Preparation method of spherical padding for sintering resistor disc of lightning arrester

Abstract

The invention provides a preparation method of a spherical padding for sintering a resistor disc of a lightning arrester, and belongs to the technical field of manufacturing of lightning arresters. The method comprises the following steps: firstly, preparing slurry by taking granulation waste as a raw material, and then preparing the spherical padding by virtue of a breakthrough titration forming process for the first time, so that the forming precision is high, the spherical quality is excellent, the use performance of the padding can be directly improved, the material structure is stable, the performance loss is low, and the original characteristics of the waste can be reserved to the greatest extent; the damage to the material performance in the preparation process is reduced. In addition, the preparation method provided by the invention is simple, the process is mature, and the use amount of additives is small, so that the production cost can be effectively reduced, and the economic value is relatively high.

Description

Technical Field

[0001] This invention belongs to the field of surge arrester manufacturing technology, specifically relating to a method for preparing spherical pads for sintering surge arrester resistor sheets. Background Technology

[0002] With the rapid iteration of power transmission and transformation technologies, ultra-high voltage AC and DC power transmission and transformation technologies have become the core direction of my country's power system construction, and the corresponding high-performance AC and DC zinc oxide resistors have also been widely used. However, the traditional pads used in the sintering of surge arrester resistors currently have significant shortcomings in terms of manufacturing process, performance, and resource utilization. Specific problems are as follows:

[0003] (1) The traditional padding material has prominent defects in preparation process and use. This type of padding material is usually made from waste resistor sheets as raw material, which is crushed, screened and calcined. It generally has many sharp corners and irregular shape. During the sintering process of resistor sheets, the sharp corners of the padding material can easily squeeze or scratch the surface of the resistor sheet in contact, thus forming holes that are difficult to repair. Impurities are easy to adhere to the surface. These defects cannot be removed after grinding, which directly leads to a decrease in the quality of resistor sheets and a decrease in the production qualification rate.

[0004] (2) Traditional padding materials cannot meet the sintering process requirements of high-performance resistor sheets. The sintering process of high-performance AC and DC surge arrester resistor sheets has extremely high requirements for the atmosphere and the stability of the padding materials. In particular, the fluctuation of the content of components such as bismuth oxide (Bi2O3) and antimony oxide (Sb2O3) in the padding materials will directly affect the key performance parameters such as the gradient and leakage current of the sintered resistor sheets. However, the traditional padding materials have poor composition uniformity and insufficient stability, resulting in a large dispersion of performance parameters of resistor sheets sintered with them. This not only leads to a low pass rate, but also further reduces the utilization rate of resistor sheets that can be put into actual use, thus restricting the mass production quality of high-performance resistor sheets.

[0005] (3) Traditional production methods suffer from serious resource waste and cost problems. In the spray granulation process of resistor sheets, a large amount of waste is generated in the cleaning granulation tower, ball mill tank and other containers, as well as in the trench. This waste has the same composition as the resistor sheets (such as zinc oxide, Bi2O3 / Sb2O3 and other additives), but due to the lack of reasonable recycling methods, it is usually disposed of as scrap. This practice not only wastes valuable raw materials, but also increases disposal costs, indirectly increasing the overall production cost of surge arrester resistor sheets, which is contrary to the current industrial demand for green manufacturing and cost reduction and efficiency improvement.

[0006] To address the aforementioned issues, existing solutions primarily involve employing new processes to improve the morphology of the padding material and precisely control its composition and proportions. Currently, engineers have developed a pelletizing disc technology that uses high-performance surge arrester resistor sheet granulated powder as raw material. The process involves batching, crushing and mixing, pelletizing with a pelletizing disc, screening, calcination, and sieving to produce spherical padding material. This type of padding material exhibits good sphericity and uniform particle size, avoiding damage to the resistor sheet surface caused by the sharp corners of traditional padding materials. This effectively improves the yield rate of resistor sheet production and also reduces waste and dust pollution problems caused by ball milling reprocessing, as illustrated in patent CN111675535A.

