High oxygen steel dip tube and methods of making and using same

Abstract

The application discloses a high-oxygen steel submergence nozzle, a preparation method and a use method thereof. The composition of the nozzle body is as follows: C: 31%-35%, Al2O3: 49%-54%, and SiO2: 13%-16%; the composition of the composite layer is as follows: MgO: 26%-30%, and Al2O3: 70%-74%; the surface of the composite layer is attached with a coating, and the composition of the coating is as follows: MgO: 99%; and the slag line part is made of zirconium carbon material. The preparation of the nozzle comprises the following steps: batching, mixing, forming and firing. The obtained submergence nozzle product is preheated and used for pouring, can realize 1600-2000 tons of continuous casting of the steel with the oxygen activity controlled in 1.5*10 ‑4 ~3.0*10 ‑4 , and has a good refractory inner surface, so that the small pieces of the refractory material cannot enter the molten steel to become inclusions after being eroded, meanwhile, the structure size of the nozzle can not be changed after the nozzle is eroded, the protective slag can not be rolled into the nozzle to cause the nozzle to flow and the protective slag to be rolled into, and the quality of the continuous casting billet is ensured.

Description

Technical Field

[0001] This invention belongs to the field of steelmaking continuous casting technology, and specifically relates to high-oxygen steel immersion nozzles and their preparation and use methods. Background Technology

[0002] Continuous casting is primarily used to produce killed steel, requiring the lowest possible oxygen content in the molten steel to ensure high purity and prevent porosity defects. However, some steels require higher oxygen content; for example, free-machining steels require 100 ppm oxygen for the formation of type I MnS, and enamel steels need a large amount of oxide inclusions to improve resistance to scaling. High-oxygen steel releases a large amount of gas during casting, causing the molten steel to boil, which is detrimental to stable production. To address this issue, existing technologies use ingot casting, but this method is inefficient and prone to problems such as uneven microstructure and numerous impurities in the cast billet. Furthermore, high-oxygen steels have an oxygen content exceeding 1.5 × 10⁻⁶. -4 When refractory contains carbon, surface decarburization makes the refractory structure porous and loose, leading to severe oxidation. Conventional refractory suffers severe corrosion and contamination after casting 200 tons of molten steel. Refractory with an internal magnesium aluminum spinel structure is also problematic because the oxygen activity of molten steel is very high. Even after high-temperature firing, organic resin binders remain in the refractory, and the structure becomes porous after decarburization, making it unable to withstand molten steel corrosion for extended periods. Therefore, there is an urgent need to develop immersion nozzles suitable for continuous casting of high-oxygen steel and to develop appropriate processes for their preparation and use.

[0003] Chinese Patent (Application No. 202220618868.8), entitled "Three Major Components for Continuous Casting of High-Oxygen Enameled Steel," is characterized by disclosing three major components for continuous casting of high-oxygen enamel-lined steel, including a stopper rod, an upper nozzle of the tundish, and an immersion-type long nozzle. The upper nozzle of the tundish connects the stopper rod and the immersion-type long nozzle. The immersion-type long nozzle includes an upper bowl section, a connecting section, a slag line section, and a nozzle section. The bottom of the upper bowl section is sequentially provided with the connecting section, the slag line section, and the nozzle section. The upper bowl section is equipped with an air blowing component. A first channel is provided at the center of the upper bowl section and the connecting section. A second channel is provided at the center of the slag line section and the nozzle section. The first channel and the second channel are connected, and the diameter of the second channel is larger than the diameter of the first channel. This patent provides a three major component for continuous casting of high-oxygen enamel-lined steel with good thermal stability, excellent corrosion resistance, and improved corrosion and oxidation resistance. A high-temperature anti-adhesion coating layer is applied to the inner wall of the sprue channel. This high-temperature anti-adhesion coating layer is made of hollow alumina spheres and has a thickness of 1–4 mm. This hollow alumina sphere material has a loose structure and reacts with Mn, Fe, and O in the molten steel to form (Mn,Fe)O·Al2O3 particles. The MnO-FeO in the molten steel continues to react with the (Mn,Fe)O·Al2O3 particles, generating a liquid phase on the refractory material. This liquid phase is easily washed away by the molten steel, causing refractory corrosion, reducing its lifespan, and affecting the quality of the steel.

