JPH1034330A - Welded structure between pipes and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the metallurgical quality and the reliability of a welding part and to reduce the man-hours of the welding by forming three-dimensional bevel surface containing a perpendicular line to the pipe axis of a branched pipe and equalizing the depth of the welding bevel with the thickness of the branched pipe. SOLUTION: An MIG welder 9 for welding the narrow bevel is fitted to the tip part of a manipulator 8 and a torch angle of the welder 9 is fixed so that the bevel surface always becomes the right angle to the pipe axis 12 of the branched pipe 2. The manipulator 8 having a function enabling the control only to two axes of the arrow marks (c) and (d) can be used. The torch of the welder 9 is inserted between the bevels to execute the welding while adjusting the position in the (c) direction by rotating along the outer periphery of the branched pipe. The inserting depth of torch of the welder 9 may be adjusted in manual in each round. The system of the welding method for the narrow bevel is not specially limited but may be used in the conventional technique of the MIG(metal inert gas) welding method, a TIG(tungsten inert gas) welding method, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for joining pipes made of a metal material to each other, and in particular, to a large-diameter thick-walled pipe used under high-temperature or high-pressure conditions, such as a boiler or a chemical plant. The present invention relates to a pipe-to-pipe welded structure suitable for joining and a method for producing the same.

[0002]

2. Description of the Related Art In a power generation boiler, various heat exchangers and the like, a large number of heat transfer tube groups and a header for collecting the heat transfer tubes are used under high temperature and high pressure conditions. FIG. 9 shows an example of a structure around a tube of a boiler heater. Connected to the header 5 are dozens of rows of heat transfer tubes 6, and further, communication tubes 7 for transferring the steam collected from these heat transfer tube groups to downstream equipment. The joining of these pipes is performed by welding. Particularly, since the header 5 and the connecting pipe 7 are as large as 80 to 120 mm in thickness, the welded portions of these thick-walled large-diameter pipes have a high quality. It is an important part.
In recent years, boilers for power generation have become larger and steam conditions have been higher,
Due to the increasing pressure, it has become indispensable to increase the wall thickness of the pipe, or to use high-Cr high-strength steel with excellent high-temperature strength and corrosion resistance. Is becoming increasingly important. FIG.
0 (a) and (b) are main pipes 1 corresponding to header 5 in FIG.
This is an example of the prior art showing a welded structure of a branch pipe 2 having a slightly smaller diameter (corresponding to the connecting pipe 7 in FIG. 9), which is widely and generally used as the simplest structure. A hole having a diameter equal to the inner diameter of the branch pipe 2 is formed in the main pipe 1, and a part of the tip of the branch pipe 2 is formed to form a groove surface 3 ′, and the main pipe 1 and the branch pipe 2 are joined at right angles. It is to be welded. In addition,
In the drawings shown below, (a) is a cross-sectional view including the pipe axis of the main pipe and parallel to the pipe axis of the branch pipe, and (b) is a cross-sectional view including the pipe axis of the branch pipe and perpendicular to the pipe axis of the main pipe. Express. The structure of the pipe material used for the high-temperature piping is usually adjusted by normalizing and tempering (or quenching and tempering) after pipe production. However, the weld metal 4 of the welded portion is used in an inhomogeneous state with a solidified structure, and there is a possibility that defects such as minute blowholes and inclusions may remain. However, FIGS. 10 (a) and 10 (b)
In the case of the general structure shown in FIG. 1, the amount of the weld metal 4 is increased, and there is a problem in the reliability of the quality of the welded portion. With respect to a method for welding a thick-walled large-diameter pipe, many proposals have been made, for example, Japanese Patent Application Laid-Open No. Sho 61-7065, Japanese Patent Publication No. Sho 62-58826, Japanese Patent Application Laid-Open No. Hei 6-47537, and others. However, most of these proposals
The present invention relates to a high degree of automation of a welding operation using a complicated and expensive manipulator of multi-axis control, and does not consider the above metallurgical problem at all. FIGS. 11A and 11B show an example in which a narrow groove welding method is used as a structure proposed to reduce the amount of weld metal. This is because both the main pipe 1 and the branch pipe 2 have a groove angle of about 45 °.
A three-dimensional groove face 3 and a groove face 3 'are formed, and the main pipe 1 and the branch pipe 2 are welded by a narrow groove welding method.
In the structure of FIGS. 11A and 11B, FIG.
As compared with the case of (b), the amount of the weld metal 4 which is a weak point in terms of strength can be greatly reduced, so that the reliability of the welded portion is greatly improved. However, since the groove shape is three-dimensional,
At the time of welding, at least three of (b: oblique vertical direction), (c: vertical direction), and (d: rotational direction) shown in FIG.
There is a problem that the axes need to be controlled, and an expensive three-axis manipulator and its control device are required.

