JP7058064B2 - Welding method - Google Patents

Description

The present invention relates to a welding method for welding a material to be welded and the like.

When joining a welded object in which two plates or other materials to be welded are overlapped, they may be joined by spot welding. Spot welding is a type of resistance welding method that uses resistance heat generation to join metals. In spot welding, the welded object is pressurized by the electrodes in a state where the materials to be welded are overlapped, a current is passed from the electrodes to the welded object, and the welded portion is heated by resistance heat generation to locally melt the welded object. , Welding objects are joined by metallurgy. In spot welding, the melt-solidified portion is called a "nugget", and the welded object is joined in the nugget.

Here, the surface of the material to be welded may be plated. When there is a plating layer at the contact portion of the stacked materials to be welded, the heat generated during welding may vaporize zinc or the like as the plating material to generate gas. When the gas expands explosively, the pressure of the gas may deform or damage the material to be welded, resulting in welding defects such as the formation of blow holes.

Therefore, in the conventional welding, the joint surface of the material to be welded is pressed in advance with a press machine or the like to form embossing in the vicinity of the welded portion of the welded surface. In this way, by providing a gap such as embossing in the vicinity of the welded portion, although it is generated, it is saved in the gap and the influence of the gas on the material to be welded is reduced (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-223634

However, the conventional welding method has a problem that it is difficult to form an appropriate gap.

For example, if the formed gap is too small, the gas cannot be sufficiently evacuated, and welding defects such as blow holes may not be suppressed. On the contrary, if the formed gap is too large, a sufficient welding area cannot be secured on the welded surface to be welded, and welding defects such as insufficient welding strength may occur. Therefore, the embossing formed on the welded surface is required to be formed with an accuracy of about 0.01 mm to 0.03 mm. On the other hand, in a general press machine, embossing is formed only with an accuracy of about 0.5 mm. As a result, in the conventional welding method, an appropriate gap may not be formed with sufficient accuracy, and welding defects may occur.

In order to solve the above problems, the welding apparatus of the present invention aims to form an appropriate gap during welding and suppress welding defects.

In order to achieve the above object, the welding method of the present invention is used when welding a plurality of materials to be welded at a predetermined welding point by using a plurality of welding machines including at least a resistance welding machine equipped with an electrode for welding. A step of passing a current from the electrode to the welded portion while pressurizing the welded portion with the electrode of the resistance welder so that a gap is formed between the materials to be welded, and a state in which the gap is formed. It is characterized by having a step of welding the welded portion by using any of the welding machines.

In this way, by forming a gap between the materials to be welded and then performing welding, the gas generated during welding can be evacuated to the gap. Therefore, it is possible to suppress damage to the material to be welded due to the explosive expansion of the gas, and it is possible to suppress the occurrence of welding defects.

Further, the step of forming the gap may be performed by a series welding machine.

In this way, by forming the gap with the series welding machine, it is possible to form the gap at a plurality of places at the same time, and it is possible to efficiently form the gap. As a result, it is possible to efficiently suppress the damage to the material to be welded due to the explosive expansion of the gas, and it is possible to efficiently suppress the occurrence of welding defects.

Further, the step of welding the welded portion may be performed by an indirect welder.

In this way, by performing indirect welding after forming a gap with a series welding machine, it is possible to perform welding after forming a gap even if electrodes cannot be provided on both sides of the object to be welded. can. Therefore, even in a state where electrodes cannot be provided on both sides of the welding target, it is possible to suppress the damage to the material to be welded due to the explosive expansion of the gas, and it is possible to suppress the occurrence of welding defects. Can be done.

