A ceramic columnar product and its preparation method and application

Abstract

The present invention discloses a ceramic columnar product and a preparation method and application thereof, which relates to the field of ceramic materials. A ceramic slurry is prepared by mixing ceramic powder with a dispersant and a binder, and then the ceramic slurry is sprayed and granulated, and then the granulated powder is dry pressed and formed, and then the dry pressed blank is cold isostatically pressed to obtain a ceramic blank, and finally the blank is heat treated to obtain a ceramic product with a density of 99.5% to 99.8%, a bending strength of more than 580MPa, a microhardness HV1 of more than 2000, and an average grain size of no more than 6μm. The method is not only suitable for the sintering preparation of conventional columnar and tubular products, but also suitable for the preparation of tubular products with an inner diameter of not less than 0.04mm, especially for the preparation of rod-shaped or tubular products with a large aspect ratio or with variable diameter or special shape.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials, specifically to a ceramic cylindrical product, its preparation method, and its application. Background Technology

[0002] In the intersection of modern materials science and advanced manufacturing, ceramic materials occupy an important position due to their superior physicochemical properties. Slender rod-shaped or tubular ceramic materials with slender pores, as well as ceramic products with special structures such as reducing pipes and irregularly shaped pipes, have indispensable applications in many key industries. Ceramic chopping knives are a prime example of such applications.

[0003] In the semiconductor packaging industry, ceramic cleavers, as precision micromachining tools, directly affect the accuracy and efficiency of chip packaging. They require extremely high hardness, wear resistance, and precise dimensional control to accurately cleave metal wires such as gold wires during ultra-fine chip wire bonding. The fabrication of these special, slender rod-shaped ceramic cleavers, with stringent requirements for end shape and size, is extremely challenging.

[0004] Traditional ceramic forming methods each have their advantages and disadvantages when handling such special shapes. For example, slip casting has the advantage of producing ceramic blanks with complex shapes, large dimensions, and relatively high precision. For tubular ceramic materials with slender pores, if the pore design and mold are properly matched, the internal pore structure can be formed in one step, reducing subsequent processing steps. However, this method also has significant drawbacks: the forming process is relatively slow, the production cycle is long, the blank strength is relatively low, and it is easily damaged during demolding and handling. Furthermore, for slender rod-shaped or tubular ceramic materials, due to their elongated shape, uneven slurry filling is prone to occur during slip casting, leading to large differences in blank density and affecting the consistency of the final product's performance. For instance, when using slip casting to form high-purity alumina ceramics, it is difficult to inject the ceramic slurry into the fine pores of the mold with the mold core when using a plaster mold. The slip casting density is low, resulting in a sintered density (density value only 3.8 g / cm³). 3 The strength values ​​(flexural strength only around 350 MPa) are below standard, resulting in a low value. The Vickers hardness HV1 is only around 1600. Conventional slip-cast high-purity alumina ceramics require sintering temperatures exceeding 1700℃, leading to excessively large grain sizes (ranging from several micrometers to tens of micrometers), failing to meet product technical requirements.

[0005] Injection molding offers advantages such as the ability to mold complex shapes, high dimensional accuracy, and automated mass production. For slender rod-shaped ceramic materials and tubular ceramic materials with slender holes, with proper mold design, it can efficiently produce preforms with high precision, making it particularly suitable for products like ceramic cleavers that require stringent dimensional accuracy and shape control. However, injection molding requires a large amount of organic binder, which needs to be removed during the subsequent debinding process. This debinding process is complex and prone to defects; for example, incomplete debinding can lead to residual carbon and other impurities inside the preform, affecting the ceramic's performance. Furthermore, the preform is prone to deformation and cracking during debinding, increasing production costs and scrap rates. For instance, when using metal molds to prepare tubular products with a length-to-diameter ratio of 125, the injection channel is narrow, requiring an injection pressure as high as 100 MPa to fill the mold cavity, and the mold core is difficult to remove. Injection molding compounds contain approximately 20% binder and plasticizer, and the subsequent debinding and sintering process is lengthy, during which slender tubular preforms are prone to deformation. The sintering temperature for injection molding of this high-purity alumina ceramic is generally above 1650℃, which causes abnormal grain growth and reduced strength. Products obtained using this method typically have a density of only 3.85 g / cm³. 3 Its bending strength is only about 400 MPa, and its Vickers hardness HV1 is about 1700.

[0006] Furthermore, for reducing pipes and special-shaped pipes, since the mold cores of slurry casting and injection molding cannot have a demolding taper, the mold core cannot be removed after molding. Therefore, these methods cannot be used to make special tubular products.

[0007] Meanwhile, during the sintering process, slender ceramic materials are prone to deformation and cracking due to uneven heat dissipation and shrinkage in different parts, resulting in a low yield rate of the final product. This significantly limits the large-scale industrial production and widespread application of such high-performance ceramic materials in ceramic cleavers and other related fields. Therefore, developing efficient, high-precision, and stable and reliable preparation methods has become an important topic in the current field of ceramic materials research, especially the optimization of preparation processes for slender or perforated tubular ceramic materials for special applications such as ceramic cleavers, which is urgently needed. Summary of the Invention

[0008] Therefore, the purpose of this invention is to provide a ceramic columnar product, its preparation method, and its application.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] <First Aspect>

[0011] A ceramic columnar product is sintered from rod-shaped or tubular products with a length not exceeding 400 mm and an outer length-to-diameter ratio not exceeding 140.

[0012] As one embodiment, the ceramic columnar product is sintered from a rod-shaped or tubular product with a length not exceeding 150 mm and an outer length-to-diameter ratio not exceeding 100.

[0013] As one implementation, when the product is tubular, the inner diameter of the ceramic cylindrical product is not less than 0.04 mm.

[0014] As one implementation, a ceramic cylindrical product is a rod-shaped or tubular product with an outer length-to-diameter ratio not exceeding 40:1.

[0015] As one implementation, the tubular product includes any one of shaped tubes, reducing tubes, and equal-diameter tubes.

[0016] As one embodiment, the ceramic cylindrical article includes any of the following technical features:

[0017] A. Rod-shaped or tubular products with a length not exceeding 5mm and an outer length-to-diameter ratio not exceeding 1.57;

[0018] B. Rod-shaped or tubular products with a length not exceeding 14mm and an outer length-to-diameter ratio not exceeding 7;

[0019] C. Rod-shaped or tubular products with a length not exceeding 70mm and an outer length-to-diameter ratio not exceeding 23.5;

[0020] D. Rod-shaped or tubular products with a length not exceeding 100mm and an outer length-to-diameter ratio not exceeding 33.4;

[0021] E. Rod-shaped or tubular products with a length not exceeding 300 mm and an outer length-to-diameter ratio not exceeding 40.

[0022] As one embodiment, the ceramic cylindrical product is a rod-shaped or tubular product with an outer diameter of not less than 2 mm.

[0023] As one implementation, when the ceramic cylindrical product is tubular, it further includes any of the following technical features:

[0024] A. The length shall not exceed 14mm, and the inner diameter shall not be less than 0.04mm;

[0025] B. The length shall not exceed 70mm, and the inner diameter shall not be less than 0.5mm;

[0026] C. The length shall not exceed 100mm, and the inner diameter shall not be less than 0.8mm.

[0027] As one implementation, when the ceramic cylindrical product is tubular, it further includes any of the following technical features:

[0028] A. The length shall not exceed 14mm, and the wall thickness shall not be less than 0.52mm;

[0029] B. The length shall not exceed 70mm, and the wall thickness shall not be less than 0.93mm;

[0030] C. The length shall not exceed 100mm and the wall thickness shall not be less than 1.1mm.

[0031] As one embodiment, the ceramic cylindrical article also includes one or more of the following technical features:

[0032] A. Density reaches 98.7% or higher;

[0033] B. Bending strength reaches 550MPa or above;

[0034] C. Microhardness HV1 reaches over 1950;

[0035] D. The average grain size does not exceed 6μm.

[0036] As one embodiment, the ceramic cylindrical article also includes one or more of the following technical features:

[0037] A. The density reaches 99.5% to 99.8%;

[0038] B. Bending strength reaches 580MPa or above;

[0039] C. Microhardness HV1 reaches over 2000;

[0040] D. The average grain size does not exceed 6μm.

[0041] As one embodiment, the ceramic columnar product is a ceramic with alumina or silicon nitride as the main components.

[0042] As one implementation, the mass percentage of the main component material in the ceramic columnar product reaches more than 85%.

[0043] <Second aspect>

[0044] A method for preparing a ceramic columnar product includes the following steps:

[0045] S1. Prepare a ceramic slurry by mixing ceramic powder, dispersant, binder and solvent;

[0046] S2. Spray granulation of ceramic slurry to obtain granulated powder, wherein the additive content in the powder is between 1.5% and 2.5%;

[0047] S3. The granulated powder is dry-pressed to obtain a dry-pressed preform with a density of 42.5-47.5%.

[0048] S4. The dry-pressed green body is then subjected to cold isostatic pressing to obtain a ceramic green body with a density of 52.5% to 57.5%.

[0049] S5. The ceramic blank is subjected to sintering and densification treatment to obtain a sintered body.

[0050] As one embodiment, the method for preparing the ceramic cylindrical article further includes, after step S5:

[0051] S6. Perform hot isostatic pressing on the sintered body.

[0052] As one embodiment, the mass ratio of the ceramic powder, dispersant, and binder is (50-60):(0-0.6):(1-1.8).

[0053] As one embodiment, the mass ratio of the ceramic powder to the solvent is (5-6):(8-14).

[0054] As one embodiment, the ceramic powder is a ceramic powder with alumina and / or silicon nitride as the main components.

[0055] As one implementation, the mass percentage of the main component material in the ceramic powder reaches more than 85%.

[0056] As one implementation scheme, the mass percentage of the main component material in the ceramic powder reaches more than 90%.

[0057] As one implementation scheme, the mass percentage of the main component material in the ceramic powder reaches more than 95%.

[0058] In one implementation scheme, the mass percentage of the main component material in the ceramic powder reaches 99.9% or more.

[0059] As one embodiment, the ceramic powder includes one or more of alumina, silicon nitride, MgO, 3Y-TZP, and Y2O3.

[0060] As one embodiment, the ceramic powder further includes one or more of MgO, 3Y-TZP, and Y2O3.

[0061] In some embodiments, when the ceramic powder is mainly composed of alumina, its mass percentage reaches 99.9% or more.

[0062] As one embodiment, the dispersant is one or more of ammonium polyacrylate, ammonium acrylate, and polycarboxylate.

[0063] In some embodiments, the dispersant is one or more of Duramax D-3019 and MQ-568.

[0064] As one embodiment, the adhesive is one or more of Duramax B-1022, polyethylene glycol, and MQ-23.

[0065] As one embodiment, the solvent is one or more of anhydrous ethanol and water.

[0066] As one implementation, the dry pressing pressure is 5-10 MPa and the time is 4-8 min.

[0067] As one implementation, the pressure of the cold isostatic pressing is 120-200 MPa, and the time is 2-10 min.

[0068] As one implementation, the sintering densification treatment is carried out at a temperature of 1450–1780°C for a time of 45–90 min.

