A steady pressure injection APG casting process for epoxy resin with metal insert sleeve

Abstract

The present application relates to the technical field of epoxy sleeve, and particularly relates to a stable pressure injection APG pouring process for an epoxy sleeve with a metal insert, which comprises the following steps: S1, epoxy paste is injected into an injection pipeline under pressure, the paste enters a mold cavity through an injection port, and the pressure of the epoxy paste under pressure is P1; S2, the paste temperature of the injection pipeline is monitored during the injection process, and the paste temperature is controlled to be T; S3, the paste pressure P2 at the front end of the injection port is monitored during the injection process, when P2 decreases, the pressure of the epoxy paste under pressure is controlled to be P1+Delta P, and the paste temperature is controlled to be T+Delta T; S4, the paste flow at the front end of the injection port is monitored during the injection process, and the injection amount in the cavity is controlled to be consistent; and S5, a mold heating system is used to heat the mold, the mold is opened after heating, and a product is obtained through secondary curing. The present application can solve the technical problems of the APG pouring process, such as injection pressure fluctuation of the injection port, improve product quality, and save production cost.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin sleeve technology, and more specifically to a pressure-stabilizing injection process for epoxy resin sleeves with metal inserts using APG casting. Background Technology

[0002] Epoxy resin is an excellent insulating material, characterized by stable insulation performance and high mechanical strength after curing, and is widely used in the production of medium and low voltage instrument transformers. Epoxy resin bushings are important insulating components in oil-immersed instrument transformers, containing inserts such as metal conductors and metal shielding rings for electrical connections. The conventional automated pressure gel (APG) casting process for epoxy resin refers to the process where, after the metal inserts (or instrument transformer windings, etc.) are installed in the mold, the epoxy resin in the storage tank is directly forced into the mold cavity through a pipeline using the pressurization system of the APG equipment, where it gels and cures within the hot mold. The epoxy resin pressure gel process is a novel epoxy resin casting process with advantages such as short curing time and minimal mold requirements.

[0003] The sleeves produced using the conventional automated pressure gel (APG) casting process for epoxy resin involve mixing and storing the epoxy resin in an injection trolley. Under external pressure, the slurry is poured into the mold cavity through the injection pipe. However, during the injection process, the viscosity of the epoxy resin slurry changes with time and temperature, causing unstable injection pressure at the injection port and resulting in process problems such as material blockage, overflow, and poor venting. Simultaneously, sleeves with metal inserts are prone to interface cracking, leading to unstable quality and issues such as appearance defects like bubbles and material shortages, as well as excessive partial discharge. Summary of the Invention

[0004] To address technical issues such as unstable injection pressure at the injection port, this invention provides a pressure-stabilized APG casting process for epoxy resin with metal insert sleeves. This process solves technical problems such as injection pressure fluctuations at the injection port in the APG casting process, improves product quality, and saves production costs.

[0005] This invention provides a process for casting pressure-stabilizing APG refractory for epoxy resin sleeves with metal inserts, comprising the following steps:

[0006] S1. The epoxy resin slurry is injected into the injection pipeline under pressure. The slurry enters the mold cavity through the injection port. The pressure of the epoxy resin slurry is P1.

[0007] S2. Monitor the slurry temperature in the injection pipeline during the injection process and control the slurry temperature to T.

[0008] S3. During the injection process, monitor the slurry pressure P2 at the front end of the injection port. When P2 decreases, control the epoxy resin slurry pressure to P1+ΔP, and at the same time control the slurry temperature to T+ΔT.

[0009] S4. Monitor the slurry flow rate at the front end of the injection port during the injection process to control the consistent amount of slurry injected into the cavity.

[0010] S5. The mold heating system heats the mold, and after heating, the mold is opened and the product is obtained through secondary curing.

