阅读说明：本技术 一种高抗蚀低膨胀镁碳砖及其制备方法 (High-corrosion-resistance low-expansion magnesia carbon brick and preparation method thereof ) 是由 罗明 刘江波 方斌祥 魏国平 王落霞 尹明强 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种高抗蚀低膨胀镁碳砖及其制备方法。以质量份计,高抗蚀低膨胀镁碳砖原料组成包括：包覆镁砂颗粒60～75份,镁砂细粉5～15份,鳞片石墨8～18份,抗氧化剂1～4份,酚醛树脂2～5份；以质量份计,包覆镁砂颗粒的原料组成包括：活性Al-(2)O-(3)微粉3～9份,活性MgO微粉2～4份,活性CaO微粉0.5～2份,沥青粉3～7份,镁砂颗粒80～95份；包覆镁砂颗粒的制备方法包括：将包覆镁砂颗粒的原料在混碾机中于150～300℃下热态混合均匀后冷却得到包覆镁砂颗粒。高抗蚀低膨胀镁碳砖的制备方法包括：将高抗蚀低膨胀镁碳砖的原料混合均匀后压制成生坯,然后将生坯置于150～220℃下烘烤6～12h,制得高抗蚀低膨胀镁碳砖。(The invention discloses a high-corrosion-resistance low-expansion magnesia carbon brick and a preparation method thereof. The high-corrosion-resistance low-expansion magnesia carbon brick comprises the following raw materials in parts by mass: 60-75 parts of coated magnesia particles, 5-15 parts of magnesia fine powder, 8-18 parts of crystalline flake graphite, 1-4 parts of antioxidant and 2-5 parts of phenolic resin; the raw materials of the coated magnesia particles comprise the following components in parts by mass: active Al 2 O 3 3-9 parts of micro powder, 2-4 parts of active MgO micro powder, 0.5-2 parts of active CaO micro powder, 3-7 parts of asphalt powder and 80-95 parts of magnesia particles; the preparation method of the coated magnesite grain comprises the following steps: mixing the raw materials of the coated magnesia particlesUniformly mixing the mixture in a rolling machine at a temperature of between 150 and 300 ℃ in a thermal state, and cooling the mixture to obtain the coated magnesia particles. The preparation method of the high-corrosion-resistance low-expansion magnesia carbon brick comprises the following steps: the raw materials of the high-corrosion-resistance low-expansion magnesia carbon brick are uniformly mixed and then pressed into a green body, and then the green body is baked for 6-12 hours at the temperature of 150-220 ℃ to obtain the high-corrosion-resistance low-expansion magnesia carbon brick.)

1. The high-corrosion-resistance low-expansion magnesia carbon brick is characterized by comprising the following raw materials in parts by mass:

the raw materials of the coated magnesite grain comprise, by mass:

the preparation method of the coated magnesite grain comprises the following steps: and uniformly mixing the raw materials of the coated magnesia particles in a mixing mill at a temperature of 150-300 ℃ in a thermal state, and cooling to obtain the coated magnesia particles.

2. The high corrosion resistance low expansion magnesia carbon brick according to claim 1, wherein the magnesia particles are fused magnesia, and the chemical components and the mass percentage content are as follows: MgO is more than or equal to 97.0 wt%, CaO is less than or equal to 1.8 wt%, and SiO₂≤0.9wt％；

The magnesite grain comprises the following components in parts by mass:

30 to 35 parts of a material with a thickness of 5 to 3mm,

3 to 1mm, excluding 3mm and 20 to 25 parts,

1-0.088 mm, excluding 1mm and 30-35 parts.

