JP2007326125A - High conductive workpiece to be welded and resistance welding method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a workpiece to be welded, which has a projection of vertically two-staged structure for making it weldable even if the workpiece has high conductivity, such as a copper member, without forming a film of low-melting metal, and to provide a resistance welding method. <P>SOLUTION: The workpiece W1 to be welded having high conductivity is resistance-welded to another metal member by passing a welding current. The workpiece W1 has the projection of vertically two-staged structure that is composed of a first projection P1, which is projected from the joint surface of the workpiece W1, and a second projection P2, which is projected from part of the joint surface side of the first projection P1. The area of the joint surface of the second projection P2 is too small to obtain a desired weld strength, but large enough so that the projection P2 is not collapsed by a pressure applied in welding. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides resistance welding of high-conductivity members that have been extremely difficult to join with conventional resistance welding methods such as copper members and copper members having high conductivity, such as workpieces made of various kinds of the same or different metal materials. The present invention relates to a highly conductive metal member having a projection structure suitable for the above and a resistance welding method thereof.

  Various methods for joining dissimilar metal materials with different characteristics such as melting point and electrical conductivity, such as metal materials of the same kind, iron-based materials and stainless steel materials, iron-based materials and copper members, or iron-based materials and aluminum materials have been proposed. However, bonding of dissimilar metal materials is often performed by bonding with a hard solder, ultrasonic bonding, or mechanical bonding such as caulking or bolting. In addition, even in resistance welding between the same kind of metal materials, a copper material and a copper material having a very good electrical conductivity or an aluminum material and an aluminum material are joined by the same means. In the bonding method, from the viewpoint of using a copper material or an aluminum material having very good electrical conductivity, the resistance of the bonding portion cannot be made small enough to be ignored. For these reasons, resistance welding between copper materials with very good electrical conductivity, aluminum materials, or between copper materials and aluminum materials is considered to be particularly difficult. Efforts have already been made, and an improved technique is disclosed that enables resistance welding between a copper member and an aluminum material by performing the following processing steps in advance (see, for example, Patent Document 1).

Since this method cannot directly resistance weld a copper member and an aluminum member, a tin film is previously formed on the bonding surface of the copper member before resistance welding, and further processing is performed to obtain an interface between the copper member and tin. After forming a tin coating layer in which a solid solution of copper and tin is formed, the tin coating layer is brought into contact with an aluminum member, and the tin coating layer formed in a solid solution is placed between the copper member and the aluminum member. Pressure is applied in a state of being interposed between the electrodes and resistance welding is performed by passing a welding current. This welding method is realized by using an inverter type welding machine, not a capacitor energy storage type welding machine, and passing a high-frequency welding current between the copper member and the aluminum member, and melting the joint between the copper member and the aluminum member. Thus, welding is performed by forming a nugget in which the molten copper and aluminum are mixed together. Further, in resistance welding of dissimilar metals, a resistance welding method and a resistance welding apparatus in which a good welding result can be obtained in advance by processing joints of dissimilar metals into an optimal special shape have already been reported (for example, (See Patent Documents 2 to 5). Also, in order to eliminate the need for pretreatment such as pickling to remove the oxide film and dirt on the joint surface such as aluminum or magnesium during diffusion bonding, projections are formed on both objects to be welded, and the tops of the projections are applied to each other. A method of welding in contact with each other is also disclosed (for example, see Patent Document 6). Furthermore, an object to be welded having a projection structure that is convenient for welding steel plates on which an electrical insulating coating or a high resistance coating is formed is also disclosed (for example, see Patent Document 7).
JP 2001-087866 A Japanese Patent Laid-Open No. 08-1118040 Japanese Patent Laid-Open No. 10-128550 Japanese Patent Laid-Open No. 10-156548 Japanese Patent Laid-Open No. 11-033737 JP 2002-103056 A Japanese Patent Application Laid-Open No. 08-71766

  However, in the resistance welding method disclosed in the above-mentioned Patent Document 1, since it is a welding method in which tin is formed on the bonding surface of the copper member and nugget is formed in the bonding portion between the copper member and the aluminum material, welding is performed. A tin film which is a low melting point metal film must be formed in advance. This has the disadvantages that a step of forming a tin film by plating or the like is necessary, and that the tin material is mixed into the joint between the copper member and the aluminum material, so that the resistance at the joint is increased. Further, there is a problem in that tin around the joint becomes dust and is scattered by the heat of the nugget formed by melting the mutual metals. Moreover, although the structure of the junction part described in the above-mentioned patent documents 2-5 is suitable for the to-be-welded object which consists of a dissimilar metal material of a specific structure, especially a copper member and a copper member, or an aluminum member and an aluminum member Alternatively, it is difficult to apply as it is to resistance welding between a copper member and an aluminum member, and a stable welding result cannot be obtained even with the resistance welding apparatus disclosed in the above-mentioned patent document.

