Joining method

Abstract

To provide a joining method that allows metal components and resin components to be joined without surface treatment of the metal components. [Solution] A joining method for joining a metal member 1 and a resin member 2 by overlapping them and using frictional heat, comprising a joining step in which a powder material 3 is placed between the metal member 1 and the resin member 2, and frictional heat is applied from the side of the metal member 1 to join the metal member 1 and the resin member 2, wherein the powder material 3 includes resin powder 4 and a reinforcing material 5.

Description

Technical Field

[0001] The present invention relates to a joining method, and more particularly, to a joining method in which a metal member and a resin member are overlapped and the metal member and the resin member are joined using frictional heat.

Background Art

[0002] In recent years, in fields such as automobiles and aircraft, the demand for energy conservation through weight reduction has been increasing. As materials for achieving such weight reduction, high-tensile steel sheets and aluminum (Al) alloys are applied, and furthermore, the use of lighter resin materials is also increasing. And the multi-materialization of combining a metal member and a resin member in an appropriate place and structuring them is also being studied. In order to realize such a multi-materialized structure, joining of dissimilar materials between a metal member and a resin member is essential, and the development of the joining technology is also in progress.

[0003] As methods for joining dissimilar materials between a metal member and a resin member, mechanical fastening using bolts or rivets, etc., and adhesion using an adhesive are common. However, mechanical fastening requires fastening fittings and has problems such as poor airtightness. Also, adhesive bonding takes time for bonding and has problems such as generation of harmful gases due to evaporation of organic solvents and deterioration of adhesive properties over time.

[0004] As one of the dissimilar material joining technologies that can solve these problems, a friction stir welding (FSW) method and a friction lap joining (FLJ) method have been proposed. The friction stir welding method is, for example, a method in which a metal member and a resin member are overlapped, a rod-shaped tool is pressed against the surface of the metal member while rotating at high speed, a protruding probe provided at the tip surface of the tool is pressed into the metal member to generate plastic flow and stir the metal member, and at the same time, the resin member in contact with the metal member is melted by the frictional heat generated between the tool and the metal member, and the two are fused together.

[0005] Friction lap welding is a joining method that applies friction stir welding, utilizing frictional heat for joining. However, it differs from friction stir welding in that the tool does not have a probe, and therefore does not involve stirring of the joining interface by a probe.

[0006] The friction stir welding and friction lap welding methods described above simultaneously perform heating by friction and pressurization of the bonding interface, making it possible to form a joint with excellent adhesion. It is believed that the formation of such a joint is achieved through the interaction between the surfaces of the materials. However, joining metal and resin components is not easy. Therefore, surface treatment of the metal component is considered effective in ensuring a more reliable bond, and several methods have been investigated to date.

[0007] For example, Patent Document 1 below discloses the following as an example of a mechanical surface treatment method that improves joint strength by forming irregularities on the surface of a metal member and utilizing the anchoring effect. Specifically, Patent Document 1 discloses a joining method for attaching a resin member to a metal member using frictional heat, wherein the metal member is a member having fine irregularities formed on the surface facing the resin member, and these fine irregularities are a plurality of fine grooves formed by laser irradiation processing.

[0008] Furthermore, Patent Documents 2 and 3 below disclose the following as an example of a chemical surface treatment method that improves bonding strength by modifying the surface of a metal component and utilizing chemical bonding forces such as hydrogen bonding forces. Specifically, Patent Document 2 discloses a method for joining a metal member and a resin member, wherein the metal member is one that has been anodized on the contact surface with the resin member, and at least one of the contact surfaces of the metal member and the resin member is subjected to corona discharge treatment before joining. Furthermore, Patent Document 3 discloses a method for thermal conduction type linear friction bonding in which a silane coupling treatment is applied to the surface of a metal member. [Problems the invention aims to solve]

[0009] The joining methods described in Patent Documents 1 to 3 above require mechanical processing or chemical treatment such as surface modification of the metal members before joining, resulting in complicated operations and time-consuming procedures. Therefore, there was a need for a method that could join metal members and resin members without requiring surface treatment of the metal members. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2023-022728 [Patent Document 2] Patent No. 5817140 [Patent Document 3] Japanese Patent Publication No. 2022-136753 [Overview of the Initiative] Means for solving the problem and their effects

[0011] The present invention has been made in view of the above problems, and aims to provide a joining method that can join a metal member and a resin member without applying surface treatment to the metal member.

[0012] As a result of various studies conducted to achieve the above objective, the inventors of the present invention discovered that by placing a specific powder material between the metal member and the resin member and performing the joining process, it is possible to join the metal member and the resin member without surface treatment of the metal member, thus completing the present invention. To achieve the above objective, the joining method (1) according to the present invention is a joining method that involves overlapping a metal member and a resin member and joining the metal member and the resin member using frictional heat, The method includes a joining step of joining the metal member and the resin member by applying frictional heat from the metal member side while the powder material is placed between the metal member and the resin member, characterized in that the powder material includes resin powder and a reinforcing material.

[0013] According to the above joining method (1), by placing the powder material between the metal member and the resin member and applying the frictional heat from the side of the metal member, the metal member and the resin member can be joined without surface treatment of the metal member.

[0014] Furthermore, the joining method (2) according to the present invention is, in the joining method (1) described above, The aforementioned joining process, A first step of forming a layer of the powder material on the surface of the resin member, A second step involves placing the metal member on top of the resin member on which the layer of the powder material is formed, The present invention is characterized by a third step in which a tool is pressed against the surface of the metal member while rotating to generate frictional heat, and at least a portion of the powder material is softened and melted by this frictional heat, and then solidified to join the metal member and the resin member.

