Manufacturing method for welded components

Abstract

To provide a welding method capable of controlling a direction in which a welding member is curved.SOLUTION: A method for manufacturing a welding member in which a first component and a second component are welded includes welding the first component and the second component so as to form a main welding part extending in a circumferential direction. A deformation point is a position located in a range from a welding start point of the main welding part to an approximate center of the main welding part in the circumferential direction, the position having a high contribution to deformation occurring in the main welding part. The deformation point is arranged at a position that contributes to a direction of thermally distorting the welding member.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a welded member. [Background Art]

[0002] Patent Document 1 discloses a welding method in which a ring including a side face orthogonal to an axial direction and a plate having an abutting face against which the side face of the ring abuts, both of which are provided in a brake device, are welded by laser welding. In this welding method, in a state where the side face and the abutting face are in contact with each other, four or more dotted welds arranged at equal intervals in the circumferential direction centered on the axis of the ring are formed, and then the plate and the ring are welded to form a circular weld along the circumferential direction, thereby reducing thermal distortion of the brake device. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2021-165560 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In the welding method described above, thermal distortion of the welded member is reduced by suppressing deformation that occurs in the circular weld of the welded member formed by welding two components, but it is difficult to control the bending direction of the welded member due to thermal distortion of the welded member.

[0005] An aspect of the present disclosure aims to provide a welding method capable of controlling the bending direction of a welded member. [Means for Solving the Problem]

[0006] One aspect of the present disclosure is a method for manufacturing a welded member comprising welding a first part and a second part together, the first part and the second part together such that a main weld is formed, which extends in the circumferential direction about an axis of the welded member that extends in the direction in which the first part and the second part are aligned. The main weld extends from a welding start point to a welding end point. A deformation point is defined as a position located in the range from the welding start point of the main weld to approximately the center of the circumferential direction of the main weld, and which contributes significantly to the deformation occurring in the main weld. The deformation point is positioned to contribute in a direction that causes thermal distortion of the welded member.

[0007] With this configuration, the direction in which the welded member bends can be controlled by adjusting the position where the deformation points of the main weld are located.

[0008] One aspect of the present disclosure may further comprise welding a first part and a second part such that one or more sub-welds are formed to temporarily fix the second part to the first part. The main weld may be formed after the sub-welds are formed. With this configuration, the temporary fixing of the first and second parts by the sub-welds can suppress misalignment of the first and second parts when forming the main weld. As a result, misalignment of the deformation points when forming the main weld can be suppressed.

[0009] In one aspect of the present disclosure, two or three sub-welds may be formed. With such a configuration, misalignment between the first and second parts when forming the main weld can be more effectively suppressed compared to the case where there is one sub-weld.

[0010] In one aspect of this disclosure, two sub-welds may be formed. The two sub-welds may be positioned approximately 180° apart from each other in the circumferential direction. In such a configuration, the temporary fixing of the first and second parts by the two sub-welds makes it easier to restrict the direction of thermal strain occurring in the main weld in a first direction and a second direction opposite to the first direction, which are perpendicular to the line connecting the two sub-welds. This makes it possible to position the deformation point of the main weld on the first direction side of the line to cause thermal strain in the first direction, or to position the deformation point of the main weld on the second direction side of the line to cause thermal strain in the second direction. As a result, the direction of bending of the welded member becomes easier to control.

[0011] In one aspect of this disclosure, the main weld may be formed by full-circumferential welding. The welding start point of the main weld may be positioned so as not to overlap with the sub-weld. With such a configuration, the bending direction of the welded member having the main weld formed by full-circumferential welding can be controlled.

[0012] In one aspect of this disclosure, the deformation point may be the welding start point and welding end point of the main weld. With this configuration, the direction in which the welded member bends can be controlled by adjusting the position where the welding start point of the main weld is located.

[0013] In one aspect of this disclosure, the first and second parts may be cylindrical parts. The end of the second part may be inserted into the first part. The main weld and sub-weld may be formed in the portion where the first and second parts overlap. With such a configuration, the bending direction of the welded member formed by welding the cylindrical first and second parts can be controlled.

