Clean smelting method for bottom blowing of oxygen-containing multi-element gas in electric arc furnace

Abstract

The invention provides an electric arc furnace bottom blowing oxygen-containing multi-element gas clean smelting method, and relates to the field of metallurgy. The method comprises the following steps: starting smelting, inputting a standard safe pressure value Pf into a main control system, and inputting a standard safe temperature value Tf into the main control system; when the temperature T of the molten pool is smaller than 1500 DEG C, the electric arc furnace is subjected to bottom blowing through argon; and when the temperature T of the molten pool is larger than or equal to 1500 DEG C, argon and oxygen-containing gas including oxygen and carbon dioxide are adopted in the electric arc furnace for bottom blowing, and the proportion and flow of the oxygen-containing gas are adjusted according to the C content of the molten pool, the bottom blowing pressure and the temperature. According to the method, oxygen-containing gas reacts with elements in steel, the utilization efficiency of oxygen in the molten steel is improved, the stirring capacity of a molten pool is enhanced, dephosphorization and denitrification of the molten steel are promoted, and it is guaranteed that components of the molten steel reach the standard. Meanwhile, the influence of oxygen-containing gas on the service life of a bottom blowing element is relieved, the smelting period is shortened, the production efficiency is improved, the smelting cost is reduced, and efficient and clean smelting of the electric arc furnace is achieved.

Description

Technical Field

[0001] The present application relates to the field of metallurgy, and in particular to a method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace. Background Art

[0002] As the market's requirements for steel quality continue to increase, clean smelting in electric arc furnaces has become the key to improving steel quality. Phosphorus is a harmful element in most steel grades, which deteriorates the plasticity and toughness of steel, resulting in cold brittleness and affecting steel quality. Therefore, dephosphorization is one of the important tasks of electric arc furnace smelting. However, due to the complex structure of electric furnace raw materials, the phosphorus content in the molten pool after smelting and cleaning fluctuates greatly, and the stirring capacity of the molten pool is poor, and the dephosphorization kinetic conditions are poor. Secondly, during the smelting process, the electric arc will ionize nitrogen in the air, resulting in an increase in the nitrogen content of the molten pool. When the nitrogen content in the steel is high, blue brittleness and other phenomena will occur, which will in turn reduce the ductility, toughness, and other properties of the steel to varying degrees. All of these show that clean smelting is still challenging for electric arc furnace steelmaking. Therefore, improving my country's electric arc furnace steelmaking process has become the key to efficient and clean smelting in electric arc furnaces.

[0003] In order to solve the problem of clean smelting in electric arc furnaces, many researchers have proposed measures to increase bottom blowing and stirring. Document CN112322839A introduces a method for degassing by blowing argon at the bottom of a medium frequency furnace, which mainly includes: setting refractory air-permeable bricks at the bottom, blowing argon at the bottom, and since the partial pressure of harmful gas elements inside the argon bubbles is zero, the gas elements in the molten steel migrate into the bubbles and are discharged from the molten steel as the argon floats up. However, argon is an inert gas and does not react with the elements in the molten steel, so its degassing and inclusion removal capacity is limited.

[0004] Document CN108251593A introduces a method for dynamically adjusting the bottom blowing CO2 flow rate to improve denitrification in converter steelmaking. During the smelting process, CO2 is blown from the bottom. CO2 is a weak oxidizing gas that reacts with elements in steel to generate twice the volume of CO, which strengthens the stirring of the molten pool. The vacuum environment of CO bubbles takes away the nitrogen in the steel, which is beneficial to the purification of molten steel. However, in the actual production process, the necessary elements in the steel are burned due to the reaction between CO2 and elements in the steel. At the same time, the single CO2 reaction absorbs heat, which will cause the bottom blowing air bricks to be blocked, thereby affecting the electric furnace smelting.

[0005] Document CN117802395A introduces a nitrogen-controlled production method for low-temperature steel. In the electric furnace smelting process, bottom blowing O2 is used to achieve low-carbon and high-oxygen steelmaking. Combined with the addition of carbon powder under deep vacuum conditions in the RH vacuum refining process, the molten steel is very easy to react with CO to form tiny bubbles, thereby achieving significant deoxidation and denitrification. However, in this patent, bottom blowing O2 provides good reaction conditions for deoxidation and denitrification in the subsequent RH vacuum refining process, and does not fundamentally achieve clean smelting in the electric furnace process. In addition, in actual production, due to the thermal and chemical effects of the O2 reaction, a single bottom blowing of O2 will cause the bottom blowing air bricks to erode, affecting the life of the bottom blowing components.

[0006] It can be seen that it is difficult to blow oxygen-containing gases (O2 and CO2) at the bottom of an electric arc furnace, which can easily cause erosion or blockage of bottom-blown air bricks and have an adverse effect on the life of bottom-blowing components. At the same time, oxygen-containing gases can also cause fluctuations in the element content of the molten pool, affecting the compliance of the steel liquid composition with the standard. Summary of the invention

[0007] The purpose of the present application is to provide a method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace to solve the above-mentioned problems.

