A low-glass phase glass-ceramic part and its preparation method

Abstract

This invention provides a low-glass phase glass-ceramic part and its preparation method, wherein the glass-ceramic part has an Ra of 0.01~0.1μm and a coefficient of thermal expansion of 5×10⁻⁶ at 100-300℃. ‑7 / k~50×10 ‑7 / k; The low-glass phase glass ceramics mentioned refer to glass ceramics with a glass phase content of less than 20wt%. The contour accuracy of the low-glass phase glass ceramic parts of the present invention can reach ±0.01mm, which can fully meet the requirements of ultra-precision applications such as optical lenses. They can be applied to electronic product housings, optical lenses, and high-temperature trays, expanding the product boundaries. The method of the present invention adopts an integrated process route of machining and thermal processing, moving the "easiest processing stage" forward to the thermoplastic stage of the base glass, and moving the "high-temperature service performance" backward to the post-ceramization stage, forming a closed-loop "shape-structure-precision" coordinated control.

Description

Technical Field

[0001] This invention relates to the field of advanced manufacturing, particularly to the field of new materials technology. Specifically, this invention relates to a low-glass phase glass-ceramic part, such as a mold, and a method for preparing the same. Background Technology

[0002] Bottlenecks in Engineering Ceramics and Traditional Processing Engineering ceramics (such as alumina, silicon nitride, and silicon carbide) possess advantages such as high hardness, high heat resistance, corrosion resistance, and insulation, and are widely used in structural components, back covers of electronic products, hot-pressing molds for optical lenses, and high-temperature heat treatment carriers (such as trays, brackets, and thermal insulation components). However, their typical drawback is: Poor machinability: Hard and brittle materials make cutting / drilling / tapping difficult, tool wear is high, and the risk of chipping / microcracks is high; High cost and long cycle: It requires high-cost processes such as grinding / polishing, which is especially difficult for complex curved surfaces; Molding and sintering defects: Sintering after molding using methods such as cold pressing, hot pressing, injection molding, and tape casting can easily introduce pores or deformation, resulting in limited yield and consistency of precision parts; When used as a glass thermoforming mold, the biggest challenge is that achieving high-precision machining is too difficult, the machining time is too long, and the resulting high costs are problems.

[0003] Traditional machinable glass ceramics (mainly mica phase) and their limitations To reduce processing difficulty, the industry has developed machinable glass ceramics. A typical system is mica-based glass ceramics with fluorophlogopite as the main crystalline phase. There are also mica-based glass ceramics formed by merging fluorophlogopite powder with a matrix glass powder and then melting / sintering. Glass ceramics (GC) products / parts are widely used in fields such as electronic product casing molding, optical lens manufacturing, and ceramic / crystal material heat treatment trays due to their high temperature resistance, high precision, and high wear resistance.

[0004] However, this type of "high machinability" often relies on the easy-machining characteristics brought about by a high proportion of glass phase and a specific layered crystal structure. Under higher temperature or prolonged high-temperature service conditions, the following challenges may arise: High temperatures increase the risk of structural relaxation, viscoelastic deformation, and surface adhesion / reaction. Dimensional stability / surface quality fluctuations caused by thermal cycling; When used as a glass thermoforming mold, problems such as insufficient lifespan or high maintenance costs may occur.

[0005] Currently, the preparation of glazed ceramic utensils / parts mainly adopts the following two technical routes: A: The "first forming - then heat treatment (crystallization / ceramization)" route for glass and ceramic products / parts A typical approach involves using a "starting glass / base glass" as a blank, obtaining its shape through casting or molding, and then transforming it into a glass-ceramic with a specific crystalline phase through heat treatment. This glass-ceramic is then used as a thermoforming mold to perform gravity sinking / thermal deformation molding of the glass blank. For example, Chinese patent CN1304311C (with related patents such as EP1391433A3) relates to a molding method for glass and glass-ceramic, disclosing a method of casting a starting glass into a mold and then heat-treating it to transform it into a glass-ceramic mold with keatite (thermal quartz / solution) as the main crystalline phase, for molding at temperatures higher than the blank's transformation temperature Tg; US patent US4059428A relates to a method for forming a drooping mold from glass-ceramic; and US patent US6363747B1 relates to the selection of materials for precision glass forming molds. The technical content disclosed in these patent documents all belong to this type of approach.

