Hybrid joining method for metal components
The hybrid joining method addresses the issue of oxide and plating films in diffusion joining by combining mechanical and diffusion processes, achieving high adhesion and improved composite member quality through a diffusion layer.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- NITTO SEIKO CO LTD
- Filing Date
- 2024-10-31
- Publication Date
- 2026-05-18
AI Technical Summary
Diffusion joining of metal members is hindered by oxide films and metal plating films that cannot be removed, leading to inadequate adhesion and increased electrical resistance in composite members.
A hybrid joining method combining mechanical and diffusion joining, where tin is added between convex and concave portions, followed by mechanical flattening and pressure application, then heating to form a diffusion layer.
The method effectively removes oxide and plating films, enabling high adhesion and solid solution strengthening with a diffusion layer, even at low melting points, enhancing the composite member's quality.
Smart Images
Figure 2026079922000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a technique for joining metal members by a plurality of joining methods, and particularly to a hybrid joining method for metal members that combines mechanical joining and diffusion joining.
Background Art
[0002] Conventionally, when manufacturing a composite member by joining a joining member and a joined member made of a metal material, depending on the use of the composite member, a high degree of adhesion is required at the joining location. For example, in a lithium battery, since a lead wire or the like is attached to an electrode terminal by welding or the like, a composite member in which a copper member having high conductivity and an aluminum member having high corrosion resistance are joined with enhanced adhesion so as not to increase the electrical resistance is required for the electrode terminal. As a joining method for metal members that meets this type of requirement, the diffusion joining method described in Japanese Patent Publication No. 59-52031 (Patent Document 1), Japanese Patent Publication No. 64-4581 (Patent Document 2), etc. is known as the optimal method.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0004] However, in diffusion joining, when an oxide film or impurities adhere to the joining interface, there is a problem that diffusion joining cannot be performed because these cannot be removed. Also, when one of these members is coated with a metal plating film that is difficult to diffusion-join, similarly, in a general integral joining method, there is a problem that diffusion joining cannot be performed because the plating film remains on the joining portion of the two members without being peeled off.
[0005] This invention was invented to solve the above problems, and aims to provide a hybrid joining method and joining structure for metal members that can stably join metal members coated with a plated film. [Means for solving the problem]
[0006] The above problem can be solved by a hybrid joining method for metal members, which includes a mechanical joining step in which tin is added between the convex portion of a metal joining member and the concave portion of a metal member to be joined, and pressure is applied in a compressive direction to both members while these convex and concave portions are fitted together, thereby flattening the outer circumference of the end face of the convex portion of the joining member outward to form an undercut portion and joining the two members together as a single unit; and a diffusion joining step in which the two members joined by the mechanical joining step are placed in a heating furnace and heated at a predetermined temperature for a predetermined time to generate a diffusion layer at the joint of the two members.
[0007] In the mechanical joining process, it is preferable to flatten the outer circumference of the end face of the protrusion of the joining member outward until the plating film on the end face of the protrusion cracks.
[0008] Furthermore, the diffusion bonding process is preferably liquid-phase diffusion bonding. [Effects of the Invention]
[0009] According to the present invention described above, even if both members are covered with an oxide film, a metal plating film that is difficult to diffuse bond, etc., the oxide film, plating film, etc. are destroyed or separated by mechanical bonding by stretching the two members in a mechanical bonding process before diffusion bonding. This generates a sufficient diffusion layer at the bonding interface, providing a composite member with high adhesion and solid solution strengthening. In particular, by adding tin to the bonding interface, diffusion bonding at a low melting point becomes possible. [Brief explanation of the drawing]
[0010] [Figure 1] The figure shows a hybrid joining method for metal members according to an embodiment of the present invention, where (a) is a diagram of the mechanical joining process and (b) is a diagram of the diffusion joining process. [Figure 2] An explanatory diagram showing the mechanical joining process of a hybrid joining method for metal members according to an embodiment of the present invention, in order of steps. [Figure 3] A longitudinal cross-sectional view showing a hybrid joining structure of metal members according to an embodiment of the present invention. [Modes for carrying out the invention]
[0011] The hybrid joining method for metal members according to the present invention will be described below with reference to the drawings. The first joining method consists of a mechanical joining process shown in Figures 1(a) and 2(a), (b), and (c), and a diffusion joining process shown in Figure 1(b).
[0012] The mechanical joining process comprises a joining member 1 made of copper material having a shaft portion 1a, a flange portion 1b, and a protrusion portion 1c; a member to be joined 2 made of columnar aluminum alloy material having a recess 2a that abuts against the flange portion 1b and fits into the protrusion portion 1c; and a receiving mold 3 and a pressing mold 4 arranged to pressurize both members. The joint is formed by pressing the member to be joined 2 to the joining member 1 by the pressing mold 4, thereby forming a composite member CC. In addition, tin is pre-added to the interface between the protrusion portion 1c and the recess 2a.
[0013] The receiving mold 3 has an enlarged hole 3a that guides a part of the member to be joined 2 and a positioning hole 3b that communicates with the enlarged hole 3a and positions the shaft portion 1a of the joining member 1. A knockout pin 5 extending concentrically is positioned to protrude from the positioning hole 3b, and the end face of the knockout pin 5 is configured to close the bottom of the positioning hole 3b. The knockout pin 5 is also configured to position the flange portion 1b of the joining member 1 within the positioning hole 3b in the enlarged hole 3a of the receiving mold 3, and to expose the protrusion 1c of the joining member 1 from the receiving mold 3. Furthermore, when the knockout pin 5 protrudes into the positioning hole 3b after the push die 4 has retracted, the shaft portion 1a of the joining member 1 located in the positioning hole 3b is removed from the receiving mold 3 together with the member to be joined 2 to which it is integrally joined.
