Composite welding device and composite welding method

Abstract

To provide a composite welding device and a composite welding method that may improve bond strength whether the work-pieces are made of different materials or the same material.SOLUTION: A composite welding device 1000 comprises a current application device 50 that conducts low current to a first work-piece 1 and a second work-piece 2 so as to become a melting point or less of the first work-piece 1 and the second work-piece 2 via a first electrode 11 and a second electrode 21 in the state that the first work-piece 1 and the second work-piece 2 are sandwiched between the first electrode 11 and the second electrode 21, then, pressurizes the first work-piece 1 and the second work-piece 2 from both sides in a thickness direction thereof by a first pressurizing shaft 13 and a second pressurizing shaft 23, and thereafter, in the state that the first work-piece 1 and the second work-piece 2 are sandwiched between the first electrode 11 and the second electrode 21, conducts current higher than the low current to the first electrode 11 and the second electrode 21, and conducts current for providing a molten joint part of the first work-piece 1 and the second work-piece 2.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a hybrid welding apparatus and a hybrid welding method. [Background technology]

[0002] JP 2017-177206 A (Patent Document 1) discloses an invention relating to a mechanical clinch-jointed part and a manufacturing method thereof, in which the mechanical clinch-jointed part is a clinch-jointed part made of two or more steel plates and has at least one joint with a peel strength of 0.200 kN / mm or more. It also discloses that after a heating process in which the steel plates are heated to a certain level or higher, in the heating process, it is preferable to satisfy a predetermined relational expression in the relationship between the carbon equivalent of the steel plates, the bottom dead center holding time during mechanical clinch joining, and the joining start temperature.

[0003] JP 2019-883 A (Patent Document 2) discloses a method for sandwiching a laminated metal foil consisting of two or more metal foils between a first metal plate and a second metal plate, and joining the metal plates and the laminated metal foil by crimping. The method includes a laser light irradiation process in which, before crimping with a punch and a die, a laser light is irradiated near the intended crimping position of the second metal plate placed on the punch side, thereby heating the second metal plate to a temperature that does not melt and that promotes plastic flow of the second metal plate when crimping is performed, and a process of performing crimping in a heated state of the second metal plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-177206 A [Patent Document 2] JP 2019-883 A Summary of the Invention [Problem to be solved by the invention]

[0005] Mechanical clinching is generally a high pressure joining process using cold plastic processing, and has a die and a punch. The punch presses the plate, causing the material to plastically flow into the shape of the die, forming an interlock. In order to cause the material to flow locally, a plate holder is also required in addition to the die and punch.

[0006] However, although mechanical clinching tends to have a higher fatigue strength than resistance spot welding, the joint strength of the interlock (crimp) is low, at approximately 50% or less than that of resistance spot welding.

[0007] In addition, resistance spot welding of dissimilar workpieces poses the issue of low joint strength due to the formation of brittle IMCs (intermetallic compounds).On the other hand, resistance spot welding of the same workpieces, which are steel plates, reduces joint strength as the strength of the steel plates increases beyond the 590 MPa class high-strength steel plate.

[0008] An object of the present disclosure is to provide a hybrid welding apparatus and a hybrid welding method that can be expected to improve the joining strength, whether the workpieces are made of different materials or the same material. [Means for solving the problem]

[0009] [1]: The present disclosure provides a hybrid welding apparatus that applies pressure to a first workpiece made of metal and a second workpiece made of metal from both sides in a thickness direction thereof and joins the first workpiece and the second workpiece to each other by passing current through the first workpiece and the second workpiece. The hybrid welding apparatus includes a pair of first and second pressure shafts that can apply pressure to the first and second workpieces from both sides in a thickness direction thereof, a first electrode that is annularly arranged around the first pressure shaft, a second electrode that is opposed to the first electrode and annularly arranged around the second pressure shaft, and a welding current is applied to the first and second electrodes when the first and second workpieces are sandwiched between the first and second electrodes. a current application device for passing a low current through the first workpiece and the second workpiece so that the temperatures of the first workpiece and the second workpiece are below the melting points of the first workpiece and the second workpiece, and then pressing the first workpiece and the second workpiece from both sides in the thickness direction using the first pressure shaft and the second pressure shaft, and then, in a state in which the first workpiece and the second workpiece are sandwiched between the first electrode and the second electrode, passing a current higher than the low current through the first electrode and the second electrode to pass a current to provide a molten joint of the first workpiece and the second workpiece, wherein the first pressure shaft includes a convex portion extending toward the second pressure shaft on a side facing the second pressure shaft, and the second pressure shaft includes a concave portion that receives the convex portion on a side facing the first pressure shaft.