[0004] In summary, when producing high-oxygen steel using existing technologies, the sprue is easily corroded under the high-oxygen conditions of molten steel. This not only reduces the service life of the sprue, but also causes small pieces of corroded refractory material to enter the molten steel as inclusions. Furthermore, after corrosion occurs, the internal structural dimensions of the sprue change, causing the molten steel to flow out of the sprue. This makes it easy for protective slag to be drawn into the continuously cast billet, thus deteriorating the quality of the continuously cast billet. Therefore, there is an urgent need to develop a high-oxygen steel immersion nozzle that is resistant to molten steel corrosion during casting, thereby improving the service life of the sprue and ensuring the quality of the molten steel, as well as its preparation and application methods. Summary of the Invention

[0005] To address the problem of easy corrosion of nozzles during the production of high-oxygen steel, this invention provides a high-oxygen steel immersion nozzle that is resistant to corrosion by molten high-oxygen steel and less prone to cracking during continuous casting of high-oxygen steel, thereby improving nozzle life and ensuring steel quality, as well as its preparation and usage methods.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] One of the technical solutions of this invention is to provide a high-oxygen steel immersion nozzle, comprising a nozzle body, steel inlets and outlets at both ends of the body, a composite layer tightly bonded to the inner wall of the cavity inside the body, and a slag line in contact with the protective slag on the outside of the body. The composition of the nozzle body, by weight percentage, is: C: 31%–35%, Al2O3: 49%–54%, SiO2: 13%–16%; the composition of the composite layer, by weight percentage, is: MgO: 26%–30%, Al2O3: 70%–74%; and a coating is attached to the surface of the composite layer, the composition of the coating, by weight percentage, is: MgO ≥ 99%.

[0008] Furthermore, the composition of the slag line, by weight percentage, is: ZrO2: 80%–85%, ZrB2: 9%–12%, C: 6%–8%.

[0009] Furthermore, the molten steel inlet is cylindrical, and the molten steel outlet is flat.

[0010] Furthermore, the thickness of the composite layer is 4–5 mm, and the thickness of the coating is 0.05–0.2 mm.

[0011] The second technical solution of this invention provides a method for preparing a high-oxygen steel immersion nozzle, comprising the following steps:

[0012] 1) Batching: Weigh the raw materials for each part of the sprue according to the required percentages. The raw material composition of the sprue body is C: 31%~35%, Al2O3: 49%~54%, SiO2: 13%~16%; the raw material composition of the composite layer is MgO: 26%~30%, Al2O3: 70%~74%.

[0013] 2) Mixing: The phenolic resin binder accounts for 3.0% to 3.5% of the raw materials for the sprue body, and the mixing time is 5 to 10 minutes; the phenolic resin binder accounts for 3.5% to 4.0% of the raw materials for the composite layer, and the mixing time is 10 to 15 minutes; the ethanol accounts for 16% to 20% of the raw materials for the coating, and the mixing time is 3 to 5 minutes.

[0014] 3) Forming: A thin layer of refractory material with a coating layer and a composite layer is formed using a mold. First, a coating with a thickness of 0.05 to 0.2 mm is sprayed on the mold forming the inner cavity. After the coating and the composite layer form a thin layer of refractory material, the mold forming the inner cavity and the thin layer of refractory material are put into the outer rubber sleeve. First, the mixture of the nozzle body is added, then the mixture of the slag line is added, and then the mixture of the nozzle body is added again. The amount of material added is controlled according to the height required for each section of the cavity. After isostatic pressing, a whole is formed to obtain the submerged nozzle.

[0015] 4) Firing: The statically pressed sprue is fired at a temperature of 1050-1200℃ to obtain the sprue product.

