阅读说明：本技术 钢包渣线用纳米碳低碳镁碳砖及制备方法 (Nano carbon low-carbon magnesia carbon brick for ladle slag line and preparation method thereof ) 是由 欧阳德刚 杨新泉 沈继胜 罗巍 李慕耘 朱万军 杨枝超 秦世民 刘中天 孙伟 杨 于 2020-07-20 设计创作，主要内容包括：本发明公开了一种钢包渣线用纳米碳低碳镁碳砖及制备方法,包括五种粒度的电熔镁砂、可分散性纳米碳和抗氧化剂,通过不同粒度电熔镁砂颗粒表面的纳米碳膜包覆、可分散性纳米碳的应用,利用纳米碳膜和可分散性纳米碳主要为无定型碳、含有少量石墨雏晶、溶剂可浸润等特点,改善纳米碳膜与可分散性纳米碳对有机结合剂的浸润吸附,实现纳米碳在镁碳砖中的均匀分散,通过纳米碳膜与可分散性纳米碳20～200纳米厚度的尺度控制,大幅度降低镁碳砖中碳粒子的尺度,显著提高了镁碳砖耐火原料与碳粒子的接触频率,保证了低碳含量条件下碳粒子性能的发挥,改善镁碳砖抗侵蚀渗透性。(The invention discloses a nano-carbon low-carbon magnesia carbon brick for a ladle slag line and a preparation method thereof, which comprises five kinds of electric melting magnesia with granularity, dispersible nano-carbon and an antioxidant, by applying the nano carbon film coating and the dispersible nano carbon on the surfaces of the fused magnesia particles with different granularities, and utilizing the characteristics that the nano carbon film and the dispersible nano carbon are mainly amorphous carbon, contain a small amount of graphite crystal, can be infiltrated by a solvent and the like, the infiltration and adsorption of the nano carbon film and the dispersible nano carbon to an organic binding agent are improved, the uniform dispersion of the nano carbon in the magnesia carbon brick is realized, the dimension of carbon particles in the magnesia carbon brick is greatly reduced by controlling the thickness of the nano carbon film and the dispersible nano carbon by 20-200 nanometers, the contact frequency of the refractory raw material of the magnesia carbon brick and the carbon particles is obviously improved, the performance of the carbon particles under the condition of low carbon content is ensured, and the erosion resistance and permeability of the magnesia carbon brick are improved.)

1. A nano-carbon low-carbon magnesia carbon brick for a ladle slag line is characterized in that: the nano-carbon low-carbon magnesia carbon brick comprises the following raw materials in percentage by weight:

the auxiliary raw materials comprise steel fibers, polyvinyl alcohol fibers and chopped carbon fibers, wherein the weight of the steel fibers accounts for 0-1% of the total weight of the main raw materials, the weight of the polyvinyl alcohol fibers accounts for 0.05-0.15% of the total weight of the main raw materials, and the weight of the chopped carbon fibers accounts for 0.02-0.2% of the total weight of the main raw materials;

the five types of fused magnesite with different granularities are sorted from small to large according to the granularity, at least two types of fused magnesite with different granularities are taken from small to large to coat a nano carbon film, the thickness of the nano carbon film is 20-200 nanometers, the fixed carbon content of the nano carbon film is not less than 90%, the fixed carbon content of dispersible nano carbon is not less than 80%, and the total carbon content of the nano carbon low-carbon magnesia carbon brick is not more than 4%.

2. The nanocarbon low-carbon magnesia carbon brick for the ladle slag line according to claim 1, characterized in that: the diameter of the steel fiber is less than or equal to 0.5mm, and the length of the steel fiber is 5-20 mm.

3. The nanocarbon low-carbon magnesia carbon brick for the ladle slag line according to claim 1, characterized in that: the melting point of the polyvinyl alcohol fiber is less than or equal to 90 ℃, and the water-soluble temperature is more than or equal to 55 ℃.

4. The nanocarbon low-carbon magnesia carbon brick for the ladle slag line according to claim 1, characterized in that: the diameter of the chopped fiber is 5-9 mu m, the length of the chopped fiber is 0.5-2.5 mm, and the carbon content is more than or equal to 95 wt%.

