Tundish prefabricated part and preparation method thereof

Abstract

The invention belongs to the technical field of refractory materials. The invention provides a tundish prefabricated member and a preparation method of the tundish prefabricated member. The preparation method comprises the following steps: uniformly mixing 37 to 39 parts of mullite, 24.5 to 26.5 parts of flint clay, 21 to 22 parts of alumina fine powder, 3 to 3.5 parts of activated alumina micro powder, 3 to 3.5 parts of quartz fine powder, 5.7 to 6.5 parts of fused magnesia fine powder, 4.8 to 5.3 parts of silicon dioxide micro powder, 2.5 to 2.8 parts of titanium aluminum carbide, 4 to 4.5 parts of acid-washed silicon nitride and 0.2 to 0.25 part of a water reducing agent to obtain a dry mixture; s2, adding 13-14.5 parts of water into the dry mixture, and continuously stirring to obtain a castable; and S3, pouring the castable into a mold, naturally curing for 24 hours, demolding, curing for 24 hours, and drying, thereby obtaining the product. According to the method disclosed by the invention, the thermal-state breaking strength at 1400 DEG C is improved while excellent thermal-state breaking strength at 1200 DEG C of the prepared (tundish permanent lining) castable sample is ensured.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, and in particular relates to a tundish preform and its preparation method. Background Technology

[0002] The permanent lining of the tundish is an important structure of the tundish prefabrication. At present, most steel plants adopt the integral casting method for the permanent lining of the continuous casting tundish. This method can save labor, reduce labor intensity, improve construction efficiency, reduce material consumption, enhance the corrosion resistance of the lining, and improve the service life of the tundish.

[0003] In existing technologies, lightweight mullite and high-grade coke particles are used as aggregates, and high-grade bauxite powder, activated alumina (α-Al2O3) micro powder, quartz powder, and binders are used as the matrix for the tundish permanent lining casting. For the tundish permanent lining, the operating temperature is generally below 1300℃, meaning it mainly operates at medium to low temperatures. However, its surface temperature can reach 1400℃ for short periods, and localized high-temperature areas in the slag line zone may exceed 1400℃.

[0004] When fused magnesia powder and silica powder are selected as the binder, cordierite is formed in large quantities at 1200℃, and magnesium aluminum spinel also begins to form at this temperature. The formation of these new phases provides the sample with high strength, resulting in excellent hot flexural strength of the castable sample at 1200℃. However, when the temperature rises to 1400℃, cordierite begins to decompose. Although spinel has formed in large quantities at this time, excessive liquid phase appears inside the material, and the hot flexural strength of the sample decreases significantly. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a tundish preform and its preparation method, using fused magnesia fine powder and silica micro powder as a bonding system to ensure that the prepared (tundish permanent lining) castable sample exhibits excellent hot flexural strength at 1200℃ while simultaneously improving its hot flexural strength at 1400℃.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing an intermediate liner preform, comprising the following steps: S1. By weight, mix 37-39 parts of mullite, 24.5-26.5 parts of calcined alumina, 21-22 parts of bauxite powder, 3-3.5 parts of activated alumina powder, 3-3.5 parts of quartz powder, 5.7-6.5 parts of fused magnesia powder, 4.8-5.3 parts of silica powder, 2.5-2.8 parts of aluminum titanium carbide, 4-4.5 parts of acid-washed silicon nitride, and 0.2-0.25 parts of water-reducing agent to obtain a dry mixture; S2. Add 13-14.5 parts of water to the dry mixture obtained in S1, and continue stirring for 2-3 minutes to obtain the casting refractory. S3. Pour the casting material into the mold, let it cure naturally for 24 hours, then demold it, cure it for another 24 hours, and then dry it at 110℃ for 24 hours to obtain the intermediate ladle preform.

[0007] Furthermore, the preparation method of the aluminum titanium carbide is as follows: A1. Put titanium carbide powder, metallic titanium powder, aluminum powder and silicon powder into a plastic container and mix them well to obtain a mixture; A2. Under argon protection, the mixture obtained in A1 is loaded into a graphite mold, heated, and hot-pressed for sintering to obtain the aluminum titanium carbide.

[0008] Further, in A1, the molar ratio of titanium carbide powder, metallic titanium powder, aluminum powder and silicon powder is 2:1:(1.0-1.1):(0.18-0.23).

[0009] Furthermore, in A2, the heating rate is 50±2℃ / min.

[0010] Furthermore, in A2, the sintering temperature is 1350-1450℃, the holding time is 2-3h, and the hot pressing pressure is 30±0.5MPa.

