Precision Casting Technology of Stainless Steel Impellers for Nuclear Power Plants

Abstract

The present invention relates to the field of precision casting and discloses a precision casting process for a stainless steel impeller for nuclear power, comprising: S1, pressing a wax mold by using an investment casting process and connecting the wax rods into a tree shape; S2, coating the surface of the wax mold with refractory material, dewaxing the mold with a dewaxing device after drying to obtain a hollow shell, and then roasting the shell at a high temperature; S3, selecting duplex stainless steel for smelting in an electric furnace, heating the molten steel to a predetermined pouring temperature, and bottom-pouring or side-pouring the shell; S4, removing the shell after natural cooling and subjecting the impeller to a solid solution treatment; S5, sandblasting, shot blasting and sand cleaning, and non-destructive testing; wherein the dewaxing device used in S2 comprises a tank body, a rotatable tray in the tank body, and a plurality of adjustable fixing clamps on the tray to meet different shell fixing requirements; the top of the tank body is provided with an inlet and a discharge port, equipped with an automatic sealing door, and the bottom is connected to a wax liquid collection tank with a liquid level sensor installed therein; the inner wall of the tank body is provided with a heating chamber equipped with a heating element, and the outer wall is wrapped with a heat-insulating material.

Description

Technical Field

[0001] The present invention relates to the field of precision casting, and in particular to a precision casting process for stainless steel impellers for nuclear power plants. Background Art

[0002] As a highly efficient, low-carbon energy source, nuclear power is playing an increasingly important role in the energy mix. The safe and stable operation of nuclear power equipment is crucial. Stainless steel impellers, as key components, are widely used in pumps, compressors, and other equipment within nuclear power systems. Their performance directly impacts the efficiency and reliability of the entire nuclear power system.

[0003] Conventional stainless steel impeller casting processes have limitations when facing the stringent requirements of the nuclear power industry for high precision, high reliability, and corrosion resistance. For example, during the dewaxing step of precision casting for nuclear power stainless steel impellers, conventional dewaxing equipment often suffers from long dewaxing times, high wax residue, and high energy consumption, impacting overall production efficiency and product quality. Therefore, developing an advanced precision casting process for nuclear power stainless steel impellers is of great practical significance. Summary of the Invention

[0004] The purpose of the present invention is to provide a precision casting process for stainless steel impellers for nuclear power, so as to solve at least one of the technical problems of traditional dewaxing equipment, namely, long dewaxing time, high wax residue and high energy consumption.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] The precision casting process of stainless steel impeller for nuclear power includes the following steps:

[0007] S1, using the investment casting process to press the wax model, and connecting the individual wax models into a tree-like structure through wax rods;

[0008] S2. Coating a refractory material on the surface of the wax mold. After the coating is completed and dried, the shell is dewaxed using a dewaxing device to hollow out the shell, and then the shell is placed in a high-temperature furnace for baking;

[0009] S3. Select duplex stainless steel and melt it in an electric furnace. Heat the molten steel to the predetermined pouring temperature and pour it into the mold shell using bottom pouring or side pouring.

[0010] S4: After the shell is naturally cooled, the shell is removed to obtain the impeller and undergo solution treatment;

[0011] S5. Remove the impeller surface and internal residues by sandblasting and shot blasting, and perform flaw detection using non-destructive testing technology;

[0012] The dewaxing equipment used in S2 includes: a controller and a tank body, a rotating motor is provided in the tank body, a tray is provided at the output end of the rotating motor, a plurality of electric slide rails are provided on the tray, and a fixing clamp is installed on the electric slide rail; a feed port and a discharge port are provided on the top of the tank body, and both the feed port and the discharge port are equipped with automatic sealing doors; a wax liquid collection tank is connected to the bottom of the tank body, and a liquid level sensor is provided in the wax liquid collection tank; a heating chamber is provided on the inner wall of the tank body, a heating element is provided in the heating chamber, and the outer wall of the tank body is wrapped with heat insulation material.

