JP7382114B2 - Spot welding method - Google Patents

Description

The present invention relates to a spot welding method, and more particularly to a technique for forming a welded portion of good quality on a plate assembly with a high plate thickness ratio by spot welding.

As is well known, spot welding involves applying a high current between two or more metal plates (often steel plates) between a pair of electrodes while applying pressure to the metal plates. This is a joining method in which a welded part (usually called a nugget) of a desired range and size is formed across metal plates by partially melting the metal by resistive heat generation and expanding the melted part.

The specific technology (welding conditions, etc.) for applying this spot welding to a plate assembly of two or three metal plates stacked on top of each other has been established to some extent. On the other hand, when spot welding is performed on a plate assembly made of four or more metal plates stacked together, (expressed as the value divided by the thickness of the thinnest metal plate located at one end in the thickness direction of the plate assembly) is large, it is difficult to form a welded part of good quality that can exhibit the required strength. It was difficult.

Therefore, a method has been proposed for welding plate assemblies with a large plate thickness ratio by appropriately setting the pressurizing force, amount of current (current value), and duration of current during spot welding (for example, Patent Document 1 and (See Patent Document 2).

Japanese Patent Application Publication No. 10-249537 Japanese Patent Application Publication No. 2010-240740

By the way, in this type of spot welding, pressurization is continued until the welded part formed between the electrodes grows beyond the boundary between the metal plate at one end in the thickness direction and the adjacent metal plate on the inside. There is a need. The electrode is usually made of a material (for example, a copper alloy) that has a higher thermal conductivity than a metal plate such as a steel plate to be welded. Further, the electrode is cooled by the cooling liquid flowing inside the electrode when electricity is applied. As a result, the metal plate is cooled by heat transfer from the metal plate at one end in the thickness direction that contacts the electrode to the electrode, and the area from the contact position with the electrode to the predetermined depth of the metal plate at one end in the thickness direction is cooled. A situation arises where the temperature is difficult to rise. Therefore, when the plate thickness ratio of the plate assembly is large, especially when the metal plate at one end in the thickness direction is the thinnest, it is necessary to adjust welding conditions such as the pressure force and the amount of current applied as described in Patent Document 1 etc. However, it was still very difficult to grow the weld to a size that would reach a thin metal plate.

In recent years, in the manufacturing of automobiles, attempts have been made to increase the proportion of high-tensile strength materials (high-tensile strength steel materials) and ultra-high-strength materials (ultra-high strength steel materials) used, with the aim of improving collision safety and fuel efficiency through weight reduction. There is a new need to establish welding technology for plate assemblies that combine mild steel plates (general-purpose steel plates). In addition, in response to the increasing demand for improved operational stability, ride comfort, and vehicle body rigidity for vehicles these days, there is an increasing need for welding for plate assemblies with extremely large plate thickness ratios (for example, 5 or more). . For the above reasons, there is an even stronger need for a new welding technique to replace the conventionally known welding techniques when forming a good quality welded part (nugget) for the above-mentioned type of plate assembly.

In view of the above circumstances, in this specification, it is possible to form a welded part of good quality in a plate assembly with a high plate thickness ratio and a thin metal plate located at least on one end side in the thickness direction. Consider it a technical issue to be solved.

The above problems are achieved by a spot welding method according to the present invention. That is, this welding method is a plate assembly in which a plurality of metal plates are stacked one on top of the other, and a relatively thin metal plate among the plurality of metal plates is arranged at one end or both ends in the thickness direction. In a spot welding method comprising a plate assembly preparation step and a welding process of forming a weld inside the plate assembly by applying pressure and current to the plate assembly with a pair of electrodes, the welding process includes a pair of plate assembly preparation steps. between at least one of the electrodes and a thin metal plate at one end in the thickness direction on the side closer to the one electrode, suppressing heat transfer from the thin metal plate at one end in the thickness direction to the one electrode side. It is characterized by the fact that the plate assembly is pressurized and energized by a pair of electrodes while the heat transfer suppressing plate is provided. Note that the term "thin metal plate" as used herein means a metal plate whose thickness is smaller than the average value of the thickness of all the metal plates constituting the plate assembly. Furthermore, the term "thick-walled metal plate" as used herein means a metal plate whose thickness dimension is larger than the average value of the thickness dimensions of all the metal plates constituting the plate assembly.

