Method for joining dissimilar materials and dissimilar material joining structure

Abstract

To provide a method of joining dissimilar metallic materials capable of easily joining different kinds of materials with high quality, especially capable of joining even members one of which is composed of a material having a low melting point without damaging the member.SOLUTION: The method of joining dissimilar metallic materials includes: a base metal arrangement step of arranging a CFRP plate (second member) 2 having a first through-hole 2a on a steel plate (first member) 1; a joining auxiliary member arrangement step of inserting a joining auxiliary member 3 having a second through-hole 3a into the first through-hole 2a; and a joining step of forming a weld metal 8 in the second through-hole 3a by arc-welding to join the joining auxiliary member 3 and the steel plate 1. In the joining auxiliary member arrangement step, a first partial contact region 6 in which the CFRP plate 2 and a flange part 4 of the joining auxiliary member 3 are in point or line contact with each other and a second partial contact region 7 in which the inner side surface of the first through-hole 2a and the shaft part 5 are in point or line contact with each other are formed, and the joining auxiliary member 3 is not brought into contact with the CFRP plate 2 in other regions.SELECTED DRAWING: Figure 1C

Description

Technical Field

[0001] The present invention relates to a method for joining dissimilar metal materials capable of joining plates made of different materials with high strength, and a dissimilar metal joined structure joined by the above joining method.

Background Art

[0002] In transportation equipment represented by automobiles, improvement of fuel efficiency during driving is constantly required for the purpose of suppressing various factors such as (1) consumption of petroleum fuel, which is a finite resource, (2) CO2, which is a greenhouse gas generated during combustion, and (3) driving costs. As means for this, in addition to improving power system technologies such as the use of electric drive, weight reduction of the vehicle body is also one of the improvement measures. For weight reduction, there is a means of replacing steel, which is the current main material, with lightweight materials such as aluminum or aluminum alloy, magnesium or magnesium alloy, carbon fiber, resin, carbon fiber reinforced resin (CFRP: Carbon Fiber Reinforced Plastics), etc. However, replacing all with these lightweight materials has problems such as increased costs and insufficient strength, and as a solution, a design method called a so-called multi-material, in which steel and lightweight materials are combined in appropriate places, has attracted attention.

[0003] By the way, Patent Document 1 discloses, for example, a joined structure in which a steel material and a non-ferrous metal material difficult to weld with the steel material are joined. The above joined structure has a first material that is a first homogeneous metal material having a protrusion and a third material that is a second homogeneous metal material having a protrusion, and the protrusions are arranged so as to face each other, and a second material of a dissimilar material having a through-hole is sandwiched between them, and the protrusions are fusion-joined to each other.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] However, in order to form the joint structure described in Patent Document 1, it is necessary to form protrusions on the third material which serves as the base plate, which increases the manufacturing process and restricts the shape of the base plate. Although Patent Document 1 also describes a structure in which no protrusions are formed, using this method also restricts the thickness of the first, second, and third materials. Furthermore, if a low-melting-point material such as resin is selected as the second material of the dissimilar material, the second material may be damaged by the heat during welding. Such problems also occur with conventional welding methods using rivets. Therefore, a method for joining high-strength members such as steel and members made of low-melting-point materials such as resin without causing damage has not yet been established.

[0006] The present invention has been made in view of the above problems, and aims to provide a method for joining dissimilar metal materials, and a joined structure of dissimilar metal materials joined by the above joining method, which can easily and with high quality join dissimilar materials, and in particular can join even a component made of a material with a low melting point without damage. [Means for solving the problem]

[0007] The above objectives of the present invention are achieved by the following configurations [1] or [2] relating to a method for joining dissimilar metal materials.

[0008] [1] A base material arrangement step of arranging a plate-shaped second member on a first member, which is made of a different material from the first member and has a first through hole that penetrates in the thickness direction of the plate, A joining auxiliary member placement step involves inserting a joining auxiliary member having a second through hole and having the same main component as the first member into the first through hole, A method for joining dissimilar metal materials, comprising: a joining step of melting at least a portion of the first member and at least a portion of the joining auxiliary member through the second through hole by arc welding, and forming a weld metal having the same main component as the first member, The joining auxiliary member comprises a flange portion disposed on the surface of the second member opposite to the contact surface with the first member, and a shaft portion inserted into the first through hole. A method for joining dissimilar metal materials, characterized in that, in the step of arranging the joining auxiliary member, a first partial contact region is formed in which the second member and the flange portion make contact at a point or along a line, and a second partial contact region is formed in which the inner circumferential surface of the first through hole and the shaft portion make contact at a point or along a line, and the joining auxiliary member is not brought into contact with the second member in the region excluding the first partial contact region and the second partial contact region.

