Welded parts and method for manufacturing same

Abstract

To improve the strength of a welded part in which a member made of copper and a member made of chromium-based stainless steel are joined by welding. [Solution] A welded part includes a first member made of chromium-based stainless steel, a second member made of copper, and a welded part joining the first member and the second member. The welded part includes a first region mainly composed of an element contained in the chromium-based stainless steel constituting the first member, and a second region mainly composed of copper and arranged to form an interface between the first region and the first region. Within the second region, a plurality of first island regions mainly composed of an element contained in the chromium-based stainless steel constituting the first member are present and separated from one another. Within the first region, a plurality of second island regions mainly composed of copper are present and separated from one another. The first region and the second region form a metallic bond at the interface.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to welded components and methods of manufacturing welded components. [Background technology]

[0002] A technique for joining a copper member and a steel member by welding has been known for some time. It is also known that an alloy of copper and iron can be used as a filler rod (filler metal) used in welding (see, for example, Patent Document 1 and Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-087688 A [Patent Document 2] JP 2020-076136 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, a copper member and a steel member can be joined by welding using a conventional method. However, when a copper member and a chromium-based stainless steel member are joined by welding, there is a problem that the strength of the welded portion is insufficient.

[0005] Therefore, it is an object of the present disclosure to improve the strength of a welded part in which a member made of copper and a member made of chromium-based stainless steel are joined by welding. [Means for solving the problem]

[0006] A welded component according to the present disclosure includes a first member made of chromium-based stainless steel, a second member made of copper, and a welded portion joining the first member and the second member. The welded portion includes a first region mainly composed of an element contained in the chromium-based stainless steel constituting the first member, and a second region mainly composed of copper, which is arranged to form an interface between the first region and the first region. In the second region, a plurality of first island regions mainly composed of an element contained in the chromium-based stainless steel constituting the first member are present and separated from each other. In the first region, a plurality of second island regions mainly composed of copper are present and separated from each other. The first region and the second region form a metallic bond at the interface.

[0007] A method for manufacturing a welded component according to the present disclosure includes the steps of: preparing a first member made of chromium-based stainless steel and a second member made of copper, supplying a filler metal into an arc formed between an electrode and the first and second members, and heating and melting the first and second members and the filler metal with the arc to form a molten pool, and solidifying the molten pool to form a weld that joins the first and second members. The filler metal contains 4.0% by mass to 4.9% by mass of iron, with the remainder being copper and unavoidable impurities. Effect of the Invention

[0008] According to the above-described welded part and manufacturing method for the welded part, in which a member made of copper and a member made of chromium-based stainless steel are joined by welding, the strength of the welded portion can be improved. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a structure of a welded part according to an embodiment. [Diagram 2] FIG. 2 is a schematic enlarged view of part A in FIG. [Diagram 3] FIG. 3 is a schematic enlarged view of part B in FIG. [Figure 4]FIG. 4 is a flow chart showing an outline of the method for manufacturing a welded component according to the embodiment. [Diagram 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 a structure of a welded part according to a modified example. [Figure 8] FIG. 8 is a schematic cross-sectional view for explaining a manufacturing method of a welded component according to a modified example. [Figure 9] FIG. 9 is a photograph showing the state of the test piece as the welded part after the tensile test. [Figure 10] FIG. 10 is a schematic cross-sectional view of a test piece used in the experiment. [Figure 11] FIG. 11 is an optical microscope photograph showing the metal structure of a portion corresponding to portion C in FIG. [Figure 12] FIG. 12 is an enlarged photograph showing the analysis results of element distribution in the Z1 portion of FIG. [Figure 13] FIG. 13 is an enlarged photograph showing the analysis results of element distribution in the Z2 portion of FIG. [Figure 14] FIG. 14 is an enlarged photograph showing the analysis results of element distribution in the Z3 portion of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Outline of the embodiment] The welded component of the present disclosure includes a first member made of chromium-based stainless steel, a second member made of copper, and a welded portion joining the first member and the second member. The welded portion includes a first region mainly composed of an element contained in the chromium-based stainless steel constituting the first member, and a second region mainly composed of copper and arranged to form an interface between the first region and the second region. In the second region, a plurality of first island regions mainly composed of an element contained in the chromium-based stainless steel constituting the first member are present and separated from each other. In the first region, a plurality of second island regions mainly composed of copper are present and separated from each other. The first region and the second region form a metallic bond at the interface.

