JPH091376A - Welding method with low residual stress structure - Google Patents

Abstract

PURPOSE: To provide a welding method having a low residual stress structure, in which welding conditions are set with a small residual stress and deformation, by paying attention to the build-up sequence of a weld pass and the accompanying residual stress and deformation. CONSTITUTION: A shape is determined by the material of a welding structure and information containing kind of groove of a joint, and then, welding conditions are determined. In this case, information is inputted containing welding method, position, core diameter and heat input. A residual stress analysis is carried out concerning the welding structure to be manufactured with the build-up sequence of the weld pass selected. From the analytical result, a residual stress value is read in at a notice point predetermined as a point to evaluate a residual stress. If the residual stress value at the notice point is smaller than that of the residual stress analysis performed so far, the build-up sequence is stored of the weld pass that is currently evaluated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding method for a low residual stress structure, and more particularly to a welding method for reducing the residual stress of the welded structure.

[0002]

2. Description of the Related Art In a conventional welded structure, it is general to remove residual stress and residual deformation by heat treatment after residual stress and residual deformation occur. A method for removing residual stress and residual deformation by heat treatment is, for example,
It is described in JP-A No. 62-17133. As a welding method for reducing residual stress and residual deformation,
In fillet welding, there is a method of heating the back side of the welding line at the same time as welding. A welding method for reducing the residual stress and the residual deformation by heating the back side of the welding line at the same time as the welding is described in, for example, JP-A-4-162978.

[0003]

In the above-mentioned heat treatment method of the prior art, the residual stress value and residual deformation value after welding are not evaluated, but the residual stress, residual stress The main purpose was to reduce deformation. That is, the residual stress and the residual deformation after the completion of welding before heat treatment were not considered.

Further, in the conventional method of heating the backside of the welding line at the same time as the fillet welding, residual stress and residual deformation are reduced by changing the heating condition of the backside during welding. However, although the heating conditions on the back side are taken into consideration, for example, the stacking order of welding passes and the like have not been taken into consideration.

The present invention has been made to solve the above-mentioned problems of the prior art, and by paying attention to the stacking sequence of welding paths and the residual stress and residual deformation associated therewith, welding with little residual stress and residual deformation is performed. An object of the present invention is to provide a welding method for a low residual stress structure in which conditions are set.

[0006]

In order to achieve the above object, the first method according to the welding method of the low residual stress structure of the present invention is to set the welding conditions according to the joint shape of the structure to be welded. When setting, the order of stacking of welding paths under specific welding conditions shall be determined, residual stress analysis by welding is performed under the specific welding conditions, and the residual stress value at a predetermined attention point as a residual stress evaluation point. The stacking order of the welding paths having the smallest value is selected by sequentially comparing the stacking order of the plurality of welding paths.

[0007] Similarly, the second method is to set various welding conditions of the structure to be welded, which are composed of at least a groove shape, a welding method, a heat input amount, and a laminating order of welding passes, and the various welding conditions described above are set. Residual stress analysis by welding is performed under welding conditions, and the various welding conditions in which the residual stress value at the predetermined attention point as the residual stress evaluation point becomes the smallest,
The various welding conditions are sequentially compared and selected.

Similarly, in the third method, when setting the welding conditions in a welded structure constructed as a combination of a plurality of welded joints, the order of stacking the respective welding passes under specific welding conditions is determined, Residual stress analysis by welding is performed under the specific welding conditions, and the stacking order of the welding paths having the smallest residual stress value at the predetermined attention point as the residual stress evaluation point is sequentially compared with the stacking order of a plurality of welding paths. And then select.

[0009] Similarly, the fourth method comprises at least a welded structure constructed as a combination of a plurality of welded joints,
When setting various welding conditions consisting of groove shape, welding method, heat input, and laminating sequence of welding passes, residual stress analysis by welding is performed under the above various welding conditions, and the residual stress evaluation point is set in advance. The various welding conditions having the smallest residual stress value at the noted point are selected by sequentially comparing the various welding conditions.

Similarly, in the fifth method, when the welding conditions are set in accordance with the joint shape of the structure to be welded, the order of stacking of welding paths under specific welding conditions is determined, and the specific welding is performed. Residual deformation analysis or residual deformation measurement by welding is performed under the conditions, and the stacking order of the welding paths with the smallest residual deformation value at the predetermined point of interest as the residual stress evaluation point is sequentially compared with the stacking order of multiple welding paths. And then select.

[0011] Similarly, the sixth method is to set various welding conditions of the structure to be welded, which are at least groove shape, welding method, heat input, and laminating order of welding paths, and set various welding conditions. Residual deformation analysis or residual deformation measurement by welding is performed under welding conditions, and the various welding conditions with the smallest residual deformation value at the predetermined point of interest as a residual stress evaluation point are successively compared with each other. To choose.

Similarly, in the seventh method, when setting the welding conditions in a welded structure constructed as a combination of a plurality of welded joints, the order of stacking of respective welding passes under specific welding conditions is determined, Residual deformation analysis or residual deformation measurement is performed by welding under the specific welding conditions, and the stacking order of the welding passes having the smallest residual deformation value at the predetermined point of interest as a residual stress evaluation point The order is sequentially compared and selected.

[0013] The eighth method is at least a welded structure constructed as a combination of a plurality of welded joints,
When setting various welding conditions consisting of groove shape, welding method, heat input, and laminating order of welding passes, residual stress deformation analysis or residual deformation measurement by welding is performed under the various welding conditions, and residual stress is measured. The above-mentioned various welding conditions are selected by sequentially comparing the above-mentioned various welding conditions with each other to obtain the smallest residual deformation value at a predetermined attention point as an evaluation point.

Similarly, the ninth method uses the first or second method for the welded structure subjected to the repeated load load to reduce the residual stress on the surface of the portion where the defect is expected to occur to the allowable value or less. It is something to set. Also the first
Method 0 is a cross-section from the surface of the site where defects are expected to occur, and the maximum load that can be applied to the welded structure that is subjected to repeated load loads, using the first or second method. This is to minimize the average value of the residual stress in the cross section perpendicular to the principal stress direction.

Similarly, the eleventh method uses the first or second method for the welded structure constituting the plant equipment, and the residual on the surface of the portion to be loaded during the operation including the start and stop. The stress is set below the allowable value. Similarly, a twelfth method is a cross-section from the surface of a site where a defect is expected to occur, as well as the starting and stopping of the welded structure that constitutes the plant equipment, using the first or second method. It is intended to minimize the average value of the residual stress in the cross section perpendicular to the maximum principal stress direction of the load to which stress is applied during operation including inside.

Similarly, a thirteenth method is a method for corroding a welded structure which constitutes plant equipment to be used under conditions where the front side and the back side of a welded joint part have different corrosion resistances, by using the first or second method. The residual stress on the surface of the structure on the poor environment side is set below the allowable value. Also the first
The method of No. 4 is for a welded structure to be used under conditions of different corrosion resistance on the front side and the back side of the welded joint, using the first or second method, for cracking in a cross section where a crack is considered to propagate. The position of the peak value of the compressive stress in the residual stress distribution in the opening direction is set to be closer to the structure surface on the environment side where the corrosion resistance is poor.

Similarly, in the fifteenth method, the unwelded portion near the tip of the unwelded portion is opened by using the first or second method in the vicinity of the welded joint portion having the unwelded portion in the welded structure. The welding condition is set by calculating so that the residual stress in the direction to be performed is less than the allowable value. Similarly, the sixteenth method uses the first or second method to set the weld line vertical residual stress at the weld toe portion to the allowable value or less for the welded structure subjected to the repeated load load. It is a thing.

Similarly, in the seventeenth method, the case-type welded structure is set by using the first or second method so that the constraint stress inside the structure generated after the welding is completed is equal to or less than the allowable value. It is a thing. Similarly, the 18th method is
For a case-type welded structure that is subjected to repeated load loads, the residual stress including the restraint stress inside the structure generated after the welding at the weld toe ends is less than the allowable value by using the first or second method. It is set to become.

Similarly, the nineteenth method uses the first or second method for a welded structure which is subjected to heat treatment after the welding is completed, according to the joint shape of the welded structure to be welded, and the order of stacking the welding passes. The residual stress is calculated in consideration of the heat treatment conditions after the welding, and the residual stress at the point of interest is set to be equal to or less than the allowable value. Also the 20th
The method of (1) uses the first or second method for the welded joint portion having unwelded portions at the root portions of both groove sides in the welded structure so that the left and right weld overlay amounts are substantially equal. In addition, welding is performed while moving the stacking order of the welding paths from the right side to the left side or from the left side to the right side at least three times.

Similarly, the twenty-first method is to perform a welding on the inner surface side by using the first or second method with respect to a circumferential weld portion having a groove on both sides of the inner and outer surfaces in a cylindrical structure. The outer surface side is welded. Similarly, the 22nd method includes at least an upper ring, an upper shell, and a core shroud in a reactor pressure vessel of a nuclear power plant.
Middle ring, middle upper half, middle lower half, lower ring,
For the circumferential weld of the lower body, using the first method,
Welding is performed from the inner surface side of the shroud of the welded portion having both sides grooves, and then the outer surface side of the shroud is welded.

Similarly, the twenty-third method includes at least an upper ring, an upper shell, an intermediate ring, an intermediate shell upper half, an intermediate shell lower half, a lower ring in a core shroud inside a reactor pressure vessel of a nuclear power plant. For the circumferential welded portion of the lower body, at least the welding conditions represented by the groove shape of the welded structure, the welding method, the heat input amount, and the order of lamination of the welding paths are determined by using the second method, and the outside of the shroud is determined. One-side groove welding in which welding paths are laminated from the surface side to the inner surface side of the shroud is performed.

Similarly, in the 24th method, the welding angle between the neutron flux instrumentation pipe of the nuclear power plant and the reactor pressure vessel lower mirror is adjusted by using the fifth method. Welding on the small pressure vessel body side, then welding on the core center side with a large inclination angle, or after welding on the pressure vessel body side with a small inclination angle with the reactor pressure vessel, By repeating the welding on the central side of the core having a large inclination angle, the stacking of the welding passes is completed.

