Method for producing titanium- and aluminum-containing ultra-low carbon steel

Abstract

A method for producing titanium- and aluminum-containing ultra-low carbon steel, comprising a converter process, an RH process, and a continuous casting process that are sequentially performed, wherein in the converter process, before tapping, an inclusion modifier coating is first formed the wall surface of a ladle, and then a passivating lime powder layer is formed; following tapping, a high-alumina slag conditioning agent is added into molten steel, and argon is blown from the bottom of the ladle to perform stirring. By means of the method, the titanium- and aluminum-containing ultra-low carbon steel can be produced in a short process, and the number of inclusions such as Al2O3 in a casting blank is reduced, thereby improving the cleanliness of the titanium- and aluminum-containing ultra-low carbon steel.

Description

A method for producing titanium-aluminum-containing ultra-low carbon steel

[0001] This application claims priority to Chinese Patent Application No. 202411580205.1, filed on November 7, 2024, entitled "A Method for Producing Titanium-Aluminum Containing Ultra-Low Carbon Steel", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of iron and steel smelting and refining technology, and in particular to a method for producing titanium-aluminum ultra-low carbon steel. Background Technology

[0003] As my country's efforts to conserve energy and reduce emissions continue to deepen, more and more steelmaking enterprises are exploring ways to eliminate the LF process to achieve economical and efficient production of steel grades. In particular, for ultra-low carbon steel such as automotive steel sheets, in order to reduce long logistics time and oxygen transfer between steel and slag caused by the LF process, more and more manufacturers are adopting the "converter-RH-continuous casting" short-process production.

[0004] However, for high-quality ultra-low carbon steel such as automotive panels, the carbon content of the steel tapped from the converter is controlled too low, the oxygen activity in the steel is too high, and the oxidizability of the final slag in the converter is too high. In order to maintain sufficient free oxygen in the steel for decarburization during the RH treatment process, aluminum-containing slag conditioner is generally added to the ladle after tapping. In order to ensure sufficient free oxygen in the steel, it is also prohibited to blow large amounts of argon to react with the steel slag after tapping. This results in poor melting of the steel slag and uneven composition. After RH deoxidation and alloying, the modification effect on inclusions such as Al2O3 in the steel is weakened, making it difficult to achieve stable production of ultra-low carbon steel such as high-cleanliness automotive panels.

[0005] Therefore, to address the aforementioned problems associated with producing high-quality ultra-low carbon steel such as automotive steel using a short-process "converter-RH-continuous casting" method, steelmaking enterprises often add auxiliary materials such as lime and fluorite during the converter tapping process, and then add an aluminum-containing slag modifier to the ladle surface after tapping to deoxidize the ladle slag. However, because the melting point of auxiliary materials such as lime is high and their density is much lower than that of molten steel, a large amount of unmelted auxiliary materials remain floating on the ladle surface after tapping, reducing the ladle slag's ability to absorb inclusions. In light of these issues, researchers have adjusted the ladle slag modifier for the short-process method, as shown in the example below:

[0006] Chinese Patent Publication No. CN107815519A discloses a ladle slag modifier and a modification treatment method. The modifier composition is: CaO 50-80%, SiO2 5-15%, MgO 5-20%, Al2O3 5-15%, S≤0.08%, P≤0.025%. The modification treatment of ladle slag using this modifier is carried out by adding the modifier during the tapping process of steelmaking. This modifier can modify the high-melting-point phase of steel slag into low-melting-point slag, thereby reducing the precipitation of the high-melting-point phase in the ladle slag, thus lowering its melting temperature and adhesion properties, overcoming the phenomenon of slag adhesion and weight increase in the ladle when producing high-silicon and high-alumina steel, and ensuring smooth production.

