JP2008023570A - Method for welding shroud of reactor core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for welding a weld structure, by which residual stress is changed into compressive stress by executing the treatment for improving the residual stress in the welded surface of the weld structure. <P>SOLUTION: The objective of the method for welding is a reactor core shroud 10, which is installed inside a reactor pressure vessel and surrounds a reactor core, piping or a vessel. The welding method for the reactor core shroud 10 is used for setting a new reactor core shroud 11 on a base reactor core shroud 12 by on-site welding when installing the reactor core shroud 10 to be welded. In the welding method for the reactor core shroud 10, after the new core shroud 11 is placed on the base core shroud 12, weld bead sequences 15 are sequentially formed by performing build-up welding of weld beads 16 by a plurality of passes from the outer or inner surface side of the shroud toward the reverse surface side thereof. In the formation of the weld bead sequences 15, welding conditions are selected according to the weld positions in the radial direction of the shroud so that the residual stress in the surface of the shroud becomes a compressive stress. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a welding technique for a welded structure such as a core shroud, pipes and containers, and in particular, welding for installing core shrouds and welding various pipes and container components such as main steam pipes and furnace pipes. The present invention relates to a method for welding a structure.

  In various power plants such as nuclear power plants, welded structures are employed for welding core shrouds and members of various pipes. Causes of the occurrence and development of stress corrosion cracking (SCC) of the welded structure, a decrease in fatigue strength, and the like include residual stress resulting from thermal expansion and plastic strain caused by welding.

  In a welded structure, as a method of reducing the residual stress due to welding, a welding solution is obtained by spraying a coolant after welding to generate a temperature difference in the material (see Patent Document 1) or by analyzing residual stress. There exists a method (refer patent document 2).

Moreover, as a method of reducing the residual stress due to additional welding, a method of reducing the residual stress of the reinforcement welded portion of the pipe (see Patent Document 3), or a method of reducing the residual stress of the square winding welded portion where the additive is welded. (See Patent Document 4).
JP 2000-343270 A JP-A-9-1376 Japanese Patent Laid-Open No. 25-182393 JP-A-4-371387

  The technology disclosed in each patent document relates to the reduction of residual stress on the welding surface of a welded structure such as a pipe, and it is difficult and difficult to reduce the residual stress on the back surface of the welded structure. .

  In order to solve the above-described problems, an object of the present invention is to provide a welding method for a welded structure in which a residual stress improvement process is performed on a welding construction surface of the welded structure to make the residual stress a compressive stress.

  Another object of the present invention is to prevent stress corrosion cracking by using a core shroud, piping / vessel, etc. as an object to be welded, and axial residual stress component and circumferential residual stress component of the welded object to be welded as compressive stress. Provided is a welding method for a welded structure which can be prevented in advance and reliably.

  In order to solve the above-described problems, a welding method for a core shroud according to the present invention uses a core shroud that is installed in a reactor pressure vessel and surrounds the core, and when the core shroud is installed, a new core shroud is used. In the welding method installed on the basic core shroud by on-site welding, after the new core shroud is placed on the basic core shroud, welding is performed in multiple passes from the outer surface of the shroud or from the inner surface side of the shroud to the opposite shroud surface. This is a method of selecting welding conditions according to the welding position in the radial direction of the shroud so that the residual stress on the surface of the shroud is compressed when the bead is piled up in the circumferential direction and the weld bead sequence is sequentially formed.

  Further, in order to solve the above-described problems, the pipe or container welding method according to the present invention uses a workpiece to be welded as a pipe or a container, but the constituent members of the pipe or container are butted together and this butted portion is in the circumferential direction. In a welding method in which welding is performed to form a weld bead sequence and integrated, the constituent members of the pipe or container are abutted with each other, and then the constituent member abutting portion is changed from one direction to the opposite direction on the inner surface or outer surface side. When welding a plurality of weld beads in the circumferential direction sequentially to form a weld bead sequence, the welding operation and the outer surface of the member are performed so that the residual stress of the welded surface of the member of the pipe or container is compressed. This is a method in which build-up welding is sequentially performed from the side or the inner surface of the member.

