A ladle heat-insulating high-strength light-weight castable

Abstract

The application discloses a ladle heat-insulating high-strength light-weight castable which is prepared from the following raw materials in percentage by mass: 45-60% of mullite hollow spheres, 5-10% of expanded perlite, 5-10% of polycrystalline mullite fiber, 5-10% of magnesium oxide fine powder, 1-5% of aluminum powder, 1-5% of binding clay, 2-8% of rho-Al2O3 micro powder, 1-5% of sodium lignosulfonate, and 1-4% of SiO2 micro powder. The castable provided by the application has high strength, low thermal conductivity and good thermal shock resistance, can be used for ladle permanent layer castable, can effectively reduce the temperature of a ladle shell, plays a ladle heat-insulating role, can reduce the temperature of molten steel when a converter is tapped, reduces energy consumption, and reduces the cost per ton of steel.

Description

Technical Field

[0001] This invention belongs to the technical field of castables for steelmaking components, specifically relating to a high-strength, lightweight castable for ladle insulation. Background Technology

[0002] Heat loss in molten steel within a ladle occurs in three ways: heat dissipation from the upper surface of the ladle, heat storage within the ladle lining, and heat conduction through the lining to the outer shell. The working layer of the ladle typically uses carbonaceous refractory materials, particularly high-thermal-conductivity magnesia-carbon bricks. This exacerbates heat loss from the molten steel, leading to more severe ladle shell deformation, increased steel temperature drop rate, and severe slag buildup, nodules, and cold steel buildup on the ladle walls. Excessively low temperatures can even force the ladle or tundish to stop casting altogether, affecting billet quality, reducing steel yield, and increasing production costs. Furthermore, ladle shell replacement or reshaping requires significant financial investment and impacts production efficiency. Therefore, the permanent layer of the ladle typically uses lightweight castables with low thermal conductivity to reduce heat conduction from the ladle shell. However, low-thermal-conductivity castables often lack sufficient strength, resulting in a reduced permanent layer lifespan. Some manufacturers add steel fibers to the castable to improve strength, but this increases the castable's thermal conductivity, failing to balance strength and thermal conductivity. Secondly, most of the permanent layer castables for steel ladles are currently made of high-alumina clinker, which are prone to cracking after repeated use. They also tend to pulverize when the temperature is too high. Furthermore, the insufficient residual strength of the castables during unpacking can cause large-scale detachment. These shortcomings have always been important reasons for restricting the safe production of steel ladles and shortening their service life.

[0003] Patent CN107200564A discloses a high-strength refractory and thermal insulation castable. The castable components, by weight, include: 50-55 parts of 1-8mm lightweight magnesia dolomite, 5-10 parts of perlite raw ore, 10-25 parts of 1-0mm lightweight Bonate, 5-10 parts of 200-mesh lightweight pyrophyllite powder, 5-10 parts of 325-mesh lightweight mullite fine powder, 5-10 parts of silica powder, 5-10 parts of Al2O3 micro powder with a particle size of 2-3μm, 3-8 parts of aluminate cement, 5-10 parts of 0.25-1.5mm vitrified microspheres, 0.31 parts of sodium hexametaphosphate, and 0.3 parts of explosion-proof fiber. The low thermal conductivity refractory energy-saving castable is prepared by stirring, vibrating, curing and firing. It has the characteristics of light weight, high strength, low thermal conductivity, high temperature resistance, low water absorption and good density. However, the castable in this patent contains phosphorus and does not involve the thermal shock resistance of the material.

[0004] Patent CN108083829A discloses a high-toughness thermal insulation castable, which is formulated from raw materials such as fused alumina, mullite, hollow alumina spheres, sillimanite powder, kyanite powder, fused mullite powder, high-alumina dust collector powder, activated alumina powder, silica powder, pure calcium aluminate cement, sodium tripolyphosphate, and sodium hexametaphosphate in a certain weight ratio. In the formulated finished castable, the fused alumina granules and hollow alumina spheres work together in a tiered configuration to reduce the bulk density of the product; while the combined effect of mullite granules, sillimanite powder, high-alumina dust collector powder, and activated alumina powder gives the product high strength and excellent thermal shock resistance; fused mullite powder and kyanite powder improve the product's high-temperature linear shrinkage rate. Industrial trials have shown that the castable formulated by this invention can meet the production requirements of linings for blast furnace blast furnaces, hot blast duct connections, molten iron ladles, and steel ladle safety layers; however, the castable in this patent contains phosphorus.

