Arc welding method for joining dissimilar materials

Abstract

Provided is an arc welding method for joining dissimilar materials, whereby high joint strength, low sputtering, and low dust can be achieved at the same time without reducing welding efficiency in joining dissimilar materials in which a steel plate and an aluminum or aluminum alloy plate are joined. In the arc welding method for joining dissimilar materials, a steel plate (12) (second member) having a first hole (12a) is disposed so as to overlap an aluminum alloy plate (11) (first member), the surface of the aluminum alloy plate (11) is melted by arc welding through the first hole (12a), and a welding metal filling the first hole (12a) is formed. The aluminum alloy plate (11) and the steel plate (12) are joined by forming a surplus height having a diameter larger than the diameter of the first hole (12a) on the welding surface (12c) of the steel plate (12). At this time, the switching frequency f is set to 7 Hz or less by using a welding method in which a period in which pulse arc welding is performed and a period in which short-circuit transition arc welding in which forward feed and reverse feed of the welding wire are performed alternately are performed.

Description

Technical Field

[0001] The present invention relates to an arc welding method for joining dissimilar materials. Background Art

[0002] Traditionally, efforts have been made to improve vehicle occupant safety by increasing the strength of vehicle bodies. Meanwhile, efforts to improve the fuel efficiency of motor vehicles are accelerating against the backdrop of the deepening global warming problem. Reducing the weight of vehicle bodies is known to be effective in improving fuel efficiency.

[0003] However, replacing all of the main materials of conveyor equipment with lightweight raw materials presents challenges such as increased costs and insufficient strength. One possible solution is to use dissimilar metal MIG (Metal Inert Gas) arc spot welding (hereinafter sometimes referred to as DASW (Dissimilar Metals Arc Spot Welding)) to join steel and lightweight raw materials in a suitable combination.

[0004] Furthermore, when arc welding components made of aluminum or aluminum alloys (hereinafter, sometimes simply referred to as aluminum alloys), especially thin plates, pulse arc welding (hereinafter, sometimes simply referred to as pulse) and short-circuit transfer arc welding (hereinafter, sometimes referred to as wire feed control or feed control) utilizing forward and reverse feeding of the welding wire are used. This is to prevent unstable droplet transfer in the low current range suitable for thin plates.

[0005] When using pulsed arc welding, high pulse peak currents are periodically generated while the average current is set low, thus stabilizing droplet transfer. However, using pulse control increases the arc length, meaning the distance between the droplet hanging from the wire and the molten pool increases. As the droplet detaches from the wire and moves into the molten pool, it can sometimes fly out of the pool, causing significant spatter. While pulsed arc welding offers advantages such as ensuring penetration with high peak currents and achieving a wide arc profile with a long arc tip, it also has the disadvantage of increasing spatter and dust production.

[0006] Meanwhile, short-circuit transfer arc welding, a control method that has become increasingly common in recent years, uses short-circuit detection to reverse the wire, thereby cutting off the droplet. This allows for smooth droplet transfer. This feed control method, which utilizes forward and reverse wire feed, is characterized by its low heat input for ultra-thin sheet metal and enables welding with low spatter and dust. However, it has the disadvantage of shallow penetration.

[0007] Patent Document 1 proposes an arc welding method that alternates between pulse arc welding and short-circuit transfer arc welding, using a welding wire made of aluminum or steel. Patent Document 1 describes, for example, a method for switching to short-circuit transfer arc welding at the point in time when a short circuit occurs during the final pulse cycle of a pulse arc welding period. This method prevents the welding state from becoming unstable even if the feed speed changes dramatically during the short-circuit period, allowing for smooth switching from pulse arc welding to short-circuit transfer arc welding.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-236222 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] However, Patent Document 1 describes the material of the welding wire, but does not fully examine the base material. Specifically, when dissimilar metal welding is performed between steel and aluminum alloys, sputtering and dust may be generated depending on the joining method and conditions. When sputtering and dust adhere to the surface of the joined joint, problems such as reduced appearance and difficulty forming the electrodeposition coating film in subsequent steps arise. Therefore, technologies are required to further reduce sputtering and dust in dissimilar metal welding between steel and aluminum alloys.

