Method and apparatus for joining metal components

Abstract

The present invention provides a method and apparatus for joining metal members that can increase the bonding area between a first member and a second member while using general-purpose equipment. [Solution] The insertion portion 12A of the second member 12 is inserted into the hole 11A of the first member 11, and the inner surface of the hole 11A and the outer surface of the insertion portion 12A are joined. The first electrode 10 is connected to the first member 11 and the second electrode 20 is connected to the cylindrical portion 12B of the second member 12. With the insertion portion 12B of the second member 12 inserted into the hole 11A of the first member 11, the conductive portion 20X of the second electrode 20 is positioned at least at a position corresponding to the hole 11A, causing resistance heating between the inner surface of the hole 11A and the outer surface of the insertion portion 12A to join them.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for joining metal members, which join by energization heating in a state where an insertion portion of a second member is inserted into a hole portion of a first member.

Background Art

[0002] A form of joining by energization heating in a state where an insertion portion of a second member is inserted into a hole portion of a first member is well known. For example, in Patent Document 1, a cylindrical first metal member and a second metal member having a shaft portion press-fitted and inserted inside the first metal member are pressurized in the axial direction by resistance welding by energization, and the shaft portion of the second metal member is press-fitted and inserted inside the first metal member, and an inner peripheral surface inside the first metal member and an outer peripheral surface of the shaft portion of the second metal member are joined. A joining apparatus for metal members (hereinafter also referred to as "prior invention") is described.

[0003] In the prior invention, a pressing means for pressing the first metal member and the second metal member in the axial direction, a first metal member side electrode that contacts the first metal member, and a second metal member side electrode that contacts the second metal member and conducts energization for the resistance welding between the first metal member side electrode are provided.

[0004] However, when the contact area between the first metal member side pressing portion and the first metal member becomes small, since the first metal member side pressing portion also serves as an electrode, during energization for resistance welding, the current density at the contact portion between the first metal member side pressing portion and the first metal member becomes too high, and there is a high possibility that the first metal member side pressing portion and the first metal member are melted due to heat generation at the contact portion.

[0005] To solve this problem, the prior invention, with reference to the reference numerals in Figure 1 of Patent Document 1, has a first metal member side pressurizing portion 3 that contacts the entire end face of the first metal member 21 opposite to the second metal member 31 in the axial direction and pressurizes the first metal member 21 toward the second metal member 31, and the first metal member side electrode 11 is configured to contact a part of the first metal member 21 that is different from the end face that the first metal member side pressurizing portion 3 contacts, and the contact area between the first metal member side electrode 11 and the first metal member 21 is larger than the contact area between the first metal member side pressurizing portion 3 and the first metal member 21. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6409732 [Overview of the project] [Problems that the invention aims to solve]

[0007] Now, for example, there is a need to commercialize a drive component consisting of a two-stage gear. In this case, a drive component consisting of a two-stage gear can be manufactured by joining a gear material (large diameter) to a hollow gear material (small diameter) that is connected coaxially with it.

[0008] However, the prior invention is based on the premise that the pressurizing portion of the first metal member 21 is composed of the electrode 11 on the first metal member side, and is not applicable to the general configuration in which the electrode and the pressurizing portion are separate, making it not versatile.

[0009] Therefore, the main object of the present invention is to provide a method and apparatus for joining metal members that can increase the joining area between a first member and a second member while using a general-purpose apparatus. [Means for solving the problem]

