JP6658293B2 - Ram head and press straightening method - Google Patents

Description

  The present invention relates to a ram head that corrects the shape of a metal material by pressing the metal material, and a press correction method for the metal material using the ram head.

  When a shape defect occurs in a manufacturing process of a metal material (for example, a tube material, a bar material, a plate material, or the like), press straightening is performed as one method of correcting the shape. In press straightening, two shim plates are placed on a surface plate (bed) at a predetermined interval so that a portion to be corrected of a metal material to be corrected (a material to be corrected) is positioned between the shim plates. After the material to be corrected is installed so as to be bridged between the shim plates, the shape of the material to be corrected is corrected by pressing the portion to be corrected from above with a tool (ram head). For example, Patent Document 1 discloses a press straightening device for a steel sheet, which is a driving device that moves an upper stake (corresponding to the ram head) and a lower stake (corresponding to the shim plate) in and out of a pass line of the steel plate. Is disclosed.

Here, when press-straightening an extremely thick high-strength material having a thickness of 80 mm or more and a yield strength of 490 MPa (50 kgf / mm ² ) or more, a large press load is required as compared with other steel types. become. For example, in the correction of extremely thick high-strength materials, pressing is performed with a pressing load close to the upper limit of the equipment capacity. However, even if the pressing is performed with such a large pressing load, there are cases where the deformation remains in the elastic range and the shape cannot be corrected. Further, even when plastic deformation can be applied, only a very small plastic strain is often applied. Therefore, in order to correct the shape of the extremely thick high-strength material, it is necessary to repeatedly perform pressing a considerable number of times, which causes a significant decrease in efficiency.

  Therefore, Patent Literature 2 discloses a ram head for correcting a steel plate, in which a surface facing the steel plate includes a contact surface that contacts the steel plate and a non-contact surface that does not contact the steel plate. It has been disclosed. In other words, the ram head described in Patent Literature 2 has a shape in which a part of the surface facing the steel plate protrudes toward the steel plate, and when the steel plate is pressed, only the protruded portion is pressed. It comes into contact with the steel sheet and presses the steel sheet.

  For example, in the press straightening device described in Patent Literature 1, a steel plate is pressed by a top bar, which is a rod-shaped member having a substantially rectangular cross section. Since all the regions come into contact with the steel plate and press the steel plate, the contact pressure between the upper berth and the steel plate becomes relatively small. This is because the press load acts on the entire contact area between the upper bar and the steel plate, and means that the press load that can be used for bending deformation per unit area is reduced. On the other hand, according to the ram head described in Patent Literature 2, since the area of the contact surface with the steel plate is smaller, the same press load is applied as compared with the case of using the upper floor bar described in Patent Literature 1. Even so, a larger contact pressure is generated between the ram head and the steel plate. This means that the press load that can be subjected to bending deformation per unit area becomes larger. Therefore, since deformation can be intensively applied to the contact area, it is possible to correct the shape of the steel sheet with a smaller number of presses, and it is possible to reduce manufacturing costs and improve manufacturing efficiency. .

Japanese Patent No. 2506248 JP 2010-260074 A

  However, when a ram head having a smaller contact surface area with a steel sheet is used, as in the ram head described in Patent Document 2, plastic deformation is more easily applied to the steel sheet, but the ram head and the steel sheet are not Due to stress concentration at the contact portion, a flaw (hereinafter, also referred to as an indentation flaw) due to the press may be generated on the surface of the steel sheet. The occurrence of such indentation flaws not only leads to a reduction in product quality, but also necessitates an additional step of surface care, which may reduce manufacturing efficiency.

  Therefore, the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a press straightening for correcting the shape of a material to be corrected, in which a pressing flaw on the surface of the material to be corrected is caused by a press. An object of the present invention is to provide a new and improved ram head and a press straightening method capable of straightening the material to be straightened into a desired shape with a smaller number of presses while suppressing the occurrence of the ram.

  In order to solve the above problems, according to an aspect of the present invention, in a press straightening for a material to be corrected which is a metal plate, in a state where the material to be corrected is placed so as to bridge between two shim plates, A ram head for pressing a portion to be corrected between the two shim plates of the material to be corrected, wherein a surface facing the material to be corrected and contacting the material to be corrected at the time of pressing has a curvature κ that satisfies the following equation (101). A ram head is provided.

Ｌ_ｄ：前記ラムヘッドの幅
α、β：補正係数
Ｐ：プレス荷重
Ｌ：２つの前記シム板の一方から前記ラムヘッドの幅方向の両端のうち前記一方のシム板に近い側の一端までの長さ
ｔ：前記被矯正材の板厚
である。

L _d : width of the ram head α, β: correction coefficient P: press load L: length from one of the two shim plates to one end closer to the one shim plate among both ends in the width direction of the ram head t: The thickness of the material to be corrected.

In the ram head, a thickness t of the material to be corrected may be 80 mm or more, and a yield strength of the material to be corrected may be 490 MPa (50 kgf / mm ² ) or more.

According to another embodiment of the present invention, there is provided a press straightening method for correcting a shape of a material to be corrected using the ram head, wherein a thickness t of the material to be corrected is A press straightening method is provided, which is 80 mm or more, and the yield strength of the material to be straightened is 490 MPa (50 kgf / mm ² ) or more.

  As described above, according to the present invention, in press straightening for correcting the shape of a material to be corrected, while suppressing occurrence of indentation flaws on the surface of the material to be corrected due to pressing, the material to be corrected is reduced in the number of presses. Can be corrected to a desired shape.

