JP5031702B2 - Multi-stage press forming method with excellent shape freezing - Google Patents

Description

  For example, in the longitudinal direction as shown in FIG. 1 (in FIG. 1A, the present invention is an X plane or an arbitrary plane outside the X plane if the plane including the flange surfaces 11 and 12 on both sides is the X plane. In FIG. 1B, if the plane including the ridgelines 15 and 16 on both sides is taken as the X plane, it will be an arbitrary direction in the X plane or outside the X plane) In press-formed products of metal members having a cross-section of a die or hat, dimensions such as twists A and B that normally occur after mold release and camber (longitudinal deviation from the regular (design) product shape), etc. The present invention relates to a press molding method that reduces accuracy defects and obtains a product with a precise shape.

When a metal part having a hat-shaped cross section having a shape curved in the longitudinal direction is manufactured by press molding, a tensile stress 1 (force represented by plus) in the longitudinal direction on the inner flange surface 11 of the curved portion shown in FIG. Occurs, and compressive stress 2 (force represented by minus) in the longitudinal direction is generated on the outer flange surface 12 of the curved portion. In this way, internal stresses having different signs are generated inside and outside the curve, which gives a twist moment to the channel cross-section and causes twist A. Further, in the molding of a U-shaped section curved in a specific in-plane direction shown in FIG. 1B, a tensile stress 3 (force represented by plus) in the longitudinal direction is generated on the vertical wall surface 13 inside the curved portion. Then, a compressive stress 4 (force represented by minus) in the longitudinal direction is generated on the vertical wall surface 14 outside the curved portion. In this case as well, a twisting moment is generated in the channel cross section, causing twist B.
It is known that the direction and amount of twisting varies depending on the degree of stress generated and the remaining amount of flange.

In the conventional technique, the amount of spring back is estimated, and the mold shape is corrected in advance, or as described in Non-Patent Document 1, non-uniform residual stress is added by adding a plate excess absorbing bead to the shrinkage deformed portion. For example, a method of obtaining a molded product having a desired shape by reducing the above is used. However, in the former, a material with a large spring back such as a high-strength steel plate or an aluminum alloy plate inevitably has a large expected amount, and as a result, a desired product shape cannot be obtained, or until trial and error is achieved There are also problems in terms of cost and construction period because it may be necessary to modify the mold once. In the latter case, man-hours and costs for adjusting the depth of the beads to be added to the shape are required, and the bead shape remains as a product shape. In particular, a component that receives a load at the time of a collision has a problem that the bead is a starting point for buckling the component, which may reduce the collision safety of the vehicle itself and cannot be applied for general purposes.
Press Form Difficulty Handbook 2nd edition, 222 pages (Nikkan Kogyo Shimbun)

  In view of the above-described problems, the present invention has a regular shape (designed) that is curved in the longitudinal direction with a U-shaped or hat-shaped cross section with high accuracy without adjusting the mold shape and with a predetermined part shape. It is possible to obtain a metal member (press-molded product) having a shape of

In order to solve the problem, the gist of the present invention is as follows.
(1) A method of forming a high strength steel plate member of 980 MPa class or higher having a U-shaped or hat-shaped cross section and a shape curved in the lateral direction and the height direction along the longitudinal direction,
For all of the longitudinal direction of the high-strength steel plate member,
In the first molding step, an intermediate product is molded with the same radius of curvature as the product shape and wider than the product shape,
In the second molding step, it is smaller than the width in the first molding step, molded without changing the radius of curvature, and the entire molded product is a product shape or a substantially product shape, a multistage press molding method,
When the line lengths in the width direction in the product shape and the intermediate product shape formed in the first forming step are LW [mm] and LWl [mm], respectively.
1 <LWl / LW <1.1
Meet the requirements of
A multi-stage press molding method with excellent shape freezing property, wherein the first molding step is draw molding or foam molding, and the second molding step is a wrist-like process for molding into a product shape .
(2) A method of forming a high strength steel plate member of 980 MPa class or higher having a U-shaped or hat-shaped cross section and a shape curved in the lateral direction and the height direction along the longitudinal direction,
For all of the longitudinal direction of the high-strength steel plate member,
In the first molding step, an intermediate product is molded with the same radius of curvature as the product shape and wider than the product shape,
In the second molding step, smaller than the width in said first molding step, the molded without changing the radius of curvature, there the whole molded article multistage press molding how to characterized in that the product shape or a substantially product shape ,
When the line lengths in the width direction in the product shape and the intermediate product shape formed in the first forming step are LW [mm] and LWl [mm], respectively.
1 <LWl / LW <1.1
Meet the requirements of
The first molding step and the second molding step are draw molding or foam molding, and have a wrist-like process for molding into a product shape after the second molding step, and are multistage with excellent shape freezing properties Press molding method.

