Dissimilar metal joint and method for manufacturing the same

Abstract

To provide a dissimilar metal joint in which an aluminum alloy plate and a surface-treated steel plate are joined together, where the joint has excellent bonding strength with a simple structure without using multiple sealants or adhesives and can prevent galvanic corrosion at the joint portion.SOLUTION: A dissimilar metal joint 1 includes an aluminum alloy plate 10, a surface-treated steel plate 20, and adhesives 31, 32 that join the two plates. The surface-treated steel plate 20 has: a first main surface region 21b facing the aluminum alloy plate 10 on one principal surface 20b; a second main surface region 21a facing the first main surface region 21b on the other principal surface 20a; and an end-face region 21c connecting the first main surface region 21b and second main surface region 21a. The adhesives 31, 32 are present at least in part between the aluminum alloy plate 10 and the first main surface region 21b of the surface-treated steel plate 20, and cover the entirety of the end-face region 21c.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a dissimilar metal joined body that has a simple structure, is joined with high strength, and is capable of preventing potentiometric corrosion, and to a method for easily producing the dissimilar metal joined body. [Background technology]

[0002] With the worsening of global warming and other issues as a backdrop, there is a constant demand for improved fuel efficiency in transportation equipment, such as automobiles, in order to reduce various factors, including (a) the consumption of petroleum fuel, which is a limited resource; (b) CO2, a greenhouse gas generated by combustion; and (c) driving costs. Effective means of improving fuel efficiency include improving powertrain technologies such as the use of electric drivetrains, as well as reducing the vehicle's weight. There has also long been a demand for improved passenger safety in vehicles, which requires, for example, the development of vehicle bodies that can ensure the necessary strength against collisions.

[0003] One way to reduce vehicle weight is to replace steel, which is currently the primary material, with lightweight materials such as aluminum or aluminum alloys, magnesium or magnesium alloys, and carbon fiber. However, replacing everything with these lightweight materials poses challenges such as high costs and insufficient strength, and as a solution, a so-called multi-material design method that combines steel and lightweight materials in the right places is attracting attention. Hereinafter, aluminum or aluminum alloys may be simply referred to as aluminum alloys.

[0004] It is known that when steel and the above-mentioned lightweight materials are joined together, corrosion called galvanic corrosion occurs at the contact area between the dissimilar metals. For example, when an aluminum alloy material with a low natural potential is brought into contact with a steel material with a high natural potential in water, a corrosion circuit is formed, causing corrosion in the aluminum alloy material. This corrosion circuit is formed by the presence of a medium that allows electricity to flow between the aluminum alloy and the steel, i.e., water.

[0005] One method for preventing such corrosion is to perform a surface treatment on the surface of the steel sheet that comes into contact with the aluminum alloy material. For example, Patent Document 1 proposes a dissimilar metal joint and a method for joining dissimilar metals that are excellent in corrosion resistance and joint strength and are joined by a mechanical joining method that also uses an adhesive. The dissimilar metal joint described in Patent Document 1 includes a zinc-based plated steel sheet, an aluminum alloy sheet, an adhesive layer disposed at least partially between them, and a joint formed by mechanically joining the laminated parts, and the components of the adhesive layer are specified.

[0006] Another method for preventing corrosion is to prevent water from penetrating into the joint. Patent Document 2 discloses a method for joining dissimilar metals that can ensure corrosion resistance using a sealant and prevent a decrease in joint strength due to residual sealant without increasing the weight of the joint or increasing costs due to new capital investment. The method for joining dissimilar metals involves irradiating a high-energy beam onto dissimilar metal materials that are stacked together after applying a sealant made of a thermosetting resin near the joint. Specifically, when irradiating the high-energy beam, a diode laser beam is irradiated directly above the end of the sealant closest to the joint, partially curing the sealant, and then the laser beam is irradiated onto the joint to join the steel plate and the aluminum alloy plate.

[0007] However, even when a surface-treated steel sheet that has been subjected to a surface treatment is used as shown in Patent Document 1, or when a method for preventing moisture from penetrating into the joint is used as shown in Patent Document 2, when joining an aluminum alloy material near the cut surface of the surface-treated steel sheet, the iron base is exposed at the end surface of the steel sheet. Because it is difficult to apply additional surface treatment to the exposed cut surface (processed end surface), a low-strength, watertight adhesive such as a sealant is generally used to protect the cut surface from corrosion.

