An apparatus and method for cold isostatic pressing of ceramic green bodies using a metal soft core

Abstract

The application discloses a device and a method for cold isostatic pressing forming of ceramic green bodies using a metal soft core, and the device comprises a forming frame, a soft core shaft and an elastic sleeve, the forming frame comprises an upper positioning disc, a lower positioning disc and a supporting shaft, the upper positioning disc and the lower positioning disc are symmetrically arranged in parallel in the height direction, and the supporting shaft is vertically and fixedly connected between the upper positioning disc and the lower positioning disc; the soft core shaft is vertically connected at the center position of the upper positioning disc and the lower positioning disc in a tensioned and straightened manner; the elastic sleeve comprises a sleeve body and an end cover, the sleeve body is sleeved on the soft core shaft and is coaxially arranged with the soft core shaft, the sleeve body is located between the upper positioning disc and the lower positioning disc, and the end cover is symmetrically embedded at the top and the bottom of the sleeve body, so that stable forming of the ceramic pipe with a large length-diameter ratio can be realized, the linear degree of the formed ceramic pipe is good, and the problem of difficult forming of the tubular ceramic body with the large diameter at both ends and the small diameter in the middle of the inner hole can be solved.

Description

Technical Field

[0001] This invention relates to the field of ceramic blank forming technology, and in particular to an apparatus and method for cold isostatic pressing of ceramic blanks using a metal soft mold core. Background Technology

[0002] Special ceramics are widely used in many fields due to their excellent high temperature resistance, chemical inertness, high hardness and wear resistance, and electrical insulation.

[0003] Traditional processing methods mainly include the following: 1. Extrusion molding using an extrusion molding machine is suitable for rapid mass production, but it has certain requirements for powder material, and when the product size changes, it is necessary to change the mold of different sizes, resulting in high equipment and mold costs and difficulty in controlling the yield. 2. Adding an internal mandrel to the cylindrical elastic mold for forming the inner diameter cavity of long tubes can basically eliminate the need for inner diameter processing. When processing the outer diameter, the mandrel provides radial and axial support, which allows for the processing of products with thinner walls. However, when the length is long and the length-to-diameter ratio is large, the mandrel is prone to bending. This can result in poor straightness of the molded body or even breakage of the molded body, leading to the scrapping of the product and the mandrel. Third, solid ceramic blanks are formed in an isostatic press using plastic molds, and the inner and outer diameters are machined on a machine tool. This method takes a long time, and some sizes of products are difficult to process or even impossible to process.

[0004] Chinese patent application number 2011205075383 discloses a cold isostatic pressing mold for manufacturing ceramic tube shells, comprising an inner mold and an outer mold. The inner mold is a cylindrical metal mold housed within a rubber tubular outer mold, and the inner and outer molds are assembled into a single unit via rubber plugs at both ends. This type of mold cannot guarantee the straightness of the product when processing ceramic tubes with long lengths and large length-to-diameter ratios. Summary of the Invention

[0005] This application provides an apparatus and method for cold isostatic pressing of ceramic blanks using a metal soft mold core. It can achieve stable forming of ceramic tubes with a large length-to-diameter ratio, and the formed ceramic tubes have good straightness. At the same time, it can also solve the problem of difficult forming of tubular ceramic blanks with large inner diameters at both ends and small inner diameters.

[0006] The first aspect of this application provides an apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core, comprising: A forming frame, comprising an upper positioning plate, a lower positioning plate, and a support shaft, wherein the upper positioning plate and the lower positioning plate are symmetrically distributed in parallel in the height direction, and the support shaft is vertically fixed between the upper positioning plate and the lower positioning plate; A flexible mold mandrel is vertically connected to the center of the upper positioning plate and the lower positioning plate in a tensioned and straightened manner. An elastic mold sleeve includes a sleeve body and an end cap that are sleeved on the soft mold mandrel and coaxially distributed with the soft mold mandrel. The sleeve body is located between the upper positioning plate and the lower positioning plate, and the end caps are symmetrically embedded at the top and bottom of the sleeve body.

[0007] In one possible implementation, the upper positioning plate, the lower positioning plate, and the support shaft are all made of the same material, namely stainless steel.

[0008] In one possible implementation, the support shafts are three in number, which are evenly spaced at 120° intervals in the horizontal direction and connected to the outer circumferences of the upper and lower positioning disks.

