Manufacturing method of the joint

Abstract

The present invention provides a method for manufacturing a bonded material that can suppress the occurrence of excessive fusion. [Solution] This method involves forming a penetration portion that extends from the second plate-shaped portion to the first plate-shaped portion at the location where the weld bead is formed, thereby joining the first plate-shaped portion and the second plate-shaped portion to manufacture a joined body. The weld bead has a first weld, a second weld, and a third weld. The first and second welds constitute a loop portion, which is a weld area with a loop shape. The third weld is formed at a position where the end of the third weld, which is the end of the weld bead, is on the inner circumference side of the loop portion. The amount of heat applied to the area to be heated when forming the third weld is controlled to be less than the amount of heat applied to the area to be heated when forming the first weld.

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a joined body. [Background Art]

[0002] For example, Patent Document 1 discloses a technique in which, when a first plate-like portion and a second plate-like portion are stacked in a plate thickness direction and welded, a loop portion, which is a welded portion shaped to draw a loop, is provided, and an end of a weld bead is arranged inside a closed region surrounded by the loop portion.

[0003] According to such a technique, the gap between the first plate-like portion and the second plate-like portion is blocked at the location where the loop portion is formed. Therefore, for example, when a fluid flow path is provided on the outer peripheral side of the loop portion and the fluid can penetrate into the gap between the first plate-like portion and the second plate-like portion, it is possible to suppress the fluid from reaching the inner peripheral side of the loop portion.

[0004] Therefore, if the end of a weld bead is provided on the inner peripheral side of such a loop portion, even if defects such as blowholes, pits, and cracks occur at the end of the weld bead, it is possible to suppress the fluid from reaching the end of the weld bead, thereby suppressing fluid leakage. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Publication No. 2024-139356 [Summary of the Invention] [Problem to be Solved by the Invention]

[0006] However, after detailed examination by the inventors, it was found that when the end of the weld bead is positioned inside the loop section as described above, excessively deep penetration can occur near the end of the weld bead. If back burning or see-through occurs due to such deep penetration, some products may not meet the required quality standards.

[0007] In one aspect of this disclosure, it is desirable to provide a method for manufacturing a bonded body that can suppress the occurrence of excessive fusion. [Means for solving the problem]

[0008] (1) One aspect of the present disclosure is a method for manufacturing a joined body, wherein a first plate-shaped portion and a second plate-shaped portion, each formed in the shape of a plate, are stacked in the thickness direction, and a heating target location along the weld line is heated from the second plate-shaped portion side, thereby forming a weld bead that extends from the start end to the end, and in doing so, a penetration portion extending from the second plate-shaped portion to the first plate-shaped portion is formed at the location where the weld bead is formed, thereby joining the first plate-shaped portion and the second plate-shaped portion to manufacture a joined body. The weld bead has a first weld, a second weld, and a third weld. The first weld, the second weld, and the third weld each constitute a part of the weld bead. The first and second welds are formed continuously, with the end of the first weld being the starting point of the second weld, and a portion of the second weld overlapping with a portion of the first weld at a location separate from the starting point of the second weld, thus forming a loop-shaped weld. The third weld is formed continuously, with the end of the second weld being the starting point of the third weld, and the end of the third weld, which is the end of the weld bead, is formed on the inner circumference side of the loop. The amount of heat applied to the heating target when forming the third weld is controlled to be less than the amount of heat applied to the heating target when forming the first weld.

[0009] In the manufacturing method of the joint configured in this way, a loop portion is formed by the first and second welds, and the end of the third weld, which is the end of the weld bead, is formed at a position on the inner circumference side of the loop portion. Moreover, the amount of heat applied to the area to be heated when forming the third weld is controlled to be less than the amount of heat applied to the area to be heated when forming the first weld.

[0010] Therefore, when forming the third weld, the amount of heat supplied to the area to be heated decreases compared to when forming the first weld. Consequently, compared to conventional techniques where there is no control to increase or decrease the amount of heat supplied to the area to be heated, excessive penetration can be suppressed.

[0011] (2) In one aspect of the present disclosure, the amount of heat supplied to the area to be heated when forming the second weld may be controlled to be less than the amount of heat supplied to the area to be heated when forming the first weld, and greater than the amount of heat supplied to the area to be heated when forming the third weld.

