A forming process of mullite phase in the manufacture of an electric porcelain insulator

Abstract

This invention relates to the field of special ceramic product manufacturing technology, and discloses a mullite phase forming process in the manufacture of electrical porcelain insulators. The process includes: multi-stage ball milling and refining of multi-element natural clay raw materials, followed by multi-stage iron removal and sieving to form a slurry; extruding cylindrical clay segments with a diameter of 25 mm through pressing and vacuum kneading; shaping the slurry into insulator green blanks with insulating skirt structures; segmental drying; rigidly reducing the heating rate to 15℃ / h to 25℃ / h in the 1050℃ to 1150℃ phase transition temperature range and maintaining this rate for 4h to 6h to limit the rate of eutectic liquid phase explosion; and high-temperature firing at 1300℃. This invention delays the eutectic reaction to construct a high-viscosity liquid phase confinement field, inhibits the erosion of mullite crystal nuclei by alkali metal ions, forms an in-situ interpenetrating needle-like mullite crystal network, eliminates over-firing deformation during sintering, enhances internal stress dissipation, and improves the electrical insulation reliability and axial mechanical load of special ceramic components.

Description

Technical Field

[0001] This invention relates to the field of special ceramic product manufacturing technology, and in particular to a mullite phase forming process in the manufacturing of electrical porcelain insulators. Background Technology

[0002] Currently, in the manufacturing of insulation components for high-voltage transmission lines, the crystallization process of high-output porcelain insulators relies on a bauxite-rich system. Through high-temperature sintering, isotropic needle-like mullite crystal phase networks are precipitated inside the green body. The interface pinning mechanism between the crystal phase framework and the glass phase is used to bear the 160KN axial mechanical output load. This approach is the standard practice for the mass production of special electrical porcelain and constitutes a technical solution that is widely recognized in the industry.

[0003] With the evolving demands for supply chain control and efficiency in power transmission and transformation projects, the use of low-alumina electrical porcelain formulations based on mineral clay components to replace bauxite has become an important attempt in the ceramics industry. However, this system is prone to exhibiting structural defects such as uncontrolled solid-liquid phase transformation rates during high-temperature firing. Because the feldspar minerals enriched in the clay contain high concentrations of alkali metal oxides, within a specific narrow temperature range during the solid-liquid phase transformation, the low-viscosity eutectic liquid phase undergoes instantaneous explosive aggregation, leading to a sharp drop in liquid phase shear resistance and the formation of low-resistance mass transfer channels. This causes free alkali metal cations to diffuse rapidly towards the periphery of the crystal nucleus along these channels, resulting in disordered high-temperature melting. This hinders the directional crystallization and development of mullite crystals along specific lattice vector directions, leading to degradation. The stoichiometric ratio of the crystal phase aspect ratio leads to excessive glass phase and coarsening and fracture of the main crystal phase inside the ceramic body, causing stress concentration fracture when the component is subjected to impact. There are also shortcomings in the high-temperature thermal field control aspect. For example, Chinese invention patent CN118580063B discloses an electrical porcelain insulator and its preparation method, which improves mechanical strength by introducing exogenously hydrothermally modified mullite whiskers and potassium hexatitanate whiskers. However, this technical solution relies on the mechanical mixing of pre-synthesized modified whiskers with specific ternary ceramic powders, which cannot address the issue of excessive glass phase and coarsening of the main crystal phase in multi-component natural clay raw materials. When the bottom-layer phase transformation dynamics are triggered by the enrichment of rock minerals, the modified whiskers introduced from outside cannot exert active micro-region rheological constraints on the high concentration of thermosensitive alkali metal oxides. Within a specific narrow temperature range in the middle of the solid-liquid phase transformation, the low-viscosity eutectic liquid phase that bursts instantaneously inside the clay causes the overall pinning effect of the external whiskers to fail due to spatial displacement. Moreover, without the control of thermal temperature field rheological damping, the disordered mass transfer of high-temperature alkali metal ions can even reverse melt and destroy the lattice topology of the external whiskers, making it difficult to eliminate the high-temperature overheating rheological and main crystal phase coarsening fault defects in the low-alumina clay formulation system.

[0004] Therefore, the technical problem to be solved by this invention is how to control the phase transformation rate in the firing temperature field under the constraint of low aluminum formulation, so as to construct a silicon-aluminum-rich high-viscosity microfield and suppress the high-temperature erosion of mullite crystal phase by alkali metals, form isotropic high aspect ratio mullite interpenetrating crystal network, and ensure the fracture resistance performance of insulating components under high output load. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a mullite phase forming process in the manufacture of electrical porcelain insulators, comprising the following steps: Step S1: The multi-element natural clay raw materials are ball-milled and refined in multiple stages and then screened to remove iron in multiple stages to form a slurry. A high-strength electromagnetic filter is used to adsorb and remove free iron impurities in the slurry, thereby reducing the conductivity of the slurry to obtain a homogenized slurry. Step S2: The homogenized mud is pressed and dewatered using a plate and frame press to form pressed mud material. The pressed mud material is fed into a vacuum mud refining equipment and continuously sheared by an axial spiral cutter while applying an axial pressure of 1.8MPa to 2.5MPa to expel internal air. Cylindrical mud segments with a diameter of 25mm are extruded and fed into a die-spinning molding equipment to be shaped into insulator blanks with insulating skirt structures. Step S3: The insulator blank is left to dry in a shaded drying room with an ambient temperature of 20°C to 25°C and a relative humidity of 70% to 75% for 48 hours, and then sent to a continuous drying oven for segmented drying until the residual moisture content is less than 0.5%. A white glaze layer with a thickness of 0.2 mm to 0.3 mm is applied to the surface of the insulator blank. Step S4: The insulator green blank after applying the white glaze layer is loaded onto the kiln car and pushed into the kiln. The thermal temperature field inside the kiln is controlled to cover the front heating zone, the middle crystallization zone and the rear cooling zone, so that needle-shaped mullite crystals and columnar mullite crystals with an aspect ratio of 6 to 12 are precipitated, forming an interpenetrating crystal network structure inside the ceramic matrix.

[0006] Preferably, the first heating range of controlling the thermal field in the furnace in step S4 includes the following sub-steps: Step S41, within the temperature range of 20℃ to 1050℃, controlling the heating rate of the thermal field in the furnace to be 80℃ / h to 100℃ / h; Step S42, controlling the dehydration rate in the first heating range to transform the kaolinite phase into the metakaolinite phase, thereby solidifying the white glaze layer and the ceramic matrix.

