Valve

Abstract

To provide a valve that can improve abrasion resistance and erosion resistance.SOLUTION: A valve of the present invention includes a valve box in which a valve box seat part is provided, and a valve body in which a valve element seat part is provided. One of the valve box seat part and the valve element seat part is formed of a built-up material of a Co group alloy, and the other of the valve box seat part and the valve element seat part is formed of a built-up material of an Fe group alloy. The built-up material of the Fe group alloy is manufactured by performing welding without using a welding rod for a built-up welding part formed by plasma arc welding.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a valve. [Background technology]

[0002] The valve includes a valve body seat portion that functions as a valve seat in the valve body and a valve disc seat portion that functions as a valve seat in the valve disc, and the valve body seat portion and the valve disc seat portion are formed from a material that has excellent wear resistance and erosion resistance.

[0003] For example, valves used in light water reactors at nuclear power plants have valve body seats and valve disc seats made of Co-based alloy cladding materials. However, since the Co-based alloy comes into contact with high-temperature, high-pressure water, Co elements may dissolve from the Co-based alloy into the reactor water. In addition, when the Co-based alloy cladding materials slide against each other during the opening and closing of the valve, they wear away, and the worn Co elements may get mixed into the reactor water. The Co elements are radioisotopes of Co 60 This has resulted in the use of Co in piping, turbines and other equipment. 60 As a result, it may become difficult to reduce the radiation exposure of workers during periodic inspections of light water reactors.

[0004] For this reason, in order to reduce the amount of Co that enters the reactor water, the use of cobalt-free materials that do not contain Co has been considered. For example, it has been proposed to combine the cladding material for the valve body seat and the cladding material for the valve disc seat with one made of a Co-based alloy and the other made of an Fe-based alloy. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6005436 Summary of the Invention [Problem to be solved by the invention]

[0006] The Fe-based alloy overlay material is formed, for example, by a powder overlay welding method using plasma arc welding. The Fe-based alloy powder is more easily oxidized than the Co-based alloy powder, so that during storage, unevenness occurs on the surface and contamination is more likely to adhere. For this reason, the contamination may melt by plasma arc welding, generating welding slag, which may be present inside the weld metal. As a result, minute defects with a size of 0.5 mm or less often occur inside the Fe-based alloy overlay material due to the contamination.

[0007] When the sliding surface of the Fe-based alloy overlay is machined to finish it, minute defects present inside the Fe-based alloy overlay may be exposed on the surface, making it difficult to ensure the quality of the valve, such as wear resistance and erosion resistance.

[0008] Therefore, an object of the present invention is to provide a valve capable of improving abrasion resistance and erosion resistance. [Means for solving the problem]

[0009] The valve of the embodiment has a valve body having a valve body seat portion and a valve body having a valve body seat portion. One of the valve body seat portion and the valve body seat portion is formed of a build-up material of a Co-based alloy, and the other of the valve body seat portion and the valve body seat portion is formed of a build-up material of an Fe-based alloy. The build-up material of the Fe-based alloy is produced by performing blunt welding on the build-up weld portion formed by plasma arc welding. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a partial cross-sectional view that illustrates a schematic configuration of a valve 10 according to an embodiment. [Diagram 2] FIG. 2 is an enlarged partial cross-sectional view showing a part of the valve 10 according to the embodiment. [Diagram 3]FIG. 3 is a diagram showing a state in which a cladding material of an Fe-based alloy is formed in the valve 10 according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view that illustrates a state in which fillet welding has been performed on the overlay weld 202 in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [A] Configuration of valve 10 Fig. 1 is a partial cross-sectional view showing a schematic configuration of a valve 10 according to an embodiment. Fig. 2 is a partial cross-sectional view showing an enlarged portion of the valve 10 according to an embodiment. Figs. 1 and 2 show a case where the valve 10 is in a fully closed state.

[0012] As shown in Fig. 1, the valve 10 has a valve body 11, a valve cover 12, a valve stem 13, a valve body 14, and a valve drive mechanism 21. The valve 10 is used, for example, as a gate valve through which reactor water passes in a light water reactor (not shown). Each part constituting the valve 10 will be described in order.