[0012] In the manufacturing method of the joint configured in this way, when forming the second weld, the amount of heat supplied to the area to be heated decreases compared to when forming the first weld. Similarly, when forming the third weld, the amount of heat supplied to the area to be heated decreases compared to when forming the second weld. Therefore, compared to conventional techniques in which there is no control to increase or decrease the amount of heat supplied to the area to be heated, it is possible to suppress the occurrence of excessive penetration.

[0013] (3) In one aspect of the present disclosure, the amount of heat applied to the heating area when forming the first weld, the second weld and the third weld may be controlled to decrease gradually in stages or continuously.

[0014] In the manufacturing method of the joint configured in this way, the amount of heat supplied to the heating target when forming the first weld, second weld, and third weld decreases gradually in stages or continuously. Therefore, compared to conventional techniques in which there is no control to increase or decrease the amount of heat supplied to the heating target, it is possible to suppress the occurrence of excessive penetration.

[0015] (4) In one aspect of the present disclosure, the control to reduce the amount of heat may be a control to reduce the output of the heating source. According to the manufacturing method for the joint configured in this way, the amount of heat supplied to the area to be heated is reduced by lowering the output of the heating source. Therefore, even when the welding speed is maintained at a constant rate, for example, the amount of heat supplied to the area to be heated can be increased or decreased.

[0016] (5) In one aspect of the present disclosure, the control that reduces the amount of heat may be a control that increases the welding speed. According to the manufacturing method for the joint configured in this way, the amount of heat supplied to the heated area is reduced by increasing the welding speed. Therefore, even when, for example, the output of the heating source is maintained at a constant output, the amount of heat supplied to the heated area can be increased or decreased.

[0017] (6) In one aspect of the present disclosure, the first weld, the second weld and the third weld have portions that extend in parallel with each other, and in the portions that extend in parallel, the third weld may be formed at a position between the first weld and the second weld. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1A is an exploded perspective view showing the joint. Figure 1B is a cross-sectional view showing a section of the joint perpendicular to the x-axis direction. [Figure 2] Figure 2A is a bottom view of the joint. Figure 2B is an enlarged view of the area near the end of the second weld line. [Figure 3]FIG. 3A is an explanatory diagram showing a state in which a first welded portion is formed. FIG. 3B is a cross-sectional view of a portion indicated by line IIIB-IIIB in FIG. 3A. [Figure 4] FIG. 4A is an explanatory diagram showing a state in which a second welded portion is formed in addition to the first welded portion. FIG. 4B is a cross-sectional view of a portion indicated by line IVB-IVB in FIG. 4A. [Figure 5] FIG. 5A is an explanatory diagram showing a state in which a third welded portion is formed in addition to the first welded portion and the second welded portion. FIG. 5B is a cross-sectional view of a portion indicated by line VB-VB in FIG. 5A. [Figure 6] It is an enlarged view of the vicinity of the terminal end of a second weld line exemplified as another embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0019] Next, a method for manufacturing the above-described joined body will be described with reference to exemplary embodiments. [Configuration of Joined Body] As shown in FIG. 1A, a joined body 1 exemplified as an embodiment of the present disclosure is a heat exchanger for cooling a heating element. Such a joined body 1 is mounted, for example, on a vehicle (not shown) and used to cool a drive battery mounted on the vehicle. The joined body 1 includes a first member 3A and a second member 3B. The constituent materials of the first member 3A and the second member 3B are not particularly limited. By way of example, they are composed of, for example, a metal material such as iron, stainless steel, or aluminum, or a resin material such as engineering plastic. Either one of these metal materials and resin materials may be used, or both may be used in combination. For example, when the first member 3A is in contact with a heating element, the first member 3A may be formed of a metal material with excellent thermal conductivity, and the uneven second member 3B may be formed of a resin material with excellent moldability.

[0020] The first member 3A includes a first plate-shaped portion 5A, which is a portion formed in a plate shape. The second member 3B includes a second plate-shaped portion 5B, which is a portion formed in a plate shape. As shown in FIG. 1B, the first member 3A and the second member 3B are in a state where the first plate-shaped portion 5A and the second plate-shaped portion 5B are overlapped in the plate thickness direction, and the welded joint is a lap joint welded by laser welding from the second plate-shaped portion 5B side. Details of the specific welding method will be described later.

