KR102010196B1 - Resistance spot welding method - Google Patents

Abstract

Even when welding is performed at several hundred spots in succession, a resistance spot welding method is provided in which a large nugget diameter can be stably formed and sufficient cross tensile strength can be secured. Resistance spot welding method according to the present invention As a method for resistance spot welding of a sheet-ply laminated superposed steel sheet, the main energization, preliminary energization before the main energization, and post-current energization after the main energization, is performed between the energizations. A non-energization time for stopping the energization is provided, and the current value of preliminary energization and post energization is higher than the current value of this energization, and the pressing force is made in two stages, and at least the pressing force of the front end until the completion of preliminary energization is F1 (kN). The pressing force at the rear end after the front end is made F2 (kN), and the pressing force is controlled so as to satisfy F2 / F1? 0.9 from the end of the preliminary energization to the end of the main energization.

Description

Resistance spot welding method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance spot welding method, which is a kind of overlap resistance welding method, and more particularly, to a technique for forming a large nugget (melt portion) without generation of scattering or the like.

In recent years, in order to achieve the reliability of a vehicle body, and to reduce the weight of a vehicle body for the purpose of reducing an air pollutant, the strength of a steel plate is advanced. By adopting a high strength steel sheet, even when it is made thinner and lighter than conventional steel, the same body rigidity is obtained. However, some problems are also pointed out. One of them is that the quality of the welded portion in the vehicle body assembly is lowered as the strength is increased.

As shown in Fig. 1, a resistance spot welding uses a pair of electrodes (bottom electrode) on the upper and lower plates of two or more superposed steel sheets (here, two sets of the lower steel sheet 1 and the upper steel sheet 2). The sandwiching part is melted by energizing with (4) and the upper electrode 5 and energizing while pressurizing, and a nugget (melting part) 6 of a required size is formed to obtain a welded joint.

The quality of the welded joint thus obtained is determined by the size of the nugget diameter or the shear tensile strength (strength when the tensile test is conducted in the shear direction of the joint) or the cross tensile strength (strength when the tensile test is performed in the peeling direction of the joint). And the magnitude of fatigue strength. In particular, while securing the strength and ductility of the steel sheet, the amount of C in the steel sheet tends to increase, but it is known that the cross tensile strength decreases in the high strength steel sheet having a large amount of C-containing components.

As means for securing the cross tensile strength of the welded joint obtained by welding the plate joint including the high strength steel sheet, it is considered to form a nugget having a larger diameter than the conventional one. Conventionally, when the thickness of the plate is t, the nugget diameter is considered to be sufficient as 5 √t, but it can be said that a larger nugget diameter is required in view of the stability at the time of construction. In particular, the welding is carried out at several hundred consecutive spots at the time of construction, but it is known that the electrode tip is worn out, and the nugget diameter obtained is gradually reduced. This problem can be solved by setting a larger nugget diameter.

As one of the problems for obtaining a large nugget diameter, when there is a plate gap between steel sheets at the time of construction, sufficient pressurization state between steel sheets is not obtained, scattering occurs, and sufficient nugget diameter cannot be secured. there is a problem. This is a particularly significant problem in plate joints comprising high strength steel sheets.

Moreover, even if the nugget formed in the plate joint containing a high strength steel plate has secured the predetermined nugget diameter, the subject that brittle fracture | ruptures with respect to a peeling direction load, and the cross tensile strength becomes low also points out. This is because the nugget formed in the plate joint containing the high strength steel sheet is hardened by quenching, and the toughness decreases.

For this problem, various resistance spot welding methods have been proposed in the past.

Patent Literature 1 discloses a method of dividing welding into three steps and suppressing the occurrence of scattering due to rapid heat generation by gradually increasing the current value in the first step of performing nugget generation.

Patent Documents 2 and 3 include a first step of forming a nugget, a second step of lowering a welding current than the first step, and an energization step consisting of a third step of expanding the nugget, and a first step and a second step. By lowering the current value of the 3rd process to the current value of the 3rd process, the dispersion | distribution at the time of energization of a 3rd process is suppressed, and the method of further expanding a nugget while suppressing generation | occurrence | production of a scattering by making a pulsation current in a 3rd process is Is disclosed.

