Valve apparatus with NANO nitride layer

Abstract

In order to improve durability and economy of operation, the present invention provides a valve apparatus with a nano nitride layer, the apparatus comprising: a valve body unit having a flow path formed therein; a valve disk which is disposed inside the valve body unit, selectively opens and closes the flow path through one-way rotation, and has a plasma nano nitride layer coated on an opening / closing surface; and a metal sheet which is disposed on each edge of the flow path, is selectively in close contact with and faces the valve disk, and has a nano nitride layer coated on a surface facing the opening / closing surface.

Description

Valve device formed with a nanonitride layer

[0001] The present invention relates to a valve device having a nanonitride layer formed thereon, and more specifically, to a valve device having a nanonitride layer formed thereon that improves durability and operational economy.

[0002] Generally, a valve device is a device installed in piping for the transport of powders or liquids to control the opening and closing of fluid flow or to regulate the flow rate.

[0003] Here, a valve device used in a power plant includes a stem that operates a disc unit that moves up and down within a body, and a seat unit that seals by wrapping around and tightly adhering to the outer surface of the disc unit.

[0004] Furthermore, when designing conventional valve devices, excellent airtightness is required to prevent leakage of the fluid being transported, and durability is required to prevent wear on the seat caused by the valve device. In addition, the fluid flow rate must be accurately controlled through the rotational operation of the disc unit. In particular, valve devices for power plants exposed to high temperature and high pressure environments must ensure consistent airtightness, durability, control accuracy, and ease of operation at all times, regardless of the volume expansion or contraction of the disc unit, even under such conditions.

[0005] Meanwhile, conventionally, disc units were manufactured using soft synthetic resin-based materials such as Teflon or by welding metal materials with high-hardness welding metal; however, while this reduces manufacturing costs, it presented the problem of very high operating torque because high pressure had to be applied to the seat unit during the assembly process. Additionally, due to the material properties of Teflon, durability was poor, leading to a shortened lifespan of the valve device.

[0006] Therefore, there have been attempts to form the disc unit from a metal material with a surface treatment layer to enable application in high-temperature and high-pressure environments. However, there was a problem in that the surface treatment layer was removed due to wear during the grinding process to correct dimensional errors caused by thermal deformation during the welding process of the valve body portion of the valve seat, which weakened durability and shortened the lifespan of the valve device.

[0007] To solve the above-mentioned problems, the present invention aims to provide a valve device formed with a nanonitride layer that improves durability and operational efficiency.

[0008] To solve the above problem, the present invention provides a valve device having a nanonitride layer formed thereon, comprising: a valve body portion having a fluid passage formed therein; a valve disc disposed inside the valve body portion and selectively opening and closing the fluid passage through unidirectional rotation, wherein a plasma nanonitride layer is coated on the opening / closing surface; and a metal sheet disposed at the edge of the fluid passage, which is opposed to and selectively in contact with the valve disc, wherein a nanonitride layer is coated on the opposing surface opposite to the opening / closing surface.

[0009] Through the above-mentioned means of solution, the present invention provides the following effects.

[0010] First, the nanonitride layer strengthens the surface and increases resistance to wear, thereby reinforcing the internal structure of the metal and increasing resistance to corrosion and wear, which can extend the sealing performance of the valve device and its service life in high pressure and high temperature environments.

[0011] Second, despite the grinding process for flattening to correct welding thermal deformation, the hardness and durability of the opposing surface can be significantly improved by alternately maintaining the high-hardness surface nitriding layer formed inside the uneven grooves created by the resin wire processing.

[0012] FIG. 1 is a cross-sectional view of a valve device having a nanonitride layer formed thereon according to an embodiment of the present invention.

[0013] FIG. 2 is an enlarged cross-sectional view of section "A" of FIG. 1.

[0014] FIG. 3a is an enlarged cross-sectional view of the opposing surface of a metal sheet according to an embodiment of the present invention.

[0015] FIG. 3b is an enlarged cross-sectional view showing the state in which the nanonitride layer on the opposing surface of a metal sheet is polished according to an embodiment of the present invention.

[0016] Hereinafter, a valve device having a nanonitride layer formed thereon according to a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0017] FIG. 1 is a cross-sectional view of a valve device having a nanonitride layer formed according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of part "A" of FIG. 1, FIG. 3a is an enlarged cross-sectional view of the opposing surface of a metal sheet according to an embodiment of the present invention, and FIG. 3b is an enlarged cross-sectional view showing the state in which the nanonitride layer on the opposing surface of a metal sheet according to an embodiment of the present invention has been polished.

