JP3542407B2 - Welding method for low residual stress structure - Google Patents

Description

[0001]
[Industrial applications]
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 a welded structure.
[0002]
[Prior art]
In a conventional welded structure, after residual stress and residual deformation have occurred, a method of removing the residual stress and residual deformation by heat treatment or the like has generally been used. A method for removing residual stress and residual deformation by heat treatment is described in, for example, JP-A-62-17133.
Further, as a welding method for reducing residual stress and residual deformation, in fillet welding, there is a method of heating the back side of a welding line simultaneously with welding. A welding method for reducing the residual stress and residual deformation by heating the back side of the welding wire at the same time as welding is described in, for example, JP-A-4-162978.
[0003]
[Problems to be solved by the invention]
In the above-mentioned conventional heat treatment methods, the magnitude of the residual stress value and residual deformation value after welding is not evaluated, and the main purpose is to reduce residual stress and residual deformation by performing heat treatment after welding. I was left. That is, no consideration was given to residual stress and residual deformation after welding before heat treatment.
[0004]
Further, in the method of heating the back side of the welding wire simultaneously with the fillet welding of the above-mentioned prior art, the residual stress and the residual deformation are reduced by changing the heating condition of the back side during welding. However, although the heating conditions on the back side are taken into consideration, for example, the order of lamination of welding paths is not taken into account.
[0005]
The present invention has been made in order to solve the above-mentioned problems of the prior art, and focuses on the lamination order of welding paths and the residual stress and residual deformation associated therewith, thereby setting welding conditions with small residual stress and residual deformation. It is an object of the present invention to provide a welding method for a low residual stress structure.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a first method according to a welding method for a low residual stress structure according to the present invention includes the steps of: setting a welding condition according to a joint shape of a structure to be welded; The order of lamination of the welding paths is determined, the residual stress analysis by welding is performed under the specific welding conditions, and the lamination order of the welding paths at which the residual stress value at the point of interest predetermined as the residual stress evaluation point is the smallest. Is selected by sequentially comparing the stacking order of a plurality of welding passes.
[0007]
Similarly, in the second method, in setting various welding conditions of a structure to be welded at least including a groove shape, a welding method, a heat input, and an order of lamination of welding paths, the various welding conditions are used. , A residual stress analysis is performed by welding, and the various welding conditions at which the residual stress value at the point of interest predetermined as the residual stress evaluation point becomes the smallest are selected by successively comparing the various welding conditions.
[0008]
Similarly, in the third method, when setting welding conditions in a welded structure configured as a combination of a plurality of welded joints, the order of lamination of each welding path under specific welding conditions is determined, and Performs residual stress analysis by welding under welding conditions and selects the stacking order of the welding paths that minimizes the residual stress value at the point of interest predetermined as the residual stress evaluation point by sequentially comparing the stacking order of multiple welding paths. Is what you do.
[0009]
Similarly, a fourth method is to set various welding conditions of a welded structure configured as a combination of a plurality of welded joints, at least including a groove shape, a welding method, a heat input amount, and a stacking order of welding paths. The residual stress analysis by welding is performed under the various welding conditions described above, and the various welding conditions at which the residual stress value at the point of interest predetermined as the residual stress evaluation point is the smallest are sequentially compared with the various welding conditions. To choose.
[0010]
Similarly, in the fifth method, when setting the welding conditions in accordance with the joint shape of the structure to be welded, the order of lamination of the welding paths under the specific welding conditions is determined, and under the specific welding conditions, Performs residual deformation analysis or residual deformation measurement by welding and selects the stacking order of the welding paths that minimizes the residual deformation value at the point of interest predetermined as the residual stress evaluation point by sequentially comparing the stacking order of multiple welding paths. Is what you do.
[0011]
Similarly, in the sixth method, in setting various welding conditions including at least a groove shape, a welding method, a heat input amount, and an order of lamination of welding paths, the various welding conditions are set for the structure to be welded. Perform residual deformation analysis or residual deformation measurement by welding, and select the various welding conditions that minimize the residual deformation value at the point of interest predetermined as a residual stress evaluation point by sequentially comparing the various welding conditions. Things.
[0012]
Similarly, in the seventh method, when setting welding conditions in a welded structure configured as a combination of a plurality of welded joints, the order of lamination of each welding path under specific welding conditions is determined, and Analysis of residual deformation or measurement of residual deformation by welding is performed under welding conditions, and the lamination order of the welding path that minimizes the residual deformation value at the point of interest set in advance as the residual stress evaluation point is sequentially determined. It is to be selected by comparison.
[0013]
Similarly, an eighth method is to set various welding conditions of a welded structure configured as a combination of a plurality of welded joints, at least including a groove shape, a welding method, a heat input amount, and an order of lamination of welding paths. The residual stress deformation analysis or the residual deformation measurement by welding is performed under the various welding conditions, and the various welding conditions under which the residual deformation value at the point of interest predetermined as the residual stress evaluation point is minimized are set to the various welding conditions. The welding conditions are sequentially compared and selected.
[0014]
Similarly, the ninth method uses the first or second method to set the residual stress on the surface of a portion where a defect is expected to occur to a value equal to or less than an allowable value for a welded structure subjected to a repeated load load. It is.
Similarly, a tenth method uses a first or second method for a welded structure that is repeatedly subjected to a load, using a cross section starting from a surface of a portion where a defect is expected to occur, and a load to be applied. The average value of the residual stress in the cross section perpendicular to the maximum principal stress direction is minimized.
[0015]
Similarly, the eleventh method allows the residual stress on the surface of a portion to be loaded during operation including start-up and stoppage of the welded structure constituting the plant equipment by using the first or second method. It is set below the value.
Similarly, in a twelfth method, a welded structure constituting a plant device is cross-sectioned using the first or second method, starting from a surface of a portion where a defect is expected to occur, and starting and stopping. The purpose of the present invention is to minimize the average value of the residual stress in a section perpendicular to the direction of the maximum principal stress of the load to which the stress is applied during operation including the inside.
[0016]
Similarly, the thirteenth method uses a first or second method for a welded structure constituting a plant device used under different conditions of corrosion resistance on the front side and the back side of the welded joint portion, and the corrosion resistance is poor. This is to set the residual stress on the surface of the structure on the environment side to an allowable value or less.
Similarly, a fourteenth method uses a first or second method for a cross-section where a crack is considered to develop for a welded structure used under different corrosion resistance conditions on the front side and the back side of the welded joint. The position of the peak value of the compressive stress of the residual stress distribution in the direction in which the crack is opened is set so as to be closer to the surface of the structure on the environment side where corrosion resistance is poor.
[0017]
Similarly, in a fifteenth method, the vicinity of the weld joint having an unwelded portion in the welded structure is determined by using the first or second method to open the unwelded portion near the unwelded tip. Calculation is performed so that the residual stress is equal to or less than an allowable value, and welding conditions are set.
Similarly, in a sixteenth method, for a welded structure subjected to a repeated load load, the first or second method is used to set the weld line vertical residual stress at the weld toe to be equal to or less than an allowable value. Things.
[0018]
Similarly, in a seventeenth method, for a housing-type welded structure, the first or second method is used to set a constraint stress generated inside the structure after the welding is completed to be equal to or less than an allowable value. .
Similarly, an eighteenth method includes, using a first or second method, for a housing-type welded structure subjected to repeated load loads, including a restraining stress inside the structure generated after the end of welding at a weld toe. The residual stress is set so as to be less than the allowable value.
[0019]
Similarly, in a nineteenth method, the order of lamination of welding paths and the end of welding are determined for a welded structure that is to be subjected to heat treatment after the end of welding by using the first or second method in accordance with the joint shape of the welded structure to be welded. The residual stress is calculated in consideration of the heat treatment conditions to be performed later, and is set so that the residual stress at the point of interest becomes equal to or less than an allowable value.
Similarly, in a twentieth method, a weld joint portion having an unwelded portion in a root portion on both sides of a groove in a welded structure is formed by using the first or second method so that the right and left weld overlays are substantially equal. Thus, the welding is performed while moving the welding path in at least three times from the right to the left or from the left to the right in the stacking order.
[0020]
Similarly, in a twenty-first method, an inner surface side is welded using a first or second method to a circumferentially welded portion having a groove on both sides of an inner and outer surface in a cylindrical structure, and then the outer surface side is welded. Is to be welded.
