Iron runner castable containing pre-synthesized eg-sic and method for preparing the same

Abstract

The application discloses an iron runner castable containing pre-synthesized EG-SiC and a preparation method thereof, and belongs to the technical field of amorphous refractory castable. According to the mass percentage, the raw material composition of the iron runner castable comprises 10-17wt% tabular corundum, 7-13wt% composite powder, 12-25wt% silicon carbide, 1-3wt% calcium aluminate cement, 1-3wt% spherical pitch, 0.1-0.2wt% anti-explosion fiber, 2-5wt% composite additive, and the balance is brown corundum particles; additionally, 1-3wt% pre-synthesized EG-SiC is added; wherein the pre-synthesized EG-SiC is nanometer silicon carbide whisker in-situ grown between worm-like expanded graphite sheet layer structures. The iron runner castable has high early strength, significantly improves the slag resistance of the iron runner castable, and improves the high-temperature mechanical properties and the ability to resist thermal stress damage of the material, and has important application prospect.

Description

Technical Field

[0001] This invention belongs to the field of monolithic refractory castable technology, specifically relating to an iron trough castable containing pre-synthesized EG-SiC and its preparation method. Background Technology

[0002] Iron tapping from the blast furnace is a crucial step in the ironmaking process. To ensure its safe and efficient operation, extremely high requirements are placed on the refractory materials used in the blast furnace. Currently, the most commonly used refractory material for blast furnaces is alumina-silicon carbide-carbonaceous blast furnace castable. Carbonaceous materials, due to their high thermal conductivity, low expansion, and resistance to slag wetting, are a vital component of the blast furnace material. They not only improve the thermal shock stability of the blast furnace material but also enhance its resistance to slag erosion. Common carbon sources used in blast furnace materials include spherical pitch, carbon black, graphite, and carbon nanotubes, typically added in composite forms. Each carbon source has its advantages and disadvantages. Spherical asphalt is easier to add to castables due to its spherical morphology, but it contains a certain amount of volatiles. Flake graphite is a graphitized carbon source, but because it is non-wetting with water, it is not easy to disperse in castables. In comparison, expanded graphite has a worm-like structure and is easier to disperse, but it has low reactivity at high temperatures and is difficult to form a ceramic reinforcing phase. Carbon nanotubes have excellent high-temperature performance, but they are more difficult to disperse than micron-sized carbon sources. Therefore, it is urgent to select a suitable carbon source to play a better role in iron trough refractory. Summary of the Invention

[0003] The purpose of this invention is to provide an iron trough castable containing pre-synthesized EG-SiC and its preparation method. This iron trough castable has high early-stage bonding strength, significantly improves its slag resistance, and enhances its high-temperature mechanical properties and resistance to thermal stress damage, thus showing significant application potential.

[0004] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0005] A castable refractory for iron trenches containing pre-synthetic EG-SiC is provided. By mass percentage, the raw material composition is: 10-17 wt% tabular corundum, 7-13 wt% composite micro powder, 12-25 wt% silicon carbide, 1-3 wt% calcium aluminate cement, 1-3 wt% spherical asphalt, 0.1-0.2 wt% explosion-proof fiber, 2-5 wt% composite additives, with the balance being brown corundum particles; plus 1-3 wt% pre-synthetic EG-SiC; wherein:

[0006] The pre-synthesized EG-SiC is a nano-silicon carbide whisker grown in situ between worm-like expanded graphite sheets.

[0007] According to the above scheme, the preparation of the pre-synthesized EG-SiC includes the following steps:

[0008] Expanded graphite (EG) was placed in a nickel acetate solution, ultrasonically stirred and dispersed, filtered and dried to obtain expanded graphite loaded with nickel acetate catalyst; then the obtained expanded graphite loaded with nickel acetate catalyst was placed in a microwave reactor, and anhydrous ethanol and methylsilane mixed vapor were introduced into the microwave reactor by nitrogen gas to carry out microwave heating reaction to prepare pre-synthesized EG-SiC.

[0009] Preferably, Ni in nickel acetate solution 2+ The concentration is 0.05-0.25 mol / L; preferably 0.15-0.25 mol / L.

