Reactive sintered silicon carbide setter plate and preparation method thereof

Abstract

The invention discloses a reaction-sintered silicon carbide setter plate and a preparation method thereof. The reaction-sintered silicon carbide setter plate product is obtained through powder granulation, compaction and reaction sintering. Wherein the silicon carbide powder of the four particle size sections is matched, the particle size sections are uniform, stacking is more reasonable, coarse particles form a frame, fine particles are filled among the coarse particles, the powder structure is compact in property, and the compactness of a green body obtained after blank pressing is guaranteed; and spray granulation is performed after ball milling, so that all the raw materials and auxiliary materials are uniformly mixed. The surface of the green body pressed by a set oil pressure mold is also provided with a concave-convex structure, so that the contact area between the load bearing plate and the bottom of the domestic porcelain is reduced, air circulation between the load bearing plate and the bottom of the domestic porcelain is increased, and adhesion is effectively avoided. The product has the advantages of long service life, high strength and fast heat conduction, solves the problems of low strength, low heat conductivity and short service life of mullite, and also solves the industrial pain point of adhesion of a reaction-sintered silicon carbide setter plate.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon carbide composite materials, and in particular relates to a reaction-sintered silicon carbide setter plate and a preparation method thereof. Background Art

[0002] At present, the main support plate of daily-use porcelain is made of mullite. The strength of mullite support plate is low and the thermal conductivity is insufficient. This problem is a pain point in the industry. The theoretical use of mullite support plate is about 150 times, with a short service life, low strength, and bending strength below 200MPa. Under full-load production conditions, its service life is less than one month, and the number of uses is about 100 times. In order to meet the load-bearing requirements, the thickness of the mullite support plate is designed to be between 1cm-1.2cm, occupying a large space in the kiln and absorbing a large amount of heat energy. Due to the low strength of mullite, it is easy for the support plate to break and cause kiln blockage. If the kiln is stopped for cleaning, the indirect loss will cost more than 100,000 yuan per time. Moreover, after the bottom plate of the mullite support plate rubs against the alumina roller for a long time, the mullite support plate in the high-temperature zone will stick to the alumina roller, causing the surface of the roller to form a bag, which significantly affects the normal operation of the kiln.

[0003] In the prior art, the silicon carbide setter plate prepared by reaction sintering will precipitate free silicon in the setter plate during continuous high-temperature use, and the free silicon will adhere to the bottom of the daily-use porcelain at high temperatures, thereby affecting the product quality of the daily-use porcelain. Therefore, the existing reaction-sintered silicon carbide setter plate must be brushed with alumina slurry on the surface before use, and the alumina slurry forms a protective coating to prevent the free silicon in the setter plate from adhering to the bottom plate of the daily-use porcelain. Since the slurry needs to be brushed and dried before each use, the process steps and production costs are increased.

[0004] Therefore, it is urgent to develop a reaction-sintered silicon carbide support plate with good use effect, long service life, strong bearing capacity and no need to brush slurry. Summary of the invention

[0005] In view of the problem in the prior art that there is a lack of reaction-sintered silicon carbide support plates with good use effect, long service life, strong bearing capacity and no need to brush slurry, the present invention provides reaction-sintered silicon carbide support plates and a preparation method thereof. The reaction-sintered silicon carbide support plate product is obtained through powder granulation, compacting and reaction sintering.

[0006] The purpose of the present invention is achieved through the following technical solutions: The method for preparing a reaction-sintered silicon carbide setter plate comprises the following steps: S1. Preparation of granulated powder: The silicon carbide powders of four particle size segments are matched according to the mass ratio of (1μm -3μm):(5μm-8μm):(10μm-15μm):(20μm-25μm)=2:3:2:3; Prepare other auxiliary materials: molding agent PEG (polyethylene glycol), polyvinyl alcohol, carbon black with an average particle size of 0.01μm to 1μm, and graphite; PEG accounts for 3%-5% of the weight of silicon carbide powder, polyvinyl alcohol accounts for 1%-3% of the weight of silicon carbide powder, carbon black accounts for 15%-20% of the weight of silicon carbide powder, and graphite accounts for 5%-10% of the weight of silicon carbide powder; The matched silicon carbide powder and other auxiliary materials are mixed together and ball-milled, and then spray-granulated to obtain granulated powder, the water content of which is 1-2%; S2, oil pressure: The granulated powder is placed in a hydraulic mold and pressed into a green body of a set shape and size. The green body density is 1.8g / cm 3 -2.0g / cm 3 ; S3, pre-sintering: pre-sinter the green body at 300℃-500℃ for 1h-2h, and take it out after cooling; S4, impregnation: place the pre-sintered green body in the resin solution, immerse at 2MPa-4MPa for 4h-8h, take out and dry; S5. Reaction sintering: Multiple green sheets are stacked horizontally, and silicon particles are filled between two adjacent layers of green sheets. The total weight of the silicon particles is 25-30% of the weight of the green sheets, and the mass ratio of two particle sizes of silicon particles (3-5) mm and (2-3) μm is 1:2. Sintering parameters: vacuum degree <30Pa, heating to 800-900℃ at a rate of 15℃ / min, keeping warm for 1h-1.5h, heating to 1200-1400℃ at a rate of 12℃ / min, keeping warm for 1h-1.5h, and then heating to 1600-1800℃ at a heating rate of 10℃ / min and keeping warm for 21-24h; S6, secondary sintering reaction: After the S5 insulation stage is finished, the secondary sintering stage is entered to form a silicon nitride film layer. The temperature is lowered to 1500℃ at a cooling rate of 5℃ / min. After vacuuming, high-purity nitrogen with a purity of ≥99.99% is filled in. The flow rate of high-purity nitrogen is 0.5L / min-1L / min. The reaction temperature is kept at 1500℃-1300℃ for 1h-2h. The high-purity nitrogen reacts with elemental silicon to form a silicon nitride film layer. The silicon nitride film layer can avoid adhesion with daily-use porcelain products. S7. After heat preservation, the temperature is lowered to below 100°C at a temperature rate of 10°C / min, cooled to room temperature, the product is taken out, and finally sandblasted to increase the surface smoothness of the product to obtain a reaction-sintered silicon carbide support plate.

