Green body for eliminating sintering blisters from high-pressure formed ceramic, and preparation method therefor

Abstract

The present application relates to the technical field of the production of sanitary ceramics, and in particular relates to a green body for eliminating sintering blisters from a high-pressure formed ceramic, and a preparation method therefor. On the basis of the mass percentage of raw materials, the green body comprises: 20%-25% of kaolin, 1%-3% of quartz, 5%-8% of ball clay, 17%-27% of high-alumina porcelain stone, 3%-8% of waste porcelain, 3%-10% of low-glaze recycled mud, 0%-5% of raw porcelain clay, 10%-15% of water-washed porcelain clay, 10%-21% of spodumene tailings and / or microcline, and 2%-5% of wollastonite. The green body is obtained by means of high-pressure slip casting, drying and sintering. In the present application, the formation and blocking mechanisms of sintering blisters are precisely determined, thereby effectively controlling the defect of sintering blisters in high-pressure formed sanitary ceramic products. In addition, a large number of industrial solid waste raw materials such as waste porcelain, waste mud and spodumene tailings are used in the formula of the green body of the present application, which helps to reduce the accumulation of industrial solid waste, reduce environmental pressure and promote the sustainable development of the sanitary ceramics industry.

Description

A green body for eliminating sintering bulges in high-pressure molded ceramics and its preparation method Technical Field

[0001] This application relates to the field of sanitary ceramics production technology, and in particular to a green body for eliminating sintering bulges in high-pressure formed ceramics and its preparation method. Background Technology

[0002] Bubbling during sintering of the ceramic body is a common product defect in the production of sanitary ceramics. Once it occurs, it will greatly affect the appearance and performance of sanitary ceramic products. Refiring (re-firing, re-firing) will not only fail to eliminate the defect but will also further aggravate it. Therefore, products with sintering bulge defects can only be scrapped, which seriously affects the yield of sanitary ceramic production, increases production costs, and wastes high-quality ceramic raw materials.

[0003] Currently, the ceramic industry generally believes that sintering bulges in ceramic blanks are mainly caused by three reasons: first, the sintering temperature range of the blank is too low, resulting in over-firing, excessive softening of the blank, and excessive gas production, leading to sintering bulges; second, too many impurities such as carbonates, sulfates, and organic matter in the blank cause excessive gas production during sintering that cannot be discharged, resulting in sintering bulges; third, cavities appear within the blank during slip casting, and the gas in these cavities expands at high temperatures, leading to sintering bulges. With the development of ceramic production technology, advanced testing methods such as X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma spectroscopy (ICP) can now efficiently and accurately determine the chemical composition of ceramic raw materials, enabling strict formula control and ensuring that the sintering range and impurity content of the blank meet production requirements; the problem of blank cavities can also be effectively avoided through precise pressure control during slip casting. However, sintering bulge defects still frequently occur in double-sided slip-cast sanitary ceramic products, especially high-pressure molded products. Clearly, the most critical factor causing sintering bulges in ceramic blanks remains undetermined.

[0004] High-pressure molding is a new molding process that has gradually become popular in the sanitary ceramics industry in recent years. Unlike traditional micro-pressure molding, where slurry is gradually dehydrated and molded through the capillary effect of a plaster mold at a low pressure of about 0.02 MPa, high-pressure molding injects slurry into a resin mold at a high pressure of about 1 MPa, allowing the water in the slurry to enter the micropores of the resin mold for rapid dehydration and molding. Simple sanitary ceramic products such as two-piece toilets, smart toilet bases, squat toilets, and washbasins can be rapidly molded using high-pressure molding, greatly improving production efficiency. However, high-pressure molded products are very prone to bulging defects at the center line of the blank after sintering, as shown in Figure 1, which seriously affects the yield of high-pressure molded products.

[0005] CN109824341A discloses a slurry and its preparation method for reducing sintering bulging defects during high-pressure forming and re-firing. By introducing a large amount of high-Al2O3 clay raw materials such as purple clay and Henan clay, the amount of feldspar raw material is reduced, thus improving the overall refractoriness of the green body material. Secondary grinding reduces the difference in particle size distribution between hard and soft materials, alleviating the sintering bulging problem to some extent. However, because the refractoriness of the micro-regions where sintering bulging occurs is not precisely and effectively controlled, the problem is not fundamentally eliminated. Furthermore, the overall increase in refractoriness leads to water absorption exceeding national standards. In addition, secondary grinding makes the slurry production process more complex and consumes more energy.

