JP6225717B2 - Formation method of welded joint - Google Patents

Description

  The present invention relates to a method for forming a welded joint, and is particularly suitable for use in performing mash seam welding on a plurality of steel plates.

For example, in the steel manufacturing process, the tip and tail ends of the coil are joined by mash seam welding in order to continuously process the coil manufactured by the cold rolling process in the subsequent process (continuous annealing process or plating process). To be done.
In mash seam welding, the overlap margin of the steel plates is made smaller than the width of the disc electrodes, and a pair of discs is pressed and energized by a pair of disc electrodes from above and below the overlap portion of the plurality of steel plates. By moving the electrode along the planned welding location while rotating the electrode, the planned welding location is continuously welded.

  When a hard steel plate such as a high-strength steel plate is welded, martensite is formed by heating and rapid cooling of the planned joint location during the welding process, so the joint (solidified and heat-affected zone of the molten metal) is hard. It becomes a brittle organization. For this reason, there exists a possibility that a junction part may fracture | rupture (in the use mentioned above, there exists a possibility that the junction part of a coil may fracture | rupture in a post process). In addition, since the joint portion is hard and brittle, the joint portion may not be easily processed.

Therefore, in resistance spot welding, after applying resistance spot welding by pressing and energizing with a pair of electrodes from above and below the overlapped portion of the steel plates, pressurizing and energizing again with the electrodes to the spot welded portion. On the other hand, it has been proposed to perform tempering (tempering) (see Patent Document 1).
In lap seam welding, in which the overlap of the steel plates is made larger than the width of the disk electrode, lap seam welding is performed, and then the temper treatment (tempering) is performed on the seam welded portion using a forming heat source. Has been proposed (see Patent Document 2).

JP 2001-170776 A JP 2010-516471 A Japanese Patent No. 4864173

Shinichi Matsuyama, Ikuo Takahashi, Kazuyoshi Hasegawa, “Basics and Practice of Resistance Welding”, Sangyo Shuppan, September 17, 2011

However, in resistance spot welding as described in Patent Document 1, since the electrode is not moved in the surface direction of the steel sheet while being in contact with the steel sheet, the technique for resistance spot welding is performed by overlapping the steel sheets while rotating the electrode. It cannot be applied as it is to seam welding in which parts are continuously welded.
In the technique described in Patent Document 2, a molding resistance heating coil, a molding induction coil, or the like is used as a molding heat source. Therefore, there is a possibility that the equipment for performing the tempering (quenching) becomes large.

By the way, when mash seam welding is performed, the thickness of the joint portion increases, so the joint portion is pressed with a swaging roll (also referred to as a “planish roll”) from above and below to reduce the thickness of the joint portion to other regions. It has been proposed to approximate the thickness (see Patent Document 3).
However, in the technique described in Patent Document 3, a steel roll different from the roll used in mash seam welding is used as the swaging roll. For this reason, there is a possibility that the equipment for performing swaging may become large.

The present invention has been made in view of the above problems, and it is a first object of the present invention to improve the mechanical characteristics of a joint formed by mash seam welding with the simplest possible structure. 1 purpose.
Further, in addition to improving the mechanical properties of the joint formed by mash seam welding, the second is to realize the control of the thickness of the overlapped portion of the steel plates with the simplest possible structure. The purpose.

A first example of a method for forming a welded joint according to the present invention is a welded joint forming method for forming a welded joint by performing mash seam welding on an overlapped portion of a plurality of steel plates. An upper disk electrode and a lower disk electrode arranged above and below, respectively, with the upper disk electrode and the lower disk electrode made of copper alloy rotated, respectively. While performing pressurization and energization with respect to the planned joining location of the overlapped portion by the side disc electrode, the upper disc electrode and the lower disc electrode are arranged in the plurality of locations along the planned joining location. A first step of performing mash seam welding on a planned joining portion of the overlapped portion by moving the steel plate relative to the steel plate, and forming the bonded portion, and after the first step, the overlap Upper circle placed above and below the mating part An electrode and a lower disk electrode, each of which is an upper disk electrode and a lower disk electrode made of a copper alloy and is rotated by the upper disk electrode and the lower disk electrode. The upper disk electrode and the lower disk electrode are moved relative to the plurality of steel plates so as to be along the bonding portion while being pressurized and energized. A second step of performing heat treatment on the part, and the upper disc electrode and the lower disc electrode used in the first step, and the second step used in the second step The upper disk electrode and the lower disk electrode are the same, and the carbon equivalent Ceq represented by the following formula (A) of at least one of the plurality of steel plates is 0.31. [Mass%] or more.
A second example of a method for forming a welded joint according to the present invention is a welded joint forming method for forming a welded joint by performing mash seam welding on a plurality of overlapped portions of steel plates, An upper disk electrode and a lower disk electrode arranged above and below, respectively, with the upper disk electrode and the lower disk electrode made of copper alloy rotated, respectively. While performing pressurization and energization with respect to the planned joining location of the overlapped portion by the side disc electrode, the upper disc electrode and the lower disc electrode are arranged in the plurality of locations along the planned joining location. A first step of performing mash seam welding on a planned joining portion of the overlapped portion by moving the steel plate relative to the steel plate, and forming the bonded portion, and after the first step, the overlap Upper circle placed above and below the mating part An electrode and a lower disk electrode, each of which is an upper disk electrode and a lower disk electrode made of a copper alloy and is rotated by the upper disk electrode and the lower disk electrode. The upper disk electrode and the lower disk electrode are moved relative to the plurality of steel plates so as to be along the bonding portion while being pressurized and energized. A carbon equivalent Ceq represented by the following formula (A) of at least one steel plate of the plurality of steel plates is 0.31 [ Mass%] or more, and a pressure applied to the overlapping portion in the first step is P1 [kN], and the upper disk electrode and the lower circle in the first step The relative movement speed of the plate electrode with respect to the plurality of steel plates. The welding speed is set to V1 [m / min], the welding current that is the value of the current flowing through the plurality of steel plates in the first step is set to I1 [kN], and the overlapping portion is set to the overlapped portion in the second step. The applied pressure that is the applied pressure is P2 [kN], and the welding speed that is the relative moving speed of the upper disk electrode and the lower disk electrode in the second step with respect to the plurality of steel plates is V2. When [m / min] and the welding current, which is the value of the current flowing through the plurality of steel plates in the second step, is I2 [kN], the following formulas (B), (C), and ( D) Formula is satisfied, It is characterized by the above.
A third example of the method for forming a welded joint according to the present invention is a welded joint forming method for forming a welded joint by performing mash seam welding on an overlapped portion of a plurality of steel plates. An upper disk electrode and a lower disk electrode arranged above and below, respectively, with the upper disk electrode and the lower disk electrode made of copper alloy rotated, respectively. While performing pressurization and energization with respect to the planned joining location of the overlapped portion by the side disc electrode, the upper disc electrode and the lower disc electrode are arranged in the plurality of locations along the planned joining location. A first step of performing mash seam welding on a planned joining portion of the overlapped portion by moving the steel plate relative to the steel plate, and forming the bonded portion, and after the first step, the overlap Upper circle placed above and below the mating part An electrode and a lower disk electrode, each of which is an upper disk electrode and a lower disk electrode made of a copper alloy and is rotated by the upper disk electrode and the lower disk electrode. The upper disk electrode and the lower disk electrode are moved relative to the plurality of steel plates so as to be along the bonding portion while being pressurized and energized. A second step of performing a heat treatment on the part, wherein the second step performs the heat treatment on the joint, and changes the thickness of the overlapping portion to the thickness of the other region. The carbon equivalent Ceq represented by the following formula (A) of at least one steel plate among the plurality of steel plates is 0.31 [% by mass] or more. It is characterized by that.
A fourth example of the method for forming a welded joint according to the present invention is a welded joint forming method for forming a welded joint by performing mash seam welding on an overlapped portion of a plurality of steel plates. An upper disk electrode and a lower disk electrode arranged above and below, respectively, with the upper disk electrode and the lower disk electrode made of copper alloy rotated, respectively. While performing pressurization and energization with respect to the planned joining location of the overlapped portion by the side disc electrode, the upper disc electrode and the lower disc electrode are arranged in the plurality of locations along the planned joining location. A first step of performing mash seam welding on a planned joining portion of the overlapped portion by moving the steel plate relative to the steel plate, and forming the bonded portion, and after the first step, the overlap Upper circle placed above and below the mating part An electrode and a lower disk electrode, each of which is an upper disk electrode and a lower disk electrode made of a copper alloy and is rotated by the upper disk electrode and the lower disk electrode. The upper disk electrode and the lower disk electrode are moved relative to the plurality of steel plates so as to be along the bonding portion while being pressurized and energized. A second step of performing heat treatment on the part, and the relative movement direction of the upper disc electrode and the lower disc electrode in the first step with respect to the plurality of steel plates, and The relative moving direction of the upper disc electrode and the lower disc electrode in the second step with respect to the plurality of steel plates is opposite, and at least one of the plurality of steel plates The carbon equivalent Ceq represented by the following formula (A) is 0 And characterized in that 31 [wt%] or more.
Ceq = [C] + [Si] / 30 + [Mn] / 20 + 2 [P] +4 [S] (A)
1.0 × P1 ≦ P2 ≦ 1.5 × P1 (B)
0.4 × V1 ≦ V2 ≦ 0.8 × V1 (C)
1.0 × I1 ≦ I2 ≦ 1.5 × I1 (D)
Here, [C], [Si], [Mn], [P], and [S] are the contents (mass%) of C, Si, Mn, P, and S, respectively.

