Magnesia-carbon refractory brick for blast furnace slag notch and preparation method thereof

Abstract

The application belongs to the technical field of refractory material preparation, and particularly relates to a magnesium-carbon refractory brick for blast furnace slag channel and a preparation method thereof. According to the mass percentage, the raw material of the magnesium-carbon refractory brick comprises 68-80% sintered magnesia aggregate and 20-32% matrix, and the matrix comprises magnesia fine powder, silicon carbide fine powder, carbon powder and antioxidant. The magnesia fine powder, the silicon carbide fine powder, the carbon powder and the antioxidant are mixed and stirred to obtain premixed fine powder, the sintered magnesia aggregate and half of the binder are mixed and kneaded for 5-15 min, the premixed fine powder and the remaining binder are added, and the mixing and kneading is continued for 25-35 min to obtain a uniform mixture; the mixture is pressed into a green brick, and is dried in two stages to obtain the magnesium-carbon refractory brick for blast furnace slag channel. The magnesium-carbon refractory brick has high density, excellent slag corrosion resistance and oxidation resistance, can stably serve in the harsh working conditions of long-term high-temperature slag corrosion and oxidation, and can effectively replace the traditional Al2O3-SiC-C castable lining.

Description

Technical Field

[0001] This invention belongs to the field of refractory material preparation technology, specifically relating to a magnesia-carbon refractory brick for blast furnace slag trenches and its preparation method. Background Technology

[0002] The blast furnace tapping trough is an important component of the blast furnace ironmaking system, mainly including key parts such as the main tapping trough, branch troughs, and slag trough. Among them, the slag trough is responsible for guiding and discharging slag, and is the area that directly contacts the high-temperature slag and is subject to chemical erosion. During its service life, the slag trough is in a high-temperature environment of 1500-1600℃ for a long time, and must withstand the erosion of multi-element slag (such as CaO-SiO2-Al2O3-MgO-FeO), as well as the oxidation effect of air and oxidizing slag.

[0003] Currently, Al2O3-SiC-C castable is widely used for the working layer lining of blast furnace slag trenches. It offers advantages such as convenient construction and good integrity, and can resist slag erosion and oxidation to a certain extent. However, under long-term high-temperature and slag scouring conditions, its shortcomings gradually become apparent. First, the carbon phase in Al2O3-SiC-C castable is easily oxidized at high temperatures, leading to a loose matrix structure and decreased material density. Second, the high porosity of the castable accelerates erosion in the highly active slag environment, further accelerating material deterioration and limiting its service life. Furthermore, the construction process of the castable requires on-site mixing, pouring, baking, and curing, resulting in a long construction cycle. Once localized damage occurs, repairs are complex, which is detrimental to the continuous and stable production of the blast furnace.

[0004] With the increasing demands for larger-scale and longer-life blast furnaces, higher requirements are being placed on the refractory materials used in the tapping and slag trough sections. Therefore, developing a refractory material suitable for blast furnace slag trough conditions, capable of replacing traditional Al2O3-SiC-C castables, and possessing excellent slag erosion resistance and oxidation resistance, is of significant engineering importance for extending the service life of the slag trough, shortening maintenance cycles, reducing maintenance costs, and ensuring the safe, stable, and efficient operation of the blast furnace. Summary of the Invention

[0005] The purpose of this invention is to provide a magnesia-carbon refractory brick for blast furnace slag trenches and its preparation method. The prepared magnesia-carbon refractory brick has high density, low apparent porosity, excellent slag erosion resistance and oxidation resistance, and can be stably used under the harsh conditions of long-term high temperature slag erosion and oxidation. It can effectively replace the traditional Al2O3-SiC-C castable lining.

[0006] The present invention is specifically achieved through the following technical solution: According to the present invention, a magnesia-carbon refractory brick for blast furnace slag ditch is provided. The raw materials include 68-80% sintered magnesia aggregate and 20-32% matrix by mass percentage. The sintered magnesia aggregate includes magnesia particles of different sizes. The matrix includes magnesia fine powder, silicon carbide fine powder, carbon powder, and antioxidant.

