Forming and processing methods

Abstract

To heat only the punched-out edges locally. [Solution] The forming process includes a punching step of punching out a steel sheet, and a heating step of heating the end face by passing an electric current through the heating coil, which is positioned perpendicular to the thickness direction of the steel sheet and not in contact with the end face of the punched edge, thereby generating an induced electromotive force in the steel sheet. The heating coil is constructed by winding a coil wire in a spiral shape at least once.

Description

Technical Field

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[0001] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Molding method That is the case. On this flight, The distance between the heating coil and the steel plate may be smaller than the diameter of the coil wire. On this flight, The diameter of the coil wire of the heating coil may be greater than the thickness of the steel plate. On this flight, In the punching process, a hole is formed in the steel plate by punching it out. The starting position of the heating coil and the ending position of the heating coil may lie on a line passing through the center of the hole and be on the same side with respect to the center. On this flight, In the punching process, a hole is formed in the steel plate by punching it out. The outer diameter of the heating coil may be larger than the diameter of the hole in the steel plate. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a molding method that allows localized heating of only the punched-out edges. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram illustrating the steps of the molding process according to this embodiment. [Figure 2] This figure shows a schematic configuration of the induction heating device according to this embodiment. [Figure 3] These are side and top views showing the configuration of the heating coil. [Figure 4] This figure shows the analysis results when CAE analysis was performed. [Figure 5] This figure shows an example of a heating jig. [Figure 6] This figure shows the state in which the heating process according to this embodiment is performed during the idling process. [Modes for carrying out the invention]

[0009] Embodiment 1 Hereinafter, the present invention will be described through this embodiment, but the invention according to the claims is not limited to the following embodiments. Also, not all of the configurations described in this embodiment are necessarily essential as means for solving the problems.

[0010] FIG. 1 is a schematic diagram schematically showing the steps of the molding method according to this embodiment. The molding method described below, for example, provides a substantially circular hole 101 in a steel plate 100 as a workpiece, and deforms the periphery of the hole 101 to form an extended flange 102.

[0011] The molding method according to this embodiment, for example, as shown in FIG. 1, includes a punching step of punching the steel plate 100, a heating step of heating the punched end 103, a cooling step of cooling the heat generated in the heating step, and an extended flange step of forming an extended flange 102 on the punched end 103.

[0012] The punching step is a step of punching the steel plate 100 fixed to a punching die (not shown) with a punching punch 200. The heating step, which will be described in detail later, is a step of heating the punched end 103 formed in the punching step.

[0013] In the heating step, the punched steel plate 100 is placed in a heating jig described later. Then, high-frequency induction heating is performed on the punched end 103 of the steel plate 100. After the heating, the steel plate 100 is removed from the heating jig.

[0014] As shown in FIG. 1, the cooling step is a step of cooling the heat of the punched end 103 heated in the heating step. Specifically, the steel plate 100 is left in a normal temperature environment for a certain period of time. The extended flange step (burring step) is a molding step of inserting a flange die 300 into the hole 101 and plastically deforming the peripheral portion of the hole 101 to form an extended flange 102.

[0015] The residual strain generated at the peripheral edge of the hole 101 by the punching process is removed in the heating process. After air cooling, it is introduced into the flanging process, so that the damage to the flanging die 300 can be reduced compared to performing the process on the steel plate 100 in the heated state. In particular, in the present embodiment, as will be described later, the punching end 103 can be locally heated, so that the residual strain can be removed well and the heating efficiency is also good.

[0016] Subsequently, the induction heating method in the heating process according to the present embodiment will be described in detail with reference to FIGS. 2 and 3. FIG. 2 is a diagram showing a schematic configuration of an induction heating apparatus according to the present embodiment. FIG. 3 is a side view and a top view showing the configuration of a heating coil.

