Special alpha-SiC ceramic grinding wheel for accurate grinding of ZrO2 gem and preparation method and application of special alpha-SiC ceramic grinding wheel

Abstract

The invention relates to the technical field of precision machining of superhard materials, in particular to a special alpha-SiC ceramic grinding wheel for fine grinding of ZrO2 gemstone, which comprises the following components in percentage by weight: 70-80% of alpha-SiC, 0.5-1 per mill of binder, 25-30 per mill of wetting agent and binding agent. The alpha-SiC is a mixture of 150 # and 180 #, the binder is 800-mesh water-soluble beta-cyclodextrin powder, and the wetting agent is water-soluble beta-cyclodextrin liquid. The binding agent is prepared by mixing and ball-milling analytically pure SiO2, Al2O3, KOH, low-melting-point borosilicate glass powder and nano cryolite according to a specific proportion. The preparation method comprises the steps of mixing, pressing, drying, sintering and the like, and a three-dimensional mixer and a high-temperature sintering furnace are adopted. The grinding wheel is used for accurate grinding of ZrO2 gemstones, the grinding parameters are that the rotating speed is 45 m / s, the feed amount is 0.015 mm, the grinding allowance is 0.05 mm, after grinding, the roughness Ra is smaller than or equal to 0.2 micron, the durability is larger than or equal to 1.2 million gemstones are trimmed once, the problems of precision, efficiency, surface defects and the like of ZrO2 gemstone grinding in the prior art can be solved, and the comprehensive performance is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of precision machining of superhard materials. Specifically, it relates to a special a-SiC ceramic grinding wheel for precision grinding of ZrO2 gemstones, its preparation method and application. Background Art

[0002] The manufacturing process of artificial gemstones is controllable and has a lower cost, so the price is more affordable. Moreover, artificial gemstones are usually superior to natural gemstones in terms of clarity, color, size, etc. During the production process, the product quality can be improved by adjusting process parameters and chemical compositions. Therefore, the comprehensive cost performance of artificial gemstones is superior to that of natural gemstones.

[0003] Gemstones are geometric bodies composed of various crystal faces. The reason why gemstones shine brightly is mainly manifested through the reflection, refraction or projection of light by the faces. Therefore, to make the light present the best optical effect when shining on the gemstone, the processing of the intersection lines between gemstone faces is required to be particularly strict. Due to differences in chemical composition and chemical bonds, different gemstone crystals have different crystal characteristics, and at the same time form different optical orientations and optical properties.

[0004] The processing of gemstones requires that each type of gemstone must be processed according to a certain optical orientation, which is specifically reflected in the requirements for the size, shape, number of crystal faces of the gemstone, and the included angles between the faces, so as to ensure that it presents the best optical effect.

[0005] In recent years, the global gemstone market scale has continued to grow. In 2023, the global gemstone and jewelry market scale was approximately 372.71 billion US dollars, and it is expected to reach 463.85 billion US dollars by 2030, with a compound annual growth rate of 3.2%. The jewelry market in China has also entered a period of rapid development. In 2023, the scale of the Chinese jewelry market reached 820 billion yuan, a year-on-year increase of 14%. Looking ahead to the next five years, the scale of the Chinese jewelry market will continue to show an upward trend.

[0006] With the increase in the demand in the jewelry market, inevitably higher requirements are put forward for the gemstone processing industry, developing towards "high speed, high precision, and high efficiency", which also poses new requirements and challenges to the abrasive and grinding tool industry.

[0007] Natural ZrO2 mostly exists as monoclinic crystals and mainly exists as the mineral "baddeleyite" in nature. Zirconia existing as cubic single crystals in nature is extremely rare, but it can be synthesized artificially and is an artificial synthetic gemstone that is widely used to replace diamonds. Cubic zirconia has a relatively high density, with a specific gravity of 5.6 to 6.0, and its hardness reaches 8.5. Although it is lower than that of diamonds, it has exceeded most natural gemstones. Its refractive index is 2.15 to 2.18, slightly lower than 2.417 of diamonds, but its surface has an adamantine luster. Its dispersion index reaches 0.058 to 0.066, exceeding that of diamonds. Almost no diamonds are completely colorless, and usually diamonds have a light yellow color. However, cubic zirconia can be made to the highest grade of diamonds, that is, D-grade color.

