JPH0790379B2 - Welding method of two metal members sandwiching a metal plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the Invention (1) Field of Industrial Application The present invention relates to welding a metal plate member with two metal members coaxially arranged with the metal plate member interposed therebetween. The present invention relates to a welding and joining method of two metal members sandwiching a metal plate material for joining.

(2) Conventional Technology Conventionally, such a welding joining method is disclosed in, for example, Japanese Patent Laid-Open No. 60-2236.
It is already known from the publication No. 71, etc.

(3) Problem to be Solved by the Invention In the above-mentioned conventional one, a plurality of welding projections are respectively provided on the opposing surfaces of the metal members facing the metal plate material, and one metal member and the metal plate material are provided. After being joined by projection welding, the other metal member and the metal plate material are joined by projection welding after a predetermined cooling time. Therefore, projection welding has two steps, and it is hard to say that the welding efficiency is excellent.

A first object of the present invention is to provide a method for welding and joining two metal members sandwiching a metal plate material, which enables two metal members to be simultaneously welded and bonded to the metal plate material to improve welding work efficiency. It is to be.

Further, for example, due to the difference in carbon content, a metal plate material,
The hardness may differ between the two metal members, and if the metal member has a higher hardness than the metal plate material, the welding projections will be applied to the metal plate material when the welding current is applied while pressing the welding projections on both sides of the metal plate material. In some cases, the contact area between the metal plate material and the welding projections is increased due to the penetration into the metal, and the heat generation efficiency is reduced due to the reduction in electric resistance, so that the welding efficiency may not be sufficiently improved.

A second object of the present invention is to sandwich two metal plate materials so that two metal members can be simultaneously weld-bonded to the metal plate material while sufficiently improving the welding efficiency to improve the welding work efficiency. A method of welding and joining metal members.

B. Structure of the Invention (1) Means for Solving the Problems According to the first feature of the present invention for achieving the above-mentioned first object, a tip is provided on a joint surface of two metal members to a metal plate material. The sharpened annular protrusions are formed to have the same diameter, and the two metal members are coaxially pressed to the metal plate member side while sandwiching the metal plate members therebetween so that the annular protrusions face each other. A welding current is passed between the metal members.

According to the second feature of the present invention for achieving the above second object, annular projections having sharpened tips are formed in the same diameter on the joining surfaces of the two metal members to the metal plate material, respectively. After the metal plate material is sandwiched between them and the annular projections are opposed to each other, both metal members are coaxially pressed against the metal plate material by the first pressing force to bring both annular projections into contact with both surfaces of the metal plate material. 1
Pressed against the metal plate material side with a second pressing force larger than the pressing force,
A welding current is applied between both metal members only when pressed by the second pressing force.

(2) Action According to the method of the first feature, two metal members are simultaneously welded and joined to the metal plate material by projection welding. Moreover, since the two annular projections facing each other with the metal plate material in between have the same diameter, the welding current flows through the plate material in the shortest distance, which enables efficient welding.

According to the method of the second characteristic, the two metal members are simultaneously weld-bonded to the metal plate material by projection welding. Further, since the two annular projections facing each other with the metal plate material sandwiched therebetween have the same diameter, the welding current flows through the metal plate material in the shortest distance, which enables efficient welding. Moreover, both metal members are pressed toward the metal plate material by the first pressing force to bring the tips of the annular projections into contact with the metal plate member, and then the welding current is applied while pressing the both metal members toward the metal plate member side with a larger second pressing force. By energizing, it is possible to avoid an increase in the contact area due to mutual erosion or crushing between the annular protrusions and the metal plate material.

(3) Embodiment One embodiment of the present invention will be described below with reference to the drawings.

First, in FIG. 1, a metal material having a relatively low carbon content, for example, a metal plate material 1 made of cold rolled steel sheet SPC (JIS) having a carbon content of about 0.12%, has a relatively high carbon content on both front and back surfaces. Material For example, carbon steel for machine structure S35C (JIS) with a carbon content of 0.35 to 0.41%
And a metal material having a relatively high carbon content, for example, a carbon content of 0.18-
A collar 3 as a metal member made of carbon steel S20C (JIS) for machine structure of about 0.23% is joined by projection welding according to the method of the present invention.