In this invention, the case where a product shape is obtained in a 1st shaping | molding process and a 2nd shaping | molding process, and the case where a product shape is obtained in the other shaping | molding process following a 2nd shaping | molding process are included. In the present invention, the product shape refers to the shape of a molded product obtained in the final molding process. For example, when completed in the second molding step, the molded product shape obtained in the second molding step becomes the product shape, and when completed in another molding step following the second molding step, The obtained molded product shape becomes the product shape. Moreover, the substantially product shape means the shape of the molded product after the second molding step before the product shape is obtained. That is, when completed in the second molding step, the shape of the molded product molded in the second molding step becomes the product shape, and when completed in another molding step following the second molding step, the second molding step The shape of the molded product molded in step is substantially the product shape. When the line length of the ridge line in the longitudinal direction in the product shape and the approximate product shape is L W [mm], L W l [mm], 1 <L W l / L W <1. Condition 1 is satisfied. Moreover, a part or all of the longitudinal direction means a part or all of one or both of the inner wall and the outer wall of the metal member.

  According to the present invention, a regular shape curved in a specific in-plane direction (in terms of design) with a U-shaped or hat-shaped cross section with high accuracy without adjusting the mold shape and with a predetermined part shape. ) Metal member (press-molded product).

  Examples of the present invention will be described below.

  In a metal part having a U-shaped or hat-shaped cross section curved in the longitudinal direction, flange surfaces 11 and 12 (see FIG. 1 (a)) and vertical wall surfaces 13 and 14 (see FIG. 1 (b)). ))), Longitudinal stresses having different signs are generated, and the stresses are released to generate springback due to twists A and B as shown in FIGS. 1 (a) and 1 (b). In order to suppress the spring back in the final product as much as possible, the tensile stress and the compressive stress in the longitudinal direction at the corresponding part (the curved part of the flange surfaces 11 and 12 or the curved part of the vertical wall surfaces 13 and 14) at the end of the final molding. However, it is sufficient that the shape rigidity is sufficiently small. The reason why the tensile stress is increased in the longitudinal direction on the inner flange surface 11 and the longitudinal wall surface 13 is that the material is stretched in the longitudinal direction as the material flows in, and the outer flange on the curve. The reason why the compressive stress is increased in the longitudinal direction on the surface 12 and the longitudinal wall surface 14 is that the material is contracted in the flanged shape so that the material is contracted in the longitudinal direction as the material flows.

  As a result of research on a molding method that sufficiently reduces the tensile stress or compressive stress in the longitudinal direction, the radius of curvature of the intermediate product is final in the first molding step for a part of the longitudinal direction of the shape curved in the longitudinal direction. Molded so that the radius of curvature is the same as the radius of curvature of the product, and the width of the intermediate product is larger than the width of the final product. In the second molding process, it is smaller than the width of the intermediate product obtained in the first molding process. The remaining part is molded without changing the curvature radius of the mold in the first molding process and the second molding process, and the entire molded product is shaped into the final product (product shape). ) Or a shape closer to the final product (substantially product shape) (see the invention according to (1) above, see FIG. 5D).

