JPWO2013161667A1 - Pressure vessel overlay welding method and pressure vessel - Google Patents

Abstract

A reactor vessel 1 having a low alloy steel as a base material 11, and a plurality of overlays formed by multilayer overlay welding with an Inconel 690 alloy molten material, which is a Ni-based alloy welding material, on the inner surface side of the base material 11 The build-up layer 22 which is the first layer on which the layers 22 to 24 are laminated and is laminated directly on the inner surface side of the base material 11 among the plurality of build-up layers 22 to 24 is performed by build-up welding with a large dilution rate. It is formed so that the concentration of Cr does not exceed 16 mass%. High corrosion resistance is obtained, and in the post-weld heat treatment after multi-layer welding, it is possible to suppress the diffusion of carbon contained in the base metal to the welding material side and the formation of a hardened layer at the weld boundary. .

Description

  The present invention relates to a build-up welding method for a pressure vessel and a pressure vessel used when multi-layer build-up welding is performed on the inner surface of a pressure vessel.

  Since pressure vessels that handle high-temperature and high-pressure gases and liquids are required to have high corrosion resistance, as described in Patent Document 1, in the case of a reactor vessel, on a base material made of low alloy steel, Ni-based alloys with excellent corrosion resistance, for example, Inconel 600 alloy containing 15 to 20% by weight of Cr (“INCONEL” is a registered trademark of Special Metals Co., Ltd., and “Inconel 600 alloy” is a material name) are used as a welding material. It is known to overlay welding.

  In the overlay welding of this reactor vessel, as a measure against stress corrosion cracking, a welding wire or a welding rod, which is a metallized alloy of Inconel 600 alloy, is used when welding the final overlay layer in contact with high-temperature high-pressure water. In recent years, however, Inconel 690 alloy ("INCONEL" is a registered trademark of Special Metals Co., Ltd., "Inconel 690 alloy" is a material name) is used as a welding material. Attempts have been made to multi-layer overlay welding of all layers.

Japanese Patent Publication No.04-026937

  The above-described overlay welding by multilayer overlay welding requires post-weld heat treatment (stress relief annealing) for removing stress and the like due to thermal strain and the like generated during welding. This stress relief annealing is performed at a temperature around 600 ° C., but under this temperature condition, carbon contained in the low alloy steel as the base material diffuses to the welding material side containing Cr, which is a carbide forming element. Then, it concentrates near the weld boundary (bond part).

  When Inconel 690 alloy containing a large amount of Cr is used as the welding material, the concentration tendency of the carbon contained in the low alloy steel near the weld boundary becomes more prominent, and the weld boundary is very A hard cured layer is formed. In other words, in the weld boundary, there is a possibility that the ductility is lowered due to such a hardened layer, and there is a risk of cracking in the subsequent side bending test. This is a problem to be solved in manufacturing the reactor vessel. It has become.

  The present invention has been made by paying attention to the above-described conventional problems, and of course includes high corrosion resistance required for pressure vessels, and is included in the base material in stress relief annealing after multi-layer overlay welding. It is an object of the present invention to provide a build-up welding method for a pressure vessel and a pressure vessel capable of suppressing the formation of a hardened layer at the weld boundary portion by concentrating carbon in the vicinity of the weld boundary portion.

  As described above, when multi-layer overlay welding is performed on a base metal made of low alloy steel with Inconel 690 alloy containing a large amount of Cr, post-weld heat treatment for removing stress caused by thermal strain and the like generated during welding When (stress relief annealing) is performed, as shown in FIG. 8, the carbon contained in the low alloy steel (SA302C) as a base material diffuses to the welding material side containing Cr which is a carbide forming element, and the welding boundary It thickens in the vicinity of the part (bond part), and a very hard hardened layer is formed at the weld boundary part.

  The present inventors use a low chromium Ni-base alloy-based welding material having a lower Cr content than Inconel 690 alloy for the first build-up layer that is directly laminated on the inner surface side of the base material. It has been found that a hardened layer can be prevented from being formed at the boundary, and has led to the present invention.

  That is, the present invention provides a method for forming a base metal inner surface of a pressure vessel having a steel material such as a low alloy steel as a base material by multi-layer overlay welding using a Ni base alloy welding material. At the stage of overlay welding of at least the first layer prior to overlay welding, overlay welding is performed so that the Cr content is less than the Cr content of the overlay layer following the at least primary layer.

