Spot welding method of aluminum or aluminum alloy material and welded joint

Abstract

Provided is a spot welding method for an aluminum or aluminum alloy material that enables welding at low current, does not require securing a prescribed edge distance, and enables lap welding of aluminum alloy sheets to be easily achieved with inexpensive equipment, and a welded joint. The method includes: a step of overlapping a first sheet material composed of an aluminum alloy with a second sheet material; a steel sheet arrangement step of arranging an end surface of a steel sheet against an end surface of the first sheet material and forming a butt joint portion between the steel sheet and the first sheet material; an electrode arrangement step of arranging the steel sheet and the first sheet and the second sheet in an overlapped state between a pair of electrodes; a current passing step of passing current between the pair of electrodes to form a nugget between the first sheet and the second sheet; and a steel sheet removal step of removing the steel sheet. In the electrode arrangement step, the positions of the pair of electrodes are adjusted so that at least a portion of the butt joint portion is included in a region in which current is passed by the pair of electrodes.

Description

Technical Field

[0001] This invention relates to a spot welding method for aluminum or aluminum alloy materials and the welded joint obtained by the spot welding method. Background Technology

[0002] Aluminum or aluminum alloys possess mechanical strength and are lightweight, making them suitable for use in various structural components such as automobile doors. Hereinafter, in this specification, aluminum or aluminum alloys will sometimes be referred to simply as aluminum alloys.

[0003] When assembling structures made of aluminum alloys, it is necessary to join the components made of these aluminum alloys together. Traditionally, fillet welds on aluminum alloys have typically used laser welding or a welding method that combines laser welding with arc welding.

[0004] For example, Patent Document 1 discloses a welding method for aluminum in which the welding position is melted by irradiation with laser diode light that has a high absorption rate for aluminum, thereby generating a MIG (Metal Inert Gas) arc for welding, and thin aluminum sheets are welded at high speed. It should be noted that Patent Document 1 describes a lap fillet weld when an upper plate of aluminum alloy or the like is overlapped with a lower plate of aluminum alloy or the like.

[0005] Furthermore, Patent Document 2 proposes a laser welding method for performing lap fillet welding by specifying the position of the laser irradiation. According to the method described in Patent Document 2, good weld quality can be ensured without increasing the size or complexity of the welding equipment.

[0006] The welding methods described in the aforementioned patent documents 1 and 2 both use lasers, but laser welding equipment is expensive and the welding operation is complex. Therefore, it is also known that resistance spot welding, which uses inexpensive equipment and can be easily performed, is applied to the lap welding of aluminum plates.

[0007] Prior art literature

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2003-170285

[0010] Patent Document 2: Japanese Patent Application Publication No. 2019-000878 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, in the resistance welding of overlapping aluminum alloy plates, JIS Z 3001-6:2013 contains a description of edge distance. The so-called edge distance refers to the distance from the center of the weld point to the nearest end of the component. Generally speaking, a specified edge distance is required when joining a pair of overlapping aluminum alloy plates by resistance spot welding.

[0013] In other words, resistance spot welding cannot be used when welding needs to be performed in confined spaces or near the end faces of sheet metal, as the edge distance cannot be guaranteed. Specifically, if resistance spot welding is to be performed near the end faces of sheet metal, the current is not applied in a straight line along the thickness direction of the sheet metal. The closer to the end face, the greater the heat accumulation and the more spatter is generated.

[0014] In addition, when spot welding aluminum alloy plates by overlapping them, aluminum has a lower volume resistivity than iron, so welding requires a large current.

[0015] The present invention was made in view of the above-mentioned problems, and its object is to provide a spot welding method for aluminum or aluminum alloy materials that can be welded with low current, does not require ensuring a specified edge distance, and can easily achieve lap welding of aluminum alloy materials with inexpensive equipment, as well as a welded joint obtained by the welding method.

[0016] Solution for solving the problem

[0017] The above-mentioned objective of the present invention is achieved by the following configuration (1) of the spot welding method for aluminum or aluminum alloy materials.

[0018] (1) Spot welding methods for aluminum or aluminum alloy materials include:

[0019] An overlapping process in which a first sheet made of aluminum or an aluminum alloy is overlapped with a second sheet made of aluminum or an aluminum alloy.

[0020] In the steel plate configuration process, the end face of the steel plate is aligned with the end face of the first plate to form a butt joint between the steel plate and the first plate.

[0021] In the electrode configuration process, the steel plate and the first plate and the second plate are arranged in an overlapping state between a pair of opposing electrodes.

[0022] An energizing process, wherein current is applied between the pair of electrodes to form a melt nugget between the first plate and the second plate; and

[0023] The steel plate removal process involves removing the steel plate.

[0024] In the electrode configuration process, the position of the pair of electrodes is adjusted such that at least a portion of the mating portion is included in the region energized by the pair of electrodes.

[0025] Furthermore, the preferred embodiments of the present invention relating to spot welding methods for aluminum or aluminum alloy materials include the following (2) to (8).

[0026] (2) The spot welding method for aluminum or aluminum alloy materials according to (1) is characterized in that, in the electrode configuration process, the position of the pair of electrodes is adjusted such that the line connecting the center of the opposing surfaces of the pair of electrodes is positioned closer to the steel plate side than the mating portion.

[0027] (3) The spot welding method for aluminum or aluminum alloy materials according to (1) or (2) is characterized in that the electrode configuration process and the energizing process are repeatedly performed at multiple locations to form multiple weld nuggets.

[0028] (4) A spot welding method for aluminum or aluminum alloy material according to any one of (1) to (3), characterized in that the energizing process includes a process of adjusting the energizing conditions in such a way that the molten metal of aluminum or aluminum alloy does not protrude from the butt joint.

[0029] (5) The spot welding method for aluminum or aluminum alloy materials according to (4) is characterized in that, in the process of adjusting the energizing conditions, at least one of the following is selected from the relative position of the pair of electrodes and the mating part, the current and the energizing time.

[0030] (6) A spot welding method for aluminum or aluminum alloy material according to any one of (1) to (5), characterized in that, prior to the steel plate arrangement process, a cut-forming process is performed to form a cut on the end face of the steel plate.

[0031] In the steel plate arrangement process, the steel plate and the first plate are arranged such that a gap is formed between the cut portion of the steel plate and the end face of the first plate.

[0032] The docking portion includes the gap portion, and in the electrode configuration process, the position of the pair of electrodes is adjusted such that at least a portion of the gap portion is located between the pair of electrodes.

[0033] (7) The spot welding method for aluminum or aluminum alloy materials according to (6) is characterized in that, in the energizing process, the first plate and the steel plate are pressed against the second plate by the pair of electrodes in the thickness direction.

[0034] When the pressure of the pair of electrodes in the energizing process is set to an applied pressure P1,

[0035] Between the energizing process and the steel plate removal process, there is a forging process in which the first plate and the steel plate and the second plate are pressed by the pair of electrodes with a pressure P2 that is higher than the applied pressure P1.