[0013] [A-1] Valve box 11 1, the valve box 11 includes an internal space 11S along the horizontal direction. The internal space 11S of the valve box 11 is a flow path through which a fluid flows. An opening 11K that communicates with the internal space 11S is formed on the upper side of the internal space 11S in the vertical direction.

[0014] [A-2] Valve 12 1, the valve cover 12 is disposed above the valve box 11 and closes an opening 11K of the valve box 11. Here, the valve cover 12 is formed with a through hole 12K that penetrates in the vertical direction.

[0015] [A-3] Valve stem 13 As shown in FIG. 1, the valve stem 13 passes through a through hole 12K of the valve lid 12 so as to extend in the vertical direction.

[0016] [A-4] Valve body 14 1, the valve element 14 is disposed at the lower end of the valve rod 13 in the vertical direction. Here, the valve element 14 is penetrated by an opening 11K of the valve box 11.

[0017] [A-5] Valve drive mechanism 21 1, the valve drive device 21 is installed at the upper end of the valve stem 13 in the vertical direction. The valve drive device 21 includes a handle 211 and a motor 212, and performs the opening and closing operation of the valve 10 by moving the valve element 14 installed on the valve stem 13 in the vertical direction.

[0018] Specifically, when performing a closing operation on the valve 10, the valve drive device 21 moves the valve element 14 attached to the valve stem 13 downward to close the flow path which is the internal space 11S. In contrast, when performing an opening operation on the valve 10, the valve drive device 21 moves the valve element 14 attached to the valve stem 13 upward to open the flow path which is the internal space 11S.

[0019] [B] Detailed configuration of valve 10 [B-1] Valve box seat part 111 2, the valve box 11 is provided with a valve box seat portion 111. The valve box seat portion 111 functions as a valve seat in the valve box 11. Here, the valve box seat portion 111 is annular, and is disposed coaxially with the opening 11K, the through hole 12K (see FIG. 1), and the valve rod 13.

[0020] In this embodiment, two valve box seat portions 111 are provided on the valve box 11. Specifically, one valve box seat portion 111 is provided in an upper portion of the internal space 11S, and the other valve box seat portion 111 is provided in a lower portion of the internal space 11S. In addition, in this embodiment, the valve box seat portion 111 is formed on the inner surface of the annular member 112, and the annular member 112 is fixed to the inner surface of the valve box 11.

[0021] [B-1] Valve body seat portion 141 2, the valve element 14 is provided with a valve element seat portion 141. The valve element seat portion 141 functions as a valve seat in the valve element 14. Here, the valve element seat portion 141 is annular and is provided on the outer circumferential surface of the valve element 14.

[0022] In this embodiment, two valve element seat portions 141 are provided on the valve element 14. Specifically, one valve element seat portion 141 is provided on an upper portion of the valve element 14, and the other valve element seat portion 141 is provided on a lower portion of the valve element 14.

[0023] 2, when the valve 10 is in a fully closed state, the inner circumferential surface of the valve body seat portion 111 and the outer circumferential surface of the valve disc seat portion 141 are in close contact with each other. Therefore, when the valve 10 is opened or closed, the outer circumferential surface of the valve disc seat portion 141 slides against the inner circumferential surface of the valve body seat portion 111.

[0024] [C] Materials of the valve body seat portion 111 and the valve body seat portion 141 One of the valve body seat portion 111 and the valve disc seat portion 141 is formed of an overlay material of a Co-based alloy. The other of the valve body seat portion 111 and the valve disc seat portion 141 is formed of an overlay material of an Fe-based alloy. In other words, when the valve body seat portion 111 is formed of an overlay material of a Co-based alloy, the valve disc seat portion 141 is formed of an overlay material of an Fe-based alloy. On the other hand, when the valve disc seat portion 141 is formed of an overlay material of a Co-based alloy, the valve body seat portion 111 is formed of an overlay material of an Fe-based alloy.

