Tricalcium silicate cement and silica sol combined iron runner castable and preparation method thereof

Abstract

The invention discloses a tricalcium silicate cement composite silica sol combined iron runner castable and a preparation method thereof, and the castable mainly comprises the following components by mass percentage: 10-17 wt% of fused compact corundum, 7-13 wt% of composite micro powder, 12-21 wt% of silicon carbide, 0.5-2 wt% of tricalcium silicate cement, 0.5-3 wt% of spherical asphalt, 0.1-0.2 wt% of explosion-proof fiber, 2-5 wt% of a composite additive, and the balance of brown fused alumina particles, the silica sol accounts for 2-5wt% of the main components by using an external additive; wherein the tricalcium silicate cement is prepared by reacting nano calcium carbonate with high-purity silica powder. The core of the invention is that the tricalcium silicate cement and the silica sol are prepared to form a composite combination system, so that the castable has excellent rapid hardening property and explosion-proof property, the hydrated phase is fine and uniform, and the rapid construction requirement is met; a hydration phase uniformly distributed at a high temperature reacts with aluminum oxide in the matrix to promote densification and optimize a pore structure, and meanwhile, nano silicon dioxide in the silica sol promotes generation of a mullite phase in the matrix, so that the high-temperature breaking strength, oxidation resistance and slag corrosion resistance of the castable are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of amorphous refractory, and particularly relates to a ferrochute castable combined with tricalcium silicate cement and silica sol and a preparation method thereof. BACKGROUND

[0002] The ferrochute castable is a refractory material made of special high-aluminum, corundum, silicon carbide and carbon, and has the technical features of strong slag erosion resistance, excellent thermal shock stability and long service life. The binder is an important component of the ferrochute castable, and has a great influence on the early construction performance and high-temperature service performance of the ferrochute castable. The calcium aluminate cement is currently the main binder used in the ferrochute castable, and is mainly composed of monoaluminate and di-aluminate. The monoaluminate has a fast hydration speed, and the di-aluminate has a slow hydration speed. The hydration products of both are micron-sized. In the on-site construction of the ferrochute, the construction time is often limited. Part of the di-aluminate in the calcium aluminate cement may not be completely hydrated. This part of unhydrated di-aluminate does not contribute to the early strength, and at high temperatures, it generates more calcium feldspar and other liquid phases due to the introduction of more calcium oxide, thereby reducing the high-temperature mechanical properties and slag erosion resistance of the ferrochute castable.

[0003] The calcium silicate cement is a commonly used concrete binder in the construction industry. The tricalcium silicate is the main component of the strength source. The hydration speed of this phase is fast, and the hydration product generated by hydration is more fine and uniform, with a size of about nanometer / sub-micron. The fine hydration product can not only improve the early strength, but also optimize the microstructure of the castable. However, the content of tricalcium silicate in the ordinary calcium silicate cement is about 50-70%, and it also contains part of dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite. If it is directly applied to the ferrochute castable, it is difficult to guarantee the construction performance and high-temperature service performance of the castable. SUMMARY

[0004] The present application provides a ferrochute castable combined with tricalcium silicate cement and silica sol and a preparation method thereof to solve the technical problems of the prior art. The ferrochute castable prepared by forming a composite binding system of tricalcium silicate cement and silica sol can quickly meet the construction strength, save construction time, has good explosion-proof performance, and has excellent high-temperature bending strength, oxidation resistance and slag erosion resistance.

[0005] The technical scheme adopted by the present application to solve the above problems is as follows: The application discloses an iron channel castable combined with tricalcium silicate cement and silica sol, and the main components of the castable include, in percentage by mass, 10-17wt% of fused dense corundum, 7-13wt% of composite powder, 12-21wt% of silicon carbide, 0.5-2wt% of tricalcium silicate cement, 0.5-3wt% of spherical pitch, 0.1-0.2wt% of explosion-proof fiber, 2-5wt% of composite additive, and the rest is brown corundum particles, wherein the silica sol accounts for 2-5wt% of the main components, and the silica sol is prepared from nano calcium carbonate and high-purity silicon powder.

