Single-step low nitrogen control process for titanium-containing steel LF

Abstract

The invention discloses a low nitrogen control process method for LF single process of titanium-containing steel, including S1, weak deoxidation is used to reduce nitrogen absorption of molten steel during steel tapping in converter, ferromanganese, ferrosilicon or silicon-manganese alloy is added to 1 / 3 of the steel tapping; lime is added to 1 / 2 of the steel tapping; aluminum iron is added to the slag surface for slag deoxidation after steel tapping, and argon is blown and stirred at the bottom of the ladle; S2, aluminum wire is fed to the molten steel for deoxidation in the argon station, and aluminum iron is added to the slag surface for pre-slag making; S3, hot casting slag is recovered from the molten steel, and hot casting slag is used to quickly slag in the early stage of LF refining, and the thickness of the liquid slag layer is increased to reduce nitrogen increase by electrode heating; S4, in order to reduce nitrogen absorption by heating of low-oxygen molten steel, aluminum alloying is not performed after the casting slag is recovered, and heating and heating are directly performed after argon blowing and stirring; S5, after the first heating is completed, lime and aluminum iron are added according to the color of the slag to further adjust the slag, and argon is blown and stirred until the slag becomes white; S6, soft argon is blown to the molten steel after slag making and titanium alloying are completed. The invention solves the problems of large nitrogen increase and unstable nitrogen control in the LF single process refining process.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking, and in particular to a single-step low-nitrogen control process method for titanium-containing steel LF. Background Art

[0002] For most steel grades, nitrogen is a harmful element, especially for high-strength steel grades containing Ti. Nitrogen easily forms brittle inclusions with edges and corners with Ti in steel, which reduces the processing and deformation performance of materials. Therefore, in order to improve the plasticity, toughness and processing performance of steel, the nitrogen content in steel must be reduced as much as possible. Titanium-containing high-strength steel grades generally require [N]≤40ppm, [S]≤20ppm. In order to achieve ultra-low sulfur smelting, titanium-containing high-strength steel needs to be heated and white slag made in LF furnace. Since LF heating and heating involves arc ionization of air to increase nitrogen, and the deep desulfurization process of white slag making requires deep deoxidation and large argon stirring, which leads to secondary oxidation and nitrogen absorption of molten steel. Therefore, the nitrogen increase in molten steel during LF refining is relatively high, generally exceeding 20ppm, and [N] reaches more than 50ppm at the end of LF refining. Therefore, in order to achieve low nitrogen control of titanium-containing high-strength steel, RH is generally used for denitrification after LF refining. After RH treatment, [N] in steel can be controlled within 40ppm (generally 30-40ppm). Although the LF+RH refining process can achieve stable control of low N and low S in titanium-containing high-strength steel, the long refining process and high LF leaving station temperature increase production costs and have a significant impact on production organization.

[0003] The increase of nitrogen in the LF refining process mainly comes from two aspects: one is the increase of nitrogen by electrode heating. During the LF heating process, a high-temperature arc is generated between the graphite electrode and the slag. The temperature of the arc can be as high as several thousand degrees Celsius. When the arc is not well buried, the high-temperature arc ionizes the surrounding air, which easily causes the increase of nitrogen in the molten steel. The second is the increase of nitrogen in the molten steel due to the deep deoxidation of the molten steel and argon blowing and stirring during the slag making deep desulfurization process. Since oxygen and nitrogen are surface active elements, when [O] in the steel is very low, [N] easily occupies the vacancies of oxygen, resulting in the increase of nitrogen in the molten steel. During the refining and desulfurization of white slag, since the molten steel needs to be deeply deoxidized by aluminum and stirred by argon blowing, aluminum and oxygen react violently, causing the [O] in the steel to decrease rapidly, and at the same time, the molten steel will contact with the air, causing the molten steel to absorb nitrogen; in the argon blowing and stirring desulfurization process, if the amount of argon blowing is too large, the slag surface will be blown open, causing a large area of ​​molten steel to be exposed, resulting in the increase of nitrogen in the molten steel. Therefore, in order to reduce the increase of nitrogen in LF refining, the key is to control the increase of nitrogen by electrode heating and the increase of nitrogen by secondary oxidation of molten steel.

