JP2010227956A - Welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To firmly fix all superposed workpieces to be welded to each other in a mechanical manner without generating any dust or spatter. <P>SOLUTION: In a welding method, a workpiece at the final position within a plurality of workpieces has one or more recesses or through holes, and other workpieces except the workpiece at the final position have one or more through holes, and are superposed on each other so that the through holes are concentric with the recess or the through hole of the workpiece at the final position. While a columnar welding member having the uniform diameter slightly larger than that of the recess or the through holes of the workpiece at the final position is pressed against the through hole of the workpiece at the initial position, a welding electrode runs the pulse-like current while applying the pressure to the columnar welding member and the workpiece, a contact part of the columnar welding member with the workpiece at the final position is subjected to the plastic flow and welded first, and the columnar welding member is further inserted in the recess or the through hole of the workpiece at the final position to execute the welding. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a welding method in which a columnar welding member is joined by being pushed into through holes or recesses of a plurality of workpieces.

  Various methods have already been proposed for joining different types of metal materials such as steel plates and steel plates, or between different types of metals such as iron-based materials and copper materials. As one of the welding methods, a capacitor-type welding method is widely known in which resistance welding or diffusion bonding is performed in a short time by instantaneously discharging the electric charge charged in the capacitor and causing a current having a large peak value to flow through the workpiece. ing. In particular, even if resistance welding is performed on two superposed workpieces, a structure in which projections cannot be formed on the superposed surface of the two workpieces, or three or more workpieces are superimposed. It is said that resistance welding of a structure or a structure in which workpieces made of different metal materials are overlapped with each other is difficult even by the capacitor welding method.

  Under such circumstances, a technique for resistance welding of a structure in which projection cannot be formed on the overlapping surface of the two workpieces described above has already been disclosed (for example, see Patent Document 1). In the embodiment of the invention disclosed in Patent Document 1, a third member having a curved surface such as a ball, or a third member having an inclined surface whose diameter decreases from one side to the other side. The third member is welded together with the through hole of the first workpiece and the recess of the second workpiece. In this method, the first workpiece and the third member are resistance-welded at the same time, and at the same time, the second workpiece and the third member are resistance-welded. The workpiece to be welded and the second workpiece to be welded are coupled.

  This welding method is such that resistance welding can be performed for those that could not be resistance welded by the conventional method, and further, it is possible to reduce running costs compared to arc welding because there is no need for welding wire or gas etc. The invention is significant in that it has an effect. However, the embodiment described in Patent Document 1 includes a third member having a curved surface such as a ball, or a third member having an inclined surface whose diameter decreases from one side to the other side. In use, the corner portion of the through hole of the first workpiece and the corner portion of the recess of the second workpiece are brought into contact with the third member for resistance welding. Accordingly, a gap is generated between the third member and the first workpiece to be welded and between the third member and the second workpiece to be welded in the vicinity of the contact points, so that compared with general projection welding or the like. Although there is little generation of dust and spatter, there is a problem that dust and spatter of such an amount that it is difficult to apply to applications where dust and spatter are not allowed are generated.

  Moreover, the Example described in patent document 1 is a 3rd member which has a curved surface like a ball | bowl, or a 3rd member which has an inclined surface where a diameter becomes small toward one side from the other side. In addition, the size of the through hole of the first workpiece and the size of the recess of the second workpiece must be adjusted separately, and the third member and the through hole, If it is not exactly aligned with both of the recesses, a desired welding strength is obtained between the third member and the first workpiece and between the third member and the second workpiece. There was also a problem that it was not possible. Even more seriously, even though the size of the through hole of the first workpiece and the size of the recess of the second workpiece are strictly adjusted and managed, the through holes of different sizes can be used in the actual manufacturing process. It is practically difficult to perform welding in a state where the alignment of the hole and the recess is strictly controlled.

  In addition, as a method of performing welding with a structure that is difficult to perform normal projection welding or welding between different metal materials, several techniques have already been disclosed in which one workpiece is pushed into the other workpiece to be welded ( For example, see Patent Document 2). According to the invention of this Patent Document 2, a tapered surface (inclined surface) is provided around the through hole or recess of one of the workpieces having a through hole or a recess, and the tapered surface is also provided on the other workpiece. Forming, pressing the two taper surfaces with an insert material interposed between them, applying a welding current while applying pressure, and pressing the other work piece into the through hole or recess of one work piece for resistance welding is doing. In the case of this welding method, since welding is started in a state where the tapered surfaces of both of the workpieces are pressed with an insert material interposed therebetween, a large amount of dust, spatter, etc. are scattered, and a large pressure and large pressure There is a problem that a welding current is required and the welding mechanism is enlarged.

JP 2001-227469 A JP-A-9-122924

  The problem to be solved by the present invention is that diffusion welding is performed on workpieces that are technically difficult to form a projection in an actual manufacturing process. Further, it is technically difficult to weld iron or an iron alloy to a dissimilar metal such as stainless steel or copper material.

  In the first invention, a plurality of stacked workpieces are formed with cylindrical holes having the same diameter, and a columnar welding member having a diameter larger than the hole by a predetermined dimension is used as the cylindrical hole. By applying a welding current while pressing and applying pressure, the contact part between the columnar welded member and the wall surrounding the hole of the work piece is plastically fluidized, and the columnar welded member is pushed into the cylindrical hole to form a columnar shape. A welding member and a plurality of workpieces are diffusion bonded.

