Manufacturing method for welded products

Abstract

To manufacture a welded article by a welding method which welds a workpiece containing copper using a mixed gas of a specific composition containing an argon gas and a helium gas as a shield gas, thereby improving penetration of the workpiece, reducing welding defects contained in the welded workpiece, making perforation difficult to occur in the workpiece, achieving high arc concentration, and providing high visibility during welding.SOLUTION: A welded article manufacturing method manufactures a welded article by welding a workpiece through TIG welding or MIG welding while spraying an inactive gas to the workpiece containing copper. The inactive gas contains a nitrogen gas of 10-60% by capacity, an argon gas of 4-40% by capacity, and a helium gas of 20-60% by capacity.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a welded article. [Background technology]

[0002] As shown in Patent Document 1 below, a method is known in which copper or a copper alloy is preheated to a temperature above 200°C and below its recrystallization temperature, and TIG welding is performed using helium gas as a shielding gas. Conventional TIG welding, which uses argon gas as a shielding gas, requires preheating to a high temperature of 800 to 900°C to achieve sufficient penetration, but the method of Patent Document 1 is said to enable welding with preheating below the recrystallization temperature of copper or a copper alloy.

[0003] The following Patent Documents 2 and 3 state that a mixed gas obtained by adding a gas such as hydrogen or nitrogen to a mixed gas of argon and helium can be used as a shielding gas when welding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 62-238077 [Patent Document 2] Patent Publication No. 2021-13955 [Patent Document 3] Japanese Patent Application Publication No. 2023-96588 Summary of the Invention [Problem to be solved by the invention]

[0005] The price of helium gas is rising sharply due to factors such as rising container shipping costs, global disruptions to logistics networks, and increased demand for helium gas itself.

[0006] The above-mentioned Patent Documents 2 and 3 state that the above-mentioned mixed gas may be used as a shielding gas. However, Patent Documents 2 and 3 do not mention the use of a workpiece containing copper. Furthermore, Patent Documents 2 and 3 do not mention the specific composition of the shielding gas.

[0007] The present invention aims to produce welded products by a welding method that uses a mixed gas of a specific composition containing nitrogen gas, argon gas, and helium gas as a shielding gas, thereby reducing the amount of helium gas used, and welding workpieces containing copper, thereby achieving good penetration of the workpiece, fewer welding defects in the workpiece after welding, less perforation in the workpiece, good arc concentration, and excellent visibility of the weld during welding. [Means for solving the problem]

[0008] The above-mentioned problems are solved by a method for producing a welded product, which comprises welding copper-containing workpieces by TIG welding or MIG welding while spraying an inert gas onto the workpieces, wherein the inert gas contains 10 to 60 volume % of nitrogen gas, 4 to 40 volume % of argon gas, and 20 to 60 volume % of helium gas.

[0009] In the method for manufacturing a welded product, it is preferable to carry out a step of preheating the workpieces so that the temperature of the workpieces is in the range of 420 to 620°C before welding the workpieces.

[0010] In the method for manufacturing a welded product, the filler metal applied to the welded portion preferably contains copper as a main component.

[0011] In the method for manufacturing a welded product, the thickness of the workpiece is preferably 5 to 40 mm. [Effects of the Invention]

[0012] According to the present invention, by using a mixed gas of a specific composition containing nitrogen gas, argon gas, and helium gas as a shielding gas to reduce the amount of helium gas used and welding workpieces containing copper, it is possible to produce welded products using a welding method that achieves good penetration of the workpiece, reduces welding defects in the workpiece after welding, is less likely to cause perforations in the workpiece, provides good arc concentration, and has excellent visibility of the weld. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 illustrates an example of a workpiece having a recess. [Figure 2] FIG. 1 is a diagram showing an example of a workpiece having a step portion. [Figure 3] FIG. 1 illustrates an example of a workpiece having a corner. [Figure 4] FIG. 2 is an explanatory diagram showing an example of TIG welding. [Figure 5] FIG. 2 is an explanatory diagram showing an example of MIG welding. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the method for manufacturing a welded product of the present invention will be described below. The embodiment described below is merely a limited example of the embodiment of the present invention, and the technical scope of the present invention is not limited to the exemplified embodiment.

[0015] The present invention is a method for producing a welded product by welding a copper-containing workpiece by TIG welding or MIG welding while spraying an inert gas onto the workpiece, wherein the inert gas contains 10 to 60 volume % nitrogen gas, 4 to 40 volume % argon gas, and 20 to 60 volume % helium gas.

[0016] In this specification, a workpiece refers to an object to be welded. A welded product refers to an article that has been welded. A welded product may be a finished product or a semi-finished product. In addition, in this specification, materials to be joined by welding are called materials to be joined.