[0013] Furthermore, the dewaxing equipment further comprises: an auxiliary dewaxing mechanism;

[0014] The auxiliary dewaxing mechanism includes: an ultrasonic dewaxing tank and an air compressor. The ultrasonic dewaxing tank is set on the tray, and multiple ultrasonic transducers are evenly distributed inside the ultrasonic dewaxing tank; the air compressor is installed on the outside of the tank body, and the air compressor is connected to the inside of the shell through a pipe. An air nozzle with an adjustable angle is installed at the end of the pipe.

[0015] Furthermore, an angle adjustment component is provided at the end of the pipe, and the angle adjustment component is used to adjust the angle of the air nozzle;

[0016] The angle adjustment assembly includes a screw rod, which is rotatably installed on the end of the pipe. A ring that can spirally move is provided on the screw rod, and a nozzle is fixed on the ring. The nozzle and the pipe are softly connected by a hose. The end of the screw rod is connected to the drive motor, and the drive motor is installed on the end of the pipe.

[0017] Furthermore, the auxiliary dewaxing mechanism further includes: a lifting assembly, which is used to enable the pipe to enter and exit the mold shell; the lifting assembly includes:

[0018] A lifting bracket installed on the top of the tank body includes a vertical guide rail and a slider that can slide up and down along the guide rail. The slider is fixedly connected to a horizontal mounting plate, and the pipe is fixedly mounted on the mounting plate.

[0019] The lifting drive module is connected to the slider transmission, and is used to drive the slider to move up and down along the guide rail, thereby driving the pipeline to move up and down, so that the pipeline can enter and exit the mold shell.

[0020] Furthermore, the lifting drive module includes: a float arranged in the wax collection tank, a connecting rod fixed on the top of the float, a bevel fixed on the other end of the connecting rod, the bevel slidingly installed on the wall of the wax collection tank, the bevel contacts with the rack on one side, the rack is slidingly installed on the wall of the wax collection tank, and a reset spring is provided on the side of the rack away from the bevel, and the rack is meshed with the gear, the gear is coaxially fixed to the bottom end of the screw, the screw is spirally connected to the slider, and the screw is rotatably installed on the lifting bracket.

[0021] Furthermore, the lifting drive module includes: an electric push rod or a hydraulic cylinder, an air compressor electrically connected to a liquid level switch, and the liquid level switch electrically connected to a liquid level sensor;

[0022] The controller is electrically connected to the liquid level sensor and the lifting drive module; when the liquid level sensor detects that the wax liquid height in the wax collection tank reaches a first set value, and the second set value is greater than the first set value, the controller controls the lifting drive module to move and lower the pipeline into the interior of the shell; when the liquid level sensor detects that the wax liquid height in the wax collection tank reaches the first set value, the air compressor starts working and the controller controls the lifting drive module to lower the pipeline.

[0023] Furthermore, a limiting block is provided on the wall of the wax liquid collecting tank, and the distance between the limiting block and the bottom wall of the lower wax liquid collecting tank serves as the movable space of the float.

[0024] Furthermore, two air nozzles are installed at the end of the pipeline and are symmetrically distributed in a Y shape.

[0025] Beneficial effects of the present invention:

[0026] (1) The rotating design of the tray in the present invention allows the mold shell to be heated more evenly during the heating process, avoiding the problem of uneven melting of the wax mold caused by local temperature differences and accelerating the overall dewaxing speed; at the same time, the ultrasonic wave generated by the ultrasonic dewaxing tank can destroy the adhesion between the wax liquid and the mold shell, making it easier for the wax liquid to flow out of the mold shell; the air compressor is combined with an air nozzle with an adjustable angle to blow air to the complex parts inside the mold shell, effectively removing residual wax liquid and further improving the dewaxing efficiency.