[0010] The embodiments of the present invention for solving the above technical problems are as follows. (First aspect) In a method for joining a first member having a hole and a second member of a metal material having a cylindrical portion, The insertion portion of the second member is inserted into the hole of the first member, and the inner surface of the hole and the outer surface of the insertion portion are joined together. The first electrode is connected to the first member, and the second electrode is connected to the cylindrical portion of the second member. With the insertion portion of the second member inserted into the hole of the first member, the conductive portion of the second electrode is positioned at least at a position corresponding to the hole. Current is passed between the conductive portion of the first electrode and the second electrode, causing resistance heating between the inner surface of the hole and the outer surface of the insertion portion to form a bond. A method for joining metal members, characterized by the features described above. (Second aspect) In a joining device for a first member having a hole formed therein and a second member of a metal material having a cylindrical portion, The insertion portion of the second member is inserted into the hole of the first member, and the inner surface of the hole and the outer surface of the insertion portion are joined together. It has a first electrode connected to the first member and a second electrode connected to the cylindrical portion of the second member, With the insertion portion of the second member inserted into the hole of the first member, the conductive portion of the second electrode is positioned at least at a location corresponding to the hole. The system includes an energizing means that conducts current between the conductive portions of the first electrode and the second electrode, thereby generating resistive heating between the inner surface of the hole and the outer surface of the insertion portion. A device for joining metal members, characterized by the features described above. [Effects of the Invention]

[0011] According to the present invention, it is possible to increase the bonding area (bonding strength) between the first member and the second member while using a general-purpose device. [Brief explanation of the drawing]

[0012] [Figure 1]It is a longitudinal sectional view showing a manufacturing form by press fitting according to the first embodiment. [Figure 2] It is a diagram showing the relationship between the second member and the first member. [Figure 3] It is a front view showing the second electrode. [Figure 4] It is a diagram showing a cross section taken along line 4-4 of the front view according to the first embodiment. [Figure 5] It is a diagram showing a cross section taken along line 5-5 of the front view according to the first embodiment. [Figure 6] It is a diagram showing a cross section taken along line 6-6 of the front view according to the first embodiment. [Figure 7] It is an explanatory diagram of a form in which a diameter-expanding member and a fixture are inserted into the second electrode. [Figure 8] [[ID=2)1]]It is a diagram showing a longitudinal section of the second electrode, a diameter-expanding member attached thereto, and a fixture. [Figure 9] It is an explanatory diagram of a diameter-expanding form by a diameter-expanding member. [Figure 10] It is a longitudinal sectional view of a press-fitting preparation stage by a press-fitting member. [Figure 11] It is a longitudinal sectional view of a press-fitting stage. [Figure 12] It is a longitudinal sectional view showing a manufacturing form by press fitting according to the second embodiment. [Figure 13] Regarding the conventional example, the press-fitting stages are sequentially shown as (a), (b), and (c). [Figure 14] It is a longitudinal sectional view of a modified form of the example shown in FIG. 10. [Figure 15] It is a longitudinal sectional view of another example of a diameter-expanding member. [Figure 16] It is a longitudinal sectional view showing a mode of expanding the diameter using another diameter-expanding member.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that the content of the present invention should be interpreted based on the matters described in the claims and should not be interpreted as being limited to the embodiments.

[0014] Before describing embodiments of the present invention, we will explain some potential problematic cases. Specifically, we will examine the resistive heat generation during joining when a cylindrical member is used as the second member.

[0015] Figure 13 illustrates a configuration in which a first member 91 and a second member 92 are joined, with the insertion portion 92A of the second member 92 being press-fitted into the central hole 91A of the first member 91. It also illustrates the flow of electricity and the heat generation associated with Joule heating at each stage. The first member 91 is connected to the first electrode 93, and the second member 92 is connected to the second electrode 94. Figure 13(c) shows the state of the second member 92 during press-fit bonding.

[0016] To explain the press-fitting process step by step, as shown in Figure 13(a), the current flow between the second electrode 94 and the first electrode 93 during press-fitting is indicated by the dashed arrow. Note that in the case of an AC power supply, the positive and negative electrodes are reversed, so the arrows are bidirectional. When press-fitting begins due to the application of current, Joule heat is generated at the joint surface in the flow path through which the electricity flows, creating a heat-generating area 95A. In this case, the heat-generating area 95A has a small contact area and a small current-carrying area, so it actively generates heat and softens, and the pressure from the second electrode 94 causes the insertion portion 92A of the second member 92 to press-fit into the hole 91A of the first member 91.

