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 through holes are provided in both a first metal plate 1 and a second metal plate 2, the first metal plate is laminated on the second metal plate, and a plug having a flange portion larger than the diameter on one side is inserted into the through hole to join the metal plates, characterized in that a pressurizing device is used in which the inner diameter of the tip portion is formed to be a certain extent larger than the outer diameter of the plug to pressurize the outer surface of the second metal plate so that the tip portion penetrates into the second metal plate to a certain depth, the second metal plate material is plastically deformed in the lateral direction of the plug to apply tightening stress to the plug, thereby joining the second metal plate and the plug, and joining the first metal plate and the second metal plate.

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 also known. Representative joining methods include bolts and nuts, mechanical clinching, rivets and the like. For example, it is disclosed in Patent Document 1. In the case of bolts and nuts, there is a problem that two types of joining members are required and the joining takes time. On the other hand, mechanical clinching or riveting is a method in which a hard punch or rivet is pressed into a soft material, and an anchor is formed by deformation of the soft material itself or the rivet, but the anchor amount is small, and gaps may occur between the soft material and the rivet, or the strength is low because the clamping force between the soft material and the rivet is weak.

[0003] Patent Document 2 discloses a joining structure and a joining device for metal members using plastic flow joining. This technology describes a method and device 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 technology cannot be directly applied to the joining of metal plate-shaped members.

[0004] Patent Document 3 discloses a technique for joining metal plates using rivets having a frustum-shaped head and shank. In this technique, a hole is formed through two metal plates by directly driving in the rivet without forming a through hole in the members to be joined beforehand, and then a groove is formed by coining the structural member around the end of the rivet shaft. Multiple shank grooves are formed on the rivet shaft, and it is described that the structural member enters these shank grooves due to plastic deformation during the coining of the structural member. In this technique, the head of the rivet enters the structural member after joining, but because the lower side of the head is frustum-shaped, the stress acts in a direction that expands the structural member and is not sufficiently transmitted to the structural member, so it is impossible for the structural member to tighten the rivet shaft with strong force or to undergo plastic flow. Plastic flow occurs in the lower structural member due to the coining and it joins with the rivet shaft. Therefore, the upper structural member is connected to the lower structural member, which is joined by rivets, only by compressive stress from the rivet tips, resulting in a weak connection.

[0005] Patent Document 4 discloses a punch rivet consisting of a head portion and a shaft portion connected longitudinally to the head portion. The shaft portion has a punching edge at the end away from the head portion, and the head portion, which is the end away from the shaft portion, has a larger diameter than the shaft portion. In this rivet, the head portion is divided into multiple sub-portions separated longitudinally. In this technology as well, two metal plates are joined by directly driving the rivet into the members to be joined without forming through holes in the members beforehand. Figure 1 of this publication shows that the material of the lower (die side) component flows into an annular recess during the riveting process, which is considered to be plastic flow. However, even in this technology, because the lower part of the head portion is divided into multiple sub-portions separated longitudinally, the stress of the head portion is not sufficiently transmitted to the structural member, making it impossible to induce plastic flow. Therefore, similar to Patent Document 3, the upper structural member is connected to the lower structural member, which is connected by rivets, only by compressive stress from the rivet tips, resulting in a weak bonding force.

[0006] The applicant has also previously provided through holes of substantially the same diameter in both the first and second metal plates, and laminated the first metal plate on the second metal plate so that the through holes overlap. A plug having a main body with a diameter approximately equal to the diameter of the through hole and a flange on one side that is larger than the diameter of the through hole is inserted into the through hole. The upper surface of the first metal plate, including the plug, is pressurized by a pressure plate or the like to cause the flange portion to penetrate into the first metal plate. Furthermore, at the end of the plug facing the flange, the punch tip is inserted into the second metal plate surrounding the plug, A method for joining metal plates was filed (Japanese Patent Application No. 2024-209370), characterized by joining the first and second metal plates through the plug by causing each metal plate material to undergo plastic flow toward the surface of the plug body and applying tightening stress to the plug. In this technology, since the area immediately surrounding the plug is pressurized by a punch, if the punch is inserted to a depth greater than the position of the groove formed in the plug, the plastically flowed metal plate material in the groove will be cut from the metal plate body, resulting in a decrease in 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 in the plug had to be formed close to the surface of the metal plate. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2013-130238 [Patent Document 2] Republished Patent Publication No. 2011 / 118219 [Patent Document 3] U.S. Patent Publication No. 6527490 [Patent Document 4] European Patent Publication EP2671654A2 [Overview of the project] [Problems that the invention aims to solve]

[0008] 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]