[0008] For example, Patent Document 3 discloses a structure that improves the hardening speed of the sealant and improves productivity without using new parts or special sealants, and a method of improving water resistance and saltwater corrosion resistance while improving seal strength by changing the application shape of the sealant.

[0009] Furthermore, Patent Document 4 proposes a vehicle understructure that suppresses potential difference corrosion in a vehicle understructure in which a fiber-reinforced resin rear floor pan is joined to a metal frame. Patent Document 4 describes that an adhesive is continuously applied from the inner edge of the upper surface of the frame to the inner end face of the frame and to the inner edge of the lower surface of the frame, preventing the inner end face of the frame, which is difficult to completely apply surface treatments such as rust prevention treatments, from being exposed to the outside. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 6393592 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-39720 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-3682 [Patent Document 4] Japanese Patent Application Publication No. 2018-16109 Summary of the Invention [Problem to be solved by the invention]

[0011] As described above, the joining methods described in Patent Documents 1 and 2 can suppress potential corrosion in the area where the surfaces of dissimilar metals are in contact with each other. However, it is difficult to completely prevent potential corrosion when the end faces of the steel sheets are included in the joint. Furthermore, the structure described in Patent Document 3 has electronic components sealed with a condensation-type silicone sealant, and is not intended for use with strength as its primary purpose, so it is unable to achieve high adhesive strength. Thus, in order to achieve both high strength and corrosion resistance (watertightness) in a joint of dissimilar metals, two types of adhesives as secondary materials must be used, and two application processes are required, which reduces manufacturing efficiency and increases manufacturing costs.

[0012] Furthermore, the vehicle undercarriage structure described in Patent Document 4 uses only one type of adhesive, which is thought to provide corrosion protection. However, while adhesives generally need to be spread very thinly to exert their strength, the structure described in Patent Document 4 requires a large amount of adhesive to be placed between the frame and the rear floor pan, making it impossible to obtain the desired bond strength.

[0013] The present invention has been made in consideration of the above problems, and has an object to provide a dissimilar metal joined body in which an aluminum alloy plate and a surface-treated steel plate are joined, which has a simple structure, excellent joining strength, and is capable of preventing potential difference corrosion at the joint without using multiple sealants or adhesives, and a method for manufacturing the same. [Means for solving the problem]

[0014] The above object of the present invention can be achieved by the following configuration [1] relating to a dissimilar metal bonded body.

[0015] [1] A dissimilar metal joined body comprising an aluminum alloy plate, a surface-treated steel plate arranged on a surface perpendicular to a thickness direction of the aluminum alloy plate, and an adhesive that joins the aluminum alloy plate and the surface-treated steel plate, the surface-treated steel sheet has a pair of main surfaces and end surfaces connecting the pair of main surfaces, and also has a first main surface region on one of the main surfaces facing the aluminum alloy sheet, a second main surface region on the other main surface facing the first main surface region, and an end surface region connecting the first main surface region and the second main surface region, A dissimilar metal joint, characterized in that the adhesive is present in at least a portion between the aluminum alloy plate and the first main surface region of the surface-treated steel plate, and covers the entire end surface region.

[0016] Furthermore, preferred embodiments of the present invention relating to the dissimilar metal bonded body relate to the following [2] to [6].

[0017] [2] The dissimilar metal bonded body according to [1], characterized in that the adhesive contains an epoxy resin.

[0018] [3] The dissimilar metal bonded body according to [1] or [2], characterized in that the adhesive covers a part of the second main surface region continuously from the end surface region.

[0019] [4] The dissimilar metal joined body according to any one of [1] to [3], characterized in that a joining region of the aluminum alloy plate facing the first main surface region of the surface-treated steel plate has a surface shape that conforms to the first main surface region.

[0020] [5] The aluminum alloy plate has a depression that follows the shape of the first main surface region of the surface-treated steel plate, The recess has a bottom surface and a wall portion rising from the bottom surface, The dissimilar metal joint body according to any one of [1] to [4], characterized in that the adhesive is filled between the end face region and the wall portion of the surface-treated steel sheet.

[0021] [6] The dissimilar metal joint body according to [5], characterized in that the depth of the depression is greater than the thickness of the surface-treated steel sheet.