[0010] Preferably, the drying process is as follows: drying at 60-80℃ for 8-12 hours.

[0011] Preferably, the ultrasonic stirring time is 15-30 min.

[0012] Preferably, the volume ratio of anhydrous ethanol to methylsilane is 1-2:1.

[0013] Preferably, the method of introducing the mixed vapor into the microwave reactor by carrying nitrogen gas is as follows: insert the nitrogen gas inlet tube into a mixed solution of anhydrous ethanol and methylsilane at 80-90°C.

[0014] Preferably, the microwave heating reaction is carried out at 1100-1200℃ for 20-45 minutes; more preferably, the microwave heating power is 700-1100W.

[0015] Preferably, the flow rate of nitrogen is controlled at 200-500 mL / min.

[0016] According to the above scheme, the Al2O3 content in the tabular corundum is >99wt%, and the particle size includes 1-0.1mm and <45μm.

[0017] According to the above scheme, the composite micro powder is a combination of two or more of ordinary silicon micro powder, high-purity 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; the high-purity silicon micro powder has a SiO2 content >99wt% and a particle size <0.5μm; and the active α-Al2O3 micro powder has an Al2O3 content >99.5wt% and a particle size <5μm.

[0018] Preferably, it contains at least ordinary silicon micro powder or high-purity silicon micro powder.

[0019] According to the above scheme, the SiC content in the silicon carbide is >98wt%, and the particle size includes 1-0.1mm and <75μm.

[0020] According to the above scheme, the Al2O3 content in the calcium aluminate cement is >70wt%, and the particle size is <45μm.

[0021] According to the above scheme, the composite additive is a combination of at least two of the following: boron carbide, elemental silicon powder, zirconium boride, metallic aluminum powder, and polycarboxylic acid dispersant. Preferably, it contains at least elemental silicon powder.

[0022] According to 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.

[0023] According to the above scheme, the particle size of the spherical asphalt is 1-0 mm.

[0024] A method for preparing an iron trench castable containing pre-synthesized EG-SiC is also provided, comprising the following steps:

[0025] Weigh out the raw materials, including tabular corundum, composite micro powder, silicon carbide, calcium aluminate cement, pre-synthetic EG-SiC, spherical asphalt, explosion-proof fiber, composite additives, and brown corundum particles, mix them evenly, add water accounting for 3-6 wt% of the total raw materials and mix evenly, then cast and vibrate to obtain iron trough castable.

[0026] According to the above plan, the castable is also cured at room temperature and dried. The room temperature curing time is 20-28 hours, and after demolding, it is dried at 100-120℃ for 20-28 hours.

[0027] This invention provides a castable trough containing pre-synthesized EG-SiC. The introduction of pre-synthesized EG-SiC allows for the in-situ growth of uniform nano-silicon carbide whiskers between worm-like expanded graphite sheets, resulting in an extremely high specific surface area. At low temperatures, this induces the formation of a cement hydration phase, improving the early bonding strength of the castable trough. Simultaneously, it forms an embedded structure of aluminosilicates and other carbonaceous raw materials, significantly improving the slag resistance of the castable trough. Furthermore, the pre-synthesized EG-SiC is a heterogeneous network structure of expanded graphite and silicon carbide whiskers. The silicon carbide whiskers are embedded in the pores of the matrix, forming a novel, toughened structure. The expanded graphite exerts its toughening effect through a lamellar slip mechanism, while the numerous silicon carbide whiskers dispersed at the tips effectively reinforce the material, significantly improving its high-temperature mechanical properties and resistance to thermal stress damage.

[0028] Furthermore, in the preparation of EG-SiC, firstly, nickel acetate is used as a catalyst, and expanded graphite is immersed in a nickel acetate solution for loading, which makes the nickel acetate more uniformly dispersed on the surface of the expanded graphite, which is conducive to the final formation of uniform silicon carbide whiskers. Secondly, anhydrous ethanol and methylsilane mixed vapors are microwave-heated with expanded graphite loaded with nickel acetate catalyst. The reducing atmosphere of ethanol cracking effectively inhibits the agglomeration and growth of nano-nickel particles, avoiding the rapid growth phenomenon of nickel oxide formed by traditional inorganic nickel salts during heating, thus ensuring catalytic efficiency. At the same time, methylsilane provides an effective silicon source for chemical vapor deposition, and the hydrocarbon gas from ethanol cracking serves as a carbon source. Under the action of the catalyst on the surface of expanded graphite, uniform silicon carbide whiskers are finally generated.