[0005] Patent CN109020582A discloses a steel ladle insulation castable and its application. It uses mullite, pyroxene, and andalusite as aggregates and clay powder, magnesite fine powder, alumina micro powder, and silica micro powder as matrix. It has developed a castable suitable for steel ladle insulation and can be used for the permanent layer of steel ladle, furnace lining, and ladle cover. However, this patent does not involve the thermal shock resistance of the material. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-strength lightweight castable for ladle insulation that addresses the shortcomings of the prior art. This castable has high strength, low thermal conductivity, and good thermal shock resistance. It can be used as a castable for the permanent layer of the ladle, effectively reducing the temperature of the ladle shell and providing insulation for the ladle. It can also reduce the temperature of molten steel tapped from the converter, reduce energy consumption, and reduce the cost per ton of steel.

[0007] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows:

[0008] A high-strength, lightweight castable refractory for steel ladle insulation is composed of the following raw materials in the indicated weight percentages: 45-60% mullite hollow spheres, 5-10% expanded perlite, 5-10% polycrystalline mullite fiber, 5-10% fine magnesium oxide powder, 1-5% metallic aluminum powder, 1-5% binding clay, 2-8% p-Al2O3 micro powder, 1-5% sodium lignosulfonate, and 1-4% SiO2 micro powder.

[0009] In the above scheme, the percentage of particles of different sizes in the total weight of the mullite hollow spheres is as follows: 3 < particle size ≤ 5 mm 20-40%, 1 < particle size ≤ 3 mm 20-40%, and 0.1 < particle size ≤ 1 mm 20-40%.

[0010] In the above scheme, the expanded perlite has a TFe content of ≤1% and a particle size of 0.1 to 3 mm.

[0011] In the above scheme, the polycrystalline mullite fiber has a diameter of 2-5 μm and a length of 20-50 mm.

[0012] In the above scheme, the particle size of the magnesium oxide fine powder is ≤0.088mm.

[0013] In the above scheme, the aluminum powder has an Al content of ≥99% and a particle size of 200 mesh.

[0014] In the above scheme, the particle size of the bonding clay is ≤0.088mm.

[0015] In the above scheme, the particle size of the SiO2 micro powder is ≤0.015mm.

[0016] In the above scheme, the mass percentage of ρ-Al2O3 in the ρ-Al2O3 micro powder is ≥80%, and the specific surface area of ​​the ρ-Al2O3 micro powder is ≥220m². 2 ·g -1 .

[0017] This invention also provides a method for preparing the above-mentioned high-strength lightweight castable for steel ladle insulation, comprising the following steps:

[0018] Weigh each raw material according to the formula. First, mix the mullite hollow spheres with expanded perlite, magnesium oxide fine powder, metallic aluminum powder, binding clay, p-Al2O3 micro powder, sodium lignosulfonate, and SiO2 micro powder. Then, add polycrystalline mullite fiber and mix well. After mixing, add water at 3-5% of the weight percentage of the mixture and stir. During the stirring process, insert a vibrator to vibrate to facilitate air degassing. Cast, cure, and heat treat to prepare a high-strength lightweight steel ladle insulation castable. The curing conditions are natural curing at room temperature for 24-30 hours. The heat treatment conditions are baking time of 4-6 hours and temperature of 800-1000℃.

[0019] The bulk density of the high-strength, lightweight steel ladle insulation castable described in this invention is no higher than 1.82 g·cm³. -3 The flexural strength at room temperature is not less than 13.5 MPa, the compressive strength at room temperature is not less than 78 MPa, the flexural strength at 1300℃ is not less than 7.5 MPa, the thermal conductivity is not higher than 0.9 W / (m·K), and the temperature drop of molten steel during ladle operation is not less than 8%.

