Magnesia-zirconia-carbon refractory brick, and preparation method and application thereof

Abstract

The application relates to the technical field of refractory materials, in particular to a magnesium-zirconium-carbon refractory brick and a preparation method and application thereof. The refractory brick takes magnesia as a main aggregate and zirconia as a fine aggregate, and a matrix comprises magnesia fine powder, zirconia fine powder, silicon carbide fine powder, rare earth oxides, carbon powder and a composite antioxidant. By optimizing particle gradation and compression molding, the density and strength of the material are improved, and the porosity is reduced. Magnesia and zirconia have poor slag wettability, can effectively inhibit slag penetration and corrosion; zirconia has a toughening effect, can improve the thermal shock resistance of the material; the rare earth oxides can stabilize zirconia and promote sintering densification, and further enhance the corrosion resistance of the material. Compared with traditional castable, the magnesium-zirconium-carbon refractory brick has the characteristics of low porosity, high density, good corrosion resistance, strong erosion resistance and excellent thermal shock stability, can significantly prolong the service life of a skimmer, and reduce maintenance cost.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, specifically to a magnesium-zirconium-carbon refractory brick, its preparation method, and its application. Background Technology

[0002] The blast furnace tapping trough is an important component of the blast furnace ironmaking system, primarily used to receive and transport high-temperature molten iron and slag, and to achieve slag-iron separation. The skimmer is located in a critical part of the blast furnace tapping trough system; its main function is to prevent molten slag from entering the molten iron channel, ensuring that the molten iron flows smoothly into the branch trough or ladle. Because the skimmer is in direct contact with high-temperature molten iron and slag for extended periods, and is subjected to molten iron scouring, slag erosion, and periodic temperature fluctuations, its service environment is extremely harsh.

[0003] Currently, Al2O3-SiC-C castable refractory is widely used for the slag skimmer section of blast furnace tapping troughs. While this type of castable refractory is convenient to install and has good overall integrity, it still has certain shortcomings during long-term service. Firstly, after on-site casting, curing, and baking, the castable refractory tends to retain many pores, resulting in limited density. Molten slag and iron can easily penetrate into the material through these pores, leading to structural deterioration. Secondly, the skimmer section is repeatedly eroded by high-temperature molten iron and slag, making the castable refractory prone to wear, erosion, and spalling. Simultaneously, the carbonaceous components are easily oxidized under high-temperature oxidizing atmospheres, further reducing the material's strength and corrosion resistance. Furthermore, the skimmer experiences frequent hot and cold cycles during tapping and shutting down, making the material susceptible to thermal stress cracks, affecting its thermal shock resistance and service life.

[0004] Therefore, existing castable refractory materials for slag skimmers still fall short of meeting the requirements for long service life and stable operation of blast furnaces in terms of slag erosion resistance, molten iron scouring resistance, and thermal shock resistance. Developing a refractory material for blast furnace tapping trough slag skimmers that is structurally dense, has good erosion resistance, strong scouring resistance, and excellent thermal shock stability is of great significance for extending the service life of slag skimmers, reducing refractory material consumption, and decreasing maintenance costs. Summary of the Invention

[0005] To address the problems of high porosity and insufficient density of existing castable refractory materials used in blast furnace tapping troughs, which are prone to erosion, spalling, and cracking under the influence of high-temperature molten iron, slag erosion, and alternating hot and cold conditions, this invention aims to provide a magnesium-zirconium-carbon refractory brick, its preparation method, and its application. This refractory brick features high density, good erosion resistance, strong scour resistance, and excellent thermal shock resistance, which can extend the service life of the slag skimmer and reduce refractory material consumption and maintenance costs.

[0006] The present invention provides a magnesium-zirconium-carbon refractory brick comprising aggregates and matrix. The aggregates include magnesia aggregates and zirconium oxide aggregates, and the matrix comprises fine magnesia powder, fine zirconium oxide powder, fine silicon carbide powder, rare earth oxides, carbon powder, and antioxidants.