  Therefore, according to the first invention, at least the columnar welding member and the workpiece to be welded at the first position, and the columnar welding member and the workpiece to be welded at the final position can be securely diffusion-bonded. The workpieces can be firmly and mechanically fixed to each other. Moreover, even if a workpiece to be welded such as a dissimilar metal is sandwiched between the workpiece to be welded at the first position and the workpiece to be welded at the final position, diffusion bonding can be performed without generating dust or spatter.

  In a second invention, in the first invention, an intermediate member made of the same or different metal material is sandwiched between the workpiece to be welded at the first position and the workpiece to be welded at the final position. The columnar welded member is made of a metal material having a plastic fluidization temperature that is equal to or higher than the plastic fluidization temperature of the intermediate member and is diffusion-bonded to the intermediate member, so that the intermediate member is welded at the initial position. It can be firmly fixed to the workpiece and the workpiece to be welded at the final position.

  3rd invention WHEREIN: In 1st invention or 2nd invention, when it equips both the front-end | tip part of a columnar welding member and the through-hole of the to-be-welded object of an initial position with the chamfered minute width inclination part, Regardless of the shape of the workpiece to be welded at the first position, since the inclined portion of the workpiece to be welded at the first position is chamfered to be equal to the inclination angle of the inclined portion at the tip of the columnar welding member, the columnar welding member Of course, it is easy to align the first position with the through-hole of the work piece in the first position, and regardless of the shape of the work piece in the first position, the work piece in the first position and the columnar welded member. Can be diffusely bonded without causing dust and spatter, and a desired welding strength can be obtained.

  According to the present invention, the column-shaped welded member is welded at the first position by superimposing the through-holes of the workpiece at the first position so as to coincide with the recesses or through-holes of the same diameter of the workpiece at the final position. Since diffusion bonding is performed by pushing into the through hole of the object, the recess of the workpiece to be welded at the final position, or the through hole, diffusion bonding can be surely performed without generating dust or spatter.

It is a figure for demonstrating the diffusion bonding method which concerns on Example 1 of this invention. It is a figure which shows an example of the cross section of the to-be-welded object welded with the diffusion bonding method which concerns on Example 1 of this invention, and a columnar welding member. It is a figure which shows the cross section of an example of the welding thing welded with the diffusion bonding method which concerns on Example 1 of this invention. It is a figure which shows the partial cross section for demonstrating an example of the welded material welded with the diffusion bonding method which concerns on Example 1 of this invention. It is a figure which shows the cross section of an example of the welding thing welded with the diffusion bonding method which concerns on Example 2 of this invention. It is a figure which shows the one part cross section of an example of the welded material welded with the diffusion bonding method which concerns on Example 3 of this invention. It is a figure which shows the specific example of the to-be-welded object welded with the diffusion bonding method which concerns on Example 4 of this invention. It is a figure which shows the chamfering of the to-be-welded object welded with the diffusion bonding method which concerns on Example 4 of this invention. It is a figure for demonstrating the state which pressed the to-be-welded objects welded with the diffusion bonding method which concerns on Example 4 of this invention.

[Example 1]
A first embodiment of diffusion bonding according to the present invention will be described with reference to FIGS. On the 1st welding electrode 1, the 1st to-be-welded object 2 and the 2nd to-be-welded object 3 which were mutually piled up are arrange | positioned. The first workpiece 2 is made of an arbitrary metal material such as iron or an iron alloy, and has a recess 2C having an opening on one surface 2A side and closed on the other surface 2B side. The recess 2C preferably comprises a cylindrical wall surface 2Ca and a circular bottom surface 2Cb. The recess 2C may be a through-hole penetrating from one surface 2A of the first workpiece 2 to the other surface 2B.

  In the first embodiment, the second workpiece 3 is made of the same metal material as the first workpiece 2. That is, the second workpiece 3 is made of a metal material having a melting temperature substantially the same as or close to the melting temperature (melting point) of the first workpiece 2. Here, the fact that the melting temperature of the metal material is the same is the same as the temperature at which the plastic fluidization is carried out. The second workpiece 3 has a surface 3A and a surface 3B that are pressed against one surface 2A of the first workpiece 2. The second workpiece 3 has a through hole 3C penetrating from one surface 3A to the other surface 3B.

  The through hole 3 </ b> C has a cylindrical surface 3 </ b> Ca that forms a cylindrical hole having the same diameter as the recess 2 </ b> C of the first workpiece 2 and has the same diameter as the recess 2 </ b> C of the first workpiece 2. It is called a through hole. Since the second workpiece 3 is superimposed on the first workpiece 2 such that the through hole 3C is positioned concentrically with the recess 2C of the first workpiece 2, FIG. As shown in FIG. 5, no step is formed at the contact portion between the recess 2C and the through hole 3C, that is, the joint between the surface 2A and the surface 3A, and the wall surface of the through hole is straight. However, the through hole 3C is chamfered by the surface 3B, and has an inclined portion 3D having a minute width by chamfering.

  Next, the columnar welding member 4 is positioned and pressed against the through hole 3 </ b> C of the second workpiece 3. In the first embodiment, the columnar welding member 4 is made of a metal material of the same system as the first workpiece 2 and the second workpiece 3. That is, the columnar welding member 4 is made of a metal material having a plastic fluidization temperature that is substantially the same as the temperature at which the first workpiece 2 and the second workpiece 3 are plastic fluidized. Therefore, the first workpiece 2 and the columnar welding member 4 and the second workpiece 3 and the columnar welding member 4 at the contact portions are plastically fluidized at substantially the same temperature almost simultaneously. The columnar welding member 4 is formed of a cylindrical straight metal member having a diameter somewhat larger than the diameter of the recess 2C of the first workpiece 2 and the through hole 3C of the second workpiece 3. Since the diameter of the columnar welding member 4 varies depending on the diameters of the through holes 3C and the recesses 2C, it is not possible to determine in general how much larger the diameter of the through holes 3C and the recesses 2C is. If there is an overlap margin of about 0.1 to 0.6 mm, desirable diffusion bonding is possible in the case of the columnar welding member 4 having a certain range of diameters.