[0020] In the castable of this invention, the thermal conductivity is mainly reduced by adding mullite hollow spheres, expanded perlite, and polycrystalline mullite fibers. The principle behind the selection of each component and the control of its weight percentage is as follows: Mullite has excellent thermal shock resistance, high hardness, and uniform expansion. Using mullite hollow spheres as aggregate can effectively reduce the self-weight of the castable, reduce structural thermal stress, improve thermal shock resistance, and reduce the thermal conductivity of the material. Adding a certain amount of expanded perlite mainly reduces the thermal conductivity of the castable, but the amount cannot be too high, because the refractoriness of expanded perlite is 1300-1360℃, and the service temperature of the permanent layer of the steel ladle is about 1300℃. Too much expanded perlite will cause a liquid phase to appear in the castable at high temperatures, making the castable more prone to pulverization. Adding polycrystalline mullite fibers can effectively form a network-like structure inside the castable, enhancing the strength of the castable and reducing thermal conductivity. The castable of the present invention also contains an appropriate amount of metallic aluminum powder. The hydration reaction of the metallic aluminum powder and the in-situ generation of magnesium aluminum spinel by the metallic aluminum powder and magnesium oxide at high temperature have the following effects: First, the volume expansion caused by the reaction can effectively fill the gaps formed by water evaporation during the baking of the ladle, thereby reducing the formation of cracks; Second, the generated magnesium aluminum spinel can enhance the strength of the castable.

[0021] Secondly, this invention uses ρ-Al2O3 micro powder as a binder and sodium lignosulfonate as a dispersant. Adding binding clay can play a role in plasticizing and aiding bonding. Adding SiO2 micro powder can enhance the medium-temperature strength of the castable. At high temperatures, ρ-Al2O3 can also form mullite with SiO2, thereby enhancing the hot strength of the castable.

[0022] The particle size distribution of aggregates in the castable has a significant impact on the performance of the castable. This invention achieves the maximum densification of the castable by strictly controlling the particle size of raw materials such as mullite hollow spheres, expanded perlite, polycrystalline mullite fiber, metallic aluminum powder, and binding clay, forming continuous and densely packed particles. This results in enhanced strength of the castable while maintaining low thermal conductivity.

[0023] Compared with existing technologies, the beneficial effects of this invention are:

[0024] (1) The steel ladle insulation high-strength lightweight castable provided by the present invention has the characteristics of high strength (flexural strength at room temperature 13.5~15Mpa, compressive strength at room temperature 78~82Mpa, flexural strength at 1300℃ hot state 7.5~8.1MPa), low thermal conductivity (0.6~0.9W / (m·K)) and high thermal shock resistance (strength retention rate of 80%~85% after 5 water cooling cycles). When used in steel ladles, it can play a role in heat preservation, reduce the temperature drop during the operation of molten steel, reduce energy consumption, and reduce the cost per ton of steel.

[0025] (2) The present invention provides a high-strength lightweight castable for steel ladle insulation that is phosphorus-free and environmentally friendly, has good thermal shock stability and high hot strength, and can extend the service life of steel ladles. Detailed Implementation

[0026] The technical solution of the present invention will be described in detail below with reference to specific embodiments. However, the described embodiments are only some embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] In the specific implementation, unless otherwise specified, the following parameters are used in the above-mentioned schemes: expanded perlite has a TFe content ≤1% and a particle size of 0.1–3 mm; polycrystalline mullite fibers have a diameter of 2–5 μm and a length of 20–50 mm; magnesium oxide fine powder has a particle size ≤0.088 mm; aluminum powder has an Al content ≥99% and a particle size of 200 mesh; bonding clay has a particle size ≤0.088 mm; SiO2 micro powder has a particle size ≤0.015 mm; and p-Al2O3 micro powder has a p-Al2O3 mass percentage content ≥80% and a specific surface area ≥220 m². 2 ·g -1 .

[0028] In the following examples and comparative examples, the castable refractory was made into strip-shaped specimens of 40mm×40mm×160mm. After mixing, stirring, molding, and curing, the specimens were heat-treated at 110℃ for 24 hours. The bulk density of the prepared castable refractory specimens was tested using YB / T5200-1993; the room temperature flexural strength and compressive strength were tested using YB / T 5201-1993; the high temperature flexural strength was tested using GB / T 3002-2007; the thermal conductivity was tested using YB / T 4130-2005; and the thermal shock resistance was tested using YB / T376.1-1995. After water cooling five times, the flexural strength of the specimens was tested, and the strength retention rate of the specimens was calculated.