[0006] CN110078471A discloses a high-pressure slurry ceramic material based on waste porcelain recycling and its preparation method and system. This method reduces the particle size of waste porcelain particles in the slurry through secondary crushing and secondary grinding processes, alleviating the problem of bulging in the green body caused by stratification of large-particle waste porcelain during high-pressure slurry casting. However, the related improvement measures only target waste porcelain as a single raw material and do not form an effective solution to comprehensively address the bulging defect in high-pressure formed green bodies during sintering. Furthermore, similar to CN109824341A, the secondary grinding process complicates the production process and increases energy consumption.

[0007] Therefore, it is urgent to clarify the reasons why high-pressure molded products are prone to bulging defects, and to develop blanks and preparation methods to eliminate bulging during sintering of high-pressure molded sanitary ceramics. Summary of the Invention

[0008] To address the aforementioned issues, this application provides a green body for eliminating sintering bulges in high-pressure molded ceramics and its preparation method, effectively solving the problem of bulging defects in high-pressure molded ceramic products, and ensuring that all properties of the green body meet the requirements for the production and use of sanitary ceramics.

[0009] To achieve the above objectives, this application adopts the following technical solution:

[0010] In a first aspect, this application provides a green body for eliminating sintering bulges in high-pressure molded ceramics. The green body, by weight percentage of raw materials, comprises: 20%-25% kaolin, 1%-3% quartz, 5%-8% clay, 17%-27% high-alumina porcelain stone, 3%-8% waste porcelain, 3%-10% low-glaze recycled mud, 0%-5% raw ore porcelain clay, 10%-15% washed porcelain clay, 10%-21% spodumene tailings and / or microcline, and 2%-5% wollastonite.

[0011] The blank is obtained by high-pressure grouting, drying and sintering.

[0012] In some embodiments, the waste ceramics are ceramic particles obtained by crushing and removing iron from sintered sanitary ceramic products that failed quality inspection.

[0013] In some embodiments, the low-glaze recycled mud is waste mud containing a small amount of waste glaze generated during the production of sanitary ceramics. The mud cake obtained after separate recycling, natural sedimentation, and pressure filtration has a waste glaze content of less than 15%.

[0014] In some embodiments, the green body comprises, by mass percentage of the raw material chemical composition: SiO 2 55%-60%, Al2O3: 24%-28%, Fe2O3: 0.5%-1.8%, TiO2: 0.5%-1%, CaO: 1%-2%, MgO: 0.2%-0.6%, K2O: 4%-4.5%, Na2O: 1%-1.5%, ZnO: 0%-0.4%, ZrO2: 0%-0.5%, Li2O: 0%-0.05%, Loss on ignition: 5%-10%.

[0015] In some embodiments, the sum of the mass percentages of SiO2 and Al2O3 is 80%-85%.

[0016] In some embodiments, the molar ratio of SiO2 to Al2O3 is (3.4-4.1):1.

[0017] In some embodiments, the molar ratio of K2O to Na2O is (2-2.8):1.

[0018] Secondly, this application provides a method for preparing a green body that eliminates the sintering bulges of high-pressure formed ceramics, comprising the following steps:

[0019] (1) Weigh the raw materials of the billet according to the proportion, add water and ball mill;

[0020] (2) After grinding and sieving, water and additives are added to obtain mud;

[0021] (3) The mud is grouted under high pressure, dried and sintered to obtain the final product.

[0022] In some embodiments, in step (1), the particle size distribution after ball milling is: D10≤3.5 μm, D50≤30.0 μm, D90≤100.0 μm.

[0023] In some embodiments, in step (2), the additive is one or more of water glass and baking soda.

[0024] In some embodiments, in step (2), the concentration of the mud is 350-360 g / 200 mL, and the yield value is 10-16 dyn / cm. 2 The fluidity V0 is 45-70 s / 200mL, and the pulping speed is 6-9 mm / 45min.

[0025] In some embodiments, in step (3), the grouting pressure is 0.8-1.2 MPa and the maximum sintering temperature is 1200 ℃.

[0026] Compared with the prior art, the beneficial effects of this application are:

[0027] During the research process, the inventors of this application discovered that high-pressure molded ceramics are prone to sintering bulging because, during the high-pressure molding of sanitary ceramic blanks, slurry particles migrate from the centerline towards the upper and lower slurry suction surfaces of the resin model under the driving force of the slurry injection pressure (approximately 1 MPa). The migration speed of small refractory clay raw materials is fast, while the migration speed of large fusible hard raw materials (microcline, spodumene tailings, etc.) is slow, resulting in a non-uniform chemical composition distribution in the blank. Fusible feldspar raw materials accumulate near the centerline, and a large amount of glassy liquid phase is generated in the centerline during sintering, forming a dense liquid phase film that hinders the exhaust of gases generated by the sintering reaction, leading to the problem of blank expansion and bulging. In response to the above findings, this application optimizes the material system of high-pressure molded sanitary ceramic green bodies. By appropriately reducing the amount of large-particle fusible hard raw materials such as microcline and spodumene tailings, and increasing the amount of refractory hard large-particle raw materials such as high-alumina ceramic stone, the raw material particles migrate directionally under high pressure, resulting in an increase in Al2O3 content and a decrease in K2O and Na2O content in the center part, thus improving refractoriness. This reduces the amount of glassy liquid phase generated in the center part during sintering, avoids the formation of a dense liquid phase film, and allows the gas generated by the sintering reaction to be smoothly discharged from the green body.