[0015] According to the above joining method (2), the first step, the second step, and the third step allow the metal member and the resin member to be joined in a simple manner without surface treatment of the metal member.

[0016] Furthermore, the joining method (3) according to the present invention is characterized in that, in the joining method (2) above, the third step includes a step of pressing the tool into the metal member while rotating it, so as to penetrate to a depth that does not reach the interface between the metal member and the powder material.

[0017] According to the above joining method (3), by causing the tool to enter to a depth that does not reach the interface between the metal member and the powder material, softening and plastic flow of the metal member can be promoted, and also, heat transfer of the frictional heat from the metal member to the powder material and the resin member can be promoted. Therefore, adhesion between the softened metal member and the melted powder material and the resin member can be enhanced, and the joining strength between the metal member and the resin member can be improved.

[0018] Further, the joining method (4) according to the present invention is characterized in that, in any one of the above joining methods (1) to (3), the resin powder has a particle size in the range of 1 to 100 μm.

[0019] According to the above joining method (4), since the resin powder has a particle size in the range of 1 to 100 μm, when the frictional heat is applied from the side of the metal member, the resin powder can be melted while flowing appropriately at the interface between the metal member and the resin member, enhancing the adhesion at the interface and making it possible to improve the joining strength.

[0020] Further, the joining method (5) according to the present invention is characterized in that, in any one of the above joining methods (1) to (4), the reinforcing material is a reinforcing fiber having an average fiber diameter of 5 to 20 μm and an average fiber length of 10 to 100 μm.

[0021] According to the above joining method (5), when the frictional heat is applied from the side of the metal member, the reinforcing fiber can be appropriately left at the interface between the metal member and the resin member, and by interposing the reinforcing fiber at the interface, an anchor effect can be produced, making it possible to improve the joining strength.

[0022] Further, the joining method (6) according to the present invention is characterized in that, in any one of the above joining methods (1) to (5), the powder material contains 10 to 40% by weight of the reinforcing material with respect to the total amount of the powder material.

[0023] According to the above joining method (6), since the powder material contains 10 to 40% by weight of the reinforcing material with respect to the total amount of the powder material, the effect of enhancing the anchor effect caused by interposing the reinforcing material at the interface between the metal member and the resin member can be enhanced.

[0024] Moreover, the joining method (7) according to the present invention is characterized in that, in any of the above joining methods (1) to (6), the resin member and the resin powder are thermoplastic resins.

[0025] According to the above joining method (7), since the resin member and the resin powder are thermoplastic resins, the adhesion at the interface between the resin member and the powder material can be enhanced by melting them with the frictional heat, and the joining strength can be improved.

[0026] Moreover, the joining method (8) according to the present invention is characterized in that, in the above joining method (7), the thermoplastic resin is an engineering plastic or a super engineering plastic.

[0027] According to the above joining method (8), since the thermoplastic resin is an engineering plastic or a super engineering plastic, a multi-material structure excellent in heat resistance, mechanical strength, etc. can be produced.

[0028] Moreover, the joining method (9) according to the present invention is characterized in that, in any of the above joining methods (1) to (8), the metal member is a light metal or a light alloy.

[0029] According to the above joining method (9), since the metal member is a light metal or a light alloy, a lightweight multi-material structure can be produced.

Brief Description of the Drawings

[0030] [Figure 1] It is a main part configuration diagram of a joining device used in the joining method according to an embodiment of the present invention. [Figure 2]This figure illustrates an example of a joining method according to an embodiment, with (a) being a perspective view of the main part showing the first step, (b) being the second step, and (c) being the third step. [Figure 3] This is a plan view showing the arrangement of the metal member and resin member and the region where the powder material layer is formed in Example 1. [Figure 4] This is a perspective view of a test specimen illustrating the tensile shear test method. [Figure 5] (a) is a plan view showing the arrangement of the metal member and resin member in Comparative Examples 1 and 2, and (b) is a plan view showing the surface treatment area where laser processing and silane coupling treatment have been applied to the joint surface of the metal member with the resin member. [Figure 6] This is an enlarged cross-sectional view showing the joint between the metal member and the resin member in Example 1. [Figure 7] (a) is a cross-sectional view showing the results of optical microscope observation of the probe passage portion of the bonding interface when the tool rotation speed was 700 rpm, and (b) is a cross-sectional view showing the results of optical microscope observation of the shoulder passage portion. [Figure 8] (a) is a cross-sectional view showing the results of optical microscope observation of the probe passage portion of the bonding interface when the tool rotation speed was 800 rpm, and (b) is a cross-sectional view showing the results of optical microscope observation of the shoulder passage portion. [Figure 9] The images show the appearance of the specimens after the tensile shear test in Example 1. (a) is an external view of the specimen with a tool rotation speed of 700 rpm, and (b) is an external view of the specimen with a tool rotation speed of 800 rpm. [Figure 10] Figure 9(a) shows the joint surface and fracture surface of the resin component of the test specimen with a tool rotation speed of 700 rpm, as observed with an optical microscope. [Figure 11] This is a cross-sectional view of the joint (test piece) of metal member 1 and resin member 2 as observed with an optical microscope (10x magnification) in Example 2. [Figure 12] This is a cross-sectional view showing the cross-section of the joint observed at a higher magnification (50x). [Figure 13]This is a front view showing the appearance of the test specimen after the tensile shear test in Example 2, and the state of the joint surfaces of the resin member and metal member after fracture. [Modes for carrying out the invention]

[0031] Hereinafter, embodiments of the joining method according to the present invention will be described with reference to the drawings. The embodiments described below are preferred specific examples of the present invention and are subject to various technically preferred limitations. However, the scope of the present invention is not limited to these forms unless otherwise stated in the following description.

