JP2008149353A - Resistance welding method between hollow tube and plate - Google Patents

Abstract

[PROBLEMS] To secure a desired joint strength while preventing bending of a member even if it is a hollow tube body having a complicated shape, while improving the overall working efficiency and having a thickness of 0.8 mm or less. To do.
[Solution]
In the resistance welding method between the hollow tube body 11 and the plate material 12, the hollow tube body 11 and the plate material 12 have a plate thickness t in the range of 0.5 mm ≦ t ≦ 3.2 mm. The interface is formed with a plurality of microprojections 16 having a height of 0.1 to 1.2 mm at a rate of 1 to 10 pieces / 10 mm ² and a bottom area of 0.5 mm ² or more. When welding the body 11 and the plate material 12, the hollow tube body 11 and the plate material 12 were pressurized while energized through the electrodes to the extent that the microprojections 16 were crushed.
[Selection] Figure 1

Description

  The present invention relates to a resistance welding method between a hollow tube body and a plate material, and more particularly to a resistance welding method suitable for securing a desired joint strength while preventing bending of a member even when the thickness is 0.8 mm or less. .

  Conventionally, when joining steel plates to metal hollow tubes, joints were often used, but there was a problem that the number of parts increased and the man-hours required for joining also increased. . Moreover, although the method of joining these hollow pipe bodies and steel plates by arc welding has been proposed, there is a drawback that thermal strain increases. Therefore, particularly in recent years, these weldings are generally performed by resistance welding.

  In order to improve the joining strength when joining the hollow tube body and the plate material by resistance welding, it is necessary to weld at a high pressure. However, in this resistance welding, it is necessary to bring the plate material into contact with the surface where the hollow tube body is desired to be welded, and sandwich the outside between the pair of upper and lower electrodes and press them. If it is high, the surface of the hollow tubular body will bend and deform. For this reason, conventionally, when resistance welding of a hollow tube body, it was not possible to improve to a desired pressure, and as a result, it was impossible to improve the joint strength by welding.

  For this reason, conventionally, in order to weld the hollow tube body under a low applied pressure, a method of resistance welding by interposing an insert material between the hollow tube body and the plate material has been proposed ( For example, see Patent Document 1.) In this method, the temperature of the welded portion is improved by adjusting the composition so that the thermite reaction occurs in the inserted insert material, and the weld strength is improved by increasing the joint area.

  However, the technique disclosed in Patent Document 1 requires an operation for applying the insert material to the surface of the hollow tube and a facility for curing the applied insert material by heat. For this reason, the technique disclosed in Patent Document 1 has a problem in that the processing cost increases as a result of an increase in work steps.

  For this reason, conventionally, a resistance welding method has also been proposed that allows a high pressure to be applied and that can improve the joint strength without using an insert material (see, for example, Patent Document 2). ). In the method disclosed in Patent Document 2, when a plate material is pressed against a hollow frame and welded, an intermediate wall is formed inside the hollow frame so that the portions to be pressed can communicate with each other.

  However, in the disclosed technique of Patent Document 2, an intermediate wall must be formed inside the hollow frame, which increases the labor burden. Further, depending on the application, the formed intermediate wall may become a barrier, and it may be necessary to remove the intermediate wall, resulting in a problem that the work process is increased.

Conventionally, a resistance welding method as shown in Patent Document 3 has also been proposed. In this resistance welding method, an insert material having a higher electrical conductivity than the metal member to be joined is inserted into the hollow tube body. As a result, a large amount of welding current flows through the insert material, which is effective not only for improving the amount of current in the welded portion, but also for applying pressure at the electrode through the insert material. For this reason, it is possible to prevent the member from bending with respect to the improvement of the applied pressure. In addition, since this insert material is considered to be a structure that can be easily attached and detached from the inside of the hollow tube body, it is possible to reduce the work effort as compared with the technology disclosed in Patent Document 2.
JP-A-8-132252 Japanese Patent Laid-Open No. 10-235477 JP-A-8-332576 JP 2003-117660 A

