JP2006068778A - Method and apparatus for forming high strength steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple forming method and forming apparatus of a high strength steel sheet by which defects in shape are prevented and required dimensional accuracy of products is realized by securing the freezability of shape when forming a flanged channel parts by using a high strength steel sheet as a base stock. <P>SOLUTION: In a press forming die consisting of a punch 1, a die 2 and a blank holder 3, a recessed part 4 and a stepped part 5 are respectively provided on the blank holder 3 and the die 2 and a rolling/bending member 6 is arranged in that recessed part 4. In a forming stage where a sheet B to be formed is inserted between this rolling/bending member 6 and the die 2 and the punch 1 is advanced, by forming a bent part 7 on the material B to be formed in the recessed part 4 and making the distribution of residual stress of the formed parts uniform by increasing the tension in a vertical wall part U of the material B to be formed, the prescribed dimensional accuracy is secured. In this way, the flanged channel parts excellent in the dimensional accuracy is manufactured by a simple mechanism. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  This invention has a shape freezing property when a generally hat-shaped flanged channel part is formed using a high-strength steel plate as a blank by a press-forming apparatus using a die comprising a punch, a die, and a blank holder. It is related with the shaping | molding method and shaping | molding apparatus of a high strength steel plate which can ensure predetermined | prescribed dimensional accuracy.

Conventionally, many flanged channel parts having a substantially hat shape have been used as components of automobile bodies. However, when forming this flanged channel part using a high-strength steel plate as a material, there is a problem that dimensional accuracy failure due to springback is likely to occur compared to the case of using a general cold-rolled steel plate as a material. . The occurrence of this springback is due to the residual stress distribution in the plate thickness direction accompanying molding, and the bending and bending that the blank undergoes when passing through the mold R part also in parts other than the mold R part of the molded product. This is a problem that is difficult to deal with, such as wall bending due to residual stress distribution in the plate thickness direction due to bending back deformation. In order to solve such a problem, as shown in FIG. 5A, a blank 14 is locally placed on the holding surface of the die 11 with a molding die having a punch 11, a die 12, and a blank holder 13. A depression 15 for pushing in, and a pressing body 16 connected to the piston 18 of the cylinder 17 for pushing the blank 14 locally into the depression 15 of the die 11 on the holding surface of the blank holder 13. A forming method and a forming apparatus for forming a flanged channel part by press-forming a tension steel blank 14 are disclosed (see Patent Document 1). In the molding die, the high-strength steel plate blank 14 is locally pressed into the recess 15 by the pressing body 16, and a bead 14b is formed between the die 11 and the blank holder 13 as shown in FIG. Therefore, the tension of the vertical wall portion of the blank 14 in the process in which the front end surface of the punch 11 reaches the bottom dead center of the punch forming process is increased, and the occurrence of springback phenomenon and wall warpage is prevented. It is intended to ensure a stable shape freezing property of the channel parts when press-molding and to ensure a predetermined dimensional accuracy.
JP-A-11-290951 ([0020] to [0023])

  However, in the molding method disclosed in Patent Document 1, it is necessary to provide a pressing body that locally presses the blank plate material in the die or the blank holder, which requires a significant modification of the press molding apparatus. In addition, the pressing body requires a drive mechanism such as a cylinder that can move forward and backward, and in order to form a bead by pressing the pressing body in the plate thickness direction, it is necessary to provide a through hole in the die or blank holder There is. For this reason, in addition to reducing the strength of the die or blank holder provided with the through-hole, when forming channel parts having different widths and heights in the longitudinal direction, in order to properly form the beads, It is necessary to strictly control the pressing amount of the pressing body.

  The present invention has been made in view of such problems of the prior art, and its problem is to ensure shape freezing when forming a substantially hat-shaped flanged channel component from a high-strength steel plate. An object is to provide a simple forming method and forming apparatus for a high-strength steel sheet which can prevent a shape defect and can realize a required product dimensional accuracy.

  In order to solve the above problems, the present invention employs the following configuration.