[0028] This application precisely defines the formation and blocking mechanism of sintering bulges, effectively controlling sintering bulge defects in high-pressure molded sanitary ceramic products. In addition, the green body formula of this application also uses a large amount of industrial solid waste raw materials such as waste porcelain, waste mud, and spodumene tailings, which helps to reduce the accumulation of industrial solid waste, reduce environmental pressure, and promote the sustainable development of the sanitary ceramics industry.

[0029] The green body formula of this application can be applied to existing preparation systems. The resulting green body has properties such as water absorption, sintering shrinkage, and flexural strength that are close to those of existing ordinary high-pressure formed green bodies. Moreover, the standard thickness deformation and deformation coefficient are relatively smaller, which is more conducive to product quality control. The green body formula of this application can meet the requirements of large-scale production of sanitary ceramic products. The sintering bulging defect rate of the products is greatly reduced, making it suitable for industrial promotion. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 shows an optical photograph of the bulging area of ​​a high-pressure molded sanitary ceramic product, where (a) is the front view and (b) is the cross-section.

[0032] Figure 2 is a schematic diagram of microparticle migration during the high-pressure molding process;

[0033] Figure 3 is a schematic diagram of the sintering bending deformation test of the billet;

[0034] Figure 4 shows the particle size distribution of the centerline and slurry absorption surface of the green body in Example 1 and Comparative Example 1;

[0035] Figure 5 shows SEM images of (a) the suction surface of Example 1; (b) the midline plane; (c) the cross-section and (d) the suction surface of Comparative Example 1; (e) the midline plane; and (f) the cross-section.

[0036] Figure 6 shows the EDS test results of Example 1 (a) suction surface; (b) centerline plane and Comparative Example 1 (c) suction surface; (d) centerline plane.

[0037] Figure 7 shows the SEM-EDS test results of the cracked area in the center plane (inside the bulge) of Comparative Example 1. Detailed Implementation

[0038] The technical solution of this application will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this application.

[0039] The chemical composition of the raw materials used in this application and comparative examples is shown in Table 1.

[0040] Table 1

[0041]

[0042] Example 1

[0043] A green body for eliminating sintering bulges in high-pressure formed ceramics is prepared by the following method:

[0044] (1) According to the mass percentage, 22% kaolin, 2% quartz, 6% ball soil, 20% high alumina porcelain stone, 5% waste porcelain, 5% low glaze recycled mud, 5% raw ore porcelain clay, 15% water-washed porcelain clay, 17% spodumene tailings and 3% wollastonite are mixed and then water is added and high alumina balls are ground to D10≤3.5 μm, D50≤30.0 μm and D90≤100.0 μm;

[0045] The green body, based on the mass percentage of the raw material chemical composition, comprises: 58.64% SiO2, 25.56% Al2O3, 1.44% Fe2O3, 0.62% TiO2, 1.58% CaO, 0.45% MgO, 4.21% K2O, 1.15% Na2O, 0.03% ZnO, 0.04% ZrO2, 0.03% Li2O, and 5.99% loss on ignition. The sum of the mass percentages of SiO2 and Al2O3 is 84.2%; the molar ratio of SiO2 to Al2O3 is 3.89:1; and the molar ratio of K2O to Na2O is 2.4:1.

[0046] (2) After grinding, sieve, add water, water glass (0.4% of the total mass of the raw material) and alkali (0.1% of the total mass of the raw material) to obtain slurry. Control the slurry concentration at 350g / 200mL and the yield value at 13 dyn / cm. 2 The fluidity V0 is 50 s / 200mL, and the pulping speed is 8 mm / 45min;

[0047] (3) The above slurry is injected into the resin mold at a grouting pressure of about 1 MPa to form the ceramic green body. After demolding and drying, the green body is sintered in a tunnel kiln at a maximum sintering temperature of 1200℃ to obtain the green body. The sintering process is shown in Table 2.

[0048] Table 2

[0049]

[0050] Example 2

[0051] The preparation method of Example 2 is the same as that of Example 1, except that:

[0052] The blank body comprises the following raw materials by weight percentage: 22% kaolin, 2% quartz, 6% ball clay, 20% high-alumina porcelain stone, 5% waste porcelain, 10% low-glaze recycled mud, 15% washed porcelain clay, 17% spodumene tailings, and 3% wollastonite.