  Further, as described in the above-mentioned Patent Document 6, even if projections are provided on both the copper member and the aluminum member and they are butt-welded to each other, the plastic fluidization of the copper member is slower than the aluminum member. However, it is often difficult to use the resistance welding method described in Patent Document 6 in an actual production line so far. Furthermore, the workpiece to be welded described in the above-mentioned Patent Document 7 has a sharp cross-sectional triangular projection that is convenient for breaking through an electrical insulating coating or high-resistance coating covering the workpiece, such as a surface-coated steel plate, during welding. In the case of such a projection structure having a sharp cross-sectional projection, the resistance welding of the workpieces whose surfaces are not covered with an electrical insulating coating or a high resistance coating is used. Since the projection having the sharp cross-sectional projection comes into direct contact with the counterpart metal material, the sharp cross-sectional projection is crushed by the pressure applied between the workpieces during welding or by pressure. In many cases, the square protrusions do not play a role of projection in welding other than the surface-coated steel sheet.

  The present invention solves the above-mentioned problems, and even if a low melting point metal film such as a tin film is not formed on the diffusion bonding surface, a highly conductive work piece having a very high conductivity such as a copper member can be obtained. The main object is to provide practical resistance welding that can perform resistance welding and that can obtain a joining result with high welding quality easily and inexpensively. Further, according to the present invention, a thin plate made of a copper material or an aluminum material having a thickness of 2 mm or less can be diffusion-bonded without forming a low melting point metal film.

  In a first aspect of the present invention, there is provided a highly conductive work piece that is resistance-welded to another metal member by passing a welding current. The high conductive work piece is formed from a joint surface of the high conductive work piece. Provided is a highly conductive work-piece having an upper and lower two-stage projection comprising a projecting first projection and a second projection projecting from a part of the first projection on the joint surface side. .

  According to a second aspect, in the first aspect, the first projection is a small pedestal or small annular projection having an arbitrary shape, and the second projection has an area on the joint surface side of the first projection. A highly conductive object to be welded is characterized by being one or more projections smaller than the projection.

  According to a third invention, in the first invention or the second invention, the initial bonding area of the second projection is small to obtain a desired bonding strength, but the applied pressure applied during welding In contrast, the present invention provides a highly conductive work piece having a size that is difficult to crush.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, when the first projection is an arbitrary annular protrusion having a central hole at a central portion, the central hole is the protrusion. The present invention provides a highly conductive workpiece characterized by being deeper than the height.

  A fifth invention provides a highly conductive work piece according to any one of the first to fourth inventions, wherein an outer peripheral groove is formed around the first projection. To do.

  According to a sixth aspect of the present invention, there is provided a resistance welding method for a highly conductive workpiece that is resistance-welded by passing a current between the highly conductive workpiece and another metal member. A step of forming a projection having a step structure, a step of bringing the projection of the upper and lower two-step structure formed on the highly conductive workpiece into contact with the other metal member, and the high conductivity being in contact with each other. Resistance welding of a highly conductive workpiece comprising a step of applying a pulsed welding current in a state where the weldable workpiece and the other metal member are pressurized with an applied pressure including elastic force Provide a method.

  According to a seventh invention, in the sixth invention, the step of forming the projection of the upper and lower two-stage structure on the highly conductive work piece includes a protrusion serving as a first projection on the high conductive work piece. The present invention provides a resistance welding method for a highly conductive workpiece, characterized by comprising forming and forming at least one small projection serving as a second projection on the projection.

  The eighth invention is the sixth invention or the seventh invention, wherein the other metal member is a thin plate made of a copper material or an aluminum material on which the projections of the upper and lower two-stage structures are not formed. Provided is a resistance welding method for a highly conductive workpiece, wherein the thickness of the thin material is 2 mm or less.

  According to a ninth invention, in any one of the sixth to eighth inventions, the highly conductive work piece is made of a copper material or an aluminum material. Provide a welding method.

  According to a tenth aspect of the present invention, in any one of the sixth to ninth aspects, the pulsed welding current has a time required for the current to rise to a peak value of 10 ms or less. A resistance welding method for a highly conductive workpiece is provided.

  Since the first to third inventions have a two-stage upper and lower projections in which the second projection is formed on the first projection, a low melting point metal film such as tin is formed on the bonding surface. Therefore, it is possible to provide a highly conductive workpiece such as a copper member or an aluminum member, which can easily obtain a large welding strength. In addition, since resistance welding can be stably performed without forming a low melting point metal film having a conductivity lower than that of a highly conductive work piece as in the prior art, the low melting point metal is not scattered as dust, and the joint portion Since the low melting point metal is not mixed in, the resistance of the joint portion does not increase.

  According to the fourth invention, in addition to the effects obtained in the first to third inventions, in the process in which the projection of the upper and lower two-stage structure plastically fluidizes during resistance welding, Since the part of the workpiece to be welded corresponding to the hole enters the central hole, the area of the joint surface will be enlarged, especially in resistance welding of highly conductive workpieces, improving the welding strength. be able to.