  That is, the method for forming a high-strength steel sheet according to claim 1 is a press-forming apparatus using a forming die composed of a punch, a die, and a blank holder, and a high-strength steel sheet blank is placed between the die and the blank holder. A method for forming a high-strength steel sheet that forms a flanged channel part by advancing a punch with a punch, and is provided with a recess on the holding surface of the die or the blank holder, or on both holding surfaces of the die and the blank holder. A bending part is formed in the concave part in the concave part in a molding process in which a rolling bending member is disposed in the concave part and the punch is advanced by sandwiching the blank between the rolling bending member and the holding surface of the die or the blank holder. And the vertical wall part tension | tensile_strength of a blank is increased and predetermined | prescribed molded product dimension accuracy is ensured.

  In this way, if a blank (formed plate) of a high-strength steel plate is sandwiched between the rolling bending member and the holding surface of the die or blank holder, as the punch advances, Since the bending angle of the blank is increased and the bending resistance is increased, the tension of the blank vertical wall portion is greatly increased in the final stroke of the punch. Thereby, the residual stress distribution in the blank is made uniform, shape freezing property, that is, shape accuracy is ensured, and predetermined dimensional accuracy can be realized. In addition, when providing the said recessed part in the holding surface of any one of a die | dye or a blank holder, it is necessary to make a bending part of a blank easy by providing a level | step difference in the holding surface in the other.

  In the method for forming a high-strength steel sheet according to claim 2, the distance between the holding surfaces of the die and the die holder in the forward direction of the punch is opened larger than the blank thickness at the initial stage of the forming process. The interval is set to be equal to the plate thickness from the time when 90% of the total stroke is advanced to the final stroke.

  In this way, the bending / unbending deformation in the vicinity of the die R portion is alleviated, so that the wall warp of the molded product is reduced. At the end of the molding process that has reached 90% of the entire punch stroke, the distance is made as small as the blank thickness, before the rolling bending member has finished moving to the punch-side end of the recess. Since it wraps around the die R portion, the R portion of the molded product from the flange portion to the vertical wall portion is more reliably formed.

  A press molding apparatus according to claim 3 includes a molding die including a punch, a die, and a die holder, and the flanged channel component is formed by advancing the punch with a blank interposed between the die and the blank holder. A press forming apparatus for forming a concave portion on the holding surface of the die or the blank holder or both the holding surface of the die and the blank holder, and a rolling bending member is disposed in the concave portion, and the rolling bending is performed. A bending portion is formed in the blank in the concave portion in a molding process in which the punch is advanced with the blank interposed between the member and the holding surface of the die or the blank holder.

  By using such a press forming apparatus, a bead can be easily formed in the concave portion, the tension of the vertical wall portion of the blank in the final stage of punching is greatly increased, the spring back phenomenon is suppressed, and the shape is frozen. And stable dimensional accuracy of the molded product is obtained.

  According to the present invention, a recess is provided in one or both of the die of the press molding die and the holding surface of the blank holder, and a high strength is provided between the rolling bending member inserted into the recess and the holding surface of the die or blank holder. Since the punch is advanced with the blank of the steel plate sandwiched, the bent part of the blank can be easily formed in the recess, and the punch forming is performed by the bending resistance of the bent part by this rolling bending member. As a result of increasing the vertical wall tension of the blank in the process, the shape freezing property is ensured and a molded product with stable dimensional accuracy is obtained.

  The distance between the holding surfaces of the die and the die holder is set to be larger than the blank thickness at the beginning of the molding process, and the distance is defined as the thickness at the end of the molding process in which the punch has advanced 90% of the entire process. By narrowing to the same extent, the occurrence of residual stress due to bending and unbending deformation near the die R part is alleviated, so that the wall warp of the molded product is reduced and more reliably from the flange part to the vertical wall part. R portion can be formed.

  Embodiments of the present invention will be described below with reference to the accompanying FIGS.

