WO2024042593A1

WO2024042593A1 - Manufacturing method and blank for press-formed product

Info

Publication number: WO2024042593A1
Application number: PCT/JP2022/031656
Authority: WO
Inventors: 稔菅原; 康治田中; 貴行野崎; 昂山本
Original assignee: 日本製鉄株式会社
Priority date: 2022-08-23
Filing date: 2022-08-23
Publication date: 2024-02-29
Also published as: JP7216937B1

Abstract

This manufacturing method for a press-formed product comprises: sandwiching a blank (10) between a support surface (140) of a first press mold (100) and a support surface (340) of a third press mold (300); and pushing a second press mold (200) into the first press mold (100) to draw-form the blank (10). A ridgeline (130) at an edge of a press hole (123) of the first press mold (100) is provided with a curved region (131) that extends in a curved manner. When a prescribed corner end (11) is defined, the corner end (11) between an intersection M and an intersection N of the blank (10) includes all of a line segment MO and all of a line segment NO, and a portion of the corner end (11) is outside an area between the line segment MO and the line segment NO.

Description

Manufacturing method and blank for press-formed products

The present invention relates to a method for producing a press-formed product and a blank.

2. Description of the Related Art Electric vehicles are being rapidly deployed with the goal of reducing CO ₂ emissions, such as regulations based on CAFE (Corporate Average Fuel Efficiency). Currently, high-priced electric vehicles are the mainstream, but in order to reduce the price of electric vehicles, it is necessary to develop parts that use metals such as steel materials. As an example, molding technologies are being developed for battery boxes, front pillar lowers, door inners, etc. that use steel materials.

Typically, these parts (e.g., trays) are constructed to include a bottom plate, a vertical wall, and a flange, where the vertical wall has a curved corner (also referred to as a corner) and has multiple members. Manufactured by welding and assembling. However, with conventional forming techniques, when the radius of curvature of the corner is relatively small or when the depth of press forming is deep, wrinkles may occur in the flange near the corner. Specifically, it is common practice to manufacture products shaped like trays by drawing. The flanges adjacent the corners of the tray may be drawn and wrinkled as a result. This flange forming is called shrinkage flange forming. This is because the width of the flange in the circumferential direction decreases as the flange is formed. Wrinkles occur as a result of the circumferential width of the flange being reduced. This tendency becomes more pronounced as the object to be processed is a high-strength material. Further, as the height of the vertical wall of the tray increases, the amount of shrinkage of the flange increases, and therefore wrinkles are more likely to occur in the flange. The wrinkles created by the shrinkage flange remain even when the workpiece is drawn from the flange into the vertical wall of the tray. That is, wrinkles also occur on the vertical walls of the tray. Even if the radius of curvature of the corners of the tray is small, wrinkles are likely to occur on the flanges and vertical walls. Furthermore, if the radius of curvature of the corner of the tray is small, cracks may occur along the ridgeline of the vertical wall extending from the corner of the tray. This crack is more likely to occur as the radius of curvature of the corner of the tray becomes smaller. Furthermore, the higher the strength of the material to be processed, the more likely this crack will occur.

As a method for suppressing wrinkles in the flange portion, for example, the technique disclosed in Patent Document 1 attempts to provide a bead on the pressing surface of the mold to control the flow direction of the material during drawing. However, with the technique of Patent Document 1, there is a high possibility that bead marks or scratches will be formed on the product after press molding, which may impair the appearance. Further, with the technique of Patent Document 1, when press forming a high-strength steel material or the like, there is a high possibility that the desired effect cannot be achieved, and it is difficult to perform stable production.

Japanese Patent No. 2560416

The inventors have conducted extensive studies on the causes of suppressing the occurrence of wrinkles and cracks.
Geometrically, the outer flanges at the corners of the tray shrink as they become narrower as they are drawn toward the vertical walls. In addition, in a molded product with wrinkles on the outer flange of the corner of the tray, wrinkles also occur on the edges of the molded product. From this, it is easy to think that the entire outer flange of the corner of the tray is shrinking and deforming.
Because the inflow resistance from the flange toward the vertical wall is different between the straight ridgeline between the flange and the vertical wall of the tray and the corner, the flow resistance from the flange to the vertical wall is different between the flange and corner ridgeline adjacent to the straight ridgeline before and after forming. Looking at the relative positions of the flanges, after molding, the flanges adjacent to the corner ridgeline and their surroundings bulge away from the ridgeline. From this, the inventors thought that the end of the flange (the edge of the workpiece) was actually stretched. This hypothesis was confirmed to be correct through finite element analysis and actually forming the blank by scratching it.
The inventors further investigated and found that when assuming a rectangular area in the blank that perpendicularly crosses the bisector of the corner of the blank, the rectangular area becomes convex toward the corner of the blank as it is formed. The inventors thought that it deforms into an arch shape. The inventors thought that the concave side of the arch shape is compressively deformed and wrinkles occur. The inventor believes that the convex side of the arch shape undergoes tensile deformation, but if this tensile deformation is alleviated, the deformation to the arch shape is alleviated, and as a result, the compressive deformation of the concave side of the arch shape is also alleviated, thereby suppressing the occurrence of wrinkles. thought. Specifically, the inventors made the distance between the edge of the corner of the die hole and the edge of the blank wider than before, compared to the distance between the edge of the die hole and the edge of the blank, which extend straight. We came up with the idea of suppressing deformation into an arch shape. The inventors have come up with the idea that the occurrence of wrinkles can be suppressed by setting the positional relationship between the edge of the die hole and the edge of the blank in this manner. Furthermore, the inventors came up with the idea of suppressing cracks that occur at the ridgeline of the vertical wall extending from the corner of the tray when the radius of curvature of the corner of the tray is small.