[0011] The present inventors have investigated ways to improve the strength of a welded part in which a member made of copper and a member made of chromium-based stainless steel are joined by welding, and have obtained the following findings.

[0012] When joining a member made of copper and a member made of chromium-based stainless steel by welding, it is difficult to form a weld in which copper and chromium-based stainless steel are uniformly mixed because copper and iron do not easily form a solid solution. Therefore, the weld has a first region whose main component is an element contained in the chromium-based stainless steel and a second region whose main component is copper, and an interface is formed between the first region and the second region.

[0013] In the welded component of the present disclosure, a plurality of first island regions, each mainly composed of an element contained in the chromium-based stainless steel, are present and separated from one another in the second region. A plurality of second island regions, each mainly composed of copper, are present and separated from one another in the first region. The first region and the second region form a metallic bond at the interface. As a result, according to the welded component of the present disclosure, in a welded component in which a member made of copper and a member made of chromium-based stainless steel are joined by welding, the strength of the weld can be improved.

[0014] In the welded component, the chromium-based stainless steel may be a ferritic stainless steel. Ferritic stainless steel is suitable as the chromium-based stainless steel constituting the first member in the welded component of the present disclosure.

[0015] In the welded component, the ferritic stainless steel may be JIS standard SUS430 series stainless steel, which is suitable as the ferritic stainless steel constituting the first member in the welded component of the present disclosure.

[0016] In the above welded part, the first member and the second member may have a tubular shape. A longitudinal end of either the first member or the second member may include a joint portion into which an insert portion, which is a longitudinal end of the other member, is inserted. The first member and the second member may be joined to each other by a weld portion at the end of the joint portion with the insert portion inserted into the joint portion. In a welded part in which members having a tubular shape are joined to each other, the strength of the weld portion may be a problem due to the influence of a fluid flowing inside, the influence of vibration, and the like. The welded part of the present disclosure, which has improved strength at the weld portion, is suitable for application to such parts.

[0017] In the above welded component, the insert portion may be included in the first member, and the joint portion may be included in the second member. This structure is suitable as a joining structure between a first member made of chromium-based stainless steel and a second member made of copper.

[0018] The manufacturing method of the welded parts disclosed herein includes the steps of: preparing a first member made of chromium-based stainless steel and a second member made of copper, supplying a filler metal into an arc formed between the first member, the second member and the electrode, heating the first member, the second member and the filler metal with the arc to melt them and form a molten pool, and solidifying the molten pool to form a weld that joins the first member and the second member. The filler metal contains 4.0% by mass to 4.9% by mass of iron, with the remainder being copper and unavoidable impurities.

[0019] According to the inventors' investigations, by using a filler metal containing 4.0 mass % to 4.9 mass % iron with the remainder being copper and unavoidable impurities in arc welding, it becomes easy to achieve a state in which a plurality of first island regions are present separately from one another in the second region and a plurality of second island regions are present separately from one another in the first region, and the first region and the second region form a metallic bond. Therefore, according to the manufacturing method for a welded part disclosed herein, it is possible to improve the strength of the welded part in which a member made of copper and a member made of chromium-based stainless steel are joined by welding.

[0020] [Details of the embodiment] Next, an example of an embodiment of the welded component 10 of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated.

