Method for joining different materials and joined body of different materials

Abstract

To stably and firmly join different materials to each other.SOLUTION: A method for joining different materials is a method for joining two members 1, 2 of different melting points to each other, and includes: a step S1 of providing one or more hole portions 3 in a high-melting-point member 2, which has a relatively high melting point of the two members 1, 2; and a step S2 of, while keeping the two members 1, 2 overlapped, heating and melting a low-melting-point member 1, which has a relatively low melting point of the two members 1, 2, and pushing a melted portion 6 toward the high-melting-point member 2 to cause the melted portion to enter the hole portion 3.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for joining dissimilar materials and a joined body of dissimilar materials. [Background technology]

[0002] Conventionally, a method for joining, for example, iron-based materials and aluminum-based materials has been to mechanically join them by disposing specially shaped fastening elements (such as flow drill screws or self-piercing rivets) across the two materials. However, the problem with this method is the high cost, including the need for dedicated equipment.

[0003] For example, in the manufacturing process of automobile bodies, spot welding is used to join steel plates together at multiple points. If this welding equipment could be utilized, it would be possible to join dissimilar materials without increasing costs.

[0004] However, when attempting to join dissimilar materials, such as iron and aluminum, by spot welding, a relatively brittle intermetallic compound layer forms at the joint interface, making it difficult to obtain a stable and sufficiently strong joint using this method.

[0005] In order to solve this type of problem, for example, Patent Document 1 discloses a method for joining aluminum material and steel material, in which only the steel material of overlapping aluminum material and steel material is heated and the aluminum material and steel material are pressed together to join them, in which only the portion of the steel material that comes into contact with the aluminum material is heated by high-frequency induction heating. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-82934 Summary of the Invention [Problem to be solved by the invention]

[0007] According to the method described in Patent Document 1, only the steel material is heated, which is expected to shorten the time required for cooling compared to when both materials are heated, and to suppress the formation of intermetallic compounds. However, with this method of joining by heating only one material, there is no penetration into both metals as occurs with spot welding, so it remains difficult to obtain sufficient joint strength.

[0008] In view of the above circumstances, the technical problem to be solved in this specification is to enable strong joining of dissimilar materials at low cost. [Means for solving the problem]

[0009] The above-mentioned problem is solved by a method for joining dissimilar materials according to the present invention. That is, this joining method is a method for joining two members having different melting points, and is characterized by comprising the steps of: forming one or more holes in the high-melting-point member having the higher melting point of the two members; and heating and melting the low-melting-point member having the lower melting point of the two members while the two members are overlapped, and then forcing the melted portion into the high-melting-point member so that it penetrates into the hole.

[0010] In this way, the joining method of the present invention utilizes the difference in melting points to melt the component with a relatively lower melting point (the low-melting-point component) and then push the melted portion into a hole provided in the component with a relatively higher melting point. In this way, the portion of the low-melting-point component that has penetrated the hole functions as a catch (engagement portion) for the high-melting-point component. This allows the two components to be mechanically joined, thereby achieving a strong joint even when combining dissimilar materials that are difficult to melt together. Furthermore, since only equipment for heating the low-melting-point component and equipment for pushing the heated and melted portion toward the high-melting-point component are required, multi-point joining can be performed at low cost without using auxiliary materials such as bolts or rivets.

[0011] In the dissimilar material joining method according to the present invention, at least two of the plurality of holes may be formed to extend in different directions.

[0012] By forming at least two holes in different directions, the portions of the low-melting-point material that penetrate the holes can function as catches against loads coming from different directions, thereby further increasing the joining strength.

[0013] In addition, in the dissimilar material joining method according to the present invention, the two members may be sandwiched between a pair of electrodes and pressurized and electrified to heat and melt the low-melting point member, causing the melted portion to enter the hole.

[0014] As described above, the joining method according to the present invention requires that the low-melting-point member be melted by heating and the melted portion be forced into the hole. In this regard, for example, a pair of electrodes used in spot welding can clamp two members (preferably two plate-shaped members) to be joined and apply pressure and current to the clamped portion. Resistance heating occurs in the pressurized and current-applied portion, allowing the low-melting-point member to be heated and melted. Furthermore, since the melted portion can be forced toward the hole by applying pressure, it is possible to smoothly and quickly insert a portion of the low-melting-point member into the hole during the above-described pressurization and current application. Furthermore, the above-described method allows the use of existing spot welding equipment, thereby enabling multi-point joining at low cost without requiring new capital investment.

