Joint structure, and manufacturing method of the joint structure

Abstract

The present invention provides a joint structure comprising aluminum members, which can be manufactured using general-purpose equipment, is inexpensive, can be manufactured quickly, and does not cause cracking due to thermal distortion, and a method for manufacturing the same. [Solution] A joint structure according to one aspect of the present disclosure comprises an aluminum member and one or more metal members, the metal member having one or more through holes, the aluminum member having one or more projections inserted through the through holes, the projections having an outer peripheral portion at their tip that extends outside the through hole beyond the edge of the through hole, at least the outer peripheral portion of the projection is a molten and solidified portion, the chemical composition of the molten and solidified portion differs from that of the non-molten portion of the aluminum member, the distribution of the chemical composition of the molten and solidified portion is non-uniform near the boundary between the molten and solidified portion and the non-molten portion of the aluminum member, and part or all of the non-molten portion of the aluminum member is inside the through hole.

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 a molten aluminum alloy into a mold at high pressure and then cooling the aluminum alloy at high speed, or the casting method thereof. Aluminum die-casting is used, for example, as a material for the front shock tower, rear shock tower, and subframe of an automobile.

[0003] In addition, in recent years, a manufacturing technology called gigacasting has been developed. Gigacasting is a technology for manufacturing a huge part 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 3 disclose various methods for joining an aluminum die-casting member and another member.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

[0006] One method for joining aluminum components to other components is adhesive. However, bonding aluminum components to other components requires a curing process. Until the adhesive hardens, the components to be joined must be held in a temporary state. Therefore, bonding aluminum components requires auxiliary materials such as self-piercing rivets, bolts, and FDS. The use of auxiliary materials increases the manufacturing cost and weight of the mechanical structural components. Furthermore, using auxiliary materials may require specialized joining equipment.

[0007] Another example of a method for joining aluminum components to other components is riveting. Examples of riveting include SPR (self-piercing rivets) and FDS (registered trademark) (flow drilling screws). However, aluminum components have low elongation. When riveting is applied to aluminum components, cracks are likely to occur in the aluminum components.

[0008] Furthermore, welding is difficult to use as a means of joining aluminum components to other components. For example, when an aluminum die-cast component is welded to steel, brittle intermetallic compounds are formed in the weld metal. These brittle intermetallic compounds significantly reduce the joint strength of the weld.

[0009] In the technology described in Patent Document 1, an iron-based material and an aluminum-based material are joined by filling a space provided in the iron-based material with aluminum welding material. Similar technologies are disclosed in Patent Documents 2 to 4. However, these technologies have the problem of large thermal distortion at the joint.

[0010] In view of the above circumstances, this disclosure provides a joint structure comprising an aluminum member, which can be manufactured using general-purpose equipment, is inexpensive and quick to manufacture, and does not cause cracking due to thermal distortion, and a method for manufacturing the same. [Means for solving the problem]

[0011] The gist of this disclosure is as follows:

[0012] (1) A joint structure according to one aspect of the present disclosure comprises an aluminum member and one or more metal members, the metal member having one or more through holes, the aluminum member having one or more projections inserted through the through holes, the projections having an outer peripheral portion at their tip that extends outward from the edge of the through hole, and at least the outer peripheral portion of the projection is a molten and solidified portion, the chemical composition of the molten and solidified portion is different from that of the non-molten portion of the aluminum member. (2) Preferably, in the joint structure described in (1) above, a part of the aluminum member is the molten and solidified portion. (3) Preferably, in the joint structure described in (1) or (2) above, part or all of the non-melted portion of the aluminum member is located inside the through hole. (4) Preferably, in the joint structure described in any one of the above items (1) to (3), the aluminum member is an aluminum die-cast member. (5) Preferably, in the joint structure described in (4) above, the non-molten portion of the projection is formed during die casting. (6) Preferably, in the joint structure described in any one of the above items (1) to (5), the portion of the metal member that is in contact with the projection is a non-molten portion. (7) Preferably, in the joint structure described in any one of the above items (1) to (6), the metal member is plated steel. (8) Preferably, in the joint structure described in (7) above, the plated steel material is an aluminum-plated steel material or a zinc-plated steel material. (9) Preferably, in the joint structure described in any one of the above items (1) to (8), the material of the metal member is an aluminum alloy. (10) Preferably, in the joint structure described in any one of the above items (1) to (9), the through hole has a tapered shape in which the cross-sectional area increases from the base end to the tip of the projection.