  In the first molding step, if the width of a part of the molded product is molded in a shape larger than the final product, the material is formed inside the curve when molded into the product shape or substantially product shape in the second molding step. Since it is compressed in the longitudinal direction along with the inflow, the tensile stress generated in the first molding step and the compressive stress generated in the second molding step cancel each other, and the longitudinal stress approaches zero. Similarly, on the outer side of the curve, the material is pulled in the longitudinal direction along with the inflow in the second molding process, the compressive stress generated in the first molding process and the tensile stress generated in the second molding process cancel each other, and the stress in the longitudinal direction is zero. Get closer to. Thereby, it can suppress that a springback etc. generate | occur | produce by the stress which generate | occur | produced in the product, and can improve the precision of a product shape.

  Further, for all of the longitudinal direction of the shape curved in the longitudinal direction, in the first molding step, the same radius of curvature as the product shape is formed, and the entire width of the intermediate product is molded in a shape larger than the final product, In the second molding step, the effect of canceling the generated stress can be obtained even by molding the width of the intermediate product small without changing the radius of curvature of the intermediate product obtained in the first molding step. Generation | occurrence | production can be suppressed (invention based on said (2)).

  The curvature radius of the curved portion in the intermediate product shape may be the same as the curvature radius of the curved portion in the product shape, but the amount of change in the line length in the width direction of the shape changing portion 5 as shown in FIG. When (LWl−LW) becomes too large, wrinkles are generated in the second molding step, or traces are left on the molded product. For this reason, when the line length in the width direction of the shape changing portion 5 in the product shape and the intermediate product shape is LW [mm] and LWl [mm], it is more preferably within the range of 1 <LWl / LW <1.1. Is preferably set within the range of 1 <LW1 / LW <1.05 (the invention according to (3) above).

  As the process of forming the intermediate product, if the first forming process is draw (draw-bending) forming or foam forming, and the second forming process is a wrist-like process for forming into a product shape, the first forming process is performed. (Invention according to (4)).

  In addition, when the first molding process is a first-stage draw molding or foam molding and the second molding process is a second-stage draw molding or foam molding to form a product shape or a substantially product shape, the first molding process The intermediate molding process may be used, and when there is a wrist-like process that molds the product after the second molding process, the second molding process is molded into a substantially product shape as the intermediate molding process. (Invention according to (5) above). The molding step here refers to a step of forming into a product-shaped outer shape, and refers to a step that does not include a step for punching or cutting, such as punching (piercing) and outer cutting (trim). That is, a process such as punching may be appropriately performed according to the product shape.

  In the case of molding an intermediate product, the molding height does not have to be molded up to the height of the product shape, but it is preferable that an intermediate product having a height of half or more of the product shape is molded.

  If the ridgeline between the intermediate product shape and the product shape is large, the intermediate product may become difficult to fit into the mold in the second molding process, or the shape may be displaced, so positioning pins, guides, etc. It is desirable to use an apparatus or a jig.

  When the width of the curved outer portion is made larger than the product width as an intermediate product shape, and the amount of deviation of the ridge line becomes large, it fits into the lower mold (punch) 10 in the second molding step as shown in FIG. A wrist-like process of forming with the upper die (die) 7 without using a presser (holder) is sufficient. However, it is desirable to use a pin or a guide for positioning the intermediate product.

  FIG. 4 shows the product shape studied in the present invention. The steel plate uses a 980 MPa grade steel plate having a thickness of 1.2 mm, the height of the hat-shaped cross section (distance between the surface of the ceiling portion 17 and the surfaces of the flanges 11 and 12) H is 40 mm, and the width W1 of the ceiling portion 17 is A member having 60 mm, a length L1 of 500 mm, a width W2 of each flange 11 and 12 of 20 mm, a curvature radius of 300 mm of the curved inner portion 21 and a curvature radius of 360 mm of the curved outer portion 22 was formed. As a comparative example, in one-step molding using a mold having a shape corresponding to the product shape, 40 ton of wrinkle holding load is applied as a molding condition, and draw molding is performed, and a cross section at both ends of the obtained molded product is measured with a shape measuring machine. did. When the angle (deviation amount) of the ceiling portion 17 when the cross sections at both ends of the molded product are overlapped is evaluated as a twist angle, the shape after the first molding step (the shape of the product obtained in the comparative example) is 2.5. A twist of ° occurred.

