A slag-removing outer tube material of a tapered oxygen lance for a converter and a method for preparing the outer tube

Abstract

This invention provides a slag-removing outer tube material and a method for preparing the outer tube for a tapered oxygen lance used in a converter, belonging to the field of steelmaking equipment and accessories. The slag-removing outer tube material includes a base layer, a transition layer, and an outer coating layer; wherein the base layer is made of rare-earth heat-resistant austenitic stainless steel, and the composition of the stainless steel, by mass percentage, includes: C: 0.021-0.035%; Si: 0.10-0.30%; Mn: 2.5-3.0%; P: ≤0.001%; ​​S: 0≤0.001%; ​​Cr: 22.0-23.5%; Ni: 19.0-21.5%; N: 0.05-0.10%; Nb+Ta: 0.03-0.0 9%, and Ta=(3-4)Nb; Nd: 0.005-0.015%; W: 2.0-4.0%; B: 0.002-0.005%; Ce: 0.02-0.05%; Al: 0.01-0.02%; the balance is Fe and unavoidable impurities; austenite grains 20-50um; the transition layer is an Al-permeable layer and an α-Al2O3 film; the Al-permeable layer penetrates the substrate surface to a thickness of 0.02-0.2mm; the outer coating is α-Al2O3 and Y3Al5O 12 Eutectic ceramic layer. This invention improves the properties of the oxygen lance outer tube itself through improvements to the outer tube material and heat treatment, and forms an outer protective layer, reducing the adhesion of steel slag and increasing the oxygen lance's lifespan.

Description

Technical fields:

[0001] This invention belongs to the field of steelmaking equipment and accessories, specifically relating to a slag-removing outer tube material and a method for preparing the outer tube for a conical oxygen lance used in a converter. Background technology:

[0002] Converter steelmaking uses molten iron, scrap steel, and ferroalloys as main raw materials. The steelmaking process is completed in the converter by generating heat through the physical heat of the molten iron itself and the chemical reactions between its components. Oxygen is blown into the converter, along with slagging agents, to remove excess carbon and other impurities from the molten iron. Oxygen is typically introduced into the converter through oxygen lances, including top blowing, bottom blowing, and a combination of top and bottom blowing. During the blowing process, steel slag easily adheres to the outer tube and nozzle of the oxygen lance, affecting not only the oxygen blowing efficiency but also the lance lifting speed. Furthermore, cleaning an oxygen lance with a large amount of slag is time-consuming and labor-intensive, shortening its lifespan. Therefore, researchers have focused on reducing slag buildup on oxygen lances and extending their service life.

[0003] Oxygen lances for converters are generally designed in a conical shape and consist of a nozzle, a lance body, and a lance tail. The nozzle is usually a detachable and replaceable component. The lance body consists of an inner oxygen tube, a middle tube, and an outer tube from the inside out. The outer tube is divided into multi-angle conical sections, a cylindrical section, and an inverted conical section from bottom to top, and is the part that comes into the most contact with molten steel and slag.

[0004] In existing technologies, the amount of slag adhering to the outer tube is generally reduced by spraying an anti-sticking layer or a slag release agent onto the outer tube. For example, Chinese patent number 201911104259.X discloses a slag release agent for oxygen lances, which designs a new composition including a ratio of C≥55%, Al2O3:5~8%, SiO2:8~12%, CaO≥3%, and MgO≥2%, with a fineness of 200~300 mesh and a pH value of 4~6.5. Simultaneously, 0.5~0.8% of ammonium polyacrylate by total mass is added. This release agent is sprayed onto the surface of the oxygen lance to form a protective film, reducing cleaning difficulty. However, the composition of this release agent is similar to that of steel slag; although it is easier to peel off, it is also more likely to adhere to steel slag, potentially increasing the frequency of lance lifting. Chinese patent application number 201810845976.7 discloses a method for preparing an anti-stick steel coating on the surface of an oxygen lance and an oxygen lance with the anti-stick steel coating. The method involves steps such as removing residual metal from the surface, sandblasting, spraying an adhesive layer, and spraying a ceramic anti-stick layer to spray an anti-stick steel coating on the outer surface of the front section of the oxygen lance body, consisting of an adhesive layer and a ceramic anti-stick layer arranged sequentially from the inside out. However, the adhesive layer still maintains a simple adhesion relationship with the outer tube, and due to the difference in expansion coefficients, problems such as easy detachment still exist. Summary of the Invention:

[0005] To address the aforementioned problems, this invention provides a slag-removing outer tube material and a method for preparing the outer tube for a converter tapered oxygen lance. By improving the outer tube material and heat-treating it, the properties of the oxygen lance outer tube itself are improved. Then, by spraying an intermediate layer and an anti-sticking layer, the intermediate layer and the improved outer tube are simultaneously heat-treated to form a chemically bonded layer, which better forms an outer protective layer with the anti-sticking layer, reducing the adhesion of steel slag and improving the oxygen lance's lifespan.

