阅读说明：本技术 接合构件的制造方法 (Method for manufacturing joining member ) 是由 安田圭吾 于 2021-03-26 设计创作，主要内容包括：本公开涉及一种通过进行电阻焊接来制造接合构件的制造方法,在该制造方法中,在工件中的与电极接触的表面上形成有镀层。在第1电极接触第1板材中的第1区域且第2电极接触第2板材中的第2区域的状态下,开始使第1电极与第2电极之间通电,并形成熔核,其中,第1区域沿循第1电极的顶端部的形状而呈曲面状,第2区域沿循第2电极的顶端部的形状而呈曲面状。(The present disclosure relates to a manufacturing method of manufacturing a joined member by performing resistance welding, in which a plating layer is formed on a surface of a workpiece that is in contact with an electrode. In a state where the 1 st electrode is in contact with the 1 st region of the 1 st plate material and the 2 nd electrode is in contact with the 2 nd region of the 2 nd plate material, the 1 st region is curved along the shape of the tip of the 1 st electrode and the 2 nd region is curved along the shape of the tip of the 2 nd electrode, energization between the 1 st electrode and the 2 nd electrode is started to form nuggets.)

1. A method of manufacturing a joined member, which is manufactured by sandwiching a workpiece including a plurality of stacked plate materials with a 1 st electrode and a 2 nd electrode and by resistance welding the workpiece, characterized in that,

a 1 st plate material of the work in contact with the 1 st electrode is formed with a plating layer on a surface in contact with the 1 st electrode, and a 2 nd plate material of the work in contact with the 2 nd electrode is formed with a plating layer on a surface in contact with the 2 nd electrode,

the manufacturing method of the joint member includes the steps of: and starting to form a nugget by passing current between the 1 st electrode and the 2 nd electrode in a state where the 1 st electrode contacts a 1 st region of the 1 st plate material and the 2 nd electrode contacts a 2 nd region of the 2 nd plate material, wherein the 1 st region is curved along a shape of a tip portion of the 1 st electrode, and the 2 nd region is curved along a shape of the tip portion of the 2 nd electrode.

2. The method of manufacturing a joint member according to claim 1,

also comprises the following steps: before starting to electrify the 1 st electrode and the 2 nd electrode, the 1 st region in a curved shape is formed on the 1 st plate material, and the 2 nd region in a curved shape is formed on the 2 nd plate material.

3. The method of manufacturing a joint member according to claim 2,

the step of forming the 1 st region in a curved shape on the 1 st plate material and forming the 2 nd region in a curved shape on the 2 nd plate material includes: the workpiece is clamped by a pair of clamping components and is pressurized.

4. The method of manufacturing a joint member according to claim 3,

the pair of clamping components are the 1 st electrode and the 2 nd electrode.

5. The method of manufacturing a joining member according to claim 3 or 4,

by sandwiching and pressing the workpiece by the pair of nip members, a gap having a size of 20% or more of the thickness of the 1 st plate material is formed between the 1 st plate material and the 2 nd plate material around the pressed portion.

6. The method of manufacturing a joining member according to any one of claims 1 to 5,

the coating is an aluminum-containing layer.

7. The method of manufacturing a joining member according to any one of claims 1 to 6,

the plurality of plate materials constituting the workpiece are plate materials before the quenching step.

Technical Field

The present disclosure relates to a technique for welding a plate material having a surface subjected to plating treatment.

Background

Resistance welding has been conventionally used for joining metal steel plates. When joining plate materials, such as hot-stamped metal, which have been plated on their surfaces by resistance welding, the plated metal tends to adhere to the electrodes during welding. Therefore, when welding is continuously performed using the electrode, the amount of adhesion of the plating metal to the electrode increases as the number of times of welding (hereinafter, also referred to as the number of hits) increases, and a welding failure is likely to occur. In japanese patent application laid-open No. 2013-35045, the adhesion of the plating metal is suppressed by softening the plating layer by passing an initial current smaller than the welding current.

Disclosure of Invention

In the technique disclosed in japanese patent application laid-open No. 2013-35045, although the plating layer can be softened by the initial current, the plating layer between the electrode and the welding material cannot be completely eliminated, and therefore, there is a possibility that the adhesion of the plating metal to the electrode cannot be sufficiently suppressed. In this case, the number of dots cannot be sufficiently ensured.