[0007] Furthermore, the magnesia aggregate and magnesia powder are both selected from at least one of fused magnesia and sintered magnesia; Furthermore, by mass percentage, magnesia aggregate accounts for 60-70 wt%, zirconium oxide aggregate accounts for 10-15 wt%, magnesia fine powder accounts for 5-10 wt%, zirconium oxide fine powder accounts for 4-10 wt%, silicon carbide fine powder accounts for 2-6 wt%, rare earth oxides account for 1-3 wt%, carbon powder accounts for 2-5%, and antioxidants account for 3-8 wt%.

[0008] Furthermore, the magnesia aggregate adopts a three-stage particle size distribution, including magnesia aggregate with particle sizes of 5-3mm, 3-1mm and 1-0mm; the fine magnesia powder has a particle size of ≤74μm.

[0009] Furthermore, the zirconia aggregate is partially stabilized zirconia (i.e., 3 mol% yttrium oxide stabilized tetragonal zirconia) with a particle size of 1-0 mm; the fine zirconia powder has a particle size ≤74 μm.

[0010] Furthermore, the particle size of the silicon carbide fine powder is ≤74μm.

[0011] Furthermore, the toner includes graphite and carbon black.

[0012] Furthermore, the antioxidant is selected from one or more of Al powder, Si powder, and B4C powder, wherein the particle size of Al powder is ≤74μm, the particle size of Si powder is ≤100μm, and the particle size of B4C powder is ≤45μm.

[0013] Furthermore, the particle size of the graphite is ≤200μm, and the particle size of the carbon black is ≤500nm; Furthermore, the rare earth oxide is selected from one or more of yttrium oxide, lanthanum oxide, and cerium oxide.

[0014] Furthermore, the particle size of the rare earth oxide is ≤74μm.

[0015] This invention also provides a method for preparing magnesium-zirconium-carbon refractory bricks, specifically including the following steps: (1) Aggregate premixing: Magnesia aggregate of different particle sizes, zirconium oxide aggregate and a portion of phenolic resin liquid are mixed according to the formula to obtain premixed aggregate; Matrix premixing: Fine magnesium oxide powder, fine zirconium oxide powder, fine silicon carbide powder, rare earth oxides, carbon powder, antioxidants and phenolic resin powder are mixed in proportion to obtain a premixed matrix material; (2) Mixing: Mix the premixed aggregate, premixed matrix material and the remaining phenolic resin liquid evenly to obtain a uniform mixture; (3) Molding: The mixture is pressed into a blank by hydraulic molding or isostatic pressing; (4) Drying: The molded blank is dried and cured in stages.

[0016] Furthermore, the mixing time in step (1) is 10-15 min.

[0017] Furthermore, the mixing time in step (2) is 20-30 min.

[0018] Furthermore, the molding pressure in step (3) is 100-200 MPa.

[0019] Furthermore, the total amount of phenolic resin solution and phenolic resin powder added in steps (1) and (2) is 3-5 wt%.

[0020] Furthermore, the staged drying and curing process described in step (4) specifically involves heat-treating the blank at 60℃, 120℃, and 200℃ for 6-12 hours respectively.

[0021] The aforementioned magnesium-zirconium-carbon refractory bricks are used as refractory materials for the slag skimmer section of the blast furnace tapping trough.

[0022] Compared with traditional castable linings, the present invention has the following advantages: (1) This invention optimizes particle size distribution and uses a pressing molding process to prepare magnesium zirconium carbon refractory bricks, thereby forming a dense and stable skeleton structure. Compared with traditional castables, the refractory bricks of this invention have low porosity and high bulk density, which can effectively reduce the penetration of slag, molten iron and oxidizing gases into the material, and improve the overall strength and structural stability of the material.

[0023] (2) The magnesium-zirconium-carbon refractory brick of the present invention uses magnesia as the main aggregate. Magnesium oxide has good chemical stability to alkaline slag and poor wettability with slag, which can reduce the erosion and penetration of slag on the material. The introduction of zirconium oxide further improves the material's resistance to slag erosion, making the refractory brick more suitable for the high-temperature molten slag environment of the blast furnace tapping trough skimmer section.