[0007] Furthermore, step S5 reaction sintering also includes: covering the bottom and surface of the impregnated green body with support members, horizontally stacking multiple green bodies, separating two adjacent layers of green bodies by support members, filling the support members with silicon particles, and the support members are graphite rings or graphite rods coated with boron nitride on the surface.

[0008] Furthermore, the setter plate prepared by the above steps has the following properties: ① Density is 2.9g / cm 3 -3.1g / cm 3 , flexural strength is 280MPa-320MPa, fracture toughness is 3.0MPa / m 1 / 2 -4.1MPa / m 1 / 2 ; ② High temperature resistance, medium temperature kiln operating temperature ≥1250℃, high temperature kiln operating temperature ≥1380℃, and strong thermal shock resistance; ③Long service life, can be used more than 1000 times; ④Bending degree <2mm, thickness 4mm-6mm, large plate flatness deviation <±0.1%; ⑤ Long-term bearing strength of the support plate is 5kg-50kg; ⑥ After sintering in a high-temperature environment, the support plate and the product will not stick together and will not corrode each other.

[0009] Furthermore, the spheroidal graphite treatment described in step S1 specifically includes: adding two types of silicon carbide grinding balls with sizes of 6mm-8mm and 1mm-2mm in a mass ratio of 1:1 as grinding media, the mass ratio of grinding balls to the total amount of powder raw materials is 2:1, the rotation speed is 100r / min-200r / min, and the grinding media is filtered out after grinding for 6h-10h.

[0010] Furthermore, the inner cavity surface of the oil pressure mold described in step S2 is provided with a concave-convex structure, such as a concave circle, a flat groove structure, a triangular prism structure, a square grid structure, etc., and a convex symmetrical structure is generated on the surface of the green body after oil pressure.

[0011] Furthermore, the oil pressing step in step S2 specifically also includes: for large-sized green bodies, isostatic pressing treatment is performed after oil pressing to improve the strength of the product, the green body is placed in a waterproof rubber sleeve, placed in an isostatic pressing equipment, 150MPa-200MPa, isostatic pressing treatment at room temperature for 2min-6min, and the green body after isostatic pressing treatment is obtained.

[0012] In step S6, a mass flow controller is provided on the nitrogen pipeline to accurately control the flow rate of high-purity nitrogen to 1 L / min, with a purity of ≥99.99%. The flow rate of nitrogen is accurately controlled during the reaction process to ensure the uniformity of the reaction atmosphere and the adequacy of the reaction. The flow rate of nitrogen is 1 L / min, and a slight positive pressure is maintained in the reaction chamber to prevent air infiltration.

[0013] Furthermore, in step S6, the nitrogen is first heated to above 800° C. through a preheating pipe before entering the sintering furnace. Ensure that the entire gas delivery system is well sealed to avoid gas leakage and ensure the accuracy of the gas flow rate.

[0014] The present invention also relates to a reaction-sintered silicon carbide setter plate, which is obtained by using the above-mentioned method for preparing the reaction-sintered silicon carbide setter plate. The prepared setter plate has the following properties: ① Density is 2.9g / cm 3 -3.1g / cm 3 , flexural strength is 280MPa-320MPa, fracture toughness is 3.0MPa / m 1 / 2 -4.1MPa / m 1 / 2 ; ② High temperature resistance, medium temperature kiln ≥1250℃, high temperature kiln ≥1380℃, and strong thermal shock resistance; ③Long service life, more than 1,000 times of use (more than 1 year); ④Bending degree <2mm, thickness 4mm-6mm, large plate flatness deviation <±0.1%; ⑤ Long-term bearing strength of the support plate is 5kg-50kg; ⑥ After sintering in a high-temperature environment, the support plate and the daily-use porcelain products will not stick together and will not corrode each other.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The method for preparing the reaction-sintered silicon carbide setter of the present invention adopts silicon carbide powder of four particle size segments, and the particle size distribution is uniform, and the sintered finished product after grading has good performance; silicon carbide grinding balls are used for ball milling, which can avoid the pollution of powder by grinding with stainless steel grinding balls; 2. The method for preparing the reaction-sintered silicon carbide setter of the present invention, in the process of reaction sintering of silicon carbide, the added carbon black and graphite not only participate in the sintering reaction, but also affect the microstructure and macroscopic properties of the material, mainly having the following functions: ① Participate in the reaction as a carbon source: The preparation principle of reaction-sintered silicon carbide is to use α-SiC and C as raw materials, add an appropriate amount of binder for molding and drying, and then put it into the embedding material containing Si; when the green body is heated in the furnace, the Si around the green body melts and penetrates into the capillaries of the green body to react with the C in the green body to generate SiC. The generated SiC gradually fills the pores in the green body and connects the original α-SiC, finally achieving the densification of the product and obtaining a finished product with strength that meets the requirements.