[0004] In order to achieve low nitrogen and ultra-low sulfur smelting in LF refining, many manufacturers have also conducted extensive research:

[0005] The invention patent with the publication number "CN201410237276" discloses a method for refining low-nitrogen steel in an LF furnace. This method replaces the solid graphite electrode of the traditional LF with a hollow graphite electrode. During the smelting process, argon flows through the hollow graphite electrode to form an inert protective atmosphere on the surface of the steel slag, reducing the increase in nitrogen in the molten steel. At the same time, the bottom blowing argon stirring of the LF refining furnace is combined to denitrify the molten steel using a vacuum chamber formed by argon bubbles. Although this method can reduce the increase in nitrogen in the molten steel, it requires the replacement of the electrode, the addition of a gas source device and a carrier gas control system, and the actual production transformation is difficult.

[0006] The invention patent with the publication number "CN201510462321" discloses a method for preventing nitrogen increase in LF furnace refining low-nitrogen steel, which controls the argon flow rate to avoid exposure of molten steel, controls the heating gear and current to shorten the existence time of high-temperature slag, controls the feeding sequence to avoid long-term heating and stirring caused by slag agglomeration, and controls the deoxidation timing to reduce nitrogen absorption of molten steel in a low-oxygen state; thereby achieving the effect of reducing the amount of nitrogen increase in molten steel during the refining process. Due to the slow slag removal in the early stage of refining, unstable electrode arc, and long heating and slag making time, the amount of nitrogen increase in molten steel is still relatively large.

[0007] The invention patent with the publication number of "CN201410050292.X" discloses a control method for preventing nitrogen increase in LF furnace refining treatment. Before refining, submerged arc heating is implemented by supplementing slag; in the early stage of refining treatment, a large flow of argon is blown through the bottom of the ladle to produce white slag, and low-grade current and voltage are used for power supply; in the middle stage of refining treatment, high-grade current and voltage are used for power supply, and the number of heating times and the frequency of opening the furnace door for temperature measurement and sampling are reduced to improve the heating efficiency; in the late stage of refining treatment, weak flow of argon is blown through the bottom of the ladle, and low-grade current and voltage are used for power supply. The average nitrogen increase of this method is controlled at 3-5ppm. This method supplements slag for submerged arc heating before refining, and there are also problems of slow slag removal and unstable electrode submerged arc in the early stage. In addition, a large flow of argon is used to blow white slag in the early stage of refining, and there is also the problem of secondary oxidation and nitrogen increase.

[0008] The invention patent with the publication number "CN201811236253.3" discloses a method for controlling the nitrogen content in molten steel. The present invention controls the nitrogen content in molten steel by comprehensively controlling the denitrification amount or nitrogen control amount in the converter smelting, LF refining and slab continuous casting process. In the LF refining process, the number of power transmissions and the amount of power transmission are adjusted to control the nitrogen increase in the molten steel in the LF refining process to be within 20ppm. The LF refining nitrogen increase of this method is about 20ppm, and the finished product [N] is about 60ppm, which is difficult to meet the low nitrogen control requirements of titanium-containing high-strength steel.

[0009] The invention patent with the publication number "CN201911156013.7" discloses a single LF process low nitrogen control method for dual-phase automotive steel DP590. The low sulfur before entering the furnace is combined with LF refining desulfurization to control the realization of low S. In this process, the low N smelting process is completed by the deoxidation system after the converter is finished, the aluminum alloy addition control of LF, the slag addition control and the bottom blowing argon control. This method has strict requirements on the converter terminal temperature, terminal [O] and molten steel [S]. The actual production fluctuates greatly and it is difficult to meet the requirements. In addition, due to the high steel tapping [O] and the high LF arrival [O], the LF refining white slag is difficult, and the slag making time is long, the refining cycle is increased, and the production rhythm is affected. Summary of the invention

[0010] The purpose of the present invention is to overcome the shortcomings of the above-mentioned background technology and provide a single-step low-nitrogen control process method for titanium-containing steel LF to solve the problem of low-nitrogen smelting difficulties in the existing single-step refined steel molten steel of titanium-containing high-strength steel LF, thereby achieving smooth production and reducing costs.

