An abnormal ceramic antenna cover body forming die and a forming method

Abstract

The present application relates to a kind of special-shaped ceramic radome body forming mould and forming method, forming mould includes rigid outer sleeve, flexible inner sleeve, end cap, bottom disc;The rigid outer sleeve is set in flexible inner sleeve outside, the inner shape surface of outer mould forming part is combined with the outer shape surface of inner mould forming part, and the forming cavity is obtained, and the forming cavity is communicated with loading cavity;The end cap is equipped with tapered through hole or stepped hole, and the end cap also includes the plug of detachable connection with tapered through hole or stepped hole;Realize through cold isostatic pressing preparation ceramic body realizes the near size simulation of special-shaped ceramic radome and is formed with high forming precision, and ceramic radome curvature changes, size is big, simultaneously, special-shaped ceramic radome body avoids the cracking of forming body, deformation damage etc. in the release process due to the internal stress of different parts and "elastic aftereffect", realizes quality controllable.

Description

Technical Field

[0001] This invention relates to the field of ceramic radome technology, specifically to the field of forming molds and forming methods for irregularly shaped ceramic radome blanks. Background Technology

[0002] The radome protects the radar guidance system's internal seeker from external high-speed aerodynamic heat ablation and effectively transmits electromagnetic waves. Therefore, the radome combines heat protection, load-bearing capacity, and wave transmission functions. The radome is a non-uniform thin-walled spun body, i.e., an irregular structure. The development of ceramic radomes with high strength and high wave transmission performance has become one of the research hotspots at home and abroad.

[0003] The fabrication of the radome blank is a crucial step in the ceramic radome manufacturing process. The radome blank needs to achieve uniform particle density, high strength, and a certain porosity to avoid increasing the dielectric constant and dielectric loss. Traditional methods for fabricating radome blanks mainly involve 3D printing and cold isostatic pressing. However, 3D printing suffers from high binder content, cracking and deformation during binder removal, and even with successful binder removal, excessive porosity can lead to low strength. Without 3D printing, different cross-sections of irregularly shaped radome blanks have different structures and dimensions, resulting in significant curvature variations. This can easily lead to stress concentration at curvature transition points, inducing cracking in weak areas of the pressed blank. Furthermore, larger components are more difficult to distribute internal stress evenly.

[0004] During cold isostatic pressing, the uneven particle density in different parts of the cavity, the "elastic aftereffect" after particle compression molding, and the large-size irregular structure exacerbating the differences in internal stress distribution in different parts of the blank, all lead to problems such as frequent cracking and uncontrollable quality of the molded blank, which can no longer meet the development requirements of ceramic radomes.

[0005] Therefore, how to prepare irregularly shaped ceramic blanks through cold isostatic pressing to achieve near-size imitation molding with high molding accuracy, and how to ensure that the ceramic radome has large curvature and large size; the radome has a certain porosity and high density; and how to avoid cracking, deformation and damage of the irregularly shaped ceramic radome blanks due to internal stress in different parts and "elastic aftereffect" during the release process, so as to achieve quality control, has become a technical problem to be solved in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a molding die and molding method for irregularly shaped ceramic radome blanks, achieving near-size imitation molding of irregularly shaped ceramic radomes with high molding accuracy, and allowing for changes in curvature and large dimensions of the ceramic radome; the radome has a certain porosity and high density, while the irregularly shaped ceramic radome blank avoids cracking, deformation, and damage during the release of internal stress and "elastic aftereffects" in different parts, thus achieving controllable quality.

[0007] In one aspect, the present invention provides a molding die for forming an irregularly shaped ceramic radome blank, comprising a rigid outer mold sleeve, a flexible inner mold sleeve, an end cap, and a base; the rigid outer mold sleeve includes a first connecting part, a second connecting part, and an outer mold forming part, the outer mold forming part being provided with a first cavity; the first cavity includes a small-diameter end and a large-diameter end, the large-diameter end of the first cavity being open;

[0008] The outer mold forming part is connected to the first connecting part near the small diameter end; the outer mold forming part is connected to the second connecting part near the large diameter end.

[0009] The first connecting part includes a feeding part and an end connector. The feeding part is provided with a feeding cavity, which is in communication with the first cavity. The end connector is detachably connected to the end cap.

[0010] The flexible inner mold sleeve includes an inner mold forming part and a third connecting part. The inner mold forming part is provided with a second cavity. The first cavity is open at one end near the large diameter end of the first cavity.

[0011] The inner surface of the outer mold forming part is designed to conform to the outer surface of the irregular ceramic radome, and the outer surface of the inner mold forming part is designed to mimic the inner surface of the irregular ceramic radome.

[0012] The rigid outer mold sleeve is fitted outside the flexible inner mold sleeve. The inner surface of the outer mold forming part and the outer surface of the inner mold forming part are combined to form a forming cavity. The forming cavity is connected to the feeding cavity.

[0013] The second connecting part is detachably connected to the chassis, and the third connecting part is partially or entirely located between the second connecting part and the chassis;

[0014] The end cap is provided with a tapered through hole or a stepped hole, and the end cap also includes a plug that is detachably connected to the tapered through hole or the stepped hole.

[0015] Compared with the prior art, the present invention has the following beneficial effects: the rigid outer mold sleeve is fitted outside the flexible inner mold sleeve, and the inner surface of the outer mold forming part is combined with the outer surface of the inner mold forming part to form a forming cavity. The forming cavity is connected to the feeding cavity, so that the ceramic particles are added into the forming cavity through the feeding cavity. The ceramic particles in the forming cavity are cold isostatically pressed to obtain the irregular ceramic radome blank.