[0014] One aspect of the present disclosure may further comprise welding a first part and a second part such that, after the formation of the main weld, a compensating weld is formed that causes the welded member to thermally deform in a direction opposite to the direction in which the welded member thermally deforms. With such a configuration, by forming a compensating weld after the formation of the main weld, the direction in which the welded member bends can be controlled, and the deformation occurring in the main weld can be offset by the deformation occurring in the compensating weld. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1A is a schematic cross-sectional view along the central axis showing the state in which a sub-weld joint has been formed, and Figure 1B is a schematic cross-sectional view along the central axis showing the welded member of the first embodiment. [Figure 2] Figure 2A is a cross-sectional view of the line IIA-IIA in Figure 1B, and Figures 2B to 2E are cross-sectional views perpendicular to the central axis, showing the direction of thermal strain when the welding start and end points are located at different positions in the circumferential direction compared to the example shown in Figure 2A. [Figure 3] Figure 3A is a cross-sectional view perpendicular to the central axis showing the direction of thermal strain caused by the formation of only the main weld in a modified example of the first embodiment, and Figure 3B is a cross-sectional view along the central axis schematically showing how the welded member bends due to thermal strain in a predetermined direction. [Figure 4] This is a cross-sectional view perpendicular to the central axis, showing the direction of thermal strain resulting from the formation of one sub-weld and one main weld in a modified example of the first embodiment. [Figure 5] Figure 5A is a cross-sectional view perpendicular to the central axis showing the direction of thermal strain resulting from the formation of three sub-welds and a main weld in a modified example of the first embodiment. Figure 5B is a cross-sectional view perpendicular to the central axis showing the direction of thermal strain when the welding start and end points are located at different circumferential positions than in the example shown in Figure 5A. [Figure 6]Figure 6A is a cross-sectional view perpendicular to the central axis showing the direction of thermal strain resulting from the formation of four sub-welds and a main weld in a modified example of the first embodiment. Figure 6B is a cross-sectional view perpendicular to the central axis showing the direction of thermal strain when the welding start and end points are located at different circumferential positions than in the example shown in Figure 6A. [Figure 7] This is a cross-sectional view perpendicular to the central axis, showing the direction of thermal strain resulting from the formation of only the main weld, which is an arc, in a modified version of the first embodiment. [Figure 8] This is a cross-sectional view perpendicular to the central axis, showing the direction of thermal strain resulting from the formation of two sub-welds and a main weld, which is an arc, in a modified version of the first embodiment. [Figure 9] Figure 9A is a schematic cross-sectional view along the central axis showing the state in which a sub-weld joint has been formed, Figure 9B is a schematic cross-sectional view along the central axis showing the state in which a main weld joint has been formed, and Figure 9C is a schematic cross-sectional view along the central axis showing the welded member of the second embodiment. [Figure 10] Figure 10A is a cross-sectional view of the line XA-XA in Figure 9C, and Figures 10B to 10E are cross-sectional views perpendicular to the central axis showing the direction of thermal strain and the arrangement of adjustment welds that cancel out said thermal strain when the welding start and end points are located at different positions in the circumferential direction than in the example shown in Figure 10A. [Figure 11] This is a cross-sectional view perpendicular to the central axis showing the arrangement of adjustment welds that compensate for thermal distortion caused by the formation of only the main weld in a modified example of the second embodiment. [Figure 12] This is a cross-sectional view perpendicular to the central axis showing the arrangement of an adjustment weld that cancels out the thermal distortion caused by the formation of one sub-weld and one main weld in a modified example of the second embodiment. [Figure 13] Figure 13A is a cross-sectional view perpendicular to the central axis showing the arrangement of adjustment welds that cancel out the thermal strain caused by the formation of three sub-welds and a main weld in a modified example of the second embodiment. Figure 13B is a cross-sectional view perpendicular to the central axis showing the direction of thermal strain and the arrangement of adjustment welds that cancel out the thermal strain when the welding start and end points are located at different positions in the circumferential direction than in the example shown in Figure 13A. [Figure 14] Fig. 14A is a cross-sectional view orthogonal to the central axis showing the arrangement of adjustment welds that offset thermal strain generated by forming four sub-welds and a main weld in a modified example of the second embodiment. Fig. 14B is a cross-sectional view orthogonal to the central axis showing the direction of thermal strain when welding start / end points are arranged at different positions in the circumferential direction from the example shown in Fig. 14A, and the arrangement of adjustment welds that offset the thermal strain. [Figure 15] A cross-sectional view orthogonal to the central axis showing the arrangement of adjustment welds that offset thermal strain generated by forming only an arc-shaped main weld in a modified example of the second embodiment. [Figure 16] A cross-sectional view orthogonal to the central axis showing a modified example of a linear sub-weld. [Figure 17] A cross-sectional view orthogonal to the central axis showing a modified example of a sub-weld with different linear lengths. [Figure 18] A cross-sectional view orthogonal to the central axis showing a modified example of a forming method for a main weld. DETAILED DESCRIPTION OF EMBODIMENTS

[0016] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. First Embodiment] [1-1. Configuration] The welded member 100 shown in Fig. 1B is an in-vehicle component mounted on a vehicle. Examples of the in-vehicle component include exhaust system components that constitute at least a part of a flow path for passing exhaust gas from an internal combustion engine mounted on a vehicle.

[0017] As shown in Fig. 1A and Fig. 1B, the welded member 100 includes a first component 1, a second component 2, a sub-weld SW, and a main weld MW. In the present embodiment, the welded member 100 has a central axis A extending linearly. The welded member 100 is manufactured by welding the first component 1 and the second component 2, which are arranged side by side along the central axis A, for example, by arc welding.

[0018] The first part 1 and the second part 2 are cylindrical tubes with a constant diameter. The inner diameter of the first part 1 is larger than the outer diameter of the second part 2. However, the inner diameter of the first part may be approximately the same as the outer diameter of the second part. Preferably, there is no gap in the radial direction between the end of the first part 1 and the end of the second part, but a gap may be present. The central axes of the first part 1 and the second part 2 coincide with the central axis A of the welded member 100. In this embodiment, the first part 1 and the second part 2 are connected with the end of the second part 2 inserted into the opening on one end side of the first part 1.

