Methyl sodium silicate modified silica sol combined corundum-mullite castable and preparation method thereof

Abstract

The invention discloses a methyl sodium silicate modified silica sol combined corundum-mullite castable and a preparation method thereof, and belongs to the technical field of refractory castable. The castable comprises 40-50% of brown fused alumina particles, 18-28% of mullite particles, 16-20% of compact corundum powder, 2-5% of silica powder, 7-14% of activated alumina powder, 1-2% of a composite additive, 0.06-0.12% of a water reducing agent and 7.2-8.5% of externally added methyl sodium silicate modified silica sol, wherein in the methyl sodium silicate modified silica sol, methyl sodium silicate accounts for 0.5-2% of the mass of the silica sol. The obtained castable is low in porosity, the material is more compact, the sintering degree of castable particles in a high-temperature environment is high, and the low-temperature demolding strength and the high-temperature strength are remarkably improved; meanwhile, the process is simple, rapid baking hardening of the castable can be achieved, the construction period is remarkably shortened, and good economic benefits and wide development prospects are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory castables, and particularly relates to a sodium methyl silicate-modified silica sol combined with corundum-mullite castable and a preparation method thereof. Background Art

[0002] The safe operation and longevity of blast furnaces and hot blast furnaces are key to ensuring stable steel production and improving corporate profitability. Therefore, the harsh environments within these furnaces, such as high temperature, high pressure, and dust erosion, place higher demands on the furnace lining materials. Currently, the lining materials for blast furnaces and hot blast furnaces are cast using high-aluminum castables in an integrated process. However, the intense erosion of high-temperature slag and the long-term erosion of various impurities make the furnace lining material extremely susceptible to severe impact, resulting in deformation such as cracking and concavity. In severe cases, it can even lead to collapse and shedding of the lining, posing a serious threat to people's lives and property.

[0003] Corundum-mullite castables have excellent properties such as good structural organization, high purity, low creep rate, small thermal expansion, good thermal shock resistance, and strong resistance to chemical corrosion. They are mainly used for linings of blast furnaces, hot blast furnaces and other kilns. Aluminate cement is widely used as a binder for corundum-mullite castables due to its good rheological properties and high early strength. However, its low medium and high temperature strength, poor durability, and long construction period limit its large-scale use in mullite-corundum castables. With the continuous research and application of nanotechnology in the refractory industry, silica sol as a binder for refractory castables has become one of the research hotspots at home and abroad. Compared with aluminate cement, silica sol binding system can avoid the introduction of Ca 2+ Therefore, the castable will not generate low-melting products such as calcium feldspar, calcium aluminum feldspar, and tricalcium aluminate at high temperatures, which significantly enhances the castable's corrosion resistance and medium- and high-temperature strength. At the same time, silica sol does not produce hydration products and has little crystallization water. The castable can be quickly constructed and baked, significantly shortening the construction period. However, a major problem with silica sol-bonded castables is its very low low-temperature demoulding strength. This is because the low-temperature demoulding strength of the castable is mainly generated by the condensation reaction of a small amount of silanol groups (-Si-OH). The degree of spontaneous condensation reaction of -Si-OH in the system is extremely low, and the bonding force is weak, resulting in the inability of the particles to bond tightly together. Therefore, the low low-temperature demoulding strength of the castable seriously limits the large-scale promotion and application of silica sol-bonded corundum-mullite castables. Summary of the Invention The purpose of the present invention is to address the deficiencies in the prior art and provide a sodium methyl silicate-modified silica sol-bonded corundum-mullite castable and a preparation method thereof, which significantly improves the low-temperature demoulding strength and high-temperature performance of the castable, and is conducive to the large-scale promotion and application of the silica sol-bonded corundum-mullite castable.

