Spot welding machine and method for manufacturing spot welded joints

Abstract

The present invention provides a spot welding machine and a method for manufacturing spot-welded joints that can perform welding and tempering of welded joints without increasing the size of the manufacturing equipment or complicating the manufacturing process. [Solution] The spot welding machine (1) of the present invention comprises a first welding electrode (2) and a second welding electrode (3) arranged to face each other, a first tempering electrode (4), and a first holding member (5) that holds the first welding electrode (2) and the first tempering electrode (4). Furthermore, the first holding member (5) is characterized by having a switching mechanism that can switch the arrangement of the electrodes between a welding configuration in which the first welding electrode (2) and the second welding electrode (3) face each other at a predetermined welding position, and a tempering configuration in which the first tempering electrode (4) and the second welding electrode (3) face each other at a predetermined tempering position.

Description

Technical Field

[0001] The present invention relates to a spot welding machine and a method for manufacturing a spot welded joint.

Background Art

[0002] In recent years, high-strength steel sheets used in various fields such as automobiles, home appliances, and building materials have been increasingly developed. For example, in the automotive field, in order to reduce the weight of the vehicle body and parts and improve fuel efficiency, the use of high-strength steel sheets with a thin thickness has been increasing.

[0003] On the other hand, the assembly of the vehicle body and the attachment of parts of an automobile are mainly performed by spot welding from the viewpoints of cost and manufacturing efficiency. However, in spot welding of high-strength steel sheets with a tensile strength of 440 MPa or more, the welded part may break due to insufficient joint strength, and the designed performance of the member may not be obtained. Therefore, even when using high-strength steel sheets, a joining process in which the welded part is difficult to break is required.

[0004] As one such joining process, a post energization method is known in which the structure of the nugget part and the heat affected zone is modified by annealing the welded part. However, the post energization method has not been put into practical use because the range of conditions under which the desired effect can be obtained is narrow and the robustness against production disturbances is low. As a technique for dealing with such problems of the post energization method, for example, in Patent Document 1, a technique has been proposed in which, in an annealing process separate from the welding process for forming a nugget, a plurality of steel sheets are energized in an inclined direction to anneal the nugget.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the technology proposed in Patent Document 1 requires a tempering device in addition to the welding device, which may lead to an increase in the size of the manufacturing equipment for spot-welded joints. Furthermore, when the welded plate assembly (welded joint) is transferred from the welding device to the tempering device, it becomes necessary to align the tempering target area of ​​the welded plate assembly with the tempering electrode, which may complicate the manufacturing process.

[0007] This invention has been made in view of the above circumstances, and aims to provide a spot welding machine and a method for manufacturing spot-welded joints that can perform welding and tempering of welded joints without increasing the size of the manufacturing equipment or complicating the manufacturing process. [Means for solving the problem]

[0008] The present invention includes the following embodiments.

[0009] (Aspect 1) A first welding electrode and a second welding electrode are arranged facing each other, First electrode for tempering, A first holding member that holds the first welding electrode and the first tempering electrode, Equipped with, A spot welding machine characterized in that the first holding member has a switching mechanism that can switch the arrangement of electrodes between a welding configuration in which the first welding electrode and the second welding electrode face each other at a predetermined welding position, and a tempering configuration in which the first tempering electrode and the second welding electrode face each other at a predetermined tempering position.

[0010] (Aspect 2) A first welding electrode and a second welding electrode are arranged facing each other, A first tempering electrode and a second tempering electrode are arranged to face each other, A first holding member that holds the first welding electrode and the first tempering electrode, A second holding member that holds the above-mentioned second welding electrode and the above-mentioned second tempering electrode, Equipped with, A spot welding machine characterized in that each of the above-mentioned first holding member and the above-mentioned second holding member has a switching mechanism that can switch the arrangement of electrodes between a welding configuration in which the first welding electrode and the second welding electrode face each other at a predetermined welding position, and a tempering configuration in which the first tempering electrode and the second tempering electrode face each other at a predetermined tempering position.

[0011] (Aspect 3) The spot welding machine according to embodiment 1 or 2, characterized in that the switching mechanism is a rotating mechanism that rotates each electrode.

[0012] (Aspect 4) The spot welding machine described above is characterized by further comprising a drive device for moving the first holding member closer to or further away from the second welding electrode, and a stopper for restricting the movement of the first tempering electrode when the electrode arrangement is in the welding configuration, as described in any of embodiments 1 to 3 above.

[0013] (Aspect 5) The above spot welding machine further comprises an elastic member disposed between the first tempering electrode and the first holding member, The spot welding machine according to embodiment 4, characterized in that the first tempering electrode is held in the first holding member via the elastic member.

[0014] (Aspect 6) A method for manufacturing a spot-welded joint, which involves performing welding and tempering of the welded joint using a single spot welding machine, The above spot welding machine comprises a first welding electrode and a second welding electrode arranged to face each other, and a first tempering electrode. A welding process in which a plate assembly consisting of multiple overlapping steel plates is clamped between the first welding electrode and the second welding electrode of the spot welding machine described above and current is applied to form a welded part, An electrode switching step of releasing the first welding electrode and the second welding electrode and switching the arrangement form of the first welding electrode and the first tempering electrode so that the first tempering electrode and the second welding electrode face each other at a predetermined tempering position; A tempering step of tempering the welded portion by sandwiching and energizing the plate assembly after welding with the first tempering electrode and the second welding electrode; A method for manufacturing a spot weld joint, characterized by comprising the above.

[0015] (Aspect 7) A method for manufacturing a spot weld joint, which performs welding and tempering of a welded portion using a single spot welding machine, The spot welding machine includes a first welding electrode and a second welding electrode arranged to face each other, and a first tempering electrode and a second tempering electrode; A welding step of forming a welded portion by sandwiching and energizing a plate assembly composed of a plurality of stacked steel plates with the first welding electrode and the second welding electrode of the spot welding machine; An electrode switching step of releasing the first welding electrode and the second welding electrode, and switching the arrangement form of the first welding electrode and the first tempering electrode and the arrangement form of the second welding electrode and the second tempering electrode so that the first tempering electrode and the second tempering electrode face each other at a predetermined tempering position; A tempering step of tempering the welded portion by sandwiching and energizing the plate assembly after welding with the first tempering electrode and the second tempering electrode; A method for manufacturing a spot weld joint, characterized by comprising the above.

[0016] (Aspect 8) The electrode switching step is characterized in that the arrangement form of each electrode is switched by rotating and moving each electrode, and the method for manufacturing a spot weld joint according to the above aspect 6 or 7.

[0017] (Aspect 9) The above welding process is characterized by bringing the first welding electrode and the second welding electrode closer together to clamp the plate assembly while restricting the movement of the first tempering electrode, as described in any of embodiments 6 to 8 above.

[0018] (Aspect 10) The above spot welding machine is A first holding member that holds the first welding electrode and the first tempering electrode, A drive device for moving the first holding member toward or toward the second welding electrode, The device further comprises an elastic member disposed between the first tempering electrode and the first holding member, The first tempering electrode is held by the first holding member via the elastic member. The method for manufacturing a spot welded joint according to embodiment 9, characterized in that the tempering step is performed by bringing the first tempering electrode, which is held in the first holding member by the drive device, close to the second welding electrode to clamp the plate assembly after welding, and applying pressure from the first tempering electrode to the plate assembly using the elastic member.