One aspect of the present disclosure preferably proposes a technique capable of achieving an extension in the life of an electrode.

One aspect of the present disclosure is a method of manufacturing a joined member, which sandwiches a workpiece including a plurality of stacked plate materials with a 1 st electrode and a 2 nd electrode, and manufactures the joined member by resistance welding the workpiece. In the manufacturing method, a 1 st plate material in the work in contact with a 1 st electrode is formed with a plating layer on a surface in contact with the 1 st electrode, and a 2 nd plate material in the work in contact with a 2 nd electrode is formed with a plating layer on a surface in contact with the 2 nd electrode. The manufacturing method of the joint member includes the steps of: in a state where the 1 st electrode is in contact with the 1 st region of the 1 st plate material and the 2 nd electrode is in contact with the 2 nd region of the 2 nd plate material, the 1 st region is curved along the shape of the tip of the 1 st electrode and the 2 nd region is curved along the shape of the tip of the 2 nd electrode, energization between the 1 st electrode and the 2 nd electrode is started to form nuggets.

According to the above manufacturing method, since the 1 st region and the 2 nd region of the plate material have shapes that follow the tip portions of the 1 st electrode and the 2 nd electrode (hereinafter, the 1 st electrode and the 2 nd electrode are simply referred to as electrodes), the electrode tip portions are easily brought into contact with the plate material, and the contact area increases. Therefore, since the electrode tip portions are easily brought into contact with the plate material, even if the plated metal adheres to the electrodes, the contact area between the electrodes and the plate material is not easily reduced. Further, since the contact area between the electrode and the workpiece is large from the beginning, even if a partial decrease or increase in the contact area occurs due to the adhesion of the plating metal to the electrode, the rate of change of the contact area as a whole is small. For this reason, even when welding is repeated, the resistance value between the electrode and the workpiece is not easily changed, and therefore, for example, when the current is constant, the voltage is not easily changed, and as a result, the change in the amount of heat generation can be suppressed. Therefore, the welding defects that occur when the number of dotting increases can be suppressed, and the electrode life can be extended. In addition, the contact between the electrode and the workpiece described herein includes a case where the electrode and the workpiece are contacted via the plating metal adhered to the tip end portion of the electrode.

In the above manufacturing method, the following steps may be further included: before starting to electrify the 1 st electrode and the 2 nd electrode, a 1 st region with a curved surface shape is formed on the 1 st plate material, and a 2 nd region with a curved surface shape is formed on the 2 nd plate material. According to the above manufacturing method, the 1 st region and the 2 nd region can be formed in the plate material in which the 1 st region and the 2 nd region are not formed.

In the above manufacturing method, the step of forming the 1 st region of the curved shape in the 1 st plate material and the 2 nd region of the curved shape in the 2 nd plate material may include: the workpiece is clamped by a pair of clamping components and is pressurized. According to the above-described manufacturing method, the 1 st region and the 2 nd region can be reliably formed.

In the above manufacturing method, the pair of compression members may be the 1 st electrode and the 2 nd electrode. In the above manufacturing method, the curved 1 st region and 2 nd region can be formed by pressing the electrode against the workpiece. In addition, the 1 st region and the 2 nd region are each in good contact with the electrode tip portion, and the welding state can be further highly stabilized.

In the above manufacturing method, a gap having a size of 20% or more of the thickness of the 1 st plate material and a size of the 2 nd plate material may be formed between the 1 st plate material and the 2 nd plate material around the pressing portion by sandwiching and pressing the workpiece by the pair of nip members. According to the above manufacturing method, the electrode tip portion and the workpiece can be brought into good contact with each other.

In the above production method, the plating layer may be an aluminum-containing layer. Since aluminum is easily alloyed, if an aluminum-based material is contained in the plating layer, the plating metal is easily adhered to the electrode at the time of welding, and the life of the electrode is easily shortened. However, according to the above-described manufacturing method, adverse effects caused by adhesion of the plating metal to the electrode can be suppressed, and therefore, the life of the electrode can be extended even if the plating layer contains aluminum.

