JP2004344936A - Method for welding metal tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for welding a metal tube with which even in the case of welding a long metal tube, a metal tube having small inner diameter, a metal tube having bending, such as an elbow etc., a blockade member is easily fixed in the tube and after welding, the blockade member can simply be removed and further, this welding can be used in a little amount of water. <P>SOLUTION: In the welding method of the metal tubes 10, welded under shut-off state to the back surface of the welding part 12 of both metal tubes 10, 11 from the atmosphere 14 with back shielded gas 13, round cross sectional ice columns 15, 16 closable in the metal tubes 10, 11 are fixed as the sealing state at least anyone of the inner peripheries 22, 23 of the metal tubes 10, 11 with coil-state cooling pipes 20, 21 composed of a flexible synthetic resin wound to the outer peripheries 17, 18 of the metal tubes 10, 11 and coolable to the ice columns 15, 16 through a coolant 19 flowing in the inner part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for welding a metal pipe in which a back surface of a welded part of the metal pipe is shielded from the atmosphere by a back shield gas.
[0002]
[Prior art]
Conventionally, for example, when welding stainless steel pipes used in chemical plant equipment, in order to prevent oxidation and nitridation of the inner surface of the weld metal and the stainless steel pipe, as a back shield gas, for example, an argon gas is used to weld the welded portion. Welded with the back side shielded from the atmosphere. As one method of shielding the back surface of the welded portion with a back shield gas, the opposite end portions of a pair of stainless steel pipes whose opposite end surfaces are disposed in contact with each other are closed with a plug material, and a plug at one end portion is plugged. An inert gas is injected into both stainless steel pipes through an inlet formed in the material, and is discharged through an outlet at the other end. In this method, if the length of the stainless steel pipe becomes long, the amount of inert gas to be injected increases, which is uneconomical.Therefore, plug materials are provided on both sides near the welded portion, and the space between the two plug materials is inert. A method is known in which a gas is supplied to form a back shield gas and welding is performed. In this case, a plug made of a water-soluble material that dissolves in balloons or water that expands and contracts is used as the plug material (for example, see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 05-245633 (abstract, FIGS. 1 to 3)
[0004]
[Problems to be solved by the invention]
However, the conventional method of welding a metal pipe in a state of being shielded from the atmosphere by the back shield gas has the following problems to be solved.
When the plug material is a balloon, it is difficult to take in (insert) and remove the balloon filled with gas, which causes a problem especially with a long metal tube, a small diameter metal tube, and a bent metal tube such as an elbow. It was big.
Also, when the plug material is a water-soluble material, the plug material is fixed with an adhesive and the welded plug material is removed by dissolving it by flowing water, so depending on the adhesive strength of the adhesive. The plug material remained in the pipe and the pipe was clogged, and a large amount of water was required.
[0005]
The present invention has been made in view of such circumstances, and even in welding a long metal tube, a metal tube having a small inner diameter, or a bent metal tube such as an elbow, it is easy to fix the closing member in the tube, and An object of the present invention is to provide a method for welding a metal pipe, in which a closing member can be easily removed after welding and a small amount of water is used.
[0006]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a method for welding a metal pipe, the method comprising: welding a back surface of a welded portion of the metal pipes with a back shield gas shielding the atmosphere from the atmosphere;
A coil-shaped cooling pipe made of a synthetic resin material having flexibility, which is capable of closing the inside of the metal tube and having a circular cross section, which is wound around the outer periphery of the metal tube, and which can cool the ice column through a refrigerant flowing through the inside. Thereby, the metal tube is fixed to the inner periphery of at least one of the metal tubes in a sealed state.
This makes it possible to cool the icicles through the refrigerant flowing therein, and by winding a coil-shaped cooling pipe made of a synthetic resin material having flexibility around the outer periphery of the metal pipe, an icicle having a circular cross section capable of closing the inside of the metal pipe is provided. Can be fixed in a sealed state on the inner periphery, and welding can be performed in a state where the back surface of the welded portion between the metal tubes is shielded from the atmosphere by the back shield gas.
