JP2002205192A - Welding method for piping - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method for piping, that consumes no inert gas in large quantities, that enables inter-equipment piping to be soundly welded to each other, and that makes smooth fluid flow possible in the piping after the welding. SOLUTION: The method of welding inter-equipment piping 1a, 1b to each other to be the final joints comprises the steps of: a step of inserting each shield partition wall 2a, 2b made of a water-soluble material from the abutting end of the piping; a step in which, after the piping 1a, 1b is abutted on each other, with a fine tube 5 inserted from the groove 3, an inert gas is supplied through this fine tube 5 into the piping 1a, 1b, and in which the piping space including the groove 3 divided by the two shield partition walls 2a, 2b is replaced with an inert gas atmosphere; a step of welding the groove 3 of the piping 1a, 1b; and a step of making water flow through the piping 1a, 1b, dissolving the shield partition walls 2a, 2b and discharging them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding a pipe, and more particularly to a method for welding a pipe in which a process for making the inside of the pipe an inert gas atmosphere during welding is improved.

[0002]

2. Description of the Related Art In order to perform sound welding of a pipe, it is necessary to replace the inside of the pipe with an inert gas atmosphere at the time of welding to prevent oxidation of a welding beat on the inner surface side.

[0003] Conventionally, in order to weld the final joint of a pipe connecting two devices, the pipes are butt-connected, a thin tube is inserted from a groove, and an inert gas such as argon gas is passed through the thin tube. A method is employed in which the gas is supplied into a pipe to replace the inside of the pipe with an inert gas atmosphere, and the groove of the pipe is welded.

[0004]

However, in the above-mentioned conventional welding method, a large amount of inert gas is required because the gas in all the pipes including the entire equipment is replaced with an inert gas. Not only is required, but also the welding cost is increased due to the use of a large amount of inert gas.

According to the present invention, pipes serving as final joints located between devices can be welded soundly without consuming a large amount of inert gas, and fluid flow in the pipes after welding can be smoothly performed. It is an object of the present invention to provide a method for welding a pipe that can be formed into a single piece.

Further, according to the present invention, when a part of a pipe located between devices is replaced with a new pipe, the old pipe and the new pipe can be welded soundly without consuming a large amount of inert gas. Another object of the present invention is to provide a pipe welding method capable of facilitating fluid flow in a pipe after welding.

Further, the present invention makes it possible to weld the pipes which are the final joints of the nitric acid plant soundly without consuming a large amount of inert gas, and to reduce the flow of nitric acid water in the pipes after welding. An object of the present invention is to provide a method for welding pipes that can be smoothly performed.

[0008]

A method for welding pipes according to the present invention is a method for welding pipes, which are final joints located between devices, in a method of welding a pipe made of a water-soluble material from a butt end of each pipe. A step of inserting a partition wall, and abutting the pipes, inserting a thin tube from a groove thereof, and then supplying an inert gas into the pipe through the narrow pipe to open the partition formed by the two shield partitions. Replacing the space including the tip with an inert gas atmosphere;
A step of welding a groove portion of the pipe; and a step of flowing water through each pipe to dissolve and flow out each of the shield partition walls.

Another pipe welding method according to the present invention is a method for welding an old pipe and a new pipe in order to cut off a portion of a pipe located between devices which requires repair and replace the pipe with a new pipe. Cutting off portions of the pipes located between the devices that require repair, and inserting a shield partition made of a water-soluble material into the inside of each of the old pipes from the end of the old pipe on each device side; and The ends of the new pipe are abutted against the ends of the new pipe, and a thin tube is inserted from one of the groove portions. After that, an inert gas is supplied into the old pipe and the new pipe through the thin pipe to thereby form the second pipe. Replacing the piping space including the two groove portions partitioned by the two shield partitions with an inert gas atmosphere, welding the groove portions of the old pipe and the new pipe, and Flow water into the new pipe Dissolving the respective shield bulkhead Te and it is characterized by comprising a step of flowing out.