[0019] One or more sub-weld sections SW are formed at predetermined positions in the circumferential direction centered on the central axis A in the portion where the first part 1 and the second part 2 overlap, and temporarily fix the second part 2 to the first part 1. The sub-weld sections SW are formed by partially welding a welding path that circumfers the outer surfaces of the first part 1 and the second part 2. As shown in Figures 2A to 2E, in this embodiment, the shape of the sub-weld sections SW is point-like, and two sub-weld sections SW are formed, for example, by arc welding. When viewed along the central axis A, the two sub-weld sections SW are positioned approximately 180° apart from each other in the circumferential direction, with respect to the center point of each sub-weld section SW. That is, the two sub-weld sections SW face each other with respect to the central axis A.

[0020] As a result, the welding path is divided into two paths in the drawing by a straight line L connecting the two sub-welds SW: a first welding path located above the straight line L, and a second welding path located below the straight line L. In the following explanation, in the drawing, the direction perpendicular to the straight line L that goes upward (i.e., towards the first welding path) will be referred to as the first direction D1, and the direction opposite to the first direction D1 that goes downward (i.e., towards the second welding path) will be referred to as the second direction D2.

[0021] As shown in Figure 1B, the main weld MW is formed to extend circumferentially to the overlapping portion of the first part 1 and the second part 2, joining the first part 1 and the second part 2. In other words, the main weld MW permanently fixes the temporarily fixed first part 1 and the second part 2 with a stronger joint than the temporary fixing joint. The main weld MW is formed at the same position as the sub-weld SW is formed in the direction along the central axis A. In the examples shown in Figures 2A to 2E, the welding direction of the main weld MW is clockwise. The welding direction may also be counterclockwise. In this embodiment, the main weld MW is formed by welding around the entire circumference along the welding path. In full-circumference welding, the welding start point and welding end point overlap. Hereinafter, the welding start point and welding end point in the main weld MW will be referred to as the welding start point S. That is, as shown in Figures 2A to 2E, in a cross-section perpendicular to the central axis A, the shape of the main weld MW is a closed circle along the welding path. Furthermore, the condition "the welding start point and welding end point overlap" includes the condition where the welding start point and welding end point overlap completely or partially.

[0022] The welding start point S of the main weld MW is preferably positioned in a location that does not overlap with the sub-weld SW in the circumferential direction. However, the welding start point S may be positioned in a location that overlaps with the sub-weld SW in the circumferential direction. The condition that "the welding start point S overlaps with the sub-weld SW in the circumferential direction" includes the condition in which the welding start point S and the sub-weld SW overlap completely or partially.

[0023] [1-2. Method for manufacturing welded members] Next, the manufacturing method of the welded member 100 will be explained using Figures 1A, 1B, and 2A. Specifically, the welding method between the first part 1 and the second part 2 included in the manufacturing method of the welded member 100 will be explained.

[0024] First, the end of the second part 2 is inserted into the opening at one end of the first part 1 to connect the first part 1 and the second part 2. Then, as shown in Figures 1A and 2A, the first part 1 and the second part 2 are partially welded in the circumferential direction so that two opposing sub-welds SW are formed with respect to the central axis A.

[0025] Next, as shown in Figures 1B and 2A, after the sub-weld SW is formed, the first part 1 and the second part 2 are welded all around along the circumferential direction so that the main weld MW is formed on top of the sub-weld SW. At this time, the position of the welding start point S of the main weld MW is adjusted so that the welded member 100 bends in the desired direction at the joining position of the first part 1 and the second part 2, and welding of the main weld MW is started. In other words, the welding start position is adjusted so that the main welding start point S is positioned in the direction in which thermal distortion is to be caused in the welded member 100 at the joining position of the first part 1 and the second part 2, and welding of the main weld MW is started.

[0026] In arc welding of the main weld MW, deformation is likely to occur in the weld due to its formation. Furthermore, in full-circumference welding, the weld overlaps at points located from the welding start point to approximately the center of the circumferential direction of the weld, particularly at the welding end point. This increases the time the welding heat is transferred to the workpiece, thus increasing the heat capacity. Therefore, in the case where a sub-weld SW is not formed, the welding end point S becomes the center of deformation in the main weld MW formed by full-circumference arc welding. The center of deformation is, for example, the part of the weld that experiences the greatest deformation due to thermal strain. Consequently, as shown in Figure 3A, without temporary fixing by the sub-weld SW, the formation of the main weld MW causes thermal strain in the direction from the central axis A toward the welding end point S. Hereafter, thermal strain in a predetermined direction means that the weld member 100 bends so that the sections on both sides of the joint position in the weld member 100 tilt in that predetermined direction (see Figure 3B).

[0027] On the other hand, in this embodiment, before the formation of the main weld MW, two sub-welds SW are formed, which are spaced approximately 180° apart from each other in the circumferential direction, and the first part 1 and the second part 2 are temporarily fixed in place. This makes it easier to restrict the direction of thermal strain occurring in the main weld MW to the first direction D1 and the second direction D2. For this reason, in this embodiment, the direction of thermal strain occurring in the main weld MW is not the direction from the central axis A toward the welding start point S, but rather one of the first direction D1 and the second direction D2. In other words, in this embodiment, the welding start point S is not the center of the deformation occurring in the main weld MW, but rather functions as a position that contributes a high degree to the deformation occurring in the main weld MW.