In the above-described manufacturing method, the plurality of plate materials constituting the workpiece may be plate materials before the quenching step. Since the workpiece which has not undergone the quenching step does not have an oxide film formed thereon, the plating metal is likely to adhere to the electrode, and the life of the electrode is likely to be shortened. However, according to the above-described manufacturing method, even when the plate material is welded before the quenching step, the life of the electrode can be extended.

Drawings

Fig. 1 is a schematic explanatory view of a workpiece and a welding apparatus of the embodiment.

FIGS. 2A to 2D are views for explaining a welding process, in which FIG. 2A is a view before pressurization by the 1 st electrode and the 2 nd electrode; FIG. 2B is a view showing after pressurization; FIG. 2C is a diagram showing the 1 st and 2 nd electrodes after energization; fig. 2D is a view showing the 1 st and 2 nd electrodes after leaving the workpiece.

FIGS. 3A-3D are diagrams illustrating a welding process performed after FIGS. 2A-2D, wherein FIG. 3A is a diagram showing the electrode 1 and the electrode 2 before pressurization; FIG. 3B is a view showing after pressurization; FIG. 3C is a diagram showing the 1 st and 2 nd electrodes after energization; fig. 3D is a view showing the 1 st and 2 nd electrodes after leaving the workpiece.

FIGS. 4A to 4D are views for explaining a conventional welding process, wherein FIG. 4A is a view showing the 1 st electrode and the 2 nd electrode when current is applied; FIG. 4B is a diagram showing the 1 st and 2 nd electrodes as they exit the workpiece; fig. 4C is a diagram showing when power is supplied again;

fig. 4D is a diagram showing the electrode being off the workpiece after fig. 4C.

Fig. 5 is a diagram showing a workpiece according to a modification.

Fig. 6 is a diagram showing a workpiece according to a modification.

Detailed Description

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings.

[1. embodiment ]

[1-1. workpiece and welding apparatus ]

Fig. 1 shows a workpiece 10 and a welding device 20. The workpiece 10 includes a plurality of sheet materials stacked. In the present embodiment, the workpiece 10 includes two overlapped plate materials, i.e., the 1 st plate material 11 and the 2 nd plate material 12. The welding apparatus 20 joins the 1 st plate 11 and the 2 nd plate 12 by resistance spot welding using the 1 st electrode 21 and the 2 nd electrode 22, which will be described later, to manufacture a joined member. Hereinafter, when the 1 st electrode 21 and the 2 nd electrode 22 are referred to without distinction, or when both the 1 st electrode 21 and the 2 nd electrode 22 are referred to, they are also simply referred to as electrodes. In addition, in the drawings used in the following description, an end face of the workpiece 10 after being cut at a portion abutting on the electrode is schematically shown.

< workpiece >

The 1 st plate 11 has a 1 st body 11a, a 1 st outer plating layer 11b, and a 1 st inner plating layer 11 c. The 1 st body 11a is a main part of the 1 st plate 11, and is in a plate-like shape. The 1 st outer plating layer 11b is formed on one surface of the 1 st body 11a, and has a surface capable of contacting the 1 st electrode 21. The one surface is a surface on the other side of the two main surfaces of the 1 st plate material 11 opposite to the side on which the 2 nd plate material 12 is arranged. The 1 st inner plating layer 11c is formed on the other surface of the 1 st body 11a opposite to the one surface.

The 2 nd plate material 12 has a 2 nd main body 12a, a 2 nd outer plating layer 12b, and a 2 nd inner plating layer 12 c. The 2 nd body 12a is a main part of the 2 nd plate 12, and is in a plate-like shape. The 2 nd outer plating layer 12b is formed on one surface of the 2 nd body 12a, and has a surface capable of contacting the 2 nd electrode 22. The one surface is a surface on the other side of the two surfaces of the 2 nd plate material 12 opposite to the side on which the 1 st plate material 11 is disposed. That is, when the 1 st plate 11 and the 2 nd plate 12 stacked in the work 10 are regarded as one plate, the 1 st outer plating layer 11b is formed on one surface of the plate, and the 2 nd outer plating layer 12b is formed on the other surface. The 2 nd inner plating layer 12c is formed on the surface of the 2 nd main body 12a opposite to the surface on which the 2 nd outer plating layer 12b is formed.