5. The nanocarbon low-carbon magnesia carbon brick for the ladle slag line according to claim 1, characterized in that: the antioxidant is a mixed metal powder antioxidant consisting of metal aluminum powder, metal silicon powder and magnesium aluminum alloy powder, and the particle size is less than 0.074 mm; the organic binder is thermosetting phenolic resin.

6. The nanocarbon low-carbon magnesia carbon brick for the ladle slag line according to claim 1, characterized in that: the main raw materials comprise the following components in percentage by weight:

7. the nanocarbon low-carbon magnesia carbon brick for the ladle slag line according to claim 1, characterized in that: the main raw materials comprise the following components in percentage by weight:

8. the nanocarbon low-carbon magnesia carbon brick for the ladle slag line according to claim 1, characterized in that: the main raw materials comprise the following components in percentage by weight:

9. the nanocarbon low-carbon magnesia carbon brick for the ladle slag line according to claim 1, characterized in that: the main raw materials comprise the following components in percentage by weight:

10. the preparation method of the nano-carbon low-carbon magnesia carbon brick for the ladle slag line according to claim 1 is characterized by comprising the following steps: the preparation method comprises the following steps:

1) crushing fused magnesia into raw materials with three specifications of 5-3 mm, 3-1 mm and 1-0.15 mm, further grinding the fused magnesia, and classifying the fused magnesia into raw materials with two specifications of 180 meshes and 325 meshes to form five specifications of raw materials in total;

2) carrying out chemical vapor deposition coating of a nano carbon film on the surfaces of the fused magnesite with different granularities to finish the coating preparation of the nano carbon film of the fused magnesite with different granularities, wherein the fixed carbon content of the nano carbon film is more than or equal to 90 percent, and the thickness of the nano carbon film is 20-200 nanometers; and collecting fine particle products in waste gas discharged by a chemical vapor deposition device in the preparation process of the carbon nano-film to obtain the required dispersible nano-carbon, wherein the particle size is 20-200 nanometers, and the content of the fixed carbon is more than or equal to 80 percent.

3) Weighing corresponding raw materials according to the raw material composition and weight percentage in claim 1, adding the organic binding agent and absolute ethyl alcohol into a stirring tank, and stirring and mixing for 10-15 minutes to obtain the organic binding agent which is uniformly diluted by the absolute ethyl alcohol;

4) adding the solid raw materials weighed in the step 3) into a wheel-grinding type mixer, carrying out wheel-grinding mixing for 10-15 minutes, adding the diluted organic binder, carrying out wheel-grinding mixing for 15-25 minutes, discharging, and standing for ageing for 8-15 hours to obtain a brick-making mixture;

5) adding the brick making mixture prepared in the step 4) into a mould, and preparing a green brick by adopting a combined type friction brick press through striking molding, wherein the striking molding pressure is 150-200 MPa, and the striking frequency is not lower than 12 times;

6) and naturally placing the formed green brick for 16-24 hours for forming, and then, putting the green brick into a drying kiln for heat treatment, wherein the curing temperature is 180-240 ℃, and the curing time is 18-24 hours, so that the required low-carbon magnesia carbon brick is prepared.

Technical Field

The invention belongs to the technical field of refractory materials, and particularly relates to a nano-carbon low-carbon magnesia carbon brick for a ladle slag line and a preparation method thereof.