[0016] By conforming the inner surface of the outer mold forming part to the outer surface of the irregular ceramic radome, and by making the outer surface of the inner mold forming part conforming to the inner surface of the irregular ceramic radome, the near-size imitation forming of the irregular ceramic radome blank is achieved;

[0017] By fitting the rigid outer mold sleeve over the flexible inner mold sleeve, the flexible inner mold sleeve is compressed and rebounds tightly against the blank under external pressure. This helps avoid the elastic aftereffects of the blank when depressurizing, thus preventing cracking and damage to asymmetrical parts of the ceramic radome blank during depressurization. Simultaneously, it ensures contact between the flexible inner mold sleeve and the inner surface of the ceramic radome blank, and between the rigid outer mold sleeve and the outer surface of the ceramic radome blank, avoiding inaccurate curvature of the outer surface of the ceramic radome. Furthermore, it helps prevent cracking of the ceramic radome blank due to the greater curvature variation and larger component size caused by different cross-sections and dimensions of the irregular radome.

[0018] The end cap is provided with a tapered through hole or a stepped hole, which can extract air from the molding cavity, thereby helping to avoid the problem of delamination cracking in the ceramic antenna cover blank.

[0019] Furthermore, the irregular ceramic radome blank forming mold also includes an inner rigid sleeve;

[0020] The inner rigid hurdle sleeve includes a first rigid hurdle sleeve and a second rigid hurdle sleeve;

[0021] The first rigid guardrail includes a plurality of first rigid guardrails, a plurality of first connecting rods, and a first top plate; the first rigid guardrails are hinged to the edges of the first top plate; one end of the first connecting rod is hinged to the first top plate, and the end of the first connecting rod away from the first top plate is slidably connected to the first rigid guardrail;

[0022] The second rigid guardrail includes a plurality of second rigid guardrails and a second top plate; the edges of the second rigid guardrails and the second top plate are hinged.

[0023] The first rigid guardrail is fitted inside the second rigid guardrail, the first top plate is elastically connected to the second top plate, and the first rigid guardrail is elastically connected to the second rigid guardrail.

[0024] The first rigid guardrail is enclosed by several second rigid guardrails to form an adjustable accommodating space;

[0025] The outer surfaces of the first and second top plates are designed to mimic the inner surface of the flexible inner mold sleeve.

[0026] The second rigid guardrail and / or the first rigid guardrail are detachably connected to the chassis via a plurality of first elastic connectors;

[0027] Preferably, the first connecting rod includes a first sleeve, a second sleeve, and a plurality of first sleeves; a plurality of third sleeves are sleeved and connected, and the first sleeve and the second sleeve are respectively sleeved and connected to the third sleeves. The end of the first sleeve away from the second sleeve is hinged to the first top plate, and the end of the first sleeve away from the second sleeve is slidably connected to the first rigid guardrail.

[0028] More preferably, the first rigid rail is provided with a guide groove, and the first connecting rod is partially or entirely located in the guide groove.

[0029] The beneficial effect of the previous step is that, by having the inner rigid guardrail sleeve, which includes a first rigid guardrail sleeve and a second rigid guardrail sleeve, and the second rigid guardrail plate and / or the first rigid guardrail plate being detachably connected to the chassis through a plurality of first elastic connecting members, the inner rigid guardrail sleeve and the flexible inner mold sleeve are elastically connected; and by having the first rigid guardrail plate and the second rigid guardrail plate elastically connected, the first rigid guardrail sleeve and the second rigid guardrail sleeve are elastically connected.

[0030] The first rigid guardrail is hinged to the edge of the first top plate; one end of the first connecting rod is hinged to the first top plate, and the end of the first connecting rod away from the first top plate is slidably connected to the first rigid guardrail. This allows the space inside the first rigid guardrail to expand under pressure and increased pressure, and then the second rigid guardrail to contact and compress with the flexible inner mold sleeve. This ensures high curvature accuracy of the inner surface of the forming cavity that contacts the flexible inner mold sleeve, preventing a decrease in the accuracy of the inner surface of the ceramic radome due to the flexible inner mold sleeve. At the same time, when the pressure inside the first rigid guardrail decreases, the pressure transmitted from the first rigid guardrail to the flexible inner mold sleeve decreases slowly and evenly. This further helps to avoid the elastic aftereffect of the blank when depressurizing after pressurization, that is, it helps to avoid cracking and damage in asymmetrical parts of the ceramic radome blank during the depressurization process.

[0031] The first sleeve is hinged to the first top plate at one end away from the second sleeve, and the first sleeve is slidably connected to the first rigid guardrail when the first rigid guardrail is subjected to pressure and the pressure increases. At the same time, the first connecting rod supports the first rigid guardrail and moves closer to the flexible inner mold sleeve.

[0032] At the same time, it helps to solve the problem that different cross-sections of irregular radomes have different structures and sizes, and that the greater the curvature change and the larger the component size, the more difficult it is to distribute the internal stress evenly during the molding process, which makes the ceramic radome blank prone to cracking.

[0033] Furthermore, the rigid outer mold sleeve is made of structural steel or alloy material, and the wall thickness of the rigid outer mold sleeve is 15-30mm;

[0034] The flexible inner mold sleeve is made of polyurethane or rubber, and the wall thickness of the flexible inner mold sleeve is 6-15mm.

[0035] and / or

[0036] The third connecting part is interference-fitted to the outside of the second connecting part, the chassis is in partial contact with the third connecting part, and is detachably connected to the second connecting part.

[0037] The beneficial effect of the previous step is that, by using polyurethane or rubber as the material of the flexible inner mold sleeve, the flexible inner mold sleeve has both strength and flexibility. By using a wall thickness of 6-15mm for the flexible inner mold sleeve, the flexible inner mold sleeve will not undergo significant deformation when pressurized, but will slowly transmit pressure when depressurized.

[0038] In another aspect, the present invention provides a method for forming an irregularly shaped ceramic radome blank, wherein an irregularly shaped ceramic radome blank is prepared using any of the irregularly shaped ceramic radome blank forming molds described in any one of the present invention, specifically including the following steps:

[0039] A mixed powder is prepared, wherein the mixed powder comprises silicon nitride powder and auxiliary powder in a mass ratio of 100:(6-30); the auxiliary powder comprises one or more of alumina, boron nitride, and rare earth oxide powder; and the rare earth oxide powder comprises one of lanthanum oxide and yttrium oxide.