[0015] Furthermore, in the case where a pair of electrodes is used, in the dissimilar material joining method according to the present invention, an electrode having a flat tip surface may be used as the electrode that is brought into contact with at least the low-melting point member.

[0016] The pair of electrodes, particularly the electrode that contacts the low-melting-point material, heats and melts the region of the low-melting-point material facing the hole by applying pressure and current, and then pushes the melted portion toward the hole. Therefore, by making the tip surface of the electrode flat, it becomes possible to heat the low-melting-point material over as wide an area as possible and push it toward the hole. Therefore, even if many holes are provided, if each hole is large, or if the distance between holes is large, it is possible to make part of the low-melting-point material (the melted portion) penetrate into the hole to fill it.

[0017] Furthermore, when an electrode having a flat tip surface is used, in the dissimilar material joining method according to the present invention, an electrode that can cover with its tip surface all of the openings of the multiple holes that face the low-melting point material may be used as the electrode that is brought into contact with at least the low-melting point material.

[0018] By setting the size (area) of the tip end face as described above, it is possible to reliably make a portion of the low melting point member enter all of the holes.

[0019] The above-mentioned problems are also solved by a dissimilar material joined body according to the present invention. That is, this joined body is a dissimilar material joined body formed by joining two members made of materials with different melting points, characterized in that one or more holes are formed in the high-melting-point member having the relatively higher melting point of the two members, and when the two members are overlapped, part of the low-melting-point member having the relatively lower melting point of the two members penetrates into the holes.

[0020] By configuring it in this way, a portion of the low-melting-point member that has entered the hole functions as a catch for the high-melting-point member. Therefore, the two members can be mechanically joined, making it possible to obtain a strong joint even when combining dissimilar materials that are difficult to melt together. Furthermore, as described above, if a portion of the low-melting-point member has entered the hole provided in the adjacent high-melting-point member, all that is required is equipment for heating the low-melting-point member and equipment for pushing the heated and melted portion toward the high-melting-point member. This makes it possible to perform multi-point joining at low cost without using auxiliary materials such as bolts or rivets. [Effects of the Invention]

[0021] As described above, the dissimilar material joining method and dissimilar material joined body according to the present invention make it possible to obtain strong joining of dissimilar materials at low cost. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of a main part illustrating an overview of a dissimilar material joining method according to an embodiment of the present invention. [Figure 2] 2 is a plan view showing an example of a hole provided in the high-melting-point member shown in FIG. 1. FIG. [Figure 3] FIG. 2 is a cross-sectional view of a main part showing an example of an embodiment of a method for joining dissimilar materials using the joining device shown in FIG. 1, in which a part of the low-melting point member is heated and melted by applying pressure and current. [Figure 4] FIG. 2 is a cross-sectional view of a main part showing an example of an embodiment of a method for joining dissimilar materials using the joining device shown in FIG. 1, showing a state in which a part of the low-melting point material melted by applying pressure and current has entered the hole. [Figure 5] 2 is a cross-sectional view of a dissimilar material joint obtained by carrying out a dissimilar material joining method using the joining apparatus shown in FIG. 1. FIG. [Figure 6] 1A and 1B are a plan view and a side view showing a first modified example of a hole according to the present invention; [Figure 7] FIG. 10 is a cross-sectional view showing a second modified example of a hole according to the present invention. [Figure 8]FIG. 10 is a cross-sectional view showing a third modified example of a hole according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, a method for joining dissimilar materials according to one embodiment of the present invention will be described with reference to the drawings.

[0024] 1 is a cross-sectional view of a main part showing an outline of a method for joining dissimilar materials according to one embodiment of the present invention. This method is for joining two members 1 and 2 having different melting points, and includes the steps of forming one or more holes 3 in the high-melting-point member 2, which has the relatively higher melting point, of the two members 1 and 2 (hole forming step S1), melting the low-melting-point member 1, which has the relatively lower melting point, by heating and allowing the melted part to enter the holes 3 (hole entering step S2), and solidifying a part of the entered low-melting-point member 1 (solidifying step S3).

[0025] The low melting point member 1 is preferably made of, for example, an aluminum-based material, and at least the joint portion with the high melting point member 2 is preferably plate-shaped. The high melting point member 2 is preferably made of, for example, an iron-based material such as steel, and at least the joint portion with the low melting point member 1 is preferably plate-shaped.