[0011] To achieve the above object, the present invention is implemented through the following technical solutions:

[0012] A single-step low-nitrogen control process method for titanium-containing steel LF, comprising:

[0013] S1. Weak deoxidation is used in converter tapping to reduce nitrogen absorption of molten steel: tapping is carried out after the converter blowing is completed, and ferromanganese alloy, ferrosilicon alloy or silicon-manganese alloy is added when one-third of the steel is tapped; lime is added through the high-level silo when one-half of the steel is tapped by utilizing the intense stirring effect of high-temperature molten steel during the tapping process; after the tapping is completed, aluminum iron is added to the slag surface for slag deoxidation, and argon is blown at the bottom of the ladle for stirring;

[0014] S2, argon station for pre-slag making to reduce LF refining slag making and increase nitrogen: molten steel is fed with aluminum wire in the argon station to deoxidize the molten steel; aluminum iron is added to the surface of the ladle slag for pre-slag making, and while adding aluminum iron, argon is blown and stirred at the bottom of the ladle;

[0015] S3, the molten steel after pre-slag making is transported to the LF furnace, and receives hot casting slag in the refining-continuous casting span. The hot casting slag is recovered in the early stage of LF refining for rapid slag removal, and the thickness of the liquid slag layer is increased to ensure the electrode arc is buried and reduce heating and nitrogen addition;

[0016] S4, after recovering the casting slag, argon is blown into the molten steel to promote slag melting and uniform slag surface;

[0017] S5. In order to reduce nitrogen absorption during heating, aluminum is not adjusted after the casting slag is recovered. The molten steel is directly heated and heated after argon blowing and stirring. The number of heating times is controlled to be ≤2 times, and the target temperature of the first heating is controlled at 1575-1595°C.

[0018] S6. After the first heating is completed, lime and aluminum iron are added to the slag surface according to the color of the slag to further adjust the slag, and argon blowing and stirring are performed;

[0019] S7. Feed titanium wire to carry out titanium alloying. After slag making and titanium alloying are completed, soft argon blowing is carried out on the molten steel.

[0020] Preferably, in step S1, the amount of lime added is 2-4‰ of steel; the amount of aluminum and iron added is 0.5-1‰ of steel.

[0021] Preferably, in step S1, argon is blown at the bottom of the ladle for 5 to 8 minutes, and the blowing intensity is 0.15 to 0.45 Nm 3 / h·ton of steel.

[0022] Preferably, in step S2, the amount of aluminum wire added is 0.3-0.6‰ of steel; the amount of aluminum-iron pre-slag added is 0.6-1.2‰ of steel.

[0023] Preferably, in step S2, argon blowing and stirring are performed on the bottom of the ladle, the stirring time is 5 to 8 minutes, and the argon blowing intensity is 0.10 to 0.30 Nm 3 / h·ton of steel.

[0024] Preferably, in step S3, before reusing the hot casting slag, half of the casting slag is poured out into a slag pot, and the casting slag is directly poured onto the surface of the molten steel.

[0025] Preferably, in step S4, the argon blowing intensity is 0.25 to 0.45 Nm 3 / h·ton steel, blowing argon for 1 to 3 minutes.

[0026] Preferably, in step S6, the amount of lime added is 0.85-1.75‰ of steel; the amount of aluminum and iron added is 0.5-1‰ of steel.

[0027] Preferably, in step S6, the argon blowing intensity is 0.40 to 0.70 Nm 3 / h·ton steel, blowing argon for 5 to 8 minutes.

[0028] Preferably, in step S7, the argon blowing intensity is 0.10-0.30 Nm 3 / h·ton steel, the argon blowing and stirring time is 5 to 8 minutes.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] The process method of the present invention effectively reduces LF refining nitrogen addition, realizes LF single-step refining of titanium-containing high-strength steel, the finished titanium-containing high-strength steel product [S] ≤ 20ppm, the finished product [N] is stably controlled within 40ppm, the refining process is simplified, and the production cost is reduced. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation scheme of the present invention is described below in conjunction with specific examples, but it should not be understood as a limitation of this patent.

