JP7085368B2 - Welding method and radioactive material containment vessel - Google Patents

Description

The present disclosure relates to a welding method for performing welding between members having different thermal conductivity, and a radioactive material storage container that can be manufactured using the method.

As a container for storing radioactive materials (for example, spent nuclear fuel) handled in a nuclear reactor or the like, a so-called cask is known as a radioactive material containment vessel. In this type of radioactive material containment vessel, in order to release the decay heat generated from the radioactive material stored inside to the outside, the main body that stores the radioactive material and the outer cylinder that is coaxially arranged on the outside of the main body Heat transfer fins are provided between them. Such heat transfer fins are formed of a material having excellent thermal conductivity, such as copper, and are welded to a main body body made of carbon steel, stainless steel, or the like.

Since stainless steel, carbon steel, etc. and copper have different thermal conductivity and have the property of being difficult to solidly melt with each other, welding of these different materials is incompatible, and even if the penetration is deepened, welding cracks are likely to occur. Therefore, Patent Document 1 discloses that the quality of dissimilar material welding is improved by adopting composite welding in which one molten pool is formed by TIG arc and MIG arc. Further, Patent Document 2 describes that the weldability of dissimilar material welding is improved and weld cracking is prevented by performing temporary welding before performing main welding in composite welding as in Patent Document 1. There is.

Japanese Unexamined Patent Publication No. 2016-11845 Japanese Unexamined Patent Publication No. 2016-107305

In Patent Document 2, temporary welding is performed at temporary attachment positions set at predetermined intervals on the welding line on which the main welding is performed. Such temporary attachment positions are set at equal intervals on the welding line, but depending on the construction order of temporary attachment welding for each temporary attachment position, distortion due to welding heat may occur in the heat transfer fins having a longitudinal shape. There is a risk of welding. In particular, when a copper heat transfer fin is welded to the main body copper such as stainless steel or carbon steel, heat is likely to be accumulated on the heat transfer fin side having excellent heat conductivity, and the heat transfer fin is likely to be distorted.

At least one embodiment of the present invention has been made in view of the above circumstances, and is a welding construction method capable of achieving good welding quality by suppressing the generation of strain due to welding heat in dissimilar material welding, and the method. It is an object of the present invention to provide a radioactive material storage container that can be manufactured using.

(1) The welding construction method according to at least one embodiment of the present invention solves the above-mentioned problems.
It is a welding construction method for welding the end surface of the first member having a longitudinal shape along the longitudinal direction to a joint portion formed by abutting the end face of the first member having a thermal conductivity smaller than that of the first member. ,
A process of performing temporary welding at a plurality of first temporary attachment positions specified for each first interval on the welding line from the welding start position to the welding end position of the joint portion to be main welded.
At least one second temporary attachment position is defined between each of the adjacent first temporary attachment positions, and the second temporary attachment position outside the weld line from the second temporary attachment position on the center side of the weld line. The process of performing temporary welding toward the temporary attachment position,
The step of performing the main welding along the welding line including the first temporary attachment position and the second temporary attachment position, and
To prepare for.

According to the method (1) above, prior to the construction of the main welding, the temporary welding is sequentially performed in two stages with respect to the first temporary attachment position and the second temporary attachment position. The first temporary attachment position is set on the welding line at a wider interval than the second temporary attachment position, and by performing temporary attachment welding, accurate positioning can be performed while suppressing distortion due to welding heat. .. On the other hand, the second temporary attachment position is set at a narrower interval on the welding line than the first temporary attachment position, and the second temporary attachment position on the center side of the welding line is on the outside of the welding line. Temporary welding is performed toward the attachment position. As a result, the strain generated during the temporary welding can be released from the center side of the welding line to the outside, and it is possible to effectively prevent the temporary welding from cracking during the main welding.

(2) In some embodiments, in the method (1) above,
Temporarily set the temporary attachment position at predetermined intervals on the welding line,
Among the temporary attachment positions, the temporary attachment position located at each first interval larger than the predetermined interval is set as the first temporary attachment position.
The remaining temporary attachment positions other than the first temporary attachment position are set as the second temporary attachment position.

According to the method (2) above, the first temporary attachment position and the second temporary attachment position can be accurately set on the welding line.

(3) In some embodiments, in the method (1) or (2) above,
In the main welding, a welding bead along the welding line is divided into a plurality of sub-beads and formed.
Each end of each of the sub-beads corresponds to the first temporary attachment position or the second temporary attachment position.

According to the method (3) above, in the main welding, the weld bead along the weld line is divided into a plurality of sub-beads and formed. As a result, the strain generated by the welding heat can be effectively reduced. In particular, each sub-bead is formed so that both ends correspond to the first temporary attachment position or the second temporary attachment position, so that the molten pool at the time of forming the sub-bead can be stopped at each temporary attachment position. It is possible to suitably prevent the occurrence of fusion failure at the temporary attachment position.

