JP2011152565A - Welding method of butt-welding groove joint of pipe using back shield member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding method for simply and easily executing the shield of an inner surface of a steel tube in the butt welding of the steel tube without leaving foreign matters behind. <P>SOLUTION: In a butt welding method for executing the back shield, wherein a pipe 3, a pipe 5 having a γ plug hole 7 for welding inspection, and a back shield member 1 are included. The back shield member 1 having a strip-like heat-resistant cloth spirally wound corresponding to the inside diameter of the pipe 3 is attached to the inner surface of the pipe. One end of from the center of the back shield member, and one end from the center of the back shield member 1 by attaching the back shield member to the groove side from the γ plug hole 7 of the pipe 5 are drawn out of the γ plug hole 7, grooves are matched with each other, and both pipes are groove-welded after supplying back shield gas. By pulling one end of the back shield member 1 drawn out of the γ plug hole 7 after completing the welding, the back shield member 1 in the pipe 5 and the back shield member in the pipe 3 are successively drawn out, and the back shield member 1 is removed from both pipes. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a welding method for a butt-welded joint of a pipe using a back shield material that does not leave a foreign substance in the pipe easily and butt-welding a steel pipe.

  Conventionally, in welding butt welded pipe joints, a shield gas is used to form a smooth and good back bead by first layer welding so that the surface of the back weld metal does not oxidize when exposed to the atmosphere. It is necessary to use and back it to obtain a smooth molten metal on the back surface. The back shield material for the gas shield needs to be provided with a size suitable for various pipe sizes.

  As an example of back shield material, a method of installing a disc that matches the inner diameter of the pipe before and after the welding groove, connecting the discs with connecting fittings to create a shield gas space, and projecting multiple gas blowout small holes A cylindrical gas outlet pipe and a plurality of leaf springs provided in the front-rear direction of the outlet pipe to blow out argon gas from the center of the outlet pipe (see, for example, Patent Document 1), and before and after the welding groove A method has been proposed in which a front balloon and a rear balloon are installed in the air and air is blown into the balloon by a conduit from a welding inspection γ plug hole to inflate, thereby providing a shield gas space (see, for example, Patent Document 2).

JP-A-5-154694 JP-A-8-309529

  However, in the case of a back shield using a disk in the conventional back shield method, a plate of a size that matches the inner diameter of the pipe is held on the inner surface of the pipe. There is a disadvantage in that a gap is generated between the two, the shield gas leaks from the gap, and a large amount of shield gas needs to be sealed, and a shield plate needs to be prepared for various pipe sizes. Moreover, in the conventional back shield method including the above cited reference 1, it is possible to move and use the back shield device up to the next welded part in the pipe constituted by straight lines in continuous pipe welding. There are also disadvantages in that the work inside the pipe becomes a fall of the disk and the adhesiveness with the inner surface of the pipe decreases. Furthermore, there is a problem that it cannot be removed from the pipe after the final welding is completed.

  In the case of a back shield device using a balloon as disclosed in Patent Document 2, a γ plug hole larger than the balloon is designed so that the balloon is pulled out from the γ plug hole for welding inspection after welding is completed. Therefore, there is a problem that the processing cost and welding cost of the γ plug hole and the plug increase. It is also necessary to prevent the rubber from being damaged when the balloon is pulled out. When a balloon is installed in the vicinity of the weld, there is a problem that the rubber cannot be reused because the rubber is cured by residual heat or welding heat. Although it is a balloon having elasticity, there is a limit to applying it to a similar pipe inner diameter, so it is necessary to prepare a balloon of a size suitable for each pipe inner diameter.

  The present invention can arrange the back shield material close to the welded portion, can reduce the consumption of shield gas, can be used as a back seal material for vertical piping that could not be applied conventionally, It aims at providing the welding method of the butt-welding joint of piping which can be removed without leaving a residue inside piping after completion of welding.

In order to solve the above problems, the present invention mainly adopts the following configuration.
One pipe constituting one groove of the weld groove joint, the other pipe constituting the other groove and having a γ plug hole for welding inspection, and mounted in the one and other pipes A welding method for butt welding the pipe while holding the shield gas in the pipe,
A step of attaching a back shield material in which a belt-like, string-like or linear heat-resistant cloth is spirally wound corresponding to the inner diameter dimension of the one pipe to the pipe inner surface of the one pipe;
A step of pulling out one end of the back shield member attached to the one pipe from the γ plug hole,
A step of attaching the back shield material in which the heat-resistant cloth is wound in a spiral shape corresponding to the inner diameter dimension of the other pipe, to the groove inner side of the pipe inner surface of the other pipe and from the γ plug hole When,
A step of pulling out one end of the back shield material attached to the other pipe from the γ plug hole,
Combining the respective grooves of the one and the other pipes, supplying a back shield gas from between the grooves to the space surrounded by the back shield material, and then welding the two pipes;
By pulling the one end portion of the back shield material drawn out from the γ plug hole after the welding is completed, the back shield material attached to the other pipe and the back shield material attached to the one pipe are sequentially pulled out. The step of removing the back shield material from both pipes is configured to simplify the gas shield on the inner surface of the pipe of the welded portion, and to leave no foreign matter in the pipe.