[0011] Furthermore, the preparation method of the pickled silicon nitride is as follows: silicon nitride powder is placed in hydrochloric acid solution for acidification treatment, then filtered and washed with deionized water until the washing solution is neutral, and then dried to obtain the pickled silicon nitride.

[0012] Furthermore, the concentration of the hydrochloric acid solution is 0.01-0.012 mol / L.

[0013] Furthermore, the water-reducing agent is sodium tripolyphosphate.

[0014] Secondly, the present invention provides an intermediate package preform, which is prepared by the above-described preparation method.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. In the preparation of the intermediate tundish preform of the present invention, pickled silicon nitride and aluminum titanium carbide are introduced simultaneously. On the one hand, silicon nitride preferentially reacts with O2 at 1400°C, consumes the partial pressure of oxygen in the environment, inhibits the oxidation process of aluminum titanium carbide, and weakens or even offsets the negative impact of adding aluminum titanium carbide alone. On the other hand, in the locally inert atmosphere created by silicon nitride, titanium aluminum carbide undergoes controlled decomposition, precipitating nano-sized TiC particles and metallic Al. TiC has extremely high hardness (close to diamond) and excellent high-temperature stability, serving as a hard support point uniformly distributed in the matrix. Metallic Al can react with silicon nitride to generate needle-like AlN crystals, forming a solid solution with Al2O3 in the matrix, strengthening the continuity of the matrix. TiC particles and AlN crystals intertwine to form a three-dimensional network skeleton that penetrates the gaps between aggregates, connecting mullite and spinel particles into a whole, effectively transferring the load to the entire material system; thereby synergistically improving the hot flexural strength.

[0016] 2. The silicon nitride introduced in this invention preferentially reacts with O2 at 1400℃ to generate SiO2. SiO2 itself can form an aluminosilicate glass phase with excess Al2O3 in the matrix, and its viscosity increases exponentially with the increase of SiO2 content. This transforms the harmful liquid phase into a rigid binder phase. The high-viscosity binder phase fills the pores and coats the aggregate particles, weakening the void defects. The generated SiO2 can also coat the surface of cordierite particles, isolating them from direct contact with slag and atmosphere, blocking the decomposition path caused by chemical corrosion. The unreacted silicon nitride particles can also act as inert fillers, filling the gaps between aggregates and inhibiting liquid phase penetration, thereby improving the hot flexural strength.

[0017] 3. The silicon nitride introduced in this invention is acid-washed silicon nitride. As is well known, the surface of silicon nitride particles contains a certain density of silanol groups. When exposed to water (in the preparation of casting materials), they often form an immovable water molecule layer on the surface of the silicon nitride particles through hydrogen bonding. The surface of unwashed silicon nitride powder contains more silanol groups, so it is easy to form a multi-water molecule adsorption layer on the powder surface. However, after acid washing, the oxidation degree of the silicon nitride powder surface is reduced, and the density of silanol groups is relatively reduced. Therefore, it is easy to form a single water molecule adsorption layer on the powder surface, which can maintain good lubricity and fluidity, and is conducive to further improving its own effect and synergistic effect. Attached Figure Description

[0018] Figure 1 This is a comparative trend chart of the flexural strength data of the castable samples prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention at 1400℃. Figure 2 This is a comparative trend chart showing the flexural strength data of the castable samples prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention at 1200℃. Detailed Implementation

[0019] 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.

[0020] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0021] Example 1: (a) Preparation of aluminum titanium carbide, the preparation method is as follows: A1. Put titanium carbide powder, metallic titanium powder, aluminum powder and silicon powder into a plastic container at a molar ratio of 2:1:1.05:0.21 and mix well to obtain a mixture.

[0022] A2. The mixture obtained in A1 is placed into a graphite mold and heated to 1400°C at a heating rate of 50°C / min under argon protection. Hot pressing sintering is then carried out at a pressure of 30 MPa and the temperature is maintained for 2.5 hours to obtain aluminum titanium carbide.

[0023] Titanium carbide powder (content ≥99.9%, type IiC) was purchased from Shanghai Jinxindun Metal Materials Technology Co., Ltd. Titanium metal powder (content ≥99.7%, type KN-Ti) and silicon powder (content ≥99.9%, type KN-Si) were both purchased from Keneng (Xi'an) Materials Technology Co., Ltd. Aluminum powder (content 97-99.5%) was purchased from Zhengzhou Jinxiang Aluminum Co., Ltd.

