Joining method and joined body

Abstract

To provide a joined body exhibiting good joint efficiency even in abutting joint of extreme thin plates, and a joining method capable of manufacturing the same.SOLUTION: A joining method includes a preparation step of making a first joined material abutted on a second joined material, and a joining step of joining the first joined material and the second joined material by heating with a tool for friction stir welding, wherein the thicknesses of the first and second joined materials are 1 mm or less, the tool for friction stir welding has a body part, a shoulder part projecting from the body part, and a probe part projecting from the shoulder part, a ratio of the diameter of the probe part to the diameter of the shoulder part is 0.2 or more and 0.4 or less, the diameter of the shoulder part is 3 times or more and 8 times or less of the thickness of the first joined material, and in the joining step, the rotation speed of the tool for friction stir welding is 5,000 rpm or more and 50,000 rpm or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a bonding method and a bonded body. [Background technology]

[0002] From the viewpoint of the electrification of automobiles and the weight reduction of structures accompanying the development of the aerospace industry, there has been active research and development into the joining of materials to be joined that contain different metals (dissimilar material joining). By implementing the dissimilar material joining, it is possible to manufacture a joined body that is lighter than a joined body of steel plates. For example, Patent Document 1 listed below discloses a friction stir welding method for joining an aluminum alloy plate and a steel plate in overlapping relation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-164942 Summary of the Invention [Problem to be solved by the invention]

[0004] From the perspective of demands for further weight reduction in structures, whether joining the same material or dissimilar materials, there is a demand for thinner welded materials. However, when the welded materials are extremely thin plates with a thickness of 1 mm or less, there is a problem that the joints formed by butt-joining the welded materials are prone to deformation or breakage. In addition, depending on the material contained in the extremely thin plate, there is also the problem that the joint is prone to contain intermetallic compounds. Due to the above-mentioned problems, the joint efficiency of welded bodies (dissimilar material welded bodies) formed by butt-joining extremely thin plates using friction stir welding has not yet reached a practical level.

[0005] An object of one aspect of the present disclosure is to provide a dissimilar material joint that exhibits good joint efficiency even when butt-joining extremely thin plates, and a joining method that can produce the same. [Means for solving the problem]

[0006] A joining method according to one aspect of the present disclosure includes a preparation step of butting a first material to be joined against a second material to be joined, and a joining step of joining the first material to be joined and the second material to be joined by heating with a friction stir welding tool, wherein the thickness of the first and second materials to be joined is 1 mm or less, the friction stir welding tool has a main body portion, a shoulder portion protruding from the main body portion, and a probe portion protruding from the shoulder portion, the ratio of the diameter of the probe portion to the diameter of the shoulder portion being 0.2 or more and 0.4 or less, and the diameter of the shoulder portion being 3 times or more and 8 times or less the thickness of the first material to be joined, and wherein the rotational speed of the friction stir welding tool in the joining step is 5,000 rpm or more and 50,000 rpm or less.

[0007] A joined body according to one aspect of the present disclosure is a joined body of a first material to be joined and a second material to be joined, wherein the thickness of the first material to be joined and the thickness of the second material to be joined are each 1 mm or less, and only the first material to be joined has an insertion mark of a friction stir welding tool, and the friction stir welding tool has a main body portion, a shoulder portion protruding from the main body portion, and a probe portion protruding from the shoulder portion, and the ratio of the diameter of the probe portion to the diameter of the shoulder portion is 0.2 or more and 0.4 or less, and the diameter of the shoulder portion is 3 times or more and 8 times or less the thickness of the first material to be joined. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, it is possible to provide a joined body that exhibits good joint efficiency even when very thin plates are butt-joined together, and a joining method capable of producing the same. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing a bonded body according to an embodiment. [Figure 2] FIG. 2 is a schematic side view showing a joining tool. [Figure 3] 3(a) and (b) are schematic cross-sectional views for explaining the bonding method according to the embodiment. [Figure 4]Fig. 4(a) is a diagram showing a cross-sectional SEM image of a bonded portion of a bonded body according to one specific example produced by the bonding method, and Fig. 4(b) is an enlarged view of a main portion of Fig. 4(a). [Figure 5] 5(a) is a photograph showing a main part of the joined body of dissimilar materials of Experimental Example 1. FIG. 5(b) is a photograph showing a cross section of a main part of the joined body of dissimilar materials of Experimental Example 1. [Figure 6] 6(a) is a photograph showing a main part of the joined body of dissimilar materials of Experimental Example 2. FIG. 6(b) is a photograph showing a cross section of a main part of the joined body of dissimilar materials of Experimental Example 2. [Figure 7] FIG. 7 is a graph showing the relationship between the rotational pitch and the joint strength. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, identical elements or elements having the same functions will be designated by the same reference numerals, and redundant explanations will be omitted. In this specification, the term "same" and similar words are not limited to "completely identical." Furthermore, since the drawings are intended to conceptually explain the embodiments, the dimensions and ratios of the depicted components may differ from the actual dimensions.