[0053] The green body, based on the mass percentage of the raw material chemical composition, comprises: 57.83% SiO2, 25.92% Al2O3, 1.45% Fe2O3, 0.63% TiO2, 1.74% CaO, 0.47% MgO, 4.13% K2O, 1.21% Na2O, 0.05% ZnO, 0.06% ZrO2, 0.03% Li2O, and 6.21% loss on ignition. The sum of the mass percentages of SiO2 and Al2O3 is 83.75%; the molar ratio of SiO2 to Al2O3 is 3.79:1; and the molar ratio of K2O to Na2O is 2.25:1.

[0054] Example 3

[0055] The preparation method of Example 3 is the same as that of Example 1, except that:

[0056] The blank body comprises the following raw materials by weight percentage: 22% kaolin, 2% quartz, 6% ball clay, 20% high-alumina porcelain stone, 10% waste porcelain, 10% low-glaze recycled mud, 10% washed porcelain clay, 17% spodumene tailings, and 3% wollastonite.

[0057] The green body, based on the mass percentage of the raw material chemical composition, comprises: 57.88% SiO2, 26.04% Al2O3, 1.41% Fe2O3, 0.64% TiO2, 1.83% CaO, 0.49% MgO, 4.13% K2O, 1.27% Na2O, 0.07% ZnO, 0.08% ZrO2, 0.03% Li2O, and 5.87% loss on ignition. The sum of the mass percentages of SiO2 and Al2O3 is 83.92%; the molar ratio of SiO2 to Al2O3 is 3.77:1; and the molar ratio of K2O to Na2O is 2.14:1.

[0058] Example 4

[0059] The preparation method of Example 4 is the same as that of Example 1, except that:

[0060] The body comprises the following raw materials by weight percentage: 23% kaolin, 6% ball clay, 20% high-alumina porcelain stone, 10% raw ore porcelain clay, 20% washed porcelain clay, 3% wollastonite, and 18% microcline.

[0061] The green body, based on the mass percentage of the raw material chemical composition, comprises: 58.74% SiO2, 25.47% Al2O3, 1.50% Fe2O3, 0.59% TiO2, 1.33% CaO, 0.41% MgO, 4.39% K2O, 1.08% Na2O, and 6.19% loss on ignition. The sum of the mass percentages of SiO2 and Al2O3 is 84.21%; the molar ratio of SiO2 to Al2O3 is 3.91:1; and the molar ratio of K2O to Na2O is 2.68:1.

[0062] Example 5

[0063] The preparation method of Example 5 is the same as that of Example 1, except that:

[0064] The blank body comprises the following raw materials by weight percentage: 17% kaolin, 2% quartz, 6% ball clay, 20% high-alumina porcelain stone, 15% waste porcelain, 15% low-glaze recycled mud, 4% original ore porcelain clay, 4% washed porcelain clay, 14% spodumene tailings, and 3% wollastonite.

[0065] The green body, based on the mass percentage of the raw material chemical composition, comprises: 58.49% SiO2, 25.53% Al2O3, 1.36% Fe2O3, 0.67% TiO2, 2.09% CaO, 0.52% MgO, 4.16% K2O, 1.21% Na2O, 0.10% ZnO, 0.12% ZrO2, 0.02% Li2O, and 6.38% loss on ignition. The sum of the mass percentages of SiO2 and Al2O3 is 84.01%; the molar ratio of SiO2 to Al2O3 is 3.89:1; and the molar ratio of K2O to Na2O is 2.25:1.

[0066] Example 6

[0067] The preparation method of Example 6 is the same as that of Example 1, except that:

[0068] The body comprises the following raw materials by weight percentage: 22% kaolin, 6% ball clay, 27% high-alumina porcelain stone, 10% waste porcelain, 10% low-glaze recycled mud, 10% washed porcelain clay, 12% spodumene tailings, and 3% wollastonite.

[0069] The green body, based on the mass percentage of the raw material chemical composition, comprises: 55.17% SiO2, 27.97% Al2O3, 1.49% Fe2O3, 0.77% TiO2, 1.84% CaO, 0.53% MgO, 4.49% K2O, 0.99% Na2O, 0.07% ZnO, 0.08% ZrO2, 0.02% Li2O, and 6.31% loss on ignition. The sum of the mass percentages of SiO2 and Al2O3 is 83.13%; the molar ratio of SiO2 to Al2O3 is 3.35:1; and the molar ratio of K2O to Na2O is 2.99:1.

[0070] Example 7

[0071] The preparation method of Example 7 is the same as that of Example 1, except that:

[0072] The blank body comprises the following raw materials by weight percentage: 22% kaolin, 5% quartz, 6% ball clay, 17% high-alumina porcelain stone, 1% waste porcelain, 5% low-glaze recycled mud, 5% original ore porcelain clay, 15% washed porcelain clay, 21% spodumene tailings, and 3% wollastonite.