  In the first embodiment, the tip of the columnar welding member 4 is also formed with an annular inclined portion 4A having a minute width by chamfering. An annular inclined portion 3D by chamfering is formed in the through hole 3C of the second workpiece 3 and an annular inclined portion 4A formed by chamfering is also formed at the tip of the columnar welding member 4. And positioning of the columnar welding member 4 with respect to the through-hole 3C becomes easy, but if any one is chamfered, there is no problem in diffusion bonding. When the inclined portion 4A is formed at the tip of the columnar welding member 4 and the inclined portion 3D is formed in the through hole 3C of the second workpiece 3, both the inclined portions 4A and the inclined portions 3D In order to obtain a good diffusion result, it is important to uniformly contact each other with no gap on the entire circumferential surface. Moreover, after combining the 1st to-be-welded object 2 and the 2nd to-be-welded object 3, you may form the through-hole 3C and the recess 2C in them later using the drilling apparatus not shown. For example, if the first workpiece 2 and the second workpiece 3 are structures that constitute a part of the device, the through-hole 3C is formed at one or a plurality of desired positions after the device is assembled. And the recess 2C can be easily formed. This has a great practical effect in terms of eliminating the need to precisely align the through hole 3C of the second workpiece 3 with the recess 2C of the first workpiece 2.

  The second welding electrode 5 that is paired with the first welding electrode 1 is fixed to the lifting / pressurizing mechanism 6, moves in the vertical direction in FIG. 1, is pressed against the columnar welding member 4, and columnar welding is performed. The member 4 is pressurized. The elevating / pressurizing mechanism 6 may be a general electric mechanism such as a hydraulic cylinder, a pneumatic cylinder, a combination thereof, or a motor. The raising / lowering / pressurizing mechanism 6 advances (lowers) the second welding electrode 5 to softly press the second welding electrode 5 against the second workpiece 3 and applies a predetermined pressing force that rapidly increases. One end of a power supply conductor 7 that is one output conductor of the welding power source is connected to the first welding electrode 1, and flexible power supply that is the other output conductor of the welding power source is connected to the second welding electrode 5 that moves in the vertical direction. One end of the conductor 8 is connected. A secondary winding 9B of a welding transformer 9 is connected to the other end of the feeding conductor 7 and the other end of the flexible feeding conductor 8, and an inverter circuit or a semiconductor switch is connected to the primary winding 9A magnetically coupled thereto. A discharge circuit 10 such as a circuit is connected.

  Connected to the discharge circuit 10 are an energy storage capacitor 11 and a charging circuit 12 for charging the capacitor 11. The charging circuit 12 charges the energy storage capacitor 11 by converting three-phase AC power from the AC power supply terminals 13A, 13B, and 13C into DC. The energy storage capacitor 11 is formed by connecting a number of electrolytic capacitors corresponding to the required welding current in parallel. Since the power supply portion may be a known one filed by the present applicant, it will not be described in detail. Of course, the input power source may be a single-phase AC power source or the like instead of the three-phase AC power source, if necessary.

  Next, an example of performing diffusion bonding by this method will be described. First, as shown in FIGS. 1 and 2, a first welding electrode 2 and a second welding object 3 that are overlapped so that the through hole 3 </ b> C coincides with the recess 2 </ b> C are connected to the first welding electrode. 1 is arranged at a predetermined position above 1. Next, the columnar welding member 4 is positioned and arranged in the through hole 3C of the second workpiece 3 and the columnar welding member 4 is held in the aligned state by a pressing mechanism (not shown), The pressure mechanism 6 is operated to lower the second welding electrode 5. At this time, the chamfered inclined portion 3D of the through-hole 3C of the second workpiece 3 is in contact with the chamfered inclined portion 4A of the tip end portion of the columnar welding member 4. When the second welding electrode 5 is pressed against the columnar welding member 4, the lifting / pressurizing mechanism 6 applies a rapidly increasing applied pressure to the second welding electrode 5. At the same time, the discharge circuit 10 is turned on to discharge the energy (charge) stored in the energy storage capacitor 11 through the primary winding 9A and the secondary winding 9B of the welding transformer 9 in a short time, A pulsed welding current is passed through the first workpiece 2, the second workpiece 3, and the columnar welding member 4 that are subjected to pressure applied by the first welding electrode 1 and the second welding electrode 5.

  Since the secondary winding 9B of the welding transformer 9 has a significantly smaller number of turns than the primary winding 9A, a current having a large peak value corresponding to the turn ratio flows through the secondary winding 9B. The welding current flowing at this time is, for example, a current having a large peak value having a pulse width of 20 to 30 ms or less, for example, a pulsed current having a peak value of several thousand to several million amperes. As described above, this welding current is generated between the chamfered inclined portion 3D of the through hole 3C of the second workpiece 3 and the chamfered inclined portion 4A of the tip of the columnar welding member 4 that are in contact with each other. Concentrates on the contact surface. Since both the inclined portion 3D and the inclined portion 4A are annular surfaces having a sufficiently small width, the current density flowing through the contact surface is sufficiently high, and a large amount of heat is generated even if the contact resistance is small. The vicinity of the inclined portion 3D of the through-hole 3C of the workpiece 3 and the vicinity of the inclined portion 4A chamfered at the tip of the columnar welding member 4 are first plastically fluidized at first.

