JP6897840B1 - Press molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press molding method capable of suppressing cracks in a flange portion and suppressing wrinkles in a top plate portion and a vertical wall portion during press molding of a press-molded product which is concavely curved in a top view. SOLUTION: The press molding method according to the present invention has a top plate portion 3, a vertical wall portion 7 continuous from the top plate portion 3 via a punch shoulder portion 5, and a vertical wall portion 7 through a die shoulder portion 9. A press-molded product 1 having a continuous flange portion 11 and having a curved portion 13 curved in a concave shape in a top view is press-molded, and the bending radius of the punch shoulder portion 5 at the curved portion 13 is set. It is characterized in that it increases from the central portion of the curve toward the end side. [Selection diagram] Fig. 1

Description

The present invention relates to a press forming method, in particular, a top plate portion, a vertical wall portion continuous from the top plate portion via a punch shoulder portion, and a flange portion continuous from the vertical wall portion via a die shoulder portion. The present invention relates to a press molding method for a press molded product having a curved portion curved in a concave shape in a top view.

Press molding is a manufacturing method capable of manufacturing metal parts at low cost and in a short time, and is used for manufacturing many automobile parts. Further, in recent years, in order to improve the collision safety of automobiles and reduce the weight of the vehicle body, higher strength metal plates have been used for automobile parts. The main problems in press forming a high-strength metal plate are the occurrence of cracks due to a decrease in ductility and the occurrence of wrinkles due to an increase in yield strength.

For example, as shown in FIG. 9, in press molding in which a press-molded product 101 in which the vertical wall portion 107 is curved in a concave shape in a top view is set as a target shape, the flange portion 111 in the curved portion 113 is pulled in the circumferential direction. , Cracks are likely to occur. Further, as the reaction force, deformation that contracts in the circumferential direction occurs at the top plate portion 103 and the punch shoulder portion 105 at the curved portion 113, so that wrinkles are likely to occur. This deformation is called stretch flange deformation. Therefore, it is important in press molding of the press-molded product 101 to suppress the occurrence of cracks and wrinkles in such stretch flange deformation.

As a technique for suppressing cracks and wrinkles in a press-molded product that is curved in a concave shape when viewed from above, for example, Patent Document 1 describes the ceiling via a top plate portion and a bent portion having a portion that is curved in an arc shape. A press molding method for press-molding an L-shaped part connected to a plate portion and having a vertical wall portion having a flange portion on the opposite side of the bent portion from a material metal plate is disclosed. Then, according to the press molding method, the portion of the material metal plate corresponding to the top plate portion is pressed by the pad, and the L-shaped lower part of the material metal plate is L-shaped. The end of the portion corresponding to the side portion is allowed to slide (in-plane movement), and the portion corresponding to the lower L-shaped portion is pulled toward the vertical wall portion and the vertical wall portion and the flange portion. It is said that the occurrence of cracks in the flange portion and the occurrence of wrinkles in the top plate portion can be suppressed by molding.

Further, Patent Document 2 describes a press for press-molding a part having a hat-shaped or U-shaped cross-sectional shape and having a curved portion curved in the longitudinal direction and a straight side portion connected to both ends of the curved portion. The molding method is disclosed. Then, according to the press molding method, it is said that the occurrence of cracks due to the elongation flange deformation can be suppressed by causing the material movement that alleviates the tensile deformation in the circumferential direction that occurs in the flange portion of the curved portion. There is.

Japanese Patent No. 5168429 Japanese Patent No. 6028956

In the technique disclosed in Patent Document 1, as shown in FIG. 10, the moving direction of the blank (metal plate) material flowing out from the top plate portion 103 to the flange portion 111 side is such that the material is pulled by the elongation flange deformation. It does not match the direction (dotted line in the circumferential direction). Then, when the material movement of such a blank is decomposed into vectors in two directions as shown in FIG. 11, the movement from the end side to the center portion of the curved portion 113 (the black solid line arrow in the figure) extends. Although it is effective in suppressing the cracking of the flange portion 111 due to the flange deformation, the movement from the top plate portion 103 to the vertical wall portion 107 (black arrow in the figure) does not contribute to the suppression of the stretch flange deformation.
Further, even if the material moves toward the central portion of the curved portion 113, the material movement near the central portion of the curved portion 113 (white arrow in the figure) induces wrinkles in the vicinity of the top plate portion 103 and the punch shoulder portion 105. There are concerns.