3. The high erosion resistance low expansion magnesia carbon brick of claim 1 wherein said activated Al is₂O₃The chemical composition and the mass percentage content of the micro powder are Al₂O₃≥98.00wt％，SiO₂≤0.4wt％，Fe₂O₃≤0.4wt％，Na₂O≤0.6wt％；

The active Al₂O₃The particle size of the micropowder is<1μm。

4. The high corrosion resistance low expansion magnesia carbon brick according to claim 1, wherein the chemical composition and mass percentage of the active MgO micro powder are MgO ≥ 90.00 wt%, SiO₂≤3.00wt％，Fe₂O₃Less than or equal to 0.60 wt%, less than or equal to 2.00 wt% of CaO, and less than or equal to 5.00 wt% of ignition loss at 1000 ℃;

the particle size of the active MgO micro powder is less than 2 μm.

5. The high corrosion resistance low expansion magnesia carbon brick according to claim 1, wherein the chemical composition and mass percentage content of the active CaO micro powder are CaO more than or equal to 90.00 wt%, SiO₂≤3.00wt％，Fe₂O₃≤2.0wt％，Al₂O₃Less than or equal to 2.00wt percent, and less than or equal to 5.00wt percent loss on ignition at 1000 ℃;

the particle size of the active CaO micro powder is less than 2 μm.

6. The high corrosion resistance low expansion magnesia carbon brick according to claim 1, wherein said asphalt powder has the following indexes: the softening point is 100-250 ℃, the coking value at 550 ℃ is 50-85%, the carbon residue rate at 800 ℃ in a carbon burying atmosphere is 60-85 wt%, and the particle size is less than 0.088 mm.

7. The high corrosion resistance low expansion magnesia carbon brick according to any one of claims 1 to 6, wherein the coated magnesia particles have a particle size distribution, in parts by mass, of:

20 to 25 parts of a resin having a thickness of 5 to 3mm,

3 to 1mm, excluding 3mm and 20 to 25 parts,

1-0.088 mm, excluding 1mm and 20-25 parts.

8. The high corrosion resistance low expansion magnesia carbon brick according to claim 1, wherein the magnesite powder is fused magnesite, and the chemical composition and the mass percentage content of the magnesite powder are as follows: MgO is more than or equal to 97.0 wt%, CaO is less than or equal to 1.8 wt%, and SiO₂≤0.9wt％；

The granularity of the magnesite fine powder is less than 0.088 mm;

the chemical components of the flake graphite are more than or equal to 94.0 wt%, and the granularity is less than 0.088 mm;

the phenolic resin is thermosetting phenolic resin.

9. The high corrosion resistance low expansion magnesia carbon brick according to claim 1, wherein said antioxidant is ultra fine elemental Si powder, whose chemical composition is Si ≥ 97.0 wt%, particle size <0.5 μm.

10. The method for preparing the high corrosion resistance low expansion magnesia carbon brick according to any one of claims 1 to 9, comprising: and uniformly mixing the raw materials of the high-corrosion-resistance low-expansion magnesia carbon brick, pressing into a green body, and then baking the green body at the temperature of 150-220 ℃ for 6-12 hours to obtain the high-corrosion-resistance low-expansion magnesia carbon brick.

Technical Field

The invention relates to the technical field of refractory materials for steelmaking, in particular to a high-corrosion-resistance low-expansion magnesia carbon brick and a preparation method thereof.

Background

Ladles are important thermal equipment in the metallurgical industry, the most primitive and basic functions of which are to receive, transfer and pour molten steel. With the rapid development and technical progress of metallurgical industry, the requirements of various industries and various fields on the quality and performance of steel are higher and higher, secondary refining outside a furnace is generally carried out on molten steel before pouring, and the secondary refining mainly comprises desulfurization, degassing, inclusion removal, molten steel component adjustment, temperature adjustment and the like, and the related main steelmaking processes comprise LF, RH + OB, VD, VOD, LATS and the like. The refining process is essentially performed in a ladle, making the ladle more functional from a previous singulation during use.

The magnesia carbon brick is widely applied to the slag line part of the refining ladle due to the excellent thermal shock stability, slag corrosion resistance, permeability and the like. Along with the smelting requirements of clean steel and high-quality steel grades, the external refining proportion of the molten steel furnace is increased, the smelting time is prolonged, and the temperature of the molten steel is high, and the retention time in a ladle is long. Meanwhile, the refining process can cause the molten slag and the molten steel to continuously roll in the steel ladle, thereby providing high requirements on the thermal expansion, the thermal shock performance, the erosion resistance and the like of the slag line magnesia carbon brick.

