Cold isostatic pressing die

Abstract

The utility model discloses a cold isostatic pressing die, which relates to the field of ceramic material preparation, and comprises a cavity for placing a rod-shaped product to be pressed, and an elastic die sleeve covering the side surface of the cavity and used for radially pressing the rod-shaped product, when the elastic die sleeve covers the side surface, the bottom surface and the top surface of the cavity, the elastic die sleeve is used for axially pressing a rod-shaped product; when the hard mold core is arranged in the cavity, the hard mold core is used for supporting an inner hole of a tubular product to be pressed and is used for preparing the tubular product in an axial or radial pressing mode. The cold isostatic pressing die is not only suitable for cold isostatic pressing of conventional columnar and tubular products, but also suitable for cold isostatic pressing of tubular products with the inner diameter not smaller than 0.04 mm, and especially suitable for cold isostatic pressing of rod-shaped or tubular products with the large length-diameter ratio or the variable diameter or the special shape.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of ceramic material preparation, concretely relates to a cold isostatic pressing mould. BACKGROUND

[0002] In the cross field of modern material science and advanced manufacturing industry, ceramic materials occupy an important position due to their excellent physical and chemical properties. Elongated rod-shaped or tubular ceramic materials with elongated holes, as well as special structure ceramic products such as variable diameter tubes and irregular tubes, have indispensable applications in many key industries, and ceramic cleavers are a typical application example.

[0003] In the semiconductor packaging industry, ceramic cleavers, as a kind of precision micro-processing tool, their quality and performance are directly related to the precision and efficiency of chip packaging. It requires high hardness, wear resistance and precise size control to meet the precise cleaving operation of metal wires such as gold wires in the ultra-fine chip wire bonding process. However, the preparation of such special elongated rod-shaped ceramic cleavers with strict requirements on end shape and size is extremely difficult.

[0004] Traditional ceramic forming methods have their own advantages and disadvantages when dealing with such special shapes. For example, slip casting has the advantage of being able to manufacture ceramic bodies with complex shape, large size and relatively high precision. For tubular ceramic materials with elongated holes, if the hole design and mold cooperation are appropriate, the internal hole structure can be formed at one time, reducing subsequent processing procedures. However, this method also has obvious disadvantages. The forming process is relatively slow, the production cycle is long, the strength of the body is relatively low, and it is easy to be damaged during demolding and handling. And for elongated rod-shaped or tubular ceramic materials, due to their own elongated shape, it is easy to cause uneven filling of the slurry during slip casting, resulting in large differences in body density and affecting the performance consistency of the final product. For example, when slip casting high-purity alumina ceramics, it is difficult for the ceramic slurry to be injected into the fine hole of the mold with a mold core. The low density of slip casting leads to a low sintering density (the density value is only about 3.8 g / cm3), resulting in a low strength value (the bending strength is only about 350 MPa). The Vickers hardness HV1 is only about 1600. The conventional slip casting of high-purity alumina ceramics has a sintering temperature of 1700℃ or higher, resulting in grain size growth (grain size in several microns to several tens of microns), which cannot meet the product technical requirements.

[0005] Injection molding has the advantages of complex shape, high dimensional accuracy and automation mass production. For slender rod-shaped ceramic materials and tubular ceramic materials with slender holes, as long as the mold design is reasonable, high-precision green bodies can be efficiently produced, especially for ceramic choppers which are strict in size accuracy and shape. However, injection molding needs to use a large amount of organic binder which needs to be removed in the subsequent debinding process. The debinding process is complex and prone to defects, such as incomplete debinding which leads to the presence of impurities such as carbon in the green body, affecting the performance of the ceramic, and the green body is prone to deformation, cracking and other problems during the debinding process, increasing the production cost and waste rate. For example, when a metal mold is used to form a long-diameter ratio pipe product with a long-diameter ratio of 125, the injection channel is narrow, and an injection pressure as high as 100 MPa is needed to fill the inner cavity of the mold. In addition, the mold core is difficult to extract. The injection molding compound contains about 20% binder and plasticizer, and the post-exhaust sintering process takes a long time. The slender pipe green body is prone to deformation during the exhaust process. The sintering temperature of the high-purity alumina ceramic obtained by injection molding is generally above 1650 DEG C, causing abnormal grain growth and strength reduction. The density of the product obtained by this method is only about 3.85 g / cm3, the bending strength is only about 400 MPa, and the Vickers hardness HV1 is about 1700.

[0006] In addition, for variable-diameter pipes and special-shaped pipes, the mold core of the injection molding and injection molding cannot be brought out of the mold due to the absence of a demolding taper, so these methods cannot be used for special pipe products.

[0007] At the same time, during the sintering process, the ceramic material with a slender structure is prone to deformation, cracking and other problems due to uneven heat dissipation and shrinkage of each part, resulting in a low qualified rate of the final product, which greatly limits the large-scale industrial production and wide application of such high-performance ceramic materials in ceramic choppers and other related fields. Therefore, the development of an efficient, high-precision and stable and reliable preparation method has become an important task in the field of ceramic material research, especially the optimization of the preparation process of slender or hole-tubular ceramic materials for special applications such as ceramic choppers. Practical new type content

[0008] Therefore, the purpose of the present application is to provide a cold isostatic pressing mold.

[0009] The purpose of the present application is achieved by the following technical solutions:

[0010] <First aspect>

[0011] A cold isostatic pressing die for radial pressing of rod-shaped products, comprising a cavity for placing a rod-shaped product to be pressed, and an elastic die sleeve covering the side surface of the cavity, the length-diameter ratio of the cavity is not more than 140, and the length is not more than 400 mm.

[0012] <Second aspect>

[0013] A cold isostatic pressing die for radial pressing of tubular products, comprising a cavity for placing a tubular product to be pressed, an elastic die sleeve covering the side surface of the cavity, and a hard die core provided in the cavity for supporting the inner hole of the tubular product to be pressed, the length-diameter ratio of the hard die core is not more than 310, and the length is not more than 400 mm.

[0014] As a preferred embodiment, the thickness of the elastic die sleeve between adjacent cavities is 0.2-2 times the width of the cavity, and a plurality of cavities are uniformly distributed on the elastic die sleeve; the side surface of the cavity is provided with one or more concave cavities, which are uniformly distributed and extend through the side surface of the cavity in the axial direction, and if there are multiple concave cavities, the axial symmetry planes of adjacent concave cavities do not coincide (the included angle between the symmetry planes of the two adjacent cavities is not less than 12°).

[0015] In some embodiments, the thickness of the elastic die sleeve between adjacent cavities is 0.24-1 times the width of the cavity.

[0016] As an embodiment, the distribution of the cavities is as follows:

[0017] A cavity is provided in the center of the elastic die sleeve, and a plurality of virtual regular polygons are arranged outwardly from the center cavity as the symmetry point, the adjacent vertices of adjacent polygons are collinear, and the cavities are arranged at the vertex positions of the polygons.

[0018] As an embodiment, cavities are also provided on the edges of the second layer of polygons from the inside to the outside of the elastic die sleeve.

[0019] In some embodiments, the cavities located on the edges of the polygons are arranged at the center positions of the edges.

[0020] As a preferred embodiment, the elastic die sleeve is a one-piece structure or a split structure, and when it is a split structure, it comprises an elastic outer die shell with a plurality of accommodating cavities and an elastic inner die shell which can be embedded in the accommodating cavities, and the cavities are through holes penetrating the elastic inner die shell; the material of the elastic die sleeve is a high-molecular elastomer with a Shore hardness of 60A-80A, specifically one or more of polyurethane, polyamide, and synthetic rubber (in some embodiments, the elastomer is selected from neoprene or polyurethane).

[0021] As a preferred embodiment, a hard mold core is arranged in the cavity for supporting the inner hole of the tubular product to be pressed, the outer length-diameter ratio of the hard mold core is not more than 310, the length is not more than 400 mm, and the material is one or more of ceramic material, hard alloy, non-ferrous alloy and steel; the hard mold core is an integral structure or a split structure, and the split structure is a plurality of segmented mold cores spliced in the axial direction or a main mold core and an outer mold core sleeved on the outer side of the main mold core in the radial direction.

[0022] <Third aspect>

[0023] A cold isostatic pressing mold for axially pressing a cylindrical product, comprising a cavity for placing a rod-shaped product to be pressed, and an elastic mold sleeve covering the side, bottom and top of the cavity, the inner length-diameter ratio of the cavity is not more than 4.5.