  Preferably, an Inconel 690 alloy molten material is used as the Ni-based alloy-based welding material, and the concentration of Cr is increased by increasing the dilution rate at least at the first layer of the overlay welding prior to the overlay welding with the Inconel 690 alloy molten material. It is set as the structure which performs overlay welding so that it may not exceed 16 mass%.

  Preferably, prior to overlay welding with the Ni-base alloy welding material, at least the first layer overlay welding is performed with a low chromium Ni-base alloy welding material having a lower Cr content than the Ni-base alloy welding material. The configuration is to be performed.

  Preferably, an Inconel 690 alloy melt is used as the Ni-base alloy welding material, and an Inconel 600 alloy melt having a lower Cr content than the Inconel 690 alloy melt is used as the low chromium Ni-base alloy welding material.

  Further, the present invention is a pressure vessel having a steel material as a base material, and a plurality of overlay layers formed by multilayer overlay welding with a Ni-based alloy welding material are laminated on the inner surface side of the base material. The initial layer that is directly laminated at least on the inner surface side of the base material of the plurality of the built-up layers is formed with a Cr content lower than that of the built-up layer that follows the at least the first layer. The configuration is as follows.

  Preferably, an Inconel 690 alloy molten material is used as the Ni-based alloy-based welding material, and at least the initial layer directly laminated on the inner surface side of the base material has a Cr concentration of 16 mass by overlay welding with a large dilution ratio. %. The structure is formed so as not to exceed%.

  In the build-up welding method and pressure vessel of the pressure vessel according to the present invention, the build-up layer is formed by plasma welding, TIG welding, and submerged welding, but is not limited to these types of welding.

  In the pressure vessel overlay welding method and the pressure vessel according to the present invention, the inner surface of the base material constituting the pressure vessel is subjected to multilayer overlay welding with a Ni-based alloy-based welding material, for example, Inconel 690 alloy molten material. High corrosion resistance will be obtained.

  At this time, at the stage of overlay welding of the first layer that is directly laminated on at least the inner surface side of the base material among the plurality of overlay layers prior to overlay welding with the Inconel 690 alloy melt, the dilution rate is increased and Cr is increased. The build-up welding is performed so that the concentration of the steel does not exceed 16 mass%, or the build-up layer as the first layer is a low chromium Ni-base alloy welding material having a lower Cr content than the Ni-base alloy welding material, for example, Since the Inconel 600 alloy is formed of a molten material, in the post-weld heat treatment after multi-layer welding, diffusion of carbon contained in the base metal to the welding material side is suppressed, and a hardened layer is formed at the weld boundary. The formation is avoided, and the fear of cracking in the subsequent side bending test can be eliminated.

  In the overlay welding method of the pressure vessel according to the present invention, since it has the above-described configuration, it goes without saying that the high corrosion resistance required for the pressure vessel is obtained, and is included in the base material in the post-weld heat treatment after multilayer overlay welding. It is possible to prevent the formation of a hardened layer at the weld boundary by suppressing the diffusion of carbon to the welding material side, and as a result, it is possible to enhance the safety of the pressure vessel. Is brought about.

It is a schematic structure explanatory view of a reactor vessel showing one example of a pressure vessel concerning the present invention. It is a mimetic diagram of a specimen formed by half lap imitating the build-up welding part of a pressure vessel concerning one example of the present invention. FIG. 3 is a cross-sectional photograph of an overlay weld that shows an enlarged weld boundary showing a result of a penetrant inspection when a side bending test is performed after stress relief annealing on a specimen formed by the half lap of FIG. 2. . It is a graph which shows the measurement result of the penetration flaw inspection of FIG. It is a schematic structure explanatory drawing of the reactor vessel which shows other examples of the pressure vessel concerning the present invention. The weld boundary part which shows the result of a penetration inspection at the time of performing a side bending test after stress-relieving annealing with respect to the build-up weld part formed by the build-up welding method of the pressure vessel concerning other examples of the present invention. It is a schematic diagram of the overlay welding part represented with the expanded cross-section photograph. It is an expanded cross-sectional photograph of the weld boundary part which shows the result of the penetration | inspection flaw inspection at the time of performing a side bending test after stress relief annealing with respect to the build-up weld part formed by the conventional build-up welding method. It is an expanded sectional photograph of the welding boundary part which shows the result of a penetration inspection at the time of performing a side bending test after stress relief annealing similarly to the built-up welding part similarly formed by the conventional build-up welding method. It is a microscope picture after stress removal annealing of the welding boundary part formed by the conventional overlay welding method.

Hereinafter, the present invention will be described with reference to the drawings.
FIG. 1 shows a nuclear reactor vessel as a pressure vessel manufactured by using a pressure vessel overlay welding method according to an embodiment of the present invention.