Further, the welding device of the present invention is a welding device that continuously welds a plurality of materials to be welded at a plurality of welding points, pressurizes a welding target composed of the plurality of the materials to be welded, and supplies a current to the welding target. The first electrode to which the It has a drive device to be moved, a power supply device for individually applying a current to each of the first electrode and the second electrode, and a control device for controlling the operation of the drive device and the power supply device. The first electrode only forms a gap between the materials to be welded, the second electrode only welds, and current is applied to the first electrode and the second electrode. Is performed at the same time, and after applying a current to the first electrode and the second electrode, the first electrode and the second electrode are subjected to the first from the second electrode to the welding target. It is characterized in that a plurality of the welded portions are continuously welded by repeating the relative movement toward the electrodes of the above.

In this way, since the gap can be formed and welded at the same time by the pair of electrodes, it is possible to form a gap at the next welded portion while welding at the welded portion where the gap was formed earlier. .. Therefore, when welding continuously at a plurality of welding points, it is possible to suppress the damage to the material to be welded due to the explosive expansion of the gas while efficiently performing the welding, and to suppress the occurrence of welding defects. Can be done.

As described above, according to the present invention, an appropriate gap can be formed and welding defects can be suppressed.

The figure which illustrates the schematic structure of the welding apparatus in Embodiment 1. The figure which illustrates the formation of the gap in the welding method of this invention, and the state of the material to be welded at the time of welding. A flow chart illustrating the welding method of the present invention. The figure explaining the gas evasion in the welding method of this invention. The schematic diagram explaining the welding method in Embodiment 2. The flow diagram explaining the welding method in Embodiment 2. The figure which illustrates the welding object of this invention. Diagram illustrating an automobile production line

(Embodiment 1)
First, a configuration example of a welding apparatus used in the welding method of the present invention will be described with reference to FIG.

FIG. 1 is a diagram illustrating a schematic configuration of a welding apparatus according to the first embodiment.

As illustrated in FIG. 1, the welding device 1 in the first embodiment is a series welding machine, and is a pair of electrodes 3, a robot 7 having a robot arm 5 that holds the electrodes 3 and is movable, and a pair. It includes a transformer 9 for passing a current between the electrodes 3, a timer 11 for controlling the current flowing through the electrodes 3, and a control device 13 for controlling the operation of the timer 11 and the robot 7.

In the welding device 1, the electrode 3 can pass a current through the welding target 15 and pass a current between the electrodes 3 by pressurizing the welding target 15 and applying a predetermined current to the welding target 15. As will be described in detail with reference to FIG. 2 in the latter stage, the welding target 15 is a stack of a plurality of materials to be welded. In the welding target 15, adjacent materials to be welded in the thickness direction are joined by welding.

The electrode 3 can form a gap between the materials to be welded and weld between the materials to be welded by pressurizing the object 15 to be welded and passing a predetermined current through the object 15 to be welded. When welding between the materials to be welded, the welding target 15 is pressurized by the electrode 3 and an electric current is passed through the welding target 15 to heat and melt the welding target 15 to weld the welding target 15. When forming a gap between the materials to be welded, the electrode 3 pressurizes the welding target 15 with a smaller pressing force than when welding, and applies a current with a lower current value from the electrode 3 to the welding target 15 than when welding. .. The applied pressure of the electrode 3 is adjusted by the robot 7. The current value of the current applied from the electrode 3 can be determined according to the thickness of the welding target 15, the thickness of each material to be welded, the required welding strength, and the like, and is adjusted by the transformer 9.

The transformer 9 converts the current supplied via the timer 11 into a predetermined current value, and then applies the converted current to the electrode 3. For example, a current of several A at 400 V supplied via the timer 12 is converted into a current of 15000 A at 3 to 5 V and applied to the electrode 3. The timer 11 controls the timing of applying a current to the electrode 3 via the transformer 9. The transformer 9 is controlled by the control device 13, and the control device 13 can also control the transformer 9 via the timer 11.

The robot 7 includes an electrode 3 and a robot arm 5. The robot 7 has a configuration in which the electrode 3 can be moved to an arbitrary position within a predetermined range by the robot arm 5, and the electrode 3 is moved to a predetermined welding position.