[0040] A ceramic slurry is prepared by mixing powder, dispersant, binder, and solvent; the ceramic slurry is then spray-dried to produce primary ceramic particles.

[0041] The primary ceramic particles are surface modified to obtain secondary ceramic particles;

[0042] The secondary ceramic particles are cold isostatically pressed into a shaped ceramic radome blank using a shaped ceramic radome blank forming mold.

[0043] Compared with the prior art, the present invention has the following beneficial effects: by including ceramic powder and rare earth oxide powder in the mixed powder, it is beneficial to achieve high strength of ceramic radome and to avoid agglomeration of the formula powder in the process of preparing ceramic slurry;

[0044] Surface modification of the ceramic particles improves their fluidity and lubricity, which helps avoid stress accumulation in the green body and strengthens the green body.

[0045] By conforming the inner surface of the outer mold forming part to the outer surface of the irregular ceramic radome, and by making the outer surface of the inner mold forming part conforming to the inner surface of the irregular ceramic radome, the near-size imitation forming of the irregular ceramic radome blank is achieved;

[0046] By fitting the rigid outer mold sleeve over the flexible inner mold sleeve, the flexible inner mold sleeve is compressed and rebounds tightly against the blank under external pressure. This helps to avoid the elastic aftereffects of the blank when depressurizing, thus preventing cracking and damage to asymmetrical parts of the ceramic radome blank during depressurization. Simultaneously, it ensures contact between the flexible inner mold sleeve and the inner surface of the ceramic radome blank, and between the rigid outer mold sleeve and the outer surface of the ceramic radome blank, thereby avoiding inaccurate curvature of the outer surface of the ceramic radome.

[0047] The end cap is provided with a tapered through hole or a stepped hole, which can extract air from the molding cavity, thereby helping to avoid the problem of delamination cracking in the ceramic antenna cover blank.

[0048] By using an inner rigid sleeve, the curvature accuracy of the inner surface in contact with the flexible inner mold sleeve in the forming cavity is high when the flexible inner mold sleeve is pressurized, and the accuracy of the inner surface of the ceramic radome is not reduced due to the flexible inner mold sleeve. When the pressure inside the flexible inner mold sleeve is reduced, the pressure of the flexible inner mold sleeve decreases uniformly and slowly, which further helps to avoid the elastic aftereffect problem of the blank when depressurization after pressurization. That is, it helps to avoid cracking and damage in asymmetrical parts of the ceramic radome blank during the depressurization process.

[0049] Furthermore, the method for preparing the ceramic slurry includes the following steps:

[0050] The binder and solvent are added to the grinding equipment, and then the dispersant and mixed powder are added and ground and mixed for 8-24 hours to obtain the ceramic slurry.

[0051] The mass ratio of the binder, solvent, dispersant, and mixed powder is (2-5):100:(0.2-2):(70-90);

[0052] The adhesive includes a first adhesive and a second adhesive;

[0053] The first binder comprises liquid paraffin; the second binder comprises one or both of polyvinyl butyral and dibutyl phthalate.

[0054] The solvents include ethanol and butanone;

[0055] The dispersant includes one or two of castor oil, glycerol, and triethyl phosphate; the median particle size of the mixed powder is between 0.5 and 1.5 μm.

[0056] The beneficial effect of the previous step is that, by using the binder, which includes a first binder and a second binder, the amount of binder added can be less while ceramic particles are being formed. This is beneficial to achieving a low porosity in the final irregularly shaped ceramic radome, thereby improving the strength of the irregularly shaped ceramic radome.

[0057] By using different types of the first and second binders, the second binder can be removed from the ceramic particles before cold isostatic pressing, while the first binder is retained. This ensures that the ceramic particles are not broken, and further facilitates the crushing or cracking of the ceramic particles during cold isostatic pressing. This improves the density of the irregularly shaped ceramic radome blank, ensures uniform distribution of ceramic powder, and helps avoid cracking in asymmetrical areas of the irregularly shaped radome caused by elastic aftereffects.

[0058] The median particle size of the ceramic formulation powder is between 0.5-1.5 μm, which further helps to avoid the agglomeration of the formulation powder during the preparation of ceramic slurry. At the same time, it avoids the problem of excessively large particle size, which would lead to excessively high porosity and excessively large pore size in the ceramic radome blank after subsequent ceramic particle molding, resulting in excessively low strength of the finished ceramic radome blank.

[0059] Furthermore, the primary ceramic particles include primary ceramic particles with a median particle size of 80-120 μm and primary ceramic particles with a median particle size of 10-30 μm;

[0060] The mass ratio of primary ceramic particles with a median particle size of 80-120 μm to primary ceramic particles with a median particle size of 10-30 μm is (10-30):10.

[0061] The beneficial effect of the previous step is that, by using ceramic particles with a median particle size of 80-120μm and ceramic particles with a median particle size of 10-30μm in a mass ratio of (10-30):10, a high ceramic particle filling rate and low porosity between ceramic particles are achieved in the radome molding die. By including ceramic particles with a median particle size of 10-30μm, it is beneficial to avoid the problem of rough appearance and to avoid the problems of poor fluidity, low plasticity, and large internal stress accumulation due to mutual meshing during compression molding when ceramic particles are added to the radome molding die.

[0062] Furthermore, the proportion of larger 80-120μm ceramic particles is greater than that of smaller 10-30μm ceramic particles. This is beneficial to increasing the content of cracks caused by the extrusion of ceramic particles during cold isostatic pressing, which in turn helps to improve the density of the ceramic radome blank, the uniform distribution of ceramic powder, and avoids cracking in asymmetrical areas of the radome caused by the elastic aftereffect of the ceramic radome blank.