[0018] As seen in FIGS. 1 to 3b, a valve device (100) having a nanonitride layer formed according to one embodiment of the present invention includes a valve body (10), a valve disc (20), a metal seat (30), and a valve stem (40).

[0019] Here, the valve body (10) has a flow path (10a) formed inside, and since a high-temperature, high-pressure fluid flows through the flow path, the valve body (10) is formed of a metal material.

[0020] In addition, the valve disc (20) is positioned inside the valve body (10) and selectively opens and closes the flow path (10a) through unidirectional up-and-down movement, and a plasma nanonitride layer (50) is formed as a coating on the surface that contacts the metal sheet (30) when the flow path (10a) is closed. Here, the surface of the valve disc (20) that comes into mutual contact when the valve device (100) is closed is called the opening / closing surface (21), and the surface of the metal sheet (30) that faces the opening / closing surface is called the opposing surface (31).

[0021] Additionally, the metal sheet (30) is positioned at the edge of the fluid path (10a) and is selectively in close contact with the valve disc (20) in opposition to it. A nanonitride layer is formed on the opening / closing surface (21) and the opposing surface (31), which face each other and come into surface contact when closed. Here, the bodies of the valve disc (20) and the metal sheet (30) are each provided with the same material, and may be provided with stainless steel such as STS316.

[0022] Through this, even when ultra-low temperature powder or fluid at -197°C or high temperature or high pressure powder or fluid at 750°C or higher flows through the above Euro (10a), the above valve disc (20) and the above metal sheet (30), which have a constant expansion coefficient, can be maintained in a state of close contact without being separated from each other.

[0023] Meanwhile, so that the valve disc (20) may be selectively raised and lowered to open and close the fluid path (10a), the lower end of the valve stem (40) may be connected to the valve disc (20) and the upper end may be exposed to the outside of the valve body (10). At this time, the opening and closing state of the fluid flow is controlled by vertical frictional movement between the valve disc (20) and the metal seat (30) caused by the raising and lowering operation of the valve stem (40).

[0024] That is, when the valve device (100) is opened, the valve stem (40) moves up and down, causing the valve disc (20) to rise vertically. At this time, when the valve disc (20) rises, the close contact with the metal seat (30) is released, and the fluid passage (10a) through which the fluid passes is opened. Additionally, when the valve disc (20) is fully raised, the valve device (100) is fully opened, allowing the fluid flow to be maximized.

[0025] Conversely, the valve disc (20), which is lowered by operating the valve stem (40), can have its flow path (10a) blocked as it comes into complete contact with the metal seat (30).

[0026] As such, since the opening and closing process through friction between the valve disc (20) and the metal seat (30) is performed repeatedly, the surfaces (21, 31) that are frictionally rubbed during this process must have excellent characteristics regarding structural strength, machining precision, hardness, corrosion resistance, and erosion resistance.

[0027] As shown in FIG. 3a, a surface serration layer for forming a surface irregular groove (32) is formed on the opposing surface (31) of the metal sheet (30) opposite the opening / closing surface (21) of the valve disc (20), and a nanonitride layer is formed on the outer surface of the surface serration layer. Here, the opening / closing surface (21) and the opposing surface (31) can be understood as surfaces that come into mutual contact when the valve device (100) is closed.

[0028] At this time, the depth of the uneven groove (32) of the resin wire processing layer may be formed in the range of 15 to 30 μm. In addition, the nanonitriding layer (50) preferably includes a surface nitriding layer (51) with a thickness of 2 to 5 μm and a penetrating nitriding layer (52) with a thickness of 50 to 70 μm.

[0029] In detail, the resin wire processing layer can be formed by a rotating resin wire processing machine as a type of surface roughening process, with fine grooves (32) having a depth of 15 to 30 μm alternately formed on the surface.

[0030] Additionally, a plasma nanonitride layer is coated on each opening / closing surface (21) and opposing surface (31) of the valve disc (20) and each of the metal sheets (30). Specifically, the valve disc (20) and the metal sheet (30) are placed on a jig provided inside a chamber, and an inert gas containing argon is filled inside the chamber so that the inside of the chamber is substantially vacuumed.

[0031] Subsequently, the process includes a heating step in which hydrogen gas and nitrogen gas are injected into the chamber and heated until a preset first temperature is reached. At this time, it is preferable that the first temperature be set to 460 to 470°C.

