CN102962411B - Production method of low-carbon and medium-carbon steel - Google Patents

Abstract

The invention provides a method for producing medium and low carbon steel with an aluminum weight percentage of less than 0.01%. The method includes: controlling the sulfur content in the molten iron to be below 0.015wt%; performing primary smelting on the molten iron to form molten steel, and tapping the molten steel into a ladle; Oxygen content in molten steel at the end point Add 1.5-4.5Kg/ton of deoxidizer containing no more than 2.0wt% aluminum to the ladle; add 1.0-3.5Kg to the ladle during the process of tapping 80wt%-90wt% The ladle slag modifier per ton of steel is used to control the sum of FeO and MnO content in the ladle slag to not exceed 10wt%; the molten steel is refined by argon blowing; the molten steel is poured by a continuous casting process to obtain a slab. The method of the present invention does not require LF ladle furnace refining and calcium treatment, so that the pourability of molten steel is effectively improved, the nozzle blockage phenomenon is alleviated, and the continuous casting of tundishes in the continuous casting process of low aluminum content medium and low carbon steel The number of furnaces is more than 10 furnaces, achieving the purpose of economical production.

Description

Production method of medium and low carbon steel with aluminum weight percentage less than 0.01%

technical field

The invention relates to the technical fields of iron and steel metallurgy and continuous casting, and more specifically relates to a method capable of increasing the number of continuous casting furnaces for medium and low carbon steel.

Background technique

In the prior art, during the continuous casting process of casting medium and low carbon steel, the high melting point alumina (Al ₂ O ₃ )-based inclusions and calcium silicate (CaSiO ₃ ) inclusions in molten steel are easy to Adhesion to the inner wall of the submerged nozzle of the crystallizer makes it blocked, so the number of continuous casting furnaces per tundish is low (for example, less than 6 furnaces), the production cost increases, and the production organization is greatly affected. Especially when casting continuous cast slabs with small cross-sections (for example, the cross-section is not greater than 40000mm ² ), blockage is more serious due to the small inner diameter of the submerged nozzle of the crystallizer.

In order to overcome the above-mentioned problems, calcium treatment and other methods are used in the prior art to denature the Al ₂ O ₃ inclusions with high melting point to transform them into Al ₂ O ₃ inclusions with low melting point, so as to improve the pourability of molten steel. sexual purpose. For example, a Chinese invention patent with publication number CN102634638A discloses a calcium treatment method for rod and wire alloy steel. This invention adopts the production process of "converter smelting→LF refining→RH refining→billet continuous casting". , Feed iron-calcium wire, silicon-calcium wire or solid calcium wire into the molten steel at a speed of 50-250m/min, control the mass percentage of calcium-aluminum in the molten steel to (0.08-0.16), and then carry out soft blowing RH treatment, light calcium treatment after RH treatment, feed iron-calcium wire, silicon-calcium wire or solid calcium wire to molten steel, feed line speed 50-250m/min, control the mass percentage of calcium-aluminum in molten steel as ( 0.04～0.08), then perform soft blowing and pouring. The calcium treatment method of the invention produces high-quality steel, the level of inclusions will not deteriorate, the pourability of molten steel is good, the number of continuous casting furnaces is increased, the calcium content of molten steel is low without affecting the pouring performance, and at the same time, the inclusions are plasticized and improved. Mechanical properties of steel. This patent adopts a calcium treatment process in improving the pourability of molten steel, but this method will cause an increase in steelmaking costs.

Contents of the invention

Aiming at the deficiencies in the prior art, the present invention provides a method for producing medium and low carbon steel with an aluminum weight percentage of less than 0.01%, which can improve the production of medium and low carbon steel with an aluminum weight percentage of less than 0.01%. Molten steel pourability. More specifically, the method is especially suitable for casting medium and low carbon steel with an acid-soluble aluminum percentage of less than 0.01% by adopting a billet continuous casting process with a small and medium section (for example, the cross-sectional area of the billet is not more than 40,000 mm ² ). , Improve the pourability of molten steel.