[0004] To achieve the above object, the technical solution adopted by the present invention is: Provided is a sodium methyl silicate-modified silica sol combined with corundum-mullite castable, comprising, by mass percentage: 40-50% brown corundum particles, 18-28% mullite particles, 16-20% dense corundum powder, 2-5% silica powder, 7-14% activated alumina powder, 1-2% composite additives, 0.06-0.12% water reducer, and 7.2-8.5% sodium methyl silicate-modified silica sol; wherein: In the silica sol modified by sodium methyl silicate, sodium methyl silicate accounts for 0.5~2% of the mass of the silica sol.

[0005] According to the above scheme, the silica sol modified with sodium methyl silicate is prepared by adding sodium methyl silicate into silica sol, stirring and ultrasonically mixing the sodium methyl silicate to fully dissolve the sodium methyl silicate.

[0006] Preferably, the stirring time is 10 to 15 min; and the ultrasonic mixing time is 20 to 30 min.

[0007] According to the above scheme, the mass fraction of SiO2 in the silica sol is 25-35%; preferably, the pH is 6-8.

[0008] According to the above solution, the particle size of the silica sol is 10-30 nm.

[0009] According to the above solution, the particle size of the sodium methyl silicate is ≤0.074 mm. Preferably, the CH5SiO3Na content is ≥99%.

[0010] According to the above scheme, the brown corundum particles are made by mixing three types of dense corundum particles with particle sizes of 5~3 mm, 3~1 mm, and 1~0 mm in a mass ratio of 1: 2.8~3.2: 2.3~2.7; wherein the Al2O3 content is ≥98%.

[0011] According to the above scheme, the mullite particles are formed by mixing three types of mullite particles with particle sizes of 5-3 mm, 3-1 mm, and 1-0 mm in a mass ratio of 1: 2.8-3.2: 2.3-2.7; wherein the Al2O3 content is ≥60%.

[0012] According to the above scheme, the Al2O3 content in the dense corundum powder is ≥98% and the particle size is ≤0.074mm.

[0013] According to the above scheme, SiO2 in the silicon micropowder is ≥96%.

[0014] According to the above solution, the particle size of the silicon micropowder is ≤5μm.

[0015] According to the above scheme, the Al2O3 content in the activated alumina powder is ≥98%.

[0016] According to the above solution, the particle size of the activated alumina powder is ≤1.5μm.

[0017] According to the above scheme, the composite additive is a mixture of magnesium oxide and boron carbide, wherein the mass ratio of magnesium oxide to boron carbide is 1:2.5~3.5.

[0018] According to the above solution, the particle size of the composite additive is ≤0.088mm.

[0019] According to the above solution, the water reducer is one or more of sodium hexametaphosphate, sodium pyrophosphate, and sodium tripolyphosphate.

[0020] According to the above solution, the particle size of the water reducer is ≤0.074 mm.

[0021] A method for preparing the sodium methyl silicate-modified silica sol combined with corundum-mullite castable is provided, comprising the following steps: Brown corundum particles, mullite particles, dense corundum powder, silica powder, activated alumina powder, composite additives and water reducer are mechanically stirred to form dry uniform aggregate, and then silica sol modified by sodium methyl silicate is added, and the mixture is fully mixed and stirred to obtain corundum-mullite castable.