[0006] In the above scheme, the main components include, in percentage by mass, 10-17wt% of fused dense corundum, 7-13wt% of composite powder, 12-21wt% of silicon carbide, 0.5-1wt% of tricalcium silicate cement, 0.5-3wt% of spherical pitch, 0.1-0.2wt% of explosion-proof fiber, 2-5wt% of composite additive, and the rest is brown corundum particles, wherein the silica sol accounts for 3-4wt% of the main components, and the tricalcium silicate cement is prepared by uniformly mixing nano calcium carbonate and high-purity silicon powder through ball milling, quenching after sintering and heat preservation.

[0007] In the above scheme, the preparation method of the tricalcium silicate cement is as follows. The nano calcium carbonate and the high-purity silicon powder are uniformly mixed in a planetary ball mill, and the tricalcium silicate cement is prepared by quenching after sintering and heat preservation at 1450-1550 DEG C for 3-9h, wherein the quenching mode is air cooling, and the temperature is reduced to below 500 DEG C within 2h during the quenching process. The molar ratio of the nano calcium carbonate to the high-purity silicon powder is 3:1, the content of CaCO3 in the nano calcium carbonate is greater than 99wt%, and the particle size is less than 100nm; the content of SiO2 in the high-purity silicon powder is greater than 99wt%, and the particle size is less than 0.5um.

[0008] In the above scheme, the content of SiO2 in the silica sol is 30-40wt%, and the particle size is less than 30nm.

[0009] In the above scheme, the composite powder is a composite of ordinary silicon powder and active alpha-Al2O3 powder, wherein the content of SiO2 in the ordinary silicon powder is greater than 95wt%, and the particle size is less than 0.5um; the content of Al2O3 in the active alpha-Al2O3 powder is greater than 99.5wt%, and the particle size is less than 5um.

[0010] In the above scheme, the composite additive is a composite of at least two of boron carbide, elemental silicon powder, metallic aluminum powder and polycarboxylic acid dispersant.

[0011] In the above scheme, the content of Al2O3 in the electrofused dense corundum is >99wt%, and the particle size includes 1-0.1mm and <45μm.

[0012] In the above scheme, the SiC content in the silicon carbide is >98wt%, and the particle size includes 1-0.1mm and <75μm.

[0013] In the above scheme, the content of Al2O3 in the brown fused alumina particles is >95wt%, and the particle size includes 3-1mm, 5-3mm, and 8-5mm.

[0014] In the above scheme, the particle size of the spherical asphalt is 1-0 mm.

[0015] In the above scheme, the explosion-proof fiber is polypropylene fiber.

[0016] The preparation method of the above-mentioned tricalcium silicate cement composite silica sol bonded iron trough castable includes: The fused dense corundum, composite micro powder, silicon carbide, tricalcium silicate cement, silica sol, spherical asphalt, explosion-proof fiber, composite additives and brown corundum particles are mixed evenly to obtain a mixture. Water is added in proportion of 2.5-5 wt% of the mixture and then mixed evenly. The mixture is then cast and vibrated to obtain a tricalcium silicate cement composite silica sol bonded iron trough castable.

[0017] This invention provides a tricalcium silicate cement-silica sol-bonded castable for iron trenches. Compared to the hydration products of calcium aluminate cement, the CSH generated by tricalcium silicate hydration is finer and more uniform, with nano / submicron sizes and a larger specific surface area, while the size of calcium aluminate hydration products is in the range of several to tens of micrometers. Furthermore, after the addition of tricalcium silicate cement and silica sol, the nano-silica in the silica sol exhibits high reactivity, reacting with calcium hydroxide (Ca(OH)2) generated during tricalcium silicate hydration to generate more CSH. Moreover, the nanoparticles of the silica sol provide more nucleation sites, controlling the hydration reaction rate of tricalcium silicate. Therefore, the tricalcium silicate-silica sol-bonded castable for iron trenches hardens faster than that bonded with calcium aluminate cement, helping to save construction time. The formation of more nano-sized CSH in the matrix reduces the formation of large-sized calcium hydroxide, optimizing the matrix structure, improving early strength, and enhancing the explosion-proof performance of the castable for iron trenches. At high temperatures, fine and uniform CSH helps promote a more uniform distribution of calcium oxide. Silicate-induced densification optimizes the pore structure, thereby reducing the deteriorating effect of liquid phase enrichment such as anorthite on high-temperature performance. At the same time, nano-silica in silica sol also promotes the formation of more mullite in the matrix, significantly improving the high-temperature strength of the castable.