[0006] To achieve the above objectives, the technical solutions adopted in the embodiments of the present invention are as follows:

[0007] In a first aspect, embodiments of the present invention provide a slag-removing outer tube material for a tapered oxygen lance used in a converter, the oxygen lance outer tube comprising a base layer, a transition layer, and an outer coating layer; wherein, the base layer is made of rare-earth heat-resistant austenitic stainless steel, and the composition of the stainless steel, by mass percentage, comprises:

[0008] C: 0.021-0.035%; Si: 0.10-0.30%; Mn: 2.5-3.0%; P: ≤0.001%; ​​S: 0≤0.001%; ​​Cr: 22.0-23.5%; Ni: 19.0-21.5%; N: 0.05-0.10%; Nb+Ta: 0.03-0.09%, and Ta=(3-4)Nb; Nd: 0.005-0.015%; W: 2.0-4.0%; B: 0.002-0.005%; Ce: 0.02-0.05%; Al: 0.01-0.02%; balance Fe and unavoidable impurities; austenite grains 20-50µm;

[0009] The transition layer consists of an Al-permeated layer and an α-Al₂O₃ film; the Al-permeated layer penetrates the substrate surface with a thickness of 0.02-0.2 mm; the α-Al₂O₃ film outside the substrate has a thickness of 0.001-0.01 mm.

[0010] The outer coating is α-Al2O3 and Y3Al5O3. 12 Eutectic ceramic layer; thickness 0.05-0.5mm.

[0011] The following is a detailed explanation of the principles behind the addition of various components to steel.

[0012] C: Carbon (C) forms carbides under high-temperature operating conditions, giving the stainless steel used as the outer tube of the oxygen lance the required high-temperature strength. To ensure the amount of carbide precipitation that forms the strengthening mechanism, the C content needs to be at least 0.21% by mass. However, if the C content is excessive, exceeding 0.035% by mass, coarse carbides will form, preventing further strengthening. The C content is preferably between 0.021% by mass and 0.035% by mass, and more preferably 0.025-0.030%.

[0013] Si: Si acts as a deoxidizer in molten steel, and trace amounts of Si can effectively improve the oxidation resistance of steel. To effectively utilize the effects of silicon, the Si content needs to be above 0.1% by mass. However, if the Si content exceeds 0.30% by mass and is excessive, it will lead to the formation of the σ phase, thereby reducing toughness. The Si content is preferably above 0.10% by mass and below 0.30% by mass.

[0014] Mn: Both Mn and Si have deoxidizing effects in molten steel. Furthermore, when the Mn content is above 2.5% by mass, it also stabilizes austenite. However, if the Mn content exceeds 3.0% by mass and is excessive, it hinders hot workability.

[0015] P and S are unavoidable impurities. Increased P content impairs weldability, while increased S content deteriorates hot workability. Therefore, it is necessary to control both P and S to below 0.001% by mass.

[0016] Cr: Cr gives stainless steel its corrosion resistance, and the Cr content generally needs to be above 22% by mass. However, too high a Cr content will increase the ferrite in the steel, reducing the steel's high-temperature strength.

[0017] Ni: Ni plays a role in stabilizing austenite. However, increasing the Ni content will increase the cost of steel.

[0018] Nitrogen (N): Nitrogen can improve the high-temperature strength of steel through solid solution strengthening, allowing the oxygen lance to maintain its original shape when used at high temperatures. The addition amount is 0.03% by mass or more. However, if too much nitrogen is added, it will affect the hot workability of the steel.