[0022] The present invention provides a sodium methyl silicate-modified silica sol combined with a corundum-mullite castable. The sodium methyl silicate-modified silica sol is combined with brown corundum particles, mullite particles, dense corundum powder, silica powder, activated alumina powder, composite additives, and a water reducer to significantly improve the low-temperature demoulding strength and high-temperature performance of the castable. The specific mechanism is as follows: Sodium methyl silicate is a solid powder, belonging to organic sodium silicate, an ionic compound, chemically stable, environmentally friendly and non-toxic, and has good water solubility. When an appropriate amount of sodium methyl silicate is added to the silica sol, sodium methyl silicate can be hydrolyzed to generate OH - and -Si-OH, the reaction process can be expressed as CH3Na3SiO3+3H2O=CH3Si(OH)3+3NaOH; on the one hand, the hydrolysis product -Si-OH can undergo dehydration condensation reaction with -Si-OH on the surface of silica sol. Since the content of -Si-OH participating in the reaction in the whole system increases, the dehydration condensation reaction of silica sol is promoted. On the other hand, another hydrolysis product NaOH in the solution makes the solution highly alkaline, OH -Combined with the hydroxyl groups on the surface of silica sol to form stable silicate anions, this combination can reduce the charge density on the surface of silica sol, reduce the electrostatic repulsion between particles, facilitate the bridging effect between particles, and promote the dehydration condensation reaction of silica sol; in addition, as the above reaction proceeds, the hydrolysis of sodium methyl silicate is further promoted, and as the hydrolysis proceeds, more and more water in the silica sol system is consumed, increasing the probability of silica sol particle collision, and promoting the dehydration condensation reaction between the original -Si-OH in the silica sol. Therefore, by modifying silica sol with sodium methyl silicate, the dehydration condensation reaction between -Si-OH in the system is promoted, the formation of a three-dimensional network structure is accelerated, the particle skeleton is formed, and the binding force between the powder and the particles is increased, thereby improving the low-temperature demolding strength of silica sol combined with corundum-mullite castables. At the same time, combined with the very small amount of Na in sodium methyl silicate, + The formed liquid phase prompts the particles to fill the gaps, which is also beneficial to promoting sintering between particles, improving the dense packing degree of the castable, and significantly improving the high-temperature strength of the castable.

[0023] The beneficial effects of the present invention are as follows: 1. The present invention provides a sodium methyl silicate-modified silica sol combined with a corundum-mullite castable. By combining the sodium methyl silicate-modified silica sol with brown corundum particles, mullite particles, dense corundum powder, silicon micropowder, activated alumina powder, composite additives and a water reducer, the degree of spontaneous condensation reaction of -Si-OH in the system is effectively improved, the bonding force between the particles is stronger, the porosity of the castable is reduced, the material is denser, the degree of sintering between the castable particles is high in a high-temperature environment, and the low-temperature demoulding strength and high-temperature strength of the castable are significantly improved, thus having important application prospects.

[0024] 2. The present application provides a method for preparing a corundum-mullite castable, in which silica sol is modified with sodium methyl silicate to achieve a significant improvement in the performance of the silica sol combined with the castable; sodium methyl silicate is cheap and easily available, is a solid powder, has stable properties, can effectively reduce costs, and is easy to use; the preparation process is simple, the equipment requirements are low, and the castable can be quickly baked and hardened, significantly shortening the construction period, which is conducive to large-scale promotion and application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] In the following examples and comparative examples, the raw material indicators used are: The brown corundum particles are made by mixing three types of dense corundum particles with particle sizes of 5~3 mm, 3~1 mm, and 1~0 mm in a mass ratio of 1:2.8~3.2:2.3~2.7; wherein the Al2O3 content is ≥98%.

[0027] The mullite granular material is prepared by mixing three types of mullite granules with particle sizes of 5-3 mm, 3-1 mm and 1-0 mm in a mass ratio of 1:2.8-3.2:2.3-2.7; wherein the Al2O3 content is ≥60%.

[0028] The Al2O3 content in dense corundum powder is ≥98% and the particle size is ≤0.074mm.

[0029] The SiO2 content in silicon micropowder is ≥96% and the particle size is ≤5μm.

[0030] The Al2O3 content in the activated alumina powder is ≥98% and the particle size is ≤1.5μm.

[0031] The composite additive is a mixture of magnesium oxide and boron carbide, with a mass ratio of 1:3; the particle size of the composite additive is ≤0.088 mm.

[0032] The water reducing agent is one or more sodium tripolyphosphates, and the particle size is ≤0.074mm.

[0033] The mass fraction of SiO2 in the silica sol is 30%, the particle size is 10~30nm, and the pH is 6~8.