[0007] Compared to traditional pads, spherical pads, due to their regular shape, avoid scratching damage to the surface of the resistor element. Simultaneously, precisely controlled component ratios ensure a stable sintering atmosphere, significantly reducing the dispersion of resistor element performance parameters. This effectively improves the mass production quality and efficiency of high-performance surge arrester resistor elements. However, some problems and drawbacks still exist in practical applications. For example, the development of new processes such as pelletizing using pelletizing discs to prepare spherical pads from granulated micropowder requires long-term experimental verification and equipment debugging. Furthermore, the waste material from cleaning is disposed of as scrap, resulting in resource waste. Moreover, most existing preparation methods use 8-mesh sieves, resulting in coarse particle sizes, poor flowability, and uneven gaps, which easily affect the grinding effect of the finished product. The process is also complex, involving numerous steps, increasing production costs. Therefore, how to simplify the preparation process, reduce energy consumption, and minimize environmental pollution while ensuring performance is a pressing issue in the current resistor element manufacturing field. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide a method for preparing spherical pads for sintering surge arrester resistor sheets. This method achieves high molding precision and excellent spherical quality, directly improving the performance of the pads. Furthermore, the method is simple, the process is mature, and the amount of additives used is small, effectively reducing production costs and possessing high economic value.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] This invention provides a method for preparing spherical pads for sintering surge arrester resistor sheets, comprising the following steps:

[0011] S1: Provide slurry; the slurry, by molar percentage, comprises 60-65 mol% mixed waste, 0.6-1.0 mol% dispersant, 1.0-1.5 mol% binder, 0.1-0.2 mol% defoamer, and 30-35 mol% solvent; the mixed waste includes bismuth oxide, antimony oxide, and granulation waste;

[0012] S2: The slurry provided in step S1 is dripped and molded. After the obtained molded blank is debonded and sintered, a spherical pad is obtained.

[0013] The titration equipment includes a peristaltic pump and a dropper. The flow rate of the peristaltic pump is 5~8 mL / h, and the distance between the dropper and the surface of the titration medium is 5~8 cm.

[0014] Preferably, the dispersant is selected from any one or more of D-134C or BYK.

[0015] Preferably, the adhesive is selected from PVA.

[0016] Preferably, the defoamer is selected from tributyl phosphate.

[0017] Preferably, the solvent is selected from water, and the water is pure water.

[0018] Preferably, the molar ratio of bismuth oxide, antimony oxide and granulation waste in the mixed waste is (1~4):(2~3):(93~97), specifically it can be 4:3:93, 1:2:97, 3:3:94, 4:2:94 or 1:3:96, etc.

[0019] Preferably, the viscosity of the slurry is 500~800 mPa·s.

[0020] Preferably, the verticality of the dripper is ≤1°.

[0021] Preferably, the temperature of the shaping medium is 40~50℃ and the surface tension is 25~30 mN / m.

[0022] Preferably, the shaping medium is selected from food-grade soybean oil or silicone oil.

[0023] Preferably, the shaping medium is subjected to filtration treatment.

[0024] Preferably, a buffer medium is provided at the bottom of the shaping medium, and the buffer medium is selected from quartz sand.

[0025] Preferably, the molded blank is cleaned and dried before being debonded and sintered.

[0026] Preferably, the residual moisture content of the dried blank is ≤1 wt%.

[0027] Preferably, the temperature for discharging the adhesive is 400~500℃, and the heat preservation time is 2~3 hours.