[0013] Furthermore, high joint strength is also required in the dissimilar metal joining of aluminum alloy materials and steel materials. To achieve high joint strength by forming a weld metal composed of an aluminum alloy on an aluminum alloy material, a large molten interface area between the aluminum alloy material and the weld metal is required. Therefore, pulse welding, which easily achieves penetration, is suitable as a welding method for such base metals. However, as mentioned above, this is not preferred from the perspectives of increased spattering and dust, appearance, and the formation of an electrodeposited coating film.

[0014] On the other hand, short-circuit transfer arc welding is suitable for achieving low spatter and low dust. However, short-circuit transfer arc welding has a low heat input, so the molten interface area becomes small and sufficient joint strength cannot be obtained.

[0015] When joining dissimilar materials using only pulse welding, it is speculated that low current and prolonged arc time can reduce spatter and dust. Alternatively, when joining dissimilar materials using only short-circuit transfer arc welding, it is speculated that prolonged arc time can ensure a molten interface area and improve joint strength. However, even when any of these methods are employed, welding efficiency is reduced, making them unsuitable for practical use. Furthermore, in short-circuit transfer arc welding, even if the current is increased and the wire feed speed is increased to improve welding efficiency, it is difficult to increase the wire feed speed because there is no time to perform forward and reverse feed.

[0016] The present invention has been completed in view of the above-mentioned problems, and its purpose is to provide an arc welding method for joining dissimilar materials, which can achieve high joint strength and low spatter and low dust without reducing welding efficiency in joining dissimilar materials such as joining steel plates and aluminum or aluminum alloy plates.

[0017] Solutions to Problems

[0018] The above-mentioned object of the present invention is achieved by the following structure (1) of the arc welding method for joining dissimilar materials.

[0019] (1) An arc welding method for joining dissimilar materials, wherein a first member made of aluminum or an aluminum alloy is joined to a second member made of steel.

[0020] The arc welding method for joining dissimilar materials is characterized by:

[0021] a first hole forming step of providing a first hole penetrating the second member in a plate thickness direction of the second member;

[0022] a base material placement step of placing the second member on the first member so as to overlap the first member; and

[0023] a joining step comprising: using a surface of the second member opposite to the surface facing the first member as a welding surface, melting the surface of the first member through the first hole by arc welding to form a weld metal that fills the first hole, and forming a joining head having a diameter larger than a diameter of the first hole on the welding surface of the second member, thereby joining the first member and the second member;

[0024] In the joining process, a welding method is used in which a period of pulse arc welding is alternately switched with a period of short-circuit transfer arc welding in which the welding wire is alternately fed forward and reversely.

[0025] When the welding time of the continuous pulse arc welding is tp, the welding time of the continuous short-circuit transfer arc welding is tw, and the number of times the series of pulse arc welding and short-circuit transfer arc welding are repeated per unit time is the switching frequency f,

[0026] The switching frequency f calculated from the formula (1): f=1 / (tp+tw) is 7 Hz or less.

[0027] Furthermore, preferred embodiments of the present invention of the arc welding method for joining dissimilar materials relate to the following (2) to (5).

[0028] (2) The arc welding method for joining dissimilar materials according to (1), wherein the switching frequency f is 0.5 Hz or more.

[0029] (3) The arc welding method for joining dissimilar materials according to (1) or (2), characterized in that:

[0030] When the ratio of the pulse arc welding time to the total time of the continuous pulse arc welding time and the continuous short-circuit transfer arc welding time is defined as a pulse ratio rp,

[0031] The pulse ratio rp calculated from the formula (2): rp={tp / (tp+tw)}×100 is greater than or equal to 5% and less than or equal to 90%.

[0032] (4) The arc welding method for joining dissimilar materials according to any one of (1) to (3), characterized in that:

[0033] The first member and the weld metal are made of aluminum or an aluminum alloy having the same composition or different compositions.

[0034] At least one of the first member and the weld metal contains magnesium.

[0035] (5) The arc welding method for joining dissimilar materials according to any one of (1) to (4), wherein:

[0036] The arc welding method for joining dissimilar materials includes a step of inserting a joining auxiliary member made of aluminum or an aluminum alloy into the first hole between the first hole forming step and the joining step.