[0019] (Aspect 11) The above spot welding machine is A first holding member that holds the first welding electrode and the first tempering electrode, A drive device for moving the first holding member toward or toward the second welding electrode, The device further comprises an elastic member disposed between the first tempering electrode and the first holding member, The first tempering electrode is held by the first holding member via the elastic member. The method for manufacturing a spot welded joint according to embodiment 9, characterized in that the tempering step is performed by bringing the first tempering electrode, which is held in the first holding member by the drive device, close to the second tempering electrode to clamp the plate assembly after welding, and applying pressure from the first tempering electrode to the plate assembly using the elastic member. [Effects of the Invention]

[0020] According to the present invention, welding and tempering of the welded area can be performed with a single spot welding machine without increasing the size of the manufacturing equipment or complicating the manufacturing process. [Brief explanation of the drawing]

[0021] [Figure 1] Figure 1 is a schematic cross-sectional view of a spot welding machine 1 according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view showing a modified example of the spot welding machine 1 in Figure 1. [Figure 3] Figure 3 is a schematic cross-sectional view of a spot welding machine 10 according to another embodiment of the present invention. [Figure 4] Figure 4 is a schematic diagram illustrating the usage configuration of the spot welding machine 10 shown in Figure 3. [Modes for carrying out the invention]

[0022] To achieve the above objective, the inventors focused on the common structure of welding and tempering equipment and conducted thorough research. As a result, the inventors discovered that by providing welding electrodes and tempering electrodes in a single spot welding machine, and by providing a means for switching the arrangement of these electrodes, both the welding and tempering processes can be performed with a single spot welding machine. With such a spot welding machine, even if the tempering electrode has a different shape from the welding electrode, the tempering process can be performed in the same spot welding machine as the welding process, making it possible to perform the tempering process easily without causing misalignment.

[0023] The present invention has been completed based on these findings and includes the embodiments described below.

[0024] A spot welding machine according to one embodiment of the present invention comprises a first welding electrode and a second welding electrode arranged to face each other, a first tempering electrode, and a first holding member that holds the first welding electrode and the first tempering electrode. Furthermore, the first holding member has a switching mechanism that can switch the arrangement of the electrodes between a welding configuration in which the first welding electrode and the second welding electrode face each other at a predetermined welding position, and a tempering configuration in which the first tempering electrode and the second welding electrode face each other at a predetermined tempering position.

[0025] The following describes in detail a spot welding machine according to one embodiment of the present invention with reference to the drawings. Figure 1 is a schematic cross-sectional view of a spot welding machine 1 according to one embodiment of the present invention.

[0026] <Spot welding machine> As shown in Figure 1, a spot welding machine 1 according to one embodiment of the present invention comprises a first welding electrode 2 as a movable electrode and a second welding electrode 3 as a fixed electrode, which are arranged to face each other; a first tempering electrode 4, which is arranged horizontally to the first welding electrode 2; and a first holding member 5 that holds the first welding electrode 2 and the first tempering electrode 4.

[0027] Furthermore, as shown in Figure 1, the spot welding machine 1 further includes a drive device 6 that moves the first holding member 5 closer to or further away from the second welding electrode 3, which is the fixed electrode, and arm members 7 to which the drive device 6 and the second welding electrode 3 are attached, respectively, on the upper and lower sides in the vertical direction.

[0028] In this embodiment, the first welding electrode 2 is fixed to the first holding member 5 via a shank 21. Similarly, the first tempering electrode 4 is fixed to the first holding member 5 via a shank 41. Since the first holding member 5, which holds these electrodes, is movable vertically by a drive device 6, more specifically to approach or move away from the second welding electrode 3, the first welding electrode 2 and the first tempering electrode 4 become movable electrodes.

[0029] On the other hand, the second welding electrode 3 is fixed to the arm member 7 via the shank 31, and therefore becomes the fixed electrode. In the spot welding machine 1 shown in Figure 1, the upper side of the arm member 7 is the movable side, and the lower side is the fixed side.

[0030] In this embodiment, the first holding member 5 has a switching mechanism that can switch the arrangement of the electrodes between a welding configuration in which the first welding electrode 2 and the second welding electrode 3 face each other at a predetermined welding position, and a tempering configuration in which the first tempering electrode 4 and the second welding electrode 3 face each other at a predetermined tempering position.

[0031] In this specification, "each electrode facing each other" means a positional relationship where the tips of each electrode face each other, and where a plate assembly consisting of multiple steel plates placed between the tips of each electrode is in a positional relationship that allows current to be passed between the tips of each electrode. In this case, it is not necessary for the axes of each electrode to be located on the same straight line. That is, the axes of each electrode may be located on the same straight line, or they may not be located on the same straight line as long as current can be passed through the plate assembly between the tips of each electrode. Therefore, even if the tips of two electrodes are in a positional relationship that faces each other, if the axes of each electrode are separated by a certain distance or more, and current necessary for welding or tempering cannot be passed through the plate assembly placed between the tips of each electrode, then the relationship does not constitute "each electrode facing each other."

[0032] The spot welding machine 1 of this embodiment is used as follows. First, the first holding member 5 of the spot welding machine 1, whose electrode arrangement is the welding configuration described above, is lowered by the drive device 6, thereby clamping the plate assembly made up of multiple steel plates between the first welding electrode 2 and the second welding electrode 3.

[0033] Next, by applying current to the plate assembly while pressurizing it with the first welding electrode 2 and the second welding electrode 3, a welded joint is formed around the overlapping surfaces of the multiple steel plates within the plate assembly.

[0034] After welding, the first holding member 5 is raised by the drive device 6, thereby releasing the first welding electrode 2 and the second welding electrode 3.

[0035] Then, the switching mechanism of the first holding member 5 moves the first welding electrode 2 and the first tempering electrode 4, thereby switching the electrode arrangement so that the first tempering electrode 4 and the second welding electrode 3 face each other at a predetermined tempering position. In other words, the electrode arrangement is switched from the welding configuration to the tempering configuration. During this time, the welded plate assembly is cooled by the heat within the plate assembly being dissipated into the air.

[0036] After switching the electrode arrangement, the drive device 6 lowers the first holding member 5, so that the welded plate assembly is held between the first tempering electrode 4 and the second welding electrode 3. Next, the welded plate assembly is tempered by applying current while applying pressure with the first tempering electrode 4 and the second welding electrode 3.

[0037] After tempering, the first holding member 5 is raised by the drive device 6, thereby opening the first tempering electrode 4 and the second welding electrode 3. After the electrodes are opened, the tempered plate assembly (i.e., the spot-welded joint) is removed.

[0038] Subsequently, the switching mechanism of the first holding member 5 moves the first welding electrode 2 and the first tempering electrode 4 again, thereby switching the electrode arrangement so that the first welding electrode 2 and the second welding electrode 3 face each other at a predetermined welding position. In other words, the electrode arrangement is switched from the tempering configuration to the welding configuration. This allows the next welding to be performed.

[0039] In this specification, "welded area" refers to the entire portion of a plate assembly after welding, i.e., a spot-welded joint, including the nugget and the heat-affected zone (HAZ). "Nugget" refers to the metal that has melted and solidified during spot welding.

[0040] (Effects and Benefits) As described above, the spot welding machine 1 of this embodiment can perform both welding and tempering of the welded area with a single spot welding machine, eliminating the need for a separate tempering device. Furthermore, in the spot welding machine 1 of this embodiment, after welding, the welded plate assembly and the fixed-side electrode, the second welding electrode 3, do not move, and only the movable-side electrode moves, switching the electrode arrangement. Therefore, unlike conventional methods, there is no need to align the welded plate assembly when transferring it from the welding device to the tempering device.

[0041] Therefore, the spot welding machine 1 of this embodiment can perform both welding and tempering of the welded part with a single spot welding machine without increasing the size of the manufacturing equipment or complicating the manufacturing process.

[0042] The configuration of the spot welding machine 1 of this embodiment will be described in more detail below.