The control device 13 controls the operation of the robot 7 and at the same time controls the operation of the timer 11. The timer 11 controls the transformer 9 so as to control the current applied from the electrode 3 to the welding target 15 according to the instruction of the control device 13.

It is preferable that the welding device 1 further has a cooling device. The cooling device is a device for cooling the electrode 3, and cools the electrode 3 when a current is applied from the electrode 3 to the welding target 15. During welding, an electric current flows through the electrode 3, so that the electrode 3 is heated and softened. At this time, since the electrode 3 pressurizes the welding target 15, the softened electrode 3 receives the force from the welding target 15. Therefore, the tip of the electrode 3 is deformed or damaged by repeated welding. The shape of the tip of the electrode 3 affects the current density of the current supplied to the welding target 15 and the pressing force on the welding target 15 depending on the area in contact with the welding target 15. Since the current density and the pressing force affect the welding accuracy, the electrode 3 is cooled during welding. Cooling can be performed, for example, by circulating cooling water through the electrode 3.

Further, in FIG. 1, the timer 11 related to the supply of the current to the electrode 3 and the control device 13 and the like are illustrated as a configuration in which the power is supplied from another power source, but the power is supplied from a common power source. Alternatively, each device may be supplied with electric power from another power source as needed.

Further, the electrode 3 is driven by the robot 7 functioning as a driving device in response to an instruction from the control device 13.

Further, the timer 11 and the transformer 9 function as a power supply device for supplying a current to the electrode 3. The power supply device may have other configurations as long as it can supply the current of the predetermined application conditions to the electrode 3.

In the welding line, a plurality of various welding machines such as a resistance welding machine such as the welding device 1 and a laser welding machine are arranged around the conveyor, and the product being manufactured flowing on the conveyor is placed at a welding point or the like. Welding is often performed at multiple locations using a suitable welding machine.

Specifically, as shown in FIG. 8, in the welding line of the automobile production line, in addition to the above-mentioned welding device 1 around the conveyor through which the white body (body shell before painting) flows, other (A total of 6 welding devices 1'and 5 other welding devices 1'in the illustrated example) are arranged. In such a welding line, not only the welding to a predetermined place is performed only by the welding device 1 and the welding of other parts is performed by the other welding device 1', but also a part of the welding process is welded. It is also possible to do it with the device 1 and do the rest with another welding device 1'. As described above, the welding method of the present invention may be performed by the welding device 1 alone or in cooperation with the welding device 1 and another welding device 1'.

Next, the welding method of the present invention will be described with reference to FIGS. 1 to 3. In the following description, unless otherwise specified, the description will be made on the premise that the welding device 1 independently welds a predetermined position.

FIG. 2 is a diagram illustrating the formation of a gap in the welding method of the present invention and the state of the material to be welded during welding, and FIG. 3 is a flow diagram illustrating the welding method of the present invention.

As described above, the welding target 15 is a stack of a plurality of materials to be welded. In the example shown in FIG. 2, the object to be welded 15 is composed of the material to be welded 17 and the material to be welded 19, and the material to be welded 17 and the material to be welded 19 are joined by welding at a welded portion 21. Plating 23 is applied to the joint surface of the material 17 to be welded. Then, in the welding method of the present invention, first, the welded portion 21 is aligned and the material to be welded 17 and the material to be welded 19 are overlapped with each other (step 1 in FIG. 2A and FIG. 3).

When such the material to be welded 17 and the material to be welded 19 are welded at the welded portion 21, then the welded portion 21 between the material to be welded 17 and the material to be welded 19 is used by the above-mentioned series welding machine. A gap t is provided in the vicinity of (FIG. 2B, step 2 in FIG. 3). Therefore, the material 17 to be welded at the upper part of the welded portion 21 is pressed by the electrode 3, and a current is applied to the welded portion 21 from the electrode 3. In this way, by applying an electric current from the electrode 3 to the welded portion 21, the welded portion 21 is heated and softened. At the same time, by pressurizing the material to be welded 17 using the electrode 3, the material to be welded 17 bends, and a gap t is generated between the material to be welded 17 and the material to be welded 19 in the vicinity of the welded portion 21.