A through hole 4 is formed in the metal plate material 1. The nut 2 is
It is formed basically in a tubular shape while extending in a direction orthogonal to the metal plate material 1, and at one axial end thereof, a flange portion 6 which projects radially outward so as to face the metal plate material 1 is integrally formed. It is provided. Moreover, the surface of the collar portion 6 facing the other end side in the axial direction is formed in a taper shape whose diameter decreases toward the other end side in the axial direction. Further, the nut 2 has a large-diameter hole portion 7a having an inner diameter substantially corresponding to the hole diameter of the through hole 4 and a small-diameter hole portion 7b coaxially connected to the large-diameter hole portion 7a via a step portion 7c on the flange portion 6 side. A hole 7 is formed coaxially in this order, and a female screw is engraved on the small diameter portion 7b.

In FIG. 2, on the facing surface of the nut 2 facing the metal plate material 1, an annular projection 8 is formed at the outer peripheral edge thereof toward the metal plate material 1 side.
And a flat annular stopper surface 5 adjacent to the inner side of the annular groove 9 is formed. Moreover, the annular projection 8 is formed so that the cross-sectional shape thereof becomes a triangle that becomes narrower toward the tip, and the angle α of the annular projection 8 is to improve the heat generation effect during projection welding. It is set to 80-110 degrees.

The collar 3 has a hole 3a having an inner diameter substantially corresponding to the through hole 4 and extends in a direction orthogonal to the metal plate material 1 and is basically formed in a cylindrical shape.
An annular projection 11 having a triangular cross-section is provided on the opposite surface facing the metal plate 1 at the outer peripheral edge thereof, and an annular groove 12 adjacent to the inside of the annular projection 11 is further provided. A flat annular stopper surface adjacent to the inside of the annular groove 12
And 10 are formed. Thus, the annular projection 11 is formed to have the same shape as the annular projection 8 with the same tip diameter.

FIG. 3 and FIG. 4 show a projection welding apparatus. The projection welding apparatus includes a fixed lower electrode 13, a vertically movable positioning pin 14, an vertically movable upper electrode 15, and a positioning piston 14. A lifting pneumatic cylinder 16 is connected, and a pressurizing pneumatic cylinder 17 is connected to the upper electrode 15.

The projection welding device consists of a vertically fixed frame 18
And a support block at the bottom of the frame 18.
19 are fixed. Thus, the lifting pneumatic cylinder 16 is fixedly arranged on the bracket 20 fixed to the lower end of the support block 19 while having the axis line extending vertically with the piston rod 16a as the upper position.

On the other hand, an elevating rod 21 having an axis extending vertically in parallel with the piston rod 16a is movably inserted into guide members 22 and 23 provided on the support block 19 at positions vertically spaced apart from each other. The rod 16a and the lifting rod 21 are connected via a connecting member 24. Therefore, the lifting rod 21 is moved according to the expansion and contraction of the lifting pneumatic cylinder 16.
Will move up and down.

An electrode holder 25 is fixedly disposed above the support block 19, and the lower electrode 13 is fixedly supported by the electrode holder 25. Thus, the lower electrode 13 is formed in a cylindrical shape into which the elevating rod 21 can be inserted, and the upper end surface of the lower electrode 13 is formed to have a sufficient area for mounting the collar 3.

A positioning pin 14 is provided on the upper end of the elevating rod 21.
The positioning pin 14 is formed to have an outer surface shape substantially corresponding to the inner surface shape of the nut 2.
In order to prevent the collar 3 and the collar 3 from electrically conducting through the positioning pin 14, a coating made of a non-conductive material such as ceramics is formed on the outer surface of the positioning pin 14.

By the way, as shown in FIG. 1, the positioning pin 14 moves up and down between an upper position where the collar 3 and the nut 2 are fitted, and a lower position where at least the upper end is lower than the upper surface of the metal plate material 1. In order to regulate the rising end of the elevating rod 21 or the piston rod 16a, a nut 26 is screwed onto the upper end of the piston rod 16a so as to be able to advance and retreat in the axial direction, and can come into contact with the nut 26. Stopper 27
Are fixed to the guide member 23.

A cooling water passage 28 is provided in the electrode holder 25, and the cooling water passage 28 is connected to a cooling water source (not shown).