[0008] To achieve the above objectives, this application adopts the following technical solutions: A method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace, comprising: S1: Smelting starts, the system is initialized, and the standard safety pressure value P f Input to the main control system and set the standard safety temperature value T f Input to the main control system; S2: When the molten pool temperature T is less than 1500°C, the electric arc furnace uses argon gas for bottom blowing; S3: When the molten pool temperature T≥1500°C, the electric arc furnace uses argon and / or oxygen-containing gas including oxygen and carbon dioxide for bottom blowing, and adjusts the proportion and flow rate of the oxygen-containing gas according to the content of the molten pool C; The bottom blowing pressure sensor transmits the bottom blowing working pressure signal P to the main control system. w , the bottom blowing temperature sensor transmits the bottom blowing working temperature signal T to the main control system w The main control system adjusts the ratio of CO2 and O2 in the oxygen-containing gas by comparing the bottom blowing working parameters with the bottom blowing safety parameters, so that the bottom blowing working pressure is within the safety pressure range P f -ΔP~P f +ΔP, bottom blowing working temperature is within the safe temperature range T f -ΔT~T f+ΔT, where ΔP is the safety pressure tolerance and ΔT is the safety temperature tolerance; the ratio of O2 before adjustment is x0, the adjustment ratio is Δx, and the ratio after adjustment is x; the ratio of CO2 before adjustment is y0, and the ratio after adjustment is y; the volume ratio of oxygen and carbon dioxide in the oxygen-containing gas is x+y; The specific control strategies are: (1) When the C content [wt%C] in the molten pool is greater than 0.3%, the volume ratio x+y of oxygen and carbon dioxide in the oxygen-containing gas is 40-60%, wherein the initial ratio of O2 is set to 10%-20% and the initial ratio of CO2 is set to 30%-40%; (2) When the C content in the molten pool is 0.1%≤[wt%C]≤0.3%, the volume ratio x+y of oxygen and carbon dioxide in the oxygen-containing gas is 20-40%, wherein the initial ratio of O2 is set to 5%-10% and the initial ratio of CO2 is set to 15%-30%; (3) When the C content [wt%C] in the molten pool is less than 0.1%, the volume ratio x+y of oxygen and carbon dioxide in the oxygen-containing gas is 0-20%, wherein the initial ratio of O2 is set to 0%-5% and the initial ratio of CO2 is set to 0%-15%; (4) When the bottom blowing working pressure of the electric arc furnace is P w >P f +ΔP, or bottom blowing operating temperature T w <T f At -ΔT, the main control system of the bottom blowing of the electric arc furnace increases the O2 ratio Δx and reduces the CO2 ratio Δx, that is, at this time the O2 ratio x=x0+Δx, and the CO2 ratio is y=y0-Δx; (5) When the bottom blowing working pressure of the electric arc furnace is P f -ΔP≤P w ≤P f +ΔP, and bottom blowing working temperature T f -ΔT≤T w ≤T f At +ΔT, the main control system of the bottom blowing of the electric arc furnace controls the ratio of O2 and CO2 to remain unchanged, that is, at this time, the O2 ratio is x=x0, and the CO2 ratio is y=y0; (6) When the bottom blowing working pressure of the electric arc furnace is P w <P f -ΔP, or bottom blowing operating temperature T w >T f +ΔT, the main control system of the bottom blowing of the electric arc furnace reduces the O2 ratio Δx and increases the CO2 ratio Δx, that is, at this time the O2 ratio x=x0-Δx, and the CO2 ratio is y=y0+Δx; (7) When the bottom blowing working pressure of the electric arc furnace is P w >P f +2ΔP or P w<P f When -2ΔP, the pressure alarm is enabled, and the CO2 and O2 bottom blowing are cut off, and pure Ar bottom blowing is adopted; (8) When the bottom blowing temperature of the arc furnace is T w >T f +2ΔT or T w <T f When -2ΔT, the temperature alarm is enabled, and the CO2 and O2 bottom blowing are cut off, and pure Ar bottom blowing is adopted; (9) The main control system controls the O2 flow controller to adjust the O2 flow rate to Q according to the total flow rate Q of the oxygen-containing gas blown at the bottom and the execution results of the ratio of each medium. O2 =Q×x, the CO2 flow controller controls the CO2 flow rate to be Q CO2 =Q×y, control the Ar flow controller to pass the Ar flow rate to Q Ar =Q×(100%-xy); S4: After the above judgment is executed, if the electric arc furnace has not yet tapped steel, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

[0009] Preferably, in S2, the bottom blowing argon gas flow rate is 20-30 NL / min.

[0010] Preferably, in S3, the total flow rate of the oxygen-containing gas is 30-50 NL / min.

[0011] Preferably, in S3, the standard safety pressure value P f It is 0.2-0.6MPa, and the safety pressure tolerance ΔP is 0.15MPa.

[0012] Preferably, at the beginning of a furnace service period, a bottom blowing safety temperature value T is set. f0 The bottom blowing safety temperature value T is 1600℃ for every 100 furnaces of molten steel produced. f0 Reduce by 30℃.

[0013] Preferably, in S3, Δx is 1%-5%.

[0014] Preferably, the bottom-blown air-permeable bricks used in the electric arc furnace are capillary-type, the diameter of the bottom-blown air-permeable bricks is 200-400 mm, the capillary diameter is 1-2 mm, and the number of capillaries is 12-50.

[0015] Preferably, a plurality of bottom blowing points are arranged at the bottom of the electric arc furnace.

[0016] Preferably, the method is used to produce low-nitrogen and low-phosphorus steel, and the target composition of this type of steel smelted in an electric arc furnace is: C0.1~0.3wt%, P<0.01wt%, N<0.005wt%.

