Shielding gas and method for manufacturing welded component

Abstract

To provide a shield gas and a method for manufacturing a welded component, capable of reducing the occurrence of welding failure in a weld zone without adopting a special welding method when joining a member formed of copper and a member formed of stainless steel by welding.SOLUTION: The shielding gas is used for non-consumable electrode type gas shielded arc welding of a first member formed of stainless steel and a second member formed of copper, and contains 10 vol% or more and 20 vol% or less of helium, with the balance being argon.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a shielding gas and a method for producing a welded part. [Background technology]

[0002] BACKGROUND ART A method for welding a copper member made of copper and a stainless steel member made of stainless steel has been known (see, for example, Patent Document 1).

[0003] The method described in Patent Document 1 includes a melting step in which a copper member and a stainless steel member are melted by an arc to form a molten pool, and a solidification step in which the molten pool is solidified. In the melting step, an electrode is moved so that the heat input to the copper is greater than the heat input to the stainless steel. Specifically, the electrode is moved back and forth between a position corresponding to the copper member and a position corresponding to the stainless steel member so as to straddle the butt joint between the copper member and the stainless steel member.

[0004] It is generally known that copper has a higher thermal conductivity than stainless steel. Therefore, when the same amount of heat is input to the butt joint between copper and stainless steel, the amount of copper that dissolves in the weld is smaller than that of the stainless steel, which can result in poor welding. However, according to Patent Document 1, by inputting a larger amount of heat into the copper than into the stainless steel, the amount of copper that dissolves can be made sufficient. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-92555 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if a special welding method is adopted in which the electrode is moved so that the heat input to the copper is greater than the heat input to the stainless steel, there is a problem in that the productivity of welded parts decreases.

[0007] Therefore, one of the objects of the present disclosure is to provide a shielding gas and a method for manufacturing welded parts that can reduce the occurrence of welding defects in welds when joining a member made of copper and a member made of stainless steel by welding, without having to employ a special welding method. [Means for solving the problem]

[0008] The shielding gas according to the present disclosure is a shielding gas used in non-consumable electrode gas-shielded arc welding of a first member made of stainless steel and a second member made of copper, and contains 10% by volume or more and 20% by volume or less of helium, with the remainder being argon.

[0009] A method for manufacturing a welded component according to the present disclosure includes the steps of: arranging a first portion, which is a part of a first member made of stainless steel, adjacent to a second portion, which is a part of a second member made of copper; forming an arc between the first portion and the second portion and an electrode in the shielding gas to form a molten pool in which the first portion and the second portion are melted; and solidifying the molten pool to form a weld that joins the first member and the second member. [Effects of the Invention]

[0010] According to the above-described shielding gas and method for manufacturing welded parts, when joining copper and stainless steel members by welding, it is possible to reduce the occurrence of poor welding and surface burns at the welded portion without using a special welding method. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the structure of a welded part according to an embodiment. [Figure 2] FIG. 2 is a schematic enlarged view of part A in FIG. [Figure 3] FIG. 3 is a schematic enlarged view of part B in FIG. 2 as viewed from the surface. [Figure 4] FIG. 4 is a flowchart showing an outline of the method for manufacturing a welded component according to the embodiment. [Figure 5] FIG. 5 is a schematic front view for explaining the method for manufacturing the welded component according to the embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view for explaining the method for manufacturing the welded component according to the embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing the structure of a welded part according to a first modified example. [Figure 8] FIG. 8 is a schematic cross-sectional view for explaining a method for manufacturing a welded component according to a first modified example. [Figure 9] FIG. 9 is a schematic cross-sectional view showing the structure of a welded part according to a second modification. [Figure 10] FIG. 10 is a schematic enlarged view of part C in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be described. The shielding gas of the present disclosure is a shielding gas used in non-consumable electrode gas-shielded arc welding between a first member made of stainless steel and a second member made of copper. The shielding gas contains 10% by volume or more and 20% by volume or less of helium, with the remainder being argon.

[0013] During arc discharge, the electrical conductivity of helium is lower than that of argon. Therefore, when a shielding gas contains 10% or more helium by volume, it is easier to constrict the base of the arc shielded by the shielding gas. This concentrates energy near the molten pool, making it more likely to heat up. As a result, copper and stainless steel are more likely to penetrate sufficiently, reducing the occurrence of welding defects. When a shielding gas contains 20% or less helium by volume, it reduces excessive constriction of the arc. This reduces the occurrence of surface burns on the weld (bead).

[0014] The shielding gas of the present disclosure may contain helium in an amount of 12% by volume or more and 18% by volume or less, which can further reduce the occurrence of poor welding and burn marks on the bead surface in the welded portion.

[0015] The method for manufacturing a welded component according to the present disclosure may include the steps of: arranging a first portion, which is a part of a first member made of stainless steel, adjacent to a second portion, which is a part of a second member made of copper; forming an arc between the first and second portions and an electrode in the shielding gas to form a molten pool in which the first and second portions are melted; and solidifying the molten pool to form a weld that joins the first and second members. This configuration facilitates increasing the temperature of the molten pool and ensuring sufficient penetration of copper and stainless steel. As a result, the occurrence of welding defects can be reduced. Furthermore, the shielding gas contains 20% or less helium by volume, which reduces the occurrence of surface burns at the weld.