[0007] Patent CN117488184A discloses a method for using a slag modifier in a converter-driven direct-flow silicon-killed steel ladle. This method involves adding 2.0–5.0 kg / t of lime, 0–1.0 kg / t of fluorite, and 0–1.0 kg / t of silica sand at the beginning of tapping; after tapping, adding 1.5–3 kg / t of pre-melted ladle slag modifier and 0–1.0 kg / t of ferrosilicon; strong argon blowing at the bottom of the ladle for slag formation; after strong blowing, medium-intensity argon blowing for 2–5 minutes; after medium-intensity argon blowing, calcium treatment can be performed according to the steel grade's process requirements; after calcium treatment, soft argon blowing is used to homogenize the composition, temperature, and remove inclusions. This method achieves efficient desulfurization under direct-flow silicon-killed steel converter conditions and ensures the castability of the molten steel under low oxidation conditions.

[0008] The two patents mentioned above involve adding lime, fluorite, or ladle slag modifiers during or at the beginning of the tapping process to modify inclusions in the ladle slag or steel. This can achieve a slag washing effect on the molten steel to some extent. Especially when combined with the LF process for heating and strong stirring in the later stages, the slag-metal reaction can be effectively realized, thus modifying the inclusions in the steel. However, for ultra-low carbon steel that undergoes RH directly without LF, it is difficult to achieve complete melting of the added solid slag and a sufficient slag-metal reaction within just 4-6 minutes of tapping.

[0009] Chinese patent CN118600149A discloses a production method for small-section aluminum-containing rectangular billets using a direct-up slag washing process. This method involves controlling the final steel temperature at the converter to 1670–1680℃; adding fluorine-free slag wash material, high-calcium ash, medium-carbon ferromanganese, and aluminum blocks after the furnace to wash and alloy the steel; blowing large amounts of argon gas to melt the top slag during and after tapping for 3–5 minutes; then feeding calcium wire and followed by soft argon blowing for 12–15 minutes; the amount of fluorine-free slag wash material is 1 kg / t of steel, and the amount of high-calcium ash is 4 kg / t of steel. Compared to the normal slag-free washing process, this method extends the argon blowing time, and the smelting cycle of the direct-up slag washing process is significantly shorter than the traditional refining process.

[0010] The aforementioned patent employs a "strong stirring + weak stirring" process after tapping, which achieves better modification of inclusions in steel than the traditional slag washing process. However, strong stirring after the furnace and prolonged argon blowing result in significant losses of molten steel temperature and free oxygen in the steel, making it unsuitable for the production of pre-deoxidized steels such as ultra-low carbon steel.

[0011] Therefore, for the short-process converter-RH-continuous casting process of titanium-containing ultra-low carbon steel, it is of great significance to improve the residual Al2O3 inclusions in the steel in order to obtain molten steel with higher purity. Summary of the Invention

[0012] The technical problem solved by this invention is to provide a method for producing titanium-aluminum-containing ultra-low carbon steel. The method provided in this application can stably control inclusions in steel and ensure the cleanliness of the steel.

[0013] In view of this, this application provides a method for producing titanium-aluminum ultra-low carbon steel, comprising: a converter process, an RH process, and a continuous casting process performed sequentially;

[0014] In the converter process, before tapping, an inclusion modifier coating is first formed on the surface of the ladle wall, followed by a passivating lime powder layer; after tapping, a high-alumina slag conditioner is added to the molten steel, and then argon is blown from the bottom of the ladle for stirring.

[0015] Preferably, the inclusion modifier of the inclusion modifier coating comprises, by mass percentage: CaO: 64-74%, Al2O3: 15.5-19.5%, SiO2: 0-4.5%, TiO2: 3-6%, and Re: 0.5%-0.9%.

[0016] Preferably, the inclusion modifier is a pre-melted material obtained by melting and grinding lime, corundum slag and rutile.

[0017] Preferably, the thickness of the inclusion modifier coating is 2-5 mm, and the thickness of the passivated lime powder layer is 2-5 mm.

[0018] Preferably, after adding the high-alumina slag conditioner, the ladle slag TFe ≤ 5% and the Ca / Al ratio is 2.5 to 2.8.

[0019] Preferably, the argon flow rate of the bottom-blown argon agitator in the ladle is 350-500 NL / min, and the argon blowing time is 0.5-1.5 min.

