Flux-cored wire for brazing aluminum and steel, and method for joining parts using the flux-cored wire

Abstract

Flux-cored wire, comprising: a rod comprising an aluminum-silicon (Al-Si) alloy powder and a halide flux powder; and a sheath comprising a zinc (Zn) alloy and surrounding the rod, wherein the zinc alloy comprises aluminum (Al) in an amount of 3 to 20 wt.%, silicon (Si) in an amount of 0.1 to 1.0 wt.% and zinc as the remainder of the zinc alloy, wherein all wt.% data refer to the total weight of the zinc alloy.

Description

TECHNICAL FIELD

[0001] The present invention relates to a filler wire for joining different materials, such as aluminum and steel, and a method for joining parts using the filler wire. BACKGROUND

[0002] When aluminum and steel are welded, their relative solubility is extremely low, preventing the formation of a stable alloy and resulting in a highly brittle intermetallic compound. This means that the strength of the joint cannot be guaranteed.

[0003] For this reason, in vehicles, ships, the aerospace industry and the like, despite increased costs and weight, mechanical joining such as rivets and the like is usually used to join aluminum and steel, and welding or soldering is not used in mass production.

[0004] In order to achieve thermal bond strength between two metals, the technology of welding and brazing (self-brazing) was developed in the early 2000s, in which aluminum base material is fused together with a solid aluminum-based or zinc-based filler wire and brazed to a surface of steel base material that is in a solid state.

[0005] However, self-brazing technology is only used for steel with certain plating layers, such as galvanized steel (GI), and for galvannealed steel (GA) or uncoated steel, a thickness of the Al-Fe intermetallic compound cannot be properly controlled, so that an interface failure may occur between a brazing pad and a steel base material during lap shear evaluation.

[0006] On the other hand, a flux containing chloride or fluoride has been used to remove oxide or foreign matter on the surface of a base material to reduce the energy of interface formation when brazing molten aluminum to galvanized steel or uncoated steel, thereby facilitating the control of the thickness of the Al-Fe intermetallic compound.

[0007] Taking advantage of the above-mentioned advantages, the state of the art, as in Fig. 1, a flux cored wire (FCW), which is formed from a solid wire (cladding) and a flux introduced into the solid wire, is applied to galvanized steel or uncoated steel.

[0008] With such a flux cored wire, the flux can be agglomerated in the aluminum-silicon sheath and effectively dispersed during brazing, preventing the flux from reacting with a base material. Furthermore, some of the flux may remain on the surface after brazing, generating a large amount of sludge, as shown in Fig. 2, or cannot form a stable solder interface, as shown in Fig. 3. This makes it easy to create a disconnected area.

[0009] In addition, the unstable evaporated flux can create a number of pores in a solder joint, as in Fig. 4, which can also be a factor in deteriorating joint strength. For example, when using flux, a certain amount of time is required for the flux to react stably with the base material, making it difficult to ensure a stable solder interface at high speed.

[0010] A brazing process using the flux cored wire can mostly be performed at a speed of 1 m / min or less, and an actual laser brazing process for a vehicle body can generally be performed under the condition of 3 m / min or more.

[0011] Therefore, in order to overcome the disadvantage of the flux cored wire described above, a flux mixed rod (FMR) was tested, which was obtained by mixing an aluminum-based sheath and a flux which were in a powder state as described in Fig. 5 shown.

[0012] In the flux-mixed rod, flux powder can be evenly distributed in aluminum alloy powder that will form a brazing bead, so that a stable surface reaction of the base material can occur during brazing, which can improve the external appearance and improve the joint adhesion strength compared with the flux-cored wire.

[0013] However, since the flux-mixed rod is produced by extruding mixed powder, the material itself has very low ductility, so even a slight deformation will cause fracture, as shown in Fig.6. Accordingly, the flux-mixed rod cannot be wound on a wheel and used for laser or arc brazing like a conventional flux-cored wire. Therefore, most flux-mixed rods can be thinly sliced ​​and placed on the base material for furnace brazing.

[0014] However, furnace brazing cannot be applied in the process of assembling a body of a transportation means such as a vehicle, a ship, an aircraft, and the like in terms of productivity, and since laser or arc brazing is used in most processes, a filler metal mixed with a flux can have very limited application in mass production in the transportation means industry.

