Welding method and manufacturing method for pressure vessel

Abstract

To achieve reduction in manufacturing cost when welding with use of a butt joint with plate thickness difference.SOLUTION: A welding method for welding a first component 1 and a second component 2 with plate thickness difference using a butt joint performs welding by correcting a focal position of high energy beam when keyhole welding from a butt surface 3 between a face 12 of the first component 1 and a face 22 of the second component 2 to a side of a face near a high energy beam irradiation head 4 with a step difference 73, which occurs when the face 12 of the first component 1 and the face 22 of the second component 2 are butted together by a specified quantity.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a welding method and a method for manufacturing a pressure vessel. [Background technology]

[0002] For example, Patent Document 1 describes a method for welding together thick-walled metal workpieces that are joined by at least two weld layers and have a wall thickness of greater than 6 mm, and for providing a groove preparation portion on the cross-section of the weld object for a full-surface connection before welding in the welding area for the at least two weld layers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5519494 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, when welding a butt joint with a difference in plate thickness, if taper processing is performed in addition to groove processing, precision control of the processed part is required, making it difficult to reduce manufacturing costs. In addition, when post-processing is performed to improve the appearance of the welded part, such as additional welding or cutting, it becomes even more difficult to reduce manufacturing costs.

[0005] An object of the present disclosure is to reduce manufacturing costs when welding butt joints having different plate thicknesses. [Means for solving the problem]

[0006] The welding method disclosed herein is a welding method for butt-welding a first member and a second member having different thicknesses, and includes a step for welding the first member and the second member by correcting the focal position of a high-energy beam during keyhole welding by a predetermined amount from a butt surface between the first member and the second member to a surface closer to the irradiation head of the high-energy beam, the step being generated when the first member and the second member are butted together. death The predetermined amount may be 90% or less of the focused diameter of the focal position. In this case, the amount of melting of the member on the surface close to the irradiation head can be increased. where The predetermined amount may be 50% or less of the focused diameter of the focal position. In this case, the amount of melting of the member on the surface close to the irradiation head can be increased. Also The amount of melting caused by the keyhole welding may be greater on one of the surfaces of the first member and the second member that is closer to the irradiation head than on the other. In this case, the gap between the first member and the second member can be filled more reliably. moreover The keyhole welding may be performed by a main laser, the focus position of which is corrected, and an auxiliary laser disposed around the main laser. In this case, it is possible to melt a wide range. Furthermore, the keyhole welding may be laser welding or electron beam welding, which allows welding with high energy. Furthermore, the welding conditions for the penetration depth Y of the keyhole welding are as follows: TIFF0007667480000001.tif46137 In this case, the penetration depth of the keyhole welding can be ensured. Furthermore, the gap tolerance range GAP between the first member and the second member is TIFF0007667480000002.tif26133 In this case, the gap between the first member and the second member can be filled more reliably.