  In the welding method for a welded structure (core shroud, pipe, or container) according to the present invention, since the residual stress improvement processing of the welding construction surface of the welded structure is attempted and the residual stress is a compressive stress, the SCC Measures can be taken, and a core shroud and piping / vessel that can prevent the occurrence of stress corrosion cracking can be provided.

  Further, in the present invention, the occurrence of stress corrosion cracking is prevented in advance by using both the axial residual stress component and the circumferential residual stress component of the welded portion of the core shroud, which is a welded structure, and the pipe / vessel as compressive stress. be able to.

  An embodiment of a welding method for a welded structure according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
1 and 2 show an example in which a core shroud 10 that is installed in a reactor pressure vessel of a boiling water reactor and surrounds the core is an object to be welded. In the boiling water reactor, when the core shroud 10 is installed or replaced, the new core shroud 11 is placed on the old core shroud 12 when replaced, and the core shroud (hereinafter referred to as the new core disposed below) when newly installed. (Referred to as a shroud) 11 is piled up and installed on a basic core shroud 12 disposed at the lower portion by circumferential all-around welding 13. The old core shroud 12 constitutes a basic core shroud.

  The old core shroud 12 is mainly formed of an Inconel material, and is integrally formed by welding a torus and a washer-like stainless steel ring body having the same diameter on a cylindrical body made of Inconel. The old core shroud 12 is installed on a shroud support installed in the reactor pressure vessel.

  The new core shroud 11 is made of, for example, stainless steel, and is installed on the old core shroud 12 by field welding to constitute the core shroud 10. The core shroud 10 is installed in a nuclear reactor, has a diameter of several mφ, has a shroud plate thickness (wall thickness) of several tens mm, preferably 40 mm to 50 mm, and the axial height of the core shroud 10 is several m to 10 m. It is. As an example, in a 800 MW or 1100 MW class boiling water reactor, the thickness of the shroud is about 40 mm to 50 mm, and the axial height of the new core shroud 11 is about 7 m. The ring core axial height of the old core shroud 12 is several hundred mm, for example, 300 mm to 400 mm.

  In FIG. 2, the work of welding the new core shroud 11 on the old core shroud 12 over the entire circumference and overlaying the inner core surface (the outer surface of the core shroud 10 from the outer surface (outer surface) side to the shroud opposite side) Shown below is an example of installation toward the inner surface) side. As shown in FIG. 3, the welding operation of the core shroud 10 is usually performed by using two welding machines 14 that are opposed to each other in the diametrical direction by approximately 180 °. The two welding machines 14 are arranged opposite to the inner side of the core shroud 12, but may be arranged outside the shroud.

  The installation work of the core shroud 10 is generally performed in consideration of SCC generation prevention measures, and is performed by several stages, for example, three stages of welding work. The welding operation for installing the new core shroud 11 on the old core shroud 12 is performed by depositing the weld beads 16 in order from the outer surface of the shroud to the inner surface thereof, as shown by a weld bead sequence 15 in FIG.

  In the first step in the initial stage of welding, a plurality of passes, for example, a 1 to 3 pass weld bead is formed, and about a fraction of the shroud thickness is welded by the build-up of the weld bead. First, welding in the first pass (circumferential welding in the circumferential direction) was performed in a cooling environment state in which the inner and outer surfaces of the shroud were exposed to the atmospheric environment with a heat input of 10 KJ / cm or less. Next, in the second pass to several passes, for example, the third pass, welding was performed with substantially the same heat input as in the first pass, but the outer surface of the shroud was forcedly blown to cool down, and the surface temperature of the shroud material was increased. Welding was performed with forced cooling to decrease.

  Here, the amount of heat input is determined by the magnitude of current and voltage used for welding and the welding speed.

  After the completion of the welding in the third pass, for example, the third pass, it was confirmed that the environment between the inner surface of the shroud and the outer surface was isolated by welding, and the outer surface of the core shroud 10 was filled with water to reduce exposure. . Thereafter, welding was performed to a position near about ¼ of the shroud plate thickness (thickness) with a heat input as low as the initial heat input.

