Tundish composite coating material for clean steel and preparation method of tundish composite coating material

Abstract

The invention relates to the technical field of refractory materials, and provides a tundish composite coating material for clean steel and a preparation method of the tundish composite coating material. The tundish composite coating material comprises the following raw materials in parts by weight: 30-70 parts of forsterite, 5-15 parts of magnesia, 3-10 parts of silicon carbide, 3-5 parts of a mixed auxiliary agent, 0.8-2.5 parts of a binding agent, 0.1-0.3 part of crystalline flake graphite, 0.5-1 part of bentonite, 0.5-1 part of Weiluo white mud, 0.6-1.5 parts of organic fibers and 0.2-0.6 part of a water reducing agent, and the raw materials of the mixed auxiliary agent comprise silica powder, magnesium oxide micro powder, polyvinyl acetate and ethyl 2-aminoisonicotinate. According to the technical scheme, the problem that the tundish coating material for clean steel is insufficient in strength at high temperature in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refractory materials, in particular to a tundish composite coating material for clean steel and a preparation method thereof. BACKGROUND

[0002] Clean steel is a general term for steel with low impurities and high purity, and the production process puts high requirements on the cleanliness control of molten steel at the continuous casting stage. The tundish, as a key transition container for molten steel from ladle to mold during continuous casting, the high-temperature mechanical properties of the working layer of the tundish lining composed of coating material are directly related to the temperature maintenance, purity control of molten steel, and the smoothness and efficiency of continuous casting production.

[0003] At present, the tundish coating material is mainly based on sintered magnesia, which has the advantage of strong resistance to alkaline slag erosion, but the thermal expansion coefficient of magnesia is high, and microcracks are easily generated due to thermal stress under temperature cycling conditions. These cracks not only cause the penetration of molten steel into the deep layer of the lining, increasing the risk of lining spalling, but also become the attachment and growth carrier of non-metallic inclusions in steel, directly affecting the requirement of clean steel on inclusion content.

[0004] Therefore, clean steel production usually turns to using coating material based on forsterite. The thermal expansion coefficient of forsterite is only about 8*10 -6 / ℃, and it has excellent thermal shock resistance, which can effectively reduce the structural damage caused by temperature cycling, however, the forsterite-based coating material itself has obvious shortcomings, its refractoriness is relatively low, and it is easy to soften under long-term high temperature, causing insufficient strength, resulting in reduced resistance to molten steel erosion and shortened service life. Therefore, it is necessary to prepare a tundish composite coating material for clean steel with high high-temperature mechanical properties to ensure the stability of clean steel quality. SUMMARY

[0005] The present application provides a tundish composite coating material for clean steel and a preparation method thereof, which solves the problem of insufficient mechanical properties of the tundish coating material for clean steel at high temperature in the related art.

[0006] The technical scheme of the present application is as follows: The present application provides a tundish composite coating material for clean steel, which comprises the following components by weight: forsterite 30-70 parts, magnesia 5-15 parts, silicon carbide 3-10 parts, mixed additives 3-5 parts, binder 0.8-2.5 parts, flaky graphite 0.1-0.3 parts, bentonite 0.5-1 part, vermiculite 0.5-1 part, organic fiber 0.6-1.5 parts, and water reducing agent 0.2-0.6 parts. The raw materials of the mixed additives include silicon powder, magnesium oxide powder, polyvinyl acetate, and 2-aminoisonicotinic acid ethyl ester.

[0007] The water reducing agent added in the intermediate ladle composite coating material for clean steel can effectively reduce the mixing water consumption of the slurry, significantly improve the fluidity and construction spreading property of the slurry, and make the slurry more easily and uniformly coated. In addition, the reduction of water consumption can also reduce the shrinkage stress in the drying process, and the anti-cracking effect of the organic fiber can further inhibit the generation of cracks, thereby improving the construction quality and structural stability of the coating material.

[0008] As a further technical solution, the mass ratio of the silicon powder, magnesium oxide powder, polyvinyl acetate and 2-aminoethyl isonicotinate is 35:25:4:1~3, for example, it can be 35:25:4:1, 35:25:4:1.5, 35:25:4:2, 35:25:4:3, and preferably 35:25:4:2.