[0015] In addition, when using the flux-mixed rod, an interface can be stably formed only at low speed (e.g., 1 m / min), and at high speed, as with the flux-cored wire, an unbonded area may occur between a brazing joint and the steel base material, and it is difficult to ensure the desired joint strength.

[0016] The embodiments described in the description of the prior art are intended to provide a better understanding of the background of the present disclosure and may include what was previously unknown to a person of ordinary skill in the art to which this disclosure pertains.

[0017] US 2011 / 0123824 A1 discloses an alloy material that may comprise an aluminum alloy and a zinc alloy. The two alloys may be bonded together and formed into a wire.

[0018] AT 500 494 A1 relates to a filler material for the thermal production of a joint or a material coating metallically bonded to the base material of or on objects made of light metal and / or zinc alloys with a thermal conductivity of higher than 110 W / mK, as well as to a method for producing the same. SUMMARY OF THE INVENTION

[0019] In preferred aspects, the present invention provides a flux cored wire for brazing aluminum and steel, which can ensure joining strength of brazing between aluminum and steel and improve productivity.

[0020] In one aspect of the present invention, a flux cored wire is provided comprising a rod comprising an aluminum-silicon (Al-Si) alloy powder and a halide flux powder, and a sheath comprising a zinc (Zn) alloy surrounding the rod.

[0021] As used herein, the term "aluminum-silicon (Al-Si) alloy powder" refers to an alloy material that can be formed into particles or powders with diameters ranging from nanometers (e.g., 10-990 nm) to micrometers (e.g., 1 µm to 990 µm), without limitation to shapes or weights thereof. Preferably, the powder has a size (diameter measured at the maximum length) of about 100 nm to about 100 µm. In a particular aspect, the Al-Si alloy powder may comprise aluminum and silicon as main components, for example, an amount of approximately 50 wt%, 60 wt%, 70 wt%, 80 wt%, 85 wt%, 90 wt%, or 95 wt% or more of aluminum and an amount of approximately 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt%, 40 wt%, or 50 wt% or more of silicon based on the total weight of the alloy powder composition. Preferably, the powder has an Al content of approximately 70 wt% to 90 wt%.-% and a Si content of approximately 10 wt% to 30 wt%, an Al content of approximately 80 wt% to 90 wt% and a Si content of approximately 10 wt% to 20 wt%.

[0022] An "aluminum-silicon (Al-Si)" alloy, as referred to herein, may optionally comprise one or more materials in addition to aluminum or silicon, or the alloy may consist essentially of aluminum or silicon, or the alloy may consist exclusively of aluminum and silicon. It is understood that the Al-Si alloy may be obtained from a 4000 series aluminum alloy, such as A4043, A4047 ISO AlSi5, and AlSi12, which may also include further processing for a suitable use (e.g., powder).

[0023] The term "halide flux powder" as used herein refers to a flux or agent capable of removing an aluminum oxide layer during aluminum brazing or welding, and which may be formed into particles or powder ranging from nanometers (e.g., 10 nm to 990 nm) to micrometers (e.g., 1 µm to 990 µm), without limitation to shapes or weights thereof. Preferably, the powder may have a size (diameter measured at the maximum length) of approximately 100 nm to approximately 100 µm. Preferably, the halide flux material may be suitably applied during a brazing process to ensure proper functioning, for example, in joining a joint by brazing for assembling a body or parts of a vehicle, a ship, an aircraft, and the like. Brazing may include arc brazing, laser brazing, and furnace brazing.In a particular aspect, the halide flux powder may suitably contain halide as an additive, for example in the form of a halide compound, of less than about 50 wt%, 40 wt%, 30 wt%, 25 wt%, 20 wt%, 15 wt%, 10 wt%, or 5 wt%, based on the total weight of the powder composition. It is understood that the halide flux powder is provided from halide flux materials, for example, NOCOLOK® or NOCOLOK® Flux 7028-9028 (Solvay, Germany), which may also include further processing for suitable use herein.

[0024] The term "zinc (Zn) alloy" as used herein refers to an alloy material comprising zinc as a major component, for example, at a content of approximately 80 wt%, 85 wt%, 90 wt%, 92 wt%, 94 wt%, 96 wt%, 98 wt%, or 99 wt% based on the total weight of the alloy material. The zinc alloy suitably comprises other metallic elements (e.g., Al, Cu, Pb, Fe, Ca, Mg, or the like) or non-metallic elements (e.g., C, Si, N, P, S, O, or the like).