[0009] [2] A base material arrangement step of arranging a plate-shaped second member on the first member, which is made of a different material from the first member and has a first through hole that penetrates in the thickness direction of the plate, A joining auxiliary member placement step involves inserting a joining auxiliary member having a second through hole and having the same main component as the first member into the first through hole, A method for joining dissimilar metal materials, comprising: a joining step of melting at least a portion of the first member and at least a portion of the joining auxiliary member through the second through hole by arc welding, and forming a weld metal having the same main component as the first member, The joining auxiliary member comprises a flange portion disposed on the surface of the second member opposite to the contact surface with the first member, and a shaft portion inserted into the first through hole. A method for joining dissimilar metal materials, characterized in that, in the step of arranging the joining auxiliary member, a first partial contact region is formed in which the second member and the flange portion contact at a point or along a line, and the joining auxiliary member is not brought into contact with the second member in the region excluding the first partial contact region.

[0010] Furthermore, preferred embodiments of the present invention relating to a method for joining dissimilar metal materials are described in the following [3] to [7].

[0011] [3] The method for joining dissimilar metal materials according to [1] or [2], characterized in that the melting point of the material constituting the second member is lower than the melting point of the material constituting the first member.

[0012] [4] The method for joining dissimilar metal materials according to any one of [1] to [3], characterized in that the second member is made of resin.

[0013] [5] The method for joining dissimilar metal materials according to any one of [1] to [4], characterized in that the thermal conductivity of the joining auxiliary member is lower than the thermal conductivity of the first member.

[0014] [6] The method for joining dissimilar metal materials according to any one of [1] to [5], characterized in that the outer diameter of the shaft portion of the joining auxiliary member has a tapered shape that decreases from the flange portion end to the other end.

[0015] [7] The method for joining dissimilar metal materials according to any one of [1] to [6], characterized in that the inner diameter of the second through hole in the joining auxiliary member has a tapered shape that decreases from the flange end to the other end.

[0016] The above objectives of the present invention are achieved by the configurations described below in [8] or [9] relating to dissimilar metal joint structures.

[0017] [8] First member and, A second member is disposed on a plane perpendicular to the thickness direction of the first member, is made of a different material from the first member, and has a first through hole. A joining auxiliary member having a shaft portion and a flange portion, and a second through hole parallel to the axial direction of the shaft portion, wherein the shaft portion is inserted into the first through hole, The weld metal has a molten portion formed inside the second through hole, in which at least a portion of the first member and at least a portion of the joining auxiliary member are molten, The joining auxiliary member and the welding metal each have the same main component as the first member, and are a dissimilar metal joining structure in which the first member and the second member are joined by the joining auxiliary member and the welding metal, a first partial contact region where the second member and the flange portion are in point or line contact, and a second partial contact region where the inner peripheral surface of the first through hole and the shaft portion are in point or line contact are formed, and the joining auxiliary member and the second member do not contact each other in a region excluding the first partial contact region and the second partial contact region. A dissimilar metal joining structure characterized by this.

[0018] [9] A first member, a second member that is disposed so as to overlap the first member, is made of a material different from that of the first member, and has a first through hole, a joining auxiliary member having a shaft portion and a flange portion and having a second through hole parallel to the axial direction of the shaft portion, the shaft portion being inserted into the first through hole, a welding metal formed inside the second through hole and including a molten portion in which at least a part of the first member and at least a part of the joining auxiliary member are melted, The joining auxiliary member and the welding metal each have the same main component as the first member, and are a dissimilar metal joining structure in which the first member and the second member are joined by the joining auxiliary member and the welding metal, a first partial contact region where the second member and the flange portion are in point or line contact is formed, and the joining auxiliary member and the second member do not contact each other in a region excluding the first partial contact region. A dissimilar metal joining structure characterized by this. [Advantages of the Invention]

[0019] According to the present invention, it is possible to easily join dissimilar materials with high quality. In particular, it is possible to join a member made of a material having a low melting point without damage. A method for joining dissimilar metal materials, and a joining structure of dissimilar metal materials joined by the above joining method can be provided. [Brief Description of the Drawings]