[0028] Preferably, the sintering includes: pre-firing at 850~950℃ for 2~3 h, and holding at 1050~1150℃ for 2~3 h.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention provides a method for preparing spherical pads for sintering surge arrester resistor sheets. The method first prepares a slurry using granulation waste as raw material, and then, for the first time, utilizes a titration molding process to prepare the spherical pads. This not only results in high molding precision and excellent spherical quality, directly improving the performance of the pads, but also ensures stable material structure, low performance loss, and maximizes the preservation of the original characteristics of the waste material, minimizing damage to material properties during the preparation process. Furthermore, the preparation method provided by this invention offers high process flexibility and wide adaptability. By adjusting the binder ratio and dispersant type in the slurry, it can be adapted to waste materials with different particle sizes and flowability without significant equipment modifications. Moreover, the spherical pad preparation method of this invention is simple, mature, and uses minimal additives, thus effectively reducing production costs and possessing high economic value. Attached Figure Description

[0031] Figure 1 This is a graph showing the debinding and sintering process in this invention. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Compared with existing technologies, this invention mainly solves the following technical problems: 1) It reuses the waste material cleaned during the granulation process of surge arrester resistors, realizing waste resource utilization. This reduces the waste of valuable raw materials from the source and lowers waste treatment costs, indirectly reducing the overall production cost of surge arrester resistors; 2) By precisely controlling the ratio of bismuth oxide to antimony oxide, a stable atmosphere is provided for the sintering of high-performance surge arrester resistors, ultimately resulting in better resistor performance, significantly improved stability, and enhanced durability. This not only fully meets the technical standards of high-performance surge arresters but also greatly improves the production quality and pass rate of resistors; 3) The titration molding method is introduced into the preparation process. This process is simple and mature, giving the pad material good mechanical strength, a dense and uniform internal structure, high sphericity, good morphological uniformity, and a longer service life; 4) The spherical pad material formed by this method has strong controllability in particle size, fine particle size, and good flowability. It can be screened through a 100-mesh sieve, with most of the particle size distributed within 150 mm. With a thickness of approximately μm, the bonding and separation between resistor elements can be well guaranteed, effectively avoiding damage to the surface and further improving the pass rate and utilization rate of resistor element production.

[0034] To solve the above-mentioned technical problems, the technical solution of the present invention mainly adopts the following technical means: (1) Using the titration molding method to prepare spherical pads from waste materials, and using ball milling process to prepare slurry to ensure the uniformity of slurry. At the same time, the solid content of slurry should be precisely controlled, and the viscosity of slurry should be adjusted to make it have good fluidity and dripping properties. (2) Using a specific titration device to allow droplets to roll freely to form spherical blanks, and controlling droplet generation by pressure or flow rate. (3) After the droplets are formed, they need to be solidified. After they are shaped, they are collected by gravity in the coolant (oil-based medium) and formed into green blanks.

[0035] The present invention provides a preparation method for preparing spherical pads using waste materials via a titration molding method. The core of this method is the use of a synergistic "slurry-tipping-shaping" system, followed by sintering, to obtain spherical pads that are "non-reactive with zinc oxide, have fine and uniform particle size, matched expansion coefficients, and are high-temperature resistant and impact-resistant," suitable for sintering zinc oxide resistance sheets (temperature 800~1200℃). This method involves uniformly dispersing waste materials in a liquid phase to form a slurry, utilizing fluid surface tension to achieve droplet spheroidization, and precisely adding the slurry to a shaping medium to form spherical droplets based on surface tension. Finally, through solidification and sintering, the waste materials are transformed into regularly shaped and stable spherical pads.

[0036] Specifically, the present invention will be described in detail below.

[0037] This invention provides a method for preparing spherical pads for sintering surge arrester resistor sheets, comprising the following steps:

[0038] S1: Provide slurry; the slurry, by molar percentage, comprises 60-65 mol% mixed waste, 0.6-1.0 mol% dispersant, 1.0-1.5 mol% binder, 0.1-0.2 mol% defoamer, and 30-35 mol% solvent; the mixed waste includes bismuth oxide, antimony oxide, and granulation waste;

[0039] S2: The slurry provided in step S1 is dripped and molded. After the molded blank is debonded and sintered, a spherical pad is obtained.

[0040] According to the present invention, a slurry is first provided.