Similarly, the twenty-second method includes, in a core shroud inside a reactor pressure vessel of a nuclear power plant, at least an upper ring, an upper shell, an intermediate ring, an upper half of an intermediate shell, a lower half of an intermediate shell, a lower ring, and a lower shell. For the circumferential direction welded portion, the first method is used to perform welding from the inner surface side of the shroud of the welded portion having a groove on both sides, and then to perform welding on the outer surface side of the shroud.
[0021]
Similarly, the twenty-third method includes, in a core shroud inside a reactor pressure vessel of a nuclear power plant, at least an upper ring, an upper shell, an intermediate ring, an upper half of an intermediate shell, a lower half of an intermediate shell, a lower ring, and a lower shell. For the circumferential weld, the second method is used to determine at least the groove shape of the welded structure, the welding method, the amount of heat input, and the welding conditions represented by the order of lamination of the welding pass, and from the outer surface side of the shroud, This is for performing welding on one side of the groove where a welding path is laminated on the inner surface side of the shroud.
[0022]
Similarly, in a twenty-fourth method, a pressure vessel having a small inclination angle with respect to a reactor pressure vessel lower mirror is used for a weld portion between a neutron flux instrumentation pipe of a nuclear power plant and a reactor pressure vessel lower mirror using the fifth method. Welding on the fuselage side, and then welding on the center side of the reactor core with a large inclination angle, or welding on the pressure vessel body side with a small inclination angle with the reactor pressure vessel, By repeatedly performing the welding on the center side of the large core, the lamination of the welding paths is completed.
[0023]
Similarly, the twenty-fifth method uses the sixth method for at least the groove shape of the welded structure, the welding method, and the heat input for the welded portion of the neutron flux instrumentation pipe of the nuclear power plant and the reactor pressure vessel bottom mirror. The welding conditions represented by the order of lamination of the welding paths are determined, welding is performed on the pressure vessel body with a small inclination angle with the reactor pressure vessel bottom mirror, and then on the core side with a large inclination angle. Welding with a smaller heat input than welding at 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, The welding at the center of the core with a large angle is repeatedly performed with a smaller heat input than the welding at a cross section with a small inclination angle, thereby completing the lamination of the welding paths.
[0024]
[Action]
According to the first and third methods, by analyzing the residual stress of the welded structure, an effect of obtaining the stacking order of the welding paths can be obtained.
According to the second method and the fourth method, various welding conditions including the lamination order of the welding paths and the groove shape can be obtained from the relationship between the change in the welding condition and the change in the residual stress.
[0025]
According to the fifth method and the seventh method, by analyzing the residual deformation of the welded structure, it is possible to obtain the effect of obtaining the stacking order of the welding paths.
According to the sixth method and the eighth method, various welding conditions including the lamination order of the welding paths and the groove shape can be obtained from the relationship between the change in the welding condition and the change in the residual stress.
[0026]
According to the ninth method and the eleventh method, in addition to the operations of the first and second methods, an operation of setting the surface residual stress of a portion of the welded structure where a defect is likely to occur to an allowable value or less. Is obtained.
According to the tenth method and the twelfth method, in addition to the actions of the first method and the second method, a cross section starting from the surface of a portion where a defect of the welded structure is likely to occur, and The effect of minimizing the residual stress in the section perpendicular to the direction of the maximum principal stress of the applied load is obtained.
[0027]
According to the thirteenth method, in addition to the operations of the first and second methods, an operation of setting the residual stress on the surface side of the welded structure having poor corrosion resistance to an allowable value or less can be obtained.
According to the fourteenth method, in addition to the actions of the first method and the second method, in addition to the action of the first structure and the second method, the cross-section of the welded structure in which the crack is expected to grow closer to the environment-side surface having poor corrosion resistance is considered. An effect is obtained in which the position of the peak value of the compressive stress in the residual stress distribution comes.
[0028]
According to the fifteenth method and the twentieth method, in addition to the actions of the first method and the second method, the residual stress in the direction of opening the unwelded portion near the tip of the unwelded portion of the welded joint is reduced. The effect of reducing the value to the allowable value or less is obtained.
According to the sixteenth method, in addition to the operations of the first and second methods, an operation of setting the residual stress in the direction perpendicular to the weld line at the weld toe of the welded structure to be equal to or less than an allowable value is obtained. Can be
[0029]
According to the seventeenth method, in addition to the operations of the first and second methods, an operation of reducing the restraining stress inside the welded structure to an allowable value or less can be obtained.
According to the eighteenth method, in addition to the actions of the first and second methods, an action of reducing the residual stress including the constraint stress inside the welded structure to a permissible value or less can be obtained. According to the nineteenth method, in addition to the effects of the first and second methods, the residual stress including the lamination order of the welding paths of the welded structure subjected to heat treatment after welding and the heat treatment process is reduced to an allowable value or less. Is obtained.
[0030]
According to the twenty-first method, the twenty-second method, and the twenty-third method, a circumferential welded portion having a cylindrical structure and both sides of the inner and outer surfaces, that is, a core inside a reactor pressure vessel of a nuclear power plant. In the shroud, at least the upper ring, upper body, middle ring, middle body upper half, middle body lower half, lower ring, and lower body, the circumferential weld of the lower body, the thirteenth method and the fourteenth method are effective. can get.
According to the twenty-fourth method and the twenty-fifth method, the operations of the fifth method and the sixth method can be obtained for the welded portion between the neutron flux instrumentation pipe of the nuclear power plant and the lower mirror of the reactor pressure vessel.
[0031]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 29.
[Example 1]
FIG. 1 is a flowchart showing a welding procedure evaluation method for a welded structure in which the welding method according to one embodiment of the present invention is focused on residual stress and takes into account the stacking order of welding paths. In the following description, step numbers in parentheses () indicate step numbers in the flowchart of FIG. It is.
As shown in FIG. 1, in order to evaluate the welding procedure of a welded structure, first, the shape of a target welded structure is determined (step 101). At this time, information including the material of the welded structure (Step 102) and the type of the groove of the joint (Step 103) is input to an arithmetic control unit (not shown).
[0032]
Next, the welding conditions of the target weld are determined (step 104). At this time, information including a welding method (step 105), a welding posture (step 106), a welding rod diameter (step 107), and a heat input (step 108) is input.
The parameter n is set to 1 in order to count the number of m times (m types) to be evaluated as the welding pass lamination order (step 109).
Here, the lamination order of the m-th welding pass to be evaluated is arranged in order from the first to the m-th welding pass, and of these, the lamination order of the n-th welding pass is selected (step 110). That is, when the parameter n is 1, the stacking order of the welding pass counted first in the stacking order of the m welding passes to be evaluated is selected.
[0033]
A residual stress analysis by welding is performed on the welded structure to be manufactured in the selected welding path in the stacking order (step 111). The residual stress can be obtained by a numerical analysis such as a thermo-elasto-plastic analysis or an intrinsic strain analysis. Alternatively, the residual strain can be measured experimentally, and the residual stress can be analyzed from the relational expression between the elastic stress and the elastic strain.
From the result of the residual stress analysis, a residual stress value at a point of interest determined in advance as a point for evaluating the residual stress is read (step 112). Here, not only one point of interest but a plurality of points may be determined.
[0034]
Here, the residual stress value at the point of interest is compared with the residual stress value at the point of interest by the residual stress analysis performed so far (step 113). If there is only one point of interest, only that point is compared. If there are a plurality of points of interest, the respective 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 by the residual stress analysis performed so far, the stacking order of the welding path currently being evaluated is stored (step 114). This storage enables overwriting, and always stores the lamination order with the smallest residual stress value at the point of interest.
[0035]
If there is only one point of interest, the stacking order of 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 importance in evaluation, and the stacking order of the smaller residual stress values is stored for the plurality of points of interest as a whole.
If the residual stress value at the point of interest is not smaller than the residual stress value at the point of interest by the residual stress analysis performed so far, the processing in step 114 is ignored.
[0036]
It is determined whether or not the parameter n is equal to the number m of times evaluated as the welding pass stacking order (step 115), and if they are equal, the welding pass stacking order stored in step 114 is set as the welding order (step 117). ). If the parameter n is not equal to the number m of evaluations as the welding pass stacking order, the parameter n for counting the welding pass stacking order is increased by one (step 116). Thereafter, the process returns to step 110, and the stacking order of a certain welding pass is evaluated again.
[0037]
By performing the above-described 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 stress according to the present invention.