[0025] [C-1] Composition of Fe-based alloy As the Fe-based alloy, for example, NOREM02 (manufactured by Electric Power Research Institute) can be used. Specifically, the chemical composition of the overlay material, which is an Fe-based alloy, is preferably, in mass percentage, Cr is 23.0% or more and 26.0% or less, Mo is 1.8% or more and 2.2% or less, Si is 3.1% or more and 3.5% or less, C is 1.10% or more and 1.35% or less, Ni is 3.7% or more and 5.0% or less, Mn is 4.0% or more and 5.0% or less, B is 0% or more and less than 0.002%, S is 0% or more and less than 0.01%, P is 0% or more and less than 0.020%, N is 0% or more and less than 0.18%, and the balance is Fe and unavoidable impurities.

[0026] The reasons for setting the above ranges for the main chemical components of the Fe-based alloy will be explained below.

[0027] In Fe-based alloys, Cr is a necessary component for maintaining corrosion resistance. On the other hand, if the Cr content is too high, the wear resistance may decrease. For this reason, the Cr content is set within the above range.

[0028] In Fe-based alloys, Si is added to improve hardness and wear resistance. On the other hand, if the Si content is too high, weld cracks may occur. For this reason, the Si content is set within the above range.

[0029] In Fe-based alloys, C is added to improve hardness and wear resistance and to stabilize austenite. On the other hand, if the C content is too high, it may increase the susceptibility to weld cracking. For this reason, the Si content is set within the above range.

[0030] In Fe-based alloys, Ni is added as an austenite stabilizing element, and has the effect of improving weldability, etc. On the other hand, if the Ni content is too high, it may cause a decrease in hardness and wear resistance. For this reason, the Ni content is set to the above range.

[0031] In Fe-based alloys, Mn is added as an austenite stabilizing element. However, if the Mn content is too high, there is a risk of weld crack susceptibility occurring. For this reason, the Mn content is set within the above range.

[0032] [C-2] Composition of Co-based alloy As the Co-based alloy, for example, Stellite (registered trademark) can be used. Specifically, the chemical composition of the cladding material, which is a Co-based alloy, is preferably, for example, in mass percentage, Cr is 25.0% or more and 32.0% or less, Mo is 0% or more and 1.0% or less, Si is 0% or more and 2.0% or less, C is 0.70% or more and 1.40% or less, Ni is 0% or more and 3.0% or less, Fe is 0% or more and 5.0% or less, Mn is 0% or more and 2.0% or less, W is 3.0% or more and 6.0% or less, S is 0% or more and 0.03% or less, P is 0% or more and 0.03% or less, and the balance is Co and unavoidable impurities.

[0033] [D] Vickers hardness In this embodiment, it is preferable that the Vickers hardness of the Co-based alloy cladding material is greater than that of the Fe-based alloy cladding material, and the difference in Vickers hardness between the Co-based alloy cladding material and the Fe-based alloy cladding material is HV50 or more. In this case, the Fe-based alloy is mainly worn during the opening and closing operation of the valve 10, so that the wear of the Co-based alloy is suppressed. This makes it possible to suppress the Co component from being mixed into the reactor water due to the wear of the Co-based alloy. As a result, the amount of radiation exposure of workers during periodic inspection work of the light water reactor of the nuclear power plant is reduced, and safety can be improved.

[0034] The Fe-based alloy cladding material preferably has a Vickers hardness of HV350 or more and 400 or less. If it is less than the lower limit of the above range, the Fe-based alloy cladding material is likely to wear, and the wear resistance may decrease. On the other hand, if it exceeds the upper limit of the above range, the Co-based alloy cladding material is likely to wear, and the worn components of the Co-based alloy may be mixed into the reactor water. In addition, if the Vickers hardness of the Fe-based alloy cladding material is outside the above range, welding cracks may occur during the formation of the Fe-based alloy. The Vickers hardness can be determined by the test method shown in "JIS Z 2244:2009 Vickers Hardness Test".