[0024] As an embodiment, the cold isostatic pressing mold for axially pressing a cylindrical product comprises an upper mold sleeve provided with a first blind hole and a lower mold sleeve provided with a second blind hole, the elastic mold sleeve is split, the upper mold sleeve and the lower mold sleeve are nested together (the upper part of the lower mold sleeve has an outer diameter matched with the inner diameter of the first blind hole, and the outer side of the upper part of the lower mold sleeve is provided with an arc convex ring, and the inner side of the lower part of the upper mold sleeve is provided with an arc concave ring matched with the convex ring), forming a cold isostatic pressing mold with a cavity inside, the cavity is used for accommodating the product to be pressed.

[0025] As an embodiment, the cold isostatic pressing mold further comprises a hard mold core, the diameter of the hard mold core is not less than 0.04 mm, the distance between the outer side wall of the elastic mold sleeve and the outer side wall of the hard mold core is not less than 2 mm, and the bottom surface of the first blind hole of the upper mold sleeve and the bottom surface of the second blind hole of the lower mold sleeve are both provided with a blind hole matched with the hard mold core; the hard mold core is an integral structure or a split structure, and the split structure is a plurality of segmented mold cores spliced in the axial direction or a main mold core and an outer mold core sleeved on the outer side of the main mold core in the radial direction.

[0026] In some embodiments, the diameter of the hard mold core is not less than 0.15 mm.

[0027] Compared with the prior art, the utility model has the following beneficial effects:

[0028] The utility model provides a cold isostatic pressing mould for cold isostatic pressing ceramic dry pressing body, the unique elastic sealing structure and pressure equalization system of this cold isostatic pressing mould further ensure that all -round even pressure is applied in the isostatic pressing process, make ceramic cylindrical product integral structure more dense even. Especially when being used for pressing the dry pressing body of above -mentioned density reaches 42.5~47.5%, the density of pressed ceramic body reaches 52.5~57.5%. This cold isostatic pressing mould not only is suitable for the cold isostatic pressing of conventional cylindrical, tubular product, but also is suitable for the cold isostatic pressing of tubular product with inner diameter not less than 0.04mm, especially can be used for the cold isostatic pressing of rod or tubular product with larger length-diameter ratio or with variable diameter or special shape.

[0029] The cold isostatic pressing mould provided by the utility model, when being used in the preparation process of tubular product with larger length-diameter ratio or with variable diameter or special shape, adopts the method that first divides the product into a plurality of relatively regular and easy-to-shape split pressing dry pressing bodies, then utilizes the accurate positioning of the cold isostatic pressing mould to combine the body, even through the split design of part components (such as hard die core) in the mould, can press the tubular body with special structure, and then carries out subsequent heat treatment, gets rid of the conventional integral molding idea, effectively solves the problems of molding difficulty and many defects caused by special shape during integral molding. The preparation process of ceramic product with special results such as large length-diameter ratio, special shape and variable diameter is optimized, the physical properties of the product are improved, which is conducive to promoting the technical development and wide application of ceramic materials in the fields of aviation, chemical industry and energy. BRIEF DESCRIPTION OF DRAWINGS

[0030] Other features, objects and advantages of the utility model will become more apparent through reading the following detailed description of non-restrictive embodiments with reference to the accompanying drawings:

[0031] Figure 1 It is the structure schematic drawing of dry pressing mould and cold isostatic pressing mould of the utility model embodiment 1, wherein, Figure 1 (A) is the exploded view of dry pressing mould, Figure 1 (B) is the sectional view of dry pressing mould, Figure 1 (C) is Figure 1 (A) the partial close -up view of A part; Figure 1 (D) is the exploded view of cold isostatic pressing mould, Figure 1 (E) is the sectional view of cold isostatic pressing mould;

[0032] Figure 2 It is the structure schematic drawing of dry pressing body prepared in the utility model embodiment 1;

[0033] Figure 3 It is the SEM diagram of sample in the utility model embodiment 1, wherein Figure 3(A) Corresponding to the sintered body in step S5. Figure 3 (B) Sintered body corresponding to step S6;

[0034] Figure 4 This is a cross-sectional view of the ceramic product prepared according to Embodiment 1 of this utility model;

[0035] Figure 5 This is a schematic diagram of the dry pressing mold and the cold isostatic pressing mold of Embodiment 2 of this utility model, 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;

[0036] Figure 5 This is a schematic diagram of the dry-pressed blank prepared in Embodiment 2 of this utility model;

[0037] Figure 6 This is a schematic diagram of the structure of the firing plate used in Embodiment 2 of this utility model;

[0038] Figure 7 This is a schematic diagram of the structure of the ceramic product prepared according to Embodiment 2 of this utility model;

[0039] Figure 8 This is a schematic diagram of the dry pressing mold and the cold isostatic pressing mold of Embodiment 3 of this utility model, 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;

[0040] Figure 9 This is a side view of the dry-pressed blank prepared in Embodiment 3 of this utility model. Figure 10 (A)) and front view ( Figure 10 (B));

[0041] Figure 10 SEM image of the sample in the embodiment 3 of the present application, wherein Figure 11 (A) corresponds to the sintered body of S5 step, Figure 11 (B) corresponds to the sintered body of S6 step;

[0042] Figure 11 Structure schematic view of the ceramic product prepared in the embodiment 3 of the present application;

[0043] Figure 12 Structure schematic view of the dry pressing mold and cold isostatic pressing mold in the embodiment 4 of the present application, wherein, Figure 13 (A) is a cross-sectional schematic view of the dry pressing mold; Figure 13 (B) is a partial cut schematic view of the prepared dry pressing body; Figure 13 (C) is Figure 13 (A) E part of the partial enlarged view, Figure 13 (D) is a structure schematic view of the prepared dry pressing body; Figure 13 (E) is Figure 13 (D) F part of the partial enlarged schematic view, Figure 13 (F) is a three-dimensional schematic view of the cold isostatic pressing mold, Figure 13 (G) is a top view of the cold isostatic pressing mold, Figure 13 (H) is Figure 13 (G) G part of the partial enlarged view, Figure 13 (I) is an assembly schematic view of two dry pressing bodies and hard mold cores;

[0044] Figure 13 (A) and longitudinal sectional view (B) of the dry pressing body prepared in the embodiment 4 of the present application are shown in the side view (A) and longitudinal sectional view (B); Figure 14 Figure 14 (A) and longitudinal sectional view (B) of the dry pressing body prepared in the embodiment 4 of the present application are shown in the side view (A) and longitudinal sectional view (B);

[0045] Figure 14 Structure schematic view of the ceramic product prepared in the embodiment 4 of the present application;

[0046] Figure 15 Figure 16 Structure schematic view of the dry pressing mold and cold isostatic pressing mold in the embodiment 5 of the present application, wherein, Figure 16 (A) is a longitudinal cross-sectional schematic view of the prepared dry pressing body; Figure 16 (B) is a cross-sectional schematic view of the prepared dry pressing body; Figure 16 (C) is a structure schematic view of the prepared dry pressing body; Figure 16 (C) J part of the partial enlarged schematic view, Figure 16 (E) is a three-dimensional schematic view of the cold isostatic pressing mold, Figure 16 (F) is a top view of the cold isostatic pressing mold,​​Figure 16 (G) is a schematic view of a partial section of a cold isostatic pressing die;

[0047] Figure 16 is a side view (A) and a longitudinal section view (B) of the dry-pressed body prepared in the embodiment 5 of the present application; Figure 17 (A)) and a longitudinal section view (B) of the ceramic product prepared in the embodiment 5 of the present application; Figure 17 (A)) and a longitudinal section view (B) of the ceramic product prepared in the embodiment 5 of the present application;

[0048] Figure 17 is a side view (A) and a longitudinal section view (B) of the dry-pressed body prepared in the embodiment 5 of the present application; Figure 18 (A)) and a longitudinal section view (B) of the ceramic product prepared in the embodiment 5 of the present application; Figure 18 (A)) and a longitudinal section view (B) of the ceramic product prepared in the embodiment 5 of the present application;

[0049] Figure 18 is a schematic view of the sintering process of the step S5 in the embodiments 1 to 5 of the present application.