It is a figure for explaining an outline of press straightening. It is a figure for explaining a contact state of a ram head and a to-be-corrected material during press straightening. It is a figure for explaining a contact state of a ram head and a to-be-corrected material during press straightening. It is a figure showing the result of the elasto-plastic analysis about the ram head and the material to be corrected during pressing. It is a figure showing the schematic structure of the press straightening device concerning this embodiment. It is a figure showing the section perpendicular to the extension direction of the ram head concerning this embodiment. It is a figure showing the shape of the beam before deformation. It is a figure which shows the shape after deformation | transformation of the beam shown in FIG. Based on a difference ΔZ amount of deformation of the beam shown in FIG. 8 is a diagram for explaining a method of determining the curvature radius R _Z of the upper surface of the beam.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(1. Background of the Invention)
Prior to describing the preferred embodiments of the present invention, in order to make the present invention clearer, the present inventors have described the contents of the study on the conventional press straightening, and based on the examination results, The background that the inventors came to the present invention will be described. In the present invention, the sheet material is subjected to press straightening. In the following description, when simply described as a material to be corrected, the description means a plate material unless otherwise specified. Further, in each of the drawings described below, the deformation of the material to be corrected may be excessively illustrated for convenience of explanation.

(1-1. Outline of press straightening)
The outline of press correction will be described with reference to FIG. FIG. 1 is a diagram for explaining an outline of press correction. As shown in FIG. 1, in press straightening, a cover is placed between two shim plates 120 so as to be positioned between the two shim plates 120 installed at a predetermined interval. The correction material 2 is installed. Then, the shape of the material to be corrected 2 is corrected by pressing the portion to be corrected of the material to be corrected 2 from above by the ram head 801 movable in the vertical direction.

  In the following description, the pressing direction (that is, the vertical direction) is defined as the Z-axis direction. Further, a direction orthogonal to the Z-axis direction and an arrangement direction of the two shim plates 120 is defined as an X-axis direction. A direction orthogonal to the X-axis direction and the Z-axis direction is defined as a Y-axis direction.

  FIG. 1 shows a conventional general ram head 801. The ram head 801 is a rod-shaped member extending in the Y-axis direction (that is, the depth direction in the drawing of FIG. 1), and has a substantially rectangular cross section perpendicular to the extending direction, as shown in the drawing. The ram head 801 is a rod-shaped member having a substantially uniform cross-sectional shape whose cross-sectional area perpendicular to the extending direction is substantially constant in the extending direction.

  Here, similarly to the ram head 801, the shim plate 120 also has a rod shape extending in the Y-axis direction and having a substantially rectangular cross section. In FIG. 1, the cross-sectional shape of the shim plate 120 is triangular for convenience of description of the fulcrum, the point of force, and the point of action. Therefore, the deformation in the cross section (that is, the cross section in the xz plane) of the material to be corrected 2 shown in FIG. Can be approximated to be substantially uniform in the Y-axis direction (that is, the shape is substantially the same no matter where the cross-section is viewed in the Y-axis direction). That is, in this predetermined region, the deformation of the material to be corrected 2 can be regarded as a two-dimensional deformation in an XZ plane perpendicular to the Y-axis direction. In the following description, the above-described predetermined area in which the deformation of the material to be corrected 2 can be regarded as a two-dimensional deformation will be referred to as a two-dimensional deformation area.

  The two-dimensionally deformed region is the ram head 801 in the extending direction (Y-axis direction) of the ram head 801 and the shim plate 120 among the portions (that is, the portions to be corrected) located between the shim plates 120 of the material to be corrected 2. And a region having a predetermined length shorter than the length of the shim plate 120. Generally, the length in the stretching direction is shorter in the ram head 801 than in the shim plate 120, so that the two-dimensional deformation region can be defined by the length of the ram head 801. As a result of the study by the present inventors, it has been found that the length of the two-dimensional deformation region in the extending direction of the ram head 801 can be regarded as about １ ／ of the length of the ram head 801.

  In the two-dimensional deformation region, the “shape” of the material to be corrected 2 to be corrected in press correction can be regarded as the shape of the cross section of the material to be corrected 2 in the XZ plane. In the following description, regarding the deformation of the material to be corrected 2 during press correction, the deformation in the two-dimensional deformation region will be discussed. In the following description, for a portion touching the shape of the material to be corrected 2 in the context of the object to be corrected, the shape is the cross-sectional shape of the material to be corrected 2 in the XZ plane unless otherwise specified. Shall mean.

In FIG. 1, in the case where the material to be corrected 2 having a convex shape (state A ₁ ) is pressed upward by a ram head 801 so that the plate surface is corrected to have a horizontal shape (state A ₃ ). The state of deformation of the material to be corrected 2 is shown. As shown in FIG. 1, when correcting the material to be corrected 2 so that the plate surface has a horizontal shape, the ram head 801 is pushed below the state where the plate surface is horizontal (state A ₂ ), Then it is necessary to unload. This is because elastic recovery (spring back) in deformation of the metal material is considered. As described above, in the press correction, the stroke amount (target stroke amount) of the ram head 801 for finally obtaining a desired shape is determined in consideration of the springback amount of the material 2 to be corrected. In the present specification, the stroke amount of the ram head 801 in press correction is defined as the downward movement of the ram head 801 from when the lower end of the ram head 801 comes into contact with the material to be corrected 2 until the load is unloaded (to the bottom dead center). Defined as quantity.

(1-2. Study on press straightening for extremely thick and high-strength materials)
Here, in the press straightening, there is a case where the straightened material 2 having a relatively large thickness and a relatively large yield strength, which is a so-called extra-thick high-strength material, is targeted. In this specification, an extremely thick high-strength material is defined as a plate having a thickness of 80 mm or more and a yield strength of 490 MPa (50 kgf / mm ² ) or more.

