Joint structure, and manufacturing method of the joint structure

Abstract

The present invention provides a joint structure comprising aluminum members that can be manufactured inexpensively, quickly, and without cracking, and that can suppress wobbling at the joint, as well as a method for manufacturing the same. [Solution] A joint structure according to one aspect of the present disclosure is a joint structure comprising an aluminum member and one or more metal members, wherein the aluminum member has one or more protrusions, and the metal members have one or more through holes, the protrusions are inserted into the through holes and crimped, and the through holes have burrs at their ends that protrude outward from the through holes, and the burrs penetrate into the aluminum member. A method for manufacturing a joint structure according to another aspect of the present disclosure is to form burrs at the ends of the through holes that protrude outward from the through holes when forming through holes in the metal members, and to allow the burrs to penetrate into the aluminum member when crimping the protrusions into the through holes.

Description

Technical Field

[0001] The present invention relates to a joined structure and a method for manufacturing the joined structure.

Background Art

[0002] In recent years, the application of aluminum die-casting to various mechanical structural parts has been promoted. Aluminum die-casting refers to an aluminum alloy casting obtained by filling molten aluminum alloy into a mold at high pressure and then cooling the aluminum alloy at high speed, or a casting method thereof. Aluminum die-casting is used, for example, as a material for front shock towers, rear shock towers, and subframes of automobiles.

[0003] Also, in recent years, a manufacturing technology called gigacasting has been developed. Gigacasting is a technology for manufacturing huge parts by molding a plurality of aluminum parts as one part using large-scale casting equipment. By making large-scale cast parts of the parts constituting an automobile body, the weight, manufacturing cost, manufacturing process, etc. of the automobile can be reduced. Therefore, it is expected that the application of gigacasting will expand in the future. Furthermore, with the progress of electrification of automobiles, aluminum die-casting has also begun to be applied to inverter cases, battery modules, and battery packs.

[0004] The members made of aluminum die-casting exemplified above need to be joined to other members. The other members are, for example, press-formed steel plates and aluminum rolled materials. For example, Patent Documents 1 to 5 disclose various methods for joining an aluminum die-cast member and other members.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

[0006] Welding is not a suitable method for joining aluminum die-cast parts to steel materials. For example, welding aluminum die-cast parts to steel materials generates brittle intermetallic compounds in the weld metal. These brittle intermetallic compounds significantly reduce the joint strength of the weld.

[0007] Another possible method of joining aluminum die-cast materials to steel is mechanical joining using fastening members. However, aluminum die-cast materials have the problem that the joint formed by mechanical joining is prone to cracking. Stress concentration easily causes deformation at the joint. Since aluminum die-cast materials have low ductility, deformation at the joint easily causes cracking of the aluminum die-cast material.

[0008] Furthermore, Patent Document 1 proposes a joining method in which a protrusion is provided on a die-cast part, the protrusion is inserted into a hole in a metal plate, and the protrusion is crimped. However, the present inventors have found that the joined structure obtained by such a joining method is prone to looseness at the joint.

[0009] In view of the above circumstances, this disclosure provides a joint structure comprising an aluminum member that can be manufactured inexpensively and quickly without cracking, and that can suppress wobbling at the joint, and a method for manufacturing the same. [Means for solving the problem]

[0010] The gist of this disclosure is as follows:

[0011] (1) A joint structure according to one aspect of the present disclosure is a joint structure comprising an aluminum member and one or more metal members, wherein the aluminum member has one or more projections, the metal members have one or more through holes, the projections are inserted into and crimped into the through holes, the through holes have burrs at their ends that protrude outward from the through holes, and the burrs penetrate into the aluminum member. (2) Preferably, in the joint structure described in (1) above, the aluminum member has a main body portion which is the part of the aluminum member other than the protrusion, and the burr portion penetrates the main body portion. (3) Preferably, in the joint structure described in (1) above, the projection has a tip portion at the end of the projection that is larger in diameter than the through hole, and the burr portion penetrates the tip portion. (4) Preferably, in the joint structure described in any one of the above items (1) to (3), the penetration depth of the burr is 0.05 mm or more and 1.0 mm or less. (5) Preferably, in the joint structure described in any one of the above items (1) to (4), the aluminum member is an aluminum die-cast member. (6) Preferably, in the joint structure described in (5) above, the projection of the aluminum member is formed during die casting. (7) Preferably, in the joint structure described in any one of the above items (1) to (6), the metal member comprises a base metal member and a plating layer provided on the surface of the base metal member. (8) Preferably, in the joint structure described in (7) above, the base metal member is made of steel. (9) Preferably, in the joint structure described in (7) or (8) above, the plating layer is a zinc-based plating layer or an aluminum-based plating layer. (10) Preferably, in the joint structure described in (9) above, the metal member has a coating or chromate-free treatment layer provided on the surface of the zinc-based plating layer or the aluminum-based plating layer. (11) Preferably, in the joint structure described in any one of the above items (1) to (10), the projection has a tip portion at the end of the projection that is larger in diameter than the through hole, and the hardness H1 of the tip portion of the projection and the hardness H2 of the aluminum member at a location 10 mm or more away from the projection satisfy H1 ≤ 1.1 × H2.