  Next, in the second step in the middle of welding, the heat input after 1/4 of the shroud plate thickness is made larger than the initial heat input in the range of 10 to 30 KJ / cm, and about 3% of the shroud plate thickness under the increased heat input condition. / 4 welding was carried out. As a specific example, the heat input is gradually increased from 10 KJ / cm from about 1/4 of the shroud plate thickness to near the center, welding is performed at 20 to 30 KJ / cm, for example, 25 KJ / cm near the center, and then 3 Up to about / 4, welding was performed with a heat input slightly smaller than the central region (near). In the middle stage of welding, which is the welding in the intermediate region, the range of 1/4 to 3/4 of the shroud plate thickness is welded. In the second step of this middle stage of welding, the middle stage heat input is larger than the initial heat input, and The amount of heat input was changed stepwise or continuously in the range of 10 to 30 KJ / cm, or the central region was increased, or welding was performed with a constant amount of heat input.

  Further, in the third step in the latter stage of welding in which about 3/4 or more of the shroud plate thickness is welded, the heat input amount is again made lower than the intermediate heat input amount, and the cooling rate of the inner surface of the shroud is faster than that in the atmosphere. In addition, air was forcibly blown to the inner surface of the shroud or welding was performed in a forced cooling environment. The late heat input of the shroud plate thickness was lower than the medium heat input, and welding was performed in a required range that was equal to, greater than, or smaller than the initial heat input.

  Welding work to install the new core shroud 11 on the old core shroud 12, which is the basic core shroud, is performed in a radially inward direction from the outer surface of the shroud to the inner surface of the shroud to a position flush with the inner surface of the shroud. After this, the inner surface of the shroud was added with several passes, for example, 3 passes of all-around buildup welding, and the additional welded portion 17 was formed with several passes of circumferential weld beads.

  In this method of welding the core shroud 10, the inner surface of the shroud is forced so that the cooling rate of the inner surface of the shroud is higher than that of welding in the atmosphere from the viewpoint of suppressing or preventing SCC from about 3/4 of the thickness of the shroud. By blowing the cooling air, the residual stress of compression is prevented from changing to the tension side.

  4A and 4B compare the residual stress distribution on the outer surface of the shroud of the core shroud formed by performing the conventional core shroud welding method and the core shroud welding method according to the present invention.

  In the conventional core shroud welding method shown in FIG. 4A, no SCC generation suppression measures are taken. In the conventional core shroud welding method, there is no idea or idea considering the heat input condition of welding from the viewpoint of suppressing the occurrence of SCC. In a conventional core shroud, the welding cooling environment is such that welding of 1 to 3 passes is performed in an environment where the inner and outer surfaces of the shroud are exposed to the atmosphere, and water is poured into the outer surface of the shroud after the fourth pass. Welding was performed underwater in the atmosphere on the inner surface of the shroud. No special consideration is given to the heat input conditions of welding. The axial residual stress component in the vicinity of the welded area between the new core shroud and the old core shroud welded by the conventional core shroud welding method was compression, but the circumferential residual stress component was tensile, and this was the cause of SCC generation. It has become.

  On the other hand, FIG. 4B shows the residual stress distribution on the outer surface of the shroud obtained by performing the core shroud welding method according to the present invention.

  In the welding method of the core shroud 10 of the present invention in which the occurrence of SCC is prevented or suppressed, the heat input amount in one to several passes, for example, the third pass in the first step is reduced, and the cooling rate is increased to increase the outer surface of the shroud. The range of the tensile residual stress that occurs is narrowed and the maximum value is kept low. Further, since the residual stress on the outer surface of the shroud is compressed by welding in the vicinity of the center of the shroud plate thickness, the residual stress of compression is further increased by increasing the heat input (medium amount of heat input). Furthermore, in the last part of the welding of the core shroud 10, the residual stress on the outer surface of the shroud is on the tension side again, so in order to suppress the adverse effects of welding for SCC countermeasures, by lowering the heat input and increasing the cooling rate, Prevents compressive residual stress from changing to tension.

  As a result, the core shroud 10 can compress both the axial residual stress component and the circumferential residual stress component of the welded portion on the shroud surface side, and tensile stress does not remain as a residual stress component.

