Refractory brick and method of making same

Abstract

A refractory brick and its preparation method are disclosed, belonging to the field of refractory material preparation. The refractory brick, by weight, comprises the following components: 65-85 parts high-purity magnesium oxide, 8-16 parts modified flake graphite, 0.5-1.5 parts zirconium oxide, 3-4 parts composite binder, 1-3 parts antioxidant, and 3-6 parts liquid phenolic resin. The modified flake graphite is prepared from liquid polyborosilazane, an initiator, and flake graphite. The composite binder is composed of alumina nano-sol, calcium lignosulfonate, hydrated magnesium silicate fiber, and octyl borate. The refractory brick prepared by this invention exhibits good room-temperature compressive strength, high-temperature flexural strength, and slag corrosion resistance, meeting the needs of some existing markets.

Description

Technical Field

[0001] This invention belongs to the field of refractory material preparation, and in particular relates to a refractory brick and its preparation method. Background Technology

[0002] Magnesia refractory bricks (commonly known as magnesia bricks) are basic shaped refractory materials made primarily from high-purity magnesia through high-temperature firing or electrofusion recrystallization. Magnesia refractory bricks are the most important product among basic refractory bricks, possessing high refractoriness and excellent resistance to basic slag and iron slag, making them an important type of high-grade refractory brick. They are mainly used in open-hearth furnaces, oxygen converters, electric furnaces, and non-ferrous metal smelting. Pure magnesia refractory bricks have good resistance to basic slag, but their flexural strength is generally average, and their resistance to slag corrosion is relatively weak in oxidizing atmospheres. Therefore, to meet the demands for high performance and high quality, especially for corrosion resistance, it is necessary to continuously develop magnesia-carbon brick products with a better balance of various properties. Summary of the Invention

[0003] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a refractory brick and its preparation method.

[0004] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: A refractory brick, by weight, comprises the following components: 65-85 parts of high-purity magnesium oxide, 8-16 parts of modified flake graphite, 0.5-1.5 parts of zirconium oxide, 3-4 parts of composite binder, 1-3 parts of antioxidant, and 3-6 parts of liquid phenolic resin. The modified flake graphite is prepared from liquid polyborosilazane, an initiator, and flake graphite, and the composite binder is composed of alumina nanosol, calcium lignosulfonate, hydrated magnesium silicate fiber, and octyl borate.

[0005] The modified flake graphite is prepared as follows: By weight, 10 parts of flake graphite were vacuum dried at 120-125℃ for 1.5-2 hours. At 60℃, 1.5-2 parts of liquid polyborosilazane and 0.002-0.003 parts of initiator were mixed evenly and then atomized and sprayed into a mixer to mix with the flake graphite for 15-20 minutes. In an inert atmosphere, the temperature was raised to 120-150℃ and kept at that temperature for 2-3 hours to complete the crosslinking and curing. The modified graphite was obtained by passing it through a 200-mesh sieve.

[0006] The initiator is azobisisoheptanenitrile.

[0007] The preparation method of the composite binder includes the following steps: A1: Mix AlCl3·6H2O, ethyl silicate, and boric acid evenly and reflux at 80-85℃ for 2-2.5h to obtain alumina nanosol; A2: By weight, take 3.3-3.5 parts of alumina nano sol, add 2-3 parts of calcium lignosulfonate, 1.5-1.8 parts of hydrated magnesium silicate fiber and 0.2-0.3 parts of zinc borate while stirring at 40-45℃, continue shearing for 30-40 minutes, spray dry to obtain composite binder.

[0008] The molar ratio of Al:Si:B in AlCl3·6H2O, ethyl silicate, and boric acid is 1:1:0.3-0.4.

[0009] The antioxidant is one or more of carbides, borides, and nitrides.

[0010] The method for preparing the refractory brick is as follows: High-purity magnesium oxide and zirconium oxide are mixed and dry-mixed at 120-130℃ for 2-3 minutes. Liquid phenolic resin is added and stirred evenly. Modified flake graphite is added and mixed at 110-120℃ for 3-5 minutes. The mixture is then cooled to 60℃, and a composite binder and antioxidant are added and mixed evenly to obtain a mixture. The mixture is filled into a mold and pressed into shape at 200-300 MPa. Then it is dried at 160-180℃ for 8-10 hours and fired at 1300-1400℃ for 20-24 hours. After cooling, refractory bricks are obtained.