[0016] ② Influence on the viscosity and pH value of the slurry: The addition of carbon black will affect the viscosity and pH value of the slurry. As the carbon black content increases, the slurry viscosity increases and the pH value gradually increases, which will affect the stability of the slurry and the molding process; adding an appropriate amount of carbon black can make the stability and molding of the entire slurry reach the best state.

[0017] ③ Influence on the volume density and flexural strength of the sintered body: The increase of carbon black content will increase the volume density and flexural strength of the sintered body, but when the carbon black content is too high, the sintered body will burst and a black "cold" area will appear inside, resulting in a sharp drop in volume density and flexural strength; therefore, the appropriate amount of carbon black content plays an important role in the density and strength of the finished product.

[0018] ④ Influence on the microstructure of the sintered body: The addition of carbon black and graphite will affect the microstructure of the sintered body, and then affect its mechanical properties. The appropriate ratio of carbon black and graphite can optimize the structure of the sintered body and improve its mechanical properties.

[0019] ⑤ Increase the bulk density of the green body and reduce the apparent porosity of the fired sample: Carbon black replaces a certain amount of graphite as the carbon source for reaction-sintered silicon carbide, which can increase the bulk density of the green body and reduce the apparent porosity of the fired sample, thereby improving the mechanical properties of the sample.

[0020] ⑥ Reduce the content of free Si: The addition of carbon black can reduce the content of free Si in the finished product after sintering, thereby improving the mechanical properties of the finished product.

[0021] ⑦ Improve the sintering performance and mechanical properties of ceramics: Graphite will be coated on the surface of silicon carbide particles during the ball milling process, significantly reducing the friction between silicon carbide particles, improving the fluidity of the powder, and thus reducing the molding pressure of the ceramic green body, avoiding damage to the mold and press by hard powder, ensuring production safety, while increasing the density of the green body and the uniformity of the internal structure, further improving the sintering performance of ceramics and the mechanical properties of ceramic products.

[0022] ⑧ Generate β-silicon carbide to improve the density and service life of ceramics: The graphite layer on the surface of silicon carbide reacts with metallic silicon during the silicon infiltration and sintering stage, and the generated β-silicon carbide is firmly adsorbed on the raw material α-silicon carbide, making the sintered silicon carbide ceramics denser and with fewer defects between particles, further improving the mechanical properties of the ceramics and extending the service life of the ceramics.

[0023] 3. The method for preparing the reaction-sintered silicon carbide support plate described in the present invention is to use a steel mold with a concave-convex pattern on one side of the inner surface during oil pressing, and a corresponding concave-convex structure is generated on the surface of one side of the green body obtained after pressing, and a support plate with a concave-convex structure is obtained after sintering, which has a good anti-slip and anti-stick effect. By selecting the appropriate type of concave-convex pattern, the heat conduction, friction, air flow channel, anti-adhesion and structural strength of the support plate can be optimized according to specific application requirements. The concave-convex structure can be a wave dot pattern, a grid pattern, a strip pattern, a honeycomb pattern, a wave pattern or a spiral pattern, etc.; the support plate can be rectangular, fish-shaped or other shapes according to the use requirements. The spiral concave-convex pattern is arranged along the spiral direction, providing a special stress distribution and air flow channel effect; the honeycomb concave-convex pattern provides a hexagonal support unit with high strength and stability, which is suitable for applications requiring high bearing capacity and deformation resistance. The prepared support plate product has a concave-convex wave-dot structure on the surface, forming multiple independent support points on the surface, which can reduce the contact area with daily-use porcelain and prevent adhesion to the bottom of daily-use porcelain. It is suitable for the sintering process of easily adhered materials.

[0024] 4. In the preparation method of the reaction-sintered silicon carbide support plate described in the present invention, support members are laid between each layer of green billets during sintering, which can provide good support for the green billets and avoid surface deformation of the support plate during the reaction sintering process. On the other hand, graphite rings or graphite rods coated with boron nitride on the surface are used as support members, which will not adhere to the support plate or silicon particles, will not affect the melting and infiltration of silicon particles into the billet, and will not affect the adhesion of silicon to the surface of the support plate after the reaction with nitrogen.

