High-precision and high-rigidity ceramic plate spring and preparation method thereof

Abstract

This invention provides a high-precision, high-stiffness ceramic leaf spring and its preparation method, relating to the field of ceramic materials. The preparation method involves ball milling ceramic powder, ceramic fiber, sintering aid, binder, plasticizer, dispersant, and ball milling solvent, followed by scraping and casting to obtain a cast sheet. The cast sheet is placed in a ceramic leaf spring forming mold, heated to set, and then demolded to obtain a ceramic leaf spring blank. This blank is then sintered to obtain a high-precision, high-stiffness ceramic leaf spring. This invention specifically overcomes the shortcomings of existing metal springs (low temperature resistance) and existing similar-sized helical cylindrical ceramic springs (low stiffness, low load capacity). It also solves the problems of difficult dimensional accuracy control and easy deformation during sintering in existing ceramic leaf springs. The prepared ceramic leaf spring possesses high stiffness, high load-bearing capacity, and excellent high-temperature resistance, with uniform elastic stiffness, uniform load distribution, good resistance to brittle fracture, and good thermal shock and high-temperature service performance.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials, and in particular to a high-precision, high-stiffness ceramic leaf spring and its preparation method. Background Technology

[0002] A helical cylindrical metal spring is an elastic mechanical part with a cylindrical shape and a circular cross-section. It is typically made of spring steel wire wound into a helix, utilizing the elastic deformation of the metal material to absorb energy, mitigate impact, and provide a restoring force. While helical cylindrical metal springs have wide applications in many fields, they suffer from poor temperature resistance: when the ambient temperature rises, the elastic modulus of the helical cylindrical metal spring decreases significantly, directly leading to a reduction in its stiffness and load-bearing capacity. Furthermore, under prolonged high loads and high temperatures, the helical cylindrical metal spring will also experience stress relaxation. These shortcomings directly limit the application of helical cylindrical metal springs in high-temperature and other high-end applications.

[0003] Due to the strong covalent bonding characteristics of the ceramic material used in helical cylindrical ceramic springs, the bond energy is much higher than that of metal bonds. Thermal vibration is difficult to shake its bonding strength. It can maintain its strength performance at room temperature in a long-term working environment of 1000℃ and hardly undergoes stress relaxation, exhibiting excellent temperature resistance. At the same time, helical cylindrical ceramic springs also have the characteristics of low density and high temperature corrosion resistance, making them an effective replacement for metal springs in high-temperature working conditions.

[0004] However, existing helical cylindrical ceramic springs of similar size have the disadvantages of low stiffness and low load capacity, which need to be addressed, and this disadvantage directly limits their application scenarios. In the prior art, leaf springs naturally have the advantages of high stiffness and high load capacity, but the inventors found the following technical bottlenecks in the process of preparing leaf springs using ceramic materials: (1) The dimensional accuracy of ceramic leaf springs is difficult to control during the molding process, and problems such as demolding cracking, uneven thickness, and uneven shrinkage are prone to occur during the molding process; (2) Ceramic leaf springs have self-weight creep and shrinkage anisotropy during the sintering process, and are prone to deformation such as sintering bending and warping, making it difficult to maintain a regular leaf spring structure. The above technical bottlenecks directly lead to large dispersion of elastic stiffness at various positions of the prepared ceramic leaf springs and uneven overall load distribution; and ceramic leaf springs are prone to local stress concentration during the stress process, which can easily induce brittle fracture; and the thermal shock resistance and high temperature service performance of ceramic leaf springs are poor. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a high-precision, high-stiffness ceramic leaf spring and its preparation method. It specifically overcomes the shortcomings of existing metal springs, such as low temperature resistance, and existing similar-sized helical cylindrical ceramic springs, which have low stiffness and can only provide small loads. At the same time, it solves the problems of difficult control of molding dimensional accuracy and easy deformation during sintering of existing ceramic leaf springs. The prepared ceramic leaf spring has high stiffness, large load-bearing capacity and excellent high-temperature resistance, and has uniform elastic stiffness, uniform load distribution, good resistance to brittle fracture, good thermal shock resistance and high-temperature service performance.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing a high-precision, high-stiffness ceramic leaf spring includes the following steps: preparing a cast film, shaping with a mold, and sintering; The method for preparing the cast film is as follows: ceramic powder, ceramic fiber, sintering aid, binder, plasticizer, dispersant, and ball milling solvent are ball milled to obtain a casting slurry with a solid content of 65-70 wt%; after degassing, the casting slurry is coated and dried to obtain the cast film. The ceramic powder is one of the following: alumina powder, zirconium oxide powder, or silicon nitride powder; The method for mold shaping is to place the cast sheet in the ceramic leaf spring forming mold, heat it to shape it, and then demold it to obtain the ceramic leaf spring blank. The sintering method is as follows: after the bottom of the sintering crucible is filled with ceramic balls, the ceramic leaf spring blank is placed flat on the ceramic balls at the bottom of the sintering crucible, and then the sintering powder is filled into the sintering crucible. The crucible is then heated and sintered in a sintering atmosphere to obtain a high-precision, high-rigidity ceramic leaf spring.