[0016] In the method for manufacturing a welded component according to the present disclosure, in the step of forming the molten pool, the electrode may be moved along the boundary between the first and second parts while the arc intersects the boundary. With this configuration, when joining dissimilar metals, the electrode can be moved in the same manner as in joining the same metals. As a result, it is easy to join dissimilar metals using automated welding technology with a robot.

[0017] In the method for manufacturing a welded component according to the present disclosure, in the step of forming the molten pool, a filler metal may be supplied into an arc formed between the first and second portions and an electrode, and the first and second portions and the filler metal are heated by the arc to melt, thereby forming the molten pool. The filler metal may contain 4.5% to 4.9% by mass of iron, with the remainder consisting of copper and unavoidable impurities. With this configuration, when the molten pool solidifies to form a weld joining the first and second members, the weld includes a first region and a second region disposed to form an interface with the first region. The first region is primarily composed of elements contained in the stainless steel constituting the first member. The second region is primarily composed of elements contained in the copper constituting the second member. The first and second regions form a metallic bond at the interface. As a result, the strength of the weld can be improved in a welded component in which a copper member and a stainless steel member are welded together.

[0018] [Details of the embodiment of the present invention] Next, embodiments of the shielding gas and the method for manufacturing the welded component 10 according to the present disclosure will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and descriptions thereof will not be repeated.

[0019] The shielding gas according to this embodiment is used in non-consumable electrode gas-shielded arc welding of a first member 1 made of stainless steel and a second member 2 made of copper. The non-consumable electrode gas-shielded arc welding according to this embodiment is TIG welding.

[0020] FIG. 1 is a schematic cross-sectional view showing an enlarged view of the vicinity of a welded portion 3 in a welded part 10. FIG. 2 is a schematic enlarged view of part A in FIG. 1. FIG. 3 is a schematic plan view showing an enlarged view of the surface of part B in FIG. 2. In this embodiment, the direction from the first member 1 to the second member 2 is defined as a "first direction D1," and the opposite direction is defined as a "second direction D2."

[0021] The welded part 10 is a part formed by joining a first member 1 and a second member 2 by welding. Referring to Fig. 1, the welded part 10 includes the first member 1, the second member 2, and a welded portion 3 that joins the first member 1 and the second member 2 together.

[0022] (First member 1) The first member 1 is made of stainless steel. Nickel-chromium stainless steel or chromium stainless steel can be used as the stainless steel. Nickel-chromium stainless steel includes austenitic stainless steel. Examples of austenitic stainless steel include JIS standard SUS304 and JIS standard SUS316. Chromium stainless steel is stainless steel that contains chromium but not nickel, including ferritic stainless steel and martensitic stainless steel. Examples of ferritic stainless steel include JIS standard SUS430 stainless steel (JIS G 4304:2012 and JIS G 4305:2012). Examples of ferritic stainless steel include JIS standard SUS430 stainless steel, as well as SUS405, SUS410L, SUS429, SUS434, SUS436L, SUS436J1L, SUS443J1, SUS444, SUS445J1, SUS445J2, SUS447J1, and SUSXM27. JIS standard SUS430 series stainless steel includes JIS standard SUS430 and those with symbols added to the end of the name. For example, SUS430, SUS430LX, SUS430J1L, and SUS430F fall under the category of "JIS standard SUS430 series stainless steel."

[0023] Here, in the present disclosure, "nickel-free" includes those that can be considered to be nickel-free, and is not "nickel-free" in the strict sense. For example, in a stainless steel containing chromium, if the nickel content is 1 mass% or less, it falls into the category of chromium-based stainless steel.

[0024] The first member 1 according to this embodiment is formed in a flat plate shape. The first member 1 has a first surface 11 and a second surface 12 opposite to the first surface 11. In this embodiment, both the first surface 11 and the second surface 12 are flat. However, the shape of the first member 1 is not limited to a flat plate shape, and may be, for example, a pipe shape or a block shape.

[0025] (Second member 2) The second member 2 is made of pure copper, that is, copper with a purity of 99.9% by mass or more. The second member 2 according to this embodiment is formed in a flat plate shape. The second member 2 has a first surface 21 and a second surface 22 opposite to the first surface 21. In this embodiment, the first surface 21 and the second surface 22 are both flat. However, the shape of the second member 2 is not limited to a flat plate shape, and may be, for example, a pipe shape or a block shape.

[0026] In the welded part 10 according to this embodiment, the first surface 21 of the second member 2 is located on the same plane as the first surface 11 of the first member 1. In the welded part 10, the second surface 22 of the second member 2 is located on the same plane as the second surface 12 of the first member 1.