[0063] Furthermore, the surface modification of ceramic particles includes the following steps:

[0064] Paraffin wax is heated to 80-100℃ to obtain molten liquid paraffin wax. Then, the molten liquid paraffin wax is mixed with water and the temperature is maintained at 80-100℃ to obtain a mixed solution. The mixed solution is then sprayed onto the surface of primary ceramic particles, and after cooling, it is dried at 30-60℃. The volume ratio of the molten liquid paraffin wax to water is (50-70):(30-50).

[0065] A modified solution is prepared by mixing polyvinyl butyral with ethanol, or by mixing fumed silica with water.

[0066] The primary ceramic particles are sprayed with a modified solvent after drying, and then dried again to obtain the secondary ceramic particles at a drying temperature of 60-100℃.

[0067] The beneficial effect of the previous step is that, firstly, by spraying the mixed solution onto the surface of the ceramic particles, the strength and waterproof performance of the ceramic particle surface are improved, thereby helping to avoid the problem of cracking or breaking of the ceramic particles when the solution is sprayed.

[0068] The volume ratio of molten liquid paraffin to water is (50-70):(30-50), which helps to avoid the problem of thick paraffin adhering to the surface of ceramic particles;

[0069] By spraying a modified solvent onto the surface of the dried primary ceramic particles, the fluidity and lubricity of the modified ceramic particles are improved, which helps to reduce the problem of internal stress accumulation during the forming of the green body and improves the strength of the irregular ceramic radome green body.

[0070] Furthermore, the secondary ceramic particles are subjected to supercritical CO2 extraction before surface modification;

[0071] Supercritical CO2 fluid is introduced into the secondary ceramic particles to extract part of the binder in the secondary ceramic particles. The CO2 extraction pressure is 20MPa-30MPa, the extraction temperature is 60℃-70℃, the extraction time is 0.8h-2.5h, and the extraction flow rate is 0.5L / h-0.8L / h.

[0072] The beneficial effect of the previous step is that by performing supercritical CO2 extraction on the secondary ceramic particles, the second binder in the secondary ceramic particles is removed, thereby reducing the binder content in the ceramic particles. Furthermore, the ceramic powder in the secondary ceramic particles will not react at a lower temperature, avoiding the problem of increased strength in the secondary ceramic particles due to the higher temperature during the binder removal process. Ultimately, this is beneficial to prevent the secondary ceramic particles from being crushed or developing a large number of cracks during the cold isostatic pressing process.

[0073] Furthermore, the process of obtaining the irregularly shaped ceramic radome blank through cold isostatic pressing using a mold for forming the irregularly shaped ceramic radome blank includes the following steps:

[0074] A rigid outer mold sleeve is fitted over the flexible inner mold sleeve, and the third connecting part of the flexible inner mold sleeve is interference-fitted with the second connecting part of the rigid outer mold sleeve.

[0075] The chassis is in partial contact with the third connecting part and is detachably connected to the second connecting part;

[0076] The inner surface of the outer mold forming part of the rigid outer mold sleeve and the outer surface of the inner mold forming part of the flexible inner mold sleeve are combined to form a forming cavity, which is connected to the feeding cavity.

[0077] Secondary ceramic particles are added to the molding cavity through the feeding cavity. After filling, the end cap is detachably connected to the end connector of the rigid outer mold sleeve.

[0078] Excess gas is extracted from the molding cavity through a tapered through hole or a stepped hole on the end cap, and then the plug is detachably connected to the tapered through hole or the stepped hole.

[0079] Then, the assembled irregular ceramic radome blank forming mold and the internal secondary ceramic particles are rotated 180°, with the end cap as the bottom surface, and moved into the isostatic pressing cylinder to complete the isostatic pressing forming.

[0080] During pressurization, step pressurization is adopted, followed by step depressurization through a tapered through-hole; after step depressurization, the chassis and end cap are removed, and then the rigid outer mold sleeve is separated from the flexible inner mold sleeve to obtain the ceramic radome blank;

[0081] The step pressurization process involves holding pressure at each step pressure point; the pressurization rate is no greater than 0.4 MPa / s, and the maximum molding pressure is between 30-200 MPa; the depressurization rate is no greater than 0.2 MPa / s; the step pressurization process includes 1-4 step pressure points.

[0082] Furthermore, the process of obtaining the irregularly shaped ceramic radome blank through cold isostatic pressing using a mold for forming the irregularly shaped ceramic radome blank also includes the following steps:

[0083] After filling the molding cavity with secondary ceramic particles through the feeding cavity and detachably connecting the end cap to the end connector of the rigid outer mold sleeve, the inner rigid sleeve is fitted into the flexible inner mold sleeve, and then the second rigid guard plate of the inner rigid sleeve is detachably connected to the chassis through several first elastic connectors.

[0084] Excess gas is extracted from the molding cavity through a tapered through hole or a stepped hole on the end cap, and then the plug is detachably connected to the tapered through hole or the stepped hole.

[0085] Then, the assembled irregular ceramic radome blank forming mold and the internal secondary ceramic particles are rotated 180°, with the end cap as the bottom surface, and moved into the isostatic pressing cylinder to complete the isostatic pressing forming.

[0086] During pressurization, step pressurization is followed by step depressurization; after step depressurization, the inner rigid sleeve, chassis, and end cap are removed, and then the rigid outer mold sleeve is separated from the flexible inner mold sleeve to obtain the ceramic radome blank.

[0087] The beneficial effect of the previous step is that a molding cavity is obtained by combining the inner surface of the outer mold forming part of the rigid outer mold sleeve with the outer surface of the inner mold forming part of the flexible inner mold sleeve, thereby realizing the molding of secondary ceramic particles in the molding cavity; and the molding cavity is connected to the feeding cavity, thereby realizing the addition of secondary ceramic particles into the molding cavity through the feeding cavity.

[0088] Excess gas can be extracted from the molding cavity by providing tapered through holes or stepped holes in the end cap, which helps to avoid the problem of delamination cracking in the ceramic radome blank.