[0017] The shape of the workpiece is not particularly limited as long as it can be used to join one workpiece to the other. For example, as shown in FIGS. 1 to 3, copper materials may have a recess 14a between one workpiece 11a and the other workpiece 12a, a step 14b between one workpiece 11b and the other workpiece 12b, or a corner 14c between one workpiece 11c and the other workpiece 12c. In these examples, the recess 14a, the step 14b, or the corner 14c are welded. In the example shown in FIG. 1, one workpiece 11a and the other workpiece 12a are placed on top of a third workpiece 13. The first workpiece 11a, the second workpiece 12a, and the third workpiece 13 are joined by welding. As in the examples of FIGS. 4 and 5, the ends of one workpiece to be joined and the other workpiece to be joined may be butted together.

[0018] Examples of the shape of the workpiece include a plate, a pipe, a block, and the like. The thickness of the workpiece is not particularly limited, but is preferably in the range of 5 to 40 mm. For a pipe-shaped workpiece, the thickness of the workpiece refers to the thickness of the plate material that forms the pipe. When multiple materials are stacked, the thickness of the workpiece refers to the total thickness of the stacked materials.

[0019] The shape of the recess is not limited, and can be any appropriate shape, such as a slit-shaped groove, a V-shaped recess, or an arc-shaped depression.

[0020] The workpiece is preferably a workpiece containing 90% by mass or more of copper, more preferably 98% by mass or more of copper, with the upper limit being preferably 100% by mass or less of copper, excluding unavoidable impurities.

[0021] The welding method is TIG (Tungsten Inert Gas) welding or MIG (Metal Inert Gas) welding.

[0022] In TIG welding, as shown in Figure 4, a welding power source 27a electrically connected to a workpiece 21a and an electrode 23a generates an arc 24a between the electrode 23a and the workpiece 21a. The electrode 23a is made of tungsten. An inert gas 25a is sprayed from the tip of a nozzle 22a toward the workpiece 21a, enveloping the arc 24a. A filler metal 26 (welding rod) is brought close to the arc and melted, and droplets are applied to the welding point, such as a recessed hole in the workpiece 21a. The droplets form a molten pool 28a in the recessed hole, which is the welding point, and solidify as the temperature drops.

[0023] In MIG welding, as shown in FIG. 5, a welding power source 27b electrically connected to a workpiece 21b and an electrode 23b generates an arc 24b between the electrode 23b and the workpiece 21b. The electrode 23b has the same chemical composition as the filler metal 16, and when melted, it acts as a filler metal. An inert gas 25b is sprayed from the tip of the nozzle 22b toward the workpiece 21b, enveloping the arc 24b. The tip of the electrode 23b melts, and droplets are applied to the recessed hole in the workpiece 21b. The droplets form a molten pool 28b in the recessed hole, which is the welding location, and solidify as their temperature drops. As indicated by the arrow in FIG. 5, the electrode 23b is sequentially fed to the tip of the nozzle 22b by a driving means such as a roller (not shown).

[0024] The filler metal applied to the welded portion preferably contains copper as its main component. The filler metal preferably contains 90% by mass or more of copper, and more preferably 98% by mass or more of copper. The upper limit of the copper content, excluding unavoidable impurities, is preferably 100% by mass or less. The filler metal may contain 0.1 to 0.5% by mass of Sn. The filler metal may also contain 0.1 to 0.5% by mass of Mn.

[0025] The inert gas contains nitrogen gas, argon gas, and helium gas in a ratio of 10 to 60% by volume of nitrogen gas, 4 to 40% by volume of argon gas, and 20 to 60% by volume of helium gas. The nitrogen gas may be 30 to 55% by volume, the argon gas 18 to 38% by volume, and the helium gas 20 to 40% by volume.

[0026] It is preferable to use argon gas consisting only of argon, excluding inevitable impurities. If the purity is low, for example, use gas containing 95% or more by volume of argon molecules (atoms). In this case, the upper limit is the content of argon atoms, excluding inevitable impurities, of 100% by volume or less.

[0027] It is preferable to use nitrogen gas consisting only of nitrogen, excluding inevitable impurities. If the purity is low, it is preferable to use one containing, for example, 95% or more by volume of nitrogen molecules. In this case, the upper limit is the content of nitrogen molecules, excluding inevitable impurities, of 100% by volume or less.

[0028] It is preferable to use a helium gas consisting only of helium, excluding inevitable impurities. If the purity is low, it is preferable to use one containing, for example, 95% or more by volume of helium atoms. In this case, the upper limit is the content of nitrogen molecules, excluding inevitable impurities, of 100% by volume or less.