  Since such an extremely thick high-strength material is unlikely to be plastically deformed, in the press straightening, a relatively large number of presses are performed repeatedly by a relatively large press load, for example, which is close to the limit of the facility capacity. Therefore, the efficiency has been greatly reduced. In press correction of an extremely thick high-strength material, the press load is large, so that a press-in flaw caused by the press may be generated on the surface of the material 2 to be corrected. As described above, in press straightening of an extremely thick and high-strength material, it has been required to correct the shape to a desired shape with a smaller number of presses and to suppress the occurrence of indentation flaws on the surface.

  For example, in order to perform press straightening more efficiently, a ram head having a smaller contact area with the material to be straightened 2 as described in Patent Document 2 has been developed. According to the ram head, the contact area between the ram head and the material to be corrected 2 at the time of pressing can be further increased due to the smaller contact area with the material to be corrected 2. Thus, it is possible to perform press straightening more efficiently. However, when such a ram head having a smaller contact area with the material to be corrected 2 is used, the occurrence of indentation flaws becomes more remarkable due to stress concentration at the contact portion between the ram head and the material to be corrected 2. turn into. As described above, in the ram head described in Patent Literature 2, although there is a possibility that the efficiency can be improved, the occurrence of the indentation flaw cannot be suppressed.

  In view of the above circumstances, the present inventors, in particular, in press correction for extremely thick high-strength material, to correct the desired shape with a smaller number of presses, and to further suppress the occurrence of indentation flaws on the surface. And intensive studies on the technology to achieve both.

  The present inventors paid attention to the contact state between the ram head and the material to be corrected. Specifically, as described above, the conventional ram head 801 has a substantially rectangular shape in a cross section perpendicular to the extending direction. That is, the lower surface of the ram head 801, that is, the contact surface with the material to be corrected 2 has a planar shape having a predetermined area. On the other hand, as shown in FIG. 1, during pressing, the shape of the material to be corrected 2 is in a state of being convex upward, a state in which the plate surface is substantially horizontal, or a state of being convex downward. Can change. Therefore, the present inventors considered that the contact state between the ram head 801 and the material to be corrected 2 may change in the process of pushing the material to be corrected 2.

  FIGS. 2 and 3 are views for explaining a contact state between the ram head 801 and the material to be corrected 2 during press correction. Here, as in FIG. 1, as an example, a case is considered where the material to be corrected 2 having a convex shape is pressed upward and the shape is corrected so that the plate surface is horizontal.

  Here, as described above, in the press correction, in at least the two-dimensional deformation region, the deformation of the material to be corrected 2 in one section on the XZ plane may be considered. Accordingly, the deformation of the material to be corrected 2 during press straightening is performed by using the points supported by the two lower shim plates 120 on the lower surface in the cross section as fulcrums, and using the contact point with the ram head 801 on the upper surface in the cross section as the load application point. Can be approximated by beam bending.

  According to this concept, as shown in FIG. 2, immediately after the press is started, the ram head 801 comes into contact with the portion having a convex shape toward the material 2 to be corrected. It can be considered that the correction material 2 is in contact with one point. That is, in this case, it can be said that the bending state of the material to be corrected 2 is a state where the material is supported at two points and is bent under a load at one point (hereinafter, referred to as three-point bending).

  On the other hand, as shown in FIG. 3, when the material to be corrected 2 is deformed by the ram head 801 until the material to be corrected 2 has a downwardly convex shape in consideration of the spring back in consideration of the springback, the ram head The 801 and the material to be corrected 2 can be considered to be in contact at two points corresponding to both ends of the ram head 801 in the width direction (x-axis direction). That is, in this case, it can be said that the bending state of the material to be corrected 2 is a state where the material is supported at two points and is bent under a load at two points (hereinafter, referred to as four-point bending).

  As described above, during the press straightening, the present inventors change the bending state of the material to be corrected 2 from three-point bending according to the contact state between the ram head 801 and the material to be corrected 2 according to the progress of the press. It was thought that it had changed to four-point bending. Here, the conventional ram head 801 having a substantially uniform cross-sectional shape was examined. However, the ram head described in Patent Document 2 also has a small contact area with the material to be corrected 2, but the shape of the lower surface (contact surface) thereof The same can be said for is a planar shape.

  Furthermore, when the present inventors investigated in detail the indentation flaws actually generated on the surface of the material to be corrected 2 after pressing, the indentation flaws correspond to the portions corresponding to both ends in the width direction of the ram head 801, that is, 4. It was found that remarkable occurrence occurred at the contact portion between the ram head 801 and the material to be corrected 2 during point bending. In other words, when the material to be corrected 2 has a downwardly convex shape during the pressing and is bent at four points, the ram head 801 and the material to be corrected 2 are partially connected to the lower surface of the ram head 801 (at both ends in the width direction). Therefore, a large press load acts on the material to be corrected 2 in a very small area of the contact portion. For this reason, an extremely large contact pressure is applied to the material to be corrected 2, and it is considered that a pushing flaw may be generated at the contact portion. In the case of three-point bending, in the above description, the point of application of the load is described as one point for convenience, but in reality, a region having a certain area or more on the lower surface of the ram head 801 having a planar shape is formed. Since it is considered that it is in contact with the upper surface of the material to be corrected 2, it is considered that indentation flaws are not significantly generated at the contact portion.