[0012] (12) A method for manufacturing a jointed structure according to another aspect of the present disclosure is a method for manufacturing a jointed structure having an aluminum member and one or more metal members, comprising the steps of: forming a through hole in the metal member; inserting a projection of the aluminum member into the through hole; and deforming the tip of the projection while heating it to crimp the projection into the through hole, wherein when forming the through hole in the metal member, a burr is formed at the end of the through hole that protrudes outward from the through hole, and when crimping the projection into the through hole, the burr is inserted into the aluminum member. (13) Preferably, in the method for manufacturing the joint structure described in (12) above, the through hole is formed by punching using a set of dies, and the clearance of the set of dies is set to 10 to 50% of the plate thickness of the base steel member. (14) Preferably, in the method for manufacturing the joint structure described in (12) or (13) above, the projection is heated and the tip of the projection is deformed using a spot welding electrode. [Effects of the Invention]

[0013] According to this disclosure, a joint structure comprising an aluminum member, and a method for manufacturing the same, can be manufactured inexpensively and quickly without cracking, and can suppress wobbling at the joint. [Brief explanation of the drawing]

[0014] [Figure 1] This is a cross-sectional view of a joint structure in which a burr has penetrated the main body of an aluminum component. [Figure 2] This is a cross-sectional view of a joint structure in which a burr has penetrated the tip of a protrusion on an aluminum component. [Figure 3]It is an enlarged cross-sectional view of the process of forming a through-hole in a mold. [Figure 4] It is a cross-sectional view of a joined structure in which a burr portion does not penetrate into an aluminum member. [Figure 5] It is a schematic diagram of the process of forming a through-hole. [Figure 6] It is a schematic diagram of the process of inserting a protrusion into a through-hole. [Figure 7] It is a schematic diagram of the process of deforming the tip of a protrusion using a direct spot welding machine. [Figure 8] It is a schematic diagram of the process of deforming the tip of a protrusion using an indirect spot welding machine. [Figure 9] It is a cross-sectional photograph of an example of a through-hole and burrs formed during hot stamping. [Figure 10] It is a cross-sectional photograph of the through-hole of Example A. [Figure 11] It is a cross-sectional photograph of the joined structure of Example A. [Figure 12] It is a cross-sectional photograph of the through-hole of Example B. [Figure 13] It is a cross-sectional photograph of the joined structure of Example B. [Figure 14] It is a cross-sectional photograph of the through-hole of Example C. [Figure 15] It is a cross-sectional photograph of the joined structure of Example C.

Mode for Carrying Out the Invention

[0015] (1. Joined Structure 1) The joined structure 1 according to one aspect of the present disclosure includes an aluminum member 11 and one or more metal members 12. The aluminum member 11 has one or more protrusions 111, the metal member 12 has one or more through-holes 121, the protrusions 111 are inserted into the through-holes 121 and caulked, and the through-holes 121 have a burr portion 1211 that protrudes outward from the end of the through-hole 121, and the burr portion 1211 penetrates into the aluminum member 11. Hereinafter, the details of the joined structure 1 according to the present embodiment will be described while referring to FIGS. 1 and 2 and the like.

[0016] (Aluminum component 11) The jointed structure 1 includes an aluminum member 11. The aluminum member 11 is a mechanical structural member manufactured from an aluminum alloy. Specific examples of aluminum alloys will be described later.

[0017] Various shapes can be applied to the aluminum member 11 depending on its application. Suitable examples of applications for the aluminum member 11 include front shock towers, rear shock towers, bumpers, and subframes of automobiles. Components that make up the electrical system of electric vehicles, such as inverter cases, battery modules, and battery packs, can also be made of aluminum member 11. A single joint structure 1 may comprise two or more aluminum members 11.

[0018] (Metal member 12) The jointed structure 1 further comprises one or more metal members 12. The metal members 12 are mechanical structural members manufactured from metal materials. Various shapes can be applied to the metal members 12 depending on their intended use. The metal members 12 are primarily formed into various shapes by cold or hot press forming (hot stamping).

[0019] (Protrusion 111 and through hole 121) The aluminum member 11 has a projection 111. The metal member 12 has a through hole 121. The projection 111 of the aluminum member 11 is inserted through the through hole 121 of the metal member 12. The projection 111 is also crimped. Specifically, the projection 111 has a tip portion 1112 and a shaft portion 1111, and the tip portion 1112 is plastically deformed by the crimping process. The shaft portion 1111 is the part of the projection 111 that is located inside the through hole 121. The tip portion 1112 is the tip-side part of the projection 111 that is located outside the through hole 121.

[0020] The diameter of the shaft portion 1111 is approximately the same as, or smaller than, the diameter of the through hole 121. The diameter of the tip portion 1112 is enlarged beyond the diameter of the through hole 121 due to plastic deformation. The tip portion 1112 prevents the projection 111 from detaching from the through hole 121. The projection 111 functions to join the aluminum member 11 and the metal member 12, like a rivet. However, the projection 111 differs from a rivet in that it is integral with the aluminum member 11.

[0021] The tip portion 1112 is preferably formed by hot riveting. Hot riveting is a riveting process performed while the tip portion 1112 is softened by heat. This prevents cracking of the projection portion 111.

[0022] The aluminum member 11 may have two or more protrusions 111. The metal member 12 may have two or more through holes 121. In this case, it is preferable that each of the multiple protrusions 111 is inserted through and crimped into the multiple through holes 121. The cross-sectional shape of the protrusions 111 and the through holes 121 can be, for example, a circle, an ellipse, or a polygon.

[0023] (Burst portion 1211 of through hole 121) A burr portion 1211 is provided at the end of the through hole 121 of the metal member 12. The burr portion 1211 is a thin material portion that protrudes from the gap in the die 3 during the punching process that forms the through hole 121. The burr portion 1211 protrudes outward from the through hole 121.

[0024] Figure 3 shows a schematic diagram of the inner surface of a through-hole 121 where a burr has been formed by punching. The die 3 on the left side of the paper is pressed into the metal member 12 shown in Figure 2, toward the bottom of the paper. As a result, the die 3 on the left side of the paper cuts off a portion of the metal member 12, forming the through-hole 121.

[0025] During the formation of the through hole 121, the end face of the metal member 12 undergoes plastic deformation in the direction in which the mold 3 on the left side is pressed. The downward arrow in Figure 2 indicates the direction in which the mold 3 on the left side is pressed. As a result, a sag portion 1212 is formed on the upper side of the metal member 12 in Figure 2. The sag portion 1212 is the shrinkage of the material caused by pressing the mold 3. In addition, a burr portion 1211 is formed on the lower side of the metal member 12 in Figure 2.

