Recycled short carbon fiber reinforced low-carbon magnesia carbon brick for steel ladle and preparation method of recycled short carbon fiber reinforced low-carbon magnesia carbon brick

Abstract

According to the technical scheme, after 0.5-1.5 wt% of recycled short carbon fibers are dispersed through an organic dispersing agent, 85-95 wt% of fused magnesite, 3-8 wt% of metal silicon micro powder, 1.0-2.5 wt% of graphite, 0.5-3 wt% of silicon carbide powder and 3-6 wt% of liquid phenolic resin are added into the mixture, and the mixture is stirred to be uniform, so that the low-carbon magnesia carbon brick for the steel ladle reinforced by the recycled short carbon fibers is obtained. The carbon fiber reinforced low-carbon magnesia carbon brick is prepared by grinding and mixing the raw materials, carrying out compression molding, and carrying out heat treatment at 1000-1400 DEG C in a protective atmosphere. According to the invention, a certain proportion of short carbon fiber is added to replace a corresponding graphite addition amount, so that the performance can be improved, and the low carbon content can be maintained at the same time. The prepared carbon fiber reinforced magnesia carbon brick has the characteristics of low carbon content, excellent room-temperature and high-temperature mechanical properties, good erosion resistance, good thermal shock resistance, excellent anti-stripping performance and the like. The method realizes effective utilization of the recycled short carbon fibers in the low-carbon magnesia carbon brick for the steel ladle, and has both social and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of performance enhancement and preparation technology of low-carbon magnesia-carbon bricks for steel ladles, and in particular, a low-carbon magnesia-carbon brick for steel ladles reinforced with recycled short-cut carbon fibers and its preparation method. Background Technology

[0002] Traditional magnesia-carbon bricks for steel ladles are made from high-purity magnesia and graphite as core raw materials (carbon content typically ranges from 10% to 25%). Their key characteristics include a dense structure leading to low apparent porosity, and excellent composite performance—effectively resisting chemical erosion by molten slag while inhibiting its penetration and diffusion into the material's interior, along with superior thermal shock resistance and high thermal conductivity. This material is primarily used in the harsh environments of the metallurgical industry, including but not limited to: the high-temperature reaction zone of the ladle in oxygen converters for steelmaking, key components of the furnace lining in high-power / ultra-high-power electric arc furnaces, and refractory linings in ladle refining furnaces. In recent years, with the rapid development of ultra-low carbon steel and clean steel smelting technologies, the graphite content of traditional magnesia-carbon bricks has become a key factor restricting the control of carbon content in molten steel. Studies have shown that when the graphite content in magnesia-carbon bricks exceeds 12%, significant carbon dissolution occurs during high-temperature smelting, leading to an increase in carbon content in the molten steel of 0.02% to 0.05%. This poses a significant challenge to the production of ultra-low carbon steel, which requires a carbon content of ≤0.03%. Therefore, the industry is accelerating technological innovation in the low-carbonization of magnesia-carbon bricks. By employing new materials such as nano-carbon additives and composite antioxidants, the graphite content can be controlled below 8% while maintaining the brick's erosion resistance, thus meeting the stringent requirements of modern metallurgical processes for material performance. Existing patents, such as the patent for "A low-carbon magnesia-carbon refractory material reinforced with nano-carbon fibers and its preparation method" (CN202310336181.4), although using nano-carbon fibers to reinforce the low-carbon magnesia-carbon refractory material and improving its performance, suffer from the problem that the low-dimensional nano-carbon fibers are prone to agglomeration, increasing the difficulty of dispersion and complicating the dispersion process. Furthermore, the nano-carbon fibers are added externally, increasing the carbon content in the matrix. Furthermore, the high cost of preparing carbon nanofibers makes them difficult to promote and apply in industrial production. Therefore, this invention proposes to prepare low-carbon magnesia-carbon bricks for steel ladles using recycled short-cut carbon fibers. The recycled short-cut carbon fibers themselves are also a "carbon" source, which can replace part of the graphite content in low-carbon magnesia-carbon bricks and also serve as a high-temperature reinforcing phase, improving the anti-stripping performance of magnesia-carbon bricks for steel ladles and enabling them to maintain excellent high-temperature performance during service. Summary of the Invention