[0032] The experimental methods or test methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are all obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0033] In order to solve the problems of large nitrogen increase and unstable nitrogen control in the LF single-step refining process, the following technical ideas are adopted: weak deoxidation is used in converter steelmaking to reduce nitrogen absorption by molten steel; since the hot casting slag is a high-basicity reducing slag with strong premelting property and high sulfur capacity, its recycling can not only promote rapid slagging and slagging in the early stage of LF furnace, but also has good desulfurization function. Therefore, the hot casting slag is recycled in the early stage of LF refining for rapid slagging, and the thickness of the liquid slag layer is increased to ensure the buried arc of the electrode, thereby reducing nitrogen increase by heating; less aluminum is heated in the early stage of LF, and aluminum is added to adjust the slag in the middle stage to reduce nitrogen absorption by heating; weak argon stirring is used throughout the refining process to reduce nitrogen increase.

[0034] The main technical features and technical parameters are as follows:

[0035] (1) After the converter blowing is completed, steel is tapped. Manganese iron alloy, silicon iron alloy or silicon manganese alloy is added when one-third of the steel is tapped. By utilizing the intense stirring effect of the high-temperature molten steel during the tapping process, 2.0-4.0 kg / t of lime is added through the high-level silo when half of the steel is tapped. After the tapping is completed, aluminum iron is added to the slag surface for slag deoxidation. The amount of aluminum iron added is 0.5-1.0 kg / t of steel. At the same time, argon is blown at the bottom of the ladle for stirring for 5-8 minutes, and the argon blowing intensity is 0.15-0.45 Nm 3 / h·ton steel;

[0036] (2) Aluminum wire is fed into the molten steel at the argon station to deoxidize the molten steel. The amount of aluminum wire added is 0.3-0.6 kg / ton of steel. Aluminum iron is added to the surface of the ladle slag at a rate of 0.6-1.2 kg / ton of steel to pre-slag. While adding aluminum iron, argon is blown and stirred at the bottom of the ladle. The stirring time is 5-8 minutes, and the argon blowing intensity is 0.10-0.30 Nm 3 / h·ton steel;

[0037] (3) The molten steel after pre-slag making is transported to the LF furnace and receives hot casting slag in the refining-continuous casting span. In order to avoid a significant increase in the amount of slag after the hot casting slag is reused, half of the casting slag is poured into the slag pot before the hot casting slag is reused, and the casting slag is directly poured onto the surface of the molten steel;

[0038] (4) After recovering the casting slag, argon is blown into the molten steel to promote slag melting and uniform slag surface. The argon blowing intensity is 0.25~0.45Nm 3 / h·ton steel, argon blowing 1~3min;

[0039] (5) Heating the molten steel, controlling the heating times to ≤ 2 times, wherein the target temperature of the first heating is controlled at 1575-1595°C. Since the top slag is in a semi-molten state, the medium-short arc gear is selected for heating to increase the heating speed and reduce the heating time;

[0040] (6) After the first heating is completed, add 0.85-1.75 kg / t lime and 0.5-1.0 kg / t steel, aluminum and iron to the slag surface according to the color of the slag to further adjust the slag, and blow argon for stirring. The argon blowing intensity is 0.40-0.70 Nm 3 / h·ton steel, argon blowing 5~8min;

[0041] (7) After slag making and titanium alloying, soft argon blowing is performed on the molten steel with an argon blowing intensity of 0.10 to 0.30 Nm 3 / h·ton steel, the argon blowing and stirring time is 5 to 8 minutes.

[0042] Based on the above process, the method of the present invention was applied to a 150t ladle furnace. The following are specific embodiments.

[0043] Example 1

[0044] The 150t ladle furnace produces titanium-containing high-strength steel with [N]≤40ppm, [S]≤20ppm, and [Ti]0.03~0.05%.

[0045] The smelting process route is: molten iron pretreatment – ​​converter smelting – LF treatment – ​​continuous casting.

[0046] (1) After the converter blowing is completed, the temperature is measured, and the end point temperature is 1652°C, and the end point [O] is 610ppm; then the steel is tapped, and manganese iron alloy and silicon iron alloy are added when one-third of the steel is tapped; when one-half of the steel is tapped, 2.0kg / t of lime is added through the high-level silo; after the steel is tapped, aluminum iron is added to the slag surface for slag deoxidation, and the amount of aluminum iron added is 0.5kg / t of steel. At the same time, argon is blown at the bottom of the ladle for 5 minutes, and the argon blowing intensity is 0.15Nm 3 / h·ton of steel.

