JP7573201B2 - Welding method and can body manufacturing method - Google Patents

Description

This disclosure relates to a welding method and a method for manufacturing a can body.

Patent Document 1 discloses a method for manufacturing a liquid tank by welding, which prevents the formation of steps or gaps on the inner and outer surfaces of the tank that could cause corrosion. This method for manufacturing a liquid tank involves joining a lid having a tapered portion that extends radially outward on the periphery to a cylindrical body by arc welding, to manufacture the liquid tank. In this method for manufacturing a liquid tank, the body is inserted inside the tapered portion during arc welding.

JP 1992-009276 A

This disclosure provides a welding method that can suppress burn-through, and a method for manufacturing a can body.

The welding method disclosed herein is a welding method for joining a first plate material and a second plate material, in which the first plate material has a first surface portion and a first end portion that is an end portion of the first surface portion, and the first end portion has a first bent portion that is raised at an acute angle with respect to the first surface portion toward a side in a first direction perpendicular to the first surface portion, and the second plate material has a second surface portion along the first surface portion and a second end portion that is an end portion of the second surface portion, and the second end portion has a second bent portion that is raised at an obtuse angle along the first bent portion toward the side in the first direction, and the second surface portion is positioned with a shift from the first surface portion in the first direction by at least the plate thickness of the first surface portion, and the first bent portion is welded by heating the first bent portion while the first bent portion and the second bent portion are butted together.

The welding method and can body manufacturing method disclosed herein can prevent the heated first and second bent portions from sagging. This can prevent burn-through.

FIG. 1 is a perspective view of a can body according to a first embodiment; 1 is a cross-sectional view of a can body according to a first embodiment. Enlarged view of FIG. FIG. 3 is a cross-sectional view of the head plate and the body in a state where they are set in the welding device according to the first embodiment; Enlarged view of FIG. 1 is a cross-sectional view of a head plate and a fuselage after pressing in accordance with the first embodiment; Enlarged view of FIG. 4 is a cross-sectional view of a first end portion and a second end portion before welding in a comparative example; Cross-sectional view of a bead after welding in a comparative example

(The knowledge and other information that formed the basis of this disclosure)
At the time when the inventors came to this disclosure, the technology of the welding method between plate materials was in a state where both ensuring the quality of the welding and improving the productivity were required. Therefore, in the industry, a technology of improving the weldability by deforming the end of the plate material as described in Patent Document 1 was proposed with the aim of improving the quality of the welding. Under such circumstances, the inventors came up with the idea of improving the productivity of welding by performing welding at a higher speed than the general welding speed of about 400 mm/min as described in Patent Document 1. Then, the inventors discovered that there is a problem that when the welding speed is increased using a conventional welding method, the melted part during welding burns through, and the welding performance deteriorates. In particular, in a hot water storage tank used in a hot water supply device, the body plate is large, heavy, and has a weak rigidity compared to the head plate, so the problem of burning through to the inner diameter side due to shrinkage during welding becomes more pronounced. In response to this, the inventors have come to constitute the subject of the present disclosure in order to solve this problem.
Therefore, the present disclosure provides a welding method capable of suppressing burn-through.

Hereinafter, the embodiments will be described in detail with reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters or duplicate description of substantially the same configuration may be omitted.
It should be noted that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

(Embodiment 1)
Hereinafter, the first embodiment will be described with reference to FIGS.
[1-1. Configuration of can body]
Fig. 1 is a perspective view of a can body 1 manufactured using the welding method of the present disclosure. Fig. 2 is a cross-sectional view of the can body 1 cut in the radial direction. An axis AX in the figure is an axis passing through the center of the cylindrical shape formed by the first surface portion 11 and the second surface portion 21.
The can body 1 is a generally cylindrical container and is used as a hot water storage tank for a hot water supply system. The can body 1 has two generally hemispherical end plates (first plate material) 10 and a cylindrical body (second plate material) 20. The can body 1 is manufactured by joining the end plates 10 and the body 20, each of which is formed as an individual plate material, by arc welding.

The mirror plate 10 is a metal plate having a cylindrical first surface 11 and a dome-shaped dome portion 19. The thickness of the first surface 11 is plate thickness T1. In this embodiment, the metal constituting the mirror plate 10 is stainless steel. The mirror plate 10 is work-hardened by processing during manufacturing, and has greater rigidity than the body 20.