[0007] The aforementioned magnesia-carbon refractory bricks for blast furnace slag troughs contain sintered magnesia aggregates that are a mixture of magnesia particles with a particle size of 5-3 mm, 3-1 mm, and 0.2-1 mm. Specifically, the 5-3 mm magnesia particles constitute 35-40% of the total mass of the sintered magnesia aggregate, the 3-1 mm magnesia particles constitute 30-35%, and the 0.2-1 mm magnesia particles constitute 30-35%.

[0008] In the aforementioned magnesia-carbon refractory bricks for blast furnace slag troughs, the mass percentages of the fine magnesia powder, fine silicon carbide powder, carbon powder, and antioxidant to the total mass of the raw materials are 10-20%, 2-8%, 0.5-6%, and 3-8%, respectively.

[0009] In the aforementioned magnesia-carbon refractory bricks for blast furnace slag troughs, the sintered magnesia aggregate and magnesia fine powder are selected from one or a mixture of two types of fused magnesia and sintered magnesia.

[0010] The aforementioned magnesia-carbon refractory bricks for blast furnace slag troughs have a particle size of ≤74 μm for fine magnesia powder and ≤100 μm for fine silicon carbide powder.

[0011] The aforementioned magnesia-carbon refractory bricks for blast furnace slag troughs contain carbon powder selected from one or a mixture of graphite and carbon black, wherein the graphite particle size is ≤200 μm and the graphite mass accounts for 2-6% of the total mass of the raw materials; the carbon black particle size is ≤0.5 μm and the carbon black mass accounts for 0.5-2% of the total mass of the raw materials.

[0012] The aforementioned magnesia-carbon refractory bricks for blast furnace slag troughs contain antioxidants selected from one or more of aluminum powder, silicon powder, B4C powder, Ti3SiC2 powder, and Ti3AlC2 powder, wherein the particle size of aluminum powder is ≤74 μm, the particle size of silicon powder is ≤74 μm, the particle size of B4C powder is ≤74 μm, the particle size of Ti3SiC2 powder is ≤100 μm, and the particle size of Ti3AlC2 powder is ≤100 μm.

[0013] The aforementioned magnesia-carbon refractory bricks for blast furnace slag trenches are prepared according to the following method: (1) Take raw materials according to the mass percentage. The raw materials include 68-80% sintered magnesia aggregate and 20-32% matrix. The sintered magnesia aggregate includes magnesia particles of different sizes. The matrix includes magnesia fine powder, silicon carbide fine powder, carbon powder, and antioxidant. Take a certain mass of binder. The binder is selected as phenolic resin or asphalt. The mass of the binder added accounts for 2-5% of the total mass of the raw materials. First, add magnesia fine powder, silicon carbide fine powder, carbon powder, and antioxidant into a mixer and mix and stir for 10-20 minutes to obtain premixed fine powder. (2) Add sintered magnesia aggregate and half of the binder to the mixer and mix for 5-15 minutes. Then add the premixed fine powder and the remaining binder and mix for 25-35 minutes to obtain a uniform mixture. (3) Press the obtained uniform mixture into brick blanks by hydraulic molding or cold isostatic pressing. The molding pressure is 150-220 MPa. After molding, the brick blanks are first dried at 100-120℃ for 6-12 hours, and then dried at 180-220℃ for 12-24 hours to obtain magnesia-carbon refractory bricks.

[0014] Further, according to mass percentage, the raw materials in step (1) include 68-80% sintered magnesia aggregate, 10-20% magnesia fine powder, 2-8% silicon carbide fine powder, 0.5-6% carbon powder, and 3-8% antioxidant. The sintered magnesia aggregate and magnesia fine powder are selected from one or a mixture of fused magnesia and sintered magnesia. The sintered magnesia aggregate is a mixture of magnesia particles with a particle size of 5-3 mm, 3-1 mm, and 0.2-1 mm. The particle size of the magnesia fine powder is ≤74 μm. The particle size of the silicon carbide fine powder is ≤100 μm. The carbon powder is selected from one or a mixture of graphite and carbon black. The graphite particle size is ≤200 μm, and the graphite mass accounts for 2-6% of the total raw material mass. The carbon black particle size is ≤0.5 μm, and the carbon black mass accounts for 0.5-2% of the total raw material mass. %; the antioxidant is selected from one or more of aluminum powder, silicon powder, B4C powder, Ti3SiC2 powder and Ti3AlC2 powder, with aluminum powder particle size ≤74 μm, silicon powder particle size ≤74 μm, B4C powder particle size ≤74 μm, Ti3SiC2 powder particle size ≤100 μm, and Ti3AlC2 powder particle size ≤100 μm.