According to the present invention, mash seam welding and heat treatment are performed using a disc electrode made of the same kind of copper alloy. Therefore, it is possible to improve the mechanical characteristics of the joint formed by mash seam welding with the simplest possible structure.
In addition, with the same kind of copper alloy disk electrode, when the heat treatment is performed, the processing for reducing the thickness of the overlapped portion is also performed at the same time. Therefore, in addition to improving the mechanical properties of the joint formed by mash seam welding, it is possible to control the thickness of the overlapping portion with the simplest possible structure.

It is a figure which shows an example of a structure of a seam welder. It is a figure which shows an example of arrangement | positioning of the steel plate at the time of performing mash seam welding, an upper disc electrode, and a lower disc electrode. It is a figure which shows notionally an example of the method of performing mash seam welding and heat processing. It is a figure which shows notionally the 1st example of the mode of a junction part. It is a figure explaining an example of swaging. It is a figure which shows notionally the 2nd example of the mode of a junction part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
First, a first embodiment of the present invention will be described.
<Configuration of seam welder>
FIG. 1 is a diagram illustrating an example of the configuration of the seam welder 100. For convenience of explanation, only necessary portions are simplified in each drawing as necessary. In addition, the x, y, and z coordinates given to each figure indicate the relationship of directions in each figure, and the origin of the x, y, and z coordinates is not necessarily at the position shown in each figure.

  In FIG. 1, a seam welder 100 includes an upper disc electrode 110a, a lower disc electrode 110b, an upper electrode head 120a, a lower electrode head 120b, an upper arm portion 130a, a lower arm portion 130b, The pressure device 140, the body 150, and the welding power source 160 are included.

The upper disk electrode 110a and the lower disk electrode 110b are disk-shaped electrodes. Both the upper disk electrode 110a and the lower disk electrode 110b are electrodes made of a copper alloy. In the present embodiment, the upper disk electrode 110a and the lower disk electrode 110b are both electrodes made of a Cu—Cr alloy. In the present embodiment, the upper disk electrode 110a and the lower disk electrode 110b are the same.
The shape of the tip surfaces of the upper disk electrode 110a and the lower disk electrode 110b (the surface where the upper disk electrode 110a and the lower disk electrode 110b face each other in FIG. 1) is a smooth flat shape (so-called flat shape; F type).

The upper disk electrode 110a and the lower disk electrode 110b are attached to the upper electrode head 120a and the lower electrode head 120b, respectively, so as to be rotatable. In the present embodiment, the upper disk electrode 110a is rotated by a rotation mechanism such as a gear disposed on the upper electrode head 120a, and the lower disk electrode 110b is rotated along with the rotation of the upper disk electrode 110a. I am doing so. That is, in this embodiment, the upper disk electrode 110a is driven to drive the lower disk electrode 110b.
In the present embodiment, the rotation mechanism is configured so that the upper electrode head 120a and the lower electrode head 120b rotate in the normal rotation and the reverse rotation, respectively. The upper disk electrode 110a and the lower disk electrode 110b rotate in opposite directions. For example, when the upper disk electrode 110a rotates in the clockwise direction, the lower disk electrode 110b rotates in the counterclockwise direction.

The upper arm portion 130a is for supporting the upper electrode head 120a to which the upper disk electrode 110a is attached. As shown in FIG. 1, the upper electrode head 120a is attached so that the upper surface of the upper electrode head 120a faces the lower surface of the movable shaft 141 of the pressurizing device 140 disposed inside the upper arm portion 130a. In the present embodiment, the movable shaft 141 disposed on the upper arm portion 130a is attached to the body 150 so as to be movable in the height direction (z-axis direction) by the operation of the pressurizing device 140 described later. It is attached.
The lower arm portion 130b is for supporting the lower electrode head 120b to which the lower disk electrode 110b is attached. As shown in FIG. 1, the lower electrode head 120b is attached to the lower arm portion 130b so that the lower surface of the lower electrode head 120b faces the upper surface of the lower arm portion 130b. In the present embodiment, the lower arm portion 130b is attached (fixed) to the body 150 so as not to move.

The pressurizing device 140 is attached to the upper arm portion 130a, and pressurizes a steel plate as a material to be welded via the upper arm portion 130a, the upper electrode head 120a, and the upper disk electrode 110a. As shown in FIG. 1, the pressure device 140 is attached to the upper arm portion 130a so that the lower surface of the movable shaft 141 disposed in the pressure device 140 faces the upper surface of the upper electrode head 120a.
The welding power source 160 is electrically connected to the upper disk electrode 110a and the lower disk electrode 110b via the upper electrode head 120a and the lower electrode head 120b, and connects the upper disk electrode 110a and the lower disk electrode 110b. In order to supply electric power to the steel plate which is a material to be welded. In the present embodiment, the welding power source 160 is a single-phase AC power source and continuously supplies single-phase AC power.

In addition, it can implement | achieve with the well-known seam welding machine which performs mash seam welding except that the upper disk electrode 110a and the lower disk electrode 110b perform forward rotation and reverse rotation.
For example, the shapes of the tip surfaces of the upper disk electrode 110a and the lower disk electrode 110b are not limited to the shapes described above. For example, the curvature radius R is about 1 [mm] to 5 [mm] (R1 to R5) at both ends (both ends in the x-axis direction in FIG. 1) of the tip surfaces of the upper disk electrode 110a and the lower disk electrode 110b. Degree) chamfering may be performed. If it does in this way, it can suppress that an invalid shunt increases by the both ends of the front end surface of the upper disk electrode 110a and the lower disk electrode 110b contacting the steel plate which is a to-be-welded material. Further, at least one of the front end surfaces of the upper disc electrode 110a and the lower disc electrode 110b may have a curvature radius R of about 150 [mm] to 250 [mm].

Further, the driving method of the upper disk electrode 110a and the lower disk electrode 110b is not limited to the axial driving, and, for example, a circumferential driving (a system in which the circumferential portion of the disk electrode is driven by a knurling or the like) is employed. May be.
The welding power source 160 is not limited to a single-phase AC power source, but is another power source applicable to mash seam welding (for example, a three-phase AC power source, a single-phase rectification type DC power source, a DC inverter, an AC inverter, etc.). There may be. Further, the welding power source 160 may not be continuously energized (that is, intermittently energized).

  In addition, in FIG. 1, when the upper disk electrode 110a and the lower disk electrode 110b are arranged so that the surface directions of the upper disk electrode 110a and the lower disk electrode 110b face the y-axis direction (so-called horizontal seam). Welding machine) is shown as an example, but it is not always necessary to do so. For example, the upper disk electrode 110a and the lower disk electrode 110b may be arranged so that the surface directions of the upper disk electrode 110a and the lower disk electrode 110b are in the x-axis direction (so-called vertical seam welding). Machine).