[0020] Preferably, in the RH process, before aluminum deoxidation and alloying, a small amount of argon is blown from the bottom of the ladle, with an argon flow rate of 140-180 NL / min; before titanium alloying, the argon flow rate is reduced to 80-130 NL / min.

[0021] Preferably, in the continuous casting process, after the ladle starts pouring, the ladle bottom blowing argon flow rate is 70-110 NL / min. When the ladle is poured to 1 / 4-1 / 3, the ladle bottom blowing argon flow rate is adjusted to 50-90 NL / min. When the ladle is poured to 2 / 3-3 / 4, the bottom blowing argon is stopped.

[0022] Preferably, the inclusion modifier comprises: CaO: 65-72%, Al2O3: 16-18%, SiO2: 0.5-4.0%, TiO2: 3.2-5.0%, and Re: 0.6%-0.8%.

[0023] Preferably, the composition of the titanium-aluminum ultra-low carbon steel, by mass percentage, includes: C≤0.0035%, Si≤0.020%, Mn 0.11~0.16%, P≤0.010%, S≤0.012%, Al 0.03~0.06%, Ti 0.05~0.07%, with the balance being Fe.

[0024] This application provides a method for producing titanium-aluminum-containing ultra-low carbon steel, comprising a converter process, an RH process, and a continuous casting process performed sequentially. In the converter process, before tapping, an inclusion modifier coating is first formed on the ladle wall surface, followed by a passivating lime powder layer. After tapping, a high-alumina slag conditioner is added to the molten steel, and then argon is blown from the bottom of the ladle for stirring. In this application, by spraying the inclusion modifier onto the inner wall of the ladle in the converter process, and then spraying passivating lime powder on top of the modifier, and by blowing argon from the bottom of the ladle during and after tapping, the molten steel washes against the ladle wall, causing the outer passivating lime powder to undergo a strong slag-metal reaction with the molten steel, generating liquid slag. Compared to the original addition of solid lime additives, this method achieves rapid and stable modification of the ladle slag after converter tapping. In the RH decarburization process… During the continuous casting process, due to the circulation of molten steel in the vacuum chamber and ladle, the passivated lime on the ladle wall further dissolves into the steel. After aluminum deoxidation, the deoxidation product Al2O3 in the steel reacts with the dissolved CaO in the steel and the inclusion modifier on the ladle wall to generate low-melting-point calcium-aluminum inclusions. The ladle then begins bottom blowing argon, further improving the kinetics of the slag-metal reaction and promoting the flotation and removal of inclusions. The continuous casting process in the ladle further modifies inclusions such as Al2O3 in the steel while promoting their flotation. In the later stages of ladle casting, the Al2O3 in the steel has been basically modified, and argon blowing is stopped to prevent ladle slag from being drawn into the tundish. Furthermore, the inclusion modifier contains an appropriate amount of TiO2, which can effectively reduce the burn-off of Ti elements in the steel and stabilize the accuracy of the molten steel composition.

[0025] The method for producing titanium-aluminum-containing ultra-low carbon steel provided in this application effectively avoids the problems of difficult modification of inclusions and low steel cleanliness caused by conventional short-process production. The method provided in this application effectively improves the cleanliness of titanium-aluminum-containing ultra-low carbon steel under short-process conditions, reducing the number of Al2O3 inclusions larger than 3μm in the billet by more than 50% and the number of TiO2-Al2O3 inclusions by more than 65%. The improvement in steel cleanliness ensures the stability of the formulation of high-end products such as automotive steel sheets, and has significant economic and social benefits. Detailed Implementation

[0026] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0027] Given the limited modification effect of Al2O3 and other inclusions in the short-process production of ultra-low carbon steel in existing technologies, which makes it difficult to achieve high-purity ultra-low carbon steel production, this invention discloses a method for producing titanium-aluminum-containing ultra-low carbon steel. This method involves spraying an inclusion modifier onto the inner wall of the ladle and applying passivating lime powder to the surface of the inclusion modifier during the converter process. This facilitates a full reaction between the non-metallic oxides of the steel and the inclusion modifier on the inner wall of the ladle, effectively modifying the Al2O3 inclusions in the steel. The subsequent continuous casting process promotes the flotation and removal of inclusions in the steel and further modifies the residual Al2O3 inclusions, resulting in steel with high purity. Specifically, this application provides a method for producing titanium-aluminum-containing ultra-low carbon steel, comprising: a converter process, an RH process, and a continuous casting process performed sequentially.