[0036] (8) The spot welding method for aluminum or aluminum alloy materials according to (6) or (7), characterized in that, in the energizing process, the first plate and the steel plate are pressed against the second plate by the pair of electrodes in the thickness direction.

[0037] When the conditions in the energizing process are set such that the diameter of the indentation formed on the first plate and the steel plate by the pressing of the pair of electrodes is R (mm),

[0038] On the end face of the steel plate, the width of the cut in the direction orthogonal to the thickness direction of the steel plate is set to R (mm) or more.

[0039] Furthermore, the above-mentioned objective of the present invention is achieved by the following structure (9) of the welded joint.

[0040] (9) A welded joint, which is formed by spot welding of aluminum or aluminum alloy materials as described in any one of (1) to (8), characterized in that,

[0041] A weld nugget is provided between the overlapping first and second plates to join the first and second plates together.

[0042] The fusion nugget is exposed on the end face of the first plate.

[0043] Furthermore, the preferred embodiments of the present invention relating to the welded joints are as follows (10) to (11).

[0044] (10) A welded joint, which is formed by spot welding of aluminum or aluminum alloy materials as described in any one of (6) to (8), characterized in that,

[0045] There is a weld nugget between the overlapping first and second plates, which joins the first and second plates together.

[0046] The first plate has a protrusion extending from its end face.

[0047] The molten core is exposed on the end face of the first plate.

[0048] The protrusion includes at least a portion of the molten core.

[0049] (11) The welded joint according to (9) or (10) is characterized in that the weld nugget is not exposed on the side opposite to the face of the second plate in the first plate.

[0050] Invention Effects

[0051] The spot welding method for aluminum or aluminum alloys according to the present invention enables welding with low current, eliminates the need to ensure a specified edge distance, and allows for easy lap welding of aluminum alloys using inexpensive equipment. Furthermore, the welded joints for aluminum or aluminum alloys according to the present invention can be easily manufactured using inexpensive equipment. Attached Figure Description

[0052] Figure 1 This is a schematic diagram illustrating a spot welding method for aluminum alloy materials according to the first embodiment of the present invention.

[0053] Figure 2 It is Figure 1 A partial enlarged cross-sectional view.

[0054] Figure 3 This is a photographic representation of a welded joint obtained by the spot welding method according to the first embodiment of the present invention.

[0055] Figure 4 This is a cross-sectional view showing an example of a poorly shaped welded joint.

[0056] Figure 5 yes Figure 4 The top view of the welded joint shown.

[0057] Figure 6A This is a top view showing the cut-forming process before the steel plate arrangement process in the spot welding method for aluminum alloy materials according to the second embodiment of the present invention.

[0058] Figure 6B This is a top view showing the electrode arrangement process in the spot welding method for aluminum alloy materials according to the second embodiment of the present invention.

[0059] Figure 7A This is a cross-sectional view showing the energizing process in the spot welding method for aluminum alloy materials according to the third embodiment of the present invention.

[0060] Figure 7B This is a cross-sectional view showing the forging process after the energizing process.

[0061] Figure 8 It is a graph showing the welding conditions in each process of the third embodiment when the vertical axis is set as the pressure and current value between the electrodes.

[0062] Figure 9This is a photographic representation of a welded joint obtained by the spot welding method according to the second embodiment of the present invention.

[0063] Figure 10 This is a schematic diagram illustrating the method for determining the fracture area.

[0064] Figure 11 This is a cross-sectional view showing the spot welding method used to obtain the welded joint used in the shear test.

[0065] Figure 12 It is a graph that uses shear strength as the vertical axis and fracture area as the horizontal axis to represent the relationship between shear strength and fracture area.

[0066] Figure 13 This is a schematic diagram illustrating a spot welding method used to form multiple weld nuggets.

[0067] Figure 14 This is a schematic diagram illustrating a laser welding method implemented as a comparative example.

[0068] Figure 15 This is a diagram used to illustrate the dimensions of the cuts in a steel plate.

[0069] Figure 16 This is a schematic diagram showing the location used to determine the fracture area after a shear test.

[0070] Figure 17 It is a graph showing the shear strength with the vertical axis set to shear strength, the horizontal axis set to the area of ​​the semi-ellipse, and the width of the reference example and the cut changed to various inventive examples.

[0071] Figure 18 This is a photographic representation of the appearance of a welded joint when using steel plates with cuts of various sizes.

[0072] Figure 19 This is a photographic representation of the appearance of a welded joint when using steel plates with cuts of various sizes.

[0073] Figure 20 This is a photographic representation of the appearance of a welded joint when using steel plates with cuts of various sizes.

[0074] Figure 21 This is a photographic representation of the appearance of a welded joint when using steel plates with cuts of various sizes.

[0075] Figure 22 This is a photographic representation of the appearance of a welded joint when using steel plates with cuts of various sizes.

[0076] Explanation of reference numerals in the attached figures:

[0077] 13 First Electrode

[0078] 13a front face

[0079] 15 Second Electrode

[0080] 15a front face

[0081] 21 First Board

[0082] 22 steel plate

[0083] 23 Second board material

[0084] 24 docking section

[0085] 25 molten cores

[0086] 27 Welded joints

[0087] 28 protrusions

[0088] 29 Boundary Section

[0089] 33 laser

[0090] 41 indentations

[0091] 42 voids

[0092] 44 protrusions

[0093] 50 incisions. Detailed Implementation

[0094] The inventors of this application have conducted in-depth research on a welding method for joining the end faces of one aluminum alloy material near the lap joint by spot welding. First, a pair of electrodes are positioned near the end face at a distance generally required for lap welding, for example, more than 15 mm, and spot welding is performed. As a result, as the electrodes are brought closer to the end face, the shape of the weld nugget deteriorates, resulting in spatter and making welding impossible. It should be noted that welding conditions that allow welding even when the electrodes are closer to the end face have been studied, but near the end face of one aluminum alloy material, even with various adjustments to the welding conditions, it is impossible to join the overlapping aluminum alloy materials.

[0095] Next, the inventors of this application investigated a method for heating by resistance of iron. The results showed that by aligning the end face of a steel plate with the end face of one of the aluminum alloy materials and energizing the mating area, resistance heating of iron could be utilized to form a molten nugget between the overlapping aluminum alloy materials.

[0096] The following describes in detail the spot welding method for aluminum or aluminum alloy materials and the embodiments of the welded joints of the present invention, based on the accompanying drawings. It should be noted that the present invention is not limited to the embodiments described below, and can be implemented in any manner without departing from the spirit of the invention.

[0097] [Spot Welding Method]

[0098] <First Implementation Method>

[0099] Figure 1 This is a schematic diagram illustrating a spot welding method for aluminum alloy materials according to the first embodiment of the present invention. Additionally, Figure 2 It is Figure 1 A partially enlarged cross-sectional view. (Using...) Figure 1 First, let me briefly explain the spot welding device.