[0026] The burr portion 1211 penetrates the aluminum member 11, as illustrated in Figures 1 and 2. The burr portion 1211 may also penetrate the main body portion 112 of the aluminum member 11, as shown in Figure 1. The main body portion 112 of the aluminum member 11 refers to the portion of the aluminum member 11 other than the projection portion 111. The burr portion 1211 may also penetrate the tip portion 1112 of the projection portion 111 of the aluminum member 11, as shown in Figure 2.

[0027] Whether or not the burr portion 1211 has penetrated the main body portion 112 of the aluminum member 11 is determined based on the surface 112S of the main body portion 112 of the aluminum member 11 that faces the metal member 12, in the vicinity of the projection portion 111. Hereinafter, the surface of the main body portion 112 of the aluminum member 11 that faces the metal member 12 in the vicinity of the projection portion 111 will be simply referred to as the "surface 112S of the main body portion". When the joint structure 1 is cut by a plane that passes through approximately the center of the projection portion 111 and is perpendicular to the surface of the joint structure 1, the burr formed in the through hole 121 can be visually observed, as shown in Figure 1. If the tip of the burr portion 1211 is on the side of the main body portion 112 of the aluminum member 11 that is greater than the imaginary line VL1 along the surface 112S of the main body portion, it is determined that the burr portion 1211 has penetrated the aluminum member 11.

[0028] Whether or not the burr portion 1211 has penetrated the tip portion 1112 of the aluminum member 11 is determined based on the surface 1112S of the tip portion 1112 of the projection 111 that faces the metal member 12. Hereinafter, the surface 1112S of the tip portion 1112 of the projection 111 that faces the metal member 12 will be simply referred to as "the tip surface 1112S". When the joint structure 1 is cut by a plane that passes through approximately the center of the projection 111 and is perpendicular to the surface of the joint structure 1, the burr formed in the through hole 121 can be visually observed, as shown in Figure 2. If the tip of the burr portion 1211 is on the side of the tip portion 1112 of the projection 111 that is greater than the imaginary line VL2 along the tip surface 1112S, it is determined that the burr portion 1211 has penetrated the aluminum member 11.

[0029] On the other hand, in the joint structure 4 illustrated in Figure 4, it is not determined that the burr portion 1211 has penetrated the aluminum member 11. In the joint structure 4 of Figure 4, the burr portion 1211 is crushed when the aluminum member 11 and the metal member 12 are joined. As a result, the burr portion 1211 did not penetrate into the interior of the aluminum member 11. The burr portion 1211 formed a gap G between the metal member 12 and the aluminum member 11. In the joint structure 4 of Figure 4, the tip of the burr portion 1211 is on the side of the projection 111 of the aluminum member 11, relative to the imaginary line VL1 along the surface 112S of the main body.

[0030] (Effects and Benefits) In the joint structure 1 according to this embodiment, the projection 111 of the aluminum member 11 and the through hole 121 of the metal member 12 form a joint by crimping. Therefore, welding between the aluminum member 11 and the metal member 12 is not required.

[0031] Furthermore, in the joining structure 1 according to this embodiment, the projection 111 is part of the aluminum member 11. Therefore, in the process of joining the aluminum member 11 and the metal member 12, it is not necessary to assemble the projection 111 to the aluminum member 11. Accordingly, the manufacturing of the joining structure 1 according to this embodiment is easy.

[0032] Furthermore, the tip of the projection 111 provided on the aluminum member 11 can be easily crimped using a spot welding machine, which is a general-purpose piece of equipment. A spot welding machine has a spot welding electrode 2, a pressurizing device for moving the spot welding electrode 2, and a transformer for supplying current to the spot welding electrode 2. The spot welding electrode 2 applies pressure while locally heating the material to be welded by applying current.

[0033] A spot welding machine can be easily adapted for crimping the projection 111 of the aluminum member 11. The spot welding machine can electrically heat the projection 111 of the aluminum member 11 that has been inserted through the through hole 121 of the metal member 12. This heats the tip of the projection 111, allowing it to be thermally softened. The spot welding machine can also apply pressure to the projection 111 of the aluminum member 11. By applying pressure to the tip 1112 of the thermally softened projection 111, the tip 1112 can be easily plastically deformed. Therefore, in manufacturing the jointed structure 1 according to this disclosure, no special equipment for joining is required. Joining can be easily performed using a spot welding machine, which is a general-purpose welding device.

[0034] Furthermore, crimping using a spot welding machine is inexpensive and can be performed in a short time, and does not cause cracks in the protrusions 111. Electrical heating using electrodes can cause thermal softening of the tip 1112 of the protrusions 111 of the aluminum member 11 within a few seconds. Therefore, the crimping work can be completed in a very short time and at low cost. In addition, although the aluminum alloy that makes up the aluminum member 11 is prone to cracking during plastic deformation, the thermally softened aluminum alloy does not crack due to plastic deformation.

[0035] Furthermore, in the joint structure 1 according to this embodiment, the burr portion 1211 penetrates the aluminum member 11. The burr portion 1211 suppresses wobbling at the joint.

[0036] In addition, there is no need to provide an additional procedure for forming the burr portion 1211 during the manufacturing of the joint structure 1. For example, punching with a clearance C amount within a predetermined range can simultaneously form both the through hole 121 and the burr portion 1211. Furthermore, the operation of inserting the burr portion 1211 into the aluminum member 11 can be performed simultaneously with the operation of crimping the protrusion. Therefore, the burr portion 1211 of the joint structure 1 according to this embodiment does not complicate the manufacturing process.

[0037] For the reasons stated above, the joint structure 1 according to this embodiment can be manufactured inexpensively and quickly without cracking, and looseness at the joint can be suppressed.

[0038] The most basic embodiment of the joint structure 1 according to this embodiment has been described above. A more preferred embodiment will be described below.

[0039] (Location of burr section 1211) As illustrated in Figure 1, the burr portion 1211 may penetrate the main body portion 112 of the aluminum member 11. In this case, the burr portion 1211 will be provided at the end of the through hole 121 on the aluminum member 11 side. On the other hand, as illustrated in Figure 2, the burr portion 1211 may penetrate the tip portion 1112 of the projection 111 of the aluminum member 11. In this case, the burr portion 1211 will be provided at the end of the through hole 121 on the tip portion 1112 side.