[0025] 5. The method for preparing the reaction-sintered silicon carbide support plate of the present invention, wherein two kinds of silicon particles of different particle sizes are placed during reaction sintering: the mass ratio of (3-5) mm to (2-3) μm is 1:2, and the total weight of the silicon particles is 25%-30% of the total weight of the green body to be sintered. First, the silicon particles react with the C element (i.e., carbon black and graphite) in the green body of the support plate. During the reaction, the silicon particles in the sintering furnace melt at high temperature and penetrate into the green body to react with carbon. By using two kinds of silicon particles of different particle sizes, the melting degree of silicon particles of different particle sizes is different to a certain extent. The melting degree of silicon in the furnace at different periods is adjusted by a suitable particle size ratio to ensure that in the reaction sintering step S5, the carbon black and graphite in the support plate react completely with the silicon, and at the same time, all the remaining silicon reacts with the high-purity nitrogen in the secondary sintering step S6 to generate silicon nitride, thereby avoiding the attachment of excess and unreacted silicon to the surface of the support plate. The silicon particles are then subjected to a secondary sintering reaction with high-purity nitrogen to produce a silicon nitride film layer. By forming a silicon nitride film layer on the surface of the silicon carbide support plate, the silicon carbide support plate is isolated on the surface, thereby preventing trace amounts of free silicon or silicon dioxide in the support plate from floating to the surface in an excessively high-temperature working environment and causing adhesion between the daily-use porcelain and the support plate.

[0026] 6. In the method for preparing the reaction-sintered silicon carbide support plate described in the present invention, the heating rate in step S5 is a key factor affecting the reaction progress. Too fast or too slow a heating rate may cause the degree of conversion of silicon nitride α phase to β phase to exceed the degree of internal reaction, thereby affecting the completeness of the reaction of silicon powder. The length of the reaction time in step S5 will affect the formation of silicon nitride and the uniformity of the reaction. If the reaction time is too short, the surface of the support plate cannot be completely covered with a complete silicon nitride layer. If the reaction time is too long, the silicon nitride layer on the surface of the support plate is prone to uneven thickness. The present invention finds the optimal sintering heating rate and reaction time through multiple experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0028] Figure 1 This is a sample picture of the silicon carbide setter plate prepared in Example 1 of the present invention; Figure 2 This is a sample picture of the silicon carbide setter plate prepared in Example 2 of the present invention; Figure 3 This is a sample picture of the silicon carbide setter plate prepared in Example 3 of the present invention; Figure 4 A diagram of a steel mold for preparing a silicon carbide setter plate in Example 3 of the present invention (a concave circular hole is provided on the inner surface of one side of the steel mold, and a convex wave point pattern structure is generated on the surface of the green body after oil pressure); Figure 5 This is a sample diagram of setting a flat groove structure on the surface of the silicon carbide setter plate by using a hydraulic mold in the preparation of Example 4 of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in 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 part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1: The method for preparing a reaction-sintered silicon carbide setter plate is used to prepare a small plate with a size of 300×300×5 mm, including the following steps: S1. Preparation of granulated powder: Silicon carbide powder of 4 particle size segments is matched: 1-3μm: 5-8μm: 10-15μm: 20-25μm = 2:3:2:3; Other auxiliary materials: molding agent PEG is 3% of the weight of silicon carbide powder, polyvinyl alcohol is 1% of the weight of silicon carbide powder, the average particle size is 0.01μm~1μm, carbon black is 18% of the weight of silicon carbide powder, and graphite is 5% of the weight of silicon carbide powder; The granulated powder was obtained by ball milling and spray granulation, and the moisture content of the granulated powder was 2%; S2, oil pressure green density 1.91g / cm 3 ; S3, pre-sintering the green body at 300℃ for 1.5h; S4, immerse in resin solution, 3Mpa for 6h, take out and dry; S5. Reaction sintering: multiple green bodies are stacked horizontally, and silicon particles are filled between two adjacent layers of green bodies. The total weight of the silicon particles is 26% of the weight of the green bodies, and the mass ratio of the two particle sizes of silicon particles (3-5) mm and (2-3) μm is 1:2; the vacuum degree is 28-30 Pa, and the temperature is increased to 900°C at a rate of 15°C / min, and kept at this temperature for 1 hour, and then the temperature is increased to 1700°C at a rate of 10°C / min and kept at this temperature for 21 hours; S6. After the insulation stage, enter the secondary sintering stage to generate silicon nitride. The temperature is cooled to 1500°C at a rate of 5°C / min. Vacuum and fill with nitrogen. The flow rate of high-purity nitrogen (purity ≥99.99%) is 1 L / min, and the temperature is kept for 1.5 hours.

[0031] Test results: Finished product density 3.02 g / cm 3 , fracture toughness 3.82 MPa / m 1 / 2, flexural strength 305 MPa, flatness deviation <±0.16%, tried 20 times, no adhesion to daily porcelain products.

