A method for clean smelting by bottom-blowing oxygen-containing multi-component gas in an electric arc furnace

Abstract

This application provides a method for clean smelting of an electric arc furnace with bottom blowing of oxygen-containing multi-component gas, which relates to the metallurgy field. The method includes: at the beginning of smelting, input the standard safety pressure value P f into the main control system, and input the standard safety temperature value T f into the main control system; when the molten bath temperature T < 1500 °C, argon is used for bottom blowing in the electric arc furnace; when the molten bath temperature T ≥ 1500 °C, argon and oxygen-containing gas including oxygen and carbon dioxide are used for bottom blowing, and the proportion and flow rate of the oxygen-containing gas are adjusted according to the C content in the molten bath, the bottom blowing pressure and temperature. This method utilizes the reaction between the oxygen-containing gas and the elements in the steel, improves the utilization efficiency of oxygen in the molten steel, strengthens the stirring ability of the molten bath, promotes dephosphorization and denitrification of the molten steel, and ensures that the composition of the molten steel meets the standards. At the same time, it slows down the influence of the oxygen-containing gas on the service life of the bottom blowing element, shortens the smelting cycle, improves the production efficiency, reduces the smelting cost, and realizes the high-efficiency and clean smelting of the electric arc furnace.

Description

Technical Field

[0001] This application relates to the metallurgical field, and particularly to a method for clean smelting of an electric arc furnace by bottom-blowing oxygen-containing multi-component gas. Background Art

[0002] With the continuous improvement of the market's quality requirements for steel, the clean smelting of electric arc furnaces has become the key to improving the quality of steel. Phosphorus is a harmful element in the vast majority of steel grades, which makes the plasticity and toughness of steel poor, resulting in cold brittleness and affecting the quality of steel. Therefore, dephosphorization is one of the important tasks in the smelting of electric arc furnaces. However, due to the complex structure of the raw materials in the electric furnace, the phosphorus content in the molten pool fluctuates greatly after melting, and the stirring ability of the molten pool is poor, resulting in poor dephosphorization kinetic conditions. Secondly, during the smelting process, the arc will ionize nitrogen in the air, resulting in an increase in the nitrogen content in the molten pool. When the nitrogen content in the steel is high, phenomena such as blue brittleness occur, and the ductility, toughness, and other properties of the steel are reduced to varying degrees. All these indicate that clean smelting still poses challenges for electric arc furnace steelmaking. Therefore, improving the electric arc furnace steelmaking process in China has become the key to efficient and clean smelting of electric arc furnaces.

[0003] To solve the problem of clean smelting of electric arc furnaces, many researchers have proposed measures to increase bottom-blowing stirring. Document CN112322839A introduces a method for degassing by bottom-blowing argon in an intermediate frequency furnace, which mainly includes: setting a refractory permeable brick at the bottom and bottom-blowing argon. 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 ability is limited.

[0004] Document CN108251593A introduces a method for dynamically adjusting the bottom-blowing CO2 flow rate in converter steelmaking to improve denitrification. During the smelting process, CO2 is bottom-blown. CO2 is a weakly oxidizing gas and can react with the elements in the steel to generate twice the volume of CO, strengthening the stirring of the molten pool. The vacuum environment of the CO bubbles takes away the nitrogen elements in the steel, which is beneficial to the purification of the molten steel. However, in the actual production process, due to the reaction between CO2 and the elements in the steel, the necessary elements in the steel are burned out, and at the same time, the single CO2 reaction is endothermic, which will cause the bottom-blowing permeable brick to be blocked, thus affecting the electric furnace smelting.

[0005] Document CN117802395A introduces a method for controlling nitrogen production of low-temperature steel. In the electric furnace smelting process, bottom blowing O2 is used to achieve low-carbon and high-oxygen tapping. Combining 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, thus 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, but does not fundamentally achieve clean smelting in the electric furnace process. And in actual production, due to the thermal effect and chemical effect of the O2 reaction, single bottom blowing O2 will erode the bottom blowing permeable brick, affecting the service life of the bottom blowing element.

[0006] It can be seen that it is difficult to bottom blow oxygen-containing gases (O2 and CO2) in the electric arc furnace, which is easy to cause erosion or blockage of the bottom blowing permeable brick, have an adverse impact on the service life of the bottom blowing element, and at the same time, the oxygen-containing gas will also cause fluctuations in the content of molten pool elements, affecting the compliance of the molten steel composition. Summary of the Invention

[0007] The purpose of this application is to provide a method for clean smelting of bottom blowing oxygen-containing multi-component gases in an electric arc furnace to solve the above problems.