[0007] Preferably, the process of feeding the pressed mud into the vacuum mud-refining equipment in step S2 includes the following sub-steps: step S21, controlling the axial spiral cutter to continuously shear and apply an axial pressure of 1.8MPa to 2.5MPa to remove the internal air of the pressed mud; step S22, continuously extruding cylindrical mud segments with a diameter of 25mm through a die head with a predetermined outlet orifice.

[0008] Preferably, the process of feeding the cylindrical clay segment into the die-spinning forming equipment in step S2 includes the following sub-steps: Step S23, positioning the cylindrical clay segment on the central axis of the die-spinning mold, and controlling the die-spinning forming equipment to spin-form according to the preset contour trajectory; Step S24, adjusting the force distribution of the die-spinning forming equipment to shape the cylindrical clay segment into an insulator blank with an insulating skirt structure.

[0009] Preferably, the process of sending the insulator green blanks into the continuous drying chamber for segmented drying in step S3 includes the following sub-steps: Step S31, introducing the residual heat of the kiln as the drying heat source, and sending the insulator green blanks after static drying into the continuous drying chamber; Step S32, controlling the maximum drying temperature of the continuous drying chamber to be 105°C to 110°C, and controlling the drying cycle to be 24h to 30h, so that the residual moisture content of the insulator green blanks is less than 0.5%.

[0010] Preferably, the process of applying a white glaze layer to the surface of the insulator blank in step S3 includes the following sub-steps: step S33, immersing the dried insulator blank in glaze slurry and controlling the immersion time and pulling rate; step S34, forming a white glaze layer with a thickness of 0.2 mm to 0.3 mm on the insulating skirt structure and outer surface of the insulator blank.

[0011] Preferably, the mid-stage crystallization zone in step S4 includes the following sub-steps: Step S43, controlling the heating rate of the furnace thermal field to be 15℃ / h to 25℃ / h within a temperature range of 1100℃ to 1350℃; Step S44, controlling the furnace thermal field to be held at a temperature range of 1100℃ to 1350℃ for 3h to 5h to complete the crystallization of aluminum-silicon components in the ceramic matrix.

[0012] Preferably, the process of precipitating needle-shaped mullite crystals and columnar mullite crystals in step S4 includes the following sub-steps: Step S45, adjusting the holding time in the middle crystallization zone to control the aspect ratio of the needle-shaped mullite crystals and columnar mullite crystals precipitated in the ceramic matrix to be 6 to 12; Step S46, interweaving the needle-shaped mullite crystals and columnar mullite crystals with an aspect ratio of 6 to 12 to construct an interpenetrating crystal network structure inside the ceramic matrix.

[0013] Preferably, the later cooling section in step S4 includes the following sub-steps: step S47, controlling the kiln to cool down to the liquid phase solidification point at a cooling rate of 30℃ / h to 50℃ / h in the later stage of firing; step S48, after cooling down to the liquid phase solidification point, allowing the furnace temperature to cool down to room temperature along with the furnace to reduce the residual stress of the ceramic matrix.

[0014] The beneficial effects of this invention are: 1. In the manufacturing of electrical porcelain insulators, by selecting specific proportions of bauxite, feldspar, Ji'an clay, Hunan clay, Guangdong clay, and Zhangzhou clay and combining them together, and controlling the transition to a low-rate heating in the mid-temperature phase transition region, the instantaneous burst speed of the micro-region eutectic reaction of the multi-component clay components is limited. This constructs a high-viscosity microphase field rich in silicon and aluminum inside the green body, suppresses the sudden drop in viscosity of the eutectic liquid phase that leads to the overall rheological changes of the green body, alleviates the disordered erosion of mullite crystal nuclei by alkali metal oxides at high temperatures, maintains the structural balance of liquid-solid phase volume fraction during high-temperature sintering, improves the thermal stability of the ceramic matrix in the solid-liquid coexistence state, and eliminates the structural defects of high-temperature overheating deformation that are prone to occur in traditional low-alumina systems.

[0015] 2. Under the constraint of this high-viscosity micro-phase field, the corundum phase and active silica steadily carry out interfacial mass transfer reaction during the holding stage at the highest firing temperature. This provides the in-situ generated mullite grains with the kinetic conditions for directional development, allowing the grains to crystallize and grow in a directional manner along a specific lattice vector direction. This results in the precipitation of needle-like and columnar mullite crystals with high aspect ratios, constructing an interpenetrating crystal network topology within the ceramic matrix. This enhances the interfacial pinning effect of the crystal phase in the glass matrix, locks the slip channels of the high-temperature liquid phase, and prevents unimpeded transgranular brittle fracture of cracks under stress concentration. It directly transforms the brittle tearing mode into an energy dissipation mode, improving the flexural strength of the finished product.

[0016] 3. Through cascade ball milling, cascade iron removal and sieving, and plate and frame pressing dehydration, the multi-element natural clay raw materials achieve a highly uniform particle size distribution. Combined with high-strength electromagnetic adsorption to remove free iron impurities in specific areas, the conductivity fluctuations within the slurry are reduced, preventing micropores and sintering cracks caused by impurity accumulation. This improves the density of the structure during continuous clay preparation and vacuum extrusion, ensuring that the skirt structure of the formed electrical porcelain has uniform crystalline phase symmetry. It also eliminates residual internal stress caused by uneven slurry moisture content, ensuring the electrical insulation reliability and dimensional stability of each batch of special ceramic components in the mass production process. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a flowchart of the mullite phase forming process in the manufacture of the electrical porcelain insulator of the present invention. Figure 2 This is a diagram showing the mullite phase forming process in the manufacture of the electrical porcelain insulator of this invention. Detailed Implementation

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0019] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0020] Secondly, an embodiment or embodiment referred to herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. Embodiments appearing in different places in this specification do not all refer to the same embodiment, nor are they separate or selective embodiments that are mutually exclusive with other embodiments.

[0021] This invention is described in detail with reference to the schematic diagrams. When describing the embodiments of this invention, for ease of explanation, the cross-sectional views of the device structure will be partially enlarged without adhering to the general scale. Moreover, the schematic diagrams are only examples and should not limit the scope of protection of this invention. In addition, in actual manufacturing, the three-dimensional spatial dimensions of length, width and depth should be included.