Here, the movement of the point to be processed before and after press forming will be explained.
FIGS. 17A and 17B are explanatory diagrams for explaining the movement of points (a, b, c, d) to be processed before and after conventional press forming, based on finite element analysis results. FIG. 17A is an explanatory diagram showing points to be processed before conventional press forming based on finite element analysis results. FIG. 17B is an explanatory diagram showing points to be processed after press forming, based on finite element analysis results.
Points a and b are points located at the ends of the curved portion of the ridgeline (edge of the die hole) of the mold after molding. Points c and d are points at the end of the press-formed product that are on a line that passes through the end of the curved part of the mold and is perpendicular to the extending direction of the ridgeline of the mold after molding. If you use the function of the finite element analysis software to back-calculate the blank shape from the product shape as shown in the developed diagram, the points (a, b, c, d) to be processed in Fig. 17B will be located at the positions in Fig. 17A before forming. become.
The inflow of the workpiece accompanying molding includes an inflow FA that is sucked into the straight ridgeline of the mold, and an inflow _FB that is sucked into the curved portion of the ridgeline of _the mold. The inflow _FA has deformation resistance that causes the workpiece to be bent by the ridgeline of the mold. In addition to the deformation resistance in which the workpiece is bent by the ridgeline of the mold, the inflow F _B has deformation resistance in which the workpiece is compressed in a direction that crosses the inflow direction as the workpiece approaches the curved part of the mold ridgeline. . That is, the deformation resistance of the inflow F _B is higher than that of the inflow F _A. Therefore, the inflow amounts of inflow F _A and inflow F _B are not uniform. As a result of the fact that the inflow amounts of the inflow F _A and the inflow F _B are not uniform, the width of the flange of the molded product (width from the ridgeline of the mold to the edge of the molded product) becomes wider at the location where the inflow F _B occurs. Furthermore, the width of the flange of the molded product is widened by the workpiece pushed out from the location where the inflow F _B occurs at the location where the inflow F _A occurs around the location where the inflow F _B occurs. From another point of view, the flange of the molded product may be damaged by the workpiece being pulled out by the inflow F _A from the location where the inflow F _B occurs, even at the location where the inflow F _A occurs around the location where the inflow F _B occurs. The width becomes wider.
A region H surrounded by points a, b, c, and d is deformed into an arch-like convex shape in the same direction as the convex curve of the curved portion of the ridgeline of the mold due to molding. The shaded area H in FIG. 17A corresponds to the corner flange after molding. After molding, region H in FIG. 17A transforms into region H shown by diagonal lines in FIG. 17B. As shown in FIGS. 17A and 17B, points a, b, c, and d move during molding. For example, point a has an inflow trajectory as shown in FIG. 17B.
Wrinkles occur in the molded product because points a and b become closer together during molding. The inventor thought that if the arch-like deformation of the region H surrounded by points a, b, c, and d could be alleviated, the generation of wrinkles could be suppressed. It is thought that if the stretch between points c and d can be suppressed, the arch-like deformation can be alleviated.

The inventors thought that by stretching the corners of the blank outward, it would be possible to suppress the stretching between points c and d. FIGS. 18A and 18B are explanatory diagrams for explaining the movement of the processing target point (a, b, c, d) before and after press forming according to the present disclosure, based on the finite element analysis results. FIG. 18A is an explanatory diagram showing points to be processed before press forming according to the present disclosure, based on finite element analysis results. FIG. 18B is an explanatory diagram showing points to be processed after press forming according to the present disclosure, based on finite element analysis results.
The dotted line in FIG. 18A shows the shape of a conventional 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. As shown in FIG. 18A, the blank (workpiece) extends outward from points c and d. It has been found that this reduces the stretching between points c and d due to molding. There are two main reasons for this. First, even if the workpiece is drawn into the curved part of the mold ridge line by the same length, the rate at which the distance between points e and f becomes closer is smaller than the rate at which the distance between points c and d approaches. small. That is, a portion of the blank located at the edge of points c and d prevents points c and d of the blank from approaching each other. Second, since the number of points drawn in by the inflow F _A has increased between points c and e (between points d and f), the stress stretching between points c and d has been alleviated. Ru. When the stress is relaxed, the elongation deformation is also relaxed.

The present disclosure has been made in view of the above, and an object of the present disclosure 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 the vicinity thereof. shall be.

(1) A method for manufacturing a press-formed product according to one aspect of the present disclosure includes sandwiching a blank between a support surface of a first press mold and a support surface of a third press mold, and placing the second press mold in the second press mold. drawing and forming the blank by pressing it into a press mold, wherein the edge line of the press hole of the first press mold has a curved area extending in a curved manner, when viewed from the vertical direction of the blank. In this case, a first normal line passing through a first end of the curved area in the extending direction of the ridge line is a straight line L1, and a second normal line passing through a second end of the curved area in the extending direction of the ridge line is a straight line L1. The normal line is a straight line L2, the intersection of the straight line L1 and the edge of the blank is an intersection point M, the intersection of the straight line L2 and the edge of the blank is an intersection point N, and a line that passes through the intersection M and is perpendicular to the straight line L1 A straight line is a straight line L4, a straight line passing through the intersection N and perpendicular to the straight line L2 is a straight line L3, the intersection of the straight line L3 and the straight line L4 is an intersection point O, and a line segment connecting the intersection point M and the intersection O is a line segment MO. , when the line segment connecting the intersection point N and the intersection point O is defined as a line segment NO, the corner end between the intersection point M and the intersection point N of the blank is the line segment MO and the line segment NO. A portion of the corner end is outside a region between the line segment MO and the line segment NO.