Similarly, the twenty-fifth method uses the sixth method for the welded portion of the neutron flux instrumentation piping of the nuclear power plant and the reactor pressure vessel lower mirror, and uses at least the groove shape of the welded structure and the welding method. , The heat input, and the welding conditions represented by the sequence of welding path stacking are determined, welding is performed on the fuselage side of the pressure vessel with a small inclination angle with the reactor pressure vessel lower mirror, and then the core with a large inclination angle. After performing welding on the center side with a heat input smaller than the heat input by welding on a cross section with a small inclination angle, or after welding on the pressure vessel body side with a small inclination angle with the reactor pressure vessel lower mirror. In addition, the stacking of welding passes is completed by repeating the welding on the core center side having a large inclination angle with a heat input amount smaller than the heat input amount by welding on a cross section having a small inclination angle.

[0024]

According to the first and third methods, the residual stress of the welded structure is analyzed to obtain the function of determining the stacking sequence of the welding passes. According to the second method and the fourth method, various welding conditions including the stacking order of welding paths and the groove shape can be obtained from the relationship between changes in welding conditions and changes in residual stress.

According to the fifth method and the seventh method, by analyzing the residual deformation of the welded structure, the effect of obtaining the stacking sequence of the welding passes can be obtained. According to the sixth method and the eighth method, various welding conditions including the stacking order of welding paths and the groove shape can be obtained from the relationship between changes in welding conditions and changes in residual stress.

According to the ninth and eleventh methods, the first method
In addition to the effects of the above method and the second method, it is possible to obtain the effect of setting the surface residual stress of the portion of the welded structure where defects are likely to occur to be equal to or less than the allowable value. According to the tenth method and the twelfth method, in addition to the effects of the first method and the second method, a cross section from the surface of the portion of the welded structure where defects are likely to occur is the starting point, and during operation The effect of minimizing the residual stress in the section perpendicular to the direction of maximum principal stress of the applied load is obtained.

According to the thirteenth method, in addition to the effects of the first and second methods, the effect of setting the residual stress on the surface side of the welded structure, which has poor corrosion resistance, to the allowable value or less is provided. can get. According to the fourteenth method, in addition to the actions of the first method and the second method, in the cross section where the crack is considered to propagate closer to the surface of the welded structure on the environment side where the corrosion resistance is poor, The effect that the position of the peak value of the compressive stress of the residual stress distribution comes is obtained.

According to the fifteenth method and the twentieth method, in addition to the effects of the first method and the second method, the unwelded portion near the tip of the unwelded portion of the welded joint is opened. The effect of reducing the residual stress to the allowable value or less is obtained. Sixteenth
According to the method (1), in addition to the functions of the first method and the second method, the function of setting the residual stress in the weld line vertical direction at the weld toe of the welded structure to be equal to or less than the allowable value can be obtained.

According to the seventeenth method, in addition to the effects of the first and second methods, the effect of reducing the restraint stress inside the welded structure to the allowable value or less can be obtained. According to the eighteenth method, in addition to the effects of the first method and the second method, the effect of reducing the residual stress including the constraint stress inside the welded structure to the allowable value or less is obtained. According to the nineteenth method, in addition to the actions of the first method and the second method,
It is possible to obtain the action of making the residual stress including the stacking sequence of the welding paths and the heat treatment process of the welded structure which is subjected to heat treatment after welding less than the allowable value.

According to the twenty-first method, the twenty-second method and the twenty-third method, a circumferential weld having a cylindrical structure having both inner and outer surfaces of the groove, that is, a reactor pressure vessel of a nuclear power plant. At least the upper ring, the upper shell, the middle ring, the upper half of the intermediate shell, the lower half of the intermediate shell, the lower ring, and the circumferential welds of the lower shell in the inner core shroud
The effects of the third method and the fourteenth method can be obtained. 24th
According to the method No. 25 and the method No. 25, the effects of the fifth method and the sixth method can be obtained for the welded portion of the neutron flux instrumentation pipe of the nuclear power plant and the reactor pressure vessel lower mirror.

[0031]

Embodiments of the present invention will now be described with reference to FIGS. 1 to 29.
This will be described with reference to FIG. [Embodiment 1] FIG. 1 is a flow chart showing a welding procedure evaluation method for a welded structure in consideration of a stacking order of welding paths, which is a welding method according to an embodiment of the present invention and which is focused on residual stress. In the following description, the numbers in parentheses are the step numbers in the flowchart of FIG. It is. As shown in FIG. 1, in order to evaluate the welding procedure of the welded structure, first, the shape of the target welded structure is determined (step 10).
1). At that time, the material of the welded structure (step 102)
Alternatively, information including the type of joint groove (step 103) is input to a calculation control means (not shown).

Next, the welding conditions of the target welded portion are determined (step 104). At that time, information including the welding method (step 105), the welding posture (step 106), the welding rod diameter (step 107), and the heat input amount (step 108) is input. The parameter n is set to 1 in order to count the number of m times (m ways) to be evaluated as the stacking order of the welding passes (step 109). Here, the stacking order of the m welding passes to be evaluated is arranged in order from the first to the mth, and the stacking order of the welding passes counted in the nth time is selected (step 110). That is, when the parameter n is 1, the stacking order of the welding passes counted first in the stacking order of the m welding passes to be evaluated is selected.

Residual stress analysis by welding is carried out for the welded structure manufactured in the selected laminating order of welding paths (step 111). The residual stress can be obtained by numerical analysis such as thermo-elasto-plastic analysis and intrinsic strain analysis. It is also possible to experimentally measure the residual strain amount and analyze the residual stress from the relational expression between the elastic stress and the elastic strain. From the residual stress analysis result, the residual stress value at the point of interest that has been determined in advance as a point for evaluating the residual stress is read (step 112). Here, the attention point is not limited to one place, but a plurality of places may be decided.

Here, the residual stress value at the target point is compared with the residual stress value at the target point by the residual stress analysis performed so far (step 113). If there is only one point of interest, compare only that point. When there are a plurality of points of interest, the points are compared. If the residual stress value at the target point is smaller than the residual stress value at the target point obtained by the residual stress analysis performed so far, the stacking order of the welding paths currently evaluated is stored (step 11).
4). This memory enables overwriting, and always stores the stacking order with the smallest residual stress value at the point of interest.

When there is only one point of interest, the laminating order with the smaller residual stress value is simply stored. When there are a plurality of points of interest, each point is weighted in advance in consideration of the degree of importance in evaluation, and the stacking order having the smaller residual stress value is stored for the plurality of points of interest as a whole. If the residual stress value at the target point is not smaller than the residual stress value at the target point obtained by the residual stress analysis performed so far, the process of step 114 is ignored.

It is determined whether or not the parameter n is equal to the number of times m of evaluation as the stacking order of the welding passes (step 115), and if they are equal, the stacking order of the welding passes stored in step 114 is set as the welding sequence. (Step 117). If the parameter n and the number m of times of evaluation as the stacking order of the welding passes are not equal, the parameter n for counting the stacking order of the welding passes is increased by 1 (step 116). Then return to step 110,
Again, the stacking order of a certain welding pass is evaluated.

By carrying out the above procedure,
It is possible to evaluate the welding procedure of the welded structure, which is one embodiment for providing the welding method considering the residual stress according to the present invention.

[Embodiment 2] FIG. 2 is a flow chart showing a welding procedure evaluation method of a welded structure in consideration of the stacking order of welding passes, which is a welding method according to another embodiment of the present invention, in which residual deformation is noted. It is a figure. In the following description,
The numbers in parentheses are the step numbers in the flowchart of FIG. It is. As shown in FIG. 2, in order to evaluate the welding procedure of the welded structure, first, the shape of the target welded structure is determined (step 201). At that time, the material of the welded structure (step 202) and the type of joint groove (step 203)
Enter the information including.

Next, the welding conditions of the target welded portion are determined (step 204). At that time, information including the welding method (step 205), the welding posture (step 206), the welding rod diameter (step 207), and the heat input amount (step 208) is input. The parameter n is set to 1 in order to count the number of m times (m ways) evaluated as the stacking order of the welding passes (step 209). Here, the stacking sequence of the m welding passes to be evaluated is arranged in order from the first to the mth, and the stacking sequence of the welding passes counted in the nth is selected (step 210). That is, when the parameter n is 1, the stacking order of the welding passes counted first in the stacking order of the m welding passes to be evaluated is selected.

Residual deformation analysis by welding is carried out for the welded structure manufactured in the selected welding path stacking order (step 211). The residual deformation can be obtained by numerical analysis such as thermoelastic-plastic analysis. It is also possible to experimentally determine the residual deformation. From the residual deformation analysis result, the residual deformation value at the point of interest that is predetermined as a point for evaluating the residual deformation is read (step 212). Here, the attention point is not limited to one place, but a plurality of places may be decided.

Here, the residual deformation value at the target point is compared with the residual deformation value at the target point by the residual deformation analysis performed so far (step 213). If there is only one point of interest, compare only that point. When there are a plurality of points of interest, the points are compared. If the residual deformation value at the point of interest is smaller than the residual deformation value of the point of interest obtained by the residual deformation analysis performed so far, the stacking order of the welding paths currently evaluated is stored (step 21).
4). This memory enables overwriting, and always stores the stacking order with the smallest residual stress value at the point of interest.

When there is only one point of interest, the laminating order with the smaller residual deformation value is simply stored. When there are a plurality of points of interest, each point is weighted in advance in consideration of the degree of importance in evaluation, and the stacking order having the smaller residual deformation value is stored for the plurality of points of interest as a whole. If the residual deformation value at the point of interest is not smaller than the residual deformation value of the point of interest obtained by the residual deformation analysis performed so far, the process of step 214 is ignored.

It is determined whether or not the parameter n is equal to the number of times m of evaluation of the welding pass stacking order (step 215). If they are equal, the welding pass stacking order stored in step 214 is set as the welding order. (Step 217). If the parameter n is not equal to the number m of evaluations of the welding pass stacking order, the parameter n counting the welding pass stacking order is incremented by 1 (step 216). Then return to step 210,
Again, the stacking order of a certain welding pass is evaluated.