[0089] The inner rigid sleeve is placed inside the flexible inner mold sleeve, and then the second rigid plate of the inner rigid sleeve is detachably connected to the chassis through several first elastic connectors. This helps to avoid the elastic aftereffect of the blank when the pressure is reduced after the pressure is applied, that is, it helps to avoid cracking and damage in the asymmetrical parts of the ceramic radome blank during the pressure reduction process.

[0090] By flipping the irregular ceramic radome blank forming mold and the internal secondary ceramic particles by 180°, and using the end cap as the bottom surface, it is moved into the isostatic pressing cylinder to complete the isostatic pressing forming. This further helps to achieve a uniform distribution of secondary ceramic particles in the forming cavity and helps to avoid the problem of delamination at the small diameter end of the irregular ceramic radome blank.

[0091] The step-up and step-down pressure design helps to alleviate the internal stress of the blank forming, reduce the elastic aftereffect and stress field distribution differences in various parts of the irregular ceramic radome blank, and solve the cracking problem caused by the circumferential curvature difference of the irregular ceramic radome blank. Detailed Implementation

[0092] To better understand the technical solution of the present invention, the present invention will be further described below with reference to specific embodiments.

[0093] Example 1

[0094] One aspect of this embodiment provides a molding die for forming an irregularly shaped ceramic radome blank, including a rigid outer mold sleeve, a flexible inner mold sleeve, an end cap, and a base; the rigid outer mold sleeve includes a first connecting part, a second connecting part, and an outer mold forming part, the outer mold forming part being provided with a first cavity; the first cavity includes a small-diameter end and a large-diameter end, the large-diameter end of the first cavity being open;

[0095] The rigid outer mold sleeve is made of structural steel and has a wall thickness of 23mm; the flexible inner mold sleeve is made of polyurethane and has a wall thickness of 11mm.

[0096] The outer mold forming part is connected to the first connecting part near the small diameter end; the outer mold forming part is connected to the second connecting part near the large diameter end.

[0097] The first connecting part includes a feeding part and an end connector. The feeding part is provided with a feeding cavity, which is in communication with the first cavity. The end connector is detachably connected to the end cap.

[0098] The flexible inner mold sleeve includes an inner mold forming part and a third connecting part. The inner mold forming part is provided with a second cavity. The first cavity is open at one end near the large diameter end of the first cavity.

[0099] The inner surface of the outer mold forming part is designed to conform to the outer surface of the irregular ceramic radome, and the outer surface of the inner mold forming part is designed to mimic the inner surface of the irregular ceramic radome.

[0100] The rigid outer mold sleeve is fitted outside the flexible inner mold sleeve. The inner surface of the outer mold forming part and the outer surface of the inner mold forming part are combined to form a forming cavity. The forming cavity is connected to the feeding cavity.

[0101] The second connecting part is detachably connected to the chassis, and the third connecting part is partially or entirely located between the second connecting part and the chassis; the third connecting part is interference-fitted to the outside of the second connecting part, and the chassis is in partial contact with the third connecting part and is detachably connected to the second connecting part;

[0102] The end cap is provided with a tapered through hole, and the end cap also includes a plug that is detachably connected to the tapered through hole.

[0103] Another aspect of this embodiment provides a method for forming an irregularly shaped ceramic radome blank, which prepares the irregularly shaped ceramic radome blank using any of the irregularly shaped ceramic radome blank forming molds described in any one of the embodiments, specifically including the following steps:

[0104] A mixed powder is prepared, wherein the mixed powder comprises silicon nitride powder and auxiliary powder in a mass ratio of 100:18; the auxiliary powder comprises alumina powder and lanthanum oxide.

[0105] A ceramic slurry is prepared by mixing powder, dispersant, binder, and solvent; the method for preparing the ceramic slurry includes the following steps:

[0106] The binder and solvent are added to the grinding equipment, and then the dispersant and mixed powder are added and ground for 16 hours to obtain the ceramic slurry.

[0107] The mass ratio of the binder, solvent, dispersant, and mixed powder is 3:100:1.1:85;

[0108] The binder includes a first binder and a second binder; the first binder includes liquid paraffin; the second binder includes polyvinyl butyral; the solvent includes ethanol and butanone; the dispersant includes glycerol; and the median particle size of the mixed powder is 1 μm.

[0109] Primary ceramic particles are prepared by spray drying the ceramic slurry.

[0110] The primary ceramic particles include primary ceramic particles with a median particle size of 100 μm and primary ceramic particles with a median particle size of 20 μm;

[0111] The mass ratio of primary ceramic particles with a median particle size of 100 μm to primary ceramic particles with a median particle size of 20 μm is 20:10.

[0112] The primary ceramic particles are surface-modified to obtain secondary ceramic particles; the surface modification of the ceramic particles includes the following steps:

[0113] Paraffin wax is heated to 90°C to obtain molten liquid paraffin wax. Then, the molten liquid paraffin wax is mixed with water and the temperature is maintained at 90°C to obtain a mixed solution. The mixed solution is then sprayed onto the surface of primary ceramic particles, cooled, and dried at 45°C. The volume ratio of the molten liquid paraffin wax to water is 60:40.

[0114] A modified solution is prepared by mixing polyvinyl butyral with ethanol;

[0115] The primary ceramic particles are sprayed with a modified solvent after drying, and then dried again to obtain the secondary ceramic particles at a drying temperature of 80°C.

[0116] The secondary ceramic particles are cold isostatically pressed into a shaped ceramic radome blank using a shaped ceramic radome blank forming mold.

[0117] The process of obtaining a shaped ceramic radome blank through cold isostatic pressing using a shaped ceramic radome blank forming mold includes the following steps:

[0118] A rigid outer mold sleeve is fitted over the flexible inner mold sleeve, and the third connecting part of the flexible inner mold sleeve is interference-fitted with the second connecting part of the rigid outer mold sleeve.

[0119] The chassis is in partial contact with the third connecting part and is detachably connected to the second connecting part;

[0120] The inner surface of the outer mold forming part of the rigid outer mold sleeve and the outer surface of the inner mold forming part of the flexible inner mold sleeve are combined to form a forming cavity, which is connected to the feeding cavity.

