JPH0379590B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention. A control valve that is suitable for regulating the pressure and flow rate of high-temperature, high-pressure fluids, especially those used in steam power plant start-up bypass valves, feedwater flow rate control valves, spray flow rate control valves, and feedwater pump recirculation valves. Regarding. [Prior Art] Generally, a control valve includes a casing including an inlet flow path, an outlet flow path, and a valve chamber, and a valve seat formed in the valve chamber of the casing. The valve body is movable toward and away from the valve body, and the pressure and flow rate of the fluid flowing in from the inlet channel is controlled by a variable restrictor formed between the valve body and the valve seat. The fluid can be continuously adjusted and discharged from the outlet channel. By the way, in the above-mentioned control valve, since the flow velocity of the fluid increases rapidly at the variable restrictor formed between the valve body and the valve seat, foreign objects in the fluid or the fluid itself can violently attack the valve body and the valve seat. They collide and easily erode them, and sometimes cause local cavitation, which causes cavitation erosion and fluid leakage between the valve body and the valve seat closure. Changes in the area of the constriction formed between the valve body and the valve seat may impede the flow rate adjustment characteristics. In addition, in control valves that handle high-temperature water, the interaction between the electric charge of suspended particles such as iron ions contained in the water and the electrostatic force on both metal surfaces of the valve body or valve seat causes iron to be deposited, especially near the throttle part. Suspended particles such as ions are attracted to the metal surface, causing scale to adhere and accumulate on the surface of the valve body or valve seat. This buildup of scale can cause fluid leakage between the valve body and valve seat closure, reduce the area of the constriction formed between the valve body and the valve seat, and sometimes cause a significant increase in the discharge flow rate. This results in a shortage and it becomes impossible to adjust the flow rate. Conventionally, in order to protect the liquid-contact surfaces of the valve body and valve seat from erosion near the throttle part, cobalt alloys such as stellite, which have high corrosion resistance, are integrally formed on these surfaces by metal welding, etc. A control valve whose valve body and seat itself are made of martensitic heat-treated hardened stainless steel such as SUS440C is used to reduce the amount of corrosion. [Problems to be Solved by the Invention] However, in recent years, the operating conditions for each control valve have become stricter due to increases in the design pressure and temperature of the above-mentioned power plants and the frequent start-up/stop operation of plants. It has become difficult for control valves to deal with erosion. Furthermore, no simple and effective method for preventing scale adhesion and accumulation on the valve body or valve seat of a control valve that regulates high-pressure, high-temperature water has yet to be proposed. The present invention aims to provide a control valve that improves the corrosion resistance of the valve body and valve seat, prevents scale from adhering to the valve body and valve seat, and provides good controllability over a long period of time. . [Means for Solving the Problems] The present invention includes a casing including an inlet flow path, an outlet flow path, and a valve chamber, a valve seat supported by the casing, and a valve seat formed in the valve chamber of the casing. and a valve body that is movable toward and away from the valve seat, the surfaces of the valve seat and the valve body are coated with titanium carbonitride (TiCN), titanium nitride (TiN), and alumina. A composite multiple coating material consisting of (Al ₂ O ₃ ) is applied. [Function] According to the present invention, the surfaces of the valve seat and the valve body are formed of a composite multi-coating material which is a ceramic material with extremely high erosion resistance. Therefore, it is possible to improve the corrosion resistance of the valve body and valve seat, prevent scale from adhering to the valve body and valve seat, and obtain a control valve with good controllability over a long period of time. . [Embodiment] FIG. 1 is a sectional view showing a control valve 10 according to an embodiment of the present invention. The control valve 10 has an inlet flow path 11
a casing 14 including an outlet flow path 12 and a valve chamber 13; a valve seat 15 disposed inside the casing 14; It has a valve body (valve stem) 16. The valve seat 15 is fixed to the casing 14 in a screwed state, and includes a guide portion 17 that guides the intermediate portion of the valve body 16.
