Method for inhibiting expansion plug rod of casting furnace for continuous casting of low-silicon aluminum-containing steel

Abstract

The invention discloses a method for inhibiting a plug expansion rod of a low-silicon aluminum-containing steel continuous casting casting furnace and application, and belongs to the technical field of ferrous metallurgy. The method can be suitable for the low-silicon aluminum-containing steel with less than or equal to 0.03% of Si, more than or equal to 0.025% of Al, extremely low Si content and relatively high Al content; the method comprises the operation steps of molten iron pretreatment, converter smelting, ladle furnace smelting, RH smelting and casting of a continuous casting casting furnace. Wherein the casting speed for casting is controlled by low casting speed, high casting speed and constant casting speed. According to the method for inhibiting the plug expansion of the casting furnace for continuous casting of the low-silicon aluminum-containing steel, direct casting of the casting furnace for continuous casting of the low-silicon aluminum-containing steel can be realized, and the plug expansion phenomenon is inhibited.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and more particularly to a method for inhibiting the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel. Background Art

[0002] When Si≤0.10% and Al≥0.015% in the molten steel, if oxygen contacts the molten steel, Al in the molten steel will be oxidized before Si to form Al2O3 inclusions, resulting in plugging behavior at the water inlet during the continuous casting process, affecting the castability of the molten steel. In particular, when this type of steel is used as a pouring furnace for direct pouring in continuous casting, it will inevitably come into contact with oxygen, resulting in a sharp increase in the difficulty of pouring. In order to solve this problem, a patent application with publication number CN 110923397A provides a method for pouring low-carbon, low-silicon aluminum-containing steel without drainage, which is achieved through converter deoxidation and alloying and slag washing, slag making, argon flow adjustment and heavy calcium treatment during ladle furnace smelting, continuous casting baking system specifications, argon blowing operation specifications and calcium feeding line before pouring, so that the molten steel can be successfully poured in continuous casting. With the development of the steel industry, customers have higher and higher requirements on Si and Al in molten steel. There are more and more corresponding steel grades with Si≤0.03% and Al≥0.025%, and the carbon content in steel is no longer limited to low-carbon steel. The Si content requirement is extremely low and the Al content requirement is further increased, which makes Al very easy to oxidize, resulting in serious deterioration of continuous casting castability.

[0003] When low silicon aluminum steel with Si≤0.03% and Al≥0.025% is directly poured in the continuous casting furnace, the oxidizing atmosphere in the continuous casting tundish is strong because the continuous casting tundish has just been baked and is not covered with molten steel and covering agent. Secondly, since the Si content in the steel is extremely low and the Al content is relatively high, the Al element in the molten steel is very easy to oxidize and form Al2O3 inclusions. During the continuous casting process, the Al2O3 inclusions adhere to the plug rod head, the immersion nozzle bowl and the inner wall of the nozzle, resulting in a smaller inner diameter cross-sectional area of ​​the nozzle, nozzle nodules, and a serious increase in the plug rod, and the pouring is stopped unplanned. Therefore, how to achieve direct pouring of low silicon aluminum steel with Si≤0.03% and Al≥0.025% in continuous casting is a common problem that needs to be solved urgently by steel enterprises.

[0004] In order to solve the problem of low silicon aluminum steel with Si≤0.03% and Al≥0.025% for pouring expansion plugs, there are usually two methods. One is that when there is a connection zone between low silicon aluminum steel and ordinary steel, ordinary steel is used as the pouring furnace to ensure the success of pouring, and the low silicon aluminum steel is poured in the second furnace in the subsequent pouring; the other is that when there is no connection zone between low silicon aluminum steel and ordinary steel, ordinary steel can also be used as the pouring furnace to ensure the success of pouring, and the second furnace in the subsequent pouring reuses the tundish to replace the molten steel in the tundish. When the second method is adopted, since there is no connection zone between ordinary steel and low silicon aluminum steel, all the cast billets poured during the molten steel replacement process are scrapped. When these two methods are adopted, the difficulty of production organization increases. When there is no customer order for ordinary steel, it cannot be scheduled for production, which directly limits the development of such steel. Summary of the invention

[0005] Aiming at the problem that a low-silicon aluminum-containing steel with Si≤0.03% and Al≥0.025% is unable to directly start pouring due to serious stopper rod swelling during continuous casting, the present invention provides a method for suppressing stopper rod swelling in a low-silicon aluminum-containing steel continuous casting furnace. By controlling the formation timing and amount of Al2O3 inclusions in the smelting process, controlling the secondary oxidation of molten steel, optimizing the pouring operation and improving protective pouring, the direct pouring of the low-silicon aluminum-containing steel in the continuous casting furnace is achieved and the stopper rod swelling phenomenon is suppressed.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for suppressing the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel, comprising the following steps:

[0008] S1. Hot metal pretreatment: Hot metal is subjected to KR pretreatment to control the S content of the hot metal at the exit to below 0.003%;

[0009] S2. Converter smelting: Mix low-sulfur scrap steel and molten iron after KR pretreatment for converter smelting, use slide plates and slag balls to block slag, ensure that there is no slag when tapping the converter, and control the sulfur content of the tapped steel below 0.010%; add aluminum blocks for deoxidation during the tapping process, so that the Al content of the ladle furnace entering the station is ≥0.045%;