[0121] Secondary ceramic particles are added to the molding cavity through the feeding cavity. After filling, the end cap is detachably connected to the end connector of the rigid outer mold sleeve.

[0122] Excess gas is extracted from the molding cavity through a tapered through hole or a stepped hole on the end cap, and then the plug is detachably connected to the tapered through hole or the stepped hole.

[0123] Then, the assembled irregular ceramic radome blank forming mold and the internal secondary ceramic particles are rotated 180°, with the end cap as the bottom surface, and moved into the isostatic pressing cylinder to complete the isostatic pressing forming.

[0124] During pressurization, step pressurization is adopted, followed by step depressurization through a tapered through-hole; after step depressurization, the chassis and end cap are removed, and then the rigid outer mold sleeve is separated from the flexible inner mold sleeve to obtain the ceramic radome blank;

[0125] The step pressurization process involves holding pressure at each step pressure point; the pressurization rate is 0.3 MPa / s, the maximum molding pressure is 160 MPa, and the depressurization rate is 0.12 MPa / s; the step pressurization process includes 3 step pressure points.

[0126] Example 2

[0127] The features that are the same as those in Embodiment 1 will not be repeated here. The features that are different from those in Embodiment 1 are: the irregular ceramic radome blank forming mold provided in one aspect of this embodiment also includes an inner rigid sleeve.

[0128] The inner rigid hurdle sleeve includes a first rigid hurdle sleeve and a second rigid hurdle sleeve;

[0129] The first rigid guardrail includes a plurality of first rigid guardrails, a plurality of first connecting rods, and a first top plate; the first rigid guardrails are hinged to the edges of the first top plate; one end of the first connecting rod is hinged to the first top plate, and the end of the first connecting rod away from the first top plate is slidably connected to the first rigid guardrail;

[0130] The second rigid guardrail includes a plurality of second rigid guardrails and a second top plate; the edges of the second rigid guardrails and the second top plate are hinged.

[0131] The first rigid guardrail is fitted inside the second rigid guardrail, the first top plate is elastically connected to the second top plate, and the first rigid guardrail is elastically connected to the second rigid guardrail.

[0132] The first rigid guardrail is enclosed by several second rigid guardrails to form an adjustable accommodating space;

[0133] The outer surfaces of the first and second top plates are designed to mimic the inner surface of the flexible inner mold sleeve.

[0134] The second rigid guardrail is detachably connected to the chassis via several first elastic connectors;

[0135] The first connecting rod includes a first sleeve, a second sleeve, and a plurality of first sleeves; a plurality of third sleeves are sleeved and connected, and the first sleeve and the second sleeve are respectively sleeved and connected to the third sleeve. The end of the first sleeve away from the second sleeve is hinged to the first top plate, and the end of the first sleeve away from the second sleeve is slidably connected to the first rigid guardrail.

[0136] The first rigid rail is provided with a guide groove, and the first connecting rod is partially or entirely located in the guide groove;

[0137] The rigid outer mold sleeve has a wall thickness of 28mm; the flexible inner mold sleeve is made of polyurethane or rubber and has a wall thickness of 13mm.

[0138] Another aspect of this embodiment provides a method for forming an irregularly shaped ceramic radome blank.

[0139] The secondary ceramic particles are subjected to supercritical CO2 extraction before surface modification.

[0140] Supercritical CO2 fluid is introduced into the secondary ceramic particles to extract part of the binder in the secondary ceramic particles. The CO2 extraction pressure is 25 MPa, the extraction temperature is 65°C, the extraction time is 1.2 h, and the extraction flow rate is 0.65 L / h.

[0141] The process of obtaining a shaped ceramic radome blank through cold isostatic pressing using a shaped ceramic radome blank forming mold also includes the following steps:

[0142] After filling the molding cavity with secondary ceramic particles through the feeding cavity and detachably connecting the end cap to the end connector of the rigid outer mold sleeve, the inner rigid sleeve is fitted into the flexible inner mold sleeve, and then the second rigid guard plate of the inner rigid sleeve is detachably connected to the chassis through several first elastic connectors.

[0143] Excess gas is extracted from the molding cavity through a tapered through hole or a stepped hole on the end cap, and then the plug is detachably connected to the tapered through hole or the stepped hole.

[0144] Then, the assembled irregular ceramic radome blank forming mold and the internal secondary ceramic particles are rotated 180°, with the end cap as the bottom surface, and moved into the isostatic pressing cylinder to complete the isostatic pressing forming.

[0145] During pressurization, step pressurization is followed by step depressurization; after step depressurization, the inner rigid sleeve, chassis, and end cap are removed, and then the rigid outer mold sleeve is separated from the flexible inner mold sleeve to obtain the ceramic radome blank.

[0146] The mixed powder comprises silicon nitride powder and auxiliary powder in a mass ratio of 100:28; the auxiliary powder comprises alumina powder and yttrium oxide.

[0147] The mass ratio of the binder, solvent, dispersant, and mixed powder is 3.5:100:1.8:82;

[0148] The binder includes a first binder and a second binder; the first binder includes liquid paraffin; the second binder includes dibutyl phthalate; the dispersant includes triethyl phosphate; the median particle size of the mixed powder is between 1.3 μm;

[0149] The primary ceramic particles include primary ceramic particles with a median particle size of 110 μm and primary ceramic particles with a median particle size of 28 μm;

[0150] The mass ratio of primary ceramic particles with a median particle size of 110 μm to primary ceramic particles with a median particle size of 28 μm is 28:10.

[0151] Paraffin wax is heated to 95°C to obtain molten liquid paraffin wax. Then, the molten liquid paraffin wax is mixed with water and the temperature is maintained at 95°C to obtain a mixed solution. The mixed solution is then sprayed onto the surface of primary ceramic particles, cooled, and dried at 50°C. The volume ratio of the molten liquid paraffin wax to water is 65:35.