[0025] The halide flux powder can be a fluoride flux powder or a chloride flux powder.

[0026] Preferably, the halide flux powder may be the fluoride flux powder.

[0027] The zinc alloy sheath may suitably have a thickness of approximately D / 2×0.1 to D / 2×0.5, where D is a diameter of the filler wire.

[0028] In addition, a plurality of bending grooves may be formed on the filler wire at predetermined intervals in the longitudinal direction.

[0029] A length of each of the bending grooves in the longitudinal direction may suitably be approximately D to D×10, where D is a diameter of the filler wire.

[0030] Furthermore, the predetermined distance between the bending grooves may be equal to or less than approximately D×30.

[0031] In addition, each of the bending grooves may suitably have a depth of approximately D / 2×0.1 to D / 2×0.7.

[0032] Each of the bending grooves may have a longitudinal length of approximately D to D×10 and a depth of approximately D / 2×0.1 to D / 2×0.7, and the predetermined distance between the bending grooves may be equal to or less than approximately D×30, where D is a diameter of the filler wire.

[0033] The zinc alloy sheath comprises aluminum in an amount of 3 to 20 wt.%, silicon in an amount of 0.1 to 1.0 wt.% and zinc as the remainder of the zinc alloy, based on the total weight of the zinc alloy sheath.

[0034] Further, a method for joining parts is provided. The method includes applying the filler wire as described herein to a brazing portion, and the brazing portion joins one or more parts comprising different materials together.

[0035] The "different materials" as used herein refer to two other materials that can be distinguished from each other by their composition, constituent content, physical properties (e.g., hardness, tensile strength, elongation strength, and the like), or weight. Preferably, the different materials may include an aluminum alloy or steel (e.g., an iron alloy, carbon steel, or the like) that form parts and can be joined by brazing. For example, the different materials may include an aluminum alloy and steel.

[0036] Other aspects of the invention are disclosed below. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view illustrating a conventional flux cored wire in the prior art. Fig.Figure 2 shows an exemplary problem caused by the conventional flux cored wire in the prior art. Fig. 3 shows another exemplary problem caused by the conventional flux cored wire in the prior art. Fig. Figure 4 shows another exemplary problem caused by the conventional prior art flux cored wire. Fig. Figure 5 shows a conventional flux mixed rod of the prior art. Fig. Figure 6 shows a problem caused by the conventional flux-mixed rod of the prior art. Fig. 7 shows a section of an exemplary filler wire in the width direction according to an exemplary embodiment of the present invention. Fig.8 shows a section of an exemplary filler wire in the width direction according to an exemplary embodiment of the present invention. Fig. 9 shows an exemplary sample using an exemplary filler wire according to an exemplary embodiment of the present invention. Fig. 10 shows an interface obtained by an exemplary embodiment of the present invention. Fig. 11 shows the result of a scanning electron microscope (SEM) analysis for a part of the Fig. 10 shown interface. Fig. 12 shows an interface obtained by a comparative example. Fig. Figure 13 shows the result of a scanning electron microscope analysis for a part of the interface of Fig. 12. Fig. 14 shows an interface obtained by another comparative example. Fig.Figure 15 shows the result of a scanning electron microscope analysis for a part of the interface of Fig. 14. DETAILED DESCRIPTION

[0037] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is further understood that the terms "comprising," "including," "having," etc., when used in this specification, specify the presence of stated features, ranges, integers, steps, acts, elements, and / or components, but do not preclude the presence or addition of one or more other features, ranges, integers, steps, acts, elements, components, and / or combinations thereof.

[0038] It is understood that the term "vehicle" or "vehicular" or other similar terms, as used herein, generally encompasses motor vehicles, such as passenger cars, including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft, including a variety of boats and ships, aircraft, and the like, as well as hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel motor vehicles (e.g., fuels derived from resources other than petroleum). As noted herein, a hybrid vehicle is a vehicle that has two or more power sources, for example, both gasoline-powered and electric-powered vehicles.

[0039] Furthermore, unless specifically stated or obvious from the context, the term "about" as used herein is to be understood as within a range of normal tolerance in the art, for example, within 2 standard deviations of the mean. "Approximately" may be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise apparent from the context, all numerical values ​​provided herein are modified by the term "about."