[0009] The intermediate ladle composite coating material for clean steel limits the mass ratio of the silicon powder, magnesium oxide powder, polyvinyl acetate and 2-aminoethyl isonicotinate to 35:25:4:1~3, which can further improve the high-temperature mechanical properties of the intermediate ladle composite coating material. The addition of silicon powder and magnesium oxide powder can synergistically fill the interstitial gaps to improve the density, while the introduction of polyvinyl acetate and 2-aminoethyl isonicotinate can improve the dispersibility of silicon powder and magnesium oxide powder. When the amount of 2-aminoethyl isonicotinate is insufficient, the polar groups in its molecule cannot fully act on the hydroxyl groups on the surface of silicon powder and magnesium oxide powder, resulting in agglomeration and uneven dispersion of the two, which cannot effectively improve the mechanical properties of the coating material. If the amount of 2-aminoethyl isonicotinate is too much, excessive 2-aminoethyl isonicotinate will be introduced, which will easily produce excessive gas during the high-temperature carbonization process, resulting in the formation of many pores inside the material, destroying the structural density, and weakening the high-temperature performance, thereby reducing the high-temperature mechanical properties of the coating material.

[0010] As a further technical solution, the preparation method of the mixing aid includes the following steps: adding polyvinyl acetate and 2-aminoethyl isonicotinate into a solvent and dispersing uniformly, then adding silicon powder and magnesium oxide powder and mixing, and drying to obtain the mixing aid.

[0011] As a further technical solution, the solvent is anhydrous ethanol.

[0012] As a further technical solution, the mixing temperature is 40℃, and the mixing time is 2h.

[0013] As a further technical solution, the forsterite is composed of 1mm<particle size≤3mm forsterite, 0.088mm<particle size≤1mm forsterite and 0<particle size≤0.088mm forsterite with a mass ratio of 3:2:1~2. The magnesia is composed of 0.088mm≤particle size≤1mm magnesia and 0< particle size≤0.074mm magnesia with a mass ratio of 2:1.

[0014] As a further technical solution, the particle size of the bentonite is 0.02mm~0.064mm. The particle size of the vermiculite is 0.9um~3um.

[0015] As a further technical solution, the organic fiber includes one or more of hemp fiber, polyethylene fiber and wood fiber.

[0016] As a further technical solution, the organic fiber is composed of hemp fiber and polyethylene fiber with a mass ratio of 1:2.

[0017] As a further technical solution, the binding agent includes asphalt, magnesium chloride, phenolic resin and 2-acetylamino-5-amino pyridine.

[0018] The present application adds asphalt, magnesium chloride, phenolic resin and 2-acetylamino-5-amino pyridine in the tundish composite coating material for clean steel, and the high-temperature mechanical properties of the coating material are improved through the synergy between the components, wherein the magnesium chloride acts as an inorganic binding agent, forms a gel body with water molecules at room temperature during use to provide initial strength, the asphalt and the phenolic resin are carbonized at high temperature in turn to jointly build a stable and dense high-temperature carbon skeleton, greatly enhancing the bending strength and thermal stability of the material; in addition, the 2-acetylamino-5-amino pyridine effectively improves the dispersity and compatibility of the binding agent through its polar group, ensures the uniform distribution of the binding agent, reduces stress concentration at high temperature, and inhibits crack generation, thereby further improving the high-temperature mechanical properties of the coating material.

[0019] As a further technical solution, the mass ratio of the asphalt, magnesium chloride, phenolic resin and 2-acetylamino-5-amino pyridine is 35:30:4:3~5.

[0020] As a further technical solution, the water reducing agent includes one or both of sodium tripolyphosphate and sodium hexametaphosphate.

[0021] As a further technical solution, the water reducing agent is composed of sodium tripolyphosphate and sodium hexametaphosphate with a mass ratio of 1:1.

[0022] The present application also proposes a preparation method of the tundish composite coating material for clean steel, which is used for preparing the above-mentioned tundish composite coating material for clean steel and includes the following steps: uniformly mixing the raw materials to obtain the tundish composite coating material for clean steel.