[0016] Furthermore, the composition of the slag line section during batching is ZrO2: 80%–85%, ZrB2: 9%–12%, C: 6%–8%, with ZrO2 particle size of 0.10–0.40 mm, ZrB2 particle size of 0.20–0.50 mm, and C particle size of 0.02–0.06 mm; during mixing, the phenolic resin binder in the raw materials of the slag line section accounts for 3%–5%, and the mixing time is 5–10 min.

[0017] Furthermore, during the batching process, the particle size of C in the main body raw material is 0.02–0.06 mm, the particle size of Al2O3 is 0.10–0.40 mm, and the particle size of SiO2 is 0.20–0.50 mm; the particle size of MgO in the composite layer raw material is 0.05–0.15 mm, and the particle size of Al2O3 is 0.10–0.20 mm.

[0018] Furthermore, the isostatic pressing pressure during molding is controlled at 150–300 MPa, and the holding time is controlled at 30–60 s.

[0019] The third technical solution of this invention provides a method for using a high-oxygen steel immersion inlet, specifically including:

[0020] a) The high-oxygen steel immersion inlet is installed below the tundish for preheating, and the preheating time is 1.3 to 1.8 hours;

[0021] b) Continuous casting with high-oxygen steel immersion nozzle and oxygen content of 1.5 × 10⁻⁶ -4 ~3.0×10 -4 The high-oxygen steel is produced with a superheat of 30±5℃ during casting, a continuous casting billet thickness of 150~180mm, a continuous casting billet width of 1800~2200mm, and a billet pulling speed of 1.0-1.3m / min, enabling the continuous casting of 1600~2000 tons of high-oxygen steel.

[0022] Furthermore, the preheating time includes: a1) from room temperature to 700-750°C, the preheating time is controlled within 15-30 min; a2) from 700-750°C to 1180-1200°C, the preheating time is controlled within 63-78 min.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. This invention controls oxygen activity at 1.5 × 10⁻⁶. -4 ~3.0×10 -4This invention enables continuous casting of 1600-2000 tons of high-oxygen steel using various steel grades, while maintaining a good inner surface of the refractory material. This prevents small pieces of refractory material from being corroded and entering the molten steel as inclusions. In conventional refractory materials, Al₂O₃ reacts with Mn, Fe, and O in the molten steel to form (Mn,Fe)O·Al₂O₃ particles. The MnO-FeO in the molten steel then reacts with these (Mn,Fe)O·Al₂O₃ particles, forming a liquid phase on the refractory material. This liquid phase is easily washed away by the molten steel, causing refractory corrosion, reducing its lifespan, and affecting steel quality. This invention, by forming MgO and MgO·Al₂O₃ in the refractory coating and composite layer, avoids the reaction between FeO and MnO in the molten steel and the refractory material. It also prevents changes in the internal structure and dimensions of the tundish after erosion, which could lead to slag entrapment and ensure the quality of the continuously cast billet.

[0025] 2. This invention enables continuous casting of 1600-2000 tons of high-oxygen steel, reduces the amount of cut-off heads and tails of continuously cast billets and residual steel in the ladle, improves steel yield, reduces steel consumption, saves production costs, and enhances enterprise competitiveness.

[0026] 3. The high-oxygen steel immersion nozzle used in this invention and its preparation and use methods are simple in structure, easy to operate, require little investment, and do not require additional equipment. Attached Figure Description

[0027] Figure 1 Left view of the immersion nozzle;

[0028] Figure 2 : Front view of the immersion nozzle.

[0029] In the diagram: 1. Steel inlet, 2. Coating, 3. Composite layer, 4. Inlet body, 5. Slag line, 6. Steel outlet. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The described embodiments are merely some, not all, of the embodiments of this invention. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0031] To further describe the present invention, the following detailed description is provided in conjunction with embodiments:

[0032] 1. High-oxygen steel immersion inlet

[0033] like Figure 1 ,2 As shown, the high-oxygen steel immersion nozzle includes a steel inlet 1, a coating 2, a composite layer 3, a nozzle body 4, a slag line 5, and a steel outlet 6. The nozzle body 4 has a composition of C: 31%–35%, Al₂O₃: 49%–54%, and SiO₂: 13%–16%. The composite layer 3 has a thickness of 4–5 mm and a composition of MgO: 26%–30% and Al₂O₃: 70%–74%. The composite layer 3 is tightly bonded to the nozzle body 4. The coating 2 is attached to the composite layer 3, and its composition is MgO content ≥99%, with a thickness of 0.05–0.2 mm. Molten steel enters the immersion nozzle through the steel inlet 1. The refractory material, coating, and composite layer are composed of MgO and MgO·Al₂O₃, which can inhibit the formation of (Mn,Fe)O·Al₂O₃ particles on the surface of the refractory composite layer, thereby preventing the surface of the refractory composite layer from being eroded. The slag line composition is ZrO2: 80%–85%, ZrB2: 9%–12%, C: 6%–8%. Molten steel enters the continuous casting mold through molten steel outlet 6. During casting at the immersion nozzle, the slag line portion in contact with the protective slag is made of zirconium carbide to improve the erosion resistance of the immersion nozzle. Molten steel inlet 1 is cylindrical, and molten steel outlet 6 is flat, suitable for casting thin slabs. Relevant parameters for various parts of the nozzle in the examples and comparative examples are shown in Table 1.

[0034] Table 1 Parameters of various parts of the water inlet

[0035]

[0036] As shown in Table 1, the comparative example has no coating, and the composite layer composition is C: 4%–6%, Al2O3: 22%–26%, and SiO2: 68%–74%. Under the action of molten high-oxygen steel, the C and SiO2 in the composite layer react with FeO and MnO, making the surface of the refractory composite layer rough. FeO and MnO react with Al2O3 in the refractory to form (Mn,Fe)O·Al2O3 particles. FeO and MnO further react with (Mn,Fe)O·Al2O3 to form a liquid phase. This liquid phase is easily washed away by the molten steel, causing refractory corrosion, reducing the refractory's lifespan, and affecting the steel quality. This invention, by forming MgO and MgO·Al2O3 in the refractory coating and composite layer, avoids the reaction of FeO and MnO with the refractory, prevents the inner surface of the refractory from being eroded, and solves the problem of low molten steel volume in continuous casting of high-oxygen steel.

[0037] 2. Preparation of high-oxygen steel immersion nozzle

[0038] The preparation of a high-oxygen steel immersion nozzle includes the following steps:

[0039] 1) Batching: Weigh the raw materials for each part of the sprue according to the required percentages. The composite layer 3 has the following composition: MgO: 26%–30%, Al2O3: 70%–74%, with MgO particle size of 0.05–0.15 mm and Al2O3 particle size of 0.10–0.20 mm. The sprue body 4 has the following composition: C: 31%–35%, Al2O3: 49%–54%, SiO2: 13%–16%, with C particle size of 0.05–0.15 mm. The particle size of ZrO2 is 0.02–0.06 mm, the particle size of Al2O3 is 0.10–0.40 mm, the particle size of SiO2 is 0.20–0.50 mm, and the composition of the slag line section is ZrO2: 80%–85%, ZrB2: 9%–12%, C: 6%–8%, with ZrO2 particle size of 0.10–0.40 mm, ZrB2 particle size of 0.20–0.50 mm, and C particle size of 0.02–0.06 mm.

[0040] 2) Mixing: The ethanol content in the coating is 16% to 20%, and the mixing time is 3 to 5 minutes. When mixing the raw materials of composite layer 3, the phenolic resin binder content is 3.5% to 4.0%, and the mixing time is 10 to 15 minutes. When mixing the raw materials of water nozzle body 4, the phenolic resin binder content is 3.0% to 3.5%, and the mixing time is 5 to 10 minutes. When mixing the raw materials of slag line 5, the phenolic resin binder content is 3% to 5%, and the mixing time is 5 to 10 minutes.

