Metal joint body, impeller, pump, and manufacturing method for metal joint body

Abstract

To provide a metal joint body, an impeller, a pump, and a manufacturing method for the metal joint body that can reduce fluid resistance.SOLUTION: A metal joint body 100 comprises metal plates 110 and 130 (first metal plates), a metal plate 120 (second metal plate) butted against the metal plates 110 and 130 in a T-shape, and a joint part 140 joining the metal plates 110 and 130 and the metal plate 120. The joint part 140 comprises: a first joint part 141 arranged on the side of one surface 121 of the metal plate 120; and a second joint part 142 arranged on the side of the other surface 122 of the metal plate 120, and smaller than the first joint part 141.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a metal joined body, an impeller, a pump, and a method for manufacturing a metal joined body.

Background Art

[0002] Patent Document 1 below discloses an impeller used in a pump for pumping a liquid. This impeller includes a main plate having a through hole into which a rotating shaft of the pump is inserted, a plurality of blades fixed to the main plate, and a side plate having a fluid inlet. The plurality of blades are joined to the main plate and the side plate by projection welding.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above T-shaped projection welding used for manufacturing an impeller or a guide vane, there is a problem that the joint portion protruding from the blade increases the fluid resistance.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a metal joined body, an impeller, a pump, and a method for manufacturing a metal joined body that can reduce fluid resistance.

Means for Solving the Problems

[0006] (1): The metal joint according to one aspect of the present invention includes a first metal plate, a second metal plate that is butted against the first metal plate in a T shape, and a joint portion that joins the first metal plate and the second metal plate. The joint portion includes a first joint portion disposed on one surface side of the second metal plate and a second joint portion disposed on the other surface side of the second metal plate and smaller than the first joint portion.

[0007] (2): In the metal joint according to (1), the second joint portion may include a flat portion.

[0008] (3): In the metal joint according to (2), the flat portion may include a first flat portion along the first metal plate and a second flat portion along the second metal plate.

[0009] (4): In the metal joint according to (3), the angle formed by the first flat portion and the second flat portion may be a right angle.

[0010] (5): The impeller according to one aspect of the present invention includes the metal joint according to any one of (1) to (4). The first metal plate forms at least one of a main plate and a side plate, the second metal plate forms a plurality of blades joined to the main plate and the side plate, the second joint portion is disposed on the positive pressure surface side of the blade, and the first joint portion is disposed on the negative pressure surface side of the blade.

[0011] (6): The pump according to one aspect of the present invention includes the impeller according to (5).

[0012] (7): The method for manufacturing a metal joint according to one aspect of the present invention is to butt a second metal plate against a first metal plate in a T shape and perform projection welding, form a first joint portion on one surface side of the second metal plate, and form a second joint portion smaller than the first joint portion on the other surface side of the second metal plate.

[0013] (8) In the method for manufacturing the metal bonded body according to (7), the projection welding may be performed in a state where the ceramic plate is brought into contact with the other surface side of the second metal plate, and then the ceramic plate may be removed.

Effect of the Invention

[0014] According to one aspect of the present invention, it is possible to provide a metal bonded body, an impeller, a pump, and a method for manufacturing a metal bonded body that can reduce fluid resistance.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0016] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0017] FIG. 1 is a cross-sectional configuration diagram of a metal bonded body 100 according to one embodiment. As shown in FIG. 1, the metal bonded body 100 includes a metal plate 110, a metal plate 120, and a metal plate 130. The metal plate 120 is joined in a state of being butted against the metal plate 110 in a T shape. Further, the metal plate 120 is joined in a state of being butted against the metal plate 130 in a T shape.

[0018] Note that the "T-shape" includes not only the state where the angle between the metal plate 110 and the metal plate 120 is a right angle (90°) as shown in FIG. 1, but also the state where the angle is approximately a right angle. "Approximately a right angle" means an angle allowing a tilt of about 90° ± 10°, for example. Similarly, the angle between the metal plate 120 and the metal plate 130 may be not only a right angle but also approximately a right angle.

[0019] In the following description, an XYZ orthogonal coordinate system may be set, and the positional relationship of each member may be described with reference to this XYZ orthogonal coordinate system. In FIG. 1, the X-axis direction is set in the thickness direction of the metal plate 120. Also, the Y-axis direction and the Z-axis direction are set along the main surface (plate surface) of the metal plate 120.