  According to the present invention, a back shield material is formed using a heat-resistant cloth, and a welding joint welding method that can be taken out from the γ plug hole after the welding operation is completed is a method that does not leave residue in the pipe. A back shield can be formed and back wave welding can be performed.

  The back shield can be formed to a size that matches the required inner diameter of the pipe, and it is stretchable by heat-resistant cloth, so it can be applied to pipes other than standard products, curved pipes, and vertical pipes, and has good adhesion to the inner surface of the pipe. It is improved and it is nonflammable, so it can be installed in a very close position to the welding groove, enabling a stable gas shield and reducing the amount of shield gas consumption to the limit.

  Further, since the heat-resistant cloth is wound up in a roll shape, it is possible to completely remove the back shield foreign matter without leaving the inside of the pipe by pulling out the tip of the heat-resistant cloth as it is after the completion of welding. Furthermore, the taken out back shield can be re-rolled with a hoisting device as it is, and can be reused, and can be used many times for a long time.

In the welding method of the butt-welding groove joint of piping concerning the embodiment of the present invention, it is an arrangement configuration figure before attachment of a back shield material. It is the arrangement block diagram which attached the back shield material in the welding method of the butt-welding groove joint of piping concerning this embodiment. In the welding method of the butt-welding groove joint of the piping which concerns on this embodiment, it is an arrangement block diagram which implements a back shield. It is explanatory drawing which pulls out a back shield material through gamma plug hole in the welding method of the butt-welding groove joint of piping concerning this embodiment. It is a figure which shows the winding apparatus of the heat shield cloth for back shields used for the welding method of the butt-welding groove joint of piping which concerns on this embodiment.

  A welding method for a butt weld groove joint for piping according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 4 show a process from attachment before welding of the back shield material according to the present embodiment to extraction after welding, and FIG. 5 shows a back shield material winding device according to the present embodiment.

  In the drawings, 1 is a back shield material, 2 is a back shield material end, 3 is a pipe (anti-γ plug hole side), 4 is a weld groove (anti-γ plug hole side), and 5 is a pipe (γ plug hole side). , 6 is a welding groove (γ plug hole side), 7 is a γ plug hole (a hole for inserting a γ ray source for welding inspection after welding), 8 is a heat-resistant tape, 9 is a copper pipe, 10 is a shielding gas, 11 is a heater coil, 12 is a welded part, 21 is a back shield material, 22 is an end face alignment base of a heat resistant cloth, 23 is a winding central axis of a hoisting machine, 24 is a wound back shield material, and 25 is A stop member at the end of the back shield material, 26 is a handle for rotating the hoisting machine, 27 is a guide for preventing breakage of the end face of the heat-resistant cloth, and 30 is an end of the wound back shield material.

  In FIG. 1, a groove 4 is formed at one end of a pipe 3 to be butt welded, and a groove 6 is formed at the end of the other pipe 5 in the same manner. 5 is prepared. The back shield material 1 is formed by winding a belt-like, linear or string-like heat-resistant cloth, and can be configured to change the winding diameter of the winding by increasing or decreasing the number of windings to match the inner diameter of the pipe. it can. Further, since the back shield material 1 is made of a cloth, it has elasticity and good adhesion to the inner surface of the pipe. Further, the end portion 2 extends from the innermost peripheral side of the back shield material 1, and the extended end portion 2 is a γ plug hole (for welding inspection after welding) provided in the other pipe 5. It is long enough to be inserted through a hole for inserting the γ-ray source into the pipe.

  In FIG. 2, the back shield material 1 is attached as shown in the vicinity of the groove 4 of one pipe 3 to be butt welded. At the time of this attachment, the end portion 2 of the back shield material 1 is pulled out through a γ plug hole 7 provided in the other pipe 5. Next, before attaching the back shield 1 in the vicinity of the groove 6 of the other pipe 5, the end 2 is pulled out from the γ plug hole 7, and the back shield 1 is set to the groove 6. At this time, the end 2 of the back shield material 1 attached to one pipe 3 is interposed between the outermost peripheral part of the back shield material 1 attached to the other pipe 5 and the inner wall of the pipe 5. . The interposed end portion 2 does not hinder the shielding performance of the back shield material 1 due to the stretchability of the heat-resistant cloth of the back shield material 1.

  Next, as shown in FIG. 3, the welding grooves 4 and 6 are combined, and the groove of the groove is covered with heat-resistant tape 8 to provide airtightness. Thereafter, the copper pipe 9 is enclosed in the pipe surrounded by the back shield material 1 in both pipes 3 and 5 and covered with the heat-resistant tape 8, and the shield gas 10 existing at the end of the copper pipe 9 is passed through the copper pipe 9. Fill the pipe with shielding gas.