[0034] The CH5SiO3Na content in sodium methyl silicate is ≥99%, and the particle size is ≤0.074mm.

[0035] Example 1 Provided is a sodium methyl silicate-modified silica sol combined with corundum-mullite castable, wherein the components and their mass percentages are as follows: 42% brown corundum particles, 25% mullite particles, 17% dense corundum powder, 4% silica powder, 10% activated alumina powder, 1.93% composite additives, 0.07% sodium tripolyphosphate, and 7.6% sodium methyl silicate-modified silica sol. The mass fraction of SiO2 in the silica sol used is 30%. The silica sol modified with sodium methyl silicate was prepared by adding 1% sodium methyl silicate by mass of the silica sol into the silica sol, mechanically stirring for 10 minutes, and then ultrasonically mixing for 25 minutes to fully dissolve the sodium methyl silicate.

[0036] According to the above formula, brown corundum particles, mullite particles, dense corundum powder, silica powder, activated alumina powder, composite additives and water reducer are mechanically stirred and mixed into dry uniform aggregate, packaged and transported to the construction site, and then the freshly prepared silica sol modified with sodium methyl silicate is added and stirred and mixed evenly to obtain corundum-mullite castable, which can be used in blast furnace and hot blast furnace lining casting construction.

[0037] The performance test results of the corundum-mullite castable obtained in this example are shown in Table 1.

[0038] Comparative Example 1 A silica sol combined with corundum-mullite castable is provided. The specific raw materials and proportions are the same as those in Example 1, except that the silica sol is not modified.

[0039] The performance test results of the corundum-mullite castable obtained in this comparative example are shown in Table 1.

[0040] Example 2 Provided is a sodium methyl silicate-modified silica sol combined with corundum-mullite castable, wherein the components and their mass percentages are as follows: 40% brown corundum particles, 28% mullite particles, 17% dense corundum powder, 3% silica powder, 10% activated alumina powder, 1.91% composite additives, 0.09% sodium tripolyphosphate, and 7.4% sodium methyl silicate-modified silica sol. The mass fraction of SiO2 in the silica sol used is 30%, wherein: The silica sol modified with sodium methyl silicate was prepared by adding 0.5% of sodium methyl silicate by mass of the silica sol into the silica sol, mechanically stirring for 15 minutes, and then ultrasonically mixing for 20 minutes to fully dissolve the sodium methyl silicate.

[0041] The performance test results of the corundum-mullite castable obtained in this example are shown in Table 1.

[0042] Comparative Example 2 A silica sol combined with corundum-mullite castable is provided. The specific raw material ratio is the same as that of Example 2, except that the silica sol is not modified.

[0043] The performance test results of the corundum-mullite castable obtained in this comparative example are shown in Table 1.

[0044] Example 3 Provided is a sodium methyl silicate-modified silica sol combined with corundum-mullite castable, wherein the components and their mass percentages are as follows: 48% brown corundum particles, 18% mullite particles, 20% dense corundum powder, 4% silica powder, 8% activated alumina powder, 1.9% composite additives, 0.1% sodium tripolyphosphate, and 7.9% sodium methyl silicate-modified silica sol. The mass fraction of SiO2 in the silica sol used is 30%, wherein: The silica sol modified with sodium methyl silicate was prepared by adding 2% of the mass of the silica sol to the silica sol, mechanically stirring for 15 minutes, and then ultrasonically mixing for 20 minutes to fully dissolve the sodium methyl silicate.

[0045] The performance test results of the corundum-mullite castable obtained in this example are shown in Table 1.

[0046] Comparative Example 3 A silica sol combined with corundum-mullite castable is provided. The specific raw materials and proportions are the same as those in Example 3, except that the silica sol is not modified.

[0047] The performance test results of the corundum-mullite castable obtained in this comparative example are shown in Table 1.