[0024] (II) Preparation of pickled silicon nitride, the preparation method is as follows: Silicon nitride (powder) is placed in a hydrochloric acid solution with a concentration of 0.011 mol / L, the solid-liquid ratio is 1:10 (W / V), and stirred at 300 rpm for 50 min at room temperature. Then it is filtered and washed with deionized water until the washing solution is neutral (pH=7.0), and then dried at 100℃ for 8 h to obtain pickled silicon nitride.

[0025] Among them, silicon nitride (content ≥99%, model KN-Si3N4) was purchased from Keneng (Xi'an) Materials Technology Co., Ltd.

[0026] (III) A method for preparing an intermediate tundish preform, comprising the following steps: S1. By weight, mix 38 parts of light mullite, 25.5 parts of premium calcined alumina, 21.5 parts of premium bauxite powder, 3.2 parts of activated alumina (α-Al2O3) micro powder, 3.2 parts of quartz powder, 6.1 parts of fused magnesia powder, 5.1 parts of silica powder, 2.7 parts of aluminum titanium carbide, 4.2 parts of acid-washed silicon nitride, and 0.23 parts of water-reducing agent to obtain a dry mixture.

[0027] S2. Add 13.8 parts of water to the dry mixture obtained in S1 and continue stirring for 2.5 minutes to obtain the casting refractory.

[0028] S3. Pour the castable into the mold, with a specific casting size of 160mm×40mm×40mm. After natural curing for 24 hours, demold and then cure for another 24 hours. After drying at 110℃ for 24 hours, the tundish precast part (castable sample) is obtained.

[0029] The composition includes: lightweight mullite (60% by weight of particles <1mm, 40% by weight of particles 1-3mm); premium grade calcined alumina (70% by weight of particles <1mm, 30% by weight of particles 1-3mm); premium grade bauxite powder (Al2O3≥80%, Fe2O3≤1.8%) with a particle size of 250-325 mesh; activated alumina (α-Al2O3) micro powder with a particle size of 325-2000 mesh; fused magnesia powder (60% by weight of particles 1 < ≤ 3mm, 40% by weight of particles 0.1 < ≤ 1mm); and industrial grade sodium tripolyphosphate as the water-reducing agent.

[0030] Example 2: The difference between this example and Example 1 is that a method for preparing an intermediate liner preform includes the following steps: S1. By weight, mix 37 parts of lightweight mullite, 24.5 parts of premium calcined alumina, 21 parts of premium bauxite powder, 3 parts of activated alumina micro powder, 3 parts of quartz fine powder, 5.7 parts of fused magnesia fine powder, 4.8 parts of silica micro powder, 2.5 parts of aluminum titanium carbide, 4 parts of acid-washed silicon nitride, and 0.2 parts of water-reducing agent to obtain a dry mixture.

[0031] S2. Add 13 parts of water to the dry mixture obtained in S1 and continue stirring for 2 minutes to obtain the casting material.

[0032] S3. Pour the refractory into the mold, let it cure naturally for 24 hours, then demold it, cure it for another 24 hours, and then dry it at 110℃ for 24 hours to obtain the intermediate ladle preform (refractory sample).

[0033] Example 3: The difference between this example and Example 1 is that: a method for preparing an intermediate tundish preform includes the following steps: S1. By weight, mix 39 parts of lightweight mullite, 26.5 parts of premium calcined alumina, 22 parts of premium bauxite powder, 3.5 parts of activated alumina micro powder, 3.5 parts of quartz fine powder, 6.5 parts of fused magnesia fine powder, 5.3 parts of silica micro powder, 2.8 parts of aluminum titanium carbide, 4.5 parts of acid-washed silicon nitride, and 0.25 parts of water-reducing agent to obtain a dry mixture.

[0034] S2. Add 14.5 parts of water to the dry mixture obtained in S1 and continue stirring for 3 minutes to obtain the casting material.

[0035] S3. Pour the refractory into the mold, let it cure naturally for 24 hours, then demold it, cure it for another 24 hours, and then dry it at 110℃ for 24 hours to obtain the intermediate ladle preform (refractory sample).

[0036] Comparative Example 1: The difference between this comparative example and Example 1 is that aluminum titanium carbide and pickled silicon nitride are not added in the preparation of the intermediate tundish preform.

[0037] Specifically, a method for preparing an intermediate ladle preform includes the following steps: S1. By weight, mix 38 parts of lightweight mullite, 25.5 parts of premium calcined bauxite, 21.5 parts of premium bauxite fine powder, 3.2 parts of activated alumina micro powder, 3.2 parts of quartz fine powder, 6.1 parts of fused magnesia fine powder, 5.1 parts of silica micro powder and 0.23 parts of water-reducing agent to obtain a dry mixture.