[0010] S3. Ladle furnace smelting: composition adjustment is completed in the early stage of ladle furnace smelting; lime and high-aluminum synthetic slag are used for slag making; aluminum particles are used for deoxidation in the early stage of smelting, silicon carbide is used for deoxidation in the later stage of smelting, the refining white slag is maintained for ≥30min, and violent tumbling of molten steel is avoided in the middle and late stages of smelting; the calcium line is fed for more than 200m before leaving the station;

[0011] S4.RH smelting: keep the vacuum degree below 67Pa for ≥35min, and the slag interface should fluctuate slightly during soft blowing after breaking the vacuum. The Al content in the steel should be controlled according to the lower limit of the internal control content before pouring on the stage;

[0012] S5. Continuous casting furnace pouring operation: The argon pressure of the continuous casting long nozzle circulation is 1.0MPa, and the argon pressure of the direct current is 0.4MPa. Before the large tank is poured, the tundish is purged with argon;

[0013] In step S5, when the large tank starts pouring, calcium wire is added to the steel receiving area of ​​the tundish, and then a covering agent is added to the steel receiving area and the pouring area of ​​the tundish for the first time; when the liquid level in the pouring area of ​​the tundish is ≥200mm, the covering agent is added to the steel receiving area and the pouring area of ​​the tundish for the second time to protect the pouring; carbonized rice husk is added to the tundish for heat preservation under the condition of ensuring sufficient covering agent, and the tundish steel liquid surface is black slag operated;

[0014] The tundish is an integral tundish, and the immersion nozzle is used for protection casting. A sufficient amount of protective slag is added into the crystallizer to ensure that the protective slag of the crystallizer is also black slag.

[0015] The pulling speed of the pouring is controlled by low pulling speed-high pulling speed-constant pulling speed.

[0016] In some possible implementations, in step S1, after the molten iron enters the KR pretreatment station, the molten iron slag is firstly scraped off, and then a desulfurizer is added to the molten iron for stirring and desulfurization. The desulfurization treatment time is ≥30 minutes. After the desulfurization is completed, the slag is scraped off.

[0017] In some possible implementations, in step S3, when aluminum particles are used for deoxidation in the early stage of smelting, the amount of aluminum particles added is 1.3 kg / t to 1.6 kg / t.

[0018] In some possible implementations, in step S3, when silicon carbide is used for deoxidation in the later stage of smelting, the amount of silicon carbide added is 0.2 kg / t to 0.6 kg / t.

[0019] In some possible implementations, in step S3, the amount of refined slag added is 15 kg / t to 17 kg / t.

[0020] In some possible implementations, in step S3, the composition of the refined final slag is CaO: 45-50%, SiO2: 8-12%, Al2O3: 30-35%, MgO: 8-15%, MnO: 0.01-0.05%, TFe: 0.2-0.6%. In this case, since the slag has a low melting point and good fluidity, it is conducive to the adsorption of inclusions in the molten steel.

[0021] In some possible implementations, in step S3, the refining white slag is maintained for 30 min to 40 min.

[0022] In some possible implementations, in step S4, the preferred vacuum degree is 30 Pa to 67 Pa, and the vacuum maintaining time is 35 min to 40 min.

[0023] In some possible implementations, in step S5, the tundish is purged with argon for 20 min to 30 min.

[0024] In some possible implementations, in step S5, when calcium wire is added to the steel receiving zone of the tundish, the amount of calcium wire added is 30 m.

[0025] In some possible implementations, in step S5, the amount of the covering agent added for the first time is 8 kg / t to 9 kg / t.

[0026] In some possible implementations, in step S5, the amount of the covering agent added for the second time is 2 kg / t to 3 kg / t.

[0027] In some possible implementations, in step S5, the covering agent is a conventional material in the field and does not need to be particularly limited in the present invention, but as an example, the covering agent can be composed of the following components in mass fractions: CaO: 40% to 50%, SiO2: 10% to 12%, Al2O3: 30% to 40%, MgO: 6% to 12%, Fe2O3: 0.01% to 0.1%, and R2O: 3% to 5%.

[0028] Wherein, R2O represents an alkaline metal oxide, and R represents Na or K. In some possible implementations, in step S5, the protective slag is a conventional material in the art, and there is no need to make special limitations in the present invention, but as an example, the protective slag can be selected as follows: low-carbon steel uses the 10A protective slag for rectangular billets exported by Xixia Longcheng Metallurgical Materials Co., Ltd., medium-carbon steel uses the special protective slag for medium-carbon special steel of Xixia Longcheng Metallurgical Materials Co., Ltd., and high-carbon steel uses the high-carbon steel protective slag of Xixia Longcheng Metallurgical Materials Co., Ltd.

[0029] In some possible implementations, in step S5, the low pulling speed is 0.5 m / min to 0.7 m / min, and the holding time is 25 s to 35 s.

[0030] In some possible implementations, in step S5, the high pulling speed is 2.1 m / min to 2.6 m / min, and the holding time is 55 s to 65 s.

[0031] In some possible implementations, in step S5, the constant pulling speed is 1.9 m / min to 2.4 m / min.

[0032] In some possible implementations, in step S5, the constant pulling speed is lower than the high pulling speed.