[0047] (2) The ladle is transported to the argon station, where aluminum wire is fed to deoxidize the molten steel. The amount of aluminum wire added is 0.3 kg / ton of steel. Aluminum iron is added to the surface of the ladle slag at a rate of 1.2 kg / ton of steel to pre-slag. While adding aluminum iron, argon is blown and stirred at the bottom of the ladle. The stirring time is 8 minutes, and the argon blowing intensity is 0.30 Nm 3 / h·ton of steel.

[0048] (3) The molten steel is transported to the LF furnace and receives hot casting slag in the refining-continuous casting span. In order to avoid a significant increase in the slag volume after the hot casting slag is reused, half of the casting slag is poured into the slag tank before the hot casting slag is reused, and the casting slag is directly poured onto the surface of the molten steel.

[0049] (4) After the casting slag is recovered, argon is blown into the molten steel to promote slag melting and uniform slag surface. The argon blowing intensity is 0.45Nm 3 / h·ton steel, argon blowing for 1min.

[0050] (5) The molten steel was heated to a temperature of 1575°C at level 7. After the first heating for 10 minutes, the temperature of the molten steel was measured to be 1575°C.

[0051] (6) After the first heating is completed, 0.85kg / t lime and 1.0kg / ton steel, aluminum and iron are added to the slag surface according to the color of the slag to further adjust the slag, and argon blowing and stirring are carried out. The argon blowing intensity is 0.70Nm 3 / h·ton steel, argon blowing for 5 minutes.

[0052] (7) Add silicon and manganese alloy, and stir with argon blowing for 3 minutes at an argon blowing intensity of 0.30 Nm 3 / h·ton steel, temperature measurement and sampling, the measured temperature is 1558℃.

[0053] (8) The molten steel was heated for the second time, and the heating level was selected to be 5, and the heating time was 8 minutes. After the heating was completed, the corresponding alloy was added according to the Si and Mn components, and argon was blown and stirred for 3 minutes, and the argon blowing intensity was 0.30 Nm 3 / h·ton of steel, then temperature measurement and sampling were carried out, and the measured temperature was 1585℃.

[0054] (9) Titanium wire is fed for titanium alloying. After the titanium alloying is completed, soft argon blowing is performed on the molten steel with an argon blowing intensity of 0.30 Nm 3 / h·ton steel, argon blowing and stirring time is 5min.

[0055] After refining, steel samples were taken for component analysis, and the analysis results were: [N] 0.0035%, [S] 0.0015%, [Ti] 0.042%.

[0056] Example 2

[0057] The 150t ladle furnace produces titanium-containing high-strength steel with [N]≤40ppm, [S]≤20ppm, and [Ti]0.05~0.075%.

[0058] The smelting process route is: molten iron pretreatment – ​​converter smelting – LF treatment – ​​continuous casting.

[0059] (1) After the converter blowing is completed, the temperature is measured, and the end point temperature is 1660°C, and the end point [O] is 580ppm; then the steel is tapped, and ferromanganese alloy and ferrosilicon alloy are added when one-third of the steel is tapped; when one-half of the steel is tapped, 4.0kg / t of lime is added through the high-level silo; after the steel is tapped, aluminum iron is added to the slag surface for slag deoxidation, and the amount of aluminum iron added is 0.75kg / t of steel. At the same time, argon is blown at the bottom of the ladle for 6 minutes, and the argon blowing intensity is 0.45Nm 3 / h·ton of steel.

[0060] (2) The ladle is transported to the argon station, where aluminum wire is fed to deoxidize the molten steel. The amount of aluminum wire added is 0.4 kg / ton of steel. Aluminum iron is added to the surface of the ladle slag at a rate of 0.6 kg / ton of steel to pre-slag. While adding aluminum iron, argon is blown and stirred at the bottom of the ladle. The stirring time is 5 minutes and the argon blowing intensity is 0.10 Nm 3 / h·ton of steel.