[0009] In order to solve the above-mentioned problems, the present invention provides a metal plate joining method in which through holes of substantially the same diameter are provided in both a first metal plate and a second metal plate, the first metal plate is laminated on the second metal plate so that the through holes overlap, and a plug having a main body portion with an outer shape substantially equal to the outer shape of the through hole and a flange portion on one side that is larger than the diameter is inserted into the through hole to join the metal plates together. Using a pressurizing device in which the inner diameter of the tip is formed to be a certain extent larger than the outer diameter of the plug, the outer surface of the second metal plate is pressed to cause the tip to penetrate into the second metal plate to a certain depth, and the second metal plate material is plastically deformed in the lateral direction of the plug, thereby applying tightening stress to the plug and joining the second metal plate and the plug. The result is characterized by joining the first metal plate and the second metal plate.

[0010] In this coupling method, the flange portion of the plug is pressed with a pressing plate or the like to cause the flange portion to enter the first metal plate. It is also preferable to bond the first metal plate and the plug by causing the first metal plate material to undergo plastic flow toward the surface of the plug body, thereby applying a tightening stress to the plug.

[0011] It is preferable that at least a portion of the main surface of the plug has a plurality of grooves perpendicular to the axial direction of the plug, and it is also preferable that a flat portion without grooves is provided on the lower surface side of the plug body facing the flange. It is preferable that the length of the flat portion is less than or equal to the groove width of the grooves.

[0012] 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.

[0013] 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.

[0014] 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]

[0015] The metal plate joining method according to the present invention requires less stress for joining compared to the conventional method of directly driving rivets into the metal plates to be joined without pre-drilling holes in them. Furthermore, by using a pressing plate to insert the flange portion of the plug into the upper metal plate, the material inside the metal plate can be plastically flowed toward the plug body, thereby joining the plug and the metal plate. Additionally, at the end of the plug facing the flange portion, a pressing device (punch) can be inserted into the lower metal plate surrounding the plug, causing the metal plate material to plastically flow toward the surface of the plug body, thereby applying tightening stress to the plug and joining the lower metal plate and the plug. As a result, the two metal plates are joined through the plug. A further feature of the present invention is that, except for the parts close to the upper and lower surfaces of the plug, multiple grooves perpendicular to the axial direction are formed on the entire side surface, and a gap is provided between the inner circumference of the punch and the outer circumference of the plug. This allows the metal plate material to plastically flow throughout the plug grooves without cutting the material when the punch is inserted deeply into the metal plate, making it possible to join the metal plates with high strength. 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. For this reason, it is possible to use work-hardened materials or tempered materials with poor ductility as soft materials. It should be noted that, as is common with mechanical bonding methods, bonding is possible even if the laminate materials are dissimilar materials, such as a combination of aluminum plate and steel plate. [Brief explanation of the drawing]

[0016] [Figure 1] It is a cross-sectional view showing the step of joining metal plates to each other according to the first embodiment of the metal plate joining method according to the present invention. [Figure 2] It is a cross-sectional view showing the state of two metal plates joined by the metal plate joining method shown in Figure 1. [Figure 3] It is an explanatory view showing the difference in the plastic flow range depending on the penetration depth of the punch in the metal plate joining method according to the present invention. [Figure 4] It is an explanatory view showing the relationship among the plug, the metal plate and the punch in the metal plate joining method according to the present invention. [Figure 5] This is the analysis result of the correlation between the parameters of the plug, the metal plate and the punch. [Figure 6] This is the analysis result of the correlation between the parameters of the plug, the metal plate and the punch. [Figure 7] It is a partial cross-sectional view of a metal plate joined according to the second embodiment of the present invention. [Mode for Carrying Out the Invention]

[0017] Hereinafter, preferred embodiments of the present invention will be described based on the drawings. Figure 1 shows an explanatory diagram of the process in the first embodiment of the metal plate joining method according to the present invention. This joining method will be described below. A first metal plate 1 and a second metal plate 2 having through holes are stacked, and a plug 10 is inserted through the through holes 101 and 102. The plug 10 has a lower flat portion 11B near the lower surface 14 facing the flange portion 15, and a groove portion 12 is formed on the surface of the main body 10. The total length of the plug is configured to be approximately equal to the combined thickness of the first metal plate 1 and the second metal plate 2. In this state, a pressing plate 50 is lowered from above to press the flange portion 15 of the plug 10 so that the upper surface 13 of the plug 10 is flush with the surface of the first metal plate 1. This state is shown in Figure 1. Although not described in detail in Figure 1, at this time, the material of the first metal plate 1 enters a part of the groove portion 12 below the flange portion 15 by plastic flow. This connects the first metal plate 1 to the plug 10. Meanwhile, a lower punch 30 is positioned below the second metal plate 2 as a pressurizing device. A cavity 32 is provided in the center of the lower punch 30, having an inner circumference larger than the outer circumference of the plug 10. A lower punch tip 31, narrower than the punch body, is provided on the upper surface of the lower punch 30. The lower punch 30 is raised, causing the tip 31 to enter the second metal plate 2. This action causes the metal plate material around the lower punch tip 31 to plastically flow and move into the groove 12 of the plug 10, thereby connecting the plug 10 and the second metal plate 2. As a result, the first metal plate 1 and the second metal plate 2 are connected via the plug 10.