In the method for manufacturing a press-formed product with the above configuration, it is possible to define an appropriate flow control area for the blank, thereby suppressing the occurrence of wrinkles in the flange portion of the press-formed product and cracks at the corner and its vicinity. can.

(2) The blank according to one aspect of the present disclosure is adjacent to a corner of the first rectangle, each side of which passes only through the edge and the outside of the blank, and the length of one side is 40 mm of the short side of the first rectangle. % square area, the blank touches both two sides of a second rectangle with each side passing only through the edges and inside of the blank, and the two sides of the second rectangle and the two sides of the blank In the region of the rectangle that passes through the contact point and whose corners overlap the first rectangle, the blank touches both two sides of the first rectangle.
(3) The blank described in (2) above extends between the two sides of the first rectangle within 10% of the length of the short side of the first rectangle from the corner of the first rectangle. May be in contact with both.

In the blank with the above configuration, the flow control area is defined on the plate surface of the corner of the blank corresponding to the corner area of the mold, so there are wrinkles in the flange part of the press-formed product and cracks in the corner part and its vicinity. The occurrence of can be suppressed.

According to the press-formed product manufacturing method and blank of the present disclosure, it is possible to suppress the occurrence of wrinkles in the flange portion of the press-formed product, and cracks in the corner portions and their vicinity.

FIG. 2 is a schematic perspective view showing the vicinity of a corner area of a first press mold according to an embodiment of the present disclosure. FIG. 2 is a diagram showing the vicinity of a corner region of a first press mold according to an embodiment of the present disclosure, and is a schematic plan view in a plan view in a direction perpendicular to the bottom surface. 3 is a schematic cross-sectional view of the first press mold taken along a plane passing along the line A-A' in FIG. 2. FIG. FIG. 1 is a schematic perspective view for explaining a set of press molds according to an embodiment of the present disclosure. FIG. 1 is a schematic plan view for explaining a method for manufacturing a press-formed product according to an embodiment of the present disclosure. 5A is a plan view showing the vicinity of a part of the corner ends shown in FIG. 5A. FIG. FIG. 3 is a schematic plan view for explaining a method for manufacturing a press-formed product of a comparative example. FIG. 7 is a schematic plan view for explaining a modification of the method for manufacturing a press-formed product according to an embodiment of the present disclosure. FIG. 7 is a schematic plan view for explaining a modified example of the blank according to an embodiment of the present disclosure. FIG. 3 is a schematic perspective view for explaining a corner area according to an embodiment of the present disclosure. 1 is a diagram illustrating an example of a product in which the present disclosure can be preferably used. FIG. 1 is a diagram illustrating an example of a product in which the present disclosure can be preferably used. FIG. 1 is a diagram illustrating an example of a product in which the present disclosure can be preferably used. FIG. 1 is a diagram illustrating an example of a product in which the present disclosure can be preferably used. FIG. 1 is a diagram illustrating an example of a product in which the present disclosure can be preferably used. FIG. FIG. 3 is a schematic plan view of the blank of Experimental Example 1. FIG. 3 is a diagram showing the distribution of maximum principal strain obtained by finite element analysis when the blank of Experimental Example 1 was press-formed. FIG. 3 is a schematic plan view of the blank of Experimental Example 2. FIG. 7 is a schematic plan view of the blank of Experimental Example 3. FIG. 4 is a schematic plan view of a blank of Experimental Example 4. FIG. 2 is an explanatory diagram showing points to be processed before conventional press forming based on finite element analysis results. FIG. 2 is an explanatory diagram showing points to be processed after conventional press forming based on finite element analysis results. FIG. 2 is an explanatory diagram showing points to be processed before press forming according to the present disclosure, based on finite element analysis results. FIG. 2 is an explanatory diagram showing points to be processed after press forming according to the present disclosure, based on finite element analysis results.

The present inventors investigated the shape of a blank to be press-formed in order to suppress wrinkles that occur in the flange part of a press-formed product, and found that by providing an extra part in the shape of a conventional blank, it was possible to suppress wrinkles during press-forming. It has been found that the flow direction of the material can be controlled, leading to the suppression of wrinkles in the flange, cracks in the corners, and their vicinity. However, on the other hand, the present inventors have also found that simply providing a surplus portion does not effectively suppress such wrinkles. As a result of extensive research, they discovered that wrinkles in the flange portion of a press-formed product can be effectively suppressed by setting an appropriate area according to the shape of the blank and the shape of the mold.

Hereinafter, embodiments of the present disclosure will be described using examples, but it is obvious that the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be illustrated, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained. Moreover, each component of the following embodiments can be combined with each other.