[0007]
A method for welding a metal pipe according to a second aspect of the present invention is the method for welding a metal pipe according to the first aspect, wherein a seal tape is attached in a circumferential direction so as to cover the gap between the welded portions and close the gap. The welding portion is sequentially moved in the circumferential direction while partially peeling off the sealing tape for welding. Thereby, the weld can be sufficiently shielded from the atmosphere by the back shield gas for welding.
The method for welding a metal pipe according to a third aspect of the present invention is the method for welding a metal pipe according to the first and second aspects, wherein water is sprayed near a fixed position of the icicle in the metal pipe, and An ice ring is formed and fixed on the inner periphery of the metal tube, and the ice column inserted into the metal tube is positioned by contacting the ice ring. Thereby, the ice pillar can be installed at an optimum position in the metal tube by the ice ring.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.
Here, FIG. 1A is a configuration diagram in a method for welding a metal tube according to an embodiment of the present invention, FIG. 1B is a cross-sectional view taken along the line AA of FIG. FIG. 3 is a schematic configuration diagram of a cool air supply unit that supplies a refrigerant to a cooling pipe used in a welding method, FIG. 3 is an explanatory view showing a method of welding the metal pipe, and FIG. 4 is a metal according to another embodiment of the present invention. FIG. 5 is an explanatory view of a method of welding a pipe, FIG. 5 is an arrangement view illustrating a method of welding a metal pipe according to an embodiment of the present invention, and FIG. 6 is an explanatory view of a method of positioning an icicle.
[0009]
As shown in FIGS. 1 to 3, a method for welding a metal pipe according to an embodiment of the present invention is performed, for example, in a processing facility such as a chemical plant by backing a back surface of a weld 12 between metal pipes 10 and 11. This is a method of welding in a state of shielding from the atmosphere 14 by an argon gas 13 which is an example of a shielding gas, wherein ice pillars 15 and 16 having circular cross sections capable of closing the inside of the metal tubes 10 and 11 are formed around the outer periphery of the metal tubes 10 and 11. A metal tube is formed by coil-shaped cooling tubes 20 and 21 made of polyurethane, which is an example of a synthetic resin material having flexibility, which can cool the icicles 15 and 16 via a refrigerant 19 which is wound around 17 and 18 and flows inside. It is fixed to the inner circumferences 22 and 23 of 10 and 11 in a sealed state. Hereinafter, these will be described in detail.
[0010]
As shown in FIG. 1, for example, a groove for welding is formed on each end face 24, 25 of the welded portion 12 of the metal pipes 10, 11 made of stainless steel pipe, and the metal pipes 10, 11 are straightened. To place. In addition, a substantially small gap G is formed between the end faces 24 and 25.
Back the back surface of the welded portion 12 at a position in the metal tubes 10 and 11 away from the end surfaces 24 and 25 of the metal tubes 10 and 11 by distances M and N (for example, M = 100 to 150 mm, N = 100 to 150 mm). The icicles 15, 16 which are shielded from the atmosphere 14 by the shield gas are fixed to the inner circumferences 22, 23 of the metal tubes 10, 11 in a sealed state. In order to fix the icicles 15 and 16 in a sealed state, a cool air supply means 26 for cooling the icicles shown in FIG. 2 is used. Since the cold air supply means 26 is used in the final connecting pipe work of the processing equipment, various pipes may be provided in a narrow place, so that the cool air supply means 26 is configured as compact as possible.
[0011]
As shown in FIG. 2, the cold air supply means 26 for cooling the icicles includes, for example, a small refrigerator 27 for compressing Freon gas, which becomes the refrigerant 19 at a high pressure, into the cooling tubes 20 and 21, and the refrigerator 27 and the respective cooling tubes. Dry columns 28 and 28a provided for each of the pipes 20a and 21a (copper pipe or polyurethane tube) connecting the pipes 20 and 21 to remove moisture in the pipes 20a and 21a, and the filling amount of the refrigerant 19 in the pipes 20a and 21a. , And expansion valves 30, 30a for adjusting the flow and temperature of the refrigerant 19. Therefore, the icicles 15, 16 are cooled by cooling the icicles 15, 16 via the metal tubes 10, 11 with the extremely low temperature (-15 to -20 ° C.) refrigerant 19 supplied to the cooling tubes 20, 21, so that the icicles 15, 16 are cooled. 10 and 11 can be fixed.