[0011] (1) Overview of joining method In the joining method according to the present embodiment, workpieces containing different metals are joined by friction stir welding using a welding tool described below. Specifically, the joining method according to the present embodiment includes a preparation step of butting a first workpiece containing a first metal against a second workpiece containing a second metal different from the first metal, and a joining step of heating at least one of the first workpiece and the second workpiece with a friction stir welding tool to join the first and second workpieces, wherein the thicknesses of the first and second workpieces are each 1 mm or less, the friction stir welding tool has a main body, a shoulder protruding from the main body, and a probe protruding from the shoulder, the ratio of the diameter of the probe to the diameter of the shoulder being 0.2 to 0.4, the diameter of the shoulder being 3 to 8 times the thickness of the first workpiece, and the rotation speed of the friction stir welding tool in the joining step is 5,000 rpm to 50,000 rpm. The dissimilar material joined body according to this embodiment, manufactured by the above-described joining method, is a dissimilar material joined body of a first material to be joined that includes a first metal and a second material to be joined that includes a second metal different from the first metal, in which the thickness of the first material to be joined and the thickness of the second material to be joined are each 1 mm or less, the hardness of the first material to be joined is lower than the hardness of the second material to be joined, and insertion marks of the friction stir welding tool are formed only on the first material to be joined.

[0012] (2) Details of joining method Next, the bonding method according to this embodiment will be described in detail. First, a bonded body produced by the bonding method according to this embodiment will be described with reference to FIG.

[0013] FIG. 1 is a cross-sectional schematic diagram showing a bonded body according to this embodiment. As shown in FIG. 1, the bonded body 1 is a structure including a first member 2, a second member 3, and a bonded portion 4 that bonds the first member 2 and the second member 3. The bonded body 1 is used, for example, as a part of an automobile, transportation equipment, or the like. In this embodiment, the bonded body 1 has a plate shape, but is not limited thereto. For example, the bonded body 1 may have a tubular shape. In one example, the bonded body 1 having a plate shape is molded to obtain the bonded body 1 having a tubular shape.

[0014] The first member 2 and the second member 3 are materials to be joined together by a joint 4. Therefore, in the joined body 1, the first member 2 and the second member 3 are integrated with each other. The first member 2 and the second member 3 are, for example, plate members having a rectangular shape. In the joined body 1, the first member 2 and the second member 3 are butt-joined.

[0015] In this embodiment, the thickness of the first member 2 is the same as the thickness of the second member 3. In addition, the thickness of the first member 2 and the thickness of the second member 3 are each 1 mm or less. That is, the first member 2 and the second member 3 are each an extremely thin plate. From the viewpoint of reducing the weight of the joined body 1, the thickness of the first member 2 and the second member 3 may each be 0.8 mm or less, 0.6 mm or less, 0.5 mm or less, or 0.4 mm or less. From the viewpoint of the strength of the joined body 1, the thickness of the first member 2 and the second member 3 is, for example, 0.1 mm or more, 0.15 mm or more, or 0.2 mm or more.

