JP4090028B2 - Mold equipment for press forming thin steel sheet - Google Patents

Description

【００２２】
【表２】

【００２３】
９８０ＭＰａ級の高張力鋼板を素材とし、図４に示すような金型を使用してフォームベンド法で曲げ成形し、高さがそれぞれ１．０ｍｍ（試験番号２），２．０ｍｍ（試験番号３）になるようにビードを形成したものでは、割れは発生せず、しかも壁反り量（１／ρ）もそれぞれ４．３５（試験番号２），２．８９（試験番号３）と小さく、寸法精度にも十分満足できる成形品を得ることができた。特に試験番号３は良好な形状の製品が得られた。
これに対して、９８０ＭＰａ級の高張力鋼板を素材とし、図４に示すような金型を使用してフォームベンド法で曲げ成形しても、形成するビードの高さが所定値に満たない（試験番号１）と、割れは生じないものの、壁反り量（１／ρ）はやや大きく、若干の矯正作業を必要とした。これは、ビード形成により付与される張力が小さいために、残存する応力を低減できなかったためである。
逆に、形成するビードの高さが高すぎると（試験番号４）と、割れが発生して欠陥品となった。これは、ビード形成により付与される張力が鋼板の引張強さを上回ったためである。
また、高張力鋼板を、従来の金型装置を用いてドローベンド法で曲げ成形した（試験番号５）場合、割れは発生しないが、壁反り量（１／ρ）は９．８５にもなり、一般冷延鋼板の場合の約３．６倍にもなっている。したがって、大幅な手直し矯正が必要になった。
なお、一般の冷延鋼板は、従来の金型装置を用いてドローベンド法で曲げ成形しても（試験番号６）、問題なく成形できる。
【００２４】
【発明の効果】
以上に説明したように、本発明法により、ハット型断面部品をプレス成形法を成形する際に、素材として高張力鋼板を用いても、壁反りの少ない製品を得ることができるので、その後の矯正作業を必要とせず低コストで品質の高いハット型断面部品を製造することができる。
さらに、本発明プレス成形金型装置は、パンチと平坦なフランジ加圧面を有する上金型を上部スライドに装着し、フランジ加圧面を有する固定ダイとクッションパットを一体化した下金型をボルスタ上に載設し、クッションピンを介してダイクッション装置からの加圧力をクッションパットに伝達するように構成されているので、従来の機械プレス装置の金型と容易に置換えることができ、本発明法を実施するために専用のプレス装置を設置する必要がなく、この点からも品質の高いハット型断面部品を低コストで製造することができる。
【図面の簡単な説明】
【図１】 ハット型断面部品を成形するため従来の曲げプレス金型装置の概略を説明する正面図
【図２】 曲げ・曲げ戻し変形を受けた素材縦壁部断面内の残留応力状態を説明する図
【図３】 離型した成形品の壁反りの状態を示す図
【図４】 ハット型断面部品を成形するための本発明金型装置の概略を説明する正面図で、曲げ成形行程の初期段階の状態を示す図
【図５】 本発明法で素材板を成形するときの、成形行程途中の段階の状態を示す図
【図６】 本発明法で素材板を成形するときの、成形行程末期に近い段階のビードを押圧成形した状態を示す図
【図７】 本発明金型装置の他の態様の概略を説明する正面図
【図８】 壁反り量の測定方法を模式的に説明する図
【符号の説明】
１：素材 ２：下金型 ３：上金型
１１：スライド １２：ボルスタ １３：ヘッド
１４：ダイクッション装置 １５：ピンプレート １６：クッションピン
２１：固定ダイ ２２：ダイ側フランジ加圧面 ２３：ビード形成窪み
２４：開口部 ２５：下金型プレート ２６：クッションパット
２７：スライドガイドポール ２８：ストッパープレート ２９：貫通孔
３０：固定ダイ肩Ｒ部
３１：可動パンチ ３２：パンチ側フランジ加圧面 ３３：ビード形成凸部
３４：可動パンチ肩Ｒ部 ３５：クリアランス ３６：スリット
３７：ビード形成押込み治具 ３８：留め金具
４１：固定パンチ ４２：可動ダイ ４３：しわ押え工具
５１：フラット部 ５２：縦壁部 ５３：フランジ部
Ｔ：引張り応力 Ｃ：圧縮応力[0001]
[Industrial application fields]
The present invention relates to a die apparatus for press forming a thin steel plate for forming the thin steel plate into a flanged U-shaped cross section (hat type cross section).