Background

The magnesia carbon brick is a non-burning carbon composite refractory material which is prepared by taking magnesia and high-melting point graphite carbon material which is difficult to be infiltrated by slag as main raw materials, adding various non-oxide additives and adopting a carbonaceous binder. Because the graphite has the properties of small thermal expansion coefficient, large thermal conductivity, high melting point, difficult wetting by slag and the like, the magnesia carbon brick has the excellent characteristics of high temperature resistance, strong slag resistance, high thermal shock resistance, low high-temperature creep and the like, and is widely applied to the steelmaking process. Because the total carbon content of the conventional MgO-C brick is higher and is about 10-20%, the commonly used carbon material is mainly flake graphite, the heat conductivity of the magnesia carbon brick is high, and the consumption of graphite resources is large; meanwhile, due to the unique lamellar structure of the crystalline flake graphite, an elastic effect is easily generated in the direction parallel to the brick forming pressure direction, so that the brick structure is subjected to spalling and heat transfer anisotropy, internal stress of the brick is concentrated, and the structural damage of the brick is accelerated; in addition, the easy oxidation performance of the carbon material causes the oxidation and decarburization of the surface layer of the magnesia carbon brick, so that the surface layer structure of the brick body is degraded, and the erosion resistance and the stripping resistance of the brick body are reduced. With the continuous development of high-quality pure steel smelting technology, the influence of the quality of refractory materials on the quality of molten steel and low-cost smelting technology is more and more highly concerned by the industry; according to the report of related data, the influence of the existing magnesia carbon brick on the molten steel quality and the low-cost smelting technology is mainly as follows: (1) the heat loss is large due to high heat conductivity, so that the tapping temperature is increased, and the corrosion of refractory materials is increased; (2) in the case of smelting quality steel or ultra-low carbon steel, the problem of carburization is caused. Therefore, reducing the total carbon content of the ladle slag line magnesia carbon brick and improving the service performance become the hot problems of continuous concern in domestic and foreign industries, and a large amount of researches on low-carbon magnesia carbon bricks and ultra-low-carbon magnesia carbon bricks for the ladle slag line are carried out. The low-carbon magnesia carbon brick generally means that the total carbon content is not more than 8 percent, and the total carbon content of the ultra-low-carbon magnesia carbon brick is not more than 4 percent.

The magnesia carbon brick is developed by adding graphite on the basis of the magnesia brick, and the excellent performance of the magnesia carbon brick is that the graphite is added, so that the problems of reduced thermal shock stability, reduced slag resistance permeability and the like can be caused by simply reducing the carbon content in the magnesia carbon brick. According to the research status and development of the Zhu bolt, Zhang Wenje and the low-carbon magnesia carbon brick reported in Wuhan university of science and technology, 2008, No.3, the main problems caused by the reduction of the carbon content in the magnesia carbon brick are the reduction of the thermal shock stability and the slag penetration resistance; it is known that, after the carbon content in the magnesia carbon brick is reduced, the thermal conductivity of the brick is reduced, the elastic modulus is increased, the thermal shock resistance stability of the brick is deteriorated, the wettability of slag and molten steel with the material is enhanced, and the slag and molten steel permeability of the material is deteriorated. Aiming at the problem, the literature systematically summarizes the research results of the low-carbon technology of the magnesia carbon bricks at home and abroad, and summarizes the related improvement approaches, which are as follows:

(1) the carbon structure of the bonded carbon is improved, and the thermal shock stability and the high-temperature strength of the low-carbon magnesia carbon brick are improved. The binding agent of the traditional magnesia carbon brick is mostly phenolic resin, and the carbon structure after the binding agent is carbonized is in an isotropic glass state, so that the magnesia carbon brick is brittle, has high elastic modulus, is unfavorable for the thermal stability of a product, and has low high-temperature strength; therefore, a japanese scholars can introduce a graphitizable carbon precursor into phenolic resin to prepare a composite bonding agent, and can carbonize the composite bonding agent into secondary carbon with a flowing or mosaic structure under the using environment of the magnesia carbon brick, or form nano carbon fibers in situ to improve the bonded carbon structure.