[0016] The first member 2 and the second member 3 each have a metal phase that can be metallurgically joined together. In this embodiment, the first member 2 and the second member 3 contain different materials. That is, the joined body 1 is a joined body of dissimilar materials. The metal contained in the first member 2 and the metal contained in the second member 3 are, for example, aluminum, iron, magnesium, copper, titanium, nickel, cobalt, niobium, zirconium, silver, etc. The first member 2 and the second member 3 may each contain an alloy containing the above metal (for example, an aluminum alloy, a steel such as carbon steel, a nickel-chromium steel, Invar (alloy), a titanium alloy, a stainless steel, a copper alloy, a magnesium alloy, etc.). In one example, the hardness of the first member 2 is lower than the hardness of the second member 3. In another example, the melting point of the metal (first metal) contained in the first member 2 is lower than the melting point of the metal (second metal) contained in the second member 3. In this embodiment, the first member 2 (first member to be joined) is a metal material containing aluminum (first metal), and the second member 3 (second member to be joined) is a metal material containing copper (second metal). Note that the metal material in this specification is not limited to members made of metal only, but also includes alloy materials.

[0017] The joint 4 is a portion (joint) in the joined body 1 where the first member 2 and the second member 3 are butt-joined. The joint 4 may contain both the metal contained in the first member 2 and the metal contained in the second member 3. In one example, the joint 4 may have a mixed phase portion of the metal contained in the first member 2 and the metal contained in the second member 3. In this embodiment, the joint 4 is formed using a joining tool 10 (see FIG. 2, which will be described later). In FIG. 1, the joint 4 is located between the first member 2 and the second member 3, but this is not limited thereto. For example, the first member 2 and the second member 3 may overlap each other in the thickness direction of the joined body 1 in at least a portion of the joint 4.

[0018] Next, a joining tool used in the joining method according to this embodiment will be described with reference to FIG. 2. FIG. 2 is a schematic side view showing the joining tool. As shown in FIG. 2, the joining tool 10 is a member (friction stir welding tool) used to friction stir weld a first member 2 and a second member 3 that are butted against each other. The joining tool 10 has a main body 20, a shoulder 30 protruding from the main body 20, and a probe 40 protruding from the shoulder 30. In the joining tool 10, the main body 20, the shoulder 30, and the probe 40 are formed integrally with each other, but this is not limiting. The joining tool 10 is formed, for example, from a known tool steel.

[0019] The main body 20 is a portion of the joining tool 10 that is attached to an external device or the like and includes a main portion 21 and a connecting portion 22 that connects the main portion 21 to the shoulder portion 30. The main portion 21 has, for example, a cylindrical shape, and the connecting portion 22 has, for example, a truncated cone shape. The shoulder portion 30 connects the main body 20 to the probe portion 40 and has, for example, a substantially cylindrical shape. The shoulder portion 30 is in close proximity to at least one of the first member 2 and the second member 3 during the formation of the joined body 1. Therefore, during the formation of the joined body 1, heat conduction from the shoulder portion 30 to at least one of the first member 2 and the second member 3 can occur. The probe portion 40 is a tip portion that contacts at least one of the first member 2 and the second member 3 during the formation of the joined body 1 and has, for example, a substantially cylindrical shape. The probe portion 40 has a tip surface 41.

[0020] The size of the joining tool 10 (particularly, the dimensions of the shoulder portion 30 and the probe portion 40) is set according to the thickness of the first member 2 and the thickness of the second member 3. This makes it possible to prevent insufficient or excessive heat conduction from the joining tool 10 to both the first member 2 and the second member 3 during the joining method. For example, the diameter D1 of the shoulder portion 30 is 1.5 to 8 times the thickness of the first member 2 and the second member 3. In this embodiment, the diameter D1 is 6 mm or less. The diameter D1 may be 5 mm, 4 mm, 3 mm, or 2.5 mm. For example, the diameter D2 of the probe portion 40 is 1.5 to 3 times the thickness of the first member 2 and the second member 3. In this embodiment, the diameter D2 is 3 mm or less. The diameter D2 may be 2.5 mm, 2 mm, or 1.5 mm. In one example, from the viewpoint of preventing contact between the shoulder portion 30 and the first and second members 2 and 3, the protrusion amount P1 of the probe portion 40 is 0.8 to 1.5 times the thickness of the first and second members 2 and 3. In this embodiment, the protrusion amount P1 is 1 mm or less. The protrusion amount P1 may be 0.8 mm, 0.6 mm, 0.5 mm, 0.45 mm, or 0.4 mm.