[0017] As the press-fitting progresses further, the contact area increases, as shown in (b), and a larger heat-generating area 95B is created.

[0018] Next, as the press-fitting progresses further, the cross-sectional area of ​​the insertion portion 92A becomes smaller than the area of ​​the joint (the wall thickness Lb of the insertion portion 92A becomes smaller than the thickness La of the first member 91), and as shown in (c), electricity is generated in the wall thickness Lb portion of the insertion portion 92A, creating a heat-generating portion 95C.

[0019] Thus, when the heating element 95B moves to the heating element 95C of the insertion element 92A, the amount of heat generated at the joint to be press-fitted decreases thereafter, and the press-fitting does not proceed or proceeds at a slow speed. Furthermore, if the heating element 95C of the insertion part 92A generates heat, the degree of softening of that part increases, which could lead to deformation of the insertion part 92A.

[0020] If the press-fitting stops at the stage when the heat-generating part 95C is generated, as shown in (c), a sufficient bonding area cannot be obtained, or a gap G remains between the first member 91 and the main body portion of the second member 92. In this configuration, as shown in Figure 1, which represents an embodiment of the present invention, no step is visible between the main body portion of the second member 12 and the insertion portion 12A, no gap remains, and the outer surface of the first member 11 and the outer surface of the second member 12 cannot be joined in a continuous manner.

[0021] On the other hand, when considering the proportional relationship from the perspective of strength, in order to obtain the desired joint strength, it is necessary to deliberately increase the cross-sectional area of ​​the insertion portion 92A (increase the thickness Lb of the insertion portion 92A) in order to prevent the cross-sectional area of ​​the insertion portion 92A from becoming smaller than the area of ​​the joint (the wall thickness Lb of the insertion portion 92A from becoming smaller than the thickness La of the first member 91). Furthermore, if this measure was not adopted, it would be necessary to settle for a joint strength lower than the desired strength.

[0022] This presented a problem, for example, in the manufacturing of drive components and other parts that require a large bonding area (high bonding strength).

[0023] Furthermore, this problem remains the same even if there is no step between the insertion portion 92A and the main body portion of the second member 92, and the outer surface of the insertion portion 92A is flush with the main body portion, and even if the cross-sectional area of ​​the insertion portion 92A of the second member 92 is small.

[0024] (First Embodiment) A first embodiment for solving the aforementioned problem will be described with reference to Figures 1 to 11. In the first embodiment, in joining a first member 11 made of a metal material with a hole 11A and a second member 12 made of a metal material having a cylindrical portion 12B, the insertion portion 12A of the second member 12 is inserted into the hole 11A of the first member 11, and the inner surface of the hole 11A and the outer surface of the insertion portion 12A are joined.

[0025] Furthermore, as typically shown in Figure 1, the first electrode 10 is connected to the first member 11 and the second electrode 20 is connected to the cylindrical portion 12B of the second member 12. With the insertion portion 12A of the second member 12 inserted into the hole 11A of the first member 11, the conductive portion 20X of the second electrode 20 is positioned at least at a location corresponding to the hole 11A. Current is then passed between the first electrode 10 and the conductive portion 20X of the second electrode 20, causing resistive heating between the inner surface of the hole 11A and the outer surface of the insertion portion 12A, thereby joining the metal members. Furthermore, it is desirable that the joint between the inner surface of the hole 11A and the outer surface of the insertion portion 12A be a "solid-state joint". Figure 1 shows an example of a heat-generating portion Z at the joint surface.

[0026] On the other hand, as shown in Figure 2, it is desirable that a press-fit region is formed in advance between the first member 11 and the second member 12, where the outer diameter of the insertion portion 12A is larger than the inner diameter of the hole 11A. It is also desirable that the insertion portion 12A of the second member 12 is inserted into the hole 11A of the first member 11 by press-fitting, thereby joining the inner surface of the hole 11A with the outer surface of the insertion portion 12A.

