In-situ silicon carbide whisker toughened iron channel castable and preparation method thereof

Abstract

The application discloses an in-situ silicon carbide whisker toughened iron runner castable and a preparation method thereof. The iron runner castable comprises the following raw materials in parts by weight: 65-75 parts of fused dense corundum, 10-18 parts of silicon carbide, 4-10 parts of active alumina micropowder, 1-2 parts of cement, 2-4 parts of nano silicon dioxide, 1-3 parts of porous carbon material, 1-2 parts of carbon black, 2-3 parts of metal silicon powder, 1-3 parts of composite explosion-proof agent, 0.2-0.5 parts of antioxidant, 0.1-0.3 parts of composite water reducing agent and 0.1-0.4 parts of catalyst. The porous carbon material, the carbon black, the nano silicon dioxide, the metal silicon powder and the catalyst are mixed by ball milling in advance. The in-situ silicon carbide whisker toughened iron runner castable has the characteristics of good oxidation resistance, high-temperature washing resistance, slag-iron chemical corrosion resistance, good thermal shock resistance, simple process, long service life and the like.

Description

Technical Field

[0001] This invention belongs to the field of blast furnace trough castable technology, specifically relating to an in-situ silicon carbide whisker toughened trough castable and its preparation method. Background Technology

[0002] Currently, Al2O3-SiC-C castables are commonly used in blast furnace troughs, with silicon carbide content mostly exceeding 10%. Silicon carbide is known for its high strength and wear resistance, but it is easily oxidized at high temperatures, affecting the service life of the castable. With the continuous advancement of blast furnace smelting technology, blast furnaces are gradually developing towards larger scale and longer service life, with increasing smelting intensity. Longer tapping times and higher iron throughput are inevitable development directions for blast furnace tapping troughs. Due to long-term exposure to high-temperature slag and molten iron erosion, as well as unstable operating temperatures, blast furnace trough castables are highly susceptible to silicon carbide oxidation, which in turn affects service life and molten iron quality. Therefore, there is an urgent need to develop a blast furnace trough castable with excellent strength, good thermal shock resistance, good oxidation resistance, and superior performance.

[0003] CN105777146A discloses a boron nitride-reinforced iron trough material. This invention uses raw materials such as brown corundum, silicon carbide, silica micropowder, hexagonal boron nitride, Si micropowder, and graphite to prepare the boron nitride-reinforced iron trough material. This method improves the slag erosion resistance and thermal shock stability of the iron trough material to a certain extent. However, its main drawbacks are: (1) the amount of hexagonal boron nitride added is relatively large, resulting in high production costs; (2) hexagonal boron nitride is oxidized at 900℃ to form boron oxide, which reacts with alumina in the material to form aluminum borate. This process is accompanied by a certain volume expansion, which easily causes cracking and other phenomena in the iron trough material.

[0004] CN110240486A discloses a whisker-reinforced Al2O3-SiC-C iron channel castable and its preparation method. This invention uses 45-65 wt% corundum aggregate, 15-35 wt% silicon carbide, 2-4 wt% carbon black, 2-10 wt% aluminum powder / ceramic microcapsules, 4-6 wt% α-alumina powder, 2-4 wt% silica powder, and 4-6 wt% calcium aluminate cement as raw materials. Whisker-reinforced Al2O3-SiC-C iron channel castable is prepared by adding 0.1-0.3 wt% catalyst and 0.1-0.3 wt% water-reducing agent. This method optimizes the erosion resistance and thermal shock stability of the Al2O3-SiC-C castable to a certain extent. However, its main drawback is that the production process of mullite fiber-reinforced Al2O3-SiC-C refractory castable is extremely complex and costly: Aluminum powder is placed in pressurized steam for 10–35 minutes to obtain surface-corroded aluminum powder; the surface-corroded aluminum powder is then placed in alkaline silica sol for 10–60 minutes to obtain a mixed slurry; this slurry is then vacuum-filtered and calcined at 500–700°C for 2–8 hours to obtain aluminum powder ceramic membrane microcapsules, which are then used to generate mullite fiber-reinforced refractory castable through in-situ reaction. Furthermore, this method suffers from the inability to effectively control the aspect ratio of whiskers and fibers.