[0037] The joint auxiliary member has a second hole that penetrates in a direction substantially the same as the direction in which the first hole penetrates.

[0038] The joining step includes melting at least a portion of the surface of the first member and at least a portion of the joining auxiliary member through the second hole of the joining auxiliary member by arc welding.

[0039] Effects of the Invention

[0040] According to the present invention, an arc welding method for dissimilar metal joining can be provided, which can achieve both high joint strength and low spatter and dust without reducing welding efficiency in dissimilar metal joining of a steel plate and an aluminum or aluminum alloy plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1A It is a diagram showing the arc welding method for joining dissimilar materials according to the first embodiment of the present invention in order of steps, and is a cross-sectional view showing a first hole forming step and a base material placement step.

[0042] Figure 1B The figures show the arc welding method for joining dissimilar materials according to the first embodiment of the present invention in order of steps, and are cross-sectional views showing the joining steps.

[0043] Figure 1C The figures show the arc welding method for joining dissimilar materials according to the first embodiment of the present invention in order of steps, and are cross-sectional views showing the state of the obtained weld metal.

[0044] Figure 2 This is a graph schematically showing states of current values ​​during pulse arc welding and short-circuit transfer arc welding, with the vertical axis representing current value and the horizontal axis representing time.

[0045] Figure 3 It is a cross-sectional view showing one step of the arc welding method for joining dissimilar materials according to the second embodiment of the present invention.

[0046] Figure 4 These are photographs in lieu of drawings showing the states of dust in Comparative Examples and Inventive Examples. DETAILED DESCRIPTION

[0047] The inventors of this application conducted intensive research to establish a technology that achieves both high joint strength and low spatter and dust without compromising welding efficiency. As a result, they discovered that a welding method using an aluminum alloy plate as the lower plate and a steel plate having a hole as the upper plate, melting the surface of the aluminum alloy plate through the hole to form weld metal that fills the hole, can solve the aforementioned problems by alternately switching between pulse arc welding and short-circuit transfer arc welding under specified conditions.

[0048] Hereinafter, an arc welding method for joining dissimilar materials according to an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment described below, and can be implemented with arbitrary modifications within the scope of the present invention.

[0049] [Arc welding method for joining dissimilar materials]

[0050] (First embodiment)

[0051] Figure 1A to Figure 1C This is a cross-sectional view showing the process sequence of an arc welding method for joining dissimilar materials according to a first embodiment of the present invention. This embodiment is an arc welding method for joining a first member (aluminum alloy plate 11) made of aluminum or an aluminum alloy to a second member (steel plate 12) made of steel.

[0052] <First hole forming step>

[0053] like Figure 1A As shown, first, a first hole 12 a is formed in the steel plate 12 so as to penetrate the steel plate 12 in the plate thickness direction.

[0054] <Base material placement process>

[0055] Next, the steel plate 12 is placed on the aluminum alloy plate 11. In this embodiment, the upper surface of the steel plate 12, that is, the surface of the steel plate 12 opposite to the surface facing the aluminum alloy plate 11, is defined as the welding surface 12c.

[0056] <Joining process>

[0057] Afterwards, if Figure 1B As shown, a welding torch 14 is positioned above the first hole 12a. While shielding gas 16 is flowing, current is passed between an aluminum alloy welding wire 13 held by the welding torch 14 and the aluminum alloy plate 11, generating an arc 15. In this embodiment, periods of pulse arc welding and periods of short-circuit transfer arc welding, in which the welding wire is alternately fed forward and backward, are alternately switched. Hereinafter, the arc welding of this embodiment will sometimes be referred to as pulse-feed controlled alternating arc welding. Specific conditions for pulse-feed controlled alternating arc welding are described in detail below.

[0058] (Switching frequency f: 7 Hz or less)

[0059] Figure 2This is a graph schematically showing the current values ​​during pulse arc welding and short-circuit transfer arc welding, with the vertical axis being the current value and the horizontal axis being the time. In this embodiment, by appropriately controlling the number of pulse arc welding and short-circuit transfer arc welding cycles repeated per unit time, a large melting area and reduced spatter and dust can be achieved. Specifically, Figure 2 As shown, the value of the switching frequency f represented by the following equation (1) is controlled when the welding time of continuous pulse arc welding is tp and the welding time of continuous short-circuit transfer arc welding is tw.

