Nano steel-clad magnesia-carbon brick and its preparation process

Abstract

The present invention discloses a nano-clad magnesia carbon brick and its preparation process, which relates to the technical field of nano-clad magnesia carbon bricks. The brick comprises the following raw materials: 65-80% magnesia, with a MgO content of ≥96%; 5-12% flake graphite; 2-7% plant fiber, which is one or more of sisal fiber, bamboo fiber, and flax fiber; 1-3% nano-SiC with a particle size of 20-50nm; 0.5-2% nano-Al2O3 with a particle size of 30-80nm; 6-10% binder; and 0.1-0.5% dispersant. The nano-clad magnesia carbon brick, incorporating plant fiber, forms uniformly distributed micron-sized pores after high-temperature carbonization, effectively absorbing and dispersing stress generated by thermal shock and reducing crack propagation. Furthermore, the carbonized plant fiber forms a chaotic layered carbon structure, with the carbonized fiber layer covering the graphite surface, which can block oxygen diffusion. The activated carbon produced by fiber pyrolysis can preferentially react with O2, protecting the main components MgO and graphite.

Description

Technical Field

[0001] The invention relates to the technical field of nano-clad magnesia-carbon bricks, in particular to a nano-clad magnesia-carbon brick and a preparation process thereof. Background Art

[0002] Ladle magnesia carbon brick is a refractory product used in the lining of steelmaking furnaces and is widely used due to its good performance.

[0003] Existing magnesia carbon bricks still have the following shortcomings:

[0004] Side effects of antioxidants: metal powder expands in volume after oxidation, causing the brick structure to become brittle;

[0005] Uneven dispersion of carbon source: micron-sized carbon black tends to agglomerate, forming local weakened areas;

[0006] Unmodified nanomaterials: Directly adding nanoparticles (such as nano-MgO) will easily agglomerate due to high surface energy and will not play a reinforcing role;

[0007] The present invention aims to solve the above problems and improve the performance of ladle magnesia carbon bricks by the following methods:

[0008] Nanomaterial modification: Nano-silicon carbide (SiC) and nano-aluminum oxide (Al2O3) are used to synergistically strengthen the matrix, fill micropores and inhibit slag penetration;

[0009] Dispersion process optimization: solving the problem of nanoparticle agglomeration through surface modification technology;

[0010] Improved structural stability: Constructing a "nano-network + micro-skeleton" composite structure to balance thermal shock resistance and high-temperature strength. Summary of the Invention

[0011] In view of the deficiencies in the prior art, the present invention provides a nano-clad magnesia-carbon brick and a preparation process thereof, which solves the problems raised in the above background technology.

[0012] To achieve the above objectives, the present invention is implemented through the following technical solutions: A nano steel-clad magnesia-carbon brick, comprising the following raw materials:

[0013] Magnesia, flake graphite, plant fiber, nano-SiC, nano-Al2O3, binder, dispersant;

[0014] The specific proportions by mass percentage are as follows:

[0015] Magnesia: 65-80%, the MgO content must be ≥96%;

[0016] Flake graphite: 5-12%;

[0017] Plant fiber: 2-7%, plant fiber includes one or more of sisal fiber, bamboo fiber and flax fiber:

[0018] Nano-SiC: 1-3%, with a particle size of 20-50nm;

[0019] Nano-Al2O3: 0.5-2%, particle size 30-80nm;

[0020] Binder: 6-10%;

[0021] Dispersant: 0.1-0.5%.

[0022] Optionally, the carbon content in the flake graphite needs to be ≥95%.

[0023] Optionally, the binder is one or more of phenolic resin, epoxy resin, coal tar, and modified asphalt.

[0024] Optionally, the dispersant is one of polycarboxylate, fatty alcohol polyoxyethylene ether, and polyvinyl pyrrolidone.

[0025] Optionally, the specific proportion of the raw materials of the nano-ladle magnesia carbon bricks by mass percentage is as follows:

[0026] Magnesia: 74.2%;

[0027] Flake graphite: 8.9%;

[0028] Sisal fiber: 5.3%:

[0029] Nano-SiC: 1.8%;

[0030] Nano-Al2O3: 1.3%;

[0031] Phenolic resin: 8.2%;

[0032] Polycarboxylate: 0.3%.