[0007] Viewed from another perspective, the method for manufacturing a pressure vessel according to the present disclosure is a method for manufacturing a pressure vessel, comprising keyhole welding the pressure vessel using the welding method described above. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram illustrating a welding method according to the first embodiment. [Diagram 2] 11A and 11B are diagrams for explaining the amount of correction, where (a) illustrates an example where the amount of correction is 0%, (b) illustrates an example where the amount of correction is 50%, and (c) illustrates an example where the amount of correction is 90%. [Diagram 3] FIG. 11 is a diagram for explaining an application example using multiple high-energy beams, where (a) is a diagram of the first member and the second member as viewed from the irradiation head side, and (b) is a cross-sectional view taken along line IIIb-IIIb in (a). [Figure 4] FIG. 13 is a diagram illustrating a welded portion of a butt joint formed by a main beam and an auxiliary beam. [Diagram 5] 6A to 6C are diagrams illustrating a welding method according to a second embodiment. [Figure 6] FIG. 11 is a diagram for explaining an application example using multiple high-energy beams, where (a) is a diagram of the first member and the second member as viewed from the irradiation head side, and (b) is a cross-sectional view taken along line VIb-VIb in (a). [Figure 7] FIG. 13 is a diagram illustrating a welded portion of a butt joint formed by a main beam and an auxiliary beam. [Figure 8] 13A to 13C are diagrams illustrating a welding method according to a third embodiment. [Figure 9] FIG. 2 is a diagram for explaining an irradiation head, where (a) is a plan view showing an irradiation head in the first embodiment and the second embodiment, and (b) is a plan view showing an irradiation head in a first modified example. [Figure 10] 13A and 13B are diagrams for explaining a welding method in a second modified example, where (a) is a diagram of the first member and the second member as viewed from the irradiation head side, and (b) is a cross-sectional view taken along line Xb-Xb in (a). [Figure 11]FIG. 13 is a diagram for explaining the welding conditions, where (a) is a diagram of the first and second members as viewed from the irradiation head side, (b) is a cross-sectional view taken along line XIb-XIb in (a), and (c) shows the weld formed by keyhole welding. [Figure 12] 1A and 1B are diagrams for explaining application examples in which the present embodiment is applied to a pressure vessel, and show examples in which the thickness of the partition wall of the pressure vessel is different. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. [First embodiment] FIG. 1 is a diagram illustrating a welding method according to a first embodiment. The first embodiment shown in Fig. 1 is a case where a first member 1 and a second member 2 are butt-welded. The welding in this case is keyhole welding, which utilizes the fact that a high power density causes metal vaporization and creates a depression on the surface.

[0010] An irradiation head 4 for laser welding is disposed facing the end face 11 of the first member 1 and the end face 21 of the second member 2. The irradiation head 4 includes a condenser lens (not shown) that condenses laser light transmitted from an oscillator 8 through an optical fiber 81, and irradiates a high-energy beam 41 for keyhole welding in an irradiation direction A.

[0011] More specifically, a virtual abutment surface 3 indicated by a dashed line is located at the abutment portion between the end surface 11 of the first member 1 and the end surface 21 of the second member 2. In other words, the abutment surface 3 is located between the end surface 11 of the first member 1 and the end surface 21 of the second member 2.

[0012] Here, the first member 1 has a plate thickness t1, and the second member 2 has a plate thickness t2. The plate thicknesses t1 and t2 are not the same, and there is a plate thickness difference between the first member 1 and the second member 2. More specifically, in the first embodiment, the plate thickness t1 of the first member 1 is thinner than the plate thickness t2 of the second member 2 (t1 <t2)。

[0013] Further, the second member 2 is formed with a step 23 extending towards the first member 1. The step 23 has a bottom surface 24 facing the inner surface 13 of the first member 1. Thus, the step 23 has a generally L-shaped cross section formed by the end surface 21 and the bottom surface 24. The inner surface 13 referred to here is located on the opposite side to the surface 12 of the first member 1. Further, a chamfered portion 14 is formed at a portion connecting the end surface 11 and the inner surface 13 of the first member 1 to each other. More specifically, the step 23 of the second member 2 is located on the side farther from the surface 22 of the first member 1 in the irradiation direction A. The first member 1 and the second member 2 may be in the shape of a flat plate or a cylinder.

[0014] Next, the positional relationship between the surface 12 of the first member 1 and the surface 22 of the second member 2 with respect to the irradiation head 4 when the first member 1 and the second member 2 are butted against each other will be described. The surface 12 of the first member 1 and the surface 22 of the second member 2 are located at different positions relative to the irradiation head 4 in the irradiation direction A. That is, when the end surface 11 of the first member 1 and the end surface 21 of the second member 2 are butted against each other, a step portion 73 is generated in the second member 2. Such a step portion 73 is a corner where the end surface 21 and the surface 22 of the second member 2 are connected to each other. More specifically, in the case of the first embodiment, the surface 22 of the second member 2 is closer to the irradiation head 4 than the surface 12 of the first member 1. In other words, the surface 22 of the second member 2 having a thick plate thickness is closer to the irradiation head 4, and the surface 12 of the first member 1 having a thin plate thickness is farther from the irradiation head 4.

