Material for inner hole of continuous casting anti-blocking submerged nozzle

Abstract

The application discloses a continuous casting anti-blocking submerged nozzle inner hole body material, the inner hole body is an Al2O3-BN-C material, and the material raw materials are as follows in percentage by mass: corundum 39-55%, alumina powder 6-10%, boron nitride 15-35%, graphite 12-20%, antioxidant 2-6%, and additional binder 4-7%. The antioxidant is boron carbide and boron glass powder, and the boron carbide is 1-3% and the boron glass powder is 1-3%. The binder is phenolic resin. The inner hole body material has excellent thermal shock resistance, erosion resistance, metal liquid infiltration resistance and oxidation inclusion deposition and adhesion resistance, and has good electrical conductivity, can be used under an external electric field, realizes anti-blocking and anti-clogging of the submerged nozzle through electric field-material coupling, and meets the anti-blocking requirements of continuous casting of multiple steel grades with complex inclusions.

Description

Technical Field

[0001] This invention relates to the field of continuous casting technology in steelmaking, and in particular to an inner hole material for a continuous casting anti-clogging submersible nozzle, which can be used in continuous casting anti-clogging submersible nozzles under an applied electric field. Background Technology

[0002] The submerged entry nozzle (DIV) is a crucial functional component connecting the tundish and the crystallizer, and it is made of refractory materials. Molten steel enters the crystallizer through the DIV, affecting the steel throughput and the production efficiency of the continuous casting machine. The DIV determines the liquid level in the crystallizer, thus influencing the quality of the continuously cast billet. During continuous casting, molten steel inevitably comes into contact with the inner wall of the DIV. Inclusions in the molten steel adhere to and accumulate on the inner wall of the nozzle, forming nodules over time. These nodules are easily washed into the crystallizer by the molten steel, remaining as large inclusions in the continuously cast billet. Furthermore, the irregular shape of these nodules causes instability in the stopper rod control and significant fluctuations in the liquid level in the crystallizer, potentially leading to nozzle blockage and even production stoppages. Nodules or blockages can also cause molten steel to flow off course inside the DIV, affecting the flow field. In actual production, DIV blockage is not caused by a single factor but is the result of multiple factors working together. This includes the reaction of metallic elements in steel with refractory materials, oxidation of metallic elements in molten steel due to air intake at the nozzle, endogenous deoxidation products, and precipitation caused by temperature drops. Inclusion particles flowing with the molten steel are suspended in the molten steel. When they reach the interface between the molten steel and the nozzle, some particles come into contact with the molten steel. Because the interfacial energy between the inclusion and the molten steel is greater than the interfacial energy between the inclusion and the refractory material, the inclusion particles adhere to the surface of the refractory material. These inclusion particles continuously aggregate and sinter, forming nodules and blockages. The formation of nozzle nodules is a complex physicochemical process involving numerous and interconnected influencing factors and conditions.

[0003] Based on the sources and formation mechanisms of immersion nozzle blockage, current control measures to reduce or mitigate immersion nozzle blockage mainly include: improving nozzle material and structure, reducing or modifying inclusions, and optimizing molten steel flow. Researchers have conducted extensive work and employed various technical approaches to reduce immersion nozzle blockage. To avoid altering the steelmaking process and operations, anti-blocking technologies related to nozzle materials and structures are commonly used. Many anti-blocking materials exist for immersion nozzles, with the mainstream technology involving the design of an inner lining material on the inner wall of the nozzle where it contacts the steel flow. The most widely used inner lining material is the carbon-free Al2O3-SiO2 system. However, ZrO2-CaO materials offer superior anti-blocking performance. The Al2O3 in the molten steel reacts with CaO and SiO2 in the material to form low-melting-point feldspar or calcium aluminate, which is washed away by the molten steel, thus preventing nozzle blockage. ZrO2 in the material can improve its corrosion resistance and extend its service life. However, because the amount of Al2O3 in the molten steel and the amount of CaO in the material are constantly changing, the resulting calcium aluminate is complex, and its phase composition is also constantly changing, including many high-melting-point compounds, making it difficult to control its formation direction. Therefore, the current ZrO2-CaO anti-clogging submersible nozzle material lacks sufficient anti-clogging stability in multi-furnace continuous casting. Another type of anti-clogging submersible nozzle inner hole material is Al2O3-MgO spinel anti-clogging material. Spinel has low reactivity with Al2O3, making it difficult for Al2O3 in the molten steel to adhere. Furthermore, because the material does not contain C or SiO2, it does not increase the carbon or silicon content of the molten steel, which is beneficial to improving the quality of the molten steel. It is one of the better anti-clogging technologies for ultra-low carbon steel. Existing anti-clogging technologies are mostly applied in aluminum-killed steel and low-carbon steel, mainly to prevent the formation of inclusions such as alumina, spinel, and calcium aluminate.