[0027] Furthermore, it is desirable to form a first chamfered portion 11s over the entire entrance portion of the hole 11A of the first member 11, leave the corner portion 12e at the tip of the insertion portion 12A of the second member 12 at 90 degrees, or form a second chamfered portion of 0.35 mm or less, so that the inner surface of the hole 11A of the first member 11 and the outer surface of the insertion portion of the second member 12 overlap radially, with the center of the hole 11A, forming an overlapping overlap R.

[0028] The length of the first chamfered portion 11s means that the horizontal length wL is 0.35 mm or less and the vertical length hL is 0.35 mm or less. Generally, it has a chamfer angle of 45 degrees and is an inclined surface, but it may also be an arcuate surface in which the cross-sectional surface bulges or is concave.

[0029] In this case, it is desirable to keep the overlap allowance per side to 0.55 mm or less. The lower limit of the wrap allowance R is preferably 0.09 mm. Therefore, the overlap allowance R is preferably 0.09 to 0.55 mm, more preferably 0.13 mm to 0.50 mm, and especially preferably 0.15 mm to 0.45 mm.

[0030] If the overlap allowance R is excessively short, the amount of plastic deformation of the first member 11 and the first member 12 will be reduced, making it difficult to prevent or suppress the occurrence of unjointed sections. If it is excessively long, it will be necessary to increase the plastic deformation of the first member 11 and the first member 12, which will place an excessive burden on them and may lead to the occurrence of unjointed sections from this perspective as well.

[0031] Furthermore, it has already been determined that the first chamfered portion 11s preferably has an inclination angle θ of 10 to 70 degrees with respect to the surface of the first member 11 (the upper surface in Figure 2), and a surface length wL in plan view of 0.25 mm or more and 0.75 mm or less. The inclination angle θ is the tangent angle of the vertical length H hL with respect to the surface length wL.

[0032] The material of the first and second members according to the present invention can be selected from a range of suitable metal materials, such as aluminum or aluminum alloy, carbon steel, alloy steel, and stainless steel. While steel is particularly preferable, it is clear from the principle of joining by electrical heating that even if other metal materials as exemplified above, which allow for easier plastic deformation, are used, it is possible to obtain a stable joined product that suppresses the occurrence of unjointed areas and enhances joint strength. Furthermore, it has high industrial value, especially when applied to jointed products of steel materials such as carbon steel (S35C, etc.), steel materials (HRC18-50, etc.), and high-strength steel materials (SPF590, SPF980, etc.). Regarding hardness, the hardness of the second component can be made higher than that of the first component.

[0033] The first member 11 can be a gear, lever, sprocket, plate, disc, or other drive component, or a metal element component. The thickness of the first member (at least the thickness around the hole) should preferably be 1.5 mm to 13 mm, and especially 2.5 mm to 5.5 mm. Furthermore, to ensure sufficient joint strength, a thickness of 3.7 mm to 5.5 mm is desirable. If the plate thickness is too small, it will be difficult to obtain sufficient joint strength.

[0034] The hole 11A of the first member 11 is circular in plan view, and the diameter of the hole 11 is constant. The plan view shape of the hole 11 may be other shapes besides a perfect circle, such as an ellipse or a polygon (quadrilateral, etc.), but if it is polygonal, stress will be generated at the corners of the hole 11A during joining, and the stress will not be distributed uniformly, so it is preferable to make it circular.

[0035] The second member 12 has an insertion portion 12A with a wall thickness of 2.0 mm to 12.0 mm, preferably 4.0 mm to 8.0 mm. The plate thickness of the first member is, for example, 1.5 mm to 13 mm. From the viewpoint of obtaining a jointed product with high joint strength according to the present invention, it is desirable that the second member 12 be configured as a part of a drive system that requires torque in particular. For example, the outer surface of the first member 11 can be gear-machined, and the outer surface of the second member 12 can also be gear-machined to create a stepped composite gear. Furthermore, the outer surface of the second member 12 can be configured as a sprocket, and the torque from the drive system can be received by the sprocket to provide rotational force to the first member 11.

