Preparation process of umbrella-shaped vacuum ceramic tube shell

Abstract

The invention belongs to the technical field of umbrella-shaped vacuum ceramic tube shells, and particularly relates to a preparation process of an umbrella-shaped vacuum ceramic tube shell, which comprises the following steps: firstly, designing a die sleeve; the die sleeve is made of an organic elastic material, and corrugations are prefabricated on the inner circular surface of the die sleeve; the steel mold core is arranged in the mold sleeve, and a cavity area formed by the steel mold core and the mold sleeve is filled with aluminum oxide powder; covering a steel plug on the upper side of the alumina powder to form a to-be-pressed whole; the whole to be pressed is subjected to isostatic pressing forming, the die sleeve and the aluminum oxide powder are compressed and formed towards the center of the steel die core at the same time through the corrugated shape of an inner cavity of the die sleeve under the applied pressure, and a blank piece is formed; after isostatic pressing is finished, pressure relief is started, and the steel mold core, the blank piece and the mold sleeve rebound; and removing the steel plug, and taking out the formed aluminum oxide blank to obtain the umbrella-shaped vacuum ceramic tube shell. The problem that in existing machining, turning is needed, and the quality of finished products cannot be guaranteed is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of umbrella-shaped vacuum ceramic tube shells, and in particular relates to a preparation process of an umbrella-shaped vacuum ceramic tube shell. Background Art

[0002] At present, manufacturers of umbrella-shaped vacuum ceramic tube shells all use isostatic pressing to form the blanks first, and then the blanks are machined and formed. Figure 1 As shown, the specific process of forming the blank is: 1) Assemble a 5mm rubber mold sleeve outside the steel mold core and seal the lower end with a clamp.

[0003] 2) Alumina powder is injected into the steel mold core and the mold sleeve cavity for filling; during the process, the alumina powder is filled and vibrated to ensure dense filling.

[0004] 3) Add the upper rubber cover and seal it with a clamp.

[0005] 4) Add the mold as a whole and put it into isostatic pressing; 5) After isostatic pressing is completed, take out the mold and remove the clamp on the upper end of the mold.

[0006] 6) Take out the pressed blank.

[0007] The later turning process will produce corrugations on the two end faces and the outer cylindrical surface of the blank. Turning requires a processing allowance of 6-8mm, resulting in a material utilization rate of only about 50%, and the strength of the ceramic blank is less than 2Mpa. The clamping process of turning is prone to product cracks, which are difficult to remove in the later process, seriously affecting the product quality. The turning process generates a lot of dust, which is harmful to people, equipment and environment.

[0008] Therefore, how to directly shape umbrella-shaped ceramic tubes has become a difficult problem in the industry. Summary of the invention

[0009] The purpose of the present invention is to provide an umbrella-shaped vacuum ceramic tube shell and a preparation process thereof, which solves the problem that the quality of the finished product cannot be guaranteed in the existing processing that requires lathing.

[0010] The present invention is achieved through the following technical solutions: The invention discloses a preparation process of an umbrella-shaped vacuum ceramic tube shell, comprising the following steps: Step 1: First, design a mold sleeve; the mold sleeve is made of an organic elastic material, and the inner circular surface of the mold sleeve is prefabricated with a corrugated shape matching the vacuum ceramic tube shell to be processed and formed; Step 2: insert the steel mold core into the mold sleeve, and fill the cavity area formed by the steel mold core and the mold sleeve with alumina powder; Step 3: Cover the upper side of the alumina powder with a steel plug and seal it with a clamp to form a whole to be pressed; Step 4: isostatically press the whole to be pressed. By utilizing the corrugated shape of the inner cavity of the die sleeve, the die sleeve and the alumina powder are compressed and formed toward the center of the steel mold core at the same time under the pressure. The alumina powder is pressed at both ends to form a smooth plane to form a blank. Step 5: After the isostatic pressing is completed, the pressure is released, and the steel mold core, the blank and the mold sleeve rebound. The rebound of the blank is greater than that of the steel mold core; Step 6: Remove the clamp and the steel plug, take out the formed alumina blank, and obtain an umbrella-shaped vacuum ceramic tube shell.

[0011] Furthermore, in step 2, a binder and a plasticizer are added to the alumina powder.

[0012] Furthermore, in step 4, the isostatic pressing pressure is 100-130 MPa.

[0013] Furthermore, in step 1, the Shore hardness of the designed mold sleeve is 50-55 degrees.