[0015] The high-energy beam 41 of the irradiation head 4 is focused on the surface 22 of the second member 2 which is closer to the irradiation head 4 , rather than on the surface 12 of the first member 2 which is farther from the irradiation head 4 . The focal position of the high-energy beam 41 is not located on the butted surface 3 but is shifted in the direction of the surface 22 of the second member 2 , which is the surface closer to the irradiation head 4 . The amount of deviation of the focal position is a predetermined amount 71. This deviation is obtained by correcting the focal position of the high-energy beam 41 from the position of the abutting surface 3 toward the second member 2 in order to accommodate the step generated by the first member 1 and the second member 2. The amount of deviation can be called a correction amount.

[0016] As described above, in the first embodiment, the focal position of high energy beam 41 during keyhole welding is shifted by a predetermined amount 71 from the butted surfaces 3 toward the surface 22 of the second member 2 . The gap 72 at the butted portion between the end face 11 of the first member 1 and the end face 21 of the second member 2 is within a predetermined range. This range is called the gap tolerance. The details will be described later.

[0017] 1 shows a schematic configuration example in which keyhole welding is performed by laser welding using a high-power laser beam. Instead of the above-mentioned laser welding, which is one type of beam welding, keyhole welding may be performed by electron beam welding. Such electron beam welding uses high energy obtained by accelerating electrons emitted from, for example, a vacuum tube. To explain a schematic configuration example of electron beam welding, an electron gun is provided with a filament (cathode), an anode (positive electrode), and a Wehnelt electrode (grid). In a high vacuum state, thermoelectrons emitted from the tip of the filament heated by a heating power source are converged by the Wehnelt electrode and accelerated by the anode. Then, the thermoelectrons are converged by an electromagnetic convergence coil using the action of an electromagnetic field, generating an electron beam, which is a high-energy beam 41.

[0018] FIG. 2 is a diagram for explaining the correction amount, where (a) illustrates a case where the correction amount is 0%, (b) illustrates a case where the correction amount is 50%, and (c) illustrates a case where the correction amount is 90%. 2(a), the focal position of the high-energy beam 41 is aimed at the butt surfaces 3 and is not corrected. More specifically, the high-energy beam 41 (see FIG. 1) is focused as a focusing area 91 centered on a focusing position 90, and has a focusing diameter of 70.

[0019] 2(b) shows an example in which the focal position of the high-energy beam 41 is shifted by a predetermined amount 71 from the butting surface 3 toward the second member 2, and the correction amount is 50%. More specifically, in FIG. 2(b), the high-energy beam 41 is focused on a focusing region 92 centered on a focusing position 90, and the focused diameter is the same as in FIG. 2(a).

[0020] 2(b), in order to explain the amount of correction, light collection area 91 shown in FIG. 2(a) is shown by a dashed line in contrast to light collection area 92 which is shifted by a predetermined amount 71. The predetermined amount 71 is a ratio to light collection diameter 70, and is 50% as a correction amount. In other words, light collection area 92 in FIG. 2(b) is shifted in the direction of second member 2 by an amount that is half the light collection diameter 70 of light collection area 91 in FIG. 2(a).

[0021] 2(c) shows an example in which the focal position of the high-energy beam 41 is shifted from the butt surface 3 toward the second member 2 by a predetermined amount 71, which is further shifted toward the second member 2 than in the example of FIG. 2(b), and the correction amount is 90%. More specifically, in FIG. 2(c), the high-energy beam 41 is focused on a focusing region 93 centered on a focusing position 90 on the surface 22 of the second member 2, and the focused diameter is the same as in FIG. 2(a) and FIG. 2(b).

[0022] 2(c) also shows the light collection area 91 shown in FIG. 2(a) by a dashed line in contrast to the light collection area 93 which is shifted by a predetermined amount 71. The light collection area 93 in FIG. 2(c) is shifted in the direction of the second member 2 by an amount of 90% of the light collection diameter 70 of the light collection area 91.