[0013] (11) 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, wherein the aluminum member has one or more protruding base material portions, and the metal members have one or more through holes, and the manufacturing method comprises the steps of inserting the protruding base material portion into the through hole, and melting the tip of the protruding base material portion, wherein when melting the tip of the protruding base material portion, a filler material is supplied to the molten pool, and when melting the tip of the protruding base material portion, a part or all of the protruding base material portion is kept solid at the base end of the protruding base material portion. (12) Preferably, in the method for manufacturing the joint structure described in (11) above, the length of the projection base material portion is 0.2 to 5.0 times the depth of the through hole. (13) Preferably, in the method for manufacturing the joint structure described in (11) or (12) above, the projection base material portion has a tapered shape in which the cross-sectional area decreases from the base end to the tip of the projection base material portion. (14) Preferably, in the method for manufacturing a joint structure described in any one of the above items (11) to (13), the through hole has a tapered shape in which the cross-sectional area increases from the first end to the second end, and when inserting the projection base material portion through the through hole, the first end of the through hole is positioned on the side of the base end of the projection base material portion, and the second end of the through hole is positioned on the side of the tip of the projection base material portion. (15) Preferably, in the method for manufacturing the joining structure according to any one of (11) to (14) above, the protruding base material portion has a tapered shape in which the cross-sectional area decreases from the base end to the tip of the protruding base material portion, the through-hole has a tapered shape in which the cross-sectional area increases from the first end to the second end, and when inserting the protruding base material portion into the through-hole, the first end of the through-hole is arranged on the side of the base end of the protruding base material portion, and the second end of the through-hole is arranged on the side of the tip of the protruding base material portion.

Effect of the Invention

[0014] According to the present disclosure, it is possible to provide a joining structure including an aluminum member that can be manufactured by general-purpose equipment, is inexpensive and can be manufactured in a short time without causing cracks due to thermal distortion, and a method for manufacturing the same.

Brief Description of the Drawings

[0015] [Figure 1] It is a schematic cross-sectional view of an example of the joining structure. [Figure 2] It is a schematic cross-sectional view of another example of the joining structure. [Figure 3] It is a schematic cross-sectional view of an example of a joining structure in which a part of the aluminum member is not a melted and solidified portion. [Figure 4] It is a schematic cross-sectional view of an example of a joining structure in which the non-melted portion of the aluminum member is not inside the through-hole. [Figure 5] It is a schematic cross-sectional view of an example of a joining structure in which the through-hole has a tapered shape. [Figure 6] It is a schematic view of the step of inserting the protruding base material portion into the through-hole. [Figure 7] It is a schematic view of the step of melting the protruding base material portion. [Figure 8] It is a schematic view of the joining structure after completion of melting of the protruding base material portion. [Figure 9] It is a schematic cross-sectional view of an example of a through-hole and a protruding base material portion having a tapered shape. [Figure 10] It is a cross-sectional photograph of Example No. 1 of the joining structure. [Figure 11]This is a cross-sectional photograph of example No. 2 of the joint structure. [Figure 12] This is a cross-sectional photograph of example No. 3 of the joint structure. [Modes for carrying out the invention]

[0016] (1.Joint structure) A joint structure 1 according to one aspect of the present disclosure comprises an aluminum member 11 and one or more metal members 12, wherein the metal member 12 is provided with one or more through holes 121, and the aluminum member 11 has one or more projections 111 inserted through the through holes 121, the projections 111 having an outer peripheral portion 1112 at their tip that protrudes outside the through holes 121 beyond the edge of the through holes 121, and at least the outer peripheral portion 1112 of the projections 111 is a molten and solidified portion 11M, the chemical composition of the molten and solidified portion 11M is different from that of the non-molten portion 11B of the aluminum member 11. The details of the joint structure 1 according to this embodiment will be described below with reference to Figures 1 and 2, etc.

[0017] (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.

[0018] 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, and subframes of automobiles. Components that constitute 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.

[0019] (Metal member 12) The jointed structure 1 further includes a metal member 12. The metal member 12 is a mechanical structural member made from metal. Various shapes can be applied to the metal member 12 depending on its application. A suitable example of the material for the metal member 12 is plated steel sheet. Specific examples of the metals that make up the metal member 12 will be described later.

[0020] (Protrusion 111 and through hole 121) The metal member 12 has one or more through holes 121. The aluminum member 11 has one or more protrusions 111. The protrusions 111 of the aluminum member 11 are inserted through the through holes 121 of the metal member 12. The part of the aluminum member 11 other than the protrusions 111 is referred to as the main body 112.

[0021] (Outer periphery 1112) The projection 111 has an outer circumference 1112 at its tip. The outer circumference 1112 is the portion of the projection 111 that extends beyond the edge of the through hole 121. When the through hole 121 has a tapered shape as shown in Figure 5, the edge of the through hole 121 is the edge of the narrowest part of the through hole 121. Figures 1, 2, and 5 show a dashed line along the edge of the through hole 121. The portion of the projection 111 that is outside the dashed line is the outer circumference 1112. The portion of the projection 111 other than the outer circumference 1112 is called the central part 1111. In Figures 1, 2, and 5, the portion of the projection 111 that is inside the dashed line is the central part 1111.

[0022] The outer periphery 1112 prevents the projection 111 of the aluminum member 11 from falling out of the through hole 121 of the metal member 12. The metal member 12 is sandwiched between the outer periphery 1112 of the projection 111 and the main body 112 of the aluminum member 11. The outer periphery 1112 joins the aluminum member 11 and the metal member 12.