[0020] [Figure 1A] FIG. 1A is a diagram showing a method for joining dissimilar metal materials according to the first embodiment of the present invention, and is a cross-sectional view showing a base material arrangement step. [Figure 1B] FIG. 1B is a diagram showing a method for joining dissimilar metal materials according to the first embodiment of the present invention, and is a cross-sectional view showing a joining auxiliary member arrangement step. [Figure 1C] FIG. 1C is a cross-sectional view showing a dissimilar metal joined structure obtained by the method for joining dissimilar metal materials according to the first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a method for joining dissimilar metal materials according to the second embodiment of the present invention, and is a cross-sectional view showing a joining auxiliary member arrangement step. [Figure 3] FIG. 3 is a schematic diagram showing the size of the joining auxiliary member used in the examples. [Figure 4A] FIG. 4A is a drawing substitute photograph showing a cross-section of a dissimilar metal joined structure manufactured by the method for joining dissimilar metal materials of the examples. [Figure 4B] FIG. 4B is a drawing substitute photograph showing an enlarged view of the flange portion shown in FIG. 4A. [Figure 5A] FIG. 5A is a drawing substitute photograph showing a cross-section of a dissimilar metal joined structure manufactured by the method for joining dissimilar metal materials of the comparative example. [Figure 5B] FIG. 5B is a drawing substitute photograph showing an enlarged view of the flange portion shown in FIG. 5A. [Figure 6A] FIG. 6A is a drawing substitute photograph showing an enlarged view of the region (a) in FIG. 5A. [Figure 6B] FIG. 6B is a drawing substitute photograph showing an enlarged view of the region (b) in FIG. 5A.

MODE FOR CARRYING OUT THE INVENTION

[0021] The inventors of this invention have conducted various studies on the causes of damage to a low-melting-point material when joining dissimilar metal materials, particularly when one of the materials is a low-melting-point material. First, using a general rivet method, an upper plate made of resin was placed on a lower plate made of steel, a steel joining auxiliary member was inserted into a hole formed in the upper plate, and this joining auxiliary member and the lower plate were joined by arc welding. As a result, the inventors of this application discovered that when arc welding, the heat from the arc is conducted to the upper plate through the joining support member, damaging the upper plate, which has a low melting point, and causing a faulty joint. In other words, by reducing the contact area between the joining support member and the upper plate as much as possible, and by performing welding with the joining support member positioned in a way that prevents the conduction of arc heat to the upper plate, damage to the upper plate can be prevented, and a high-quality joint can be achieved. This invention is based on these findings.

[0022] Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiments described below, and can be modified and implemented as such without departing from the spirit of the invention.

[0023] [Methods for joining dissimilar metal materials] (First Embodiment) Figures 1A to 1C are cross-sectional views showing a method for joining dissimilar metal materials according to the first embodiment of the present invention, in order of steps. The embodiment described below is a method for joining a steel plate (first member) 1 and a CFRP plate (second member) 2 by element arc spot welding.

[0024] <Base material placement process> As shown in Figure 1A, a first through-hole 2a is formed in the CFRP plate 2 at the planned joining position with the steel plate 1, extending through in the thickness direction. Next, the CFRP plate 2 is placed on a surface perpendicular to the thickness direction of the steel plate 1.

[0025] <Joining support member placement process> Subsequently, as shown in Figure 1B, a steel joining auxiliary member 3 is inserted into the first through hole 2a. The joining auxiliary member 3 has a disc-shaped flange portion 4 and a shaft portion 5 whose axis is coaxial with the central axis of the disc shape. The joining auxiliary member 3 also has a second through hole 3a that penetrates in the same axial direction as the shaft portion 5. Inserting the joining auxiliary member 3 into the first through hole 2a means inserting the shaft portion 5 of the joining auxiliary member 3 into the first through hole 2a, and at this time, the flange portion 4 is positioned on the surface of the CFRP plate 2 opposite to the contact surface with the steel plate 1, i.e., on the upper surface 2b.

[0026] In this embodiment, the flange portion 4 of the joining auxiliary member 3 is inclined toward the shaft portion 5 as it approaches its radial end. Furthermore, the outer diameter Do of the shaft portion 5 is formed to decrease from the flange portion 4 side toward the other end, thus forming a tapered shape. Similarly, the inner diameter Di of the second through hole 3a in the joining auxiliary member 3 is also formed to decrease from the flange portion 4 side toward the other end, thus forming a tapered shape.

[0027] Therefore, in this embodiment, when the joining auxiliary member 3 is inserted into the first through hole 2a, the upper surface 2b of the CFRP plate 2 and the outer diameter side end of the flange portion 4 make line contact along the circumferential direction of the flange portion 4, forming a first partial contact region 6. In addition, the end of the CFRP plate 2 on the upper surface 2b side of the inner circumferential surface of the first through hole 2a and the shaft portion 5 of the joining auxiliary member 3 make line contact along the circumferential direction of the shaft portion 5, forming a second partial contact region 7. Thus, in the joining auxiliary member placement process, the joining auxiliary member 3 is positioned so that it does not come into contact with the CFRP plate 2 in areas other than the first partial contact region 6 and the second partial contact region 7, thereby forming a gap 9.