The welding method of patent document 4 is a two-stage or three-stage energization system, and suppression of scattering is carried out by making the 1st electricity supply process which is full electricity supply low current with respect to the 2nd electricity supply process which is this electricity supply which forms a nugget, and after It is said that improvement of cross tensile strength can be achieved by making the 3rd electricity supply process of electricity supply low current.

Patent Document 1: Japanese Patent Publication No. 2003-236674 Patent Document 2: Japanese Patent Publication No. 2010-207909 Patent Document 3: Japanese Patent Publication No. 2010-247215 Patent Document 4: Japanese Patent Publication No. 5418726

However, in the resistance spot welding method described in Patent Documents 1 to 4, a large diameter nugget can be stably formed and sufficient cross tensile strength cannot be secured, and in particular, when welding is performed at several hundred spots continuously, This problem becomes remarkable.

The present invention has been made in view of the above problems, and even in the case where welding is carried out at several hundred spots in succession, a resistance spot welding method capable of stably forming a large diameter nugget and securing sufficient cross tensile strength can be provided. For the purpose of

In order to solve the said subject, the inventors examined the resistance spot welding joint of the plate joint which contains a high tensile strength steel plate. The inventors paid attention to the relationship between the hardness distribution of the high strength steel sheet constituting the welded joint and the occurrence of scattering.

That is, the hardness distribution of the electrode A surface vicinity A shown in FIG. 2 and the hardness distribution of the B vicinity center region of the plate | leaf joint were investigated, and the relationship with generation | occurrence | production of scattering was examined. In addition, A has shown the area | region within 0.2 mm from the electrode side surface of the steel plate 2, and B has shown the area | region within 0.2 mm from the center of the plate | leaf joint 3 in the steel plate 2. As shown in FIG.

As a result, it was found that there is a correlation between the relationship between the hardness distribution in the vicinity of the electrode side surface A of the high strength steel sheet constituting the weld joint and the hardness distribution in the vicinity of the center of the sheet joint and the generated current value of scattering.

In the case where the hardness distributions of the area A near the electrode-side surface and the area B near the center of the sheet joint are compared, the area affected by the welding (heat affected zone) and the heat affected zone soften than the base metal due to the thermal influence of the weld. If attention is paid to one area (hereinafter, the softening part), if the diameter of the heat affected part (width of the heat affected part in the direction of the plate surface) of the electrode A near the surface side B is wider than the center B of the plate joint, there is no scattering and a large nugget diameter It could be seen that you can secure.

If the diameter of the heat affected zone A near the electrode side surface is formed wider than the diameter of the heat affected zone B around the center of the leaf joint, it is considered that the following effects are obtained.

If the nugget is formed, the electrode can be heated to a wider range on the electrode side surface A than the center B near the plate joint, i.e., the electrode A near the plate side center B can be heated more extensively. The surface of the steel sheet in contact with the soften sufficiently. Thereby, the electrode 4 and the steel plate 1, and the electrode 5 and the steel plate 2 fully contact, the pressure force is widely transmitted between the steel plates 1 and 2, and as a result, the nugget 6 is formed. At the time, it is considered that generation of scattering is suppressed.

Further, the surface of the steel sheet in contact with the electrode is softened sufficiently, and the contact range between the electrode and the steel sheet is widened, so that the temperature at the contact portion between the electrode (copper electrode) and the plated layer on the surface of the steel sheet at the time of electrode opening also changes to the low temperature side. . In the case where the contact range between the electrode and the steel sheet is narrow, cooling after completion of welding is not sufficient, and the plating layer and the copper electrode react chemically, which causes the wear of the copper electrode when the electrode is opened. By softening sufficiently and widening the contact range of an electrode and a steel plate, it is thought that this reaction can be suppressed and a favorable electrode state can be maintained. It is estimated by this that a favorable electrode state can be maintained also in a continuous spot test.

Although the above is a change during welding, the inventors also found the influence of the softening portion on the breaking strength of the formed joint. That is, the fracture | rupture in a cross tension test can be suppressed by enlarging a softening part and increasing the width | variety (hereinafter softening width) of the softening part in the plate surface direction. When the peeling direction of the joint like the cross tensile test is in the load direction, the opening stress applied to the nugget end is reduced by the yielding of the softened portion. As a result, by expanding the softening width, the break at the nugget can be suppressed, and as a result, the cross tensile strength can be improved. This softening width was found to be obtained by appropriately performing post-current energization after nugget formation.