By performing the above procedure,
It is possible to evaluate the welding procedure of the welded structure, which is one embodiment for providing the welding method in consideration of the residual deformation according to the present invention.

[Embodiment 3] FIG. 3 shows a welding method according to still another embodiment of the present invention, in which the welding procedure of the welded structure is evaluated in consideration of the shape and welding conditions of the welded structure and the stacking order of the welding paths. It is a flowchart figure which shows the method. In the following description, the numbers in parentheses are the step numbers in the flowchart of FIG. It is. As shown in FIG. 3, in order to evaluate the welding procedure of the welded structure, first, the values of n and q are respectively used as parameters for evaluating the shape and welding conditions of the target welded structure and the stacking order of the welding paths. Is set to 1 (step 301).

Next, the shape of the target welded structure and the welding conditions of the welded portion are set (step 302). that time,
Information including the shape of the welded structure to be evaluated and the welding condition material, the joint groove type, the welding method, the welding posture, the welding rod diameter, and the heat input amount, which are considered as the welding conditions of the welded part,
Enter the street. Here, the shape of the welded structure to be evaluated and the welding conditions of the welded portion are arranged in order from the first time to the p-th time,
Among them, the shape of the welded structure counted at the q-th time and the welding condition of the welded portion are selected. The parameter n is set to 1 in order to count the number of m times evaluated as the stacking order of the welding passes (step 303). Here, the stacking sequence of m welding passes to be evaluated is arranged in order from the first to the mth, and the stacking sequence of the welding passes counted in the nth is selected.

Residual stress analysis by welding is carried out for the selected welded structure shape, the welding conditions of the welded portion, and the welded structure manufactured in the order of stacking the welding passes (step 3).
04). The residual stress can be obtained by numerical analysis. It is also possible to experimentally measure the residual strain amount and analyze the residual stress from the relational expression between the elastic stress and the elastic strain. From the residual stress analysis result, the residual stress value at the point of interest that has been determined in advance as the point for evaluating the residual stress is read (step 305). Here, the attention point is not limited to one place, but a plurality of places may be decided.

Here, the residual stress value at the target point is compared with the residual stress value at the target point by the residual stress analysis performed so far (step 306). If there is only one point of interest, compare only that point. When there are a plurality of points of interest, the points are compared. If the residual stress value at the point of interest is smaller than the residual stress value at the point of interest obtained by the residual stress analysis performed so far, the shape of the welded structure being evaluated this time, the welding conditions of the weld, and the stacking of the welding paths The order is stored (step 307). This memory enables overwriting, and always stores the stacking order with the smallest residual stress value at the point of interest.

When there is only one point of interest, the shape of the welded structure having the smaller residual stress value, the welding condition of the welded portion, and the laminating order of the welding paths are simply stored. If there are multiple points of interest, each point is weighted in advance in consideration of the importance of evaluation, and the shape of the welded structure, the welding conditions of the welded part, and the stacking order of the welding paths are set for the entire points of interest. Remember. If the residual stress value at the target point is not smaller than the residual stress value at the target point obtained by the residual stress analysis performed so far, the process of step 307 is ignored.

It is determined whether the parameter n is equal to the number of times m of evaluation as the stacking order of welding passes (step 308). If they are equal, the process proceeds to the next step. Also, the parameter n
If the number m of evaluations as the stacking order of the welding passes is not equal, the parameter n for counting the stacking order of the welding passes is increased by 1 (step 309). Then, returning to step 303, the stacking sequence of a certain welding pass is evaluated again under the same shape of the welded structure and the welding conditions of the welded portion.

If the parameter q is not equal to the shape p of the welded structure and the number p of times of evaluation as welding conditions, the parameter q is increased by 1 (step 311). Then, the process returns to step 302, the shape of the next welded structure and the welding conditions are set, and the evaluation is repeated. If the parameters q and p are equal, the shape of the welded structure, the welding conditions, and the stacking order of the welding paths stored in step 307 are set as the welding procedure (step 312).

By performing the above procedure,
It is possible to evaluate the shape of the welded structure, the welding conditions, and the stacking sequence of the welding passes, which is one embodiment for providing the welding method considering the residual stress according to the present invention.

[Embodiment 4] FIG. 4 is a flow chart showing a welding procedure evaluation method for a welded structure virtually having a plurality of welded joint portions in a welding method according to still another embodiment of the present invention. . In the following description, the numbers in parentheses are the step numbers in the flowchart of FIG. It is. As shown in FIG. 4, in order to evaluate the welding procedure of the welded structure, first, the shape of the target welded structure is determined (step 40).
1). At that time, the material of the welded structure (step 402)
Alternatively, information including the type of groove (step 403) at a place where a plurality of welded joints are formed when the welded structure is virtually divided is input.

Next, the parameter q representing the number of a plurality of welded joints when the welded structure is virtually divided is set to 1 (step 404). The welding conditions of the p virtual welded joints evaluated here are arranged in order from the first to the pth, and the stacking order of the welding passes counted at the qth time is selected (step 405). That is, when the parameter q is 1, the welding condition of the welded joint counted for the first time is selected from the welding conditions of the p virtual welding joints to be evaluated.

Welding conditions for the target virtual welded joint are set (step 406). At that time, information including a welding method (step 407), a welding posture (step 408), a welding rod diameter (step 409), and a heat input amount (step 410) is input. It is determined whether the parameter q is equal to the number p of times of evaluation as the welding condition of the virtual welded joint portion (step 411), and if they are equal, step 41
Proceed to 2. If the parameter q is not equal to the number p of times of evaluation as the welding condition of the virtual welded joint portion, the process returns to step 406, and the welding condition of a certain virtual welded joint portion is evaluated again.

The parameter n is set to 1 in order to count the number of times of m times evaluated as the stacking order of the welding passes (step 412). Here, the stacking sequence of the m welding passes to be evaluated is arranged in order from the first to the mth, and the stacking sequence of the welding passes counted from the nth is selected (step 41).
3). That is, when the parameter n is 1, m to be evaluated
Select the stacking sequence of the welding passes counted first in the stacking sequence of the welding passes.

Residual stress analysis by welding is carried out on the welded structure manufactured in the selected laminating order of the welding paths (step 414). The residual stress can be obtained by numerical analysis such as thermo-elasto-plastic analysis and intrinsic strain analysis. It is also possible to experimentally measure the residual strain amount and analyze the residual stress from the relational expression between the elastic stress and the elastic strain. From the residual stress analysis result, the residual stress value at the point of interest that has been previously determined as the point for evaluating the residual stress is read (step 415). Here, the attention point is not limited to one place, but a plurality of places may be decided.

Here, the residual stress value at the target point is compared with the residual stress value at the target point by the residual stress analysis performed so far (step 416). If there is only one point of interest, compare only that point. When there are a plurality of points of interest, the points are compared. When the residual stress value at the target point is smaller than the residual stress value at the target point obtained by the residual stress analysis performed so far, the stacking sequence of the welding paths currently evaluated is stored (step 41).
7). This memory enables overwriting, and always stores the stacking order with the smallest residual stress value at the point of interest.

When there is only one point of interest, the laminating order with the smaller residual stress value is simply stored. When there are a plurality of points of interest, each point is weighted in advance in consideration of the degree of importance in evaluation, and the stacking order having the smaller residual stress value is stored for the plurality of points of interest as a whole. If the residual stress value at the target point is not smaller than the residual stress value at the target point obtained by the residual stress analysis performed so far, the process of step 417 is ignored.

It is determined whether or not the parameter n is equal to the number of times m of evaluation as the welding pass stacking order (step 418). If they are equal, the welding pass stacking order stored in step 417 is set as the welding order. (Step 420). If the parameter n and the number m of times of evaluation as the welding pass stacking order are not equal, the parameter n for counting the welding pass stacking order is incremented by 1 (step 419). Then return to step 413,
Again, the stacking order of a certain welding pass is evaluated.

By carrying out the above procedure,
It is one example for giving the welding method considering the residual stress according to the present invention, and it is possible to evaluate the welding procedure of the welded structure having virtually a plurality of welded joints.

[Embodiment 5] As shown in the flowchart of FIG. 1, one embodiment in which a welding procedure evaluation method for a welded structure in which the stacking order of the welding paths is taken into consideration and attention is paid to the residual stress is applied is shown in FIGS. This will be described with reference to FIG. FIG.
6 is an exploded perspective view of a boiling water reactor pressure vessel to which a welding procedure as shown in the flowchart of FIG. 1 is applied. FIG. 6 is a perspective view showing a core shroud of the boiling water reactor pressure vessel of FIG. FIG. 7 is an enlarged cross-sectional view of the intermediate ring and the circumferential welded portion of the upper half of the intermediate shell of the core shroud of FIG. 6.

FIG. 8 is an explanatory view showing a first example of the stacking order of the welding paths of the intermediate ring and the upper half of the intermediate shell of the core shroud shown in FIG. 6, and FIG. 9 is the same core shroud. FIG. 10 is an explanatory view showing a second example of the stacking order of the welding paths of the intermediate ring and the upper half of the intermediate shell, and FIG. 10 is a welding path of the intermediate ring and the upper half of the intermediate shell of the same core shroud. 11 is an explanatory view showing a third example of the stacking sequence of FIG. 11, and FIG. 11 is a shaft in a heat-affected zone of the middle ring of the core shroud welded in the stacking sequence of the welding paths of FIG. 12 is a diagram showing the directional residual stress, and FIG. 12 shows the axial residual stress in the heat-affected zone of the intermediate ring and the upper half of the intermediate shell of the core shroud welded in the stacking order of the welding paths in FIG. Diagram and Fig. 13 are core shrouds welded in the stacking order of the welding paths of Fig. 10. Is a graph showing the axial residual stress in the weld heat affected zone of the welded portion of the intermediate portion ring and the intermediate cylinder upper half of de.