[0060] Formula (1): f = 1 / (tp + tw)

[0061] As shown in the above formula (1), the switching frequency f represents the number of times a series of pulse arc welding and short-circuit transfer arc welding is repeated per unit time. When the switching frequency f exceeds 7 Hz, the period of low current generated during switching increases, the average current value decreases, and the amount of melt at the interface decreases. In addition, it is believed that due to the increased switching frequency, the welding method is switched to another welding method before it stabilizes, resulting in arc instability and increased sputtering. Therefore, the switching frequency f is set to 7 Hz or less, and preferably 6 Hz or less.

[0062] On the other hand, while the lower limit of the switching frequency f is not particularly limited, a frequency of 0.5 Hz or higher prevents excessively prolonged continuous welding using each welding method, suppresses the increase in spatter and dust, and maintains joint strength. Therefore, the switching frequency f is preferably set to 0.5 Hz or higher, and more preferably 1.0 Hz or higher.

[0063] (Pulse ratio rp: 5% or more and 90% or less)

[0064] In this embodiment, pulse-feed controlled alternating arc welding is performed to achieve a balance between a large melting area and reduced spatter and dust. Specifically, a preferred value of the pulse ratio rp expressed by the following formula (2) is defined.

[0065] Formula (2): rp={tp / (tp+tw)}×100

[0066] As shown in the above formula (2), the pulse ratio rp represents the ratio of the pulse arc welding time to the total of the continuous pulse arc welding time tp and the continuous short-circuit transfer arc welding time tw. When the pulse ratio rp is 5% or greater, the pulse arc welding effect is achieved by ensuring the molten interface area, thereby achieving good joint strength. Therefore, the pulse ratio rp is preferably 5% or greater. In addition, as the pulse ratio increases, the joint strength can be further improved. Therefore, the pulse ratio rp is more preferably 15% or greater, and even more preferably 35% or greater.

[0067] On the other hand, when the pulse ratio rp is 90% or less, the time for short-circuit transfer arc welding can be ensured, thereby reducing the generation of spatter and dust. Therefore, the pulse ratio rp is preferably 90% or less, and more preferably 70% or less.

[0068] As described above, pulse-feed control alternating arc welding is performed while controlling the switching frequency f, and Figure 1C As shown, at least the surface of the aluminum alloy plate 11 is melted through the first hole 12a, forming weld metal 18 that fills the first hole 12a. Arc welding is then continued, forming a weld head 18a having a diameter larger than that of the first hole 12a on the weld surface 12c of the steel plate 12. In this manner, the aluminum alloy plate 11 and the steel plate 12 are joined.

[0069] According to the arc welding method for joining dissimilar materials of the first embodiment described above, since both the aluminum alloy plate 11 and the welding wire 13 are made of aluminum alloy, the weld metal 18 is firmly bonded to the aluminum alloy plate 11. Furthermore, since the weld metal 18 has a larger excess height 18a than the first hole 12a, the steel plate 12 is sandwiched between the excess height 18a and the aluminum alloy plate 11, being mechanically fixed. Consequently, the aluminum alloy plate 11 and the steel plate 12 can be joined by arc welding.

[0070] In addition, in the present embodiment, in the joining process, pulse-feed controlled alternating arc welding is performed while controlling the switching frequency. Therefore, it is possible to achieve both an improvement in joint strength due to pulse arc welding and a reduction in spattering and dust due to short-circuit transfer arc welding without reducing welding efficiency. In addition, by changing the pulse ratio, the ratio of joint strength to the amount of spattering and dust generated is changed, so the pulse ratio can be changed and adjusted according to the required joint characteristics. Moreover, according to the present embodiment, the joint can be made lighter than when steel materials are joined together, and the joint strength can be increased compared to when aluminum alloy materials are joined together. As a result, when the arc welding method for joining dissimilar materials according to the present embodiment is used to manufacture the body of an automobile, etc., it is possible to improve fuel economy and safety.