[0022] The above object of the present invention is achieved by the following configuration [7] relating to a method for producing a dissimilar metal bonded body. [7] A method for producing a dissimilar metal bonded body according to any one of [1] to [6], A joining region in the aluminum alloy plate where the surface-treated steel plate is to be joined, and a peripheral portion of the periphery of the joining region are set, an adhesive placement step of placing the adhesive on at least a part of the intended joining region and placing the adhesive on the peripheral portion so that the height of the adhesive placed on the intended joining region is higher than that of the adhesive placed on the intended joining region; A joining process in which the aluminum alloy plate and the surface-treated steel plate are overlapped and joined together so that the intended joining region and the first main surface region face each other, a bonding step of bonding the surface-treated steel plate and the aluminum alloy plate together such that the adhesive applied to the peripheral portion covers the entire end face region of the surface-treated steel plate.

[0023] Furthermore, preferred embodiments of the present invention relating to the method for producing a dissimilar metal bonded body relate to the following [8] to

[11] .

[0024] [8] The method for producing a dissimilar metal joined body according to [7], characterized in that in the joining step, the surface-treated steel plate and the aluminum alloy plate are overlapped so that the adhesive placed on the peripheral portion extends from the end face region and covers a part of the second main surface region.

[0025] [9] The intended joining region of the aluminum alloy plate has a surface shape that follows the first main surface region of the surface-treated steel plate, [7] or [8], characterized in that in the joining step, the region to be joined of the aluminum alloy plate and the first main surface region of the surface-treated steel plate are brought into close contact with each other via the adhesive.

[0026]

[10] A processing step of forming a recess in the aluminum alloy plate that follows the shape of the first main surface region of the surface-treated steel plate, before the adhesive disposing step, In the adhesive applying step, the adhesive is applied to at least a part of the intended joining region inside the recess and to the periphery of the intended joining region; [7] to [9], the method for producing a dissimilar metal joined body, characterized in that in the joining step, the surface-treated steel plate and the aluminum alloy plate are overlapped so that the adhesive is filled between the end face region of the surface-treated steel plate and a wall portion that forms the recess.

[0027]

[11] The method for producing a dissimilar metal joint body according to

[10] , wherein in the processing step, the recess is formed so that the depth of the recess is greater than the plate thickness of the surface-treated steel sheet. [Effects of the Invention]

[0028] According to the present invention, it is possible to provide a dissimilar metal bonded body that has a simple structure, excellent bonding strength, and can prevent potential difference corrosion at the bonded portion without using multiple sealants or adhesives, and a method for manufacturing the same. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a view showing the order of steps in a method for producing a dissimilar metal bonded body according to a first embodiment of the present invention, and is a perspective view showing an aluminum alloy plate. [Figure 2] FIG. 2 is a perspective view showing the step subsequent to that of FIG. 1 in the method for producing a dissimilar metal bonded body according to the first embodiment of the present invention, and showing an adhesive applying step. [Figure 3] FIG. 3 is a perspective view showing a step subsequent to that shown in FIG. 2 in the method for producing a dissimilar metal bonded body according to the first embodiment of the present invention, and showing a bonding step. [Figure 4] FIG. 4 is a perspective view showing a dissimilar metal bonded body produced by the production method according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a cross-sectional view showing a dissimilar metal bonded body produced by the production method according to the first embodiment of the present invention. [Figure 6] FIG. 6 is a perspective view showing an aluminum alloy plate, illustrating the process steps of a method for producing a dissimilar metal bonded body according to a second embodiment of the present invention. [Figure 7] FIG. 7 is a perspective view showing the step subsequent to FIG. 6 in the method for producing a dissimilar metal bonded body according to the second embodiment of the present invention, and showing an adhesive applying step. [Figure 8] FIG. 8 is a perspective view showing a dissimilar metal bonded body produced by the production method according to the second embodiment of the present invention. [Figure 9] FIG. 9 is a cross-sectional view showing a dissimilar metal bonded body produced by the production method according to the second embodiment of the present invention. [Figure 10] FIG. 10 is a top view showing a test material of a dissimilar metal bonded body for a corrosion test. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the embodiment described below, and can be carried out with any modifications within the scope of the gist of the present invention.

[0031] The present inventors have conducted extensive research to obtain a dissimilar metal joined body capable of preventing corrosion due to a potential difference occurring between the processed end surface of a surface-treated steel sheet and an aluminum alloy sheet. As a result, they have found that in order to prevent potential difference corrosion with a simple structure without using two or more types of adhesives, it is effective to configure the processed end surface of the surface-treated steel sheet so that it is covered with an adhesive that joins the surface-treated steel sheet and the aluminum alloy sheet. Hereinafter, a dissimilar metal joined body and a method for manufacturing the same according to this embodiment will be described in detail with reference to the drawings. First, a method for manufacturing a dissimilar metal joined body will be described.