[0038]
[Example 2]
FIG. 2 is a flowchart illustrating a welding procedure evaluation method for a welded structure in consideration of a residual deformation in a welding method according to another embodiment of the present invention, in consideration of a stacking order of welding paths. In the following description, step numbers in the parentheses indicate 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 this time, information including the material of the welded structure (step 202) and the type of groove of the joint (step 203) is input.
[0039]
Next, the welding conditions for the target weld are determined (step 204). At this time, information including a welding method (Step 205), a welding posture (Step 206), a welding rod diameter (Step 207), and a heat input (Step 208) is input.
The parameter n is set to 1 in order to count the number of m times (m types) evaluated as the lamination order of the welding pass (step 209).
Here, the order of lamination of the m-th welding pass to be evaluated is arranged in order from the first to the m-th, and among them, the lamination order of the n-th welding pass is selected (step 210). That is, when the parameter n is 1, the stacking order of the welding pass counted first in the stacking order of the m welding passes to be evaluated is selected.
[0040]
A residual deformation analysis by welding is performed on the welded structures manufactured in the selected welding path in the stacking order (step 211). The residual deformation can be obtained by a numerical analysis such as a thermo-elasto-plastic analysis. Further, the residual deformation can be experimentally obtained.
From the residual deformation analysis result, a residual deformation value at a point of interest determined in advance as a point for evaluating the residual deformation is read (step 212). Here, not only one point of interest but a plurality of points may be determined.
[0041]
Here, the residual deformation value at the point of interest is compared with the residual deformation value at the point of interest by the residual deformation analysis performed so far (step 213). If there is only one point of interest, only that point is compared. If there are a plurality of points of interest, the respective points are compared.
If the residual deformation value at the point of interest is smaller than the residual deformation value at the point of interest in the residual deformation analysis performed so far, the stacking order of the welding paths currently being evaluated is stored (step 214). This storage enables overwriting, and always stores the lamination order with the smallest residual stress value at the point of interest.
[0042]
If there is only one point of interest, the stacking order of the smaller residual deformation value is simply stored. If there are a plurality of points of interest, each point is weighted in advance in consideration of the importance in evaluation, and the stacking order of 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 processing in step 214 is ignored.
[0043]
It is determined whether or not the parameter n is equal to the number m of times of evaluation as the welding pass stacking order (step 215). ). If the parameter n is not equal to the number m of evaluations as the welding pass stacking order, the parameter n counting the welding pass stacking order is increased by one (step 216). Thereafter, the process returns to step 210, and the stacking order of a certain welding pass is evaluated again.
[0044]
By performing the above-described procedure, it is possible to evaluate a welding procedure for a welded structure, which is one embodiment for providing a welding method in consideration of residual deformation according to the present invention.
[0045]
[Example 3]
FIG. 3 is a flowchart illustrating a welding procedure evaluation method for a welded structure in consideration of a shape of a welded structure, welding conditions, and a stacking order of welding paths in a welding method according to still another embodiment of the present invention. In the following description, the numbers in parentheses indicate 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 used as parameters for evaluating the shape and welding conditions of the target welded structure and the stacking order of the welding paths, respectively. Is set to 1 (step 301).
[0046]
Next, the shape of the target welded structure and the welding conditions for the welded portion are set (step 302). At this time, information including the material of the welded structure, the type of joint groove, welding method, welding position, welding rod diameter, and heat input, which can be considered as the shape of the welded structure to be evaluated and the welding conditions of the welded part Is input p times. 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 pth time, and the shape of the welded structure counted in the qth time and the welding condition of the welded portion are selected. I do.
The parameter n is set to 1 in order to count the number of m times evaluated as the welding pass stacking order (step 303). Here, the lamination order of the m-th welding pass to be evaluated is arranged in order from the first to the m-th, and among them, the lamination order of the n-th welding pass is selected.
[0047]
Residual stress analysis by welding is performed on the selected welded structure to be manufactured according to the shape of the welded structure, the welding condition of the welded portion, and the stacking order of the welding paths (step 304). The residual stress can be determined by numerical analysis. Alternatively, the residual strain can be measured experimentally, and the residual stress can be analyzed from the relational expression between the elastic stress and the elastic strain.
From the result of the residual stress analysis, a residual stress value at a point of interest determined in advance as a point for evaluating the residual stress is read (step 305). Here, not only one point of interest but a plurality of points may be determined.
[0048]
Here, the residual stress value at the point of interest is compared with the residual stress value at the point of interest by the residual stress analysis performed so far (step 306). If there is only one point of interest, only that point is compared. If there are a plurality of points of interest, the respective 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 from the residual stress analysis performed so far, the shape of the welded structure and the welding conditions of the welded part and the lamination of the welding path being evaluated this time The order is stored (step 307). This storage enables overwriting, and always stores the lamination order with the smallest residual stress value at the point of interest.
[0049]
If there is only one point of interest, the shape of the welded structure having the smaller residual stress value, the welding conditions of the welded portion, and the stacking order of the welding paths are simply stored. When there are a plurality of points of interest, each point is weighted in advance in consideration of the importance in evaluation, and the shape of the welded structure, the welding conditions of the welded portion, and the stacking order of the welding path are determined for the plurality of points of interest as a whole. Remember.
If the residual stress value at the point of interest is not smaller than the residual stress value at the point of interest by the residual stress analysis performed so far, the processing in step 307 is ignored.
[0050]
It is determined whether or not the parameter n is equal to the number m of evaluations as the order of lamination of the welding paths (step 308). If the parameter n is not equal to the number m of evaluations as the welding pass stacking order, the parameter n counting the welding pass stacking order is increased by one (step 309). Thereafter, the process returns to step 303, and the stacking order of a certain welding path is evaluated again based on the same welding structure shape and welding conditions of the welding portion.
[0051]
If the parameter q is not equal to the number of times p evaluated as the shape of the welded structure and the welding condition, the parameter q is increased by 1 (step 311). Thereafter, the process returns to step 302, where 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 a welding procedure (step 312).
[0052]
By performing the above-described procedure, it is possible to evaluate a shape of a welded structure, welding conditions, and a stacking order of welding paths, which is one embodiment for providing a welding method in consideration of residual stress according to the present invention. Can be.
[0053]
[Example 4]
FIG. 4 is a flowchart showing a welding procedure evaluation method for a welding structure having a plurality of virtually welded joints in a welding method according to still another embodiment of the present invention. In the following description, the numbers in parentheses indicate step numbers in the flowchart of FIG. It is.
As shown in FIG. 4, to evaluate the welding procedure of a welded structure, first, the shape of the target welded structure is determined (step 401). At this time, information including the material of the welded structure (step 402) and the type of groove (step 403) at which a plurality of welded joints are formed when the welded structure is virtually divided is input.
[0054]
Next, a 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 p-th, and among these, the stacking order of the qth welding pass is selected (step 405). That is, when the parameter q is 1, the welding condition of the first welded joint among the p virtual welded joints to be evaluated is selected.
[0055]
The welding conditions for the target virtual weld joint are set (step 406). At this time, information including a welding method (step 407), a welding posture (step 408), a welding rod diameter (step 409), and a heat input (step 410) is input.
It is determined whether or not the parameter q is equal to the number of times p evaluated as the welding condition of the virtual welded joint (step 411). If they are equal, the process proceeds to step 412. If the parameter q is not equal to the number of times p evaluated as the welding condition of the virtual welded joint, the process returns to step 406, and the welding condition of the virtual welded joint is evaluated again.
[0056]
The parameter n is set to 1 in order to count the number of m times evaluated as the stacking order of the welding pass (step 412).
Here, the order of lamination of the m-th welding pass to be evaluated is arranged in order from the first to the m-th, and among these, the lamination order of the n-th welding pass is selected (step 413). That is, when the parameter n is 1, the stacking order of the welding pass counted first in the stacking order of the m welding passes to be evaluated is selected.
[0057]
A residual stress analysis by welding is performed on the welded structures manufactured in the selected welding path in the stacking order (step 414). The residual stress can be obtained by a numerical analysis such as a thermo-elasto-plastic analysis or an intrinsic strain analysis. Alternatively, the residual strain can be measured experimentally, and the residual stress can be analyzed from the relational expression between the elastic stress and the elastic strain.
From the result of the residual stress analysis, a residual stress value at a point of interest determined in advance as a point for evaluating the residual stress is read (step 415). Here, not only one point of interest but a plurality of points may be determined.
