JP5625423B2 - Indirect spot welding method - Google Patents

Description

  The present invention presses a welding electrode while pressing a welding electrode against a metal plate from one surface side against a member in which at least two metal plates are overlapped, and feed terminal at a position away from the metal plate on the other surface side And an indirect spot welding method in which welding is performed by energizing between the welding electrode and the power supply terminal.

  Conventionally, resistance spot welding, mainly direct spot welding, has been used for welding automobile bodies and parts, but recently, series spot welding, indirect spot welding, and the like have been used.

The characteristics of the above three types of spot welding will be described with reference to FIG.
In any spot welding, there is no change in that at least two superposed steel plates are joined by welding.
FIG. 1A shows the direct spot welding method. In this welding, as shown in the figure, a current is applied while pressing a pair of electrodes 3 and 4 from above and below between the two stacked metal plates 1 and 2, and the resistance heating of the metal plates is used. This is a method for obtaining a spot-like welded portion 5. Each of the electrodes 3 and 4 includes pressurization control devices 6 and 7 and a current control device 8, so that the pressurizing force and the current value to be energized can be controlled by these.

  In the series spot welding method shown in FIG. 1 (b), a pair of electrodes 13 and 14 are pressed from the same surface side (in the same direction) at a position apart from two superimposed metal plates 11 and 12. In this method, a current is passed to obtain the spot welds 15-1 and 15-2.

  In the indirect spot welding method shown in FIG. 1 (c), the electrode 23 is pressed against one metal plate 21 while pressing the two metal plates 21, 22, and the other metal plate 22 is pressed against the other metal plate 22. Is a method of forming a spot-like welded portion 25 on the metal plates 21 and 22 by attaching the power supply terminal 24 at a distant position and energizing between them.

Of the three types of welding methods described above, direct spot welding is used when there is sufficient space and an opening that sandwiches the metal plate from above and below is obtained.
However, in actual welding, there are many cases where there is not enough space or the metal plate cannot be sandwiched from above and below with a closed cross-sectional structure. In such cases, the series spot welding method or the indirect spot welding method is used. Used.

  However, when the series spot welding method or the indirect spot welding method is used for the above-mentioned applications, the stacked metal plates are pressed by the electrode only from one direction, and the opposite side is a hollow with no support. It is in a state. Therefore, it is not possible to apply a high applied pressure directly under the electrodes as in the direct spot welding method in which the electrodes are sandwiched from both sides. Further, since the electrode sinks into the metal plate during energization, the contact state between the electrode-metal plate and the metal plate-metal plate changes. For these reasons, there is a problem in that the current energization path is not stable between the stacked metal plates, and it is difficult to form a melt-bonded portion.

  In order to solve the above-mentioned problem, for series spot welding, in Patent Document 1, “To form a nugget at a contact point where metal plates are overlapped, a large current is passed in the initial stage of welding to form an electrode nugget. , A steady current is passed ”. Further, in Patent Document 2, “welding is sufficient without a back electrode by forming a seat surface that is one step higher than the other parts at the position where the electrode is brought into contact, and press-contacting so as to crush the seat surface. It is described that strength can be obtained.

  On the other hand, for indirect spot welding, as a technique that can be applied to series spot welding, Patent Document 3 states, “When a series spot welding or indirect spot welding is energized, a time zone in which a current value is kept high and a current value are made low. A welding method that consists of alternately repeating the time period to maintain, and further, the time period in which the current value is kept high as the time period in which the current value is kept high and the time period in which the current value is kept low are alternately repeated. A welding method comprising “gradually increasing the current value” is disclosed.

Japanese Patent Laid-Open No. 11-333569 JP 2002-239742 A JP 2006-198676

However, Patent Document 1 is considered effective for series spot welding, but has a problem that it is not always effective for indirect spot welding with different welding methods.
Patent Document 2 is also considered effective for series spot welding, but is not necessarily effective for indirect spot welding, and is one step higher than the other parts at the position where the electrode is brought into contact. There is a problem that a process of forming the seating surface with a press or the like is required.