[0073] The green body, based on the mass percentage of the raw material chemical composition, comprises: 60.70% SiO2, 24.02% Al2O3, 1.36% Fe2O3, 0.54% TiO2, 1.50% CaO, 0.41% MgO, 3.98% K2O, 1.33% Na2O, 0.02% ZnO, 0.03% ZrO2, 0.03% Li2O, and 5.82% loss on ignition. The sum of the mass percentages of SiO2 and Al2O3 is 84.73%; the molar ratio of SiO2 to Al2O3 is 4.29:1; and the molar ratio of K2O to Na2O is 1.97:1.

[0074] Comparative Example 1

[0075] Comparative Example 1 is a common high-pressure molded preform widely used in sanitary ceramics production. Its preparation method is the same as that of Example 1, except that:

[0076] The ordinary high-pressure molded blank contains the following raw materials by mass percentage: 22% kaolin, 2% quartz, 6% ball clay, 12% high-alumina porcelain stone, 5% waste porcelain, 5% low-glaze recycled mud, 5% original ore porcelain clay, 15% washed porcelain clay, 25% spodumene tailings, and 3% wollastonite.

[0077] The green body, based on the mass percentage of the raw material chemical composition, comprises: 61.22% SiO2, 23.67% Al2O3, 1.36% Fe2O3, 0.46% TiO2, 1.58% CaO, 0.4% MgO, 3.86% K2O, 1.61% Na2O, 0.03% ZnO, 0.04% ZrO2, and 5.49% loss on ignition. The sum of the mass percentages of SiO2 and Al2O3 is 84.89%; the molar ratio of SiO2 to Al2O3 is 4.39:1; and the molar ratio of K2O to Na2O is 1.58:1.

[0078] Comparative Example 2

[0079] Comparative Example 2 is a high-sodium high-pressure molded preform made by replacing part of the spodumene tailings with albite based on the ordinary high-pressure molded preform formula. The preparation method is the same as that of Example 1, except that:

[0080] The high-pressure molded blank comprises the following raw materials by weight percentage: 20% kaolin, 2% quartz, 6% ball clay, 12% high-alumina porcelain stone, 5% waste porcelain, 5% low-glaze recycled mud, 7% raw ore porcelain clay, 15% washed porcelain clay, 15% spodumene tailings, 10% albite, and 3% wollastonite.

[0081] The green body, based on the mass percentage of the raw material chemical composition, comprises: 61.08% SiO2, 23.72% Al2O3, 1.34% Fe2O3, 0.46% TiO2, 1.59% CaO, 0.41% MgO, 3.54% K2O, 2.17% Na2O, 0.03% ZnO, 0.04% ZrO2, and 5.34% loss on ignition. The sum of the mass percentages of SiO2 and Al2O3 is 84.89%; the molar ratio of SiO2 to Al2O3 is 4.39:1; and the molar ratio of K2O to Na2O is 1.58:1.

[0082] Specifically, the raw material composition of the billets in Examples 1-7 and Comparative Examples 1-2 is shown in Table 3, and the chemical composition of the raw materials is shown in Table 4.

[0083] Table 3 (Unit: wt%)

[0084]

[0085] Table 4

[0086]

[0087] The relevant test methods and test equipment in Examples 1-7 and Comparative Examples 1-2 are as follows:

[0088] Particle size testing: Shimadzu Corporation, Japan, laser particle size analyzer (SALD-2201);

[0089] Sintering temperature test: Fluke Corporation, USA, temperature measuring ring (BTC005, 900-1200℃).

[0090] Sintering shrinkage test: By comparing 10×20×250 mm 3 The shrinkage rate of the rectangular bar is calculated by the change in length before and after sintering. The formula is λ = (L0 - L) / L0 × 100%. In the formula, λ is the linear shrinkage rate of the bar; L0 is the length of the bar before sintering; and L is the length of the bar after sintering.

[0091] Water absorption test: The water absorption of the ceramic samples was tested using an electronic balance in accordance with ASTM C373-88 (2006) standard.

[0092] Standard thickness deformation test: Measured at 10×20×250 mm 3 The deflection and thickness of the cuboid specimen after sintering on a refractory support with a span of 200 mm were calculated to eliminate the influence of specimen thickness differences, resulting in the bending deformation of the standard-sized specimen. The calculation formula is W=Sh. 2 / 100, where W is the bending deformation, S is the deflection of the sintered specimen, and h is the thickness of the sintered specimen. A schematic diagram of the sintering bending deformation is shown in Figure 3.