  According to the fifth aspect of the invention, in addition to the effects obtained in the first to fourth aspects of the invention, in the process in which the projection of the upper and lower two-stage structure plastically fluidizes during resistance welding, Since the projection of the upper and lower two-stage structure that extends to the side fits in the outer peripheral groove, the joint area of the projection is practically almost not widened. Therefore, particularly in resistance welding of a highly conductive work piece, it is stable and good. This leads to resistance welding results.

  In the sixth to tenth aspects of the present invention, not only a highly conductive workpiece has a two-stage upper and lower projection, but also a pulsed welding current is applied in a state of being pressurized with an applied pressure including elastic force. Therefore, without forming a low-melting-point metal film such as tin on the joint surface, it is possible to easily resistance-weld highly conductive workpieces such as copper members or aluminum members, and obtain stable and good welding results. Can do. Particularly, it is resistance welding between copper members or aluminum members with very high conductivity, or between copper members and aluminum members, and even if one member is a thin plate of 2 mm or less, it is joined between welding electrodes. Resistance welding can be performed stably and satisfactorily without occurring.

[Embodiment 1]
Embodiment 1 of the workpiece to be welded according to the present invention will be described with reference to FIG. FIG. 1 is a diagram for explaining a basic structure of a two-stage projection of a highly conductive workpiece according to Embodiment 1. First, the range to which the present invention can be applied is resistance welding of various general metal materials of the same kind or welded objects made of various different kinds of metal materials. In the following description, resistance welding between copper or copper alloys, which is considered to be extremely difficult, is taken as an example. In this specification, “copper member” means “copper or copper alloy”. Since the copper member or the aluminum member generally has higher conductivity than the steel plate or the stainless steel material, resistance welding between the copper members or between the aluminum members, or between the copper member and the aluminum member is considered to be particularly difficult. Embodiment 1 This point will be described before description.

  In resistance welding of metal materials, plastic flow, that is, softening occurs at the contact surfaces of both metal materials due to heat generated by the resistance of the metal materials when a welding current flows, and bonding is performed. However, since the resistance of the copper member is extremely small, the amount of heat generated by the resistance is insufficient, and it is difficult to obtain a satisfactory resistance welding result unless the required bonding strength is extremely small. That is why. Diffusion bonding with extremely low required bonding strength is possible, but in order to satisfy the actual required bonding strength, the shape and surface state of the joint of the copper member, which is a highly conductive workpiece, welding Various restrictions such as current conditions and various characteristics of the welding equipment are severe, and a low melting point metal film such as a tin film must be formed in advance, so it was difficult to apply to an actual production line. . For example, if the copper member is pure copper, the resistance of the widely used copper alloy welding electrode is higher than that of the copper member, so the heat generation at the welding electrode is larger than the heat generation at the copper member. Naturally, the heat generation at the interface between the welding electrode and the copper member is larger than that at the bonding surface between the copper members, and the welding electrode and the copper member are disadvantageously bonded. This is remarkable when the copper member is a thin plate having a thickness of several mm or less, particularly a thin plate having a thickness of about 2 mm or less because the resistance in the thickness direction of the copper member is extremely small. Even if various conditions such as resistance welding equipment are selected, if a low-melting point metal film with a relatively large resistance, such as a tin film, is not present on the joint surface between copper members, satisfactory welding results including stability will be achieved. Was not obtained. In the first embodiment, the upper and lower sides 2 that make it possible to easily and simply apply the resistance welding process to an actual production line without forming a low melting point metal film such as a tin film on the joint surfaces of the copper members. A copper member having a stepped projection and a resistance welding method thereof are provided.

  1A, 1B, and 1C, a projection P having an upper and lower two-stage structure is formed on one surface of a first workpiece W1 that is a copper member. The projection P having the upper and lower two-stage structure is formed so as to project from the upper surface of the first projection P1 and the first projection P1 formed so as to project from the small surface area of one surface of the first workpiece W1. And a plurality of second projections P2. The first projection P1 is a small disk having a height that is easy to make, for example, a height of 0.5 to 1.0 mm, which is about the same as a general projection. The area is determined by conditions such as required bonding strength, and is various because the required bonding strength is obtained. The first projection P1 functions to limit the welding current, that is, the heat generation from spreading laterally at the joint surface, and is a projection that plastically fluidizes during welding. The projection may be a square shape (including a diamond shape) or an annular shape. Here, the small circular plate-shaped or small rectangular plate-shaped protrusion is referred to as a small pedestal-shaped protrusion. Since the first projection P1 is a projection formed by processing the first workpiece W1, the material of the first projection P1 is naturally the same as that of the first workpiece W1. The small pedestal-like protrusion may have an arbitrary trapezoidal shape as shown in FIGS. 1B and 1C or a rectangular shape not shown.