[0006] B: "Direct machining" route for machinable glass ceramics (such as mica-based / fluorinated phlogopite-based materials) This technical route is relatively mature. A typical approach involves using materials already in a glass-ceramic state of "glass phase + crystalline phase" (e.g., fluorophlogopite as the main crystalline phase), directly obtaining structural components through conventional machining (cutting, drilling, tapping, grinding, polishing). For example, WO2010008443A1 relates to a high-strength, machinable glass-ceramic material system and its preparation; Chinese application CN105906212A relates to a mica-based glass-ceramic and its preparation method; Chinese application CN1609028A discloses a technology for preparing machinable fluorophlogopite glass-ceramics using waste glass sintering; and Chinese application CN108779019B discloses a sintering auxiliary glass for machinable folin silicate-based structures. The technical content disclosed in these patent documents all belong to this type of technical route.

[0007] Route A emphasizes "glass-ceramic molds for glass forming," but fails to integrate "machining—thermal processing (hot pressing / hot bending / reshaping)—ceramization heat treatment—finishing" into a unified, collaborative process to achieve the comprehensive goals of "high precision + high-temperature service + low cost." In existing technologies, the process integration between machining (such as cutting, grinding, and polishing) and thermal processing (such as crystallization heat treatment, hot pressing / hot bending forming) has the following deficiencies: 1. Insufficient precision: Thermal processing (such as crystallization heat treatment) can easily lead to mold deformation. Existing machining processes have limited ability to correct deformation, which cannot meet the requirements of high-precision scenarios such as optical lenses (accuracy ±0.01mm level).

[0008] 2. Poor surface quality: Relying solely on mechanical processing to optimize surface finish without combining it with thermal processing to enhance material properties results in insufficient wear and corrosion resistance of the mold under high temperature and high friction scenarios (such as heat treatment trays).

[0009] 3. Weak scenario adaptability: The mold appearance (planar / non-planar combination), thickness and processing technology are not designed in coordination, making it difficult to meet the needs of multiple scenarios such as electronic product shells (curved surface forming), optical lenses (optical surface precision), and high-temperature trays (uniform heating of parallel surfaces).

[0010] 4. Low process efficiency: The sequence of machining and heat treatment processes is chaotic, and the rework rate is high, resulting in long processing cycles and high costs.

[0011] Route B emphasizes "machinability," but typical mica-based machinable glass ceramics often contain a high proportion of glass phase, which may limit their dimensional stability, creep resistance, adhesion resistance, corrosion resistance, and lifespan under higher temperatures and more demanding thermal cycling. Conversely, a low glass phase (nearly fully ceramized) is beneficial for high-temperature service stability, creep resistance, corrosion resistance, and lifespan. However, with increasing ceramization, the material typically becomes harder and more brittle, increasing the difficulty of processing.

[0012] Therefore, there is an urgent need in the field for a synergistic process that can organically connect the "most suitable processing stage (basic glass / partial ceramic state)" with the "final high-temperature service stage (full ceramic state)" to prepare low glass phase (nearly full ceramic) glass-ceramic parts such as molds. Summary of the Invention

[0013] One object of the present invention is to provide a low-glass phase glass-ceramic part, wherein the Ra of the low-glass phase glass-ceramic part is 0.01~0.1μm, and the coefficient of thermal expansion at 100-300℃ is 5×10⁻⁶. -7 / k~50×10 -7 / k; The low glass phase glass ceramics refer to glass ceramics with a glass phase content of less than 20 wt%.

[0014] In one embodiment, the low-glass phase glass-ceramic part of the present invention further has at least one of the following characteristics: Overall cavity contour dimensional tolerance: less than ±0.01mm; Overall profile of the curved surface: 0.01±0.005mm; Vickers hardness: 800 kgf / mm 2 above.

[0015] According to this application, the low-glass phase glass-ceramic part of the present invention can be a precision structural component or a precision functional component. The precision functional component can be a glass thermoforming mold, a heat treatment carrier, an insulating component, an aerospace component, a wear-resistant ceramic bearing, a medical device, an artificial bone, or a denture. Preferably, the precision functional component is a glass thermoforming mold.

[0016] In one embodiment, the low glass phase glass-ceramic part of the present invention is a glass thermoforming mold having a parallelism of less than 0.005 mm between the upper and lower mold mating surfaces and a clearance of 0.003-0.008 mm between the upper and lower molds.