[0017] Compared with the prior art, the beneficial effects of this application include: The present application provides a method for clean smelting of electric arc furnace bottom blowing oxygen-containing multi-element gas. In the process of electric arc furnace smelting, oxygen-containing gas is added on the basis of bottom blowing Ar process. The oxygen-containing gas includes O2 and CO2. The oxygen-containing gas blown into the furnace reacts with elements such as C in the molten pool, improves the utilization efficiency of oxygen, strengthens the stirring capacity of the molten pool, and is conducive to clean smelting such as dephosphorization, denitrification, and inclusion removal of molten steel. After the scrap steel in the furnace is melted, the main control system first adjusts the total proportion of oxygen-containing gas according to the molten pool C content signal fed back by the bottom blowing system to prevent the bottom blowing of oxygen-containing gas from causing fluctuations in the composition of the molten pool, and then dynamically adjusts the bottom blowing ratio and flow rate of O2 and CO2 in the oxygen-containing gas according to the working pressure signal and bottom blowing temperature signal fed back by the bottom blowing system to ensure that the bottom blowing working pressure and bottom blowing working temperature are always within a safe range. The method provided by the present application improves the purity of molten steel, shortens the smelting cycle, and reduces smelting costs while ensuring the smooth progress of efficient and clean smelting in the electric arc furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0019] Figure 1 This is a schematic diagram of an electric arc furnace bottom blowing oxygen-containing multi-element gas clean smelting system used in an embodiment of the present application.

[0020] Reference numerals: 1-O2 gas source device; 2-CO2 gas source device; 3-Ar gas source device; 4-O2 flow controller; 5-CO2 flow controller; 6-Ar flow controller; 7-computer and main control system; 8-gas mixing device; 9-pressure sensor; 10-pressure alarm device; 11-bottom blowing air brick; 12-arc furnace; 13-infrared thermometer; 14-temperature sensor; 15-temperature alarm device; 16-element analyzer. DETAILED DESCRIPTION

[0021] In order to better explain the technical solution provided by this application, before the embodiments, the devices used and the basic principles are described as follows: Since bottom blowing of oxygen-containing gas is difficult, the chemical effect and thermal effect of O2 can easily cause melting and erosion of bottom-blown air-permeable bricks in the electric arc furnace, and CO2 can easily clog air-permeable bricks due to its endothermic reaction. Both have an adverse effect on the service life of air-permeable bricks. At the same time, oxygen-containing gas can also affect the content of elements such as C in the molten steel. Therefore, after the scrap steel in the furnace is melted, the main control system of this application first adjusts the total proportion of oxygen-containing gas according to the C content signal of the molten pool fed back by the bottom blowing system to prevent the fluctuation of the composition in the molten pool caused by the bottom blowing of oxygen-containing gas, and then dynamically adjusts the bottom blowing ratio and flow rate of O2 and CO2 in the oxygen-containing gas according to the working pressure signal and bottom blowing temperature signal fed back by the bottom blowing system to ensure that the bottom blowing working pressure and bottom blowing temperature are always within a safe range, thereby preventing the failure of bottom-blown air-permeable bricks and ensuring the smooth progress of efficient and clean smelting in the electric arc furnace.

[0022] The method provided in this application is exemplarily adopted as follows Figure 1 The smelting system shown in the figure is operated. The system includes: O2 gas source device 1, CO2 gas source device 2, Ar gas source device 3, O2 flow controller 4, CO2 flow controller 5, Ar flow controller 6, computer and main control system 7, gas mixing device 8, bottom blowing pressure sensor 9, pressure alarm device 10, bottom blowing air permeable brick 11, arc furnace 12, infrared thermometer 13, bottom blowing temperature sensor 14, temperature alarm device 15 and element analyzer 16.

[0023] In the bottom blowing system of electric arc furnace, the bottom blowing working pressure signal P w And bottom blowing working temperature signal T w The bottom blowing pressure sensor and bottom blowing temperature sensor are provided to the main control system respectively. The C content signal [%C] in the molten pool is provided to the main control system by the element analyzer. The molten pool temperature signal T is provided to the main control system by the infrared thermometer. When the bottom blowing pressure is abnormal, the abnormal pressure signal is provided to the main control system by the pressure alarm device. When the bottom blowing temperature is abnormal, the abnormal temperature signal is provided to the main control system by the temperature alarm device. The main control system jointly adjusts each gas flow control valve according to the bottom blowing working pressure signal, bottom blowing working temperature signal, molten pool C content signal and molten pool temperature signal, so that the clean smelting of the electric arc furnace bottom blowing oxygen-containing multi-element gas can proceed smoothly.

[0024] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0025] Example 1 This embodiment provides a method for clean smelting of an electric arc furnace bottom blowing oxygen-containing multi-element gas, which is applied in a 70t AC electric arc furnace of a certain factory. The raw material structure of the electric arc furnace of the factory is all scrap steel, there are four bottom blowing points at the bottom of the electric arc furnace, the bottom blowing air brick is a capillary type, the air brick diameter is 300mm, the capillary diameter is 2mm, and the number of capillaries is 20.

[0026] In the bottom blowing system of electric arc furnace, the bottom blowing working pressure signal P w And bottom blowing working temperature signal T w The bottom blowing pressure sensor 9 and the bottom blowing temperature sensor 14 provide the computer and the main control system 7 respectively, the C content signal [%C] in the molten pool is provided to the computer and the main control system 7 by the element analyzer 16, and the molten pool temperature signal T is provided to the computer and the main control system 7 by the infrared thermometer 13. When the bottom blowing pressure is abnormal, the abnormal pressure signal is provided to the computer and the main control system 7 by the pressure alarm device 10. When the bottom blowing temperature is abnormal, the abnormal temperature signal is provided to the computer and the main control system 7 by the temperature alarm device 15. The computer and the main control system 7 jointly adjust the O2 flow controller 4, the CO2 flow controller 5, and the Ar flow controller 6 according to the bottom blowing working pressure signal, the bottom blowing working temperature signal, the molten pool C content signal and the molten pool temperature signal, so that the bottom blowing oxygen-containing multi-gas clean smelting of the electric arc furnace proceeds smoothly.

