JP2003225764A - Method and device for welding thin-walled tube to thick plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To weld a heat transfer tube to a tube plate without causing any melt-down or high-temperature oxidation of the inner surface part of the heat transfer tube due to the welding heat input. <P>SOLUTION: A back shield gas pipe 2 to eject back shield gas 24 from a tip opening 22a is held by a welding torch 21. The tip opening 22a of the back shield gas pipe 22 is disposed in the direction of the tip of the welding torch 21. When the end part of the heat transfer tube 4 is inserted into a fitting hole 15 formed in the tube plate 2 and a groove 16 formed at the end part of the fitting hole 15 is welded by the welding torch 21, the back shield gas 24 is blown through the back shield gas pipe 22 to the inner surface part of the heat transfer tube 4 forming a part located on the opposite side of the groove 16. The welding heat input is suppressed by cooling the inner surface part of the heat transfer tube 4 by the back shield gas 24. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to welding a thin-walled tube such as a heat transfer tube to a thick-walled plate such as a tube plate in a heat exchanger used for recovering heat generated in the fields of petroleum, chemistry and energy. The present invention relates to a method for welding a thin-walled pipe to a thick-walled plate used for mounting and a welding apparatus used for carrying out the welding method.

[0002]

2. Description of the Related Art A heat exchanger for recovering energy by exchanging heat between two fluids having different temperatures is shown in FIG. High temperature side tube sheet 2 made of carbon steel or SUS
And the low temperature side tube sheet 3 are arranged to face each other, and the tube sheet 2
Attach a number of SUS heat transfer tubes 4 between
The high temperature fluid 9 introduced from the high temperature fluid inlet 7 of the high temperature side cover plate portion 5 is discharged from the high temperature fluid outlet 8 of the low temperature side cover plate portion 6 through each of the heat transfer tubes 4, and the low temperature side of the main body 1 is The low temperature fluid inlet 10 is provided on the side wall portion near the tube sheet 3, and the low temperature fluid outlet 11 is provided on the side wall portion of the main body body 1 near the high temperature side tube sheet 2. The low temperature fluid 12 that has flowed into the main body 1 is discharged from the low temperature fluid outlet 11 through the low temperature fluid flow path 14 formed by the baffle 13 in the main body cylinder 1, and the high temperature fluid 9 flowing in the heat transfer tube 4 and the main body cylinder The low temperature fluid 12 flowing through the low temperature fluid flow path 14 in 1 is indirectly heat-exchanged via the heat transfer tube 4.

In the above heat exchanger, the portions where the heat transfer tubes 4 are attached to the tube plates 2 and 3 on the high temperature side and the low temperature side are required to have a sealing property. As shown by enlarging the side, a mounting hole 15 penetrating in the thickness direction is formed in the tube sheets 2 and 3, and the heat transfer tube 4 is inserted into the mounting hole 15.
End portion of the mounting hole 15 that is located on the outer surface side of the tube plates 2 and 3 by inserting the end portion of The groove 16 is formed in the circumferential direction in the portion, and the groove 16 is welded in the circumferential direction to attach the ends of the heat transfer tubes 4 to the tube sheets 2 and 3, and
The sealability between the heat transfer tube 3 and the heat transfer tube 4 is obtained.
Reference numeral 17 indicates a weld metal.

[0004]

However, in the case of the heat exchanger of the above type, the tube plates 2 and 3 have high thermal stress due to the contact of the high temperature fluid 9 and the low temperature fluid 12 on their inner and outer surfaces (front and back surfaces). Therefore, a so-called thick-walled plate having a large wall thickness is adopted, while a so-called thin-walled tube having a small wall thickness is adopted as the heat transfer tube 4 so as to obtain high heat transfer characteristics. Therefore, the heat transfer tube 4 that is a thin tube cannot be welded unless the tube sheets 2 and 3 that are thick plates are melted, but the groove 16 is formed in the tube sheets 2 and 3 that are thick plates as described above. When the above is performed, there is a problem that the inner surface of the heat transfer tube 4, which is a thin-walled tube, is melted down or oxidized at high temperature due to the effect of welding heat input. Therefore, until now, the welding work of the tube sheets 2 and 3 and the heat transfer tube 4 was restricted so that the welding heat input would not be excessive, and the welding heat input was strictly controlled. The reality is that it depends on skill and skill.