As described above, in the spot welding method according to the present invention, in a plate assembly in which a plurality of metal plates are stacked one on top of the other, a relatively thin metal plate among the plurality of metal plates is arranged at one end or both ends in the thickness direction. When a plate assembly is to be welded, between at least one electrode and a thin metal plate at one end in the thickness direction on the side close to this electrode, heat transfer from the thin metal plate to one electrode is suppressed. With the heat transfer suppressing plate disposed, the plate assembly was energized under pressure using a pair of electrodes. By providing the heat transfer suppressing plate in this way, it is possible to suppress or prevent as much as possible the situation in which the heat generated in the thin metal plate on one end side in the thickness direction escapes to one electrode side during pressurization and energization. Therefore, the temperature of the thin metal plate at one end in the thickness direction can be increased more easily than in the past, and melting into the thin metal plate (expansion of the molten part in the thickness direction) can be promoted. Therefore, it is possible to relatively easily form a sufficiently large welded portion spanning all the metal plates including the thin metal plate at one end in the thickness direction. In addition, by interposing the heat transfer suppressing plate between one electrode and the thin metal plate at one end in the thickness direction, the thin metal plate at one end in the thickness direction and the metal located inside this metal plate when pressurized and energized. Since the contact area with the plate can be reduced, it becomes easier to increase the current density between both metal plates. Therefore, this also promotes the growth of the weld, making it possible to relatively easily form a weld of sufficient size spanning all the metal plates.

Further, according to the spot welding method according to the present invention, it is only necessary to arrange a heat transfer suppressing plate between at least one thin metal plate on one end side in the thickness direction and the electrode (one electrode) on the side closer to this metal plate. For example, by using existing welding equipment and welding conditions (pressurizing and energizing conditions, etc.), it is possible to form a welded portion of sufficient size to reach the thin metal plate. Therefore, it is sufficient to substantially increase the cost of preparing the heat transfer suppressing plate, and it is possible to form a welded portion of sufficient size for the plate assembly with a high plate thickness ratio without causing a significant increase in cost. becomes possible.

The spot welding method according to the present invention may further include a removal step of removing the heat transfer suppressing plate from the plate assembly after forming the welded portion on the plate assembly in the welding process.

In this way, by removing the heat transfer suppressing plate from the plate assembly after the welding process, heat transfer can be suppressed regardless of whether the heat transfer suppressing plate is fixed to the thin metal plate at one end in the thickness direction during the welding process. It becomes possible to reliably separate the plate from the thin metal plate and obtain a plate-like component made of a plate assembly having a predetermined structure. Of course, even if the heat transfer suppressing plate is fixed to the thin metal plate, this removal step can be omitted if it does not substantially affect the performance or evaluation of the plate-shaped component. It is.

Furthermore, in the spot welding method according to the present invention, the thickness of the heat transfer suppressing plate may be set to 0.7 mm or less.

As a result of the present inventors verifying the relationship between the thickness dimension of the heat transfer suppressing plate and the size of the welded part (range of penetration), it was found that when the thickness dimension of the heat transfer suppressing plate is 0.8 mm or more, the heat transfer suppressing plate It has been found that there is a possibility that penetration may proceed beyond the boundary between the metal plate and the thin metal plate at one end in the thickness direction and reach the heat transfer suppressing plate. From the above results, by setting the thickness of the heat transfer suppressing plate to less than 0.8 mm, preferably to 0.7 mm or less, it is possible to prevent melting into the heat transfer suppressing plate and ensure a stable and sufficient thickness. This makes it possible to form a welded part with a high degree of accuracy.