[0008] ZrO2 is an artificial gemstone that is more wear-resistant and harder than most natural gemstones. It has high gloss and refractive index, can almost rival natural diamonds, and is relatively inexpensive. Due to its hard texture, it is more difficult to process.

[0009] In the prior art, although grinding wheels for grinding sapphires are disclosed, both the grinding precision and efficiency need to be improved. In addition, sapphire and ZrO2 gemstones are two different gemstones. For example, Chinese Patent No. CN201910463496.9 discloses a grinding tool for processing single-crystal sapphire. By adding phase change materials, reinforcing materials, modified polysaccharide binders, etc., the regulation of the friction heat distribution at the processing interface is realized, and the thermal damage on the surface of single-crystal sapphire is reduced. However, since the cutting force of the grinding wheel in this patent is poor and the grinding efficiency is low, it cannot improve the precision between the gemstone surfaces. Summary of the Invention

[0010] The purpose of the present invention is to provide a special a-SiC ceramic grinding wheel for precision grinding of ZrO2 gemstones, its preparation method and application, so as to solve the problems proposed in the above background technology.

[0011] To achieve the above purpose, the present invention provides a special a-SiC ceramic grinding wheel for precision grinding of ZrO2 gemstones, which includes the following raw materials by weight percentage: 70%-80% of a-SiC, 5‰-10‰ of binder, 25‰-30‰ of wetting agent, and the balance is the binder.

[0012] Preferably, the specifications of the a-SiC are a mixture of 150# and 180#; the particle size of the binder is 800 mesh.

[0013] Preferably, the binder is water-soluble β-cyclodextrin powder; the wetting agent is water-soluble β-cyclodextrin solution.

[0014] Preferably, the preparation method of the binder includes the following steps:

[0015] S11: Mix and proportion each component in the raw materials to obtain a mixture. The raw materials are composed of the following components by weight percentage:

[0016] Analytical pure SiO₂ 51%-61%, analytical pure Al₂O₃ 12%-22%, analytical pure KOH 4%-14%, low-melting-point borosilicate glass powder 5%-15%, and the balance is nano-cryolite;

[0017] S12: Ball-mill the mixture in step S11 for 5.5 - 6.5 hours, and pass it through a sieve with 80 - 100 meshes to obtain a binder.

[0018] Preferably, the mass percentages of each chemical component in the low-melting-point borosilicate glass powder are as follows: silicon dioxide 71%-74%, aluminum oxide <1.5%, iron oxide <0.1%, K₂O + Na₂O <8.5%, boron trioxide 18%-19%, loss on ignition <0.1%; the refractoriness is 740 - 760 °C.

[0019] On the other hand, the present invention also provides a preparation method for a special a-SiC ceramic grinding wheel for precision grinding of ZrO₂ gems, including the following steps:

[0020] S21: Add a wetting agent to a-SiC, mix for 18 - 22 min, then add a binder and a bonding agent and mix for 25 - 35 min, pass through a sieve with 12 - 20 meshes, and keep the material in a closed state at room temperature for ≥72 hours to obtain a mixed material;

[0021] S22: Put the mixed material into a mold, keep the pressure at 15 - 20 MPa for 25 - 35 s to form a shape, then dry at 80 °C - 120 °C for ≥52 hours, and finally sinter at 910 - 940 °C for 20 - 28 hours. After demolding, a special a-SiC ceramic grinding wheel for precision grinding of ZrO₂ gems is obtained.

[0022] Preferably, the mixing of the mixed materials in steps S12 and S21 is carried out using a three-dimensional solid mixer.

[0023] Preferably, the sintering process in step S22 is carried out using a high-temperature sintering furnace.

[0024] In addition, the present invention also provides an application of a ceramic grinding wheel in the precision grinding of ZrO₂ gems. The grinding wheel is used for precision grinding of ZrO₂ gems. After grinding, the surface roughness Ra ≤ 0.2 μm, and the durability is ≥12,000 gems for one dressing.