[0022] Furthermore, in the description of this invention, it should be noted that the terms such as "upper," "lower," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or component referred to has a specific orientation, or is constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] Unless otherwise explicitly specified and limited, the terms installation, connection, and linking in this invention should be interpreted broadly. For example, they can refer to fixed connection, detachable connection, or integrated connection; similarly, they can refer to mechanical connection, electrical connection, or direct connection, or indirect connection through an intermediate medium, or internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] A mullite phase forming process in the manufacture of electrical porcelain insulators includes the following steps: Step S1: The multi-element natural clay raw materials are ball-milled and refined in multiple stages and then screened to remove iron in multiple stages to form a slurry. A high-strength electromagnetic filter is used to adsorb and remove free iron impurities in the slurry, thereby reducing the conductivity of the slurry to obtain a homogenized slurry. Step S2: The homogenized mud is pressed and dewatered using a plate and frame press to form pressed mud material. The pressed mud material is fed into a vacuum mud refining equipment and continuously sheared by an axial spiral cutter while applying an axial pressure of 1.8MPa to 2.5MPa to expel internal air. Cylindrical mud segments with a diameter of 25mm are extruded and fed into a die-spinning molding equipment to be shaped into insulator blanks with insulating skirt structures. Step S3: The insulator blank is left to dry in a shaded drying room with an ambient temperature of 20°C to 25°C and a relative humidity of 70% to 75% for 48 hours, and then sent to a continuous drying oven for segmented drying until the residual moisture content is less than 0.5%. A white glaze layer with a thickness of 0.2 mm to 0.3 mm is applied to the surface of the insulator blank. Step S4: The insulator green blank after applying the white glaze layer is loaded onto the kiln car and pushed into the kiln. The thermal temperature field inside the kiln is controlled to cover the front heating zone, the middle crystallization zone and the rear cooling zone, so that needle-shaped mullite crystals and columnar mullite crystals with an aspect ratio of 6 to 12 are precipitated, forming an interpenetrating crystal network structure inside the ceramic matrix.

[0025] Preferably, the first heating range of controlling the thermal field in the furnace in step S4 includes the following sub-steps: Step S41, within the temperature range of 20℃ to 1050℃, controlling the heating rate of the thermal field in the furnace to be 80℃ / h to 100℃ / h; Step S42, controlling the dehydration rate in the first heating range to transform the kaolinite phase into the metakaolinite phase, thereby solidifying the white glaze layer and the ceramic matrix.

[0026] Preferably, the process of feeding the pressed mud into the vacuum mud-refining equipment in step S2 includes the following sub-steps: step S21, controlling the axial spiral cutter to continuously shear and apply an axial pressure of 1.8MPa to 2.5MPa to remove the internal air of the pressed mud; step S22, continuously extruding cylindrical mud segments with a diameter of 25mm through a die head with a predetermined outlet orifice.

[0027] Preferably, the process of feeding the cylindrical clay segment into the die-spinning forming equipment in step S2 includes the following sub-steps: Step S23, positioning the cylindrical clay segment on the central axis of the die-spinning mold, and controlling the die-spinning forming equipment to spin-form according to the preset contour trajectory; Step S24, adjusting the force distribution of the die-spinning forming equipment to shape the cylindrical clay segment into an insulator blank with an insulating skirt structure.

[0028] Preferably, the process of sending the insulator green blanks into the continuous drying chamber for segmented drying in step S3 includes the following sub-steps: Step S31, introducing the residual heat of the kiln as the drying heat source, and sending the insulator green blanks after static drying into the continuous drying chamber; Step S32, controlling the maximum drying temperature of the continuous drying chamber to be 105°C to 110°C, and controlling the drying cycle to be 24h to 30h, so that the residual moisture content of the insulator green blanks is less than 0.5%.

[0029] Preferably, the process of applying a white glaze layer to the surface of the insulator blank in step S3 includes the following sub-steps: step S33, immersing the dried insulator blank in glaze slurry and controlling the immersion time and pulling rate; step S34, forming a white glaze layer with a thickness of 0.2 mm to 0.3 mm on the insulating skirt structure and outer surface of the insulator blank.

[0030] Preferably, the mid-stage crystallization zone in step S4 includes the following sub-steps: Step S43, controlling the heating rate of the furnace thermal field to be 15℃ / h to 25℃ / h within a temperature range of 1100℃ to 1350℃; Step S44, controlling the furnace thermal field to be held at a temperature range of 1100℃ to 1350℃ for 3h to 5h to complete the crystallization of aluminum-silicon components in the ceramic matrix.

[0031] Preferably, the process of precipitating needle-shaped mullite crystals and columnar mullite crystals in step S4 includes the following sub-steps: Step S45, adjusting the holding time in the middle crystallization zone to control the aspect ratio of the needle-shaped mullite crystals and columnar mullite crystals precipitated in the ceramic matrix to be 6 to 12; Step S46, interweaving the needle-shaped mullite crystals and columnar mullite crystals with an aspect ratio of 6 to 12 to construct an interpenetrating crystal network structure inside the ceramic matrix.

[0032] Preferably, the later cooling section in step S4 includes the following sub-steps: step S47, controlling the kiln to cool down to the liquid phase solidification point at a cooling rate of 30℃ / h to 50℃ / h in the later stage of firing; step S48, after cooling down to the liquid phase solidification point, allowing the furnace temperature to cool down to room temperature along with the furnace to reduce the residual stress of the ceramic matrix.

[0033] Example 1: During the large-scale production of suspension porcelain insulators for high-voltage transmission lines, the multi-component natural clay raw materials are affected by fluctuations in the physicochemical properties of incoming batches and are subjected to continuous heating. Due to the presence of 2% to 7% potassium oxide and 0.1% to 0.2% sodium oxide by mass of feldspar minerals enriched in the clay, the green body undergoes explosive accumulation of low-viscosity eutectic liquid phase within the solid-liquid phase transition temperature range of 1050℃ to 1150℃, leading to high-temperature overmelting and overheating deformation. At this time, free alkali metal cations diffuse along low-resistance mass transfer channels to the periphery of mullite crystal nuclei and cause high-temperature erosion, hindering the crystallization and development of mullite crystals. This results in a degradation of the aspect ratio of the main crystalline phase, accompanied by grain coarsening and corrosion, causing enrichment of the glassy phase inside the ceramic matrix and local crystal fractures. Consequently, the components exhibit transgranular brittle fracture when subjected to axial mechanical loads, resulting in a flexural strength of less than 160KN for the finished porcelain insulator.