  When the vicinity of the inclined portion 3D of the through-hole 3C of the second workpiece 3 and the vicinity of the chamfered inclined portion 4A of the columnar welding member 4 are plastically fluidized, heat generation and heat conduction by the welding current cause a very short time. Further, the contact portion between the columnar welding member 4 and the through hole 3C of the second workpiece 3 is plastically fluidized. At this time, when the contact portion between the columnar welding member 4 and the through hole 3C of the second workpiece 3 is plastically fluidized, the tip of the columnar welding member 4 is moved by the pressure applied by the elevating / pressurizing mechanism 6. 2 is advanced through the through hole 3C of the work piece 3 and is further pushed into the through hole 3C of the second work piece 3 while being fluidized one after another in a very short time due to heat generation and heat conduction by the welding current. Proceed to the back of the through hole 3C.

  That is, since the plastic fluidization temperatures of the columnar welding member 4 and the second workpiece 3 are substantially the same at the contact portion between the columnar welding member 4 and the through hole 3C of the second workpiece 3, the columnar welding member 4 and the wall surface portion of the through hole 3C of the work piece 3 are plastically fluidized, and therefore, preferable diffusion bonding is performed at the contact portion. A broken line X1 shown in FIG. 3 indicates a diffusion bonding interface between the columnar welding member 4 and the second workpiece 3 and diffusion bonding between the columnar welding member 4 and the second workpiece 3 is performed in the vicinity of the broken line X1. It has been broken. 4 indicates the wall surface position of the through hole 3C of the original second workpiece 3 and the recess 2C of the first workpiece 2 before diffusion bonding.

  Subsequently, both of the contact portion between the columnar welding member 4 and the wall surface of the recess 2C of the first workpiece 2 are plastically fluidized by heat generation and heat conduction due to the welding current. The desired diffusion bonding of the workpiece 2 is performed, and a desired welding strength is obtained. A broken line X2 indicates a diffusion bonding interface between the columnar welding member 4 and the first workpiece 2 and diffusion bonding between the columnar welding member 4 and the first workpiece 2 is performed in the vicinity of the broken line X2. The elevating / pressurizing mechanism 6 stops pressurization when the columnar welding member 4 is pushed to a predetermined position in the recess 2 </ b> C of the first workpiece 2. At this time, the pulsed welding current is also stopped. In addition, when the columnar welding member 4 is pushed into the through hole 3C of the second workpiece 3, the plastic fluidized metal of the columnar welding member 4 and the second workpiece 3 is slightly penetrated by the through hole 3C. Pushed out of the. Further, when the columnar welding member 4 is pushed into the recess 2C of the first workpiece 2, the plastic fluidized metal of the columnar welding member 4 and the first workpiece 2 due to the applied pressure is slightly recessed 2C. Extruded. This slightly extruded metal is plastically fluidized and integrated with these workpieces, and does not peel off even if it is cooled, so that conventional dust and spatter do not occur.

  As described above, the columnar welding member 4 is plastically fluidized at the contact portion with the through hole 3C of the second workpiece 3 and the contact portion with the recess 2C of the first workpiece 2 during welding. Since all the through holes 3C and the predetermined positions of the recesses 2C are advanced, the front end surface 4B of the columnar welding member 4 has a diameter substantially the same as the initial diameter of the recesses 2C. This is sufficiently achieved by the interface X1 between the columnar welding member 4 and the through hole 3C of the second workpiece 3 and the recess 2C of the columnar welding member 4 and the first workpiece 2 and the interface X2. Indicates that diffusion bonding has been performed. Thus, those metal materials to be welded without forming even a minute gap between the columnar welding member 4 and the second workpiece 3 and between the columnar welding member 4 and the first workpiece 2. Since the diffusion bonding is performed in a state where both of them are plastic fluidized, the metal fluidized plastically is slightly pushed out as described above, but dust and spatter are not generated.

  In the present invention, as described above, at the interface X1 between the columnar welding member 4 and the second workpiece 3 and at the interface X2 between the columnar welding member 4 and the first workpiece 2, the columnar shape is formed at the stage of plastic fluidization. At least the pulsed welding current is increased so that the welding member 4 is further pushed into the through holes 3C of the second workpiece 3 and the recesses 2C of the first workpiece 2 to be recessed. It is important to add between the first welding electrode 1 and the second welding electrode 5 in the process. In addition, although the 2nd to-be-welded object 3 was demonstrated by one, even if it consists of two or more metal plates which consist of a metal material which has the through-hole of the same diameter and is the plastic fluidization temperature of the same grade. Diffusion bonding can be performed in the same manner as described above. Moreover, in Example 1, the 2nd to-be-welded object 3 and the 1st to-be-welded object 2 are respectively corresponded to the to-be-welded object of the first position and the to-be-welded object of the last position of Claim 1.

[Example 2]
The welded material shown in FIG. 5 is made of the same type of metal material having a plastic fluidization temperature similar to the plastic fluidization temperature on the first workpiece 2 made of a metal material having a high plastic fluidization temperature. The intermediate member 23 is stacked, and the second workpiece 3 made of a metal material having a plastic fluidization temperature that is the same as that of the first workpiece 2 and the plastic fluidization temperature is further stacked on the intermediate member 23. The product 2 and the second work piece 3 are diffusion-bonded using a columnar columnar welding member 4 made of a metal material having a plastic fluidization temperature of the same plastic fluidization temperature. Prior to diffusion bonding, as in the first embodiment, the second workpiece 3 has a short cylindrical through hole having the same diameter as the shallow recess 2C of the first workpiece 2 and the intermediate member 23. Also have a cylindrical through hole having the same diameter as the recess 2C of the first workpiece 2 and the through hole of the second workpiece 3.