A pressurizing pneumatic cylinder 17 is fixedly provided on an upper portion of the frame body 18 while having an axial line extending vertically with the piston rod 17a thereof located at a lower position. This piston rod 17a
A lifting body 29 made of a conductive metal is connected to the
The upper electrode 15 is fixedly supported by the electrode holder 30 fixed to 29. Thus, the upper electrode 15 has a bottomed cylindrical portion 15a coaxial with the axis of the lower electrode 13 at the lower end and is fixedly supported by the electrode holder 30, and the opening end surface of the bottomed cylindrical portion 15a is The nut 2 comes into contact with the surface of the collar portion 6 opposite to the annular projection 8. Moreover, the opening end surface of the bottomed cylindrical portion 15a is also formed in a taper shape in correspondence with the taper of the surface of the collar portion 6 opposite to the annular projection 8. In addition, a recess 31 which is a part of the cooling water passage is provided at the upper end of the upper electrode 15. Moreover, in the electrode holder 30, a pipe 32 that projects into the recess 31 is arranged, and the pipe 32 is connected to a cooling water source (not shown). Thus, the cooling water is introduced from the inside of the pipe 32 into the recess 31, and is also led out through the annular passage 33 between the pipe 32 and the electrode holder 30.

An electrically conductive member 35 formed by stacking a plurality of electrically conductive plate members in an endless manner is interposed between a receiving member 34 fixedly provided at an intermediate portion in the vertical direction of the frame body 18 and the elevating body 29. Therefore, by bending the conductive member 35 up and down, the upper electrode 15 can always be energized regardless of the lifting operation.

A guide rod 36 parallel to the piston rod 17a is inserted through the cylinder body 37 of the pressurizing pneumatic cylinder 17, and the guide rod 36 is connected to the lifting body 29. The guide rod 36 prevents the lifting body 29, that is, the upper electrode 15 from rotating around the axis of the piston rod 17a.

FIG. 5 shows an air pressure circuit for supplying air pressure to the pressurizing pneumatic cylinder 17, and the pressurizing pneumatic cylinder 17 is formed in a tandem type. That is, the cylinder main body 37 of the pressurizing pneumatic cylinder 17 has two upper and lower cylinder holes separated by a partition wall 38, and the pistons 39 and 40 are slidably fitted in these cylinder holes to hermetically seal the partition wall 38. Further, the pistons 39 and 40 are commonly fixed to the piston rod 17a that penetrates movably. Then the cylinder body 3
Inside 7, there is an upper piston side air pressure chamber 41 that faces the upper surface of the upper piston 39, an upper rod side air pressure chamber 42 that faces the lower surface of the piston 39, and a lower piston side air pressure chamber that faces the upper surface of the lower piston 40. 43, the lower rod side air pressure chamber 44 that faces the lower surface of the piston 40 is defined.

The upper rod side air pressure chamber 41 has an upper piston side air pressure chamber.
One-way valve that allows only pressurized air to flow to the 41 side
A pipe line 47 having a parallel circuit composed of 45 and a variable throttle 46 is connected, a silencer 48 is connected to the upper rod side air pressure chamber 42, a pipe line 49 is connected to the lower piston side air pressure chamber 43, and a lower rod side. The pneumatic chamber 44 includes a parallel circuit including a one-way valve 50 and a variable throttle 51 that allow only pressurized air to flow toward the lower rod-side pneumatic chamber 44.
52 is connected.

On the other hand, an on-off valve 54 and a filter 55 are sequentially connected to the pressurized air source 53, and the filter 55 is connected to a regulator valve.
Line 57 with 56 and line 59 with regulator valve 58
And are connected in parallel. Therefore, the set pressures of the regulator valves 56 and 58 are different from each other.
The set pressure of is set smaller than the set pressure of the regulator valve 56.

Between the pipelines 57, 59 and the pipeline 60, a position for communicating the pipeline 59 with the pipeline 60 and a position for communicating the pipeline 57 with the pipeline 60 are switched as shown in FIG. A possible switching control valve 61 is provided. Further, the pipelines 47, 52, the pipeline 60 and the silencer 62,
Between the pipe 63 and the position where the pipe 60 communicates with the pipe 52 and the pipe 47 communicates with the silencer 63.
A switching control valve 64 is provided which can communicate with the valve 47 and can switch the position where the pipe 52 communicates with the silencer 62. Further, between the line 60 and the silencer 65 and the line 49,
The position where the pipe 49 communicates with the silencer 65, and the pipes 49, 60
A switching control valve 66 capable of switching between a position for communicating the two is provided.

