Conjugate and method for producing the same

Abstract

To provide a joined body which can prevent conductive liquid such as water from entering into a joined part between members composed of dissimilar metal materials, and thereby can prevent electric corrosion.SOLUTION: A joined body 10 has a contact surface 35 in which a closed cross-sectional space S1 is formed therein, and a first metal member 21 and a second metal member 31 are brought into contact with each other, and a contact surface 36 where weld metal 61 is brought into contact with any one of the first metal member 21 and the second metal member 31, wherein the weld metal 61 joins the first metal member 21 and the second metal member 31 on the contact surface 35. The closed cross-sectional space S1 is filled with a first seal material 71, thereby a contact surface inner end 52 facing the closed cross-sectional space S1 in the contact surface 35 is blocked from outside the joined body 10. A first outer end 51 facing the outside the joined body 10 in the contact surface 35, and a second outer end 55 facing the outside the joined body 10 in the contact surface 36 are covered with a second seal material 72.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a joined body formed by joining different metal members, and to a joined body capable of preventing galvanic corrosion occurring between different metal members and a method for manufacturing the same.

Background Art

[0002] In recent years, when manufacturing metal structures, a joined body in which different metal members are joined is used for the purpose of ensuring rigidity or reducing weight.

[0003] However, for example, when a conductive liquid such as water enters a contact portion where different metal members are in contact, such as between an aluminum or aluminum alloy material and a steel material, corrosion called galvanic corrosion or electrolytic corrosion occurs, and there is a problem that the strength of the joined body decreases.

[0004] Here, Patent Document 1 proposes a method for joining different metals in which, when overlapping and joining materials made of different metals, welding is performed in a state where a sealing material is disposed around a joining planned site between the two overlapping materials.

[0005] Also, Patent Document 2 describes a method for joining a frame structure body in which a foaming resin is filled between a steel first and second frame and a reinforcing member made of an aluminum alloy to avoid direct contact between the steel and the aluminum alloy. According to Patent Document 2, by adding the strength of the foaming resin, the joint portion can be strengthened and galvanic corrosion can be prevented.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the joining method described in Patent Document 1, it is necessary to arrange a sealing material for each part to be joined or to form a concave or convex portion surrounding the part to be joined. This increases the number of steps before joining and makes the joining process itself complicated. Further, when a sealing material is arranged at the part to be joined, since the sealing material is arranged between dissimilar metal materials, it is difficult to replace the sealing material when it deteriorates.

[0008] Also, according to the joining method of the frame structure described in Patent Document 2, it is possible to prevent direct contact between steel and an aluminum alloy due to the interposition of a foaming resin. However, depending on the shape of the structure, it is necessary to directly join dissimilar metals, and it is difficult to prevent galvanic corrosion in the case where there is a region where dissimilar metals are in contact with each other by the method described in Patent Document 2.

[0009] Taking the above Patent Document 2 as an example, the frame structure will be specifically described below. The frame structure in Patent Document 2 is formed by welding a frame having a U-shaped cross section and a thin plate to form a closed cross-sectional shape. In such a structure, when the metal material constituting the frame is different from the metal material constituting the thin plate, the joining method according to Patent Document 2 cannot prevent the occurrence of galvanic corrosion at the joint between the frame and the thin plate.

[0010] The present invention has been made in view of such problems, and an object thereof is to provide a joined body capable of preventing a conductive liquid such as water from entering the joint between members made of dissimilar metal materials, thereby preventing galvanic corrosion, and a method for manufacturing the same.

Means for Solving the Problems

[0011] (1) A first metal member, A second metal member made of a metal material different from the first metal member, A welding metal that joins the first metal member and the second metal member, A joined body that includes and has a closed cross-sectional space formed inside, At least a part of the closed cross-sectional space is formed by being surrounded by the first metal member and the second metal member, The joined body, A contact surface where the first metal member and the second metal member abut, A contact surface where either one of the first metal member and the second metal member contacts the welding metal, The welding metal joins the first metal member and the second metal member at the contact surface, At least a part of the closed cross-sectional space is filled with a first sealing material, so that the inner end of the contact surface facing the closed cross-sectional space is closed from the outside of the joined body, Among the contact surfaces, a first outer end facing the outside of the joined body is covered with a second sealing material, A joined body, characterized in that a second outer end of the contact surface facing the outside of the joined body is covered with a third sealing material.