[0017] Another object of the present invention is to provide a method for preparing low-glass phase glass-ceramic parts, the method comprising the following steps in sequence: 1) Pre-processing The base glass is subjected to at least one rough mechanical processing and / or thermal processing to obtain a preform with the target shape; 2) Ceramicization heat treatment The resulting shaped green body is subjected to at least one ceramic heat treatment, which includes two stages: nucleation treatment and crystallization treatment. 3) Cooling After heat treatment, the ceramized preform is cooled to room temperature to obtain the desired low-glass phase glass-ceramic parts. The low glass phase glass ceramic refers to glass ceramic with a glass phase content of less than 20 wt%, preferably less than 15 wt%, and more preferably less than 10 wt%.

[0018] According to this application, the pre-processing step 1) of the method of the present invention employs one or more of CNC milling, grinding and drilling, and the thermal processing employs one or more of hot pressing, hot bending, casting hot pressing and in-mold reshaping.

[0019] In one embodiment, the method of the present invention further includes the step of: 4) Finishing The obtained glass-ceramic parts are subjected to at least one finishing process to correct the deformation caused by heat treatment, thereby improving the contour accuracy and reducing the surface roughness.

[0020] According to this application, the finishing step 4) of the method of the present invention includes one or more of milling, grinding and polishing.

[0021] In one embodiment, after the cooling step 3) of the method of the present invention is completed and before the finishing step 4), at least one more rough machining operation may be performed, the rough machining operation including one or both of CNC milling and grinding.

[0022] According to this application, the base glass used in the method of the present invention can be a blank of base glass, molten glass of base glass, or a casting of base glass.

[0023] According to this application, the base glass used in the method of the present invention comprises SiO2, Al2O3, and Li2O, in molar percentages. SiO2 accounts for 54-75 mol% of the total composition of the base glass. Al2O3 accounts for 12-24 mol% of the total composition of the base glass. Li2O accounts for 5-15.5 mol% of the total composition of the base glass. The sum of the molar percentages of all components in the base glass is 100 mol.

[0024] In one embodiment, in the pre-processing step 1) of the method of the present invention, 1-2 cm of the base glass can be removed by mechanical rough processing.

[0025] According to this application, in the pre-processing step 1) of the method of the present invention, hot pressing is performed according to the following method: At temperatures of 800~1700℃, the viscosity is 3×10 3 ~4×10 10 A base glass in the centipoise range is placed in a mold, and then a certain pressure is applied to form the base glass. The applied pressure is generally above 0.1 MPa, preferably above 0.3 MPa, and more preferably above 0.45 MPa.

[0026] Preferably, the mold used in the pre-processing step 1) of the method of the present invention is a cast iron mold with a fixed shape.

[0027] In one embodiment, after the pre-processing step 1) and before the ceramicizing heat treatment step 2) of the method of the present invention, the base glass is annealed after molding to form a molded preform with the target shape.

[0028] According to this application, in the ceramicizing heat treatment step 2) of the method of the present invention, the ceramicizing heat treatment is performed according to the following steps: a) The obtained preform is subjected to nucleation treatment at a temperature of 650℃~740℃ for a time of 4~30 h; b) After the nucleation process is completed, the temperature is raised to 780~980℃, and the nucleated blank is crystallized in situ for 0.3~40 h.

[0029] In one embodiment, according to the method of the present invention, during the ceramicization heat treatment, in step a), the formed green body is heated from the initial temperature to the nucleation temperature at a first heating rate; In step b), the nucleated preform is heated from the nucleation temperature to the crystallization temperature at a second heating rate; The first heating rate may be the same as or different from the second heating rate.

[0030] In one embodiment, during the ceramization heat treatment, the first heating rate is 1~20℃ / min, and the second heating rate is 1~15℃ / min.

[0031] According to this application, in the cooling step 3) of the method of the present invention, the ceramicized green body can be cooled from the crystallization temperature to room temperature by natural cooling or by a certain cooling rate.

[0032] In one embodiment, the cooling step 3) of the method of the present invention cools the ceramicized preform from the crystallization temperature to room temperature at a certain cooling rate, preferably 1~10℃ / min.