[0020] Note that the "main surface" refers to the set of the two largest surfaces of the hexahedron when the metal plate 120 is regarded as a hexahedron surrounded by six quadrilaterals. The same applies to the metal plates 110 and 130.

[0021] Hereinafter, for convenience of explanation, the side of the metal plate 110 with respect to the metal plate 120 (+Z side) is referred to as the upper side, and the side of the metal plate 130 with respect to the metal plate 120 (-Z side) is referred to as the lower side, but the Z-axis direction does not necessarily coincide with the gravitational direction.

[0022] The metal plate 110 extends along the X-Y plane. The metal plate 110 has an upper surface 111 facing the +Z side and a lower surface 112 facing the -Z side. The upper surface 111 and the lower surface 112 are the main surfaces (plate surfaces) of the metal plate 110.

[0023] The metal plate 120 extends along the Y-Z plane. The metal plate 120 has one surface 121 (left side surface) facing the -X side and the other surface 122 (right side surface) facing the +X side. The one surface 121 and the other surface 122 are the main surfaces (plate surfaces) of the metal plate 120.

[0024] The metal plate 130 extends along the X-Y plane. The metal plate 130 has an upper surface 131 facing the +Z side and a lower surface 132 facing the -Z side. The upper surface 131 and the lower surface 132 are the main surfaces (plate surfaces) of the metal plate 130.

[0025] The upper end surface 123 of the metal plate 120 is joined to the lower surface 112 of the metal plate 110 by a joint portion 140. Also, the lower end surface 124 of the metal plate 120 is joined to the lower surface 112 of the metal plate 110 by the joint portion 140. These joint portions 140 are welding metals by projection welding described later.

[0026] The joint portion 140 includes a first joint portion 141 disposed on one surface 121 side of the metal plate 120 and a second joint portion 142 disposed on the other surface 122 side of the metal plate 120 and smaller than the first joint portion 141. Note that "smaller than the first joint portion 141" means that in the cross-sectional view shown in FIG. 1, the cross-sectional area of the second joint portion 142 is smaller than the cross-sectional area of the first joint portion 141.

[0027] The first joint portion 141 bulges outward in a convex shape at the butting portion of the metal plate 110 (similarly for the metal plate 130) and the metal plate 120. Specifically, the first joint portion 141 has a quarter-circular shape (a sector shape that is 1 / 4 of a circle) in the cross-sectional view shown in FIG. 1. Note that the first joint portion 141 is not limited to a quarter-circular shape and may be, for example, a shape that is 1 / 4 of an ellipse, or a convex or concave parabolic shape. Also, the first joint portion 141 may have a curved surface or an uneven surface that cannot be defined by a circle, an ellipse, or a parabola.

[0028] The second joint portion 142 is formed in a concave shape inward at the butting portion of the metal plate 110 (similarly for the metal plate 130) and the metal plate 120. Specifically, the second joint portion 142 has an L shape in the cross-sectional view shown in FIG. 1. The second joint portion 142 shown in FIG. 1 includes a first plane portion 142a along the metal plate 110 (similarly for the metal plate 130) and a second plane portion 142b along the metal plate 120.

[0029] The first flat portion 142a is formed with a constant thickness along the lower surface 112 of the metal plate 110. Also, the second flat portion 142b is formed with a constant thickness along the other surface 122 of the metal plate 110. The angle formed by the first flat portion 142a and the second flat portion 142b is a right angle, which is due to the manufacturing method of the metal joint 100 described later. Note that the connection portion (corner portion) between the first flat portion 142a and the second flat portion 142b may include a curved surface.

[0030] Next, a method for manufacturing the metal joint 100 having the above configuration will be described.

[0031] FIG. 2 is a diagram showing a step of a method for manufacturing the metal joint 100 according to an embodiment. Specifically, FIG. 2 shows a state in which the metal plate 120 is butted against the metal plate 110 in a T shape and projection welding is performed. Note that in FIGS. 2(a) and 2(b), the viewing directions of the objects (metal plates 110, 120, etc.) are different.