[0012]
In addition, since the cooling pipes 20 and 21 are made of flexible polyurethane, the cooling pipes 19, which are initially linear, are wound in a coil shape along the outer circumferences 17 and 18 of the metal pipes 10 and 11, and the coolant 19 is allowed to flow therethrough. After use, the metal pipes 10 and 11 are removed from the outer circumferences 17 and 18 of the metal pipes 10 and 11 so that the original shape is obtained. Therefore, the usability is better than that of a cooling pipe made of a conventional copper pipe. That is, in the case of a copper tube, there is a possibility that it will be disposable only once because of the frequency of winding around the metal tube. In addition, the method of winding a copper tube around a metal tube such as stainless steel easily causes a problem in terms of quality. On the other hand, the polyurethane tube is extremely easy to be attached to and detached from the metal tubes 10 and 11, and has excellent adhesion to the metal tubes 10 and 11, so that the winding and removing operations are compared with those of the copper tube. Can be easily done. In particular, when the working space is narrow, workability is improved. It should be noted that the thermal conductivity of polyurethane is not much different from that of copper.
[0013]
As shown in FIG. 1 and FIG. 3, two aluminum sealing tapes 31 and 32 are joined at the lower ends (points O in the drawings) of the metal tubes 10 and 11 at one ends thereof to form a gap between the welded portions 12. Paste in the circumferential direction covering G. The other ends of the sealing tapes 31 and 32 close the gap G at the upper end so that a supply port 34 for supplying the argon gas 13 between the icicles 15 and 16 is formed at the upper end of the metal tubes 10 and 11. Not.
[0014]
As shown in FIG. 3, the supply port 34 is inserted, the tip 36 of a small-diameter gas supply pipe 35 made of stainless steel is disposed between the ice columns 15 and 16, and the air between the ice columns 15 and 16 is purged by the argon gas 13. Replace. The welding can be performed in a state where the back surface of the welded portion 12 is shielded from the atmosphere 14 by the argon gas 13. The welding is performed by sequentially moving the welded portion 12 in the circumferential direction while partially peeling off the seal tapes 31 and 32 alternately. That is, in the present embodiment, welding is performed from the lower end portion to the upper end portion while alternately repeating counterclockwise and clockwise. Note that the base end of the gas supply pipe 35 is connected to an argon gas supply source via a joint (not shown) and a flow control valve.
[0015]
Next, an operation procedure of the method for welding a metal pipe according to one embodiment of the present invention will be described with reference to FIGS.
(1) As shown in FIGS. 1 and 2, the end faces 24 and 25 of the metal pipes 10 and 11 to be welded are opposed to each other, and the welded portion 12 is temporarily attached.
(2) The cooling pipes 20 and 21 are wound around the outer circumferences 17 and 18 of the metal pipes 10 and 11 corresponding to the positions where the ice pillars 15 and 16 are to be fixed.
(3) As shown in FIG. 2, a cool air supply means 26 is connected to the respective supply ports and discharge ports of the cooling pipes 20 and 21.
(4) The pipings 20a and 21a through which the refrigerant 19 passes, including the cooling pipes 20 and 21, are sufficiently evacuated by a vacuum pump (not shown).
[0016]
(5) The liquefied Freon gas is injected into the evacuated refrigerator 27 from a Freon gas cylinder as the refrigerant 19.
(6) The refrigerator 27 is operated, the filling amount of the refrigerant 19 in the pipes 20a, 21a is measured by the flow meters 29, 29a, and the flow and temperature of the refrigerant 19 are adjusted by the expansion valves 30, 30a.