[0032] [First embodiment] <Method of manufacturing dissimilar metal bonded body> 1 to 3 are perspective views showing the order of steps in a method for producing a dissimilar metal bonded body according to a first embodiment of the present invention, Fig. 4 is a perspective view showing a dissimilar metal bonded body produced by the production method according to the first embodiment of the present invention, and Fig. 5 is a cross-sectional view thereof.

[0033] (Adhesive placement process) As shown in Fig. 1 and Fig. 3, an aluminum alloy sheet 10 and a surface-treated steel sheet 20 are prepared. The surface-treated steel sheet 20 has a pair of main surfaces 20a, 20b and an end surface 20c connecting the pair of main surfaces 20a, 20b. Furthermore, a plating layer (not shown in Fig. 3) is formed on the main surfaces 20a, 20b of the surface-treated steel sheet 20 by surface treatment. However, since the steel sheet is processed into a desired shape after surface treatment, no plating layer is formed on the end surface 20c, and the iron base is exposed.

[0034] Next, as shown in Fig. 1, a planned joining region 11, which is a region where the surface-treated steel plate 20 is to be joined, and a region where the end face 20c of the surface-treated steel plate 20 is to be disposed, i.e., a peripheral edge portion 12, which is a region on the periphery of the planned joining region 11, are set on one main surface of the aluminum alloy plate 10. Thereafter, as shown in Fig. 2, an adhesive 31 is placed on at least a part of the planned joining region 11. In addition, an adhesive 32 is placed on all of the peripheral edges 12 of the planned joining region 11 so that the adhesive 32 is higher than the adhesive 31 placed on the planned joining region 11. Note that the adhesives 31 and 32 are made of the same material, and the placement of the adhesives 31 and 32 is performed successively.

[0035] (Joining process) 3, the surface-treated steel plate 20 is joined to the aluminum alloy plate 10. Here, the region of one main surface 20b of the surface-treated steel plate 20 that is to be joined to the aluminum alloy plate 10, i.e., the region facing the planned joining region 11 of the aluminum alloy plate 10, is referred to as a first main surface region 21b. Furthermore, the region of the other main surface 20a of the surface-treated steel plate 20 that faces the first main surface region 21b is referred to as a second main surface region 21a. Furthermore, the region connecting the first main surface region 21b and the second main surface region 21a is referred to as an end surface region 21c.

[0036] In the joining step, the aluminum alloy plate 10 and the surface-treated steel plate 20 are overlapped so that the intended joining region 11 and the first main surface region 21b face each other. At this time, the surface-treated steel plate 20 and the aluminum alloy plate 10 are overlapped so that the adhesive 32 disposed on the peripheral portion 12 of the intended joining region 11 covers all of the end surface regions 21c of the surface-treated steel plate 20, and they are pressed in a direction to bring them closer to each other. This results in a dissimilar metal joined body 1 in which the surface-treated steel plate 20 and the aluminum alloy plate 10 are joined together.

[0037] According to the manufacturing method of the present embodiment, when an adhesive is applied to the surface of the aluminum alloy plate 10, the adhesive 32 is applied to the entire peripheral portion 12 of the intended joining region 11 so that the adhesive 32 is higher than the adhesive 31 applied to the intended joining region 11. By using the same material for the adhesives 32 and 31, the adhesive can be applied continuously to the intended joining region 11 and the peripheral portion 12. Therefore, potentiostatic corrosion can be prevented without the need for a different material for adhesion, such as a sealant, and the efficiency of the work required to prevent potentiostatic corrosion can be improved. Furthermore, since the entire first main surface region 21b and the entire end surface region 21c of the surface-treated steel plate 20 are fixed to the aluminum alloy plate 10 by the adhesive, excellent bonding strength can be obtained.

[0038] Furthermore, in this embodiment, the intended joining region 11 of the aluminum alloy plate 10 has a surface shape that conforms to the first main surface region 21b of the surface-treated steel plate 20, and in the joining step, the intended joining region 11 and the first main surface region 21b can be adhered to each other via a thinly spread adhesive 31. Therefore, the joining strength between the aluminum alloy plate 10 and the surface-treated steel plate 20 can be further improved, and the rigidity of the region joined by the adhesive can be improved.