[0152] The modified solution is obtained by mixing fumed silica with water;

[0153] The step pressurization process involves holding pressure at each step pressure point; the pressurization rate is 0.38 MPa / s, and the maximum molding pressure is between 180 MPa; the depressurization rate is 0.18 MPa / s; the step pressurization process includes 4 step pressure points.

[0154] Example 3

[0155] The features that are the same as those in Embodiment 2 will not be repeated here. The features that are different from those in Embodiment 2 are as follows: In one aspect of this embodiment, a mold for forming an irregular ceramic radome blank is provided, wherein the rigid outer mold sleeve has a wall thickness of 18mm; the flexible inner mold sleeve is made of polyurethane or rubber material, and the flexible inner mold sleeve has a wall thickness of 9mm.

[0156] Another aspect of this embodiment provides a method for forming an irregularly shaped ceramic radome blank.

[0157] The secondary ceramic particles are subjected to supercritical CO2 extraction before surface modification.

[0158] Supercritical CO2 fluid is introduced into the secondary ceramic particles to extract part of the binder in the secondary ceramic particles. The CO2 extraction pressure is 22 MPa, the extraction temperature is 68°C, the extraction time is 2.2 h, and the extraction flow rate is 0.78 L / h.

[0159] The mixed powder comprises silicon nitride powder and auxiliary powder in a mass ratio of 100:15; the auxiliary powder comprises silicon nitride powder, alumina powder, and lanthanum oxide.

[0160] The mass ratio of the binder, solvent, dispersant, and mixed powder is 2.2:100:0.8:82;

[0161] The primary ceramic particles include primary ceramic particles with a median particle size of 85 μm and primary ceramic particles with a median particle size of 15 μm;

[0162] The mass ratio of the primary ceramic particles with a median particle size of 85 μm to the primary ceramic particles with a median particle size of 15 μm is 12:10.

[0163] Paraffin wax is heated to 85°C to obtain molten liquid paraffin wax. Then, the molten liquid paraffin wax is mixed with water and the temperature is maintained at 85°C to obtain a mixed solution. The mixed solution is then sprayed onto the surface of primary ceramic particles, cooled, and dried at 40°C. The volume ratio of the molten liquid paraffin wax to water is 68:48.

[0164] The modified solution was prepared by mixing polyvinyl butyral with ethanol;

[0165] The step pressurization process involves holding pressure at each step pressure point; the pressurization rate is 0.35 MPa / s, and the maximum molding pressure is 100 MPa; the depressurization rate is no greater than 0.15 MPa / s; the step pressurization process includes 3 step pressure points.

[0166] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A molding die for forming an irregularly shaped ceramic radome blank, characterized in that, Includes rigid outer mold sleeve, flexible inner mold sleeve, end cap, and chassis; The rigid outer mold sleeve includes a first connecting part, a second connecting part, and an outer mold forming part. The outer mold forming part is provided with a first cavity. The first cavity includes a small-diameter end and a large-diameter end, and the large-diameter end of the first cavity is open. The outer mold forming part is connected to the first connecting part near the small diameter end; the outer mold forming part is connected to the second connecting part near the large diameter end. The first connecting part includes a feeding part and an end connector. The feeding part is provided with a feeding cavity, which is in communication with the first cavity. The end connector is detachably connected to the end cap. The flexible inner mold sleeve includes an inner mold forming part and a third connecting part. The inner mold forming part is provided with a second cavity. The first cavity is open at one end near the large diameter end of the first cavity. The inner surface of the outer mold forming part is designed to conform to the outer surface of the irregular ceramic radome, and the outer surface of the inner mold forming part is designed to mimic the inner surface of the irregular ceramic radome. The rigid outer mold sleeve is fitted outside the flexible inner mold sleeve. The inner surface of the outer mold forming part and the outer surface of the inner mold forming part are combined to form a forming cavity. The forming cavity is connected to the feeding cavity. The second connecting part is detachably connected to the chassis, and the third connecting part is partially or entirely located between the second connecting part and the chassis; The end cap is provided with a tapered through hole or a stepped hole, and the end cap also includes a plug that is detachably connected to the tapered through hole or the stepped hole.

2. The irregular ceramic radome blank forming mold according to claim 1, characterized in that, The irregular ceramic radome blank forming mold also includes an inner rigid sleeve; The inner rigid hurdle sleeve includes a first rigid hurdle sleeve and a second rigid hurdle sleeve; The first rigid guardrail includes a plurality of first rigid guardrails, a plurality of first connecting rods, and a first top plate; the first rigid guardrails are hinged to the edges of the first top plate; one end of the first connecting rod is hinged to the first top plate, and the end of the first connecting rod away from the first top plate is slidably connected to the first rigid guardrail; The second rigid guardrail includes a plurality of second rigid guardrails and a second top plate; the edges of the second rigid guardrails and the second top plate are hinged. The first rigid guardrail is fitted inside the second rigid guardrail, the first top plate is elastically connected to the second top plate, and the first rigid guardrail is elastically connected to the second rigid guardrail. The first rigid guardrail is enclosed by several second rigid guardrails to form an adjustable accommodating space; The outer surfaces of the first and second top plates are designed to mimic the inner surface of the flexible inner mold sleeve. The second rigid guardrail and / or the first rigid guardrail are detachably connected to the chassis via a plurality of first elastic connectors.

3. The irregular-shaped ceramic radome blank forming mold according to claim 1, characterized in that, The rigid outer mold sleeve is made of structural steel or alloy material, and the wall thickness of the rigid outer mold sleeve is 15-30mm. The flexible inner mold sleeve is made of polyurethane or rubber, and the wall thickness of the flexible inner mold sleeve is 6-15mm. and / or The third connecting part is interference-fitted to the outside of the second connecting part, the chassis is in partial contact with the third connecting part, and is detachably connected to the second connecting part.