  The principle of this diffusion bonding method is the same as that of the first embodiment. At the time of diffusion bonding, the columnar welding member 4 and the second workpiece 3 and the columnar welding member 4 and the first workpiece 2 are the same as in the first embodiment. Thus, diffusion bonding is performed. At the contact portion between the columnar welding member 4 and the intermediate member 23, the plastic fluidization temperatures of the columnar welding member 4 and the intermediate member 23 are substantially the same, so that the wall of the through hole of the intermediate member 23 and the columnar welding member 4 are substantially the same. At the same time, the plastic fluidization is performed, and diffusion bonding is sequentially performed at the contact portion between the columnar welding member 4 and the intermediate member 23 by heat generation and heat conduction. A broken line X3 indicates a diffusion bonding interface between the columnar welding member 4 and the intermediate member 23, and diffusion bonding is performed in the vicinity of the broken line X3.

  Also in the second embodiment, when the contact portion between the columnar welding member 4 and the second workpiece 3 and the contact portion between the columnar welding member 4 and the first workpiece 2 are plastically fluidized, FIG. The lifting / pressurizing mechanism 6 shown is at least pulsed so that the columnar welding member 4 is pushed from the through hole 3C of the second workpiece 3 into the depth of the recess 2C of the first workpiece 2. It is important to add between the 1st welding electrode 1 and the 2nd welding electrode 5 in the process in which the shape welding current is increasing. In the second embodiment, a plurality of intermediate members 23 may be included.

  In the second embodiment, when the thickness of the second workpiece 3 and the intermediate member 23 is larger than that of the first embodiment, the waveform of the welding current may be controlled as follows. In FIG. 1, an inverter circuit is used as the discharge circuit 10, and a general output rectifier circuit (not shown) is connected to the secondary winding 9B of the welding transformer 9. The inverter circuit is preferably switched at a high frequency (20 kHz or higher) above the audible frequency, and the energy stored in the energy storage capacitor 11 is intermittently discharged at the high frequency. The output rectifier circuit rectifies the high-frequency alternating current flowing in the secondary winding 9B of the welding transformer 9 and converts it into a pulsating pulsed direct current to obtain a welding current.

  Compared with the case where the thickness of the second workpiece 3 and the intermediate member 23 is small, the contact between the columnar welding member 4 and the second workpiece 3 and the columnar welding member 4 and the intermediate member 23 as diffusion bonding proceeds. Since the area naturally increases, the rate of dispersion of the welding current increases, and the current flowing from the tip of the columnar welding member 4 to the second workpiece 3 and the intermediate member 23 decreases. Therefore, by controlling the pulse width of the inverter circuit at a high frequency and widening the pulse width at each cycle of the high frequency (when switching at 20 kHz, a time width of 0.05 ms) as the diffusion junction progresses, Can be increased so that the welding current flowing from the tip of the columnar welding member 4 to the second workpiece 3 and the intermediate member 23 can be set to a desired magnitude. If such pulse width control is performed, the welding current flowing between the first welding electrode 1 and the second welding electrode 5 is not shown, but a predetermined pulse width (for example, a time width of several tens of ms). In this period, the dc current increases while pulsating at a high frequency, and the energy stored in the energy storage capacitor 11 is released while being interrupted at a high frequency. The width can be increased. This is preferable for reliable diffusion bonding because the heat conduction generated during diffusion bonding takes longer as the thickness of the second workpiece 3 and the intermediate member 23 increases.

[Example 3]
The welded material shown in FIG. 6 is a first workpiece 2 made of a metal plate having a relatively large or long strip-shaped plastic fluidization temperature, a similar large-area or long strip-shaped relatively plastic fluidization temperature. A material obtained by superimposing intermediate members 23 made of high-conductivity metal plates having a low thickness and diffusion-bonded using the second workpiece 3 made of a metal plate having a small area and the columnar welding members 4 as described above. It is. In Example 3, the 2nd to-be-welded object 3 works not as an original welding member but as a welding auxiliary member. This second workpiece 3 is not necessary when the columnar welding member 4 can be firmly diffusion bonded to the intermediate member 23 and the first workpiece 2. The first workpiece 2 has the recess 2C as described above, and the intermediate member 23 has a through-hole having the same diameter as the recess 2C of the first workpiece 2 as described above. These through holes and recesses 2 </ b> C may be drilled in a state where the first workpiece 2 and the intermediate member 23 are overlapped.

  The second member 3 to be welded is made of a metal material having a plastic fluidization temperature comparable to that of the first workpiece 2 and is a small-area circular or polygonal metal plate. The through hole having the same diameter as that of the recess 2C of the workpiece 2 and the through hole of the intermediate member 23 may be provided so long as a desired welding strength can be obtained. The columnar welding member 4 is made of a metal material having a plastic fluidization temperature that is the same as or higher than that of the first workpiece 2 and the second workpiece 3. The columnar welding member 4 is a columnar member having a diameter larger than the diameter of the recess 2C of the first workpiece 2 and the through hole of the intermediate member 23 and the through hole of the second workpiece 3.