FIG. 5 shows a pressure vessel of a boiling water reactor of a nuclear power plant. Inside the pressure vessel 1,
Various devices such as the core shroud 2, the upper lattice plate 3, the core support plate 4, and the jet pump 5 are attached.
Among them, the core shroud 2 is a cylindrical structure inside the pressure vessel 1. FIG. 6 shows the core shroud 2 and its peripheral parts taken out. The core shroud 2 has an upper ring 21, an upper shell 22, an upper shell 22, an intermediate ring 23, an intermediate ring 23, an intermediate shell upper half 24, and an intermediate shell upper half 2 each having a cylindrical shape.
4 and the intermediate lower half 25, the intermediate lower half 25 and the lower ring 26, the lower ring 26 and the lower body 27, etc. are manufactured by circumferential welding.

FIG. 7 shows a circumferential welded joint connecting the intermediate ring 23 and the intermediate shell upper half 24 of the core shroud,
It shows an example of a cross section of a welded portion. The radial distribution of the axial residual stress in the heat affected zone of the intermediate ring has a great influence on the initiation and propagation of stress corrosion cracking from the inner surface of the intermediate ring. Therefore, the points of interest are the inner surface on the straight line in the radial direction in the heat affected zone of the intermediate ring and the point where the maximum value of the compressive stress is present, and the axial residual stress is taken as the direction of the residual stress of interest. It is desirable for prevention of stress corrosion cracking that the residual stress in the axial direction at the point of interest is as small as possible on the inner surface, the part having the maximum value of the compressive stress is as close to the inner surface as possible, and has a large compressive stress.

The circumferential welding for connecting the intermediate ring 23 of the core shroud and the upper half 24 of the intermediate shell is carried out by step No. 1 in the flow chart of FIG. This will be described with reference to FIG. First, the shape and dimensions of the core shroud are determined (step 10).
1). The material is austenitic stainless steel JIS standard SUS304 steel (step 102), and the type of groove is a double-sided groove (step 103).

Next, the welding conditions are determined (step 10).
4). The welding method is gas tungsten welding for the first layer and submerged arc welding for the second and subsequent layers (step 10).
5). The welding posture is downward (step 106), and the diameter of the welding rod is 4 mm for the first layer and 5 mm for the second and subsequent layers (step 107). Heat input is 20 kJ / cm (Step 1
08). The parameter n is set to 1 in order to count the number of m times evaluated as the stacking order of the welding passes (step 10).
9). In the case of this embodiment, m is 3.

FIGS. 8, 9 and 10 show an example of the stacking sequence of the welding paths in the cross section of the weld portion of the circumferential weld joint connecting the intermediate ring 23 and the intermediate shell upper half 24 of the core shroud. 8, 9 and 10 are explanatory views showing an example of the stacking sequence of the welding paths of the intermediate ring of the boiling water reactor pressure vessel core shroud and the welded portion of the upper half of the intermediate shell in cross section. The multilayer welded joint in the circumferential direction has an axially symmetric shape when viewed in the final cross section after welding is completed, and thus any cross section has such a cross section.

The numbers in FIG. 8 indicate the stacking sequence of welding passes. First, the outer surface side of the groove on both sides is welded to about 1/2, then the inner surface side is welded to the final layer, and then the remaining about 1/2 of the outer surface side is welded to the final layer. Similarly, FIG. 9 and FIG.
The number in 0 is the stacking order of the welding passes, and in FIG. 9, the inner surface side of the groove on both sides is first welded, and then the outer surface side is welded. In FIG. 10, first, the outer surface sides of the groove on both sides are welded,
Next, the inner surface side is welded. Here, the stacking order of the three welding passes to be evaluated is arranged in order from the first time to the third time, and the stacking order of the welding passes taught at the first time is selected (step 110). In this case, the welding sequence is shown in FIG.

Residual stress analysis by welding is carried out for the welded structure manufactured in the selected laminating order of welding paths (step 111). As an example, the residual stress at this time is as shown in FIG. 11 with the inner surface side of the core shroud as the starting point in the radial residual stress distribution in the radial direction in the intermediate ring welding heat affected zone. FIG. 11 is a radial distribution (outer surface) of the axial residual stress in the weld heat-affected zone of the middle ring and the upper half of the middle shell of the boiling water reactor pressure vessel core shroud starting from the inner surface. After welding the side to about 1/2,
FIG. 6 is a diagram of a case where the inner surface side is welded and then the remaining about ½ on the outer surface side is welded. Tensile stress is about 3 on the inner surface
It is 50 MPa, and when it enters about 5 mm inside, the tensile stress is about 400 MPa. After that, the stress value decreases, the stress value becomes 0 when it enters the inside of about 15 mm, and the peak value of the compressive stress takes the value when it enters the inside of about 30 mm, and the value is about -250 MPa.

From the residual stress analysis result, the residual stress value at the point of interest which is predetermined as a point for evaluating the residual stress is read (step 112). In this case, the tensile stress on the inner surface is about 350 MPa, and the peak value of the compressive stress is about -250 MPa when it enters about 30 mm inside. Here, the residual stress value at the target point is compared with the residual stress value at the target point by the residual stress analysis performed so far (step 113). Since this is the first evaluation, the tensile stress on the inner surface is about 350 MPa, and the peak value of compressive stress of about -250 MPa when it enters about 30 mm inside is inevitably treated as smaller than the value in other welding orders. Be seen.

When the residual stress value at the target point is smaller than the residual stress value at the target point obtained by the residual stress analysis performed so far, the stacking order of the welding paths currently evaluated is stored (step 114). . In this case, the stacking order shown in FIG. 8 is stored. The parameter n that teaches the stacking order of the welding passes is incremented by 1 (step 115). In this case, the parameter n is set to 2. Parameter n = 1
Then, it is determined whether or not the number m = 3 of evaluations of the welding pass stacking order is equal (step 115), and the number of evaluations of the parameter n = 1 and the welding pass stacking order m = 3.
Are not equal to each other, the parameter n for counting the stacking order of the welding passes is increased by 1 (step 116). In this case, the parameter n is set to 2. Then step 1
Return to 10.

Next, the stacking sequence of the welding passes counted for the second time is selected from the stacking sequences of the three welding passes to be evaluated (step 110). In this case, the welding paths are stacked as shown in FIG. Residual analysis by welding is performed on the welded structure manufactured in the stacking order of the selected welding passes (step 111). As an example, the residual stress at this time is as shown in FIG. 12 from the inner surface side of the core shroud as the starting point in the radial residual stress distribution in the radial direction in the intermediate ring welding heat affected zone.

FIG. 12 is a radial distribution of the axial residual stress in the welding heat affected zone of the middle ring of the boiling water reactor pressure vessel core shroud and the weld heat-affected zone of the upper half of the intermediate shell starting from the inner surface. It is a diagram of (when the inner surface side is welded and then the outer surface side is welded). Tensile stress is about 200MP on the inner surface
a. After that, the stress value decreases, and about 10 mm inward
When entering, the stress value becomes 0, and when entering about 18 mm inside, the peak value of compressive stress is taken, and the value is about −
It is 250 MPa.

From the residual stress analysis result, the residual stress value at the point of interest previously determined as the point for evaluating the residual stress is read (step 112). In this case, the tensile stress on the inner surface is about -200 MPa. Here, the residual stress value at the target point is compared with the residual stress value at the target point by the residual stress analysis performed so far (step 113). The information currently stored is the residual stress from the first analysis, the tensile stress on the inner surface is about 350 MPa, and the peak value of the compressive stress when it enters about 30 mm inside is about -2.
It is 50 MPa.

Judging from the judgment criteria that the axial residual stress at the point of interest is as small as possible on the inner surface, the part with the maximum value of the compressive stress is as close to the inner surface as possible, and the compressive stress is large, The result of the analysis performed shows that the tensile stress on the inner surface is smaller and the maximum value of the compressive stress is about the same, but the location with the compressive stress is closer to the inner surface. Therefore, if the residual stress value at the point of interest is smaller than the residual stress value at the point of interest obtained by the residual stress analysis performed so far, the stacking sequence of the welding paths being evaluated this time is stored. Figure 9 used for evaluation
The stacking order of is stored (step 114).

The parameter n, which counts the stacking order of the welding passes, is incremented by 1 (step 115). In this case, the parameter n is set to 3. It is determined whether or not the parameter n = 2 is equal to the number of times m = 3 of evaluation as the stacking order of the welding passes (step 115), and the parameter n = 2.
Since the number m = 3 of evaluations as the stacking order of the welding paths is not equal, the parameter n for counting the stacking order of the welding paths is increased by 1 (step 116). In this case, the parameter n is set to 3. Then, step 110
Return to

Next, the stacking sequence of the welding passes counted for the third time is selected from the stacking sequence of the three welding passes to be evaluated (step 110). In this case, the stacking order of welding paths is as shown in FIG. Residual analysis by welding is performed on the welded structure manufactured in the stacking order of the selected welding passes (step 111). For example, the residual stress at this time is as shown in FIG. 13 with the inner surface side of the core shroud as the starting point in the radial residual stress distribution in the radial direction in the intermediate ring welding heat affected zone.

FIG. 13 is a radial distribution of the axial residual stress originating from the inner surface of the weld heat-affected zone of the intermediate ring of the boiling water reactor pressure vessel core shroud and the weld of the upper half of the intermediate shell. It is a diagram of (when the outer surface side is welded and then the inner surface side is welded). As shown in FIG. 13, the tensile stress on the inner surface is about 250 MPa. After that, the stress value decreases, the stress value becomes 0 when entering the inside of about 15 mm, and the peak value of the compressive stress is taken when entering the inside of about 35 mm, and the value is about −200 MPa.

From the residual stress analysis result, the residual stress value at the point of interest previously determined as the point for evaluating the residual stress is read (step 112). In this case, the tensile stress on the inner surface is about 250 MPa, and the peak value of the compressive stress at the position of about 35 mm inside is about 200 MPa.
Here, the residual stress value at the target point is compared with the residual stress value at the target point by the residual stress analysis performed so far (step 113). The information currently stored is the residual stress from the second analysis, and the tensile stress on the inner surface is about 20.
The peak value of the compressive stress at 0 MPa and about 18 mm inside is about -250 MPa.