4. A method for forming an irregularly shaped ceramic radome blank, characterized in that, The irregular ceramic radome blank is prepared using the irregular ceramic radome blank forming mold according to any one of claims 1-3, specifically including the following steps: A mixed powder is prepared, wherein the mixed powder comprises silicon nitride powder and auxiliary powder in a mass ratio of 100:(6-30); the auxiliary powder comprises one or more of alumina, boron nitride, and rare earth oxide powder; and the rare earth oxide powder comprises one of lanthanum oxide and yttrium oxide. A ceramic slurry is prepared by mixing powder, dispersant, binder, and solvent; the ceramic slurry is then spray-dried to produce primary ceramic particles. The primary ceramic particles are surface modified to obtain secondary ceramic particles; The secondary ceramic particles are cold isostatically pressed into a shaped ceramic radome blank using a shaped ceramic radome blank forming mold.

5. The method for forming an irregularly shaped ceramic radome blank according to claim 4, characterized in that, The method for preparing the ceramic slurry includes the following steps: The binder and solvent are added to the grinding equipment, and then the dispersant and mixed powder are added and ground and mixed for 8-24 hours to obtain the ceramic slurry. The mass ratio of the binder, solvent, dispersant, and mixed powder is (2-5):100:(0.2-2):(70-90); The adhesive includes a first adhesive and a second adhesive; The first binder comprises liquid paraffin; the second binder comprises one or both of polyvinyl butyral and dibutyl phthalate. The solvents include ethanol and butanone; The dispersant includes one or two of castor oil, glycerol, and triethyl phosphate; The median particle size of the mixed powder is between 0.5 and 1.5 μm.

6. The method for forming an irregularly shaped ceramic radome blank according to claim 4, characterized in that, The primary ceramic particles include primary ceramic particles with a median particle size of 80-120 μm and primary ceramic particles with a median particle size of 10-30 μm; The mass ratio of primary ceramic particles with a median particle size of 80-120 μm to primary ceramic particles with a median particle size of 10-30 μm is (10-30):

10.

7. The method for cold isostatic pressing of a ceramic radome blank according to claim 4, characterized in that, Surface modification of ceramic particles includes the following steps: Paraffin wax is heated to 80-100℃ to obtain molten liquid paraffin wax. Then, the molten liquid paraffin wax is mixed with water and the temperature is maintained at 80-100℃ to obtain a mixed solution. The mixed solution is then sprayed onto the surface of primary ceramic particles, and after cooling, it is dried at 30-60℃. The volume ratio of the molten liquid paraffin wax to water is (50-70):(30-50). A modified solution is prepared by mixing polyvinyl butyral with ethanol, or by mixing fumed silica with water. The primary ceramic particles are sprayed with a modified solvent after drying, and then dried again to obtain the secondary ceramic particles at a drying temperature of 60-100℃.

8. The method for cold isostatic pressing of a ceramic radome blank according to claim 4, characterized in that, The secondary ceramic particles are subjected to supercritical CO2 extraction before surface modification. Supercritical CO2 fluid is introduced into the secondary ceramic particles to extract part of the binder in the secondary ceramic particles. The CO2 extraction pressure is 20MPa-30MPa, the extraction temperature is 60℃-70℃, the extraction time is 0.8h-2.5h, and the extraction flow rate is 0.5L / h-0.8L / h.

9. The method for cold isostatic pressing of a ceramic radome blank according to claim 4, characterized in that, The process of obtaining a shaped ceramic radome blank through cold isostatic pressing using a shaped ceramic radome blank forming mold includes the following steps: A rigid outer mold sleeve is fitted over the flexible inner mold sleeve, and the third connecting part of the flexible inner mold sleeve is interference-fitted with the second connecting part of the rigid outer mold sleeve. The chassis is in partial contact with the third connecting part and is detachably connected to the second connecting part; The inner surface of the outer mold forming part of the rigid outer mold sleeve and the outer surface of the inner mold forming part of the flexible inner mold sleeve are combined to form a forming cavity, which is connected to the feeding cavity. Secondary ceramic particles are added to the molding cavity through the feeding cavity. After filling, the end cap is detachably connected to the end connector of the rigid outer mold sleeve. Excess gas is extracted from the molding cavity through a tapered through hole or a stepped hole on the end cap, and then the plug is detachably connected to the tapered through hole or the stepped hole. Then, the assembled irregular ceramic radome blank forming mold and the internal secondary ceramic particles are rotated 180°, with the end cap as the bottom surface, and moved into the isostatic pressing cylinder to complete the isostatic pressing forming. During pressurization, step pressurization is followed by step depressurization; after step depressurization, the chassis and end caps are removed, and then the rigid outer mold sleeve is separated from the flexible inner mold sleeve to obtain the ceramic radome blank. The step pressurization process involves holding pressure at each step pressure point; the pressurization rate is no greater than 0.4 MPa / s, and the maximum molding pressure is between 30-200 MPa; the depressurization rate is no greater than 0.2 MPa / s; the step pressurization process includes 1-4 step pressure points.

10. The method for cold isostatic pressing of a ceramic radome blank according to claim 9, characterized in that, The process of obtaining a shaped ceramic radome blank through cold isostatic pressing using a shaped ceramic radome blank forming mold also includes the following steps: After filling the molding cavity with secondary ceramic particles through the feeding cavity and detachably connecting the end cap to the end connector of the rigid outer mold sleeve, the inner rigid sleeve is fitted into the flexible inner mold sleeve, and then the second rigid guard plate of the inner rigid sleeve is detachably connected to the chassis through several first elastic connectors. Excess gas is extracted from the molding cavity through a tapered through hole or a stepped hole on the end cap, and then the plug is detachably connected to the tapered through hole or the stepped hole. Then, the assembled irregular ceramic radome blank forming mold and the internal secondary ceramic particles are rotated 180°, with the end cap as the bottom surface, and moved into the isostatic pressing cylinder to complete the isostatic pressing forming. During pressurization, step pressurization is followed by step depressurization; after step depressurization, the inner rigid sleeve, chassis, and end cap are removed, and then the rigid outer mold sleeve is separated from the flexible inner mold sleeve to obtain the ceramic radome blank.