[0009] In one possible implementation, the soft mold mandrel is a steel wire skeleton structure with a wire diameter of 1mm to 3mm. The upper positioning plate and the lower positioning plate are respectively equipped with tension bolts at their center positions, and the top and bottom ends of the soft mold mandrel are inserted and connected to the corresponding tension bolts.

[0010] In one possible implementation, the soft mold mandrel is a screw-connected shaft, the axis of the soft mold mandrel coincides with the central axis of the upper positioning plate and the lower positioning plate, a tension bolt is respectively passed through the center of the upper positioning plate and the lower positioning plate, and the axes of the two tension bolts are collinear, and the top and bottom ends of the soft mold mandrel are respectively provided with threaded holes adapted to the tension bolts, and the two are threadedly connected.

[0011] In one possible implementation, the surface of the soft mold mandrel is polished and boron nitride powder is coated on the mandrel.

[0012] In one possible implementation, the elastic sleeve is a rubber sleeve with a hardness of A45±5°.

[0013] In one possible implementation, the upper positioning plate and the lower positioning plate have the same thickness, both being 10mm to 15mm, and the sleeve body has a thickness of 2mm to 4mm.

[0014] The second aspect of this application provides a method for forming a ceramic blank using the apparatus described above for cold isostatic pressing with a metal soft mold core, comprising the following steps: S1, the upper positioning plate and the lower positioning plate are fixedly connected by the support shaft, the forming frame is assembled, and then one end of the soft mold core shaft is fixed at the center position of the lower positioning plate; S2, pass the soft mold mandrel through the end cap near the lower side, and then through the center of the sleeve body, sealing the end cap near the lower side into the bottom of the sleeve body; S3, Powder is filled into the sleeve body, and then the end cap near the upper side moves along the soft mold core at the center position until it is embedded in the top of the sleeve body, thus completing the sealing of the molding cavity. S4, fix the other end of the soft mold mandrel to the center of the upper positioning plate, and keep the soft mold mandrel in a taut and straight state; S5, the entire device is placed in a high-pressure container for static pressure molding; S6, demolding.

[0015] In one possible implementation, in step S5, the pressure value of the high-pressure vessel is 110 MPa, and the soft mold mandrel is always kept taut and straight during the pressing process.

[0016] Compared with the prior art, the beneficial effects of the apparatus and method for cold isostatic pressing of ceramic blanks using a metal soft mold core provided in this application are as follows: (1) It can achieve stable molding of ceramic tubes with large length-to-diameter ratio. The upper and lower positioning plates straighten and fix the soft mold mandrel, which can overcome the difficulty of the mandrel being easy to bend, and the straightness of the molded ceramic tube is good. (2) It is suitable for forming tubular ceramic blanks with large inner diameter at both ends and small diameter in the middle, which solves the problem of demolding. Using this device, the characteristic of omnidirectional pressure is not lost during isostatic pressing, thus ensuring the density and consistency of the ceramic blank. (3) Apply boron nitride powder to the mandrel to reduce the friction between the mandrel and the inner wall of the product, making it easier to demold.

[0017] These and other objects, features and advantages of the present invention will become fully apparent from the following detailed description. Attached Figure Description

[0018] Figure 1 A partial cross-sectional view of the apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core is shown in this application.

[0019] Figure 2 A schematic diagram of the screw coupling shaft in this application is shown. Detailed Implementation

[0020] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0021] Those skilled in the art should understand that, in the disclosure of this specification, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present invention.

[0022] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will also be understood that terms, such as those defined in commonly used dictionaries, shall be interpreted as having a meaning consistent with their meaning in the context of the relevant art and shall not be interpreted as having an idealized or overly formal meaning unless expressly so defined herein.

[0023] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0024] refer to Figure 1 and Figure 2 The first aspect of this application provides an apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core, comprising a forming frame 10, a soft mold core shaft 20, and an elastic mold sleeve 30. The forming frame 10 includes an upper positioning plate 11, a lower positioning plate 12, and a support shaft 13. The upper positioning plate 11 and the lower positioning plate 12 are symmetrically distributed parallel to each other in the height direction, while the support shaft 13 is vertically fixed between the upper positioning plate 11 and the lower positioning plate 12. The upper positioning plate 11, the lower positioning plate 12, and the support shaft 13 are all made of the same material, stainless steel.