Judging from the judgment criteria that the axial residual stress at the point of interest is as small as possible on the inner surface, the part having the maximum value of the compressive stress is as close to the inner surface as possible, and the compressive stress is large, The result of the analysis performed shows that the tensile stress on the inner surface is larger, the location of the compressive stress is closer to the outer surface, and the maximum value of the compressive stress is also larger. Therefore, if the residual stress value at the point of interest is smaller than the residual stress value at the point of interest obtained by the residual stress analysis performed so far, the stacking sequence of the welding paths being evaluated this time is stored. The process proceeds to the next step without storing the stacking order of FIG. 10 used for the evaluation (step 113).

It is determined whether or not the parameter n = 3 and the number m = 3 of evaluations of the welding pass stacking order are equal to each other (step 115), and the number of evaluations m = 3 of the parameter n = 3 and the welding pass stacking order m = 3. Are equal, the welding sequence currently stored as shown in FIG. 9 is determined (step 117).

As described above, the welding procedure prediction method in which the stacking sequence of the welding paths is taken into consideration, which is an embodiment of the present invention shown in FIG. 1, is applied to the intermediate ring 23 and the intermediate shell of the core shroud. As a result of the application to the circumferentially welded joint connecting the halves 24, it is possible to determine the welding sequence as shown in FIG. Also in the case of paying attention to the residual deformation of the circumferential welded joint that connects the intermediate ring 23 and the intermediate shell upper half 24 of the core shroud, the same result can be obtained by performing the residual deformation analysis similarly using the flow of FIG. Obtainable.

[Embodiment 6] Next, the intermediate shell upper half 2 of the boiling water reactor pressure vessel core shroud 2 as shown in FIG.
A method for determining welding conditions such as the stacking order of welding paths and the groove shape will be described with reference to the flow of FIG. FIG. 3 is a flowchart of a welding procedure prediction method for a welded structure according to another embodiment of the present invention, in which the shape and welding conditions of the welded structure and the stacking order of welding paths are taken into consideration.

The intermediate body upper half 24 and the intermediate body lower half 25 are joined as a butt joint. The groove shape of this peripheral joint is considered to be a. Further, the heat input amount may be b, the welding rod diameter may be c, the welding method may be d, and the welding posture may be e. There are p possible welding conditions including all of these. Here, it is expressed as P = a × b × c × d × e.

Welding conditions of p ways (step 302)
For m, the residual stresses in the possible stacking sequence of welding paths (step 303) are analyzed, and the welding conditions and the stacking sequence of welding paths that minimize the residual stress value at the target point are selected (step 312). The criterion at the point of interest is that the axial residual stress at the point of interest is as small as possible on the inner surface, as with the circumferentially welded joint connecting the intermediate ring 23 and the intermediate shell upper half 24 of the core shroud described above. The criterion is that the location having the maximum value of the compressive stress is as close to the inner surface as possible and the compressive stress is large.

14 to 19 shown below as an example.
Shows an example of the stacking sequence of welding passes for one possible groove shape. 14 to FIG.
FIG. 3 is an explanatory view showing an example of a stacking order of welding paths in a circumferential welding portion of an upper half of the intermediate shell and a lower half of the intermediate shell of a boiling water reactor pressure vessel core shroud in cross section.

In the example of FIG. 14, after the inner surface side is welded, the outer surface side is welded. In the example of FIG. 15, the order of welding paths is shown when the inner surface side is welded to about 1/2, the outer surface side is welded, and then the remaining about 1/2 on the inner surface side is welded. ing. Furthermore, in the example of FIG. 16, the inner surface side is welded to about 1/2 and then the outer surface side is welded to about 1/2.
The following shows the stacking sequence of the welding paths when welding is performed up to and after that, the remaining about 1/2 on the inner surface side is welded, and the remaining about 1/2 on the outer surface side is welded again.

Next, the example of FIG. 17 shows the stacking sequence of the welding paths when the outer surface side is welded and then the inner surface side is welded. In the example of FIG. 18, the outer surface side is about 1/2
After welding up to, the inner surface side is welded, and then the remaining approximately 1/2 of the outer surface side is welded, showing the stacking sequence of the welding paths. Further, in the example of FIG. 19, after the outer surface side is welded to about 1/2, the inner surface side is welded to about 1/2, then the remaining about 1/2 of the outer surface side is welded, and the inner surface side is again welded. 3 shows the stacking order of welding paths when the remaining about 1/2 of the above is welded.

FIG. 20 is a cross-sectional view showing an example of the stacking order of the welding paths in the welded portion of the boiling water reactor pressure vessel core shroud in which the groove dimensions of the upper half and the lower half of the intermediate barrel are changed. FIG. Although the explanation of the specific procedure is omitted here, the groove shape, heat input, welding rod diameter, and welding method are analyzed for each stacking order of these welding passes to see how the welding position parameters work. Can be asked for. Further, if the analyzed results of evaluation are stored as a database, it is not necessary to evaluate all cases when an analysis target having a similar shape appears.

FIG. 21 shows a radial direction starting from the inner surface of the axial residual stress in the heat affected zone of the weld in the upper half and the lower half of the middle shell of the boiling water reactor pressure vessel core shroud. It is a diagram showing an example of the distribution of. That is, in the circumferential welding of the intermediate shell upper half 24 and the intermediate shell lower half 25 of the core shroud 2, the welding heat affected zone is determined by the welding conditions such as the stacking order of the welding paths and the groove shape determined by the flow of FIG. The distribution of the residual stress in the axial direction of is shown in the radial direction. As shown in FIG. 21, the compressive stress on the inner surface is about −5.
0 MPa. After that, the stress value decreases to about 1
The peak value of the compressive stress is taken at a distance of 5 mm, and the value is about -300 MPa. After that, the stress value gradually increases and becomes 0 when entering the inside of about 35 mm, and the tensile stress of the outside surface is about 100 MPa.

[Embodiment 7] Next, an example of an embodiment in which a residual stress in a portion where a defect is expected to occur in a welded structure subjected to repeated load is evaluated will be described. FIG. 22 is a perspective view showing a cross-sectional shape of a part of the welded structure 6 which is subjected to repeated load. Part of the cross section of this welded structure is a fillet joint, and the web 6
1 and the flange 62 are connected by a welded portion 63. Further, the fillet joint is repeatedly subjected to the applied load P in the direction of the arrow in the figure. At this time, the largest stress is generated in the fillet joint at the weld toe 64, and it is considered that defects are most likely to occur.

Therefore, as an example, the stacking sequence of the welding passes is determined so that the residual stress in the load direction at the welding toe portion 64, which is the point of interest, is not more than the allowable value by the flow shown in FIG. This makes it possible to obtain a desirable residual stress distribution in terms of preventing fatigue fracture of the welded structure 6 that is subjected to repeated load loads. In addition, from another viewpoint of preventing fatigue fracture of the welded structure, a cross section starting from the surface of the site where defects are expected to occur and a cross section perpendicular to the direction of the maximum principal stress of the applied load. It is desirable to determine the stacking sequence of the welding passes so as to minimize the average residual stress at.

Similarly, in a case-type welded structure composed of the above-mentioned structural elements, the structure shown in FIG.
By setting the constraint stress generated inside the structure after the welding is completed to the allowable value or less by the flow shown in, it is possible to obtain a desirable residual stress distribution in ensuring the soundness of the welded structure. it can. Further, in a case-type welded structure that is subjected to repeated load loads, the residual stress including the restraining stress inside the structure that occurs after the end of welding at the weld toe is allowed by the flow shown in FIG. 1 or 3. By setting the value to be equal to or less than the value, a desirable residual stress distribution can be obtained in order to guarantee the soundness of the welded structure.

[Embodiment 8] Next, an example of an embodiment in which the residual stress on the surface of the portion to be loaded during the operation including the start and stop of the welded structure constituting the plant equipment is evaluated will be described. To do. FIG. 23 is a perspective view showing an attachment welding portion of a core monitor housing which penetrates a pressure vessel of a boiling water reactor. Core monitor housing 7
The attachment welding part 71 of (1) is multi-layer welded in an elliptical shape in the circumferential direction on the inner surface side of the pressure vessel of the hole penetrating the end plate 11 of the lower part of the pressure vessel and the end plate overlay welding part 12 of the lower part of the pressure vessel.
Since the core monitor housing 7 is in a corrosive environment during operation, it is desirable to reduce the stress at the site where defects are expected to occur in order to prevent stress corrosion cracking.

In the core monitor housing 7, in addition to the residual stress due to welding at the time of attachment, stress due to heat and internal pressure is generated during operation including during starting and stopping. The stress due to heat and internal pressure becomes a large stress on the inner and outer surfaces of the core monitor housing of the weld toe 72 and the weld root 73. Therefore, by determining the stacking order of the welding paths so that the sum of the residual stress and the operating capacity on the inner and outer surfaces of the core monitor housing of the weld toe portion 72 and the weld root portion 73 is less than the allowable value, stress corrosion cracking may occur. On the other hand, it is possible to distribute stress without any problem.

In addition, the welding pass that minimizes the average value of the residual stress in the cross section perpendicular to the maximum principal stress in the cross section that connects the inner and outer surfaces of the core monitor housing of the weld toe portion 72 and the welding root portion 73 is minimized. Determining the stacking order is also convenient for preventing stress corrosion cracking. Also, parameters such as the shape of the welded part of the core monitor housing, the groove shape, the welding conditions, and the stacking order of the welding paths are used as parameters.
By using the flow shown in FIG. 3, it is possible to obtain a structural shape and residual stress that are not problematic for stress corrosion cracking.
Various welding conditions such as the shape of the welded portion, the groove shape, the welding conditions, and the stacking order of the welding paths can be obtained.

[Embodiment 9] Next, an example of an embodiment in which the residual stress of the welded structure constituting the plant equipment used under the condition that the front side and the back side of the welded joint are different in corrosion resistance is evaluated will be described. FIG. 24 is a partial perspective view showing a welded portion of the upper half and the lower half of the intermediate shell of the boiling water reactor pressure vessel core shroud, and FIGS. 25 to 29 are intermediate views of the boiling water reactor pressure vessel core shroud. FIG. 6 is a diagram showing an example of a distribution of axial residual stress in a weld heat affected zone in a welded portion of the upper half of the body and a lower half of the intermediate body in a radial direction starting from the inner surface.