  In order to confirm this hypothesis, the present inventors have created a calculation model simulating the ram head 801 and the material to be corrected 2 at the time of press correction, and have performed deformation and deformation of the material to be corrected 2 during pressing by elasto-plastic analysis. The contact pressure at the contact surface was analyzed. FIG. 4 shows the results. FIG. 4 is a diagram showing the results of elasto-plastic analysis of the ram head 801 and the material to be corrected 2 during pressing. FIG. 4 shows the result when the material to be corrected 2 has a downwardly convex shape during pressing and is bent at four points. In FIG. 4, the upper part schematically illustrates the deformation of the material to be corrected 2 as a result of the simulation, and the lower part illustrates a graph of the contact pressure between the ram head 801 and the material to be corrected 2 corresponding to the deformation. I have. In this graph, the horizontal axis indicates the position of the material to be corrected 2 shown in the upper row in the X-axis direction, and the vertical axis indicates the contact pressure, and the relationship between the two is plotted.

  As shown in FIG. 4, as a result of the elasto-plastic analysis, when four-point bending is performed, at the positions corresponding to the contact portions between the ram head 801 and the material to be corrected 2 at both ends in the width direction of the ram head 801, It was found that a very large contact pressure occurred. The results can be said to support the above hypothesis. In addition, as described above, four-point bending occurs during the pressing, and a very large contact pressure is generated at the contact portion. In addition to the fact that the lower surface of the ram head 801 has a planar shape, the flatness of the ram head during the pressing is reduced. This is probably because the ram head 801 is hardly elastically deformed.

  As described above, the present inventors have obtained the following knowledge by conducting detailed studies on press straightening using the conventional ram head 801. That is, during press straightening, the contact state between the ram head 801 and the straightened material 2 changes as the shape of the straightened material 2 is deformed. At this time, when the ram head 801 having a flat lower surface is used, only the portions corresponding to both widthwise ends of the lower surface of the ram head 801 are formed when the material to be corrected 2 has a downwardly convex shape. A four-point bending state is brought into contact with the material to be corrected 2. In the four-point bending state, since a large press load acts on the material to be corrected 2 at the contact portion having an extremely small area, it is considered that a pressing flaw may be significantly generated at the contact portion. In addition, it is considered that the press load acts on the material to be corrected 2 only in a partial area of the lower surface, so that it becomes difficult to efficiently deform the material to be corrected 2. It is also considered to be the cause of increasing the number of times.

  The present inventors have arrived at the present invention based on the results of the above studies. According to the present invention, by paying attention to the contact state between the ram head and the material to be corrected 2 during pressing, particularly in press correction for extremely thick high-strength materials, it is possible to correct the shape to a desired shape with a smaller number of presses, It is possible to achieve both suppression of indentation flaws on the surface. Hereinafter, preferred embodiments of the present invention conceived by the present inventors will be described in detail.

(2. Configuration of press straightening device)
A configuration of a press straightening device according to a preferred embodiment of the present invention will be described. FIG. 5 is a diagram illustrating a schematic configuration of the press straightening device according to the present embodiment.

  Referring to FIG. 5, the press straightening device 10 according to the present embodiment includes a bed 110 serving as a base for pressing, and two shim plates 120 placed on the bed 110 at a predetermined interval. , A pressing mechanism 130 disposed above the bed 110, and a control device 140 that integrally controls the driving of the press correction device 10.

  The shim plate 120 is formed of a material having sufficient hardness, such as steel, for example, and has a rod-like shape having a substantially rectangular cross section and extending in the y-axis direction (the depth direction in the drawing of FIG. 5). The distance between the two shim plates 120 can be adjusted as appropriate.

  The pressing mechanism 130 includes a cylinder 132 movable in the Z-axis direction (vertical direction), and a ram head 131 attached to a lower end of the cylinder 132. The cylinder 132 is configured to be movable in a vertical direction by a specified movement amount under the control of the control device 140 by, for example, hydraulic pressure. The ram head 131 is formed of a material having sufficient hardness, such as steel, for example, and has a rod-like shape extending in the Y-axis direction (the depth direction in the drawing of FIG. 3).

  In the present embodiment, the shape of the cross section perpendicular to the extending direction of the ram head 131 is substantially uniform in the extending direction, and the lower surface in the cross section has an arc shape. That is, the ram head 131 is formed such that its lower surface has a predetermined curvature κ. FIG. 6 shows only the ram head 131 extracted from the press straightening device 10 in FIG. FIG. 6 is a diagram illustrating a cross-sectional shape perpendicular to the extending direction of the ram head 131 according to the present embodiment. As illustrated, the lower surface of the ram head 131 in a cross section perpendicular to the extending direction has an arc shape with a radius of curvature R (curvature κ = 1 / R).

  By giving the curvature κ to the lower surface of the ram head 131, when the material to be corrected 2 has a downwardly convex shape during pressing, the arc-shaped lower surface of the ram head 131 and the upper surface of the material to be corrected 2 are: As compared with the case where the lower surface has a planar shape as in the above-described conventional ram head 801, the contact is made with a wider contact area. Therefore, since the press load acts on the material to be corrected 2 through the area having a larger area, it is possible to prevent stress concentration on a part of the area, and it is possible to reduce the occurrence of indentation flaws. become. Further, since the pressing load can be applied to the material to be corrected 2 more efficiently, the material to be corrected 2 can be corrected into a desired shape by a smaller number of presses.

  As described above, by using the ram head 131, it is possible to perform the press correction with a smaller number of presses and further suppressing the occurrence of the indentation flaw. Accordingly, it is possible to perform press straightening more efficiently, and it is not necessary to perform an additional process for indentation flaws, so that productivity can be improved. As described above, in the press correction of an extremely thick and high-strength material, a relatively large press load is required, and therefore, the occurrence of indentation flaws and the increase in the number of presses can be remarkable. Therefore, the ram head 131 according to the present embodiment can further exert its effects by being applied to press straightening of a particularly thick and high-strength material.

  As described above, one of the major features of the present embodiment is that the curvature κ is provided on the lower surface of the ram head 131. The shape of the ram head 131 will be described in more detail below (3. Shape of ram head).

