Joining structure

Abstract

A second member 20 is composed of a material that is difficult to weld to a first member 10. A third member 30 is welded to the first member 10 through a perforation 21 in the second member 20. A fourth member 40 is composed of a filler material that can be welded to the second member 20. The fourth member 40 covers the surface of the third member 30 and is welded to the second member 20.

Description

[Technical field]

[0001] The present invention relates to a joint structure. [Background technology]

[0002] Patent Document 1 discloses a joining structure in which a first metal material and a dissimilar material that is difficult to weld to the first metal material are overlapped, and a filler material (welding wire) is arc-welded through a penetration part of the dissimilar materials.

[0003] At this time, a flange is formed by the molten filler metal so as to cover the outer periphery of the upper surface side of the penetration part of the dissimilar material, whereby the dissimilar material and the first metal material are fixed together by the compressive fixing force between the flange and the first metal material caused by the solidification and shrinkage of the filler metal relative to the first metal material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 030272 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the invention of Patent Document 1, there is a risk that moisture may penetrate from the outside through a gap in the overlapping surface between the flange portion of the third metal material and the second metal material. The invaded moisture may cause electrolytic corrosion in the overlapping portion between the flange portion of the third metal material and the second metal material, which may reduce the joint strength.

[0006] The present invention has been made in consideration of the above-mentioned points, and has an object to suppress the occurrence of electrolytic corrosion in an area where a metal material and a different material overlap. [Means for solving the problem]

[0007] An embodiment of the present disclosure is directed to a joining structure in which a first member made of a metal material, a second member made of a material that is difficult to weld to the first member, and a third member made of a filler material welded to the first member are joined together, and the following solution has been provided.

[0008] That is, in the first aspect, the second member has a through-hole formed therein that penetrates toward the first member, the third member is welded to the first member through the through portion, A fourth member is provided, the fourth member being made of a filler material that is weldable to the second member, covering a surface of the third member and welded to the second member.

[0009] In a first embodiment, the third member is welded to the first member through the penetration. The fourth member is made of a filler material that can be welded to the second member. The fourth member covers a surface of the third member and is welded to the second member.

[0010] In this way, by covering the surface of the third member with the fourth member and welding the fourth member to the second member to seal the gap between the second member and the third member with the fourth member, it is possible to prevent moisture from entering from the outside into the overlapping portion of the second member and the third member.

[0011] This makes it possible to prevent electrolytic corrosion from occurring in the area where the second member and the third member overlap, and ensure the joining strength.

[0012] The second aspect is the first aspect, The third member has a flange portion on a surface of the second member opposite to the first member, the flange portion protruding radially outward beyond the through portion and pressing against a peripheral edge portion of the through portion.

[0013] In the second aspect, the flange portion presses against the surface of the second member opposite the first member, thereby enabling the second member to be compressed and fixed between the flange portion and the first member.

[0014] This allows the overlapping portions of the second and third members to be tightly attached to each other, making it difficult for moisture to penetrate from the outside.

[0015] The third aspect is the first aspect, The through portion has a tapered portion that tapers toward the first member, The third member presses the tapered portion.

[0016] In the third aspect, by providing a tapered portion in the through portion and solidifying the third member into a shape that conforms to the tapered portion, the thickness of the third member protruding from the second member can be reduced, and thus the thickness of the fourth member protruding from the second member can also be reduced.

[0017] The fourth aspect is the first aspect, The second member has a step portion that opens on a surface opposite to the first member, and the through portion formed in a bottom surface of the step portion.

[0018] In the fourth aspect, a through-hole is formed on the bottom surface of the step of the second member. This makes it possible to place the third member inside the step and prevent the third member from protruding from the second member. Also, it is possible to reduce the thickness of the fourth member protruding from the second member.

[0019] The fifth aspect is the fourth aspect, The bottom surface of the step portion is inclined toward the through portion.

[0020] In the fifth aspect, by inclining the bottom surface of the step portion toward the through-hole, the molten filler metal of the third member can easily flow toward the center of the through-hole.

[0021] The sixth aspect is the first aspect, the second member has a step portion that opens at a surface where the second member and the first member are joined together, and the through portion is formed in a bottom surface of the step portion, The first member has a bulging portion that bulges toward the step portion.