On the other hand, as another method for limiting the welding heat input, after closing one end of each heat transfer tube 4, one end of each heat transfer tube 4 to be welded is closed, and both ends are closed. Although the welding work was carried out in a state in which an inert gas (Ar) was put in the heat transfer tube 4 and the back shield was used, this method requires a great deal of time and labor for setup before welding. In addition, there is a problem that the cost impact increases, so it is rarely adopted.

In view of the fact that burn-through and high-temperature oxidation on the inner surface of a thin pipe are the effects of excessive welding heat input and a high oxygen atmosphere, the present invention is intended to eliminate burn-through and high-temperature oxidation regardless of the skill of the welding engineer. An object of the present invention is to provide a welding method and apparatus that enable a thin pipe to be welded to a thick plate without causing a weld.

[0007]

According to the present invention, in order to solve the above-mentioned problems, an end portion of a thin-walled tube is inserted into a mounting hole formed in a thick plate to form an end edge portion of the mounting hole. In the welding method of circumferentially welding the ends of the thin-walled pipe to the thick-walled plate using the formed groove, when the ends of the thin-walled pipe are welded to the thick-walled plate, the thin-walled inner side of the welded part is formed. A back shield gas is continuously flown toward the inner surface of the pipe, and the inner surface of the thin-walled pipe is cooled by the back shield gas and the outer periphery of the thin wall pipe is welded in the circumferential direction while maintaining a low oxygen atmosphere. In addition to the welding torch, a back shield gas pipe capable of ejecting a back shield gas from the tip opening is held integrally with the welding torch. Open the tip opening of the shield gas pipe,
A welding device having a structure in which the back shield gas pipe and the welding torch can be moved together in the circumferential direction of the thin-walled pipe at a position in front of the tip of the welding torch and close to the welding torch.

When a thin-walled pipe is welded to a thick-walled plate, the inner surface of the thin-walled pipe, which is a portion located on the back side of the welded portion, is cooled by the back shield gas and a low oxygen atmosphere is maintained. The heat input to welding is suppressed, and burn-through and high-temperature oxidation of the inner surface of the thin-walled pipe are prevented.

If the cooled back shield gas is used, the welding heat input can be suppressed more effectively.

Further, by forming the back shield gas pipe into a flexible structure, the back shield gas pipe is
It can be properly arranged according to the groove shape, the wall thickness of the heat transfer tube, and the like.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and shows an example of application to the part on the high temperature side tube sheet 2 side of the heat exchanger shown in FIG. That is, the end portion of the heat transfer tube 4 which is a thin tube is inserted into the mounting hole 15 which is formed in the tube plate 2 which is a thick plate so as to slightly project to the outer surface side of the tube plate 2, and then the mounting hole 15 In the method of circumferentially welding the end portion of the heat transfer tube 4 to the tube sheet 2 by utilizing the groove 16 formed at the end edge portion, the dedicated welding device 18 is used.

The welding device 18 includes a welding torch 21 which is designed to melt a welding wire (not shown) by the heat of an arc generated at the tip of the electrode 20 while releasing a shield gas (inert gas) 19 from the tip. Have TIG
In the welding device, the base end side of a back shield gas pipe 22 having a required length, the base end of which is connected to a back shield gas cylinder (not shown) via a hose 25, is attached to the welding torch 21 by a mounting jig 23. And the back shield gas pipe 22 is curved appropriately so that the tip opening 22a is located at the front position on the extension line of the tip of the welding torch 21 and at a required distance from the tip of the welding torch 21. When the heat transfer tube 4 is welded to the tube plate 2 by the welding torch 21, the back shield gas (inert gas) 24 fed from the back shield gas cylinder is replaced with the back shield gas. The tip 22a of the tube 22 allows the heat transfer tube 4 to be continuously jetted to the inner surface of the welded portion, and the welding torch 21 and the back seal are provided. So that the gas pipe 22 can be moved in the circumferential direction together. The back shield gas pipe 22
In order to be able to arbitrarily deform and hold the deformed shape, a flexible material such as a copper tube or a flexible metal tube is used.