[0019] Nb and Ta: Nb and Ta can precipitate carbides, nitrides, or carbonitrides, effectively improving high-temperature strength. Some of the precipitates form are at grain boundaries, while others precipitate within the grains. Ta tends to precipitate within the grains, acting as a solid solution and effectively increasing the internal stress of the grains, thus improving high-temperature strength. Nb tends to precipitate at grain boundaries, acting as a pinning agent, effectively inhibiting grain growth. This improves high-temperature strength through grain refinement and promotes Cr diffusion, enhancing corrosion resistance. However, if the precipitates at the grain boundaries become a covering, or if there are too many precipitates within the grains, the strength decreases. Therefore, the total Nb+Ta content should be maintained at 0.03-0.09%, satisfying Ta = (3-4)Nb. Preferably, the Nb+Ta content is 0.05-0.07%. Most preferably, Nb is 0.01-0.02%, and Ta is 0.04-0.05%.

[0020] Nd, as a La-series element, is a close neighbor of Ta and Nb. It works synergistically with Ta to improve the stress resistance of steel, thereby increasing its strength. However, excessive Nd content can increase the toughness of the steel while significantly reducing its strength. The optimal addition amount is 0.005-0.015% by mass. Preferably, the content is 0.010-0.012%.

[0021] W: Small amounts of W can effectively improve the high-temperature strength of steel through solid solution treatment. However, excessive W, especially when the W content exceeds 4% by mass, promotes the formation of the σ phase and reduces the corrosion resistance of the steel. Therefore, the optimal addition amount is 2.0-4.0%. Preferably, the content is 2.5-3.5%.

[0022] B: In steel, B, through solid solution, strengthens grain boundaries and thus improves stress resistance and corrosion resistance when added at a level of 0.002% or higher. However, excessive B can lead to a decrease in hot workability and weldability, so it needs to be controlled below 0.005% by mass.

[0023] Ce: The addition of the rare earth element Ce can effectively promote the modification of precipitates, improve the high-temperature performance of steel, and thus further enhance the high-temperature strength of the steel. However, excessive Ce can lead to changes in the precipitates, affecting the solid solution effect and increasing costs. Therefore, the Ce content needs to be controlled between 0.02-0.05%. Preferably, the content is 0.03-0.04%.

[0024] Al: Al not only aids in deoxidation but also improves the oxidation and corrosion resistance of steel at high temperatures. Furthermore, in the subsequent aluminizing process, it facilitates aluminum penetration and promotes the formation of an α-Al₂O₃ film, thus creating a transition layer. Therefore, the Al content needs to be controlled between 0.01% and 0.02%.

[0025] Secondly, based on the aforementioned tapered oxygen lance outer tube, embodiments of the present invention also provide a tapered oxygen lance.

[0026] Including the outer tube, the material of the tapered oxygen lance outer tube is the same as the slag-removing outer tube material of the tapered oxygen lance for converters mentioned above.

[0027] Thirdly, based on the material of the oxygen lance outer tube, this embodiment of the invention also provides a method for preparing a tapered oxygen lance outer tube for a converter, the method comprising:

[0028] Step S1: Melt stainless steel with a carbon content of 0.5% to 1.0% and a temperature of 1570℃ to 1590℃ in a medium-frequency induction furnace and pour it into an AOD furnace. Top-blown oxygen is used for decarbonization, and nitrogen is used for stirring. During the decarbonization process, lime and dolomite are added to make preliminary fine adjustments to the Si content, while simultaneously removing P and S. Then, lime and CaF2 are added to reduce and desaturate the molten steel. After reduction, slag is skimmed off, the slag basicity is adjusted, the temperature of the molten steel is measured, and samples are taken to analyze the content of alloying elements in the molten steel.

[0029] Step S2: According to the element content, ferrosilicon, ferromanganese, ferrochrome, chromium-nickel master alloy, and ferrotungsten are added to the molten steel to adjust the Si, Mn, Cr, Ni, and W composition of the molten steel to meet the specified requirements.

[0030] Step S3: After adjusting the steel composition, argon gas is blown into the AOD furnace side. After argon blowing is completed, samples are taken for analysis. Steel is tapped immediately when the mass ratio of the steel composition meets the requirements. The tapping conditions include: C: 0.021-0.035%; Si: 0.10-0.30%; Mn: 2.5-3.0%; P: ≤0.001%; ​​S: 0≤0.001%; ​​Cr: 22.0-23.5%; Ni: 19.0-21.5%; N: 0.05-0.10%; W: 2.0-4.0%.

