Low-carbon magnesia carbon brick for converter for smelting ultra-low-carbon clean steel and like

Abstract

The invention relates to the technical field of refractory materials, and discloses a low-carbon magnesia carbon brick for a converter for smelting ultralow-carbon clean steel and the like, and the low-carbon magnesia carbon brick comprises the following components in parts by weight: 75-85 parts of magnesia, 2-8 parts of graphite, 2-6 parts of nanocarbon, 0.5-2.5 parts of an antioxidant, 0.5-3 parts of a thermal shock stabilizer and 2.5-3.5 parts of a binding agent. A nanoscale carbon source is adopted to replace part of crystalline flake graphite, the carbon content in the magnesia carbon brick is reduced, and recarburization of furnace lining bricks on molten steel in the smelting process is reduced; the nanoscale carbon source is large in specific surface area and high in reaction activity, a uniform carbon network structure can be formed in the material, thermal stress is effectively absorbed and dispersed, and the thermal shock resistance is improved; and meanwhile, tiny pores in the filling material reduce the infiltration capacity of the slag. The Al-B4C composite antioxidant thermal shock stabilizer is introduced, and the test block is slightly expanded through adjustment, so that the thermal shock stability is improved. The problem of molten steel recarburization caused by high carbon content of a traditional magnesia carbon brick is solved, and meanwhile, good thermal shock resistance and permeation resistance are kept.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, and more specifically, to low-carbon magnesia-carbon bricks for converters used in the production of ultra-low carbon clean steel. Background Technology

[0002] With the gradual completion of large-scale infrastructure projects and urbanization in my country, the traditional market for construction steel has shrunk significantly. At the same time, emerging manufacturing industries such as automobiles are gradually rising, leading to an increasing demand for high-end special steels such as ultra-low carbon steel and stainless steel. In order to seek survival space and adapt to market changes, steel plants have begun to upgrade and transform traditional converters to adapt to the increasingly sophisticated steel products.

[0003] In traditional processes, the carbon in magnesia-carbon bricks used in converters primarily comes from graphite. This is because graphite is heat-resistant, has minimal mass loss, and exhibits minimal volume expansion and contraction. It also has poor wettability to slag, and when combined with slag splashing techniques for converter protection, it significantly extends furnace life. Therefore, magnesia-carbon bricks are widely used in traditional converters. However, for smelting ultra-low carbon steel and stainless steel, traditional magnesia-carbon bricks, due to their higher carbon content, can introduce carbon into the molten steel during smelting, leading to substandard steel composition and requiring secondary blowing, thus impacting production efficiency. Traditional magnesia-carbon bricks have revealed the following drawbacks in adapting to this change: Magnesia-carbon bricks generally have a carbon content of 14%-20%. When used as converter lining materials for smelting special steels such as ultra-low carbon steel and stainless steel, this increases the carbon content of the molten steel, failing to meet the smelting standards for low-carbon clean steel; the high thermal conductivity causes increased heat loss from the furnace during the smelting process, leading to higher temperatures in the metallurgical containers, deformation or damage, and increased energy consumption; and it consumes a large amount of valuable graphite resources, increasing CO2 and CO emissions. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides low-carbon magnesia-carbon bricks for converters used in the production of ultra-low carbon clean steel.

[0005] A low-carbon magnesia-carbon brick for use in a converter for smelting ultra-low carbon clean steel comprises, by weight: 75-85 parts magnesia, 2-8 parts graphite, 2-6 parts nano-carbon, 0.5-2.5 parts antioxidant, 0.5-3 parts thermal shock stabilizer, and 2.5-3.5 parts binder; wherein the magnesia comprises 15-30 parts magnesia aggregate with a particle size of 5-3 mm, 25-35 parts magnesia aggregate with a particle size of 3-1 mm, 15-25 parts magnesia aggregate with a particle size of 1-0 mm, and 10-20 parts magnesia fine powder with a particle size of 0.074 mm.

[0006] Preferably, the binder is a thermoplastic liquid phenolic resin or a thermosetting liquid phenolic resin.

[0007] Preferably, the graphite is flake graphite with a carbon content of 96% or more.

[0008] Preferably, the nano-carbon is one or more of carbon nanotubes, carbon nanospheres, carbon nanofibers, and nano-carbon black.

[0009] Preferably, the antioxidant is one or more of aluminum powder, silicon carbide, and aluminum-based composite materials.

[0010] Preferably, the thermal shock stabilizer is one or more of boron carbide, zirconium oxide, calcium aluminate, and microporous magnesium-rich spinel.

