Tundish casting material and preparation method thereof

Abstract

The application belongs to the technical field of refractory materials, and provides a tundish castable and a preparation method thereof.The tundish castable comprises the following components in parts by weight: bauxite clinker 54-57 parts, coke 23.5-25 parts, kyanite powder 3.8-4.2 parts, alpha-alumina micropowder 3-3.2 parts, high-aluminum cement 4.7-5.2 parts, silica ash 6.8-7.3 parts and lithium-doped magnesium oxide nano powder 2.7-3 parts.The application increases the amount / content of silica ash, reduces the apparent porosity of the prepared sample after 1400 DEG C heat treatment, and further improves the strength.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, and in particular relates to an intermediate ladle castable and its preparation method. Background Technology

[0002] The tundish, as a container for holding molten steel in the steelmaking process, has evolved from a simple storage and distribution vessel into a reactor with metallurgical functions such as preventing secondary oxidation of the molten steel, removing impurities to purify the steel, and enabling microalloying. The tundish's construction structure generally consists of three layers: an insulation layer, a permanent lining, and a working lining. The permanent lining area has limited construction space, and the inner wall of the tundish shell is usually equipped with anchoring devices, preventing vibratory equipment from penetrating deeply. Therefore, the use of ordinary vibratory castables is limited. Currently, the permanent lining in the domestic and international markets is generally made of high-alumina, low-cement self-flowing castable, cast as a single piece.

[0003] It is known in existing technology that silica fume (microsilica / silica powder) has small particle size, large surface area, and high reactivity. In the preparation of high-alumina, low-cement self-flowing castables for permanent lining of tundishes, adding an appropriate amount of silica fume can significantly improve the flowability of the castable, reduce its water demand, and improve its density and post-firing strength. With the increase of silica fume addition within a certain range, the filling effect and water-reducing properties of silica fume continuously improve, resulting in a continuous decrease in apparent porosity after heat treatment at 1400℃. Furthermore, with the increase of silica fume addition, the amount of mullite formed in the matrix after heat treatment at 1400℃ increases, leading to improved strength.

[0004] However, when the amount of silica fume added increases excessively, the content of fine Al2O3 powder in the matrix becomes relatively smaller, and the amount of residual quartz increases, which hinders the bonding performance of mullite needle-like crystals. The increase in residual quartz causes the material to expand excessively, increasing internal stress and causing cracks to form inside the material, which in turn leads to a decrease in the strength of the sample. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes an intermediate ladle castable and its preparation method. By increasing the amount / content of silica fume, the apparent porosity of the obtained sample after heat treatment at 1400℃ is reduced, while its strength is further improved.

[0006] To achieve the above objectives, in a first aspect, the present invention provides an intermediate ladle castable, comprising, by weight, the following components: 54-57 parts of bauxite clinker, 23.5-25 parts of calcined bauxite, 3.8-4.2 parts of kyanite powder, 3-3.2 parts of α-alumina micro powder, 4.7-5.2 parts of high-alumina cement, 6.8-7.3 parts of silica fume, and 2.7-3 parts of lithium-doped magnesium oxide nanoparticles.

[0007] Furthermore, the preparation method of the lithium-doped magnesium oxide nanopowder is as follows:

[0008] Step 1: Dissolve 23-24g of magnesium nitrate hexahydrate in 250mL of distilled water to obtain a magnesium nitrate solution; dissolve 18.5-19.2g of citric acid in 250mL of distilled water to obtain a citric acid solution.

[0009] Step 2: Add 0.27-0.31g of lithium nitrate to the magnesium nitrate solution obtained in Step 1, stir on a magnetic stirrer for two minutes, then add the citric acid solution obtained in Step 1, and then add 5-7g of template agent. In a water bath at 80±2℃ for 3-4 hours, it first becomes a sol, and then a gel.

[0010] Step 3: Place the gel obtained in Step 2 into a muffle furnace and calcine it to obtain lithium-doped magnesium oxide nanopowder.

[0011] Furthermore, in step two, the template agent is PEG2000.

[0012] Furthermore, in step three, the specific operation of the heat calcination treatment is as follows: first heat-treat at 150±5℃ for 1-1.5h, and then calcinate at 600±10℃ in air for 1-1.2h.

[0013] Furthermore, the particle size of the bauxite clinker is <5mm.

[0014] Furthermore, in the bauxite clinker, the mass percentage of particles with a diameter ≤0.074mm is 1 / 5 to 1 / 4.

