JP2000254777A - Tube welding method and repair method for existing tube joint part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a crack of a fillet weld joint and a stress corrosion crack of a tube joint part. SOLUTION: After a seal weld layer 5 adhering to the end face C of a large diameter tube 1 and the outer face of a small diameter tube 2 is formed, a cooling fluid is caused to flow to the insides of both tubes 1, 2. A fillet welded joint 6 connecting the large diameter tube 1 and the small diameter tube 2 is formed. Cladding by welding layers 7, 8 to the end face C outer face of the large diameter tube 1 is successively formed so as to overlap adjacent weld beads by whole peripheral welding and to change the start position of whole peripheral welding at each pass in the direction apart from the fillet weld joint 6. Cladding by welding layers 9, 10 is successively formed to the outer face of the fillet weld joint 6 and the end part outer face of the small diameter tube 2 so as to overlap adjacent weld beads by whole peripheral welding and to change the start position of whole peripheral welding at each pass in the direction apart from the large diameter tube 1. A compression residual stress field is evenly generated to the whole periphery of the joint inner face of both tubes 1, 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding a pipe material and a method for repairing an existing pipe joint.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional pipe joint structure applied to a small-diameter pipe having a nominal diameter of 100 A or less.
A small-diameter pipe 2 such as a pipe through which a high-temperature and high-pressure fluid flows is inserted into the end of the large-diameter pipe 1 and the small-diameter pipe 2 adjacent thereto.
Weld the entire circumference to the outer surface of the small diameter pipe 2 against the large diameter pipe 1
Are connected by a fillet weld joint 3.

[0003] The large-diameter tubing 1 and the small-diameter tubing 2 are made of steel or stainless steel so as to have the same thickness.
The inner diameter of the large-diameter tube 1 is formed to be slightly larger than the outer diameter of the small-diameter tube 2, and a distance of 1 mm or less between the inner surface of the large-diameter tube 1 and the outer surface of the small-diameter tube 2 at the pipe joint. A minute gap 4 is formed.

[0004]

However, in the pipe joint structure shown in FIG. 4, when the fillet weld joint 3 is formed,
At the welding start point, the large-diameter tubing 1 and the small-diameter tubing 2 are pulled in the direction in which they approach each other.
The gap 4 at a position shifted by 80 degrees becomes excessively large, and cracks due to shrinkage may occur in the fillet weld joint 3 after welding is completed.

[0005] The minute gap 4 is also a factor of causing stress corrosion cracking on the inner surfaces of the joints of the two pipes 1 and 2.

The present invention has been made in view of the above circumstances, and has as its object to prevent cracks in fillet weld joints and stress corrosion cracks in pipe joints.

[0007]

According to a first aspect of the present invention, a small-diameter pipe is inserted into an end of a large-diameter pipe, and the end face of the large-diameter pipe is connected to the end face of the large-diameter pipe. After temporarily fixing the outer surface of the adjacent small-diameter pipe to the outer surface by welding all around, a cooling fluid is circulated or retained inside the two pipes, and the end of the large-diameter pipe is connected to the outer surface of the small-diameter pipe adjacent thereto. A fillet weld joint is formed, a weld overlay is formed on the outer surface of the end of the large-diameter pipe material, and adjacent weld beads are overlapped by full circumference welding, and the start position of full circumference welding is changed for each pass, and fillet welding is performed. Formed sequentially in the direction away from the joint,
A weld overlay is formed on the outer surface of the fillet weld joint and on the outer surface of the end of the small-diameter tube, and the adjacent weld beads are overlapped by full-peripheral welding, and the start position of full-peripheral welding is changed for each pass. Formed sequentially in the direction away from each other.

In the pipe material welding method according to the second aspect of the present invention, a small-diameter pipe is inserted into an end of a large-diameter pipe, and an end surface of the large-diameter pipe and an outer surface of a small-diameter pipe adjacent thereto are temporarily welded by full-circumference welding. After the fixing and fixing, the cooling fluid is allowed to flow or stagnate inside the two pipes, the weld overlay is formed on the outer surface of the fillet weld joint and the outer end of the small-diameter pipe, and the adjacent weld beads are overlapped by full circumference welding. In addition, the start position of the full circumference welding is changed for each pass, and the fillet weld joint is formed sequentially in a direction away from the large-diameter pipe, and connects the end of the large-diameter pipe to the outer surface of the small-diameter pipe adjacent thereto. A direction in which a weld overlay is formed on the outer surface of the end of the large-diameter pipe material, the adjacent weld beads are overlapped by full circumference welding, and the starting position of full circumference welding is changed for each pass to separate from the fillet weld joint. Are sequentially formed.