[0029] Furthermore, during the heat treatment process, the residual catalyst in the pre-synthesized EG-SiC will also promote the reaction between elemental silicon and silicon micropowder (which promotes the formation of silicon monoxide vapor at high temperatures) and CO in the iron trough castable, thereby strengthening the heterogeneous network structure of expanded graphite-silicon carbide whiskers and further improving the performance of the iron trough castable.

[0030] The beneficial effects of this invention are as follows:

[0031] 1. This invention provides an iron trough castable containing pre-synthesized EG-SiC. By introducing pre-synthesized EG-SiC, silicon carbide whiskers are uniformly dispersed on expanded graphite, making them easy to disperse in the iron trough castable and significantly increasing the content of small-sized silicon carbide whiskers in the castable. At the same time, its high specific surface area can induce cement hydration behavior, which can improve the early strength of the castable. Furthermore, it forms an embedded structure of aluminosilicates and other carbonaceous raw materials in the matrix, which can significantly optimize the slag resistance of the iron trough castable at high temperatures. In addition, the heterogeneous network structure of expanded graphite-silicon carbide whiskers significantly improves the high-temperature mechanical properties and resistance to thermal stress damage of the material.

[0032] 2. Furthermore, the present invention uses microwave chemical vapor deposition to prepare EG-SiC, which is fast, efficient and low-cost, and the silicon carbide whiskers are more evenly distributed on the surface of expanded graphite, which is beneficial to fully exert its performance-enhancing effect in iron trough castables. Attached Figure Description

[0033] Figure 1 This is an electron microscope image of the preloaded expanded graphite obtained in Example 1.

[0034] Figure 2 This is an electron microscope image of the pre-synthesized EG-SiC obtained in Example 1.

[0035] Figure 3 This is an electron microscope image of the pre-synthesized EG-SiC obtained in Example 6. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail through the following embodiments. The specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0037] To avoid repetition, the materials involved in the specific implementation methods are described uniformly as follows, and will not be repeated in the examples:

[0038] The Al2O3 content in the tabular corundum is >99wt%, and the particle size of the tabular corundum is 1-0.1mm and <45μm.

[0039] The active α-Al2O3 micro powder contains >99.5wt% Al2O3 and has a particle size <5μm.

[0040] The content of SiO2 in ordinary silicon micro powder is >95wt%, and the particle size of silicon micro powder is <0.5μm.

[0041] The high-purity silicon micropowder has a SiO2 content of >99wt% and a particle size of <0.5μm.

[0042] The SiC content in silicon carbide is >98wt%, including SiC fine powder and SiC particles. The particle size of SiC particles is 1-0.1mm, and the particle size of SiC micro powder is <75μm.

[0043] The content of Al2O3 in calcium aluminate cement is >70wt%, and the particle size of calcium aluminate cement is <45μm.

[0044] The carbon source is pre-synthesized EG-SiC and spherical asphalt, wherein the spherical asphalt has a particle size of 1-0 mm.

[0045] The composite additive is a combination of at least two of the following: boron carbide, elemental silicon powder, zirconium boride, metallic aluminum powder, and polycarboxylic acid dispersants.

[0046] The content of Al2O3 in brown fused alumina particles is >95wt%, and the particle size includes 3-1mm, 5-3mm, and 8-5mm.