[0002]
[Prior art]
An automobile body is usually composed of a large number of molded members obtained by press-forming thin steel plates, and flanged U-shaped cross-section parts (hereinafter referred to as “hat-shaped cross-section parts”) and the like are often used. The hat-shaped cross-sectional component is made of a mechanical press apparatus equipped with a die composed of a U-shaped punch 41, a movable die 42 and a wrinkle presser tool 43 as shown in FIG. In general, it is obtained by so-called hat bending, in which a thin steel plate is drawn and bent at a time.
However, such a processing method has a drawback that a springback occurs due to elastic recovery and a wall warp occurs in the vertical wall portion. When assembling a vehicle body using the obtained processed product as a component, In some cases, the welding by spot welding did not work, resulting in manufacturing problems.
[0003]
The so-called hat-type bending process is a processing method in which a material is bent once when passing through a die shoulder R portion and then stretched to be bent back to form a vertical wall. For this reason, a peculiar phenomenon of leaving a bending wrinkle in the die shoulder portion occurs. As shown in FIG. 2, the outer surface layer of the vertical wall portion 52 is temporarily compressed when passing through the shoulder portion of the die and is stretched after passing, so that a tensile stress T remains in the press direction. Since the inner surface of the portion 52 is once stretched when passing through the shoulder portion of the die and compressed after the passage, the compressive stress C remains, so that a non-uniform stress distribution occurs in the thickness direction. When the molded body is released from the mold while leaving a non-uniform stress distribution, the vertical wall portion 52 that should be processed perpendicularly to the flat portion 51 is released from the constraint of the mold. Due to elastic recovery, so-called spring back, as shown in FIG. 3, a defective shape such that the vertical wall warps outward occurs.
The amount of wall warp due to this springback varies greatly depending on the shape of the work material, the shape of the punch, die and wrinkle pressing tool used for press work, and the material characteristics. For example, when the material strength of the material is large or when the plate thickness of the material is small, the amount of wall warp tends to be larger.
[0004]
On the other hand, from the viewpoint of weight reduction and collision safety in recent years, high-strength steel sheets that are thinner than ordinary cold-rolled steel sheets are increasingly used as materials for automobile bodies. It is a problem.
Therefore, various press forming methods for suppressing wall warpage during hat bending and approaching a predetermined part shape have been proposed.
In Japanese Patent Laid-Open No. 56-117831, the bending radius at the die shoulder is 1.0 to 2.5 times the plate thickness, and the punch-die clearance is 1.0 to 1.4 times the plate thickness. It is proposed to set.
In Japanese Patent Application Laid-Open No. 11-290951, at the end of the punch forming process, the material is locally pressed between the die holding surface and the wrinkle pressing tool holding surface to form an indentation bead on the flange, and the vertical wall portion where the material is bent There has been proposed a bending straightening method for removing bending wrinkles in the vertical wall portion by applying a tension due to the formation of the indentation bead until a uniform tensile deformation is applied.
[0005]
In JP-A-61-82930, when press molding is performed with a mold device composed of a movable die attached to the lower surface of a slide of a press device and a punch installed on a bolster of the press device, The material portion at a distant position is pressed and deformed, and a bending rod in the opposite direction to the spring back is attached in advance, and then bent at a specified bending angle between the punch and the movable die, and the spring back generated by this bending It has been proposed to perform bending processing with excellent dimensional accuracy by offsetting the bending wrinkles.