[0025] The flexible mold mandrel 20 is vertically connected to the center of the upper positioning plate 11 and the lower positioning plate 12 in a tensioned and straightened manner. The flexible mold mandrel 20 does not shrink during the molding process; therefore, the diameter of the flexible mold mandrel 20 is the inner diameter of the target product.

[0026] The elastic mold sleeve 30 includes a sleeve body 31 and an end cap 32 that are sleeved on the soft mold mandrel 20 and coaxially distributed with the soft mold mandrel 20. The sleeve body 31 is located between the upper positioning plate 11 and the lower positioning plate 12, and the end cap 32 is symmetrically embedded at the top and bottom of the sleeve body 31.

[0027] The soft mold mandrel 20 and the elastic mold sleeve 30 are fitted together with the end caps 32 at both ends to form a molding cavity.

[0028] In one embodiment, there are three support shafts 13, which are evenly spaced at 120° intervals in the horizontal direction and connected to the outer circumference of the upper positioning plate 11 and the lower positioning plate 12 to ensure the stability of the entire forming frame 10.

[0029] In one embodiment, the elastic sleeve 30 is a rubber sleeve with a hardness of A45±5°.

[0030] In one embodiment, the surface of the soft mold mandrel 20 is polished and boron nitride powder is coated on the mandrel to ensure the smoothness of the inner wall of the molded product, thereby ensuring that the product can be demolded quickly and smoothly.

[0031] In one embodiment, the upper positioning plate 11 and the lower positioning plate 12 have the same thickness, which is 10mm to 15mm, while the thickness of the sleeve body 31 is 2mm to 4mm.

[0032] The second aspect of this application provides a method for forming a ceramic blank using the apparatus described above for cold isostatic pressing with a metal soft mold core, comprising the following steps: S1, the upper positioning plate 11 and the lower positioning plate 12 are fixedly connected by the support shaft 13, the forming frame 10 is assembled, and then one end of the soft mold core shaft 20 is fixed at the center position of the lower positioning plate 12. S2, the soft mold mandrel 20 is passed through the end cap 32 near the lower side, and then through the center of the sleeve body 31, sealing the end cap 32 near the lower side into the bottom of the sleeve body 31. S3, Powder is filled into the sleeve body 31, and then the end cap 32 near the upper side moves along the soft mold core shaft 20 at the center position until it is embedded in the top of the sleeve body 31, thus completing the sealing of the molding cavity. S4, fix the other end of the soft mold mandrel 20 to the center of the upper positioning plate 11, and keep the soft mold mandrel 20 in a taut and straight state; S5, the entire device is placed in a high-pressure container for static pressure molding; S6, demolding.

[0033] Preferably, in step S5, the pressure value of the high-pressure container is 110 MPa, and during the pressing process, the soft mold mandrel 20 is always kept taut and straight.

[0034] In some embodiments, the flexible mold mandrel 20 is a wire skeleton structure, the main body of which is made of multiple strands of twisted or woven wires, with the diameter of a single wire ranging from 1mm to 3mm. Simultaneously, tension bolts 14 are respectively installed at the center positions of the upper positioning plate 11 and the lower positioning plate 12, and the top and bottom ends of the flexible mold mandrel 20 are inserted and connected to the corresponding tension bolts 14. That is, the top end of the flexible mold mandrel 20 is inserted and connected to the tension bolt 14 on the upper positioning plate 11, and the bottom end of the flexible mold mandrel 20 is inserted and connected to the tension bolt 14 on the lower positioning plate 12. This facilitates assembly and ensures the accuracy of the installation position of the flexible mold mandrel 20. The tension bolt 14 can also be called a wire rope tensioner (or turnbuckle, rigging spiral buckle). The wire rope ends at the top and bottom ends of the flexible mold mandrel 20 are formed into connecting ends by crimping or casting rope sections and are inserted and connected to the connecting holes of the corresponding wire rope tensioners. By rotating the adjusting nut or screw of the wire rope tensioner, the connecting parts at both ends can be moved towards or away from each other, thereby applying an axial tension to the soft mold mandrel 20 between the upper positioning plate 11 and the lower positioning plate 12. This structure ensures that the soft mold mandrel 20 maintains a predetermined tensioned and straight state throughout the entire operation, effectively avoiding deviations in forming accuracy caused by wire bending and deformation.