[0021] The first member 3A has an inflow port 7A and an outflow port 7B. Both the inflow port 7A and the outflow port 7B are cylindrical portions protruding from the first member 3A. A through hole having the same diameter as the inner diameters of the inflow port 7A and the outflow port 7B is formed in the first member 3A, and the inflow port 7A and the outflow port 7B protrude from the periphery of the through hole of the first member 3A.

[0022] The second member 3B has a recessed portion 8. However, the recessed portion 8 may be provided on the first member 3A side, or may be provided on both the first member 3A and the second member 3B. That is, there is no limitation on which of the first member 3A and the second member 3B the recessed portion 8 is provided on. Hereinafter, in the present embodiment, the description will be continued by taking as an example the case where the recessed portion 8 is provided on the second member 3B side. The recessed portion 8 is a portion obtained by recessing the second member 3B in the negative z-axis direction shown in FIG. 1A, and when the recessed portion 8 is viewed from the positive z-axis direction, it has a U-shaped curved shape. More specifically, the recessed portion 8 includes a first groove portion 8A, a second groove portion 8B, and a third groove portion 8C.

[0023] The first groove portion 8A is a section that extends straight along the x-axis direction. The second groove portion 8B is a section that continuously extends from the first groove portion 8A, is curved with the z-axis as the center of curvature, and has a central angle of 180 degrees at the curved portion, that is, is a semicircular arc section. The third groove portion 8C is a section that continuously extends from the second groove portion 8B, and is a section that extends straight along the x-axis direction at a position parallel to the first groove portion 8A. The second plate-shaped portion 5B is a portion of the second member 3B other than the recessed portion 8.

[0024] As shown in Figure 1B, when the first plate-shaped portion 5A and the second plate-shaped portion 5B are stacked in the thickness direction, the space enclosed by the first member 3A and the recess 8 forms a U-shaped flow path 9 through which the refrigerant flows. The refrigerant flows from the supply pipe through the inlet 7A into the flow path 9 and flows out from the flow path 9 through the outlet 7B into the discharge pipe. The refrigerant passing through the flow path 9 cools the heat-generating element in contact with the first member 3A. Note that liquid or gaseous refrigerants can be used.

[0025] [Explanation of welding method] Next, the welding method for joint 1 will be described. The first member 3A and the second member 3B are welded together at the first plate-like portion 5A and the second plate-like portion 5B. Figure 2A shows the first weld line 11 and the second weld line 12, which represent the weld locations of the first member 3A and the second member 3B. The first weld line 11 extends from the starting end 11A in a loop around the perimeter of the recess 8 to the end 11B. At the intersection 13A, the first weld lines 11 intersect. The first weld line 11 is designed to be a line that can be drawn in a single continuous line from the starting end 11A to the end 11B.

[0026] The second weld line 12 has its starting end 12A on the outer circumference side of the first weld line 11, intersects with the first weld line 11 at intersection 13B, and extends toward the inner circumference side of the first weld line 11. The portion of the second weld line 12 that extends straight along the x-axis from the starting end 12A passes between the first groove 8A and the third groove 8C in the recess 8 and reaches the end 12B near the second groove 8B in the recess 8. The second weld line 12 is designed to be a line that can be drawn in a single stroke from the starting end 12A to the end 12B.

[0027] Figure 2B shows a magnified view of the shape near the end 12B of the second weld line 12. The second weld line 12 extends straight in the positive x-axis direction from the starting end 12A, then curves with the z-axis as the center of curvature, reaching a position where the central angle of the curved portion is 180 degrees. Hereafter, this point will be referred to as the boundary point 15A. From the boundary point 15A, the second weld line 12 extends straight in the negative x-axis direction, then curves with the z-axis as the center of curvature, reaching a position where the central angle of the curved portion is 180 degrees. Hereafter, this point will be referred to as the boundary point 15B. From the boundary point 15B, the second weld line 12 extends straight in the positive x-axis direction to the end 12B.

[0028] Laser welding is performed from the second plate-like portion 5B side along the first welding line 11 and the second welding line 12 as described above. The first welding line 11 is located around the outer circumference of the recess 8 which becomes the flow path 9 (see Figure 1B), and intersects at intersection 13A, forming a closed loop. Therefore, when laser welding is performed with the area along the first welding line 11 as the heating target, the flow path 9 can be confined to the inner circumference of the welded area, which is formed in a closed loop shape. Consequently, even if the fluid introduced into the flow path 9 penetrates the gap between the first plate-like portion 5A and the second plate-like portion 5B, it will not leak out to the outer circumference of the welded area along the first welding line 11.