[0005] CN 111484348 A discloses a mullite fiber-reinforced Al2O3-SiC-C refractory castable for blast furnace tapping troughs and its preparation method. This invention provides strength to the castable by adding short-cut mullite fibers (1-3 mm in length and 0.003-0.015 mm in diameter) as a reinforcing agent to the Al2O3-SiC-C refractory castable for blast furnace tapping troughs. However, its main drawbacks are: 1) the added mullite fibers are very fine and difficult to disperse in the castable; 2) the added mullite fibers negatively affect the water content and flowability of the castable; and 3) the amount added is small, making it difficult to achieve an effective effect. Summary of the Invention

[0006] The purpose of this invention is to provide an in-situ silicon carbide whisker-toughened iron trench castable and its preparation method. The castable has good oxidation resistance, high temperature erosion resistance and slag-iron chemical corrosion resistance, as well as good thermal shock resistance. The process is simple and the service life is long.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An in-situ silicon carbide whisker-toughened iron trench castable is provided, comprising the following raw materials by weight: 65-75 parts by weight of fused dense corundum, 10-18 parts by weight of silicon carbide, 4-10 parts by weight of activated alumina micro powder, 1-2 parts by weight of cement, 2-4 parts by weight of nano-silica, 1-3 parts by weight of porous carbon material, 1-2 parts by weight of carbon black, 2-3 parts by weight of metallic silicon powder, 1-3 parts by weight of composite explosion-proof agent, 0.2-0.5 parts by weight of antioxidant, 0.1-0.3 parts by weight of composite water-reducing agent, and 0.1-0.4 parts by weight of catalyst; wherein:

[0009] Porous carbon material, carbon black, nano-silica, metallic silicon powder and catalyst are mixed by ball milling to obtain a reaction precursor powder for generating silicon carbide whiskers. The obtained reaction precursor powder is then mixed evenly with the remaining components to obtain in-situ silicon carbide whisker toughened iron groove castable.

[0010] According to the above scheme, the ball milling time is 5 to 8 hours during the preparation of the reaction precursor powder.

[0011] According to the above scheme, the electrofused dense corundum is composed of a portion with a particle size of 8-5 mm, a portion with a particle size of 5-3 mm, a portion with a particle size of 3-1 mm, a portion with a particle size of 1-0.074 mm, and a portion with a particle size ≤0.074 mm, with the mass ratios of these portions being 40-50%, 20-25%, 10-15%, 8-12%, and 8-12%, respectively.

[0012] According to the above scheme, the silicon carbide is composed of a portion with a particle size of 1 to 0.074 mm and a portion with a particle size of ≤0.074 mm, wherein the mass ratio of the portion with a particle size of 1 to 0.074 mm and the portion with a particle size of ≤0.074 mm are 40 to 50% and 50 to 60%, respectively.

[0013] According to the above scheme, the activated alumina micro powder d 50 ≤2μm, Al2O3≥99%.

[0014] According to the above scheme, the cement is pure calcium aluminate cement, wherein Al2O3 ≥ 68%.

[0015] According to the above scheme, the particle size of the nano-silica powder is 50-80 nm; preferably, SiO2 ≥ 99.99%. Nano-silica has high purity, small particle size, and high specific surface activity, which can reduce the sintering temperature and react rapidly with carbonaceous elements at high temperatures to generate silicon carbide whiskers.

[0016] According to the above scheme, the porous carbon material is one or more of activated carbon, pyrolytic carbon, and carbonized rice husk, with a particle size ≤2mm and a pore size distribution range of 0.1~50μm.

[0017] According to the above scheme, the carbon black has a carbon content of ≥99% and a particle size of ≤2μm.

[0018] According to the above scheme, the particle size of the metallic silicon powder is ≤0.44μm, and the silicon content is ≥98%.