[0061] (3) The molten steel is transported to the LF furnace and receives hot casting slag in the refining-continuous casting span. In order to avoid a significant increase in the slag volume after the hot casting slag is reused, half of the casting slag is poured into the slag tank before the hot casting slag is reused, and the casting slag is directly poured onto the surface of the molten steel.

[0062] (4) After recovering the casting slag, argon is blown into the molten steel to promote slag melting and uniform slag surface. The argon blowing intensity is 0.25Nm 3 / h·ton steel, argon blowing for 3min.

[0063] (5) The molten steel was heated to a temperature of 1585°C by selecting the 6th gear for heating. After the first heating for 9 minutes, the temperature of the molten steel was measured to be 1585°C.

[0064] (6) After the first heating is completed, 1.0kg / t lime and 0.5kg / ton steel, aluminum and iron are added to the slag surface according to the color of the slag to further adjust the slag, and argon blowing and stirring are carried out. The argon blowing intensity is 0.40Nm 3 / h·ton steel, argon blowing for 8 minutes.

[0065] (7) Add silicon and manganese alloy, and stir with argon blowing for 4 minutes at an argon blowing intensity of 0.20 Nm 3 / h·ton steel, temperature measurement and sampling, the measured temperature is 1570℃.

[0066] (8) The molten steel was heated for a second time, and the heating level was 5, and the heating time was 6 minutes. After the heating was completed, the corresponding alloy was added according to the Si and Mn components, and argon was blown and stirred for 3 minutes, and the argon blowing intensity was 0.10 Nm 3 / h·ton of steel, then temperature measurement and sampling were carried out, and the measured temperature was 1583℃.

[0067] (9) Titanium wire is fed for titanium alloying. After the titanium alloying is completed, soft argon is blown into the molten steel at an argon blowing intensity of 0.20 Nm3 / h·ton steel, the argon blowing and stirring time is 8min.

[0068] After refining, steel samples were taken for component analysis, and the analysis results were: [N] 0.0032%, [S] 0.0017%, [Ti] 0.072%.

[0069] Example 3

[0070] The 150t ladle furnace produces titanium-containing high-strength steel with [N]≤40ppm, [S]≤20ppm, and [Ti]0.075~0.10%.

[0071] The smelting process route is: molten iron pretreatment – ​​converter smelting – LF treatment – ​​continuous casting.

[0072] (1) After the converter blowing is completed, the temperature is measured, and the end point temperature is 1670°C, and the end point [O] is 650ppm. Then, the steel is tapped. When one-third of the steel is tapped, ferromanganese alloy and ferrosilicon alloy are added. When one-half of the steel is tapped, 3.0 kg / t of lime is added through the high-level silo. After the steel is tapped, aluminum iron is added to the slag surface for slag deoxidation. The amount of aluminum iron added is 1.0 kg / t of steel. At the same time, argon is blown at the bottom of the ladle for 8 minutes, and the argon blowing intensity is 0.35 Nm 3 / h·ton of steel.

[0073] (2) The ladle is transported to the argon station, where aluminum wire is fed to deoxidize the molten steel. The amount of aluminum wire added is 0.6 kg / ton of steel. Aluminum iron is added to the surface of the ladle slag at a rate of 0.8 kg / ton of steel to pre-slag. While adding aluminum iron, argon is blown and stirred at the bottom of the ladle. The stirring time is 7 minutes and the argon blowing intensity is 0.20 Nm 3 / h·ton of steel.

[0074] (3) The molten steel is transported to the LF furnace and receives hot casting slag in the refining-continuous casting span. In order to avoid a significant increase in the slag volume after the hot casting slag is reused, half of the casting slag is poured into the slag tank before the hot casting slag is reused, and the casting slag is directly poured onto the surface of the molten steel.

[0075] (4) After recovering the casting slag, argon is blown into the molten steel to promote slag melting and uniform slag surface. The argon blowing intensity is 0.35Nm 3 / h·ton steel, blowing argon for 2min.

[0076] (5) The molten steel was heated to a temperature of 1582°C at level 5. After the first heating for 8 minutes, the temperature of the molten steel was measured to be 1582°C.