[0014] Furthermore, the particle size of the alumina powder is 60-240 mesh.

[0015] Furthermore, the surface finish of the steel mold core is less than 0.1 micrometer.

[0016] Furthermore, the roughness of the contact portion between the steel plug and the die sleeve is 3.6-12.5 microns.

[0017] Furthermore, the steel mold core is a stepped shaft, and a 5±1×45° chamfer is adopted at a transition of the step surface of the stepped shaft.

[0018] Furthermore, the requirements for organic elastic materials are: they can be compressed without absorbing pressure during the pressurization process, and transfer the pressure to the pressed object; at the same time, they play a sealing role under pressure to prevent the pressurized solution from entering the mold cavity; after the pressure is gradually withdrawn, they separate from the molded material and gradually return to their original state.

[0019] Furthermore, the organic elastic material uses polyurethane.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects: The invention discloses a preparation process of an umbrella-shaped vacuum ceramic shell. An elastic mold sleeve is manufactured according to the outer dimensions of the umbrella-shaped ceramic shell. The inner circular surface of the mold sleeve is prefabricated with a corrugated shape matching the vacuum ceramic shell to be processed and formed. The elastic mold sleeve does not lose pressure after being compressed and has excellent strength support, so any shape can be formed by thermoplastic molding. By eliminating the lathe processing link, an umbrella-shaped vacuum ceramic shell with a corrugated shape can be directly prepared, the whole preparation process is more simplified, and the utilization of raw materials is increased from 50% to 80%. This umbrella-shaped vacuum ceramic shell preparation process completely gets rid of the existing subsequent lathe processing, which usually requires special lathe equipment and skilled operators. By eliminating the lathe processing step, there is no need to purchase or rent a lathe, which reduces the capital investment and maintenance cost of the equipment. At the same time, it also saves the man-hours required for lathe processing and reduces the labor cost. For example, in the traditional process, if it takes 1-2 hours of manual operation time to lathe a vacuum ceramic shell, calculated at a labor cost of 50 yuan per hour, the labor cost of a shell can be saved by about 50-100 yuan.

[0021] The turning process will produce cutting waste of materials. If turning is not required, the waste of ceramic materials caused by cutting can be avoided. For ceramic materials such as alumina, the cost of raw materials is relatively high. This process can effectively utilize the filling powder, improve material utilization, and reduce production costs.

[0022] Turning may cause fluctuations in product dimensional accuracy and surface quality due to factors such as tool wear and differences in the technical level of operators. With this molding process, the vacuum ceramic shell is formed into the desired shape during the isostatic pressing process, which can better ensure the dimensional accuracy and shape consistency of the product. For example, in the preparation of high-precision vacuum ceramic shells for electronic equipment, the inner diameter dimensional accuracy is required to be within ±0.05mm. This process can more stably achieve this accuracy requirement, while turning may cause dimensional deviations due to various factors.

[0023] Turning will generate cutting stress on the ceramic surface, which may introduce defects such as microcracks, thereby reducing the mechanical strength and fatigue resistance of the product. Without the turning step, mechanical damage to the product surface is avoided, so that the product can maintain good mechanical properties, and improve the reliability and service life of the product. For example, in a vacuum environment system where a vacuum ceramic shell is used to withstand a certain pressure, a product without surface microcracks can better withstand the internal and external pressure difference, reducing the risk of leakage caused by the decline of mechanical properties.

[0024] Furthermore, the present invention finally selected polyurethane as the mold sleeve material. Polyurethane has excellent elasticity. During the isostatic pressing process, when pressure is applied to the mold sleeve and the alumina powder, the polyurethane mold sleeve can be elastically deformed well, causing the powder to be compressed toward the center of the steel mold core. After the pressure is released, it can quickly return to its original shape.

[0025] Due to its good elasticity, polyurethane can be easily prefabricated into a corrugated inner surface that matches the vacuum ceramic shell to be processed. This corrugated structure can effectively guide the flow and molding of alumina powder during the molding process, so that the shell forms the required umbrella shape. Compared with some rigid materials, polyurethane can better fit the deformation process of powder under pressure, ensuring the accuracy of the product shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the installation structure of the steel mold core and the mold sleeve during the blank forming in the prior art; Figure 2 It is a schematic diagram of the installation structure of the steel mold core and the mold sleeve during isostatic pressing in the preparation process of the umbrella-shaped vacuum ceramic tube shell of the present invention.