Furthermore, in Japanese Patent Application Laid-Open No. 2002-224754, when a plate-shaped material is formed by a die having a cavity and a punch having a flange portion protruding from the outer periphery of the lower portion, the punch is moved in the vicinity of the flange portion. And the flange part protruding from the lower part of the movable punch is made slightly larger than the outer dimension of the movable punch to prevent the material from being folded during molding and It has been proposed to eliminate the accumulation of strain that causes springback on the side wall of the product. Furthermore, in this publication, after forming a flange on the material by the action of the flange portion provided at the lower part of the movable punch, a flange-shaped bead is provided on the flange portion as a measure for increasing the rigidity in the flange longitudinal direction of the molded product. Or a joggle having a stepped shelf shape so as not to cause an overlapping step at the end of the molded product, the bead or joggle can be molded simultaneously for the purpose of shortening the molding process. Variations on the mold have also been proposed.
[0006]
[Problems to be solved by the invention]
The method proposed in Japanese Patent Laid-Open No. 56-117831 is intended to suppress wall warpage by controlling the reverse bending at the time of bending and unbending at the die shoulder to cancel the residual moment. However, the appropriate amount of reverse bending strongly depends on the thickness and strength of the material. Therefore, at the time of actual molding, the allowable control range is narrow, so that the amount of wall warp varies greatly depending on the accuracy of the plate thickness, and the die cost increases due to the need to ensure sufficient accuracy in the radius of the die shoulder R. There are problems.
In the method proposed in Japanese Patent Application Laid-Open No. 11-290951, when the material passes through the die shoulder R portion, the bending wrinkle once generated is localized at the end of molding corresponding to only 3 to 10% of the entire molding process. Since it is intended to be eliminated by the action of tension applied when the bead is formed by pressing, it is not possible to apply tension enough to eliminate the springback because of the danger of cracking. When a high tensile steel having a tensile strength exceeding 690 MPa is used as a material, a sufficient straightening effect cannot be obtained. In addition, a special press device is required, which is difficult to implement with a normal press device.
[0007]
In the above method, a hat-shaped cross-section part is formed by pressing a flange with a holder and pressing a punch into a die while applying a crease pressing force (hereinafter referred to as “draw bend forming”). Therefore, even if various straightening methods are applied, the uneven stress remaining on the vertical section of the hat-shaped cross section cannot be eliminated, and the wall warpage of the vertical wall section cannot be completely suppressed, resulting in a defective shape. easy. On the other hand, the methods proposed in Japanese Patent Laid-Open Nos. 61-82930 and 2002-224754 are so-called foam bend molding in which a punch is pressed into a die without applying a crease pressing force. Therefore, the uneven stress remaining in the vertical wall portion of the hat-shaped cross section is relatively small, and the amount of wall warpage is small compared to the draw bend forming method. However, the method proposed in Japanese Patent Application Laid-Open No. 61-82930 has a problem that shape defects such as wrinkles and twists are likely to occur because no crease pressing force is applied. Moreover, among the methods proposed in Japanese Patent Application Laid-Open No. 2002-224753, when forming a bead in the same process for shortening the process, although there is an improvement effect even for shape defects such as wrinkles and twists, If an unnecessarily large bead is to be provided, there is a problem in that there is a possibility that the bead tension becomes too large and causes cracking.
[0008]
The present invention has been devised to solve such a problem, and a hat-shaped cross-section part is pressed using a high-tensile steel plate, which tends to have a larger wall warpage than a general cold-rolled steel plate. When molding, it can be carried out using a normal mechanical press without using a special mold, and it is affected by errors in plate thickness accuracy while suppressing shape defects due to wrinkles and twisting. It is an object of the present invention to provide a die forming apparatus for press forming of a thin steel sheet to be press-formed that can stably control the wall warpage within a small range.