(7) After confirming the cooling state of the metal tubes 10 and 11 by the cooling tubes 20 and 21, the insertion ice columns 15 a and 16 a which are the bases of the ice columns 15 and 16 are arranged at predetermined positions.
[0017]
(8) After the insertion icicles 15a, 16a are inserted, water is sprayed by spraying into the gaps between the insertion icicles 15a, 16a and the inner circumferences 22, 23 of the metal tubes 10, 11, so that icing portions are formed in the gaps. The icicles 15 and 16 can be fixed to the metal tubes 10 and 11 (see FIG. 6).
(9) As shown in FIGS. 1 and 3, seal tapes 31 and 32 are attached to the outer peripheries 17 and 18 of the welded portions 12 of the metal tubes 10 and 11 to close most of the gaps G, and the argon gas 13 is placed on an icicle. A supply port 34 for supplying between 15 and 16 is formed.
(10) As shown in FIG. 3, the gas supply pipe 35 is inserted into the metal pipes 10 and 11 through the supply port 34.
[0018]
(11) While continuously supplying the argon gas 13 between the icicles 15 and 16 from the distal end portion 36 of the gas supply pipe 35, the welding portions 12 are welded in the following order as shown in FIG. The portions of the seal tapes 31 and 32 corresponding to the portions to be welded are appropriately peeled off from the outer peripheries 17 and 18 of the metal tubes 10 and 11.
part a (from point O to point A) → part b (from point O to point B) → part c (from point A to point C) → part d (from point B to point D) → part e (from point C) (To point E) → f part (from point D to point E)
In addition, near the point E, immediately after the argon gas 13 is sufficiently blown, welding is performed so as to close the hole near the point E.
[0019]
FIG. 4 illustrates a method for welding a metal pipe according to another embodiment of the present invention.
A metal tube 39 penetrating the building wall 37 and projecting a distance L (for example, L = 80 to 250 mm) from the surface 38 of the wall 37, and a short metal tube arranged to face the metal tube 39 This is a case where the welding portion 41 with the welding portion 40 is welded.
As shown in FIG. 4, an ice column 43 having a length H (= LK) is fixed at a position away from the end surface 42 of the metal tube 39 by a distance K (for example, K = 30 to 50 mm). A coil-shaped cooling tube 45 made of a synthetic resin material having flexibility is provided on the outer surface 44 of the metal tube 39 corresponding to the position of 43. On the other hand, no icicles are provided in the metal tube 40, and therefore, no cooling tube is provided, and a sealing cap 46 is provided at the end on the side remote from the welded portion 41. The procedure for welding the welded portion 41 is based on the procedure of the method of the above-described embodiment, with a seal tape applied to close most of the gap, and the welded portion 41 is shielded from the atmosphere 14 by the argon gas 13. Weld.
[0020]
【Example】
Referring to FIG. 5, an embodiment of a method for welding a metal pipe will be described.
A metal tube 49 penetrating through the wall 47 of the building and projecting from the surface 48 of the wall 47 by a distance P (for example, P = 80 to 250 mm), and a metal tube 49 parallel to and along the surface 48 of the wall 47. And a metal pipe 50 arranged perpendicular to the metal pipe 50 by welding via an elbow (an example of a metal pipe) 51.
First, when welding the welded portion 52 between the metal tube 49 and the elbow 51, the ice column 53 is fixed in a sealed state on the inner periphery of the metal tube 49 by the cooling tube 54 wound around the outer periphery of the metal tube 49. The ice column 55 is fixed to the inner periphery of the elbow 51 in a sealed state by the cooling pipe 56 wound around the outer periphery of the elbow 51. Next, when welding the welded portion 57 between the elbow 51 and the metal pipe 50, the ice column 55 is fixed to the inner circumference of the elbow 51 in a sealed state by the cooling pipe 56 wound around the outer circumference of the elbow 51. The ice column 58 is fixed to the inner periphery of the metal tube 50 in a sealed state by the cooling tube 59 wound around the outer periphery of the tube 50. Then, in accordance with the method according to the above-described embodiment, most of the gaps are closed by sticking a seal tape, and the welded portions 52 and 57 are welded while being shielded from the atmosphere 14 by the argon gas 13.