[0032] On the upper end surface 123 of the metal plate 120, a protrusion 125 (projection) protruding in the +Z direction is formed. The metal plate 120 is fixed to the jig 200. The jig 200 includes a housing groove 201 for housing the metal plate 120 as shown in FIG. 2(a). The housing groove 201 houses the ceramic plate 300 together with the metal plate 120.

[0033] The ceramic plate 300 extends along the Y-Z plane. The metal plate 120 has one surface 301 (left side surface) facing the -X side and the other surface 302 (right side surface) facing the +X side. One surface 301 and the other surface 302 are the main surfaces (plate surfaces) of the ceramic plate 300.

[0034] One surface 301 of the ceramic plate 300 is in contact with the other surface 122 of the metal plate 120. Also, the upper end surface 303 of the ceramic plate 300 is installed to coincide with the upper end surface 123 of the metal plate 120. As shown in FIG. 2(b), the dimension of the ceramic plate 300 in the Y-axis direction (plate width direction) is larger than the dimension of the protrusion 125 in the Y-axis direction.

[0035] Projection welding means that, in the state shown in Fig. 2, the protrusion 125 of the metal plate 120 is pressed against the metal plate 110, a large current is passed through the protrusion 125 from an electrode (not shown), and the protrusion 125 is melted to perform resistance welding (spot welding) between the metal plate 110 and the metal plate 120.

[0036] When the protrusion 125 melts, the lower surface 112 of the metal plate 110 and the upper end surface 123 of the metal plate 120 approach each other in the Z-axis direction. The molten metal of the protrusion 125 extruded from between the lower surface 112 of the metal plate 110 and the upper end surface 123 of the metal plate 120 protrudes to one side 121 and the other side 122 of the metal plate 120. However, since the ceramic plate 300 is arranged on the other side 122 of the metal plate 120, most of the molten metal of the protrusion 125 protrudes to one side 121 of the metal plate 120. Thereby, the first joint portion 141 shown in Fig. 1 is formed.

[0037] Also, the remaining part of the molten metal of the protrusion 125 protrudes to the other side 122 of the metal plate 120. The molten metal enters the gap between the lower surface 112 of the metal plate 110 and the upper end surface 123 of the ceramic plate 300, and the gap between the other side 122 of the metal plate 120 and one side 301 of the ceramic plate 300. After the molten metal solidifies, the metal plate 120 and the ceramic plate 300 are taken out from the accommodation groove 201, and the ceramic plate 300 is removed. Thereby, the second joint portion 142 having a flat portion shown in Fig. 1 is formed.

[0038] In addition, when a resin plate or a metal plate is used instead of the ceramic plate 300, it will be welded to the metal plate 110 or the metal plate 120, but the ceramic plate 300 can be easily removed.

[0039] As described above, the first joint portion 141 can be formed on one side 121 of the metal plate 120, and the second joint portion 142 smaller than the first joint portion 141 can be formed on the other side 122 of the metal plate 120.

[0040] Note that the first joint portion 141 and the second joint portion 142 smaller than the first joint portion 141 can also be formed by the following method.

[0041] FIG. 3 is a diagram showing a step of a method for manufacturing the metal joined body 100 according to the first modification. In FIG. 3, electrodes 210 and 220 through which current flows during projection welding are illustrated. The electrode 210 is disposed on the upper surface 111 side of the metal plate 110. The electrode 220 is disposed on the lower end surface 124 side of the metal plate 120.

[0042] The method shown in FIG. 3 uses an insulating material 310. As shown in FIG. 3(a), the insulating material 310 is disposed between the upper surface 111 of the metal plate 120 and the electrode 210 on the other surface 122 side of the metal plate 120. According to this configuration, the current density during projection welding is biased toward one surface 121 side of the metal plate 120, so that a large first joint portion 141 can be formed on one surface 121 side of the metal plate 120, and a small second joint portion 142 can be formed on the other surface 122 side of the metal plate 120.

[0043] FIG. 4 is a diagram showing a step of a method for manufacturing the metal joined body 100 according to the second modification. The method shown in FIG. 4 forms a convex portion 330 on the jig 200 instead of the ceramic plate 300 or the insulating material 310.