[0024] (3) The magnesium zircon carbon refractory brick of the present invention adds rare earth oxides to the matrix, which can stabilize the zirconium oxide phase structure, promote the sintering and densification of the material, enhance the bonding strength between magnesia, zirconium oxide and matrix fine powder, and further improve the high temperature strength and slag penetration resistance of the refractory brick.

[0025] (4) Compared with existing slag skimmer castables, the magnesium zirconium carbon refractory bricks of the present invention have the characteristics of low porosity, high density, good erosion resistance, strong scour resistance and excellent thermal shock resistance, which can significantly extend the service life of slag skimmers, reduce refractory material consumption and maintenance costs, and improve the operational stability of the blast furnace tapping trough system. Detailed Implementation

[0026] To better understand the content of this invention, specific embodiments will be used to further illustrate the invention below. The following embodiments are based on the technology of this invention and provide detailed implementation methods and operating steps; however, the scope of protection of this invention is not limited to the following embodiments.

[0027] The performance testing procedures in the following examples and comparative examples are consistent. The bulk density, apparent porosity, room temperature flexural strength, high temperature flexural strength, and thermal shock resistance of the samples were tested according to national standards GB / T 2997-2015, GB / T 3001-2007, GB / T 3002-2007, and GB / T 30873-2014. The slag resistance performance of the samples was evaluated using a rotary slag resistance test, with blast furnace slag as the slag source, and the test conditions were erosion at 1500℃ for 3 hours.

[0028] In the examples and comparative examples, the particle size of magnesia fine powder is ≤74μm, the zirconium oxide aggregate is partially stabilized zirconium oxide with a particle size of 1-0mm; the particle size of zirconium oxide fine powder is ≤74μm, the particle size of silicon carbide fine powder is ≤74μm, the particle size of Al powder is ≤74μm, the particle size of Si powder is ≤100μm, the particle size of B4C powder is ≤45μm, the particle size of graphite is ≤200μm, the particle size of carbon black is ≤500nm, and the particle size of rare earth oxides is ≤74μm.

[0029] Example 1: A magnesia-zirconium-carbon refractory brick for a blast furnace tapping trough skimmer has the following raw material composition (by mass percentage): 65% sintered magnesia aggregate (of which 5-3mm particle size sintered magnesia aggregate accounts for 40% of the total mass of sintered magnesia aggregate, 3-1mm particle size sintered magnesia aggregate accounts for 40% of the total mass of sintered magnesia aggregate, and 1-0mm particle size sintered magnesia aggregate accounts for 20% of the total mass of sintered magnesia aggregate), 10% zirconium oxide aggregate, and 6% sintered magnesia fine powder. The mixture comprises 8% zirconium oxide fine powder, 3% SiC fine powder, 3% flake graphite, 0.5% carbon black, 1% yttrium oxide powder, 2% aluminum powder, 1% silicon powder, 0.5% boron carbide powder, and phenolic resin liquid and phenolic resin powder as binders. The amount of phenolic resin liquid added is 2% (i.e., the mass of the added phenolic resin liquid accounts for 2% of the total mass of the above raw materials), and the amount of phenolic resin powder added is 1.5% (i.e., the mass of the added phenolic resin powder accounts for 1.5% of the total mass of the above raw materials).

[0030] The preparation method is as follows: (1) Mix the above-mentioned sintered magnesia aggregate, zirconium oxide aggregate and 40wt% phenolic resin liquid for 10min to form a premixed aggregate; mix the sintered magnesia fine powder, zirconium oxide fine powder, SiC fine powder, yttrium oxide powder, flake graphite, carbon black, aluminum powder, silicon powder, boron carbide powder and phenolic resin powder for 10min to form a premixed matrix material; (2) Add the premixed aggregate and premixed matrix to the remaining 60wt% phenolic resin liquid and continue mixing for 20min to obtain a uniform mixture; (3) The above mixture is pressed at 120 MPa using isostatic pressing. (4) The shaped brick blanks are first dried at 60℃ for 6 hours, then dried at 120℃ for 6 hours, and finally dried at 200℃ for 12 hours.

