Metal plate bonding method

Abstract

This invention provides a method for joining metal plates that enables high-strength and high-precision bonding even between dissimilar materials. [Solution] The present invention relates to a metal plate joining method in which two metal plates having through holes are stacked, a plug having a cross-sectional shape substantially equal to the cross-sectional shape of the through hole is inserted into the through hole, and the area around the plug is simultaneously pressurized with a pressurizing device to plastically deform each metal plate material in the direction of the side of the plug and apply tightening stress to the plug, thereby joining the two metal plates. The method is characterized in that, except for the parts adjacent to the top and bottom surfaces of the plug, a plurality of grooves perpendicular to the axial direction of the plug are formed on the side surface of the plug, the inner diameter of the tip of the pressurizing device is formed to be a certain extent larger than the outer diameter of the plug, and the two metal plates are joined by inserting the pressurizing device into the metal plates to a certain depth.

Description

TECHNICAL FIELD

[0001] The present invention relates to a metal plate joining method capable of firmly joining even dissimilar materials.

BACKGROUND ART

[0002] Metal plates are used in many fields, and many types of joining methods therefor are known. Typical joining methods include bolts and nuts, mechanical clinching, rivets, and the like, which are disclosed in, for example, Patent Document 1. In the case of bolts and nuts, there is a problem that two types of joining materials are required and the joining takes time. On the other hand, mechanical clinching and riveting are methods in which a hard punch or rivet is pressed into a soft material to form an anchor, but it is difficult to secure a large anchor amount, and a gap may be generated between the soft material and the rivet, or the strength is low due to the weak clamping force between the soft material and the rivet.

[0003] Patent Document 2 discloses a joining structure and a joining device for metal members using plastic flow joining. This technique describes a method and apparatus for joining a first metal member having an annular portion to a second metal member having a shaft portion using a restraining ring. Although high-strength and high-precision metal joining can be performed by utilizing plastic flow joining, this technique cannot be directly applied to the joining of metal plate-shaped members.

[0004] The applicant has also previously filed a patent application (Japanese Patent Application No. 2023-171170) for a method of joining metal plates, characterized by forming through holes in the same location on multiple stacked metal plates, inserting a plug having a cross-sectional shape substantially equal to the cross-sectional shape of the through hole and having a higher hardness than any of the metal plates into the through hole, and applying pressure around the plug on the surface of at least two of the outermost metal plates to plastically deform each metal plate toward the surface of the plug, thereby applying tightening stress to the plug and joining the multiple metal plates through the plug. In this technique, since the area immediately surrounding the plug is pressed by a punch, there was a problem that if the punch was inserted to a depth greater than the position of the groove formed in the plug, the plastically flowed metal plate material in the groove would be cut from the metal plate body, reducing the bonding strength. Furthermore, in this method, the punch pressure does not reach deep parts of the metal plate and plastic flow cannot be expected, so the groove of the plug had to be formed close to the surface of the metal plate. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-130238 [Patent Document 2] Republished Patent Publication No. 2011 / 118219 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In view of the above-mentioned problems, the present invention aims to provide a method for joining metal plates that can bond dissimilar materials with high strength and precision. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides a metal plate joining method comprising: stacking two metal plates having through holes aligned in the position of the through holes; inserting a plug having a cross-sectional shape substantially equal to the cross-sectional shape of the through hole and having a higher hardness than either of the metal plates into the through hole; and simultaneously applying pressure around the plug on the outer surface of both metal plates with a pressurizing device to plastically deform each metal plate material in the lateral direction of the plug, thereby applying tightening stress to the plug and joining the two metal plates, Except for the portions adjacent to the top and bottom surfaces of the plug, the side surface of the plug has multiple grooves formed perpendicular to the axial direction of the plug. The inner diameter of the tip of the pressurizing device is formed to be a certain extent larger than the outer diameter of the plug, and by inserting the pressurizing device into the metal plate to a certain depth, It is characterized by joining two metal plates together.

[0008] It is desirable that the length of the portion adjacent to the upper and lower surfaces of the plug be less than or equal to the width of the groove. Furthermore, when the depth of the groove is D, the distance between the side surface of the plug and the inner circumference of the tip of the pressurizing device is C, and the width of the tip of the pressurizing device is W, 1.5D ≤ W ≤ 5D and 1.5D ≤ C ≤ 5D It is preferable to satisfy the following conditions.