In such a pneumatic circuit, when the pressurizing pneumatic cylinder 17 is contracted, the switching positions of the switching control valves 61, 64, 66 are set as shown in FIG. Then, the pressurized air source 53
Pressurized air from the regulator valve 58, switching control valves 61, 64
Then, the air is supplied to the lower rod-side air pressure chamber 44 through the one-way valve 50, the pistons 39 and 40 move upward, and the piston rod 17a contracts. At this time, the air from the upper piston side air pressure chamber 41 is released from the silencer 63 via the variable throttle 46 and the switching control valve 64, and the air is introduced into the upper rod side air pressure chamber 42 via the silencer 48, and the lower piston side. The air from the pneumatic chamber 43 passes through the switching control valve 66 and the silencer.
Escaped from 65.

When the pressurizing pneumatic cylinder 17 is extended, first, the switching control valve so that the regulator valve 58 communicates with the pipe line 60.
Switch 60 positions. Next, the position of the switching control valve 64 is switched so that the conduit 60 is communicated with the conduit 47 and the conduit 52 is communicated with the silencer 62. Then, the pressurized air regulated by the regulator valve 58 is introduced into the upper piston side air pressure chamber 41 through the one-way valve 45, the pistons 39 and 40 move downward, and the piston rod 17a extends. At this time, the air from the upper rod-side air pressure chamber 42 is released from the silencer 48, and the air from the lower rod-side air pressure chamber 44 is changed by the variable throttle 51.
And escaped from the silencer 62 via the switching control valve 64,
Air is introduced into the lower piston-side air pressure chamber 43 through a silencer 65 and a switching control valve 66.

After the switching control valve 64 is switched as described above, when a certain time has elapsed, the switching control valve 66 is switched to a position where the pipe 60 communicates with the pipe 49. As a result, the pressurized air adjusted by the regulator valve 58 is introduced into the lower piston side air pressure chamber 43, and the pressing force of the piston rod 17a is further increased.

That is, according to the pneumatic circuit described above, the pressing force when the pressurizing pneumatic cylinder 17 extends is as shown in FIG.
After the first pressure P ₁ until the pressure increases rapidly, the first pressure P ₁ is sustained period of time, then a second pressure P ₂ until the pressure increases rapidly. Therefore, when the first pressurizing force P ₁ is rapidly increased and when the second pressurizing force P ₂ is rapidly increased, the pressurizing force jumps due to the characteristics of the pneumatic cylinder.
By letting air escape through the variable throttle 51, the jump can be suppressed.

Next, a procedure for welding and joining the nut 2 and the collar 3 to both surfaces of the metal plate material 1 will be described. First, the pressurizing pneumatic cylinder 17 is contracted to raise the upper electrode 15 and the lifting cylinder 16 is contracted. The collar 3 is positioned and supported on the lower electrode 13 by operating the positioning pin 14 and lowering it to the lower position. That is, the collar 3 is coaxially mounted on the upper end surface of the lower electrode 13 in the vertical posture with the joint surface 10 as the upper position.

Next, the metal plate 1 is placed on the collar 43 so that the through hole 4 is coaxial with the collar 3, and the positioning pin 14 is raised by the lifting cylinder 16. At this time, the annular projection 11 at the upper end of the collar 3 is in contact with the lower surface of the metal plate 1, and the positioning pin 14 penetrates the through hole 4 and projects above the metal plate material 1.

In this state, the nut 2 in the posture in which the annular projection 8 is located at the lower end position is used as a positioning pin for the large diameter hole 7a and the small diameter hole 7b.
14 is inserted and placed on the metal plate 1. As a result, the nut 2 is arranged substantially coaxially with the collar 3, and the annular projection 8 substantially opposes the annular projection 11 of the collar 3 with the metal plate material 1 interposed therebetween.

Thereafter, the pressurizing pneumatic cylinder 17 is extended and the nut 2 is fitted with the bottomed cylindrical portion 15a of the upper electrode 15 from above. At this time, the opening end surface of the bottomed cylindrical portion 15a is tapered, and the surface of the collar portion 6 of the nut 2 facing the opening end surface is also tapered, so that the axis of the nut 2 is the axis of the upper electrode 15. Can be matched exactly. Therefore, by arranging the axes of the lower electrode 13 and the upper electrode 15 at the same position, the axes of the collar 3 and the nut 2 can be accurately aligned with each other, so that the annular protrusions 8 and 11 can also be precisely disposed. Become. At this time, pressurizing pneumatic cylinder 17
The pressing force by is the first pressing force P ₁ , and the first pressing force P ₁
Then, while avoiding the annular projections 8 and 11 having a higher hardness than the metal plate material 1 due to the high carbon content from biting into the metal plate material 1, the both annular projections 8 and 11 face each other on both sides of the metal plate material 1 and face each other. It is in a state of being let.