  After welding, only the residual stress in the vicinity of the welded portion on the inner surface of the shroud was improved by peening or polishing.

  In the welding of the core shroud 10 shown in the first embodiment, an example has been shown in which the new core shroud 11 is installed on the old core shroud 11 by welding 20 or more passes. Or 20 or more passes, for example, 50 passes.

  In the first embodiment, in order to install the new core shroud 11 on the old core shroud 12, build-up welding is sequentially repeated over the entire circumference from the shroud outer surface (outer periphery) side to the shroud inner surface (inner periphery) side. Although several examples have been shown, this welding may be performed by a weld bead sequence in which welding is sequentially repeated from the inner side of the shroud toward the outer side of the shroud.

[Second Embodiment]
5 and 6 show a second embodiment of the welding method for a welded structure according to the present invention.

  2nd Embodiment also shows the example made into the welded structure which made object the core shroud 10A installed in the reactor pressure vessel of a boiling water reactor.

  This core shroud 10A welding method is a method in which build-up welding of several passes, for example, three passes, is performed on the inner surface (inner peripheral surface) of the core shroud 10A from the welding center to a required position over the entire circumference. Since other configurations and operations are not substantially different from the welding method of the welded structure shown in the first embodiment, the same components are denoted by the same reference numerals and redundant description is omitted.

  In this core shroud 10A, after welding to install the new core shroud 11 on the old core shroud 12, as shown in FIG. 5, a required position several tens of millimeters away from the welding center on the inner surface of the shroud, for example, a position separated by about 50 mm. In addition, several passes, for example, three passes of additional welding 18 were performed over the entire circumference, and a weld bead was formed over the entire circumference.

  6 (A) and 6 (B) compare the residual stress distribution on the outer surface of the shroud after welding when welding of the conventional core shroud and the core shroud 10A according to the present invention are performed.

  In the conventional core shroud welding method, as shown in FIG. 6 (A), the core shroud has a compressive axial residual stress component in the welded portion of the outer surface of the shroud, but the circumferential residual stress component becomes tensile, This is the result of creating the SCC generation factor. FIG. 6A corresponds to FIG.

  In contrast, as shown in FIG. 6B, in the core shroud 10A, the axial residual stress component and the circumferential residual stress component of the welded portion on the outer surface of the shroud are both compressed, and an SCC measure can be taken on the welded portion. .

  In FIG. 5 (B), an additional weld 18 is placed at a required position from the welding center of the inner surface of the shroud of the core shroud 10A, for example, at a position of about 50 mm, and the axial height ranges from 10 mm to several tens of mm, preferably 10 to 20 mm. By optimizing and welding under the same heat input condition as the side heat input condition, a residual tensile stress is generated at the required position from the welding center on the shroud surface, but the residual tensile stress near the weld is eliminated or reduced. be able to.

  From the viewpoint of stress corrosion cracking (SCC), it is possible to reduce or eliminate the residual stress in the vicinity of the weld, which is the heat affected zone, and to improve only the residual stress near the weld on the inner surface of the shroud after welding by peening or polishing. it can.

[Third Embodiment]
7 to 9 show a third embodiment of a welding method for a welded structure according to the present invention.

  In describing the third embodiment, the same components as those of the welding method of the welded structure shown in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  3rd Embodiment also shows the example made into the welded structure which made object the core shroud 10B installed in the reactor pressure vessel of a boiling water reactor.

  For welding the core shroud 10B, as shown in FIG. 7, four welding machines 14 and 20 are used. The four welding machines 14 and 20 are installed in pairs at a diameter position 180 degrees apart as in normal welding, and the remaining two machines are two sets of welding machines 14 and 14. It is installed so as to chase and weld. The welding conditions are normal welding conditions, and after performing normal welding, as shown in FIG. 8, two-dimensional additional welding 21 is performed within a required range from the welding center on the inner surface of the shroud to both axial sides of the core shroud 10B. Carried out.

  FIGS. 9A and 9B compare the residual stress distribution on the outer surface of the shroud after welding in the example in which the conventional core shroud welding and the two-dimensional additional welding 21 as in this embodiment are performed. is there.