[0050] In the figure, 1 is an outer die sleeve; 2 is a lower die core; 21 is a boss; 22 is an annular groove; 3 is an upper die core; 31 is an annular groove; 32 is a rough straight die section, 33 is a reduced diameter die section, 34 is a fine straight die section; 35 is an expanded diameter die section; 36 is a round rectangular protrusion; 37 is a flat die section; 38 is an outer expanded die section; 4 is an inner core rod; 5 is an elastic die sleeve; 51 is an upper die sleeve; 52 is a lower die sleeve; 53 is an elastic outer die shell; 54 is an elastic inner die shell; 6 is a hard die core; 61 is a conical die core section; 62 is a variable diameter die core section; 63 is a die core column; 64 is an outer expanded diameter tube; 7 is a dry-pressed body; 71 is a flange; 72 is a rough straight hole section, 73 is a reduced diameter hole section, 74 is a fine straight hole section; 75 is an expanded diameter hole section; 76 is a flat hole section; 77 is an expanded hole section; 8 is a ceramic body; 9 is a supporting plate; 10 is a furnace bottom plate. DETAILED DESCRIPTION

[0051] The present application will be described in detail below with reference to the embodiments. The following embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be pointed out that those skilled in the art can make some adjustments and improvements without departing from the concept of the present application. These all belong to the protection scope of the present application.

[0052] For the convenience of understanding, the terms mentioned in the following text are first explained:

[0053] The length-diameter ratio refers to the ratio of the length of the outer part of the columnar product to the outer diameter (if the cross section is circular, the diameter of the circle, if it is other shapes, the size of the narrowest cross section) of the rod-like or tubular structure, which is used to describe the overall size ratio of the columnar product.

[0054] Inner length-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, the diameter of the circle, if it is of other shapes, the size of the narrowest cross section), used to describe the internal size proportion relationship of the cylindrical product with an inner hole.

[0055] Preparation method

[0056] In this specific embodiment, first, a ceramic cylindrical product preparation method is provided, comprising the following steps:

[0057] S1, mixing ceramic powder and dispersant, binder to prepare ceramic slurry;

[0058] S2, the ceramic slurry is spray granulated to obtain granulated powder;

[0059] S3, the granulated powder is dry pressed to obtain a dry pressed body;

[0060] S4, the dry pressed body is cold isostatic pressed to obtain a ceramic green body;

[0061] S5, the ceramic green body is sintered and densified to obtain a sintered body;

[0062] S6, the sintered body is hot isostatic pressed to obtain a ceramic product.

[0063] S1, the ceramic powder is mixed in a certain proportion, then a dispersant is added, and then a first ball milling treatment is performed, then a binder is added, and then a second ball milling treatment is performed, and the powder is ground to D50 between 0.3-1 μm; wherein the mass of the dispersant is 0.2-1% of the mass of the ceramic powder, and the amount of the binder can be added according to any of the following principles:

[0064] A, the mass of the binder is 2-3% of the mass of the ceramic powder;

[0065] B, the viscosity of the slurry is controlled within the range of 40-80 mPa·S.

[0066] S2, the ceramic slurry is spray granulated, the inlet temperature is 120-340℃, the outlet temperature is 60-110℃, and the particle size D50 of the granulated powder is controlled to 60-90 μm by adjusting the parameters of the spray machine, the loose bulk density is controlled to 0.9-1.2 g / cm3, and the additive content is controlled to 1.5-2.5%.

[0067] S3, the granulated powder is loaded into a dry pressing mold for pre-pressing at 5-10 MPa for 2-5 min, then for bidirectional pressing at 5-10 MPa for 2-5 min, then demolding to take out the dry pressed body.

[0068] S4, the dry-pressed blank is loaded into a dry bag cold isostatic pressing die, and is pressed at a pressure of 120-200 MPa for 5 min, and then is unloaded and the ceramic blank is taken out.

[0069] S5, the ceramic blank is placed into a sintering furnace for sintering, the sintering temperature is 1450-1780℃, the sintering time is 45-90 min, the oxide ceramic is sintered in an air atmosphere, and the nitride ceramic is sintered in a nitrogen atmosphere.

[0070] S6, the sintered body is subjected to hot isostatic pressing at 1420-1650℃ and 200 MPa for 30-50 min.

[0071] Dry-pressing die

[0072] In the embodiment, the dry-pressing die is made of one or more of cemented carbide, die steel and high-speed steel.

[0073] The structure of the dry-pressing die comprises an outer die sleeve with a through hole, a lower die core and an upper die core, the upper part of the lower die core is adapted to the lower part of the through hole of the outer die sleeve, and the lower part of the upper die core is adapted to the upper part of the through hole of the outer die sleeve.

[0074] In use, the upper part of the lower die core is inserted into the through hole of the outer die sleeve, the powder material is loaded, and then the lower part of the upper die core is inserted into the through hole of the outer die sleeve, so that a relatively sealed and regular pressing space is formed between the upper die core and the lower die core and the outer die sleeve, and the powder material is effectively compressed and formed in the pressing space.

[0075] (1) Suitable for axial dry-pressing molding

[0076] When the cross section of the through hole has a length-width ratio (or length-diameter ratio) of not more than 4:1, such as a circular shape, a square shape, an ellipse with a length-diameter ratio of not more than 4:1, a rectangle with a length-width ratio of not more than 4:1, etc., the dry-pressing die is used for pressing rod-shaped materials with a small length-diameter ratio (not more than 4:1).

[0077] The dry-pressing die further comprises an inner core rod, which is used for pressing tubular materials with a length-diameter ratio of not more than 4:1, at this time, a blind hole adapted to the inner core rod is formed in the center of the upper surface of the lower die core, and a through hole adapted to the inner core rod is formed in the upper die core.

[0078] In use, the upper part of the lower die core is inserted into the through hole of the outer die sleeve, the inner core rod is inserted into the blind hole of the lower die core, the powder material is loaded, and then the lower part of the upper die core is inserted into the through hole of the outer die sleeve, so that the tubular material can be pressed.

[0079] Especially, when the aperture of the tubular material is small, such as no more than 0.5mm, if using horizontal (radial) overall dry compression molding, because the aperture is small, the powder dry compression process, because of the uneven density, the core is easy to deform or break due to uneven stress. The dry compression mold provided by the utility model does not have this problem.

[0080] (2) Suitable for radial dry compression molding

[0081] When the cross section of the through hole is rectangular, it is used for pressing materials with a large length-diameter ratio (more than 4:1).

[0082] At this time, the cross-sectional shape of the pressing surface of the lower mold and the upper mold located in the outer sleeve is a shape suitable for the shape to be pressed, such as a circular arc, a straight line, a straight line with a protrusion / recess, a fan-shaped folding surface, etc., and the longitudinal cross-sectional shape is rectangular, trapezoidal, arc-shaped, etc., or even irregular shape.

[0083] Cold isostatic pressing mold

[0084] In this embodiment, a cold isostatic pressing mold suitable for use in a dry bag type cold isostatic pressing device is also provided, which includes an elastic sleeve with a through hole suitable for rod-shaped materials with a large length-diameter ratio, and the through hole of the elastic sleeve is matched with the rod-shaped material to be pressed.

[0085] Further, the cold isostatic pressing mold also includes a mold core suitable for the pressing of tubular materials with a short length-diameter ratio.

[0086] When the length-diameter ratio is long, whether it is axial pressing or radial pressing, the tubular material is not suitable for one-time molding. For variable-diameter pipes and special-shaped pipes, one-time molding mold cannot be used for pressing.

[0087] Further, the cold isostatic pressing mold is improved, and a cold isostatic pressing mold for pressing tubular materials is suitable for tubular materials with a large length-diameter ratio, variable diameter, and special shape. Specifically:

[0088] The tubular material is divided into at least two parts in the longitudinal direction for dry compression, and a split body is obtained;

[0089] The split body is assembled in the cold isostatic pressing mold, and then cold isostatic pressing is performed.

[0090] Further, for the cold isostatic pressing mold of rod-shaped or tubular material with a small length-diameter ratio, the elastic sleeve mold needs to be wrapped around the material to be pressed, therefore, the elastic sleeve mold is divided into upper and lower parts, the lower sleeve mold is provided with an inner recess for placing the dry compression body after dry compression, and the upper sleeve mold is arranged above the inner recess of the lower sleeve mold; if the material to be pressed is a tubular material, the cold isostatic pressing mold also includes a mold core matched with the tubular inner hole, and blind holes are arranged on the opposite surfaces of the upper sleeve and the lower sleeve for inserting the mold core.

