JPH0140714B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a welding method, and particularly to a welding method for welding cylindrical members such as pipes, tanks, and flanges.

[Technical background of the invention and its problems]

Conventionally, when welding pipes, tanks, flanges, etc., pipe 1 is welded as shown in Figure 1.
A groove is provided on the outer periphery of the joining portion of a and 1b, and this groove is welded using an arc heat source such as TIG or plasma. As another method, as shown in FIG. 2, there is a method in which grooves are provided on the outer circumferential side and the inner circumferential side of the joint portion of the flange 2 and the pipe 1, respectively, and arc welding is performed.

In the above-described welding method, weld metal often protrudes as excess on the outer and inner circumferential sides of each welded portion 3 , 3 . When a normal pipe or the like is used, fluid flows inside, so there is a problem in that the flow of the fluid is disturbed by the extra buildup, especially the extra buildup on the inner circumferential surface. Therefore, there is a drawback that the excess portion of the inner circumferential surface must be finished smooth by machining after welding. In addition, as shown in Figure 1, it is extremely difficult in terms of welding technology to produce extra buildup all around the inner circumferential surface by welding the first layer. It also has the drawbacks that the amount of metal is large, defects such as welding distortion are likely to occur, and processing after welding is highly necessary.

Furthermore, in recent years, instead of arc welding, welding methods using high energy density heat sources such as lasers and electron beams have come into widespread use. As shown in Fig. 3, such welding using a laser or the like is performed by irradiating the joined portion of the pipes 1a and 1b with a laser or electron beam from the outer circumferential side (in the direction of the arrow in the figure). In order to perform thick penetration welding, pipes 1a and 1b are
There is usually an excess of about 1 mm on the inner peripheral surface of the joint. Therefore, it has the disadvantage that it is necessary to smoothen the excess portion after welding is completed. In addition, if welding conditions are selected so as to reduce the height of the excess buildup, there is a drawback that partial penetration is insufficient and welding defects are likely to occur.

Furthermore, in laser or electron beam welding, the penetration width is very narrow, so if the direction of the laser or electron beam shifts slightly, as shown in Figure 4, the joining part of pipes 1a and 1b may It also has the disadvantage that no welding is performed on the inner circumferential side. This is not a problem if the direction of the welding beam and the direction of the joint surface are exactly matched, but it is extremely difficult in practice because a high precision of about ±0.1 to 0.2 mm is usually required.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a welding method that can reduce finishing work after welding and eliminate welding defects such as insufficient penetration.

[Summary of the invention]

In order to achieve the above object, the welding method of the present invention includes:
In a welding method for joining members having a cylindrical shape such as pipes, tanks, flanges, etc., welding is performed from the outer periphery of the joining part of the above members using a high energy density heat source so as to leave an unwelded part on the inner periphery of the joining part. At the same time, welding is performed from the inner peripheral side of the joint portion to the welding portion by the high energy density heat source using the arc heat source.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 5 to 10.

FIG. 5 shows an embodiment of the present invention.
In this embodiment, the end surfaces of the real pipes 1a and 1b are brought together, and a laser beam is irradiated from the outer periphery of this joined portion as a high energy density heat source. The above-mentioned laser is generated by a laser oscillator (not shown) such as a carbon dioxide laser oscillator, and after being reflected by a beam bender 4, it passes through a condensing lens 5 and directs the joint between the pipes 1a and 1b in a direction perpendicular to the central axis of the pipes. It is irradiated from
In addition, a TIG welding torch 6 is installed inside the pipe 1a.
is provided so that its tip is oriented toward the inner circumferential side of the joining portion of the pipes 1a and 1b.

In this embodiment, laser welding is performed from the outer periphery of the joined portion of the pipes 1a and 1b, and this welding is performed so as to leave an unwelded portion of about 2 mm or less on the inner periphery of the joined portion. Then, TIG welding is performed from the inner peripheral side of the joint part using a TIG welding torch 6, and the welding conditions at this time are such that the welding depth reaches the welding part 7 by the laser, and both welding parts 7, 8 are set so that they overlap by about 1 mm.

At this time, in this embodiment, the pipes 1a, 1
b is configured to rotate continuously around its central axis, so that welding can be performed without moving the laser and welding torch 6.

Therefore, in the above embodiment, pipe 1
Since there is almost no excess on the inner circumferential side of the joining part of pipes 1a and 1b, the amount of finishing work after welding can be reduced, and the joining part of both pipes 1a and 1b does not remain unwelded. Stable quality can be obtained.

In addition, the tip of the laser welded part 7 is TIG
Since the welding part 8 is remelted, welding defects such as blowholes and cold shots that tend to occur at the welding tip of laser welding can be removed.

FIG. 6 shows another embodiment of the present invention,
An engaging protrusion 9 formed by extending the inner circumferential edge of the pipe 1b in the axial direction is provided on the joint surface of one pipe 1b, and an engaging protrusion 9 that engages with the engaging protrusion 9 is provided on the joint surface of the other pipe 1a. A cutout step portion 10 is provided.
The engaging protrusion 9 may have a wall thickness of 0.5 to 2 mm and a protrusion length of 0.2 to 1 mm. Then, the engaging protrusion 9 is engaged with the notch step 10 to join both pipes 1a and 1b.

In addition, arrow A in the figure is the welding direction of the laser, and arrow B is
1 and 2 respectively indicate the welding directions of TIG welding, and similarly to the above embodiment, laser welding is performed from the outer circumferential side of the pipes 1a and 1b, and TIG welding is performed from the inner circumferential side.
At this time, conditions are set so that the welded part 7 by laser welding reaches the part where the engaging protrusion 9 and the notched step part 10 are engaged, and the TIG
Conditions are set so that the welded part 8 by welding overlaps the laser welded part 7 by about 1 mm.