[0029] Example 1

[0030] A high-strength, lightweight castable refractories for steel ladle insulation is composed of the following raw materials by weight percentage: 55% mullite hollow spheres, 8% expanded perlite, 8% polycrystalline mullite fiber, 8% fine magnesium oxide powder, 4% metallic aluminum powder, 4% binding clay, 6% p-Al2O3 micro powder, 4% sodium lignosulfonate, and 3% SiO2 micro powder. The percentage of different particle sizes in the mullite hollow spheres by weight is as follows: 3 < particle size ≤ 5 mm 35%, 1 < particle size ≤ 3 mm 35%, and 0.1 < particle size ≤ 1 mm 30%.

[0031] The preparation method of the above-mentioned high-strength lightweight castable for steel ladle insulation includes the following steps:

[0032] Weigh each raw material according to the formula. First, mix the aggregate (mullite hollow spheres) and matrix materials (expanded perlite, magnesium oxide fine powder, metallic aluminum powder, binding clay, ρ-Al2O3 micro powder, sodium lignosulfonate, and SiO2 micro powder) evenly. Then, add polycrystalline mullite fibers and mix evenly. After mixing, add water at 5% of the weight percentage of the mixture and stir. During the stirring process, insert a vibrator to vibrate and facilitate air degassing. Cast, cure, and heat treat to prepare a high-strength lightweight steel ladle insulation castable. The curing conditions are natural curing at room temperature for 24 hours. The heat treatment conditions are baking time of 4 hours and temperature of 800℃.

[0033] The aforementioned high-strength lightweight castable for ladle insulation, after being tested in the permanent layer of the ladle, reduced the temperature drop of molten steel by 10% during ladle operation. Testing of the prepared castable revealed a bulk density of 1.71 g·cm³. -3 The room temperature flexural strength is 13.6 MPa, the room temperature compressive strength is 78.1 MPa, the hot flexural strength at 1300℃ is 7.6 MPa, the thermal conductivity is 0.68 W / (m·K), and the strength retention rate after 5 water cooling cycles is 85%.

[0034] Example 2

[0035] A high-strength, lightweight castable refractories for steel ladle insulation is composed of the following raw materials by weight percentage: 55% mullite hollow spheres, 8% expanded perlite, 8% polycrystalline mullite fiber, 8% fine magnesium oxide powder, 4% metallic aluminum powder, 4% binding clay, 6% p-Al2O3 micro powder, 4% sodium lignosulfonate, and 3% SiO2 micro powder. The percentage of different particle sizes in the mullite hollow spheres by weight is as follows: 3 < particle size ≤ 5 mm 40%, 1 < particle size ≤ 3 mm 40%, and 0.1 < particle size ≤ 1 mm 20%.

[0036] Weigh each raw material according to the formula. First, mix the aggregate (mullite hollow spheres) and matrix materials (expanded perlite, magnesium oxide fine powder, metallic aluminum powder, binding clay, ρ-Al2O3 micro powder, sodium lignosulfonate, and SiO2 micro powder) evenly. Then, add polycrystalline mullite fibers and mix evenly. After mixing, add water at 5% of the weight percentage of the mixture and stir. During the stirring process, insert a vibrator to vibrate and facilitate degassing. Cast, cure, and heat treat to prepare a high-strength lightweight steel ladle insulation castable. The curing conditions are natural curing at room temperature for 24 hours. The heat treatment conditions are baking time of 4 hours and temperature of 800℃.

[0037] The aforementioned high-strength lightweight castable for ladle insulation, after trial use in the permanent layer of the ladle, reduced the temperature drop of molten steel by 9.2% during ladle operation. Testing of the prepared castable revealed a bulk density of 1.81 g·cm³. -3 The flexural strength at room temperature is 14.1 MPa, the compressive strength at room temperature is 79.8 MPa, the flexural strength at 1300℃ is 7.7 MPa, the thermal conductivity is 0.78 W / (m·K), and the strength retention rate after 5 water cooling cycles is 82%.