[0028] <Joining process> Subsequently, as shown in Figure 1C, arc welding is used to melt at least a portion of the steel plate 1 and at least a portion of the joining auxiliary member 3 through the second through hole 3a, and to melt a welding wire (not shown) to form weld metal 8. Since the joining auxiliary member 3 and the steel plate 1 are joined by the weld metal 8, the joining auxiliary member 3 and the welding wire are made of a material that can be joined to the steel plate 1, i.e., they have the same main components as the steel plate 1.

[0029] According to the joining method of this embodiment, since the joining auxiliary member 3, the steel plate 1, and the weld metal 8 all have the same main component, they are firmly fixed together by welding. Furthermore, the CFRP plate 2 is physically fixed to the steel plate 1 by the flange portion 4 of the joining auxiliary member 3. Therefore, a dissimilar metal joint structure 10 in which the steel plate 1 and the CFRP plate 2 are joined can be obtained.

[0030] Furthermore, in this embodiment, the joining auxiliary member 3 and the CFRP plate 2 are in contact only in the first partial contact area 6 and the second partial contact area 7. Because the contact area is extremely small, damage to the CFRP plate 2 due to heat conduction during welding can be suppressed. In addition, since the inner diameter of the second through hole 3a in the joining auxiliary member 3 is formed in a tapered shape, the joining auxiliary member 3 and the steel plate 1 can be joined with only a small amount of weld metal. Therefore, the amount of heat during welding can be reduced even further, and damage to the CFRP plate 2 can be further suppressed. As a result, dissimilar materials can be easily joined with high quality.

[0031] (Second Embodiment) Referring to Figure 2, a method for joining dissimilar metal materials according to the second embodiment of the present invention will be described below. Note that in the second embodiment, the contact area between the joining auxiliary member 3 and the CFRP plate 2 is different from that of the first embodiment, so Figure 2 is shown as a replacement for Figure 1B, and drawings showing other processes are omitted.

[0032] <Base material placement process> Similar to the first embodiment, a CFRP plate 2 having a first through hole 2a is placed on a surface perpendicular to the thickness direction of the steel plate 1. As shown in Figure 2, in the second embodiment, an annular groove 22 for positioning the joining auxiliary member 3 is provided on the upper surface 2b of the CFRP plate 2, radially outward from the first through hole 2a.

[0033] <Joining support member placement process> Next, a steel joining auxiliary member 3 is inserted into the first through hole 2a. Similar to the first embodiment, the joining auxiliary member 3 has a disc-shaped flange portion 4 and a shaft portion 5, and a second through hole 3a is formed therein. The flange portion 4 of the joining auxiliary member 3 is inclined toward the shaft portion 5 as it approaches its radial end. However, the outer diameter of the shaft portion 5 and the inner diameter of the second through hole 3a are formed to be the same size from the flange portion 4 side toward the other end.

[0034] In the second embodiment, when the joining auxiliary member 3 is inserted into the first through hole 2a, the outer diameter end on the lower surface of the flange portion 4 fits into the groove 22 of the CFRP plate 2, positioning the joining auxiliary member 3. At this time, the flange portion 4 of the joining auxiliary member 3 and the CFRP plate 2 are in circumferential line contact in the region where the groove 22 is formed, forming first partial contact regions 26a and 26b. However, the shaft portion 5 of the joining auxiliary member 3 and the CFRP plate 2 do not come into contact, forming a gap 9.

[0035] <Joining process> Subsequently, arc welding is used to melt at least a portion of the steel plate 1 and at least a portion of the joining auxiliary member 3 through the second through hole 3a, and to melt a welding wire (not shown) to form weld metal 8 in the same manner as in Figure 1C.

[0036] In the joining method according to the second embodiment, a dissimilar metal joint structure in which a steel plate 1 and a CFRP plate 2 are joined can be obtained. Furthermore, in this embodiment, the joining auxiliary member 3 and the CFRP plate 2 are in contact only in the first partial contact areas 26a and 26b, and the contact area is extremely small. In addition, since the first partial contact areas 26a and 26b are separated from the area to which high welding heat is applied, damage to the CFRP plate 2 due to heat conduction during welding can be further suppressed. As a result, dissimilar materials can be easily joined with high quality.

[0037] Furthermore, the method for positioning the joining auxiliary member 3 is not limited to forming a groove 22 in the CFRP plate 2, but various methods can be used, such as using other members or devices. Also, in the second embodiment, two first partial contact regions 26a and 26b are formed, but the number of first partial contact regions where the flange portion 4 and the CFRP plate 2 come into contact may be one or three or more, as long as they are in contact at a point or along a line. Moreover, in this embodiment, the shape of the shaft portion 5 of the joining auxiliary member 3 does not need to be formed to be the same size from the flange portion 4 side toward the other end, and may be tapered, as in the first embodiment.