[0069] As one implementation, the hot isostatic pressing treatment is performed at a temperature of 1420–1650°C, a pressure of 150–200 MPa, and a time of 30–50 min.

[0070] As one implementation, in step S4, one or more dry-pressed blanks are subjected to cold isostatic pressing. When there are multiple dry-pressed blanks, a single ceramic blank is obtained after cold isostatic pressing.

[0071] <Third aspect>

[0072] A dry pressing mold is made by pressing with a hard material, which includes one or more of the following: cemented carbide, mold steel, and high-speed steel.

[0073] As one implementation, the dry pressing mold can be used to press rod-shaped or tubular products by axial pressing or radial pressing.

[0074] As one implementation, the dry pressing mold includes an outer mold sleeve, a lower mold core, and an upper mold core. The shapes of the upper surface of the lower mold core and the lower surface of the upper mold core match the shape of the sample to be pressed. The outer mold sleeve has a mold cavity through hole for accommodating the lower part of the upper mold core and the upper part of the lower mold core.

[0075] As one implementation, when the dry pressing mold is used for axial pressing, it also includes an inner core rod for pressing tubular products, and the upper surface of the lower mold core and the lower surface of the upper mold core are provided with holes adapted to the inner core rod.

[0076] As one implementation, when the dry pressing mold is used for axial pressing, it is used to press tubular products with an inner diameter of not less than 0.04 mm and a wall thickness of not less than 2 mm.

[0077] As one implementation, when the dry pressing die is used for axial pressing, the length-to-diameter ratio of the through hole in the die cavity is not greater than 4.5.

[0078] In some embodiments, when the dry pressing die is used for axial pressing, the inner length-to-diameter ratio of the die cavity through hole is approximately 4.3.

[0079] As one implementation, when the dry pressing die is used for radial pressing, the length-to-diameter ratio of the through hole in the die cavity is not greater than 30.

[0080] As one embodiment, when the dry pressing die is used for radial pressing, it includes any of the following features:

[0081] A. The length of the through hole in the mold cavity shall not exceed 20mm, and the inner length-to-diameter ratio shall not be greater than 6.5;

[0082] B. The length of the through hole in the mold cavity shall not exceed 100mm, and the inner length-to-diameter ratio shall not be greater than 25.

[0083] C. The length of the through hole in the mold cavity shall not exceed 400mm, and the inner length-to-diameter ratio shall not be greater than 30.

[0084] <Fourth Aspect>

[0085] A dry pressing mold for pressing dry-pressed ceramic powder blanks.

[0086] As one embodiment, the dry pressing mold is used to press granulated powder in which the additive content is between 1.5% and 2.5%, and the granulated powder includes one or more of alumina, silicon nitride, MgO, 3Y-TZP, and Y2O3.

[0087] As one embodiment, the granulated powder contains a binder, which is one or more of Duramax B-1022, polyethylene glycol, and MQ-23.

[0088] As one embodiment, the granulated powder contains a solvent, which is one or more of anhydrous ethanol and water.

[0089] As one embodiment, the granulated powder contains a dispersant, which is one or more of ammonium polyacrylate, ammonium acrylate, and polycarboxylate.

[0090] As one implementation, the density of the dry-pressed blank pressed using the dry-pressing die reaches 42.5% to 47.5%.

[0091] In some embodiments, the density of the dry-pressed blank pressed using the dry-pressing die reaches 45%.

[0092] As one implementation, the length of the dry-pressed blank pressed by the dry-pressing die does not exceed 400mm, and the aspect ratio is not greater than 140.

[0093] <Fifth Aspect>

[0094] A cold isostatic pressing mold includes an elastic mold sleeve with a cavity, wherein the elastic mold sleeve is a side-covering structure or a full-coverage structure.

[0095] In some embodiments, the elastic mold sleeve is used to cover the side surface of the blank to be pressed, but not the bottom and top surfaces.

[0096] In some embodiments, the elastic mold sleeve is used to fully cover the blank to be pressed.

[0097] As one embodiment, the cold isostatic pressing mold further includes a hard mold core, the hard mold core and the cavity having the same length, and the diameter of the hard mold core being smaller than the diameter of the cavity.

[0098] As one implementation, the rigid mold core is either an integral structure or a split structure.

[0099] As one implementation, the rigid mold core is composed of multiple segments of mold core that can be spliced ​​along the axial direction.

[0100] As one implementation, the rigid mold core consists of a radially extending main mold core and an outer mold core sleeved outside the main mold core.

[0101] In one embodiment, the cold isostatic pressing mold has several regularly distributed cavities on the elastic sleeve.

[0102] As one implementation, the cavity has at least two recesses on its side.

[0103] As one implementation, the recesses are evenly distributed on the sides of the cavity.

[0104] As one implementation, the concave cavity extends axially through the side of the cavity.

[0105] In one implementation, the thickness of the elastic sleeve between adjacent cavities is 0.2 to 2 times the width of the cavity.

[0106] In some embodiments, the thickness of the elastic sleeve between adjacent cavities is 0.24 to 1 times the width of the cavity.

[0107] As one implementation, the cavity has a planar symmetrical shape along the axial direction, and the respective planar symmetry planes of two adjacent cavities do not coincide.

[0108] As one implementation, the included angle between the planes of symmetry of two adjacent cavities is not less than 12°.

[0109] As one implementation scheme, the cavity is configured as follows:

[0110] The elastic sleeve has a cavity at its center. With the cavity at the center as the point of symmetry, several virtual regular polygons are arranged outward in sequence. The vertices of adjacent polygons are collinear with the point of symmetry. The cavity is located at the apex of each polygon.

[0111] As one implementation, the elastic sleeve has cavities on its edges, starting from the second layer of polygons from the inside out.

[0112] In some embodiments, the cavity located on the edge of the polygon is located at the center of the edge.

[0113] As one implementation, the elastic mold sleeve is a split structure, including an elastic outer mold shell with several receiving cavities and an elastic inner mold shell that can be embedded in the receiving cavities, wherein the cavity is a through hole penetrating the elastic inner mold shell.

[0114] As one implementation, the elastic sleeve is made of an elastomer with a Shore hardness between 60A and 80A.

[0115] As one implementation, the elastomer is a polymeric elastomer.

[0116] As one embodiment, the elastomer is one or more of polyurethane, polyamide, and synthetic rubber.

[0117] In some embodiments, the elastomer is selected from chloroprene rubber or polyurethane.

[0118] As one implementation, the mold core is made of one or more of the following materials: ceramic, cemented carbide, non-ferrous metal alloy, and steel.

[0119] As one implementation, when the cold isostatic pressing die is used to axially press rod-shaped products, the elastic mold sleeve is composed of an upper mold sleeve and a lower mold sleeve nested together.

[0120] As one implementation, when the cold isostatic pressing mold is used to axially press tubular products, the elastic mold sleeve is composed of an upper mold sleeve with a first blind hole and a lower mold sleeve with a second blind hole, the second blind hole covering the upper part of the upper mold sleeve.

[0121] As one implementation, the outer diameter of the upper part of the lower mold sleeve matches the inner diameter of the first blind hole.

[0122] As one implementation, the upper outer surface of the lower mold sleeve is provided with a convex ring, the convex surface being arc-shaped, and the lower inner surface of the upper mold sleeve is provided with an arc-shaped concave ring that matches the convex surface.

[0123] As one implementation, the bottom surface of the first blind hole of the upper mold is provided with a blind hole that matches the hard mold core.

[0124] As one implementation, the bottom surface of the second blind hole of the lower mold is provided with a blind hole that matches the hard mold core.

[0125] As one implementation, when the cold isostatic pressing mold is used for axial pressing, the length-to-diameter ratio of the cavity is not greater than 4.5.

[0126] In some embodiments, when the cold isostatic pressing die is used for axial pressing, the inner length-to-diameter ratio of the cavity is approximately 4.3.

[0127] As one implementation, the cold isostatic pressing die is used for axial pressing of tubular products with an inner diameter of not less than 0.04 mm and a wall thickness of not less than 2 mm.

[0128] As one implementation, the cold isostatic pressing die is used for axial pressing of tubular products with an inner diameter of not less than 0.15 mm and a wall thickness of not less than 2 mm.

[0129] In some embodiments, when the cold isostatic pressing die is used for axial pressing, it is used for pressing tubular products with an inner diameter of not less than 0.19 mm and a wall thickness of not less than 2.25 mm.

[0130] As one implementation, when the cold isostatic pressing die is used for radial pressing, the length-to-diameter ratio of the cavity is not greater than 30.

[0131] As one implementation, when the cold isostatic pressing mold is used for radial pressing, the cavity length does not exceed 400mm and the inner length-to-diameter ratio is not greater than 140.

[0132] <Sixth Aspect>

[0133] An application of a cold isostatic pressing mold is to press dry-pressed ceramic powder blanks using a cold isostatic pressing method.

[0134] As one implementation, the cold isostatic pressing die is used for axially pressing rod-shaped or tubular products with an outer length-to-diameter ratio of no more than 4.5;

[0135] As one implementation, the cold isostatic pressing die is used to axially press tubular products with an inner diameter of not less than 0.04 mm and a wall thickness of not less than 2 mm;

[0136] As one implementation, the cold isostatic pressing mold is used to radially press rod-shaped or tubular products with an outer length-to-diameter ratio not greater than 140 and a length not exceeding 400 mm. If the product is tubular, the inner length-to-diameter ratio is not greater than 310.

[0137] As one implementation, the cold isostatic pressing die is used for cold isostatic pressing of a single dry-pressed blank.

[0138] As one implementation, the cold isostatic pressing die is used for cold isostatic pressing of at least two dry-pressed blanks, for pressing multiple dry-pressed blanks separately into one piece.

[0139] As one embodiment, the density of the dry-pressed preform is between 42.5% and 47.5%, and the dry-pressed preform includes one or more of alumina, silicon nitride, MgO, 3Y-TZP, and Y2O3.

[0140] As one embodiment, the dry-pressed preform also contains a binder, which is one or more of Duramax B-1022, polyethylene glycol, and MQ-23.

[0141] As one embodiment, the dry-pressed preform also contains a solvent, which is one or more of anhydrous ethanol and water.

[0142] As one embodiment, the dry-pressed preform also contains a dispersant, which is one or more of ammonium polyacrylate, ammonium acrylate, and polycarboxylate.

[0143] As one embodiment, the dry-pressed preform is made by pressing granulated powder with an additive content between 1.5% and 2.5%.

[0144] As one implementation method, the density of the ceramic green body pressed by cold isostatic pressing mold reaches 52.5% to 57.5%.

[0145] In some embodiments, the density of the ceramic preform pressed using a cold isostatic pressing mold reaches 55%.

[0146] Compared with the prior art, the present invention has the following beneficial effects:

[0147] This invention provides an improved dry pressing mold for dry pressing ceramic powder. During the dry pressing process, a specially designed pressure transmission component significantly improves the uniformity of pressure on the ceramic raw material powder, reduces density differences between different parts of the product, effectively reduces internal stress concentration caused by density inhomogeneity, and reduces the risk of cracking during subsequent processing and use. Especially when used for dry pressing ceramic powder with a low additive content (e.g., 1.5–2.5%), the density of the prepared dry-pressed blank reaches 42.5–47.5%. This dry pressing mold is suitable not only for the dry pressing of conventional columnar and tubular products, but also for the dry pressing of tubular products with an inner diameter of not less than 0.04 mm. It is particularly suitable for pressing ceramic dry-pressed blanks with a large aspect ratio, or those with variable diameters or irregular shapes.