The traditional magnesia carbon brick can show better service life in the using process, but with the improvement of the external refining proportion, the using process still has some problems:

1) oxidation and thermal spalling problems occur during baking and use: increasing the content of metal antioxidants such as Al, Si, etc. can effectively alleviate the problem of oxidation spalling, but the above additives react inside the material to generate expansion, which causes the material to generate thermal spalling. At the same time, the addition of the above-mentioned antioxidants reduces the slag erosion resistance of the material to some extent.

2) The melting loss of 'cracks' and 'steamed bread-like' is easy to generate in the using process: because the magnesia carbon brick has a large self thermal expansion rate at high temperature, a vertical joint is easy to generate, and the thermal stress between bricks at the brick joint is large, the magnesia carbon brick preferentially becomes a damaged channel under the scouring of molten steel and slag, and finally, the problem of melting loss in a shape of a steamed bun is caused.

The patent specification with publication No. CN 111960805A discloses that aluminum chloride or aluminum sulfate saturated solution is used as a bonding agent, and the surface of magnesite grains is tightly coated with a layer of alpha-Al₂O₃And (3) micro-powder, namely low-expansion spinel is generated around the magnesite grains to absorb the thermal expansion of the magnesite grains.

The patent specification with the publication number of CN 111875356A discloses the application of nano carbon film coating and dispersible nano carbon on the surfaces of fused magnesite grains with different particle sizes, so that the performance of carbon grains is ensured under the condition of low carbon content, and the slag corrosion resistance and the permeability of the magnesia carbon brick are improved.

Disclosure of Invention

Aiming at the defects in the field, the invention provides the high-corrosion-resistance low-expansion magnesia carbon brick which has the advantages of low thermal expansion coefficient, high-temperature oxidation resistance, slag corrosion resistance and good permeability, can avoid the problems of cracking and steamed bread shape in the using process, and can greatly prolong the service life when being used as a steel ladle slag line working lining refractory material.

A high-corrosion-resistance low-expansion magnesia carbon brick comprises the following raw materials in parts by mass:

the raw materials of the coated magnesite grain comprise, by mass:

the preparation method of the coated magnesite grain comprises the following steps: and uniformly mixing the raw materials of the coated magnesia particles in a mixing mill at a temperature of 150-300 ℃ in a thermal state, and cooling to obtain the coated magnesia particles.

The invention firstly prepares the coated magnesia aggregate particles by adding active Al₂O₃The micro powder, the active MgO micro powder, the active CaO micro powder, the asphalt powder and the magnesia particles are subjected to thermal mixing in a mixing mill at the temperature of 150-300 ℃, so that the components are uniformly coated on the surfaces of the magnesia particles. In the using process of the magnesia carbon brick, the pitch is carbonized to form a graphitized carbon structure which is uniformly coated on the surface of magnesia particles. On the other hand, Al is generated under high temperature condition in the using process of the magnesia carbon brick₂O₃MgO and CaO form Calcium Aluminate (CA) and calcium dialuminate (CA) in the magnesia particle coating layer₂) And a spinel phase. The synergistic effect of the components is obviously superior to that of the coating of a single component.

The high-corrosion-resistance low-expansion magnesia carbon brick adopts the coated magnesia particles as the aggregates, so that a flexible graphite layer is formed between the aggregate of the magnesia particles and the fine powder, the direct thermal expansion effect of the magnesia particles is favorably relieved in the high-temperature use process, the high-temperature thermal expansion performance of the magnesia carbon brick is reduced, and meanwhile, the corrosion and the permeation of slag to the magnesia particles are favorably reduced.