[0018] The synthesis of tricalcium silicate cement selects nano calcium carbonate and high-purity silicon powder as raw materials, wherein the uniform mixing of nano calcium carbonate and micron spherical SiO2 can enhance the reaction activity, promote the solid phase reaction, and be beneficial to the synthesis of tricalcium silicate cement with higher purity; and the rapid quenching after high-temperature synthesis of tricalcium silicate inhibits the decomposition of tricalcium silicate into dicalcium silicate and free CaO.

[0019] Compared with the prior art, the beneficial effects of the present application are: (1) The tricalcium silicate cement composite silicon sol combined iron runner castable provided by the present application can quickly meet the construction performance and save construction time.

[0020] (2) The tricalcium silicate cement composite silicon sol combined iron runner castable provided by the present application forms a composite combined system by preparing tricalcium silicate cement and silicon sol, and the prepared castable has excellent high-temperature bending strength, oxidation resistance and slag corrosion resistance. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The electron microscope graph of the tricalcium silicate cement hydration product prepared for the embodiment 4 of the present application. DETAILED DESCRIPTION

[0022] The technical solutions of the present application will be described in detail below in combination with specific embodiments, but the described embodiments are only part of the embodiments of the present application, and all other embodiments obtained by those skilled in the art without creative labor on the basis of the embodiments in the present application all belong to the protection scope of the present application.

[0023] In the specific embodiment, the content of CaCO3 in the nano calcium carbonate used is >99wt%, and the particle size is <100nm; The content of SiO2 in the high-purity silicon powder is >99wt%, and the particle size is <0.5μm; The composite powder is a composite of ordinary silicon powder and active alpha-Al2O3 powder; the content of SiO2 in the ordinary silicon powder is >95wt%, and the particle size is <0.5μm; the content of Al2O3 in the active alpha-Al2O3 powder is >99.5wt%, and the particle size is <5μm; The content of SiO2 in the silicon sol is 30-40wt%, and the particle size is <30nm; The content of Al2O3 in the electrically fused dense corundum is >99wt%, and the particle size contains 1-0.1mm and <45μm; The content of SiC in the silicon carbide is >98wt%, and the particle size contains 1-0.1mm and <75μm; The content of Al2O3 in the brown corundum particles is >95wt%, and the particle size contains 3-1mm, 5-3mm and 8-5mm; The spherical pitch has a particle size of 1-0 mm; The explosion-proof fiber is a polypropylene fiber; The composite additive is at least two of boron carbide, elemental silicon powder, aluminum powder, and polycarboxylic acid dispersant.

[0024] Example 1 A tricalcium silicate cement composite silica sol combined iron runner castable and a preparation method thereof are provided, including the following steps: 1) Preparation of tricalcium silicate cement The nano calcium carbonate and high-purity silicon powder are mixed uniformly in a planetary ball mill at a molar ratio of 3:1, and then tricalcium silicate cement is obtained by sintering at 1500°C in air atmosphere for 3h and then quenching. The quenching method is air cooling, and the temperature is reduced to below 500°C within 2h during the quenching process.

[0025] 2) Preparation of iron runner castable 17wt% of fused dense corundum, 10wt% of composite powder, 16wt% of silicon carbide, 1wt% of tricalcium silicate cement, 2wt% of spherical pitch, 0.1wt% of explosion-proof fiber, 2wt% of composite additive, and 51.9wt% of brown corundum particles are weighed. 3wt% of silica sol is added.