[0091] Performance test method description

[0092] The dry-pressing mold, the cold isostatic pressing mold and the ceramic cylindrical product preparation method involved in the present embodiment are specifically introduced below through several embodiments, and the method for testing the performance of the prepared samples is as follows:

[0093] Ceramic three-point bending strength test method: GB / T6569-2006 Fine Ceramics Bending Strength Test Method;

[0094] Fine ceramic Vickers hardness HV1 test method: GBT16534-2009 Fine Ceramics Room Temperature Hardness Test Method;

[0095] Ceramic elastic modulus test method: GB / T10700-2006 Fine Ceramics Elastic Modulus Test Method, Bending Method;

[0096] Ceramic density test method: GB / T25995-2010 Fine Ceramics Density and Apparent Porosity Test Method.

[0097] It should be noted that the test data in each of the following embodiments is the average value after testing of multiple samples, and the relative deviation is not greater than 5%.

[0098] Example 1

[0099] The present embodiment provides a preparation method of a ceramic capillary product with a small aspect ratio.

[0100] Raw materials and additives:

[0101] The raw materials are:

[0102] The Al2O3 powder with a purity of 99.9% (D50=2um) and the MgO powder with a purity of 99% (D50=0.5um) are in a mass ratio of 99.9:0.1.

[0103] The additives are:

[0104] The dispersant is Duramax D-3019 (belonging to polyacrylic acid ammonium salt), and the mass is 0.20% of the raw materials;

[0105] The solvent is deionized water, and the mass is 166.67% of the raw materials;

[0106] The binder is Duramax B-1022, and the mass is 2% of the raw materials.

[0107] The S1 step is specifically:

[0108] The raw materials and dispersant are put into a sand mill and stirred, dispersed and ground to D50=0.3μm. The grinding media are high-purity alumina balls with a diameter of φ1mm and a ball-to-material ratio of 3:1~5:1 (3:1 in this embodiment). The grinding media occupy 30~40% of the grinding cylinder volume (35% in this embodiment).

[0109] 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.

[0110] In this embodiment, the binder is added 2 hours before the grinding process.

[0111] Step S2 is as follows:

[0112] Centrifugal spray granulator was used for spray granulation, 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, the loose density was 1.2g / cm3, and the additive content was controlled to be 2.0±0.5% by adjusting the parameters of the sprayer.

[0113] The granulated powder was examined with an optical microscope and found to be solid spherical. The particle size distribution of the granulated particles was examined with a laser particle size analyzer and found to be normally distributed, as shown in Figure D10=10μm and D90=95μm.

[0114] The S3 steps are as follows:

[0115] The dry pressing mold in this embodiment is as follows: Figure 19 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,

[0116] Outer mold sleeve 1, height is The material is SKD11 mold steel, with a heat treatment hardness of HRC=55, and a cylindrical mold cavity through hole is provided.

[0117] 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;

[0118] 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.

[0119] The inner core rod 4 is made of cemented carbide with grade YG8.

[0120] Dry pressing molds also require the use of support components and release modules.

[0121] In this embodiment, a circular groove 22 is formed obliquely downward at the base of the boss 21. The support member has a height of... The supporting member can be a whole ring with a through hole, sleeved outside the lower mold core 2 (with a gap), used for supporting the outer mold sleeve 1, or can be several equal-height split blocks, uniformly distributed around the lower mold core 2, used for supporting the outer mold sleeve 1, and the area of the supporting member is not less than 20% of the bottom surface of the outer mold sleeve 1. In this embodiment, the material of the supporting member is a SKH9 steel strip.

[0122] The demolding block has a height L and a shape similar to that of the supporting member, and can be a whole ring sleeved outside the lower mold core 2 or can be several equal-height split blocks uniformly distributed around the lower mold core 2. In this embodiment, the material of the demolding block is 45# steel.

[0123] During operation, the outer mold sleeve 1 is placed on the press platform, and a SKH9 steel strip is used to support the outer mold sleeve 1, with a support height of 5-8 mm. The boss 21 is placed into the mold cavity of the outer mold sleeve 1 with the convex surface facing up, and then the inner core rod 4 is inserted into the blind hole of the boss 21. The granulation powder is then loaded into the mold cavity, which is leveled using a plastic or nylon scraper. Then, the upper mold core 3 is assembled.

[0124] The assembled mold is pushed into the center of the press platform for pressure forming. First, a pre-pressing pressure of 5 MPa is applied for 3 minutes, and then the steel strip is removed. Then, bidirectional pressing is performed at a pressure of 12 MPa for 5 minutes. After completion, the entire mold is turned over and the demolding block is placed on it for demolding.

[0125] In this embodiment, the size relationship of the components in the dry pressing mold is as follows:

[0126] .

[0127] This arrangement ensures that the sample is located in the middle of the mold cavity during pressing and can ensure smooth ejection during ejection. In other embodiments, the same arrangement is used and will not be described again.

[0128] In this embodiment, the length of the through hole of the mold cavity is 20 mm, and the diameter is 4.69 mm, with an inner length-diameter ratio of about 4.3.

[0129] In this embodiment, 0.23 g of granulation powder is used to press the dry pressing blank 7. The structure of the prepared dry pressing blank 7 is as shown in Figure 1 The length of the dry pressing blank 7 is 7.5 mm, the diameter is 4.69 mm, the inner hole diameter is 0.19 mm, the outer length-diameter ratio of the dry pressing blank 7 is about 1.6, and the inner length-diameter ratio is about 39.5.

[0130] The density of the prepared dry pressing blank 7 is 1.8 g / cm3, which is 45% of the theoretical density of the porcelain body (calculated as 3.98 (g / cm3)).

[0131] It is worth mentioning that the axial pressing dry pressing die can be used to press the tubular product with thin inner hole, such as the inner hole diameter is not less than 0.04 mm and the wall thickness is not less than 2 mm.

[0132] The S4 step is specifically:

[0133] The cold isostatic pressing die in the embodiment is as shown in Figure 2 As shown in (D) and (E), the elastic die sleeve 5 (material: polyurethane) and the hard die core 6 (material: YG8 hard alloy) are composed of two parts.

[0134] The elastic die sleeve 5 is divided into two parts, the lower part is the lower die sleeve 52 provided with a second blind hole, and the upper surface is a convex ring structure with the same diameter as the inner recess, and a circle of arc convex ring is arranged on the outer side of the convex ring; the upper part is the upper die sleeve 51 provided with a first blind hole, the first blind hole is correspondingly matched with the second blind hole, the inner recess of the upper die sleeve 51 is matched with the convex ring structure of the lower die sleeve 52, and blind holes matched with the hard die core 6 are arranged at the centers of the inner recesses of the two; the outer diameter of the upper part of the lower die sleeve 52 matches the inner diameter of the first blind hole, so as to ensure the nesting sealing.

[0135] In operation, the lower die sleeve 52 is placed on the workbench, the hard die core 6 is inserted, the dry pressing blank 7 is loaded, and then the upper die sleeve 51 is covered.

[0136] In the embodiment, the diameter of the dry pressing blank 7 is 4.69 mm, and the thickness of the lower die sleeve 52 is 3 mm.

[0137] The assembled die is pushed into the pressurizing cavity of the dry bag press, the die is constrained by the upper and lower pistons, and the die is kept at a pressure of 120 MPa for 5 min, then the die is taken out, the upper die sleeve 51 is opened, the blank is taken out, and the hard die core 6 is extracted, so that the complete ceramic blank is obtained.

[0138] The dry pressing blank 7 is densified and homogenized by cold isostatic pressing, the density of the prepared ceramic blank is 2.2 g / cm3, which reaches 55% of the theoretical density (calculated as 3.98 (g / cm3)) of the ceramic body.

[0139] The S5 step is specifically:

[0140] The ceramic blank is placed on the silicon molybdenum rod sintering furnace sintering furnace (the axis is along the horizontal direction), and the calcined corundum sand is scattered between each layer of the tube blank for isolation of the blank.

[0141] As shown in Figure 1 , the sintering temperature is 1450 ℃, the sintering time is 60 min, and the sintered body is obtained. The bending strength of the prepared sintered body reaches 570 MPa, the density reaches 3.91 g / cm3, which reaches 98.7% of the theoretical density, and the average grain size of the sintered body is 2 μm, as shown in Figure 19(A) shown.

[0142] The sintered body is trimmed in shape, in this embodiment, the sintered body is positioned and installed on an external grinding machine with a center hole, rough grinding and intermediate arc-shaped groove profiling of the outer circle are performed, then the outer circle is fine ground using a centerless grinding machine, and the two ends of the ceramic capillary tube are ground using a flat grinder, completing product processing.

[0143] The S6 step is specifically:

[0144] The trimmed sintered body is subjected to hot isostatic pressing (HIP) at 1420°C and 200MPa argon pressure for 40min.