[0047] Example 1

[0048] A method for preparing iron trench castable containing pre-synthesized EG-SiC is provided, comprising the following steps:

[0049] 1) Preparation of pre-synthesized EG-SiC

[0050] Expanded graphite is placed in Ni 2+Expanded graphite slurry with catalyst supported was obtained by ultrasonic stirring in a 0.1 mol / L nickel acetate solution for 20 min. The expanded graphite slurry with catalyst supported was filtered and dried at 80 °C for 12 hours to obtain pre-loaded expanded graphite. The pre-loaded expanded graphite was placed in the middle of a quartz tube and then placed in the central reaction zone of a microwave reactor. A nitrogen vent pipe was inserted into a mixed solution of anhydrous ethanol and methylsilane (volume ratio 2:1) heated to 80 °C in a water bath. The mixed vapor was introduced into the microwave reactor by nitrogen gas carrying the mixed vapor, with the nitrogen flow rate controlled at 250 mL / min. The reactor was microwave heated to 1100 °C with a power of 900 W and held for 30 min to obtain pre-synthesized EG-SiC.

[0051] 2) Weigh the raw materials:

[0052] Weigh out 16 wt% tabular corundum, 9 wt% composite micro powder, 16.4 wt% silicon carbide, 2 wt% calcium aluminate cement, 2 wt% spherical asphalt, 0.1 wt% explosion-proof fiber, 2.5 wt% composite additive, and 52 wt% brown corundum particles. Add 1 wt% of the pre-synthesized EG-SiC obtained in step 1).

[0053] 3) Mix the raw materials weighed in step 2) evenly, add water accounting for 4.2wt% of the total raw materials and mix evenly, then pour and vibrate to form.

[0054] The molded castable was then subjected to curing, drying, and heat treatment in sequence, followed by performance testing; among which:

[0055] 1) The curing process is as follows: cure at room temperature for 24 hours.

[0056] 2) The drying process is as follows: dry at 110℃ for 24 hours.

[0057] 3) The heat treatment process is as follows: heat treatment at 1450℃ for 3 hours and test its cold compressive strength; calculate the compressive strength retention rate of the sample after quenching at 900℃; test the high-temperature flexural strength of the sample after holding at 1400℃ for 0.5 hours; use the static crucible method to hold at 1550℃ for 3 hours and test the slag line erosion depth of the sample profile. See Table 1 for specific performance test results.

[0058] Figure 1 Expanded graphite with a supported catalyst Figure 2 EG-SiC was catalytically grown from expanded graphite supported with a nickel ion concentration of 0.1 mol / L after treatment at 1100 °C. Figure 2 The results show that a small amount of SiC whiskers are formed on the expanded graphite.

[0059] Example 2

[0060] The specific details are the same as in Example 1, except that the content of the added pre-synthesized EG-SiC is 2wt%. For the specific performance test results, please refer to Table 1.

[0061] Example 3

[0062] The specific details are the same as in Example 2, except that the microwave heat treatment temperature is 1200℃ and held for 30 minutes, and the content of the pre-synthesized EG-SiC is 3wt%. For specific performance test results, please refer to Table 1.

[0063] Example 4

[0064] The specific details are the same as in Example 1, except that the Ni in the nickel acetate solution is different. 2+ The concentration was 0.2 mol / L. For specific performance test results, please refer to Table 1.

[0065] Example 5

[0066] The specific details are the same as in Example 2, except that the Ni in the nickel acetate solution... 2+ The concentration was 0.2 mol / L. For specific performance test results, please refer to Table 1.

[0067] Example 6

[0068] The specific details are the same as in Example 3, except that the Ni in the nickel acetate solution... 2+ The concentration was 0.2 mol / L. For specific performance test results, please refer to Table 1.

[0069] Figure 3 The figure shows EG-SiC catalytically grown from expanded graphite with a nickel ion concentration of 0.2 mol / L after treatment at 1200℃. The figure also shows the formation of a large number of SiC whiskers on the expanded graphite.

[0070] Comparative Example 1

[0071] A conventional iron trough castable and its preparation method are provided, including the following steps:

[0072] 1) Weigh the raw materials:

[0073] Weigh out 16 wt% tabular corundum, 9 wt% composite micro powder, 16.4 wt% silicon carbide, 2 wt% calcium aluminate cement, 2 wt% spherical asphalt, 0.1 wt% explosion-proof fiber, 2.5 wt% composite additive, and 52 wt% brown corundum particles.