[0025] Preferably, the grinding parameters of the a-SiC ceramic grinding wheel are controlled as follows: the grinding wheel speed is 45 m / s, the feed rate is 0.015 mm, and the grinding allowance is 5 silk, that is, 0.05 mm.

[0026] Compared with the prior art, the beneficial effects of the present invention:

[0027] 1. The present invention optimizes the types and particle size ranges of abrasives. The a-SiC abrasive belongs to a hexagonal structure, has a stable crystal structure and chemical properties, and has a very high hardness, high thermal conductivity, and a small thermal expansion coefficient. Compared with traditional silicon carbide abrasives, it can significantly improve the comprehensive grinding effect of the special ceramic grinding wheel for fine grinding of ZrO2 gemstones. In addition, abrasives with sharp crystal shapes and narrow particle size ranges are selected to solve problems such as scratching and burning of ZrO2 gemstones, and at the same time, the grinding ratio, grinding efficiency are improved, and the frequency of dressing the grinding wheel is reduced, etc.

[0028] 2. When preparing the grinding wheel of the present invention, aiming at the problem of out-of-tolerance accuracy between the fine grinding surfaces of ZrO2 gemstones, a special formula with high density and low binder is adopted, thereby solving the problems of frequent dressing and low efficiency required during the grinding of ZrO2 gemstones. While reducing the dressing frequency, the service life of the grinding wheel is also improved.

[0029] 3. The special ceramic grinding wheel for fine grinding of ZrO2 gemstones of the present invention performs fine grinding on ZrO2 gemstones, and can ensure that the accuracy between surfaces meets the requirements after testing. The durability is to dress once for 12,000 ZrO2 gemstones. After grinding, the surface roughness Ra ≤ 0.2 μm, and there are no surface defects such as burning, vibration marks, and scratches. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are further explained in detail, but do not constitute a limitation to the present invention.

[0031] Figure 1 is a photo of the ZrO2 gemstone after fine grinding using this patent;

[0032] Figure 2 is a photo of the ZrO2 gemstone after fine grinding using Embodiments 1 and 2 of the present invention;

[0033] Figure 3 is a photo of the ZrO2 gemstone after fine grinding using Embodiments 1 and 3 of the present invention;

[0034] Figure 4 is a photo of the ZrO2 gemstone after fine grinding using Embodiments 1 and 4 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present invention.

[0036] The model specifications and manufacturers of the materials used in the specific embodiments are as follows:

[0037] Silica, analytical reagent grade. Manufacturer: Xilong Science Co., Ltd. Its main chemical components are as follows:

[0038]

[0039] Aluminum oxide, analytical reagent grade. Manufacturer: Sinopharm Chemical Reagent Co., Ltd. Its main chemical components are as follows:

[0040]

[0041] Potassium hydroxide, analytical reagent grade. Manufacturer: Sinopharm Chemical Reagent Co., Ltd. Its main chemical components are as follows:

[0042]

[0043] Nano-cryolite, with a specification of 600 nm. Manufacturer: Tianjin Huasheng Chemical Reagent Co., Ltd. Its main chemical components are as follows:

[0044] Chloride Sulfate Silicate Iron Heavy metal ≤0.001 ≤0.003 ≤0.01 ≤0.005 ≤0.002

[0045] The binder used in the following embodiments is water-soluble β-cyclodextrin powder. The viscosity of a 16.8% solution at 25°C should be greater than 1.44E, and the solubility at 25°C should be ≥97.6%. The particle size is 800 mesh. Manufacturer: Shandong Xiwang Sugar Industry Co., Ltd.;

[0046] The wetting agent used in the following embodiments is water-soluble β-cyclodextrin solution, with a specific gravity of 1.09 g / cm3 - 1.13 g / cm3. Manufacturer: Shandong Xiwang Sugar Industry Co., Ltd.;

[0047] The silicon carbide used in the following embodiments is a-SiC, with particle sizes of 150# and 180#. Manufacturer: Shanghai Liantian Material Technology Co., Ltd.