(2) The matrix structure of the magnesia carbon brick is optimized, the thermal shock stability and the slag penetration resistance of the magnesia carbon brick are improved, and the thermal conductivity is reduced. Under the condition of greatly reducing the carbon content, the contact frequency of the aggregate particles and the carbon particles is improved, and the method is an important way for ensuring the performance of a small amount of carbon particles to be fully exerted. Therefore, a japanese scholars synthesizes composite graphitized carbon black consisting of partially graphitized carbon black with a nanometer scale and metal carbide by using carbon black and metal as raw materials and a self-propagating combustion (SHS) method; the development of a low-carbon magnesia carbon brick with a nano-structure matrix is developed by introducing a composite graphitized carbon black modified phenolic resin binding agent, carbon blacks (single-sphere type and aggregation type) with different shapes and nano-scales and a composite graphitized carbon black carbon source into the matrix, the thermal shock resistance of the low-carbon magnesia carbon brick is improved by the flexibility among nano-particles, the escape of volatile components of the binding agent resin and the absorption of expansion with heat and contraction with nano-pores generated by controlling a carbonization process, wherein the spalling resistance thermal cycle times of the magnesia carbon brick added with 1.5% of carbon nano-particles are equivalent to that of a traditional magnesia carbon brick with flake graphite content of 18%, and the problem of recarburization of the traditional magnesia carbon brick on molten steel is effectively solved. In addition, the fine pores also contribute to improving the slag resistance of the material; through comparison and detection, compared with the traditional magnesia carbon brick, the developed low-carbon magnesia carbon brick has obvious improvement and improvement on the aspects of thermal shock resistance, oxidation resistance, slag resistance, thermal conductivity and the like.

(3) Introducing high-efficiency antioxidant. One of the main reasons for the damage of the magnesia carbon bricks is the oxidation of carbon in the bricks, which causes the corrosion and penetration of steel slag, so that the protection of carbon oxidation in the bricks is particularly important for the low-carbon magnesia carbon bricks; therefore, scholars at home and abroad develop the research of the high-efficiency antioxidant for the magnesia carbon brick, strengthen the anti-oxidation protection of the carbon material in the low-carbon magnesia carbon brick, and form a series of patent technologies of single use or compound use of metal powder, alloy powder and non-oxide powder, but the commonly introduced high-efficiency antioxidant has higher cost, the dispersion uniformity of the high-efficiency antioxidant is not easy to control, and the improvement on the anti-erosion performance, especially the high-temperature mechanical performance of the material is not obvious.