[0011] A method for preparing a low-carbon magnesia-carbon brick includes the following steps:

[0012] Nano-carbon, antioxidants, thermal shock stabilizers and magnesia fine powder are premixed to obtain premixed material A;

[0013] Pour the magnesia aggregate into a mixer and mix for 60-120 seconds. Add the binder and continue mixing for 60-120 seconds. Add graphite to obtain aggregate B.

[0014] Add premixed small material A into the mixer and mix it with large material B until it is evenly stirred to obtain mud.

[0015] The clay is pressed into shape using a molding machine and then baked.

[0016] Preferably, the particle size of the nano-carbon, antioxidant, and thermal shock stabilizer in the premixed material A is 200 mesh.

[0017] Preferably, the magnesia aggregate is added to the mixer in the order of particle size of 5-3mm, 3-1mm, and 1-0mm.

[0018] The beneficial effects of this invention are as follows:

[0019] 1. Reduce carbon content and minimize carbon addition to molten steel. By replacing some of the flake graphite with nano-grade carbon sources, the carbon content in magnesia-carbon bricks is reduced to 8%-9%, a significant decrease compared to the 14%-20% carbon content of traditional magnesia-carbon bricks. This effectively reduces the carbon addition to molten steel by the furnace lining bricks during smelting, meets the smelting standards for ultra-low carbon clean steel, avoids secondary blowing, and improves production efficiency.

[0020] 2. Improved thermal shock resistance. Nanoscale carbon sources have a large specific surface area and high reactivity, enabling the formation of a uniform carbon network structure within the material. This effectively absorbs and disperses thermal stress, reducing crack propagation caused by differences in thermal expansion coefficients. The introduction of an Al-B4C composite antioxidant thermal shock stabilizer generates liquid-phase B2O3 and magnesium borate at high temperatures. The volume expansion of the aluminum powder neutralizes the sintering shrinkage, resulting in slight expansion of the sample. Experimental results show that the optimized low-carbon magnesia-carbon brick did not crack after six thermal shocks at 1000℃, demonstrating significantly improved thermal shock resistance.

[0021] 3. Enhanced impermeability. Nanoscale carbon sources can fill the tiny pores in the material, reducing the permeability of molten slag. Their tight bonding with magnesia particles forms a denser structure, reducing direct contact between molten slag and magnesia, and improving the ability of magnesia-carbon bricks to resist molten slag erosion.

[0022] 4. Improved compressive strength. The optimized low-carbon magnesia-carbon bricks have a room temperature compressive strength of 48.81 MPa, which can withstand greater pressure without cracking or compressive deformation, maintaining structural integrity and extending service life. Detailed Implementation

[0023] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0024] Example 1

[0025] This embodiment proposes a low-carbon magnesia-carbon brick for a converter used in smelting ultra-low carbon clean steel, comprising, by weight:

[0026] 80 parts magnesia, 5 parts graphite, 4 parts nano-carbon, 1.5 parts antioxidant, 2 parts thermal shock stabilizer, and 3 parts binder;

[0027] The magnesia comprises 22 parts of magnesia aggregate with a particle size of 4 mm, 30 parts of magnesia aggregate with a particle size of 2 mm, 20 parts of magnesia aggregate with a particle size of 1-0 mm, and 15 parts of magnesia fine powder with a particle size of 0.074 mm.

[0028] in:

[0029] The binder is a thermoplastic liquid phenolic resin.

[0030] The graphite is flake graphite with a carbon content of 96% or more.

[0031] The nano-carbon refers to carbon nanotubes.

[0032] The antioxidant is aluminum powder.

[0033] The thermal shock stabilizer is boron carbide.

[0034] Example 2

[0035] The difference between this embodiment and Embodiment 1 is that:

[0036] This embodiment proposes a low-carbon magnesia-carbon brick for a converter used in smelting ultra-low carbon clean steel, comprising, by weight:

[0037] 75 parts magnesia, 2 parts graphite, 2 parts nano-carbon, 0.5 parts antioxidant, 0.5 parts thermal shock stabilizer, and 2.5 parts binder;

[0038] The magnesia comprises 15 parts of magnesia aggregate with a particle size of 5 mm, 25 parts of magnesia aggregate with a particle size of 3 mm, 15 parts of magnesia aggregate with a particle size of 1-0 mm, and 10 parts of magnesia fine powder with a particle size of 0.074 mm.

[0039] in:

[0040] The binder is a thermosetting liquid phenolic resin.

[0041] The graphite is flake graphite with a carbon content of 96% or more.