[0038] In the first and second embodiments described above, examples were shown in which a steel plate 1 was used as the first member, a CFRP plate 2 as the second member, and a steel joining auxiliary member 3 was used. However, the present invention is not limited to such combinations. The first member and the joining auxiliary member 3 can be made from various metal materials. Specifically, the material for the first member can be steel, aluminum, magnesium, etc. Similarly, the material for the joining auxiliary member 3 can be steel, aluminum, magnesium, etc.

[0039] Furthermore, the present invention has the effect of preventing damage to the second member even when a second member made of a material with a low melting point is used. Therefore, the effects of the present invention can be fully realized by using a material having a lower melting point than the material making up the first member as the material constituting the second member. For example, aluminum die-cast, resin, etc. can be used as the material for the second member. In order to further realize the effects of the present invention, it is more preferable to select a resin as the material for the second member, and among resins, it is even more preferable to use carbon fiber reinforced resin (CFRP), which is lightweight and has excellent strength.

[0040] Furthermore, it is more preferable that the joining auxiliary member 3 be made of a material having a lower thermal conductivity than the first member. If the joining auxiliary member 3 has low thermal conductivity, the amount of heat during welding will not be easily transferred to the joining auxiliary member 3, thereby reducing the thermal impact on the second member and further suppressing the occurrence of damage.

[0041] Furthermore, the shape of the joining auxiliary member 3 is not particularly limited in the present invention. The outer shape of the shaft portion 5 does not need to be a tapered shape that becomes smaller as it approaches the lower end. As shown in the first embodiment, the outer diameter of the shaft portion 5 can be designed so that the shaft portion 5 and the inner circumferential surface of the first through hole 2a of the CFRP plate 2 make contact at a point or along a line. For example, a projection may be formed on the outer circumferential surface of the shaft portion 5 of the joining auxiliary member 3, and the projection may be made to make contact with the first through hole 2a. Also, as shown in the second embodiment, the shaft portion 5 of the joining auxiliary member 3 and the CFRP plate 2 do not need to be in contact.

[0042] The flange portion 4 of the joining auxiliary member 3 is not limited to the inclined shape shown in Figures 1B and 2. A projection may be formed on the surface of the flange portion 4 facing the second member, so that the projection comes into contact with the second member, or the projection may be formed so that it fits into a groove.

[0043] The second through-hole 3a formed in the joining auxiliary member 3 does not necessarily need to have a tapered shape that becomes smaller as it approaches the lower end, but as mentioned above, a smaller inner diameter of the second through-hole 3a can prevent damage to the CFRP plate due to heat during welding. On the other hand, if the inner diameter of the second through-hole 3a is too small, the weld metal 8 shown in Figure 1C will become smaller, which may reduce the joining strength. Therefore, it is preferable to select the size and shape of the inner diameter of the second through-hole 3a according to the material constituting the second member and the required joining strength.

[0044] Furthermore, the shape of the first member does not need to be plate-shaped, and various shapes can be used. Regarding the shape of the second member, it is preferable that the joint portion with the first member be flat, but it can be freely selected to have a partially bent shape or a shape with different thicknesses in parts. In other words, in this specification, "plate-shaped second member" means that only the joint portion needs to be plate-shaped.

[0045] Furthermore, in this specification, "contact at a point or line" means that the flange portion 4 and shaft portion 5 of the joining auxiliary member 3 and the second member only need to be in contact at a point or line. Specifically, it is necessary to make contact over a smaller area compared to the case where the flange portion 4 of the joining auxiliary member 3 is in complete contact with the upper surface of the second member, or where the shaft portion 5 of the joining auxiliary member 3 is in complete contact with the inner circumferential surface of the first through hole 2a of the second member. For example, in this embodiment, the total area of ​​the first partial contact region 6 is preferably 30% or less, and more preferably 10% or less, compared to the area when the flange portion 4 and the upper surface of the second member are in complete contact. Also, the area of ​​the second partial contact region 7 is preferably 30% or less, and more preferably 10% or less, compared to the area when the shaft portion 5 and the inner circumferential surface of the first through hole 2a of the second member are in complete contact.

[0046] The first partial contact area 6 and the first partial contact areas 26a and 26b, and the second partial contact area 7 may each include multiple point contact areas and line contact areas. In the case of line contact, it is not necessarily required that the area is in continuous contact in the circumferential direction of the flange area 4 or the shaft area 5; there may be areas that are not in contact, or there may be a mixture of point contact areas and line contact areas.