The body 20 is a metal plate having a cylindrical second surface 21. The second surface 21 is oriented along the first surface 11, and the respective axes AX are coincident. The thickness of the second surface 21 is plate thickness T2. The inner diameter D2 of the second surface 21 is larger than the inner diameter D1 of the first surface 11. In this embodiment, specifically, the inner diameter D2 is larger than the inner diameter D1 by at least twice the plate thickness T1 of the first surface 11. In this embodiment, the metal constituting the body 20 is stainless steel.

In the can body 1, a bead 30 is formed between the first end 13, which is the end of the first surface 11, and the second end 23, which is the end of the second surface 21. The bead 30 is a portion of the first end 13 and the second end 23 that were melted by welding before welding and then solidified.

Figure 3 is an enlarged view of the bead 30 in the cross-sectional view of Figure 2. As shown in Figure 3, in the can body 1 of the first embodiment, the first surface 11 and the second surface 21 are arranged at positions shifted by a misalignment d in the radial direction (the radial direction of the cylindrical shape formed by the first surface 11 and the second surface 21) with respect to the inner diameter side surfaces of each. The misalignment d is larger than the plate thickness T1 of the first surface 11 and corresponds to half the difference between the inner diameter D2 and the inner diameter D1. Since the misalignment d is larger than the plate thickness T1 of the first surface 11, the second surface 21 is arranged on the radially outward direction DO (first direction) side of the outer diameter surface of the first surface 11. The radially outward direction DO is the direction from the inside to the outside of the radial direction of the cylindrical shape formed by the first surface 11 and the second surface 21.

The cross-sectional shape of the bead 30 connecting the head plate 10 and the body 20 is inclined radially outward in the DO direction from the first end 13 to the second end 23, and is a flat shape with little radial bulge. When the bead 30 has such a flat shape, stress concentration in the bead 30 is reduced.

In particular, the internal pressure and temperature of the can body 1 used as the hot water storage tank of a hot water supply device such as that of embodiment 1 change from moment to moment depending on the hot water supply conditions. For this reason, the can body 1 is repeatedly subjected to the effects of changes in tensile stress due to changes in internal pressure and thermal stress due to changes in temperature. Therefore, in order to improve the durability of the can body 1, it is important to form the bead 30 flat and suppress stress concentration on the bead 30.

In this embodiment, the first surface 11 and the second surface 21 are intentionally misaligned by the amount of misalignment d to suppress burn-through during welding and achieve the flat bead 30 shown in FIG. 3. The manufacturing method of the can body 1 is described below.

[1-2. Manufacturing method of can body]
Next, a method for manufacturing the above-mentioned can body 1 by welding the head plate 10 and the body 20 together will be described.
[1-2-1. Pre-welding process]
Fig. 4 is a cross-sectional view of the head plate 10 and the body 20 when set in the welding device W, showing a cross-section of the head plate 10 and the body 20 cut vertically along the axis AX. Fig. 5 is an enlarged view of Fig. 4, showing the first end 13 and the second end 23.

As shown in FIG. 4, the welding device W has a clamp W1 and two torches W2. The clamp W1 holds two end plates 10 in the direction of the axis AX, and holds the body 20 between the two end plates 10. At this time, the axis AX is horizontal. The clamp W1 can move in the direction of the axis AX of the first surface portion 11 and the second surface portion 21. The clamp W1 can also rotate in the circumferential direction of the first surface portion 11 and the second surface portion 21 around the axis AX of the first surface portion 11 and the second surface portion 21. The torch W2 is a device that generates heat by arc discharge and performs welding using the generated heat. The torch W2 is provided near the first end portion 13 and the second end portion 23, and performs arc discharge vertically from above to below. Also, as shown in FIG. 4, the welding device W may be configured to have a ring-shaped jig W3 that fixes the center of the body 20. The jig W3 is a tool that fastens and fixes substantially the entire circumference of the body 20 from the radially outward direction DO side, and can rotate around the axis AX in the circumferential direction of the first surface portion 11 and the second surface portion 21. The jig W3 prevents the body 20, which has a lower rigidity than the head plate 10, from bending and deforming. The jig W3 also makes it easier to position the body 20 relative to the head plate 10.

