Method for stably controlling hydrogen content in molten steel

Abstract

The invention discloses a method for stably controlling the content of hydrogen in molten steel, which specifically comprises the following steps: (1) baking waste steel fed into a converter, and controlling the loading proportion of the waste steel; (2) the charging proportion of molten iron is controlled, blowing slag charge is added within 8 min before blowing, the using amount and adding time of cold charge are controlled, and slag charge and cold charge with high moisture content are forbidden to be added 10 min after blowing; (3) alloying is carried out when the tapping amount of the converter is 5-20 t, the alloy is baked through a furnace rear alloy baking device and then added into a steel ladle, and the adding amount of the alloy after the converter accounts for 95-100% of the total adding amount of the alloy; pre-melting type refining slag is added along with molten steel during tapping, lime is added after tapping is finished, and the argon flow of a steel ladle is adjusted; (4) supplementing a small amount of lime in the LF refining process, and adjusting the argon flow of a steel ladle; and carrying out alloying after power transmission and temperature rise in refining, adding no alloy or less alloy in refining, then carrying out deoxidation operation, and carrying out soft blowing and online hydrogen determination after the components and the temperature are qualified, and then carrying out continuous casting and pouring on a crane ladle.

Description

Technical Field

[0001] The invention relates to a method for stably controlling the hydrogen content in molten steel. Background Art

[0002] The presence of a certain amount of hydrogen in steel can cause defects such as "hydrogen embrittlement", white spots and point segregation, which have a great impact on the performance and quality of steel. Therefore, reducing and controlling the hydrogen content in steel is crucial to improving the quality of special steels. In the entire steelmaking process, the hydrogen in the molten steel mainly comes from scrap steel, lime, fluorite, alloy raw materials, refined slag, etc. The solubility of hydrogen in liquid molten steel is much greater than its solubility in solid steel, so it is very necessary to control the hydrogen treatment of the molten steel before pouring it. Dehydrogenation mainly relies on vacuum treatment equipment, but it will greatly increase the cost, so it is necessary to further reduce the hydrogen content without increasing the vacuum treatment process. The present invention can control the hydrogen content in the molten steel to ≤3.0ppm at low cost, stably and accurately, realize that some steel grades do not go through the vacuum process, expand the rolling specifications of non-vacuum steel grades, and improve production efficiency.

[0003] CN116855682A-A non-vacuum hydrogen controlled steelmaking method. The invention first adds scrap steel to the converter, tilts it back and forth, and then adds molten iron; after the converter slags, only sintered ore is added to adjust the temperature; the steel is alloyed and pre-melted refined slag, carburizer and lime in a separate watertight package are added. This method can ensure that the hydrogen content of molten steel is ≤4ppm. Problems with this method: scrap steel is first added to the converter, and due to the baking time and temperature, the moisture in the scrap steel cannot be completely dried by tilting it back and forth; the moisture in the alloy after the furnace cannot be effectively controlled; lime in a separate watertight package is used for steel tapping, which will increase the lime cost, and the final hydrogen content of the molten steel is controlled at ≤4ppm, and cannot be accurately and stably controlled at ≤3ppm.

[0004] CN103555891B-A non-vacuum treatment method for reducing the hydrogen content in steel. The method includes recycling the casting slag from the previous furnace or adding pre-melted slag; baking the alloy for more than 8 hours before adding it to the molten steel; not using slag steel and iron sheet during converter smelting; and baking the tundish for 3-8 hours. In this method, recycling the casting slag is not conducive to controlling the purity of the molten steel, baking the alloy for more than 8 hours and baking the tundish for 3-8 hours will result in high energy consumption; and the water content in the scrap steel with a large amount of added to the converter is not controlled, which will affect the stability of controlling the hydrogen content.

[0005] CN105441636A A method for controlling hydrogenation in a steelmaking process. In this method, lime particles and fluorite particles are evenly added to the slag surface after steel is discharged from a converter; after refining begins, the argon flow rate is slowly increased to completely evaporate the moisture in the material, thereby controlling the hydrogenation during steelmaking to be reduced to less than 1ppm, while ensuring that the hydrogen content of molten steel is less than 4ppm when the refining station is discharged. This method can only partially remove the moisture added to the lime after the converter, and cannot effectively remove the moisture in scrap steel and alloys, and cannot effectively reduce the hydrogen content of steels with a large amount of alloys. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for stably controlling the hydrogen content in molten steel in view of the shortcomings of the above-mentioned prior art, stably controlling the hydrogen content in molten steel, realizing that some steel grades do not need to go through the vacuum process, expanding the rolling specifications, improving production efficiency, and saving process costs.