[0028] In the converter process, before tapping, an inclusion modifier coating is first formed on the surface of the ladle wall, followed by a passivating lime powder layer; after tapping, a high-alumina slag conditioner is added to the molten steel, and then argon is blown from the bottom of the ladle for stirring.

[0029] The method for producing titanium-aluminum ultra-low carbon steel in a short process provided in this application includes a converter process, an RH process, and a continuous casting process performed sequentially. No other processes are performed between these three processes, and except for the improvements described below, the other technical means of the three processes are not adjusted and are still performed in a manner well known to those skilled in the art.

[0030] The composition of the titanium-aluminum-containing ultra-low carbon steel described in this application, by mass percentage, includes: C≤0.0035%, Si≤0.020%, Mn 0.11~0.16%, P≤0.010%, S≤0.012%, Al 0.03~0.06%, Ti 0.05~0.07%, with the balance being Fe; specifically, the content of C is 0.0010~0.0035%, the content of Si is 0.010~0.020%, the content of Mn is 0.11~0.16%, the content of P is 0.005~0.009%, the content of S is 0.004~0.012%, the content of Al is 0.03~0.06%, and the content of Ti is 0.05~0.07%. The percentage of carbon is 0.0025–0.0029%, the content of silicon is 0.016–0.018%, the content of mn is 0.12–0.15%, the content of phosphorus is 0.006–0.009%, the content of sulfur is 0.008–0.010%, the content of al is 0.04–0.05%, the content of tungsten is 0.05–0.06%, and the balance is Fe.

[0031] In the converter process, this application first forms an inclusion modifier coating on the ladle wall surface before tapping, and then forms a passivated lime powder layer; the above-mentioned inclusion modifier coating and passivated lime powder layer can be formed in a manner known to those skilled in the art, for example, they can be formed on the ladle wall surface by spraying. The inclusion modifier coating comprises, by mass percentage: CaO: 64-74%, Al2O3: 15.5-19.5%, SiO2: 0-4.5%, TiO2: 3-6%, Re: 0.5%-0.9%; the remainder being unavoidable impurities. Specifically, the inclusion modifier comprises: CaO: 65-72%, Al2O3: 16-18%, SiO2: 0.5-4.0%, TiO2: 3.2-5.0%, Re: 0.6%-0.8%, the remainder being unavoidable impurities. For example, in this application, the CaO content is 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, and 73%; the Al2O3 content is 15.5% and 16%. 0%, 16.5%, 17.0%, 17.5%, 18.0%, 18.5%, 19.0%, 19.5%; SiO2 content is 0.5%, 0.8%, 1.0%, 1.3%, 1.5%, 1.7%, 2.0%, 2.2%, 2.5%, 2.6%, 2.8%, 3.0%, 3.2%, 3.4%, 3.5%, 3.8%. The content of TiO2 is 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, and 4.9%; the content of Re is 0.5%, 0.6%, 0.7%, 0.8%, and 0.9%. The inclusion modifier is a pre-melted material, obtained by melting and grinding lime, corundum slag, and rutile in a certain proportion.

[0032] In this application, the thickness of the inclusion modifier coating is 2-5 mm, and the thickness of the passivated lime powder layer is 2-5 mm; more specifically, the thickness of the inclusion modifier coating is 2 mm, 3 mm, 4 mm or 5 mm, and the thickness of the passivated lime powder layer is 2 mm, 3 mm, 4 mm or 5 mm.