[0071] <Second embodiment>

[0072] Figure 3 1 is a cross-sectional view showing one step of the arc welding method for joining dissimilar materials according to the second embodiment of the present invention. Figure 3 In the second embodiment shown, for Figure 1B In the first embodiment shown, the same components are denoted by the same reference numerals, and detailed description thereof is omitted or simplified.

[0073] First, the first hole forming step and the base material placement step are performed in the same manner as in the first embodiment. Figure 3 As shown, a joining aid member 20 is inserted into the first hole 12a of the steel plate 12. The joining aid member 20 is made of, for example, an aluminum alloy and comprises a main body 20a having an outer diameter suitable for insertion into the first hole 12a, and a head 20b formed continuously with the main body 20a and having an outer diameter larger than that of the first hole 12a. Furthermore, the joining aid member 20 has a second hole 20c formed therein, which, when inserted into the first hole 12a, extends in a direction substantially identical to that of the first hole 12a.

[0074] (Joining process)

[0075] Next, a welding torch is positioned above the joining auxiliary member 20, and pulse-feed controlled alternating arc welding is performed. The arc welding conditions are as described above. Thus, arc welding is performed through the second hole 20c of the joining auxiliary member 20, melting at least a portion of the surface of the aluminum alloy plate 11 and at least a portion of the joining auxiliary member 20, forming weld metal 18 that fills the second hole 20c.

[0076] According to the second embodiment thus constructed, the joint assisting member 20 includes a head portion 20b having a larger diameter than the first hole 12a. Thus, similar to the excess height of the first embodiment, the second hole 20c is filled with weld metal to form a joint head portion. The steel plate 12 is clamped between the joint head portion and the aluminum alloy plate 11, mechanically securing the steel plate 12. Consequently, the aluminum alloy plate 11 and the steel plate 12 can be joined by arc welding.

[0077] Furthermore, as in the first embodiment described above, pulse-feed controlled alternating arc welding is performed, so even when welding using the joining auxiliary member 20 , both the improvement of the joint strength and the reduction of the spatter and dust caused by the short-circuit transfer arc welding can be achieved.

[0078] In addition, when the joining auxiliary member 20 is used, the timing of inserting the joining auxiliary member 20 is not particularly limited as long as it is between the first hole forming step and the joining step.

[0079] Hereinafter, a base material and a welding wire that can be used in the arc welding method for joining dissimilar materials according to an embodiment of the present invention will be described in detail.

[0080] (First component)

[0081] The first member constituting the lower plate is not particularly limited as long as it is made of aluminum or an aluminum alloy and can be appropriately selected based on the required properties. Specifically, 1000 series (pure aluminum), 5000 series (Al-Mg), and 6000 series (Al-Mg-Si) alloy plates, extruded materials, and die-cast materials can be used as the first member.

[0082] It should be noted that the dust reduction achieved in this embodiment is believed to be mainly caused by the evaporation and solidification of magnesium contained in at least one of the first member and the welding wire into fine particles, and the oxidation of these fine particles and adhesion to the base material to form dust. Therefore, it is believed that the greater the welding heat input, the more likely dust is generated. In addition, sputtering is fine particles (aluminum alloy particles) that fly during arc welding. When magnesium is contained in the first member or the welding wire, it may also become a source of dust. The arc welding method for joining dissimilar materials according to the embodiment of the present invention can be appropriately used for welding that is prone to sputtering and dust. In other words, when at least one of the first member and the weld metal contains magnesium, it is preferable to use the welding method according to the embodiment of the present invention that can effectively reduce sputtering and dust.

[0083] (Second component)

[0084] The second member constituting the upper plate is not particularly limited as long as it is made of steel and can be appropriately selected based on the required properties. Examples include cold-rolled steel sheets such as SPCC, high-tensile steel sheets, hot-stamped steel sheets, hot-rolled steel sheets, stainless steel sheets such as SUS304 and SUS430, and general structural rolled steel materials such as SS400.

[0085] The shape and size of the first hole formed in the second member are not particularly limited. Specifically, the first hole may be formed in a shape and size that enables conventional arc welding using the hole, or may be formed in a shape extending in one direction.