[0027] In this embodiment, at the beginning of the furnace service period, the bottom blowing safety temperature value T is set. f0 1600℃. Due to the continuous erosion of bottom blowing bricks during the smelting process, the bottom blowing safety temperature value T f Reduced to 1570℃, bottom blowing safety temperature tolerance ΔT is 30℃. Bottom blowing safety pressure value P f It is 0.35MPa, and the safety pressure tolerance ΔP is 0.15MPa.

[0028] The specific control steps are as follows: S1: Smelting starts, the system is initialized, and the bottom blowing safety pressure value P f Input to the main control system and set the bottom blowing safety temperature value T f Input to the main control system; the O2 ratio before adjustment is x0, the adjustment ratio Δx is 1%, and the ratio after adjustment is x; suppose the CO2 ratio before adjustment is y0, and the ratio after adjustment is y; the oxygen-containing gas ratio is x+y.

[0029] S2: When the molten pool temperature T is less than 1500℃, the scrap steel in the furnace is not completely melted, and the bottom blowing of the electric furnace adopts pure Ar bottom blowing, and the bottom blowing flow rate is 22NL / min; S3: When the molten pool temperature T≥1500℃, the scrap steel has been melted and a flat molten pool has been formed in the furnace. On the basis of ensuring the original Ar bottom blowing stirring, oxygen-containing gas is added, and the proportion and flow of oxygen-containing gas are adjusted according to the content of molten pool C. The total flow of bottom blowing mixed gas at this stage is 35NL / min. The bottom blowing pressure sensor 9 transmits the bottom blowing working pressure signal P to the computer and main control system 7. w The bottom blowing temperature sensor 14 transmits the bottom blowing working temperature signal T to the computer and the main control system 7. w The computer and the main control system 7 adjust the ratio of CO2 and O2 in the oxygen-containing gas by comparing the bottom blowing working parameters with the bottom blowing safety parameters, so that the bottom blowing working pressure is within the safety pressure range of 0.20~0.50MPa and the bottom blowing working temperature is within the safety temperature range of 1540℃~1600℃. The specific control strategy is: (1) When the C content [%C] in the molten pool is greater than 0.3%, the oxygen-containing gas ratio x+y is 45%, and the Ar ratio is 55%, where the initial O2 ratio is set to 13% and the initial CO2 ratio is set to 32%.

[0030] (2) When the C content in the molten pool is 0.1%≤[%C]≤0.3%, the oxygen-containing gas ratio x+y is 25%, the Ar ratio is 75%, among which the initial O2 ratio is set to 6% and the initial CO2 ratio is set to 19%.

[0031] (3) When the C content [%C] in the molten pool is less than 0.1%, the oxygen-containing gas ratio x+y is 10%, the Ar ratio is 90%, where the initial O2 ratio is set to 2% and the initial CO2 ratio is set to 8%.

[0032] (4) When the arc furnace bottom blowing working pressure P w >0.50MPa, or bottom blowing working temperature T w When the temperature is less than 1540℃, the main control system of the bottom blowing of the electric arc furnace increases the O2 ratio by 1% and reduces the CO2 ratio by 1%. That is, at this time, the O2 ratio is x=x0+1%, and the CO2 ratio is y=y0-1%.

[0033] (5) When the bottom blowing working pressure of the electric arc furnace is 0.20MPa≤P w ≤0.50MPa, and bottom blowing working temperature 1540℃≤T w When the temperature is ≤1600℃, the main control system of the bottom blowing of the electric arc furnace controls the ratio of O2 and CO2 to remain unchanged, that is, at this time the O2 ratio is x=x0, and the CO2 ratio is y=y0.

[0034] (6) When the arc furnace bottom blowing working pressure P w <0.20MPa, or bottom blowing working temperature T wWhen the temperature is higher than 1600℃, the main control system of the bottom blowing of the electric arc furnace reduces the O2 ratio by 1% and increases the CO2 ratio by 1%. That is, at this time, the O2 ratio is x=x0-1%, and the CO2 ratio is y=y0+1%.

[0035] (7) When the bottom blowing working pressure of the electric arc furnace is P w >0.65MPa or P w When the pressure is less than 0.05MPa, the pressure alarm is activated, and the CO2 and O2 bottom blowing are cut off, and pure Ar bottom blowing is used.

[0036] (8) When the bottom blowing temperature of the electric arc furnace is T w >1650℃ or T w When the temperature is less than 1400℃, the temperature alarm is activated, and the CO2 and O2 bottom blowing are cut off, and pure Ar bottom blowing is used.

[0037] S4: The main control system controls the O2 flow controller to pass the O2 flow rate to Q according to the total flow rate of the bottom blowing mixed gas and the proportion of each medium. O2 =Q×x, the CO2 flow controller controls the CO2 flow rate to be Q CO2 =Q×y, control the Ar flow controller to pass the Ar flow rate to Q Ar =Q×(100%-xy).

[0038] S5: After the above judgment is executed, if the electric arc furnace has not yet tapped steel, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

[0039] After adopting the above method, the carbon content of the steel produced is 0.18%, the phosphorus content is 0.008%, and the nitrogen content is 0.0048%. Compared with bottom blowing argon, the life of the bottom blowing air brick is reduced by 0%, the smelting cycle is shortened by 5-8 minutes, and the production cost is reduced by 7-9 yuan / t. 钢 .

[0040] Example 2 This embodiment provides a method for clean smelting of an electric arc furnace bottom blowing oxygen-containing multi-element gas, which is applied in a 90t AC electric arc furnace of a certain factory. The raw material structure of the electric arc furnace of the factory is all scrap steel, there are 2 bottom blowing points at the bottom of the electric arc furnace, the bottom blowing air brick is a capillary type, the air brick diameter is 350mm, the capillary diameter is 2mm, and the number of capillaries is 25.