[0021]
In the above, the method for positioning the icicle on the metal tube has not been described, but one method for positioning will be described with reference to FIG.
In the on-site piping work, for example, a negative pressure is applied to the inside of the metal pipe 60 due to the operation related to the blower and the test operation of the apparatus. For this reason, in a normal installation method (for example, an operator moves and positions an icicle inserted in a metal tube with a rod-shaped object), a flow of air is generated due to a negative pressure, and the surface of the icicle is melted. In addition, the weld cannot be shielded from the atmosphere 14 by the argon gas 13. Therefore, the method of installing the icicles at the time of negative pressure is performed in the following manner. However, FIG. 6 illustrates a case where two insertion ice pillars 61 and 62 are installed in the metal tube 60 in order to securely install the ice pillars and completely shield from the atmosphere 14.
[0022]
(1) Before inserting the insertion icicle 61 into the metal tube 60, water is sprayed near the fixing position of the insertion icicle 61, and an ice ring 63 is formed on the inner periphery 64 of the metal tube 60 by the cooling pipe 33. I do. Note that the shape of the ice ring 63 is approximately the same as the back bead.
(2) The icicle 61 for insertion is inserted into the metal tube 60 and is brought into contact with the ice ring 63. (Since the flow of air in the metal tube 60 is restricted by the ice column 61 for insertion, the formation of the ice ring 65, the insertion of the ice column 62 for insertion, and the freezing of the ice column 62 for insertion can be easily performed later.)
[0023]
(3) Immediately after the insertion of the ice column 61, an ice ring 65 is formed at a predetermined position in the metal tube 60 in the same manner as the ice ring 63.
(4) The ice column 62 for insertion is inserted into the metal tube 60 and is positioned by being brought into contact with the ice ring 65.
(5) Water is sprayed into a gap between the insertion icicle 62 and the metal pipe 60, and the cooling pipe 33 forms the gap as an iced portion 66.
[0024]
The present invention is not limited to the above-described embodiments, and changes can be made without departing from the spirit of the present invention. For example, some or all of the above-described embodiments and modifications are described. The case where the metal pipe welding method of the present invention is configured in combination is also included in the scope of the present invention.
In the above-described embodiment, the icicles for insertion 15a and 16a are inserted into the metal tubes 10 and 11 from the ends apart from the welded portion 12, respectively. However, the present invention is not limited to this. It can also be inserted from the 12 side.
[0025]
Although the two metal tubes 10 and 11 are connected in a straight line, the present invention is not limited to this, and the two metal tubes can be welded and connected in a T-shape as needed.
The gap G of the welded portion 12 is closed with a pair of two sealing tapes 31 and 32, and while the sealing tapes 31 and 32 are partially peeled off, the welded portion 12 is alternately rotated clockwise and counterclockwise in the circumferential direction. However, the present invention is not limited to this, and it is also possible to perform welding in one direction with a single piece of sealing tape as needed.
Although two insertion ice columns 61 and 62 are installed in the metal tube 60, the present invention is not limited to this, and only one insertion ice column can be fixed by one ice ring depending on the situation.
Polyurethane was used as the material of the cooling pipe, but the material is not limited to this, and polyethylene, vinyl, and the like can also be used.
The two cooling pipes 20, 21 were connected to the refrigerator 27 to form two icicles 15, 16, but the present invention is not limited to this. If necessary, three or more cooling pipes may be used. The above icicles can also be formed. Further, although one ice column is formed by one cooling pipe, a plurality of ice columns can be formed at a plurality of locations by one cooling pipe having a long length.