  The description of the press straightening device 10 will be continued. Although not shown in FIG. 5, the press straightening device 10 is provided with an input device for the operator to perform various operation inputs and an output device for outputting guidance for the operation. For example, the input device is a touch panel, a switch, a lever, or the like, and the operator issues an instruction (movement of the press, stop of the press (that is, unloading), etc.) for movement of the cylinder 132 via the input device. Can be entered. The control device 140 moves the cylinder 132 based on the instruction. The output device is, for example, a display device such as a display device and a lamp, or a sound output device such as a speaker. For example, under the control of the control device 140, the output device can provide guidance related to press correction (for example, guidance that the installation of the material to be corrected 2 is completed and press can be started, and press end (that is, exclusion of the press). Guidance) to load) is output. Based on the guidance, the operator can input an instruction via the input device.

  When performing press straightening, the material to be straightened 2 is conveyed by a roller conveyor and installed so as to be bridged over two shim plates 120 on the bed 110. Normally, the material to be corrected 2 is transported such that the Y-axis direction (the depth direction in the drawing) is the plate width direction and the X-axis direction (the left-right direction in the drawing) is the longitudinal direction. At this time, the material to be corrected 2 is set so that the correction target portion of the material to be corrected 2 is located between the two shim plates 120 and directly below the ram head 131. The driving of the roller conveyor may also be controlled by the control device 140 in accordance with an instruction from the operator via the input device. In this state, when the cylinder 132 moves downward, the ram head 131 presses the material to be corrected 2 and the shape of the material to be corrected 2 is corrected.

  The control device 140 corrects the material to be corrected 2 by controlling the amount of movement of the cylinder 132 in the vertical direction, that is, the amount of stroke. For example, the operator inputs, via the input device, a target stroke amount for obtaining a desired shape after pressing in consideration of the springback amount, and the control device 140 causes the cylinder 132 to operate in accordance with the input target stroke amount. Is moved in the vertical direction, thereby performing press correction on the material to be corrected 2. In addition, the calculation of the target stroke amount includes, for example, a metal material of the same type as the material to be corrected 2 acquired in advance as described in JP-A-63-43722 and JP-A-2-192820. A method for obtaining the target stroke amount based on the relationship between the press load and the stroke amount in the deformation can be used. However, the present embodiment is not limited to such an example, and the target stroke amount may be calculated by various known methods.

  Here, control device 140 may be any device that can execute arithmetic processing, and its specific configuration may be arbitrary. For example, the control device 140 may be various processors such as a CPU (Central Processing Unit), or may be a control board or the like on which a processor and a storage element such as a memory are mounted. Control device 140 may be a general-purpose information processing device such as a personal computer (PC). Alternatively, the control device 140 may not be a single device, but may be configured by a plurality of devices, and the functions of the control device 140 may be realized by cooperation of the plurality of devices. The functions of the control device 140 described above are realized by the processor constituting the control device 140 executing arithmetic processing according to a predetermined program, and the press straightening method according to the present embodiment can be executed.

  The schematic configuration of the press straightening device 10 has been described above.

(3. Ram head shape)
The shape of the ram head 131 will be described in more detail. Here, a method of determining the curvature κ of the lower surface of the ram head 131 will be described.

  As described above, in the present embodiment, by imparting the curvature κ to the lower surface of the ram head 131, even when the material to be corrected 2 has a downwardly convex shape, the ram head 131 has a larger area. And the upper surface of the material to be corrected 2 comes into contact. At this time, if the curvature κ is too small, the lower surface of the ram head 131 has a shape close to a flat surface. Therefore, when the material to be corrected 2 has a downwardly convex shape during pressing, the ram head 131 is moved in the width direction. Only two points at both ends are in contact with the material to be corrected 2 (ie, a four-point bending state), and the occurrence of indentation flaws cannot be effectively suppressed. On the other hand, if the curvature κ is too large, the lower surface of the ram head 131 has a shape that protrudes greatly downward, so that when the material to be corrected 2 has a downwardly convex shape during pressing, Only one point at the center of the lower surface of the ram head 131 that is most protruding in the width direction comes into contact with the material to be corrected 2 (ie, a three-point bending state), and a large contact pressure is generated at the contact point. As a result, the occurrence of indentation flaws cannot be effectively suppressed.

  As described above, it is considered that the curvature κ to be provided to the lower surface of the ram head 131 has a predetermined range that can appropriately suppress the occurrence of the indentation flaw. In the present embodiment, the range of the curvature κ to be provided to the lower surface of the ram head 131 so that the occurrence of the indentation flaw can be suitably suppressed is defined, and the ram head is set so that the curvature κ of the lower surface is included in the range. 131 is formed.

  Hereinafter, a method of defining the range of the curvature κ will be described. First, the ideal curvature κ of the lower surface of the ram head 131, which can minimize the occurrence of indentation flaws, will be examined. Since the indentation flaw is generated by the concentration of the press load on a portion having a relatively small contact area, the lower surface of the ram head 131 and the material to be corrected when the material to be corrected 2 has a downwardly convex shape. If the area of the contact surface with the upper surface of 2 is large, it is possible to further suppress the occurrence of indentation flaws. That is, if the curvature κ that maximizes the contact area is given to the lower surface of the ram head 131, the occurrence of the push flaw can be suppressed most.

And if the contact area is maximized, if the lower surface curvature of the ram head 131 kappa matches the curvature kappa _Z of the upper surface of the to be straightened material 2 in the case where the correction material 2 becomes convex downward It is. Therefore, it can be said that the curvature kappa underside of the ideal ram head 131, the curvature kappa _Z of the upper surface of the to be straightened material 2.