As described above, according to the present invention, it is possible to form a welded portion of good quality in a plate assembly with a high plate thickness ratio and in which a thin metal plate is located at least at one end in the thickness direction. . Further, since the above-described welded portion can be formed using existing welding equipment and welding conditions, it is possible to form a welded portion of good quality without causing a significant increase in cost.

1 is a flowchart showing the flow of a spot welding method according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a board assembly prepared in the preparation process shown in FIG. 1. FIG. (a) to (c) are all cross-sectional views for explaining the outline of the welding process according to the present invention. (a) to (c) are all cross-sectional views for explaining the outline of a welding process according to the prior art. FIG. 3 is a cross-sectional view for explaining an overview of a spot welding method according to another embodiment of the present invention. FIG. 3 is a cross-sectional view for explaining an overview of a spot welding method according to another embodiment of the present invention. FIG. 3 is a cross-sectional view for explaining an overview of a spot welding method according to another embodiment of the present invention.

Hereinafter, the details of a spot welding method according to an embodiment of the present invention will be explained based on the drawings.

FIG. 1 is a flowchart showing the flow of a spot welding method according to an embodiment of the present invention. As shown in FIG. 1, the spot welding method according to the present invention includes a preparation step S1 of preparing a plate assembly to be welded, a welding step S2 of performing spot welding on the prepared plate assembly, and a welding step S2 of performing spot welding on the prepared plate assembly. and a removal step S3 of removing the heat transfer suppressing plate from the plate assembly. Each step will be explained in order below.

(S1) Preparation Step In this step S1, a plate assembly to be spot welded is prepared. FIG. 2 shows a cross-sectional view of an example of the plate assembly 1 to be welded. As shown in FIG. 2, this plate assembly 1 is formed by stacking a plurality of metal plates 2 to 5. Among these, the metal plates 2 and 5 located at both ends in the thickness direction of the plate assembly 1 are thinner than the metal plates 3 and 4 located at the center side in the thickness direction of the plate assembly 1, and in this embodiment, Four metal plates 2 to 5 are arranged in the order of first thin metal plate 2, first thick metal plate 3, second thick metal plate 4, and second thin metal plate 5. Here, the thickness relationship between the first thin metal plate 3 and the second thin metal plate 5 is arbitrary as long as it satisfies the above relationship, and in this embodiment, as shown in FIG. The thickness t1 of the thin metal plate 2 is smaller than the thickness t4 of the second thin metal plate 5. That is, the thickness dimension t1 of the first thin metal plate 2 is the smallest among all the metal plates 2 to 5 constituting the plate assembly 1. Further, the thickness relationship between the first thick metal plate 3 and the second thick metal plate 4 is also arbitrary as long as the above-mentioned relationship is satisfied, and in this embodiment, as shown in FIG. The thickness t2 of the first thick metal plate 3 is equal to the thickness t3 of the second thick metal plate 4. In this case, the magnitude relationship of the thickness dimensions of the metal plates 2 to 5 described above is t1<t4<t2=t3. Further, the plate thickness ratio of the plate assembly 1 (here, the total plate thickness T of the plate assembly 1/thickness dimension t1 of the first thin metal plate 2) is 4 or more, or 5 or more.

Further, as each of the thin metal plates 2 and 5, for example, a mild steel plate having a tensile strength of 300 MPa or less can be used, and specifically, a hot-dip galvanized steel plate can be used. Further, as each of the thick metal plates 3 and 4, for example, a high tensile strength steel plate (so-called high tensile strength material) having a tensile strength of 490 MPa or more or an ultra high tensile strength steel plate (so called ultra high tensile strength material) having a tensile strength of 980 MPa or more can be used. In this embodiment, the thick metal plates 3 and 4 are both high-tensile steel plates made of the same material, and specifically, ultra-high-tensile steel plates made of cold-rolled steel plates can be used. Of course, the thin metal plates 2 and 5 may be made of different materials. Similarly, the thick metal plates 3 and 4 may be made of different materials.