  This feature is that the first workpiece 3 is aligned with the through hole of the second workpiece 3 in each of the through holes of the intermediate member 23 stacked on the first workpiece 2. Are aligned and placed. Next, the columnar welding member 4 is aligned and pressed against the through-hole of the second workpiece 3 and the second welding electrode 5 shown in FIG. A pressurizing force is applied and a pulsed welding current is applied as described above. As this welding current flows through the contact portion between the wall surface portion of the through hole of the second workpiece 3 and the columnar welding member 4, the contact portion generates heat due to contact resistance and plastically flows, as described above. The columnar welding member 4 advances through the through hole of the second workpiece 3 by the applied pressure, and diffusion bonding is performed. At this time, since the second workpiece 3 has a small area, the heat generated during diffusion bonding is difficult to escape in the lateral direction in the drawing, and the amount of heat transmitted in the direction in which the columnar welding member 4 is pushed in increases. Diffusion bonding proceeds well.

  Next, the columnar welding member 4 advances to the through hole of the intermediate member 23. At this time, the temperature of the tip of the columnar welding member 4 naturally rises in the state of plastic fluidization with the second workpiece 3 and the wall of the through hole of the intermediate member 23 is also near the interface X1. The temperature rises due to heat conduction in Therefore, both the columnar welding member 4 and the intermediate member 23 are instantaneously plastically fluidized by heat generation and heat conduction when the welding current flows through the contact portion, and the columnar welding member 4. Advances to the through hole of the intermediate member 23 and reaches the recess 2 </ b> C of the first workpiece 2. The diffusion bonding at the interface X2 between the columnar welding member 4 and the wall surface of the recess 2C of the first workpiece 2 is as described above. A broken line X3 indicates a diffusion bonding interface between the columnar welding member 4 and the intermediate member 23, and diffusion bonding is performed in the vicinity of the broken line X3. The wall surface of the original through-hole before diffusion bonding in the intermediate member 23 is the through-hole 3C of the original workpiece 3 before diffusion bonding and the first workpiece 2 before diffusion bonding, as indicated by the one-dot chain line Y in FIG. It is in the position which tied the wall surface of the recess 2C.

  In this way, the columnar welding member 4 is diffusion-bonded to the second workpiece 3, the intermediate member 23, and the first workpiece 2 sequentially in a very short time. However, when the plastic fluidization of the columnar welding member 4 or the intermediate member 23 becomes incomplete due to the material of the intermediate member 23 or the like, at the interface X3 between the columnar welding member 4 and the wall surface of the through hole of the intermediate member 23. In some cases, satisfactory diffusion bonding is not performed. Even in such a case, in this embodiment, the diffusion welding is reliably performed between the columnar welding member 4, the second workpiece 3 and the first workpiece 2, and desired welding strength can be obtained.

[Example 4]
Next, a specific fourth embodiment according to the present invention will be described with reference to FIGS. 7A, 7B, 8A, 8B, and 9. FIG. FIG. 7A shows a partial cross section of the first workpiece 2 or the second workpiece 3 and the second welding electrode 5, and FIG. 7B shows the first workpiece as viewed from the side. 2 shows a partial cross section of the workpiece 2 and the second workpiece 3 and welding electrodes. FIG. 8A is a front view of the chamfered inclined portion 3D of the through hole 3C of the pipe-shaped second workpiece 3, and FIG. 8B is a pipe-shaped second workpiece. It is a figure which shows the cross section which looked at the inclined part 3D which chamfered 3 C of through holes from the side surface. The first workpiece 2 is firmly clamped to the first welding electrode 1 by a clamping mechanism (not shown).

  The first workpiece 2 is surrounded by a pipe-like second workpiece 3 having a relatively small thickness. For example, the first workpiece 2 is a cast iron casting. In a state where the second workpiece 3 is wound around the first workpiece 2, four recesses 2C (1) to 2C (4) and through holes 3C (1) to 3C are formed by a drilling device (not shown). (4) are formed at equal intervals together. As another method, the second workpiece 3 in which the through holes 3C (1) to 3C (4) are formed is replaced with the first workpiece in which the recesses 2C (1) to 2C (4) are formed. The weldment 3 may be wound so that the through holes 3C (1) to 3C (4) coincide with the recesses 2C (1) to 2C (4). In such a structure, even if the first workpiece 2 and the second workpiece 3 are in contact with each other without a gap, they are displaced from each other when vibration or rotational force is applied between them. It is necessary to fix it mechanically firmly. As described above, the pipe-like second workpiece 3 is made of the same metal material as the first workpiece 2, and the plastic fluidization temperature is substantially the same as that of the first workpiece 2.

  When welding is performed using the contact resistance between the first workpiece 2 and the second workpiece 3, a projection cannot be formed between the first workpiece 2 and the second workpiece 3. Therefore, it is impossible to perform projection welding. The welding method described in the above-mentioned Patent Document 1 realized the welding of the first workpiece 2 and the second workpiece 3 of such a structure, using the third member. The third member and the first workpiece 2 are resistance-welded, and the third member and the second workpiece 3 are resistance-welded together, thereby the first member via the third member. The work piece 2 and the second work piece 3 are fixed. Example 4 is an improvement of the welding method.