  On the first projection P1, a second projection P2 having a lattice pattern is formed as shown in FIG. A lattice portion is indicated by Pa, and an island portion surrounded by the lattice portion Pa is indicated by Pb. The lattice-shaped portion Pa is a protruding portion, and the island-shaped portion Pb is recessed from the lattice-shaped portion Pa is the lattice-shaped protrusion shown in FIG. 1B, and the lattice-shaped portion Pa is a groove. Thus, the island-shaped protrusions shown in FIG. 1C are the island-shaped portions Pb protruding higher than the lattice-shaped portions Pa. In the first embodiment, the second projection P2 may be formed of any of the above-described lattice-shaped protrusions or island-shaped protrusions. Here, the lattice pattern is not limited to the quadrangular shape as shown in FIG. 1A, but the island-shaped portion Pb surrounded by the lattice-shaped portion Pa is a rhombus, a circular shape, a triangular shape, or a pentagon or more. It is sufficient that the lattice portion Pa is formed in an arbitrary shape so as to have an arbitrary polygonal shape. The upper end surface of the second projection P2 comes into contact with the second workpiece W2 indicated by a broken line, and the initial joining surface A is formed.

  Unlike the case of resistance welding such as steel plates where nuggets are formed at the joint, resistance welding of highly conductive workpieces is substantially performed in the projection area. One projection P1 must have an area on the side of the bonding surface that is larger than the required bonding strength. To obtain a desired bonding strength, a current that is large as in the prior art is required. Must be washed away. The second projection P2 is for reducing the initial contact area that comes into contact with the second workpiece W2. For example, if the initial contact area with the second workpiece W2 in the second projection P2 is 1/3 as compared with the area on the joining surface side of the first projection P1, the second projection The current density of the welding current flowing through the initial contact area between P2 and the second workpiece W2 can be almost tripled, and the second projection P2 is greatly easily plasticized. However, generally, during resistance welding, a large pressure (forging pressure) is applied between the first workpiece W1 and the second workpiece W2, so that the second projection P2 is plastically fluidized by the welding current. Even if it is acceptable to be deformed by the applied pressure, the second projection P2 does not fully function if it is crushed, that is, crushed, and the effect of providing the second projection P2 is effective. It will fade. Therefore, in the second projection P2, the initial contact area, that is, the bonding area A is small to obtain a desired bonding strength, but the protrusion has a size that is difficult to be crushed against the applied pressure applied during welding. Must be a structure. Therefore, the height of the projections forming the second projection P2 is not limited, but when a large pressure is applied between the first workpiece W1 and the second workpiece W2, FIG. In the case of the grid-like projections shown in (B), at least the height is such that the island-like part Pb does not come into contact with the second workpiece W2 even if the grid part Pa is deformed, as shown in FIG. In the case of the island-shaped projections shown, the island-shaped portion Pb must have such a height that the lattice portion Pa does not come into contact with the second workpiece W2 even if the island-shaped portion Pb is deformed.

[Embodiment 2]
Next, a workpiece to be welded of Embodiment 2 having another upper and lower two-stage projection will be described with reference to FIG. FIG. 2 shows an enlarged cross section near the projection P having a two-stage structure. In FIG. 2, the same symbols as those used in FIG. 1 indicate the same names. The first projection P1 of the projection P having the upper and lower two-stage structure formed in the small surface area on one side of the first workpiece W1, which is a highly conductive workpiece such as a copper member, is shown in FIG. Since it is the same as that, the description is omitted. The second projection P2 formed on the first projection P1 is formed of an annular protrusion that is recessed so that the center is equal to the upper surface of the first projection P1. The annular second projection P2 may be an annular protrusion, or may be an arbitrary polygonal annular protrusion. Further, the annular protrusion does not have to be a continuous annular shape, and may be an annular protrusion divided by a groove (not shown). (Here, in order to argue that the second projection P2 may have various structures, it is better to briefly describe a specific structural example different from that of the first embodiment. How about you?)
The second projection P2, which is an annular protrusion having an arbitrary shape, is applied at the time of welding, although the upper end surface thereof, that is, the area of the initial joining surface A is small to obtain a desired joining strength, as in the first embodiment. The protrusion structure must be of a size that is difficult to crush against the applied pressure. An annular outer circumferential groove X is formed around the first projection P1. The shape of the annular outer peripheral groove X may be an arbitrary shape such as a trapezoidal shape, a V shape, a U shape, or a square shape in cross section. The annular outer circumferential groove X will be described in detail in an example of resistance welding to be described later. However, the annular outer groove X accepts a part of the projection P that mainly plastically fluidizes during welding, and the projection P that plastically fluidizes during welding and spreads outward. Since the outer circumferential groove X is accommodated in the outer circumferential groove X, the expansion of the area of the projection P is suppressed during the welding process, so that it is possible to prevent the current density of the welding current from decreasing. Further, since the outer circumferential groove X substantially increases the height of the first projection P1 by the depth, the amount of heat scattered in the first projection P1 during welding is reduced in the lateral direction. This is particularly important for resistance welding of highly conductive workpieces having extremely high electrical conductivity and extremely good thermal conductivity because they affect the welding strength.