[0021] Fig. 1 is a schematic cross-sectional view showing the structure of a welded part 10 according to an embodiment. Fig. 2 is an enlarged view of a portion A in Fig. 1, and is a schematic view showing a welded portion 3. Fig. 3 is an enlarged view of a portion B in Fig. 2, and is a schematic view showing the structure of the welded portion 3. Referring to Fig. 1, the welded part 10 of the present embodiment includes a first member 1 made of chromium-based stainless steel, a second member 2 made of copper, and a welded portion 3 that joins the first member 1 and the second member 2 together.

[0022] The chromium-based stainless steel constituting the first member 1 is a stainless steel containing chromium and not containing nickel, and examples thereof include ferritic stainless steel. For example, JIS standard SUS430-based stainless steel (JIS G 4304:2012 and JIS G 4305:2012) can be used as the ferritic stainless steel. In addition to JIS standard SUS430-based stainless steel, examples of the ferritic stainless steel include SUS405, SUS410L, SUS429, SUS434, SUS436L, SUS436J1L, SUS443J1, SUS444, SUS445J1, SUS445J2, SUS447J1, and SUSXM27. JIS standard SUS430-based stainless steel includes JIS standard SUS430 and those with a symbol at the end of the JIS standard. For example, SUS430, SUS430LX, SUS430J1L, and SUS430F are in the category of "JIS standard SUS430-based stainless steel". Furthermore, the chromium-based stainless steel constituting the first member 1 is not limited to ferritic stainless steel, and may be martensitic stainless steel. The second member 2 is made of pure copper, that is, copper with a purity of 99.9 mass % or more.

[0023] Here, in the present disclosure, "nickel-free" includes those that can be considered to be nickel-free, and does not mean "nickel-free" in the strict sense. For example, in stainless steel that contains 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 includes a first main body portion 11 and a joint portion 12. The joint portion 12 is a portion into which the longitudinal end portion of the second member 2 is inserted. In this embodiment, the portion of the second member 2 that is inserted into the joint portion 12 is referred to as an "insertion portion 22." The joint portion 12 extends from the longitudinal end portion of the first main body portion 11 along the central axis. The joint portion 12 is included in the longitudinal end portion of the first member 1.

[0025] In the first member 1, the first main body portion 11 includes an outer peripheral surface 111 and an inner peripheral surface 112. The outer peripheral surface 111 has a cylindrical surface shape. The inner peripheral surface 112 has a cylindrical surface shape having a common central axis with the outer peripheral surface 111. The outer peripheral surface 111 and the inner peripheral surface 112 are concentrically arranged when viewed along the central axis. The first member 1 has a flow path (hereinafter, sometimes referred to as a first flow path 13) formed by being surrounded by the inner peripheral surface 112. The first member 1 has a tubular shape. The first member 1 is a pipe made of chromium-based stainless steel.

[0026] The joint part 12 includes an outer peripheral surface (hereinafter referred to as "joint outer peripheral surface 121") and an inner peripheral surface (hereinafter referred to as "joint inner peripheral surface 122"). The joint outer peripheral surface 121 has a cylindrical surface shape. The diameter of the joint outer peripheral surface 121 is longer than the diameter of the outer peripheral surface 111. The outer peripheral surface 111 and the joint outer peripheral surface 121 are connected via an outer connecting surface 123. The outer connecting surface 123 is inclined with respect to the outer peripheral surface 111 and the joint outer peripheral surface 121 so as to move radially outward as it moves from the outer peripheral surface 111 to the joint outer peripheral surface 121 in the central axis direction. The joint inner peripheral surface 122 has a cylindrical surface shape having a common central axis with the joint outer peripheral surface 121. The diameter of the joint inner peripheral surface 122 (the inner diameter of the joint part 12) is longer than the diameter of the inner peripheral surface 112. The diameter of the joint inner circumferential surface 122 (the inner diameter of the joint portion 12) is equal to the outer diameter of the second member 2. In this disclosure, "equal" includes a range in which objects to be compared are substantially the same. For example, pipes with the same nominal diameter have the same diameter.