Further, the technique disclosed in Patent Document 1 suppresses wrinkles in the top plate portion by pressing a portion corresponding to the top plate portion in the material metal plate with a pad, but the higher the strength of the steel plate, the more wrinkles. Since it is necessary to increase the pad load for pressurizing the metal, there is a concern that the pressure generator such as a gas cylinder installed in the mold will become huge. As a result, there is a problem that the space for installing the pad in the mold may not be secured, and there is a problem that the cost increases due to the increase in size of the mold.
Further, when the technique of Patent Document 1 is applied to the press molding of the press-molded product 101 shown in FIG. 9, the punch shoulder 105 cannot be pressed by the pad, so that the wrinkles on the punch shoulder 105 cannot be suppressed.

Further, in both Patent Document 1 and Patent Document 2, for example, in a press-molded product in which it is necessary to impart a bead shape to the top plate portion 103 in the curved portion 113, a portion corresponding to the top plate portion 103 in the curved portion 113 shown in FIG. It may not be possible to move the material of No. 1 to the flange portion 111 where the stretched flange is deformed, and it becomes difficult to suppress wrinkles.

The present invention has been made to solve the above-mentioned problems, and in a press-molded product having a top plate portion, a vertical wall portion, and a flange portion and curved in a concave shape in a top view, the stretch flange deformation occurs. It is an object of the present invention to propose a press forming method capable of suppressing cracking in a flange portion and suppressing wrinkles in a top plate portion and a punch shoulder portion on the flange portion side.

(1) The press molding method according to the present invention includes a top plate portion, a vertical wall portion continuous from the top plate portion via a punch shoulder portion, and a flange portion continuous from the vertical wall portion via a die shoulder portion. A press-molded product having a curved portion that is concavely curved in a top view is press-molded.
It is characterized in that the bending radius of the punch shoulder portion at the curved portion is increased from the central portion of the curved portion toward the end portion side.

(2) In the item described in (1) above,
It is characterized in that the bending radius of the die shoulder portion at the curved portion is reduced from the central portion of the curved portion toward the end portion side.

(3) In the item described in (1) above,
It is characterized in that the minimum bending radius of the die shoulder portion is made smaller than the minimum bending radius of the punch shoulder portion.

(4) In any of the above (1) to (3),
It is characterized in that a rotary motion restraint shape portion that restrains the rotary motion of the blank in the press molding process is formed on the top plate portion on the end side of the curve.

(5) In any of the above (1) to (4),
The flange width of the flange portion at the curved portion is characterized by widening the central portion as compared with the end side of the curved portion.

(6) In any of the above (1) to (5),
The blank to be used for press molding of the press-molded product is characterized in that it is a metal plate having a tensile strength of 440 MPa class to 1600 MPa class.

(7) A press-molding method in which a press-molded product press-molded by the press-molding method according to any one of (1) to (6) above is used as an intermediate-molded product, and the intermediate-molded product is further press-molded into a target shape. hand,
The intermediate molded product is characterized in that the bending radius of the punch shoulder portion on the end side of the curved portion is made larger than the target shape.

In the present invention, it has a top plate portion, a vertical wall portion continuous from the top plate portion via a punch shoulder portion, and a flange portion continuous from the vertical wall portion via a die shoulder portion, and is viewed from above. When press-molding a press-molded product having a curved portion curved in a concave shape, the bending radius of the punch shoulder portion at the curved portion is increased from the central portion of the curvature toward the end side, thereby increasing the bending end. Since the material can be moved from the top plate portion on the portion side toward the flange portion in the central portion of the curve, cracking of the curved portion in the flange portion is suppressed, and the flange portion in the curved portion is suppressed. Wrinkles on the top plate portion and the punch shoulder portion on the side can be suppressed.