[0039] When the dissimilar metal bonded body according to this embodiment is applied to transportation equipment such as automobiles, it may be difficult to ensure the strength required for the transportation equipment using only an adhesive. Therefore, it is necessary to fasten the aluminum alloy plate 10 and the surface-treated steel plate 20 using a self-piercing rivet (SPR). In this embodiment, the intended joining region 11 and the first main surface region 21b are both flat and butt-jointed to each other, so they can be fastened together using SPR. Even when fastening them together using SPR, it is important to temporarily fasten them with high strength using an adhesive in areas such as automobile doors where the adhesive may shift when the adhesive hardens. Therefore, this embodiment, which can obtain high joining strength, is an extremely effective method compared to conventional joining methods and structures.

[0040] Furthermore, in this embodiment, in the joining step, the surface-treated steel sheet 20 can be overlapped with the adhesive 32 disposed on the peripheral edge 12 of the intended joining region 11 so as to cover a part of the second principal surface region 21a continuously from the end surface region 21c of the surface-treated steel sheet 20. According to this method, as shown in Figures 4 and 5, the adhesive 32 reaches the second principal surface region 21a by climbing over the corner 21d between the end surface region 21c and the second principal surface region 21a, and an upper surface covering portion 32a is formed.

[0041] The plating layer 22 is not formed on the end surface of the surface-treated steel sheet 20, and depending on the processing conditions of the surface-treated steel sheet 20, the plating layer 22 may peel off or may be prone to peeling even near the corners 21d in the second principal surface region 21a. Therefore, as shown in this embodiment, by forming the upper surface covering portion 32a so that part of the adhesive 32 covers the periphery of the corners 21d, the adhesive 32 can also cover the region where the plating layer 22 is prone to peeling, thereby further preventing corrosion due to potential difference.

[0042] Next, the dissimilar metal bonded body 1 produced by the above-described production method will be described with reference to FIGS.

[0043] <Dissimilar metal joined body> 4 and 5, the dissimilar metal joined body 1 includes an aluminum alloy plate 10, a surface-treated steel plate 20 arranged on a surface perpendicular to the thickness direction of the aluminum alloy plate, and adhesives 31 and 32 that join the aluminum alloy plate 10 and the surface-treated steel plate 20. As described above, the surface-treated steel plate 20 has a pair of main surfaces 20a and 20b and an end surface 20c connecting the main surface 20a and the main surface 20b. The surface-treated steel plate 20 also has a first main surface region 21b that is a region of one main surface 20b facing the aluminum alloy plate 10, a second main surface region 21a that is a region of the other main surface facing the first main surface region 21b, and an end surface region 21c that is a region connecting the first main surface region 21b and the second main surface region 21a. In this embodiment, the adhesive 31 is present in at least a portion between the aluminum alloy plate 10 and the first main surface region 21b of the surface-treated steel plate 20, and the adhesive 32 covers the entire end surface region 21c of the surface-treated steel plate 20. The adhesives 31 and 32 are made of the same material, and in the above-mentioned manufacturing method, the placement of the adhesive 31 and the placement of the adhesive 32 are carried out successively.

[0044] In the dissimilar metal joined body 1 configured as described above, the end surface region 21c of the surface-treated steel plate 20, which has not been subjected to surface treatment, is entirely covered with an adhesive. Therefore, it is possible to prevent a potential difference from occurring between the surface-treated steel plate 20 and the aluminum alloy plate 10, and to suppress the occurrence of corrosion due to the potential difference. Furthermore, the first main surface region 21b of the surface-treated steel plate 20 is bonded to the aluminum alloy plate 10 by the adhesive 31, and the end surface region 21c is bonded to the aluminum alloy plate 10 by the adhesive 32. Therefore, excellent joint strength can be obtained.

[0045] Furthermore, in this embodiment, the high-strength adhesive 31 that bonds the first main surface region 21b of the surface-treated steel plate 20 to the aluminum alloy plate 10 can be used directly to cover the end surface region 21c. Therefore, there is no need to prepare both an adhesive for bonding and a sealant for preventing moisture penetration, which reduces material costs. Furthermore, when both an adhesive and a sealant are used, an applicator for applying the adhesive and an applicator for applying the sealant are required, and each application process is required. In contrast, in this embodiment, only one type of adhesive 31 is used, so that the effects of bonding and corrosion prevention can be achieved with a single applicator, and the number of steps required to manufacture the dissimilar metal joined body 1 can be significantly simplified.