[0031] The resulting magnesia-zirconium-carbon refractory bricks were heat-treated at 1500℃ for 3 hours under carbon-embedded conditions, and their performance was tested according to national standards. Their key properties are as follows: apparent porosity 8.1%, bulk density 3.25 g / cm³. 3 The flexural strength at room temperature is 44.5 MPa, and the flexural strength at high temperature is 37.8 MPa. After three water-cooled thermal shock cycles at 1100℃, the flexural strength retention rate is 87.7%, and the erosion layer thickness is 0.9 mm. (The last sentence appears to be incomplete and possibly refers to a 1200m...) 3 Application verification of blast furnace tapping trough skimmer shows that, compared with the traditional Al2O3-SiC-C castable, material consumption is reduced by 87% and iron throughput is increased by 72%.

[0032] Example 2: A magnesia-zirconium-carbon refractory brick for a blast furnace tapping trough skimmer has the following raw material composition (by mass percentage): 60% sintered magnesia aggregate (of which 5-3mm sintered magnesia aggregate accounts for 45% of the total mass of sintered magnesia aggregate, 3-1mm sintered magnesia aggregate accounts for 40% of the total mass of sintered magnesia aggregate, and 1-0mm sintered magnesia aggregate accounts for 15% of the total mass of sintered magnesia aggregate), 13% zirconium oxide aggregate, 5% sintered magnesia fine powder, 10% zirconium oxide fine powder, 3% SiC fine powder, 3% flake graphite, 0.5% carbon black, 1% lanthanum oxide powder, 2% aluminum powder, 2% silicon powder, 0.5% boron carbide powder, with added phenolic resin liquid and phenolic resin powder as binders, wherein the amount of added phenolic resin liquid is 2% and the amount of added phenolic resin powder is 1.5%.

[0033] The preparation method is as follows: (1) Mix the above-mentioned sintered magnesia aggregate, zirconium oxide aggregate and 40wt% phenolic resin liquid for 10min to form a premixed aggregate; mix the sintered magnesia fine powder, zirconium oxide fine powder, SiC fine powder, lanthanum oxide powder, flake graphite, carbon black, aluminum powder, silicon powder, boron carbide powder and phenolic resin powder for 15min to form a premixed matrix material; (2) Add the premixed aggregate and premixed matrix to the remaining 60wt% phenolic resin liquid and continue mixing for 25min to obtain a uniform mixture; (3) The above mixture is pressed at 150 MPa using isostatic pressing. (4) The shaped brick blanks are first dried at 60℃ for 6 hours, then dried at 120℃ for 12 hours, and finally dried at 200℃ for 12 hours.

[0034] The resulting magnesia-zirconium-carbon refractory bricks were heat-treated at 1500℃ for 3 hours under carbon-embedded conditions, and their performance was tested according to national standards. Their key properties are as follows: apparent porosity 7.7%, bulk density 3.31 g / cm³. 3 The flexural strength at room temperature is 48.6 MPa, and the flexural strength at high temperature is 41.3 MPa. After three water-cooled thermal shock cycles at 1100℃, the flexural strength retention rate is 89.2%, and the eroded layer thickness is 0.8 mm. (This is followed by a seemingly unrelated sentence about a 2000m...) 3 Application verification of blast furnace tapping trough skimmer shows that, compared with the traditional Al2O3-SiC-C castable, material consumption is reduced by 92% and iron throughput is increased by 75%.

[0035] Example 3: A magnesia-zirconium-carbon refractory brick for a blast furnace tapping trough skimmer has the following raw material composition (by mass percentage): 60% sintered magnesia aggregate (of which 5-3mm sintered magnesia aggregate accounts for 40% of the total mass of sintered magnesia aggregate, 3-1mm sintered magnesia aggregate accounts for 40% of the total mass of sintered magnesia aggregate, and 1-0mm sintered magnesia aggregate accounts for 20% of the total mass of sintered magnesia aggregate), 15% zirconium oxide aggregate, 5% sintered magnesia fine powder, 8% zirconium oxide fine powder, 3% SiC fine powder, 3% flake graphite, 0.5% carbon black, 1% cerium oxide powder, 3% aluminum powder, 1% silicon powder, 0.5% boron carbide powder, with added phenolic resin liquid and phenolic resin powder as binders, wherein the amount of added phenolic resin liquid is 2% and the amount of added phenolic resin powder is 1.5%.