[0148] This invention provides an improved cold isostatic pressing mold for cold isostatic pressing ceramic dry-pressed blanks. The mold's unique elastic sealing structure and pressure equalization system further ensure uniform pressure application throughout the entire process, resulting in a denser and more uniform overall structure for the ceramic cylindrical products. In particular, when used to press dry-pressed blanks with a density of 42.5%–47.5%, the density of the pressed ceramic blank reaches 52.5%–57.5%. This cold isostatic pressing mold is suitable not only for conventional cylindrical and tubular products but also for tubular products with an inner diameter of not less than 0.04 mm. It is especially suitable for cold isostatic pressing of rod-shaped or tubular products with a large aspect ratio, or those with varying diameters or irregular shapes.

[0149] This invention provides a method for preparing ceramic columnar products. By improving the formula and process, granulated powder with a small additive content (e.g., 1.5-2.5%) is first prepared, and then dry-pressed and cold isostatically pressed to obtain a ceramic green body with high density. Then, sintering and densification treatment is carried out to obtain a ceramic sintered body with a density of over 98.7%, a flexural strength of over 550 MPa, a microhardness HV1 of over 1950, and an average grain size of no more than 6 μm. Finally, hot isostatic pressing treatment is carried out to obtain a ceramic product with a density of 99.5%-99.8%, a flexural strength of over 580 MPa, a microhardness HV1 of over 2000, and an average grain size of no more than 6 μm. This method is not only suitable for the sintering preparation of conventional columnar and tubular products, but also for the preparation of tubular products with an inner diameter of not less than 0.04 mm. In particular, it is used for the preparation of rod-shaped or tubular products with a large aspect ratio or with variable diameter or irregular shape. It can further eliminate the internal stress of ceramic products, optimize their microstructure, and improve their overall performance.

[0150] The method for preparing ceramic cylindrical products provided by this invention, when used in the preparation of tubular products with a large aspect ratio, variable diameter, or irregular shape, employs a method of first dividing the product into multiple relatively regular and easily formable split-pressed blanks, then using a cold isostatic pressing mold for precise positioning and assembly of the blanks, and even through the split design of some components in the mold (such as a hard mold core), it is possible to press tubular blanks with special structures, followed by subsequent heat treatment. This method breaks away from the conventional one-piece molding approach and effectively solves the problems of molding difficulties and numerous defects caused by special shapes in one-piece molding. It optimizes the preparation process of ceramic products with special results such as large aspect ratios, irregular shapes, and variable diameters, improves the physical properties of the products, and is conducive to promoting the technological development and widespread application of ceramic materials in aerospace, chemical, energy, and other fields. Attached Figure Description

[0151] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0152] Figure 1 This is a schematic diagram of the dry pressing mold and the cold isostatic pressing mold of Embodiment 1 of the present invention, wherein, Figure 1 (A) is an exploded view of the dry pressing die. Figure 1 (B) is a cross-sectional view of the dry pressing die. Figure 1 (C) is Figure 1 (A) is a magnified view of part A. Figure 1 (D) is an exploded view of the cold isostatic pressing die. Figure 1 (E) is a cross-sectional view of the cold isostatic pressing die;

[0153] Figure 2 This is a schematic diagram of the dry-pressed blank prepared in Example 1 of the present invention;

[0154] Figure 3 Here is a SEM image of the sample in Example 1 of this invention, wherein Figure 3 (A) corresponds to the sintered body in step S5, and S3(B) corresponds to the sintered body in step S6.

[0155] Figure 4 This is a cross-sectional view of the ceramic product prepared in Example 1 of the present invention;

[0156] Figure 5 This is a schematic diagram of the dry pressing mold and the cold isostatic pressing mold of Embodiment 2 of the present invention, wherein, Figure 5 (A) is a schematic diagram of the dry pressing mold. Figure 5 (B) is a schematic diagram of the structure of the prepared dry-pressed preform; Figure 5 (C) is Figure 5 A magnified view of part C in (B). Figure 5(D) is a schematic diagram of the cross-section of the dry pressing die. Figure 5 (E) is Figure 5 A magnified view of part B in (D). Figure 5 (F) is a schematic diagram of the longitudinal section of the dry pressing die. Figure 5 (G) is a top view of a cold isostatic pressing die. Figure 5 (H) is a partial cross-sectional view of the cold isostatic pressing mold;

[0157] Figure 6 This is a schematic diagram of the dry-pressed blank prepared in Example 2 of the present invention;

[0158] Figure 7 This is a schematic diagram of the structure of the firing plate used in Embodiment 2 of the present invention;

[0159] Figure 8 This is a schematic diagram of the structure of the ceramic product prepared in Example 2 of the present invention;

[0160] Figure 9 This is a schematic diagram of the dry pressing mold and the cold isostatic pressing mold of Embodiment 3 of the present invention, wherein, Figure 9 (A) is a schematic diagram of the cross-section of the dry pressing die. Figure 9 (B) is a schematic diagram of the longitudinal section of the dry pressing die. Figure 9 (C) is a schematic diagram of the structure of the prepared dry-pressed preform; Figure 9 (D) is Figure 9 A magnified view of part D in (C). Figure 9 (E) is a three-dimensional structural diagram of a cold isostatic pressing mold. Figure 9 (F) is a top view of a cold isostatic pressing mold;

[0161] Figure 10 This is a side view of the dry-pressed blank prepared in Example 3 of the present invention. Figure 10 (A)) and front view ( Figure 10 (B));

[0162] Figure 11 Here is a SEM image of the sample in Example 3 of this invention, wherein Figure 11 (A) corresponds to the sintered body of step S5, and S12 (B) corresponds to the sintered body of step S6.

[0163] Figure 12 This is a schematic diagram of the structure of the ceramic product prepared in Example 3 of the present invention;

[0164] Figure 13 This is a schematic diagram of the dry pressing mold and the cold isostatic pressing mold of Embodiment 4 of the present invention, wherein, Figure 13 (A) is a schematic diagram of the cross-section of the dry pressing mold; Figure 13 (B) is a partial cross-sectional view of the prepared dry-pressed blank; Figure 13(C) is Figure 13 A magnified view of part E in (A). Figure 13 (D) is a schematic diagram of the structure of the prepared dry-pressed preform; Figure 13 (E) is Figure 13 A magnified view of part F in (D). Figure 13 (F) is a three-dimensional schematic diagram of a cold isostatic pressing mold. Figure 13 (G) is a top view of a cold isostatic pressing die. Figure 13 (H) is Figure 13 A magnified view of part G in (G). Figure 13 (I) is a schematic diagram of the assembly of two dry-pressed blanks and a hard mold core;

[0165] Figure 14 This is a side view of the dry-pressed blank prepared in Example 4 of the present invention. Figure 14 (A) and longitudinal section view ( Figure 14 (B));

[0166] Figure 15 This is a cross-sectional view of the ceramic product prepared in Example 4 of the present invention;

[0167] Figure 16 This is a schematic diagram of the dry pressing mold and the cold isostatic pressing mold of Embodiment 5 of the present invention, wherein, Figure 16 (A) is a schematic diagram of the longitudinal section of the prepared dry-pressed blank; Figure 16 (B) is a schematic diagram of the cross-section of the prepared dry-pressed blank; Figure 16 (C) is a schematic diagram of the structure of the prepared dry-pressed preform; Figure 16 (D) is Figure 16 (C) is a partially enlarged schematic diagram of part J. Figure 16 (E) is a three-dimensional schematic diagram of a cold isostatic pressing mold. Figure 16 (F) is a top view of a cold isostatic pressing die. Figure 16 (G) is a partial cross-sectional view of the cold isostatic pressing mold;

[0168] Figure 17 This is a side view of the dry-pressed blank prepared in Example 5 of the present invention. Figure 17 (A) and longitudinal section view ( Figure 17 (B));

[0169] Figure 18 This is a side view of the ceramic product prepared in Example 5 of the present invention. Figure 18 (A) and sectional view ( Figure 18 (B));

[0170] Figure 19 This is a schematic diagram of the sintering process in step S5 of Examples 1 to 5 of the present invention.

[0171] In the diagram, 1. Outer mold sleeve; 2. Lower mold core; 21. Boss; 22. Annular groove; 3. Upper mold core; 31. Annular groove; 32. Coarse straight mold section; 33. Reducing diameter mold section; 34. Fine straight mold section; 35. Expanding diameter mold section; 36. Rounded rectangular protrusion; 37. Flat straight mold section; 38. Outer expanding mold section; 4. Inner mandrel; 5. Elastic mold sleeve; 51. Upper mold sleeve; 52. Lower mold sleeve; 53. Elastic 54. Outer mold shell; 6. Elastic inner mold shell; 7. Hard mold core; 8. Conical mold core section; 9. Variable diameter mold core section; 10. Mold core column; 11. Outer diameter expansion tube; 22. Dry-pressed billet; 23. Flange; 44. Coarse straight hole section; 55. Reduced diameter hole section; 66. Fine straight hole section; 77. Expanded diameter hole section; 8. Ceramic billet; 9. Firing support plate; 10. Furnace bottom plate. Detailed Implementation

[0172] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0173] To facilitate understanding, the terms mentioned below will be explained first:

[0174] Length-to-diameter ratio: refers to the ratio of the overall length of a cylindrical product with a rod- or tubular structure to its outer diameter (the diameter of the circle if the cross-section is circular, and the dimension at the narrowest point of the cross-section if it is another shape). It is used to describe the overall dimensional proportions of a cylindrical product.

[0175] Inner length-to-diameter ratio: refers to the ratio of the length of the inner hole space of a cylindrical product with an inner hole to the diameter of the inner hole (if the cross-section of the inner hole is circular, it is the diameter of the circle; if it is other shapes, it is the dimension at the narrowest point of the cross-section). It is used to describe the proportional relationship of the internal dimensions of a cylindrical product with an inner hole.

[0176] Preparation method

[0177] In this specific embodiment, a method for preparing a ceramic columnar product is first provided, including the following steps:

[0178] S1. Prepare ceramic slurry by mixing ceramic powder with dispersant and binder;

[0179] S2. Spray granulation of ceramic slurry to obtain granulated powder;

[0180] S3. The granulated powder is dry-pressed into a blank to obtain a dry-pressed preform;

[0181] S4. The dry-pressed green body is subjected to cold isostatic pressing to obtain a ceramic green body;

[0182] S5. The ceramic blank is subjected to sintering and densification treatment to obtain a sintered body;

[0183] S6. The sintered blank is subjected to hot isostatic pressing to obtain ceramic products.

[0184] S1. Mix ceramic powder in a certain proportion, then add a dispersant, and perform a first ball milling process. Then add a binder and continue with a second ball milling process to grind the powder to a D50 between 0.3 and 1 μm. The mass of the dispersant is 0.2% to 1% of the ceramic powder, and the amount of binder added can be determined according to any of the following principles:

[0185] A. The mass of the binder is 2-3% of the ceramic powder;

[0186] B. The viscosity of the slurry should be controlled within the range of 40 to 80 mPa·s.