In the present embodiment, the curvature κ _Z of the upper surface of the material to be corrected 2 when the material to be corrected 2 has a downwardly convex shape is determined by the following procedure. That is, first, the deformation amount of the material to be corrected 2 when the pressing load P is applied using a conventional ram head 801 having a flat lower surface as shown in FIG. The deformation of the straightening member 2 is obtained by approximating the deformation of the beam. At this time, the amount of deformation at two different points on the material to be corrected 2 is obtained, and the difference ΔZ between the amounts of deformation is obtained. Then, using a deformation amount of the difference ΔZ obtained from geometrical considerations, determine the radius of curvature R _Z of the upper surface of the straightening member 2 at the time of deformation. It can be determined curvature kappa _Z as the inverse of the curvature radius R _Z.

  With reference to FIGS. 7 to 9, a method of obtaining the curvature of the upper surface of the correction target material 2 when the correction target material 2 has a downwardly convex shape will be described in more detail. First, a procedure for obtaining the deformation amount of the material to be corrected 2 by approximating the deformation of the beam will be described. FIG. 7 is a diagram illustrating a shape of a beam before deformation. FIG. 8 is a diagram illustrating a shape of the beam illustrated in FIG. 7 after deformation. FIG. 8 shows only the upper surface of the beam shown in FIG.

As shown in FIG. 7, the deformation of the material to be corrected 2 during pressing by the ram head 801 having a flat lower surface causes a load P at two different points on the beam 201 supported by two different fulcrums 203. Can be approximated to the deformation of the beam 201 when. Here, the fulcrum 203 corresponds to a contact point between the shim plate 120 and the material to be corrected 2 shown in FIG. That is, the distance l between the fulcrum 203 corresponds to the distance _{L s} between the shim plate 120. The points of action of the load P correspond to both ends of the ram head 801 in the width direction. That is, the spacing between the working point corresponds to the width L _d of the ram head 801.

Now, for simplicity, it is assumed that the load P acts on a position symmetrical with respect to the center of the beam 201 in the extending direction. In this case, if the distance from one supporting point 203 to the point of application of load P of the pivot 203 side _{by L,} can be expressed as L d = l-2L.

  Consider the deformation of the beam 201 in the situation described above. In this situation, the deformation of the beam 201 is symmetrical in the range of 0 <x <l / 2 and the range of l / 2 <x <l, so only one of the ranges needs to be considered (x is , With one end of the beam 201 as a reference (zero) in the extending direction of the beam 201). Here, the deformation of the beam 201 in the range of 0 <x <l / 2 will be considered.

  From the deflection equation of the beam, the amount of deformation y of the beam 201 in the vertically downward direction based on the horizontal state of the beam 201 is obtained as in the following equations (1) and (2). Here, E is the Young's modulus of the beam 201 (that is, the material to be corrected 2), and I is the second moment of area of the beam 201 (that is, the material to be corrected 2).

Here, as shown in FIG. 8, the maximum deformation amount of the beam 201 is defined as y _max , and the deformation amount at the point of _{application of} the load P is defined as y _L. Since the maximum deformation amount y _max is the deformation amount y at the point of x = 1/2, and the deformation amount y _L is the deformation amount y at the point of x = L, from the above equations (1) and (2), The deformation amounts y _max and y _L can be obtained as in the following equations (3) and (4), respectively.

When the difference between the deformation amount y _max and the deformation amount y _L is defined as ΔZ, the deformation amount difference ΔZ can be obtained from Expressions (3) and (4) as in Expression (5) below.

Here, in the above formula (5), E is a constant determined by the material of the material to be corrected 2, so that the (1 / 8E) portion can be summarized as a constant term. 7, the thickness of the beam 201 shown in FIG. 7 (that is, the thickness of the material 2 to be corrected) is represented by t, and the length of the beam 201 in the depth direction of the paper surface (that is, the paper surface of the material 2 to be corrected). the depth direction length. Usually the corresponding) to the length of the plate width direction of the straightening member 2 if w, can be calculated as ^{I = w × t 3/12} . Here, as described above with reference to FIG. 1, the material to be corrected 2 can be regarded as being uniformly deformed in the extending direction of the ram head 801 and the shim plate 120 in the two-dimensional deformation region. Since the deformation of the beam 201 in FIGS. 7 and 8 means that the material 2 to be corrected in the two-dimensional deformation region is considered, the length w is the length of the material 2 to be corrected in the plate width direction. It can be said that it represents the length of the portion corresponding to the two-dimensional deformation area. As described above, the length of the material to be corrected 2 in the plate width direction in the two-dimensional deformation region (that is, the length of the two-dimensional deformation region in the extending direction of the ram head 801 and the shim plate 120) is equal to the length of the ram head 801. If the length of the ram head 801 does not change, the length w can be considered to be constant. Therefore, the length w can also be summarized as a constant term. Further, in the above equation (5), the deformation amount difference ΔZ is derived on the assumption that the beam 201 is elastically deformed. However, since the material to be corrected 2 is elasto-plastically deformed during pressing, it is more strict. In order to obtain the deformation amount difference ΔZ, it is preferable to introduce a correction coefficient relating to plastic deformation.

  From the above examination, in the present embodiment, the deformation amount difference ΔZ is calculated according to the following equation (6) obtained by improving the above equation (5). By using the following equation (6), it is possible to more accurately determine ΔZ in consideration of plastic deformation.

  Here, α is a correction coefficient related to a constant term, and specifically, α = 1 / (8E) × 1 / (w / 12). Β is a correction coefficient corresponding to the plastic deformation of the material 2 to be corrected, and is a value that can take a range of 0 <β ≦ 1. The case of β = 1 corresponds to elastic deformation.