[0007] Preferably, the particle size D of the ceramic powder is... 50 The particle size is 0.2-1 μm, and the purity is not less than 99.0 wt%. The ceramic fiber is one of the following: alumina fiber, silicon carbide whisker, or silicon nitride fiber; the added weight of the ceramic fiber is 0.5-3% of the oven-dry weight of the ceramic powder.

[0008] Preferably, when the ceramic powder is alumina powder, the sintering aid is at least one of the following: SiO2, MgO, CaO, and the total amount of sintering aid added is 2-4.5% of the oven-dry weight of the alumina powder; When the ceramic powder is zirconia powder, the sintering aid is at least one of the following: Y2O3, CeO2, CaO, MgO, and the total amount of sintering aid added is 1-3% of the oven-dry weight of the zirconia powder; When the ceramic powder is silicon nitride powder, the sintering aid is at least one of the following: Y2O3, Al2O3, MgO, La2O3, and the total weight of the sintering aid is 5-8% of the oven-dry weight of the silicon nitride powder.

[0009] Preferably, the binder is one of the following: polyvinyl butyral, ethyl cellulose, acrylic resin, carboxymethyl cellulose, or polyurethane; the weight of the binder added is 3-6% of the oven-dry weight of the ceramic powder. The plasticizer is one of the following: dibutyl phthalate, polyethylene glycol 400, or polyethylene glycol 600; the weight of the plasticizer added is 1.5-4% of the oven-dry weight of the ceramic powder. The dispersant is one of the following: fish oil, oleic acid, or phosphate ester dispersants; the weight of the dispersant added is 1-1.5% of the oven-dry weight of the ceramic powder; The ball milling solvent consists of toluene and anhydrous ethanol in a weight ratio of 6-7:3-4.

[0010] Furthermore, in the mold shaping process, the ceramic leaf spring forming mold includes: an upper mold and a lower mold; The lower end of the upper mold has a first forming surface, and the upper end of the lower mold has a second forming surface; After the upper mold and the lower mold are engaged, the first forming surface and the second forming surface enclose each other to form a forming cavity; The middle part of the molding cavity has an upward arched arc structure, and the outer contour shape of the molding cavity is consistent with the outer contour of the ceramic leaf spring.

[0011] Preferably, in the mold setting process, the heating setting is carried out in an air atmosphere, heating to 35-45℃, holding the temperature for 10-20 hours, and then continuing to heat to 60-70℃ and holding the temperature for 5-10 hours.

[0012] Preferably, in the sintering process, the ceramic balls are one of the following: silicon nitride ceramic balls, zirconium oxide ceramic balls, and alumina ceramic balls; The diameter of the ceramic spheres is 0.1-0.3 mm; The thickness of the ceramic balls at the bottom of the sintering crucible is 0.2-0.4 mm.

[0013] Furthermore, in the sintering process, the heating sintering is carried out in a sintering atmosphere, heating to 500-600℃, holding at that temperature for 60-120 minutes; controlling the heating rate at 2-5℃ / min, continuing to heat to 1000-1200℃, controlling the heating rate at 1.5-3℃ / min, continuing to heat to the sintering temperature, holding at that temperature for 120-240 minutes, and then cooling down to obtain a high-precision, high-rigidity ceramic leaf spring.

[0014] Preferably, when the ceramic powder is alumina powder, the sintering powder used in the sintering process is high-purity alumina powder, the sintering atmosphere is air, and the sintering temperature is 1580-1620℃. When the ceramic powder is zirconium oxide powder, the sintering powder used in the sintering process is yttrium-stabilized zirconium oxide powder or alumina powder, the sintering atmosphere is air, and the sintering temperature is 1450-1500℃. When the ceramic powder is silicon nitride powder, the sintering powder used is a mixture of silicon nitride and hexagonal boron nitride, or a mixture of hexagonal boron nitride, yttrium oxide, and alumina. The sintering atmosphere is nitrogen, and the sintering temperature is 1750-1850℃.

[0015] A high-precision, high-stiffness ceramic leaf spring is prepared using the aforementioned method.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The preparation method of the high-precision, high-rigidity ceramic leaf spring of the present invention involves ball milling ceramic powder, ceramic fiber, sintering aid, binder, plasticizer, dispersant and ball milling solvent, followed by scraping and casting to obtain a cast sheet; placing the cast sheet in a ceramic leaf spring forming mold, heating and shaping it, and then demolding it to obtain a ceramic leaf spring blank; and then sintering it to obtain a high-precision, high-rigidity ceramic leaf spring; the aforementioned technical means cooperate and work together to overcome the shortcomings of existing metal springs with low temperature resistance and existing similar-sized spiral cylindrical ceramic springs with low stiffness and low load capacity, while solving the problems of difficult control of forming size accuracy and easy deformation during sintering of existing ceramic leaf springs; the prepared ceramic leaf spring has high stiffness, high load capacity and excellent high temperature resistance, and has uniform elastic stiffness, uniform load distribution, good resistance to brittle fracture, good thermal shock resistance and high temperature service performance.

