks. The edge of the corner end 11 of the blank 10 is located outside the area sandwiched by the line segment MO and the line segment NO, and the edge of the corner end 11 of the blank 10 is not located inside the area sandwiched by the line segment MO and the line segment NO.
[0074] In this way, a part of the corner end 11 of the blank 10 is located outside the area between the line segment MO and the line segment NO. That is, the blank 10 is in a shape in which the corner end 11 protrudes outward. In other words, the corner end 11 is convex toward the outside of the corner of the blank 10. In addition, it can also be said that the corner end 11 is arched toward the outside of the corner of the blank 10. By setting the corner end 11 of the blank 10 in this shape, the tensile deformation at the corner end 11 can be alleviated, and the generation of wrinkles can be suppressed.
[0075] In addition, the corner end portions 11 do not need to be provided at all corner portions of the blank 10 , and the corner end portions 11 may be provided only at a portion thereof.
[0076] In the manufacturing method of the stamped product of the present embodiment, it is possible to define an appropriate corner end portion 11 for the blank, thereby suppressing the occurrence of wrinkles in the flange portion of the stamped product, and cracks in the corner portion and its vicinity. In the corner portion, cracks in the corner portion 112a can be suppressed in particular. The corner portion 112a is a portion that is continuously stretched from the beginning to the end of the stamping process and is the portion most likely to crack.
[0077] (Variation of the method for producing a press-formed product)
[0078] Figure 6 This is a schematic plan view for explaining a modified example of the method for producing a press-formed product according to one embodiment of the present invention. Figure 6 The figure shows the position of the edge line 130 of the punch hole and the edge of the blank 10 when the blank 10 is placed on the punch die (first punch die 100) and clamped by the blank holder (third punch die 300). Figure 6 The vicinity of one of the corner ends 11 of the blank 10 is shown in FIG.
[0079] exist Figure 6 In the variation shown, Figure 5B Similarly, a portion of the corner end 11 of the blank 10 is also located outside the area between the line segment MO and the line segment NO. That is, the blank 10 is in a shape in which the corner extends outward. In other words, the corner end 11 is convex toward the outside of the corner of the blank 10. In addition, it can also be said that the corner end 11 is arched toward the outside of the corner of the blank 10. By setting the corner end 11 of the blank 10 in such a shape, the tensile deformation at the corner end 11 can be alleviated, and the generation of wrinkles can be suppressed.
[0080] (Blank)
[0081] The blank 10 of this embodiment is described in detail. In this embodiment, the blank 10 is used. Figure 5A as well as Figure 5B The following describes a rectangular blank 10. Figure 5B 1 shows a portion of the corner end 11 of the blank 10 and its vicinity. The corner end 11 refers to a portion where the first side S1 and the second side S2 of the roughly linear blank 10 intersect when viewed from above in a direction perpendicular to the plate surface of the blank 10 .
[0082] Figure 5A as well as Figure 5B The visual field assumes that there is a square area A1 adjacent to the corner of the first rectangle R1 whose sides only pass through the edge of the blank 10 and the outside, and the length of one side is 40% of the short side of the rectangular cut plate. Figure 5CIf the blank 10 is formed to a depth such that the corner of the mold's ridgeline 1300 cannot enter the region A1 as shown, there is a concern that cracks may occur even using the insights of the present invention. In the case where the corner of the mold's ridgeline 1300 does not enter the region A1 and the molding is performed to a degree that no cracks occur, the width of the flange becomes excessive. In other words, the yield rate is poor. In the above-mentioned region A1, the blank 10 is tangent to each side only through the edge of the blank 10 and the two sides of the inner second rectangle R2. In the rectangular region A2 that passes through the two tangent points of the two sides of the second rectangle R2 and the blank 10 and whose corners overlap with the first rectangle R1, the blank 10 is tangent to the two sides of the first rectangle R1. As Figure 5B As shown, in the region A2, the blank 10 is tangent to two points X1 and X2 on both sides of the two sides of the first rectangle R1. In addition, from the two points X1 and X2 to the corner of the rectangular cut plate, the edge of the blank 10 and the edge of the rectangular cut plate may also be consistent. Furthermore, it is preferred that the two points X1 and X2 are located within a range of 10% of the short side length of the rectangular cut plate from the corner of the rectangular cut plate. By setting in this way, the tensile deformation of the corner end 11 of the blank 10 can be further alleviated.
[0083] Each side of the first rectangle R1 passes only through the edge and the outside of the blank. The first rectangle R1 is in the shape of a rectangular cut plate. Each side of the second rectangle R2 passes only through the edge and the inside of the blank. The second rectangle passes through the intersection N and the intersection M with the intersection O as an angle.
