Refractory silicon carbide castable and preparation process thereof

Abstract

The invention relates to the technical field of refractory materials, and provides a refractory silicon carbide castable which comprises the following components in parts by weight: 30-50 parts of silicon carbide particles, 10-20 parts of silicon carbide fine powder, 5-15 parts of corundum fine powder, 5-10 parts of calcium aluminate cement, 3-8 parts of silica powder, 0.5-2 parts of a dispersing agent, 0.5-2 parts of a water reducing agent, 0.1-0.5 part of explosion-proof fibers and 5-10 parts of water. Through matching of silicon carbide, corundum fine powder, calcium aluminate cement and the like with specific raw material granularity and components, the castable is stable in structure at high temperature, high in refractoriness, capable of effectively resisting erosion, good in mechanical property, capable of keeping stable and reliable under different working conditions, suitable for various high-temperature industrial kilns, safe and efficient in production and suitable for industrial production. By adopting a step-by-step mixing mode of dry mixing and wet mixing, the dispersing and water reducing effects can be better exerted, so that the performance of the castable is more stable and reliable, and the production efficiency and the stability of the product quality are improved.

Description

Technical Field

[0001] The invention relates to the technical field of refractory materials, in particular to a refractory silicon carbide castable and a preparation process thereof. Background Art

[0002] Refractory materials play a key role in the high-temperature industrial field. They can withstand high-temperature environments while maintaining stable performance and are widely used in metallurgy, ceramics and other industries. Among them, castables, as an important refractory material, have unique advantages. They are made of a variety of raw materials mixed in a specific proportion, such as silicon carbide, corundum fine powder and other ingredients that work together and are processed through scientific preparation processes. In actual applications, castables can be cast on-site according to the shape and needs of different industrial kilns. After molding, they can effectively resist erosion and scouring by high-temperature melts, ensure the stability and durability of the kiln lining, thereby improving the efficiency and safety of industrial production and reducing equipment maintenance costs.

[0003] Traditional refractory castables have many limitations in raw material selection and preparation technology. The raw materials often lack precise particle size and composition control, resulting in poor structural stability of the castables at high temperatures and inability to effectively resist the erosion and scouring of high-temperature melts. Moreover, traditional preparation processes usually adopt a simple and extensive mixing method, which makes it difficult to fully and evenly mix the components and easily lead to agglomeration, resulting in uneven product quality and low production efficiency, making it difficult to meet the urgent needs of modern industry for high-quality, high-performance refractory materials. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a refractory silicon carbide castable and a preparation process thereof, which solves the problems in the prior art of lack of control over the particle size and composition of the raw materials for preparing the castable and the imperfect preparation process.

[0005] To achieve the above objectives, the present invention is implemented through the following technical scheme: a refractory silicon carbide castable, comprising the following components in parts by weight: 30-50 parts of silicon carbide particles, 10-20 parts of silicon carbide fine powder, 5-15 parts of corundum fine powder, 5-10 parts of calcium aluminate cement, 3-8 parts of silicon micropowder, 0.5-2 parts of dispersant, 0.5-2 parts of water reducer, 0.1-0.5 parts of explosion-proof fiber and 5-10 parts of water.

[0006] Preferably, the particle size of the silicon carbide particles is 3-8 mm, and the particle size of the silicon carbide fine powder is less than 0.08 mm.

[0007] Preferably, the particle size of the corundum fine powder is less than 0.045 mm, and the Al2O3 content is greater than 95%.

[0008] Preferably, the Al2O3 content in the calcium aluminate cement is 70-80%, and the CaO content is 20-30%.

[0009] Preferably, the SiO2 content of the silicon micropowder is greater than 90% and the particle size is less than 0.01 mm.

[0010] Preferably, the dispersant is one or both of sodium tripolyphosphate and sodium hexametaphosphate.

[0011] Preferably, the water reducer is a polycarboxylate water reducer.

[0012] Preferably, a process for preparing a refractory silicon carbide castable comprises the following steps: S1. Add silicon carbide particles, corundum powder, calcium aluminate cement, and silicon powder into a mixer in proportion and dry mix for 3-5 minutes; S2. The dispersant and water reducing agent are added to water and stirred to obtain a mixed solution; S3. Add the mixed solution to the mixer and wet mix for 5-8 minutes; S4. Add silicon carbide fine powder and explosion-proof fiber, continue stirring for 3-5 minutes, and obtain refractory silicon carbide castable.

[0013] Preferably, the stirring speed of the stirrer is 100-200 r / min.