[0008] To achieve the above purpose, this application adopts the following technical solutions:

[0009] A method for clean smelting of bottom blowing oxygen-containing multi-component gases in an electric arc furnace, including:

[0010] S1: At the start of smelting, the system is initialized, and the standard safety pressure value P f is input into the main control system, and the standard safety temperature value T f is input into the main control system;

[0011] S2: When the molten pool temperature T < 1500 °C, argon is used for bottom blowing in the electric arc furnace;

[0012] S3: When the molten pool temperature T ≥ 1500 °C, argon and / or oxygen-containing gases including oxygen and carbon dioxide are used for bottom blowing in the electric arc furnace, and the proportion and flow rate of the oxygen-containing gas are adjusted according to the C content in the molten pool;

[0013] The bottom blowing pressure sensor transmits the bottom blowing working pressure signal P w to the main control system, and the bottom blowing temperature sensor transmits the bottom blowing working temperature signal T w to the main control system. The main control system adjusts the proportion 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, and the bottom blowing working temperature is within the safety temperature range T f -ΔT~Tf within +ΔT, where ΔP is the safety pressure tolerance and ΔT is the safety temperature tolerance; the proportion of O2 before adjustment is x0, the adjustment proportion is Δx, and the proportion after adjustment is x; the proportion of CO2 before adjustment is y0, and the proportion after adjustment is y; the volume ratio of oxygen and carbon dioxide in the oxygen-containing gas is x + y;

[0014] The specific control strategy is as follows:

[0015] (1) When the C content [wt%C] in the molten pool > 0.3%, the volume ratio x + y of oxygen and carbon dioxide in the oxygen-containing gas is 40 - 60%, where the initial proportion of O2 is set to 10% - 20%, and the initial proportion of CO2 is set to 30% - 40%;

[0016] (2) When the C content 0.1% ≤ [wt%C] ≤ 0.3% in the molten pool, the volume ratio x + y of oxygen and carbon dioxide in the oxygen-containing gas is 20 - 40%, where the initial proportion of O2 is set to 5% - 10%, and the initial proportion of CO2 is set to 15% - 30%;

[0017] (3) When the C content [wt%C] in the molten pool < 0.1%, the volume ratio x + y of oxygen and carbon dioxide in the oxygen-containing gas is 0 - 20%, where the initial proportion of O2 is set to 0% - 5%, and the initial proportion of CO2 is set to 0% - 15%;

[0018] (4) When the bottom-blowing working pressure P of the electric arc furnace w > P f + ΔP, or the bottom-blowing working temperature T w < T f - ΔT, the main control system of the bottom-blowing of the electric arc furnace increases the O2 proportion by Δx and decreases the CO2 proportion by Δx, that is, at this time, the O2 proportion x = x0 + Δx, and the CO2 proportion is y = y0 - Δx;

[0019] (5) When the bottom-blowing working pressure P of the electric arc furnace f - ΔP ≤ P w ≤ P f + ΔP, and the bottom-blowing working temperature T f - ΔT ≤ T w ≤ T f + ΔT, the main control system of the bottom-blowing of the electric arc furnace controls the proportions of O2 and CO2 unchanged, that is, at this time, the O2 proportion x = x0, and the CO2 proportion is y = y0;

[0020] (6) When the bottom-blowing working pressure P of the electric arc furnace w < P f - ΔP, or the bottom-blowing working temperature T w > T fAt +ΔT, the main control system of the bottom blowing of the electric arc furnace reduces the O2 ratio by Δx and increases the CO2 ratio by Δx. That is, at this time, the O2 ratio x = x0 - Δx, and the CO2 ratio is y = y0 + Δx;

[0021] (7)When the working pressure P of the bottom blowing of the electric arc furnace w >P f +2ΔP or P w <P f -2ΔP, enable the pressure alarm, cut off the bottom blowing of CO2 and O2, and adopt pure Ar bottom blowing;

[0022] (8)When the working temperature T of the bottom blowing of the electric arc furnace w >T f +2ΔT or T w <T f -2ΔT, enable the temperature alarm, cut off the bottom blowing of CO2 and O2, and adopt pure Ar bottom blowing;

[0023] (9)The main control system controls the O2 flow controller to have an O2 flow of Q O2 =Q×x according to the total flow Q of the oxygen-containing gas in the bottom blowing and the execution result of each medium ratio, controls the CO2 flow controller to have a CO2 flow of Q CO2 =Q×y, and controls the Ar flow controller to have an Ar flow of Q Ar =Q×(100%-x-y);

[0024] S4: After the above judgments are executed, if the electric arc furnace has not tapped steel yet, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

[0025] Preferably, in S2, the flow rate of bottom blowing argon is 20 - 30 NL / min.

[0026] Preferably, in S3, the total flow rate of the oxygen-containing gas is 30 - 50 NL / min.

[0027] Preferably, in S3, the standard safety pressure value P f is 0.2 - 0.6 MPa, and the safety pressure tolerance ΔP is 0.15 MPa.

[0028] Preferably, at the beginning of a furnace campaign, the bottom blowing safety temperature value T f0 is set to 1600 °C, and for every 100 heats of molten steel produced, the bottom blowing safety temperature value T f0 decreases by 30 °C.

[0029] Preferably, in S3, Δx is 1% - 5%.