[0022] In a sixth aspect, the bulging portion of the first member bulges toward the stepped portion of the second member, so that when the second member is superimposed on the first member, the stepped portion is fitted into the bulging portion, making it easy to align the first member and the second member.

[0023] A seventh aspect is any one of the first to sixth aspects, The third member has a first joint portion welded to the first member, and a second joint portion welded to the first joint portion and pressing down a peripheral portion of the penetrating portion.

[0024] In the seventh aspect, by forming the third member separately into a first joint and a second joint, it is possible to select welding methods or welding conditions that take into account the material properties of the second member.

[0025] For example, when welding the molten filler metal of the third member to the first member through the penetration, short-circuit arc welding, which repeats short-circuit and arc states and has a small arc spread with the heat input required for penetration, can be performed to form the first joint. Then, positive polarity or AC pulse welding, which has a large arc spread and has a low heat input that does not melt the second member, can be performed to form the second joint. This makes it possible to form the second joint while suppressing the amount of heat input to the second member.

[0026] An eighth aspect is any one of the first to seventh aspects, The fourth member has a central portion covering a central portion of a surface of the third member, and an outer periphery welded to the central portion and the second member along an outer periphery of the central portion.

[0027] In the eighth aspect, the fourth member is formed by dividing it into a central portion and an outer peripheral portion. For example, the central portion is formed by arc welding to cover the central portion of the surface of the third member, and then the outer peripheral portion is formed by arc welding along the outer peripheral edge of the central portion, so that the central portion and the outer peripheral portion are blended together.

[0028] In addition, an outer periphery may be formed by arc welding to cover the outer periphery of the surface of the third component, and then a central portion may be formed by arc welding the central portion of the surface of the third component to blend the central portion and the outer periphery together. Effect of the Invention

[0029] According to the aspects of the present disclosure, it is possible to suppress the occurrence of electrolytic corrosion in an area where a metal material and a dissimilar material overlap. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a side cross-sectional view for explaining a joint structure according to the first embodiment. [Diagram 2] FIG. 2 is a side cross-sectional view for explaining a joint structure according to the second embodiment. [Diagram 3] FIG. 3 is a side cross-sectional view for explaining a joint structure according to the third embodiment. [Figure 4] FIG. 4 is a side cross-sectional view for explaining a joint structure according to the fourth embodiment. [Diagram 5] FIG. 5 is a side cross-sectional view for explaining a joint structure according to the fifth embodiment. [Figure 6] FIG. 6 is a side cross-sectional view for explaining a joint structure according to the sixth embodiment. [Figure 7] FIG. 7 is a side cross-sectional view for explaining a joint structure according to the seventh embodiment. [Figure 8] FIG. 8 is a side cross-sectional view for explaining a joint structure according to the eighth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following description of the preferred embodiment is merely illustrative in nature and is not intended to limit the present invention, its applications, or its uses.

[0032] First Embodiment FIG. 1 shows a joining structure for joining together a first member 10 made of a metal material, a second member 20 made of a material that is difficult to weld to the first member 10, and a third member 30 made of the first filler metal as a filler metal.

[0033] The first member 10 is a plate-like member made of a metal material.

[0034] The second member 20 is a plate-like member made of a material that is difficult to weld to the first member 10. The second member 20 is overlapped on the upper side of the first member 10. The second member 20 has a circular through-hole 21.

[0035] In this embodiment, the through-hole 21 is described as a circular through-hole, but it may be an elliptical or elongated through-hole.

[0036] The third member 30 is made of a filler metal that is the same type of metal material as the first member 10. Here, the term "homogeneous metal materials" refers to metals that can be welded to each other, and refers to metal materials that have good weldability, such as not only metals of the same material but also metals that have good weldability such as ferrous metals and non-ferrous metals. In other words, the term "homogeneous metal materials" refers to materials of the same type that have good welding compatibility.

[0037] Specifically, the combinations of the first member 10 and the third member 30 during welding include the following. For example, combinations of ferrous metal materials include mild steel and mild steel, stainless steel and stainless steel, mild steel and high-tensile steel (high-tensile steel), high-tensile steel and high-tensile steel, etc. Furthermore, combinations of non-ferrous metal materials include aluminum and aluminum, aluminum and aluminum alloy, aluminum alloy and aluminum alloy, etc.