[0027] The second member 2 includes a second body portion 21 and an insertion portion 22. The insertion portion 22 protrudes from a longitudinal end of the second body portion 21 along the central axis. The inner diameter of the second body portion 21 and the inner diameter of the insertion portion 22 are the same length. In this embodiment, the second body portion 21 and the insertion portion 22 are formed integrally without any seams. The inner diameter of the insertion portion 22 may be shorter or longer than the inner diameter of the second body portion 21.

[0028] In the second member 2, the second main body portion 21 and the insertion portion 22 include an outer peripheral surface 211 and an inner peripheral surface 212. The diameter of the outer peripheral surface 211 is the same as the diameter of the outer peripheral surface 111 of the first member 1, and the outer peripheral surface 211 and the insertion portion 22 have a cylindrical shape having a common central axis. The diameter of the inner peripheral surface 212 is the same as the diameter of the inner peripheral surface 112 of the first member 1, and the second member 2 has a cylindrical shape having a common central axis with the inner peripheral surface 212. The inner peripheral surface 212 has a common central axis with the outer peripheral surface 111. The second member 2 has a flow path (hereinafter, sometimes referred to as a second flow path 23) formed by being surrounded by the inner peripheral surface 212. The second member 2 has a tubular shape. The second member 2 is a pipe made of copper. When the insertion portion 22 is inserted into the joint portion 12, the first flow path 13 and the second flow path 23 communicate with each other to form one flow path.

[0029] By making the diameter of the inner circumferential surface 112 of the first member 1 (the inner diameter of the first member 1) and the diameter of the inner circumferential surface 212 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. The outer diameter of the first main body portion 11 in the first member 1 and the outer diameter of the second member 2 may be different lengths.

[0030] 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 12 in a state where the insertion portion 22 is inserted into the joint portion 12. With reference 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 chromium-based stainless steel constituting the first member 1. The second region 32 is a region mainly composed of copper. The first region 31 is located closer to the first member 1 than the interface 33 in the longitudinal direction (direction along the central axis) of the welded part 10. The second region 32 is located closer to the second member 2 than the interface 33 in the longitudinal direction (direction along the central axis) of the welded part 10. The interface 33 crosses the welded portion 3 within the thickness of the welded portion 3. The interface 33 may be an uneven surface, a curved surface, or a flat surface.

[0031] Referring to FIG. 3, in the second region 32, a plurality of first island regions 321 mainly composed of elements contained in the chromium-based stainless steel constituting the first member 1 are present and separated from each other. The plurality of first island regions 321 are present 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. In the first region 31, a plurality of second island regions 311 mainly composed of copper are present and separated from each other. The plurality of second island regions 311 are present 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. The first region 31 and the second region 32 form a metallic bond at the interface 33. Here, the state in which a metallic bond is formed at the interface 33 means a state in which the lattice of metal atoms constituting the first region 31 and the lattice of metal atoms constituting the second region 32 have continuity at the interface 33.

[0032] In the welded component 10 of the present embodiment, the second region 32 contains a plurality of first island regions 321 containing as a main component an element contained in the chromium-based stainless steel constituting the first member 1. The first region 31 contains a plurality of second island regions 311 containing as a main component copper. 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 the present embodiment has improved strength of the welded portion 3.

[0033] Next, an example of a method for manufacturing the welded part 10 of the present embodiment will be described. Fig. 4 is a flow chart showing an outline of 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.

[0034] With reference to Fig. 4, in the manufacturing method of the welded part 10 of the present embodiment, a material preparation step is first performed as step S10. In this step S10, a first member 1 made of chromium-based stainless steel and a second member 2 made of copper are prepared as materials. With reference to Fig. 5, the first member 1 has a first body portion 11 and a joint portion 12. The second member 2 has a second body portion 21 and an insertion portion 22. The first body portion 11 and the second body portion 21 have, for example, a hollow cylindrical shape having the same inner diameter and outer diameter. In step S10, the first member 1 and the second member 2 are arranged such that the insertion portion 22 is inserted into the joint portion 12.