[0033] In a second aspect, the present invention provides an application of the above-mentioned method for suppressing the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel in the production of low-silicon aluminum-containing steel.

[0034] The method for suppressing the expansion of stopper rods in a low-silicon aluminum-containing steel continuous casting furnace provided by the present invention has at least the following beneficial technical effects compared with the prior art:

[0035] (1) The method for suppressing stopper rod expansion in a continuous casting furnace of low-silicon aluminum-containing steel provided by the present invention is aimed at the problem of stopper rod expansion when low-silicon aluminum-containing steel with Si≤0.03% and Al≥0.025% is directly poured in a continuous casting furnace. From a process perspective, the formation of Al2O3 inclusions is controlled throughout the entire process, Al2O3 inclusions in the molten steel are removed to the maximum extent, and Al2O3 inclusions are denatured as much as possible, so that the stopper rod expansion phenomenon is finally suppressed when the low-silicon aluminum-containing steel is directly poured in the continuous casting furnace.

[0036] (2) The method provided by the present invention for suppressing stopper rod expansion in a continuous casting furnace of low-silicon aluminum-containing steel can suppress the stopper rod expansion phenomenon regardless of whether low-carbon, medium-carbon or high-carbon steel is being prepared. This method is suitable for solving the stopper rod expansion problem when low-silicon aluminum-containing steel with different carbon contents in the range of Si≤0.03% and Al≥0.025% is directly cast in a continuous casting furnace, and can be applied to the development of different types of steel.

[0037] (3) The method provided by the present invention for suppressing the expansion of stopper rods in the continuous casting furnace of low-silicon aluminum-containing steel does not need to consider the problem of connecting the components with ordinary steel grades and the problem that special steel grades cannot be directly cast, thereby reducing the difficulty of production organization.

[0038] (4) The method provided by the present invention for inhibiting the expansion of stopper rods in the continuous casting furnace of low-silicon aluminum-containing steel is as follows: in step S2, low-sulfur scrap steel and molten iron pretreated by KR are mixed for converter smelting, which can prevent high-sulfur steel tapping from causing aluminum loss and increased inclusions during the large argon stirring desulfurization process in the ladle furnace; the converter tapping adopts a slide plate and a slag stopper to block slag to prevent the slag from causing the oxidizability of the molten steel to increase; the use of a slide plate and a slag stopper to block slag can ensure that the converter tapping does not cause slag. In step S4, the vacuum treatment time is ensured to be ≥35min, and inclusions are further removed in RH. After breaking the air, the slag interface fluctuates slightly to prevent secondary oxidation. Before pouring on the stage, the Al in the steel is controlled according to the lower limit of the internal control component of the steel grade. Taking the internal control of 0.025% to 0.035% as an example, Al should be controlled according to the target 0.029%. In step S5, low pulling speed-high pulling speed-constant pulling speed control is adopted. The low pulling speed can ensure that a primary ingot shell with sufficient strength is first formed in the crystallizer, and then the high pulling speed is used to prevent the plugger rod head from being overcooled and accumulating nodules. Finally, a constant pulling speed is used for continuous casting ingot production.

[0039] (5) The method provided by the present invention for inhibiting the expansion of stopper rods in the continuous casting furnace of low silicon aluminum steel requires that the S of the molten steel in the casting furnace should be low before entering the ladle furnace for smelting, ensure that a large amount of Al element oxidation does not occur during the smelting process of the ladle furnace, maintain good refining slag fluidity to remove inclusions in the molten steel, control the timing of aluminum addition and feed a sufficient amount of calcium wire to inhibit the formation of Al2O3 inclusions during the smelting process of the ladle furnace, ensure that the RH has enough vacuum time to further remove inclusions in the molten steel, optimize the RH soft blowing operation, the continuous casting argon blowing system and the pouring operation to reduce the secondary oxidation of the molten steel. When this method is used, the pouring furnace of low silicon aluminum steel with Si≤0.03% and Al≥0.025% can be directly poured during continuous casting and the expansion of stopper rods can be inhibited.

[0040] (6) The method provided by the present invention for suppressing the expansion of the stopper rod in the continuous casting furnace of low-silicon aluminum-containing steel solves the greater difficulty of castability of low-silicon aluminum-containing steel and has a wider range of applicable steel grades with carbon content.

[0041] (7) The method provided by the present invention for inhibiting the expansion of stopper rods in the continuous casting furnace of low-silicon aluminum steel adds a new KR desulfurization process, standardizes the use of scrap steel, strictly controls the slag to ensure that the ladle furnace does not absorb oxygen due to argon stirring desulfurization, inhibits the oxidation of aluminum in the molten steel, and reduces the oxidizability of the molten steel. A new RH treatment process is added to further float and remove aluminum-containing inclusions to ensure the cleanliness of the molten steel.