[0048] Comparative Example 4 Provided is a modified silica sol combined with corundum-mullite castable, wherein the components and their mass percentages are as follows: 48% brown corundum particles, 18% mullite particles, 20% dense corundum powder, 4% silica powder, 8% activated alumina powder, 1.9% composite additives, 0.1% sodium tripolyphosphate, and 7.9% modified silica sol. The mass fraction of SiO2 in the silica sol used is 30%, wherein: The modified silica sol was prepared by adding 0.2% sodium methyl silicate by mass of the silica sol into the silica sol, mechanically stirring for 15 minutes, and then ultrasonically mixing for 20 minutes to fully dissolve the silica sol.

[0049] The performance test results of the corundum-mullite castable obtained in this comparative example are shown in Table 1.

[0050] Comparative Example 5 Provided is a modified silica sol combined with corundum-mullite castable, wherein the components and their mass percentages are as follows: 48% brown corundum particles, 18% mullite particles, 20% dense corundum powder, 4% silica powder, 8% activated alumina powder, 1.9% composite additives, 0.1% sodium tripolyphosphate, and 7.9% modified silica sol. The mass fraction of SiO2 in the silica sol used is 30%.

[0051] The modified silica sol was prepared by adding 2.5% sodium methyl silicate by mass of the silica sol into the silica sol, mechanically stirring for 15 minutes, and then ultrasonically mixing for 20 minutes to fully dissolve the silica sol.

[0052] The performance test results of the corundum-mullite castable obtained in this comparative example are shown in Table 1.

[0053] Comparative Example 6 Provided is a silane coupling agent-modified silica sol combined with corundum-mullite castable, wherein the components and their mass percentages are as follows: 48% brown corundum particles, 18% mullite particles, 20% dense corundum powder, 4% silica powder, 8% activated alumina powder, 1.9% composite additives, 0.1% sodium tripolyphosphate, and 7.9% modified silica sol. The mass fraction of SiO2 in the silica sol used is 30%. The modified silica sol was prepared by adding 2% of the mass of the silica sol to the silane coupling agent (KH-570), mechanically stirring for 15 minutes, and then ultrasonically mixing for 20 minutes to fully dissolve the silane coupling agent.

[0054] The performance test results of the corundum-mullite castable obtained in this comparative example are shown in Table 1.

[0055] Table 1. Performance test results of Examples 1-3 and Comparative Examples 1-6

[0056] From Table 1 we can see that: The present invention modifies silica sol with an appropriate amount of sodium methyl silicate and then uses the modified silica sol as a binder for a corundum-mullite castable. The resulting castable exhibits significantly higher flexural and compressive strengths at low, medium, and high temperatures than those of unmodified silica sol-bound corundum-mullite castables. In particular, after curing at 110°C for 24 hours, the flexural and compressive strengths of the unmodified silica sol-bound corundum-mullite castable are only approximately 4.5 MPa and 25 MPa, while the flexural and compressive strengths of the sodium methyl silicate-modified silica sol-bound corundum-mullite castable exceed 8.5 MPa and 32 MPa, respectively. This is primarily due to the extremely low degree of spontaneous condensation reaction (-Si-OH + HO-Si- = -Si-O-Si-) in the unmodified silica sol-bound castable, resulting in weaker bonding between particles and, consequently, lower low-temperature demolding strength. By modifying the silica sol with this technical solution, the degree of spontaneous condensation reaction of -Si-OH in the system is effectively improved, which accelerates the formation of a three-dimensional network structure and a particle skeleton, thereby increasing the bonding force between the powder and the particles, thereby improving the low-temperature demoulding strength of the silica sol-bonded corundum-mullite castable. When the bonding force between the particles is strong, the porosity of the castable is significantly reduced (see Table 1), making the material more dense. Therefore, the degree of sintering between the castable particles in a high-temperature environment is significantly improved. At the same time, the very small amount of Na in sodium methyl silicate + The formed liquid phase prompts the particles to fill the gaps, which is also beneficial to promoting sintering between particles, improving the stacking degree of the castable, and effectively reducing the linear change rate of the castable after firing (see Table 1). The high-temperature strength of the castable is significantly improved.