Moreover, the cross tensile strength can also be improved by diffusing and reducing P segregation of the nugget edge part by heating at high temperature at the time of energization after nugget formation.

By thus softening the area A near the electrode-side surface wider than the area B near the center of the plate joint and stably forming a nugget while suppressing the occurrence of scattering, a sufficient nugget diameter can be obtained even when welding at several hundred consecutive spots. I found something that I could secure.

As described above, in order to soften the area A near the electrode-side surface before and after nugget formation, pre-current and post-current energization with current values higher than the current value of the current energization that forms the nugget 6 before and after the nugget 6 is formed. This can be achieved by executing

For that purpose, the high current density is increased in the vicinity of the electrode by increasing the pre-current current before nugget formation. As a result, a predetermined amount of heat is obtained in the vicinity of the electrode, and A near the electrode side surface is softened before nugget formation. In addition, in order to enlarge the softening part, it is necessary to set an appropriate non-energization (cooling) time between each energization. This is because, during the period of non-energization time, the temperature away from the electrode is increased by the heat transfer to soften the portion away from the electrode and enlarge the softening portion.

In order to obtain this effect, it is necessary to set the pressing force higher than the pressing force of this energization in preliminary energization. This is to secure a wide contact portion between the electrode and the steel sheet by making the pressing force in the preliminary energization a higher pressure in order to obtain a wider heat generation during the initial high current energization.

In addition, after the nugget formation, after energizing at a current value higher than the current value forming the nugget 6, high current density is obtained in the vicinity of the electrode, and as a result, a predetermined amount of heat is obtained in the vicinity of the electrode, resulting in nugget formation. Afterwards, it is considered that A near the electrode side surface can be softened. In addition, when enlarging the softening part after nugget formation by the said electricity supply, the nugget 6 can be heated to high temperature, and P segregation of a nugget edge part can be alleviated. Moreover, by disposing an appropriate non-energization (cooling) between the main energization and the post energization after nugget formation, it is possible to keep the vicinity of the electrode at a low temperature and not to cure it.

The present invention has been obtained as a result of this study, and the gist structure is as follows.

[1] A method of resistance spot welding of a sheet-ply superimposed steel plate, comprising: pre-power supply before the main power supply, pre-power supply after the main power supply, and post-current power supply after the main power supply, with no interruption of the current supply. The preliminary time is provided, the current value of preliminary energization and post-current energization is higher than the current value of this energization, and the pressing force is made into two stages, and the pressing force of the front end until at least the completion of preliminary electricity supply is F1 (kN), and the rear end after the said front end The resistance spot welding method of controlling the pressing force so as to satisfy the formula (1) after the completion of preliminary energization, with the pressing force of F2 (kN):

F2 / F1≤0.9 (1).

[2] The resistance spot welding method according to [1], which further satisfies Formula (2):

0.5≤F2 / F1 (2).

[3] The current value of this energization is Im [kA], the energization time is Tm [ms], the current value of preliminary energization is Ip [kA], and the energization time is Tp [ms]. When the non-energization time of Tcp [ms], the current value of post-current energization is Ir [kA], the energization time is Tr [ms], and the non-energization time between the current and post-current energization is Tcr [ms]. The resistance spot welding method as described in [1] or [2], which satisfies the formulas (3) to (8):

1.05 × Im≤Ip≤2.0 × Im (3)

1.05 × Im≤Ir≤2.0 × Im (4)

40ms≤Tp≤100ms (5)

40ms≤Tr≤100ms (6)

10ms≤Tcp≤60ms (7)

80 ms ≤ Tcr ≤ 300 ms (8).

[4] The resistance spot welding method according to [3], which further satisfies the following formulas (9) and (10):

160ms≤Tm≤500ms (9)

0.25≤Rpm≤0.95 (10)

However, Rpm = (Ip / Im) ² × (Tp / Tm).

[5] The resistance spot welding method according to [3] or [4], which further satisfies the following formula (11):

0.10≤Rmr≤1.50 (11)

However, Rmr = (Ir / Im) ² × (Tr / Tm).

[6] Preliminary energization is performed two or more times, and a non-energization time for stopping the energization is provided between each preliminary energization, and preliminary energization after the second is performed at a current value equal to or less than the current value of the previous preliminary energization. The resistance spot welding method according to any one of [1] to [5].

[7] The resistance spot welding method according to any one of [1] to [6], wherein the energization is performed two or more times, and a non-energization time for stopping the energization is provided between each subsequent energization.