As shown in FIG. 5, the first end 13 of the head plate 10 before welding has a first bent portion 15 that is raised toward the radially outward direction (direction perpendicular to the first surface portion) DO. The first bent portion 15 is raised in a direction such that the angle it forms with the first surface portion 11 is angle A1. Angle A1 is an acute angle. The first bent portion 15 is formed around the entire circumference of the first end 13, and the length of the first bent portion 15 in the direction in which the angle it forms with the first surface portion 11 is angle A1 is length L1. In this embodiment, length L1 is at least twice the plate thickness T1.

At the first end 13, a first corner 17 is formed between the first surface 11 and the first bent portion 15. The first corner 17 is a fold formed by the process of forming the first bent portion 15, and is a rounded corner.

As described above, the inner diameter D2 of the second surface 21 of the body 20 sandwiched between the two mirror plates 10 is larger than the inner diameter D1 of the first surface 11 of the mirror plate 10 by more than twice the plate thickness T1 of the first surface 11. Also, as described above, the second surface 21 is located radially outward in the DO direction by the misalignment d from the first surface 11, and the second end 23 of the second surface 21 is positioned radially outward in the DO direction from the outer diameter surface of the first surface 11.

As a result, as shown in FIG. 5, the second end 23 of the body 20 is held in contact with the first end 13 from the radially outer side. In addition, the force of the clamp W1 clamping the mirror plate 10 in the direction of the axis AX causes the second end 23 of the body 20 to come into contact with the outer slope of the first corner portion 17 and the first bent portion 15, and the body 20 is positioned relative to the mirror plate 10. This makes it easy to position the body 20 and the mirror plate 10.

After the head plates 10 and the body 20 have been set on the welding device W, the welding device W applies pressure by moving the clamp W1 in a direction in which the two head plates 10 press against each other in the direction of the axis AX. As a result, the head plates 10 and the body 20 are strongly pressed against each other along the direction of the axis AX.

Figure 6 is a cross-sectional view of the head plate 10 and body 20 set in the welding device W after pressure is applied, showing a cross-section of the head plate 10 and body 20 cut vertically along the axis AX. Figure 7 is an enlarged view of Figure 6, showing the first end 13 and the second end 23. Figure 6 shows the pressure direction of the clamp W1.

As shown in Figures 6 and 7, the clamp W1 moves and the head plate 10 and the body 20 are pressed firmly against each other along the axis AX, forming a second bent portion 25 and a second corner portion 27 at the second end 23.

The second bent portion 25 is formed by pressing the second end portion 23 strongly against the first bent portion 15, and is raised from the second surface portion 21 in the radially outward direction DO. The second bent portion 25 is raised in a direction such that the angle it forms with the second surface portion 21 is angle A2. Angle A2 is an obtuse angle. The sum of angles A1 and A2 is approximately 180 degrees, and the second bent portion 25 follows the first bent portion 15 while making surface contact with the first bent portion 15.

The second bent portion 25 is formed around the entire circumference of the second end portion 23, and has a length L2 in a direction in which the angle it forms with the second surface portion 21 is angle A2. The length L2 of the second bent portion 25 is shorter than the length L1 of the first bent portion 15 by at least the plate thickness T2. In other words, the length L1 of the first bent portion 15 is longer than the length L2 of the second bent portion 25 by at least the plate thickness T2. For this reason, the contact area between the first bent portion 15 and the second bent portion 25 is set large. In addition, the tip 15a of the first bent portion 15 is exposed toward the radially outward direction DO without being covered by the second bent portion 25.

The second corner 27 is a corner formed between the second surface 21 and the second bent portion 25 at the second end 23. The second corner 27 is a rounded corner, and the radius of curvature of the second corner 27 is smaller than the radius of curvature of the first corner 17. Therefore, at the second end 23 rising from the second surface 21 located on the radially outer side DO side of the first surface 11, the radially inner end 25b of the second bent portion 25 tends to be located radially inner. This makes it easier for the area of contact of the second bent portion 25 with the first bent portion 15 to be large.

When the second bent portion 25 is formed, the pre-welding process is completed and the welding process begins.