  By the way, there is a case where a plate material has to be welded not only to a straight hollow tube body but also to a hollow tube body having a complicated shape. A hollow tube having a complicated shape is often molded by hydroforming. This hydroforming is a method of processing a steel pipe of a predetermined shape while bulging by applying internal pressure with liquid to the hollow tube body that is the raw material and simultaneously applying a pushing force from the pipe end in the pipe axis direction. It is. According to this method, a product having a complicated shape can be processed with a smaller number of steps. In addition, by properly controlling the hydraulic pressure and the pushing force, the wall thickness can be processed uniformly, which is effective for reducing the weight of the product. For this reason, hydroforming parts are often applied particularly as parts for automobiles, and their needs are increasing in recent years.

  Since it is difficult to attach or remove the insert material disclosed in Patent Document 3 to the hollow tube body having a complicated shape manufactured through such hydroforming, and requires excessive labor, The construction period will be extended.

  In addition, the resistance welding method of hydroforming components is proposed conventionally (for example, refer patent document 4). In this method, a projection is formed on a hydroforming component, and a contact portion between the components is projection welded through the projection. Through this projection, it is possible to stably contact the steel plate even at a low applied pressure, and it is possible to concentrate a current through the projection and improve the current density. As a result, it is possible to minimize a decrease in deformation resistance due to a temperature increase during energization heating and a decrease in contact area due to deformation around the weld. In particular, since stable contact can be obtained even with a low applied pressure, the occurrence of scattering can be suppressed.

  However, the method described in Patent Document 4 has a problem that it is difficult to ensure the required welding strength even when projection welding is used when the thickness of the hydroforming component is 0.8 mm or less. It was.

  In addition, the technique disclosed in Patent Document 4 employs a configuration in which welding is performed through a single projection. However, in the case of one-point projection, a size (diameter) corresponding to the plate thickness is required to ensure the bonding strength. For example, it has been found that when the plate thickness of a part to be welded is 0.8 mm, a projection diameter of about 2.0 mm to about 3.0 mm is required. However, although the plate thickness to be welded is as small as 0.8 mm or less, the required pressure increases as the projection diameter increases. For this reason, when pressed with such increased pressure, the projection is crushed in the initial stage of energization, and effective heat generation cannot be obtained.

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is to improve the overall working efficiency even if the hollow tubular body has a complicated shape. In addition, an object of the present invention is to propose a resistance welding method between a hollow tube body and a plate material that can ensure a desired joint strength while preventing the bending of the member even if the thickness is 0.8 mm or less.

In order to solve the above-described problems, the present inventor sets the thickness t of the hollow tube to be welded and the plate material in a range of 0.5 mm ≦ t ≦ 3.2 mm, and 1 to A plurality of fine projections having a height of 0.1 to 1.2 mm at a ratio of 10 pieces / 10 mm ² and a bottom area of 0.5 mm ² or more are formed, and a hollow tube body and a plate material are formed. When welding, by pressing the hollow tube and the plate while energizing through the electrodes to the extent that the microprotrusions are crushed, the required nugget or the interface between the hollow tube and the plate is contacted. The inventors have invented a resistance welding method capable of generating a forged joint that ensures the required joint strength.

That is, the resistance welding method according to claim 1 of the present application is a resistance welding method between a hollow tube body and a plate material, and each of the hollow tube body and the plate material has a thickness t of 0.5 mm ≦ t ≦ 3. .2 mm, and the plate interface has a height of 0.1 to 1.2 mm at a rate of 1 to 10 pieces / 10 mm ² and a bottom area of 0.5 mm ² or more. When a plurality of microprotrusions are formed and the hollow tube body and the plate material are welded, the hollow tube body and the plate material are added while energizing the electrodes to the extent that the microprojections are crushed. By pressing, the deformation of the hollow tube body is suppressed, and further heat generation by local energization is promoted by the minute protrusions, so that the required nugget or the required bonding strength is obtained at the interface where the hollow tube body and the plate material are in contact. The special feature is that the forged joints to be secured are generated. To.