[8] The resistance spot welding method according to any one of [1] to [7], wherein at least one steel sheet in the plate joint is a high strength steel sheet having a tensile strength of 780 MPa or more.

According to the present invention, it is possible to provide a resistance spot welding method capable of stably forming a large nugget while preventing generation of scattering and ensuring sufficient cross tensile strength.

1 is a diagram showing an outline of resistance spot welding.
2 is a view for explaining a resistance spot welding method according to the present invention.
It is a figure which shows the relationship between the energization time and electric current value of the resistance spot welding method which concerns on this invention.

In the resistance spot welding method of the present invention, as shown in FIG. 1, a pair of electrodes 4 and 5 is disposed on the plate joint 3 overlapping a plurality of steel sheets (the lower steel sheet 1 and the upper steel sheet 2). ) And energized while pressurizing to form a nugget 6 of a required size to obtain a welded joint.

This spot welding method includes a pair of electrodes 4 and 5 which are upper and lower, and can be energized while pressurizing by arranging a portion to be welded between the pair of electrodes 4 and 5, and the pressing force and welding during welding It can implement using the welding apparatus which has the pressure control function and welding current control function which can control an electric current, respectively. The pressurization mechanism (air cylinder, servo motor, etc.), the current control mechanism (AC, DC, etc.), the type (political type, robot gun, etc.) of a welding apparatus are not specifically limited.

In the resistance spot welding method of the present invention, the main energization for growing the nugget 6 to a predetermined diameter, preliminary energization before the main energization, and after energization after the main energization are performed.

In the resistance spot welding method according to the present invention, preliminary energization is performed at a current value higher than the current value of the main current forming the nugget 6, so that the electrode side surface A shown in FIG. 2 is sufficiently softened before nugget formation. Then, after preliminary energization, the energization is stopped to increase the ambient temperature by heat transfer during non-energization, soften the portion away from the electrode, and enlarge the softening portion near the electrode side surface A before nugget formation.

Thereby, in this energization which forms the nugget 6, near-electrode side surface A is softened sufficiently, and the electrode 4 and the steel plate 1, the electrode 5, and the steel plate 2 are made to fully contact. Can be.

Fig. 3A is a diagram showing the relationship between the energization time and the current value of one example of the resistance spot welding method according to the present invention.

In the present invention, before and after nugget formation, in order to sufficiently soften the vicinity A of the electrode side surface, the current values of pre-current and post-current energization are both set higher than the current values of current energization. The present invention further provides a pressing force of two stages, at least the pressing force of the front end until the end of preliminary energization is set to F1 (kN), and the pressing force of the rear stage after the shearing is set to F2 (kN). The pressing force is controlled to satisfy. The timing for reducing the pressing force is preferably between the end of the preliminary energization and the end of the main energization. That is, it is preferable to control the pressing force so as to satisfy the formula (1) between the end of the preliminary energization and the end of the main energization.

F2 / F1≤0.9 (1)

This is because, in the case of F2 / F1> 0.9, no significant difference is obtained in the contact area between the electrode and the surface of the steel sheet. In addition, although F1 is not specifically limited, It is preferable that it is 3 kN or more, and it is more preferable that it is 4 kN or more from the point which fully secures the contact area of an electrode and the steel plate surface. In addition, although F1 is not specifically limited, From a viewpoint of nugget formation, it is preferable that it is 10 kN or less, and it is more preferable that it is 9 kN or less.

Moreover, it is preferable to satisfy Formula (2).

0.5≤F2 / F1 (2)

In the case of F2 / F1 <0.5, the pressure in the vicinity of the nugget is not sufficient, which causes scattering. F2 / F1 is more preferably 0.6 or more, and more preferably 0.7 or more.

In addition, the current value of this energization is Im [kA], the energization time is Tm [ms], the preliminary current value is Ip [kA], and the energization time is Tp [ms]. When the time is Tcp [ms], the current value of the later energization is Ir [kA], the energization time is Tr [ms], and the non-energization time between this energization and the later energization is Tcr [ms]. It is preferable that the spot welding method satisfies the following formulas (3) to (8).