[0011] Furthermore, in step S1, the mold cavity contains a metal insert, the surface of which is sandblasted to control the surface roughness to 3.2 μm. This process adds a pretreatment step to the metal insert, improving the problem of weak adhesion and easy cracking between the metal insert and the epoxy resin interface.

[0012] Furthermore, the sandblasting method involves performing two sandblasting processes on the surface of the metal insert, following the order of abrasive mesh size from small to large.

[0013] Furthermore, in step S1, the epoxy resin slurry undergoes degassing treatment. The degassing treatment method is as follows: after mixing the epoxy resin, the mixture is evacuated for 30 minutes under a vacuum of 0-200 Pa; then the temperature is raised to 60-70°C, and the mixture is evacuated again for 40 minutes. The resulting epoxy resin slurry is stored in an injection trolley at a storage temperature of 50-60°C.

[0014] Furthermore, in step S1, the mold is preheated before the slurry enters the mold cavity. The preheating temperature is 120-135℃ and the preheating time is 3-4 hours.

[0015] Furthermore, in step S1, P1 = 0.1–0.15 MPa; in step S2, T = 50–60 °C.

[0016] Furthermore, in step S3, ΔP = +0.20 to +0.25 MPa, ΔT = +2 to +5 °C; the epoxy resin slurry is maintained at a pressure of P1 + ΔP for 25 minutes to ensure the internal density of the epoxy resin.

[0017] Furthermore, the heating time in step S5 is 30 minutes; the heating temperature for the secondary curing is 130°C, and the holding time is 8 hours.

[0018] Furthermore, the casting process employs the following equipment: a mold system, a pressure-stabilizing injection system, a pneumatic pressure supply system, and a control system.

[0019] The mold system includes molds;

[0020] The pressure-stabilizing injection system includes an injection trolley, whose discharge port is connected to the mold via an injection pipeline, and the injection pipeline is equipped with an injection port.

[0021] The pressure-stabilized injection system includes a temperature feedback device and an electromagnetic flow meter. The temperature feedback device includes a temperature detection component and a heating component installed in the injection pipeline.

[0022] The temperature feedback device is connected to the control system and is used for slurry temperature feedback and slurry heating;

[0023] An electromagnetic flow meter is installed on the injection pipeline at the front end of the injection port and connected to the control system to monitor the flow rate and pressure of the slurry in the injection pipeline.

[0024] The pneumatic pressure supply system is connected to the control system, and the pressure supply port of the pneumatic pressure supply system is connected to the pressure port of the injection trolley through a pipeline for supplying pressure to the injection trolley.

[0025] Furthermore, the mold system also includes a mold heating system for heating the mold cavity, and a mechanical sliding mechanism for opening the mold.

[0026] The beneficial effects of this invention are as follows: The pressure-stabilized APG casting process for epoxy resin sleeves with metal inserts provided by this invention can monitor and provide feedback on the injection port, solving the process problems such as blockage, overflow, and poor venting caused by fluctuations in injection pressure at the injection port in conventional APG casting. At the same time, this invention improves the quality of epoxy resin sleeves with metal inserts by optimizing APG casting process parameters (mold injection temperature, casting pressure, slurry stabilization temperature, casting time, mold pressure holding time after casting, secondary curing temperature, and curing time), making the cast products of uniform quality, improving the electrical performance of the products, and reducing slurry waste. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of the pressure-stabilized APG casting device in Embodiment 1 of the present invention.

[0029] In the diagram, 1-pneumatic pressure supply system, 2-control system, 3-temperature feedback device, 4-electromagnetic flow meter, 5-injection trolley, 6-injection port, 7-mold heating system, 8-mold, 9-mechanical sliding mechanism, 10-injection pipeline. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0031] Example 1

[0032] like Figure 1 The present invention employs the following pressure-stabilized APG casting device, including a mold system, a pressure-stabilized injection system, a pneumatic pressure supply system 1, and a control system 2;

[0033] The mold system includes a mold 8, a mold heating system 7 for heating the mold cavity, and a mechanical sliding mechanism 9 for opening the mold.