[0004] With the diversification of steel grades and the increasing demand for high-quality steel, anti-clogging submersible nozzles have also seen diverse technological advancements. For example, Chinese patent CN1727309A relates to a refractory material for an anti-clogging lining of an anti-clogging submersible nozzle, composed of zirconium mullite, β-silicon, alumina, fused silica, silicon carbide, and metallic silicon. This aluminum-killed steel, used in continuous casting, can prevent nozzle clogging caused by alumina inclusions. Chinese patent CN104174837A discloses a carbon- and silicon-free spinel lining material that significantly reduces Al2O3 nodule formation, ensuring normal casting flow and steel quality. Chinese patent CN102335738A discloses a composite submersible nozzle, comprising an outer body, an outer slag line segment, and an inner layer. The outer body contains flake graphite, white corundum, and aluminum titanate; the outer slag line segment contains flake graphite, zirconium oxide, and aluminum titanate; and the inner layer material contains white corundum and aluminum titanate. This patented technology slows down or prevents nodule formation and blockages the sprue by incorporating a composite carbon-free layer on the inner wall of the sprue and adding aluminum titanate, eliminating silicon, and preventing SiO2 generation. It has good anti-nodule and anti-corrosion effects on low-carbon steel, medium-carbon steel, and high-oxygen steel.

[0005] In-depth research on the nodule deposits after use on different steel grades revealed that the nodule deposits on the inner wall typically consist of an erosion layer of the nodule material, a sintered layer of inclusions, and a layer of steel-containing inclusions. The thickness of each layer and the composition of the nodule deposits vary depending on the steel grade. After casting molten steel containing active elements such as Al, Ti, Mn, and rare earth elements, the erosion layer contains multi-element oxides, sulfides, and spinel inclusions. For molten steel with high sulfur content, there are inclusions such as CaS with a high melting point; the sintered layer of inclusions has the same composition as the inclusions in the steel; the steel-containing inclusion layer contains more solidified steel particles, iron oxide particles, and more low-melting-point sulfides. Therefore, it is difficult to achieve a stable anti-clogging effect for multiple steel grades throughout the entire process by using the same anti-clogging technology or anti-nodule material. Summary of the Invention

[0006] The purpose of this invention is to provide an internal material for a continuous casting anti-clogging submersible nozzle. This internal material has excellent thermal shock resistance, erosion resistance, resistance to molten metal wetting and oxide inclusion deposition and adhesion, and good electrical conductivity. It can be used under an external electric field, and the electric field-material coupling is used to prevent nodule formation and clogging in the submersible nozzle.

[0007] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0008] A continuous casting anti-clogging submersible nozzle inner hole material, wherein the inner hole body is an Al2O3-BN-C material, and the raw materials of the material by mass percentage are: corundum 39-55%, alumina powder 6-10%, boron nitride 15-35%, graphite 12-20%, antioxidant 2-6%; and external binder +4-7%.

[0009] The antioxidant is boron carbide and borosilicate glass powder.

[0010] The composition includes 1-3% boron carbide and 1-3% borosilicate glass powder.

[0011] The binder is phenolic resin.

[0012] The resistivity of the inner pore material is 1.4 × 10⁻⁶. -5 ~2.2×10 -5 Ω·m, flexural strength of 6.1–7.1 MPa, porosity of 17–19%, compressive strength of 30.4–32.9 MPa, and thermal shock resistance greater than 20 cycles.

[0013] The main raw material of the inner bore of the continuous casting anti-clogging submerged entry nozzle of this invention is boron nitride (BN), with a content of 15-35% of the material's mass. The interfacial wetting behavior between the refractory material and the molten steel and slag has a significant impact on its erosion and nodule formation kinetics. One way to prevent nodule formation and clogging in submerged entry nozzles is to use materials with poor wettability to molten steel. Therefore, the main raw material of the inner bore of the submerged entry nozzle of this invention is designed to be boron nitride (BN). Boron nitride (BN) is non-wetting to molten metal and has lubricating physical properties, which can significantly reduce the adhesion and friction of molten metal and oxide inclusions to the inner wall of the nozzle, reduce the formation of double-layer charge structures, and promote the stability of the electric field interface formed by the applied electric field, significantly improving the nodule formation phenomenon. In addition, the boron nitride (BN) in this invention has the same structure as graphite, has good compatibility, and complements graphite materials well. BN itself has excellent thermal shock resistance and its oxidation resistance is significantly better than that of graphite. Therefore, the submerged entry nozzle of this invention has superior overall performance.