[0042] (8) The method provided by the present invention for suppressing the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel reduces the melting point of the final refined slag, improves the fluidity of the refined slag, and ensures the adsorption capacity of inclusions. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0044] Figure 1 A stopper rod curve diagram of a method for suppressing stopper rod expansion in a low-silicon aluminum-containing steel continuous casting furnace in Example 1 of the present invention;

[0045] Figure 2 A stopper rod curve diagram of a method for suppressing stopper rod expansion in a low-silicon aluminum-containing steel continuous casting furnace in Example 2 of the present invention;

[0046] Figure 3 A stopper rod curve diagram of a method for suppressing stopper rod expansion in a low-silicon aluminum-containing steel continuous casting furnace in Example 3 of the present invention;

[0047] Figure 4A stopper rod curve diagram of a method for suppressing stopper rod expansion in a low-silicon aluminum-containing steel continuous casting furnace in Comparative Example 1 of the present invention;

[0048] Figure 5 A stopper rod curve diagram of a method for suppressing stopper rod expansion in a low-silicon aluminum-containing steel continuous casting furnace in Comparative Example 2 of the present invention;

[0049] Figure 6 This is a stopper rod curve diagram of a method for suppressing stopper rod expansion in a low-silicon aluminum-containing steel continuous casting furnace in Comparative Example 3 of the present invention.

[0050] Description of the drawings: In the drawings, the horizontal axis represents the pouring time (min), and the vertical axis represents the stopper rod rise value (mm);

[0051] Different curve colors represent 8 different stopper rod curves in the 8-machine 8-stream 150 square small-section casting machine: green represents the first flow stopper rod curve, red represents the second flow stopper rod curve, yellow represents the third flow stopper rod curve, black represents the fourth flow stopper rod curve, blue represents the fifth flow stopper rod curve, purple represents the sixth flow stopper rod curve, cyan represents the seventh flow stopper rod curve, and gray represents the eighth flow stopper rod curve;

[0052] Represents 4 different stopper rod curves in a 4-machine, 4-stream, 150 square small-section casting machine: green represents the first stream stopper rod curve, red represents the second stream stopper rod curve, yellow represents the third stream stopper rod curve, and black represents the fourth stream stopper rod curve.

[0053] The purpose, features and advantages of this figure will be further described in conjunction with the embodiments with reference to the accompanying drawings. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described and illustrated in conjunction with the embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0055] Obviously, the following descriptions are only some examples or embodiments of the present invention, and for those of ordinary skill in the art, the present invention can also be applied to other similar scenarios without creative work. In addition, it can also be understood that although the efforts made in such a development process may be complex and lengthy, for those of ordinary skill in the art related to the contents disclosed in the present invention, some changes in design, manufacturing or production based on the technical contents disclosed in the present invention are just conventional technical means, and should not be understood as the contents disclosed in the present invention being insufficient.

[0056] However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present invention and is not intended to limit the subject matter described in the claims.

[0057] If not otherwise specified, all embodiments and optional embodiments of the present invention may be combined with each other to form a new technical solution, and all technical features and optional technical features of the present invention may be combined with each other to form a new technical solution.

[0058] The term "content" refers to the mass fraction.

[0059] The following is a specific embodiment of the method for suppressing the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel.

[0060] For the convenience of explanation, in the following embodiments and comparative examples:

[0061] Low carbon steel uses the 10A protective slag for rectangular billets exported by Xixia Longcheng Metallurgical Materials Co., Ltd., medium carbon steel uses the special protective slag for medium carbon special steel from Xixia Longcheng Metallurgical Materials Co., Ltd., and high carbon steel uses the high carbon steel protective slag from Xixia Longcheng Metallurgical Materials Co., Ltd.

[0062] Example 1

[0063] Take the production of low-carbon, low-silicon aluminum-containing steel (0.05%≤C≤0.09%, Si≤0.03%, 0.035%≥Al≥0.025%) on an 8-machine, 8-strand, 150-square-meter small-section casting machine as an example.

[0064] Example 1 provides a method for inhibiting the expansion of stopper rods in a low-silicon aluminum-containing steel continuous casting furnace, the steps being as follows:

[0065] S1-1. Hot metal pretreatment: Hot metal from the pouring furnace enters KR for pretreatment. The desulfurization treatment time is 35 minutes. The sulfur content of the hot metal leaving the station is 0.002%.

[0066] S1-2. Converter smelting: pre-treated molten iron is fed into the converter for smelting, and slide plates and slag-blocking balls are used to block slag before steel is tapped. The sulfur content of the tapped steel is 0.008%.

[0067] S1-3. Ladle furnace smelting: The final slag composition of the ladle furnace refining slag is: CaO: 48%, SiO2: 10%, Al2O3: 32%, MgO: 9.4%, MnO: 0.04%, TFe: 0.56%. The total amount of slag is 16kg / t, the refining white slag maintenance time is 32min, and the steel liquid is prevented from rolling violently in the middle and late stages of smelting. The calcium feeding line out of the station is 210m.

[0068] S1-4.RH smelting: RH is kept at a vacuum degree of 55Pa for 35min. During soft blowing after breaking the air, the slag interface is required to fluctuate slightly. The Al content in the molten steel is detected to be 0.031% before pouring on the stage.

[0069] S1-5. Continuous casting furnace pouring operation: The continuous casting long nozzle circulation argon blowing pressure is 1.0MPa, and the direct current argon blowing pressure is 0.4MPa. Before the large tank starts pouring, the tundish is purged with argon, and the purging time is 22min.