In addition, when the magnesia carbon brick is used, CA and CA formed on the surface of magnesia particles in situ₂Spinel phase, CaO, SiO in steel slag₂During the erosion of the components, a mixture containing calcium disilicate aluminate and dicalcium aluminosilicate (CAS) is formed₂-C₂AS) and the like, on one hand, the densification of the matrix at the hot end of the magnesia carbon brick is promoted, the through pore channel is blocked, and the oxidation resistance of the hot end face is effectively improved, so that the addition amount of the antioxidant in the material can be reduced; on the other hand, the existence of the spinel further improves the viscosity of a liquid phase, and a protective layer is formed on the contact surface of the magnesia carbon brick and the slag, so that the slag is prevented from further permeating and corroding; thirdly, the high-viscosity liquid phase reduces the expansion of the hot end face of the magnesia carbon brick and relieves the magnesia carbonThe hot end face of the brick generates thermal stress, and the problems of cracking, vertical seams, steamed bread-shaped erosion and the like of the hot end face in the using process are avoided.

Preferably, in the raw material of the coated magnesite grain, active Al is contained₂O₃The sum of the mass parts of the micro powder, the active MgO micro powder, the active CaO micro powder, the asphalt powder and the magnesia particles is 100 parts.

Preferably, the sum of the parts by mass of the coated magnesia particles, the magnesia fine powder, the flake graphite and the antioxidant in the raw materials of the high-corrosion-resistance low-expansion magnesia carbon brick is 100 parts.

Preferably, the magnesite grain is fused magnesite, and the fused magnesite grain comprises the following chemical components in percentage by mass: MgO is more than or equal to 97.0 wt%, CaO is less than or equal to 1.8 wt%, and SiO₂≤0.9wt％。

Preferably, the magnesite grain has a grain size distribution of, by mass:

30 to 35 parts of a material with a thickness of 5 to 3mm,

3 to 1mm, excluding 3mm and 20 to 25 parts,

1-0.088 mm, excluding 1mm and 30-35 parts.

Preferably, the active Al₂O₃The chemical composition and the mass percentage content of the micro powder are Al₂O₃≥98.00wt％，SiO₂≤0.4wt％，Fe₂O₃≤0.4wt％，Na₂O≤0.6wt％。

Preferably, the active Al₂O₃The particle size of the micropowder is<1μm。

Preferably, the chemical composition and the mass percentage content of the active MgO micro powder are that MgO is more than or equal to 90.00wt percent and SiO₂≤3.00wt％，Fe₂O₃Less than or equal to 0.60 wt%, less than or equal to 2.00 wt% of CaO, and less than or equal to 5.00 wt% of ignition loss at 1000 ℃.

Preferably, the particle size of the active MgO fine powder is <2 μm.

Preferably, the chemical composition and the mass percentage content of the active CaO micro powder are that CaO is more than or equal to 90.00wt percent, and SiO₂≤3.00wt％，Fe₂O₃≤2.0wt％，Al₂O₃Less than or equal to 2.00wt percent, and less than or equal to 5.00wt percent loss on ignition at 1000 ℃.

Preferably, the particle size of the active CaO micro powder is <2 μm.

Preferably, the indexes of the asphalt powder are as follows: the softening point is 100-250 ℃, the coking value at 550 ℃ is 50-85%, the carbon residue rate at 800 ℃ in a carbon burying atmosphere is 60-85 wt%, and the particle size is less than 0.088 mm.

Preferably, the coated magnesite grain has a grain size distribution of, by mass:

20 to 25 parts of a resin having a thickness of 5 to 3mm,

3 to 1mm, excluding 3mm and 20 to 25 parts,

1-0.088 mm, excluding 1mm and 20-25 parts.

Preferably, the magnesite powder is fused magnesite, and the fused magnesite powder comprises the following chemical components in percentage by mass: MgO is more than or equal to 97.0 wt%, CaO is less than or equal to 1.8 wt%, and SiO₂≤0.9wt％。

Preferably, the magnesite powder has a particle size of <0.088 mm.

Preferably, the chemical components of the flake graphite are more than or equal to 94.0 wt% and the particle size is less than 0.088 mm.