(Manufacturing method of press molded product)
The method for manufacturing a press-formed product according to the present embodiment includes sandwiching a blank between a support surface of a first press mold and a support surface of a third press mold (blank clamping step), and inserting a second press mold into the second press mold. 1) Pressing the blank into a press mold and drawing the blank (blank drawing process).
First, an example of a press mold that can carry out the blank clamping process and the blank drawing process will be described.

(Press mold)
FIG. 1 shows an example of a press mold (first press mold 100) that can be employed in the method for manufacturing a press-formed product according to the present embodiment. Moreover, FIG. 2 is a schematic diagram showing the vicinity of the corner region 121 of the side surface 120 of the first press mold 100, and shows a plan view in a direction perpendicular to the bottom surface 110. In the example of FIGS. 1 and 2, the X axis is parallel to the direction in which one plane area (plane area 122a) of the side surface 120 extends, and the Y axis is parallel to the direction in which the other plane area (plane area 122b) of the side surface 120 extends. It is parallel to the extending direction, and the Z axis is parallel to the perpendicular to the bottom surface 110.

FIG. 1 is a schematic perspective view showing the vicinity of a corner region 121 of a side surface 120 of the first press mold 100. The first press mold 100 shown in FIG. and a supporting surface 140 to be connected.

The bottom surface 110 may 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 part of the outer edge 111 may be connected to the side surface 120. A portion of the outer edge 111 includes a corner 111 a corresponding to a corner region 121 of the side surface 120 . The bottom surface 110 and the side surface 120 may be connected via a bottom surface side ridgeline 112 provided along the outer edge 111. In a cross-sectional view 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. A portion of the bottom side ridgeline 112 that is connected to the corner region 121 of the side surface 120 is referred to as a corner 112a. The bottom surface 110 may have a concave portion or a convex portion facing out of the surface of the bottom surface 110 to provide an uneven portion on the press-formed product.

The side surface 120 is connected to the bottom surface 110 and stands up toward the outside of the bottom surface 110. Part or all of the side surface 120 may be parallel to the normal to the bottom surface 110 or may be inclined relative to the normal to the bottom surface 110. As shown in FIG. 1 or 2, the side surface 120 has a corner region 121 that is curved in a plan view in a direction perpendicular to the bottom surface 110. The corner area 121 is connected to the plane area 122 (plane area 122a and plane area 122b) of the side surface 120 at the end portion 121a and the end portion 121b. The corner region 121 may be connected to another corner region having a different radius of curvature in a plan view perpendicular to the bottom surface 110 or to a region of the side surface 120 that is gently curved. Alternatively, the end of the corner region 121 may be the end of the side surface 120. In the examples of FIGS. 1 and 2, the plane area 122a and the plane area 122b are orthogonal to each other when viewed from above in a direction perpendicular to the bottom surface 110, but when viewed from above in a direction perpendicular to the bottom surface 110, the plane area 122a The angle formed by 122b is not limited to this.

The side surface 120 is connected to the support surface 140 via the ridgeline 130 at the end opposite to the end to which the bottom surface 110 is connected. In a cross-sectional view perpendicular to the extending direction of the ridge line 130 at each point of the ridge line 130, the support surface 140 is provided on the side opposite to the bottom surface 110 with respect to the side surface 120. A portion of the ridgeline 130 that is connected to the corner region 121 of the side surface 120 is referred to as a curved region 131. The curved region 131 of the ridgeline 130 is connected to the straight region 132 (straight region 132a and straight region 132b) of the ridgeline 130 at the terminal end 131a and the terminal end 131b. The curved region 131 may be connected to another curved region having a different radius of curvature in a plan view perpendicular to the bottom surface 110 or to a region of the ridge line 130 that curves gently. Alternatively, the terminal end of the curved region 131 may be the end of the ridgeline 130. The terminal ends (terminal end 131a and terminal end 131b) of the curved region 131 each include a terminal point (first end) P1 and a terminal point (second end) P2, which will be described later.

FIG. 3 shows a schematic cross-sectional view of the first press mold 100 taken along a plane passing along the line A-A' in FIG. 2. As shown in FIG. 3, the bottom surface 110 and the corner region 121 of the side surface 120 are smoothly connected via the corner 112a of the bottom surface side ridgeline 112, and the corner region 121 of the side surface 120 and the support surface 140 are connected to each other through the curve of the ridgeline 130. They are smoothly connected via region 131. In the example of FIG. 3, the corner region 121 of the side surface 120 is inclined with respect to the normal to the bottom surface 110. However, the corner region 121 may be perpendicular to the bottom surface 110 in each cross section orthogonal to the bottom surface 110. The first press mold 100 has a press hole 123. The second press mold 200 is pushed into the press hole 123 by relatively moving the first press mold 100 and the second press mold 200, which will be described later, in a direction in which they approach each other. The ridgeline 130 of the edge of the press hole 123 (the edge on the second press mold 200 side) includes a curved region 131 that extends in a curved manner.

The first press mold 100 may include one or more corner regions 121. The bottom surface 110 of the first press mold 100 corresponds to the bottom plate part of the press molded product, the side surface 120 corresponds to the vertical wall part of the press molded product, and the support surface 140 corresponds to the flange part of the press molded product.

Press molding is performed by a set of press molds 1000 including the first press mold 100, the second press mold 200, and the third press mold 300 described above. FIG. 4 shows an example of a set of press molds 1000 including a first press mold 100, a second press mold 200, and a third press mold 300. Although FIG. 4 illustrates a press mold 1000 including a first press mold 100 having four corner regions 121, the shape of the press mold is not limited to this, and the number of corner regions 121 and the shape of the bottom surface 110 are not limited to this shape. is not particularly limited.