[Embodiment 3]
Next, a workpiece to be welded of Embodiment 3 having another upper and lower two-stage projection will be described with reference to FIG. FIG. 3 shows an enlarged cross section near the projection P having a two-stage upper and lower structure. In FIG. 3, the same symbols as those used in FIGS. 1 and 2 indicate the same names. A central hole Y is formed in the center of the first projection P1 of the upper and lower two-stage projection P1 formed in the small surface area on one side of the first workpiece W1 which is a highly conductive workpiece such as a copper member. Is formed. Therefore, the first projection P1 of the third embodiment is composed of an annular protrusion. The annular protrusion may be an annular or arbitrary polygonal protrusion. A plurality of island-shaped projections second projections P2 are formed on the upper surface of the annular first projection P1. When the first projection P1 is formed of an annular protrusion, the current density of the welding current is determined when the area of the upper surface on the joining side of the first projection P1 is the same as that of a conventional pedestal-shaped projection that is not annular. The outer diameter of the annular first projection P1 can be increased by the area of the central hole Y without being reduced as compared with the pedestal-shaped projection.

  In the process of plastic fluidization between the second projection P2 and the first projection P1 during welding and the joint portion of the second workpiece to be welded (not shown), when the second workpiece is also the same copper member A part of the second projection P2 and the first projection P1 which are plastically fluidized is accommodated in the central hole Y. When the joint surface is observed microscopically, the projection P bites into the second work piece in the process of plastic fluidization of the projection P, and the surface area portion of the second work piece corresponding to the center hole Y. Since the welding current hardly flows, plastic fluidization does not occur. Therefore, as the projection P plastic fluidizes, the surface area portion of the second work piece enters the central hole Y. This results in at least bonding at the inner peripheral portion surrounding the central hole Y in the first projection P1, and as a result, the bonding area is larger than that of the pedestal-shaped projection, so that the bonding strength is higher than that of the pedestal-shaped projection. Can be improved. When the second workpiece is made of an aluminum member, since aluminum has a lower hardness and higher resistivity than copper, the second workpiece is more likely to be plastically fluidized, so that the projection P is the second workpiece. It is easy to bite by the welded material.

  The center hole Y is desirably deeper than the height of the projection P, that is, deeper than the upper surface B of the first workpiece W1. In such a deep case, the surface area portion of the second workpiece to be welded (not shown) enters the central hole Y in the process of plastic fluidization of the first projection P1, and the upper surface B of the first workpiece W1. Since it can penetrate more deeply, the bonding strength can be further improved. Further, in the process in which the surface area portion of the second workpiece (not shown) enters the central hole Y, the plastic fluidized part of the projection P is also accommodated in the central hole Y, so that the resistance welding (diffusion bonding) area is further increased. To further improve the welding strength. As described above, the second projection P2 is small in that the upper end surface, that is, the initial joining surface A, is small in order to obtain a desired joining strength, but is difficult to be crushed against the applied pressure applied during welding. This is the protrusion structure.

[Embodiment 4]
Next, a workpiece to be welded according to Embodiment 4 having another upper and lower two-stage projection that is preferable with reference to FIG. 4 will be described. FIG. 4 shows an enlarged cross section near the projection P having a two-stage structure. In FIG. 4, the same symbols as those used in FIGS. 1 to 3 indicate the same names. Around the first projection P1 of the upper and lower two-stage projection P1 formed in the small surface area on one side of the first workpiece W1 which is a highly conductive workpiece such as a copper member, An outer peripheral groove X is formed, and a central hole Y is formed in the center of the first projection P1. Therefore, the first projection P1 of the fourth embodiment also includes an annular protrusion. On the upper surface of the annular first projection P1, a plurality of island-shaped or arbitrary-shaped thin annular, grid-like second projections P2 are formed. The annular first projection P1 has a trapezoidal cross section. Therefore, the cross section of the outer peripheral groove X and the central hole Y is easy to make and has an inverted trapezoidal shape into which the plastic fluidized projection P easily enters.

  The outer peripheral groove X formed around the annular first projection P1 performs the same function as described in the second embodiment, accepts a part of the projection P mainly plastically fluidized at the time of welding, weld strength, etc. To improve. Further, the central hole Y performs the same function as described in the third embodiment, and the surface area portion corresponding to the central hole Y in the second work piece (not shown) is the process of plastic fluidization of the first projection P1. Thus, since it is possible to enter the center hole Y deeper than the upper surface B of the first workpiece W1, the welding strength can be further improved. The central hole Y is preferably formed deeper than the height of the projection P, that is, deeper than the upper surface B of the first workpiece W1.