[0036] The preparation method is as follows: (1) Mix the above-mentioned sintered magnesia aggregate, zirconium oxide aggregate and 40wt% phenolic resin liquid for 15min to form a premixed aggregate; mix the sintered magnesia fine powder, zirconium oxide fine powder, SiC fine powder, cerium oxide powder, flake graphite, carbon black, aluminum powder, silicon powder, boron carbide powder and phenolic resin powder for 15min to form a premixed matrix material; (2) Add the premixed aggregate and premixed matrix to the remaining 60wt% phenolic resin liquid and continue mixing for 30min to obtain a uniform mixture; (3) The above mixture is pressed at 150 MPa using isostatic pressing. (4) The shaped brick blanks are first dried at 60℃ for 12 hours, then dried at 120℃ for 12 hours, and finally dried at 200℃ for 12 hours.

[0037] The resulting magnesia-zirconium-carbon refractory bricks were heat-treated at 1500℃ for 3 hours under carbon-embedded conditions, and their performance was tested according to national standards. Their key properties are as follows: apparent porosity 7.5%, bulk density 3.34 g / cm³. 3 The flexural strength at room temperature is 50.4 MPa, and the flexural strength at high temperature is 42.7 MPa. After three water-cooled thermal shock cycles at 1100℃, the flexural strength retention rate is 90.8%, and the eroded layer thickness is 0.7 mm. (The last sentence appears to be incomplete and possibly refers to a 1200m...) 3 Application verification of blast furnace tapping trough skimmer shows that, compared with the traditional Al2O3-SiC-C castable, material consumption is reduced by 96% and iron throughput is increased by 79%.

[0038] Comparative Example 1: To compare the performance of the magnesium zirconium carbon refractory brick of the present invention, the Al2O3-SiC-C castable currently used in the blast furnace tapping trough skimmer was selected as the comparative material.

[0039] By mass percentage, the main raw materials of this Al2O3-SiC-C castable include 58% brown fused alumina aggregate (of which, brown fused alumina particles with a diameter of 8-5 mm account for 35% of the mass of brown fused alumina aggregate, brown fused alumina particles with a diameter of 5-3 mm account for 35% of the mass of brown fused alumina aggregate, brown fused alumina particles with a diameter of 3-1 mm account for 20% of the mass of brown fused alumina aggregate, and brown fused alumina particles with a diameter of less than 1 mm account for 10% of the mass of brown fused alumina aggregate), 6% fine brown fused alumina powder (particle size ≤74 μm), 12% SiC aggregate (of which, SiC particles with a diameter of 3-1 mm and SiC particles with a diameter of less than 1 mm each account for 50% of the mass of SiC aggregate), 6% fine SiC powder (particle size ≤100 μm), 6% alumina micro powder (particle size ≤10 μm), 3% silica micro powder (particle size ≤1 μm), and 2% graphite (particle size ≤200 μm). The mixture consists of 0.5% spherical asphalt (particle size 0.2-1 mm), 3% silica fume (particle size ≤74 μm), 0.5% aluminum powder (particle size ≤100 μm), and 3% aluminate cement binder. Water is added and stirred, with the water amounting to 5% of the total mass of the raw materials. After mixing, the mixture is vibrated and cast into molds. After natural curing for 24 hours, it is dried at 110℃ for 24 hours.

[0040] The obtained Al2O3-SiC-C castable was heat-treated at 1500℃ for 3 hours under carbon embedding conditions, and its performance was tested according to national standards. Its key properties are as follows: bulk density is 2.64 g / cm³. 3 The apparent porosity is 15.1%, the flexural strength at room temperature is 14.7 MPa, the flexural strength at high temperature is 9.8 MPa, and after three water-cooled thermal shocks at 1100℃, the flexural strength retention rate is 37.8%, and the thickness of the eroded layer is 5.1 mm.