At this time, the pressing force applied to the material 17 to be welded by the electrode 3 is made smaller than the pressing force during welding described later. Further, the current value of the current applied from the electrode 3 to the material 17 to be welded is made smaller than the current value at the time of welding described later. Then, by adjusting at least one of the pressing force, the current value, the time for applying the current, and the like, the gap t is formed without welding the welded portion 21. Further, since delicate adjustment can be made by the pressing force, the current value, the time for applying the current, and the like, the gap t can be easily adjusted to the optimum interval.

Next, the material to be welded 17 and the material to be welded 19 are welded at the welded portion 21 (step 3 in FIG. 3). For example, following the step of forming the gap t described above, the pressure applied by the electrode 3 to pressurize the material 17 to be welded is increased, and the current value of the current applied from the electrode 3 to the material 17 to be welded is increased. In this way, in particular, by increasing the current value of the current applied from the electrode 3 to the material to be welded 17, heating of the material to be welded 17 and the material to be welded 19 is promoted at the welded portion 21, and the material to be welded 17 and the material to be welded 19 and the welded material 19 are heated. The material 19 to be welded is melted and fused and bonded. Similar to the above-mentioned step of forming the gap t, the welding state such as the welding strength and the welding range can be adjusted by the pressing force, the current value, the time for applying the current, and the like. In this way, following the formation of the gap t, the pressing force, the current value, the time for applying the current, and the like can be adjusted to weld between the welded material 17 and the welded material 19 at the welded portion 21.

Welding is not limited to using a series welding machine following the formation of the gap t, and can be performed by any other method such as spot welding such as welding using a direct welding machine or an indirect welding machine, laser welding, or the like. It is also possible to weld.

For example, as shown in FIG. 2C, after the gap t is formed, welding can be performed using a direct welding machine. At this time, the electrodes 3 are arranged on the surfaces of the material to be welded 17 and the material to be welded 19 so as to sandwich the welded portion 21. Then, the material 17 to be welded and the material 19 to be welded are sandwiched between the two electrodes 3 and pressurized at a predetermined pressure, and a current is passed between the two electrodes 3 under predetermined application conditions to pass a current through the welded portion 21. As a result, the welded material 17 and the welded material 19 can be welded at the welded portion 21.

Further, as shown in FIG. 2D, after the gap t is formed, welding can be performed using an indirect welding machine. At this time, the ground 25 is connected to the material 19 to be welded. Then, the electrode 3 pressurizes the material 17 to be welded with a predetermined pressure, and a current is passed from the electrode 3 to the ground 25 under predetermined application conditions to pass a current through the welded portion 21. As a result, the welded material 17 and the welded material 19 can be welded at the welded portion 21.

Next, the effect of the welding method of the present invention will be described with reference to FIG.

FIG. 4 is a diagram illustrating gas retreat in the welding method of the present invention.

As shown in FIG. 4A, it is assumed that the joint surface of the material to be welded 17 is plated with plating 23, and the material to be welded 17 and the material to be welded 19 are welded as the welding target 15.