[0058]
Here, the residual stress value at the point of interest is compared with the residual stress value at the point of interest by the residual stress analysis performed so far (step 416). If there is only one point of interest, only that point is compared. If there are a plurality of points of interest, the respective 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 by the residual stress analysis performed so far, the lamination order of the welding path currently being evaluated is stored (step 417). This storage enables overwriting, and always stores the lamination order with the smallest residual stress value at the point of interest.
[0059]
If there is only one point of interest, the stacking order of 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 importance in evaluation, and the stacking order of the smaller residual stress values is stored for the plurality of points of interest as a whole.
If the residual stress value at the point of interest is not smaller than the residual stress value at the point of interest by the residual stress analysis performed so far, the processing in step 417 is ignored.
[0060]
It is determined whether or not the parameter n is equal to the number m of evaluations as the welding pass stacking order (step 418), and if equal, the welding pass stacking order stored in step 417 is set as the welding order (step 420). ). If the parameter n is not equal to the number m of evaluations as the welding pass stacking order, the parameter n counting the welding pass stacking order is increased by one (step 419). Thereafter, the process returns to step 413, and the stacking order of a certain welding pass is evaluated again.
[0061]
By performing the above-described procedure, a welding procedure for a welded structure having a plurality of virtually welded joints, which is an embodiment for providing a welding method in consideration of the residual stress according to the present invention, is evaluated. be able to.
[0062]
[Example 5]
One embodiment in which a welding procedure evaluation method for a welded structure taking into account the stacking order of welding paths and paying attention to residual stress as shown in the flowchart shown in FIG. 1 will be described with reference to FIGS. 5 to 13. .
FIG. 5 is an exploded perspective view of a boiling water reactor pressure vessel to which the welding procedure as shown in the flowchart shown in FIG. 1 is applied, and 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 a circumferentially welded portion of the intermediate ring and the upper half of the intermediate shell of the core shroud of FIG.
[0063]
FIG. 8 is an explanatory view showing a first example of a stacking order of welding paths of an intermediate portion ring of the core shroud shown in FIG. 6 and a welded portion of the upper half of the intermediate cylinder, and FIG. 9 is a diagram showing an intermediate portion of the same core shroud. FIG. 10 is an explanatory view showing a second example of the stacking order of the welding path of the ring and the upper half of the middle shell, and FIG. 10 is the stacking order of the welding path of the middle ring of the same core shroud and the upper half of the middle shell. FIG. 11 shows axial residual stress in the weld heat-affected zone of the middle ring and the upper half of the middle shell of the core shroud welded in the welding pass stacking order of FIG. 12 is a diagram showing the axial residual stress in the weld heat-affected zone of the intermediate ring of the core shroud and the upper half of the intermediate shell welded in the stacking order of the welding pass of FIG. 9, FIG. 13 shows an intermediate portion of a core shroud welded in the order of lamination of the welding passes of FIG. It is a graph showing the axial residual stress in the weld heat affected zone of the weld ring and the intermediate cylinder upper half.
[0064]
FIG. 5 shows a pressure vessel of a boiling water reactor of a nuclear power plant. Inside a pressure vessel 1, various components such as a core shroud 2, an upper lattice plate 3, a core support plate 4, and a jet pump 5 are provided. Equipment is 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 periphery. The core shroud 2 has a cylindrical shape, and includes an upper ring 21 and an upper shell 22, an upper shell 22 and an intermediate ring 23, an intermediate ring 23 and an intermediate upper half 24, and an intermediate upper half 24 of the core shroud 2. The middle lower half 25, the lower middle half 25 and the lower ring 26, the lower ring 26 and the lower body 27, etc. are manufactured by circumferential welding.
[0065]
FIG. 7 shows an example of a cross section of a welded portion of a circumferential welded joint connecting the intermediate ring 23 of the core shroud and the upper half 24 of the intermediate shell.
The distribution of the axial residual stress in the heat-affected zone of the intermediate ring in the radial direction greatly affects the occurrence and propagation of stress corrosion cracking from the inner surface of the intermediate ring. Therefore, the point of interest is the radially inner surface of the heat-affected zone of the intermediate ring and the location where the maximum value of the compressive stress is present, and the residual stress in the axial direction is taken as the direction of the residual stress of interest. It is desirable from the viewpoint of preventing 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 location where the maximum value of the compressive stress is located as close to the inner surface as possible, and the compressive stress is large.
[0066]
Circumferential welding for connecting the intermediate ring 23 of the core shroud and the upper half 24 of the intermediate shell is performed in Step No. of the flowchart of FIG. This will be described with reference to FIG.
First, the shape and dimensions of the core shroud are determined (Step 101). The material is austenitic stainless steel JIS standard SUS304 steel (step 102), and the groove type is a double-sided groove (step 103).
[0067]
Next, welding conditions are determined (step 104). The welding method is gas tungsten welding for the first layer and submerged arc welding for the second and subsequent layers (step 105). The welding position 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). The heat input is 20 kJ / cm (step 108).
The parameter n is set to 1 in order to count the number of m evaluations as the welding pass stacking order (step 109). In this embodiment, m is 3.
[0068]
FIGS. 8, 9, and 10 show an example of the stacking order of the welding paths in the cross section of the welded portion of the circumferential weld joint connecting the intermediate ring 23 of the core shroud and the upper half 24 of the intermediate shell.
FIGS. 8, 9, and 10 are cross-sectional views each showing an example of a stacking order of a welding path of an intermediate ring of a boiling water reactor pressure vessel core shroud and a welding portion of an upper half of an intermediate cylinder.
The multilayer welded joint in the circumferential direction has an axially symmetrical shape when viewed in a final cross section after welding is completed.
[0069]
The numbers in FIG. 8 indicate the order of lamination of the welding paths. 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, the numbers in FIGS. 9 and 10 indicate the order of lamination of the welding paths. In FIG. 9, first, the inner surface side of the groove on both sides is welded, and then the outer surface side is welded. In FIG. 10, first, the outer surface side of the groove on both sides is welded, and then the inner surface side is welded.
Here, the order of lamination of the three welding passes to be evaluated is arranged in order from the first to the third, and the lamination order of the welding pass taught the first time is selected (step 110). In this case, the welding order is as shown in FIG.
[0070]
A residual stress analysis by welding is performed on the welded structure to be manufactured in the selected welding path in the stacking order (step 111). The residual stress at this time is, for example, as shown in FIG. 11 in the axial residual stress distribution in the radial direction in the heat-affected zone of the intermediate ring welding starting from the inner surface side of the core shroud.
Fig. 11 shows the radial distribution (outer surface) of the axial residual stress in the weld heat-affected zone between the middle ring and the upper half of the middle shell of the boiling water reactor pressure vessel core shroud. FIG. 5 is a diagram of a case where the inner surface side is welded after the side is welded to about 1/2, and then the remaining about 1/2 of the outer surface side is welded).
On the inner surface, the tensile stress is about 350 MPa, and when it enters about 5 mm inward, the tensile stress becomes about 400 MPa. Thereafter, the stress value decreases, and the stress value becomes 0 when it enters about 15 mm inside, and the peak value of the compressive stress is taken when it enters about 30 mm inside, and the value is about -250 MPa.
[0071]
From the result of the residual stress analysis, a residual stress value at a point of interest determined in advance as a point for evaluating the residual stress is read (step 112). In this case, the peak value of the compressive stress is about -250 MPa when the tensile stress on the inner surface is about 350 MPa and the inner side is about 30 mm.
Here, the residual stress value at the point of interest is compared with the residual stress value at the point of interest 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 the compressive stress of about -250 MPa when it enters about 30 mm inside is treated as necessarily smaller than the value in other welding orders. Is
[0072]
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 order of the welding path currently being evaluated is stored (step 114). In this case, the stacking order shown in FIG. 8 is stored.
The parameter n indicating the welding pass stacking order is increased by 1 (step 115). In this case, the parameter n is set to 2.
It is determined whether or not the parameter n = 1 is equal to the number of evaluations m = 3 as the welding pass stacking order (step 115), and the parameter n = 1 and the number of evaluations m = 3 as the welding pass stacking order are not equal. Therefore, the parameter n for counting the order of lamination of the welding paths is increased by 1 (step 116). In this case, the parameter n is set to 2. Thereafter, the process returns to step 110.
[0073]
Next, the stacking order of the welding path counted the second time is selected from the three stacking orders of the welding paths to be evaluated (step 110). In this case, the order of the welding passes is as shown in FIG.