[0145] The prepared ceramic capillary tube product with a smaller aspect ratio has a bending strength of 590MPa, a density of 3.96g / cm3, reaching 99.8% of its theoretical density, and in the case of substantially unchanged grain size, such as Figure 3 (B) shown, the three-point bending strength is increased by 20MPa.

[0146] Product parameters

[0147] The structure of the ceramic capillary tube product prepared in this embodiment is shown in Figure 3 with a length of 5mm, an outer diameter of 3.2mm, an inner hole diameter of 0.2mm (outer aspect ratio 1.56:1, inner aspect ratio 25:1), a cylindrical upper and lower bottom surface with a chamfered edge C0.2, a waist-shaped arc-shaped groove at the middle position of the outer side surface, and an arc-shaped groove radius of 0.25mm, and the relevant technical requirements are shown in Figure 6 .

[0148] Example 2

[0149] This embodiment provides a method for preparing a ceramic solid rod product with a larger aspect ratio.

[0150] Raw materials and additives:

[0151] The raw materials are basically the same as those in Example 1, and the relative amounts are consistent, except that the Al2O3 powder has a purity of 99.8% and a D50 of 2um.

[0152] The dispersant, solvent, and binder are selected in the same way as the corresponding materials in Example 1, and the relative amount of the binder is consistent, but the mass of the dispersant is 0.25% of the raw materials.

[0153] The S1 step is specifically:

[0154] During the grinding process, the ball-to-material ratio is 3:1~5:1 (5:1 in this embodiment), the grinding medium balls account for 60~90% of the volume of the grinding cylinder (70% in this embodiment), and the other parameters are consistent with those in Example 1.

[0155] Step S2 is as follows:

[0156] During the spray granulation process, the parameters are basically the same as those in Example 1, with the following differences:

[0157] The loose packing density during parameter adjustment is controlled within the range of 1.1~1.2 g / cm3.

[0158] The S3 steps are as follows:

[0159] The dry pressing mold in this embodiment is as follows: Figure 4 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,

[0160] The outer mold sleeve 1 has a through hole for the mold cavity with an aspect ratio of approximately 30:1;

[0161] Lower mold core 2, with an aspect ratio of approximately 30:1, and a height of... 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;

[0162] Upper mold core 3, length-to-width ratio approximately 30:1, height is 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.

[0163] In this embodiment, all components of the dry pressing mold are made of mold steel SKD11, and the heat treatment hardness reaches HC=55.

[0164] Dry pressing molds also require the use of support components and release modules.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] The assembled mold is pushed into the center of the press platform for pressure shaping, first pre-pressing at 5 MPa pressure, constant pressure for 2 min, then withdrawing the steel strip, then bidirectional pressing, 10 MPa constant pressure for 2 min, after completion, turning over the entire mold, and placing a demolding block for demolding.

[0169] In this embodiment, the through hole of the mold cavity is rectangular prism shape, the length is 395 mm, the width is 13.66 mm, and the inner length-diameter ratio is about 29.

[0170] In this embodiment, 98 g of granulated powder is weighed for pressing the dry compact 7, and the structure of the prepared dry compact 7 sample is as shown in the figure, the length is 395 mm, the diameter is 13.16 mm, and the opposite two sides have a flange 71 with a thickness of 3 mm, and the length-width ratio is approximately 131.7. Figure 5 The density of the prepared dry compact 7 is 1.77 g / cm3, which reaches 45% of the theoretical density of the porcelain body (calculated as 3.95 (g / cm3)).

[0171] The S4 step is specifically:

[0172] In this embodiment, the cold isostatic pressing mold is as shown in figures (G) and (H), which is an elastic mold sleeve 5 (the material is a high polymer elastomer with a Shore hardness of 60A-80A, specifically one of polyurethane, polyamide, and synthetic rubber) with uniformly distributed cylindrical through hole cavities, the size of the cavities is matched with the dry compact 7 of the S3 step; the thickness of the elastic mold sleeve between adjacent cavities is 0.2-2 times the width of the cavity, and a plurality of cavities are uniformly distributed on the elastic mold sleeve.

[0173] Figure 6 In use, the dry compact 7 is inserted into the cavity, and the cold isostatic pressing mold assembly is completed.

[0174] In this embodiment, the width of the dry compact 7 is 13.16 mm, and the thinnest thickness of the elastic mold sleeve 5 is 6.48 mm.

[0175] The assembled mold is pushed into the dry bag press pressure cavity, and the mold is constrained by the upper and lower pistons, and then the mold is taken out, the mold is demolded to take out the compact, and a rod-shaped ceramic compact is obtained.

[0176] The density of the prepared rod-shaped ceramic compact is 2.17 g / cm3, which reaches 55% of the theoretical density of the porcelain body (calculated as 3.95 (g / cm3)).

[0177] The S5 step is specifically:

[0178]

[0179] ​​The ceramic green body is layered and placed on a silicon carbide ceramic support plate 9 of a silicon molybdenum rod sintering furnace for re-sintering. In this embodiment, as shown in Figure 5 FIG. 1, a V-shaped notch is formed on the support plate 9 for restraining each rod-shaped ceramic green body 8, and the support plate 9 is at an angle of about 60° with the furnace bottom plate 10 for reducing the frictional resistance of the ceramic solid rod green body during sintering shrinkage.

[0180] As shown in Figure 7 FIG. 2, the sintering temperature is 1450°C, and the sintering time is 45 min, to obtain a sintered body.

[0181] The prepared sintered body has a bending strength of 550 MPa and a density of 3.91 g / cm3, reaching 98.9% of the theoretical density.

[0182] The sintered body is trimmed in shape. In this embodiment, the ceramic solid rod is bonded with an auxiliary positioning connecting block at both ends, and is positioned and installed on an external cylindrical grinding machine through the center hole of the connecting block. Resin-based diamond grinding wheels are used, with a diamond concentration of 75%-110% and a particle size of 120-180 mesh. External cylindrical rough grinding is then performed, and then the external cylindrical surface is precisely ground using a centerless grinding machine with a particle size of 180-240 mesh resin-based diamond grinding wheels. Then, the two end sizes of the ceramic capillary tube are ground in batches using a surface grinding machine (since the ceramic capillary tube has no magnetism, it is fixed by melting and solidifying solid paraffin). The product processing is completed.

[0183] The S6 step is specifically as follows:

[0184] The trimmed sintered body is subjected to hot isostatic pressing at 1420°C and 200 MPa for 30 min.

[0185] The prepared ceramic solid rod product with a large aspect ratio has a bending strength of 580 MPa and a density of 3.93 g / cm3, reaching 99.5% of the theoretical density, and the three-point bending strength is increased by 30 MPa.

[0186] Product parameters

[0187] The structure of the ceramic solid rod product prepared in this embodiment is shown in Figure 19 FIG. 3, with a length of 300 mm, an outer diameter of 10±0.05 mm, and an outer aspect ratio of 30:1.

[0188] Example 3

[0189] This embodiment provides a preparation method of a ceramic capillary tube product with a large aspect ratio.

[0190] In this embodiment, the granulation powder in Example 2 is used.

[0191] The S3 step is specifically as follows:

[0192] The dry pressing mold in this embodiment is as shown inFigure 8 (A) to (D) are shown, consisting of an outer sleeve 1, a lower mold core 2 and an upper mold core 3, wherein,

[0193] The dry pressing mold in this embodiment is basically the same as that in Embodiment 2, with the difference being that:

[0194] The upper surface of the lower mold core 2 is provided with an arc-shaped groove penetrating in the length direction, and the central angle of the arc corresponding to the cross section of the arc-shaped groove is less than 180°.

[0195] The lower surface of the upper mold core 3 is provided with a semicircular protrusion penetrating in the length direction.

[0196] The projection width of the upper surface of the lower mold core 2 is w, and the radius of the arc-shaped groove is r. In this embodiment, w > r.

[0197] The processes of sample loading, pressing and demolding are referred to Embodiment 2.

[0198] In this embodiment, the mold cavity through hole is in the shape of a rectangular prism, with a length of 127.5 mm and a width of 4.4 mm, and the inner length-diameter ratio is about 29.

[0199] In this embodiment, 2.1 g of granulated powder is weighed for pressing the dry compact 7, and the structure of the prepared dry compact 7 is shown in Figure 9 , which is in the shape of a semicircular ring cylinder, and the arc side wall adjacent to the plane is respectively provided with a flange 71 with a thickness of 1 mm; the length is 127.5 mm, the outer arc surface radius is 2.2 mm, the inner arc surface radius is 0.5 mm, and the outer length-diameter ratio of the dry compact 7 is 127.5.