[0021] In this embodiment, the ratio of the diameter D2 of the probe portion 40 to the diameter D1 of the shoulder portion 30 is 0.2 to 0.4. Therefore, for example, when the diameter D1 is 3 mm, the diameter D2 is 0.6 mm to 1.2 mm. In this embodiment, the ratio of the thickness of the first member 2, the diameter D2 of the probe portion 40, and the diameter D1 of the shoulder portion 30 is 1:2:6. Note that this ratio does not need to be exact. For example, the ratio of the thickness of the first member 2 rounded to two significant digits, the diameter D2 rounded to two significant digits, and the diameter D1 rounded to two significant digits is 1:2:6. Note that if the thickness of the first member 2 is within ±20% of the protrusion amount P1 of the probe portion 40, the thickness of the first member 2 in the above ratio may be replaced with the protrusion amount P1.

[0022] (Joining method) An example of the joining method according to this embodiment will be described in detail below with reference to Figures 3(a) and (b). Figures 3(a) and (b) are cross-sectional schematic views for explaining the joining method according to this embodiment. Note that Figure 3(b) shows direction A. Direction A corresponds to the moving direction of the joining tool 10 in the joining process described below. In other words, direction A corresponds to the extending direction of the joining portion 4 formed in the joining process described below.

[0023] First, as shown in Fig. 3(a), the first member 2 is butted against the second member 3 (preparation step). In this preparation step, one end 2a of the first member 2 is butted against one end 3a of the second member 3. This forms an interface B between the first member 2 and the second member 3. The interface B can become part of the interface to be joined when the first member 2 and the second member 3 are later joined.

[0024] Next, the interface B between the first member 2 and the second member 3 is heated by the joining tool 10, thereby joining the first member 2 and the second member 3 (joining process). In this joining process, first, as shown in FIG. 3(b), the tip surface 41 of the probe portion 40 of the joining tool 10 is positioned near the interface B. At this time, the tip surface 41 contacts only the first member 2 so that the probe portion 40 does not overlap with the interface B. In one example, the distance L (offset) between the probe portion 40 and the interface B is 0.05 mm or more and 0.3 mm or less in the direction perpendicular to the direction A.

[0025] Next, the joining tool 10 is rotated and pushed toward the first member 2. As a result, frictional heat generated between the first member 2 and the probe portion 40 causes a portion of the first member 2 to plastically flow, and the probe portion 40 is inserted into the first member 2. As a result, a portion (fluid) of the flowing first member 2 is pushed toward the second member 3 and fixed thereto. At this time, the fluid may be mixed with the softened portion of the second member 3. As a result, friction stir welding of the first member 2 and the second member 3 is performed, and a weld 4 is formed. By performing friction stir welding with the joining tool 10 in contact only with the first member 2 in this manner, insertion marks of the joining tool 10 are left only in the first member 2, making it possible to suppress the occurrence of welding defects between the first member 2 and the second member 3. After the above joining process, a joined body 1 is produced from the first member 2 and the second member 3, which contain different metals. Note that during the joining process, one end 3a of the second member 3 and its vicinity may deform mainly due to heat transfer from the first member 2.