[0187] S2. Ceramic slurry is spray-granulated at an inlet temperature of 120–340℃ and an outlet temperature of 60–110℃. The particle size D50 of the granulated powder is controlled to be 60–90 μm by adjusting the parameters of the sprayer, and the loose density is controlled to be 0.9–1.2 g / cm³. 3 The additive content is controlled between 1.5% and 2.5%.

[0188] S3. Load the granulated powder into the dry pressing mold and pre-press it at 5-10 MPa for 2-5 minutes. Then, apply bidirectional pressure at 5-10 MPa for 2-5 minutes. Finally, demold and remove the dry pressing blank.

[0189] S4. Place the dry-pressed blank into a dry bag-type cold isostatic pressing mold, press it under a pressure of 120-200MPa for 5 minutes, and then demold and remove the ceramic blank.

[0190] S5. Place the ceramic blank into a sintering furnace for sintering at a temperature of 1450–1780℃ for 45–90 minutes. Oxide ceramics are sintered in an air atmosphere, while nitride ceramics are sintered in a nitrogen atmosphere.

[0191] S6. The sintered body is subjected to hot isostatic pressing at 1420-1650℃ and 200MPa for 30-50 minutes.

[0192] Dry pressing mold

[0193] In this specific embodiment, a dry pressing mold is also provided, which is made of one or more materials selected from cemented carbide, mold steel, and high-speed steel.

[0194] A dry pressing mold includes an outer mold sleeve with a through hole, a lower mold core, and an upper mold core. The upper part of the lower mold core is adapted to the lower part of the through hole of the outer mold sleeve, and the lower part of the upper mold core is adapted to the upper part of the through hole of the outer mold sleeve.

[0195] During use, the upper part of the lower mold core extends into the through hole of the outer mold sleeve, and the powder material is loaded. Then, the lower part of the upper mold core extends into the through hole of the outer mold sleeve, ensuring that a relatively sealed and regular pressing space is formed between the upper mold core, the lower mold core, and the outer mold sleeve, and the powder material is effectively compressed and formed in the pressing space.

[0196] (1) Suitable for axial dry pressing

[0197] When the cross-section of the through hole has an aspect ratio (or length-to-diameter ratio) of no more than 4:1, such as a circle, a square, an ellipse with an aspect ratio of no more than 4:1, or a rectangle with an aspect ratio of no more than 4:1, it is used to press rod-shaped materials with a small aspect ratio (no more than 4:1).

[0198] The dry pressing die also includes an inner core rod, which is used to press tubular materials with a length-to-diameter ratio not exceeding 4:1. In this case, the lower die core has a blind hole at the center of its upper surface that matches the inner core rod, and the upper die core has a through hole that matches the inner core rod.

[0199] In use, the upper part of the lower mold core extends into the through hole of the outer mold sleeve, then the inner core rod is inserted into the blind hole of the lower mold core, and powder material is loaded. Then the lower part of the upper mold core extends into the through hole of the outer mold sleeve. This allows tubular materials to be pressed.

[0200] In particular, when the pore size of the tubular material is small, such as no more than 0.5 mm, if horizontal (radial) integral dry pressing is used, the small pore size and uneven density during the dry pressing process can cause uneven stress on the mold core, making it prone to deformation or breakage. However, the dry pressing mold provided by this invention does not have this problem.

[0201] (2) Suitable for radial dry pressing

[0202] When the through-hole cross-section is rectangular, it is used to press materials with a large length-to-diameter ratio (more than 4:1).

[0203] At this time, the cross-sectional shape of the pressing surface of the lower mold and the upper mold located in the outer mold sleeve is a shape that matches the shape to be pressed, such as arc, straight line, straight line with protrusions / concavities, folding fan shape, etc., and the longitudinal cross-sectional shape is rectangular, trapezoidal, arc, etc., or even an irregular shape.

[0204] Cold isostatic pressing mold

[0205] In this specific embodiment, a cold isostatic pressing mold is also provided, which is suitable for use in dry bag cold isostatic pressing equipment. It includes an elastic mold sleeve with a through hole, which is suitable for rod-shaped materials with a large length-to-diameter ratio. The through hole of the elastic mold sleeve is adapted to the rod-shaped material to be pressed.

[0206] Furthermore, cold isostatic pressing dies also include a core, suitable for pressing tubular materials with a short length-to-diameter ratio.

[0207] When the length-to-diameter ratio is long, tubular materials are not suitable for one-time molding, whether axially or radially pressed.

[0208] For reducing pipes and special-shaped pipes, it is not possible to use a one-time molding mold for pressing.

[0209] Furthermore, improvements were made to the cold isostatic pressing die, resulting in a cold isostatic pressing die for pressing tubular materials, suitable for tubular materials with large length-to-diameter ratios, varying diameters, and irregular shapes. Specifically:

[0210] The tubular material is divided into at least two parts along the longitudinal direction and then dry-pressed to obtain a split blank;

[0211] The split blanks are then assembled in a cold isostatic pressing mold and subjected to cold isostatic pressing.

[0212] Furthermore, for cold isostatic pressing dies for rod-shaped or tubular materials with a small length-to-diameter ratio, the elastic outer mold needs to cover the material to be pressed. Therefore, the elastic outer mold is divided into upper and lower parts. The lower outer mold has an inner cavity to hold the dry-pressed blank after dry pressing, and the upper outer mold is located above the inner cavity of the lower outer mold. If the material to be pressed is tubular, the cold isostatic pressing die also includes a mold core that matches the tubular inner hole, and blind holes are provided on the opposite surfaces of the upper and lower mold sleeves for inserting the mold core.

[0213] Performance Testing Methodology Description

[0214] The following examples illustrate the methods for preparing dry pressing molds, cold isostatic pressing molds, and ceramic cylindrical products involved in this specific embodiment. The methods for testing the performance of the prepared samples are as follows:

[0215] Three-point bending strength test method for ceramics: GB / T 6569-2006 Test method for bending strength of fine ceramics;

[0216] Test method for Vickers hardness HV1 of fine ceramics: GB / T 16534-2009 Test method for room temperature hardness of fine ceramics;

[0217] Test method for elastic modulus of ceramics: GB / T 10700-2006 Test method for elastic modulus of fine ceramics, bending method;

[0218] Ceramic density test method: GB / T 25995-2010 Test method for density and apparent porosity of fine ceramics.

[0219] It should be noted that the test data in the following embodiments are the average values ​​after testing multiple samples, and the relative deviation is no greater than 5%.

[0220] Example 1

[0221] This embodiment provides a method for preparing a ceramic capillary product with a small aspect ratio.

[0222] Raw materials and additives:

[0223] The raw materials are:

[0224] Al2O3 powder with a purity of 99.9% (D 50 =2um) and MgO powder with a purity of 99% (D 50 =0.5um), and the mass ratio of the two is 99.9:0.1.

[0225] The additives are:

[0226] The dispersant used is Duramax D-3019 (belonging to ammonium polyacrylate), with a mass of 0.20% of the raw materials;

[0227] The solvent is deionized water, which accounts for 166.67% of the raw material mass.

[0228] The adhesive used is Duramax B-1022, which accounts for 2% of the raw material weight.

[0229] Step S1 is as follows:

[0230] The raw materials and dispersant are placed in a sand mill and stirred, dispersed, and ground to a fine powder (D). 50 =0.3μm, wherein the grinding media balls are made of The high-purity alumina balls have a ball-to-material ratio of 3:1 to 5:1 (3:1 in this example), and the grinding media balls occupy 30 to 40% of the grinding cylinder volume (35% in this example).

[0231] In this embodiment, grinding media balls are first loaded into the grinding cylinder of the sand mill, deionized water and dispersant are added, the machine is turned on to circulate the liquid, and the external cooling circulation is activated. Then, the raw materials are added into the grinding cylinder through the feeding port.

[0232] In this embodiment, the binder is added 2 hours before the grinding process.

[0233] Step S2 is as follows:

[0234] Centrifugal spray granulation was performed with an inlet temperature of 340℃ and an outlet temperature of 110℃. The particle size D50 of the granulated powder was controlled to be 90μm and the loose pack density to be 1.2g / cm³ by adjusting the parameters of the sprayer. 3 The additive content is controlled at 2.0±0.5%.

[0235] The granulated powder was examined using an optical microscope and found to be solid spherical. The particle size distribution of the granulated particles was examined using a laser particle size analyzer and found to be normally distributed, as shown in Figure D10 = 10 μm and D90 = 95 μm.

[0236] The S3 steps are as follows:

[0237] The dry pressing mold in this embodiment is as follows: Figure 1 As shown in (A) to (C), it consists of an outer mold sleeve 1, a lower mold core 2, an upper mold core 3, and an inner core rod 4, wherein,

[0238] Outer mold sleeve 1, height h 外 The material is SKD11 mold steel, with a heat treatment hardness of HRC=55, and a cylindrical mold cavity through hole is provided.

[0239] The lower mold core 2 is made of high-speed steel of grade SKH-9, and the center of the upper surface has a boss 21 with a blind hole;

[0240] The upper mold core 3 is made of high-speed steel of grade SKH-9, with through holes in the upper and lower directions, and several annular grooves 31 on the lower circumferential side.

[0241] The inner core rod 4 is made of cemented carbide with grade YG8.

[0242] Dry pressing molds also require the use of support components and release modules.

[0243] In this embodiment, a circular groove 22 is formed obliquely downward at the root of the boss 21. The support member has a height of h. 支 It can be a single ring with a through hole, fitted around the outside of the lower mold core 2 (with gaps) to support the outer mold sleeve 1, or it can be composed of several separate blocks of equal height, evenly distributed around the lower mold core 2, with the area used to support the outer mold sleeve 1 not less than 20% of the bottom surface of the outer mold sleeve 1. In this embodiment, the support material is high-speed steel bar with grade SKH9.

[0244] The detachable module, with a height of L, is similar in shape to the support component. It can be a whole that fits over the outside of the lower mold core 2, or it can be composed of several separate blocks of equal height, evenly distributed around the lower mold core 2. In this embodiment, the detachable module is made of 45# steel.

[0245] During operation, place the outer mold sleeve 1 on the press workbench and support the outer mold sleeve 1 with a high steel bar of grade SKH9. The support height is between 5 and 8 mm. Place the boss 21 facing upward into the mold cavity of the outer mold sleeve 1, then insert the inner core rod 4 into the blind hole of the boss 21. Then, fill the mold cavity with granulating powder and smooth it with a plastic or nylon scraper. Finally, assemble the mold core 3.

[0246] The assembled mold is pushed into the center of the press platform for pressure shaping. First, a pre-pressure of 5MPa is applied and maintained for 3 minutes. Then, the steel bar is removed and bidirectional pressure is applied again, maintaining a constant pressure of 12MPa for 5 minutes. After completion, the entire mold is flipped over, and a demolding plate is placed on top for demolding.

[0247] In this embodiment, the dimensional relationships of the components in the dry pressing mold are as follows:

[0248]

[0249] This configuration ensures that the sample is positioned in the center of the mold cavity during pressing, and that it can be easily demolded. Other embodiments follow the same configuration, which will not be described in detail here.

[0250] In this embodiment, the length of the through hole in the mold cavity is 20mm, the diameter is 4.69mm, and the inner length-to-diameter ratio is approximately 4.3.