[0018] Figure 2 shows a cross-sectional view of the metal plates joined using the joining method shown in Figure 1. As described above, by lowering the pressing plate 50 and inserting the flange portion 15 of the plug 10 into the first metal plate 1, the material of the first metal plate 1 enters a part of the groove portion 12 below the flange portion 15 by plastic flow. In Figure 2, the punch mark 4 is the trace left after the lower punch tip portion 31 has entered the second metal plate 2. In order to allow the metal plate material to plastically flow into all of the groove portions 12 on the plug 10 that are within the thickness of the second metal plate 2, the punch is inserted deeper than in the applicant's previous patent application (Japanese Patent Application No. 2024-209370). In addition, a certain distance (gap) is provided between the plug 10 and the punch mark 4. This is because the inner circumference of the punch is larger than the outer circumference of the plug. As a result, the metal plate material enters all of the groove portions 12 on the side of the plug 10 by plastic flow, and each metal plate and the plug 10 are firmly joined. In this embodiment, a cylindrical tempered steel (HRC30) with a diameter of 10 mm was used as the plug 10, a 2 mm thick aluminum material was used as the first metal plate 1, and a 1.6 mm thick steel plate (SC) was used as the second metal plate 2. The groove width was 0.3 mm and the punch penetration depth was 0.95 mm. In this embodiment, the horizontal cross-section of the plug and through hole was circular, but the cross-sectional shape can be changed without departing from the spirit of the present invention.

[0019] Figure 3 is a schematic diagram showing the range of plastic flow in a metal sheet depending on the punch penetration depth. Figure 3(a) shows the case when the punch penetration depth is shallow. Plastic flow mainly occurs from the inclination direction of approximately 30° to 45° or more from the center of the punch tip to the side. Therefore, the metal sheet material enters the groove 12 close to the punch mark 4 through plastic flow, but near the center of the metal, away from the punch mark 4, the angle becomes smaller and plastic flow does not occur. As a result, the number of grooves that undergo plastic flow is reduced, and sufficient strength may not be obtained. In contrast, in Figure 3(b), because the punch penetration depth is deep, plastic flow occurs even near the center of the metal sheet in the thickness direction, and the metal sheet material enters the groove 12 of the plug 10.

[0020] Figure 4 shows the dimensional relationships between the plug, metal plate, and punch. For convenience, Figure 1 has been inverted vertically. When the width of the punch tip 31 is W, the distance (gap) between the punch tip 31 and the outer circumference of the plug 10 is C, the punch penetration depth is S, the length of the flat side portion near the upper surface of the plug 10 is L, the width of the groove 12 on the plug 10 is P, and the groove depth of the groove 12 is D, the correlation between these parameters was analyzed.

[0021] Figure 5 shows the results of an analysis performed using the finite element method under the following conditions: plate thickness t=2.0mm, plug groove width P=0.3mm, groove depth D=0.15mm, number of grooves 2, punch width W=0, 0.25, 0.5, 1.0mm, punch entry depth S=0.4mm, and gap C between plug and punch=0, 0.25, 0.5mm. Here, too, the top and bottom are reversed compared to Figure 1. The results showed that at W=1.0, the entire plate deformed. This can be said to be because the punch width was too large relative to the plate thickness. At C=0, the flow of the plate material into the groove was good. This is thought to be because a flat section without grooves was provided above the groove, and the punch only entered up to the bottom of the flat section. In the case of C=0.25, plastic flow occurred in the 30-degree forward direction at W=0.25, and plastic flow occurred in the 45-degree forward direction at W=0.5. At C=0.5, plastic flow mainly occurred in the lateral direction.