Therefore, in this embodiment, welding can be performed without leaving any unwelded parts and with almost no excess on the inner circumferential surfaces of the joint portions of the pipes 1a and 1b, as in the above embodiments. Further, since both the pipes 1a and 1b are joined by engaging the engaging protrusion 9 and the notch step 10, it is easy to maintain the joint of the pipes 1a and 1b. Can be joined accurately. In this case, TIG welding from the inner circumference of the pipe is
Since the welding width is wide, even if the engaging protrusion 9 and the notch step 10 are provided, insufficient melting or unwelded portions will not occur.

FIG. 7 shows another embodiment of the present invention,
An example is shown in which a flange 2 is joined to one end of a pipe 1. A step 11 that engages with the pipe 1 is provided on the joint surface of the flange 2, and by engaging the end of the pipe 1 with the step 11, the pipe 1 and the flange 2 are joined. .

Then, as in each of the above embodiments, laser welding is performed from the direction of arrow A, and from the direction of arrow B.
TIG weld. At this time, the laser beam is irradiated at a slight angle, and the appropriate irradiation angle is practically in the range of about 5° to 20°. For example, when the wall thickness of the pipe 1 is 9 mm and the height difference of the stepped portion 11 is 0.5 mm, the irradiation angle is set to about 5 degrees.

In this embodiment as well, welding can be performed without any excess on the inner peripheral surface of the pipe and without any unwelded parts, and the pipe 1 and flange 2 can be joined easily and accurately.

FIG. 8 shows still another embodiment of the present invention, in which a joint portion 12 is provided in which the inner peripheral edge of the flange 2 on the joint side extends in the axial direction with the same wall thickness as the pipe 1. Similarly to the embodiment shown in FIG. 6, a cutout step 10 and an engaging protrusion 9 are provided on the end face of the joint 12 and the end face of the pipe 1, respectively. In this embodiment, by engaging the notch step portion 10 and the engagement protrusion 9,
The flange 2 and the pipe 1 are joined together, and laser welding is performed from the direction of arrow A, and TIG welding is performed from the direction of arrow B.

Therefore, similar to the above embodiment, welding can be performed with a small amount of excess welding, and furthermore, even when welding the flange 2 and the pipe 1, it can be performed in the same way as welding pipes together, so the welding work can be simplified. This makes it possible to easily reduce the stress concentration on the flange 2 portion.

FIG. 9 shows another embodiment of the present invention, in which notches 1 each having a V-shaped cross section are provided at the outer and inner peripheral edges of the joint portion of both pipes 1a and 1b.
3, 13 are provided, and this notch 13 is
It has a depth of about 0.2 to 1.0 mm, and may also have a rectangular shape.

In this embodiment, the notch 13 makes it easier to detect the joining position of the pipes 1a and 1b with a sensor such as an optical sensor when automating welding work, and prevents the welding position from shifting during automatic welding. It becomes possible to do so. Furthermore, the notch 13
This allows you to reduce the amount of leftover food.

Furthermore, FIG. 10 shows another embodiment of the present invention, in which a V-shaped opening having a depth of 1/2 or less of the wall thickness of the pipes is formed on the outer peripheral side of the joint portion of the pipes 1a and 1b. A tip 14 is provided, and a cutout step 10 and an engaging protrusion 9 are provided on the inner circumferential side, respectively, similar to the embodiment shown in FIG. In this example, after welding both pipes 1a and 1b by laser welding from the direction of arrow A and TIG welding from the direction of arrow B, the groove is welded while supplying the filler wire to the laser heat source. A bead 15 is welded to 14.

Therefore, it is possible to weld even thick pipes, and it is particularly suitable when using an oscillator that can only provide an output with a laser penetration depth of 10 mm or less.

In each of the above embodiments, the case where a laser is used as a high-energy density heat source is explained, but other means such as an electron beam may also be used, and furthermore, the case where TIG welding is used as arc welding is explained. Of course, similar effects can be obtained by means such as plasma.

〔Effect of the invention〕

As described above, the welding method according to the present invention involves welding cylindrical members from the outer periphery side of the joint part using a high energy density heat source so as to leave an unwelded part on the inner periphery side, and arcing from the inner periphery side of the joint part. Since the heat source welds all the way to the joint by the high energy density heat source, it is possible to eliminate unwelded parts and insufficient melting in the joint, resulting in stable quality welding with no welding defects. Can perform welding. Furthermore, since the excess buildup remaining on the inner circumferential surface of the joint portion can be significantly reduced, the amount of finishing work after welding can be reduced.

[Brief explanation of drawings]

FIGS. 1 and 2 are partial vertical sectional views showing welding conditions using a conventional arc heat source, and FIGS. 3 and 4 are partial vertical sectional views showing welding conditions using a conventional laser, respectively. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9, and FIG. 10 are partial vertical sectional views showing one embodiment of the present invention, respectively. 1... Pipe, 2... Flange, 3, 7, 8...
... Welding part, 4 ... Beam bender, 5 ... Condensing lens, 6 ... TIG welding torch, 9 ... Engaging protrusion,
10... Notch step, 11... Step, 12... Joint, 13... Notch, 14... Bevel, 15... Bead.

Claims (1)

[Claims] 1. In a welding method for joining members having a cylindrical shape such as pipes, tanks, and flanges, welding is performed from the outer periphery of the joining part of the above members using a high energy density heat source so as to leave an unwelded part on the inner periphery of the joining part. In addition, a welding method characterized in that welding is carried out from the inner circumferential side of the joint part using an arc heat source up to the part to be welded by the high energy density heat source.