[0042] The nano-carbon is carbon nanospheres.

[0043] The antioxidant is silicon carbide.

[0044] The thermal shock stabilizer is zirconium oxide.

[0045] Example 3

[0046] The difference between this embodiment and Embodiment 1 is that:

[0047] This embodiment proposes a low-carbon magnesia-carbon brick for a converter used in smelting ultra-low carbon clean steel, comprising, by weight:

[0048] 85 parts magnesia, 8 parts graphite, 6 parts nano-carbon, 2.5 parts antioxidant, 3 parts thermal shock stabilizer, and 3.5 parts binder;

[0049] The magnesia comprises 30 parts of magnesia aggregate with a particle size of 3 mm, 35 parts of magnesia aggregate with a particle size of 1 mm, 25 parts of magnesia aggregate with a particle size of 1-0 mm, and 20 parts of magnesia fine powder with a particle size of 0.074 mm.

[0050] in:

[0051] The nano-carbon refers to carbon nanotubes, carbon nanospheres, carbon nanofibers, and nano-carbon black.

[0052] The antioxidant is a composite material of metallic aluminum powder, silicon carbide, and aluminum.

[0053] The thermal shock stabilizer is boron carbide, zirconium oxide, calcium aluminate, and microporous magnesium-rich spinel.

[0054] Example 4

[0055] This embodiment proposes a method for preparing low-carbon magnesia-carbon bricks, comprising the following steps:

[0056] Nano-carbon, antioxidants, thermal shock stabilizers and magnesia fine powder are premixed to obtain premixed material A;

[0057] Pour the magnesia aggregate into a mixer and mix for 60-120 seconds. Add the binder and continue mixing for 60-120 seconds. Add graphite to obtain aggregate B.

[0058] Add premixed small material A into the mixer and mix it with large material B until it is evenly stirred to obtain mud.

[0059] The clay is pressed into shape using a molding machine and then baked.

[0060] The particle size of nano-carbon, antioxidant and thermal shock stabilizer in premix A is 200 mesh.

[0061] Magnesia aggregates are added to the mixer in the order of particle size: 5-3mm, 3-1mm, and 1-0mm.

[0062] Example 1

[0063] Premixed materials A are obtained by premixing 3% nano-carbon, 0.5% antioxidant with a particle size of 200 mesh, 0.5% thermal shock stabilizer with a particle size of 200 mesh, and 15% magnesia fine powder with a particle size of 200 mesh.

[0064] 25% magnesia aggregate with a particle size of 5-3mm, 29% magnesia aggregate with a particle size of 3-1mm, and 19% magnesia aggregate with a particle size of 1-0mm are poured into a mixer and mixed for 60-120 seconds. Then, 3% resin is added and the mixture is continued for 60-120 seconds. Finally, 5% graphite is added to obtain aggregate B.

[0065] Premixed small material A is added to the mixer and mixed with large material B. After stirring evenly, a semi-finished mud is obtained. The mud is pressed and shaped by a molding machine and then baked to obtain low-carbon magnesia-carbon bricks for converters used in smelting stainless steel, ultra-low carbon clean steel and other materials.

[0066] Example 2

[0067] Premixed material A is obtained by premixing 4% nano-carbon, 0.5% antioxidant with a particle size of 200 mesh, 1% thermal shock stabilizer with a particle size of 200 mesh, and 14.5% magnesia powder with a particle size of 200 mesh.

[0068] 25% magnesia aggregate with a particle size of 5-3mm, 29% magnesia aggregate with a particle size of 3-1mm, and 19% magnesia aggregate with a particle size of 1-0mm are poured into a mixer and mixed for 60-120 seconds. Then, 3% resin is added and the mixture is continued for 60-120 seconds. Finally, 4% graphite is added to obtain aggregate B.

[0069] Premixed small material A is added to the mixer and mixed with large material B. After stirring evenly, a semi-finished mud is obtained. The mud is pressed and shaped by a molding machine and then baked to obtain low-carbon magnesia-carbon bricks for converters used in smelting stainless steel, ultra-low carbon clean steel and other materials.

[0070] Example 3

[0071] Premixed material A is obtained by premixing 5% nano-carbon, 0.5% antioxidant with a particle size of 200 mesh, 1.5% thermal shock stabilizer with a particle size of 200 mesh, and 14% magnesia fine powder with a particle size of 200 mesh.