[0030] Preferably, the bottom-blowing porous plug used in the electric arc furnace is of the capillary type. The diameter of the bottom-blowing porous plug is 200 - 400 mm, the capillary diameter is 1 - 2 mm, and the number of capillary pores is 12 - 50.

[0031] Preferably, a plurality of bottom-blowing points are arranged at the bottom of the electric arc furnace.

[0032] Preferably, the method is used for producing low-nitrogen and low-phosphorus steel. The target tapping composition of this type of steel smelted in the electric arc furnace is: C 0.1 - 0.3 wt%, P < 0.01 wt%, N < 0.005 wt%.

[0033] Compared with the prior art, the beneficial effects of the present application include:

[0034] The method for clean smelting of bottom-blowing oxygen-containing multi-component gas in the electric arc furnace provided by the present application incorporates oxygen-containing gas on the basis of the bottom-blowing Ar process during the electric arc furnace smelting 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, improving the utilization efficiency of oxygen and enhancing the stirring ability of the molten pool, which is beneficial to clean smelting such as dephosphorization, denitrification, and inclusion removal of the molten steel. After the scrap steel in the furnace is melted and cleared, the main control system first adjusts the total proportion of the oxygen-containing gas according to the molten pool C content signal fed back by the bottom-blowing system to prevent fluctuations in the composition within the molten pool caused by the bottom-blowing oxygen-containing gas. Then, according to the working pressure signal and bottom-blowing temperature signal fed back by the bottom-blowing system, the bottom-blowing ratio and flow rate of O2 and CO2 in the oxygen-containing gas are dynamically adjusted to ensure that the bottom-blowing working pressure and bottom-blowing working temperature are always within the safe range. The method provided by the present application improves the purity of the molten steel, shortens the smelting cycle, and reduces the smelting cost while ensuring the smooth progress of efficient and clean smelting of the electric arc furnace. Description of the Drawings

[0035] 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 some embodiments of the present application and should not be regarded as limiting the scope of the present application.

[0036] Figure 1 It is a schematic diagram of the system for clean smelting of bottom-blowing oxygen-containing multi-component gas in the electric arc furnace used in the embodiments of the present application.

[0037] Reference Signs:

[0038] 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 permeable brick; 12 - electric arc furnace; 13 - infrared thermometer; 14 - temperature sensor; 15 - temperature alarm device; 16 - element analyzer. Specific implementation mode

[0039] To better explain the technical solution provided by this application, before the embodiments, the devices used and the basic principles are stated as follows:

[0040] Since it is difficult to bottom - blow oxygen - containing gas, the chemical effect and thermal effect of O2 are likely to cause melting and erosion of the bottom - blowing permeable brick in the electric arc furnace. CO2 is likely to block the permeable brick due to its endothermic reaction. Both have an adverse impact on the service life of the permeable brick. At the same time, oxygen - containing gas will also affect the content of elements such as C in the molten steel. Therefore, after the scrap steel in the furnace is melted clean, the main control system first adjusts the total proportion of oxygen - containing gas according to the signal of the C content in the molten pool fed back by the bottom - blowing system to prevent fluctuations in the composition in the molten pool caused by bottom - blowing oxygen - containing gas. Then, according to the working pressure signal and bottom - blowing temperature signal fed back by the bottom - blowing system, it dynamically adjusts the bottom - blowing proportion and flow rate of O2 and CO2 in the oxygen - containing gas to ensure that the bottom - blowing working pressure and bottom - blowing temperature are always within the safe range, thereby preventing the failure of the bottom - blowing permeable brick and ensuring the smooth progress of efficient and clean smelting in the electric arc furnace.

[0041] The method provided by this application is exemplarily operated using a smelting system as Figure 1 shown. 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 permeable brick 11, electric arc furnace 12, infrared thermometer 13, bottom - blowing temperature sensor 14, temperature alarm device 15 and element analyzer 16.

[0042] In the bottom - blowing system of the electric arc furnace, the bottom - blowing working pressure signal P w and the bottom - blowing working temperature signal T wThey are provided to the main control system by a bottom-blowing pressure sensor and a bottom-blowing temperature sensor respectively. The C content signal [%C] in the molten bath is provided to the main control system by an elemental analyzer. The molten bath temperature signal T is provided to the main control system by an infrared thermometer. When the bottom-blowing pressure is abnormal, the abnormal pressure signal is provided to the main control system by a pressure alarm device. When the bottom-blowing temperature is abnormal, the abnormal temperature signal is provided to the main control system by a temperature alarm device. The main control system jointly adjusts each gas flow control valve according to the bottom-blowing working pressure signal, the bottom-blowing working temperature signal, the molten bath C content signal and the molten bath temperature signal, so as to smoothly carry out the clean smelting of oxygen-containing multi-component gas at the bottom of the electric arc furnace.