[0028] Therefore, as shown in Figures 2A to 2D, by forming the main weld MW such that the welding start point S is located on the first welding path on the side of the first direction D1 relative to the straight line L, thermal strain in the first direction D1 can be generated. Furthermore, even if the circumferential position of the welding start point S differs as long as it is on the first welding path, thermal strain in the first direction D1 can still be generated.

[0029] Furthermore, as shown in Figure 2E, by forming the main weld MW such that the welding start point S is positioned on the second welding path on the second direction D2 side of the straight line L, thermal strain in the second direction D2 can be generated. Although only one example of the position of the welding start point S on the second welding path is shown, just as with the first welding path, it is possible to generate thermal strain in the second direction D2 even if the position of the welding start point S in the circumferential direction is different on the second welding path.

[0030] In other words, among the welding paths, the position on the first welding path is a position that contributes to thermal distortion of the welded member 100 in the first direction D1, and the position on the second welding path is a position that contributes to thermal distortion of the welded member 100 in the second direction D2. As described above, by placing the welding start / end point S on the first or second welding path, it is possible to intentionally cause thermal distortion in the first direction D1 or the second direction D2 that occurs in the main weld MW, and to control the bending direction of the welded member 100.

[0031] [1-3. Effects] According to the first embodiment described in detail above, the following effects can be obtained. (1a) In the first embodiment, two sub-welds SW are formed so as to be separated from each other by approximately 180° in the circumferential direction. After the formation of the two sub-welds SW, the main weld MW is formed by full-circumferential welding. Therefore, the temporary fixing of the first part 1 and the second part 2 by the two sub-welds SW makes it easier to restrict the direction of thermal strain generated in the main weld MW to the first direction D1 and the second direction D2. Accordingly, the welding start point S of the main weld MW can be placed on the first welding path to generate thermal strain in the first direction D1, or the welding start point S of the main weld MW can be placed on the second welding path to generate thermal strain in the second direction D2.

[0032] In this way, by positioning the welding start point S on either the first welding path or the second welding path, the bending direction of the welded member 100 can be easily controlled.

[0033] (1b) In the first embodiment, a sub-weld SW is formed before the main weld MW is formed, and the first part 1 and the second part 2 are temporarily fixed in place. Therefore, the sub-weld SW can suppress misalignment of the first part 1 and the second part 2 when forming the main weld MW. As a result, the positional accuracy of the welding start point S is improved, and consequently, the accuracy of controlling the bending direction of the welded member 100 can be improved. In the first embodiment, the welding start point S corresponds to an example of a deformation point.

[0034] [1-4. Other Embodiments] Although the first embodiment of this disclosure has been described above, it goes without saying that this disclosure is not limited to the first embodiment and can take various forms.

[0035] (2a) In the first embodiment described above, two sub-welds SW were formed, but the number of sub-welds is not limited to this. For example, as shown in Figure 3A, it is not necessary for any sub-welds SW to be formed. Specifically, it is possible that no sub-welds SW are formed before the main weld MW is formed. That is, only the main weld MW may be formed. In this case, the formation of the main weld MW causes thermal strain in the direction from the central axis A toward the welding start point S. Therefore, by adjusting the position where the welding start point S of the main weld MW is located, the bending direction of the welded member 100 can be easily controlled.

[0036] Furthermore, as shown in Figure 4, for example, one sub-weld section SW may be formed. Specifically, a main weld section MW may be formed after the formation of one sub-weld section SW. In this case as well, the formation of the main weld section MW causes thermal strain in the direction from the central axis A toward the welding start point S. Note that even if the relative position of the welding start point S and one sub-weld section SW on the welding path changes, thermal strain will still occur in the direction from the central axis A toward the welding start point S. Therefore, by adjusting the position where the welding start point S of the main weld section MW is located, the bending direction of the welded member 100 can be easily controlled.

[0037] Furthermore, as shown in Figures 5A and 5B, for example, three sub-weld sections SW may be formed at equal intervals along the circumferential direction. Specifically, the main weld section MW may be formed after the three sub-weld sections SW have been formed. In this case as well, the formation of the main weld section MW causes thermal strain in the direction from the central axis A toward the welding start point S. Even if the position of the welding start point S on the welding path changes, thermal strain will still occur in the direction from the central axis A toward the welding start point S. Therefore, by adjusting the position where the welding start point S of the main weld section MW is located, the bending direction of the welded member 100 can be easily controlled.

[0038] Furthermore, as shown in Figures 6A and 6B, for example, four sub-weld sections SW may be formed at equal intervals along the circumferential direction. Specifically, the main weld section MW may be formed after the four sub-weld sections SW have been formed. In this case as well, the formation of the main weld section MW causes thermal strain in the direction from the central axis A toward the welding start point S. Even if the position of the welding start point S on the welding path changes, thermal strain will still occur in the direction from the central axis A toward the welding start point S. Therefore, by adjusting the position where the welding start point S of the main weld section MW is located, the direction in which the welded member 100 bends can be easily controlled.