[0043] (First electrode for welding) In the spot welding machine 1 shown in Figure 1, the first welding electrode 2 is held by a first holding member 5 that is movable vertically by a drive device 6. That is, the first welding electrode 2 is positioned as a movable electrode in the spot welding machine 1. In this embodiment, the first welding electrode 2 is not limited to such a movable electrode, but may also be positioned as a fixed electrode. In that case, the first holding member 5 having the above-described switching mechanism will also be positioned on the fixed side (downward side) of the arm member 7 together with the first tempering electrode 4.

[0044] The first welding electrode 2, together with the opposing second welding electrode 3, clamps a plate assembly consisting of multiple overlapping steel plates, and by applying current while applying pressure, a welded area can be formed centered on the overlapping surfaces of the multiple steel plates within the plate assembly.

[0045] The electrode that can be used as the first welding electrode 2 is not particularly limited, and electrodes used in ordinary spot welding machines can be used. Examples of such electrodes include dome-shaped (D-type) electrodes and dome-radius type (DR-type) electrodes.

[0046] (Second electrode for welding) In the spot welding machine 1 shown in Figure 1, the second welding electrode 3 is fixed to the arm member 7 via a shank 31 and is positioned as a fixed electrode. In this embodiment, the second welding electrode 3 is not limited to such a fixed electrode, but may also be positioned as a movable electrode. In that case, the second welding electrode 3 is held by a holding member that can move vertically by a drive device.

[0047] The second welding electrode 3, together with the opposing first welding electrode 2, clamps a plate assembly consisting of multiple overlapping steel plates, and by applying current while applying pressure, a weld can be formed around the overlapping surfaces of the multiple steel plates within the plate assembly. In addition, the second welding electrode 3 is also used when tempering the welded portion within the plate assembly after welding. That is, the second welding electrode 3, together with the first tempering electrode 4 which is switched from the first welding electrode 2 by the first holding member 5, clamps the plate assembly after welding, and by applying current while applying pressure, the structure of the weld can be modified.

[0048] Furthermore, the second welding electrode 3 may be used only for welding and not for tempering the weld, as shown in the modified example described later. In that case, a different electrode, namely the second tempering electrode, is used for tempering the weld.

[0049] The electrode that can be used as the second welding electrode 3 is the same electrode as the first welding electrode 2 described above.

[0050] (1st electrode for tempering) In the spot welding machine 1 shown in Figure 1, the first tempering electrode 4 is held by a first holding member 5 that is movable vertically by a drive device 6. That is, the first tempering electrode 4 is also arranged as a movable electrode together with the first welding electrode 2 in the spot welding machine 1. In this embodiment, the first tempering electrode 4 is not limited to such a movable electrode, but may also be arranged as a fixed electrode. In that case, the first holding member 5 having the above-described switching mechanism will also be arranged on the fixed side (downward side) of the arm member 7 together with the first welding electrode 2.

[0051] The first tempering electrode 4 is used to temper the welded portion within the plate assembly after welding. Together with the opposing second welding electrode 3, it can modify the structure of the welded portion by clamping the plate assembly after welding and applying pressure while applying current.

[0052] The electrode that can be used as the first tempering electrode 4 is not particularly limited as long as it can temper the welded area within the plate assembly, and electrodes used in ordinary spot welding machines or round rod-shaped conductive members extending in the direction of the plate surface perpendicular to the plate thickness direction (horizontal direction in Figure 1) of the plate assembly can be used. Examples of electrodes used in ordinary spot welding machines include dome-shaped (D-type) electrodes and dome radius-type (DR-type) electrodes.

[0053] The first tempering electrode 4 may consist of two or more electrodes, as long as the current path between it and the second welding electrode 3 overlaps with at least a portion of the nugget in the plate assembly after welding. Specifically, the first tempering electrode 4 may consist of two or more electrodes arranged in the plate surface direction (horizontal direction in Figure 1) perpendicular to the plate thickness direction of the plate assembly.

[0054] For example, when the first tempering electrode 4 is composed of two electrodes, it is preferable that each electrode is positioned so as to sandwich the nugget in the plate assembly from the direction of the plate surface, and that the distance between each electrode in the direction of the plate surface, i.e., the distance between electrodes, is greater than the nugget diameter of the nugget in the plate assembly. By arranging the two electrodes constituting the first tempering electrode 4 in this manner, a wide area including the nugget and the heat-affected zone can be tempered. It is even more preferable that the distance between the two electrodes constituting the first tempering electrode 4 is twice or more the nugget diameter.

[0055] If the first tempering electrode 4 is composed of two or more electrodes, these electrodes may be fixed to the first retaining member 5 with or without the member that holds them.

[0056] (First retaining member) In the spot welding machine 1 shown in Figure 1, the first holding member 5 is attached to the drive unit 6 and is arranged to be movable by the drive unit 6 in the vertical direction, that is, to approach or move away from the welding second electrode 3 of the fixed electrode. The first holding member 5 has a switching mechanism that can switch the electrode arrangement between a welding configuration in which the welding first electrode 2 and the welding second electrode 3 face each other at a predetermined welding position, and a tempering configuration in which the tempering first electrode 4 and the welding second electrode 3 face each other at a predetermined tempering position.

[0057] When the welding configuration is set with the first welding electrode 2 and the second welding electrode 3 facing each other, the first holding member 5 is lowered together with the first welding electrode 2 by the drive device 6, and the plate assembly consisting of multiple overlapping steel plates is clamped between the first welding electrode 2 held by the first holding member 5 and the second welding electrode 3 positioned to face it from below. Furthermore, the first holding member 5 is subjected to a force in the direction of downward movement by the drive device 6, that is, in the direction of approaching the second welding electrode 3, and the plate assembly is pressed down by the first welding electrode 2 and the second welding electrode 3. When current is passed while this pressurized force is applied, a weld is formed within the plate assembly.

[0058] Next, the first holding member 5 is raised together with the first welding electrode 2 by the drive device 6, and the first welding electrode 2 and the second welding electrode 3 are opened. Then, the first holding member 5 switches the arrangement of the first welding electrode 2 and the first tempering electrode 4 by a switching mechanism such as a rotation mechanism, so that the first tempering electrode 4 and the second welding electrode 3 face each other at a predetermined tempering position in a tempering configuration.

[0059] Subsequently, the first holding member 5 is lowered by the drive unit 6 together with the first tempering electrode 4, and the welded plate assembly is held between the first tempering electrode 4 and the second welding electrode 3, which are held by the first holding member 5. When current is applied while the plate assembly is held in this position, the welded parts within the plate assembly are tempered.

[0060] Then, the first holding member 5 is raised together with the first tempering electrode 4 by the drive device 6, and the first tempering electrode 4 and the second welding electrode 3 are opened. Next, the first holding member 5 is switched by a switching mechanism such as a rotation mechanism to change the arrangement of the first tempering electrode 4 and the first welding electrode 2, so that the first welding electrode 2 and the second welding electrode 3 face each other at a predetermined welding position in a welding configuration. In this way, welding and tempering of the weld can be performed repeatedly.

[0061] In this embodiment, the switching mechanism of the first holding member 5 is not particularly limited as long as it can switch the electrode arrangement between the welding configuration and the tempering configuration described above. Examples of such switching mechanisms include a rotation mechanism that rotates the first welding electrode 2 and the first tempering electrode 4, a sliding mechanism that slides the first welding electrode 2 and the first tempering electrode 4 in the direction of the plate surface of the plate assembly (horizontal direction in Figure 1), and an inversion mechanism that inverts the first welding electrode 2, which is positioned below the first holding member 5, and the first tempering electrode 4, which is positioned above the first holding member 5.

[0062] In particular, the switching mechanism is preferably a rotating mechanism that rotates the first welding electrode 2 and the first tempering electrode 4, from the viewpoint of saving space in the spot welding machine 1 and ensuring the positional accuracy of the electrodes after switching.