[0035] Next, a molten pool forming step is performed as step S20. In this step S20, referring to Fig. 6, in a state in which an arc 6 is formed between the end portion (tip portion of joint portion 12) of first member 1 prepared in step S10, a portion (second body portion 21) of second member 2 adjacent to insertion portion 22, and electrode 42, a filler rod 5 is supplied as a filler material into arc 6, and joint portion 12, second body portion 21, and filler rod 5 are heated and melted by arc 6 to form molten pool 7. The molten pool 7 is formed in the inside corner formed by the end portion of joint portion 12 and second body portion 21.

[0036] The electrode 42 is made of a high melting point metal material such as tungsten (W). The outer peripheral surface of the electrode 42, except for the tip, is surrounded by a hollow cylindrical nozzle 41, and the tip of the electrode 42 is exposed to the outside from the nozzle 41. The nozzle 41 and the electrode 42 constitute a welding torch 4. A shielding gas is discharged from an annular space between the outer peripheral surface of the electrode 42 and the inner peripheral surface of the nozzle 41 along the arrow A toward the outer peripheral surface (joint outer peripheral surface 121) of the joint part 12 and the outer peripheral surface 211 of the second body part 21. For example, an inert gas such as argon (Ar) can be used as the shielding gas. A mixed gas of Ar and helium (He) may be used as the shielding gas.

[0037] The arc 6 is isolated from the outside air by the shielding gas being discharged along the arrow A. The filler rod 5 melts as it is heated by the arc 6, and reaches the molten pool 7 as a molten droplet 51. The molten pool 7 is composed of the molten first component 1, the molten second component 2, and the molten filler rod 5. The filler rod 5 contains 4.0% by mass or more and 4.9% by mass or less of iron, with the remainder being copper and unavoidable impurities.

[0038] Next, a solidification step is performed as step S30. In this step S30, the molten pool 7 formed in step S20 is solidified to form a welded portion 3 that joins the first member 1 and the second member 2. Specifically, the first member 1 and the second member 2 in which the molten pool 7 is formed in step S20 are rotated in the circumferential direction by a predetermined angle, for example, about 5° to 10°. As a result, the arc 6 forms a new molten pool 7 in an area adjacent to the previously formed molten pool 7, and the previously formed molten pool 7 solidifies to become a welded portion 3 (bead) (see FIG. 1). This procedure is repeated to form the welded portion 3 over the entire circumference of the first member 1 and the second member 2, thereby completing the manufacturing method of the welded component 10 of this embodiment, and the welded component 10 of this embodiment is obtained.

[0039] In step S20 of the manufacturing method of the welded component 10 of the present embodiment, a filler rod 5 (filler metal) containing 4.0% by mass or more and 4.9% by mass or less of iron, with the balance being copper and unavoidable impurities, is used. This makes it easy to achieve a state in which a plurality of first island regions 321 exist in the second region 32 and a plurality of second island regions 311 exist in the first region 31, and the first region 31 and the second region 32 form a metallic bond. As a result, the manufacturing method of the welded component 10 of the present embodiment can improve the strength of the welded portion 3. The filler rod 5 preferably contains 4.0% by mass or more and 4.8% by mass or less of iron, with the balance being copper and unavoidable impurities. Since the melting point of iron is higher than that of copper, in a temperature range exceeding the melting point of copper and below the melting point of iron, solid phase iron and liquid phase copper coexist. 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.

[0040] The diameter of the filler rod 5 is preferably 1.2 mm or less, and more preferably 0.9 mm or less. By using such a filler rod 5, it is easy to achieve a state in which a plurality of first island regions 321 exist in the second region 32 and a plurality of second island regions 311 exist in the first region 31, and the first region 31 and the second region 32 form a metallic bond.