[0014] The internal material of the continuous casting anti-clogging submersible nozzle of this invention contains a high carbon content, which accounts for more than 12% of the raw material mass, ranging from 12% to 20%. Unlike existing carbon-free materials, the anti-clogging internal material of this invention possesses excellent electrical conductivity due to its high carbon content, making it suitable for use under an applied electric field and further enhancing its anti-clogging function. Simultaneously, the graphite material exhibits good resistance to corrosion and metal solution wettability, which also helps reduce nozzle nodule formation.

[0015] The antioxidant in the inner hole material of the continuous casting anti-clogging submersible nozzle of this invention is a combination of boron carbide and borosilicate glass powder, with the content accounting for 2-6% of the material's raw material mass. The borosilicate glass powder undergoes a solid-phase reaction at high temperatures to form a disordered, homogeneous glass body with low expansion, good thermal shock stability, and low melting and sealing temperatures, increasing the strength and erosion resistance of the ceramic material. At high temperatures, a liquid phase forms to seal the material's pores, improving the material's oxidation resistance and ensuring the long service life of the submersible nozzle of this invention.

[0016] The main raw material of the submersible nozzle inner bore material for continuous casting anti-clogging is corundum, which accounts for 39-55% of the material's mass. The corundum can be fused alumina or sintered alumina, with an Al2O3 content greater than or equal to 99.0% and a particle size of 2-0 mm. Alumina powder is also added to the submersible nozzle inner bore material, accounting for 6-10% of the material's mass, with an Al2O3 content greater than or equal to 98.5% and a particle size ≤10 μm. An external binder, phenolic resin, is also required for the submersible nozzle inner bore material; this is a commercially available product.

[0017] The anti-clogging submersible nozzle inner hole material of this invention is made of corundum, boron nitride and graphite as the main raw materials and phenolic resin as the binder. It has excellent thermal shock resistance, corrosion resistance, resistance to metal liquid wetting and oxide inclusion deposition and adhesion. The inner hole itself has very good anti-nodulation and anti-clogging properties.

[0018] This invention relates to an anti-clogging submersible nozzle inner bore material. When designing the chemical composition and content of the material, it considers not only the thermal shock resistance and corrosion resistance of the inner bore material, but also its electrical conductivity and anti-wetting properties. The requirements for the electrical conductivity and anti-wetting properties of the inner bore material are primarily based on electrochemical anti-clogging technology in high-temperature molten steel during steelmaking continuous casting. This technology is relatively new in the field of steelmaking continuous casting. Electrochemical anti-clogging technology in high-temperature molten steel during steelmaking continuous casting controls the migration of inclusions in the molten steel inside the submersible nozzle by applying an external electric field. This reduces the probability of inclusions migrating to and adhering to the inner wall of the nozzle, lowering the rate of nodule formation on the inner wall. This not only improves the nozzle clogging situation but also extends the service life of the nozzle.

[0019] Compared with existing technologies, the advantages of this invention are as follows: The inner pore material of the submersible nozzle of this invention is an Al2O3-BN-C material, which has excellent thermal shock resistance, corrosion resistance, resistance to molten metal wetting, and resistance to oxide deposition and adhesion. It also has good electrical conductivity, allowing application under an applied electric field. Through electric field-material coupling, it prevents nodule formation and clogging in the submersible nozzle, meeting the anti-clogging requirements of continuous casting with complex inclusion compositions and multiple steel grades. This invention provides excellent, comprehensive, and stable anti-nodule and anti-clogging effects, effectively ensuring efficient and high-quality continuous casting production. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of an immersion gate structure.

[0021] In the diagram: 1. Body, 2. Slag line segment, 3. Inner hole body. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] This invention, in designing the inner bore material for continuous casting anti-clogging submersible nozzles, not only considers the thermal shock resistance and erosion resistance of the inner bore material, but also its good electrical conductivity and anti-wetting properties. It can be applied under the condition of applying an external electric field to control the migration of inclusions in the molten steel inside the submersible nozzle, reduce the probability of inclusions migrating to and adhering to the inner wall of the nozzle, and reduce the rate of nodule formation on the inner wall of the nozzle. This not only improves the nozzle clogging situation, but also extends the service life of the nozzle.