The invention provides a method for producing medium and low carbon steel with an aluminum weight percentage of less than 0.01%, the method comprising the following steps: controlling the sulfur content in molten iron to be below 0.015wt%; performing primary smelting on molten iron to form molten steel , tap the molten steel into the ladle; in the process of tapping 20wt% to 30wt%, according to the oxygen content in the molten steel at the end of the initial smelting, add 1.5 to 4.5Kg of a deoxidizer containing no more than 2.0wt% aluminum to the ladle / ton of steel; in the process of tapping 80wt% to 90wt%, add a ladle slag modifier of 1.0 to 3.5Kg/ton of steel to the ladle to control the sum of FeO and MnO contents in the ladle slag not exceeding 10wt%, preferably The sum of the FeO and MnO contents in the ladle slag is controlled to be 4-8wt%, the molten steel is refined by blowing argon, and the molten steel is poured by a continuous casting process to obtain a slab.

According to an embodiment of the method for producing medium and low carbon steel with an aluminum weight percentage content less than 0.01% of the present invention, the step of refining the molten steel by argon blowing may also include feeding no more than 1.2Kg/ton of steel into the molten steel The aluminum wire is used to adjust the oxygen content in the molten steel in the range of 0.002-0.006wt%.

According to one embodiment of the method for producing medium and low carbon steel with an aluminum weight percentage of less than 0.01% of the present invention, the deoxidizer can be a silicon-calcium-barium alloy, and the silicon-calcium-barium alloy can be composed of 10wt% to 20wt% calcium , 60wt%-70wt% of silicon, 10wt%-20wt% of barium and 0-2.0wt% of aluminum.

According to an embodiment of the method for producing medium and low carbon steel with an aluminum weight percentage of less than 0.01% in _the present invention, the composition of the ladle slag modifier may contain CaO≥55wt%, _Al2O3≤5wt %, MgO: 5-12wt%, CaF ₂ ≥ 3wt%, and the gas generation capacity of the ladle slag modifier ≥ 90L/Kg.

According to one embodiment of the method for producing medium and low carbon steel with an aluminum weight percentage content less than 0.01% of the present invention, the argon blowing intensity of the step of carrying out argon blowing refining on molten steel can be 0.8～1.5NL/(ton steel·minute ), and the argon blowing time may be 5 to 15 minutes.

According to an embodiment of the method for producing medium and low carbon steel with an aluminum content of less than 0.01% by weight of the present invention, the cross-sectional area of the cast slab formed by casting according to the above method is not greater than 40000mm ² . When the cross-sectional area of the slab formed by casting is not greater than 40000 mm ² , the method of the invention can increase the number of tundish continuous casting furnaces to more than 10 furnaces.

Compared with the prior art, the present invention effectively improves the castability of molten steel, alleviates the clogging of the continuous casting nozzle, and makes the low aluminum content In the continuous casting process of medium and low carbon steel, the number of tundish continuous casting furnaces is more than 10 furnaces, which achieves the purpose of economical production. In addition, the method of the present invention can increase the number of continuous pouring furnaces for a single tundish to more than 10 furnaces without refining in a refining furnace and without calcium treatment. In addition, the method of the present invention is especially suitable for solving the problem of nozzle blockage in the continuous casting process with the cross-sectional area of the slab not greater than 40000 mm ² .

Detailed ways

Hereinafter, the present invention will be described in detail with reference to exemplary embodiments. It should be noted that, in this specification, the percentages involved refer to percentages by weight, which will not be described in detail below.

According to the present invention, the production method of medium and low carbon steel with an aluminum weight percentage content less than 0.01% comprises the following steps: controlling the sulfur content in the molten iron to be below 0.015%; performing preliminary refining on the molten iron to form molten steel, and tapping the molten steel into a ladle Middle; in the process of tapping 20% to 30%, according to the oxygen content in the molten steel at the end of the initial smelting, add a deoxidizer with an aluminum content of not more than 2.0% to the ladle at 1.5 to 4.5Kg/ton of steel; % to 90%, add 1.0 to 3.5Kg/ton of steel ladle slag modifier to the ladle to control the sum of FeO and MnO content in the ladle slag not to exceed 10wt%; carry out argon blowing refining to molten steel; The casting process carries out molten steel pouring and obtains slabs.

