A method for producing magnesia carbon brick by low carbon reduction of magnesia

Abstract

This invention relates to the field of refractory materials technology, specifically to a method for producing magnesia-carbon bricks from low-carbon reduced magnesia. The method includes the following steps: Weighing 80-90 parts by weight of magnesia, 3-5 parts of functional reinforcing agent, 1-3 parts of aluminum powder, 0.3-1 parts of aluminum nitride, 2-3 parts of carbon black, 3-5 parts of flake graphite, and 3-5 parts of phenolic resin; mixing the magnesia (excluding fine magnesia) with the phenolic resin, adding the remaining raw materials, mixing at low speed, adding the fine magnesia, and then mixing at high speed to obtain a mixed slurry; injecting the mixed slurry into a prepared mold, and then pressing and heat-treating to obtain magnesia-carbon bricks; the magnesia-carbon bricks produced by this invention not only have excellent mechanical properties but also excellent thermal shock resistance and oxidation resistance; effectively ensuring the quality and performance of the produced magnesia-carbon bricks while extending their service life to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, specifically to a method for producing magnesia-carbon bricks from low-carbon reduced magnesia. Background Technology

[0002] Magnesia-carbon bricks are widely used as linings in metallurgical equipment such as converters, electric furnaces, and ladles due to their excellent high-temperature resistance and slag erosion resistance. Traditional magnesia-carbon bricks typically contain 8-20% carbon, and while the high carbon content improves their slag resistance and thermal shock stability, it also leads to problems such as excessively high thermal conductivity, easy oxidation, increased energy consumption, and carbon addition from the molten steel during use. With the development of clean steelmaking technologies, the demand for low-carbon magnesia-carbon bricks is becoming increasingly urgent.

[0003] However, reducing the carbon content leads to a significant decrease in the strength and thermal shock resistance of magnesia-carbon bricks. To address this issue, existing technologies often employ the addition of metal powders (such as Al, Si, Mg), carbides (such as SiC, B4C), and borides as antioxidants and reinforcing phases. These additives react at high temperatures to generate a ceramic bonding phase or promote magnesium vapor circulation, thereby compensating for the performance loss caused by the reduced carbon content. However, these additives often have limited functionality and improvement effects, and they are difficult to form an effective multi-level reinforcing structure and self-healing mechanism within the material. Therefore, this invention provides a method for producing magnesia-carbon bricks from low-carbon reduced magnesia sand to solve the aforementioned technical problems. Summary of the Invention

[0004] The purpose of this invention is to provide a method for producing magnesia-carbon bricks from low-carbon reduced magnesia. The magnesia-carbon bricks produced not only have excellent mechanical properties, but also excellent thermal shock resistance and oxidation resistance, effectively ensuring the quality of the produced magnesia-carbon bricks while extending their service life to a certain extent.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for producing magnesia-carbon bricks from low-carbon reduced magnesia includes the following steps:

[0007] Step 1: Weigh out 80-90 parts by weight of magnesia, 3-5 parts by weight of functional enhancer, 1-3 parts by weight of aluminum powder, 0.3-1 parts by weight of aluminum nitride, 2-3 parts by weight of carbon black, 3-5 parts by weight of flake graphite and 3-5 parts by weight of phenolic resin for later use.

[0008] Among them, the magnesium oxide content in the magnesia is ≥97%, and the particle size composition of the magnesia is as follows: 3-5mm magnesia accounts for 20-25%, 1-3mm magnesia accounts for 23-26%, 0.074-1mm magnesia accounts for 20-25%, and the remainder is fine magnesia ≤0.074mm.

[0009] Step 2: Mix magnesia (excluding fine magnesia) with phenolic resin. After mixing, add the remaining raw materials (excluding fine magnesia), mix at low speed, add fine magnesia, and then mix at high speed to obtain a mixed slurry. Pour the mixed slurry into a prepared mold, and then press and heat treat it to obtain magnesia-carbon bricks.