[0093] Deformation coefficient test: Measured in 10×20×250 mm 3 The deflection and thickness of the cuboid specimen after sintering on the refractory support, along with the span of the refractory support, were used to calculate the deformation coefficient of the billet material. The calculation formula is PI=4Sh. 2 / 3L 4 Where PI is the deformation coefficient, S is the deflection of the sintered specimen, h is the thickness of the sintered specimen, and L is the span of the refractory support.

[0094] Bending strength test: The three-point bending strength of a round bar with a length of 120 mm and a diameter of 15 mm was tested using the Shimadzu AG-IS universal testing machine (Japan) in accordance with the GB / T 6569-2006 standard.

[0095] Chemical composition analysis: Bruker Ltd., UK; X-ray fluorescence spectroscopy (XRF).

[0096] Phase analysis: Rigaku Corporation, Japan, X-ray diffractometer (XRD).

[0097] Microscopic morphology analysis: Zeiss AG, Germany, field emission scanning electron microscope (SEM).

[0098] Elemental composition analysis: Energy dispersive spectrometer (EDS) from Oxford, UK.

[0099] The performance test results of the green bodies prepared in Examples 1-7 and Comparative Examples 1-2 are shown in Table 5. The sintering bulging defects of the trial production products in Examples 1-7 and Comparative Examples 1-2 are statistically shown in Table 6.

[0100] Table 5

[0101]

[0102] Table 6

[0103]

[0104] Based on Table 5, and comparing Examples 1-7 with Comparative Examples 1 and 2, it can be seen that the properties of the green bodies in Examples 1-4, such as water absorption, sintering shrinkage, and flexural strength, are close to those of the ordinary high-pressure molded green body in Comparative Example 1. Moreover, the standard thickness deformation and deformation coefficient are smaller than those in Comparative Example 1, which is more conducive to product quality control and can meet the requirements of large-scale production of sanitary ceramic products.

[0105] Compared with Example 1, the standard thickness deformation, deformation coefficient and bulging defect rate of Examples 2 and 3 increase sequentially. This is because the amount of low-glaze recycled mud and waste porcelain used in Examples 2 and 3 gradually increases, while the amount of raw ore porcelain clay and washed porcelain clay gradually decreases. The waste porcelain and low-glaze recycled mud contain more fusible components such as CaO, MgO, Na2O, and ZnO, which reduces the refractoriness of the green body, increases the amount of glass phase generated during sintering, increases bulging defects, and increases deformation.

[0106] Example 4, which did not use industrial solid waste raw materials such as low-glaze recycled mud, waste porcelain, and spodumene tailings, exhibited similar performance to Example 1. This indicates that low-glaze recycled mud, waste porcelain, and spodumene can be interchanged with ceramic plastic clay raw materials, lean raw materials, and fluxing agents, respectively. However, without the use of industrial solid waste raw materials, the formulation cost was higher, which is not conducive to large-scale industrialization. Example 5, on the other hand, used a large amount of industrial solid waste raw materials such as low-glaze recycled mud and waste porcelain, resulting in excessively high levels of fusible components such as CaO, MgO, Na2O, and ZnO derived from waste glaze and waste porcelain in the green body, leading to greater deformation.

[0107] Example 6 used a large amount of high-alumina ceramic stone, resulting in a high Al2O3 content in the body, a low molar ratio of SiO2 to Al2O3, and a high molar ratio of K2O to Na2O. It had high refractoriness, but was not fully sintered, had a water absorption rate greater than 0.5%, and low strength. Furthermore, the high Al2O3 raw material cost was high, and the high Al2O3 body density was high, leading to higher transportation costs, which is not conducive to large-scale industrialization. Example 7 used less high-alumina ceramic stone, resulting in a lower Al2O3 content in the body, a high molar ratio of SiO2 to Al2O3, and a low molar ratio of K2O to Na2O. It had lower refractoriness and greater deformation, making it difficult to meet the needs of sanitary ceramic product production and use.

[0108] Taking into account the water absorption rate, deformation, strength and cost of the billet, Example 1 is the optimal example.

[0109] Referring to Table 6, a comparison of Examples 1-7 and Comparative Examples 1 and 2 shows that the trial production products of Examples 1-4 and 6 exhibited no bulging defects during the first firing, and the bulging defect rate during refiring was also extremely low. In contrast, Comparative Examples 1 and 2 had a higher bulging defect rate during the first firing, exceeding 1%, and an even higher bulging defect rate during refiring, exceeding 7%. This indicates that by appropriately reducing the amount of large-particle, easily fusible hard raw materials such as microcline and spodumene tailings, and increasing the amount of refractory large-particle, hard raw materials such as high-alumina ceramic stone, the refractoriness of the central part of the green body can be improved, the amount of glassy liquid phase generated in the central part during sintering can be reduced, and the formation of a dense liquid phase film encapsulating gas expansion bulging can be avoided, almost completely eliminating sintering bulging defects.