[0044] The convex portion 330 is a part of the metal jig 200 and is disposed on the other surface 122 side of the metal plate 120. The convex portion 330 protrudes toward the +Z side toward the metal plate 120. According to this configuration, the current density during projection welding is biased toward one surface 121 side of the metal plate 120, so that a large first joint portion 141 can be formed on one surface 121 side of the metal plate 120, and a small second joint portion 142 can be formed on the other surface 122 side of the metal plate 120.

[0045] Next, application examples of the metal joined body 100 will be described.

[0046] FIG. 5 is a plan view of the impeller 3 according to one embodiment. FIG. 6 is a cross-sectional view of the impeller 3 according to one embodiment. As shown in these figures, the impeller 3 includes a main plate 3a, side plates 3b, and a plurality of blades 3c. The main plate 3a is formed in a disc shape, and an insertion hole for inserting a rotating shaft (not shown) is formed at its center. The side plates 3b are formed in an annular shape coaxial with the main plate 3a and are arranged with a gap in the axial direction from the main plate 3a. The main plate 3a and the side plates 3b are connected via a plurality of blades 3c. The space surrounded by the main plate 3a, the side plates 3b, and the plurality of blades 3c serves as a flow path for guiding the fluid radially outward. The side plates 3b form the suction port of the impeller 3.

[0047] The impeller 3 includes the metal joined body 100 shown in FIG. 1. Specifically, the main plate 3a corresponds to the metal plate 130, the side plates 3b correspond to the metal plates 110, and the blades 3c correspond to the metal plates 120. As shown in FIG. 6, the second joining portion 142 is arranged on the positive pressure surface 3c2 side of the blade 3c, and the first joining portion 141 is arranged on the negative pressure surface 3c1 side of the blade 3c. Note that the "positive pressure surface 3c2 of the blade 3c" is the surface facing the front side in the rotation direction of the impeller 3. Also, the "negative pressure surface 3c1 of the blade 3c" is the surface facing the rear side in the rotation direction of the impeller 3.

[0048] FIG. 7 is a cross-sectional configuration view of the pump 1 according to one embodiment. The pump 1 shown in FIG. 7 is a vertical multi-stage pump including a rotating shaft 2 extending in the vertical direction and a plurality of the above-described impellers 3 fixed to the rotating shaft 2. Specifically, the pump 1 includes a pump section 10, a motor section (not shown), and a coupling section 30. The coupling section 30 is arranged above the pump section 10 and connects the rotating shaft 2 of the pump section 10 and the rotating shaft 6 of the motor section via couplings 4, 5. Note that the couplings 4, 5 are covered from the outside by a guard member 37a.

[0049] The pump section 10 includes a cylindrical casing 11 that houses the impeller 3. The casing 11 forms a pump chamber 10A inside for boosting the pressure of the liquid by the impeller 3. The casing 11 includes an intermediate casing 11a, an upper casing 11b disposed above the intermediate casing 11a, a lower casing 11c disposed below the intermediate casing 11a, and an outer casing 11d disposed radially outside the intermediate casing 11a and the upper casing 11b.

[0050] The intermediate casing 11a is formed into a bottomed cylindrical shape by press-forming a steel plate or the like, and an opening through which the rotating shaft 2 is inserted is formed at the center of the bottom thereof. The intermediate casings 11a are stacked in multiple stages according to the number of impellers 3. A suction plate 13 is attached to the bottom lower surface of the intermediate casing 11a by welding. Further, a return vane 14 is attached to the lower surface of the suction plate 13 by welding. And a liner 15 for preventing leakage of the liquid to the suction side of the impeller 3 is attached to the inner wall of the bottom opening of the intermediate casing 11a.

[0051] The upper casing 11b is formed into a bottomed cylindrical shape similar to the intermediate casing 11a and is stacked on the uppermost stage of the intermediate casing 11a. A plurality of communication holes 11b1 are formed in the peripheral wall of the upper casing 11b. The outer casing 11d is formed into a cylindrical shape surrounding the outside in the radial direction of the intermediate casing 11a and the upper casing 11b. The outer casing 11d forms an annular flow path communicating with the communication holes 11b1 on the outside in the radial direction of the intermediate casing 11a and the upper casing 11b.

[0052] The lower casing 11c has a suction port 10a communicating with the center of the bottom of the lowermost intermediate casing 11a (the suction side of the impeller 3) and a discharge port 10b communicating with the above-described annular flow path inside the outer casing 11d. The suction port 10a and the discharge port 10b are arranged on the lower side surface of the pump section 10 back to back and on the same straight line. The lower casing 11c supports the lower end portions of the intermediate casing 11a and the outer casing 11d.