[0041] As can be seen from the above embodiments and comparative examples, the magnesia-zirconium-carbon refractory bricks for the blast furnace tapping trough skimmer of the present invention have significant advantages over traditional Al2O3-SiC-C castables: the material has high density, low porosity, excellent high-temperature mechanical properties, and outstanding resistance to thermal shock and erosion. Under the same slag and heat treatment conditions, the refractory bricks are less susceptible to erosion, are less prone to spalling or localized damage during service, can significantly reduce refractory material consumption, extend the service life of the skimmer, and improve the blast furnace iron feeding efficiency.

[0042] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A magnesium-zirconium-carbon refractory brick, characterized in that, It includes aggregates and matrix. The aggregates include magnesia aggregates and zirconia aggregates. The matrix includes fine magnesia powder, fine zirconia powder, fine silicon carbide powder, rare earth oxides, carbon powder, and antioxidants. By mass percentage, magnesia aggregates account for 60-70 wt%, zirconia aggregates account for 10-15 wt%, fine magnesia powder accounts for 5-10 wt%, fine zirconia powder accounts for 4-10 wt%, and fine silicon carbide powder accounts for 2-6 wt%. Rare earth oxides account for 1-3 wt%, carbon powder accounts for 2-5%, and antioxidants account for 3-8 wt%.

2. The magnesium-zirconium-carbon refractory brick as described in claim 1, characterized in that, The magnesia aggregate and magnesia powder are both selected from at least one of fused magnesia and sintered magnesia; the rare earth oxides are selected from one or more of yttrium oxide, lanthanum oxide and cerium oxide; the carbon powder includes graphite and carbon black.

3. The magnesium-zirconium-carbon refractory brick as described in claim 1, characterized in that, The antioxidant is selected from one or more of Al powder, Si powder, and B4C powder, wherein the particle size of Al powder is ≤74μm, the particle size of Si powder is ≤100μm, and the particle size of B4C powder is ≤45μm.

4. The magnesium-zirconium-carbon refractory brick as described in claim 1, characterized in that, The particle size of the silicon carbide fine powder is ≤74μm; the particle size of the graphite is ≤200μm; the particle size of the carbon black is ≤500nm; and the particle size of the rare earth oxide is ≤74μm.

5. The magnesium-zirconium-carbon refractory brick as described in claim 1, characterized in that, The magnesia aggregate adopts a three-stage particle size distribution, including magnesia aggregate with particle sizes of 5-3mm, 3-1mm and 1-0mm; the fine magnesia powder has a particle size of ≤74μm; the zirconium oxide is partially stabilized zirconium oxide with a particle size of 1-0mm; the fine zirconium oxide powder has a particle size of ≤74μm.

6. A method for preparing magnesium-zirconium-carbon refractory bricks as described in any one of claims 1-5, characterized in that, Specifically, the following steps are included: (1) Aggregate premixing: Magnesia aggregate of different particle sizes, zirconium oxide aggregate and a portion of phenolic resin liquid are mixed to obtain premixed aggregate; Matrix premixing: Fine magnesium oxide powder, fine zirconium oxide powder, fine silicon carbide powder, rare earth oxides, carbon powder, antioxidants and phenolic resin powder are mixed to obtain a premixed matrix material; (2) Mixing: Mix the premixed aggregate, premixed matrix material and the remaining phenolic resin liquid evenly to obtain a mixture; (3) Molding: The mixture is pressed into a blank by hydraulic molding or isostatic pressing; (4) Drying: The molded blank is dried and cured in stages.

7. The method for preparing magnesium-zirconium-carbon refractory bricks as described in claim 6, characterized in that, The mixing time in step (1) is 10-15 min; the mixing time in step (2) is 20-30 min; and the molding pressure in step (3) is 100-200 MPa.

8. The method for preparing magnesium-zirconium-carbon refractory bricks as described in claim 6, characterized in that, The total amount of phenolic resin solution and phenolic resin powder added in steps (1) and (2) is 3-5 wt%.

9. The method for preparing magnesium-zirconium-carbon refractory bricks as described in claim 6, characterized in that, The step (4) of performing the drying and curing process in stages specifically involves heat-treating the blank at 60℃, 120℃, and 200℃ for 6-12 hours respectively.

10. The magnesium-zirconium-carbon refractory brick as described in any one of claims 1-5 is used as a refractory material for the slag skimmer section of the blast furnace tapping trough.