[0048] Example 1

[0049] Example 1 provides a method for preparing a binder for a ceramic grinding wheel. The specific steps are as follows:

[0050] 1) Mix and proportion the components in the raw materials to obtain a mixture. The raw materials are composed of the following components by weight percentage: 56% of silica, analytical reagent grade; 17% of aluminum oxide, analytical reagent grade; 9% of potassium hydroxide, analytical reagent grade; 10% of low-melting borosilicate glass; 8% of nano-cryolite;

[0051] 2) Ball mill the mixture in step 1) for 6 hours and pass through a 100-mesh sieve to obtain the binder.

[0052] In Step 1), the characteristics of the low-melting borosilicate glass powder are as follows:

[0053] a. Chemical composition (by mass percentage): silica 71% - 74%, aluminum oxide < 1.5%, iron oxide < 0.1%, K2O + Na2O < 8.5%, boron trioxide 18% - 19%, ignition loss < 0.1%;

[0054] b. Refractoriness is between 740 - 760 °C.

[0055] The addition of analytical pure SiO2, Al2O3, and KOH increases the purity of the binder and also improves the strength of the binder. Among them, analytical pure SiO2 is the main component of the binder, which increases the chemical stability, strength, and grinding sharpness of the binder. In addition, the introduction of nano-cryolite in the binder mainly serves to improve the wear resistance of the special a-SiC ceramic grinding wheel for fine grinding ZrO2 gemstones. The use of nano-scale cryolite in the binder can reduce the refractoriness of the binder while increasing the reaction activity of the binder compared with ordinary cryolite. By introducing low-melting borosilicate glass powder and taking advantage of its low refractoriness, the strength of the binder can be increased. Under the same grinding wheel hardness, the addition amount of the grinding wheel binder of the present invention is less, which improves the grinding efficiency of the abrasive grains and reduces the dressing frequency of the grinding wheel, effectively avoiding the burning of ZrO2 gemstones during the fine grinding process.

[0056] Example 2

[0057] A special a-SiC ceramic grinding wheel for fine grinding ZrO2 gemstones. The ceramic grinding wheel described in Example 2 is used for fine grinding ZrO2 gemstones. By weight percentage, the formula of the grinding wheel is: a-SiC 150# 40%, a-SiC 180# 40%, water-soluble β-cyclodextrin powder 10‰, water-soluble β-cyclodextrin solution with a specific gravity of 1.12 g / cm3 25‰, and the binder described in Example 1 20%.

[0058] The preparation method of the special ceramic grinding wheel for fine grinding ZrO2 gemstones specifically comprises the following steps:

[0059] (1) First, add a wetting agent to the abrasive a-SiC and mix for 20 min using a three-dimensional mixer, then add the binder and the binder and mix and stir for 30 min. Finally, pass through a 20-mesh fine sieve and stuff the material for 72 hours;

[0060] (2) Use a 400-ton cold press to press and form at a pressure of 17.5 MPa for 30 s, and then dry at 100 °C for 72 hours; sinter using a high-temperature sintering furnace, the sintering temperature is 920 °C, and the heat preservation time is 24 hours to obtain.

[0061] Example 3

[0062] A special a-SiC ceramic grinding wheel for fine grinding of ZrO2 gemstones. The ceramic grinding wheel described in Example 3 is used for fine grinding of ZrO2 gemstones. By weight percentage, the formula of the grinding wheel is: a-SiC 150# 39%, a-SiC 180# 39%, water-soluble β-cyclodextrin powder 10‰, water-soluble β-cyclodextrin solution with a specific gravity of 1.12 g / cm3 27‰, and the binder described in Example 2 22%.

[0063] The preparation method of Example 3 is the same as that of Example 2.

[0064] Example 4

[0065] A special a-SiC ceramic grinding wheel for fine grinding of ZrO2 gemstones. The ceramic grinding wheel described in Example 4 is used for fine grinding of ZrO2 gemstones. By weight percentage, the formula of the grinding wheel is: a-SiC 150# 38%, a-SiC 180# 38%, water-soluble β-cyclodextrin powder 10‰, water-soluble β-cyclodextrin solution with a specific gravity of 1.12 g / cm3 30‰, and the binder described in Example 2 24%.