Aiming at the improvement ways in the three aspects, domestic scholars also develop a great deal of research, and the development of the preparation and application technology of the magnesia carbon brick in China is greatly promoted. Such as: the Chinese patent' Jiaxianling, seal autumn, full palm, etc., phenolic resin containing nano carbon powder, nano carbon modified low carbon magnesia carbon brick and the preparation method, the patent numbers are: ZL 200810049163.3' discloses a method for preparing phenolic resin binder containing nano carbon powder by adopting phenol, formaldehyde, dispersant, nano carbon powder and ultrasonic dispersion technology, and also discloses components and a process method for preparing low-carbon magnesia carbon bricks by adopting the phenolic resin binder containing the nano carbon powder. The inner pore size distribution is mainly concentrated in the range of several nanometers by the combination of the nano carbon particles with the resin and the uniform dispersion among coarse particles, fine particles, additives and other materials of the refractory material, and filled in the inside of the pores and among the gaps. The flexibility among nano particles in the nano-structure matrix and the volatile escape of the binder resin are utilized, and the nano-pores generated in the carbonization process are controlled to absorb the severe thermal expansion and contraction caused by thermal shock, improve the thermal shock stability, the erosion resistance and the oxidation resistance of the magnesia carbon brick, reduce the thermal conductivity, and the minimum thermal conductivity is 6.2W (m.K)^-1. However, the modification effect of the binding agent needs to be further verified in production and application, and further research needs to be carried out on how to realize industrial production. Such as: chinese patent Liuhao, Jiesao, Wang Zhou Fu and the like, low-carbon magnesiumCarbon brick and its preparation method, patent application no: 201910649280.1', magnesia particles with the granularity of 1-5 mm are pretreated by placing 78-93 wt% of magnesia particles, 0.1-2 wt% of organic additives and 5-20 wt% of absolute ethyl alcohol in a stirrer, stirring for 2-6 hours at the rotating speed of 300-600 r/min, drying for 12-24 hours at the temperature of 80-110 ℃ and then sieving, wherein the organic additives are polyvinylpyrrolidone or polypropylene glycol. The surface structure and morphology of the magnesia particles are regulated and controlled by pretreating the magnesia particles, so that reasonable and controllable particle accumulation is easily formed, the distribution and microstructure development states of the magnesia fine powder, the crystalline flake graphite, the antioxidant and the like among the magnesia particles are favorably regulated, and the prepared low-carbon magnesia carbon brick has high-temperature breaking strength and slag erosion resistance. Through detection and analysis, the volume density of the prepared low-carbon magnesia carbon brick is more than 2.98g/cm³The apparent porosity is less than 7.2 percent, and the normal-temperature compressive strength is more than 52 MPa; the high-temperature rupture strength (1400 ℃ multiplied by 0.5h) is more than 11.2MPa, the residual rupture strength (1100 ℃ air cooling circulation for 1 time) is more than 6.8MPa, and no obvious corrosion and penetration are seen in a slag resistance test (oxidizing atmosphere, 1600 ℃ multiplied by 3 h); however, the pretreatment amount of the magnesite grains is large, the pretreatment time is long, the pretreatment process is difficult, and reports of practical production application cannot be found at present. Chinese patent 'Chong Zhongxiang, Mayiliang, Caoyuan and the like, a metal composite low-carbon magnesia carbon brick for a ladle slag line and a preparation method thereof, and an authorization publication No. CN 101244940B' discloses a metal composite low-carbon magnesia carbon brick with the carbon content less than or equal to 6% and a preparation method thereof, and is mainly characterized in that 3-15% of metal powder with the granularity less than 0.088mm and 0.5-3% of boron-containing antioxidant are added into material components; the metal powder is one or a composite of more than two of aluminum powder, silicon powder, magnesium powder, zinc powder and magnesium-aluminum alloy powder, not only plays an anti-oxidation role, but also mainly generates a non-oxide through an in-situ reaction in the high-temperature use process, and then is filled and inserted into a periclase skeleton structure to play a role in strengthening and toughening, so that the high-temperature strength and the thermal shock resistance of the magnesia carbon brick are obviously improved, and the oxidation resistance and the slag resistance of the magnesia carbon brick are improved; the boron-containing antioxidant is at least one of boron carbide, boron nitride, zirconium boride and calcium boride powder, and effectively prevents graphiteAnd non-oxide oxidation, so that the magnesia carbon brick is not easy to wet and permeate by the steel slag. The volume density of the prepared metal composite low-carbon magnesia carbon brick for the ladle slag line is more than or equal to 2.96g/cm³The apparent porosity is less than or equal to 6 percent, the normal-temperature compressive strength is more than or equal to 45MPa, the carbon-buried high-temperature breaking strength at 1400 ℃ is more than or equal to 25MPa, the carbon content is less than or equal to 6 percent, the MgO content is more than or equal to 80 percent, and the thermal shock resistance is measured by an air quenching method at 1100 ℃ and air cooling once, wherein the retention rate of the residual strength is 70-80 percent (the retention rate of the residual strength of the conventional magnesia carbon brick is 50-; but the metal powder and the antioxidant are high in cost, so that the metal powder and the antioxidant cannot be popularized and applied at present. The Chinese patent' Mabeiyue, Ninxinging, Suchang and the like, a nano-carbon reinforced low-carbon magnesia carbon brick and a preparation method thereof, the patent application numbers are as follows: 201810613284. X' discloses a low-carbon magnesia carbon brick with 2-4% of nano-carbon content and a preparation method thereof, and the low-carbon magnesia carbon brick comprises the following raw materials in percentage by mass: 90-95% of magnesia as a raw material, 2-4% of nano carbon, 2-3% of antioxidant and 4% of bonding agent; wherein, the carbon content percentage in the nano carbon is more than or equal to 98 percent and is nano graphite oxide sheets, carbon nano tubes, carbon black, active carbon, coke or the mixture of the two in any ratio; obviously, the carbon content percentage in the coke is more than or equal to 98 percent, and in addition, the patent does not describe how the nano carbon easy to agglomerate is uniformly dispersed in the magnesia carbon brick, so the industrial implementation is difficult.