  FIGS. 1A to 1C show a method of forming a substantially hat-shaped flanged channel component made of a high-strength steel plate as a material from one center to the other side of the molding die. A molding die comprising a punch 1, a die 2, and a blank holder 3, a recess 4 is formed on the holding surface 3 a of the blank holder 3, and a step 5 is formed on the holding surface 2 a of the die 2. A metal ball 6 such as steel, which is a rolling bending member, is arranged in the concave portion 4 on a guide groove (not shown) provided in the rolling direction in the concave portion 4, and is a blank of high-strength steel plate (molded plate). B is placed between the die 2 and the blank holder 3 so as to contact the metal ball 6. As shown in FIGS. 2 (a) and 2 (b), the shoulder portion of the step 5 provided on the holding surface 2a of the die 2 is provided with R, and a blank (molded plate) is formed by a metal ball 6 of a rolling bending member. ) The bent portion 7 is easily formed on the flange portion F of B. The size (diameter) of the metal sphere 6 can be determined as follows. That is, as shown in FIG. 1B, when the die 2 is lowered and the molding plate B is sandwiched between the die 2 and the metal ball 6, the molding plate B is deformed along the metal ball 6. In addition, the size of the metal ball 6 is such that the distance between the holding surface 2a, 3a of the die 2 and the blank holder 3 can be maintained. More specifically, the size of the metal ball 6 is the same as that of the holding surface 2a of the die 2. The size of the holding surface 3a of the blank holder 3 is large enough to maintain an interval at which the forming plate B can be lightly pressed to the extent that the forming plate B can move within the die 2 as the punch 1 advances. It is desirable to do. Further, the recess 4 is formed by optimizing its depth H and width W (see FIG. 1C) in advance, so that the height of the channel component, that is, the entire stroke (advance distance) of the punch 1 is met. Thus, the tension of the vertical wall portion U of the molding plate B can be increased from a predetermined position of the punch 1.

  As the punch 1 is raised, that is, moved forward from the state shown in FIG. 1B, the metal ball 6 is punched in the space 8 formed by the recess 4 and the step 5, as shown in FIG. Rolls to the end on the side, that is, to the end E1 of the recess 4. In this process, as the metal ball 6 approaches the end E1, the plate B to be molded is supported between the holding surfaces 2a and 3a of the die 2 and the blank holder 3, and compared with FIGS. 2 (a) and 2 (b). As shown, since the angle θ bent by the metal sphere 6 increases, the bending resistance of this portion increases. As a result, at the end of the punching process, the tension of the vertical wall portion U of the plate to be molded shown in FIG. Due to this increase in tension, the residual stress distribution in the vertical wall portion U and the mold R portion becomes uniform, and shape freezing property, that is, shape accuracy is ensured.

  The distance in the forward direction of the punch 1 between the holding surface 2a of the die 2 and the holding surface 3a of the blank holder 3 is such that the holding surface 2a of the die 2 is a rolling bending member in the initial stage of molding, that is, in the initial molding process of the punch 1. Bending and bending in the vicinity of the die R portion (see FIG. 1 (a)) if the metal ball 6 is opened to a large extent within the range where the metal ball 6 bends the forming plate B and is located below the top of the metal ball 6. The occurrence of residual stress due to the return deformation is alleviated, and the wall warp of the molded product is suppressed. Even if the interval is wide as it is in the forming process in which the punch 1 further advances, if the metal ball 6 rolls to the end of the concave space 8 on the punch 1 side, the metal ball 6 causes the plate B to be formed. Since the forming plate B is wound around the die R portion by the bending resistance at the bending portion 7, the R portion of the molded product is sufficiently formed. However, at the final stage of the molding that reaches 90% of the entire stroke of the punch 1, the metal ball 6 becomes the end of the concave space 8 on the punch 1 side by reducing the distance to be equal to the thickness of the plate B to be molded. Before finishing moving to the portion (end E1 of the recess 4) (see FIG. 2A), the molding plate B wraps around the die R portion, so that the molded product from the flange portion F to the vertical wall portion U The R portion is more reliably formed.