Preferably, the phenolic resin is a thermosetting phenolic resin.

Preferably, the antioxidant is superfine elemental Si powder, the chemical component of the antioxidant is more than or equal to 97.0 wt% of Si, and the granularity of the antioxidant is<0.5 μm. The invention adopts the particle size of<0.5 mu m superfine elemental Si powder is used as an antioxidant, so that the phenomenon that the conventional magnesia carbon brick commonly adopts conventional metal Al powder and Si powder with larger grain diameter as the antioxidant and Al is generated in the using process of the magnesia carbon brick is avoided₂O₃、AlN、Al₄C₃Spinel, SiC cause a problem of severe expansion. In the invention, because the granularity of the simple substance Si is small, the activity is high, and good oxidation resistance can be achieved under the condition of low addition amount; in addition, the micro-nano SiC phase formed in situ generates pores for sealing the material matrix through volume micro expansion, so that the thermal expansion rate of the material is not increased, and the density of the material matrix is improved, thereby improving the erosion resistance.

The high-corrosion-resistance low-expansion magnesia carbon brick adopts the coated magnesia particles and the superfine elemental Si powder, so that a layer of graphitized carbon structure can be coated on the surface of the magnesia particles in the using process of the material, and meanwhile, CA and CA are formed in situ in the coating layer₂And the spinel phase is beneficial to reducing the high-temperature thermal expansion of the magnesia carbon brick, improving the erosion resistance of the hot end face of the magnesia carbon brick, reducing the thermal expansion and thermal stress of the hot end face, improving the oxidation resistance and the like, thereby improving the comprehensive performance of the material.

The invention also provides a preparation method of the high-corrosion-resistance low-expansion magnesia carbon brick, which comprises the following steps: and uniformly mixing the raw materials of the high-corrosion-resistance low-expansion magnesia carbon brick, pressing into a green body, and then baking the green body at the temperature of 150-220 ℃ for 6-12 hours to obtain the high-corrosion-resistance low-expansion magnesia carbon brick.

Compared with the prior art, the invention has the main advantages that:

the invention firstly synthesizes Al in advance₂O₃MgO, CaO and asphalt, and then preparing the magnesia carbon brick by using the coated magnesia particles. In the using process of the magnesia carbon brick, CA and CA are formed on the surface of magnesia particles in situ at medium temperature and high temperature₂Spinel and graphitized carbon structure, graphite structure is favorable to forming the flexible layer in magnesia granule and fine powder interface department, reduces the high temperature expansion of magnesia carbon brick, improves the erosion and the infiltration that the magnesia granule resisted the slag simultaneously. In addition, CA₂CaO, SiO of spinel in steel slag₂During the erosion of the plasma phase, spinel-CAS is formed₂-C₂As high-viscosity liquid phase such AS AS improves the oxidation resistance of the hot end face of the magnesia carbon brick, reduces the high-temperature expansion of the hot end face and reduces the problem of steamed-bun-shaped erosion. Meanwhile, a high-viscosity protective layer is formed at the interface of the hot end by the high-viscosity liquid phase, so that the further penetration and erosion of the slag are avoided.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are conducted under conditions not specified, usually according to conventional conditions, or according to conditions recommended by the manufacturer. Unless otherwise specified, the amounts of the respective raw material components are in parts by mass.

Table 1 shows the raw material composition of the magnesia carbon bricks of the respective examples and comparative examples, and table 2 shows the raw material composition of the coated magnesia particles of the respective examples and comparative examples, wherein:

the magnesite grains are fused magnesite, and the fused magnesite comprises the following chemical components in percentage by mass: MgO is more than or equal to 97.0 wt%, CaO is less than or equal to 1.8 wt%, and SiO₂≤0.9wt％。

Active Al₂O₃The chemical composition and the mass percentage content of the micro powder are Al₂O₃≥98.00wt％，SiO₂≤0.4wt％，Fe₂O₃≤0.4wt％，Na₂O≤0.6wt％。

Active Al₂O₃The particle size of the micropowder is<1μm。

The chemical composition and mass percentage content of the active MgO micro powder are that MgO is more than or equal to 90.00wt percent and SiO₂≤3.00wt％，Fe₂O₃Less than or equal to 0.60 wt%, less than or equal to 2.00 wt% of CaO, and less than or equal to 5.00 wt% of ignition loss at 1000 ℃.