Residual analysis by welding is performed on the welded structure manufactured in the selected welding path in the stacking order (step 111). The residual stress at this time is, as an example, the radial residual stress distribution in the heat-affected zone of the intermediate ring weld as shown in FIG. 12 starting from the inner surface of the core shroud.
[0074]
FIG. 12 shows the radial distribution (internal surface) of the axial residual stress in the weld heat-affected zone between the intermediate ring and the upper half of the intermediate shell of the boiling water reactor pressure vessel core shroud. FIG. 7 is a diagram of a case where the outer surface side is welded after the side is welded).
On the inner surface, the tensile stress is about 200 MPa. Thereafter, the stress value decreases, and the stress value becomes 0 when it enters about 10 mm inside, and the peak value of the compressive stress is taken when it enters about 18 mm inside, and the value is about -250 MPa.
[0075]
From the result of the residual stress analysis, a residual stress value at a point of interest determined in advance as a 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 point of interest is compared with the residual stress value at the point of interest by the residual stress analysis performed so far (step 113). The information currently stored is the residual stress obtained by the first analysis. The tensile stress on the inner surface is about 350 MPa, and the peak value of the compressive stress when the inner surface enters about 30 mm is about -250 MPa.
[0076]
Based on the criterion that the residual stress in the axial direction at the point of interest is as small as possible on the inner surface, the location where the maximum value of the compressive stress is near the inner surface as much as possible, and the compressive stress becomes large, the analysis performed this time In the result, the tensile stress on the inner surface is smaller, and the maximum value of the compressive stress is almost the same, but the portion where the compressive stress is present is located 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 by the residual stress analysis performed so far, the lamination order of the welding path currently being evaluated is stored. The stacking order of FIG. 9 used for the evaluation is stored (step 114).
[0077]
The parameter n counting the stacking order of the welding pass is increased 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 evaluations m = 3 as the welding pass stacking order (step 115), and the parameter n = 2 and the number of evaluations m = 3 as the welding pass stacking order are not equal. Therefore, the parameter n for counting the order of lamination of the welding paths is increased by 1 (step 116). In this case, the parameter n is set to 3. Thereafter, the process returns to step 110.
[0078]
Next, the stacking order of the welding pass counted the third time is selected from the stacking order of the three welding passes to be evaluated (step 110). In this case, the order of the welding passes is as shown in FIG.
Residual analysis by welding is performed on the welded structure manufactured in the selected welding path in the stacking order (step 111). The residual stress at this time is, for example, as shown in FIG. 13 in the radial residual stress distribution in the heat affected zone of the intermediate ring welding starting from the inner surface side of the core shroud.
[0079]
FIG. 13 is a radial distribution (outer surface) of the axial residual stress at the weld heat-affected zone between the middle ring and the upper half of the middle shell of the boiling water reactor pressure vessel core shroud. FIG. 7 is a diagram of a case where the inner surface side is welded after the side is welded).
As shown in FIG. 13, the inner surface has a tensile stress of about 250 MPa. Thereafter, the stress value decreases, and the stress value becomes 0 when it enters about 15 mm inside, and the peak value of the compressive stress is taken when it enters about 35 mm inside, and the value is about -200 MPa.
[0080]
From the result of the residual stress analysis, a residual stress value at a point of interest determined in advance as a 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 when the inner surface enters about 35 mm is about 200 MPa.
Here, the residual stress value at the point of interest is compared with the residual stress value at the point of interest by the residual stress analysis performed so far (step 113). The information currently stored is the residual stress obtained by the second analysis. The peak value of the tensile stress at the inner surface is about 200 MPa, and the peak value of the compressive stress at about 18 mm inside is about -250 MPa.
[0081]
Based on the criterion that the residual stress in the axial direction at the point of interest is as small as possible on the inner surface, the location where the maximum value of the compressive stress is near the inner surface as much as possible, and the compressive stress becomes large, the analysis performed this time In the result, the tensile stress on the inner surface is larger, the portion having the compressive stress is near the outer surface, and the maximum value of the compressive stress is larger. Therefore, if the residual stress value at the point of interest is smaller than the residual stress value at the point of interest by the residual stress analysis performed so far, the lamination order of the welding path currently being evaluated is stored. The process proceeds to the next step without storing the stacking order of FIG. 10 used for the evaluation (step 113).
[0082]
It is determined whether or not the parameter n = 3 is equal to the number of evaluations m = 3 as the stacking order of the welding pass (step 115). Since the parameter n = 3 is equal to the number m = 3 of evaluations as the stacking order of the welding pass, Then, the currently stored welding order as shown in FIG. 9 is determined (step 117).
[0083]
As described above, the welding procedure prediction method taking into account the stacking order of the welding paths, which focuses on the residual stress, which is one embodiment of the present invention shown in FIG. 1, is performed by using the intermediate ring 23 and the upper half 24 of the core shroud. As a result of applying to the connecting circumferential welding joints, the welding order as shown in FIG. 9 can be determined.
Similar attention is paid to the residual deformation of the circumferential weld joint connecting the intermediate ring 23 of the core shroud and the upper half 24 of the intermediate shell, and the same result is obtained by performing the residual deformation analysis in the same manner using the flow of FIG. Obtainable.
[0084]
[Example 6]
Next, the example of the circumferential welding of the upper half 24 and the lower half 25 of the intermediate water shell of the boiling water reactor pressure vessel core shroud 2 as shown in FIG. A method for determining welding conditions such as a groove shape will be described.
FIG. 3 is a flowchart of a welding procedure prediction method for a welded structure according to another embodiment of the present invention, taking into account the shape of the welded structure, the welding conditions, and the stacking order of the welding paths.
[0085]
The middle trunk upper half 24 and the middle trunk lower half 25 are joined as a butt joint. The groove shape of this peripheral joint can be considered a. Further, it is conceivable that the heat input amount is b, the welding rod diameter is c, the welding method is d, and the welding position is e. There are p possible welding conditions including all of these. Here, P = a × b × c × d × e.
[0086]
With respect to the p kinds of welding conditions (step 302), the residual stresses of the m possible welding lamination orders (step 303) are analyzed, and the welding conditions and the welding paths at which the residual stress value at the point of interest is minimized are analyzed. The stacking order is 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 circumferential welded joint connecting the intermediate ring 23 and the upper half 24 of the core shroud described above, The location where the maximum value of the compressive stress is located is as close to the inner surface as possible and is a criterion for determining that the compressive stress is large.
[0087]
As an example, FIGS. 14 to 19 shown below show examples of the stacking order of welding paths for one possible groove shape.
14 to 19 are cross-sectional views each showing an example of a stacking order of welding paths in a circumferentially welded portion of the upper half and the lower half of the intermediate shell of the boiling water reactor pressure vessel core shroud. .
[0088]
In the example of FIG. 14, after welding the inner surface side, the outer surface side is welded.
In the example of FIG. 15, the order of lamination of welding paths when the inner surface side is welded to about １ ／, the outer surface side is welded, and then the remaining about の on the inner surface side are welded is shown. ing.
Further, in the example of FIG. 16, after the inner surface side is welded to about 1/2, the outer surface side is welded to about 1/2, then the remaining about 1/2 of the inner surface side is welded, and the outer surface side again. Shows the stacking order of the welding paths when the remaining half is welded.
[0089]
Next, in the example of FIG. 17, the order of lamination of the welding paths when the outer surface side is welded and then the inner surface side is welded is shown.
In the example of FIG. 18, the outer surface side is welded to about ２, the inner surface side is welded, and then the remaining about １ ／ of the outer surface side is welded. Is shown.
Further, in the example of FIG. 19, after welding the outer surface side to about ２, the inner surface side is welded to about そ の 後, then the remaining about １ ／ of the outer surface side is welded, and the inner surface side again. Shows the stacking order of the welding paths when about the remaining half is welded.
[0090]
FIG. 20 is a cross-sectional view illustrating an example of a stacking order of welding paths in a weld portion in which the groove dimensions of the upper half and the lower half of the intermediate trunk of the boiling water reactor pressure vessel core shroud are changed. It is.
Although the specific procedure is not described here, it analyzes how the welding posture parameters work, including the groove shape, heat input, welding rod diameter, and welding method for each of these welding pass stacking orders. Can be sought. If the analysis results of the evaluation are stored as a database, it is not necessary to evaluate all cases when an analysis target having a similar shape appears.
[0091]
FIG. 21 shows the distribution of the axial residual stress in the weld heat-affected zone in the upper half and lower half of the middle shell 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. That is, in the circumferential welding of the upper half 24 and the lower half 25 of the intermediate shroud 2 of the core shroud, the welding heat affected zone is determined by the welding conditions such as the lamination order of the welding paths and the groove shape determined by the flow of FIG. 3 shows the distribution of the axial residual stress in the radial direction.