[0015] The aforementioned magnesia-carbon refractory bricks for blast furnace slag trenches have an apparent porosity of 7.5-8.5% and a bulk density of 3.1-3.2 g / cm³. 3 .

[0016] Compared with the prior art, the present invention has at least the following advantages: (1) The magnesia-carbon refractory bricks of the present invention use magnesia aggregate and magnesia fine powder, which can effectively avoid reaction with slag, especially alkaline slag, enhance the refractory bricks' resistance to slag erosion, and slow down the erosion failure of the slag trench lining. The present invention also introduces Ti3SiC2 or Ti3AlC2 powder into the raw materials. These layered antioxidants can partially replace graphite, thereby reducing the carbon content of the magnesia-carbon refractory bricks, reducing the oxidation of carbon components, and improving the oxidation resistance of the refractory bricks. At the same time, after Ti3SiC2 and Ti3AlC2 powders react with slag, they generate high-melting-point phases, forming a high-melting-point barrier layer, which can significantly reduce the penetration of molten slag and further improve the erosion resistance of the refractory bricks.

[0017] (2) The magnesia-carbon refractory bricks of the present invention, after being mixed with raw materials and pressed into shape, have high bulk density and low apparent porosity, which can effectively resist slag penetration and oxidation of carbonaceous components, thereby improving the erosion resistance and oxidation resistance of the slag trench. These magnesia-carbon refractory bricks can be directly used for construction without on-site pouring, baking, and curing, significantly shortening the construction cycle. In the event of localized damage to the slag trench, they can be quickly replaced, making maintenance convenient and greatly reducing repair time. At the same time, under the same conditions, the material consumption of magnesia-carbon refractory bricks is significantly reduced, and their service life is extended, resulting in good economic benefits and engineering promotion value. Attached Figure Description

[0018] Figure 1 These are photographs of the magnesia-carbon refractory bricks prepared in Example 1 and the Al2O3-SiC-C castable prepared in the comparative example after erosion resistance tests.

[0019] Figure 2 These are on-site photos of the magnesia-carbon refractory bricks prepared in Example 1 being used in a blast furnace slag ditch. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] Unless otherwise specified, all conditions in the following embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Raw materials and reagents whose manufacturers are not specified are all commercially available products. Unless otherwise specified, the scientific and technical terms and experimental methods in this invention are based on the conventional understanding and existing standard methods of those skilled in the art. It should be understood that the parameters such as temperature and holding time involved in this invention are approximate values ​​and are used for illustrative purposes; those skilled in the art can make reasonable adjustments according to actual needs.

[0022] All percentages in the following examples are by mass. The particle size of the magnesia powder used is ≤74 μm, the silicon carbide powder is ≤100 μm, the graphite powder is ≤200 μm, the aluminum powder is ≤74 μm, the silicon powder is ≤74 μm, the B4C powder is ≤74 μm, the Ti3SiC2 powder is ≤100 μm, and the Ti3AlC2 powder is ≤100 μm.

[0023] Example 1 According to mass percentage, the raw material composition of the magnesia-carbon refractory bricks for blast furnace slag trenches in this embodiment is as follows: 75% sintered magnesia aggregate (of which, magnesia particles with a diameter of 5-3 mm account for 40% of the mass of sintered magnesia aggregate, magnesia particles with a diameter of 3-1 mm account for 30% of the mass of sintered magnesia aggregate, and magnesia particles with a diameter of 0.2-1 mm account for 30% of the mass of sintered magnesia aggregate), 13% sintered magnesia fine powder, 3% flake graphite, 3% silicon carbide fine powder, 2% aluminum powder, and 4% Ti3SiC2 powder. Phenolic resin is added as a binder, with the phenolic resin accounting for 4% of the total mass of the above raw materials.