[0019] According to the above scheme, the composite explosion-proof agent is a mixture of two or three of the following: metallic aluminum powder, aluminum lactate, and explosion-proof fiber. Preferably, the explosion-proof fiber is polypropylene fiber with a length of 3-5 mm.

[0020] According to the above scheme, the antioxidant is composed of two or three of boron carbide, titanium boride, and zirconium boride.

[0021] According to the above scheme, the composite water-reducing agent is a mixture of two or three of sodium tripolyphosphate, FDN (sodium polymethylene naphthyl sulfonate), and polycarboxylate high-efficiency water-reducing agent.

[0022] According to the above scheme, the catalyst is one or a mixture of several of the elements iron, cobalt, and nickel.

[0023] A method for preparing the above-mentioned in-situ silicon carbide whisker-toughened iron trench castable includes the following steps:

[0024] a) Preparation of reaction precursor powder: Weighed porous carbon material, carbon black, nano silica, metallic silicon powder and catalyst are ball-milled and mixed to obtain reaction precursor powder for generating silicon carbide whiskers.

[0025] b) Mix the reaction precursor powder from step a with fused dense corundum, silicon carbide, cement, activated alumina micro powder, antioxidant, composite explosion-proof agent, and composite water-reducing agent until the materials are fully and evenly mixed to obtain in-situ silicon carbide whisker toughened iron trench castable.

[0026] According to the above scheme, in step a), the mixture is ball-milled in a planetary ball mill.

[0027] According to the above scheme, in step a), the ball milling time is 5 to 8 hours.

[0028] According to the above scheme, in step b), the mixture is stirred in a forced mixer.

[0029] According to the above scheme, in step b), the stirring time is 10 to 20 minutes.

[0030] This invention provides an in-situ silicon carbide whisker-toughened iron trench castable. Porous carbon material, carbon black, nano-silica, metallic silicon powder, and a catalyst are pre-mixed by ball milling to obtain a precursor powder for generating silicon carbide whiskers. Specifically: Firstly, ball milling increases the specific surface area of ​​the various substances, ensuring sufficient contact and imparting a certain activation energy to the reactants, forming the precursor powder, which ultimately enables faster generation of silicon carbide whiskers under high-temperature operating conditions. Secondly, the introduced solid porous carbon, utilizing its porous structure, facilitates the entry of carbon black, nano-silica, metallic silicon powder, and catalyst into the pores of the solid porous carbon through ball milling. The reaction equation under high-temperature conditions is as follows:

[0031] 2C (s) + O2 (g) = 2 CO(g) (1)

[0032] SiO2 (s) + C (s) = SiO (g) + CO(g) (2)

[0033] SiO (g) + CO(g) = SiC (s) + CO2 (g) (3)

[0034] Under the operating temperature conditions, the outermost porous carbon material in the precursor powder is first oxidized to generate CO, placing the reactants in an atmosphere inherently favorable for the reaction. This provides atmospheric protection and growth space for the in-situ reaction of carbonaceous and silicon raw materials to generate silicon carbide whiskers, which is beneficial for the in-situ growth and development of silicon carbide whiskers. The generation of CO increases the partial pressure of CO in the material, which is conducive to the progress of reaction (3). The SiC generated by this in-situ reaction is grown under the condition that the air inside the material is consumed, so it is not easily oxidized; moreover, the in-situ generated SiC occupies the voids in the material, further increasing the density of the submaterial, preventing air from entering, and also playing an anti-oxidation role. Meanwhile, the raw materials for generating silicon carbide whiskers, carbon black, nano-silica, metallic silicon powder, and catalyst, coexist in the pores of porous carbon. As the porous carbon is uniformly dispersed in the casting material, the raw materials for generating silicon carbide whiskers are also uniformly dispersed. This not only allows the spatial limitation of the porous carbon pores to control the length of the silicon carbide whiskers generated after sintering, but also ensures the uniform dispersion of the generated silicon carbide whiskers in the casting material, avoiding local aggregation. This achieves the consistency of the properties of each part of the material and significantly improves the toughening effect of silicon carbide whiskers.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1. This invention provides an in-situ silicon carbide whisker-toughened iron trench castable. By pre-mixing porous carbon material, carbon black, nano-silica, metallic silicon powder, and catalyst through ball milling, in-situ generation of silicon carbide whiskers is achieved. The length of the generated silicon carbide whiskers is controllable and they are evenly distributed in the castable, significantly improving the toughening effect of the silicon carbide whiskers and further enhancing the material's density, which is beneficial for oxidation resistance. The resulting castable has good oxidation resistance, high-temperature erosion resistance, and resistance to slag and iron chemical corrosion. It also has good thermal shock resistance and a long service life.