[0038] Example 3

[0039] A high-strength, lightweight castable refractories for steel ladle insulation is composed of the following raw materials by weight percentage: 60% mullite hollow spheres, 7% expanded perlite, 7% polycrystalline mullite fiber, 7% fine magnesium oxide powder, 4% metallic aluminum powder, 5% binding clay, 5% p-Al2O3 micro powder, 3% sodium lignosulfonate, and 2% SiO2 micro powder. The percentage of different particle sizes in the mullite hollow spheres by weight is as follows: 3 < particle size ≤ 5 mm 40%, 1 < particle size ≤ 3 mm 20%, and 0.1 < particle size ≤ 1 mm 40%.

[0040] Weigh each raw material according to the formula. First, mix the aggregate (mullite hollow spheres) and matrix materials (expanded perlite, magnesium oxide fine powder, metallic aluminum powder, binding clay, ρ-Al2O3 micro powder, sodium lignosulfonate, and SiO2 micro powder) evenly. Then, add polycrystalline mullite fibers and mix evenly. After mixing, add water at 5% of the weight percentage of the mixture and stir. During the stirring process, insert a vibrator to vibrate and facilitate degassing. Cast, cure, and heat treat to prepare a high-strength lightweight steel ladle insulation castable. The curing conditions are natural curing at room temperature for 24 hours. The heat treatment conditions are baking time of 4 hours and temperature of 800℃.

[0041] The aforementioned high-strength lightweight castable for ladle insulation, after trial use in the permanent layer of the ladle, reduced the temperature drop of molten steel during ladle operation by 8.3%. Testing of the prepared castable revealed a bulk density of 1.74 g·cm³. -3 The room temperature flexural strength is 14.9 MPa, the room temperature compressive strength is 81.6 MPa, the hot flexural strength at 1300℃ is 8.1 MPa, the thermal conductivity is 0.88 W / (m·K), and the strength retention rate after 5 water cooling cycles is 84%.

[0042] Example 4

[0043] A high-strength, lightweight castable refractories for steel ladle insulation is composed of the following raw materials by weight percentage: 50% mullite hollow spheres, 9% expanded perlite, 9% polycrystalline mullite fiber, 9% fine magnesium oxide powder, 5% metallic aluminum powder, 4% binding clay, 8% p-Al2O3 micro powder, 4% sodium lignosulfonate, and 2% SiO2 micro powder. The percentage of different particle sizes in the mullite hollow spheres by weight is as follows: 3 < particle size ≤ 5 mm 30%, 1 < particle size ≤ 3 mm 35%, and 0.1 < particle size ≤ 1 mm 35%.

[0044] Weigh each raw material according to the formula. First, mix the aggregate (mullite hollow spheres) and matrix materials (expanded perlite, magnesium oxide fine powder, metallic aluminum powder, binding clay, ρ-Al2O3 micro powder, sodium lignosulfonate, and SiO2 micro powder) evenly. Then, add polycrystalline mullite fibers and mix evenly. After mixing, add water at 4% of the weight percentage of the mixture and stir. During the stirring process, insert a vibrator to vibrate and facilitate air degassing. Cast, cure, and heat treat to prepare a high-strength lightweight steel ladle insulation castable. The curing conditions are natural curing at room temperature for 24 hours. The heat treatment conditions are baking time of 4 hours and temperature of 800℃.

[0045] The aforementioned high-strength lightweight castable for ladle insulation, after trial use in the permanent layer of the ladle, reduced the temperature drop of molten steel by 9.0% during ladle operation. Testing of the prepared castable revealed a bulk density of 1.82 g·cm³. -3 The room temperature flexural strength is 14.2 MPa, the room temperature compressive strength is 79.3 MPa, the hot flexural strength at 1300℃ is 7.7 MPa, the thermal conductivity is 0.72 W / (m·K), and the strength retention rate after 5 water cooling cycles is 81%.