[0010] [2]: The composite welding apparatus according to [1], wherein the first electrode and the second electrode are made of at least one material selected from the group consisting of copper, copper alloy, tungsten, and molybdenum.

[0011] [3]: The hybrid welding method disclosed herein is a hybrid welding method using the hybrid welding apparatus described in either [1] or claim [2], and includes the steps of: clamping the first workpiece and the second workpiece with the first electrode and the second electrode; using the current application device, applying a low current to the first electrode and the second electrode so that the temperature of the first workpiece and the second workpiece is equal to or lower than the melting point of the first workpiece and the second workpiece, thereby softening the first workpiece and the second workpiece; and, while the first workpiece and the second workpiece are held between the first electrode and the second electrode, the step of sandwiching the first workpiece and the second workpiece with the first pressure shaft and the second pressure shaft and applying pressure so that the convex portion of the first pressure shaft fits into the concave portion of the second pressure shaft, thereby forming a crimped area between the first workpiece and the second workpiece; and the step of, with the first workpiece and the second workpiece sandwiched between the first electrode and the second electrode, using the current application device to pass a current higher than the low current to the first electrode and the second electrode, thereby passing a current for providing a molten joint in the first workpiece and the second workpiece. Effect of the Invention

[0012] According to the present disclosure, it is possible to provide a hybrid welding apparatus and a hybrid welding method that can be expected to improve the joining strength, whether the workpieces are made of different materials or the same material. [Brief description of the drawings]

[0013] [Figure 1] 1 is a vertical cross-sectional view that shows a schematic view of a hybrid welding device according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a perspective view of the first pressure applying shaft as viewed from the pressure applying surface side. [Diagram 3] FIG. 4 is a perspective view of the second pressure applying shaft as viewed from the pressure applying surface side. [Figure 4] FIG. 4 is a cross-sectional view showing a schematic state in which current is applied to each workpiece. [Diagram 5] 1A and 1B are diagrams showing the state in which each workpiece is pressed by a pair of pressure shafts. [Figure 6] FIG. 11 is a cross-sectional view illustrating a state in which current is re-applied to each workpiece. [Figure 7] FIG. 13 is a diagram showing the relationship between pressure and time. [Figure 8] FIG. 13 is a diagram showing the relationship between current value and time. [Figure 9] FIG. 4 is a cross-sectional view showing the final joining state of the workpieces. [Figure 10] 4 is a cross-sectional view showing a fusion-bonded state when the first workpiece and the second workpiece are made of different materials. FIG. [Figure 11] 4 is a cross-sectional view showing a fusion-bonded state when the first workpiece and the second workpiece are made of the same material. FIG. [Figure 12] 1 is a cross-sectional view showing a molten joint of a workpiece. [Figure 13] 6A to 6C are cross-sectional views showing different shapes of the tip surface of the protrusion of the first pressure applying shaft. [Figure 14] 1A to 1C are cross-sectional views showing different fusion joints of a workpiece. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The hybrid welding apparatus and the hybrid welding method according to the embodiment will be described below with reference to the drawings. In the comparative examples and the embodiment described below, when the number, amount, etc. are mentioned, the scope of the present invention is not necessarily limited to the number, amount, etc., unless otherwise specified. The same reference numbers are given to the same parts and corresponding parts, and duplicate descriptions may not be repeated. It is intended from the beginning that the configurations in the embodiment will be used in appropriate combination.

[0015] [Combined welding device 1000] A hybrid welding device 1000 according to an embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a vertical cross-sectional view showing the hybrid welding device 1000 in outline, Fig. 2 is a perspective view seen from the pressing surface side of the first pressing shaft 13, and Fig. 3 is a perspective view seen from the pressing surface side of the second pressing shaft 23.

[0016] The hybrid welding apparatus 1000 is an apparatus for joining a plurality of workpieces stacked on top of one another by passing an electric current through the plurality of workpieces to form softened regions in the plurality of workpieces and plastically deforming the softened regions.