[0100] The spot welding apparatus 11 includes a pair of electrodes (a first electrode 13 and a second electrode 15), a welding transformer section 17 connected to the first electrode 13 and the second electrode 15, a power supply section 18, a control section 19 supplying welding power from the power supply section 18 to the welding transformer section 17, and an electrode drive section 20 for moving the first electrode 13 and the second electrode 15 axially. The control section 19 comprehensively controls the current value, energizing time, electrode pressure, energizing timing, and pressure timing.

[0101] The front end face 13a of the first electrode 13 and the front end face 15a of the second electrode 15 are, for example, dome-radius shaped (DR-shaped) electrodes. The welding transformer section 17 energizes the first electrode 13 and the second electrode 15.

[0102] The spot welding apparatus 11 clamps the component to be welded between the first electrode 13 and the second electrode 15. In this embodiment, the first plate 21 and the second plate 23, both made of aluminum alloy, are joined, but a steel plate 22 is used as a joining auxiliary component. Details of the spot welding method will be described later.

[0103] Furthermore, by driving the first electrode 13 and the second electrode 15 through the electrode driving unit 20, pressure is applied to the first plate 21, steel plate 22, and second plate 23 in the thickness direction. Under this pressure, based on the command from the control unit 19, the welding transformer unit 17 energizes between the first electrode 13 and the second electrode 15. As a result, a weld nugget 25 is formed in the area of ​​the boundary 29 between the first plate 21 and the second plate 23 that is sandwiched between the first electrode 13 and the second electrode 15, resulting in a welded joint 27 that integrates the first plate 21 and the second plate 23.

[0104] use Figure 2 The spot welding method for aluminum or aluminum alloy materials according to the first embodiment of the present invention will be described in further detail.

[0105] (Overlapping processes)

[0106] like Figure 1 As shown, a first plate 21 made of aluminum alloy and a second plate 23 made of aluminum alloy are prepared. After the second plate 23 is configured as the lower plate, the first plate 21 is overlapped and configured at a predetermined joining position on the second plate 23.

[0107] (Steel plate preparation process)

[0108] Subsequently, the end face 22a of a steel plate 22 having the same thickness as the first plate 21 is mated with the end face 21a of the first plate 21, forming a mating portion 24 between the steel plate 22 and the first plate 21, consisting of the end faces 22a and 21a. It should be noted that, in this specification, the end face 21a of the first plate 21 refers to a surface orthogonal to the surface of the first plate 21 that faces the second plate 23. In other words, the end face 21a of the first plate 21 refers to a surface parallel to the thickness direction of the first plate 21. Similarly, the end face 22a of the steel plate 22 refers to a surface orthogonal to the surface of the steel plate 22 that faces the second plate 23, that is, a surface parallel to the thickness direction of the steel plate 22.

[0109] It should be noted that the steel plate configuration process can also be carried out before the overlapping process.

[0110] (Electrode configuration process)

[0111] Steel plates 22 and first and second plates 21 are arranged in an overlapping state between the opposing first electrode 13 and second electrode 15. At this time, the positions of the first electrode 13 and second electrode 15 are adjusted such that at least a portion of the mating portion 24 is included in the area energized by the pair of electrodes (first electrode 13 and second electrode 15). In this embodiment, the area energized by the first electrode 13 and second electrode 15 is... Figure 2 The area between the dashed lines b1 and b2 in the diagram.

[0112] (Electrification process)

[0113] While clamping and pressing the steel plates 22, 21, and 23, which are assembled by butt joint and overlap, with the first electrode 13 and the second electrode 15, energizes the area between the first electrode 13 and the second electrode 15 through the welding transformer section 17. It should be noted that in the electrode configuration process described above, the positions of the first electrode 13 and the second electrode 15 are adjusted so that at least a portion of the mating portion 24 is included in the area between the dotted lines b1 and b2. Therefore, in this energizing process, at least a portion of the mating portion 24 is energized.

[0114] Specifically, current is applied between the first electrode 13 and the second electrode 15 via the steel plate 22 and the second plate 23, and also between the first electrode 13 and the second electrode 15 via the first plate 21 and the second plate 23. The steel plate 22 has the property that current is less likely to flow compared to the first plate 21, which is made of aluminum alloy; therefore, resistance heating is generated by applying current to the steel plate 22. Furthermore, resistance heating is also generated between the first plate 21 and the second plate 23, although the heating temperature is lower than that of the steel plate 22. Moreover, through this resistance heating, a portion of the second plate 23 near the end face of the first plate 21, including the end face 21a, and in the region opposite to that end face, melts, forming a melt nugget 25 at the boundary 29 between the first plate 21 and the second plate 23. Therefore, the first plate 21 and the second plate 23 are joined near the end face of the first plate 21.

[0115] It should be noted that the above electrode configuration process and the above energizing process can be repeatedly performed at multiple locations to form multiple fusion nuggets 25. In this way, if the first plate 21 and the second plate 23 are joined by multiple fusion nuggets 25, the joint strength can be significantly improved.

[0116] (Steel plate removal process)

[0117] Then, the steel plate 22 that is mated with the end face 21a of the first plate 21 is removed.

[0118] Figure 3 This is a photographic representation of a welded joint obtained by the spot welding method according to the first embodiment of the present invention. By removing the steel plate 22, as... Figure 3 As shown, a welded joint 27 is obtained by joining the first plate 21 and the second plate 23 through a weld nugget 25.

[0119] According to the spot welding method of this embodiment described above, the resistance heating of the steel plate 22 melts the first plate 21 and the second plate 23 made of aluminum alloy. Therefore, the temperature rises from the end face 21a of the first plate 21, which is in contact with the end face 22a of the steel plate 22, particularly near the boundary 29 with the second plate 23, and a weld nugget 25 is formed along the boundary 29. Therefore, compared to spot welding aluminum alloy plates together using conventional methods, welding can be performed with low current using the same inexpensive equipment as when joining steel plates together.

[0120] For example, when spot welding ordinary aluminum alloys, a welding current of 17 kA is required in the 5000 series and a large current of 19 kA or more is required in the 6000 series. In contrast, in this embodiment, spot welding of aluminum alloys can be performed even when using a power supply device for iron, for example, welding of the ends of aluminum alloys can be performed with a welding current of 15 kA or less.

[0121] Furthermore, according to this embodiment, since heat generated from the steel plate 22 is utilized, it is not necessary to ensure the specified edge distance, and the lap welding of aluminum alloy materials can be easily achieved.

[0122] Next, the first plate 21, the second plate 23, and the steel plate 22 that can be used in this embodiment will be described below.