In the method for repairing an existing pipe joint according to a third aspect of the present invention, a cooling fluid is circulated or retained inside the large-diameter pipe and the small-diameter pipe connected by the fillet welded joint, and the large-diameter pipe is repaired. A weld overlay is formed on the outer surface of the end by sequentially forming a weld overlay layer in which the adjacent weld beads overlap by full circumference welding and the start position of full circumference welding is changed for each pass, in a direction away from the fillet weld joint. A weld overlay is formed on the outer surface of the welded joint as well as on the outer surface of the end of the small-diameter tube. Are sequentially formed in the directions.

[0010] In the method for repairing an existing pipe joint according to a fourth aspect of the present invention, a cooling fluid is circulated or retained inside the large-diameter pipe and the small-diameter pipe connected by the fillet welded joint. In the direction away from the large-diameter pipe, the welding overlay is formed on the outer surface of Formed sequentially, a weld overlay is formed on the outer surface of the end of the large-diameter pipe material, the adjacent weld beads are overlapped by full circumference welding, and the starting position of full circumference welding is changed for each pass to separate from the fillet weld joint. Are sequentially formed in the directions.

In each of the pipe material welding method according to the first and second aspects of the present invention and the existing pipe joint repairing method according to the third and fourth aspects of the present invention, a large-diameter pipe material and a small-diameter pipe material are used. Cooling of the inner surfaces of both pipes by the flow or stagnation of the cooling fluid inside the pipes, formation of fillet weld joints that connect both pipes, and welding of the outer surfaces of the joints and fillet weld joints of both pipes Due to the formation of the build-up layer, a compressive residual stress field is generated around the entire inner surface of the joint portion of the pipe.

In the method for repairing an existing pipe joint according to claims 3 and 4 of the present invention, the pipe material is formed by a weld overlay layer formed on the outer surfaces of the existing two pipe materials and the outer surface of the fillet weld joint. To ensure the thickness of the

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 show an example of an embodiment of a pipe material welding method according to the present invention. In the drawings, the portions denoted by the same reference numerals as those in FIG. 4 represent the same components.

A small-diameter pipe 2 such as a pipe through which a high-temperature and high-pressure fluid flows is inserted into a large-diameter pipe 1 such as a socket, and the inner periphery of the end face C of the large-diameter pipe 1 and its adjacent portion are welded by one-pass full circumference welding. A seal welding layer 5 is formed so that the outer surface of the small-diameter tube 2 is fixed to each other so that the outer surface of the small-diameter tube 2 can be kept liquid-tight.

Next, cooling water (cooling fluid) is circulated or retained inside the two pipes 1 and 2 to cool the inner surfaces of the two pipes 1 and 2, and the entire circumference is welded to the end face of the large-diameter pipe 1. A fillet weld joint 6 connecting the outer surface of the small diameter pipe member 2 adjacent thereto is formed.

Once the fillet weld joint 6 has been formed, the entire circumference is welded to the outer surface of the end of the large-diameter tube 1 by a half-lap in which a part of the adjacent weld bead is overlapped and as shown in FIG. The start position of the full circumference welding is shifted by a predetermined angle (for example, 45 degrees or 90 degrees) in the circumferential direction of the large-diameter pipe 1 for each pass P1, P2,..., In the direction of arrow A away from the fillet weld joint 6. The weld overlay 7 is formed sequentially.

Further, another weld overlay 8 is formed on the outer surface of the weld overlay 7 by the same construction procedure as that of the weld overlay 7.

Further, the entire circumference is welded to the outer surface of the fillet weld joint 6 and the outer surface of the end portion of the small diameter pipe 2 to form a half-lap in which a part of the adjacent weld bead is overlapped, and FIG.
As shown in the figure, the start position of the full circumference welding is determined by each pass P1, P2.
At predetermined angles (for example, 45 degrees or 90 degrees) in the circumferential direction of the fillet weld joint 6 and the small-diameter pipe 2 for each
Construction is sequentially performed in the direction of arrow B away from the large-diameter pipe material 1 to form a weld overlay 9.