[0040] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meanings as those commonly understood by one of ordinary skill in the art to which the present invention belongs. Furthermore, it is to be understood that terms, such as those defined in commonly used dictionaries, should be interpreted to have a meaning consistent with their meaning in the context of the prior art and the present invention, and should not be interpreted in an idealized or overly formal sense unless expressly stated herein.

[0041] In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by various exemplary embodiments of the present invention, reference should be made to the accompanying drawings and the content in the accompanying drawings which illustrate the exemplary embodiments of the present invention.

[0042] In describing the exemplary embodiments of the present invention, known techniques or repeated descriptions that may unnecessarily obscure the gist of the present invention are reduced or omitted.

[0043] Fig. 7 shows a section of an exemplary filler wire according to an exemplary embodiment of the present invention in the width direction, and Fig.Figure 8 shows a longitudinal section of an exemplary filler wire according to an exemplary embodiment of the present invention.

[0044] In the following, the flux cored wire for brazing aluminum and steel according to an exemplary embodiment of the present invention will be described with reference to Fig. 7 and Fig. 8 described.

[0045] The present invention provides a flux cored wire that can be used to ensure joint strength in brazing between aluminum and steel and to ensure the joint strength between aluminum and steel so that productivity can be improved compared with a conventional flux cored wire or a flux mixed rod.

[0046] Advantageously, the stable bonding strength between aluminum and Fe, which have low solubility, can be improved and ensured, and residues such as sludge and the like can be minimized after brazing to obtain a favorable appearance. Furthermore, when the manufactured wire wound around a wheel is released and applied to a laser or arc heat source, the wire cannot be deformed or broken. Furthermore, the bonding strength can be stably ensured even under high-speed brazing conditions (e.g., 3 m / min) without interfacial fracture of the wire.

[0047] The present invention provides a flux-mixed flexible wire with a zinc (Zn) sheath (FMW) capable of satisfying the above-mentioned conditions. Fig. 7 and Fig. 8 show views showing sections of the above wire in the thickness and length directions, respectively.

[0048] The cored wire of the present invention can be formed by wrapping an alloy sheath around a rod 10 made of alloy powder (hereinafter referred to as "alloy powder-coated rod"). In other words, the cored wire comprises a rod 10 containing an alloy powder and a sheath 20 containing an alloy (a zinc alloy).

[0049] In order to improve the process of feeding the flux-mixed rod, the zinc alloy sheath 20 may be in close contact with the alloy powder-coated rod 10 and wound around it under high pressure.

[0050] The alloy powder rod 10 contains aluminum-silicon (Al-Si) alloy powder and halide flux powder.

[0051] The Al-Si powder can be formed by pulverizing an alloy of mixed aluminum and silicon.

[0052] In addition, the Al-Si alloy powder can generally be used for brazing of Al-Si alloy.

[0053] The halide flux powder may comprise a fluoride flux powder and a chloride flux powder.

[0054] However, fluoride powder is preferable to chloride flux powder because chloride flux powder can cause corrosion.

[0055] In addition, the zinc alloy sheath 20 can fix the alloy powder inside the rod, so that the alloy powder can be supplied to a target point without being broken or deformed when the wire (rod) is bent.

[0056] However, a thickness t of the zinc alloy sheath 20 may be suitably set within a certain range to avoid the problem that the powders inside are not well dispersed during soldering such as the flux cored wire.

[0057] In addition, in order to improve the bendability, a plurality of bending grooves H may be formed on the filler wire at regular intervals or at a predetermined interval in the longitudinal direction of the filler wires so that, when the wire is bent, deformation can be induced at a portion with a reduced radius when the wire is bent to prevent breakage of the alloy powder in the wire.

[0058] The distance between the bending grooves H and the depth of each bending groove can be considered according to the thickness t of the zinc alloy shell 20.

[0059] If the distance between the bending grooves H is smaller than the specified distance or the depth of each bending groove is larger than the specified range, the groove may act as a notch and cause fracture in a corresponding section. Conversely, if the distance is larger than the specified distance, no improvement in bendability can be expected.