[0033] After tapping, a high-alumina slag conditioner is added to the molten steel, followed by bottom blowing with argon for stirring. During this process, the high-alumina slag conditioner is a well-known slag conditioner, and this application does not impose any particular restrictions on it. The addition of the high-alumina slag conditioner ensures that the ladle slag TFe ≤ 5% and the Ca / Al ratio is 2.5–2.8. The argon blowing flow rate for bottom blowing with argon is 350–500 NL / min, and the blowing time is 0.5–1.5 min; specifically, the argon blowing flow rate is 380–480 NL / min, and the blowing time is 0.8–1.2 min; more specifically, the argon blowing flow rate is 400–430 NL / min, and the blowing time is 0.9–1.1 min.

[0034] In the converter process, during and after tapping, molten steel is spun by argon blowing from the bottom of the ladle, and the molten steel washes against the ladle wall. The passivated lime powder on the outer layer reacts strongly with the molten steel to generate liquid slag. This method achieves rapid and stable modification of ladle slag during converter tapping. The TiO2 added to the inclusion modifier can effectively reduce the burning loss of Ti element in the steel and stabilize the accuracy of the molten steel composition.

[0035] After the converter process, the RH process begins. In the RH process, argon is blown into the ladle at the bottom. Before aluminum deoxidation and alloying are added after the RH decarburization is completed, a small amount of argon is blown into the ladle at the bottom, with a flow rate of 140-180 NL / min. Before the titanium alloy is added, the argon flow rate is reduced to 80-130 NL / min, and argon blowing is stopped until the process is completed. Specifically, the argon flow rates are 140 NL / min, 150 NL / min, 160 NL / min, 170 NL / min, and 180 NL / min, and the argon flow rates are reduced to 80 NL / min, 90 NL / min, 100 NL / min, 110 NL / min, 120 NL / min, and 130 NL / min. During the RH decarburization process, due to the circulation of molten steel in the vacuum chamber and ladle, the passivating lime on the ladle wall is further dissolved in the steel. After aluminum deoxidation, the deoxidation product Al2O3 in the steel reacts with the dissolved CaO in the steel and the inclusion modifier on the ladle wall to generate low-melting-point calcium-aluminum inclusions. At this time, the ladle begins to bottom blow small amounts of argon, which further improves the kinetic conditions of the slag-metal reaction and promotes the flotation and removal of inclusions.

[0036] Following the RH process, a continuous casting process is performed. In this process, after the ladle begins casting, the bottom-blowing argon flow rate is 70–110 NL / min. When 1 / 4 to 1 / 3 of the ladle has been poured, the flow rate is adjusted to 50–90 NL / min. When 2 / 3 to 3 / 4 of the ladle has been poured, bottom-blowing argon is stopped. Further variations exist: after the ladle begins casting, the bottom-blowing argon flow rate is 80 NL / min, 90 NL / min, and 100 NL / min; and then adjusted to 60 NL / min, 70 NL / min, and 80 NL / min. During the early and middle stages of continuous casting, the ladle continues to receive small amounts of bottom-blowing argon to further modify inclusions such as Al2O3 in the steel and promote their flotation. In the later stages of casting, when the Al2O3 in the steel has been largely modified, argon blowing is stopped to prevent slag from being drawn into the tundish.

[0037] The method for producing titanium-aluminum-containing ultra-low carbon steel provided in this application can improve the cleanliness of titanium-aluminum-containing ultra-low carbon steel in a short process, reducing the number of Al2O3 inclusions larger than 3μm in the billet by more than 50% and the number of TiO2-Al2O3 inclusions by more than 65%. The improved steel cleanliness ensures the stability of the formulation of high-end products such as automotive steel sheets. The method provided in this application can be extended to high-quality steels such as pipeline steel, SPHC, and STB series, and is also suitable for inclusion modification of long-process steel grades. It can achieve stable control of inclusions in steel and low-cost clean production of steel grades, with significant economic and social benefits.