[0041] [Modification of welded parts] In the above embodiment, the first member 1 and the second member 2 are joined by the welded portion 3 with the insertion portion 22 inserted into the joint portion 12. However, as shown in FIG. 7, the first member 1 and the second member 2 may be joined by butt welding. FIG. 7 is a schematic cross-sectional view showing a structure of a welded part 10 according to a modified example. FIG. 8 is a schematic cross-sectional view showing a state before welding in the welded part 10 according to the modified example. With reference to FIG. 7, the diameter of the inner circumferential surface 112 of the first member 1 is the same as the diameter of the inner circumferential surface 212 of the second member 2. The diameter of the outer circumferential surface 111 of the first member 1 is the same as the diameter of the outer circumferential surface 211 of the second member 2.

[0042] 8, among the end faces of the first member 1 in the central axis direction, the end face (hereinafter referred to as "first end face 14") facing the second member 2 includes a tapered surface. Among the end faces of the second member 2 in the central axis direction, the end face (hereinafter referred to as "second end face 24") facing the first member 1 includes a tapered surface. The tapered surface of the first end face 14 and the tapered surface of the second end face 24 are inclined with respect to a virtual plane perpendicular to the central axis of the first member 1 and the second member 2 so that the distance between them increases as they move radially outward. The angle of the tapered surface with respect to the virtual plane (hereinafter referred to as 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. By configuring in this way, it is easy to form the first region and the second region through the interface 33 in the welded part.

[0043] Each of the first end face 14 and the second end face 24 may have a root face. The root face is a plane perpendicular to the central axis of the first member 1 and the second member 2 at the end faces 14, 24. In the present embodiment, the root face is a face other than the tapered face at the end faces 14, 24. When the first member 1 and the second member 2 are arranged so that their central axes coincide with each other and in a position where they can be welded, the root faces face each other with a predetermined gap (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. By configuring in this way, it is easy to form the first region 31 and the second region 32 through the interface 33 in the welded portion.

[0044] The welded portion 3 joins the first member 1 and the second member 2. As the shielding gas, an inert gas such as argon can be used as in the above embodiment. In the molten pool forming step, a back shielding gas is flowed through the first flow passage 13 and the second flow passage 23. As in the shielding gas, an inert gas such as argon or a mixed gas of argon and helium can be used as the back shielding gas. As described in the manufacturing method of the above embodiment, the welded portion 3 is formed by solidifying the molten pool 7 formed between the first member 1 and the second member 2 in the solidification step. The welded portion 3 is formed over the entire circumference of the first member 1 and the second member 2, thereby obtaining a welded part 10.

[0045] [Other variations] In the above embodiment, the first member 1 and the second member 2 are both pipes, but in the present disclosure, the first member 1 and the second member 2 do not have to be pipes. For example, the first member 1 may be a welded pipe joint made of chromium-based stainless steel, and the second member 2 may be a pipe made of copper. In addition, the first member 1 and the second member 2 may be members having a shape other than a cylindrical shape (for example, a flat plate shape, a block shape, etc.).

[0046] Although the first member 1 according to the above embodiment is formed only from chromium-based stainless steel, impurities may be contained in the first member 1. Moreover, the second member 2 may also contain impurities.

[0047] In the above embodiment, the first member 1 has the joint portion 12 and the second member 2 has the insertion portion 22, but the first member 1 may have the insertion portion 22 and the second member 2 may have the joint portion 12. EXAMPLES

[0048] The welded component 10 of the present disclosure was fabricated, and an experiment was conducted to confirm the effects of the welded component 10 of the present disclosure and to confirm the metal structure of the welded portion 3. The procedure of the experiment is as follows. However, the welded component 10 of the present disclosure is not limited to the following examples.