[0007] The technical solution of the present invention to solve the above technical problems is: a method for stably controlling the hydrogen content in molten steel, the method specifically comprising the following steps: (1) Bake the scrap steel fed into the converter and control the scrap steel loading ratio to 15-25%; (2) Control the molten iron charging ratio to 75-85%, add the blowing slag within 8 minutes before blowing, and control the amount and timing of adding cold material. Do not add slag and cold material with high moisture content after 10 minutes of blowing; (3) The steel output from the converter is between 5 and 20 tons, and alloying is performed. The alloy is baked in the alloy baking device after the furnace and then added to the ladle. The amount of alloy added after the converter accounts for 95-100% of the total alloy addition. Pre-melted refined slag is added with the molten steel during steel output. After the steel output is completed, lime is added, and the argon flow rate of the ladle is reduced. After baking for 2-3 minutes, the argon flow rate is increased. (4) During the LF refining process, add a small amount of lime, reduce the argon flow rate of the ladle, and increase the argon flow rate after baking for 2-3 minutes; after the refining power is sent to increase the temperature, alloying is carried out, and the alloy addition ratio is ≤5%, and then deoxidation operation is carried out. After the composition and temperature are qualified, soft blowing is carried out. After the hydrogen is determined online, continuous casting can be carried out on the hanging ladle.

[0008] The present invention further defines the scheme: Preferably, the drying temperature in (1) is 600-900°C.

[0009] Preferably, the blowing slag material in (2) is one or a mixture of limestone, lime, dolomite, magnesite and magnesium balls, the cold material has a moisture content of ≥3%, the amount of cold material added is ≤1 ton, and all of it is added within 8 minutes before blowing.

[0010] Preferably, in the above (3), the alloy baking temperature is ≥500°C, the argon gas flow rate is 20-40L / min, and the slag surface is slightly creeping, and the slag surface cannot be exposed.

[0011] Preferably, the amount of lime added in (4) is controlled within 100 kg, the argon flow rate is controlled at 20-40 L / min, and the slag surface is allowed to creep slightly, and the slag surface cannot be exposed.

[0012] The beneficial effects of the present invention are as follows: the present invention realizes that some bar steel grades do not go through the vacuum process, and expands the rolling specifications of the non-vacuum steel grades, improves production efficiency, and saves process costs. At the same time, the present invention can stably control the hydrogen content of molten steel at low cost, so that the hydrogen content before continuous casting on the hanging ladle is accurately and stably controlled at ≤3.0ppm, and the scrap steel is added to the converter after being preheated, which can reduce the initial hydrogen content, and at the same time reduce the converter blowing time and improve the converter smelting efficiency; the alloy after the converter furnace is alloy-baked at ≥500°C, and 95-100% of the required alloy is pre-placed in the converter furnace and added, and LF is supplemented or less added by ≤5%, which can further reduce the hydrogen content of the molten steel, and at the same time reduce the temperature drop of the alloy on the molten steel, greatly reduce the LF refining pressure, improve the production rhythm, and reduce the production cost. Attached photos

[0013] Figure 1 This is a diagram showing the hydrogen setting results before continuous casting on the hanging ladle after refining in Example 1 of the present invention; Figure 2 This is a diagram showing the results of hydrogen setting before continuous casting on the hanging ladle after refining in Example 2 of the present invention. DETAILED DESCRIPTION Example

[0014] This embodiment provides a method for stably controlling the hydrogen content in molten steel, the method specifically comprising the following steps: (1) The scrap steel fed into the converter is baked at a temperature of 650°C, and the scrap steel loading ratio is controlled at 18%; (2) Control the iron charging ratio to 82%, add the blowing slag within 7 minutes before blowing, add the cold material within 7 minutes, the amount of cold material added is 900 kg, and it is forbidden to add slag and cold material with high moisture content after 10 minutes of blowing. Add about 1000 kg of sintered pellets to reduce the furnace temperature. It is forbidden to add slag and cold material with high moisture content after 10 minutes of blowing. The blowing slag is one or a mixture of limestone, lime, dolomite, magnesite and magnesium balls, and the cold material is sludge balls with a moisture content of ≥3%; (3) Alloying is carried out when the output of the converter is 15t. The alloy is baked in the alloy baking device after the furnace and then added to the ladle. The alloy baking temperature is 700℃ to ensure that the moisture in the alloy is completely removed and the hydrogen content in the molten steel is further reduced. The amount of alloy added after the converter accounts for 98% of the total alloy addition. 4.0kg / t pre-melting type refined slag is added with the molten steel during tapping. After the tapping is completed, the argon flow rate of the ladle is reduced and controlled at 20L / min. Then 4.5kg / t of lime is added. After baking for 3min, the argon flow rate is increased to 40L / min. The high temperature of the molten steel is used to bake out the residual moisture in the lime before the slag reaction is carried out. (4) From the ladle to the LF refining process, the argon flow rate of the ladle is adjusted to 25 L / min, 90 kg of lime is added and baked for 3 minutes, and then the argon flow rate is increased to 40 L / min; after the refining power is supplied to increase the temperature, alloying is carried out, and the alloy addition ratio is 2%, and then deoxidation operation is carried out. After the composition and temperature are qualified, soft blowing is carried out, hydrogen is determined online, and the hydrogen content is 2.0ppm, and continuous casting is performed on the hanging ladle. Example