At this time, if welding is performed in a state where the material 17 to be welded and the material 19 to be welded are in close contact with each other, the plating 23 is vaporized by the heat during welding and gas is generated. Since the material 17 to be welded and the material 19 to be welded are in close contact with each other, there is no place for the generated gas to go, and the gas presses the material 17 to be welded and the material 19 to be welded. When the gas expands explosively, the material to be welded 17 or the material to be welded 19 is damaged due to the influence of the gas, and the surface of the material to be welded 17 or the material to be welded 19 is damaged, resulting in welding failure. was there. Further, when the gas stays in the welding target 15 and the welding is completed as it is, as shown in FIG. 4B, a blow hole 26 is generated in the welding target 15, and the welding strength is insufficient. In some cases,

On the other hand, according to the welding method of the present invention, the material to be welded 17 and the material to be welded 19 are brought into contact with each other at the welded portion 21 by heating and pressurizing the material to be welded 17 on the welded portion 21 prior to welding. While doing so, a gap t can be provided in the vicinity of the welded portion 21 between the material to be welded 17 and the material to be welded 19. By performing welding in this state, the material to be welded 17 and the material to be welded 19 are in close contact with each other at the welded portion 21, so that appropriate welding is possible. In addition, since there is a gap t around the welded portion 21, the generated gas can be evacuated to the gap t, and the influence of the gas on the material to be welded 17 and the material to be welded 19 can be suppressed. Therefore, it is possible to prevent welding failure due to the influence of the generated gas.

In particular, when a gap t is formed by applying a current from the electrode 3 and passing a current through the welding target 15 while pressurizing the material 17 to be welded by the electrode 3, the accuracy is higher than when embossing is formed by a press or the like. The gap t can be formed well. For example, in the case of general press working, embossing can be formed only with an accuracy of about 0.5 mm. On the other hand, when the gap t is formed by using the electrode 3, the formation of the gap t can be controlled by the pressing force of the electrode 3, the application condition of the applied current, etc., so that the accuracy is about 0.01 mm to 0.03 mm. A gap t can be formed. Therefore, it is possible to perform welding with high accuracy while suppressing welding defects more reliably.

As described above, when not only the welding device 1 but also other welding devices 1'can cooperate with each other to perform welding as in the welding line shown in FIG. 8, the welding flowing on the conveyor is performed. After forming a gap t with respect to the target 15 (white body in the illustrated example) using a resistance welding machine such as the welding device 1, welding is performed using another welding device 1'optimal for welding the welded portion. It can be carried out. As a result, the gap t can be efficiently formed and welded, and welding can be efficiently performed while suppressing welding defects due to the influence of the generated gas.
(Embodiment 2)

Next, the welding method according to the second embodiment will be described with reference to FIGS. 1 and 7 with reference to FIGS. 5 to 7.

FIG. 5 is a schematic diagram illustrating a welding method according to the second embodiment, and is a diagram illustrating a schematic configuration of a welding apparatus used in the welding method according to the second embodiment and each welding process. FIG. 6 is a flow chart illustrating the welding method according to the second embodiment, and FIG. 7 is a diagram illustrating a welding target of the present invention.

As shown in FIG. 5A, the welding apparatus 27 used in the welding method of the second embodiment includes an electrode 3a and an electrode 3b. The electrode 3a is an electrode used for forming the gap t. The electrode 3b is an electrode used for welding the material to be welded 17 and the material to be welded 19. The electrodes 3a and 3b are individually connected to the transformer 9, and it is possible to apply a current to the welding target 15 simultaneously or separately under different application conditions. Further, the electrodes 3a and 3b can pressurize the welding target 15 at different pressures at the same time or separately. Therefore, the electrode 3a pressurizes the welding target 15 with an optimum pressing force in order to bend the material 17 to be welded and form a gap t between the material 17 to be welded and the material 19 to be welded, which is optimal. A current can be applied to the welding target 15 under the application conditions. At the same time, the electrode 3b can pressurize the welding target 15 with an optimum pressure to weld the material 17 to be welded and the material 19 to be welded, and apply a current to the welding target 15 under the optimum application conditions. .. As a result, a gap t is formed between the material to be welded 17 and the material to be welded 19 by the electrode 3a at a certain place, and at the same time, the material to be welded 17 and the material to be welded 19 are welded by the electrode 3b at another place. Can be done.