[0057] In summary, the present invention modifies silica sol by using sodium methyl silicate, and uses the modified silica sol as a binder for a corundum-mullite castable. The low-temperature strength of the corundum-mullite castable is greatly improved compared to the unmodified silica sol-bonded castable, while improving its high-temperature performance. This provides an effective solution to the problem of low demoulding strength of silica sol-bonded corundum-mullite castable at low temperatures, and further promotes the promotion and application of silica sol-bonded corundum-mullite castables. At the same time, the sodium methyl silicate of the modified silica sol is environmentally friendly and non-toxic, cheap and easily available, with stable performance, which can significantly reduce production costs. In addition, the preparation process of the mullite-corundum castable of the present invention is simple and effective, has low equipment requirements, can be produced on a large scale industrially, and has good economic benefits and broad development prospects.

[0058] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A sodium methyl silicate-modified silica sol combined with corundum-mullite castable, characterized in that: Calculated by mass percentage, it includes: 40-50% brown corundum particles, 18-28% mullite particles, 16-20% dense corundum powder, 2-5% silica powder, 7-14% activated alumina powder, 1-2% composite additives, 0.06-0.12% water reducer, and 7.2-8.5% silica sol modified with sodium methyl silicate; of which: In the silica sol modified by sodium methyl silicate, sodium methyl silicate accounts for 0.5~2% of the mass of the silica sol.

2. The casting material according to claim 1, characterized in that The sodium methyl silicate-modified silica sol is prepared by adding sodium methyl silicate into silica sol, stirring and ultrasonically mixing the sodium methyl silicate to fully dissolve the sodium methyl silicate.

3. The casting material according to claim 2, characterized in that The stirring time is 10~15 min; the ultrasonic time is 20~30 min.

4. The casting material according to claim 1, characterized in that The mass fraction of SiO2 in the silica sol is 25-35%.

5. The casting material according to claim 1, characterized in that The particle size of the silica sol is 10-30 nm; the particle size of the sodium methyl silicate is ≤0.074 mm.

6. The casting material according to claim 1, characterized in that The brown corundum particles are formed by mixing three types of dense corundum particles with particle sizes of 5-3 mm, 3-1 mm, and 1-0 mm in a mass ratio of 1: 2.8-3.2: 2.3-2.7; wherein the Al2O3 content is ≥98%; the mullite particles are formed by mixing three types of mullite particles with particle sizes of 5-3 mm, 3-1 mm, and 1-0 mm in a mass ratio of 1: 2.8-3.2: 2.3-2.7; wherein the Al2O3 content is ≥60%; the Al2O3 content in the dense corundum powder is ≥98%, and the particle size is ≤0.074 mm.

7. The casting material according to claim 1, characterized in that The particle size of the silicon micropowder is ≤5 μm; the particle size of the activated alumina powder is ≤1.5 μm.

8. The casting material according to claim 1, characterized in that The composite additive is a mixture of magnesium oxide and boron carbide, wherein the mass ratio of magnesium oxide to boron carbide is 1:2.5~3.5; the water reducer is one or more of sodium hexametaphosphate, sodium pyrophosphate, and sodium tripolyphosphate.

9. The casting material according to claim 1, characterized in that The particle size of the composite additive is ≤0.088 mm; the particle size of the water reducer is ≤0.074 mm.

10. A method for preparing the sodium methyl silicate-modified silica sol combined with corundum-mullite castable according to any one of claims 1 to 9, characterized in that: The following steps are involved: Brown corundum particles, mullite particles, dense corundum powder, silica powder, activated alumina powder, composite additives and water reducer are mechanically stirred to form dry uniform aggregate, and then silica sol modified by sodium methyl silicate is added, and the mixture is fully mixed and stirred to obtain corundum-mullite castable.

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