  The point that this Example 4 is different from the welding method described in Patent Document 1 is that the recess 2C of the first work piece 2 is formed in the invention of Example 4 as is clear from Examples 1-3. The diameter and the diameter of the through hole 3 </ b> C of the second workpiece 3 are the same, and the columnar welding members 4 (1) to 4 (4) are the first workpiece 2 and the second workpiece 3. The columnar welded members 4 (1) to 4 (4) are not a member having a spherical surface or an inclined portion but a straight columnar metal. Thus, the diameter of the through holes 2C (1) to 2C (4) of the first workpiece 2 and the diameter of the through holes 3C (1) to 3C (4) of the second workpiece 3 are somewhat larger. It has a diameter, and is specially chamfered at the entrance of the through hole 3C of the pipe-shaped second workpiece 3 having a relatively small thickness.

  By having such a feature, even if the second workpiece 3 is a pipe having a relatively thin thickness, the columnar columnar welding members 4 (1) to 4 (4) are used. Therefore, as will be described later, preferable diffusion bonding is performed between the columnar welding members 4 (1) to 4 (4) and the second workpiece 3 and the columnar welding members 4 (1) to 4 ( Even a small gap is not formed between 4) and the second work piece 3 and the first work piece 2, so that good diffusion bonding can be performed without generating dust and spatter.

  As in the first to third embodiments, the columnar welding members 4 (1) to 4 (4) chamfer the corresponding through holes 3C (1) to 3C (4) of the second workpiece 3 to be welded. It is pressed against the inclined portion 3D having a very small width. The small-width inclined portions 3D chamfered in the through holes 3C (1) to 3C (4) are in uniform contact with the chamfered small-width annular inclined portions 4A of the columnar welding members 4 over the entire circumference. Of course, the inner diameter of the inclined portion 3D is equal to the diameter of each of the through holes 3C (1) to 3C (4). In FIG. 8, the outline corresponds to the cylindrical outer surface of the pipe-shaped second workpiece 3, and the length direction of the pipe-shaped second workpiece 3 (the direction of the dashed line ZZ ′). The shape of the ellipse is somewhat larger and slightly smaller in the circumferential direction. That is, the inclined portion 3D by chamfering the second work piece 3 is somewhat longer in the direction of the alternate long and short dash line ZZ ′ and somewhat shorter in the circumferential direction, and the inclination angle of the inclined portion 3D is the entire circumference. The inclination angle is equal to that of the inclined portion 4 </ b> A of the columnar welding member 4. Therefore, as shown in FIG. 9, the chamfered minute width inclined portion 4A of the columnar welding member 4 is in uniform contact with the entire circumferential surface pressed against the chamfered minute width inclined portion 3D. This is one of the reasons that good diffusion bonding results can be obtained.

  In a state where the chamfered inclined portion 4A of the columnar welding member 4 is in uniform contact with the chamfered inclined portion 3D over the entire circumference, the columnar welding member 4 is formed by the respective second welding electrodes 5 (1) to 5 (4). Is pressed in the direction in which the through holes 3C (1) to 3C (4) of the second workpiece 3 extend. In this state, the columnar welding members 4 (1) and 4 (3) and the columnar welding members 4 (2) and 4 (4) are subjected to pressures in opposite directions. The first workpiece 2 is firmly clamped to the first welding electrode 1, and the first welding electrode 1 is common to the four second welding electrodes 5 (1) to 5 (4). Works as a welding electrode.

  The principle of the diffusion bonding method is the same as in the first to fourth embodiments described above, but the welding current is simultaneously applied between the first welding electrode 1 and the second welding electrodes 5 (1) to 5 (4). The four parts may be diffusion-bonded at the same time, or the welding current may be individually flowed separately to perform diffusion bonding one by one. In the case where diffusion welding is performed one by one by sequentially passing welding currents individually, diffusion welding is possible even if the second welding electrode is only 5 (1) as an example. The welded article 2 and the second workpiece 3 are rotated by 90 degrees, and the columnar welding member is sequentially supplied to the through hole of the second workpiece 3 at the position of the second welding electrode 5 (1). The second welding electrode may be diffusion bonded as described above with 5 (1) lowered.

  By performing diffusion bonding as described above, the columnar welding members 4 (1) to 4 (4) are naturally formed in the through holes 3C (1) to 3C (4) of the second workpiece 3 in Example 4 as well. First, plastic flow occurs at the contact portion with the wall of the column, and then the columnar welding members 4 (1) to 4 (4) are connected to the walls of the recesses 2C (1) to 2C (4) of the first workpiece 2 to be welded. The plastic flow continuously occurs at the contact portion of the material and diffusion bonding is performed. Accordingly, the first workpiece 2 and the second workpiece 3 are diffusion-bonded with desired welding strength via the columnar weld members 4 (1) to 4 (4). Even if a large rotational force is applied between the workpiece 2 and the second workpiece 3, there is no movement. The number of the recesses in the first workpiece 2 and the through-holes in the second workpiece 3 is not limited to four, and may be any number.

  In the above embodiment, the capacitor type diffusion bonding method has been described as a preferable example. However, since the columnar welding member 4 has a small diameter and the welded portion has a small area, the required welding is performed. When the current is small, it is not a capacitor type diffusion bonding method, but an inverter type diffusion bonding method in which an AC input is converted into a direct current by an unillustrated input rectifier circuit and a welding current having a desired current waveform is output by an inverter circuit. Therefore, a small current having a desired pulse width, for example, a pulsed current of about several hundred amperes may flow through the welding transformer and the output side rectifier circuit.

  In the embodiments described above, iron-based materials and materials of the same system as the workpieces and columnar welding members have been described as examples. However, the present invention is not limited to specific metal materials. However, the first workpiece 2 and the second workpiece 3 are preferably made of a metal material having the same or relatively close plastic fluidization temperature from the viewpoint of obtaining good welding strength. . In addition, the columnar welding member 4 is located at the center of the welding, and its heat radiation is lower than that of the workpiece 2 and the second workpiece 3 and so on, so that the columnar welding member 4 has the first and second workpieces 2 and 2. Good weld strength can be obtained if the plastic fluidization temperature is the same as that of the workpiece 3 or if the plastic fluidization temperature is somewhat higher than that of the workpiece.