The 1 st plate material 11 and the 2 nd plate material 12 are assumed to be steel sheets subjected to a process called hot stamping (hot pressing), for example, on plated steel sheets. The plating layer is formed to impart rust-proofing function to the material. Specific materials such as metals for forming the plating layer are not particularly limited. The plating layer may be formed of, for example, aluminum, zinc, or the like. In the present embodiment, the plating layer is formed of aluminum. The aluminum plating layer has excellent heat resistance, crack resistance, hardenability, and the like. The plating layer formed of aluminum may be added with other elements to improve the performance. On the other hand, aluminum is easily alloyed with a metal such as copper constituting an electrode. Further, the zinc plating may be, for example, pure zinc plating or zinc alloy plating.

In addition, the steel sheet may be subjected to a quenching process to improve the strength thereof. For example, quenching may be performed after hot stamping. In the present embodiment, welding of a workpiece 10 made of a plurality of plate materials before the quenching step is performed is exemplified. Of course, the workpiece 10 may be formed of a plurality of steel sheets having undergone the quenching step.

< soldering apparatus >

The welding device 20 includes a 1 st electrode 21 and a 2 nd electrode 22, and the 1 st electrode 21 and the 2 nd electrode 22 sandwich the workpiece 10 from the thickness direction of the workpiece 10. The welding device 20 further includes a welding control unit 23, and the welding control unit 23 controls the pressurizing force and the amount of current applied to the workpiece 10 via the electrodes. The thickness direction means a stacking direction and a stacking direction of the 1 st plate member 11 and the 2 nd plate member 12.

The 1 st electrode 21 and the 2 nd electrode 22 are disposed on a welding torch, not shown, with their tips facing each other. In the present embodiment, the 1 st electrode 21 is fixed to a welding gun. The 2 nd electrode 22 is provided on the torch so as to be capable of advancing and retreating in the axial direction thereof with respect to the 1 st electrode 21. That is, the workpiece 10 is sandwiched between the 1 st electrode 21 and the 2 nd electrode 22 and pressurized by the operation of the 2 nd electrode 22. As described above, the workpiece 10 may be pressed only by the movement of one electrode, or the workpiece 10 may be pressed by the movement of two electrodes.

The 1 st electrode 21 and the 2 nd electrode 22 are made of a material having good electrical conductivity. Examples of the material include, but are not limited to, copper or a copper alloy. The 1 st electrode 21 and the 2 nd electrode 22 have curved surfaces at their tips.

The welding control unit 23 includes a drive control unit 31, a current control unit 32, and the like. The drive control unit 31 is configured to control the forward and backward drive control of the 2 nd electrode 22 so as to control the pressurizing force applied to the workpiece 10 from the 1 st electrode 21 and the 2 nd electrode 22. The current control unit 32 is configured to control the currents supplied to the 1 st electrode 21 and the 2 nd electrode 22.

[1-2. welding Process ]

Fig. 2A shows a state in which the 1 st electrode 21 and the 2 nd electrode 22 sandwich the workpiece 10. At this time, no pressing force is applied to the workpiece 10 to deform the plate material. In addition, the electrodes are also not energized.

Fig. 2B is a step subsequent to fig. 2A. Here, the drive control unit 31 applies a predetermined pressure to the 2 nd electrode 22 to operate the 2 nd electrode 22, thereby pressurizing the workpiece 10. Here, the pressing force applied to the workpiece 10 is sufficiently larger than the pressing force used in the conventional method, that is, a general pressing force applied while the current is applied. As described above, the pressing is performed with a large pressing force, and a large gap is generated between the plate materials even when the power is not supplied. As a result, the peripheries of the pressed portions of the 1 st plate member 11 and the 2 nd plate member 12 are deformed to bulge outward, and at the same time, a gap 41 is formed between the 1 st plate member 11 and the 2 nd plate member 12.