[0023] (The molten and solidified portion 11M and the non-molten portion 11B of the projection 111) The projection 111 is divided into a molten and solidified portion 11M and a non-molten portion 11B based on its metallurgical structure. The molten and solidified portion 11M is the part that melted and solidified during the joining process of the aluminum member 11 and the metal member 12. The non-molten portion 11B is the part that did not melt during the joining process of the aluminum member 11 and the metal member 12. The boundary between the molten and solidified portion 11M and the non-molten portion 11B of the aluminum member 11 is called the molten boundary 11FL.

[0024] The term "melting" in the terms "molten and solidified portion 11M" and "non-molten portion 11B" refers to the melting that occurs during the joining process of the aluminum member 11 and the metal member 12. Whether or not melting occurs during operations other than the joining process is not considered when identifying the molten and solidified portion 11M and the non-molten portion 11B. For example, if the aluminum member 11 is an aluminum die-cast member, the aluminum member 11 melts and solidifies throughout its entirety during die casting. However, the fact that melting and solidification occurred during die casting is not considered when identifying the molten and solidified portion 11M and the non-molten portion 11B in this embodiment.

[0025] As illustrated in Figures 10, 11, and 12, the molten and solidified portion 11M and the non-molten portion 11B can be easily distinguished by etching the cross-section of the joint structure 1. Furthermore, as will be described later, the composition of the molten and solidified portion 11M differs from that of the non-molten portion 11B. Details of the cross-sectional photographs in Figures 10 to 12 will be described later.

[0026] In the projection 111, at least the outer periphery 1112 is a molten and solidified portion 11M. The portion of the projection 111 other than the outer periphery 1112 may be either a molten and solidified portion 11M or a non-molten portion 11B. For example, in the joint structure 1 illustrated in Figure 1, most of the projection 111 is a molten and solidified portion 11M. Specifically, the entire surface of the projection 111 is covered by the molten and solidified portion 11M. Furthermore, the molten and solidified portion 11M extends into the interior of the through hole 121. On the other hand, in the joint structure 1 illustrated in Figure 2, almost the entire area other than the outer periphery 1112 is not a molten and solidified portion 11M. Both configurations are acceptable in the joint structure 1 according to this embodiment.

[0027] The entire projection 111 may be a molten and solidified portion 11M. On the other hand, it is preferable that a part of the projection 111 is a molten and solidified portion 11M and a part is a non-molten portion 11B. Specifically, it is preferable that at the base end of the projection 111, a part or all of the projection 111 is a non-molten portion 11B. It is preferable that the non-molten portion 11B at the base end of the projection 111 is located inside the through hole 121. Furthermore, the main body portion 112 of the aluminum member 11 is also a non-molten portion 11B, at least in the vicinity of the projection 111.

[0028] (Chemical composition of the molten and solidified portion 11M) The chemical composition of the molten and solidified portion 11M differs from that of the non-molten portion 11B of the aluminum member 11. Such a molten and solidified portion 11M can be obtained, for example, by (1) providing protrusions on the aluminum member 11 in advance before joining the metal member 12 and the aluminum member 11, (2) melting the protrusions when joining the two, and (3) adding a filler material to the molten pool created by melting the protrusions. Hereinafter, the protrusions provided on the aluminum member 11 in advance before joining the metal member 12 and the aluminum member 11 will be referred to as the "protrusion base material portion 113" and will be distinguished from the protrusions 111 provided on the joining structure 1.

[0029] When the protrusion 111 is melted and solidified to form the molten and solidified portion 11M, if no filler material is added to the molten pool, the chemical composition of the molten and solidified portion 11M will be substantially the same as and uniform as the chemical composition of the non-molten portion 11B.

[0030] The terms "filler material" and "molten pool" are both well-known terms in the field of welding. Filler material is a material added during welding, and is also called filler metal. A molten pool is a pool of molten metal formed by heat such as an arc during welding.

[0031] The molten and solidified portion 11M can be manufactured using commonly used welding equipment. Therefore, in this disclosure, the details of the joint structure 1 according to this embodiment and its manufacturing method will be described with the appropriate use of welding terminology. However, it is not essential that the joint structure 1 according to this embodiment has a welded portion, nor is it essential that the materials be welded in the manufacturing method of the joint structure 1 according to this embodiment.

[0032] The chemical composition of the molten and solidified portion 11M and the chemical composition of the non-molten portion 11B of the aluminum member 11 will be compared using the following procedure. First, the joint structure 1 is cut. The cut surface will be perpendicular to the surface of the metal member 12. The cut surface will also be approximately aligned with the central axis of the through hole. Next, after preparing the cut surface as appropriate, the components of the molten and solidified portion 11M and the non-molten portion 11B will be locally analyzed. The local analysis of the components will be performed using EDS.