1.05 × Im≤Ip≤2.0 × Im (3)

1.05 × Im≤Ir≤2.0 × Im (4)

If the current value Ip of preliminary energization is 1.05xIm or more, the softening effect of A near electrode side surface will become high. Moreover, when the current value Ir of post-current supply is 1.05 * Im or more, the softening effect of A near an electrode side surface will become high, and the effect of post-current power supply which alleviates the segregation of P of the nugget edge part will further be improved. If the current value Ip of preliminary electricity supply and the current value Ir of post electricity supply are 2.0xIm or less, melting will become suitable and it will become easy to suppress generation | occurrence | production of scattering further. Ip and Ir are more preferably 1.80 × Im or less, and more preferably 1.60 × Im or less.

40ms≤Tp≤100ms (5)

40ms≤Tr≤100ms (6)

Similarly, when the energization time Tp of preliminary energization is 40 ms or more, the softening effect of A near electrode side surface becomes high. Moreover, when the energization time Tr of post electricity supply is 40 ms or more, the softening effect of A near an electrode side surface will become high further, and the effect of post electricity supply to relieve segregation of P of the nugget edge further will be heightened. When the energization time Tp of preliminary electricity supply and the electricity supply time Tr of the post electricity supply are 100 ms or less, melting becomes suitable and it becomes easy to suppress generation | occurrence | production of scattering further.

10ms≤Tcp≤60ms (7)

If the non-energization time Tcp is 10 ms or more, it can suppress that heat generate | occur | produces by the next energization, and the effect of softening becomes further high. If the non-energization time Tcp is 60 ms or less, cooling will not progress too much and reheating time in this electricity supply will not become excessive.

80ms≤Tcr≤300ms (8)

If the non-energization time Tcr is 80 ms or more, it will become easy to suppress that scattering arises by becoming too high and remelting in post electricity supply. If the non-energization time Tcr is 300 ms or less, the time for reheating in subsequent energization will not be excessive.

In addition, it is preferable that the energization time Tm of this electricity supply satisfies Formula (9).

160ms≤Tm≤500ms (9)

If the energization time Tm is 160 ms or more, formation of the nugget is stabilized, and the required nugget diameter can be obtained more easily. More preferably, Tm is 200 ms or more. If the energization time Tm is larger than 500 ms, the welding time becomes long and there is a fear that the productivity deteriorates.

Moreover, it is preferable to satisfy Formula (10).

0.25≤Rpm≤0.95 (10)

However, let Rpm = (Ip / Im) ² × (Tp / Tm).

Rpm means the ratio of the input energy of preliminary energization to the input energy of this energization. If Rpm is 0.25 or more, heat generation is sufficiently obtained and the effect of softening is further increased. When Rpm is 0.95 or less, it becomes easy to suppress generation | occurrence | production of the scattering resulting from steep heat generation. Rpm is more preferably 0.85 or less, and even more preferably 0.75 or less.

Regarding post energization, it is preferable to satisfy the formula (11).

0.10≤Rmr≤1.50 (11)

However, let Rmr = (Ir / Im) ² × (Tr / Tm).

Rmr means the ratio of the input energy of the post current to the input energy of this current. If Rmr is 0.10 or more, the heat generation does not become too small and the effect of segregation relaxation is further enhanced. When Rmr is 1.50 or less, it becomes easy to suppress remelting by steep heat generation further. Rmr is more preferably 0.15 or more, and still more preferably 0.20 or more. Further, Rmr is more preferably 1.25 or less, and more preferably 1.00 or less.

In addition, as shown in FIG.3 (b), preliminary energization is performed 2 or more times as needed, a non-energization (cooling) is provided between each preliminary energization, and the preliminary energization after the 2nd time is performed last time. The current value is less than or equal to the current value of preliminary energization. Thereby, the effect which softens A near the electrode side surface before formation of the nugget by this energization becomes high. It is preferable that the time of non-energization between each said preliminary energization is 10 ms or more and 60 ms or less similarly to the non-energization time Tcp between preliminary electricity supply and this electricity supply.

In addition, by performing two or more post-current energizations after the main energization, and providing no energization (cooling) between each post-current energization, the effect of softening A near the electrode side surface is further enhanced, and segregation of P at the nugget end is alleviated. The effect is higher. It is preferable that the time of non-energization between each said electricity supply is 80 ms or more and 300 ms or less similarly to the non-energization time Tcr between this electricity supply and the after electricity supply.

As described above, in the present invention, by setting the pressing force high in preliminary energization, the heat generated by the initial high current energization can be obtained more widely, and the surface A near the electrode side surface shown in FIG. 2 can be sufficiently softened.