[0022] Next, Figure 6 shows the results of an analysis with a large number of internal grooves under the above conditions and a punch penetration depth S = 0.8 mm. Here again, the top and bottom are reversed compared to Figure 1. When C = 0, the punch cut through the sheet metal that had flowed into the groove. This is because the punch penetrated to the position of the groove. When W = 1.0, the entire sheet metal was deformed. In the case of C = 0.25, plastic flow occurred more than 60 degrees forward in both W = 0.25 and W = 0.5, and the sheet metal almost completely filled three or more grooves. In the case of C = 0.5, plastic flow occurred 30 degrees forward in W = 0.25, and the flow into the third groove was somewhat insufficient. In W = 0.5, plastic flow occurred in the 45-degree forward direction, and the sheet metal filled about 50% of the third groove.

[0023] Based on the above analysis results, it is desirable that the relationship between the length L of the lower flat portion of the plug 10 and the width P of the groove 12 be L ≤ P. This is because, when the punch tip enters the metal plate, the pressure increases downward and diagonally downward from the tip, so even if a groove 12 is provided near the lower surface of the plug 10, the plastic flow effect is small.

[0024] It is desirable that the width W of the punch tip 31 be 1.5D ≤ W ≤ 5D. If the width W of the punch tip 31 is too narrow, the pressure on the punch tip 31 will be applied only downwards, reducing the movement of the metal sheet material in the direction of the groove 12 of the plug 10. Also, if the width W of the punch tip 31 is too wide, the pressure will not be properly transmitted to the metal sheet material below the punch tip 31, and plastic flow will not occur.

[0025] The distance (gap) C between the punch tip 31 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] Figure 2 shows a second embodiment of the metal plate joining method according to the present invention. This figure is a cross-sectional view showing the state after joining the first metal plate 1 and the second metal plate 2. In this embodiment, the plug 10 used does not have a groove 12 in the lower body portion of the flange portion 15, and is made into an upper flat portion 11A. However, a groove 12 is formed between the vicinity of the boundary between the first metal plate 1 and the second metal plate 2 and the lower flat portion 11B. Also, the length of the plug body 10 excluding the flange portion 15 is configured to be approximately equal to the combined thickness of the first metal plate 1 and the second metal plate 2. In the first embodiment shown in Figure 1, the total length of the plug 10 including the flange portion 15 is configured to be approximately equal to the combined thickness of the first metal plate 1 and the second metal plate 2, but in this embodiment, it is configured to be longer by the width of the flange portion 15. In this embodiment, the first metal plate 1 and the plug 10 are not directly joined, but are sandwiched between the second metal plate 2, which is joined to the plug 10, and the flange portion 15 of the plug 10. Therefore, the strength is weaker than in the first embodiment. [Explanation of Symbols]

[0030] 1. First metal plate 2. Second metal plate 4 punch marks 10 plugs 11A Upper flat part 11B Lower flat part 12 grooves 13 Upper surface 14 Lower surface 15. Tsuba (guard) 30 Lower punch 31 Lower punch tip 32 Cavity 33 gaps 50 Pressing Plate 101 First metal plate through hole 102 Second metal plate through hole

Claims

1. In a metal plate joining method, through holes of substantially the same diameter are provided in both a first metal plate and a second metal plate, the first metal plate is laminated on the second metal plate so that the through holes overlap, and a plug having a main body with an outer shape substantially equal to the outer shape of the through hole and a flange on one side larger than the diameter is inserted into the through hole to join the metal plates, Using a pressurizing device in which the inner diameter of the tip is formed to be a certain extent larger than the outer diameter of the plug, the outer surface of the second metal plate is pressed to cause the tip to penetrate into the second metal plate to a certain depth, and the second metal plate material is plastically deformed in the lateral direction of the plug, thereby applying tightening stress to the plug and joining the second metal plate and the plug. A method for joining metal plates, characterized by joining a first metal plate and a second metal plate as a result.

2. The flange portion of the plug is pressed with a pressing plate or the like to cause the flange portion to enter the first metal plate. The metal plate joining method according to claim 1, characterized in that the first metal plate material is plastically flowed toward the surface of the plug body to apply a tightening stress to the plug, thereby joining the first metal plate and the plug.

3. The metal plate joining method according to either claim 1 or 2, characterized in that a plurality of grooves perpendicular to the axial direction of the plug are formed on at least a part of the main surface of the plug.

4. The metal plate joining method according to claim 3, characterized in that a flat portion without the groove is provided on the lower surface side of the plug body facing the flange portion.

5. The metal plate joining method according to claim 4, characterized in that the length of the flat portion is less than or equal to the groove width of the groove portion.

6. 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 any one of claims 1 to 5, characterized in that it satisfies the following conditions.

7. When the groove 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 A method for joining metal plates according to any one of claims 1 to 6, characterized in that it satisfies the following conditions.

8. The metal plate joining method according to any one of claims 1 to 7, 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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