[0041] In this invention, the slurry must meet the following requirements: high solids content (to ensure density after sintering), low viscosity (to ensure smooth dripping), and suitable thixotropy (to prevent deformation after dripping). It adopts a water-based system (environmentally friendly and easy to solidify), and by molar percentage comprises 60-65 mol% mixed waste, 0.6-1.0 mol% dispersant, 1.0-1.5 mol% binder, 0.1-0.2 mol% defoamer, and 30-35 mol% solvent. The mixed waste includes bismuth oxide, antimony oxide, and granulation waste, with a molar ratio of (1-4):(2-3):(93-97), specifically 4:3:93, 1:2:97, 3:3:94, 4:2:94, or 1:3:96, etc. The granulation waste is obtained by drying waste slurry collected from containers such as granulation towers and ball mills.

[0042] In this invention, the aforementioned mixed waste material serves to determine strength and high-temperature resistance, and to ensure the firing atmosphere. It is generally added in 2-5 stages during slurry preparation, preferably in 3 stages, with high-speed dispersion after each addition to prevent agglomeration. The specific dosage is 60-65 mol%, such as 60 mol%, 60.5 mol%, 61 mol%, 61.5 mol%, 62 mol%, 62.5 mol%, 63 mol%, 63.5 mol%, 64 mol%, 64.5 mol%, or 65 mol%, etc.

[0043] The aforementioned dispersant is used to break up powder agglomerates and reduce slurry viscosity, and generally requires good compatibility with the slurry. Specifically, the dispersant can be selected from any one or more of D-134C or BYK. In some embodiments of the present invention, the amount of the dispersant is 0.6~1.0 mol%, such as 0.6 mol%, 0.7 mol%, 0.08 mol%, 0.9 mol%, or 1.0 mol%.

[0044] The aforementioned binder is used to improve the strength of the preform and prevent cracking after curing. PVA is generally preferred as it allows for easy removal of adhesive without residue. In some embodiments of the present invention, the amount of the binder is 1.0~1.5 mol%, such as 1.0 mol%, 1.1 mol%, 1.2 mol%, 1.3 mol%, 1.4 mol%, or 1.5 mol%.

[0045] The aforementioned defoamer is used to eliminate air bubbles generated during slurry preparation. Generally, a small amount is sufficient to avoid affecting surface tension. The specific dosage is 0.1~0.2 mol%, such as 0.1 mol%, 0.12 mol%, 0.15 mol%, 0.18 mol%, or 0.2 mol%. In some embodiments of the present invention, the defoamer is selected from tributyl phosphate.

[0046] The solvent mentioned above is used to adjust the solid content of the slurry, preferably water, more preferably pure water, and preferably has a resistivity greater than 10 MΩ / cm. 3 To avoid the influence of impurities.

[0047] In some embodiments of the present invention, the method for preparing the slurry includes the following steps:

[0048] (1) Preparation of base solution: Add solvent (such as deionized water), dispersant and defoamer to beaker according to the ratio, stir with magnetic stirrer to ensure that the dispersant is completely dissolved;

[0049] (2) Dispersion of mixed waste: Add the mixed waste in 2 to 5 times, preferably in 3 times. After all the waste is added, disperse it with a high-speed disperser for 20 to 25 minutes. During this period, use a microscope to sample and observe to ensure that there are no obvious agglomerates.

[0050] (3) Binder and viscosity adjustment: Reduce the rotation speed, add binder (PVA) and stir for 20~60 min, preferably 30 min, let stand for 5~20 min, preferably 15 min to eliminate air bubbles; use a rotational viscometer to test the viscosity, which should be controlled at 500~800 mPa·s (if the viscosity is too low, the droplets will easily break, and if the viscosity is too high, the dropper will easily become clogged).

[0051] (4) Stability verification: The slurry is sealed and left to stand for 24 hours. If no stratification or sedimentation is observed (settling rate < 2%), it is considered to be in good condition for suspension stability.

[0052] In this invention, the key to the preparation method of the above-mentioned slurry is that it is uniformly dispersed and free of bubbles.

[0053] After the above slurry is prepared, it is titrated and molded according to the present invention.