[0040] As shown in Figure 1, when the burr portion 1211 is provided on the side of the tip portion 1112 of the projection portion 111, it is easier to increase the penetration depth of the burr portion 1211. This further suppresses wobbling at the joint. Furthermore, from the viewpoint of further increasing the joint strength of the joint structure 1, it is preferable to penetrate the main body portion 112, as shown in Figure 2.

[0041] (Intrusion depth of burr section 1211) The penetration depth of the burr portion 1211 is preferably 0.05 mm or more and 1.0 mm or less. When the burr portion 1211 penetrates and forces into the main body portion 112, the penetration depth is the distance between the imaginary line VL1 shown in Figure 1 and the tip of the burr. When the burr portion 1211 penetrates and forces into the tip portion 1112, the penetration depth is the distance between the imaginary line VL2 shown in Figure 2 and the tip of the burr.

[0042] By setting the penetration depth of the burr portion 1211 to 0.05 mm or more, the looseness of the joint can be further suppressed. Preferably, the penetration depth of the burr portion 1211 is 0.1 mm or more, 0.2 mm or more, or 0.03 mm or more. On the other hand, by setting the penetration depth of the burr portion 1211 to 1.0 mm or less, the fracture of the aluminum member 11 in the area where the burr portion 1211 has penetrated can be suppressed, and the joint strength of the joint structure 1 can be further improved. Preferably, the penetration depth of the burr portion 1211 is 0.9 mm or less, 0.8 mm or less, or 0.6 mm or less.

[0043] (Aluminum die-cast component) A preferred example of the aluminum component 11 is an aluminum die-cast component. An aluminum die-cast component is a mechanical structural component made from aluminum die-casting. Aluminum die-casting is an aluminum alloy casting obtained by filling a mold with molten aluminum alloy under high pressure and then rapidly cooling the aluminum alloy. Aluminum die-cast components have excellent strength and can be manufactured in a short time.

[0044] When observing the cross-section of an aluminum die-cast component, a fibrous metallic structure called metal flow can be observed. Metal flow is a trace of the flow of molten aluminum during casting. An aluminum component 11 exhibiting metal flow is considered to be an aluminum die-cast component.

[0045] Specific examples of aluminum alloys that make up the aluminum component 11 are ADC10, ADC12, AC4CH, AC4C, Al-Si-Mg alloys, and Al-Mg-Si-Mn alloys.

[0046] (Metal flow of projection 111) The method for manufacturing the projection 111 is not limited. For example, the projection 111 can be formed by cutting the aluminum member 11 or by welding a projection 111, which is manufactured separately from the aluminum member 11, to the aluminum member 11.

[0047] If the aluminum member 11 is a die-cast member, it is preferable that the projection 111 of the aluminum member 11 is formed during die-casting. This reduces the number of steps required to form the projection 111 and suppresses cracking of the projection 111 and its surrounding area.

[0048] When the cross-section of a projection 111 of an aluminum component 11 formed during die casting is corroded and observed, metal flow can be visually observed inside the projection 111. The cross-section is corroded using a mixture of ammonia and water at a volume ratio of 10%, or Keller's solution. The projection 111 having metal flow has chill crystals on its surface and columnar crystals on its interior. Furthermore, equiaxed crystals may also be present inside the metal flow. The columnar crystals are present radially from the inside to the outside of the projection 111.

[0049] The shapes of chill crystals, columnar crystals, and equiaxed crystals are schematically shown, for example, in Figure 2.9 "Typical Macro-Solidification Structure" on page β-3 of β3 "Processing Engineering and Processing Equipment" in the "Handbook of Mechanical Engineering β. Design Edition" (edited by the Japan Society of Mechanical Engineers, Maruzen Co., Ltd., published April 30, 2008). Chill crystals, columnar crystals, and equiaxed crystals can be identified by observing the etched cross-section. Furthermore, the protrusions 111 on which crystals are arranged, as shown in (a) and (b) of the drawing, are considered to be protrusions 111 formed during die casting.

[0050] Furthermore, the protrusions 111 formed during die casting are integrally formed with the aluminum member 11. Therefore, the protrusions 111 that have a metal flow extending along the surface of the protrusions 111 and are integrally formed with the aluminum member 11 are considered to be the protrusions 111 formed during die casting.

[0051] Metal flow may also be observed in the cross-section of the protrusion 111 formed by cutting. However, if the protrusion is formed by casting and then subjected to machining such as cutting, the chill crystals may be removed by cutting. In that case, the protrusion 111 will consist only of columnar crystals, or of columnar crystals and equiaxed crystals. In addition, cutting marks may remain on the surface of the protrusion 111 formed by cutting. Therefore, the protrusion 111 formed by cutting and the protrusion 111 formed during die casting can be distinguished by surface observation and cross-sectional observation.

[0052] (Metal member 12) The metal member 12 is preferably made from a metal harder than the aluminum member 11. This makes it easier for the burrs formed at the end of the through-hole of the metal member 12 to penetrate into the aluminum member. The material of the metal member 12 is preferably steel. Examples of steel include unplated steel sheets that have been hot-rolled or cold-rolled, and unplated hot-stamped steel sheets that have been shot-blasted after hot stamping. The material of the metal member 12 may also be stainless steel. Furthermore, any aluminum alloy such as the 3000 series, 5000 series, 6000 series, or 7000 series may be used as the material of the metal member 12, as long as it is a metal harder than the aluminum member 11.

[0053] (Base material and plating layer of metal component 12) The metal member 12 may have a base metal member and a plating layer provided on the surface of the base metal member. That is, the metal member 12 may be a plated metal member. A suitable example of the base metal member is steel. That is, the base metal member may be a steel member, i.e., a base steel member.