[0027] (Welded part 3) The first member 1 and the second member 2 are joined to each other by a welded portion 3. Referring to FIG. 2, the welded portion 3 includes a first region 31 and a second region 32. An interface 33 is formed between the first region 31 and the second region 32. That is, the second region 32 is disposed so as to form the interface 33 with the first region 31. The first region 31 is a region mainly composed of elements contained in the stainless steel constituting the first member 1. The second region 32 is a region mainly composed of copper constituting the second member 2. The first region 31 is located closer to the first member 1 than the interface 33 on an axis parallel to the first direction D1. The second region 32 is located closer to the second member 2 than the interface 33 on an axis parallel to the first direction D1. The interface 33 traverses the welded portion 3 so as to separate the welded portion 3 into a region in contact with the first member 1 (i.e., first region 31) and a region in contact with the second member 2 (i.e., second region 32) within the thickness of the welded portion 3. The interface 33 may be an uneven surface, a curved surface, or a flat surface.

[0028] Referring to FIG. 3 , a plurality of first island regions 321, each composed primarily of an element contained in the stainless steel constituting the first member 1, are present and separated from one another within the second region 32. The plurality of first island regions 321 exist within the thickness of the second region 32, and some of the plurality of first island regions 321 appear on the surface of the second region 32. A plurality of second island regions 311, each composed primarily of copper, are present and separated from one another within the first region 31. The plurality of second island regions 311 exist within the thickness of the first region 31, and some of the plurality of second island regions 311 appear on the surface of the first region 31. A metallic bond is formed between the first region 31 and the second region 32 at the interface 33. Here, a state in which a metallic bond is formed at the interface 33 means that the lattice of metal atoms constituting the first region 31 and the lattice of metal atoms constituting the second region 32 are continuous at the interface 33.

[0029] In the welded component 10 of this embodiment, the second region 32 contains a plurality of first island regions 321 containing elements contained in the stainless steel constituting the first member 1 as a main component. The first region 31 contains a plurality of second island regions 311 containing copper as a main component. As described above, the first region 31 and the second region 32 form a metallic bond at the interface 33. As a result, the welded component 10 of this embodiment has improved strength of the welded portion 3.

[0030] (Manufacturing method) Next, an example of a method for manufacturing the welded part 10 of this embodiment will be described. Fig. 4 is a flowchart outlining the method for manufacturing the welded part 10. Figs. 5 and 6 are schematic views for explaining the method for manufacturing the welded part 10.

[0031] Referring to FIG. 4, in the manufacturing method of the welded component 10 of this embodiment, a material preparation step is first performed as step S10. In step S10, a first member 1 made of stainless steel and a second member 2 made of copper are prepared as materials. Referring to FIG. 5, in step S10, the first member 1 and the second member 2 are arranged in a position where they can be welded. The surface of the first member 1 facing the second member 2 (referred to as a first opposing surface 131) and the surface of the second member 2 facing the first member 1 (referred to as a second opposing surface 231) face each other with a predetermined distance between them. In this embodiment, the predetermined distance between the first opposing surface 131 and the second opposing surface 231 may be referred to as the "root spacing W." The root spacing W is preferably 0.01 mm or more and 0.5 mm or less, and more preferably 0.1 mm or more and 0.4 mm or less. This configuration facilitates the formation of the first region 31 and the second region 32 in the weld 3 via the interface 33.

[0032] Next, a molten pool formation step is performed as step S20. In step S20, referring to FIG. 6 , an arc 5 is formed between an end portion (first portion 13) of the first member 1 prepared in step S10, including the first opposing surface 131, an end portion (second portion 23) of the second member 2, including the second opposing surface 231, and the electrode 72. In step S20, the electrode 72 is moved along a boundary portion K1 between the first member 1 and the second member 2 so that the arc 5 intersects the boundary portion K1. In other words, in step S20, the electrode 72 is moved along the boundary portion K1 while keeping the arc 5 in contact with the boundary portion K1 between the first member 1 and the second member 2. In this embodiment, the boundary portion K1 between the first member 1 and the second member 2 refers to a region including the first opposing surface 131, the second opposing surface 231, and the space between the first opposing surface 131 and the second opposing surface 231.

[0033] The "first portion 13" here refers to the portion at the end of the first member 1 that is melted by the arc 5. The "second portion 23" refers to the portion at the end of the second member 2 that is melted by the arc 5. In the first member 1, the portion other than the first portion 13 may be referred to as the "first main body portion 14." Similarly, in the second member 2, the portion other than the second portion 23 may be referred to as the "second main body portion 24."

[0034] 6, with the arc 5 formed, a filler rod 6 is supplied as a filler material into the arc 5, and the first portion 13, the second portion 23, and the filler rod 6 are heated and melted by the arc 5 to form a molten pool 4. In this embodiment, the molten pool 4 is formed between the first body portion 14 and the second body portion 24.

[0035] The electrode 72 is made of a high-melting-point metal material such as tungsten (W). The outer peripheral surface of the electrode 72, excluding the tip, is surrounded by a hollow cylindrical nozzle 71, and the tip of the electrode 72 is exposed to the outside from the nozzle 71. The nozzle 71 and the electrode 72 form a welding torch 7. A shielding gas is discharged from the annular space between the outer peripheral surface of the electrode 72 and the inner peripheral surface of the nozzle 71 in the direction of arrow A toward the first member 1 and the second member 2.