(4) In some embodiments, in the method (3) above,
The adjacent sub-beads are formed so as to overlap each other at the first temporary attachment position or the second temporary attachment position.

According to the method (4) above, by forming adjacent sub-beads so as to overlap each other at the temporary attachment position, it is possible to suitably prevent the occurrence of fusion failure at the temporary attachment position.

(5) In some embodiments, in the method (3) or (4) above,
The main welding is performed so that the two continuously formed sub-beads are not adjacent to each other.

According to the method (5) above, the formation of a plurality of sub-beads in the main welding is performed so that the two continuously formed sub-beads are not adjacent to each other. As a result, the welding heat generated during the main welding can be dispersed over the entire welding line, and the generation of distortion due to the welding heat can be prevented more effectively.

(6) In some embodiments, in the method of (5) above,
A first sub-bead is formed at both ends of the weld line, and then a second sub-bead is formed between the first sub-beads.

According to the method (6) above, the first sub-beads are first formed at both ends of the welding line, and then the second sub-beads are formed between the first sub-beads to prevent the strain generated during the main welding. It can be alleviated and the occurrence of weld cracks can be effectively prevented.

(7) The welding construction method according to at least one embodiment of the present invention solves the above-mentioned problems.
It is a welding construction method for welding the end surface of the first member having a longitudinal shape along the longitudinal direction to a joint portion formed by abutting the end face of the first member having a thermal conductivity smaller than that of the first member. ,
The process of performing temporary welding at the temporary attachment positions specified at predetermined intervals on the welding line from the welding start position to the welding end position of the joint to be main welded.
The process of performing main welding by forming a weld bead along the weld line by dividing it into a plurality of sub-beads whose both ends correspond to the temporary attachment positions.
To prepare for.

According to the method (7) above, when the main welding is performed after the temporary welding, the welding bead along the welding line is divided into a plurality of sub-beads and formed. As a result, the strain generated by the welding heat can be effectively reduced. In particular, each sub-bead is formed so that both ends correspond to each temporary attachment position, so that the molten pool at the time of forming the sub-bead can be stopped at each temporary attachment position, resulting in poor fusion at the temporary attachment position. Occurrence can be suitably prevented.

(8) In some embodiments, in the method (7) above,
The adjacent sub-beads are formed so as to overlap each other at the temporary attachment position.

According to the method (8) above, by forming adjacent sub-beads so as to overlap each other at the temporary attachment position, it is possible to suitably prevent the occurrence of fusion failure at the temporary attachment position.

(9) In some embodiments, in the method (7) or (8) above,
The main welding is performed so that the two continuously formed sub-beads are not adjacent to each other.

According to the method (9) above, the formation of a plurality of sub-beads in the main welding is performed so that the two continuously formed sub-beads are not adjacent to each other. As a result, the welding heat generated during the main welding can be dispersed over the entire welding line, and the generation of distortion due to the welding heat can be prevented more effectively.

(10) In some embodiments, in the method (9) above,
A first sub-bead is formed at both ends of the weld line, and then a second sub-bead is formed between the first sub-beads.

According to the method (10) above, the first sub-beads are first formed at both ends of the welding line, and then the second sub-beads are formed between the first sub-beads to prevent the strain generated during the main welding. It can be alleviated and the occurrence of weld cracks can be effectively prevented.

(11) In some embodiments, in any one of the above methods (1) to (10),
The first member is a heat transfer fin that is inclined with respect to the radial direction of the main body between the main body and an outer cylinder coaxially arranged on the outside of the main body.
The second member is a main body that can store radioactive substances inside.

According to the method (11) above, welding of the body of the main body constituting the radioactive material containment vessel and the heat transfer fins can be preferably performed.

(12) In some embodiments, in the method of (11) above,
The joint portion is an acute-angled fillet joint portion formed by the outer surface of the main body and the heat transfer fin.

According to the above method (12), the above-mentioned welding method is applied to the acute-angled side of the fillet joint formed by the outer surface of the main body and the heat transfer fins. As a result, good welding quality can be realized in the fillet joint portion on the acute angle side where the throat thickness of the welded portion is larger than that on the obtuse angle side.

(13) In some embodiments, in the method of (11) above,
The joint portion is an obtuse-angled fillet joint portion formed by the outer surface of the main body and the heat transfer fin.

According to the method (13) above, the above welding method is applied to the obtuse angle side of the fillet joint portion formed by the outer surface of the main body and the heat transfer fins. As a result, good welding quality can be realized at the fillet joint portion on the obtuse angle side.