[0017] (2) The method for preparing high-precision, high-rigidity ceramic leaf springs of the present invention involves preparing a cast sheet by casting with a casting slurry and preparing a ceramic leaf spring by molding with a ceramic leaf spring molding die. The casting process ensures the uniformity of the thickness of the prepared ceramic leaf spring and effectively improves the stability of the application performance of the ceramic leaf spring. At the same time, the molding with a ceramic leaf spring molding die can achieve the diversity of structural dimensions and meet the customized needs of different application scenarios.

[0018] (3) The method for preparing high-precision, high-rigidity ceramic leaf springs of the present invention adopts the method of filling the bottom of the sintering crucible with ceramic microspheres and filling and embedding sintering powder during the sintering process, which can maintain the stability of the ceramic leaf springs in terms of free sintering shrinkage and shape.

[0019] (4) The method for preparing high-precision, high-rigidity ceramic leaf springs of the present invention produces ceramic leaf springs with high stiffness, good temperature resistance, good thickness uniformity, good tensile strength and fracture toughness, and good application stability, which can be widely applied to working scenarios that traditional metal leaf springs cannot handle.

[0020] (5) The method for preparing high-precision, high-stiffness ceramic leaf springs of the present invention has readily available raw materials, a simple process flow, and easy control of the preparation process, which is conducive to industrial production and application. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the mold forming mold for ceramic leaf springs in an embodiment of the present invention; in the figure, 1-upper mold, 2-lower mold, 3-ceramic leaf spring blank. Detailed Implementation

[0022] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] This invention provides a method for preparing a high-precision, high-stiffness ceramic leaf spring, which includes the following steps: preparing a casting sheet, shaping with a mold, and sintering.

[0025] The method for preparing the cast film is as follows: ceramic powder, ceramic fiber, sintering aid, binder, plasticizer, dispersant and ball milling solvent are ball milled to obtain a casting slurry with a solid content of 65-70 wt%; after degassing, the casting slurry is coated and dried to obtain the cast film.

[0026] Specifically, the method for preparing the cast film is as follows: ceramic powder, dispersant, and ball milling solvent are ball-milled, with the ball-to-material ratio controlled at 2.2-2.5:1 and the ball milling speed at 500-600 rpm. After ball milling for 12-14 hours, sintering aid, binder, and plasticizer are added, and ball milling continues for 4-6 hours. Then, ceramic fibers are added, and after ball milling until uniform, large particles and agglomerates are removed by sieving to obtain a cast slurry with a solid content of 65-70 wt%. The cast slurry is then vacuum degassed for 20-40 minutes, and the doctor blade height (i.e., doctor blade gap) is controlled at 1.1-1.5 mm. The film is then coated and dried to obtain the cast film.

[0027] The ceramic powder is one of the following: alumina powder, zirconium oxide powder, or silicon nitride powder; the ceramic powder is a low-agglomeration spherical ultrafine powder with a particle size D. 50 The particle size is controlled within 0.2-1μm, and the maximum particle size does not exceed 2μm; the ceramic powder has a purity of not less than 99.0wt%; by limiting the particle size, purity, morphology and specific surface area of ​​the raw material powder, the uniformity of the thickness of the subsequent green body is ensured, the anisotropy of sintering shrinkage and sintering deformation are reduced, the dimensional accuracy of the product is improved, and internal defects are reduced and density is increased, which significantly improves the tensile strength and brittle fracture resistance of ceramic leaf springs.

[0028] The ceramic fiber is one of the following: alumina fiber, silicon carbide whisker, silicon nitride fiber; the weight of the added ceramic fiber is 0.5-3% (preferably 1-2.5%) of the oven-dry weight of the ceramic powder.

[0029] When the ceramic powder is alumina powder, the sintering aid is at least one of the following: SiO2, MgO, CaO, preferably a combination of MgO and SiO2, and the total weight of the sintering aid is 2-4.5% of the oven-dry weight of the alumina powder; when the ceramic powder is zirconia powder, the sintering aid is at least one of the following: Y2O3, CeO2, CaO, MgO, and the total weight of the sintering aid is 1-3% of the oven-dry weight of the zirconia powder; when the ceramic powder is silicon nitride powder, the sintering aid is at least one of the following: Y2O3, Al2O3, MgO, La2O3, preferably a combination of Y2O3 and Al2O3, or a combination of Y2O3 and MgO, and the total weight of the sintering aid is 5-8% of the oven-dry weight of the silicon nitride powder.