Disclosure of Invention

The invention aims to provide a nano-carbon low-carbon magnesia carbon brick for a ladle slag line and a preparation method thereof, aiming at the defects of the technology, the nano-carbon low-carbon magnesia carbon brick has the characteristics of low total carbon content (less than or equal to 4%), low thermal conductivity, large volume density, high mechanical strength, excellent oxidation resistance, slag corrosion permeation resistance, heat stripping resistance and the like, and achieves the comprehensive purposes of prolonging the service life of the ladle slag line, reducing the heat dissipation loss of the slag line, inhibiting recarburization of molten steel and the like.

In order to achieve the aim, the nano-carbon low-carbon magnesia carbon brick for the ladle slag line, which is designed by the invention, comprises the following raw materials in percentage by weight:

the auxiliary raw materials comprise steel fibers, polyvinyl alcohol fibers and chopped carbon fibers, wherein the weight of the steel fibers accounts for 0-1% of the total weight of the main raw materials, the weight of the polyvinyl alcohol fibers accounts for 0.05-0.15% of the total weight of the main raw materials, and the weight of the chopped carbon fibers accounts for 0.02-0.2% of the total weight of the main raw materials;

the five types of fused magnesite with different granularities are sorted from small to large according to the granularity, at least two types of fused magnesite with different granularities are taken from small to large to coat a nano carbon film, the thickness of the nano carbon film is 20-200 nanometers, the fixed carbon content of the nano carbon film is not less than 90%, the fixed carbon content of dispersible nano carbon is not less than 80%, and the total carbon content of the nano carbon low-carbon magnesia carbon brick is not more than 4%.

Furthermore, the diameter of the steel fiber is less than or equal to 0.5mm, and the length of the steel fiber is 5-20 mm.

Furthermore, the melting point of the polyvinyl alcohol fiber is less than or equal to 90 ℃, and the water-soluble temperature is more than or equal to 55 ℃.

Furthermore, the diameter of the chopped fiber is 5-9 μm, the length of the chopped fiber is 0.5-2.5 mm, and the carbon content is more than or equal to 95 wt%.

Further, the antioxidant is a mixed metal powder antioxidant consisting of metal aluminum powder, metal silicon powder and magnesium aluminum alloy powder, and the particle size is less than 0.074 mm; the organic binder is thermosetting phenolic resin.

Further, the main raw materials comprise the following components in percentage by weight:

further, the main raw materials comprise the following components in percentage by weight:

further, the main raw materials comprise the following components in percentage by weight:

further, the main raw materials comprise the following components in percentage by weight:

the preparation method of the nano-carbon low-carbon magnesia carbon brick for the ladle slag line comprises the following steps:

1) crushing fused magnesia into raw materials with three specifications of 5-3 mm, 3-1 mm and 1-0.15 mm, further grinding the fused magnesia, and classifying the fused magnesia into raw materials with two specifications of 180 meshes and 325 meshes to form five specifications of raw materials in total;

2) carrying out chemical vapor deposition coating of a nano carbon film on the surfaces of the fused magnesite with different granularities to finish the coating preparation of the nano carbon film of the fused magnesite with different granularities, wherein the fixed carbon content of the nano carbon film is more than or equal to 90 percent, and the thickness of the nano carbon film is 20-200 nanometers; and collecting fine particle products in waste gas discharged by a chemical vapor deposition device in the preparation process of the carbon nano-film to obtain the required dispersible nano-carbon, wherein the particle size is 20-200 nanometers, and the content of the fixed carbon is more than or equal to 80 percent.

3) Weighing corresponding raw materials according to the raw material composition and weight percentage in claim 1, adding the organic binding agent and absolute ethyl alcohol into a stirring tank, and stirring and mixing for 10-15 minutes to obtain the organic binding agent which is uniformly diluted by the absolute ethyl alcohol;

4) adding the solid raw materials weighed in the step 3) into a wheel-grinding type mixer, carrying out wheel-grinding mixing for 10-15 minutes, adding the diluted organic binder, carrying out wheel-grinding mixing for 15-25 minutes, discharging, and standing for ageing for 8-15 hours to obtain a brick-making mixture;

5) adding the brick making mixture prepared in the step 4) into a mould, and preparing a green brick by adopting a combined type friction brick press through striking molding, wherein the striking molding pressure is 150-200 MPa, and the striking frequency is not lower than 12 times;

6) and naturally placing the formed green brick for 16-24 hours for forming, and then, putting the green brick into a drying kiln for heat treatment, wherein the curing temperature is 180-240 ℃, and the curing time is 18-24 hours, so that the required low-carbon magnesia carbon brick is prepared.