FIG. 2 is a diagram illustrating an example of an arrangement of a steel plate, which is a material to be welded, and an upper disc electrode 110a and a lower disc electrode 110b when performing mash seam welding. Specifically, FIG. 2A is a diagram showing an arrangement when viewed from a direction along the welding direction (y-axis direction), and FIG. 2B is a direction in which welding is performed (y-axis direction). It is a figure which shows arrangement | positioning at the time of seeing in horizontal direction.
First, a steel plate that is a material to be welded according to the present embodiment will be described.
In this embodiment, the carbon equivalent Ceq represented by the following formula (1) of at least one of the two or more steel plates that are the welded materials is 0.31 [% by mass] or more. .
Ceq = [C] + [Si] / 30 + [Mn] / 20 + 2 [P] +4 [S] (1)

In the formula (1), [C], [Si], [Mn], [P] and [S] are the contents (mass%) of C, Si, Mn, P and S, respectively. In the following description, the carbon equivalent Ceq represented by the formula (1) is abbreviated as carbon equivalent Ceq as necessary.
The carbon equivalent Ceq indicates the cracking sensitivity of the joint. It has been confirmed that when the carbon equivalent Ceq is 0.31 [% by mass] or more, breakage of the joint due to mash seam welding (break in the nugget etc.) is likely to occur, and the characteristics of the joint deteriorate. For this reason, the mechanical properties of the joint can be improved by performing a heat treatment described later on such a joint. Even if the carbon equivalent Ceq of all the steel plates to be welded is less than 0.31 [mass%], the heat treatment described later can be performed, but with such steel plates, joining by mash seam welding is possible. The deterioration of the characteristics of the part is small (the significance of performing the heat treatment described later is small). Therefore, in the present embodiment, as described above, the carbon equivalent Ceq of at least one of the two or more steel plates as the welded material is set to 0.31 [% by mass] or more.

  Here, based on the equation (4.9b) on page 243 of Non-Patent Document 1, the carbon equivalent in the case of short-time holding in resistance spot welding was adopted. This equation shows the carbon equivalent Ceq of the resistance spot weld. Resistance spot welding does not move the electrode in the plane of the steel plate during welding, but resistance spot welding and mash seam welding are the same resistance welding, and there is no significant difference in heating / cooling patterns at individual joints. From the viewpoint, this formula is adopted in the present embodiment. Here, the carbon equivalent in the case of holding for a short time without adopting the carbon equivalent in the case of holding for a long time is adopted in the mash seam welding in which the disk electrode rotates and is positioned at the upper and lower positions of the joint. Because it does not stop.

  In this embodiment, as long as the carbon equivalent Ceq of at least one steel plate is 0.31 [% by mass] or more, the type of the steel plate is not limited. For example, a high strength steel plate, a mild steel plate, a high carbon steel, a hardenable alloy steel, a martensitic stainless steel, or the like can be used. Moreover, plating may be given to the single side | surface or both surfaces of the steel plate, and it does not need to be given. The plating type is not particularly limited.

Other conditions for the steel sheet may be the general conditions employed for mash seam welding.
For example, as the thickness of one steel plate (before mash seam welding is performed), a thickness within the range of 0.4 [mm] to 6.0 [mm] can be employed. In addition, as shown in FIG. 2, in the present embodiment, the case where the number of steel plates to be mash seam welded is described as an example, but the number of steel plates to be mash seam welded is limited to two. Instead, it may be three or four.

In FIG. 2A, the total thickness To of the steel plate before mash seam welding is set to 7.0 [mm] or less.
Further, in FIG. 2A, the range of the following equation (2) can be adopted as the overlap margin L ₀ of the steel plate before performing mash seam welding.
1.0 × t ≦ L ₀ ≦ 2.0 × t (2)
As shown in FIG. 2 (a), the overlap margin L ₀ of the steel sheet prior to the mash seam welding it is smaller than the width w of the upper circular plate electrodes 110a and the lower disc electrode 110b. This is the same even after performing mash seam welding or after performing a heat treatment described later. The range of overlap space L ₀ shown in equation (2) is a common range overlap margin L ₀ when performing the mash seam welding to a plurality of steel plates.

Next, an example of a method for forming a welded joint by performing mash seam welding and heat treatment on the overlapping portion of the plurality of steel plates 210a and 210b as described above will be described.
FIG. 3 is a diagram conceptually illustrating an example of a method for performing mash seam welding and heat treatment. Specifically, FIG. 3A is a diagram conceptually illustrating an example of a method of performing mash seam welding, and FIG. 3B is a diagram conceptually illustrating an example of a method of performing heat treatment.
FIG. 4 is a diagram conceptually illustrating an example of a state of the joint portion. Specifically, FIG. 4A is a cross-sectional view showing a state in the vicinity of the overlapped portion of the steel plates 210a and 210b before performing mash seam welding, and FIG. 4B shows a state after performing mash seam welding. FIG. 4C is a cross-sectional view showing a state near the overlapping portion of the steel plates 210a and 210b, and FIG. 4C is a cross-sectional view showing a state near the overlapping portion of the steel plates 210a and 210b after the heat treatment.

First, steel sheets 210a described above, the end of the 210 b, is disposed between the upper disc electrode 110a and the lower disc electrode 110b overlapping with the overlapping margin L ₀ as described above (see Figure 4 (a)).
Then, while the upper disk electrode 110a and the lower disk electrode 110b are rotated, the upper disk electrode 110a and the lower disk electrode 110b are pressed and energized to the steel plates 210a and 210b while the upper disk electrode 110a and the lower disk electrode 110b are rotated. The region between the plate electrode 110a and the lower disk electrode 110b is along the first direction (the negative direction of the y axis) of the planned joining location (scheduled welding location) of the overlapped portion of the steel plates 210a and 210b. The steel plates 210a and 210b are sent out so as to move (see FIG. 3A). Thereby, the upper disk electrode 110a and the lower disk electrode 110b are (relative to the steel plates 210a and 210b) in the negative y-axis direction (the direction of the white arrow shown in FIG. 3A). To).

  In this embodiment, by doing in this way, as shown in FIG.4 (b), the overlap part of the steel plates 210a and 210b joins. FIG. 4B shows a state in which a melted nugget 410 is formed. However, in mash seam welding, the formation of such a nugget 410 is not always necessary, and the steel plates 210a and 210b are formed only by solid phase bonding. May be joined.

The pressure in the above mash seam welding is P1 [kN], the welding speed is V1 [m / min], and the welding current is I1 [kA].
In the present embodiment, the applied pressure refers to a pressure applied by the pressurizing device 140 from the upper disk electrode 110a to the overlapping portion of the steel plates 210a and 210b. The welding speed refers to the feeding speed of the steel plates 210a and 210b (the relative moving speed (relative speed) of the upper disc electrode 110a and the lower disc electrode 110b with respect to the steel plates 210a and 210b). Further, the welding current refers to a value (effective value) of a current supplied from the welding power source 160 to the steel plates 210a and 210b via the upper disk electrode 110a and the lower disk electrode 110b.

Normally, the joints of the steel plates 210a and 210b are quenched by mash seam welding. That is, the steel plate 210a, joining planned portion of the 210b will be heated to a temperature not lower than A ₃ transformation point by heating by mash seam welding, transformed into austenitic structure is immediately cooled from the time the mash seam welding has been completed, 1-2 [ It is cooled to a temperature below the Ms point in a time of about [second].

  Next, in the present embodiment, while pressing and energizing the steel plates 210a and 210b, the upper disc electrode 110a and the lower disc electrode 110b are rotated in the opposite direction to that during mash seam welding, and the upper disc is rotated. The region between the electrode 110a and the lower disc electrode 110b moves along the second direction (positive direction of the y-axis) of the joint formed in the overlapping portion of the steel plates 210a and 210b. Then, the steel plates 210a and 210b are sent out (see FIG. 3B). Thus, the relative movement direction of the upper disk electrode 110a and the lower disk electrode 110b with respect to the steel plates 210a and 210b is opposite to that during mash seam welding (the positive direction of the y-axis (FIG. 3B)). The direction of the white arrow)

  In this embodiment, by doing in this way, the joint part of the steel plates 210a and 210b formed by mash seam welding is heat-treated, and the mechanical properties of the joint part of the steel plates 210a and 210b are determined when mash seam welding is completed. Better than. As described above, when the joints of the steel plates 210a and 210b are quenched by mash seam welding, it is preferable to temper the joints of the steel plates 210a and 210b by this heat treatment. In order to surely perform tempering, a predetermined time may be secured between the end of the mash seam welding and the start of the heat treatment, or the place where the mash seam welding is finished (the steel plates 210a and 210b). Cooling treatment such as spraying cooling water on the surface area) may be performed.

However, if the mechanical properties of the joints of the steel plates 210a and 210b are improved by heat treatment as compared with when the mash seam welding is completed, it is not always necessary to perform quenching and tempering. Here, improving the mechanical properties of the joint of the steel plates means reducing internal strain, softening the structure, and improving toughness.
In the following description, such heat treatment after mash seam welding is referred to as post-heat treatment as necessary.