Further, in the present invention, by appropriately controlling the energization time Tp and the current value Ip of preliminary energization, the electrode side surface A is sufficiently softened before nugget formation, and in this energization, sufficient pressing force is secured and the energization path is widened. A large nugget diameter can be obtained more stably while further suppressing the occurrence of scattering. In addition to this, by appropriately controlling the non-energization time after preliminary energization, the softening portion near the electrode side surface A can be further enlarged before the nugget formation.

In particular, when assembling a vehicle body, tens to hundreds of points are welded continuously, but the tip of the electrode is worn out, and the nugget diameter obtained is gradually reduced. On the other hand, by applying this invention, even if it is a case where welding is performed at several hundred spots continuously, a large nugget diameter can be obtained stably.

It is preferable to apply this invention to the welding of the plate joint 3 containing at least 1 high strength steel plate. Compared with a normal steel sheet, the high strength steel sheet tends to be scattered due to the plate gap. Therefore, the effect of the present invention can be further enjoyed by applying the present invention to the welding of such a plate joint. Specifically, in the case where at least one steel sheet in the plate joint is a high strength steel sheet having a tensile strength of 780 MPa or more, it is preferable to apply the present invention.

Example

As an embodiment of the present invention, as shown in FIG. 1 described above, resistance spot welding is performed on a plate joint 3 in which two steel sheets (the lower steel sheet 1 and the upper steel sheet 2) are superposed, Resistance spot welded seams were fabricated. The apparatus used for resistance spot welding is a C gun type welding apparatus which presses an electrode by a servo motor. In addition, a power supply is a DC power supply.

The energization at this time was performed under the conditions shown in Table 1.

As the electrodes 4 and 5, a DR-type electrode of alumina dispersion copper having a radius of curvature R40 at the tip and a tip diameter of 8 mm was used.

In Table 1, the result of having investigated about the nugget diameter (it represents with "diameter" in a table | surface) is shown. In addition, the nugget diameter was evaluated in the etching structure of the cut section (section cut | disconnected so that it may be perpendicular | vertical to the surface of a board and pass about the center of a welding point based on description of JIS Z 3139). The nugget diameter was set to t with a plate thickness of 5.5 √t or more ◎, 5.0√t or more and less than 5.5√t t and less than 5.0√t ×. In addition, cross tensile strength (CTS) was evaluated in accordance with JIS Z 3137. In addition, after performing 300 RBI welding with the same steel plate at 20 mm pitch, the nugget diameter was similarly evaluated and the change was evaluated. In addition, Tf of Table 1 shows the time (ms) from starting preliminary energization by pressing force F1, and stopping pressurization by said F1.

TABLE 1

As shown in Table 1, when resistance spot welding was carried out according to the present invention, compared with the comparative example, even after performing the continuous spot, there is no scattering and a large nugget diameter of 5.0√t or more is formed, and cross tensile strength is achieved. It can be seen that even higher than other conditions.

One; Lower Grater 2 Upper Grater
3; Leaf joint 4; Bottom electrode
5; Upper electrode 6; Nugget

Claims (24)