[0027] (2) In the present invention, the liquid level sensor monitors the wax liquid height in real time, and the controller accurately controls the operation of the lifting drive module and the air compressor according to the liquid level conditions, ensuring that the pipeline enters and exits the mold shell at the right time, and the air is blown into the mold shell at the right time, thereby ensuring the accuracy and stability of the dewaxing process; and the air nozzles symmetrically distributed in a Y shape at the end of the pipeline can cover a wider area inside the mold shell, so that the compressed air can act evenly on the inside of the mold shell, reducing wax liquid residue and improving the dewaxing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the accompanying drawings.

[0029] Figure 1 It is a process step diagram of the present invention;

[0030] Figure 2 It is a partial three-dimensional schematic diagram of the dewaxing equipment in the present invention;

[0031] Figure 3 for Figure 2 Bottom diagram of ;

[0032] Figure 4 It is a structural schematic diagram of the lifting assembly in the present invention;

[0033] Figure 5 It is a structural schematic diagram of the angle adjustment component in the present invention.

[0034] Description of the drawings: 1. Tank body; 2. Rotating motor; 3. Tray; 4. Electric slide rail; 5. Fixing fixture; 6. Wax liquid collecting tank; 7. Heating chamber; 8. Heating element; 9. Auxiliary dewaxing mechanism; 91. Ultrasonic dewaxing tank; 92. Ultrasonic transducer; 93. Pipeline; 94. Air nozzle; 95. Angle adjustment assembly; 951. Screw; 952. Ring; 953. Hose; 954. Drive motor; 96. Lifting assembly; 961. Lifting bracket; 962. Guide rail; 963. Slider; 964. Mounting plate; 965. Lifting drive module; 9651. Float; 9652. Connecting rod; 9653. Rack; 9654. Gear; 9655. Screw; 967. Limit block. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] See also Figure 1-Figure 5 As shown, the present invention is a precision casting process for stainless steel impellers for nuclear power, comprising the following steps:

[0037] S1, using the investment casting process to press the wax model, and connecting the individual wax models into a tree-like structure through wax rods;

[0038] S2. Coating a refractory material on the surface of the wax mold. After the coating is completed and dried, the shell is dewaxed using a dewaxing device to hollow out the shell, and then the shell is placed in a high-temperature furnace for baking;

[0039] S3. Select duplex stainless steel and melt it in an electric furnace. Heat the molten steel to the predetermined pouring temperature and pour it into the mold shell using bottom pouring or side pouring.

[0040] S4: After the shell is naturally cooled, the shell is removed to obtain the impeller and undergo solution treatment;

[0041] S5. Remove the impeller surface and internal residues by sandblasting and shot blasting, and perform flaw detection using non-destructive testing technology;

[0042] The dewaxing equipment used in S2 includes: a controller and a tank body 1, a rotating motor 2 is provided in the tank body 1, a tray 3 is provided at the output end of the rotating motor 2, a plurality of electric slide rails 4 are provided on the tray 3, and a fixing fixture 5 is installed on the electric slide rail 4; a feed port and a discharge port are provided at the top of the tank body 1, and both the feed port and the discharge port are equipped with automatic sealing doors; a wax liquid collection tank 6 is connected to the bottom of the tank body 1, and a liquid level sensor is provided in the wax liquid collection tank 6; a heating chamber 7 is provided on the inner wall of the tank body 1, and a heating element 8 is provided in the heating chamber 7, and the outer wall of the tank body 1 is wrapped with heat-insulating material. The controller is electrically connected to the electrical components;

[0043] The dewaxing equipment further comprises: an auxiliary dewaxing mechanism 9;

[0044] The auxiliary dewaxing mechanism 9 includes an ultrasonic dewaxing tank 91 and an air compressor. The ultrasonic dewaxing tank 91 is arranged on the tray 3 and has multiple ultrasonic transducers 92 evenly distributed inside the ultrasonic dewaxing tank 91. The air compressor is installed outside the tank body 1 and connected to the interior of the mold shell via a pipe 93. The end of the pipe 93 is equipped with an adjustable air nozzle 94. There are two air nozzles 94 installed at the end of the pipe 93, and they are symmetrically distributed in a Y shape.