[0060] These conditions shall be determined taking into account the conditions for feeding laser or arc wire and the bendability of the wire and can be summarized as shown in Table 1. Table 1 Diameter (D) of the wire Thickness of the shell (t; mm) Longitudinal direction (a; mm) Distance between bending grooves (b; mm) Depth (d; mm) D / 2×0.1~D / 2×0.5 D~D×10 Max. D×30 D / 2×0.1~D / 2×0.7

[0061] The zinc alloy sheath 20 contains aluminum in an amount of approximately 3 to 20 wt.%, silicon in an amount of 0.1 to 1.0 wt.%, and zinc as the remainder of the zinc alloy sheath, with all wt.% being based on the total weight of the zinc alloy sheath.

[0062] Zinc, as used herein, can exhibit high ductility and can be advantageous for bending. For example, when aluminum is added to zinc, the melting point of zinc is lowered to a temperature of approximately 400°C. Since this melting point is significantly lower than the melting point of approximately 500 to 600°C of the internal mixed powder, it is possible that zinc will melt first during brazing, and therefore, zinc cannot prevent the internal powder from melting and flowing into a base material.

[0063] If aluminum and zinc are not within the specified content mentioned above, the zinc alloy coating may have an elevated melting point and adversely affect soldering.

[0064] In addition, zinc and silicon as used herein may have a high affinity for iron (Fe), so that when the Fe of a solid-state steel base material diffuses into the fusible wire and the aluminum base material at the time of brazing, zinc and silicon inhibit the formation of Fe-Al-based intermetallic compounds with high brittleness or form Fe-Al-Zn or Fe-Al-Si-based intermetallic compounds with brittleness lower than that of Fe-Al-based intermetallic compounds. Thus, zinc and silicon can increase brazing strength.

[0065] Especially when silicon is added, silicon can effectively inhibit the formation of intermetallic compounds and at the same time stably form an interface under the condition that the heat input is inevitably increased during high-speed soldering.

[0066] However, if the silicon content is increased, the melting point in the ternary phase diagram Al-Si-Zn can be greatly increased, so that a silicon content of no more than approximately 1 wt.% may be used.

[0067] In addition, the zinc can form a thin layer between the mixed powder that begins to melt and the steel base material, so that the molten mixed powder can spread over the steel base material in a short time and the flux inside the filler wire can react with the base material more quickly, thus stably promoting the formation of a brazing interface at high speed ratios.

[0068] According to the present invention, as described above, various exemplary cored wires having a specific thickness range and having specific bending grooves can be formed by wrapping the alloy sheath of mixed zinc, aluminum, and silicon around the rod provided with the alloy powder. In this way, the joining strength and productivity of brazing can be improved, reducing the cost and weight compared to a conventional mechanical joining between aluminum and steel.

[0069] Fig.9 shows an exemplary test specimen for demonstrating the present invention described above, wherein the test specimen has a roof-side connection structure with a steel side facing outward. For example, a steel exterior and an aluminum roof were subjected to laser brazing using the filler wire of the present invention, and the result was used as a test specimen.

[0070] As a result, stable joint strength was achieved because even under a high-speed condition (3 m / min) during brazing, no fracture was generated at the interface and pores of less than about 3% were formed in the brazing joint, which is the condition conforming to ISO 13919-2.

[0071] In addition, no sludge or other residue was found on the outside of the soldering section, eliminating the need for an additional cleaning process after soldering.

[0072] Table 2 shows the test results of the test specimens according to an example of the present invention and comparative examples. Table 2 Criteria Example 1 Comparison example 1 Comparison example 2 Comparison example 3 Diameter of the wire - 1.2 mm↑ Composition of the shell (%) - Al; 15.0, Si; 0.5 and Zn; Rem. Al; 15.0, Zn; balance Al; 25.0, Si; 5.0 and Zn; balance Zn100 Soldering rate 3 m / min. Whether a wire break occurs during feeding Fraction × Fraction × Fraction × Fraction × - Joint strength (N / mm) 140 (interfacial fracture ×) 160 (interface fracture ×) 120 (interfacial fracture) 110 (interface fracture ×) - External appearance There should be no flux sludge or other contamination. Good Good Good - Porous (%) Less than 3 1,5 1,5 1,5 - remark · - The heat input is increased in accordance with the rapid laser transmission. → It is necessary to further inhibit the formation of intermetallic compounds. A reason for the increase in the melting point of the mantle is to be expected. Sheath breakage occurs during a process of pressing the (FMW) flux mixed flexible wire with a zinc sheath due to lack of sheath strength.