[0032] Figure 1 is a diagram showing the main components of a joining device used in the joining method according to the embodiment. The joining device 10 is a device that joins a metal member 1 and a resin member 2 by overlapping them and utilizing frictional heat, and is equipped with a mechanism that can perform friction stir welding (FSW) or friction lap welding (FLJ).

[0033] The joining apparatus 10 comprises a table 11, a joining tool unit 20, and a powder layer forming unit 30. A resin member 2 is placed on the table 11, a powder material 3 is placed on top of the resin member 2, and a metal member 1 is placed on top of that. The table 11 is provided with a fixing jig 12 for positioning and fixing the metal member 1 and resin member 2 placed on the table 11. The table 11 may also be configured to be movable in the Y-axis direction by being attached to a one-axis linear motion mechanism (not shown). In that case, the one-axis linear motion mechanism can be used to move the resin member 2 and metal member 1 placed on the table 11 in the Y-axis direction, making it possible to adjust their positional relationship with the joining tool unit 20 and the powder layer forming unit 30.

[0034] The joining tool unit 20 comprises a tool 21 that contacts the metal member 1, a chuck portion 22 on which the tool 21 is mounted, a rotary motor 23 for rotating the tool 21 mounted on the chuck portion 22 at high speed in a predetermined rotational direction, and a main body portion 24 to which the chuck portion 22 and the rotary motor 23 are attached. The unit has the function of applying frictional heat to the metal member 1 by rotating the tool 21 while pressing it against the metal member 1.

[0035] The joining tool unit 20 is attached to the pressing and moving mechanism 25. The pressing and moving mechanism 25 is equipped with a mechanism that can move the joining tool unit 20 in at least one direction (the X-axis direction) while pressing it in the vertical direction (Z-axis direction). The pressing and moving mechanism 25 may be configured to include, for example, a two-axis (XZ-axis) combination Cartesian robot, or a horizontal articulated robot or a vertical articulated robot. This pressing and moving mechanism 25 makes it possible to control the pressing load applied to the metal member 1 and the resin member 2, control the pressing position (depth) of the tool 21, or retract the tool 21 from the metal member 1.

[0036] The tool 21 comprises a roughly cylindrical main body 21a, a shoulder 21b provided at one end of the main body 21a, and a probe 21c protruding from approximately the center of the shoulder 21b. The shoulder 21b is the surface that is pressed against the metal member 1. The probe 21c is provided coaxially with the shoulder 21b, and the outer diameter of the probe 21c is smaller than the outer diameter of the shoulder 21b. The outer diameter of the shoulder 21b, the shape of the pressing surface, the outer diameter, shape, and protrusion length of the probe 21c can be appropriately set according to the shape, thickness, material, etc., of the metal member 1 and resin member 2 to be joined. The protrusion length of the probe 21c is designed to be shorter than the thickness of the metal member 1. Furthermore, the tool 21 is made of a material such as tool steel that has higher hardness than the metal member 1 and resin member 2, and also has excellent heat resistance and wear resistance. Furthermore, the joining device 10 can be fitted with a probeless type tool 21A, which does not have a probe 21c, instead of the tool 21 which has a probe 21c.

[0037] The powder layer forming unit 30 is a device for forming a layer of powder material 3 in a predetermined area on a resin member 2 placed on a table 11, and comprises a filling section 31 into which the powder material 3 is filled, and a dispensing section 32 for dispensing the powder material 3 filled in the filling section 31. The dispensing section 32 has a function for dispensing a fixed amount of powder material 3, and the dimensions and shape of its dispensing port can be set as appropriate, for example, it may be needle-shaped or slit-shaped, and it may also be a form in which a mesh filter is provided at the dispensing port. Such a powder layer forming unit 30 may be configured to include, for example, a powder dispenser.

[0038] The powder layer forming unit 30 is attached to a moving mechanism 35. The moving mechanism 35 is configured to move the powder layer forming unit 30 on an XYZ plane, for example. The moving mechanism 35 may include a horizontal articulated robot, or it may include a three-axis (XYX axis) combination orthogonal robot. The powder layer forming unit 30 may further be equipped with a leveling tool for leveling the powder material 3 discharged from the discharge section 32 onto the resin member 2 to a uniform thickness, and a moving mechanism for moving the leveling tool at least horizontally (neither of which are shown).

[0039] Furthermore, the joining device 10 includes a control unit 40 that controls the operation of each part of the device, such as the joining tool unit 20, the pressing and moving mechanism 25, the powder layer forming unit 30, and the moving mechanism 35. The control unit 40 is configured to include a computer device such as a programmable controller.

[0040] Figure 2 is a diagram illustrating an example of the joining process in the joining method according to the embodiment, and (a) is a perspective view of the main part showing the first step, (b) is the second step, and (c) is the third step.

[0041] The joining method according to the embodiment is a joining method in which a metal member 1 and a resin member 2 are overlapped and joined using frictional heat, and includes a joining step in which a powder material 3 is placed between the metal member 1 and the resin member 2, and frictional heat is applied from the side of the metal member 1 to join the metal member 1 and the resin member 2. The joining process includes a first step, a second step, and a third step.