The second press mold 200 has a bottom surface 210 corresponding to the bottom surface 110 of the first press mold 100, a side surface 220 corresponding to the side surface 120 of the first press mold 100, and a corner area 121 of the first press mold 100. A corner area 221 corresponding to the corner area 221 is provided. The outer surface shapes of the bottom surface 210 and side surfaces 220 of the second press mold 200 correspond to the outer surface shapes of the bottom surface 110 and side surfaces 120 of the first press mold 100. With the blank, which is the workpiece, placed between the first press die 100 and the second press die 200, the bottom surface 110 of the first press die 100 and the bottom surface 210 of the second press die 200 are close to each other. By relatively moving the first press die 100 and the second press die 200 in the direction (pressing direction), the blank is plastically deformed between the first press die 100 and the second press die 200. let The first press mold 100 is also called a die. The second press die 200 is also referred to as a punch.

The third press mold 300 includes a support surface 340 corresponding to the support surface 140 of the first press mold 100. The support surface 140 of the first press mold 100 and the support surface 340 of the third press mold 300 are arranged to face each other. , can hold the blank, which is the workpiece. The blank is held between the support surface 140 of the first press mold 100 and the support surface 340 of the third press mold 300 so that it can move in the in-plane direction without moving in the out-of-plane direction. When relatively moving the first press die 100 and the second press die 200 with the blank sandwiched between the first press die 100 and the third press die 300, the second press die 200 moves relative to the third press die 300. The third press mold 300 is also referred to as a holder.

The first press mold 100, the second press mold 200, and the third press mold 300 may each be constructed from a single member, or each may be constructed from a divided mold. Further, the press mold 1000 may include molds other than these molds.

The corner end portion 11 of the blank 10 will be explained. FIG. 5A is a schematic plan view for explaining the method for manufacturing a press-formed product according to the present embodiment of the present disclosure. FIG. 5A is a plan view of the plate-shaped blank 10 in a direction perpendicular to the plate surface. FIG. 5B shows the vicinity of a part of the corner ends 11 of the blank 10 shown in FIG. 5A. FIG. 5B shows the ridgeline 130 of the die hole (press hole 123) and the ridge line 130 of the blank 10 when the blank 10 is placed on the die (first press mold 100) and sandwiched between the blank holders (third press mold 300). Indicates the position of the edge.
When viewed from the vertical direction of the blank 10, the first normal line passing through the first end P1 in the extending direction of the ridgeline 130 of the curved region 131 is the straight line L1, and the second normal line in the extending direction of the ridgeline 130 of the curved region 131 is The second normal passing through the end P2 of is the straight line L2, the intersection of L1 and the end of the blank 10 is the intersection M, the intersection of the straight line L2 and the end of the blank 10 is the intersection N, passing through the intersection M, the straight line The straight line perpendicular to L1 is the straight line L4, the straight line passing through the intersection N, the straight line perpendicular to the straight line L2 is the straight line L3, the intersection of the straight line L3 and the straight line L4 is the intersection point O, the line segment connecting the intersection point M and the intersection point O is the line segment MO, the intersection point A line segment connecting N and intersection O is defined as line segment NO. The end of the blank 10 between the intersection M and the intersection N is defined as a corner end 11. The corner end portion 11 is a portion outside the blank 10 from the line segment MN connecting the intersection point M and the intersection point N. As shown in FIG. 5B, when the blank 10 is sandwiched between the first press mold 100 and the third press mold 300, the corner end 11 includes all the line segments MO and NO, and one part of the corner end 11 includes the line segment MO and the line segment NO. is outside the area between line segment MO and line segment NO. Note that line segment MO and line segment NO have the shapes of the ends of a conventional blank. The edge of the corner end 11 of the blank 10 is located outside the region sandwiched between the line segment MO and the line segment NO, and the edge of the corner end 11 of the blank 10 is located inside the region sandwiched between the line segment MO and the line segment NO. There isn't.

In this way, a part of the corner end 11 of the blank 10 is outside the area between the line segment MO and the line segment NO. That is, the blank 10 has a shape in which the corner end portions 11 protrude outward. In other words, the corner end portion 11 has a convex shape toward the outside of the corner of the blank 10. Further, the corner end portion 11 can also be said to have an arch shape toward the outside of the corner of the blank 10. By forming the corner end 11 of the blank 10 into such a shape, tensile deformation at the corner end 11 is alleviated, and the generation of wrinkles is suppressed.

Note that the corner ends 11 do not need to be set at all corners in the blank 10, and the corner ends 11 may be set only at some of the corners.

In the method for manufacturing a press-formed product according to the present embodiment, it is possible to define an appropriate corner end 11 for the blank, so wrinkles in the flange portion of the press-formed product and cracks in the corner portion and the vicinity thereof can be prevented. It can be suppressed. In the corner portions, cracking can be particularly suppressed at the corner portions 112a. The corner portion 112a is a portion that continues to be stretched from the start to the end of press molding, and is the portion where cracks are most likely to occur.