[0063] Furthermore, the first holding member 5 is not particularly limited in terms of its other structure, as long as it holds the first welding electrode 2 and the first tempering electrode 4 and has the switching mechanism described above.

[0064] (Drive system) In the spot welding machine 1 shown in Figure 1, the drive device 6 is a drive device that moves the first holding member 5, which holds the first welding electrode 2 and the first tempering electrode 4, in the vertical direction, that is, to approach or move away from the opposing second welding electrode 3. The drive device 6 is a drive device that performs the operations of clamping, pressing, and releasing the plate assembly by the first welding electrode 2 and the second welding electrode 3, and the operations of clamping the plate assembly and releasing the plates by the first tempering electrode 4 and the second welding electrode 3.

[0065] The drive device 6 that can be used in this embodiment is not particularly limited as long as it can perform the operations described above, and examples include a servo motor, a cylinder device such as an air cylinder or hydraulic cylinder, and a drive device such as a ball screw.

[0066] (Arm component) In the spot welding machine 1 shown in Figure 1, the arm member 7 has a drive unit 6 attached to its upper side in the vertical direction, and a second welding electrode 3 attached to its lower side, supporting the drive unit 6 and the second welding electrode 3 in predetermined positions.

[0067] The arm member 7 has a roughly U-shaped structure with an open end in the horizontal direction, as shown in Figure 1, due to the relative positions of the drive unit 6 and the second welding electrode 3. The structure of the arm member 7 is not limited to this roughly U-shaped structure; it may have other structures as long as they can support the drive unit 6 and the second welding electrode 3 in predetermined positions.

[0068] The spot welding machine 1 of this embodiment can use various power sources such as inverter DC power supplies, inverter AC power supplies, and single-phase AC power supplies. Furthermore, the welding machine may be a stationary type as shown in Figure 1, or it may be a spot welding robot system combining a welding gun and an industrial robot.

[0069] The components of the spot welding machine 1 described above can be appropriately combined, substituted, or modified within the scope that achieves the effects of the present invention.

[0070] Below, several modifications of the spot welding machine 1 will be described in detail with reference to the drawings. Here, Figure 2 is a schematic cross-sectional view showing a modification of the spot welding machine 1 of Figure 1. Note that, apart from the characteristic configuration described below, the spot welding machine 1 shown in Figure 2 is basically the same as the spot welding machine 1 shown in Figure 1, so the explanation will be omitted.

[0071] The spot welding machine 1 shown in Figure 2 comprises a first welding electrode 2 as a movable electrode and a second welding electrode 3 as a fixed electrode, which are arranged facing each other, a first tempering electrode 4a arranged horizontally to the first welding electrode 2, and a second tempering electrode 4b arranged horizontally to the second welding electrode 3. The first tempering electrode 4a and the second tempering electrode 4b can each be electrodes similar to the first tempering electrode of the spot welding machine 1 shown in Figure 1.

[0072] Furthermore, the spot welding machine 1 shown in Figure 2 includes a first holding member 5a that holds the first welding electrode 2 and the first tempering electrode 4a, and a second holding member 5b that holds the second welding electrode 3 and the second tempering electrode 4b. Note that the first holding member 5a and the second holding member 5b can each be the same type of holding member as the first holding member 5 of the spot welding machine 1 shown in Figure 1.

[0073] Furthermore, in the spot welding machine 1 shown in Figure 2, each of the first holding member 5a and the second holding member 5b has a switching mechanism that can switch the electrode arrangement between a welding configuration in which the first welding electrode 2 and the second welding electrode 3 face each other at a predetermined welding position, and a tempering configuration in which the first tempering electrode 4a and the second tempering electrode 4b face each other at a predetermined tempering position.

[0074] The spot welding machine 1 shown in Figure 2 is used as follows. First, the first holding member 5a of the spot welding machine 1, whose electrode arrangement is the welding configuration described above (i.e., the configuration shown in Figure 2), is lowered by the drive device 6, thereby clamping the plate assembly made up of multiple steel plates between the first welding electrode 2 and the second welding electrode 3.

[0075] Next, by applying current to the plate assembly while pressurizing it with the first welding electrode 2 and the second welding electrode 3, a welded joint is formed around the overlapping surfaces of the multiple steel plates within the plate assembly.

[0076] After welding, the first holding member 5a is raised by the drive device 6, thereby releasing the first welding electrode 2 and the second welding electrode 3.

[0077] Then, the switching mechanism of the first holding member 5a moves the first welding electrode 2 and the first tempering electrode 4a, and the switching mechanism of the second holding member 5b moves the second welding electrode 3 and the second tempering electrode 4b, thereby switching the electrode arrangement so that the first tempering electrode 4a and the second tempering electrode 4b face each other at a predetermined tempering position. In other words, the electrode arrangement is switched from a welding configuration to a tempering configuration. During this time, the plate assembly after welding is cooled by the heat inside the plate assembly being dissipated into the air.

[0078] After switching the electrode arrangement, the drive device 6 lowers the first holding member 5a so that the welded plate assembly is held between the first tempering electrode 4a and the second tempering electrode 4b. Next, the welded portion within the plate assembly is tempered by applying current while applying pressure to the welded plate assembly with the first tempering electrode 4a and the second tempering electrode 4b.

[0079] After tempering, the first holding member 5a is raised by the drive device 6, thereby opening the first tempering electrode 4a and the second tempering electrode 4b. After the electrodes are opened, the tempered plate assembly (i.e., the spot-welded joint) is removed.

[0080] Subsequently, the switching mechanism of the first holding member 5a moves the first welding electrode 2 and the first tempering electrode 4a again, and the switching mechanism of the second holding member 5b moves the second welding electrode 3 and the second tempering electrode 4b again, thereby switching the electrode arrangement so that the first welding electrode 2 and the second welding electrode 3 face each other at a predetermined welding position. In other words, the electrode arrangement is switched from the tempering configuration to the welding configuration. This makes it possible to perform the next welding.

[0081] (Effects and Benefits) As described above, the spot welding machine 1 shown in Figure 2 can perform both welding and tempering of the welded area with a single spot welding machine, eliminating the need for a separate tempering device. Therefore, the spot welding machine 1 shown in Figure 2 can also perform both welding and tempering of the welded area with a single spot welding machine without increasing the size of the manufacturing equipment or complicating the manufacturing process.

[0082] Next, a spot welding machine according to another embodiment of the present invention, which is also a further modification of spot welding machine 1, will be described in detail with reference to the drawings. Here, Figure 3 is a schematic cross-sectional view of spot welding machine 10 according to another embodiment of the present invention. In the spot welding machine 10 of the embodiment shown in Figure 3, other than the characteristic configuration described below, it is basically the same as the spot welding machine 1 shown in Figure 1, so the description will be omitted.

[0083] The spot welding machine 10 shown in Figure 3, similar to the embodiment shown in Figure 1 above, comprises a first welding electrode 2 and a second welding electrode 3 arranged to face each other, a first tempering electrode 40, and a first holding member 5 that holds the first welding electrode 2 and the first tempering electrode 40.

[0084] The spot welding machine 10 also further includes a drive device 6 that moves the first holding member 5 closer to or further away from the second welding electrode 3, which is the fixed electrode, and arm members 7 to which the drive device 6 and the second welding electrode 3 are attached, respectively, on the upper and lower sides in the vertical direction.

[0085] Furthermore, in the spot welding machine 10, the first holding member 5 has a switching mechanism that can switch the arrangement of the electrodes between a welding configuration in which the first welding electrode 2 and the second welding electrode 3 face each other at a predetermined welding position, and a tempering configuration in which the first tempering electrode 40 and the second welding electrode 3 face each other at a predetermined tempering position.