[1-2-2. Welding process]
In the welding process, the welding device W performs arc welding with the torch W2 while the clamp W1 rotates the head plate 10 and the body 20 around the axis AX. At this time, the clamp W1 applies a force to the head plate 10 in a direction along the axis AX in a direction in which the head plate 10 and the body 20 press against each other. This makes it easier for the first bent portion 15 and the second bent portion 25 to come into surface contact. In addition, since the first bent portion 15 and the second bent portion 25 are inclined with respect to the axis AX, the first bent portion 15 and the second bent portion 25 press against each other, so that the head plate 10 and the body 20 are less likely to be displaced from each other.

The welding device W has a touch sensor (not shown) that detects the position of the tip 15a of the vertically upper portion of the first bent portion 15 formed around the entire circumference of the first end 13. Using the position information detected by the touch sensor, the welding device W moves the torch W2 in the direction of the axis AX and in the radial direction, and causes the torch W2 to arc discharge, aiming at the inside of the target range R in FIG. 7. The target range R is the range from the tip 15a of the first bent portion 15 to the tip 25a of the second bent portion 25. In other words, the target range R is the portion of the first bent portion 15 that is radially outward in the DO direction from the tip 25a of the second bent portion 25.

The torch W2 performs an arc discharge on the target range R of the entire circumference of the first bent portion 15, so that the first end 13 and the second end 23 are joined together around the entire circumference via the bead 30, as shown in FIG. 3. This completes the welding process and the manufacture of the can body 1.

In the welding process, as described above, the torch W2 performs arc discharge on the target range R of the entire circumference of the first bent portion 15. For this reason, it is important to increase the welding speed in order to shorten the time required for welding. However, it is generally known to set the welding speed to about 400 mm/min, as described in Patent Document 1. In general, when the welding speed is increased, the heat input per unit time must also be increased, and the amount of metal that melts and exists as liquid during welding increases, making it easier for burn-through to occur due to the action of gravity and the contraction of the molten part. That is, one of the reasons why the welding speed is not set to more than 400 mm/min in the conventional welding method is that burn-through is more likely to occur and the quality of the weld is more likely to become unstable. In addition, in the conventional welding method, if the welding speed is set to more than 400 mm/min and the heat input per unit time is reduced to an extent that burn-through does not occur, it is considered difficult to form a flat bead. In fact, the inventors have confirmed that by using a comparative welding method different from that of the first embodiment, welding is performed in the range of 600 to 1200 mm/min, with the heat input reduced to a level that does not cause burn-through, and a bead with large bulges or dents is formed. Details of the comparative example will be described later.

In contrast, in this embodiment, the occurrence of burn-through can be suppressed even if the welding speed is set in the range of 600 to 1200 mm/min due to the radial positional deviation of the misalignment d between the first surface 11 of the head plate 10 and the second surface 21 of the body 20. Below, we will use Figure 7 to explain how the welding method of this embodiment can be used to suppress burn-through during the welding process.

In the welding process, the torch W2 mainly inputs heat to the target range R of the first bent portion 15. This heats up the first bent portion 15, causing the temperature to rise. The second bent portion 25, which is in surface contact with the first bent portion 15, is mainly heated by thermal conduction from the first bent portion 15, causing the temperature to rise. As the temperature rises, the first bent portion 15 and the second bent portion 25 undergo a phase transition from solid to liquid, and tend to sag downward (inward radially) under the influence of gravity.

After the first bent portion 15 has transitioned to the liquid phase, it tends to sag downward as indicated by the arrow M1 in FIG. 7 due to the action of gravity and contraction accompanying solidification. As described above, the first bent portion 15 is raised in a direction such that the angle it forms with the first surface portion 11 is an acute angle A1. Therefore, the first bent portion 15 that has transitioned to the liquid phase is easily received by the first surface portion 11, and the first bent portion 15 is less likely to melt down toward the inner diameter side of the first surface portion 11.