[0036] The shielding gas contains 10% by volume or more and 20% by volume or less of helium. The lower limit of the helium content in the shielding gas is preferably 12% by volume, more preferably 13% by volume, and even more preferably 14% by volume. If the helium content in the shielding gas is equal to or greater than the above-mentioned lower limit, the occurrence of insufficient copper penetration in the welded portion 3 can be reduced. The upper limit of the helium content in the shielding gas is preferably 18% by volume, more preferably 17% by volume, and even more preferably 16% by volume. If the helium content in the shielding gas is equal to or less than the above-mentioned upper limit, the occurrence of surface burn of the welded portion 3 (bead) can be reduced. The helium content in the shielding gas can be measured, for example, using a thermal conductivity detector (TCD). If the shielding gas is commercially available, the value listed in the test report (or catalog) of the commercially available product can be used as the helium content.

[0037] The remainder of the shielding gas is argon. Specifically, the argon content in the shielding gas is, for example, 80% by volume or more, preferably 82% by volume or more, more preferably 83% by volume or more, and even more preferably 84% by volume or more. The argon content in the shielding gas is, for example, 90% by volume or less, preferably 88% by volume or less, more preferably 87% by volume or less, and even more preferably 86% by volume or less. In addition to helium and argon, the shielding gas may contain impurities that are inevitably contained in the production of the shielding gas. Examples of impurities include nitrogen and oxygen. The impurity content in the shielding gas is 0.01% by volume or less. The respective argon and impurity contents in the shielding gas can be measured using a thermal conductivity detector.

[0038] Shielding gas is discharged along arrow A, insulating the arc 5 from the outside air. The filler rod 6 is heated by the arc 5 and melts, forming droplets 61 that reach the molten pool 4. The molten pool 4 is composed of the molten first member 1 that constitutes the first portion 13, the molten second member 2 that constitutes the second portion 23, and the molten filler rod 6. The filler rod 6 contains 4.0% by mass or more and 4.9% by mass or less of iron, with the remainder consisting of copper and unavoidable impurities.

[0039] Next, a solidification step is performed as step S30. In step S30, the molten pool 4 formed in step S20 is solidified to form a weld 3 joining the first member 1 and the second member 2. Specifically, the first member 1 and the second member 2, on which the molten pool 4 was formed in step S20, are moved a predetermined distance along the boundary K1. As a result, the arc 5 forms a new molten pool 4 in an area adjacent to the previously formed molten pool 4, and the previously formed molten pool 4 solidifies to form a weld 3 (bead) (see FIG. 1 ). This procedure is repeated until the weld 3 is formed along the entire length of the boundary K1 between the first member 1 and the second member 2, thereby completing the method for manufacturing the welded component 10 of this embodiment and obtaining the welded component 10 of this embodiment.

[0040] As described above, step S20 of the manufacturing method for the welded component 10 of this embodiment employs a filler rod 6 (filler metal) containing 4.0% to 4.9% by mass of iron, with the remainder consisting of copper and unavoidable impurities. This facilitates achieving a state in the welded portion 3 where multiple first island regions 321 are present in the second region 32 and multiple second island regions 311 are present in the first region 31, thereby forming a metallic bond between the first region 31 and the second region 32. As a result, the manufacturing method for the welded component 10 of this embodiment can improve the strength of the welded portion 3. Preferably, the filler rod 6 contains 4.0% to 4.8% by mass of iron, with the remainder consisting of copper and unavoidable impurities. Because the melting point of iron is higher than that of copper, solid iron and liquid copper coexist in the temperature range above the melting point of copper and below the melting point of iron. By reducing the iron content to 4.8 mass % or less, iron segregation is suppressed, which contributes to improving the strength of the welded portion 3.

[0041] The diameter of the filler rod 6 is preferably 1.2 mm or less, and more preferably 0.9 mm or less. By using such a filler rod 6, it becomes easier to achieve a state in which a plurality of first island regions 321 exist within the second region 32 and a plurality of second island regions 311 exist within the first region 31, and the first region 31 and the second region 32 form a metallic bond.

[0042] In the manufacturing method for welded component 10 according to this embodiment, step S20 uses a shielding gas containing 10% by volume or more and 20% by volume or less of helium, with the remainder being argon. Therefore, even if electrode 72 is moved along boundary K1 between first member 1 and second member 2 so that arc 5 intersects with boundary K1 during the process of forming molten pool 4, the occurrence of welding defects and surface burns on the welded portion 3 can be reduced. Therefore, according to the manufacturing method for welded component 10 according to this embodiment, the occurrence of welding defects and surface burns on the welded portion 3 can be reduced without using a special welding technique, such as increasing the heat input to copper compared to the heat input to stainless steel. As a result, joining of dissimilar metals can be easily achieved using automated welding technology using robots, facilitating mass production of welded components 10 that require joining of copper and stainless steel.