[0024] The preparation method is as follows: (1) Add sintered magnesia fine powder, silicon carbide fine powder, flake graphite, aluminum powder and Ti3SiC2 powder to a mixer for premixing and stirring for 12 minutes to obtain premixed fine powder.

[0025] (2) Add sintered magnesia aggregate and half of the binder to the mixer and mix for 10 minutes. Then add the premixed fine powder and the remaining binder and continue mixing for 25 minutes to obtain a uniform mixture.

[0026] (3) The obtained uniform mixture is pressed into brick blanks under a hydraulic press at a pressure of 160 MPa. The brick blanks are dried at 120℃ for 6 hours and then dried at 200℃ for 12 hours to finally obtain magnesia-carbon refractory bricks.

[0027] The obtained magnesia-carbon refractory bricks were heat-treated at 1500℃ for 3 hours under carbon-embedded conditions. Their bulk density, apparent porosity, and oxidation resistance were tested according to national standards GB / T 2997-2015 and GB / T 13244-1991. Their slag resistance (erosion layer thickness) was tested according to the rotary slag resistance test evaluation method in GB / T 8931-2007, using blast furnace slag as the slag source. The test conditions were erosion at 1500℃ for 3 hours. The results are as follows: apparent porosity 8.5%, bulk density 3.15 g / cm³. 3 The oxide layer thickness is 2.7 mm, and the etched layer thickness is 1.8 mm. (The text abruptly ends here, seemingly mid-sentence.) 3Application verification of blast furnace slag troughs shows that, under the same conditions, compared with the traditional Al2O3-SiC-C castable (i.e., the comparative Al2O3-SiC-C castable), the consumption of magnesia-carbon refractory bricks prepared in this embodiment is reduced by 52% in actual application.

[0028] Example 2 The raw material composition of the magnesia-carbon refractory bricks for blast furnace slag trenches in this embodiment, by mass percentage, is as follows: 77% sintered magnesia aggregate (of which magnesia particles with a diameter of 5-3 mm account for 35% of the mass of sintered magnesia aggregate, magnesia particles with a diameter of 3-1 mm account for 35% of the mass of sintered magnesia aggregate, and magnesia particles with a diameter of 0.2-1 mm account for 30% of the mass of sintered magnesia aggregate), 11% sintered magnesia fine powder, 2.5% flake graphite, 3% silicon carbide fine powder, 1% aluminum powder, 4.5% Ti3SiC2 powder, and 1% boron carbide powder. Phenolic resin is added as a binder, with the phenolic resin accounting for 4% of the total mass of the above raw materials.

[0029] The preparation method is as follows: (1) Add sintered magnesia fine powder, flake graphite, silicon carbide fine powder, aluminum powder, Ti3SiC2 powder and boron carbide powder to a mixer for premixing and stirring for 10 minutes to obtain premixed fine powder.

[0030] (2) Add the sintered magnesia aggregate and half of the binder into the mixer and mix for 15 minutes. Then add the premixed fine powder and the remaining binder and continue mixing for 30 minutes to obtain a uniform mixture.

[0031] (3) The obtained uniform mixture is pressed into brick blanks under a hydraulic press at a pressure of 180 MPa. The brick blanks are dried at 120℃ for 12 hours and then dried at 200℃ for 12 hours to finally obtain magnesia-carbon refractory bricks.

[0032] The obtained magnesia-carbon refractory bricks were heat-treated at 1500℃ for 3 hours under carbon-embedded conditions. Their bulk density, apparent porosity, and oxidation resistance were tested according to national standards GB / T 2997-2015 and GB / T 13244-1991. Their slag resistance (erosion layer thickness) was tested according to the rotary slag resistance test evaluation method in GB / T 8931-2007, using blast furnace slag as the slag source. The test conditions were erosion at 1500℃ for 3 hours. The results are as follows: apparent porosity 8.1%, bulk density 3.17 g / cm³. 3 The oxide layer thickness is 2.4 mm, and the etched layer thickness is 1.5 mm. After 2000 m... 3Application verification of blast furnace slag troughs showed that, under the same conditions, compared with the traditional Al2O3-SiC-C castable (i.e., the comparative Al2O3-SiC-C castable), the consumption of magnesia-carbon refractory bricks prepared in this embodiment was reduced by 68% in actual application.