[0011] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art: 1. In the preparation of modified flake graphite, liquid polyborosilazane initiator undergoes cross-linking and curing at 120-150℃ in an inert atmosphere. The surface of polyborosilazane is covalently bonded to the hydroxyl and carboxyl groups on the surface of flake graphite. At high temperature, the liquid polyborosilazane initiator forms a dense SiBCN ceramic, which organizes the oxidation of graphite and improves the corrosion resistance and high-temperature flexural strength of the prepared refractory brick.

[0012] 2. Alumina nanosol reacts with magnesium oxide at high temperature to grow a magnesium aluminum spinel shell on the particle surface; calcium lignosulfonate leaves a nanoporous carbon skeleton after pyrolysis, providing spinel nucleation sites and absorbing thermal stress; hydrated magnesium silicate fibers are dehydrated and transformed into amorphous magnesium silicate needle-like skeletons that penetrate the interparticle gaps and play a microscale reinforcing role; zinc borate forms a boron-zinc oxide liquid phase at around 1000℃, which spreads along the graphite edge, inhibiting oxygen diffusion and enhancing its corrosion resistance.

[0013] The silicon carbide whiskers generated during the preparation of aluminum-magnesium spinel and modified flake graphite form a three-dimensional interlocked structure of shell-bridge-whisker on the surface of magnesium oxide. At the same time, the growth of aluminum-magnesium spinel and silicon carbide whiskers can fill the shrinkage gaps at the graphite-magnesium oxide interface, increasing its room temperature compressive strength. Detailed Implementation

[0014] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Example 1

[0015] This embodiment prepares a refractory brick.

[0016] A refractory brick, by weight, comprises the following components: 70 parts high-purity magnesium oxide, 12 parts modified flake graphite, 1 part zirconium oxide, 3.5 parts composite binder, 2 parts antioxidant, and 4.5 parts liquid phenolic resin.

[0017] The modified flake graphite is prepared as follows: By weight, 10 parts of flake graphite were vacuum dried at 125℃ for 1.7h. 1.7 parts of liquid polyborosilazane and 0.003 parts of initiator were mixed evenly at 60℃ and then atomized and sprayed into a mixer to mix with the flake graphite for 17min. In an inert atmosphere, the temperature was raised to 135℃ and kept at that temperature for 2-3h to complete the crosslinking and curing. Modified graphite was obtained by passing through a 200-mesh sieve.

[0018] The initiator is azobisisoheptanenitrile.

[0019] The preparation method of the composite binder includes the following steps: A1: AlCl3·6H2O, ethyl silicate, and boric acid were mixed evenly and refluxed at 85°C for 2.5 h to obtain alumina nanosol; A2: By weight, take 3.4 parts of alumina nano sol, add 2.5 parts of calcium lignosulfonate, 1.65 parts of hydrated magnesium silicate fiber and 0.25 parts of zinc borate in sequence while stirring at 45°C, continue shearing for 35 minutes, spray dry to obtain composite binder.

[0020] The molar ratio of Al:Si:B in AlCl3·6H2O, ethyl silicate, and boric acid is 1:1:0.35.

[0021] The antioxidant is one or more of carbides, borides, and nitrides.

[0022] The method for preparing the refractory brick is as follows: High-purity magnesium oxide and zirconium oxide were mixed and dry-mixed at 125°C for 2.5 min. Liquid phenolic resin was added and stirred evenly. Modified flake graphite was added and mixed at 115°C for 4 min. The mixture was then cooled to 60°C, and a composite binder and antioxidant were added and mixed evenly to obtain a mixture. The mixture was filled into a mold and pressed at 250 MPa. The mold was then dried at 170°C for 9 h and fired at 1350°C for 22 h. After cooling, refractory bricks were obtained. Example 2

[0023] This embodiment prepares a refractory brick.

[0024] A refractory brick, by weight, comprises the following components: 65 parts high-purity magnesium oxide, 8 parts modified flake graphite, 0.5 parts zirconium oxide, 3 parts composite binder, 1 part antioxidant, and 3 parts liquid phenolic resin.