[0043] When a special welding technique is used, such as increasing the heat input to copper compared to stainless steel, the welded part can be identified as having been formed using the special welding technique by etching the welded part and taking a cross-sectional macrophotograph of the weld. With the special welding technique, the portion of the weld where the copper or stainless steel penetration depth is greatest is offset from the boundary K1 in the cross-sectional macrophotograph. In other words, a shallower penetration depth exists between the portion with the greatest penetration depth and the opposing surfaces 131 and 231. In contrast, in the cross-sectional macrophotograph of the welded part 10 according to the present embodiment, the portion of the weld 3 where the copper and stainless steel penetration depth is greatest overlaps the boundary K1. This allows welded parts manufactured using the method for manufacturing a welded part according to the present embodiment to be distinguished from conventional welded parts manufactured using the special welding technique.

[0044] [First Modification of Welded Part 10] In the above embodiment, the first member 1 and the second member 2 are formed in a flat plate shape. However, as shown in FIG. 7, they may be formed in a pipe shape. FIG. 7 is a schematic cross-sectional view showing the structure of a welded part 10 according to a first modified example. FIG. 8 is a schematic cross-sectional view showing the welded part 10 according to the first modified example in a state before welding. Referring to FIG. 7, the diameter of the inner circumferential surface 15 of the first member 1 is the same as the diameter of the inner circumferential surface 25 of the second member 2. The diameter of the outer circumferential surface 16 of the first member 1 is the same as the diameter of the outer circumferential surface 26 of the second member 2. The first member 1 has a flow path (hereinafter referred to as the first flow path 17). The first flow path 17 is a space surrounded by the inner circumferential surface 15 of the first member 1. The second member 2 has a flow path (hereinafter referred to as the second flow path 27). The second flow path 27 is a space surrounded by the inner circumferential surface 25 of the second member 2.

[0045] Referring to FIG. 8 , among the end faces of the first member 1 in the central axis direction, a first opposing surface 131 facing the second member 2 includes a tapered surface 132. Among the end faces of the second member 2 in the central axis direction, a second opposing surface 231 facing the first member 1 includes a tapered surface 232. The tapered surface 132 of the first opposing surface 131 and the tapered surface 232 of the second opposing surface 231 are inclined with respect to an imaginary plane perpendicular to the central axes of the first member 1 and the second member 2 so that the distance between them increases radially outward. The angle of the tapered surfaces 132, 232 with respect to the imaginary plane (hereinafter referred to as the bevel angle θ) is preferably 10 degrees or more and 45 degrees or less, more preferably 15 degrees or more and 30 degrees or less. This configuration facilitates the formation of the first region 31 and the second region 32 via the interface 33 in the welded portion 3.

[0046] Referring to FIG. 8 , the first opposing surface 131 and the second opposing surface 231 may each have a root surface 133, 233. The root surface 133, 233 is a flat surface at the end surface that is perpendicular to the central axis of the first member 1 and the second member 2. In this modification, the root surface 133, 233 is a surface on the opposing surface 131, 231 other than the tapered surface 132, 232. When the first member 1 and the second member 2 are arranged so that their central axes coincide and in a position where they can be welded, the root surfaces 133, 233 face each other with a predetermined distance (root spacing W) between them. The root spacing W is preferably 0.01 mm or more and 0.5 mm or less, and more preferably 0.1 mm or more and 0.4 mm or less. This configuration facilitates the formation of the first region 31 and the second region 32 via the interface 33 in the welded portion 3.

[0047] 7, a welded portion 3 joins a first member 1 and a second member 2. As in the above embodiment, a shielding gas containing 10% by volume or more and 20% by volume or less of helium, with the remainder being argon, is used. In step S20 (molten pool formation step), a back shielding gas is flowed through the first flow path 17 and the second flow path 27. As the back shielding gas, for example, an inert gas such as argon or a mixed gas of argon and helium may be used, or a shielding gas containing 10% by volume or more and 20% by volume or less of helium, with the remainder being argon, as in the shielding gas, may be used.

[0048] In step S30 (solidification step), the weld 3 is formed by solidifying the molten pool 4 formed between the first member 1 and the second member 2. Specifically, the first member 1 and the second member 2, in which the molten pool 4 was formed in step S20, are rotated circumferentially by a predetermined angle, for example, about 5 to 10 degrees. This causes the arc 5 to form a new molten pool 4 in an area adjacent to the previously formed molten pool 4, and the previously formed molten pool 4 solidifies to become the weld 3. This procedure is repeated until the weld 3 is formed around the entire circumference of the first member 1 and the second member 2, completing the method for manufacturing the welded part 10 according to this modified example, and the welded part 10 can be obtained.

[0049] As in the embodiment, in step S20, a filler rod 6 (filler metal) containing 4.0 mass % to 4.9 mass % iron, with the remainder being copper and unavoidable impurities, is used. This makes it easy to achieve a state in the weld 3 where multiple first island regions 321 exist in the second region 32 and multiple second island regions 311 exist in the first region 31, and where the first region 31 and the second region 32 form a metallic bond.