[0026] In principle, the thickness relationship between the low-melting-point member 1 and the high-melting-point member 2 is arbitrary, but if the thickness difference is too great, poor welding may occur. In other words, if the thickness of the low-melting-point member 1 is significantly smaller than that of the high-melting-point member 2, it will be difficult to penetrate into the hole 3 and achieve sufficient penetration to fill the hole 3. Alternatively, if the thickness of the high-melting-point member 2 is significantly smaller than that of the low-melting-point member 1, the high-melting-point member 2 may be heated and melt, and in some cases, the melted high-melting-point member 2 may itself block the hole 3. From these perspectives, it is best to set the thicknesses of the low-melting-point member 1 and the high-melting-point member 2. In Figure 1, the thickness of the low-melting-point member 1 is set to be larger than that of the high-melting-point member 2 to ensure sufficient penetration.

[0027] One or more holes 3 are formed in the high melting point member 2 at the joint portion with the low melting point member 1. The holes 3 are formed in the high melting point member 2 before it is joined to the low melting point member 1 (hole forming step S1). In this embodiment, multiple holes 3 are formed. Here, each hole 3 is formed so as to extend in a direction inclined with respect to the contact direction between the low melting point member 1 and the high melting point member 2 (here, the plate thickness direction of the high melting point member 2) (see FIG. 1). Furthermore, in this embodiment, each hole 3 is formed so as to penetrate the high melting point member 2.

[0028] Here, the inclination direction of the plurality of holes 3 is, in principle, arbitrary, and in this embodiment, as shown in Fig. 2, the plurality of holes 3 extend radially from a surface (first surface) 2a of the high-melting point member 2 that abuts against the low-melting point member 1 toward a surface (second surface) 2b that is farther from the low-melting point member 1. In this case, the first openings 3a of the holes 3 that open to the first surface 2a are located closer to each other than the second openings 3b of the holes 3 that open to the second surface 2b. Furthermore, the centers of the first openings 3a are located on a common imaginary perfect circle, and the centers of the second openings 3b are located on an imaginary perfect circle that is larger than the imaginary perfect circle that passes through the centers of the first openings 3a.

[0029] The hole 3 having the above configuration may be formed by a predetermined process, for example, after forming the entire high-melting point member 2. Of course, if possible, the hole 3 may be formed simultaneously with the formation of the entire high-melting point member 2.

[0030] When joining the above-mentioned low-melting point member 1 and high-melting point member 2, a heating means is used that can heat and melt the portion of the low-melting point member 1 that faces the portion of the high-melting point member 2 where the hole portion 3 is provided (the overlapping portion) while the low-melting point member 1 and the high-melting point member 2 are overlapped, and a pushing means is used that can push the portion of the low-melting point member 1 that has been melted by the heating means toward the hole portion 3.

[0031] In this embodiment, a pair of electrodes 4, 5 used for spot welding is used as both a heating means and a pushing means (see FIG. 1). The pair of electrodes 4, 5 is configured to be able to apply pressure and current to the low-melting-point member 1 and the high-melting-point member 2 that are superimposed on each other. The pressure and current conditions at this time can be set by a predetermined control device (not shown).

[0032] The tip surfaces 4a, 5a of the electrodes 4, 5 can have any shape. In this embodiment, each of the tip surfaces 4a, 5a has a flat, perfect circular shape. Furthermore, as shown in FIG. 1, the tip surface 4a of the first electrode 4 that contacts the low-melting point member 1 is formed to a size that can cover all of the first openings 3a (openings on the low-melting point member 1 side) of the multiple holes 3 that face each other across the low-melting point member 1. In this embodiment, the tip surface 5a of the second electrode 5 that contacts the high-melting point member 2 is formed to have the same size and shape as the tip surface 4a of the first electrode 4.

[0033] Next, an example of the dissimilar material joining method according to this embodiment will be described mainly with reference to FIGS.

[0034] First, as shown in FIG. 1 , the first electrode 4 of the pair of electrodes 4, 5 is brought into contact with the surface (second surface 1b) of the low-melting-point member 1 farther from the high-melting-point member 2, and the second electrode 5 is brought into contact with the portion of the second surface 2b of the high-melting-point member 2 where the hole 3 is formed. This causes heat to be generated primarily at the boundary between the low-melting-point member 1 and the high-melting-point member 2 (between the first surface 1a of the low-melting-point member 1 and the first surface 2a of the high-melting-point member 2 that are in contact with each other) and at each of the members 1, 2 themselves. This heat heats the low-melting-point member 1 and the high-melting-point member 2, respectively. This heating melts the low-melting-point member 1. In this case, a molten portion 6 is formed on the side of the low-melting-point member 1 closer to the high-melting-point member 2 (see FIG. 3 ). Furthermore, the low-melting-point member 1 near the molten portion 6 is softened by the heat.