[0017] In this embodiment, the multiple workpieces include a first workpiece 1 and a second workpiece 2. The first workpiece 1 and the second workpiece 2 are made of metal such as iron or aluminum. In general, the first workpiece 1 and the second workpiece 2 may be made of different materials or the same type of material. The first workpiece 1 and the second workpiece 2 are formed, for example, in a flat plate shape.

[0018] The hybrid welding device 1000 has a pair of pressure shafts, a first pressure shaft 13 and a second pressure shaft 23. The first pressure shaft 13 and the second pressure shaft 23 are capable of applying pressure to the first workpiece 1 and the second workpiece 2 from both sides in the thickness direction thereof. The first pressure shaft 13 and the second pressure shaft 23 are driven to reciprocate along their axial directions by a drive source (such as a servo press machine) not shown.

[0019] The first pressure applying shaft 13 is a so-called punch type, and includes, on the side facing the second pressure applying shaft 23, a convex portion 13a extending toward the second pressure applying shaft 23. The second pressure applying shaft 23 is a so-called die type, and includes, on the side facing the first pressure applying shaft 13, a concave portion 23a for receiving the convex portion 13a.

[0020] The hybrid welding apparatus 1000 has a first electrode 11 arranged in a ring shape so as to surround the axis of a first pressure shaft 13, and a second electrode 21 arranged opposite the first electrode 11 and arranged in a ring shape so as to surround the axis of a second pressure shaft 23.

[0021] The first electrode 11 has a first replacement electrode 11a and a first body electrode 11b, and the first replacement electrode 11a is provided detachably to the first body electrode 11b and is provided so as to be periodically replaced by a screw-on structure. The second electrode 21 has a second replacement electrode 21a and a second body electrode 21b, and the second replacement electrode 21a is provided detachably to the second body electrode 21b and is provided so as to be periodically replaced by a screw-on structure. The first electrode 11 and the second electrode 21 are preferably made of copper.

[0022] A current application device 50 is connected to the first electrode 11 and the second electrode 21, which applies a current to generate resistance heat below the melting point at the contact point between the first work 1 and the second work 2 while the first pressure application shaft 13 and the second pressure application shaft 23 are holding the first work 1 and the second work 2 together.

[0023] [Combined welding method] A hybrid welding method using hybrid welding apparatus 1000 having the above-mentioned structure will be described with reference to Figures 4 to 8. Figure 4 is a cross-sectional view showing a state in which current is being applied to each workpiece, Figure 5 is a view showing a state in which each workpiece is pressed by a pair of pressing shafts, Figure 6 is a cross-sectional view showing a state in which current is being applied to each workpiece again, Figure 7 is a view showing the relationship between pressing force and time, and Figure 8 is a view showing the relationship between current value and time.

[0024] 4, the first electrode 11 and the second electrode 21 are each moved toward the work (in the direction of the arrow F1 in FIG. 4), and the first work 1 and the second work 2 are sandwiched between the first electrode 11 and the second electrode 21. At this time, since the first electrode 11 and the second electrode 21 each have an annular shape and pressurize and sandwich the first work 1 and the second work 2, the first work 1 and the second work 2 do not move even in the crimping process described below. As a result, even when this hybrid welding device 1000 is mounted on a robot hand, for example, the fixation of the work to be processed can be stably performed.

[0025] Next, using the current application device 50, a low current is applied to the first electrode 11 and the second electrode 21 so that the temperature is below the melting points of the first workpiece 1 and the second workpiece 2 (first current application). This makes it possible to soften the area indicated by A in Fig. 4. Although the current value differs depending on the plate thickness and material of the first workpiece 1 and the second workpiece 2, a current of about 1.0 kA to 6.0 kA is applied for about 0.05 to 0.3 seconds.

[0026] Referring to Figure 5, while the first workpiece 1 and the second workpiece 2 are sandwiched between the first electrode 11 and the second electrode 21, the first pressure shaft 13 and the second pressure shaft 23 are moved toward the works (in the direction of arrow F2 in Figure 5) to sandwich the first workpiece 1 and the second workpiece 2 between the first pressure shaft 13 and the second pressure shaft 23, and pressure is applied so that the convex portion 13a of the first pressure shaft 13 fits into the concave portion 23a of the second pressure shaft 23, thereby forming a crimping area R1 between the first workpiece 1 and the second workpiece 2.