  FIG. 5 is a diagram for explaining changes in the shape of the intermediate product and the width of the product shape implemented in the present invention. Here, FIG. 5 is a view of the product (or intermediate product) shown in FIG. 4 as viewed from above, and the flanges 11 and 12 are omitted.

  FIG. 5A shows an example in which the width is larger than the product width while the curvature radius of the curved portion is constant (360 mm) for all of the curved outer portion 22 in the first molding step. That is, as shown by the broken line in FIG. 5A, the width between the curved outer portion 22 and the curved inner portion 21 in the intermediate product is the width W1 (60 mm) between the curved outer portion 22 and the curved inner portion 21 in the product. The first molding step is performed so as to be larger than. Specifically, in the first molding step, draw molding is performed with the width of the curved outer portion 22 and the curved inner portion 21 being 62, 64, 66 mm, and in the second molding step, the curvature radius of the curved outer portion 22 is 360 mm, Forming was performed with the width W1 of the ceiling portion 17 being 60 mm. Further, the remaining portion (the portion excluding the curved outer portion 22) is not changed in the shape of the mold in the first molding step and the second molding step, that is, the curved inner portion 21 has the same shape, and the entire molded product is second. The restorative process was used to form the final product shape in the molding process.

  FIG. 5B shows an example in which the width is larger than the product width while the curvature radius of the curved portion remains constant (300 mm) for the entire curved inner portion 21 in the first molding step. That is, as shown by a broken line in FIG. 5B, the width between the curved outer portion 22 and the curved inner portion 21 in the intermediate product is larger than the width W1 (60 mm) of the curved outer portion 22 and the curved inner portion 21 in the product. The first molding step is performed to increase the size. Specifically, in the first molding process, the width of the curved outer portion 22 and the curved inner portion 21 is draw-molded with 63, 66, 69 mm, and in the second molding step, the radius of curvature of the curved inner portion 21 is 300 mm. The foam was molded with the width W1 of the ceiling portion 17 set to 60 mm. Further, the remaining portion (the portion excluding the curved inner portion 21) is not changed in the shape of the mold in the first molding step and the second molding step, that is, the curved outer portion 22 has the same shape, and the entire molded product is second. The restorative process was used to form the final product shape in the molding process.

  FIG. 5C shows the first forming step in which the curvature radius of the curved portion remains constant for all of the curved inner portion 21 and the curved outer portion 22 (the curvature radius of the curved inner portion 21 is 300 mm, In this example, the radius of curvature is 360 mm) and the width is increased. That is, as shown by a broken line in FIG. 5C, the width between the curved outer portion 22 and the curved inner portion 21 in the intermediate product is larger than the width W1 (60 mm) of the curved outer portion 22 and the curved inner portion 21 in the product. The first molding step is performed to increase the size. Specifically, in the first molding step, the width between the curved outer portion 22 and the curved inner portion 21 is 61 (one-side shape change width 0.5 mm), 62 (one-side shape change width 1.0 mm), 63 ( In the second molding step, the radius of curvature of the curved inner portion 21 is 300 mm, the radius of curvature of the curved outer portion 22 is 360 mm, and the curved outer portion 22 and the curved portion inner portion are drawn. Forming was performed with a width of 21 and 60 mm. In addition, the rest-like process in which the entire molded product is made the final product shape in the second molding process without changing the shape other than the mold width in the first molding process and the second molding process. In addition, in FIG.5 (c), although the shape change width of the curved outer side part 22 and the curved inner side part 21 is made equal, you may make it different.