[0012] (2) The joined body according to (1), characterized in that the first sealing material contains a foaming resin.

[0013] (3) The joined body according to (1) or (2), characterized in that the closed cross-sectional space is formed by being surrounded by the first metal member and the second metal member.

[0014] (4) The joined body according to any one of (1) to (3), characterized in that the third sealing material is made of the same material as the second sealing material and is formed continuously with the second sealing material.

[0015] (5) A first metal member, A second metal member made of a metal material different from the first metal member, Comprising, with a closed cross-sectional space formed inside, A method for manufacturing a joined body in which at least a part of the closed cross-sectional space is formed by being surrounded by the first metal member and the second metal member, a joining step of bringing the first metal member and the second metal member into contact with each other to form a contact surface, and welding the first metal member and the second metal member on the contact surface to form a weld metal; a first sealing material filling step of filling at least a part of the closed cross-sectional space with a first sealing material to close an inner end portion of the contact surface facing the closed cross-sectional space from the outside of the joined body; a covering step with a second sealing material of covering a first outer end portion of the contact surface facing the outside of the joined body with a second sealing material; a covering step with a third sealing material of covering a second outer end portion of a contact surface where either one of the first metal member and the second metal member contacts the weld metal and faces the outside of the joined body with a third sealing material, the method for manufacturing a joined body being characterized by including these steps.

[0016] (6) The method for manufacturing a joined body according to (5), wherein the third sealing material is made of the same material as the second sealing material, and the covering step with the third sealing material is continuously performed after the covering step with the second sealing material.

[0017] (7) In the joining step, the weld metal is formed by arc welding, The method for manufacturing a joined body according to (5) or (6), further characterized by having an electrodeposition coating step of performing cationic electrodeposition coating on the joined first metal member and second metal member after the joining step.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a joined body and a method for manufacturing the same that can prevent a conductive liquid such as water from entering a joint portion between members made of different metal materials, thereby preventing electrolytic corrosion.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Mode for Carrying Out the Invention

[0020] The present inventor has conducted various studies on a method for preventing electrolytic corrosion of a joined body in which dissimilar metal members are joined, particularly a joined body in which a closed cross-sectional space is formed by dissimilar metal members. As a result, the path through which liquid or the like enters the surface where the dissimilar metals are in contact has been clarified. In particular, it has been found that by filling the closed cross-sectional space with a sealing material such as a foamed resin, the intrusion of liquid from the closed cross-sectional space can be prevented.

[0021] Hereinafter, the joined body and its manufacturing method according to the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the embodiments described below, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

[0022] [Joined Body] (First Embodiment) Figure 1 is a cross-sectional view partially showing a joined body according to the first embodiment of the present invention. As shown in FIG. 1, the joined body 10 includes a flat plate-shaped first metal member 21 and a second metal member 31 made of a metal material different from that of the first metal member 21. The first metal member 21 is made of, for example, an aluminum alloy, and the second metal member 31 is made of, for example, steel. Further, the second metal member 31 has a flat plate portion 32 and a concave portion 34 having a shape recessed from the flat plate portion 32. And in the region surrounding the concave portion 34, the flat plate portion 32 and the first metal member 21 are in contact with each other, and a contact surface 35 where different metal members come into contact with each other is formed.

[0023] In the present embodiment, the first metal member 21 extends laterally more than the flat plate portion 32 of the second metal member 31, and the end face 21a of the first metal member 21 and the end face 31a of the second metal member 31 are arranged at positions shifted from each other.

[0024] A plurality of holes 33 are provided in the flat plate portion 32 of the second metal member 31, and a welding metal 61 made of the same metal material as the first metal member 21 is formed in the holes 33. The welding metal 61 is formed by melting a welding material together with a part of the first metal member 21 exposed by the holes 33, and has a surplus 61a formed with a diameter larger than that of the holes 33 on the upper surface of the second metal member 31. Therefore, the second metal member 31 is physically fixed to the first metal member 21 by the surplus 61a of the welding metal 61, and a joined body 10 in which the first metal member 21 and the second metal member 31 are joined is formed. Further, a closed cross-sectional space S1 surrounded by the concave portion 34 and the first metal member 21 is formed inside the joined body 10. In a state where the welding metal 61 is formed, the welding metal 61 and the second metal member 31 are in contact with each other, and a contact surface 36 where different metals come into contact with each other is formed.