[0010] Still another method of welding pipes according to the present invention is a method of welding pipes to be final joints of a nitric acid plant, wherein a shield partition made of a copper base material and water-soluble paper is joined from a butt end of each pipe. And a step of inserting each of the pipes, abutting each of the pipes, inserting a capillary from the groove thereof, and then supplying an inert gas into the pipe through the capillary to partition the groove with the two shield partitions. A step of replacing a space including the portion with an inert gas atmosphere, and a step of welding a groove of the pipe.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

(First Embodiment) FIGS. 1 (a) to 1 (c)
FIG. 3 is a cross-sectional view showing a pipe welding step in the first embodiment.

First, as shown in FIG.
Pipes 1a and 1b, which are final joints of two devices (not shown)
Shield partitions 2a and 2b made of discs made of tape-shaped water-soluble paper (trade name, manufactured by Synthetic Chemical Co., Hiselon) are inserted into the inside of each of the butt ends.
Subsequently, the pipes 1a and 1b are butted together, and the groove 3
Then, a thin tube 5 at the tip of the gas introducing tube 4 is inserted, and an inert gas, for example, an argon gas is supplied into the pipes 1a and 1b.
At this time, the piping space 6 including the groove 3 partitioned by the two shield partitions 2a and 2b is replaced with an argon gas atmosphere.

Next, as shown in FIG.
The welding torch 7 of the welding machine is connected to the groove 3 of the pipes 1a and 1b.
And TIG welding is performed.

Next, as shown in FIG. 1 (c), water is supplied into the pipes 1a, 1b connected by the welding beats 8 to thereby form shield partitions 2a, 2b made of discs formed by winding the water-soluble paper. Dissolve and elute and remove.

As described above, according to the first embodiment, the two pipes 1
a, 1b, a shield partition 2 composed of a disk formed by rolling a water-soluble material, for example, a tape-shaped water-soluble paper, from the butt end portion 2
a and 2b, respectively, and abutting the pipes 1a and 1b to form the two shield bulkheads 2a and 2b.
A small-volume piping space 6 including the groove 3 can be defined by a and 2b. Thereafter, the thin tube 5 is removed from the groove 3.
After the inert gas is inserted, the inert gas is supplied into the pipes 1a and 1b through the thin tube 5, whereby the inert gas atmosphere can be replaced with the inert gas atmosphere by supplying a small amount of inert gas. . After replacing the inside of the pipe space 6 with the inert gas atmosphere in this way, for example, by performing TIG welding on the groove 3 of the pipes 1a and 1b, the oxidation of the welding beat 8 on the inner surface side of the pipes 1a and 1b is performed. Prevention and sound welding can be performed.

Further, after the welding, the shield partition wall 2 is formed.
Since a and 2b are made of discs formed by winding a tape-shaped water-soluble paper, which is a water-soluble material, by flowing water into the pipes 1a and 1b, the partition walls 2a and 2b are easily dissolved to form water. And can be removed together. As a result, a fluid can be smoothly circulated in the welded pipes 1a and 1b.

Accordingly, the pipes located between the devices can be welded soundly without consuming a large amount of inert gas and shortening the welding preparation time.

If the pressure in the piping space 6 rises during the replacement operation of the argon gas, welding defects such as holes and recesses are likely to occur, but the tape-shaped water-soluble paper is used as the shielding partition walls 2a and 2b. If a disc having the above-mentioned air permeability is used, it is possible to prevent the pressure in the piping space 6 from increasing.

(Second Embodiment) FIGS. 2 (a) to 2 (c)
FIG. 6 is a cross-sectional view illustrating a pipe welding process according to the second embodiment.

First, for example, as shown in FIG.
Pipes 1a and 1b, which are final joints of two devices (not shown)
Frustum-shaped shield partition walls 9a and 9b each having sugar hardened therein are inserted from the butted ends of the above from the smaller diameter side. Specifically, as shown in FIG. 3, the shield partitions 9a and 9b are formed by joining a plurality of sugar cubes 10 with a water-soluble glue or starch syrup and processing the outer shape into a disk shape with a cutter or the like. Subsequently, the pipes 1a and 1b are abutted with each other, and the thin tube 5 at the tip of the gas introduction pipe 4 is inserted into the groove 3 so that an inert gas, for example, argon gas is supplied to the pipes 1a and 1b.
1b. At this time, the two shield partitions 2
The piping space 6 including the groove 3 defined by a and 2b is replaced with an argon gas atmosphere.