[0032] Embodiment 2: The method for preparing a reaction-sintered silicon carbide setter plate is used to prepare a small plate with a size of 300×300×5 mm, including the following steps: S1, silicon carbide powder ratio is the same as that in Example 1; Other auxiliary materials: molding agent PEG is 4% of the weight of silicon carbide powder, polyvinyl alcohol is 3% of the weight of silicon carbide powder, the average particle size is 0.01μm~1μm, carbon black is 20% of the weight of silicon carbide powder, and graphite is 10% of the weight of silicon carbide powder; The granulated powder was prepared in the same manner as in Example 1; S2, oil pressure green density 1.93g / cm 3 , which is different from Example 1 in that the mold surface used has a corrugated structure; S3, pre-sintering the green body at 300℃ for 2h; S4, impregnation: the green body is immersed in the resin solution at 3MPa for 4h, and then taken out and dried; S5. Reaction sintering: Multiple green sheets are stacked horizontally, and silicon particles are filled between two adjacent layers of green sheets. The total weight of silicon particles is 28% of the weight of the green sheets. The mass ratio of silicon particles of two sizes (3-5) mm and (2-3) μm is 1:2. The vacuum degree is 28-30 Pa, and the temperature is increased to 900 ° C at a rate of 15 ° C / min, and the temperature is kept for 1.5 hours. Then the temperature is increased to 1700 ° C at a rate of 10 ° C / min and the temperature is kept for 22-24 hours. S6. Secondary sintering: cool down to 1500°C at a rate of 5°C / min, evacuate and fill with nitrogen, the flow rate of high-purity nitrogen (purity ≥99.99%) is 1 L / min, and keep warm for 2h.

[0033] Test results: Finished product density 3.05 g / cm 3 , fracture toughness 3.79 MPa / m 1 / 2 , flexural strength 298 MPa, flatness deviation <±0.15%, tried 20 times, no adhesion to daily porcelain products.

[0034] Embodiment 3: The method for preparing a reaction-sintered silicon carbide setter plate is used to prepare a fish-shaped flat plate of 280×408×5 mm, which includes the following steps: S1, silicon carbide powder ratio is the same as that in Example 1; Other auxiliary materials: molding agent PEG is 1% of the weight of silicon carbide powder, polyvinyl alcohol is 2% of the weight of silicon carbide powder, the average particle size is 0.01-1μm, carbon black is 15% of the weight of silicon carbide powder, and graphite is 8% of the weight of silicon carbide powder; The granulated powder was prepared in the same manner as in Example 1; S2, oil pressure green density 1.89g / cm 3 , which is different from Example 1 in that the whole structure is a fish-shaped structure; S3, pre-sintering the green body at 350℃ for 2h; S4, the green body is immersed in the resin solution at 2Mpa for 8h, and then taken out and dried; S5. Reaction sintering: multiple green bodies are stacked horizontally, and silicon particles are filled between two adjacent layers of green bodies. The total weight of the silicon particles is 30% of the weight of the green bodies, and the mass ratio of the two particle sizes of silicon particles (3-5) mm and (2-3) μm is 1:2; the vacuum degree is 28-30 Pa, and the temperature is increased to 800°C at a rate of 15°C / min, and kept at this temperature for 1.5 hours, and then the temperature is increased to 1800°C at a rate of 10°C / min and kept at this temperature for 22-24 hours; S6. Secondary sintering: cool down to 1500°C at a rate of 5°C / min, evacuate and fill with nitrogen, the flow rate of high-purity nitrogen (purity ≥99.99%) is 1 L / min, and keep warm for 1h.

[0035] Test results: Finished product density 3.08 g / cm 3 , fracture toughness 3.84 MPa / m 1 / 2 , flexural strength 311 MPa, flatness deviation <±0.18%, tried 20 times, no adhesion with daily porcelain products, such as Figure 4 The figure shows a steel mold for preparing a silicon carbide support plate in Example 3 (a concave circular hole is provided on the inner surface of one side of the steel mold, and a raised wave dot pattern structure is generated on the surface of the green body after oil pressure).

[0036] Embodiment 4: The method for preparing a reaction-sintered silicon carbide setter plate is used to prepare a rectangular large plate of 400×450×5 mm, comprising the following steps: The difference from Example 1 is: Step S2: Put the granulated powder into a hydraulic mold and press it into a green body of a set shape and size. The green body is then isostatically pressed. After the process, the particle size is 1.92 g / cm 3 ; like Figure 5 As shown, it is a sample diagram of setting a flat groove structure on the surface of the setter plate by a hydraulic mold in the preparation of the silicon carbide setter plate of Example 4; Step S5: The bottom and surface of the impregnated green body are covered with support members, multiple green bodies are stacked horizontally, two adjacent layers of green bodies are separated by support members, silicon particles are filled inside the support members, and the support members are graphite rings coated with boron nitride on the surface, and adjacent graphite rings fit closely to each other; the total weight of the silicon particles is 30% of the weight of the green body, and the mass ratio of the two particle sizes of silicon particles (3-5) mm and (2-3) μm is 1:2.

[0037] Test results: Finished product density 3.04 g / cm 3 , fracture toughness 3.69 MPa / m 1 / 2 , flexural strength 285 MPa, flatness deviation <±0.2%, after 20 trials, there is no adhesion between the silicon carbide support plate and daily-use porcelain products.

[0038] Comparative Example 1: The size of the small plate is 300*300*5mm, and the main preparation steps are the same as those in Example 1, except that: there are no steps S3 pre-sintering, S4 impregnation and S6 secondary sintering, the total weight of silicon particles with a particle size of 2-3μm in step S5 is 26% of the weight of the green body, and after the insulation is completed, the temperature is directly lowered to the furnace opening temperature before the furnace is opened.