Among them, in the process of tapping 80% to 90%, adding a ladle slag modifier of 1.0 to 3.5Kg/ton of steel to the ladle is to ensure that the added ladle slag modifier melts well, so that the ladle slag can be effectively treated. modified. If the ladle slag modifier is added too early, it reacts excessively with molten steel and loses the modification effect on the ladle slag; if it is added too late, the ladle slag modifier does not melt well and cannot achieve the modification effect on the ladle slag. The amount of ladle slag modifier added should be controlled according to the oxidizability of the end point molten steel. If the end point molten steel oxidizes high, it is necessary to increase the amount of ladle slag modifier added; when the end point molten steel oxidizes low, reduce the addition of ladle slag modifier The specific control target is that the oxidizability of ladle slag (the sum of FeO and MnO content) does not exceed 10wt%.

In an exemplary embodiment of the present invention, the composition of the ladle slag modifier contains CaO ≥ 55%, Al ₂ O ₃ ≤ 5%, MgO: 5-12%, CaF ₂ ≥ 3%, and the The gas generation capacity of the ladle slag modifier is ≥90L/Kg. The ladle slag modifier of the invention should avoid excessive foaming while modifying the ladle slag. Specifically, the composition of the ladle slag modifier can be appropriately adjusted according to the specific production conditions. Those skilled in the art should understand that for different smelting conditions and technical levels, the oxygen content of the molten steel at the end of the initial smelting is controlled differently, and the slag during the tapping process is controlled differently. The control of the quantity is also different, so the composition of the ladle slag modifier can be properly adjusted according to the specific production conditions. The basic principle is to control the oxidizability of the ladle slag within a reasonable range. Oxidation will continue to occur in the ladle slag; if the oxidizing property of the ladle slag is too low, the aluminum content in the molten steel will be controlled too high and affect the castability of the molten steel. The sum of the contents does not exceed 10wt%, preferably the sum of FeO and MnO contents in the ladle slag is controlled to be 4-8wt%.

In an exemplary embodiment of the present invention, the step of refining the molten steel by argon blowing may further include feeding aluminum wire not greater than 1.2Kg/ton of steel into the molten steel to adjust the oxygen content in the molten steel to a range of 0.002 ~0.006%. If the added amount of aluminum is greater than 1.2Kg/ton of steel, the aluminum content in the molten steel is too high, which will cause the deterioration of the castability of the molten steel. In an example of the present invention, the aluminum wire is a 0.2-0.25Kg/m aluminum solid wire.

In an exemplary embodiment of the present invention, the deoxidizer can be a silicon-calcium-barium alloy, and the silicon-calcium-barium alloy can be composed of 10% to 20% of calcium, 60% to 70% of silicon, 10% to 20% % barium and 0-2.0% aluminum. The deoxidizer of the present invention is not limited thereto, and those skilled in the art should understand that the range of oxygen content at the primary smelting end point required by the smelting process of different steel types is also different, so the addition amount and type of deoxidizer can also be selected accordingly . For example, the aluminum-free deoxidizer of the present invention or the deoxidizer substantially free of aluminum (for example, the aluminum content is not more than 2% by weight) can be silicon-barium alloy, silicon-iron alloy and the like.

In an exemplary embodiment of the present invention, the intensity of argon blowing in the step of refining molten steel by argon blowing may be 0.8-1.5 NL/(ton of steel·min), and the argon blowing time may be 5-15 minutes. Here, if the amount of argon blowing is too small, it is unfavorable for the floating of inclusions in the molten steel, and if the amount of argon blowing is too large, it is easy to cause the molten steel to be oxidized. If the argon blowing time is not enough, the removal rate of deoxidized products in the molten steel is small, and if the argon blowing time is too long, it is easy to cause serious temperature loss of the molten steel.

In an exemplary embodiment of the present invention, the cross-sectional area of the cast slab cast by the method of the present invention is not greater than 40000 mm ² . When the cross-sectional area of the slab formed by casting is not greater than 40000 mm ² , the method of the invention can increase the number of tundish continuous casting furnaces to more than 10 furnaces.

Specifically, the method of the present invention can be implemented using the following process steps:

(1) Hot metal pretreatment

The sulfur content of the molten iron is controlled at ≤0.015% by means of pretreatment of the molten iron.