[0027] Among them, 1. mold sleeve; 2. alumina powder; 3. steel mold core; 4. steel plug. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0029] The components described and shown in the drawings and embodiments of the present invention may be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0030] It should be noted that the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, so that a process, element, method, article or equipment that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to the process, element, method, article or equipment.

[0031] The invention discloses a preparation process of an umbrella-shaped vacuum ceramic tube shell, comprising the following steps: Step 1: First, design a mold sleeve 1; the mold sleeve 1 is made of an organic elastic material, and the inner circular surface of the mold sleeve 1 is prefabricated with a corrugated shape matching the vacuum ceramic shell to be processed and formed; Elastic materials have the following characteristics: the pressurized link can compress without absorbing pressure, and transfer the pressure to the pressed object; at the same time, it can play a sealing role under high pressure to prevent the pressurized solution from entering the mold cavity; after the pressure is gradually withdrawn, it separates from the molded material and gradually returns to its original state.

[0032] Step 2: insert the steel mold core 3 into the mold sleeve 1, and fill the cavity area formed by the steel mold core 3 and the mold sleeve 1 with alumina powder 2; Step 3: Cover the upper side of the alumina powder 2 with a steel plug 4 and seal it with a clamp to form a whole to be pressed; Step 4: isostatically press the whole to be pressed. By utilizing the corrugated shape of the inner cavity of the die sleeve 1, the die sleeve 1 and the alumina powder 2 are simultaneously compressed and formed toward the center of the steel mold core 3 under the pressure. The alumina powder 2 is pressed at both ends to form a smooth plane, thereby forming a blank. Step 5: After the isostatic pressing is completed, the pressure is released, and the steel mold core 3, the blank and the mold sleeve 1 rebound. The rebound of the blank is greater than that of the steel mold core 3, and a gap is generated between the two, so that the blank can be easily demolded; Step 6: Remove the clamp and the steel plug 4, take out the formed alumina blank, and obtain an umbrella-shaped vacuum ceramic tube shell.

[0033] Specifically, 0.8-2% of a binder and 0.5-1.5% of a plasticizer are added to the alumina powder 2 to increase the density and strength of the green body.

[0034] In step 4, the isostatic pressing pressure is 100-130 MPa.

[0035] The Shore hardness of the mold sleeve 1 is 50-55 degrees.

[0036] The particle size of the alumina powder 2 is between 60-240 meshes, and the particles have optimal fluidity and high packing density.

[0037] The surface finish of the mold core is less than 0.1 micron to ensure that the inner diameter of the molded blank is smooth and meets the requirements of the final drawing.

[0038] The roughness of the contact part between the steel plug 4 and the die sleeve 1 is 3.6-12.5 microns to ensure that there is a certain friction resistance between the die sleeve 1 and the plug, so that the die sleeve 1 will not fall off.

[0039] Preferably, Figure 2As shown, the steel mold core 3 is a stepped shaft, specifically including a first cylindrical shaft and a second cylindrical shaft connected in one piece, the diameter of the first cylindrical shaft is larger than that of the second cylindrical shaft, the first cylindrical shaft is located at the bottom, and the transition between the upper plane of the first cylindrical shaft and the second cylindrical shaft adopts a 5±1×45° chamfer design to facilitate demoulding. If the transition angle is too small, it is easy to stick to the mold, and if it is too large, it does not meet the requirements of the later drawings. After testing, the rounding test results are not good, and a 45-degree chamfer is the best.

[0040] In multiple cycles of isostatic pressing experiments, the polyurethane mold sleeve 1 can still recover to its original state after being subjected to a pressure of 100-200 MPa, and its shape recovery rate can reach more than 98%, which is very beneficial for reusing the mold sleeve 1 for batch production. The present invention finally uses polyurethane to prepare the mold sleeve 1.

[0041] The features and performances of the present invention are further described in detail below in conjunction with the embodiments.

[0042] Taking advantage of the fact that polyurethane does not lose pressure after being compressed and has excellent strength support, it can be thermoformed into any shape. According to the outer dimensions of the umbrella-shaped ceramic tube shell, a polyurethane mold sleeve cavity (hardness 50-55) was commissioned to be made by a polyurethane manufacturer.

[0043] This embodiment discloses a process for preparing an umbrella-shaped vacuum ceramic tube shell, which specifically includes the following steps: 1. According to Figure 2 Assemble the mold.

[0044] 2. The cavities of the steel mold core 3 and the polyurethane mold sleeve 1 are filled with alumina powder 2, and the particle size of the alumina powder 2 is 100 mesh.