[0041] 3) Forming: A thin layer of refractory material with a coating layer and a composite layer is formed using a steel mold. First, a coating layer 2 with a thickness of 0.05-0.2 mm is sprayed onto the mold forming the inner cavity. The MgO particle size in coating layer 2 is 0.01-0.02 mm, and the ethanol content is 16%-20%. The ethanol evaporates and is removed from the coating quickly without causing any side effects. After obtaining the thin layer of refractory material, the mold forming the inner cavity and the thin layer of refractory material are placed together into the outer rubber sleeve. First, the mixture of the nozzle body 4 is added, then the mixture of the slag line is added, and then the mixture of the nozzle body 4 is added again. The amount of material added is controlled according to the height required for each section of the cavity. After isostatic pressing, a whole is formed. The isostatic pressing pressure is controlled at 150-300 MPa, and the pressure holding time is 30-60 s. The submerged nozzle is obtained.

[0042] 4) Firing: The isostatically pressed sprue is fired at a temperature of 1050–1200°C to obtain the sprue product. Relevant parameters for each part of the sprue in the examples and comparative examples are shown in Table 2.

[0043] Table 2. Sprue process parameters

[0044]

[0045]

[0046] The particle size of the comparative composite layer C is 0.02-0.06 mm, the particle size of Al2O3 is 0.10-0.40 mm, the particle size of SiO2 is 0.20-0.50 mm, and the particle size of MgO is 0.05-0.15 mm. When the raw materials of the composite layer are mixed, the proportion of phenolic resin binder is 3.5%-4.0%, and the mixing time is 10-15 min. As can be seen from Table 2, there is little difference in the preparation process.

[0047] 3. Use of high-oxygen steel immersion inlet

[0048] a) The high-oxygen steel immersion inlet is installed below the tundish for preheating, with a preheating time of 1.3–1.8 hours. Specifically, a1) from room temperature to 700–750°C, the preheating time is controlled within 15–30 minutes; a2) from 700–750°C to 1180–1200°C, the preheating time is controlled within 63–78 minutes.

[0049] The oxygen content of the continuous casting process using high-oxygen steel immersion nozzles is 1.5 × 10⁻⁶. -4 ~3.0×10 -4 The high-oxygen steel was produced by casting molten steel with a superheat of 30±5℃, a continuous casting billet thickness of 150-180mm, a billet width of 1800-2200mm, and a casting speed of 1.0-1.3m / min, enabling the continuous casting of 1600-2000 tons of high-oxygen steel. After casting a certain weight of molten steel, the tundish was removed, and the changes in the inner surface of the tundish were observed after cooling. The results are shown in Table 3.

[0050] Table 3. Water Inlet Usage and Effects

[0051]

[0052]

[0053] In summary, as shown in Table 3, casting using a three-layer composite immersion nozzle, with the active oxygen content controlled at 1.5 × 10⁻⁶, is effective. -4 ~3.0×10 -4 When using the immersion nozzle of this invention, continuous casting of 1600-2000 tons of high-oxygen steel can be achieved, which significantly increases the continuous casting weight of molten steel. It will not cause the nozzle refractory to be corroded and enter the steel to form foreign inclusions. At the same time, it will not cause changes in the internal shape due to the corrosion of the nozzle refractory, resulting in the phenomenon of molten steel deviation and slag entrapment. It effectively ensures the quality of the continuously cast billet and helps to reduce production costs.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-oxygen steel immersion nozzle, comprising a nozzle body (4), steel inlets (1) and steel outlets (6) at both ends of the body, a composite layer (3) tightly bonded to the inner wall of the cavity inside the body, and a slag line (5) in contact with protective slag on the outside of the body, characterized in that, The composition of the main body of the water inlet (4) by weight percentage is: C: 31%~35%, Al2O3: 49%~54%, SiO2: 13%~16%; the composition of the composite layer (3) by weight percentage is: MgO: 26%~30%, Al2O3: 70%~74%; the surface of the composite layer (3) is coated with a coating (2), the composition of the coating (2) by weight percentage is: MgO≥99%; the composition of the slag line (5) by weight percentage is: ZrO2: 80%~85%, ZrB2: 9%~12%, C: 6%~8%.