[0009] Furthermore, when the width of the groove is P, the number of grooves is n, the depth to which the tip of the pressurizing device penetrates the metal plate is S, and the thickness of the metal plate is t, 3 ≤ n ≤ t / P and P ≤ S ≤ t / 2 It is also desirable to satisfy this condition.

[0010] It is preferable that the cross-sectional shape of the through-hole is circular, and that the cross-sectional shape of the plug is also circular. [Effects of the Invention]

[0011] The metal plate joining method according to the present invention involves applying pressure to the surface of the metal plate with the tip of a punch, causing the metal plate material to flow into grooves provided in a plug made of a hard material. This allows for a strong bond by utilizing the resistance of the material to shear deformation. A further feature of the present invention is that multiple grooves perpendicular to the axial direction are formed on the entire side surface of the plug, except for portions adjacent to the upper and lower surfaces. By creating a gap between the inner circumference of the punch and the outer circumference of the plug, the metal plate material can be plastically flowed throughout the plug grooves without cutting the material when the punch is deeply inserted into the metal plate, enabling high-strength joining of the metal plates. Furthermore, because the plastic flow at the joint is deformation under compressive stress, there is a low possibility of defects such as cracks occurring in the plate material. Therefore, it is possible to use work-hardened materials or tempered materials with poor ductility as the soft material. It should be noted that, as is common with mechanical joining methods, joining is possible even if the laminate materials are dissimilar, such as a combination of aluminum and steel plates. [Brief explanation of the drawing]

[0012] [Figure 1] This is a partial cross-sectional view showing a method for joining metal plates together according to one embodiment of the metal plate joining method according to the present invention. [Figure 2] This is a cross-sectional view showing the state of two metal plates joined together using the metal plate joining method shown in Figure 1. [Figure 3] This is an explanatory diagram showing the difference in the plastic flow range depending on the punch penetration depth in the metal plate bonding method according to the present invention. [Figure 4] This is an explanatory diagram showing the relationship between the plug, metal plate, and punch in the metal plate joining method according to the present invention. [Figure 5] This is the result of an analysis of the correlation between parameters in the plug, metal plate, and punch. [Figure 6] This is the result of an analysis of the correlation between parameters in the plug, metal plate, and punch. [Modes for carrying out the invention]

[0013] Preferred embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows a cross-sectional view of a metal plate joining method according to an embodiment of the present invention. A first metal plate 1 is laminated on a second metal plate 2, and plugs 10 are fitted into through holes 101 and 102 that penetrate each metal plate. The side surface of the plug 10 consists of a flat portion 11 and a grooved portion 12, and the grooved portion 12 is formed on the entire side surface except for the flat portions 11A and 11B located near the upper surface 13 and the lower surface 14. The length of the plug 10 is set to be approximately equal to the total thickness of the first metal plate 1 and the second metal plate 2. An upper punch 20 is positioned above the first metal plate 1 as a pressurizing device. A cavity 22 is provided in the center of the upper punch 20, having an inner circumference larger than the outer circumference of the plug 10. An upper punch tip 21, which is narrower than the punch body, is provided on the lower surface of the upper punch 20. A lower punch 30 is positioned below the second metal plate 2. The lower punch 30 is also provided with a cavity 32 and a lower punch tip 31, similar to the upper punch 20. In this state, the upper punch 20 and the lower punch 30 simultaneously pressurize the surfaces of the respective metal plates, causing the respective punch tips to enter the respective metal plates. This action causes the metal plate material around each punch tip to plastically flow and move into the groove 12 of the plug 10, thereby bonding the plug 10 to the respective metal plates. As a result, the first metal plate 1 and the second metal plate 2 are bonded together via the plug 10.

[0014] A cross-sectional view of the metal plate joined by the joining method shown in Fig. 1 is shown in Fig. 2. In Fig. 2, the punch mark 3 is a trace after the tip portion 21 of the upper punch has penetrated into the first metal plate 1. Similarly, the punch mark 4 is a trace of the tip portion 31 of the lower punch penetrating into the second metal plate 2. In order to cause plastic flow of the metal plate material into all of the grooves 12 formed in the plug 10, the punch is caused to penetrate deeper than in the earlier patent application (Japanese Patent Application No. 2023-171170) filed by the applicant. Further, a certain distance (gap) is provided between the plug 10 and the punch marks 3 and 4. This is because the inner periphery of each punch is configured to be larger than the outer periphery of the plug. As a result, the metal plate material enters all of the grooves 12 on the side surface of the plug 10 by plastic flow, and the respective metal plates and the plug 10 are firmly joined. In this example, a cylindrical tempered steel (HRC30) with a diameter of 10 mm is used as the plug 10, an aluminum material with a plate thickness of 2 mm is used as the first metal plate 1, and a steel plate (SC) with a plate thickness of 1.6 mm is used as the second metal plate 2. Further, the groove width is 0.3 mm, and the punch penetration depth is 0.95 mm. In the present example, the horizontal cross sections of the plug and the through hole are circular, but the cross-sectional shape can be changed without departing from the spirit of the present invention.

