Manufacturing method of steel plate member

Abstract

To provide a manufacturing method of a steel plate member which enables reduction of a thickness of a steel plate itself while securing a fitting length by fitting.SOLUTION: A manufacturing method of a steel plate member according to one embodiment of the disclosure includes: a step in which induction heating is performed to a peripheral edge part of a through hole formed at a steel plate by punching to eliminate strain; a step in which a thickness of the peripheral edge part from which the strain is eliminated is increased by forging; and a step in which a bush is press-fitted into the through hole having the peripheral edge part with the increased thickness.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a steel plate member. [Background technology]

[0002] As disclosed in Patent Document 1, the inventors developed a method of removing strain from the peripheral portion of a through hole formed in a steel plate by punching by induction heating, and then burring the peripheral portion. Burring is also called stretch flanging. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-116635 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have developed a steel plate member in which a bushing is press-fitted into a through hole formed in the steel plate by punching. Before punching the through hole, the peripheral edge of the through hole is thickened by forging to ensure the fitting length required for the press-fitting. However, there is a limit to the thickness that can be increased by forging before punching, and in order to ensure the fitting length, it was necessary to increase the thickness of the steel plate itself.

[0005] The present disclosure has been made in consideration of the above circumstances, and provides a method for manufacturing a steel plate member that allows the steel plate itself to be thinned while ensuring a fitting length due to press fitting. [Means for solving the problem]

[0006] A method for manufacturing a steel plate member according to one embodiment of the present disclosure includes: a step of induction heating a peripheral portion of a through hole formed in the steel plate by punching to remove distortion; a step of increasing the thickness of the peripheral portion from which strain has been removed by forging; and press-fitting a bushing into the through hole having the thickened peripheral edge portion.

[0007] A method for manufacturing a steel plate member according to one aspect of the present invention includes the steps of induction heating a peripheral portion of a through hole formed in a steel plate by punching to remove strain, and forging the peripheral portion from which strain has been removed. In other words, since the peripheral portion of the through hole from which strain has been removed is thickened by forging, the amount of thickness increase can be greater than the thickness increase by forging before punching. Therefore, the steel plate itself can be thinned while ensuring the fitting length by press fitting.

[0008] The step of removing the strain from the peripheral edge portion and the step of increasing the thickness of the peripheral edge portion from which the strain has been removed may be repeated. With this configuration, the amount of increase in thickness of the peripheral edge portion of the through hole can be increased, and the steel plate itself can be made thinner while ensuring the fitting length by press-fitting.

[0009] When induction heating the peripheral edge portion, an induction heating coil may be inserted into the through hole, thereby making it possible to heat the peripheral edge portion of the through hole with a simple configuration. [Effects of the Invention]

[0010] The present disclosure makes it possible to provide a manufacturing method for a steel plate member that can thin the steel plate itself while ensuring the fitting length due to press fitting. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a partial cross-sectional view showing a steel plate member according to a first embodiment. [Figure 2] 3 is a flowchart showing a method for manufacturing a steel plate member according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing step ST1 in FIG. [Figure 4] FIG. 3 is a cross-sectional view showing step ST2 in FIG. [Figure 5]FIG. 3 is a cross-sectional view showing step ST3 in FIG. 2. [Figure 6] FIG. 5 is a cross-sectional view showing a modified example of the forging machine shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, specific embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments. In addition, the following description and drawings have been simplified appropriately for clarity of explanation.

[0013] (First embodiment) <Structure of steel plate components> First, the configuration of a steel plate member according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a partial cross-sectional view of the steel plate member according to the first embodiment. The steel plate member shown in Fig. 1 is not particularly limited, but is, for example, a steel plate member for an automobile, and more specifically, a steel plate member for a suspension.

[0014] Naturally, the right-handed XYZ Cartesian coordinate system shown in Figure 1 and other drawings is for the convenience of explaining the positional relationships of the components. Normally, in Figure 1 and other drawings, the positive direction of the Z axis is vertically upward, and the XY plane is the horizontal plane, which is common among the drawings.

[0015] The steel plate member shown in FIG. 1 includes a steel plate 10 and a bushing BS. A through hole 11 is formed at the end of a steel plate 10 shown in Fig. 1. As shown in Fig. 1, an annular thickened portion 12 is formed on the upper surface of the steel plate 10 around the periphery of the through hole 11 so as to protrude upward. As shown in Fig. 1, a cylindrical bushing BS is press-fitted into the through hole 11. The thickened portion 12 ensures the fitting length of the bushing BS when pressed in.

[0016] The through hole 11 is formed, for example, by punching a steel plate 10. As will be described in detail later, the thickened portion 12 is formed by induction heating the peripheral portion of the through hole 11 to remove distortion, and then forging the peripheral portion. For example, the peripheral portion of the through hole 11 is induction heated by inserting a cylindrical induction heating coil into the through hole 11. The peripheral portion of the through hole 11 may be repeatedly subjected to induction heating and thickened by forging.

[0017] Although not particularly limited, the steel plate 10 is, for example, a high-strength steel plate having a thickness of about 0.5 to 10 mm and a tensile strength of 780 MPa or more. The heating conditions for the steel plate 10 are, for example, a heating temperature of about 500 to 830°C and a heating time of 10 seconds or less. However, the heating time may exceed 10 seconds.

[0018] As described above, in the steel plate member according to this embodiment, the thickened portion 12 is formed by forging around the peripheral portion of the through hole 11 from which strain has been removed. Therefore, the amount of thickening can be made larger than that of a steel plate member thickened by forging before punching. In other words, the steel plate itself can be made thinner while ensuring the fitting length by press fitting.