[0009]
[Means for Solving the Problems]
Steel sheet press-molding die apparatus of the present invention, the movable punch which forms a convex shape, the movable punch flange pressing surface provided integrally with the movable punch on each side of, and along with provided on the flange pressing surface , has a smaller bead forming convex portion than the amount of protruding the movable punch from the flange pressing surface, and the mold on which is provided on the lower surface of the slide, a fixed die with an opening, vertically opening within cushion pad provided freely moving, and comprises a lower die having said flange pressing surface formed on both sides the upper surface of the fixed die, and depressions for bead formation provided in the flange pressing surface, the movable When the material sandwiched between the punch and the cushion pad is bent into a hat-shaped cross-sectional shape, the opening of the material is caused by the lowering of the movable punch accompanying the lowering of the slide. The material is bent into a U cross section, and at the end of the molding immediately before the slide reaches bottom dead center, the bead forming convex portion and the bead forming depression are directed upward to the flange of the hat cross section. An indentation bead is formed .
Bead forming convex portion includes a slit formed in the flange pressing surface of the movable punch, Rutotomoni fitted in the slit, also protruding amount from the flange pressing surface is replaced by a small bead formed indentation jig than the movable punch Good.
Further, the cushion pad is preferably integrated with the stopper plate via a slide guide pole penetrating a through hole provided in the lower mold plate, and is supported by the die cushion device using a cushion pin. .
Furthermore, it is preferable that the height of the pushing bead is set to 0.8 to 2.0 mm.
[0010]
Embodiment
First, the mold apparatus used by this invention is demonstrated based on FIG.
FIG. 4 shows a die cushion for generating a wrinkle pressing force inside a bed 13 to which a die composed of a conventional punch, die and wrinkle pressing tool can be mounted and the bolster 12 of the press apparatus main body is fixed. The state which mounted | worn with the metal mold | die apparatus of this invention to the general-purpose draw-bending machine press apparatus which incorporated the apparatus 14 is shown. FIG. 4 also shows an initial stage of a forming process using a high-strength steel plate as the material 1. The mold apparatus includes a concave lower mold 2 having a cushion pad 26 and a fixed die 21 installed on the bolster 12, a movable punch 31 attached to the lower surface of the slide 11, and a flange pressurizing surface 32 on the side of the punch. It is comprised by the upper metal mold | die 3 which makes | forms the downward convex shape provided with.
[0011]
As shown in FIG. 4, the fixed die 21 is placed on the lower mold plate 25, and a bead forming convexity is formed on the die side flange pressing surface 22 for pressurizing and forming the flange of the hat-shaped cross-sectional component. A recess 23 is provided in the portion 33 to push the material 1 locally. A concave opening 24 is formed on the inner lower surface of the fixed die 21, and a cushion pad 26 is accommodated in the opening 24. The cushion pad 26 is integrated with a stopper plate 28 through a slide guide pole 27 that penetrates the through hole 29 of the lower mold plate 25, and has a structure that can move up and down using the die cushion device 14 of the press body as a drive source. It has become.
In general, a general-purpose drawing bending machine press apparatus is equipped with a die cushion device 14 having a pneumatic or hydraulic drive source as a standard inside a bed 13 to which a bolster 12 is fixed. If the pin plate 15 and the cushion pin 16 are used, the applied pressure generated by the die cushion device 14 can be transmitted to the cushion pad 26 of the mold device of the present invention.
[0012]
On the other hand, the upper die 3 has a downwardly convex shape, a punch 31 for forming the material 1 in a U cross section, and a flat punch side provided integrally with the movable punch 31 to form a flange. The flange pressing surface 32 is configured. The punch-side flange pressing surface 32 has a protruding amount from the flange pressing surface 32 smaller than that of the movable punch 31, and is applied to the material 1 at the end of molding immediately before the slide 11 descends to reach bottom dead center in the press molding process . A bead forming convex portion 33 for forming a pushing bead for applying a tension is provided.
[0013]
Next, based on FIGS. 4-6, the procedure which press-forms a thin steel plate to a cross-sectional hat type | mold using this invention die apparatus is demonstrated.
First, as shown in FIG. 4, when the material 1 is placed on the cushion pad 26 and the press device is activated, the material 1 is fixed between the cushion pad 26 and the movable punch 31. Further, when the movable punch 31 descends as the slide 11 descends, the material 1 enters the clearance 35 between the two tools between the fixed die shoulder R portion 30 and the movable punch shoulder R portion 34 as shown in FIG. In addition, bending is performed to make a U shape.
