JPH0694077B2 - Reinforcement welding method for existing pipe weld defect - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for reinforcing welding of a welding defect portion, and more particularly to a welding method for efficiently performing reinforcing welding of a joint portion of an existing steel pipe from the inner surface.

[Prior Art] As a reinforcing means for a weld defect portion of an existing steel pipe, a method such as removal and replacement of the pipe, or attachment of a repair band from the outer surface of the pipe is adopted. For example, Japanese Patent Laid-Open No. 62-158570 discloses a reinforcing member (repair band) around a defective portion of an existing pipe.
A reinforced welding method for automatically welding is disclosed.

Also, when a worker cannot enter the inside of a pipe such as a small-medium diameter pipe, as a device that remotely reinforces the inside of the pipe,
The thing of Unexamined-Japanese-Patent No. 56-114577 is known.

[Problems to be Solved by the Invention] However, the method of reinforcing from the outer surface disclosed in Japanese Patent Laid-Open No. 62-158570 has been adopted at present because other structural obstacles, regional environmental obstacles, traffic obstacles and the like occur. At the same time, there are some difficulties, and there is the inconvenience of not being able to work due to space restrictions, such as when reinforcing the back of abutments or overhangs.

Further, the other device disclosed in Japanese Patent Laid-Open No. Sho 56-114577 discloses a mechanism for performing the reinforcement welding of the inner surface of the pipe by remote control, but the place to be weld-reinforced is in a state suitable for welding. I haven't paid any attention to what is going on.

That is, in general, gas arc welding is easily affected by contamination of the base material, and it is required to sufficiently remove oil, water, rust and the like. In addition, organic substances and inorganic substances may be deposited and deposited on the inner surface of the actual reinforcing portion.If these deposits penetrate to the deep portion of the defective portion, all of the defective portion should be transferred to the grinder etc. It is difficult to remove unless ground and ground. However, at present, a means for selectively and effectively grinding a predetermined reinforced portion on the inner surface of the pipe has not been developed.

Therefore, in the case of reinforcement welding from the inner surface of the pipe, there may be a case where it is necessary to perform welding while leaving such adhered deposits. As a result, these deposits caused welding defects such as pits, blowholes, humming, and bead drop.

The present invention solves such a problem, and when reinforcing the defective portion of the existing pipe from the inner surface side, even if the adhered deposit that adversely affects the welding remains at the welded portion, sufficient quality is obtained. It is an object of the present invention to provide a reinforcement welding method capable of obtaining a reinforcement welded portion without defects.

[Means for Solving the Problem] The reinforcing welding method of the present invention for achieving this object is to adhere to the welding defect portion before the main welding when the welding defect portion of the existing pipe is subjected to the reinforcement welding from the inner surface of the pipe. After the pretreatment for burning and melting the deposit, the defective portion is main-welded. The pretreatment for burning and melting this deposit is
It is preferable to use the same welding equipment as that using the consumable electrode used for the main welding and to utilize the arc heat.

[Operation] In the present invention, since the welding defect portion to be a reinforcing portion is pretreated by arc heat or the like, the adhered deposit remaining on the defect portion is almost completely burned and consumed, and the subsequent main welding is hindered. It can be carried out without any trouble and a good quality reinforcing welded portion can be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION The welding method of the present invention will be described in detail below with reference to the drawings.

FIG. 1 schematically shows an example of the process of the present invention, in which the existing welded portion is formed by welding from the outer surface side 1A of the joint portion of the existing pipes 1 and 2 having a pipe diameter of approximately 600 mm and a plate thickness of approximately 9.5 mm. The case where the tube having 3 is taken as an example is shown. When the groove-shaped defect portion 4 is present on the inner surface side 1B of the existing welded portion 3 of this existing pipe, leaving the groove-shaped defect portion 4 will cause damage to the pipe. Therefore, reinforcement welding is performed at the position of the defective portion 4.

The welding equipment for this reinforcement welding is required to have a structure that can be inserted into an existing pipe to smoothly carry out various necessary operations. An example is shown. That is, the welding machine 15 at the front is equipped with necessary polishing and cleaning members, welding torches, welding equipment such as an inspection machine, and its drive / control mechanism, and following the carriage 15, the wire carriage 15, the clamp carriage 17, and the drive. (Cylinder) carriage 18, valve carriage 19 and the like are arranged.

Since fats and oils, rust 5 and the like are adhered and deposited inside the welding defect portion 4, first, in the present invention, the defect portion, that is, the reinforcing portion is pre-treated in advance by a gas arc welding apparatus for performing main welding. Carry out welding. In this pretreatment welding, since it is not necessary to weld the reinforcing portion, arc heat is generated under the condition that the amount of welding is small (low heat input), and the deposit 5 inside the defect portion 4 is burned and melted. 6 in FIG. 1 (b)
Indicates the pretreatment weld.