[0003] The present invention aims to overcome the shortcomings of existing magnesia-carbon bricks for steel ladles, such as poor high-temperature service performance and high carbon content. The purpose is to adopt a simple, low-cost process and use recycled carbon fiber as a "carbon source" to enhance the preparation method of low-carbon magnesia-carbon bricks for steel ladles. The low-carbon magnesia-carbon bricks for steel ladles prepared by this method have the characteristics of low cost, long service life, low carbon content, excellent thermal shock resistance, erosion resistance and spalling resistance.

[0004] To achieve the above objectives, the present invention overcomes the technical bottleneck through the following detailed steps: Step 1: Disperse 0.5~1.5wt% of recycled short-cut carbon fibers with an organic dispersant. The organic dispersant prevents the carbon fibers from agglomerating and makes them more uniformly dispersed, ultimately obtaining an organic mixed slurry containing 0.5~1.5wt% of recycled short-cut carbon fibers. Step 2: Mix 85-95 wt% fused magnesia with 3-8 wt% metallic silicon micro powder, 1.0-2.5 wt% graphite, 0.5-3 wt% silicon carbide powder, 3-6 wt% liquid phenolic resin and a mixed slurry containing 0.5-1.5 wt% short-cut carbon fibers to obtain the final mixed raw material for preparing low-carbon magnesia-carbon bricks. Step 3: Allow the mixture described in Step 2 to air-dry for 24 hours to allow the liquid phenolic resin to fully coat the particle surface, thereby increasing the bonding force between particles. Step 4: Pour the mixed material after being trapped in Step 3 directly into the mold, and after pressing, obtain a low-carbon magnesia-carbon brick blank with a certain size. Step 5: Dry the low-carbon magnesia-carbon brick blank obtained in Step 4, and then subject the dried low-carbon magnesia-carbon brick blank to carbon embedding heat treatment at 1000-1400℃. After cooling, the carbon fiber reinforced low-carbon magnesia-carbon brick for steel ladles is obtained.

[0005] The MgO content in the fused magnesia is not less than 98 wt%, and the particle size of the fused magnesia particles is 0.048–3 mm, while the particle size of the fine fused magnesia powder is less than 0.048 mm.

[0006] The recycled short-cut carbon fiber has a single filament diameter of 8μm, an aspect ratio of 5:1 to 10:1, a carbon content of ≥97%, and a fineness of 50 mesh. This type of carbon fiber has advantages such as good electrical conductivity, low coefficient of linear expansion, and high tensile strength.

[0007] The silicon metal powder has a Si content of ≥98wt% and a particle size of ≤0.045mm.

[0008] The silicon carbide micro powder contains more than 99 wt% SiC and has a particle size of less than 0.045 mm.

[0009] The graphite has a carbon content greater than 95 wt% and a particle size less than 0.038 mm.

[0010] By adopting the above-described technical solutions, the present invention has the following advantages compared with the prior art: 1. The preparation technology used in this invention mainly involves conventional mixing, molding, and heat treatment, with a simple process flow that is easy to implement for industrial production. The fused magnesia particles and fine powder, organic dispersant, graphite, metallic silicon powder, silicon carbide micro powder, liquid phenolic resin, and recycled short-cut carbon fiber used in this invention are all conventional industrial production raw materials. Among them, the proportion of recycled short-cut carbon fiber and organic dispersant is relatively low, resulting in a generally low cost of raw materials. Therefore, this invention has the advantages of a simple process flow and low production cost.