[0014]
Further, at the final stage of molding immediately before the slide 11 reaches the bottom dead center after the molding process has progressed, as shown in FIG. 6, a bead forming convex portion 33 protruding from the punch-side flange pressing surface 32 on the outer periphery of the movable punch 31 is formed. A part of the material 1 is pressed into the recess 23 of the die-side flange pressing surface 22 that makes contact with both ends of the material 1 and is paired with the bead forming convex portion 33 to form a bead, thereby completing the molding.
After that, the molded product left in the opening 24 of the fixed die 21 before the slide 11 starts to rise and reaches the top dead center is operated by a knockout (not shown) and the cushion pad 26 is raised. It is released by that.
[0015]
In addition, since the bead of the flange portion is a protrusion that is not necessary for the completed part, it may be trimmed and removed in the next step as necessary.
Further, instead of the bead forming convex portion 33 provided on the punch side flange pressing surface 32, as shown in FIG. 7, a slit 36 is integrally provided on the punch side flange pressing surface 32, and various heights are provided in the slit 36. It is also possible to change the stock exchange and replace the flange, and attach the bead formation pushing jig 37 whose protrusion amount from the flange pressing surface 32 is smaller than that of the movable punch 31 and fix it with the fastener 38. In this case, the height of the bead can be changed according to the type of material, and the tension applied to the material can be adjusted. In addition, since it is possible to eliminate the replacement of the upper mold due to wear of the bead forming convex portion 33, it is also effective in reducing the mold maintenance cost.
[0016]
[Action / Effect]
The present invention performs so-called foam bend forming, in which a material is bent into a cross-sectional hat shape by pressing a punch into a die without applying a crease pressing force. For this reason, as in the conventional draw bend forming method, the bending deformation amount at the tool shoulder is not a large bending where the die shoulder R is bent once to 90 degrees and then bent back straightly at the vertical wall. Is small. Therefore, the non-uniform stress remaining in the vertical wall portion of the hat-shaped cross section is relatively small, and the wall warp is small as compared with the conventional method.
However, although it is small, tensile stress remains on the outer surface layer of the vertical cross section of the hat-shaped cross section, and compressive stress remains on the inner surface.
[0017]
Therefore, by forming an upward indentation bead on the flange of the hat-shaped section at the end of molding, compressive stress is applied to the upper surface of the flange and tensile stress is applied to the lower surface, reducing the residual stress on the vertical wall of the hat-shaped section. As a result, the wall warp was further reduced.
Thus, according to the present invention, the combination of so-called foam bend forming method and indentation bead formation can reduce wall warpage that is likely to occur when a hat-shaped cross-section part is manufactured by bending a material. It is.
At the final stage of molding, the flange portion of the material 1 is pressed by the punch-side flange pressing surface 32 and the die-side flange pressing surface 22, so that it is possible to prevent occurrence of shape defects such as wrinkles and twists on the flange. it can.
[0018]
An upper die having a punch and a flat flange pressing surface is mounted on the upper slide, and a lower die in which a fixed die having a flange pressing surface and a cushion pad are integrated is placed on a bolster, and a cushion pin is interposed therebetween. If the die device is configured to transmit the pressure applied from the die cushion device to the cushion pad, the die of the mechanical press device that was equipped with the conventional die for drawing or drawing bending is simply replaced. Only the press forming method of the thin steel plate of the present invention can be carried out.
In other words, in a general-purpose mechanical press apparatus conventionally used for drawing or drawing bending, the conventional draw bend forming method and the combined forming method of foam bend forming and indentation bead forming of the present invention can be performed by simply replacing the mold. It is possible to use them properly (see FIGS. 1 and 4). For this reason, it is not necessary to separately install different mechanical press devices according to the molding method, and the economy is excellent.
[0019]
【Example】
An embodiment in which bending is performed using the mold apparatus of the present invention will be described.