As a method of spot welding the plate joints overlapping steel sheets,
The non-energization time for carrying out this energization, preliminary energization before this energization, and after energization after this energization, and stopping energization between each said energization is provided,
The current value of preliminary energization and post-current energization is higher than the current value of this energization,
In addition, the pressing force is set to two stages, and the pressing force at least before the end of the preliminary energization is set to F1 (kN), and the pressing force at the rear end of the preceding stage is set to F2 (kN), and the pressing force is satisfied after the completion of preliminary energization. Resistance spot welding method characterized in that for controlling:
F2 / F1≤0.9 (1). The method of claim 1,
The resistance spot welding method further characterized by the following equation (2):
0.5≤F2 / F1 (2). The method according to claim 1 or 2,
The current value of this energization is Im [kA], the energization time is Tm [ms],
Ip [kA] is the current value of preliminary energization and Tp [ms],
The non-energization time between the standby energization and this energization is Tcp [ms],
Current value of Ir [kA], time of Tr [ms],
When the non-energization time between this energization and the after energization is set to Tcr [ms],
A resistance spot welding method characterized by satisfying the following formulas (3) to (8):
1.05 × Im≤Ip≤2.0 × Im (3)
1.05 × Im≤Ir≤2.0 × Im (4)
40ms≤Tp≤100ms (5)
40ms≤Tr≤100ms (6)
10ms≤Tcp≤60ms (7)
80 ms ≤ Tcr ≤ 300 ms (8). The method of claim 3, wherein
A resistance spot welding method characterized by further satisfying the following formulas (9) and (10):
160ms≤Tm≤500ms (9)
0.25≤Rpm≤0.95 (10)
However, Rpm = (Ip / Im) ² × (Tp / Tm). The method of claim 3, wherein
A resistance spot welding method, which further satisfies the following formula (11):
0.10≤Rmr≤1.50 (11)
However, Rmr = (Ir / Im) ² × (Tr / Tm). The method of claim 4, wherein
A resistance spot welding method, which further satisfies the following formula (11):
0.10≤Rmr≤1.50 (11)
However, Rmr = (Ir / Im) ² × (Tr / Tm). The method according to claim 1 or 2,
Carry out preliminary energization two or more times,
Between each preliminary energization, a non-energization time for stopping the energization is provided.
A resistance spot welding method, wherein the preliminary energization after the second time is performed at a current value equal to or less than the current value of the previous preliminary energization. The method of claim 3, wherein
Carry out preliminary energization two or more times,
Between each preliminary energization, a non-energization time for stopping the energization is provided.
A resistance spot welding method, wherein the preliminary energization after the second time is performed at a current value equal to or less than the current value of the previous preliminary energization. The method of claim 4, wherein
Carry out preliminary energization two or more times,
Between each preliminary energization, a non-energization time for stopping the energization is provided.
A resistance spot welding method, wherein the preliminary energization after the second time is performed at a current value equal to or less than the current value of the previous preliminary energization. The method of claim 5,
Carry out preliminary energization two or more times,
Between each preliminary energization, a non-energization time for stopping the energization is provided.
A resistance spot welding method, wherein the preliminary energization after the second time is performed at a current value equal to or less than the current value of the previous preliminary energization. The method of claim 6,
Carry out preliminary energization two or more times,
Between each preliminary energization, a non-energization time for stopping the energization is provided.
A resistance spot welding method, wherein the preliminary energization after the second time is performed at a current value equal to or less than the current value of the previous preliminary energization. The method according to claim 1 or 2,
After the power is applied twice or more,
A resistance spot welding method, wherein a non-energization time for stopping the energization is provided between the respective energizations. The method of claim 3, wherein
After the power is applied twice or more,
A resistance spot welding method, wherein a non-energization time for stopping the energization is provided between the respective energizations. The method of claim 4, wherein
After the power is applied twice or more,
A resistance spot welding method, wherein a non-energization time for stopping the energization is provided between the respective energizations. The method of claim 5,
After the power is applied twice or more,
A resistance spot welding method, wherein a non-energization time for stopping the energization is provided between the respective energizations. The method of claim 6,
After the power is applied twice or more,
A resistance spot welding method, wherein a non-energization time for stopping the energization is provided between the respective energizations. The method of claim 7, wherein
After the power is applied twice or more,
A resistance spot welding method, wherein a non-energization time for stopping the energization is provided between the respective energizations. The method according to claim 1 or 2,
At least one steel sheet in the plate joint is a resistance spot welding method, characterized in that the high strength steel sheet having a tensile strength of 780 MPa or more. The method of claim 3, wherein
At least one steel sheet in the plate joint is a resistance spot welding method, characterized in that the high strength steel sheet having a tensile strength of 780 MPa or more. The method of claim 4, wherein
At least one steel sheet in the plate joint is a resistance spot welding method, characterized in that the high strength steel sheet having a tensile strength of 780 MPa or more. The method of claim 5,
At least one steel sheet in the plate joint is a resistance spot welding method, characterized in that the high strength steel sheet having a tensile strength of 780 MPa or more. The method of claim 6,
At least one steel sheet in the plate joint is a resistance spot welding method, characterized in that the high strength steel sheet having a tensile strength of 780 MPa or more. The method of claim 7, wherein
At least one steel sheet in the plate joint is a resistance spot welding method, characterized in that the high strength steel sheet having a tensile strength of 780 MPa or more. The method of claim 12,
At least one steel sheet in the plate joint is a resistance spot welding method, characterized in that the high strength steel sheet having a tensile strength of 780 MPa or more.

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