[0053] A pump base 12 is provided at the lower part of the lower casing 11c. The pump base 12 is axially connected by a coupling part 30 and a plurality of casing bolts and nuts (not shown). By tightening the plurality of casing bolts and nuts (not shown), the multi-stage intermediate casing 11a, the upper casing 11b, and the lower casing 11c are axially clamped.

[0054] According to the pump section 10 configured as described above, when the impeller 3 rotates, liquid (fluid) is sucked into the lower casing 11c from the suction port 10a. The liquid sucked into the lower casing 11c is pressurized by the first-stage impeller 3 in the lowermost intermediate casing 11a. The liquid discharged from the first-stage impeller 3 is guided to the suction side of the next-stage impeller 3 through the flow path formed by the return vane 14 and the suction plate 13.

[0055] In this way, the liquid is multi-stage pressurized by the plurality of impellers 3 and flows into the upper casing 11b. A plurality of communication holes 11b1 are formed in the upper casing 11b, and the liquid in the upper casing 11b descends through the annular flow path formed outside the upper casing 11b from the communication holes 11b1 and is discharged to the outside from the discharge port 10b of the lower casing 11c.

[0056] Here, as shown in FIGS. 5 and 6, the impeller 3 includes a first joint portion 141 disposed on the negative pressure surface 3c1 side of the blade 3c, and a second joint portion 142 disposed on the positive pressure surface 3c2 side of the blade 3c and smaller than the first joint portion 141. According to this configuration, since the protruding second joint portion 142 on the positive pressure surface 3c2 side of the blade 3c is small, the flow path resistance of the impeller 3 that guides the liquid radially outward can be reduced. In addition, the second joint portion 142 includes a flat portion, and it is difficult for vortices and stagnation of the liquid to occur, so the performance of the pump 1 is improved.

[0057] As described above, the metal joint 100 according to this embodiment includes metal plates 110 and 130 (first metal plates), a metal plate 120 (second metal plate) that abuts against the metal plates 110 and 130 in a T shape, and a joint portion 140 that joins the metal plates 110 and 130 and the metal plate 120. The joint portion 140 includes a first joint portion 141 disposed on one surface 121 side of the metal plate 120 and a second joint portion 142 disposed on the other surface 122 side of the metal plate 120 and smaller than the first joint portion 141. According to this configuration, the flow path resistance on the other surface 122 side of the metal plate 120 can be reduced.

[0058] Further, in this embodiment, the second joint portion 142 includes a flat portion. According to this configuration, when the metal joint 100 of this embodiment is applied to a fluid machine, it is difficult for vortices or stagnation of the fluid to occur on the other surface 122 side of the metal plate 120, so the performance of the fluid machine is improved.

[0059] Further, in this embodiment, as the flat portion, it includes a first flat portion 142a along the metal plates 110 and 130 and a second flat portion 142b along the metal plate 120. According to this configuration, generation of vortices or stagnation of the fluid on the surfaces of the metal plates 110 and 130 and the surface of the metal plate 120 can be suppressed.

[0060] Further, in this embodiment, the angle formed by the first flat portion 142a and the second flat portion 142b is a right angle. According to this configuration, since there is no convex shape on the other surface 122 side of the metal plate 120, the flow path resistance can be further reduced.

[0061] Further, the impeller 3 according to this embodiment includes the above metal joint 100. The metal plates 110 and 130 form at least one of the main plate 3a and the side plate 3b. The metal plate 120 forms a plurality of blades 3c joined to the main plate 3a and the side plate 3b. The second joint portion 142 is disposed on the positive pressure surface 3c2 side of the blade 3c, and the first joint portion 141 is disposed on the negative pressure surface 3c1 side of the blade 3c. According to this configuration, the flow path resistance of the impeller 3 can be reduced.

[0062] Further, the pump 1 according to the present embodiment includes the impeller 3. According to this configuration, the performance of the pump 1 can be improved.