[0023] In this way, by increasing the predetermined amount 71 as the correction amount, the amount of the high-energy beam 41 irradiated to the surface 22 of the second member 2 increases, the melted area of ​​the second member 2 becomes wider, and the melted amount of the second member 2 having the step portion 73 (see FIG. 1) increases. The predetermined amount 71 is 90% or less of the focused light diameter at the focal position. On the other hand, if the predetermined amount 71 as the correction amount becomes too large, the amount of the high-energy beam 41 irradiated to the surface 12 of the first member 1 decreases, and the amount of melting of the first member 1 decreases, which may result in a decrease in the weld strength. Therefore, the predetermined amount 71 is more preferably 50% or less.

[0024] Next, an application example of the first embodiment will be described with reference to FIG. 3A and 3B are diagrams for explaining an application example using multiple high-energy beams 41 and 51, in which (a) is a diagram of the first member 1 and the second member 2 as viewed from the side of the high-energy beams 41 and 51, and (b) is a cross-sectional view taken along line IIIb-IIIb in (a). Fig. 3B corresponds to Fig. 1. In (a) and (b), the dashed dotted lines indicating the butting surfaces 3 are shown continuously to clarify the corresponding positional relationship. As shown in FIG. 3(a), in an application example of the first embodiment, a high-energy beam 51 is disposed around a high-energy beam 41. The high energy beam 41 and the high energy beam 51 are integrated and move together in the welding direction B.

[0025] 3(b), a high-energy beam 41 is irradiated from the irradiation head 4, and another high-energy beam 51 is irradiated. The irradiation area of ​​the high-energy beam 51 is the surrounding area excluding the irradiation area of ​​the high-energy beam 41, and has a so-called doughnut shape. In the following description, the high energy beam 41 from the irradiation head 4 may be referred to as the main beam 41, and the high energy beam 51 may be referred to as the auxiliary beam 51. The main beam 41 has a higher output than the auxiliary beam 51.

[0026] 3(b), the main beam 41 is irradiated onto the surface 22 of the second member 2, and the auxiliary beam 51 is irradiated onto both the surface 12 of the first member 1 and the surface 22 of the second member 2. Due to the misalignment of the irradiation head 4, the irradiation amount of the auxiliary beam 51 is greater on the surface 22 of the second member 2 than on the surface 12 of the first member 1. Furthermore, by adjusting the focal points of the high-energy beams 41 and 51 to the surface 22 of the second member 2, the second member 2 can be irradiated with the high-energy beams 41 and 51 having higher energy than the first member 1.

[0027] Fig. 4 is a diagram illustrating a welded portion 6 of a butt joint formed by a main beam 41 and an auxiliary beam 51. Note that Fig. 4 shows the state after melting, while the above-mentioned Fig. 3 shows the state before melting. As shown in Fig. 4, a portion including the step portion 73 is melted by the main beam 41 and the auxiliary beam 51. The molten metal moves to the first member 1 side and enters the gap 72, thereby filling the gap 72 including the space widened by the chamfered portion 14, and forming the welded portion 6 of the butt surface joint. The gap 72 is filled by the melting of both the first member 1 and the second member 2. To explain further, the amount of melting of the second member 2 filling the gap 72 is greater than the amount of melting of the first member 1.

[0028] In this way, by adopting a welding method in which the focal position of the main beam 41 is shifted by a predetermined amount toward the surface 22 of the second member 2, which is the surface closer to the irradiation head 4, rather than to the position of the butt joint 3, any gap 72 is filled to form a weld 6. In addition, it becomes possible to omit groove processing and taper processing when welding the first member 1 and the second member 2 at a butt joint. Although an example of keyhole welding using the main beam 41 and the auxiliary beam 51 has been described, keyhole welding using only the main beam 41 without using the auxiliary beam 51 is similar, and therefore illustrations and detailed description thereof will be omitted.