[0046] Example 5

[0047] A high-strength, lightweight castable refractories for steel ladle insulation is composed of the following raw materials by weight percentage: 58% mullite hollow spheres, 6% expanded perlite, 6% polycrystalline mullite fiber, 8% fine magnesium oxide powder, 4% metallic aluminum powder, 4% binding clay, 5% p-Al2O3 micro powder, 5% sodium lignosulfonate, and 4% SiO2 micro powder. The percentage of different particle sizes in the mullite hollow spheres by weight is as follows: 3 < particle size ≤ 5 mm 35%, 1 < particle size ≤ 3 mm 35%, and 0.1 < particle size ≤ 1 mm 30%.

[0048] Weigh each raw material according to the formula. First, mix the aggregate (mullite hollow spheres) and matrix materials (expanded perlite, magnesium oxide fine powder, metallic aluminum powder, binding clay, ρ-Al2O3 micro powder, sodium lignosulfonate, and SiO2 micro powder) evenly. Then, add polycrystalline mullite fibers and mix evenly. After mixing, add water at 4% of the weight percentage of the mixture and stir. During the stirring process, insert a vibrator to vibrate and facilitate air degassing. Cast, cure, and heat treat to prepare a high-strength lightweight steel ladle insulation castable. The curing conditions are natural curing at room temperature for 24 hours. The heat treatment conditions are baking time of 4 hours and temperature of 800℃.

[0049] The aforementioned high-strength lightweight castable for ladle insulation, after trial use in the permanent layer of the ladle, reduced the temperature drop of molten steel during ladle operation by 8.6%. Testing of the prepared castable revealed a bulk density of 1.78 g·cm³. -3 The room temperature flexural strength is 14.1 MPa, the room temperature compressive strength is 80.8 MPa, the hot flexural strength at 1300℃ is 8.1 MPa, the thermal conductivity is 0.81 W / (m·K), and the strength retention rate after 5 water cooling cycles is 84%.

[0050] Example 6

[0051] A high-strength, lightweight castable refractories for steel ladle insulation is composed of the following raw materials by weight percentage: 52% mullite hollow spheres, 9% expanded perlite, 9% polycrystalline mullite fiber, 9% fine magnesium oxide powder, 5% metallic aluminum powder, 3% binding clay, 7% p-Al2O3 micro powder, 4% sodium lignosulfonate, and 2% SiO2 micro powder. The percentage of different particle sizes in the mullite hollow spheres by weight is as follows: 3 < particle size ≤ 5 mm 25%, 1 < particle size ≤ 3 mm 35%, and 0.1 < particle size ≤ 1 mm 40%.

[0052] Weigh each raw material according to the formula. First, mix the aggregate (mullite hollow spheres) and matrix materials (expanded perlite, magnesium oxide fine powder, metallic aluminum powder, binding clay, ρ-Al2O3 micro powder, sodium lignosulfonate, and SiO2 micro powder) evenly. Then, add polycrystalline mullite fibers and mix evenly. After mixing, add 5% water by weight of the mixture and stir. During the stirring process, insert a vibrator to vibrate and facilitate degassing. Cast, cure, and heat treat to prepare a high-strength lightweight steel ladle insulation castable. The curing conditions are natural curing at room temperature for 24 hours. The heat treatment conditions are baking time of 4 hours and temperature of 800℃.

[0053] The aforementioned high-strength lightweight castable for ladle insulation, after trial use in the permanent layer of the ladle, reduced the temperature drop of molten steel during ladle operation by 9.2%. Testing of the prepared castable revealed a bulk density of 1.75 g·cm³. -3The room temperature flexural strength is 13.8 MPa, the room temperature compressive strength is 78.7 MPa, the hot flexural strength at 1300℃ is 7.7 MPa, the thermal conductivity is 0.74 W / (m·K), and the strength retention rate after 5 water cooling cycles is 80%.

[0054] Comparative Example 1

[0055] A castable refractory is composed of the following raw materials in the following weight percentages: 55% mullite, 8% expanded perlite, 8% polycrystalline mullite fiber, 8% fine magnesium oxide powder, 4% metallic aluminum powder, 4% binding clay, 6% p-Al₂O₃ micro powder, 4% sodium lignosulfonate, and 3% SiO₂ micro powder. The percentage of different particle sizes in the total weight of the mullite is as follows: 3 < particle size ≤ 5 mm 35%, 1 < particle size ≤ 3 mm 35%, and 0.1 < particle size ≤ 1 mm 30%.