[0015] Furthermore, the particle size of the fused gemstone is 0.074-5 mm.

[0016] Furthermore, the particle size of the kyanite powder is 180 mesh.

[0017] In a second aspect, the present invention provides a method for preparing the above-mentioned intermediate ladle castable, comprising the following steps: mixing bauxite clinker, coke, kyanite powder, α-alumina micro powder, high-alumina cement, silica fume and lithium-doped magnesium oxide nanopowder evenly to obtain the intermediate ladle castable.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] In the preparation of the tundish castable of the present invention, a high dosage / content of silica fume is used to better exert its filling effect and water reduction performance, so as to reduce the apparent porosity of the tundish castable sample (1400℃×3h) and increase the introduction of lithium-doped magnesium oxide nanopowder.

[0020] On the one hand, at 1400℃, lithium-doped magnesium oxide nanopowder induces the formation of a small amount of liquid phase in the system. The liquid phase has good fluidity and can better flow / penetrate into the microcracks inside the material caused by excessive silica fume. On the other hand, lithium doping can change the reaction path between the nano-magnesium oxide and the matrix, generating a more significant and dense phase (such as reacting with SiO2 and Al2O3 to form lithium magnesium aluminum spinel), which effectively compensates / fills the microcracks and plays a "strong bonding" role. In turn, it synergistically improves the room temperature flexural strength of the intermediate ladle casting sample (1400℃×3h). Attached Figure Description

[0021] Figure 1 This is a comparison chart of the apparent porosity and room temperature flexural strength data of the tundish casting samples (1400℃×3h) of Examples 1-3 and Comparative Examples 1-4 in the test examples of this invention. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0024] Example 1: (a) The preparation method of lithium-doped magnesium oxide nanopowder is as follows:

[0025] Step 1: Dissolve 23.5g of magnesium nitrate hexahydrate in 250mL of distilled water to obtain a magnesium nitrate solution; dissolve 19g of citric acid in 250mL of distilled water to obtain a citric acid solution.

[0026] Step 2: Add 0.3g of lithium nitrate to the magnesium nitrate solution obtained in Step 1, place it on a magnetic stirrer and stir at 300r / min for 2min, then add the citric acid solution obtained in Step 1, and then add 6g of template agent PEG2000. In an 80℃ water bath, it first becomes a sol and then a gel.

[0027] Step 3: Place the gel obtained in Step 2 into a muffle furnace, heat-treat it at 150°C for 1.2 hours, and then calcine it at 600°C for 1 hour in air to obtain lithium-doped magnesium oxide nanopowder.

[0028] (II) The preparation method of tundish castable is as follows: by weight, 55 parts of bauxite clinker, 24 parts of charcoal, 4 parts of kyanite powder, 3.1 parts of α-alumina micro powder, 5 parts of high-alumina cement, 7 parts of silica fume and 2.9 parts of lithium-doped magnesium oxide nanoparticles are dry mixed evenly to obtain tundish castable.

[0029] The bauxite clinker includes fine powder with a particle size ≤0.074mm and medium powder with a particle size of 0.074-5mm; and the mass proportion of fine powder with a particle size ≤0.074mm in the bauxite clinker is 1 / 5. Specifically, there are 11 parts of fine powder and 44 parts of medium powder.

[0030] The particle size of the calcined alumina is 0.074-5mm. The particle size of the kyanite powder is 180 mesh. The high-alumina cement is specifically 625 cement.

[0031] Example 2: The difference between this example and Example 1 is that the preparation method of the tundish castable is as follows: by weight, 54 parts of bauxite clinker, 23.5 parts of calcined bauxite, 3.8 parts of kyanite powder, 3 parts of α-alumina micro powder, 4.7 parts of high-alumina cement, 6.8 parts of silica fume and 2.7 parts of lithium-doped magnesium oxide nanoparticles are dry mixed evenly to obtain the tundish castable.

[0032] Example 3: The difference between this example and Example 1 is that the preparation method of the tundish castable is as follows: by weight, 57 parts of bauxite clinker, 25 parts of charcoal, 4.2 parts of kyanite powder, 3.2 parts of α-alumina micro powder, 5.2 parts of high-alumina cement, 7.3 parts of silica fume and 3 parts of lithium-doped magnesium oxide nanopowder are dry mixed evenly to obtain the tundish castable.

[0033] Comparative Example 1: The difference between this comparative example and Example 1 is that in the preparation of the intermediate ladle casting material, the silica fume was reduced from 7 parts to 5 parts, and the bauxite clinker was increased from 55 parts to 57 parts (specifically, the fine powder was increased from 11 parts to 13 parts); and lithium-doped magnesium oxide nanopowder was not added.