It is a figure which shows an example of the press-molded article to be molded in the press-molding method which concerns on embodiment of this invention ((a) perspective view, (b) top view). It is a figure explaining the reason why cracking can be suppressed by the press molding method which concerns on embodiment of this invention ((a) top view, (b) cross-sectional view of the end side of curvature, (c) curvature. Cross-sectional view of the central part of. It is a figure which shows an example of the press-molded article which is the object of molding in the press-molding method which concerns on another aspect of embodiment of this invention ((a) perspective view, (b) top view). It is a figure explaining the reason why the wrinkle can be suppressed by the press molding method which concerns on another aspect of the Embodiment of this invention ((a) top view, (b) the cross-sectional view of the curved end side. (C) Cross-sectional view of the central portion of the curve). A press-molded product which is a molding target in the press-molding method according to the embodiment of the present invention and has a shape in which rotational movement is restrained in a horizontal plane parallel to the top plate portion by a vertical wall portion formed at a blank end portion. It is a figure which shows an example. It is a figure which shows the other example of the press-molded article which was the object of molding in the press-molding method which concerns on embodiment of this invention, and formed the shape which restrained the rotational movement in the horizontal plane parallel to the top plate part by a bead. .. It is a figure which shows an example of the press-molded article which was targeted for molding in the press-molding method which concerns on embodiment of this invention, and the flange width of the flange part in the central part of a curve was widened. It is a figure explaining the reason why cracking can be suppressed in the press-molded article which widened the flange width of the flange portion in the central part of a curve by the press-molding method which concerns on embodiment of this invention. It is a figure explaining the crack and the wrinkle which occur in the press molding of the press-molded article which has the concave curved part in the top view. It is a figure explaining the mechanism that a crack occurs in the process of press-molding a press-molded article which is curved in a concave shape in the top view. It is a figure explaining the material movement in the press molding of the press-molded article which was curved concavely in the top view.

The press molding method according to the embodiment of the present invention will be described below with reference to FIGS. 1 to 8.

As an example, as shown in FIG. 1, the press molding method according to the present embodiment includes a top plate portion 3, a vertical wall portion 7 continuous from the top plate portion 3 via a punch shoulder portion 5, and a vertical wall portion 7. It has a flange portion 11 that is continuous from the die shoulder portion 9 to the die, and extends linearly from both ends of the curved portion 13 that is concavely curved in the top view and both ends of the curvature (broken line in FIG. 1). A press-molded product 1 having a straight line portion 15 to be formed is press-molded, and the bending radius of the punch shoulder portion 5 at the curved portion 13 is increased from the central portion of the curvature toward the end portion side. ..

In the press molding method according to the present embodiment, the reason why both the crack of the flange portion 11 and the wrinkles of the top plate portion 3 and the punch shoulder portion 5 at the curved portion 13 of the press molded product 1 can be suppressed is press molding. The movement of the material in the process will be described with reference to FIG. 2, which schematically shows the movement of the material. The broken line in FIG. 2 indicates both ends of the curve (the boundary between the curved portion 13 and the straight portion 15).

The punch shoulder portion 5 has a bending radius R _{p, 1} (FIG. 2 (b)) at the curved end (AA'cross section) and a bending radius R _{p, 2 at the curved center (BB' cross section).} The bending radius increases from the central portion of the curve toward the end side so as to be larger than that in FIG. 2 (c). Therefore, as shown by the black arrow in FIG. 2, the material easily moves along the ridgeline direction (vertical direction on the paper surface) from the end side of the curve of the punch shoulder 5 toward the center, and the center of the curve. Is pulled into the flange portion 11 side of the.
On the other hand, since the bending radius of the curved central portion of the punch shoulder portion 5 is smaller than that of the curved end side, it is difficult for the material to move in the ridge line direction in the press molding process.

Therefore, in the press molding process of the press-molded product 1, the material can be moved from the top plate portion 3 on the curved end side toward the flange portion 11 in the central portion of the curved portion, so that the flange portion in the curved portion 13 can be moved. While suppressing the cracking of 11, it is possible to suppress wrinkles in the top plate portion 3 and the punch shoulder portion 5 of the curved portion 13.

Further, in the press molding method according to the present embodiment, it is preferable that the minimum bending radius of the die shoulder portion 9 is smaller than the minimum bending radius of the punch shoulder portion 5.
Here, the minimum bending radius of the die shoulder portion 9 is the smallest bending radius of the die shoulder portion 9 at the curved portion 13. In the press-molded product 1, as shown in FIG. 2, since the bending radius R _d of the die shoulder portion 9 is constant from the central portion to the end side of the curvature, the minimum bending radius of the die shoulder portion 9 is R. It becomes _d.
On the other hand, the minimum bending radius of the punch shoulder portion 5 is the smallest bending radius of the punch shoulder portion 5 at the curved portion 13. Then, in the press-molded product 1, as shown in FIG. 2, since the bending radius of the punch shoulder portion 5 increases from the central portion of the curve toward the end side, the minimum bending radius of the punch shoulder portion 5 is set. , The bending radius R _{p, 2} at the center of the curve.
In this way, by making the minimum bending radius (= R _d ) of the die shoulder portion 9 smaller than the minimum bending radius (= R _{p, 2} ) of the punch shoulder portion 5, the material in the die shoulder portion 9 in the press molding process. By restraining the movement, the material can be strongly drawn from the top plate portion 3 side to the flange portion 11 side in the press molding process. As a result, cracks in the flange portion 11 at the center of the curve and wrinkles in the top plate portion 3 and the punch shoulder portion 5 can be further suppressed.