[0070] When the large tank is poured, 30m calcium wire is added to the steel receiving area of ​​the tundish, and then 8.2kg / t of covering agent is added to the steel receiving area and the pouring area of ​​the tundish for the first time; when the liquid level in the pouring area of ​​the tundish is 250mm, 2.5kg / t of covering agent is added for the second time to protect the pouring. Carbonized rice husk is added to the tundish to keep it warm while ensuring that the covering agent is sufficient, and the black slag is operated on the liquid surface of the molten steel in the tundish. Among them, the covering agent is composed of the following components by mass fraction: CaO: 45%, SiO2: 10%, Al2O3: 35%, MgO: 6%, Fe2O3: 0.1%, R2O: 3.9%; among them, R is Na.

[0071] The tundish is an integral tundish, and the immersion nozzle is used for protection pouring. A sufficient amount of protective slag is added to the crystallizer to ensure that the protective slag of the crystallizer is also black slag. The casting speed is kept at 0.6m / min for 30s, and then increased to 2.3m / min for 60s, and then reduced to a constant speed of 2.0m / min. The plug rod curve is as attached to the instruction manual. Figure 1 As shown, the stopper value of continuous casting in the pouring furnace increases steadily and the castability is good.

[0072] Example 2

[0073] Take the production of medium carbon, low silicon aluminum-containing steel (0.28%≤C≤0.35%, Si≤0.03%, 0.040%≥Al≥0.025%) on a 4-machine, 4-strand, 150 square meter small-section casting machine as an example.

[0074] Example 2 provides a method for inhibiting the expansion of stopper rods in a low-silicon aluminum-containing steel continuous casting furnace, the steps of which are as follows:

[0075] S2-1. Hot metal pretreatment: Hot metal from the pouring furnace enters KR for pretreatment. The desulfurization treatment time is 31 minutes. The sulfur content of the hot metal leaving the station is 0.003%.

[0076] S2-2. Converter smelting: Pre-treated molten iron is fed into the converter for smelting. Slide plates and slag-blocking balls are used to block slag before steel is tapped. The sulfur content of the tapped steel is 0.007%.

[0077] S2-3. Ladle furnace smelting: The main components of the final slag of ladle furnace refining are: CaO: 49%, SiO2: 11%, Al2O3: 31%, MgO: 8.5%, MnO: 0.05%, TFe: 0.45%, the total amount of slag is 16kg / t, the refining white slag maintenance time is 34min, the steel liquid should be avoided from tumbling violently in the middle and late stages of smelting, and the calcium feeding line is 220m out of the station.

[0078] S2-4.RH smelting: RH is kept at a vacuum degree of 43Pa for 38 minutes. The slag interface is required to fluctuate slightly during soft blowing after breaking the air. The Al content in the molten steel is tested to be 0.030% before pouring on the stage.

[0079] S2-5. Continuous casting furnace pouring operation: The circulating argon blowing pressure of the continuous casting long nozzle is 1.0MPa, and the direct current argon blowing pressure is 0.4MPa. Before the large tank starts pouring, the tundish is purged with argon, and the purging time is 24min.

[0080] When the large tank is poured, 30m calcium wire is added to the steel receiving area of ​​the tundish, and then 8.4kg / t high alkalinity covering agent is added to the steel receiving area and the pouring area of ​​the tundish; when the liquid level in the pouring area of ​​the tundish is 200mm, 2.8kg / t covering agent is added for the second time to protect the pouring. Carbonized rice husk is added to the tundish to keep it warm under the condition of ensuring sufficient covering agent, and black slag is operated on the liquid surface of the molten steel in the tundish. Among them, the covering agent is composed of the following components by mass fraction: CaO: 44%, SiO2: 11%, Al2O3: 33%, MgO: 7.5%, Fe2O3: 0.05%, R2O: 4.45%; among them, R is K.

[0081] The tundish is an integral tundish, and the immersion nozzle is used for protection pouring. A sufficient amount of protective slag is added to the crystallizer to ensure that the protective slag of the crystallizer is also black slag. The casting speed is 0.6m / min and maintained for 50s, then increased to 2.6m / min and maintained for 60s, and then reduced to a constant speed of 2.4m / min. The plug rod curve is as attached to the instruction manual. Figure 2 As shown, the stopper value of continuous casting in the pouring furnace increases steadily and the castability is good.

[0082] Example 3

[0083] Take the production of high-carbon, low-silicon aluminum-containing steel (0.55%≤C≤0.70%, Si≤0.03%, 0.040%≥Al≥0.025%) on a 4-machine, 4-strand, 150 square meter small-section casting machine as an example.

[0084] Example 3 provides a method for suppressing the expansion of stopper rods in a low-silicon aluminum-containing steel continuous casting furnace, the steps are as follows:

[0085] S3-1. Hot metal pretreatment: Hot metal from the pouring furnace enters KR for pretreatment. The desulfurization treatment time is 35 minutes. The sulfur content of the hot metal leaving the station is 0.003%.

[0086] S3-2. Converter smelting: Pre-treated molten iron is fed into the converter for smelting. Slide plates and slag-blocking balls are used to block slag before steel is tapped. The sulfur content of the tapped steel is 0.009%.

[0087] S3-3. Ladle furnace smelting: The main components of the final slag of the ladle furnace refining slag are: CaO: 46%, SiO2: 10%, Al2O3: 35%, MgO: 8.6%, MnO: 0.02%, TFe: 0.38%. The total amount of slag is 16kg / t, the refining white slag maintenance time is 30min, the steel liquid is prevented from rolling violently in the middle and late stages of smelting, and the calcium feeding line is 200m out of the station.