[0086] In the spot welding machine 10, as shown in Figure 3, the first tempering electrode 40 is held in the first holding member 5 via an elastic member 9. A shank 41 is connected to the first tempering electrode 40, extending in the direction opposite to the electrode tip (upward in the vertical direction in Figure 3). This shank 41 is not fixed to the first holding member 5, but extends through an insertion hole formed in the first holding member 5, and a flange portion 41a is formed at the end opposite to the electrode tip.

[0087] Furthermore, as shown in Figure 3, the spot welding machine 10 is equipped with a stopper 8 provided on the upper horizontal portion of the arm member 7 and extending downward from the arm member 7 in a substantially L-shape. As shown in Figure 3, the stopper 8 is provided on the arm member 7 at a position that substantially corresponds vertically to the position of the first tempering electrode 40 when the electrode arrangement is the welding configuration described above.

[0088] Near the end of the stopper 8, a recess 8a is formed that is recessed in the horizontal direction (in Figure 3, from the front to the back in the horizontal direction). This recess 8a is sized and shaped so that the shank 41 extending from the first tempering electrode 40 can slide through it, but the flange portion 41a cannot pass through it.

[0089] As shown in Figure 3, when the electrode arrangement is the welding configuration described above, the shank 41 extending from the tempering first electrode 40 is slidably positioned in the recess 8a. However, in this welding configuration, when the tempering first electrode 40 descends to a predetermined position, the recess 8a of the stopper 8 and the flange portion 41a of the shank 41 engage, thereby restricting the movement of the tempering first electrode 40 connected to the lower end of the shank 41. At this time, since the tempering first electrode 40 is held by the first holding member 5 via the elastic member 9, and the shank 41 extending from the tempering first electrode 40 also extends through the insertion hole of the first holding member 5 and is not directly fixed to the first holding member 5, even if the vertical movement of the tempering first electrode 40 is restricted, the first holding member 5 can still move vertically.

[0090] The position at which the downward movement of the first tempering electrode 40 is restricted by the stopper 8 is set to a position that does not interfere with the plate assembly held between the first welding electrode 2 and the second welding electrode 3.

[0091] When the electrode arrangement is switched to the tempering configuration described above, the shank 41 moves away from the recess 8a of the stopper 8 as the first tempering electrode 40 moves. As a result, the first tempering electrode 40, together with the first holding member 5 which is held via the elastic member 9, can move freely in the vertical direction.

[0092] When the tempering electrode 40 descends in the tempering configuration and clamps the welded plate assembly together with the welding electrode 3, the elastic member 9, which is positioned between the tempering electrode 40 and the first holding member 5, is compressed. The resulting extension force (rebound force) of the elastic member 9 pressurizes the welded plate assembly clamped between the tempering electrode 40 and the welding electrode 3.

[0093] The spot welding machine 10 of this embodiment, which has the characteristic configuration described above, is used as follows. Here, Figure 4 is a schematic explanatory diagram showing the usage form of the spot welding machine 10 shown in Figure 3. Although a plate assembly consisting of multiple steel plates is not shown in Figure 4, the plate assembly is arranged so that the contact position L1 between the electrode tips of the first welding electrode 2 and the second welding electrode 3 in Figure 4(a), or the contact position L1 between the electrode tips of the first tempering electrode 40 and the second welding electrode 3 in Figure 4(d), is the center in the thickness direction of the plate assembly.

[0094] (How to use) When using the spot welding machine 10 of this embodiment, first, the first holding member 5 of the spot welding machine 10, which has the electrode arrangement configuration described above for welding, is lowered by the drive device 6. At this time, the first tempering electrode 40 also descends along with the lowering of the first holding member 5, but when it reaches a predetermined position in the vertical direction, the recess 8a of the stopper 8 and the flange portion 41a of the shank 41 engage, restricting the movement of the first tempering electrode 40.

[0095] Even after the movement of the first tempering electrode 40 is restricted, the first holding member 5 continues to descend while compressing the elastic member 9 positioned between the first tempering electrode 40 and the first holding member 5, so that the plate assembly made up of multiple steel plates is held between the first welding electrode 2 and the second welding electrode 3, as shown in Figure 4(a).

[0096] Next, by applying current while pressurizing the plate assembly with the first welding electrode 2 and the second welding electrode 3, a welded joint is formed centered on the overlapping surfaces of the multiple steel plates within the plate assembly.

[0097] After welding, the drive unit 6 raises the first holding member 5, releasing the first welding electrode 2 and the second welding electrode 3 as shown in Figure 4(b). At this time, as the first holding member 5 rises, the elastic member 9 that was compressed between the first tempering electrode 40 and the first holding member 5 stretches. However, when the first holding member 5 rises to a predetermined position, the elastic member 9 stops stretching, and the first tempering electrode 40 begins to rise. This rise of the first tempering electrode 40 causes the recess 8a of the stopper 8 and the flange portion 41a of the shank 41 to separate, and the engagement between the two is released.

[0098] Then, by moving the first welding electrode 2 and the first tempering electrode 40 using the switching mechanism of the first holding member 5, the electrode arrangement is switched so that the first tempering electrode 40 and the second welding electrode 3 face each other at a predetermined tempering position, as shown in Figure 4(c). In other words, the electrode arrangement is switched from the welding configuration to the tempering configuration. During this time, the plate assembly after welding is cooled by the heat inside the plate assembly being dissipated into the air.

[0099] After switching the electrode arrangement, as shown in Figure 4(d), the drive device 6 lowers the first holding member 5, so that the welded plate assembly is held between the tempering first electrode 40 and the welding second electrode 3. At this time, the elastic member 9, which is placed between the tempering first electrode 40 and the first holding member 5, is compressed, and the resulting stretching force (rebound force) of the elastic member 9 pressurizes the welded plate assembly held between the tempering first electrode 40 and the welding second electrode 3.

[0100] Next, the welded portion within the plate assembly is tempered by applying current while pressurizing the plate assembly with the first tempering electrode 40 and the second welding electrode 3.

[0101] After tempering, the first holding member 5 is raised by the drive device 6, which opens the first tempering electrode 40 and the second welding electrode 3, as shown in Figure 3(e). After the electrodes are opened, the tempered plate assembly (i.e., the spot-welded joint) is removed.

[0102] Subsequently, the switching mechanism of the first holding member 5 moves the first welding electrode 2 and the first tempering electrode 40 again, thereby switching the electrode arrangement so that the first welding electrode 2 and the second welding electrode 3 face each other at a predetermined welding position. In other words, the electrode arrangement is switched from the tempering configuration to the welding configuration. This allows the next welding to be performed.

[0103] (Effects and Benefits) As described above, the spot welding machine 10 of this embodiment can perform both welding and tempering of the welded area with a single spot welding machine, eliminating the need for a separate tempering device. Furthermore, in the spot welding machine 10 of this embodiment, after welding, the welded plate assembly and the fixed-side electrode, the second welding electrode 3, do not move, and only the movable-side electrode moves, switching the electrode arrangement. Therefore, unlike conventional methods, there is no need to align the welded plate assembly when transferring it from the welding device to the tempering device.

[0104] Therefore, the spot welding machine 10 of this embodiment can also perform welding and tempering of the welded part with a single spot welding machine without increasing the size of the manufacturing equipment or complicating the manufacturing process.

[0105] Furthermore, as shown in Figure 4(a), the spot welding machine 10 is equipped with a stopper 8 that restricts the movement of the first tempering electrode 40 when the electrode arrangement is in the welding configuration. Therefore, when the first welding electrode 2 and the second welding electrode 3 clamp the plate assembly, the first tempering electrode 40 does not interfere with the plate assembly. As a result, the spot welding machine 10 of this embodiment can further reduce processes such as plate assembly alignment, and can more reliably suppress the complexity of the manufacturing process.