[0034] A mixture of various natural clay raw materials was weighed and blended according to the following weight percentages: bauxite 16% to 19%, feldspar 16% to 18%, Ji'an clay 16.5% to 18%, Hunan clay 27% to 30%, Guangdong clay 1.5% to 3.5%, and Zhangzhou clay 16% to 19%. This mixture was then fed into a rolling ball mill lined with high-alumina bricks. The material, ball, and water weight ratio was controlled at 1:2:0.65, and the milling was continuously performed for 18 to 22 hours until the residue on a standard inspection sieve with a 0.045 mm aperture was less than 0.1%, thus forming a slurry. A high-strength electromagnetic filter was then used to adsorb and remove free iron impurities from the slurry. To improve the quality of the mud and reduce its conductivity to achieve homogenization, the high-strength electromagnetic filter is equipped with a magnetohydrodynamic (MHD) coil. By inputting an excitation current of 15 to 25 amperes, a high-strength, homogeneous static magnetic field of 1.5 to 2.2 Tesla is generated in the central region of its flow channel. This field efficiently captures micron-sized free iron, iron oxide, and paramagnetic iron-containing mineral impurities in the mud. As these free iron impurities are adsorbed and removed, the charge density of mobile cations within the mud decreases significantly, reducing the mud conductivity from an initial 320 microsiemens per meter to below 85 microsiemens per meter. The conductivity fluctuation is controlled within 5% to obtain a uniform and homogenized slurry. The homogenized slurry is then dewatered using a plate and frame press to form pressed mud. This pressed mud is fed into a vacuum refining equipment, where continuous shearing by an axial spiral cutter and high axial pressure remove residual air. An axial pressure of 1.8 MPa to 2.5 MPa is applied, and a cylindrical mud segment with a diameter of 25 mm and a highly dense structure is extruded through a die head with a predetermined outlet diameter. This cylindrical mud segment is then fed into a die-spinning and shaping equipment and spinned according to a preset contour trajectory. The force distribution is adjusted to shape the cylindrical mud segment into... Insulator green blanks with a predetermined insulating skirt topology are prepared. The green blanks are then left to dry in a shaded drying room at an ambient temperature of 20°C to 25°C and a relative humidity of 70% to 75% for 48 hours. Next, the green blanks are pushed into a continuous drying oven using waste heat from the kiln as a heat source for long-term, stepped drying. The maximum drying temperature of the oven is controlled at 105°C to 110°C, and the drying cycle is maintained for 24 to 30 hours, reducing the final residual moisture content of the green blanks to below 0.5%. Finally, a uniform characteristic white glaze is applied to the surface of the dried green blanks using an impregnation glaze process, with the glaze thickness controlled to be 0.2 mm to 0 mm.3mm; In specific operation, this glazing process is achieved by completely immersing the dried insulator green blank into the prepared glaze slurry. The immersion time of the green blank in the glaze slurry is controlled to be 3 to 6 seconds to ensure that the glaze slurry can fully adhere and undergo uniform capillary adsorption on the surface of the green blank. The robotic arm of the die-spinning equipment is controlled to lift the green blank vertically upward from the glaze slurry surface at a constant lifting speed of 12 cm / s to 18 cm / s. Utilizing the surface tension and fluid viscosity resistance of the glaze slurry itself, it naturally flows and levels on the insulating skirt structure and outer surface of the green blank, thereby precisely forming a dense and airless structure with a thickness of 0.2mm to 0.3mm. The white glaze layer on the insulator is applied by loading the green insulator blanks onto kiln cars and pushing them into a shuttle kiln. The furnace temperature is controlled within a low-temperature range of 20℃ to 1050℃, maintaining a heating rate of 80℃ / h to 100℃ / h to allow the kaolinite phase to transform into a metakaolinite phase and solidify the white glaze layer and ceramic matrix. When the furnace temperature transitions to the phase transition temperature range of 1050℃ to 1150℃, the heating rate is rigidly reduced to 15℃ / h to 25℃ / h and maintained for 4 to 6 hours to limit the rate of eutectic liquid phase eruption. This forms a high-viscosity liquid phase layer rich in silica and alumina inside the green insulator, delaying the eutectic phase transition. The melting reaction employs a heating rate of 80℃ / h to 100℃ / h in the initial heating range of 20℃ to 1050℃, switching to a slower heating rate of 15℃ / h to 25℃ / h in the phase transition temperature range of 1050℃ to 1150℃. To accommodate the collaborative management needs of multiple kilns deployed in a cluster within the production line, the central control unit is equipped with a collaborative management module. This module collects real-time thermal load data for each kiln and the peak and valley status of the power grid supply. It distributes adjustment quantities using a target allocation strategy based on energy consumption balance. When the material currently loaded in the kiln is in a high feldspar variant condition, the feedback signal output after the initial heating reaches 1050℃ triggers a control mode reconfiguration. The mid-section crystallization zone automatically extends and covers the temperature range of 1100℃ to 1350℃. Within this range, a uniform slow crystallization drive signal of 15℃ / h to 25℃ / h is maintained. The holding time in the mid-section crystallization zone is adjusted to 3h to 5h. When the volume fraction of the high-temperature glass phase is high, a continuous low-rate energy supply is provided for the crystallization of the aluminum-silicon component. When the material belongs to the standard low feldspar formulation, after the mid-section phase transformation temperature zone ends, the sintering logic of 1150℃ to 1300℃ is directly adopted, and the temperature is increased to the maximum firing temperature of 1300℃ at a rate of 50℃ / h to 60℃ / h and held for 2.5h to 3h.In 5 hours, smooth switching of multi-modal process control is achieved. To coordinate the thermal adaptive requirements of different billet thicknesses and alkali metal contents, the multi-segment control logic of the furnace thermal temperature field is bridged by the process mode switching matrix of the central control unit. When the system detects that the material is a large-size or high-feldspar variant, the billet thermal state signal output after the front-end heating to 1150℃ will trigger process switching, so that the middle-stage crystallization zone is automatically covered and extended to a wide temperature range of 1100℃ to 1350℃. Within this wide temperature range, the control... The control unit refactors the original phased rapid heating command into a uniform slow crystallization drive signal of 15℃ / h to 25℃ / h throughout the process, and extends the holding output command to 3h to 5h. This ensures a continuous low-rate energy supply for the crystallization kinetics of the aluminum-silicon component when the volume fraction of the glass phase is high at high temperatures. Conversely, under standard operating conditions, it directly undertakes the accelerated sintering logic from 1150℃ to 1300℃. This achieves a smooth transition and compatibility between the two temperature field control modes through modal reconfiguration of the control signal.