The robot 7 can relatively move the electrodes 3a and 3b and the welding target 15. As a result, the electrodes 3a and 3b can move on the welding target 15 in the direction from the electrodes 3b to the electrodes 3a. Since the configurations other than the above configurations are the same as those of the welding apparatus 1 described in the first embodiment, the description thereof will be omitted.

When welding is performed using the welding device 27 having the above configuration, first, the welded material 17 and the welded material 19 are aligned and overlapped with each other (FIG. 5 (a), FIG. Step 1 of 6). It is assumed that the welded portions 21a, 21b, and 21c are welded to the welding target 15.

Next, a gap t is formed between the material to be welded 17 and the material to be welded 19 in the vicinity of the welded portion 21a by the electrode 3a (step 2 in FIG. 5B, FIG. 6). At this time, the electrodes 3a and 3b are moved relative to the welding target 15 so that the electrodes 3a are arranged above the welded portion 21a. Then, the electrode 3a is a welding target with an optimum pressing force for bending the material 17 to be welded to form a gap t between the material 17 to be welded and the material 19 to be welded at the upper portion of the welded portion 21a. 15 is pressurized, and a current is applied to the welding target 15 under the optimum application conditions. As a result, a gap t between the material to be welded 17 and the material to be welded 19 can be formed in the vicinity of the welded portion 21a. At this time, since the electrodes 3a and 3b are independent of each other, the electrodes 3b can be prevented from being pressurized or applied with a current.

Next, the electrode 3a and the electrode 3b are moved relative to the welding target 15 in the direction of the arrow in the figure, the electrode 3a is arranged on the upper portion of the welded portion 21b, and the electrode 3b is arranged on the upper portion of the welded portion 21a. (FIG. 5 (c), step 3 of FIG. 6).

Next, the electrode 3a forms a gap t in the vicinity of the welded portion 21b, and the electrode 3b welds the material to be welded 17 and the material to be welded 19 at the welded portion 21a (FIGS. 5C and 6). Step 4). At this time, the electrode 3b can pressurize the welding target 15 with a pressure different from that of the electrode 3a, and can apply a current under application conditions different from that of the electrode 3a. Similar to step 2, the electrode 3a bends the material to be welded 17 to form a gap t between the material to be welded 17 and the material to be welded 19, and applies the welding target 15 with an optimum pressing force. Pressure is applied and a current is applied to the welding target 15 under the optimum application conditions. The electrode 3b pressurizes the welding target 15 with an optimum pressure to weld the material 17 to be welded and the material 19 to be welded, and applies a current to the welding target 15 under the optimum application conditions. As a result, the welded material 17 and the welded material 19 can be welded at the welded portion 21a at the same time while forming the gap t in the vicinity of the welded portion 21b.

Next, it is determined whether or not the gap t formed in step 4 is formed in the vicinity of the last welded portion of the welded portion scheduled to be welded (step 5 in FIG. 6). If a gap t is formed around the last welded portion, the process is shifted to step 6, and if the portion where the gap t is formed is not near the final welded portion, the processes of steps 3 to 5 are performed. repeat. Here, since the welded portion 21b is not the final welded portion, the electrode 3a and the electrode 3b are moved relative to the welding target 15, and the electrode 3a forms a gap t in the vicinity of the welded portion 21c. The welded material 17 and the welded material 19 are welded at the welded portion 21b by the electrode 3b. Since the welded portion 21c is the last welded portion of the welded portion scheduled to be welded, the process is then shifted to step 6.

Next, the electrodes 3a and 3b are moved relative to the welding target 15 in the direction of the arrow in the figure, and the electrodes 3a and 3b are welded so that the electrodes 3b are arranged above the welded portion 21c. It is moved relative to the target 15 (step 6 in FIG. 6).

Finally, the electrode 3b is used to weld the material 17 to be welded and the material 19 to be welded at the welded portion 21c (step 7 in FIG. 6). As a result, the welding of all the welding points 21a, 21b, 21c is completed. At this time, since the electrodes 3a and 3b are independent of each other, the electrodes 3a can be prevented from being pressurized or applied with a current.