The particle size of the active MgO micropowder is <2 μm.

The chemical composition and the mass percentage content of the active CaO micro powder are that CaO is more than or equal to 90.00wt percent, and SiO₂≤3.00wt％，Fe₂O₃≤2.0wt％，Al₂O₃Less than or equal to 2.00wt percent, and less than or equal to 5.00wt percent loss on ignition at 1000 ℃.

The particle size of the active CaO micro powder is less than 2 μm.

The asphalt powder has the following indexes: the softening point is 100-250 ℃, the coking value at 550 ℃ is 50-85%, the residual carbon rate under 800 ℃ carbon-buried atmosphere is 60-85 wt%, and the particle size is less than 0.088 mm.

The magnesite fine powder is fused magnesite, and comprises the following chemical components in percentage by mass: MgO is more than or equal to 97.0 wt%, CaO is less than or equal to 1.8 wt%, and SiO₂≤0.9wt％。

The particle size of the magnesite fine powder is less than 0.088 mm.

The chemical components of the flake graphite are more than or equal to 94.0 wt%, and the granularity is less than 0.088 mm.

The chemical components of the superfine simple substance Si powder are more than or equal to 97.0wt percent and the granularity is less than 0.5 mu m.

TABLE 1

TABLE 2

Examples 1-5 and comparative examples 2-3 the raw materials according to table 2 were mixed in a mixer mill at 200 ℃ and cooled to obtain corresponding coated magnesite particles, carbon-coated fused magnesite, and Al₂O₃The micro powder is coated with fused magnesia.

The raw materials in the table 1 are uniformly mixed and then pressed into green bodies, and then the green bodies are baked for 8 hours at 190 ℃ to prepare the corresponding magnesia carbon bricks.

Table 3 shows the performance parameters of the magnesia carbon bricks of the examples and comparative examples.

TABLE 3

As is clear from tables 1, 2 and 3, the Al content in the fused magnesia grains was adjusted₂O₃The content of the micro powder, the MgO micro powder, the CaO micro powder and the asphalt powder is adjusted, and meanwhile, the content of different coated fused magnesia particles, fused magnesia fine powder, flake graphite fine powder, superfine simple substance Si powder and phenolic resin is adjusted, so that the high-corrosion-resistance low-expansion magnesia carbon brick in the embodiment 5 has the best test performance, the compressive strength is 38MPa after carbon burying treatment at 1000 ℃, and the change rate of the residual line is + 0.32%; after carbon burying treatment at 1600 ℃, the compressive strength is 53MPa, and the residual linear change rate is + 0.70%; the high-temperature rupture strength at 1400 ℃ is 21.5MPa under the carbon-buried atmosphere for 0.5 h; the strength retention rates after water cooling for 1 time, 2 times, 3 times and 4 times at 1100 ℃ are respectively 86%, 79.5%, 73% and 63%; oxidation weight loss rate and oxidation layer thickness under 1000 deg.C x 3hThe degrees are respectively 3.5 percent and 2.2 mm; the oxidation weight loss rate and the oxide layer thickness are respectively 5.3 percent and 4.1mm under 1600 ℃ multiplied by 3 h; the high-temperature thermal expansion rate in the process of increasing from room temperature to 1500 ℃ under the reducing atmosphere is 1.67 percent; under the test condition of 1600 ℃ multiplied by 5h, the slag alkalinity is 3.0 to carry out the anti-corrosion experiment, and the anti-slag corrosion index is 77 percent.

Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the above description of the present invention, and equivalents also fall within the scope of the invention as defined by the appended claims.