[0038] To further understand the present invention, the method for producing titanium-aluminum ultra-low carbon steel provided by the present invention will be described in detail below with reference to embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0039] Comparative Example 1

[0040] The steelmaking process adopts the "converter process - RH process - continuous casting process" flow, and the product composition is shown in Table 1:

[0041] Table 1 Main Component Requirements for Steel Grades / wt%

[0042] Converter process: When the converter has tapped 1 / 4 of the steel, add active lime and fluorite to the ladle at amounts of 3.5 kg / t steel and 1.0 kg / t steel, respectively; after tapping, add high-alumina slag conditioner to the ladle surface at an amount of 2.5 kg / ton steel; post-furnace argon blowing: after tapping, blow argon strongly for 3 minutes at a flow rate of 300 NL / min; then blow argon weakly for 5 minutes at a flow rate of 150 NL / min.

[0043] RH process: No bottom blowing of argon into the ladle;

[0044] Continuous casting process: No bottom blowing of argon into the ladle.

[0045] Comparative Example 2

[0046] The steelmaking process adopts the "converter process - RH process - continuous casting process" flow, and the product composition is shown in Table 2:

[0047] Table 2 Main Component Requirements for Steel Grades / wt%

[0048] Converter process: Before tapping, the ladle wall is sprayed with a 3mm thick inclusion modifier, the composition of which is as follows by mass percentage: CaO: 65%, Al2O3: 19.5%, SiO2: 0.5%, TiO2: 4.5%, Re: 0.9%, and the remainder is unavoidable impurities;

[0049] After tapping, a high-alumina slag conditioner is added to the steel to make the ladle slag TFe ≤ 5% and the Ca / Al ratio between 2.5 and 2.8. After the addition is completed, the bottom of the ladle is blown with argon for stirring. The argon flow rate is 350 NL / min and the argon blowing time is 1.0 min.

[0050] RH process: Before adding aluminum deoxidation and alloying after RH decarburization, start bottom blowing of argon into the ladle at a flow rate of 140 NL / min; before adding titanium alloy, reduce the flow rate to 110 NL / min, and stop blowing argon after the process is completed.

[0051] Continuous casting process: After the ladle is opened for pouring, the ladle bottom blowing argon flow rate is 110NL / min to perform soft blowing argon on the molten steel. When the ladle is filled with 1 / 4 of the molten steel, the ladle bottom blowing flow rate is adjusted to 80NL / min. When the ladle is filled with 2 / 3 of the molten steel, the bottom blowing argon is turned off.

[0052] Example 1

[0053] The steelmaking process adopts the "converter process - RH process - continuous casting process" flow, and the product composition is shown in Table 3:

[0054] Table 3 Main Component Requirements for Steel Grades / wt%

[0055] Converter process: Before tapping, the ladle wall is first sprayed with a 3mm thick inclusion modifier, the composition of which by mass percentage is: CaO: 65%, Al2O3: 19.5%, SiO2: 0.5%, TiO2: 4.5%, Re: 0.9%, the remainder being unavoidable impurities; then a 4mm thick passivating lime powder layer is sprayed on.

[0056] After tapping, a high-alumina slag conditioner is added to the steel to make the ladle slag TFe ≤ 5% and the Ca / Al ratio between 2.5 and 2.8. After the addition is completed, the bottom of the ladle is blown with argon for stirring at a flow rate of 350 NL / min and a blowing time of 1.5 min.

[0057] RH process: Before adding aluminum deoxidation and alloying after RH decarburization, start bottom blowing of argon into the ladle at a flow rate of 140 NL / min; before adding titanium alloy, reduce the flow rate to 110 NL / min, and stop blowing argon after the process is completed.

[0058] Continuous casting process: After the ladle is opened for pouring, the ladle bottom blowing argon flow rate is 110NL / min to perform soft blowing argon on the molten steel. When the ladle is filled with 1 / 4 of the molten steel, the ladle bottom blowing flow rate is adjusted to 80NL / min. When the ladle is filled with 2 / 3 of the molten steel, the bottom blowing argon is turned off.

[0059] Example 2

[0060] The steelmaking process adopts the "converter process - RH process - continuous casting process" flow, and the product composition is shown in Table 4:

[0061] Table 4 Main Component Requirements for Steel Grades / wt%

[0062] Converter process: Before tapping, the ladle wall is first sprayed with a 5mm thick inclusion modifier, the composition of which is: CaO: 70%, Al2O3: 15.5%, SiO2: 2.2%, TiO2: 3.2%, Re: 0.5% by mass percentage, the remainder being unavoidable impurities; then a 2mm thick passivating lime powder layer is sprayed on.