[0014] Preferably, after the stirring in S4 is completed, the castable is vibrated at a frequency of 30-50 Hz for 1-3 minutes, and then cured for 24-48 hours in an environment with a temperature of 10-30° C. and a humidity of 40-60%.

[0015] The present invention provides a refractory silicon carbide castable and a preparation process thereof, which has the following beneficial effects: 1. The present invention combines silicon carbide, corundum fine powder, calcium aluminate cement and other raw materials with specific particle size and composition, so that the castable has a stable structure at high temperature, high refractoriness, can effectively resist erosion, has good mechanical properties, can remain stable and reliable under different working conditions, is suitable for a variety of high-temperature industrial kilns, and ensures safe and efficient production.

[0016] 2. The preparation process of the present invention adopts a step-by-step mixing method, first dry mixing and then wet mixing, which is conducive to the full and uniform mixing of the components. Dry mixing avoids the agglomeration phenomenon caused by direct wet mixing. During wet mixing, the solution prepared by the dispersant and the water reducer is added to better exert its dispersing and water reducing effects, making the performance of the castable more stable and reliable, and improving the production efficiency and the stability of product quality. DETAILED DESCRIPTION

[0017] The following will be combined with 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 making creative work are within the scope of protection of the present invention.

[0018] Embodiment 1: An embodiment of the present invention provides a refractory silicon carbide castable, and raw materials are prepared according to the following weight parts: 40 parts of silicon carbide particles with a particle size of 5 mm, 15 parts of silicon carbide fine powder with a particle size of less than 0.08 mm, 10 parts of corundum fine powder with a particle size of less than 0.045 mm and an Al2O3 content of 97%, 8 parts of calcium aluminate cement with an Al2O3 content of 75% and a CaO content of 25%, 5 parts of silicon micropowder with a SiO2 content of 92% and a particle size of less than 0.01 mm, 1 part of sodium tripolyphosphate as a dispersant, 1 part of polycarboxylic acid water reducer, 0.3 parts of explosion-proof fiber and 8 parts of water.

[0019] Specifically, silicon carbide has the characteristics of high melting point, high strength, good thermal conductivity and thermal shock resistance, which enables the castable to maintain structural stability in high temperature environment and effectively resist the erosion and scouring of high temperature melt. It is suitable for harsh use scenarios such as high-temperature industrial kilns, such as steel smelting furnaces, ceramic firing kilns, etc., which significantly prolongs the service life of the kiln and reduces the company's equipment maintenance costs and replacement frequency; corundum fine powder has high hardness and chemical stability, and synergizes with silicon carbide to further improve the overall strength and corrosion resistance of the castable, and enhances its ability to withstand mechanical stress and chemical erosion at high temperatures; calcium aluminate cement is used as a binder, and the hydration products formed during the hydration process can combine other aggregates and powders together, giving the castable a certain initial strength, so that it can maintain shape stability during construction and maintenance, and is convenient for forming complex-shaped refractory products to meet the diverse needs of different industrial kiln structure designs; the micro-powder characteristics of silicon micropowder can fill the gaps between other particles, optimize the particle grading of the castable, and improve the casting The density of the castable is improved, and its active ingredients can react with other substances at high temperatures to further enhance the bonding strength and improve the high-temperature performance of the castable. As a dispersant, sodium tripolyphosphate can effectively reduce the agglomeration of materials, so that the components are evenly dispersed during the mixing process, improve the uniformity and fluidity of the castable, facilitate casting construction, ensure that the castable can be filled into every corner of the mold, form refractory products with uniform quality, reduce product quality problems caused by construction defects, and improve the product yield rate. Polycarboxylic acid water reducer can reduce water consumption and water-cement ratio without affecting the strength of the castable, thereby reducing the shrinkage rate of the castable during drying and baking, reducing the risk of cracking, improving the dimensional accuracy and appearance quality of the product, and facilitating the production of high-precision refractory parts. During the hardening and baking process of the castable, the explosion-proof fiber can effectively prevent the bursting caused by rapid evaporation of water and poor gas discharge, ensure the structural integrity of the castable during construction and maintenance, and improve the reliability and stability of the product.