[0033] The inventors performed local analysis under the following conditions. However, it is possible to use different analysis conditions as long as the analysis conditions for the molten and solidified portion 11M and the non-molten portion 11B are the same. For example, instead of making the shape of the analysis area a 1 mm square, the area may be 1 mm 2 It can also be represented as a rectangle. ·Device name: JSM-7000F • Acceleration voltage: Approximately 15kV ·Irradiation current: approx. 4.4nA • Elapsed time: Approximately 28 seconds • Counting rate: approximately 40,000 cps Analysis area: 1mm x 1mm

[0034] The location for analyzing the chemical composition of the molten and solidified portion 11M is the centroid of the molten and solidified portion 11M. The centroid is determined by analyzing a photograph of the molten and solidified portion 11M using image processing software. The analysis of the chemical composition of the non-molten portion 11B is performed at a location on the main body portion 112 of the aluminum member 11 that is at least 2 mm away from the molten and solidified portion 11M.

[0035] The content of major elements other than aluminum, identified by local analysis, is used in comparing the chemical composition of the molten and solidified portion 11M and the non-molten portion 11B. If the following formula is satisfied, the chemical composition of the molten and solidified portion 11M is considered to be different from that of the non-molten portion 11B of the aluminum member 11. (X1-X2) / X2≧0.1×X2 Here, X1 is the larger of the two content levels of major element X in the molten and solidified portion 11M and the non-molten portion 11B, and X2 is the smaller of the two content levels of major element X in the molten and solidified portion 11M and the non-molten portion 11B. Major elements are, for example, the elements that are present in the second largest quantity after aluminum in the chemical composition of the aluminum member 11.

[0036] (Melting and solidification of aluminum component 11) The molten and solidified portion 11M may consist only of filler material. For example, when creating the molten and solidified portion 11M, the protruding base material portion 113 is not melted, and molten metal is supplied to the outer surface of the protruding base material portion 113, thereby obtaining a molten and solidified portion 11M consisting only of filler material. A schematic cross-sectional view of such a molten and solidified portion 11M is shown in Figure 3. In the cross-section of the joint structure 1 manufactured without melting the protruding base material portion 113, the shape of the molten boundary 11FL substantially coincides with the shape of the protruding base material portion 113.

[0037] On the other hand, the molten and solidified portion 11M may be formed by mixing the protruding base material portion 113 and the filler material. That is, it is preferable that a part of the aluminum member 11 is a molten and solidified portion 11M in or near the protruding portion 111. When a part of the aluminum member 11 is molten and solidified to form a molten and solidified portion 11M, the shape of the molten boundary 11FL becomes irregular, as shown in the schematic diagrams in Figures 1 and 2, and the cross-sectional photographs in Figures 10, 11, and 12. Therefore, by observing the cross-section of the protruding portion, it is easy to determine whether or not a part of the aluminum member 11 is a molten and solidified portion 11M.

[0038] (Location of non-molten portion 11B) As shown in Figures 1 and 2, it is preferable that a portion of the non-melted portion 11B of the aluminum member 11 is located inside the through hole 121. That is, it is preferable that a portion of the projection 111 of the aluminum member 11 is the non-melted portion 11B, and that this non-melted portion 11B is inserted into the through hole 121. In the cross-section of the joint structure 1, if the non-melted portion 11B is located on the side of the tip of the projection 111 that is greater than the line along the surface of the metal member 12 on the aluminum member 11 side, it is determined that a portion of the non-melted portion 11B of the aluminum member 11 is located inside the through hole 121.

[0039] One example of a means of placing a portion of the non-molten portion 11B of the aluminum member 11 inside the through hole 121 is to provide the aluminum member 11 with a projection base material portion 113 (described later) and to form a projection 111 by melting and solidifying a portion of the projection base material portion 113. If the surface of the aluminum member 11 is made flat and the projection 111 is formed by pouring molten filler material into the through hole 121, the non-molten portion 11B will not be placed inside the through hole 121, as shown in Figure 4. Similarly, if the projection base material portion 113 is melted down to its base, the non-molten portion 11B will not be placed inside the through hole 121.

[0040] (Effects and Benefits) In the joint structure 1 according to this embodiment, as shown in Figures 1 and 2, the metal member 12 and the aluminum member 11 are mechanically joined by the outer peripheral portion 1112 provided on the projection 111. This allows for free selection of the material of the metal member 12.

[0041] In the joint structure 1 according to this embodiment, as shown in Figures 1 and 2, the outer peripheral portion 1112 provided on the projection 111 is a molten and solidified portion 11M. Such an outer peripheral portion 1112 can be easily formed using general-purpose welding equipment such as an arc welding machine.

[0042] In the joint structure 1 according to this embodiment, the chemical composition of the molten and solidified portion 11M is different from that of the non-molten portion 11B of the aluminum member 11. Such a molten and solidified portion 11M is obtained by manufacturing the outer periphery 1112 while adding a filler material to the molten pool. By adding a filler material, it becomes easy to enlarge the shape of the outer periphery 1112.