[0066] The preparation method of Example 4 is the same as that of Example 2.

[0067] Application test

[0068] The a-SiC ceramic grinding wheels prepared in Examples 2, 3, and 4 are used for fine grinding of ZrO2 gemstones. The specific fine grinding method is as follows:

[0069] When fine grinding, the grinding allowance of ZrO2 gemstones is 5 filaments. Before fine grinding, the roughness Ra is 1.0 μm. After grinding, the required roughness of ZrO2 gemstones is Ra ≤ 0.2 μm. The use speed of the grinding wheel is 45 m / s, the feed rate of the grinding wheel is 0.015 mm, and the grinding wheel is dressed once for every 9000 - 10000 ZrO2 gemstones ground on average. It is required that the straightness between the surfaces of ZrO2 gemstones after fine grinding is less than 0.01 mm.

[0070] During grinding, the average particle diameter of ZrO2 gemstones is 13 mm - 15 mm. Note: The reference standard for fine grinding of ZrO2 gemstones is "Technical Data Handbook for Gemstone Identification, Processing and Application".

[0071] Test results

[0072] Currently, ZrO2 gemstone processing manufacturers use conventional grinding wheels for fine grinding, which require frequent dressing of the grinding wheel, have low durability, short service life, low grinding efficiency, and the straightness between the surfaces after grinding exceeds the standard. Sometimes, problems such as scratching or burning may also occur.

[0073] 1. Compared with the grinding of ZrO2 gemstones in the prior art, for the grinding wheels produced in Examples 1 and 2, after testing, the hardness values of the 28 grit chambers (hardness test grade) in three tests are 4.2, 4.3, and 4.2 respectively.

[0074] Through actual grinding tests on the grinding wheel (the tested grinding wheel specification is P-305x50x65), the roughness of the ZrO2 gemstone meets the requirements, but the straightness between surfaces is out of tolerance (the photo of the ZrO2 gemstone after grinding is as Figure 2 shown). The specific test result data is: the straightness between surfaces is 0.018 mm, the durability is to dress the wheel once for every 10,000 gemstones, the roughness Ra after grinding is 0.2 μm, and there are no surface defects such as burns, vibration marks, or scratches on the workpiece surface.

[0075] 2. Compared with the grinding of ZrO2 gemstones in the prior art, for the grinding wheels produced in Examples 1 and 3, after testing, the hardness values of the 28 grit chambers (hardness test grade) in three tests are 3.8, 3.8, and 3.9 respectively.

[0076] Through actual grinding tests on the grinding wheel (the tested grinding wheel specification is P-305x50x65), both the roughness of the ZrO2 gemstone and the straightness between surfaces meet the requirements (the photo of the ZrO2 gemstone after grinding is as Figure 3 shown). The specific test result data is: the straightness between surfaces is 0.007 mm, the durability is to dress the wheel once for every 12,000 gemstones, the roughness Ra after grinding is 0.16 μm, and there are no surface defects such as burns, vibration marks, or scratches on the workpiece surface.

[0077] 3. Compared with the grinding of ZrO2 gemstones in the prior art, for the grinding wheels produced in Examples 1 and 4, after testing, the hardness values of the 28 grit chambers (hardness test grade) in three tests are 3.5, 3.6, and 3.5 respectively.

[0078] Through actual grinding tests on the grinding wheel (the tested grinding wheel specification is P-305x50x65), both the roughness of the ZrO2 gemstone and the straightness between surfaces meet the requirements (the photo of the ZrO2 gemstone after grinding is as Figure 4 shown). The specific test result data is: the straightness between surfaces is 0.006 mm, the durability is to dress the wheel once for every 8,000 gemstones, the roughness Ra after grinding is 0.12 μm, and there are slight burns and vibration marks on the workpiece surface.

[0079] When using the grinding wheel of the present invention to grind ZrO2 gemstones, compared with the conventional grinding wheel for ZrO2 gemstones, under the condition of meeting the grinding requirements, the service life of the grinding wheel of the present invention can be increased by 65%.