[0030] The binder is one of the following: polyvinyl butyral, ethyl cellulose, acrylic resin, carboxymethyl cellulose, or polyurethane; the weight of the binder added is 3-6% of the oven-dry weight of the ceramic powder.

[0031] The plasticizer is one of the following: dibutyl phthalate, polyethylene glycol 400, or polyethylene glycol 600; the weight of the plasticizer added is 1.5-4% of the oven-dry weight of the ceramic powder.

[0032] The dispersant is one of the following: fish oil, oleic acid, or phosphate ester dispersants; the weight of the added dispersant is 1-1.5% of the oven-dry weight of the ceramic powder.

[0033] The ball milling solvent consists of toluene and anhydrous ethanol in a weight ratio of 6-7:3-4.

[0034] The mold-forming method involves using a ceramic leaf spring molding mold manufactured via 3D printing. The mold includes an upper mold 1 and a lower mold 2. The lower end of the upper mold 1 has a first forming surface, and the upper end of the lower mold 2 has a second forming surface. After the upper mold 1 and lower mold 2 are engaged, the first and second forming surfaces enclose and form a molding cavity. The center of the molding cavity has an upwardly arched arc structure, and the outer contour of the molding cavity is consistent with the outer contour of the ceramic leaf spring. Simultaneously, both ends of the molding cavity are provided with horizontally extending support steps to fit against the straight step surfaces at both ends of the ceramic leaf spring.

[0035] like Figure 1 As shown, during the mold setting process, the cast sheet is placed in the lower mold 2 of the ceramic leaf spring forming mold, and the cast sheet is cut to match the size of the forming cavity of the ceramic leaf spring forming mold; after the upper mold 1 and the lower mold 2 are fastened together, they are placed in an oven, and the oven temperature is controlled at 35-45℃ in an air atmosphere for 10-20 hours of heat setting; the oven temperature is then controlled to rise to 60-70℃ for 5-10 hours of heat setting; the weight loss rate during the mold setting process is controlled at 0.1-0.3wt%, and the mold is demolded to obtain the ceramic leaf spring blank 3.

[0036] The sintering method is as follows: To ensure the leaf spring can contract freely while maintaining its shape, ceramic balls (0.1-0.3 mm in diameter) are first laid on the bottom of the sintering crucible, with a thickness of 0.2-0.4 mm. Then, the ceramic leaf spring blank 3 is placed flat on the ceramic balls at the bottom of the sintering crucible. The remaining space in the sintering crucible is then completely filled with sintering powder to ensure uniform heating of the ceramic leaf spring blank 3 during sintering and to prevent deformation of any protruding parts. The sintering crucible is then placed in a sintering atmosphere, with a heating rate controlled at 1-2... Heat the material at a rate of ℃ / min to 500-600℃, hold for 60-120 minutes to remove adhesives, plasticizers, residual solvents, and other components from the green body; control the heating rate at 2-5℃ / min, continue heating to 1000-1200℃, do not hold and control the heating rate at 1.5-3℃ / min, continue heating to the sintering temperature, hold for sintering for 120-240 minutes, then cool down to 800-1200℃ at a rate of 1-5℃ / min, and cool with the furnace to obtain a high-precision, high-rigidity ceramic leaf spring.

[0037] Among them, the ceramic ball is one of the following: silicon nitride ceramic ball, zirconia ceramic ball, or alumina ceramic ball.

[0038] When the ceramic leaf spring blank 3 is prepared using alumina powder, the sintering powder used is high-purity alumina powder; the sintering atmosphere is air, and the sintering temperature is 1580-1620℃; when the ceramic leaf spring blank 3 is prepared using zirconium oxide powder, the sintering powder used is yttrium-stabilized zirconium oxide powder or alumina powder, the sintering atmosphere is air, and the sintering temperature is 1450-1500℃; when the ceramic leaf spring blank 3 is prepared using silicon nitride powder, the sintering powder used is a mixture of silicon nitride and hexagonal boron nitride, or a mixture of hexagonal boron nitride, yttrium oxide, and alumina powder, the sintering atmosphere is nitrogen, and the sintering temperature is 1750-1850℃.

[0039] The present invention also provides high-precision, high-stiffness ceramic leaf springs prepared using the aforementioned method.

[0040] The present invention will be further described below with reference to some specific embodiments.

[0041] Example 1 This embodiment provides a method for manufacturing high-precision, high-stiffness ceramic leaf springs, specifically as follows: 1. Preparation of cast film Ceramic powder, dispersant, and ball milling solvent were ball-milled at a ball-to-powder ratio of 2.3:1 and a ball milling speed of 500 rpm for 12 hours. Then, sintering aid, binder, and plasticizer were added, and ball milling continued for another 4 hours. Ceramic fibers were then added. After the mixture was ball-milled until homogeneous, it was sieved to remove large particles and agglomerates, resulting in a casting slurry with a solid content of 65 wt%. The casting slurry was then vacuum degassed for 20 minutes. The doctor blade height was controlled at 1.1 mm, and the slurry was coated to form a wet film, which was then dried to obtain a cast sheet.