By performing the press deformation as described above, the 1 st region 51 in a curved shape is formed at the portion on the 1 st outer plating layer 11b side in the 1 st plate material 11, and the 2 nd region 52 in a curved shape is formed at the portion on the 2 nd outer plating layer 12b side in the 2 nd plate material 12. The 1 st region 51 has a concavely curved surface shape following the shape of the distal end portion 21a of the 1 st electrode 21. The 2 nd region 52 has a concavely curved surface shape following the shape of the distal end portion 22a of the 2 nd electrode 22. The 1 st region 51 and the 2 nd region 52 are not formed only by plating, but are formed by deforming the 1 st body 11a and the 2 nd body 12a, which are main portions of the plate material.

When the pressurization is performed as shown in fig. 2B, the energization is not performed yet. That is, the 1 st region 51 and the 2 nd region 52 are formed before the start of the energization between the 1 st electrode 21 and the 2 nd electrode 22.

Fig. 2C is a step subsequent to fig. 2B. Here, the nuggets 61 are formed by passing current between the 1 st electrode 21 and the 2 nd electrode 22. More specifically, in a state where the 1 st electrode 21 is in contact with the 1 st region 51 and the 2 nd electrode 22 is in contact with the 2 nd region 52, the 1 st electrode 21 and the 2 nd electrode 22 start to be energized, and the nugget 61 is formed. In the above manner, the joining member joining the 1 st plate material 11 and the 2 nd plate material 12 together by resistance spot welding was manufactured.

The 1 st region 51 and the 2 nd region 52 have a curved surface shape along the electrode tip portion. Therefore, the contact area between the electrode and the plate is larger than that when the portion in contact with the electrode is planar. If the contact area is large, the resistance value at the time of energization becomes small, and therefore, the amount of current necessary for obtaining the heat quantity for welding becomes large as compared with the case of welding a plate material in which the portion contacting the electrode is flat.

Fig. 2D is a diagram showing a state of the electrode after welding. The adherends 62 that adhere due to melting of the plating layer adhere to the surfaces of the distal end portion 21a and the distal end portion 22 a. The adherent 62 may contain a metal constituting the plating layer, and an alloy of the metal and the metal of the tip portion of the electrode. The adhesive 62 is adhered to a wide range of the distal end portion 21a and the distal end portion 21 b. This is because the distal end portion 21a widely contacts the 1 st region 51 and the distal end portion 22a widely contacts the 2 nd region 52 when current is applied.

Fig. 3A to 3D are diagrams illustrating a next welding process performed using the electrodes welded in fig. 2A to 2D.

Fig. 3A shows a state in which the 1 st electrode 21 and the 2 nd electrode 22 sandwich the workpiece 10, similarly to fig. 2A. Since the adhesive 62 adheres to the distal end portion 21a and the distal end portion 22a, the workpiece 10 and the electrode contact each other through the adhesive 62.

Fig. 3B shows a state in which the drive control unit 31 applies a predetermined pressure to the 2 nd electrode 22 and operates the 2 nd electrode 22 to pressurize the workpiece 10, as in fig. 2B. The workpiece 10 is deformed in the same manner as in the case illustrated in fig. 2B, and the 1 st region 51 and the 2 nd region 52 having concave curved surfaces are formed. The 1 st region 51 is in good contact with the 1 st electrode 21 via the sticker 62. In addition, the 2 nd region 52 is in good contact with the 2 nd electrode 22 via the adherent 62. As described above, the workpiece 10 is deformed by the pressing and then energized, thereby forming the nugget 61 shown in fig. 3C.

As shown in fig. 3C, although the adhesive 62 is interposed, the 1 st electrode 21 and the 2 nd electrode 22 are in contact with the 1 st plate 11 and the 2 nd plate 12 over a wide range. Therefore, since the conduction resistance does not change much compared to the previous welding shown in fig. 2C, and the change in the amount of heat generation is suppressed, the nugget 61 suitable for welding can be formed similarly to the previous welding. The above-described effect can be achieved even in a state where the adherend 62 is widely adhered to the entire tip end portion of the electrode as shown in fig. 2D and fig. 3A to 3C. Even if the adhesive 62 adheres only to a part of the electrode tip portion, the 1 st region 51 and the 2 nd region 52 of the workpiece 10 are curved along the shape of the tip portion, and therefore contribute to the contact between the electrode and the plate material. As a result, the entire contact area is large, and variation in resistance value is suppressed, so that welding can be completed satisfactorily.