[0003]

The above-mentioned prior art relates to a high degree of automation of welding work using an expensive multi-axis control manipulator, and does not deal with the amount of weld metal and metallurgical problems. Was not taken into account.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and in a pipe-to-pipe welded structure and a method of manufacturing the same, it is possible to easily perform welding groove processing and welding. Another object of the present invention is to provide a pipe-to-pipe welded structure which can minimize the amount of weld metal as much as possible, has good metallurgical quality at the welded portion, and has high reliability, and a method for producing the same.

[0005]

Means for Solving the Problems In order to achieve the object of the present invention, the present invention is configured as described in the claims. That is, the present invention provides a welded structure comprising a main pipe and a branch pipe, wherein the main pipe and the branch pipe each have a groove around the entire groove surface of the weld groove. The surface includes a line perpendicular to the pipe axis of the branch pipe, and forms a three-dimensional groove face in which the depth of the welding groove is equal to the wall thickness of the branch pipe, and is narrowed with respect to the groove face. A pipe-to-pipe welded structure joined by a first welding method. According to a second aspect of the present invention, there is provided a method for producing a pipe-to-pipe welded structure according to the first aspect, wherein a welding machine is inserted inside a branch pipe, and the welding machine is installed. A method for producing a pipe-to-pipe welded structure that performs welding from the inner surface side of the branch pipe by reciprocating in the pipe axis direction of the branch pipe while rotating about the pipe axis of the branch pipe. . According to a third aspect of the present invention, there is provided a method for producing a pipe-to-pipe welded structure according to the first aspect, wherein a hole having a diameter equal to the inner diameter of the branch pipe is provided on the main pipe side. Thereafter, a torch for gas cutting or plasma cutting is inserted inside the hole, and the torch is reciprocated in the pipe axis direction of the branch pipe while rotating the torch about the pipe axis of the branch pipe.
The present invention provides a method for producing a welded structure in which a welding groove is formed by cutting from the inside of the hole. The pipe-to-pipe welded structure according to the present invention includes a line perpendicular to the pipe axis of the branch pipe over the entire circumference of each of the weld grooves of the main pipe and the branch pipe. The groove surface is machined into a three-dimensional shape so that the groove depth is equal to the thickness of the branch pipe, and the groove surface is joined by a narrow groove welding method. Since the groove surface is a narrow groove parallel to the plate thickness direction and the groove depth is equal to the thickness of the branch pipe over the entire circumference of the joint, the conventional groove surface is inclined with respect to the plate thickness direction. It is possible to realize a highly reliable pipe-to-pipe welded structure having a metallurgically-quality welded portion with a smaller amount of deposited metal than that of the conventional structure. Further, since the welding torch can always be fixed in a direction perpendicular to the pipe axis of the branch pipe as described in the second aspect, in addition to the common effect of the first aspect, a simple and inexpensive 2 can be obtained. There is an effect that automatic welding can be easily performed using the manipulator of the axis control. Further, as described in the third aspect, the present invention does not make the welding groove shape (structure) itself a novel shape which has never existed before.
A groove can be easily formed by using a simple and inexpensive manipulator with a simple axis control, and the amount of weld metal (weld metal) can be minimized by a narrow groove welding method, similarly to the common effect of claim 1. To improve the metallurgical quality and obtain a highly reliable welded structure.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. <Embodiment 1> FIG. 1 shows the basic shape of a welding groove according to the present invention. First, the shape of a welding groove on the main pipe side and a processing method thereof will be described. A hole having a diameter equal to the inner diameter of the branch pipe 2 is formed in the outer surface of the main pipe 1, and a circular shape equal to the outer diameter of the branch pipe 2 is projected from the direction of the pipe axis 12 of the branch pipe onto the opening of the main pipe 1. Let the shape be curve D. Next, always set the pipe axis 1 of the branch pipe.
The welding groove is machined so as to include a straight line perpendicular to 2, for example, the straight line A, B or C in FIG. The depth of the three-dimensional groove surface 3 thus obtained is always equal to the thickness of the branch pipe 2. Groove surface 3 'on branch pipe 2 side
4 (a) and 4 (b)] are processed so as to be substantially parallel to the groove surface 3 on the main pipe 1 side. Next, a specific example of the groove processing procedure will be described. In recent years, since NC-controlled processing machines have become widespread, it is possible to precisely machine the welding groove of the present invention, but in the present embodiment, it is easy to use such an expensive machine without using such an expensive machine. FIG. 2 shows an example of beveling on the main pipe side by gas cutting as a method that can be machined.
In the figure, a hole having a diameter equal to the inner diameter of the branch pipe 2 is formed on the outer surface of the main pipe 1, and then a groove surface is formed from the periphery of the hole by a gas cutting torch 10 attached to the tip of the manipulator 8. The manipulator 8 may be of a two-axis control type that can be controlled only by arrows (c) [vertical direction] and (d) [rotation direction] in FIG. The gas cutting is performed while rotating the gas cutting torch 10 in the direction (d) and reciprocating in the direction (c) to adjust the position. After cutting,
Although the cut surface needs to be polished smoothly, the groove surface 3 having the shape shown in FIG. 1 can be easily processed.
The groove face 3 'on the side of the branch pipe 2 can be processed by the same method as that on the side of the main pipe 1, as shown in FIG. FIGS. 4 (a) and 4 (b) show the shapes of the main pipe 1 and the branch pipe 2 in which the groove surfaces are processed as described above. The welding groove processing method disclosed in FIGS. 2 and 3 can be applied to most materials such as carbon steel and ferritic low alloy steel, which are often used as piping materials for boilers and the like. However,
In recent years, it has been difficult to apply gas cutting to 9-12% Cr-based ferritic steel, which has been widely used, due to Cr oxide generated on the cut surface. For such a material, the same effect as in the case of gas cutting can be obtained by using the plasma cutting method. The method of performing the plasma cutting method is the same as in FIGS. 2 and 3 described above, and a plasma cutting torch may be attached instead of the gas cutting torch 10. Next, a welding method will be described. FIGS. 5 (a) and 5 (b) show the main pipe 1 and the branch pipe 2,
Shows the combined state for welding. In the present embodiment, a MIG welding machine 9 for narrow groove welding is attached to the tip of the manipulator 8 and used. As described in FIG. 1, the groove face can always fix the torch angle of the welding machine at right angles to the pipe axis 12 of the branch pipe.
The manipulator 8 is similar to the one used for groove processing,
It may have a function that can be controlled only in the two axial directions indicated by arrows (c) and (d) in the figure. The torch of the welding machine 9 is inserted between the grooves, and the welding is performed while adjusting the position in the (C) direction while rotating along the outer periphery of the branch pipe 2. Welding machine 9
The insertion depth of the torch may be manually adjusted for each rotation. The type of the narrow groove welding method is not particularly limited, but may be a method used in a conventional technique such as a MIG welding method or a TIG welding method. However, 9-12% Cr
For new high-strength steels, the TIG welding method is preferably used because the MIG welding method forms a Cr oxide film on the surface of the weld metal and deteriorates welding workability.
FIG. 6 is an enlarged view showing a state where the main pipe 1 and the branch pipe 2 are combined for welding and a state after welding. As shown in the figure, in the present embodiment, the groove depth W is equal to the plate thickness of the branch pipe 2 over the entire circumference of the joint, so that the amount of the weld metal 4 is minimized, and the conventional technique shown in FIG. The amount of the weld metal 4 can be remarkably reduced as compared with the welding structure in which the groove surface is inclined with respect to the thickness direction of the branch pipe.