[0033] According to this application, the low glass phase glass-ceramic parts prepared by the present invention can be precision structural parts or precision functional components. The precision functional components include, but are not limited to, glass thermoforming molds, heat treatment carriers, insulating parts, aerospace components, wear-resistant ceramic bearings, medical devices, artificial bones, dentures, etc.

[0034] In one embodiment, the low glass phase glass-ceramic part involved in this invention is a glass thermoforming mold, and when used for glass thermoforming, the mold is designed according to the following formula to ensure that the glass being processed can fit into the mold during heat treatment, and can be easily demolded after cooling and reach the target size: Lm0=Lf×(1+xΔT) / (1+aΔT) in: Lm0 is the initial size of the glass thermoforming mold at room temperature; Lf is the preset final product size of the glass being processed; x is the coefficient of thermal expansion of the glass being processed; ΔT is the temperature difference between the heat treatment temperature and room temperature; 'a' represents the coefficient of thermal expansion of the glass thermoforming mold.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Breakthrough in precision: Through a cyclical process of "preliminary hot forming + rough mechanical finishing + heat treatment + fine mechanical / hot finishing", the contour accuracy of glass and ceramic parts such as molds can reach ±0.01mm, which can fully meet the ultra-precision requirements of optical lenses and other applications. In contrast, the contour accuracy obtained by traditional processes is only ±0.05mm.

[0036] 2. Surface quality and lifespan optimization: The synergistic effect of multiple machining processes (grinding, polishing) and heat treatment material reinforcement significantly improves the surface finish of the prepared glass-ceramic parts, such as molds. Especially in high-temperature scenarios (such as heat treatment trays), the lifespan of the prepared molds can be extended by more than 30%.

[0037] 3. Seamless adaptation to multiple scenarios: The appearance structure (planar / non-planar), thickness and processing technology are deeply coordinated, so that the prepared glass ceramic parts, such as molds, can be used simultaneously in electronic product shells (curved surface forming), optical lenses (optical surface precision), and high-temperature trays (uniform heating of parallel surfaces), expanding the product boundaries.

[0038] 4. Process efficiency innovation: Optimized process sequence reduces rework and shortens the overall processing cycle by 20% - 30%, resulting in significant cost reduction and efficiency improvement.

[0039] 5. Improved processing efficiency: Before the ceramicization heat treatment, the machinability / thermoplasticity of the base glass is used to complete most of the excess material removal and shaping, which significantly reduces the high cost of grinding on hard and brittle ceramics after ceramicization.

[0040] 6. Cost reduction: Reduced tool wear, shorter machining cycle time, and lower rework rate.

[0041] 7. High precision and consistency: Fine finishing after ceramization is used to correct heat treatment deformation, achieving controllable contour accuracy and surface quality.

[0042] 8. High-temperature lifespan and stability: Low glass phase (nearly fully ceramicized) GC exhibits better dimensional stability and lifespan during high-temperature forming / heat treatment cycles.

[0043] 9. Advantages of mold application: When used for glass thermoforming, it can significantly improve the lifespan of molds compared to graphite molds and reduce the dependence on protective atmospheres (such as nitrogen).

[0044] 10. Replacement for high-hardness metal molds: Compared with high-hardness molds such as tungsten alloys, the GC solution has advantages such as easier processing, lower material costs, and more convenient realization of complex curved surfaces.

[0045] 11. Wide range of applications: It can cover glass thermoforming molds, heat treatment carriers, and various structural / insulating parts. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the manufacturing process of the low glass phase glass-ceramic part of the present invention.

[0047] Figure 2 This is a photograph of the 3D glass-ceramic mold sample prepared in Example 4.

[0048] Figure 3This is the XRD pattern of the 3D glass-ceramic mold sample prepared in Example 4, where au represents strength.

[0049] Figure 4 This is the JADE phase diagram of the 3D glass-ceramic mold sample prepared in Example 4.

[0050] Figure 5 This is a SEM image of the 3D glass-ceramic mold sample prepared in Example 4. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] Existing machinable GCs typically involve "pure machining after forming" to avoid heat treatment. However, this invention creatively proposes a combination of "high-efficiency forming / rough machining before ceramization and shape correction and finishing after ceramization," establishing a window and process synergy for "low glass phase / near-full ceramization" systems, which can simultaneously meet the requirements of high-temperature life and processing efficiency.