[Embodiment 5]
Next, the first workpiece W1 which is a highly conductive workpiece such as a copper member on which such an annular two-stage projection P is formed, and the highly conductive workpiece such as a copper member. An example of a capacitor accumulating type resistance welding apparatus suitable for realizing resistance welding (diffusion bonding) with the second workpiece W2 as described above will be briefly described with reference to FIG. A support mechanism 2 is fixed to a floor or base member 1 on which the resistance welding apparatus is installed. A pressurizing mechanism 3 made of a cylinder device or the like is attached to the support mechanism 2, and a movable block 4 made of a metal material is attached to the tip of the pressurizing mechanism 3. A pressurizing auxiliary member 5 such as a spring or an electromagnetic pressurizing device is provided between the movable block 4 and the support member 6 and plays an auxiliary role to improve the pressurization response of the welding electrode. In the resistance welding between the highly conductive members, particularly the copper member and the copper member, the function of the pressure assisting member 5 is great. Here, the supporting member 6 is made of a metal material such as copper which is directly or indirectly coupled to the lower end portion of the pressure assisting member 5 and also functions as a power feeding portion. The upper welding electrode 7 is supported by the support member 6, and the lower welding electrode 8 is disposed at a position facing the upper welding electrode 7. An L-shaped intermediate connection member 9 is fixed to the movable block 4 located at a height that is not affected by the expansion and contraction of the pressure assisting member 5. A flexible first flexible conductive member 10 that connects between the support member 6 and the L-shaped intermediate connection member 9 is provided, and a second flexible conductor is provided between the L-shaped intermediate connection member 9 and one power supply conductor 12. They are connected by a conductive member 11. The upper welding electrode 7 and the lower welding electrode 8 are made of, for example, a copper alloy.

  The secondary winding N2 of the welding transformer 14 is connected between the power supply conductor 12 and the other power supply conductor 13 connected to the lower welding electrode 8, and the primary winding N1 magnetically coupled thereto is connected to the primary winding N1. A discharge circuit 15 such as an inverter circuit or a semiconductor switch circuit is connected. Connected to the discharge circuit 15 are an energy storage capacitor 16 and a charging circuit 17 for charging the capacitor. In resistance welding, since most of the welding current that contributes to welding is current from the rise to the vicinity of the peak value, in the resistance welding of the fifth embodiment, the time for the welding current to rise to the vicinity of the peak value is about 10 ms or less. 7 ms is preferable. In order to allow such a steep pulse current with a narrow pulse width to flow between the copper members, the discharge circuit 15, the welding transformer 14, the power supply conductors 12 and 13, etc. The energization path through which the discharge current flows has a circuit configuration that minimizes inductance. In this structure, the upper welding electrode 7 is supported by a supporting member 6 that can move up and down with a slight external force, and at the same time, is coupled to a pressurizing auxiliary member 5 that can provide highly responsive elastic force. Therefore, the upper welding electrode 7 and the second workpiece to be welded by plastic flow between the projection P having the upper and lower two-stage structure of the first workpiece W1 and the second workpiece W2 in the surface area in contact therewith. The upper welding electrode 7 can immediately respond to a slight change in the applied pressure between W2 and W2. Symbols 18 to 20 represent three-phase AC input terminals.

  Next, resistance welding according to the fifth embodiment will be described with reference to FIG. 6 showing an outline of a resistance welding circuit. First, the first workpiece W1 is placed on the lower welding electrode 8, and the second workpiece W2 is placed thereon. Next, the pressurizing mechanism 3 in FIG. 5 operates downward, and accordingly, the entire upper welding head composed of the movable block 4, the pressurizing auxiliary member 5, the support member 6, and the upper welding electrode 7 descends, The welding electrode 7 applies a predetermined pressing force to the second workpiece W2. At this time, the partial surface area of the lower surface of the second workpiece W2 is pressurized to the initial joining surface A (FIGS. 1 to 4) of the second projection P2 of the first workpiece W1. During the application of the predetermined pressure, or when the pressure becomes substantially constant, the discharge circuit 15 is turned on, and the charge already charged in the energy storage capacitor 16 by the charging circuit 17 is welded. It is discharged to the primary winding N1 of the transformer 14. Along with this, a large current is generated in the secondary winding N2 having one or two turns which is significantly smaller than the primary winding N1, and is sandwiched between the upper welding electrode 7 and the lower welding electrode 8. A steep pulsed welding current flows through the first workpiece W1 and the second workpiece W2 that are being welded.