[0026] 3) The raw materials weighed in step 2) are mixed uniformly to obtain a mixture, 3wt% of water based on the mixture is added and then mixed uniformly, and then poured and vibrated to form.

[0027] The castable after forming is sequentially cured, dried, and heat treated, and performance tests are conducted; wherein: 1) The curing process is: curing at room temperature for 24h.

[0028] 2) The drying process is: drying at 110°C for 24h.

[0029] 3) The heat treatment process is: heat treatment at 1450°C for 3h, and the cold compressive strength and oxidation layer thickness are tested; the high-temperature bending strength of the sample is tested at 1400°C for 0.5h; the static crucible method is used to test the erosion depth of the sample cross-section slag line at 1550°C for 3h, and the specific performance test results are shown in Table 1.

[0030] Example 2 Specifically the same as example 1, the difference is only that 4wt% of silica sol is added; the water addition amount is 2.5wt%, and the specific performance test results are shown in Table 1.

[0031] Example 3 The difference between the embodiment 1 and the embodiment 2 is that: the nano calcium carbonate and the high-purity silicon powder are mixed in a planetary ball mill at a molar ratio of 3:1, and then the mixture is sintered at 1500 DEG C in an air atmosphere for 6 hours, and then quenched to obtain the tricalcium silicate cement; and the water addition amount is 3wt%, and the specific performance test results are shown in Table 1.

[0032] Embodiment 4 The difference between the embodiment 3 and the embodiment 4 is that: 4wt% of the silica sol is added; and the water addition amount is 2.5wt%, and the specific performance test results are shown in Table 1. Figure 1 The figure is an electron microscope image of the tricalcium silicate cement hydration product in the embodiment, and it can be seen from the figure that: after the tricalcium silicate cement is cured at 25 DEG C for 24 hours, the hydration phase product is nano / sub-micron C-S-H and micron Ca(OH)2, and compared with the hydration product of the calcium aluminate cement, the size of the hydration product is smaller and more uniform.

[0033] Comparative Example 1 A conventional iron runner castable and a preparation method thereof are provided, which comprises the following steps: 1) weighing raw materials: 16wt% of fused dense corundum, 10wt% of composite powder, 16wt% of silicon carbide, 2wt% of calcium aluminate cement, 2wt% of spherical pitch, 0.1wt% of anti-explosion fiber, 2wt% of composite additive, and 51.9wt% of brown corundum particles are weighed; 2) the raw materials weighed in step 1) are mixed uniformly to obtain a mixture, 4wt% of water based on the mixture is added and then mixed uniformly, and then the mixture is poured and vibrated to form.

[0034] The formed castable is cured, dried and heat treated in sequence according to the method of the embodiment 1, and the performance test is carried out, and the specific performance test results are shown in Table 1.

[0035] Comparative Example 2 The difference between the embodiment 1 and the embodiment 2 is that: 3wt% of the silica sol is not added; and the water addition amount is 4wt%, and the specific performance test results are shown in Table 1.

[0036] Table 1: differences and performance test results of the embodiments 1-4 and the comparative examples 1-2

[0037] It can be seen from Table 1 that: after the tricalcium silicate cement and the silica sol are used as the binder of the iron runner castable, the early construction performance and the high-temperature performance of the material are obviously improved; mainly because the hydration product of the tricalcium silicate is finer and more uniform, and under the compounding of the silica sol, the structure of the material matrix can be further optimized, and it is beneficial to the formation of mullite at high temperature, and the performance of the castable is obviously improved.

[0038] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art, according to the technical solution and the improvement concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, and should be covered within the protection scope of the present application.