[0042] The first step shown in Figure 2(a) is to form a layer of powder material 3 on the surface of the resin member 2. Since this bonding method utilizes frictional heat, it is preferable that the resin member 2 be made of a thermoplastic resin. Examples of thermoplastic resins constituting the above-mentioned thermoplastic resin components include general-purpose plastics, engineering plastics, super engineering plastics, and mixtures thereof. More specifically, examples include polyolefin resins such as polypropylene (PP), polyester resins such as polyethylene terephthalate (PET), polyacrylate resins such as polymethyl methacrylate (PMMA), polyether resins such as polyether ether ketone (PEEK), polyacetal resins (POM), polyphenylene sulfide resins (PPS), polyamide resins (PA), polycarbonate resins (PC), polyurethane resins, and fluoropolymer resins. From the viewpoint of excellent properties such as mechanical strength, it is preferable to use engineering plastics or super engineering plastics as the above-mentioned thermoplastic resins, and it is particularly preferable to use super engineering plastics such as polyphenylene sulfide resins (PPS). Note that PPS is a polymer having a molecular structure in which benzene rings (phenyl groups) and sulfur (S) are alternately repeated, and there are crosslinked, linear, or semi-crosslinked structures. Furthermore, these thermoplastic resins may be reinforced with carbon fibers, glass fibers, or inorganic fillers.

[0043] In Figure 2, the resin member 2 is exemplified as having a substantially flat plate shape overall, but the shape is not limited to this, and only the portion that overlaps with the metal member 1 may have a substantially flat plate shape. The thickness of the resin member 2 is 2 to 10 mm, preferably 2 to 5 mm, in the portion that overlaps with the metal member 1, but is not limited to this. In Figure 2, the resin members 2 are exemplified as being arranged in parallel in a direction approximately perpendicular to the X-axis direction (direction of arrow A shown in Figure 2(c)) of the relative movement direction of the tool 21 (Y-axis direction), and with a gap between adjacent resin members 2, but the resin members 2 may be arranged without a gap. Furthermore, adjacent resin members 2 may be arranged with parts overlapping, or only one resin member 2 may be arranged.

[0044] The powder material 3 is composed of resin powder 4 and reinforcing material 5. Since this bonding method utilizes frictional heat, the resin powder 4 is preferably a thermoplastic resin powder. The thermoplastic resin constituting the above thermoplastic resin powder is the same as the thermoplastic resin constituting the resin member 2 described above. Furthermore, the resin powder 4 and the resin member 2 may be composed of the same thermoplastic resin, for example, it is preferable to use an engineering plastic or a super engineering plastic, and in particular it is preferable to use a super engineering plastic such as polyphenylene sulfide resin (PPS). With such a configuration, it is possible to obtain a multi-material structure with excellent heat resistance and mechanical strength.

[0045] Furthermore, it is preferable that the resin powder 4 is composed of particles with a particle size in the range of 1 to 100 μm. With this configuration, when frictional heat is applied, the resin powder 4 can be melted while flowing appropriately at the interface between the metal member 1 and the resin member 2, thereby improving the adhesion between the metal member 1 and the resin member 2 at the interface.

[0046] The reinforcing material 5 is composed of reinforcing fibers. The reinforcing fibers may be composed of, for example, carbon fibers, glass fibers, or aramid fibers, but carbon fibers are preferred from the viewpoint of superior strength. The reinforcing fibers are preferably milled fibers, which are powdery short fibers with an average fiber diameter of 5 to 20 μm and an average fiber length of 10 to 100 μm. The average fiber diameter and average fiber length mentioned above are the average values ​​obtained when the reinforcing fibers are observed under an optical microscope and a predetermined number of fiber diameters and fiber lengths are measured using an image analysis device or the like, i.e., number-average fiber diameter and number-average fiber length.

[0047] Furthermore, the powder material 3 contains 10 to 40% by weight of the reinforcing material 5 relative to the total amount of powder material. With this configuration, when frictional heat is applied, the reinforcing material 5, which consists of reinforcing fibers, can be appropriately left at the interface between the metal member 1 and the resin member 2. By interposing the reinforcing fibers at this interface, an anchoring effect can be generated, thereby improving the bonding strength.

[0048] The first step is to form a layer of powder material 3 on the surface (upper surface) of the resin member 2 placed on the table 11 (Figure 1) using a picking robot (not shown), at least in the area where it is joined to the metal member 1 (the area through which the tool 21 passes). The layer of powder material 3 is formed by moving the powder layer forming unit 30 shown in Figure 1 above the resin member 2, and moving the powder layer forming unit 30 along the joining region while quantitatively discharging the powder material 3 from the discharging section 32. In order to make the thickness of the powder material 3 discharged onto the resin member 2 more uniform, a leveling operation may be performed using a leveling tool. The thickness of the powder material 3 layer formed in the first step is approximately 500 to 1000 μm, but is not limited to this.

[0049] The second step, shown in Figure 2(b), is to place the metal member 1 on top of the resin member 2, which has a layer of powder material 3 formed in the first step. Metal member 1 is, for example, an untreated metal that has not undergone surface processing or surface treatment. The type of metal member 1 is not particularly limited and can be made of, for example, aluminum, aluminum alloys such as the 5000 series and 6000 series, steel, magnesium, magnesium alloys, titanium, titanium alloys, etc. From the viewpoint of weight reduction, light metals such as aluminum and light alloys such as aluminum alloys are preferably used. With this configuration, it is possible to obtain a lightweight multi-material structure.

[0050] Furthermore, the thickness of the metal member 1 is approximately 1 to 5 mm in the portion that overlaps with the resin member 2, but is not limited to this. Note that the thickness of the metal member 1 is set to be greater when using the tool 21 with the probe 21c than when using the probeless type tool 21A.

[0051] The metal member 1 is placed on the resin member 2, which has a layer of powder material 3 formed on it, by a pickup robot (not shown) or the like. During this overlapping process, the positions are adjusted so that the area on the resin member 2 where the layer of powder material 3 is formed and the joining area of ​​the metal member 1 overlap. The resin member 2 and the metal member 1, which are overlapped on the table 11, are positioned and fixed by the fixing jig 12 shown in Figure 1.