Further, the resistance welding method according to claim 2 of the present application is a resistance welding method between a hollow tube body and a plate material, in which the plate thickness t of each of the hollow tube body and the plate material is 0.5 mm ≦ t ≦ 3. .2 mm, and the plate interface has a height of 0.1 to 1.2 mm at a rate of 1 to 10 pieces / 10 mm ² and a bottom area of 0.5 mm ² or more. When a plurality of microprotrusions are formed and the hollow tube body and the plate material are welded, the hollow tube body and the plate material are added while energizing the electrodes to the extent that the microprojections are crushed. After the pressure is applied, the electrode is fixed and held by a brake to suppress the deformation of the hollow tube body, and further, the interface between the hollow tube body and the plate material is brought about by promoting the heat generation by local energization with the fine protrusions. Ensure the required nugget or required joint strength Wherein the forge welding unit has to be generated.

  In the present invention having the above-described configuration, the plate material is brought into contact with the hollow tube body through the minute protrusion. As a result, the contact area of the plate material with the hollow tube can be reduced. For this reason, even if the applied pressure by the upper electrode and the lower electrode is reduced, it is possible to obtain good contact of the hollow tube body with the plate material (microprojections). That is, it is possible to obtain good contact between the plate material (microprojections) and the hollow tube even with a small applied pressure, so that the applied pressure by the upper electrode and the lower electrode can be suppressed. Even when the plate thickness of the hollow tube and / or the plate material is 0.8 mm or less, it is possible to prevent the inner tube from being deformed inward and bent. That is, according to the present invention, it is possible to join with a predetermined pressure to a thin hollow tube or plate.

  Further, in the resistance welding method to which the present invention is applied, it is possible to reduce the contact area between the tip of the microprojection formed on the plate material and the hollow tube body in the initial stage of pressurization, and as a result, It is possible to increase the electrical resistance at the contact portion. Under such a state, the current passed between the upper electrode and the lower electrode flows through the contact portion between the micro-projection having a large resistance and the hollow tube body, and the heat generation due to the improvement of the current density is achieved. Can be realized.

  In particular, in the resistance welding method to which the present invention is applied, it is an essential constituent requirement to provide a plurality of minute protrusions to be formed on the plate material. For this reason, compared with the prior art that forms a single projection, it is possible to disperse the applied pressure, and also to disperse the current resistance. It becomes possible to form a uniform nugget with good balance.

  Hereinafter, as a best mode for carrying out the present invention, a resistance welding method between a hollow tube body and a plate material for resistance welding the hollow tube body and a plate material will be described in detail with reference to the drawings.

  FIG. 1 is a diagram for explaining a resistance welding method to which the present invention is applied. Below, the case where the board | plate material 12 contact | abutted to this is joined to the hollow tube 11 is demonstrated to an example, and is demonstrated.

  The hollow tube 11 is a tube made of metal such as steel having a hollow cross section, and is applied to, for example, automobile parts, home appliances, air conditioners, and the like. The hollow tube 11 has a thickness t in the range of 0.5 mm ≦ t ≦ 3.2 mm. From the viewpoint of required strength and product weight, the hollow tube body 11 applied to automobile parts and the like is practically used with a minimum plate thickness of about 0.5 mm. In addition, in a structural member having a skeleton such as an automobile chassis, the maximum plate thickness is about 3.2 mm in practical use because of its formability, required strength, product weight, and the like.

  The hollow tube body 11 may be configured not only with a square cross section but also with a circular cross section. Further, in addition to the case where the hollow tube body 11 is configured as a straight tube body, the hollow tube body 11 may be configured in, for example, a winding complex shape, or may be formed by so-called hydroforming. Good.