In this example, press oil is applied to a high-tensile cold-rolled steel sheet having a thickness of 1.2 mm, a sheet width of 30 mm, and a length in the rolling direction of 200 mm, the characteristics of which are shown in Table 1, and the punch width is 39.2 mm. Using a bending press die apparatus having the same basic configuration as that shown in FIG. 4 and composed of a tool having a radius of 3 mm, a die shoulder radius of 3 mm, and a clearance between the punch and the die of 1.4 mm, a molding stroke of 50 mm and a cushion pad back pressure of 1 kN Under the above molding conditions, the hat-shaped cross-sectional component was molded by changing the height of the bead to be molded.
[0020]
As a comparative example of the forming method, a forming test using the conventional mold apparatus shown in FIG. 1 having a wrinkle pressing tool (wrinkle pressing force 3 kN) instead of bead formation was also performed. Furthermore, in the test of the conventional forming method using a normal mold apparatus, a test using a general cold-rolled steel sheet was added.
As schematically shown in FIG. 8, the wall warp amount (1 / ρ) obtained by measuring the radius of curvature of the vertical wall portion of the cross section of the molded product is compared with two items of presence or absence of cracks. It was. A smaller wall warp value means a smaller wall warp and a better shape.
The molding conditions and evaluation results are summarized in Table 2.
[0021]
[Table 1]

[0022]
[Table 2]

[0023]
A high-tensile steel plate of 980 MPa class is used as a raw material, and it is bent by a foam bend method using a mold as shown in FIG. 4, and the height is 1.0 mm (test number 2) and 2.0 mm (test number 3), respectively. In the case where the bead is formed so as to satisfy the following conditions, cracks do not occur, and the wall warpage (1 / ρ) is also small as 4.35 (test number 2) and 2.89 (test number 3), respectively. A molded product with satisfactory accuracy could be obtained. In particular, test number 3 gave a product with a good shape.
On the other hand, even when a 980 MPa class high-tensile steel plate is used as a raw material, and the bend method is used for bending using a mold as shown in FIG. Although test number 1) and cracking did not occur, the amount of wall warp (1 / ρ) was somewhat large, requiring some correction work. This is because the residual stress cannot be reduced because the tension applied by the bead formation is small.
On the other hand, when the height of the bead to be formed was too high (test number 4), cracking occurred and the product was defective. This is because the tension applied by the bead formation exceeded the tensile strength of the steel sheet.
Further, when a high-tensile steel plate is bent by a draw bend method using a conventional mold apparatus (test number 5), cracks do not occur, but the wall warp amount (1 / ρ) is 9.85, It is about 3.6 times that of a general cold-rolled steel sheet. Therefore, a major correction was required.
Note that a general cold-rolled steel sheet can be formed without any problem even if it is bent by a draw bend method using a conventional mold apparatus (test number 6).
[0024]
【The invention's effect】
As described above, according to the method of the present invention, when a hat-shaped cross-section part is formed by a press molding method, a product with less wall warpage can be obtained even if a high-tensile steel plate is used as a material. High-quality hat-shaped cross-section parts can be manufactured at low cost without the need for straightening work.
Further, the press molding die apparatus according to the present invention is configured such that an upper die having a punch and a flat flange pressing surface is mounted on the upper slide, and a lower die integrated with a fixed die having a flange pressing surface and a cushion pad is mounted on the bolster. Since the pressure applied from the die cushion device is transmitted to the cushion pad via the cushion pin, it can be easily replaced with the mold of the conventional mechanical press device. It is not necessary to install a dedicated press device for carrying out the method, and a high-quality hat-shaped cross-sectional component can be manufactured at a low cost also from this point.