[0052] The third step, shown in Figure 2(c), involves pressing the tool 21 onto the surface of the metal member 1 while rotating it to generate frictional heat. This frictional heat softens and melts at least a portion of the powder material 3, which is then solidified to join the metal member 1 and the resin member 2. In the third step shown in Figure 2(c), overlapping line joining is performed to join the metal member 1 and the resin member 2 while moving the position where frictional heat is applied to the metal member 1 in the direction indicated by arrow A (X-axis direction) by the rotation and load application operation of the tool 21. However, overlapping point joining is also possible.

[0053] Furthermore, as shown in Figure 2(c), the side where the rotation direction R of tool 21 coincides with the relative movement direction (direction of arrow A) indicating the joining direction is called the advancing side (AS), and the side facing the opposite direction is called the retreating side (RS). In the third step, the tool 21 is pressed into the metal member 1 while rotating it, and the amount (depth) of the tool 21 is set so that the tip of the tool 21 (in this case, the probe 21c) penetrates to a depth that does not reach the interface between the metal member 1 and the powder material 3. With this configuration, it is possible to promote the softening and plastic flow of the metal member 1, and to promote the transfer of frictional heat from the metal member 1 to the powder material 3 and the resin member 2, thereby improving the adhesion between the softened metal member 1 and the molten powder material 3 and the resin member 2.

[0054] According to the joining method of the above embodiment, by placing the powder material 3 between the metal member 1 and the resin member 2 in the first, second, and third steps described above, it becomes possible to join the metal member 1 and the resin member 2 by applying frictional heat generated by the pressing rotation of the tool 21 from the side of the metal member 1. Thus, the metal member 1 and the resin member 2 can be joined without applying surface treatment such as laser processing or activation treatment to the surface of the metal member 1.

[0055] Furthermore, according to the above joining method, the powder material 3 can be appropriately flowed at the interface between the metal member 1 and the resin member 2, melting at least a portion of the resin powder 4 and the resin member 2. This enhances adhesion at the interface, and by interposing the reinforcing material 5 at the interface, an anchoring effect is created, thereby improving the joining strength.

[0056] In the above embodiment, the case in which an untreated metal is used as the metal member 1 was described, but in another embodiment, a metal that has undergone surface processing or surface treatment may be used as the metal member 1. For example, the metal member 1 may have fine grooves formed on its bonding surface to the resin member 2 by laser irradiation or the like, or it may have an activation treatment applied to its bonding surface to the resin member 2. Examples of such activation treatments include applying polar functional groups such as hydroxyl groups (C-OH), carboxyl groups (O=C-OH), or amide groups (CONH) to the surface of the metal member 1, applying a silane coupling treatment to the surface of the metal member 1, or forming an oxide film. [Examples]

[0057] Examples and comparative examples are described below. In the following examples and comparative examples, experiments were conducted to join a metal member 1 and a resin member 2 using friction stir welding or friction lap welding, and the joining state was evaluated by observation of the joint cross-section and tensile shear tests.

[0058] [Example 1] (1) The joining device 10 used a machining center equipped with a joining tool unit 20, and friction stir welding was performed by attaching a tool 21 having a probe 21c to the joining tool unit 20. The tool 21 used was made of tool steel with a shoulder diameter of 20 mm, a probe diameter of 5 mm, and a probe protrusion of 2 mm. (2) The joining conditions were set to a tool rotation speed of 700 rpm and 800 rpm, a tool feed rate of 500 mm / min, and a shoulder indentation amount of 0.15 mm. (3) For the metal component 1, an unsurface-treated, flat (70mm x 230mm x 3mm thick) Al alloy plate of A6063, an aluminum alloy of the 6000 series, was used. (4) For the resin member 2, a flat plate-shaped member (100 mm x 25 mm x 3 mm thick) of polyphenylene sulfide (PPS) resin was used.

[0059] (5) Powder material 3 included PPS resin powder as resin powder 4 and carbon fiber as reinforcing material 5. Powder material 3 was formulated with PPS resin powder at a ratio of 59 wt% or more, carbon fiber at a ratio of 40 wt% or less, and other additives at a ratio of 1 wt% or less. The PPS resin powder had a particle size in the range of 1 to 100 μm. The carbon fiber was milled fiber with an average fiber diameter in the range of 5 to 20 μm and an average fiber length in the range of 10 to 100 μm.

[0060] (6) Figure 3 is a plan view showing the arrangement of the metal member 1 and the resin member 2 in Example 1, and the region where the powder material 3 layer is formed. The resin members 2 described above were used as the bottom plate, with their longitudinal direction oriented in the Y-axis direction and arranged in parallel with predetermined intervals in the X-axis direction. A layer of powder material 3 was applied to one end region (25 mm x 20 mm) of the upper surface of each resin member 2. Next, a metal member 1, with its longitudinal direction oriented in the X-axis direction, was placed on top of the resin members 2 on which the powder material 3 layer had been formed, as the top plate. The metal member 1 and the resin members 2 were superimposed such that the layer of powder material 3 was located directly below the tool passage region 1a of the metal member 1. Then, the tool 21 was pushed in from the metal member 1 side while rotating it, and the joining was performed by feeding the tool 21 in the longitudinal direction (X-axis direction) of the metal member 1. A preheating section P in which the feed speed of the tool 21 was gradually increased and a steady-state section S in which the feed speed of the tool 21 was constant were provided. The joining portion between the metal member 1 and the resin member 2 was positioned within the steady-state section.

[0061] (7) The condition of the joint was evaluated by cross-sectional observation of the joint, visual observation of fracture surfaces, etc., and strength measurement by tensile shear test in accordance with JIS K 6850 (method of measurement by tensile shear load parallel to the joint surface). Figure 4 is a perspective view of the test specimen illustrating the tensile shear test method. In the tensile shear test, the tensile axis was taken in the same direction as the longitudinal direction of the resin member 2. In addition, the width of the test specimen was adjusted to 25 mm for the tensile shear test.