Assuming that the pressure in the post heat treatment is P2 [kN], the welding speed is V2 [m / min], and the welding current is I2 [kA], in this embodiment, the following expressions (3), (4), and ( 5) Make the formula hold.
1.0 × P1 ≦ P2 ≦ 1.5 × P1 (3)
0.4 × V1 ≦ V2 ≦ 0.8 × V1 (4)
1.0 × I1 ≦ I2 ≦ 1.5 × I1 (5)

First, the reason for prescribing as in equation (3) will be described.
As shown in FIGS. 4 (a) and 4 (b), the overlap margin of the steel plates 210a and 210b increases from L ₀ to L ₁ by mash seam welding, and the thickness of the overlap portion of the steel plates 210a and 210b is as follows. Decrease from T ₀ to T ₁ . For this reason, even if the overlapping portion of the steel plates 210a and 210b is pressurized with the same pressure as during mash seam welding during the post heat treatment, the surface pressure that the overlapping portion of the steel plates 210a and 210b receives from the upper disk electrode 110a during the post heat treatment. (Pressure force per unit area) is lower than that during mash seam welding. Accordingly, in the post heat treatment, at least a pressing force equivalent to the pressing force P1 in mash seam welding is required. As described above, when the pressure P2 in the post heat treatment is set to be equal to or higher than the pressure P1 in the mash seam welding, a good heat treatment can be performed. On the other hand, when the applied pressure P2 in the post heat treatment is lower than the applied pressure P1 in the mash seam welding, there is a possibility that defects such as spatter and pits may occur at the joints of the steel plates 210a and 210b.

  Further, by applying a maximum pressure of 1.5 times the pressure P1 in mash seam welding, the post-heat treatment is applied to the steel plates 210a and 210b to compensate for the aforementioned decrease in surface pressure. And good heat treatment is possible. On the other hand, when the applied pressure P2 in the post heat treatment exceeds 1.5 times the applied pressure P1 in the mash seam welding, the deformation of the joint portions of the steel plates 210a and 210b increases. For this reason, the heat input with respect to the junction part of the steel plates 210a and 210b falls, and there exists a possibility that appropriate heat processing cannot be performed.

Next, the reason for defining as in equation (4) will be described.
By reducing the welding speed V2 in the post-heat treatment until the welding speed V2 in the post-heat treatment becomes 0.4 times the welding speed V1 in the mash seam welding, the re-entry heat to the joint portions of the steel plates 210a and 210b in the post-heat treatment. Can be increased. On the other hand, when the welding speed V2 in the post heat treatment is less than 0.4 times the welding speed V1 in the mash seam welding, the welding speed is remarkably slowed, and it becomes difficult to use from the viewpoint of productivity.
Further, even if the welding speed V2 in the post heat treatment is increased until the welding speed V2 in the post heat treatment becomes 0.8 times the welding speed V1 in mash seam welding, Heat input can be performed sufficiently. Further, as the welding speed V2 in the post heat treatment is increased within this range, the time during which the upper disk electrode 110a and the lower disk electrode 110b are in contact with the steel sheets 210a and 210b is shortened. For this reason, it can be expected that the joined portions of the reheated steel plates 210a and 210b are gradually cooled to perform an effective heat treatment. On the other hand, if the welding speed V2 in the post-heat treatment exceeds 0.8 times the welding speed V1 in the mash seam welding, the re-entry heat to the joint portions of the steel plates 210a and 210b in the post-heat treatment becomes insufficient, and a good heat treatment is performed. There is a risk that it will not be possible.

Next, the reason for defining as in equation (5) will be described.
As described above, by mash seam welding, by mash seam welding, the overlap margin of the steel plates 210a and 210b increases from L ₀ to L _1, and the thickness of the overlap portion of the steel plates 210a and 210b decreases from T ₀ to T ₁ . (See FIG. 4 (a) and FIG. 4 (b)). For this reason, even if a current having the same magnitude (effective value) as in mash seam welding is passed through the joint of the steel plates 210a and 210b during post-heat treatment, the current density of the current flowing through the joint of the steel plates 210a and 210b during post-heat treatment (Current value per unit area) is lower than that during mash seam welding. Accordingly, in the post heat treatment, at least a welding current equivalent to the welding current I1 in mash seam welding is required. By setting the welding current I2 in the post heat treatment to be equal to or higher than the welding current I1 in the mash seam welding, a favorable heat treatment can be performed. On the other hand, when the welding current I2 in the post heat treatment is lower than the welding current I1 in the mash seam welding, there is a fear that the heat input to the joints of the steel plates 210a and 210b is insufficient, and it is impossible to realize a good heat treatment.

  In addition, by supplying a welding current that is 1.5 times the maximum of the welding current I1 in mash seam welding, a welding current that compensates for the decrease in current density described above is supplied to the steel plates 210a and 210b during post-heat treatment. And good heat treatment is possible. On the other hand, when the welding current I2 in the post heat treatment exceeds 1.5 times the welding current I1 in the mash seam welding, there is a possibility that the heat treatment cannot be performed due to remelting of the joint portions of the steel plates 210a and 210b.

As described above, in the present embodiment, while the upper disk electrode 110a and the lower disk electrode 110b are rotated, the upper disk with respect to the steel plates 210a and 210b is pressed and energized with respect to the steel plates 210a and 210b. Mash seam welding is performed so that the relative movement direction of the electrode 110a and the lower disk electrode 110b is along the planned joining position of the overlapping portion of the steel plates 210a and 210b. Thereafter, while the upper disk electrode 110a and the lower disk electrode 110b are rotated in the direction opposite to that during mash seam welding, the upper side with respect to the steel sheets 210a and 210b is pressed and energized with respect to the steel sheets 210a and 210b. Post-heat treatment is performed so that the relative movement direction of the disc electrode 110a and the lower disc electrode 110b is opposite to that during mash seam welding.
Therefore, the mechanical characteristics of the joints of the steel plates 210a and 210b obtained by mash seam welding are improved by using the same type of electrodes as the mash seam welded electrodes (upper disk electrode 110a and lower disk electrode 110b). Therefore, a post heat treatment can be performed. Therefore, it is possible to improve the mechanical characteristics of the joints of the steel plates 210a and 210b formed by mash seam welding with the simplest possible structure.

  In particular, in the present embodiment, the same electrode (upper disk electrode 110a and lower disk electrode 110b) is used during mash seam welding and post heat treatment, and the upper disk electrode 110a and lower disk electrode are used. The relative movement direction of the plate electrode 110b with respect to the steel plates 210a and 210b is reversed. Therefore, the facility for performing mash seam welding and the facility for performing post heat treatment can be made common, and the work time required from the start of mash seam welding to the end of post heat treatment can be shortened. Therefore, it is possible to easily and quickly realize suppression of breakage of the joint portion of the steel plates 210a and 210b formed by mash seam welding and improvement of workability of the joint portion of the steel plates 210a and 210b formed by mash seam welding. be able to.

  Further, the relationship between the pressure P1, welding speed V1, welding current I1 during mash seam welding and the pressure P2, welding speed V2, welding current I2 during post-heat treatment is the above-mentioned formulas (3) to (5). It was made to satisfy. Therefore, it is possible to more surely improve the mechanical properties of the joints of the steel plates 210a and 210b formed by mash seam welding.

<Modification>
In the present embodiment, the steel plates 210a and 210b are sent out at a substantially constant speed. However, this is not always necessary. For example, the upper and lower disk electrodes 110a and 110b may be moved while the steel plates 210a and 210b are fixed.
Further, as in the present embodiment, when the relative moving direction of the upper disk electrode 110a and the lower disk electrode 110b with respect to the steel plates 210a and 210b is reversed between the mash seam welding and the post heat treatment, the above-described case is performed. It is preferable because the obtained effect can be obtained. However, this is not always necessary.
For example, the relative moving direction of the upper disk electrode 110a and the lower disk electrode 110b with respect to the steel plates 210a and 210b may be the same during mash seam welding and post heat treatment.

  In this case, for example, after the mash seam welding is finished, the positional relationship between the upper disk electrode 110a and the lower disk electrode 110b and the steel plates 210a and 210b is changed to the positional relationship before the mash seam welding is started. In the same manner as in mash seam welding, the region between the upper disk electrode 110a and the lower disk electrode 110b is the first direction (y The steel plates 210a and 210b can be sent out so as to move relatively along the negative direction of the shaft. In this case, the upper disk electrode 110a and the lower disk electrode 110b can be rotated only in one direction.