[0054] In this invention, titration molding is a crucial step in forming a spherical preform from the slurry. It requires precise control of equipment parameters and design of the molding medium to ensure that the droplets naturally form a perfect sphere after detaching from the dropper. The key control points are as follows:

[0055] (1) Titration equipment and parameter optimization

[0056] It employs a high-precision peristaltic pump titration system (flow accuracy ±0.5%), paired with a liftable stainless steel dripper (inner diameter 0.8~1.2 mm).

[0057] If the flow rate of the high-precision peristaltic pump is too low, it can easily cause drip head blockage; if the flow rate is too high, it can easily lead to continuous dripping (double / multiple balls). Observation through trial drops is necessary: ​​the optimal time for a single drop to detach from the drip head is 1-2 seconds. After screening and verification, the preferred flow rate of the high-precision peristaltic pump is controlled at 5-8 mL / h, such as 5 mL / h, 5.5 mL / h, 6 mL / h, 6.5 mL / h, 7 mL / h, 7.5 mL / h, or 8 mL / h.

[0058] If the stainless steel dropper is too close to the surface of the shaping medium, the droplet impact is small but it is prone to sticking to the wall; conversely, if it is too far, the droplet is easily deformed by airflow disturbance. The ideal distance is for the droplet to form a complete sphere after falling into the medium. Screening and verification have shown that the preferred distance between the stainless steel dropper and the surface of the shaping medium is 5-8 cm, such as 5 cm, 5.5 cm, 6 cm, 6.5 cm, 7 cm, 7.5 cm, or 8 cm.

[0059] Furthermore, if the stainless steel dropper is tilted, the droplet will deviate, requiring calibration with a level to ensure that the droplet falls vertically into the center of the medium. Preferably, the verticality of the stainless steel dropper is ≤1°.

[0060] (2) Design of fixed media

[0061] The sizing medium in this invention needs to be selected to have a density that differs from the slurry (to allow the droplets to sink slowly), is not miscible with the slurry (to avoid droplet diffusion), and is easy to remove subsequently (without leaving any pollution).

[0062] In this invention, the shaping medium is selected from food-grade soybean oil and / or silicone oil, preferably food-grade soybean oil (density 0.92~0.93 g / cm³). 3 The density of the liquid is significantly different from that of the slurry, and the droplet sinking speed is 1~2 cm / s, allowing sufficient time for curing.

[0063] It should be noted that the shaping medium needs to be controlled as follows:

[0064] i. Temperature: 40~50℃, such as 40℃, 42℃, 45℃, 48℃ or 50℃, which can be controlled by a constant temperature oil bath. The reason for controlling this parameter is that if the temperature is too low, the curing is slow and the material is prone to agglomeration; if the temperature is too high, the adhesive will cure prematurely, causing the surface of the droplets to form a shell and crack.

[0065] ii. Surface tension: 25~30 mN / m, such as 25 mN / m, 26 mN / m, 27 mN / m, 28 mN / m, 29 mN / m or 30 mN / m, etc. This range is close to the surface tension value of the slurry, which can ensure that the droplets do not spread in the medium and naturally shrink into spheres;

[0066] iii. Cleanliness: Filter (0.45 μm pore size filter membrane) before use to remove impurities and particles and avoid scratching the surface of the droplets.

[0067] (3) Finalization process

[0068] First, conduct a test drop verification: After starting the peristaltic pump, observe the state of the first 10 drops: If the droplets are flat, broken, or continuous, the parameters need to be adjusted (e.g., increase the dropper height for flat droplets, and reduce the flow rate for continuous droplets).

[0069] Secondly, batch shaping: After the droplets stabilize, a 1-3 cm, preferably 1-2 cm, thick buffer medium, such as quartz sand (preferably with a particle size of 0.5-1 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm, etc.), is laid at the bottom of the medium to reduce the impact force of the droplets settling and collect the droplets; the shaping time is 2-3 hours, ensuring that the blank is not deformed or broken when picked up with tweezers;

[0070] Finally, the green body is cleaned: After the shaping is completed, the green body is taken out of the medium and soaked in an organic solvent, such as anhydrous ethanol, for 1 to 10 minutes, preferably 5 minutes to remove residual grease on the surface. Then it is placed in a vacuum drying oven at 60 to 70°C and dried for 0.5 to 3 hours, preferably 1 hour, to remove ethanol.