[0043] The implementation scheme of the present application will be described in detail below in conjunction with specific embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0044] Example 1

[0045] This embodiment provides a method for clean smelting of oxygen-containing multi-component gas at the bottom of an electric arc furnace. This method is applied to a 70t AC electric arc furnace in a certain factory. The raw material structure of the electric arc furnace in this factory is all scrap steel. There are a total of four bottom-blowing points at the bottom of the electric arc furnace. The bottom-blowing porous plug is of the capillary type. The diameter of the porous plug is 300mm, the capillary diameter is 2mm, and the number of capillary holes is 20.

[0046] In the bottom-blowing system of the electric arc furnace, the bottom-blowing working pressure signal P w and the bottom-blowing working temperature signal T w are provided to the computer and the main control system 7 by a bottom-blowing pressure sensor 9 and a bottom-blowing temperature sensor 14 respectively. The C content signal [%C] in the molten bath is provided to the computer and the main control system 7 by an elemental analyzer 16. The molten bath temperature signal T is provided to the computer and the main control system 7 by an 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 a 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 a 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 bath C content signal and the molten bath temperature signal, so as to smoothly carry out the clean smelting of oxygen-containing multi-component gas at the bottom of the electric arc furnace.

[0047] In this embodiment, at the beginning of the furnace campaign, the set bottom-blowing safety temperature value T f0 is 1600 °C. Due to the continuous erosion of the bottom-blowing brick during the smelting process, when producing the 100th heat of molten steel, the bottom-blowing safety temperature value Tf is reduced to 1570 °C, and the bottom-blowing safety temperature tolerance ΔT is 30 °C. The bottom-blowing safety pressure value P f is 0.35 MPa, and the safety pressure tolerance ΔP is 0.15 MPa.

[0048] The specific control steps are as follows:

[0049] S1: At the start of smelting, the system is initialized, and the bottom-blowing safety pressure value P f is input into the main control system, and the bottom-blowing safety temperature value T f is input into the main control system; the pre-regulation ratio of O2 is x0, the regulation ratio Δx is 1%, and the post-regulation ratio is x; let the pre-regulation ratio of CO2 be y0, and the post-regulation ratio be y; the proportion of oxygen-containing gas is x + y.

[0050] S2: When the molten bath temperature T < 1500 °C, at this time the scrap in the furnace has not been completely melted, and the bottom blowing of the electric furnace uses pure Ar bottom blowing, and the bottom-blowing flow rate is 22 NL / min;

[0051] S3: When the molten bath temperature T ≥ 1500 °C, at this time the scrap has been completely melted, and a flat molten bath is formed in the furnace. On the basis of ensuring the original Ar bottom-blowing stirring, oxygen-containing gas is incorporated, and the proportion and flow rate of the oxygen-containing gas are adjusted according to the C content in the molten bath. The total bottom-blowing mixed gas flow rate at this stage is 35 NL / min. The bottom-blowing pressure sensor 9 transmits the bottom-blowing working pressure signal P w to the computer and the main control system 7, and the bottom-blowing temperature sensor 14 transmits the bottom-blowing working temperature signal T w to the computer and the main control system 7. The computer and the main control system 7 adjust the proportion 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 safe pressure range of 0.20 - 0.50 MPa, and the bottom-blowing working temperature is within the safe temperature range of 1540 °C - 1600 °C. The specific control strategy is:

[0052] (1) When the C content [%C] in the molten bath > 0.3%, the proportion of oxygen-containing gas x + y is 45%, and the proportion of Ar is 55%. Among them, the initial proportion of O2 is set to 13%, and the initial proportion of CO2 is set to 32%.

[0053] (2) When the C content in the molten bath 0.1% ≤ [%C] ≤ 0.3%, the proportion of oxygen-containing gas x + y is 25%, and the proportion of Ar is 75%. Among them, the initial proportion of O2 is set to 6%, and the initial proportion of CO2 is set to 19%.

[0054] (3) When the C content [%C] in the molten bath < 0.1%, the proportion of oxygen-containing gas x + y is 10%, and the proportion of Ar is 90%. Among them, the initial proportion of O2 is set to 2%, and the initial proportion of CO2 is set to 8%.

[0055] (4) When the bottom-blowing working pressure P of the electric arc furnace w > 0.50 MPa, or the bottom-blowing working temperature T w < 1540 °C, the main control system of the bottom-blowing of the electric arc furnace increases the O2 ratio by 1% and decreases the CO2 ratio by 1%. That is, at this time, the O2 ratio x = x0 + 1%, and the CO2 ratio is y = y0 - 1%.

[0056] (5) When the bottom-blowing working pressure of the electric arc furnace 0.20 MPa ≤ P w ≤ 0.50 MPa, and the bottom-blowing working temperature 1540 °C ≤ T w ≤ 1600 °C, the main control system of the bottom-blowing of the electric arc furnace controls the O2 and CO2 ratios to remain unchanged. That is, at this time, the O2 ratio x = x0, and the CO2 ratio is y = y0.