[0046] Furthermore, in this embodiment, the joining region (planned joining region 11) of the aluminum alloy plate 10 facing the first main surface region 21b of the surface-treated steel plate 20 has a surface shape that conforms to the first main surface region 21b. If the joining region and the first main surface region 21b had different surface shapes, the aluminum alloy plate 10 and the surface-treated steel plate 20 would be bonded together by the adhesive 31, but the thickness of the adhesive 31 between the joining region and the first main surface region 21b would be uneven, resulting in a low joining strength. However, in this embodiment, the joining region and the first main surface region 21b are both planar, and the joining region and the first main surface region 21b are in close contact over the entire surfaces thereof via adhesive 31 of approximately the same thickness, thereby achieving a high joining strength.

[0047] 5, in this embodiment, a portion of the adhesive 32 that covers the end surface region 21c of the surface-treated steel sheet 20 continues from the end surface region 21c to cover a portion of the second principal surface region 21a, forming an upper surface covering portion 32a. That is, a portion of the adhesive 32 also covers the vicinity of the corner 21d, including the corner 21d between the end surface region 21c and the second principal surface region 21a. Therefore, since the adhesive 32 and the upper surface covering portion 32a cover the peripheral region of the corner 21d, including the corner 21d, corrosion due to potential differences can be further prevented.

[0048] In the present invention, the top surface covering portion 32a does not necessarily have to be present. However, depending on the state of the plating layer 22 in the second principal surface region 21a, it is preferable that the top surface covering portion 32a be formed in at least a portion near the corner 21d in the second principal surface region 21a, and it is more preferable that the top surface covering portion 32a be formed so as to cover the entire area of ​​the corner 21d.

[0049] The material of the adhesives 31 and 32 is not particularly limited, but adhesives containing a highly extensible urethane resin (including modified urethane resin), acrylic resin, a mixture of a silicone adhesive and a sealant, etc. However, in order to bond the aluminum alloy plate 10 and the surface-treated steel plate 20 with high strength, it is preferable to use an adhesive containing an epoxy resin (including modified epoxy resin).

[0050] [Second embodiment] <Method of manufacturing dissimilar metal bonded body> 6 and 7 are perspective views showing the order of steps in a method for producing a dissimilar metal bonded body according to a second embodiment of the present invention. FIG. 8 is a perspective view showing a dissimilar metal bonded body produced by the production method according to the second embodiment of the present invention, and FIG. 9 is a cross-sectional view thereof. The second embodiment shown in FIGS. 6 to 9 differs from the first embodiment shown in FIGS. 1 to 5 only in the shape of the aluminum alloy plate 10. Therefore, in FIGS. 6 to 9, the same components as those in FIGS. 1 to 5 are designated by the same reference numerals, and detailed description thereof will be omitted or simplified.

[0051] (Processing process) 6, a depression 13 is formed in the aluminum alloy plate 10, the depression 13 following the shape of the first main surface region 21b of the surface-treated steel plate 20. The depression 13 has a bottom surface portion 13a and a wall portion 13b rising from the bottom surface portion 13a, and the size of the bottom surface portion 13a is formed to be larger than the size of the first main surface region 21b.

[0052] (Adhesive placement process) Next, a planned joining region 11, which is a region where the surface-treated steel sheet 20 is to be joined, and a region where the end face 20c of the surface-treated steel sheet 20 is to be disposed, i.e., a peripheral portion 12 of the planned joining region 11, are set on the bottom surface portion 13a. Thereafter, as shown in Fig. 7, adhesive is applied to at least a part of the planned joining region 11 inside the recess 13 and to the peripheral portion 12 of the planned joining region 11, in the same manner as in the first embodiment.

[0053] (Joining process) 7 to 9, the surface-treated steel plate 20 is arranged so as to be inserted into the depression 13 of the aluminum alloy plate 10. In this joining step, the surface-treated steel plate 20 and the aluminum alloy plate 10 are overlapped and pressed in a direction to bring them closer to each other so that the adhesive 32 is filled between the end surface region 21c of the surface-treated steel plate 20 and the wall portion 13b that constitutes the depression 13. Thereafter, the aluminum alloy plate 10 and the surface-treated steel plate 20 are fastened together using, for example, an SPR. As a result, a dissimilar metal joined body 2 in which the surface-treated steel plate 20 and the aluminum alloy plate 10 are joined together is obtained.