[0038] S2. Add 13.8 parts of water to the dry mixture obtained in S1 and continue stirring for 2.5 minutes to obtain the casting refractory.

[0039] S3. Pour the refractory into the mold, let it cure naturally for 24 hours, then demold it, cure it for another 24 hours, and then dry it at 110℃ for 24 hours to obtain the intermediate ladle preform (refractory sample).

[0040] Comparative Example 2: The difference between this comparative example and Example 1 is that aluminum titanium carbide is not added in the preparation of the intermediate tundish preform; and pickling silicon nitride is replaced with silicon nitride.

[0041] Specifically, a method for preparing an intermediate ladle preform includes the following steps: S1. By weight, mix 38 parts of lightweight mullite, 25.5 parts of premium calcined alumina, 21.5 parts of premium bauxite powder, 3.2 parts of activated alumina powder, 3.2 parts of quartz powder, 6.1 parts of fused magnesia powder, 5.1 parts of silica powder, 4.2 parts of silicon nitride, and 0.23 parts of water-reducing agent to obtain a dry mixture.

[0042] S2. Add 13.8 parts of water to the dry mixture obtained in S1 and continue stirring for 2.5 minutes to obtain the casting refractory.

[0043] S3. Pour the refractory into the mold, let it cure naturally for 24 hours, then demold it, cure it for another 24 hours, and then dry it at 110℃ for 24 hours to obtain the intermediate ladle preform (refractory sample).

[0044] Comparative Example 3: The difference between this comparative example and Example 1 is that aluminum titanium carbide is not added in the preparation of the intermediate tundish preform.

[0045] Specifically, a method for preparing an intermediate ladle preform includes the following steps: S1. By weight, mix 38 parts of lightweight mullite, 25.5 parts of premium calcined alumina, 21.5 parts of premium bauxite powder, 3.2 parts of activated alumina powder, 3.2 parts of quartz powder, 6.1 parts of fused magnesia powder, 5.1 parts of silica powder, 4.2 parts of acid-washed silicon nitride, and 0.23 parts of water-reducing agent to obtain a dry mixture.

[0046] S2. Add 13.8 parts of water to the dry mixture obtained in S1 and continue stirring for 2.5 minutes to obtain the casting refractory.

[0047] S3. Pour the refractory into the mold, let it cure naturally for 24 hours, then demold it, cure it for another 24 hours, and then dry it at 110℃ for 24 hours to obtain the intermediate ladle preform (refractory sample).

[0048] Comparative Example 4: The difference between this comparative example and Example 1 is that no pickling silicon nitride is added in the preparation of the intermediate tundish preform.

[0049] Specifically, a method for preparing an intermediate ladle preform includes the following steps: S1. By weight, mix 38 parts of lightweight mullite, 25.5 parts of premium calcined alumina, 21.5 parts of premium bauxite powder, 3.2 parts of activated alumina powder, 3.2 parts of quartz powder, 6.1 parts of fused magnesia powder, 5.1 parts of silica powder, 2.7 parts of aluminum titanium carbide, and 0.23 parts of water-reducing agent to obtain a dry mixture.

[0050] S2. Add 13.8 parts of water to the dry mixture obtained in S1 and continue stirring for 2.5 minutes to obtain the casting refractory.

[0051] S3. Pour the refractory into the mold, let it cure naturally for 24 hours, then demold it, cure it for another 24 hours, and then dry it at 110℃ for 24 hours to obtain the intermediate ladle preform (refractory sample).

[0052] Test Example: Test Subjects: Castable refractory samples prepared in Examples 1-3 and Comparative Examples 1-4. Test Items and Methods: Each castable refractory sample was heated to 1200℃ and 1400℃ respectively, and held at this temperature for 0.5h. Then, the hot flexural strength of the sample at this temperature was tested. Test Results: See Table 1.

[0053] Table 1. Test Data for Experimental Examples Flexural strength at 1200℃ (MPa) Flexural strength at 1400℃ (MPa) Example 1 8.0 2.7 Example 2 7.9 2.7 Example 3 7.9 2.6 Comparative Example 1 7.5 1.6 Comparative Example 2 7.7 2.0 Comparative Example 3 7.8 2.3 Comparative Example 4 7.4 1.5 Results Analysis: Combining the data in Table 1 and... Figures 1-2 Analysis of Examples 1-3 shows that the hot flexural strength of the castable samples prepared by the present invention (Examples 1-3) reaches 7.9 MPa or more at 1200℃; and its hot flexural strength at 1400℃ reaches 2.6 MPa or more.