[0011] 2. This invention uniformly disperses recycled short-cut carbon fibers in an organic dispersant and uses carbon fibers as a "carbon" source to replace other forms of carbon addition. This not only gives full play to the characteristics of carbon fiber reinforcement matrix, but also achieves low-carbon preparation, which significantly improves the strength, toughness and thermal shock resistance of magnesia-carbon bricks for steel ladles.

[0012] 3. This invention uses recycled short-cut carbon fibers instead of graphite. Through the action of organic dispersants, the carbon fibers can be uniformly dispersed in the matrix. The process is simple and reduces the use of other impurities, so that the magnesia-carbon bricks for steel ladles achieve the effects of reinforcement and carbon content reduction.

[0013] 4. The low-carbon magnesia-carbon bricks for steel ladles prepared by this invention have a longer service life in practical applications. Compared with similar products, their wear and cracking behavior is significantly reduced under the same number of uses, avoiding the waste of raw materials and energy in production, improving production efficiency and safety, and increasing production benefits for enterprises.

[0014] The low-carbon magnesia-carbon bricks for carbon fiber reinforced steel ladles prepared by this invention were tested and found to have a bulk density of 2.90–3.28 g / cm³. 3 The apparent porosity is 3.6–8.8%; the carbon content is less than or equal to 3 wt%; the compressive strength at room temperature is 40–80 MPa; the flexural strength at room temperature is 10–30 MPa; the flexural strength at high temperature is 15–35 MPa; after six thermal shock tests using the 1100℃ water-cooling method, the strength retention rate is 68–88%; after a high-temperature oxidation resistance test at 1400℃, the decarburized layer thickness is 2.1–3.5 mm; and the steel molten corrosion layer thickness is 0.15–0.45 mm.

[0015] Therefore, the present invention has the characteristics of low production cost, low equipment requirements, simple and easy operation process and good carbon fiber reinforcement effect. The low carbon magnesium carbon brick for steel ladle prepared by the method has the advantages of excellent mechanical properties at room temperature and high temperature, low carbon content, good thermal shock resistance, oxidation resistance and liquid erosion resistance. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments, but this is not intended to limit the scope of protection of the present invention.

[0017] A low-carbon magnesia-carbon brick for steel ladles reinforced with recycled short-cut carbon fibers and its preparation method. The preparation method described in this specific embodiment is as follows: Step 1: Disperse 0.5~1.5wt% of recycled short-cut carbon fibers with an organic dispersant. The organic dispersant prevents the carbon fibers from agglomerating and makes them more uniformly dispersed, ultimately obtaining an organic mixed slurry containing 0.5~1.5wt% of recycled short-cut carbon fibers. Step 2: Mix 85-95 wt% fused magnesia with 3-8 wt% metallic silicon micro powder, 1.0-2.5 wt% graphite, 0.5-3 wt% silicon carbide powder, 3-6 wt% liquid phenolic resin and a mixed slurry containing 0.5-1.5 wt% short-cut carbon fibers to obtain the final mixed raw material for preparing low-carbon magnesia-carbon bricks. Step 3: Allow the mixture described in Step 2 to air-dry for 24 hours to allow the liquid phenolic resin to fully coat the particle surface, thereby increasing the bonding force between particles. Step 4: Pour the mixed material after being trapped in Step 3 directly into the mold, and after pressing, obtain a low-carbon magnesia-carbon brick blank with a certain size. Step 5: Dry the low-carbon magnesia-carbon brick blank obtained in Step 4, and then subject the dried low-carbon magnesia-carbon brick blank to carbon embedding heat treatment at 1000-1400℃. After cooling, the carbon fiber reinforced low-carbon magnesia-carbon brick for steel ladles is obtained.

[0018] The MgO content in the fused magnesia is not less than 98 wt%, and the particle size of the fused magnesia particles is 0.048–3 mm, while the particle size of the fine fused magnesia powder is less than 0.048 mm.