(2) Converter Primary Smelting

The molten iron is initially smelted in the converter, and then the molten steel after the initial smelting is tapped into the ladle. During the process of tapping to 20-30%, an appropriate amount of aluminum-free or almost aluminum-free deoxidizer is added to the ladle according to the oxidation property of the molten steel at the end point of the converter. Here, in addition to adding a deoxidizer to the steel, alloys and carburizers can also be added at the same time as the deoxidizer is added according to the requirements of the steel type on the molten steel composition and/or in order to optimize the process conditions. Here, the purpose of adding alloys and carburizers is to adjust the composition of molten steel to the range required by the steel grade. However, the present invention is not limited thereto. For example, for those skilled in the art, for different steel grades, the amount and type of alloy added can be different; in addition, the alloy weight required for the steel grade composition can also be added in the ladle refining process To adjust the alloy composition in molten steel. Adding carburizer can adjust the composition of molten steel to a certain extent and optimize the subsequent process to a certain extent. The deoxidizer that does not substantially contain aluminum is preferably a silicon-calcium-barium alloy, and the silicon-calcium-barium alloy can be composed of 10% to 20% of calcium, 60% to 70% of silicon, 10% to 20% of barium and 0 to 2.0% aluminum composition.

After the deoxidizer and alloy are added, a ladle slag modifier of 1.0 to 3.5 kg/ton of steel is added to the ladle during tapping to 80% to 90%. The composition of the ladle slag modifier may contain CaO≥55%, Al ₂ O ₃ ≤5%, MgO: 5-12%, CaF _2≥3 %, and the gas generation capacity of the ladle slag modifier is ≥90L /Kg.

(3) Argon blowing after tapping

After the steel is tapped, argon blowing refining is carried out at the argon blowing station to fully float the deoxidized product and improve the purity of molten steel. The molten steel is refined by blowing argon for 5 to 10 minutes to determine the oxygen, and according to the oxygen determination data, feed the aluminum wire of 0 to 1.2Kg/ton of steel, and control the oxygen content in the range of 0.002 to 0.006%. The total refining time of the molten steel by blowing argon is 5 to 15 minutes.

(4) Continuous casting

The molten steel is protected by the well-known protective casting method during continuous casting, including the protective tube of the ladle lower nozzle, the hydrogen blowing between the ladle lower nozzle and the protective tube, the molten steel in the tundish is well covered, and the mold immersion nozzle is used, and the crystallizer is used for protection. scum. Preferably, a gasket is used to seal between the ladle water outlet and the protective tube.

The exemplary embodiments of the present invention will be further described below in combination with examples.

Example 1

Q195 steel is produced by 120t converter smelting, argon blowing after tapping, and 200×200mm billet continuous casting process. Usually, the aluminum content [A1] in the finished steel product is less than 0.01%, and the finished product [C] content is 0.07% to 0.11%. , using silicon calcium barium deoxidation.

The sulfur content of the molten iron blended into the converter is 0.011%, and the [C] content of the converter smelting end point is 0.05%. When the steel is tapped to about 25%, 4.1Kg/ton of steel calcium calcium barium is added as a deoxidizer to deoxidize the molten steel, and add 6.3Kg/ton of steel ferromanganese and 0.8Kg/ton of steel ferrosilicon are alloyed in molten steel, and 3.0Kg/ton of steel ladle slag modifier is added to the ladle when the steel is tapped to about 85%. Refining by argon blowing after the steel is tapped, the intensity of argon blowing is 1.3NL/(ton of steel·min), the oxygen is fixed when the argon is blowing for 8 minutes, the oxygen activity is 0.0083%, the aluminum wire is fed 0.33Kg/ton of steel, and the argon blowing is continued for 10 minutes Oxygen is timed, and the oxygen activity is 0.0051%. The total refining time of molten steel by argon blowing is 13 minutes, and the temperature of molten steel after argon blowing is 1598°C. Refining by blowing argon to fully float the deoxidized product and improve the purity of molten steel, so as to obtain deoxidized alloyed molten steel, the composition of which is: C: 0.09%, Si: 0.18%, Mn: 0.48%, P: 0.011%, S : 0.011%, A1: 0.004%, the balance is Fe and trace impurities.