[0110] The bulging defect rate in Examples 5 and 7 during the first firing was slightly higher than that in Examples 1-4 and 6. Numerous bulging defects also appeared during refiring. This is because Example 5 used a larger amount of low-glaze recycled clay and waste porcelain, resulting in excessively high levels of fluxing components such as CaO and ZnO from the waste glaze and waste porcelain in the green body. This reduced the refractoriness of the centerline area, making it easier to form a dense liquid phase film, leading to sintering bulging. Example 7 used less high-alumina porcelain stone, resulting in lower refractoriness of the centerline area compared to Examples 1-4 and 6. Therefore, a larger amount of glassy liquid phase was generated during sintering, making it easier to form a continuous liquid phase film, causing sintering bulging defects. Furthermore, the bulging defect rate in Examples 5 and 7 and Comparative Examples 1 and 2 during refiring was significantly higher than that during the first firing. This is because the secondary sintering allowed for a more complete formation of the liquid phase film containing gas in the centerline area of ​​the green body, exacerbating the sintering bulging problem.

[0111] Meanwhile, comparing Comparative Example 1 and Comparative Example 2, it can be seen that the re-firing bulging defect rate of Comparative Example 2 is significantly higher than that of Comparative Example 1. The main difference between Comparative Example 2 and Comparative Example 1 lies in the addition of hard, large-particle albite raw material, which has a better fluxing effect than microcline and spodumene tailings. The increase in fusible hard, large-particle albite results in a higher Na2O content and lower refractoriness in the central part of the green body of Comparative Example 2. During sintering, a larger amount of glassy liquid phase is generated in the central part, making it easier to form a dense liquid phase film, which hinders the exhaust of gases generated by the sintering reaction, thus causing an increase in the re-firing bulging defect rate of the green body.

[0112] The particle size of the powder taken from the centerline and slurry-absorbing surface of the green body in Example 1 and Comparative Example 1 was detected using a laser particle size analyzer. The particle size distribution curves are shown in Figure 4. It can be seen that compared with the particle size distribution curve of the slurry-absorbing surface, the curve of the centerline is shifted towards the direction of higher particle size. The differential distribution curves of the two intersect at about 40 μm. Large particles above 40 μm are significantly more numerous in the centerline than in the slurry-absorbing surface, while small particles are significantly less numerous. This indicates that during high-pressure molding, the slurry particles migrate from the centerline to the upper and lower slurry-absorbing surfaces of the resin model under the driving force of the injection high pressure (about 1 MPa). Large particles migrate slowly and are more distributed near the centerline plane, while small particles migrate quickly and are more distributed near the slurry-absorbing surface. This results in a non-uniform chemical composition distribution from the centerline of the green body to the slurry-absorbing surface. This migration of small particles under high pressure is the physical process of bulging formation, as shown in Figure 2.

[0113] The microstructure of the slurry-absorbing surface, centerline plane, and cross-section of Example 1 and Comparative Example 1 was observed using scanning electron microscopy (SEM). The results are shown in Figure 5. It can be seen that the slurry-absorbing surface has finer particles and fewer pores, while the centerline plane is significantly rougher, containing many large particles and pores. The cross-sectional SEM image also shows a large number of concentrated pores in the centerline area. This further demonstrates that after high-pressure forming, more large particles in the preform material system are distributed near the centerline. Furthermore, Figure 5(e) also shows obvious cracking in the centerline plane (inside the bulge) of Comparative Example 1.

[0114] The elemental composition of the midline plane and the suction surface of Example 1 and Comparative Example 1 in Figure 5 was measured by energy dispersive spectroscopy (EDS). The results are shown in Figure 6. It can be seen that the content of fusible components such as Na2O and K2O in the midline plane is significantly higher than that in the suction surface. This is caused by the slow migration speed of large-particle spodumene tailings / microcline raw materials rich in Na2O and K2O under high pressure. The aggregation of fusible components such as Na2O and K2O directly leads to a larger amount of glassy liquid phase generated in the midline part during the sintering process of Comparative Example 1, which easily forms a dense liquid phase film to encapsulate the gas, resulting in a higher incidence of bulging defects. In Example 1, the plane contained more refractory Al2O3 and less SiO2 and Na2O than in Comparative Example 1. This indicates that after replacing spodumene tailings with high-alumina ceramic stone, a large amount of refractory hard high-alumina ceramic stone with high Al2O3, low SiO2, and low Na2O was distributed near the centerline, which significantly improved the refractoriness of the centerline of the green body, avoided the formation of a dense liquid phase film to encapsulate gas expansion bulges during the sintering process, and eliminated sintering bulge defects.