Of the physical quantities included in the above equation (6), as the press load P, a set value set as a press condition can be used. As for the correction coefficient α, the Young's modulus E of the material to be corrected 2 is known from literature values and the like, and the length w of the two-dimensional region in the plate width direction can be determined according to the length of the ram head 801. can do. The correction coefficient β can be obtained, for example, by performing an experiment, a simulation, or the like on a metal material of the same type as the material to be corrected 2 before pressing. The length L can be determined according to the positional relationship between the shim plate 120 and the ram head 801 in the press straightening device 10. Width _{L d} of the ram head 801 can be determined according to the shape of the ram head 801. Thus, the load P, the correction coefficient alpha, beta, length L, a width L _d, for which may be a known value before press straightening, using these values, in accordance with the above equation (5), of ΔZ The value can be determined.

With this deformation amount difference [Delta] Z, it is possible to determine the radius of curvature R _Z of the upper surface of the beam 201 shown in FIG. A method of obtaining the radius of curvature _RZ will be described with reference to FIG. Figure 9 is a diagram for explaining a method of determining the curvature radius R _Z of the upper surface of the beam 201 based on the deformation amount of the difference ΔZ of the beam 201 shown in FIG.

As shown in FIG. 9, consider a part of the arc of a radius R _Z. The arc corresponds to the upper surface of the beam 201 shown in FIG. 8, the radius R _Z is a radius of curvature R _Z of the upper surface of the beam 201 to be determined.

Ends E _1, E ₂ of the arc, if corresponding to the working point of the load P, the length of the perpendicular line beat from the arc midpoint C in chord connecting the two ends E _1, E ₂ are, above This corresponds to the calculated deformation amount difference ΔZ. The length of the chord connecting the two ends _E 1, _{E 2} of the arc corresponds to the width _{L d} of the ram head 801.

Further, if the circumferential angle of the arc is 2θ, the length of a perpendicular line extending from the center O of the arc to a chord connecting both ends E ₁ and E ₂ of the arc can be expressed as R _Z cos θ. The half length of the string can be expressed as R _Z sin θ. Therefore, using these lengths, the relationships shown in the following mathematical expressions (7) and (8) can be obtained geometrically.

The equation (7), simultaneous equations (8), by solving for the radius _{R Z,} the radius _{R Z,} that is, to determine the radius of curvature _{R Z} of the upper surface of the beam 201. Specifically, the radius of curvature _RZ is obtained as in the following equation (9). Further, the curvature κ _Z of the upper surface of the beam 201 can be obtained as the reciprocal of the radius of curvature R _Z as in the following Expression (10).

Therefore, by substituting the value of the deformation amount difference ΔZ obtained from the above equation (6) into the above equations (9) and (10), the curvature radius R _Z and the curvature κ _Z of the upper surface of the beam 201 can be obtained. it can. If the ram head 131 is formed such that the lower surface has the curvature κ _Z obtained in this way, it is possible to realize an ideal ram head 131 that can minimize the occurrence of indentation flaws.

However, even if the lower surface of the ram head 131 is formed so as to have the curvature κ _Z calculated from the above equation (10), there is a case where the curvature κ _Z cannot be realized accurately due to processing variations and the like. Further, the curvature κ _Z obtained from the above equation (10) is an ideal curvature, so to speak, if the ram head 131 is formed such that the lower surface has a curvature within a predetermined range including the curvature κ _Z in practice. There is a possibility that the indentation flaw can be sufficiently suppressed.

Therefore, in the present embodiment, a predetermined range is set for the curvature κ _Z obtained from the above equation (10), and the ram head 131 is formed such that the lower surface includes the curvature κ. Specifically, the shape of the lower surface of the ram head 131 is formed so that the curvature κ of the lower surface of the ram head 131 satisfies the following mathematical expression (11).

Here, the coefficients A ₁ and A ₂ are coefficients defining the lower and upper limits of the curvature κ, respectively (hereinafter, referred to as curvature coefficients). Curvature factor A ₁ which defines the lower limit of the curvature κ is a state in which the straightening member 2 in the press if it becomes convex toward the bottom, ram head 131 is in contact only at two points in the width direction at both ends ( That is, it is appropriately determined as a value that does not result in a four-point bending state). The curvature factor A ₂ which defines the upper limit of the curvature κ, when the straightening member 2 becomes convex downward in the press, the ram head 131 is in contact only with one point in the width direction center It is determined as a value that does not result in a state (ie, a state of three-point bending).

Appropriate values of the curvature coefficients A ₁ and A ₂ affect the pressing conditions (for example, the interval between the shim plates 120, the shape of the material to be corrected 2, the material of the material to be corrected 2, and the press load). Various conditions). Therefore, as the curvature coefficients A ₁ and A ₂ , appropriate values corresponding to supposed pressing conditions may be appropriately obtained by experiments, simulations, and the like. In addition, as a result of examination by the present inventors, at least in press straightening for extremely thick high-strength materials, indentation is performed under various pressing conditions by, for example, setting a curvature coefficient A ₁ = 0.2 and A ₂ = 2.0. It has been found that the curvature κ that can suppress the generation of flaws can be defined. Details of specific examples of the curvature coefficients A ₁ and A ₂ will be described in Examples below.

In order to confirm the effects of the present invention and to confirm appropriate ranges of the curvature coefficients A ₁ and A ₂ that define the lower and upper limits of the curvature κ of the lower surface of the ram head shown in the above equation (11), the following experiment was performed. went. In the experiment, a ram head having various curvatures κ on its lower surface was prepared, and the ram head was applied to an actual press straightening device having the same configuration as the press straightening device 10 shown in FIG. Press straightening was performed. As the material to be corrected, an extremely thick high-strength material was used, and press correction was performed so that the plate surface of the material to be corrected was corrected substantially horizontally. The pressing conditions are as follows.