After the argon blowing treatment, the molten steel is sent to continuous casting for steel pouring. The continuous casting adopts protective pouring. The cross-sectional size of the billet is 200×200mm billet. The molten steel has good castability, and the number of continuous casting furnaces in the tundish is 10 furnaces.

Example 2

B steel is produced by 120t converter smelting, argon blowing after tapping, and Φ200mm round billet continuous casting. Usually, the aluminum content [Al] in the finished steel product is less than 0.01%, and the [C] content in the finished product is 0.17% to 0.22%. , using silicon calcium barium deoxidation.

The sulfur content of the molten iron blended into the converter is 0.012%, and the [C] content of the converter smelting end point is 0.06%. When the steel is tapped to about 30%, 3.2Kg/ton of silicon-calcium-barium alloy is added as a deoxidizer to deoxidize the molten steel, and Add 7.2Kg/ton of steel ferromanganese, 1.1Kg/ton of steel ferrosilicon and 1.4Kg/ton of steel carburizer for molten steel alloying and carburization, and add 2.2Kg to the ladle when tapping reaches about 80% Ladle slag modifier per ton of steel. Refining by argon blowing after the steel is tapped, the intensity of argon blowing is 1.1NL/(ton of steel·minute), the oxygen is fixed when blowing argon for 5 minutes, the oxygen activity is 0.0068%, the aluminum wire is fed 0.16Kg/ton of steel, and the argon blowing is continued for 9 minutes Oxygen was determined at regular intervals, and the oxygen activity was 0.0047%. The total refining time of molten steel by argon blowing is 11 minutes, and the temperature of molten steel after argon blowing is 1583°C. Refining by blowing argon to fully float the deoxidized product and improve the purity of molten steel, so as to obtain deoxidized alloyed molten steel, the composition of which is: C: 0.19%, Si: 0.24%, Mn: 0.56%, P: 0.008%, S : 0.010%, A1: 0.007%, the balance is Fe and trace impurities.

After the argon blowing treatment, the molten steel is sent to continuous casting for steel pouring. The continuous casting adopts protective pouring. The cross-sectional size of the billet is Φ200mm round billet. The molten steel has good castability, and the number of continuous casting furnaces in the tundish is 12 furnaces.

Example 3

45 steel is produced by smelting in a 120t converter, argon blowing after tapping, and continuous casting of 200×200mm billets. Usually, the aluminum content of the finished product [Al] of this steel is less than 0.01%, and the content of the finished product [C] is 0.42% to 0.50 %, using silicon calcium barium deoxidation.

The sulfur content of the molten iron blended into the converter is 0.009%, and the [C] content of the converter smelting end point is 0.10%. When the steel is tapped to about 30%, 2.3Kg/ton of steel calcium calcium barium is added as a deoxidizer to deoxidize the molten steel, and add 2.8Kg/ton steel ferrosilicon, 7.3Kg/ton steel ferromanganese and 4.1Kg/ton steel recarburizer for molten steel alloying and carburization, add 1.2Kg/ton to the ladle when the steel is about 85% Ladle slag modifier for steel. Refining is carried out by blowing argon after the steel is tapped. The intensity of blowing argon is 1.0NL/(ton steel·minute), and the oxygen is fixed when blowing argon for 6 minutes, and the oxygen activity is 0.0038%. The total refining time of the molten steel by argon blowing is 10 minutes, and the temperature of the molten steel after the argon blowing is 1563°C. Refining by blowing argon to fully float the deoxidized product and improve the purity of molten steel, so as to obtain deoxidized alloyed molten steel, the composition of which is: C: 0.45%, Si: 0.26%, Mn: 0.57%, P: 0.013%, S : 0.010%, A1: 0.005%, the balance is Fe and trace impurities.

After the argon blowing treatment, the molten steel is sent to continuous casting for steel pouring. The continuous casting adopts protective pouring. The cross-sectional size of the billet is 200×200mm billet. The molten steel has good castability, and the number of continuous casting furnaces in the tundish is 11 furnaces.