[0026] From the viewpoint of generating a good flow of the first member 2, the joining tool 10 in the joining step may be rotated at a high speed. The rotation speed of the joining tool 10 may be, for example, 5,000 rpm or more and 5,000 rpm or less, 5,000 rpm or more and 20,000 rpm or less, or 4,000 rpm or more and 15,000 rpm or less. In this case, an appropriate amount of heat is likely to be applied to the first member 2 and the second member 3. From the viewpoint of preventing poor joining, the movement speed of the joining tool 10 along direction A may be, for example, 300 mm / min or more and 1,800 mm / min or less. From the viewpoint of preventing damage to the first member 2 and the strength of the joint 4 (joint strength), the rotation pitch of the joining tool 10 in the joining step may be, for example, 0.05 mm / revolution or more and 0.4 mm / revolution or less, 0.1 mm / revolution or more and 0.2 mm / revolution or less. From the viewpoint of joint efficiency of the joining portion 4, the insertion amount of the probe portion 40 into the first member 2 in the joining process is 10% to 80% of the thickness of the first member 2. From the viewpoint of preventing damage to the joining tool 10, the angle (inclination angle) formed by the rotation axis of the joining tool 10 with respect to the thickness direction of the first member 2 is, for example, greater than 0° and equal to or less than 5°.

[0027] In one example, after the joining step, the joined body 1 is formed into a desired shape (forming step). In this forming step, the joined body 1 is formed into a tubular shape by a known method such as drawing. This allows the production of a pipe with an extremely thin thickness.

[0028] The effects of the bonded body manufactured by the bonding method according to this embodiment will be described below with reference to Figures 4(a) and (b). Figure 4(a) is a diagram showing a cross-sectional SEM image of the bonded portion of a bonded body according to one specific example manufactured by the bonding method. Figure 4(b) is an enlarged view of a main part of Figure 4(a). In the bonded body shown in Figures 4(a) and (b), one of the bonded materials is an aluminum alloy plate, and the other is a pure copper plate. Each of the bonded materials has a thickness of 0.5 mm, a width of 25 mm, and a length of 100 mm.

[0029] With the recent trend toward electrification of automobiles, weight reductions are desired for automotive electrical components such as busbars and crimp terminals to improve fuel efficiency. One example of weight reduction for automotive electrical components is replacing some copper components with aluminum. Therefore, the establishment of copper-aluminum joining technology (especially for joining small components) is desirable. When joining copper and aluminum using melting processes such as TIG welding and MIG welding, aluminum melting can occur. On the other hand, brazing copper and aluminum alloys poses productivity challenges, especially for joining small components. Therefore, solid-state joining techniques such as friction stir welding (FSW) have been considered for joining dissimilar materials, such as copper and aluminum. However, joining extremely thin plates with thicknesses of 1 mm or less presents challenges, such as deformation and breakage, even with solid-state welding. In particular, joining dissimilar materials with different physical properties, such as thermal effects, (e.g., copper and aluminum) presents challenges, such as the formation of intermetallic compound layers during solid-state welding. In addition to simply performing friction stir welding, spot joining using a flat tool and rolling after friction stir welding were also considered, but the above problems in joining extremely thin plates were not satisfactorily resolved.

[0030] In contrast, in this embodiment, by friction stir welding the first member 2 and the second member 3 using the joining tool 10, wrinkles and deformations are not formed in the joined body 1, and copper and aluminum can be well stirred at the welded portion 4. For example, as shown in FIGS. 4(a) and 4(b), the surface of the stirred portion of the joined body is smooth, and no wrinkles or deformations were observed in the welded materials. In addition, it was confirmed that copper and aluminum were well stirred at the welded portion of the joined body. Furthermore, no defects were observed on the surface or cross section of each welded material, and almost no intermetallic compounds were formed. From the above, by using the joining tool 10 with a shape and size suitable for the first member 2 and the second member 3, which are ultrathin plate welded materials, and by ensuring the peripheral speed and heat input of the joining tool 10 necessary to induce material flow, the first member 2 and the second member 3 can be well joined without deformations. In particular, by rotating the joining tool 10 at high speed, the first member 2 and the second member 3 can be joined well. In fact, the base material strength of the aluminum alloy plate was 300 MPa, and the joint strength of the joined body shown in FIGS. 4(a) and (b) was 210 MPa. In other words, the joint efficiency of the joined body shown in FIGS. 4(a) and (b) was approximately 70%. Note that the joint efficiency obtained by friction stir welding an aluminum alloy plate having a thickness of more than 1 mm to a pure copper plate is also approximately 70%. As described above, according to the joining method of this embodiment, a joined body 1 exhibiting good joint efficiency can be obtained even when butt-joining extremely thin plates containing different metals.