(14) In some embodiments, in the method (11) above,
The joint portion is a first fillet joint portion on an acute angle side formed by the outer surface of the main body and the heat transfer fin, and an obtuse angle side formed by the outer surface of the main body and the heat transfer fin. Includes the second fillet joint of.

According to the method (14) described above, the above-mentioned welding is performed on both the first fillet joint portion on the acute angle side and the second fillet joint portion on the obtuse angle side formed by the outer surface of the main body body and the heat transfer fins. The construction method is applied. As a result, good welding quality can be realized in the fillet joint portion on the acute angle side and the obtuse angle side.

(15) In some embodiments, in the method of (14) above,
After any one of the above methods (1) to (10) is applied to the first fillet joint portion, any one of the above methods (1) to (10) is applied to the second fillet joint portion. It will be carried out.

According to the method (15) above, after welding is performed on the first fillet joint portion on the acute angle side where the throat thickness of the welded portion is larger than that on the obtuse angle side, the second fillet joint portion on the obtuse angle side is formed. By performing welding on the surface, better welding quality can be realized.

(16) In some embodiments, in any one of the above methods (1) to (15),
The first member is made of copper and is made of copper.
The second member is made of carbon steel or stainless steel.

According to the method (16) above, dissimilar welding of carbon steel or stainless steel and copper can be preferably performed.

(17) The radioactive material containment vessel according to at least one embodiment of the present invention is used to solve the above problems.
With the main body and
An outer cylinder coaxially arranged on the outside of the main body,
A heat transfer fin having a longitudinal shape and inclinedly arranged between the main body and the outer cylinder,
A welded portion extending along the longitudinal direction between the end face of the heat transfer fin along the longitudinal direction and the outer surface of the body of the main body, and a welded portion extending along the longitudinal direction.
Equipped with
The welded part is
A first temporary welded portion formed at each first interval along the extending direction of the welded portion, and a first temporary welded portion.
The second temporary welded portion formed between each of the adjacent first temporary welded portions and the second temporary welded portion.
The main welded portion formed along the welding line including the first temporarily attached welded portion and the second temporarily attached welded portion, and the main welded portion.
including.

The radioactive material containment vessel having the above-mentioned configuration (17) can be suitably manufactured by the above-mentioned welding method (including the above-mentioned various forms). The radioactive material containment vessel manufactured in this way is less likely to crack in the temporary welding during welding, and a high-quality finish can be obtained.

(18) The radioactive material containment vessel according to at least one embodiment of the present invention is used to solve the above problems.
With the main body and
An outer cylinder coaxially arranged on the outside of the main body,
A heat transfer fin having a longitudinal shape and inclinedly arranged between the main body and the outer cylinder,
A welded portion extending along the longitudinal direction between the end face of the heat transfer fin along the longitudinal direction and the outer surface of the body of the main body, and a welded portion extending along the longitudinal direction.
Equipped with
The welded part is
A plurality of temporary welded portions formed at predetermined intervals along the extending direction of the welded portion, and
A main weld portion extending along the extension direction and having a plurality of sub-beads at both ends corresponding to the temporary welded portion.
including.

The radioactive material containment vessel having the above-mentioned configuration (18) can be suitably manufactured by the above-mentioned welding method (including the above-mentioned various forms). The radioactive material containment vessel manufactured in this way is less likely to crack in the temporary welding during welding, and a high-quality finish can be obtained.

According to at least one embodiment of the present invention, a welding construction method capable of achieving good welding quality by suppressing the generation of strain due to welding heat in dissimilar material welding, and a radioactive substance that can be manufactured using the method. A storage container can be provided.

It is sectional drawing along the axial direction of a radioactive material containment vessel. FIG. 3 is a cross-sectional view taken along the line AA of FIG. It is an enlarged view near the heat transfer fin of FIG. It is a flowchart which shows the whole process of the welding construction method which concerns on one Embodiment of this invention. It is a flowchart which shows an example of the setting method of the temporary attachment position in step S10 of FIG. This is an example of setting the temporary attachment position. This is an example of setting the first temporary attachment position. This is an example of setting the second temporary attachment position. It is a figure which shows the state of forming the weld bead from a plurality of sub-beads in step S40 schematically. 9 is an enlarged cross-sectional view of a part of the weld bead of FIG.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, but are merely explanatory examples. do not have.
For example, expressions that represent relative or absolute arrangements such as "in one direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a tolerance or a state of relative displacement at an angle or distance to the extent that the same function can be obtained.
Further, for example, the expression representing a shape such as a quadrangular shape or a cylindrical shape not only represents a shape such as a quadrangular shape or a cylindrical shape in a geometrically strict sense, but also a concavo-convex portion or a concavo-convex portion within a range where the same effect can be obtained. The shape including the chamfered portion and the like shall also be represented.
On the other hand, the expressions "to have", "to have", "to have", "to include", or "to have" one component are not exclusive expressions that exclude the existence of other components.