[0043] In order to form a sufficiently large outer circumference 1112 without adding filler material, it is necessary to increase the size of the projection base material portion 113 and increase the amount of heat input to the projection base material portion 113. In this case, the thermal distortion of the projection portion 111 increases, and the joint strength decreases.

[0044] Furthermore, in the joint structure 1 according to this embodiment, it is preferable that a portion of the aluminum member 11 is a molten and solidified portion 11M, as shown in Figures 1 and 2. This makes it less likely for fracture to occur at the molten boundary 11FL. As a result, as shown in Figure 3, a joint structure 1 with even better joint strength can be obtained than a joint structure 1 in which the aluminum member 11 is not molten and solidified.

[0045] Furthermore, in the joint structure 1 according to this embodiment, as shown in Figures 1 and 2, part or all of the non-melted portion 11B of the aluminum member 11 may be located inside the through hole 121. This results in a joint structure 1 with even higher shear strength than the joint structure 1 shown in Figure 4, where the non-melted portion 11B is not located inside the through hole 121.

[0046] Even if the chemical composition of the molten and solidified portion 11M is controlled as described above, the strength of the molten and solidified portion 11M is often less than the strength of the non-molten portion 11B. Therefore, it is preferable to place the non-molten portion 11B in the stress concentration region of the joint structure 1. Here, when a shear load is applied to the joint structure 1, the base of the projection 111 becomes a stress concentration region. Therefore, by placing the non-molten portion 11B of the aluminum member 11 inside the through hole 121 and making part or all of the base of the projection 111 the non-molten portion 11B, the resistance of the projection 111 to shear load is further increased.

[0047] 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.

[0048] (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.

[0049] 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.

[0050] 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.

[0051] (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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] (Molten and solidified portion 11M of the metal member 12) The metal member 12 may have a molten and solidified portion 11M near the through hole 121. The molten and solidified portion 11M of the metal member 12 may be fused with the molten and solidified portion 11M of the projection 111. That is, the metal member 12 and the projection 111 may be welded together. If the difference between the melting point of the metal member 12 and the melting point of the aluminum member 11 is small, the metal member 12 may melt when forming the outer periphery 1112 of the projection 111. Melting of the metal member 12 is permissible.

[0058] On the other hand, the metal member 12 does not necessarily have to have a molten and solidified portion 11M near the through hole 121. That is, the portion of the metal member 12 that is in contact with the projection 111 may be a non-molten portion 11B. In this case, there is no weld between the metal member 12 and the aluminum member 11.

[0059] If the material of the metal member 12 is a metal that readily forms brittle intermetallic compounds with aluminum, it is preferable that the portion of the metal member 12 that comes into contact with the protrusion 111 be a non-melted portion 11B. This further increases the bonding strength of the joint structure 1.

[0060] (Material of metal component 12) A preferred material for the metal member 12 is plated steel. Plated steel comprises a base steel and a plating layer provided on the surface of the base steel. The base steel of plated steel has high strength. Therefore, plated steel contributes to increasing the strength and reducing the weight of the joint structure 1. In addition, the plating layer of plated steel suppresses corrosion of the base steel. Therefore, plated steel contributes to ensuring the corrosion resistance of the joint structure 1.

[0061] Suitable examples of plated steel materials are aluminum-based plated steel materials and zinc-based plated steel materials. Aluminum-based plated steel materials are steel sheets having a base steel material and an aluminum-based plating layer provided on the surface of the base steel material, wherein the average concentration of aluminum in the plating layer is 20% by mass or more. Zinc-based plated steel materials are steel sheets having a base steel material and a zinc-based plating layer provided on the surface of the base steel material, wherein the average concentration of zinc in the plating layer is 30% or more. Both the aluminum-based plating layer and the zinc-based plating layer exhibit the effect of further suppressing galvanic corrosion between the base steel material and the aluminum member 11.

[0062] 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.

[0063] The material of the metal member 12 may be an aluminum alloy, similar to the aluminum member 11. Specific examples of the material of the metal member 12 include 5000 series, 6000 series, or 7000 series wrought aluminum alloys. Alternatively, the metal member 12 may be an aluminum die-cast having a through hole 121.

[0064] (Shape of the through hole 121) As shown in Figure 5, preferably, the through hole 121 has a tapered shape in which the cross-sectional area increases from the base end to the tip of the projection 111. By providing a taper in the through hole 121, the molten filler material can flow more easily into the through hole 121, further improving the strength of the projection 111. The taper angle of the through hole 121 is preferably 1 to 2 degrees.