[0036] On the other hand, current is supplied from the second electrode 20 to the second member 12 through a conductive portion 20X, which is the part of the inner surface of the cylindrical portion 12B of the second member 12 that contacts the second electrode 20 and conducts current. The configuration of the second electrode 20, including the conductive portion 20X, can be such that, for example, as shown in Figures 3 to 6, it is divided into multiple circumferential sections (the illustrated configuration is divided into four sections) and has multiple flexible divided conductive portions 22, the outer surface of each divided conductive portion 22 constituting the conductive portion 20X of the second electrode 20.

[0037] To further explain the configuration example of the second electrode 20, a hole is formed in the center, giving it a recessed hole portion 21. In addition, through holes 23, 23 are formed on the lower side, penetrating from left to right, and four slits 24 are formed from these through holes 23, 23 to the lower end, forming four divided conductive portions 22. Furthermore, as clearly shown in Figure 9, below the push-in hole 21 is a smaller diameter tip push-in hole 21b, into which the enlarged diameter portion 30A, where the outer surface of the enlarged diameter member 30 expands towards the rear, enters.

[0038] By pushing the diameter-expanding member 30 into the central part surrounded by multiple segmented conductive parts 22, each segmented conductive part 22 is expanded radially from the center, and the outer surfaces of each segmented conductive part 22 are pressed against the inner surface of the insertion part 12A of the second member 12, the conductive part 20X comes into close contact with the inner surface of the cylindrical part 12B of the second member 12, thereby ensuring that current is supplied by the second electrode 20.

[0039] An example of the diameter-expanding member 30, as shown in Figure 7, has a diameter-expanding portion 30A whose outer surface expands toward the rear. The diameter-expanding member 30 is pushed from rear to front into the central part surrounded by a plurality of divided conductive portions 22, thereby expanding each divided conductive portion 22 radially from the center. With this configuration, each segmented conductive part 22 can be expanded with a uniform expansion force in the radial direction from the center.

[0040] Although this partially overlaps with what has already been explained, the second electrode 20 has a push-in hole 21 in the center, and this push-in hole 21 is connected to the center of the conductive portion 20X. An expanding member 30 having an expanding portion whose outer circumferential surface expands toward the rear can be pushed from rear to front through the push-in hole 21 into the center surrounded by a plurality of divided conductive portions 22, thereby expanding each divided conductive portion 22 radially from the center.

[0041] In this embodiment, a groove 21a is formed on the inner surface of the push-in hole 21, and by screwing in the fixing device 40 that fits into this groove 21a, the expandable diameter member 30 can be pushed in from the rear to the front via the rear surface of the expandable diameter member 30. In this configuration, the fixing device 40 is screwed into the groove 21a, ensuring that a uniform diameter-expanding force is applied to each segmented conductive part 22 in a radial direction from the center, and the position of the diameter-expanding member 30 is stable, so that the conductive part 20X does not separate from the inner surface of the cylindrical part 12B of the second member 12 during energization.

[0042] The configuration of the conductive portion 20X and the means by which the conductive portion 20X contacts and adheres to the inner surface of the cylindrical portion 12B of the second member 12 can be modified as appropriate.

[0043] A known energizing means 60 can be connected to the first electrode 10 and the second electrode 20 to provide energy. The energizing means 60 may include an AC power supply or a DC power supply.

[0044] When pressing the second member 12 into the first member 11, a suitable piston mechanism such as pneumatic or hydraulic can be used. Furthermore, as shown in Figure 1, an annular press-fit member 50 having a fixing hole 50a is provided on one end face of the second member 12, and the second electrode 20 is fitted into the fixing hole 50a. By interposing the press-fit member 50 and applying pressure to one end face of the second member 12, the insertion portion 12A can be press-fitted. The press-fit member 50 can be made of an insulator.