[0020] A preparation process of a refractory silicon carbide castable is as follows: first, the silicon carbide particles with a particle size of 5 mm, the corundum fine powder with a particle size of less than 0.045 mm and an Al2O3 content of 97%, the calcium aluminate cement with an Al2O3 content of 75% and a CaO content of 25%, and the silicon micropowder with an SiO2 content of 92% and a particle size of less than 0.01 mm are added into a mixer with a stirring speed of 150 r / min according to the above proportions, and dry mixed for 4 minutes; then, sodium tripolyphosphate and polycarboxylate water reducer are added into water and stirred evenly, and then added into the mixer and wet mixed for 6 minutes; then, silicon carbide fine powder with a particle size of less than 0.08 mm and explosion-proof fiber are added, and stirring is continued for 4 minutes; after stirring is completed, the castable is vibrated and formed, the vibration frequency is 40 Hz, the vibration time is 2 minutes, and finally, it is cured for 36 hours in an environment with a temperature of 20°C and a humidity of 50%.

[0021] Specifically, the preparation process adopts a step-by-step mixing method, first dry mixing and then wet mixing, which is conducive to the full and uniform mixing of the components. Dry mixing can make the solid particles initially mixed evenly to avoid agglomeration caused by direct wet mixing; adding a solution prepared by a dispersant and a water reducer during wet mixing can better exert its dispersing and water reducing effects, making the performance of the castable more stable and reliable, ensuring the quality consistency of each batch of castables, and improving production efficiency and product quality stability; controlling the vibration frequency and time during the vibration molding process can make the castable more compact in the mold, expel bubbles, and improve the density and strength of the castable.

[0022] The refractoriness of the castable in this embodiment reaches 1700° C., and the compressive strength at room temperature is 100 MPa, which meets the requirements for the lining of general industrial furnaces.

[0023] Embodiment 2: An embodiment of the present invention provides a refractory silicon carbide castable, and raw materials are prepared according to the following weight parts: 35 parts of silicon carbide particles with a particle size of 4 mm, 12 parts of silicon carbide fine powder with a particle size of less than 0.08 mm, 8 parts of corundum fine powder with a particle size of less than 0.045 mm and an Al2O3 content of 96%, 6 parts of calcium aluminate cement with an Al2O3 content of 72% and a CaO content of 28%, 4 parts of silicon micropowder with a SiO2 content of 91% and a particle size of less than 0.01 mm, 0.8 parts of sodium hexametaphosphate as a dispersant, 1.2 parts of polycarboxylic acid water reducer, 0.2 parts of explosion-proof fiber and 6 parts of water.

[0024] First, put silicon carbide particles with a particle size of 4mm, corundum fine powder with a particle size of less than 0.045mm and an Al2O3 content of 96%, calcium aluminate cement with an Al2O3 content of 72% and a CaO content of 28%, and silicon micropowder with a SiO2 content of 91% and a particle size of less than 0.01mm into a mixer with a stirring speed of 120r / min and dry mix for 3.5 minutes; then mix the dispersant and water reducer with water and add them to the mixer for wet mixing for 7 minutes; then add silicon carbide fine powder with a particle size of less than 0.08mm and explosion-proof fiber and stir for 3.5 minutes; after stirring, vibrate and mold at a vibration frequency of 35Hz for 1.5 minutes, and cure for 40 hours at 15℃ and 45% humidity. The castable has been tested to have a refractoriness of 1650℃ and a room temperature flexural strength of 15MPa, which can be used for high-temperature equipment components with high strength requirements.

[0025] Embodiment three: The embodiment of the present invention provides a refractory silicon carbide castable, and raw materials are prepared according to the following weight parts: 45 parts of silicon carbide particles with a particle size of 6 mm, 18 parts of silicon carbide fine powder with a particle size less than 0.08 mm, 12 parts of corundum fine powder with a particle size less than 0.045 mm and an Al2O3 content of 98%, 9 parts of calcium aluminate cement with an Al2O3 content of 78% and a CaO content of 22%, 6 parts of silicon micropowder with a SiO2 content of 93% and a particle size less than 0.01 mm, 0.5 parts each of sodium tripolyphosphate and sodium hexametaphosphate as dispersants, 1.5 parts of polycarboxylic acid water reducer, 0.4 parts of explosion-proof fiber and 9 parts of water.

[0026] Silicon carbide particles with a particle size of 6 mm, corundum fine powder with a particle size of less than 0.045 mm and an Al2O3 content of 98%, calcium aluminate cement with an Al2O3 content of 78% and a CaO content of 22%, and silicon micropowder with a SiO2 content of 93% and a particle size of less than 0.01 mm are added to a mixer with a stirring speed of 180 r / min for dry mixing for 4.5 minutes; the dispersant and water reducer are stirred evenly in water and added to a mixer for wet mixing for 7.5 minutes; silicon carbide fine powder with a particle size of less than 0.08 mm and explosion-proof fiber are added and stirred for 4 minutes; then vibration molding is performed, the vibration frequency is 45 Hz, the vibration time is 2.5 minutes, and the environment is maintained at 25°C and 55% humidity for 45 hours. The refractoriness of the castable of this embodiment reaches 1750°C, and the high temperature flexural strength is 10MPa at 1200°C, which is suitable for working environments with high temperatures and certain mechanical stresses, such as the key parts of metallurgical furnaces.