[0088] S3-4.RH smelting: RH is kept at a vacuum degree of 35Pa for 40min. The slag interface is required to fluctuate slightly during soft blowing after breaking the air. The Al content in the molten steel is detected to be 0.029% before pouring on the stage.

[0089] S3-5. Continuous casting furnace pouring operation: The circulating argon blowing pressure of the continuous casting long nozzle is 1.0MPa, and the direct current argon blowing pressure is 0.4MPa. Before the large tank starts pouring, the tundish is purged with argon, and the purging time is 25min.

[0090] When the large tank is poured, 30m calcium wire is added to the steel receiving area of ​​the tundish, and then 8.5kg / t of covering agent is added to the steel receiving area and the pouring area of ​​the tundish for the first time; when the liquid level in the pouring area of ​​the tundish is 270mm, 2.8kg / t of sufficient covering agent is added for the second time to protect the pouring. Carbonized rice husk is added to the tundish to keep it warm under the condition of ensuring sufficient covering agent, and black slag is operated on the surface of the molten steel in the tundish. Among them, the covering agent is composed of the following components by mass fraction: CaO: 48%, SiO2: 12%, Al2O3: 30%, MgO: 6%, Fe2O3: 0.05%, R2O: 3.95%; among them, R is Na.

[0091] The tundish is an integral tundish, and the immersion nozzle is used for protection pouring. A sufficient amount of protective slag is added to the crystallizer to ensure that the crystallizer protective slag is also black slag. The casting speed is maintained at 0.6m / min for 50s, increased to 2.3m / min for 60s, and then reduced to a constant speed of 1.9m / min.

[0092] The plug rod curve is as shown in the instruction manual. Figure 3 As shown, the stopper value of continuous casting in the pouring furnace increases steadily and the castability is good.

[0093] Comparative Example 1

[0094] In Comparative Example 1, taking the production of low-carbon, low-silicon aluminum-containing steel (0.05%≤C≤0.09%, Si≤0.03%, 0.035%≥Al≥0.025%) in an 8-machine, 8-stream, 150-square-meter small-section casting machine as an example, a method for continuous casting of low-silicon aluminum-containing steel is provided, and the steps are as follows:

[0095] D1-1. Converter smelting: molten iron is put into converter for smelting, and slide plate is used to block slag for steel production.

[0096] D1-2. Ladle furnace smelting: The final slag composition of the ladle furnace refining slag is: CaO: 55%, SiO2: 10%, Al2O3: 22%, MgO: 12%, MnO: 0.11%, TFe: 0.89%. The total amount of slag is 11kg / t, the refining white slag maintenance time is 20min, the steel liquid is strictly tumbling violently in the middle and late stages of smelting, and the calcium feeding line is 250m out of the station.

[0097] D1-3.RH smelting: RH is kept at a vacuum degree of 43Pa for 8 minutes. After breaking the vacuum, the slag interface is required to fluctuate slightly during soft blowing.

[0098] D1-4. Continuous casting furnace pouring operation: The continuous casting long nozzle circulation argon blowing pressure is 1.0MPa, and the direct current argon blowing pressure is 0.4MPa. Before the large tank starts pouring, the tundish is purged with argon, and the purging time is 20min.

[0099] When the large tank is poured to the tundish level of 250mm, 12kg / t of covering agent is added to the steel receiving area and pouring area of ​​the tundish, and then carbonized rice husk is added to the tundish for heat preservation, and the black slag operation is performed on the molten steel surface of the tundish. The covering agent is composed of the following mass fractions: CaO: 48%, SiO2: 9%, Al2O3: 32%, MgO: 7%, Fe2O3: 0.1%, R2O: 3.9%; among which R is Na.

[0100] The tundish is an integral tundish with an immersed nozzle for protection pouring. Sufficient protective slag is added into the crystallizer to ensure that the crystallizer protective slag is also black slag.

[0101] The plug rod curve is as shown in the instruction manual. Figure 4 As shown, the value of the stopper rod in the continuous casting furnace increased unsteadily, and it kept rising to the top, and the pouring was stopped.

[0102] Comparative Example 2

[0103] In comparative example 2, taking the production of medium-carbon low-silicon aluminum-containing steel (0.28%≤C≤0.35%, Si≤0.03%, 0.040%≥Al≥0.025%) in a 4-machine 4-stream 150 square small-section casting machine as an example, a method for continuous casting of low-silicon aluminum-containing steel is provided, and the steps are as follows:

[0104] D2-1. Converter smelting: molten iron is put into converter for smelting, and slide plates are used to block slag for steel production.

[0105] D2-2. Ladle furnace smelting: The main components of the final slag of ladle furnace refining are: CaO: 57%, SiO2: 12%, Al2O3: 19%, MgO: 11%, MnO: 0.13%, TFe: 0.87%, the total amount of slag is 10.5kg / t, the refining white slag maintenance time is 18min, the molten steel is prohibited from tumbling violently in the middle and late stages of smelting, and the calcium feeding line is 250m out of the station.