[0019] The recycled short-cut carbon fiber has a single filament diameter of 8μm, an aspect ratio of 5:1 to 10:1, a carbon content of ≥97%, and a fineness of 50 mesh. This type of carbon fiber has advantages such as good electrical conductivity, low coefficient of linear expansion, and high tensile strength.

[0020] The silicon metal powder has a Si content of ≥98wt% and a particle size of ≤0.045mm.

[0021] The silicon carbide micro powder contains more than 99 wt% SiC and has a particle size of less than 0.045 mm.

[0022] The graphite has a carbon content greater than 95 wt% and a particle size less than 0.038 mm.

[0023] The details will not be repeated in the examples. Example 1

[0024] A low-carbon magnesia-carbon brick for steel ladles reinforced with recycled short-cut carbon fibers and its preparation method are described in this embodiment. Step 1: Disperse 0.5-0.7 wt% of recycled short-cut carbon fibers with an organic dispersant. The organic dispersant prevents the carbon fibers from agglomerating, making them more uniformly dispersed, and finally obtaining an organic mixed slurry containing 0.5-0.7 wt% recycled short-cut carbon fibers. Step 2: Mix 85-87 wt% fused magnesia with 7-8 wt% metallic silicon micro powder, 2.2-2.5 wt% graphite, 0.5-1.0 wt% silicon carbide powder, 3.0-3.6 wt% liquid phenolic resin and a mixed slurry containing 0.5-0.7 wt% short-cut carbon fibers to obtain the final mixed raw material for preparing low-carbon magnesia-carbon bricks. Step 3: Allow the mixture described in Step 2 to air-dry for 24 hours to allow the liquid phenolic resin to fully coat the particle surface, thereby increasing the bonding force between particles. Step 4: Pour the mixed material after being trapped in Step 3 directly into the mold, and after pressing, obtain a low-carbon magnesia-carbon brick blank with a certain size. Step 5: Dry the low-carbon magnesia-carbon brick blank obtained in Step 4, and then subject the dried low-carbon magnesia-carbon brick blank to carbon embedding heat treatment at 1000-1080℃. After cooling, the carbon fiber reinforced low-carbon magnesia-carbon brick for steel ladles is obtained.

[0025] The low-carbon magnesia-carbon bricks for steel ladles reinforced with recycled short-cut carbon fibers prepared in this embodiment were tested and found to have a bulk density of 3.16–3.28 g / cm³. 3 The apparent porosity is 3.6–4.6%; the carbon content is less than or equal to 3 wt%; the compressive strength at room temperature is 60–70 MPa; the flexural strength at room temperature is 16–22 MPa; the flexural strength at high temperature is 15–20 MPa; after six thermal shock tests using the 1100℃ water-cooling method, the strength retention rate is 68–78%; after a high-temperature oxidation resistance test at 1400℃, the decarburized layer thickness is 2.1–2.4 mm; and the steel molten corrosion layer thickness is 0.33–0.39 mm. Example 2

[0026] A low-carbon magnesia-carbon brick for steel ladles reinforced with recycled short-cut carbon fibers and its preparation method are described in this embodiment. Step 1: Disperse 0.7-0.9 wt% of recycled short-cut carbon fibers with an organic dispersant. The organic dispersant prevents the carbon fibers from agglomerating, making them more uniformly dispersed, and finally obtaining an organic mixed slurry containing 0.7-0.9 wt% recycled short-cut carbon fibers. Step 2: Mix 87-89 wt% fused magnesia with 6-7 wt% metallic silicon micro powder, 2.0-2.2 wt% graphite, 1.0-1.5 wt% silicon carbide powder, 3.6-4.2 wt% liquid phenolic resin and a mixed slurry containing 0.7-0.9 wt% short-cut carbon fibers to obtain the final mixed raw material for preparing low-carbon magnesia-carbon bricks. Step 3: Allow the mixture described in Step 2 to air-dry for 24 hours to allow the liquid phenolic resin to fully coat the particle surface, thereby increasing the bonding force between particles. Step 4: Pour the mixed material after being trapped in Step 3 directly into the mold, and after pressing, obtain a low-carbon magnesia-carbon brick blank with a certain size. Step 5: Dry the low-carbon magnesia-carbon brick blank obtained in Step 4, and then subject the dried low-carbon magnesia-carbon brick blank to carbon embedding heat treatment at 1080-1160℃. After cooling, the carbon fiber reinforced low-carbon magnesia-carbon brick for steel ladles is obtained.