[0053] The GC part processing method of the present invention adopts an integrated process route of machining and thermal processing, moves the "easiest processing stage" forward to the thermoplastic stage of the base glass, and moves the "high temperature service performance" backward to the stage after ceramization (low glass phase / near full ceramization), forming a closed-loop "shape-structure-precision" coordinated control.

[0054] Furthermore, according to this application, the low-glass phase glass-ceramic parts, such as molds, prepared by this invention can meet the needs of multiple scenarios through customized design of "surface features + appearance morphology + thickness adaptation": Surface characteristics: The surface finish of the mold working surface (roughness range Ra is 1.6-0.05μm) can be customized to suit different precision scenarios, such as Ra≤0.8μm for electronic product shells and Ra≤0.1μm for optical lenses.

[0055] Appearance: It can be combined in various planar / non-planar ways. The parallel structure is suitable for GC ceramicization and ceramic heat treatment trays (to ensure uniform heating); the non-planar structure is suitable for the curved surfaces of electronic product shells and the curved surfaces of optical lenses.

[0056] Thickness and application: The thickness of the mold can also be customized according to the strength and lightweight requirements of different scenarios, such as 5-10mm for heat treatment trays and 3-5mm for optical lenses.

[0057] When the low glass phase glass-ceramic part prepared by this invention is used as a mold, the difference in the coefficients of thermal expansion between the glass and the ceramic mold should be carefully considered when designing the size profile of the glass and the ceramic mold to ensure that the glass can fit well with the mold during heat treatment and can be easily demolded and reach the target size after cooling.

[0058] Given the material properties of the glass to be processed (coefficient of thermal expansion x, density y) and the ceramic mold (coefficient of thermal expansion a, density b), for the process of heating from room temperature T0 to heat treatment temperature T1 (temperature difference ΔT = T1), The T0 process is designed to ensure that the glass can completely fit the mold cavity at T1 and reach the preset final product size Lf after cooling back to T0. At the same time, it ensures that the glass will not crack due to thermal stress and can be demolded smoothly, avoiding mold jamming.

[0059] When the temperature changes, the size change of the material can be approximated as linear: for glass, its initial size Lg0 at room temperature T0 will become Lg = Lg0 × (1 + xΔT) when the temperature rises to T1. Correspondingly, the initial size Lm0 of the ceramic mold cavity at room temperature T0 will become Lm = Lm0 × (1 + aΔT) at temperature T1.

[0060] To ensure the glass adheres to the mold at a high temperature T1 and reaches the target size Lf after cooling to room temperature T0, the mold's design size Lm0 at room temperature should be compensated based on the coefficients of thermal expansion of both, using the following formula: Lm0=Lf×(1+xΔT) / (1+aΔT) The formula ensures dimensional matching at high temperatures by compensating for the difference in thermal expansion (x and a) between the glass and the mold, so that the glass shrinks exactly to Lf after cooling.

[0061] In this application, the term "base glass" refers to glass that has not undergone nucleation or crystallization treatment.

[0062] In this application, the term "ceramization" refers to the process of obtaining a homogeneous composite material of microcrystals and glass phase by directionally precipitating a large number of fine crystals inside a base glass through controlled crystallization heat treatment. Simply put, it is the process of transforming a base glass into a microcrystalline glass that combines glass-forming properties with ceramic properties.

[0063] In this application, the term "nucleation" refers to the growth of tiny crystal nuclei from nucleating material in a base glass through heat treatment.

[0064] In this application, the term "crystallization" means growing a base glass into a crystal based on a nucleus through heat treatment.

[0065] In this application, the term "crystal phase" refers to a single type of crystal precipitated in a glass-ceramic, which has a definite crystal structure and chemical composition.

[0066] Example 1. Preparation Examples Examples 1-6 were prepared using the following methods, wherein the glass-ceramic molds prepared in Examples 1-3 were 2.5D molds, and the glass-ceramic molds prepared in Examples 4-6 were 3D molds.

[0067] 1.1 Preparation of basic glass preform The base glass used is provided by Hubei Gobija Optoelectronic Technology Co., Ltd. This base glass belongs to the lithium aluminum silicon glass system, and its formula and properties are listed in Table 1 below. The base glass is placed in a high-temperature furnace and melted at 1600℃ to obtain a base glass blank. This glass blank is in a fluid state with a viscosity of 5475 centipoise, leaving a processing allowance of approximately 2 cm.