  In the mold configuration in which the die 2 and the blank holder 3 of the molding die shown in FIG. 1 are arranged upside down and the punch 1 is lowered from above to form the flanged channel part, the die 2 and the blank are also provided. The holding surface 2a, 3a of the holder 3 is provided with the concave portion 4 and the step 5, respectively, and a metal ball 6 as a rolling bending member is inserted into the concave portion 4, so that the vertical wall portion of the plate B to be molded as described above. The tension of U can be increased. Further, a plurality of metal balls 6 of the rolling bending member can be arranged according to the length of the molded product, that is, the length of the mold.

  A blank (formable plate) B of a high-strength steel plate having a plate thickness of 1.4 mm and a tensile strength of 590 MPa or more is roughly outlined with a width of 50 mm and a height of 70 mm using the forming method of the embodiment shown in FIG. Molded into a hat-shaped flanged channel part. At that time, the holding surface 2a of the die 2 is provided with a step 5 having a depth of 5 mm as shown in FIG. 1, and the holding surface 3a of the blank holder 3 is provided with a concave portion 4 having a rectangular groove shape having a depth of 5 mm. In order to prevent rotation in the recess 4 during rolling, a round bar having an outer diameter of 10 mm is used as a rolling bending member instead of the metal ball 6 in the space 8 formed by the recess 4 and the step 5. Both end portions thereof are arranged along the wall surfaces of the recess 4 and the step 5. As shown in FIG. 1A, the high-strength steel plate B is disposed between the die 2 and the blank holder 3 so as to contact the round bar of the rolling bending member, and FIG. In the state where the die 2 is lowered and the distance between the holding surfaces 2a and 3a with the blank holder 3 is set to be slightly larger than the blank plate thickness, for example, about 0.5 mm, the punch 1 Moved forward. The shaped plate B flows into the die 2 with the advance of the punch 1 as indicated by an arrow in FIG. 2A, and the round bar of the rolling bending member is moved into the space 8 by the frictional force with the shaped plate B. As shown in FIG. 2 (b), the end E1 is guided toward the end of the punch (not shown) side, that is, toward the end E1 of the recess 4 of the die holder 3 and immediately before the end of the punch forming process. Until the end of the punch molding process. After the completion of molding, the punch 1 was retracted and unloaded, and the molded product A was taken out. On the other hand, the step 5 and the recess 4 are not provided on the holding surfaces of the die 2 and the blank holder 3, and the distance between the die 2 and the blank holder 3 is kept equal to the blank thickness of the high-tensile steel plate, and the punch 1 is formed. The molded product B was molded in the same manner as the molded product having a width of 50 mm and a height of 70 mm. The results of measuring the shapes of the molded product A according to the present invention and the molded product B according to the prior art are shown in FIG. As can be seen from FIG. 3, in the molded product A according to the present invention, almost no wall warpage was observed, and the shape of the portion of the die R portion was also formed satisfactorily. On the other hand, in the molded product B according to the prior art, the occurrence of wall warp is remarkably recognized, and it can be seen that the shape accuracy is not ensured.