[0035] Then, by continuing to apply pressure and current even after the molten portion 6 is formed in the low-melting point member 1, the first electrode 4 is pressed into the softened low-melting point member 1, and the molten portion 6 located directly below the pressed-in portion is pressed toward the hole 3 provided on the side of the high-melting point member 2. As a result, the molten portion 6 enters the hole 3 through the first opening 3a (see FIG. 4).

[0036] When the molten portion 6 penetrates into the hole 3 to a predetermined longitudinal position in this manner, the application of pressure and current is terminated, and the portion of the molten portion 6 that penetrated into the hole 3 (penetration portion 7) is cooled and solidified. As a result, the penetration portion 7 is integrated with the low-melting point member 1, and a dissimilar material joined body 8 is obtained in which the low-melting point member 1 and the high-melting point member 2 are mechanically joined by the penetration portion 7 (see FIG. 5). A recess 9 of a predetermined shape and size is formed in the portion of the second surface 1b of the low-melting point member 1 that is pressurized by the first electrode 4.

[0037] At this time, it is advisable to set the current flow pattern (current value history) of the pair of electrodes 4, 5 so that the high-melting point member 2 does not melt until the low-melting point member 1 melts and the melted portion (molten portion 6) penetrates the hole portion 3 to a predetermined longitudinal position.

[0038] At this time, it is preferable to set a pressure pattern (pressure history) by the pair of electrodes 4, 5 so that the molten portion 6 of the low melting point member 1 penetrates into all of the hole portions 3 to predetermined positions in the longitudinal direction.

[0039] As described above, the dissimilar material joining method according to this embodiment utilizes the difference in melting points to melt the low-melting-point member 1, which has a relatively low melting point, and then push the melted portion into the hole 3 provided in the high-melting-point member 2, which has a relatively high melting point. This allows the melted portion 6 (intrusion portion 7) that has penetrated the hole 3 to function as a catch (engagement portion) for the high-melting-point member 2. This allows the low-melting-point member 1 and the high-melting-point member 2 to be mechanically joined, thereby achieving a strong joint even when combining dissimilar materials that are difficult to melt together. Furthermore, since only equipment for heating the low-melting-point member 1 and equipment for pushing the heated and melted portion into the high-melting-point member 2 are required, multi-point joining can be performed at low cost without using auxiliary materials such as bolts or rivets.

[0040] Furthermore, by forming at least two holes 3 to extend in different directions as in this embodiment (see FIGS. 1 and 2), parts of the low-melting point member 1 (penetration parts 7) that penetrate these holes 3 can function as catches against loads in different directions. Therefore, the joining method according to this configuration can further increase the joining strength.

[0041] In particular, as in this illustrated example, by forming the plurality of holes 3 to extend radially, it is possible to achieve a configuration in which the penetration portions 7 are caught on the high-melting point member 2 in all directions. Therefore, it is possible to obtain a very strong dissimilar material joint 8.

[0042] Furthermore, as in this embodiment, by sandwiching the low-melting point member 1 and the high-melting point member 2 between a pair of electrodes 4, 5 and applying pressure and current, the low-melting point member 1 can be heated and melted and forced into the hole 3 continuously during the above-mentioned application of pressure and current. This makes it possible to join the low-melting point member 1 and the high-melting point member 2 smoothly and in a short time. Furthermore, with this method, spot welding equipment can be used as is, making it possible to achieve multi-point joining at low cost without investing in new equipment.

[0043] In particular, as in this illustrated example, when joining a low-melting-point member 1 and a high-melting-point member 2 by applying pressure and current to a pair of electrodes 4, 5, forming a plurality of holes 3 extending radially allows the molten zone 6 to penetrate all of the holes 3 without leaking with a single electrode 4. Therefore, it is possible to efficiently form a very strong dissimilar material joined body 8 at low cost.

[0044] Although one embodiment of the present invention has been described above, the dissimilar material joining method and dissimilar material joined body according to the present invention can also adopt configurations other than those described above within the scope of the spirit thereof.