[0033] Optionally, the specific proportion of the raw materials of the nano-ladle magnesia carbon bricks by mass percentage is as follows:

[0034] Magnesia: 68.2%;

[0035] Flake graphite: 11.3%;

[0036] Bamboo fiber: 6.8%:

[0037] Nano-SiC: 2.3%, with a particle size of 20-50nm;

[0038] Nano-Al2O3: 1.8%, particle size 30-80nm;

[0039] Epoxy resin: 9.2%;

[0040] Fatty alcohol polyoxyethylene ether: 0.4%.

[0041] A preparation process of nano steel-clad magnesia-carbon bricks comprises the following specific steps:

[0042] Step 1: Pretreatment of nanomaterials: Mix nano-SiC and nano-Al2O3 with a dispersant and ball mill for 2-4 hours at a ball mill speed of 300 r / min to form a uniform suspension;

[0043] Step 2: Plant fiber processing, as follows:

[0044] (1) Immerse the fiber in a 5% NaOH solution for 100-150 min at a temperature of 60-75 °C to remove hemicellulose and lignin;

[0045] (2) After soaking, wash with water until neutral;

[0046] (3) Spread the fibers evenly in a dryer and dry them at a temperature of 90-120°C until the moisture content drops to 30-40%.

[0047] Step 3: Mixing: add magnesia, graphite, treated plant fiber, pretreated nanomaterials, and binder into a mixer and dry mix for 10 minutes and wet mix for 20 minutes;

[0048] Step 4: Molding, using isostatic pressing, holding pressure for 5 minutes to obtain bricks, the pressure value of which is 150-200MPa;

[0049] Step 5: Curing and sintering, as follows:

[0050] Curing: Keep the temperature at 200℃ for 2 hours in a nitrogen atmosphere to achieve initial carbonization of the resin;

[0051] Sintering: Raise the temperature to 1350-1450℃ (heating rate 5℃ / min) and keep it warm for 3h to form a nano-micro composite structure.

[0052] The present invention provides a nano-clad magnesia carbon brick and a preparation process thereof, which has the following beneficial effects:

[0053] The composite of SiC and Al2O3 nanomaterials is used to achieve synergistic modification, thereby improving slag resistance and high-temperature strength. Ball milling + dispersant pretreatment is used to solve the problem of nanoparticle dispersion. At the same time, low-temperature curing + high-temperature sintering is used to avoid nanostructure damage.

[0054] Adding plant fiber to the raw materials of magnesia carbon bricks can significantly improve the material properties through its unique physical and chemical effects. Plant fibers (such as sisal and bamboo fibers) form uniformly distributed micron-level pores (pore size 1-10μm) after high-temperature carbonization, which can effectively absorb and disperse the stress generated by thermal shock and reduce crack propagation. For magnesia carbon bricks with 2% sisal fiber, the number of thermal shock cycles can be increased from 15 to more than 25 times. In addition, the chaotic carbon structure generated by the carbonization of plant fibers can jointly construct a "nano-micron multi-level reinforcement phase" with nano-SiC / Al2O3. At the same time, the fiber carbonization layer covers the graphite surface, which can block the diffusion of oxygen, and the activated carbon produced by fiber pyrolysis can preferentially react with O2 to protect the main components MgO and graphite. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0056] Example 1: A nano-steel-clad magnesia-carbon brick comprising the following raw materials:

[0057] Magnesia, flake graphite, plant fiber, nano-SiC, nano-Al2O3, binder, dispersant;

[0058] The specific proportions by mass percentage are as follows:

[0059] Magnesia: 74.2%, the MgO content must be ≥96%;

[0060] Flake graphite: 8.9%, carbon content must be ≥95%;

[0061] Sisal fiber: 5.3%:

[0062] Nano-SiC: 1.8%, with a particle size of 20-50nm;

[0063] Nano-Al2O3: 1.3%, particle size 30-80nm;

[0064] Phenolic resin: 8.2%;

[0065] Polycarboxylate: 0.3%.