[0017] As shown in FIG. 3(a), the heating coil 1 is in a non-contact state with the end face 104 of the punching end 103 by the punching process. Further, the heating coil 1 is arranged such that a horizontal plane P including the heating coil 1 is substantially perpendicular to the plate thickness direction X of the steel plate 100. In other words, the heating coil 1 is arranged such that a horizontal plane P including the heating coil 1 is substantially parallel to the steel plate 100.

[0018] For example, as shown in FIG. 2(b), a current is passed through the heating coil 1 from an AC power supply 4 or the like to generate an induced electromotive force in the steel plate 100, thereby heating the end face 104 of the punching end 103. The AC power supply 4 outputs a current of approximately 450 A at a high frequency of approximately 220 kHz, for example.

[0019] As shown in FIG. 3(b), the heating coil 1 is formed by winding the coil wire 11 in a spiral shape at least one turn or more so that the diameter of the heating coil 1 expands. The heating coil 1 is formed by winding the coil wire 11, for example, four turns, but is not limited thereto, and the number of turns of the coil wire 11 may be arbitrary. By increasing the number of turns of the coil wire 11 of the heating coil 1, a larger induced electromotive force can be generated in the steel plate 100, and the end face 104 of the punching end 103 can be heated more strongly.

[0020] As shown in Figure 3(a), it is preferable that the diameter d of the coil wire 11 of the heating coil 1 is greater than the thickness t of the steel plate 100 (d>t). For example, if the thickness t of the steel plate 100 is 2.9 mm, the diameter d of the coil wire 11 is about 5 mm. This allows more current to flow through the heating coil 1, generating a larger induced electromotive force in the steel plate 100.

[0021] The punched-out end 103 of the steel plate 100 is formed in the shape of a circular hole, for example, as shown in Figure 2. When the punched-out end 103 has a roughly circular hole shape, the induced current flowing through the end face 104 connects and forms a loop, allowing for more efficient heating.

[0022] As shown in Figure 3(b), it is preferable that the starting position S of the heating coil 1 and the ending position E of the heating coil 1 lie on the line L passing through the center O of the hole 101, and are on the same side with respect to the center O. This ensures that the number of turns is equal in any cross-section when the heating coil 1 is cut vertically, making it easier to obtain a stable magnetic field.

[0023] The outer diameter D of the heating coil 1 is preferably larger than the diameter of the hole 101 in the steel plate 100, as shown in Figure 3(b). For example, if the diameter of the hole 101 in the steel plate 100 is 50 mm, the outer diameter D of the heating coil 1 is approximately 62.5 mm. As a result, the end face 104 of the punched end 103 of the steel plate 100 is located directly below the coil wire 11 of the heating coil 1, generating a large induced electromotive force in the steel plate 100 and allowing the end face 104 of the punched end 103 to be heated more strongly. It is also preferable that the outer diameter D of the heating coil 1 is larger than the diameter of the hole 101 in the steel plate 100 and smaller than (diameter of hole 101 + diameter of coil wire 11 d × 3).

[0024] As shown in Figure 3(a), the distance s between the lower surface of the heating coil 1 and the steel plate 100 is preferably smaller than the diameter d of the coil wire 11. Furthermore, it is even more preferable that the distance s between the lower surface of the heating coil 1 and the steel plate 100 be smaller than the diameter d of the coil wire 11 of the heating coil 1, and as small as possible without causing sparks. For example, if the diameter d of the coil wire 11 of the heating coil 1 is 5 mm, the distance s between the heating coil 1 and the steel plate 100 is approximately 2.9 mm.

[0025] By bringing the heating coil 1 closer to the end face 104 of the punched edge 103 of the steel plate 100, within the range where sparks do not occur, a larger induced electromotive force can be generated in the steel plate 100, and the end face 104 of the punched edge 103 can be heated more strongly.

[0026] The heating coil 1 may be covered with an insulator. In this case, the heating coil 1 covered with the insulator and the steel plate 100 may be in slight contact.