Next, after the completion of the pretreatment welding, as shown in FIG. 1 (c), two-pass main welding is immediately performed by the welding device. In the figure, 7a is the weld portion of the first pass of the main welding, and 7b is the weld portion of the second pass. In the first pass of the main welding, the welding including the pretreatment welded portion 6 is performed. As a result, the pretreatment welded portion 6 is remelted and integrated with the main welding, and as a result, the pretreatment welded portion 6 is obtained. Even if there is a defect, the final welding can ensure stable welding quality.

FIG. 1 (d) shows an example in which the main welding is performed in 6 passes. 8a to 8f show welds of 6 passes, respectively, and the pretreatment weld 6 is remelted in the main welding of pass 8c.

This pretreatment welding has relatively low heat input and arc breakage compared to the main welding with the smallest possible welding amount, so that the deposited metal does not drop and does not adversely affect the main welding. Therefore, about 4.5 KJ / cm is preferable. However, in the welding posture, for example, in the welding such as the downward welding in which the sagging does not occur, the heat input weight can be increased.

In the above illustrated example, the pretreatment welding is performed using the welding equipment using the same consumable electrode as the main welding, but the present invention is not limited to this and, for example, welding In addition to the torch, a suitable combustion burner may be provided in the vicinity of the torch to burn the deposited deposit.
However, it is of course preferable to use the same welding equipment in consideration of the complexity of equipment and work.

[Example] An artificial defect joint shown in Fig. 3 (base material JIS SS41, plate thickness 10
mm, groove size, width 5 mm, depth 5 mm) was produced, and tar 10 was applied to the groove 9 at 0.3 g / cm to carry out the reinforcement welding of the present invention and conventional welding. The welding conditions at that time are as shown in Table 1 below.

As a result of the above welding, according to the method of the present invention, FIG.
As shown in (1), the weld bead 11 in the first pass of the main welding had a beautiful appearance without any defects, and the tensile strength thereof was also a sufficiently satisfactory value. On the other hand, according to the conventional method, as shown in FIG. 2 (b), defects such as the welding bead 12 pit 13 and the sag 14 of the first pass are seen, and the bead height and the bead width vary greatly. If reinforcement welding is not performed again after grinding the bead, sufficient quality of the reinforcement cannot be secured.

[Advantages of the Invention] By using the method of the present invention as described above, it becomes possible to weld a defective portion of an existing pipe even in a state where the reinforcing portion cannot be sufficiently ground, and thus a large pipe is required. It can be reinforced from the inner surface of the pipe without requiring external reinforcement work. In addition, since the welding equipment using the same consumable electrode as the large welding is used and the pretreatment is performed by utilizing the arc heat, the pretreatment by this arc can be carried out without requiring a special device, so it is extremely It is both economical and efficient.
Furthermore, since the arc heat uses welding equipment with a consumable electrode, the electrode is automatically fed, so even if the arc is temporarily interrupted, it will recover immediately and a continuous stable arc will be obtained. be able to.

[Brief description of drawings]

FIGS. 1 (a), (b), (c) and (d) show process diagrams for carrying out reinforcement welding of a welded joint portion for explaining the method of the present invention. 2 (a) and 2 (b) are bead appearance views obtained by the reinforcement welding of the method of the present invention and the conventional method, respectively, and FIG. 3 is a cross-sectional view showing the outline of test materials in the examples of the present invention. The figure is a schematic view showing a welding carriage used when carrying out the welding method of the present invention and a group of various carriages connected to the welding carriage. 1,2 …… Existing pipe, 3 …… Existing welded part, 4 …… Welding defect part,
5 ... Adhered deposits, 6 ... Pretreatment welds, 7,8 ... Main welds, 9 ... Grooves, 10 ... Tar, 11,12 ... Weld beads, 13 ... Pits, 14 ... Drooping part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Sakoma 5-11-61 Torishima, Konohana-ku, Osaka City, Osaka Prefecture (11-61) Inside the Pipeline Technology Center, Osaka Gas Co., Ltd. (72) Masatoshi Tsuchiya 5-Toroshima, Konohana-ku, Osaka City, Osaka Prefecture 11-61 Osaka Gas Co., Ltd. Conduit Technology Center (56) Reference JP-A-60-92074 (JP, A)

Claims (1)

[Claims] 1. When the welding defective portion of an existing pipe is reinforced and welded from the inner surface of the pipe, the same welding equipment using the consumable electrode used for the main welding is used before the main welding, and the arc heat is used to make use of the welding defective portion. A method for reinforcing welding of a welding defect portion, which comprises performing a pretreatment for sintering and melting the deposit adhered to, and immediately transferring to main welding.