[0038] In addition, the second member 20 as a dissimilar material is made of a material different from the first member 10 and the third member 30 as the same type of metal material, and is made of a material that is difficult to weld to the first member 10 and the third member 30.

[0039] For example, if the first member 10 and the third member 30 as the homogeneous metal materials are made of ferrous metal materials, the second member 20 as the dissimilar material is made of a non-ferrous metal material such as copper or aluminum.

[0040] The third member 30 is welded to the first member 10 via the through-hole 21. The third member 30 is provided with a flange portion 31 that presses the peripheral portion of the through-hole 21. Then, the third member 30 solidifies and shrinks relative to the first member 10, whereby the second member 20, which is a different material, is compressed and fixed between the flange portion 31 and the first member 10.

[0041] However, in the portion where the flange portion 31 of the third member 30 and the second member 20 overlap, there is a risk that electrolytic corrosion will occur due to the intrusion of moisture from the outside.

[0042] Therefore, in this embodiment, the gap between the overlapping portions of the second member 20 and the third member 30 is filled with the fourth member 40.

[0043] Specifically, the fourth member 40 is configured of a second filler metal that is a filler metal of the same type that can be welded to the second member 20. The fourth member 40 covers the surface of the third member 30. The fourth member 40 is welded to the second member 20.

[0044] In the following explanation, a case will be described in which mild steel is used as the first member 10, aluminum is used as the second member 20, mild steel is used as the third member 30 which is a filler material for the first member 10, and aluminum is used as the fourth member 40 which is a filler material for the second member 20.

[0045] The arc welding machine 1 includes a nozzle 2 and a tip 3. The nozzle 2 supplies a shielding gas and the like to a welding portion of an object to be welded. The tip 3 supplies a welding current to a third member 30.

[0046] The arc welding machine 1 generates an arc 5 by supplying a welding current while feeding the third member 30 to the first member 10 through the penetration portion 21. The third member 30 melted by the arc welding is fused and bonded to the first member 10, and is layered inside the penetration portion 21. After filling up the inside of the penetration portion 21, the molten third member 30 flows out to the peripheral portion on the upper surface side of the penetration portion 21 and spreads out in a flange shape.

[0047] In the process in which the molten third member 30 becomes a bead, a flange portion 31 that presses the peripheral edge of the through-hole portion 21 is provided on the third member 30. The flange portion 31 protrudes radially outward from the through-hole portion 21 on the surface of the second member 20 opposite to the first member 10 (the upper surface in FIG. 1).

[0048] Then, the third member 30 solidifies and shrinks relative to the first member 10, so that the second member 20, which is a different material, is compressed and fixed between the flange portion 31 and the first member 10.

[0049] In this manner, the welding wire serving as the filler material, which is the third member 30, is melted and supplied to the first member 10 through the penetration portion 21 of the second member 20, whereby a flange-shaped bead for ensuring strength is formed on the second member 20, and the second member 20 can be clamped in place by compression.

[0050] It is not necessary that the second member 20 and the third member 30 are melt-bonded together. Even if an intermetallic compound is formed by melt-bonding, this does not pose a problem because the purpose is compression fixing by the flange shape.

[0051] The arc welding machine 1 covers the surface of the third member 30 with a filler metal (fourth member 40) that can be welded to the second member 20, and welds it to the second member 20. Specifically, when welding the filler metal to the second member 20, the arc welding machine 1 performs pulse welding using a pulse waveform that alternates between a peak current and a base current in DC welding with positive polarity or AC welding with switching polarity. In pulse welding, the spread of the arc 5 can be increased with a low heat input that does not melt the second member 20, and the heat input to the filler metal side as a welding electrode can be increased, thereby increasing the amount of deposition.

[0052] In pulse welding, a molten droplet generated at the tip of the filler metal is detached from the filler metal once per pulse consisting of a peak current and a base current, and detaches and transfers to the flange portion 31 or the second member 20 side.