[0033] Example 3 The raw material composition of the magnesia-carbon refractory bricks for blast furnace slag trenches in this embodiment, by mass percentage, is as follows: 72% sintered magnesia aggregate (of which magnesia particles with a diameter of 5-3 mm account for 40% of the mass of sintered magnesia aggregate, magnesia particles with a diameter of 3-1 mm account for 30% of the mass of sintered magnesia aggregate, and magnesia particles with a diameter of 0.2-1 mm account for 30% of the mass of sintered magnesia aggregate), 18% sintered magnesia fine powder, 2% flake graphite, 3% silicon carbide fine powder, 1% silicon powder, and 4% Ti3AlC2 powder. Phenolic resin is added as a binder, with the mass of the phenolic resin accounting for 3.5% of the total mass of the above raw materials.

[0034] The preparation method is as follows: (1) Add sintered magnesia fine powder, flake graphite, silicon carbide fine powder, silicon powder, and Ti3AlC2 powder to a mixer for premixing and stirring for 15 minutes to obtain premixed fine powder.

[0035] (2) Add the sintered magnesia aggregate and half of the binder into the mixer and mix for 10 minutes. Then add the premixed fine powder and the remaining binder and continue mixing for 35 minutes to obtain a uniform mixture.

[0036] (3) The obtained uniform mixture is pressed into brick blanks by cold isostatic pressing at a pressure of 150 MPa. The brick blanks are dried at 120℃ for 12 hours and then dried at 220℃ for 12 hours to finally obtain magnesia-carbon refractory bricks.

[0037] The obtained magnesia-carbon refractory bricks were heat-treated at 1500℃ for 3 hours under carbon-embedded conditions. Their bulk density, apparent porosity, and oxidation resistance were tested according to national standards GB / T 2997-2015 and GB / T 13244-1991. Their slag resistance (erosion layer thickness) was tested according to the rotary slag resistance test evaluation method in GB / T 8931-2007, using blast furnace slag as the slag source. The test conditions were erosion at 1500℃ for 3 hours. The results are as follows: apparent porosity 7.8%, bulk density 3.19 g / cm³. 3 The oxide layer thickness is 2.2 mm, and the etched layer thickness is 1.3 mm. (After 3200 m...) 3Application verification of blast furnace slag troughs shows that, under the same conditions, compared with the traditional Al2O3-SiC-C castable (i.e., the comparative Al2O3-SiC-C castable), the consumption of magnesia-carbon refractory bricks prepared in this embodiment is reduced by 75% in actual application.

[0038] Comparative Example This comparative example uses Al2O3-SiC-C castable, which is widely used in blast furnace slag troughs, as the comparative material. By mass percentage, the main raw materials of this Al2O3-SiC-C castable include 55% brown fused alumina aggregate (of which 40% are 8-5mm diameter, 35% are 5-3mm diameter, 15% are 3-1mm diameter, and 10% are 0.2-1mm diameter), 8% fine brown fused alumina powder (particle size ≤ 74 μm), 15% SiC aggregate (of which 50% each are 3-1mm and 0.2-1mm diameter), 5% fine SiC powder (particle size ≤ 100 μm), and 5% alumina micro powder (particle size ≤ 100 μm). The mixture comprises 3% silica powder (≤1μm), 2% graphite (≤200μm), 1% spherical asphalt (0.2-1 mm), 2.5% silica powder (≤74μm), 0.5% aluminum powder (≤100μm), and 3% binder (aluminate cement). Water is added and stirred, with the water content accounting for 5% of the total mass of the raw materials. After mixing, the mixture is vibrated and cast into molds, naturally cured for 24 hours, and then dried at 110℃ for 24 hours.