[0029] Furthermore, the starting end 11A and ending end 11B of the first weld line 11 are positioned on the outer circumference of the loop-shaped weld area. Therefore, even if the fluid introduced into the flow path 9 penetrates the gap between the first plate-shaped part 5A and the second plate-shaped part 5B, the fluid will not reach the weld area near the starting end 11A or the weld area near the ending end 11B. Defects such as blowholes, pits, and cracks are prone to occur at the weld area near the starting end 11A and the weld area near the ending end 11B during welding. However, as described above, the fluid does not reach these areas prone to defects, thus improving the sealing performance of the fluid.

[0030] When laser welding is performed on the area along the second welding line 12, the gap between the first plate-like portion 5A and the second plate-like portion 5B can be closed at the position between the first groove portion 8A and the third groove portion 8C in the recess 8. Therefore, short-circuiting between the first groove portion 8A and the third groove portion 8C through the gap between the first plate-like portion 5A and the second plate-like portion 5B can be suppressed, and the cooling performance of the U-shaped flow path 9 can be achieved as designed.

[0031] The starting end 12A of the second weld line 12 is positioned on the outer circumference of the weld area, which is formed in a closed loop along the first weld line 11. Therefore, even if the fluid introduced into the flow path 9 penetrates the gap between the first plate-like part 5A and the second plate-like part 5B, the fluid will not reach the weld area near the starting end 12A. Defects such as blowholes, pits, and cracks are prone to occur at the weld area near the starting end 12A during welding. However, as described above, the fluid does not reach these areas prone to defects, thus improving the sealing performance of the fluid.

[0032] Near the end 12B of the second weld line 12, welding is performed along the second weld line 12 as shown in an enlarged view in Figure 2B, and control is performed to adjust the amount of heat supplied to the area to be heated. Specifically, in the first section 17A until it reaches the boundary point 15A, heat Q1 is supplied to the area to be heated. Subsequently, in the second section 17B from the boundary point 15A to the boundary point 15B, heat Q2 is supplied to the area to be heated. Subsequently, in the third section 17C from the boundary point 15B to the end 12B, heat Q3 is supplied to the area to be heated.

[0033] These heat quantities Q1, Q2, and Q3 satisfy the inequality: Q1 ≥ Q2 > Q3, meaning that the amount of heat supplied to the heating area gradually decreases in stages. The specific values ​​of heat quantities Q1, Q2, and Q3 can be adjusted as appropriate, but as an example, if heat quantity Q1 is the standard amount of heat during welding, then heat quantity Q2 should be about 80% of heat quantity Q1, and heat quantity Q3 should be about 40% of heat quantity Q1.

[0034] Furthermore, specific methods for gradually reducing the heat quantities Q1, Q2, and Q3 are also optional. For example, the heat quantities Q1, Q2, and Q3 can be gradually reduced by adjusting the output of the heating source. Alternatively, if the output of the heating source is constant, increasing the welding speed reduces the amount of heat supplied to the welding area at a predetermined distance, so the heat quantities Q1, Q2, and Q3 can be gradually reduced by gradually increasing the welding speed.

[0035] Furthermore, although the above example described gradually decreasing the heat quantities Q1, Q2, and Q3 in stages, the heat quantities may be decreased in more stages, or the heat quantities may be configured to decrease continuously without any steps. Also, as clearly shown in the above inequality, the heat quantities Q1 and Q2 may be kept equal, and the heat quantities Q2 and Q3 may be decreased gradually in stages or without any steps.

[0036] When welding is performed in the first section 17A, a weld bead 21 is formed along the first section 17A, as shown in Figures 3A and 3B. Hereinafter, the weld bead 21 formed along the first section 17A will also be referred to as the first welded portion 21A. At the location where the first welded portion 21A is formed, a penetration portion 23A is formed extending from the second plate-like portion 5B to the first plate-like portion 5A, as shown in Figure 3B.

[0037] When welding is performed in the second section 17B following the first section 17A, a weld bead 21 is formed along the second section 17B, as shown in Figures 4A and 4B. Hereinafter, the weld bead 21 formed along the second section 17B will also be referred to as the second weld 21B. At the location where the second weld 21B is formed, a penetration portion 23B is formed, extending from the second plate-like portion 5B to the first plate-like portion 5A, as shown in Figure 4B.