[0031] Step S4, tapping steel; During tapping, molten steel is poured from the AOD furnace into a ladle that has been preheated at 400-500℃. When the amount of molten steel tapped reaches 2 / 5 of the total amount of molten steel, ferroboron is added to the ladle and aluminum wire is fed in; After tapping, the temperature of the molten steel and the thickness of the slag layer are measured. The temperature of the molten steel is controlled at 1570℃~1600℃, and the thickness of the slag layer in the ladle is controlled at 100mm~120mm.

[0032] Step S5: Nb+Ta wire, Nd wire and Ce wire are fed in according to the weight and composition of molten steel; the ladle is stirred by low-pressure argon blowing; when the temperature of molten steel reaches 1510℃~1530℃, the billet is obtained by continuous casting.

[0033] Step S6: The billet is heated, pierced, expanded, rolled, cooled and cut to obtain a three-section conical hollow tube, including a multi-angle conical section near the nozzle, a cylindrical section and an inverted conical section;

[0034] Step S7: The three-section conical hollow tube is subjected to aluminizing treatment, and then the aluminized substrate is subjected to oxidation treatment to form an α-Al2O3 film on the outer surface of the substrate layer. The aluminized layer and the α-Al2O3 film together form a transition layer outside the substrate layer.

[0035] Step S8: Using alcohol as a medium, α-Al2O3 and Y2O3 nanoparticles are prepared into a uniform suspension slurry; using thermal spraying, the slurry is sprayed onto the outside of the transition layer to form an amorphous coating of α-Al2O3 and Y2O3, which is then crystallized in a muffle furnace at 950-1200℃ to form α-Al2O3 and Y3Al5O3. 12 A eutectic ceramic layer serves as the outer coating.

[0036] In step S6, the three-section conical hollow tube is manufactured by forging. The outer tube of the oxygen lance, as the outermost tube of the oxygen lance, needs to support the oxygen lance during high-temperature operation and must achieve a predetermined high-temperature strength; this is achieved through the base layer of the outer tube. Additionally, the outer layer needs to provide some isolation from slag in the molten steel, preventing excessive slag adhesion, which would affect the lifting operation of the oxygen lance; this is achieved through the outer coating of the oxygen lance. As the outermost layer of the oxygen lance, the three sections include a multi-angle conical section near the nozzle, a cylindrical section, and an inverted conical section. The taper of each section is controlled during forging according to the shape requirements of the outer tube. The multi-angle conical section near the nozzle protects the nozzle and, through its gradually transitioning taper, reduces slag adhesion while facilitating the entry and exit of the oxygen lance from the molten steel. The cylindrical section serves as a connecting section, effectively linking the multi-angle conical section and the inverted conical section. The inverted conical section, with a taper opposite to that of the multi-angle conical section, connects to the guide ring controlling the oxygen lance, increasing the force applied to the oxygen lance.

[0037] The solutions of the embodiments of the present invention have the following beneficial effects:

[0038] The slag-removing outer tube material and its preparation method for the tapered oxygen lance for converter provided in this embodiment of the invention improve the properties of the outer tube itself by improving the outer tube material and heat treatment. Then, by spraying an intermediate layer and an anti-sticking layer, the intermediate layer and the improved outer tube are heat-treated at the same time to form a chemical bonding layer, which better forms an outer protective layer with the anti-sticking layer, reduces the adhesion of steel slag, and improves the service life of the oxygen lance.

[0039] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached image description:

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a flowchart of the preparation method of the oxygen lance outer tube according to Embodiment 1 of the present invention;

[0042] Figure 2 This is a schematic diagram of the oxygen lance structure provided in Embodiment 1 of the present invention;

[0043] Figure 3 This is a schematic diagram of the external shape structure of the oxygen lance outer tube provided in Embodiment 1 of the present invention.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1- Nozzle; 2- Inner oxygen tube; 3- Middle tube; 4- Outer tube; 41- Nozzle head; 42- Multi-angle conical section; 43- Cylindrical section; 44- Inverted conical section; 5- Guide ring; Detailed implementation method:

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can also be combined with each other.

[0047] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, the terms "first," "second," "third," "fourth," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0048] Example 1

[0049] This embodiment provides a slag-removing outer tube material for a tapered oxygen lance used in a converter and its preparation method.