[0086] (Welding wire)

[0087] In embodiments of the present invention, a welding wire made of aluminum or an aluminum alloy can be used, thereby enabling the resulting weld metal to be firmly bonded to a first member made of aluminum or an aluminum alloy. However, the welding wire and the first member may have the same composition or may be composed of aluminum or an aluminum alloy with different compositions. Therefore, as long as the welding wire and the first member fuse and the resulting weld metal can be bonded to the first member with the desired strength, the weld metal and the first member may have the same or different compositions.

[0088] Note that, as described above, when the welding wire contains magnesium, it is preferable to use the welding method according to the embodiment of the present invention, which can effectively reduce spatter and dust.

[0089] (Other welding conditions)

[0090] In the embodiment of the present invention, welding conditions other than the switching frequency f and pulse ratio rp, such as the type and flow rate of shielding gas, wire feed speed, arc time, etc., are not particularly limited, and the same conditions as those of a normal arc welding method can be applied.

[0091] [Joints of dissimilar materials]

[0092] The dissimilar metal joint is formed by the arc welding method for dissimilar metal joining of the present invention. A specific example of the arc welding method for dissimilar metal joining is as described above, but the arc welding method for dissimilar metal joining is not limited to the above embodiment and can be arbitrarily modified and implemented without departing from the scope of the present invention.

[0093] Example

[0094] As described below, dissimilar metal joints were produced by arc welding an aluminum alloy plate and a steel plate under various conditions, and the joint strength and dust amount of the obtained dissimilar metal joints were evaluated.

[0095] [Fabrication of dissimilar material joints]

[0096] First, if Figure 1A As shown, an aluminum alloy plate 11 is used as the first member (lower plate), and a steel plate 12 having a first hole 12a formed therein is used as the second member (upper plate). The steel plate 12 is placed on top of the aluminum alloy plate 11. Figure 1B As shown, gas shielded arc welding was performed using an aluminum alloy welding wire, aiming at the center of the first hole 12a, under various welding conditions. In this case, for an example where the thickness of the steel plate 12 and the aluminum alloy plate 11 are the same, the wire feed speed was made the same so that the deposition efficiency was equal. Figure 1CAs shown, a weld metal 18 is formed to fill the first hole 12a, and a relief 18a having a diameter larger than the diameter of the first hole 12a is formed on the weld surface 12c of the steel plate 12 to join the aluminum alloy plate 11 and the steel plate 12 to obtain a dissimilar metal joint.

[0097] Table 1 below shows the type and thickness of the steel plate 12 used, the type and thickness of the aluminum alloy plate 11 used, the pulse ratio rp, and the switching frequency f. Other welding conditions are shown below.

[0098] Welding wire: A5356-WY specified in JIS Z 3232, wire diameter 1.2 mm

[0099] Type and flow rate of shielding gas: 100% Ar, 25 liters / minute

[0100] (About Inventive Examples No. 1 to 4 and Comparative Examples No. 1 to 4)

[0101] Diameter of the first hole: 5.0mm

[0102] Wire feed speed: 650 (cm / min)

[0103] Arc time: 2.0 seconds

[0104] (About Inventive Examples No. 5 to 12 and Comparative Examples No. 5 to 8)

[0105] Diameter of the first hole: 7.0mm

[0106] Wire feeding speed: 1000 (cm / min)

[0107] Arc time: 2.0 seconds

[0108] [Evaluation of joints]

[0109] (Joint strength)

[0110] Test specimens were taken from the resulting welded joints and subjected to tensile shear testing (TSS) in accordance with JIS Z 3136 to measure their tensile shear strength. As the evaluation criteria for joint strength, under common conditions, values ​​exceeding the tensile shear strength (reference strength) at a pulse ratio of 0% (short-circuit transition ratio of 100%) were rated as good (◯), while values ​​below the reference strength were rated as poor (×).

[0111] (Dust amount)

[0112] The weld surface of the resulting weld joint was photographed, and the resulting image was binarized to calculate the area of ​​dust adhering to the weld surface. It should be noted that dust is believed to be formed by the oxidation of fine particles formed by the evaporation and solidification of magnesium in the welding wire, and sputtering is believed to be fine particles scattered during arc welding and may be a source of dust. Therefore, it is speculated that the amount of dust adhering is also affected by the amount of sputtering. Therefore, by calculating the dust adhering amount, which is easy to measure, using the above method, it is possible to evaluate the amount of sputtering and dust generated. As a standard for evaluating the amount of dust, under common conditions, examples with a dust adhering amount (baseline adhering amount) less than a pulse ratio of 100% (short-circuit transfer ratio of 0%) are rated as good (0), and examples with a value exceeding the base adhering amount are rated as poor (×).