  The plate 12 is in the range of 0.5 mm ≦ t ≦ 3.2 mm of the plate thickness t. The plate material 12 is a steel material including a flat plate desired to be attached to the hollow tube body 11. Therefore, since the plate 12 is combined with the hollow tube 11 by welding or the like to form a structure, it is equivalent to the plate thickness range of the hollow tube 11 described above from the viewpoint of strength and weight. The lower limit of the plate thickness is set to 0.5 mm. The hollow tube body currently applied to automobile parts and the like is practically a plate thickness of 0.5 mm due to structural problems such as shape, member strength and weight. This is because is almost the lower limit.

Note that a plurality of minute protrusions 16 are formed on the bonding interface 12 a with the hollow tube 11 in the plate member 12. The minute protrusions 16 may be provided over the entire surface of the bonding interface 12a, or may be partially formed at least in a region corresponding to the welding position. FIG. 2 is a bottom view showing a case where the minute protrusions 16 are partially formed at the bonding interface 12a of the plate material 12. FIG. The microprotrusions 16 are formed at a ratio of 1 to 10 in the range of 10 mm ² of 10 mm square at the bonding interface 12a. Incidentally, the height of the minute protrusion 16 is in the range of 0.1 to 1.2 mm. Further, the bottom area of the minute protrusion 16 is set to 0.5 mm ² or more.

  When the height of the microprotrusions 16 is less than 0.1 mm, if welding is performed with a normal pressure, the protrusions are crushed before energization, and the steel sheets are brought into full contact with each other, and local effective heat generation cannot be obtained. On the other hand, if the thickness exceeds 1.2 mm, the protrusions are not sufficiently crushed by a normal pressure. As a result, when welding heat input (for example, welding current) is small, the projections remain after welding and a gap is formed between the steel plates. On the other hand, when welding heat input is large, the projections are not crushed. Appropriate welding conditions do not exist or condition selection becomes difficult, for example, severe scattering occurs. In view of the above, the height of the effective protrusion is set in the range of 0.1 mm to 1.2 mm.

  Furthermore, the shape of the microprotrusions 16 may be any shape such as a button shape, a cone shape, a pyramid shape, or a substantially elliptical cross section. If the microprotrusions 16 are configured in a cone shape or a pyramid shape, the tips may be rounded or flattened.

  When the plate member 12 is actually welded to the hollow tube body 11, first, as shown in FIG. 1, the bonding interface 12 a of the plate member 12 on which the fine protrusions 16 are formed as described above is formed on the hollow tube body 12. Press against the top surface to abut each other.

  Next, the hollow tube body 11 and the plate material 12 are sandwiched between the upper electrode 14 and the lower electrode 15 in the spot welder. The spot welder is provided with an upper electrode 14 and a lower electrode 15 so as to face each other vertically. During the welding operation, the upper electrode 14 is pushed down from the upper standby position via a pressing force such as an air cylinder (not shown), and the hollow tube as a workpiece to be welded with the lower electrode 15 held at a predetermined welding position. By applying a current in a state where the body 11 and the plate 12 are clamped, they can be resistance-welded.

  When welding the hollow tube body 11 and the plate material 12, the hollow tube body 11 and the plate material 12 are pressurized while being energized through the electrodes 14 and 15 to the extent that the microprojections 16 are crushed. In addition, the hollow tube body 11 is prevented from being deformed at this time.

  Finally, at the joining interface 12a where the hollow tube body 11 and the plate member 12 are in contact with each other, the required nugget 19 or the forged joint portion 20 that secures the required joining strength is generated as shown in FIG. 3, and resistance welding is realized. It will be.