[0084] In a square region A1 adjacent to a corner of the first rectangle R1 and having one side 40% the length of the short side of the first rectangle R1, the blank 10 is tangent to both sides of the second rectangle R2. Figure 5B In the illustrated region, the edge of the blank 10 passes through the intersection point M and the intersection point N.
[0085] In the rectangular area A2 where the two sides of the second rectangle R2 overlap the two tangent points of the blank and the first rectangle R1, the blank 10 is tangent to both sides of the two sides of the first rectangle R1. In the area surrounded by the edge of the cut plate, the straight line L1, and the straight line L2, the edge of the blank 10 is tangent to the edge of the cut plate. However, in the actual cutting of the blank 10, it is not necessary to use the blank to the edge of the cut plate.
[0086] When the positions of the intersection points M and N of the blank 10 of this shape and the ridge line 130 of the die hole (punching hole 123) of the die are arranged as described in the above-mentioned method for manufacturing a stamped product and stamping is performed, the method for manufacturing a stamped product of the present invention can be implemented.
[0087] (Deformation example of blank)
[0088] Figure 7 This is a schematic plan view for explaining a modified example of the blank according to one embodiment of the present invention.
[0089] exist FIG. 5A to FIG. 7 In the example of FIG. 1 , a rectangular blank 10 is shown, but the shape of the blank 10 is not limited thereto, and the corner end 11 may be provided only at the corner portion that is the setting object for achieving the subject. A portion of the corner end 11 may also become a portion of the flange of the stamped product after stamping. The flange of the stamped product may also be trimmed to adjust the shape. In this case, the blank 10 is a shape that includes the corner end 11 at the corner of the blank 10.
[0090] The blank 10 may be a steel plate, an aluminum alloy plate, a titanium alloy plate or a composite material thereof. As the blank 10, a steel plate having a tensile strength of 270 to 440 MPa is more preferably used from the viewpoint of material elongation. In addition, the blank 10 may also be a high-strength steel plate, for example, a steel plate having a tensile strength of 980 MPa or more. In the case where the tensile strength of the blank 10 of the present embodiment is high, the effect of suppressing wrinkles and cracks can also be obtained. In addition, for the purpose of rust prevention and corrosion prevention, the blank 10 may also be subjected to electroplating and other processing.
[0091] In the blank 10 of this embodiment, the corner end 11 is defined on the plate surface of the corner of the blank 10. Therefore, wrinkles on the flange of the stamped product stamped from the blank 10 and cracks in and around the corner can be suppressed.
[0092] In the above embodiment, the corner region to be set as the corner end 11 is a corner region that protrudes from the bottom surface side to the support surface side relative to the side surface in a plan view in a direction perpendicular to the bottom surface of the first stamping die. That is, in a plan view in a direction perpendicular to the bottom surface of the first stamping die, a corner region that protrudes from the support surface side to the bottom surface side relative to the side surface is not a target of the above embodiment. For example, Figure 8 The side surface region B of the first press die shown is convex from the support surface side toward the bottom surface side relative to the side surface, and is not subject to the method of setting the corner end portion 11 of the present invention.
[0093] In the above embodiment, when a plurality of corner regions having different curvature radii are connected in a plan view in a direction perpendicular to the bottom surface, the corner end is set as one corner region. Figure 8 The side surface region C of the first press die shown in the figure includes a plurality of corner regions having different curvature radii, such as a corner region 121 ′ and a corner region 121 ″. Figure 8The side surface region C of the first press die shown in the figure is convex from the bottom surface side to the support surface side with respect to the side surface, and can be set as a setting object of the method for setting the corner end portion 11 of the present invention.
[0094] The plate thickness of the blank of the above-mentioned embodiment is more preferably appropriately set according to the required characteristics of the stamped product obtained by stamping the blank. The plate thickness of the blank may also be the average plate thickness of the metal plate as the processed material. The average plate thickness may be the average value of the plate thickness at a plurality of arbitrary points of the metal plate (for example, 3 points within the range of the longitudinal wall portion and the bottom plate portion formed). In addition, the plate thickness of the metal plate may also be substantially the same as the plate thickness of the longitudinal wall preformed portion or the bottom plate preformed portion of the preformed product, or the plate thickness of the longitudinal wall portion or the bottom plate portion of the stamped product. In addition, the plate thickness of the metal plate may also be substantially the same as the gap between the first die and the second die, or the gap between the fourth die and the fifth die.
[0095] If the radius of curvature of the corner is small, the problem of cracks and wrinkles becomes significant. In this case, if the stamping method of the present invention is implemented, the generation of cracks and wrinkles can also be suppressed. In the blank 10 with a tensile strength of 980 MPa or more, the bending of the ridgeline 130 of the die hole (punching hole 123) of the die, where the problem of cracks becomes significant, has a minimum curvature radius of 20 mm or less. This radius of curvature is equivalent to 30 times the thickness of the blank. That is, in a blank with a tensile strength of 980 MPa or more, when the minimum curvature radius of the bending of the ridgeline 130 of the edge of the die hole in the extension direction is less than 30 times that of the blank, if the stamping method of the present invention is implemented, the generation of cracks and wrinkles can be suppressed.