Further, another welding overlay 10 is formed on the outer surface of the welding overlay 9 by the same construction procedure as that of the welding overlay 9.
To form

In forming the weld overlay 7, 9, the working distance of the weld overlay 7, 9 in the pipe axis direction (the completion of the formation of the weld overlay 7, 9 from the end face C of the large-diameter pipe 1). End E1, E
(Distance to 2) D1 and D2 are set so as to satisfy the following relationship.

[0022]

√ (RT) ≦ D1 (or D2) R: radius of pipes 1 and 2 T: wall thickness of pipes 1 and 2

In addition, TIG welding is applied to the formation of the fillet weld joint 6 and the weld overlay layers 7, 8, 9, and 10 described above.

In the pipe material welding method shown in FIGS. 1 to 3, the inner surfaces of the two pipe materials 1 and 2 are cooled while the cooling water flows or stays inside the two pipe materials 1 and 2, and Since the weld overlay 7, 8, 9, 10 is formed,
The inner surfaces of the joints of the two pipes 1 and 2 are distorted so as to be depressed outward in the radial direction of the pipes, and a compressive residual stress field is generated on the seal welding layer 5 and the entire inner surfaces of the joints of the two pipes 1 and 2.

When forming the weld overlays 7, 8, 9, and 10, the start position of the full circumference welding is determined by each pass P1, P2,.
Each time, the pipes 1 and 2 or the fillet welded joint 6 are shifted by a predetermined angle in the circumferential direction, so that the thermal stress does not act locally on both the pipes 1 and 2 and the fillet welded joint 6, and The compression stress distribution becomes uniform.

Therefore, stress corrosion cracking due to the tensile residual stress field does not occur on the inner surfaces of the joints of the two pipe members 1 and 2 immersed in a high temperature and high pressure fluid, and the reliability of the pipeline can be improved. become.

In order to prevent cracks in the existing pipe joint of the conventional structure as shown in FIG. 4, cooling water is circulated or retained inside the two pipes 1 and 2 and then the construction described above is performed. According to the procedure, the weld overlays 7, 8, 9, and 10 as shown in FIGS. 1 to 3 are sequentially formed.

As a result, a compressive residual stress field is generated around the entire inner surface of the existing fillet welded joint 3 and the joints of the two pipes 1 and 2, and the joints of the two pipes 1 and 2 immersed in a high-temperature and high-pressure fluid. Even if stress corrosion cracking due to the tensile residual stress field does not occur on the inner surface, and the wall loss due to corrosion progresses on both pipes 1 and 2, the weld overlay 7, 8, 9, and 10 determine the thickness. Since the thickness of the pipe is compensated, the reliability of the pipeline can be improved.

The method of welding a pipe material and the method of repairing an existing pipe joint according to the present invention are not limited to the above-described embodiment, and a weld overlay is provided on the outer surface of a fillet welded joint and the outer surface of a small diameter pipe. After the formation, a weld overlay may be formed on the outer surface of the large-diameter pipe material, and it goes without saying that changes can be made without departing from the spirit of the present invention.

[0030]

As described above, according to the pipe welding method and the existing pipe joint repairing method of the present invention, the following various excellent effects can be obtained.

(1) The pipe welding method according to claims 1 and 2 of the present invention, and the existing pipe joint repairing method according to claims 3 and 4 of the present invention have a large diameter. Cooling of the inner surfaces of both pipes by the flow or stagnation of the cooling fluid inside the pipes and small diameter pipes, formation of fillet welded joints connecting both pipes, outer joints of both pipes and outer faces of fillet welded joints By forming the weld overlay on the pipe, the inner surface of the joint is distorted so as to be depressed outward in the radial direction of the pipe, and a compressive residual stress field is generated all around the inner surface of the pipe joint. The starting position of girth welding is shifted by a predetermined angle in the circumferential direction of both pipes and fillet welded joints for each pass to achieve uniform compression stress distribution on the inner surfaces of both pipes. Avoid stress corrosion cracking on the inner surfaces of both pipes immersed in high temperature and high pressure fluid Rukoto can, thereby improving the reliability of the pipe.

(2) In the method for repairing an existing pipe joint according to the third and fourth aspects of the present invention, even if wall thinning due to corrosion is progressing on both existing pipes, the outer surfaces and corners of both pipes are improved. A predetermined thickness can be ensured by the weld overlay formed on the outer surface of the meat weld joint.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an example of a pipe material welding method according to the present invention.