[0015] Fig. 3 is a schematic diagram showing the plastic flow range of the metal plate due to the difference in punch penetration depth. Fig. 3(a) shows the case where the punch penetration depth is shallow. Plastic flow mainly occurs from an inclination direction of about 30° to 45° or more from the center of the punch tip to the side surface. Therefore, the metal plate material enters the groove 12 close to the punch mark 3 by plastic flow, but in the vicinity of the central portion of the metal plate away from the punch mark 3, the angle becomes small and plastic flow does not occur. As a result, the number of grooves where plastic flow occurs decreases, and sufficient strength may not be obtained. On the other hand, in Fig. 3(b), since the punch penetration depth is large, plastic flow occurs even in the vicinity of the central portion in the thickness direction of the metal plate, and the metal plate material enters the grooves 12 of the plug 10.

[0016] Figure 4 shows the dimensional relationships among the plug, metal plate, and punch. When the width of the punch tip portion 21 is defined as W, the distance (gap) between the punch tip portion 21 and the outer peripheral portion of the plug 10 is defined as C, the punch penetration depth is defined as S, the length of the side flat portion near the upper surface of the plug 10 is defined as L, the width of the groove portion 12 on the plug 10 is defined as P, and the groove depth of the groove portion 12 is defined as D, the correlation between these parameters was analyzed.

[0017] The analysis results obtained by the finite element method under the conditions of plate thickness t=2.0 mm, plug groove width P=0.3 mm, groove depth D=0.15 mm, number of grooves=2, punch width W=0, 0.25, 0.5, 1.0 mm, punch penetration depth S=0.4 mm, and gap C between the plug and the punch=0, 0.25, 0.5 mm are shown in Figure 5. As a result, when W=1.0, the entire plate was deformed. It can be said that the punch width is too large relative to the plate thickness. When C=0, the flow of the plate material into the groove portion was favorable. This is considered to be because a flat portion without a groove is provided above the groove portion, and the punch only penetrates exactly to the lower part of the flat portion. When C=0.25, plastic flow occurred in the forward direction at 30 degrees when W=0.25, and plastic flow occurred in the forward direction at 45 degrees when W=0.5. When C reached 0.5, plastic flow occurred mainly in the lateral direction.

[0018] Next, Figure 6 shows the analysis results obtained by setting the number of inner grooves among the above conditions to a large number and setting the punch penetration depth S=0.8 mm. When C=0, the punch cut the plate material that had flowed into the groove portion. This is because the punch penetrated to the position of the groove portion. When W=1.0, the entire plate was still deformed. When C=0.25, plastic flow occurred forward at 60 degrees or more for both W=0.25 and W=0.5, and three or more grooves were substantially filled with the plate material. When C=0.5, plastic flow occurred forward at 30 degrees when W=0.25, and the flow into the third groove was somewhat insufficient. When W=0.5, plastic flow occurred in the forward direction at 45 degrees, and the third groove was also filled with the plate material by about 50%.

[0019] Based on the above analysis results, it is desirable that the relationship between the length L of the flat side portion and the width P of the groove portion 12 be L ≤ P. This is because when the punch tip enters the metal sheet, the pressure increases downwards and diagonally downwards from the tip, so even if the groove portion 12 is provided near the upper surface of the plug 10, the plastic flow effect is small.

[0020] It is desirable that the width W of the punch tip 21 be 1.5D ≤ W ≤ 5D. If the width W of the punch tip 21 is too narrow, the pressure on the punch tip 21 will be applied only downwards, reducing the movement of the metal sheet material in the direction of the groove 12 of the plug 10. Conversely, if the width W of the punch tip 21 is too wide, the pressure will not be properly transmitted to the metal sheet material below the punch tip 21, and plastic flow will not occur.

[0021] The distance (gap) C between the punch tip 21 and the outer circumference of the plug 10 is preferably 1.5D ≤ C ≤ 5D. If the gap is too narrow, the metal plate material between the punch tip 21 and the outer circumference of the plug 10 will be cut from the metal plate body, reducing the bonding strength. Conversely, if the gap is too wide, the movement of the metal plate material due to plastic flow will not reach the groove.