After the second bent portion 25 has been phase-transitioned to the liquid phase, it tends to sag downward along the first bent portion 15 as shown by the arrow M2 in FIG. 7. As described above, the length L1 of the first bent portion 15 is longer than the length L2 of the second bent portion 25 by at least the plate thickness T2, and the radius of curvature of the second corner portion 27 is smaller than the radius of curvature of the first corner portion 17, so that the contact area between the first bent portion 15 and the second bent portion 25 tends to be large. Therefore, when the second bent portion 25 sags downward along the first bent portion 15, the second bent portion 25 is less likely to sag due to frictional force. Also, as described above, the second bent portion 25 is formed by rising from the second surface portion 21, which is disposed radially outward in the direction DO from the first surface portion 11 by the amount of the misalignment d. Therefore, even if the second bent portion 25 that has undergone a phase transition to a liquid phase hangs below the second surface portion 21, the second bent portion 25 is likely to come into contact with the first bent portion 15 or the first corner portion 17. This makes it difficult for the second bent portion 25 to melt down toward the inner diameter side of the first surface portion 11.

In this way, in this embodiment, the welding speed is set in the range of 600 to 1200 mm/min, which is faster than normal, and burn-through can be suppressed even when the heat input per unit time is greater than normal welding conditions. Therefore, even in cases where burn-through is likely to occur, such as in the case of a can body 1 that is a hot water storage tank for a hot water supply system, a flat bead 30 as shown in FIG. 3 can be formed.

In the above, the welding speed setting range is set to 600 to 1200 mm/min, but this range includes 600 mm/min, 700 mm/min, 800 mm/min, 900 mm/min, 1000 mm/min, 1100 mm/min, and 1200 mm/min.

[1-3. Effects, etc.]
As described above, in this embodiment, the welding method is a welding method for joining the head plate 10 and the body 20, in which the head plate 10 has a first surface portion 11 and a first end portion 13 which is an end portion of the first surface portion 11, and the first end portion 13 has a first bent portion 15 which is raised at an acute angle with respect to the first surface portion 11 toward the side of the circumferential outer direction DO which is perpendicular to the first surface portion 11, and the body 20 has a second surface portion 21 which is aligned with the first surface portion 11, and a second end 23 which is an end of portion 21, the second end 23 having a second bent portion 25 raised at an obtuse angle along the first bent portion 15 toward the radially outward direction DO, the second surface portion 21 being positioned offset from the first surface portion 11 toward the radially outward direction DO by at least the plate thickness T1 of the first surface portion 11, and the first bent portion 15 and the second bent portion 25 being butted together are welded by heating the first bent portion 15.
As a result, when the first bent portion 15 melts and drips, it is easily received by the first surface portion 11, and when the second bent portion 25 melts and drips, it is easily brought into contact with the first end portion 13. For this reason, even when the welding speed is increased and the heat input is increased, the occurrence of burn-through can be suppressed.

In addition, in the welding method of this embodiment, the first surface portion 11 and the second surface portion 21 are cylindrical in shape, and the first surface portion 11 and the second surface portion 21 are welded while being pressed against each other along the direction of the axis AX of the first surface portion 11.
As a result, the head plate 10 and the body 20 are positioned by the first bent portion 15 and the second bent portion 25 pressing against each other, which makes it easier to position the head plate 10 and the body 20. Also, misalignment between the head plate 10 and the body 20 during welding is less likely to occur.

In addition, in the welding method of the present embodiment, the inner diameter D2 of the second surface portion 21 is formed to be larger than the inner diameter D1 of the first surface portion 11.
As a result, the head plate 10 and the body 20 are positioned, and the second surface portion 21 is disposed to be shifted in the radially outward direction DO with respect to the first surface portion 11. This makes it possible to suppress the occurrence of burn-through.

In addition, in the welding method of this embodiment, the second bent portion 25 is formed by pressing the head plate 10 and the body 20 against each other along the direction of the axis AX of the second surface portion 21 with the second end portion 23 in contact with the first bent portion 15.
As a result, when the second bent portion 25 is formed, the second bent portion 25 and the first bent portion 15 are butted against each other. Therefore, welding can be performed immediately after the second bent portion 25 is formed, and the efficiency of the welding operation can be improved.

In the welding method of the present embodiment, the first bent portion 15 is formed to be longer than the second bent portion 25 .
This increases the contact area between the first bent portion 15 and the second bent portion 25. This improves the efficiency of heat conduction from the heated first bent portion 15 to the second bent portion 25, thereby improving the welding efficiency. In addition, friction between the first bent portion 15 and the second bent portion 25 increases when the second bent portion 25 tries to sag, so that the occurrence of burn-through can be suppressed.