[0034] Specifically, the preparation method of the tundish castable is as follows: by weight, 57 parts of bauxite clinker, 24 parts of charcoal, 4 parts of kyanite powder, 3.1 parts of α-alumina micro powder, 5 parts of high-alumina cement and 5 parts of silica fume are dry-mixed evenly to obtain the tundish castable.

[0035] Among them, bauxite clinker includes fine powder with a particle size ≤0.074mm and medium powder with a particle size of 0.074-5mm; 13 parts of fine powder and 44 parts of medium powder.

[0036] Comparative Example 2: The difference between this comparative example and Example 1 is that in the preparation of the intermediate ladle casting material, the silica fume was reduced from 7 parts to 6 parts, and the bauxite clinker was increased from 55 parts to 56 parts (specifically, the fine powder was increased from 11 parts to 12 parts); and lithium-doped magnesium oxide nanoparticles were not added.

[0037] Specifically, the preparation method of the tundish castable is as follows: by weight, 56 parts of bauxite clinker, 24 parts of charcoal, 4 parts of kyanite powder, 3.1 parts of α-alumina micro powder, 5 parts of high-alumina cement and 6 parts of silica fume are dry-mixed evenly to obtain the tundish castable.

[0038] Among them, bauxite clinker includes fine powder with a particle size ≤0.074mm and medium powder with a particle size of 0.074-5mm; 12 parts of fine powder and 44 parts of medium powder.

[0039] Comparative Example 3: The difference between this comparative example and Example 1 is that lithium-doped magnesium oxide nanopowder is not added in the preparation of the intermediate ladle casting material.

[0040] Specifically, the preparation method of the tundish castable is as follows: by weight, 55 parts of bauxite clinker, 24 parts of charcoal, 4 parts of kyanite powder, 3.1 parts of α-alumina micro powder, 5 parts of high-alumina cement and 7 parts of silica fume are dry-mixed evenly to obtain the tundish castable.

[0041] Among them, bauxite clinker includes fine powder with a particle size ≤0.074mm and medium powder with a particle size of 0.074-5mm; 11 parts of fine powder and 44 parts of medium powder.

[0042] Comparative Example 4: The difference between this comparative example and Example 1 is that in the preparation of the intermediate ladle casting material, the silica fume was reduced from 7 parts to 6 parts, and the bauxite clinker was increased from 55 parts to 56 parts (specifically, the fine powder was increased from 11 parts to 12 parts).

[0043] Specifically, the preparation method of the tundish castable is as follows: by weight, 56 parts of bauxite clinker, 24 parts of charcoal, 4 parts of kyanite powder, 3.1 parts of α-alumina micro powder, 5 parts of high-alumina cement, 6 parts of silica fume and 2.9 parts of lithium-doped magnesium oxide nanoparticles are dry-mixed evenly to obtain the tundish castable.

[0044] Among them, bauxite clinker includes fine powder with a particle size ≤0.074mm and medium powder with a particle size of 0.074-5mm; 12 parts of fine powder and 44 parts of medium powder.

[0045] Experimental Example: 7% by weight of water was added to the intermediate ladle castables prepared in Examples 1-3 and Comparative Examples 1-4, respectively. After thorough mixing, the mixture was vibrated and cast into strip-shaped specimens of 40mm×40mm×160mm. After curing at room temperature for 24 hours, the specimens were demolded and then naturally cured for another 24 hours. They were then dried at 110℃ for 24 hours, followed by heat treatment at 1400℃ for 3 hours. The heat-treated strip-shaped specimens were then tested for ① apparent porosity and ② flexural strength at room temperature. Test results are shown in Table 1.

[0046] Table 1. Test Results Data for Experimental Cases

[0047] Apparent porosity (%) Flexural strength at room temperature (MPa) Example 1 16.5 17.7 Example 2 16.7 17.6 Example 3 16.6 17.6 Comparative Example 1 17.8 16.6 Comparative Example 2 17.1 17.3 Comparative Example 3 16.7 16.9 Comparative Example 4 17.1 17.2

[0048] Results Analysis: Combining the data in Table 1 and... Figure 1 Analysis of Examples 1-3 shows that the apparent porosity of the intermediate ladle casting sample (1400℃×3h) prepared by the present invention is as low as 16.7%, and the room temperature flexural strength is as high as 17.6MPa or more.