[0077] (6) After the first heating is completed, 1.75kg / t lime and 0.75kg / ton steel, aluminum and iron are added to the slag surface according to the color of the slag to further adjust the slag, and argon blowing and stirring are carried out. The argon blowing intensity is 0.50Nm 3 / h·ton steel, argon blowing for 6 minutes.

[0078] (7) Add silicon and manganese alloy, and stir with argon blowing for 3 minutes at an argon blowing intensity of 0.30 Nm 3 / h·ton steel, temperature measurement and sampling, the measured temperature is 1575℃.

[0079] (8) The molten steel was heated for a second time, with the 6th gear selected for heating and heating for 7 minutes. After heating, the corresponding alloy was added according to the Si and Mn components, and argon was blown and stirred for 3 minutes with an argon blowing intensity of 0.20 Nm 3 / h·ton of steel, then temperature measurement and sampling were carried out, and the measured temperature was 1581℃.

[0080] (9) Titanium wire is fed for titanium alloying. After the titanium alloying is completed, soft argon is blown into the molten steel at an argon blowing intensity of 0.25 Nm 3 / h·ton steel, argon blowing and stirring time is 7min.

[0081] After refining, steel samples were taken for component analysis, and the analysis results were: [N] 0.0036%, [S] 0.0014%, [Ti] 0.09%.

[0082] Example 4

[0083] The 150t ladle furnace produces titanium-containing high-strength steel with [N]≤40ppm, [S]≤20ppm, and [Ti]0.10~0.125%.

[0084] The smelting process route is: molten iron pretreatment – ​​converter smelting – LF treatment – ​​continuous casting.

[0085] (1) After the converter blowing is completed, the temperature is measured, and the end point temperature is 1666°C, and the end point [O] is 625ppm; then the steel is tapped, and ferromanganese alloy and ferrosilicon alloy are added when one-third of the steel is tapped; when one-half of the steel is tapped, 3.5kg / t of lime is added through the high-level silo; after the steel is tapped, aluminum iron is added to the slag surface for slag deoxidation, and the amount of aluminum iron added is 0.8kg / t of steel. At the same time, argon is blown at the bottom of the ladle for 6 minutes, and the argon blowing intensity is 0.40Nm 3 / h·ton of steel.

[0086] (2) The ladle is transported to the argon station, where aluminum wire is fed to deoxidize the molten steel. The amount of aluminum wire added is 0.4 kg / ton of steel. Aluminum iron is added to the surface of the ladle slag at a rate of 1.0 kg / ton of steel to pre-slag. While adding aluminum iron, argon is blown and stirred at the bottom of the ladle. The stirring time is 6 minutes, and the argon blowing intensity is 0.25 Nm3 / h·ton of steel.

[0087] (3) The molten steel is transported to the LF furnace and receives hot casting slag in the refining-continuous casting span. In order to avoid a significant increase in the slag volume after the hot casting slag is reused, half of the casting slag is poured into the slag tank before the hot casting slag is reused, and the casting slag is directly poured onto the surface of the molten steel.

[0088] (4) After the casting slag is recovered, argon is blown into the molten steel to promote slag melting and uniform slag surface. The argon blowing intensity is 0.30Nm 3 / h·ton steel, argon blowing for 3min.

[0089] (5) The molten steel was heated to a temperature of 1588°C by selecting the 6th gear for heating. After the first heating for 10 minutes, the temperature of the molten steel was measured to be 1588°C.

[0090] (6) After the first heating is completed, 1.05kg / t lime and 0.65kg / ton steel, aluminum and iron are added to the slag surface according to the color of the slag to further adjust the slag, and argon blowing and stirring are carried out. The argon blowing intensity is 0.60Nm 3 / h·ton steel, argon blowing for 7min.

[0091] (7) Add silicon and manganese alloy, and stir with argon blowing for 3 minutes at an argon blowing intensity of 0.20 Nm 3 / h·ton steel, temperature measurement and sampling, the measured temperature is 1577℃;

[0092] (8) The molten steel was heated for the second time, and the heating level was selected to be 7, and the heating time was 4 minutes. After the heating was completed, the corresponding alloy was added according to the Si and Mn components, and argon was blown and stirred for 3 minutes, and the argon blowing intensity was 0.25Nm 3 / h·ton of steel, then temperature measurement and sampling were carried out, and the measured temperature was 1590℃.