[0113] Table 1 below shows the measurement results of the tensile shear strength and the dust adhesion area, and the evaluation results of the joint strength and the dust amount.

[0114] [Table 1]

[0115]

[0116] As shown in Table 1 above, the base material conditions for Inventive Examples Nos. 1 to 4 and Comparative Examples Nos. 1 to 4 were identical, but the welding conditions were different. Specifically, Inventive Examples Nos. 1 to 4 employed pulse-feed controlled alternating arc welding with a switching frequency f set to 7 Hz or less. Consequently, Inventive Examples Nos. 1 to 4 achieved higher tensile shear strengths than Comparative Example No. 1 (baseline strength under the same conditions) and lower dust adhesion than Comparative Example No. 2 (baseline adhesion under the same conditions). In Comparative Examples Nos. 3 and 4, since the switching frequency f exceeded the upper limit of the range specified in the present invention, the heat input decreased, resulting in lower joint strength.

[0117] Figure 4 : is a substitute drawing photograph showing the state of dust of the comparative example and the invention example. Figure 4 As shown, Inventive Example No. 4, which uses a pulse ratio of 50%, shows improved joint strength compared to Comparative Example No. 1, which uses a pulse ratio of 0%, and a reduced dust adhesion area compared to Comparative Example No. 2, which uses a pulse ratio of 100%. Thus, using the arc welding method for joining dissimilar materials of the present invention, it is possible to achieve a good dissimilar joint with a well-balanced joint strength and dust reduction.

[0118] Inventive Examples No. 5-8 and Comparative Examples No. 5 and 6 share the same base material conditions, but differ in welding conditions. Specifically, Inventive Examples No. 5-8 employ pulse-feed controlled alternating arc welding, with the switching frequency f set to 7 Hz or less. Consequently, Inventive Examples No. 5-8 achieve higher values ​​for tensile shear strength (baseline strength under the same conditions) than Comparative Example No. 5, and lower values ​​for dust adhesion area (baseline adhesion amount under the same conditions) than Comparative Example No. 6. It should be noted that in Inventive Examples No. 5-8, the pulse ratio rp is varied between 5% and 90% while maintaining the switching frequency f at 5 Hz. The results show that as the pulse ratio rp increases, the tensile shear strength generally increases, while as the pulse ratio rp decreases, the dust adhesion area decreases.

[0119] Inventive Examples Nos. 9-12 and Comparative Examples Nos. 7 and 8 share the same base material conditions, but differ in welding conditions. Specifically, Inventive Examples Nos. 9-12 employ pulse-feed controlled alternating arc welding, with the switching frequency f set to 7 Hz or less. Consequently, Inventive Examples Nos. 9-12 achieve higher values ​​for tensile shear strength (baseline strength under the same conditions) than Comparative Example No. 7, and lower values ​​for dust adhesion area (baseline adhesion amount under the same conditions) than Comparative Example No. 8. It should be noted that in Inventive Examples Nos. 9-12, the pulse ratio rp is varied between 5% and 70% while maintaining the switching frequency f at 5 Hz. The results show that increasing the pulse ratio rp generally increases the tensile shear strength, while decreasing the pulse ratio rp decreases the dust adhesion area.

[0120] While various embodiments have been described above, the present invention is not limited to these examples. Those skilled in the art will readily be able to devise various variations or modifications within the scope of the patented technical proposal, and these variations are understood to fall within the technical scope of the present invention. Furthermore, the various components of the above embodiments may be arbitrarily combined without departing from the spirit of the invention.

[0121] It should be noted that the present application is based on Japanese patent application (Japanese Patent Application No. 2023-009614) filed on January 25, 2023, the contents of which are incorporated herein by reference.

[0122] Description of reference numerals:

[0123] 2.12 Steel plate (second component)

[0124] 11 Aluminum alloy plate (first component)

[0125] 12a First hole

[0126] 18a Yu Gao

[0127] 18 Weld Metal

[0128] 20c Second hole

[0129] 20 Engage auxiliary components.