[Embodiment 2] FIGS. 7 and 8 show a pipe-to-pipe welded structure exemplified in this embodiment and a method of manufacturing the same. The groove shape is basically the same as that of the first embodiment. However, in the first embodiment, the groove is machined from the outside of the main pipe 1 and welded from the outer surface side of the branch pipe 2. In the embodiment, a groove is formed from the inside of the main pipe 1 and welded from the inner surface side of the branch pipe 2. FIG. 7 shows a groove processing method. As in the case of FIG. 2, after machining a hole equal to the inner diameter of the branch pipe 2 in the main pipe 1, the gas cutting torch 10 is inserted into this hole, and while rotating the gas cutting torch 10 in the (d) direction, In this method, the position is adjusted by reciprocating in the direction (c) and the groove is machined from the inside of the main pipe 1 by gas cutting or plasma cutting. At this time, if the rotation axis of the manipulator 8 is matched with the pipe axis 12 of the branch pipe,
Since the tip of the torch always moves on a concentric circle centered on the pipe axis 12 of the branch pipe, the positioning of the manipulator 8 can be easily performed. The present invention is applicable when the inner diameter of the hole is large enough to insert the gas cutting torch 10, but the workability is good because the flame of the gas cutting torch 10 always strikes the cut surface of the main pipe 1 at right angles. . 8 (a), 8 (b),
(C) shows a welding method. The welding machine 9 is inserted into the inside of the branch pipe 2, and while rotating the welding machine 9 in the direction (d), the welding machine 9 is reciprocated in the direction (c) to adjust the position.
Welding from inside of In this embodiment, the present invention is applicable only when the inner diameter of the branch pipe 2 is sufficiently large with respect to the dimension of the welding machine 9. Are better. In particular, it is suitably used for welding large-diameter pipes. Even if the arm of the manipulator 8 is bent, no problem occurs if the axis of (d) is aligned with the axis of the branch pipe 2. 2, 3, 5, 7, and 8, the gas cutting torch 10 or the welding machine 9 is attached to a manipulator that rotates around the pipe shaft 12 of the branch pipe, and is rotated. A guide rail may be fixed to the inside or outside of 2 and rotated along the guide rail.