Further, the upper disk electrode 110a and the lower disk electrode 110b may be provided separately for mash seam welding and for post heat treatment.
In this case, for example, the upper disk electrode 110a and the lower disk electrode 110b for post heat treatment are made of steel plates so as to follow the upper disk electrode 110a and the lower disk electrode 110b for mash seam welding. You may move relatively with respect to 210a, 210b.

Further, the upper disk electrode 110a and the lower disk electrode 110b for mash seam welding and the upper disk electrode 110a and the lower disk electrode 110b for post heat treatment are connected in the x-axis direction (welding of the steel plates 210a and 210b). You may arrange | position at intervals in the direction perpendicular | vertical with respect to the direction along a planned location in the direction along the surface of the steel plates 210a and 210b. In this case, after the mash seam welding is completed, the steel plates 210a and 210b are moved to the positions where the upper disc electrode 110a and the lower disc electrode 110b for post heat treatment are arranged, and post heat treatment is performed. Post-heat treatment is performed using the upper disk electrode 110a and the lower disk electrode 110b. Further, in this case, the relative moving direction of the upper disk electrode 110a and the lower disk electrode 110b with respect to the steel plates 210a and 210b is set to the same direction during mash seam welding and post heat treatment. Can also be reversed.
Further, a control signal for performing the above-described mash seam welding and post-heat treatment may be generated by an information processing apparatus and output to the seam welding machine 100 so that mash seam welding and post-heat treatment are automatically performed.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the first embodiment, the case where post-heat treatment is performed after mash seam welding has been described as an example. On the other hand, in the present embodiment, the post-heat treatment is performed by changing the conditions of the pressure, welding speed, and welding current in the post-heat treatment described in the first embodiment (conditions of equations (3) to (5)). In addition, the case where swaging (pressure deformation processing) is reliably performed will be described as an example. As described above, the present embodiment and the first embodiment are mainly different in the conditions of the applied pressure, welding speed, and welding current in the post-heat treatment, and the hardware (seam welder) of the present embodiment is the first It is realizable with the same thing as what was demonstrated by embodiment (a modification example). Therefore, in the description of the present embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals as those in FIGS.

First, swaging in this embodiment is defined.
In the present embodiment, swaging refers to the overlapping portion of a plurality of steel plates such that the upsetting rate e [%] represented by the following formula (6) is 30 [%] or more and 50 [%] or less. It means to reduce the thickness.
e = {(To−T) ÷ To} × 100 (6)
In the equation (6), To is the thickness [mm] of the overlapped portion of the plurality of steel plates before performing mash seam welding. T is the final thickness [mm] of the overlapping portion of the plurality of steel plates. Here, the final thickness of the overlapped portion of the plurality of steel plates refers to the thickness of the overlapped portion of the plurality of steel plates after only the post-heat treatment described in the first embodiment, or after-heat It is the thickness of the overlapping part of a plurality of steel plates after performing an aging treatment.

  FIG. 5 is a diagram illustrating an example of swaging. FIG. 5 shows an example in which the number of steel plates to be swaged is two. However, it goes without saying that this number varies depending on the number of steel plates subjected to mash seam welding.

  FIG. 6 is a diagram conceptually illustrating an example of a state of the joint portion. Specifically, FIG. 6A is a cross-sectional view showing a state in the vicinity of the overlapping portion of the steel plates 210a and 210b before mash seam welding, and FIG. 6B is a diagram after mash seam welding is performed. FIG. 6C is a cross-sectional view showing a state in the vicinity of the overlapping portion of the steel plates 210a and 210b, and FIG. 6C shows a state in the vicinity of the overlapping portion of the steel plates 210a and 210b after performing the post heat treatment and swaging simultaneously. It is sectional drawing. FIG. 6 corresponds to FIG.

6 (a) and 6 (b) are the same as FIGS. 4 (a) and 4 (b), respectively. On the other hand, if FIG. 4C shows a state in which only the post-heat treatment is performed and no swaging is performed, the post-heat treatment and the swaging are performed simultaneously as shown in FIG. 6C. steel 210a, 210b overlap space L ₃ of the after is greater than 4 steel 210a after heat treatment after shown in (c), 210 b overlap margin L ₂ of. In addition, the thickness T ₃ of the overlapped portion of the steel plates 210a and 210b after the post-heat treatment and the swaging are performed simultaneously becomes thinner than the thickness T ₂ of the overlapped portion of the steel plates 210a and 210b after the post-heat treatment.

  When performing mash seam welding, as in the first embodiment, the region between the upper disk electrode 110a and the lower disk electrode 110b is the first joining point of the overlapping portion of the steel plates 210a and 210b. Relative to each other along the direction (negative direction of the y-axis) (see FIG. 3A). On the other hand, when the post heat treatment and the swaging are performed simultaneously, the region between the upper disk electrode 110a and the lower disk electrode 110b is mash seam welded as in the post heat treatment described in the first embodiment. It moves relatively in the opposite direction to the time (see FIG. 3B).

In this embodiment, by doing in this way, the joint part of the steel plates 210a and 210b formed by mash seam welding is heat-treated, and the mechanical properties of the joint part of the steel plates 210a and 210b are determined when mash seam welding is completed. It is possible to achieve further improvement and to make the thicknesses of the joints of the steel plates 210a and 210b closer to (preferably match) the thicknesses of other regions.
In the following description, performing post heat treatment and swaging simultaneously after mash seam welding is referred to as post heat / swaging treatment as necessary.

Assuming that the pressure in the post-heat / swaging process is P3 [kN], the welding speed is V3 [m / min], and the welding current is I3 [kA], in this embodiment, the following equations (7) and (8) Equations (9) and (9) are established.
1.2 × P1 ≦ P3 ≦ 1.5 × P1 (7)
0.4 × V1 ≦ V3 ≦ 0.8 × V1 (8)
1.2 × I1 ≦ I3 ≦ 1.5 × I1 (9)

First, the reason for prescribing as in equation (7) will be described.
As described with respect to the expression (3) in the first embodiment, by setting the pressure P3 in the post-heating / swaging process to be equal to or higher than the pressure P1 in the mash seam welding, a favorable heat treatment can be performed. However, in order to perform swaging, the applied pressure P3 in the post-heat / swaging process needs to be 1.2 times or more of the applied pressure in mash seam welding.
Further, although swaging is possible even if the applied pressure P3 in the post-heat / swaging process exceeds 1.5 times the applied pressure P1 in mash seam welding, the formula (3) of the first embodiment is applicable. As described above, if the applied pressure P3 in the post-heat / swaging process exceeds 1.5 times the applied pressure P1 in the mash seam welding, there is a possibility that the post-heat treatment cannot be performed properly.

Next, the reason for prescribing as in equation (8) will be described.
As explained with respect to the expression (4) of the first embodiment, until the welding speed V3 in the post-heat / swaging process becomes 0.4 times the welding speed V1 in mash seam welding, the post-heat / swell By lowering the welding speed V3 in the aging process, the re-entry heat to the joints of the steel plates 210a and 210b in the post-heat / swaging process can be increased, and swaging can be performed in addition to good post-heat treatment. . On the other hand, if the welding speed V3 in the post-heating / swaging process is less than 0.4 times the welding speed V1 in the mash seam welding, the welding speed is remarkably reduced, which makes it practically difficult from the viewpoint of productivity.

  Further, even if the welding speed V3 in the post-heating / swaging process is increased until the welding speed V3 in the post-heating / swaging process becomes 0.8 times the welding speed V1 in the mash seam welding, Re-entry heat can be sufficiently applied to the joined portions of the steel plates 210a and 210b in the aging treatment. Further, as the welding speed V3 in the post-heating / swaging process is increased in this range, the time during which the upper disk electrode 110a and the lower disk electrode 110b are in contact with the steel sheets 210a and 210b is shortened. For this reason, the joint part of the reheated steel plates 210a and 210b is gradually cooled, and the swaging treatment can be effectively performed together with the heat treatment. On the other hand, if the welding speed V3 in the post-heating / swaging process exceeds 0.8 times the welding speed V1 in the mash seam welding, the re-entry heat to the joints of the steel plates 210a and 210b in the post-heating / swaging process is not good. There is a risk that not only the heat treatment but also the swaging treatment cannot be performed satisfactorily.