[0057] (6) When the bottom-blowing working pressure P of the electric arc furnace w < 0.20 MPa, or the bottom-blowing working temperature T w > 1600 °C, the main control system of the bottom-blowing of the electric arc furnace decreases the O2 ratio by 1% and increases the CO2 ratio by 1%. That is, at this time, the O2 ratio x = x0 - 1%, and the CO2 ratio is y = y0 + 1%.

[0058] (7) When the bottom-blowing working pressure P of the electric arc furnace w > 0.65 MPa or P w < 0.05 MPa, activate the pressure alarm and cut off the bottom-blowing of CO2 and O2, and use pure Ar bottom-blowing.

[0059] (8) When the bottom-blowing working temperature T of the electric arc furnace w > 1650 °C or T w < 1400 °C, activate the temperature alarm and cut off the bottom-blowing of CO2 and O2, and use pure Ar bottom-blowing.

[0060] S4: The main control system controls the O2 flow controller to have an O2 flow of Q O2 = Q × x according to the total flow of the bottom-blowing mixed gas and the execution results of the ratios of each medium, controls the CO2 flow controller to have a CO2 flow of Q CO2 = Q × y, and controls the Ar flow controller to have an Ar flow of Q Ar = Q × (100% - x - y).

[0061] S5: After the above judgments are executed, if the electric arc furnace has not tapped steel yet, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

[0062] After adopting the above method in this embodiment, the tapping carbon content is 0.18%, the phosphorus content is 0.008%, and the nitrogen content is 0.0048%. Compared with bottom blowing argon, the service life of the bottom blowing permeable 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 。

[0063] Example 2

[0064] This embodiment provides a method for clean smelting of an electric arc furnace with bottom blowing of oxygen-containing multi-component gas, which is applied to a 90t AC electric arc furnace in a certain factory. The raw material structure of the electric arc furnace in this factory is all scrap steel. There are 2 bottom blowing points at the bottom of the electric arc furnace. The bottom blowing permeable brick is of capillary type, with a permeable brick diameter of 350mm, a capillary diameter of 2mm, and 25 capillary holes.

[0065] In the bottom blowing system of the electric arc furnace, the bottom blowing working pressure signal P w and the bottom blowing working temperature signal T w are respectively provided to the computer and the main control system 7 by the bottom blowing pressure sensor 9 and the bottom blowing temperature sensor 14. The C content signal [%C] in the molten bath is provided to the computer and the main control system 7 by the elemental analyzer 16. The molten bath 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 bath C content signal, and the molten bath temperature signal, so as to ensure the smooth progress of the clean smelting of the electric arc furnace with bottom blowing of oxygen-containing multi-component gas.

[0066] In this embodiment, at the beginning of the furnace campaign, the safe temperature value T f0 of the bottom blowing brick is set to 1600°C. Due to the continuous erosion of the bottom blowing brick during the smelting process, when producing the 300th heat of molten steel, the safe temperature value T f is reduced to 1510°C, and the tolerance of the bottom blowing safe temperature ΔT is 30°C. The safe pressure value P f of the bottom blowing is 0.4MPa, and the tolerance of the safe pressure ΔP is 0.15MPa.

[0067] The specific control steps are as follows:

[0068] S1: At the start of smelting, the system is initialized, and the bottom blowing safe pressure value P f is input into the main control system, and the bottom blowing safe temperature value T fInput to the main control system; the proportion of O2 before adjustment is x0, the adjustment proportion Δx is 1%, and the proportion after adjustment is x; let the proportion of CO2 before adjustment be y0, and the proportion after adjustment be y; the proportion of the oxygen-containing gas is x + y.

[0069] S2: When the molten bath temperature T < 1500 °C, at this time the scrap steel in the furnace is not completely melted, and the bottom blowing of the electric furnace uses pure Ar bottom blowing, and the bottom blowing flow rate is 25 NL / min;

[0070] S3: When the molten bath temperature T ≥ 1500 °C, at this time the scrap steel has been completely melted, and a flat molten bath is formed in the furnace. On the basis of ensuring the original Ar bottom blowing stirring, oxygen-containing gas is incorporated, and the proportion and flow rate of the oxygen-containing gas are adjusted according to the C content in the molten bath. The total flow rate of the bottom blowing mixed gas at this stage is 40 NL / 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 , and the bottom blowing temperature sensor 14 transmits the bottom blowing working temperature signal T to the computer and the main control system 7 w , and the computer and the main control system 7 adjust the proportion 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 safe pressure range of 0.25 - 0.55 MPa, and the bottom blowing working temperature is within the safe temperature range of 1480 °C - 1540 °C. The specific control strategy is as follows:

[0071] (1) When the C content [%C] in the molten bath > 0.3%, the proportion of the oxygen-containing gas x + y is 50%, and the proportion of Ar is 50%. Among them, the initial proportion of O2 is set to 15%, and the initial proportion of CO2 is set to 35%.