[0029] It is preferable to carry out preheating prior to welding. During preheating, it is preferable to make the temperature of the workpiece to be in the range of 420 to 620°C. There are no particular restrictions on the heating method, but it is convenient to use an external heating means such as a gas burner. The temperature during preheating can be measured with a radiation thermometer.

[0030] The current value during welding is not particularly limited, but can be set to 400 to 500A, for example. [Example]

[0031] The welding method of the present invention will be described below with reference to examples. The examples shown below are merely limited examples of embodiments of the present invention, and the technical scope of the present invention is not limited to the examples shown.

[0032] Experiment 1 [Example 1] As shown in Figure 4, a V-shaped groove 9 mm deep was formed by cutting at the butt joint between the end of a 10 mm thick first copper material and the end of a 10 mm thick second copper material. The length of the groove was 200 mm. Welding was performed by TIG welding along the groove formed in this test piece. A welding rod conforming to the JIS YCu standard was used as the filler metal for welding. The chemical composition of the welding rod was 0.3 mass% Sn, 0.3 mass% Mn, and the remainder Cu. The welding conditions were as follows: The test piece was C-1020 (oxygen-free copper with a purity of 99.96% or higher).

[0033] Welding conditions Preheat temperature: None Inert gas used: See Table 1 Welding machine output: 400~500A Welding machine: Panasonic YC-500WX4T00

[0034] The test piece was used as the base material, and the test piece was connected to a welding power source with a current-carrying cable, and the electrode was electrically connected to the welding power source with a current-carrying cable. The welding machine was operated with the above output, and welding was performed by manually bringing the welding rod close to the arc generated at the tip of the nozzle.

[0035] The argon gas, nitrogen gas, and helium gas used were of high purity and contained no other components except for unavoidable impurities.

[0036] The workability during welding for each item listed in Table 1 was evaluated according to the following criteria. Workpiece penetration ○: The molten metal is melted into the welding groove without any gaps. ×: There is a gap between the molten metal and the welding groove, and there are areas where the metal has not melted.

[0037] Blow in the workpiece ○: 0 to 1 blowholes observed in the welded area. △: 2 to 3 blowholes observed in the welded area. ×: Four or more blowholes are observed in the welded part.

[0038] Arc concentration A tungsten electrode with a diameter of 4.8 mm was used, and the arc diameter was adjusted to 6 to 9 mm. ◯: The arc can be easily adjusted within the range of 6 to 9 mm. △: It takes time, but the arc can be adjusted to the range of 6 to 9 mm. ×: The arc cannot be easily adjusted within the range of 6 to 9 mm.

[0039] Visibility ◯: Almost no fumes are generated, and the tip of the nozzle and the area where the arc hits the base material can be seen. △: Fumes (smoke) are generated, but the tip of the nozzle and the area where the arc hits the base material can be seen. ×: Fumes (smoke) are generated, and the nozzle tip and the area where the arc hits the base material cannot be seen unless the fumes are allowed to diffuse.

[0040] ·Perforation ◯: No formation of through holes due to overheating of the base material is observed. ×: Through holes are formed due to overheating of the base material.

[0041] Welding speed The time taken to weld the groove from one end to the other was used to determine the rating: 〇: Less than 5 minutes △: 5 minutes or more and less than 8 minutes ×: 8 minutes or more

[0042] [Comparative Examples 1 to 6] Test pieces were welded in the same manner as in Example 1, except that the composition of the inert gas used was changed as shown in Table 1 below.

[0043] Table 1 shows the composition of the inert gas and the workability during welding evaluated according to the above criteria.

[0044] [Table 1]

[0045] The method of Example 1 obtained good results for all evaluation items shown in Table 1. The methods of Comparative Examples 2 to 6 had inferior results compared to the method of Example 1 in at least one of the items shown in Table 1. A comparison of Comparative Examples 3 to 6 shows that as the nitrogen content increases, there is a tendency for overheating, resulting in the generation of fumes, perforation, and arc diffusion. Comparative Examples 1 and 2 show that as the nitrogen content decreases, there is a tendency for insufficient heating, resulting in insufficient penetration of the workpiece. The method of Example 1 can reduce the amount of helium gas used and achieve good workability during welding.

[0046] Experiment 2 [Example 2] A first copper plate and a second copper plate, both 10 mm thick, were placed on a 10 mm thick copper plate, with the first and second copper plates spaced 15 mm apart to form a 15 mm wide welding groove. The groove was 200 mm long. MIG welding was performed along the groove formed in the test piece. A filler metal conforming to the JIS YCu standard was used as the electrode for welding. The chemical composition of the filler metal was 0.3 mass% Sn, 0.3 mass% Mn, and the remainder Cu. The welding conditions were as follows: The test piece was C-1020 (oxygen-free copper with a purity of 99.96% or higher).