[0029] [Second embodiment] Next, a second embodiment will be described. Since the second embodiment has a common configuration with the first embodiment, the common configuration is denoted by the same reference numerals in the drawings, but the description thereof may be omitted in the specification. FIG. 5 is a diagram for explaining a welding method in the second embodiment, and corresponds to FIG. 1 for explaining the first embodiment. The second embodiment shown in Fig. 5 shows a welding method in which the first member 1 and the second member 2 are welded by a butt joint, and the irradiation head 4 is the same as in the case of the first embodiment (see Fig. 1) in that it irradiates a high-energy beam 41.

[0030] Here, the plate thickness t1 of the first member 1 is the same as in the case of the first embodiment (see Fig. 1) in that it is thinner than the plate thickness t2 of the second member 2 (t1 < t2). On the other hand, the surface 12 of the first member 1 is different from the case of the first embodiment (see Fig. 1) in which the surface 22 of the second member 2 is closer to the irradiation head 4 in that the surface 12 of the first member 1 is closer to the irradiation head 4 than the surface 22 of the second member 2.

[0031] In the second embodiment, the high-energy beam 41 of the irradiation head 4 is focused on the surface 12 of the first member 1, which is the surface closer to the irradiation head 4, and the focal position of the high-energy beam 41 is shifted not in the direction of the surface 22 of the second member 2, which is the side of the surface farther from the irradiation head 4, but in the direction of the surface 12 of the first member 1, which is the side of the surface closer to the irradiation head 4. In this regard, it is different from the case of the first embodiment (see Fig. 1). Note that the first member 1 and the second member 2 may be flat or cylindrical, as in the case of the first embodiment.

[0032] Next, an application example in the second embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram for explaining an application example using a plurality of irradiation heads 4 (a) is a view when the first member 1 and the second member 2 are viewed from the side of the irradiation heads 4 and 5, and (b) is a cross-sectional view taken along line VIb-VIb in (a). Fig. 6 corresponds to Fig. 3 for explaining the first embodiment. The application example in the second embodiment shown in Fig. 6(a) is the same as in the case of the first embodiment in that a high-energy beam 51 that moves in the welding direction B together with the high-energy beam 41 is disposed around the high-energy beam 41.

[0033] As shown in FIG. 6(b), this embodiment differs from the first embodiment in that the main beam 41 is irradiated to the surface 12 of the first member 1, and the auxiliary beam 51 is irradiated to both the surface 12 of the first member 1 and the surface 22 of the second member 2. Also, the irradiation amount of the auxiliary beam 51 is greater on the surface 12 of the first member 1 than on the surface 22 of the second member 2 due to the deviation of the main beam 41, which is different from the first embodiment. In this manner, the present embodiment differs from the first embodiment in that the first member 1 can be irradiated with high-energy beams 41, 51 having higher energy than the second member 2.

[0034] FIG. 7 is a diagram for explaining a welded portion 6 of a butt joint formed by a main beam 41 and an auxiliary beam 51, and corresponds to FIG. 4 for explaining the first embodiment. 7, the portion including the step portion 73 is melted by the main beam 41 and the auxiliary beam 51. The molten metal moves to the second member 2 side and enters the gap 72, thereby filling the gap 72 including the space expanded by the chamfered portion 14, and the welded portion 6 of the butt surface joint is formed.

[0035] [Third embodiment] Next, a third embodiment will be described. Since the third embodiment has a common configuration with the first embodiment, the common configuration is denoted by the same reference numerals in the drawings, but the description thereof may be omitted in the specification. FIG. 8 is a diagram for explaining a welding method in the third embodiment, and corresponds to FIG. 1 for explaining the first embodiment. The third embodiment shown in FIG. 8 illustrates a welding method for welding a first member 1 and a second member 2 together with a butt joint, and the irradiation head 4 is the same as that in the first embodiment (see FIG. 1) in that it irradiates a high-energy beam 41.

[0036] Here, the plate thickness t1 of the first member 1 is thicker than the plate thickness t2 of the second member 2 (t1>t2), which differs from the first embodiment (see FIG. 1) and also from the second embodiment (see FIG. 5). On the other hand, surface 12 of first member 1 is closer to irradiation head 4 than surface 22 of second member 2, which is different from the first embodiment (see Figure 1) but the same as the second embodiment (see Figure 5).