  A heater coil 11 for performing the preheat treatment required for welding is installed in the vicinity of the groove (between the groove and the γ plug hole). Thereafter, the shield gas 10 is filled into the pipes covered with the back shield material 1 and the heat-resistant tape 8 in both pipes, and a seal gas is blown from a welding machine (not shown) to infiltrate oxygen into the covered pipes. Welding is performed while preventing to form the illustrated welded portion 12.

  After the end of the butt welding of the pipe by forming the welded portion 12 shown in FIG. 4, first, by pulling the end portion 2 of the back shield material 1 in the pipe 5 protruding from the γ plug hole 7, The back shield material 1 is unwound from the center and extracted. Subsequently, by pulling the end portion 2 (projecting from the γ plug hole 7) of the back shield material 1 in the pipe 3 (pipe faced to face the pipe 5 provided with the γ plug hole 7), The back shield material 1 in the pipe 3 is unwound from the center and extracted. In this way, by leaving the end or tip of the heat-resistant cloth (band-like, string-like, or linear) as it is using the γ plug hole 7, the foreign matter of the back shield material 1 remains in the pipes 5, 3. Can be completely removed without Furthermore, the taken out back shield material 1 can be used again by being wound up again as it is.

  FIG. 5 shows a backshield heat-resistant cloth winding apparatus according to this embodiment. In FIG. 5, the back shield material 21 drawn after the end of the welding shown in FIG. 4 has a belt-like or tape-like heat-resistant cloth temporarily fixed at its end 30 to a stop member 25 at the end of the back shield material in the illustrated example. By rotating the rotating handle 26 of the hoisting machine, the end face alignment base 22 of the heat resistant cloth and the end face misalignment prevention guide 27 of the heat resistant cloth are guided by the both ends of the hoisting machine so that the hoisting center axis 23 of the hoisting machine is the center of rotation. It will be rolled up. If the numerical value indicating the diameter of the back shield material 1 wound up on the end face aligning table 22 is displayed, the back shield material 1 corresponding to the inner diameter of the pipes 3 and 5 can be formed.

  As described above, the welding method of the butt-welded joint of the pipe using the back shield material in the embodiment of the present invention includes the back shield material formed in a roll shape according to the inner diameter of the pipe using a hoisting device. This is a mounting method in which the tip of both heat-resistant cloths is pulled out from the γ plug hole, and the existing γ is installed after the end of the welding operation that requires a back shield. By pulling the end of the heat-resistant cloth drawn out from the plug hole, the roll-shaped back shield material can be taken out from the center, and the back shield material residue is not left inside the piping. To do.

1 Back shield material 2 Back shield material edge 3 Piping (anti-γ plug hole side)
4 Welding groove (anti-γ plug hole side)
5 Piping (γ plug hole side)
6 Weld groove (γ plug hole side)
7 γ plug hole 8 heat resistant tape 9 copper tube 10 shield gas 11 heater coil 12 welded portion 21 back shield material 22 end face alignment base of heat resistant cloth 23 winding central axis of hoisting machine 24 wound back shield material 25 end portion of back shield material Stopping member 26 Handle for rotating the winding machine 27 Guide for preventing breakage of the end face of the heat-resistant cloth 30 End portion of the wound back shield material

Claims (3)

One pipe constituting one groove of the weld groove joint, the other pipe constituting the other groove and having a γ plug hole for welding inspection, and mounted in the one and other pipes A welding method for butt welding the pipe while holding the shield gas in the pipe,
A step of attaching a back shield material in which a belt-like, string-like or linear heat-resistant cloth is spirally wound corresponding to the inner diameter dimension of the one pipe to the pipe inner surface of the one pipe;
A step of pulling out one end of the back shield member attached to the one pipe from the γ plug hole,
A step of attaching the back shield material in which the heat-resistant cloth is wound in a spiral shape corresponding to the inner diameter dimension of the other pipe, to the groove inner side of the pipe inner surface of the other pipe and from the γ plug hole When,
A step of pulling out one end of the back shield material attached to the other pipe from the γ plug hole,
Combining the respective grooves of the one and the other pipes, supplying a back shield gas from between the grooves to the space surrounded by the back shield material, and then welding the two pipes;
By pulling the one end portion of the back shield material drawn out from the γ plug hole after the welding is completed, the back shield material attached to the other pipe and the back shield material attached to the one pipe are sequentially pulled out. Removing the back shield material from both pipes. A welding method for a welded groove joint of a pipe using the back shield material. In claim 1,
Before the groove welding, a preheating heater coil is wound around a pipe between the groove and the γ plug hole, and a welding method for a welded joint of a pipe using a back shield material. In claim 1 or 2,
The back shield material having heat resistance is stretchable and breathable, and can be applied to pipes having no roundness as a cross-sectional shape, and has a sealing effect. Welding method for welded groove joints.

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