[0053] Here, positive polarity DC welding refers to welding using DC current in which the filler metal as the welding electrode is the negative pole (negative pole) and the first member 10 and the second member 20 as the base metal are the positive pole (positive pole), thereby increasing the heat input to the filler metal as the welding electrode. This reduces the heat input to the base metal and promotes the melting of the filler metal as the welding electrode.

[0054] In AC welding using AC with switched polarity, for example, the peak current waveform is reversed to the positive polarity, and the base current waveform is positive to the negative polarity. During peak current of reverse polarity, the first member 10 and the second member 20 as the base material are set to the negative polarity, and the filler metal as the welding electrode is set to the positive polarity. During base current of positive polarity, the first member 10 and the second member 20 as the base material are set to the positive polarity, and the filler metal as the welding electrode is set to the negative polarity.

[0055] In this way, AC welding using AC with reversible polarity involves increasing the heat input to the base metals, the first member 10 and the second member 20, during peak current of reverse polarity, and increasing the heat input to the filler metal, the welding electrode, during base current of positive polarity. This reduces the heat input to the base metal compared to DC welding, and promotes melting of the filler metal, the welding electrode.

[0056] Although positive polarity pulse welding has been described, short-circuit arc welding in which an arc state and a short-circuit state are repeated may be performed as a welding method in which the spread of the arc 5 is small but the heat input to the second member 20 is suppressed.

[0057] The arc welding machine 1 generates an arc 5 by supplying a welding current while feeding a filler metal (fourth member 40) to the surface of the third member 30. The fourth member 40 melted by the arc welding is fused and joined to the second member 20, and is layered so as to cover the surface of the third member 30.

[0058] As described above, in the joint structure according to this embodiment, the surface of the third member 30 is covered with the fourth member 40, and the fourth member 40 is welded to the second member 20, so that the gap between the second member 20 and the third member 30 is blocked by the fourth member 40 to prevent moisture from entering from the outside. In this way, it is possible to prevent moisture from entering the overlapping portion of the second member 20 and the third member 30 from the outside.

[0059] This makes it possible to prevent electrolytic corrosion from occurring in the overlapping portion between the second member 20 and the third member 30, and ensure the joining strength.

[0060] In this way, unlike the third member 30, a second welding is performed using a second filler metal (fourth member 40) made of the same material as the second member 20, and the molten metal is welded so as to cover the flange-shaped bead formed by the third member 30, forming a bead larger than the flange-shaped size. This enables fusion joining by the fourth member 40 made of the same material as the second member 20.

[0061] In addition, by melting and joining the same materials, it is possible to prevent the intrusion of moisture from the outside and to suppress electrolytic corrosion without using different construction methods such as commonly used adhesives, sealants, and sealing agents.

[0062] Basically, the first member 10 and the third member 30 are made of a material having a higher melting point than the second member 20 and the fourth member 40. Therefore, the interface between the third member 30 and the fourth member 40 is not melt-bonded or is only slightly melt-bonded.

[0063] As a result, even if the fourth member 40 is formed as a bead on the flange-shaped bead of the third member 30, the bead of the fourth member 40 can be formed without having any effect such as deforming the flange shape of the third member 30.

[0064] Second Embodiment Hereinafter, the same parts as those in the first embodiment will be denoted by the same reference numerals, and only the differences will be described.

[0065] 2, the second member 20 has a through-hole 21. The through-hole 21 has a tapered portion 22 that tapers toward the first member 10.

[0066] The third member 30 is melted by arc welding. The molten third member 30 flows along the tapered portion 22 of the through portion 21 so as to gather at the center side of the through portion 21, and is melt-bonded to the first member 10.

[0067] The molten third member 30 fills up the inside of the through portion 21 and spreads onto the upper surface of the tapered portion 22 in a flange shape.

[0068] In the process in which the molten third member 30 becomes a bead, the third member 30 is provided with a flange portion 31 that presses the tapered portion 22 of the through portion 21.

[0069] Then, the third member 30 solidifies and shrinks relative to the first member 10, so that the second member 20, which is a different material, is compressed and fixed between the flange portion 31 and the first member 10.

[0070] Thereafter, a welding current is supplied while feeding the fourth member 40 onto the surface of the third member 30, thereby generating an arc 5. The fourth member 40 melted by arc welding is fused and bonded to the second member 20, and is layered so as to cover the surface of the third member 30.