(Modified example of manufacturing method of press-formed product)
FIG. 6 is a schematic plan view for explaining a modification of the method for manufacturing a press-formed product according to an embodiment of the present disclosure. FIG. 6 shows the position of the edge line 130 of the die hole and the edge of the blank 10 when the blank 10 is placed on the die (first press die 100) and sandwiched between the blank holders (third press die 300). ing. Note that FIG. 6 shows the vicinity of one corner end 11 of the corner ends of the blank 10.
Also in the modification shown in FIG. 6, a part of the corner end 11 of the blank 10 is located outside the region between the line segment MO and the line segment NO, similar to FIG. 5B. That is, the blank 10 has a shape in which the corners protrude outward. In other words, the corner end portion 11 has a convex shape toward the outside of the corner of the blank 10. Further, the corner end portion 11 can also be said to have an arch shape toward the outside of the corner of the blank 10. By forming the corner end 11 of the blank 10 into such a shape, tensile deformation at the corner end 11 is alleviated, and the generation of wrinkles is suppressed.

(blank)
The blank 10 according to this embodiment will be explained in detail. In this embodiment, a blank 10 having a rectangular shape will be described using FIGS. 5A and 5B. 5B shows the vicinity of some of the corner ends 11 of the blank 10, but the corner ends 11 are approximately straight lines in a plan view in a direction perpendicular to the plate surface of the blank 10. This is the point where the first side S1 and the second side S2 of the shaped blank 10 intersect.
The field of view in FIGS. 5A and 5B is a square of 40% of the short side of a rectangular cutting board, adjacent to a corner of a first rectangle R1, each side of which passes only the edge and outside of the blank 10. An area A1 is assumed. If the blank 10 is molded so deeply that the corner of the ridgeline 1300 of the mold does not fit within this area A1 as shown in FIG. 5C, there is a concern that cracks may occur even using the knowledge of the present disclosure. If the corner of the ridge line 1300 of the mold does not fall within this region A1 and molding is performed to the extent that cracks do not occur, the width of the flange becomes excessive. In other words, the yield is poor. In the area A1, the blank 10 is in contact with both two sides of the second rectangle R2, each side of which passes only through the edges and inside of the blank 10, and the two sides of the second rectangle R2 and the two contact points of the blank 10. In a rectangular area A2 passing through and whose corners overlap with the first rectangle R1, the blank 10 touches both of the two sides of the first rectangle R1. As shown in FIG. 5B, in area A2, blank 10 touches two points X1 and X2 on both sides of first rectangle R1. Further, the edge of the blank 10 and the edge of the rectangular cutting plate may coincide with each other from the two points X1 and X2 to the corner of the rectangular cutting plate. Furthermore, it is desirable that the two points X1 and X2 be within 10% of the length of the short side of the rectangular cut plate from the corner of the rectangular cut plate. By doing so, the tensile deformation of the corner end portion 11 of the blank 10 can be further alleviated.

Each side of the first rectangle R1 passes only through the edge and outside of the blank. The first rectangle R1 has the shape of a rectangular cut plate. Each side of the second rectangle R2 passes only through the edge and inside of the blank. The second rectangle passes through intersections N and M with intersection O as its corner.
In a square area A1 adjacent to the corner of the first rectangle R1, the length of one side of which is 40% of the short side of the first rectangle R1, the blank 10 is placed on both two sides of the second rectangle R2. come into contact with In the region illustrated in FIG. 5B, the edge of the blank 10 passes through the intersections M and N.
In a rectangular area A2 where the two sides of the second rectangle R2 and the two contact points of the blank overlap with the first rectangle R1, the blank 10 contacts both of the two sides of the first rectangle R1. The edge of the blank 10 touches the edge of the cutting plate in a region surrounded by the edge of the cutting plate, the straight line L1, and the straight line L2. However, in actually cutting out the blank 10, it is not necessary to use the blank up to the edge of the cutting board.

Press forming is performed by arranging the positions of the intersection point M and the intersection point N of the blank 10 having such a shape and the ridge line 130 of the die hole (press hole 123) as explained in the above-mentioned method for manufacturing a press-formed product. Then, the method for manufacturing a press-formed product of the present disclosure can be carried out.

(Blank modification example)
FIG. 7 is a schematic plan view for explaining a modification of the blank according to an embodiment of the present disclosure.

In the examples of FIGS. 5A to 7, a rectangular (rectangular) blank 10 is shown, but the shape of the blank 10 is not limited to this. may be provided. A part of the corner end 11 may become a part of the flange of the press-formed product after press-forming. The shape of the press-formed product may be adjusted by trimming the flange. In this case, the blank 10 has a shape that includes corner ends 11 at the corners of the blank 10 .

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, it is more preferable to use a steel plate having a tensile strength of 270 to 440 MPa from the viewpoint of material elongation. Further, the blank 10 may be a high-strength steel plate, for example, a steel plate having a tensile strength of 980 MPa or more. Even when the tensile strength of the blank 10 according to this embodiment is high, the effect of suppressing wrinkles and cracks can be obtained. Furthermore, the blank 10 may be subjected to processing such as plating for the purpose of rust prevention and corrosion prevention.

In the blank 10 according to the present embodiment, a corner end 11 is defined on the plate surface of the corner of the blank 10. Therefore, it is possible to suppress the occurrence of wrinkles in the flange portion of a press-formed product press-formed from this blank 10 and cracks in the corner portion and the vicinity thereof.