[0014] The mechanical joining process preferably includes a pre-molding die 6 having a pre-molding hole 6a, as shown in Figure 2(a). The pre-molding die 6 is configured to pre-form the member to be joined 2, which fits into the protrusion 1c of the joining member 1, into a pan-head shaped portion 2b. The pre-molding hole 6a of this pre-molding die 6 allows the excess material of the member to be joined 2 to extend in a direction intersecting its pressurizing direction. Furthermore, during the pre-molding of the member to be joined 2, the pre-molding die 6 is configured to form a part of the member to be joined 2 that fits into the protrusion 1c of the joining member 1 into a shape along the enlarged hole 3a of the receiving die 3, and to make it adhere closely to the flange portion 1b of the joining member 1.
[0015] As shown in Figures 2(b) and 2(c), the press mold 4 is configured to plastically deform the pre-formed pan-head-shaped molded portion 2b into a flat plate-shaped head 2d of a predetermined thickness after the pre-formed member to be joined 2, thereby joining the two members together as a single unit. Furthermore, similar to the pre-forming mold 6, the press mold 4 is configured to increase the hardness of the member to be joined 2 by work hardening the member to be joined 2, which has low hardness, during the molding process, and to press the convex portion 1c of the joining member 1, which has high hardness, through the inner wall of its concave portion 2a.
[0016] Although the joining member 1 is made of copper, it may be made of a harder metal material such as iron.
[0017] The heating furnace 7 in the diffusion bonding process, as shown in Figure 1(b), only needs to have a structure that heats the composite member CC that is placed inside the furnace. It is heated in an atmospheric environment at 550°C, the eutectic point of copper and aluminum, for 2 hours or more, preferably about 4 hours. This is configured to cause a eutectic reaction at the joint of the composite member CC, thereby creating a diffusion layer on the newly formed surface. Since diffusion bonding is possible simply by heating the composite member placed in this heating furnace 7, a large number of composite members CC can be placed in the heating furnace 7.
[0018] Furthermore, the diffusion bonding method is not limited to the liquid-phase diffusion bonding described above, but may also be solid-phase diffusion bonding. It is also preferable to heat the materials of the bonding member and the member to be bonded at a eutectic point and for a heating time appropriate to the materials.
[0019] As shown in FIG. 3, in the mechanical joining step, the hybrid joining structure CC formed by the above hybrid joining method is such that, as shown in FIG. 3, while plastically deforming so that the end face of the convex portion 1c of the joining member 1, that is, the upper end face 10 extends in a direction intersecting the pressing direction, the outer periphery of the upper end becomes flat outward and an undercut portion 1ca is formed. Along with this, the joined member 2 also plastically deforms, so that the surplus material thereof wraps around the back surface 11 of the undercut portion 1ca, and the joined member 2 adheres to the entire surface of the undercut portion 1ca, and the joining member 1 and the joined member 2 are mechanically joined to produce the composite member CC. At this time, with respect to the plating film covering the joining member 1, the plating film on the upper surface of the undercut portion 1ca is broken and removed because it is flattened outward. On the other hand, on the back surface of the undercut portion 1ca, the plating film is compressed and the thickness increases.
[0020] Thereafter, in the diffusion joining step, the composite member CC formed in the mechanical joining step is put into the heating furnace 7 in the heating step and heated at a predetermined temperature. At this time, the upper end face 10 of the undercut portion 1ca of the joining member 1 has the plating film removed, the joining member 1 and the joined member 2 are in close contact, there is no air layer at the joining portion of the two members, and the atmosphere does not circulate into the joining portion. Therefore, a new oxide film does not cover the newly generated surfaces formed on both members constituting the joining portion, the adhesion between the two members is very high, and a diffusion layer of sufficient thickness is generated on the newly generated surfaces as shown. Thereby, it is possible to manufacture the composite member CC joined at a joining portion with high solid solution strengthening and high adhesion. Also, since tin is added in advance to the joining interface, it is possible to realize diffusion joining at a low melting point.
[0021] On the other hand, the joining interface between the joining member 1 and the joined member 2, except for the upper surface 10 of the undercut portion 1ca, has the plating film compressed and the thickness increased in the process of the mechanical joining step, so this becomes a barrier and no eutectic reaction occurs. Since the diffusion layer is inferior in durability, the fact that the diffusion layer is not generated in the portion P where the joining interface is in contact with the external environment leads to an improvement in quality.
[0022] The specific configuration of each part of the present invention is not limited to only the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention.
Explanation of Reference Numerals
[0023] CC... composite member 1 joining member 1a shaft portion 1b flange portion 1c convex portion 1ca undercut portion 2 joined member 2a concave portion 3 receiving type 4 pressing type
Claims
1. A mechanical joining process is performed in which tin is added between the protrusions of a metal joining member and the recesses of a metal member to be joined, and pressure is applied in a compressive direction to both members while these protrusions and recesses are fitted together, thereby flattening the outer circumference of the end face of the joining member outward to form an undercut portion, and joining the two members together as a single unit. A diffusion bonding process is performed by placing the two members joined by a mechanical bonding process into a heating furnace and heating them at a predetermined temperature for a predetermined time to generate a diffusion layer at the joint between the two members. A hybrid joining method for metal members, characterized by having [a specific feature].
2. The hybrid joining method for metal members according to claim 1, characterized in that, in the mechanical joining process, the outer circumference of the end face of the protrusion of the joining member is flattened outward until the plating film or oxide film on the end face of the protrusion of the joining member cracks.
3. The hybrid bonding method for metal members according to claim 1 or 2, characterized in that the diffusion bonding step is liquid-phase diffusion bonding.