[0037] In the third embodiment, the high-energy beam 41 of the irradiation head 4 is focused on the surface 12 of the first member 1, which is the surface closer to the irradiation head 4, rather than the surface 22 of the second member 2, which is the surface farther from the irradiation head 4. Also, in the third embodiment, the focal position of the high-energy beam 41 is shifted in the direction of the surface 12 of the first member 1, which is the surface closer to the irradiation head 4, rather than in the direction of the surface 22 of the second member 2, which is the surface farther from the irradiation head 4. In this respect, it is different from the first embodiment (see FIG. 1) and is the same as the second embodiment (see FIG. 5). Although illustration and description of application examples of the third embodiment will be omitted, it is possible to adopt a configuration similar to that of the application examples of the first and second embodiments (see Figures 3 and 6).

[0038] [Variations] 9A and 9B are diagrams for explaining the high-energy beams 41 and 51, in which (a) is a plan view showing the high-energy beams 41 and 51 in the first and second embodiments, and (b) is a plan view showing the high-energy beams 41, 51A, and 51B in the first modified example. As shown in Fig. 9(a), one high-energy beam 51 is disposed so as to extend circumferentially so as to continuously surround the periphery of the high-energy beam 41. This is the same as the application examples of the first and second embodiments described above (Figs. 3(a) and 6(a)).

[0039] In the first modified example shown in Fig. 9(b), unlike the case of Fig. 9(a), the high-energy beam 41 is surrounded by two high-energy beams 51A and 51B. In other words, in the first modified example, two high-energy beams 51A and 51B with different outer diameters are arranged with the high-energy beam 41 at the center. The high-energy beam 51A has a large diameter, and the high-energy beam 51B has a small diameter. In other words, the high-energy beam 51B is located between the high-energy beam 41 and the high-energy beam 51A. The widths of the high energy beams irradiated from the high energy beams 51A and 51B may be the same or different. The first modification is applicable to any of the first, second, and third embodiments described above.

[0040] FIG. 10 is a diagram for explaining a welding method in the second modified example, in which (a) shows an irradiation head 4 1(b) is a cross-sectional view taken along line Xb-Xb in FIG. 1(a). 10, the high-energy beam 41 is disposed so as to be shifted by a predetermined amount 71 toward the surface 22 of the second member 2, which is the surface closer to the irradiation head 4, with respect to the abutting surface 3. This point is common to the first embodiment described above.

[0041] On the other hand, in the second modified example, in addition to the high-energy beam 41, a high-energy beam 51C and a high-energy beam 51D are provided. The high-energy beam 51C and the high-energy beam 51D are positioned so as to sandwich the high-energy beam 41. In other words, the high-energy beam 41 is positioned between the high-energy beam 51C and the high-energy beam 51D.

[0042] The high-energy beam 51C irradiates the surface 12 of the first member 1, and the high-energy beam 51D irradiates the surface 22 of the second member 2. More specifically, unlike the auxiliary beam 51 shown in the above-mentioned application example (see FIG. 3(b) and FIG. 6(b)), the high-energy beams 51C and 51D are not doughnut-shaped but are circular in shape including the center.

[0043] Moreover, the irradiation areas of the high-energy beam 51C and the high-energy beam 51D have different outer diameters, and the irradiation area of ​​the high-energy beam 51D has a larger outer diameter and is wider than the irradiation area of ​​the high-energy beam 51C. Therefore, more high energy is input to the second member 2 having the step portion 73, and the amount of melting of the second member 2 increases. In this way, according to the second modified example, the energy irradiated to the thicker second member can be made high-output or wide-range.

[0044] In the above-described first embodiment and the like, an example is shown in which the high-energy beam 41 and the high-energy beams 51, 51C to 51D are irradiated perpendicularly to the surfaces 12, 22, but the present invention is not limited to this. That is, in addition to a welding method in which the irradiation angle is perpendicular, the irradiation angle may be oblique.