[0022] For the number of grooves n on the plug, it is preferable that 3 ≤ n ≤ t / P, where t is the thickness of the metal plate. Furthermore, for the punch penetration depth S, it is preferable that P ≤ S ≤ t / 2, where P is the width P of the groove 12.

[0023] The metal plate joining method according to the present invention, as shown in the above embodiment, is characterized by the fact that by applying pressure to the surface of a soft material with the tip of the punch, the material of the metal plate flows into the plug groove provided in the hard material plug, and a strong bond is formed by utilizing the resistance force of the shear deformation of the material. In addition, the soft plate material is pressed with high pressure against the smooth part of the plug, and the tightening pressure (residual stress) is maintained even after the pressure applied by the punch is released, and this frictional resistance force of tightening is utilized. Furthermore, because the spatial volume of the plug groove through which the plate material flows is small, the punch stroke is usually small, about 1 mm or less, and there is no relative movement between the plate material and the plug, resulting in high precision of the joined product. Moreover, because the plastic flow of the joint is deformation under compressive stress, there is a low possibility of defects such as cracks occurring in the plate material. For this reason, it is also possible to use work-hardened materials or tempered materials with poor ductility as the soft material. It should be noted that, as is common with mechanical joining methods, joining is possible even if the materials of the laminate are dissimilar materials.

[0024] For plug materials, when the metal plates to be joined are aluminum plates, rolled steel plates, or soft steel plates such as SS400, tempered steel (HRC30 to 40) is preferable. Furthermore, when using high-tensile steel plates with a tensile strength of 780 MPa or higher, it is preferable to use hardened and tempered steel as the plug. Additionally, if the hardness is higher than that of the metal plate, non-metallic materials such as ceramics can also be used as plugs.

[0025] In Figure 1 of the above embodiment, the upper and lower punches are shown to join the boards simultaneously, but if the strengths of the board materials differ, they can be joined one at a time. Also, when joining the soft board side, there will be no problems with joining by taking measures such as adding a stopper to the punch. [Explanation of Symbols]

[0026] 1. First metal plate 2. Second metal plate 3 punch marks 4 punch marks 10 plugs 11A Flat part 11B Flat part 12 grooves 13 Upper surface 14 Lower surface 20 Upper punch 21 Upper punch tip 22 Cavity 23 gaps 30 Lower punch 31 Lower punch tip 32 Cavity 33 gaps 101 First metal plate through hole 102 Second metal plate through hole

Claims

1. In a metal plate joining method, two metal plates having through holes are stacked with the positions of the through holes aligned, a plug having a cross-sectional shape substantially equal to the cross-sectional shape of the through hole and having a higher hardness than either of the metal plates is inserted into the through hole, and the area around the plug on the outer surface of both metal plates is simultaneously pressed with a pressurizing device to plastically deform the respective metal plate materials in the lateral direction of the plug, thereby applying tightening stress to the plug, the two metal plates are joined together. Except for the portions adjacent to the top and bottom surfaces of the plug, the side surface of the plug has multiple grooves formed perpendicular to the axial direction of the plug. The inner diameter of the tip of the pressurizing device is formed to be a certain extent larger than the outer diameter of the plug, and by inserting the pressurizing device into the metal plate to a certain depth, A method for joining metal plates, characterized by joining two metal plates together.

2. The metal plate joining method according to claim 1, characterized in that the length of the portion adjacent to the upper and lower surfaces of the plug is less than or equal to the width of the groove.

3. When the depth of the groove is D, the distance between the side surface of the plug and the inner circumference of the tip of the pressurizing device is C, and the width of the tip of the pressurizing device is W, 1.5D ≤ W ≤ 5D and 1.5D ≤ C ≤ 5D A method for joining metal plates according to either claim 1 or 2, characterized in that it satisfies the following conditions.

4. When the width of the groove is P, the number of grooves is n, the penetration depth of the tip of the pressurizing device into the metal plate is S, and the thickness of the metal plate is t, 3 ≤ n ≤ t / P and P ≤ S ≤ t / 2 A method for joining metal plates according to any one of claims 1 to 3, characterized in that it satisfies the following conditions.

5. The metal plate joining method according to any one of claims 1 to 4, characterized in that the cross-sectional shape of the through hole is circular and the cross-sectional shape of the plug is also circular.

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