[0038] When welding is performed in the second section 17B, the temperature of the area to be heated has already risen to a certain extent because it is immediately after welding has been performed in the first section 17A. However, in this embodiment, when welding is performed in the second section 17B, a heat quantity Q2 is supplied to the area to be heated, as described above.

[0039] Therefore, the amount of heat supplied to the area to be heated is reduced compared to when welding is performed in the first section 17A, thereby suppressing the formation of excessively deep penetration portions 23B. Consequently, compared to continuing welding without changing the amount of heat, back-burning and back-burning on the first plate-like portion 5A side can be suppressed, and the smoothness of the first plate-like portion 5A side can be appropriately maintained.

[0040] The end of the first weld 21A and the beginning of the second weld 21B, which are located at the boundary point 15A, are formed to overlap at the same position as the boundary point 15A. Furthermore, the end of the second weld 21B is located at a different location from the beginning of the second weld 21B, and even near the end of the second weld 21B, a portion of the second weld 21B is formed to overlap with a portion of the first weld 21A. As a result, the first weld 21A and the second weld 21B form a loop portion 25, which is a welded area with a loop shape.

[0041] In the second weld line 12, the second section 17B does not reach the point where it overlaps with the first section 17A, but because the weld bead 21 has a predetermined width, the second weld section 21B reaches the point where it overlaps with the first weld section 21A. As a result, the loop section 25 becomes a closed loop. In other words, the loop section 25 becomes a loop with no open sections along the circumferential direction.

[0042] In this embodiment, due to the predetermined width of the weld bead 21, the area on the inner circumference side of the loop portion 25 is completely filled without any gaps. However, even if there is no gap on the inner circumference side, it is still included in the loop portion as defined in this disclosure. In other words, in the loop portion as defined in this disclosure, it is not necessary to consider whether or not there is a gap at the position on the inner circumference side of the loop portion.

[0043] When welding is performed in the third section 17C following the second section 17B, a weld bead 21 is formed along the third section 17C, as shown in Figures 5A and 5B. Hereinafter, the weld bead 21 formed along the third section 17C will also be referred to as the third weld 21C. A penetration portion 23C is formed at the location where the third weld 21C is formed, as shown in Figure 5B.

[0044] When welding is performed in the third section 17C, the temperature of the area to be heated has already risen to a certain extent because it is immediately after welding has been performed in the first section 17A and the second section 17B. Moreover, the third welded section 21C is formed in a position that overlaps with the first welded section 21A and the second welded section 21B. However, in this embodiment, when welding is performed in the third section 17C, as described above, a heat quantity Q3 is supplied to the area to be heated.

[0045] Therefore, the amount of heat supplied to the area to be heated is further reduced compared to when welding is performed in the second section 17B, thereby suppressing the formation of excessively deep penetration areas 23C. Consequently, compared to continuing welding without changing the amount of heat, back-burning and back-burning on the first plate-like portion 5A side can be suppressed, and the smoothness of the first plate-like portion 5A side can be appropriately maintained.

[0046] At the location where the loop portion 25 is formed, the gap between the first plate-shaped portion 5A and the second plate-shaped portion 5B is closed in a closed loop shape. Therefore, even if the fluid introduced into the flow path 9 enters the gap between the first plate-shaped portion 5A and the second plate-shaped portion 5B, the fluid will not enter the position on the inner circumference side of the loop portion 25.

[0047] The end of the third weld 21C, which is also the end of the weld bead 21, is formed on the inner circumference side of the loop 25. Therefore, even if the fluid introduced into the flow path 9 penetrates the gap between the first plate-like part 5A and the second plate-like part 5B, the fluid will not reach the weld area near the end 12B. Defects such as blowholes, pits, and cracks are prone to occur at the weld area near the end 12B during welding. However, as mentioned above, the fluid does not reach the area where such defects are likely to occur, thus improving the sealing performance of the fluid.

[0048] [effect] As described above, according to the manufacturing method of the joined body 1, the loop portion 25 is formed by the first weld portion 21A and the second weld portion 21B, and the end of the third weld portion 21C, which is the end of the weld bead 21, is formed at a position on the inner circumference side of the loop portion 25. Moreover, the amount of heat Q3 applied to the area to be heated when forming the third weld portion 21C is controlled to be less than the amount of heat Q1 applied to the area to be heated when forming the first weld portion 21A.