[0066] A preparation process of nano steel-clad magnesia-carbon bricks comprises the following specific steps:

[0067] Step 1: Pretreatment of nanomaterials: Mix nano-SiC and nano-Al2O3 with a dispersant and ball mill for 2-4 hours at a ball mill speed of 300 r / min to form a uniform suspension;

[0068] Step 2: Plant fiber processing, as follows:

[0069] (1) Immerse the fiber in a 5% NaOH solution for 100-150 min at a temperature of 60-75 °C to remove hemicellulose and lignin;

[0070] (2) After soaking, wash with water until neutral;

[0071] (3) Spread the fibers evenly in a dryer and dry them at a temperature of 90-120°C until the moisture content drops to 30-40%.

[0072] Step 3: Mixing: add magnesia, graphite, treated plant fiber, pretreated nanomaterials, and binder into a mixer and dry mix for 10 minutes and wet mix for 20 minutes;

[0073] Step 4: Molding, using isostatic pressing, holding pressure for 5 minutes to obtain bricks, the pressure value of which is 150-200MPa;

[0074] Step 5: Curing and sintering, as follows:

[0075] Curing: Keep the temperature at 200℃ for 2 hours in a nitrogen atmosphere to achieve initial carbonization of the resin;

[0076] Sintering: Raise the temperature to 1350-1450℃ (heating rate 5℃ / min) and keep it warm for 3h to form a nano-micro composite structure.

[0077] Example 2: A nano-steel-clad magnesia-carbon brick comprising the following raw materials:

[0078] Magnesia, flake graphite, plant fiber, nano-SiC, nano-Al2O3, binder, dispersant;

[0079] The specific proportions by mass percentage are as follows:

[0080] Magnesia: 68.2%, the MgO content must be ≥96%;

[0081] Flake graphite: 11.3%, carbon content must be ≥95%;

[0082] Bamboo fiber: 6.8%:

[0083] Nano-SiC: 2.3%, with a particle size of 20-50nm;

[0084] Nano-Al2O3: 1.8%, particle size 30-80nm;

[0085] Epoxy resin: 9.2%;

[0086] Fatty alcohol polyoxyethylene ether: 0.4%.

[0087] A preparation process of nano steel-clad magnesia-carbon bricks comprises the following specific steps:

[0088] Step 1: Pretreatment of nanomaterials: Mix nano-SiC and nano-Al2O3 with a dispersant and ball mill for 2-4 hours at a ball mill speed of 300 r / min to form a uniform suspension;

[0089] Step 2: Plant fiber processing, as follows:

[0090] (1) Immerse the fiber in a 5% NaOH solution for 100-150 min at a temperature of 60-75 °C to remove hemicellulose and lignin;

[0091] (2) After soaking, wash with water until neutral;

[0092] (3) Spread the fibers evenly in a dryer and dry them at a temperature of 90-120°C until the moisture content drops to 30-40%.

[0093] Step 3: Mixing: add magnesia, graphite, treated plant fiber, pretreated nanomaterials, and binder into a mixer and dry mix for 10 minutes and wet mix for 20 minutes;

[0094] Step 4: Molding, using isostatic pressing, holding pressure for 5 minutes to obtain bricks, the pressure value of which is 150-200MPa;

[0095] Step 5: Curing and sintering, as follows:

[0096] Curing: Keep the temperature at 200℃ for 2 hours in a nitrogen atmosphere to achieve initial carbonization of the resin;

[0097] Sintering: Raise the temperature to 1350-1450℃ (heating rate 5℃ / min) and keep it warm for 3h to form a nano-micro composite structure.

[0098] The experimental results of the nano-clad magnesia carbon bricks of Example 1 and Example 2 are compared with those of the existing traditional magnesia carbon bricks to prove the scientific basis for the improvement of their slag resistance, high temperature strength, thermal shock stability and other performances:

[0099] 1. Comparison of slag erosion resistance

[0100] Test items Traditional magnesia carbon bricks Example 1 Example 2 Static crucible method slag erosion resistance (1500℃, 2h) 35-40% 12-15% 10-13% Slag penetration depth (mm) 4.5-5.0 1.8-2.2 1.5-2.0

[0101] analyze:

[0102] Nano-SiC and Al2O3 form a dense protective layer at high temperatures (SiC oxidizes to form SiO2 glass phase, and Al2O3 reacts with CaO in the slag to form a high-melting-point CA6 phase), significantly inhibiting slag penetration. The porous structure of carbonized plant fibers further hinders slag diffusion.