[0035] Within the high-temperature sintering region of 1150℃ to 1300℃ in the furnace, the heating rate is controlled to rise to 50℃ / h to 60℃ / h, and the temperature is held at the maximum firing temperature of 1300℃ for 2.5 to 3.5 hours. This allows the corundum phase and active silica to undergo an in-situ interfacial mass transfer reaction in a high-viscosity liquid phase layer rich in silica and alumina. This process blocks the erosion of the crystal nuclei by alkali metal cations and inhibits the later-stage melting and coarsening of the mullite phase, promoting the development of the main crystalline phase and precipitating needle-like and columnar mullite crystals with an aspect ratio of 6 to 12 within the ceramic matrix. An interpenetrating crystal network structure is formed in situ within the ceramic matrix. This crystal network, formed by the interweaving of needle-like and columnar mullite crystals, generates a grain boundary pinning effect and a stress transmission closed loop within the ceramic matrix. This transforms the transgranular tearing mode under localized stress concentration into stress dissipation through deflection and circumduction of cracks within the needle-like crystal network. This improves the mechanical output and electrical insulation reliability of the finished porcelain insulator, enabling it to achieve a mechanical output of 160 kN. It also enhances the component's resistance to physical impacts in the power grid service environment. The chemical composition of each element within the ceramic matrix is ​​maintained at a certain mass percentage. 45% to 55% 35% to 40% 0.05% to 0.15%, 0.2% to 1% 0.2% to 3% 0.02% to 0.8% The phase equilibrium range is 0.1% to 0.2%.

[0036] Example 2: Verification of a mullite phase forming process in the manufacture of electrical porcelain insulators on a special ceramics manufacturing test platform. The test environment consisted of a high-alumina brick-lined rolling ball mill, a high-strength electromagnetic iron separator, a two-stage vacuum ply mill, and a shuttle kiln equipped with a platinum-rhodium thermocouple temperature control system. The temperature control system of the kiln had a temperature control accuracy better than ±1℃ and a sampling frequency set to 1Hz to supply in-situ temperature acquisition data stream. When determining the key parameter of the heating rate in the middle phase transformation temperature zone of the shuttle kiln, its value was mainly controlled by the formation rate of the eutectic liquid phase induced by alkali metal oxides in the natural clay raw material, and the mullite crystals. The in-situ precipitation kinetics of the phase involves a technical trade-off between slowing down the burst rate of the eutectic liquid phase to maintain the confinement field of the high-viscosity, silica-alumina-rich liquid phase and reducing kiln thermal energy consumption and shortening the firing cycle. The control rule follows this: when the mass percentage of alkali metal oxides in the slurry tends towards the upper limit of the protection range, the heating rate is adjusted to its lower limit to enhance the mass transfer resistance of the high-viscosity liquid phase; conversely, when the concentration of alkali metal cations is low, the heating rate tends towards its upper limit to improve production efficiency. For a typical operating condition with a feldspar mass percentage of 17.0% and a potassium oxide mass percentage of 4.5%, the control rule is applied to... The heating rate within the 1050℃ to 1150℃ range was locked at 20℃ / h as the standard setting for this gradient verification experiment. To verify the boundary effect of process parameters within the phase transition temperature range on mullite network development, a comparative gradient was set. In the 1050℃ to 1150℃ temperature range of the mid-crystallization interval, if the heating rate was set to 30℃ / h (above 25℃ / h), the eutectic liquid phase would produce instantaneous explosive aggregation, leading to a sharp decrease in the high-temperature viscosity of the micro-region glass phase. Free alkali metal ions would accelerate the erosion of mullite crystal nuclei, reducing the average aspect ratio of the precipitated mullite crystals to below 5, making it impossible to construct an interpenetrating network structure, resulting in a poor finished product. The ultimate flexural strength of porcelain insulators deteriorates to below 145 kN. If the heating rate is set to 10℃ / h instead of 15℃ / h, although the liquid phase viscosity is maintained within a reasonable range, the residence time in the phase transition temperature zone is extended to more than 10 hours, resulting in grain coarsening and fragmentation of the main crystalline phase, reducing production efficiency, and increasing the thermal energy consumption of the kiln. In addition, if the continuous holding time in the phase transition temperature zone is shortened to 3 hours instead of 4 hours, the crystallization kinetics of the aluminum-silicon components in the ceramic matrix is ​​incomplete, the needle-like and columnar mullite crystals cannot be fully interwoven in space, the interface pinning effect is weakened, and the high-temperature liquid phase sliding channels cannot be locked, resulting in the flexural strength of the finished product degrading to 145 kN.8KN; If the continuous holding time is extended to 8 hours (more than 6 hours), the excessive eutectic liquid phase leads to overheating and deformation, and the twisted wire shrinkage rate of the finished porcelain insulator exceeds 3%, resulting in loss of dimensional stability. Experimental results show that the process window with a heating rate of 15℃ / h to 25℃ / h and a holding time of 4 to 6 hours is the optimal working window that balances material consistency, stress dissipation performance, and dimensional accuracy. In order to construct a multi-dimensional comparison system to fully confirm the synergistic effect and parameter boundaries of the mullite phase forming process, the experiment was divided into multiple test groups including gradient problems. Among them, the sample groups of this invention include a low-interference sample group with a total mass percentage of 2.15% of potassium oxide and sodium oxide in the raw materials, a medium-interference sample group with a total mass percentage of 4.52% of potassium oxide and sodium oxide, and a high-interference sample group with a total mass percentage of 6.88% of potassium oxide and sodium oxide, respectively, using the complete process path. The control groups included a conventional linear heating control group, an out-of-range heating control group one, an out-of-range heating control group two, and an out-of-range holding control group three. Specifically, the conventional linear heating control group maintained a linear heating rate of 90℃ / h within the temperature range of 1050℃ to 1150℃; the out-of-range heating control group one increased the heating rate in the middle phase transition temperature zone to 30℃ / h; the out-of-range heating control group two reduced the heating rate to 10℃ / h; and the out-of-range holding control group three maintained a heating rate of 20℃ / h but shortened the holding and crystallization time in that temperature zone to 3.0h. All green bodies were vacuum extruded under the same pressure of 2.15MPa and coated with a 0.25mm thick white glaze layer to eliminate measurement bias interference caused by geometric anisotropy.

[0037] During the high-temperature crystallization thermal process in a shuttle kiln, intermediate mass transfer kinetic data at various stages within the ceramic green body were obtained using an online high-temperature in-situ rheological measurement system. When the furnace temperature entered the middle phase transition temperature zone of 1050℃ to 1150℃, the measurement data showed that the traditional linear heating control group, due to the rapid heating of 90℃ / h, experienced instantaneous explosive melting of feldspar minerals, and the high-temperature viscosity of the residual glass phase in its micro-region decreased to [missing value] at 1100℃. Pa The disordered expansion of the low-viscosity eutectic phase reduces the high-temperature creep shear resistance of the green body. In the control group with an over-range heating rate of 30℃ / h, the viscosity of the micro-region glass phase is... Pa The long-range mass transfer diffusion rate of alkali metal cations remains at s. m 2 / s, correspondingly, the low-interference, medium-interference, and high-interference sample groups using the process path of this invention were subjected to a low-rate heating of 20℃ / h within the range of 1050℃ to 1150℃, so that the transformation rate of metakaolinite to mullite precursor was consistent with the formation rate of the eutectic liquid phase. The high-temperature viscosity of the micro-region residual liquid phase of each sample group was measured at 1100℃ as follows: Pa s、 Pa s and Pa s, generates a high-viscosity liquid-phase confinement field rich in silicon and aluminum with high mass transfer resistance inside the green body, reducing the diffusion coefficient of free alkali metal cations to m 2 / s, which restricts its dynamic migration by spatial steric hindrance.