[0123] (First board material, second board material)

[0124] In this embodiment, both the first plate 21 and the second plate 23 are made of aluminum or aluminum alloy. The composition of the first plate 21 and the second plate 23 is not particularly limited, but as a plate made of pure aluminum, plates from the 1000 series can be cited. Furthermore, as a plate made of aluminum alloy, plates made of 2000 series, 3000 series, 5000 series, 6000 series, and 7000 series aluminum alloys can be cited. The shapes of the first plate 21 and the second plate 23 do not need to be flat; generally, they are shapes that allow for spot welding, as long as the end face of the steel plate can be joined to the end face 21a of the first plate 21.

[0125] (steel plate)

[0126] In this embodiment, the composition of the steel plate 22 is not particularly limited, but cold-rolled steel plate (SPCC: Steel Plate Cold Commercial) or high-tensile steel can be used. The shape of the steel plate 22 is only required to allow its end face 22a to mate with the end face 21a of the first plate 21. Furthermore, in this embodiment, since the first electrode 13 and the second electrode 15 clamp the mating portion 24 between the steel plate 22 and the first plate 21, it is preferable that the thickness of the end face 22a of the steel plate 22 is the same as the thickness of the end face 21a of the first plate 21. However, as long as the current can flow in the desired region, the thickness of the end face 22a of the steel plate 22 and the thickness of the end face 21a of the first plate 21 can be slightly different.

[0127] (Spot welding conditions)

[0128] In this embodiment, the welding conditions are not particularly limited. However, in order to form a weld nugget 25 that joins the first plate 21 and the second plate 23, it is preferable to appropriately adjust the welding current, the energizing time, and the positions of the first and second electrodes. In the spot welding method of this embodiment, the following terminology is used... Figure 2 The preferred electrode positions are explained.

[0129] exist Figure 2In this embodiment, the line connecting the center of the front end face 13a of the first electrode 13 and the center of the front end face 15a of the second electrode 15 aligns with the docking portion 24. As described above, in this embodiment, the positions of the first electrode 13 and the second electrode 15 are adjusted such that at least a portion of the docking portion 24 is included in the region energized by the first electrode 13 and the second electrode 15, i.e., between the dashed lines b1 and b2. Therefore, the positions of these electrodes can be adjusted to... Figure 2 The negative (-) side, i.e., the side of steel plate 22, shown can also be moved towards... Figure 2 The positive (+) side, i.e. the side of the first plate 21, is moved as shown.

[0130] For example, if the positions of the first electrode 13 and the second electrode 15 are moved towards the steel plate 22 side within a specified range, the current flowing to the steel plate 22 side increases, thus increasing the heat generated and enabling the formation of the desired melt nugget with a shorter energizing time. Therefore, in the area energized by the first electrode 13 and the second electrode 15, within the range including at least a portion of the mating portion 24, the positions of the first electrode 13 and the second electrode 15 are preferably arranged on the steel plate 22 side.

[0131] It should be noted that even when the positions of the first electrode 13 and the second electrode 15 are moved toward the first plate 21, the steel plate 22 will heat up when energized. Therefore, by increasing the current and the energizing time, the desired melt nugget can be formed.

[0132] However, if the current or the energizing time is increased too much, the weld joint may sometimes be deformed. Figure 4 This is a cross-sectional view showing an example of a poorly shaped welded joint. Additionally, Figure 5 yes Figure 4 The diagram shows a top view of the welded joint. For example, if the energizing time is extended while the electrode positions are set to the same, molten metal may sometimes fly out from the joint 24 between the steel plate 22 and the first plate 21 midway through the welding process. Moreover, after the molten metal has cooled, if the steel plate 22 is removed, as shown... Figure 4 and Figure 5 As shown, sometimes a protrusion 28 protruding from the weld nugget 25 is formed on the end face 21a of the first plate 21, which deteriorates the appearance of the weld joint 27. The protrusion 28 can be removed after the steel plate removal process, but a process is required to remove the protrusion 28, increasing manufacturing costs. In addition, depending on the amount of molten metal ejected, the bond strength may sometimes decrease.

[0133] Furthermore, it is believed that increasing the current while maintaining the same energizing time will also result in the formation of the aforementioned protrusion 28. Therefore, it is preferable to adjust the electrode position, current, and energizing time to prevent molten metal from flying out of the joint 24 between the steel plate 22 and the first plate 21. Specifically, in the event of molten metal flying out, adjustments such as moving the electrode position towards the first plate 21, reducing the current, and shortening the energizing time can suppress the flying out of molten metal and prevent the formation of the protrusion 28.

[0134] In this embodiment, the shapes of the first electrode 13 and the second electrode 15 are not particularly limited. In the above embodiment, a dome-radius (DR) shaped electrode is used, but electrodes of various shapes such as radius (R), flat (F), conical (CF), and point (P) can also be used.

[0135] <Second Implementation Method>

[0136] Figure 6A This is a top view showing the cut-out forming process before the steel plate arrangement process in the spot welding method for aluminum alloy materials according to the second embodiment of the present invention. Additionally, Figure 6B This is a top view showing the electrode configuration process. It should be noted that... Figure 6A and Figure 6B In the second embodiment shown, for the... Figure 1 and Figure 2 Components that are identical to those shown are labeled with the same reference numerals in the accompanying drawings, and their detailed descriptions are omitted or simplified.

[0137] (Incision Formation Process)

[0138] First, before the above-mentioned steel plate configuration process, such as Figure 6A As shown, a cut 50 is formed on the end face 22a of the steel plate 22. In this embodiment, the cut 50 is a trapezoidal shape with the long side on the end face 22a side of the steel plate 22 when viewed from above, and extends through the thickness direction of the steel plate 22. It should be noted that the width of the cut 50 (the length of the cut in the end face 22a of the steel plate 22 in the direction orthogonal to the thickness direction of the steel plate 22) is, for example, set to 6.0 mm, and the depth of the cut 50 (the length of the cut in the direction orthogonal to the end face 22a of the steel plate 22) is, for example, set to 1.0 mm. Preferred dimensions of the cut 50 will be described later.

[0139] (Steel plate preparation process)

[0140] After that, as Figure 6BAs shown, the end face 22a of the steel plate 22 is mated with the end face 21a of the first plate 21. This creates a gap 42 between the cut 50 of the steel plate 22 and the first plate 21. Furthermore, the mating surfaces of the end faces 22a and 21a, along with the gap 42, constitute a mating portion 24.

[0141] (Electrode configuration process)

[0142] Then, in a pair of opposing electrodes ( Figure 2 The first plate 21 and the steel plate 22 are connected between the first electrode 13 and the second electrode 15 shown. Figure 6B The second plate not shown in the figure ( Figure 2 The second plate 23 shown is arranged in an overlapping state.