Next, as shown in FIG.
The welding torch 7 of the welding machine is connected to the groove 3 of the pipes 1a and 1b.
And TIG welding is performed.

Next, as shown in FIG. 2 (c), water is supplied into the pipes 1a, 1b connected by the welding bead 8, so that the frustoconical shield partition walls 9a, 9a,
9b is dissolved and discharged and removed.

As described above, according to the second embodiment, the two pipes 1
a, 1b from the abutting ends, into which a water-soluble material, for example, sugar, is solidified.
b is inserted from the end having the smaller diameter, and the pipes 1a and 1b are abutted to define a small-volume pipe space 6 including the groove 3 by the two shield partitions 9a and 9b. be able to. Then, after inserting the thin tube 5 from the groove portion 3, the inert gas is supplied into the pipes 1a and 1b through the thin tube 5,
By supplying a small amount of inert gas, the inside of the piping space 6 can be replaced with an inert gas atmosphere. After the inside of the pipe space 6 is replaced with an inert gas atmosphere in this manner, for example, T
By performing the IG welding on the groove 3 of the pipes 1a and 1b, it is possible to prevent the welding beat 8 on the inner surface side of the pipes 1a and 1b from being oxidized and to perform sound welding.

Further, after the welding, the shielding bulkhead 9 is welded.
Since a and 9b are made from a truncated cone of hardened sugar, which is a water-soluble material, by flowing water through the pipes 1a and 1b, the partition walls 9a and 9b are easily dissolved and removed together with the water. Can be. As a result, the welded pipe 1
Fluid can be smoothly circulated in a and 1b.

In particular, since sugar has a higher solubility in water than the water-soluble paper used in the above-described first embodiment, a smaller amount of water is used as compared to the first embodiment.
1b, the shield partition walls 9a, 9b can be easily dissolved and removed in a short time.

In fact, after welding a 60 mm diameter pipe,
By flowing about 1.5 liters of water through those pipes, the two shield walls of the frusto-conical cone with the solidified sugar dissolved.
Could be removed.

Therefore, the pipes located between the devices can be welded soundly without consuming a large amount of inert gas and shortening the welding preparation time.

If the pressure in the piping space 6 rises during the replacement operation of the argon gas, welding defects such as holes and recesses are likely to occur, but the partition walls 9a and 9b have air permeability in which sugar is solidified. If a truncated cone is used, an increase in pressure in the piping space 6 can be prevented.

Further, by forming the shield partition walls 9a, 9b into a truncated cone made of hardened sugar, it becomes possible to insert these shield partition walls 9a, 9b into the pipes 1a, 1b smoothly.

The shape of the shield partitions 9a and 9b is not limited to a truncated cone with hardened sugar, but may be a disk.

(Third Embodiment) FIGS. 4 (a) and (b) and FIGS. 5 (c) and 5 (d) show welding for replacing a part of piping between devices in the third embodiment. It is sectional drawing which shows a process.

First, as shown in FIG. 4A, a portion between the first device 11a and the second device 11b which requires repair of a pipe (old pipe) 12 made of, for example, stainless steel is cut off, End 13a of old pipe 12 on one device 11a side
And a frustum-shaped shield partition wall 14 in which sugar is solidified from the end 13b of the old pipe 12 on the second device 11b side.
a and 14b are inserted from the smaller diameter side, respectively. Then, as shown in FIG. 4B, both ends of a new pipe (new pipe) 15 made of stainless steel to be replaced are brought into contact with the two ends 13a and 13b of the old pipe 12, and two grooves are formed. The thin tube 18 at the tip of the gas introduction pipe 17 is inserted into one of the groove portions (for example, 16a) of one of 16a and 16b, and an inert gas, for example, argon gas is supplied to the old pipe 1.
2 and into the new pipe 15. At this time, the piping space 19 including the two groove portions 16a and 16b partitioned by the two shield partitions 14a and 14b is replaced with an argon gas atmosphere.

Next, as shown in FIG.
Replace the welding torch of the welding machine with the old piping 1 on the first device 11a side.
2 and the groove 16a of the new pipe 15 are brought close to each other, and TIG welding is performed so that the end of the old pipe 12 on the equipment 11a side and the new pipe 15
Is joined with a welding beat 20a. Then, T
The welding torch 21 of the IG welding machine is brought close to the groove 16b of the old pipe 12 and the new pipe 15 on the second device 11b side,
A part of the old pipe 12 between the first and second devices 11a and 11b is replaced with a new pipe 15 by performing IG welding.