[0115] The microstructure and elemental composition of the cracked area inside the bulge in Comparative Example 1 were analyzed by SEM-EDS, as shown in Figure 7. It can be seen that the SiO2 content is relatively high at positions ①-⑥ near the crack, with positions ③, ④, and ⑥ reaching over 80%. This indicates the presence of a large amount of quartz crystals near the crack. Since quartz crystals have a large coefficient of thermal expansion, areas with concentrated quartz crystal distribution will experience significant deformation and tensile stress during sintering and cooling, leading to cracking. In Example 1, due to the significantly lower SiO2 content and smaller coefficient of thermal expansion compared to Comparative Example 1, cracking is less likely to occur during sintering and cooling, resulting in more stable mechanical properties.

[0116] In Figure 7, except for positions ③, ④, and ⑥ with extremely high SiO2 content, positions ①, ②, and ⑤ have relatively high K2O and Na2O contents, indicating that the central part of the blank in Comparative Example 1 generally contains a large amount of glass phase. This further proves that a large amount of glassy liquid phase was generated in the central part during the sintering process of Comparative Example 1. Positions ③, ④, and ⑥ with extremely high SiO2 content should be large-particle quartz crystals, i.e., the protrusions and burrs inside the bulge in Figure 1. Although the K2O and Na2O contents in these areas are lower than in other areas, they are still considerable, indicating that there is also glass phase attached to their surfaces. The glass phase forms a continuous film in the central part of the blank. Based on the depth measured by EDS, the thickness of this film can be determined to be approximately several micrometers. During the sintering process, the formation of a continuous glassy liquid phase film in the central part directly leads to the difficulty in venting the gas generated by the sintering reaction, causing the blank to expand and bulge.

[0117] The present application has been further described above with reference to specific embodiments. However, it should be understood that the specific descriptions herein should not be construed as limiting the substance and scope of the present application. Various modifications made by those skilled in the art to the above embodiments after reading this specification are all within the scope of protection of the present application.

Claims

1. A green body for eliminating bulging during high-pressure forming ceramic sintering, characterized in that, The green body, by weight percentage of raw materials, comprises: 20%-25% kaolin, 1%-3% quartz, 5%-8% ball clay, 17%-27% high-alumina porcelain stone, 3%-8% waste porcelain, 3%-10% low-glaze recycled mud, 0%-5% raw ore porcelain clay, 10%-15% washed porcelain clay, 10%-21% spodumene tailings and / or microcline, and 2%-5% wollastonite; the green body is obtained by high-pressure slurry casting, drying and sintering.

2. The green body for eliminating sintering bulges in high-pressure formed ceramics according to claim 1, characterized in that, The green body comprises, by mass percentage of the chemical composition of the raw materials: SiO 2 55%-60%, Al2O3: 24%-28%, Fe2O3: 0.5%-1.8%, TiO2: 0.5%-1%, CaO: 1%-2%, MgO: 0.2%-0.6%, K2O: 4%-4.5%, Na2O: 1%-1.5%, ZnO: 0%-0.4%, ZrO2: 0%-0.5%, Li2O: 0%-0.05%, Loss on ignition: 5%-10%.

3. The green body for eliminating sintering bulges in high-pressure formed ceramics according to claim 2, characterized in that, The sum of the mass percentages of SiO2 and Al2O3 is 80%-85%; and / or, the molar ratio of SiO2 to Al2O3 is (3.4-4.1):

1.

4. The green body for eliminating sintering bulges in high-pressure formed ceramics according to claim 2, characterized in that, The molar ratio of K2O to Na2O is (2-2.8):

1.

5. A method for preparing a green body with eliminated high-pressure forming ceramic sintering bulges as described in claim 1, characterized in that, Includes the following steps: (1) Weigh the raw materials of the billet according to the proportion, add water and ball mill; (2) After grinding and sieving, water and additives are added to obtain mud; (3) The mud is grouted under high pressure, dried and sintered to obtain the final product.

6. The method for preparing a green body with eliminated high-pressure forming ceramic sintering bulges according to claim 5, characterized in that, In step (1), the particle size distribution after ball milling is: D10≤3.5 μm, D50≤30.0 μm, D90≤100.0 μm.

7. The method for preparing a green body with eliminated high-pressure forming ceramic sintering bulges according to claim 5, characterized in that, In step (2), the additive is one or more of water glass and baking soda.

8. The method for preparing a green body with eliminated high-pressure forming ceramic sintering bulges according to claim 5, characterized in that, In step (2), the concentration of the mud is 350-360 g / 200 mL, and the yield value is 10-16 dyn / cm. 2 The fluidity V0 is 45-70 s / 200mL, and the pulping speed is 6-9 mm / 45min.

9. The method for preparing a green body with eliminated high-pressure forming ceramic sintering bulges according to claim 5, characterized in that, In step (3), the grouting pressure is 0.8-1.2 MPa and the maximum sintering temperature is 1200 ℃.

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