[0049] Combining the data in Table 1 and Figure 1 Analysis of Example 1 and Comparative Examples 1-4, specifically comparing Comparative Examples 1, 2 and 3, shows that as the amount of silica fume added increases (5 parts → 6 parts → 7 parts), the apparent porosity of the intermediate ladle casting sample (1400℃×3h) continuously decreases, while the room temperature flexural strength first increases and then decreases.

[0050] This is mainly because, regarding apparent porosity, as the amount of silica fume increases, the filling effect and water-reducing properties of silica fume continuously improve, thus continuously reducing the apparent porosity of the sample after heat treatment at 1400℃. Regarding room temperature flexural strength, as the amount of silica fume increases, more mullite is formed in the matrix after heat treatment at 1400℃, increasing the room temperature flexural strength. However, when the amount of silica fume increases excessively (more than 6 parts in this invention), the content of fine Al2O3 powder in the matrix relatively decreases, and the amount of residual quartz increases, hindering the bonding performance of mullite needle-like crystals. The increased residual quartz causes excessive expansion of the material, increasing internal stress and leading to internal cracks, which in turn reduces the room temperature flexural strength.

[0051] Specifically, by comparing Comparative Example 2 and Comparative Example 4, it can be seen that compared with Comparative Example 2 (6 parts of silica fume), Comparative Example 4, by introducing lithium-doped magnesium oxide nanopowder of the present invention, showed no significant change in apparent porosity and room temperature flexural strength of the intermediate ladle casting sample (1400℃×3h).

[0052] Comparing Comparative Example 3 and Example 1, it can be seen that, compared to Comparative Example 3 (7 parts silica fume), Example 1, with the addition of the lithium-doped magnesium oxide nanopowder of the present invention, did not show a significant change in the apparent porosity of the tundish casting sample (1400℃×3h), but the room temperature flexural strength was significantly improved. This indicates that a higher silica fume content (7 parts) is beneficial for further reducing the apparent porosity of the tundish casting sample (1400℃×3h); at the same time, the addition of lithium-doped magnesium oxide nanopowder can synergistically improve the room temperature flexural strength of the tundish casting sample (1400℃×3h).

[0053] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A type of tundish castable, characterized in that, By weight, it includes the following components: 54-57 parts of bauxite clinker, 23.5-25 parts of calcined bauxite, 3.8-4.2 parts of kyanite powder, 3-3.2 parts of α-alumina micro powder, 4.7-5.2 parts of high-alumina cement, 6.8-7.3 parts of silica fume, and 2.7-3 parts of lithium-doped magnesium oxide nanoparticles.

2. The tundish castable according to claim 1, characterized in that, The preparation method of the lithium-doped magnesium oxide nanopowder is as follows: Step 1: Dissolve 23-24g of magnesium nitrate hexahydrate in 250mL of distilled water to obtain a magnesium nitrate solution; dissolve 18.5-19.2g of citric acid in 250mL of distilled water to obtain a citric acid solution. Step 2: Add 0.27-0.31g of lithium nitrate to the magnesium nitrate solution obtained in Step 1, stir, then add the citric acid solution obtained in Step 1, and then add 5-7g of template agent. In a water bath at 80±2℃, the mixture first becomes a sol and then a gel. Step 3: Place the gel obtained in Step 2 into a muffle furnace and calcine it to obtain lithium-doped magnesium oxide nanopowder.

3. The tundish castable according to claim 2, characterized in that, In step two, the template agent is PEG2000.

4. The tundish castable according to claim 2, characterized in that, In step three, the specific operation of the heat calcination treatment is as follows: first heat treatment at 150±5℃ for 1-1.5h, and then calcination at 600±10℃ for 1-1.2h.

5. The tundish castable according to claim 1, characterized in that, The particle size of the bauxite clinker is <5mm.

6. The tundish castable according to claim 5, characterized in that, In the bauxite clinker, the mass percentage of particles with a diameter ≤0.074mm is 1 / 5 to 1 / 4.

7. The tundish castable according to claim 1, characterized in that, The particle size of the fused gemstone is 0.074-5 mm.

8. The tundish castable according to claim 1, characterized in that, The kyanite powder has a particle size of 180 mesh.

9. A method for preparing the intermediate ladle castable as described in any one of claims 1-8, characterized in that, The process includes the following steps: mixing bauxite clinker, coke, kyanite powder, α-alumina micro powder, high-alumina cement, silica fume, and lithium-doped magnesium oxide nanoparticles evenly to obtain the intermediate ladle castable.

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