[0143] Subsequently, similar to the first embodiment, an energizing process is performed whereby a pair of electrodes press the steel plate 22, the first plate 21, and the second plate together, and energizes the pair of electrodes. At this time, a portion of the first plate 21 melts through the energizing process, and the molten metal (molten aluminum alloy) flows into the void 42. Furthermore, resistive heating occurs not only between the first plate 21 and the second plate but also between the molten metal flowing into the void 42 and the second plate. Therefore, a molten nugget is formed at the boundary between the molten metal flowing into the first plate 21 and the void 42 and the second plate, and the first plate 21 and the second plate are joined near the end face of the first plate 21.

[0144] According to the second embodiment described above, the molten aluminum alloy flows into the void 42, where a molten nugget is also formed at the boundary with the second plate. Therefore, compared with the first embodiment, the joint strength can be improved.

[0145] It should be noted that, as shown in the second embodiment described above, even when the steel plate 22 has a notch 50, the joint strength can sometimes be the same as in the first embodiment, depending on the position of the electrodes. In such cases, by adjusting the welding conditions, the joint strength can be improved. Hereinafter, as a third embodiment, a method for adjusting the welding conditions will be described.

[0146] <Third Implementation Method>

[0147] Figure 7A This is a cross-sectional view showing the energizing process in the spot welding method for aluminum alloy materials according to the third embodiment of the present invention. Additionally, Figure 7B This is a cross-sectional view showing the forging process after the energizing process. Furthermore, Figure 8 This is a graph showing the welding conditions in each process of the third embodiment when the vertical axis is set as the applied pressure and current values ​​between the electrodes. The third embodiment is a variation of the second embodiment described above, therefore... Figure 7A and Figure 7B In the middle, to and Figure 1 , Figure 2 , Figure 6A and Figure 6B Components that are identical to those shown are labeled with the same reference numerals, and their detailed descriptions are omitted or simplified.

[0148] (Electrode configuration process)

[0149] like Figure 7A and Figure 8 As shown, similarly to the second embodiment, the steel plate 22 with the cutout 50, the first plate 21, and the second plate 23 are arranged overlapping each other between the opposing first electrode 13 and the second electrode 15. Then, the first electrode 13 and the second electrode 15 are positioned to sandwich them, and pressure is applied in a direction that brings the first electrode 13 and the second electrode 15 closer together until a pressure P1 (e.g., 2.5 kN) is applied.

[0150] (Electrification process)

[0151] Next, while pressing the steel plate 22, the first plate 21, and the second plate 23 with pressure P1, an energizer is applied for a period of 250 ms, for example, with a current of 15 kA. As a result, a portion of the first plate 21 melts, and the molten metal 43 flows into the gap 42 formed between the cut 50 and the first plate 21. It should be noted that while the first electrode 13 and the second electrode 15 are pressurized with pressure P1, pressure P1 is also applied to the area between the dashed lines b1 and b2, and an energizer is applied. At this time, depending on the depth of the cut 50, internal defects 31 may sometimes form between the molten metal and the second plate 23, failing to improve the joint strength. In such cases, to suppress the formation of internal defects 31, it is preferable to perform the subsequent forging process.

[0152] (Forging process)

[0153] like Figure 7B and Figure 8 As shown, after the above-mentioned energizing process is completed, the first plate 21 and the steel plate 22 are pressed against the second plate 23 by the first electrode 13 and the second electrode 15 for a period of, for example, 200 ms, with a pressure P2 (e.g., 5.0 kN) higher than the applied pressure P1. As a result, the interval between the dashed lines b1 and b2 widens, and the area pressed by the first electrode 13 and the second electrode 15 increases. Therefore, internal defects in the protrusion 44 formed by cooling the molten metal 43 and between the protrusion 44 and the second plate 23 can be reduced, and the joint strength can be further improved compared to the first embodiment.

[0154] If the energizing process and the pressure applied between the electrodes after the energizing process are adjusted as described above, even if the depth of the cut 50 is set to, for example, 1.5 mm, the joint strength can be improved compared to the first embodiment.

[0155] In the second and third embodiments, there is no particular limitation on the size of the cut 50 used to improve the joint strength, but the preferred size of the cut 50 that can obtain a welded joint with excellent appearance will be described below.

[0156] In the aforementioned energizing process, the first plate 21 and steel plate 22, along with the second plate 23, are pressed together in the thickness direction by the first electrode 13 and the second electrode 15. Thus, as... Figure 6B As shown, an indentation 41, generated by the pressing of the first electrode 13, is formed on the upper surfaces of the first plate 21 and the steel plate 22. The diameter of the indentation 41 varies depending on the pressure applied by the first electrode 13 and the second electrode 15, and the diameters of the first electrode 13 and the second electrode 15. In the first to third embodiments described above, the steel plate 22 is used as a joining auxiliary member to join the first plate 21 and the second plate 23. However, if the steel plate 22 is used repeatedly, it will deform due to the pressure applied by the first electrode 13 and the second electrode 15. As a result, a gap may be generated at the joint between the steel plate 22 and the first plate 21, and aluminum or aluminum alloy may flow through this gap, causing molten metal to fly out.

[0157] As described in the second and third embodiments above, forming a notch 50 in the steel plate 22 can improve the joint strength and suppress the overflow of molten metal. Furthermore, when the conditions in the energizing process are set such that the diameter of the indentation 41 is R (mm), setting the width of the notch 50 to R (mm) or more can further suppress the overflow of molten metal from between the first plate 21 and the steel plate 22.

[0158] On the other hand, even when the width of the cut 50 is too large than R (mm), molten metal overflow may still occur. Furthermore, if the depth of the cut 50 is too large, molten metal may not be filled into the cut 50, resulting in a deformed shape of the protrusion 44. Therefore, from the viewpoint of obtaining a welded joint with an excellent appearance, the width of the cut 50 is preferably less than (R ± 2.0) mm, more preferably less than (R + 1.5) mm, and even more preferably less than (R + 1.0) mm. Additionally, the depth of the cut 50 is preferably less than 3.0 mm, more preferably less than 1.8 mm, even more preferably less than 1.5 mm, and particularly preferably less than 1.0 mm.

[0159] It should be noted that even if the position of the electrode is offset towards the steel plate side in the width direction of the cut 50, as long as the two ends 50a and 50b in the width direction of the cut 50 are located on or outside the circumference of the outer diameter of the indentation 41, the effect of suppressing overflow can be improved.

[0160] [Welded joint]

[0161] (First Implementation)

[0162] The welded joint 27 of the first embodiment of the present invention is joined by the spot welding method of aluminum or aluminum alloy materials described in the first embodiment. Specifically, it is a welded joint formed by lap welding of a first plate 21 made of aluminum alloy and a second plate 23 made of aluminum alloy. Figure 3 As shown, a weld nugget 25 is formed between the first plate 21 and the second plate 23 to join the first plate and the second plate. The weld nugget 25 is exposed on the end face 21a of the first plate 21, and the exposed portion 26 of the weld nugget can be identified. It should be noted that the weld nugget 25 may sometimes be larger depending on the welding conditions when manufacturing the weld joint 27, but it is generally preferable that the weld nugget 25 is not exposed on the side 21b opposite to the side of the second plate in the first plate 21.