Next, the nut 2 and the collar 3 are pressed against the metal plate 1 by a second pressing force P ₂ which is larger than the first pressing force P ₁ , and
In the pressed state by the second pressing force P ₂ , as shown in FIG. 6, a welding current is passed between the lower electrode 13 and the upper electrode 15. As a result, projection welding by resistance between the annular protrusions 8 and 11 and the metal plate 1 is performed, and the annular protrusions 8 and 11
Melts and is crushed until the stopper surfaces 5 and 10 come into contact with each other, and as shown in FIG.
Are coaxially welded to both front and back surfaces of the metal plate material 1.

At this time, since the annular protrusions 8 and 11 are accurately opposed to each other, the welding current flows through the metal plate material 1 in the shortest distance, and efficient welding is possible. Further, if the nut 2 is pressed only in the axial direction, the lower end portion of the nut 2 is likely to expand in diameter during the welding, but the upper electrode 15 presses the flange portion 6 of the nut 2 through the tapered surface. A force is applied to the lower end of the nut 2 inward in the radial direction, which prevents the lower end of the nut 2 from expanding in diameter during welding.

Moreover, during the projection welding, the pressing force of the nut 2 and the collar 3 to the metal plate material 1 is controlled in two steps as shown in FIG. 6, and it is possible to avoid bite into the metal plate material 1. By pressing the first pressurizing force P ₁ , both annular projections 8 and 11 are pressed against both surfaces of the metal plate material 1 so that the contact area between the metal plate material 1 and the annular projections 8 and 11 is relatively small, and then the second pressurizing force is applied. Since the welding current is supplied while pressing with the pressure P ₂ , it is possible to increase the heat generation effect by energizing the welding while keeping the resistance value relatively large and enhance the welding effect to improve the welding strength. .

The annular projections 8 and 11 are provided on the outer peripheral edges of the surfaces of the metal members 2 and 3 facing the metal plate material 1, and at least the outermost circumference of the collar portion 6 of the nut 2 with respect to the metal plate material 1 is the entire circumference. Thus, at least the outermost periphery of the end surface of the collar 3 is reliably welded to the metal plate 1 over the entire circumference. Therefore, the strength of the nut 2 and the collar 3 with respect to the torque around the axis and the strength of the nut 2 and the collar 3 with respect to the metal plate material 1 are improved, and at the same time, a minute gap that causes rust due to the infiltration of water is formed in the metal plate material 1. And outside of the welded portion of the nut 2 and outside of the welded portion of the collar 3 to the metal plate material 1 are prevented.

Further, even if the nut 2 and the collar 3 are thicker than the metal plate material 1, the annular grooves 9 and 12 are adjacent to the inner sides of the annular protrusions 8 and 11 respectively.
Since it is formed, the heat generated in the annular protrusions 8 and 11 is suppressed as much as possible from flowing to the thick portion inward of the annular grooves 9 and 12, and the welding due to the melting of the annular protrusions 8 and 11 is surely performed. can do.

Moreover, since the annular projections 8 and 11 are provided on the outer peripheral edge of the surfaces of the nut 2 and the collar 3 facing the metal plate material 1, the nut 2
The welding position M (see FIG. 7) of the collar 3 and the metal plate member 1 to the metal plate member 1 is relatively distant from the through hole 4, but the annular groove
The metal plate 1 is placed on the stopper surface 5, 10 at the portion 1a (see FIG. 7) around the through hole 4 on the inner side of the portion corresponding to 9, 12.
Since the pressure is narrowed between them, the portion 1a around the through hole 4 of the metal plate material 1 is prevented from being distorted by the welding heat.

In the above embodiments, the case where the annular protrusions 8 and 11 are provided on the metal member having a high hardness, that is, the nut 2 and the collar 3 has been described. However, the annular protrusion is formed on the metal member side having a hardness lower than that of the metal plate material 1. In this case, the present invention can be applied, and in this case, it is possible to avoid an increase in the contact area due to the annular projection being crushed by being pressed against the metal plate material.