[0071] In some preferred embodiments of the present invention, the cured spherical preform is preferably dried to remove moisture. The drying temperature is 100~120℃, and the drying time is 4~8 h, preferably 6~8 h. The residual moisture content is tested using a moisture meter and found to be ≤1 wt%, to prevent the preform from cracking during subsequent processing.

[0072] It should be noted that the solidified spherical preform (green preform) still has many pores, and densification needs to be achieved through debinding and sintering to obtain spherical pads with high hardness and high strength.

[0073] In some embodiments of the present invention, the obtained green body is held at 400-500°C for 1-5 hours in an open atmosphere to remove the binder, then pre-fired at 850-950°C for 1-5 hours in a closed atmosphere, and then heated from room temperature to a sintering temperature of 1050-1150°C in a closed atmosphere for 1-5 hours to achieve ceramic densification. The binder removal and sintering curves in this invention are shown below. Figure 1 As shown.

[0074] The above-mentioned 400~500℃ can be 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃ or 500℃, etc.; the above-mentioned 850~950℃ can be 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃ or 950℃, etc.; the above-mentioned 1050~1150℃ can be 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, 1100℃, 1110℃, 1120℃, 1130℃, 1140℃ or 1150℃, etc.

[0075] The above 1~5 h can be 1 h, 2 h, 3 h, 4 h or 5 h, etc., preferably 2~3 h.

[0076] After sintering, the obtained spherical pad material can be loaded into the sintering crucible for surge arrester resistors and used.

[0077] Practical application has shown that the gradient pass rate, grinding disc pass rate, and product pass rate are all above 97%.

[0078] It is evident that the preparation method provided by this invention is not only simple and inexpensive, but also yields spherical pads with excellent performance.

[0079] To further illustrate the present invention, detailed descriptions are provided below through the following embodiments. The experimental raw materials used in the following embodiments of the present invention are all commercially available products. The granulation waste material is obtained by drying waste slurry collected from containers such as granulation towers and ball mill jars. The dispersant used in Examples 1 and 2 is D-134C, and the defoamer used in Examples 1 and 2 is tributyl phosphate, respectively.

[0080] In this invention, gradient pass rate, grinding disc pass rate, and product pass rate are technical terms known to those skilled in the art.

[0081] The gradient pass rate refers to the percentage of sintered resistor sheets that meet the product gradient requirements under a certain temperature curve out of the total batch quantity.

[0082] Grinding pass rate: refers to the percentage of resistors whose end face flatness, parallelism and other parameters meet the product technical requirements after the resistor grinding process is completed, to the total number of resistors in the batch;

[0083] Product qualification rate: refers to the percentage of resistors that have completed all production processes and whose appearance and electrical performance are qualified out of the total production quantity.

[0084] Example 1

[0085] Step 1: Use an electronic scale to mix 4 mol% bismuth oxide, 3 mol% antimony oxide, and 93 mol% granulation waste to form mixed waste; weigh the mixed waste according to the following proportions: 65 mol% mixed waste, 33 mol% pure water, 0.7 mol% dispersant, 1.2 mol% PVA, and 0.1 mol% defoamer;

[0086] Step 2: Dispersant and defoamer in pure water, stirred at 400 rpm for 15-20 min until completely dissolved. Add the mixed waste material evenly in three portions, dispersing each addition at 2-3 min intervals. After all the mixed waste material has been added, disperse at 1680 rpm for 20-25 min, observing under a microscope for no obvious agglomeration. Reduce the speed to 600 rpm, add PVA, stir for 30 min, then add the defoamer and let stand for 15 min to complete the slurry preparation (surface tension 30-35 mN / m).