[0042] The ceramic powder is alumina powder with a particle size D. 50 The particle size is 0.5 μm and the maximum particle size does not exceed 2 μm. The purity of the alumina powder is 99.0 wt%.

[0043] The ceramic fiber is alumina fiber, and the weight of alumina fiber added is 1.2% of the oven-dry weight of alumina powder.

[0044] The sintering aids are SiO2 and MgO; the weight of SiO2 added is 1% of the oven-dry weight of the alumina powder, and the weight of MgO added is 2% of the oven-dry weight of the alumina powder.

[0045] The binder is polyvinyl butyral, and the weight of the binder added is 3% of the oven-dry weight of the ceramic powder.

[0046] The plasticizer is dibutyl phthalate, and the weight of the plasticizer added is 1.5% of the oven-dry weight of the ceramic powder.

[0047] The dispersant is fish oil, and the weight of the dispersant added is 1% of the oven-dry weight of the ceramic powder.

[0048] The ball milling solvent consists of toluene and anhydrous ethanol in a weight ratio of 7:3.

[0049] 2. Mold shaping The ceramic leaf spring molding mold used in this embodiment is manufactured by 3D printing. The ceramic leaf spring molding mold includes an upper mold 1 and a lower mold 2. The lower end of the upper mold 1 has a first molding surface, and the upper end of the lower mold 2 has a second molding surface. After the upper mold 1 and the lower mold 2 are engaged, the first molding surface and the second molding surface enclose each other to form a molding cavity. The middle part of the molding cavity has an upwardly arched arc structure, and the outer contour shape of the molding cavity is consistent with the outer contour of the ceramic leaf spring. At the same time, the two ends of the molding cavity are respectively provided with support steps extending straight in the horizontal direction, which are used to fit against the straight step surfaces at both ends of the ceramic leaf spring.

[0050] The specific operation of mold setting is as follows: place the cast sheet in the lower mold 2 of the ceramic leaf spring forming mold, cut the cast sheet, and then place the upper mold 1 and the lower mold 2 in an oven. Under air atmosphere, control the oven temperature at 40℃ and keep it warm for 15 hours; control the oven temperature to rise to 65℃ and keep it warm for 7 hours; control the weight loss rate during the mold setting process to 0.1wt%, demold, and obtain the ceramic leaf spring blank 3.

[0051] 3. Sintering First, alumina ceramic balls (0.2 mm in diameter) are laid at the bottom of the sintering crucible, with the thickness of the balls controlled at 0.2 mm. Then, the ceramic leaf spring blank 3 is placed flat on the alumina ceramic balls at the bottom of the sintering crucible. Then, the remaining space of the sintering crucible is completely filled with sintering powder (high-purity alumina powder) to ensure that the sintering powder completely covers the ceramic leaf spring blank 3. Then, the sintering crucible is placed in an air atmosphere, and the heating rate is controlled at 2℃ / min to raise the temperature to 550℃. The temperature is held for 120 min to remove the binder, plasticizer, residual solvent and other components in the blank. The heating rate is controlled at 5℃ / min to continue raising the temperature to 1000℃. The temperature is not held and the heating rate is controlled at 3℃ / min to continue raising the temperature to the sintering temperature of 1620℃. The temperature is held for sintering for 180 min. Then, the temperature is lowered to 800℃ at a cooling rate of 5℃ / min and cooled with the furnace to obtain a high-precision, high-rigidity ceramic leaf spring.

[0052] This embodiment also provides a high-precision, high-stiffness ceramic leaf spring prepared using the aforementioned method, with an arch height (arc height) of 1.7 mm and a length of 22.5 mm. Testing showed that the ceramic leaf spring of this embodiment has a stiffness of 40.2 N / mm, a load of 20.3 N, and a compression of 0.5 mm; the thickness deviation at all points of the ceramic leaf spring is controlled within ±0.1 mm, and the warping deformation after sintering is ≤0.12 mm, with a dimensional shrinkage consistency error ≤±1%; the room temperature tensile strength of the ceramic leaf spring is 182 MPa, and the fracture toughness is 3.1 MPa·m. 1 / 2 The fatigue life of ceramic leaf springs exceeds 10 years. 3 After high and low temperature thermal shock cycles, the stiffness decreases by 9%, and the performance dispersion of products in the same batch can be controlled within 4.5%; at the same time, the sintering density of the ceramic leaf spring is 99.5%, the porosity is ≤0.5%, and the overall structure is stable.

[0053] Example 2 This embodiment provides a method for manufacturing high-precision, high-stiffness ceramic leaf springs, specifically as follows: 1. Preparation of cast film Ceramic powder, dispersant, and ball milling solvent were ball-milled at a ball-to-powder ratio of 2.3:1 and a ball milling speed of 500 rpm for 12 hours. Then, sintering aid, binder, and plasticizer were added, and ball milling continued for another 6 hours. Ceramic fibers were then added. After the mixture was ball-milled until homogeneous, it was sieved to remove large particles and agglomerates, resulting in a casting slurry with a solid content of 65 wt%. The casting slurry was then vacuum degassed for 40 minutes. The doctor blade height was controlled at 1.5 mm, and the slurry was coated to form a wet film, which was then dried to obtain a cast sheet.