Next, the reason for prescribing as in equation (9) will be described.
As described with respect to the expression (5) of the first embodiment, by setting the welding current I3 in the post-heat / swaging process to be equal to or higher than the welding current I1 in the mash seam welding, a favorable heat treatment can be performed. However, in order to perform swaging, it is necessary to set the welding current I3 in the post-heat / swaging process to 1.2 times or more of the welding current I1 in mash seam welding.
Further, swaging is possible even if the welding current I3 in the post-heating / swaging process exceeds 1.5 times the welding current I1 in the mash seam welding, but the expression (5) in the first embodiment is applicable. As described above, if the welding current I3 in the post-heating / swaging process exceeds 1.5 times the welding current I1 in the mash seam welding, the post-heat treatment may not be performed properly.

  As described above, in the present embodiment, the relationship between the pressure P1, the welding speed V1, and the welding current I1 during mash seam welding and the pressure P3, the welding speed V3, and the welding current I3 during post-heating and swaging processing are as follows. The aforementioned expressions (7) to (9) were satisfied. Therefore, improving the mechanical characteristics of the joints of the steel plates 210a and 210b formed by mash seam welding and making the thickness of the overlapped portion of the steel plates 210a and 210b closer to (preferably match) the thickness of other regions. Can be realized simultaneously and reliably.

  In particular, the same electrode (upper disc electrode 110a and lower disc electrode 110b) is used during mash seam welding and during post-heat / swaging treatment, and the upper disc electrode 110a and lower disc are used. If the relative movement direction of the electrode 110b with respect to the steel plates 210a and 210b is reversed, the facility for performing mash seam welding and the facility for performing post-heat / swaging treatment can be made common, and mash seam welding can be performed. The work time required from the start to the end of the post-heat / swaging process can be shortened.

In the present embodiment, swaging is defined as an upsetting rate e of 30 [%] or more and 50 [%] or less. However, in evaluating the quality of the product, the thickness of the overlapped portion of the steel plates 210a and 210b after the post-heating / swaging process may be regarded as being in a range that can be considered to be substantially equal to the thickness of the steel plates 210a and 210b. For example, it is not always necessary that the upsetting rate e is 30% or more and 50% or less.
Also in the present embodiment, various modifications described in the first embodiment can be employed.

Moreover, as a steel plate used for each embodiment mentioned above which is an example of this invention, the method demonstrated by each embodiment also in any steel plates, such as a steel plate before annealing, a steel plate before annealing, a steel plate after annealing, and various plated steel plates It is possible to apply.
It should be noted that the embodiments of the present invention described above are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. Is. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

[Example]
Next, examples of the present invention will be described. In addition, a present Example shows an example of this invention and this invention is not necessarily limited to the thing of a present Example.
In the following, mash seam welding is referred to as the first treatment, and post-heat treatment or post-heat / swaging treatment is referred to as the second treatment (note that the treatment when the desired result cannot be obtained in the second treatment). Is also included). In addition, the pressure, welding speed, and welding current in mash seam welding are referred to as the first pressure, welding speed, and welding current, respectively, and the pressure, welding speed, and welding current in post heat treatment, post heat, and swaging treatment. Are referred to as the second pressurizing force, welding speed, and welding current, respectively.

In this example, two steel plates (high-strength steel plate A) having a carbon equivalent Ceq of 0.38 [mass%] and a plate thickness of 1.0 [mm] are overlapped by 1.0 [mm]. _2. A case where a weld joint is formed by overlapping at ₀ , and two steel plates (high strength steel plate B) having a carbon equivalent Ceq of 0.36 [mass%] and a plate thickness of 1.6 [mm]. Two cases were investigated, in which a weld joint was formed by overlapping with an overlap margin L ₀ of 2 [mm]. Each of the high-strength steel plate A and the high-strength steel plate B is a steel plate as it is cold-rolled and before annealing.

In this embodiment, the seam welder 100 shown in FIG. 1 was used.
Moreover, the disk electrode shown below was used.
Disc electrode material: Cu-Cr alloy (RWMA class 2 equivalent)
Disc electrode shape: Flat type (D = 350mmφ)
Width w of disc electrode: 15 [mm]
Moreover, the welding power source shown below was used.
Power supply type: Single-phase AC power supply Frequency: 50 [Hz]
Energization method; continuous energization

  Further, how to move the disc electrodes (the upper disc electrode 110a and the lower disc electrode 110b) is as described with reference to FIG. More specifically, after performing mash seam welding as shown in FIG. 3 (a), the disk electrodes (upper disk electrode 110a and lower disk electrode 110b) are immediately rotated in the reverse direction. As shown in b), the second treatment was performed with the relative movement direction of the disc electrode with respect to the steel plate being opposite to the direction in which mash seam welding was performed.

In this example, whether or not the structure of the joint between the two steel plates when the second treatment is finished is softened and the toughness is compared with the joint between the two steel plates when the first treatment is finished. In order to confirm whether or not the improvement was made, the Vickers hardness (HV) of the joint between the two steel sheets was measured. Vickers hardness (HV) was measured according to JIS Z 2244. When the average value of Vickers hardness (HV) measured at three locations in the vicinity of the joining interface between the two steel plates was 300 or less (HV ≦ 300), the structure was considered to be soft (good).
Also, in this example, whether the internal strain of the joint between the two steel plates when the second treatment is finished is reduced with respect to the joint between the two steel plates when the first treatment is finished. In order to confirm whether or not, a hammer test was performed on the joining end portion (mash seam welding end portion) of the two steel sheets (hereinafter, this hammer test is referred to as “hammer test of the mash seam welding end portion”). Called). The Erichsen test, which is usually applied to the formability evaluation of mash seam welds, is performed by the method specified in JIS Z 2247. It is difficult to apply because the presser foot pressure becomes insufficient. Therefore, in this example, the “hammer test of the mash seam weld end” was adopted and carried out as follows.

  In order to evaluate the formability of mash seam welds in a simple manner, the steel plate after mash seam welding is used, and the mash seam weld line is located at the center of a square test piece with a side of 90 mm, as in the normal Erichsen test. After cutting the test piece and grinding the cut surface, firmly fix both sides of the mash seam weld with a restraint jig such as a vise, and then end the end of the seam weld with a round-head steel. The hammer was beaten several times until a predetermined deformation occurred, and a site when a clear change such as cracking or peeling occurred in the welded part, the heat-affected zone (HAZ) and the base material was observed and recorded. In the case where the plate thickness difference is large or a plate assembly that is difficult to deform with a high-strength material, a jig such as a chisel is separately used on the thin plate side or the steel plate side that is easily deformed.

  As a result of a hammer test of the mash seam weld end, when a deformation of 15 [mm] occurs, a crack occurs in the heat affected zone (HAZ) but no peeling occurs, or a deformation of 15 [mm] occurs. However, when neither peeling nor cracking occurs, the workability judgment is good, and in Tables 1 and 2, it is represented by “◯”. On the other hand, when a deformation of 15 [mm] occurs, if a crack occurs at the center line of the welded portion, the workability determination is not possible, and is represented by “Δ” in Tables 1 and 2. In addition, when the deformation of 15 [mm] occurs, if the peeling occurs at the bonding interface, the workability determination is not possible, and in Tables 1 and 2, it is represented by “x”.

Further, in order to confirm whether or not swaging has been performed, the thickness T (T ₂ or T ₃ ) of the overlapped portion of the steel sheet when the second treatment is completed is measured, and this is followed by mash seam welding. From the thickness To of the overlapping portion (overlapping portion) of the previous steel plate, it was evaluated whether or not the upsetting ratio e shown in the equation (6) was 30% or more and 50% or less.
The first evaluation pressure P1, welding speed V1, welding current I1, and the second application pressure P2 or P3, welding speed V2 or V3, welding current I2 or I3 are made different, and the above evaluation index (joint hardness) Tables 1 and 2 show the results of determining the thickness (Vickers hardness), the hammer test (the result of the hammer test at the seam weld end), and the upsetting rate). In the remarks column of Tables 1 and 2, Example 1 of the present invention indicates that post-heat treatment has been performed but swaging has not been performed. Example 2 of the present invention has both post-heat treatment and swaging. Indicates what is being done.
Moreover, it is determined to pass if the joint hardness (Vickers hardness) is 300 HV or less and the hammer test (the result of the hammer test at the seam weld end) is “◯”, otherwise it fails. (Refer to the column of Table 1 and Table 2 comprehensive evaluation).