[0068] 1.2 Rough Machining Using a large-diameter (φ=10mm) diamond grinding head, the excess material of the base glass blank is quickly removed, and the preliminary outline is formed by CNC machining, thus obtaining the base glass blank with the preliminary outline.

[0069] 1.3 Hot pressing At 1600℃, a basic glass preform with a viscosity of 5475 centipoise and a preliminary outline is immediately placed into a pre-designed 250×180×80mm HT200 cast iron mold (Ra≤0.8μm, 2.5D or 3D mold) and the mold cavity is filled completely. Then, a pressure of 0.5MPa is applied. After it sets, it is annealed to obtain a preliminary shaped glass mold preform.

[0070] 1.4 Ceramicization heat treatment and cooling The pre-formed glass mold blank is subjected to ceramic heat treatment, which includes two stages: nucleation treatment and crystallization treatment. In the nucleation treatment stage, the formed glass mold blank is heated from the initial temperature to the nucleation temperature at a first heating rate. In the crystallization treatment stage, the nucleated formed blank is heated from the nucleation temperature to the crystallization temperature at a second heating rate.

[0071] After the ceramization heat treatment is completed, the ceramized green body is cooled from the crystallization temperature to room temperature at a certain cooling rate.

[0072] The process conditions used and the crystal phase structure of the resulting glass-ceramic mold are listed in Table 2 below.

[0073] 1.5 Finishing 1.5.1 Preparations before processing Machine tool preparation A high-precision, high-rigidity, high-speed CNC machining center (JDMR600) was selected. The worktable and spindle taper hole were thoroughly cleaned. A warm-up procedure was performed to allow the spindle and guideways to reach a thermally stable state.

[0074] knife preparation Prepare diamond grinding heads of different diameters for machining. Use a hydraulic tool holder to clamp the grinding head shank, ensuring clamping rigidity and strictly controlling radial runout within 0.005mm. Use a tool setter to accurately measure the effective grinding length of the grinding head and the outer diameter of the grinding wheel, and enter the compensation data into the machine tool.

[0075] Workpiece clamping Use a special fixture and place a soft resin pad between the workpiece and the fixture; ensure that the clamping force is uniform and appropriate to prevent excessive tightness from cracking the workpiece; use a dial indicator to align the workpiece and ensure parallelism and perpendicularity.

[0076] 1.5.2 Processing Roughing: Using a large-diameter (φ=10mm) diamond grinding head, set the lowest feed rate to 0.5m / min, depth of cut to 0.1mm, and speed to 15000 rpm. A layered grinding method is employed, maintaining a constant grinding force to quickly and safely remove approximately 1.5mm of material. Semi-finishing: Switching to an 8mm diameter diamond grinding head for shaping, the speed is increased to 20000 rpm, the feed rate is reduced to 0.08m / min, and the depth of cut is reduced to 0.05mm. This stage leaves a uniform allowance of approximately 0.2mm for finishing. After this stage, inspect the surface for abnormal grinding marks or microcracks. Finishing: Switching to a 6mm diameter spherical diamond grinding head, using a maximum speed of 30000 rpm and a minimum feed rate of 0.2m / min, fine contour grinding is performed to achieve the final dimensions and surface finish. Corner clearing and detail machining: Use a small-diameter PCD tool with a diameter of φ=4mm and a very low feed (0.4m / min) to perform local machining to clean up narrow grooves, sharp corners and other areas that the previous tool could not reach.

[0077] 1.5.3 Post-processing Hand polishing: Using diamond polishing paste produced by Novax, from W40 to W1.0, polishing is performed on a precision grinding head from coarse to fine to further enhance the mirror effect of the cavity surface.

[0078] Ultrasonic cleaning: The glass-ceramic mold prepared by the above process is placed into an ultrasonic cleaner, and the cleaning solution is used to remove the ceramic dust attached to the micropores and gaps.

[0079] 2. Performance Testing All critical dimensions of the obtained glass-ceramic mold were inspected using a coordinate measuring machine (CMM) in accordance with ISO 10360-2 method.

[0080] The surface profile of the obtained glass-ceramic mold was inspected using a coordinate measuring machine (CMM) in accordance with ISO 1101 method.

[0081] The parallelism of the mating surfaces of the upper and lower molds of the obtained glass-ceramic mold was checked using a coordinate measuring machine (CMM) in accordance with ISO 10360 method.