By welding, the plate assembly 1 having the above-mentioned configuration becomes a steel plate component as a plate-shaped component constituting the body of an automobile, for example. In that case, each thin metal plate 2, 5 functions as an outer panel or an inner plate panel (side outer panel, side inner panel, floor panel, etc.), and each thick metal plate 3, 4 functions as a skeletal frame (side member , reinforcement, etc.).

(S2) Welding process In the welding process S2, a predetermined welded portion is formed inside the plate assembly 1 by pressurizing and energizing the plate assembly 1 prepared as described above under predetermined conditions. FIG. 3 is a sectional view showing an outline of the welding process S2. As shown in FIG. 3, in this welding step S2, a pair of electrodes 11 and 12 are arranged on both sides of the plate assembly 1 in the thickness direction, and a first thin metal plate located at one end of the plate assembly 1 in the thickness direction is 2 and one electrode 11 of the pair of electrodes 11, 12 closer to the first thin metal plate 2, a heat transfer suppressing plate 13 is disposed. The heat transfer suppressing plate 13 is made of a material having a lower thermal conductivity than each of the electrodes 11 and 12, for example, and is made of the same material as each of the metal plates 2 to 5, such as a steel plate. Made of materials that exhibit the same or similar values. As an example, the heat transfer suppressing plate 13 can be formed of the same mild steel plate as each of the thin metal plates 2 and 5.

The thickness t5 of the heat transfer suppressing plate 13 is arbitrary in principle, but it is preferably less than 0.8 mm from the viewpoint of preventing melting into the heat transfer suppressing plate 13 during pressurized energization. Even better is 0.7 mm or less. On the other hand, as will be described later, from the viewpoint of ensuring the contact area A1 between the first thin metal plate 2 in contact with the heat transfer suppressing plate 13 and the first thick metal plate 3 located inside thereof, The thickness t5 of the heat suppression plate 13 is preferably 0.4 mm or more, and even more preferably 0.5 mm or more.

In this way, with the heat transfer suppressing plate 13 disposed so as to be in contact with the thin metal plate 2 at one end in the thickness direction of the plate assembly 1, the heat transfer suppressing plate 13 and the plate assembly 1 are connected to a pair of electrodes. Electricity is applied between the pair of electrodes 11 and 12 while the electrodes 11 and 12 are sandwiched and pressurized.

At this time, a known pressure energization pattern can be applied as the pressure energization pattern to be applied. Moreover, the pressurization pattern and the energization pattern can be set in synchronization or can be set separately. For example, regarding the pressure pattern, the pressure may be maintained at a constant value during the energization period, or may be varied in a predetermined pattern. Furthermore, the variation pattern of the pressurizing force is also arbitrary; for example, the pressurizing force may be raised stepwise to a predetermined value without decreasing it, or the pressurizing force may be repeatedly increased and decreased until it reaches a predetermined value. May be increased. Alternatively, the pressing force may be increased to a predetermined value, maintained for a certain period of time, and then gradually lowered. Similarly, regarding the energization pattern, the current value as the amount of energization may be held at a constant value during the pressurizing period, or may be varied in a predetermined pattern. Furthermore, the variation pattern of the current value is also arbitrary; for example, the current value may be increased stepwise to a predetermined value without decreasing it, or the current value may be increased to a predetermined value while repeating increases and decreases. You may let them. Alternatively, the current value may be increased to a predetermined value, held for a certain period of time, and then lowered in stages.