[0019] <Method of manufacturing steel plate members> Next, a method for manufacturing a steel plate member according to a first embodiment will be described with reference to Fig. 2 to Fig. 5. Fig. 2 is a flowchart showing the method for manufacturing a steel plate member according to the first embodiment. Fig. 3 is a cross-sectional view showing step ST1 in Fig. 2. Fig. 4 is a cross-sectional view showing step ST2 in Fig. 2. Fig. 5 is a cross-sectional view showing step ST3 in Fig. 2.

[0020] First, as shown in Figures 2 and 3, the peripheral portion of a through hole 11 formed in a steel plate 10 is induction heated to remove distortion (step ST1). For example, as shown in Figure 3, a cylindrical induction heating coil IHC is inserted into the through hole 11, and the peripheral portion of the through hole 11 is induction heated to remove distortion. With the simple configuration shown in Figure 3, the peripheral portion of the through hole 11 can be effectively heated.

[0021] 2 and 4, the peripheral portion of the through hole 11 in the steel plate 10 from which strain has been removed is thickened by forging (step ST2). Here, the forging machine shown in Fig. 4 includes an upper die UD, a lower die LD, and a punch PN.

[0022] As shown in Fig. 4, the upper mold UD and the lower mold LD have a through hole for inserting the punch PN. The steel sheet 10 is clamped between the upper mold UD and the lower mold LD so that the central axis of the through hole 11 in the steel sheet 10 coincides with the central axis of the punch PN. Here, an annular groove AG for forming a thickened portion 12 is provided around the periphery of the through hole in the lower surface of the upper mold UD.

[0023] The peripheral portion of the upper surface of the punch PN shown in FIG. 4 is tapered. That is, the tip of the punch PN gradually becomes thinner. Therefore, when the punch PN rises, the tip of the punch PN is inserted into the through hole 11 of the steel sheet 10 to expand the diameter of the through hole 11, and the peripheral portion of the through hole 11 of the steel sheet 10 can be pressed into the annular groove AG of the upper die UD. With this configuration, when the punch PN rises, the diameter of the through hole 11 of the steel sheet 10 is expanded, and an increased-wall portion 12 is formed around the peripheral portion of the through hole 11. Note that steps ST1 and ST2 may be repeated. Also, in one execution of step ST2, the punch PN may be raised, that is, the forging operation of the steel plate 10 may be performed multiple times.

[0024] 2 and 5, the bushing BS is press-fitted into the thickened through hole 11 in the steel plate 10 (step ST3). As shown in Fig. 5, the thickened portion 12 formed on the periphery of the through hole 11 in step ST2 ensures the fitting length when the bushing BS is press-fitted.

[0025] <Modified forging machine> Next, a modified example of the forging machine used in step ST2 will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view showing a modified example of the forging machine shown in Fig. 4. The forging machine shown in Fig. 6 has a configuration obtained by turning the forging machine shown in Fig. 4 upside down. Like the forging machine shown in Fig. 4, the forging machine shown in Fig. 6 also includes an upper die UD, a lower die LD, and a punch PN. In the forging machine shown in Fig. 4, the punch PN rises from the lower die LD toward the upper die UD, whereas in the forging machine shown in Fig. 6, the punch PN descends from the upper die UD toward the lower die LD.

[0026] As shown in Fig. 6, the upper die UD and the lower die LD have a through hole for inserting a punch PN. The steel sheet 10 is clamped between the upper die UD and the lower die LD so that the central axis of the through hole 11 in the steel sheet 10 coincides with the central axis of the punch PN. In the forging machine shown in Fig. 6, an annular groove AG for forming a thickened portion 12 is provided not on the periphery of the through hole in the lower surface of the upper die UD but on the periphery of the through hole in the upper surface of the lower die LD.

[0027] The peripheral portion of the lower surface of the punch PN shown in Figure 6 is tapered. That is, the tip of the punch PN gradually becomes thinner. Therefore, when the punch PN descends, the tip of the punch PN is inserted into the through hole 11 of the steel sheet 10 to expand the diameter of the through hole 11, and the peripheral portion of the through hole 11 of the steel sheet 10 can be pressed into the annular groove AG of the lower die LD. With this configuration, when the punch PN descends, the diameter of the through hole 11 of the steel sheet 10 is expanded, and an increased-wall portion 12 is formed on the peripheral portion of the through hole 11.

[0028] As described above, the manufacturing method of a steel plate member according to this embodiment includes a step of induction heating the peripheral portion of the through hole 11 formed in the steel plate 10 by punching to remove strain, and a step of forging to thicken the peripheral portion of the through hole 11 from which strain has been removed. That is, because the peripheral portion of the through hole 11 from which strain has been removed is thickened by forging, the amount of thickening can be greater than the thickening by forging before punching. Therefore, the steel plate itself can be thinned while ensuring the fitting length by press fitting.

[0029] The present disclosure is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the present disclosure. [Explanation of symbols]

[0030] 10 steel plate 11 Through hole 12 Thickening section AG Annular Groove BS Bush IHC induction heating coil LD lower mold PN Punch UD upper mold

Claims

1. a step of induction heating a peripheral portion of a through hole formed in the steel plate by punching to remove distortion; a step of increasing the thickness of the peripheral portion from which strain has been removed by forging; and press-fitting a bushing into the through hole having the thickened peripheral edge portion. Manufacturing method of steel plate components.

2. Repeating a step of removing the distortion of the peripheral edge portion and a step of thickening the peripheral edge portion from which the distortion has been removed. The method for manufacturing a steel plate member according to claim 1 .

3. When induction heating the peripheral portion, an induction heating coil is inserted into the through hole. The method for manufacturing a steel plate member according to claim 1 or 2.

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