[0035] [E] Manufacturing method Of the above-mentioned manufacturing method for the valve 10, a Co-based alloy overlay material forming step using a Co-based alloy overlay material and an Fe-based alloy overlay material forming step using an Fe-based alloy overlay material will be described in order.

[0036] [E-1] Co-based alloy overlay material forming process When forming a Co-based alloy overlay material, for example, powder of the Co-based alloy having the above-mentioned chemical composition is used and overlay welded by plasma arc. The powder used is generally preferably powder produced by gas atomization, but powder produced by water atomization may also be used.

[0037] [E-2] Fe-based alloy overlay material forming process When forming an overlay material of an Fe-based alloy, for example, powder of an Fe-based alloy having the above-mentioned chemical composition is used to perform overlay construction.

[0038] Fig. 3 is a diagram showing a state in which a cladding material of an Fe-based alloy is formed in the valve 10 according to the embodiment. Fig. 3 shows a schematic diagram of a tip portion of a welding torch 300 and a base material 201 on which the cladding material is formed.

[0039] As shown in FIG. 3, welding torch 300 has a shielding gas nozzle portion 301, a powder nozzle portion 302, a plasma gas nozzle portion 303, and an electrode 304, and is configured to move in a welding direction WD.

[0040] 3, shielding gas nozzle section 301, powder nozzle section 302, and plasma gas nozzle section 303 are tubular bodies, and powder nozzle section 302 is housed inside shielding gas nozzle section 301, and plasma gas nozzle section 303 is housed inside powder nozzle section 302. Electrode 304 is a rod-shaped body made of, for example, tungsten, and is housed inside plasma gas nozzle section 303.

[0041] A flow path through which a shielding gas SG flows is provided between the shielding gas nozzle part 301 and the powder nozzle part 302. A flow path through which a powder PW, which is a cladding material, and a carrier gas CW (such as nitrogen gas) flow is provided between the powder nozzle part 302 and the plasma gas nozzle part 303. A flow path through which a plasma gas PG, such as argon gas, flows is provided between the plasma gas nozzle part 303 and the electrode 304.

[0042] When forming an overlay material of an Fe-based alloy, first, an overlay weld 202 is produced by, for example, powder plasma welding (PTA welding).

[0043] Specifically, after the plasma gas PG is turned into plasma by generating an arc between the electrode 304 and the plasma gas nozzle part 303, the plasma gas PG is made to reach the base material 201 as a plasma arc AR and is maintained in this state. At this time, the Fe-based alloy powder PW is fed into the plasma arc AR. As a result, the Fe-based alloy powder PW is introduced in a molten state into a molten pool (not shown) of the base material 201, and the overlay weld 202 is formed.

[0044] As already mentioned, in this case, minute defects DE often occur inside the overlay weld 202 of the Fe-based alloy due to contamination adhering to the Fe-based alloy powder.

[0045] For this reason, in this embodiment, filler welding (common welding) is further performed on the above-mentioned overlay welded portion 202. Filler welding is performed, for example, in a similar procedure to the above-mentioned powder plasma welding, except that the powder PW is not supplied.

[0046] FIG. 4 is a cross-sectional view that illustrates a state in which fillet welding has been performed on the overlay weld 202 in the embodiment.

[0047] As shown in Fig. 4, the surface of the overlay weld 202 is remelted by performing the fillet welding. As a result, minute defects DE present inside the surface of the overlay weld 202 are removed, and the surface of the overlay weld 202 is covered with a fillet weld 202a that is free of minute defects DE. Note that a thin film of slag 203 caused by the defects DE is formed on the surface of the fillet weld 202a formed by performing the fillet welding. However, this thin film of slag 203 is removed by final processing, so soundness is guaranteed.

[0048] [F] Summary As described above, in this embodiment, one of the valve body seat portion 111 and the valve disc seat portion 141 is formed of an overlay material of a Co-based alloy. In contrast, the other of the valve body seat portion 111 and the valve disc seat portion 141 is formed of an overlay material of an Fe-based alloy. Here, the overlay material of the Fe-based alloy is formed by performing a filler welding on the overlay weld portion 202 formed by plasma arc welding. In other words, the overlay material of the Fe-based alloy is in a state where the surface of the overlay weld portion 202 is covered with a filler weld portion 202a that is free of fine defects DE.