Next, as shown in FIG. 5D, the old pipe 1 in which the new pipe 15 is connected by welding beats 20a and 20b.
By supplying water into the inside 2, the frustoconical shield partition walls 14a, 14b in which the sugar is solidified are dissolved, flowed out and removed.

As described above, according to the third embodiment, the two ends 13a, 1a of the old pipe 12 from which a portion requiring repair is cut off.
3b, a water-soluble material, for example, a frustoconical shield partition wall 14a, 14b in which sugar is solidified is inserted, and both ends of a new pipe 15 to be replaced are connected to two ends 13 of the old pipe 12.
a, 13b, the two shield partitions 14a, 14b allow the two groove portions 16a,
A small-volume piping space 19 including 16b can be defined. Thereafter, after inserting the thin tube 19 from the groove 16a, the inert gas is passed through the thin tube 19 through the thin tube 19.
2 and the inside of the new pipe 15, the inside of the pipe space 19 can be replaced with an inert gas atmosphere by supplying a small amount of inert gas. After replacing the inside of the pipe space 19 with the inert gas atmosphere in this manner, for example, TI
G welding is performed on the groove 16 of the two old pipes 12 and the new pipe 15.
a, 16b, the welding beats 21a, 21 located on the inner surface side between the old pipe 12 and the new pipe 15
b can be prevented from being oxidized and sound welding can be performed.

After the replacement of the new pipe 15 by welding, the shield bulkheads 14a and 14b are made of a truncated cone of solidified sugar, which is a water-soluble material.
2 and the new pipe 15, the shield partition walls 14a and 14b can be easily dissolved and removed together with the water. As a result, the old pipe 1
2 and the new pipe 15 can be smoothly circulated.

Therefore, it is possible to repair and replace a part of the piping between the devices in a sound welding environment without consuming a large amount of inert gas and shortening the welding preparation time.

If the pressure in the piping space 19 rises during the argon gas replacement operation, welding defects such as holes and recesses are likely to occur, but the shielding partition walls 14a, 1
If a truncated cone with hardened sugar is used as 4b, the pressure inside the piping space 19 can be prevented from increasing.

In the third embodiment, a shield partition made of a truncated cone made of hardened sugar is used. However, the present invention is not limited to this. For example, you may use the shield partition which consists of a disk which wound the tape-shaped water-soluble paper (the product name made from a synthetic chemical company; Hitheron).

(Fourth Embodiment) FIGS. 6A to 6C.
It is sectional drawing which shows the welding process of the piping of the nitric acid plant in this 4th Embodiment.

First, as shown in FIG. 6A, a pipe 31 made of Ti or Zr, which is the final joint of the nitric acid plant.
The shield partition walls 32a and 32b are inserted into the insides of the a and 31b from the butt ends thereof. As shown in FIG. 7, the shield partition walls 32a and 32b are made of a copper base material 33 having a cylindrical truncated conical shape and a water-soluble paper (manufactured by Synthetic Chemical Co., Ltd.) attached to the large-diameter annular surface of the base material 33. And a circular plate 34 made of Hitheron). Subsequently, the pipes 31a and 31b are butted, and the groove 3
5, a thin tube 37 at the tip of the gas introduction tube 36 is inserted, and an inert gas, for example, an argon gas is supplied into the pipes 31a and 31b. At this time, the two shield partitions 32a, 3
The piping space 38 including the groove 35 defined by 2b is replaced with an argon gas atmosphere.

Next, as shown in FIG.
The welding torch 39 of the welding machine is brought close to the groove 35 of the pipes 31a and 31b, and TIG welding is performed.

After such TIG welding, the pipe 3 connected by the welding beat 40 as shown in FIG.
When nitric acid water generated in the plant is passed through 1a, 31b, the copper base material 33 in the shape of a truncated cone in the shield partition walls 32a, 32b inserted in the pipes 31a, 31b is dissolved and removed by nitric acid. , This substrate 33
The water-soluble paper (trade name, manufactured by Synthetic Chemical Co., Hiselon) circular plate 34 attached to the large-diameter annular surface is dissolved and removed by water.