[0056] The aforementioned castable was prepared using conventional castable preparation processes. The prepared castable was tested, and the results showed a bulk density of 2.8 g·cm³. -3 The thermal conductivity is 1.5 W / (m·K). Compared with Example 1, this embodiment does not use mullite hollow spheres as aggregate, therefore the performance of the castable is higher in terms of bulk density and thermal conductivity.

[0057] Comparative Example 2

[0058] A castable refractory is composed of the following raw materials in the indicated weight percentages: 55% mullite hollow spheres, 12% expanded perlite, 6% polycrystalline mullite fiber, 6% fine magnesium oxide powder, 4% metallic aluminum powder, 4% binding clay, 6% p-Al₂O₃ micro powder, 4% sodium lignosulfonate, and 3% SiO₂ micro powder. The percentage of different particle sizes in the total weight of the mullite hollow spheres is as follows: 3 < particle size ≤ 5 mm 35%, 1 < particle size ≤ 3 mm 35%, and 0.1 < particle size ≤ 1 mm 30%.

[0059] The above-mentioned castable was prepared using conventional castable preparation processes. The castable was tested, and the results were as follows: flexural strength at room temperature was 11.2 MPa, compressive strength at room temperature was 72.1 MPa, flexural strength at 1300℃ was 6.6 MPa, thermal conductivity was 0.63 W / (m·K), and the strength retention rate after 5 water cooling cycles was 78%. In this embodiment, compared to Example 1, the amount of expanded perlite was too high; therefore, the performance of the castable was lower in terms of strength and thermal conductivity compared to Example 1.

[0060] Comparative Example 3

[0061] A castable refractory is composed of the following raw materials in the indicated weight percentages: 59% mullite hollow spheres, 8% expanded perlite, 8% polycrystalline mullite fiber, 8% fine magnesium oxide powder, 4% binding clay, 6% p-Al₂O₃ micro powder, 4% sodium lignosulfonate, and 3% SiO₂ micro powder. The percentage of different particle sizes in the total weight of the mullite hollow spheres is as follows: 3 < particle size ≤ 5 mm 35%, 1 < particle size ≤ 3 mm 35%, and 0.1 < particle size ≤ 1 mm 30%.

[0062] The above-mentioned castable was prepared using a conventional castable preparation process. The castable was tested, and the results were as follows: flexural strength at room temperature was 11.8 MPa, compressive strength at room temperature was 73.6 MPa, flexural strength at 1300℃ was 7.1 MPa, thermal conductivity was 0.7 W / (m·K), and the strength retention rate after 5 water cooling cycles was 83%. Compared to Example 1, this embodiment did not use aluminum powder; therefore, the strength of the castable is reduced compared to Example 1.

[0063] Comparative Example 4

[0064] A castable refractory is composed of the following raw materials in the indicated weight percentages: 60% mullite hollow spheres, 9% expanded perlite, 8% magnesia fine powder, 5% metallic aluminum powder, 5% binding clay, 6% p-Al₂O₃ micro powder, 4% sodium lignosulfonate, and 3% SiO₂ micro powder. The percentage of different particle sizes in the mullite hollow spheres is as follows: 3 < particle size ≤ 5 mm 35%, 1 < particle size ≤ 3 mm 35%, and 0.1 < particle size ≤ 1 mm 30%.

[0065] The aforementioned castable was prepared using conventional castable preparation processes. The prepared castable was tested, and the results showed a bulk density of 1.86 g·cm³. -3 The room temperature flexural strength is 11.26 MPa, the room temperature compressive strength is 71.9 MPa, the hot flexural strength at 1300℃ is 7.2 MPa, the thermal conductivity is 0.74 W / (m·K), and the strength retention rate after 5 water cooling cycles is 79%. Compared to Example 1, this embodiment does not use polycrystalline mullite fiber; therefore, the performance of the castable is different from Example 1, with increased bulk density and thermal conductivity, decreased strength, and reduced thermal shock resistance.

[0066] Comparative Example 5

[0067] A castable refractory is composed of the following raw materials by weight percentage: 55% mullite hollow spheres, 8% expanded perlite, 8% polycrystalline mullite fiber, 8% fine magnesium oxide powder, 4% metallic aluminum powder, 4% binding clay, 6% p-Al₂O₃ micro powder, 4% sodium lignosulfonate, and 3% SiO₂ micro powder. The percentage of different particle sizes in the total weight of the mullite hollow spheres is as follows: 3 < particle size ≤ 5 mm 100%.