As shown in Tables 1 and 2, the joint hardness (Vickers hardness) exceeds 300 HV unless the conditions of (3) and (7) are satisfied. The result of the hammer test was “Δ” or “×” (numbers 7, 10, 19, 22).
If the conditions of the equations (4) and (8) are not satisfied, the joint hardness (Vickers hardness) exceeds 300 HV, and the hammer test (result of the hammer test at the seam weld end) is “△ "Or" x "(numbers 8, 11, 20, 23).
If the conditions of the formulas (5) and (9) are not satisfied, the joint hardness (Vickers hardness) exceeds 300 HV, and the hammer test (the result of the hammer test at the seam weld end) is “△ "Or" x "(numbers 9, 12, 21, 24).

On the other hand, when the conditions of the expressions (3), (4), and (5) are satisfied but the conditions of the expressions (7) and (9) are not satisfied, the upsetting rate e is 30%. Although less than, the joint hardness (Vickers hardness) was 300 HV or less, and the hammer test (the result of the hammer test at the seam weld end) was “◯” (numbers 1, 2, 3, 13, 14, 15).
Further, when the conditions of the expressions (7), (8), and (9) are satisfied, the upsetting rate e is 30 [%] to 50 [%], and the joint hardness (Vickers hardness) ) Was 300 HV or less, and the hammer test (result of the hammer test at the seam weld end) was “◯” (numbers 4, 5, 6, 16, 17, 18).

Further, the present inventors can change the type and number of steel plates (plate thickness) and the overlap allowance L ₀ within the range of general conditions when performing mash seam welding. Even if the shape and type of the welding power source are changed, the same tendency as the results shown in Table 1 and Table 2 is obtained (if the conditions shown in the formulas (3) to (5) are satisfied, the joint hardness (Vickers (Hardness) is 300 HV or less, and the hammer test (result of hammer test at the seam weld end) is “◯” and if the conditions shown in equations (7) to (9) are satisfied, It was confirmed that the upsetting rate was 30 [%] to 50 [%].

  DESCRIPTION OF SYMBOLS 100; Seam welder, 110a; Upper disk electrode, 110b; Lower disk electrode, 120a; Upper electrode head, 120b; Lower electrode head, 130a; Upper arm part, 130b; Lower arm part, 140; 150; Airframe, 160; Welding power supply, 210a and 210b; Steel plate

Claims (20)