[0106] D2-3.RH smelting: RH is kept at a vacuum degree of 37Pa for 8 minutes. After breaking the vacuum, the slag interface is required to fluctuate slightly during soft blowing.

[0107] D2-4. Continuous casting furnace pouring operation: The continuous casting long nozzle circulation argon blowing pressure is 1.0MPa, and the direct current argon blowing pressure is 0.4MPa. Before the large tank starts pouring, the tundish is purged with argon, and the purging time is 30min.

[0108] When the large tank is poured to the tundish level of 240mm, 12kg / t high basicity covering agent is added to the steel receiving area and pouring area of ​​the tundish, and then carbonized rice husk is added to the tundish for heat preservation, and black slag is operated on the molten steel surface of the tundish. The covering agent is composed of the following mass fractions: CaO: 50%, SiO2: 7%, Al2O3: 33%, MgO: 6%, Fe2O3: 0.1%, R2O: 3.9%; where R is K.

[0109] The tundish is an integral tundish with an immersed nozzle for protection pouring. Sufficient protective slag is added into the crystallizer to ensure that the crystallizer protective slag is also black slag.

[0110] The plug rod curve is as shown in the instruction manual. Figure 5 As shown, the value of the stopper rod in the continuous casting furnace increased unsteadily, and it kept rising to the top, and the pouring was stopped.

[0111] Comparative Example 3

[0112] In comparative example 3, taking the production of high-carbon, low-silicon aluminum-containing steel (0.55%≤C≤0.70%, Si≤0.03%, 0.040%≥Al≥0.025%) in a 4-machine, 4-stream, 150-square-meter small-section casting machine as an example, a method for continuous casting of low-silicon aluminum-containing steel is provided, and the steps are as follows:

[0113] D3-1. Converter smelting: molten iron is put into converter for smelting, and slide plates are used to block slag for steel production.

[0114] D3-2. Ladle furnace smelting: The main components of the final slag of the ladle furnace refining slag are: CaO: 56%, SiO2: 7%, Al2O3: 24%, MgO: 12.3%, MnO: 0.05%, TFe: 0.65%. The total amount of slag is 12kg / t, the refining white slag maintenance time is 20min, the steel liquid is prohibited from violent rolling in the middle and late stages of smelting, and the calcium feeding line out of the station is 260m.

[0115] D3-3.RH smelting: RH is kept at a vacuum degree of 55Pa for 8 minutes. After breaking the vacuum, the slag interface is required to fluctuate slightly during soft blowing.

[0116] D3-4. Continuous casting furnace pouring operation: Circulation argon blowing pressure of continuous casting long nozzle is 1.0MPa, DC argon blowing pressure is 0.4MPa. Before the large tank starts pouring, the tundish is purged with argon, and the purging time is 22min.

[0117] When the large tank is poured to the tundish level of 240mm, 13kg / t high basicity covering agent is thrown in the steel receiving area and pouring area of ​​the tundish, and then carbonized rice husk is added to the tundish for heat preservation, and black slag is operated on the molten steel surface of the tundish. The covering agent is composed of the following mass fractions: CaO: 52%, SiO2: 6%, Al2O3: 32%, MgO: 7%, Fe2O3: 0.3%, R2O: 2.7%; among which R is Na.

[0118] The tundish is an integral tundish with an immersed nozzle for protection pouring. Sufficient protective slag is added into the crystallizer to ensure that the crystallizer protective slag is also black slag.

[0119] The plug rod curve is as shown in the instruction manual. Figure 6 As shown, the value of the stopper rod in the continuous casting furnace increased unsteadily, and it kept rising to the top, and the pouring was stopped.

[0120] Attached to the instruction manual Figure 1 to Figure 6 At least the following conclusions can be drawn:

[0121] (1) The method for suppressing stopper rod expansion in the continuous casting furnace of low-silicon aluminum-containing steel provided in the embodiment of the present invention is aimed at the problem of stopper rod expansion when low-silicon aluminum-containing steel with Si≤0.03% and Al≥0.025% is directly poured in the continuous casting furnace. From the process perspective, the formation of Al2O3 inclusions is controlled throughout the entire process, the Al2O3 inclusions in the molten steel are removed to the maximum extent, and the Al2O3 inclusions are denatured as much as possible, so that the stopper rod expansion phenomenon is finally suppressed when the low-silicon aluminum-containing steel is directly poured in the continuous casting furnace.

[0122] (2) The method for suppressing stopper rod expansion in a continuous casting furnace of low-silicon aluminum-containing steel provided in an embodiment of the present invention can suppress the stopper rod expansion phenomenon regardless of whether low-carbon, medium-carbon or high-carbon steel is being prepared. This method is suitable for solving the stopper rod expansion problem when low-silicon aluminum-containing steel with different carbon contents in the range of Si≤0.03% and Al≥0.025% is directly cast in a continuous casting furnace, and can be applied to the development of different types of steel.

[0123] The above-described method for inhibiting the expansion of the plug rod in the pouring furnace of low-silicon aluminum-containing steel is not restrictive, and the steel types shown in the text are only a few implementation cases of the present invention, and the actual method is not limited to them. Therefore, if ordinary technicians in this field are inspired by it and design embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the scope of protection of the present invention.