[0050] [Second Modification of Welded Part 10] In the above embodiment, the first member 1 and the second member 2 are joined by butt welding, but as shown in Fig. 9, the first member 1 and the second member 2 may be joined by fillet welding in a state in which the insertion portion 29 of the second member 2 is inserted into the joint portion 19 of the first member 1. Fig. 9 is a schematic cross-sectional view showing the structure of a welded part 10 according to this modification. Fig. 10 is a schematic enlarged view of part C in Fig. 9.

[0051] The first member 1 includes a first main body portion 18 and a joint portion 19. The joint portion 19 is a portion into which the longitudinal end portion of the second member 2 is inserted. In this modification, the portion of the second member 2 that is inserted into the joint portion 19 is referred to as the "insertion portion 29." The joint portion 19 extends from the longitudinal end portion of the first main body portion 18 along the central axis. The joint portion 19 is included in the longitudinal end portion of the first member 1.

[0052] In the first member 1, the first main body portion 18 includes an outer peripheral surface 181 and an inner peripheral surface 182. The outer peripheral surface 181 has a cylindrical surface shape. The inner peripheral surface 182 has a cylindrical surface shape that shares a central axis with the outer peripheral surface 181. The outer peripheral surface 181 and the inner peripheral surface 182 are arranged concentrically when viewed along the central axis. The first member 1 has a flow path (first flow path 17) that is formed by being surrounded by the inner peripheral surface 182. The first member 1 is formed in a tubular shape.

[0053] The joint portion 19 includes an outer peripheral surface (hereinafter referred to as the "joint outer peripheral surface 191") and an inner peripheral surface (hereinafter referred to as the "joint inner peripheral surface 192"). The joint outer peripheral surface 191 has a cylindrical surface shape. The diameter of the joint outer peripheral surface 191 is longer than the diameter of the outer peripheral surface 181. The outer peripheral surface 181 and the joint outer peripheral surface 191 are connected via an outer connecting surface 193. The outer connecting surface 193 is inclined relative to the outer peripheral surface 181 and the joint outer peripheral surface 191 so as to extend radially outward in the central axial direction from the outer peripheral surface 181 to the joint outer peripheral surface 191. The joint inner peripheral surface 192 has a cylindrical surface shape that shares a common central axis with the joint outer peripheral surface 191. The diameter of the joint inner peripheral surface 192 (the inner diameter of the joint portion 19) is longer than the diameter of the inner peripheral surface 182. The diameter of the joint inner circumferential surface 192 (the inner diameter of the joint portion 19) is equal to the outer diameter of the second member 2. In this disclosure, "equal" includes a range in which the objects being compared are substantially the same. For example, pipes with the same nominal diameter have equal diameters.

[0054] The second member 2 includes a second main body portion 28 and an insertion portion 29. The insertion portion 29 protrudes from a longitudinal end of the second main body portion 28 along the central axis. The inner diameter of the second main body portion 28 and the inner diameter of the insertion portion 29 are the same length. In this modification, the second main body portion 28 and the insertion portion 29 are formed integrally without any seams. The inner diameter of the insertion portion 29 may be shorter or longer than the inner diameter of the second main body portion 28.

[0055] In the second member 2, the second main body portion 28 and the insertion portion 29 include an outer peripheral surface 281 and an inner peripheral surface 282. The diameter of the outer peripheral surface 281 is the same as the diameter of the outer peripheral surface 181 of the first member 1, and the second member 281 has a cylindrical shape with a common central axis with the outer peripheral surface 181. The diameter of the inner peripheral surface 282 is the same as the diameter of the inner peripheral surface 182 of the first member 1, and the second member 281 has a cylindrical shape with a common central axis with the inner peripheral surface 182. The inner peripheral surface 282 has a common central axis with the outer peripheral surface 281. The second member 2 has a flow path (second flow path 27) formed by being surrounded by the inner peripheral surface 282. The second member 2 is formed in a tubular shape. When the insertion portion 29 is inserted into the joint portion 19, the first flow path 17 and the second flow path 27 communicate with each other to form a single flow path.

[0056] By making the diameter of the inner circumferential surface 182 of the first member 1 (the inner diameter of the first member 1) and the diameter of the inner circumferential surface 282 of the second member 2 (the inner diameter of the second member 2) the same length, pressure loss is unlikely to occur in the fluid flowing through the flow path. However, the outer diameter of the first main body portion 18 of the first member 1 and the outer diameter of the second member 2 may be different lengths.

[0057] The first member 1 and the second member 2 are joined to each other by the welded portion 3 at the tip of the joint portion 19, with the insertion portion 29 inserted into the joint portion 19. As in the above embodiment, the shielding gas used contains 10% by volume or more and 20% by volume or less of helium, with the remainder being argon.