[0071] As described above, according to the joint structure of this embodiment, by providing the tapered portion 22 in the through portion 21 and solidifying the flange portion 31 into a shape that conforms to the tapered portion 22, it is possible to reduce the thickness of the flange portion 31 protruding from the second member 20. This also makes it possible to reduce the thickness of the fourth member 40 protruding from the second member 20.

[0072] Third Embodiment As shown in FIG. 3, the second member 20 has a step portion 25 that opens on the surface opposite to the first member 10 (the upper surface in FIG. 3), and a through portion 21 formed on the bottom surface of the step portion 25.

[0073] The third member 30 is melted by arc welding. The melted third member 30 is melt-bonded to the first member 10.

[0074] Then, the molten third member 30 fills up the inside of the through portion 21, and then flows out onto the periphery on the upper surface side of the through portion 21, that is, onto the bottom surface of the step portion 25, and spreads out in a flange shape.

[0075] In the process in which the molten third member 30 becomes a bead, a flange portion 31 that presses the peripheral edge portion of the through portion 21 is provided on the third member 30.

[0076] Then, the third member 30 solidifies and shrinks relative to the first member 10, so that the second member 20, which is a different material, is compressed and fixed between the flange portion 31 and the first member 10.

[0077] Thereafter, a welding current is supplied while feeding the fourth member 40 onto the surface of the third member 30, thereby generating an arc 5. The fourth member 40 melted by the arc welding is fusion-bonded to the step portion 25 of the second member 20, and is layered so as to cover the surface of the third member 30.

[0078] As described above, according to the joining structure of this embodiment, the flange portion 31 of the third member 30 is disposed within the step portion 25, and it is possible to prevent the flange portion 31 from protruding from the second member 20. In addition, the thickness of the fourth member 40 protruding from the second member 20 can be reduced.

[0079] Fourth Embodiment 4, the second member 20 has a step portion 25 that opens on a surface opposite to the first member 10 (the upper surface in FIG. 4), and a through portion 21 formed on a bottom surface of the step portion 25. The bottom surface of the step portion 25 is inclined toward the through portion 21.

[0080] The third member 30 is melted by arc welding. The melted third member 30 is melt-bonded to the first member 10. When the melted third member 30 comes onto the inclined surface of the step portion 25, it flows along the inclined surface of the step portion 25 toward the penetrating portion 21 and is melt-bonded to the first member 10.

[0081] Then, after the molten third member 30 fills up the inside of the through portion 21, it flows out onto the peripheral portion on the upper side of the through portion 21, i.e., onto the bottom surface of the stepped portion 25, and spreads out in a flange shape onto the inclined surface of the stepped portion 25.

[0082] In the process in which the molten third member 30 becomes a bead, a flange portion 31 that presses the inclined surface of the step portion 25 is provided on the third member 30.

[0083] Then, the third member 30 solidifies and shrinks relative to the first member 10, so that the second member 20, which is a different material, is compressed and fixed between the flange portion 31 and the first member 10.

[0084] Thereafter, a welding current is supplied while feeding the fourth member 40 onto the surface of the third member 30, thereby generating an arc 5. The fourth member 40 melted by arc welding flows along the inclined surface of the step portion 25. More specifically, it flows effectively so as to close the gap between the third member 30 and the second member 20 from the outside. Then, the melted fourth member 40 is melt-bonded to the second member 20, and is layered so as to cover the surface of the third member 30.

[0085] As described above, according to the joint structure of this embodiment, by inclining the bottom surface of the step portion 25 toward the through portion 21, the molten third member 30 can easily flow toward the through portion 21.

[0086] In addition, the molten fourth member 40 flows along the inclined surface of the step portion 25, thereby effectively sealing the gap between the third member 30 and the second member 20 from the outside, and is molten and bonded to the second member 20.

[0087] Moreover, by disposing the flange portion 31 of the third member 30 within the step portion 25, it is possible to prevent the flange portion 31 from protruding from the second member 20. Moreover, the thickness of the fourth member 40 protruding from the second member 20 can be reduced.