It is a method for forming a welded joint that forms a welded joint by performing mash seam welding on the overlapping portion of a plurality of steel plates,
An upper disk electrode and a lower disk electrode disposed above and below the overlapping portion, each of the upper disk electrode and the lower disk electrode made of copper alloy being rotated. The upper disc electrode and the lower disc are arranged so as to be along the planned joining portion while performing pressurization and energization to the joining planned location of the overlapping portion by the plate electrode and the lower disc electrode. By moving the electrode relative to the plurality of steel plates, performing a mash seam welding on the joint planned portion of the overlapping portion, and forming a joint portion;
After the first step, an upper disk electrode and a lower disk electrode disposed above and below the overlapping portion, each rotating an upper disk electrode and a lower disk electrode made of copper alloy. In this state, the upper disc electrode and the lower disc electrode are arranged so as to be along the junction while pressing and energizing the junction with the upper disc electrode and the lower disc electrode. A second step of performing heat treatment on the joint by moving a disk electrode relative to the plurality of steel plates,
The upper disk electrode and the lower disk electrode used in the first process, and the upper disk electrode and the lower disk electrode used in the second process are the same. ,
A method for forming a welded joint, wherein a carbon equivalent Ceq represented by the following formula (A) of at least one of the plurality of steel plates is 0.31 [% by mass] or more.
Ceq = [C] + [Si] / 30 + [Mn] / 20 + 2 [P] +4 [S] (A)
Here, [C], [Si], [Mn], [P], and [S] are the contents (mass%) of C, Si, Mn, P, and S, respectively. The applied pressure, which is the pressure applied to the overlapping portion in the first step, is P1 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the first step A welding speed that is a relative moving speed with respect to the steel plate is V1 [m / min], and a welding current that is a value of a current flowing through the plurality of steel plates in the first step is I1 [kN],
The applied pressure, which is the pressure applied to the overlapping portion in the second step, is P2 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the second step When the welding speed that is a relative moving speed with respect to the steel plate is V2 [m / min], and the welding current that is the value of the current flowing through the plurality of steel plates in the second step is I2 [kN], (B) Formula, (C) Formula, and (D) Formula hold | maintained, The formation method of the welded joint of Claim 1 characterized by the above-mentioned.
1.0 × P1 ≦ P2 ≦ 1.5 × P1 (B)
0.4 × V1 ≦ V2 ≦ 0.8 × V1 (C)
1.0 × I1 ≦ I2 ≦ 1.5 × I1 (D)   The second step is characterized in that the heat treatment is performed on the bonding portion and the processing of bringing the thickness of the overlapping portion closer to the thickness of other regions is performed simultaneously. 2. A method for forming a welded joint according to 1. 4. The method for forming a welded joint according to claim 3, wherein the processing is performed by setting an upsetting rate e shown in the following expression (E) to 30 [%] or more and 50 [%] or less.
e = [(To−T) ÷ To] × 100 (E)
Here, To is the thickness [mm] of the overlapping portion (overlapping portion) of the steel plate before mash seam welding, and T is the thickness [mm] of the overlapping portion after the second step is finished. is there. The applied pressure, which is the pressure applied to the overlapping portion in the first step, is P1 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the first step A welding speed that is a relative moving speed with respect to the steel plate is V1 [m / min], and a welding current that is a value of a current flowing through the plurality of steel plates in the first step is I1 [kN],
A pressing force that is a pressure applied to the overlapping portion in the second step is P3 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the second step When the welding speed, which is a relative moving speed with respect to the steel plate, is V3 [m / min], and the welding current, which is the value of the current flowing through the plurality of steel plates in the second step, is I3 [kN], (F) Formula, (G) Formula, and (H) Formula are formed, The formation method of the welded joint of Claim 4 characterized by the above-mentioned.
1.2 × P1 ≦ P3 ≦ 1.5 × P1 (F)
0.4 × V1 ≦ V3 ≦ 0.8 × V1 (G)
1.2 × I1 ≦ I3 ≦ 1.5 × I1 (H) Relative movement directions of the upper disk electrode and the lower disk electrode in the first process with respect to the plurality of steel plates, and the upper disk electrode and the lower disk electrode in the second process The method of forming a welded joint according to any one of claims 1 to 5 , wherein a relative moving direction with respect to the plurality of steel plates is opposite. It is a method for forming a welded joint that forms a welded joint by performing mash seam welding on the overlapping portion of a plurality of steel plates,
An upper disk electrode and a lower disk electrode disposed above and below the overlapping portion, each of the upper disk electrode and the lower disk electrode made of copper alloy being rotated. The upper disc electrode and the lower disc are arranged so as to be along the planned joining portion while performing pressurization and energization to the joining planned location of the overlapping portion by the plate electrode and the lower disc electrode. By moving the electrode relative to the plurality of steel plates, performing a mash seam welding on the joint planned portion of the overlapping portion, and forming a joint portion;
After the first step, an upper disk electrode and a lower disk electrode disposed above and below the overlapping portion, each rotating an upper disk electrode and a lower disk electrode made of copper alloy. In this state, the upper disc electrode and the lower disc electrode are arranged so as to be along the junction while pressing and energizing the junction with the upper disc electrode and the lower disc electrode. A second step of performing heat treatment on the joint by moving a disk electrode relative to the plurality of steel plates,
Said at least one steel plate of the plurality of steel plates, carbon equivalent Ceq is represented by the following formula (A) state, and are 0.31 [wt%] or more,
The applied pressure, which is the pressure applied to the overlapping portion in the first step, is P1 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the first step A welding speed that is a relative moving speed with respect to the steel plate is V1 [m / min], and a welding current that is a value of a current flowing through the plurality of steel plates in the first step is I1 [kN],
The applied pressure, which is the pressure applied to the overlapping portion in the second step, is P2 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the second step When the welding speed that is a relative moving speed with respect to the steel plate is V2 [m / min], and the welding current that is the value of the current flowing through the plurality of steel plates in the second step is I2 [kN], (B) Formula, (C) Formula, and (D) Formula are formed, The formation method of the welded joint characterized by the above-mentioned.
Ceq = [C] + [Si] / 30 + [Mn] / 20 + 2 [P] +4 [S] (A)
1.0 × P1 ≦ P2 ≦ 1.5 × P1 (B)
0.4 × V1 ≦ V2 ≦ 0.8 × V1 (C)
1.0 × I1 ≦ I2 ≦ 1.5 × I1 (D)
Here, [C], [Si], [Mn], [P], and [S] are the contents (mass%) of C, Si, Mn, P, and S, respectively. The upper disk electrode and the lower disk electrode used in the first process and the upper disk electrode and the lower disk electrode used in the second process are the same. The method for forming a welded joint according to claim 7 . Relative movement directions of the upper disk electrode and the lower disk electrode in the first process with respect to the plurality of steel plates, and the upper disk electrode and the lower disk electrode in the second process The method of forming a welded joint according to claim 7 , wherein a relative moving direction of the plurality of steel plates is in a reverse direction. It is a method for forming a welded joint that forms a welded joint by performing mash seam welding on the overlapping portion of a plurality of steel plates,
An upper disk electrode and a lower disk electrode disposed above and below the overlapping portion, each of the upper disk electrode and the lower disk electrode made of copper alloy being rotated. The upper disc electrode and the lower disc are arranged so as to be along the planned joining portion while performing pressurization and energization to the joining planned location of the overlapping portion by the plate electrode and the lower disc electrode. By moving the electrode relative to the plurality of steel plates, performing a mash seam welding on the joint planned portion of the overlapping portion, and forming a joint portion;
After the first step, an upper disk electrode and a lower disk electrode disposed above and below the overlapping portion, each rotating an upper disk electrode and a lower disk electrode made of copper alloy. In this state, the upper disc electrode and the lower disc electrode are arranged so as to be along the junction while pressing and energizing the junction with the upper disc electrode and the lower disc electrode. A second step of performing heat treatment on the joint by moving a disk electrode relative to the plurality of steel plates,
In the second step, the heat treatment is performed on the bonding portion, and the processing of bringing the thickness of the overlapping portion closer to the thickness of the other region is performed simultaneously.
A method for forming a welded joint, wherein a carbon equivalent Ceq represented by the following formula (A) of at least one of the plurality of steel plates is 0.31 [% by mass] or more.
Ceq = [C] + [Si] / 30 + [Mn] / 20 + 2 [P] +4 [S] (A)
Here, [C], [Si], [Mn], [P], and [S] are the contents (mass%) of C, Si, Mn, P, and S, respectively. 11. The method for forming a welded joint according to claim 10 , wherein the processing is to set an upsetting ratio e shown in the following formula ( B ) to 30 [%] or more and 50 [%] or less.
e = [(To−T) ÷ To] × 100 ( B )
Here, To is the thickness [mm] of the overlapping portion (overlapping portion) of the steel plate before mash seam welding, and T is the thickness [mm] of the overlapping portion after the second step is finished. is there. The applied pressure, which is the pressure applied to the overlapping portion in the first step, is P1 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the first step A welding speed that is a relative moving speed with respect to the steel plate is V1 [m / min], and a welding current that is a value of a current flowing through the plurality of steel plates in the first step is I1 [kN],
A pressing force that is a pressure applied to the overlapping portion in the second step is P3 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the second step When the welding speed, which is a relative moving speed with respect to the steel plate, is V3 [m / min], and the welding current, which is the value of the current flowing through the plurality of steel plates in the second step, is I3 [kN], ( C ) type | formula, ( D ) type | formula, and ( E ) type | formula are formed, The formation method of the welded joint of Claim 11 characterized by the above-mentioned.
1.2 × P1 ≦ P3 ≦ 1.5 × P1 ( C )
0.4 × V1 ≦ V3 ≦ 0.8 × V1 ( D )
1.2 × I1 ≦ I3 ≦ 1.5 × I1 ( E ) The upper disk electrode and the lower disk electrode used in the first process and the upper disk electrode and the lower disk electrode used in the second process are the same. The method for forming a welded joint according to any one of claims 10 to 12 , wherein: Relative movement directions of the upper disk electrode and the lower disk electrode in the first process with respect to the plurality of steel plates, and the upper disk electrode and the lower disk electrode in the second process The method for forming a welded joint according to any one of claims 10 to 13 , wherein a relative movement direction of the plurality of steel plates is opposite. It is a method for forming a welded joint that forms a welded joint by performing mash seam welding on the overlapping portion of a plurality of steel plates,
An upper disk electrode and a lower disk electrode disposed above and below the overlapping portion, each of the upper disk electrode and the lower disk electrode made of copper alloy being rotated. The upper disc electrode and the lower disc are arranged so as to be along the planned joining portion while performing pressurization and energization to the joining planned location of the overlapping portion by the plate electrode and the lower disc electrode. By moving the electrode relative to the plurality of steel plates, performing a mash seam welding on the joint planned portion of the overlapping portion, and forming a joint portion;
After the first step, an upper disk electrode and a lower disk electrode disposed above and below the overlapping portion, each rotating an upper disk electrode and a lower disk electrode made of copper alloy. In this state, the upper disc electrode and the lower disc electrode are arranged so as to be along the junction while pressing and energizing the junction with the upper disc electrode and the lower disc electrode. A second step of performing heat treatment on the joint by moving a disk electrode relative to the plurality of steel plates,
Relative movement directions of the upper disk electrode and the lower disk electrode in the first process with respect to the plurality of steel plates, and the upper disk electrode and the lower disk electrode in the second process And the relative movement direction with respect to the plurality of steel plates is the reverse direction,
A method for forming a welded joint, wherein a carbon equivalent Ceq represented by the following formula (A) of at least one of the plurality of steel plates is 0.31 [% by mass] or more.
Ceq = [C] + [Si] / 30 + [Mn] / 20 + 2 [P] +4 [S] (A)
Here, [C], [Si], [Mn], [P], and [S] are the contents (mass%) of C, Si, Mn, P, and S, respectively. The applied pressure, which is the pressure applied to the overlapping portion in the first step, is P1 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the first step A welding speed that is a relative moving speed with respect to the steel plate is V1 [m / min], and a welding current that is a value of a current flowing through the plurality of steel plates in the first step is I1 [kN],
The applied pressure, which is the pressure applied to the overlapping portion in the second step, is P2 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the second step When the welding speed that is a relative moving speed with respect to the steel plate is V2 [m / min], and the welding current that is the value of the current flowing through the plurality of steel plates in the second step is I2 [kN], formula (B), (C) formula, and forming method of the welded joint according to claim 1 5, characterized in that (D) expression holds.
1.0 × P1 ≦ P2 ≦ 1.5 × P1 (B)
0.4 × V1 ≦ V2 ≦ 0.8 × V1 (C)
1.0 × I1 ≦ I2 ≦ 1.5 × I1 (D) The second step is characterized in that the heat treatment is performed on the bonding portion and the processing of bringing the thickness of the overlapping portion closer to the thickness of other regions is performed simultaneously. 15. The method for forming a welded joint according to 15 . 18. The method for forming a welded joint according to claim 17 , wherein the processing is performed by setting an upsetting ratio e shown in the following expression (E) to 30 [%] or more and 50 [%] or less.
e = [(To−T) ÷ To] × 100 (E)
Here, To is the thickness [mm] of the overlapping portion (overlapping portion) of the steel plate before mash seam welding, and T is the thickness [mm] of the overlapping portion after the second step is finished. is there. The applied pressure, which is the pressure applied to the overlapping portion in the first step, is P1 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the first step A welding speed that is a relative moving speed with respect to the steel plate is V1 [m / min], and a welding current that is a value of a current flowing through the plurality of steel plates in the first step is I1 [kN],
A pressing force that is a pressure applied to the overlapping portion in the second step is P3 [kN], and the plurality of the upper disc electrode and the lower disc electrode in the second step When the welding speed, which is a relative moving speed with respect to the steel plate, is V3 [m / min], and the welding current, which is the value of the current flowing through the plurality of steel plates in the second step, is I3 [kN], The method for forming a welded joint according to claim 18 , wherein the following expressions (F), (G), and (H) are satisfied.
1.2 × P1 ≦ P3 ≦ 1.5 × P1 (F)
0.4 × V1 ≦ V3 ≦ 0.8 × V1 (G)
1.2 × I1 ≦ I3 ≦ 1.5 × I1 (H) The upper disk electrode and the lower disk electrode used in the first process and the upper disk electrode and the lower disk electrode used in the second process are the same. The method for forming a welded joint according to any one of claims 15 to 19 , wherein:

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