[0025] The closed cross-section space S1 is filled with a first sealing material 71 having a waterproof function. As a result, among the contact surfaces 35, the inner end portion 52 of the contact surface facing the closed cross-section space S1 is blocked from the outside of the joined body 10. Further, a second sealing material 72 is applied so as to cover the boundary portion between the weld metal 61 and the second metal member 31 and the end face 31a of the second metal member 31. As a result, among the contact surfaces 35, the first outer end portion 51 facing the outside of the joined body 10 is covered with the second sealing material 72. Similarly, among the contact surfaces 36 between the weld metal 61 and the second metal member 31, the second outer end portion 55 facing the outside of the joined body 10 is covered with the second sealing material 72.

[0026] Here, the mechanism of galvanic corrosion and the process that led to obtaining a joined body in which the occurrence of galvanic corrosion is prevented will be described in detail below. As described above, when a conductive liquid such as water touches a region where dissimilar metals come into contact, electricity flows from the noble metal to the base metal, and there is a possibility that the base metal is ionized and corrosion due to galvanic corrosion occurs.

[0027] The following two conditions are required for galvanic corrosion. [A] A large potential difference between the contacting metals [B] The presence of a conductive liquid such as water

[0028] Based on the above, galvanic corrosion can be prevented by avoiding at least one of the two conditions [A] and [B]. Therefore, as methods for preventing galvanic corrosion due to contact between dissimilar metals as described above, the methods [1] to [4] shown below can be cited. [1] A method of preventing water or the like from adhering to the contact surface between metals [2] A method of eliminating the potential difference between metals. That is, a method of using metals having the same potential difference or a small potential difference [3] A method of blocking the current path. That is, a method of insulating the contact surface of the metal [4] A method of preventing direct contact between metals

[0029] In this embodiment, electrolytic corrosion is prevented by satisfying the conditions of [1] above. In the joined body 10 according to this embodiment, the paths through which conductive liquids such as water can penetrate into the contact surface 35 and the contact surface 36 where different materials are in contact or touching will be specifically described.

[0030] (First penetration path) Penetration from the inner end 52 of the contact surface facing the closed cross-sectional space S1 among the contact surfaces 35 where the first metal member 21 and the second metal member 31 are in contact.

[0031] (Second penetration path) Penetration from the first outer end 51 facing the outside of the joined body 10 among the contact surfaces 35 where the first metal member 21 and the second metal member 31 are in contact.

[0032] (Third penetration path) Penetration from the second outer end 55 facing the outside of the joined body 10 among the contact surfaces 36 where the welding metal 61 and the second metal member 31 are in contact.

[0033] In this embodiment, in order to prevent the penetration of liquid from the first penetration path, the closed cross-sectional space S1 surrounded by the recess 34 of the first metal member 21 and the second metal member 31 is filled with a first sealing material 71 having a waterproof function. Further, in order to prevent the penetration of liquid from the second penetration path and the third penetration path, a second sealing material 72 is applied so as to entirely cover the boundary portion between the welding metal 61 and the second metal member 31 and the end face 31a of the second metal member 31.

[0034] As a result, in the joined body 10, it is possible to effectively prevent the liquid from penetrating into the contact surface 35 from the inner end 52 of the contact surface, and it is also possible to prevent the liquid from penetrating into the contact surface 35 from the first outer end 51 and the liquid from penetrating into the contact surface 36 from the second outer end 55. As a result, the occurrence of electrolytic corrosion can be prevented, and the desired strength can be maintained.

[0035] In addition, in the present embodiment, the weld metal 61 and the first metal member 21 are firmly joined by welding between the same type of metals, and the flat plate portion 32 of the second metal member 31 is physically fixed to the first metal member 21 by the excess 61a of the weld metal 61. Therefore, the first metal member 21 and the flat plate portion 32 can be firmly joined to each other despite being different types of metals.

[0036] In the present embodiment, the hole 33 is formed in the second metal member 31 and the weld metal 61 that fills the hole 33 is formed. However, a hole may be formed in the first metal member 21 and a weld metal made of the same type of metal material as the second metal member 31 may be formed. In that case, a contact surface where different types of metals come into contact is formed between the first metal member 21 and the weld metal 61.

