Annular area simultaneous welding device, annular area simultaneous welding method, water heater manufacturing method, and compressor manufacturing method

Abstract

To obtain an annular region simultaneous welding device that can easily adjust laser power per unit area without changing the center diameter of a ring-like region to be welded.SOLUTION: An annular region simultaneous welding device includes: a collimator lens 3 that changes a laser beam 2 to parallel light; and a second optical system that converts the laser beam 2 being parallel light to a ring-shape, converges the light and radiates the ring-like irradiation area 7 to a workpiece. In the second optical system, the center diameter of the ring-like irradiation area 7 is unchanged between the second optical system and the workpiece of the second optical system.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an annular area simultaneous welding device that simultaneously welds annular areas using a laser beam, an annular area simultaneous welding method, a water heater manufacturing method, and a compressor manufacturing method. [Background technology]

[0002] Conventionally, circumferential welding using a laser beam has been performed by moving a laser beam focused into a small spot in a circular pattern relative to the workpiece. Since this method can only weld one location per laser beam, there is also a technique in which the laser beam is optically split and focused at multiple locations, and the focused point is mechanically moved to weld a wider area. In this technique, circumferential welding is performed by moving the focused point relative to the workpiece, which takes a long time to complete, and the welding quality deteriorates due to overlap between the welding start point and the welding end point.

[0003] In Patent Document 1, laser light output from a laser oscillator is expanded and collimated by an expander and a collimator, then a parallel ring-shaped beam is formed by a pair of axicon lenses, and the parallel ring-shaped beam is irradiated onto a workpiece to perform ring-shaped processing such as cutting, drilling, welding, exposure, etc., all at once. In addition, the inner and outer diameters of the ring-shaped beam on the workpiece are controlled by controlling the distance between the expander and collimator or the distance between the pair of axicon lenses. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-28428 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, it is possible to adjust the inner and outer diameters of the ring-shaped beam by adjusting the distance between the lenses, such as the distance between the expander and collimator or the distance between a pair of axicon lenses. However, in Patent Document 1, when this adjustment is made, the center position of the ring-shaped region of the ring-shaped beam (the central diameter of the ring-shaped region) also changes as the distance between the lenses is adjusted. Therefore, Patent Document 1 has a problem in that it is difficult to adjust the laser power per unit area without changing the central diameter of the ring-shaped region to be welded.

[0006] The present disclosure has been made in consideration of the above, and aims to provide an annular area simultaneous welding device that can easily adjust the laser power per unit area without changing the central diameter of the ring-shaped area to be welded. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the annular area simultaneous welding device in the present disclosure includes a first optical system that converts a laser beam into a parallel beam, and a second optical system that converts the parallel beam into a ring-shaped beam. The axicon lens focuses the converted ring-shaped laser beam onto the workpiece. The light is emitted and a ring-shaped irradiation area is projected onto the workpiece. a condenser lens; and a second optical system, and a simultaneous annular area welding device for simultaneously welding an annular area of ​​a workpiece using a ring-shaped irradiation area, the second optical system comprising: Condenser lens The central diameter of the ring-shaped irradiation area does not change between the laser and the workpiece. [Effects of the Invention]

[0008] The annular area simultaneous welding device of the present disclosure has the advantage of being able to easily adjust the laser power per unit area without changing the central diameter of the ring-shaped area to be welded. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a conceptual diagram showing a configuration example of an annular area simultaneous welding device according to a first embodiment. [Figure 2]FIG. 1 is a cross-sectional view showing an area irradiated with an annular laser beam at a focal point by an annular area simultaneous welding device according to a first embodiment; [Figure 3] FIG. 1 is a diagram showing an area irradiated with an annular laser beam before and after a focal point by an annular area simultaneous welding device according to a first embodiment. [Figure 4] 1 is a conceptual diagram showing a configuration example of an annular area simultaneous welding device according to a second embodiment. [Figure 5] 10 is a conceptual diagram showing a configuration example of an annular area simultaneous welding device according to a fifth embodiment. [Figure 6] FIG. 13 is a diagram showing an example of a workpiece according to a sixth embodiment. [Figure 7] FIG. 10 shows a welding shape according to a sixth embodiment. [Figure 8] FIG. 13 is a diagram showing another example of a workpiece according to the sixth embodiment. [Figure 9] FIG. 13 is a diagram showing another example of a workpiece according to the sixth embodiment. [Figure 10] FIG. 13 is a diagram showing an example of the appearance of a pressure vessel according to an eighth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an annular area simultaneous welding device, an annular area simultaneous welding method, a water heater manufacturing method, and a compressor manufacturing method according to embodiments will be described in detail with reference to the drawings.