[0031] In one example, the diameter of the probe portion 40 may be 1.5 to 3 times the thickness of the first member 2. In this case, wrinkles, deformation, and the like are less likely to occur in the first member 2 and the second member 3 during friction stir welding. In addition, the ratio of the protrusion amount of the probe portion 40, the diameter of the probe portion 40, and the diameter of the shoulder portion 30 may be 1:2:6. In this case, friction stir welding of extremely thin plates can be performed more effectively.

[0032] For example, in the joining step, the probe portion 40 of the joining tool 10 does not need to overlap with the interface B. Also, in the joining step, the distance between the probe portion 40 and the interface B may be 0.05 mm or more and 0.3 mm or less in the direction perpendicular to the direction A. In these cases, defects are less likely to occur in the joint 4 between the first member 2 and the second member 3.

[0033] For example, in the above-described joining step, the rotation pitch of the joining tool 10 may be 0.05 mm / revolution or more and 0.4 mm / revolution or less.

[0034] The bonding method and bonded body according to the present disclosure are as described in the following [1] to

[12] , and have been described in detail based on the above embodiments. [1] a preparation step of butting a first workpiece to be welded against a second workpiece; a joining step of joining the first workpiece and the second workpiece by heating at least one of the first workpiece and the second workpiece with a friction stir welding tool; Equipped with The thickness of the first workpiece and the thickness of the second workpiece are each 1 mm or less, The friction stir welding tool has a main body, a shoulder protruding from the main body, and a probe protruding from the shoulder, a ratio of the diameter of the probe portion to the diameter of the shoulder portion is 0.2 or more and 0.4 or less; The diameter of the shoulder portion is 3 to 8 times the thickness of the first workpiece, In the joining step, the rotation speed of the friction stir welding tool is 5,000 rpm or more and 50,000 rpm or less. Joining method. [2] The joining method according to [1], wherein the ratio of the protrusion amount of the probe portion, the diameter of the probe portion, and the diameter of the shoulder portion is 1:2:6. [3] The joining method according to [1] or [2], wherein the diameter of the probe portion is 1.5 to 3 times the thickness of the first workpiece. [4] The joining method according to any one of [1] to [3], wherein in the joining process, the probe portion of the friction stir welding tool does not overlap with the joining interface between the first workpiece and the second workpiece. [5] The joining method according to any one of [1] to [4], wherein in the joining process, the distance between the joining interface of the first workpiece and the second workpiece and the probe portion is 0.05 mm or more and 0.3 mm or less in a direction perpendicular to the moving direction of the friction stir welding tool. [6] The welding method according to any one of [1] to [5], wherein in the welding step, the rotation pitch of the friction stir welding tool is 0.05 mm / revolution or more and 0.4 mm / revolution or less. [7] The first material to be joined is a metal material containing aluminum, the second material to be joined is a metal material containing copper, The welding method according to any one of [1] to [6], wherein in the welding step, a probe part included in the friction stir welding tool overlaps only with the first material to be welded. [8] The joining method according to any one of [1] to [7], wherein the thickness of the first material to be joined and the thickness of the second material to be joined are each 0.5 mm or less. [9] The joining method according to any one of [1] to [8], further comprising a forming step of, after the joining step, forming the first material to be joined, the second material to be joined, and a joined body having a joint between the first material to be joined and the second material to be joined into a tubular shape.

[10] A method for producing a bonded body of dissimilar materials, comprising producing a bonded body of the first material to be bonded and the second material to be bonded by the bonding method according to any one of [1] to [9].

[11] A dissimilar material joined body of a first joined material and a second joined material, Only the first workpiece has an insertion mark of a friction stir welding tool provided thereon, The friction stir welding tool has a main body, a shoulder protruding from the main body, and a probe protruding from the shoulder, a ratio of the diameter of the probe portion to the diameter of the shoulder portion is 0.2 or more and 0.4 or less; The diameter of the shoulder portion is 3 to 8 times the thickness of the first workpiece. Joined body of different materials.