In the embodiment described above, the corner region where the corner end portion 11 is set is convex from the bottom side to the supporting surface side with respect to the side surface in a plan view in a direction perpendicular to the bottom surface of the first press mold. The corner area is That is, in a plan view in a direction perpendicular to the bottom surface of the first press mold, a corner region that is convex from the support surface side to the bottom surface side with respect to the side surface is not a target of the above embodiment. For example, the side area B of the first press die shown in FIG. 8 is convex from the supporting surface side to the bottom side with respect to the side surface, and is not subject to the method for setting the corner end 11 according to the present disclosure. .

In the above embodiment, when a plurality of corner regions having mutually different radii of curvature are connected in a plan view in a direction perpendicular to the bottom surface, the above-mentioned corner end portion is set with these plurality of corner regions as one corner region. do. For example, the side region C of the first press mold shown in FIG. 8 includes a plurality of corner regions 121' and 121'' having different radii of curvature. The side surface area C of the first press die shown in FIG. 8 is convex from the bottom side to the supporting surface side with respect to the side surface, and can be set as a setting target of the setting method of the corner end 11 according to the present disclosure.

It is more preferable that the thickness of the blank according to the above embodiment is appropriately set depending on the characteristics required of a press-formed product obtained by press-molding the blank. The thickness of the blank may be the average thickness of the metal plate that is the workpiece. The average plate thickness may be the average value of the plate thicknesses at a plurality of arbitrary points on the metal plate (for example, three points in the range formed into the vertical wall portion or the bottom plate portion). Further, the thickness of the metal plate may be substantially the same as the thickness of the vertical wall preformed part or the bottom plate preformed part of the preformed product, or the thickness of the vertical wall part or the bottom plate part of the press formed product. . Further, the thickness of the metal plate may be substantially the same as the clearance between the first mold and the second mold, or the clearance between the fourth mold and the fifth mold.

If the radius of curvature of the corners is small, problems with cracks and wrinkles become apparent. Even in such a case, by implementing the press molding method of the present disclosure, the occurrence of cracks and wrinkles can be suppressed. In the blank 10 having a tensile strength of 980 MPa or more, the smallest radius of curvature of the curvature in the extending direction of the ridge line 130 of the die hole (press hole 123) where the problem of cracking becomes apparent is 20 mm or less. This radius of curvature corresponds to 30 times the thickness of the blank. That is, in a blank having a tensile strength of 980 MPa or more, when the smallest radius of curvature in the extending direction of the ridge line 130 at the edge of the die hole is 30 times or less of the blank, if the press forming method of the present disclosure is performed, It can suppress the occurrence of cracks and wrinkles.
Furthermore, when the pressing depth is large, problems such as cracks and wrinkles become apparent. Even in that case, the occurrence of cracks and wrinkles can be suppressed by the press forming method of the present disclosure.

In the above embodiment, the angle between the tangent to the ridgeline at the termination point P1 and the tangent to the ridgeline at the termination point P2 is not particularly limited. For example, it can be an acute angle as shown in FIG. Further, in a plan view in a direction perpendicular to the bottom surface of the first press mold, it is more preferable that the angle between the tangent to the ridgeline at the termination point P1 and the tangent to the ridgeline at the termination point P2 is 30° or more and 150° or less. . Further, in the above embodiment, it is preferable that the planar region of the side surface of the first press die has a radius of curvature of 500 mm or more when viewed from above in a direction perpendicular to the bottom surface. Further, in the embodiment described above, it is more preferable that the height of the side surface of the first press mold is 20 times or more and 200 times or less the thickness of the blank 10.

In the above embodiment, the width of the flange portion of the blank 10 may be asymmetrical. That is, the length of the line segment OM and the length of the line segment ON may be different. Even in such a case, since an appropriate flow control region can be defined for the blank 10, 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 the vicinity thereof.

In the above embodiments, the press-formed product may be a final product, or an intermediate product to be further processed (press-forming, cutting, bending, welding, heating/cooling, plating, painting) into a final product. There may be.

The press-formed product according to the above embodiment has a corner portion corresponding to the corner area of the first press mold, and is suitable for use in vehicles such as battery boxes, front pillar lowers, door inners, etc. represented by battery boxes for vehicles. It can be preferably used for parts. 9A to 12 are diagrams for explaining an example of a product in which the press-formed product manufacturing method and blank according to the present disclosure can be preferably used. The press-molded product illustrated in FIG. 9A is a corner part 301 of a battery box, and has two corner parts 331 and 331'. The press-molded product illustrated in FIG. 9B is a corner part 302 of a battery box, and has a corner part 332. The entire battery box may be formed by joining these press-molded products with other members. The press-molded product illustrated in FIG. 10 is a front pillar 303 having a corner portion 333. The present disclosure can also be preferably applied to such a member whose entire body is curved into an L-shape. The press-molded product illustrated in FIG. 11 is a C-pillar stiffener 304, and the vertical wall is high near the corner portion 334. In this way, the present disclosure can be preferably applied to members whose vertical walls are not uniform in height. The press-molded product illustrated in FIG. 12 is a door inner 305. The present disclosure can also be preferably applied to a press-molded product having a plurality of corner portions 335 and 335' having different curvature radii and opening angles, such as the door inner 305.

Examples of the present disclosure will be described below.
In this example, press forming was performed on each blank having corner portions shaped as shown in FIGS. 13A, 14, 15, and 16, and the strain distribution at the flange portion of the press-formed product was verified by finite element analysis. . The figures shown in FIGS. 13A, 14, 15, and 16 show the vicinity of some corners of each blank. Common to all blanks, the tensile strength of the blank was 270 MPa, and the plate thickness was 0.8 mm.