[0096] In addition, when the punching depth is large, the problems of cracks and wrinkles also become significant. In this case, the punching method of the present invention can also suppress the generation of cracks and wrinkles.
[0097] In the above embodiment, the angle formed by the tangent line of the ridgeline at the end point P1 and the tangent line of the ridgeline at the end point P2 is not particularly limited. Figure 6 . In addition, in the plan view in the direction perpendicular to the bottom surface of the first stamping die, the angle formed by the tangent line of the ridgeline at the end point P1 and the tangent line of the ridgeline at the end point P2 is preferably greater than 30° and less than 150°. In addition, in the above-mentioned embodiment, the planar area of the side surface of the first stamping die is preferably an area whose radius of curvature is greater than 500 mm in the plan view in the direction perpendicular to the bottom surface. In addition, in the above-mentioned embodiment, the height of the side surface of the first stamping die is more preferably greater than 20 times and less than 200 times the thickness of the blank 10.
[0098] In the above embodiment, the width of the flange portion of the blank 10 may also be asymmetric. That is, the length of the line segment OM may be different from the length of the line segment ON. In this case, it is also possible to define an appropriate flow control region for the blank 10, thereby suppressing the generation of wrinkles on the flange portion of the stamped product, the corner portion and the cracks near the corner portion.
[0099] In the above-mentioned embodiment, the stamped product may be a final product, or may be an intermediate product that is further processed (stamping, cutting, bending, welding, heating and cooling, electroplating, painting) to become a final product.
[0100] The press-formed product of the above embodiment can be preferably used for vehicle components such as battery boxes, front pillar lowers, and door inner parts, which have corners corresponding to the corner regions of the first press die and are typified by vehicle battery boxes. Figures 9A to 12 This is a diagram for explaining an example of a product to which the method for producing a press-formed product and the blank of the present invention can be preferably applied. Fig.9A The stamped product illustrated in FIG. 1 is a corner member 301 of a battery box, and has two corner portions 331 and 331 ′. Fig. 9B The press-formed product illustrated in FIG. 1 is a corner member 302 of a battery box, and has a corner portion 332. These press-formed products may be joined to other components to form the entire battery box. Fig.10 The press-formed product exemplified in FIG. 1 is a front pillar 303 having a corner portion B. The present invention can also be preferably applied to such a member that is bent in an L-shape as a whole. Fig.11 The press-formed product exemplified in FIG. 3 is a C-pillar reinforcement 304, and the vertical wall becomes higher near the corner portion 334. As described above, the present invention can also be preferably applied to a component having a non-uniform vertical wall height. Fig.12 The press-formed product exemplified in FIG. 1 is a door inner panel 305. The present invention can also be preferably applied to a press-formed product having a plurality of corner portions 335 and 335' having different curvature radii and opening angles, such as the door inner panel 305.
[0101] Example
[0102] Hereinafter, examples of the present invention will be described.
[0103] In this embodiment, Fig.13A , Fig.14 , Fig.15 , Fig.16 Each blank with a corner shape as shown was stamped, and the strain distribution of the flange of the stamped product was verified based on finite element analysis. Fig.13A , Fig.14 , Fig.15 , Fig.16The figure shows the vicinity of a corner of each blank. All the blanks have a common tensile strength of 270 MPa and a plate thickness of 0.8 mm.
[0104] For each blank 500, 600, 700, 10, the distribution of the maximum principal strain obtained by finite element analysis of the stamping forming situation was verified. The principal strain refers to the three components of the vertical strain when the coordinate system Cp where the shear strain becomes zero is used as the reference. The principal strain is defined as "maximum principal strain (ε1)", "intermediate principal strain (ε2)", and "minimum principal strain (ε3)" in order from the larger value. The maximum principal strain is generally used to evaluate the maximum tensile strain applied to the material. If the maximum principal strain is large, it can be judged to be easy to crack. In addition, the maximum principal strain can be obtained by general finite element analysis software. As a function of the software generally used in forming analysis, there is a function of inversely calculating the blank shape from the product shape as an unfolded view (unfolded blank analysis). By using this function to perform analysis, it is a general blank design for those skilled in the art to conduct research based on the shape of the unfolded blank.
[0105] (Experimental Example 1)
[0106] Fig.13A : is a schematic plan view of the blank 500 of Experimental Example 1. The corner end 511 of the blank 500 is located inside the region between the line segment MO and the line segment NO. That is, the blank 500 is a conventional example.