  Since the second projection P2 of the first workpiece W1 is not crushed by the applied pressure applied during welding, the pulsed welding current as described above is first applied to the first workpiece. It flows for a short time in a concentrated manner on the initial joining surface A of the second projection P2 of the welded article W1 and the surface area of the first workpiece W1 in contact therewith. As described above, the initial joining surface A of the second projection P2 having a smaller area than the first projection P1 of the first workpiece W1 is formed by the upper welding electrode 7 and the second workpiece W2. And the contact area between the lower welding electrode 8 and the first workpiece W1 are much smaller than the current density of the welding current flowing through these contact areas. The current density of the welding current flowing in the contact surface area where the initial joining surface A of the second projection P2 in the welded product W1 contacts the second workpiece W2 is significantly large. Therefore, even if the copper members having very high electrical conductivity, particularly the second workpiece W2 is a thin plate having a thickness of 2 mm or less, the contact surface between the upper welding electrode 7 and the second workpiece W2; In addition, compared with the heat generated at the contact surface between the lower welding electrode 8 and the first workpiece W1, the initial joining surface A of the second projection P2 and the second welding target in the first workpiece W1 are compared. The heat generated at the contact surface with the object W2 is greatly increased. Further, since the heat generation is not transmitted in the lateral direction on the joint surface, first, the second projection P2 is plastically flowed by the heat generation, and the heat is transferred to the first projection P1 along with the plastic flow of the second projection P2. Since the first projection P1 is transmitted and also generates heat, the first projection P1 starts plastic flow. Similarly, the plastic flow occurs in the small surface area of the second workpiece W2 that is in contact with the second projection P2, and further in the contact surface of the second workpiece W2 that is in contact with the first projection P1. Arise.

  In the process of plastic flow, most of the second projection P2 flows into the outer peripheral groove X and the central hole Y, a part of the first projection P1 bites into the second workpiece W2, and the other part is the outer peripheral groove. X and the central hole Y are accommodated, and good resistance welding (diffusion bonding) is performed. Even if the second workpiece W2 is a copper thin plate having a thickness of 2 mm or less, joining does not occur at the contact surface between the thin plate and the upper welding electrode 7. As described above, the resistance welding between the first workpiece W1 and the second workpiece W2 can provide good welding quality and welding strength largely due to the projection P having a two-stage structure. 5 is also greatly affected by the characteristics of the resistance welding apparatus described in FIG. Therefore, the resistance welding method using the resistance welding apparatus shown in FIG. 5 will be described in more detail.

  First, when the pressurizing mechanism 3 operates and operates in the downward direction, the entire upper welding head including the movable block 4, the pressurizing auxiliary member 5, the support member 6 and the upper welding electrode 7 is lowered. On the other hand, although not shown in FIG. 5, as described above with reference to FIG. 6, the first and second workpieces W1 and W2 are set on the lower welding electrode 8 and the upper welding electrode 7 is lowered. It abuts on the second workpiece W2. The upper welding electrode 7 and the support member 6 stop at that position, but as the pressurizing mechanism 3 further descends, the pressurizing auxiliary member 5 is contracted, and the movable block 4 descends together with the pressurizing mechanism 3. To do. Further, as the movable block 4 is lowered, the second flexible conductive member 11 is greatly bent, and the first flexible conductive member 10 is moved together with the movable block 4 and the support member 6, so that it is lowered in the initial state. As described above, when the support member 6 is stopped and the movable block 4 is lowered while the pressurizing auxiliary member 5 is contracted, it is slightly deformed from the initial state. However, as described above, the first flexible conductive member 10 is made to be more easily bent than the second flexible conductive member 11, so that resistance to movement of the support member 6 and the upper welding electrode 7 is reduced. Therefore, the responsiveness of the upper welding electrode 7 is improved.

  As described above, the pressure assisting member 5 contracts during the downward movement of the pressure mechanism 3 and the pressure between the upper welding electrode 7 and the lower welding electrode 8 reaches a predetermined level. Then, a pulse welding current having a short pulse width is supplied from the welding transformer 14 and the power supply conductors 12 and 13 to the upper welding electrode 7 and the lower welding electrode 8, and as described above, the two-stage structure of the first workpiece W1. The contact portion between the projection P and the second workpiece W2 is plastic fluidized and resistance welding is performed. Here, when the weld cross section is observed, it is confirmed that no nugget is formed on the joint surface between the first workpiece W1 and the second workpiece W2, and this resistance welding is diffusion bonding. ing.

  Although the explanation will return a little, plastic fluidization of the projection P having the upper and lower two-stage structure of the first workpiece W1 and further plastic fluidization of the contact portion of the second workpiece W2 that is in contact with the projection P. As the pressure assisting member 5 shown in FIG. 5 is an elastic member such as a spring, the elastic member instantly expands the joint at the initial stage of welding. Since the elastic member constantly applies pressure to the joint portion, the elastic member is constantly applied to the sink due to plastic flow between the first workpiece W1 and the second workpiece W2. Pressure can be applied. As the response speed of the pressure assisting member 5 increases, the pulse welding current with a short pulse width, that is, the current energy is concentrated in a short time to concentrate the first workpiece W1 and the second workpiece W2 Even if it has a very good thermal conductivity such as a copper member, it can be plastically fluidized to a desirable state, which is one reason that satisfactory resistance bonding can be achieved even between copper members. It has become. In this way, the above-described upper and lower two-stage projection P is formed on one highly conductive work piece, the response speed of the welding electrode is fast, and the time T required to rise to the peak value is about 10 ms or less. Since a narrow pulsed welding current is used, resistance welding can be performed more stably and satisfactorily without forming a low melting point metal film even between copper members.