[0106] The stopper 8 that can be used in this embodiment is not limited to those shown in Figures 3 and 4 above, as long as it can restrict the movement of the first tempering electrode 40 when the electrode arrangement is in a welding configuration. For example, the stopper 8 may be composed of a projection that engages with a recess formed in a shank 41 extending from the first tempering electrode 40, or the shank 41 extending from the first tempering electrode 40 may be composed of a ball screw, and the stopper 8 may be composed of a movement-restricting member provided on the ball screw.

[0107] Furthermore, the spot welding machine 10 is equipped with an elastic member 9 positioned between the first tempering electrode 40 and the first holding member 5, and since the first tempering electrode 40 is held by the first holding member 5 via the elastic member 9, even if the downward movement of the first tempering electrode 40 is restricted when the electrode arrangement is in the welding configuration, the vertical movement of the first holding member 5 is possible. In addition, when the first tempering electrode 40 descends in the tempering configuration and clamps the welded plate assembly together with the second welding electrode 3, the elastic member 9, positioned between the first tempering electrode 40 and the first holding member 5, is compressed, and the resulting stretching force (rebound force) of the elastic member 9 pressurizes the welded plate assembly clamped between the first tempering electrode 40 and the second welding electrode 3. In other words, the spot welding machine 10 can achieve the complex movement control of the tempering first electrode 40 described above without the need to add a drive device such as a servo motor, thanks to the elastic member 9 positioned between the tempering first electrode 40 and the first holding member 5.

[0108] The elastic member 9 that can be used in this embodiment is not particularly limited as long as it is positioned between the first tempering electrode 40 and the first holding member 5, can elastically support the first tempering electrode 40, and can apply a predetermined pressing force to the welded plate assembly sandwiched between the first tempering electrode 40 and the second welding electrode 3 by the tensile force generated when it is compressed. For example, the elastic member 9 may be a coil spring having a helical structure or a leaf spring. In particular, it is preferable to use a coil spring because it can save space in the spot welding machine 10 by inserting the shank 41 extending from the first tempering electrode 40 into the inside of the helical structure.

[0109] In the spot welding machine 10 of this embodiment, the configurations other than the characteristic configuration described above, namely the first welding electrode 2, the second welding electrode 3, the first tempering electrode 40, the drive device 6, the arm member 7, etc., are the same as those in the embodiment shown in Figure 1 above, so their description will be omitted.

[0110] Next, a method for manufacturing a spot-welded joint according to yet another embodiment of the present invention will be described. In the following description, a manufacturing method using the spot welding machine 1 shown in Figure 1 will be described, but even when using the spot welding machine 10 shown in Figure 3, the process is the same except for matters related to the movement control of the first tempering electrode 40, which is achieved by the stopper 8 and the elastic member 9. In other words, the method for manufacturing a spot-welded joint according to this embodiment can also be carried out using the spot welding machine 10 shown in Figure 3.

[0111] <Method for manufacturing spot welded joints> The method for manufacturing a spot-welded joint according to this embodiment is a method for manufacturing a spot-welded joint that uses a single spot welding machine 1 equipped with a first welding electrode 2 and a second welding electrode 3 arranged to face each other, and a first tempering electrode 4, to perform welding and tempering of the welded joint. The manufacturing method according to this embodiment has the following welding steps, electrode switching steps, and tempering steps.

[0112] The welding process involves clamping a plate assembly consisting of multiple overlapping steel plates between the first welding electrode 2 and the second welding electrode 3 of the spot welding machine 1 and applying an electric current to form a welded joint.

[0113] The electrode switching process involves opening the first welding electrode 2 and the second welding electrode 3, and switching the arrangement of the first welding electrode 2 and the first tempering electrode 4 so that the first tempering electrode 4 and the second welding electrode 3 face each other at a predetermined tempering position.

[0114] The tempering process involves clamping the welded plate assembly between a first tempering electrode 4 and a second welding electrode 3, and applying an electric current to temper the welded portion.

[0115] (Effects and Benefits) As described above, the manufacturing method of this embodiment allows welding and tempering of the welded area to be performed using a single spot welding machine 1, eliminating the need for a separate tempering device. Furthermore, in the manufacturing method of this embodiment, after welding, the welded plate assembly and the fixed-side electrode, the second welding electrode 3, do not move, and only the movable electrode moves, switching the electrode arrangement. Therefore, there is no need to align the welded plate assembly when transferring it from the welding device to the tempering device, as is done in the conventional method.

[0116] Therefore, the manufacturing method of this embodiment allows welding and tempering of the welded joint to be performed with a single spot welding machine 1 without increasing the size of the manufacturing equipment or complicating the manufacturing process, and as a result, a spot welded joint with excellent joint strength can be obtained.

[0117] The following describes in detail each step in the method for manufacturing the spot-welded joint according to this embodiment.

[0118] (Welding process) In this embodiment, the welding process involves clamping a plate assembly consisting of multiple overlapping steel plates between the first welding electrode 2 and the second welding electrode 3 of the spot welding machine 1 and applying current to form a weld on the overlapping surface of the steel plates within the plate assembly and the surrounding area. More specifically, the process involves clamping a plate assembly consisting of multiple overlapping steel plates between the first welding electrode 2 and the second welding electrode 3 of the spot welding machine 1, and then applying pressure while applying current in the thickness direction at a predetermined current and energizing time to form a weld on the overlapping surface of the steel plates within the plate assembly and the surrounding area.

[0119] The energizing conditions in the welding process should be set according to the desired joint strength and other factors. Examples of energizing conditions include the energizing current, energizing time, and the pressure applied by the electrodes. Examples of current values ​​include 4kA to 12kA. Examples of energizing time include 12 cycles to 60 cycles. Note that when the power supply frequency is 50Hz, 1 cycle is 1 / 50 of a second. Examples of pressure applied by the electrodes include 250kgf to 700kgf (approximately 2.451kN to approximately 6.864kN).

[0120] In the welding process, the number of times the current is applied is not particularly limited; for example, it may be applied only once or multiple times (two or more). Furthermore, in the welding process, pre-application of current may be performed as long as it does not hinder the effects of the present invention.

[0121] (Switching process) In this embodiment, the electrode switching step involves opening the first welding electrode 2 and the second welding electrode 3 after welding, and switching the arrangement of the first welding electrode 2 and the first tempering electrode 4 so that the first tempering electrode 4 and the second welding electrode 3 face each other at a predetermined tempering position. That is, after opening the first welding electrode 2 and the second welding electrode 3, the electrode arrangement is switched by moving the first welding electrode 2 and the first tempering electrode 4 so that the first tempering electrode 4 and the second welding electrode 3 face each other at a predetermined tempering position.

[0122] During the period from electrode opening to the completion of electrode switching, the plate assembly, consisting of multiple steel plates after welding, is cooled by the heat released into the air. This cooling causes the nugget formed during the welding process to undergo martensitic transformation.

[0123] In this embodiment, after welding, the first welding electrode 2 and the second welding electrode 3 of the spot welding machine 1 may not be opened. Instead, the welded plate assembly may be held in an unpowered state by these electrodes, allowing the heat within the plate assembly to dissipate to the electrodes. In this case, the electrode switching process can be performed after the welded plate assembly has cooled.

[0124] In the electrode switching process, the movement mode of the first welding electrode 2 and the first tempering electrode 4 is not particularly limited. Examples of movement modes for the first welding electrode 2 and the first tempering electrode 4 include a mode in which the first welding electrode 2 and the first tempering electrode 4 are rotated, a mode in which the first welding electrode 2 and the first tempering electrode 4 are slid in the direction of the plate surface of the plate assembly (horizontal direction in Figure 1), and a mode in which the first welding electrode 2, which is positioned on the lower side in the vertical direction, and the first tempering electrode 4, which is positioned on the upper side in the vertical direction, are inverted vertically.