[0065] (2. Method for manufacturing the jointed structure 1) A method for manufacturing a jointed structure 1 according to another aspect of the present disclosure is a method for manufacturing a jointed structure 1 having an aluminum member 11 and one or more metal members 12, wherein the aluminum member 11 has one or more protruding base material portions 113, and the metal members 12 have one or more through holes 121, and the manufacturing method comprises the steps of inserting the protruding base material portion 113 into the through holes 121 and melting the tip of the protruding base material portion 113, wherein when melting the tip of the protruding base material portion 113, a filler material is supplied to the molten pool, and when melting the tip of the protruding base material portion 113, a part or all of the protruding base material portion 113 is kept solid at the base end of the protruding base material portion 113. The details of the method for manufacturing the jointed structure 1 are described below. The preferred embodiment of the jointed structure 1 described above can also be applied to the method for manufacturing the jointed structure 1.

[0066] (Material of joint structure 1) The jointed structure 1 is manufactured by joining an aluminum member 11 with one or more metal members 12. The metal member 12 has one or more through holes 121. The aluminum member 11 has one or more protrusions. The protrusions before the joining process are referred to as the protrusion base material portion 113. The aforementioned protrusions 111 are obtained by melting and solidifying the protrusion base material portion 113 while adding a filler material. If there are two or more through holes 121 and protrusions, the positions of the multiple through holes 121 correspond to the positions of the multiple protrusions.

[0067] (Insertion S1) In the manufacturing method of the jointed structure 1, first, as shown in Figure 6, the protruding base material portion 113 of the aluminum member 11 is inserted through the through hole 121 of the metal member 12. An adhesive may be provided between the aluminum member 11 and the metal member 12. In this case, it is preferable to apply the adhesive to the metal member 12 and / or the aluminum member 11 before inserting the protruding base material portion 113 of the aluminum member 11 through the through hole 121 of the metal member 12.

[0068] (Melting S2 of the protruding base material portion 113) Next, the tip of the protruding base material portion 113 is melted. This creates a molten pool at the tip of the protruding base material portion 113.

[0069] The method for melting the tip of the projection base material portion 113 is not particularly limited, but it is preferable to use an arc welding torch 3, as shown in Figure 7. By using an arc welding torch 3, the cost of the joining work can be reduced.

[0070] When melting the tip of the protruding base material portion 113, filler material is supplied to the molten pool. This allows for the formation of an outer peripheral portion 1112 that extends beyond the edge of the through hole 121, as shown in Figure 8, and enables the manufacture of the joint structure 1. By supplying filler material to the tip of the protruding base material portion 113 while melting the tip of the protruding base material portion 113, the chemical composition of the molten and solidified portion 11M can be made different from that of the non-molten portion 11B of the aluminum member 11.

[0071] Furthermore, when melting the tip of the projection base material portion 113, it is preferable not to melt the entire projection base material portion 113. At the base end of the projection base material portion 113, it is preferable to maintain part or all of the projection base material portion 113 in a solid state. This makes it possible to manufacture a joint structure in which part or all of the non-melted portion 11B of the aluminum member 11 is located inside the through hole 121. In addition, as long as it is possible to melt the tip of the projection base material portion 113 and form the molten solidified portion 11M, it is preferable that the amount of melting of the projection base material portion 113 be small.

[0072] The most basic embodiment of the manufacturing method for the jointed structure 1 according to this embodiment has been described above. A more preferred embodiment will be described below.

[0073] (Length of the projection base material portion 113) The length H of the projection base material portion 113 is not particularly limited, but it is preferable to set it to, for example, 0.2 to 2.5 times the depth D of the through hole 121. By setting the length of the projection base material portion 113 to 0.2 times or more the depth of the through hole 121, it becomes easier to make part or all of the base end of the projection 111 a non-molten portion 11B. By setting the length of the projection base material portion 113 to 2.5 times or less the depth of the through hole 121, the amount of heat input to the projection base material portion 113 can be suppressed, and the thermal distortion of the projection 111 can be reduced. It is even more preferable that the length of the projection base material portion 113 be 0.5 times or more, 0.8 times or more, 1.0 times or more, or 1.2 times or more the length of the through hole 121. It is even more preferable that the length of the projection base material portion 113 be 2.2 times or less, 2.0 times or less, or 1.5 times or less the length of the through hole 121.

[0074] The length H of the projection base material portion 113 is a value measured along a direction perpendicular to the surface of the aluminum member 11, as shown in Figure 9. The surface of the aluminum member 11 refers to the surface in the vicinity of the projection base material portion 113 that faces the metal member 12.

[0075] (Shape of the protruding base material portion 113) As shown in Figure 9, it is preferable that the projection base material portion 113 has a tapered shape in which the cross-sectional area decreases from the base end to the tip. By providing a taper to the projection base material portion 113, the molten filler material can flow more easily into the through hole 121, and the strength of the projection portion 111 can be further improved. In addition, by providing a taper to the projection base material portion 113, it becomes easier to insert the projection base material portion 113 into the through hole 121. The taper angle of the projection base material portion 113 is preferably 1 to 2 degrees.