[0039] The Al2O3-SiC-C castable obtained in this comparative example was heat-treated at 1500℃ for 3 hours under carbon-embedded conditions. Its bulk density, apparent porosity, and oxidation resistance were tested according to national standards GB / T 2997-2015 and GB / T 13244-1991. Its slag resistance (erosion layer thickness) was tested according to the rotary slag resistance test evaluation method in GB / T8931-2007, using blast furnace slag as the slag source. The test conditions were erosion at 1500℃ for 3 hours. The results are as follows: apparent porosity is 15.7%, and bulk density is 2.59 g / cm³. 3 The oxide layer thickness is 5.1 mm, and the etched layer thickness is 5.7 mm.

[0040] The performance test results of the magnesia-carbon refractory bricks prepared in Examples 1-3 and the Al2O3-SiC-C castables in the comparative example are shown in Table 1: Table 1. Performance test results of magnesia-carbon refractory bricks in Examples 1-3 and Al2O3-SiC-C castables in comparative examples As shown in Table 1, compared with Al2O3-SiC-C castables, the magnesia-carbon refractory bricks for blast furnace slag trenches prepared by this invention have the advantages of dense structure and low apparent porosity, which can effectively inhibit slag penetration and erosion, and reduce carbon phase oxidation. Furthermore, the magnesia-carbon refractory bricks for blast furnace slag trenches prepared by this invention have smaller erosion layer and oxide layer thicknesses under the same slag and temperature conditions, making them less prone to erosion and spalling during high-temperature service.

[0041] To better compare the erosion resistance of the magnesia-carbon refractory bricks prepared in Examples 1-3 with the Al2O3-SiC-C castable in the comparative example, an Al2O3-SiC-C castable was prepared according to the comparative example method. During preparation, the magnesia-carbon refractory bricks prepared in Example 1 were embedded into the Al2O3-SiC-C castable. An erosion resistance test was conducted at 1500℃, with a furnace rotation speed of 5 r / min and an erosion time of 2 h. The test results are as follows: Figure 1 As shown, under the same experimental conditions, the comparative Al2O3-SiC-C castable ( Figure 1 The material marked as "castable refractory" has a loose structure and is significantly corroded by slag. In contrast, the magnesia-carbon refractory brick prepared in Example 1 (… Figure 1 The structure of the refractory brick (marked as "refractory brick") is dense and almost unaffected by slag erosion, exhibiting good resistance to slag erosion.

[0042] Figure 2 The photos show the magnesia-carbon refractory bricks prepared in Example 1 of the present invention being used in a blast furnace slag ditch. It can be seen that the magnesia-carbon refractory bricks can still maintain a good shape under the erosion of high-temperature slag liquid, and the performance is excellent.

[0043] 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 magnesia-carbon refractory brick for blast furnace slag trenches, characterized in that, The raw materials, by mass percentage, consist of 68-80% sintered magnesia aggregate and 20-32% matrix. The sintered magnesia aggregate comprises magnesia particles of different sizes, and the matrix comprises magnesia fine powder, silicon carbide fine powder, carbon powder, and antioxidant.

2. The magnesia-carbon refractory brick for blast furnace slag trenches as described in claim 1, characterized in that, The sintered magnesia aggregate is a mixture of magnesia particles with a size of 5-3 mm, 3-1 mm, and 0.2-1 mm. The 5-3 mm magnesia particles account for 35-40% of the total mass of the sintered magnesia aggregate, the 3-1 mm magnesia particles account for 30-35% of the total mass of the sintered magnesia aggregate, and the 0.2-1 mm magnesia particles account for 30-35% of the total mass of the sintered magnesia aggregate.

3. The magnesia-carbon refractory brick for blast furnace slag trenches as described in claim 1, characterized in that, The percentages of the total mass of magnesia fine powder, silicon carbide fine powder, carbon powder, and antioxidant are 10-20%, 2-8%, 0.5-6%, and 3-8%, respectively.

4. The magnesia-carbon refractory brick for blast furnace slag trenches as described in claim 1 or 3, characterized in that, Sintered magnesia aggregate and magnesia fine powder are selected from one or a mixture of two types of fused magnesia and sintered magnesia.