[0041] In the bottom blowing system of electric arc furnace, the bottom blowing working pressure signal P w And bottom blowing working temperature signal T wThe bottom blowing pressure sensor 9 and the bottom blowing temperature sensor 14 provide the computer and the main control system 7 respectively, the C content signal [%C] in the molten pool is provided to the computer and the main control system 7 by the element analyzer 16, and the molten pool temperature signal T is provided to the computer and the main control system 7 by the infrared thermometer 13. When the bottom blowing pressure is abnormal, the abnormal pressure signal is provided to the computer and the main control system 7 by the pressure alarm device 10. When the bottom blowing temperature is abnormal, the abnormal temperature signal is provided to the computer and the main control system 7 by the temperature alarm device 15. The computer and the main control system 7 jointly adjust the O2 flow controller 4, the CO2 flow controller 5, and the Ar flow controller 6 according to the bottom blowing working pressure signal, the bottom blowing working temperature signal, the molten pool C content signal and the molten pool temperature signal, so that the bottom blowing oxygen-containing multi-gas clean smelting of the electric arc furnace proceeds smoothly.

[0042] In this embodiment, at the beginning of the furnace service period, the bottom blowing brick safety temperature value T is set f0 1600℃. Due to the continuous erosion of bottom blowing bricks during the smelting process, the bottom blowing safety temperature value T f Reduced to 1510℃, bottom blowing safety temperature tolerance ΔT is 30℃. Bottom blowing safety pressure value P f It is 0.4MPa, and the safety pressure tolerance ΔP is 0.15MPa.

[0043] The specific control steps are as follows: S1: Smelting starts, the system is initialized, and the bottom blowing safety pressure value P f Input to the main control system and set the bottom blowing safety temperature value T f Input to the main control system; the O2 ratio before adjustment is x0, the adjustment ratio Δx is 1%, and the ratio after adjustment is x; suppose the CO2 ratio before adjustment is y0, and the ratio after adjustment is y; the oxygen-containing gas ratio is x+y.

[0044] S2: When the molten pool temperature T is less than 1500℃, the scrap steel in the furnace is not completely melted, and the bottom blowing of the electric furnace adopts pure Ar bottom blowing, and the bottom blowing flow rate is 25NL / min; S3: When the molten pool temperature T≥1500℃, the scrap steel has been melted and a flat molten pool has been formed in the furnace. On the basis of ensuring the original Ar bottom blowing stirring, oxygen-containing gas is added, and the proportion and flow of oxygen-containing gas are adjusted according to the content of molten pool C. The total flow of bottom blowing mixed gas at this stage is 40NL / min. The bottom blowing pressure sensor 9 transmits the bottom blowing working pressure signal P to the computer and the main control system 7. w The bottom blowing temperature sensor 14 transmits the bottom blowing working temperature signal T to the computer and the main control system 7. wThe computer and the main control system 7 adjust the ratio of CO2 and O2 in the oxygen-containing gas by comparing the bottom blowing working parameters with the bottom blowing safety parameters, so that the bottom blowing working pressure is within the safety pressure range of 0.25~0.55MPa and the bottom blowing working temperature is within the safety temperature range of 1480℃~1540℃. The specific control strategy is: (1) When the C content [%C] in the molten pool is greater than 0.3%, the oxygen-containing gas ratio x+y is 50%, the Ar ratio is 50%, and the initial O2 ratio is set to 15% and the initial CO2 ratio is set to 35%.

[0045] (2) When the C content in the molten pool is 0.1%≤[%C]≤0.3%, the oxygen-containing gas ratio x+y is 30%, the Ar ratio is 70%, where the initial O2 ratio is set to 8% and the initial CO2 ratio is set to 22%.

[0046] (3) When the C content [%C] in the molten pool is less than 0.1%, the oxygen-containing gas ratio x+y is 15%, and the Ar ratio is 85%, where the initial O2 ratio is set to 3% and the initial CO2 ratio is set to 12%.

[0047] (4) When the arc furnace bottom blowing working pressure P w >0.55MPa, or bottom blowing working temperature T w When the temperature is less than 1480℃, the main control system of the bottom blowing of the electric arc furnace increases the O2 ratio by 2% and reduces the CO2 ratio by 2%. That is, at this time, the O2 ratio is x=x0+2%, and the CO2 ratio is y=y0-2%.

[0048] (5) When the bottom blowing working pressure of the electric arc furnace is 0.25MPa≤P w ≤0.55MPa, and bottom blowing working temperature 1480℃≤T w When the temperature is ≤1540℃, the main control system of the bottom blowing of the electric arc furnace controls the ratio of O2 and CO2 to remain unchanged, that is, at this time the O2 ratio is x=x0, and the CO2 ratio is y=y0.

[0049] (6) When the arc furnace bottom blowing working pressure P w <0.25MPa, or bottom blowing working temperature T w When the temperature is higher than 1540℃, the main control system of the bottom blowing of the electric arc furnace reduces the O2 ratio by 2% and increases the CO2 ratio by 2%. That is, at this time, the O2 ratio is x=x0-2%, and the CO2 ratio is y=y0+2%.

[0050] (7) When the bottom blowing working pressure of the electric arc furnace is P w >0.7MPa or P w When the pressure is less than 0.1MPa, the pressure alarm is activated, and the CO2 and O2 bottom blowing are cut off, and pure Ar bottom blowing is used.

[0051] (8) When the bottom blowing temperature of the electric arc furnace is Tw >1570℃ or T w When the temperature is less than 1450℃, the temperature alarm is activated, and the CO2 and O2 bottom blowing are cut off, and pure Ar bottom blowing is used.