Furthermore, Patent Document 3 discloses that when the metal structure of the overlapped portion of the metal plates 11 and 12 welded by the energization pattern according to the technique disclosed in the same document is observed, the metal in the overlapped portion of the metal plates 11 and 12 is conventionally Compared to ordinary nuggets, a large number of finely melted and recrystallized items are observed, which is the case of joining in the so-called diffusion bonding state. There are also cases where they are joined by different events "(paragraph [0038] of the same document 3), and it is necessarily formed into a meteorite shape in a completely melted state like a nugget seen in direct spot welding. There was a problem that was not limited.
The current management standards for spot welds in transportation equipment manufacturers often require that they be a meteorite-shaped nugget that has been completely melted, as obtained by direct spot welding, so that joint strength can be obtained. However, if a meteorite-shaped nugget formed in a completely molten state is not obtained, there is a problem that the management standard is not satisfied.

  The present invention has been developed in view of the above-described present situation, and the superimposed metal plates are pressurized with an electrode only from one direction, and the opposite side is melted during indirect spot welding for welding in a hollow state without support. It is an object to propose an indirect spot welding method capable of stably obtaining a meteorite-shaped nugget formed in a state.

As a result of intensive studies to solve the above problems, the inventors have obtained the following knowledge.
a) When the superimposed metal plates are pressed with an electrode only from one direction and indirect spot welding is performed in a hollow state with no support on the opposite side, directly under the electrode as in the direct spot welding method sandwiched between the electrodes from both sides Since a high applied pressure cannot be applied locally, a high current density cannot be obtained between the stacked metal plates directly under the electrodes, and the electrodes sink into the steel plate during energization. The contact area between the metal plate and the metal plate increases, and the current density between the electrode and the metal plate and between the metal plate and the metal plate decreases. Therefore, in indirect spot welding, it is difficult to obtain a heat generation enough to form a melted portion between the metal plates stacked immediately below the electrodes as in the direct spot welding method, and it is difficult to form a melted joint.
b) In order to solve the above problem, the current value during energization and its time are finely controlled, or the applied pressure and time during energization of the electrode are finely controlled. It is effective to finely control the pressure and time.
c) In particular, the energization time and the pressurization time from the start of energization are each independently divided into three stages, and the current value and / or the applied pressure of the electrode at each stage of the energization time and the pressurization time are individually controlled, It is possible to stably form a melt-bonded portion made of a healthy meteorite-shaped nugget.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
1. Pressing the welding electrode against the metal plate from one side while pressing the welding electrode against a member on which at least two metal plates are overlapped, and feeding the terminal on the other side of the metal plate at a position separated from the welding electrode In the indirect spot welding method in which welding is performed by energizing between the welding electrode and the power supply terminal, three time zones t ₁ and t ₂ from the start of energization are applied to the electrode pressing force and the current value to be energized. , divided into t _3, the first time period t _1, by energizing pressurized and current value C ₁ under a pressure F ₁ to initiate the formation of the fusion zone, in the next time period t _2, from F ₁ It is energized further grow the fused portion at high current value C ₂ than pressurize and C ₁ at a low pressure F ₂ also further in the next time period t _3, lower than the same or F ₂ and F ₂ the melted portion by energizing at high current value C ₃ than pressurize and C ₂ with pressure F ₃ Indirect spot welding method characterized by gradually grown al.
2. In the above 1, the energization times in the time zones t ₁ , t ₂ , and t ₃ are t ₁ : 0.02 to 0.30 s, t ₂ : 0.02 to 0.30 s, and t ₃ : 0.10 to 0.60 s, respectively. _1, t _2, pressure in the t _{3, respectively, F 1: 300~2000N, F 2} : 100~1500N, F 3: a 100～1500N, and each time slot t _1, current at t _2, t ₃ The indirect spot welding method, wherein the values are C ₁ : 2.0 to 10.0 kA, C ₂ : 2.5 to 11.0 kA, and C ₃ : 3.0 to 12.0 kA, respectively.