The preparation method comprises the following steps of coating a nano carbon film on the surface of fused magnesia by chemical vapor deposition, wherein the nano carbon film is prepared by adopting equipment disclosed by a powder rotating chemical vapor deposition device (application publication No. CN 103668112A) applied in Chinese patent, acetylene is used as a carbon source gas, the chemical vapor deposition temperature is 650-750 ℃, the deposition time is 0.5-5 hours, and the nano carbon film is coated on the surface of the fused magnesia by chemical vapor deposition, the fixed carbon content of the nano carbon film is more than or equal to 90%, and the thickness of the nano carbon film can be controlled within the range of 20-200 nanometers. And collecting fine particle products in waste gas discharged by a chemical vapor deposition device in the preparation process of the carbon nano-film to obtain the required dispersible nano-carbon, wherein the particle size or the thickness of the required dispersible nano-carbon is 20-200 nanometers, and the content of the fixed carbon is more than or equal to 80 percent. Under the chemical vapor deposition process conditions, the nano carbon film and the dispersible nano carbon are mainly amorphous carbon, contain a small amount of graphite crystal and can be soaked by a solvent.

Compared with the prior art, the invention has the following beneficial effects:

according to the nano-carbon low-carbon magnesia carbon brick for the ladle slag line, the nano-carbon film coating and the dispersible nano-carbon on the surfaces of the fused magnesia particles with different granularities are applied, and the characteristics that the nano-carbon film and the dispersible nano-carbon are mainly amorphous carbon, contain a small amount of graphite crystal, can be infiltrated by a solvent and the like are utilized, so that the infiltration and adsorption of the nano-carbon film and the dispersible nano-carbon on an organic binding agent are improved, the uniform dispersion of the nano-carbon in the magnesia carbon brick is realized, the size of carbon particles in the magnesia carbon brick is greatly reduced through the size control of the nano-carbon film and the dispersible nano-carbon with the thickness of 20-200 nanometers, the contact frequency of a refractory raw material of the magnesia carbon brick and the carbon particles is obviously improved, the performance of the carbon particles under the condition of low carbon content is ensured; in addition, by adopting the nano-carbon introduction mode of coating the nano-carbon film on the surface of the fused magnesia, the extremely high contact frequency and contact interface area of the refractory raw material of the magnesia carbon brick and carbon particles are ensured, the efficient close compounding of different raw materials and the optimized coupling of material performance are realized, on the basis of greatly reducing the carbon content of the magnesia carbon brick, inhibiting the recarburization of molten steel and reducing the heat dissipation loss of a slag line of a steel ladle, the heat shock resistance of the low-carbon magnesia carbon brick is improved by the flexibility among the nano particles, the escape of volatile components of the binder resin and the absorption of expansion with heat and contraction with cold deformation of nano pores generated by controlling the carbonization process, the comprehensive use performance of the magnesia carbon brick is further improved, and the comprehensive use effects of delaying the damage process of the low-carbon magnesia carbon brick, prolonging the service life of the low-carbon magnesia carbon brick of a slag line of a steel ladle, reducing the consumption cost of refractory materials of the steel ladle, improving the turnover rate of the steel ladle, reducing the tapping temperature of a converter and the like are achieved.