[0072] (2) When the C content 0.1% ≤ [%C] ≤ 0.3% in the molten bath, the proportion of the oxygen-containing gas x + y is 30%, and the proportion of Ar is 70%. Among them, the initial proportion of O2 is set to 8%, and the initial proportion of CO2 is set to 22%.

[0073] (3) When the C content [%C] in the molten bath < 0.1%, the proportion of the oxygen-containing gas x + y is 15%, and the proportion of Ar is 85%. Among them, the initial proportion of O2 is set to 3%, and the initial proportion of CO2 is set to 12%.

[0074] (4) When the bottom blowing working pressure P of the electric arc furnace w > 0.55 MPa, or the bottom blowing working temperature T w < 1480 °C, the main control system of the electric arc furnace bottom blowing increases the O2 proportion by 2% and decreases the CO2 proportion by 2%, that is, at this time the O2 proportion x = x0 + 2%, and the CO2 proportion is y = y0 - 2%.

[0075] (5) When the bottom blowing working pressure of the electric arc furnace 0.25 MPa ≤ P w ≤ 0.55 MPa, and the bottom blowing working temperature 1480 °C ≤ Tw When the temperature is ≤1540°C, the main control system for bottom blowing in the electric arc furnace keeps the ratios of O2 and CO2 unchanged, that is, at this time, the O2 ratio x = x0 and the CO2 ratio is y = y0.

[0076] (6) When the working pressure P of the bottom blowing in the electric arc furnace w <0.25 MPa, or the working temperature T of the bottom blowing w >1540°C, the main control system for bottom blowing in 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 x = x0 - 2% and the CO2 ratio is y = y0 + 2%.

[0077] (7) When the working pressure P of the bottom blowing in the electric arc furnace w >0.7 MPa or P w <0.1 MPa, the pressure alarm is enabled, and the bottom blowing of CO2 and O2 is cut off, and pure Ar bottom blowing is adopted.

[0078] (8) When the working temperature T of the bottom blowing in the electric arc furnace w >1570°C or T w <1450°C, the temperature alarm is enabled, and the bottom blowing of CO2 and O2 is cut off, and pure Ar bottom blowing is adopted.

[0079] S4: The main control system controls the O2 flow controller to have an O2 flow of Q O2 = Q×x according to the total flow of the bottom blowing mixed gas and the execution result of the ratio of each medium, controls the CO2 flow controller to have a CO2 flow of Q CO2 = Q×y, and controls the Ar flow controller to have an Ar flow of Q Ar = Q×(100% - x - y).

[0080] S5: After the above judgments are executed, if the electric arc furnace has not tapped steel yet, return to S2; if the electric arc furnace is in the tapping process, return to S1.

[0081] After adopting the above method in this embodiment, the carbon content in the tapped steel is 0.20%, the phosphorus content is 0.007%, and the nitrogen content is 0.0045%. Compared with bottom blowing argon, the service life of the bottom blowing permeable 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 。

[0082] Example 3

[0083] This embodiment provides a method for clean smelting of oxygen-containing multi-component gas by bottom blowing in an electric arc furnace, which is applied to a 120 t AC electric arc furnace in a certain factory. The raw material structure of the electric arc furnace in this factory is all scrap steel. There are 4 bottom blowing points at the bottom of the electric arc furnace. The bottom blowing permeable brick is of capillary type, with a permeable brick diameter of 400 mm, a capillary diameter of 2 mm, and 30 capillary holes.

[0084] In the bottom blowing system of the electric arc furnace, the bottom blowing working pressure signal P w and the bottom blowing working temperature signal T w are provided to the computer and the main control system 7 by the bottom blowing pressure sensor 9 and the bottom blowing temperature sensor 14 respectively. The C content signal [%C] in the molten bath is provided to the computer and the main control system 7 by the elemental analyzer 16. The molten bath 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 bath C content signal, and the molten bath temperature signal, so as to ensure the smooth progress of the clean smelting of the oxygen-containing multi-component gas in the bottom blowing of the electric arc furnace.

[0085] In this embodiment, at the beginning of the furnace campaign, the bottom blowing safety temperature value T f0 is set to 1600 °C. Due to the continuous erosion of the bottom blowing brick during the smelting process, when producing the 500th heat of molten steel, the bottom blowing safety temperature value T f is reduced to 1450 °C, and the bottom blowing safety temperature tolerance ΔT is 30 °C. The bottom blowing safety pressure value P f is 0.45 MPa, and the safety pressure tolerance ΔP is 0.15 MPa.

[0086] The specific control steps are as follows:

[0087] S1: At the start of smelting, the system is initialized, and the bottom blowing safety pressure value P f is input into the main control system, and the bottom blowing safety temperature value T f is input into the main control system; the pre-regulation ratio of O2 is x0, the regulation ratio Δx is 1%, and the post-regulation ratio is x; let the pre-regulation ratio of CO2 be y0, and the post-regulation ratio be y; the proportion of the oxygen-containing gas is x + y.