[0037] 2. This invention prepares a reaction precursor powder for generating silicon carbide whiskers by pre-mixing porous carbon material, carbon black, nano-silica, metallic silicon powder and catalyst through ball milling. The obtained reaction precursor powder is then mixed evenly with the remaining components to obtain an in-situ silicon carbide whisker-toughened iron groove castable. The preparation process is simple, the silicon carbide whisker toughening effect is significant, the oxidation resistance is excellent, the sintering temperature is low, and it has promising industrial application prospects. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The raw material specifications used in the in-situ silicon carbide whisker-toughened iron trench castable in this embodiment of the invention are as follows:

[0040] The electrofused dense corundum is composed of a portion with a particle size of 8-5 mm, a portion with a particle size of 5-3 mm, a portion with a particle size of 3-1 mm, a portion with a particle size of 1-0.074 mm, and a portion with a particle size ≤0.074 mm, with the following mass ratios being 40-50%, 20-25%, 10-15%, 8-12%, and 8-12%, respectively.

[0041] The silicon carbide consists of a portion with a particle size of 1 to 0.074 mm and a portion with a particle size of ≤0.074 mm, wherein the mass ratio of the portion with a particle size of 1 to 0.074 mm and the portion with a particle size of ≤0.074 mm are 40 to 50% and 50 to 60%, respectively.

[0042] The activated alumina micro powder d 50 ≤2μm, Al2O3≥99%.

[0043] The cement is pure calcium aluminate cement, wherein Al2O3 ≥ 68%.

[0044] The nano-silica powder has a particle size of 50–80 nm and a SiO2 content of ≥99.99%.

[0045] The porous carbon material is one or more of activated carbon, pyrolytic carbon, and carbonized rice husk, with a particle size ≤2mm and a pore size distribution range of 0.1~50μm.

[0046] The carbon black has a carbon content of ≥99% and a particle size of ≤2μm.

[0047] The silicon powder has a particle size ≤0.44μm and a silicon content ≥98%.

[0048] The composite explosion-proof agent is a mixture of two or three of the following: metallic aluminum powder, aluminum lactate, and explosion-proof fiber; the explosion-proof fiber is polypropylene fiber with a length of 3-5 mm.

[0049] The antioxidant is a mixture of two or three of boron carbide, titanium boride, and zirconium boride.

[0050] The composite water-reducing agent is a mixture of two or three of sodium tripolyphosphate, FDN, and polycarboxylate superplasticizer.

[0051] The catalyst is one or a mixture of elements such as iron, cobalt, and nickel.

[0052] The preparation method of in-situ silicon carbide whisker-toughened iron trench castable in this embodiment of the invention includes the following steps:

[0053] a) Preparation of reaction precursor powder: Weighed porous carbon material, carbon black, nano silica, metallic silicon powder and catalyst were added to a planetary ball mill and ball-milled for 6 hours to obtain reaction precursor powder that produces silicon carbide whiskers.

[0054] b) Mix the reaction precursor powder from step a) with fused dense corundum, silicon carbide, cement, activated alumina micro powder, antioxidant, composite explosion-proof agent, and composite water-reducing agent for 15 minutes to ensure that the materials are fully and evenly mixed to obtain in-situ silicon carbide whisker toughened iron trench castable.