[0050] The oxygen lance outer tube has a three-layer material structure: a base layer, a transition layer, and an outer coating layer; wherein the base layer is made of rare-earth heat-resistant austenitic stainless steel, and the composition of the stainless steel, by mass percentage, includes:

[0051] C: 0.021%; Si: 0.10%; Mn: 2.5%; P: ≤0.001%; ​​S: ≤0.001%; ​​Cr: 23.5%; Ni: 19.0%; N: 0.05%; Nb: 0.02%; Ta: 0.07%; Nd: 0.015%; W: 4.0%; B: 0.002%; Ce: 0.05%; Al: 0.01%; balance Fe and unavoidable impurities; austenite grains 20-50 μm;

[0052] The transition layer consists of an Al-permeable layer and an α-Al₂O₃ film; the Al-permeable layer penetrates the substrate surface with a thickness of 0.02 mm; the α-Al₂O₃ film outside the substrate has a thickness of 0.001 mm.

[0053] The outer coating is α-Al2O3 and Y3Al5O3. 12 Eutectic ceramic layer; thickness is 0.05 mm.

[0054] like Figure 1 As shown, the method for preparing the oxygen lance outer tube is as follows;

[0055] Step S1: Melt stainless steel with a carbon content of 0.5% to 1.0% and a temperature of 1570℃ to 1590℃ in a medium-frequency induction furnace and pour it into an AOD furnace. Top-blown oxygen is used for decarbonization, and nitrogen is used for stirring. During the decarbonization process, lime and dolomite are added to make preliminary fine adjustments to the Si content, while simultaneously removing P and S. Then, lime and CaF2 are added to reduce and desaturate the molten steel. After reduction, slag is skimmed off, the slag basicity is adjusted, the temperature of the molten steel is measured, and samples are taken to analyze the content of alloying elements in the molten steel.

[0056] Step S2: According to the element content, add ferrosilicon, ferromanganese, ferrochrome, chromium-nickel master alloy, and ferrotungsten to the molten steel to adjust the Si, Mn, Cr, Ni, and W composition of the molten steel to meet the specified requirements.

[0057] Step S3: After adjusting the steel composition, argon gas is blown into the AOD furnace side; after argon blowing is completed, samples are taken for analysis, and the steel is tapped immediately when the mass ratio of the steel composition meets the requirements; the tapping conditions include: C: 0.021%; Si: 0.10%;

[0058] Mn: 2.5%; P: ≤0.001%; ​​S: 0≤0.001%; ​​Cr: 23.5%; Ni: 19.0%; N: 0.05-%;

[0059] W: 4.0%;

[0060] Step S4, tapping steel; During tapping, molten steel is poured from the AOD furnace into a ladle that has been preheated at 400-500℃. When the amount of molten steel tapped reaches 2 / 5 of the total amount of molten steel, ferroboron is added to the ladle and aluminum wire is fed in; After tapping, the temperature of the molten steel and the thickness of the slag layer are measured. The temperature of the molten steel is controlled at 1570℃~1600℃, and the thickness of the slag layer in the ladle is controlled at 100mm~120mm.

[0061] Step S5: Nb+Ta wire, Nd wire and Ce wire are fed in according to the weight and composition of molten steel; the ladle is stirred by low-pressure argon blowing; when the temperature of molten steel reaches 1510℃~1530℃, the billet is obtained by continuous casting.

[0062] Step S6: The billet is heated, pierced, expanded, rolled, cooled and cut to obtain a three-section conical hollow tube, including a nozzle 41, a multi-angle conical section 42, a cylindrical section 43 and an inverted conical section 44.

[0063] Step S7: The three-section conical hollow tube is subjected to aluminizing treatment, and then the aluminized substrate is subjected to oxidation treatment to form an α-Al2O3 film on the outer surface of the substrate layer. The aluminized layer and the α-Al2O3 film together form a transition layer outside the substrate layer.

[0064] Step S8: Using alcohol as a medium, α-Al2O3 and Y2O3 nanoparticles are prepared into a uniform suspension slurry; using thermal spraying, the slurry is sprayed onto the outside of the transition layer to form an amorphous coating of α-Al2O3 and Y2O3, which is then crystallized in a muffle furnace at 1200℃ to form α-Al2O3 and Y3Al5O3. 12 A eutectic ceramic layer serves as the outer coating.

[0065] like Figure 2 and Figure 3 As shown, the oxygen lance includes a nozzle 1, an inner oxygen tube 2, a middle tube 3, an outer tube 4, and a guide ring 5. The outer tube 5 is the oxygen lance outer tube prepared by the above preparation method.