[0052] S4: The main control system controls the O2 flow controller to pass the O2 flow rate to Q according to the total flow rate of the bottom blowing mixed gas and the proportion of each medium. O2 =Q×x, the CO2 flow controller controls the CO2 flow rate to be Q CO2 =Q×y, control the Ar flow controller to pass the Ar flow rate to Q Ar =Q×(100%-xy).

[0053] S5: After the above judgment is executed, if the electric arc furnace has not yet tapped steel, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

[0054] After adopting the above method, the carbon content of the steel produced is 0.20%, the phosphorus content is 0.007%, and the nitrogen content is 0.0045%. Compared with bottom blowing argon, the life of the bottom blowing air brick is reduced by 0%, the smelting cycle is shortened by 7-9 minutes, and the production cost is reduced by 5-6 yuan / t. 钢 .

[0055] Example 3 This embodiment provides a method for clean smelting of an electric arc furnace bottom blowing oxygen-containing multi-element gas, which is applied in a 120 t AC electric arc furnace of a certain plant. The raw material structure of the electric arc furnace of the plant is all scrap steel, there are 4 bottom blowing points at the bottom of the electric arc furnace, the bottom blowing air brick is a capillary type, the air brick diameter is 400 mm, the capillary diameter is 2 mm, and the number of capillaries is 30.

[0056] In the bottom blowing system of electric arc furnace, the bottom blowing working pressure signal P w And bottom blowing working temperature signal T w The bottom blowing pressure sensor 9 and the bottom blowing temperature sensor 14 provide the computer and the main control system 7 respectively, the C content signal [%C] in the molten pool is provided to the computer and the main control system 7 by the element analyzer 16, and the molten pool temperature signal T is provided to the computer and the main control system 7 by the infrared thermometer 13. When the bottom blowing pressure is abnormal, the abnormal pressure signal is provided to the computer and the main control system 7 by the pressure alarm device 10. When the bottom blowing temperature is abnormal, the abnormal temperature signal is provided to the computer and the main control system 7 by the temperature alarm device 15. The computer and the main control system 7 jointly adjust the O2 flow controller 4, the CO2 flow controller 5, and the Ar flow controller 6 according to the bottom blowing working pressure signal, the bottom blowing working temperature signal, the molten pool C content signal and the molten pool temperature signal, so that the bottom blowing oxygen-containing multi-gas clean smelting of the electric arc furnace proceeds smoothly.

[0057] In this embodiment, at the beginning of the furnace service period, the bottom blowing safety temperature value T is set. f0 1600℃. Due to the continuous erosion of bottom-blowing bricks during the smelting process, the bottom-blowing safety temperature value T f Reduced to 1450℃, bottom blowing safety temperature tolerance ΔT is 30℃. Bottom blowing safety pressure value P f It is 0.45MPa, and the safety pressure tolerance ΔP is 0.15MPa.

[0058] The specific control steps are as follows: S1: Smelting starts, the system is initialized, and the bottom blowing safety pressure value P f Input to the main control system and set the bottom blowing safety temperature value T f Input to the main control system; the O2 ratio before adjustment is x0, the adjustment ratio Δx is 1%, and the ratio after adjustment is x; suppose the CO2 ratio before adjustment is y0, and the ratio after adjustment is y; the oxygen-containing gas ratio is x+y.

[0059] S2: When the molten pool temperature T is less than 1500℃, the scrap steel in the furnace is not completely melted, and the bottom blowing of the electric furnace adopts pure Ar bottom blowing, and the bottom blowing flow rate is 25NL / min; S3: When the molten pool temperature T≥1500℃, the scrap steel has been melted and a flat molten pool has been formed in the furnace. On the basis of ensuring the original Ar bottom blowing stirring, oxygen-containing gas is added, and the proportion and flow of oxygen-containing gas are adjusted according to the content of molten pool C. The total flow of bottom blowing mixed gas at this stage is 45NL / min. The bottom blowing pressure sensor 9 transmits the bottom blowing working pressure signal P to the computer and main control system 7. w The bottom blowing temperature sensor 14 transmits the bottom blowing working temperature signal T to the computer and the main control system 7. w The computer and the main control system 7 adjust the ratio of CO2 and O2 in the oxygen-containing gas by comparing the bottom blowing working parameters with the bottom blowing safety parameters, so that the bottom blowing working pressure is within the safety pressure range of 0.30MPa~0.60MPa, and the bottom blowing working temperature is within the safety temperature range of 1420℃~1480℃. The specific control strategy is: (1) When the C content [%C] in the molten pool is greater than 0.3%, the oxygen-containing gas ratio x+y is 55%, the Ar ratio is 45%, and the initial O2 ratio is set to 17% and the CO2 ratio is set to 38%.

[0060] (2) When the C content in the molten pool is 0.1%≤[%C]≤0.3%, the oxygen-containing gas ratio x+y is 35%, and the Ar ratio is 65%, where the initial O2 ratio is set to 10% and the initial CO2 ratio is set to 25%.

[0061] (3) When the C content [%C] in the molten pool is less than 0.1%, the oxygen-containing gas ratio x+y is 20%, and the Ar ratio is 80%, where the initial O2 ratio is set to 5% and the initial CO2 ratio is set to 15%.

[0062] (4) When the bottom blowing working pressure of the electric arc furnace is P w >0.60MPa, or bottom blowing working temperature T w When the temperature is less than 1420℃, the main control system of the bottom blowing of the electric arc furnace increases the O2 ratio by 3% and reduces the CO2 ratio by 3%. That is, at this time, the O2 ratio is x=x0+3%, and the CO2 ratio is y=y0-3%.