[0045] When joining the inner surface of the hole portion 11A of the first member 11 and the outer surface of the insertion portion 12A of the second member 2, as shown in FIG. 1, the axial length range of the joint surface (in the embodiment, it corresponds to the thickness of the first member 11) L0 and the axial length L1 of the conductive portion 20X of the second electrode 20 are particularly in the relationship of 0.6L0 < L1 < 1.4L0, and the effects of the present invention are显著 manifested. Preferably, 0.8L0 < L1 < 1.2L0, more preferably 0.9L0 < L1 < 1.1L0, optimally L0 = L1, and it may also be 0.95L0 < L1 < 1.05L0. If the axial length L1 of the conductive portion 20X is excessively short, it is difficult to increase the axial length range L0 of the joint surface. If the axial length L1 of the conductive portion 20X is excessively long, the heat affected zone becomes wider than necessary, leading to a decrease in dimensional accuracy including the joint surface.

[0046] (Second Embodiment) In the first embodiment, the diameter expanding member 30 and the fixture 40 are pushed into the second electrode 20 from above to below. On the contrary, as shown in FIG. 12, a second embodiment in which the diameter expanding member 30Y and the fixture 40Y are pushed into the second electrode 20Y from below to above may be adopted. Since the basic configuration of this second embodiment is the same as that of the first embodiment, the description is omitted.

[0047] (Other Embodiments) On the other hand, since the diameter expanding member 30 is pushed forward into the insertion hole portion 21 of the second electrode 20 to expand each divided conductive portion 22 in the radial direction from the center, each time the diameter is expanded, the acute-angle shoulder portion in the insertion hole portion 21 may be worn or damaged. Therefore, as shown in FIG. 14 which is an enlarged view of the main part of FIG. 10, the acute-angle shoulder portion in the insertion hole portion 21 can be made into a curved surface or a chamfered surface 21a to prevent wear.

[0048] Also, the means for bringing the conductive portion 20X into contact and adhesion with the inner surface of the cylindrical portion 12B of the second member 12 can be appropriately changed by those skilled in the art.

[0049] As an example, in the aforementioned example, the diameter-expanding member is pushed in from above to below, but it is also possible to expand the diameter of the conductive portion of the second electrode 20 by pulling the diameter-expanding member up from below to above.

[0050] For example, the diameter-expanding member 30X shown in Figure 15 can be used. The diameter-expanding member 30X has a tapered portion 31 that widens downwards at the lower part of the drawing, and the upper part is a connecting portion 32 with the lifting member 41. In addition, a splitting portion 33 is formed from the lower end upwards. Multiple splitting portions 33 are formed in the circumferential direction (for example, three or four). Furthermore, a splitting window portion 34 is formed connected to each splitting portion 33.

[0051] As shown in Figure 16, the diameter-expanding member 30X can be inserted into the recessed hole 21 of the second electrode 20, and a lifting member 41 can be connected to the connecting portion 32 of the diameter-expanding member 30X, for example, by screw connection. By pulling the lifting member 41 upward, the inner surface of the recessed hole 21 of the second electrode 20 can be expanded, thereby expanding the diameter of the conductive portion 20X radially from the center. As the diameter-expanding member 30X is pulled up, the tapered portion 31 advances while the slotted portion 33 connected to the slotted window portion 34 in the diameter-expanding member 30X is deformed, and the diameter expansion stops once it has advanced to a certain point. Thus, a uniform radial expansion force can be reliably applied to each segmented conductive part 22 in the radial direction from the center. In this configuration, the lifting member 41 is not used, and the length of the diameter-expanding member 30X is increased, allowing the upper part to be chucked and pulled upward by a chuck mechanism (not shown) selected as appropriate.