[0087] Step 3: Install the peristaltic pump and stainless steel dripper. Adjust the peristaltic pump flow rate to 7 mL / h and the dripper height to 5 cm. Calibrate the dripper verticality to ≤1°. Perform a test run with pure water to ensure no leakage and uniform liquid output. Filter food-grade soybean oil (surface tension 25~30 mN / m) through a 0.45 μm filter membrane and pour it into a 40~50℃ constant temperature oil bath. Place a 1 cm thick layer of 0.5~1 mm quartz sand at the bottom of the bath.

[0088] Step 4: Perform 10 drops as a trial, and adjust the parameters until the spherical billet is free from flattening, breakage, or continuous dripping. Then, begin batch titration. When picking up the billet with tweezers, ensure that it is free from deformation and breakage.

[0089] Step 5: After the shaping is completed, the blank is taken out of the medium, soaked in anhydrous ethanol for 5 minutes to remove residual grease on the surface, and then placed in a vacuum drying oven at 60℃ for 1 hour to remove ethanol.

[0090] Step 6: Dry the cured spherical preform by placing it in a vacuum drying oven at 100~120℃ for 8 hours; measure the moisture content every 2 hours, and remove it after cooling if the residual moisture is ≤1 wt%.

[0091] Step 7: The obtained green body is sintered under open atmosphere conditions, held at 450℃ for 2 hours for debinding, held at 900℃ for 2 hours for pre-firing, and held at 1080℃ for 2 hours for sintering.

[0092] Step 8: After sintering, the spherical pad material is sieved through a 100-mesh sieve to remove lumps and fragments. At this point, the spherical pad material is completed and is placed into the sintering crucible for the surge arrester resistor sheet.

[0093]

[0094] Example 2

[0095] Step 1: Use an electronic scale to mix 2 mol% bismuth oxide, 4 mol% antimony oxide, and 94 mol% granulation waste to form mixed waste; weigh the mixed waste according to the following proportions: 65 mol% mixed waste, 33 mol% pure water, 0.7 mol% dispersant, 1.2 mol% PVA, and 0.1 mol% defoamer;

[0096] Step 2: Dispersant and defoamer in pure water, stirred at 400 rpm for 15-20 min until completely dissolved. Add the mixed waste material evenly in three portions, dispersing each addition at 2-3 min intervals. After all the mixed waste material has been added, disperse at 1850 rpm for 20-25 min, observing under a microscope for no obvious agglomeration. Reduce the speed to 650 rpm, add PVA, stir for 30 min, then add the defoamer and let stand for 15 min to complete the slurry preparation (surface tension 30-35 mN / m).

[0097] Step 3: Install the peristaltic pump and stainless steel dripper. Adjust the peristaltic pump flow rate to 7 mL / h and the dripper height to 6 cm. Calibrate the dripper verticality to ≤1°. Perform a test run with pure water to ensure no leakage and uniform liquid output. Filter food-grade soybean oil (surface tension 25~30 mN / m) through a 0.45 μm filter membrane and pour it into a 40~50℃ constant temperature oil bath. Place a 1 cm thick layer of 0.5~1 mm quartz sand at the bottom of the bath.

[0098] Step 4: Perform 10 drops as a trial, and adjust the parameters until the spherical billet is free from flattening, breakage, or continuous dripping. Then, begin batch titration. When picking up the billet with tweezers, ensure that it is free from deformation and breakage.

[0099] Step 5: After the shaping is completed, the blank is taken out of the medium, soaked in anhydrous ethanol for 5 minutes to remove residual grease on the surface, and then placed in a vacuum drying oven at 60℃ for 1 hour to remove ethanol.

[0100] Step 6: Dry the cured spherical preform by placing it in a vacuum drying oven at 100~120℃ for 8 hours; measure the moisture content every 2 hours, and remove it after cooling if the residual moisture is ≤1 wt%.