[0010] Furthermore, the low-speed stirring speed is 50-80 r / min, and the stirring time is 3-5 min; the high-speed stirring speed is 100-150 r / min, and the stirring time is 30-60 min.

[0011] Furthermore, the heat treatment temperature is 180-220℃, and the heat treatment time is 15-20h; and a 1000T electric spiral brick press is used for pressing and molding.

[0012] Furthermore, the preparation method of the functional enhancer is as follows:

[0013] Step 1: 30% of the total amount of boron carbide, aluminum powder, and calcium powder are fed into a ball mill and ball-milled at a rate of 250-350 r / min for 2-3 h under argon protection. Then, the compound pore-forming agent and the remaining boron carbide powder are added, and ball milling continues for 3-4 h under argon protection. The resulting mixed powder is then spray-granulated to obtain composite microspheres with a particle size of 30-50 μm. The obtained microspheres are sintered at high temperature under argon protection and then naturally cooled to room temperature to obtain porous microspheres. The mass ratio of boron carbide, aluminum powder, calcium powder, and compound pore-forming agent is 65-80:10-25:5-15:25-35.

[0014] Step 2: Adjust the pH of the 0.05-0.15 mol / L tetrabutyl titanate ethanol solution to 3.3-3.8 with dilute nitric acid, add porous microspheres at a dosage ratio of 30-60 g / L, disperse by ultrasonication, and then keep the resulting mixed phase at 180-200℃ for 6-10 h. After the reaction is complete, filter, wash and sinter the reaction product at high temperature to obtain modified porous microspheres.

[0015] The third step involves placing the modified porous microspheres in a plasma processing chamber, introducing a mixture of argon and oxygen, and plasma etching the modified porous microspheres at 45-60 Pa for 30-40 minutes; once etching is complete, the functional enhancer is obtained.

[0016] Furthermore, the compound pore-forming agent is composed of starch and polymethyl methacrylate in a mass ratio of 2-4:1.

[0017] Furthermore, the inlet temperature during spray granulation is 220-260℃, the outlet temperature is 90-110℃, and the atomization pressure is 0.4-0.6MPa.

[0018] Furthermore, the specific operation of high-temperature sintering in the first step is as follows: under argon protection, the temperature inside the sintering equipment is raised to 1100-1300℃ at a rate of 5-10℃ / min, and then held at this temperature for 2-3 hours.

[0019] Furthermore, the flow rate ratio of argon to oxygen during plasma etching is 3-5:1, and the etching power is set to 250-400W.

[0020] Furthermore, in the second step, the ultrasonic dispersion frequency is 25-35kHz, and the ultrasonic dispersion time is 20-30min.

[0021] Furthermore, in the second step, high-temperature sintering is carried out under a nitrogen atmosphere, and the high-temperature sintering temperature is 450-550℃, and the high-temperature sintering time is 2-3 hours.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention prepares porous microspheres with a pore size of 0.5-1 μm using boron carbide powder, aluminum powder, calcium powder, and a compound pore-forming agent as raw materials. Using these porous microspheres as the core framework, spiky nano-titanium dioxide with high-temperature catalytic activity is loaded onto the surface and porous structure of the microspheres via a sol-gel method, resulting in modified porous microspheres. The spiky nano-titanium dioxide promotes carbon gasification and carbothermic reduction of magnesia at high temperatures, continuously generating magnesium vapor. This magnesium vapor reacts with slag or re-oxidizes and deposits at the erosion interface of magnesia-carbon bricks, dynamically sealing pores and cracks to form a dense healing layer, thereby endowing magnesia-carbon bricks with excellent self-healing capabilities and resistance to slag penetration and erosion. Finally, the surface of the functional enhancer, after plasma etching, forms abundant micron-grooves with high roughness and activity. This not only improves its dispersibility in magnesia-carbon bricks but also strengthens the interfacial bonding with magnesia and the binder, ensuring effective stress transfer and efficient functioning of the functional components.