Furthermore, in the welding method of this embodiment, a first corner portion 17 is formed between the first bent portion 15 and the first surface portion 11, and a second corner portion 27 is formed between the second bent portion 25 and the second surface portion 21, and the radius of curvature of the second corner portion 27 is smaller than the radius of curvature of the first corner portion 17.
This increases the contact area between the first bent portion 15 and the second bent portion 25. This improves the efficiency of heat conduction from the heated first bent portion 15 to the second bent portion 25, thereby improving the welding efficiency. In addition, friction between the first bent portion 15 and the second bent portion 25 increases when the second bent portion 25 tries to sag, so that the occurrence of burn-through can be suppressed.

In this embodiment, the manufacturing method for the can body 1 is a manufacturing method for a can body in which the can body 1 is manufactured by welding the end plate 10 and the cylindrical body 20 together, and the end plate 10 and the body 20 are welded together using the welding method described above.
This makes it possible to manufacture can bodies while suppressing burn-through, thereby improving the welding speed and productivity of can body manufacturing.

Comparative Example
As described above, the inventors performed welding by setting the welding speed in the range of 600 to 1200 mm/min for the welding method of the comparative example, which is different from that of the first embodiment. However, in the comparative example, the inventors performed welding after reducing the heat input from the torch W2 in the first embodiment to a level at which no burn-through occurs even in the welding method of the comparative example. Details of the comparative example will be described below.

FIG. 8 is a cross-sectional view of the first end portion 13 and the second end portion 123 before welding in a comparative example.
In the comparative example, welding was performed using the head plate 10 of the above-mentioned embodiment 1 and a body 120 having a different shape from the body 20 of embodiment 1. Specifically, the inner diameter of the cylindrical second surface portion 121 of the body 120 is equal to the inner diameter D1 of the first surface portion 11, not the inner diameter D2 of the second surface portion 21 of embodiment 1. Therefore, as shown in Fig. 8, in the comparative example, the first surface portion 11 and the second surface portion 121 are disposed substantially flush with each other.

In addition, the second end 123, which is the end of the second surface portion 121, is formed with a second bent portion 125 and a second corner portion 127 having substantially the same shape as the second bent portion 25 and the second corner portion 27 formed in the second end 23 of the first embodiment. However, in the comparative example, the length L3 of the second bent portion 125 is set to be longer than the length L2 of the second bent portion 25 in the first embodiment so that the first bent portion 15 is exposed in the circumferential outward direction DO over a range the same as the target range R in the first embodiment.

9 is a cross-sectional view of the bead 130 after welding in the comparative example. As shown in FIG. 9, the bead 130 in the comparative example has a shape with large radial bulges and dents, and is not flat compared to the bead 30 in the first embodiment shown in FIG. 3. In particular, the recess 131 formed between the bead 130 and the body 120 is likely to be subjected to a large load due to stress concentration. This is because the welding method in the comparative example is more likely to cause burn-through than the welding method in the first embodiment, and therefore the heat input per unit time is set smaller than that in the first embodiment in order to prevent burn-through in the welding method in the comparative example. In the comparative example, the heat input per unit time cannot be made sufficiently large, so the bulge and dent of the bead 130 become large due to the unmelted second bend portion 125 as shown in FIG. 9. On the other hand, in the comparative example, when the heat input per unit time is set to the same value as in the first embodiment, defects due to burn-through are more likely to occur, especially in the second bend portion 125. In this way, if a welding method is used in which the positioning of the first surface portion 11 and the second surface portion 21 is not offset by the misalignment d, and the welding speed is set in the range of 600 to 1200 mm/min, it is difficult to achieve welding with consistent quality.

Other Embodiments
As described above, the first embodiment has been described as an example of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. In addition, it is also possible to combine the components described in the first embodiment to create a new embodiment.
Therefore, other embodiments will be exemplified below.

In the first embodiment, it has been described that the second bent portion 25 and the second corner portion 27 are formed by pressing the second end portion 23 against the first bent portion 15, but this is just one example. The second bent portion 25 and the second corner portion 27 do not need to be formed by pressing them against the first bent portion 15, and may be formed in a process before the body 20 is set in the welding device W.

