Nano ladle magnesia carbon brick and preparation process thereof

Abstract

The invention discloses a nano steel ladle magnesia carbon brick and a preparation process thereof, and relates to the technical field of nano steel ladle magnesia carbon bricks, the nano steel ladle magnesia carbon brick comprises the following raw materials: 65-80% of magnesia, the MgO content of which is greater than or equal to 96%; 5-12% of crystalline flake graphite; the plant fiber adopts one or more of sisal fiber, bamboo fiber and linen fiber: 1-3% of nano SiC, and the particle size of the nano SiC is 20-50 nm; 0.5-2% of nano Al2O3, the particle size of which is 30-80 nm; 6-10% of a binding agent; and 0.1 to 0.5 percent of dispersing agent. According to the nano ladle magnesia carbon brick, plant fibers are added, uniformly-distributed micron-sized pores are formed after high-temperature carbonization, stress generated by thermal shock can be effectively absorbed and dispersed, crack propagation is reduced, a disordered layer carbon structure is generated after the plant fibers are carbonized, meanwhile, the surface of graphite is covered with a fiber carbonization layer, oxygen diffusion can be blocked, and the heat resistance of the brick is improved. And active carbon generated by fiber pyrolysis can preferentially react with O2, so that main components MgO and graphite can be protected.

Description

Technical Field

[0001] The present invention relates to the technical field of nano ladle magnesia-carbon bricks, and specifically to a nano ladle magnesia-carbon brick and its preparation process. Background Art

[0002] Ladle magnesia-carbon bricks are refractory products used in the inner lining of steelmaking furnaces and are widely used due to their good application effects.

[0003] The existing magnesia-carbon bricks still have the following deficiencies: Side effects of antioxidants: After the metal powder oxidizes, its volume expands, leading to embrittlement of the brick structure; Uneven dispersion of carbon source: Micron-sized carbon black is prone to agglomeration, forming local weakening areas; Unmodified nanomaterials: Direct addition of nanoparticles (such as nano-MgO) is prone to agglomeration due to high surface energy and cannot play an enhancing role; The present invention aims to solve the above problems and improve the performance of ladle magnesia-carbon bricks in the following ways: Modification of nanomaterials: Using nano-silicon carbide (SiC) and nano-aluminum oxide (Al2O3) to synergistically reinforce the matrix, fill micropores and inhibit slag penetration; Optimization of dispersion process: Solving the problem of nanoparticle agglomeration through surface modification technology; Improvement of structural stability: Constructing a "nano-network + micron-skeleton" composite structure to balance thermal shock resistance and high-temperature strength. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a nano ladle magnesia-carbon brick and its preparation process, which solves the problems raised in the above background art.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A nano ladle magnesia-carbon brick includes the following constituent raw materials: Magnesite, flake graphite, plant fiber, nano-SiC, nano-Al2O3, binder, dispersant; The specific proportion by mass percentage is as follows: Magnesite: 65 - 80%, and its MgO content needs to be ≥96%; Flake graphite: 5 - 12%; Plant fiber: 2 - 7%, and the plant fiber adopts one or more of sisal fiber, bamboo fiber, and linen fiber: Nano-SiC: 1 - 3%, and its particle size is 20 - 50 nm; Nano-Al2O3: 0.5 - 2%, and its particle size is 30 - 80 nm; Binder: 6 - 10%; Dispersant: 0.1 - 0.5%.

[0006] Optionally, the carbon content in the flake graphite shall be ≥ 95%.

[0007] Optionally, the binder is one or more of phenolic resin, epoxy resin, coal tar pitch, and modified pitch.

[0008] Optionally, the dispersant is one of polycarboxylate, fatty alcohol polyoxyethylene ether, and polyvinylpyrrolidone.

[0009] Optionally, the specific proportion of the raw materials of the nano ladle magnesia-carbon brick by mass percentage is as follows: Magnesia: 74.2%; Flake graphite: 8.9%; Sisal fiber: 5.3%; Nano SiC: 1.8%; Nano Al2O3: 1.3%; Phenolic resin: 8.2%; Polycarboxylate: 0.3%.