First, a welded structure to which the welding construction method according to at least one embodiment of the present invention is applied will be described. In the following description, as shown in FIGS. 1 to 3, a radioactive material containment vessel capable of storing radioactive material inside is exemplified as a welded structure, but the present invention is limited to this unless otherwise specified. It's not something.

1 is a cross-sectional view taken along the axial direction of the radioactive material containment vessel 1, FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, and FIG. 3 is an enlarged view of the vicinity of the heat transfer fin 10 of FIG. ..

The radioactive material containment vessel 1 includes a main body 2 capable of storing radioactive materials (for example, a spent fuel assembly) inside. The main body 2 has a bottomed substantially cylindrical shape, and is configured as a forged product made of carbon steel having a γ-ray shielding function. The opening 7 of the main body 2 is closed by attaching the lid 6 to the flange surface thereof. The lid portion 6 has a substantially disk shape, and is formed of carbon steel, for example, like the main body body 2 described above.

For the main body 2 and the lid 6, stainless steel may be used, or cast products such as spheroidal graphite cast iron and carbon steel cast steel may be used.

Inside the main body 2, a basket 3 capable of individually storing a plurality of radioactive substances is provided. In the basket 3, a plurality of cells for individually storing a plurality of radioactive substances are partitioned by combining plate-shaped members in a grid pattern.

An outer cylinder 4 is coaxially arranged on the outside of the main body 2 via a predetermined gap. As shown in FIG. 2, a plurality of copper heat transfer fins 10 for heat transfer are provided between the outer peripheral surface of the main body 2 and the inner peripheral surface of the outer cylinder 4 at predetermined intervals. There is. In the space partitioned by the main body 2, the outer cylinder 4, and the heat transfer fin 10, a resin (neutron shield) containing boron or a boron compound which is a polymer material containing a large amount of hydrogen and has a neutron shielding function. 8 is injected in a fluid state through a pipe or the like (not shown) and solidified.

As the heat transfer fin 10, a copper plate material made of copper such as pure copper having high thermal conductivity is used. As a result, the decay heat generated from the radioactive material stored inside the main body 2 is promoted to be dissipated to the outside by the heat transfer fins 10, and the heat removal performance of the radioactive material containment vessel 1 is improved.

As shown in FIG. 2, the plurality of heat transfer fins 10 are arranged so as to be inclined in the gap formed between the main body body 2 and the outer cylinder 4. Here, as shown in FIG. 3, the end surface 12 of the heat transfer fins 10 along the longitudinal direction on the main body body 2 side is abutted against the outer surface 2a of the main body body 2 at a predetermined angle α, which will be described later. It is joined by the fillet joint portion 20 constructed by the welding construction method. The fillet joint portion 20 on the main body body 2 side has a first fillet joint portion 20a on the acute angle side and a second fillet joint portion 20b on the obtuse angle side, respectively, which are made of weld beads.

The end face 14 of the heat transfer fins 10 along the longitudinal direction on the outer cylinder 4 side is also abutted against the inner surface 4a of the outer cylinder 4 and is joined by the fillet joint portion 30. The fillet joint portion 30 on the outer cylinder 4 side has a fillet joint portion 30a on the acute angle side and an obtuse angle side fillet joint portion 30b, which are made of weld beads, respectively. In the following description, the case where the welding construction method according to the present embodiment is applied to the fillet joint portion 20 on the main body body 2 side is illustrated, but the same applies to the fillet joint portion 30 on the outer cylinder 4 side. You may.

Subsequently, a case where the fillet joint portion 20 on the main body body 2 side is formed by applying the welding construction method according to at least one embodiment of the present invention to the radioactive material containment vessel 1 having the above configuration will be described as an example. .. FIG. 4 is a flowchart schematically showing the entire process of the welding construction method according to the embodiment of the present invention.

In this method, first, the temporary attachment position 40 for performing temporary attachment welding to the first fillet joint portion 20a on the acute angle side is set (step S10). Here, the temporary welding is a welding performed prior to the main welding, and is shorter than the welding bead 50 formed by the main welding with respect to the end face 12 along the longitudinal direction of the heat transfer fin 10. It is a weld that forms the bead 60.

Such temporary welding includes a first temporary welding and a second temporary welding that is performed following the first temporary welding. That is, the temporary attachment welding is performed in two stages, and the temporary attachment position 40a set in step S10 is provided with the first temporary attachment position 40a on which the first temporary attachment welding is applied and the second temporary attachment welding. The second temporary attachment position 40b and the like are included.