[12] The first material to be joined is a metal material containing aluminum, The dissimilar material joined body according to

[11] , wherein the second material to be joined is a metal material containing copper.

[0035] However, one aspect of the present disclosure is not limited to the above embodiment and the above [1] to

[12] . One aspect of the present disclosure can be further modified within the scope of the gist thereof. For example, in the above embodiment, dissimilar material joining is performed, but this is not limited to this. The joining method according to the present disclosure can also be applied to butt joining of ultra-thin plates formed from the same material. A joined body obtained by butt joining such ultra-thin plates also exhibits the same effects as the above embodiment. In other words, a joined body exhibiting good joint efficiency can be obtained. [Example]

[0036] The present disclosure will be explained in more detail by the following experimental examples, but the present disclosure is not limited to these examples.

[0037] (Experimental Example 1) The first material to be joined was an aluminum alloy (model number: A6061-T6) plate member (Al), and the second material to be joined was an oxygen-free copper (model number: C1020P-1 / 4H) plate member (Cu). Each plate member was 100 mm long, 25 mm wide, and 0.5 mm thick.

[0038] Next, the first workpiece and the second workpiece were butted together. The probe of a friction stir welding tool made of tool steel (SKD61) was then placed on the first workpiece. The friction stir welding tool had a shoulder diameter of 3 mm, a probe diameter of 1 mm, and a protrusion of 0.45 mm. The distance from the probe to the interface between the first and second workpieces in the butting direction was 0.1 mm.

[0039] Next, the first and second workpieces were friction stir welded together under conditions of a rotation speed of 6000 rpm, a movement speed of 600 mm / min, and a probe tilt angle of 1°. This resulted in the production of a dissimilar metal welded body. The dissimilar metal welded body of Experimental Example 1 is shown in FIGS. 5(a) and 5(b). FIG. 5(a) is a photograph showing a main portion of the dissimilar metal welded body of Experimental Example 1. FIG. 5(b) is a photograph showing a cross section of a main portion of the dissimilar metal welded body of Experimental Example 1. Each of FIGS. 5(a) and 5(b) is a photograph obtained with an optical microscope. As shown in FIG. 5(b), no unwelded portions were observed between the first and second workpieces in Experimental Example 1.

[0040] (Experimental Example 2) Friction stir welding was performed under the same conditions as in Experimental Example 1, except that the moving speed was set to 1200 mm / min, and a dissimilar metal welded body was produced. The dissimilar metal welded body of Experimental Example 2 is shown in Figures 6(a) and (b). Figure 6(a) is a photograph showing a main part of the dissimilar metal welded body of Experimental Example 2. Figure 6(b) is a photograph showing a cross section of a main part of the dissimilar metal welded body of Experimental Example 2. Each of Figures 6(a) and (b) is a photograph obtained with an optical microscope. As shown in Figure 6(b), no unwelded portion was observed between the first and second workpieces in Experimental Example 2 either.

[0041] <Rotational pitch and tensile strength of joint> A plate member made of a first aluminum alloy (model number: A6061-T6) or a plate member made of a second aluminum alloy (model number: A5052) was used as the first material to be welded. A plate member made of oxygen-free copper (model number: C1020P-1 / 4H) was used as the second material to be welded. These first and second materials to be welded were friction-stir welded under the same conditions as in Experimental Example 1, except for the rotation pitch. Friction-stir welding was performed once or multiple times at a predetermined rotation pitch. This resulted in multiple dissimilar metal welded bodies, both when the first aluminum alloy and the second aluminum alloy were used. Subsequently, the joint strength (maximum tensile strength) of each dissimilar metal welded body was measured. The joint strength was measured along the butt direction of the first and second materials to be welded, using an autograph testing machine (Shimadzu Corporation, SHIMADZU Autograph AG-10TB). The distance between the grippers was 80 mm and the crosshead speed was 1 mm / min.