  FIG. 9A shows the residual stress distribution on the outer surface of the shroud of the core shroud when the core shroud is subjected to normal welding conditions. As shown in FIG. 9A, under normal welding conditions in which the new core shroud is installed on the old core shroud, the axial residual stress component in the vicinity of the weld on the outer surface of the shroud is compression, but the circumferential residual component is tensile. It becomes stress and the condition of SCC generation occurs.

  On the other hand, as shown in FIG. 9 (B), after the core shroud 10B in which the new core shroud 11 is installed on the old core shroud 12 is welded under normal welding conditions as shown in the third embodiment. The inner surface (inner peripheral surface) is provided with a two-dimensional additional welded portion 21 on both sides of the welding center (both sides in the axial direction of the core shroud 10B) in a required range, for example, 20 mm to several tens of mm, preferably 50 mm, so The residual stress in the vicinity of the weld on the inner surface could be reduced. As shown in FIG. 9B, the two-dimensional additional welded portion 21 can be carried out over a range of required additional welding by welding in one direction from the lower side to the upper side of the core shroud 10B.

  From the viewpoint of measures against stress corrosion cracking (SCC) associated with the welding operation of the core shroud 10B, the residual stress in the vicinity of the welded portion, which is the weld heat affected zone, can be reduced or eliminated. Only the residual stress in the vicinity of the welded portion on the inner surface of the shroud after welding can be improved by peening or polishing.

  In addition, since the four welding machines 14 and 20 are used in groups of two, even if two-dimensional welding (surface welding) is added to the inner surface of the shroud, the net welding time is longer than that of the conventional core shroud. In addition, the welding operation can be performed without significantly changing the current welding process.

[Fourth Embodiment]
10 to 12 show a fourth embodiment of a welding method for a welded structure according to the present invention.

  In the fourth embodiment, the main steam pipe of the nuclear power plant, the pipe in the furnace, or various pipes of various plants are welded objects (objects to be welded), and the constituent members of the pipes are integrally connected by welding overlay. The example which comprises welding piping is shown.

  In describing the welding method for piping according to the fourth embodiment, the same components as those illustrated in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. 4th Embodiment has shown the welding technique of the piping which faced together the piping members of various piping, and was integrated by the whole circumference buildup.

  The piping 25 shown in FIGS. 10 and 11 shows an example in which the outer diameters of the piping members 25a and 25b are 150 mm to 300 mm, for example, the outer diameter is about 200 mm and the wall thickness is 8 mm. This pipe member 25a, 25b is an example in which several passes, for example, five passes of weld beads 27 are sequentially built up and joined over the entire circumference from the pipe inner surface side toward the outer surface side.

  Among all five passes of pipe welding, the weld beads 27 in the first to third passes are welded in an environment in which both the inner and outer surfaces of the pipe are open to the atmosphere, and the remaining four and fifth pass weld beads are used. No. 27 was subjected to build-up welding over the entire circumference with water in the pipe 25.

  The pipe 25 is joined by joining the pipe members 25a and 25b to each other, forming a welded portion 26 with several passes of weld beads from the inside to the outside of the pipe. In the welding operation of the pipe 25, the residual stress distribution on the pipe inner surface in the welded portion 26 between the pipe members 25a and 25b appears as shown in FIG.

  The residual stress distribution on the inner surface of the pipe in the welded portion 26 of the pipe 25 appears as shown in FIG. The pipe inner surface welded portion 26 is compressed with respect to both the axial residual stress component and the circumferential residual stress component, and there is no problem in SCC countermeasures. By improving only the residual stress in the vicinity of the welded portion on the outer surface of the pipe by peening, for example, shot peening, the SCC resistance can be improved.

  In addition, although the welding method of piping was demonstrated in 4th Embodiment, it can apply similarly when it replaces with piping and uses it as a container.

  Moreover, as a modification, it is needless to say that the additional welded portion 21 shown in the second embodiment may be newly performed on the pipe shown in the fourth embodiment as necessary.

[Fifth Embodiment]
FIGS. 13 to 15 are views for explaining a fifth embodiment of the welding method for a welded structure according to the present invention.