[0054] Suitable examples of plated metal members are aluminum-plated steel members and zinc-plated steel members. An aluminum-plated steel member is a steel sheet having a base steel member and an aluminum-plated layer provided on the surface of the base steel member, wherein the average concentration of aluminum in the plating layer is 20% by mass or more. A zinc-plated steel member is a steel member having a base steel member and a zinc-plated layer provided on the surface of the base steel member, wherein the average concentration of zinc in the plating layer is 30% or more. Both the aluminum-plated layer and the zinc-plated layer exhibit the effect of suppressing galvanic corrosion between the base steel material and the aluminum member 11.

[0055] A specific example of aluminum-plated steel is aluminum-plated hot-stamped steel sheet. Specific examples of zinc-plated steel include zinc-plated hot-stamped steel sheet, GA-plated (alloyed hot-dip galvanized) steel sheet, GI-plated (hot-dip galvanized) steel sheet, EG-plated (electro-galvanized) steel sheet, Zn-Ni-plated steel sheet, Zn-Al-Mg-plated steel sheet, and Zn-Mg-plated steel sheet.

[0056] The plated steel member may further have a coating or chromate-free treatment layer provided on the surface of the zinc-based plating layer. Both the coating and the chromate-free treatment layer contribute to ensuring the corrosion resistance of the joint structure 1 and suppressing galvanic corrosion between the base steel material and the aluminum member 11. A preferred example of the coating is an electrodeposited coating.

[0057] (Hot crimping) Preferably, the projection 111 is hot-crimped. The tip 1112 of the projection 111 is a hot-crimped portion. Hot crimping can suppress cracking of the projection 111 during the crimping process. In addition, hot crimping prevents work hardening of the tip 1112. Furthermore, hot crimping makes it easier to insert the burr 1211 into the aluminum member 11.

[0058] Whether the projection 111 is manufactured by hot riveting or cold riveting can be determined based on the presence or absence of work hardening at the tip portion 1112. Work hardening is significantly observed at the tip portion 1112 of a cold-riveted projection 111. If the hardness H1 of the tip portion 1112 of the projection 111 and the hardness H2 of the aluminum member 11 at a location 10 mm or more away from the projection 111 satisfy H1 ≤ 1.1 × H2, the projection 111 is considered to have been hot-riveted.

[0059] The hardness H1 of the tip 1112 of the projection 111 is measured in the cross-section of the projection 111 passing through its approximate center. The maximum Vickers hardness measured at any five points in the cross-section of the tip 1112 of the projection 111 is considered to be H1. In addition, the average Vickers hardness measured at any five points in the cross-section of the aluminum member 11, at a distance of 10 mm or more from the projection 111, is considered to be H2. The test force used for all Vickers hardness measurements is the same.

[0060] (2. Method for manufacturing the jointed structure 1) A method for manufacturing a joint structure 1 according to another aspect of the present disclosure is a method for manufacturing a joint structure 1 having an aluminum member 11 and one or more metal members 12, comprising the steps of forming a through hole 121 in the metal member 12, inserting a projection 111 of the aluminum member 11 into the through hole 121, and deforming the tip of the projection 111 while heating it to crimp the projection 111 into the through hole 121, wherein when forming the through hole 121 in the metal member 12, a burr portion 1211 protruding outward from the through hole 121 is formed at the end of the through hole 121, and when crimping the projection 111 into the through hole 121, the burr portion 1211 is made to penetrate the aluminum member 11. Details of the method for manufacturing a joint structure 1 according to this embodiment will be described below. The preferred embodiments of the joint structure 1 described above can also be applied to the method for manufacturing a joint structure 1 according to this embodiment.

[0061] (Aluminum member 11 and metal member 12) In the manufacturing method of the jointed structure 1 according to this embodiment, an aluminum member 11 and a metal member 12 are joined together. The aluminum member 11 has one or more protrusions 111. In the jointed structure 1, the protrusions 111 are inserted through holes 121. Therefore, it is necessary to appropriately select the position of the protrusions 111. Preferably, the protrusions 111 are formed during the casting of the aluminum member. Alternatively, the protrusions 111 can be formed by cutting the aluminum member.

[0062] (Formation of through hole 121 in S1) First, as shown in Figure 5, a through hole 121 is formed in the metal member 12. The position of the through hole 121 corresponds to the position of the projection 111. In addition, when forming the through hole 121 in the metal member 12, a burr portion 1211 is formed at the end of the through hole 121. The means for forming the through hole 121 are not particularly limited. However, when forming the through hole 121, it is necessary to optimize the processing conditions so that a burr portion 1211 of sufficient height is formed.

[0063] As shown in Figure 2, when the means for forming the through hole 121 is punching, the clearance C, which is the distance between a set of dies 3, is set to 10-50% of the plate thickness of the metal member 12. If the clearance C is less than 10%, a burr portion 1211 of sufficient height cannot be obtained. More preferably, the lower limit of the clearance C is 12% or more, 15% or more, 18% or more, or 20% or more. On the other hand, if the clearance C is greater than 50%, it becomes difficult to form the through hole 121. More preferably, the upper limit of the clearance C is 45% or less, 40% or less, 35% or less, or 30% or less. Before crimping the projection 111, it is preferable that the height of the burr portion be, for example, 0.05 mm or more and 1.0 mm or less.

[0064] (S2 Insertion of projection 111 into through hole 121) Next, as shown in Figure 6, the projection 111 is inserted through the through hole 121.

[0065] Alternatively, an adhesive may be provided between the metal member 12 and the aluminum member 11 to bond them together. In this case, the adhesive is applied to one or both of the aluminum member 11 and the metal member 12 before inserting the projection 111 through the through hole 121. Then, while inserting the projection 111 through the through hole 121, the area on one member to which the adhesive has been applied is pressed against the surface of the other member. This allows the two members to be bonded together.

[0066] (S3 Deformation of the tip of projection 111) Then, the tip of the projection 111 is deformed as shown in Figure 7 or Figure 8. This causes the projection 111 to be crimped into the through hole 121. As the projection 111 is crimped into the through hole 121, the tip portion 1112 is formed, and the aluminum member 11 and the metal member 12 are joined together.