[0062] [Example 2] (1) The joining device 10 used a machining center equipped with a joining tool unit 20, and friction lap joining was performed by attaching a probeless type tool 21A to the joining tool unit 20. The tool 21A used was made of tool steel with a shoulder diameter of 20 mm. (2) The joining conditions were set to a tool rotation speed of 800 rpm, a tool feed rate of 500 mm / min, and a shoulder indentation amount of 0.35 mm. (3) For the metal component 1, an untreated, flat (61 mm x 200 mm x 1 mm thick) Al alloy plate made of A6061, an aluminum alloy of the 6000 series, was used. (4) For the resin member 2, the same as in Example 1 was used, namely a flat plate-shaped member (100 mm × 25 mm × 3 mm thick) made of polyphenylene sulfide (PPS) resin. (5) The same powder material 3 as in Example 1 was used. (6) The arrangement of the metal member 1 and the resin member 2, and the application position of the powder material 3 were the same as in Example 1 shown in Figure 3. However, in Example 2, five resin members 2 were arranged in parallel, and, as in Example 1, the tool 21A was rotated and pushed in from the metal member 1 side, and the joining was performed by feeding the tool 21 in the longitudinal direction (X-axis direction) of the metal member 1. (7) The joint condition was evaluated in the same manner as in Example 1, by cross-sectional observation of the joint, visual observation of the fracture surface, etc., and strength measurement by tensile shear test.

[0063] [Comparative Examples 1 and 2] (1) In Comparative Example 1, a laser processing treatment was performed on the bonding region between the metal member 1 and the resin member 2 to create a protruding (needle-shaped) microstructure. A laser processing machine was used to process the microstructure. A pulsed laser was used for laser processing, and processing was performed under the conditions of output 30W, pulse interval 12.5ns, scan speed 100mm / s, and scan count 2 and 5 times. (2) In Comparative Example 2, silane coupling treatment was performed on the bonding region between the metal member 1 and the resin member 2. Shin-Etsu Chemical Co., Ltd. KBE-903 was used as the silane coupling agent. The silane coupling agent and purified water were mixed to prepare 300 ml of a 1% solution. The treatment procedure was as follows: the metal member 1 was degreased with ethanol and immersed in a tray containing the 1% silane coupling agent solution for 10 minutes. After removing the metal member 1 from the tray, it was dried in an electric furnace set to 100°C for 20 minutes.

[0064] (3) The joining device 10 used a machining center equipped with the same joining tool unit 20 as in Example 1, and friction stir welding was performed by attaching a tool 21 having a probe 21c to the joining tool unit 20. (4) The joining conditions were set to a tool rotation speed of 800 rpm, a tool feed rate of 500 mm / min, and a shoulder indentation amount of 0.15 mm. (5) For the metal component 1, a flat (70mm x 230mm x 3mm thick) Al alloy plate made of A6063, an aluminum alloy of the 6000 series, was used. (6) For the resin member 2, a flat plate-shaped member (100 mm x 25 mm x 3 mm thick) of polyphenylene sulfide (PPS) resin was used. (7) Figure 5(a) shows the arrangement of the metal member 1 and the resin member 2 in Comparative Examples 1 and 2, and Figure 5(b) is a plan view showing the surface treatment area 1b where laser processing and silane coupling treatment have been applied to the joint surface of the metal member 1 with the resin member 2. The arrangement of the metal member 1 and the resin member 2 is the same as in Example 1 shown in Figure 3, as shown in Figure 5(a). The resin members 2 are superimposed on the surface treatment area 1b of the metal member 1 shown in Figure 5(b). Also, as in Example 1, the tool 21A was pushed in from the metal member 1 side while rotating it, and the joining was performed by feeding the tool 21 in the longitudinal direction (X-axis direction) of the metal member 1. (8) The joint condition was evaluated in the same manner as in Example 1, by cross-sectional observation of the joint and strength measurement by tensile shear test.

[0065] [Results of Comparative Examples 1 and 2] In Comparative Example 1, where the joining surface (surface treatment area 1b) of the metal member 1 was laser processed, all three of the three test pieces were successfully joined. When these joined cross-sections were observed with a scanning electron microscope (SEM), needle-like microstructures (uneven shapes) were confirmed on the joining surface of the metal member 1. It was confirmed that a portion of the resin member 2 had melted and entered into the uneven areas of the joining interface and solidified there, and that there were voids in some places within the uneven areas. On the other hand, in Comparative Example 2, where silane coupling treatment was applied to the joint surface of metal member 1, all three test pieces could not be joined. Therefore, the joint cross-section could not be observed.

[0066] [Results of tensile shear test] For Comparative Example 1, since a jointed body was obtained, a test specimen was prepared and a tensile shear test was performed. As a result, a maximum tensile strength of 8.76 MPa was obtained for the test specimen of Comparative Example 1. In the case of Comparative Example 2, a joint could not be obtained, and therefore a tensile shear test could not be performed.