  In particular, in the resistance welding method to which the present invention is applied, the plate material 12 is brought into contact with the hollow tube body 11 through the minute protrusions 16. As a result, the contact area of the plate 12 with the hollow tube 11 can be reduced. For this reason, even if the applied pressure by the upper electrode 14 and the lower electrode 15 is reduced, it is possible to obtain good contact of the hollow tubular body 11 with the plate material 12 (microprojections 16). Even if this is a small pressing force, it is possible to obtain good contact between the plate material 12 (microprojections 16) and the hollow tube 11, so that the pressing force by the upper electrode 14 and the lower electrode 15 can be suppressed. As a result, even when the plate thickness of the hollow tube 11 and / or the plate member 12 is 0.8 mm or less, it is possible to prevent the tube from being deformed inward and bent with respect to the applied pressure. In other words, according to the present invention, it is possible to join the thin hollow tube body 11 and the plate member 12 with a predetermined pressure.

  Further, in the resistance welding method to which the present invention is applied, it becomes possible to reduce the contact area between the tips of the microprotrusions 16 formed on the plate 12 and the hollow tube body 11 in the initial stage of pressurization. As a result, it is possible to increase the electrical resistance at the contact portion. Under such a state, the current to be passed between the upper electrode 14 and the lower electrode 15 flows through the contact portion between the small protrusion 16 having a large resistance and the hollow tube body 11, and the efficiency due to the improvement of the current density. Heat generation can be realized.

  In some cases, the micro projections 16 are selectively formed on the plate member 12 so as to correspond to at least a region where welding with the hollow member 11 is desired. In such a case, the melting point at the contact portion between the microprotrusions 16 and the hollow tube body 11 can be selected locally, and the welding point can be stably melted to the periphery thereof, so that A more optimal nugget 19 can be formed.

  In particular, in the resistance welding method to which the present invention is applied, it is an indispensable constituent requirement to provide a plurality of fine protrusions 16 to be formed on the plate material 12. For this reason, compared with the prior art that forms a single projection, it is possible to disperse the applied pressure, and also to disperse the current resistance. It becomes possible to form a uniform nugget with good balance. In addition, the diameter of the microprojections 16 can be set smaller than in the case of forming a single projection, and the applied pressure can be reduced.

However, if the minute protrusions 16 are formed at a ratio exceeding 10 pieces / 10 mm ² at the bonding interface 16 of the plate member 12, the applied pressure and the electric resistance are excessively dispersed, and the heat generation is concentrated. I can't plan. For this reason, as described above, it is defined as a requirement that the fine protrusions 16 are formed on the surface of the plate member 12 at a rate of 1 to 10 pieces / 10 mm ² .

Further, when the microprojections 16 are formed on the surface of the plate 12 at a ratio of 1/10 mm ² (when the microprojections 16 are formed at the minimum formation density, a nugget is formed at a plurality of locations if there is a shunt of the welding current. However, in such a case, sufficient pressurizing force and welding current cannot be obtained, and good nuggets are not formed at a plurality of locations, but rather may be scattered as scattered. Is higher.

For this reason, in this invention, it shall be able to apply to the case where a single nugget is formed to the last by arrange | positioning the microprotrusion 16 in multiple numbers. In addition, as a minimum formation density of the microprojections 16 in which a single nugget is formed without forming a plurality of nuggets, 1 piece / 10 mm ² is set as the lower limit.

  Further, in the resistance welding method to which the present invention is applied, when the hollow tube body 11 and the plate material 12 are welded, the hollow tube body is energized through the electrodes 14 and 15 to the extent that the microprojections 16 are crushed. 11 and the plate 12 are pressurized. If the microprotrusions 16 are not crushed, the current density becomes too high. Therefore, in the present invention, the microprotrusions 16 are intentionally crushed so that the contact area is gradually expanded, and resistance welding or solid phase bonding is performed. It is easy to realize.

  In the present invention, when the hollow tube body 11 and the plate member 12 are welded, the hollow tube is energized through the electrodes 14 and 15 until the height of the microprojections 16 is destroyed by 10 to 30%. The body 11 and the plate material 12 may be pressurized. By crushing the height of the microprotrusion 16 to 10 to 30%, it becomes possible to cause thermal expansion of the microprotrusion 16, and the pressurizing force based on the reaction force due to the thermal expansion is applied to the microprotrusion 16 and the hollow. It can be generated at the melted portion in the contact portion with the tube body 11. As a result, the applied pressure between the upper electrode 14 and the lower electrode 15 can be reduced.