[0088] S2: When the molten bath temperature T < 1500 °C, at this time the scrap in the furnace has not been completely melted, and the bottom blowing of the electric furnace uses pure Ar for bottom blowing, and the bottom blowing flow rate is 25 NL / min;

[0089] S3: When the molten bath temperature T ≥ 1500 °C, at this time the scrap has been completely melted, and a flat molten bath is formed in the furnace. On the basis of ensuring the original Ar bottom blowing stirring, oxygen-containing gas is incorporated, and the proportion and flow rate of the oxygen-containing gas are adjusted according to the C content in the molten bath. The total bottom blowing mixed gas flow rate at this stage is 45 NL / min. The bottom blowing pressure sensor 9 transmits the bottom blowing working pressure signal P w to the computer and the main control system 7, and the bottom blowing temperature sensor 14 transmits the bottom blowing working temperature signal T to the computer and the main control system 7w 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:

[0090] (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%.

[0091] (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%.

[0092] (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%.

[0093] (4) When the arc furnace bottom blowing working pressure 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%.

[0094] (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.

[0095] (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%.

[0096] (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.

[0097] (8)When the bottom blowing working temperature T of the electric arc furnace w > 1510 °C or T w < 1390 °C, enable temperature alarm, cut off the bottom blowing of CO2 and O2, and adopt pure Ar bottom blowing.

[0098] S4: According to the total flow rate of the bottom blowing mixed gas and the execution results of the proportion of each medium, the main control system controls the O2 flow controller so that the O2 flow rate is Q O2 = Q × x, controls the CO2 flow controller so that the CO2 flow rate is Q CO2 = Q × y, controls the Ar flow controller so that the Ar flow rate is Q Ar = Q × (100% - x - y).

[0099] S5: After the above judgments are executed, if the electric arc furnace has not tapped steel yet, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

[0100] After adopting the above method in this embodiment, the carbon content in the tapped steel is 0.22%, the phosphorus content is 0.008%, and the nitrogen content is 0.0044%. Compared with bottom blowing argon, the service life of the bottom blowing permeable 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 .

[0101] Comparative Example 1

[0102] This comparative example only provides pure argon bottom blowing for the electric arc furnace.

[0103] For a 90 t AC electric arc furnace, its raw material structure is all scrap steel. There are 2 bottom blowing points at the bottom of the electric arc furnace. The bottom blowing permeable brick is of capillary type, with a permeable brick diameter of 350 mm, a capillary diameter of 2 mm, and 30 capillary holes.

[0104] The specific steps are as follows:

[0105] S1: At the start of smelting, when the molten pool temperature T < 1500 °C, the scrap steel in the furnace has not melted completely at this time, and the bottom blowing of the electric furnace adopts pure Ar bottom blowing with a bottom blowing flow rate of 25 NL / min;

[0106] S2: When the molten pool temperature T ≥ 1500 °C, the scrap steel has melted completely at this time, a flat molten pool is formed in the furnace, and the bottom blowing of the electric furnace adopts pure Ar bottom blowing with a bottom blowing flow rate of 45 NL / min;

[0107] S3: After the above judgments are executed, if the electric arc furnace has not tapped steel yet, return to S2; if the electric arc furnace is in the process of tapping steel, return to S1.

[0108] After adopting the above method in this comparative example, the tapping carbon content is 0.15%, the phosphorus content is 0.015%, and the nitrogen content is 0.0073%. Compared with bottom blowing argon, the service life of the bottom blowing permeable brick is reduced by 0%, the smelting cycle is shortened by 0 min, and the production cost is reduced by 0 yuan / t 钢 。

[0109] Comparative Example 2

[0110] In this comparative example, the electric arc furnace uses argon and oxygen-containing gases including oxygen and carbon dioxide for bottom blowing. During the entire smelting process, the proportion of the oxygen-containing gas is a fixed value and is not controlled by the program.

[0111] A 90 t AC electric arc furnace with a raw material structure of all scrap steel. There are 2 bottom blowing points at the bottom of the electric arc furnace. The bottom blowing permeable brick is of capillary type, with a permeable brick diameter of 350 mm, a capillary diameter of 2 mm, and 30 capillary holes.

[0112] The specific steps are as follows:

[0113] S1: At the start of smelting, when the molten bath temperature T < 1500 °C, at this time the scrap steel in the furnace has not melted completely, and pure Ar bottom blowing is used for the bottom blowing of the electric furnace, with a bottom blowing flow rate of 25 NL / min;

[0114] S2: When the molten bath temperature T ≥ 1500 °C, at this time the scrap steel has melted completely and a flat molten bath is formed in the furnace. On the basis of ensuring the original Ar bottom blowing stirring, oxygen-containing gas is incorporated. The total bottom blowing flow rate is 45 NL / min, the Ar ratio is 40%, and the oxygen-containing gas ratio is 60%, among which the O2 ratio is 30% and the CO2 ratio is 30%;

[0115] S3: The main control system controls the O2 flow controller to have an O2 flow rate of Q O2 = 45 NL / min × 30% = 13.5 NL / min, controls the CO2 flow controller to have a CO2 flow rate of Q CO2 = 45 NL / min × 30% = 13.5 NL / min, and controls the Ar flow controller to have an Ar flow rate of Q Ar = 45 NL / min × 40% = 18 NL / min.