In this way, by heating and pressurizing the material to be welded 17 on the welded portion 21 prior to welding, the material to be welded 17 and the material to be welded 19 are brought into contact with each other at the welded portion 21. A gap t can be provided in the vicinity of the welded portion 21 between the welded material 19 and the welded material 19. By performing welding in this state, since the material to be welded 17 and the material to be welded 19 are in close contact with each other at the welded portion 21, proper welding is possible, but there is a gap t in the vicinity of the welded portion 21. The generated gas can be evacuated to the gap t, and the influence of the gas on the welded material 17 and the welded material 19 can be suppressed. Therefore, it is possible to prevent welding failure due to the influence of the generated gas. Further, the electrodes 3a and 3b are movable relative to the welding target 15, and the electrodes 3a and 3b pressurize the welding target 15 with individual pressures, and the welding target 15 is subjected to individual application conditions. It is configured so that a current can be applied to the. Therefore, at the same time as forming the gap t at the electrode 3a, welding between the material to be welded 17 and the material to be welded 19 can be performed at the electrode 3b. As a result, a gap t can be formed in the vicinity of the next welded portion while welding, and welding can be performed efficiently and accurately.

The distance between the electrodes 3a and 3b can be made variable according to the distance between the welded portions 21a, 21b, and 21c. Since the distance between the electrodes 3a and 3b is variable, even if the distance between the welded portions 21a, 21b, and 21c is not constant, the gap t is continuously adjusted while adjusting the distance between the electrodes 3a and 3b. It is possible to efficiently perform forming and welding.

Next, a configuration example of the welding target will be described with reference to FIGS. 5 and 7.

In the example shown in FIG. 7, the ceiling 31 is attached to the vehicle body 29 of the automobile by welding. Then, the vehicle body 29 and the ceiling 31 are welded at a plurality of welding points 21 along the framework of the vehicle body 29. At this time, the welded portion 21 is welded in order from the end. At the time of welding, at each welding point 21, a gap t is provided between the vehicle body 29 and the ceiling 31 in the vicinity thereof, and then welding is performed. In the welding method of the second embodiment, a gap t is formed in the vicinity of the welded portion 21a by the electrode 3a. After that, while welding the welded portion 21a with the electrode 3b, a gap t is formed in the vicinity of the welded portion 21b with the electrode 3a. After that, this operation is repeated until the welding of all the welding points 21 is completed. In this way, the electrodes 3a and 3b allow the formation of the gap t in the vicinity of the next welding portion 21 and the welding to be performed at the same time, so that welding can be performed efficiently.

In each of the above embodiments, the welding in the present invention can be used for welding the lower back, the under front, the center front, the kick reinforcement, etc., in addition to attaching the ceiling 31 to the vehicle body 29.

Further, FIG. 2B shows an example in which a gap t is formed by a series welding machine in which the material 17 to be welded is pressed by two electrodes 3 and a current is passed through the welded portion 21, but the gap t is directly welded. It is also possible to use another welding machine such as a machine or an indirect welding machine. Further, if the material 17 to be welded can be pressurized while being heated, the gap t can be formed by another method.

1 Welding device 3 Electrode 13 Control device 15 Welding target 17 Welding material 19 Welding material 21 Welding point 23 Plating 25 Earth 26 Blow hole 27 Welding device

Claims (1)

When welding multiple materials to be welded at a predetermined weld using multiple welders, including at least a resistance welder with electrodes for welding.
By applying a current from the electrode to the welded portion while pressurizing the welded portion with the electrode of the resistance welder, the welded portion is not welded and the space between the welded materials is around the welded portion. The first step of forming a gap and
A welding method comprising a second step of performing welding using any of the welding machines at the same place as the welding place where the gap is formed in the periphery by the first step .

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