In this way, when the plate assembly 1 is pressurized and energized in a predetermined pattern, the first and second thin metal plates 2 and 5 located at both ends of the plate assembly 1 in the thickness direction are caused to e.g. By deforming as shown in 3(b), it comes into contact with each of the thick metal plates 3 and 4 located at the center of the plate assembly 1 in the thickness direction. Then, the current density at the contact portion between each of the metal plates 2 to 5 increases, causing heat generation. Here, for example, when the heat transfer suppressing plate 13 is not disposed and the other conditions are the same as those of this embodiment when pressurized current is applied (see FIG. 4(a)), the first thin metal plate 2 is connected to the pair of electrodes 11. , 12, directly contacts one electrode 11 on the side closer to the first thin metal plate 2. The electrodes 11 and 12 are usually made of a material (for example, a copper alloy) that has higher thermal conductivity than the metal plates 2 to 5 to be welded. Furthermore, the electrodes 11 and 12 are cooled by the cooling liquid that is passed through the electrodes 11 and 12 when electricity is applied. Therefore, the metal plate 2 on the one end side in the thickness direction that contacts the electrode 11 easily causes heat transfer (heat radiation) to the electrode 11, resulting in a situation where the temperature does not easily rise. As a result, the growth of the welded part 6' formed inside the plate assembly 1 in the thickness direction becomes insufficient, increasing the possibility that the welded part 6' will not be formed in the first thin metal plate 2 (Fig. 4(c)).

On the other hand, according to the spot welding method according to the present invention, the heat transfer suppressing plate 13 disposed between the one electrode 11 and the first thin metal plate 2 allows It is possible to suppress or prevent the heat generated in the first thin metal plate 2 located on the side from escaping to the one electrode 11 side. Therefore, the temperature of the first thin metal plate 2 can be increased more easily than in the past, and melting into the first thin metal plate 2 (expansion of the molten part in the thickness direction) can be promoted. Therefore, as shown in FIG. 3(c), it is possible to relatively easily form a sufficiently large welded portion 6 spanning all the metal plates 2 to 5 including the first thin metal plate 2. .

Furthermore, when applying pressure and electricity to the plate assembly 1 in a predetermined pattern, the first and second thin metal plates 2 and 5 located at both ends of the plate assembly 1 in the thickness direction soften due to the pressure and heat generation. For example, by deforming as shown in FIG. 3(b), surface contact is made with each of the thick metal plates 3 and 4 located at the center of the plate assembly 1. In addition, at this time, by applying pressure and electricity with the heat transfer suppressing plate 13 disposed adjacent to the first thin metal plate 2, the heat transfer suppressing plate 13 is integrated with the first thin metal plate 2. It can be transformed into. As a result, the contact area A1 between the first thin metal plate 2 and the first thick metal plate 3 adjacent to the inner side of the first thin metal plate 2 can be changed to the contact area A1 of the first thin metal plate 2 when pressurized and energized without disposing the heat transfer suppressing plate 13. This can be made smaller than the contact area A2 between the thin metal plate 2 and the first thick metal plate 3 (see FIG. 4(b)). By adopting such a contact form, it is possible to bring the first thin metal plate 2 and the first thick metal plate 3 into surface contact in a relatively small area, especially in the early stage of pressurization and energization, and these metal plates This makes it easier to increase the current density at the contact portion between 2 and 3. Therefore, this also promotes the growth of the welded portion 6 in the thickness direction, making it possible to relatively easily form a sufficiently large welded portion 6 spanning all the metal plates 2 to 5.

In particular, as in the present embodiment, melting into the heat transfer suppressing plate 13 is prevented by setting the thickness t5 of the heat transfer suppressing plate 13 to less than 0.8 mm, preferably 0.7 mm or less. , it becomes possible to form a stable and sufficient welded portion 6.