[0082] The Ra value was measured using a white light interferometer manufactured by Mitutoyo in accordance with ISO 25178, and the corners and seams of the obtained glass-ceramic mold were examined with a microscope for microscopic chipping or cracks.

[0083] The gap between the upper and lower molds of the obtained glass-ceramic mold was measured using a coordinate measuring machine (CMM) in accordance with ISO 10360-2 method.

[0084] According to GB / T 37900-2019 "Test Methods for Hardness and Fracture Toughness of Ultrathin Glass - Small Load Vickers Hardness Indentation Method", the Vickers hardness of the obtained glass-ceramic mold was tested using a Matsuzawa MMT-X7B-HRE microhardness tester from Japan.

[0085] The coefficient of thermal expansion of the obtained glass-ceramic mold was tested using the DIL 402 PC manufactured by NETZSCH, based on the DIL 402 PC method.

[0086] The obtained glass-ceramic mold has been tested and found to meet all the requirements of glass thermoforming molds, and can completely replace traditional graphite molds. The average values ​​of the measurement results are listed in Table 3 below.

[0087] Table 1. Formulation of the base glass used

[0088] Table 2. Process conditions used in the ceramicization heat treatment and characteristics of the resulting glass-ceramic molds.

[0089] Table 3 Test results of the obtained glass-ceramic molds

[0090] XRD tests were also performed on the glass-ceramic mold samples prepared in each embodiment. The results showed that highly crystalline crystals were formed inside the glass-ceramic molds, and the crystal phases of the crystals are listed in Table 2. Figure 3 The image shows the XRD pattern of the 3D glass-ceramic mold sample prepared in Example 4, which indicates that the crystal phase of the formed crystal is spodumene, with the chemical formula LiAlSi2O6.

[0091] The 3D glass-ceramic mold sample prepared in Example 4 was subjected to JADE phasing, and the phasing results are shown in [Figure 4]. Figure 4 . Figure 4 Further analysis revealed that the sample's crystalline phase was spodumene, with the chemical formula LiAlSi2O6, a crystal ratio of 100% (i.e., a crystallinity of 100wt%), and a grain size of 791.2 nm.

[0092] Similarly, crystallinity and grain size data of glass-ceramic molds of other embodiments were obtained and the results are listed in Table 2. It can be seen from the data in Table 2 that the glass-ceramic mold of the present invention is approximately ceramicized and the crystallinity can reach up to 100 wt%.

[0093] The 3D glass-ceramic mold sample prepared in Example 4 was scanned by electron microscopy, and its SEM image is shown below. Figure 5 .from Figure 5 It can be seen that the crystals are densely distributed, and the grains are aggregated together to form elliptical particles with a particle size of about 1 μm. There is no obvious glass phase region in the entire sample.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-glass phase glass-ceramic part, characterized in that, The Ra of the low-glass phase glass-ceramic part is 0.01~0.1μm, and the coefficient of thermal expansion at 100-300℃ is 5×10⁻⁶. -7 / k~50×10 -7 / k; The low glass phase glass ceramics refer to glass ceramics with a glass phase content of less than 20 wt%.

2. The low-glass phase glass-ceramic part according to claim 1, characterized in that, The low-glass phase glass-ceramic part also has at least one of the following characteristics: Overall cavity contour dimensional tolerance: less than ±0.01mm; Overall profile of the curved surface: 0.01±0.005mm; Vickers hardness: 800 kgf / mm 2 above.

3. The low-glass phase glass-ceramic part according to claim 2, characterized in that, The low glass phase glass-ceramic parts are precision structural components or precision functional components, including glass thermoforming molds, heat treatment carriers, insulating components, aerospace parts, wear-resistant ceramic bearings, medical devices, artificial bones, or dentures.

4. The low-glass phase glass-ceramic part according to claim 3, characterized in that, The low glass phase glass-ceramic part is a glass thermoforming mold, which has a parallelism of less than 0.005 mm between the upper and lower mold mating surfaces and a gap of 0.003-0.008 mm between the upper and lower molds.

5. A method for preparing the low-glass phase glass-ceramic part according to claim 1, characterized in that, The method includes the following steps in sequence: 1) Pre-processing The base glass is subjected to at least one rough mechanical processing and / or thermal processing to obtain a preform with the target shape; 2) Ceramicization heat treatment The resulting shaped green body is subjected to at least one ceramic heat treatment, which includes two stages: nucleation treatment and crystallization treatment. 3) Cooling After heat treatment, the ceramized preform is cooled to room temperature to obtain the desired low-glass phase glass-ceramic parts.