3 . Pressing the welding electrode against the metal plate from one side while pressing the welding electrode against a member on which at least two metal plates are overlapped, and feeding the terminal on the other side of the metal plate at a position separated from the welding electrode In the indirect spot welding method in which welding is performed by energizing between the welding electrode and the power supply terminal, the electrode pressing force is applied to three time zones t _F1 , t _F2 and t _F3 from the start of energization. In the first time zone t _F1 , pressurization is performed with the pressurizing force F ₁ , in the next time zone t _F2 , pressurization is performed with the pressurizing force F ₂ lower than F ₁ , and in the next time zone t _F3 , F is applied. while pressurizing the same or F ₂ low pressure F ₃ than _2, with respect to the current value to be supplied, the time period t _F1, t _F2, t _F3 independently of the three time periods t from start of energization _C1, divided into t _C2, t _C3, the first time period t _C1, by energizing a current value C ₁ soluble Start the formation parts, in the next time period t _C2, high further grow the fused portion by energizing at high current value C ₂ than C _1, further in the next time period t _C3, than C ₂ current indirect spot welding method characterized in that will further grow the fused portion by energizing a value C _3.
4). In the above 3, the energization times in the time zones t _F1 , t _F2 , and t _F3 are t _F1 : 0.02 to 0.30 s, t _F2 : 0.02 to 0.30 s, and t _F3 : 0.10 to 0.60 s, respectively. _F1, t _F2, pressure at t _{F3, respectively, F 1: 300~2000N, F 2} : 100~1500N, F 3: a 100～1500N, also the time zone t _C1, t _C2, t energizing time at _C3 Are t _C1 : 0.02 to 0.30 s, t _C2 : 0.02 to 0.30 s, and t _C3 : 0.10 to 0.60 s . The current values in the respective time zones t _C1 , t _C2 , and t _C3 are C ₁ : 2.0 , respectively. _{~10.0 kA, C 2: 2.5~11.0 kA} , C 3: 3.0~12.0 indirect spot welding method, which is a kA.

5 . 5. The indirect spot welding method according to any one of 1 to 4 , wherein an electrode having a curved tip is used as the welding electrode.

  According to the present invention, it is possible to stably obtain a meteorite-shaped nugget formed in a molten state, which has been conventionally difficult in indirect spot welding.

It is explanatory drawing of the welding point of the direct spot welding method (a), the series spot welding method (b), and the indirect spot welding method (c). It is the figure which showed the relationship (a) of basic energization time and pressurization force according to this invention, and the relationship (b) of energization time and electric current value. It is explanatory drawing of the welding point of Example 1. FIG.

Hereinafter, the present invention will be specifically described with reference to the drawings.
FIGS. 2A and 2B show the basic relationship between energization time and applied pressure and the relationship between energization time and current value, respectively.
In the present invention, with respect to the electrode pressing force and the current value to be energized, the time zone from the start of energization is divided into three simultaneously or independently, and the electrode pressing force F and the current value C to be energized in each time zone. Control both. Here, when the pressing force F and the current value C are controlled simultaneously, the divided time zones are t ₁ , t ₂ and t _3, and when the pressing force F and the current value C are controlled independently. , T _F1 , t _F2 , t _F3 are time zones for dividing the applied pressure F, t _C1 , t _C21 , t _C3 are time zones for dividing the current value C, and the applied pressure in each time zone is F ₁ , F ₂ and F ₃ current values are indicated by C ₁ , C ₂ and C ₃ .

In the present invention, in the time zone t ₁ , the pressure is increased with the applied pressure F ₁ and the current value C ₁ is energized.
This time zone t ₁ is a time zone in which energization is started while pressing the metal plate on which the electrodes are overlapped, and the formation of the melted portion is started from the heat generated by the contact resistance between the metal plates. When the superimposed metal plates are pressed with an electrode only from one direction and indirect spot welding is performed in a hollow state with no support on the opposite side, the direct pressure welding method in which the pressing force F ₁ is sandwiched between the electrodes from both sides However, if the pressure F ₁ is too low, the contact area between the electrode and the metal plate becomes extremely small, and the current density increases excessively near the surface of the metal plate. Melt preferentially. On the other hand, heat generation and melting cannot be obtained between the metal plates because the energization path is not stable. Further, when the applied pressure F ₁ is low, there may be a problem that the molten metal is scattered due to volume expansion accompanying melting and the surface shape is significantly impaired. Therefore, it is necessary to select the pressurizing force F ₁ as appropriate so that the heat generation and the molten state between the metal plates can be obtained, and the above-described surface shape defects do not occur.