FIG. 5D is an example in which, in the first molding step, the width of the curved outer portion 22 is made larger than the product width while the curvature radius of the curved portion remains constant (360 mm). That is, as shown by the broken line in FIG. 5D, the width between the curved outer portion 22 and the curved inner portion 21 in the intermediate product is the width W1 (60 mm) between the curved outer portion 22 and the curved inner portion 21 in the product. The first molding step is performed so as to be larger than. Specifically, in the first molding step, at the C-side edge 23 of the ceiling portion 17, the curvature radius of the curved outer portion 22 is 360 mm, the width between the curved outer portion 22 and the curved inner portion 21 is 60 mm, and the ceiling portion 17. In the second molding step, the curved outer portion 22 is formed by draw molding with the radius of curvature of the curved outer portion 22 being 360 mm and the width of the curved outer portion 22 and the curved inner portion 21 being 61, 62, 63 mm. The foam was molded with the curvature radius of 22 being 360 mm and the width between the curved outer portion 22 and the curved inner portion 21 being 60 mm. Further, the remaining portions (portions other than the curved outer portion 22) are the same in the first molding step and the second molding step without changing the shape of the mold, that is, all of the curved inner portion 21 and part of the curved outer portion 22 are the same. As a shape, the entire molded product was a re-stoic process in which the final product shape was formed in the second molding process.

  Table 1 shows the experimental conditions and the shape measurement results. The twist angle is the angle (deviation amount) of the ceiling portion 17 when the cross sections at both ends of the product obtained in the molding process described above are overlapped, and the twist angle of 0.5 ° or less is ◎, 0.5 to 1.0. The case where the angle was greater than 1.0 ° and the case where the angle was greater than 1.0 ° was evaluated as x. As for the surface properties of the final product, a case where the width of the scratch that causes wrinkles was 5 mm or more was evaluated as △, a case where the width of the scratch was as small as less than 5 mm, or a thing that could not be visually confirmed was evaluated as ◯. .

  FIG. 6 shows the product shape studied in the present invention. In this product, the height of the hat-shaped cross section increases from one end side to the other end side, and the width of the ceiling portion 17 increases from one end side to the other end side. Further, the widths of the flanges 11 and 12 change from the both end sides toward the intermediate portion. Furthermore, this product has two curved inner portions 21 and two curved outer portions 22.

  The steel plate is a 980 MPa grade steel plate having a thickness of 1.2 mm. The maximum height Hmax of the hat-shaped cross section is 40 mm, the maximum width W3 of the ceiling portion 17 is 80 mm, the length L2 is 525 mm, and the flanges 11 and 12 are the maximum. A member having a large W4 of 30 mm, a curvature radius of 300 mm of the curved inner portion 21 and a curvature radius of 360 mm of the curved outer portion 22 was formed. As a comparative example, in one-stage draw molding using a mold having a shape corresponding to the product shape, molding is performed by applying a wrinkle holding load of 40 ton as a molding condition, and the cross section at both ends of the obtained molded product is copied with a shape measuring machine. It was measured. When the angle of the ceiling portion 17 when the cross sections at both ends of the molded product (final product) are overlapped is evaluated as the twist angle, the shape after the first molding step (the shape of the product obtained in the comparative example) is 1.5. A twist of ° occurred.

  FIG. 7 is a diagram for explaining the change in the width of the intermediate product shape and the product shape implemented in the present invention. Here, FIG. 7 is a view when the product (or intermediate product) shown in FIG. 6 is viewed from above, and the flanges 11 and 12 are omitted.