[0032] Here, an electrode for generating high-density plasma is provided in the chamber, and the electrode may be positioned along the inner wall surface of the chamber. At this time, a cover is placed on the top of the chamber to confine the discharged plasma particles and direct them downward to form high-density plasma and nitrogen atomic ions. At this time, the cover may be an insulator such as ceramic, glass, or quartz, or it may be configured such an insulator in contact with the electrode and a high-temperature heat-resistant metal further disposed thereon. Furthermore, if the cover in contact with the electrode is made of the same metal material as the electrode, a floating discharge may be induced by applying an alternating current voltage.

[0033] In addition, when voltage is applied to the electrode through a separate voltage application device, high-density plasma and nitrogen ions formed in the part surrounded by the electrode can settle on the valve disc (20) and metal sheet (30), which are the workpieces, and nitriding treatment can be performed. At this time, the temperature required for nitriding treatment can be reached solely by the temperature generated by applying power to the electrode without using a separate heater, and the electrode can be configured as a screen type.

[0034] Through this, the nanonitride layer (50) is formed by nano-sizing high-density, low-energy active nitrogen atoms and adsorbing, penetrating, and diffusing them onto the opening / closing surface (21) and the opposing surface (31) to form a coating treatment on the surface. In this way, the nanonitride layer (50) can improve the durability of the valve device (100) by strengthening the surface hardness and increasing resistance to wear, thereby increasing resistance to corrosion and wear.

[0035] The difference in hardness between the stainless steel material and the stainless steel material with the nanonitride layer (50) formed thereon is as shown in Table 1 below. At this time, the measured value is the average value measured after polishing the surface of the measurement surface.

[0036] Material Measurements Stainless Steel 520 HV Stainless Steel + Stellite Weld Bead Coating Layer 642 HV Stainless Steel + Stellite Weld Bead Coating Layer + Nanonitride Layer 857 HV

[0037] As shown in the table above, stainless steel with a nanonitride layer (50) formed thereon can provide an improvement in hardness value (HV) that is 60% higher than that of ordinary stainless steel. Through this, the hardness of the surfaces of the valve disc (20) and the metal sheet (30) is improved, and the airtightness at the surfaces (21, 31) that are in contact is increased, so leakage can be prevented even under high pressure conditions.

[0038] Meanwhile, for the aforementioned surface treatment, it is significantly more economically advantageous to manufacture and assemble the metal sheet (30) separately from the valve body (10). Accordingly, it is preferable that the metal sheet (30) be welded to the valve body (10) to form a welded portion (35).

[0039] At this time, during the process of forming the welded portion (35), deformation may occur in which the metal sheet (30) expands due to welding heat. As a result, deformation may occur inwardly on a part of the opposing surface (31) formed on the metal sheet (30). At this time, it was confirmed that the amount of expansion deformation of a part of the opposing surface (31) due to welding is in the range of 15 to 30 μm.

[0040] Therefore, after the formation of the welded portion (35), the opposing surface (31) needs to be polished to correct the deformation caused by the welding and flatten it. However, in the conventional structure, there was a problem in that the aforementioned nanonitride layer was substantially cut off during the polishing process, resulting in a decrease in hardness.

[0041] To solve this, it is preferable that before the nanonitride layer is formed, the opposing surface (31) of the metal sheet (30) has alternating fine grooves (32) formed by resin wire processing to a depth of 15 to 30 μm. In this way, the nanonitride layer (50) is formed on the opposing surface (31) in which the fine grooves (32) are formed.

[0042] Referring to FIGS. 3a and 3b, the nano-nitriding layer (40) may be formed on the opposing surface (31) in which fine uneven grooves (32) are formed by the resin wire processing, and the nano-nitriding layer (40) may include a surface nitriding layer (41) with a thickness of 2 to 5 μm and a penetrating nitriding layer (52) with a thickness of 60 to 70 μm. At this time, the surface nitriding layer (51) has a higher hardness than the penetrating nitriding layer (52). Therefore, it is important to ensure that the surface nitriding layer (51) is maintained at least partially.

[0043] At this time, when forming a welded portion (35) to join the metal sheet (30) to the valve body portion (10), the amount of thermal deformation caused by expansion on at least a portion of the opposing surface (31) was measured to be 15 to 30 μm. That is, it is preferable that the amount of thermal deformation and the depth of the uneven groove (32) of the resin wire processing layer be set to be equal to each other.

[0044] Accordingly, the polishing process for flattening the thermally deformed opposing surface (31) of the metal sheet (30) is limited to a depth of 15 to 30 μm. Through this, the opposing surface (31) of the metal sheet (30) is polished and flattened, but the hardness improved by the nanonitride layer (50) is maintained, thereby ensuring high sealing performance and durability.