[0027] The heating temperature of the heating coil 1 is adjusted, for example, so that the end face 104 of the punched end 103 is between 200°C and below the Ac1 point. Heating within this temperature range allows for proper removal of residual strain. In particular, if the temperature is heated above the Ac1 point, the steel sheet 100 will undergo austenite transformation, which will soften and reduce strength when cooled by air, and increase hardness when rapidly cooled by flowing water, reducing formability in the stretch flange process. Therefore, it is preferable to keep the temperature below the Ac1 point.

[0028] In this embodiment, the heating coil 1 is positioned on the front (upper) side of the steel plate 100, but is not limited to this. It may also be positioned on the back (lower) side of the steel plate 100, or on both the front and back sides of the steel plate 100.

[0029] Next, we will explain the analysis results obtained when heating was performed using the induction heating method described above and then CAE (computer-aided engineering) analysis was conducted.

[0030] The CAE analysis conditions were as follows: the outer diameter of the heating coil 1 was 62.5 mm, the diameter of the coil wire 11 was 5 mm, the distance d between the heating coil 1 and the steel plate 100 was 1 mm, and the thickness of the steel plate 100 was 2.9 mm.

[0031] Steel plate 100 is a 980MP class steel plate with dimensions of 150mm x 150mm. A hole 101 with a diameter of 50mm is punched out approximately in the center of steel plate 100. The current value of AC power supply 4 is set to 450A and the frequency to 220kHz. The CAE analysis type is a coupled analysis of frequency response analysis and thermal analysis, and the mesh is a hexahedron (6-sided) mesh.

[0032] Figure 4 shows the analysis results when CAE analysis was performed under the conditions described above. Figure 4(a) shows the temperature distribution of the steel plate 100 after 1 second of heating. Figure 4(b) shows the relationship between the temperature of the end face 104 of the punched edge 103 of the steel plate 100 and the heating time.

[0033] As shown in Figure 4(a), it can be seen that the induction heating method according to this embodiment allows for particularly concentrated heating of only the vicinity of the end face 104 of the punched edge 103 of the steel plate 100. Furthermore, as shown in Figure 4(b), it can be seen that the induction heating method according to this embodiment allows for heating of the vicinity of the end face 104 of the punched edge 103 of the steel plate 100 to the target temperature in a short time (approximately 2 to 3 seconds).

[0034] Next, an example of a molded product produced by the molding method according to this embodiment will be described. A molded product produced by the molding method according to this embodiment is a molded product that includes stretch flange molding parts, such as hole-expanding molding parts that widen holes, and flange molding parts that create flanges with curvature, and includes molding parts in which the line length of the end face is significantly increased before and after processing.

[0035] A specific molded product is a front-engine, rear-wheel-drive (FR) lower arm used in the suspension of a vehicle. The bush press-fit portion, hole widening portion such as the work hole, and flange portion such as the crotch portion of the FR lower arm may be formed by the molding process according to this embodiment.

[0036] In the forming method described above, the example of creating a hole 101 in the steel plate 100 was explained, but the punching process for punching out the steel plate 100 is not limited to creating a hole 101; it may also be used to cut off the unnecessary portion. In the stretch flange process, the flange die 300 is pressed against the punched end 103 from which the unnecessary portion has been cut off to form the stretch flange. The flange forming portions of the A-pillar lower and B-pillar outer lower are formed in this manner, as shown below.

[0037] As an example of the molded product described above, an A-pillar lower used in the window pillar of a vehicle is conceivable. The flange-formed portions of the A-pillar lower, such as the corners, may be formed by the molding process according to this embodiment. As another example of the molded product described above, an B-pillar outer lower of a vehicle is conceivable. The flange-formed portions of the B-pillar outer lower, such as the corners, may be formed by the molding process according to this embodiment.

[0038] Embodiment 2 In this second embodiment, the steel sheet molded product punched out in the punching process is placed in a heating jig in the heating process and heated. Figure 5 shows an example of a heating jig.