  In FIG. 7A, in the first molding step, the curvature radius of the curved portion is constant (curvature radius of the curved inner portion 21 is 300 mm, curvature radius of the curved outer portion 22 is 360 mm) for all of the curved A side 31. This is an example in which the width is increased. That is, as shown by the broken line in FIG. 7A, the width between the curved A side 31 and the curved B side 32 in the intermediate product is larger than the width between the curved A side 31 and the curved B side 32 in the product. In addition, the first molding step is performed. Here, the difference between the width of the curved A side 31 and the curved B side 32 in the intermediate product and the width of the curved A side 31 and the curved B side 32 in the product are equal in the longitudinal direction of the molded product. Specifically, in the first molding step, the maximum width between the curved A side 31 and the curved B side 32 is 82 mm, and in the second molding step, the curvature radius of the curved inner portion 21 on the curved A side 31 is 300 mm, The foam was molded with a curvature radius of 360 mm of the curved outer portion 22 and a maximum width between the curved A side 31 and the curved B side 32 of 80 mm. Further, the remaining portion (the portion excluding the curved A side 31) is not changed in the shape of the mold in the first molding step and the second molding step, that is, the curved B side 32 has the same shape, and the entire molded product is second. The final product shape was formed in the molding process.

  FIG. 7B shows the width of the first forming step with the curvature radius of the curved portion being constant (curvature radius of the curved inner portion 21 is 300 mm and curved radius of the curved outer portion is 360 mm) for the entire curved B side 32. This is an example of increasing. That is, as shown by a broken line in FIG. 7B, the width between the curved A side 31 and the curved B side 32 in the intermediate product is larger than the width between the curved A side 31 and the curved B side 32 in the product. In addition, the first molding step is performed. Here, the difference between the width of the curved A side 31 and the curved B side 32 in the intermediate product and the width of the curved A side 31 and the curved B side 32 in the product are equal in the longitudinal direction of the molded product. Specifically, in the first molding step, the maximum width between the curved A side 31 and the curved B side 32 is 83 mm, and in the second molding step, the curvature radius of the curved inner portion 21 on the curved B side 32 is 300 mm. The foam was formed with a curvature radius of 360 mm of the curved outer portion 22 and a maximum width between the curved A side 31 and the curved B side 32 of 80 mm. Further, the remaining portion (the portion excluding the curved B side 3 2) does not change the shape of the mold in the first molding step and the second molding step, that is, the curved A side 31 has the same shape, and the entire molded product is second. The restorative process was used to form the final product shape in the molding process.

  FIG. 7C shows the first forming step in which the curvature radius of the curved portion is constant for all of the curved A side 31 and the curved B side 32 (the curved inner side portion for each of the curved A side 31 and the curved B side 32). In this example, the width is increased while the curvature radius of 21 is 300 mm and the curvature radius of the curved outer portion 22 is 360 mm. That is, as shown by the broken line in FIG. 7C, the width between the curved A side 31 and the curved B side 32 in the intermediate product is larger than the width between the curved A side 31 and the curved B side 32 in the product. In addition, the first molding step is performed. Here, the difference between the width of the curved A side 31 and the curved B side 32 in the intermediate product and the width of the curved A side 31 and the curved B side 32 in the product are equal in the longitudinal direction of the molded product. Specifically, in the first molding step, the maximum width between the curved A side 31 and the curved B side 32 is 83 mm (one-side shape change width 1.5 mm), and in the second molding step, the curved A side For each of 31 and the curved B side 32, foam molding is performed with the curvature radius of the curved inner portion 21 being 300 mm, the curvature radius of the curved outer portion 22 being 360 mm, and the maximum width between the curved A side 31 and the curved B side 32 being 80 mm. Was a re-like process in which the product shape was formed in the second molding process. In FIG. 7C, the shape change widths of the curved A side 31 and the curved B side 32 are made equal, but may be different.

  Table 2 shows the experimental conditions and the shape measurement results. The twist angle is the angle of the ceiling of the cross section at both ends of the product obtained in the molding process described above, the twist angle is 0.5 ° or less ◎, 0.5-1.5 ° is ○, 1.5 ° The case where it was large was also marked with x. As for the surface texture of the final product, a case where the width of the scratches causing wrinkles was 5 mm or more was evaluated as Δ, a case where the scratches were as small as less than 5 mm, or a case where the scratches could not be visually confirmed was evaluated as ◯.