[0068] The aforementioned castable was prepared using conventional castable preparation processes. The prepared castable was tested, and the results showed a bulk density of 1.78 g·cm³. -3 The flexural strength at room temperature is 8.3 MPa, the compressive strength at room temperature is 61.2 MPa, the flexural strength at 1300℃ is 5.1 MPa, the thermal conductivity is 0.72 W / (m·K), and the strength retention rate after 5 water cooling cycles is 69%. Compared with Example 1, the aggregate particle size distribution was not performed in this embodiment, therefore the performance of the castable is lower in strength and thermal shock resistance compared with Example 1.

[0069] In summary, the high-strength lightweight castable for ladle insulation provided by this invention has high strength, low thermal conductivity, and good thermal shock resistance. When used in ladle insulation, it can reduce the temperature drop during the operation of molten steel.

[0070] 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 high-strength, lightweight castable refractory for steel ladle insulation, characterized in that, The product is composed of the following raw materials by weight percentage: 52-60% mullite hollow spheres, 5-9% expanded perlite, 5-10% polycrystalline mullite fiber, 5-10% fine magnesium oxide powder, 1-5% metallic aluminum powder, 1-5% binding clay, 2-8% p-Al2O3 micro powder, 1-5% sodium lignosulfonate, and 1-4% SiO2 micro powder; the percentage of different particle sizes in the total weight of the mullite hollow spheres is: 3 Particle size ≤5mm 20~40%, 1 Particle size ≤3mm, 20~40%, 0.1 Particle size ≤1mm 20~40%; The bulk density of the high-strength lightweight castable for ladle insulation is not higher than 1.82 g·cm³. -3 The flexural strength at room temperature is not less than 13.5 MPa, the compressive strength at room temperature is not less than 78 MPa, the flexural strength at 1300℃ is not less than 7.5 MPa, the thermal conductivity is not higher than 0.9 W / (m•K), and the temperature drop of molten steel during ladle operation is not less than 8%.

2. The high-strength lightweight castable for steel ladle insulation according to claim 1, characterized in that, The expanded perlite has a TFe content of ≤1% and a particle size of 0.1~3mm.

3. The high-strength lightweight castable for steel ladle insulation according to claim 1, characterized in that, The polycrystalline mullite fibers have a diameter of 2~5μm and a length of 20~50mm.

4. The high-strength lightweight castable for steel ladle insulation according to claim 1, characterized in that, The particle size of the magnesium oxide fine powder is ≤0.088mm.

5. The high-strength lightweight castable for steel ladle insulation according to claim 1, characterized in that, The aluminum powder contains ≥99% Al and has a particle size of 200 mesh.

6. The high-strength lightweight castable for steel ladle insulation according to claim 1, characterized in that, The particle size of the bonding clay is ≤0.088mm; the particle size of the SiO2 powder is ≤0.015mm.

7. The high-strength lightweight castable for steel ladle insulation according to claim 1, characterized in that, The ρ-Al2O3 micro powder contains ≥80% ρ-Al2O3 by mass, and the ρ-Al2O3 micro powder has a specific surface area ≥220 m². 2 ·g -1 .

8. A method for preparing a high-strength lightweight castable for steel ladle insulation according to any one of claims 1 to 7, characterized in that, Includes the following steps: Weigh each raw material according to the formula. First, mix the mullite hollow spheres with expanded perlite, magnesium oxide fine powder, metallic aluminum powder, binding clay, p-Al2O3 micro powder, sodium lignosulfonate, and SiO2 micro powder. Then, add polycrystalline mullite fiber and mix well. After mixing, add water at 3-5% of the weight percentage of the mixture and stir. During the stirring process, insert a vibrator to vibrate. Cast into shape, cure, and heat treat to prepare a high-strength lightweight steel ladle insulation castable. The curing conditions are natural curing at room temperature for 24-30 hours. The heat treatment conditions are baking time of 4-6 hours and temperature of 800-1000℃.