It includes a closing portion 18 that connects the inlet flow path 11 and the outlet flow path 12, a pocket portion 19, and a discharge hole portion 20. Further, the valve body 16 forms a constricted portion between the shut-off portion 21 that can be brought into close contact with the shut-off portion 18 of the valve seat 15 and the shut-off portion 18 of the valve seat 15, and the area of the constricted portion is determined by the valve opening degree. The plug portion 22 has a predetermined contour shape that is variable as the shape changes. A portion of the valve body 16 that protrudes from the casing 14 is provided with a threaded portion 23 to which a valve opening/closing actuator can be connected. Further, a packing 24 is disposed between the intermediate portion of the valve body 16 and the casing 14. Further, a breech block 27 is disposed at the lower part of the casing 14 via a packing 26 supported on the back side by a breech screw 25 screwed into the casing 14.
Breach block 27 has a drain hole 29 which is closed by a plug 28. Therefore, the closing portion 18, pocket portion 19 of the valve seat 15,
Each of the fluid contact parts mainly including the discharge hole 20, the shutoff part 21 of the valve body 16, and the plug part 22 is made of Stellite (a trademark of Haynes Co., Ltd.) on a base material made of stainless steel. ), etc., or SUS440C.
Three types of ceramics: titanium carbonitride (TiCN), titanium nitride (TiN), and alumina (Al ₂ O ₃ ) are deposited on the underground surface of martensitic stainless steel, which has been heat-treated to a specified hardness. A thin film of a composite multilayer coating material is formed by sequentially layering materials in a tightly adhered state, as shown in FIG. 2, for example. In the chemical vapor deposition method of the above-mentioned composite multiple coating material, the workpiece is placed in a sealed retort heated to a temperature in the range of approximately 700 to 1050°C, and gaseous TiCl ₄ or AlCl ₃ and H ₂ , CH ₄ , and N ₂ are used. , CO ₂ are supplied to chemically form the above-mentioned composite multi-layered coating material on the surface of the object to be treated. The basic chemical reaction formula is as follows. 2TiCl ₄ +N ₂ +3H ₂ +CH ₄ →2TiCN+8HCl+H ₂ 2TiCl ₄ +N ₂ +4H ₂ →2TiN+8HCl 2AlCl ₃ +3CO ₂ +3H ₂ →Al ₂ O ₃ +3CO+6HCl This chemical vapor deposition coating method requires a high processing temperature, so Atoms such as C actively diffuse between the surfaces of the treated product, resulting in strong adhesion. Moreover, a uniform coating can be obtained even on a workpiece having a complicated shape. Table 1 shows the physical properties of each material constituting the above composite multiple coating material.
It is as follows. _Al2O3 has oxidation resistance, corrosion resistance _,
It has excellent heat resistance and an extremely low coefficient of friction. As the stellite, for example, stellite No. 6 and stellite No. 12 as shown in Table 2 are used. FIG. 3 is a diagram showing the surface hardness of valve seats and valve bodies coated with various materials. child

【table】

According to Figure 3 of [Table], the surface hardness of the composite multi-layered coating material shown in Figure 2 coated on the surface of Stellite No. 6 deposited on the base material of SUS316 is the same as that of other treatment methods. It is extremely hard compared to HmV3000 (microbits hardness).
It is recognized that the hardness is extremely high. FIG. 4 is a diagram showing weight loss based on accelerated erosion test using high-pressure water. According to this Figure 4, Stellite No. 1 is deposited on the base material of SUS316.
It is recognized that the reduced weight of the test piece obtained by coating the surface of No. 6 with the composite multiple coating material shown in FIG. 2 has extremely high corrosion resistance. That is, as seen in FIGS. 3 and 4 above, according to the control valve 10 in which a thin film of the composite multiple coating material is formed on each of the fluid contact parts of the valve seat 15 and the valve body 16, the throttle It is clear that the valve seat 15 and the valve body 16 can be strongly protected from the collision of high-speed fluid or cavitation that sometimes occurs, and the occurrence of erosion can be prevented. In addition, in the accelerated erosion test using high-pressure water shown in Figure 4, in order to intentionally cause erosion damage to the test piece in a short period of time, the ultra-high pressure water flux is violently collided with the local part of the test piece from a sharp slit to accelerate the damage. It goes without saying that the absolute values of the damage time and the amount of damage do not directly apply to the control valve 10 according to the above embodiment, as this was a comparative test using a testing device designed to perform the same. Next, the operation of the above embodiment will be explained. Due to the operation of the valve opening/closing actuator, the valve body 16
is moved in the axial direction, and when the plug part 22 of the valve body 16 forms a constriction part with a predetermined gap between the plug part 22 of the valve body 16 and the shutoff part 18 of the valve seat 15, the fluid flowing into the valve chamber 13 from the inlet channel 11 passes through the constriction part. When passing through the chamber, the pressure or flow rate is adjusted and the fluid is discharged from the pocket 19 of the valve seat 15 to the outlet passage 12 via the discharge hole 20. Here, the high-speed fluid that is rapidly accelerated by the constriction section moves between the plug section 22 of the valve body 16 and the shutoff section 2.