[0039] (2b) In the first embodiment, the main weld MW was formed by full-circumferential welding, but the method of forming the main weld is not limited to this. For example, the main weld may be formed by welding a predetermined length of section of a welding path that encircles the outer surface of the member. Specifically, as shown in Figure 7, in a cross section perpendicular to the central axis A, the shape of the main weld MWa may be an arc in which the welding path does not close.

[0040] In arc-shaped welding, the heat capacity tends to increase because the time it takes for the welding heat to be transferred to the workpiece is longer in the range from the welding start point of the weld to approximately the center of the circumferential direction of the weld. In the arc-shaped main weld MWa, the deformation point T located in the range from the welding start point S1a of the main weld MWa to approximately the center of the circumferential direction of the main weld MWa is the position that becomes the center of the deformation occurring in the main weld MWa. The range from the welding start point of the main weld to approximately the center of the circumferential direction of the main weld is, for example, approximately 180 degrees from the welding start point when the circumferential angle of the main weld is 360 degrees, and approximately 90 degrees from the welding start point when the circumferential angle of the main weld is 180 degrees. Therefore, as shown in Figure 7, when there is no sub-weld SW and only the main weld MWa is formed, thermal strain occurs in the direction from the central axis A toward the deformation point T due to the formation of the main weld MWa.

[0041] For convenience, in Figures 7 and 8, the deformation point T is shown as being at the center of the main weld MWa. However, the deformation point T is not limited to the center, as long as it is at the center of deformation within the range from the welding start point S1a of the main weld MWa to approximately the center in the circumferential direction of the main weld MWa. Furthermore, the position of the welding start point S1a is not limited to the position shown in Figures 7 and 8, but may be located at the other end of the arc.

[0042] On the other hand, as shown in Figure 8, if two sub-welds SW are formed before the main weld MWa, separated by approximately 180° in the circumferential direction, and the first part 1 and the second part 2 are temporarily fixed, then, similar to the first embodiment described above, the direction of thermal strain occurring in the main weld MWa is more easily restricted to the first direction D1 and the second direction D2. Therefore, the direction of thermal strain occurring in the main weld MWa is not the direction from the central axis A toward the deformation point T, but rather one of the first direction D1 and the second direction D2. In other words, the deformation point T is not the center of the deformation occurring in the main weld MWa, but functions as a position that contributes a high degree to the deformation occurring in the main weld MWa.

[0043] Therefore, as shown in Figure 8, by forming the main weld MWa such that the deformation point T is located on the first welding path on the side of the first direction D1 relative to the straight line L, thermal strain in the first direction D1 can be generated. Also, although not shown in the figure, by forming the main weld such that the deformation point T is located on the second welding path on the side of the second direction D2 relative to the straight line L, thermal strain in the second direction D2 can be generated. Thus, similar to the first embodiment described above, the bending direction of the welded member 100 can be controlled by placing the deformation point T on the first or second welding path.

[0044] [2. Second Embodiment] In the welding method disclosed in the aforementioned Japanese Patent Publication No. 2021-165560, it may not be possible to sufficiently reduce the thermal distortion of the welded member formed by welding two parts together. Therefore, a new method for suppressing the thermal distortion of the welded member is desired.

[0045] A new method for suppressing thermal distortion of welded members is described below. As will be explained in detail later, after the formation of the main weld MW, an adjustment weld CW shown in Figure 9C is formed to control the bending direction of the welded member 100a, thereby suppressing thermal distortion of the welded member 100a.

[0046] As shown in Figures 9A to 9C and Figure 10A, the second embodiment differs from the first embodiment in that the welded member 100a has an adjustment weld section CW. Since the basic configuration of the welded member 100a is the same as in the first embodiment, the same reference numerals are used for components common to the first embodiment, and their descriptions are omitted. The description will focus on the components that differ from the first embodiment.

[0047] [2-1. Structure] As shown in Figure 9C, the adjustment weld CW is formed in the overlapping portion of the first part 1 and the second part 2, specifically, in the direction along the central axis A, at the same position as where the sub-weld SW and the main weld MW are formed. The adjustment weld CW is formed by partially welding a welding path that circumferentially surrounds the outer surfaces of the first part 1 and the second part 2. As shown in Figure 10A, in this embodiment, the shape of the adjustment weld CW is linear, extending a predetermined length along the circumferential direction, and one adjustment weld CW is formed, for example, by arc welding. The adjustment weld CW is positioned on the welding path where thermal strain can be generated in the opposite direction to the thermal strain caused by the formation of the main weld MW after the formation of the two sub-welds SW.

[0048] [2-2. Method for manufacturing welded members] Next, the manufacturing method for the welded member 100a will be explained using Figures 9A to 9C and Figure 10A. Specifically, the welding method between the first part 1 and the second part 2 included in the manufacturing method of the welded member 100a will be explained.

[0049] First, the end of the second part 2 is inserted into the opening at one end of the first part 1 to connect the first part 1 and the second part 2. Then, as shown in Figures 9A and 10A, the first part 1 and the second part 2 are partially welded in the circumferential direction so that two opposing sub-welds SW are formed with respect to the central axis A.

[0050] Next, as shown in Figures 9B and 10A, the first part 1 and the second part 2 are welded together all around the circumference along the circumferential direction so that the main weld MW is formed on top of the sub-weld SW after the sub-weld SW has been formed.