FIG. 24 shows the circumferential welding of the upper middle half 24 and the lower middle half 25 of the core shroud 2 of the boiling water reactor. Upper middle half 24 and middle lower half 25
The circumferential welded portions 30 of and are connected by multi-layer welding. The inner surface side of the core shroud 2 has poorer corrosion resistance than the outer surface side. Therefore, the residual stress in the axial direction, which is the direction to open the crack in the weld heat affected zone of the inner surface where a plane crack perpendicular to the axial direction is considered to occur, is as small as possible, and It is desirable that the position of the peak of the compressive stress in the axial residual stress distribution, which is the direction of opening the crack in the cross section, be as close to the inner surface side as possible.

For the circumferential welded portion 30, various residual stresses can be obtained by using the flow shown in FIG. 3 with parameters such as the shape of the welded portion, the groove shape, the welding conditions, and the stacking order of the welding passes. The distribution is obtained. 25 to 29 show examples of these. The axial residual stress along the radial distance from the inner surface of the intermediate body is displayed. Comparing these residual stress distributions, the residual stress on the inner surface is the smallest in the distribution shown in FIG. 29, and thereafter becomes larger in the order of the distributions shown in FIGS. 26 and 28 and FIGS. 27 and 25. Also, the position where the compressive stress peaks is shown in FIG. 27 and FIG.
8 and the distribution shown in FIG. 29 are located on the innermost surface side, and FIG.
The distribution shown in FIG. 25 is on the outer surface side compared to that.

Therefore, according to the flow shown in FIG. 3, various welding conditions such as the shape of the welded portion, the groove shape, the welding conditions, and the stacking order of the welding paths that can obtain the axial residual stress distribution shown in FIG. 29 are obtained. If evaluated and selected, it is possible to set so that the structural shape and residual stress will be no problem for stress corrosion cracking. Similarly, in circumferential welding of a cylindrical structure, when the corrosion resistance on the inner surface side is worse than the corrosion resistance on the outer surface side, the groove shape of the welded structure is used by using the method of FIG. , Welding method, heat input, and various welding conditions represented by the order of lamination of welding paths are determined, and after the inner surface is welded, the outer surface is welded to prevent stress corrosion cracking. It can be a stress distribution.

On the contrary, in the circumferential welding of a cylindrical structure, when the corrosion resistance on the outer surface side is worse than the corrosion resistance on the inner surface side, the method of FIG. 3 is used to Prevents stress corrosion cracking by determining various welding conditions such as groove shape, welding method, heat input, and laminating sequence of welding paths, welding the outer surface, and then welding the inner surface. The desired residual stress distribution can be obtained.

[Embodiment 10] Next, an example of an embodiment in which the residual stress of an unwelded portion where a defect is expected to occur in a welded structure having an unwelded portion subjected to a repeated load is evaluated will be described. FIG. 30 is a perspective view showing a partial cross-sectional shape of a welded structure having an unwelded portion that is subjected to repeated load loads. A part of the cross section of the welded structure 8 having the unwelded portion is a fillet joint, and the web 81 and the flange 82 are connected by the welded portion 83. The welded portion 83 has an unwelded portion 84.
Further, the fillet joint is repeatedly subjected to the applied load P in the direction of the arrow in the figure.

At this time, in the fillet joint, the largest stress is generated in the unwelded portion 84 in the load direction, and it is considered that defects are most likely to occur. Therefore, as an example, the stacking sequence of the welding paths is determined by the flow shown in FIG. 1 so that the residual stress in the load direction at the welding toe 85, which is the point of interest, is not more than the allowable value. This allows
A desirable residual stress distribution can be obtained in order to prevent fatigue fracture of the welded structure 6 that is subjected to repeated load.

Further, from the viewpoint of preventing fatigue fracture of the welded structure, a cross section starting from the surface of the portion where a defect is expected to occur and a cross section perpendicular to the maximum principal stress direction of the applied load. It is also desirable to determine the stacking order of the welding passes so as to minimize the average residual stress at. Similarly, in the case-type welded structure constituted by the structural elements as described above, the restraint stress inside the structure generated after the welding is finished is equal to or less than the allowable value by the flow shown in FIG. 1 or 3. By setting to, it is possible to obtain a desirable residual stress distribution in ensuring the soundness of the welded structure.

Further, in the welded structure subjected to the repeated load load, the residual stress including the restraining stress inside the structure generated after the end of the welding at the weld toe portion is allowed by the flow shown in FIG. 1 or 3. By setting the value to be equal to or less than the value, a desirable residual stress distribution can be obtained in order to guarantee the soundness of the welded structure.

Still further, for example, in the welded joint portion having unwelded portions at the root portions of both groove sides in the welded structure, the laminating order of the welding paths is made so that the left and right weld buildup amounts are substantially equal. By performing the welding while moving at least three times from the right side to the left side or from the left side to the right side, it is possible to obtain a desirable residual stress distribution in ensuring the soundness of the welded structure.

[Embodiment 11] In a welded structure which is subjected to heat treatment after completion of welding, it remains after considering the order of stacking of welding paths and the heat treatment condition after completion of welding in accordance with the joint shape of the welded structure to be welded. An example of an example in which stress is evaluated will be described. For example, when a structure as shown in FIG. 7 undergoes heat treatment, it is considered that defects are most likely to occur in the order of stacking of welding paths and the residual stress generated by the subsequent heat treatment, for example, by using the flow of FIG. Set so that the residual stress in the affected part is below the allowable value. This makes it possible to obtain a desired residual stress distribution in ensuring the soundness of the welded structure. In addition, FIG.
The same can be said when the structures shown in FIGS. 23, 24, and 30 are subjected to heat treatment. Of course, the same applies to structures having other shapes.

[Embodiment 12] Next, regarding the welding method obtained as a result of evaluating the residual stress at the attention point in the welded portion between the neutron flux instrumentation pipe of the nuclear power plant and the reactor pressure vessel lower mirror explain. In this case, as a place where stress corrosion cracking is likely to occur, there is a portion immersed in the reactor water on the inner and outer surfaces of the pipe. In order to make the residual stress at these portions below the allowable value, the residual stress is evaluated using, for example, the flow shown in FIG.

FIG. 31 is a perspective view showing a welded portion between a neutron flux instrumentation pipe and a reactor pressure vessel lower mirror of a nuclear power plant. At the welded portion between the neutron flux instrumentation pipe 7A of the nuclear power plant and the end plate 11 of the lower part of the reactor pressure vessel, welding is performed on the pressure vessel body side 74 having a small inclination angle with the end plate 11 of the lower part of the reactor pressure vessel, Next, welding is performed on the core center side 75 having a large inclination angle. Alternatively, after welding on the pressure vessel body side 74 having a small inclination angle with the end plate 11 below the reactor pressure vessel, the core center side 7 having a large inclination angle 7
By repeating the welding of No. 5, the lamination of the welding passes is completed.

Further, in the welded portion between the neutron flux instrumentation pipe 7A of the nuclear power plant and the end plate 11 at the lower part of the reactor pressure vessel, the groove shape of the welded structure, the welding method, the heat input, and the order of stacking the welding paths. The welding conditions represented by are determined, welding is performed at the lower end of the reactor pressure vessel with the end plate 11 on the pressure vessel body side 74 with a small inclination angle, and then on the core center side 75 with a large inclination angle. It is also possible to carry out with a heat input amount smaller than the heat input amount due to welding in a cross section having a small inclination angle.

Alternatively, the end plate 11 under the reactor pressure vessel
After welding on the pressure vessel fuselage side 74 with a small inclination angle with the welding, the welding on the core center side 75 with a large inclination angle is performed with a heat input amount smaller than the heat input amount by welding on a cross section with a small inclination angle. The stacking of welding passes can also be completed by repeating. In this way, the welding method can be determined by evaluating the residual stress in the welded portion between the neutron flux instrumentation pipe 7A of the nuclear power plant and the end plate 11 under the reactor pressure vessel.

The present invention is not limited to the above-mentioned embodiments, and other welding structures having a low residual stress structure can be inferred from these embodiments.
Needless to say, it is included in the present invention.

[0114]

As described in detail above, each method of the present invention has the following effects. According to the first method
By analyzing the residual stress of the welded structure in consideration of the welding sequence, it is possible to obtain the effect that the stacking sequence of the welding paths can be obtained. According to the second method, it is possible to obtain the effect that the stacking sequence of the welding paths can be obtained from the relationship between the change in welding conditions and the change in residual stress.

According to the third method, it is possible to obtain the stacking order of the welding paths by analyzing the residual stress of the welded structure configured as a combination of a plurality of welded joints in consideration of the welding order. Is obtained. According to the fourth method, it is possible to obtain the welding conditions including the stacking order of the welding paths from the relationship between the change in the welding conditions and the change in the residual stress of the welded structure configured as a combination of a plurality of welded joints. The effect that can be obtained is obtained.

According to the fifth method, by analyzing the residual deformation of the welded structure in consideration of the welding sequence, it is possible to obtain the effect that the stacking sequence of the welding passes can be obtained. Sixth
According to the method (1), it is possible to obtain the effect that the welding condition including the stacking order of the welding paths can be obtained from the relationship between the change in the welding condition and the change in the residual stress.

According to the seventh method, by analyzing the residual deformation of the welded structure configured as a combination of a plurality of welded joints in consideration of the welding sequence, the stacking sequence of the welding paths can be obtained. Is obtained. According to the eighth method, it is possible to obtain the welding conditions including the stacking order of the welding paths from the relationship between the changes in the welding conditions and the changes in the residual stress of the welded structure configured as a combination of a plurality of welded joints. The effect that can be obtained is obtained.

According to the ninth method, in addition to the effects of the first and second methods, the effect of being able to set the surface residual stress of the portion of the welded structure where defects are likely to occur to be equal to or less than the allowable value is obtained. can get. According to the tenth method, in addition to the effects of the first and second methods, a cross-section from the surface of the portion of the welded structure where defects are likely to occur is the starting point, and the maximum load applied during operation is the maximum. The effect that the residual stress in the cross section perpendicular to the stress direction can be minimized is obtained.