[0027] The low-carbon magnesia-carbon bricks for steel ladles reinforced with recycled short-cut carbon fibers prepared in this embodiment were tested and found to have a bulk density of 3.08–3.20 g / cm³. 3 The apparent porosity is 4.6–5.6%; the carbon content is less than or equal to 3 wt%; the compressive strength at room temperature is 50–60 MPa; the flexural strength at room temperature is 15–20 MPa; the flexural strength at high temperature is 18–24 MPa; after six thermal shock tests using the 1100℃ water-cooling method, the strength retention rate is 68–80%; after a high-temperature oxidation resistance test at 1400℃, the decarburized layer thickness is 2.4–2.6 mm; and the steel molten corrosion layer thickness is 0.27–0.33 mm. Example 3

[0028] A low-carbon magnesia-carbon brick for steel ladles reinforced with recycled short-cut carbon fibers and its preparation method are described in this embodiment. Step 1: Disperse 0.9~1.1wt% of recycled short-cut carbon fibers with an organic dispersant. The organic dispersant prevents the carbon fibers from agglomerating and makes them more uniformly dispersed, ultimately obtaining an organic mixed slurry containing 0.9~1.1wt% of recycled short-cut carbon fibers. Step 2: Mix 89-91 wt% fused magnesia with 5-6 wt% metallic silicon micro powder, 1.8-2.0 wt% graphite, 1.5-2.0 wt% silicon carbide powder, 4.2-4.8 wt% liquid phenolic resin and a mixed slurry containing 0.9-1.1 wt% short-cut carbon fibers to obtain the final mixed raw material for preparing low-carbon magnesia-carbon bricks. Step 3: Allow the mixture described in Step 2 to air-dry for 24 hours to allow the liquid phenolic resin to fully coat the particle surface, thereby increasing the bonding force between particles. Step 4: Pour the mixed material after being trapped in Step 3 directly into the mold, and after pressing, obtain a low-carbon magnesia-carbon brick blank with a certain size. Step 5: Dry the low-carbon magnesia-carbon brick blank obtained in Step 4, and then subject the dried low-carbon magnesia-carbon brick blank to carbon embedding heat treatment at 1160-1240℃. After cooling, the carbon fiber reinforced low-carbon magnesia-carbon brick for steel ladles is obtained.

[0029] The low-carbon magnesia-carbon bricks for steel ladles reinforced with recycled short-cut carbon fibers prepared in this embodiment were tested and found to have a bulk density of 3.02–3.15 g / cm³. 3 The apparent porosity is 5.6–6.6%; the carbon content is less than or equal to 3 wt%; the compressive strength at room temperature is 65–75 MPa; the flexural strength at room temperature is 20–26 MPa; the flexural strength at high temperature is 22–28 MPa; after six thermal shock tests using the 1100℃ water-cooling method, the strength retention rate is 78–88%; after a high-temperature oxidation resistance test at 1400℃, the decarburized layer thickness is 2.5–2.8 mm; and the steel melt erosion layer thickness is 0.21–0.27 mm. Example 4