[0076] (Through hole 121) As shown in Figure 9, it is preferable that the through hole 121 has a tapered shape in which the cross-sectional area increases from the first end 1211 to the second end 1212. When inserting the projection base material portion 113 through the through hole 121, it is preferable to position the first end 1211 of the through hole towards the base end of the projection base material portion 113 and the second end 1212 of the through hole towards the tip of the projection base material portion 113. This provides the through hole 121 with a taper in which the cross-sectional area increases toward the torch 3. In this case, the molten filler material can flow more easily into the through hole 121, further improving the strength of the projection portion 111. It is also possible to provide a taper in both the projection base material portion 113 and the through hole 121.

[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. The preferred embodiments exemplified below are applicable to both the joint structure 1 and its manufacturing method unless otherwise specified.

[0078] (Filler material components) The composition of the filler material is preferably selected based on the composition of the aluminum member 11. A filler material suitable for welding the aluminum alloy constituting the aluminum member 11 can be used as the filler material for creating the outer periphery 1112. An example of a filler material is A4043-WY.

[0079] (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.

[0080] The larger the through-hole 121, the easier it becomes to insert the projection 111 into the through-hole 121. Furthermore, the larger the through-hole 121, the greater the joint strength.

[0081] 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. From the viewpoint of facilitating the joining work, it is preferable that the depth of the through-hole 121 be 5.0 mm or less. From the viewpoint of ensuring joining strength, it is preferable that the depth of the through-hole 121 be 0.6 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.

[0082] (Diameter of the central part 1111 of the protruding portion 111) In the joint structure 1, the maximum diameter of the central part 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 filler material flows between the through hole 121 and the projection base material portion 113.

[0083] The diameter of the projection base material portion 113 before its tip is melted is preferably smaller than the diameter of the through hole 121. The difference between the diameter of the projection base material portion 113 and the diameter of the through hole 121 is preferably 0.3 mm or more. This makes it easier to insert the projection base material portion 113 into the through hole 121.

[0084] More preferably, the diameter of the projection base material portion 113 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 makes it even easier to flow filler material between the projection base material portion 113 and the through hole 121. The diameter of the projection 111 is the diameter of the projection 111 if it is circular, and the maximum diameter if the projection 111 is elliptical or polygonal in shape.

[0085] (Shape of the outer circumference 1112) The diameter of the outer circumference 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 outer circumference 1112 is the diameter of the outer circumference 1112 if it is a circle, and the maximum diameter if the outer circumference 1112 is not a circle. The thickness of the outer circumference 1112 is preferably 1.0 to 9.0 mm. The thickness of the outer circumference 1112 is the distance between the surface of the metal member 12 and the tip of the projection 111 in the joint structure 1. Larger diameters and thicknesses of the outer circumference 1112 are preferable because they increase the joint strength.

[0086] (glue) 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 13 has been applied is pressed against the surface of the other member. This allows the two to be bonded together. The adhesive further improves the bonding strength between the aluminum member 11 and the metal member 12.

[0087] The type of adhesive 13 is not particularly limited. Preferred examples of adhesive 13 include structural epoxy adhesives, rubber adhesives, and urethane adhesives. Adhesive 13 may also be a structural adhesive with excellent vibration damping properties, such as a composite of epoxy and rubber. Adhesive 13 may also be a rubber-based sealant with airtight, dustproof, and waterproof properties. [Examples]

[0088] 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.

[0089] A jointed structure was manufactured by joining a metal member having a through hole and an aluminum member having a protruding base material, as described in Table 1. The manufacturing conditions for the jointed structure are described in Table 2. In the manufacturing of No. 1 and No. 3, the torch was fixed. Therefore, the torch movement speed for these examples is not described in Table 2. In the manufacturing of No. 2, the torch was moved along the side of the protruding base material.

[0090] [Table 1]

[0091] [Table 2]

[0092] Figure 10 shows a cross-sectional photograph of joint structure No. 1. Figure 11 shows a cross-sectional photograph of joint structure No. 2. Figure 12 shows a cross-sectional view of joint structure No. 3. These cross-sectional photographs were taken using the following procedure. First, the joint structure was cut by a plane that passed approximately through the center of the protrusion and perpendicular to the surface of the metal member. Next, the joint structure was embedded in resin and the cut surface was polished. Furthermore, the cut surface was etched to reveal the molten boundary. The etching solution was a mixture of ammonia and water in a volume ratio of 10:1.

[0093] In both No. 1 and No. 3, an outer periphery was provided at the tip of the projection that extended beyond the edge of the through hole. Also, in both No. 1 and No. 3, part or all of the unmelted portion of the aluminum member was inside the through hole. Furthermore, in both No. 1 and No. 3, the metal member did not melt. Since the melting point of the steel plate is higher than that of the aluminum member, it was possible to melt the base material of the projection of the aluminum member while avoiding melting of the steel plate.