[0200] In this embodiment, the side edge of the flange of the dry compact coincides with the side of the circumscribed square of the circle of the outer arc surface.

[0201] The density of the prepared dry compact 7 is 1.8 g / cm3, which reaches 45% of the theoretical density of the porcelain body (calculated as 3.98 (g / cm3)).

[0202] The S4 step is specifically:

[0203] In this embodiment, the cold isostatic pressing mold is shown in Figure 10 (E) and (F), which is an elastic mold sleeve 5 (the material is neoprene, a high polymer elastomer with a Shore hardness between 60A-80A, specifically one of polyurethane, polyamide and synthetic rubber) with uniformly distributed through-hole cavities, and the shape of each cavity is adapted to the shape of the two dry compacts 7 after assembly in the S3 step; the side of the cavity is provided with a plurality of concave cavities, which are uniformly distributed and penetrate the cavity side in the axial direction, and the axial symmetry planes of adjacent concave cavities do not coincide (the included angle is not less than 12°). In this embodiment, the two dry compacts 7 are in contact with each other at the plane opposite to the outer arc surface, forming a combined compact. The plane where the contact surface of the combined compact is located is a virtual division plane of the cavity.

[0204] In the present embodiment, the cold isostatic pressing mold further comprises a hard mold core 6 which is adapted to the inner hole of the combined green body; the material of the hard mold core is one or more of ceramic material, cemented carbide, non-ferrous alloy, steel and iron, and is an integral structure or a split structure which is a multi-section mold core spliced along the axial direction or a main mold core and an outer mold core sleeved outside the main mold core along the radial direction.

[0205] In the present embodiment, the cavity distribution mode is as follows:

[0206] A cavity is arranged at the center of the upper and lower surfaces of the elastic mold sleeve 5, and two layers of virtual squares are arranged outwardly from the center cavity as the symmetry point, the diagonal lines of the two virtual squares coincide, and the cavities are arranged at the top corner positions of each square, and cavities are also arranged at the center of the edges of the outer virtual square.

[0207] In the present embodiment, the flange 71 arranged in the dry-pressed green body 7 has the following effects:

[0208] In any two adjacent cavities, any two adjacent virtual division surfaces do not coincide, which is beneficial to the uniform transmission of pressure to the ceramic green body by the elastic outer mold sleeve during dry bag pressing of the ceramic green body.

[0209] Insert the combined green body into the cavity, and then insert the hard mold core 6 to complete the assembly of the cold isostatic pressing mold.

[0210] In the present embodiment, the width of the combined green body 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.

[0211] Push the assembled mold into the pressurizing cavity of the dry bag press, constrain the mold with the upper and lower pistons, and then take out the mold after constant pressure at 200 MPa for 5 min, and then take out the tube blank to obtain the capillary tube ceramic green body.

[0212] In the present embodiment, the inner hole diameter of the pressed ceramic green body is 1 mm, the inner length-diameter ratio is 127.5, and the outer length-diameter ratio is 63.75.

[0213] The density of the prepared capillary tube ceramic green body is 2.17 g / cm3, which reaches 55% of the theoretical density of the ceramic body (calculated as 3.98 (g / cm3)).

[0214] The S5 step is specifically:

[0215] Layered capillary tube ceramic green bodies are placed on a silicon molybdenum rod sintering furnace re-sintered silicon carbide ceramic support firing plate (reference embodiment 2).

[0216] As shown in Figure 9 the sintering temperature is 1450℃, and the sintering time is 45 min to obtain a sintered body.

[0217] The sintered body has a bending strength of 650 MPa, a density of 3.93 g / cm3, reaching 98.7% of its theoretical density, and a grain size of 0.8 μm on average, as shown in Figure 19 (A), and a microhardness HV1 of 1950.

[0218] The sintered body is subjected to contour modification, and the modification method is as described in Example 2.

[0219] The S6 step is specifically as follows:

[0220] The modified sintered body is subjected to hot isostatic pressing at 1420°C and 200 MPa for 30 min, and has a bending strength of 700 MPa, a density of 3.97 g / cm3, reaching 99.8% of its theoretical density, and a grain size of 0.8 μm on average, as shown in Figure 11 (B), the three-point bending strength is increased by 50 MPa, and the microhardness HV1 is increased to 2000.

[0221] Product parameters

[0222] The ceramic capillary product prepared in this example has a structure as shown in Figure 11 , with a length of 100 mm, an outer diameter of 3 mm (outer length-to-diameter ratio of about 33.33:1), and an inner diameter of 0.8 mm (inner length-to-diameter ratio of 125:1).

[0223] Example 4

[0224] This example provides a method for preparing a ceramic variable-diameter capillary product (hereinafter referred to as a variable-diameter tube).

[0225] Raw materials and additives:

[0226] The raw materials are:

[0227] Al2O3 powder with a purity of 99.9% (D50=2um) and 3Y-TZP powder with a purity of 99.0% (D50=1um) in a mass ratio of 85:15.

[0228] The additives are:

[0229] The dispersant is MQ-568 (anionic modified polycarboxylate), and the mass is 1% of the raw materials;

[0230] The solvent is deionized water, and the mass is 200% of the raw materials;

[0231] The binder is MQ-23, and the mass is 2% of the raw materials.

[0232] The S1 step is specifically as follows:

[0233] In the grinding process, the ball-to-material ratio was 3:1 to 5:1 (3:1 in this embodiment), and other parameters were consistent with those in Example 2. Stirring and dispersion were performed until the D50 was 0.2 μm.

[0234] The S2 step specifically includes:

[0235] In the spray granulation process, the steps were basically consistent with those in Example 1, except that:

[0236] The device used was replaced with a double-fluid granulator.

[0237] The inlet temperature was 250°C, the outlet temperature was 110°C, the granulation particle size D50 was 60 μm, the loose bulk density was controlled in the range of 1.0 to 1.2 g / cm3, and the additive content was controlled in the range of 2.0 ± 0.5%.

[0238] The S3 step specifically includes:

[0239] In this embodiment, the dry pressing mold is as shown in Figure 12 (A) to (E), which is basically consistent with that in Example 3, except that:

[0240] The upper surface of the lower mold core 2 is provided with an arc-shaped slot extending in the length direction, and the central angle of the circular arc corresponding to the arc-shaped slot in the cross section is less than 120°.

[0241] The lower surface of the upper mold core 3 is in the shape of V in the cross section, and the tip of the V is in the shape of arc convex to the inside of the V.

[0242] In the length direction, part of the arc convex of the upper mold core 3 is in the state of continuous diameter change.

[0243] Further, from one end of the upper mold core 3, the arc convex is in turn a thick straight mold segment 32, a reduced diameter mold segment 33, and a thin straight mold segment 34.

[0244] In this embodiment, a diameter expansion mold segment 35 is further provided at the rear end of the thin straight segment. The chord length of the arc-shaped slot of the lower mold core 2 is less than the projection width of the lower mold core 2.

[0245] In this embodiment, the opening angle of the V of the lower surface of the upper mold core 3 is 120°.

[0246] The processes of sample loading, pressing, and demolding refer to Example 3.

[0247] In this embodiment, the through hole of the mold cavity is in the shape of a rectangular prism, with a length of 18.5 mm and a width of 3.03 mm, and the inner length-to-diameter ratio is about 6.1.

[0248] In this embodiment, 0.104 g of the granulation powder was weighed for pressing the dry compact 7, and the structure of the prepared dry compact 7 is as shown in Figure 13As shown, the cross section is in the shape of a sector, and at the two side edges of the outer arc surface, there are lengthwise flanges 71, the edge thickness of the flanges 71 is 0.2mm; the length is 18.5mm, the outer arc surface radius is 1.75mm, the length of the thick straight hole section 72 (corresponding to the thick straight mold core section) is 11.53mm, the inner arc surface radius is 0.6mm, the length of the reduced diameter hole section 73 (corresponding to the reduced diameter mold core section) is 5.47mm, the length of the thin straight hole section 74 (corresponding to the thin straight mold core section) is 0.5mm, the inner arc surface radius is 0.03mm, and the remaining length is the expanded diameter hole section 75 (corresponding to the expanded diameter mold core section), the end inner arc surface radius is 0.29mm, and the length-diameter ratio of the dry press blank 7 is 92.5.

[0249] The density of the prepared dry press blank 7 is 1.91g / cm3, which reaches 45% of the theoretical density of the porcelain body (calculated as 4.25g / cm3).