[0027] Comparative Example: The raw materials of the conventional castable are prepared according to the following weight parts: 30 parts of refractory aggregate with a particle size of 5 mm, 10 parts of refractory fine powder with a particle size less than 0.08 mm, 6 parts of aluminate cement and 7 parts of water.

[0028] The preparation process is as follows: directly add refractory aggregate, refractory fine powder and aluminate cement into a mixer with a stirring speed of 100r / min, add water and water reducer and wet mix for 8 minutes, then vibrate and form with a vibration frequency of 30Hz and a vibration time of 1 minute, and cure for 30 hours in an environment of 10℃ and 40% humidity.

[0029] The castables prepared in the above-mentioned embodiments and comparative examples were tested for refractoriness, room temperature compressive strength, strength flexural strength and high temperature flexural strength, and the tested data are shown in the following table: Castable Refractoriness (℃) Room temperature compressive strength (MPa) Flexural strength at room temperature (MPa) High temperature flexural strength 1200℃, MPa) Embodiment 1 1700 100 15 11 Embodiment 2 1650 95 15 12 Embodiment 3 1750 98 13 10 Comparative Example 1400 60 8 6 In summary, the refractory silicon carbide castable provided by the embodiment of the present invention has significant advantages over the traditional castable. Through the comparison of actual test data, the castable of the embodiment of the present invention far exceeds the traditional castable in key indicators such as refractoriness, room temperature compressive strength, room temperature flexural strength and high temperature flexural strength, and can better meet the use requirements in different high temperature industrial scenarios.

[0030] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A refractory silicon carbide castable, characterized in that: The invention comprises the following components in parts by weight: 30-50 parts of silicon carbide particles, 10-20 parts of silicon carbide fine powder, 5-15 parts of corundum fine powder, 5-10 parts of calcium aluminate cement, 3-8 parts of silicon micropowder, 0.5-2 parts of dispersant, 0.5-2 parts of water reducing agent, 0.1-0.5 parts of explosion-proof fiber and 5-10 parts of water.

2. A refractory silicon carbide castable according to claim 1, characterized in that: The particle size of the silicon carbide particles is 3-8 mm, and the particle size of the silicon carbide fine powder is less than 0.08 mm.

3. A refractory silicon carbide castable according to claim 1, characterized in that: The particle size of the corundum fine powder is less than 0.045 mm, and the Al2O3 content is greater than 95%.

4. A refractory silicon carbide castable according to claim 1, characterized in that: The Al2O3 content of the calcium aluminate cement is 70-80%, and the CaO content is 20-30%.

5. A refractory silicon carbide castable according to claim 1, characterized in that: The SiO2 content of the silicon micropowder is greater than 90%, and the particle size is less than 0.01 mm.

6. A refractory silicon carbide castable according to claim 1, characterized in that: The dispersant is one or both of sodium tripolyphosphate and sodium hexametaphosphate.

7. A refractory silicon carbide castable according to claim 1, characterized in that: The water reducer is a polycarboxylate water reducer.

8. The process for preparing a refractory silicon carbide castable according to claim 1, characterized in that: The following steps are involved: S1. Add silicon carbide particles, corundum powder, calcium aluminate cement, and silicon powder into a mixer in proportion and dry mix for 3-5 minutes; S2. The dispersant and water reducing agent are added to water and stirred to obtain a mixed solution; S3. Add the mixed solution to the mixer and wet mix for 5-8 minutes; S4. Add silicon carbide fine powder and explosion-proof fiber, continue stirring for 3-5 minutes, and obtain refractory silicon carbide castable.

9. A process for preparing a refractory silicon carbide castable according to claim 8, characterized in that: The stirring speed of the stirrer is 100-200r / min.

10. The process for preparing a refractory silicon carbide castable according to claim 1, characterized in that: After S4 mixing is completed, the castable is vibrated at a frequency of 30-50 Hz for 1-3 minutes, and then cured for 24-48 hours in an environment with a temperature of 10-30°C and a humidity of 40-60%.