(Press conditions)
Plate thickness t of the material to be corrected: 170 (mm)
Plate width of the material to be corrected (length in the stretching direction of the ram head and the shim plate): 2100 (mm)
Length w in the plate width direction of the material to be corrected in the two-dimensional deformation region: 100 (mm)
Yield strength of the material to be corrected: 784 (MPa) ( 80 (kgf / mm ² ) )
Young's modulus E of the material to be corrected: 2.1 × 10 ⁵ (N / mm ² )
The width of the ram head _L d: 150 (mm)
Interval L _s between shim plates: 450 (mm)
Distance L from one shim plate to one end closer to the one shim plate among both ends in the width direction of the ram head: 150 (mm)
Press load: 3000 (ton)

In the press straightening under these conditions, when the deformation amount difference ΔZ was calculated using the above equation (6), ΔZ = about 1.0 (mm). At this time, for simplicity, the material to be corrected is elastically deformed, and the correction coefficient β = 1. Further, using the value of the deformation amount difference ΔZ, the radius of curvature R _Z and the curvature κ _Z were obtained in accordance with the above equations (9) and (11). R _Z = about 2925 (mm) and κ _Z = about .0. 0003 (1 / mm).

In this experiment, the curvature of the lower surface of the ram head kappa and κ = A × κ _Z, while variously changing the curvature coefficients A, created a ram head having a plurality of different curvatures kappa. Then, press correction was actually performed using these ram heads under the above-described press conditions, and the presence or absence of indentation flaws on the surface of the material to be corrected after the press was visually confirmed.

  The results are shown in Table 1 below. In Table 1, for each curvature coefficient A, the number of presses required to correct the shape to a desired shape, and the presence or absence of indentation flaws are collectively shown.

  As shown in Table 1 above, when the curvature coefficient A was 0.15 or less, indentation flaws were confirmed on the surface of the material to be corrected after press correction at the portions corresponding to both ends in the width direction of the ram head. Was. This is because the curvature κ of the lower surface of the ram head is too small, so that when the material to be corrected has a downwardly convex shape during pressing, only the both ends in the width direction of the lower surface of the ram head are the same as the material to be corrected. It is considered that this is because the contact state (that is, the state of four-point bending) occurred, and a large contact pressure was generated at the contact portion.

  On the other hand, when the curvature coefficient A was 2.25 or more, indentation flaws were confirmed at the portion corresponding to the center in the width direction of the ram head on the surface of the material to be corrected after press correction. This is because the curvature κ of the lower surface of the ram head is too large, so that when the material to be corrected has a downwardly convex shape during pressing, only the center in the width direction of the lower surface of the ram head is the same as the material to be corrected. It is considered that this is because a contact state (that is, a three-point bending state) was caused, and a large contact pressure was generated at the contact portion.

  Also, from Table 1, when the curvature coefficient A is small, the number of presses required to deform the material to be corrected into a desired shape increased, whereas the number of presses increased as the curvature coefficient A increased. When the curvature coefficient A became smaller than a predetermined value, the number of presses became substantially constant. This is because, when the material to be corrected is deformed by the four-point bending because the curvature coefficient A is small, the area where the press load acts on the material to be corrected is extremely small. It indicates that it is not done well.

From the results shown in Table 1, in order to suppress the occurrence of indentation flaws while reducing the number of presses, for example, it is considered preferable to set the curvature coefficient A to a value between 0.2 and 2.00. . In other words, by giving a curvature κ satisfying 0.2 × κ _Z ≦ κ ≦ 2.0 × κ _Z to the lower surface of the ram head and performing press correction using the ram head, while reducing the number of presses, It is possible to suppress the occurrence of indentation flaws.

  Furthermore, the present inventors conducted similar experiments under various pressing conditions other than the above conditions (including a very thick high strength material and a material to be corrected other than the very thick high strength material). As a result, under some pressing conditions, similar results were obtained in a preferable range of the curvature coefficient A. Among them, in the press straightening of the extremely thick high-strength material, a similar result was obtained in the preferable range of the curvature coefficient A under any of the trial press conditions. From the results, at least in press straightening of extremely thick high-strength material, by suitably setting the curvature coefficient A to a value between 0.2 and 2.0, the number of presses can be reduced, and the occurrence of indentation flaws can be reduced. It is considered possible to suppress it.

(4. Supplement)
As described above, the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention pertains can conceive various changes or modifications within the scope of the technical idea described in the claims. It is understood that these also belong to the technical scope of the present invention.

Reference Signs List 10 press straightening device 110 bed 120 shim plate 130 pressing mechanism 131, 801 ram head 132 cylinder 140 control device 201 beam 203 fulcrum

Claims (3)

In the press straightening of the material to be corrected, which is a metal plate, a portion to be corrected between the two shim plates of the material to be corrected is pressed in a state where the material to be corrected is placed so as to bridge between two shim plates. A ram head,
A surface facing the material to be corrected and contacting the material to be corrected at the time of pressing has a curvature κ that satisfies the following equation (101):
Ram head.

L _d : width of the ram head α, β: correction coefficient P: press load L: length from one of the two shim plates to one end closer to the one shim plate among both ends in the width direction of the ram head t: The thickness of the material to be corrected. The thickness t of the material to be straightened is 80 mm or more, and the yield strength of the material to be straightened is 490 MPa (50 kgf / mm ² ) or more.
The ram head according to claim 1. A press straightening method for correcting the shape of the material to be corrected using the ram head according to claim 1,
The thickness t of the material to be straightened is 80 mm or more, and the yield strength of the material to be straightened is 490 MPa (50 kgf / mm ² ) or more.
Press straightening method.

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