Further, the current value C ₁ needs to be a current value high enough to start melting due to heat generation between the metal plates, but if it is too high, heat generation near the surface of the metal plate in contact with the electrode The metal plates are brought into close contact with each other by melting, the contact area between the metal plates is increased before heat generation and melting starts, and the current density is lowered, so that sufficient heat generation until melting is not obtained. When the current value C ₁ further increases, the metal plate preferentially melts in the vicinity of the surface of the metal plate in contact with the electrode as described above, and the molten metal is scattered, resulting in a poor shape, and the joint strength is also significantly impaired. Deteriorating defects may occur. Therefore, the current value C ₁ is a current density that suppresses heat generation and melting near the surface of the metal plate, maintains a proper contact area between the metal plates, and obtains sufficient heat generation until melting. It is necessary to select appropriately so that the above-described surface shape defects do not occur.

Next, at time period t _2, pressurized with pressure F _2, the current value C ₂ is energized.
This time zone t ₂ is a stage in which the melted portion that has been formed in the time zone t ₁ is further grown. However, the metal plate around the electrode softens due to heat generated by energization, and when the indirect spot welding is performed in a hollow state with no support on the opposite side of the electrode, the tip of the electrode sinks into the metal plate when the metal plate softens. Since the contact area between the electrode and the metal plate or between the metal plate and the metal plate is increased and the current density is lowered, heat generation sufficient for growing the nugget cannot be obtained. Accordingly, in this time zone t ₂ , it is necessary to suppress the electrode tip from sinking into the metal plate by setting the pressure F ₂ to be lower than the pressure F ₁ .

On the other hand, regarding the current value C ₂ , it is important to suppress the current density from being lowered due to the increase in the contact area due to the above-described sinking of the electrode as a current value higher than the current value C ₁ . However, the current value C ₂ is too high, the softening of the metal plate is facilitated by heating in the vicinity of the surface of the metal plate in contact with the electrode, the electrode tip increases the contact area between the metal plates sink to the metal plate current Since the density decreases, heat generation sufficient to further expand the melted portion formed in the time zone t ₁ cannot be obtained. Further, if the current value C ₂ is increased, the side of the metal plate in contact with the electrode, or the opposite side of the scattered molten metal from the surface of the metal plate, not only the appearance becomes scooped shape is seriously impaired, even joint strength decreases Malfunction may occur. Therefore, the current value C ₂ suppresses softening due to heat generation on the surface of the metal plate and suppresses the sinking of the electrode tip into the metal plate, so that the contact area between the metal plates is properly maintained, and the time zone t ₁ It is necessary to select appropriately so that the current density is such that sufficient heat generation can be obtained to further expand the melted portion formed in step 1, and the above-described surface shape defects do not occur.

Next, in the time zone t ₃ , the pressure value F ₃ is pressurized and the current value C ₃ is energized.
This time zone t ₃ is a stage in which the melted portion formed up to the time zone t ₂ is further grown. However, the metal plate around the electrode softens due to heat generated by energization, and when the indirect spot welding is performed in a hollow state with no support on the opposite side of the electrode, the tip of the electrode sinks into the metal plate when the metal plate softens. Since the contact area between the electrode and the metal plate or between the metal plate and the metal plate is increased and the current density is lowered, heat generation sufficient for growing the nugget cannot be obtained. Accordingly, in this time zone t ₃ , it is necessary to suppress the electrode tip from sinking into the metal plate by setting the pressure F ₃ to be lower than the pressure F ₂ . However, when the applied pressure F ₂ is sufficiently low, the applied pressure F ₃ can be made the same as the applied pressure F ₂ .

On the other hand, regarding the current value C ₃ , it is important that the current value is higher than the current value C ₂ to prevent the current density from being lowered due to the increase in the contact area caused by the above-described electrode sinking. However, if the current value C ₃ is too high, the softening of the metal plate is facilitated by heating in the vicinity of the surface of the metal plate in contact with the electrode, the electrode tip increases the contact area between the metal plates sink to the metal plate current Since the density is lowered, heat generation sufficient to further expand the melted portion formed in the time zone t ₂ cannot be obtained. When the current value C ₃ further increases, the molten metal scatters from the surface of the metal plate in contact with the electrode or the opposite side of the metal plate, resulting in a poor shape, and the joint strength also decreases. Problems may occur. Therefore, the current value C ₃ suppresses softening due to heat generation on the surface of the metal plate, and suppresses sinking of the electrode tip into the metal plate, so that the contact area between the metal plates is properly maintained, and the time zone t ₂ It is necessary to select appropriately so that the current density is such that sufficient heat generation can be obtained to further expand the melted portion formed in step 1, and the above-described surface shape defects do not occur.