[0045] 3. Cover with steel plug 4 and tighten with clamps.

[0046] 4. Put the mold as a whole into isostatic pressing. Using the corrugated shape of the polyurethane inner cavity, the polyurethane mold sleeve 1 and the alumina powder 2 are compressed and formed toward the center of the steel mold core 3 at the same time under the pressure of the isostatic press. The two ends are steel plugs 4, and the isostatic pressure cannot be transmitted to the powder. The powder is pressed by the mold at both ends to form a smooth plane. After the isostatic pressing is completed, the alumina powder 2 is compressed and dense due to the addition of binder to the powder, and the outer diameter of the blank is the same as the size of the polyurethane inner cavity.

[0047] During the isostatic pressure relief stage, the steel mold core 3, the blank and the polyurethane cavity rebound after being compressed, making demoulding easy.

[0048] 5. Take out the entire mold from the isostatic press, remove the steel end clamps and the steel plug 4; then take out the formed alumina blank.

[0049] After measurement, the prepared alumina blank meets the requirements, has a smooth surface, and a blank strength of 3.5-4.0Mpa, which is 1.5-2.0Mpa greater than the original process blank strength.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A process for preparing an umbrella-shaped vacuum ceramic tube shell, characterized in that: The following steps are involved: Step 1: first design a mold sleeve (1); the mold sleeve (1) is made of an organic elastic material, and the inner circular surface of the mold sleeve (1) is prefabricated with a corrugated shape matching the vacuum ceramic tube shell to be processed and formed; Step 2: insert the steel mold core (3) into the mold sleeve (1), and fill the cavity area formed by the steel mold core (3) and the mold sleeve (1) with alumina powder (2); Step 3: Cover the upper side of the alumina powder (2) with a steel plug (4) and seal it with a clamp to form a whole to be pressed; Step 4: isostatically pressing the entire part to be pressed, utilizing the corrugated shape of the inner cavity of the die sleeve (1). Under pressure, the die sleeve (1) and the alumina powder (2) are simultaneously compressed toward the center of the steel die core (3), and the alumina powder (2) is compressed at both ends to form a smooth plane, thereby forming a blank. Step 5: After the isostatic pressing is completed, the pressure is released, and the steel mold core (3), the blank and the mold sleeve (1) rebound, and the rebound of the blank is greater than that of the steel mold core (3); Step 6: Remove the clamp and the steel plug (4), take out the formed alumina blank, and obtain an umbrella-shaped vacuum ceramic tube shell.

2. The process for preparing an umbrella-shaped vacuum ceramic tube shell according to claim 1, characterized in that: In step 2, a binder and a plasticizer are added to the alumina powder (2).

3. The process for preparing an umbrella-shaped vacuum ceramic tube shell according to claim 1, characterized in that: In step 4, the isostatic pressing pressure is 100-130 MPa.

4. The process for preparing an umbrella-shaped vacuum ceramic tube shell according to claim 1, characterized in that: In step 1, the Shore hardness of the designed mold sleeve (1) is 50-55 degrees.

5. The process for preparing an umbrella-shaped vacuum ceramic tube shell according to claim 1, characterized in that: The particle size of the alumina powder (2) is 60-240 mesh.

6. The process for preparing an umbrella-shaped vacuum ceramic tube shell according to claim 1, characterized in that: The surface finish of the steel mold core (3) is less than 0.1 micrometer.

7. The process for preparing an umbrella-shaped vacuum ceramic tube shell according to claim 1, characterized in that: The roughness of the contact portion between the steel plug (4) and the die sleeve (1) is 3.6-12.5 microns.

8. The process for preparing an umbrella-shaped vacuum ceramic tube shell according to claim 1, characterized in that: The steel mold core (3) is a stepped shaft, and the step surface transition of the stepped shaft adopts a 5±1×45° chamfer.

9. The process for preparing an umbrella-shaped vacuum ceramic tube shell according to claim 1, characterized in that: The requirements for organic elastic materials are: they can be compressed without absorbing pressure during the pressurization process, and transfer the pressure to the pressed object; at the same time, they play a sealing role under pressure to prevent the pressurized solution from entering the mold cavity; after the pressure is gradually withdrawn, they separate from the molded material and gradually return to their original state.

10. The process for preparing an umbrella-shaped vacuum ceramic tube shell according to claim 1, characterized in that: The organic elastic material is polyurethane.

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