[0063] In addition, the manufacturing method of the metal bonded body 100 according to the present embodiment projects the metal plate 120 onto the metal plate 110 in a T shape and performs projection welding to form a first joint portion 141 on one surface 121 side of the metal plate 120, and on the other surface 122 side of the metal plate 120, a second joint portion 142 smaller than the first joint portion 141 is formed.

[0064] In addition, in the present embodiment, with the ceramic plate 300 abutted against the other surface 122 side of the metal plate 120, projection welding is performed, and then the ceramic plate 300 is removed. According to this method, a metal bonded body 100 having a flat portion can be manufactured. Further, since the ceramic plate 300 does not adhere to the metal plate 120 or the like, it is easy to remove.

[0065] As described above, according to the present embodiment, it is possible to provide a metal bonded body 100, an impeller 3, a pump 1, and a method for manufacturing the metal bonded body 100 that can reduce fluid resistance.

[0066] As described above, the preferred embodiments of the present invention have been described and explained, but it should be understood that these are exemplary of the present invention and should not be considered as limiting. Additions, omissions, substitutions, and other changes can be made without departing from the scope of the present invention. Therefore, the present invention should not be regarded as being limited by the foregoing description, but rather by the scope of the claims.

[0067] For example, in FIG. 7, the impeller 3 including the metal bonded body 100 is applied to a vertical multi-stage pump, but it may also be applied to other centrifugal pumps. In addition, the metal bonded body 100 may be applied only between the main plate 3a and the blade 3c shown in FIG. 6, or may be applied only between the side plate 3b and the blade 3c. In addition, the metal bonded body 100 may be applied not only to the impeller 3 but also to other fluid machines and fluid components.

Description of Symbols

[0068] 1 Pump 2 Rotating Shaft 3 Impeller 3a Main Board 3b Side Plate 3c Blade 3c1 Suction Surface 3c2 Pressure Surface 4 Coupling 5 Coupling 6 Rotating Shaft 10 Pump Section 10a Suction Port 10A Pump Chamber 10b Discharge Port 11 Casing 11a Intermediate Casing 11b Upper Casing 11b1 Communication Hole 11c Lower Casing 11d Outer Casing 12 Pump Stand 13 Suction Plate 14 Blade 15 Liner 30 Coupling Section 37a Guard Member 100 Metal Bonding Body 110 Metal Plate (First Metal Plate) 111 Upper Surface 112 Lower Surface 120 Metal Plate (Second Metal Plate) 121 One Surface 122 The Other Surface 123 Upper End Surface 124 Lower End Surface 125 Protrusion 130 Metal Plate 131 Upper Surface 132 Lower Surface 140 Joint 141 First Joint 142 Second Joint 142a First Flat Surface 142b Second Flat Surface 200 Fixture 201 Accommodation groove 210 Electrode 220 Electrode 300 Ceramic plate 301 One side 302 The other side 303 Upper end face 310 Insulating material 330 Convex part

Claims

1. a first metal plate, a second metal plate abutting against the first metal plate in a T-shape, and a joint portion joining the first metal plate and the second metal plate, wherein the joint portion comprises a first joint portion disposed on one surface side of the second metal plate, and a second joint portion disposed on the other surface side of the second metal plate and smaller than the first joint portion, a metal joint.

2. The second joint portion comprises a flat portion, The metal joint according to Claim 1.

3. As the flat portion, a first flat portion along the first metal plate, and a second flat portion along the second metal plate, The metal joint according to Claim 2.

4. The angle formed by the first flat portion and the second flat portion is a right angle, The metal joint according to Claim 3.

5. comprising the metal joint according to any one of Claims 1 to 4, wherein the first metal plate forms at least one of a main plate and a side plate, the second metal plate forms a plurality of wings joined to the main plate and the side plate, the second joint portion is disposed on the positive pressure surface side of the wing, and the first joint portion is disposed on the negative pressure surface side of the wing, an impeller.

6. comprising the impeller according to Claim 5, a pump.

7. The second metal plate is abutted against the first metal plate in a T-shape and projection welded to form a first joint portion on one surface side of the second metal plate, and a second joint portion smaller than the first joint portion on the other surface side of the second metal plate, A method for manufacturing a metal joint.

8. The projection welding is performed with a ceramic plate abutted against the other surface side of the second metal plate, and then the ceramic plate is removed, The method for manufacturing a metal joint according to Claim 7.

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