[0035] When the flexible mold mandrel 20 undergoes slight plastic elongation due to long-term alternating loads or temperature effects, resulting in tension attenuation, the wire skeleton mandrel can be easily tensioned twice or multiple times by simply rotating the tension bolt 14 with a tool, until its initial set tensile stress value is restored and it remains in a taut and straightened state. This maintenance adjustment function significantly extends the service life of the flexible mold mandrel 20 and ensures the long-term stable uniformity of wall thickness and dimensional consistency of the ceramic preform during the forming process.

[0036] Example 1: An apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core, comprising a rigid soft mold core 20 and an elastic mold sleeve 30. The elastic mold sleeve 30 can be designed to be 1.2 times the outer diameter of the target product, with a thickness of 2-4 mm, and a length of 1.2 times the length of the target product plus the embedding depth of the end cap 32. The end cap 32 and the elastic mold sleeve 30 are made of the same material. The support shaft has a diameter of 15-20 mm and a length the same as that of the soft mold core 20. The upper and lower positioning plates are both 10-15 mm thick, and their diameters are designed to be 3 times the diameter of the elastic mold sleeve 30.

[0037] An apparatus for cold isostatic pressing of ceramic green bodies using a soft metal mold core is designed to form silicon nitride ceramic green bodies with an inner diameter of 2 mm, an outer diameter of 60 mm, and a length of 200 mm. The forming method, based on a shrinkage rate of 0.7, includes the following steps: S1, the upper positioning plate 11 and the lower positioning plate 12 are fixedly connected by the support shaft 13 to assemble the forming frame 10. Then, one end of the soft mold mandrel 20 is fixed at the center of the lower positioning plate 12. The bottom end of the soft mold mandrel 20 is inserted and connected to the lower soft mold core tension bolt 14. The soft mold mandrel 20 is made of stainless steel, with a diameter of 2 mm and a length of 400 mm. The surface is mirror polished and boron nitride powder is applied to the mandrel. The end cap is embedded to a depth of 15 mm and a diameter of 86 mm to ensure that it fits tightly with the sleeve body 31 after assembly.

[0038] S2, the soft mold mandrel 20 is passed through the end cap 32 near the lower side, and then through the center of the sleeve body 31. The end cap 32 near the lower side is sealed and embedded at the bottom of the sleeve body 31. The elastic mold sleeve is made of PU material with a hardness of A45°. The elastic mold sleeve has a thickness of 3mm, a length of 320mm, and an inner diameter of 86mm.

[0039] S3, Powder is poured into the molding cavity, and then moved along the soft mold core shaft 20 at the center position through the end cap 32 near the upper side until it is embedded in the top of the sleeve body 31, thus completing the sealing of the molding cavity and compacting it with vibration.

[0040] S4. Note that the other end of the soft mold core shaft 20 is fixed to the soft mold core tension bolt 14 at the upper positioning plate 11, and the soft mold core shaft 20 is kept taut and straight. The upper and lower positioning plates are 10mm thick and 240mm in diameter. The support shaft is 15mm in diameter and 400mm in length.

[0041] S5. The entire device is placed in a cold isostatic press for pressing and static molding at a pressure of 110 MPa.

[0042] S6, Demolding. After pressing according to the program, demold. The final molded body dimensions are: inner diameter 2mm, outer diameter 60mm, and length 202mm.

[0043] The mold filled with powder and this fixing device are placed together in a cold isostatic press for pressing. Due to the tensioning and straightening effect of the upper and lower positioning plates on the soft mold mandrel 20, the difficulty of the mandrel being easy to bend is overcome. The ceramic tube after molding has good straightness, and in the early stage of densification, the pressure is more evenly distributed in the axial and radial directions of the molded body, which provides a guarantee for the good straightness and uniform density of the subsequent molded body.

[0044] Example 2: An apparatus for cold isostatic pressing of ceramic green bodies using a metal soft mold core, designed to form silicon nitride ceramic green bodies with an inner diameter of 3mm, an outer diameter of 60mm, and a length of 400mm, and based on a shrinkage rate of 0.7, includes the following steps: S1, the upper positioning plate 11 and the lower positioning plate 12 are fixedly connected by the support shaft 13 to assemble the forming frame 10. Then, one end of the soft mold core shaft 20 is fixed at the center of the lower positioning plate 12. The bottom end of the soft mold core shaft 20 is inserted and connected to the lower soft mold core tensioning bolt 14. The soft mold core shaft 20 is made of stainless steel, with a diameter of 3mm and a length of 700mm. The surface is mirror polished and boron nitride powder is applied to the core. The end cap 32 is embedded to a depth of 15mm and a diameter of 86mm to ensure that it fits tightly with the sleeve body 31 after assembly.

