JPS62127170A - Butt welding method - Google Patents

Abstract

PURPOSE:To execute efficiently welding without executing a tack welding by executing the welding by changing a welding condition by interposed and non- interposed parts of a weldable spacer which has been interposed at an interval in a root gap of a body to be welded such as a pipeline, etc. CONSTITUTION:For instance, when bringing pipelines 1, 1 to butt welding, an edge preparation of a bevel angle theta1 and a root face width (d) is performed to the end part of both of them, and both the pipelines form a root gap 2 of width l by their root face 1a. In this state, plural pieces of spacers 3 consisting of a material of the same quality is that of the pipes 1, 1 and having a side face of a trapezoidal shape are inserted and attached at a suitable interval to the gap 2 along the longitudinal direction of the face 1a. Thereafter, welding is executed automatically by a welding robot along the butt part of the pipes 1, 1, but in the interposed and non-interposed parts of the spacer 3, welding sectional areas are different, therefore, as for the interposed part, a welding condition which has expected an increase portion of the welding sectional area is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a butt welding method suitable for butt welding pipes and the like.

[Conventional technology 1 Conventionally, when butt welding objects to be welded such as piping,
In the so-called temporary attachment, the root gap is temporarily fixed by welding, and then the actual welding is performed.

[Problems to be Solved by the Invention] However, it is extremely troublesome to perform temporary welding prior to main welding. Moreover, when applying the so-called single-sided uranami welding method, which welds from one side and produces an uranami,
In order to sufficiently combine the uranami from welding and the uranami from main welding, the tack welding described above requires face-to-face work when the weld bead of the tack weld is processed with a grinder before the main welding.
This was a major factor in reducing the efficiency of welding work.

In addition, in order to omit temporary welding, a welding method has been proposed in which an insert ring of the same diameter as the pipe is i%tW in the root gap, and this insert ring and the pipe are TIG welded. Although this is effective when the machining accuracy of the piping is high, it is important to properly insert the insert ring into the root gap when the machining accuracy is not good, such as for piping used in long-distance vibrating lines. There is a drawback. In addition, this welding method has the problem that the insert ring is expensive and TIG welding that does not use a filler rod is adopted, resulting in a long welding time.

[Means for Solving the Problems] In view of this situation, the present invention interposes spacers made of a weldable material at predetermined intervals in the root gap of the welded object, and connects the part where the spacers are interposed. Butt welding is performed while changing the welding conditions for the uninterposed part.

[Example 1 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 and FIG. 2, which is a cross-sectional view of the same figure taken along the line X--X, show an embodiment in which the welding method according to the present invention is applied to butt welding of pipes 1 and 1.

As shown in FIG. 1, the ends of the pipes 1, 1 to be welded are beveled with a bevel angle θ1 (for example, 30”) and a root face width d. are arranged so that a root gap of width 1 is formed by their root face surfaces 1a.

In an embodiment of the invention, a spacer 3, as illustrated in FIG. 3, is used, which is made of the same material as the tubes 1,1. This spacer 3 has trapezoidal side surfaces, and therefore its wall thickness becomes thinner toward both ends.

Now, assuming that the outer diameter of the pipe 1 is 318.5M, the wall thickness e is 8°2mm, the root face width d is 1.5may, and the width l of the root gap 2 is 3M, the pipe 1 is used. The length 81 width and height C of the spacer 3 are set to, for example, a=25 mm, b=3ffl, and c=2 mm, respectively.

As shown in FIG. 2, a plurality of spacers 3 are inserted into the root gap 2 at appropriate intervals of 4M along the length of the root face 1a, and the spacers 3 are inserted into the root gap 2 at appropriate intervals along the length of the root face 1a.
In this case, for example, 8 pieces are inserted at intervals of about 125 meters.

Note that the angle θ2 of the slope 3 shown in FIG. 3 is, for example, 30
” is set.

After the spacer 3 is inserted, automatic welding is performed by a welding robot along the butt portions of the tubes 1 and 1, but at this point, there is a part where the spacer 3 is interposed and a part where the spacer 3 is not interposed. It is necessary to change the welding conditions.

That is, the melting cross-sectional area of the spacer 3 intervening part and the non-intervening part are naturally different. For example, in the pipe 1, the melting cross-sectional area of the spacer intervening part increases by about 27% compared to that of the non-intervening part. Therefore, the welding conditions must be different between the spacer-interposed part and the non-spacer-interposed part.

Note that the increase in the melting cross-sectional area is comparable to the melting cross-sectional area when the root gap is 1 dark.

Regarding the welding conditions, a theory has been established by C. E., Jacs On, etc. that ``if the molten cross-sectional area of the groove is the same, the same weld penetration can be obtained regardless of the cross-sectional shape.''

Therefore, in this embodiment, a torch (not shown) is used as a second torch.
The root gap width is 3# until reaching the 81st point shown in the figure.
Welding conditions I are applied, and while the torch moves from the 81st point to the 22nd point, welding conditions that take into account the increase in the fusion cross-sectional area are applied. Thus spacer 3
Since both ends of the spacer 3 are formed thin, the back waves of the spacer-free part and the back surface of the spacer-interposed part are well bonded.

While performing the above welding, the root gap 2
The width l is maintained by spacers 3 interposed in other parts. In other words, the spacer 3 prevents the root gap width from changing due to welding thermal stress.

In order to make the welding robot change the welding conditions, it is necessary to teach the robot the position of the spacer 3 in advance, or to make the robot itself recognize the position of the spacer 3 using an appropriate sensor.

The present invention can be effectively applied to welding objects to be welded other than piping. However, it cannot be applied to objects to be welded where the groove opens due to thermal stress such as submerging. This is because there is a risk that the spacer 3 may fall during welding.

[Advantageous Effects of the Invention 1] According to the present invention, butt welding of pipes, etc. can be performed for tack welding without welding.

Therefore, the tack welding and the tack attachment of the dam that connects the back waves do not require grinding of the welded part, thereby making it possible to simplify and speed up the welding work.

[Brief explanation of drawings]

1 and 2 are conceptual diagrams illustrating embodiments of the butt welding method according to the present invention, and FIG. 3 is a perspective view illustrating an example of a spacer. 1... Piping, 1a... Root face, 2... Root gap, 3... Spacer.

Claims (2)

[Claims] (1) Spacers made of a meltable material are interposed at predetermined intervals in the root gap of the welded object, and butt welding is performed while changing the welding conditions between the part where the spacer is interposed and the part where the spacer is not interposed. A butt welding method characterized by: (2) Claim No. 1, in which the spacer is formed so that both end portions are thinner than the center portion.
Butt welding method as described in section.