[0024] The functional reinforcing agent prepared in this invention can serve as a reinforcing phase for magnesia-carbon bricks. Its multi-level structure significantly improves the interfacial bonding strength of the composite material through mechanical interlocking effects. Nanoparticles provide point contact anchoring, micron-grooves achieve surface contact interlocking, and internal pores promote matrix pinning effects. Simultaneously, boron carbide reacts chemically with aluminum and calcium powders under high-temperature conditions to generate a composite glass-ceramic protective film with high-melting-point, low-volatility calcium borate as the framework and aluminum borate as the reinforcing phase. This protective film is extremely stable and dense at ultra-high temperatures, enabling it to cover the graphite surface more persistently and effectively, isolating oxygen penetration and slag erosion, thereby significantly delaying the oxidation loss of the core carbon-bonded phase. Furthermore, the spike-like nano-titanium dioxide structure helps improve the high-temperature stability and potential catalytic purification capabilities of magnesia-carbon bricks.

[0025] In summary, magnesia-carbon bricks produced using functional enhancers as raw materials not only possess excellent mechanical properties but also exhibit outstanding thermal shock resistance and oxidation resistance, effectively ensuring the quality and performance of the produced magnesia-carbon bricks while extending their service life to a certain extent. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] A method for producing magnesia-carbon bricks from low-carbon reduced magnesia includes the following steps:

[0029] Step 1: Weigh out 80 parts by weight of magnesia, 3 parts by weight of functional enhancer, 1 part by weight of aluminum powder (average particle size 350 mesh), 0.3 parts by weight of aluminum nitride (average particle size 80 nm), 2 parts by weight of carbon black (average particle size 150 nm), 3 parts by weight of flake graphite (average particle size 0.12 mm), and 3 parts by weight of phenolic resin (viscosity 10000 cp at 25℃) for later use.

[0030] Among them, the magnesium oxide content in the magnesia is ≥97%, and the particle size composition of the magnesia is as follows: 20% of the 3mm magnesia, 23% of the 1mm magnesia, 25% of the 0.074mm magnesia, and the remainder is fine magnesia ≤0.074mm.

[0031] Step 2: Mix magnesia (excluding fine magnesia) with phenolic resin. After mixing, add the remaining raw materials (excluding fine magnesia), mix at low speed, add fine magnesia, and then mix at high speed to obtain a mixed slurry. Pour the mixed slurry into a prepared mold, and then press and heat treat it to obtain magnesia-carbon bricks.

[0032] The low-speed stirring speed is 50 r / min and the stirring time is 5 min; the high-speed stirring speed is 100 r / min and the stirring time is 60 min.

[0033] The heat treatment temperature is 180℃ and the heat treatment time is 20h; and a 1000T electric spiral brick press is used for pressing and molding.

[0034] The preparation method of the functional enhancer is as follows:

[0035] Step 1: 30% of the total amount of boron carbide, aluminum powder, and calcium powder are fed into a ball mill and ball-milled at 250 r / min for 3 h under argon protection. Then, the composite pore-forming agent and the remaining boron carbide powder are added, and ball milling continues for another 3 h under argon protection. The resulting mixed powder is then spray-granulated to obtain composite microspheres with a particle size of 30 μm. The obtained microspheres are sintered at high temperature under argon protection and then naturally cooled to room temperature to obtain porous microspheres. The mass ratio of boron carbide, aluminum powder, calcium powder, and composite pore-forming agent is 65:10:5:25.

[0036] The compound pore-forming agent is composed of starch and polymethyl methacrylate in a mass ratio of 2:1.

[0037] The inlet temperature for spray granulation is 220℃, the outlet temperature is 90℃, and the atomization pressure is 0.4MPa.

[0038] The specific operation of high-temperature sintering in the first step is as follows: Under argon protection, the temperature inside the sintering equipment is raised to 1100℃ at a rate of 5℃ / min, and then held at this temperature for 3 hours.