As described above, according to the fourth embodiment, the shield partitions 32a and 32b are inserted into the pipes 31a and 31b, which are the final joints of the nitric acid plant, from the butt ends thereof, and the pipes 31a and 31b are butt-connected. By doing so, the two shield partitions 32a, 32b
Thus, a small-volume piping space 38 including the groove 35 can be defined. Thereafter, the thin tube 37 is moved from the groove 35 to the thin tube 37.
After the inert gas is inserted, the inert gas is supplied into the pipes 31a and 31b through the thin tube 37, whereby the inside of the pipe space 38 can be replaced with an inert gas atmosphere by supplying a small amount of inert gas. . After the inside of the piping space 38 is replaced with an inert gas atmosphere in this manner, for example, TI
By performing G welding on the groove portions 35 of the pipes 31a and 31b, the welding beat 4 on the inner surface side of the pipes 31a and 31b is formed.
0 can be prevented from being oxidized and sound welding can be performed.

Further, after welding, the shield partition wall 3
As shown in FIG. 7, reference numerals 2a and 32b denote a copper-made base material 33 in the shape of a cylindrical truncated cone and a water-soluble paper (trade name, manufactured by Synthetic Chemical Company; ), The partition walls 32a, 32b can be easily dissolved and removed together with the nitric acid solution by allowing the nitric acid solution generated in the plant to flow through the pipes 31a, 31b. it can. As a result, the operation of the nitric acid plant can be smoothly performed without the shield partition walls 32a and 32b obstructing the flow of the nitric acid solution.

Therefore, the pipes, which are the final joints of the nitric acid plant, can be welded soundly without consuming a large amount of inert gas and shortening the welding preparation time.

Further, by forming the copper base material 33 constituting the shield partitions 32a and 32b into a truncated conical cylinder, the shield partitions 32a and 32b can be smoothly inserted into the pipes 31a and 31b. Will be possible.

In the fourth embodiment described above, the shield partition walls 32a and 32b having the structure shown in FIG. 7 are used. However, the present invention is not limited to this. For example, FIG.
As shown in FIG. 3B, a copper base material 43 having a wide circular truncated conical ring portion 42 integrally formed on the outer periphery of a disk 41 and the base material 43
Water-soluble paper tape 44 wound around the outer peripheral surface of the ring portion 42
Thus, the shield partitions 32a and 32b may be configured.

The shield partitions 32a and 32b shown in FIGS. 8A and 8B are inserted into the pipes 31a and 31b as shown in FIG. 6A, and the pipes 31a and 31b are butted. By doing so, the two shield partitions 32
a, 32b, a small-volume piping space 3 including the groove 35
8 can be partitioned and supply of a small volume of inert gas into the pipes 31a, 31b by pipes 31a, 31b.
Oxidation of the welding beat on the inner surface side can be prevented, and sound welding can be performed.

Further, after the welding, the shielding bulkhead 3
As shown in FIG. 8, reference numerals 2 a and 32 b denote a copper base material 43 in which a wide circular truncated conical ring portion 42 is integrally formed on the outer periphery of a circular plate 41 and a water-soluble paper wound around the outer peripheral surface of the ring portion 42 of the base material 43 Since it is composed of the tape 44 and the nitric acid solution generated in the plant, the copper base material 43 is dissolved and removed by nitric acid by flowing through the pipes 31a and 31b, and the ring portion 42 of the copper base material 43 is removed. The water-soluble paper tape 44 wound around the outer peripheral surface can be dissolved and removed by water. As a result, the operation of the nitric acid plant can be smoothly performed without the shield partition walls 32a and 32b obstructing the flow of the nitric acid solution.

[0052]

As described above in detail, according to the present invention, it is possible to weld pipes, which are final joints located between devices, soundly without consuming a large amount of inert gas, and It is possible to provide a pipe welding method capable of facilitating fluid flow in a pipe after welding.

Further, according to the present invention, when replacing a part of the pipe located between the devices with a new pipe, the old pipe and the new pipe can be welded soundly without consuming a large amount of inert gas. And a pipe welding method capable of smoothing fluid flow in the pipe after welding can be provided.