In the press molding method according to the present embodiment, as in the press molded product 1 shown in FIG. 1, the bending radius of the punch shoulder portion 5 at the curved portion 13 is increased from the central portion to the end portion of the curved portion 13. However, in the press molding method according to another aspect of the present embodiment, the bending radius of the punch shoulder portion 25 at the curved portion 33 is set to the center of the curvature, as in the press molded product 21 shown as an example in FIG. The bending radius of the die shoulder portion 29 at the curved portion 33 may be decreased from the central portion of the curvature of the curved portion 33 toward the end portion side while increasing from the portion toward the end portion side.

As described above, regarding the action and effect of reducing the bending radius of the die shoulder portion 29 from the central portion to the end side of the curvature at the curved portion 33, the movement of the material in the press molding process of the press molded product 21 is schematically represented. This will be described with reference to FIG. The broken line in FIG. 4 indicates both ends of the curve (the boundary between the curved portion 33 and the straight portion 35).

The die shoulder portion 29 has a bending radius R d, 1 (FIG. 4 (b)) at the end side of the curve (A−A ′ cross section), and a bending radius R _{d, 1 at} the center portion (BB ′ cross section) of the curvature _{. It is smaller than 2} (Fig. 4 (c)). Therefore, in the extension flange deformation, the material can be easily moved toward the curved recess (D shown in FIG. 4A, the base of the flange portion 31 in the curvature with the vertical wall portion 27), and the circumferential direction of the curvature in the flange portion 31. It is difficult for the material to move due to pulling, and it is possible to prevent the flange from cracking.

As a result, in the press molding process of the press-molded product 21, cracking of the flange portion 31 at the curved portion 33 can be further suppressed.

Further, in the press molding method according to another aspect of the present embodiment, it is preferable that the minimum bending radius of the die shoulder portion 29 at the curved portion 33 is smaller than the minimum bending radius of the punch shoulder portion 25.
Here, the minimum bending radius of the die shoulder portion 29 is the smallest bending radius of the die shoulder portion 29 at the curved portion 33, and as shown in FIG. 4 (b), the bending radius R _{d, on the curved end side.} It is _1.
On the other hand, the minimum bending radius of the punch shoulder portion 25 is the smallest bending radius of the punch shoulder portion 25 at the curved portion 33, and as shown in FIG. 4 (c), the bending radius R _{p, 2} at the central portion of the curvature. is there.
In this way, by making the minimum bending radius (= R _{d, 1} ) of the die shoulder 29 smaller than the minimum bending radius (= R _{p, 2} ) of the punch shoulder 25, the curved end of the punch shoulder 25 Since the bending radius R _{p, 1 on the portion side is further larger than the minimum bending radius R p, 2} (at the center of the curvature) of the punch shoulder portion 25, the material is pressed from the top plate portion 23 side to the flange portion 31 in the press forming process. Can be pulled strongly to the side. As a result, cracks in the flange portion 31 at the curved portion 33 and wrinkles in the top plate portion 23 and the punch shoulder portion 25 can be further suppressed.

In the above description, the bending radius of the punch shoulder portion 5 is changed as shown in FIG. 1, and further, the bending radius of the punch shoulder portion 25 and the die shoulder portion 29 is changed as shown in FIG. However, the press molding method according to the present invention applies to the top plate portion 43 on the end side of the curved portion 53 and the straight portion 55, and to the top plate portion 43 in the press molding process, as in the press molded product 41 shown in FIG. The rotary motion restraint shape portion 57 that constrains the rotary motion of the blank in the parallel horizontal plane may be formed.

The rotational movement restraint shape portion 57 is a bent shape formed between the vertical wall portion 59 and the top plate portion 43 that are continuous on the side opposite to the vertical wall portion 47 of the straight portion 55.
Further, the punch shoulder portion 45 is formed so that the bending radius increases from the central portion of the curve toward the end portion side, similarly to the punch shoulder portion 5 of the press-molded product 1 described above.

In this way, by forming the rotary motion restraint shape portion 57 in the press molding process, the rotary motion of the blank in the horizontal plane parallel to the top plate portion 43 is suppressed in the press molding process, and the curved end side and the curved end portion side and The material can be moved from the top plate portion 43 of the straight portion 55 to the flange portion 51 at the center of the curve via the punch shoulder portion 45, and the wrinkles of the top plate portion 43 and the punch shoulder portion 45 at the curved portion 53 can be formed. It can be sufficiently suppressed.