  The fifth embodiment is an example in which the pipe 25 is an object to be welded (object to be welded), similar to that shown in the fourth embodiment, and has the same configuration as that shown in the fourth embodiment. The same reference numerals are given and redundant description is omitted.

  13 and 14 show a pipe 25 having an outer diameter of about 200 mmφ and a wall thickness of 8 mm as an object to be welded. In this pipe 25, the end faces of the pipe members 25 a and 5 b are aligned, and the welded portion 26 is constituted by a total number of passes, for example, five-pass weld beads 27, and the pipe members 25 a and 25 b are integrally joined.

  In this pipe 25, the pipe members 25 a and 25 b are brought into contact with each other, and build-up welding is sequentially performed with the weld beads 27 of all passes from the inner side (inner peripheral side) to the outer side of the pipe 25 over the entire circumference. The piping members 25a and 25b are integrally joined to each other. In the pipe 25, for example, all five passes of welding are performed in an environment where the inner and outer surfaces of the pipe are open to the atmosphere. After the pipe members 25a and 25b were butted together and welded together, two-dimensional build-up welding 28 was performed over a range of several tens of mm, for example, about 30 mm, from the welding center of the pipe 25 to both sides of the pipe outer surface.

  Since the thickness of the pipe 25 shown in the fifth embodiment is about 8 mm, which is thinner than the thickness of the core shroud of about 40 mm to 50 mm, the range of the two-dimensional build-up welding 28 after welding is also several tens of mm. For example, it was 30 mm. The additional build-up welding 28 was performed from the pipe outer surface side so as to cover the joint portion 26 of the pipe 25.

  After the pipe members 25a and 25b are welded together, the welded portion 26 of the pipe 25 is additionally welded with a weld bead of several passes to several dozen passes over the entire circumference on the pipe outer surface side. The residual stress distribution is expressed as shown in FIG.

  Also in this case, the residual stress in the vicinity of the welded portion on the inner surface of the pipe 25 is compressed, and an SCC countermeasure is taken. For this reason, the SCC resistance can be improved by improving only the residual stress in the vicinity of the welded portion on the outer surface of the pipe 25 by peening, for example, shot peening.

The block diagram which shows 1st Embodiment of the welding method of the welded structure which concerns on this invention. FIG. 2 is a partial longitudinal sectional view showing a welded portion of the core shroud shown in FIG. 1. The top view which illustrates the example of arrangement | positioning of the welding machine which welds a core shroud. (A) And (B) is a residual-stress distribution map of the outer surface of the shroud after welding which compares and shows the conventional welding example of a core shroud, and the welding example of 1st Embodiment. The fragmentary longitudinal cross-section which shows 2nd Embodiment of the welding method of the welded structure which concerns on this invention. (A) And (B) is the residual-stress distribution map of the outer surface of the shroud after welding which compares and shows the welding example of the conventional core shroud, and the welding example in 2nd Embodiment. The simplified top view which shows 3rd Embodiment of the welding method of the welded structure which concerns on this invention. The longitudinal cross-sectional view which shows partially the welding part of the core shroud shown by 3rd Embodiment. (A) And (B) is the residual-stress distribution map of the outer surface of the shroud after welding which compares and shows the conventional welding example of a core shroud, and the welding example by 3rd Embodiment. The block diagram which shows 4th Embodiment of the welding method of the welded structure which concerns on this invention. The fragmentary longitudinal cross-section which shows the piping welding part shown by 4th Embodiment. The residual stress distribution map of the pipe inner surface after welding shown in the fourth embodiment. The block diagram which shows 5th Embodiment of the welding method of the welded structure which concerns on this invention. The fragmentary longitudinal cross-section which shows the piping welding part shown by 5th Embodiment. The residual stress distribution map of the pipe inner surface after welding shown in the fifth embodiment.