1 violently collides with the valve seat 15, and furthermore, the valve seat 15 is
8. Impact is also applied to the pocket 19, but the surface of those parts in contact with the fluid is made of cobalt alloy such as stellite, which has very high corrosion resistance as described above, or
Because the surface of martensitic stainless steel such as SUS440C is coated with a thin film of the above-mentioned composite multi-layered coating material having ultra-high hardness,
Not easily eroded. Further, even if the fluid supplied to the control valve 10 is high-pressure, high-temperature water and contains suspended particles such as iron ions, the plug portion 22 of the valve body 16 forming the throttle portion, the shut-off portion 21, or The surfaces of the shutoff portion 18, pocket portion 19, and discharge hole portion 20 of the valve seat 15 are covered with the composite multi-coating material, which is an inert inorganic material with high non-adhesive properties, so that it does not adhere to the metal surface. In addition to suppressing the generated electrostatic force, even if suspended particles such as iron ions are attracted to the plug portion 22 and the shutoff portion 21 of the valve body 16 or the shutoff portion 18 of the valve seat 15, the non-resistance of the composite multiple coating material Due to its adhesive properties, it does not easily adhere to them and is discharged from the outlet channel 12 while remaining contained in the fluid, making it possible to prevent a large shortage of fluid due to scale adhesion. . Furthermore, even when the valve is fully closed, it is possible to obtain reliable shut-off performance by making it difficult for scale to adhere to the shut-off portion 21 of the valve body 16 or the shut-off portion 18 of the valve seat 15. It is also possible to prevent erosion damage in the closing portions 18, 21 due to jamming. That is, according to the above embodiment, when adjusting the flow rate, it is possible to reduce the occurrence of erosion and the adhesion and accumulation of scale caused by the presence of the constriction portion formed between the valve seat 15 and the valve body 16. becomes possible. Therefore, the valve seat 15 and the valve body 16 will not have to be replaced frequently due to the occurrence of erosion, and the adhesion of scale will not cause a significant shortage of flow rate, which will result in the inability to adjust. [Effects of the Invention] As described above, the present invention includes a casing that includes an inlet flow path, an outlet flow path, and a valve chamber, a valve seat that is supported by the casing, and that is formed in the valve chamber of the casing. and a valve body that is movable toward and away from the valve seat, the surfaces of the valve seat and the valve body are coated with titanium carbonitride (TiCN), titanium nitride (TiN), and alumina. A composite multiple coating material consisting of (Al ₂ O ₃ ) is applied. Therefore,
It is possible to improve the corrosion resistance of the valve body and valve seat, prevent scale from adhering to the valve body and valve seat, and obtain a control valve with good controllability over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a control valve according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the state of application of the composite multiple coating material in the present invention, and FIG. 3 is a surface hardness of the composite multiple coating material. FIG. 4 is a diagram showing the results of an accelerated erosion test using high-pressure water. 10... Control valve, 11... Inlet channel, 12...
Outlet flow path, 13... valve chamber, 14... casing,
15... Valve seat, 16... Valve body.

Claims (1)

[Claims] 1. A casing including an inlet flow path, an outlet flow path, and a valve chamber, a valve seat formed in the valve chamber of the casing, and a valve seat supported by the casing and in contact with the valve seat within the valve chamber of the casing. In a control valve having a valve body that is movable in the direction of separation, the surfaces of the valve seat and the valve body are coated with titanium carbonitride (TiCN), titanium nitride (TiN), or alumina (Al ₂ O ₃ ). A control valve characterized by being coated with a composite multiple coating material. 2. The control valve according to claim 1, wherein the composite multiple coating material is adhered to the surface of a cobalt alloy-based hardened material that is hardened and formed on the surface of a base material that forms the valve seat and the valve body. .