As described above, the case where the energization is divided into three time zones and both the pressing force F and the current value C are controlled at the same time has been described. However, the pressing force F and the current value C can be controlled independently.
That is, the applied pressure F is divided into time zones t _F1 , t _F2 and t _F3 from the start of energization, the applied pressure F ₂ is made lower than the applied pressure F ₁ , and the applied pressure F ₃ is made lower than the applied pressure F ₂ . On the other hand, the current value C is divided into time zones t _C1 , t _C2 , and t _C3 from the start of energization independently of the time zones t _F1 , t _F2 , and t _{F3. Alternatively} , ₂ may be set higher than the current value C ₁ and the current value C ₃ may be set higher than the current value C ₂ . Thus, a higher effect can be acquired by controlling a pressurizing force and an electric current value each independently.

Here, when it is divided into three time zones t ₁ , t ₂ , t ₃ from the start of energization and both the applied pressure F and the current value C are controlled simultaneously, the energization time in the time zones t ₁ , t ₂ , t ₃ Are preferably about t ₁ : 0.02 to 0.30 s, t ₂ : 0.02 to 0.30 s, and t ₃ : about 0.10 to 0.60 s. In addition, the applied pressure in each of the time zones t ₁ , t ₂ , and t ₃ is F ₁ : 300 to 2000 N, F ₂ : 100 to 1500 N, F ₃ : 100 to 1500 N, and the current values are C ₁ : 2.0 to 10.0 kA, C ₂ : 2.5 to 11.0 kA, and C ₃ : 3.0 to 12.0 kA are preferable.
Further, when the pressure F and the current value C are controlled independently, t _F1 : 0.02 to 0.30 s, t _F2 : 0.02 to 0.30 s, t _F3 : 0.10 to 0.60 s. The applied pressure in each of the time zones t _F1 , t _F2 , t _F3 is set to about F ₁ : 300 to 2000 N, F ₂ : 100 to 1500 N, F ₃ : 100 to 1500 N, and the current value C , T _C1 : 0.02 to 0.30 s, t _C2 : 0.02 to 0.30 s, t _C3 : 0.10 to 0.60 s, and current values in the respective time zones t _C1 , t _C2 , and t _C3 are C ₁ : 2.0 to 10.0 kA, respectively. C ₂ : 2.5 to 11.0 kA, C ₃ : preferably about 3.0 to 12.0 kA.

  Furthermore, in the indirect spot welding of the present invention, it is preferable to use an electrode having a curved end at the tip as the welding electrode. By making the tip of the electrode a curved surface, a sufficient contact area between the electrode and the metal plate is ensured in the initial stage of energization, the current density increases excessively, the metal plate surface is melted and scattered, and the surface shape is Problems that are significantly impaired can be avoided, and furthermore, a necessary and sufficient pressure contact state is formed between the metal plates, the current density is appropriately maintained, and sufficient heat generation is obtained to start melting. Also, in the latter half of the energization, due to heat generation and softening of the metal plate, the tip of the electrode sinks into the metal plate, increasing the contact area between the electrode and the metal plate, and between the metal plate and the metal plate. Although heat generation sufficient for growth may not be obtained, by making the tip of the electrode a curved surface, it is possible to avoid a uniform increase in contact area with respect to the sinking of the tip of the electrode.

  The curved surface of the electrode tip can have a uniform curvature, or a relatively large curvature on the side near the tip with a circle having a predetermined radius centered on the tip, and a relatively small curvature on the side far from the tip. In the case of a uniform curvature, the radius of curvature is desirably 10 to 80 mm. In addition, when a circle with a predetermined radius centered on the tip is a boundary and a relatively large curvature is near the tip, and a relatively small curvature is on the side far from the tip, the radius of the predetermined circle centered on the tip is It is desirable that the radius of curvature on the side close to the tip is 4 to 10 mm, 10 to 80 mm, and the radius of curvature on the side far from the tip is 4 to 12 mm.