Fig. 3D is a diagram showing a state of the electrode after the second welding. On the surfaces of the distal end portion 21a and the distal end portion 22a, an adherend 63 newly adhered by melting of the plating layer adheres to the adherend 62. The sticker 63 and stickers that adhere later with an increase in the number of hits are finally widely adhered to the surfaces of the tip portion 21a and the tip portion 22 a. Therefore, the 1 st region 51 and the 2 nd region 52 of the workpiece 10 are curved along the shape of the tip portion, thereby suppressing the change in the resistance value.

< summary of welding Process according to Prior Art >

For reference, a process of performing welding using the related art will be briefly described. As shown in fig. 4A, if welding is performed without applying a large pressing force to the workpiece by the electrode, a nugget 61 is formed, and further, as shown in fig. 4B, an adherent 71 adheres to the electrode tip portion. The adhesive 71 is formed intensively in the center of the tip end portion of the electrode. This is the same as the case where a gap is generated between the plate materials by applying a pressing force to the workpiece and applying an electric current. If the next welding is performed in the state shown in fig. 4B, the adherend 71 easily contacts the work as shown in fig. 4C. As a result, as shown in fig. 4D, the adherend 72 is formed so as to cover the adherend 71, in other words, the adherend 72 is formed over a wider range than the adherend 71. If the adherent is increased in the above manner, the contact area between the electrode and the workpiece gradually changes. Since the resistance value changes, the amount of heat generation gradually changes, and insufficient or excessive heating of the welding occurs, thereby impairing the stability of the welding. For the above reasons, the conventional electrode has a short life. In the configuration of the present embodiment, however, since the change in the contact area is suppressed, the frequency of required maintenance is reduced compared to the conventional one, and the life of the electrode is extended.

[1-3. Effect ]

According to the embodiments described in detail above, the following effects can be obtained.

(1a) According to the manufacturing method of the present embodiment, it is possible to suppress a welding failure occurring when the number of dotting increases, and to extend the life of the electrode. The reason for this is as follows. The 1 st region 51 and the 2 nd region 52 of the workpiece 10 have a shape following the electrode tip portion, and therefore have the following characteristics: (i) the electrode tip portion is likely to contact the plate material, and (ii) the contact area between the electrode tip portion and the plate material is increased. In the above (i), particularly in the case where the adherend 62 is widely adhered to the electrode tip portion as in the present embodiment, the electrode can widely contact the 1 st region 51 or the 2 nd region 52 of the plate material via the adherend 62. Further, if the electrode tip portion is likely to contact the plate material, the variation in the contact area is small, and since the contact area is large as described in (ii), the rate of change is small even if the contact area varies. That is, even if welding is repeated, the resistance value between the electrode and the workpiece 10 is not easily changed, and thus a change in the amount of heat generation can be suppressed. As a result, even if the same electrode is used, excellent resistance welding can be achieved, and the life of the electrode can be extended.

In addition, the contact between the electrode and the workpiece 10 (i.e., the electrode and the plate material, or the electrode and the 1 st region 51 and the electrode and the 2 nd region 52) includes the case where the electrode and the workpiece 10 are in contact via the plating metal adhered to the tip end portion of the electrode.

The size of the gap 41 (the size in the thickness direction of the workpiece 10) which can provide a particularly excellent effect is related to the thickness of the plate material. For example, when the size of the gap 41 is 20% or more of the thickness of the 1 st plate 11, a good effect is exerted on the 1 st electrode 21, and when it is 30% or more, a particularly excellent effect is exerted. The same applies to the 2 nd plate 12. When the thicknesses of the 1 st plate member 11 and the 2 nd plate member 12 are different, the effects may be different depending on the plate thicknesses of the plate members.

(1b) According to the manufacturing method of the present embodiment, the curved 1 st region 51 and 2 nd region 52 can be formed by pressing the electrode against the workpiece 10. In addition, in this manufacturing method, the 1 st region 51 and the 2 nd region 52 are each in good contact with the tip end of the electrode, whereby the welding state can be further highly stabilized. That is, the life of the electrode can be further extended.