[0088] Fifth Embodiment As shown in FIG. 5, the second member 20 has a step portion 25 that opens at the surface where the second member 20 overlaps with the first member 10 (the lower surface in FIG. 5), and a through portion 21 formed in the bottom surface of the step portion 25.

[0089] The first member 10 has a bulging portion 15 that bulges toward the step portion 25. The bulging portion 15 is fitted into the step portion 25.

[0090] The third member 30 is melted by arc welding. The melted third member 30 is melt-bonded to the first member 10.

[0091] Then, the molten third member 30 fills up the inside of the through portion 21, and then flows out onto the peripheral portion on the upper surface side of the through portion 21 and spreads out in a flange shape.

[0092] In the process in which the molten third member 30 becomes a bead, a flange portion 31 that presses the peripheral edge portion of the through portion 21 is provided on the third member 30.

[0093] Then, the third member 30 solidifies and shrinks relative to the first member 10, so that the second member 20, which is a different material, is compressed and fixed between the flange portion 31 and the first member 10.

[0094] Thereafter, a welding current is supplied while feeding the fourth member 40 onto the surface of the third member 30, thereby generating an arc 5. The fourth member 40 melted by arc welding is fused and bonded to the second member 20, and is layered so as to cover the surface of the third member 30.

[0095] As described above, according to the joining structure of this embodiment, when the second member 20 is superimposed on the first member 10, the step portion 25 is fitted into the bulge portion 15, whereby the first member 10 and the second member 20 can be easily aligned.

[0096] In addition, when the third member 30 is melted to the first member 10 by arc welding, by utilizing the empty space on the back side of the bulge 15 in the first member 10, a back bead can be sufficiently formed on the back side of the first member 10, which is the surface opposite to the second member 20. This forms a weld bead from the back side of the first member 10 as if it had been welded, so-called back bead welding, and the strength can be further increased.

[0097] Furthermore, by providing an open space on the rear side of the bulge 15 in the first member 10, a space can be secured in the event that the weld bead partially protrudes from the rear surface side of the first member 10 as a back wave.

[0098] Sixth Embodiment As shown in FIG. 6, the second member 20 has a through portion 21.

[0099] The third member 30 is melted by arc welding. The third member 30 has a first joint portion 35 welded to the first member 10, and a second joint portion 36 welded to the first joint portion 35 to form the flange portion 31.

[0100] Specifically, when the molten third member 30 is welded to the first member 10 via the penetration portion 21, short-circuit arc welding is performed in which a short circuit state and an arc state are repeated, with the heat input required for penetration and with a small spread of the arc 5, to form the first joint 35. Thereafter, positive polarity or AC pulse welding is performed, with a low heat input that does not melt the second member 20 and with a large spread of the arc 5, to form the second joint 36. This makes it possible to form the flange portion 31 while suppressing the amount of heat input to the second member 20.

[0101] In the process in which the molten third member 30 becomes a bead, a first bonding portion 35 and a second bonding portion 36 are provided on the third member 30. The first bonding portion 35 is melt-bonded to the first member 10. The second bonding portion 36 is melt-bonded to the first bonding portion 35 to form a flange portion 31 that presses the peripheral portion of the through portion 21.

[0102] The upper portion of the first joint portion 35 is preferably welded so that the center is recessed.

[0103] This makes it easier to determine the welding position when welding the second bonding portion 36 to the first bonding portion 35. Also, the molten second bonding portion 36 tends to gather at the recessed center side of the first bonding portion 35, making it possible to more uniform the shape of the second bonding portion 36.

[0104] Then, the third member 30 solidifies and shrinks relative to the first member 10, so that the second member 20, which is a different material, is compressed and fixed between the flange portion 31 and the first member 10.

[0105] Thereafter, a welding current is supplied while feeding the fourth member 40 onto the surface of the third member 30, thereby generating an arc 5. The fourth member 40 melted by arc welding is fused and bonded to the second member 20, and is layered so as to cover the surface of the third member 30.

[0106] As described above, according to the joining structure of this embodiment, by forming the third member 30 separately into the first joining portion 35 and the second joining portion 36, it is possible to select welding methods or welding conditions that take into account the material properties of the second member 20.