[0049] Therefore, when forming the third weld 21C, the amount of heat supplied to the area to be heated decreases compared to when forming the first weld 21A. Consequently, compared to conventional techniques where there is no control to increase or decrease the amount of heat supplied to the area to be heated, excessive penetration can be suppressed.

[0050] Furthermore, in this embodiment, when forming the second weld 21B, the amount of heat supplied to the area to be heated decreases compared to when forming the first weld 21A. Similarly, when forming the third weld 21C, the amount of heat supplied to the area to be heated decreases compared to when forming the second weld 21B. Therefore, compared to conventional technology in which there is no control to increase or decrease the amount of heat supplied to the area to be heated, it is possible to suppress the occurrence of excessive penetration.

[0051] [Other embodiments] Although the method for manufacturing the joined body has been described above with reference to exemplary embodiments, the above-described embodiments are merely illustrative examples of one aspect of the present disclosure. In other words, the present disclosure is not limited to the above-described exemplary embodiments and can be implemented in various forms without departing from the technical spirit of the present disclosure.

[0052] For example, in the above embodiment, a specific shape was given as an example regarding the shape near the end 12B of the second weld line 12, but the shape near the end 12B of the second weld line 12 is not limited to the example given above. To give a specific example, as shown in Figure 6, the first section 37A and the second section 37B may intersect at intersection 33A to form a loop section 45. In this case as well, the end 32B of the second weld line 32, which is the end of the third section 37C, can be placed on the inner circumference side of the loop section 45. The loop section 45 referred to here is the section in which a welded area equivalent to the loop section 25 in the above embodiment is formed.

[0053] Even when forming a weld bead along such a second weld line 32, if the amount of heat is gradually or continuously reduced in the order of the first section 37A, the second section 37B, and the third section 37C, excessive penetration near the end of the weld bead can be suppressed.

[0054] In the example shown in Figure 6, the first section 37A and the second section 37B intersect at intersection 33A. However, if the fusion at intersection 33A becomes excessive, the boundary point 35B may be set to a position closer to boundary point 35A than intersection 33A. In other words, the first section 37A and the third section 37C may be configured to intersect at intersection 33A. If the fusion at intersection 33B becomes excessive, the heat content may be further reduced near intersection 33B.

[0055] Furthermore, in the above embodiment, a heat exchanger for cooling a heating element was given as a specific example of the joint 1, but the method for manufacturing the joint described herein can also be used when manufacturing products other than heat exchangers.

[0056] Furthermore, multiple functions realized by one component as exemplified in the above embodiment may be realized by multiple components. One function realized by one component as exemplified in the above embodiment may be realized by multiple components. Multiple functions realized by multiple components as exemplified in the above embodiment may be realized by one component. One function realized by multiple components as exemplified in the above embodiment may be realized by one component. Some of the configurations exemplified in the above embodiment may be omitted. At least a part of the configuration exemplified in one of the above embodiments may be added to or replaced with the configuration exemplified in the other embodiments.

[0057] [Technical concepts disclosed in this specification] [Item 1] This method involves overlapping a first plate-shaped portion and a second plate-shaped portion, each formed in a plate shape, in the thickness direction, and heating the area to be heated along the weld line from the second plate-shaped portion side, thereby forming a weld bead that extends from the beginning to the end. At the same time, a penetration portion is formed at the location where the weld bead is formed, extending from the second plate-shaped portion to the first plate-shaped portion, thereby joining the first plate-shaped portion and the second plate-shaped portion to manufacture a joined body. The weld bead has a first weld, a second weld, and a third weld, each of which constitutes a part of the weld bead. The first weld and the second weld are formed continuously, with the end of the first weld being the starting point of the second weld, and a portion of the second weld overlapping with a portion of the first weld at a location separate from the starting point of the second weld, thereby forming a loop-shaped weld. The third weld is formed such that the end of the second weld is the starting point of the third weld, and the second and third welds are formed continuously, and the end of the third weld, which is the end of the weld bead, is formed at a position on the inner circumference side of the loop portion. The amount of heat supplied to the area to be heated when forming the third weld is controlled to be less than the amount of heat supplied to the area to be heated when forming the first weld. A method for manufacturing a composite body.