(S3) Removal Step In the removal step S3, the heat transfer suppressing plate 13 is removed from the plate assembly 1 spot-welded in the welding step S2. At this time, if the heat transfer suppressing plate 13 is not substantially fixed to the first thin metal plate 2, the heat transfer suppressing plate 13 is removed from the first thin metal plate 2 by hand. In addition, if the heat transfer suppressing plate 13 is fixed to the first thin metal plate 2 to some extent (integrated by close contact or partial melting) at the pressurized and energized location by the pair of electrodes 11 and 12, a chisel, etc. The heat transfer suppressing plate 13 is removed from the first thin metal plate 2 by destroying the fixed portion using a tool. Thereby, a steel plate component as a plate-shaped component consisting of the plate assembly 1 having a predetermined structure is obtained. Note that when the heat transfer suppressing plate 13 is removed from the plate assembly 1 (first thin metal plate 2) using a tool or the like, there will be traces of removal of the heat transfer suppressing plate 13 on the surface of the first thin metal plate 2. Although it is possible that the surface may remain, if the surface constitutes the surface of the vehicle body, it will be painted after welding, so there is no risk of impairing visibility (design). Furthermore, if the surface does not constitute the surface of the vehicle body, there is no particular problem since it does not affect the visibility of the vehicle body in the first place.

Although one embodiment of the present invention has been described above, the spot welding method according to the present invention may have a configuration other than the above without departing from the spirit thereof.

For example, regarding the shape of the heat transfer suppressing plate 13, in the above embodiment, the case where the cross-sectional shape at the welding location (pressurized and energized location) is the same as that of the first thin metal plate 2 was exemplified (see FIG. 3). , of course, is not limited to this. Since the heat transfer suppressing plate 13 has a different required role and function from each of the metal plates 2 to 5 of the plate assembly 1, which are steel plate parts, for example, as shown in FIG. 5, the heat transfer suppressing plate 14 is It may be configured to integrally include a plurality of abutting portions 15 that abut the electrodes 11 and a connecting portion 16 that connects the plurality of abutting portions 15. In other words, the first thin metal plate 2 and one electrode 11 are connected only to the area of the heat transfer suppressing plate 14 where it is necessary to suppress heat transfer from the first thin metal plate 2 to one electrode 11 side. It is also possible to provide a portion that comes into contact with. In this case, the planar shape of the heat transfer suppressing plate 13 (the shape when the heat transfer suppressing plate 13 is viewed from the thickness direction) is the planar shape of the first thin metal plate 2 at least in the portion corresponding to the connecting portion 16. different from. Of course, it is necessary to set each contact portion 15 to a predetermined size and shape so that the first thin metal plate 2 undergoes desired deformation when spot welding is performed at a plurality of locations.

Further, matters other than the planar shape of the heat transfer suppressing plates 13 and 14 (material, thickness, surface treatment, etc.) are not particularly limited to those described in the above embodiments. The heat transfer suppressing plates 13 and 14 can have any configuration as long as the heat transfer from the first thin metal plate 2 to one electrode 11 can be suppressed.

In addition, in the above explanation, heat is transferred to the thin metal plate (first thin metal plate 2) with the smaller thickness among the two thin metal plates 2 and 5 located at both ends in the thickness direction of the plate assembly 1. Although the case where the suppression plate 13 (14) is brought into direct contact and pressurized current is applied by the pair of electrodes 11 and 12 has been exemplified, the present invention is not limited to this, of course. For example, although not shown, depending on the welding environment, such as the three-dimensional shape of each metal plate 2 to 5 and the positional relationship with other spot welding points, the thin metal plate with the larger thickness (in Fig. 3, the The heat transfer suppressing plate 13 (14) is brought into direct contact with the second thin metal plate 5), in other words, the heat transfer suppressing plate 13 (14) is placed between the second thin metal plate 5 and the other electrode 12. Pressure energization may be applied using a pair of electrodes 11 and 12 with .