[0039] Test results: Density 2.58 g / cm 3 , fracture toughness 2.79 MPa / m 1 / 2 , flexural strength 268 MPa, flatness deviation ±0.2%, during the third trial, obvious adhesion between the surface of the support plate and the daily-use porcelain products appeared.

[0040] Compared with the test results of the support plate in Example 1, it can be seen that in Example 1, there are no steps S3 pre-firing, S4 impregnation and S6 secondary sintering, and the density, fracture toughness and flexural strength of the finished product are significantly lower than those in Example 1, and the product showed obvious adhesion with the daily-use porcelain product after the third trial use, indicating that the product adopts a scheme similar to the reaction sintering step in the prior art (that is, the green body after oil pressing is directly sintered to obtain the silicon carbide support plate), the density and strength of the product are low, and adhesion cannot be avoided without additional application of alumina slurry during use.

[0041] Comparative Example 2: The size of the small plate is 300*300*5mm. The main preparation steps are the same as those in Example 1, except that there is no pre-sintering in step S3 and no secondary sintering in step S6. The total weight of silicon particles with a particle size of 2-3μm in step S5 is 26% of the weight of the green body. After the insulation is completed, the temperature is directly lowered to the furnace opening temperature before the furnace is opened.

[0042] Test results: Finished product density 2.72 g / cm 3 , fracture toughness 2.99 MPa / m1 / 2 , flexural strength 282, flatness deviation ±0.18%, during the third trial, obvious adhesion between the surface of the support plate and the daily-use porcelain products appeared.

[0043] Compared with the test results of the support plate of Example 1, it can be seen that in Example 2, there is no pre-firing in step S3 and no secondary sintering in step S6. The density, fracture toughness and flexural strength of the finished product are significantly lower than those in Example 1, and obvious adhesion with the daily-use porcelain product occurred after the third trial use; the density and strength of Comparative Example 2 are higher than those of Comparative Example 1, indicating that the reaction sintering after the green body is impregnated can improve the density and strength of the finished product.

[0044] Comparative Example 3: The size of the small plate is 300*300*5mm. The main preparation steps are the same as those in Example 1, except that there is no secondary sintering in step S6. The total weight of silicon particles with a particle size of 2-3 μm in step S5 is 26% of the weight of the green body. After the insulation is completed, the temperature is directly lowered to the furnace opening temperature before the furnace is opened.

[0045] Test results: Finished product density 2.92 g / cm 3 , fracture toughness 3.62 MPa / m 1 / 2 , flexural strength 298 MPa, flatness ±0.2%, adhesion between the support plate and the daily-use porcelain product occurred during the fourth trial.

[0046] Compared with the test results of the supporting plate of Example 1, it can be seen that in Example 3, there is only one particle size of silicon particles, and there is no secondary sintering in step S6. The density, fracture toughness and flexural strength of the finished product are slightly lower than those in Example 1, and obvious adhesion with daily-use porcelain products appeared after the fourth trial, indicating that the absence of secondary sintering in step S6 will reduce the anti-adhesion performance of the finished product; the density and strength of Comparative Example 3 are significantly higher than those of Comparative Example 1, and the anti-adhesion performance is not much different from that of Comparative Example 1 during the trial, indicating that adding step S3 pre-firing and step S4 impregnation treatment can effectively improve the density and strength of the finished product.

[0047] Comparative Example 4: The size of the small plate is 300*300*5mm, and the main preparation steps are the same as those in Example 1, except that the total weight of silicon particles with a particle size of 2-3 μm in step S5 is 26% of the weight of the green body, and the purity of nitrogen in the secondary sintering in step S6 is 85-90%.

[0048] Test results: Finished product density 2.95 g / cm 3 , fracture toughness 3.65 MPa / m 1 / 2 , flexural strength 299 MPa, flatness ±0.27%, the thickness of the silicon nitride film on the surface of the support plate is uneven, and local adhesion between the support plate and the daily-use porcelain product occurred during the 8th trial.

[0049] Compared with the test results of the supporting plate of Example 1, it can be seen that there is only one particle size of silicon particles in Comparative Example 4, the nitrogen purity in the secondary sintering of step S6 is lower than that of Example 1, the density, fracture toughness and flexural strength of the finished product are slightly lower than those of Example 1, and local adhesion with daily-use porcelain products occurs when the trial is carried out for the 8th time; the density, fracture toughness and strength of Comparative Example 4 are higher than those of Comparative Example 1, and the anti-adhesion property is better than that of Comparative Example 1 during the trial, indicating that after the reaction sintering treatment of step S5, the secondary sintering of step S6 is added, and when the nitrogen purity is 85-90%, a silicon nitride film layer can be generated on the surface of the finished product as a protective isolation layer, which effectively improves the anti-adhesion performance of the finished product.

[0050] Comparative Example 5: The size of the small plate is 300*300*5mm, and the main preparation steps are the same as those in Example 1, except that the total weight of the silicon particles with a particle size of 2-3 μm in step S5 is 26% of the weight of the green body, and the purity of the nitrogen in step S6 is 95%; Test results: Density 2.89 g / cm 3 , fracture toughness 2.99 MPa / m 1 / 2 , flexural strength 289 MPa, flatness ±0.3%, the thickness of the silicon nitride film on the surface of the support plate is uneven, and local adhesion between the support plate and the daily-use porcelain product occurs during the 10th trial.