[0063] (5) When the bottom blowing working pressure of the electric arc furnace is 0.30MPa≤P w ≤0.60MPa, and bottom blowing working temperature 1420℃≤T w When the temperature is ≤1480℃, the main control system of the bottom blowing of the electric arc furnace controls the ratio of O2 and CO2 to remain unchanged, that is, at this time the O2 ratio is x=x0, and the CO2 ratio is y=y0.

[0064] (6) When the bottom blowing working pressure of the electric arc furnace is P w <0.30MPa, or bottom blowing working temperature T w When the temperature is higher than 1480℃, the main control system of the bottom blowing of the electric arc furnace reduces the O2 ratio by 3% and increases the CO2 ratio by 3%. That is, at this time, the O2 ratio is x=x0-3%, and the CO2 ratio is y=y0+3%.

[0065] (7) When the bottom blowing working pressure of the electric arc furnace is P w >0.75MPa or P w When the pressure is less than 0.15MPa, the pressure alarm is activated, and the CO2 and O2 bottom blowing are cut off, and pure Ar bottom blowing is used.

[0066] (8) When the bottom blowing temperature of the arc furnace is T w >1510℃ or T w When the temperature is less than 1390℃, the temperature alarm is activated, and the CO2 and O2 bottom blowing are cut off, and pure Ar bottom blowing is used.

[0067] S4: The main control system controls the O2 flow controller to pass the O2 flow rate to Q according to the total flow rate of the bottom blowing mixed gas and the proportion of each medium. O2 =Q×x, the CO2 flow controller controls the CO2 flow rate to be Q CO2 =Q×y, control the Ar flow controller to pass the Ar flow rate to Q Ar =Q×(100%-xy).

[0068] S5: After the above judgment is executed, if the electric arc furnace has not yet tapped steel, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

[0069] After adopting the above method, the carbon content of the steel produced is 0.22%, the phosphorus content is 0.008%, and the nitrogen content is 0.0044%. Compared with bottom blowing argon, the life of the bottom blowing air brick is reduced by 0%, the smelting cycle is shortened by 5-6 minutes, and the production cost is reduced by 6-7 yuan / t. 钢 .

[0070] Comparative Example 1 This comparative example only provides pure argon gas blown from the bottom of the electric arc furnace.

[0071] The raw material structure of the 90 t AC electric arc furnace is all scrap steel. There are two bottom blowing points at the bottom of the electric arc furnace. The bottom blowing air bricks are capillary type. The diameter of the air bricks is 350 mm, the capillary diameter is 2 mm, and the number of capillary holes is 30.

[0072] The specific steps are as follows: S1: At the beginning of smelting, when the molten pool temperature T is less than 1500℃, the scrap steel in the furnace is not completely melted, and the bottom blowing of the electric furnace adopts pure Ar bottom blowing with a bottom blowing flow rate of 25NL / min; S2: When the molten pool temperature T≥1500℃, the scrap steel has been melted and a flat molten pool is formed in the furnace. The bottom blowing of the electric furnace adopts pure Ar bottom blowing, and the bottom blowing flow rate is 45NL / min; S3: After the above judgment is executed, if the electric arc furnace has not yet tapped steel, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

[0073] After the comparative example adopts the above method, the carbon content of the steel is 0.15%, the phosphorus content is 0.015%, and the nitrogen content is 0.0073%. Compared with bottom blowing argon, the life of the bottom blowing air brick is reduced by 0%, the smelting cycle is shortened by 0min, and the production cost is reduced by 0 yuan / t 钢 .

[0074] Comparative Example 2 The comparative electric arc furnace adopts argon and oxygen-containing gases including oxygen and carbon dioxide for bottom blowing. During the whole smelting process, the proportion of oxygen-containing gas is a fixed value and is not controlled by the program.

[0075] The raw material structure of the 90 t AC electric arc furnace is all scrap steel. There are two bottom blowing points at the bottom of the electric arc furnace. The bottom blowing air bricks are capillary type. The diameter of the air bricks is 350 mm, the capillary diameter is 2 mm, and the number of capillary holes is 30.

[0076] The specific steps are as follows: S1: At the beginning of smelting, when the molten pool temperature T is less than 1500℃, the scrap steel in the furnace is not completely melted, and the bottom blowing of the electric furnace adopts pure Ar bottom blowing with a bottom blowing flow rate of 25NL / min; S2: When the molten pool temperature T≥1500℃, the scrap steel has been melted and a flat molten pool is formed in the furnace. On the basis of ensuring the original Ar bottom blowing stirring, oxygen-containing gas is added. The total bottom blowing flow is 45NL / min, the Ar ratio is 40%, the oxygen-containing gas ratio is 60%, of which the O2 ratio is 30% and the CO2 ratio is 30%; S3: The main control system controls the O2 flow controller to pass the O2 flow rate to Q according to the total flow rate of the bottom blowing mixed gas and the proportion of each medium. O2 =45NL / min×30%=13.5NL / min, the CO2 flow controller controls the CO2 flow rate to Q CO2 =45NL / min×30%=13.5NL / min, control the Ar flow controller to pass the Ar flow rate to Q Ar =45NL / min×40%=18NL / min.

[0077] S4: After the above judgment is executed, if the electric arc furnace has not yet tapped steel, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

[0078] After the comparative example adopts the above method, the carbon content of the steel is 0.05%, the phosphorus content is 0.012%, and the nitrogen content is 0.0060%. Compared with bottom blowing argon, the life of the bottom blowing air brick is reduced by 30%, the smelting cycle is shortened by 0min, and the production cost increases by 5 yuan / t. 钢 .