[0054] Combining the data in Table 1 and Figures 1-2 Analysis was conducted on Example 1 and Comparative Examples 1-4, specifically comparing Comparative Examples 1 and 2. It was found that, compared to Comparative Example 1, Comparative Example 2, by introducing silicon nitride into the raw material components, resulted in an increase in the flexural strength of the castable sample at 1200℃ from 7.5 MPa (Comparative Example 1) to 7.7 MPa (Comparative Example 2), and an increase in the flexural strength at 1400℃ from 1.6 MPa (Comparative Example 1) to 2.0 MPa (Comparative Example 2). This indicates that simply introducing silicon nitride can significantly improve the flexural strength of the castable sample at 1400℃.

[0055] By comparing with Comparative Example 3, it can be seen that replacing silicon nitride with the acid-washed silicon nitride of this invention can further improve the hot flexural strength of the prepared castable sample at 1400℃.

[0056] Specifically, comparing Comparative Examples 1 and 4, it can be seen that, compared to Comparative Example 1, the addition of aluminum titanium carbide to the raw material composition of Comparative Example 4 resulted in a decrease in the flexural strength of the castable sample at 1200℃ from 7.5 MPa (Comparative Example 1) to 7.4 MPa (Comparative Example 4), and a decrease in the flexural strength at 1400℃ from 1.6 MPa (Comparative Example 1) to 1.5 MPa (Comparative Example 4). This indicates that simply adding aluminum titanium carbide can actually lead to a decrease in the flexural strength of the castable sample at 1400℃.

[0057] This is mainly because when aluminum titanium carbide is introduced alone, it can react with O2 to produce CO gas in a high-temperature oxygen-containing atmosphere, which increases the internal porosity and destroys the compactness; at the same time, the generated TiO2 and other materials are in a loosely packed state and cannot effectively bear the load, resulting in a decrease in hot flexural strength.

[0058] In comparison with Example 1, it can be seen that the simultaneous introduction of acid-washed silicon nitride and aluminum titanium carbide can produce a synergistic effect, which can synergistically improve the hot flexural strength of the prepared castable sample (1200℃ / 1400℃).

[0059] 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 method for preparing an intermediate liner preform, characterized in that, Includes the following steps: S1. By weight, mix 37-39 parts of mullite, 24.5-26.5 parts of calcined alumina, 21-22 parts of bauxite powder, 3-3.5 parts of activated alumina powder, 3-3.5 parts of quartz powder, 5.7-6.5 parts of fused magnesia powder, 4.8-5.3 parts of silica powder, 2.5-2.8 parts of aluminum titanium carbide, 4-4.5 parts of acid-washed silicon nitride, and 0.2-0.25 parts of water-reducing agent to obtain a dry mixture; S2. Add 13-14.5 parts of water to the dry mixture obtained in S1 and continue stirring to obtain the casting refractory. S3. Pour the casting material into the mold, let it cure naturally for 24 hours, then demold it, cure it for another 24 hours, and then dry it to obtain the intermediate ladle preform.

2. The method for preparing the intermediate tundish preform according to claim 1, characterized in that, The preparation method of the aluminum titanium carbide is as follows: A1. Mix titanium carbide powder, metallic titanium powder, aluminum powder and silicon powder to obtain a mixture; A2. Under argon protection, the mixture obtained in A1 is loaded into a graphite mold, heated, and hot-pressed for sintering to obtain the aluminum titanium carbide.

3. The method for preparing the intermediate tundish preform according to claim 2, characterized in that, In A1, the molar ratio of titanium carbide powder, metallic titanium powder, aluminum powder and silicon powder is 2:1:(1.0-1.1):(0.18-0.23).

4. The method for preparing the intermediate tundish preform according to claim 2, characterized in that, In A2, the heating rate is 50±2℃ / min.

5. The method for preparing the intermediate tundish preform according to claim 2, characterized in that, In A2, the sintering temperature is 1350-1450℃, the holding time is 2-3h, and the hot pressing pressure is 30±0.5MPa.

6. The method for preparing the intermediate tundish preform according to claim 1, characterized in that, The preparation method of the pickled silicon nitride is as follows: silicon nitride powder is placed in hydrochloric acid solution for acidification treatment, then filtered and washed with deionized water until the washing solution is neutral, and then dried to obtain the pickled silicon nitride.

7. The method for preparing the intermediate tundish preform according to claim 6, characterized in that, The concentration of the hydrochloric acid solution is 0.01-0.012 mol / L.

8. The method for preparing the intermediate tundish preform according to claim 1, characterized in that, The water-reducing agent is sodium tripolyphosphate.

9. A precast intermediate liner, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

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