[0011] Embodiment 1 1 is a conceptual diagram showing a configuration example of an annular area simultaneous welding apparatus according to embodiment 1. The annular area simultaneous welding apparatus of embodiment 1 includes a fiber laser 1, a collimating lens 3 as a first optical system, an axicon lens 4 and a condenser lens 5 as a second optical system, and a cover glass 9.

[0012] In Figure 1, a laser beam 2 is emitted from the output port of a fiber laser 1, which serves as a laser oscillator. The laser beam 2 diverges at a constant divergence angle as it travels. The laser oscillator may be a YAG laser or a CO2 laser, instead of a fiber laser 1. The laser beam 2 is converted into a parallel beam parallel to the optical axis 20 by a collimating lens 3 and then enters an axicon lens 4. The parallel light entering the axicon lens 4 is deflected toward the periphery by differences in the angle of incidence and the optical path length, which is the distance the light travels within the lens. The ring-shaped laser beam 2 then enters a condenser lens 5, which also serves as an objective lens, where it is focused and converged. The focused laser beam 2 forms a ring-shaped irradiation area 7 at the focal point. By placing a workpiece (not shown) in the irradiation area 7, simultaneous welding of the annular area of ​​the workpiece is possible.

[0013] The laser beam 2 focused into a ring shape has a ring diameter central axis 10 at the position of the central diameter of the ring region. As shown in Fig. 1, the position of the ring diameter central axis 10 on a plane perpendicular to the optical axis 20 does not change in the focused region from the focusing lens 5 to the workpiece.

[0014] FIG. 2 is a cross-sectional view showing the irradiation area 7 of the annular laser beam 2 at the focal point of the annular area simultaneous welding device according to the first embodiment. The laser beam 2 emitted from the annular area simultaneous welding device has a ring-shaped irradiation area 7. Therefore, when the laser is irradiated onto the workpiece, an area equivalent to the irradiation area 7 is melted and solidified simultaneously all around. However, in order to simultaneously melt a certain area, a high-power laser with an output of 500 W or more is required. Furthermore, the workpiece to be irradiated is most preferably an iron-based material with a cylindrical shape such as a pipe.

[0015] A cover glass 9 is placed between the condenser lens 5 and the workpiece to protect the condenser lens 5 and other components from metal vapors generated during melting. The irradiation time of the laser beam 2 on the workpiece is, for example, 0.1 to 5 seconds. The irradiation area 7 here refers to an area where the power density is above a certain level, and is expressed in terms of power per unit area, for example, W / mm 2 A certain threshold is set, and the area above this is defined as the irradiation area. The ring-shaped irradiation area 7 at the focal point has an inner diameter F1, an outer diameter F2, and a ring width W, where W = (F2 - F1) / 2. Here, the inner diameter F1 is in the range of 1 mm to 1000 mm, and the ring width W is in the range of 0.1 mm to 10 mm.

[0016] 3 is a diagram showing an irradiation area 6 of an annular laser beam 2 before and after the focal point in the annular area simultaneous welding device according to the first embodiment. When the inner diameter of the irradiation area 6 is F1', the outer diameter is F2', and the ring width is W', F1'<F1、F2’> The relationship F2, W' > W holds. This relationship holds in both underfocus and overfocus states. Therefore, if the ring width W at the focal point is too small, it can be adjusted by moving the condenser lens 5 closer to or farther away from the irradiation position. In other words, the ring width W of the ring-shaped irradiation area 7 can be changed by defocusing. This allows fine adjustment of the power density by widening or narrowing the irradiation area 7 simply by moving the condenser lens 5 relative to the workpiece.