[0045] 11 is a diagram for explaining the welding conditions, where (a) is a diagram of the first member 1 and the second member 2 as viewed from the irradiation head 4, (b) is a cross-sectional view taken along line XIb-XIb in (a), and (c) shows the welded portion 6 formed by keyhole welding. Note that, for example, Fig. 11(a) corresponds to Fig. 5, (b) corresponds to Fig. 6(b), and (c) corresponds to Fig. 7.

[0046] 11(b), the first member 1, which is the thinner of the first member 1 and the second member 2, has a plate thickness t, its chamfered portion 14 has a chamfer length c, and the main beam 41 is at a position of a correction amount p. Also, the main beam 41 has a beam output w. Also, as shown in FIG. 1(a), it is assumed that the main beam 41 moves in the welding direction B at a speed s during welding. The penetration depth Y shown in FIG.

[0047]

number

[0048] Furthermore, if the focused diameter of the main beam 41 is D as shown in FIG. 11(b), the gap tolerance range GAP, which is the tolerance of the gap 72 when the gap 72 is filled with the molten material of the first member 1 and the second member 2, can be calculated by the following formula. If the gap 72 is larger than the gap tolerance range GAP, it is difficult to form a filled weld 6 (see, for example, FIG. 4).

[0049]

number

[0050] [Example of application] 12 is a diagram for explaining an example of application of this embodiment to a pressure vessel 100, where (a) and (b) show examples of different thicknesses of the partition walls of the pressure vessel 100. Note that the pressure vessel 100 includes a body pipe and a top plate, and for ease of explanation, hereinafter the top plate will be referred to as the first member 1 and the body pipe as the second member 2. In the pressure vessel 100 shown in Fig. 12(a), the outer diameter of the second member 2 is larger than that of the first member 1, and the second member 2 has a step portion 73. For this reason, the welding method according to the first embodiment described above (see Fig. 1, for example) is applied. That is, the focal position of the high-energy beam 41 is shifted toward the second member 2. This allows the pressure vessel 100 to be keyhole welded.

[0051] In the pressure vessel 100 shown in Fig. 12(b), the outer diameter of the second member 2 is smaller than that of the first member 1, and the first member 1 has a step portion 73. For this reason, the welding method according to the second embodiment described above (see Fig. 5, for example) is applied. That is, the focal position of the high-energy beam 41 is shifted toward the first member 1. This makes it possible to keyhole weld the pressure vessel 100.

[0052] Although the embodiment has been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims. [Explanation of symbols]

[0053] 1...first member, 11, 21...end surface, 12, 22...surface, 2...second member, 3...butt surface, ..., 4, 5...irradiation head, 41, 51...high energy beam, 6...welded portion, 70...focused beam diameter, 73...step portion, ..., 71...predetermined amount, 100...pressure vessel

Claims

1. A welding method for butt-welding a first member and a second member having a plate thickness difference, comprising: a focal position of a high-energy beam during keyhole welding is corrected by a predetermined amount from a butted surface between a surface of the first member and a surface of the second member to a surface closer to an irradiation head of the high-energy beam of a step generated when the surface of the first member and the surface of the second member are butted together; The predetermined amount is 90% or less of the light collection diameter at the focal position. Welding method.

2. The predetermined amount is 50% or less of the light collection diameter at the focal position. The welding method according to claim 1.

3. The amount of melting by the keyhole welding is greater on one of the surfaces of the first member and the second member that is closer to the irradiation head than on the other. The welding method according to claim 1.

4. The keyhole welding is performed by a main laser in which the focal position is corrected and an auxiliary laser disposed around the main laser. The welding method according to claim 1.

5. The keyhole welding is laser welding or electron beam welding. The welding method according to claim 1.

6. The welding conditions for the penetration depth Y of the keyhole welding are as follows: That is, The welding method according to claim 1.

7. The gap tolerance range GAP between the first member and the second member is That is, The welding method according to claim 1.

8. A pressure vessel is keyhole welded using the welding method of claim 1. A method for manufacturing a pressure vessel.

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