In the above description, the heat transfer suppressing plate 13 ( 14) is shown as an example (see FIG. 3), but it is of course possible to use other arrangements. For example, as shown in FIG. 7, a heat transfer suppressing plate is provided between one electrode 11 of a pair of electrodes 11 and 12 and a first thin metal plate 2 at one end in the thickness direction near the other electrode 11. 13, and a heat transfer suppressing plate 17 may be provided between the other electrode 12 and the second thin metal plate 5 on the other end in the thickness direction on the side closer to the other electrode 12. .

In addition, in the above explanation, the plate assembly 1 (Fig. Although the case where the present invention is applied to 2) has been illustrated, it is of course possible to apply the present invention to the board assembly 1 having a configuration other than this. For example, as shown in FIG. 6, the present invention applies to a plate assembly 1 in which a thin metal plate (first thin metal plate 2) is arranged only on one side in the thickness direction of two thick metal plates 3 and 4. can also be applied. In this case, the heat transfer suppressing plate 13 is disposed between the first thin metal plate 2 and one electrode 11. In this way, the number of metal plates constituting the plate assembly 1 is arbitrary. The number may be three or five or more.

Furthermore, in the above description, the first and second thin metal plates 2 and 5 are made of mild steel plates, and the first and second thick metal plates 3 and 4 are made of high-tensile steel plates or ultra-high-tensile steel plates. Although illustrated, it is of course possible to apply the present invention to the board assembly 1 related to other combinations. That is, all metal plates 2 to 5 may be made of mild steel plates, or all metal plates 2 to 5 may be made of high tensile strength steel plates or ultra high tensile strength steel plates. Further, one of the first and second thin metal plates 2 and 5 may be a mild steel plate, and the other may be a high tensile strength steel plate or an ultra high tensile strength steel plate. Similarly, one of the first and second thick metal plates 3 and 4 may be a mild steel plate, and the other may be a high tensile strength steel plate or an ultra high tensile strength steel plate. Of course, it is also possible to apply the present invention to a plate assembly 1 that includes at least one metal plate other than a steel plate.

Further, in the above explanation, the case where the present invention is applied to the plate assembly 1 which is a steel plate component constituting the body of an automobile was illustrated, but of course, the present invention may be applied to other plate assemblies 1. It's okay. That is, the present invention may be applied to the plate assembly 1 that is a plate-shaped component other than a steel plate component. Further, the present invention may be applied to a plate assembly 1 that is a steel plate component (plate-shaped component) that constitutes a product other than an automobile body.

1 Plate assembly 2, 5 Thin metal plate 3, 4 Thick metal plate 5 Thin metal plate 6 Welding part 11, 12 Electrode 13, 14, 17 Heat transfer suppressing plate 15 Contact part 16 Connection part A1, A2 Contact area S1 Preparation Process S2 Welding process S3 Removal process

Claims (1)

A plate assembly preparation step of preparing a plate assembly in which a plurality of metal plates are stacked one on top of the other, in which a relatively thin metal plate among the plurality of metal plates is arranged at one end or both ends in the thickness direction. and,
A spot welding method comprising a welding step of forming a welded part inside the plate assembly by applying pressure and electricity to the plate assembly with a pair of electrodes,
In the welding step, between at least one of the pair of electrodes and the thin metal plate on the one end side in the thickness direction that is closer to the one electrode, the thin metal plate on the one end side in the thickness direction is Pressurizing and energizing the plate assembly with the pair of electrodes in a state where a heat transfer suppressing plate that suppresses heat transfer to one electrode side is provided ,
Due to the heating and softening caused by the pressurized energization, the heat transfer suppressing plate is integrally formed with the thin metal plate at one end in the thickness direction, and the heat transfer suppressing plate is integrally formed with the thin metal plate at one end in the thickness direction, and the metal plate adjacent to the thin metal plate at one end in the thickness direction is The thin metal plate on the one end side in the thickness direction is brought into surface contact with the thick metal plate, and the thin metal plate on the one end side in the thickness direction is brought into surface contact with the other end. A spot welding method characterized by forming a gap between the thin metal plate and the thick metal plate .

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