[0015] This embodiment provides a method for stably controlling the hydrogen content in molten steel, the method specifically comprising the following steps: (1) The scrap steel fed into the converter is baked at a temperature of 700°C, and the scrap steel loading ratio is controlled at 25%; (2) Control the iron charging ratio to 80%, add the blowing slag within 7 minutes before blowing, add the cold material within 7 minutes, the amount of cold material added is 800 kg, and it is forbidden to add slag and cold material with high moisture content after 10 minutes of blowing. Add about 900 kg of sintered pellets to reduce the furnace temperature. It is forbidden to add slag and cold material with high moisture content after 10 minutes of blowing. The blowing slag is one or a mixture of limestone, lime, dolomite, magnesite and magnesium balls, and the cold material is sludge balls with a moisture content of ≥3%; (3) Alloying is carried out when the output of the converter is 10t. The alloy is baked in the alloy baking device after the furnace and then added to the ladle. The alloy baking temperature is 650℃ to ensure that the moisture in the alloy is completely removed and the hydrogen content in the molten steel is further reduced. The amount of alloy added after the converter accounts for 95% of the total alloy addition. 3.5kg / t pre-melting refined slag is added with the molten steel during tapping. After the tapping is completed, the argon flow rate of the ladle is reduced and controlled at 25L / min. The slag surface is allowed to creep slightly and the slag surface cannot be exposed. Then 5kg / t of lime is added and baked for 2min. Then the argon flow rate is increased to 40L / min. The high temperature of the molten steel is used to bake out the residual moisture in the lime before the slag reaction is carried out. (4) From the ladle to the LF refining process, the argon flow rate of the ladle is adjusted to 30L / min, 80kg of lime is added and baked for 2min, and then the argon flow rate is increased to 40L / min; after the refining power is supplied to increase the temperature, alloying is carried out, and the alloy addition ratio is 5%, and then deoxidation operation is carried out. After the composition and temperature are qualified, soft blowing is carried out, hydrogen is determined online, and the hydrogen content is 2.8ppm, and continuous casting is performed on the hanging ladle.

[0016] In summary of the above embodiments, the method of the present invention can stably control the hydrogen content of molten steel at low cost, so that the hydrogen content before continuous casting on the ladle can be accurately and stably controlled at ≤3.0ppm, which can achieve the goal of not going through the vacuum process for some steel grades, expand the rolling specifications, improve production efficiency, and save process costs.

[0017] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for stably controlling the hydrogen content in molten steel, characterized in that: The method specifically comprises the following steps: (1) Bake the scrap steel fed into the converter and control the scrap steel loading ratio to 15-25%; (2) Control the molten iron charging ratio to 75-85%, add the blowing slag within 8 minutes before blowing, and control the amount and timing of adding cold material. Do not add slag and cold material with high moisture content after 10 minutes of blowing; (3) The steel output from the converter is between 5 and 20 tons, and alloying is performed. The alloy is baked in the alloy baking device after the furnace and then added to the ladle. The amount of alloy added after the converter accounts for 95-100% of the total alloy addition. Pre-melted refined slag is added with the molten steel during steel output. After the steel output is completed, lime is added, and the argon flow rate of the ladle is reduced. After baking for 2-3 minutes, the argon flow rate is increased. (4) During the LF refining process, add a small amount of lime, reduce the argon flow rate of the ladle, and increase the argon flow rate after baking for 2-3 minutes; after the refining power is sent to increase the temperature, alloying is carried out, and the alloy addition ratio is ≤5%, and then deoxidation operation is carried out. After the composition and temperature are qualified, soft blowing is carried out. After the hydrogen is determined online, continuous casting can be carried out on the hanging ladle.

2. A method for stably controlling hydrogen content in molten steel according to claim 1, characterized in that: The drying temperature in (1) is 600-900°C.

3. A method for stably controlling hydrogen content in molten steel according to claim 1, characterized in that: The blowing slag material in (2) is one or a mixture of limestone, lime, dolomite, magnesite and magnesium balls, the cold material moisture content is ≥3%, the amount of cold material added is ≤1 ton, and all of it is added within 8 minutes before blowing.

4. The method for stably controlling the hydrogen content in molten steel according to claim 1, characterized in that: In the above-mentioned (3), the alloy baking temperature is ≥500°C, the argon gas flow rate is 20-40L / min, and the slag surface is allowed to creep slightly, and the slag surface cannot be exposed.

5. The method for stably controlling the hydrogen content in molten steel according to claim 1, characterized in that: In the step (4), the amount of lime added is controlled within 100 kg, the argon flow rate is controlled at 20-40 L / min, and the slag surface is allowed to creep slightly, and the slag surface cannot be exposed.

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