[0045] An angle adjustment component 95 is provided at the end of the pipe 93, and the angle adjustment component 95 is used to adjust the angle of the air nozzle 94;

[0046] The angle adjustment assembly 95 includes a screw rod 951, which is rotatably mounted on the end of the pipe 93. A collar 952 capable of spiral motion is sleeved on the screw rod 951, and a nozzle is fixedly mounted on the collar 952. The nozzle and the pipe 93 are softly connected by a hose 953. The end of the screw rod 951 is connected to a drive motor 954, which is mounted on the end of the pipe 93.

[0047] The auxiliary dewaxing mechanism 9 further includes: a lifting assembly 96, which is used to enable the pipe 93 to enter and exit the mold shell; the lifting assembly 96 includes:

[0048] A lifting bracket 961 is installed at the top of the tank body 1. The lifting bracket 961 includes a vertical guide rail 962 and a slider 963 that can slide up and down along the guide rail 962. A horizontal mounting plate 964 is fixedly connected to the slider 963. The pipe 93 is fixedly mounted on the mounting plate 964.

[0049] The lifting drive module 965 is in transmission connection with the slider 963 and is used to drive the slider 963 to move up and down along the guide rail 962, thereby driving the pipe 93 to move up and down, so that the pipe 93 can enter and exit the mold shell.

[0050] The controller is electrically connected to the liquid level sensor and the lifting drive module 965; when the liquid level sensor detects that the wax liquid height in the wax liquid collection tank 6 reaches a first set value, the second set value is greater than the first set value, and the controller controls the lifting drive module 965 to operate, so that the pipeline 93 descends into the interior of the mold shell; when the liquid level sensor detects that the wax liquid height in the wax liquid collection tank 6 reaches a first set value, while the air compressor starts working, the controller controls the lifting drive module 965 to descend the pipeline 93.

[0051] In the present invention, the mold shell coated with refractory material and dried is placed on the tray 3 through the feed port on the top of the tank body 1, taking advantage of the opportunity when the automatic sealing door is opened; at this time, the operator can control the electric slide 4 through the controller to adjust the position of the fixing clamp 5 to adapt to mold shells of different sizes and shapes and firmly fix the mold shell on the tray 3; the controller controls the heating element 8 in the heating chamber 7 to start working, heating the inside of the tank body 1, so that the wax pattern in the mold shell gradually melts; at the same time, the controller controls the rotary motor 2 to start, driving the tray 3 to rotate, so that the mold shell is heated more evenly, accelerating the melting speed of the wax pattern, and the melted wax liquid flows along the mold shell into the wax liquid collection tank 6 at the bottom of the tank body 1;

[0052] The liquid level sensor in the wax liquid collecting tank 6 monitors the wax liquid height in real time; when the liquid level sensor detects that the wax liquid height reaches a second set value, the second set value is greater than the first set value, and the controller controls the lifting drive module 965 to operate;

[0053] When the liquid level sensor detects that the wax liquid height in the wax liquid collecting tank 6 reaches a first set value, the liquid level switch controls the air compressor to start working, and the compressed air is delivered to the interior of the mold shell through the pipe 93; at the same time, the controller can control the drive motor 954 to drive the screw 951 to rotate, so that the collar 952 spirals on the screw 951, thereby adjusting the angle of the air nozzle 94 to ensure that the compressed air can be blown to the complex parts of the interior of the mold shell at a suitable angle; because the air nozzles 94 at the end of the pipe 93 are symmetrically distributed in a Y shape, they can blow air into the interior of the mold shell more comprehensively and blow out the residual wax liquid;

[0054] In addition, the ultrasonic transducer 92 in the ultrasonic dewaxing tank 91 on the tray 3 starts working under the control of the controller, generating high-frequency ultrasonic waves to accelerate the melting of the wax pattern and the separation of the wax liquid from the shell, thereby assisting the dewaxing process to be more efficient; after the dewaxing is completed, the hollow shell is taken out through the discharge port and the automatic sealing door at the top of the tank body 1 and placed in a high-temperature furnace for baking to improve the strength and air permeability of the shell.