[0038] After the shuttle kiln completed the final sintering cycle at the highest firing temperature of 1300℃ and held for 3.0 hours, the surface morphology of the punched sections of each sample group was characterized using scanning electron microscopy. A high-precision hydraulic universal testing machine was used to apply axial tensile loads to the finished suspension porcelain insulators to determine their ultimate flexural strength. Test data showed that in the conventional linear heating control group without ultra-low-speed heating control in the phase transformation temperature zone, the aspect ratio of the mullite grains inside the matrix was only 2.1, and the grains exhibited a high-temperature melting morphology. Secondary enrichment of the glassy phase occurred locally, leading to a degradation of the final axial flexural strength of the finished insulator to 122.5 kN. Furthermore, uneven linear shrinkage of the blank caused distortion and deformation. In the boundary parameter calculation, the over-range heating control group 1, due to the heating rate exceeding the upper limit, resulted in incomplete development of needle-like crystals, with a mullite aspect ratio of 4.1 and a final flexural strength of 141.2 KN. In contrast, the over-range heat preservation control group 3, due to insufficient crystallization heat preservation time, resulted in incomplete development of the interpenetrating network structure, with a mullite aspect ratio of 4.6 and a final flexural strength of 145.8 KN. This indicates that the defined parameter range constitutes a working window capable of preventing surface structure degradation. Simultaneously, the mullite main crystal phase aspect ratios of the low-interference, medium-interference, and high-interference sample groups of this invention remained stable at 11.4, 9.2, and 6.3, respectively, forming a uniformly interwoven interpenetrating crystal network within the ceramic matrix. The tested values ​​of the ultimate flexural strength of the finished products were 174.6 KN, 168.4 KN, and 161.8 KN, indicating that as the alkali metal cation content increases, the ultimate flexural strength exhibits a regular monotonically decreasing trend. However, even under interference conditions where the alkali metal cation concentration approaches the upper limit, the high-viscosity liquid phase confinement field can still stably maintain the overall mechanical output above 160 KN, proving the adaptability of the process path of this invention to raw material fluctuations. Through quantitative data calculation and surface structure confirmation of the above-mentioned multi-dimensional gradient control test, it is shown that changing the external thermal injection process parameters within the phase transition temperature range directly intervenes in the evolution law of solid-liquid phase transition inside the ceramic matrix, at 1050℃ to Within the 1150℃ temperature range, the high-temperature viscosity of the micro-region liquid phase is controlled by rigidly limiting the heating rate, forming a high-viscosity liquid phase confinement field that can delay the mass transfer rate of the low eutectic reaction. This is the process condition that induces the directional growth of needle-like and columnar mullite crystals and the spontaneous construction of an isotropic interpenetrating network. The establishment of this specific surface morphology determines the reconstruction of the mechanical stress dissipation path inside the finished porcelain insulator from a causal chain perspective, transforming localized concentrated stress into the deflection and bypassing of cracks within the network. Thus, without changing the low-cost properties of the raw materials, the ultimate flexural strength and electrical insulation reliability of the special ceramic components are improved, achieving closed-loop verification from precise control of physical process parameters to stable overall mechanical output.

[0039] Example 3: In this example, multi-component natural clay raw materials are fed into a multi-stage ball mill for refining. After multi-stage iron removal and sieving, a slurry is obtained. A high-strength electromagnetic filter is used to remove free iron impurities from the slurry, reducing its conductivity to below a predetermined threshold, resulting in a homogenized slurry. The homogenized slurry is then pressed and dewatered using a plate and frame press to obtain pressed clay. This pressed clay is then fed into a vacuum refining equipment. Under the continuous shearing and axial pressure of an axial spiral cutter, residual gas is extruded, resulting in dense cylindrical clay segments with a diameter of 25mm. These segments are then fed into a press... The molding and spinning equipment is used to process insulator blanks with a predetermined insulating skirt topology. The insulator blanks are placed in an indoor environment with an ambient temperature of 20℃ to 25℃ and a relative humidity of 70% to 75% and left to dry for 48 hours. The blanks are then pushed into a continuous drying oven that utilizes the waste heat of the kiln for step drying. The drying temperature of the oven is set at 105℃ to 110℃ and the drying cycle is 24 hours to 30 hours, so that the residual moisture content of the blanks is reduced to below 0.5%. A white glaze layer is applied to the surface of the blanks using an impregnation glazing process, and the glaze layer thickness is controlled to be 0.2 mm to 0.3 mm.

[0040] The glazed greenware is loaded onto kiln cars and pushed into a shuttle kiln. The temperature field is controlled in three characteristic zones: the initial heating zone (20℃ to 1050℃) with a heating rate of 80℃ to 100℃; the phase transformation zone (1050℃ to 1150℃) with a heating rate reduced to 15℃ / h to 25℃ / h and maintained for 4 to 6 hours to suppress the formation rate of the eutectic phase; and the high-temperature firing zone (50℃ / h to 60℃ / h) with the temperature continuing to rise to 1300℃ and fired at a constant temperature. This process reduces the erosion effect of alkali metal ions on mullite nuclei by constructing a high-viscosity liquid phase confinement field in the phase transformation zone, promotes the in-situ formation of interpenetrating needle-like mullite crystal networks, and eliminates over-firing deformation during sintering.