[0049] A test piece was produced as the welded part 10 in which a flat chromium-based stainless steel and copper were joined by the manufacturing method for the welded part 10 described in the above embodiment. A flat ferritic stainless steel plate was used as the chromium-based stainless steel constituting the first member 1. JIS standard SUS430 was adopted as the ferritic stainless steel. Ar gas was adopted as the shielding gas. The flow rate of the shielding gas was 15 L / min. The diameter of the electrode 42 was 2.4 mm, and the inner diameter of the nozzle 41 was 6 mm. Tungsten (W) with 2 mass % of cerium (Ce) added was adopted as the material constituting the electrode 42.

[0050] A DC welding power source was used, and a pulse welding method was used to control the current. The frequency of the pulse control was 400 Hz. The base current / pulse peak current was 12 A / 60 A. Referring to FIG. 10, a copper plate was placed as the second member 2 on a ferritic stainless steel plate as the first member 1, and welding was performed between the tip of the second member 2 and the main surface of the first member 1.

[0051] The composition of the filler rod 5 was 4.5 mass% iron and 95.5 mass% copper (4.5 mass% iron, with the remainder being copper and unavoidable impurities), and three test pieces were prepared under the same conditions. The obtained test pieces were subjected to (1) confirmation of workability and (2) tensile tests as follows.

[0052] (1) Checking workability Welding was performed according to the procedure described in the above embodiment, and it was confirmed whether or not a good weld was achieved. If a weld was visually good, it was judged as "passed," and if a weld was not visually good, for example because a large number of voids were generated, it was judged as "failed."

[0053] (2) Tensile test A tensile test was conducted in which the welded part 10 was pulled in the longitudinal direction and broken. The test was conducted with the test piece at room temperature. If the break occurred at a place other than the welded part 3, it was judged as "passed", and if the break occurred at the welded part 3, it was judged as "failed".

[0054] Next, the results of the experiments related to (1) and (2) above will be described. All three welded components 10 were judged to have passed the workability test and also to have passed the tensile test.

[0055] FIG. 9 is a photograph showing the state of the welded part 10 after the tensile test. As is clear from FIG. 9, the test piece broke in an area other than the welded portion 3, specifically, in the second member 2. In the tensile test, the maximum stress until the break was equivalent to the tensile strength of copper O material (annealed material). Thus, in all of the test pieces, no cracks were generated in the welded portion 3 in the tensile test, and the test piece broke in the second member 2, which supports the fact that the tensile strength of the welded portion 3 is stronger than that of the second member 2.

[0056] Next, the state of the metal structure of the welded portion 3 of the prepared test piece was confirmed. Figures 11, 12, 13, and 14 are optical microscope photographs showing the metal structure of the welded portion 3. Figure 11 is an optical microscope photograph of a portion corresponding to portion C in Figure 10. Figure 12 is a photograph of Zone 1 (Z1 portion) of the first region 31 in Figure 11, enlarged 1000 times. Figure 13 is a photograph of Zone 2 (Z2 portion) of the first region 31 in Figure 11, enlarged 1000 times. Figure 14 is a photograph of Zone 3 (Z3 portion) of the second region 32 in Figure 11, enlarged 1000 times. Table 1 shows the results of analyzing the distribution of elements in the welded portion 3 using EDS (Energy Dispersive X-ray Spectroscopy).

[0057] [Table 1] 11, in first region 31 mainly composed of elements contained in chromium-based stainless steel, the element distribution was analyzed in two locations: a location (zone 1) close to interface 33 with second region 32, and a location (zone 2) far from interface 33. In second region 32 mainly composed of elements contained in copper, the element distribution in Zone 3 was analyzed. 11 to 14 and Table 1, the welded portion 3 includes a first region 31 mainly composed of elements (Fe, Cu, Ni, and Cr) contained in SUS430 constituting the first member 1, and a second region 32 mainly composed of Cu, with an interface 33 as a boundary. In the second region 32, there are a plurality of first island regions 321 (Fe phase in Table 1) mainly composed of elements contained in SUS430, and in the first region 31, there are a plurality of second island regions 311 (Cu phase in Table 1) mainly composed of copper. The reason why a trace amount of Ni is contained in the Fe phase is thought to be that Ni was measured as an impurity contained in chromium-based stainless steel.