[0017] In the annular area simultaneous welding apparatus of the first embodiment, as shown in FIG. 1, the axicon lens 4 is configured so that the ring diameter center axis 10, which indicates the position of the central diameter of the ring-shaped laser beam 2, does not change between the focusing lens 5 and the workpiece. In other words, the central diameter of the ring-shaped irradiation areas 6 and 7 does not change between the focusing lens 5 and the workpiece. The central diameter of the ring-shaped laser beam 2 is expressed as (F1 + F2) / 2. Because the position of the ring diameter center axis 10 of the ring-shaped laser beam 2 does not change after the focusing lens 5, changing the workpiece distance, which is the distance between the focusing lens 5 and the workpiece in the direction parallel to the optical axis 20, does not change the position of the ring diameter center axis 10; only the ring width W can be changed. This allows the laser power per unit area to be changed without changing the central diameter of the welding area to be melted. Laser power per unit area is one of the important condition parameters when melting metal, and being able to change only the laser power per unit area by changing the workpiece distance has significant practical advantages.

[0018] In this way, in the first embodiment, by moving the condenser lens 5 and the workpiece relative to each other, only the ring width W can be changed without changing the position of the ring diameter center axis 10 of the ring-shaped laser beam 2. Therefore, by moving the condenser lens 5 and the workpiece relative to each other, it is possible to change the laser power per unit area without changing the central diameter of the welding region.

[0019] Embodiment 2 4 is a conceptual diagram showing a configuration example of an annular area simultaneous welding apparatus according to embodiment 2. The annular area simultaneous welding apparatus according to embodiment 2 includes a fiber laser 1, a collimator lens 3, an axicon lens 40, a condenser lens 5, and a cover glass 9. In embodiment 2, components having the same functions as those in embodiment 1 are denoted by the same reference numerals, and redundant explanations will be omitted.

[0020] In the second embodiment, the axicon lens 40 is selected so that the ring diameter of the ring-shaped laser beam 2 in the irradiation area increases as it approaches the workpiece from the condenser lens 5. In other words, the axicon lens 40 is selected so that the position of the ring diameter center axis 10 of the ring-shaped laser beam 2 moves toward the outer diameter as it approaches the workpiece from the condenser lens 5. The condenser lens 5 then condenses the ring-shaped laser beam 2 in an area outside the diameter of the condenser lens 5.

[0021] This setting allows the diameter of the lens group including the collimator lens 3, the axicon lens 40, the condenser lens 5, etc. to be reduced. Since lens groups are expensive, this leads to cost reduction for the lens group. Furthermore, metal vapor and the like are generated from the molten region, and if the metal vapor adheres to the lens, the lens will be contaminated. However, if the molten region can be formed on the outer diameter side of the lens, it is possible to reduce or avoid contamination of the lens by metal vapor and the like.

[0022] As described above, in the second embodiment, the axicon lens 40 is set so that the ring diameter of the ring-shaped laser beam 2 increases as it approaches the workpiece from the focusing lens 5. This makes it possible to reduce the size of the lens and reduce or avoid contamination of the lens.

[0023] Embodiment 3 In the third embodiment, the axicon lens 4 is set so that F1'=F1, F2'>F2, and W'>W are satisfied in the configuration of the annular area simultaneous welding device shown in Fig. 1. In other words, when the condenser lens 5 and the workpiece are moved relative to each other, only the ring width W can be changed without changing the inner diameter position of the ring-shaped irradiation area.

[0024] 1, the axicon lens 4 may be set so that F1'>F1, F2'=F2, and W'>W are satisfied. In this case, by moving the condenser lens 5 and the workpiece relative to each other, it is possible to change only the ring width W without changing the outer diameter position of the ring-shaped irradiation area.

[0025] In this way, in the third embodiment, when the condenser lens 5 and the workpiece are moved relative to each other, only the ring width W can be changed without changing either the inner or outer diameter position of the ring-shaped irradiation area. Therefore, it is possible to expand the irradiation area or fine-tune the power density while maintaining the inner or outer diameter position of the irradiation area.

[0026] Embodiment 4 In the fourth embodiment, in the configuration of the annular area simultaneous welding device shown in FIG. 1, when the focusing lens 5 and the workpiece are moved relative to each other, the outer diameter position and inner diameter position of the irradiation area are changed while the ring width W is kept constant, thereby making it possible to adjust the ring diameter.