[0023] The working principle and beneficial effects of the present application are as follows: In the clean steel intermediate ladle composite coating of this invention, the addition of mixed additives effectively improves the high-temperature mechanical properties of the coating. In existing technologies, silica powder and magnesium oxide powder are added to improve the high-temperature mechanical properties of magnesium olivine-based coatings. However, silica powder and magnesium oxide powder are prone to agglomeration, limiting the effectiveness in improving the high-temperature mechanical properties and stability of the material. The raw materials for the mixed additives in this invention include silica powder, magnesium oxide powder, polyvinyl acetate, and ethyl 2-aminoisonicotinic acid. Polyvinyl acetate effectively improves the dispersibility between silica powder and magnesium oxide powder; simultaneously, the polar groups in the ethyl 2-aminoisonicotinic acid molecule can form hydrogen bonds with the hydroxyl groups on the surface of silica powder and magnesium oxide powder, further promoting the uniform dispersion of inorganic powders in the coating system. Moreover, its aromatic ring structure can participate in the carbonization reaction under high-temperature conditions during use, further improving the mechanical properties of the coating at high temperatures. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] In the following examples and comparative examples: Forsterite is composed of forsterite with a mass ratio of 3:2:2, consisting of forsterite with a particle size of 1 mm < ≤ 3 mm, forsterite with a particle size of 0.088 mm < ≤ 1 mm, and forsterite with a particle size of 0 < ≤ 0.088 mm. The sintered magnesia is composed of sintered magnesia with a particle size of 0.088 mm < ≤ 1 mm and sintered magnesia with a particle size of 0 < ≤ 0.074 mm in a mass ratio of 2:1. The average particle size of silicon carbide is 45 μm; The average particle size of the silica powder is 2000 mesh; The average particle size of the magnesium oxide powder is 2000 mesh. The average particle size of bentonite is 0.035 mm; The average particle size of Vero white clay is 3 μm; The diameter of hemp fibers is 20μm and the length is 6mm; The polyethylene fiber has a diameter of 12μm and a length of 4mm; The average particle size of the flake graphite is 2000 mesh; Asphalt, type: 70, manufacturer: Foshan Nanhai Hongxian Municipal Engineering Co., Ltd. Polyvinyl acetate, model: DH5405, manufacturer: Donghao Chemical (Shandong) Co., Ltd.

[0026] Example 1 A composite coating material for intermediate ladle of clean steel comprises the following raw materials in parts by weight: 30 parts magnesium olivine, 5 parts magnesia, 3 parts silicon carbide, 3 parts mixing additives, 0.8 parts binder, 0.1 parts flake graphite, 0.5 parts bentonite, 0.5 parts vernix caseosa, 0.2 parts hemp fiber, 0.4 parts polyethylene fiber, 0.1 parts sodium tripolyphosphate, and 0.1 parts sodium hexametaphosphate, wherein the binder is composed of asphalt and magnesium chloride in a mass ratio of 35:30; The preparation method of the mixed additive includes the following steps: polyvinyl acetate and ethyl 2-aminoisonicotinic acid are added to anhydrous ethanol and dispersed evenly; then silica powder and magnesium oxide powder are added and mixed at 40°C for 2 hours, followed by drying to obtain the mixed additive. The mass ratio of silica powder, magnesium oxide powder, polyvinyl acetate and ethyl 2-aminoisonicotinic acid is 35:25:4:1; the mass ratio of silica powder and magnesium oxide powder to the volume ratio of anhydrous ethanol is 1 g:8 mL. A method for preparing a composite coating for a clean steel tundish includes the following steps: After the above raw material components are mixed evenly, a composite coating material for intermediate ladles of clean steel is obtained.

[0027] Example 2 A composite coating material for a clean steel intermediate ladle comprises the following raw materials in parts by weight: 55 parts magnesium olivine, 10 parts magnesia, 6 parts silicon carbide, 4 parts mixing additives, 1.4 parts binder, 0.2 parts flake graphite, 0.7 parts bentonite, 0.7 parts vernix caseosa, 0.4 parts hemp fiber, 0.8 parts polyethylene fiber, 0.2 parts sodium tripolyphosphate, and 0.2 parts sodium hexametaphosphate, wherein the binder is composed of asphalt and magnesium chloride in a mass ratio of 35:30; The preparation method of the mixed additive includes the following steps: polyvinyl acetate and ethyl 2-aminoisonicotinic acid are added to anhydrous ethanol and dispersed evenly; then silica powder and magnesium oxide powder are added and mixed at 40°C for 2 hours, followed by drying to obtain the mixed additive. The mass ratio of silica powder, magnesium oxide powder, polyvinyl acetate and ethyl 2-aminoisonicotinic acid is 35:25:4:1; the mass ratio of silica powder and magnesium oxide powder to the volume ratio of anhydrous ethanol is 1 g:8 mL. A method for preparing a composite coating for a clean steel tundish includes the following steps: After the above raw materials are mixed evenly, a composite coating material for intermediate ladles of clean steel is obtained.