[0103] 2. High temperature flexural strength (HMOR, 1400℃)

[0104] sample Compressive strength at room temperature (MPa) High temperature flexural strength (1400℃, MPa) Traditional magnesia carbon bricks 45-50 8-10 Example 1 65-70 18-22 Example 2 70-75 20-24

[0105] analyze:

[0106] Nanoparticles fill the gaps between magnesia particles and strengthen the matrix through the "pinning effect"; the chaotic layer carbon formed after the carbonization of plant fibers synergistically enhances the interfacial bonding force with the nanoparticles.

[0107] 3. Thermal shock stability (number of water cooling cycles at 1100°C)

[0108] sample Thermal shock cycles to cracking Residual strength retention (after 20 times) Traditional magnesia carbon bricks 15-18 40-45% Example 1 25-28 75-80% Example 2 28-32 80-85%

[0109] analyze:

[0110] The uniform micropores formed by carbonization of plant fibers (SEM shows pore size 1-10μm) effectively absorb thermal stress, and the nanoparticles inhibit crack propagation (TEM shows cracks deflect at SiC particles).

[0111] 4. Oxidation resistance (weight loss rate after air oxidation at 1000℃)

[0112] sample Oxidation weight loss rate (3h) Traditional magnesia carbon bricks 12-15% Example 1 4-5% Example 2 3-4%

[0113] analyze:

[0114] The carbonized layer of plant fiber covers the graphite surface, blocking oxygen; the SiO2 film generated by oxidation of nano-SiC further seals the pores (β-SiC and SiO2 phases are detected by XRD).

[0115] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A preparation process of nano steel-clad magnesia-carbon bricks, characterized in that: The composition includes the following raw materials: Magnesia, flake graphite, plant fiber, nano-SiC, nano-Al2O3, binder, dispersant; The specific proportions by mass percentage are as follows: Magnesia: 65-80%, the MgO content must be ≥96%; Flake graphite: 5-12%, the carbon content of the flake graphite must be ≥95%; Plant fiber: 2-7%, plant fiber includes one or more of sisal fiber, bamboo fiber and flax fiber; Nano-SiC: 1-3%, with a particle size of 20-50nm; Nano-Al2O3: 0.5-2%, particle size 30-80nm; Binder: 6-10%, the binder is one or more of phenolic resin, epoxy resin, coal tar, and modified asphalt; Dispersant: 0.1-0.5%, the dispersant is one of polycarboxylate, fatty alcohol polyoxyethylene ether, and polyvinyl pyrrolidone; The specific steps include: Step 1: Pretreatment of nanomaterials: Mix nano-SiC and nano-Al2O3 with a dispersant and ball mill for 2-4 hours at a ball mill speed of 300 r / min to form a uniform suspension; Step 2: Plant fiber processing, as follows: (1) Immerse the fiber in 5% NaOH solution for 100-150 min at a 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 dry them at a temperature of 90-120°C until the moisture content drops to 30-40%. Step 3: Mixing: add magnesia, graphite, treated plant fiber, pretreated nanomaterials, and binder into a mixer and dry mix for 10 minutes and wet mix for 20 minutes; Step 4: Molding, using isostatic pressing, holding pressure for 5 minutes to obtain bricks, the pressure value of which is 150-200MPa; Step 5: Curing and sintering, as follows: Curing: Keep the temperature at 200℃ for 2 hours in a nitrogen atmosphere to achieve initial carbonization of the resin; Sintering: heating to 1350-1450℃, heating rate 5℃ / min, keeping warm for 3h to form nano-micro composite structure.

2. The preparation process of a nano-clad magnesia-carbon brick according to claim 1, characterized in that: The specific proportion of the raw materials of the nano steel ladle magnesia carbon bricks 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%.

3. The preparation process of a nano-clad magnesia-carbon brick according to claim 1, characterized in that: The specific proportion of the raw materials of the nano steel ladle magnesia carbon bricks 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 20-50nm; Nano-Al2O3: 1.8%, particle size 30-80nm; Epoxy resin: 9.2%; Fatty alcohol polyoxyethylene ether: 0.4%.