[0037] Furthermore, in the present embodiment, the entire closed cross-sectional space S1 is filled with the first sealing material 71, and since the volume of the first sealing material 71 is large, the effect of preventing liquid from entering the contact surface 35 from the open end of the closed cross-sectional space S1 is significantly enhanced. Also, regarding the first outer end portion 51 that faces the outside of the joined body 10 among the contact surfaces 35 and the second outer end portion 55 that faces the outside of the joined body 10 among the contact surfaces 36, since both face the outside, the second sealing material 72 can be easily added or replaced.

[0038] As the second sealing material 72 that entirely covers the end face 31a (the second intrusion path) of the second metal member 31 and the boundary portion (the third intrusion path) between the weld metal 61 and the second metal member 31, it is preferable to use a liquid sealing material such as a silicone-based or urethane-based material. Examples of the method of covering the desired region with the second sealing material 72 include application and the use of a spray. Alternatively, a sealing material having flexibility that can follow the shape of the region to be covered may be pasted.

[0039] In this embodiment, the shape of the recess 34 of the second metal member 31 is not particularly limited. For example, it may have a shape extending in one direction, or may be formed in a T-shape, cross-shape, rectangular shape, etc. according to the purpose. Since the recess 34 may be formed in various shapes, the contact surface 35 between the first metal member 21 and the flat plate portion 32 of the second metal member 31 has a wide range, and the closed cross-sectional space S1 may have a complex shape. Therefore, as the first sealing material 71 that covers the inner end portion 52 of the contact surface (the first intrusion path) facing the closed cross-sectional space S1 among the contact surfaces 35, it is preferable to use the first sealing material 71 containing a foamed resin from the viewpoint of workability. As the first sealing material 71 containing a foamed resin, it is preferable to use a foamed urethane resin, a foamed styrene resin, a foamed olefin resin, etc.

[0040] Conventionally, such foamed resins have sometimes been used for improving strength, preventing noise, and preventing vibration, but there have been no examples of using them for preventing the intrusion of liquids such as water. In this embodiment, by filling the closed cross-sectional space S1, where it is particularly difficult to prevent the intrusion of liquids, with a foamed resin, the inner end portion 52 of the contact surface, which is the first intrusion path, can be more effectively blocked, and furthermore, an additional electrolytic corrosion prevention effect can be obtained.

[0041] In the present invention, only a part of the closed cross-sectional space S1 may be filled with the first sealing material 71, and it is only necessary that the inner end portion 52 of the contact surface facing the closed cross-sectional space S1 among the contact surfaces 35 is blocked from the outside of the joined body 10. For example, even if the first sealing material 71 is filled only at the open end portion of the closed cross-sectional space S1, it is possible to prevent the intrusion of liquid from the inner end portion 52 side of the contact surface facing the closed cross-sectional space S1 to the contact surface 35. In such a state, if the first sealing material 71 deteriorates, by adding the first sealing material 71 to the closed cross-sectional space S1, the effect of easily preventing the intrusion of liquid can be improved.

[0042] In addition, in the present embodiment, the second immersion path and the third immersion path are covered in one step by the second sealing material 72, and the continuous second sealing material 72 is formed. However, the present invention is not limited to this. For example, when the location where the weld metal 61 is formed and the first outer end portion 51 are separated, or when the flat plate portion 32 of the second metal member 31 extends more laterally than the first metal member 21. In such a case, the boundary portion between the weld metal 61 and the second metal member 31 may be covered by the second sealing material, and the end face 31a of the second metal member 31 may be covered by the third sealing material. Also, the second sealing material and the third sealing material may be made of different materials from each other.

[0043] The joined body 10 shown in FIG. 1 is an example of a joined body in which a closed cross-sectional space S1 is formed inside. A part of the joined body 10 is shown in a cross-sectional view. However, in the present invention, the shape of the joined body is not particularly limited. Hereinafter, other examples of the shape of the joined body will be described below with reference to FIGS. 2 and 3. Note that the differences between the second embodiment shown in FIG. 2 and the third embodiment shown in FIG. 3 from the first embodiment are only the shape of the joined body. Therefore, in FIGS. 2 and 3, the same reference numerals are given to the same components as in FIG. 1, and detailed descriptions are omitted or simplified.

[0044] (Second Embodiment) FIG. 2 is a cross-sectional view showing a joined body according to the second embodiment of the present invention. As shown in FIG. 2, the joined body 20 is formed by joining a first metal member 22 made of an aluminum alloy having a hat-shaped cross section and a second metal member 25 made of steel having a hat-shaped cross section. That is, the first metal member 22 has a recess 23 extending in one direction and flat plate portions 24 provided on both sides of the recess 23. Similarly, the second metal member 25 has a recess 26 extending in one direction and flat plate portions 32 provided on both sides of the recess 23.