[0045] S2, the soft mold mandrel 20 is passed through the end cap 32 near the lower side, and then through the center of the sleeve body 31. The end cap 32 near the lower side is sealed and embedded at the bottom of the sleeve body 31. The elastic mold sleeve 30 is made of PU material with a hardness of A45°. The elastic mold sleeve has a thickness of 3mm, a length of 605mm, and an inner diameter of 86mm.

[0046] S3, Powder is poured into the molding cavity, and then moved along the soft mold core shaft 20 at the center position through the end cap 32 near the upper side until it is embedded in the top of the sleeve body 31, thus completing the sealing of the molding cavity and compacting it with vibration.

[0047] S4. Note that the other end of the soft mold core shaft 20 is fixed to the soft mold core tension bolt 14 at the upper positioning plate 11, and the soft mold core shaft 20 is kept taut and straight. The upper and lower positioning plates are 10mm thick and 240mm in diameter. The support shaft is 15mm in diameter and 700mm in length.

[0048] S5. The entire device is placed in a cold isostatic press for pressing and static molding at a pressure of 110 MPa.

[0049] S6, Demolding. After pressing according to the program, demold. The final molded body dimensions are: inner diameter 2mm, outer diameter 60mm, and length 202mm.

[0050] The mold filled with powder and this fixing device are placed together in a cold isostatic press for pressing. Due to the tensioning and straightening effect of the upper and lower positioning plates on the soft mold mandrel 20, the difficulty of the mandrel being easy to bend is overcome. The ceramic tube after molding has good straightness, and in the early stage of densification, the pressure is more evenly distributed in the axial and radial directions of the molded body, which provides a guarantee for the good straightness and uniform density of the subsequent molded body.

[0051] In other embodiments, the flexible mold mandrel 20 adopts a variable diameter screw structure with larger diameters at both ends and a smaller diameter in the middle, i.e., the flexible mold mandrel is a screw-connected shaft, and the axis of the flexible mold mandrel 20 coincides with the central axis of the upper positioning plate 11 and the lower positioning plate 12. Tensioning bolts 14 are respectively installed at the center of the upper positioning plate 11 and the lower positioning plate 12, and the axes of the two tensioning bolts 14 are collinear. The top and bottom ends of the flexible mold mandrel 20 are respectively provided with threaded holes adapted to the tensioning bolts 14, and the two are threadedly connected.

[0052] The assembly and adjustment method is as follows: by rotating the tension bolts 14 in the forward or reverse direction, the soft mold mandrel 20 can be driven to make a slight axial extension and retraction displacement. Since the soft mold mandrel 20 has a structure that is large at both ends and small in the middle, it can directly form a tubular ceramic blank that is large at both ends and small in the middle. At the same time, by adjusting the tension bolts 14 on both sides synchronously or asynchronously, the verticality of the soft mold mandrel 20 can be corrected to ensure that it is always aligned between the upper positioning plate 11 and the lower positioning plate 12 and remains in a taut and straight state.

[0053] Example 3: An apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core, comprising a rigid screw coupling shaft and an elastic mold sleeve 30. The elastic mold sleeve 30 is made of rubber with a hardness of A45±5°, and its inner diameter can be designed to be 1.2 times the outer diameter of the target product, its thickness can be designed to be 2-4 mm, and its length can be designed to be 1.2 times the length of the target product. The end of the screw coupling shaft is threadedly connected to a tension bolt 14 at the center of the upper and lower positioning plates, facilitating assembly and ensuring the accuracy of the screw coupling shaft's position. The screw coupling shaft is installed, fixed, and pre-tightened by rotating the tension bolt 14. The screw coupling shaft and the elastic mold sleeve 30 are fitted together with upper and lower end caps 32 to form a molding cavity.

[0054] The screw coupling shaft is a steel mold that is large at both ends and small in the middle, connected to the tension bolt 14 via threads. The screw coupling shaft does not shrink during the molding process; therefore, its diameter is the inner diameter of the target product. The surface of the screw coupling shaft is polished and coated with boron nitride powder to ensure the smoothness of the inner wall of the molded product and to ensure smooth demolding.

[0055] The support shaft 13 has a diameter of 15-20mm and a length that is the same as the screw docking shaft. The upper and lower positioning plates have a thickness of 10-15mm and a diameter designed to be 3 times the diameter of the elastic mold sleeve.