[0045] 6 shows the shape and arrangement of holes 10 according to another embodiment (first modified example) of the present invention. Each of the multiple holes 10 according to this embodiment is inclined with respect to the thickness direction of the high-melting point member 2. The first opening 10a of each hole 10 is formed at a position where it overlaps with the second opening 10b of the adjacent hole 10 in the thickness direction. In the case shown in FIG. 6, when the first surface 2a is viewed from above (the state shown in FIG. 6(a)), the second opening 10b of the lower right hole 10 overlaps with the first opening 10a of the lower left hole 10 that is adjacent to the lower right hole 10 in the clockwise direction (see FIG. 6(b)). Similarly, the second opening 10b of the lower left hole 10 overlaps in the thickness direction with the first opening 10a of the upper left hole 10 adjacent to it in the clockwise direction, the second opening 10b of the upper left hole 10 overlaps in the thickness direction with the first opening 10a of the upper right hole 10 adjacent to it in the clockwise direction, and the second opening 10b of the upper right hole 10 overlaps in the thickness direction with the first opening 10a of the lower right hole 10 adjacent to it in the clockwise direction.

[0046] 1, the entire area of ​​the hole 10 can be accommodated between the pair of electrodes 4, 5 while keeping the first openings 10a and the second openings 10b of the hole 10 as far apart as possible. This makes it possible to push the molten zone 6 as far as possible into the hole 10 (toward the second opening 10b).

[0047] FIG. 7 shows a cross-sectional view of a hole 11 according to a second modification of the present invention. This hole 11 is composed of a small-diameter portion 11a located on the first surface 2a side of the high-melting-point member 2 and a large-diameter portion 11b located on the second surface 2b side of the high-melting-point member 2. By configuring the hole 11 in this manner and melting the low-melting-point member 1 to penetrate into the hole 11, an intrusion portion (not shown) having a relatively small diameter on the side closer to the low-melting-point member 1 and a relatively large diameter on the side farther from the low-melting-point member 1 can be formed integrally with the low-melting-point member 1. In this case, the large-diameter region of the intrusion portion functions as a catch for the high-melting-point member 2. Therefore, even if the hole 11 is formed so as to extend parallel to the plate thickness direction, as shown in FIG. 7, the intrusion portion can function as a catch for the high-melting-point member 2 against loads in all directions, including the peeling direction of the low-melting-point member 1.

[0048] Although Figure 7 illustrates an example in which the high-melting point member 2 is provided with a hole 11 having a small diameter portion 11a and a large diameter portion 11b, for example, the hole 11 may have a shape of only the small diameter portion 11a, and the tip surface 5a of the second electrode 5 may be provided with a recess (not shown) having a shape corresponding to the large diameter portion 11b shown in Figure 7.

[0049] 8 shows a cross-sectional view of a hole 12 according to a third modified example of the present invention. This hole 12 has a shape that tapers in diameter from the first surface 2a side to the second surface 2b side of the high-melting-point member 2. By configuring the hole 12 in this manner and melting the low-melting-point member 1 to penetrate the hole 12, an intrusion portion (not shown) that expands in diameter as it moves away from the main body of the low-melting-point member 1 can be formed integrally with the low-melting-point member 1. Therefore, even in this case, even if the hole 12 is formed to extend parallel to the plate thickness direction, the intrusion portion can function as a catch for the high-melting-point member 2 against loads in all directions.

[0050] Of course, the holes 3, 10, 11, and 12 described above are merely examples. The shape, number, size, and the like of the holes 3, 10, 11, and 12 can be set arbitrarily as long as they are caught when a load is applied in a direction generally intended to separate the low-melting point member 1 and the high-melting point member 2, such as by peeling or shear peeling.

[0051] In the above explanation, a spot welding device equipped with a pair of electrodes 4, 5 has been exemplified as a device for generating the molten portion 6 in the low-melting point member 1 by heating and for forcing the molten portion 6 toward the holes 3, 10, 11, and 12, but of course, the device is not limited to this. Any configuration is possible as long as it is possible to melt only the low-melting point member 1 by heating and forcing the molten portion toward the holes 3, 10, 11, and 12. Of course, it does not matter whether the heating means and forcing means are integrated or separate. [Explanation of symbols]

[0052] 1 Low melting point materials 2. High-melting-point materials 3,10,11,12 Hole 4,5 electrodes 4a,5a Tip surface 6 Welding zone 7 Intrusion part 8 Dissimilar materials joined body 9 Recess

Claims

1. A method for joining two members having different melting points to each other, comprising the steps of: providing one or more holes in the high-melting-point member having a relatively higher melting point of the two members; a step of melting the low-melting-point member having a relatively lower melting point by heating while the two members are overlapped, and then forcing the melted portion into the high-melting-point member so that it penetrates into the hole.

2. A dissimilar material bonded body formed by bonding two members made of materials with different melting points to each other, One or more holes are provided in the high-melting-point member having a relatively higher melting point of the two members, A dissimilar material joint, in which when the two members are overlapped, a part of the low-melting point member of the two members, which has a relatively low melting point, penetrates into the hole.

Images