The indirect spot welding method was performed with a configuration as shown in FIG. The upper steel plate has a thickness of 0.7mm and the chemical strength shown in Table 1. The tensile strength is 270 MPa or more SPC270 steel plate, and the lower steel plate has a thickness of 1.2mm and the same chemical composition shown in Table 1. The SPC270 steel plate to be formed was placed on a concave metal jig as shown in the figure, the support interval was set to 30 mm, a ground electrode was attached to the lower part of the jig, and the electrode was pressurized from above and welded. In addition, by constraining both ends of the lower steel plate on the jig with the clamps above, and bringing the upper and lower steel plates into close contact with each other, it is easy to cause a shunt between the steel plates when energized, and intentionally directly under the electrodes Conditions were set to make nuggets difficult to form. Table 2 shows the time periods from the start of energization of the applied pressure and current value, and the applied pressure and current values in each time period. Under all conditions, the time from the start to the end of energization was 0.28 s.
For welding, an electrode having a uniform curvature with a radius of curvature of 40 mm and a DC inverter type power source were used.

In Table 2, Invention Examples 1 to 6, in the time period t _1, t _2, t _3, the pressure F ₂ lower than F _1, or F ₂ and the same city to the F ₃ below F _2, In addition, the current value C ₂ is set higher than C ₁ and C ₃ is set higher than C ₂ , and both the pressing force F and the current value C are controlled simultaneously. In Invention Examples 7 to 12, with respect to the pressurizing force F, it is divided into time zones t _F1 , t _F2 , t _F3 from the start of energization, and is the pressurizing force F ₂ lower than F ₁ and F ₃ lower than F ₂ ? or the same city as F _2, with respect to the current value C, and independent of the time zone _{t F1, t F2, t F3} , divided from the start of energization to the time zone _{t C1, t C2, t C3} , the current value C ₂ Is higher than C ₁ , C ₃ is higher than C ₂ , and both the applied pressure F and the current value C are controlled independently.
In Comparative Examples 1 to 6, pressure F, when carried out at a constant current value C to end the energization start, Comparative Example 7, in the time period t _1, t _2, the pressure F ₂ from F ₁ When both the applied pressure F and the current value C are controlled at the same time with the current value C ₂ being lower than C ₁ and the current value C ₂ being simultaneously controlled, the comparative example 8 is the time zone t _F1 , It is _divided into t _F2 , the applied pressure F ₂ is set lower than F ₁ , and the current value C is divided into time zones t _C1 and t _C2 from the start of energization independently of the time zones t _F1 and t _F2 , This is a case where the current value C ₂ is set lower than C ₁ and both the pressurizing force F and the current value C are controlled independently.

Table 3 shows the results of examining the nugget diameter, the nugget thickness, the nugget thickness / diameter, and the appearance defect of each joint when welding with the energization pattern shown in Table 2.
In Table 3, the nugget diameter is the length of the melted portion formed between the upper steel plate and the lower steel plate on the overlap line in the cross section cut around the weld. The nugget thickness was the maximum thickness of the melted portion formed between the upper steel plate and the lower steel plate in the cross section cut at the center of the weld. The nugget thickness / diameter is obtained by dividing the above-described nugget thickness by the nugget diameter. Here, if the nugget diameter is 2.5 mm or more and the nugget thickness / diameter is 0.1 or more, it can be determined as a suitable meteorite-shaped nugget formed in a molten state.
Furthermore, regarding the appearance defect caused by melting and scattering of the welded portion, it has been disclosed regarding the occurrence of surface cracking that occurs between the electrode and the steel plate.

As shown in Table 3, inventive examples 1 to 12 in which indirect spot welding was performed according to the present invention had a sufficient nugget diameter even under a condition in which nuggets were hardly formed directly under an intentionally set electrode. As a result, a molten nugget having a sufficient thickness with respect to this diameter could be obtained, and no appearance defect was observed.
On the other hand, in Comparative Example 1, surface erosion and surface scattering occurred. In Comparative Example 3, the nugget diameter was 2.7 mm, but a sufficient nugget thickness was not obtained, and the nugget thickness / diameter was smaller than 0.1. In other comparative examples, the nugget formation itself was not observed.