[0039] Step 2: Adjust the pH of the 0.05 mol / L tetrabutyl titanate ethanol solution to 3.3 with dilute nitric acid, add porous microspheres at a ratio of 30 g / L, disperse by ultrasonication, and then keep the resulting mixed phase at 180℃ for 10 h. After the reaction is complete, filter, wash and sinter the reaction product at high temperature to obtain modified porous microspheres.

[0040] The ultrasonic dispersion frequency was 25 kHz, and the ultrasonic dispersion time was 30 min; the high-temperature sintering was carried out in a nitrogen atmosphere, and the high-temperature sintering temperature was 450℃, and the high-temperature sintering time was 3 h.

[0041] The third step involves placing the modified porous microspheres in a plasma processing chamber, introducing a mixture of argon and oxygen, and plasma etching the modified porous microspheres at 45 Pa for 40 minutes; once etching is complete, the functional enhancer is obtained.

[0042] Example 2

[0043] The production method of magnesia-carbon bricks provided in this embodiment is basically the same as that in Example 1, except that the specific composition of the produced magnesia-carbon bricks and the preparation method of the functional enhancer are not exactly the same. The specific composition of the magnesia-carbon bricks and the preparation method of the functional enhancer in this embodiment are as follows:

[0044] The magnesia-carbon brick is made from the following raw materials in parts by weight: 85 parts magnesia, 4 parts functional enhancer, 2 parts aluminum powder, 0.5 parts aluminum nitride, 2.5 parts carbon black, 4 parts flake graphite and 4 parts phenolic resin.

[0045] The preparation method of the functional enhancer is as follows:

[0046] Step 1: 30% of the total amount of boron carbide, aluminum powder, and calcium powder are fed into a ball mill and ball-milled at 300 r / min for 3 h under argon protection. Then, the compound pore-forming agent and the remaining boron carbide powder are added, and ball milling continues for 4 h under argon protection. The resulting mixed powder is then spray-granulated to obtain composite microspheres with a particle size of 40 μm. The obtained microspheres are sintered at high temperature under argon protection and then naturally cooled to room temperature to obtain porous microspheres. The mass ratio of boron carbide, aluminum powder, calcium powder, and compound pore-forming agent is 70:20:10:30.

[0047] The compound pore-forming agent is composed of starch and polymethyl methacrylate in a mass ratio of 3:1.

[0048] The inlet temperature for spray granulation is 240℃, the outlet temperature is 100℃, and the atomization pressure is 0.5MPa.

[0049] The specific operation of high-temperature sintering in the first step is as follows: Under argon protection, the temperature inside the sintering equipment is raised to 1200℃ at a rate of 10℃ / min, and then held at this temperature for 3 hours.

[0050] The second step involves adjusting the pH of the 0.1 mol / L tetrabutyl titanate ethanol solution to 3.5 with dilute nitric acid, adding porous microspheres at a ratio of 40 g / L, dispersing by ultrasonication, and then incubating the resulting mixed phase at 190°C for 8 hours. After the reaction is complete, the reaction product is filtered, washed, and sintered at high temperature to obtain modified porous microspheres.

[0051] The ultrasonic dispersion frequency was 30kHz and the ultrasonic dispersion time was 25min; the high-temperature sintering was carried out in a nitrogen atmosphere, and the high-temperature sintering temperature was 500℃ and the high-temperature sintering time was 3h.

[0052] The third step involves placing the modified porous microspheres in a plasma processing chamber, introducing a mixture of argon and oxygen, and plasma etching the modified porous microspheres at 50 Pa for 35 minutes; once etching is complete, the functional enhancer is obtained.

[0053] Example 3

[0054] The production method of magnesia-carbon bricks provided in this embodiment is basically the same as that in Example 1, except that the specific composition of the produced magnesia-carbon bricks and the preparation method of the functional enhancer are not exactly the same. The specific composition of the magnesia-carbon bricks and the preparation method of the functional enhancer in this embodiment are as follows:

[0055] The magnesia-carbon brick is made from the following raw materials in parts by weight: 90 parts magnesia, 5 parts functional enhancer, 3 parts aluminum powder, 1 part aluminum nitride, 3 parts carbon black, 5 parts flake graphite and 5 parts phenolic resin.