The present invention is not limited to the rotary motion restraint shape portion 57 having the shape shown in FIG. 5, for example, the bead-shaped rotary motion restraint shape portion 63 formed on the top plate portion 43 of the press-molded product 61 of FIG. As described above, the shape may be any shape that can restrain the rotational movement of the blank in the horizontal plane parallel to the top plate portion 43 in the press molding process. When the bead is formed on the top plate portion 43, it is not limited to a concave shape such as the rotational movement restraint shape portion 63, but may be a convex shape.

Further, the rotary motion restraint shape portion 57 shown in FIG. 5 and the rotary motion restraint shape portion 63 shown in FIG. 6 are formed from the end portion of the curved portion 53 to the straight line portion 55, but the rotary motion restraint shape portion With respect to the position of forming the above, it is not excluded that the shape is formed only at the end of the curved portion 53 or only at the straight portion 55.

Further, in the press molding method according to the present invention, in addition to the bending radii of the punch shoulder portion and the die shoulder portion described above, as in the press molded product 71 illustrated in FIG. 7, the flange portion 81 in the central portion of the curved portion 83 The flange width may be wider than that of the curved end side.

The effects of press-molding the press-molded product 71 shown in FIG. 7 are as follows.
For example, as shown in FIG. 8A, the above-mentioned press-molded product 1 can be obtained by press-molding using a blank 91 having a shape that becomes the shape of the press-molded product 1 when press-molded. In this case, the flange corresponding portion 93 of the blank 91 becomes the flange portion 11 (FIG. 1) of the press-molded product 1.

On the other hand, in the press-molded product 71 shown in FIG. 7, as shown in FIG. 8 (b), a blank in which the surplus thickness (hatched region in the figure) of the flange corresponding portion 97 corresponding to the flange portion 81 is increased. It is press-molded using 95.

When the press-molded product 71 is press-molded using such a blank 95, the material of the flange portion 81 at the curved portion 83 becomes difficult to stretch, so that the material insufficient for forming the flange portion 81 is from the top plate portion 73 side. It comes to be pulled in through the punch shoulder portion 75 and the vertical wall portion 77.
As a result, the amount of material toward the central portion of the curve at the curved portion 83 increases, and cracking of the flange portion 81 can be further suppressed.

When the flange width of the flange portion 81 in the curved portion 83 is widened in the central portion as compared with the end side of the curved portion as in the press-molded product 71 shown in FIG. 7, the maximum width of the flange in the central portion of the curved portion is set to the end portion. It is preferably 1.1 to 1.5 times the flange width on the side.

If the flange width at the central portion of the curve is less than 1.1 times, the force for drawing the material from the top plate portion 73 to the flange portion 81 side in the press forming process does not increase so much.
Further, if the flange width at the central portion of the curve is made wider than 1.5 times, the flange width of the flange portion 81 is too wide and interferes with joining with other parts. Therefore, the flange width should be narrowed in a later process. Since the flange portion 81 is cut off, the number of work processes is increased, and the yield is further reduced.

In the press molding method according to the embodiment of the present invention, for example, as shown in FIG. 1, a press-molded product 1 having straight portions 15 extending from both ends of the curve of the curved portion 13 is targeted for molding. However, the present invention may be a press-molded product having only a curved portion or a press-molded product having a straight portion extending from only one end of the curvature, regardless of the presence or absence of the straight portion. Absent.

Further, in the above description, the bending radius of the punch shoulder is increased from the center of the curve toward both ends, but one end from the center of the curve. It may be increased toward the side.

Similarly, the radius of curvature of the curve of the die shoulder is also reduced from the center of the curve toward both ends, but is reduced toward one end. You may.

The above description illustrates specific embodiments of the present invention based on embodiments of the present invention. However, the present invention also includes, for example, a press-molded product 1 shown in FIG. 1 as an intermediate molded product, and the intermediate molded product is press-molded into a target shape. In the press-molded product 1 which is an intermediate molded product, the bending radius of the punch shoulder portion 5 on the end side of the curved portion 13 may be larger than the target shape. That is, the press molding method includes two steps, that is, a step of press molding the press molded product 1 which is an intermediate molded product, and a step of press molding the press molded product 1 into a press molded product having a target shape.