Explanation of symbols

10, 10A, 10B Core shroud (welded structure)
11 New core shroud 12 Old core shroud 13 Welded part 14, 20 Welding machine 15 Weld bead sequence 16 Welded bead 17, 18, 21 Additional welded part 25 Pipe 25a, 25b Pipe member 26 Welded part 27 Welded bead 28 Additional welded part

Claims (10)

In a welding method in which a workpiece is installed in a reactor pressure vessel and a core shroud surrounding the core, and when installing the core shroud, a new core shroud is installed on the basic core shroud by field welding.
After the new core shroud is placed on the basic core shroud, a weld bead sequence is sequentially formed by laminating multiple passes of weld beads in the circumferential direction from the outer surface of the shroud or the inner surface of the shroud to the opposite shroud surface. A welding method for a core shroud, wherein welding conditions are selected in accordance with a welding position in a radial direction of the shroud so that the residual stress on the surface of the shroud is compressed during the process. After placing the new core shroud on the basic core shroud, a weld bead sequence is sequentially formed by laminating a plurality of passes of weld beads in the circumferential direction from the outer surface of the shroud or the inner surface of the shroud to the opposite shroud surface. The cooling environment of the outer surface of the shroud and the inner surface of the shroud, or the heat input determined from the current, voltage, welding speed, or both the cooling environment and the heat input, can be changed according to the welding position in the radial direction of the shroud. The core shroud welding method according to claim 1, wherein the core shroud is welded. When a new core shroud is placed on the basic core shroud, a welding bead sequence is sequentially formed with a plurality of weld beads from the outer surface of the shroud toward the inner surface of the opposite shroud.
Weld the cooling environment on the outer surface of the shroud in the first few passes in an environment where the cooling rate is faster than in the air, and weld the cooling environment on the inner surface side of the shroud in the final layer in an environment where the cooling rate is faster than in the air at the cooling rate. The core shroud welding method according to claim 1 or 2, wherein the core shroud is welded. When a new core shroud is placed on the basic core shroud,
In the initial few passes of welding, the heat input is low,
In the middle region, the heat input is increased from the initial stage of welding,
3. The method for welding a core shroud according to claim 1, wherein the welding is performed with the heat input lower than that in the intermediate region at the end of welding. The method for welding a core shroud according to claim 4, wherein the position of changing the heat input amount of welding is set to approximately ¼ and ¾ of the shroud plate thickness from the start of welding. After the outer surface of the shroud and the inner surface of the shroud are sealed with a plurality of circumferential weld beads, water is poured into the outer surface of the shroud and welding is sequentially performed toward the inner surface of the shroud. The method for welding a core shroud according to claim 1 or 2, wherein the additional welding of the two-dimensional build-up is performed at a position away from the welding center on the inner surface by a required distance. After performing the welding in which the cooling environment of the outer surface of the shroud is an environment in which the cooling rate is higher than in the air, and welding beads are sequentially piled from the outer surface of the shroud toward the inner surface of the shroud to sequentially form a weld bead sequence. ,
The method for welding a core shroud according to claim 1 or 2, wherein a two-dimensional additional welding is performed in a range of a required distance on both sides from the welding center of the inner surface of the shroud. Two or more welding machines are arranged on the inner peripheral side or outer peripheral side of the core shroud, and welding is performed from the shroud outer surface side or the shroud inner surface side to the opposite shroud surface using the two or more welding machines. The core shroud welding method according to claim 1, wherein the core shroud is welded. In the welding method in which the work piece is a pipe or a container, the members of the pipe or container are butted together and the butted portion is welded in the circumferential direction to form a weld bead sequence and integrate them.
After butting together the constituent members of the pipe or container, a plurality of weld beads are sequentially built up in the circumferential direction with the constituent member butting portion directed from one direction to the opposite direction on the inner surface or outer surface side. When forming a sequence, welding is performed and build-up welding is sequentially performed from the outer surface side of the member or the inner surface side of the member so that the residual stress of the surface welding portion of the constituent member of the pipe or container is compressed. A method of welding pipes or containers. The welding object is a pipe or a container, and the members of the pipe or container are welded from one direction of the inner surface or the outer surface, and the residual stress on the back side of the member of the welding process is compressed, 10. The piping according to claim 9, wherein after the members of the pipe or container are welded from one direction, the position or range of additional welding to the members is changed in accordance with the thickness of the pipe or container. Or the welding method of the container.

Images