[0027] In the fourth embodiment, the collimator lens 3 in the first embodiment is devised so that the laser beam 2 does not become parallel light after passing through the collimator lens 3. Also, by devising a device including changing the position of the axicon lens 4 in the first embodiment, it is possible to enlarge or reduce the ring-shaped irradiation area while maintaining the ring width W constant. In other words, while maintaining W'=W, F1'>F1, F2'>F2, or while maintaining W'=W, F1' <F1、F2’<F2となるようにしている。

[0028] In this way, in the fourth embodiment, when the condenser lens 5 and the workpiece are moved relative to each other, the ring-shaped irradiation area can be enlarged or reduced while maintaining a constant ring width W. This makes it possible to adjust the ring diameter while keeping the melting width constant, and one optical system can be used to handle objects with various ring diameters.

[0029] Embodiment 5 5 is a conceptual diagram showing a configuration example of an annular area simultaneous welding apparatus according to embodiment 5. The annular area simultaneous welding apparatus according to embodiment 5 includes a fiber laser 1, a collimator lens 3, a condenser group lens 50, and a cover glass 9. In embodiment 5, components having the same functions as those in embodiment 1 are denoted by the same reference numerals, and redundant explanations will be omitted.

[0030] The laser beam 2 emitted from the emission port of the fiber laser 1 spreads as it travels. The laser beam 2 is converted into a parallel beam by the collimator lens 3 and enters the condenser group lens 50. The parallel laser beam 2 that enters the condenser group lens 50 is then focused by the condenser group lens 50. The condenser group lens 50 is an optical lens made up of a large number of condenser lenses, and by dividing and focusing the parallel incident laser beam 2 individually and allocating the irradiation positions, a ring-shaped irradiation area as shown in Figure 2 is obtained at the focusing position. By placing a workpiece in the irradiation area 7, simultaneous welding of the ring-shaped area of ​​the workpiece becomes possible.

[0031] As described above, in the fifth embodiment, a ring-shaped irradiation area is obtained by using the condenser lens group 50 having optical functions equivalent to those of the axicon lens 4 and the condenser lens 5 of the first embodiment, and a ring-shaped irradiation area can be obtained with a simple lens configuration.

[0032] It should be noted that the shape may be square or polygonal instead of ring-shaped by adjusting the irradiation position of each lens of the condenser group lens 50. Furthermore, the condenser group lens 50 may be a diffractive optical element (DOE), which is an optical element with minute irregularities on its surface.

[0033] Embodiment 6 In the sixth embodiment, a welding method using the annular simultaneous welding apparatus according to any one of the first to fifth embodiments is described. FIG. 6 is a diagram illustrating an example of a workpiece according to the sixth embodiment. The workpiece shown in FIG. 6 is a flange joint 33. Consider the case of welding the flange joint 33 shown in FIG. 6. FIG. 6 illustrates the flange joint 33, which is composed of a flat plate with a circular opening and a raised portion around the opening, called a burred joint 31, and a cylindrical pipe 32. A solid shaft member may be used instead of the cylindrical pipe 32. The end face of the burred joint 31 and the end face of the cylindrical pipe 32 are aligned flush with each other, and the flat plate with the burred joint 31 and the cylindrical pipe 32 are fixed together. FIG. 7 illustrates a weld shape 24 according to the sixth embodiment. A laser beam 2 is also shown in FIG. 7.

[0034] A shielding gas may be sprayed onto edge joint 33 to shield it from the atmosphere. Examples of the shielding gas include argon, helium, nitrogen, and mixtures of these. The shielding gas spraying mechanism may be a mechanism that sprays the shielding gas at any timing in response to the irradiation of laser beam 2 in synchronization with the laser oscillator.

[0035] 6 and 7, a hole is drilled in a steel plate and burring 31 is performed to create a raised portion around the hole. A cylindrical tube 32 or a solid shaft member having an outer diameter smaller than the inner diameter of the hole is inserted into the hole. Laser beam 2 is then applied to the opening of the steel plate and the cylindrical tube 32 or the solid shaft member using the annular region simultaneous welding device according to any one of the first to fifth embodiments, thereby joining the two members.

[0036] According to this welding method, there is no need for a multi-axis robot or drive mechanism for scanning the laser beam 2 in accordance with the joining trajectory of the workpieces, or for moving the workpieces, or there is no need to operate a multi-axis robot or drive mechanism for one joining point, so the capital investment for this welding method can be reduced or the processing time using this welding method can be shortened.