[0030] A low-carbon magnesia-carbon brick for steel ladles reinforced with recycled short-cut carbon fibers and its preparation method are described in this embodiment. Step 1: Disperse 1.1~1.3wt% of recycled short-cut carbon fibers with an organic dispersant. The organic dispersant prevents the carbon fibers from agglomerating and makes them more uniformly dispersed, ultimately obtaining an organic mixed slurry containing 1.1~1.3wt% of recycled short-cut carbon fibers. Step 2: Mix 91-93 wt% fused magnesia with 4-5 wt% metallic silicon micro powder, 1.5-1.8 wt% graphite, 2.0-2.5 wt% silicon carbide powder, 4.8-5.4 wt% liquid phenolic resin and a mixed slurry containing 1.1-1.3 wt% short-cut carbon fibers to obtain the final mixed raw material for preparing low-carbon magnesia-carbon bricks. Step 3: Allow the mixture described in Step 2 to air-dry for 24 hours to allow the liquid phenolic resin to fully coat the particle surface, thereby increasing the bonding force between particles. Step 4: Pour the mixed material after being trapped in Step 3 directly into the mold, and after pressing, obtain a low-carbon magnesia-carbon brick blank with a certain size. Step 5: Dry the low-carbon magnesia-carbon brick blank obtained in Step 4, and then subject the dried low-carbon magnesia-carbon brick blank to carbon embedding heat treatment at 1240-1320℃. After cooling, the carbon fiber reinforced low-carbon magnesia-carbon brick for steel ladles is obtained.

[0031] The low-carbon magnesia-carbon bricks for steel ladles reinforced with recycled short-cut carbon fibers prepared in this embodiment were tested and found to have a bulk density of 2.96–3.12 g / cm³. 3 The apparent porosity is 6.6–7.6%; the carbon content is less than or equal to 3 wt%; the compressive strength at room temperature is 70–80 MPa; the flexural strength at room temperature is 24–30 MPa; the flexural strength at high temperature is 28–35 MPa; after six thermal shock tests using the 1100℃ water-cooling method, the strength retention rate is 74–84%; after a high-temperature oxidation resistance test at 1400℃, the decarburized layer thickness is 2.8–3.2 mm; and the thickness of the molten steel erosion layer is 0.15–0.21 mm. Example 5

[0032] A low-carbon magnesia-carbon brick for steel ladles reinforced with recycled short-cut carbon fibers and its preparation method are described in this embodiment. Step 1: Disperse 1.3~1.5wt% of recycled short-cut carbon fibers with an organic dispersant. The organic dispersant prevents the carbon fibers from agglomerating and makes them more uniformly dispersed, ultimately obtaining an organic mixed slurry containing 1.3~1.5wt% recycled short-cut carbon fibers. Step 2: Mix 93-95 wt% fused magnesia with 3-4 wt% metallic silicon micro powder, 1.0-1.5 wt% graphite, 2.5-3.0 wt% silicon carbide powder, 5.4-6.0 wt% liquid phenolic resin and a mixed slurry containing 1.3-1.5 wt% short-cut carbon fibers to obtain the final mixed raw material for preparing low-carbon magnesia-carbon bricks. Step 3: Allow the mixture described in Step 2 to air-dry for 24 hours to allow the liquid phenolic resin to fully coat the particle surface, thereby increasing the bonding force between particles. Step 4: Pour the mixed material after being trapped in Step 3 directly into the mold, and after pressing, obtain a low-carbon magnesia-carbon brick blank with a certain size. Step 5: Dry the low-carbon magnesia-carbon brick blank obtained in Step 4, and then subject the dried low-carbon magnesia-carbon brick blank to carbon embedding heat treatment at 1320-1400℃. After cooling, the carbon fiber reinforced low-carbon magnesia-carbon brick for steel ladles is obtained.