[0074] 2) Mix the raw materials weighed in step 1) evenly, add water accounting for 4.2wt% of the total raw materials and mix evenly, then pour and vibrate to form.

[0075] The above-mentioned molded castable was cured, dried and heat-treated in sequence according to the method of Example 1, and its performance was tested. The specific performance test results are shown in Table 1.

[0076] Table 1. Differences and performance test results between Examples 1-6 and Comparative Example 1

[0077]

[0078] As shown in Table 1, the mechanical properties and slag resistance of the iron trough castable are significantly improved after the introduction of pre-synthesized EG-SiC. In particular, the increase in nickel ion concentration or the increase in microwave heat treatment temperature is conducive to the catalytic growth of more uniform EG-SiC, and the improvement in castable performance is more significant.

[0079] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A taphole castable containing pre-synthesized EG-SiC, characterized in that, The raw material composition by mass percentage comprises: 10-17wt% tabular corundum, 7-13wt% composite powder, 12-25wt% silicon carbide, 1-3wt% calcium aluminate cement, 1-3wt% spherical pitch, 0.1-0.2wt% anti-explosion fiber, 2-5wt% composite additive, and the balance is brown corundum particles; additionally, 1-3wt% pre-synthesized EG-SiC; wherein: The pre-synthesized EG-SiC is nanometer silicon carbide whisker in-situ grown between worm-like expanded graphite sheet structures, and specifically is: The expanded graphite is placed in a nickel acetate solution, and after ultrasonic stirring and dispersion, the expanded graphite loaded with the nickel acetate catalyst is obtained by filtration and drying; then the expanded graphite loaded with the nickel acetate catalyst is placed in a microwave reactor, and mixed steam of anhydrous ethanol and methylsilane carried by nitrogen is introduced into the microwave reactor, and microwave heating reaction is carried out to prepare the pre-synthesized EG-SiC.

2. The iron run channel castable according to claim 1, characterized in that, Nickel acetate solution 2+ concentration of 0.05-0.25 mol / L.

3. The iron runner castable of claim 1, wherein The drying process is: drying at 60-80℃ for 8-12 hours; the ultrasonic stirring time is 15-30min.

4. The iron runner castable of claim 1, wherein The volume ratio of anhydrous ethanol to methylsilane is 1-2:

1.

5. The iron runner castable of claim 1, wherein The microwave heating reaction is carried out at 1100-1200℃ for 20-45min.

6. The iron runner castable of claim 1, wherein The microwave heating power is 700-1100W; the flow rate of nitrogen is controlled at 200-500mL / min.

7. The iron runner castable of claim 1, wherein The content of Al2O3 in the tabular corundum is >99wt%, and the particle size comprises 1-0.1mm and <45μm; the content of SiC in the silicon carbide is >98wt%, and the particle size comprises 1-0.1mm and <75μm; the content of Al2O3 in the calcium aluminate cement is >70wt%, and the particle size is <45μm; the content of Al2O3 in the brown corundum particles is >95wt%, and the particle size comprises 3-1mm, 5-3mm, and 8-5mm; the particle size of the spherical pitch is 1-0mm.

8. The iron runner castable of claim 1, wherein, The composite powder is a composite of two or more of ordinary silicon powder, high-purity silicon powder, and active α-Al2O3 powder, wherein: the content of SiO2 in the ordinary silicon powder is >95wt%, and the particle size is <0.5μm; the content of SiO2 in the high-purity silicon powder is >99wt%, and the particle size is <0.5μm; the content of Al2O3 in the active α-Al2O3 powder is >99.5wt%, and the particle size is <5μm; the composite additive is a composite of at least two of boron carbide, elemental silicon powder, zirconium boride, metallic aluminum powder, and polycarboxylic acid dispersant.

9. A process for the preparation of a pre-sintered EG-SiC containing iron runner castable according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: The tabular corundum, composite powder, silicon carbide, calcium aluminate cement, pre-synthesized EG-SiC, spherical pitch, anti-explosion fiber, composite additive, and brown corundum particles are weighed and uniformly mixed, 3-6wt% of water based on the total amount of raw materials is added and uniformly mixed, and then pouring and vibration molding are carried out to obtain the iron runner castable.

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