[0058] In step S30 (solidification step), the weld 3 is formed by solidifying the molten pool 4 formed between the first member 1 and the second member 2. Specifically, the first member 1 and the second member 2, in which the molten pool 4 was formed in step S20, are rotated circumferentially by a predetermined angle, for example, about 5 to 10 degrees. This causes the arc 5 to form a new molten pool 4 in an area adjacent to the previously formed molten pool 4, and the previously formed molten pool 4 solidifies to become the weld 3. This procedure is repeated until the weld 3 is formed around the entire circumference of the first member 1 and the second member 2, completing the method for manufacturing the welded part 10 according to this modified example, and the welded part 10 can be obtained.

[0059] As in the embodiment, in step S20, a filler rod 6 (filler metal) containing 4.0 mass % to 4.9 mass % iron, with the remainder being copper and unavoidable impurities, is used. This makes it easy to achieve a state in the weld 3 where multiple first island regions 321 exist in the second region 32 and multiple second island regions 311 exist in the first region 31, and where the first region 31 and the second region 32 form a metallic bond. [Example]

[0060] An experiment was conducted to manufacture a welded component 10 using the method for manufacturing the welded component 10 using the shielding gas of the present disclosure, and to confirm the welded portion 3. The procedure of the experiment is as follows. However, the method for manufacturing the welded component 10 of the present disclosure is not limited to the following example.

[0061] [Test piece] Test pieces No. 1 to No. 14 were prepared as the welded part 10. The conditions for test pieces No. 1 to No. 14 were as follows: No. 1 to No. 4 were examples, and No. 5 to No. 14 were comparative examples. No.1,2 Material of first member 1: Austenitic stainless steel (JIS standard SUS304) Material of second member 2: Copper [No. 1: Oxygen-free copper (C1020), No. 2: Phosphorus-deoxidized copper (C1220)] Shape of the first member 1 and the second member 2: Plate-shaped Shielding gas: A gas containing 15% by volume of helium, the remainder being argon Welding method: The groove is formed into an I-groove. At the same time as metal melting by the arc 5 begins, the electrode 72 is moved linearly along the boundary K1 between the first member 1 and the second member 2, aiming at the center of the boundary K1. No.3,4 Material of first member 1: Ferritic stainless steel (JIS standard SUS430) Material of second member 2: Copper [No. 3: Oxygen-free copper (C1020), No. 4: Phosphorus-deoxidized copper (C1220)] Shape of the first member 1 and the second member 2: Plate-shaped Shielding gas: A gas containing 15% by volume of helium, the remainder being argon Welding method: The groove is formed into an I-groove. At the same time as metal melting by the arc 5 begins, the electrode 72 is moved linearly along the boundary K1 between the first member 1 and the second member 2 while aiming at the center of the boundary K1. No.5,6 Material of first member 1: Austenitic stainless steel (JIS standard SUS304) Material of second member 2: Copper [No. 5: Oxygen-free copper (C1020), No. 6: Phosphorus-deoxidized copper (C1220)] Shape of the first member 1 and the second member 2: Plate-shaped Shielding gas: Argon (single) Welding method: The groove is made into an I-groove. The electrode 72 is moved back and forth between the copper and the stainless steel so that the heat input to the copper is greater than the heat input to the stainless steel. No.7, 8 Material of first member 1: Austenitic stainless steel (JIS standard SUS304) Material of second member 2: Copper [No. 7: Oxygen-free copper (C1020), No. 8: Phosphorus-deoxidized copper (C1220)] Shape of the first member 1 and the second member 2: Plate-shaped Shielding gas: A gas containing 5% by volume of helium, the remainder being argon Welding method: The groove is formed into an I-groove. At the same time as metal melting by the arc 5 begins, the electrode 72 is moved linearly along the boundary K1 between the first member 1 and the second member 2 while aiming at the center of the boundary K1. No.9,10 Material of first member 1: Austenitic stainless steel (JIS standard SUS304) Material of second member 2: Copper [No. 9: Oxygen-free copper (C1020), No. 10: Phosphorus-deoxidized copper (C1220)] Shape of the first member 1 and the second member 2: Plate-shaped Shielding gas: A gas containing 25% by volume of helium, the remainder being argon Welding method: The groove is formed into an I-groove. At the same time as metal melting by the arc 5 begins, the electrode 72 is moved linearly along the boundary K1 between the first member 1 and the second member 2 while aiming at the center of the boundary K1. No.11,12 Material of first member 1: Ferritic stainless steel (JIS standard SUS430) Material of second member 2: Copper [No. 11: Oxygen-free copper (C1020), No. 12: Phosphorus-deoxidized copper (C1220)] Shape of the first member 1 and the second member 2: Plate-shaped Shielding gas: A gas containing 5% by volume of helium, the remainder being argon Welding method: The groove is formed into an I-groove. At the same time as metal melting by the arc 5 begins, the electrode 72 is moved linearly along the boundary K1 between the first member 1 and the second member 2 while aiming at the center of the boundary K1. No.13,14 Material of first member 1: Ferritic stainless steel (JIS standard SUS430) Material of second member 2: Copper [No. 13: Oxygen-free copper (C1020), No. 14: Phosphorus-deoxidized copper (C1220)] Shape of the first member 1 and the second member 2: Plate-shaped Shielding gas: A gas containing 25% by volume of helium, the remainder being argon Welding method: The groove is formed into an I-groove. At the same time as metal melting by the arc 5 begins, the electrode 72 is moved linearly along the boundary K1 between the first member 1 and the second member 2 while aiming at the center of the boundary K1.