[0054] The manufacturing method according to the second embodiment can also achieve the same effects as those of the first embodiment. Furthermore, in the joining process, the wall 13b of the recess 13 can prevent the adhesive 32 from spreading. Therefore, compared to the first embodiment, the entire end surface region 21c can be easily covered with the adhesive 32, and the amount of adhesive 32 used can be reduced. Furthermore, if the adhesive 32 reaches the second principal surface region 21a and forms the upper surface covering portion 32a, corrosion can be further prevented.

[0055] In this embodiment, a processing step of processing the aluminum alloy plate 10 is added to the first embodiment. However, the recess 13 does not have a complex shape and can be processed extremely easily by pressing or the like, so the dissimilar metal joined body 2 can be manufactured without complicating the manufacturing process of the dissimilar metal joined body 2 or increasing the manufacturing cost. Furthermore, in this embodiment, the surface-treated steel plate 20 is arranged so as to be inserted into the recess 13, so that positional deviation does not occur and mutual positioning can be realized extremely easily.

[0056] The depth of the recess 13 is not particularly limited, but if the recess 13 is formed so that its depth is greater than the thickness of the surface-treated steel plate 20, the end surface region 21c can be covered with adhesive 32 even more easily.

[0057] <Dissimilar metal joined body> As shown in Figures 8 and 9, the second embodiment can also achieve the same effects as the first embodiment. In the dissimilar metal joined body 2, the adhesive 32 is filled between the end surface region 21c of the surface-treated steel plate 20 and the wall portion 13b of the recess 13. Therefore, a strong joining force can be obtained between the end surface region 21c and the wall portion 13b. Therefore, in this embodiment, although the adhesive 32 is disposed inside the recess 13, the intended joining region 11 of the aluminum alloy plate 10 and the first main surface region 21b of the surface-treated steel plate 20 are both flat, and they are joined by a thin adhesive 32. Therefore, similar to the first embodiment, excellent joining strength can be obtained. [Example]

[0058] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples and can be practiced with modifications within the scope of the spirit of the present invention, and all such modifications are included in the technical scope of the present invention.

[0059] (Manufacturing of dissimilar metal joints) Fig. 10 is a top view showing a test material of a dissimilar metal joint for a corrosion test. As shown in Fig. 10, an aluminum alloy plate 10 (6022 alloy) having a thickness of 0.8 mm and a surface-treated steel plate 20 (GA: galvannealed steel plate) having a thickness of 1.6 mm were bonded with an adhesive by various methods. Then, the two were mechanically fastened by SPR, and the periphery of a rivet 41 was coated with a sealant 42. The resulting joint was then subjected to cathodic electrodeposition coating (integral electrodeposition coating) as a corrosion prevention measure to produce a test material.

[0060] (Corrosion test) Each of the obtained test materials was subjected to a combined cyclic salt spray test (CCT) in accordance with the automobile standard of the Society of Automotive Engineers of Japan (JASO: Japanese Automobile Standard Organization). The test conditions for the CCT test are shown in Table 1 below. The corrosion test was performed for 200 cycles, with one test cycle shown in Table 1 below, and the test materials were observed after 100 cycles, 150 cycles, and 200 cycles to confirm the presence or absence of corrosion.

[0061] The manufacturing conditions and corrosion test results for each test material are shown in Table 2 below. In Table 2 below, "individual electrodeposition" means that the surface-treated steel sheet 20 was subjected to cathodic electrodeposition coating, and then the joining process was carried out after covering it with an insulating film. Specifically, the following sequence was carried out: individual electrodeposition coating → joining process → fastening by SPR → the above-mentioned integrated electrodeposition coating. Furthermore, "pre-processed" means that the aluminum alloy sheet 10 was processed to form a recess 13 having a shape that conforms to the first main surface region 21b of the surface-treated steel sheet 20, as shown in Figs. 8 and 9.

[0062] [Table 1]

[0063] [Table 2]

[0064] As shown in Table 2 above, in the test materials Nos. 1 and 2, which are examples of the invention, the end surface region 21c of the surface-treated steel sheet 20 is completely covered with the adhesive 32. Therefore, regardless of whether the aluminum alloy sheet 10 was pre-processed or not, no corrosion occurred even after 200 cycles of corrosion testing, demonstrating good corrosion prevention performance.