[0058] Thus, the welded portion 3 includes a first region 31 and a second region 32, and in the second region 32, a plurality of first island regions 321 mainly composed of elements contained in SUS430 are present, and in the first region 31, a plurality of second island regions 311 mainly composed of copper are present. Furthermore, in the above tensile test, no cracks were generated in the welded portion 30 of any of the test pieces. From the above, it can be determined that the first region 31 and the second region 32 form a metallic bond at the interface 33. That is, it was confirmed that the strength of the welded portion 3 was improved in the test pieces as the three welded components 10 that satisfy the requirements for the welded component 10 of the present disclosure.

[0059] It should be understood that the embodiments and examples disclosed herein are illustrative in all respects and are not limiting in any respect. The scope of the present invention is defined by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. [Explanation of symbols]

[0060] 10 welding part, 1 first member, 11 first main body portion, 111 outer peripheral surface, 112 inner peripheral surface, 12 joint portion, 121 joint outer peripheral surface, 122 joint inner peripheral surface, 123 outer connecting surface, 13 first flow path, 14 first end surface, 2 second member, 21 second main body portion, 22 insertion portion, 211 outer peripheral surface, 212 inner peripheral surface, 23 second flow path, 24 second end surface, 3 weld portion, 31 first region, 311 second island region, 32 second region, 321 first island region, 33 interface, 4 welding torch, 41 nozzle, 42 electrode, 5 filler rod, 51 droplet, 6 arc, 7 molten pool, W root spacing, θ bevel angle.

Claims

1. A first member made of chromium-based stainless steel; A second member made of copper; a weld portion that joins the first member and the second member, The welded portion is A first region mainly composed of elements contained in the chromium-based stainless steel constituting the first member; a second region that is disposed so as to form an interface between the first region and the second region and that is mainly composed of copper; Including, a plurality of first island regions, each of which is separated from the other and mainly contains an element contained in the chromium-based stainless steel constituting the first member, are present in the second region; a plurality of second island regions each mainly composed of copper are present and separated from one another within the first region; The first region and the second region form a metallurgical bond at the interface.

2. The welded component of claim 1 , wherein the chromium-based stainless steel is a ferritic stainless steel.

3. 3. The welded component according to claim 2, wherein the ferritic stainless steel is JIS SUS430 stainless steel.

4. the first member and the second member have a tubular configuration; a longitudinal end portion of either the first member or the second member includes a joint portion into which an insertion portion, which is a longitudinal end portion of the other member, is inserted; 4. The welded part according to claim 1, wherein the first member and the second member are joined to each other by the weld portion at a tip end of the joint portion with the insertion portion inserted into the joint portion.

5. The insert is included in the first member, The welded component of claim 4 , wherein the joint is included in the second member.

6. Providing a first member made of chromium-based stainless steel and a second member made of copper; supplying a filler metal into an arc while forming an arc between the first member and the second member and an electrode, and heating and melting the first member, the second member, and the filler metal by the arc to form a molten pool; and solidifying the molten pool to form a weld that joins the first member and the second member. The filler metal contains 4.5% by mass or more and 4.9% by mass or less of iron, with the remainder being copper and unavoidable impurities; The welded portion formed in the step of forming the welded portion is A first region mainly composed of elements contained in the chromium-based stainless steel constituting the first member; a second region that is disposed so as to form an interface between the first region and the second region and that is mainly composed of copper; Including, a plurality of first island regions, each of which is separated from the other and mainly contains an element contained in the chromium-based stainless steel constituting the first member, are present in the second region; a plurality of second island regions each mainly composed of copper are present and separated from one another within the first region; The first region and the second region form a metallic bond at the interface. Manufacturing method for welded parts.

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