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace, characterized in that: include: S1: Smelting starts, the system is initialized, and the standard safety pressure value P f Input to the main control system and set the standard safety temperature value T f Input to the main control system; S2: When the molten pool temperature T is less than 1500°C, the arc furnace uses argon gas for bottom blowing; S3: When the molten pool temperature T≥1500°C, the electric arc furnace uses argon and / or oxygen-containing gas including oxygen and carbon dioxide for bottom blowing, and adjusts the proportion and flow rate of the oxygen-containing gas according to the content of the molten pool C; The bottom blowing pressure sensor transmits the bottom blowing working pressure signal P to the main control system. w , the bottom blowing temperature sensor transmits the bottom blowing working temperature signal T to the main control system w The main control system adjusts the ratio of CO2 and O2 in the oxygen-containing gas by comparing the bottom blowing working parameters with the bottom blowing safety parameters, so that the bottom blowing working pressure is within the safety pressure range P f -ΔP~P f +ΔP, bottom blowing working temperature is within the safe temperature range T f -ΔT~T f +ΔT, where ΔP is the safety pressure tolerance and ΔT is the safety temperature tolerance; the ratio of O2 before adjustment is x0, the adjustment ratio is Δx, and the ratio after adjustment is x; the ratio of CO2 before adjustment is y0, and the ratio after adjustment is y; the volume ratio of oxygen and carbon dioxide in the oxygen-containing gas is x+y; The specific control strategies are: (1) When the C content [wt%C] in the molten pool is greater than 0.3%, the volume ratio x+y of oxygen and carbon dioxide in the oxygen-containing gas is 40-60%, wherein the initial ratio of O2 is set to 10%-20% and the initial ratio of CO2 is set to 30%-40%; (2) When the C content in the molten pool is 0.1%≤[wt%C]≤0.3%, the volume ratio x+y of oxygen and carbon dioxide in the oxygen-containing gas is 20-40%, wherein the initial ratio of O2 is set to 5%-10% and the initial ratio of CO2 is set to 15%-30%; (3) When the C content [wt%C] in the molten pool is less than 0.1%, the volume ratio x+y of oxygen and carbon dioxide in the oxygen-containing gas is 0-20%, wherein the initial ratio of O2 is set to 0%-5% and the initial ratio of CO2 is set to 0%-15%; (4) When the bottom blowing working pressure of the electric arc furnace is P w >P f +ΔP, or bottom blowing operating temperature T w <T f At -ΔT, the main control system of the bottom blowing of the electric arc furnace increases the O2 ratio Δx and reduces the CO2 ratio Δx, that is, at this time the O2 ratio x=x0+Δx, and the CO2 ratio is y=y0-Δx; (5) When the bottom blowing working pressure of the electric arc furnace is P f -ΔP≤P w ≤P f +ΔP, and bottom blowing working temperature T f -ΔT≤T w ≤T f At +ΔT, the main control system of the bottom blowing of the electric arc furnace controls the ratio of O2 and CO2 to remain unchanged, that is, at this time, the O2 ratio is x=x0, and the CO2 ratio is y=y0; (6) When the bottom blowing working pressure of the electric arc furnace is P w <P f -ΔP, or bottom blowing operating temperature T w >T f +ΔT, the main control system of the bottom blowing of the electric arc furnace reduces the O2 ratio Δx and increases the CO2 ratio Δx, that is, at this time the O2 ratio x=x0-Δx, and the CO2 ratio is y=y0+Δx; (7) When the bottom blowing working pressure of the electric arc furnace is P w >P f +2ΔP or P w <P f When -2ΔP, the pressure alarm is enabled, and the CO2 and O2 bottom blowing are cut off, and pure Ar bottom blowing is adopted; (8) When the bottom blowing temperature of the electric arc furnace is T w >T f +2ΔT or T w <T f When -2ΔT, the temperature alarm is enabled, and the CO2 and O2 bottom blowing are cut off, and pure Ar bottom blowing is adopted; (9) The main control system controls the O2 flow controller to adjust the O2 flow rate to Q according to the total flow rate Q of the oxygen-containing gas blown at the bottom and the execution results of the ratio of each medium. O2 =Q×x, the CO2 flow controller controls the CO2 flow rate to be Q CO2 =Q×y, control the Ar flow controller to pass the Ar flow rate to Q Ar =Q×(100%-xy); S4: After the above judgment is executed, if the electric arc furnace has not yet tapped steel, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

2. The method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace according to claim 1, characterized in that: In S2, the bottom blowing argon gas flow rate is 20-30 NL / min.

3. The method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace according to claim 1, characterized in that: In S3, the total flow rate of the oxygen-containing gas is 30-50 NL / min.

4. The method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace according to claim 1, characterized in that: In S3, the standard safety pressure value P f It is 0.2-0.6MPa, and the safety pressure tolerance ΔP is 0.15MPa.

5. The method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace according to claim 1, characterized in that: At the beginning of a furnace service period, set the bottom blowing safety temperature value T f0 The bottom blowing safety temperature value T is 1600℃ for every 100 furnaces of molten steel produced. f0 Reduce by 30℃.

6. The method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace according to claim 1, characterized in that: In S3, Δx is 1%-5%.

7. The method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace according to claim 1, characterized in that: The bottom-blown air-permeable bricks used in the electric arc furnace are capillary-type, the diameter of the bottom-blown air-permeable bricks is 200-400 mm, the capillary diameter is 1-2 mm, and the number of capillaries is 12-50.

8. The method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace according to claim 1, characterized in that: A plurality of bottom blowing points are arranged at the bottom of the electric arc furnace.

9. The method for clean smelting by bottom blowing oxygen-containing multi-element gas in an electric arc furnace according to any one of claims 1 to 8, characterized in that: The method is used for producing low-nitrogen and low-phosphorus steel. The target composition of the steel produced by smelting the steel in an electric arc furnace is: C 0.1-0.3wt%, P < 0.01wt%, and N < 0.005wt%.

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