Claims

1. A tricalcium silicate cement composite silica sol-bonded castable for iron trenches, characterized in that, Its main components, by mass percentage, include: 10-17 wt% fused dense corundum, 7-13 wt% composite micro powder, 12-21 wt% silicon carbide, 0.5-2 wt% tricalcium silicate cement, 0.5-3 wt% spherical asphalt, 0.1-0.2 wt% explosion-proof fiber, 2-5 wt% composite additives, with the balance being brown corundum particles; the silica sol, as an additive, constitutes 2-5 wt% of the main components; wherein the tricalcium silicate cement is prepared by reacting nano-calcium carbonate with high-purity silica micro powder.

2. The tricalcium silicate cement composite silica sol-bonded iron trough castable according to claim 1, characterized in that, Its main components, by mass percentage, include: 10-17 wt% fused alumina, 7-13 wt% composite micro powder, 12-21 wt% silicon carbide, 0.5-1 wt% tricalcium silicate cement, 0.5-3 wt% spherical asphalt, 0.1-0.2 wt% explosion-proof fiber, 2-5 wt% composite additives, with the balance being brown alumina particles. The silica sol, calculated as an additive, constitutes 3-4 wt% of the main components. The tricalcium silicate cement is prepared by ball milling nano-calcium carbonate and high-purity silica powder, followed by quenching after firing and heat preservation.

3. The tricalcium silicate cement composite silica sol-bonded iron trough castable according to claim 2, characterized in that, The specific preparation method of the tricalcium silicate cement is as follows: The nano-calcium carbonate and the high-purity silica powder are ball-milled and mixed evenly, and then calcined at 1450-1550℃ for 3-9 hours and quenched to obtain the tricalcium silicate cement; wherein the quenching method is air cooling, and the temperature is reduced to below 500℃ within 2 hours during the quenching process. The molar ratio of the nano-calcium carbonate to the high-purity silicon micropowder is 3:1; the content of CaCO3 in the nano-calcium carbonate is >99wt%, and the particle size is <100nm; the content of SiO2 in the high-purity silicon micropowder is >99wt%, and the particle size is <0.5μm.

4. The tricalcium silicate cement composite silica sol-bonded iron trough castable according to claim 1, characterized in that, The silica sol contains 30-40 wt% SiO2 and has a particle size of <30 nm.

5. The tricalcium silicate cement composite silica sol-bonded iron trough castable according to claim 1, characterized in that, The composite micro powder is a combination of ordinary silicon micro powder and active α-Al2O3 micro powder; wherein the ordinary silicon micro powder has a SiO2 content >95wt% and a particle size <0.5μm; and the active α-Al2O3 micro powder has an Al2O3 content >99.5wt% and a particle size <5μm.

6. The tricalcium silicate cement composite silica sol-bonded iron trough castable according to claim 1, characterized in that, The composite additive is a combination of at least two of the following: boron carbide, elemental silicon powder, metallic aluminum powder, and polycarboxylic acid dispersants.

7. The tricalcium silicate cement composite silica sol-bonded iron trough castable according to claim 1, characterized in that, The content of Al2O3 in the fused dense corundum is >99wt%, and the particle size includes 1-0.1mm and <45μm; The silicon carbide contains >98 wt% SiC and has a particle size ranging from 1-0.1 mm to <75 μm.

8. The tricalcium silicate cement composite silica sol-bonded iron trough castable according to claim 1, characterized in that, The brown fused alumina particles contain >95wt% Al2O3 and have particle sizes of 3-1mm, 5-3mm, and 8-5mm.

9. The tricalcium silicate cement composite silica sol-bonded iron trough castable according to claim 1, characterized in that, The spherical asphalt has a particle size of 1-0 mm; the explosion-proof fiber is polypropylene fiber.

10. A method for preparing a tricalcium silicate cement composite silica sol-bonded iron trough castable according to any one of claims 1-9, characterized in that, include: The fused dense corundum, composite micro powder, silicon carbide, tricalcium silicate cement, silica sol, spherical asphalt, explosion-proof fiber, composite additives and brown corundum particles are mixed evenly to obtain a mixture. Water is added in proportion of 2.5-5 wt% of the mixture and then mixed evenly. The mixture is then cast and vibrated to obtain a tricalcium silicate cement composite silica sol bonded iron trough castable.

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