[0037] The shape of the joining members may be a simple open circle without burring 31 on the steel plate. The two members to be joined may be arranged so that the rising edge of the open circle with burring 31 or the end of the simple open circle is flush with the end face of the cylindrical tube 32 or solid shaft member, or any step may be provided. The inner and outer diameters of the two members to be joined may be machined into a predetermined shape around the circumference of the joint to help prevent uneven melting.

[0038] Thus, the first welding method according to the sixth embodiment includes the steps of preparing a workpiece by inserting a cylindrical member having an outer diameter smaller than the inner diameter of the opening into an opening of a member having a cylindrical or circular opening formed therein, and irradiating a ring-shaped irradiation area onto the workpiece using an annular area simultaneous welding device according to any one of the first to fifth embodiments.

[0039] Fig. 8 is a diagram showing another example of a workpiece according to embodiment 6. Edge joint 33 shown in Fig. 8 is also formed by a member that has been subjected to burring 31 and a cylindrical tube 32.

[0040] Fig. 9 is a diagram showing another example of a workpiece according to the sixth embodiment. In the joint shown in Fig. 9, a bowl-shaped member 53 is assembled to a cylindrical member 52 to join the two members. That is, the second welding method according to the sixth embodiment includes a step of preparing a workpiece by fitting a bowl-shaped member into the opening of the cylindrical member, and a step of irradiating the workpiece with a ring-shaped irradiation area using the annular area simultaneous welding device according to any one of the first to fifth embodiments.

[0041] Embodiment 7 In embodiment 7, a method for manufacturing a water heater using an annular region simultaneous welding apparatus according to any one of embodiments 1 to 5 is described. The water heater's hot water storage tank is cylindrical, with the upper and lower parts of the tank made of bowl-shaped thin plates. Pipes are connected to the hot water storage tank, and hot water is extracted from the inside of the hot water storage tank through the pipes, or hot water and water are supplied to the inside of the hot water storage tank. Generally, a nipple for connecting the pipes is attached to the hot water storage tank in order to connect the pipes to the hot water storage tank.

[0042] The hot water storage tank and nipple are formed from steel plate such as stainless steel, and the nipple is, for example, a flange joint 33 shown in Figure 6 or Figure 8. The hot water storage tank and nipple, or the heat source side for joining, are moved by a multi-axis robot or drive device in accordance with the joining trajectory, and the hot water storage tank and nipple are joined together.

[0043] That is, the manufacturing method of the water heater of embodiment 7 includes a step of preparing a hot water storage tank and a pipe joint part for connecting the piping to the hot water storage tank, and a step of joining the pipe joint part to the hot water storage tank using the first welding method of embodiment 6.

[0044] By using the annular area simultaneous welding device according to any one of embodiments 1 to 5, the driving device or driving operation for joining the hot water storage tank and the nipple can be reduced, thereby reducing the manufacturing cost or manufacturing time of the water heater.

[0045] Embodiment 8 In the eighth embodiment, a method for manufacturing a compressor using the annular region simultaneous welding apparatus according to any one of the first to fifth embodiments will be described. A pressure vessel, which is the housing of a compressor used in a domestic air conditioner or a commercial air conditioner, is generally composed of a cylindrical side member and bowl-shaped upper and lower members, similar to the hot water tank of the water heater described above. The pressure vessel is composed of thicker plates than the hot water tank. FIG. 10 is a diagram showing an example of the appearance of a pressure vessel 54 according to the eighth embodiment. The pressure vessel 54 is formed by joining the side member and the upper and lower members using the joint shown in FIG. 9 with the annular region simultaneous welding apparatus according to any one of the first to fifth embodiments.

[0046] That is, the method for manufacturing the compressor according to the eighth embodiment includes a step of preparing a cylindrical side member of the pressure vessel 54 and bowl-shaped upper and lower members for covering the openings at both ends of the side member, and a step of joining the side member and the upper and lower members by the second welding method according to the sixth embodiment.

[0047] According to the compressor manufacturing method of embodiment 8, by using the annular region simultaneous welding device of any one of embodiments 1 to 5, in the manufacturing process of the pressure vessel 54, the driving device or driving operation of the manufacturing equipment can be reduced, as in the hot water storage tank of embodiment 7, and the manufacturing cost or manufacturing time of the pressure vessel 54 can be reduced.