[0041] Example 4: In the large-scale industrial manufacturing of suspension porcelain insulators for high-voltage transmission lines, when the multi-component natural clay raw materials are affected by fluctuations in the physicochemical properties of batches and the kiln temperature field is under continuous heating, low-melting liquid phase agglomeration occurs inside the green body in the phase transition temperature range of 1050℃ to 1150℃, causing overmelting and overheating deformation during high-temperature sintering. To avoid this process bottleneck and solve the problem of crystal phase degradation caused by the disordered diffusion of alkali metal cations, the system introduces a feedback regulation mechanism based on the dynamic response of the green body's physical state in the sintering process. The regulation mechanism uses the in-situ temperature data stream collected in real time inside the kiln and the initial pressure residual fluctuations during the pressing and kneading stage as bidirectional constraint inputs. In actual operation, this feedback regulation mechanism is achieved by controlling the evolution of the surface phase through the corresponding control of the overall thermodynamic parameters. When the green body is subjected to 1.8MPa to 2.5MPa during the vacuum kneading stage...At an axial pressure of 5 MPa, minute differences in the internal density of the green body cause residual fluctuations in the extrusion pressure. This residual fluctuation value is used as an initial boundary condition input to the control system to characterize the initial porosity and particle contact density of the green body. When the furnace temperature enters the phase transition temperature range of 1050℃ to 1150℃, the transformation from kaolinite to metakaolinite and from metakaolinite to mullite precursors is accompanied by specific endothermic and exothermic effects, resulting in localized heat transfer within the green body. This, in turn, causes surface disturbances in the local temperature field heat transfer rate within the kiln. The temperature control system detects these disturbances through high-frequency data acquisition. The temperature change rate of the thermocouple is compared with the thermal absorption rate benchmark of a standard dense green body in pure clay. The slight difference in heat injection power reflects the aggregation and burst rate of the eutectic liquid phase and the mass transfer activity of alkali metal ions. By establishing an energy transfer chain between the overall heat flux and the latent heat of surface phase transformation, the system can precisely limit the development of mass transfer channels in the eutectic liquid phase by adjusting the fuel supply or electric heating power without directly observing the crystal morphology in situ. The control system has pre-stored viscosity change curves under standard conditions. Under kiln operation conditions, the control system... The system continuously collects the current temperature from the temperature detection component and determines the target viscosity by comparing it with the viscosity change curve. When the concentration of alkali metal cations in the clay raw material is high, the eutectic liquid phase aggregates, causing the interior of the green body to absorb specific phase change heat. This results in a downward deviation in the heating rate collected by the temperature detection component. The system calculates the amplitude of the downward deviation and converts it into a heat throughput fluctuation value. When the heat throughput fluctuation value exceeds 50W, it determines that a mass transfer channel has formed and outputs a downward control signal to the kiln heating actuator to reduce the opening of the gas valve and decrease the heating power, maintaining the heating rate at 15℃. Within the range of 25℃ / h to 100℃ / h, a high-viscosity liquid-phase confinement field is formed to limit the dynamic migration rate of alkali metal cations. A stress dissipation feedback matrix is ​​constructed based on the in-situ precipitation kinetics of the crystals. Using the cumulative heat effect of internal resistance in the phase transition temperature zone as input, the volume fraction and average aspect ratio of the mullite crystals are continuously calculated. When the calculated volume fraction reaches a preset threshold of 85%, the main crystal phase grain boundary pinning network is considered complete. An upward control signal is then output to the heating actuator to increase the gas valve opening and heating power, causing the furnace temperature to switch back to a rapid heating mode of 50℃ / h to 60℃ / h.

[0042] At the 1050℃ phase transition temperature starting point, the temperature control system calculates the kinetic thermal compensation requirement within the temperature range based on the real-time collected temperature field temperature and the preset reference viscosity curve. When the concentration of alkali metal oxides in feldspar minerals fluctuates upwards, leading to a decrease in local mass transfer resistance, the temperature control system automatically triggers a downward compensation action for the thermal injection power of the temperature field, setting the heating rate within the 1050℃ to 1150℃ range to 15℃ / h and maintaining this rate until a network of needle-like mullite crystals with an aspect ratio of 6 to 12 precipitates inside the green body. Based on the stress dissipation feedback model of the precipitated crystalline phase, the temperature control system adjusts the heating rate back to 50℃ / h and enters the high-temperature holding sintering stage at 1300℃, ultimately ensuring that the ultimate flexural strength of the finished insulator stably reaches over 160KN. This verifies the process adaptability and crystal structure development regulation effect of the dynamic temperature field adjustment mechanism under raw material batch fluctuations. Here, the preset reference viscosity curve... The line refers to the logarithmic viscosity distribution trajectory of the micro-region glass phase as a function of temperature in a pure kaolinite and feldspar mixture under standard low-alumina formulation constraints, measured in advance without impurity interference. The control system retrieves the corresponding target viscosity expectation value based on the currently collected real-time temperature, using this as a digital benchmark for determining the liquid phase rheological resistance. The stress dissipation feedback model is a pre-constructed multidimensional linear mapping matrix between the volume fraction of acicular mullite crystals, the average aspect ratio of grains, and the creep fracture toughness of the matrix. This model uses the cumulative thermal effect of the thermal heating rate and high-temperature holding time as inputs. By calculating the interpenetrating density of the crystal network developed by mullite along a specific lattice vector direction, it evaluates the energy dissipation resistance of the current ceramic structure against grain boundary slip. When the crystallinity index evaluated by the model reaches the preset 85% safety closed-loop threshold, it is determined that the interpenetrating network construction is complete, and the temperature control system is then triggered to output a heating callback command.

[0043] Example 5: Addressing the issue of drastic changes in liquid phase composition within the phase transition range of 1050℃ to 1150℃ in the raw material formulation, a standardized procedure based on thermal temperature field crystallization control was established. By precisely controlling the heating rate, a high-viscosity liquid phase confinement field was constructed to suppress the erosion of mullite crystal nuclei by alkali metal ions, ensuring the stability of the interpenetrating needle-like mullite crystal network. In the specific implementation process, 10 groups of porcelain insulator green blank samples with identical formulations were selected. All samples were in the same dry state, with a residual moisture content of less than 0.5%. The samples were then loaded... In a shuttle kiln, the following segmented firing steps are executed through a temperature control system. A firing temperature field curve is set, and the heating rate in the kiln is controlled at 90℃ / h in the range of 20℃ to 1050℃. When entering the phase transition temperature zone of 1050℃ to 1150℃, the samples are divided into 10 test batches, and the heating rate of each batch is set in a gradient of 2℃ / h, from 10℃ / h to 28℃ / h. After the phase transition temperature zone, the temperature in the kiln is further raised to 1300℃, and the heating rate is uniformly controlled at 55℃ / h, and constant temperature sintering is maintained for 3 hours.