[0051] Next, as shown in Figures 9C and 10A, the first part 1 and the second part 2 are further partially welded in the circumferential direction so that after the main weld MW is formed, an adjustment weld CW is formed on top of the main weld MW. At this time, the adjustment weld CW is formed at a position on the welding path where thermal strain in the opposite direction to the thermal strain in the first direction D1 or second direction D2 caused by the formation of the main weld MW after the formation of the two sub-welds SW is generated.

[0052] Specifically, as shown in Figures 10A to 10D, if the welding start / end point S of the main weld MW is located on the first welding path on the side of the first direction D1 relative to the straight line L, the adjustment weld CW is positioned approximately in the center of the second welding path on the side of the second direction D2 relative to the straight line L. This makes it easier for the thermal strain in the first direction D1 caused by the formation of the main weld MW to be offset by the thermal strain in the second direction D2 caused by the formation of the adjustment weld CW.

[0053] Furthermore, as shown in Figure 10E, if the welding start / end point S of the main weld MW is located on the second welding path which is on the second direction D2 side of the straight line L, the adjustment weld CW is positioned approximately in the center of the first welding path which is on the first direction D1 side of the straight line L. This makes it easier for the thermal strain in the second direction D2 caused by the formation of the main weld MW to be offset by the thermal strain in the first direction D1 caused by the formation of the adjustment weld CW.

[0054] As described above, after the formation of the main weld MW, an adjustment weld CW is formed to control the bending direction of the welded member 100a, thereby suppressing thermal distortion of the welded member 100a.

[0055] [2-3. Effects] According to the second embodiment described in detail above, the following effects can be obtained. (3a) In the second embodiment, after the formation of the two sub-welds SW and the main weld MW, an adjustment weld CW is formed that causes thermal distortion of the weld member 100a in a direction opposite to the first direction D1 or second direction D2 in which the weld member 100a undergoes thermal distortion. Therefore, the direction in which the weld member 100a bends can be controlled, and the deformation occurring in the main weld MW can be offset by the deformation occurring in the adjustment weld CW. Thus, thermal distortion of the weld member 100a can be suppressed.

[0056] [2-4. Other Embodiments] Although a second embodiment of this disclosure has been described above, it goes without saying that this disclosure is not limited to the second embodiment and can take various forms.

[0057] (4a) In the second embodiment described above, two sub-welds SW were formed, but the number of sub-welds is not limited to this. For example, as shown in Figure 11, it is not necessary for any sub-welds SW to be formed. Specifically, it is possible that no sub-welds SW are formed before the main weld MW is formed. That is, the main weld MW and the adjustment weld CW may be formed. In this case, the formation of the main weld MW causes thermal strain in the direction from the central axis A toward the welding start point S. For this reason, the adjustment weld CW is positioned such that its circumferential center point is approximately 180° away from the welding start point S when viewed along the central axis A. Specifically, the circumferential center point of the adjustment weld CW is positioned on the extension of the straight line connecting the welding start point S and the central axis A. That is, the adjustment weld CW and the welding start point S face each other with the central axis A as the center. This allows the bending direction of the welded member 100a to be controlled, and the thermal strain occurring in the main weld MW in the direction from the central axis A toward the welding start point S can be offset by the thermal strain occurring in the adjustment weld CW in the opposite direction. Therefore, thermal strain of the welded member 100a can be suppressed.

[0058] Furthermore, as shown in Figure 12, for example, one sub-weld section SW may be formed. Specifically, after the formation of one sub-weld section SW, a main weld section MW may be formed, and then an adjustment weld section CW may be formed. In this case as well, the formation of the main weld section MW causes thermal strain in the direction from the central axis A toward the welding start point S. Note that even if the relative position of the welding start point S and one sub-weld section SW on the welding path changes, thermal strain will still occur in the direction from the central axis A toward the welding start point S. For this reason, the adjustment weld section CW and the welding start point S are arranged to face each other with respect to the central axis A. This allows the bending direction of the welded member 100a to be controlled, and the thermal strain in the direction from the central axis A toward the welding start point S that occurs in the main weld section MW can be offset by the thermal strain in the opposite direction that occurs in the adjustment weld section CW. Thus, thermal strain of the welded member 100a can be suppressed.

[0059] Furthermore, as shown in Figures 13A and 13B, for example, three sub-weld sections SW may be formed at equal intervals along the circumferential direction. Specifically, after the formation of the three sub-weld sections SW, the main weld section MW may be formed, and then an adjustment weld section CW may be formed. In this case as well, the formation of the main weld section MW generates thermal strain in the direction from the central axis A toward the welding start point S. Even if the position of the welding start point S on the welding path changes, thermal strain will still be generated in the direction from the central axis A toward the welding start point S. For this reason, the adjustment weld section CW and the welding start point S are arranged to face each other with respect to the central axis A. This allows the bending direction of the welded member 100a to be controlled, and the thermal strain generated in the main weld section MW toward the welding start point S can be offset by the thermal strain generated in the adjustment weld section CW in the opposite direction. Thus, thermal strain of the welded member 100a can be suppressed.