[0163] In this type of welded joint, a weld nugget 25 can be formed near the end face 21a of the first plate 21, thus enabling the joining of narrow areas and obtaining welded joints 27 with complex shapes. In addition, welding can be performed with low current, and it can be easily manufactured with inexpensive equipment, thereby reducing manufacturing costs.

[0164] (Second Implementation)

[0165] Figure 9 This is a photographic representation of a welded joint obtained by the spot welding method according to the second embodiment of the present invention. Figure 9 In the middle, to and Figure 3 The same components as the welded joint 27 shown are labeled with the same reference numerals, and detailed descriptions are omitted or simplified. It should be noted that... Figure 9 In the diagram, dashed lines indicate the locations where steel plates 22 are installed. Additionally, in... Figure 9 In this context, the area with a denser color formed between the first plate 21 and the second plate 23 is called the melt nucleus 25. For example... Figure 9As shown, the first plate 21 and the second plate 23 are joined by a molten core 25. In this embodiment, since a steel plate 22 with a notch 50 is used, molten metal flows into the gap and forms a protrusion 44 by cooling it. It should be noted that even when the protrusion 44 is formed, as in the first embodiment, the molten core 25 is exposed on the end face 21a of the first plate 21 (protrusion 44), and the exposed portion 26 of the molten core can be identified. In addition, the molten core 25 is not exposed on the side of the first plate 21 opposite to the side of the second plate 23.

[0166] [Example]

[0167] [First Embodiment]

[0168] Spot welding

[0169] like Figure 2 As shown, a first plate 21 made of aluminum alloy and a second plate 23 made of aluminum alloy are overlapped, and the end face 22a of a steel plate 22 is mated with the end face 21a of the first plate 21. Next, with the steel plate 22 and the first plate 21 and second plate 23 overlapped, they are positioned between the first electrode 13 and the second electrode 15. Then, under various conditions, an electric current is applied between the first electrode 13 and the second electrode 15, and a weld nugget 25 is formed between the first plate 21 and the second plate 23. Afterwards, the steel plate 22 is removed, thereby creating a welded joint 27. The types of the first plate 21, the second plate 23, and the steel plate 22, as well as the types and shapes of the electrodes, are shown below. It should be noted that steel plates according to JIS standards are used.

[0170] First material: A5182 material, 1.0mm thick.

[0171] Second sheet material: A5182 sheet, 2.0mm thick.

[0172] Steel plate: Cold-rolled steel plate (SPCC), 1.0mm thick

[0173] Electrode: Chromium copper (CuCr) electrode, diameter 16mm - tip diameter 6mm

[0174] Electrode shape: Dome-shaped (DR-shaped) with a radius of curvature of 40mm at the front end.

[0175] In addition, as a comparative example, instead of using steel plates, electrodes were placed on the end face of a first plate made of aluminum alloy, and spot welding was performed under normal conditions.

[0176] <Evaluation of Welded Joints>

[0177] During the energizing process, observe for any protrusions of molten metal, and for the resulting weld joint, observe for the formation of a weld nugget. Additionally, peel the first and second plates after joining, and measure the area of ​​the fracture, which is taken as the fracture area.

[0178] Figure 10 This is a schematic diagram illustrating the method for determining the fracture area. For example... Figure 2 and Figure 10 As shown, during the peeling of the first plate 21 and the second plate 23, the melt nugget 25 fractures, and the fracture portion 25a can be observed on the surface of the second plate 23. The fracture portion 25a is formed in the overlapping area of ​​the first plate 21 and is semi-elliptical in shape. In this embodiment, assuming that the fracture portion 25a is an imaginary ellipse, the area of ​​the imaginary ellipse is calculated based on the major axis D2 and the minor axis (2×D1), and set to 1 / 2, thereby calculating the fracture area. The energizing conditions and evaluation results in the energizing process are shown in Table 1 below.

[0179] It should be noted that in the electrode position column of Table 1 below, -0.5 to -2.0 indicates that the line connecting the center of the front end face 13a of the first electrode 13 and the center of the front end face 15a of the second electrode 15 is positioned closer to the steel plate 22 than the mating portion 24. On the other hand, in the electrode position column, +7.0 indicates that the line connecting the center of the front end face 13a of the first electrode 13 and the center of the front end face 15a of the second electrode 15 is positioned closer to the first plate 21 than the mating portion 24.

[0180] Table 1

[0181]

[0182] [Shear test]

[0183] Using the same method as the invention example above, various variations were applied to the pressure (4 kN), current (13-15 kA), and energizing time (40-150 ms) to fabricate multiple welded joints, and the relationship between fracture area and shear strength was investigated. Figure 11 This is a cross-sectional view showing the spot welding method used to obtain the welded joint for use in shear tests. Figure 11 In the welded joint shown, with Figure 2 The only difference in the welded joints shown is the relative position and size of the first plate 21 and the second plate 23. Figure 11 In the middle, to and Figure 2 Identical components are labeled with the same reference numerals in the accompanying drawings, and their detailed descriptions are omitted.

[0184] like Figure 11As shown, the first plate 21 and the second plate 23 are overlapped, and the steel plate 22 is butted against the first plate 21. They are clamped by the first electrode 13 and the second electrode 15, and a weld nugget 25 is formed by applying electricity. Next, after the steel plate 22 is removed, a 180mm × 40mm (overlap width: 10mm) test piece is taken from the obtained weld joint, and a shear test is carried out under the conditions of a chuck distance of 100mm and a tensile speed of 10mm / min.

[0185] Figure 12 This is a graph that uses shear strength as the vertical axis and fracture area as the horizontal axis to represent the relationship between shear strength and fracture area. For example... Figure 12 As shown, a correlation exists between fracture area and shear strength; generally, the larger the fracture area, the higher the shear strength. That is, in the examples of the invention shown in Table 1, it is speculated that the side with the larger fracture area generally has higher shear strength.

[0186] As shown in Table 1 above, Comparative Example No. 1 could not be welded and the first plate 21 could not be joined to the second plate 23.

[0187] In contrast, Invention Examples No. 1 to 12 can form a weld nugget 25 near the end face 21a of the first plate 21 without ensuring the edge distance, and can join the first plate 21 and the second plate 23 by spot welding. Furthermore, since the steel plate 22 is used for resistance heating, compared to resistance spot welding of aluminum plates with a specified edge distance, the weld nugget 25 can be easily formed with a low current, allowing the use of inexpensive equipment and thus reducing manufacturing costs.

[0188] In particular, in Invention Examples No. 1-3, 5-7 and 9, the electrode position is set not too close to the side of the steel plate 22, and the energizing time is not too long. Therefore, it is possible to obtain a welded joint with no protrusion of molten metal, no need for post-processing, and excellent appearance.