(1c) In the manufacturing method of the present embodiment, even if the plating layer is aluminum, which is easily alloyed with the electrode, welding can be performed while suppressing the influence of the adhesion of the alloy on the resistance value, and therefore, the life of the electrode can be extended.

(1d) Since the workpiece which has not undergone the quenching step does not have an oxide film formed thereon, the plating metal is likely to adhere to the electrode, and the life of the electrode is likely to be shortened. However, according to the manufacturing method of the present embodiment, even when the plate material is welded before the quenching step is performed, the life of the electrode can be extended.

[2 ] other embodiments ]

The embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above embodiments, and various embodiments can be adopted within the technical scope of the present disclosure.

(2a) In the above embodiment, the method of forming the 1 st region 51 and the 2 nd region 52 by operating at least one of the 1 st electrode 21 and the 2 nd electrode 22 to pressurize the workpiece 10 has been exemplified. However, the method of forming the curved surface shape along the electrode tip portion is not limited to the method of applying pressure with the electrode.

For example, as shown in fig. 5, the 1 st and 2 nd plate materials 11 and 12 may be deformed in advance by sandwiching and pressing the 1 st and 2 nd plate materials 11 and 12 with a pair of rams 81 and 82 using a press or the like, thereby forming the 1 st and 2 nd regions 151 and 152. In this case, it is not necessary to apply pressure using an electrode to deform the plate material. When the electrode is moved to the 1 st region 151 and the 2 nd region 152 for welding, the 1 st region 151 and the 2 nd region 152 having the concave curved surfaces guide the electrode tip portions. Therefore, welding can be performed at a desired position. In addition, the 1 st and 2 nd electrodes 21 and 22, and the pair of indenters 81 and 82 are each an example of a pair of pinching members.

As shown in fig. 6, a recess may be formed in the 1 st plate member 11 and the 2 nd plate member 12 in advance to form the 1 st region 251 and the 2 nd region 252. The 1 st region 251 and the 2 nd region 252 may have a concave curved surface along the electrode tip portion. In this case as well, as in fig. 5, it is not necessary to apply pressure by an electrode to deform the plate material, and the tip end portion can be guided to the welding position.

(2b) In the above embodiment, the configuration in which the distal end portion 21a of the 1 st electrode 21 and the distal end portion 22a of the 2 nd electrode 22 have curved shapes is exemplified. However, the shape of the distal end portion is not particularly limited. Further, if the central portion of the abutting portion with the plate material in the tip end portion is the most protruded portion, and the protrusion amount is gradually reduced toward the periphery, the contact area can be appropriately increased, and the decrease in the resistance value can be sufficiently suppressed. The shape may be, for example, a curved surface shape as shown in fig. 1 or the like, or a conical shape, a truncated cone shape, or the like.

(2c) In the above embodiment, the configuration in which the 1 st region 51 and the 2 nd region 52 having a curved surface shape are formed by pressing is exemplified. That is, the following configuration is exemplified: the shape of the 1 st region 51 follows the shape of the tip portion 21a of the 1 st electrode 21 with high accuracy, and the shape of the 2 nd region 52 follows the shape of the tip portion 22a of the 2 nd electrode 22 with high accuracy. However, the shape of the 1 st region and the 2 nd region does not have to strictly follow the electrode tip portion. For example, a recess portion surrounding the electrode tip portion may be formed at least at a stage before the start of energization. According to the above configuration, the contact area can be increased as compared with a case where the plate material of the contact electrode is planar at a stage before the energization. The 1 st region and the 2 nd region may have a concave shape that can increase a contact area, for example, at a stage before the current is applied.

(2d) The plurality of functions of one constituent element in the above-described embodiments may be realized by a plurality of constituent elements, or one function of one constituent element may be realized by a plurality of constituent elements. Further, a plurality of functions possessed by a plurality of constituent elements may be realized by one constituent element, or one function realized by a plurality of constituent elements may be realized by one constituent element. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of one of the above-described embodiments may be added to the configuration of the other of the above-described embodiments, and at least a part of the configuration of one of the above-described embodiments may be replaced with the configuration of the other of the above-described embodiments.