  As shown in FIG. 1, this nuclear reactor vessel 1 is a vessel for confining a nuclear reactor main body, and includes a vessel body 2 and a lid body 3 having a base material 11 of a low alloy steel (for example, SA302C) that is a steel material. ing. A plurality of built-up layers 22 to 24 for preventing corrosion are laminated on the inner surface of the base material 11 in contact with the high temperature / high pressure water.

  The plurality of overlay layers 22 to 24 are formed by multilayer overlay welding of a Ni-based alloy welding material on the base material 11. In this embodiment, an Inconel 690 alloy solution is used as the Ni-based alloy welding material. In the built-up layer 22 that is the first layer that is directly laminated on the inner surface side of the base material 11 among the plurality of built-up layers, the Cr concentration does not exceed 16 mass% by build-up welding with a large dilution ratio. On the other hand, the build-up layers 23 and 24 following the build-up layer 22 which is the first layer are formed so that the Cr concentration becomes 16 mass% or more by build-up welding with a reduced dilution rate.

  When laminating the plurality of overlay layers 22 to 24 on the inner surface side of the base material 11 of the reactor vessel 1 described above, the first layer prior to the overlay welding with the Inconel 690 alloy molten material as the Ni-based alloy-based welding material. At the stage of build-up welding of the build-up layer 22, first, build-up layer 22 which is the first layer is formed by increasing the dilution rate and performing build-up welding so that the concentration of Cr does not exceed 16 mass%.

  Next, build-up welding is performed with an Inconel 690 alloy solution so that the dilution rate is reduced and the Cr concentration is 16 mass% or more, and the second and subsequent build-up layers 23, 23 are formed on the first build-up layer 22. After forming 24, post-weld heat treatment (stress relief annealing) is performed for 24 to 48 hours to remove stress or the like due to thermal strain or the like generated during welding. In addition, although plasma welding, TIG welding, and submerged welding can be used for this build-up welding, it is not limited to these types of welding.

  In this example, the Inconel 690 alloy solution as the Ni-base alloy welding material is an Inconel 690 alloy solution (Ni-0.04C-9Fe) which is a co-metal alloy of Inconel 690 alloy with a basic composition of Ni-29Cr-10Fe. -30Cr-0.5Mo-1Ti-1Al) was used.

  In the pressure vessel build-up welding method and the pressure vessel according to this embodiment, the inner surface of the base material 11 constituting the reactor vessel 1 is subjected to multilayer build-up welding with an Inconel 690 alloy solution, so that high corrosion resistance is achieved. Will be obtained.

  In addition, at the stage of overlay welding of the overlay layer 22 as the first layer that is directly laminated on the inner surface side of the base material 11, the dilution rate is increased so that the Cr concentration does not exceed 16 mass%. Since the build-up welding is performed, in the post-weld heat treatment after the multi-layer build-up welding, the carbon contained in the base material 11 is suppressed from diffusing to the build-up layer 22 side of the first layer, and the base material 11 and the first layer are formed. The formation of a hardened layer at the boundary between the welded layer 22 and the welded layer 22 can be avoided, and the fear of cracking in the subsequent side bending test can be eliminated.

  That is, the problem in manufacturing the reactor vessel 1 is solved, and the safety of the reactor vessel 1 can be improved.

Therefore, a specimen was manufactured by simulating the overlay weld of the reactor vessel 1 according to the above-described example.
As shown in FIG. 2, this specimen is formed by forming a plurality of overlay layers by half wrap on the base material 11 of the above-described embodiment, and corresponds to the first layer of the above-described embodiment. The build-up layer 22 is formed so that the concentration of Cr does not exceed 16 mass% by build-up welding with a large dilution ratio with the Inconel 690 alloy solution, and from the center of the figure corresponding to the layer following the first layer of the above-described embodiment. The right overlay layers 23 and 24 are formed so that the Cr concentration becomes 16 mass% or more by overlay welding with the dilution ratio reduced by the Inconel 690 alloy melt.

Table 1 shows the welding conditions for manufacturing the specimen.

  A stress bending annealing was performed on the specimen for 48 hours, and then a side bending test was performed. When the welded state of the weld boundary portion was examined by a penetrant inspection, the results shown in FIGS. 3 and 4 were obtained.