[0065] On the other hand, in the comparative examples, test materials Nos. 3 and 4, only a portion of the end surface region 21c of the surface-treated steel sheet 20 was covered with the adhesive 32. In other words, the end surface region 21c was not completely covered. Therefore, even though test material No. 3 had been subjected to individual electrodeposition, corrosion occurred after 150 cycles. Furthermore, in test material No. 4, corrosion occurred after 100 cycles. [Explanation of symbols]

[0066] 1,2 Dissimilar metal joints 10. Aluminum alloy plate 11 Planned joining area 12 Periphery 13a Bottom part 13b Wall section 20 Surface-treated steel sheets 20a,20b main surface 20c end face 21a Second principal surface area 21b First principal surface area 21c Edge area 21d Corner 22 plating layer 31,32 Adhesive 32a Upper surface coating 41 Rivet 42 Sealant

Claims

1. A dissimilar metal joined body comprising: an aluminum alloy plate; a surface-treated steel plate arranged on a surface perpendicular to a thickness direction of the aluminum alloy plate; and an adhesive that joins the aluminum alloy plate and the surface-treated steel plate, the surface-treated steel sheet has a pair of main surfaces and end surfaces connecting the pair of main surfaces, and also has a first main surface region on one of the main surfaces facing the aluminum alloy sheet, a second main surface region on the other main surface facing the first main surface region, and an end surface region connecting the first main surface region and the second main surface region, A dissimilar metal joint body, characterized in that the adhesive is present in at least a portion between the aluminum alloy plate and the first main surface region of the surface-treated steel plate, and covers the entire end surface region.

2. 2. The dissimilar metal bonded body according to claim 1, wherein the adhesive contains an epoxy resin.

3. 2. The dissimilar metal joint body according to claim 1, wherein the adhesive covers a part of the second main surface region continuously from the end surface region.

4. 2. The dissimilar metal joint body according to claim 1, wherein a joining region of the aluminum alloy plate facing the first main surface region of the surface-treated steel plate has a surface shape conforming to the first main surface region.

5. the aluminum alloy plate has a depression that follows the shape of the first main surface region of the surface-treated steel plate, The recess has a bottom surface and a wall portion rising from the bottom surface, 2. The dissimilar metal joint body according to claim 1, wherein the adhesive is filled between the end surface region and the wall portion of the surface-treated steel sheet.

6. 6. The dissimilar metal joint body according to claim 5, wherein the depth of the depression is greater than the thickness of the surface-treated steel sheet.

7. The method for producing a dissimilar metal bonded body according to any one of claims 1 to 6, A joining region in the aluminum alloy plate where the surface-treated steel plate is to be joined, and a peripheral portion of the periphery of the joining region are set, an adhesive placement step of placing the adhesive on at least a part of the intended joining region and placing the adhesive on the peripheral portion so that the height of the adhesive placed on the intended joining region is higher than that of the adhesive placed on the intended joining region; A joining process in which the aluminum alloy plate and the surface-treated steel plate are overlapped and joined together so that the intended joining region and the first main surface region face each other, a bonding step of bonding the surface-treated steel plate and the aluminum alloy plate together such that the adhesive applied to the peripheral portion covers the entire end face region of the surface-treated steel plate.

8. 8. The method for manufacturing a dissimilar metal joined body according to claim 7, wherein in the joining step, the surface-treated steel plate and the aluminum alloy plate are overlapped such that the adhesive placed on the peripheral portion extends from the end face region and covers a part of the second main surface region.

9. The intended joining region in the aluminum alloy plate has a surface shape along the first main surface region of the surface-treated steel plate, 8. The method for manufacturing a dissimilar metal joined body according to claim 7, characterized in that, in the joining step, the to-be-joined region of the aluminum alloy plate and the first main surface region of the surface-treated steel plate are brought into close contact with each other via the adhesive.

10. a processing step of forming a recess in the aluminum alloy plate that follows the shape of the first main surface region of the surface-treated steel plate before the adhesive disposing step, In the adhesive applying step, the adhesive is applied to at least a part of the intended joining region inside the recess and to the periphery of the intended joining region; 8. The method for producing a dissimilar metal joined body according to claim 7, wherein in the joining step, the surface-treated steel plate and the aluminum alloy plate are overlapped with each other so that the adhesive is filled between the end face region of the surface-treated steel plate and a wall portion that forms the recess.

11. The method for producing a dissimilar metal joint body according to claim 10, wherein in the processing step, the recess is formed so that the depth of the recess is greater than the thickness of the surface-treated steel sheet.

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