[0010] Optionally, the specific proportion of the raw materials of the nano ladle magnesia-carbon brick by mass percentage is as follows: Magnesia: 68.2%; Flake graphite: 11.3%; Bamboo fiber: 6.8%; Nano SiC: 2.3%, with a particle size of 20 - 50 nm; Nano Al2O3: 1.8%, with a particle size of 30 - 80 nm; Epoxy resin: 9.2%; Fatty alcohol polyoxyethylene ether: 0.4%.

[0011] A preparation process of a nano ladle magnesia-carbon brick includes the following specific steps: Step 1: Pretreatment of nano materials. Mix nano SiC and nano Al2O3 with a dispersant, and ball mill for 2 - 4 h at a ball mill rotation speed of 300 r / min to form a uniform suspension; Step 2: Treatment of plant fibers, specifically as follows: (1) Immerse the fibers in a 5% NaOH solution for 100 - 150 min at a solution temperature of 60 - 75 °C to remove hemicellulose and lignin; (2) After soaking, wash with water until neutral; (3) Lay the fibers evenly in a dryer and heat up for drying. Set the dryer temperature at 90 - 120 °C until the water content drops to 30 - 40%; Step 3: Mixing. Add magnesite, graphite, treated plant fiber, pretreated nanomaterial, and binder into a muller, dry mix for 10 min, and wet mix for 20 min. Step 4: Forming. Use isostatic pressing to form, keep the pressure for 5 min to obtain a brick blank, and the pressure value is 150 - 200 MPa. Step 5: Curing and sintering, specifically as follows: Curing: Keep the temperature at 200 °C for 2 h in a nitrogen atmosphere to preliminarily carbonize the resin. Sintering: Heat up to 1350 - 1450 °C (heating rate 5 °C / min), keep the temperature for 3 h to form a nano - micron composite structure.

[0012] The present invention provides a nano ladle magnesia - carbon brick and its preparation process, which has the following beneficial effects: Utilize the compounding of SiC and Al2O3 nanomaterials to achieve synergistic modification, thereby improving slag resistance and high - temperature strength. At the same time, through ball milling + dispersant pretreatment, the problem of nanoparticle dispersion is solved. Additionally, use low - temperature curing + high - temperature sintering to avoid the destruction of the nano - structure.

[0013] Adding plant fiber to the raw materials of magnesia - carbon brick can significantly improve the material properties through its unique physical and chemical effects. After high - temperature carbonization, plant fibers (such as sisal and bamboo fiber) form uniformly distributed micron - sized pores (pore diameter 1 - 10 μm), which can effectively absorb and disperse the stress generated by thermal shock and reduce crack propagation. For the magnesia - carbon brick added with 2% sisal fiber, the number of thermal shock cycles can be increased from 15 times to more than 25 times. Moreover, the disordered carbon structure generated after the carbonization of plant fibers and nano - SiC / Al2O3 jointly construct a "nano - micron multi - level reinforcement phase". At the same time, the carbonized fiber layer covers the surface of graphite, which can block the diffusion of oxygen, and the activated carbon generated by the pyrolysis of the fiber can react with O2 preferentially, protecting the main components MgO and graphite. Specific embodiments

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0015] Example 1: A nano ladle magnesia - carbon brick, including the following composition raw materials: Magnesite, flake graphite, plant fiber, nano - SiC, nano - Al2O3, binder, dispersant; The specific proportion by mass percentage is as follows: Magnesite: 74.2%, and its MgO content should be ≥96%; Flake graphite: 8.9%, and its carbon content should be ≥95%; Sisal fiber: 5.3%; Nano - SiC: 1.8%, with a particle size of 20 - 50 nm; Nano - Al2O3: 1.3%, with a particle size of 30 - 80 nm; Phenolic resin: 8.2%; Polycarboxylate: 0.3%.

[0016] A preparation process of a nano - ladle magnesia - carbon brick includes the following specific steps: Step 1: Pretreatment of nano - materials. Mix nano - SiC and nano - Al2O3 with a dispersant, and ball - mill for 2 - 4 h at a ball - mill rotation speed of 300 r / min to form a uniform suspension; Step 2: Treatment of plant fibers, specifically as follows: (1) Immerse the fibers in a 5% NaOH solution for 100 - 150 min at a solution temperature of 60 - 75 °C to remove hemicellulose and lignin; (2) After immersion, wash with water until neutral; (3) Spread the fibers evenly in a dryer and heat - dry. Set the dryer temperature at 90 - 120 °C until the water content drops to 30 - 40%; Step 3: Mixing. Add magnesia, graphite, treated plant fibers, pretreated nano - materials, and a binder to a muller, dry - mix for 10 min, and wet - mix for 20 min; Step 4: Molding. Use isostatic pressing to hold the pressure for 5 min to obtain a brick blank, with a pressure value of 150 - 200 MPa; Step 5: Curing and sintering, specifically as follows: Curing: Keep at 200 °C for 2 h in a nitrogen atmosphere to preliminarily carbonize the resin; Sintering: Heat up to 1350 - 1450 °C (heating rate 5 °C / min), and keep warm for 3 h to form a nano - micron composite structure.