[0044] The surface morphology of the sintered cross-sections of each batch of samples was analyzed using scanning electron microscopy, and the aspect ratio of the needle-like mullite crystals was determined. Aspect Ratio The calculation expression is: ,in, To determine the average length of mullite crystals within the region, The average diameter of the mullite crystals is given by the measured data. The data shows that when the heating rate in the phase transition temperature zone is controlled between 15℃ / h and 25℃ / h, the average aspect ratio of the needle-like mullite crystals stabilizes between 6 and 12, and a continuous interpenetrating crystal network structure is formed inside the ceramic matrix. When the heating rate is below 15℃ / h, the sintering cycle is too long, leading to increased energy consumption. When the heating rate is above 25℃ / h, the mullite crystal phase undergoes melting, and the aspect ratio drops below 5, resulting in deterioration of the structural strength of the ceramic component. Based on the above calibration results, the optimal process parameters for the phase transition temperature zone under this formulation system are established as follows: a heating rate of 20℃ / h, and a continuous holding time of 5 hours. Porcelain insulator components fired according to this standardized process were tested for axial bending strength on a pressure testing machine, and the average bending strength reached 165KN, confirming that these process parameters can improve the mechanical stability of the mullite crystal network inside the insulator.

[0045] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A mullite phase forming process in the manufacture of electrical porcelain insulators, characterized in that, Includes the following steps: Step S1: The multi-element natural clay raw materials are ball-milled and refined in multiple stages and then screened to remove iron in multiple stages to form a slurry. A high-strength electromagnetic filter is used to adsorb and remove free iron impurities in the slurry, thereby reducing the conductivity of the slurry to obtain a homogenized slurry. Step S2: The homogenized mud is pressed and dewatered using a plate and frame press to form pressed mud material. The pressed mud material is fed into a vacuum mud refining equipment and continuously sheared by an axial spiral cutter while applying an axial pressure of 1.8MPa to 2.5MPa to expel internal air. Cylindrical mud segments with a diameter of 25mm are extruded and fed into a die-spinning molding equipment to be shaped into insulator blanks with insulating skirt structures. Step S3: The insulator blank is left to dry in a shaded drying room with an ambient temperature of 20°C to 25°C and a relative humidity of 70% to 75% for 48 hours, and then sent to a continuous drying oven for segmented drying until the residual moisture content is less than 0.5%. A white glaze layer with a thickness of 0.2 mm to 0.3 mm is applied to the surface of the insulator blank. Step S4: The insulator green blank after applying the white glaze layer is loaded onto the kiln car and pushed into the kiln. The thermal temperature field inside the kiln is controlled to cover the front heating zone, the middle crystallization zone and the rear cooling zone, so that needle-shaped mullite crystals and columnar mullite crystals with an aspect ratio of 6 to 12 are precipitated, forming an interpenetrating crystal network structure inside the ceramic matrix.

2. The mullite phase forming process in the manufacture of electrical porcelain insulators according to claim 1, characterized in that, The first heating range of controlling the thermal field in the furnace in step S4 includes the following sub-steps: Step S41, within the temperature range of 20℃ to 1050℃, the heating rate of the thermal field in the furnace is controlled to be 80℃ / h to 100℃ / h; Step S42, the dehydration rate in the first heating range is controlled to transform the kaolinite phase into the metakaolinite phase, thereby solidifying the white glaze layer and the ceramic matrix.

3. The mullite phase forming process in the manufacture of electrical porcelain insulators according to claim 1, characterized in that, The process of feeding the pressed mud into the vacuum mud refining equipment in step S2 includes the following sub-steps: Step S21, controlling the axial spiral cutter to continuously shear and apply an axial pressure of 1.8MPa to 2.5MPa to remove the internal air of the pressed mud; Step S22, continuously extruding cylindrical mud segments with a diameter of 25mm through a die head with a predetermined outlet orifice.

4. The mullite phase forming process in the manufacture of electrical porcelain insulators according to claim 1, characterized in that, The process of feeding the cylindrical clay segment into the die-spinning forming equipment in step S2 includes the following sub-steps: Step S23, positioning the cylindrical clay segment on the central axis of the die-spinning mold, and controlling the die-spinning forming equipment to spin and form according to the preset contour trajectory; Step S24, adjusting the force distribution of the die-spinning forming equipment to shape the cylindrical clay segment into an insulator blank with an insulating skirt structure.

5. The mullite phase forming process in the manufacture of electrical porcelain insulators according to claim 1, characterized in that, The process of sending the insulator green blanks into the continuous drying chamber for segmented drying in step S3 includes the following sub-steps: Step S31, introducing the residual heat of the kiln as the drying heat source, and sending the green blanks after static drying into the continuous drying chamber; Step S32, controlling the maximum drying temperature of the continuous drying chamber to 105℃ to 110℃, and controlling the drying cycle to 24h to 30h, so that the residual moisture content of the green blanks is less than 0.5%.

6. The mullite phase forming process in the manufacture of electrical porcelain insulators according to claim 1, characterized in that, The process of applying a white glaze layer to the surface of the insulator blank in step S3 includes the following sub-steps: Step S33, immersing the dried insulator blank in the glaze slurry and controlling the immersion time and pulling rate; Step S34, forming a white glaze layer with a thickness of 0.2 mm to 0.3 mm on the insulating skirt structure and outer surface of the insulator blank.

7. The mullite phase forming process in the manufacture of electrical porcelain insulators according to claim 1, characterized in that, The intermediate crystallization zone in step S4 includes the following sub-steps: Step S43, within the temperature range of 1100℃ to 1350℃, the heating rate of the thermal field inside the furnace is controlled to be 15℃ / h to 25℃ / h; Step S44, the thermal field inside the furnace is controlled to be held at the temperature range of 1100℃ to 1350℃ for 3h to 5h to complete the crystallization of aluminum-silicon components in the ceramic matrix.

8. The mullite phase forming process in the manufacture of electrical porcelain insulators according to claim 1, characterized in that, The process of precipitating needle-shaped mullite crystals and columnar mullite crystals in step S4 includes the following sub-steps: Step S45, adjusting the holding time in the middle crystallization zone to control the aspect ratio of the needle-shaped mullite crystals and columnar mullite crystals precipitated in the ceramic matrix to be 6 to 12; Step S46, interweaving the needle-shaped mullite crystals and columnar mullite crystals with an aspect ratio of 6 to 12 to construct an interpenetrating crystal network structure inside the ceramic matrix.

9. The mullite phase forming process in the manufacture of electrical porcelain insulators according to claim 1, characterized in that, The subsequent cooling section in step S4 includes the following sub-steps: Step S47, controlling the kiln to cool down to the liquid phase solidification point at a cooling rate of 30℃ / h to 50℃ / h in the later stage of firing; Step S48, after cooling down to the liquid phase solidification point, allowing the furnace temperature to cool down to room temperature along with the furnace to reduce the residual stress of the ceramic matrix.

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