[0054] The ceramic powder is silicon nitride powder with a particle size D. 50 The particle size is 1μm and the maximum particle size does not exceed 2μm. The purity of the silicon nitride powder is 99.5wt%.

[0055] The ceramic fiber is silicon nitride fiber, and the weight of silicon nitride fiber added is 2.1% of the oven-dry weight of silicon nitride powder.

[0056] The sintering aids are Y2O3 and Al2O3; the weight of Y2O3 added is 3% of the oven-dry weight of silicon nitride powder, and the weight of Al2O3 added is 4% of the oven-dry weight of silicon nitride powder.

[0057] The binder is polyvinyl butyral, and the weight of the binder added is 6% of the oven-dry weight of the ceramic powder.

[0058] The plasticizer is dibutyl phthalate, and the weight of the plasticizer added is 3% of the oven-dry weight of the ceramic powder.

[0059] The dispersant is fish oil, and the weight of the dispersant added is 1.5% of the oven-dry weight of the ceramic powder.

[0060] The ball milling solvent consists of toluene and anhydrous ethanol in a weight ratio of 7:3.

[0061] 2. Mold shaping The structure of the ceramic leaf spring forming mold used in this embodiment is the same as that in Embodiment 1; the cast sheet is placed in the lower mold 2 of the ceramic leaf spring forming mold, the cast sheet is cut, the upper mold 1 and the lower mold 2 are fastened together and placed in an oven, and the oven temperature is controlled at 45°C under air atmosphere for 20 hours of heat preservation; the oven temperature is controlled to rise to 70°C and heat preservation is carried out for 10 hours; the weight loss rate during the mold forming process is controlled to be 0.3wt%, and the mold is demolded to obtain the ceramic leaf spring blank 3.

[0062] 3. Sintering First, a layer of silicon nitride ceramic balls (0.1 mm in diameter) is laid at the bottom of the sintering crucible, with a thickness of 0.3 mm. Then, the ceramic leaf spring blank 3 is placed flat on the silicon nitride ceramic balls at the bottom of the sintering crucible. Next, the remaining space in the sintering crucible is completely filled with sintering powder (a mixture of silicon nitride and hexagonal boron nitride in equal mass ratios), ensuring that the sintering powder completely covers the ceramic leaf spring blank 3. Then, the sintering crucible is placed under a nitrogen atmosphere, and the heating rate is controlled at 1 °C / min. The temperature is raised to 500℃ and held for 100 minutes to remove adhesives, plasticizers, residual solvents and other components from the green body. The heating rate is controlled at 3℃ / min, and the temperature is raised to 1100℃. The temperature is not held and the heating rate is controlled at 2℃ / min. The temperature is raised to sintering temperature of 1800℃ and held for sintering for 240 minutes. Then the temperature is lowered to 1200℃ at a cooling rate of 5℃ / min and cooled in the furnace to obtain a high-precision, high-rigidity ceramic leaf spring.

[0063] This embodiment also provides a high-precision, high-stiffness ceramic leaf spring prepared using the aforementioned method, with an arch height (arc height) of 1.7 mm and a length of 22.5 mm. Testing showed that the ceramic leaf spring of this embodiment has a stiffness of 79.8 N / mm, a load of 43.5 N, and a compression of 0.5 mm; the thickness deviation at all points of the ceramic leaf spring is controlled within ±0.1 mm, and the warping deformation after sintering is ≤0.1 mm, with a dimensional shrinkage consistency error ≤±1%; the room temperature tensile strength of the ceramic leaf spring is 283 MPa, and the fracture toughness is 8.6 MPa·m. 1 / 2 The fatigue life of ceramic leaf springs exceeds 10 years. 3 After high and low temperature thermal shock cycles, the stiffness decreases by 8%, and the performance dispersion of products in the same batch can be controlled within 4.0%; at the same time, the sintering density of the ceramic leaf spring is 99.6%, the porosity is ≤0.4%, and the overall structure is stable.

[0064] Example 3 This embodiment provides a method for manufacturing high-precision, high-stiffness ceramic leaf springs, specifically as follows: 1. Preparation of cast film Ceramic powder, dispersant, and ball milling solvent were ball-milled at a ball-to-powder ratio of 2.3:1 and a ball milling speed of 500 rpm for 13 hours. Then, sintering aid, binder, and plasticizer were added, and ball milling continued for another 5 hours. Ceramic fibers were then added. After the mixture was ball-milled until homogeneous, it was sieved to remove large particles and agglomerates, resulting in a casting slurry with a solid content of 65 wt%. The casting slurry was then vacuum degassed for 30 minutes. The doctor blade height was controlled at 1.5 mm, and the slurry was coated to form a wet film, which was then dried to obtain a cast sheet.