  In the fifth embodiment, resistance welding between copper members has been described. However, the first workpiece W1 and the second workpiece W2 are aluminum materials, or the first workpiece W1 is a copper material. Even if the second workpiece W2 is an aluminum material, resistance welding can be similarly performed. When welding a copper material and an aluminum material, it is important to form the above-described upper and lower two-stage projection on a copper material having high hardness and conductivity. The above-described two-stage upper and lower projections are not limited to resistance welding between highly conductive workpieces, such as highly conductive workpieces and other metal materials, normal steel plates, or stainless steel members and steel plates. The present invention can be applied to the same or different metal materials, and satisfactory resistance welding results can be obtained. Therefore, the present invention can be applied to these as required. Further, the highly conductive work piece is not limited to a plate-like member, and stable and good welding results can be obtained even in various shapes such as a pipe shape, a round bar shape, and a square bar shape.

It is a figure which shows the highly conductive to-be-welded object which has a projection of the upper and lower two steps structure concerning Embodiment 1 of this invention. It is a figure for demonstrating the projection of the 2 steps | paragraphs of upper and lower structures concerning Embodiment 2 of this invention. It is a figure for demonstrating the projection of the 2 steps | paragraphs of upper and lower structures which concerns on Embodiment 3 of this invention. It is a figure for demonstrating the projection of the 2 steps | paragraphs of upper and lower structures concerning Embodiment 4 of this invention. It is a figure which shows an example of the resistance welding apparatus for implement | achieving the resistance welding method which concerns on Embodiment 5 of this invention. It is a figure for demonstrating the resistance welding method which concerns on Embodiment 5 of this invention.

Explanation of symbols

W1 ... first workpiece (highly conductive workpiece)
W2 ... second workpiece P ... upper and lower two-stage projection P1 ... first projection P2 ... second projection Pa ... lattice part Pb ... island part X: outer peripheral groove formed around the first projection P1 Y: central hole formed in the center of the first projection P1 A: initial joint surface B of the second projection P2 ... Upper surface of first workpiece W1 1 ... Base member 2 ... Support mechanism 3 ... Pressure mechanism 4 ... Movable block 5 ... Pressurizing auxiliary member 6 ... Support Member 7 ... Upper welding electrode 8 ... Lower welding electrode 9 ... L-shaped intermediate connecting member 10 ... First flexible conductive member 11 ... Second flexible conductive member 12, 13, ...・ Feeding conductor 14 ... welding transformer 15 ... Discharge circuit 16 ... Capacitor for energy storage 17 ... Charging circuit 18-20 ... 3-phase AC input terminal

Claims (10)

In highly conductive workpieces that are resistance-welded to other metal members by passing a welding current,
The highly conductive work piece includes an upper and lower 2 formed of a first projection projecting from a joint surface of the highly conductive work piece and a second projection projecting from a part of the joint surface side of the first projection. A highly conductive workpiece having a stepped projection. In claim 1,
The first projection is a small pedestal-shaped or small annular projection of any shape,
The high-conductivity welding object, wherein the second projection is one or more protrusions having an area on the joint surface side smaller than that of the first projection. In claim 1 or claim 2,
The initial bonding area of the second projection is small in order to obtain a desired bonding strength, but is not easily crushed against the applied pressure applied during welding. Weldment. In any one of Claims 1 thru | or 3,
A highly conductive work piece characterized in that, when the first projection is an arbitrary annular protrusion having a central hole in a central portion, the central hole is deeper than the height of the protrusion. In any one of Claim 1 thru | or 4,
A highly conductive object to be welded, wherein an outer peripheral groove is formed around the first projection. In a resistance welding method for a highly conductive workpiece to be resistance welded by passing a current between the highly conductive workpiece and another metal member,
Forming a projection with a two-stage structure on the highly conductive work piece;
Contacting the other metal member with the projection of the upper and lower two-stage structure formed on the highly conductive workpiece;
Applying a pulsed welding current in a state where the highly conductive work piece and the other metal member that are in contact with each other are pressurized with a pressure including elastic force;
A resistance welding method for a highly conductive workpiece, comprising: In claim 6,
The step of forming the upper and lower two-stage projection on the highly conductive workpiece includes forming a projection as a first projection on the highly conductive workpiece, and a second projection on the projection. A method for resistance welding of a highly conductive workpiece, comprising forming one or more small protrusions. In claim 6 or claim 7,
When the other metal member is a thin plate made of a copper material or an aluminum material on which the projection of the upper and lower two-stage structure is not formed, the thickness of the thin material is 2 mm or less. Resistance welding method for workpieces. In any of claims 6 to 8,
The resistance welding method for a highly conductive workpiece, wherein the highly conductive workpiece is made of a copper material or an aluminum material. In any one of Claims 6 thru | or 9,
The pulse welding current has a time required for the current to rise to a peak value of 10 ms or less, and is a resistance welding method for a highly conductive workpiece.

Images