Then, when the press-molded product 101 having the bending radius of the conventional punch shoulder 105 as the target shape illustrated in FIG. 9 is press-molded in one step, the flange portion 111 at the curved portion 113 of the press-molded product 101 is cracked. Even when the top plate 103 and the punch shoulder 105 are wrinkled, according to the press molding method of the present invention, the flange 111 at the curved portion 113 is cracked and the top plate 103 and the punch shoulder 105 are cracked. It is possible to suppress wrinkles and obtain a press-molded product 101 having a target shape.

Similarly, in the present invention, for example, the press-molded product 21 shown in FIG. 3 is used as an intermediate molded product, and the intermediate molded product is press-molded into a press-molded product 101 (FIG. 9) having a target shape. The press-molded product 21 includes a press-molding method in which the bending radius of the die shoulder portion 29 at the central portion of the curved portion 33 is made larger than the target shape. That is, the press molding method includes a step of press molding the press molded product 21 which is an intermediate molded product and a step of press molding the press molded product 21 into the press molded product 101 having a target shape.

Even in this case, when the press-molded product 101 having the bending radius of the conventional die shoulder 109 as the target shape is press-molded in one step, the flange portion 111 at the curved portion 113 is cracked and the top plate portion 103 and the punch shoulder are punched. Although wrinkles are generated in the portion 105, according to the present invention, cracks in the flange portion 111 in the curved portion 113 and wrinkles in the top plate portion 103 and the punch shoulder portion 105 are further suppressed, and the press-molded product 101 having the target shape 101. Can be obtained.

The press molding method according to the present invention is not particularly limited in the type of metal plate used as the blank material, but can be preferably applied when a metal plate having low ductility is used. Specifically, it is preferable to use a metal plate having a tensile strength of 440 MPa class or more and 1600 MPa class or less and a plate thickness of 0.5 mm or more and 3.6 mm or less.

A metal plate having a tensile strength of less than 440 MPa class has high ductility, so that cracking due to deformation of the stretch flange is unlikely to occur, and there is little advantage in using the present invention. However, if the shape of the part is difficult to press-mold, it is preferable to use the present invention even if the metal plate has a tensile strength of less than 440 MPa class.
There is no particular upper limit to the tensile strength, but since metal plates exceeding 1600 MPa have poor ductility, cracks are likely to occur at the punch shoulders and die shoulders, making press molding difficult.

Further, the press molding method according to the present invention prevents the metal plate from cracking due to the deformation of the stretch flange in an automobile part having L-shaped, T-shaped, Y-shaped, and S-shaped parts that are curved in a top view. Can be done. As a specific example, the present invention is preferably used when a molding target is an A-pillar lower having an L-shaped portion, a B-pillar having a T-shaped portion, a rear side member having an S-shaped portion, or the like. Applicable.

A specific press molding experiment has been conducted on the action and effect of the press molding method according to the present invention, which will be described below.

In the press molding experiment, the steel sheet having the material properties shown in Table 1 was used as a blank, and the press molded product 1 (FIG. 1), the press molded product 21 (FIG. 3), and the press molded product 41 (FIG. 5) shown in the above-described embodiment were used as blanks. ), The press-molded product 61 (FIG. 6) was used as a molding target, and a foam-molded product was used as an example of the invention.

The radius of curvature of the curved portion at the center of the height of the vertical wall of each press-molded product is 153 mm, the smallest bending radius of the punch shoulder at the curved portion is 7 mm, and the smallest bending radius of the die shoulder is 6 mm. The height of the vertical wall in the press molding direction of the vertical wall is 60 mm, and the flange width of the flange is 30 mm at the center of the curve and 25 mm at the end of the curve in the press molded product 1, and the press molded products 21, 41, In 61, the central part of the curve was set to 10 mm, and the end side of the curve was set to 25 mm.

Tables 2 and 3 show _{the bending radius R p} of the punch shoulder and the bending radius R _d of the die shoulder in the press-molded product to be molded in the press molding experiment. _{The ratio of the bending radius R p} of the punch shoulder portion shown in Tables 2 and 3 is the ratio of the largest bending radius to the smallest bending radius in the ridgeline direction of the punch shoulder portion. _{Similarly, the ratio of the bending radius R d} of the die shoulder shown in Tables 2 and 3 is the ratio of the smallest bending radius to the largest bending radius in the ridgeline direction of the die shoulder.

Further, in the press molding experiment, as a comparison target, the portion corresponding to the top plate portion 103 of the press molded product 101 shown in FIG. 9 is pressed with a pad according to the method disclosed in Patent Document 1 and parallel to the top plate portion 103. The press-molded product 101, which was press-molded in a state where the rotational movement of the blank in a horizontal plane was allowed, was designated as Conventional Example 1.