[0065] The ceramic powder is silicon nitride powder with a particle size D. 50 The particle size is 0.8 μm and the maximum particle size does not exceed 2 μm. The purity of the silicon nitride powder is 99 wt%.

[0066] The ceramic fiber is silicon carbide whisker, and the weight of silicon carbide whisker added is 2.5% of the oven-dry weight of silicon nitride powder.

[0067] The sintering aid is Y2O3; the weight of Y2O3 added is 3% of the oven-dry weight of silicon nitride powder.

[0068] The binder is polyvinyl butyral, and the weight of the binder added is 4% of the oven-dry weight of the ceramic powder.

[0069] The plasticizer is dibutyl phthalate, and the weight of the plasticizer added is 2% of the oven-dry weight of the ceramic powder.

[0070] The dispersant is fish oil, and the weight of the dispersant added is 1.2% of the oven-dry weight of the ceramic powder.

[0071] The ball milling solvent consists of toluene and anhydrous ethanol in a weight ratio of 7:3.

[0072] 2. Mold shaping The structure of the ceramic leaf spring forming mold used in this embodiment is the same as that in Embodiment 1; the cast sheet is placed in the lower mold 2 of the ceramic leaf spring forming mold, the cast sheet is cut, the upper mold 1 and the lower mold 2 are fastened together and placed in an oven, and the oven temperature is controlled at 40°C under air atmosphere and kept warm for 15 hours; the oven temperature is controlled to rise to 65°C and kept warm for 8 hours; the weight loss rate during the mold setting process is controlled to be 0.2wt%, and the mold is demolded to obtain the ceramic leaf spring blank 3.

[0073] 3. Sintering First, silicon nitride ceramic spheres (0.3 mm in diameter) are laid at the bottom of the sintering crucible, with the sphere thickness controlled at 0.3 mm. Then, the ceramic leaf spring blank 3 is placed flat on the silicon nitride ceramic spheres at the bottom of the sintering crucible. Next, the remaining space of the sintering crucible is completely filled with sintering powder (a mixture of silicon nitride and hexagonal boron nitride in equal mass ratio), ensuring that the sintering powder completely covers the ceramic leaf spring blank 3. Then, the sintering crucible is placed under a nitrogen atmosphere, and the heating rate is controlled at 1.5 °C / min. The temperature is raised to 520℃ and held for 90 minutes to remove adhesives, plasticizers, residual solvents, and other components from the green body. The heating rate is controlled at 3.5℃ / min, and the temperature is raised to 1130℃. The temperature is not held and the heating rate is controlled at 2℃ / min. The temperature is raised to the sintering temperature of 1750℃ and held for sintering for 150 minutes. Then, the temperature is lowered to 1000℃ at a cooling rate of 2℃ / min and cooled in the furnace to obtain a high-precision, high-rigidity ceramic leaf spring.

[0074] This embodiment also provides a high-precision, high-stiffness ceramic leaf spring prepared using the aforementioned method, with an arch height (arc height) of 1.7 mm and a length of 22.5 mm. Testing showed that the ceramic leaf spring of this embodiment has a stiffness of 64.8 N / mm, a load of 32.5 N, and a compression of 0.5 mm; the thickness deviation at all points of the ceramic leaf spring is controlled within ±0.1 mm, and the warping deformation after sintering is ≤0.09 mm, with a dimensional shrinkage consistency error ≤±1%; the room temperature tensile strength of the ceramic leaf spring is 265 MPa, and the fracture toughness is 8.3 MPa·m. 1 / 2 The fatigue life of ceramic leaf springs exceeds 10 years. 3 After high and low temperature thermal shock cycles, the stiffness decreases by 8.6%, and the performance dispersion of products in the same batch can be controlled within 4.3%; at the same time, the sintering density of the ceramic leaf spring is 99.5%, the porosity is ≤0.5%, and the overall structure is stable.

[0075] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0076] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a high-precision, high-stiffness ceramic leaf spring, characterized in that, Includes the following steps: Preparation of cast film, mold shaping, and sintering; The method for preparing the cast film is as follows: ceramic powder, ceramic fiber, sintering aid, binder, plasticizer, dispersant, and ball milling solvent are ball milled to obtain a casting slurry with a solid content of 65-70 wt%; after degassing, the casting slurry is coated and dried to obtain the cast film. The ceramic powder is one of the following: alumina powder, zirconium oxide powder, or silicon nitride powder; The method for mold shaping is to place the cast sheet in the ceramic leaf spring forming mold, heat it to shape it, and then demold it to obtain the ceramic leaf spring blank. The sintering method is as follows: after the bottom of the sintering crucible is filled with ceramic balls, the ceramic leaf spring blank is placed flat on the ceramic balls at the bottom of the sintering crucible, and then the sintering powder is filled into the sintering crucible. The crucible is then heated and sintered in a sintering atmosphere to obtain a high-precision, high-rigidity ceramic leaf spring.