[0056] An apparatus for cold isostatic pressing of ceramic green bodies using a soft metal mold core is designed to form silicon nitride ceramic green bodies with an inner diameter of 5mm in the middle, 25mm at both ends, an outer diameter of 60mm, and a length of 200mm. The forming method, based on a shrinkage rate of 0.7, includes the following steps: S1, one end of the screw docking shaft is first fixed on the lower positioning plate 12, and the end of the screw docking shaft is threadedly connected to the tension bolt 14 at the center of the lower positioning plate 12. The screw docking shaft is made of stainless steel, with a diameter of 5mm in the middle, 25mm at both ends, and a length of 400mm. The surface is mirror polished, and boron nitride powder is applied to the mandrel to ensure that it fits tightly with the sleeve body 31 after assembly.

[0057] S2, pass the screw connecting shaft through the end cap 32 near the lower side, and then through the center of the sleeve body 31, and seal the end cap 32 near the lower side into the bottom of the sleeve body 31. The elastic sleeve 30 is made of PU material with a hardness of A45°, a thickness of 3mm, a length of 290mm, and an inner diameter of 86mm.

[0058] S3, fill the molding cavity with powder, and then move along the screw docking shaft at the center position through the end cap 32 near the upper side until it is embedded in the top of the sleeve body 31, thus completing the sealing of the molding cavity and vibrating to compact it.

[0059] S4. Note that the other end of the screw docking shaft is fixed to the soft mold core tension bolt 14 at the upper positioning plate 11, and the screw docking shaft is kept taut and straight. The upper and lower positioning plates are 10mm thick and 240mm in diameter. The support shaft is 15mm in diameter and 400mm in length.

[0060] S5. The entire device is placed in a cold isostatic press for pressing and static molding at a pressure of 110 MPa.

[0061] S6, Demolding. After pressing according to the program, demold. The final molded body dimensions are: inner diameter 5mm in the middle, 25mm at both ends, outer diameter 60mm, and length 202mm.

[0062] The mold filled with powder and this fixing device are placed together in a cold isostatic press for pressing. Due to the straightening and fixing effect of the upper and lower positioning plates on the screw docking shaft, the damage of pressure to the threaded connection is reduced. Furthermore, the method of using the threaded connection to the top double cone mold (i.e. the shape of the screw docking shaft) solves the problem of forming a tubular ceramic blank that is large at both ends and small in the middle.

[0063] Example 4: An apparatus for cold isostatic pressing of ceramic green bodies using a metal soft mold core. The apparatus is designed to form silicon nitride ceramic green bodies with an inner diameter of 5mm in the middle, 25mm at both ends, an outer diameter of 60mm, and a length of 400mm. Based on a shrinkage rate of 0.7, the forming method includes the following steps: S1, one end of the screw docking shaft is first fixed on the lower positioning plate 12, and the end of the screw docking shaft is threadedly connected to the tension bolt 14 at the center of the lower positioning plate 12. The screw docking shaft is made of stainless steel, with a diameter of 5mm in the middle and 25mm at both ends, and a length of 700mm. The surface is mirror polished, and boron nitride powder is applied to the mandrel to ensure that it fits tightly with the sleeve body 31 after assembly.

[0064] S2, pass the screw connecting shaft through the end cap 32 near the lower side, and then through the center of the sleeve body 31, and seal the end cap 32 near the lower side into the bottom of the sleeve body 31. The elastic sleeve 30 is made of PU material with a hardness of A45°, a thickness of 3mm, a length of 575mm, and an inner diameter of 86mm.

[0065] S3, fill the molding cavity with powder, and then move along the screw docking shaft at the center position through the end cap 32 near the upper side until it is embedded in the top of the sleeve body 31, thus completing the sealing of the molding cavity and vibrating to compact it.

[0066] S4. Note that the other end of the screw docking shaft is fixed to the soft mold core tension bolt 14 at the upper positioning plate 11, and the screw docking shaft is kept taut and straight. The upper and lower positioning plates are 10mm thick and 240mm in diameter. The support shaft is 15mm in diameter and 700mm in length.

[0067] S5. The entire device is placed in a cold isostatic press for pressing and static molding at a pressure of 110 MPa.

[0068] S6, Demolding. After pressing according to the program, demold. The final molded body dimensions are: inner diameter 5mm in the middle, 25mm at both ends, outer diameter 60mm, and length 402mm.