[0107] exist Fig. 13B The blank 500 is indicated by a two-dot chain line, and the shape after forming is indicated by a solid line. The location showing the maximum value of the maximum principal strain in Experimental Example 1 is Fig. 13B The maximum value is 0.85 in the area surrounded by the circle shown by the dotted line (near the bending area).
[0108] (Experimental Example 2)
[0109] Fig.14 : is a schematic plan view of the blank 600 of Experimental Example 2. The corner end 611 of the blank 600 is located inside the region between the line segment MO and the line segment NO. That is, the blank 600 is a conventional example.
[0110] The location showing the maximum value of the maximum principal strain in Experimental Example 2 is Fig. 13B The maximum value is 1.09 at the portion corresponding to the portion surrounded by the circle shown by the dotted line. That is, it can be seen that the stamped product is prone to cracking in the general blank design of those skilled in the art.
[0111] (Experimental Example 3)
[0112] Fig.151 is a schematic plan view of the blank 700 of Experimental Example 3. A portion of the corner end 711 of the blank 700 is located outside the region between the line segment MO and the line segment NO, but the corner end 711 does not include the entire line segment MO and the line segment NO.
[0113] The location showing the maximum value of the maximum principal strain in Experimental Example 3 is Fig. 13B The maximum value is 0.92, which is equivalent to the area surrounded by the circle shown by the dotted line. That is, it can be seen that even if a part of the corner end 711 is located outside the area between the line segment MO and the line segment NO, if the corner end 711 does not include all of the line segment MO and the line segment NO, the stamped product is prone to cracking.
[0114] (Experimental Example 4)
[0115] Fig.16 1 is a schematic plan view of the blank 10 of Experimental Example 4. All corner ends 11 of the blank 10 are located outside the region between the line segment MO and the line segment NO. That is, the blank 10 is an inventive example.
[0116] The location showing the maximum value of the maximum principal strain in Experimental Example 4 is Fig. 13B The maximum value of the portion corresponding to the portion surrounded by the circle indicated by the dotted line is 0.73. Compared with the conventional example, the maximum principal strain of the blank 10 can be improved.
[0117] According to the embodiment, in order to achieve improvement compared with the prior art, the corner end 11 needs to include all of the line segment MO and the line segment NO, and a part of the corner end 11 needs to be located outside the area between the line segment MO and the line segment NO.
[0118] Industrial Applicability
[0119] According to the method for manufacturing a press-formed product and the blank of the present invention, wrinkles in the flange portion of the press-formed product and cracks in the corner portion and its vicinity can be suppressed, and therefore, the method is extremely useful in industry.
[0120] Explanation of symbols
[0121] 10: blank; 11: corner end; 12: edge; 100: first stamping die; 110: bottom surface; 120: side surface; 121: corner area; 130: ridge line; 131: bending area; 140: supporting surface; 200: second stamping die; 300: third stamping die.
Claims
1. A method for manufacturing a stamped product, comprising: The blank is clamped by the supporting surface of the first punching die and the supporting surface of the third punching die; as well as The second punching die is pressed into the first punching die to perform deep drawing on the blank. The ridge line of the edge of the punching hole of the first punching die has a curved region that is curved and extended. When observing from the vertical direction of the above blank, When a first normal line passing through a first end portion of the ridgeline of the curved region in the extending direction is defined as a straight line L1, A second normal line passing through a second end portion of the ridgeline of the curved region in the extending direction is defined as a straight line L2. The intersection point of the straight line L1 and the end of the blank is defined as an intersection point M, and the intersection point of the straight line L2 and the end of the blank is defined as an intersection point N. A straight line passing through the intersection M and perpendicular to the straight line L1 is defined as a straight line L4. A straight line passing through the intersection point N and perpendicular to the straight line L2 is defined as a straight line L3. The intersection point of the straight line L3 and the straight line L4 is defined as the intersection point O. A line segment connecting the intersection point M and the intersection point O is defined as a line segment MO. When the line segment connecting the above-mentioned intersection point N and the above-mentioned intersection point O is defined as line segment NO, When the blank is clamped by the first punching die and the third punching die, The corner end (11) between the intersection point M and the intersection point N of the blank includes the entirety of the line segment MO and the line segment NO. A portion of the corner end portion (11) is located outside the region between the line segment MO and the line segment NO.
2. A blank, wherein: In a square region adjacent to a corner of a first rectangle whose sides pass only through the edge of the blank and the outside and whose length of one side is 40% of the short side of the first rectangle, the blank is tangent to both sides of two sides of a second rectangle whose sides pass only through the edge of the blank and the inside, In a rectangular region that passes through two tangent points between two sides of the second rectangle and the blank and whose corners overlap with the first rectangle, the blank is tangent to both of the two sides of the first rectangle.
3. The blank according to claim 2, wherein: The first rectangle is tangent to both of the two sides within a range within 10% of the length of the short side of the first rectangle from the corner of the first rectangle.