[0251] In this embodiment, 0.23g of granulated powder was used to press dry-pressed preform 7. The structure of the prepared dry-pressed preform 7 sample is as follows: Figure 2 As shown, the length is 7.5mm, the diameter is 4.69mm, the inner diameter is 0.19mm, the outer length-to-diameter ratio of the dry-pressed blank 7 is about 1.6, and the inner length-to-diameter ratio is about 39.5.

[0252] The density of the dry-pressed preform 7 prepared using the Archimedes method (wax sealing method) was 1.8 g / cm³. 3 To achieve its theoretical density of porcelain (based on 3.98 g / cm³). 3 (Calculated) 45%.

[0253] It is worth noting that axially pressed dry pressing dies can be used to press tubular products with relatively small inner holes, such as inner hole diameters of not less than 0.04 mm and wall thicknesses of not less than 2 mm.

[0254] The S4 steps are as follows:

[0255] In this embodiment, the cold isostatic pressing mold is as follows: Figure 1 As shown in (D) and (E), it consists of a separate elastic mold sleeve 5 (made of polyurethane) and a hard mold core 6 (made of YG8 cemented carbide), wherein,

[0256] The elastic mold sleeve 5 is divided into upper and lower parts. The lower part is the lower mold sleeve 52 with an inner cavity, and the upper surface is a convex ring structure with an inner diameter equal to that of the inner cavity. A circular arc convex ring is provided on the outer side of the convex ring. The upper part is the upper mold sleeve 51 with an inner cavity that matches the convex ring structure. The center of the inner cavity of the upper mold sleeve 51 and the lower mold sleeve 52 is provided with a blind hole that matches the hard mold core 6.

[0257] During operation, place the lower mold sleeve 52 on the worktable, insert the hard mold core 6, then put in the dry-pressed blank 7, and then cover it with the upper mold sleeve 51.

[0258] In this embodiment, the diameter of the dry-pressed blank 7 is 4.69 mm, and the thickness of the lower die sleeve 52 is 3 mm.

[0259] The assembled mold is pushed into the pressure chamber of the dry bag press, and the mold is constrained by the upper and lower pistons. It is kept under constant pressure of 120MPa for 5 minutes. Then the mold is removed, the upper mold sleeve 51 is opened, the blank is taken out, and the hard mold core 6 is extracted to obtain a complete ceramic blank.

[0260] The density of the dry-pressed green body 7 was increased and homogenized by cold isostatic pressing. The density of the prepared ceramic green body was measured to be 2.2 g / cm³ using Archimedes' method (wax sealing method). 3 To achieve its theoretical density of porcelain (based on 3.98 g / cm³). 3 (Calculated) 55%.

[0261] The S5 steps are as follows:

[0262] The ceramic blanks are stacked on the silicon carbide sintering plate of the silicon molybdenum rod sintering furnace (with the axis along the horizontal direction), and calcined corundum sand is sprinkled between each layer of tube blanks to isolate the blanks.

[0263] like Figure 19 As shown, the sintering temperature was 1450℃ and the sintering time was 60 min to obtain the sintered body. The prepared sintered body achieved a flexural strength of 570 MPa and a density of 3.91 g / cm³. 3 It reaches 98.7% of its theoretical density, and microstructural examination shows that its average grain size is 2 μm. Figure 3 As shown in (A).

[0264] The sintered body is shaped and modified. In this embodiment, the sintered body is positioned on an external cylindrical grinding machine with the center hole, and rough grinding of the outer circle and contour grinding of the arc-shaped position groove in the middle of the outer circle are performed. Then, the outer circle is finely ground with a centerless grinding machine, and then the two ends of the ceramic capillary are ground with a surface grinder to complete the product processing.

[0265] The S6 steps are as follows:

[0266] The sintered body after trimming was subjected to hot isostatic pressing (HIP) at 1420℃ and 200MPa argon pressure for 40 minutes.

[0267] The prepared ceramic capillary product with a small aspect ratio achieved a flexural strength of 590 MPa and a density of 3.96 g / cm³. 3 It reaches 99.8% of its theoretical density, while the grain size remains essentially unchanged, such as Figure 3 As shown in (B), the three-point bending strength is increased by 20 MPa.

[0268] Product parameters

[0269] The structure of the ceramic capillary product prepared in this embodiment is as follows: Figure 6 As shown, the cylinder is 5mm long, 3.2mm outer diameter, and 0.2mm inner diameter (outer length-to-diameter ratio 1.56:1, inner length-to-diameter ratio 25:1). The outer edges of the top and bottom surfaces are chamfered at C0.2. A 0.25mm radius arc-shaped groove is provided around the middle of the outer surface. Technical requirements and related elements are as follows: Figure 4 As shown.

[0270] Example 2

[0271] This embodiment provides a method for preparing a solid ceramic rod with a large aspect ratio.

[0272] Raw materials and additives:

[0273] The raw materials are basically the same as those in Example 1, with the same relative amounts. The difference lies in the purity of the Al2O3 powder (99.8%) and the D... 50 =2um.

[0274] The selection of dispersant, solvent, and binder is the same as that in Example 1, and the relative amount of binder is the same, but the mass of dispersant is 0.25% of the raw materials.

[0275] Step S1 is as follows:

[0276] During the grinding process, the ball-to-material ratio is 3:1 to 5:1 (5:1 in this embodiment), and the grinding media balls occupy 60% to 90% of the grinding cylinder volume (70% in this embodiment). Other parameters are the same as those in Embodiment 1.

[0277] Step S2 is as follows:

[0278] During the spray granulation process, the parameters are basically the same as those in Example 1, with the following differences:

[0279] The loose bulk density was controlled at 1.1–1.2 g / cm³ during parameter adjustment. 3 Within the range.

[0280] The S3 steps are as follows:

[0281] The dry pressing mold in this embodiment is as follows: Figure 5 As shown in (A) to (F), it consists of an outer mold sleeve 1, a lower mold core 2, and an upper mold core 3, wherein,

[0282] The outer mold sleeve 1 has a through hole for the mold cavity with an aspect ratio of approximately 30:1;

[0283] Lower mold core 2, with an aspect ratio of approximately 30:1 and a height of h. 下 The upper surface is provided with a semi-circular groove that runs through the length direction, and the diameter of the semi-circular groove is smaller than the width of the lower mold core 2;

[0284] Upper mold core 3 has an aspect ratio of approximately 30:1 and a height of h. 上 The lower surface is provided with a semi-circular groove that runs through the length direction, and the radius is the same as the radius of the semi-circular groove on the upper part of the lower mold core 2.

[0285] In this embodiment, all components of the dry pressing mold are made of mold steel SKD11, and the heat treatment hardness reaches HC=55.

[0286] Dry pressing molds also require the use of support components and release modules.

[0287] The support can be a single rectangular ring with a rectangular through hole, fitted around the outside of the lower mold core 2 (with gaps) to support the outer mold sleeve 1. Alternatively, several separate blocks of equal height can be used, evenly distributed around the lower mold core 2, with the area supporting the outer mold sleeve 1 not less than 20% of the bottom surface of the outer mold sleeve 1. In this embodiment, the support is made of SKH9 grade high-speed steel strip.

[0288] The detachable module, with a height of L, is similar in shape to the support component. It can be a whole that fits over the outside of the lower mold core 2, or it can be composed of several separate blocks of equal height, evenly distributed around the lower mold core 2. In this embodiment, the detachable module is made of 45# steel.

[0289] During operation, place the outer mold sleeve 1 on the press worktable, support the outer mold sleeve 1 with the support, place the upper part of the lower mold core 2 into the mold cavity of the outer mold sleeve 1 with the upper part facing upward, then fill the mold cavity with granulation powder, and scrape it flat in the mold cavity with a plastic or nylon scraper, and then assemble the upper mold core 3.

[0290] The assembled mold is pushed into the center of the press platform for pressure shaping. First, a pre-pressure of 5MPa is applied and maintained for 2 minutes. Then, the steel bar is removed and bidirectional pressure is applied again, maintaining a constant pressure of 10MPa for 2 minutes. After completion, the entire mold is flipped over, and a demolding plate is placed on top for demolding.

[0291] In this embodiment, the through hole of the mold cavity is a rectangular prism shape with a length of 395mm, a width of 13.66mm, and an inner length-to-diameter ratio of approximately 29.

[0292] In this embodiment, 98g of granulated powder was used to press dry-pressed preform 7. The structure of the prepared dry-pressed preform 7 sample is as follows. Figure 6 As shown, it is 395mm long and 13.16mm in diameter, with flanges 71 of 3mm thickness on opposite sides, and the aspect ratio is approximately 131.7.

[0293] The density of the dry-pressed preform 7 prepared using the Archimedes method (wax sealing method) was 1.77 g / cm³. 3 To achieve its theoretical density of porcelain (based on 3.95 g / cm³). 3 (Calculated) 45%.

[0294] The S4 steps are as follows:

[0295] In this embodiment, the cold isostatic pressing mold is as follows: Figure 5 As shown in (G) and (H), the elastic mold sleeve 5 (made of polyurethane with a Shore hardness between 60A and 80A) has uniformly distributed cylindrical through-hole cavities. The size of the cavity is adapted to the dry-pressed blank 7 of step S3.

[0296] When in use, insert the dry-pressed blank 7 into the cavity to complete the cold isostatic pressing mold assembly.

[0297] In this embodiment, the width of the dry-pressed blank 7 is 13.16 mm, and the thickness of the thinnest part of the elastic mold sleeve 5 is 6.48 mm.

[0298] The assembled mold is pushed into the pressure chamber of the dry bag press, and the mold is constrained by the upper and lower pistons. It is kept under constant pressure of 200MPa for 5 minutes. Then the mold is removed, the blank is demolded and removed to obtain a rod-shaped ceramic blank.

[0299] The density of the prepared rod-shaped ceramic green body, measured using Archimedes' method (wax sealing method), was 2.17 g / cm³. 3 To achieve its theoretical density of porcelain (based on 3.95 g / cm³). 3 (Calculated) 55%.

[0300] The S5 steps are as follows:

[0301] The ceramic green bodies are layered and stacked on the silicon carbide ceramic firing plate 9 of the silicon molybdenum rod sintering furnace. In this embodiment, as shown... Figure 7 As shown, the firing plate 9 has a V-shaped groove to constrain each rod-shaped ceramic blank 8. The firing plate 9 and the furnace bottom plate 10 form an angle of about 60° to reduce the frictional resistance of the solid ceramic rod blank during the sintering shrinkage process.

[0302] like Figure 19 As shown, the sintering temperature was 1450℃ and the sintering time was 45min to obtain the sintered body.

[0303] The prepared sintered body has a flexural strength of 550 MPa and a density of 3.91 g / cm³. 3 It reaches 98.9% of its theoretical density.

[0304] The sintered body is then shaped. In this embodiment, auxiliary positioning connecting blocks are bonded to both ends of the solid ceramic rod. The rod is positioned on an external cylindrical grinding machine using the center hole of the connecting block. A resin-bonded diamond grinding wheel with a diamond concentration of 75%-110% and a grit size of 120-180 mesh is used for rough grinding of the outer diameter. Then, a centerless grinding machine is used for fine grinding of the outer diameter. The centerless grinding wheel is a resin-bonded diamond grinding wheel with a grit size of 180-240 mesh. Finally, a surface grinding machine is used to grind the two ends of the ceramic capillary tubes in batches (since the ceramic capillary tubes are non-magnetic, solid paraffin wax is melted and solidified to fix them), thus completing the product processing.