  As described above, according to the present invention, the dimensional accuracy is improved as compared with the comparative example, and a hat-shaped cross-sectional component having excellent dimensional accuracy can be obtained. In addition, No. 1 of Example 1 was used. 7 is outside the scope of the present invention according to (3), but satisfies the requirements of the present invention according to (1), so that the twist in the longitudinal direction is significantly reduced compared to the comparative example. I was able to. It is sufficiently applicable to parts whose surface properties are not so important.

  In the first and second embodiments described above, a product having a hat-shaped cross section is molded. However, the same effect can be obtained when a product having a U-shaped cross section is molded.

The external view of the metal member which has a shape curved in the longitudinal direction with a hat-shaped or U-shaped cross section is shown. The top view of the intermediate product shape and product shape in this invention is shown. Sectional drawing of the 2nd shaping | molding process in this invention is shown. The product shape of Example 1 to which this invention is applied is shown. The intermediate product shape of Example 1 to which this invention is applied, and the top view of a product shape are shown. The product shape of Example 2 to which this invention is applied is shown. The intermediate product shape of Example 2 to which this invention is applied, and the top view of a product shape are shown.

Explanation of symbols

1 Tensile stress acting on the flange surface of the stretch flange 2 Compressive stress acting on the flange surface of the contraction flange 3 Tensile stress acting on the longitudinal wall surface of the stretch flange 4 Compressive stress acting on the longitudinal wall surface of the contraction flange 5 Change in shape of intermediate product and product shape Part 6 Edge line 7 of the shape change part of the intermediate product shape Upper die (die)
8 Molded product 9 Wrinkle presser (holder)
10 Lower mold (punch)
DESCRIPTION OF SYMBOLS 11 Flange surface 12 Flange surface 13 Vertical wall surface 14 Vertical wall surface 15 Edge line part 16 Edge line part 21 Curved inner side (curved inner side)
22 Curved outside (curved outside)
23 C-side edge of ceiling part 24 D-side edge 31 of ceiling part Curved A side (curved A side)
32 Curved B side (curved B side)
A Twist B Twist

Claims (2)

A method of forming a high-strength steel plate member of 980 MPa class or higher having a shape that is curved in the transverse direction and the height direction along the longitudinal direction with a U-shaped or hat-shaped cross section,
For all of the longitudinal direction of the high-strength steel plate member,
In the first molding step, an intermediate product is molded with the same radius of curvature as the product shape and wider than the product shape,
In the second molding step, smaller than the width in said first molding step, the molded without changing the radius of curvature, there the whole molded article multistage press molding how to characterized in that the product shape or a substantially product shape ,
When the line lengths in the width direction in the product shape and the intermediate product shape formed in the first forming step are LW [mm] and LWl [mm], respectively.
1 <LWl / LW <1.1
Meet the requirements of
A multi-stage press molding method with excellent shape freezing property, wherein the first molding step is draw molding or foam molding, and the second molding step is a wrist-like process for molding into a product shape . A method of forming a high-strength steel plate member of 980 MPa class or higher having a shape that is curved in the transverse direction and the height direction along the longitudinal direction with a U-shaped or hat-shaped cross section,
For all of the longitudinal direction of the high-strength steel plate member,
In the first molding step, an intermediate product is molded with the same radius of curvature as the product shape and wider than the product shape,
In the second molding step, smaller than the width in said first molding step, the molded without changing the radius of curvature, there the whole molded article multistage press molding how to characterized in that the product shape or a substantially product shape ,
When the line lengths in the width direction in the product shape and the intermediate product shape formed in the first forming step are LW [mm] and LWl [mm], respectively.
1 <LWl / LW <1.1
Meet the requirements of
The first molding step and the second molding step are draw molding or foam molding, and have a wrist-like process for molding into a product shape after the second molding step, and are multistage with excellent shape freezing properties Press molding method.

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