[0067] When deforming the tip of the projection 111, it is preferable to heat the projection 111. This softens the projection 111 and reduces its deformation resistance. The reduction in deformation resistance suppresses cracking of the projection 111 during crimping. Furthermore, the reduction in deformation resistance makes it easier to insert the burr portion 1211 into the aluminum member 11.

[0068] From the viewpoint of reducing the deformation resistance of the tip of the projection 111, preventing cracking of the projection 111, and ensuring sufficient penetration of the burr portion 1211, a larger heat input to the projection 111 is preferable. However, if the heat input is excessive, the aluminum member 11 may melt unnecessarily. Therefore, it is preferable to determine the optimal heat input by repeatedly conducting crimping tests and cross-sectional observations under various conditions.

[0069] A preferred example of a heating means for the projection 111 is a spot welding electrode 2. The spot welding electrode 2 is a rod-shaped electrode made of copper alloy that directly contacts the base material during spot welding, conducting the welding current and transmitting the applied pressure. However, in the manufacturing method of the joint structure 1 according to this embodiment, the spot welding electrode 2 is not used for welding the metal member 12 and the aluminum member 11. The spot welding electrode 2 is applied to the projection 111 while applying current. The projection 111 is softened by the resistive heat generated by the current. By applying pressure to the projection 111 in its softened state, the tip of the projection 111 is easily deformed, and a tip portion 1112 that crimps the through hole 121 is formed.

[0070] The crimping of the projection 111 using the spot welding electrode 2 may be performed by a direct spot welding machine or an indirect spot welding machine. In JIS Z 3001-6:2013 "Welding Terminology - Part 6: Resistance Welding", direct spot welding is defined as spot welding performed by directly applying pressure to the weld joint with an electrode and passing a welding current in the direction of the plate thickness. In the same standard, indirect spot welding is defined as spot welding that creates only one nugget in the base material directly below the electrode using a current flow method similar to series currenting. The following describes specific examples of crimping work performed by a direct spot welding machine or an indirect spot welding machine.

[0071] (Crimping work using a direct spot welding machine) When crimping the projection 111 using a direct spot welding machine, the projection 111 is sandwiched between a pair of spot welding electrodes 2, as illustrated in Figure 7. The tip of one spot welding electrode 2 is positioned at the tip of the projection 111. The tip of the other spot welding electrode 2 is positioned on the surface of the aluminum member 11 opposite to the projection 111. The central axes of the pair of spot welding electrodes 2 are aligned. Then, while passing current between the pair of spot welding electrodes 2, the spot welding electrodes 2 are moved to narrow the distance between the electrodes. As a result, the tip of the projection 111 is crushed, and a tip portion 1112 having a diameter larger than the through hole 121 is formed.

[0072] (Crimping work using an indirect spot welding machine) When crimping the projection 111 using an indirect spot welding machine, a pair of spot welding electrodes 2 are arranged in parallel, as illustrated in Figure 8. The tip of one spot welding electrode 2 is placed on the tip of the projection 111. The tip of the other spot welding electrode 2 is placed on the surface of the aluminum member 11 on the side where the projection 111 is provided. The central axes of the pair of spot welding electrodes 2 are not aligned. Then, while passing current between the pair of spot welding electrodes 2, the spot electrode placed on the tip of the projection 111 is pressed against the projection 111. As a result, the tip of the projection 111 is crushed, and a tip portion 1112 having a diameter larger than the through hole 121 is formed.

[0073] Crimping using a direct spot welding machine is preferable because it can be performed easily and reliably. However, when crimping using a direct spot welding machine, the spot welding electrode 2 must be positioned on the surface of the aluminum member 11 opposite to the projection 111. For example, if the aluminum member 11 has a closed cross-sectional structure, crimping using a direct spot welding machine may not be possible. Crimping using an indirect spot welding machine is suitable in such cases. This is because when crimping using an indirect spot welding machine, both of the pair of spot welding electrodes 2 are positioned on the side where the projection 111 is provided.

[0074] The power supply for the spot welding machine is preferably a single-phase AC power supply, a DC inverter power supply, or an AC inverter power supply. The tip of the spot welding electrode 2 is preferably flat, but the tip may have curvature. The material of the tip of the spot welding electrode 2 is preferably chromium copper, alumina-dispersed copper, zirconium copper, chromium-zirconium copper, and beryllium copper.

[0075] The optimal energizing conditions vary depending on the size of the projection 111 of the aluminum member 11, the diameter and depth of the through hole 121 of the metal member 12, the clearance C when forming the through hole 121 in the metal member 12, and the size of the burr portion 1211, etc.

[0076] (Effects and Benefits) In the manufacturing method of the joint structure 1 according to this embodiment, the burr portion 1211 for preventing looseness of the joint can be formed simultaneously with the through hole 121. Furthermore, in the manufacturing method of the joint structure 1 according to this embodiment, the projection portion 111 can be crimped without cracking using a spot welding machine, which is a general-purpose manufacturing piece of equipment. For these reasons, the manufacturing method of the joint structure 1 according to this embodiment can be manufactured inexpensively and quickly without cracking, and looseness of the joint can be suppressed.

[0077] While embodiments of the present disclosure have been described above, the disclosure is not limited thereto and can be modified as appropriate without departing from the technical idea. Further preferred examples of the joint structure 1 and its manufacturing method according to the present embodiment are described below.

[0078] (Diameter and depth of through hole 121) The diameter of the through-hole 121 provided in the metal member 12 is preferably, for example, 3.0 to 25.0 mm. The diameter of the through-hole 121 is the diameter of the through-hole 121 if it is circular, and the maximum diameter if the through-hole 121 is elliptical or polygonal in shape. If the through-hole 121 has a tapered shape, it is preferable that the maximum and minimum diameters of the through-hole 121 are within the above range.

[0079] The larger the through hole 121, the easier it is to insert the projection 111 into the through hole 121. The larger the through hole 121, the greater the joint strength during joining.