  Further, as described above, in one example of the present invention, the columnar welding member has a plastic flow temperature that is equal to or higher than the plastic fluidization temperature of the work piece at the first position and the work piece at the final position. Since it is made of a metal material having a heat treatment temperature, all the workpieces can be reliably fixed to each other by the columnar welding members.

  Further, as described above, in the example of the invention, the workpiece to be welded at the first position is composed of a single metal member or a plurality of metal members having an area smaller than that of the other plurality of workpieces. When the workpiece to be welded comprises the plurality of metal members, each of the plurality of metal members has one or more of the through holes, and each of the columnar welding members is diffusion-bonded to each of the through holes. Therefore, the intermediate member can be fixed to the work piece at the final position with the work piece at the first position and the columnar welding member having a small area that works as a welding auxiliary member.

  Further, as described above, in the example of the present invention, when the workpiece to be welded at the first position has a plurality of the through holes, the welding electrode and the workpiece are configured to be relatively movable so as to be diffusion bonded. Or the welding electrode is pressed against each of the columnar welding members aligned with the plurality of through-holes of the workpiece, and diffusion bonding is performed simultaneously. Can be selected. When the plurality of columnar welding members are diffusion-bonded at the same time, the welding time can be shortened.

  It can be applied to welding of workpieces made of various metal materials such as a part of a pressure vessel or a stacked structure of two or more layers.

DESCRIPTION OF SYMBOLS 1 ... 1st welding electrode 2 ... 1st to-be-welded object 2A ... One surface 2B of the 1st to-be-welded object 1 2B ... The other surface 2C of the 1st to-be-welded object 1 2C (1) to 2C (4): Recess of first workpiece 1 2Ca: Wall surface of recess 2Cb ... Bottom of recess 3 ... Second workpiece 3A ... One surface 3B of the second workpiece 3B ... The other surface 3C, 3C (1) to 3C (4) of the second workpiece 3 2nd workpiece 3 Through hole 3Ca... Wall surface of through hole 3D... Incline of minute width due to chamfering of second workpiece 3 4, 4 (1) to 4 (4) columnar welding member 4 A ··· Chamfered and slanted portion 4B of columnar welding member 4 · · · End surface of columnar welding member 4 5, 5 (1) to 5 (4) · · · Second welding electrode 6 · · · Elevation・ Pressure mechanism 7 ... Feeding conductor 8 ... Flexible power supply conductor 9 ... Transformer for welding 10 ... Discharge circuit 11 ... Capacitor for energy storage 12 ... Charging circuit 13A, 13B, 13C ... AC power supply terminal 23 ... Intermediate member X1... Contact portion between the second workpiece 3 and the columnar welding member 4 X2... Contact portion between the first workpiece 2 and the columnar welding member 4 X3. Contact portion with member 23 Y ... alternate long and short dash line indicating wall surface position of through hole 3C and recess 2C before diffusion bonding

Claims (3)

A welding method for energizing and welding a plurality of workpieces superimposed between welding electrodes to the workpiece and the columnar welding member via a columnar welding member,
The workpiece at the final position where the columnar welding member is diffusion-bonded at the end of the plurality of workpieces has one or more recesses or through holes,
The work piece excluding the work piece at the final position has one or more through holes, and the through hole is concentric with the recess or the through hole of the work piece at the final position. Are superimposed on each other,
Both the front end of the columnar welding member and the through hole of the workpiece to be welded at the first position where the columnar welding member is initially diffusion-bonded are provided with a chamfered minute width inclined portion,
Each of the recess or the through hole is formed by a cylindrical wall surface,
The columnar welding member is a cylindrical one having a larger diameter than the recess or the through hole of the workpiece.
In a state where the columnar welding member is pressed against the through-hole of the workpiece to be welded at the first position, the welding electrode has a pulse shape while applying pressure to the columnar welding member and the plurality of workpieces to be welded. A current is passed to plastically fluidize the contact point between the columnar welding member and the workpiece to be welded at the first position, and the columnar welding member is pushed into the through hole of the workpiece to be welded at the first position. Diffusion welding the columnar welded member and the workpiece to be welded at the first position;
Subsequently, the columnar welding member is pushed into the recess or through hole of the workpiece to be welded at the final position to plastically fluidize the contact portion, and the columnar welding member and the workpiece to be welded at the final position are diffusion-bonded.
A welding method comprising diffusion welding the columnar welding member and the workpiece to be welded at the first position, and the columnar welding member and the workpiece to be welded at the final position. In claim 1,
Between the workpiece at the first position and the workpiece at the final position, an intermediate member made of the same or different metal material is sandwiched between them,
The said columnar welding member consists of a metal material of the plastic fluidization temperature comparable as the plastic fluidization temperature of the said intermediate member, or higher than it, The welding method characterized by the above-mentioned. In claim 1 or claim 2,
When both the front end portion of the columnar welding member and the through hole of the workpiece to be welded at the first position are provided with the inclined portion having a chamfered minute width, regardless of the shape of the workpiece to be welded at the first position. The welding method is characterized in that the inclined portion of the workpiece to be welded at the first position is chamfered so as to be equal to the inclination angle of the inclined portion of the tip portion of the columnar welding member.

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