[0080] From the test results, it can be concluded that the ceramic bond prepared by the present invention can be used for the special ceramic grinding wheel for precision grinding of ZrO2 gemstones. When the ceramic grinding wheel is used for precision grinding of ZrO2 gemstones, it can pass the actual grinding test. Finally, the roughness of the ZrO2 gemstone and the straightness between surfaces both meet the requirements. The durability is to trim once for 12,000 workpieces. After grinding, the roughness Ra is 0.16 μm, and there are no surface defects such as burns, vibration marks, and scratches on the workpiece surface, having a relatively high service life.

[0081] The present invention provides the application of the special ceramic grinding wheel for precision grinding of ZrO2 gemstones in the precision grinding process of ZrO2 gemstones. Specifically, the special ceramic grinding wheel for precision grinding of ZrO2 gemstones is used for the precision grinding process of ZrO2 gemstones.

[0082] The longer the service life of the grinding wheel is, the better, and the fewer the dressing frequencies are, the better. This requires the bond to not only have relatively high strength but also good sharpness, and at the same time increase the bonding and holding force of the bond for the abrasive. Therefore, the bond is improved and enhanced. Based on this, on the basis of the existing bond composition, ratio and grinding wheel preparation process of the special ceramic grinding wheel for precision grinding of ZrO2 gemstones in the present invention, the performance of the bond is improved by introducing analytically pure substances instead of natural minerals, as well as low-melting glass materials, etc.

[0083] Among them, low-melting KOH and borosilicate glass powder, while effectively reducing the refractoriness of the bond, increase the melting fluidity of the bond during sintering. In this way, the bond can more fully wrap the abrasive. At the same time, when the compound ratio in the bond remains unchanged, it also increases the sharpness and strength of the grinding wheel, that is, reduces the dressing frequency and increases the service life of the grinding wheel. At the same time, it also solves the problem of foaming and blackening of the fine-grained high-hardness silicon carbide ceramic grinding wheel.

[0084] In addition, on the basis of the existing special bond for ZrO2 gemstone precision grinding ceramic grinding wheel in the present invention, nano-cryolite is introduced, which can make the bond better melt and flow, and significantly improve the grinding ratio of the prepared special ceramic grinding wheel for precision grinding of ZrO2 gemstones.

[0085] β-cyclodextrin is introduced as a binder and wetting agent. Because it has excellent chemical stability, solubility and inclusion properties, it can better wet the abrasive while making the bond better wrap the abrasive, and thus can improve the strength of the prepared special ceramic grinding wheel for precision grinding of ZrO2 gemstones.

[0086] When the grinding wheel of the present invention is prepared, the methods of three-dimensional solid mixing and isostatic pressing molding are adopted. Such an approach can ensure the best grinding use effect of the grinding wheel while improving the quality stability of the grinding wheel.

[0087] The special a-SiC ceramic grinding wheel for fine grinding of ZrO2 gemstones of the present invention, its preparation method and application have the following effects:

[0088] I. Beneficial effects in terms of the binder

[0089] 1. Improvement in purity and strength

[0090] The addition of analytically pure SiO2, Al2O3 and KOH improves the purity and strength of the binder. As the main component of the binder, SiO2 increases the chemical stability, strength and grinding sharpness of the binder. This helps the binder to better hold the abrasive grains during the grinding process of the grinding wheel, enabling the abrasive grains to maintain a stable working state during grinding, and improving the grinding efficiency and quality.

[0091] 2. Enhanced wear resistance

[0092] The introduction of nano-cryolite into the binder effectively improves the wear resistance of the special α-SiC ceramic grinding wheel for fine grinding of ZrO2 gemstones. Compared with ordinary cryolite, nano-scale cryolite reduces the refractoriness of the binder while increasing its reactivity. The lower refractoriness enables the binder to more easily form a good microstructure during sintering, and the high reactivity promotes the bonding between the binder and the abrasive grains, thereby improving the overall wear resistance of the grinding wheel and extending its service life.