[0034] The pressure-stabilizing injection system includes an injection trolley 5, the discharge port of which is connected to the mold 8 via an injection pipeline 10, and the injection pipeline 10 is provided with an injection port 6.

[0035] The pressure-stabilized injection system includes a temperature feedback device 3 and an electromagnetic flow meter 4. The temperature feedback device 3 includes a temperature detection component and a heating component installed in the injection pipeline.

[0036] Temperature feedback device 3 is connected to control system 2 and is used for slurry temperature feedback and slurry heating;

[0037] The electromagnetic flow meter 4 is installed on the injection pipeline 10 at the front end of the injection port 6 and connected to the control system 2 to monitor the flow rate and pressure of the slurry in the injection pipeline 10.

[0038] The pneumatic pressure supply system 1 is connected to the control system 2, and the pressure supply port of the pneumatic pressure supply system 1 is connected to the pressure port of the injection trolley 5 through a pipeline for supplying pressure to the injection trolley 5.

[0039] Example 2

[0040] A pressure-stabilizing APG casting process for epoxy resin sleeves with metal inserts includes the following steps:

[0041] (1) Surface treatment of metal inserts

[0042] The metal conductor and shielding mesh in the metal insert are both made of copper, resulting in weak adhesion at the interface with the epoxy resin. Before casting, the metal insert requires two sandblasting processes. Specifically, two different grit abrasives are used, with the smaller grit applied first, followed by the larger grit, to sandblast the surface of the metal insert in contact with the epoxy resin. The surface roughness is controlled to be at the 3.2μm level.

[0043] (2) Mixing and degassing treatment

[0044] After mixing the epoxy resin, the mixture is evacuated for 30 minutes under a vacuum of 0–200 Pa; then the temperature is raised to 60–70 °C, and the mixture is evacuated again for 40 minutes. The entire slurry is then uniformly mixed and stored in a dispensing trolley, with the storage temperature maintained at 50–60 °C.

[0045] (3) Mold preheating

[0046] Molds with cavities need to be preheated at 120-135℃ for 3-4 hours before injection.

[0047] (4) Static injection and pressure-holding gel

[0048] After mold preheating, ensure the mold closing pressure is 13.5–14.5 MPa. The pneumatic pressure supply system provides pressure to inject the slurry into the cavity through the injection port. The pressure bearing pressure of the injection trolley is 0.1–0.15 MPa. The APG casting main equipment uses inclined venting with an inclination angle of 5–7°. During the injection process, monitor the slurry temperature in the injection pipeline and control it to be maintained at 50–60°C. Monitor the slurry pressure at the injection port. When the pressure decreases, the control system controls the pneumatic pressure supply system to increase the pressure to 0.35 MPa and maintain it for 25 minutes. At the same time, control the heating components in the temperature feedback device to heat the slurry, raising the slurry temperature in the pipeline by 2–5°C and reducing the slurry viscosity. The mold heating system heats and holds the mold for about 30 minutes. The slurry gels and solidifies in the cavity. After the holding time, the mechanical sliding mechanism slides open the mold and removes the epoxy resin sleeve product.

[0049] (5) Secondary curing

[0050] After the mold is opened, the sleeve product is transferred to the heat preservation equipment and kept at 130℃ for 8 hours. Then it is cooled to room temperature in the furnace to complete the secondary curing of the product and obtain the finished product.

[0051] The present invention provides a pressure-stabilized APG casting process for epoxy resin sleeves with metal inserts. This process allows for monitoring and feedback at the injection port, solving problems such as blockage, overflow, and poor venting caused by fluctuations in injection pressure at the injection port in conventional APG casting. Furthermore, the present invention optimizes APG casting process parameters (mold injection temperature, casting pressure, slurry stabilization temperature, casting time, mold pressure holding time after casting, secondary curing temperature, and curing time) to improve the quality of epoxy resin sleeves with metal inserts, resulting in more uniform casting quality, improved electrical performance, and reduced slurry waste.