2. The high-oxygen steel immersion nozzle according to claim 1, characterized in that, The molten steel inlet (1) is cylindrical, and the molten steel outlet (6) is flat.

3. The high-oxygen steel immersion inlet according to claim 1 or 2, characterized in that, The thickness of the composite layer (3) is 4~5mm, and the thickness of the coating (2) is 0.05~0.2mm.

4. A method for preparing a high-oxygen steel immersion nozzle according to any one of claims 1 to 3, characterized in that, 1) Batching: Weigh the raw materials for each part of the sprue according to the required percentages. The raw material composition of the sprue body is C: 31%~35%, Al2O3: 49%~54%, SiO2: 13%~16%; the raw material composition of the composite layer is MgO: 26%~30%, Al2O3: 70%~74%. 2) Mixing: The phenolic resin binder accounts for 3.0%~3.5% of the raw materials of the sprue body, and the mixing time is 5~10 min; the phenolic resin binder accounts for 3.5%~4.0% of the raw materials of the composite layer, and the mixing time is 10~15 min; the ethanol accounts for 16%~20% of the raw materials of the coating, and the mixing time is 3~5 min. 3) Forming: A thin layer of refractory material with coating layer and composite layer is formed by using a mold. First, a coating layer (2) with a thickness of 0.05~0.2mm is sprayed on the mold forming the inner cavity. After the coating layer (2) and the composite layer form a thin layer of refractory material, the mold forming the inner cavity and the thin layer of refractory material are put into the outer rubber sleeve. First, the mixture of the nozzle body (4) is added, then the mixture of the slag line is added, and then the mixture of the nozzle body (4) is added again. The amount of material added is controlled according to the height required for each section of the cavity. After isostatic pressing, a whole is formed to obtain the submerged nozzle. 4) Firing: The isostatically pressed sprue is fired at a temperature of 1050~1200℃ to obtain the sprue product.

5. The method for preparing a high-oxygen steel immersion nozzle according to claim 4, characterized in that, The composition of the raw materials in the slag line section during batching is ZrO2: 80%~85%, ZrB2: 9%~12%, C: 6%~8%, with ZrO2 particle size of 0.10~0.40mm, ZrB2 particle size of 0.20~0.50mm, and C particle size of 0.02~0.06mm. During mixing, the phenolic resin binder in the raw materials in the slag line section accounts for 3%~5%, and the mixing time is 5~10min.

6. The method for preparing a high-oxygen steel immersion nozzle according to claim 4, characterized in that, During the batching process, the particle size of C in the raw material of the sprue body is 0.02~0.06mm, the particle size of Al2O3 is 0.10~0.40mm, and the particle size of SiO2 is 0.20~0.50mm; the particle size of MgO in the raw material of the composite layer is 0.05~0.15mm, and the particle size of Al2O3 is 0.10~0.20mm.

7. The method for preparing a high-oxygen steel immersion nozzle according to claim 4, characterized in that, During molding, the isostatic pressing pressure is controlled at 150~300MPa, and the holding time is controlled at 30~60s.

8. A method of using a high-oxygen steel immersion inlet according to any one of claims 1 to 3, characterized in that, a) The high-oxygen steel immersion inlet is installed below the tundish for preheating, and the preheating time is 1.3~1.8h; b) Continuous casting with high-oxygen steel immersion nozzle and oxygen content of 1.5 × 10⁻⁶ -4 ~3.0×10 -4 The high-oxygen steel is produced with a superheat of 30±5℃ during casting, a continuous casting billet thickness of 150-180mm, a continuous casting billet width of 1800-2200mm, and a billet pulling speed of 1.0-1.3m / min, enabling the continuous casting of 1600~2000 tons of high-oxygen steel.

9. The method of using the high-oxygen steel immersion inlet according to claim 8, characterized in that, The preheating time includes: a1) from room temperature to 700~750℃, the preheating time is controlled at 15~30min; a2) from 700~750℃ to 1180~1200℃, the preheating time is controlled at 63~78min.

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