[0250] The S4 step is specifically:

[0251] In this embodiment, the cold isostatic pressing mold is as shown in Figure 14 (F) to (I) shown, the structure is basically the same as that of embodiment 3, and the difference is that:

[0252] The shape of each cavity is adapted to the shape of the assembled dry press blank 7 of the three S3 steps of this embodiment;

[0253] The shape of the hard mold core 6 is adapted to the inner hole of the assembled dry press blank 7; the diameter of the hard mold core is not less than 0.04mm, the distance between the outer wall of the elastic mold sleeve and the outer wall of the hard mold core is not less than 2mm, and it is a split structure (the split structure can adopt a multi-section mold core splicable in the axial direction or a combination of a main mold core and an outer mold core in the radial direction), which specifically includes two sections in this embodiment, one section is a taper angle mold core section 61 corresponding to the reduced diameter section, and the other section is a variable diameter mold core section 62 of the thick straight section, the expanded diameter section and the thin straight section, which is to enable smooth demolding after pressing.

[0254] In this embodiment, during assembly, the hard mold core 6 needs to be assembled at a corresponding position of one dry press blank 7, and then the other two dry press blanks 7 are assembled, and the three dry press blanks 7 are combined in a V-shaped surface two by two, forming a cylindrical shape with flanges 71 on the outer side. Among them, the plane where the contacting planes of the combined blank body are located is a virtual division plane of the cavity.

[0255] In this embodiment, the cavity distribution mode is:

[0256] The upper and lower surfaces of the elastic mold sleeve 5 are provided with a cavity, and two layers of virtual pentagons are arranged outwardly with the central cavity as the symmetry point, and the line connecting two adjacent vertices of the two pentagons passes through the symmetry point;

[0257] The cavities are arranged at the top corners of each pentagon, and cavities are also arranged at the center of the edges of the outer pentagons.

[0258] In this embodiment, the flange 71 in the dry green body has the same effect as in Embodiment 3, and the adjacent virtual division surfaces between any dry green body and its nearest other dry green body do not coincide.

[0259] In this embodiment, as shown in Figure 13 The length of the combined green body is 18.5 mm, the width (including the flange 71) is 3.61 mm, the outer length-diameter ratio is about 5.1, and the inner length-diameter ratio of the cavity of the cold isostatic pressing mold is about 5.1.

[0260] In this embodiment, the minimum thickness of the elastic sleeve 5 between the two cavities is about 0.90 mm.

[0261] It should be noted that in this embodiment, the ceramic green body after demolding is named according to the corresponding sections of the inner hole, respectively: the coarse straight hole section 72, the reduced diameter hole section 73, the fine straight hole section 74, and the expanded diameter hole section 75.

[0262] The assembled mold is pushed into the pressurized cavity of the dry bag press, and the mold is constrained by the upper and lower pistons. After being kept at a pressure of 150 MPa for 5 minutes, the mold is taken out, the pipe green body is demolded, and a variable-diameter tube ceramic green body is obtained.

[0263] In this embodiment, the inner hole diameter of the pressed ceramic green body is 0.06 mm (corresponding to the fine straight hole section), the inner length-diameter ratio is 308.3, and the outer length-diameter ratio is 92.5.

[0264] The density of the prepared variable-diameter tube ceramic green body is 2.34 g / cm3, which reaches 55% of its theoretical density (calculated as 4.25 g / cm3).

[0265] The S5 step is specifically:

[0266] The variable-diameter tube ceramic green body is layered and placed on a silicon molybdenum rod sintering furnace re-sintered silicon carbide ceramic support firing plate (Reference Embodiment 1).

[0267] As shown in Figure 14 The sintering temperature is 1550℃, and the sintering time is 50 min, and a sintered body is obtained.

[0268] The prepared sintered body has a bending strength of 870 MPa, a density of 4.22 g / cm3, which reaches 99.3% of its theoretical density, a microstructure inspection with an average grain size of 0.7 μm, and a microhardness HV1 of 2000.

[0269] The sintered body is trimmed in shape, the variable-diameter tube is positioned and installed in the center hole on a special micro numerical control cylindrical grinding machine, and the outer circle is precisely ground, then the two ends of the ceramic variable-diameter tube are ground to the size with the outer circle positioning, in the embodiment, the region corresponding to the diameter expansion section is completely removed, finally, a tungsten steel needle with a corresponding size is used to grind a Φ0.04 micropore on the sintered body corresponding to the fine straight section, and the product processing is completed.

[0270] The S6 step is specifically:

[0271] The trimmed sintered body is subjected to hot isostatic pressing treatment at 1500 DEG C and 200 MPa for 30 min, the bending strength reaches 950 MPa, the density reaches 4.24 g / cm3, reaching 99.7% of the theoretical density, under the condition that the grain size is basically unchanged, the three-point bending strength is increased by 80 MPa, and the microhardness HV1 is increased to 2050.

[0272] Product parameters

[0273] The ceramic variable-diameter tube product prepared in the embodiment has a structure as shown in Figure 19 The total length is 14 mm, the outer diameter is 2 mm (the outer length-diameter ratio is 7:1), wherein the coarse straight hole section 72 is 9.22 mm long, and the inner hole diameter is 0.96 mm; the inner hole taper angle of the reduced-diameter hole section 73 is 12 DEG ; the fine straight hole section 74 is 0.4 mm long, the inner hole diameter is 0.04 mm, and the inner length-diameter ratio is 350:1.

[0274] Example 5

[0275] The embodiment provides a preparation method of a ceramic special-shaped capillary product (hereinafter referred to as a special-shaped tube).

[0276] Raw materials and additives:

[0277] The raw materials are:

[0278] The α-Si3N4 powder with a purity of 95% (D50=2um), the Y2O3 powder with a purity of 99.0%, and the Al2O3 powder (D50=1um) have a mass ratio of 90:5:5.

[0279] The additive is:

[0280] No dispersant is used; the solvent is anhydrous ethanol, and the mass is twice that of the raw materials;

[0281] The binder is PEG6000, and the mass is 3% of the raw materials; before use, the binder is dissolved in anhydrous ethanol to form a 10wt.% bonding solution for standby.

[0282] The S1 step is specifically:

[0283] The raw materials and dispersant are added to a sand mill and stirred, dispersed and ground to D50=0.3μm. The grinding media are high-purity silicon nitride balls with a diameter of φ3mm, and the ball-to-material ratio is 3:1~5:1 (4:1 in this example). The grinding media occupy 30~40% of the grinding cylinder volume (35% in this example).

[0284] The binder solution should be added 1 hour before the material is discharged from the mill.

[0285] Step S2 is as follows:

[0286] The spray granulation process follows the same steps and parameters as in Example 4.

[0287] The S3 steps are as follows:

[0288] The dry pressing mold in this embodiment is as follows: Figure 15 As shown in (A) to (D), the structure is basically the same as that of Example 3, except that:

[0289] 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.

[0290] 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.

[0291] 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).

[0292] The process of loading, pressing, and demolding is described in Example 3.

[0293] 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.

[0294] 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.

[0295] 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.

[0296] In this embodiment, 1.55g of granulated powder is used to press the shaped tube dry-pressed preform 7, such as...Figure 16 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.

[0297] The density of the prepared irregular tube dry-pressed blank 7, tested by Archimedes' method, was 1.44 g / cm3, which reached 45% of its theoretical density of porcelain (calculated based on 3.20 g / cm3).

[0298] The S4 steps are as follows:

[0299] In this embodiment, the cold isostatic pressing mold is as follows: Figure 17 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,

[0300] The shape of the hard mold core 6 is adapted to the inner hole of the shaped tube dry-pressed blank 7 after assembly; the hard mold core 6 is a split structure (the split structure can be a multi-segment mold core that can be spliced ​​along the axial direction or a combination of the main mold core and the outer mold core along the radial direction). In this embodiment, it specifically includes a rounded square mold core column 63 and an outer diameter tube 64 sleeved at both ends of the mold core column 63.

[0301] 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; the diameter of the rigid mold core is not less than 0.04 mm, and the distance between the outer wall of the elastic mold sleeve and the outer wall of the rigid mold core is not less than 2 mm.

[0302] 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.

[0303] 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; the material of the elastic mold sleeve is a high molecular elastomer with a Shore hardness between 60A and 80A. In this embodiment, chloroprene rubber is selected, specifically one of polyurethane, polyamide, and synthetic rubber.

[0304] In this embodiment, the function of the flange 71 in the dry-pressed blank 7 is the same as that in embodiment 3.