[0028] Example 3 A composite coating material for intermediate ladle of clean steel comprises the following raw materials in parts by weight: 70 parts magnesium olivine, 15 parts magnesia, 10 parts silicon carbide, 5 parts mixing additives, 2.5 parts binder, 0.3 parts flake graphite, 1 part bentonite, 1 part vernix caseosa, 0.5 parts hemp fiber, 1.0 part polyethylene fiber, 0.3 parts sodium tripolyphosphate, and 0.3 parts sodium hexametaphosphate, wherein the binder is composed of asphalt and magnesium chloride in a mass ratio of 35:30; The preparation method of the mixed additive includes the following steps: polyvinyl acetate and ethyl 2-aminoisonicotinic acid are added to anhydrous ethanol and dispersed evenly; then silica powder and magnesium oxide powder are added and mixed at 40°C for 2 hours, followed by drying to obtain the mixed additive. The mass ratio of silica powder, magnesium oxide powder, polyvinyl acetate and ethyl 2-aminoisonicotinic acid is 35:25:4:1; the mass ratio of silica powder and magnesium oxide powder to the volume ratio of anhydrous ethanol is 1 g:8 mL. A method for preparing a composite coating for a clean steel tundish includes the following steps: After the above raw materials are mixed evenly, a composite coating material for intermediate ladles of clean steel is obtained.

[0029] Example 4 The only difference between this embodiment and Embodiment 2 is that in this embodiment, the mass ratio of silicon micro powder, magnesium oxide micro powder, polyvinyl acetate and ethyl 2-aminoisonicotinic acid is 35:25:4:2.

[0030] Example 5 The only difference between this embodiment and Embodiment 2 is that in this embodiment, the mass ratio of silicon micro powder, magnesium oxide micro powder, polyvinyl acetate and ethyl 2-aminoisonicotinic acid is 35:25:4:3.

[0031] Example 6 The only difference between this embodiment and Embodiment 4 is that the binder in this embodiment is composed of asphalt, magnesium chloride, and phenolic resin in a mass ratio of 35:30:4.

[0032] Example 7 The only difference between this embodiment and Embodiment 4 is that the binder in this embodiment is composed of asphalt, magnesium chloride, phenolic resin and 2-acetamido-5-aminopyridine in a mass ratio of 35:30:4:3.

[0033] Example 8 The only difference between this embodiment and Embodiment 4 is that the binder in this embodiment is composed of asphalt, magnesium chloride, phenolic resin and 2-acetamido-5-aminopyridine in a mass ratio of 35:30:4:4.

[0034] Example 9 The only difference between this embodiment and Embodiment 4 is that the binder in this embodiment is composed of asphalt, magnesium chloride, phenolic resin and 2-acetamido-5-aminopyridine in a mass ratio of 35:30:4:5.

[0035] Comparative Example 1 The only difference between this comparative example and Example 2 is that the silicon micro powder, magnesium oxide micro powder, polyvinyl acetate and ethyl 2-aminoisonicotinic acid in a mass ratio of 35:25:4:1 are replaced with equal amounts of silicon micro powder, magnesium oxide micro powder and polyvinyl acetate in a mass ratio of 35:25:5.

[0036] Comparative Example 2 The only difference between this comparative example and Example 2 is that the silicon micro powder, magnesium oxide micro powder, polyvinyl acetate and ethyl 2-aminoisonicotinic acid in a mass ratio of 35:25:4:1 are replaced with an equal amount of silicon micro powder, magnesium oxide micro powder and ethyl 2-aminoisonicotinic acid in a mass ratio of 35:25:5.

[0037] Comparative Example 3 The only difference between this comparative example and Example 2 is that the silicon micro powder, magnesium oxide micro powder, polyvinyl acetate and ethyl 2-aminoisonicotinic acid in a mass ratio of 35:25:4:1 are replaced with equal amounts of silicon micro powder and magnesium oxide micro powder in a mass ratio of 35:25.