[0051] Compared with the test results of the supporting plate of Example 1, it can be seen that there is only one particle size of silicon particles in Comparative Example 5, the nitrogen purity in the secondary sintering of step S6 is slightly lower than that of Example 1, the density, fracture toughness and flexural strength of the prepared finished product are slightly lower than those of Example 1, and local adhesion with the daily-use porcelain product occurred when tried for the 7th time; the density, fracture toughness and strength of Comparative Example 5 are higher than those of Comparative Example 1 and Comparative Example 4, and the anti-adhesion property is better than that of Comparative Example 1 and Comparative Example 4 during the trial, indicating that the nitrogen purity during the secondary sintering of step S6 is increased to 95%, and the silicon nitride film layer generated on the surface of the finished product is more stable and reliable, which effectively improves the anti-adhesion performance of the finished product.

[0052] Comparative Example 6: The rectangular large plate is 400*450*5mm, and the main preparation steps are the same as those in Example 4, except that: no support is placed, a total of 4 layers of green sheets are stacked horizontally, and the surface and bottom of each layer of green sheets are covered with silicon particles of two particle sizes, and the green sheets are separated by silicon particles.

[0053] Test results: Finished product density 2.94 g / cm 3 , fracture toughness 3.60 MPa / m 1 / 2, flexural strength 275 MPa, flatness: large deformation, deformation bending 5mm-6mm, the area of ​​silicon nitride film layer attached to the surface only accounts for less than 20% of the area of ​​the support plate, and local adhesion between the support plate and the daily-use porcelain product occurs during the third trial.

[0054] Compared with the test results of the firing plate in Example 4, it can be seen that in Comparative Example 6, no support is placed between the green blanks, and each layer of green blanks is covered with silicon particles. The density, fracture toughness and flexural strength of the prepared finished product are slightly lower than those in Example 1, but the deformation is large, the deformation curvature is 5mm-6mm, the amount of silicon nitride film layer is very small, and local adhesion with daily-use porcelain products occurred when it was tried for the third time; this indicates that no support is placed between the green blanks will significantly affect the flatness of the finished product, because the silicon particles laid between the silicon carbide green blanks melt and penetrate at high temperature, thereby affecting the horizontal state of the silicon carbide green blanks, and then affecting the flatness of the finished product; and multiple green blanks are stacked horizontally, and when the silicon is melted and penetrated in step S5, the nitrogen cannot react with the silicon and evenly adhere to the entire surface of the firing plate.

[0055] By comparing the embodiments and the comparative examples, it can be seen that the advantages of the present invention are: 1. The reaction-sintered silicon carbide setter plate product prepared by the present invention is as follows: Figure 1 As shown, this is a sample picture of the silicon carbide support plate prepared in Example 1; Figure 2 As shown, this is a sample picture of the silicon carbide support plate prepared in Example 2; Figure 3 The figure shows a sample of the silicon carbide setter prepared in Example 3. The reaction-sintered silicon carbide setter prepared by the present invention has the advantages of long life, high strength and fast thermal conductivity, which solves the problems of low strength, low thermal conductivity and short service life of the setter using mullite in the prior art, and solves the industry pain point that the reaction-sintered silicon carbide setter in the prior art is easy to adhere to the daily-use porcelain products.

[0056] 2. The present invention adopts a combination of silicon carbide powders of four particle size segments, with uniform particle size segments, more reasonable stacking, coarse particles forming a framework, and fine particles filling between the coarse particles to form a relatively compact powder structure, thereby ensuring the density of the green body after compaction; spray granulation is performed after ball milling to ensure uniform mixing between the various raw and auxiliary materials; two silicon particles with different particle sizes are used to adjust the melting degree of silicon in the furnace at different times to ensure that in the step S5 reaction sintering step, the carbon black and graphite in the support plate react completely with the silicon, and at the same time, the remaining silicon reacts with the high-purity nitrogen in the secondary sintering in step S6 to generate silicon nitride, thereby avoiding excess, unreacted silicon from adhering to the surface of the support plate.

[0057] 3. The surface of the green body obtained by pressing with a set oil pressure mold in the present invention also has a concave-convex structure. The surface of the prepared silicon carbide supporting plate product has a concave-convex structure. The concave-convex structure does not affect the overall levelness of the product. The daily-use porcelain product will not be skewed after being placed. The concave-convex structure can significantly reduce the contact area between the daily-use porcelain product and the supporting plate, greatly increase the air circulation between the daily-use porcelain and the bottom of the supporting plate, and further avoid the adhesion between the daily-use porcelain and the supporting plate.