[0055] Specific embodiments of the present invention are as follows:

[0056] Example 1:

[0057] An in-situ silicon carbide whisker-toughened iron trench castable is provided, comprising the following raw materials by mass parts:

[0058] The composition includes 65 parts by weight of fused alumina, 16 parts by weight of silicon carbide, 5 parts by weight of activated alumina micro powder, 2 parts by weight of cement, 4 parts by weight of nano-silica, 3 parts by weight of activated carbon, 2 parts by weight of carbon black, 2 parts by weight of metallic silicon powder, 1 part by weight of composite explosion-proof agent (55 wt% metallic aluminum powder and 45 wt% explosion-proof fiber), 0.5 parts by weight of antioxidant (60 wt% boron carbide, 20 wt% titanium boride and 20 wt% zirconium boride), 0.3 parts by weight of composite water-reducing agent (30 wt% sodium tripolyphosphate, 50 wt% FDN and 20 wt% polycarboxylate high-efficiency water-reducing agent), and 0.4 parts by weight of catalyst (70 wt% iron and 30 wt% cobalt).

[0059] The specific performance tests of the in-situ silicon carbide whisker-toughened iron groove castable obtained in this embodiment are shown in Table 1.

[0060] Table 1 Product Performance Indicators

[0061]

[0062]

[0063] Example 2:

[0064] An in-situ silicon carbide whisker-toughened iron trench castable is provided, comprising the following raw materials by mass parts:

[0065] The composition includes 67 parts by weight of fused alumina, 14 parts by weight of silicon carbide, 8 parts by weight of activated alumina micro powder, 1 part by weight of cement, 3 parts by weight of nano-silica, 2 parts by weight of carbonized rice husk, 1.5 parts by weight of carbon black, 2.5 parts by weight of metallic silicon powder, 1 part by weight of composite explosion-proof agent (35 wt% metallic aluminum powder, 30 wt% aluminum lactate, 35 wt% explosion-proof fiber), 0.4 parts by weight of antioxidant (60 wt% boron carbide, 40 wt% zirconium boride), 0.2 parts by weight of composite water-reducing agent (20 wt% FDN, 80 wt% polycarboxylate high-efficiency water-reducing agent), and 0.3 parts by weight of catalyst (60 wt% iron, 40 wt% nickel).

[0066] The specific performance tests of the in-situ silicon carbide whisker-toughened iron groove castable obtained in this embodiment are shown in Table 2.

[0067] Table 2 Product Performance Indicators

[0068]

[0069] Example 3:

[0070] An in-situ silicon carbide whisker-toughened iron trench castable is provided, comprising the following raw materials by mass parts:

[0071] The composition includes: 68 parts by weight of fused alumina, 15 parts by weight of silicon carbide, 5 parts by weight of activated alumina micro powder, 2 parts by weight of cement, 3 parts by weight of nano-silica, 1.5 parts by weight of porous carbon material (70 wt% activated carbon and 30 wt% carbonized rice husk), 1.5 parts by weight of carbon black, 3 parts by weight of metallic silicon powder, 1 part by weight of composite explosion-proof agent (45 wt% aluminum lactate powder and 55 wt% explosion-proof fiber), 0.5 parts by weight of antioxidant (65 wt% titanium boride and 35 wt% zirconium boride), 0.3 parts by weight of composite water-reducing agent (30 wt% trimer, 50 wt% FDN and 20 wt% polycarboxylate high-efficiency water-reducing agent), and 0.4 parts by weight of catalyst (60 wt% iron, 20 wt% cobalt and 20 wt% nickel).

[0072] The specific performance tests of the in-situ silicon carbide whisker-toughened iron groove castable obtained in this embodiment are shown in Table 3.

[0073] Table 3 Product Performance Indicators

[0074]

[0075] The performance testing standards for all embodiments are as follows:

[0076] The apparent porosity and bulk density of the test sample were determined according to GB / T2997-2015.