Here, FIG. 5 is a flowchart showing an example of the setting method of the temporary attachment position 40 in step S10 of FIG. 4, FIG. 6 is a setting example of the temporary attachment position 40, and FIG. 7 is a setting of the first temporary attachment position 40a. As an example, FIG. 8 is a setting example of the second temporary attachment position 40b.

When setting the temporary attachment position 40, first, the specifications of the temporary attachment welding bead 60 formed by the temporary attachment welding are set (step S11). Specifically, the temporary attachment interval a of the temporary welding bead 60 and the temporary attachment bead length b are set. The temporary attachment interval a and the temporary welding bead length b of the temporary welding bead 60 may be determined, for example, by comprehensively considering the following criteria.
-Is it possible to obtain a supporting force to maintain a good posture of the heat transfer fins 10 before joining?
-Is the strain generated in the heat transfer fin 10 during temporary welding suppressed within the allowable range?
-Is the distortion generated in the heat transfer fin 10 due to the welding heat during the main welding performed after the temporary welding suppressed within the allowable range?
-Is the number of temporary welds on the weld line appropriate?

In consideration of the above criteria, the temporary attachment interval a may be set to, for example, about 100 mm. If the temporary attachment interval a is too long, the number of temporary attachment welding operations on the welding line can be reduced, but it is difficult to obtain a supporting force for maintaining a good posture of the heat transfer fins 10 before joining. Further, it becomes difficult to suppress the strain generated in the heat transfer fin 10 within the allowable range due to the welding heat during the main welding performed after the temporary welding. On the other hand, if the temporary attachment interval a is too short, it is easy to obtain a supporting force for maintaining a good posture of the heat transfer fins 10 before joining, and the heat is transferred by the welding heat during the main welding performed after the temporary attachment welding. It is easy to suppress the strain generated in the hot fin 10 within the allowable range, but the number of temporary welding performed on the welding line increases, and the work load increases.

Further, in consideration of the above criteria, the temporary weld bead length b may be set to, for example, 15 ± 10 mm. If the temporary welding bead length b is too large, it is easy to obtain a supporting force for maintaining a good posture of the heat transfer fins before joining, but the strain generated in the heat transfer fins 10 during the temporary welding is within the allowable range. It's hard to control. On the other hand, if the temporary welding bead length b is too small, the strain generated in the heat transfer fins 10 during temporary welding can be easily suppressed within an allowable range, but the posture of the heat transfer fins 10 before joining is maintained well. It becomes difficult to obtain support.

Subsequently, the length L of the welding wire 70 constructed by this method is set (step S12). The length L of the welding line 70 is finally set so as to correspond to the range in which the main welding described later is performed. The length L of such a weld line may be set equal to the length of the end face 12 along the longitudinal direction of the heat transfer fin 10 on the main body body 2 side, but in the present embodiment, as shown in FIG. The length L of the weld line is set in consideration of providing non-welded portions 15 having a predetermined length c at both ends of the end face 12. This is because it is necessary to provide the non-welded portions 15 at both ends of the end face 12 in consideration of the fact that the base metal is likely to be melted down due to the accumulation of welding heat during the main welding.

Subsequently, temporary welding is performed based on the conditions set in steps S11 and S12 (temporary welding interval a of the temporary welding bead 60, temporary welding bead length b, and length L of the welding wire 70). The temporary attachment position 40 to be attached is set (step S13). The temporary attachment position 40 is set so that the temporary attachment position 40 is evenly distributed over the length L of the welding line 70, for example. In the example of FIG. 6, it is shown that 30 temporary attachment positions 40 are set at predetermined intervals a over the length L of the weld line.

The temporary attachment position 40 obtained based on the conditions set in steps S11 and S12 (temporary attachment interval a of the temporary attachment weld bead 60, temporary attachment weld bead length b, and length L of the welding line 70) is obtained. If it is not preferable, the temporary attachment position 40 may be reset while finely adjusting each parameter of the condition within an allowable range. Such resetting of the temporary attachment position 40 may be performed by sequentially finding the optimum solution by using an electronic arithmetic unit such as a computer. In this case, the parameters to be finely adjusted may be the temporary attachment interval a of the temporary weld bead 60, the temporary weld bead length b, or the length L of the weld line 70, or the length of the non-welded portion 15. It may be c.

Subsequently, the first temporary attachment position 40a is selected from the temporary attachment position 40 set in step S13 (step S14). The first temporary attachment position 40a is a position where temporary attachment welding is performed prior to the second temporary attachment position 40b described later. This is because when the temporary welding is performed for all the temporary attachment positions 40 at once, the heat transfer fins 10 are distorted due to the welding heat.