In Conventional Example 1, the radius of curvature of the curve of the curved portion 113, the radius of curvature of the die shoulder portion 109, and the height of the vertical wall of the vertical wall portion 107 are the same as those of the press-molded product according to the invention example.
Then, in the conventional example 1, the smallest bending radius of the punch shoulder portion 105 is set to be constant (= 7 mm) in the ridgeline direction.

Then, cracks and wrinkles in each press-molded product according to the invention example and the conventional example were evaluated.
For the evaluation of cracks, the plate thickness reduction rate is calculated by dividing the difference between the plate thickness of the blank and the plate thickness of the flange portion tip (for example, the C portion shown in FIG. 2) at the bottom of the recess at the curved portion by the plate thickness of the blank. However, it was evaluated that the smaller the value, the better the crack suppression.
On the other hand, in the evaluation of wrinkles, the top plate and punch shoulders at the curved portion are visually evaluated, and if there is a remarkable wrinkle, it is marked with "x". Was marked with "△", and the case where wrinkles could not be visually confirmed was marked with "○".
Tables 2 and 3 above show the results of evaluating cracks and wrinkles for each press-molded product.

In Conventional Example 1, the plate thickness reduction rate was as large as 18%, and minute wrinkles were generated.

_{In Invention Example 1, a press-molded product 1 in which the bending radius R p} of the punch shoulder portion 5 is increased from the center of the curve toward the end side by a ratio of 1.1 is press-molded. As shown in Table 2, the plate thickness reduction rate was 17%, which was lower than that of Conventional Example 1, and no wrinkles were observed.

In the second invention, _{the ratio of the bending radius R p} of the punch shoulder 5 is 1.5, which is larger than that of the first invention. As shown in Table 2, the plate thickness reduction rate was 14%, which was reduced as compared with Invention Example 1, and no wrinkles were observed.

Invention Example 3 is a press-molded product 1 in which the ratio of the bending radius R _p of the punch shoulder portion 5 is 2.0, which is larger than that of Invention Example 2. As shown in Table 2, the plate thickness reduction rate was 12%, which was further reduced as compared with Invention Example 2, and no wrinkles were observed.

In Invention Example 4, the bending radius R _p of the punch shoulder portion 25 is increased by a ratio of 1.5 from the center of the curvature toward the end side, and the bending radius R _d of the die shoulder portion 29 is increased from the center portion to the end portion of the curvature. This is a press-molded product 21 whose size is reduced by a ratio of 0.9 toward the side. As shown in Table 2, the plate thickness reduction rate was 13%, which was reduced as compared with Invention Example 2 in which the ratio _{of the bending radius R p of the punch shoulder portion 25 was the same, and no wrinkles were observed.}

Invention Example 5 is a press-molded product 21 in which the ratio of the bending radius R _d of the die shoulder portion 29 is 0.75 and is smaller than that of Invention Example 4. As shown in Table 2, the plate thickness reduction rate was 12%, which was reduced as compared with Invention Example 4, and no wrinkles were observed.

_{In Invention Example 6, the ratio of the bending radius R d} of the die shoulder portion 29 is set to 0.5, which is further smaller than that of Invention Example 5. As shown in Table 2, the plate thickness reduction rate was 10%, which was reduced as compared with Invention Example 5, and no wrinkles were observed.

In Invention Example 7, _{the ratio of the bending radius R p} of the punch shoulder portion 45 is 1.5, the ratio of the bending radius of the die shoulder portion 49 is 0.75, and the rotational movement restraint shape portion between the top plate portion 43 and the vertical wall portion 59. This is a press-molded product 41 in which 57 is formed. As shown in Table 3, the plate thickness reduction rate was 14%, which was lower than that of Conventional Example 1, and no wrinkles were observed.

_{In Invention Example 8, the ratio of the bending radius R p} of the punch shoulder portion 45 to the bending radius of the die shoulder portion 49 is made equal to that of Invention Example 7, and the bead shape extends from the curved end side of the top plate portion 43 to the straight portion. This is a press-molded product 61 in which the rotational movement restraint shape portion 63 of the above is formed. As shown in Table 3, the plate thickness reduction rate was 14%, which was lower than that of Conventional Example 1, and no wrinkles were observed.