Claims

1. A method for inhibiting the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel, wherein Si≤0.03% and Al≥0.025% of the low-silicon aluminum-containing steel are used; characterized in that: The following steps are involved: S1. Hot metal pretreatment: Hot metal is subjected to KR pretreatment to control the S content of the hot metal at the exit to below 0.003%; S2. Converter smelting: Mix low-sulfur scrap steel and molten iron after KR pretreatment for converter smelting, use slide plates and slag balls to block slag, ensure that there is no slag when tapping the converter, and control the sulfur content of the tapped steel below 0.010%; add aluminum blocks for deoxidation during the tapping process, so that the Al content of the ladle furnace entering the station is ≥0.045%; S3. Ladle furnace smelting: composition adjustment is completed in the early stage of ladle furnace smelting; lime and high-aluminum synthetic slag are used for slag making; aluminum particles are used for deoxidation in the early stage of smelting, silicon carbide is used for deoxidation in the later stage of smelting, the refining white slag is maintained for ≥30min, and violent tumbling of molten steel is avoided in the middle and late stages of smelting; the calcium line is fed for more than 200m before leaving the station; S4.RH smelting: RH vacuum degree is kept below 67Pa for ≥35min. After breaking the vacuum, the slag interface is required to fluctuate slightly during soft blowing. The Al content in the steel is controlled according to the lower limit of the internal control content before pouring on the stage. S5. Continuous casting furnace pouring operation: The argon pressure of the continuous casting long nozzle circulation is 1.0MPa, and the argon pressure of the direct current is 0.4MPa. Before the large tank is poured, the tundish is purged with argon; In step S5, when the large tank starts pouring, calcium wire is added to the steel receiving area of ​​the tundish, and then the covering agent is added for the first time; when the liquid level in the pouring area of ​​the tundish is ≥200mm, the covering agent is added for the second time to protect the pouring; ensure that the covering agent is thrown into the tundish under sufficient conditions to keep the carbonized rice husk warm, and operate the black slag on the molten steel surface of the tundish; The tundish is an integral tundish, and the immersion nozzle is used for protection casting. A sufficient amount of protective slag is added into the crystallizer to ensure that the protective slag of the crystallizer is also black slag. The pulling speed of the pouring is controlled by low pulling speed-high pulling speed-constant pulling speed.

2. The method for suppressing the expansion of stopper rods in a low-silicon aluminum-containing steel continuous casting furnace according to claim 1, characterized in that: In step S3, the ratio of lime to high-aluminum synthetic slag is 5:

6.

3. The method for suppressing the expansion of stopper rods in a low-silicon aluminum-containing steel continuous casting furnace according to claim 1 or 2, characterized in that: In step S3, the amount of refined slag added is 15kg / t to 17kg / t.

4. The method for suppressing the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel according to any one of claims 1 to 3, characterized in that: In step S3, the components of the refined slag are CaO: 45% to 50%, SiO2: 8% to 12%, Al2O3: 30% to 35%, MgO: 8% to 15%, MnO: 0.01%~0.05%, TFe: 0.2%~0.6%.

5. The method for suppressing the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel according to any one of claims 1 to 4, characterized in that: In step S5, the low pulling speed is 0.5m / min to 0.7m / min, and the holding time is 25s to 35s; And / or, in step S5, the high pulling speed is 2.1 m / min to 2.6 m / min, and the holding time is 55 s to 65 s; And / or, in step S5, the constant pulling speed is 1.9 m / min to 2.4 m / min; And / or, in step S5, the constant pulling speed is lower than the high pulling speed.

6. The method for suppressing the expansion of stopper rods in a low-silicon aluminum-containing steel continuous casting furnace according to any one of claims 1 to 5, characterized in that: In step S5, the amount of the covering agent added for the first time is 8kg / t to 9kg / t; And / or, in step S5, the amount of covering agent added for the second time is 2kg / t to 3kg / t; And / or, in step S5, the covering agent is composed of the following components by mass fraction: composition: CaO: 40% to 50%, SiO2: 10% to 12%, Al2O3: 30% to 40%, MgO: 6% to 12%, Fe2O3: 0.01% to 0.1%, R2O: 3% to 5%.

7. The method for suppressing the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel according to any one of claims 1 to 6, characterized in that: In step S3, the refining white slag is maintained for ≥30 min.

8. The method for suppressing the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel according to any one of claims 1 to 7, characterized in that: In step S3, when aluminum particles are used for deoxidation in the early stage of smelting, the amount of aluminum particles added is 1.3kg / t to 1.6kg / t; And / or, in step S3, when silicon carbide is used for deoxidation in the later stage of smelting, the amount of silicon carbide added is 0.2kg / t to 0.6kg / t.

9. The method for suppressing the expansion of stopper rods in a low-silicon aluminum-containing steel continuous casting furnace according to any one of claims 1 to 8, characterized in that: In step S1, after the molten iron enters the KR pretreatment station, the molten iron slag is firstly scraped off, and then a desulfurizer is added to the molten iron for stirring and desulfurization. The desulfurization treatment time is ≥30min. After the desulfurization is completed, the slag is scraped off and the desulfurization slag is scraped off.

10. Use of the method for suppressing the expansion of stopper rods in a continuous casting furnace of low-silicon aluminum-containing steel as claimed in any one of claims 1 to 9 in the production of low-silicon aluminum-containing steel.

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