According to the eleventh method, in addition to the effects of the first and second methods, the surface residual stress of the portion of the welded structure constituting the plant equipment where defects are likely to occur is set to be equal to or less than the allowable value. The effect that can be obtained is obtained. Twelfth
In addition to the effects of the first and second methods, according to the method described in (1), a cross section from the surface of the portion of the welded structure that constitutes the plant equipment where defects are likely to occur, and the load applied during operation The effect that the residual stress in the cross section perpendicular to the maximum principal stress direction can be minimized is obtained.

According to the thirteenth method, in addition to the effects of the first and second methods, it is possible to set the residual stress on the surface side of the welded structure, which has poor corrosion resistance, to the allowable value or less. Is obtained. According to the fourteenth method, in addition to the effects of the first and second methods, the residual stress distribution in the cross section where the crack is considered to propagate closer to the surface of the welded structure where the corrosion resistance is poor on the environment side The effect of being able to distribute the peak position of the compressive stress is obtained.

According to the fifteenth method, in addition to the effects of the first and second methods, the residual stress in the direction of opening the unwelded portion near the tip of the unwelded portion of the welded joint is reduced to an allowable value or less. The effect that can be obtained is obtained. According to the sixteenth method, in addition to the effects of the first and second methods, there is an effect that the residual stress in the weld line vertical direction at the weld toe of the welded structure can be set to be equal to or less than the allowable value. can get.

According to the seventeenth method, in addition to the effects of the first and second methods, the effect that the restraint stress of the welded structure can be made equal to or less than the allowable value is obtained. According to the eighteenth method, in addition to the effects of the first and second methods, the effect that the residual stress including the restraining stress inside the welded structure can be made equal to or less than the allowable value is obtained.

According to the nineteenth method, in addition to the effects of the first and second methods, the residual stress including the stacking sequence of the welding paths and the heat treatment process of the welded structure subjected to heat treatment after welding is less than the allowable value. The effect that can be obtained is obtained.
According to the twentieth method, in addition to the effects of the first and second methods, the stacking order of the welding paths is moved to the left and right of the welded joint having grooves on both sides, so that the tip of the unwelded portion of the welded joint is It is possible to obtain the effect that the residual stress in the direction in which the unwelded portion is opened in the vicinity can be reduced to the allowable value or less.

According to the twenty-first method, it is possible to obtain the effect that the residual stress of the cylindrical structure can be set to the allowable value or less. According to the twenty-second method, the effect that the residual stress due to the circumferential welding of the core shroud inside the reactor pressure vessel of the nuclear power plant can be set to the allowable value or less is obtained. According to the twenty-third method, the residual stress can be reduced to the allowable value or less by considering the welding order of the circumferential welded portions of the core shroud inside the reactor pressure vessel of the nuclear power plant.

According to the twenty-fourth method, the residual deformation can be made equal to or less than the allowable value by considering the welding sequence in the welded portion of the neutron flux instrumentation pipe of the nuclear power plant and the reactor pressure vessel lower mirror. The effect that can be obtained is obtained. According to the twenty-fifth method, in the weld portion of the neutron flux instrumentation pipe of the nuclear power plant and the reactor pressure vessel lower mirror, the residual deformation is made equal to or less than the allowable value by considering the heat input amount and the welding sequence. The effect that can be obtained is obtained.

In summary of the above, according to the present invention, the low residual stress structure in which the welding conditions with small residual stress and residual deformation are set by paying attention to the stacking order of welding paths and the residual stress and residual deformation accompanying it. The welding method of can be provided.

[Brief description of the drawings]

FIG. 1 is a flow chart diagram showing a welding procedure evaluation method for a welded structure in consideration of a stacking sequence of welding paths, focusing on residual stress in a welding method according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a welding procedure evaluation method for a welded structure, which takes into account residual deformation and takes the stacking sequence of welding paths into consideration, in a welding method according to another embodiment of the present invention.

FIG. 3 is a welding method according to still another embodiment of the present invention,
It is a flowchart figure which shows the welding procedure evaluation method of the welded structure which considered the shape of the welded structure, the welding conditions, and the lamination order of a welding path.

FIG. 4 is a welding method according to still another embodiment of the present invention,
It is a flowchart figure which shows the welding procedure evaluation method of the welding structure which has several welding joint parts virtually.

5 is an exploded perspective view of a boiling water reactor pressure vessel to which a welding procedure such as the flowchart shown in FIG. 1 is applied.

6 is a perspective view showing a core shroud of the boiling water reactor pressure vessel of FIG. 5. FIG.

FIG. 7 is an enlarged cross-sectional view of the intermediate ring and the circumferential welded portion of the upper half of the intermediate shell of the core shroud of FIG.

FIG. 8 is an explanatory view showing an example of a stacking order of welding paths of an intermediate ring of a boiling water reactor pressure vessel core shroud and a welded portion of an upper half of an intermediate shell in a cross section.

FIG. 9 is an explanatory view showing an example of a stacking order of welding paths of an intermediate ring of a boiling water reactor pressure vessel core shroud and a welded portion of an upper half of an intermediate shell in a cross section.

FIG. 10 is an explanatory view showing an example of the stacking sequence of the welding paths of the intermediate ring and the upper half of the intermediate shell of the boiling water reactor pressure vessel core shroud in cross section.

FIG. 11 is a diagram showing a radial distribution of the axial residual stress in the weld heat-affected zone of the intermediate ring and the upper half of the intermediate shell of the boiling water reactor pressure vessel core shroud, starting from the inner surface. Is.

FIG. 12 is a diagram showing a radial distribution of the axial residual stress in the weld heat-affected zone of the intermediate ring and the upper half of the intermediate shell of the boiling water reactor pressure vessel core shroud, starting from the inner surface. Is.

FIG. 13 is a diagram showing a radial distribution of the residual axial stress in the weld heat-affected zone of the intermediate ring and the upper half of the intermediate shell of the boiling water reactor pressure vessel core shroud in the radial direction starting from the inner surface. Is.

FIG. 14 is an explanatory view showing, in a cross section, an example of a stacking order of welding paths in a circumferential weld portion of an upper half of the intermediate shell and a lower half of the intermediate shell of a boiling water reactor pressure vessel core shroud.

FIG. 15 is an explanatory view showing, in a cross section, an example of the stacking order of the welding paths in the circumferential welds of the upper half and the lower half of the middle shell of the boiling water reactor pressure vessel core shroud.

FIG. 16 is an explanatory view showing, in a cross section, an example of the stacking order of welding paths in the circumferential welded portions of the upper middle half and the lower middle half of the boiling water reactor pressure vessel core shroud.

FIG. 17 is an explanatory view showing, in a cross section, an example of the stacking order of the welding paths in the circumferential welds of the upper half and the lower half of the middle shell of the boiling water reactor pressure vessel core shroud.

FIG. 18 is an explanatory view showing, in a cross section, an example of the stacking order of the welding paths in the circumferential welds of the upper half and the lower half of the middle shell of the boiling water reactor pressure vessel core shroud.

FIG. 19 is an explanatory view showing, in a cross section, an example of the stacking order of welding paths in the circumferential welded portions of the upper middle half and the lower middle half of the boiling water reactor pressure vessel core shroud.

FIG. 20 is an explanatory view showing an example of a stacking sequence of welding paths in a welded portion in which the groove dimensions of the upper half and the lower half of the middle shell of the boiling water reactor pressure vessel core shroud are changed in a cross section. .

FIG. 21 is a diagram showing the distribution of the axial residual stress in the weld heat-affected zone of the welded portion of the upper half and the lower half of the boiling water reactor pressure vessel core shroud in the radial direction starting from the inner surface. It is a diagram showing an example.

FIG. 22 is a perspective view showing a cross-sectional shape of a part of a welded structure that is subjected to repeated load. Part of the cross section of the welded structure is a fillet joint. Further, the fillet joint is repeatedly subjected to the applied load P in the direction of the arrow in the figure.

FIG. 23 is a perspective view showing an attachment welding portion of a core monitor housing which penetrates a pressure vessel of a boiling water reactor.

FIG. 24 is a partial perspective view showing a welded portion between the upper half and the lower half of the intermediate shell of the boiling water reactor pressure vessel core shroud.

FIG. 25 is a graph showing the distribution of the axial residual stress in the weld heat-affected zone in the welds of the upper half and the lower half of the boiling water reactor pressure vessel core shroud in the radial direction starting from the inner surface. It is a diagram showing an example.

FIG. 26 is a graph showing the distribution of the axial residual stress in the weld heat-affected zone of the welded portion of the upper half and the lower half of the boiling water reactor pressure vessel core shroud in the radial direction starting from the inner surface. It is a diagram showing an example.

FIG. 27 shows the distribution of the axial residual stress in the weld heat-affected zone in the welds of the upper half and the lower half of the boiling water reactor pressure vessel core shroud in the radial direction starting from the inner surface. It is a diagram showing an example.

FIG. 28 is a graph showing the distribution of the axial residual stress in the weld heat-affected zone of the welded portion of the upper half and lower half of the boiling water reactor pressure vessel core shroud in the radial direction starting from the inner surface. It is a diagram showing an example.

FIG. 29 is a graph showing the distribution of the axial residual stress in the weld heat-affected zone in the welds of the upper half and lower half of the boiling water reactor pressure vessel core shroud in the radial direction starting from the inner surface. It is a diagram showing an example.

FIG. 30 is a perspective view showing a partial cross-sectional shape of a welded structure having an unwelded portion subjected to a repeated load.

FIG. 31 is a perspective view showing a welded portion between a neutron flux instrumentation pipe and a reactor pressure vessel lower mirror of a nuclear power plant.