[0047] Next, a dissimilar metal joint structure joined by the dissimilar metal joining method according to the present embodiment will be described.

[0048] [Dissimilar metal bonded structure] (First Embodiment) The dissimilar metal joint structure according to the first embodiment can be manufactured, for example, by the dissimilar metal joining method according to the first embodiment. As shown in Figure 1C, the dissimilar metal joint structure 10 according to the first embodiment includes a first member (steel plate 1), a plate-shaped second member (CFRP plate 2), a joining auxiliary member 3, and weld metal 8. The second member is made of a different material from the first member and is placed on top of the first member. The second member also has a first through hole 2a that penetrates in the thickness direction of the plate. The joining auxiliary member 3 has a shaft portion 5 and a flange portion 4, and has a second through hole 3a parallel to the axial direction of the shaft portion 5, with the shaft portion 5 inserted into the first through hole 2a. The weld metal 8 is formed inside the second through hole 3a and includes a molten portion formed from at least a part of the first member and at least a part of the joining auxiliary member 3. The joining auxiliary member 3 and the weld metal 8 each have the same main component as the first member, and the first member and the second member are joined together by the joining auxiliary member and the weld metal.

[0049] In this embodiment, the dissimilar metal joint structure 10 has a first partial contact region 6 in which the second member and the flange portion 4 make contact at a point or along a line, and a second partial contact region 7 in which the inner circumferential surface of the first through hole 2a and the shaft portion 5 make contact at a point or along a line. Furthermore, the joining auxiliary member 3 and the second member are not in contact in the areas other than the first partial contact region 6 and the second partial contact region 7.

[0050] (Second Embodiment) The dissimilar metal joint structure according to the second embodiment can be manufactured, for example, by the dissimilar metal joining method according to the second embodiment. In the second embodiment, the same parts as in the first embodiment will be omitted or simplified in their description. Figure 2 is a diagram of the dissimilar metal joint structure according to the second embodiment during the manufacturing process, and the configuration of the second embodiment will be described with reference to Figure 2. In the dissimilar metal joint structure according to the second embodiment, first partial contact regions 26a and 26b are formed where the CFRP plate 2 and the flange portion 4 are in contact at a point or along a line. In addition, the joining auxiliary member 3 and the CFRP plate 2 are not in contact in the areas other than the first partial contact regions 26a and 26b. Furthermore, in the dissimilar metal joint structure according to the second embodiment, similar to the dissimilar metal joint structure 10 according to the first embodiment shown in Figure 1C, a weld metal (not shown) is formed inside the second through hole 3a, and the steel plate 1 and the CFRP plate 2 are joined by this weld metal and the joining auxiliary member 3.

[0051] The dissimilar metal joint structure according to the first and second embodiments described above, configured in this manner, has an excellent appearance and desired strength because the second member (CFRP plate 2) is less likely to be damaged by welding heat during the manufacturing process. [Examples]

[0052] The following describes an example of the method for joining dissimilar metal materials according to this embodiment, in comparison with a comparative example.

[0053] <Examples> As shown in Figures 1A to 1C, a CFRP plate 2 having a first through hole 2a was placed on the upper surface of a steel plate 1, and the shaft portion 5 of a joining auxiliary member 3 having a second through hole 3a was inserted into the first through hole 2a. At this time, the shape of the joining auxiliary member 3 was designed so that the flange portion 4 of the joining auxiliary member 3 and the CFRP plate 2 made line contact along the outer surface of the flange portion 4, and the shaft portion 5 and the inner surface of the first through hole 2a of the CFRP plate 2 made line contact along this inner surface. Subsequently, the steel plate 1 and the CFRP plate 2 were joined by melting a part of the steel plate 1 and a part of the joining auxiliary member 3 by arc spot welding, forming weld metal 8 in the second through hole 3a. The shape and size of the joining auxiliary member used in this embodiment are shown in Figure 3 and will be explained below. Other welding conditions are also shown below.

[0054] (Size of joining support member) Flange section 4 outer diameter Df: 11mm The inner diameter of the second through hole 3a (end on the flange side) Di1: 6mm The inner diameter of the second through hole 3a (at the other end) Di2: 4mm Outer diameter of shaft portion 5 (end on flange side) Do1: 7mm Outer diameter of shaft portion 5 (other end) Do2: 6mm The inclination angle (angle relative to the vertical) of the outer surface of the shaft portion 5 is θ: 21° The inclination of flange portion 4 (the difference in height from the boundary between the lower surface of flange portion 4 and the outer circumferential surface of shaft portion 5 to the radial end on the lower surface of flange portion 4) Hf: 0.2 mm Flange section 4 thickness (thickness at the radial end) T: 1.2 mm Axial height He of joining auxiliary member 3: 2.6 mm Axial height Hs of the inclined portion of the shaft 5: 1.1 mm