[0048] The configurations shown in the above embodiments are examples of the contents of the present disclosure, and may be combined with other known technologies, and parts of the configurations may be omitted or modified within the scope of the gist of the present disclosure. [Explanation of symbols]

[0049] 1 Fiber laser, 2 Laser beam, 3 Collimating lens, 4,40 Axicon lens, 5 Focusing lens, 6,7 Irradiation area, 9 Cover glass, 10 Ring diameter central axis, 20 Optical axis, 24 Welding shape, 31 Burring process, 32 Cylindrical tube, 33 Helical joint, 50 Focusing group lens, 52 Cylindrical member, 53 Bowl shape, 54 Pressure vessel, F1 Inner diameter, F2 Outer diameter, W Ring width.

Claims

1. a first optical system that converts the laser beam into parallel light; a second optical system including an axicon lens that converts the laser beam of parallel light into a ring-shaped beam, and a condenser lens that condenses the converted ring-shaped laser beam onto a workpiece and irradiates the workpiece with a ring-shaped irradiation area; An annular area simultaneous welding device that simultaneously welds an annular area of ​​the workpiece using the ring-shaped irradiation area, The annular area simultaneous welding device is characterized in that the central diameter of the ring-shaped irradiation area of ​​the second optical system does not change between the condenser lens and the workpiece.

2. a first optical system that converts the laser beam into parallel light; a second optical system including an axicon lens that converts the laser beam of parallel light into a ring-shaped beam, and a condenser lens that condenses the converted ring-shaped laser beam onto a workpiece and irradiates the workpiece with a ring-shaped irradiation area; An annular area simultaneous welding device that simultaneously welds an annular area of ​​the workpiece using the ring-shaped irradiation area, the axicon lens expands a central diameter of the ring-shaped irradiation area as the ring-shaped laser beam travels from the focusing lens to the workpiece, and the focusing lens focuses the ring-shaped irradiation area to a region outside the diameter of the focusing lens.

3. a first optical system that converts the laser beam into parallel light; a second optical system including an axicon lens that converts the laser beam of parallel light into a ring-shaped beam, and a condenser lens that condenses the converted ring-shaped laser beam onto a workpiece and irradiates the workpiece with a ring-shaped irradiation area; An annular area simultaneous welding device that simultaneously welds an annular area of ​​a workpiece using the ring-shaped irradiation area, the axicon lens changes a ring width between the focusing lens and the workpiece without changing either one of an inner diameter position or an outer diameter position of the ring-shaped irradiation area.

4. a first optical system for converting the laser beam into non-parallel light; a second optical system including an axicon lens that converts the laser beam converted into non-parallel light into a ring-shaped beam, and a condenser lens that focuses the converted ring-shaped laser beam onto a workpiece to irradiate the workpiece with a ring-shaped irradiation area; An annular area simultaneous welding device that simultaneously welds an annular area of ​​the workpiece using the ring-shaped irradiation area, the axicon lens enlarges or reduces the ring-shaped irradiation area while maintaining a constant ring width between the focusing lens and the workpiece.

5. a step of preparing the workpiece by inserting a cylindrical member having an outer diameter smaller than an inner diameter of the opening into a member having a cylindrical or circular opening formed therein; A step of irradiating a ring-shaped irradiation area onto the workpiece using the annular area simultaneous welding device according to any one of claims 1 to 4; A method for simultaneous annular welding, comprising:

6. a step of fitting a bowl-shaped member into an opening of a cylindrical member to prepare the workpiece; A step of irradiating a ring-shaped irradiation area onto the workpiece using the annular area simultaneous welding device according to any one of claims 1 to 4; A method for simultaneous annular welding, comprising:

7. A step of preparing a hot water storage tank and a pipe joint part for connecting a pipe to the hot water storage tank; a step of joining the pipe joint part to the hot water storage tank by the annular region simultaneous welding method according to claim 5; A method for manufacturing a water heater, comprising:

8. a step of preparing a cylindrical side member of a pressure vessel and bowl-shaped upper and lower members for covering openings at both ends of the side member; a step of joining the side member and the upper and lower members by the annular region simultaneous welding method according to claim 6; A method for manufacturing a compressor, comprising:

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