5. The magnesia-carbon refractory brick for blast furnace slag trenches as described in claim 1 or 3, characterized in that, The particle size of magnesia fine powder is ≤74μm, and the particle size of silicon carbide fine powder is ≤100μm.

6. The magnesia-carbon refractory brick for blast furnace slag trenches as described in claim 1 or 3, characterized in that, The toner is selected from one or a mixture of graphite and carbon black, wherein the graphite particle size is ≤200 μm and the graphite mass accounts for 2-6% of the total mass of the raw materials; the carbon black particle size is ≤0.5 μm and the carbon black mass accounts for 0.5-2% of the total mass of the raw materials.

7. The magnesia-carbon refractory brick for blast furnace slag trenches as described in claim 1 or 3, characterized in that, The antioxidant is selected from one or more of aluminum powder, silicon powder, B4C powder, Ti3SiC2 powder, and Ti3AlC2 powder, wherein the particle size of aluminum powder is ≤74 μm, the particle size of silicon powder is ≤74 μm, the particle size of B4C powder is ≤74 μm, the particle size of Ti3SiC2 powder is ≤100 μm, and the particle size of Ti3AlC2 powder is ≤100 μm.

8. The magnesia-carbon refractory brick for blast furnace slag trenches as described in claim 1, characterized in that, Prepared according to the following method: (1) Take raw materials according to the mass percentage. The raw materials include 68-80% sintered magnesia aggregate and 20-32% matrix. The sintered magnesia aggregate includes magnesia particles of different sizes. The matrix includes magnesia fine powder, silicon carbide fine powder, carbon powder, and antioxidant. Take a certain mass of binder. The binder is selected as phenolic resin or asphalt. The mass of the binder added accounts for 2-5% of the total mass of the raw materials. First, add magnesia fine powder, silicon carbide fine powder, carbon powder, and antioxidant into a mixer and mix and stir for 10-20 minutes to obtain premixed fine powder. (2) Add sintered magnesia aggregate and half of the binder to the mixer and mix for 5-15 minutes. Then add the premixed fine powder and the remaining binder and mix for 25-35 minutes to obtain a uniform mixture. (3) Press the obtained uniform mixture into brick blanks by hydraulic molding or cold isostatic pressing. The molding pressure is 150-220 MPa. After molding, the brick blanks are first dried at 100-120℃ for 6-12 hours, and then dried at 180-220℃ for 12-24 hours to obtain magnesia-carbon refractory bricks.

9. The magnesia-carbon refractory brick for blast furnace slag trenches as described in claim 8, characterized in that, According to the mass percentage, the raw materials in step (1) include 68-80% sintered magnesia aggregate, 10-20% magnesia fine powder, 2-8% silicon carbide fine powder, 0.5-6% carbon powder, and 3-8% antioxidant. The sintered magnesia aggregate and magnesia fine powder are selected from one or a mixture of fused magnesia and sintered magnesia. The sintered magnesia aggregate is a mixture of magnesia particles with a particle size of 5-3 mm, 3-1 mm, and 0.2-1 mm. The particle size of the magnesia fine powder is ≤74 μm. The particle size of the silicon carbide fine powder is ≤100 μm. The carbon powder is selected from one or a mixture of graphite and carbon black. The graphite particle size is ≤200 μm, and the graphite mass accounts for 2-6% of the total raw material mass. The carbon black particle size is ≤0.5 μm, and the carbon black mass accounts for 0.5-2% of the total raw material mass. %; the antioxidant is selected from one or more of aluminum powder, silicon powder, B4C powder, Ti3SiC2 powder and Ti3AlC2 powder, with aluminum powder particle size ≤74 μm, silicon powder particle size ≤74 μm, B4C powder particle size ≤74 μm, Ti3SiC2 powder particle size ≤100 μm, and Ti3AlC2 powder particle size ≤100 μm.

10. The magnesia-carbon refractory brick for blast furnace slag trenches as described in claim 1, 8, or 9, characterized in that, Its apparent porosity is 7.5-8.5%, and its bulk density is 3.1-3.2 g / cm³. 3 .

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