[Explanation of symbols]

1 ... Pressure vessel for boiling water reactor, 2 ... Core shroud,
3 ... Upper lattice plate, 4 ... Core support plate, 5 ... Jet pump, 6 ... Weld structure receiving load, 7 ... Core monitor housing, 7A ... Neutron flux instrumentation piping, 8 ... Welding concept having unwelded portion Objects, 11 ... End plate under pressure vessel, 12 ...
End plate overlay welding part, 21 ... upper ring, 22 ... upper body, 2
3 ... middle part ring, 24 ... middle body upper half, 25 ... middle body lower half, 26 ... lower ring, 27 ... lower body, 30 ... circumferential weld, 61 ... web, 62 ... flange, 28, 29, 6
3, 71, 83 ... Welded portion, 64, 72, 85 ... Welding toe portion, 73 ... Welding root portion, 74 ... Pressure vessel body side, 75
... central part of core, 84 ... unwelded part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeo Hattori 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Yasukata Tamai 3-chome, Saiwaicho, Hitachi-shi, Ibaraki No. 1 No. 1 Hitachi Ltd., Hitachi Plant (72) Inventor, Masaki Nakagawa, 502, Kamidate-cho, Tsuchiura-shi, Ibaraki Pref., Institute of Mechanical Research, Hiritsu Manufacturing Co., Ltd. (72) Makoto Hayashi, 502, Jinmachi-cho, Tsuchiura-shi, Ibaraki In the Institute of Mechanical Research, Hiritsu Mfg. Co., Ltd. (72) Haruo Fujimori Inventor, Hitachi 1-1, Omika-cho, Hitachi City, Ibaraki Prefecture

Claims (25)

[Claims] 1. Depending on the joint shape of the structure to be welded,
In setting the welding conditions, the stacking sequence of the welding paths under the specific welding conditions shall be determined, and the residual stress analysis by welding is performed under the specific welding conditions, and the residual stress evaluation points at the predetermined attention points A welding method for a low residual stress structure, characterized in that the stacking order of welding paths having the smallest residual stress value is selected by sequentially comparing the stacking order of a plurality of welding paths. 2. When setting various welding conditions of at least a groove shape, a welding method, a heat input amount, and a laminating order of welding paths of a structure to be welded, welding is performed under the various welding conditions. A residual stress analysis is performed by the method described above, and the various welding conditions at which a residual stress value at a predetermined attention point as a residual stress evaluation point is the smallest are selected by sequentially comparing the various welding conditions. Welding method for residual stress structure. 3. When setting welding conditions in a welded structure configured as a combination of a plurality of welded joints,
The order of stacking of each welding pass under specific welding conditions shall be determined, the residual stress analysis by welding is performed under the specific welding conditions, and the residual stress value at the predetermined attention point as the residual stress evaluation point is the smallest. A welding method for a low residual stress structure, characterized in that the stacking order of the welding paths is selected by sequentially comparing the stacking order of a plurality of welding paths. 4. When setting various welding conditions including at least a groove shape, a welding method, a heat input amount, and a laminating order of welding passes of a welded structure configured as a combination of a plurality of welded joints, Performing residual stress analysis by welding under the various welding conditions, successively comparing the various welding conditions with the various welding conditions where the residual stress value at the predetermined attention point as the residual stress evaluation point is the smallest. Welding method of low residual stress structure characterized by selecting. 5. Depending on the joint shape of the structure to be welded,
In setting the welding conditions, the order of stacking of welding paths under specific welding conditions shall be determined, and residual deformation analysis or residual deformation measurement by welding under the specific welding conditions shall be carried out and determined beforehand as a residual stress evaluation point. A welding method for a low residual stress structure, characterized in that the stacking order of welding passes having the smallest residual deformation value at the point of interest is selected by sequentially comparing the stacking orders of a plurality of welding passes. 6. When setting various welding conditions of at least a groove shape, a welding method, a heat input amount, and a laminating sequence of welding passes of a structure to be welded, welding is performed under the various welding conditions. Residual deformation analysis or residual deformation measurement is performed, and the various welding conditions with the smallest residual deformation value at a predetermined point of interest as a residual stress evaluation point are selected by sequentially comparing the various welding conditions. A characteristic welding method for low residual stress structures. 7. When setting welding conditions in a welded structure configured as a combination of a plurality of welded joints,
The order of stacking of each welding pass under specific welding conditions shall be determined, and residual deformation analysis or residual deformation measurement by welding under the specific welding conditions shall be carried out, and residual deformation at a predetermined attention point as a residual stress evaluation point. A welding method for a low residual stress structure, characterized in that the stacking order of welding paths having the smallest value is selected by sequentially comparing the stacking order of a plurality of welding paths. 8. When setting various welding conditions including at least a groove shape, a welding method, a heat input amount, and a laminating order of welding paths of a welded structure configured as a combination of a plurality of welded joints, Residual stress deformation analysis or residual deformation measurement by welding is performed under the various welding conditions, and the various residual welding values at the predetermined point of interest as a residual stress evaluation point are reduced to the various welding conditions described above. A method for welding a low residual stress structure, characterized by sequentially selecting and selecting. 9. A welded structure subjected to repeated load loads, wherein the residual stress on the surface of a portion where a defect is expected to occur is set to an allowable value or less. Welding method of low residual stress structure. 10. A residual stress in a welded structure subjected to repeated load loads, in a cross section starting from the surface of a portion where a defect is expected to occur and in a cross section perpendicular to the maximum principal stress direction of the applied load. 3. The method for welding a low residual stress structure according to claim 1, wherein the average value of is minimized. 11. The residual stress on the surface of the portion of the welded structure that constitutes the plant equipment, which is loaded during operation including during start-up and stop, is set to a permissible value or less. 2. The method for welding a low residual stress structure according to any one of 2 above. 12. A welded structure constituting a plant equipment, having a cross-section starting from the surface of a portion where a defect is expected to occur, and a load applied with stress during operation including during start-up and stop. The method for welding a low residual stress structure according to claim 1, wherein an average value of residual stress in a cross section perpendicular to the maximum principal stress direction is minimized. 13. Regarding a welded structure which constitutes a plant equipment to be used under conditions where the front side and the back side of the welded joint have different corrosion resistances, the residual stress on the surface of the structure on the environment side having poor corrosion resistance is an allowable value. The method for welding a low residual stress structure according to claim 1, wherein the method is set as follows. 14. A compressive stress of a residual stress distribution in a direction in which a crack is opened in a cross section where a crack is considered to propagate in a welded structure used under conditions where the front side and the back side of a welded joint have different corrosion resistances. 3. The welding method for a low residual stress structure according to claim 1, wherein the position of the peak value is set to a position closer to the structure surface on the environment side where the corrosion resistance is poor. 15. A welded portion near an unwelded portion of a welded structure is calculated such that the residual stress in the direction of opening the unwelded portion near the unwelded tip is less than an allowable value, and welding is performed. The method for welding a low residual stress structure according to claim 1, wherein conditions are set. 16. The welded structure subjected to repeated load loads is set such that the residual stress in the weld toe perpendicular direction at the weld toe portion is set to be equal to or less than the allowable value. Welding method for low residual stress structure. 17. The casing-type welded structure is set such that the restraint stress inside the structure generated after the welding is completed is equal to or less than an allowable value. Welding method for residual stress structure. 18. In a case-type welded structure subjected to repeated load, the residual stress including the restraining stress inside the structure generated after the welding at the weld toe portion is set to be less than an allowable value. The method for welding a low residual stress structure according to any one of claims 1 and 2, wherein 19. Regarding a welded structure which is subjected to heat treatment after the completion of welding, the residual stress is calculated in consideration of the order of stacking of welding paths and the heat treatment condition after completion of welding, in accordance with the joint shape of the welded structure to be welded, The residual stress at the point of interest is set so as to be less than or equal to an allowable value.
Or the method for welding a low residual stress structure according to any one of 2 above. 20. In the welded structure, in the welded joint portion having unwelded portions in the root portions of both groove sides, the stacking order of the welding paths is set from the right side so that the left and right weld overlays are substantially equal. The welding method for a low residual stress structure according to claim 1, wherein the welding is performed while moving at least three times from the left side or from the left side to the right side. 21. With respect to a circumferential weld portion having a groove on both sides of the inner and outer surfaces of a cylindrical structure, the inner surface is welded, and then the outer surface is welded. 2. The method for welding a low residual stress structure according to any one of 2 above. 22. At least an upper ring in a core shroud inside a reactor pressure vessel of a nuclear power plant,
For the circumferential welds of the upper body, middle ring, middle body upper half, middle body lower half, lower ring, and lower body, weld from the inner surface of the shroud of the welded part with double-sided groove, and then outside the shroud. The welding method for a low residual stress structure according to claim 1, wherein the front side is welded. 23. At least an upper ring in a core shroud inside a reactor pressure vessel of a nuclear power plant,
At least the groove shape of the welded structure, the welding method, the heat input, and the order of the stacking of the welding paths for the upper body, the middle ring, the upper half of the intermediate body, the lower half of the intermediate body, the lower ring, and the circumferential welded portion of the lower body. 3. A method for welding a low residual stress structure according to claim 2, wherein various welding conditions including the following are determined, and one-side groove welding in which welding paths are laminated from the outer surface side of the shroud to the inner surface side of the shroud is performed. . 24. A welded portion between a neutron flux instrumentation pipe of a nuclear power plant and a reactor pressure vessel lower mirror is welded on the pressure vessel body side with a small inclination angle with the reactor pressure vessel lower mirror, and then, , Welding at the center side of the core with a large inclination angle, or welding on the fuselage side of the pressure vessel with a small inclination angle with the reactor pressure vessel, and then performing welding on the center side of the core with a large inclination angle. The method for welding a low residual stress structure according to claim 5, wherein the stacking of the welding passes is completed by repeating the process. 25. Regarding the welded portion of the neutron flux instrumentation pipe of a nuclear power plant and the reactor pressure vessel lower mirror, various types including at least the groove shape of the welded structure, the welding method, the heat input, and the order of stacking the welding paths. Welding conditions are determined, welding is performed on the pressure vessel fuselage side with a small inclination angle with the reactor pressure vessel lower mirror, and then welding on the core center side with a large inclination angle is performed on the cross section with a small inclination angle. The heat input is smaller than the heat input by welding, or after welding on the pressure vessel body side with a small inclination angle with the reactor pressure vessel lower mirror, welding on the core center side with a large inclination angle 7. The welding method for a low residual stress structure according to claim 6, wherein the stacking of the welding paths is completed by repeating the operation with a heat input amount smaller than the heat input amount in the cross section having a small inclination angle.