[0055] In the present invention, on the one hand, the rotating design of the tray 3 makes the mold shell more evenly heated during the heating process, avoiding the problem of uneven melting of the wax pattern caused by local temperature differences, and accelerating the overall dewaxing speed; at the same time, the ultrasonic wave generated by the ultrasonic dewaxing tank 91 can destroy the adhesion between the wax liquid and the mold shell, making it easier for the wax liquid to flow out of the mold shell; the air compressor combined with the air nozzle 94 with adjustable angle can blow air to the complex parts inside the mold shell, effectively removing residual wax liquid, and further improving the dewaxing efficiency;

[0056] On the other hand, the liquid level sensor monitors the wax liquid height in real time, and the controller accurately controls the operation of the lifting drive module 965 and the air compressor according to the liquid level conditions, ensuring that the pipe 93 enters and exits the mold shell at the right time, and the air is blown into the mold shell at the right time, ensuring the accuracy and stability of the dewaxing process; and the air nozzles 94 symmetrically distributed in a Y shape at the end of the pipe 93 can cover a wider area inside the mold shell, so that the compressed air can act evenly on the inside of the mold shell, reducing wax liquid residue and improving the dewaxing quality.

[0057] The lifting drive module 965 comprises a float 9651 disposed within the wax collection tank 6. A connecting rod 9652 is secured to the top of the float 9651. A beveled block is secured to the other end of the connecting rod 9652. The beveled block is slidably mounted on the wall of the wax collection tank 6. The beveled block contacts a rack 9653 on one side. The rack 9653 is slidably mounted on the wall of the wax collection tank 6. A return spring is provided on the side of the rack 9653 away from the beveled block. The rack 9653 meshes with a gear 9654. The gear 9654 is coaxially secured to the bottom end of a lead screw 9655. The lead screw 9655 is helically coupled to the slider 963. The lead screw 951 is rotatably mounted on the lifting bracket 961. A limit block 967 is provided on the wall of the wax collection tank 6. The distance between the limit block 967 and the bottom wall of the lower wax collection tank 6 provides movement space for the float 9651.

[0058] The lifting drive module 965 includes: an electric push rod or a hydraulic cylinder, an air compressor electrically connected to a liquid level switch, and the liquid level switch electrically connected to a liquid level sensor.

[0059] As one embodiment of the lifting drive module 965, the lifting drive module 965 is a mechanical structure consisting of a float 9651, a connecting rod 9652, a rack 9653, a gear 9654 and a lead screw 9655. As the wax liquid rises, the float 9651 rises, driving the connecting rod 9652 and the rack 9653 to move upward. The rack 9653 engages with the gear 9654, causing the gear 9654 to rotate, thereby driving the lead screw 9655 to rotate. Through the spiral transmission of the lead screw 9655 and the slider 963, the slider 963 descends along the guide rail 962, driving the mounting plate 964 and the pipe 93 to descend, so that the pipe 93 enters the interior of the shell.

[0060] As another embodiment, the lifting drive module 965 is an electric push rod or a hydraulic cylinder, and the controller directly controls its movement to realize the lowering of the pipeline 93.

[0061] The lifting drive module 965 can adopt either a mechanical structure, an electric push rod or a hydraulic cylinder. Users can choose according to actual needs and working environment, which enhances the applicability and flexibility of the equipment.