[0045] The flat plate portion 24 of the first metal member 22 extends laterally beyond the flat plate portion 32 of the second metal member 25. Further, a hole 33 is formed in the flat plate portion 32 of the second metal member 25, and the hole 33 is filled with welding metal 61, and a surplus 61a having a diameter larger than that of the hole 33 is formed. Then, the flat plate portion 32 of the second metal member 25 is sandwiched between the surplus 61a of the welding metal 61 and the flat plate portion 24 of the first metal member 22, whereby the flat plate portion 24 of the first metal member 22 and the flat plate portion 32 of the second metal member 25 are joined together.

[0046] By joining the flat plate portion 24 of the first metal member 22 and the flat plate portion 32 of the second metal member 25, a closed cross-section space S1 is formed between the recess 23 and the recess 26. The closed cross-section space S1 is filled with a first sealing material 71, whereby, of the contact surface 35 where the first metal member 22 and the second metal member 25 are in contact, the inner end portion 52 of the contact surface facing the closed cross-section space S1 is blocked from the outside of the joined body.

[0047] Also, of the contact surface 35, a first outer end portion 51 facing the outside of the joined body 20, and of the contact surface 36 between the welding metal 61 and the second metal member 31, a second outer end portion 55 facing the outside of the joined body 20 are covered with a second sealing material 72.

[0048] Also in the joined body 20 according to the second embodiment configured as described above, it is possible to prevent the intrusion of liquid from the inner end portion 52 of the contact surface and the first outer end portion 51 into the contact surface 35, and it is possible to prevent the intrusion of liquid from the second outer end portion 55 into the contact surface 36. Therefore, the occurrence of electrolytic corrosion is prevented and the desired strength can be maintained.

[0049] (Third Embodiment) FIG. 3 is a cross-sectional view showing a joined body according to the third embodiment of the present invention. As shown in FIG. 3, the joined body 30 is formed by combining and joining a first metal member 21 made of an aluminum alloy in a flat plate shape, a second metal member 27 made of steel in a curved shape, and a third metal member 28 having the same shape as the second metal member 27. The second metal member 27 is bent so that the opposing end faces of the flat plate-shaped plate material are orthogonal to each other, and is composed of flat plate portions 27a, 27b and a curved portion 27c formed by the bending. Similarly, the third metal member 28 is bent so that the opposing end faces of the flat plate-shaped plate material are orthogonal to each other, and is composed of flat plate portions 28a, 28b and a curved portion 28c formed by the bending.

[0050] The second metal member 27 and the third metal member 28 are arranged such that the flat plate portion 27a and the flat plate portion 28a overlap each other, and the two are joined by a joint portion (not shown). Holes 37 and 38 are formed in the flat plate portion 27b of the second metal member 27 and the flat plate portion 28b of the third metal member 28, respectively. The holes 37 and 38 are filled with welding metal 61, and a surplus 61a having a diameter larger than that of the hole 33 is formed. Thereby, the flat plate portion 27b of the second metal member 27 and the flat plate portion 28b of the third metal member 28 are joined to the first metal member 21. Note that the flat plate portion 27b of the second metal member 27 and the flat plate portion 28b of the third metal member 28 extend laterally from the end face of the first metal member 21.

[0051] In this embodiment, a joined body 30 is formed by joining a first metal member 21, a second metal member 27, and a third metal member 28. Further, a closed cross-sectional space S1 is formed, which is surrounded by the first metal member 21, the protruding surface 27d of the second metal member 27, and the protruding surface 28d of the third metal member 28. In other words, at least a part of the closed cross-sectional space S1 is configured by being surrounded by the first metal member 21 and the second metal member 27 made of different metal materials. Then, the first sealing material 71 is filled in the closed cross-sectional space S1, so that the inner end portion 52 of the contact surface facing the closed cross-sectional space S1 among the contact surfaces 35 is blocked from the outside of the joined body 30.

[0052] Also, in this embodiment, among the contact surfaces 35, a first outer end portion 51 facing the outside of the joined body 30 is formed on a surface of the joined body 30 opposite to the surface on which the weld metal 61 is formed. Therefore, the first outer end portion 51 is covered with a second sealing material 72, and the second outer end portion 55 is covered with a third sealing material 73.