[0077] The room temperature compressive strength of the test sample was tested according to GB / T5072-2008;

[0078] The room temperature flexural strength of the test sample was measured according to GB / T3001-2017;

[0079] High-temperature flexural strength of the test sample according to GB / T3002-2017;

[0080] The test sample change rate was determined according to GB / T5988-2022.

[0081] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the present invention are within the scope of protection of the present invention.

Claims

1. A silicon carbide whisker toughened in situ iron runner castable characterized by, By mass fraction, the following raw materials are included: 65-75 parts of fused dense corundum, 10-18 parts of silicon carbide, 4-10 parts of active alumina powder, 1-2 parts of cement, 2-4 parts of nano-silicon dioxide, 1-3 parts of porous carbon material, 1-2 parts of carbon black, 2-3 parts of metallic silicon powder, 1-3 parts of composite explosion-proof agent, 0.2-0.5 parts of antioxidant, 0.1-0.3 parts of composite water reducing agent, and 0.1-0.4 parts of catalyst; wherein: The porous carbon material, carbon black, nano-silicon dioxide, metallic silicon powder, and catalyst are mixed by ball milling in advance to prepare a reaction precursor powder for generating silicon carbide whiskers; The particle size of the porous carbon material is ≤2 mm, and the pore size distribution range is 0.1-50 μm.

2. The iron run channel castable according to claim 1, characterized in that, The fused dense corundum is composed of a 8-5 mm particle size portion, a 5-3 mm particle size portion, a 3-1 mm particle size portion, a 1-0.074 mm particle size portion, and a particle size ≤0.074 mm portion, and the mass ratio between them is 40-50%, 20-25%, 10-15%, 8-12%, and 8-12%, respectively; the silicon carbide is composed of a 1-0.074 mm particle size portion and a particle size ≤0.074 mm portion, and the mass ratio of the 1-0.074 mm particle size portion to the particle size ≤0.074 mm portion is 40-50% and 50-60%, respectively; and the cement is pure calcium aluminate cement, wherein Al2O3≥68%.

3. The iron runner castable of claim 1, wherein The active alumina micropowder d 50 ≤ 2 μm, Al203≥ 99%.

4. The iron runner castable of claim 1, wherein The nano-silicon dioxide powder has a particle size of 50-80 nm.

5. The iron runner castable of claim 1, wherein The porous carbon material is one or more of activated carbon, pyrolytic carbon, and carbonized rice husk.

6. The iron runner castable of claim 1, wherein The carbon black has a carbon content ≥99% and a particle size ≤2 μm; and the metallic silicon powder has a particle size ≤0.44 μm and a silicon content ≥98%.

7. The iron runner castable of claim 1, wherein The composite explosion-proof agent is a mixture of two or three of metallic aluminum powder, aluminum lactate, and explosion-proof fiber; the antioxidant is a mixture of two or three of boron carbide, titanium boride, and zirconium boride; the composite water reducing agent is a mixture of two or three of sodium tripolyphosphate, sodium polymethylene naphthalene sulfonate, and polycarboxylic acid superplasticizer; and the catalyst is one or more of iron, cobalt, and nickel.

8. A process for the preparation of in-situ silicon carbide whisker toughened iron channel castable according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: a) reaction precursor powder preparation: the porous carbon material, carbon black, nano-silicon dioxide, metallic silicon powder, and catalyst are ball-mixed to prepare a reaction precursor powder for generating silicon carbide whiskers; b) the reaction precursor powder in step a) is mixed and stirred with the fused dense corundum, silicon carbide, cement, active alumina powder, antioxidant, composite explosion-proof agent, and composite water reducing agent to fully mix and evenly distribute the materials to obtain in-situ silicon carbide whisker toughened iron channel castable.

9. The preparation method according to claim 8, characterized in that, In step a), the ball milling time is 5-8 h.

10. The preparation method according to claim 8, characterized in that, In step b), the stirring time is 10-20 min.

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