When the heat transfer tube 4 is attached to the tube sheet 2 by welding using the welding device 18 having the above-described structure, the end of the heat transfer tube 4 is inserted into the attachment hole 15 formed in the tube sheet 2. In the state where the tube end of the heat transfer tube 4 is positioned so as to slightly project to the outer surface side of the tube sheet 2, the opening formed at the edge of the mounting hole 15 on the outer surface side of the tube sheet 2 is opened. Destination 16
The welding torch 21 is disposed toward the inner surface of the heat transfer tube 4 and the tip opening 22a of the back shield gas tube 22 is located on the opposite side of the groove 16 which is a welding point across the wall thickness of the heat transfer tube 4. It is in a state of being placed toward the department. next,
The back shield gas pipe 22 is passed through and the tip opening 22 thereof is provided.
The back shield gas pipe 22 is integrated with the welding torch 21 while ejecting the back shield gas 24 from a.
The groove 16 is welded in the circumferential direction while moving around.

When the heat transfer tube 4 as a thin tube is welded to the tube sheet 2 as a thick plate, the back shield gas 24 ejected from the tip opening 22a of the back shield gas tube 22 is generated by the welding torch 21. Since it is continuously flown toward the inner surface portion of the heat transfer tube 4 which is the back side position of the welded portion, the inner surface of the welded portion of the heat transfer tube 4 can be simultaneously cooled, and by this cooling, the heat transfer tube It is possible to suppress heat input to the welder 4 and prevent burn-through of the inner surface of the heat transfer tube 4, and to prevent high temperature oxidation by keeping the inner surface of the heat transfer tube 4 in a low oxygen atmosphere. can do. As a result, the problem of welding a thin-walled pipe to a thick-walled plate can be solved, a sound weld can be obtained, and high reliability can be obtained.

As described above, the back shield gas pipe 22
According to the welding method in which the back shield gas 24 is flowed to the back side of the welded portion through the welding, the welding can be performed without closing the end of the heat transfer tube 4, and therefore no setup is required before welding. Further, since the back shield gas 24 can surely cool the inner surface portion of the heat transfer tube 4, it is not necessary to strictly control the restriction of the heat input for welding, and therefore, the welding work can be performed regardless of the skill of the welding engineer. It can be carried out. Further, since the welding device 18 can be manufactured by attaching the back shield gas pipe 22 to the welding torch 21 of the existing welding device, the manufacturing cost is low and advantageous.

Further, since the back shield gas pipe 22 has a flexible structure, even when the posture of the welding torch 21 is changed according to the shape of the groove 16 and the wall thickness of the heat transfer pipe 4, for example. , The tip opening 22 depending on the posture
The position and orientation of a can be easily adjusted.

Next, FIG. 2 shows another embodiment of the present invention. In the welding device 18 having the same structure as shown in FIG. 1, the back shield gas 24 is supplied to the back shield gas pipe 22. In the middle of the hose 25 that becomes a road,
A gas cooling device 26 is installed so that the back shield gas 24 in a cooled state can be ejected from the back shield gas pipe 22.

According to the embodiment shown in FIG. 2, as the back shield gas 24 which flows toward the inner surface of the heat transfer tube 4, the back shield gas cooled by the gas cooling device 26 can be used. Can be suppressed more effectively.

In the above embodiment, the case of performing the heat exchanger on the high temperature side tube sheet 2 side has been described, but the same can be done on the low temperature side tube sheet 3 side, only when the heat exchanger is manufactured. However, it is shown that it can be applied even when the heat transfer tube 4 is replaced, and the case where the TIG welding device is adopted.
The back shield gas pipe 22 may be an IG welding device or the like, and the back shield gas pipe 22 may be a welding torch 2 using a clamp tool or the like.
It may be detachable with respect to No. 1, and in addition to the tube plate and heat transfer tube of the heat exchanger, a thin wall tube may be used for the header tube that is a thick plate such as the nozzle header used in various fields. Needless to say, it can be widely adopted as long as it is a place where a thin pipe is inserted into a mounting hole of a thick plate and welded, such as a portion where a certain nozzle is mounted, and various changes can be made without departing from the scope of the present invention. .