[0025] The modified flake graphite is prepared as follows: By weight, 10 parts of flake graphite were vacuum dried at 120℃ for 1.5h. At 60℃, 1.5 parts of liquid polyborosilazane and 0.002 parts of initiator were mixed evenly and then atomized and sprayed into a mixer to mix with the flake graphite for 15min. In an inert atmosphere, the temperature was raised to 120℃ and kept at that temperature for 2h to complete the crosslinking and curing. The modified graphite was obtained by passing it through a 200-mesh sieve.

[0026] The initiator is azobisisoheptanenitrile.

[0027] The preparation method of the composite binder includes the following steps: A1: AlCl3·6H2O, ethyl silicate and boric acid were mixed evenly and refluxed at 80°C for 2 hours to obtain alumina nanosol; A2: By weight, take 3.3 parts of alumina nano sol, add 2 parts of calcium lignosulfonate, 1.5 parts of hydrated magnesium silicate fiber and 0.2 parts of zinc borate in sequence while stirring at 40℃, continue shearing for 30 minutes, spray dry to obtain composite binder.

[0028] The molar ratio of Al:Si:B in AlCl3·6H2O, ethyl silicate, and boric acid is 1:1:0.3.

[0029] The antioxidant is one or more of carbides, borides, and nitrides.

[0030] The method for preparing the refractory brick is as follows: High-purity magnesium oxide and zirconium oxide are mixed and dry-mixed at 120°C for 2 minutes. Liquid phenolic resin is added and stirred evenly. Modified flake graphite is added and mixed at 110°C for 3 minutes. The mixture is then cooled to 60°C, and a composite binder and antioxidant are added and mixed evenly to obtain a mixture. The mixture is filled into a mold and pressed at 200 MPa. It is then dried at 160°C for 8 hours and fired at 1300°C for 20 hours. After cooling, refractory bricks are obtained. Example 3

[0031] This embodiment prepares a refractory brick.

[0032] A refractory brick, by weight, comprises the following components: 85 parts high-purity magnesium oxide, 16 parts modified flake graphite, 1.5 parts zirconium oxide, 4 parts composite binder, 3 parts antioxidant, and 6 parts liquid phenolic resin.

[0033] The modified flake graphite is prepared as follows: By weight, 10 parts of flake graphite were vacuum dried at 125℃ for 2 hours. At 60℃, 2 parts of liquid polyborosilazane and 0.003 parts of initiator were mixed evenly and then atomized and sprayed into a mixer to mix with the flake graphite for 20 minutes. In an inert atmosphere, the temperature was raised to 150℃ and kept at that temperature for 3 hours to complete the crosslinking and curing. The modified graphite was obtained by passing it through a 200-mesh sieve.

[0034] The initiator is azobisisoheptanenitrile.

[0035] The preparation method of the composite binder includes the following steps: A1: AlCl3·6H2O, ethyl silicate, and boric acid were mixed evenly and refluxed at 85°C for 2.5 h to obtain alumina nanosol; A2: By weight, take 3.5 parts of alumina nano sol, add 3 parts of calcium lignosulfonate, 1.8 parts of hydrated magnesium silicate fiber and 0.3 parts of zinc borate in sequence while stirring at 45°C, continue shearing for 40 minutes, spray dry to obtain composite binder.

[0036] The molar ratio of Al:Si:B in AlCl3·6H2O, ethyl silicate, and boric acid is 1:1:0.4.

[0037] The antioxidant is one or more of carbides, borides, and nitrides.

[0038] The method for preparing the refractory brick is as follows: High-purity magnesium oxide and zirconium oxide are mixed and dry-mixed at 130°C for 3 minutes. Liquid phenolic resin is added and stirred evenly. Modified flake graphite is added and mixed at 120°C for 5 minutes. The mixture is then cooled to 60°C, and a composite binder and antioxidant are added and mixed evenly to obtain a mixture. The mixture is filled into a mold and pressed at 300 MPa. It is then dried at 180°C for 10 hours and fired at 1400°C for 24 hours. After cooling, refractory bricks are obtained. Example 4

[0039] This embodiment prepares a refractory brick.

[0040] A refractory brick, by weight, comprises the following components: 68 parts high-purity magnesium oxide, 9 parts modified flake graphite, 0.8 parts zirconium oxide, 3.4 parts composite binder, 1.5 parts antioxidant, and 4 parts liquid phenolic resin.

