JPS6137375A - Pipe welding method - Google Patents

Abstract

PURPOSE:To prevent the oxidation of the inner periphery of the joining part by forming a partitioning space with sandwiching the joining part of the pipe to be welded by an inserting tool into the pipe, by filling up an inert gas in this space and by performing a welding with this condition. CONSTITUTION:The bevel of the tip of pipes 5, 5' to be joined is held with abutting each other and an inserting tool 6 is inserted from one part of the pipe 5, 5' so that the joined part 7 thereof is made about the center of the rubber sheet 2, 2' of the inserting tool 6 into the pipe. An inert gas 8 of Ar, etc. is passed to the joined part 7 from a gas 8 releasing hole 4 which is made between the rubber sheet 2, 2' through a pipe 1. Accordingly the air is discharged from the contact part of the pipes 5, 5' and the gas 8 only is filled up and with this condition the pipe 5, 5' are joined with welding by arc welding, etc. along the bevel which is provided on the outer periphery of the joined part 7. With such method as like this the oxidation of the inner periphery of the joined part 7 due to the heating at welding time and the deterioration in the quality, performance, etc. can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention is a welding method that prevents oxidation of the inner periphery of a pipe joint due to heating during welding, particularly when joining stainless steel pipes by welding.

(b) Technical background In the pipe area, in order to butt the installed pipes and join them by welding, in addition to joining straight pipes as shown in Figure 1, for example, joining a curved pipe to a straight pipe, or joining a curved pipe to a bent pipe. There is a junction.

Conventionally, as a method of connecting such pipes, two pipes (a)
A bevel is provided on the outer periphery of each tube end of (a'), and the tube (
A) and pipe (a') were welded by butting grooves, arc welding, etc.

Welding on the outer circumference of the pipe is performed by melting the pipe base metal and the welding rod or filler metal using high temperatures such as an arc, forming a weld bead. This was done while being covered with active gas, etc.

(c) Problems with the prior art However, with this type of connection method, the circumference (b) of the joint is caused by the high temperature at the outer periphery of the joint due to welding contacting the oxygen in the air inside the pipe due to heat transfer. However, it had the disadvantage of being oxidized.

As a result, the material around the joint of the pipe changes or corrodes, significantly deteriorating its mechanical properties.

In order to solve this problem, a method has been used in which the inside of the tube is filled with an inert gas (C) such as argon or helium instead of air and then welded, but if the tube is long or the diameter of the tube is If it is large, there is a drawback that a large amount of inert gas (C) such as argon is required.

(e) Structure of the Invention In other words, the present invention is characterized in that rubber plates having approximately the same diameter as the inner diameter of the pipe to be welded are attached to the tip of the interstitial pipe at predetermined intervals, and inert gas is released into the pipe between the rubber plates. Prepare a pipe insertion tool with a hole, insert the pipe insertion tool from one side of the pipe, and the joint where the grooves provided at the ends of the pipes to be welded butt against each other will be approximately in the center between the rubber plates. The joints are welded while the space between the rubber plate and the pipe is filled with inert waste supplied to the pipe.

(f) Embodiments of the Invention When the pipe insertion tool used in the welding method of the present invention is shown in FIG. Rubber plates (2) (2') with approximately the same diameter as the inner diameter of the pipe are closed at the tip of the pipe (1) and are welded at predetermined intervals to prevent gas from passing through.A rubber plate holding plate (3) ( 3) is held and placed.

That is, on the gas supply side, a rubber plate (2) threaded and inserted into the tip of the pipe (1) is held between two rubber plate holding plates (3), and screwed together with a nut to prevent gas from leaking. .

Next, attach the rubber plate (2) on the gas supply side to the tip of the pipe (1).
Attach the rubber plate (2') in the same way as for holding. Then, a predetermined number of gas release holes (4) are bored in the pipe (1) between the rubber plate (2) and the rubber plate (2').

Next, fusion using the intraluminal insertion tool (6).

To explain the method using Fig. 3, the pipe to be joined (5) (5″
) and hold the grooves provided at the tips of the tubes so that the joint (7) is approximately at the center of the rubber plate (2) and the rubber plate (2') of the intraluminal insertion tool (6). Intraductal insertion device (6)
Insert from one side of the tube (5) (5'). Then, argon gas (8) is passed through the pipe (1) to the rubber plate (2).
(2) From the gas release hole (4) bored between the joints (
7). Thereby, the joint (7) of the pipe (5) (5') or the rubber plate (2) (2) and the pipe (5) (5')
), air is exhausted from the contact area with argancus (8
) is filled only. In this state, arc welding or the like is performed along the groove provided on the outer periphery of the joint (7).
) are welded and joined.

Fig. 4 shows the joint of the curved pipe (55) and the straight pipe (55).
A bevel is provided at the joint with the curved pipe (55') as described above.
55) Insert the intraductal insertion tool (66) attached to the tip of the flexible pipe (+1) from the side. At this time, if the tube insertion tool (66) cannot be inserted into the specified position in the tube because of the flexible vibrator (11), which is a soft part, use a flexible wire (9) that does not easily buckle, etc. for gas supply. Flexible vibe (11)
Just attach it to and insert it. Then, C1 inert gas is supplied and the joint is welded.

In addition, a fifth rubber plate (2) is placed on the side where the pipe (1) is inserted.
The cutout (21) as shown in Figure (A) or the cutout (21) shown in Figure 5 (
By making a hole (22) as shown in B), the gas that has been welded can be released to the outside, and the inside can always be filled with fresh inert gas.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a joint of a tube according to a conventional method, Fig. 2 is a sectional view of an intraductal insertion device used in the present invention, Fig. 3 is a sectional view of a joint of a pipe according to a method of the present invention using the same, and Fig. 4 1 shows another example, and 5th 1 shows the shape of the rubber plate of (2).

Claims (1)

[Claims] Rubber plates with approximately the same diameter as the inner diameter of the pipe to be welded are attached to the tip of the closed pipe at predetermined intervals, and an inert gas release hole is prepared in the pipe between the rubber plates. Insert the insertion tool from one side of the pipe, position it so that the joint where the grooves on the ends of the pipe to be welded butt against each other is approximately in the center between the rubber plates, and supply inert gas to the pipe. A pipe welding method characterized by welding a joint while filling a space partitioned by a rubber plate and a pipe.