[0055] (Other welding conditions) Steel plate 1 material and thickness: 980MPa class steel plate, 1.4mm CFRP plate 2 thickness: 2.0 mm Diameter of the first through hole 2a: 7.0 mm Material of joining support member 3: mild steel Welding wire type and diameter: JIS Z3312G59J3M1T, 1.2mm Shielding gas type and flow rate: 80% Ar + 20% CO2, 25 liters / minute Welding current / voltage: 120A, 23V Arc time: 0.8 seconds

[0056] <Comparative Example> In the same manner as in the above embodiment, the steel plate 1 and the CFRP plate 2 were arranged, and the shaft portion 5 of the joining auxiliary member 3 was inserted into the first through hole 2a. However, the joining auxiliary member 3 used in the comparative example did not have a tilted flange portion 4 or a tapered shape on the shaft portion, and was arranged so that the flange portion 4 and the upper surface of the CFRP plate 2, and the shaft portion 5 and the inner circumferential surface of the first through hole 2a of the CFRP plate 2 were in surface contact. Then, arc spot welding was performed in the same manner as in the above embodiment, melting a part of the steel plate 1 and a part of the joining auxiliary member 3, and forming weld metal to join the steel plate 1 and the CFRP plate 2. Some of the dimensions of the joining auxiliary member 3 used in the comparative example are shown below. Other dimensions and welding conditions were the same as in the embodiment.

[0057] (Size of joining support member) Inner diameter Di of the second through hole 3a: 6.0 mm Outer diameter Do of shaft 5: 7.0 mm Furthermore, the inner diameter Di of the second through hole 3a and the outer diameter Do of the shaft portion 5 are the same size from one end to the other, starting from the flange end.

[0058] Figure 4A is a photographic substitute for a drawing showing a cross-section of a dissimilar metal joint structure manufactured by the dissimilar metal joining method of the embodiment, and Figure 4B is a photographic substitute for a drawing showing a magnified view of the flange portion thereof. In Figures 4A and 4B, the same reference numerals are used for parts identical to those in Figure 1C, and their detailed descriptions are omitted or simplified. As shown in Figure 4A, in the embodiment, the joining auxiliary member 3 and the CFRP plate 2 are in contact only in the first partial contact area 6 and the second partial contact area 7, and are not in contact in other areas. Therefore, the steel plate 1 and the CFRP plate 2 could be joined without damaging the CFRP plate 2. Furthermore, as shown in Figure 4B, no damage to the CFRP plate 2 was observed when the upper surface of the dissimilar metal joint structure was examined.

[0059] Figure 5A is a photographic substitute for a drawing showing a cross-section of a dissimilar metal joint structure manufactured by the comparative example's method of joining dissimilar metal materials, and Figure 5B is a photographic substitute for a drawing showing a magnified view of the flange portion thereof. Furthermore, Figure 6A is a photographic substitute for a drawing showing a magnified view of region (a) in Figure 5A, and Figure 6B is a photographic substitute for a drawing showing a magnified view of region (b) in Figure 5A. In the comparative example, the shape of the joining auxiliary member differs from that of the embodiment, but the configuration of the flange portion and shaft portion are the same. Therefore, in Figures 5A and 5B, the same reference numerals are used for the same parts as in Figures 4A and 4B, and their detailed explanations are omitted or simplified.

[0060] The comparative example is an example in which the joining auxiliary member 3 and the CFRP plate 2 are joined in a state where they are in surface contact in at least a part of the area. However, as shown in Figure 5A, the weld metal 8 and the joining auxiliary member 3 are not completely joined, and an unjointed portion 14 is formed. As shown in Figure 5B, no damage to the CFRP plate 2 was observed when the upper surface of the dissimilar metal joint structure of the comparative example was observed. Furthermore, as shown in Figure 6A, in the region (a) separated from the joining auxiliary member 3, the CFRP plate 2 has a structure in which multiple fibers within it are arranged in the left-right direction in a first layer 11 and arranged in a direction perpendicular to this left-right direction are alternately stacked, and no damage was observed.

[0061] However, as shown in Figure 6B, in the comparative example, even though the input heat was such that an unjointed portion 14 was formed, a partially melted damaged portion 13 was observed in the region (b) close to the joining auxiliary member 3.