[0189] It should be noted that, comparing Invention Examples No. 1-4, No. 5-8, and No. 9-11 with the same electrode position, applied pressure, and current value, it is speculated that as the energizing time increases, the fracture area increases and the shear strength also increases. Furthermore, comparing Invention Examples No. 1 and 7, No. 2 and 8, No. 5 and 10, and No. 6 and 11 with the same applied pressure, current value, and energizing time, it is speculated that in most combinations, the closer the electrode position is to the steel plate 22 from the butt joint 24, the larger the fracture area and the higher the shear strength. Although there are no examples where only the current value changes, it is speculated that generally, as the current value increases, the fracture area increases and the shear strength increases.

[0190] [Second Embodiment]

[0191] Spot welding at multiple points>

[0192] In the second embodiment, the shear strength of a welded joint in which a plurality of weld nuggets 25 are formed between the first plate 21 and the second plate 23 and a welded joint obtained by laser welding are compared. Figure 13 This is a schematic diagram illustrating a spot welding method used to form multiple weld nuggets. Figure 14 This is a schematic diagram illustrating a laser welding method implemented as a comparative example.

[0193] like Figure 13 As shown, the first plate 21 and the second plate 23 are overlapped, and the steel plate 22 is butted against the first plate 21. One of the three predetermined welding positions 30 is selected, clamped by the first electrode 13 and the second electrode 15, and energized to form a weld nugget (not shown). Additionally, one of the predetermined welding positions 30 that has not been welded is selected, and energized repeatedly using the same method to form three weld nuggets (not shown). It should be noted that the interval between the three predetermined welding positions 30 is set to be 10 mm or more.

[0194] On the other hand, as a comparative example, such as Figure 14 As shown, the first plate 21 and the second plate 23 are overlapped and arranged. A laser 33 is irradiated from the upper surface of the first plate 21 along a welding predetermined line 40 set in a direction parallel to the end face 21a of the first plate 21, and the first plate 21 and the second plate 23 are joined by 26 mm.

[0195] <Evaluation of Welded Joints>

[0196] For the welded joints of the obtained inventive examples, the shear strength and fracture area were measured using the same method as in the first embodiment described above. The fracture area is a value calculated based on the measured short and long sides, where the fracture portion observed when the first and second plates after joining are approximately elliptical. Additionally, the shear strength was measured for the welded joints of the comparative examples. The welding conditions and measurement results for the inventive examples where spot welding was performed are shown in Table 2 below, and the welding conditions and measurement results for the comparative examples where laser welding was performed are shown in Table 3 below. It should be noted that the fracture areas 1 to 3 shown in Table 2 below represent the fracture areas of the weld nuggets obtained through spot welding at the first to third locations, respectively. Furthermore, the overlap width in Table 3 below represents the distance from the end face 21a of the first plate 21 to the end face 23a of the second plate 23.

[0197]

[0198] Table 3

[0199]

[0200] As shown in Tables 1 to 3 above and Figure 12 As shown, compared with Invention Examples No. 1 to 12, which only perform spot welding at one location, the shear strength of Invention Examples No. 13 to 15, which repeatedly perform spot welding at multiple locations to form multiple weld nuggets, is significantly higher.

[0201] Furthermore, although comparative examples No. 2 to 4, which implemented laser welding, produced back penetration of the weld bead and obtained a sound weld joint extending to the back side, inventive examples No. 13 to 15 were able to obtain higher shear strength compared to these comparative examples No. 2 to 4.

[0202] [Third Embodiment]

[0203] In the third embodiment, the shear strength of welded joints made using steel plates with cuts of various sizes and steel plates without cuts is compared. Figure 15 This is a diagram used to illustrate the dimensions of the cuts in a steel plate. Additionally, Figure 16 This is a schematic diagram showing the location used to determine the fracture area after a shear test. (and) Figure 2 Similarly, in the first embodiment shown, a weld nugget is formed between the first plate 21 and the second plate 23, and a welded joint is manufactured by removing the steel plate. The following shows the types of the first plate 21, the second plate 23, and the steel plate 22, the types and shapes of the electrodes, and the welding conditions. It should be noted that the steel plate used is a JIS-compliant steel plate.

[0204] First material: A5182 material, 1.2mm thick.

[0205] Second sheet material: A5182 sheet, 2.0mm thick.

[0206] Steel plate: Cold-rolled steel plate (SPCC), 1.0mm thick

[0207] Power supply method: DC inverter

[0208] Electrode: Chromium copper (CuCr) electrode, diameter 16mm - tip diameter 6mm

[0209] Electrode shape: Dome-shaped (DR-shaped) with a radius of curvature of 40mm at the front end.

[0210] The applied force P1 when energized is 2.5kN.

[0211] Power-on time: 250ms

[0212] Welding position: -1mm (moved 1mm from the end of the first plate towards the steel plate side)

[0213] It should be noted that, as a reference example, a steel plate without cuts was used, and spot welding was performed in the same manner as in the invention example. Figure 15 The dimensions of the cuts in the various steel plates shown are shown in Table 5 below.

[0214] <Evaluation of Welded Joints>

[0215] For the obtained welded joint, the first and second plates are peeled off, and the area of ​​the fracture is measured as the fracture area. For example... Figure 2 and Figure 16 As shown, when the first plate 21 and the second plate 23 are peeled off, the melt nugget 25 breaks, and the fracture portion 45 can be observed on the surface of the second plate 23. The fracture portion 45 is composed of a semi-elliptical portion 45a, which is the area where the first plate 21 and the second plate 23 overlap, and a trapezoidal portion 45b, which is the area where the protrusion 44 overlaps with the second plate 23.

[0216] In the third embodiment, assuming the semi-elliptical portion 45a is an imaginary ellipse, the area of ​​the imaginary ellipse is calculated based on the major axis D2 and the minor axis (2×D1), and then set to 1 / 2. The area of ​​the semi-elliptical portion 45a is thus calculated. Similarly, the area of ​​the trapezoidal portion 45b is calculated by multiplying the sum of a pair of parallel sides (D3+D4) by the height (t) of the trapezoidal portion 45b, and then setting this to 1 / 2. Furthermore, the area of ​​the fracture portion 45 is calculated by summing the areas of the semi-elliptical portion 45a and the trapezoidal portion 45b.

[0217] In addition, welded joints were manufactured in the same manner as those for which the fracture area was calculated. Test pieces of 180mm × 40mm (overlap width: 10mm) were taken from each welded joint, and shear tests were conducted under conditions of a chuck spacing of 100mm and a tensile speed of 10mm / min. The dimensions of the fracture portion, fracture area, and shear strength of each welded joint are shown in Table 6 below.