[0107] The shapes of the first member 10 and the second member 20 are merely examples, and other combinations may be used.

[0108] Seventh Embodiment As shown in FIG. 7, the second member 20 has a through portion 21.

[0109] The third member 30 is melted by arc welding. The melted third member 30 is melt-bonded to the first member 10. After filling up the inside of the through-hole 21, the melted third member 30 flows out onto the peripheral portion on the upper surface side of the through-hole 21 and spreads out in a flange shape.

[0110] In the process in which the molten third member 30 becomes a bead, a flange portion 31 that presses the peripheral edge portion of the through portion 21 is provided on the third member 30.

[0111] Then, the third member 30 solidifies and shrinks relative to the first member 10, so that the second member 20, which is a different material, is compressed and fixed between the flange portion 31 and the first member 10.

[0112] The fourth member 40 has a central portion 41 and an outer peripheral portion 42. The central portion 41 covers a central portion of the surface of the third member 30. The outer peripheral portion 42 is welded to the central portion 41 and the second member 20 along the outer peripheral edge of the central portion 41.

[0113] Specifically, an arc 5 is generated by supplying a welding current while feeding the fourth member 40 to a central portion of the surface of the third member 30. The fourth member 40 melted by arc welding is layered so as to cover the surface of the third member 30. As a result, a central portion 41 of the fourth member 40 is formed.

[0114] Then, the nozzle 2 of the arc welding machine 1 is rotated along the outer periphery of the central portion 41, thereby supplying the molten fourth member 40 to the outer periphery of the central portion 41. The molten fourth member 40 is welded to the central portion 41 and the second member 20. As a result, an outer periphery 42 of the fourth member 40 is formed.

[0115] As described above, according to the joining structure of this embodiment, central portion 41 is formed by arc welding to cover the central portion of the surface of third member 30, and then arc welding is performed along the outer periphery of central portion 41 to form outer periphery portion 42, thereby making central portion 41 and outer periphery portion 42 blend with each other.

[0116] Eighth embodiment As shown in FIG. 8, the second member 20 has a through portion 21.

[0117] The third member 30 is melted by arc welding. The melted third member 30 is melt-bonded to the first member 10. After filling up the inside of the through-hole 21, the melted third member 30 flows out onto the peripheral portion on the upper surface side of the through-hole 21 and spreads out in a flange shape.

[0118] In the process in which the molten third member 30 becomes a bead, a flange portion 31 that presses the peripheral edge portion of the through portion 21 is provided on the third member 30.

[0119] Then, the third member 30 solidifies and shrinks relative to the first member 10, so that the second member 20, which is a different material, is compressed and fixed between the flange portion 31 and the first member 10.

[0120] The fourth member 40 has a central portion 41 and an outer peripheral portion 42. The central portion 41 covers a central portion of the surface of the third member 30. The outer peripheral portion 42 is welded to the central portion 41 and the second member 20 along the outer peripheral edge of the central portion 41.

[0121] Specifically, the nozzle 2 of the arc welding machine 1 is rotated along the outer circumferential edge of the flange portion 31 to supply the molten fourth member 40 to the outer circumferential edge of the flange portion 31. The molten fourth member 40 is welded to the second member 20 along the outer circumferential edge of the flange portion 31. As a result, an outer circumferential portion 42 of the fourth member 40 is formed.

[0122] Then, a welding current is supplied while feeding the fourth member 40 to the central portion of the surface of the third member 30, thereby generating an arc 5. The fourth member 40 melted by arc welding is fused and bonded to the outer circumferential portion 42, and is layered so as to cover the surface of the third member 30. In this way, a central portion 41 of the fourth member 40 is formed.

[0123] As described above, according to the joining structure of this embodiment, the outer peripheral portion 42 is formed by arc welding to cover the outer peripheral portion of the surface of the third member 30, and then the central portion of the surface of the third member 30 is arc welded to form the central portion 41, thereby making it possible to blend the central portion 41 and the outer peripheral portion 42 together.

[0124] Other Embodiments The above embodiment may be configured as follows.