[0063] After tapping, a high-alumina slag conditioner is added to the steel to make the ladle slag TFe ≤ 5% and the Ca / Al ratio between 2.5 and 2.8. After the addition, the ladle is bottom-blown with argon for stirring at a flow rate of 500 NL / min and a blowing time of 0.6 min.

[0064] RH process: Before adding aluminum deoxidation and alloying after RH decarburization, start bottom blowing of argon into the ladle at a flow rate of 180 NL / min; before adding titanium alloy, reduce the flow rate to 90 NL / min, and stop blowing argon after the process is completed.

[0065] Continuous casting process: After the ladle is opened for pouring, the ladle bottom blowing argon flow rate is 70NL / min to perform soft blowing argon on the molten steel. When the ladle is filled with 1 / 3 of the molten steel, the ladle bottom blowing flow rate is adjusted to 50NL / min. When the ladle is filled with 3 / 4 of the molten steel, the bottom blowing argon is turned off.

[0066] The effects of the methods provided in the examples and comparative examples on the cleanliness of steel are shown in the table below:

[0067] Table 5. Data on the total number of inclusions larger than 3μm in the cast billet before and after implementation (individuals / mm) 2 )

[0068] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0069] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for producing titanium-aluminum-containing ultra-low carbon steel, comprising: The process is carried out sequentially: converter process - RH process - continuous casting process; In the converter process, before tapping, an inclusion modifier coating is first formed on the surface of the ladle wall, followed by a passivated lime powder layer; after tapping, a high-alumina slag conditioner is added to the molten steel, and then argon is blown from the bottom of the ladle for stirring.

2. The method according to claim 1, characterized in that, The inclusion modifier coating comprises, by mass percentage: CaO: 64-74%, Al2O3: 15.5-19.5%, SiO2: 0-4.5%, TiO2: 3-6%, and Re: 0.5%-0.9%.

3. The method according to claim 2, characterized in that, The inclusion modifier is a pre-melted material, obtained by melting and grinding lime, corundum slag and rutile.

4. The method according to claim 1, characterized in that, The thickness of the inclusion modifier coating is 2-5 mm, and the thickness of the passivated lime powder layer is 2-5 mm.

5. The method according to claim 1, characterized in that, After adding the high-alumina slag conditioner, the TFe content in the ladle slag is ≤5%, and the Ca / Al ratio is 2.5 to 2.

8.

6. The method according to claim 1, characterized in that, The argon flow rate of the bottom-blown argon stirring in the ladle is 350–500 NL / min, and the argon blowing time is 0.5–1.5 min.

7. The method according to claim 1, characterized in that, In the RH process, before aluminum deoxidation alloying, a small amount of argon is blown from the bottom of the ladle at a flow rate of 140-180 NL / min; before titanium alloying, the argon flow rate is reduced to 80-130 NL / min.

8. The method according to claim 1, characterized in that, In the continuous casting process, after the ladle starts pouring, the ladle bottom blowing argon flow rate is 70-110 NL / min. When the ladle is poured to 1 / 4-1 / 3, the ladle bottom blowing argon flow rate is adjusted to 50-90 NL / min. When the ladle is poured to 2 / 3-3 / 4, the bottom blowing argon is stopped.

9. The method according to claim 2, characterized in that, The inclusion modifier comprises: CaO: 65-72%, Al2O3: 16-18%, SiO2: 0.5-4.0%, TiO2: 3.2-5.0%, and Re: 0.6%-0.8%.

10. The method according to any one of claims 1 to 9, characterized in that, The composition of the titanium-aluminum ultra-low carbon steel, by mass percentage, includes: C≤0.0035%, Si≤0.020%, Mn 0.11~0.16%, P≤0.010%, S≤0.012%, Al 0.03~0.06%, Ti 0.05~0.07%, with the balance being Fe.

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