  As shown in the enlarged cross-sectional photograph in FIG. 3 and the graph in FIG. 4, the build-up layer on the left side of FIG. 3 formed so that the Cr concentration does not exceed 16 mass% by build-up welding with a large dilution ratio with the Inconel 690 alloy molten material. No instructions (defects such as cracks) by penetrant inspection are found at the weld boundary 22.

  On the other hand, with the base material 11 of the build-up layers 23 and 24 on the right side from the center of FIG. 3 formed so as to have a Cr concentration of 16 mass% or more by build-up welding with a reduced dilution rate by the Inconel 690 alloy melt. At each welding boundary, an instruction by penetrant inspection appeared.

  Therefore, in the overlay welding method of the pressure vessel according to this embodiment, in the post-weld heat treatment (stress relief annealing) after multilayer overlay welding, diffusion of carbon contained in the base metal to the welding material side is suppressed and welding is performed. It was proved that a hardened layer was not formed at the boundary portion and cracking was difficult to occur.

  FIG. 5 shows a nuclear reactor vessel as a pressure vessel manufactured by using a pressure vessel overlay welding method according to another embodiment of the present invention.

  As shown in FIG. 5, the reactor vessel 1 is also a vessel for confining the reactor main body, and includes a vessel body 2 and a lid 3 having a base material 11 of a low alloy steel (for example, SA302C) that is a steel material. ing. A plurality of overlay layers 12 to 15 for preventing corrosion are laminated on the inner surface side of the base material 11 in contact with the high temperature / high pressure water.

  The plurality of overlay layers 12 to 15 are formed by multilayer overlay welding of a Ni-based alloy welding material on the base material 11, and are laminated directly on the inner surface side of the base material 11 of the plurality of overlay layers. The built-up layer 12 that is the first layer is formed of a low chromium Ni-based alloy welding material having a lower Cr content than the Ni-based alloy welding material that forms the second and subsequent built-up layers 13 to 15. Has been.

  When laminating the plurality of build-up layers 12 to 15 on the inner surface side of the base material 11 of the reactor vessel 1 described above, this Ni-base alloy-based welding material is prior to build-up welding with the Ni-base alloy-based weld material. The built-up layer 12 which is the first layer is formed by directly overlay welding the inner surface side of the base material 11 with a low chromium Ni-base alloy-based welding material having a lower Cr content.

  Next, build-up welding using a Ni-based alloy welding material is performed on the build-up layer 12 which is the first layer, and the build-up layers 13 to 15 after the second layer are formed. A post-weld heat treatment (stress relief annealing) is performed for 24 to 48 hours to remove the stress caused by the stress. In addition, although plasma welding, TIG welding, and submerged welding can be used for this build-up welding, it is not limited to these types of welding.

  In this embodiment, the low-chromium Ni-base alloy-based welding material for forming the build-up layer 12 as the first layer is an Inconel 600 alloy that is a co-metal-based melt of Inconel 600 alloy having a basic composition of Ni-15.5Cr-8Fe. A melt (Ni-0.08C-3Mn-3Fe-20Cr-2.5 (Nb + Ta)) was used.

  On the other hand, the Ni-based alloy-based welding material for forming the second and subsequent build-up layers 13 to 15 is an Inconel 690 alloy solution (Ni alloy, which is a co-metal alloy of Inconel 690 alloy having a basic composition of Ni-29Cr-10Fe. -0.04C-9Fe-30Cr-0.5Mo-1Ti-1Al) was used.

  Also in the pressure vessel overlay welding method and the pressure vessel according to this embodiment, since the inner surface side of the base material 11 constituting the reactor vessel 1 is subjected to multilayer overlay welding with the Inconel 690 alloy solution, high corrosion resistance is achieved. Will be obtained.

  In addition, the built-up layer 12 as an initial layer that is directly laminated on the inner surface side of the base material 11 among the plurality of built-up layers 12 to 15 is an Inconel 600 alloy having a lower Cr content than the Inconel 690 alloy solution. In the heat treatment after welding after multi-layer overlay welding, carbon contained in the base material 11 is suppressed from diffusing to the first overlay layer 12 side, and the base material 11 and the initial material are formed. The formation of a hardened layer at the boundary between the welded layer 12 and the buildup layer 12 is avoided, and the fear of cracking in the subsequent side bending test can be eliminated.

  That is, the problem in manufacturing the reactor vessel 1 is solved, and the safety of the reactor vessel 1 can be improved.

  Then, the build-up weld formed by the build-up welding method of the pressure vessel according to the present invention, that is, the first build-up layer is formed of the Inconel 600 alloy melt, and the second and subsequent build-up layers are Inconel 690. A side bending test was conducted after 48 hours of stress-relieving annealing on the weld overlay formed of the alloy melt, and the welded state at the weld boundary was examined by penetration inspection, and the results shown in FIG. 6 were obtained. It was.