[0026]
【The invention's effect】
In the method for welding a metal tube according to any one of claims 1 to 3, the chilled column made of a synthetic resin material having flexibility capable of cooling an icicle through a refrigerant flowing therein is wound around the outer periphery of the metal tube. Therefore, the icicle having a circular cross section capable of closing the inside of the metal tube is fixed to the inner periphery in a sealed state, and the back surface of the welded portion between the metal tubes can be welded in a state where the back surface is shielded from the atmosphere by the back shield gas. When welding metal pipes, metal pipes with small diameters, or bent metal pipes such as elbows, the welded portions of the metal pipes are easily closed by icicles, and the icicles can be easily removed. Applicable.
In particular, in the metal pipe welding method according to the second aspect, the back surface of the welded portion can be sufficiently shielded from the atmosphere by the back shield gas for welding, so that oxidation and nitriding of the welded portion can be prevented, and the welded portion can be prevented. The quality is improved.
In the method for welding a metal pipe according to the third aspect, the ice pillar can be installed at an optimum position in the metal pipe by the ice ring, so that the workability of installing the ice pillar is improved, and after the welding, the ice ring is installed. Can be dissolved and removed together with the icicle.
[Brief description of the drawings]
FIG. 1A is a configuration diagram in a method for welding a metal pipe according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line AA of FIG.
FIG. 2 is a schematic configuration diagram of a cool air supply unit that supplies a refrigerant to a cooling pipe used in the method of welding the metal pipe.
FIG. 3 is an explanatory view showing a point of a welding method of the metal pipe.
FIG. 4 is an explanatory diagram of a method for welding a metal pipe according to another embodiment of the present invention.
FIG. 5 is a layout diagram illustrating a method for welding a metal pipe according to an embodiment of the present invention.
FIG. 6 is an explanatory diagram of a method of positioning an icicle.
[Explanation of symbols]
10, 11: metal tube, 12: weld, 13: argon gas (back shield gas), 14: air, 15: icicle, 15a: icicle for insertion, 16: icicle, 16a: icicle for insertion, 17, 18: Outer circumference, 19: refrigerant, 20: cooling pipe, 20a: pipe, 21: cooling pipe, 21a: pipe, 22, 23: inner circumference, 24, 25: end face, 26: cold air supply means, 27: refrigerator, 28, 28a: dry column, 29, 29a: flow meter, 30, 30a: expansion valve, 31, 32: seal tape, 33: cooling pipe, 34: supply port, 35: gas supply pipe, 36: tip, 37: wall , 38: surface, 39, 40: metal tube, 41: weld, 42: end surface, 43: icicle, 44: outer surface, 45: cooling tube, 46: cap, 47: wall, 48: surface, 49, 50: Metal tube, 51: elbow, 52: weld, 53: ice , 54: cooling pipe, 55: icicle, 56: cooling pipe, 57: weld, 58: icicle, 59: cooling pipe, 60: metal pipe, 61, 62: insertion icicle, 63: ice ring, 64: inside Zhou, 65: Ice ring, 66: Freezing part

Claims (3)

In a metal pipe welding method of welding in a state where the back surface of the welded portion of the metal tubes is shielded from the atmosphere by a back shield gas,
A coil-shaped cooling pipe made of a synthetic resin material having flexibility, which is capable of closing the inside of the metal tube and having a circular cross section, which is wound around the outer periphery of the metal tube, and which can cool the ice column through a refrigerant flowing through the inside. A metal pipe is fixed to the inner circumference of at least one of the metal pipes in a sealed state. The method for welding a metal pipe according to claim 1, wherein a seal tape is attached in a circumferential direction to cover the gap between the welded portions to close the gap, and then the welded portion is peeled while partially peeling the seal tape. A welding method for a metal pipe, wherein the metal pipe is sequentially moved in a circumferential direction and welded. 3. The method for welding a metal pipe according to claim 1, wherein water is sprayed near a fixed position of the icicle in the metal pipe, and an ice ring is formed on an inner periphery of the metal pipe by the cooling pipe. A method for welding a metal pipe, comprising: fixing and positioning the icicle inserted into the metal pipe against the ice ring.

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