[0041] The modified flake graphite is prepared as follows: By weight, 10 parts of flake graphite were vacuum dried at 121℃ for 1.7h. At 60℃, 1.6 parts of liquid polyborosilazane and 0.002 parts of initiator were mixed evenly and then atomized and sprayed into a mixer to mix with the flake graphite for 16min. In an inert atmosphere, the temperature was raised to 125℃ and kept at that temperature for 2.3h to complete the crosslinking and curing. The modified graphite was obtained by passing it through a 200-mesh sieve.

[0042] The initiator is azobisisoheptanenitrile.

[0043] The preparation method of the composite binder includes the following steps: A1: AlCl3·6H2O, ethyl silicate, and boric acid were mixed evenly and refluxed at 82℃ for 2.2h to obtain alumina nanosol; A2: By weight, take 3.35 parts of alumina nano sol, add 2.3 parts of calcium lignosulfonate, 1.55 parts of hydrated magnesium silicate fiber and 0.23 parts of zinc borate in sequence while stirring at 41℃, continue shearing for 33 minutes, spray dry to obtain composite binder.

[0044] The molar ratio of Al:Si:B in AlCl3·6H2O, ethyl silicate, and boric acid is 1:1:0.32.

[0045] The antioxidant is one or more of carbides, borides, and nitrides.

[0046] The method for preparing the refractory brick is as follows: High-purity magnesium oxide and zirconium oxide were mixed and dry-mixed at 123°C for 2.3 min. Liquid phenolic resin was added and stirred evenly. Modified flake graphite was added and mixed at 113°C for 3.5 min. The mixture was then cooled to 60°C, and a composite binder and antioxidant were added and mixed evenly to obtain a mixture. The mixture was filled into a mold and pressed at 220 MPa. The mold was then dried at 165°C for 8.5 h and fired at 1320°C for 21 h. After cooling, refractory bricks were obtained. Example 5

[0047] This embodiment prepares a refractory brick.

[0048] A refractory brick, by weight, comprises the following components: 80 parts high-purity magnesium oxide, 14 parts modified flake graphite, 1.3 parts zirconium oxide, 3.8 parts composite binder, 2.5 parts antioxidant, and 5.5 parts liquid phenolic resin.

[0049] The modified flake graphite is prepared as follows: By weight, 10 parts of flake graphite were vacuum dried at 124℃ for 1.8h. 1.8 parts of liquid polyborosilazane and 0.002 parts of initiator were mixed evenly at 60℃ and then atomized and sprayed into a mixer to mix with the flake graphite for 18min. In an inert atmosphere, the temperature was raised to 145℃ and kept at that temperature for 2.8h to complete the crosslinking and curing. Modified graphite was obtained by passing through a 200-mesh sieve.

[0050] The initiator is azobisisoheptanenitrile.

[0051] The preparation method of the composite binder includes the following steps: A1: AlCl3·6H2O, ethyl silicate, and boric acid were mixed evenly and refluxed at 84℃ for 2.4h to obtain alumina nanosol; A2: By weight, take 3.45 parts of alumina nano sol, add 2.8 parts of calcium lignosulfonate, 1.75 parts of hydrated magnesium silicate fiber and 0.28 parts of zinc borate in sequence while stirring at 44℃, continue shearing for 39 min, spray dry to obtain composite binder.

[0052] The molar ratio of Al:Si:B in AlCl3·6H2O, ethyl silicate, and boric acid is 1:1:0.38.

[0053] The antioxidant is one or more of carbides, borides, and nitrides.

[0054] The method for preparing the refractory brick is as follows: High-purity magnesium oxide and zirconium oxide are mixed and dry-mixed at 128℃ for 2-3 minutes. Liquid phenolic resin is added and stirred evenly. Modified flake graphite is added and mixed at 118℃ for 4.5 minutes. The mixture is then cooled to 60℃, and a composite binder and antioxidant are added and mixed evenly to obtain a mixture. The mixture is filled into a mold and pressed at 285 MPa. It is then dried at 175℃ for 9.5 hours and fired at 1380℃ for 23.5 hours. After cooling, refractory bricks are obtained.

[0055] The difference between Comparative Example 1 and Example 1 is that liquid polyborosilicate was not added in the preparation of the modified flake graphite.