In the first embodiment, the head plate 10 and the body 20 are described as being made of stainless steel, but this is merely an example. The head plate 10 and the body 20 may each be made of a metal other than stainless steel. Also, the head plate 10 and the body 20 may each be made of a different type of metal.

In the first embodiment, it has been described that the head plate 10 has a first bent portion 15 that forms an acute angle A1 with the first surface portion 11, and the body 20 has a second bent portion 25 that forms an obtuse angle A2 with the second surface portion 21, but this is just one example. That is, the head plate 10 may have a first bent portion 15 that forms an obtuse angle A2 with the first surface portion 11, and the body 20 may have a second bent portion 25 that forms an acute angle A1 with the second surface portion 21. In this case, the inner diameter of the first surface portion 11 is set to be the inner diameter D2, and the inner diameter of the second surface portion 21 is set to be the inner diameter D1, and the first surface portion 11 is located radially outward in the DO direction by the amount of the misalignment d from the second surface portion 21. However, as in embodiment 1, when the first bent portion 15 is formed on the highly rigid end plate 10 at an acute angle A1 with the first surface portion 11, the second bent portion 25 is easily formed when the second end portion 23 and the first bent portion 15 are pressed against each other in the pre-welding process.

In the first embodiment, the welding device W detects the position of the tip 15a of the first bent portion 15 using a touch sensor, but this is just one example. For example, instead of a touch sensor, the welding device W may detect the position of the tip 15a using a non-contact sensor such as a visual sensor or an optical sensor such as a laser displacement sensor.

In addition, in the welding method described in embodiment 1, the first surface portion 11 and the second surface portion 21, both of which are cylindrical, are joined, but this is only one example. The first surface portion and the second surface portion joined in the welding method of the present disclosure may each be flat. Even in this case, burn-through can be suppressed in the same way as in embodiment 1.

In addition, in the welding method described in the first embodiment, welding may be performed while inserting a filler material such as a filler rod or a filler wire into the arc atmosphere. In particular, by locating the filler material near the second bent portion 25, even if the second bent portion 25 melts through, the hole caused by the burn-through can be easily sealed with the filler material.

The above-described embodiments are intended to illustrate the technology disclosed herein, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

[Configuration supported by the above embodiment]
The above embodiment supports the following configurations.

(Additional Note)
(Technology 1) A welding method for joining a first plate material and a second plate material, wherein the first plate material has a first surface portion and a first end portion that is an end of the first surface portion, the first end portion having a first bent portion that is raised at an acute angle with respect to the first surface portion toward a side in a first direction perpendicular to the first surface portion, the second plate material has a second surface portion along the first surface portion and a second end portion that is an end of the second surface portion, the second end portion having a second bent portion that is raised at an obtuse angle along the first bent portion toward the side in the first direction, the second surface portion is positioned at a distance from the first surface portion in the first direction by at least the plate thickness of the first surface portion, and the first bent portion and the second bent portion are butted together and then welded by heating the first bent portion.
As a result, when the first bent portion melts and drips, it is easily received by the first surface portion, and when the second bent portion melts and drips, the second bent portion is easily brought into contact with the first end portion. Therefore, even when the welding speed is increased and the heat input is increased, the occurrence of burn-through can be suppressed.

(Technology 2) A welding method described in Technology 1, in which the first surface portion and the second surface portion are cylindrical in shape, the first direction is a radially outward direction of the first surface portion and the second surface portion, and the first plate material and the second plate material are welded while being pressed against each other along the axial direction of the first surface portion.
As a result, the first plate material and the second plate material are positioned by the first bent portion and the second bent portion pressing against each other, which makes it easier to position the first plate material and the second plate material. Also, misalignment between the first plate material and the second plate material during welding is less likely to occur.

(Technology 3) The welding method according to Technology 2, wherein the inner diameter of the second surface portion is formed larger than the inner diameter of the first surface portion.
As a result, the first plate member and the second plate member are positioned such that the second surface portion is shifted in the first direction relative to the first surface portion, thereby making it possible to suppress the occurrence of burn-through.

(Technology 4) The welding method described in Technology 3, wherein the second bent portion is formed by pressing the first plate material and the second plate material against each other along the axial direction with the second end portion in contact with the first bent portion.
As a result, when the second bent portion is formed, the second bent portion and the first bent portion are butted together, so that welding can be performed immediately after the second bent portion is formed, and the efficiency of the welding operation can be improved.