[0033] The low-carbon magnesia-carbon bricks for steel ladles reinforced with recycled short-cut carbon fibers prepared in this embodiment were tested and found to have a bulk density of 2.90–3.01 g / cm³. 3 The apparent porosity is 7.6–8.8%; the carbon content is less than or equal to 3 wt%; the compressive strength at room temperature is 40–50 MPa; the flexural strength at room temperature is 10–15 MPa; the flexural strength at high temperature is 20–30 MPa; after six thermal shock tests using the 1100℃ water-cooling method, the strength retention rate is 66–76%; after a high-temperature oxidation resistance test at 1400℃, the decarburized layer thickness is 3.2–3.5 mm; and the thickness of the molten steel erosion layer is 0.38–0.45 mm.

[0034] The preparation method of this comparative example is the same as that of Example 1, except that recycled short-cut carbon fibers are not added.

[0035] The low-carbon magnesia-carbon bricks for steel ladles prepared in this comparative example, containing organic dispersants, were tested and found to have a bulk density of 2.85–3.05 g / cm³. 3 The apparent porosity is 6.8–8.8%; the carbon content is less than or equal to 3 wt%; the compressive strength at room temperature is 35–45 MPa; the flexural strength at room temperature is 10–15 MPa; the flexural strength at high temperature is 8–12 MPa; after six thermal shock tests using the 1100℃ water-cooling method, the strength retention rate is 58–68%; after a high-temperature oxidation resistance test at 1400℃, the decarburized layer thickness is 3.2–4.2 mm; and the thickness of the molten steel erosion layer is 0.38–0.48 mm.

[0036] The preparation method for this comparative example is the same as that in Example 1, except that no organic dispersant is added.

[0037] The low-carbon magnesia-carbon bricks for steel ladles containing recycled short-cut carbon fibers prepared in this comparative example were tested and found to have a bulk density of 2.75–2.95 g / cm³. 3 The apparent porosity is 7.0–9.0%; the carbon content is less than or equal to 3 wt%; the compressive strength at room temperature is 30–40 MPa; the flexural strength at room temperature is 8–12 MPa; the flexural strength at high temperature is 6–10 MPa; after six thermal shock tests using the 1100℃ water-cooling method, the strength retention rate is 50–60%; after a high-temperature oxidation resistance test at 1400℃, the decarburized layer thickness is 3.5–4.5 mm; and the thickness of the molten steel erosion layer is 0.40–0.50 mm.

[0038] The preparation method of this comparative example is the same as that of Example 1, except that recycled short-cut carbon fibers and organic dispersants are not added.

[0039] The low-carbon magnesia-carbon bricks for steel ladles prepared in this comparative example were tested and found to have a bulk density of 2.70–2.90 g / cm³. 3The apparent porosity is 8.0–10%; the carbon content is less than or equal to 3 wt%; the compressive strength at room temperature is 40–50 MPa; the flexural strength at room temperature is 12–18 MPa; the flexural strength at high temperature is 10–15 MPa; after six thermal shock tests using the 1100℃ water-cooling method, the strength retention rate is 60–70%; after a high-temperature oxidation resistance test at 1400℃, the decarburized layer thickness is 3.0–4.0 mm; and the molten steel erosion layer thickness is 0.35–0.45 mm.

[0040] The recycled short-cut carbon fiber reinforced low-carbon magnesia-carbon bricks for steel ladles and their preparation methods described in Examples 1-5 of this invention not only possess high strength, good toughness, excellent thermal shock resistance, oxidation resistance, and erosion resistance, but also have the advantages of low carbon content and long service life. Example 4 shows that when 1.1~1.3 wt% of recycled short-cut carbon fiber is introduced, the overall performance of the low-carbon magnesia-carbon bricks for steel ladles reaches the optimal effect. Comparative Example 1 shows that when recycled short-cut carbon fiber is not added, the strength, toughness, thermal shock resistance, and erosion resistance of the low-carbon magnesia-carbon bricks for steel ladles will significantly decrease. Comparative Example 2 shows that when no organic dispersant is added, the performance of the low-carbon magnesia-carbon bricks for steel ladles with only carbon fiber added is not significantly improved. Meanwhile, Comparative Example 3 shows that when neither organic dispersant nor recycled short-cut carbon fiber is added, the performance of the resulting low-carbon magnesia-carbon bricks for steel ladles is better, but still significantly lower than that of Examples 1-4. Therefore, the present invention has the characteristics of low production cost, low equipment requirements, simple and easy operation process and good carbon fiber reinforcement effect. The low carbon magnesium carbon brick for steel ladle prepared by the method has the advantages of excellent mechanical properties at room temperature and high temperature, low carbon content, good thermal shock resistance, oxidation resistance and erosion resistance.