[0056] The difference between Comparative Example 2 and Example 1 is that alumina nanosol was not prepared in the preparation of the composite binder.

[0057] The difference between Comparative Example 1 and Example 1 is that liquid polyborosilazane was not added in the preparation of the modified flake graphite, and alumina nanosol was not prepared in the preparation of the composite binder.

[0058] The room temperature compressive strength and high temperature flexural strength were tested according to GB / T 22589-2017 and related testing standards, and the slag resistance was tested according to GB / T 8931-2007 "Test Method for Slag Resistance of Refractory Materials". The results are shown in Table 1. As can be seen from the contents of Examples 1-5 and the data in Table 1, the refractory bricks prepared by the present invention have good performance in terms of room temperature pressure resistance, high temperature flexural strength and slag erosion resistance, and can meet the current market demand.

[0059] As can be seen from Example 1 and Comparative Example 1 of the present invention, combined with the data in Table 1, the addition of liquid polyborosilazane to modified flake graphite can enhance the slag erosion resistance and high-temperature flexural strength of the prepared refractory bricks.

[0060] As can be seen from Example 1 and Comparative Examples 2 and 3 of the present invention, the preparation of alumina nano-sol in the composite binder enhances the room temperature pressure resistance and erosion resistance of refractory bricks. At the same time, the addition of liquid polyborosilazane in the preparation of modified flake graphite can synergistically enhance the comprehensive performance of the prepared refractory bricks with the alumina nano-sol in the composite binder.

[0061] The above description is only 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 inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A refractory brick, characterized in that: Based on weight, it includes the following components: 65-85 parts high-purity magnesium oxide, 8-16 parts modified flake graphite, 0.5-1.5 parts zirconium oxide, 3-4 parts composite binder, 1-3 parts antioxidant, and 3-6 parts liquid phenolic resin. The modified flake graphite is prepared from liquid polyborosilazane, an initiator, and flake graphite, and the composite binder is composed of alumina nanosol, calcium lignosulfonate, hydrated magnesium silicate fiber, and octyl borate.

2. The refractory brick according to claim 1, characterized in that: The modified flake graphite is prepared as follows: By weight, 10 parts of flake graphite were vacuum dried at 120-125℃ for 1.5-2 hours. At 60℃, 1.5-2 parts of liquid polyborosilazane and 0.002-0.003 parts of initiator were mixed evenly and then atomized and sprayed into a mixer to mix with the flake graphite for 15-20 minutes. In an inert atmosphere, the temperature was raised to 120-150℃ and kept at that temperature for 2-3 hours to complete the crosslinking and curing. The modified graphite was obtained by passing it through a 200-mesh sieve.

3. A refractory brick according to claim 2, characterized in that: The initiator is azobisisoheptanenitrile.

4. A refractory brick according to claim 1, characterized in that: The preparation method of the composite binder includes the following steps: A1: Mix AlCl3·6H2O, ethyl silicate, and boric acid evenly and reflux at 80-85℃ for 2-2.5h to obtain alumina nanosol; A2: By weight, take 3.3-3.5 parts of alumina nano sol, add 2-3 parts of calcium lignosulfonate, 1.5-1.8 parts of hydrated magnesium silicate fiber and 0.2-0.3 parts of zinc borate while stirring at 40-45℃, continue shearing for 30-40 minutes, spray dry to obtain composite binder.

5. A refractory brick according to claim 1, characterized in that: The molar ratio of Al:Si:B in AlCl3·6H2O, ethyl silicate, and boric acid is 1:1:0.3-0.

4.

6. A refractory brick according to claim 1, characterized in that: The antioxidant is one or more of carbides, borides, and nitrides.

7. A method for preparing refractory bricks as described in any one of claims 1-6, characterized in that: High-purity magnesium oxide and zirconium oxide are mixed and dry-mixed at 120-130℃ for 2-3 minutes. Liquid phenolic resin is added and stirred evenly. Modified flake graphite is added and mixed at 110-120℃ for 3-5 minutes. The mixture is then cooled to 60℃, and a composite binder and antioxidant are added and mixed evenly to obtain a mixture. The mixture is filled into a mold and pressed into shape at 200-300 MPa. Then it is dried at 160-180℃ for 8-10 hours and fired at 1300-1400℃ for 20-24 hours. After cooling, refractory bricks are obtained.

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