[0080] The depth of the through-hole 121 can be appropriately selected according to the shape of the metal member 12. The depth of the through-hole 121 is approximately the same as the thickness of the metal member 12 at the location where the through-hole 121 is provided. The thickness of the metal member 12 and the depth of the through-hole 121 are preferably, for example, 0.5 mm to 3.6 mm. From the viewpoint of facilitating the crimping work, the depth of the through-hole 121 is preferably 3.6 mm or less. From the viewpoint of ensuring joint strength, the depth of the through-hole 121 is preferably 0.5 mm or more. If the metal member 12 is plate-shaped, the through-hole 121 can be provided at any location on the metal member 12. On the other hand, if the metal member 12 is not plate-shaped, a plate-shaped flange portion can be provided on the metal member 12, and the through-hole 121 can be provided on the flange portion.

[0081] (Diameter of the shaft portion 1111 of the projection 111) In the joint structure 1, the maximum diameter of the shaft portion 1111 of the projection 111 provided on the aluminum member 11 is approximately the same as the diameter of the through hole 121. This is because the diameter of the shaft portion 1111 expands when the tip of the projection 111 is deformed. However, adhesive may be applied between the aluminum member 11 and the metal member 12. In this case, adhesive may flow between the shaft portion 1111 and the inner wall of the through hole 121, causing the diameter of the shaft portion 1111 of the projection 111 to become smaller than the diameter of the through hole 121. In the joint structure 1, preferred examples of the diameter and length of the shaft portion 1111 of the projection 111 are similar to the diameter and depth of the through hole 121 described above.

[0082] The diameter of the projection 111 before its tip is deformed is preferably smaller than the diameter of the through hole 121. The difference between the diameter of the projection 111 and the diameter of the through hole 121 is preferably 0.3 mm or more. This makes it easier to insert the projection 111 into the through hole 121.

[0083] More preferably, the diameter of the projection 111 before its tip is deformed is smaller than the diameter of the through hole 121, and the difference between the two is in the range of 0.5 to 2.5 mm. This allows adhesive to flow between the projection 111 and the through hole 121. The adhesive placed between the projection 111 and the through hole 121 suppresses galvanic corrosion between the metal member 12 and the aluminum member 11. Note that the diameter of the projection 111 is its diameter if the projection 111 is circular, and its maximum diameter if the projection 111 is elliptical or polygonal in shape.

[0084] (Amount of protrusion of projection 111 before the tip is deformed) The protrusion amount of the projection 111 before its tip is deformed is preferably 3.0 to 15.0 mm. The protrusion amount is the distance between the surface of the metal member 12 and the tip of the projection 111 when the projection 111 is inserted into the through hole 121 before its tip is deformed. If the metal member 12 and the aluminum member 11 come into contact around the projection 111 when the projection 111 is inserted into the through hole 121, the protrusion amount of the projection 111 will be the length of the projection 111 minus the depth of the through hole 121. If a gap is formed between the metal member 12 and the aluminum member 11 around the projection 111 when the projection 111 is inserted into the through hole 121, as illustrated in Figure 4, the protrusion amount of the projection 111 will be the length of the projection 111 minus the depth of the through hole 121 and the thickness of the gap.

[0085] Furthermore, when measuring the amount of protrusion of the projection 111 before the tip is deformed, no adhesive is applied. In other words, the thickness of the adhesive is not considered when determining the amount of protrusion of the projection 111 before the tip is deformed. This is because the thickness of the adhesive varies depending on the pressure applied when bonding the metal member 12 and the aluminum member 11.

[0086] The smaller the protrusion, the easier it is to deform the tip of the projection 111. On the other hand, the larger the protrusion, the larger the diameter of the tip 1112, and the greater the joint strength.

[0087] (Shape of the tip 1112) The diameter of the tip portion 1112 is preferably larger than the diameter of the through hole 121, and the difference between the two is preferably 1.5 mm or more. The diameter of the tip portion 1112 is the diameter of the tip portion 1112 if it is circular, and the maximum diameter if the tip portion 1112 is elliptical or polygonal in shape. Furthermore, the thickness of the tip portion 1112 is preferably 1.0 to 9.0 mm. The thickness of the tip portion 1112 is the distance between the surface of the metal member 12 and the tip of the projection portion 111 in the joint structure 1.

[0088] The larger the diameter and thickness of the tip portion 1112, the greater the joint strength. The smaller the diameter and thickness of the tip portion 1112, the easier it is to deform the tip of the projection portion 111.

[0089] (glue) The joint structure 1 may further include an adhesive placed between the aluminum member 11 and the metal member 12. The adhesive further improves the joint strength between the aluminum member 11 and the metal member 12. The type of adhesive is not particularly limited. Preferred examples of adhesives include structural epoxy adhesives, rubber adhesives, and urethane adhesives. Alternatively, the adhesive may be a structural adhesive with excellent vibration damping properties, such as a composite of epoxy and rubber. Alternatively, the adhesive may be a rubber-based sealant with airtight, dustproof, and waterproof functions.

[0090] (Tapered shape of through hole 121 and / or projection 111) Preferably, the through hole 121 has a tapered shape that narrows from the base end to the tip of the projection 111. Also preferably, the projection 111 before the crimping operation has a tapered shape that narrows from the base end to the tip. By applying a tapered shape to the through hole 121 and / or the projection 111, the operation of inserting the projection into the through hole 121 becomes even easier.

[0091] (Manufacturing through holes using hot stamping) If the metal component is a hot-stamped component, the through-hole may be manufactured during the hot-stamping process of the metal sheet. Hot stamping is a forming technique in which a metal sheet is heated and softened before being press-formed. By providing a punch and die in the hot-stamping mold, the through-hole can be formed simultaneously with the forming process.

[0092] When through holes are manufactured during the hot stamping process, the high temperature and soft state during molding allow for a greater increase in the height of the burrs at the ends of the through holes. Figure 9 shows a cross-sectional photograph of an example of a through hole manufactured during hot stamping. In conventional technology, burrs reduce the dimensional accuracy of parts, so it is desirable to keep them as small as possible. However, in the joint structure according to this embodiment, burrs are used to suppress wobbling of the joint. Therefore, it is even more preferable to provide through holes at the same time as hot stamping.