[0305] The S6 steps are as follows:

[0306] The sintered body after trimming was subjected to hot isostatic pressing at 1420℃ and 200MPa for 30 minutes.

[0307] The prepared ceramic solid rod with a large aspect ratio achieved a bending strength of 580 MPa and a density of 3.93 g / cm3, reaching 99.5% of its theoretical density, with a three-point bending strength increased by 30 MPa.

[0308] Product parameters

[0309] The structure of the solid ceramic rod product prepared in this embodiment is as follows: Figure 8 As shown, it is 300mm long, 10±0.05mm in outer diameter, and has an outer length-to-diameter ratio of 30:1.

[0310] Example 3

[0311] This embodiment provides a method for preparing a ceramic capillary product with a large aspect ratio.

[0312] In this embodiment, the granulated powder from Example 2 is used.

[0313] The S3 steps are as follows:

[0314] The dry pressing mold in this embodiment is as follows: Figure 9 As shown in (A) to (D), it consists of an outer mold sleeve 1, a lower mold core 2, and an upper mold core 3, wherein,

[0315] It is basically the same as the dry pressing mold in Example 2, except that:

[0316] The upper surface of the lower mold core 2 is provided with an arc-shaped groove that runs through the length direction, and the central angle corresponding to the arc of the cross-section of the arc-shaped groove is less than 180°.

[0317] The lower surface of the upper mold core 3 is provided with a semi-circular protrusion that runs through the length direction.

[0318] Let the projected width of the upper surface of the lower mold core 2 be w, and the radius of the arc groove be r. In this embodiment,

[0319] The process of loading, pressing, and demolding is described in Example 2.

[0320] In this embodiment, the through hole of the mold cavity is a rectangular prism shape with a length of 127.5 mm, a width of 4.4 mm, and an inner length-to-diameter ratio of approximately 29.

[0321] In this embodiment, 2.1g of granulated powder was used to press dry-pressed preform 7. The structure of the prepared dry-pressed preform 7 is as follows: Figure 10 As shown, it is a semi-circular cylindrical shape, and the outer arc sidewalls adjacent to the plane are respectively provided with flanges 71 with a thickness of 1mm; the length is 127.5mm, the outer arc radius is 2.2mm, the inner arc radius is 0.5mm, and the length-to-diameter ratio of the dry-pressed blank 7 is 127.5.

[0322] In this embodiment, the side of the flange of the dry-pressed blank coincides with the side of the circumscribed square of the outer arc surface.

[0323] The density of the dry-pressed preform 7 prepared using the Archimedes method (wax sealing method) was 1.8 g / cm³. 3 To achieve its theoretical density of porcelain (based on 3.98 g / cm³). 3 (Calculated) 45%.

[0324] The S4 steps are as follows:

[0325] In this embodiment, the cold isostatic pressing mold is as follows: Figure 9 As shown in (E) and (F), an elastic mold sleeve 5 (made of neoprene rubber with a Shore hardness between 60A and 80A) with uniformly distributed through-hole cavities is shown. The shape of each cavity is adapted to the shape of the two dry-pressed blanks 7 assembled from step S3. In this embodiment, the two dry-pressed blanks 7 are in contact with each other on a plane opposite to the outer arc surface to form a combined blank. The surface where the contact surface of the combined blank is located is the virtual dividing surface of the cavity.

[0326] In this embodiment, the cold isostatic pressing mold also includes a hard mold core 6, which is adapted to the inner hole of the composite blank.

[0327] In this embodiment, the cavity distribution is as follows:

[0328] A cavity is set at the center of the upper and lower surfaces of the elastic mold sleeve 5. With the central cavity as the symmetrical point, two layers of virtual squares are arranged outward in sequence. The diagonals of the two virtual squares coincide. The cavity is set at the top corner of each square, and a cavity is also set at the center of the edge of the outer virtual square.

[0329] In this embodiment, the function of providing flange 71 in dry-pressed blank 7 is as follows:

[0330] This ensures that the extensions of any two adjacent virtual dividing surfaces in the adjacent cavities do not overlap, which is beneficial for the elastic outer mold sleeve to evenly transmit pressure to the ceramic blank when pressing the ceramic blank in a dry bag.

[0331] Insert the assembled blank into the cavity, and then insert the hard mold core 6 to complete the assembly of the cold isostatic pressing mold.

[0332] In this embodiment, the width of the combined blank is 4.4 mm, and the thickness of the thinnest part of the elastic mold sleeve 5 between the two cavities is about 1.6 mm.

[0333] The assembled mold is pushed into the pressure chamber of the dry bag press, and the mold is constrained by the upper and lower pistons. It is kept under constant pressure of 200MPa for 5 minutes. Then the mold is removed, the tube blank is demolded and removed to obtain the capillary ceramic blank.

[0334] In this embodiment, the inner diameter of the pressed ceramic blank is 1 mm, the inner length-to-diameter ratio is 127.5, and the outer length-to-diameter ratio is 63.75.

[0335] The density of the prepared capillary ceramic preform, determined using the Archimedes method (wax sealing method), was 2.17 g / cm³. 3 To achieve its theoretical density of porcelain (based on 3.98 g / cm³). 3 (Calculated) 55%.

[0336] The S5 steps are as follows:

[0337] The capillary ceramic blanks are stacked in layers on the silicon carbide ceramic sintering plate in the silicon molybdenum rod sintering furnace (refer to Example 2).

[0338] like Figure 19 As shown, the sintering temperature was 1450℃ and the sintering time was 45min to obtain the sintered body.

[0339] The prepared sintered body has a flexural strength of 650 MPa and a density of 3.93 g / cm³. 3 It reaches 98.7% of its theoretical density, and microstructural examination shows that its average grain size is 0.8 μm. Figure 11 As shown in (A), the microhardness HV1 is 1950.

[0340] The sintered body is then shaped and trimmed, as described in Example 2.

[0341] The S6 steps are as follows:

[0342] The trimmed sintered body was subjected to hot isostatic pressing at 1420℃ and 200MPa for 30 minutes, achieving a flexural strength of 700MPa and a density of 3.97g / cm³. 3 It reaches 99.8% of its theoretical density, while the grain size remains essentially unchanged, such as Figure 11 As shown in (B), the three-point bending strength was increased by 50 MPa, and the microhardness HV1 was increased to 2000.

[0343] Product parameters

[0344] The structure of the ceramic capillary product prepared in this embodiment is as follows: Figure 12 As shown, it is 100mm long, 3mm in outer diameter (outer length-to-diameter ratio approximately 33.33:1), and 0.8mm in inner diameter (inner length-to-diameter ratio 125:1).

[0345] Example 4

[0346] This embodiment provides a method for preparing a ceramic variable diameter capillary tube product (hereinafter referred to as a variable diameter tube).

[0347] Raw materials and additives:

[0348] The raw materials are:

[0349] Al2O3 powder with a purity of 99.9% (D 50 =2um), and 3Y-TZP powder with a purity of 99.0% (D 50 =1um), and the mass ratio of the two is 85:15.

[0350] The additives are:

[0351] The dispersant used is MQ-568 (an anionic modified polycarboxylate), with a mass of 1% of the raw materials;

[0352] The solvent used is deionized water, with a mass of 200% of the raw materials;

[0353] The adhesive used is MQ-23, which accounts for 2% of the raw materials.

[0354] Step S1 is as follows:

[0355] During the grinding process, the ball-to-material ratio is 3:1 to 5:1 (3:1 in this example), and other parameters are the same as those in Example 2. The mixture is stirred, dispersed, and ground to D. 50 =0.2μm.

[0356] Step S2 is as follows:

[0357] The spray granulation process is basically the same as the steps in Example 1, with the following differences:

[0358] The equipment used was replaced with a dual-fluid granulator;

[0359] Inlet temperature 250℃, outlet temperature 110℃, granulation particle size D 50 =60μm, loose packing density controlled between 1.0 and 1.2 g / cm³ 3 Within the specified range, the additive content is controlled within the range of 2.0±0.5%.

[0360] The S3 steps are as follows:

[0361] In this embodiment, the dry pressing mold is as follows: Figure 13 As shown in (A) to (E), the structure is basically the same as that of Example 3, except that:

[0362] The upper surface of the lower mold core 2 is provided with an arc-shaped groove that runs through the length direction, and the central angle corresponding to the arc of the cross-section of the arc-shaped groove is less than 120°.

[0363] The lower surface of the upper mold core 3 has a V-shaped cross-section, and the tip of the V-shape protrudes into the V-shape in an arc shape;

[0364] Along the length direction, the three arc-shaped protrusions of the upper mold core are in a state of continuous diameter change.

[0365] Furthermore, starting from one end of the upper mold core 3, the arc-shaped protrusions are successively the coarse straight mold section 32, the diameter-reducing mold section 33, and the fine straight mold section 34.

[0366] In this embodiment, an expansion section 35 is also provided at the rear end of the thin straight section. The chord length of the arc groove of the lower mold core 2 is smaller than the projected width of the lower mold core 2.

[0367] In this embodiment, the V-shaped opening angle of the lower surface of the upper mold core 3 is 120°.

[0368] The process of loading, pressing, and demolding is described in Example 3.

[0369] In this embodiment, the through hole of the mold cavity is a rectangular prism shape with a length of 18.5 mm, a width of 3.03 mm, and an inner length-to-diameter ratio of approximately 6.1.

[0370] In this embodiment, 0.104g of granulated powder was used to press dry-pressed preform 7. The structure of the prepared dry-pressed preform 7 is as follows: Figure 14As shown, the cross-section is fan-shaped, and flanges 71 along the length direction are provided on both sides of the outer arc surface. The edge thickness of flange 71 is 0.2mm; the length is 18.5mm, and the outer arc radius is 1.75mm. It includes a coarse straight hole section 72 (corresponding to the coarse straight die core section) with a length of 11.53mm and an inner arc radius of 0.6mm, a diameter reduction hole section 73 (corresponding to the diameter reduction die core section) with a length of 5.47mm, a fine straight hole section 74 (corresponding to the fine straight die core section) with a length of 0.5mm and an inner arc radius of 0.03mm, and the remaining length is an enlarged hole section 75 (corresponding to the enlarged die core section) with an inner arc radius of 0.29mm at the end. The length-to-diameter ratio of the dry-pressed blank 7 is 92.5.

[0371] The density of the dry-pressed preform 7 prepared using the Archimedes method (wax sealing method) was 1.91 g / cm³. 3 To achieve its theoretical density of porcelain (4.25 g / cm³). 3 (Calculated) 45%.

[0372] The S4 steps are as follows:

[0373] In this embodiment, the cold isostatic pressing mold is as follows: Figure 13 As shown in (F) to (I), the structure is basically the same as that of Example 3, except that:

[0374] The shape of each cavity is adapted to the shape of the dry-pressed blank 7 assembled in the three S3 steps of this embodiment;

[0375] The shape of the hard mold core 6 is adapted to the inner hole of the dry-pressed blank 7 after assembly.