2. The method for preparing a high-precision, high-stiffness ceramic leaf spring according to claim 1, characterized in that, The particle size D of the ceramic powder 50 The particle size is 0.2-1 μm, and the purity is not less than 99.0 wt%. The ceramic fiber is one of the following: alumina fiber, silicon carbide whisker, or silicon nitride fiber; the added weight of the ceramic fiber is 0.5-3% of the oven-dry weight of the ceramic powder.

3. The method for preparing a high-precision, high-stiffness ceramic leaf spring according to claim 1, characterized in that, When the ceramic powder is alumina powder, the sintering aid is at least one of the following: SiO2, MgO, CaO, and the total amount of sintering aid added is 2-4.5% of the oven-dry weight of the alumina powder; When the ceramic powder is zirconia powder, the sintering aid is at least one of the following: Y2O3, CeO2, CaO, MgO, and the total amount of sintering aid added is 1-3% of the oven-dry weight of the zirconia powder; When the ceramic powder is silicon nitride powder, the sintering aid is at least one of the following: Y2O3, Al2O3, MgO, La2O3, and the total weight of the sintering aid is 5-8% of the oven-dry weight of the silicon nitride powder.

4. The method for preparing a high-precision, high-stiffness ceramic leaf spring according to claim 1, characterized in that, The binder is one of the following: polyvinyl butyral, ethyl cellulose, acrylic resin, carboxymethyl cellulose, or polyurethane; the binder is added at a weight of 3-6% of the oven-dry weight of the ceramic powder. The plasticizer is one of the following: dibutyl phthalate, polyethylene glycol 400, or polyethylene glycol 600; the weight of the plasticizer added is 1.5-4% of the oven-dry weight of the ceramic powder. The dispersant is one of the following: fish oil, oleic acid, or phosphate ester dispersants; the weight of the dispersant added is 1-1.5% of the oven-dry weight of the ceramic powder; The ball milling solvent consists of toluene and anhydrous ethanol in a weight ratio of 6-7:3-4.

5. The method for preparing a high-precision, high-stiffness ceramic leaf spring according to claim 1, characterized in that, The ceramic leaf spring forming mold used in the mold shaping process includes: an upper mold (1) and a lower mold (2). The lower end of the upper mold (1) has a first forming surface, and the upper end of the lower mold (2) has a second forming surface; After the upper mold (1) and the lower mold (2) are engaged, the first molding surface and the second molding surface are enclosed to form a molding cavity; The middle part of the molding cavity has an upward arched arc structure, and the outer contour shape of the molding cavity is consistent with the outer contour of the ceramic leaf spring.

6. The method for preparing a high-precision, high-stiffness ceramic leaf spring according to claim 1, characterized in that, In the mold setting process, the heating setting involves raising the temperature to 35-45℃ in an air atmosphere, holding the temperature for 10-20 hours, and then raising the temperature to 60-70℃ and holding the temperature for 5-10 hours.

7. The method for preparing a high-precision, high-stiffness ceramic leaf spring according to claim 1, characterized in that, In the sintering process, the ceramic balls are one of the following: silicon nitride ceramic balls, zirconium oxide ceramic balls, and alumina ceramic balls; The diameter of the ceramic spheres is 0.1-0.3 mm; The thickness of the ceramic balls at the bottom of the sintering crucible is 0.2-0.4 mm.

8. The method for preparing a high-precision, high-stiffness ceramic leaf spring according to claim 1, characterized in that, In the sintering process, the heating sintering is carried out in a sintering atmosphere, with the temperature raised to 500-600℃ and held for 60-120 minutes; the heating rate is controlled at 2-5℃ / min, and the temperature is further raised to 1000-1200℃, with the heating rate controlled at 1.5-3℃ / min, and the temperature is further raised to the sintering temperature, held for sintering for 120-240 minutes, and then cooled to obtain a high-precision, high-rigidity ceramic leaf spring.

9. The method for preparing a high-precision, high-stiffness ceramic leaf spring according to claim 8, characterized in that, When the ceramic powder is alumina powder, the sintering powder used in the sintering process is high-purity alumina powder, the sintering atmosphere is air, and the sintering temperature is 1580-1620℃. When the ceramic powder is zirconium oxide powder, the sintering powder used in the sintering process is yttrium-stabilized zirconium oxide powder or alumina powder, the sintering atmosphere is air, and the sintering temperature is 1450-1500℃. When the ceramic powder is silicon nitride powder, the sintering powder used is a mixture of silicon nitride and hexagonal boron nitride, or a mixture of hexagonal boron nitride, yttrium oxide, and alumina. The sintering atmosphere is nitrogen, and the sintering temperature is 1750-1850℃.

10. A high-precision, high-stiffness ceramic leaf spring, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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