[0056] The preparation method of the functional enhancer is as follows:

[0057] Step 1: 30% of the total amount of boron carbide, aluminum powder, and calcium powder are fed into a ball mill and ball-milled at 350 r / min for 2 hours under argon protection. Then, the composite pore-forming agent and the remaining boron carbide powder are added, and ball milling continues for 4 hours under argon protection. The resulting mixed powder is then spray-granulated to obtain composite microspheres with a particle size of 50 μm. The obtained microspheres are sintered at high temperature under argon protection and then naturally cooled to room temperature to obtain porous microspheres. The mass ratio of boron carbide, aluminum powder, calcium powder, and composite pore-forming agent is 80:25:15:35.

[0058] The compound pore-forming agent is composed of starch and polymethyl methacrylate in a mass ratio of 4:1.

[0059] The inlet temperature for spray granulation is 260℃, the outlet temperature is 90℃, and the atomization pressure is 0.6MPa.

[0060] The specific operation of high-temperature sintering in the first step is as follows: Under argon protection, the temperature inside the sintering equipment is raised to 1300℃ at a rate of 10℃ / min, and then held at this temperature for 2 hours.

[0061] The second step involves adjusting the pH of the 0.15 mol / L tetrabutyl titanate ethanol solution to 3.8 with dilute nitric acid, adding porous microspheres at a ratio of 60 g / L, dispersing by ultrasonication, and then incubating the resulting mixed phase at 200°C for 6 hours. After the reaction is complete, the reaction product is filtered, washed, and sintered at high temperature to obtain modified porous microspheres.

[0062] The ultrasonic dispersion frequency was 35kHz and the ultrasonic dispersion time was 20min; the high-temperature sintering was carried out in a nitrogen atmosphere, and the high-temperature sintering temperature was 550℃ and the high-temperature sintering time was 2h.

[0063] The third step involves placing the modified porous microspheres in a plasma processing chamber, introducing a mixture of argon and oxygen, and plasma etching the modified porous microspheres at 60 Pa for 30 minutes; once etching is complete, the functional enhancer is obtained.

[0064] The difference between the comparative example and Example 1 is that an equal amount of boron carbide is used instead of the functional enhancer in this comparative example.

[0065] Performance testing: The relevant properties of the magnesia-carbon brick samples (300mm×150mm×150mm) provided in Examples 1-3 and the comparative examples were tested respectively, and the test data are recorded in the table below:

[0066]

[0067] Note: The specific steps for the seismic performance test are as follows: after heat treatment at 1100℃, the sample is rapidly cooled by air, and then a pressure of 0.3MPa is applied. If the sample is not damaged, the next thermal shock test is carried out. The thermal shock performance is characterized by the number of thermal shock tests.

[0068] By comparing and analyzing the relevant data in the table, it can be seen that the magnesia-carbon bricks produced by this invention not only possess excellent mechanical properties but also outstanding thermal shock resistance and oxidation resistance, effectively ensuring the quality and durability of the produced magnesia-carbon bricks while extending their service life to a certain extent. This indicates that the method for producing magnesia-carbon bricks from low-carbon reduced magnesia provided by this invention has a broader market prospect and is more suitable for widespread application.