[0376] In this embodiment, during assembly, the hard mold core 6 is first assembled at the corresponding position of a dry-pressed blank 7, and then two other dry-pressed blanks 7 are assembled. The three dry-pressed blanks 7 are combined together in pairs with V-shaped surfaces to form a column with an outer flange 71. The surfaces where the contacting planes in the combined blanks are located are the virtual dividing surfaces of the cavity.

[0377] In this embodiment, the cavity distribution is as follows:

[0378] A cavity is set at the center of the upper and lower surfaces of the elastic mold sleeve 5. With the central cavity as the symmetry point, two layers of virtual pentagons are arranged outward in sequence. The line connecting two adjacent vertices of the two pentagons passes through the symmetry point.

[0379] The cavity is located at the apex of each pentagon, and a cavity is also located at the center of the edge of the outer pentagon.

[0380] In this embodiment, the flange 71 provided in the dry blank has a similar function to that in embodiment 3, such that the adjacent virtual dividing surfaces between any dry blank and its nearest other dry blank do not overlap.

[0381] In this embodiment, as Figure 14 As shown, the length of the composite blank is 18.5 mm, the width (including flange 71) is 3.61 mm, and the outer length-to-diameter ratio is approximately 5.1. Correspondingly, the inner length-to-diameter ratio of the cavity of the cold isostatic pressing mold is approximately 5.1.

[0382] In this embodiment, the minimum thickness of the elastic sleeve 5 between the two cavities is approximately 0.90 mm.

[0383] It should be noted that in this embodiment, the rigid mold core 6 is a split structure, comprising two sections: a tapered mold core section 61 corresponding to the diameter reduction section, and a variable diameter mold core section 62 consisting of a coarse straight section, an expanded diameter section, and a fine straight section. This is to ensure smooth demolding after pressing. Correspondingly, the demolded ceramic blank is named according to the names of the sections corresponding to the inner holes: coarse straight hole section 72, diameter reduction hole section 73, fine straight hole section 74, and expanded diameter hole section 75.

[0384] The assembled mold is pushed into the pressure chamber of the dry bag press, and the mold is constrained by the upper and lower pistons. It is kept under constant pressure of 150MPa for 5 minutes. Then the mold is removed, the tube blank is demolded and removed to obtain the ceramic blank of the variable diameter tube.

[0385] In this embodiment, the inner diameter of the pressed ceramic blank is 0.06 mm (corresponding to a fine straight hole section), the inner length-to-diameter ratio is 308.3, and the outer length-to-diameter ratio is 92.5.

[0386] The density of the prepared variable-diameter pipe ceramic preform, measured using Archimedes' method (wax sealing method), was 2.34 g / cm³. 3 To achieve its theoretical density of porcelain (4.25 g / cm³). 3 (Calculated) 55%.

[0387] The S5 steps are as follows:

[0388] The ceramic blanks of the variable diameter tube are stacked in layers on the silicon carbide ceramic sintering plate of the silicon molybdenum rod sintering furnace (refer to Example 1).

[0389] like Figure 19 As shown, the sintering temperature was 1550℃ and the sintering time was 50min to obtain the sintered body.

[0390] The sintered body prepared has a bending strength of 870 MPa and a density of 4.22 g / cm3, which is 99.3% of its theoretical density. Microstructural examination shows that the average grain size is 0.7 μm and the microhardness HV1 is 2000.

[0391] The sintered body is shaped and the reducing tube is positioned in the center hole and mounted on a special micro CNC cylindrical grinding machine for precision grinding of the outer diameter. Then, the two ends of the ceramic reducing tube are ground to the diameter using the outer diameter positioning. In this embodiment, the area corresponding to the diameter expansion section is completely removed. Finally, a 0.04 microhole is ground on the sintered body corresponding to the thin straight section using a tungsten steel needle of the appropriate size to complete the product processing.

[0392] The S6 steps are as follows:

[0393] The trimmed sintered body was subjected to hot isostatic pressing at 1500℃ and 200MPa for 30 minutes, achieving a flexural strength of 950MPa and a density of 4.24g / cm³. 3 It reaches 99.7% of its theoretical density. With the grain size remaining basically unchanged, the three-point bending strength is increased by 80 MPa, and the microhardness HV1 is increased to 2050.

[0394] Product parameters

[0395] The structure of the ceramic reducing pipe product prepared in this embodiment is as follows: Figure 15 As shown, the total length is 14mm and the outer diameter is 2mm (outer length-to-diameter ratio 7:1). Among them, the coarse straight hole section 72 is 9.22mm long and has an inner diameter of 0.96mm; the inner cone angle of the narrowing hole section 73 is 12°; the fine straight hole section 74 is 0.4mm long and has an inner diameter of 0.04mm, with an inner length-to-diameter ratio of 350:1.

[0396] Example 5

[0397] This embodiment provides a method for preparing a ceramic irregular capillary product (hereinafter referred to as irregular tube).

[0398] Raw materials and additives:

[0399] The raw materials are:

[0400] α-Si3N4 powder with a purity of 95% (D 50 The three powders are Y2O3 powder (D50 = 2µm) and Al2O3 powder (D50 = 1µm) with a purity of 99.0%, and the mass ratio of the three powders is 90:5:5.

[0401] The additives are:

[0402] No dispersant; the solvent is anhydrous ethanol, and its mass is twice that of the raw materials;

[0403] The binder is PEG6000, which accounts for 3% of the raw materials. Before use, it is dissolved in anhydrous ethanol to form a 10wt.% binder solution.

[0404] Step S1 is as follows:

[0405] Add the raw materials and dispersant to a sand mill, stir, disperse, and grind until fined to D. 50 =0.3μm, wherein the grinding media balls are made of The high-purity silicon nitride balls have a ball-to-material ratio of 3:1 to 5:1 (4:1 in this example), and the grinding media balls occupy 30 to 40% of the grinding cylinder volume (35% in this example).

[0406] The binder solution should be added 1 hour before the material is discharged from the mill.

[0407] Step S2 is as follows:

[0408] The spray granulation process follows the same steps and parameters as in Example 4.

[0409] The S3 steps are as follows:

[0410] The dry pressing mold in this embodiment is as follows: Figure 16 As shown in (A) to (D), the structure is basically the same as that of Example 3, except that:

[0411] The lower surface of the upper mold core 3 is provided with rounded rectangular protrusions 36 that run through the length direction, but along the length direction, some of the rounded rectangular protrusions 36 are in a state of continuous change in diameter.

[0412] In this embodiment, the cross-sectional shape of the rounded rectangular protrusion 36 is obtained by rounding the two corners of the rectangle that protrudes from the lower surface of the upper mold core 3.

[0413] In this embodiment, when viewed along the length direction, the lower surface of the upper mold core 3 has a non-variable diameter section in the middle (straight mold section 37) and outward diameter expansion sections on both sides (outward expansion mold section 38).

[0414] The process of loading, pressing, and demolding is described in Example 3.

[0415] In this embodiment, the rounded rectangular protrusion 36 has a width of 0.63mm, a height of 0.32mm, and a corner radius of 0.13mm.

[0416] The structure of the prepared shaped tube dry-pressed blank 7 has a semi-annular cross-section, and flanges 71 along the length direction are provided on both sides of the outer arc surface. The cross-section of the inner curved surface is a rounded rectangle. The size of the cross-section of the inner curved surface along the length direction gradually decreases from the outside to the inside in the part corresponding to the outer expansion section 38 (expansion section 77), while the part corresponding to the straight section 37 (straight hole section 76) is a constant value.

[0417] In this embodiment, the through hole of the mold cavity is a rectangular prism shape with a length of 91mm, a width of 3.9mm, and an inner length-to-diameter ratio of approximately 23.3.

[0418] In this embodiment, 1.55g of granulated powder is used to press the shaped tube dry-pressed preform 7, such as... Figure 17 As shown, the pressed dry-pressed blank 7 is 91mm long and has an outer diameter of 3.90mm; the outer sidewall of the arc-shaped wall adjacent to the plane is provided with a flange 71 with a thickness of 1mm; the two sides are symmetrically arranged with enlarged hole sections 77, each 7.80mm long. From one side of the plane of the dry-pressed blank 7, the inner curved surface is semi-conical with a apex angle of 6°. The rounded rectangular curved surface at the end face is 1.45mm long, 0.72mm wide, and has a rounded corner radius of 0.54mm. The length-to-diameter ratio of the dry-pressed blank 7 is 91.

[0419] The density of the prepared shaped tube dry-pressed blank 7, tested using Archimedes' method (wax sealing method), was 1.44 g / cm³. 3 To achieve its theoretical density of porcelain (based on 3.20 g / cm³). 3 (Calculated) 45%.

[0420] The S4 steps are as follows:

[0421] In this embodiment, the cold isostatic pressing mold is as follows: Figure 16 As shown in (E) and (G), the structure includes an elastic outer mold shell 53 with a through-hole cavity and a rigid mold core 6, wherein,

[0422] The shape of the hard mold core 6 is compatible with the inner hole of the assembled irregular tube dry-pressed blank 7;

[0423] The rigid mold core 6 is a split structure, including a rounded square mold core column 63 and an outer diameter tube 64 sleeved at both ends of the mold core column 63.

[0424] The dimensions of the rigid mold core 63 are adapted to the dry-pressed blank 7 corresponding to the straight section, the inner hole of the outer diameter tube 64 is adapted to the mold core 63, and the outer dimensions are adapted to the inner curved surface of the expansion section 77.

[0425] Furthermore, it also includes an elastic inner mold shell 54, which is disposed in the cavity of the elastic outer mold shell 53, and the elastic inner mold shell 54 is provided with a through-hole cavity.

[0426] In this embodiment, the through-hole cavity of the elastic outer mold shell 53 is a cylindrical hole, and the elastic inner mold shell 54 is a cylindrical tube, with the shape of the inner hole adapted to the dry-pressed blank 7.

[0427] In this embodiment, the function of the flange 71 in the dry-pressed blank 7 is the same as that in embodiment 3.

[0428] During assembly, two dry-pressed blanks 7 can be combined first, then an outer diameter tube 64 and a mold core column 63 can be inserted from one end, and finally another outer diameter tube 64 can be inserted from the other end; alternatively, the hard mold core 6 can be assembled first, then placed on the inner curved surface of a dry-pressed blank 7, and finally another dry-pressed blank 7 can be assembled.

[0429] In this embodiment, as Figure 17 As shown, the diameter of the dry-pressed blank 7 is 3.9 mm, the cavity diameter of the elastic outer mold shell 53 is 6 mm, and the thickness at the thinnest point between adjacent cavities is 2 mm; the wall thickness at the thinnest point of the elastic inner mold shell 54 is 0.81 mm, and the wall thickness at the thickest point is 1.05 mm.

[0430] The assembled mold is pushed into the pressure chamber of the dry bag press, and the mold is constrained by the upper and lower pistons. It is kept under constant pressure of 150MPa for 5 minutes. Then the mold is removed, the tube blank is demolded and removed to obtain the irregular tube ceramic blank.

[0431] In this embodiment, the inner length-to-diameter ratio of the pressed ceramic blank is approximately 144.4, and the outer length-to-diameter ratio is 45.5.