[0062] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. Precision casting process of stainless steel impeller for nuclear power, characterized by: The steps are as follows: S1, using the investment casting process to press the wax model, and connecting the individual wax models into a tree-like structure through wax rods; S2. Coating a refractory material on the surface of the wax mold. After the coating is completed and dried, the shell is dewaxed using a dewaxing device to obtain a hollow shell, and then the shell is placed in a high-temperature furnace for baking; S3. Select duplex stainless steel and melt it in an electric furnace. Heat the molten steel to the predetermined pouring temperature and pour it into the mold shell using bottom pouring or side pouring. S4: After the shell is naturally cooled, the shell is removed to obtain the impeller and undergo solution treatment; S5. Remove the impeller surface and internal residues by sandblasting and shot blasting, and perform flaw detection using non-destructive testing technology; The dewaxing equipment used in S2 includes: a controller and a tank body, a rotating motor is provided in the tank body, a tray is provided at the output end of the rotating motor, a plurality of electric slides are provided on the tray, and a fixing fixture is installed on the electric slides; a feed port and a discharge port are provided on the top of the tank body, and both the feed port and the discharge port are equipped with automatic sealing doors; a wax liquid collection tank is connected to the bottom of the tank body, and a liquid level sensor is provided in the wax liquid collection tank; a heating chamber is provided on the inner wall of the tank body, a heating element is provided in the heating chamber, and the outer wall of the tank body is wrapped with heat insulation material; the dewaxing equipment also includes: an auxiliary dewaxing mechanism; The auxiliary dewaxing mechanism includes: an ultrasonic dewaxing tank and an air compressor. The ultrasonic dewaxing tank is set on a tray, and multiple ultrasonic transducers are evenly distributed inside the ultrasonic dewaxing tank. The air compressor is installed on the outside of the tank body and connected to the inside of the shell through a pipe. The end of the pipe is equipped with an air nozzle with an adjustable angle. The end of the pipe is equipped with an angle adjustment component for adjusting the angle of the air nozzle. The angle adjustment assembly includes a screw rod, which is rotatably mounted on the end of the pipe. A collar capable of spiral motion is sleeved on the screw rod, on which a nozzle is fixed. The nozzle and the pipe are connected via a flexible hose. The end of the screw rod is connected to a drive motor, which is mounted on the end of the pipe. The auxiliary dewaxing mechanism also includes a lifting assembly, which is used to enable the pipe to enter and exit the mold shell. The lifting assembly includes: A lifting bracket installed on the top of the tank body includes a vertical guide rail and a slider that can slide up and down along the guide rail. The slider is fixedly connected to a horizontal mounting plate, and the pipe is fixedly mounted on the mounting plate. The lifting drive module is connected to the slider transmission, and is used to drive the slider to move up and down along the guide rail, thereby driving the pipeline to move up and down, so that the pipeline can enter and exit the mold shell.

2. The precision casting process for stainless steel impeller for nuclear power according to claim 1, characterized in that: The lifting drive module includes: a float arranged in the wax collection tank, a connecting rod fixed on the top of the float, an inclined block fixed on the other end of the connecting rod, the inclined block slidingly installed on the wall of the wax collection tank, the inclined block contacts with the rack on one side, the rack slidingly installed on the wall of the wax collection tank, and a reset spring is provided on the side of the rack away from the inclined block, and the rack is meshed with the gear, the gear is coaxially fixed to the bottom end of the screw, the screw is spirally connected to the slider, and the screw is rotatably installed on the lifting bracket.

3. The precision casting process for stainless steel impeller for nuclear power according to claim 2, characterized in that: A limiting block is arranged on the wall of the wax liquid collecting tank, and the distance between the limiting block and the bottom wall of the lower wax liquid collecting tank serves as the activity space of the float.

4. The precision casting process for stainless steel impeller for nuclear power according to claim 3, characterized in that: Two air nozzles are installed at the end of the pipe and are symmetrically distributed in a Y shape.

Images