For each blank 500, 600, 700, and 10, the distribution of the maximum principal strain obtained by performing finite element analysis on press forming was verified. The principal strain is three vertical strain components when the coordinate system Cp in which the shear strain is zero is used as a reference. The principal strains are defined as "maximum principal strain (ε1)," "intermediate principal strain (ε2)," and "minimum principal strain (ε3)" in order from the largest value. Maximum principal strain is generally used to evaluate the maximum tensile strain that can be applied to a material. If this maximum principal strain is large, it can be determined that the material is likely to break. Note that the maximum principal strain can be determined using general finite element analysis software. One of the functions of software commonly used in forming analysis is the function of back calculating the blank shape from the product shape as in a developed diagram (developed blank analysis). A common blank design for those skilled in the art is to analyze using this function and consider the shape of the developed blank as a reference.

(Experiment example 1)
FIG. 13A is a schematic plan view of the blank 500 of Experimental Example 1. Corner end 511 of blank 500 is inside the area between line segment MO and line segment NO. That is, blank 500 is a conventional example.
In FIG. 13B, the blank 500 is shown by a two-dot chain line, and the shape after molding is shown by a solid line. The location showing the maximum value of the maximum principal strain in Experimental Example 1 was the location surrounded by the dotted line circle in FIG. 13B (near the curved region), and the maximum value was 0.85.
(Experiment example 2)
FIG. 14 is a schematic plan view of the blank 600 of Experimental Example 2. Corner end 611 of blank 600 is inside the area between line segment MO and line segment NO. That is, blank 600 is a conventional example.
The location showing the maximum value of the maximum principal strain in Experimental Example 2 corresponds to the location surrounded by the dotted line circle in FIG. 13B, and the maximum value was 1.09. In other words, it has been found that the press-formed product is likely to break if the blank is commonly designed by those skilled in the art.
(Experiment example 3)
FIG. 15 is a schematic plan view of the blank 700 of Experimental Example 3. A part of the corner end 711 of the blank 700 is outside the area between the line segment MO and the line segment NO, but the corner end 711 does not entirely include the line segment MO and the line segment NO.
The location showing the maximum value of the maximum principal strain in Experimental Example 3 corresponds to the location surrounded by the dotted line circle in FIG. 13B, and the maximum value was 0.92. In other words, even if a part of the corner end 711 is 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 segments MO and NO, press forming It was found that the product was more likely to break.
(Experiment example 4)
FIG. 16 is a schematic plan view of the blank 10 of Experimental Example 4. All of the corner edges 11 of the blank 10 are outside the area between the line segments MO and NO. That is, blank 10 is an example of the invention.
The location showing the maximum value of the maximum principal strain in Experimental Example 4 corresponds to the location surrounded by the dotted line in FIG. 13B, and the maximum value was 0.73. Blank 10 showed an improvement in maximum principal strain compared to the conventional example.

From the embodiment, in order to improve compared to the conventional example, the corner end 11 should include all of the line segments MO and NO, and a part of the corner end 11 should be an area between the line segments MO and NO. It turns out that it is necessary to be outside of the

According to the method for manufacturing a press-formed product and the blank of the present disclosure, it is possible to suppress the occurrence of wrinkles in the flange portion of the press-formed product and the occurrence of cracks in the corner portions and their vicinity, which is extremely useful industrially.

10 blank 11 corner end 12 edge 100 first press mold 110 bottom surface 120 side surface 121 corner region 130 ridgeline 131 curved region 140 support surface 200 second press mold 300 third press mold

Claims

sandwiching the blank between the support surface of the first press die and the support surface of the third press die;
pushing a second press mold into the first press mold to draw and form the blank;
including;
The ridgeline of the edge of the press hole of the first press mold includes a curved area extending in a curved manner,
When viewed from the vertical direction of the blank,
A first normal passing through the first end of the curved area in the extending direction of the ridge line is a straight line L1,
A second normal passing through the second end of the curved area in the extending direction of the ridge line is a straight line L2,
The intersection of the straight line L1 and the edge of the blank is an intersection M, the intersection of the straight line L2 and the edge of the blank is an intersection N,
A straight line passing through the intersection M and perpendicular to the straight line L1 is a straight line L4,
A straight line passing through the intersection N and perpendicular to the straight line L2 is a straight line L3,
The intersection of the straight line L3 and the straight line L4 is an intersection point O,
A line segment connecting the intersection point M and the intersection point O is a line segment MO,
The line segment connecting the intersection point N and the intersection point O is a line segment NO,
When defined as
When the blank is sandwiched between the first press mold and the third press mold,
A corner end 11 between the intersection point M and the intersection N of the blank includes all of the line segment MO and the line segment NO,
A part of the corner end 11 is outside the area between the line segment MO and the line segment NO,
A method for manufacturing press-formed products.
In a square area of 40% of the short side of the first rectangle, adjacent to a corner of a first rectangle with each side passing only through the edges and outside of the blank, the blank has touching both of the two sides of the second rectangle that passes only through the edge and inside of the blank,
In a rectangular region that passes through two contact points of the two sides of the second rectangle and the blank and whose corners overlap with the first rectangle, the blank is a blank that touches both of the two sides of the first rectangle. .
The blank according to claim 2, wherein the blank contacts 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.