[0053] Also in the joined body 30 according to the third embodiment configured as described above, it is possible to prevent the intrusion of liquid from the first to third intrusion paths into the contact surface 35 and the contact surface 36, so the occurrence of electrolytic corrosion is prevented and the desired strength can be maintained. In this embodiment, the second metal member 27 and the third metal member 28 are made of the same material. However, for example, the third metal member 28 may be made of a material different from both the first metal member 21 and the second metal member 27. Also, the second sealing material 72 and the third sealing material 73 may be made of the same material or different materials from each other.

[0054] Next, a method for manufacturing a joined body according to an embodiment of the present invention will be described by taking the joined body 10 according to the first embodiment as an example. In FIGS. 4A to 4D, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed descriptions are omitted or simplified.

[0055] [Method for manufacturing a joined body] Figures 4A to 4D are cross-sectional views showing a method for manufacturing a joined body according to an embodiment of the present invention. Figure 4A represents the joining step (step 1), Figure 4B represents the electrodeposition coating step (step 2), Figure 4C represents the covering step with a second sealing material (step 3), and Figure 4D represents the filling step of the first sealing material (step 4).

[0056] (Step 1: Joining Step) First, as shown in Figure 4A, a second metal member 31 with a recess 34 facing the first metal member 21 is placed on a flat first metal member 21, and the flat portion 32 of the second metal member 31 is brought into contact with the first metal member 21. Next, a welding wire 65 is melted by arc spot welding to form a welding metal 61 that fills a plurality of holes 33, and by further continuing the welding, a surplus 61a (see Figure 4B) having a diameter larger than that of the holes 33 is formed on the upper surface of the flat portion 32. Thereby, the first metal member 21 and the flat portion 32 of the second metal member 31 are joined together.

[0057] (Step 2: Electrodeposition Coating Step) Thereafter, as shown in Figure 4B, a joined body 40 in which the first metal member 21 and the second metal member 31 are joined by a welding metal 61 is immersed in a tank in which a water-soluble paint is dissolved, and a cationic electrodeposition coating material is applied by electrodeposition, and then baked and cured to form a cationic electrodeposition coating film 67.

[0058] (Step 3: Covering Step with a Second Sealing Material) Thereafter, as shown in Figure 4C, a second sealing material 72 is applied to a first outer end portion 51 that faces the outside of the joined body 40 among the contact surfaces 35 between the first metal member 21 and the second metal member 31, and a second outer end portion 55 that faces the outside of the joined body 40 among the contact surfaces 36 between the welding metal 61 and the second metal member 31 to cover the first outer end portion 51 and the second outer end portion 55.

[0059] (Step 4: Filling Step of the First Sealing Material) Thereafter, as shown in Figure 4D, a first sealing material 71 containing a foaming resin having a waterproof function is filled into a closed cross-sectional space S1 surrounded by the recess 23 of the second metal member 31 and the first metal member 21.

[0060] According to the method for manufacturing a joined body according to this embodiment, by the coating step using the second sealing material, it is possible to effectively prevent the intrusion of liquid from the second intrusion path to the contact surface 35 and the intrusion of liquid from the third intrusion path to the contact surface 36. Further, by the filling step of the first sealing material, it is possible to effectively prevent the intrusion of liquid from the first intrusion path to the contact surface 35. Therefore, the occurrence of electrolytic corrosion can be prevented, and a joined body that can maintain a desired strength can be manufactured.

[0061] Also, in this embodiment, it is not necessary to previously arrange a sealing material or the like at the welding planned position or to perform uneven shape processing on the members before joining, and a joined body having excellent corrosion resistance can be manufactured extremely easily.

[0062] Furthermore, in this embodiment, after joining the first metal member 21 and the second metal member 31 by arc welding to form the weld metal 61, a cationic electrodeposition coating film 67 is formed. In this way, by forming the cationic electrodeposition coating film 67 on the surfaces of the first metal member 21 and the second metal member 31, the corrosion resistance of the surface of the joined body 10 can be improved. However, as shown in this embodiment, when arc welding is used as the method for forming the weld metal 61, if the electrodeposition coating step is performed before the joining step, the cationic electrodeposition coating film 67 in the region around where the weld metal 61 is formed may volatilize due to the arc heat, and there is a possibility of occurrence of poor welding. Therefore, when joining the first metal member 21 and the second metal member 31 by arc welding, it is preferable to perform the electrodeposition coating step after the joining step.