[0093] 3. Increase in binder strength

[0094] The introduction of low-melting-point borosilicate glass powder, taking advantage of its low refractoriness, increases the strength of the binder. Under the same hardness requirements for the grinding wheel, the amount of binder required for the grinding wheel using this binder is less. This means more space can be left for the abrasive grains, improving the abrasive removal efficiency of the abrasive grains. At the same time, it reduces the dressing frequency of the grinding wheel, lowers the production cost, and effectively reduces the risk of burning of ZrO2 gemstones during the fine grinding process.

[0095] II. Beneficial effects in terms of the grinding wheel formula

[0096] 1. Advantage of abrasive grain combination

[0097] The use of a mixture of two different specifications of abrasive grains, α-SiC150# and α-SiC180#, can give full play to the advantages of abrasive grains of different particle sizes. The coarser 150# abrasive grains can quickly remove larger amounts of stock, improving the grinding efficiency; while the finer 180# abrasive grains can perform fine grinding on the surface of the gemstone, ensuring the surface quality after grinding. This combination method enables the grinding wheel to not only ensure a high grinding efficiency when grinding ZrO2 gemstones, but also meet the requirements for the surface roughness and straightness of the gemstone.

[0098] 2. Selection of binder and wetting agent

[0099] Selecting water-soluble β-cyclodextrin powder as the binder and the corresponding wetting agent helps to achieve uniform mixing among the abrasive grains, the binder, and the adhesive. The water-soluble property enables them to disperse better during the mixing process, forming a uniform mixture, thereby ensuring the stability of the overall performance of the grinding wheel. Meanwhile, the good binding property of β-cyclodextrin powder can ensure that the abrasive grains are firmly fixed in the binder, preventing the premature shedding of the abrasive grains and improving the durability of the grinding wheel.

[0100] III. Beneficial effects in terms of preparation methods

[0101] 1. Mixing process of materials

[0102] Using a three-dimensional mixer for mixing materials can fully and uniformly mix the abrasive, the binder, and the adhesive. Compared with ordinary mixing methods, the three-dimensional mixer can achieve the movement of materials in multiple directions, avoiding local aggregation and uneven distribution of materials, thus ensuring the consistency of the performance of each part of the grinding wheel.

[0103] 2. Pressing and sintering processes

[0104] Pressurizing and holding pressure under appropriate pressure and sintering at a specific temperature contribute to the formation of a dense and uniform microstructure of the grinding wheel. Appropriate pressure can tightly combine the materials and improve the strength of the grinding wheel; while precisely controlled sintering temperature and time can enable the binder to fully play its role, making the grinding wheel reach the optimal performance state. For example, the parameters such as pressure, drying temperature, and sintering temperature adopted in the examples, after experimental verification, can prepare high-quality grinding wheels that meet the requirements of fine grinding of ZrO2 gems.

[0105] IV. Beneficial effects in terms of application effects

[0106] 1. Improvement of surface quality

[0107] Through actual grinding tests, it can be seen that using the grinding wheel prepared by the present invention for fine grinding of ZrO2 gems can effectively meet the requirements of the roughness of the gem, and there are no surface defects such as burns, vibration marks, and scratches on the workpiece surface. For example, in Example 3, the roughness Ra after grinding reaches 0.16 μm, which indicates that the grinding wheel can perform fine processing on the gem surface during the grinding process, ensuring the surface quality of the gem.

[0108] 2. Improvement of straightness

[0109] In terms of the straightness between surfaces, some examples can meet the requirement of less than 0.01 mm. For example, the straightness between surfaces in Example 3 reaches 0.007 mm, and that in Example 4 reaches 0.006 mm. This shows that the grinding wheel of the present invention can maintain good stability and precision during the grinding process, effectively solving the problem of out-of-tolerance straightness in the prior art.

[0110] 3. Improved durability

[0111] Compared with the conventional grinding wheels in the prior art, the durability of the grinding wheel of the present invention has been significantly improved. For example, the durability of the grinding wheel in Example 3 reaches once every 12,000 gem dressings, and the overall service life can be increased by 65%. This means that in actual production, using the grinding wheel of the present invention can reduce the number of grinding wheel replacements, lower production costs, and improve production efficiency.