[0021]

As described above, according to the present invention, the end portion of the thin-walled tube is inserted into the mounting hole formed in the thick plate so that the groove formed at the end edge portion of the mounting hole is inserted. In a welding method of circumferentially welding an end portion of a thin-walled pipe to a thick-walled plate, when the end portion of the thin-walled pipe is welded to the thick-walled plate, an inner surface portion of the thin-walled pipe that is an inner side of the welded portion To a thick wall plate that continuously flows the back shield gas toward and cools the inner surface of the thin-walled pipe with the back shield gas and welds the outside in the circumferential direction while maintaining a low oxygen atmosphere. The method for welding thin-walled pipes, and, in addition to the welding torch, a backshield gas pipe capable of ejecting a backshield gas from the tip opening is integrally held by the welding torch, and the tip of the backshield gas pipe is Position the opening in front of the tip of the welding torch. Since the back shield gas pipe and the welding torch can be moved together in the circumferential direction of the thin-walled pipe together with the welding torch, it is possible to weld the thin-walled pipe to the thick-walled plate. The back shield gas continuously flows through the inner surface of the thin-walled pipe, which is located on the back side of the pipe, to cool and maintain a low oxygen atmosphere, so that the inner surface of the thin-walled pipe melts down regardless of the skill of the welding engineer. And high temperature oxidation can be prevented, a sound weld can be obtained at low cost, and the heat input to the welding can be reduced by using a gas cooled by a gas cooling device as the back shield gas. This is advantageous because it can be suppressed more effectively. Furthermore, by adopting a flexible structure for the back shield gas pipe, the back seal gas pipe can be adjusted according to the groove shape and the wall thickness of the thin wall pipe. The position of the distal opening of the Dogasu tube can be properly positioned, there is exhibited an excellent effect that.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a welding device of the present invention.

FIG. 2 is a schematic view showing another embodiment of the present invention.

FIG. 3 is a schematic view showing an example of a heat exchanger.

FIG. 4 is an enlarged view of part A of FIG.

[Explanation of symbols]

2,3 Tube plate (thick plate) 4 Heat transfer tube (thin wall tube) 15 mounting holes 16 groove 18 Welding equipment 21 welding torch 22 Back shield gas pipe 22a tip opening 24 Back shield gas 26 Gas cooling device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Taka             3-2-16 Toyosu, Koto-ku, Tokyo Ishikawajima             Harima Heavy Industries Tokyo Engineering Co., Ltd.             In the center F-term (reference) 4E081 AA10 BA20 BA37 BA41 CA08                       CA11 DA12 DA31 FA11 YH03

Claims (5)

[Claims] 1. An end of a thin-walled pipe is inserted into a thick-walled plate by inserting an end of the thin-walled pipe into a mounting hole formed in the thick-walled plate and utilizing a groove formed at an edge of the mounting hole. In the welding method of welding the portion in the circumferential direction, when the end portion of the thin-walled pipe is welded to the thick-walled plate, the back shield gas is continuously flowed toward the inner surface portion of the thin-walled pipe which is the inside of the welded portion. A method for welding a thin-walled pipe to a thick-walled plate, characterized in that the inner surface portion of the thin-walled pipe is cooled by the back shield gas and the outer side of the thin-walled pipe is circumferentially welded while maintaining a low oxygen atmosphere. . 2. The method of welding a thin-walled pipe to a thick-walled plate according to claim 1, wherein the back shield gas is cooled and blown toward the inner surface of the thin-walled pipe. 3. Separately from the welding torch, a back shield gas pipe capable of ejecting a back shield gas from the tip opening is held integrally with the welding torch, and the tip opening of the back shield gas pipe is welded to the above welding. Arranged in front of the tip of the torch and close to the welding torch,
A welding apparatus having a structure in which a back shield gas pipe and a welding torch can be moved together in the circumferential direction of a thin-walled pipe. 4. The welding device according to claim 3, further comprising a gas cooling device for cooling the back shield gas ejected from the back shield gas pipe. 5. The welding apparatus according to claim 3, wherein the back shield gas pipe has a flexible structure.