[0125] In particular, the movement mode of the first welding electrode 2 and the first tempering electrode 4 is preferably such that the first welding electrode and the first tempering electrode 4 are rotated, from the viewpoint of saving space in the spot welding machine 1 and ensuring the positioning accuracy of the electrodes after switching.

[0126] (Tempering process) In this embodiment, the tempering process is a process of tempering the welded portion within the plate assembly by clamping the welded plate assembly between the first tempering electrode 4 and the second welding electrode 3 after switching the electrode arrangement configuration and applying current. In the tempering process, first, the welded plate assembly is clamped in the thickness direction between the first tempering electrode 4 and the second welding electrode 3. At this time, the welded plate assembly may be pressed in the thickness direction. By pressing in this way, the first tempering electrode 4 and the second welding electrode 3 can be made to contact the surface of the plate assembly more reliably.

[0127] When applying pressure to a plate assembly after welding, the applied pressure is preferably 30% to 70% of the pressure applied by the electrodes during welding. Setting the pressure applied during the tempering process within this range makes it less likely for deformation of the steel plate within its thickness to occur due to thermal expansion.

[0128] Then, current is applied to the welded plate assembly, which is sandwiched between the first tempering electrode 4 and the second welding electrode 3. This allows the martensitic structure in at least a portion of the welded area within the plate assembly, i.e., the nugget and its surrounding heat-affected zone (HAZ).

[0129] The energizing conditions in the tempering process can be the same as those used in a normal post-tempering energizing method, as long as the energizing path overlaps with at least a portion of the nugget. Examples of energizing conditions include the energizing current, energizing time, and electrode pressure.

[0130] These energizing conditions are usually set according to the desired joint strength, etc. For example, the tempering temperature is 500°C~A c3 Temperatures within the range of points are listed, preferably 600℃~A c1 A range of temperatures within this point range can be cited. When the tempering temperature is within this range, sufficient heat input easily reduces hardness, meaning toughness is easily improved, and re-hardening due to re-quenching is less likely to occur.

[0131] After the tempering process, the first tempering electrode 4 and the second welding electrode 3 are opened, and the tempered plate assembly, i.e., the spot-welded joint, is removed.

[0132] Subsequently, the welding electrode 2 and tempering electrode 4 are moved again to switch the electrode arrangement so that the welding electrode 2 faces the welding electrode 3. This allows the next welding to be performed.

[0133] Each step of the method for manufacturing spot-welded joints described above can be appropriately combined, substituted, or modified within the scope that achieves the effects of the present invention. Below, variations of the above-described method for manufacturing spot-welded joints will be explained.

[0134] First, we will explain the manufacturing method using the spot welding machine 1 shown in Figure 2. Note that, apart from the characteristic steps described below, this manufacturing method is basically the same as the manufacturing method of the embodiment described above, and therefore, the explanation will be omitted.

[0135] The manufacturing method using the spot welding machine 1 shown in Figure 2 is a method for manufacturing spot-welded joints, which involves welding and tempering the welded joint using a single spot welding machine 1 as shown in Figure 2, which is equipped with a first welding electrode 2 and a second welding electrode 3 arranged facing each other, and a first tempering electrode 4a and a second tempering electrode 4b arranged facing each other. This manufacturing method also includes a welding step, an electrode switching step, and a tempering step.

[0136] The welding process involves clamping a plate assembly consisting of multiple overlapping steel plates between the first welding electrode 2 and the second welding electrode 3 of the spot welding machine 1 shown in Figure 2, and applying an electric current to form a welded joint.

[0137] The electrode switching process involves opening the first welding electrode 2 and the second welding electrode 3, and switching the arrangement of the first welding electrode 2 and the first tempering electrode 4a, and the arrangement of the second welding electrode 3 and the second tempering electrode 4b, so that the first tempering electrode 4a and the second tempering electrode 4b face each other at a predetermined tempering position.

[0138] The tempering process involves clamping the welded plate assembly between a first tempering electrode 4a and a second tempering electrode 4b and applying an electric current to temper the welded area.

[0139] (Effects and Benefits) In this manufacturing method, welding and tempering of the welded area can be performed using a single spot welding machine 1, eliminating the need for a separate tempering device. Therefore, this manufacturing method also allows welding and tempering of the welded area to be performed using a single spot welding machine 1 without increasing the size of the manufacturing equipment or complicating the manufacturing process, resulting in spot-welded joints with excellent joint strength.

[0140] Furthermore, as a further modification of the above-described method for manufacturing spot-welded joints, for example, the welding process is preferably carried out by bringing the first welding electrode and the second welding electrode close together to clamp the plate assembly while restricting the movement of the first tempering electrode. Such a welding process can be carried out, for example, by using the spot welding machine 10 shown in Figure 3. That is, the spot welding machine 10 is equipped with a stopper 8 that restricts the movement of the first tempering electrode 40 when in welding configuration, so that, as shown in Figure 4(a), the downward movement of the first tempering electrode 40 can be restricted while bringing the first welding electrode 2 and the second welding electrode 3 close together to clamp the plate assembly.

[0141] When the first welding electrode 2 and the second welding electrode 3 are brought close together to clamp the plate assembly, if the downward movement of the first tempering electrode 40 is restricted, the first tempering electrode 40 will not interfere with the plate assembly, thus reducing the need for processes such as aligning the plate assembly. This makes it possible to more reliably suppress the complexity of the manufacturing process.

[0142] Furthermore, in the tempering process, it is preferable that the drive device brings the first tempering electrode, held in the first holding member, close to the second welding electrode to clamp the welded plate assembly, and that an elastic member placed between the first tempering electrode and the first holding member applies pressure from the first tempering electrode to the plate assembly. Such a tempering process can also be carried out, for example, using the spot welding machine 10 shown in Figure 3. That is, the drive device 6 of the spot welding machine 10 brings the first tempering electrode 40, held in the first holding member 5, close to the second welding electrode 3 to clamp the welded plate assembly, and an elastic member 9 placed between the first tempering electrode 40 and the first holding member 5 applies pressure from the first tempering electrode 40 to the plate assembly, as shown in Figure 4(d). Specifically, when the first tempering electrode 40 descends and clamps the welded plate assembly together with the second welding electrode 3, the elastic member 9, which is positioned between the first tempering electrode 40 and the first holding member 5, is compressed. The resulting extension force (rebound force) of the elastic member 9 pressurizes the welded plate assembly clamped between the first tempering electrode 40 and the second welding electrode 3.

[0143] According to this tempering process, the elastic member 9 positioned between the first tempering electrode 40 and the first holding member 5 eliminates the need to add a drive device such as a servo motor, and enables the complex movement control of the first tempering electrode 40 described above.

[0144] Furthermore, the tempering process may be carried out by applying the configuration of the stopper 8 and elastic member 9 of the spot welding machine 10 in Figure 3 described above to the spot welding machine 1 shown in Figure 2, bringing the first tempering electrode 4a held by the first holding member 5a close to the second tempering electrode 4b by the drive device 6 to clamp the plate assembly after welding, and applying pressure from the first tempering electrode 4a to the plate assembly by the elastic member 9.

[0145] Even in such a tempering process, the elastic member 9 positioned between the first tempering electrode 4a and the first holding member 5a eliminates the need to add a drive device such as a servo motor, and enables the complex movement control of the first tempering electrode 4a described above.

[0146] In the method for manufacturing spot-welded joints according to this embodiment, any process that is performed before or after each step, as is done in conventional spot welding, may be carried out. Examples of such optional processes include a plate assembly process, a cooling process, and a surface treatment process.