Furthermore, in the resistance welding method to which the present invention is applied, the minimum bottom area of the microprotrusions 16 is set to 0.5 mm ² . The reason for this is that when the bottom area of the microprotrusions 16 is less than 0.5 mm ² , the melted area via the microprotrusions becomes small, so that sufficient bonding strength cannot be ensured.

On the other hand, if the bottom area of the microprotrusions 16 is too large, the electrical resistance becomes small and it is difficult to generate heat. As a result, the current required to actually generate heat must be increased, and the hollow area is hollow. It can also be a factor that the tube 11 is deformed. For this reason, although the upper limit of the bottom area of the microprotrusions 16 is not set, it is desirable that the upper limit of the bottom area satisfying this is formed in forming the bonding interface 12a at a rate of 1 to 10 pieces / 10 mm ^2. .

  In the present invention, the applied pressure, current, energization time, and the like during welding are appropriately determined according to various conditions such as the formation density of the microprojections 16 and the shape and dimensions thereof. If these conditions of pressure, current, and energization time are increased too much, the deformation of the hollow tube body 11 is promoted and lacks validity in forming a stable and good nugget. It is desirable to do this.

  The resistance welding method to which the present invention is applied is not limited to the above-described embodiment. The upper electrode 14 may be fixedly held after the hollow tube body 11 and the plate material 12 are pressurized via the electrodes 14 and 15.

  FIG. 4 shows a partially enlarged view of the resistance welding machine 3 for resistance welding the plate member 12 to the hollow tube body 11. As shown in FIG. 4, in the resistance welding machine 3, an air cylinder 27 is disposed as a mechanism for displacing the upper electrode 14 in a substantially vertical direction, and the upper electrode to which a pressing force is loaded via the air cylinder 27. A brake 26 is provided so that 14 can weld the hollow tube 11 and the plate 12 with a predetermined pressure. Since the brake 26 can restrain the vertical displacement of the upper electrode 14 attached to the tip of the air cylinder 27, the stop position of the upper electrode 14 can be determined with high accuracy.

  The upper electrode 14 is fixedly held by such a brake 26. As a result, the pressure applied from the upper electrode 14 can be adjusted, and desired welding can be realized while suppressing deformation of the hollow tube body 11. Incidentally, in the present invention, it is only necessary that the electrode is fixed by a brake, and any degree of brake accuracy or binding force may be used.

  Hereinafter, an embodiment in which the hollow tube body 11 and the plate material 12 are actually welded using the above-described resistance welding method according to the present invention will be described.

  Specimen No. used in this example. 1-No. The production conditions of 3 are shown in Table 1. This test material No. 1-No. 3 is based on a hollow tube 11 made of a square hollow member as shown in FIG. No. 1-No. Each hollow tube 11 in No. 3 had a width of 50 mm, a height of 35 mm, a length of 250 mm, and a plate thickness t of 1.2 mm. By the way, No. The tensile stress (TS) of 1 to 3 was 590 MPa.

The plate 12 has a width of 50 mm, a length of 50 mm, and a plate thickness of 2.0 mm. The substantially central position of the plate 12 is used as a welding region 21. The plate material 12 had a tensile stress of 440 MPa. Specimen No. 1 is a conventional method in which the microprojections 16 are not provided. For the methods 2 and 3, the method of the present invention in which the fine protrusions 16 are provided was used. Further, the microprotrusions 16 are button-shaped, have a diameter of 1.6 mm, a height of 0.6 mm, and are formed at a ratio of 3/10 mm ^{2 at} the bonding interface 12a.

  Specimen No. For 1-2, the upper electrode 14 was not fixedly held by the brake 26. On the other hand, specimen No. 3, the upper electrode 14 was fixedly held by the brake 26.