[0024] See Figure 1 An immersion nozzle includes an outer body 1, an outer slag line segment 2, and an inner bore body 3.

[0025] A continuous casting anti-clogging submersible nozzle inner body material, wherein the inner body is an Al2O3-BN-C material, and the raw materials, by mass percentage, are: corundum 39-55%, alumina powder 6-10%, boron nitride 15-35%, graphite 12-20%, antioxidant 2-6%; and an added binder 4-7%. The antioxidant is boron carbide and borosilicate glass powder, with boron carbide 1-3% and borosilicate glass powder 1-3%. The binder is phenolic resin.

[0026] The resistivity of the inner pore material is 1.4 × 10⁻⁶. -5 ~2.2×10 -5 Ω·m, flexural strength of 6.1–7.1 MPa, porosity of 17–19%, compressive strength of 30.4–32.9 MPa, and thermal shock resistance greater than 20 cycles.

[0027] Table 1 shows five embodiments of the present invention, with units of mass percentage.

[0028] Table 1. Raw material ratios (wt%) of internal pore body materials in 5 embodiments

[0029]

[0030] According to the raw material proportions in Table 1, the manufacturing method of the submersible nozzle inner hole body of this invention is as follows: corundum, alumina powder, boron nitride, graphite, boron carbide, and borosilicate glass powder are used as raw materials, and phenolic resin is used as a binder. After conventional mixing, molding, and drying, it is compounded with aluminum-carbon body and zirconium-carbon slag line material, and formed by isostatic pressing. After firing at 1000-1200℃, the required anti-clogging submersible nozzle can be obtained.

[0031] Table 2 shows the performance indicators of five embodiments and two comparative examples of the present invention.

[0032] Table 2 Material Specifications of the Inner Hole of the Anti-clogging Immersion Water Inlet of the Invention

[0033]

[0034] According to the data in Table 2, the flexural strength of the submerged nozzle inner pore material of the present invention is 6.1–7.1 MPa, the compressive strength is 30.4–32.9 MPa, and the thermal shock resistance is greater than 20 cycles, which is higher than that of the comparative example; the porosity is 17–19%, and the molten steel slag wetting depth is 1.1–1.6, which is lower than that of the comparative example. This indicates that the inner pore material of the present invention has excellent thermal shock resistance, erosion resistance, resistance to molten metal wetting, and resistance to oxide deposition and adhesion. Meanwhile, the resistivity of the submerged nozzle inner pore material of the present invention is 1.4 × 10⁻⁶. -5 ~2.2×10 -5 The conductivity is much lower than that of the comparative sample, indicating that the internal porous material of the present invention has good electrical conductivity.

[0035] Submerged entry nozzle (SIN) clogging and blockage is a complex physicochemical process involving numerous influencing factors and conditions that interact with each other. The SIN clogging nozzle internal material of this invention possesses excellent combined properties of electrical conductivity, resistance to wetting, corrosion, and thermal shock. It allows the SIN clogging nozzle to be connected to an external power source to create an electric field. Through electric field-material coupling, SIN clogging and blockage are prevented, meeting the anti-clogging requirements of continuous casting with complex inclusion compositions and various steel grades. This is a novel electrochemical anti-clogging technology in high-temperature molten steel for steelmaking continuous casting. The coupling of novel refractory materials with an external electric field is an important technological development direction for SIN clogging prevention.

[0036] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A material for the inner bore of a continuous casting anti-clogging submersible nozzle, characterized in that: The internal porous body is made of Al2O3-BN-C material, and the raw materials, by mass percentage, are: corundum 39-55%, alumina powder 6-10%, boron nitride 15-35%, graphite 12-20%, antioxidant 2-6%; with an added binder of 4-7%. The antioxidant is boron carbide and borosilicate glass powder, with boron carbide at 1-3% and borosilicate glass powder at 1-3%. The resistivity of the inner pore material is 1.4 × 10⁻⁶. -5 ~2.2×10 -5 Ω·m, flexural strength of 6.1–7.1 MPa, porosity of 17–19%, compressive strength of 30.4–32.9 MPa, and thermal shock resistance greater than 20 cycles.

2. The continuous casting anti-clogging submersible nozzle inner hole material according to claim 1, characterized in that: The binder is phenolic resin.

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