[0042] FIG. 7 is a graph showing the relationship between rotation pitch and joint strength. In FIG. 7, the horizontal axis represents the rotation pitch of the friction stir welding tool, and the vertical axis represents the maximum tensile strength of the dissimilar metal welded body. In FIG. 7, the circular plots represent the tensile strength measurement results when the first workpiece material is a plate member made of a first aluminum alloy. The square plots represent the tensile strength measurement results when the first workpiece material is a plate member made of a second aluminum alloy. As shown in FIG. 7, regardless of the type of first workpiece material, a tendency for joint strength to increase was confirmed when the rotation pitch was approximately 0.1 to 0.2 mm / revolution. When the first workpiece material was a plate member made of the first aluminum alloy, the maximum joint efficiency was approximately 71%. When the first workpiece material was a plate member made of the second aluminum alloy, the maximum joint efficiency was approximately 87%. [Explanation of symbols]

[0043] 1...joint (dissimilar material joint), 2...first member (first member to be joined), 2a...one end, 3...second member (second member to be joined), 3a...one end, 4...joint, 10...joining tool (friction stir welding tool), 20...main body, 21...main part, 22...connection part, 30...shoulder part, 40...probe part, 41...tip surface, A...direction, B...interface, D1...diameter, D2...diameter, L...distance (offset), P1...protrusion amount.

Claims

1. a preparation step of butting a first workpiece to be joined against a second workpiece to be joined; a joining step of joining the first workpiece and the second workpiece by heating at least one of the first workpiece and the second workpiece with a friction stir welding tool; Equipped with the thickness of the first workpiece to be joined and the thickness of the second workpiece to be joined are each 1 mm or less; The friction stir welding tool has a main body, a shoulder protruding from the main body, and a probe protruding from the shoulder, a ratio of the diameter of the probe portion to the diameter of the shoulder portion is 0.2 or more and 0.4 or less; the diameter of the shoulder portion is 3 to 8 times the thickness of the first workpiece, In the joining step, the rotation speed of the friction stir welding tool is 5,000 rpm or more and 50,000 rpm or less. Joining method.

2. 2. The joining method according to claim 1, wherein a ratio of a thickness of the first workpiece to a diameter of the probe portion to a diameter of the shoulder portion is 1:2:

6.

3. 3. The joining method according to claim 1, wherein the diameter of the probe portion is 1.5 to 3 times the thickness of the first workpiece.

4. 3. The welding method according to claim 1, wherein in the welding step, the probe portion of the friction stir welding tool does not overlap with the welding interface between the first workpiece and the second workpiece.

5. 3. The joining method according to claim 1, wherein in the joining step, a distance between the probe portion and a joining interface between the first workpiece and the second workpiece is 0.05 mm or more and 0.3 mm or less in a direction perpendicular to a moving direction of the friction stir welding tool.

6. 3. The welding method according to claim 1, wherein in the welding step, a rotation pitch of the friction stir welding tool is 0.05 mm / revolution or more and 0.4 mm / revolution or less.

7. the first material to be joined is a metal material containing aluminum, the second material to be joined is a metal material containing copper, The welding method according to claim 1 or 2, wherein in the welding step, a probe portion included in the friction stir welding tool overlaps only with the first workpiece.

8. 3. The joining method according to claim 1, wherein the thickness of the first workpiece and the thickness of the second workpiece are each 0.5 mm or less.

9. 3. The joining method according to claim 1, further comprising a molding step of, after the joining step, molding a joined body having the first workpiece to be joined, the second workpiece to be joined, and a joint between the first workpiece to be joined and the second workpiece to be joined into a tubular shape.

10. 3. A method for manufacturing a joined body of dissimilar materials, comprising: manufacturing a joined body of the first material to be joined and the second material to be joined by the joining method according to claim 1 or 2.

11. A joined body of a first workpiece and a second workpiece, An insertion mark of a friction stir welding tool is provided only on the first workpiece, The friction stir welding tool has a main body, a shoulder protruding from the main body, and a probe protruding from the shoulder, a ratio of the diameter of the probe portion to the diameter of the shoulder portion is 0.2 or more and 0.4 or less; The diameter of the shoulder portion is 3 to 8 times the thickness of the first workpiece. zygote.

12. the first material to be joined is a metal material containing aluminum, The bonded body according to claim 11 , wherein the second material to be bonded is a metal material containing copper.

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