[0062] Thus, by using the dissimilar metal joining method of the embodiment, it has been demonstrated that even if the upper plate (second member) is made of a material with a low melting point, such as resin, the lower plate (first member) and the upper plate can be joined with high quality without damaging the upper plate. [Explanation of Symbols]

[0063] 1. Steel plate (first component) 2 CFRP plate (second component) 2a First through hole 3. Joining support member 3a Second through hole 4. Flange section 5. Shaft section 6 1st partial contact area 7 Second partial contact area 8. Weld metal 9 Cavity 10 Dissimilar metal bonded structure 13 Damaged area

Claims

1. A base material arrangement step involves placing a plate-shaped second member, made of a different material from the first member and having a first through-hole that penetrates in the thickness direction, on top of the first member. A joining auxiliary member placement step involves inserting a joining auxiliary member having a second through hole and the same main component as the first member into the first through hole, A method for joining dissimilar materials, comprising: a joining step of melting at least a portion of the first member and at least a portion of the joining auxiliary member through the second through hole by arc welding, and forming a weld metal having the same main component as the first member, The joining auxiliary member comprises a flange portion disposed on the surface of the second member opposite to the contact surface with the first member, and a shaft portion inserted into the first through hole. A method for joining dissimilar materials, characterized in that, in the step of arranging the joining auxiliary member, a first partial contact region is formed in which the second member and the flange portion make contact at a point or along a line, and a second partial contact region is formed in which the inner circumferential surface of the first through hole and the shaft portion make contact at a point or along a line, and the joining auxiliary member is not brought into contact with the second member in the region excluding the first partial contact region and the second partial contact region.

2. A base material arrangement step involves placing a plate-shaped second member, made of a different material from the first member and having a first through-hole that penetrates in the thickness direction, on top of the first member. A joining auxiliary member placement step involves inserting a joining auxiliary member having a second through hole and the same main component as the first member into the first through hole, A method for joining dissimilar materials, comprising: a joining step of melting at least a portion of the first member and at least a portion of the joining auxiliary member through the second through hole by arc welding, and forming a weld metal having the same main component as the first member, The joining auxiliary member comprises a flange portion disposed on the surface of the second member opposite to the contact surface with the first member, and a shaft portion inserted into the first through hole. A method for joining dissimilar materials, characterized in that, in the step of arranging the joining auxiliary member, a first partial contact region is formed in which the second member and the outer diameter side end on the lower surface of the flange portion make contact at a point or along a line, and the joining auxiliary member is not brought into contact with the second member in the region excluding the first partial contact region.

3. The method for joining dissimilar materials according to claim 1, characterized in that the melting point of the material constituting the second member is lower than the melting point of the material constituting the first member.

4. The method for joining dissimilar materials according to claim 1, characterized in that the second member is made of resin.

5. The method for joining dissimilar materials according to claim 1, characterized in that the thermal conductivity of the joining auxiliary member is lower than that of the first member.

6. The method for joining dissimilar materials according to claim 1 or 2, characterized in that the outer diameter of the shaft portion of the joining auxiliary member has a tapered shape that decreases from the flange portion end to the other end.

7. The method for joining dissimilar materials according to claim 1 or 2, characterized in that the inner diameter of the second through hole in the joining auxiliary member has a tapered shape that decreases from the flange end to the other end.

8. First member and A second member is placed on top of the first member, is made of a different material than the first member, and has a first through hole, A joining auxiliary member having a shaft portion and a flange portion, and a second through hole parallel to the axial direction of the shaft portion, wherein the shaft portion is inserted into the first through hole, The weld metal has a molten portion formed inside the second through hole, in which at least a portion of the first member and at least a portion of the joining auxiliary member are molten, The joining auxiliary member and the weld metal each have the same main component as the first member, and the first member and the second member are joined by the joining auxiliary member and the weld metal in a dissimilar material joining structure, A dissimilar material joining structure is characterized in that a first partial contact region is formed in which the second member and the flange portion are in contact at a point or along a line, and a second partial contact region is formed in which the inner circumferential surface of the first through hole and the shaft portion are in contact at a point or along a line, and the joining auxiliary member and the second member are not in contact in the region excluding the first partial contact region and the second partial contact region.

9. First member and A second member is placed on top of the first member, is made of a different material than the first member, and has a first through hole, A joining auxiliary member having a shaft portion and a flange portion, and a second through hole parallel to the axial direction of the shaft portion, wherein the shaft portion is inserted into the first through hole, The weld metal has a molten portion formed inside the second through hole, in which at least a portion of the first member and at least a portion of the joining auxiliary member are molten, The joining auxiliary member and the weld metal each have the same main component as the first member, and the first member and the second member are joined by the joining auxiliary member and the weld metal in a dissimilar material joining structure, A dissimilar material joining structure characterized in that a first partial contact region is formed where the second member and the outer diameter side end on the lower surface of the flange portion contact at a point or along a line, and the joining auxiliary member and the second member do not contact in the region excluding the first partial contact region.

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