The selection of the first temporary attachment position 40a in step S14 may be determined, for example, by comprehensively considering the following criteria.
-Is the heat transfer fin 10 evenly distributed as much as possible in order to evenly support the heat transfer fins 10 with respect to the outer surface 2a of the main body 2?
-Is it possible to obtain bearing capacity to maintain the posture of the heat transfer fins 10 before joining accurately?
-Is the strain generated in the heat transfer fin 10 during the first temporary welding suppressed within the allowable range?
-Since the heat transfer fin 10 before temporary welding is supported by a predetermined support device in order to maintain the posture of the main body body 2 with respect to the outer surface 2a, is the temporary attachment position not interfering with the support device? For example, when the heat transfer fin 10 is supported by the suction pad, is the position where the suction pad is not damaged by temporary welding).

In the example of FIG. 7, among the 30 temporary attachment positions 40 set in step S13, five temporary attachment positions located at equal intervals (first interval) including the outermost side are designated as the first temporary attachment position 40a. It has been selected (in FIG. 7, only three of the five first temporary attachment positions 40a are shown).

Subsequently, the second temporary attachment position 40b is selected from the temporary attachment position 40 set in step S13 (step S15). The second temporary attachment position 40b is selected as another temporary attachment position excluding the first temporary attachment position 40a selected in step S14. As a result, at least one second temporary attachment position 40b is located between the adjacent first temporary attachment positions 40a. In the example of FIG. 8, among the first temporary attachment positions 40a selected in step S16, a plurality of second temporary attachment positions 40b are located between the adjacent first temporary attachment positions 40a.

Returning to FIG. 4 again, when the temporary attachment position 40 (first temporary attachment position 40a and second temporary attachment position 40b) is set in this way, first, the first temporary attachment position 40a is first temporarily attached and welded. Is constructed (step S20). The first temporary welding is sequentially applied to a plurality of first temporary attachment positions 40a, but the order of construction may be arbitrary. In the example of FIG. 7, the first temporary attachment positions 40a set at a total of five locations are sequentially constructed from the right side to the left side.

Such first temporary welding is performed, for example, in order to appropriately maintain the posture of the heat transfer fin 10 with respect to the outer surface 2a of the main body body 2. The heat transfer fin 10 before the temporary welding is mechanically supported by a support device (not shown) with respect to the outer surface 2a of the main body body 2, but it is supported after the posture maintenance is ensured by the first temporary welding. The device can be removed.

The order of construction of the first temporary welding with respect to the plurality of first temporary attachment positions 40a may be the same as that of the second temporary attachment welding described later, in order from the center portion C of the welding line to the outside. In this case, it is advantageous in that the amount of strain generated in the heat transfer fin 10 due to the welding heat generated by the first temporary welding can be reduced to a considerable extent.

When the first temporary attachment welding is completed, the second temporary attachment welding is performed with respect to the second temporary attachment position 40b (step S30). The second temporary welding is performed for each of the plurality of second temporary welding positions 40b, and the order of construction is from the second temporary welding position 40b in the center C (center side) of the welding line to the outside of the welding line. It is performed toward a certain second temporary attachment position. In the example of FIG. 8, the second temporary welding is performed alternately from the second temporary attachment position 40b near the first temporary attachment position 40a located in the central portion C to the left and right. As a result, the strain generated during the temporary welding can be released from the center side of the welding line to the outside, and it is possible to effectively prevent the temporary welding from cracking during the subsequent main welding.

When the construction of a total of 30 points of temporary welding is completed for the first temporary attachment position 40a and the second temporary attachment position 40b in this way, the main welding is performed on the acute angle side (step S40). In the main welding, a welding bead 50 having a length L along the welding line is formed, and the welding bead 50 is divided into a plurality of sub-beads 50a and formed.

FIG. 9 is a diagram schematically showing how the weld bead 50 is formed from the plurality of sub-beads 50a in step S40, and FIG. 10 is an enlarged cross-sectional view of a part of the weld bead 50 of FIG.

As shown in FIG. 10, each sub-bead 50a is formed by scanning a welding torch between temporary attachment positions 40 (first temporary attachment position 40a or second temporary attachment position 40b) located at both ends of the sub-bead 50a. .. As a result, a sub-bead 50a having both ends corresponding to the temporary attachment position 40 is formed. By making both ends of each sub-bead 50a correspond to the temporary attachment position 40 in this way, the molten pool formed by the welding torch is stopped by the temporary attachment welding bead formed in advance at the temporary attachment position 40, and the molten pool hangs down. This makes it possible to suitably prevent the occurrence of fusion defects such as insufficient penetration amount.