[0305] In the assembly, two dry-pressed blanks 7 can be combined first, then one outer expanding tube 64 and the mold core column 63 are inserted from one end, and then another outer expanding tube 64 is inserted from the other end; or the hard mold core 6 can be assembled first, then placed on the inner curved surface of one dry-pressed blank 7, and then the other dry-pressed blank 7 is assembled.

[0306] In this embodiment, as shown in Figure 16 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 thinnest thickness between adjacent cavities is 2 mm; the thinnest wall thickness of the elastic inner mold shell 54 is 0.81 mm, and the thickest wall thickness is 1.05 mm.

[0307] The assembled mold is pushed into the pressurized cavity of the dry bag press, the mold is constrained by the upper and lower pistons, and the mold is kept at a pressure of 150 MPa for 5 minutes. Then the mold is taken out, the mold is removed, and the pipe blank is taken out to obtain a special-shaped tube ceramic blank.

[0308] In this embodiment, the inner length-diameter ratio of the pressed ceramic blank is about 144.4, and the outer length-diameter ratio is 45.5.

[0309] The density of the prepared special-shaped tube ceramic blank is 1.60 g / cm3, which reaches 50% of the theoretical density of the ceramic body (calculated as 3.20 g / cm3).

[0310] The S5 step is specifically:

[0311] The special-shaped tube ceramic blank is layered and placed on the silicon carbide support plate of the gas pressure sintering furnace, and a layer of BN coating is coated on the surface of the silicon carbide support plate to prevent the ceramic special-shaped tube from adhering to the support plate.

[0312] As shown in Figure 17 , the temperature is raised to 1100℃ under a vacuum of 0.1 MPa, then nitrogen is filled to 6 MPa during the temperature rising process, and the sintering temperature is 1780℃ for 90 min to obtain a special-shaped tube sintered body.

[0313] The prepared sintered body has a bending strength of 900 MPa, a density of 3.18 g / cm3, which reaches 99.4% of the theoretical density, and a microstructure of β-phase silicon nitride rod-like structure with a diameter of 1 μm and a length of about 6 μm. The microhardness HV1 is 2000.

[0314] The sintered body is trimmed, the special-shaped tube sintered body is positioned and installed on the special numerical control cylindrical grinding machine with the center hole, the outer circle is precisely ground, then the two ends of the ceramic variable diameter tube are ground to size with the outer circle of the ceramic capillary tube as the positioning, and the product processing is completed.

[0315] The S6 step is specifically:

[0316] The modified profiled tube sintered body is subjected to hot isostatic pressing treatment at 1650 DEG C, 200 MPa nitrogen pressure for 50 min, to obtain a ceramic profiled tube product. The bending strength reaches 950 MPa, the density reaches 3.19 g / cm3, reaching 99.7% of the theoretical density, the grain size is basically unchanged compared with the sintered body before hot isostatic pressing treatment, the three-point bending strength is increased by 50 MPa, and the microhardness HV1 is 2050.

[0317] Product parameters

[0318] The structure of the ceramic profiled tube product prepared in the embodiment is shown in Figure 19 Figure 18 The total length is 70 mm, the outer diameter is 3 mm, both sides are inwardly tapered holes, and the middle is a constant diameter hole. The inner hole width of the two side end portions is 1.13 mm, the round corner radius is 0.41 mm, the inwardly tapered length is 6 mm, the taper angle of the tapered hole is 6 DEG, and the inner length-diameter ratio is 140:1.

[0319] In summary

[0320] The length, outer diameter, and inner hole diameter of the rod-shaped or tubular dry-pressed green compact prepared in each embodiment of the utility model are listed in Table 1.

[0321] Table 1 Parameters of the dry-pressed green compact prepared in each embodiment

[0322]

[0323] The length, outer diameter, and inner hole diameter of the rod-shaped or tubular ceramic green compact prepared in each embodiment of the utility model are listed in Table 2.

[0324] Table 2 Parameters of the ceramic green compact prepared in each embodiment

[0325]

[0326] The length, outer diameter, and inner hole diameter of the rod-shaped or tubular ceramic product prepared in each embodiment of the utility model are listed in Table 3.

[0327] Table 3 Parameters of the ceramic columnar product prepared in each embodiment

[0328]

[0329] In principle, the upper limit of the wall thickness is not limited, and the upper limit of the inner hole diameter is also not limited.

[0330] It should be noted that the inner hole variable diameter of the above-mentioned embodiment 4 and embodiment 5 is linearly variable, that is, the inner hole diameter increases or decreases along the tube axis direction according to a certain proportion or slope. However, for those skilled in the art, the inner hole variable diameter tube with non-linear variable can also be prepared according to the above-mentioned method.

[0331] It should be noted that for the sintering process in S5, in actual implementation, appropriate adjustment is needed due to different furnace loading and sintering furnaces used.

[0332] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the specific embodiments described above, and various modifications or changes can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application.

Claims

1. A cold isostatic pressing mold characterized by comprising: The cavity has an inner length-diameter ratio of not more than 140 and a length of not more than 400 mm, and the elastic sleeve covers the side surface of the cavity.

2. The cold isostatic pressing mold according to claim 1, characterized by The thickness of the elastic sleeve between adjacent cavities is 0.2-2 times the width of the cavity, and the plurality of cavities are uniformly distributed on the elastic sleeve.

3. The cold isostatic pressing mold according to claim 1, characterized by The side surface of the cavity is provided with one or more recesses, which are uniformly distributed and extend through the side surface of the cavity in the axial direction, and if there are multiple recesses, the axial symmetry planes of adjacent recesses do not coincide.

4. The cold isostatic pressing mold according to claim 1, characterized by The elastic sleeve is provided with a cavity in the center, and a plurality of virtual regular polygons are arranged outward from the central cavity as the symmetry point, and the adjacent vertices of adjacent polygons are collinear with the symmetry point, and the cavity is arranged at the vertex position and / or edge of each polygon.

5. The cold isostatic pressing mold according to claim 1, characterized by The elastic sleeve is a one-piece structure or a split structure, and the split structure includes an elastic outer shell with a plurality of accommodating cavities and an elastic inner shell that can be embedded in the accommodating cavities.

6. The cold isostatic pressing mold according to claim 1, characterized by The material of the elastic sleeve is a high-molecular elastomer with a Shore hardness of 60A-80A, specifically one or more of polyurethane, polyamide, and synthetic rubber.

7. The cold isostatic pressing mold according to any one of claims 1 to 6, characterized in that A hard mold core is arranged in the cavity for supporting the inner hole of the tubular product to be pressed, and the outer length-diameter ratio of the hard mold core is not more than 310, and the length is not more than 400 mm, and the material is one or more of ceramic material, hard alloy, non-ferrous metal alloy, and steel.

8. The cold isostatic pressing mold according to claim 7, characterized in that The hard mold core is a one-piece structure or a split structure, and the split structure is a plurality of segmented mold cores that can be spliced in the axial direction or a main mold core and an outer mold core that is sleeved on the outer side of the main mold core.

9. Cold isostatic pressing die for axially pressing a cylindrical article, characterized in that The cavity has an inner length-diameter ratio of not more than 4.5, and the elastic sleeve is split, including an upper mold sleeve provided with a first blind hole and a lower mold sleeve provided with a second blind hole, and the upper mold sleeve and the lower mold sleeve are nested to form a mold with an internal cavity for accommodating the piece to be pressed.

10. Cold isostatic pressing die for axially pressing a cylindrical article according to claim 9, characterized in that The outer diameter of the upper part of the lower mold sleeve matches the inner diameter of the first blind hole, and the outer side of the upper part of the lower mold sleeve is provided with a convex ring, and the surface of the convex ring is arc-shaped, and the inner side of the lower part of the upper mold sleeve matches the arc-shaped convex ring.

11. Cold isostatic pressing die for axially pressing a cylindrical article according to any one of claims 9 to 10, characterized in that A hard mold core is also included, the diameter of the hard mold core is not less than 0.04 mm, the distance between the outer side wall of the elastic sleeve and the outer side wall of the hard mold core is not less than 2 mm, and the bottom surface of the first blind hole of the upper mold sleeve and the bottom surface of the second blind hole of the lower mold sleeve are provided with blind holes matching the hard mold core.

12. Cold isostatic pressing die for axially pressing a cylindrical article according to claim 11, characterized in that The hard mold core is a one-piece structure or a split structure, and the split structure is a plurality of segmented mold cores that can be spliced in the axial direction or a main mold core and an outer mold core that is sleeved on the outer side of the main mold core.

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