[0063] However, in the present embodiment, the method for joining the first metal member and the second metal member made of different materials is not particularly limited as long as it is a joining method capable of obtaining a desired strength. Examples of joining methods applicable to joining members made of different materials include, for example, bolt and nut, blind rivet, punch rivet, self-piercing riveting (SPR), mechanical clinching, FDS (Flow Drilling Screw, a registered trademark of EJOT GmbH&Co.KG), ImpAcT (Impulse Accelerated Tacking), REW (Resistance Element Welding), and joining methods using friction element welding (FEW), etc.

[0064] Note that the order of the electrocoating process, the application process of the first sealing material, and the application process of the second sealing material can be appropriately changed depending on the baking temperature after applying the cationic electrocoating paint and the type of the sealing material. Also, the order of the application process of the first sealing material and the application process of the second sealing material is not particularly limited. Furthermore, as shown in the above-described third embodiment, when the process of covering the first outer end portion 51 with the second sealing material and the process of covering the second outer end portion 55 with the third sealing material are carried out separately, the order thereof is also not particularly limited.

Explanation of Reference Numerals

[0065] 10, 20, 30 Joined body 21, 22 First metal member 23, 26, 34 Recessed portion 24, 27a, 27b, 28a, 28b, 32 Flat plate portion 25, 27, 31 Second metal member 28 Third metal member 33, 37, 38 Hole 35 Contact surface 36 Contact face 51 First outer end portion 52 Inner end portion of the contact surface 55 Second outer end portion 61 Weld metal 65 Welding wire 67 Cationic electrodeposition coating film 71 First sealing material 72 Second sealing material 73 Third sealing material S1 Closed cross-section space

Claims

1. a first metal member; a second metal member made of a metal material different from that of the first metal member; a welding metal for joining the first metal member and the second metal member; A joined body having a closed cross-sectional space formed therein, at least a part of the closed cross-sectional space is formed by being surrounded by the first metal member and the second metal member, the joined body, a contact surface where the first metal member and the second metal member abut; a contact surface where either one of the first metal member and the second metal member contacts the welding metal; and having, the welding metal joins the first metal member and the second metal member at the contact surface, at least a part of the closed cross-sectional space is filled with a first sealing material, so that the inner end portion of the contact surface facing the closed cross-sectional space is closed from the outside of the joined body, a first outer end portion of the contact surface facing the outside of the joined body is covered with a second sealing material, A joined body, wherein a second outer end portion of the contact surface facing the outside of the joined body is covered with a third sealing material.

2. The joined body according to claim 1, wherein the first sealing material contains a foaming resin.

3. The joined body according to claim 1 or 2, wherein the closed cross-sectional space is formed by being surrounded by the first metal member and the second metal member.

4. The joined body according to claim 1 or 2, wherein the third sealing material is made of the same material as the second sealing material and is formed continuously with the second sealing material.

5. a first metal member; a second metal member made of a metal material different from that of the first metal member; A manufacturing method of a joined body having a closed cross-sectional space formed therein, and at least a part of the closed cross-sectional space is formed by being surrounded by the first metal member and the second metal member, a joining step of bringing the first metal member and the second metal member into contact with each other to form a contact surface, and welding the first metal member and the second metal member at the contact surface to form a welding metal; a filling step of the first sealing material, wherein at least a part of the closed cross-sectional space is filled with the first sealing material to close the inner end portion of the contact surface facing the closed cross-sectional space from the outside of the joined body; ​ A covering step with a second sealing material, which covers a first outer end portion facing the outside of the joined body among the contact surfaces, with the second sealing material; A covering step with a third sealing material, which covers a second outer end portion facing the outside of the joined body among contact surfaces where either one of the first metal member and the second metal member contacts the weld metal, with the third sealing material, wherein the method for manufacturing a joined body is characterized by including these steps. **Claim 6** The method for manufacturing a joined body according to claim 5, wherein the third sealing material is made of the same material as the second sealing material, and the covering step with the third sealing material is continuously performed after the covering step with the second sealing material. **Claim 7** In the joining step, the weld metal is formed by arc welding. The method for manufacturing a joined body according to claim 5 or 6, further comprising an electrodeposition coating step of performing cationic electrodeposition coating on the joined first metal member and second metal member after the joining step.

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