[0072] 25% magnesia aggregate with a particle size of 5-3mm, 29% magnesia aggregate with a particle size of 3-1mm, and 19% magnesia aggregate with a particle size of 1-0mm are poured into a mixer and mixed for 60-120 seconds. Then, 3% resin is added and the mixture is continued for 60-120 seconds. Finally, 3% graphite is added to obtain aggregate B.

[0073] Premixed small material A is added to the mixer and mixed with large material B. After stirring evenly, a semi-finished mud is obtained. The mud is pressed and shaped by a molding machine and then baked to obtain low-carbon magnesia-carbon bricks for converters used in smelting ultra-low carbon clean steel.

[0074] Table 1 shows the proportions of each component in Examples 1-3:

[0075]

[0076] This invention conducts performance tests on the low-carbon magnesia-carbon bricks prepared in Examples 1-3, specifically including pressure resistance testing, chemical analysis, and thermal shock testing. The test results are shown in Table 2.

[0077] Table 2:

[0078] Example 1 Example 2 Example 3 MgO% 86.62 85.56 84.65 C％ 8.5 8.8 8.3 Pores % 1.94 2.07 2.07 <![CDATA[Body density g / cm 3 > 3.13 3.12 3.13 room temperature pressure resistance MPa 40.25 43.83 48.81 Thermal shock at 1000℃*6 times The third test block cracked. The fifth test piece cracked. Not broken Thermal shock resistance of 1000℃*6 times, pressure resistance of MPa - - 11.38

[0079] As can be seen from the results in Table 2, the low-carbon magnesia-carbon bricks prepared in Example 3 have the best thermal shock resistance and compressive strength. In practical applications, the anti-stripping performance of magnesia-carbon bricks is significantly improved, thereby enhancing the safety and service life of the overall structure. High compressive strength indicates that magnesia-carbon bricks can withstand greater pressure without cracking or compressive deformation, better maintaining the integrity of their structure and preventing damage or deformation caused by excessive pressure. They also exhibit greater durability under high temperature and high pressure environments, preventing damage or deformation caused by excessive pressure, thus improving the stability and safety of the lining, reducing the frequency of maintenance and replacement, and extending the service life of the material.

[0080] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A low-carbon magnesia-carbon brick for use in a converter for smelting ultra-low carbon clean steel, characterized in that, The composition, by weight, includes: 75-85 parts magnesia, 2-8 parts graphite, 2-6 parts nano-carbon, 0.5-2.5 parts antioxidant, 0.5-3 parts thermal shock stabilizer, and 2.5-3.5 parts binder; the magnesia includes 15-30 parts magnesia aggregate with a particle size of 5-3 mm, 25-35 parts magnesia aggregate with a particle size of 3-1 mm, 15-25 parts magnesia aggregate with a particle size of 1-0 mm, and 10-20 parts magnesia fine powder with a particle size of 0.074 mm.

2. The low-carbon magnesia-carbon brick according to claim 1, characterized in that, The binder is a thermoplastic liquid phenolic resin or a thermosetting liquid phenolic resin.

3. The low-carbon magnesia-carbon brick according to claim 1, characterized in that, The graphite is flake graphite with a carbon content of 96% or more.

4. The low-carbon magnesia-carbon brick according to claim 1, characterized in that, The nano-carbon is one or more of carbon nanotubes, carbon nanospheres, carbon nanofibers, and nano-carbon black.

5. The low-carbon magnesia-carbon brick according to claim 1, characterized in that, The antioxidant is one or more of the following: metallic aluminum powder, silicon carbide, and aluminum-based composite materials.

6. The low-carbon magnesia-carbon brick according to claim 1, characterized in that, The thermal shock stabilizer is one or more of boron carbide, zirconium oxide, calcium aluminate, and microporous magnesium-rich spinel.

7. A method for preparing low-carbon magnesia-carbon bricks according to any one of claims 1-7, characterized in that, Includes the following steps: Nano-carbon, antioxidants, thermal shock stabilizers and magnesia fine powder are premixed to obtain premixed material A; Pour the magnesia aggregate into a mixer and mix for 60-120 seconds. Add the binder and continue mixing for 60-120 seconds. Add graphite to obtain aggregate B. Add premixed small material A into the mixer and mix it with large material B until it is evenly stirred to obtain mud. The clay is pressed into shape using a molding machine and then baked.

8. The preparation method according to claim 7, characterized in that, The premixed component A contains nano-carbon, antioxidants, and thermal shock stabilizers, all with a particle size of 200 mesh.

9. The preparation method according to claim 7, characterized in that, The magnesia aggregate is added to the mixer in the order of particle size 5-3mm, 3-1mm, and 1-0mm.

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