(Technology 5) A welding method according to any one of Technologies 1 to 4, wherein the first bent portion is formed longer than the second bent portion.
This increases the contact area between the first bent portion and the second bent portion, improving the efficiency of heat conduction from the heated first bent portion to the second bent portion and improving welding efficiency. In addition, friction between the second bent portion and the first bent portion increases when the second bent portion tries to sag, suppressing the occurrence of burn-through.

(Technology 6) A welding method described in any one of Techniques 1 to 5, wherein a first corner portion is formed between the first bent portion and the first surface portion, and a second corner portion is formed between the second bent portion and the second surface portion, and a radius of curvature of the second corner portion is smaller than a radius of curvature of the first corner portion.
This increases the contact area between the first bent portion and the second bent portion, improving the efficiency of heat conduction from the heated first bent portion to the second bent portion, thereby improving welding efficiency. Also, the friction between the second bent portion and the first bent portion increases when the second bent portion tries to sag, suppressing the occurrence of burn-through.

(Technology 7) A method for manufacturing a can body, in which a head plate and a cylindrical body are welded to produce a can body, the first plate material being the head plate and the second plate material being the body, and the head plate and the body being welded using a welding method described in any one of Technologies 1 to 6.
This makes it possible to manufacture can bodies while suppressing burn-through, thereby improving the welding speed and productivity of can body manufacturing.

This disclosure is applicable to a method for welding plate materials together. In particular, this disclosure is preferably applicable to a welding method for manufacturing a container having a body and a head plate, such as a hot water storage tank.

REFERENCE SIGNS LIST 1 can body 10 head plate 11 first surface 13 first end 15 first bent portion 15a tip 17 first corner 19 dome portion 20 body 21 second surface 23 second end 25 second bent portion 25a tip 25b end 27 second corner 30 bead 120 body 121 second surface 123 second end 125 second bent portion 127 second corner 130 bead 131 recess A1 angle A2 angle AX axis D1 inner diameter D2 inner diameter DO radially outward direction L1 length L2 length L3 length M1 arrow M2 arrow R target range T1 plate thickness T2 plate thickness W welding device W1 clamp W2 torch W3 Jig d Misalignment

Claims (7)

A welding method for joining a first plate material and a second plate material, comprising:
The first plate member has a first surface portion and a first end portion which is an end portion of the first surface portion,
The first end portion has a first bent portion that is raised at an acute angle with respect to the first surface portion toward a first direction perpendicular to the first surface portion,
The second plate member has a second surface portion along the first surface portion and a second end portion which is an end portion of the second surface portion,
The second end portion has a second bent portion that is raised at an obtuse angle along the first bent portion toward the first direction,
The second surface portion is disposed so as to be shifted from the first surface portion in the first direction by a distance equal to or greater than a plate thickness of the first surface portion,
The first bent portion and the second bent portion are butted against each other, and the first bent portion is heated to weld the first bent portion.
Welding method. the first surface and the second surface are cylindrical;
the first direction is a radially outward direction of the first surface portion and the second surface portion,
The first plate material and the second plate material are welded together while being pressed against each other along the axial direction of the first surface portion.
The welding method according to claim 1. The inner diameter of the second surface portion is larger than the inner diameter of the first surface portion.
The welding method according to claim 2. The second bent portion is formed by pressing the first plate material and the second plate material against each other along the axial direction with the second end portion in contact with the first bent portion.
The welding method according to claim 3. The first bent portion is formed to be longer than the second bent portion.
The welding method according to claim 1. A first corner portion is formed between the first bent portion and the first surface portion,
A second corner portion is formed between the second bent portion and the second surface portion,
The radius of curvature of the second corner portion is smaller than the radius of curvature of the first corner portion.
The welding method according to claim 1. A method for manufacturing a can body, comprising the steps of: manufacturing a can body by welding a head plate and a cylindrical body, the method comprising the steps of:
The first plate member is the head plate, and the second plate member is the fuselage,
The head plate and the fuselage are welded using the welding method according to any one of claims 1 to 6.
Manufacturing method of can body.

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