As shown in FIG. 21, the compressive stress on the inner surface is about −50 MPa. Thereafter, the stress value decreases, and a peak value of the compressive stress is obtained when it enters about 15 mm inside, and the value is about -300 MPa. Thereafter, the stress value gradually increases, and becomes zero when it enters about 35 mm inward, and the outer surface has a tensile stress of about 100 MPa.
[0092]
[Example 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 a repeated load 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 that receives a repeated load. A cross section of a part of the welded structure is a fillet joint, and the web 61 and the flange 62 are connected by a welded portion 63. The fillet joint receives a load P repeatedly 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.
[0093]
Therefore, the stacking order of the welding paths is determined by the flow shown in FIG. 1 so that the residual stress in the load direction at the weld toe 64, which is the point of interest, is equal to or less than an allowable value. This makes it possible to obtain a desirable residual stress distribution for preventing fatigue fracture of the welded structure 6 that is repeatedly subjected to a load.
Also, from another point of view of preventing fatigue fracture of welded structures, a cross section starting from the surface of the part where a defect is 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 order of lamination of the welding paths so as to minimize the average value of the residual stress in the welding path.
[0094]
Similarly, in a housing-type welded structure constituted by the above-described structural elements, the constraint stress generated inside the structure after the end of welding is reduced to an allowable value or less by the flow shown in FIG. 1 or FIG. By setting to, a desirable residual stress distribution can be obtained in order to guarantee the soundness of the welded structure.
Also, in the case of a housing-type welded structure subjected to repeated load loads, the flow shown in FIG. 1 or FIG. 3 allows the residual stress including the constraint stress inside the structure generated after the end of welding at the weld toe. 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.
[0095]
[Example 8]
Next, a description will be given of an example of an embodiment in which the residual stress on the surface of a portion to be loaded during operation including startup and shutdown is evaluated in a welded structure constituting a plant device.
FIG. 23 is a perspective view showing a mounting weld portion of the core monitor housing penetrating the pressure vessel of the boiling water reactor. The mounting weld portion 71 of the core monitor housing 7 is multilayer-welded in a circumferential direction in an elliptical shape on the inner surface side of the pressure vessel at a hole penetrating the head plate 11 at the lower part of the pressure vessel and the overlay welding part 12 at the lower part of the pressure vessel. ing. Since the core monitor housing 7 is in a corrosive environment during operation, it is desirable to reduce stress at a portion where a defect is expected to occur in order to prevent stress corrosion cracking.
[0096]
In the core monitor housing 7, in addition to the residual stress due to welding at the time of mounting, stress due to heat and internal pressure is generated during operation including startup and shutdown. The stress due to heat and internal pressure becomes large stress on the inner and outer surfaces of the core monitor housing of the weld toe 72 and the welding root 73. Therefore, the stacking order of the welding paths is determined 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 welding toe portion 72 and the welding root portion 73 is equal to or less than an allowable value, thereby preventing stress corrosion cracking. On the other hand, it is possible to distribute stress without any problem.
[0097]
In addition, the order of lamination of the welding paths so as to minimize the average value of the residual stress in a cross section perpendicular to the maximum principal stress in the cross section connecting the inner and outer surfaces of the core monitor housing of the welding toe portion 72 and the welding root portion 73 respectively. The determination is also convenient for preventing stress corrosion cracking.
Further, by using the flow shown in FIG. 3 as parameters of the shape of the welded portion to be attached to the core monitor housing, the shape of the groove, the welding conditions, the order of lamination of the welding paths, and the like, a structure free from stress corrosion cracking can be obtained. Various welding conditions such as the shape of the welded portion, the groove shape, the welding conditions, the stacking order of the welding paths, and the like, which can result in the shape and residual stress, can also be obtained.
[0098]
[Example 9]
Next, a description will be given of an example of an embodiment in which the residual stress of a welded structure constituting a plant device used under different corrosion resistance conditions on the front side and the back side of the welded joint is evaluated. FIG. 24 is a partial perspective view showing a welded portion between the upper half and the lower half of the intermediate water cylinder of the boiling water reactor pressure vessel core shroud. FIGS. 25 to 29 are intermediate views of the boiling water reactor pressure vessel core shroud. It is a diagram which shows an example of the distribution of the axial residual stress in the welding heat affected zone in the weld part of the upper half of the trunk and the lower half of the intermediate trunk in the radial direction starting from the inner surface.
[0099]
FIG. 24 shows a circumferential welding of the upper half half 24 of the core shroud 2 of the core shroud 2 of the boiling water reactor and the lower half 25 of the middle shell. Circumferential welds 30 between the upper half 24 of the intermediate trunk and the lower half 25 of the intermediate trunk are connected by multi-layer welding. The inner surface of the core shroud 2 has lower corrosion resistance than the outer surface. Therefore, the residual stress in the axial direction, which is the direction that opens the crack in the weld heat-affected zone on the inner surface where the plane crack is considered to be perpendicular to the axial direction, is as small as possible, and the radial direction in which the crack is likely to propagate It is desirable that the peak position of the compressive stress in the residual stress distribution in the axial direction, which is the direction in which the crack is opened in the cross section, be as close to the inner surface as possible.
[0100]
Various residual stress distributions can be obtained for the circumferential direction welded portion 30 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 lamination order of the welding paths. Can be 25 to 29 show examples of these. The axial residual stress is shown along the radial distance from the inner surface of the intermediate barrel.
Comparing these residual stress distributions, the residual stress on the inner surface has the smallest distribution shown in FIG. 29, and then increases in the order of the distributions shown in FIGS. 26 and 28 and FIGS. 27 and 25. 27, 28, and 29 are located closest to the inner surface, and the distributions shown in FIGS. 26 and 25 are located closer to the outer surface.
[0101]
Therefore, various welding conditions such as the shape of the welded portion, the groove shape, the welding conditions, and the lamination order of the welding paths that can obtain the axial residual stress distribution shown in FIG. 29 are evaluated by the flow shown in FIG. If selected, it can be set so as to have a structural shape and a residual stress that are not problematic for stress corrosion cracking.
Similarly, in the circumferential welding of a cylindrical structure, when the corrosion resistance on the inner surface side is lower than the corrosion resistance on the outer surface side, the groove shape of the welded structure is determined using the method of FIG. Welding method, heat input, and various welding conditions typified by the order of lamination of welding paths are determined. After welding the inner surface, the outer surface is welded to prevent stress corrosion cracking. It can be a stress distribution.
[0102]
Conversely, in the circumferential welding of a cylindrical structure, when the corrosion resistance on the outer surface side is lower than the corrosion resistance on the inner surface side, the groove shape of the welded structure is determined using the method of FIG. Welding method, heat input, and various welding conditions typified by the order of lamination of welding paths are determined. After welding the outer surface side, the inner surface side is welded to prevent stress corrosion cracking. It can be a stress distribution.
[0103]
[Example 10]
Next, a description will be given of an example 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. FIG. 30 is a perspective view showing a cross-sectional shape of a part of a welded structure having an unwelded portion that receives a repeated load.
The cross section of a part of the welded structure 8 having the unwelded portion is a fillet joint, and the web 81 and the flange 82 are connected by a weld 83. The welded portion 83 has an unwelded portion 84. The fillet joint receives a load P repeatedly in the direction of the arrow in the figure.
[0104]
At this time, the largest stress in the fillet joint occurs at 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 order of the welding paths is determined in accordance with the flow shown in FIG. 1 such that the residual stress in the load direction at the weld toe 85, which is the point of interest, is equal to or less than an allowable value. This makes it possible to obtain a desirable residual stress distribution for preventing fatigue fracture of the welded structure 6 that is repeatedly subjected to a load.
[0105]
In addition, from the viewpoint of preventing fatigue fracture of a welded structure, the residual cross section perpendicular to the direction of the maximum principal stress of the load to be applied and the surface of the part where the defect is expected to occur is assumed to be the starting point. It is also desirable to determine the stacking order of the welding passes so as to minimize the average value of the stress.
Similarly, in a housing-type welded structure constituted by the above-described structural elements, the constraint stress generated inside the structure after the end of welding is reduced to an allowable value or less by the flow shown in FIG. 1 or FIG. By setting to, a desirable residual stress distribution can be obtained in order to guarantee the soundness of the welded structure.