FIG. 2 is a partial perspective view showing a procedure for applying a weld overlay on the outer surface of the large-diameter pipe in FIG.

FIG. 3 is a partial perspective view showing a procedure for applying a weld overlay on an outer surface of a fillet weld joint and a small-diameter pipe in FIG. 1;

FIG. 4 is a partial sectional view showing an example of a conventional pipe joint structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Large diameter pipe material 2 Small diameter pipe material 6 Fillet weld joint 7 Weld build-up layer 8 Weld build-up layer 9 Weld build-up layer 10 Weld build-up layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16L 55/18 F16L 55/18 Z (72) Inventor Takashi Hirano 1 Shinnakaharacho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Ishikawashima Harima Heavy Industries, Ltd. Yokohama Engineering Center F-term (reference) 4E081 AA02 AA05 AA12 BA01 BA19 BA27 BB15 CA01 CA07 DA06 DA08 DA11 DA12 DA14 DA16 DA62 FA03

Claims (4)

[Claims] 1. A small-diameter pipe is inserted into an end of a large-diameter pipe, and an end face of the large-diameter pipe and an outer surface of a small-diameter pipe adjacent thereto are temporarily fixed and fixed by full-circumferential welding. Form a fillet weld joint that connects the end of the large-diameter pipe and the outer surface of the small-diameter pipe adjacent to the end of the large-diameter pipe by flowing or retaining the fluid. The adjacent weld beads overlap each other, and the start position of the entire circumference welding is changed for each pass, and the weld beads are sequentially formed in a direction away from the fillet welded joint, and are formed on the outer surface of the fillet welded joint and the end outer surface of the small diameter pipe material. A pipe material welding method characterized in that a weld overlay is sequentially formed in a direction away from a large-diameter pipe material, with adjacent weld beads overlapping by full circumference welding and changing the starting position of full circumference welding for each pass, in a direction away from the large diameter pipe material. . 2. A small-diameter tube is inserted into an end of a large-diameter tube, and an end surface of the large-diameter tube and an outer surface of a small-diameter tube adjacent thereto are temporarily fixed and fixed by full-circumferential welding. A fillet weld joint connecting the end of the large-diameter pipe and the outer surface of the small-diameter pipe adjacent to the end of the large-diameter pipe is formed, and a weld-fill is formed on the outer surface of the fillet weld joint and the outer end of the small-diameter pipe. The embossed layer is sequentially formed in the direction away from the large-diameter pipe by changing the starting position of the full-circle welding in each pass so that the adjacent weld beads overlap by full-circle welding and welded to the end outer surface of the large-diameter pipe. A method of welding a pipe material, comprising: forming a build-up layer sequentially in a direction away from a fillet weld joint by changing a start position of a full-circumferential weld for each pass by overlapping adjacent weld beads by full-circumferential welding. . 3. A cooling fluid is circulated or retained inside the large-diameter pipe and the small-diameter pipe connected by the fillet welded joint, and a weld overlay is formed on the outer periphery of the end of the large-diameter pipe by full-circumferential welding. The welding bead overlaps and the starting position of the full circumference welding is changed for each pass, and the welding bead is formed sequentially in a direction away from the fillet welded joint, and the welded meat is formed on the outer surface of the fillet welded joint and the end outer surface of the small diameter pipe material. Repair of existing joints, characterized in that the embossed layer is formed sequentially in the direction away from the large-diameter pipe material by changing the starting position of the full-circle welding in each pass, with adjacent weld beads overlapping by full-circle welding, Method. 4. A cooling fluid is circulated or retained inside the large-diameter pipe material and the small-diameter pipe material connected by the fillet weld joint, and a weld overlay is formed on the outer surface of the fillet weld joint and the end outer surface of the small-diameter pipe material. The adjacent weld beads are overlapped by full circumference welding and the start position of full circumference welding is changed for each pass, and formed sequentially in the direction away from the large diameter pipe material, and the weld overlay is formed on the outer surface of the end of the large diameter pipe material. Repair of existing pipe joints characterized in that the layers are sequentially formed in a direction away from the fillet weld joint by changing the starting position of the full circumference welding for each pass, with adjacent weld beads overlapping by full circumference welding Method.