[0045] That is, during the polishing process, the protrusions of the uneven grooves (32) formed by the resin wire processing are cut and removed, but the surface nitriding layer (41) formed in the grooves of the fine uneven grooves (32) can be maintained alternately. That is, the surface nitriding layer (51) is not completely removed from the opposing surface (31) but is alternately exposed and formed. At this time, the penetrating nitriding layer (52) formed inside the opposing surface can substantially remain mostly intact.

[0046] In this way, despite the grinding process for flattening to correct welding thermal deformation, the hardness and durability of the opposing surface (31) can be significantly improved by alternately maintaining the high-hardness surface nitriding layer (51) formed inside the uneven groove (32) created by the resin wire processing.

[0047] Meanwhile, the metal sheet (30) is formed of a metal material, and it is preferable that a welding bead coating layer (30a) made of Stellite material is coated on the opposite surface (31). That is, it is preferable that a welding bead coating layer (30a) made of Stellite material is formed first on the opposite surface (31) of the metal sheet, and then an uneven groove (32) formed by a resin wire processing layer and a nanonitriding layer (50) are sequentially formed on the welding bead coating layer (30a).

[0048] Through this, the economic efficiency of the device can be improved by reducing the use of expensive Stellite material. Here, Stellite metal is an alloy of cobalt mixed with chromium, tungsten, iron, carbon, etc., and has excellent heat resistance and corrosion resistance.

[0049] Meanwhile, it is preferable that a nanonitride layer be formed only on the area facing the opposite surface (31) of the metal sheet (30) when the valve device (10) is closed on the opening / closing surface (21) of the valve disc (20).

[0050] In detail, a plurality of linear grooves (20a) formed along the lifting direction of the valve stem (40) may be formed on the remaining contact surface, excluding the opening / closing surface (31) of the valve disc (30), in order to reduce the contact area during the lifting process. At this time, the extension direction of the linear grooves (20a) is formed to coincide with the lifting direction of the valve stem.

[0051] Through this, the contact area between the remaining contact surface excluding the opening / closing surface (31) of the valve disc (30) and the opposing surface (31) of the metal sheet (30) during the lifting process can be reduced, thereby minimizing the occurrence of wear.

[0052] Ultimately, according to one embodiment of the present invention, a nanonitride layer is formed on the valve disc (20) and the metal sheet (30) to improve the hardness and wear resistance of the parts and to maximize corrosion resistance and high-temperature stability. Through this, the sealing performance and durability of the valve device (100) are improved, and it is desirable that stable performance is maintained even in high pressure and high temperature environments.

[0053] In addition, the technology for forming the uneven groove (32) and the nanonitride layer (50) by resin line processing of such a valve device (100) can be applied to various valve devices, such as globe valves or check valves, where opposing surfaces are required for sealing.

[0054] As explained above, the present invention is not limited to each of the embodiments described above, and modifications can be made by those skilled in the art without departing from the scope claimed in the claims of the present invention, and such modifications fall within the scope of the present invention.

[0055] The present invention can be applied to industrial fields for valve devices that control the flow rate of a fluid.

Claims

1. A valve body portion in which a flow path is formed internally; A valve disc disposed inside the valve body portion and selectively opening and closing the fluid path through unidirectional rotation, wherein a plasma nanonitride layer is coated and formed on the opening and closing surface; and A valve device having a nanonitride layer formed thereon, comprising a metal sheet that is disposed on the edge of the above Euro and is selectively in close contact with the above valve disc, and has a nanonitride layer coated on the opposite surface facing the opening / closing surface.

2. In Paragraph 1, A valve device having a nanonitride layer formed thereon, characterized in that a resin wire processing layer for forming surface irregularities is formed on the opposing surface of the metal sheet opposite to the opening / closing surface of the valve disc, and a nanonitride layer is formed on the outer surface of the resin wire processing layer.

3. In Paragraph 2, The unevenness depth of the above resin wire processing layer is formed in the range of 15 to 30 μm, and A valve device having a nanonitride layer formed thereon, characterized in that the nanonitride layer comprises a surface nitride layer with a thickness of 2 to 5 μm and a penetrating nitride layer with a thickness of 50 to 70 μm.

4. In Paragraph 3, A valve device having a nano-nitride layer formed thereon, characterized in that the metal sheet is welded and joined to the valve body, and the surface nitride layer is alternately exposed and formed on the opposing surface by grinding to correct deformation caused by welding heat.

5. In Paragraph 2, The above metal sheet is formed of a metal material, and a weld bead coating layer made of Stellite is formed on the opposing surface, and A valve device having a nanonitride layer formed thereon, characterized in that the resin wire processing layer and the nanonitride layer are formed on the weld bead coating layer.

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