[Brief description of the drawings]
FIG. 1 is a front view for explaining an outline of a conventional bending press mold apparatus for forming a hat-shaped cross-sectional part. FIG. 2 explains a residual stress state in a cross section of a material vertical wall subjected to bending and bending back deformation. FIG. 3 is a diagram showing the state of wall warping of a molded product that has been released. FIG. 4 is a front view for explaining the outline of the mold apparatus of the present invention for forming a hat-shaped cross-sectional part. The figure which shows the state of an initial stage. [FIG. 5] The figure which shows the state of the stage in the middle of a shaping | molding process when shape | molding a raw material board by this invention method. The figure which shows the state which carried out the press molding of the bead of the stage close | similar to the last stage of a process. [FIG. 7] The front view explaining the outline of the other aspect of this invention metal mold apparatus. FIG. Figure [Explanation of symbols]
1: Material 2: Lower mold 3: Upper mold 11: Slide 12: Bolster 13: Head 14: Die cushion device 15: Pin plate 16: Cushion pin 21: Fixed die 22: Die side flange pressing surface 23: Bead formation Recess 24: Opening 25: Lower mold plate 26: Cushion pad 27: Slide guide pole 28: Stopper plate 29: Through hole 30: Fixed die shoulder R portion 31: Movable punch 32: Punch side flange pressure surface 33: Bead formation Convex part 34: Movable punch shoulder R part 35: Clearance 36: Slit 37: Bead formation pushing jig 38: Fastener 41: Fixed punch 42: Movable die 43: Wrinkle pressing tool 51: Flat part 52: Vertical wall part 53: Flange T: Tensile stress C: Compressive stress

Claims (4)

The movable punch (31) having a convex shape, the flange pressing surface (32) provided integrally with the movable punch (31) on both sides of the movable punch (31 ) , and the flange pressing surface (32) are provided. In addition, the upper mold (3) provided on the lower surface of the slide (11) has a bead forming convex portion (33) whose protrusion amount from the flange pressing surface (32) is smaller than that of the movable punch (31 ). When,
Fixed die with an opening (24) (21), the cushion pad (26) provided vertically movably to the opening (24) in the flange pressure formed on both sides an upper surface of the fixed die (21) pressure surface (22), and the flange pressing surface (22) recess for bead formation provided in (23) the lower die having a (2)
It has been provided with a,
When bending the material (1) sandwiched between the movable punch (31) and the cushion pad (26) into a hat-shaped cross-sectional shape,
As the movable punch (31) descends as the slide (11) descends, the material (1) is pushed into the opening (24) to bend the material (1) into a U-section,
At the final stage of molding immediately before the slide (11) reaches the bottom dead center, an upward pushing bead is formed on the flange of the hat-shaped cross section by the bead forming convex portion (33) and the bead forming depression (23). A die apparatus for press forming thin steel sheets. A movable punch (31) having a convex shape, a flange pressing surface (32) provided integrally with the movable punch (31) on both sides of the movable punch (31), and a slit formed in the flange pressing surface (32) (36), and said fitted into the slit (36) Rutotomoni has a small bead formed pushing jig than (37) said flange pressing surface (32) protruding amount from said movable punch (31), the slide An upper mold (3) provided on the lower surface of (11) ;
Fixed die with an opening (24) (21), the cushion pad (26) provided vertically movably to the opening (24) in the flange pressure formed on both sides an upper surface of the fixed die (21) A pressure die (22) , and a lower mold (2) having a bead forming recess (23) provided on the flange pressure surface (22) ,
When bending the material (1) fixed between the movable punch (31) and the cushion pad (26) into a hat-shaped cross-sectional shape,
As the movable punch (31) descends as the slide (11) descends, the material (1) is pushed into the opening (24) to bend the material (1) into a U-section,
At the final stage of molding immediately before the slide (11) reaches bottom dead center, an upward pushing bead is formed on the flange of the hat-shaped cross section by the bead forming pushing jig (37) and the bead forming depression (23). A die apparatus for press forming thin steel sheets. The cushion pad (26) is integrated with the stopper plate (28) through the slide guide pole (27) that passes through the through hole (29) provided in the lower mold plate (25) , and the cushion pin (16) is attached. The die apparatus for press forming of a thin steel plate according to claim 1 or 2 , which is supported by a die cushion apparatus (14) . The die apparatus for press forming of a thin steel plate according to any one of claims 1 to 3, wherein a height of the indentation bead is set to 0.8 to 2.0 mm. .

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