[0067] [Results of Example 1] We were able to fabricate a joint between metal member 1 and resin member 2 under both joining conditions, with a tool rotation speed of 700 rpm and 800 rpm. [Results of cross-sectional observation] Figure 6 is an enlarged cross-sectional view showing the joint between the metal member 1 and the resin member 2 in Example 1. Figure 7(a) is a cross-sectional view showing the optical microscope observation results of the probe passage area (area A in Figure 6) of the bonding interface when the tool rotation speed was 700 rpm, and Figure 7(b) is a cross-sectional view showing the optical microscope observation results of the shoulder passage area (area B in Figure 6). Figures 7(a) and (b) show that at least a portion of the powder material 3 has melted and solidified, forming a layer at the interface between the metal member 1 and the resin member 2 in the joint, and no voids were observed, indicating that a good bonding interface has been formed. Furthermore, in Figures 7(a) and 7(b), it was confirmed that carbon fibers, which are the reinforcing material 5 contained in the powder material 3, are present near the interface on the resin member 2 (PPS) side, indicated by the arrows in the figures. It was confirmed that there were more of these carbon fibers near the shoulder 21b shown in Figure 7(b) than near the probe 21c shown in Figure 7(a). This phenomenon is thought to be because, due to the pressing of the tool 21, some of the carbon fibers contained in the powder material 3 flowed from the vicinity of the probe 21c towards the shoulder 21b.

[0068] Figure 8(a) is a cross-sectional view showing the optical microscope observation results of the probe passage area (area A in Figure 6) of the bonding interface when the tool rotation speed was 800 rpm, and Figure 8(b) is a cross-sectional view showing the optical microscope observation results of the shoulder passage area (area B in Figure 6). Figures 8(a) and (b) show that a layer of at least a portion of the powder material 3 has melted and solidified is formed at the interface between the metal member 1 and the resin member 2 in the joint, and no voids or other defects were observed, confirming the formation of a good joint interface. Furthermore, compared to Figure 7, it was confirmed that the thickness of the layer of at least a portion of the powder material 3 that has melted and solidified is thinner. This phenomenon can be presumed to be because, compared to the case shown in Figure 7, the frictional heat is greater due to the higher tool rotation speed, causing the molten resin of the powder material 3 to flow more towards the outer circumference of the shoulder 21b. However, even in Figures 8(a) and (b), it was confirmed that carbon fibers, which are the reinforcing material 5 contained in the powder material 3, are present near the interface on the resin member 2 (PPS) side, as indicated by the arrows in the figures.

[0069] [Results of tensile shear test] In Example 1, joints were obtained for both 700 rpm and 800 rpm tool rotation speeds. Test specimens were prepared for each case, and tensile shear tests were performed. The results showed that the specimen with a 700 rpm tool rotation speed achieved a maximum tensile strength of 31 MPa and a maximum tensile shear load of 2.5 kN. The specimen with an 800 rpm tool rotation speed achieved a maximum tensile strength of 51 MPa and a maximum tensile shear load of 3.3 kN. The joint strength was higher for the specimen with an 800 rpm tool rotation speed than for the specimen with a 700 rpm tool rotation speed. Furthermore, in both cases, base material fracture, i.e., fracture in the resin member 2 outside the portion where the shoulder 21b passes, was observed in the specimen. In addition, in the specimen with a 700 rpm tool rotation speed, fracture at the joint interface, i.e., the tool passage region 1a, was also observed. Thus, the maximum tensile strength of the specimens in Example 1 (31 MPa, 51 MPa) was greater than the maximum tensile strength of Comparative Example 1 (8.76 MPa) described above, confirming that the joint strength was improved compared to the joint when the metal member 1 was laser-treated.

[0070] Figure 9 shows the appearance of the specimen after the tensile shear test in Example 1, where (a) is the appearance of the specimen at a tool rotation speed of 700 rpm, and (b) is the appearance of the specimen at a tool rotation speed of 800 rpm. The area enclosed by the dashed lines in the metal member 1 indicates the tool passage area 1a. The specimen shown in Figure 9(a) with a tool rotation speed of 700 rpm fractured within the tool passage region 1a. The specimen shown in Figure 9(b) with a tool rotation speed of 800 rpm fractured outside the tool passage region 1a, i.e., the base material fractured.

[0071] Figure 10 shows the joint surface and fracture surface of the resin member 2 of the test specimen shown in Figure 9(a) at a tool rotation speed of 700 rpm, as observed with an optical microscope. Figure 2a shows the joint surface between the resin member 2 and the metal member 1, and Figure 2b shows the fracture surface of the resin member 2 (PPS). In the enlarged upper right photograph of the joint surface 2a, numerous reinforcing materials 5 (carbon fibers) oriented in various directions can be seen, and in the enlarged lower right photograph of the fracture surface 2b, exposed reinforcing materials 5 (carbon fibers) can be seen. From these photographs, it can be inferred that the reinforcing materials 5 present on the joint surface 2a and the fracture surface 2b enhance the mechanical fastening force, or so-called anchoring effect, at the joint interface between the metal member 1 and the resin member 2, thereby contributing to improved joint strength.

[0072] [Results of Example 2] By setting the indentation amount (depth) of shoulder 21b to 0.35 mm and conducting two bonding experiments, it was possible to create a joint between metal member 1 and resin member 2 in both cases. However, when the amount of indentation of the joined body (test piece) was measured, a value different from the set value of 0.35 mm was measured. Specifically, in the first joining experiment, the measured value of the indentation was smaller than the set value of 0.35 mm (0.11 mm). On the other hand, in the second joining experiment, the measured value of the indentation was larger than the set value of 0.35 mm (0.48 mm). The reason why the set value and the measured value of the indentation differed was presumed to be due to errors caused by slight misalignment of the fixing position of metal member 1, etc., because the thickness of metal member 1 used was thin at 1 mm.

[0073] In the first bonding experiment, bonding was confirmed in 3 out of 5 test pieces, but in 2 out of 5 test pieces, the resin member 2 peeled off from the metal member 1. The cause of this peeling is presumed to be that the measured indentation amount of the shoulder 21b, 0.11 mm, was smaller than the set value of 0.35 mm, and therefore the amount of heat input due to frictional heat from the shoulder 21b was insufficient. In the second bonding experiment, bonding was confirmed in all five test pieces, but in some test pieces, the resin component 2 of the lower plate was exposed due to excessive pressure from the shoulder 21b.