[0049] Therefore, in this embodiment, since there are no fine defects DE on the surface of the Fe-based alloy cladding material, it is possible to prevent the valve body seat portion 111 or the valve body seat portion 141, which are made of the Fe-based alloy cladding material, from easily wearing. Therefore, in this embodiment, a valve capable of improving the wear resistance and erosion resistance can be obtained.

[0050] [G] Transformation In the above embodiment, the case where the fillet welding is performed using a plasma arc has been described, but the present invention is not limited to this. The fillet welding may be performed using a heat source other than a plasma arc.

[0051] In the above embodiment, the valve 10 is used in a light water reactor, but the present invention is not limited to this. The valve 10 may be used in equipment other than a light water reactor.

[0052] In the above embodiment, a case has been described in which the valve box seat portion 111 is formed on the inner surface of the annular member 112, and the annular member 112 is fixed to the inner surface of the valve box 11. In this case, the valve 10 can be manufactured easily and efficiently. However, this is not limited to this. For example, the valve box seat portion 111 may be directly formed on the inner surface of the valve box 11 without being formed on the inner surface of the annular member 112.

[0053] In the above embodiment, the valve 10 is a gate valve, but the present invention is not limited to this. The valve body seat portion and the valve disc seat portion may be configured in the same manner as in the above embodiment in other types of valves such as a globe valve, a check valve, a safety valve, a ball valve, and a butterfly valve.

[0054] <Other> Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0055] 10... valve, 11... valve body, 11K... opening, 11S... internal space, 12... valve cover, 12K... through hole, 13... valve stem, 14... valve body, 21... valve drive mechanism, 111... valve body seat portion, 112... annular member, 141... valve body seat portion, 201... base material, 202... build-up weld portion, 202a... smooth weld portion, 211... handle, 212... motor, 300... welding torch, 301... shielding gas nozzle portion, 302... powder nozzle portion, 303... plasma gas nozzle portion, 304... electrode, AR... plasma arc, CW... cooling water, DE... defect, PG... plasma gas, PW... powder, SG... shielding gas, WD... welding direction

Claims

1. A valve body having a valve body seat portion; A valve body having a valve body seat portion; A valve having One of the valve body seat portion and the valve body seat portion is formed of a Co-based alloy cladding material, The other of the valve body seat portion and the valve disc seat portion is formed of an overlay material of an Fe-based alloy, The Fe-based alloy overlay material is produced by performing filler welding on an overlay weld portion formed by plasma arc welding. valve.

2. The Fe-based alloy is Cr is 23.0% or more and 26.0% or less, Mo is 1.8% or more and 2.2% or less, Si is 3.1% or more and 3.5% or less, C is 1.10% or more and 1.35% or less, Ni is 3.7% or more and 5.0% or less, Mn is 4.0% or more and 5.0% or less, B is 0% or more and less than 0.002%, S is 0% or more and less than 0.01%, P is 0% or more and less than 0.020%, N is 0% or more and less than 0.18%, The balance has a chemical composition consisting of Fe and unavoidable impurities.

2. The valve of claim 1.

3. Used in light water reactors of nuclear power plants, 3. A valve according to claim 1 or 2.

4. A valve body having a valve body seat portion; A valve body having a valve body seat portion; A method for manufacturing a valve having the following features: A Co-based alloy cladding material forming step of forming one of the valve body seat portion and the valve body seat portion with a Co-based alloy cladding material; a Fe-based alloy cladding material forming step of forming the other of the valve body seat portion and the valve element seat portion with a cladding material of an Fe-based alloy; having In the Fe-based alloy overlay material forming step, a fillet welding is performed on the overlay weld portion formed by plasma arc welding to produce the Fe-based alloy overlay material. A method for manufacturing a valve.

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