[0069] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0070] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for producing magnesia-carbon bricks from low-carbon reduced magnesia, characterized in that, Includes the following steps: Step 1: Weigh out 80-90 parts by weight of magnesia, 3-5 parts by weight of functional enhancer, 1-3 parts by weight of aluminum powder, 0.3-1 parts by weight of aluminum nitride, 2-3 parts by weight of carbon black, 3-5 parts by weight of flake graphite and 3-5 parts by weight of phenolic resin for later use. Among them, the magnesium oxide content in the magnesia is ≥97%, and the particle size composition of the magnesia is as follows: 3-5mm magnesia accounts for 20-25%, 1-3mm magnesia accounts for 23-26%, 0.074-1mm magnesia accounts for 20-25%, and the remainder is fine magnesia ≤0.074mm. Step 2: Mix magnesia (excluding fine magnesia) with phenolic resin. After mixing, add the remaining raw materials (excluding fine magnesia), mix at low speed, add fine magnesia, and then mix at high speed to obtain a mixed slurry. Pour the mixed slurry into a prepared mold, and then press and heat treat it to obtain magnesia-carbon bricks. The preparation method of the functional enhancer is as follows: Step 1: 30% of the total amount of boron carbide, aluminum powder, and calcium powder are fed into a ball mill and ball-milled at a rate of 250-350 r / min for 2-3 hours under argon protection. Then, the compound pore-forming agent and the remaining boron carbide powder are added, and ball milling continues for 3-4 hours under argon protection. The resulting mixed powder is then spray-granulated to obtain composite microspheres with a particle size of 30-50 μm. The obtained microspheres are sintered at high temperature under argon protection and then naturally cooled to room temperature to obtain porous microspheres. The mass ratio of boron carbide, aluminum powder, calcium powder, and compound pore-forming agent is 65-80:10-25:5-15:25-35. Step 2: Adjust the pH of the 0.05-0.15 mol / L tetrabutyl titanate ethanol solution to 3.3-3.8 with dilute nitric acid, add porous microspheres at a dosage ratio of 30-60 g / L, disperse by ultrasonication, and then keep the resulting mixed phase at 180-200℃ for 6-10 h. After the reaction is complete, filter, wash and sinter the reaction product at high temperature to obtain modified porous microspheres. The third step involves placing the modified porous microspheres in a plasma processing chamber, introducing a mixture of argon and oxygen, and plasma etching the modified porous microspheres at 45-60 Pa for 30-40 minutes; once etching is complete, the functional enhancer is obtained. The compound pore-forming agent is composed of starch and polymethyl methacrylate in a mass ratio of 2-4:

1.

2. The method for producing magnesia-carbon bricks from low-carbon reduced magnesia according to claim 1, characterized in that: The low-speed stirring speed is 50-80 r / min, and the stirring time is 3-5 min; the high-speed stirring speed is 100-150 r / min, and the stirring time is 30-60 min.

3. The method for producing magnesia-carbon bricks from low-carbon reduced magnesia according to claim 1, characterized in that: The heat treatment temperature is 180-220℃ and the heat treatment time is 15-20h; during molding, a 1000T electric screw press brick machine is used for pressing and molding.

4. The method for producing magnesia-carbon bricks from low-carbon reduced magnesia according to claim 1, characterized in that, During spray granulation, the inlet temperature is 220-260℃, the outlet temperature is 90-110℃, and the atomization pressure is 0.4-0.6MPa.

5. The method for producing magnesia-carbon bricks from low-carbon reduced magnesia according to claim 1, characterized in that, The specific operation of high-temperature sintering in the first step is as follows: Under argon protection, the temperature inside the sintering equipment is raised to 1100-1300℃ at a rate of 5-10℃ / min, and then held at this temperature for 2-3 hours.

6. The method for producing magnesia-carbon bricks from low-carbon reduced magnesia according to claim 1, characterized in that, During plasma etching, the flow rate ratio of argon to oxygen is 3-5:1, and the etching power is set to 250-400W.

7. The method for producing magnesia-carbon bricks from low-carbon reduced magnesia according to claim 1, characterized in that, In the second step, the ultrasonic dispersion frequency is 25-35kHz, and the ultrasonic dispersion time is 20-30min.

8. The method for producing magnesia-carbon bricks from low-carbon reduced magnesia according to claim 1, characterized in that, In the second step, high-temperature sintering is carried out under a nitrogen atmosphere, and the high-temperature sintering temperature is 450-550℃, and the high-temperature sintering time is 2-3 hours.

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