[0008]

According to the pipe-to-pipe welded structure of the present invention and the method for producing the same, a novel groove shape (structure) which has never existed before can be obtained without using a specially complicated and expensive processing machine or welding equipment. Since groove processing and narrow groove welding can be easily performed, the amount of weld metal can be minimized for joining large-diameter pipes with thick walls, and the metallurgical quality and reliability of the welded part can be reduced. It can be significantly improved. Further, the number of welding steps can be reduced, and a remarkable effect is obtained industrially and economically.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic shape of a welding groove exemplified in Embodiment 1 of the present invention.

FIG. 2 is a schematic view showing a method for processing a weld groove on the main pipe side exemplified in the first embodiment of the present invention.

FIG. 3 is a schematic view showing a method of processing a welding groove on a branch pipe illustrated in the first embodiment of the present invention.

FIG. 4 is a schematic view showing a shape of a welding groove of a main pipe and a branch pipe exemplified in the first embodiment of the present invention.

FIG. 5 is a schematic view showing a method for welding a main pipe and a branch pipe exemplified in the first embodiment of the present invention.

FIG. 6 is a schematic view showing a joined state of the main pipe and the branch pipe exemplified in the first embodiment of the present invention.

FIG. 7 is a schematic view showing a method for processing a weld groove on the main pipe side exemplified in the second embodiment of the present invention.

FIG. 8 is a schematic view showing a method for welding a main pipe and a branch pipe exemplified in the second embodiment of the present invention.

FIG. 9 is a schematic view showing a conventional header structure of a heat transfer tube group.

FIG. 10 is a schematic view showing a conventional joined state of a main pipe and a branch pipe.

FIG. 11 is a schematic view showing another conventional joint state of a main pipe and a branch pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Main pipe 2 ... Branch pipe 3 ... Groove face 3 '... Groove face 4 ... Weld metal 5 ... Header 6 ... Heat transfer pipe 7 ... Connecting pipe 8 ... Manipulator 9 ... Welding machine 10 ... Gas cutting torch 11 ... Welding wire 12: Pipe axis of branch pipe 13: Rotation axis of (d) 14: Trace of welding machine tip W: Depth of welding groove (d): Rotation direction (c): Vertical direction (b): Oblique vertical direction A: Line segment B: Line segment C: Line segment D: Curve

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B23K 10/00 501 B23K 10/00 501A 31/00 31/00 P 33/00 33/00 A

Claims (3)

[Claims] 1. A welded structure comprising a main pipe and a branch pipe, wherein the groove is perpendicular to the pipe axis of the branch pipe over the entire circumference of the groove of the weld groove of each of the main pipe and the branch pipe. Forming a three-dimensional grooved surface including a suitable line and having the depth of the welding groove equal to the thickness of the branch pipe, and joining the grooved surface to the grooved surface by a narrow groove welding method. A pipe-to-pipe welded structure characterized by the following. 2. The method for producing a pipe-to-pipe welding structure according to claim 1, wherein a welding machine is inserted inside the branch pipe, and the welding machine is rotated around the pipe axis of the branch pipe. A method for producing a pipe-to-pipe welded structure, wherein welding is performed from the inner surface side of the branch pipe by reciprocating in the pipe axis direction of the branch pipe. 3. A method for producing a pipe-to-pipe welded structure according to claim 1, wherein a hole having a diameter equal to the inner diameter of the branch pipe is provided on the main pipe side, and a gas is provided inside the hole. Inserting a torch for cutting or plasma cutting and reciprocating in the pipe axis direction of the branch pipe while rotating the torch about the pipe axis of the branch pipe, thereby performing cutting from the inside of the hole to form a welding groove. Forming a pipe-to-tube welded structure.