6. The method according to claim 5, characterized in that, The pre-processing step 1) includes one or more of CNC milling, grinding and drilling, and the hot processing includes one or more of hot pressing, hot bending, casting hot pressing and in-mold reshaping.

7. The method according to claim 5, characterized in that, The method further includes the following steps: 4) Finishing The obtained glass-ceramic parts are subjected to at least one finishing process to correct the deformation caused by heat treatment, thereby improving the contour accuracy and reducing the surface roughness.

8. The method according to claim 7, characterized in that, The finishing process in step 4) includes one or more of milling, grinding and polishing.

9. The method according to claim 8, characterized in that, After the cooling step 3) is completed and before the finishing step 4), at least one roughing operation is performed, which includes one or both of CNC milling and grinding.

10. The method according to any one of claims 5-9, characterized in that, The base glass is the blank of the base glass, the molten glass of the base glass, or the casting of the base glass.

11. The method according to claim 10, characterized in that, The base glass comprises SiO2, Al2O3, and Li2O, in molar percentages. SiO2 accounts for 54-75 mol% of the total composition of the base glass. Al2O3 accounts for 12-24 mol% of the total composition of the base glass. Li2O accounts for 5-15.5 mol% of the total composition of the base glass. The sum of the molar percentages of all components in the base glass is 100 mol.

12. The method according to claim 10, characterized in that, In the pre-processing step 1), 1-2 cm of the base glass is removed by rough mechanical processing.

13. The method according to claim 10, characterized in that, In pre-processing step 1), hot pressing is performed according to the following method: At temperatures of 800~1700℃, the viscosity is 3×10 3 ~4×10 10 The base glass in the centipoise range is placed in a mold, and then a certain pressure is applied to shape the base glass.

14. The method according to claim 13, characterized in that, The mold is a cast iron mold with a fixed shape.

15. The method according to claim 13, characterized in that, The pressure applied during hot pressing is above 0.1 MPa.

16. The method according to claim 15, characterized in that, The pressure applied during hot pressing is above 0.3 MPa.

17. The method according to claim 16, characterized in that, The pressure applied during hot pressing is above 0.45 MPa.

18. The method according to claim 13, characterized in that, The base glass is annealed after molding to form a preform with the target shape.

19. The method according to claim 10, characterized in that, In step 2) of the ceramicizing heat treatment, the ceramicizing heat treatment is carried out according to the following steps: a) The obtained preform is subjected to nucleation treatment at a temperature of 650℃~740℃ for a time of 4~30 h; b) After the nucleation process is completed, the temperature is raised to 780~980℃, and the nucleated blank is crystallized in situ for 0.3~40 h.

20. The method according to claim 19, characterized in that: In step a), the preform is heated from the initial temperature to the nucleation temperature at a first heating rate; In step b), the nucleated preform is heated from the nucleation temperature to the crystallization temperature at a second heating rate; The first heating rate may be the same as or different from the second heating rate.

21. The method according to claim 20, characterized in that, The first heating rate is 1~20℃ / min, and the second heating rate is 1~15℃ / min.

22. The method according to claim 19, characterized in that, In cooling step 3), the ceramicized green body is cooled from the crystallization temperature to room temperature by natural cooling or by cooling the ceramicized green body from the crystallization temperature to room temperature at a certain cooling rate.

23. The method according to claim 22, characterized in that, In cooling step 3), the ceramicized preform is cooled from the crystallization temperature to room temperature at a certain cooling rate of 1~10℃ / min.

24. The method according to claim 10, characterized in that, The low-glass phase glass-ceramic part is a glass thermoforming mold. When used for glass thermoforming, the mold is designed according to the following formula to ensure that the glass being processed can fit the mold during heat treatment, and can be easily demolded after cooling and reach the target size: Lm0=Lf×(1+xΔT) / (1+aΔT) in: Lm0 is the initial size of the glass thermoforming mold at room temperature; Lf is the preset final product size of the glass being processed; x is the coefficient of thermal expansion of the glass being processed; ΔT is the temperature difference between the heat treatment temperature and room temperature; 'a' represents the coefficient of thermal expansion of the glass thermoforming mold.

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