[0017] Example 2: A nano - ladle magnesia - carbon brick includes the following composition raw materials: Magnesia, flake graphite, plant fibers, nano - SiC, nano - Al2O3, binder, dispersant; The specific proportion by mass percentage is as follows: Magnesia: 68.2%, with a MgO content of ≥96%; Flake graphite: 11.3%, with a carbon content of ≥95%; Bamboo fibers: 6.8%; Nano - SiC: 2.3%, with a particle size of 20 - 50 nm; Nano - Al2O3: 1.8%, with a particle size of 30 - 80 nm; Epoxy resin: 9.2%; Fatty alcohol polyoxyethylene ether: 0.4%.

[0018] A preparation process of nano ladle magnesia-carbon bricks includes the following specific steps: Step 1: Pretreatment of nano materials. Mix nano SiC and nano Al2O3 with a dispersant, and ball mill for 2 - 4 h at a ball mill rotation speed of 300 r / min to form a uniform suspension; Step 2: Treatment of plant fibers, specifically as follows: (1) Immerse the fibers in 5% NaOH solution for 100 - 150 min at a solution temperature of 60 - 75 °C to remove hemicellulose and lignin; (2) After soaking, wash with water until neutral; (3) Spread the fibers evenly in a dryer and heat up for drying. Set the dryer temperature at 90 - 120 °C until the water content drops to 30 - 40%; Step 3: Mixing. Add magnesite, graphite, treated plant fibers, pretreated nano materials, and a binder into a muller, dry mix for 10 min, and wet mix for 20 min; Step 4: Molding. Use isostatic pressing to hold the pressure for 5 min to obtain a brick blank with a pressure value of 150 - 200 MPa; Step 5: Curing and sintering, specifically as follows: Curing: Keep the temperature at 200 °C for 2 h in a nitrogen atmosphere to preliminarily carbonize the resin; Sintering: Heat up to 1350 - 1450 °C (heating rate 5 °C / min) and keep the temperature for 3 h to form a nano - micron composite structure.

[0019] For the experimental result comparison and characterization of the nano ladle magnesia-carbon bricks in Example 1 and Example 2 with the existing traditional magnesia-carbon bricks, the scientific basis for proving the improvement of their slag resistance, high-temperature strength, thermal shock stability and other properties: 1. Comparison of slag erosion resistance Test Items Traditional Magnesia-Carbon Brick Example 1 Example 2 Static Crucible Method Slag Erosion Resistance Rate (1500°C, 2h) 35-40% 12-15% 10-13% Slag Penetration Depth (mm) 4.5-5.0 1.8-2.2 1.5-2.0 Analysis: Nano SiC and Al2O3 form a dense protective layer at high temperature (SiC oxidizes to form SiO2 glass phase, and Al2O3 reacts with CaO in the slag to form high-melting-point CA6 phase), significantly inhibiting the penetration of molten slag. The porous structure formed after the carbonization of plant fibers further hinders the diffusion of slag.

[0020] 2. High-temperature modulus of rupture (HMOR, 1400 °C) Sample Normal Temperature Compressive Strength (MPa) High Temperature Flexural Strength (1400°C, MPa) Traditional Magnesia-Carbon Brick 45-50 8-10 Example 1 65-70 18-22 Example 2 70-75 20-24 Analysis: Nano particles fill the gaps between magnesite particles and strengthen the matrix through the "pinning effect"; the disordered carbon formed after the carbonization of plant fibers and the nano particles synergistically enhance the interfacial bonding force.