[0094] In example No. 2, the area around the tip of the protruding base material became a molten and solidified area, but the area near the center of the tip remained unmolten and unmolten. This is presumed to be because the welding torch was moved along the side of the protruding base material. Also in example No. 2, the metal component melted near the protrusion and fused with it. This is presumed to be because the metal component was an aluminum alloy, and its melting point was close to that of the aluminum component. However, even in example No. 2, it was possible to create an outer periphery at the tip of the protrusion that extended outside the through-hole beyond the edge of the through-hole. Also, in No. 2, some or all of the unmolten portion of the aluminum component was inside the through-hole.

[0095] Table 3 shows the chemical analysis results for the molten and solidified portions and the non-molten portions of samples No. 1 to No. 3. The chemical analysis method was as described above. In the cross-section of sample No. 2, the molten and solidified portion was divided into two regions as shown in Figure 11, so the chemical analysis was performed at the centroid of the molten and solidified portion on the left side of Figure 11. The units of the content listed in Table 3 are mass percent. The symbol "ND" in Table 3 means a value below the detection limit.

[0096] [Table 3]

[0097] In all examples, the primary element other than aluminum was silicon (Si). Furthermore, in all examples, the Si content satisfied the following formula. (X1-X2) / X2≧0.1×X2 In the above formula, X1 is the larger of the Si content in the molten and solidified portion and the non-molten portion, and X2 is the smaller of the Si content in the molten and solidified portion and the non-molten portion. In all examples, it was determined that the chemical composition of the molten and solidified portion was different from that of the non-molten portion of the aluminum member. [Explanation of Symbols]

[0098] 1 Joined structure 11 Aluminum components 111 Protrusion 1111 Center 1112 Outer perimeter 112 Main body 113 Projection base material part 11M Molten and Solidified Section 11B Non-molten part 11FL melting boundary 12 Metal components 121 Through hole 1211 First end of through hole 1212 Second end of through hole 3 Torches

Claims

1. Aluminum components and One or more metal components, A joint structure comprising, The metal member is provided with one or more through holes. The aluminum member has one or more protrusions inserted through the through hole, The projection has an outer circumference at its tip that protrudes outside the through hole beyond the edge of the through hole, In the aforementioned projection, at least the outer peripheral portion is a molten and solidified portion, The chemical composition of the molten and solidified portion differs from that of the non-molten portion of the aluminum member. bonded structure.

2. The joint structure according to claim 1, characterized in that a part of the aluminum member is the molten and solidified portion.

3. The joining structure according to claim 1, characterized in that part or all of the non-melted portion of the aluminum member is located inside the through hole.

4. The joint structure according to claim 1, characterized in that the aluminum member is an aluminum die-cast member.

5. The joint structure according to claim 4, characterized in that the non-molten portion in the projection is formed during die casting.

6. The joining structure according to claim 1, characterized in that the portion of the metal member in contact with the projection is a non-melted portion.

7. The joint structure according to any one of claims 1 to 6, characterized in that the metal member is plated steel.

8. The joint structure according to claim 7, characterized in that the plated steel material is an aluminum-based plated steel material or a zinc-based plated steel material.

9. The joint structure according to any one of claims 1 to 6, characterized in that the material of the metal member is an aluminum alloy.

10. The joint structure according to any one of claims 1 to 6, characterized in that the through hole has a tapered shape in which the cross-sectional area increases from the base end to the tip of the projection.

11. A method for manufacturing a jointed structure having an aluminum member and one or more metal members, The aluminum member has one or more protruding base material portions, The metal member has one or more through holes, The aforementioned manufacturing method is The process of inserting the protruding base material portion into the through hole, A step of melting the tip of the protruding base material portion, Equipped with, When melting the tip of the protruding base material portion, filler material is supplied to the molten pool. When melting the tip of the projection base material, a part or all of the projection base material is kept solid at the base end of the projection base material. A method for manufacturing a bonded structure.

12. The method for manufacturing a joint structure according to claim 11, characterized in that the length of the projection base material portion is 0.2 to 5.0 times the depth of the through hole.

13. The method for manufacturing a joint structure according to claim 11 or 12, characterized in that the projection base material portion has a tapered shape in which the cross-sectional area decreases from the base end to the tip of the projection base material portion.

14. The through hole has a tapered shape, with the cross-sectional area increasing from the first end to the second end. When inserting the projection base material portion into the through hole, the first end of the through hole is positioned on the side of the base end of the projection base material portion, and the second end of the through hole is positioned on the side of the tip of the projection base material portion. A method for manufacturing a jointed structure according to claim 11 or 12.

15. The projection base material portion has a tapered shape in which the cross-sectional area decreases from the base end to the tip of the projection base material portion. The through hole has a tapered shape, with the cross-sectional area increasing from the first end to the second end. When inserting the projection base material portion into the through hole, the first end of the through hole is positioned on the side of the base end of the projection base material portion, and the second end of the through hole is positioned on the side of the tip of the projection base material portion. A method for manufacturing a jointed structure according to claim 11 or 12.

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