[0125] In the present embodiment, arc welding is performed on the first member 10, but the present invention is not limited to this embodiment. Specifically, the filler material for the third member 30 may be of a consumable electrode type (consumable electrode type) or a non-consumable electrode type (non-consumable electrode type). Therefore, for example, instead of the welding wire used as the consumable electrode type (consumable electrode type) filler material for the third member 30, a filler wire as a non-consumable electrode type (non-consumable electrode type) filler material may be used to perform laser filler welding on the first member 10.

[0126] In laser filler welding, a laser is irradiated onto the first member 10 to ensure thorough penetration of the surface of the first member 10, and then the laser is irradiated onto only the filler wire that is supplied, thereby melting the filler wire that is the third member 30. This makes it possible to completely fill the inside of the penetration portion 21 with the third member 30 while suppressing heat input to the second member 20.

[0127] In addition, by defocusing the laser to reduce the power density and ensuring a large beam diameter, the outer periphery of the laser beam diameter can be used to preheat the second member 20. This allows the molten filler wire, which is the third member 30, to easily conform to the second member 20. This effect can then be used to seal the gap between the second member 20 and the third member 30 to prevent moisture from entering from the outside, thereby suppressing moisture from entering the overlapping portion between the second member 20 and the third member 30 from the outside.

[0128] Moreover, the third member 30 and the fourth member 40 may be formed by hybrid welding using arc welding and laser welding. Specifically, the third member 30 may be formed by laser filler welding, and the fourth member 40 may be formed by hybrid welding by arc welding.

[0129] Alternatively, the third member 30 may be formed by arc welding using a consumable filler metal, and the fourth member 40 may be formed by laser filler welding using a filler wire as a non-consumable filler metal, thereby forming the fourth member 40 by hybrid welding.

[0130] Furthermore, a combination of these laser welding methods may be used. For example, a laser with reduced output may be defocused to reduce the power density of the laser, or the laser may be changed from continuous output to pulsed output, or the duty ratio of the pulsed output may be reduced. The laser may be preheated by irradiating at least one or more locations on the outer periphery of the penetration portion 21 of the second member 20 and the upper side of the third member 30. In this way, the compatibility of the second member 20, the third member 30, and the fourth member 40 during welding can be improved. This can prevent moisture from entering the overlapping portions of the second member 20, the third member 30, and the fourth member 40 from the outside. [Industrial Applicability]

[0131] As described above, the present invention has the highly practical effect of suppressing the occurrence of electrolytic corrosion at areas where a metal material and a dissimilar material overlap, and is therefore extremely useful and has high industrial applicability. [Explanation of symbols]

[0132] 10 First member 15 Bulge 20 Second member 21 Penetration 22 Tapered section 25 Step 30 Third Component 31 Flange 35 1st joint 36 Second joint 40 Fourth Component 41 Central part 42 Outer periphery

Claims

1. A joining structure in which a first member made of a metal material, a second member made of a material that is difficult to weld to the first member, and a third member made of a filler material welded to the first member are joined together, The second member has a through-hole formed therein, the through-hole penetrating toward the first member, the third member is welded to the first member through the through portion, A joint structure comprising a fourth member made of a filler material weldable to the second member, covering a surface of the third member and welded to the second member.

2. In claim 1, The third member has a joining structure having a flange portion on the surface of the second member opposite the first member, the flange portion protruding radially outward from the through portion and pressing against the peripheral portion of the through portion.

3. In claim 1, The through portion has a tapered portion that tapers toward the first member, The third member is a joining structure that holds the tapered portion.

4. In claim 1, The second member has a stepped portion that opens onto a surface opposite to the first member, and the through portion is formed on a bottom surface of the stepped portion.

5. In claim 4, A joint structure in which a bottom surface of the step portion is inclined toward the through portion.

6. In claim 1, the second member has a step portion that opens at a surface where the second member and the first member are joined together, and the through portion is formed in a bottom surface of the step portion, The first member has a bulging portion that bulges toward the step portion.

7. In any one of claims 1 to 6, The third member has a joint structure having a first joint portion welded to the first member and a second joint portion welded to the first joint portion to press against the peripheral portion of the through portion.

8. In any one of claims 1 to 7, The fourth member has a joint structure having a central portion covering a central portion of the surface of the third member, and an outer peripheral portion welded to the central portion and the second member along the outer peripheral edge of the central portion.

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