In Invention Example 9, a blank 91 having a shape in which a flange corresponding portion 93 is provided with a surplus thickness is used, the ratio of the bending radius of the punch shoulder portion 75 is set to 1.5, and the flange of the flange portion 81 in the central portion of the curved portion 83 is used. A press-molded product 71 having a width 1.5 times the flange width (= 25 mm) on the curved end side is press-molded. As shown in Table 3, the plate thickness reduction rate was reduced to 9%, which was a good result, and no wrinkles were observed.

In Invention Example 10, a blank 91 having a shape in which a flange corresponding portion 93 is provided with a surplus thickness is used, and similarly to Invention Example 5, the ratio of the bending radius of the punch shoulder portion 5 is 1.5, and the bending radius of the die shoulder portion R _d. This is a press-molded product 21 having a ratio of 0.75. As shown in Table 3, the plate thickness reduction rate was 7%, which was further reduced as compared with Invention Example 9, and no wrinkles were observed.

In Invention Example 11, a blank 91 having a shape in which a flange corresponding portion 93 is provided with a surplus thickness is used, and similarly to Invention Example 7, the ratio of the bending radius of the punch shoulder portion 5 is 1.5, and the bending radius R _{d of the die shoulder portion.} The press-molded product 21 in which the rotational movement restraint shape portion 57 is formed is press-molded with the ratio of 0.75. As shown in Table 3, the plate thickness reduction rate was reduced to 9%, which was a good result, and no wrinkles were observed.

_{Table 3 shows an example of the press-molded product 101 in which the bending radius R p} of the punch shoulder portion 105 is uniformly larger than that of the conventional example 1 as a comparative example 1. In Comparative Example 1, the bending radius of the ridgeline of the entire punch shoulder 105 of Conventional Example 1 was increased by 1.5 times to be constant at 10.5 mm.
As a result, the plate thickness reduction rate was as good as 9%, but remarkable wrinkles occurred, which was a problem.

As described above, it has been demonstrated that the press molding method according to the present invention can suppress the cracking of the flange portion at the curved portion and also suppress the wrinkles of the top plate portion and the punch shoulder portion at the curved portion.

1 Press-molded product 3 Top plate part 5 Punch shoulder part 7 Vertical wall part 9 Die shoulder part 11 Flange part 13 Curved part 15 Straight part 21 Press-molded product 23 Top plate part 25 Punch shoulder part 27 Vertical wall part 29 Die shoulder part 31 Flange 33 Curved part 35 Straight part 41 Press-molded product 43 Top plate part 45 Punch shoulder part 47 Vertical wall part 49 Die shoulder part 51 Flange part 53 Curved part 55 Straight part 57 Rotational motion restraint shape part 59 Vertical wall part 61 Press molding Product 63 Rotating motion restraint shape part 71 Press molded product 73 Top plate part 75 Punch shoulder part 77 Vertical wall part 79 Die shoulder part 81 Flange part 83 Curved part 85 Straight part 91 Blank 93 Flange equivalent part 95 Blank 97 Flange equivalent 101 Press Molded product 103 Top plate 105 Punch shoulder 107 Vertical wall 109 Die shoulder 111 Flange 113 Curved part 115 Straight part

Claims (7)

It has a top plate portion, a vertical wall portion continuous from the top plate portion via a punch shoulder portion, and a flange portion continuous from the vertical wall portion via a die shoulder portion, and is curved in a concave shape in a top view. A press-molding method for press-molding a press-molded product having a curved portion.
A press molding method characterized in that the bending radius of the punch shoulder portion at the curved portion is increased from the central portion of the curved portion toward the end portion side. The press molding method according to claim 1, wherein the bending radius of the die shoulder portion at the curved portion is reduced from the central portion of the curved portion toward the end portion side. The press molding method according to claim 1, wherein the minimum bending radius of the die shoulder portion is made smaller than the minimum bending radius of the punch shoulder portion. The press according to any one of claims 1 to 3, wherein a rotary motion restraint shape portion that restrains the rotary motion of the blank in the press molding process is formed on the top plate portion on the end side of the curve. Molding method. The press molding method according to any one of claims 1 to 4, wherein the flange width of the flange portion at the curved portion is widened in the central portion as compared with the end side of the curved portion. The press molding method according to any one of claims 1 to 5, wherein the blank used for press molding of the press-molded product is a metal plate having a tensile strength of 440 MPa class to 1600 MPa class. A press-molding method in which a press-molded product press-molded by the press-molding method according to any one of claims 1 to 6 is used as an intermediate-molded product, and the intermediate-molded product is further press-molded into a target shape.
The intermediate molded product is a press molding method characterized in that the bending radius of the punch shoulder portion on the end side of the curved portion is made larger than the target shape.

Images