[0062] [Welding conditions] Welding machine: DC welding power supply (WB-A350P, Daihen) Current waveform control: Pulse control method Pulse frequency: 300Hz or higher Current: 180A / 40A Shielding gas flow rate: 15 L / min (at 400 Hz) Electrode 72: tungsten (W) doped with 2% cerium (Ce), outer diameter 2.4 mm Filler rod 6: Filler rod 6 containing 4.0% by mass or more and 4.9% by mass or less of iron, with the remainder being copper and unavoidable impurities Welding method: Welding by maintaining the arc length at 1.5mm±0.3mm and maintaining the torch angle at 4° to 6°.

[0063] [evaluation] The state of the welded portion 3 was checked for each of the test pieces No. 1 to No. 14. The evaluation criteria were as follows: Welding failure: Insufficient penetration between the first member 1 and the second member 2 at the welded portion 3. Surface burn: Surface burn of the bead was confirmed in welded section 3. Good: No welding defects or surface burns are observed in the welded section 3.

[0064] The results are shown in Table 1.

[0065] [Table 1] Referring to Table 1, when a shielding gas containing 5 volume % helium and the remainder argon was used, poor welding was observed in the weld 3. When a shielding gas containing 25 volume % helium and the remainder argon was used, bead surface burns were observed in the weld 3. In contrast, when a shielding gas containing 15 volume % or less helium and the remainder argon was used, it was confirmed that a good weld 3 could be obtained even when the electrode 72 was moved linearly along the boundary K1. From this, it was confirmed that when a shielding gas containing 10 volume % to 20 volume % helium and the remainder argon was used, a good weld 3 could be obtained even when the electrode 72 was moved linearly along the boundary K1. Furthermore, it was confirmed that in both welding of austenitic stainless steel and copper and welding of ferritic stainless steel and copper, when a shielding gas containing 10% by volume or more and 20% by volume or less of helium and the remainder being argon is used, a good weld 3 can be obtained even when the electrode 72 is moved linearly along the boundary K1.

[0066] It should be understood that the embodiments disclosed herein are illustrative in all respects and are not limiting in any respect. The scope of the present invention is defined not by the above description but by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0067] 10 welded part, 1 first member, 11 first surface, 12 second surface, 13 first portion, 131 first opposing surface, 132 tapered surface, 133 root surface, 14 first main body portion, 15 inner peripheral surface, 16 outer peripheral surface, 17 first flow path, 18 first main body portion, 181 outer peripheral surface, 182 inner peripheral surface, 19 joint portion, 191 joint outer peripheral surface, 192 joint inner peripheral surface, 193 outer connecting surface, 2 second member, 21 first surface, 22 second surface, 23 second portion, 231 second opposing surface, 232 tapered surface, 233 root surface, 24 second main body portion, 25 inner peripheral surface, 26 outer peripheral surface, 27 second flow path, 28 second main body portion, 281 outer peripheral surface, 282 inner peripheral surface, 29 insertion portion, 3 welding portion, 31 First region, 311 Second island region, 32 Second region, 321 First island region, 33 Interface, 4 Weld pool, 5 Arc, 6 Filler rod, 61 Metal droplet, 7 Welding torch, 71 Nozzle, 72 Electrode, K1 Interface, W Root spacing, D1 First direction, D2 Second direction.

Claims

1. A shielding gas used in non-consumable electrode gas-shielded arc welding of a first member made of stainless steel and a second member made of copper, Contains 10% by volume or more and 20% by volume or less of helium, with the remainder being argon; Shielding gas.

2. 2. The shielding gas according to claim 1, wherein the helium content is 12% by volume or more and 18% by volume or less.

3. a step of adjacently disposing a first portion that is a part of a first member made of stainless steel and a second portion that is a part of a second member made of copper; forming an arc between the first portion and the second portion and an electrode in the shielding gas according to claim 1 or 2, and forming a molten pool in which the first portion and the second portion are melted; solidifying the molten pool to form a weld that joins the first member and the second member; A method for manufacturing a welded part, comprising:

4. 4. The method for manufacturing a welded component according to claim 3, wherein in the step of forming the molten pool, the electrode is moved along the boundary between the first portion and the second portion in a state where the arc intersects the boundary.

5. In the step of forming the molten pool, a filler material is supplied into an arc formed between the first portion, the second portion, and an electrode, and the first portion, the second portion, and the filler material are heated by the arc to melt the filler material, thereby forming the molten pool; The method for manufacturing a welded part according to claim 3, wherein the filler metal contains 4.5 mass % to 4.9 mass % of iron, with the remainder consisting of copper and unavoidable impurities.

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