[0027] 6, with the first workpiece 1 and the second workpiece 2 sandwiched between the first electrode 11 and the second electrode 21, a current higher than a low current is applied to the first electrode and the second electrode using the current application device 50 to apply a current for providing a molten joint in the first workpiece 1 and the second workpiece 2 (second current application). The current value differs depending on the plate thickness and material of the first workpiece 1 and the second workpiece 2, but a current of about 6.0 kA to 20 kA is applied for about 0.1 to 0.3 seconds.

[0028] Here, FIG. 7 shows the relationship between the pressure applied to the first workpiece 1 and the second workpiece 2 by the first pressure shaft 13 and the second pressure shaft 23 and time, and FIG. 8 shows the relationship between the current value and time in the first current supply and the second current supply.

[0029] As shown in Fig. 7, the inclined portion P1 is provided to secure the current path while the material is softened by the first current, and to perform the main pressurization after the first current has softened the material appropriately locally. If the pressing force is increased all at once from the beginning, the entire workpiece may deform (it will no longer be localized), and the load on the pressing shaft will increase due to the resistance of the unsoftened material. In addition, if the first current is applied without securing the current path, the material cannot be softened to an appropriate extent, so the pressurization and the first current are applied in parallel.

[0030] The inclined portion P2 in the first current application in Fig. 8 is provided to improve the contact between the electrode and the workpiece. If the electrode is in an unstable contact state, a sudden increase in current will prevent stable current application. Therefore, the inclined portion P2 is set to soften the material while pushing in the electrode, so that the main current application can begin in a stable contact state.

[0031] On the other hand, in the eighth second energization, a rest period during which no energization is performed is provided between the first energization and the second energization in order to perform the second energization after the crimping is formed. The magnitude of the current is second energization > first energization.

[0032] The crimping region R1 will be described with reference to Fig. 9 to Fig. 14. Fig. 9 is a cross-sectional view showing the final joined state of the workpieces, Fig. 10 is a cross-sectional view showing the fusion-joined state when the first workpiece 1 and the second workpiece 2 are made of different materials, Fig. 11 is a cross-sectional view showing the fusion-joined state when the first workpiece 1 and the second workpiece 2 are made of the same material, Fig. 12 is a cross-sectional view showing the fusion-joined portion of the workpieces, Fig. 13 is a cross-sectional view showing different tip surface shapes of the protruding portion 13a of the first pressure shaft 13, and Fig. 14 is a cross-sectional view showing different fusion-joined portions of the workpieces.

[0033] As shown in FIG. 9, according to the hybrid welding method using this hybrid welding apparatus 1000, the first workpiece 1 and the second workpiece 2 are softened by the first current flow, making it possible to form an interlock region IL in which the first workpiece 1 is pressed into the second workpiece 2.

[0034] Furthermore, the second current flow forms a molten bond between the first workpiece 1 and the second workpiece 2. As shown in Fig. 10, if the first workpiece 1 and the second workpiece 2 are made of different materials, a thin IMC (intermetallic compound) region W1 is formed on the joint surface between the first workpiece 1 and the second workpiece 2. As shown in Fig. 11, if the first workpiece 1 and the second workpiece 2 are made of the same material, a nugget region W2 is formed between the first workpiece 1 and the second workpiece 2.

[0035] In addition, the tip portion 13s of the protrusion 13a of the first pressure shaft 13 in this embodiment has a flat shape. As a result, the current flows concentratedly in the corner region of the tip portion 13t, and as shown in Fig. 12, a thick fusion joint portion D1 is likely to be formed in the region of the first work 1 that protrudes annularly toward the second work 2 side.

[0036] On the other hand, as shown in FIG. 13, when the tip portion 13s of the convex portion 13a of the first pressure shaft 13 has a curved shape, current tends to flow through the curved region, and as shown in FIG. 14, a thick molten bond area D2 tends to be formed in the central region of the first work 1 and the second work 2.

[0037] As described above, the hybrid welding apparatus 1000 of the present disclosure corresponds to a hot plastic processing method using the resistance heating of the second workpiece 2 by the first current flow, and therefore can join the first workpiece 1 with a lower pressure than the existing mechanical clinching. For example, in the cold plastic processing method, the first pressure shaft 13 and the second pressure shaft 23 require about 50 to 95 kN to drive, depending on the material, but in the present disclosure, it is possible to form the interlock region IL with a drive of 30 kN.