[0147] (steel plate) The multiple steel plates to be welded in the manufacturing method of this embodiment can be steel plates having any strength appropriate to the desired joint strength and application. Examples of such steel plates include high-strength steel plates having a tensile strength of 440 MPa or more. When such high-strength steel plates are used, the risk of the welded joint becoming brittle and fracturing after welding is significantly increased, so the present invention is particularly advantageous when such high-strength steel plates are used.

[0148] The tensile strength of the steel sheet may be 740 MPa or higher, 980 MPa or higher, 1200 MPa (1.2 GPa) or higher, 1400 MPa (1.4 GPa) or higher, 1600 MPa (1.6 GPa) or higher, 1800 MPa (1.8 GPa) or higher, or 2000 MPa (2.0 GPa) or higher. While there is no particular upper limit to the tensile strength of the steel sheet, from the standpoint of toughness and formability, the tensile strength of the steel sheet may be, for example, 4000 MPa (4.0 GPa) or lower, or 3000 MPa (3.0 GPa) or lower.

[0149] The tensile strength (TS) of a steel plate can be measured by cutting a No. 5 tensile test specimen, as specified in JIS Z2241:2011, from the steel plate and performing a tensile test in accordance with JIS Z2241:2011.

[0150] Furthermore, there are no particular limitations on the type of steel plate; any steel plate can be used that is appropriate to the characteristics required of the part to which the welded joint is applied. For example, the steel plate may be unplated steel plate, or it may be plated steel plate with zinc, aluminum, etc.

[0151] Furthermore, the number of steel plates is not particularly limited and may be any two or more plates depending on the strength required for the part to which the welded joint is applied. For example, the number of steel plates may be two, three, or four or more.

[0152] (Examples of application) As described above, the spot welding machine and the method for manufacturing spot-welded joints of the present invention can perform welding and tempering of the welded joint with a single spot welding machine without increasing the size of the manufacturing equipment or complicating the manufacturing process. Therefore, it can be applied to various structural components of transportation machinery such as automobiles and industrial machinery where high production efficiency and excellent joint strength are required. In particular, the present invention can be used in the manufacture of automobile bodies and parts.

[0153] The spot welding machine and the method for manufacturing spot welding joints of the present invention are not limited to the embodiments described above, and can be appropriately combined, substituted, or modified without departing from the purpose and spirit of the present invention. In this specification, ordinal numbers such as "1st," "2nd," etc., are used to distinguish the items to which they are assigned, and do not indicate the order, priority, importance, etc. of each item. [Explanation of Symbols]

[0154] 1 Spot welding machine 2. First electrode for welding 3. Second electrode for welding 4 1st electrode for tempering 5. First retaining member 6. Drive unit 7 Arm Member 8 Stoppers 9 Elastic members 10 Spot Welding Machines 40 1st electrode for tempering

Claims

1. A first welding electrode and a second welding electrode are arranged facing each other, First electrode for tempering, A first holding member that holds the first welding electrode and the first tempering electrode, Equipped with, A spot welding machine characterized in that the first holding member has a switching mechanism that can switch the arrangement of electrodes between a welding configuration in which the first welding electrode and the second welding electrode face each other at a predetermined welding position, and a tempering configuration in which the first tempering electrode and the second welding electrode face each other at a predetermined tempering position.

2. A first welding electrode and a second welding electrode are arranged facing each other, A first tempering electrode and a second tempering electrode are arranged facing each other, A first holding member that holds the first welding electrode and the first tempering electrode, A second holding member that holds the second welding electrode and the second tempering electrode, Equipped with, A spot welding machine characterized in that each of the first holding member and the second holding member has a switching mechanism that can switch the arrangement of electrodes between a welding configuration in which the first welding electrode and the second welding electrode face each other at a predetermined welding position, and a tempering configuration in which the first tempering electrode and the second tempering electrode face each other at a predetermined tempering position.

3. The spot welding machine according to claim 1 or 2, characterized in that the switching mechanism is a rotating mechanism that rotates each electrode.

4. The spot welding machine according to claim 1 or 2, further comprising a drive device for moving the first holding member closer to or further away from the second welding electrode, and a stopper for restricting the movement of the first tempering electrode when the electrode arrangement is in the welding configuration.

5. The spot welding machine further comprises an elastic member disposed between the first tempering electrode and the first holding member, The spot welding machine according to claim 4, characterized in that the first tempering electrode is held in the first holding member via the elastic member.

6. A method for manufacturing a spot-welded joint, which involves performing welding and tempering of the welded joint using a single spot welding machine, The spot welding machine comprises a first welding electrode and a second welding electrode arranged to face each other, and a first tempering electrode. A welding process in which a plate assembly consisting of multiple overlapping steel plates is clamped between the first welding electrode and the second welding electrode of the spot welding machine and current is applied to form a welded portion, An electrode switching step in which the first welding electrode and the second welding electrode are opened, and the arrangement of the first tempering electrode and the first tempering electrode is switched so that the tempering electrode and the second welding electrode face each other at a predetermined tempering position, The process involves a tempering step in which the welded portion is tempered by clamping the welded plate assembly between the first tempering electrode and the second welding electrode and applying current, A method for manufacturing a spot welded joint, characterized by having [a certain feature].

7. A method for manufacturing a spot-welded joint, which involves performing welding and tempering of the welded joint using a single spot welding machine, The spot welding machine comprises a first welding electrode and a second welding electrode arranged to face each other, and a first tempering electrode and a second tempering electrode arranged to face each other. A welding process in which a plate assembly consisting of multiple overlapping steel plates is clamped between the first welding electrode and the second welding electrode of the spot welding machine and current is applied to form a welded portion, An electrode switching step in which the first welding electrode and the second welding electrode are opened, and the arrangement of the first welding electrode and the first tempering electrode is switched so that the first tempering electrode and the second tempering electrode face each other at a predetermined tempering position, and the arrangement of the second welding electrode and the second tempering electrode is switched, A tempering process is performed in which the welded plate assembly is clamped between the first tempering electrode and the second tempering electrode and current is applied to temper the welded portion. A method for manufacturing a spot welded joint, characterized by having [a certain feature].

8. The method for manufacturing a spot welded joint according to claim 6 or 7, characterized in that the electrode switching step involves rotating each electrode to switch the arrangement of each electrode.

9. The method for manufacturing a spot-welded joint according to claim 6 or 7, characterized in that the welding step involves bringing the first welding electrode and the second welding electrode closer together to clamp the plate assembly while restricting the movement of the first tempering electrode.

10. The aforementioned spot welding machine is A first holding member that holds the first welding electrode and the first tempering electrode, A drive device for moving the first holding member closer to or further away from the second welding electrode, The system further comprises an elastic member disposed between the first tempering electrode and the first holding member, The first tempering electrode is held by the first holding member via the elastic member. The method for manufacturing a spot welded joint according to claim 9, characterized in that the tempering step involves bringing the first tempering electrode, held in the first holding member by the drive device, close to the second welding electrode to clamp the plate assembly after welding, and applying pressure from the first tempering electrode to the plate assembly using the elastic member.

11. The aforementioned spot welding machine is A first holding member that holds the first welding electrode and the first tempering electrode, A drive device for moving the first holding member closer to or further away from the second welding electrode, The system further comprises an elastic member disposed between the first tempering electrode and the first holding member, The first tempering electrode is held by the first holding member via the elastic member. The method for manufacturing a spot welded joint according to claim 9, characterized in that the tempering step involves bringing the first tempering electrode, held in the first holding member by the drive device, close to the second tempering electrode to clamp the welded plate assembly, and applying pressure from the first tempering electrode to the plate assembly using the elastic member.

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