[0069] The mold filled with powder and this fixing device are placed together in a cold isostatic press for pressing. Due to the straightening and fixing effect of the upper and lower positioning plates on the screw docking shaft, the damage of pressure to the threaded connection is reduced. Furthermore, the method of using the threaded connection to the top double cone mold solves the problem of forming a tubular ceramic blank that is large at both ends and small in the middle.

[0070] It should be noted that the terms "first" and "second" used in this application are for descriptive purposes only and do not indicate any order. They should not be construed as indicating or implying relative importance, and can be interpreted as names.

[0071] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the invention. The advantages of the present invention have been fully and effectively realized. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments; any variations or modifications can be made to the implementation of the present invention without departing from these principles.

Claims

1. An apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core, characterized in that, include: A forming frame, comprising an upper positioning plate, a lower positioning plate, and a support shaft, wherein the upper positioning plate and the lower positioning plate are symmetrically distributed in parallel in the height direction, and the support shaft is vertically fixed between the upper positioning plate and the lower positioning plate; A flexible mold mandrel is vertically connected to the center of the upper positioning plate and the lower positioning plate in a tensioned and straightened manner. An elastic mold sleeve includes a sleeve body and an end cap that are sleeved on the soft mold mandrel and coaxially distributed with the soft mold mandrel. The sleeve body is located between the upper positioning plate and the lower positioning plate, and the end caps are symmetrically embedded at the top and bottom of the sleeve body.

2. The apparatus for cold isostatic pressing of ceramic blanks using a soft metal mold core as described in claim 1, characterized in that, The upper positioning plate, the lower positioning plate, and the support shaft are all made of the same material, stainless steel.

3. The apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core as described in claim 2, characterized in that, The support shaft has three shafts, which are evenly spaced at 120° intervals in the horizontal direction and are connected to the outer circumference of the upper positioning plate and the lower positioning plate.

4. The apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core as described in claim 1, characterized in that, The soft mold mandrel has a steel wire skeleton structure with a wire diameter of 1mm to 3mm. The upper positioning plate and the lower positioning plate are respectively equipped with tension bolts at their center positions. The top and bottom ends of the soft mold mandrel are inserted and connected to the corresponding tension bolts.

5. The apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core as described in claim 1, characterized in that, The soft mold mandrel is a screw-connected shaft. The axis of the soft mold mandrel coincides with the central axis of the upper positioning plate and the lower positioning plate. Tensioning bolts are respectively installed at the center of the upper positioning plate and the lower positioning plate, and the axes of the two tensioning bolts are collinear. The top and bottom ends of the soft mold mandrel are respectively provided with threaded holes that are adapted to the tensioning bolts, and the two are threadedly connected.

6. The apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core as described in claim 4 or 5, characterized in that, The surface of the soft mold mandrel is polished and boron nitride powder is coated on the mandrel.

7. The apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core as described in claim 6, characterized in that, The elastic sleeve is a rubber sleeve with a hardness of A45±5°.

8. The apparatus for cold isostatic pressing of ceramic blanks using a metal soft mold core as described in claim 1, characterized in that, The upper positioning plate and the lower positioning plate have the same thickness, which is 10mm to 15mm, and the thickness of the sleeve body is 2mm to 4mm.

9. A method for forming a ceramic blank using the apparatus for cold isostatic pressing of a ceramic blank using a soft metal mold core as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1, the upper positioning plate and the lower positioning plate are fixedly connected by the support shaft, the forming frame is assembled, and then one end of the soft mold core shaft is fixed at the center position of the lower positioning plate; S2, pass the soft mold mandrel through the end cap near the lower side, and then through the center of the sleeve body, sealing the end cap near the lower side into the bottom of the sleeve body; S3, Powder is filled into the sleeve body, and then the end cap near the upper side moves along the soft mold core at the center position until it is embedded in the top of the sleeve body, thus completing the sealing of the molding cavity. S4, fix the other end of the soft mold mandrel to the center of the upper positioning plate, and keep the soft mold mandrel in a taut and straight state; S5, the entire device is placed in a high-pressure container for static pressure molding; S6, demolding.

10. The method for cold isostatic pressing of ceramic blanks using a metal soft mold core as described in claim 9, characterized in that, In step S5, the pressure value of the high-pressure container is 110 MPa, and the soft mold mandrel is always kept taut and straight during the pressing process.

Images