[0093] (Applications of joint structures) The joint structure according to this embodiment can be applied to various mechanical structural parts. For example, some automotive parts to which the joint structure according to this embodiment can be applied include front and rear shock towers, subframes, inverter cases, battery modules, battery packs, instrument panel reinforcements, rear members, rear cross members, bumpers, crash boxes, and the like. [Examples]

[0094] The effects of one aspect of this disclosure will be further illustrated by the examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effectiveness of this disclosure. This disclosure is not limited to these examples of conditions. This disclosure may adopt various conditions as long as they do not depart from its gist and achieve its objectives.

[0095] Examples A, B, and C of a jointed structure having an aluminum member and one or more metal members were manufactured. During manufacturing, a through hole was first formed in the metal member, then a projection on the aluminum member was inserted into the through hole, and the tip of the projection was heated and deformed to crimp the projection into the through hole. The crimping work was carried out using a spot welding device.

[0096] In the manufacturing of Examples B and C, when forming the through holes, burrs were formed at the ends of the through holes, protruding outwards. Furthermore, when crimping the protrusions into the through holes, the burrs were allowed to penetrate the aluminum component. The specific manufacturing conditions were as follows:

[0097] [Table 1]

[0098] The common manufacturing conditions in all examples were as follows: • Material of aluminum component: ADC12 • Thickness of metal component: 1.2 mm • Diameter of the projection before crimping: 5.9 mm • Length of the projection before crimping: 8.0 mm • Diameter of the through hole before crimping: 6.5 mm • Crimping pressure: 425 kgf • Current value during crimping: 14.0kA • Current supply time during crimping: 0.35 seconds

[0099] Two metal members with through holes were created for one example condition. One of the metal members was cut by a plane passing through the center of the through hole and perpendicular to the surface of the metal member, and a photograph of its cross-sectional shape was taken. The other metal member was used as a component of a joint structure. The joint structure was also cut by a plane passing through the center of the through hole and perpendicular to the surface of the metal member, and a photograph of its cross-sectional shape was taken.

[0100] A cross-sectional photograph of the through-hole in Example A is shown in Figure 10, and a cross-sectional photograph of the joint structure in Example A is shown in Figure 11. As shown in Figure 10, a very small burr was formed at the end of the through-hole in Example A. However, as shown in Figure 11, the burr in Example A did not penetrate the aluminum member.

[0101] Figure 12 shows a cross-sectional photograph of the through-hole in Example B, and Figure 13 shows a cross-sectional photograph of the joint structure in Example B. As shown in Figure 12, a large burr was formed at the end of the through-hole in Example B. As shown in Figure 13, the burr in Example B penetrated the tip of the projection of the aluminum member.

[0102] Figure 14 shows a cross-sectional photograph of the through-hole in Example C, and Figure 15 shows a cross-sectional photograph of the joint structure in Example C. As shown in Figure 14, a large burr was formed at the end of the through-hole in Example C. As shown in Figure 15, the burr in Example C penetrated into the main body of the aluminum member. [Explanation of Symbols]

[0103] 1 Joined structure 11 Aluminum components 111 Protrusion 1111 Shaft 1112 Tip 1112S Surface of the tip 112 Main body 112S Main body surface 12 Metal components 121 Through hole 1211 Bali section 1212 Darebu 2 Spot welding electrodes 3. Mold C Clearance

Claims

1. Aluminum components and One or more metal components, A joint structure comprising, The aforementioned aluminum member has one or more protrusions, The metal member has one or more through holes, The aforementioned projection is inserted through the through hole and crimped in place. The through hole has a burr portion at its end that protrudes toward the outside of the through hole. The burr portion has penetrated the aluminum member. bonded structure.

2. The aluminum member has a main body portion which is the part of the aluminum member other than the protrusion, The aforementioned burr portion has penetrated the main body. The joint structure according to feature 1.

3. The projection has a tip portion at its end that is larger in diameter than the through hole. The burr portion penetrates the tip portion. The joint structure according to feature 1.

4. The joint structure according to any one of claims 1 to 3, characterized in that the penetration depth of the burr portion is 0.05 mm or more and 1.0 mm or less.

5. The joining structure according to any one of claims 1 to 3, characterized in that the aluminum member is an aluminum die-cast member.

6. The joint structure according to claim 5, characterized in that the projection of the aluminum member is formed during die casting.

7. The joining structure according to any one of claims 1 to 3, characterized in that the metal member comprises a base metal member and a plating layer provided on the surface of the base metal member.

8. The joining structure according to claim 7, characterized in that the base metal member is made of steel.

9. The joining structure according to claim 7, characterized in that the aforementioned plating layer is a zinc-based plating layer or an aluminum-based plating layer.

10. The joining structure according to claim 9, characterized in that the metal member has a coating or chromate-free treatment layer provided on the surface of the zinc-based plating layer or the aluminum-based plating layer.

11. The projection has a tip portion at its end that is larger in diameter than the through hole. The joint structure according to any one of claims 1 to 3, characterized in that the hardness H1 of the tip of the projection and the hardness H2 of the aluminum member at a location 10 mm or more away from the projection satisfy H1 ≤ 1.1 × H2.

12. A method for manufacturing a jointed structure having an aluminum member and one or more metal members, The process of forming a through hole in the metal member, The process of inserting the projection of the aluminum member into the through hole, A step of heating and deforming the tip of the projection to crimp the projection into the through hole, Equipped with, When forming the through hole in the metal member, a burr portion is formed at the end of the through hole, which protrudes outward from the through hole. When crimping the projection into the through hole, the burr portion is inserted into the aluminum member. A method for manufacturing a bonded structure.

13. The aforementioned through-hole is formed by punching using a set of molds. The clearance of one set of the aforementioned molds is set to 10 to 50% of the plate thickness of the base steel member. A method for manufacturing a jointed structure according to claim 12.

14. A method for manufacturing a joined structure according to claim 12 or 13, characterized in that the projection is heated using a spot welding electrode and the tip of the projection is deformed.

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