Of the sub-beads 50a thus formed, the adjacent sub-beads 50a are formed so as to overlap each other at the temporary attachment position 40 (first temporary attachment position 40a or second temporary attachment position 40b) located at the end portion. That is, when a certain sub-bead 50a is formed first and a sub-bead is formed at a position adjacent to the sub-bead 50a, welding is performed from a position where the temporary attachment position 40 corresponding to the end of the previously formed sub-bead 50a overlaps. By starting the scanning of the torch, the sub-beads are formed so that the sub-beads 50a overlap each other at the temporary attachment position 40. Thereby, even when the weld bead 50 is divided into a plurality of sub-beads 50a and formed, it is possible to suitably prevent the occurrence of fusion failure between the sub-beads 50a.

Such a plurality of sub-beads 50a are formed in order so that two continuously formed sub-beads 50a are not adjacent to each other. As a result, the welding heat generated during the main welding can be dispersed over the entire welding line, and the generation of distortion due to the welding heat can be prevented more effectively.

In particular, in the example of FIG. 9, a first sub-bead (see the sub-bead 50a represented by “1” and “2” in FIG. 9) is formed at both ends of the weld line 70, and then a first sub-bead is formed between the first sub-beads. Two sub-beads (see sub-bead 50a represented by "3" in FIG. 9) are formed. By forming the sub-beads in this order, the strain generated during the main welding can be alleviated, and the occurrence of welding cracks can be effectively prevented.
In FIG. 9, the formation order of the sub-beads 50a created after the fourth is also shown, but this is an example and can be changed as appropriate.

When a plurality of sub-beads 50a are sequentially formed, a cooling step may be appropriately performed between them to prevent welding heat from accumulating in the base metal.

After the first fillet joint portion 20a on the acute angle side is formed in this way, the second fillet joint portion 20b on the obtuse angle side is subsequently formed by performing the main welding on the obtuse angle side (step S50). The main weld on the obtuse angle side may be divided into a plurality of sub-beads to form the weld bead, as in the main weld on the acute angle side in step S40. In this case, by forming the formation order of each subbead in the same pattern as in step S50, the distortion of the heat transfer fin 10 due to the welding heat can be reduced more effectively, and the risk of melting down due to the welding on the acute angle side is also dealt with. can.

In the present embodiment, the case where the welding method according to at least one embodiment of the present invention is applied to both the first fillet joint portion 20a and the second fillet joint portion 20b has been illustrated. Good welding quality can be achieved even when applied only to either the portion 20a or the second fillet joint portion 20b. In particular, the first fillet joint portion 20a on the acute angle side has a larger throat thickness at the welded portion than the second fillet joint portion 20b on the obtuse angle side, so that there is a great merit by applying this method.

As described above, according to the above-described embodiment, prior to the main welding, the temporary welding is sequentially performed in two stages with respect to the first temporary attachment position 40a and the second temporary attachment position 40b. The first temporary attachment position 40a is set at a wider interval on the welding line than the second temporary attachment position 40b, and by performing temporary attachment welding, accurate positioning is performed while suppressing distortion due to welding heat. Can be done. On the other hand, the second temporary attachment position 40b is set at a narrower interval than the first temporary attachment position 40a on the welding line, and temporary attachment welding is performed from the center side of the welding line to the outside. As a result, the strain generated during the temporary welding can be released from the center side of the welding line to the outside, and it is possible to effectively prevent the temporary welding from cracking during the main welding.

In this way, according to at least one embodiment of the present invention, it is possible to provide a welding method capable of achieving good welding quality by suppressing the occurrence of distortion due to welding heat in welding different materials.

At least one embodiment of the present invention can be used for a welding method for performing welding between members having different thermal conductivity, and for a radioactive material storage container that can be manufactured using the method.

1 Radioactive material storage container 2 Main body 2a Outer surface 3 Basket 4 Outer cylinder 6 Lid 7 Opening 10 Heat transfer fins 12, 14 End face 15 Non-welded parts 20, 30 Fillet joint 40 Temporary attachment position 40a First temporary attachment Position 40b Second temporary attachment position 50 Welding bead 50a Sub bead 60 Temporary welding bead 70 Welding line

Claims (15)