Claims

1. An arc welding method for joining dissimilar materials, wherein a first member made of aluminum or an aluminum alloy is joined to a second member made of steel, characterized in that: The arc welding method for joining dissimilar materials comprises: a first hole forming step of providing a first hole penetrating the second member in a plate thickness direction of the second member; a base material placement step of placing the second member on the first member so as to overlap the first member; and a joining step comprising: using a surface of the second member opposite to the surface facing the first member as a welding surface, melting the surface of the first member through the first hole by arc welding to form a weld metal that fills the first hole, and forming a joining head having a diameter larger than a diameter of the first hole on the welding surface of the second member, thereby joining the first member and the second member; In the joining process, a welding method is used in which a period of pulse arc welding is alternately switched with a period of short-circuit transfer arc welding in which the welding wire is alternately fed forward and reversely. When the welding time of the continuous pulse arc welding is tp, the welding time of the continuous short-circuit transfer arc welding is tw, and the number of times the series of pulse arc welding and short-circuit transfer arc welding are repeated per unit time is the switching frequency f, The switching frequency f calculated from the formula (1): f=1 / (tp+tw) is 7 Hz or less.

2. The arc welding method for joining dissimilar materials according to claim 1, wherein: The switching frequency f is greater than 0.5 Hz.

3. The arc welding method for joining dissimilar materials according to claim 1 or 2, wherein: When the ratio of the pulse arc welding time to the total time of the continuous pulse arc welding time and the continuous short-circuit transfer arc welding time is defined as a pulse ratio rp, The pulse ratio rp calculated from the formula (2): rp={tp / (tp+tw)}×100 is greater than or equal to 5% and less than or equal to 90%.

4. The arc welding method for joining dissimilar materials according to claim 1 or 2, wherein: The first member and the weld metal are made of aluminum or an aluminum alloy having the same composition or different compositions. At least one of the first member and the weld metal contains magnesium.

5. The arc welding method for joining dissimilar materials according to claim 3, wherein: The first member and the weld metal are made of aluminum or an aluminum alloy having the same composition or different compositions. At least one of the first member and the weld metal contains magnesium.

6. The arc welding method for joining dissimilar materials according to claim 1 or 2, wherein: The arc welding method for joining dissimilar materials includes a step of inserting a joining auxiliary member made of aluminum or an aluminum alloy into the first hole between the first hole forming step and the joining step. The joint auxiliary member has a second hole that penetrates in a direction substantially the same as the direction in which the first hole penetrates. The joining step includes melting at least a portion of the surface of the first member and at least a portion of the joining auxiliary member through the second hole of the joining auxiliary member by arc welding.

7. The arc welding method for joining dissimilar materials according to claim 3, wherein: The arc welding method for joining dissimilar materials includes a step of inserting a joining auxiliary member made of aluminum or an aluminum alloy into the first hole between the first hole forming step and the joining step. The joint auxiliary member has a second hole that penetrates in a direction substantially the same as the direction in which the first hole penetrates. The joining step includes melting at least a portion of the surface of the first member and at least a portion of the joining auxiliary member through the second hole of the joining auxiliary member by arc welding.

8. The arc welding method for joining dissimilar materials according to claim 4, wherein: The arc welding method for joining dissimilar materials includes a step of inserting a joining auxiliary member made of aluminum or an aluminum alloy into the first hole between the first hole forming step and the joining step. The joint auxiliary member has a second hole that penetrates in a direction substantially the same as the direction in which the first hole penetrates. The joining step includes melting at least a portion of the surface of the first member and at least a portion of the joining auxiliary member through the second hole of the joining auxiliary member by arc welding.

9. The arc welding method for joining dissimilar materials according to claim 5, wherein: The arc welding method for joining dissimilar materials includes a step of inserting a joining auxiliary member made of aluminum or an aluminum alloy into the first hole between the first hole forming step and the joining step. The joint auxiliary member has a second hole that penetrates in a direction substantially the same as the direction in which the first hole penetrates. The joining step includes melting at least a portion of the surface of the first member and at least a portion of the joining auxiliary member through the second hole of the joining auxiliary member by arc welding.

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