[0058] [Item 2] A method for manufacturing a joint described in item 1, The amount of heat supplied to the area to be heated when forming the second weld is controlled to be less than the amount of heat supplied to the area to be heated when forming the first weld, and greater than the amount of heat supplied to the area to be heated when forming the third weld. A method for manufacturing a composite body.

[0059] [Item 3] A method for manufacturing a joint described in item 2, The amount of heat applied to the heating area when forming the first weld, the second weld, and the third weld is controlled to decrease gradually, either in stages or continuously. A method for manufacturing a composite body.

[0060] [Item 4] A method for manufacturing a joint according to any one of items 1 to 3, The control that reduces the amount of heat is a control that reduces the output of the heating source. A method for manufacturing a composite body.

[0061] [Item 5] A method for manufacturing a joint according to any one of items 1 to 4, The control that reduces the amount of heat is a control that increases the welding speed. A method for manufacturing a composite body.

[0062] [Item 6] A method for manufacturing a joint according to any one of items 1 to 5, The first weld, the second weld, and the third weld each have portions that extend in parallel with each other, and in these parallel portions, the third weld is formed at a position between the first weld and the second weld. A method for manufacturing a composite body. [Explanation of Symbols]

[0063] 1...Joint, 3A...First member, 3B...Second member, 5A...First plate-like part, 5B...Second plate-like part, 7A...Inlet, 7B...Outlet, 8...Recess, 8A...First groove, 8B...Second groove, 8C...Third groove, 9...Flow path, 11...First weld line, 12,32...Second weld line, 11A,12A...Starting end, 11B,12B,32B...End, 13A,1 3B, 33A... Intersection, 15A, 15B, 35B... Boundary point, 17A, 37A... First section, 17B, 37B... Second section, 17C, 37C... Third section, 21... Weld bead, 21A... First weld, 21B... Second weld, 21C... Third weld, 23A, 23B, 23C... Penetration section, 25... Loop section, 45... Loop section.

Claims

1. This method involves overlapping a first plate-shaped portion and a second plate-shaped portion, each formed in a plate shape, in the thickness direction, and heating the area to be heated along the weld line from the second plate-shaped portion side, thereby forming a weld bead that extends from the start end to the end end. At the same time, a penetration portion is formed at the location where the weld bead is formed, extending from the second plate-shaped portion to the first plate-shaped portion, thereby joining the first plate-shaped portion and the second plate-shaped portion to manufacture a joined body. The weld bead has a first weld portion, a second weld portion, and a third weld portion, each of which constitutes a part of the weld bead. The first weld and the second weld are formed continuously, with the end of the first weld being the starting point of the second weld, and a portion of the second weld overlapping with a portion of the first weld at a location separate from the starting point of the second weld, thereby forming a loop-shaped weld. The third weld is formed such that the end of the second weld is the starting point of the third weld, and the second and third welds are formed continuously, and the end of the third weld, which is the end of the weld bead, is formed at a position on the inner circumference side of the loop portion. The amount of heat applied to the area to be heated when forming the third weld is controlled to be less than the amount of heat applied to the area to be heated when forming the first weld. A method for manufacturing a composite body.

2. A method for manufacturing a joint according to claim 1, The amount of heat supplied to the area to be heated when forming the second weld is controlled to be less than the amount of heat supplied to the area to be heated when forming the first weld, and greater than the amount of heat supplied to the area to be heated when forming the third weld. A method for manufacturing a composite body.

3. A method for manufacturing a joint according to claim 2, The amount of heat applied to the heating area when forming the first weld, the second weld, and the third weld is controlled to decrease gradually, either in stages or continuously. A method for manufacturing a composite body.

4. A method for manufacturing a joint according to any one of claims 1 to 3, The control that reduces the amount of heat is a control that reduces the output of the heating source. A method for manufacturing a composite body.

5. A method for manufacturing a joint according to any one of claims 1 to 3, The control that reduces the amount of heat is a control that increases the welding speed. A method for manufacturing a composite body.

6. A method for manufacturing a joint according to any one of claims 1 to 3, The first weld, the second weld, and the third weld each have portions that extend in parallel with each other, and in these parallel portions, the third weld is formed at a position between the first weld and the second weld. A method for manufacturing a composite body.

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