[0038] Experimental Example 1 The intermediate package composite coating materials obtained in Examples 1-9 and Comparative Examples 1-3 were added to 15% water by total mass and stirred evenly. After molding and curing, they were calcined at 200°C for 2.5 hours and their performance was determined according to the following test method. Compressive strength: The compressive strength was tested at 110℃ for 24 hours according to Method 3 of GB / T 5072-2023 "Test Method for Compressive Strength of Refractory Materials at Room Temperature"; the compressive strength was tested at 1500℃ for 3 hours according to Method 3 of GB / T 34218-2017 "Test Method for Compressive Strength of Refractory Materials at High Temperature"; the heating rate during the test was 10℃ / min; the test results are recorded in Table 1. Table 1 Performance test results of Examples 1-9 and Comparative Examples 1-3

[0039] The compressive strength of the intermediate treasury coatings obtained in Examples 1-5 is higher than that of Comparative Examples 1-3, indicating that the addition of the mixed additives composed of silica powder, magnesium oxide powder, polyvinyl acetate and ethyl 2-aminoisonicotinic acid can improve the high-temperature mechanical properties of the intermediate treasury composite coating.

[0040] The compressive strength of the intermediate treasury coatings obtained in Examples 7-9 is higher than that in Examples 4 and 6, indicating that the addition of asphalt, magnesium chloride, phenolic resin and 2-acetamido-5-aminopyridine as binders in this invention can improve the high-temperature mechanical properties of the intermediate treasury composite coating.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. 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 composite coating material for intermediate ladles used in clean steel, characterized in that, The raw materials include the following components by weight: 30-70 parts of magnesium olivine, 5-15 parts of magnesia, 3-10 parts of silicon carbide, 3-5 parts of mixed additives, 0.8-2.5 parts of binder, 0.1-0.3 parts of flake graphite, 0.5-1 part of bentonite, 0.5-1 part of vernix caseosa, 0.6-1.5 parts of organic fiber, and 0.2-0.6 parts of water-reducing agent. The raw materials of the mixed additives include silica powder, magnesium oxide powder, polyvinyl acetate, and ethyl 2-aminoisonicotinic acid.

2. The composite coating material for tundishes used in clean steel according to claim 1, characterized in that, The mass ratio of the silicon micro powder, magnesium oxide micro powder, polyvinyl acetate and ethyl 2-aminoisonicotinic acid is 35:25:4:1~3.

3. The composite coating material for tundishes used in clean steel according to claim 1, characterized in that, The preparation method of the mixed additive includes the following steps: polyvinyl acetate and ethyl 2-aminoisonicotinic acid are added to a solvent and dispersed evenly, then silica powder and magnesium oxide powder are added and mixed, and then dried to obtain the mixed additive.

4. The composite coating material for tundishes used in clean steel according to claim 1, characterized in that, The forsterite is composed of forsterite with a mass ratio of 3:2:1~2, consisting of forsterite with a particle size of 1 mm < ≤ 3 mm, forsterite with a particle size of 0.088 mm < ≤ 1 mm, and forsterite with a particle size of 0 < ≤ 0.088 mm. The magnesia is composed of magnesia with a particle size of 0.088 mm < ≤ 1 mm and magnesia with a particle size of 0 < ≤ 0.074 mm in a mass ratio of 2:

1.

5. The composite coating material for tundishes used in clean steel according to claim 1, characterized in that, The bentonite has a particle size of 0.02 mm to 0.064 mm; The particle size of the Vero white clay is 0.9μm~3μm.

6. The composite coating material for tundishes used in clean steel according to claim 1, characterized in that, The organic fibers include one or more of hemp fibers, polyethylene fibers, and wood fibers.

7. The composite coating material for tundishes used in clean steel according to claim 1, characterized in that, The binder includes asphalt, magnesium chloride, phenolic resin, and 2-acetamido-5-aminopyridine.

8. The composite coating material for tundishes used in clean steel according to claim 7, characterized in that, The mass ratio of the asphalt, magnesium chloride, phenolic resin and 2-acetamido-5-aminopyridine is 35:30:4:3~5.

9. The composite coating material for tundishes used in clean steel according to claim 1, characterized in that, The water-reducing agent includes one or both of sodium tripolyphosphate and sodium hexametaphosphate.

10. A method for preparing a composite coating for tundishes used in clean steel, used to prepare the composite coating for tundishes according to any one of claims 1 to 9, characterized in that, Includes the following steps: After the raw materials are mixed evenly, a composite coating material for intermediate ladle of clean steel is obtained.

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