Further, according to the present invention, it is possible to weld the pipes to be the final joints of the nitric acid plant without consuming a large amount of inert gas, and to use nitrate water in the pipes after welding. A pipe welding method capable of facilitating distribution can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a pipe welding process according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a pipe welding process according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing a shield partition used in a pipe welding step according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a welding process for replacing a part of a pipe between devices in a third embodiment of the present invention.

FIG. 5 is a sectional view showing a welding process for replacing a part of a pipe between devices according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a process of welding pipes of a nitric acid plant according to a fourth embodiment of the present invention.

FIG. 7 is a perspective view showing a shield partition used in a pipe welding step according to a fourth embodiment of the present invention.

FIG. 8 is a perspective view showing another shield partition used in a pipe welding step according to the fourth embodiment of the present invention.

[Explanation of symbols]

1a, 1b, 12, 15, 31a, 32b ... piping, 2a, 2b, 9a, 9b, 14a, 14b, 32a, 3
2b: shield partition wall, 3, 16a, 16b, 35 ... groove, 5, 18, 37 ... thin tube, 7, 20, 39 ... welding torch, 8, 21a, 21b, 40 ... welding beat.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minoru Nakajima 1-1-1 Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo Prefecture Inside Mitsubishi Heavy Industries, Ltd.Kobe Shipyard (72) Inventor Yasuo Koide Hyogo-ku, Kobe-shi, Hyogo 1-1-1 Wadazakicho Mitsubishi Heavy Industries, Ltd. Kobe Shipyard F-term (reference) 4E001 AA03 BB07 CC03 DD01 DD02

Claims (9)

[Claims] 1. A method for welding pipes, which are final joints located between devices, wherein a step of inserting a shield partition made of a water-soluble material from a butt end of each pipe, and butt each pipe, After the thin tube is inserted from the groove, an inert gas is supplied into the pipe through the thin tube to replace the pipe space including the groove partitioned by the two shield partitions with an inert gas atmosphere. A step of welding a groove portion of the pipe, and a step of flowing water through the pipe to dissolve and flow out the shield partition walls. 2. The pipe welding method according to claim 1, wherein the shield partition wall is formed of a disk formed by winding a tape-shaped water-soluble paper. 3. The pipe welding method according to claim 1, wherein the shield partition wall is made of a hardened sugar disk. 4. A method for cutting a portion of a pipe located between devices requiring repair and welding the old pipe and the new pipe to replace the pipe with a new pipe, the repair of the pipe located between the devices. A step of cutting off the necessary parts, inserting a shield partition made of a water-soluble material into the old pipe ends from the respective equipment side, and attaching both ends of the new pipe to the ends of the old pipes. Butt, after inserting a thin tube from any one of the groove portions, an inert gas is supplied into the old pipe and the new pipe through this thin pipe to separate the two pipes partitioned by the two shield partition walls. Replacing the pipe space including the groove with an inert gas atmosphere, welding the groove of the old pipe and the new pipe, and flowing water into each of the old pipe and the new pipe. Dissolve shield partition, Welding method of the pipe, characterized by comprising a step of out. 5. The pipe welding method according to claim 4, wherein the shield partition is made of a disk formed by winding a tape-shaped water-soluble paper. 6. The pipe welding method according to claim 4, wherein said shield partition wall is made of a hardened sugar disk. 7. A method for welding pipes to be final joints of a nitric acid plant, wherein a step of inserting a shield partition made of a copper base material and water-soluble paper from a butt end of each pipe, respectively, Butt and after inserting a thin tube from the groove, an inert gas is supplied into the pipe through the thin tube, and the pipe space including the groove section divided by the two shield partitions is turned into an inert gas atmosphere. A method for welding a pipe, comprising: a step of replacing; and a step of welding a groove of the pipe. 8. The piping according to claim 7, wherein the shield partition comprises a ring-shaped copper base material and a water-soluble paper disc adhered to one annular surface of the base material. Welding method. 9. The shield partition wall comprises a copper base material having a wide ring portion integrally formed on the outer periphery of a disk and a water-soluble paper tape wound around the outer periphery of the ring portion of the base material. The method for welding a pipe according to claim 7, wherein the pipe is welded.