  According to the present invention, in an indirect spot welding in which the stacked metal plates are pressed with an electrode only from one direction and the opposite side is carried out in a hollow state without support, a sufficient nugget diameter and against this diameter A meteorite-shaped molten nugget having a sufficient thickness can be stably formed.

1, 2 Metal plate 3, 4 Electrode 5 Welded part 6, 7 Pressure controller 8 Current controller
11, 12 Metal plate
13, 14 electrodes
15-1, 15-2 Welded part
21,22 Metal plate
23 electrodes
24 Power supply terminal
25 welds

Claims (5)

Pressing the welding electrode against the metal plate from one side while pressing the welding electrode against a member on which at least two metal plates are overlapped, and feeding the terminal on the other side of the metal plate at a position separated from the welding electrode In the indirect spot welding method in which welding is performed by energizing between the welding electrode and the power supply terminal, three time zones t ₁ and t ₂ from the start of energization are applied to the electrode pressing force and the current value to be energized. , divided into t _3, the first time period t _1, by energizing pressurized and current value C ₁ under a pressure F ₁ to initiate the formation of the fusion zone, in the next time period t _2, from F ₁ It is energized further grow the fused portion at high current value C ₂ than pressurize and C ₁ at a low pressure F ₂ also further in the next time period t _3, lower than the same or F ₂ and F ₂ the melted portion by energizing at high current value C ₃ than pressurize and C ₂ with pressure F ₃ Indirect spot welding method characterized by gradually grown al. The time zone t according to claim 1. ₁ , T ₂ , T _Three Energizing time at t ₁ : 0.02 to 0.30 s, t ₂ : 0.02 to 0.30 s, t _Three : 0.10 to 0.60 s, each time zone t ₁ , T ₂ , T _Three The applied pressure at F is F ₁ : 300-2000N, F ₂ : 100-1500N, F _Three : 100-1500N, and each time zone t ₁ , T ₂ , T _Three Current values at C are respectively C ₁ : 2.0 to 10.0 kA, C ₂ : 2.5-11.0 kA, C _Three : 3.0 to 12.0 kA, an indirect spot welding method. Pressing the welding electrode against the metal plate from one side while pressing the welding electrode against a member on which at least two metal plates are overlapped, and feeding the terminal on the other side of the metal plate at a position separated from the welding electrode In the indirect spot welding method in which welding is performed by energizing between the welding electrode and the power supply terminal, the electrode pressing force is applied to three time zones t _F1 , t _F2 and t _F3 from the start of energization. In the first time zone t _F1 , pressurization is performed with the pressurizing force F ₁ , in the next time zone t _F2 , pressurization is performed with the pressurizing force F ₂ lower than F ₁ , and in the next time zone t _F3 , F is applied. while pressurizing the same or F ₂ low pressure F ₃ than _2, with respect to the current value to be supplied, the time period t _F1, t _F2, t _F3 independently of the three time periods t from start of energization _C1, divided into t _C2, t _C3, the first time period t _C1, by energizing a current value C ₁ soluble Start the formation parts, in the next time period t _C2, high further grow the fused portion by energizing at high current value C ₂ than C _1, further in the next time period t _C3, than C ₂ current indirect spot welding method characterized in that will further grow the fused portion by energizing a value C _3. The time zone t according to claim 3 _F1 , T _F2 , T _F3 Energizing time at t _F1 : 0.02 to 0.30 s, t _F2 : 0.02 to 0.30 s, t _F3 : 0.10 to 0.60 s, each time zone t _F1 , T _F2 , T _F3 The applied pressure at F is F ₁ : 300-2000N, F ₂ : 100-1500N, F _Three : 100-1500N, and time zone t _C1 , T _C2 , T _C3 Energizing time at t _C1 : 0.02 to 0.30 s, t _C2 : 0.02 to 0.30 s, t _C3 : 0.10 to 0.60 s, each time zone t _C1 , T _C2 , T _C3 Current values at C are respectively C ₁ : 2.0 to 10.0 kA, C ₂ : 2.5-11.0 kA, C _Three : 3.0 to 12.0 kA, an indirect spot welding method. In any one of claims 1 to 4, as the welding electrode, indirect spot welding method characterized by using an electrode tip is curved.

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