  4 (a) to 4 (c) show other embodiments, and the holding surface 2a of the die 2 is formed with a recess 4a instead of the step 5 formed on the die 2 in the embodiment of FIG. ing. From the initial state in which the forming plate B shown in FIG. 4A is set, as shown in FIG. 4B, the die 2 descends and covers the metal ball 6 of the rolling bending member. The forming plate B is deformed along the metal ball 6 with the forming plate B interposed therebetween. When the punch 1 rises from this state, that is, moves forward, as shown in FIG. 4C, the metal ball 6 rolls to form the concave portion 4 formed on the holding surface 3 a of the die holder 3 and the holding surface of the die 2. It rolls to the punch 1 side end part of the recessed space 8 formed by the recessed part 4a formed in 2a, and the bending angle θ of the forming plate B becomes large, and the vertical wall of the forming plate B is caused by the bending resistance. The tension of the part increases. Thus, by providing the concave portion 4a on the holding surface 2a of the die 2, the shape freezing property is ensured and a predetermined dimensional accuracy is realized. In addition, as shown in FIG. 4, when providing the recessed part 4a and 4 in both the die | dye 2 and the blank holder 3, as shown in FIG. 1 and FIG. In any case where the step 5 is provided, the position of the end E1 of the recess 4 on the blank holder 3 side is the position of the bending portion 7 of the molding plate B formed by the movement of the rolling bending member 6. Since the degree of R is defined, the position of the end E2 of the recess 4a on the die 2 side or the step 5 of the die 2 and the same position with respect to the moving (rolling) direction of the rolling bending member 6, Or as shown in FIG. 2, it is desirable to form in the position which shifted | deviated to the outer side direction of the flange part F. As shown in FIG.

  The rolling bending member is not limited to a spherical or round bar shape, but may be any shape that can roll in the recess space by frictional force with the blank. In addition, for flanged channel parts with complex shapes, rolling is performed in order to control the blank bending resistance in the vicinity of the recess space end in detail and to ensure a predetermined dimensional accuracy stably. A displacement sensor that measures the displacement of the bending member and a drive device that finely adjusts the position of the rolling bending member based on the output thereof can also be provided.

  INDUSTRIAL APPLICABILITY The present invention can be used as a press molding method and a molding apparatus that can ensure a predetermined shape and dimensional accuracy of a flanged channel part that is frequently used as a component of an automobile body with a simple mechanism.

(A)-(c) It is explanatory drawing which shows the formation method of the high strength steel plate of embodiment of this invention. (A), (b) It is explanatory drawing which shows the increase in the bending angle of the blank accompanying rolling of a rolling bending member. It is explanatory drawing which compared the shape of the molded product by this invention and prior art. (A)-(c) It is explanatory drawing which shows the shaping | molding method of the high strength steel plate of other embodiment. (A) It is an example of the prior art which shows the shaping | molding method of the channel component with a flange. (B) It is sectional drawing which shows the bead formed in the to-be-molded board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Punch 2 ... Die 3 ... Blank holder 2a, 3a ... Holding surface 4, 4a ... Recessed part 5 ... Step 6 ... Metal ball (rolling bending member)
7 ... Bending part 8 ... Space B ... Blank (molded plate)
E1, E2 ... End F ... Flange U ... Vertical wall

Claims (3)

  A flanged channel component is formed by advancing the punch with a high-strength steel sheet blank sandwiched between the die and the blank holder in a press-forming device using a molding die comprising a punch, die, and blank holder. A method for forming a high-strength steel sheet, wherein a concave portion is provided on the holding surface of the die or the blank holder or both holding surfaces of the die and the blank holder, and a rolling bending member is disposed in the concave portion, and this rolling bending is performed. In the molding process in which the punch is advanced with the blank sandwiched between the member and the holding surface of the die or blank holder, a bent portion is formed in the blank within the recess, and the vertical wall portion tension of the blank is increased to perform a predetermined molding. A method for forming a high-strength steel sheet, which ensures product dimensional accuracy.   The distance between the holding surfaces of the die and the die holder in the forward direction of the punch is set to be larger than the blank thickness at the beginning of the forming process, and the punch reaches the final process from the point where 90% of the entire process has advanced. The method for forming a high-strength steel sheet according to claim 1, wherein the interval is set equal to the plate thickness. A press molding apparatus comprising a molding die composed of a punch, a die, and a die holder, and forming a flanged channel component by advancing the punch with the blank sandwiched between the die and the blank holder, The holding surface of the die or blank holder or both holding surfaces of the die and the blank holder is provided with a recess, and a rolling bending member is disposed in the recess, and the rolling bending member and the holding surface of the die or blank holder A press forming apparatus characterized in that a bending portion is formed in the blank in the concave portion in a forming step in which the punch is advanced with a blank interposed therebetween.

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