[0052] As those skilled in the art can infer from the above descriptions of each form, when adopting a form in which the conductive portion 20X of the second electrode 20 is expanded radially from the center, the mechanism of a known machine tool's collect chuck can be appropriately applied. [Explanation of Symbols]

[0053] 10 1st electrode 11. First Member 11A hole 11s First chamfered section 12 Second Member 12A Insertion section 12B Cylinder part 20 2nd electrode 20X conductive parts 22 divided conductive parts 24 slits 30, 30X diameter expanding member 33 Slit section 40 Fixtures 41 Lifting member 50 Press-fit member 60 Energizing means R Wrap fee Z Heating element

Claims

1. In a method for joining a first member of a metal material having a hole formed therein to a second member of a metal material having a cylindrical portion, The insertion portion of the second member is inserted into the hole of the first member, and the inner surface of the hole and the outer surface of the insertion portion are joined together. The first electrode is connected to the first member, and the second electrode is connected to the cylindrical portion of the second member. With the insertion portion of the second member inserted into the hole of the first member, the conductive portion of the second electrode is positioned at least at a location corresponding to the hole. Current is passed between the conductive portion of the first electrode and the second electrode, causing resistance heating between the inner surface of the hole and the outer surface of the insertion portion to form a bond. A method for joining metal members, characterized by the features described above.

2. A press-fitting region is formed in advance between the first member and the second member, where the outer diameter of the insertion portion is larger than the inner diameter of the hole. A method for joining metal members according to claim 1, comprising inserting the insertion portion of the second member into the hole of the first member by press-fitting, thereby joining the inner surface of the hole and the outer surface of the insertion portion.

3. The conductive portion is divided in the circumferential direction into a plurality of flexible segmented conductive portions, and each segmented conductive portion constitutes a part of the second electrode. A method for joining metal members according to claim 1 or 2, comprising: pushing an expanding member into the central part surrounded by the plurality of divided conductive parts; expanding the diameter of each divided conductive part radially from the center; and pressing the outer surfaces of each of the plurality of divided conductive parts against the inner surface of the insertion part of the second member.

4. The method for joining metal members according to claim 3, wherein the diameter-expanding member has a diameter-expanding portion whose outer surface expands toward the rear, and the diameter-expanding member is pushed from rear to front into a central part surrounded by a plurality of divided conductive parts, thereby expanding each divided conductive part radially from the center.

5. The method for joining metal members according to claim 3, wherein the second electrode has a push-in hole in the center and is connected to the center of the conductive portion, and the expanding member has an expanding diameter portion in the center surrounded by a plurality of divided conductive portions, the outer surface of which expands toward the rear, is pushed from rear to front to expand the diameter of each divided conductive portion radially from the center.

6. The method for joining metal members according to claim 5, wherein a groove is formed on the inner surface of the push-in hole, and the expandable member is pushed from rear to front through the rear surface of the expandable member by screwing in a fastener that is screwed into the groove.

7. A method for joining metal members according to claim 2, wherein an annular press-fitting member having a fixing hole is provided on one end face of the second member, the second electrode is fitted into the fixing hole, and the press-fitting member is used to interpose a pressing force on one end face of the second member to press-fit the insertion portion.

8. The method for joining metal members according to claim 1, wherein the axial length range L0 of the joining surface between the inner surface of the hole and the outer surface of the insertion portion and the axial length L1 of the conductive portion of the second electrode are in a relationship of 0.6L0 < L1 < 1.4L0.

9. In a joining device for a first member having a hole formed therein and a second member of a metal material having a cylindrical portion, The insertion portion of the second member is inserted into the hole of the first member, and the inner surface of the hole and the outer surface of the insertion portion are joined together. It has a first electrode connected to the first member and a second electrode connected to the cylindrical portion of the second member, With the insertion portion of the second member inserted into the hole of the first member, the conductive portion of the second electrode is positioned at least at a location corresponding to the hole. The system includes an energizing means that conducts current between the conductive portions of the first electrode and the second electrode, thereby generating resistive heating between the inner surface of the hole and the outer surface of the insertion portion. A device for joining metal members, characterized by the features described above.

10. A press-fitting region is formed in advance between the first member and the second member, where the outer diameter of the insertion portion is larger than the inner diameter of the hole. The metal member joining device according to claim 9, further comprising a press-fitting means for inserting the insertion portion of the second member into the hole of the first member by press-fitting, thereby joining the inner surface of the hole with the outer surface of the insertion portion.

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