[0047] Welding conditions Preheat temperature: 520℃ Inert gas: Nitrogen gas 14% by volume, Argon gas 28% by volume, Helium gas 58% by volume Welding machine output: 400~500A Welding machine: Daihen Corporation (P-500L)

[0048] The preheating was performed by bringing the flame of a gas burner into contact with the welding point, and the preheating temperature was measured with a radiation thermometer.

[0049] The test piece was used as the base material, and the test piece was connected to a welding power source with a current-carrying cable, and the welding nozzle was connected to the welding power source with a current-carrying cable. The filler metal was sequentially supplied to the nozzle as an electrode from a supply device. The inert gas was also supplied to the nozzle.

[0050] The argon gas, nitrogen gas, and helium gas used were of high purity and contained no other components except for unavoidable impurities.

[0051] [Example 3] Copper workpieces were welded in the same manner as in Example 2, except that the preheating step was not performed.

[0052] [Example 4] Copper workpieces were welded in the same manner as in Example 2, except that the welding machine was changed to the TIG welding machine used in Example 1. The electrodes of the TIG welding machine were tungsten. The welding rods used were JIS YCu standard welding rods. The chemical composition of the welding rods was 0.3 mass% Sn, 0.3 mass% Mn, and the remainder Cu.

[0053] [Example 5] Copper workpieces were welded in the same manner as in Example 4, except that the preheating step was not carried out.

[0054] Appearance evaluation criteria The appearance of the workpieces welded by the methods of Examples 2, 3, 4, and 5 was visually inspected and evaluated according to the following criteria. ○: The surface of the weld is relatively smooth. △: The appearance shows many small irregularities formed at the weld marks.

[0055] Welding speed standards The welding speeds of the workpieces welded by the methods of Examples 2, 3, 4, and 5 were evaluated based on the time taken to weld the groove from one end to the other, as follows: 〇: Less than 2 minutes 30 seconds △: Over 2 minutes 30 seconds and under 3 minutes ×: 3 minutes or more In the method of Example 2, when the gas used was changed to helium gas only, the welding speed was as follows. Tig welding (with preheat): 3 minutes 10 seconds Tig welding (no preheating): 7 minutes 20 seconds Mig welding (with preheat): 1 minute 55 seconds Mig welding (no preheat): 2 minutes 8 seconds

[0056] Welding defects (PT inspection) The workpieces welded in Examples 2, 3, 4, and 5 were treated in the following order of pretreatment, immersion treatment, removal treatment, and development treatment, and the welds were evaluated for deep defects. The results are summarized in Table 2. ○: The number of stained areas 1 mm or longer is 0 to 1. △: The number of stained areas 1 mm or longer is 2 to 3. ×: The number of stained areas 1 mm or longer is 4 or more.

[0057] (Pretreatment) Use a cleaning solution (Marktec Co., Ltd. UR-ST) to remove dirt from the sides of the welded area and inside the scratches. (immersion treatment) Apply the penetrating liquid (Marktec Co., Ltd. UP-ST(J)) to the side of the welded area and leave it for 5 to 60 minutes to allow it to soak into the wound. (Removal process) Remove excess penetrant with a rag. (Development processing) Apply a thin, even layer of developer (Marktec Co., Ltd. UD-ST) to the side of the welded area and leave it for 10 to 30 minutes. (observation) Visually observe.

[0058] [Table 2]

[0059] The results in Table 2 show that Examples 2 and 3 exhibit superior results to Examples 4 and 5 in terms of both the appearance after welding and the welding speed.

[0060] The results in Table 2 confirmed that when no preheating was performed as in Examples 3 and 5, the size of the stained portion in the PT inspection tended to be larger compared to when preheating was performed as in Examples 2 and 4. Furthermore, when TIG welding was performed as in Examples 4 and 5, the size of the stained portion in the PT inspection tended to be larger compared to when MIG welding was performed as in Examples 2 and 3. These results confirmed that MIG welding reduced weld defects compared to TIG welding, and that when preheating was performed, weld defects were reduced compared to when preheating was not performed.

Claims

1. A method for manufacturing a welded product, comprising welding a workpiece containing 90% by mass or more of copper by TIG welding or MIG welding while spraying an inert gas onto the workpiece, The inert gas contains 10 to 60% by volume of nitrogen gas, 4 to 40% by volume of argon gas, and 20 to 60% by volume of helium gas.

2. 2. The method for manufacturing a welded product according to claim 1, wherein a step of preheating the workpieces to a temperature in the range of 420 to 620° C. is carried out before welding the workpieces.

3. 3. The method for manufacturing a welded product according to claim 1, wherein the filler metal applied to the welded portion contains copper as a main component.

4. 3. The method for manufacturing a welded product according to claim 1, wherein the thickness of the workpiece is 5 to 40 mm.

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