[0074] [Results of cross-sectional observation] Figure 11 is a cross-sectional view of the joint (test piece) of metal member 1 and resin member 2 observed with an optical microscope (10x magnification) in Example 2. Figure 12 is a cross-sectional view of the joint observed at an even higher magnification (50x magnification). The observed joint is the test piece that was successfully joined in the first joining experiment described above. From the cross-section of the joint shown in Figure 11, it was confirmed that a layer of powder material 3 existed between the metal member 1 and the resin member 2. The layer of powder material 3 was observed throughout the entire tool passage region 1a. The thickness of the powder material 3 layer in this case was approximately 172 μm. In the enlarged cross-section of the joint shown in Figure 12, it was observed that carbon fibers, which are the reinforcing material 5, and PPS resin powder, which is the resin powder 4 that is not in paste form, were dispersed at the bonding interface between the metal member 1 and the powder material 3. Furthermore, in the cross-section of the test specimens that were successfully joined in the second joining experiment described above, a clear layer of powder material 3 as shown in Figure 11 was not observed. It was presumed that the proportion of powder material 3 that flowed and was extruded to the outside of the shoulder 21b increased due to the pressing of the shoulder 21b.

[0075] [Results of tensile shear test] Figure 13 shows the appearance of the test specimens in Example 2 after the tensile shear test, and is a front view showing the state of the joint surfaces of the resin member 2 and metal member 1 after fracture. The test specimens shown in Figure 13 are the five specimens that were joined in the second joining experiment described above. The area below the dashed line shown on the resin member 2 side is the tool passage region 1a, the area enclosed by the circle frame indicates the fracture location, and the area between the dashed lines shown on the metal member 1 side is the tool passage region 1a.

[0076] Test specimen No. 1 was delaminated during specimen preparation. Test specimen No. 2 fractured on the resin member 2 side within the tool passage region 1a. Test specimen No. 3 fractured on the metal component 1 side, where it had slightly penetrated the tool passage area 1a. Test specimens No. 4 and 5 fractured on the resin member 2 side, where it had slightly penetrated the tool passage area 1a. In test specimens No. 2, 4, and 5, where the resin member 2 side fractured, the resin member 2 within the tool passage area 1a remained bonded to the metal member 1 without separating. It was presumed that test specimen No. 3 fractured because the tool 21A was pushed in too far, causing the metal member 1 to become thin and brittle.

[0077] The maximum tensile shear load was approximately 2.6 kN for specimen No. 4, and the average value for these specimens was approximately 2.3 kN. Although this value was slightly lower than the maximum tensile shear load of the specimen in Example 1, which used tool 21 with probe 21c, it was confirmed that by precisely controlling the amount of indentation of shoulder 21b, it is possible to obtain a joint strength comparable to that of Example 1, which used friction stir welding, even when using a probeless type tool 21A for friction lap bonding.

[0078] The present invention is not limited to the embodiments described above, and various modifications are possible, which are also included within the scope of the present invention. The present invention is widely applicable in fields such as joining technologies that aim to reduce the weight of structures by using multi-material construction with dissimilar materials. By applying the present invention to such fields, it can be widely used in the manufacture of structures and parts used in automobiles, aircraft, and other applications where weight reduction is particularly required while ensuring strength. [Explanation of Symbols]

[0079] 1 Metal component 1a Tool passage area 1b Surface treatment area 2 Resin component 3 Powder material 4. Resin powder 5 Reinforcement material 10 Bonding equipment 11 Tables 12 Fixing fixtures 20 Joining Tool Units 21, 21A Tools 21a Main body 21b Shoulder 21b probe 22 Chuck part 23 Rotary motors 24 Main body 25 Pressing and moving mechanism 30 Powder layer forming unit 31 Filling section 32 Discharge part 35 Moving mechanism 40 Control Unit

Claims

1. A joining method in which a metal member and a resin member are overlapped and the metal member and the resin member are joined by using frictional heat, The process includes a joining step in which a powder material is placed between the metal member and the resin member, and frictional heat is applied from the side of the metal member to join the metal member and the resin member, A bonding method characterized in that the powder material comprises resin powder and a reinforcing material.

2. The aforementioned joining process, The first step is to form a layer of the powder material on the surface of the resin member, A second step involves placing the metal member on top of the resin member on which the layer of the powder material is formed, The joining method according to claim 1, further comprising a third step of pressing a tool onto the surface of the metal member while rotating it to generate frictional heat, softening and melting at least a portion of the powder material with this frictional heat, and then solidifying it to join the metal member and the resin member.

3. The joining method according to claim 2, characterized in that the third step includes a step of pressing the tool into the metal member while rotating it, so as to penetrate to a depth that does not reach the interface between the metal member and the powder material.

4. The bonding method according to any one of claims 1 to 3, characterized in that the resin powder has a particle size in the range of 1 to 100 μm.

5. The joining method according to any one of claims 1 to 3, characterized in that the reinforcing material is a reinforcing fiber having an average fiber diameter of 5 to 20 μm and an average fiber length of 10 to 100 μm.

6. The joining method according to any one of claims 1 to 3, characterized in that the powder material contains 10 to 40% by weight of the reinforcing material relative to the total amount of the powder material.

7. The joining method according to any one of claims 1 to 3, characterized in that the resin member and the resin powder are thermoplastic resins.

8. The joining method according to claim 7, characterized in that the thermoplastic resin is an engineering plastic or a super engineering plastic.

9. The joining method according to any one of claims 1 to 3, characterized in that the metal member is a light metal or a light alloy.

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