[0039] As shown in Figure 5, the heating jig 400 includes a heating coil 1 for heating the punched end 103 of the steel sheet molded product X, a positioning guide 2 for positioning the steel sheet molded product X in a predetermined position, and a base portion 3. Each heating coil 1 is connected to an AC power supply 4 that supplies power to each heating coil 1. A control panel 5 that controls the AC power supply 4 is connected to the AC power supply 4.

[0040] The coil wire 11 of the heating coil 1 may be configured as a pipe with coolant flowing through it. In this case, the chiller device 6 may cool the heating coil 1 by supplying coolant to the coil wire 11 of the heating coil 1.

[0041] The shape and arrangement of the positioning guide 2 are set so that the position of the steel sheet molded product X is automatically set simply by placing the steel sheet molded product X on the positioning guide 2. The transport robot 7 may be configured to grasp the steel sheet molded product X and place it on the positioning guide. The heating coil 1 and the positioning guide 2 are arranged on the base portion 3 in accordance with the shape of the steel sheet molded product X and the position of the heating portion.

[0042] The position, number, and shape of the heating coil 1 are not limited to the example shown in Figure 5 and can be set arbitrarily. Similarly, the position, number, and shape of the positioning guide 2 are not limited to the example shown in Figure 5 and can be set arbitrarily.

[0043] By using the heating jig 400 according to this embodiment, it is not necessary to heat the steel plate molded product X from above or below while holding it, as in the conventional method, and the steel plate molded product X can be easily placed on the heating jig 400 and heated.

[0044] The heating step according to this embodiment may be performed in an idling step between the punching step and the forming step, as shown in Figure 6. The idling step is a step in which the transport pitch is adjusted when transporting the steel sheet formed product X from the punching step to the forming step, and is a waiting step in which no processing is performed.

[0045] This allows for efficient heating of the punched steel sheet product X by utilizing the idling process, which was previously used to hold the punched steel sheet product X after the punching process and before the forming process. Therefore, productivity is improved as there is no need to introduce an additional heating process.

[0046] Furthermore, for example, within the press machine, processes such as forming, punching, and idling are carried out continuously at a predetermined conveying pitch while the steel sheet formed product X is continuously transported. Therefore, by simply placing the heating jig 400 at the position corresponding to the idling process, the idling process within the press machine can be easily replaced with a heating process.

[0047] The heating process may be carried out during any process other than the idling process in the press machine, such as the molding process or the punching process, provided that the heating jig 400 can be positioned.

[0048] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0049] 1 Heating coil, 2 Positioning guide, 3 Base unit, 4 AC power supply, 5 Control panel, 6 Chiller device, 7 Transfer robot, 11 Coil wire, 100 Steel plate, 101 Hole, 102 Stretch flange, 103 Punched end, 104 End face, 200 Punch, 300 Flange mold, 400 Heating jig

Claims

1. The punching process for cutting out steel plates, A heating step is performed in which a heating coil is positioned in a non-contact manner with respect to the end face of the punched-out end produced by the punching process, and perpendicular to the thickness direction of the steel plate, and an electric current is passed through the heating coil to generate an induced electromotive force in the steel plate, thereby heating the end face; A molding process that includes, The heating coil is constructed by winding a coil wire in a spiral shape at least once. Molding processing method.

2. A molding process according to claim 1, The distance between the heating coil and the steel plate is smaller than the diameter of the coil wire. Molding processing method.

3. A molding process according to claim 1, The diameter of the coil wire of the heating coil is greater than the thickness of the steel plate. Molding processing method.

4. A molding process according to claim 1, In the punching process, a hole is formed in the steel plate by punching it out. The starting position of the heating coil and the ending position of the heating coil lie on a line passing through the center of the hole and are on the same side with respect to the center. Molding processing method.

5. A molding process according to claim 1, In the punching process, a hole is formed in the steel plate by punching it out. The outer diameter of the heating coil is larger than the diameter of the hole in the steel plate. Molding processing method.

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