C. Effects of the Invention As described above, according to the first feature of the present invention, the annular projections having sharpened tips are formed in the same diameter on the joining surfaces of the two metal members to the metal plate, respectively. Both metal members are coaxially pressed toward the metal plate while the annular projections are opposed to each other with the plate material sandwiched between them, and a welding current is passed between the two metal members in the pressed state. It is possible to improve the welding efficiency by simultaneously welding and joining two metal members to a metal plate material by projection welding by applying a welding current at the shortest distance.

Further, according to the second feature of the present invention, annular projections having sharpened tips are formed on the joining surfaces of the two metal members to the metal plate member, respectively, with the same diameter, and the metal plate members are sandwiched between them to form an annular shape. After the two metal members are coaxially pressed to the metal plate member side by the first pressing force while the protrusions are opposed to each other to bring both annular protrusions into contact with both surfaces of the metal plate member, the second pressing force larger than the first pressing force is applied. The pressure is applied to the metal plate side, and the welding current is passed between the two metal members only when the second pressing force is applied. Therefore, the welding current is made to flow in the shortest distance between the two annular projections, and the two metal members are projected by welding. It is possible to improve the welding efficiency by simultaneously weld-bonding to the metal plate material, and to avoid the increase of the contact area due to the biting or crushing between both annular projections and the metal plate material to enhance the heat generation effect and improve the welding efficiency and welding strength. To improve Can.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a main part of a projection welding apparatus when projection welding is executed, FIG. 2 is an enlarged view of a II part of FIG. 1, and FIG. FIG. 4 is a vertical sectional front view of the projection welding apparatus,
Fig. 3 is a sectional view taken along the line III-III, Fig. 4 is a sectional view taken along the line IV-IV in Fig. 3, Fig. 5 is a pneumatic circuit diagram, Fig. 6 is a characteristic diagram for controlling welding force and welding current during projection welding, and Fig. FIG. 7 is a vertical cross-sectional view after the completion of welding connection. 1 ... Metal plate material, 2 ... Nut as metal member, 3 ...
… Collar as metal member, 5,10 …… Joining surface, 8,11 ……
Annular protrusion, P ₁ ...... First pressing force, P ₂ ...... Second pressing force

Claims (4)

[Claims] 1. A metal plate material for sandwiching a metal plate material (1) between two metal members (2, 3) coaxially arranged with the metal plate material (1) interposed therebetween. Two metal members (2,3) in welding method of two metal members
The annular projections (8, 11) with sharp tips are formed in the joint surfaces (5, 10) of the metal plate material (1) of the same diameter, and the metal plate material (1) is sandwiched between them to form an annular shape. Both metal members (2, 3) are coaxially pressed to the metal plate (1) side while the projections (8, 11) are opposed to each other, and both metal members (3, 3) are pressed in the pressed state.
4) A method for welding and joining two metal members sandwiching a metal plate material, which is characterized in that a welding current is applied between them. 2. A metal plate material for welding and joining two metal members (2, 3) arranged coaxially with each other with the metal plate material (1) interposed therebetween. Two metal members (2,3) in welding method of two metal members
The annular projections (8, 11) with sharp tips are formed in the joint surfaces (5, 10) of the metal plate material (1) of the same diameter, and the metal plate material (1) is sandwiched between them to form an annular shape. While the protrusions (8, 11) are opposed to each other, both metal members (2, 3) are coaxially pressed against the metal plate material (1) side by the first pressing force (P ₁ ) to form the annular protrusions (8, 11). ) Is contacted with both sides of the metal plate material (1),
It is pressed against the metal plate (1) side with a second pressing force (P ₂ ) larger than the pressing force (P ₁ ), and only between the two metal members (2, 3) when pressing with the second pressing force (P ₂ ). A method for welding and joining two metal members sandwiching a metal plate material, which is characterized in that a welding current is applied. 3. The annular projections (8, 11) have a tip angle of 80 to 11
The method for welding and joining two metal members sandwiching the metal plate member according to the item (1) or (2), wherein the method is set to 0 degree. 4. The metal plate material (1) according to claim 1, wherein the carbon content of the metal plate material (1) and the carbon content of both metal members (2, 3) are different. Method for welding and joining metal members.