  Such test material No. 1-No. 3 was sandwiched between the upper electrode 14 and the lower electrode 15, and spot welding was performed under the conditions shown in Table 2. Incidentally, the upper electrode 14 is a movable electrode, is F type and has a diameter of 16 and is made of a Cr—Cu alloy. On the other hand, the lower electrode 15 is a fixed electrode, is F type and has a diameter of 16 and is made of a Cr—Cu alloy.

  As shown in Table 2, the pressure applied by the upper electrode 14 and the lower electrode 15 is 1.5 kN, and the energization time is No. 1 when the commercial frequency is 50 Hz. No. 1 is 14 cycles, no. 2 and 3 were 8 cycles. The welding current I is No. No. 1 14.3 kA, No. 1 2 for 11.5 kA, no. 3 was 10.2 kA.

When resistance welding was performed under the above-described conditions, No. No occurrence of scattering was observed in 1. In contrast, No. 1 as the method of the present invention. For 2 and 3, the occurrence of scattering from the microprojections 16 was observed. However, since this scattering is a minute thing that can occur even in a normal welding state, it does not have a particularly adverse effect. No. 1 as an example of the present invention. In 2 to 3, nuggets were formed around the microprojections 16, the diameter of the nugget was about φ3.2, and the number of nuggets corresponded to the number of microprojections 16 (three per 10 mm ² ). On the other hand, No. as a comparative method. In No. 1, the formation of nuggets could not be confirmed.

It is a front view for demonstrating the resistance welding method to which this invention is applied. It is a bottom view for demonstrating the resistance welding method to which this invention is applied. It is a figure for demonstrating the effect of this invention. It is a figure which shows the elements on larger scale of the resistance welding machine for resistance-welding a board | plate material with respect to a hollow tubular body. It is a figure for demonstrating an Example.

Explanation of symbols

11 hollow tube 12 plate 14 upper electrode 15 lower electrode 16 minute projection 21 welding region

Claims (3)

In the resistance welding method between the hollow tube and the plate material,
The hollow tube body and the plate material have a thickness t of 0.5 mm ≦ t ≦ 3.2 mm,
In the bonding interface of the plate material, the height is in a range of 0.1 to 1.2 mm at a rate of 1 to 10 pieces / 10 mm ² , and a plurality of microprojections having a bottom area of 0.5 mm ² or more are formed,
When welding the hollow tube body and the plate material, the hollow tube body and the plate material are pressurized while energizing through the electrodes to such an extent that the microprotrusions are crushed. While suppressing body deformation,
Furthermore, by promoting heat generation due to local energization with microprojections, a desired nugget or a forged joint that ensures the required joint strength is generated at the interface where the hollow tube body and the plate material are in contact with each other. Resistance welding method to do. In the resistance welding method between a hollow tube body and a plate material for resistance welding the hollow tube body and a plate material,
The hollow tube body and the plate material have a thickness t of 0.5 mm ≦ t ≦ 3.2 mm,
In the bonding interface of the plate material, the height is in a range of 0.1 to 1.2 mm at a rate of 1 to 10 pieces / 10 mm ² , and a plurality of microprojections having a bottom area of 0.5 mm ² or more are formed,
When welding the hollow tube body and the plate material, the hollow tube body and the plate material are pressurized while being energized through the electrode to such an extent that the microprotrusions are crushed. While suppressing the deformation of the hollow tube by holding it fixed by the brake,
Furthermore, by promoting heat generation due to local energization with microprojections, a desired nugget or a forged joint that ensures the required joint strength is generated at the interface where the hollow tube body and the plate material are in contact with each other. Resistance welding method to do. When welding the hollow tube body and the plate material, the hollow tube body and the plate material are energized through the electrodes until the height of the microprojections is collapsed to 10 to 30%. The resistance welding method according to claim 1, wherein pressurization is performed.

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