[0218] Table 4

[0219]

[0220] Table 5

[0221]

[0222] Table 6

[0223]

[0224] As shown in Tables 4 to 6 above, in Invention Examples No. 1 to 18 using steel plates with notches, the average shear strength is improved compared to the average shear strength of Reference Examples No. 1 to 9. Figure 17 This is a graph showing the shear strength when the vertical axis is set to shear strength, the horizontal axis to the area of ​​the semi-ellipse, and the width of the reference example and the notch is changed to various inventive examples. It should be noted that... Figure 17 In one example, the width of the cut is set to 1mm. For example... Figure 17 As shown, when comparing Invention Examples No. 1-3, 7-9, and 13-15 with a cut depth N4 of 1 mm with Reference Examples No. 1-9, the shear strength of all Invention Examples exceeded 2000 N, and the strength was significantly improved compared with Reference Examples.

[0225] [Fourth Embodiment]

[0226] In the fourth embodiment, for the inventive example N using the aforementioned steel plate number S6... o Welded joints manufactured by applying a pressure P2 greater than the pressure P1 applied during the energizing process (e.g., .10-12) were compared in shear strength. The types of the first plate, the second plate, and the steel plate, as well as the types and shapes of the electrodes, were the same as in the third embodiment described above. The welding conditions are shown in Table 7 below, and the dimensions of the fractured portion and the evaluation results are shown in Table 8 below.

[0227] Table 7

[0228]

[0229]

[0230] As shown in Tables 4, 7, and 8 above, compared to the case where the notch depth N4 is set to 1.5 mm, the average shear strength is significantly improved by performing a forging process with a pressure of 5 kN after the energizing process. From the third and fourth embodiments above, it can be seen that the welded joint using a steel plate with a notch exhibits superior overall strength compared to the case using a steel plate without a notch. It should be noted that although the degree of strength improvement varies depending on the size of the notch, the strength of the welded joint can be further improved by performing a forging process after the energizing process with a pressure P2 greater than that applied during the energizing process.

[0231] [Fifth Embodiment]

[0232] In the fifth embodiment, the appearance of the welded joint manufactured using steel plates with various sizes of cuts shown in Table 4 above is observed. The types of the first plate, the second plate, and the steel plates, as well as the types and shapes of the electrodes, are the same as in the third embodiment described above. Figures 18-22 This is a provisional photograph illustrating the appearance of a welded joint when using steel plates with cuts of various sizes. It should be noted that in this embodiment, the conditions during the energizing process are set such that the diameter of the indentation 41 formed on the first plate and the steel plate is 6 mm. Figures 18-22As shown, in the invention examples where the cut width N1 is set to 6.0 mm, 6.5 mm, and 7.0 mm, no protrusion 28 is formed due to the ejection of molten metal, resulting in an excellent appearance. Furthermore, in the invention examples where the cut depth N4 is set to 1.0 mm and 1.5 mm, the cut portion is filled with molten metal, and the shape of the protrusion 44 is also excellent.

Claims

1. A spot welding method for aluminum or aluminum alloy materials, characterized in that, The spot welding method for the aluminum or aluminum alloy material includes: An overlapping process in which a first sheet made of aluminum or an aluminum alloy is overlapped with a second sheet made of aluminum or an aluminum alloy. In the steel plate configuration process, the end face of the steel plate is aligned with the end face of the first plate to form a butt joint between the steel plate and the first plate. In the electrode configuration process, the steel plate and the first plate and the second plate are arranged in an overlapping state between a pair of opposing electrodes. An energizing process, wherein current is applied between the pair of electrodes to form a melt nugget between the first plate and the second plate; and The steel plate removal process involves removing the steel plate. In the electrode configuration process, the position of the pair of electrodes is adjusted such that at least a portion of the mating portion is included in the region energized by the pair of electrodes.

2. The spot welding method for aluminum or aluminum alloy materials according to claim 1, characterized in that, In the electrode configuration process, the position of the pair of electrodes is adjusted such that the line connecting the center of the opposing surfaces of the pair of electrodes is positioned closer to the steel plate side than the mating portion.

3. The spot welding method for aluminum or aluminum alloy materials according to claim 1, characterized in that, The electrode configuration process and the energizing process are repeatedly performed at multiple locations to form multiple melt nuclei.

4. The spot welding method for aluminum or aluminum alloy materials according to claim 1, characterized in that, The energizing process includes a step of adjusting the energizing conditions in a manner that prevents the molten metal of aluminum or aluminum alloy from protruding from the mating portion.

5. The spot welding method for aluminum or aluminum alloy materials according to claim 4, characterized in that, In the process of adjusting the energizing conditions, at least one of the following is adjusted: the relative position of the pair of electrodes and the docking portion, the current, and the energizing time.

6. The spot welding method for aluminum or aluminum alloy materials according to claim 1, characterized in that, Prior to the steel plate arrangement process, a notch forming process is performed to form a notch on the end face of the steel plate. In the steel plate arrangement process, the steel plate and the first plate are arranged such that a gap is formed between the cut portion of the steel plate and the end face of the first plate. The docking portion includes the gap portion, and in the electrode configuration process, the position of the pair of electrodes is adjusted such that at least a portion of the gap portion is located between the pair of electrodes.

7. The spot welding method for aluminum or aluminum alloy materials according to claim 6, characterized in that, During the energizing process, the first plate and the steel plate are pressed together with the second plate in the thickness direction by the pair of electrodes. When the pressure of the pair of electrodes in the energizing process is set to an applied pressure P1, Between the energizing process and the steel plate removal process, there is a forging process in which the first plate and the steel plate and the second plate are pressed by the pair of electrodes with a pressure P2 that is higher than the applied pressure P1.

8. The spot welding method for aluminum or aluminum alloy materials according to claim 6, characterized in that, During the energizing process, the first plate and the steel plate are pressed together with the second plate in the thickness direction by the pair of electrodes. When the conditions in the energizing process are set such that the diameter of the indentation formed on the first plate and the steel plate by the pressing of the pair of electrodes is R, On the end face of the steel plate, the width of the cut in a direction orthogonal to the thickness direction of the steel plate is set to R or more, wherein the unit of R is mm.

9. A welded joint, which is formed by spot welding of aluminum or aluminum alloy materials according to any one of claims 1 to 8, characterized in that, A weld nugget is provided between the overlapping first and second plates to join the first and second plates together. The fusion nugget is exposed on the end face of the first plate.

10. The welded joint according to claim 9, characterized in that, The molten core is not exposed on the side opposite to the face of the second plate in the first plate.

11. A welded joint, which is formed by spot welding of aluminum or aluminum alloy materials according to any one of claims 6 to 8, characterized in that, A weld nugget is provided between the overlapping first and second plates to join the first and second plates, and The first plate has a protrusion extending from its end face. The molten core is exposed on the end face of the first plate. The protrusion includes at least a portion of the molten core.

12. The welded joint according to claim 11, characterized in that, The molten core is not exposed on the side opposite to the face of the second plate in the first plate.

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