[0058] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a reaction-sintered silicon carbide setter, characterized in that: The following steps are involved: S1. Preparation of granulated powder: The silicon carbide powders of four particle size segments are matched according to the mass ratio of (1μm -3μm):(5μm-8μm):(10μm-15μm):(20μm-25μm)=2:3:2:3; Prepare other auxiliary materials: molding agent PEG, polyvinyl alcohol, carbon black with an average particle size of 0.01μm to 1μm, and graphite; PEG accounts for 3%-5% of the weight of silicon carbide powder, polyvinyl alcohol accounts for 1%-3% of the weight of silicon carbide powder, carbon black accounts for 15%-20% of the weight of silicon carbide powder, and graphite accounts for 5%-10% of the weight of silicon carbide powder; The prepared powder raw materials and other auxiliary materials are mixed together and then ball-milled, and then spray-granulated to obtain granulated powder, the moisture content of which is 1-2%; S2, oil pressure: The granulated powder is placed in a hydraulic mold and pressed into a green body of a set shape and size. The green body density is 1.8g / cm 3 -2.0g / cm 3 ; S3, pre-sintering: pre-sinter the green body at 300℃-500℃ for 1h-2h, and take it out after cooling; S4, impregnation: place the pre-sintered green body in the resin solution, immerse at 2MPa-4MPa for 4h-8h, take out and dry; S5. Reaction sintering: Multiple green sheets are stacked horizontally, and silicon particles are filled between two adjacent layers of green sheets. The total weight of the silicon particles is 25-30% of the weight of the green sheets, and the mass ratio of the two particle sizes of silicon particles (3-5) mm and (2-3) μm is 1:

2. Sintering parameters: vacuum degree <30Pa, heating to 800-900℃ at a rate of 15℃ / min, keeping warm for 1h-1.5h, heating to 1200-1400℃ at a rate of 12℃ / min, keeping warm for 1h-1.5h, and then heating to 1600-1800℃ at a heating rate of 10℃ / min and keeping warm for 21-24h; S6, secondary sintering reaction: After the S5 heat preservation stage is completed, the temperature is lowered to 1500°C at a cooling rate of 5°C / min, and high-purity nitrogen is filled in after vacuuming. The flow rate of high-purity nitrogen is 0.5L / min-1L / min. The reaction temperature is kept at 1500°C-1300°C for 1h-2h. High-purity nitrogen reacts with elemental silicon to form a silicon nitride film layer on the surface of the support plate; S7. After heat preservation, the temperature is lowered to below 100°C at a temperature rate of 10°C / min, cooled to room temperature, the product is taken out, and finally sandblasted to increase the surface smoothness of the product to obtain a reaction-sintered silicon carbide support plate.

2. The method for preparing a reaction-sintered silicon carbide setter according to claim 1, characterized in that: Step S5 reaction sintering also includes: covering the bottom and surface of the impregnated green body with support members, placing multiple green bodies horizontally stacked, separating two adjacent layers of green bodies by support members, filling the interior of the support members with silicon particles of two particle sizes, and the support members are graphite rings or graphite rods coated with boron nitride on the surface.

3. The method for preparing a reaction-sintered silicon carbide setter according to claim 1, characterized in that: The spheroidal graphite treatment described in step S1 specifically includes: adding two types of silicon carbide grinding balls with particle sizes of 6mm-8mm and 1mm-2mm in a mass ratio of 1:1 as grinding media, the mass ratio of grinding balls to the total amount of powder raw materials is 2:1, the rotation speed is 100r / min-200r / min, and the grinding media is filtered out after grinding for 6h-10h.

4. The method for preparing a reaction-sintered silicon carbide setter according to claim 1, characterized in that: The inner cavity surface of the oil pressure mold described in step S2 is provided with a concave-convex structure, and the concave-convex structure includes one of a concave circular hole, a flat groove structure, a triangular prism structure or a square grid structure.

5. The method for preparing a reaction-sintered silicon carbide setter according to claim 1, characterized in that: The oil pressing step in step S2 specifically also includes: for large-sized green bodies, isostatic pressing treatment is performed after oil pressing, the green bodies are placed in a waterproof rubber sleeve, placed in an isostatic pressing device, and isostatic pressing treatment is performed at 150MPa-200MPa at room temperature for 2min-6min to obtain green bodies after isostatic pressing treatment.

6. The method for preparing a reaction-sintered silicon carbide setter according to claim 1, characterized in that: In step S6, a mass flow controller is provided on the nitrogen pipeline to accurately control the flow rate of high-purity nitrogen to 1 L / min, and the purity is ≥99.99%.

7. The method for preparing a reaction-sintered silicon carbide setter according to claim 1, characterized in that: In step S6, the nitrogen is first heated to above 800° C. through a preheating pipe before entering the sintering furnace.

8. Reaction sintered silicon carbide setter, characterized in that: The method for preparing a reaction-sintered silicon carbide setter plate according to any one of claims 1 to 7 is used to obtain the setter plate, and the prepared setter plate has the following properties: ① Density is 2.9g / cm 3 -3.1g / cm 3 , flexural strength is 280MPa-320MPa, fracture toughness is 3.0MPa / m 1 / 2 -4.1MPa / m 1 / 2 ; ②High temperature resistance, working temperature ≥1380℃; ③Long service life, can be used more than 1000 times; ④Bending degree <2mm, thickness 4mm-6mm, large plate flatness deviation <±0.1%; ⑤ Long-term bearing strength of the support plate is 5kg-50kg; ⑥ After sintering in a high-temperature environment, the support plate and the product will not stick together and will not corrode each other.

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