[0106]
Also, in a welded structure subjected to a repeated load load, the residual stress including the constraint stress inside the structure generated after the end of welding at the weld toe by the flow shown in FIG. By setting as such, a desirable residual stress distribution can be obtained in order to guarantee the soundness of the welded structure.
[0107]
Still further, for example, in a welded joint portion having an unwelded portion at the root portion on both sides of the groove in the welded structure, the lamination order of the welding paths is changed from the right side so that the right and left weld overlays are substantially equal. By performing welding while moving at least three times from the left side or from the left side to the right side, a desirable residual stress distribution can be obtained in order to guarantee the soundness of the welded structure.
[0108]
[Example 11]
An example of an embodiment in which, in a welded structure subjected to a heat treatment after the completion of welding, residual stress was evaluated in consideration of the order of lamination of welding paths and heat treatment conditions after the end of welding, in accordance with the joint shape of the welded structure to be welded. Will be described.
For example, when a structure as shown in FIG. 7 is subjected to a heat treatment, the order of lamination of welding passes and the residual stress generated by the subsequent heat treatment are considered to be most likely to cause defects using the flow of FIG. Is set so that the residual stress at the part to be removed is equal to or less than the allowable value. This makes it possible to obtain a desired residual stress distribution in order to guarantee the soundness of the welded structure.
The same can be said for the case where the structure as shown in FIG. 22, FIG. 23, FIG. 24, and FIG. Of course, the same applies to structures having other shapes.
[0109]
[Example 12]
Next, a description will be given of a welding method obtained as a result of evaluating a residual stress at a point of interest in a welding portion between a neutron flux instrumentation pipe of a nuclear power plant and a reactor pressure vessel lower mirror.
In this case, as a place where stress corrosion cracking is likely to occur, there is a part immersed in reactor water on the inner and outer surfaces of the pipe. In order to reduce the residual stress at these portions to a permissible value or less, the residual stress is evaluated using, for example, the flow shown in FIG.
[0110]
FIG. 31 is a perspective view showing a welded portion between a neutron flux instrumentation pipe of a nuclear power plant and a lower mirror of a reactor pressure vessel.
At a welding portion between the neutron flux instrumentation pipe 7A of the nuclear power plant and the head plate 11 under the reactor pressure vessel, welding is performed on the pressure vessel body side 74 having a small inclination angle with the head plate 11 under the reactor pressure vessel, Next, welding is performed on the core center side 75 having a large inclination angle.
Alternatively, welding of the lower part of the reactor pressure vessel with the end plate 11 on the pressure vessel body side 74 having a small inclination angle and then welding of the core center side 75 having a large inclination angle are repeated to complete the lamination of the welding path. Let it.
[0111]
In addition, 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 groove shape of the welded structure, the welding method, the heat input, and the stacking order of the welding path are represented. Welding conditions are determined, welding is performed on the pressure vessel body side 74 having a small inclination angle with the head plate 11 at the lower part of the reactor pressure vessel, and then welding on the core center side 75 having a large inclination angle is performed with the inclination angle. It is also possible to perform the heat input with a smaller heat input than the welding with a small cross section.
[0112]
Alternatively, after welding on the pressure vessel body side 74 having a small inclination angle with the head plate 11 at the lower part of the reactor pressure vessel, welding on the core center side 75 having a large inclination angle is performed by welding at a cross section having a small inclination angle. By repeating the process with a smaller heat input, the lamination of the welding paths can be completed.
In this manner, 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.
[0113]
It should be noted that the present invention is not limited to the embodiments described above, and the present invention also includes other welding methods of low residual stress structures of welded structures that can be inferred from these embodiments. Needless to say,
[0114]
【The invention's effect】
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 order, the effect of obtaining the stacking order of the welding paths can be obtained.
According to the second method, it is possible to obtain the effect that 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.
[0115]
According to the third method, by analyzing the residual stress of a welded structure configured as a combination of a plurality of welded joints in consideration of the welding order, it is possible to obtain the effect that the stacking order of the welding paths can be 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.
[0116]
According to the fifth method, by analyzing the residual deformation of the welded structure in consideration of the welding order, it is possible to obtain an effect that the stacking order of the welding paths can be obtained.
According to the sixth method, it is possible to obtain the effect that the welding conditions including the stacking order of the welding paths can be obtained from the relationship between the change in the welding conditions and the change in the residual stress.
[0117]
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 order, the effect of obtaining the stacking order of the welding paths can be obtained. .
According to the eighth method, it is possible to obtain welding conditions including a stacking order of welding paths from a relationship between a change in welding conditions and a change in residual stress of a welded structure configured as a combination of a plurality of welded joints. The effect that can be obtained is obtained.
[0118]
According to the ninth method, in addition to the effects of the first and second methods, there is obtained an effect that the surface residual stress at a portion where a defect of the welded structure is likely to occur can be set to an allowable value or less.
According to the tenth method, in addition to the effects of the first and second methods, in addition to the cross section starting from the surface of the portion where the defect of the welded structure is likely to occur, and the maximum main load applied during operation, This has the effect of minimizing the residual stress in the cross section perpendicular to the stress direction.
[0119]
According to the eleventh method, in addition to the effects of the first and second methods, it is possible to set the surface residual stress of a portion where a defect of the welded structure constituting the plant equipment is likely to occur to a tolerance or less. The effect is obtained.
According to the twelfth method, in addition to the effects of the first and second methods, a cross section starting from the surface of a portion where a defect of the welded structure constituting the plant equipment is likely to occur and being added during operation is added. This has the effect of minimizing the residual stress in the cross section perpendicular to the direction of the maximum principal stress of the applied load.
[0120]
According to the thirteenth method, in addition to the effects of the first and second methods, an effect that the residual stress on the surface side of the welded structure having poor corrosion resistance can be set to an allowable value or less can be obtained. .
According to the fourteenth method, in addition to the effects of the first and second methods, the residual stress distribution in a cross section where a crack is considered to propagate to a position closer to the environment-side surface of the welded structure having poor corrosion resistance is considered. The effect of being able to distribute the peak position of the compressive stress is obtained.
[0121]
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 in the vicinity of the tip of the unwelded portion of the welded joint can be 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, the effect that the residual stress in the direction perpendicular to the weld line at the weld toe of the welded structure can be set to an allowable value or less is obtained. can get.
[0122]
According to the seventeenth method, in addition to the effects of the first and second methods, an effect that the constraint stress of the welded structure can be reduced to an allowable value or less can be obtained.
According to the eighteenth method, in addition to the effects of the first and second methods, an effect is obtained in which the residual stress including the constraint stress inside the welded structure can be reduced to an allowable value or less.
[0123]
According to the nineteenth method, in addition to the effects of the first and second methods, the residual stress including the lamination order of the welding paths of the welded structure subjected to the heat treatment after welding and the heat treatment process is set to an allowable value or less. 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 path is moved between the left and right sides of the welded joint having the groove on both sides, so that the tip of the unwelded portion of the welded joint is formed. The effect that the residual stress in the direction in which the unwelded portion is opened in the vicinity can be reduced to an allowable value or less can be obtained.
[0124]
According to the twenty-first method, it is possible to obtain an effect that the residual stress of the cylindrical structure can be reduced to an allowable value or less.
According to the twenty-second method, there is an effect that the residual stress due to circumferential welding of the core shroud in the reactor pressure vessel of the nuclear power plant can be made equal to or less than an allowable value.
According to the twenty-third method, by considering the welding order of the circumferentially welded portion of the core shroud inside the reactor pressure vessel of the nuclear power plant, the effect of reducing the residual stress to an allowable value or less can be obtained.
[0125]
According to the twenty-fourth method, in the welded portion between the neutron flux instrumentation pipe of the nuclear power plant and the lower mirror of the reactor pressure vessel, there is an effect that the residual deformation can be reduced to an allowable value or less by considering the welding order. can get.
According to the twenty-fifth method, the residual deformation is reduced to an allowable value or less by considering the heat input and the welding sequence in the welding portion between the neutron flux instrumentation pipe of the nuclear power plant and the reactor pressure vessel bottom mirror. The effect that can be obtained is obtained.
[0126]
Summarizing the above, according to the present invention, by focusing on the lamination order of the welding paths and the residual stress and residual deformation associated therewith, the method for welding a low residual stress structure in which welding conditions for small residual stress and residual deformation are set Can be provided.