[0101] Step 7: The obtained green body is sintered under open atmosphere conditions, held at 450℃ for 2 hours for debinding, held at 900℃ for 2 hours for pre-firing, and held at 1080℃ for 2 hours for sintering.

[0102] Step 8: After sintering, the spherical pad material is sieved through a 100-mesh sieve to remove lumps and fragments. At this point, the spherical pad material is completed and is placed into the sintering crucible for the surge arrester resistor sheet.

[0103]

[0104] As can be seen, this invention uses granulation waste as raw material and employs a titration molding method to prepare spherical pads. The essence lies in using surface tension to drive spheroidization as the core, transforming the granulation waste recovered during the granulation process into regularly shaped and stable spherical pads, which are ultimately used for the sintering of surge arrester resistor sheets, exhibiting excellent yield rates. Furthermore, the key to this invention lies in precisely controlling the slurry viscosity, titration parameters, shaping medium characteristics, and glue removal sintering process to ensure that the spherical shape is maintained and the pad performance is improved at each step, ultimately meeting the sintering requirements of surge arrester resistor sheets, while simultaneously solving the defects and resource waste problems of traditional pads.

[0105] In summary, this invention addresses the granulation waste generated during the spray granulation process in surge arrester resistor manufacturing (traditionally treated as scrap). By using this granulation waste as a pad material in a titration molding method, the invention utilizes it. This granulation waste possesses the same high-quality components as the surge arrester resistor substrate, allowing for direct preparation of the slurry without additional composition adjustments. This avoids the performance dispersion issues caused by compositional fluctuations in traditional pad materials prepared from waste resistors, while also achieving waste resource utilization, reducing raw material waste and production costs, and minimizing the environmental pressure from waste disposal, aligning with green manufacturing principles. Therefore, this invention has broad market application prospects and demand.

[0106] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing spherical pads for sintering surge arrester resistor sheets, characterized in that, Includes the following steps: S1: Provide slurry; the slurry, by molar percentage, comprises 60-65 mol% mixed waste, 0.6-1.0 mol% dispersant, 1.0-1.5 mol% binder, 0.1-0.2 mol% defoamer, and 30-35 mol% solvent; the mixed waste includes bismuth oxide, antimony oxide, and granulation waste; S2: The slurry provided in step S1 is dripped and molded. After the obtained molded blank is debonded and sintered, a spherical pad is obtained. The titration equipment includes a peristaltic pump and a dropper. The flow rate of the peristaltic pump is 5~8 mL / h, and the distance between the dropper and the surface of the titration medium is 5~8 cm.

2. The preparation method according to claim 1, characterized in that, The dispersant is selected from any one or more of D-134C or BYK; The adhesive is selected from PVA; The defoamer is selected from tributyl phosphate; The solvent is selected from water, and the water is pure water.

3. The preparation method according to claim 1 or 2, characterized in that, In the mixed waste, the molar ratio of bismuth oxide, antimony oxide and granulation waste is (1~4):(2~3):(93~97).

4. The preparation method according to any one of claims 1 to 3, characterized in that, The viscosity of the slurry is 500~800 mPa·s.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The verticality of the dripper is ≤1°.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The temperature of the shaping medium is 40~50℃, and the surface tension is 25~30 mN / m; The shaping medium is selected from any one or more of food-grade soybean oil or silicone oil; The shaping medium is subjected to filtration treatment; A buffer medium is provided at the bottom of the shaping medium, and the buffer medium is selected from quartz sand.

7. The preparation method according to any one of claims 1 to 6, characterized in that, After the molded blank is cleaned and dried, it is then debonded and sintered.

8. The preparation method according to any one of claims 7, characterized in that, The residual moisture content of the dried blank is ≤1 wt%.

9. The preparation method according to any one of claims 1 to 8, characterized in that, The temperature for discharging the adhesive is 400~500℃, and the heat preservation time is 2~3 hours.

10. The preparation method according to any one of claims 1 to 9, characterized in that, The sintering process includes: pre-firing at 850~950℃ for 2~3 hours, and holding at 1050~1150℃ for 2~3 hours.

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