[0038] Furthermore, the hybrid welding device 1000 of the present disclosure can be mounted on a robot hand with a payload of 210 kg or less. This allows the range of application to be expanded to actual production lines for automobiles, etc. Furthermore, in addition to being able to locally soften the material by resistance heating, the electrode itself acts as a clamp, eliminating the need for a separate plate clamp.

[0039] Furthermore, since this method is also considered a thermoplastic processing method as described above, it can be applied not only to joining dissimilar materials such as aluminum and iron, but also to joining high-strength homogeneous materials and joining die-cast materials.

[0040] Furthermore, since the first electrode 11 and the second electrode 21 are arranged separately from the first pressure shaft 13 and the second pressure shaft 23, the durability of the electrodes is improved. In the case of normal resistance spot welding, the maximum pressure is about 5 to 10 kN, but in the case of the composite welding apparatus 1000 disclosed herein, the workpiece can be clamped with a higher pressure than normal resistance spot welding, so electrode deformation, which occurs in mechanical clinching methods using a resistance spot welding apparatus, does not occur, and crimping joining can be achieved in a short period of time.

[0041] Thus, the hybrid welding apparatus and hybrid welding method disclosed herein have a simple configuration, which allows the apparatus to be made smaller and makes it easier to apply to an actual production line.

[0042] Furthermore, the second current causes a molten bond to be formed between the first workpiece 1 and the second workpiece 2. As a result, a double bond of a swage and a molten part can be achieved, and the double bond makes it possible to improve the bond strength and fatigue strength more than conventional mechanical clinching and resistance spot welding.

[0043] It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is indicated by the claims, not by the description of the embodiments above, and further includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0044] 1 first workpiece, 2 second workpiece, 11 first electrode, 11a first replacement electrode, 11b first main electrode, 13 first pressure shaft, 13a convex portion, 21 second electrode, 21a second replacement electrode, 21b second main electrode, 23 second pressure shaft, 23a concave portion, 50 current application device, 1000 composite welding device.

Claims

1. 1. A hybrid welding apparatus that joins a first workpiece made of a metal and a second workpiece made of a metal to each other by applying pressure to both sides of the first workpiece and the second workpiece in a thickness direction and passing a current through the first workpiece and the second workpiece, a pair of first and second pressurizing shafts capable of applying pressure to the first and second workpieces from both sides in a thickness direction of the first and second workpieces; A first electrode disposed annularly so as to surround the first pressure shaft; a second electrode disposed opposite the first electrode and annularly disposed around the second pressurizing shaft; a current application device for applying a low current to the first and second electrodes in a state in which the first and second workpieces are sandwiched between the first and second electrodes so that the current is equal to or lower than the melting points of the first and second workpieces, and then applying pressure to the first and second workpieces from both sides in a thickness direction thereof using the first and second pressure shafts, and then applying a current higher than the low current to the first and second electrodes in a state in which the first and second workpieces are sandwiched between the first and second electrodes to pass a current for providing a molten joint between the first and second workpieces; Equipped with the first pressure applying shaft includes a protrusion extending toward the second pressure applying shaft on a side facing the second pressure applying shaft, The second pressure applying shaft includes a recess for receiving the protrusion on a side facing the first pressure applying shaft. Complex welding equipment.

2. The first electrode and the second electrode are made of at least one material selected from copper, a copper alloy, tungsten, and molybdenum. The hybrid welding apparatus of claim 1 .

3. A hybrid welding method using the hybrid welding apparatus according to claim 1 or 2, a step of sandwiching the first workpiece and the second workpiece between the first electrode and the second electrode; a step of applying a low current to the first electrode and the second electrode using the current application device so that the first workpiece and the second workpiece are at or below the melting points of the first workpiece and the second workpiece, thereby softening the first workpiece and the second workpiece; a step of sandwiching the first workpiece and the second workpiece with the first pressure shaft and the second pressure shaft while the first workpiece and the second workpiece are sandwiched between the first electrode and the second electrode, and applying pressure so that the convex portion of the first pressure shaft fits into the concave portion of the second pressure shaft, thereby forming a crimped region between the first workpiece and the second workpiece; a step of applying a current higher than the low current to the first electrode and the second electrode using the current application device while the first workpiece and the second workpiece are sandwiched between the first electrode and the second electrode to apply a current for providing a molten joint to the first workpiece and the second workpiece; A composite welding method comprising:

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