[0093] (9) Titanium wire is fed for titanium alloying. After the titanium alloying is completed, soft argon is blown into the molten steel at an argon blowing intensity of 0.35 Nm 3 / h·ton steel, argon blowing and stirring time is 8min.

[0094] After refining, steel samples were taken for composition analysis, and the analysis results were: [N] 0.0035%, [S] 0.0015%, [Ti] 0.115%.

[0095] The above are only specific embodiments of the present invention. It should be pointed out that any changes or substitutions that can be easily thought of by any technician familiar with the field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. The rest not described in detail are prior arts.

Claims

1. A single-step low-nitrogen control process for titanium-containing steel grade LF, characterized in that: include: S1. Weak deoxidation is used in converter tapping to reduce nitrogen absorption by molten steel: tapping is carried out after the converter blowing is completed, and ferromanganese alloy, ferrosilicon alloy or silicon-manganese alloy is added when one-third of the steel is tapped; the high-temperature molten steel is vigorously stirred during the tapping process, and lime is added through the high-level silo when half of the steel is tapped; after the tapping is completed, aluminum iron is added to the slag surface for slag deoxidation, and argon is blown at the bottom of the ladle for stirring; the bottom of the ladle is blown with argon for stirring for 5 to 8 minutes, and the argon blowing intensity is 0.15 to 0.45 Nm 3 / h·ton steel; S2. Pre-slag making at the argon station to reduce LF refining slag making and increase nitrogen: aluminum wire is fed into the argon station to deoxidize the molten steel; aluminum iron is added to the surface of the ladle slag to pre-slag. While adding aluminum iron, argon is blown and stirred at the bottom of the ladle. The stirring time is 5 to 8 minutes, and the argon blowing intensity is 0.10 to 0.30 Nm 3 / h·ton steel; S3, the molten steel after pre-slag making is transported to the LF furnace, and receives hot casting slag in the refining-continuous casting span. The hot casting slag is recovered in the early stage of LF refining for rapid slag removal, and the thickness of the liquid slag layer is increased to ensure the electrode arc is buried and reduce heating and nitrogen addition; S4. After recovering the casting slag, argon is blown into the molten steel to promote slag melting and uniform slag surface; the argon blowing intensity is 0.25~0.45Nm 3 / h·ton steel, argon blowing 1~3min; S5. In order to reduce nitrogen absorption during heating, aluminum is not adjusted after the casting slag is recovered. The molten steel is directly heated and heated after argon blowing and stirring. The number of heating times is controlled to be ≤2 times, and the target temperature of the first heating is controlled at 1575-1595°C. S6. After the first heating, add lime and aluminum iron to the slag surface according to the color of the slag to further adjust the slag, and blow argon to stir; the argon blowing intensity is 0.40~0.70Nm 3 / h·ton steel, argon blowing 5~8min; S7, feed titanium wire for titanium alloying, after slag making and titanium alloying, soft argon blowing is performed on the molten steel, and the argon blowing intensity is 0.10~0.30Nm 3 / h·ton steel, the argon blowing and stirring time is 5 to 8 minutes.

2. The single-step low-nitrogen control process method for titanium-containing steel LF according to claim 1 is characterized in that: In step S1, the amount of lime added is 2-4‰ of steel; the amount of aluminum and iron added is 0.5-1‰ of steel.

3. The single-step low nitrogen control process method for titanium-containing steel LF according to claim 1 is characterized in that: In step S2, the amount of aluminum wire added is 0.3-0.6‰ of steel; the amount of aluminum iron added is 0.6-1.2‰ of steel.

4. The single-step low nitrogen control process method for titanium-containing steel LF according to claim 1 is characterized in that: In step S3, before the hot casting slag is recycled, half of the casting slag is poured into a slag pot, and the casting slag is directly poured onto the surface of the molten steel.

5. The single-step low nitrogen control process method for titanium-containing steel LF according to claim 1 is characterized in that: In step S6, the amount of lime added is 0.85-1.75‰ of steel; the amount of aluminum and iron added is 0.5-1‰ of steel.