[0066] The slag-removing outer tube material and its preparation method for the tapered oxygen lance for converter provided in this embodiment improve the properties of the outer tube itself by improving the outer tube material and heat treatment. Then, by spraying an intermediate layer and an anti-sticking layer, the intermediate layer and the improved outer tube are heat-treated at the same time to form a chemical bonding layer, which better forms an outer protective layer with the anti-sticking layer, reducing the adhesion of steel slag and improving the service life of the oxygen lance.

[0067] Example 2

[0068] This embodiment also provides a slag-removing outer tube material for a converter tapered oxygen lance and its preparation method. The material structure of the oxygen lance outer tube is also three layers. The preparation method includes steps S1-S7 as described in Embodiment 1. The oxygen lance provided is basically the same as that in Embodiment 1, except that the designed component content, transition layer, and outer coating thickness are different. The specific parameters used are as follows:

[0069] C: 0.035%; Si: 0.30%; Mn: 3.0%; P: ≤0.001%; ​​S: ≤0.001%; ​​Cr: 22.0%; Ni: 21.5%; N: 0.10%; Nb: 0.007%; Ta: 0.023%; Nd: 0.005%; W: 2.0%; B: 0.005%; Ce: 0.02%; Al: 0.02%; balance Fe and unavoidable impurities; austenite grains 20-50 μm;

[0070] The thickness of the Al layer penetrating into the substrate surface is 0.2 mm; the thickness of the α-Al2O3 film formed outside the substrate is 0.005 mm.

[0071] The outer coating is α-Al2O3 and Y3Al5O 12 The eutectic ceramic layer has a thickness of 0.5 mm.

[0072] Example 3

[0073] This embodiment also provides a slag-removing outer tube material for a converter tapered oxygen lance and its preparation method. The material structure of the oxygen lance outer tube is also three layers. The preparation method includes steps S1-S7 as described in Embodiment 1. The oxygen lance provided is basically the same as that in Embodiment 1, except that the designed component content, transition layer, and outer coating thickness are different. The specific parameters used are as follows:

[0074] C: 0.025%; Si: 0.20%; Mn: 2.8%; P: ≤0.001%; ​​S: ≤0.001%; ​​Cr: 23.0%; Ni: 20.5%; N: 0.08%; Nb: 0.018%; Ta: 0.054%; Nd: 0.012%; W: 3.0%; B: 0.003%; Ce: 0.03%; Al: 0.015%; balance Fe and unavoidable impurities; austenite grains 20-50 μm;

[0075] The thickness of the Al layer penetrating into the substrate surface is 0.10 mm; the thickness of the α-Al2O3 film formed outside the substrate is 0.01 mm.

[0076] The outer coating is α-Al2O3 and Y3Al5O 12 Eutectic ceramic layer; thickness is 0.3 mm.

[0077] The above description is merely a preferred embodiment of the present invention and an explanation of the technical principles employed, and is not intended to limit the scope of the claimed invention, but merely to illustrate preferred embodiments of the invention. Those skilled in the art should understand that the scope of the invention is not limited to the specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A slag-removing outer tube material for a tapered oxygen lance used in a converter, characterized in that, The oxygen lance outer tube material includes a base layer, a transition layer, and an outer coating layer; The base layer is made of rare-earth heat-resistant austenitic stainless steel, and the composition of the stainless steel, by mass percentage, includes: C: 0.021-0.035%; Si: 0.10-0.30%; Mn: 2.5-3.0%; P: ≤0.001%; ​​S: 0≤0.001%; ​​Cr: 22.0-23.5%; Ni: 19.0-21.5%; N: 0.05-0.10%; Nb+Ta: 0.03-0.09%, and Ta=(3-4)Nb; Nd: 0.005-0.015%; W: 2.0-4.0%; B: 0.002-0.005%; Ce: 0.02-0.05%; Al: 0.01-0.02%; balance Fe and unavoidable impurities; austenite grains 20-50µm; The transition layer consists of an Al-permeated layer and an α-Al₂O₃ thin film; the Al-permeated layer penetrates the substrate surface to a thickness of 0.02-0.2 mm. The outer coating is α-Al2O3 and Y3Al5O3. 12 Eutectic ceramic layer.

2. The slag-removing outer tube material for the tapered oxygen lance in a converter according to claim 1, characterized in that, The thickness of the α-Al₂O₃ film outside the substrate is 0.001-0.01 mm; α-Al₂O₃ and Y₃Al₅O 12 Eutectic ceramic layer; thickness 0.05-0.5mm.