[0052] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A pressure-stabilizing APG casting process for epoxy resin tubing with metal inserts, characterized in that, Includes the following steps: S1. The epoxy resin slurry is injected into the injection pipeline under pressure. The slurry enters the mold cavity through the injection port. The pressure of the epoxy resin slurry is P1. S2. Monitor the slurry temperature in the injection pipeline during the injection process and control the slurry temperature to T. S3. During the injection process, monitor the slurry pressure P2 at the front end of the injection port. When P2 decreases, control the epoxy resin slurry pressure to P1+ΔP, and at the same time control the slurry temperature to T+ΔT. S4. Monitor the slurry flow rate at the front end of the injection port during the injection process to control the consistent amount of slurry injected into the cavity. S5. The mold heating system heats the mold, and after heating, the mold is opened and the product is obtained through secondary curing. In step S1, P1 = 0.1~0.15MPa; in step S2, T = 50~60℃; In step S3, ΔP = +0.20~+0.25MPa, ΔT = +2~+5℃.

2. The pressure-stabilizing APG casting process for epoxy resin tubing with metal inserts as described in claim 1, characterized in that, In step S1, the mold cavity contains a metal insert, the surface of which is sandblasted to control the surface roughness to 3.2 μm.

3. The pressure-stabilizing APG casting process for epoxy resin tubing with metal inserts as described in claim 2, characterized in that, The sandblasting method involves sandblasting the surface of the metal insert twice, first with a small abrasive mesh and then with a large abrasive mesh.

4. The pressure-stabilizing APG casting process for epoxy resin tubing with metal inserts as described in claim 1, characterized in that, In step S1, the epoxy resin slurry undergoes degassing treatment. The degassing treatment method is as follows: after mixing the epoxy resin, the mixture is evacuated for 30 minutes under a vacuum of 0~200Pa; then the temperature is raised to 60~70℃, and the mixture is evacuated again for 40 minutes. The resulting epoxy resin slurry is stored in an injection trolley at a storage temperature of 50~60℃.

5. The pressure-stabilizing APG casting process for epoxy resin sleeves with metal inserts as described in claim 1, characterized in that, In step S1, the mold is preheated before the slurry enters the mold cavity. The preheating temperature is 120~135℃ and the preheating time is 3~4h.

6. The pressure-stabilizing APG casting process for epoxy resin tubing with metal inserts as described in claim 1, characterized in that, The heating time in step S5 is 30 minutes; the heating temperature for the second curing is 130°C, and the holding time is 8 hours.

7. The pressure-stabilizing APG casting process for epoxy resin tubing with metal inserts as described in claim 1, characterized in that, The casting process employs the following equipment: a mold system, a pressure-stabilizing injection system, a pneumatic pressure supply system, and a control system. The mold system includes molds; The pressure-stabilizing injection system includes an injection trolley, whose discharge port is connected to the mold via an injection pipeline, and the injection pipeline is equipped with an injection port. The pressure-stabilized injection system includes a temperature feedback device and an electromagnetic flow meter. The temperature feedback device includes a temperature detection component and a heating component installed in the injection pipeline. The temperature feedback device is connected to the control system and is used for slurry temperature feedback and slurry heating; The electromagnetic flow meter is installed on the injection pipeline at the front end of the injection port and is connected to the control system to monitor the flow rate and pressure of the slurry in the injection pipeline. The pneumatic pressure supply system is connected to the control system, and the pressure supply port of the pneumatic pressure supply system is connected to the pressure port of the injection trolley through a pipeline for supplying pressure to the injection trolley.

8. The pressure-stabilizing APG casting process for epoxy resin sleeves with metal inserts as described in claim 7, characterized in that, The mold system also includes a mold heating system for heating the mold cavity, and a mechanical sliding mechanism for opening the mold.

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