  Moreover, after carrying out stress relief annealing for 48 hours at a time for the build-up weld part formed by the conventional build-up welding method, ie, the two-layer build-up weld part in which all the layers were formed with the Inconel 690 alloy molten material. When the side bending test was performed and the welding state of the welding boundary part was investigated by the penetration inspection, the results shown in FIGS. 7A and 7B were obtained.

  As shown in the enlarged cross-sectional photograph in FIG. 6, when an instruction (defect such as a crack) by penetration inspection is found in the weld boundary portion of the build-up weld formed by the pressure vessel build-up welding method according to the present invention. Absent.

  On the other hand, as shown in each enlarged cross-sectional photograph of FIG. 7A and FIG. 7B corresponding to the enlarged portion of FIG. 6, each weld boundary portion of the two-pattern overlay weld formed by the conventional overlay welding method In both cases, instructions by penetrant inspection appeared.

  Therefore, in the overlay welding method for a pressure vessel according to the present invention, in post-weld heat treatment (stress relief annealing) after multi-layer overlay welding, diffusion of carbon contained in the base metal to the welding material side is suppressed and the weld boundary is reduced. It was proved that a hardened layer was not formed on the part and cracking was difficult to occur.

  In the above-described embodiment, the Inconel 690 alloy melt is used as the Ni-base alloy welding material, and the Inconel 600 alloy melt is used as the low chromium Ni-base alloy welding material having a lower Cr content than the Inconel 690 alloy melt. However, it is not limited to this.

  Moreover, in the above-mentioned Example, only the build-up layer 12 which is the first layer laminated | stacked directly on the inner surface side of the base material 11 among the several build-up layers formed by multilayer build-up welding on the base material 11 is carried out. Although it is made to form with the low chromium Ni base alloy type welding material with little Cr content, it is not limited to this, For example, the 2nd build-up layer 13 is also low with little Cr content. You may make it form with a chromium Ni base alloy type welding material.

  Furthermore, although the case where the pressure vessel which concerns on this invention was a reactor vessel was shown in the above-mentioned Example, it is not limited to this.

  The build-up welding method of a pressure vessel and the configuration of the pressure vessel according to the present invention are not limited to the configurations of the above-described embodiments.

1 Reactor vessel (pressure vessel)
2 Container body 3 Lid 11 Base material 12, 22 Overlay layer 13-15, 23, 24 which is the first layer Overlay layer after 2 layers

Claims (6)

When multi-layer overlay welding of the base material inner surface side of the pressure vessel having a steel material as a base material with a Ni-based alloy based welding material,
In the stage of overlay welding of at least the first layer prior to overlay welding with the Ni-based alloy-based welding material, overlaying is performed so that the Cr content is less than the Cr content of the overlay layer subsequent to the first layer. A build-up welding method for pressure vessels characterized by welding.   Inconel 690 alloy solution is used as the Ni-base alloy welding material, and at the stage of build-up welding of at least the first layer prior to build-up welding with the Inconel 690 alloy solution, the dilution ratio is increased so that the Cr concentration is 16 mass%. The build-up welding method of the pressure vessel of Claim 1 which performs build-up welding so that it may not exceed.   Prior to overlay welding with the Ni-base alloy welding material, build-up welding of at least the first layer is performed with a low chromium Ni-base alloy welding material having a lower Cr content than the Ni-base alloy welding material. The overlay welding method of the pressure vessel as described in 1.   4. The pressure according to claim 3, wherein an Inconel 690 alloy melt is used as the Ni-base alloy welding material, and an Inconel 600 alloy melt with a lower Cr content than the Inconel 690 alloy melt is used as the low-chromium Ni-base alloy welding material. Overlay welding method for containers. A pressure vessel based on a steel material,
On the inner surface side of the base material, a plurality of overlay layers formed by multilayer overlay welding with a Ni-based alloy welding material are laminated,
The initial layer that is directly laminated at least on the inner surface side of the base material among the plurality of the built-up layers is formed with a Cr content less than that of the built-up layer that follows the at least the first layer. A pressure vessel characterized by that.   Inconel 690 alloy molten material is used as the Ni-base alloy welding material, and at least the initial layer directly laminated on the inner surface side of the base material has a Cr concentration exceeding 16 mass% by overlay welding with a large dilution ratio. The pressure vessel according to claim 5 formed so as not to exist.

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