[0073] As summarized in Table 2, when the flux cored wire of Example of the present invention was used, no breakage occurred during soldering during wire feeding, so that satisfactory joining strength and external appearance were achieved, and few pores were formed.

[0074] In comparative examples 1 and 2, however, the joint strength did not meet the criteria and partial interface fracture occurred.

[0075] Furthermore, in comparative example 3, in which the sheath consisted only of zinc, a fracture of the sheath itself occurred.

[0076] Fig. 10 shows an interface that occurred in Example 1 and was observed with an optical microscope, and Fig.11 is a scanning electron microscope analysis result of a box section in Fig. 10. For example, in Example 1, the wettability was improved, the intermetallic compound was controlled to less than about 10 g, and the stable joint strength was obtained without the occurrence of interface cracks.

[0077] In addition, Fig. 12 an interface observed with the optical microscope in Comparative Example 1, and Fig. 13 is a scanning electron microscope analysis result of a box section in Fig. 12.

[0078] Although the connection area in Fig. 12 seemed to be good, were along the intermetallic compounds, as in Fig. 13, cracks were observed, so cracks may be a factor in deterioration of joint strength.

[0079] Fig. 14 shows an interface observed with the optical microscope in Comparative Example 2, and Fig. 15 is a scanning electron microscope analysis result of a box section in Fig. 14. For example, wettability (increase in wetting angle) deteriorated as the melting point of the shell was increased and interfacial microcracks were observed, as in Fig. 15, which can deteriorate the connection strength.

[0080] By applying the flux cored wire to aluminum-steel brazing according to various exemplary embodiments of the present invention, the interface may not be peeled even under high-speed brazing conditions, so that the stable joint strength can be maintained, and pores are generated in the brazing joint in a number of less than 3%, which condition satisfies the ISO 13919-2 standard.

[0081] Since there is no sludge or other residue on the outside of the soldering section, no additional cleaning process is required after soldering.

[0082] As described above, when applying the flux cored wire of the present invention, the joining strength of the brazing portion between aluminum and steel can be improved and the productivity can be increased, so that the cost and weight can be reduced compared with the conventional mechanical joining under the condition that aluminum is inevitably used to reduce the weight of a vehicle.

[0083] Although the present invention has been described above with reference to the illustrated drawings, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the present invention. Accordingly, it is understood that such changes or additions fall within the scope of the claims of the present invention, and the scope of the present invention should be interpreted based on the appended claims.

Claims

[1] Flux-cored wire comprising: a rod comprising an aluminum-silicon (Al-Si) alloy powder and a halide flux powder; and a sheath comprising a zinc (Zn) alloy and surrounding the rod, wherein the zinc alloy comprises aluminum (Al) in an amount of 3 to 20 wt.%, silicon (Si) in an amount of 0.1 to 1.0 wt.% and zinc as the remainder of the zinc alloy, wherein all wt.% data refer to the total weight of the zinc alloy. [2] The filler wire according to claim 1, wherein the halide flux powder is a fluoride flux powder or a chloride flux powder. [3] The filler wire according to claim 2, wherein the halide flux powder is the fluoride flux powder. [4] A filler wire according to claim 1, wherein the sheath has a thickness of approximately D / 2×0.1 to D / 2×0.5, where D is the diameter of the filler wire. [5] A filler wire according to claim 1, wherein a plurality of bending grooves are formed on the filler wire at a predetermined pitch in the longitudinal direction. [6] The filler wire according to claim 5, wherein the bending groove has a longitudinal length of approximately D to D×10, where D is the diameter of the filler wire. [7] A filler wire according to claim 5, wherein the predetermined distance between the bending grooves is equal to or less than about D×30. [8] A filler wire according to claim 5, wherein each of the bending grooves has a depth of approximately D / 2×0.1 to D / 2×0.

7. [9] The filler wire according to claim 5, wherein each of the bending grooves has a longitudinal length of approximately D to D×10 and a depth of approximately D / 2×0.1 to D / 2×0.7, and the predetermined distance between the bending grooves is equal to or less than approximately D×30, where D is the diameter of the filler wire. [10] A method of joining parts comprising applying a filler wire according to claim 1 to a brazing portion, wherein the brazing portion joins one or more parts comprising different materials. [11] The method of claim 10, wherein the different materials comprise aluminum alloy and steel.

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