[0116] S4: After the above judgments and executions are completed, if the electric arc furnace has not tapped steel yet, return to S2; if the electric arc furnace is in the tapping process, return to S1.

[0117] After adopting the above method in this comparative example, the tapping carbon content is 0.05%, the phosphorus content is 0.012%, and the nitrogen content is 0.0060%. Compared with bottom blowing argon, the service life of the bottom blowing permeable brick is reduced by 30%, the smelting cycle is shortened by 0 min, and the production cost is increased by 5 yuan / t 钢 。

[0118] 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 them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and 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-component gas in an electric arc furnace, characterized in that, Including: S1: Smelting starts, the system is initialized, and the standard safety pressure value P f is input into the main control system, and the standard safety temperature value T f is input into the main control system; S2: When the molten bath temperature T < 1500 °C, the electric arc furnace is bottom-blown with argon. S3: When the molten bath temperature T ≥ 1500 °C, the electric arc furnace is bottom-blown with argon and / or an oxygen-containing gas including oxygen and carbon dioxide, and the ratio and flow rate of the oxygen-containing gas are adjusted according to the C content in the molten bath. The bottom-blowing pressure sensor transmits the bottom-blowing working pressure signal P to the main control system w , and 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, and the bottom-blowing working temperature is within the safety 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 strategy is as follows: (1) When the C content [wt%C] in the molten bath > 0.3%, the volume ratio x + y of oxygen and carbon dioxide in the oxygen-containing gas is 40 - 60%, where 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 bath 0.1% ≤ [wt%C] ≤ 0.3%, the volume ratio x + y of oxygen and carbon dioxide in the oxygen-containing gas is 20 - 40%, where 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 bath < 0.1%, the volume ratio x + y of oxygen and carbon dioxide in the oxygen-containing gas is 0 - 20%, where 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 P of the electric arc furnace w > P f + ΔP, or when the bottom-blowing working temperature T w < T f - ΔT, the main control system of the bottom blowing of the electric arc furnace increases the O2 ratio by Δx and decreases the CO2 ratio by 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 P of the electric arc furnace f -ΔP ≤ P w ≤ P f +ΔP, and the bottom-blowing working temperature T f -ΔT ≤ T w ≤ T f +ΔT, the main control system of the bottom blowing of the electric arc furnace controls the proportion of O2 and CO2 to remain unchanged, that is, at this time, the O2 proportion x = x0 and the CO2 proportion is y = y0; (6) When the bottom-blowing working pressure P of the electric arc furnace w < P f - ΔP, or when the bottom-blowing working temperature T w > T f + ΔT, the main control system of the bottom blowing of the electric arc furnace reduces the O2 ratio by Δx and increases the CO2 ratio by 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 P of the electric arc furnace w > P f + 2ΔP or P w < P f - 2ΔP, pressure alarm is enabled, and the bottom blowing of CO2 and O2 is cut off, and pure Ar bottom blowing is adopted; (8) When the working temperature T of the bottom blowing of the electric arc furnace w > T f + 2ΔT or T w < T f - 2ΔT, the temperature alarm is enabled, and the bottom blowing of CO2 and O2 is cut off, and pure Ar bottom blowing is adopted; The main control system controls the O2 flow controller to make the O2 flow rate be Q according to the total flow rate Q of the oxygen-containing gas blown from the bottom and the execution result of the proportion of each medium. O2 = Q×x, controls the CO2 flow controller to make the CO2 flow rate be Q CO2 = Q×y, controls the Ar flow controller to make the Ar flow rate be Q Ar = Q×(100% - x - y); S4: After the above judgments are executed, if the electric arc furnace has not tapped yet, return to S2; if the electric arc furnace is in the tapping process, return to S1. The method is used for producing low-nitrogen and low-phosphorus steel, and the tapping target composition of this variety of steel smelted in the electric arc furnace is: C 0.1 - 0.3 wt%, P < 0.01 wt%, N < 0.005 wt%.

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

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

5. The method for clean smelting by bottom blowing oxygen-containing multi-component gas in an electric arc furnace according to claim 1, characterized in that, At the beginning of a campaign, set the bottom-blowing safety temperature value T f0 to 1600 °C. For every 100 heats of molten steel produced, the bottom-blowing safety temperature value T f0 is reduced by 30 °C.

6. The method for clean smelting of an electric arc furnace with bottom blowing of an oxygen-containing multi-component gas 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-component gas in an electric arc furnace according to claim 1, characterized in that, The bottom-blowing porous plug used in the electric arc furnace is of the capillary type. The diameter of the bottom-blowing porous plug is 200 - 400 mm, the capillary diameter is 1 - 2 mm, and the number of capillary holes is 12 - 50.

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

Images