3. The slag-removing outer tube material for the tapered oxygen lance in a converter according to claim 1, characterized in that, The carbon content is 0.025-0.030%.

4. The slag-removing outer tube material for the tapered oxygen lance in a converter according to claim 1, characterized in that, The Nb+Ta content is 0.05-0.07%; of which Nb is 0.01-0.02% and Ta is 0.04-0.05%.

5. The slag-removing outer tube material for the tapered oxygen lance in a converter according to claim 1, characterized in that, The Nd content is 0.010-0.012%.

6. The slag-removing outer tube material of the tapered oxygen lance for converter according to claim 1, characterized in that, The W content is 2.5-3.5%.

7. The slag-removing outer tube material for the tapered oxygen lance in a converter according to claim 1, characterized in that, The Ce content is 0.03-0.04%.

8. A tapered oxygen lance, characterized in that, Includes an outer tube, wherein the material of the tapered oxygen lance outer tube is the slag-removing outer tube material of the tapered oxygen lance for converter as described in any one of claims 1-7.

9. A method for preparing a tapered oxygen lance outer tube for a converter, characterized in that, The preparation method includes: Step S1: Melt stainless steel with a carbon content of 0.5% to 1.0% in a medium-frequency induction furnace and pour it into an AOD furnace. Top-blown oxygen is used for decarbonization, and nitrogen is used for stirring. During the decarbonization process, lime and dolomite are added to make preliminary fine adjustments to the Si content, while simultaneously removing P and S. Then, lime and CaF2 are added to reduce and decarbonize the molten steel. After reduction, slag is removed, alkali is adjusted, temperature is measured, and samples are taken to analyze the content of alloying elements in the molten steel. Step S2: According to the element content, ferrosilicon, ferromanganese, ferrochrome, chromium-nickel master alloy, and ferrotungsten are added to the molten steel to adjust the Si, Mn, Cr, Ni, and W composition of the molten steel to meet the specified requirements. Step S3: After adjusting the steel composition, argon gas is blown into the AOD furnace side. After argon blowing is completed, samples are taken for analysis. Steel is tapped immediately when the mass ratio of the steel composition meets the requirements. The tapping conditions include: C: 0.021-0.035%; Si: 0.10-0.30%; Mn: 2.5-3.0%; P: ≤0.001%; ​​S: 0≤0.001%; ​​Cr: 22.0-23.5%; Ni: 19.0-21.5%; N: 0.05-0.10%; W: 2.0-4.0%. Step S4, tapping steel; During tapping, molten steel is poured from the AOD furnace into a ladle that has been preheated at 400-500℃. When the amount of molten steel tapped reaches 2 / 5 of the total amount of molten steel, ferroboron is added to the ladle and aluminum wire is fed in; After tapping, the temperature of the molten steel and the thickness of the slag layer are measured. The temperature of the molten steel is controlled at 1570℃~1600℃, and the thickness of the slag layer in the ladle is controlled at 100mm~120mm. Step S5: Nb+Ta wire, Nd wire and Ce wire are fed in according to the weight and composition of molten steel; the ladle is stirred by low-pressure argon blowing; when the temperature of molten steel reaches 1510℃~1530℃, the billet is obtained by continuous casting. Step S6: The billet is heated, pierced, expanded, rolled, cooled and cut to obtain a three-section conical hollow tube; Step S7: The three-section conical hollow tube is subjected to aluminizing treatment, and then the aluminized substrate is subjected to oxidation treatment to form a thin film on the outer surface of the substrate layer. The aluminized layer and the α-Al2O3 film together form a transition layer outside the substrate layer. Step S8: Using alcohol as a medium, α-Al2O3 and Y2O3 nanoparticles are prepared into a uniform suspension slurry; using thermal spraying, the slurry is sprayed onto the outside of the transition layer to form an amorphous coating of α-Al2O3 and Y2O3, which is then crystallized in a muffle furnace at 950-1200℃ to form α-Al2O3 and Y3Al5O3. 12 A eutectic ceramic layer serves as the outer coating.

10. The method for preparing the outer tube of the tapered oxygen lance for a converter according to claim 9, characterized in that, The three-section conical hollow tube includes a multi-angle conical section near the nozzle, a cylindrical section, and an inverted conical section.

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