Aiming at the adverse effect of low carbonization on the thermal shock stability of the magnesia carbon brick, the invention further realizes the volatilization of an organic binder and the rapid discharge of cracking and deflation of the binder through the low-temperature melting and high-temperature carbonization shrinkage of the added polyvinyl alcohol fiber to shrink the fine pore residue, thereby preventing the formation of the heat treatment micro-cracks of the magnesia carbon brick and enhancing the heterogeneous toughening effect of the pores; the application performance of the magnesia carbon brick is improved and the thermal shock stability is improved through the high strength, excellent high-temperature performance, good erosion resistance and drawing toughening effect of the added chopped carbon fibers, and the winding and agglomeration of the carbon fibers in the conventional stirring, mixing and dispersing process are avoided through the limitation of the length of the chopped carbon fibers, so that the uniform dispersion of the chopped carbon fibers is ensured; the drawing toughening of the additional heat-resistant steel fiber improves the breaking strength and the thermal shock stability of the magnesia carbon brick, prevents the resilience in the green brick pressing process by limiting the diameter and the length of the heat-resistant steel fiber, and improves the compactness and the overall dimension precision of the magnesia carbon brick. Through compounding of multiple reinforcing and toughening materials in the magnesia carbon brick, the multiphase composite reinforcing and toughening effect of the magnesia carbon brick is realized, the thermal shock stability of the low-carbon magnesia carbon brick is further improved, thermal shock cracks are prevented from being stripped and damaged, and therefore the adverse effect of low-carbon treatment on the thermal shock stability of the magnesia carbon brick is effectively overcome.

According to the microstructure characteristics of the nano carbon film coated fused magnesia and dispersible nano carbon, as well as the characteristics of good surface wettability and organic solvent adsorption of the micro carbon film coated fused magnesia and dispersible nano carbon, anhydrous alcohol is added into the organic binding agent for dilution, so that the problems of poor rheological property of the organic binding agent and difficulty in dispersion in refractory raw materials caused by the adsorption of the nano carbon film and the dispersible nano carbon on the solvent in the organic binding agent are avoided, and the dispersion uniformity of the organic binding agent in the material mixing process is ensured; through the control of the wheel milling mixing time of the solid raw materials of various specifications and types and the diluted organic binding agent added in the preparation method, the uniform mixing and dispersion of the organic binding agent in the solid raw material mixture are realized under the condition of realizing the uniform mixing of the solid raw materials, and through long-time standing and ageing, the sufficient infiltration, permeation and adsorption of the binding agent on the surface of the solid raw materials are realized, the high-efficiency exertion of the functions of the binding agent is realized, and the compactness and the bonding strength of the low-carbon magnesia carbon brick are improved. The green brick density is improved and the apparent porosity is reduced by limiting the molding pressure and the striking frequency in the preparation method; the formed green brick is naturally placed, so that further permeation, diffusion and homogenization of the binding agent and volatilization of the organic solvent are facilitated, and the defects caused by rapid volatilization of the organic solvent in the heat treatment process are avoided; the full solidification of organic combination is ensured and the bonding strength of the low-carbon magnesia carbon brick is improved by limiting the heat treatment temperature and time in the green brick drying kiln in the preparation method.

By scientific and reasonable selection of the novel nano carbon source and optimization of raw material components and the preparation method, the prepared low-carbon magnesia carbon brick has the following physical and chemical properties: the total carbon content is less than or equal to 4 percent, and the volume density is 2.98-3.18 g/cm³The normal temperature breaking strength is more than 30MPa, the thermal conductivity is less than or equal to 9.5w/m DEG C, the thermal shock resistance frequency is more than or equal to 9 times (according to the national standard of the thermal shock resistance test of the magnesia carbon brick, namely, air quenching is carried out after 950 ℃ heat treatment, then 0.3MPa pressure is applied, the next thermal shock resistance test is carried out when a sample is not damaged, the thermal shock resistance performance is represented by the thermal shock resistance frequency), an oxidation resistance test is carried out at 1500 ℃ under the air atmosphere with the heat preservation time of 1h, the thickness of an oxidation layer of the sample is less than or equal to 1.5mm, a slag resistance test is carried out under the heat preservation time of 1600 ℃ for 3h under the carbon. Therefore, the various performance indexes of the nano-carbon low-carbon magnesia carbon brick are obviously superior to those of the conventional magnesia carbon brick.

Detailed Description

The present invention will be described in further detail with reference to specific examples and comparative examples to facilitate a clearer understanding of the present invention, but the present invention is not limited thereto.