[0112] In summary, through the optimization of the binder formula, the reasonable combination of the grinding wheel formula, and the precise control of the preparation method, the α-SiC ceramic grinding wheel for ZrO2 gem fine grinding prepared by the present invention has achieved significant beneficial effects in terms of surface quality, straightness, and durability, and has good market application prospects.

[0113] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A special a-SiC ceramic grinding wheel for ZrO2 gemstone fine grinding, characterized in that: Calculated by weight percentage, the raw materials include: a-SiC 70%-80%, binder 5‰-10‰, wetting agent 25‰-30‰, and the balance is a binder.

2. The a-SiC ceramic grinding wheel for ZrO2 gemstone fine grinding according to claim 1, characterized in that: The specifications of the a-SiC are a mixture of 150# and 180#; the particle size of the binder is 800 mesh.

3. The a-SiC ceramic grinding wheel for ZrO2 gemstone fine grinding according to claim 1, characterized in that: The binder is water-soluble beta-cyclodextrin powder; the wetting agent is water-soluble beta-cyclodextrin liquid.

4. The a-SiC ceramic grinding wheel for ZrO2 gemstone fine grinding according to claim 1, characterized in that: The preparation method of the binder comprises the following steps: S11: Mixing the components in the raw material to obtain a mixture, wherein the raw material consists of the following components in weight percentage: Analytical pure SiO2 51%-61%, analytical pure Al2O3 12%-22%, analytical pure KOH 4%-14%, low melting point borosilicate glass powder 5%-15%, the balance is nano-cryolite; S12: ball-mill the mixture in step S11 for 5.5-6.5 hours, and pass it through a 80-mesh to 100-mesh sieve to obtain a binder.

5. The a-SiC ceramic grinding wheel for ZrO2 gemstone fine grinding according to claim 4, characterized in that: The mass percentages of the chemical components in the low-melting-point borosilicate glass powder are: silicon dioxide 71%-74%, aluminum oxide <1.5%, iron oxide <0.1%, K2O+Na2O <8.5%, boron oxide 18%-19%, ignition loss <0.1%; the refractoriness is 740-760°C.

6. A method for preparing a-SiC ceramic grinding wheel for ZrO2 gemstone fine grinding, comprising the a-SiC ceramic grinding wheel for ZrO2 gemstone fine grinding according to any one of claims 1 to 5, characterized in that: The steps include: S21: adding a wetting agent to a-SiC, mixing and stirring for 18-22 minutes, then adding a binder and an adhesive, mixing and stirring for 25-35 minutes, passing through a 12-mesh to 20-mesh sieve, and stuffing at room temperature for ≥72 hours to obtain a mixed material; S22: putting the mixed material into a mold, pressing and molding at a pressure of 15-20 MPa for 25-35 seconds, then drying at 80°C-120°C for ≥52 hours, and finally sintering at 910-940°C for 20-28 hours. After demolding, a-SiC ceramic grinding wheel for ZrO2 gemstone fine grinding is obtained.

7. The method for preparing a-SiC ceramic grinding wheel for ZrO2 gemstone fine grinding according to claim 6, characterized in that: The mixed materials in steps S12 and S21 are mixed by a three-dimensional mixer.

8. The method for preparing a-SiC ceramic grinding wheel for ZrO2 gemstone fine grinding according to claim 6, characterized in that: The sintering process in step S22 is performed in a high-temperature sintering furnace.

9. An application of a ceramic grinding wheel as claimed in any one of claims 1 to 8 in fine grinding of ZrO2 gemstones, characterized in that: The grinding wheel is used for precision grinding of ZrO2 gemstones. The roughness Ra after grinding is ≤0.2μm, and the durability is ≥12,000 ZrO2 gemstones can be trimmed once.

10. The use of a-SiC ceramic grinding wheel in ZrO2 gemstone according to claim 9, characterized in that: The a-SiC ceramic grinding wheel controlled grinding parameters are: grinding wheel speed 45m / s, feed amount 0.015mm, grinding allowance 5 wires, that is, 0.05mm.

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