For medium and low carbon steels with a cross-sectional area of not more than ^40000mm2 , controlling the content of [A1] in molten steel is the key. If the content of [A1] in molten steel is too high, Al ₂ O ₃ will easily be generated during the pouring process and cause nozzle blockage; if the content of [A1] in molten steel is too low, it will lead to poor deoxidation of molten steel and affect the quality of steel. The method of the invention modifies the ladle slag by adding a ladle slag modifier in the tapping process, so that the ladle slag can fully absorb the _Al2O3 inclusions produced in the deoxidation process and clean the molten steel _. At the same time, by controlling the oxygen content of molten steel in the range of 0.002-0.006%, it not only ensures good deoxidation of molten steel, but also avoids re-oxidation during pouring caused by excessive [A1] content in molten steel, thereby reducing nozzle blockage and realizing economical production.

In summary, the present invention does not require refining in LF ladle furnace, calcium treatment, and only one argon blowing treatment by adopting suitable deoxidation process and process control [A1] mode, ladle slag modification and other methods The pourability of molten steel is effectively improved, the clogging of nozzles is alleviated, and the number of tundish continuous casting furnaces in the continuous casting process of low aluminum content medium and low carbon steel is more than 10 furnaces, and the purpose of economical production is achieved.

Although the present invention has been described above in conjunction with the exemplary embodiments, it should be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined in the claims. Change.

Claims (8)

1. a production method of aluminum weight percentage less than 0.01% medium and low carbon steel, it is characterized in that, described method comprises the following steps: Control the sulfur content in molten iron below 0.015wt%; Primary smelting of molten iron to form molten steel, which is tapped into ladles; In the process of tapping 20wt% to 30wt%, according to the oxygen content in the molten steel at the end of the initial smelting, add 1.5 to 4.5Kg/ton of deoxidizer with an aluminum content of no more than 2.0wt% to the ladle; In the process of tapping 80wt% to 90wt%, adding a ladle slag modifier of 1.0 to 3.5Kg/ton of steel to the ladle to control the sum of FeO and MnO contents in the ladle slag does not exceed 10wt%; Refining molten steel by blowing argon; The continuous casting process is used to pour molten steel and obtain cast slabs. 2. The method for producing medium and low carbon steel with an aluminum weight percentage of less than 0.01% according to claim 1, characterized in that, in the process of tapping 80wt% to 90wt%, adding ladle slag to the ladle for modification agent to control the sum of FeO and MnO content in ladle slag to be 4-8wt%. 3. The method for producing medium and low carbon steel with an aluminum weight percentage less than 0.01% according to claim 1, characterized in that the composition of the ladle slag modifier contains CaO≥55wt%, Al ₂ O ₃ ≤ 5wt%, MgO: 5-12wt%, CaF ₂ ≥ 3wt%, and the gas generation capacity of the ladle slag modifier ≥ 90L/Kg. 4. The method for producing medium and low carbon steel with an aluminum weight percentage of less than 0.01% according to claim 1, wherein the step of refining molten steel by argon blowing further includes feeding no more than 1.2 Aluminum wire of Kg/ton of steel to adjust the oxygen content in molten steel to a range of 0.002-0.006wt%. 5. the method for producing medium and low carbon steel with an aluminum weight percent content of less than 0.01% according to claim 1, wherein the deoxidizer is a silicon-calcium-barium alloy, and the silicon-calcium-barium alloy consists of 10wt% to 20wt% calcium, 60wt%-70wt% silicon, 10wt%-20wt% barium and 0-2.0wt% aluminum. 6. The production method of medium and low carbon steel with an aluminum weight percentage of less than 0.01% according to claim 1, characterized in that the argon blowing intensity of the step of refining molten steel by blowing argon is 0.8 to 1.5 NL/ (tons of steel·min), and the argon blowing time is 5 to 15 minutes. 7. The method for producing medium and low carbon steel with an aluminum weight percentage of less than 0.01% according to any one of claims 1 to 6, characterized in that the cross-sectional area of the cast slab is not greater than 40000 mm ² . 8. The method for producing medium and low carbon steel with an aluminum weight percentage less than 0.01% according to claim 7, characterized in that the production method can increase the number of tundish continuous casting furnaces to more than 10 furnaces.