[Brief description of the drawings]
FIG. 1 is a flowchart illustrating a welding procedure evaluation method for a welded structure in which a residual stress is focused on in a welding method according to an embodiment of the present invention and the order of lamination of welding paths is considered.
FIG. 2 is a flowchart illustrating a welding procedure evaluation method for a welded structure in consideration of a residual deformation in a welding method according to another embodiment of the present invention, in consideration of a stacking order of welding paths.
FIG. 3 is a flowchart illustrating a method for evaluating a welding procedure of a welded structure in a welding method according to still another embodiment of the present invention, in consideration of a shape of the welded structure, welding conditions, and a stacking order of welding paths.
FIG. 4 is a flowchart showing a method for evaluating a welding procedure of a welded structure having a plurality of virtually welded joints in a welding method according to still another embodiment of the present invention.
5 is an exploded perspective view of a boiling water reactor pressure vessel to which a welding procedure as in the flowchart shown in 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 sectional view of a circumferentially welded portion of an intermediate ring and an upper half of an intermediate cylinder of the core shroud of FIG. 6;
FIG. 8 is an explanatory diagram showing a cross section of an example of a stacking order of welding paths of a middle ring of a boiling water reactor pressure vessel core shroud and a welding portion of an upper half of a middle cylinder.
FIG. 9 is an explanatory view showing, in cross section, an example of a stacking order of welding paths of an intermediate ring of a boiling water reactor pressure vessel core shroud and a welding portion of an upper half of an intermediate cylinder.
FIG. 10 is an explanatory view showing, in cross section, an example of a stacking order of welding paths of an intermediate ring of a boiling water reactor pressure vessel core shroud and a welding portion of an upper half of an intermediate cylinder.
FIG. 11 is a diagram of a radial distribution starting from an inner surface of an axial residual stress in a weld heat-affected zone of an intermediate ring and an upper half of a middle shell of a boiling water reactor pressure vessel core shroud. It is.
FIG. 12 is a diagram of a radial distribution starting from an inner surface of an axial residual stress in a weld heat-affected zone of an intermediate ring and an upper half of a middle cylinder of a boiling water reactor pressure vessel core shroud. It is.
FIG. 13 is a diagram of a radial distribution starting from the inner surface of an axial residual stress in a weld heat-affected zone of an intermediate ring and an upper half of a middle shell of a boiling water reactor pressure vessel core shroud. It is.
FIG. 14 is an explanatory diagram showing an example of a stacking order of welding paths in a circumferentially welded portion of an upper half and a lower half of an intermediate barrel of a boiling water reactor pressure vessel core shroud in cross section.
FIG. 15 is an explanatory view showing a cross section of an example of a stacking order of welding paths in a circumferentially welded portion of an upper half of an intermediate shell and a lower half of an intermediate shell of a boiling water reactor pressure vessel core shroud.
FIG. 16 is an explanatory view showing in cross section an example of a stacking order of welding paths in a circumferentially welded portion of an upper half and a lower half of an intermediate trunk of a boiling water reactor pressure vessel core shroud.
FIG. 17 is an explanatory view showing a cross section of an example of a stacking order of welding paths in a circumferentially welded portion of an upper half of an intermediate cylinder and a lower half of an intermediate cylinder of a boiling water reactor pressure vessel core shroud.
FIG. 18 is an explanatory view showing an example of a stacking order of welding paths in a circumferentially welded portion of an upper half of an intermediate cylinder and a lower half of an intermediate cylinder of a boiling water reactor pressure vessel core shroud in a cross section.
FIG. 19 is an explanatory view showing, in cross section, an example of a stacking order of welding paths in a circumferentially welded portion of an upper half and a lower half of an intermediate barrel of a boiling water reactor pressure vessel core shroud.
FIG. 20 is an explanatory diagram showing, in cross-section, an example of a stacking order of welding paths in a welding portion in which a groove dimension of the upper half of the middle barrel and a lower half of the middle barrel of the boiling water reactor pressure vessel core shroud are changed. .
FIG. 21 shows the distribution of the axial residual stress in the weld heat-affected zone in the upper half and lower half of the middle shell 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 receives a repeated load. Part of the cross section of the welded structure is a fillet joint. The fillet joint receives a load P repeatedly in the direction of the arrow in the figure.
FIG. 23 is a perspective view showing a mounting weld portion of a core monitor housing that penetrates a pressure vessel of a boiling water reactor.
FIG. 24 is a partial perspective view showing a welded portion between an upper half of the intermediate barrel and a lower half of the intermediate barrel of the boiling water reactor pressure vessel core shroud.
FIG. 25 shows the distribution of the axial residual stress in the weld heat-affected zone in the upper half and lower half of the middle shell 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 shows the distribution of the axial residual stress in the weld heat-affected zone in the upper half and lower half of the middle shell 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 of the upper half and the lower half of the intermediate shell 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 shows the distribution of the axial residual stress in the weld heat-affected zone of the upper half and lower half of the middle shell 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 shows the distribution of the axial residual stress in the weld heat-affected zone of the upper half and the lower half of the middle shell 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 cross-sectional shape of a part of a welded structure having an unwelded portion that receives a repeated load.
FIG. 31 is a perspective view showing a welded portion between a neutron flux instrumentation pipe of a nuclear power plant and a lower mirror of a reactor pressure vessel.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Pressure vessel of boiling water reactor, 2 ... Core shroud, 3 ... Upper lattice plate, 4 ... Core support plate, 5 ... Jet pump, 6 ... Welded structure under load load, 7 ... Core monitor housing, 7A ... neutron flux instrumentation piping, 8 ... welding concept having an unwelded part, 11 ... head plate at the lower part of the pressure vessel, 12 ... head plate overlay welding part, 21 ... upper ring, 22 ... upper body, 23 ... middle part ring, Reference numeral 24: Upper half of the middle trunk, 25: Lower half of the middle trunk, 26: Lower ring, 27: Lower trunk, 30: Welding in the circumferential direction, 61: Web, 62: Flange, 28, 29, 63, 71, 83: Welding Parts, 64, 72, 85 ... weld toe, 73 ... welding root part, 74 ... pressure vessel body side, 75 ... core part, 84 ... unwelded part.

Claims (6)

In setting welding conditions according to the joint shape of the structure to be welded, the order of lamination of welding paths under specific welding conditions shall be determined,
Perform the residual stress analysis by welding under the specific welding conditions, and sequentially compare the stacking order of the welding paths with the smallest residual stress value at the point of interest predetermined as the residual stress evaluation point and the stacking order of a plurality of welding paths. A welding method for a low residual stress structure, wherein the welding method is selected. In setting the various welding conditions consisting of at least the groove shape, welding method, heat input, and stacking order of the welding path of the structure to be welded,
Perform the residual stress analysis by welding under the various welding conditions, and sequentially compare the various welding conditions, in which the residual stress value at the point of interest predetermined as the residual stress evaluation point becomes the smallest, the various welding conditions. Welding method of low residual stress structure characterized by selecting. In setting welding conditions in a welded structure configured as a combination of a plurality of welded joints,
The order of lamination of each welding path 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 point of interest predetermined as the residual stress evaluation point is the smallest. A welding method for a low residual stress structure, wherein a stacking order of a plurality of welding paths is sequentially selected and selected. In setting a variety of welding conditions consisting of at least a groove shape, a welding method, a heat input amount, and an order of lamination of a welding path of a welded structure configured as a combination of a plurality of welded joints,
Perform the residual stress analysis by welding under the various welding conditions, and sequentially compare the various welding conditions, in which the residual stress value at the point of interest predetermined as the residual stress evaluation point becomes the smallest, the various welding conditions. Welding method of low residual stress structure characterized by selecting. In setting welding conditions according to the joint shape of the structure to be welded, the order of lamination of welding paths under specific welding conditions shall be determined,
The residual deformation analysis or the residual deformation measurement by welding is performed under the specific welding conditions, and the stacking order of the welding paths in which the residual deformation value at the point of interest predetermined as the residual stress evaluation point is the smallest is determined by stacking a plurality of welding paths. A welding method for a low residual stress structure, wherein the order is sequentially compared and selected. In setting the various welding conditions consisting of at least the groove shape, welding method, heat input, and stacking order of the welding path of the structure to be welded,
Perform the residual deformation analysis or residual deformation by welding under the various welding conditions, and set the various welding conditions under which the residual deformation value at the point of interest predetermined as the residual stress evaluation point is the smallest, the various welding conditions. A welding method for a low residual stress structure, which is selected by successive comparison.

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