[0060] Furthermore, as shown in Figures 14A and 14B, for example, four sub-weld sections SW may be formed at equal intervals along the circumferential direction. Specifically, after the formation of the four sub-weld sections SW, the main weld section MW may be formed, and then the adjustment weld section CW may be formed. In this case as well, the formation of the main weld section MW causes thermal strain in the direction from the central axis A toward the welding start point S. Even if the position of the welding start point S on the welding path changes, thermal strain will still occur in the direction from the central axis A toward the welding start point S. For this reason, the adjustment weld section CW and the welding start point S are arranged to face each other with respect to the central axis A. This allows the bending direction of the welded member 100a to be controlled, and the thermal strain in the direction from the central axis A toward the welding start point S that occurs in the main weld section MW can be offset by the thermal strain in the opposite direction that occurs in the adjustment weld section CW. Thus, thermal strain of the welded member 100a can be suppressed.

[0061] (4b) In the second embodiment described above, the main weld MW was formed by full-circumferential welding, but the method of forming the main weld is not limited to this. For example, the main weld may be formed by welding a predetermined length of section of a welding path that circles the outer surface of the member. Specifically, as shown in Figure 15, in a cross section perpendicular to the central axis A, the shape of the main weld MWa may be an arc in which the welding path does not close. The circumferential length of the adjustment weld CW is shorter than the circumferential length of the arc-shaped main weld MW.

[0062] In arc-shaped welding, the heat capacity tends to increase at points located in the range from the welding start point of the weld to approximately the center of the circumferential direction of the weld, because the time it takes for the welding heat to be transferred to the workpiece is longer. In the arc-shaped main weld MWa, the deformation point T located in the range from the welding start point S1a of the main weld MWa to approximately the center of the circumferential direction of the main weld MWa is the position that becomes the center of the deformation occurring in the main weld MWa. The range from the welding start point of the main weld to approximately the center of the circumferential direction of the main weld is, for example, approximately 180 degrees from the welding start point when the circumferential angle of the main weld is 360 degrees, and approximately 90 degrees from the welding start point when the circumferential angle of the main weld is 180 degrees. Therefore, as shown in Figure 15, when there is no sub-weld SW and an adjustment weld CW is formed after the main weld MWa is formed, thermal strain occurs in the direction from the central axis A toward the deformation point T due to the main weld MWa. Therefore, the adjustment weld CW and the deformation point T are positioned opposite each other with respect to the central axis A. This allows the bending direction of the welded member 100a to be controlled, and the thermal strain generated in the main weld MW in the direction from the central axis A to the deformation point T can be offset by the thermal strain generated in the adjustment weld CW in the opposite direction. Thus, thermal strain of the welded member 100a can be suppressed.

[0063] For convenience, Figure 15 shows the deformation point T as being at the center of the main weld MWa. However, the deformation point T is not limited to the center, as long as it is at the center of deformation within the range from the welding start point S1a of the main weld MWa to approximately the center in the circumferential direction of the main weld MWa. Furthermore, the position of the welding start point S1a is not limited to the position shown in Figure 15, but may be located at the other end of the arc.

[0064] (4c) In the second embodiment described above, the shape of the adjustment weld CW was linear, but the shape of the adjustment weld is not limited to this. For example, the adjustment weld may be formed as a point.

[0065] (4d) In the second embodiment described above, there was one adjustment weld CW, but for example, multiple adjustment welds may be formed.

[0066] [3. Other embodiments common to the first and second embodiments] (5a) In the above embodiments, the shape of the sub-weld SW was point-shaped, but the shape of the sub-weld is not limited to this. For example, the sub-weld may be formed in a linear shape extending along the circumferential direction. For example, as shown in Figure 16, if a plurality of linearly formed sub-weld SWa are provided, each sub-weld SWa may be arranged at equal intervals with space between them so as not to overlap. The three sub-weld SWa shown in Figure 16 may have the same circumferential length. Also, for example, as shown in Figure 17, the three sub-weld SWb1 to SWb3 arranged with space between them so as not to overlap may have different circumferential lengths.

[0067] Furthermore, if multiple sub-welds are provided, they do not need to be arranged at equal intervals. Also, for example, both point-shaped and linear sub-welds may be provided.

[0068] (5b) In each of the above embodiments, the main weld was welded all around in a single operation in the circumferential direction. However, for example, the all-circumferential welding may be performed by welding in multiple steps. For example, as shown in Figure 18, after the formation of two sub-welds SW, the main weld MWb may be formed by welding in two steps such that the welding start points S1 and S2 overlap. In this case as well, by forming the main weld MWb such that the welding start points S1 and S2 are located on the first welding path on the side of the first direction D1 from the straight line L, thermal strain in the first direction D1 can be generated. Although not shown in the figure, after the formation of the main weld MWb, an adjustment weld CW may be formed approximately in the center of the second welding path on the side of the second direction D2 from the straight line L. This allows the thermal strain in the first direction D1 caused by the formation of the main weld MW to be offset by the thermal strain in the second direction D2 caused by the formation of the adjustment weld CW.

[0069] (5c) In each of the above embodiments, the first part 1 and the second part 2 were connected with one end of the first part 1 inserted into an opening at one end. However, for example, the first part and the second part may be connected with one end of the first part and the end of the second part butted together. In this case, the sub-weld, main weld and adjustment weld are formed at the portion where the first part and the second part are connected.