[0021] 3. Thermal shock stability (number of water-cooling cycles at 1100 °C) Sample Number of Thermal Shock Cycles to Cracking Residual Strength Retention Rate (after 20 times) Traditional Magnesia-Carbon Brick 15-18 40-45% Example 1 25-28 75-80% Example 2 28-32 80-85% Analysis: The uniform micropores formed by carbonization of plant fibers (pore diameter 1 - 10 μm shown by SEM) effectively absorb thermal stress, and nanoparticles inhibit crack propagation (cracks deflect at SiC particles shown by TEM).

[0022] 4. Oxidation resistance (weight loss rate of air oxidation at 1000 °C) Sample Oxidation Weight Loss Rate (3h) Traditional Magnesia-Carbon Brick 12-15% Example 1 4-5% Example 2 3-4% Analysis: The carbonized layer of plant fibers covers the graphite surface, blocking oxygen; the SiO2 film formed by oxidation of nano-SiC further seals the pores (β-SiC and SiO2 phases detected by XRD).

[0023] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A nano ladle magnesia-carbon brick, characterized in that, It includes the following raw materials: Magnesite, flake graphite, plant fiber, nano-SiC, nano-Al2O3, binder, dispersant; The specific proportion by mass percentage is as follows: Magnesite: 65 - 80%, and its MgO content should be ≥ 96%; Flake graphite: 5 - 12%; Plant fiber: 2 - 7%, and the plant fiber is one or more of sisal fiber, bamboo fiber and linen fiber; Nano-SiC: 1 - 3%, and its particle size is 20 - 50 nm; Nano-Al2O3: 0.5 - 2%, and its particle size is 30 - 80 nm; Binder: 6 - 10%; Dispersant: 0.1 - 0.5%.

2. The nano ladle magnesia-carbon brick according to claim 1, characterized in that: The carbon content in the flake graphite should be ≥ 95%.

3. The nano ladle magnesia-carbon brick according to claim 1, characterized in that: The binder is one or more of phenolic resin, epoxy resin, coal tar pitch, modified pitch.

4. A nano ladle magnesia-carbon brick according to claim 1, characterized in that: The dispersant is one of polycarboxylate, fatty alcohol polyoxyethylene ether, polyvinylpyrrolidone.

5. A nano ladle magnesia-carbon brick according to claim 1, characterized in that: The specific proportion by mass percentage of the raw materials of the nano ladle magnesia-carbon brick is as follows: Magnesite: 74.2%; Flake graphite: 8.9%; Sisal fiber: 5.3%; Nano-SiC: 1.8%; Nano-Al2O3: 1.3%; Phenolic resin: 8.2%; Polycarboxylate: 0.3%.

6. A nano ladle magnesia-carbon brick according to claim 1, characterized in that: The specific proportion by mass percentage of the raw materials of the nano ladle magnesia-carbon brick is as follows: Magnesite: 68.2%; Flake graphite: 11.3%; Bamboo fiber: 6.8%; Nano-SiC: 2.3%, and its particle size is 20 - 50 nm; Nano-Al2O3: 1.8%, and its particle size is 30 - 80 nm; Epoxy resin: 9.2%; Fatty alcohol polyoxyethylene ether: 0.4%.

7. A preparation process for the nano ladle magnesia-carbon brick according to any one of claims 1 to 6 above, characterized in that, It includes the following specific steps: Step 1: Pretreatment of nano materials. Mix nano-SiC and nano-Al2O3 with the dispersant, ball mill for 2 - 4 h, and the rotation speed of the ball mill is 300 r / min to form a uniform suspension; Step 2: Treatment of plant fiber, specifically as follows: (1) Immerse the fiber in 5% NaOH solution for 100 - 150 min, and the solution temperature is 60 - 75 °C to remove hemicellulose and lignin; (2) After soaking, wash it with water until it is neutral; (3) Spread the fiber evenly in the dryer and heat it to dry. The temperature of the dryer is set at 90 - 120 °C until the water content drops to 30 - 40%; Step 3: Mixing. Add magnesite, graphite, treated plant fiber, pretreated nano materials, and binder into the muller, dry mix for 10 min, and wet mix for 20 min; Step 4: Molding. Use isostatic pressing to hold the pressure for 5 min to obtain a brick blank, and the pressure value is 150 - 200 MPa; Step 5: Curing and sintering, specifically as follows: Curing: Keep it at 200 °C for 2 h in a nitrogen atmosphere to preliminarily carbonize the resin; Sintering: Heat it up to 1350 - 1450 °C and keep it warm for 3 h to form a nano-micron composite structure.