[0432] The density of the prepared irregularly shaped tube ceramic green body, measured using Archimedes' method (wax sealing method), was 1.60 g / cm³. 3 To achieve its theoretical density of porcelain (based on 3.20 g / cm³). 3 (Calculated) 50%.

[0433] The S5 steps are as follows:

[0434] The irregularly shaped ceramic blanks are stacked in layers on the silicon carbide firing plate of the gas pressure sintering furnace. The surface of the silicon carbide firing plate is coated with a layer of BN coating to prevent the irregularly shaped ceramic blanks from sticking to the firing plate.

[0435] like Figure 19 As shown, the temperature was raised to 1100℃ under a vacuum of 0.1MPa, and then nitrogen was introduced to 6MPa during the heating process. The temperature was then held at 1780℃ for 90 minutes to obtain the sintered body of the shaped tube.

[0436] The prepared sintered body achieved a flexural strength of 900 MPa and a density of 3.18 g / cm³. 3 It reaches 99.4% of its theoretical density. Microstructural examination shows that the main grain size is 1 μm in diameter (as shown), and the β-phase silicon nitride rod structure is about 6 μm in length. The microhardness HV1 is 2000.

[0437] The sintered body is shaped and mounted on a special CNC cylindrical grinding machine with the center hole for precision grinding of the outer diameter. Then, the outer diameter of the ceramic capillary tube is used for positioning and grinding of both ends of the ceramic reducing tube to the dimension, thus completing the product processing.

[0438] The S6 steps are as follows:

[0439] The sintered, trimmed shaped tube was subjected to hot isostatic pressing at 1650℃ and 200MPa nitrogen pressure for 50 minutes to obtain ceramic shaped tube products. The flexural strength reached 950MPa, and the density reached 3.19g / cm³.3 It reaches 99.7% of its theoretical density, the grain size is basically unchanged from the sintered body before hot isostatic pressing, the three-point bending strength is increased by 50MPa, and the microhardness HV1 is 2050.

[0440] Product parameters

[0441] The structure of the ceramic shaped tubular product prepared in this embodiment is as follows: Figure 18 As shown, the total length is 70mm, the outer diameter is 3mm, the two sides are inwardly tapered holes, and the middle is a constant diameter hole. The inner hole width at both ends is 1.13mm, the fillet radius is 0.41mm, the inward tapering length is 6mm, the cone angle of the tapered hole is 6°, and the inner length-to-diameter ratio is 140:1.

[0442] In summary

[0443] The length, outer diameter, and inner diameter of the rod-shaped or tubular dry-pressed blanks prepared in the various embodiments of the present invention are listed in Table 1.

[0444] Table 1. Parameters of the dry-pressed preforms prepared in each embodiment.

[0445] Length / mm outer diameter / mm Outer length-to-diameter ratio Inner hole diameter / mm Inner length-to-diameter ratio Pipe wall thickness / mm Example 1 7.5 4.69 1.60 0.19 39.47 2.95 Example 2 395 3～13.66 131.67 / / / Example 3 127.5 1～1.7 127.5 / / / Example 4 18.5 0.2～1.73 92.5 / / / Example 5 91 1～2.32 91 / / /

[0446] The length, outer diameter, and inner diameter of the rod-shaped or tubular ceramic blanks prepared in the various embodiments of the present invention are listed in Table 2.

[0447] Table 2 Parameters of the ceramic green bodies prepared in each embodiment

[0448]

[0449]

[0450] The length, outer diameter, and inner diameter of the rod-shaped or tubular ceramic products prepared in the various embodiments of the present invention are listed in Table 3.

[0451] Table 3. Parameters of the ceramic columnar products prepared in each embodiment.

[0452] Length / mm outer diameter / mm Outer length-to-diameter ratio Inner hole diameter / mm Inner length-to-diameter ratio Pipe wall thickness / mm Example 1 5 3.2 1.56 0.2 25 1.5 Example 2 300 10 30 / / / Example 3 100 3 33.33 0.8 125 1.1 Example 4 14 2 7 0.04～0.96 350 0.52～0.98 Example 5 70 3 23.33 0.5～1.13 140 0.93～1.25

[0453] In principle, there is no upper limit to the wall thickness, nor is there an upper limit to the inner diameter.

[0454] It should be noted that the inner diameter variation in Examples 4 and 5 is linear and gradual, meaning the inner diameter increases or decreases along the tube axis at a certain ratio or slope. However, those skilled in the art can also adjust the above method to prepare a non-linearly gradual inner diameter variation tube.

[0455] It should be noted that the sintering process in step S5 needs to be adjusted appropriately in actual implementation due to differences in furnace loading and the sintering furnace used.

[0456] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A ceramic cylindrical product, characterized in that: The ceramic columnar product is sintered from a rod-shaped or tubular product with a length not exceeding 400 mm and an external aspect ratio not exceeding 140. In the case of a tubular product, the inner hole diameter before sintering is not less than 0.04 mm.

2. The ceramic columnar product according to claim 1, characterized in that: It also includes one or more of the following technical features: A. Density reaches more than 98.7%; B. Flexural strength reaches above 550MPa; C. Microhardness HV1 reaches above 1950; D. The average grain size does not exceed 6μm.

3. The ceramic columnar product according to claim 2, characterized in that: It also includes one or more of the following technical features: A. Density reaches 99.5% to 99.8%; B. Flexural strength reaches above 580MPa; C. Microhardness HV1 reaches above 2000; D. The average grain size does not exceed 6μm.

4. A method for preparing a ceramic columnar product, characterized in that: The method for preparing the ceramic cylindrical product according to any one of claims 1 to 3 comprises the following steps: S1, mixing ceramic powder, dispersant, binder and solvent to prepare ceramic slurry; S2, spray granulating the ceramic slurry to obtain granulated powder, wherein the additive content in the powder is between 1.5% and 2.5%; S3, dry-pressing the granulated powder to obtain a dry-pressed blank with a density of 42.5-47.5%; S4, performing cold isostatic pressing on the dry pressed green body to obtain a ceramic green body with a density of 52.5-57.5%; S5, sintering and densifying the ceramic body to obtain a sintered body.

5. The method for preparing a ceramic columnar product according to claim 4, characterized in that: After step S5, the method further includes: S6, subjecting the sintered body to hot isostatic pressing treatment, wherein the hot isostatic pressing treatment is performed at a temperature of 1420 to 1650° C., a pressure of 150 to 200 MPa, and a time of 30 to 50 minutes.

6. The method for preparing a ceramic columnar product according to claim 4, characterized in that: It also includes one or more of the following technical features: A. The mass ratio of the ceramic powder, dispersant and binder is: (50-60): (0-0.6): (1-1.8); B. The mass ratio of the ceramic powder to the solvent is: (5-6): (8-14); C. The ceramic powder is a ceramic powder with aluminum oxide and / or silicon nitride as main components; D. The mass of the material as the main component in the ceramic powder accounts for more than 85%; E. The ceramic powder includes one or more of alumina, silicon nitride, MgO, 3Y-TZP, and Y2O3; F. The dispersant is one or more of ammonium polyacrylate, ammonium acrylate, and polycarboxylate; G. The solvent is one or more of anhydrous ethanol and water; H. The binder is one or more of Duramax B-1022, polyethylene glycol, and MQ-23.

7. The method for preparing a ceramic columnar product according to claim 4, characterized in that: It also includes one or more of the following technical features: A. The dry pressing pressure is 5-10 MPa and the time is 4-8 min; B. The cold isostatic pressing pressure is 120-200 MPa and the time is 2-10 min; C. The sintering densification treatment is performed at a temperature of 1450 to 1780°C and for a time of 45 to 90 minutes.

8. The method for preparing a ceramic columnar product according to any one of claims 4 to 7, characterized in that: In the step S4, one or more dry pressed green sheets are subjected to cold isostatic pressing. When there are multiple dry pressed green sheets, an integral ceramic green sheet is obtained after cold isostatic pressing.

9. A dry pressing mold, characterized in that: Used to prepare the ceramic cylindrical product according to any one of claims 1 to 3, the dry pressing mold comprises an outer mold sleeve, a lower mold core and an upper mold core, the shapes of the upper surface of the lower mold core and the lower surface of the upper mold core match the shape of the sample to be pressed, the outer mold sleeve is provided with a mold cavity through hole for accommodating the lower part of the upper mold core and the upper part of the lower mold core, and is used for pressing rod-shaped or tubular products; the length of the mold cavity through hole does not exceed 400 mm, and the inner aspect ratio is not greater than 30; When used to press tubular products, the upper surface of the lower mold core and the lower surface of the upper mold core are provided with holes adapted to the inner core rod, which are used to press tubular products with an inner hole diameter of not less than 0.04 mm and a wall thickness of not less than 0.5 mm.

10. A cold isostatic pressing die, characterized in that: Used to prepare the ceramic cylindrical product according to any one of claims 1 to 3, the cold isostatic pressing mold includes an elastic mold sleeve provided with one or more cavities, the elastic mold sleeve is a side-covering structure or a full-covering structure, the material of the elastic mold sleeve is an elastomer with a Shore hardness between 60A and 80A, and when the cold isostatic pressing mold is used for radial pressing, the length of the cavity does not exceed 400 mm, and the inner aspect ratio is not greater than 140.

11. The cold isostatic pressing die according to claim 10, characterized in that: The side of the cavity is provided with one or more concave cavities, and also includes one or more of the following technical features: A. The concave cavities are evenly distributed on the sides of the cavity; B. The concave cavity axially penetrates the side surface of the cavity; C. The concave cavity is symmetrical along the axial plane; D. When there are multiple concave cavities, the symmetry planes of two adjacent concave cavities do not overlap.

12. The cold isostatic pressing die according to claim 10, characterized in that: It also includes one or more of the following technical features: A. The thickness of the elastic mold sleeve between adjacent cavities is 0.2 to 2 times the width of the cavity; B. The plurality of cavities are evenly distributed on the elastic mold sleeve; C. A cavity is set in the center of the elastic mold sleeve, and a number of virtual regular polygons are arranged in sequence outward with the central cavity as the symmetry point. Adjacent vertices of adjacent polygons are collinear with the symmetry point, and the cavity is set at the vertex position and / or edge of each polygon.

13. The cold isostatic pressing die according to claim 10, characterized in that: The elastic mold sleeve is a split structure, including any one of the following technical features: A. It comprises an elastic outer mold shell with a plurality of accommodating cavities and an elastic inner mold shell that can be embedded in the accommodating cavities, wherein the cavities are through holes that penetrate the elastic inner mold shell; B. The elastic mold sleeve is composed of an upper mold sleeve provided with a first blind hole and a lower mold sleeve provided with a second blind hole, and the second blind hole cover is arranged on the upper part of the upper mold sleeve.

14. The cold isostatic pressing die according to any one of claims 10 to 13, characterized in that: It also includes a hard mold core, the hard mold core and the cavity have the same length, the diameter of the hard mold core is smaller than the diameter of the cavity, and the hard mold core also includes one or more of the following technical features: A. The hard mold core is an integrated structure or a split structure; C. When the hard mold core is a split structure, it is composed of multiple sections of mold cores that can be spliced ​​along the axial direction; D. When the hard mold core is a split structure, it is composed of a main mold core along the radial direction and an outer mold core sleeved on the outer side of the main mold core.

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