[0041] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-carbon magnesia-carbon brick for steel ladles reinforced with recycled short-cut carbon fibers and its preparation method, characterized in that... Includes the following steps: Step 1: Disperse 0.5~1.5wt% of recycled short-cut carbon fibers with an organic dispersant. The organic dispersant prevents the carbon fibers from agglomerating and makes them more uniformly dispersed, ultimately obtaining an organic mixed slurry containing 0.5~1.5wt% of recycled short-cut carbon fibers. Step 2: Mix 85-95 wt% fused magnesia with 3-8 wt% metallic silicon micro powder, 1.0-2.5 wt% graphite, 0.5-3 wt% silicon carbide powder, 3-6 wt% liquid phenolic resin and a mixed slurry containing 0.5-1.5 wt% short-cut carbon fibers to obtain the final mixed raw material for preparing low-carbon magnesia-carbon bricks. Step 3: Allow the mixture described in Step 2 to air-dry for 24 hours to allow the liquid phenolic resin to fully coat the particle surface, thereby increasing the bonding force between particles. Step 4: Pour the mixed material after being trapped in Step 3 directly into the mold, and after pressing, obtain a low-carbon magnesia-carbon brick blank with a certain size. Step 5: Dry the low-carbon magnesia-carbon brick blank obtained in Step 4, and then subject the dried low-carbon magnesia-carbon brick blank to carbon embedding heat treatment at 1000-1400℃. After cooling, the carbon fiber reinforced low-carbon magnesia-carbon brick for steel ladles is obtained.

2. The method for preparing low-carbon magnesia-carbon bricks for carbon fiber reinforced steel ladles according to claim 1, characterized in that... The MgO content in the fused magnesia is not less than 98 wt%, and the particle size of the fused magnesia particles is 0.048–3 mm, while the particle size of the fine fused magnesia powder is less than 0.048 mm.

3. The method for preparing low-carbon magnesium-carbon bricks for carbon fiber reinforced steel ladles according to claim 1, wherein the recycled short-cut carbon fiber has a single filament diameter of 8 μm, an aspect ratio of 5:1 to 10:1, a carbon content of ≥97%, and a fineness of 50 mesh. This type of carbon fiber has advantages such as good electrical conductivity, low coefficient of linear expansion, and high tensile strength.

4. The method for preparing low-carbon magnesium-carbon bricks for carbon fiber reinforced steel ladles according to claim 1, wherein the Si content of the metallic silicon micropowder is greater than or equal to 98 wt%, and the particle size of the metallic silicon micropowder is less than 0.045 mm.

5. The method for preparing low-carbon magnesium-carbon bricks for carbon fiber reinforced steel ladles according to claim 1, wherein the silicon carbide micro powder has a SiC content greater than 99 wt% and a particle size of less than 0.045 mm.

6. The method for preparing low-carbon magnesia-carbon bricks for carbon fiber reinforced steel ladles according to claim 1, wherein the C content of the graphite is greater than 95 wt% and the particle size of the graphite is less than 0.038 mm.

7. A method for preparing low-carbon magnesia-carbon bricks for steel ladles using recycled short-cut carbon fibers, characterized in that... The prepared low-carbon brick for carbon fiber reinforced steel ladles is prepared according to any one of claims 1 to 6.