It is a welding construction method for welding the end surface of the first member having a longitudinal shape along the longitudinal direction to a joint portion formed by abutting the end face of the first member having a thermal conductivity smaller than that of the first member. ,
A process of performing temporary welding at a plurality of first temporary attachment positions specified for each first interval on the welding line from the welding start position to the welding end position of the joint portion to be main welded.
At least one second temporary attachment position is defined between each of the adjacent first temporary attachment positions, and the second temporary attachment position outside the weld line from the second temporary attachment position on the center side of the weld line. The process of performing temporary welding toward the temporary attachment position,
The step of performing the main welding along the welding line including the first temporary attachment position and the second temporary attachment position, and
Equipped with
In the main welding, a welding bead along the welding line is divided into a plurality of sub-beads and formed.
Both ends of each of the sub-beads correspond to the first temporary attachment position or the second temporary attachment position.
A welding method in which adjacent sub-beads are formed so as to overlap each other at the first temporary attachment position or the second temporary attachment position . Temporarily set the temporary attachment position at predetermined intervals on the welding line,
Among the temporary attachment positions, the temporary attachment position located at each first interval larger than the predetermined interval is set as the first temporary attachment position.
The welding construction method according to claim 1, wherein the remaining temporary attachment positions other than the first temporary attachment position are set as the second temporary attachment position. The welding method according to claim 1 or 2 , wherein the main welding is performed so that the two continuously formed sub-beads are not adjacent to each other. The welding method according to claim 3 , wherein the first sub-beads are formed at both ends of the welding line, and then the second sub-beads are formed between the first sub-beads. It is a welding construction method for welding the end surface of the first member having a longitudinal shape along the longitudinal direction to a joint portion formed by abutting the end face of the first member having a thermal conductivity smaller than that of the first member. ,
The process of performing temporary welding at the temporary attachment positions specified at predetermined intervals on the welding line from the welding start position to the welding end position of the joint to be main welded.
The process of performing main welding by forming a weld bead along the weld line by dividing it into a plurality of sub-beads whose both ends correspond to the temporary attachment positions.
Equipped with
A welding method in which adjacent sub-beads are formed so as to overlap each other at the temporary attachment position . The welding method according to claim 5 , wherein the main welding is performed so that the two continuously formed sub-beads are not adjacent to each other. The welding construction method according to claim 6 , wherein a first sub-bead is formed at both ends of the welding line, and then a second sub-bead is formed between the first sub-beads. The first member is a heat transfer fin that is inclined with respect to the radial direction of the main body between the main body and an outer cylinder coaxially arranged on the outside of the main body.
The welding method according to any one of claims 1 to 7 , wherein the second member is a main body body capable of storing radioactive substances inside. The welding method according to claim 8 , wherein the joint portion is an acute-angled fillet joint portion formed by the outer surface of the main body and the heat transfer fin. The welding method according to claim 8 , wherein the joint portion is an obtuse-angled fillet joint portion formed by the outer surface of the main body and the heat transfer fin. The joint portion is a first fillet joint portion on an acute angle side formed by the outer surface of the main body and the heat transfer fin, and an obtuse angle side formed by the outer surface of the main body and the heat transfer fin. The welding method according to claim 8 , further comprising the second fillet joint portion of the above. The welding method according to any one of claims 1 to 7 is applied to the first fillet joint portion, and then the welding method according to any one of claims 1 to 7 is applied to the first fillet joint portion. The welding construction method according to claim 11 , which is carried out for a two fillet joint portion. The first member is made of copper and is made of copper.
The welding method according to any one of claims 1 to 12 , wherein the second member is made of carbon steel or stainless steel. With the main body and
An outer cylinder coaxially arranged on the outside of the main body,
A heat transfer fin having a longitudinal shape and inclinedly arranged between the main body and the outer cylinder,
A welded portion extending along the longitudinal direction between the end face of the heat transfer fin along the longitudinal direction and the outer surface of the body of the main body, and a welded portion extending along the longitudinal direction.
Equipped with
The welded part is
A first temporary welded portion formed at each first interval along the extending direction of the welded portion, and a first temporary welded portion.
The second temporary welded portion formed between each of the adjacent first temporary welded portions and the second temporary welded portion.
The main welded portion formed along the welding line including the first temporarily attached welded portion and the second temporarily attached welded portion, and the main welded portion.
Including
The main weld is configured as a weld bead containing a plurality of sub-beads formed along the weld line.
Both ends of each of the sub-beads correspond to the first temporary attachment position or the second temporary attachment position.
Adjacent sub-beads are radioactive material containment vessels formed so as to overlap each other at the first temporary attachment position or the second temporary attachment position . With the main body and
An outer cylinder coaxially arranged on the outside of the main body,
A heat transfer fin having a longitudinal shape and inclinedly arranged between the main body and the outer cylinder,
A welded portion extending along the longitudinal direction between the end face of the heat transfer fin along the longitudinal direction and the outer surface of the body of the main body, and a welded portion extending along the longitudinal direction.
Equipped with
The welded part is
A plurality of temporary welded portions formed at predetermined intervals along the extending direction of the welded portion, and
A main weld portion extending along the extension direction and having a plurality of sub-beads at both ends corresponding to the temporary welded portion.
Including
Adjacent sub-beads are formed so as to overlap each other at the temporary attachment position, and are radioactive material containment vessels.

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