[0070] Furthermore, the first part 1 and the second part 2 may be arranged such that the end of the first part 1 is inserted into the opening on one end of the second part 2.

[0071] (5d) In the above embodiments, the first part 1 and the second part 2 were cylindrical parts, but the shapes of the first part and the second part are not limited to these. For example, the first part and the second part may be cylindrical parts of a shape other than a circle, or they may be solid parts. The solid parts may be plate-shaped, block-shaped, columnar, etc.

[0072] (5e) In each of the above embodiments, the central axis A of the welded member 100 extended in a straight line, but for example, the central axis of the welded member may be curved.

[0073] (5f) The functions of one component in each of the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. Also, some of the configurations of the above embodiments may be omitted. Also, at least some of the configurations of the above embodiments may be added to, replaced with, or otherwise modified in relation to the configurations of other above embodiments.

[0074] [Technical concepts disclosed in this specification] [Item 1] A method for manufacturing a welded member in which a first part and a second part are welded together, The first part and the second part are welded together such that a main weld is formed that extends in the circumferential direction with respect to the axis of the welded member, which extends in the direction in which the first part and the second part are aligned. The aforementioned main weld extends from the welding start point to the welding end point, The deformation point is defined as a position located within the range from the welding start point of the main weld to approximately the center of the circumferential direction in the main weld, and which contributes significantly to the deformation occurring in the main weld. A method for manufacturing a welded member, wherein the deformation point is positioned at a location that contributes to thermal deformation of the welded member.

[0075] [Item 2] A method for manufacturing a welded member as described in item 1, The method further comprises welding the first part and the second part such that one or more sub-welded sections are formed to temporarily fix the second part to the first part, A method for manufacturing a welded member, wherein the main welded portion is formed after the sub-welded portion is formed.

[0076] [Item 3] A method for manufacturing a welded member as described in item 2, A method for manufacturing a welded member, wherein two or three sub-welded sections are formed.

[0077] [Item 4] A method for manufacturing a welded member as described in item 3, Two of the aforementioned sub-welded sections are formed, A method for manufacturing a welded member, wherein the two sub-welded portions are arranged approximately 180° apart from each other in the circumferential direction.

[0078] [Item 5] A method for manufacturing a welded member as described in any one of items 2 to 4, The main welded section is formed by full-circumferential welding. A method for manufacturing a welded member, wherein the welding start point of the main weld portion is positioned so as not to overlap with the sub-welded portion.

[0079] [Item 6] A method for manufacturing a welded member as described in item 5, A method for manufacturing a welded member, wherein the deformation point is the welding start point and the welding end point of the main welded portion.

[0080] [Item 7] A method for manufacturing a welded member as described in any one of items 2 to 5, The first and second parts are cylindrical parts, The end of the second part is inserted into the first part. A method for manufacturing a welded member, wherein the main weld and the sub-weld are formed in the portion where the first part and the second part overlap.

[0081] [Item 8] A method for manufacturing a welded member as described in any one of items 1 to 7, A method for manufacturing a welded member, further comprising welding the first part and the second part such that, after the formation of the main weld, an adjustment weld is formed that causes the welded member to be thermally distorted in a direction opposite to the direction in which the welded member is thermally distorted. [Explanation of Symbols]

[0082] 1...First part, 2...Second part, 100, 100a...Welding member, A...Central axis, CW...Adjustment weld, L...Straight line, MW, MWa, MWb...Main weld, S...Start and end point of welding, S1, S1a, S2...Start point of welding, SW, SWa, SWb1~SWb3...Sub-weld, T...Deformation point.

Claims

1. A method for manufacturing a welded member in which a first part and a second part are welded together, The first and second parts are welded together along a predetermined axis such that two sub-welds are formed to temporarily fix the second part to the first part, After the formation of the two sub-welded sections, the first and second parts are welded together around their entire circumference so that a main weld extending in the circumferential direction around the axis is formed. Equipped with, The two sub-welded sections are arranged approximately 180° apart from each other in the circumferential direction. The aforementioned main weld extends from the welding start point to the welding end point, A method for manufacturing a welded member, wherein the welding start point and welding end point of the main weld are positioned in a location that does not overlap with the two sub-welded sections in the circumferential direction.

2. A method for manufacturing a welded member according to claim 1, The first and second parts are cylindrical parts, The end of the second part is inserted into the first part. A method for manufacturing a welded member, wherein the main weld and the two sub-welds are formed in the portion where the first part and the second part overlap.

3. A method for manufacturing a welded member according to claim 1 or claim 2, The first part and the second part are further welded together such that an adjustment weld is formed after the main weld is formed. A method for manufacturing a welded member, wherein the adjustment weld portion is formed on one of two paths that are part of the circular path that encircles the first and second parts, and which is located on the path opposite to the path where the welding start and end point of the main weld portion is located, between the two paths that are situated on a straight line connecting the two sub-welded portions.

4. A method for manufacturing a welded member according to Claim 3, A method for manufacturing a welded member, wherein the adjustment weld portion is formed by overlapping it with the main weld portion.

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